CN1460054A - Safety systems for power equipment - Google Patents

Abstract

Safety systems for power equipment are disclosed. The safety systems include a detection system adapted to detect a dangerous condition between a person and a working portion of a machine, such as accidental contact with the working portion, and a reaction system associated with the detection system to cause a predetermined action to take place relative to the working portion upon detection of the dangerous condition by the detection system. The detection system may be adapted to capacitively impart an electric charge on the working portion and to detect when that charge drops. The reaction system may be a brake system to stop the working portion, a retraction system to retract the working portion, a system to cover the working portion, or some other system. The safety systems include other features and elements, as disclosed. Machines equipped with safety systems are also disclosed, such as saws, jointers, and other woodworking machines. The machines include a working portion, such as a cutter or blade, a detection system adapted to detect a dangerous condition between a person and the working portion, and a reaction system associated with the detection system to cause a predetermined action to take place upon detection of the dangerous condition, such as a brake system to stop the working portion, a retraction system to retract the working portion, or a system to cover the working portion. The machines may include a control system adapted to control the operability of one or more of the working portion, the detection system and the reaction system. The machines include other features and elements, as disclosed.

Description

Safety systems for power-driven equipment

CROSS REFERENCE TO RELATED APPLICATIONS This patent application statement precedes the following US patent applications: Serial No. 60/157,340, filed October 1, 1999; Serial No. 60/182,866, filed February 16, 2000; Filed August 14, 2000; Serial No. 60/225,057, filed August 14, 2000; Serial No. 60/225,058, filed August 14, 2000; Serial No. 60/225,059, filed August 14, 2000 ; Serial No. 60/225,089 filed August 14, 2000; Serial No. 60/225,094 filed August 14, 2000; Serial No. 60/225,169 filed August 14, 2000; Serial No. 60/225,170 filed August 14, 2000 Filed on August 14, 2000; Serial No. 60/225,200, filed on August 14, 2000; Serial No. 60/225,201, filed on August 14, 2000; Serial No. 60/225,206, filed on August 14, 2000; 60/225,210, filed August 14, 2000; Serial No. 60/225,211, filed August 14, 2000; Serial No. 60/225,212, filed August 14, 2000; and Serial No. 60/233,459, filed August 14, 2000 Submitted on August 18. All of the above applications are therefore represented by the index.

technical field

This invention relates to safety systems, and more particularly to a high speed safety stop mechanism for use on powered equipment.

technical background

Beginning with the Industrial Revolution and continuing to the present day, mechanized equipment has allowed workers to produce products at a higher rate and with less labor than manually operated tools. Unfortunately, the power and high operating speeds of mechanized equipment create hazards for those operating such machines. Thousands of people are injured or killed each year in accidents involving powered equipment.

As might be expected, a number of systems have been developed to minimize the risk of injury while using powered equipment. Perhaps the most common safety feature is a guard that prevents the operator from physically contacting hazardous elements of the machine, such as belts, shafts, or saw blades. In many cases guards are effective in reducing the risk of injury, however there are many instances where the work to be done essentially precludes the use of guards which completely prevent access to hazardous machine components.

Various systems have been proposed to prevent accidental injury where effective use of guards is not possible. For example, U.S. Patent Nos.: 941,726, 2,978,084, 3,011,610, 3,047,116, 4,195,722, and 4,321,841, etc., which --- the disclosures of which are incorporated herein by reference --- all disclose security system. These systems utilize cables attached to the operator's wrist that either pull the user's hand back from the work area while the machine is operating, or prevent the operation of the machine until the user's hand is clear of the hazard. US Patent Nos. 3,953,770, 4,075,961, 4,470,046, 4,532,501, and 5,212,621, the disclosures of which are incorporated herein by reference, disclose radio frequency security systems. These safety systems use radio frequency signals to detect the presence of the user's hand in the danger zone of the machine, and if found, prevent or interrupt the operation of the machine.

U.S. Patent Nos. 4,959,909, 5,025,175, 5,122,091, 5,198,702, 5,201,684, 5,272,946, and 5,510,685 disclose safety systems for use with meat skinning equipment, which are incorporated into this specification by reference. These systems interrupt or reverse the power to the machine or disengage the clutch when the user's hand touches any dangerous part of the machine. Generally speaking, contact between the user and the machine is detected by monitoring the electrical contact between a fine metal mesh placed in a glove worn by the user and certain metal elements in the hazardous area of the machine. Although such systems are commonly used with meat peeling machines, they are relatively slow at stopping the movement of the machine's cutting elements because they rely on the operation of solenoid valves or must overcome the inertia of the motor quality. However, since these systems operate at relatively low speeds, the saw blade does not need to be stopped quickly to prevent serious injury to the user.

U.S. Patent Nos. 3,785,230 and 4,026,177, the disclosures of which are incorporated into this specification by reference, disclose a safety system for use on a circular saw to stop the saw when the user's hand approaches the blade. saw blade. This system uses the saw blade as an antenna in an electromagnetic proximity detector to detect the proximity of the user's hand to the saw blade before the user's hand actually touches the saw blade. Once the user's hand is detected, the system engages a brake using a standard solenoid. Unfortunately, such systems are prone to false triggering and are relatively slow to operate due to the solenoid valves. U.S. Patent No. 4,117,752, the disclosure of which is also incorporated herein by reference, discloses a similar braking system for band saws in which braking is accomplished by physical contact of the user's hand with the blade to trigger. However, the described system for detecting contact of the saw blade is clearly not effective in achieving a precise and reliable detection of contact. In particular, the system relies on standard electromagnetic brakes to operate to cut off the supply voltage to stop the saw blade and the pulley of the band saw. It is believed that such braking will take 50 milliseconds to 1 second to stop the blade. Thus, this system is too slow to stop the saw blade quickly to avoid serious injury.

These existing systems are used with commonly used power tools, none of which are fast enough and/or reliable enough to prevent serious injury. Although, proximity sensors can be used in some devices to increase the time available to stop moving objects, in many cases the user's hand must be brought fairly close to the machine during normal operation. at the cutting element. For example, many types of woodworking equipment require the user's hand to pass in close proximity to the cutting tool. As a result, existing proximity type detectors, which are relatively imprecise, have not proven effective for use in this type of equipment. Even where proximity detectors are practical, in many cases existing braking systems do not operate fast enough to prevent serious injury.

In devices where proximity detectors have not been proven to be practical, the cutting tool must stop very quickly if contacted by the user's hand to avoid serious injury. For example, a user may feed a piece of wood through a table saw at a rate of approximately one foot per second. Assuming an average reaction time of about one-tenth of a second, the hand could have moved significantly more than an inch before the user even knew it. This distance is far greater than would be required to cause the loss of many fingers, sever vital blood vessels and tendons, or even amputate a hand entirely. If a brake is triggered immediately upon contact with the chainsaw blade, the blade must be stopped within about a hundredth of a second to limit the depth of the injury to no more than an eighth of an inch. Standard solenoid valves or other electromagnetic devices are generally not designed to operate on such timescales, especially where significant forces must be generated. For example, in the case of solenoid valves or electromagnetic brakes operating on 60Hz mains power, it is possible that when the brakes are triggered, the power is in a low voltage phase, even before the voltage reaches a high enough level to start actually moving the brakes. Previously, many milliseconds had passed before the goal of completely stopping the saw blade or cutting tool was not far off.

brief reveal

The present invention discloses a safety system for power equipment, the safety system comprising a detection system adapted to detect a dangerous situation between a person and a processing part of a machine, such as an accidental contact between a person and a processing part, and a detection system associated with the detection system A response system that causes a predetermined action to take place when a dangerous situation is detected by the detection system. The detection system may be adapted to transfer charge capacitively to the processing part and detect when the charge level drops. The reaction system may be a braking system that brakes the processing part, a retraction system that retracts the processing part, a system that covers the processing part, or some other system, the safety system including other features and elements disclosed.

The present invention also discloses various machines equipped with the safety stop system of the present invention, such as electric saws, joint planers and the like. These machines consist of a processing part such as a slicing or saw blade, a detection system adapted to detect a dangerous situation between a person and the processing part of the machine, and a detection system connected so that when a dangerous situation is detected, the A reaction system that causes a predetermined action, such as a brake system to stop the machined part, a retraction system to retract the machined part, or a system to cover the machined part. These machines may include a control system designed to control the operability of one or more of the process components, the detection system and the reaction system. The machine includes other features and elements disclosed.

A brief description of the drawing

Figure 1 is a simplified block diagram of a machine with a swift action safety system.

2 is a diagram of an example safety system in the context of a machine with a circular saw blade.

Figure 3 is a generalized circuit diagram of the electronic subsystem for the security system of Figure 1, including the activation system, contact detection system and transmitter equipment.

Fig. 4 is a generalized circuit diagram of a first alternative electronic subsystem of the security system of Fig. 1, including the activation system, contact detection system and transmitter equipment.

Figure 5 is a block diagram illustrating the arrangement of a second alternative electronics subsystem.

FIG. 6 is a schematic diagram of the excitation system of the subsystem in FIG. 5. FIG.

Figure 7 shows an example of signal attenuation that occurs when a user's finger comes into contact with the saw blade.

FIG. 8 is a schematic diagram of the touch sensing portion of the subsystem of FIG. 5 .

FIG. 9 is a simplified diagram of a power supply for the subsystem of FIG. 5 .

FIG. 10 is a schematic diagram of the boost regulator portion and the transmit portion of the subsystem of FIG. 5. FIG.

FIG. 11 is a schematic diagram of the motor control portion of the subsystem of FIG. 5 .

FIG. 12 is a schematic diagram of the rotation sensor portion of the subsystem of FIG. 5. FIG.

FIG. 13 is a schematic diagram of the user interface portion of the subsystem of FIG. 5 .

Figure 14 is a block diagram of second, and third alternative electronics subsystems.

FIG. 15 is a schematic diagram of a portion of the excitation system of the subsystem of FIG. 14. FIG.

FIG. 16 is a schematic diagram of the contact detection portion of the second alternative subsystem of FIG. 14. FIG.

FIG. 17 is a schematic diagram of the contact detection portion of the third alternative subsystem of FIG. 14. FIG.

FIG. 18 is a schematic diagram of the power supply and transmission system portion of the subsystem of FIG. 14. FIG.

Figure 19 is a schematic diagram of a test of an example specific setup showing the electrical isolation of the saw blade from the arbor and charging plate mounts to capacitively couple to the saw blade. Shown in dotted lines is a support frame for fixing the charging plate, a spacer between the charging plate and the saw blade, and a contact brush fixed on the cutter shaft unit. FIG. 20 is an enlarged cross-sectional view taken generally along line 20--20 of FIG. 19. FIG. It should be clarified here that the fastening brackets shown in FIG. 19 are not shown.

Figure 21 is a schematic cross-sectional view of another example embodiment where the arbor is electrically isolated from the arbor unit and the charging plate is capacitively coupled to the arbor.

Figure 22 is a top plan view showing insulation from the shaft of a contractor's table saw, and capacitive coupling.

Fig. 23 is a cross-sectional view of the embodiment of Fig. 22 taken generally along the central longitudinal axis of the arbor and viewed from a position remote from the arbor unit.

24 is a top plan view showing another assembly for coupling the charging plate to the arbor of a contractor's table saw.

FIG. 25 is a cross-sectional view taken generally along line 25-25 in FIG. 24 .

Figure 26 is a side view of a further embodied device in the context of a band saw.

FIG. 27 is an enlarged cross-sectional view taken generally along line 27-27 of FIG. 26. FIG.

Figure 28 is a side view of another embodiment of detecting contact with a guardrail in the context of a circular arm saw.

Figure 29 is a schematic side view of a table saw with a retraction system.

Figure 30 is a schematic side view of the second side of the table saw with retraction system.

Figure 31 is a schematic side view of a saw with another retraction system embodiment.

Figure 32 is a cross-sectional view of a retraction system using a deformable sleeve.

Figure 33 is a schematic side view of a miter saw with a retraction system.

FIG. 34 is a cross-sectional view of the miter saw shown in FIG. 33 .

Figure 35 shows another embodiment of a miter saw with a retraction system.

Figure 36 shows a simplified diagram of a retraction system using a spring to retract a cutting tool.

37 is a cross-sectional view of the retraction system shown in FIG. 36 .

FIG. 38 is also a cross-sectional view of the retraction system shown in FIG. 36 .

Figure 39 is a simplified diagram of a band saw with a retraction system.

Figure 40 is a top view of the roller used in the system shown in Figure 39 .

41 is a simplified diagram of the safety system of FIG. 2 including another spring biased braking mechanism.

42 is a simplified diagram of the safety system of FIG. 2 including another spring biased braking mechanism.

43 is a simplified diagram of the safety system of FIG. 2 including another spring biased braking mechanism.

44 is a simplified diagram of the safety system of FIG. 2 including another spring biased braking mechanism.

45 is a simplified diagram of the safety system of FIG. 2 including another spring biased braking mechanism.

Figure 46 is a fragment of a top plan view of another spring biased brake mechanism.

Figure 47 is a fragment of a top plan view of another spring biased brake mechanism.

Figure 48 is a side view fragment of another spring biased brake mechanism.

Figure 49 is a side view fragment of another spring biased brake mechanism.

Figure 50 is a fragmentary side view of another spring biased brake mechanism.

Figure 51 is a side view fragment of another spring biased brake mechanism.

Figure 52 is a side cross-sectional view of another spring biased brake mechanism.

Figure 53 is an end view of the brake mechanism of Figure 52.

Figure 54 is a side cross-sectional view of another spring biased brake mechanism.

Figure 55 is a side cross-sectional view of another spring biased brake mechanism.

Figure 56 is a top plan view of another spring biased brake mechanism.

Figure 57 is a side view of another spring biased brake mechanism.

Figure 58 is a bottom view of the brake mechanism of Figure 57.

Figure 59 is a side view of another spring biased brake mechanism.

Figure 60 is a side view of a brake mechanism including a pawl.

Figure 61 is a side view of part of another brake mechanism.

Figure 62 is a side view of another pawl.

Figure 63 is a side view of another pawl.

Figure 64 is a side view of another pawl.

Figure 65 is a side view of another pawl.

Figure 66 is a side view of another pawl.

Figure 67 is a side view of another pawl.

Figure 68 is a side view of another pawl.

Figure 69 is a side view of another pawl.

Figure 70 is a side view of another pawl.

Figure 71 is a side view of another pawl.

Figure 72 is a side view of another pawl.

Figure 73 is a side view of another pawl.

Figure 74 is a side view of another braking mechanism.

Figure 75 is a side view of another braking mechanism.

Figure 76 is a side view of another braking mechanism.

Fig. 77 is a side view of another braking mechanism.

FIG. 78 is a top plan view of the brake mechanism of FIG. 77. FIG.

Figure 79 is a side view of a brake mechanism with a translating pawl.

Figure 80 is a side view of another brake mechanism with a translating pawl.

Figure 81 is a side view of another brake mechanism with a translating pawl.

Figure 82 is a side view of another brake mechanism with a translating pawl.

Figure 83 is a side view of a brake mechanism including a plurality of pawls.

Figure 84 is a fragmentary side view of another brake mechanism including a plurality of pawls.

Figure 85 is a top plan view of another brake mechanism.

Figure 86 shows a possible design of the fusible member.

Figure 87 shows various specific arrangements of fusible members.

Figure 88 shows a specific arrangement of the launch subsystem to be used with a machine having a swift action safety system.

Fig. 89 shows the specific device of another transmitting subsystem.

Figure 90 still shows the specific device of another transmitting subsystem.

Figure 91 shows a transmit subsystem mounted on a printed circuit board.

Figure 92 shows a cross-sectional view of an electrode used in the transmit subsystem.

Figure 93 shows a launch subsystem in a cartridge to be used with a machine with a swift action safety system.

Figure 94 shows two electrodes in contact with a fusible member.

Figure 95 shows a graph of data regarding time to fuse wire under various conditions.

Figure 96 also shows a graph of data regarding time to fuse wire under various conditions.

Figure 97 also shows a graph of data regarding time to fuse wire under various conditions.

Figure 98 shows a graph of data regarding time to fuse wire under various conditions.

Figure 99 shows an explosive charge that can be triggered by the launch subsystem.

Figure 100 is a side view fragment of a safety system with a replaceable brake mechanism housed in a cartridge.

Figure 101 is a side view of the interior of another cartridge.

FIG. 102 is an isometric view of the cartridge of FIG. 101. FIG.

Figure 103 is a side view of the cartridge of Figure 101 with one pawl in the engaged position with the saw blade.

Figure 104 is a side view of another cartridge.

Figure 105 is an isometric view of the interior of another cartridge.

FIG. 106 is an isometric view of a variation of the cartridge of FIG. 105. FIG.

Figure 107 is an isometric view showing the cartridge of Figure 106 installed in a machine.

Figure 108 is a side view fragment of another cartridge.

Figure 109 is a side view fragment of another cartridge.

Figure 110 is a side view of the brake positioning system.

Figure 111 is a side view of the adjustable brake positioning system.

Figure 112 is a sectional view of the brake positioning system of figure 111 along line 112-112.

Figure 113 is a sectional view of the brake positioning system of figure 111 along line 113-113.

Fig. 114 is a circuit diagram of the saw blade-pawl spatial measurement system.

Figure 115 is a side view of another brake positioning system.

Figure 116 is an isometric view of another brake positioning system.

Figure 117 is a top view fragment of another brake positioning system.

Figure 118 is a flow diagram of an example self-test logic sequence.

Figures 119A-C are a flow diagram of an example self-test and operation sequence.

Figure 120 is a simplified block diagram of a logic controller.

Figure 121 is a simplified diagram of a user interface.

Figure 122 is a simplified schematic of a launch capacitor charging and testing circuit.

Figure 123 is a simplified block diagram of a logic controller.

Figure 124 is a simplified schematic of a launch capacitor charging and testing circuit.

Figure 125 is an isometric view of an example pawl suitable for determining pawl-to-blade spacing.

Figure 126 is a schematic diagram of an example circuit used to measure blade to pawl spacing.

Fig. 127 is a partial cross-sectional view of an example magnetic sensor assembly, here, the knife shaft is not in the cross-sectional view.

Figure 128 is a schematic diagram of an example circuit for use with a magnetic sensor assembly.

Figure 129 is a schematic diagram of an example EMF sensor assembly.

Fig. 130 is a partial cross-sectional view of an example light sensor assembly, where the blade axis is not in the cross-sectional view.

Figure 131 is a side view of another light sensor assembly.

Figure 132 is a cross-sectional view of another example light sensor assembly of figure 131 taken along line 132-132.

Figure 133 is a schematic diagram of an example circuit for use with a light sensor assembly.

Figure 134 is a partial cross-sectional view of an example electrical sensor assembly, where the knife shaft is not in the cross-sectional view.

Figure 135 is a simplified diagram of another electrical sensor assembly.

Figure 136 is a side view of a circular arm saw equipped with a safety system.

Figure 137 is a side view of a miter or chop saw with a safety system.

Figure 138 is a side view of a pneumatic chop saw with a safety system.

Figure 139 is a side view of a pneumatic chop saw with another safety system.

Figure 140 is a side view of a pneumatic chop saw with another secondary safety system.

Figure 141 is a fragmentary side view of a reaction system.

Figure 142 is a schematic diagram of another reaction system.

143 is a cross-sectional view of the ribbon of the reaction system of FIG. 142 taken along line 143-143 of FIG. 142. FIG.

Figure 144 is a top side view of the hook at the end of the strap of Figure 143.

Figure 145 is a schematic diagram of another reaction system for blocking saw blades.

Figure 146 is a schematic diagram of an alternative reaction system for breaking up saw teeth.

Figure 147 is a top view of an alternative reactive system for winding saw teeth.

Figure 148 shows a cover for the reaction system of Figure 147.

Figure 149 shows a table saw.

Figure 150 is a schematic side view of one side of a table saw with an improved safety system.

151 is a schematic side view of a second side of the table saw of FIG. 150. FIG.

FIG. 152 is a simplified bottom view of the table saw of FIG. 150. FIG.

153 is a schematic perspective view of the table saw of FIG. 150. FIG.

Figure 154 is a schematic side view of a miter saw with an improved safety system.

155 is a top plan cross-sectional view of the miter saw of FIG. 154. FIG.

Figure 156 is a side view of another miter saw.

Figure 157 is a side view of another miter saw.

Figure 158 is a side view of another miter saw.

Figure 159 is a side view of another miter saw.

Figure 160 is a fragment of a cross-sectional view of an electrically insulating saw blade.

Fig. 161 is a side view of an example tool for safety braking in the context of a table saw.

Figure 162 is a side view of an example tool for safety braking in the context of a circular saw.

Figure 163 is a side view of an example tool for safety braking in the context of a band saw.

FIG. 164 is a close up view of the security system of FIG. 163 .

DETAILED DESCRIPTION OF THE INVENTION AND DISCLOSURE OF THE BEST MODE

Figure 1 illustrates a machine incorporating a safety system, which machine is generally designated at 10 . Machine 10 may be one of a range of different machines suitable for wood, plastic, etc. workpieces. These machines include table saws, miter saws, crushing saws, radial arm saws, circular saws, band saws, joint planers, planers, and more. The machine 10 includes an operating structure including a cutting tool 14 and a motor assembly 16 for driving the cutting tool. The machine 10 also includes a safety system 18 for reducing the potential for serious injury to an occupant of the machine 10 . Safety system 18 is used to detect the occurrence of one or more hazardous conditions during use of machine 10 . If a similar hazardous situation is detected, the safety system 18 is used to engage the running structure 12 to limit any injury to the user from the hazardous situation.

Machine 10 also includes a power source 20 for driving operating device 12 and safety system 18 . The power source 20 may be either an external power source, such as line current, or an internal power source, such as a power supply. Another situation is the power source 20 which is a combination of internal and external power sources. Still further, power source 20 may include two or more separate power sources, each power source being used to drive a different portion of machine 10 . As can be appreciated from the context, the operating structure 12 may take any of a variety of forms based on the type of machine 10 . For example, the running structure 12 may include a stationary housing designed to support a motor assembly 16 for engaging the cutting tool 14 . Another possibility is that the running structure 12 comprises a movable structure designed to carry the cutting tool 14 to and from a plurality of operating positions. As a further modification, the running structure 12 may include one or more conveying mechanisms. Such mechanisms are used to move the workpiece closer to and/or away from the cutting tool 14 .

The motor assembly 16 includes one or more motors for driving the cutting tool 14, the motors may be directly or indirectly connected to the cutting tool, and may also be used to drive the workpiece transport mechanism. Cutting tool 14 generally includes one or more blades, or other suitable cutting tools for cutting or removing portions of a workpiece. The specific form of cutting tool 14 depends on the specific form of machine 10 . For example, in table saws, miter saws, circular saws, and radial arm saws, the cutting tool 14 typically includes one or more rotating saw blades that include a plurality of teeth along the edge of the saw blade. In a jointer or planer, the cutting tool typically includes a plurality of radially spaced saw blades. The cutting tool of a band saw consists of a long, narrow, circular band with serrations.

Safety system 18 includes a detection subsystem 22 , a response subsystem 24 and a control subsystem 26 . Control subsystem 26 may be configured to receive input from a variety of sources including detection subsystem 22 , response subsystem 24 , operating structure 12 , and motor assembly 16 . The control subsystem may also include one or more sensors for monitoring selected parameters of machine 10 . In addition, control subsystem 26 typically includes one or more devices operated by the operator to control the machine.

Detection subsystem 22 is designed to detect one or more dangerous or triggering states in use of machine 10 . For example, the detection subsystem may be designed to detect that a portion of the user's body is dangerously close to or in contact with a portion of the cutting tool 14 . In another example, the detection subsystem can be designed to detect rapid movement of the workpiece caused by cutting tool kickback. In some embodiments, detection subsystem 22 may notify control subsystem 26 of the hazardous condition. The control subsystem then activates the response subsystem 24. In other embodiments, the detection subsystem may be used to directly activate the response subsystem.

Once activated by a hazardous situation, the reaction subsystem 24 is designed to quickly engage the running structure 12 to prevent serious injury to the user. As will be appreciated herein, the particular response employed by response subsystem 24 will depend on the type of machine 10 and/or the hazardous situation detected. For example, the reaction subsystem 24 may be designed to take one or more of the following actions: stopping the cutting tool 14, powering the cutting motor assembly 16 to the power source 20, placing a blocking object between the cutting tool and the user. Or withdraw the cutting tool from its operating position, etc. The response subsystem can be designed to take any one or combination of steps to protect the user from serious injury. These are described in more detail below.

The design of the reactive subsystem 24 generally depends on the actions it is to take. In the example depicted in FIG. 1 , reaction subsystem 24 is used to prevent movement of cutting tool 14 . It includes a detent mechanism 28 , a bias mechanism 30 , a restraint mechanism 32 , and a release mechanism 34 . The braking mechanism 28 is used to engage the running structure 12 under the push of the biasing mechanism 30 . Under normal operating conditions of the machine 10, the restraint mechanism 32 maintains the braking mechanism and the operating structure in a disengaged state. However, when the activation signal is received by the response subsystem 24, the release mechanism 34 releases the brake mechanism from the restraint mechanism, and the brake mechanism then rapidly engages at least a portion of the running structure to brake the cutting tool.

Those skilled in the art will appreciate that the example shown in FIG. 1 and the above description can be implemented in various ways depending on the type and design of the operating structure 12 . Attention is now turned to FIG. 2 , which illustrates one of many possible embodiments of security system 18 . System 18 is designed to engage an operating structure comprising a cutting tool in the form of a circular saw blade 40 mounted on a drive shaft or arbor 42 . The saw blade 40 includes a plurality of teeth (not shown) arranged on the outer edge of the saw blade. As will be described in greater detail below, braking mechanism 28 is used to engage the teeth of saw blade 40 to brake rotation of the saw blade. Other systems for braking cutting tools are also described below. Furthermore, the safety system 18 will be illustrated below with respect to each specific type of machine 10 .

In an example, the detection subsystem 22 is used to detect a dangerous situation where a user is approaching the saw blade 40 . The detection system includes a sensor arrangement such as contact detection plates 44 and 46 which are capacitively coupled to the blade 40 to detect any contact of the user's body with the blade. Generally, some of the larger components of the saw blade or cutting tool 14 are electrically isolated from the rest of the machine 10 . In another approach, detection subsystem 22 may include different sensor devices designed to detect contact in other ways. These methods include light detection or resistance detection and so on. In any event, the detection subsystem is used to signal the control subsystem upon detection of user contact with the saw blade. Various specific devices and embodiments of detection subsystem 22 are described in more detail below.

The control subsystem includes one or more devices 48 operated by the user to control the movement of the saw blade 40 . Device 48 may include a start/stop switch, speed control, direction control, and the like. Control subsystem 26 is also coupled to a logic controller 50 that receives user input via device 48 . The logic controller 50 is also connected to receive contact detection signals from the detection subsystem 22 . Still further, the logic controller can be designed to receive input signals from other sources such as blade motion sensors, workpiece sensors, and the like. In any event, the logic controller is designed to control the operating structure 12 in response to user input via the device 48 . However, upon receiving the contact detection signal from the detection subsystem 22, the logic controller overrides the control input from the user and activates the response subsystem 24 to brake the movement of the saw blade. Various specific devices and embodiments of the control subsystem 26 are described in more detail below.

In the exemplary arrangement, the detent mechanism 28 includes a selectively movable pawl 60 mounted near the edge of the saw blade 40 to engage and grip the teeth of the saw blade. The pawl 60 can be made of any material suitable for engaging and braking the saw blade. For example, the pawl can be made from a higher strength thermoplastic such as polycarbonate, ultrahigh molecular weight polyethylene (UHMW) or acrylonitrile butadiene styrene (ABS), or from a metal such as aluminum, material. It will be appreciated that the configuration of the pawl 60 depends on the design of the saw blade 40 . In any event, the pawl is urged by a biasing mechanism in the form of a spring 66 against the blade. In the exemplary embodiment shown in FIG. 2 , pawl 60 is rotated into the teeth of saw blade 40 . It should be understood that sliding or rolling of pawl 60 may also be used. The spring is used to push the pawl 60 into the teeth of the blade with sufficient force to grip the blade and bring it to a quick stop.

A restraining member in the form of a fusible member 70 keeps the pawl away from the blade edge. The fusible member is made of a material suitable to constrain the bias to the pawl from the spring 66 and meltable at a defined current density. Suitable materials for fusible material 70 include, for example, nickel-chromium alloy materials, stainless steel wire, and the like. The fusible member is connected between the pawl and the contact post 72 . Preferably, the structure 70 holds the pawl closer to the edge of the blade so as to reduce the distance the pawl 60 must travel to engage the blade 40 . Placing the pawl closer to the edge of the blade reduces the time it takes for the pawl to engage and brake the blade. Typically, the pawl is held by the fusible member 70 between 1/32 inch and 1/4 inch from the blade edge, although other pawl-to-blade spacings may be used.

Firing subsystem 76 releases pawl 60 from an inactive or energized ready position to engage saw blade 40 . The launch subsystem is connected to the contact post 72 and is configured to send a surge current to the fusible member to

The fusible member 70 is melted. Reflective subsystem 76 is connected to logic controller 50 and is activated by signals from the logic controller. When the logic controller receives a contact detection signal from the detection subsystem 22, the logic controller sends an activation signal to the firing subsystem 76, which melts the fusible member 70, thereby releasing the pawl to brake the saw piece. Various specific devices and embodiments of the reaction subsystem 24 are described in more detail below.

It will be appreciated that activation of the braking mechanism requires replacement of one or more parts of the safety system 18 . For example, pawl 60 and fusible member 70 typically must be replaced before the security system is ready to be reused. Therefore, it is desirable to make one or more parts of the security system 18 in a cartridge for easy replacement. For example, in the exemplary implementation shown in FIG. 2 , the security system 18 includes a replaceable cartridge 80 with an outer cover 82 . Detent 60 , spring 66 , fusible member 70 and contact post 72 are mounted within housing 82 . Another approach is to house the rest of the security system within the enclosure. In any case, after the reactive system is activated, the security system can be reset after cartridge 80 replacement. The portion of the security system 18 that is loaded into the cartridge can be replaced separately or reused as appropriate. Specific arrangements and embodiments of various security systems using replaceable cartridges are described in more detail below.

While a particular embodiment of security system 18 has been described, it will be appreciated that many variations and modifications are possible. Several exemplary arrangements of the security system 18 are described throughout in part to illustrate the various designs, arrangements, applications, and combinations of the various disclosed security systems. For clarity, the following descriptions are arranged into sections with general description headings. These chapters are: Chapter 1: Detection Signal Characteristics and Circuits Chapter 2: Detection of Hazardous Conditions Chapter 3: Soluble Systems Chapter 4: Spring-Biased Braking System Chapter 5: Brake Mechanism Chapter 6: Emission Subsystem Chapter 7: Potential Replacing the Brake CartridgeChapter 8: Brake SettingChapter 9: Logic ControlChapter 10: Motion DetectionChapter 11: Translation BrakeChapter 12: Cutting Tool RemovalChapter 13: Table SawChapter 14: Miter SawChapter 15: Circular Saw

It will be understood that sections and headings are used only to provide a document structure for the disclosure and should not be construed as limiting the disclosure in any way. For example, while Section 7 describes various example cartridges, Section 7 also describes other components. Furthermore, several other chapters will also illustrate example installations of cartridges. Chapter 1: Detection signal characteristics and circuits

As mentioned above, some examples of security system 18 include a contact detection subsystem 22 . The detection subsystem may take any of a variety of different forms. An example contact subsystem includes an electronics subsystem 100 as shown in FIG. 3 . Electronic subsystem 100 is used to work with the two-plate capacitive coupling system described in Section 2 below. The electronics subsystem 100 includes an actuation system 101 and a monitoring or touch sensing system 102 . Of course, for someone so electronics savvy, the example design of electronics subsystem 100 shown in FIG. 3 is only one of many that could be used. Therefore, it will be appreciated that any suitable specific arrangement or design may be used.

As shown in FIG. 3 , the excitation system 101 includes an oscillator circuit capable of generating a square wave input signal such as an amplitude of 12V and a frequency close to 200KHZ. In other approaches, excitation system 101 may be designed to generate signals of different frequencies and/or different amplitudes and/or different waveforms. The oscillator consists of a CD4040 pair of inverters 103, 104 forming a bistable oscillator. The output of the inverter 103 is connected to the input of the inverter 104 via a 100pF capacitor 105 and a 100K resistor 106 . A 10K resistor 107 is connected between the output of the inverter 104 and the junction of the capacitor 105 and the resistor 106 . The output of inverter 104 is connected to the input of inverter 103 . A 10K resistor 108 is connected between the output of the inverter 103 and the input of another inverter 109 . The inverter acts as an output buffer to drive the input wave signal to the saw blade. A 20K resistor 110 is used to attenuate the high frequency content of the signal to reduce any ringing of the input signal.

It will be appreciated that the particular form of the oscillator signal may vary, and that many suitable waveforms and frequencies may be used. The waveform with the maximum noise ratio can be selected. For example, a frequency may be selected at which the human body has the lowest impedance, or the highest capacitance relative to the workpiece being cut. As an additional variation, the property of asymmetrical signals at high frequencies to make potentially large differences in the electrical properties of wood and the human body can be exploited without significantly increasing radio transmit power. For example, without increasing the radio transmission energy, using a 250KHZ square wave with a duty cycle of 5% will produce a signal with high-frequency characteristics 10 times higher than the fundamental frequency. Furthermore, there are many different oscillators which are well known in the art and which are also suitable for generating excitation signals.

The input signal generated by the oscillator is sent to the charging board 44 by the shielded cable 111 . The shielded cable 111 serves to isolate the input signal from any electrical noise present in the operating environment to ensure a “clean” input signal is transmitted to the charging pad 44 . Also, shielded cables reduce crosstalk between the drive signal and the probed signal. This crosstalk occurs when the cables are close to each other. Additionally, other methods can also be used to block noise in the input signal. As a further option, monitoring system 102 may include a filter to remove any noise in the incoming signal or other noise that would be detected by charging pad 46 . Radio emissions can also be reduced relative to unshielded cables 111 .

As described in more detail in Section 2 below, the input signal is coupled from charging plate 44 to charging plate 46 through saw blade 40 . As shown in FIG. 3, the signal received by the charging plate 46 is sent through the shielded wire 112 to the monitoring system 102, which is designed to detect signal changes caused by the contact of the user's body with the saw blade. It will be appreciated that monitoring system 102 may be made in a number of different design configurations. In the example device shown in FIG. 3 , the monitoring system 102 compares the amplitude of the input signal received by the charging pad 46 to a defined reference voltage. The monitoring system generates an output signal from the reactive subsystem 24 when the input signal received by the charging board 46 is lower than the reference voltage for a certain time limit. The reaction subsystem is designed to receive this output signal and act immediately to brake the saw blade.

The particular elements of monitoring system 102 may vary depending on a variety of factors. These factors include the application, the sensitivity required, the availability of components, the type of voltage that can be used, etc. In an exemplary arrangement, a shielded cable 112 is connected between the charging board 46 and the voltage divider 113 . The voltage divider 113 consists of two 1M resistors 114, 115 connected in series between the supply voltage (typically about 12 volts) and ground. The voltage divider biases the output signal from the charging board 46 to an average value of half the supply voltage. The deflected signal is applied to the positive input of operational amplifier 116 . Operational amplifier 116 may be one of many suitable operational amplifiers known in the art. An example of such an amplifier is the TL082 operational amplifier, the negative input of which is connected to the reference voltage source 117 . In this example device, the reference voltage source consists of a 10K potentiometer connected in series with two 10K resistors 119,120. Two 10K resistors 119, 120 are connected to ground and supply voltage source respectively. A 0.47uF capacitor 121 is used to stabilize the reference voltage output.

Those skilled in the art will appreciate that operational amplifier 116 functions as a comparator for an input signal and a reference voltage. Generally, the voltage reference is adjusted to a value slightly lower than the maximum input signal voltage from the charging board 46 . As a result, the op amp output is low when the signal voltage from the charging board is lower than the reference voltage. The op amp output is high when the signal voltage from the charging board is greater than the reference voltage. Where the input signal is a periodic signal such as a square wave generated by drive system 101, the output of operational amplifier 116 will be a similar periodic signal. However, when the user touches the saw blade, the maximum input signal voltage will decrease to a level lower than the reference voltage, and the output of the operational amplifier will not increase any more.

The output of the operational amplifier 116 is connected to a charging circuit 122 . The charging circuit 122 includes a 240uF capacitor 123 connected between the output of the operational amplifier 116 and ground. A 100K discharge resistor is connected in parallel with the capacitor 123 . When the output of the operational amplifier 116 is high, the capacitor 123 is charged. Conversely, when the output of operational amplifier 116 is low, the charge from capacitor 123 is discharged through resistor 123 with a time constant of about 24 microseconds. Thus, unless capacitor 123 is repeatedly charged by pulses from the operational amplifier, the voltage on capacitor 123 will discharge to less than half the supply voltage in about 25-50 microseconds. Diode 125 prevents the capacitor from discharging into operational amplifier 96 . Diode 125 may be one of many diodes known in the art, such as an IN914 diode. It will be appreciated that the required discharge time of the capacitor 123 can be adjusted by selecting a different value capacitor or a different value resistor 124 .

As explained above, as long as the detected signal is received substantially attenuated from its reference value at the operational amplifier 116, the charging circuit 122 will be repeatedly charged and the voltage across the capacitor 123 will remain at a high voltage state. The voltage from capacitor 123 is applied to the negative input of operational amplifier 126 . Operational amplifier 126 may be one of many operational amplifiers known in the art, such as the TL082 operational amplifier. The positive input of the operational amplifier 126 is connected to a reference voltage that is approximately equal to half the supply voltage. In the exemplary device shown in FIG. 3 , the reference voltage is provided by a reference voltage source 117 .

As long as the charging circuit 122 is recharged, the output of the operational amplifier 126 will be low. However, if the output of the operational amplifier 116 does not rise within a period of 25--50 microseconds, the voltage across the capacitor 123 will decay to less than the reference voltage, and the operational amplifier 126 will output a high voltage to indicate the user's physical contact with the saw blade. As will be explained in more detail in Sections 4-6 below, the output signal of the operational amplifier 126 is connected to activate the reaction subsystem 24 and stop the saw blade. The length of time between contact and activation of the reaction system can be adjusted by selecting the time constants of capacitor 123 and resistor 124 .

It should be noted that electrical contact between the operator and the blade will often be intermittent depending on the size, construction and number of teeth on the blade and the location of contact with the operator. Therefore, the time required for the system to detect contact should be less than or equal to the time it takes for a sawtooth to come into contact with a finger or other part of the user. For example, assume a 10-inch saw blade is spinning at 4,000 revolutions per minute, and the contact distance is about a quarter of an inch (one is about the width of a finger), at a point on the surface of the saw blade, like the tooth The tip of the tooth will be in contact with the user for about 100 microseconds, after this contact time there will usually be a non-contact time until the next tooth reaches the finger. The length of contact and non-contact time will depend on factors such as the number of teeth and the rotational speed of the saw blade.

It is not necessary, but preferred, to be able to detect contact with the first sawtooth. Because the time interval to the second tooth can be quite long for a saw blade with a relatively small number of teeth. Furthermore, any delay in detection increases the depth of cut experienced by the operator. Thus, in this example arrangement, the charging circuit is designed to decay within about 25-50 microseconds to ensure that the detection system 102 is able to respond to even momentary contact between the user and the saw blade. Taking it a step further, the oscillator is designed to generate a 200KHZ signal with a pulse every 5 microseconds. As a result, each touch generates several pulses of the input signal, thereby increasing the probability of touch detection. Alternatively, the oscillator and charging circuit can be designed to make the detection system respond faster or slower. In general, it is desirable to maximize the reliability of contact detection while minimizing the possibility of false detection.

As noted above, depending on the size and arrangement of the teeth, contact between the user's body and the teeth of the saw blade 64 may be intermittent. The monitoring system 102 is typically designed to detect contact within as short a time as 25--50 microseconds, but the contact signal received by the second circuit may resume once the first tooth of the saw blade has passed the user's body. Go to the normal state until the next sawtooth is in contact with the user's body. As a result, although the output signal of operational amplifier 126 will go high due to the first contact, the output signal may return to a low state once the first contact is over. As a result, the output signal may not remain at a high potential long enough to start the reactive system. For example, fusible member 70 may not melt if the output signal is not held at a high potential long enough to activate release subsystem 76 . Thus, the monitoring system 102 may have at the output of the operational amplifier 126 a pulse stretcher in the form of a charging circuit 127 similar to charging circuit 122 . Once the operational amplifier 126 generates a high output signal, the charging circuit 127 acts to ensure that the output signal remains high long enough to sufficiently discharge the charge storage device to melt the fusible member. In this exemplary device, the charging circuit 127 includes a 0.47uF capacitor 128 connected across the output of the operational amplifier 126 and the power ground. When the output of the operational amplifier 126 is high, the capacitor 128 is charged to the output signal.

If the op amp 126 output goes back low, the voltage across capacitor 128 discharges through 10K resistor 129 with a time constant of about 4.7 microseconds. A diode such as IN914 prevents the capacitor 128 from discharging through the operational discharger 126, which pulse stretcher ensures that even a brief contact with a single sawtooth will result in activation of the reactive system.

The system described above is capable of detecting the occurrence of contact and activating the reactive system within about 50 microseconds. As detailed in Sections 4-6 below, in the context of a reactive system braking a saw blade, the brakes can be released in approximately less than 100 microseconds and as short as 20 microseconds. The brake makes contact with the blade in about 1 to 3 milliseconds. The saw blade will usually stop after no more than 2--10MS of brake engagement. As a result, injury to the operator in the event of accidental contact with the cutting tool is minimized. With proper selection of components, it is possible to brake the saw blade in 2MS or less.

Although exemplary arrangements of the excitation system and monitor 102 have been described above with particular elements having particular values and arranged in a particular configuration, it will be appreciated that these systems may be configured in a variety of ways as may be desired or preferred for a particular application. Different structures, components and values to build fit to complete. The above structures, elements and numerical values are only used to illustrate a specific embodiment which has been proven to be effective, and should be regarded as an illustration of the present invention rather than a limitation of the present invention.

Figure 4 shows an excitation system 101 and a monitoring system 102, as well as an alternative arrangement for the transmission system 76 which will be described in Section 6 below. An alternative excitation system 101 is designed to use only a comparator 133 such as an LM393 comparator to generate a square wave signal. A 1M resistor 134 is connected between the high input terminal of the comparator 133 and a low voltage source V. A 1M resistor 136 is connected between the comparator high input and the output. A 100NF capacitor 136 is connected between the low input of the comparator and ground. A 27K resistor 138 is connected between the comparator low input and output. A 3.3K resistor 139 is connected between the low voltage source V and the comparator output. An alternative oscillator shown in Figure 6 produces a square wave with a frequency of approximately 3-500 kHz. A 1K resistor 140 is connected between the output terminal of the comparator and the shielded cable 111 to reduce ringing. It will be apparent from this description that the value of one or more elements in alternative system 101 may be changed to produce signals having different frequencies, waveforms, and the like.

As with the example apparatus described above, the signal generated by the alternative excitation system 101 is sent to the charging plate 44 through the shielded wire 111 , and the signal is capacitively coupled to the charging plate 40 through the saw blade 40 . Alternative monitoring system 102 receives a signal from charging pad 46 via shielded wire 112 and compares it to a reference voltage. If the signal falls below the reference voltage for a period of typically about 25 microseconds, an output signal is generated to indicate that contact between the saw blade and the user's body has occurred.

Alternative monitoring system 102 includes a voltage divider 113 consisting of 22K resistors 141 and 142 . The voltage divider biases the signal received via the cable 112 to half of the low voltage supply V. Resistors 141, 142 having lower resistances than resistors 114, 115 reduce 60 Hz noise because low frequency signals are attenuated. This biased signal is fed to the negative input of a second comparator similar to the LM393 comparator. The positive input terminal of the comparator 143 is connected to the reference voltage source 143 . In the particular arrangement described, the reference voltage source consists of a potentiometer connected in series between two 100K resistors 146,147. The resistors 146, 147 are respectively connected between the low voltage source V and the ground. A 0.1uF capacitor 148 stabilizes the reference voltage output. As before, this reference voltage is used to adjust the trigger point.

The output of the second comparator 143 is connected to an NPN bipolar junction transistor 149 such as a 2N3904 transistor. The base of the transistor 149 is also connected to the low voltage source V through a 100K resistor 150 and connected to the ground through a 220uF capacitor 151 . Potentiometer 145 is adjusted so that the potential at the positive input of comparator 143 is slightly lower than the peak value of the signal received at the negative input of the second comparator when there is no contact between the saw blade and the user's body. Thus, each high cycle of the signal causes the output of the second comparator to go low, thereby discharging capacitor 151. As long as there is no contact between the user's body and the saw blade, the output of the second comparator will remain low, preventing capacitor 151 from being charged through resistor 150 and turning on transistor 149 . However, when the user's body is in contact with the saw blade or other insulating element, the signal received at the negative input of the second comparator remains below the reference potential at the positive terminal, and the output of the second comparator maintains at high potential. As a result, the capacitor 151 can be charged through the resistor 150 and turn on the transistor 149 .

The collector of the triode 149 is connected to the voltage source V, and the reflector is connected to the 680Ω resistor 152 . When transistor 149 is connected, it provides an output signal of about 40 mA through resistor 152 which is sent to alternative transmission system 76 . As will be described in detail in Section 6 below, the alternative transmitter circuit includes a fusible member 76 connected between a high voltage source HV and a thyristor 613, such as an NTE5552 thyristor. The gate of the thyristor is connected to a resistor 152 . Therefore, when the transistor 149 is turned on, a current of about 40 mA flowing through the resistor 152 turns on the thyristor SCR 613 to discharge the high voltage source HV through the fusible member 70 to ground. Once the SCR is turned on, it will continue to conduct even if the current to the gate terminal is removed as long as the current through the fusible member 70 remains above the holding current of about 40 mA. Thus, the thyristor will conduct current through the fusible member until the fusible member is melted or the high voltage source is depleted or removed. The fact that the thyristor remains conductive once triggered causes it to respond to a short pulse through resistor 152 as well.

FIG. 4 also illustrates an example electrical supply system 154 designed to provide a low voltage source V and a high voltage source HV from standard 120VAC line voltage. Electrical power supply system 154 is connected to provide low voltage source V and high voltage source HV to alternative excitation system 101 , alternative monitoring system 102 and alternative transmission system 76 . The line voltage is connected to a 1000 uF charge storage capacitor 157 through a 100 ohm resistor 155 and a diode 156 such as an IN4002 diode. The diode passes only the positive portion of the line voltage, whereby capacitor 157 is charged to a potential of approximately 160V relative to ground. The positive terminal of capacitor 157 is connected to fusible member 70 as a high voltage source HV. When the contact between the saw blade and the user's body is detected and the thyristor 613 is turned on, the charge stored in the capacitor 157 is discharged through the fusible member until the fusible member melts. It can be understood from the description herein that the size of the capacitor 157 can be changed according to the current required to melt the fusible member 70 . As mentioned in Section 6, using a high voltage capacitor will cause a large current surge, thus causing the fusible element to blow faster than using a low voltage system.

The positive terminal of capacitor 157 also provides a step-down transformer supply as a low voltage source V. The low voltage source includes a diode 159 connected between the positive terminal of capacitor 157 and an inverting 40V Zener diode. The function of diode 159 is to maintain a relatively constant 40V potential at the junction of the diode and resistor 158 . It can be seen that the current flowing through the 12K resistor will be approximately 10mA. Most of this current is taken by the low voltage power supply, which requires a relatively constant current of about 8mA. It should be noted that while resistor 158 and diode 159 drain some current from capacitor 157, the line voltage source continues to recharge this capacitor to maintain the high voltage supply. A 0.1 NF capacitor 160 is connected in parallel with diode 159 to buffer the 40V voltage from the diode which is then connected to the input of an adjustable voltage regulator 161 such as an LM317 voltage regulator. The resistance ratio of a 1K ohm resistor connected between the output terminal and the adjustment terminal to a 22K resistor connected between the adjustment terminal and the ground is used to set the output voltage of the adjustable voltage regulator 161 at about 30V. A 50uF capacitor 164 is connected to the output of the voltage regulator 161 to temporarily store enough charge to ensure that the low voltage source V can provide the short 40A pulse used to turn on the SCR 613 . The low voltage source is advantageous due to its low cost and simple construction.

It should be noted that when the high voltage source HV is discharged through the fusible member 70, the input voltage of the regulated voltage source 161 may temporarily drop below 30V, thus causing a corresponding drop in the low voltage source V. However, since the reaction system has already been triggered, it is no longer necessary for the detection system to continue functioning as described above, and any potential drop of the low voltage source V will not impair the function of the safety system 18 .

Those skilled in the electrical arts will appreciate that alternative example arrangements of excitation system 101, monitoring system 102, emission system 76, and power supply system 154 may be placed within a single substrate and/or within a single package. In addition, the specific values of the above-mentioned various circuit elements may be changed depending on the application thereof.

One limitation of the monitoring systems shown in Figures 3 and 4 is that they activate the reaction system when the magnitude of the signal from the charging pad 46 falls below a predetermined threshold. In most cases, this represents a reliable trigger mechanism. However, when cutting green wood, a significantly increased capacitive, resistive load is coupled to the saw blade. The moisture in green wood gives it a high dielectric constant, and relative conductivity to dry wood. In fact, when cutting very green wood, eg above 50% moisture content, the signal amplitude on the charging plate 46 can drop to a level relative to the signal amplitude when the user is in contact with the saw blade. Thus, the systems in Figures 3, 4 limit their protective capabilities when dealing with greenwood.

5-13 illustrate another physical embodiment of an electrical subsystem 100 for treating green wood and providing other specific benefits. As shown in FIG. 5 , the system 100 includes an excitation system 101 connected to a microcontroller 171 in the form of a class C amplifier. The system 100 also includes a monitoring system 102 connected to the controller 171 in the form of contact sensors. The power supply 173 provides power to various elements of the system 100 . A motor controller 174 is used to activate and

Turn off the motor. A boost regulator 175 operates to charge the transmit system 176 . A rotation sensing circuit 177 detects rotation of the cutting tool. Finally, a user interface is provided to allow the user to control the operation of the chainsaw and to provide feedback on the status of the system.

Figure 6 illustrates the circuit of the Class C amplifier in more detail. The amplifier includes an output driver connected to pole 44 as shown in FIG. The output drive is about 500KHZ sine wave, the signal amplitude is adjustable between about 3V and 25V. A 32V input supply line from the power supply supplies power to the amplifier. The base frequency is provided by a 500KHZ square wave input from the controller. The signal amplitude is controlled by pulse width modulation from the controller.

The controller is programmed to adjust the drive voltage output from the amplifier so as to maintain a predetermined amplitude at plate 46 under varying capacitive loads. Therefore, when cutting green wood, the controller linearly increases the driving voltage to maintain the required voltage of the pole plate 46 . The controller is preferably capable of twisting the drive voltage between 1% and 50% per millisecond, and more preferably between 1% and 10%. This allows the system to maintain a constant output level under varying loads. This varying load may be caused by sawing the wood or placing a conductive member such as a guard fence near the saw blade. The controller should preferably not twist the drive voltage by more than 50% per millisecond, which would prevent a signal drop caused by a user touch event.

Fig. 7 shows the change in signal amplitude of the plate 46 when the teeth of a 10 inch, 36-tooth saw blade come into contact with a user's finger at a speed of 4000 revolutions per minute. Each drop in signal amplitude results from a single sawtooth sliding across the skin of the finger. For example, it can be seen that the signal amplitude drops by about 30% in about 50 microseconds when the second sawtooth strikes the finger. When cutting very green wood, the attenuation of the signal at contact will be more likely 15%, but again within 50 microseconds. Therefore, as long as the system can detect contact events that cause 5-25% or more dips in less than 100 microseconds, and slopes around 10% per millisecond it will not override an actual event. It will be appreciated that the slope and trigger threshold can be adjusted as desired. The main limiting factor is that the trigger threshold cannot be so small that noise produces false triggers, unless false triggers are acceptable.

Figure 8 shows the details of the system's touch sensing circuitry. The touch sensing circuit receives input from paddle 46 . In this particular arrangement, the required capacitive coupling between the saw blade and the drive plate is about 30 pF, and the capacitive coupling between the saw blade and the plate 46 is about 10 pF. For a given common capacitance of the two plates, larger driver plates improve signal transmission. The actual value is not critical and the same value can be used. Generally speaking, the capacitance of the driving board should be equivalent to the capacitance of the detected person, that is, 10-200pF.

The input from the pad 46 is sent to a high pass filter 179 to attenuate low frequency noise picked up by the pad 46 such as 60 Hz noise. Filter 179 also provides the signal with the magnitude necessary for amplification. The output of the filter is sent to a pair of comparators 180,181. If the maximum signal amplitude from the filter exceeds the voltage set by voltage divider 182 at the positive input of comparator 180, comparator 180 outputs a brief high pulse. The comparator output is sent to the controller. The controller samples in a 200 microsecond window and modulates the drive amplitude in an attempt to maintain the detected voltage at a certain level. This voltage level should cause 50% of the waveform cycle to pass through comparator 180 to generate a pulse. If pulses are generated for less than 50% of the waveform cycle, the controller increases the drive voltage by a certain value. Likewise, if more than 50% of the waveform period is pulsed, the drive voltage is reduced. The system can be designed to determine the size of the adjustment step based on the observed deviation from 50% within a specified window. For example, if 45 pulses are observed, the system may increase the drive amplitude by 1%. Obviously, if 35 pulses are observed, the system may increase the drive amplitude by 5%. The system will continuously adjust to maintain the proper drive level. Depending on the size of the selection window and the size of the adjustment value, the warp rate can be controlled to the above desired level.

Comparator 181 pulses every cycle of the waveform as long as the detected voltage exceeds a lower trigger threshold set by voltage divider 182 . Therefore, under normal conditions, the pulse frequency is 500KHz. The output pulse of the comparator 181 is sent to a divide-by-four circuit composed of two D flip-flops, which reduces the frequency to 125KHz---or 8Ns pulse period. The divide-by-four output is sent to the controller. The controller monitors this line to ensure at least one pulse every 18Ns. Therefore, if more than half of the pulses are missing within 18Ns, the controller will trigger the reaction system. Of course, the specific period can be chosen to maximize the reliability of detecting contacts and minimize false triggers. The benefit of the above system arrangement is that the absence of one or even two pulses eg due to noise will not trigger the system. However, if more pulses are missing, the system will still be reliably triggered. The specific trigger level for missing pulses is set by a voltage divider. For the system described herein, this trigger level is typically between 5% and 40%.

FIG. 9 illustrates the circuit of the power supply 173 . The circuit includes an unregulated 32 volt output and regulated 5, 15 and 24 volt outputs. The 24 volt output supplies power to the excitation system with a larger voltage, and the 32 volt output supplies power to the capacitor charging circuit described below. The 5-volt output charges controllers and other logic circuits, while the 15-volt output is used for most analog electronics. The controller monitors a low voltage output to ensure the presence of proper voltage for operating the system.

FIG. 10 illustrates skip boost regulator 175 and transmit system 176 . The boost regulator includes a jump boost regulator 183 that boosts the 32 volt supply output to 180 volts to charge the transmitter circuit. The controller provides a 125KHz input to modulate the skip boost cycle of the charger. A voltage regulator circuit 184 monitors the voltage from the transmit circuit and turns the charger on and off as needed to maintain the charger voltage near 180 volts. The regulator circuit

FIG. 11 illustrates the circuitry of the motor controller 174 . The motor controller receives a logic level control signal from the controller to turn the motor on or off in accordance with input from the access panel, as will be described in more detail below. The motor control also turns off the motor when a trigger event occurs. The logic signal is electrically isolated from the motor voltage by an opto-isolated triac. In this way, the detection system ground wire is insulated from the motor power ground wire. A mechanical relay or similar device may also be used to provide similar isolation. When the opto-isolated thyristor receives a signal from the controller, it turns on the Q6040k7 triac to supply power to the machine.

Figure 12 shows the rotation sensing circuit. The purpose of this rotation sensing circuit is to ensure that the contact detection system is not turned off until the cutter or saw blade has stopped. The rerotation detection system uses a Hall-effect sensor placed near a rotating part of the machine. A small magnet is inserted into the rotating part to send a signal to the Hall effect sensor. The output of the Hall effect sensor is sent to the controller. It will be described in more detail in the following sections 9, 10. The controller monitors the output of the Hall effect sensor to determine when the cutter is coming to a stop. Once the cutter stops moving, any detected contact will no longer trigger the reaction system. It should be understood that the rotation of the cutter may also be detected by other means.

For example, a small eccentricity may be mounted on the cutter or other insulating structure that rotates with the cutter, such as the cutter shaft. The eccentricity can be placed through the sensing plate 46 or a separate sensing plate. As long as the cutter is spinning, the centrifuge will modulate the amplitude of the detected signal. This modulation can be monitored to detect rotation. If the spinner is sensed by the sensing pad 46, it should be small enough that the resulting signal modulation will not be registered as a contact event. As another alternative, rotation may be detected by electromagnetic feedback from the motor. These and other examples are described in Section 10 below.

The controller can also be designed to monitor the line voltage to ensure that the proper voltage is present to operate the system. For example, the AC voltage depending on the electrical safety system connected to the chainsaw may drop by nearly half during the motor's run. If the voltage drops below a safe level, the controller will shut off the chainsaw motor. Alternatively, the controller can include a capacitor with sufficient capacitance. This capacitor allows the chainsaw to run the system for a few seconds without power input when activated.

FIG. 13 shows the usage panel 178 . The user panel includes buttons for start, stop and bypass to control the operation of the chainsaw. A bypass button allows the user to disable the contact detection system during a single on/off cycle of the chainsaw. This enables the sawing of metal or other materials that trigger the reaction system. The user panel also includes red and green LEDs for reporting the system to the user. The operation of the appropriate user panel is described in more detail in Section 9 below.

Figures 14-18 show two additional electronics for the detection subsystem 22. As shown in Figure 15, the alternative detection system uses a microcontroller 171 to manage and monitor various functions. An excitation system sends a 350KHz sinusoidal drive signal to the saw blade through the plate 44 . Figure 15 schematically illustrates this circuit for generating the drive signal. The excitation circuit uses a 700KHz oscillator whose output is fed to a frequency multiplier to generate a 1.4MHz signal. The frequency multiplier output is sent to a pair of S---R flip-flops to take out phase signals with 90-degree intervals. The phase signal is used to drive a synchronous detection system employing one of the two embodiments of FIGS. 14-18 and shown in more detail in FIG. 17 . The 350KHz, 180-degree phase square wave signal is sent to a Q=10, 350KHz band-pass filter through two inverters and a buffer amplifier.

The bandpass filter output is a 350KHz sine wave. This sine wave is connected to the sense amplifier 190 shown in FIG. 16 through another buffer amplifier. The sense amplifier output is sent to plate 44 and the input from plate 46 is fed back to the negative input. When a user touches the cutter 40, the feedback from the sense amplifier is reduced, thus causing the output of the amplifier to rise. The result of this arrangement is that the drive amplitude of the saw blade is small during normal use and only increases when the user touches the saw blade or cuts green wood. In this embodiment, the best capacitive coupling of the plates to the saw blades is 9OpF each, although other values may be used.

The output of the sense amplifier is sent through a buffer to a 350KHz bandpass filter to filter out any noise picked up from the saw blade or plate. The bandpass filter is sent through a buffer to an amplitude detector. The magnitude detector produces a dc output proportional to the magnitude of the sense amplifier. The amplitude detector output is smoothed by an RC circuit to reduce ripple and sent to a differentiator. The differentiator produces an output that is proportional to the change in the sense amplifier's output amplitude.

As mentioned above, the output of the sense amplifier changes only when the user touches the saw blade or cuts green wood. The changes caused by cutting green wood are relatively slow relative to the user's contact with the saw blade. Thus, the differential is tuned to react to user touch and only minimally to green wood. The output of the differentiator is then sent to a comparator which acts as a threshold detector to determine whether the output of the differentiator has reached a level predetermined by a voltage divider network. The output of the threshold detector is fed to a Schmitt trigger. This trigger signals the controller when a contact event occurs. An RC network used as a pulse extender ensures that the signal lasts long enough to be detected by the controller.

The output of the level detector is also sent to an analog to digital input on the controller. Perhaps in some cases, such as when cutting very green wood, the response of the sense amplifier is nearly saturated. If this happens, the amplifier may no longer be able to respond to touch events. To provide warning of this condition, the controller monitors this line to ensure that the detected signal stays low enough to allow subsequent contacts to be detected. If an excessive resistive load is detected, the controller shuts down the chainsaw without triggering the reaction system to provide a warning to the user. If the user wishes to continue using the chainsaw, they can activate the bypass mode described above.

The second of the two alternative detection systems in Figures 14-18 is a synchronous detector. The detector uses the flip-flops in Figure 15 to generate phase information only. This system drives the plate 44 through the ALT driving circuit shown in FIG. 15 . The ALT drive circuit and the detection circuit in FIG. 17 are used in place of the circuit in FIG. 16. As shown in Figure 17, the signal from plate 46 is sent to a pair of analog switches through a pair of buffer/amplifiers. The pair of switches is controlled by phase information from the inverter. Due to the synchronous detection, this design produces an output signal proportional to the amplitude of the signal detected by the plate 46 and has improved noise immunity. This output signal is sent to the differentiator and threshold detection circuit detailed previously. These circuits send a trigger signal to the controller when the detected signal amplitude drops fast enough that the interrogator produces an output that exceeds a threshold level.

Figure 18 illustrates a power supply and transmission system for use with these two alternative devices. The power supply generates plus and minus 15 volts as well as 5 volt levels. Capacitors in the transmit system are charged around the transformer secondary input. This design provides isolation of the system ground from the machine ground and avoids boosting the supply voltage to the capacitor voltage as done by a boost regulator.

The capacitor charging circuit is regulated by the enable line from the controller. By disabling the charging circuit, the controller can monitor the capacitor voltage through an output on the controller to the A/D line. When the capacitor is not charged, it will discharge to ground at a relatively known rate through various paths. By monitoring the rate of discharge, the controller can ensure that the capacitor has sufficient capacitance to melt the fusible member. Trigger control from the controller is used to trigger the SCR to melt the fusible member.

Using any of the above electronic subsystems it is possible to avoid triggering when cutting metal or sheet metal by only looking at whether the signal amplitude or rate of change falls below a certain threshold. Depending on the system, this can be done by observing whether the signal amplitude or rate of change falls within a window or bandwidth. More specifically, when cutting metal, the detected signal will drop almost to zero and will drop within a cycle. Accordingly, the controller or threshold detection circuit can be designed to observe a trigger event with a magnitude change of greater than 10% or less than 100%. This avoids triggering when machining metal or other conductive workpieces that typically short the signal to ground completely.

It will be noted, again not necessarily, that all detailed arrangements operate at a relatively high frequency, greater than 100 KHz. This high frequency is believed to have two advantages. First, with high frequencies, contacts can be detected faster and multiple waveform cycles can be sampled in a short time. This allows the detection system to look for multiple missing pulses rather than a single missing pulse. A single pulse can be generated by the noise and trigger the reaction system. In addition, high frequency is believed to provide better double noise when cutting green wood. Greenwood has lower impedance at low frequencies.

The contact detection system, detection signal characteristics, circuits, methods and machines are described in the following note paragraphs. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

1.1 A machine suitable for handling workpieces and including a contact detector consists of:

An electronic conductivity sensor located in a potentially hazardous location in the machine. In these dangerous places, the sensor may come into contact with the workpiece or the user;

A contact detection system that is connected to a sensor and receives signals from it. The contact detection system is designed to distinguish between user or workpiece contact with the sensor based on the rate at which the signal changes when contact occurs.

1.2 A wood processing machine includes:

a cutter for cutting the workpiece;

An excitation system for providing an electrical signal having a first amplitude and period. the electrical signal is coupled to the cutter to induce a corresponding second magnitude electrical signal on the cutter;

and a touch-sensing system for sensing electrical signals induced on the cutter. The contact sensor senses the user's contact with the cutter according to the change of the detected electric signal within a detection period. The detection period is between 5 and 150 milliseconds and is at least twice the period of the electrical signal.

1.2.1 The machine of paragraph 1.2, wherein the excitation system adjusts the first amplitude in accordance with the detected electrical signal characteristic.

1.2.1.1 The machine of paragraph 1.2.1, where the excitation system is used to adjust the first amplitude to maintain a predetermined second amplitude.

1.2.1.2 The machine of paragraph 1.2.1, where the rate of adjustment of the first amplitude does not exceed 10% per millisecond.

1.3 A processing machine includes:

a cutter for cutting the workpiece;

An activation system having an electrical output that induces an electrical signal of a first amplitude on the knife. The excitation system is used to adjust the amplitude of the electrical output to maintain a sufficiently constant first amplitude when the electrical load of the cutter changes within a certain range.

1.3.1 The tooling system in paragraph 1.3. Here, the range includes a maximum rate of change of the electrical load.

1.4 A contact detection system consists of:

a sensor;

An excitation system for generating drive signals. The drive signal is coupled to the sensor to induce a corresponding sense signal on the sensor. Here, the ratio of the driving signal to the sensed signal varies depending on the distance between the object and the sensor;

and a control system for adjusting the amplitude of the drive signal to maintain a sufficiently constant amplitude of the sensed signal as various objects approach the sensor. Chapter 2: Detection of Hazardous Situations

As mentioned above, the contact detection pads 44 and 46 are used to detect contact between the user's body and the cutting tool 14 . It will be appreciated that the detection subsystem 22 may employ one or more of a number of different methods for detecting contact of the saw blade with the user's body. In view of the high response speed of electrical signals and circuits, one method used involves the use of electronic circuits to detect the electrical connection between the user and the cutting tool. It has been found that the capacitance of the user's body is between about 25 - 200 pF as measured by dry contact with a part of the user's body. The measured contact capacitance tends to increase with increasing body size and body-to-ground coupling.

Due to the intrinsic capacitance of the user's body, when the user touches the cutting tool 14, the capacitance of the user's body is electrically coupled to the intrinsic capacitance of the cutting tool, thereby producing an effective capacitance greater than the intrinsic capacitance of the cutting tool itself. capacitance. Accordingly, probing subsystem 22 may be electrically coupled to measure the electrical capacitance of the cutting tool. Thus, any substantial change in detected capacitance will indicate contact between the user's body and the cutting tool.

The example arrangement shown in FIG. 2 illustrates a detection subsystem 22 designed to detect user contact with a cutting tool through capacitive coupling between the saw blade and the plates 44,46. The detection system 22 includes suitable electrical circuitry (such as detailed in Section 1 above) to send an input signal to the pad 44 and to detect the input signal through the pad 44 . The pole plate 46 is mounted adjacent to but spaced from the saw blade. The plate 44 is capacitively coupled to the saw blade by its size and the advantage of being spaced parallel to the saw blade. A pole plate 46 is also mounted close to but spaced from the blade to create a second capacitive coupling. It will be appreciated that the size and location of the charging pads may vary.

The effect of this arrangement is to form two capacitors in series with the blade and create a capacitive shunt at the capacitor junction. Plates 46, and 46 act as capacitor charging plates. The input signal is capacitively coupled from the pole plate 44 to the saw blade 40 , which is then capacitively coupled from the saw blade to the charging plate 46 . Any change in the capacitance of the saw blade will change the signal coupled to the charging plate 46 .

When the user touches the saw blade 40, the capacitance of the user's body creates a capacitive load on the saw blade. As a result, the magnitude of the capacitive shunt between the charging plate and the saw blade is increased, thereby reducing the amount of charge reaching the plate 46 . Thus, when the user touches the blade, the magnitude of the input signal through the blade to the plate 46 is reduced. The detection subsystem 22 is designed to detect this change in the input signal and transmit the contact detection signal to the logic controller 50 .

In some cases, there is a significant resistance between the dry skin of the user and the contact point of the saw blade. This impedance may reduce capacitive coupling from the user's body to the saw blade. However, as the teeth penetrate the outer layers of the user's skin, the inherent moisture in the tissue within the skin will tend to reduce the impedance of the skin/blade contact, thereby establishing a strong electrical connection. The sensitivity of the detection subsystem 22 can be adjusted as necessary to recognize even small changes in the input signal.

In general, the distance from the blade to the charging plate is not critical and can vary depending on the area of the charging plate and the required capacitive coupling to the saw blade. However, it is preferable to separate the plate and blade by a selected distance to reduce the effect of blade deflection on the capacitance between the plate and blade. For example, if the load generated during a cutting operation moves the saw blade 1/3 inch toward one of the plates, the capacitance of that plate increases. Since capacitance is proportional to plate area divided by plate spacing, a relatively large spacing will reduce the relative effect of a given blade displacement. A spacing in the range of about 1/32 to about 1/2 inch has proven effective, although spacing values outside this range may be used where appropriate.

It will be appreciated that the charging plate may be placed adjacent to one or both sides of the saw blade and/or the edge of the saw blade. In the example setup, the pole plate is placed relatively close to the center of the saw blade. Since the deflection of the saw blade is usually minimized around the axis on which it is mounted, placing the charging plate close to the axis of the cutter has the advantage of minimizing the effect of blade deflection on the blade, capacitive coupling between the plates. In various alternative arrangements, at least one outer edge of the charging plate is positioned radially at 50%, 40%, 30%, 20% or 10% of the radius of the saw blade from the center of the saw blade.

The charging pad may be mounted in machine 10 in any suitable manner. These means are known to those skilled in the art. For example, in the exemplary device shown in FIG. 19 , the operating structure 12 includes a knife shaft hinge unit 250 for supporting the knife shaft 42 . The charging board is mounted on a support member 251 (dashed line in FIG. 19 ), which is attached to the arbor unit 250 . As a result, the charging plates 44 and 46 rotate together with the arbor unit, thereby maintaining their position adjacent the saw blade. Alternatively, the charging pad can be housed in a fixed unit.

In another arrangement, at least one of the charging plates may include one or more insulating spacers attached to the blade side of the charging plate, as shown in FIGS. 19 and 20 . Spacer 252 acts as a physical barrier that prevents the blade from coming too close to the charging plate. This can be especially useful when the charging plate is relatively close to the saw blade. Spacers can be made of any suitable electrically insulating material, including ceramics, glass, plastics and the like. In the exemplary arrangement shown in Figs. 19 and 20, the spacer 252 covers only a minimum portion of the area between the charging plate and the saw blade. Therefore, the shim has relatively little effect on the capacitance between the charging plate and the saw blade. Alternatively, the shim may cover a sufficiently large portion, or even all, of the space between the charging plate and the saw blade. In this latter case, the spacer will at least partially act as a dielectric between the charging plate and the conductive surface of the saw blade. Therefore, the capacitance between the charging plate and the saw blade will depend on the dielectric constant of the pad.

In addition to one or more shims provided between the charging plate and the blade, facing shims may be provided on the side of the blade facing away from the charging plate to prevent the blade from drifting too far from the charging plate. Alternatively, one charging plate can be mounted on the opposite side of the saw blade relative to the other charging plate. Still further, the shim can be designed to move across the face of the saw blade as the saw blade moves. Additionally, if the charging plate is mounted so that it moves in and out of the side of the blade, and is elastically biased toward the blade, the charging plate and shim will move with any deflection of the blade, so even when the blade is deflected, Also keeps the pad in contact with the blade. An advantage of this arrangement is the ability to establish and maintain a close spacing. Therefore reduce the plate size and maintain a fixed capacitance between the charging plate and the saw blade.

It will be appreciated that the size of the charging pads 44 and 46 may also vary. Typical values for plate area are between 1 and 10 square inches. Of course many different sizes are possible, including sizes outside of this typical range. In the exemplary device, the pad size, along with the pad spacing and dielectric, are selected to provide a pad one-to-blade capacitance comparable to (eg, within the same order of magnitude) the capacitance of a human body. This design serves to improve the signal-to-noise ratio of the signal detected by the charging pad 46 . Still further, the charging plate 44 may be a different size than the charging plate 46 and/or be placed near or far from the saw blade to provide a different electrical capacity. For example, it may be desirable for the drive plate 44 to be larger than the sense plate 46, which increases the coupling of the drive charge plate.

An example of a suitable charge plate material is a relatively stiff, flat-thin copper printed wiring board. Other examples include any relatively conductive material such as gold, aluminum, copper, iron, brass, and the like. The charging pad can take any shape that fits the particular space of the machine 10 . Where there is a large grounded metal structure near the blade, a larger drive charge plate 44 can be used to partially shield the blade from capacitive coupling to the ground structure. Although larger plates will also have increased capacitive coupling to grounded structures, due to the detection system being able to drive a larger capacitive load than would be generated in these cases. This does not interfere with the operation of the detection subsystem 22 .

Those familiar with the art will understand that the saw blade 40 should be insulated from ground to allow the input signal to be capacitively coupled from the charging plate 44 to the charging plate 46 . In the exemplary arrangement shown in Figures 19 and 20, the saw blade 40 is electrically isolated from the arbor 42 on which it rests, thereby isolating the saw blade from ground and the rest of the machine structure. Electrical isolation of the saw blade from the arbor can be provided in various suitable ways. Depending on the particular design of machine 10, these approaches can vary. For example, in the case of a 5/8 inch arbor 42, the saw blade 40 may consist of a one inch diameter circular hole and a 3/16 inch thick cylindrical plastic bushing 253 embedded therein, as shown in Figures 19 and 20. as shown. Insulating washers 254 are placed on both sides of the saw blade to insulate the saw blade from the shaft flange 255 and shaft washer 256 . The insulating washer should be thick enough to provide negligible capacitance between the blade and the grounded shaft flange and washer. A typical thickness is on the order of about 1/8 inch, although, depending on other factors, sizes of 1/32 inch or less may also be suitable. Additionally, it is possible to make some or all of the arbor components out of a non-conductive material, such as ceramic, to reduce or eliminate the electrical isolation requirements for the arbor.

A cutter shaft nut 257 clamps the entire saw blade assembly on the cutter shaft 42 . The die set up by tightening the arbor nut allows the torque from the arbor to be transmitted to the saw blade. Although not required, it is desirable for the saw blade to slide slightly on the arbor to reduce the mass that must be stopped and reduce stress on the blade, arbor and/or other components in the saw's drive system in the event of a sudden brake caused by the brake blade. damage. Furthermore, it is best to make the bushing out of a material that is soft enough to deform under braking. For example, depending on the type of actuation system employed, a substantial radial shock load may be transmitted to the arbor upon actuation of the brake. A deformable bushing can be used to absorb some of the shock and reduce the possibility of damage to the arbor. Additionally, a combination of suitable brake mounting locations and a deformable bushing can be used to move the saw blade away from the user when the brake is activated. This is described in more detail in Section 3 below.

It will be appreciated that the blade insulation assembly described above does not require a special blade as described in US Pat. No. 4,026,177. In fact, the arbor 42 can be sized to fit into a plastic bushing received with a standard saw blade 40 having a 5/8 inch hole diameter. In this way, the operator can use any standard saw blade with the machine 10 .

As an alternative to insulating the saw blade shaft, the shaft and/or a portion of its support frame may be insulated from ground. One benefit of this arrangement is that if the saw blade is coupled to the arbor, the arbor itself can be used to capacitively couple the input signal from the charging plate 44 to the charging plate 46 . As a result, the charging plate is less likely to interfere with loading and unloading the saw blade, and thus is less likely to be removed or damaged by the user. The fixed implementation of this particular alternative will vary depending on the cutting tool design. Figure 21 illustrates an example setup.

As shown, the saw blade 40 is mounted directly on the arbor 42 . As in Figure 20, the saw blade is secured to the arbor by the arbor flange 255, arbor washer 256 and arbor nut 257. The cutter shaft is supported by one or more bearings 258 for possible rotation relative to the cutter shaft unit 250 . These bearings are mounted on the cutter shaft unit and are separated along the axis of the cutter shaft. Of course, the bearing 258 is not in direct contact with the cutter shaft. Instead an electrically insulating sleeve 259 is placed between the cutter shaft and the bearing. The arbor unit 250 is movable to allow the saw blade to be raised or lowered, as well as tilted for angled cuts. A motor (not shown) drives the knife shaft via a belt 260 wrapped around a pulley at the end of the knife shaft opposite the blade. The belt is generally not live and therefore does not electrically couple the knife shaft to ground.

Sleeve 259 may be made of any suitable relatively durable and non-conductive material. These materials include plastics, ceramics, etc. The sleeve can be designed to fit a fixed diameter arbor as shown, or the arbor can be cut to accommodate the sleeve so that the outer diameter of the sleeve aligns with the outer diameter of the arbor. Further, it will be appreciated that there are many other methods of electrically insulating the cutter shaft. As just some examples, a sleeve 259 could be placed between the bearing 258 and the arbor unit 250, or at least a portion of the bearing could be made of a non-conductive material. For example, ceramic bearings can be used. Additionally, the larger portion of the arbor can be insulated from the rest of the saw.

In any case, the charging plates 44 and 46 are positioned laterally, but slightly separated from the arbor. Charge plates are generally shaped and aligned relative to the tool axis to ensure adequate capacitive coupling. For example, the charging plate could be grooved to fit the cylindrical knife shaft, as shown in Figure 21. Alternatively, the plates may be annular or barrel-shaped to completely surround the radially separated portions of the cutter shaft. The charging board half is supported on the arbor unit 250 as a bracket 262 extending from the frame. This design ensures that when the position and angle of the saw blade are adjusted, the charging plate and the cutter shaft are arranged in a straight line. The bracket is generally designed to electrically insulate the charging pad from the frame. The charging plate can be placed very close to the knife axis because it does not deflect during use like a saw blade, thus allowing a smaller charging plate to be used.

Turning attention to FIGS. 22 and 23, another arrangement for capacitively coupling the charging plates 44 and 46 to the saw blade 40 is illustrated. This design has proven suitable for use with those contractor style table saws from a wide variety of manufacturers. Arbor unit 250 includes two separate, and generally parallel, support members 263 . This member is used to receive the bearing 258 in the center switchboard 264 . An electrically insulating bushing 265 is placed in the bearing and serves to receive the knife shaft 42 . Each bushing 265 includes an outer rim or flange 266 adjacent the outer periphery of the bearing. The bushing can be made of ERTYLITE (PET--P), or any other electrically insulating material suitable for supporting the electric shaft in the bearing.

The cutter shaft flange 255 is integrated with the cutter shaft 42 and adjacent to one of the shaft sleeves 256 . The other end of the shaft 42 is collared to receive one or more jam nuts 267 . A nut tightens the flange of the other sleeve 265 to hold the bearing 258 on the arbor 42 . The pulley 261 is mounted on the part of the cutter shaft close to the locking nut 267.

As shown in Figure 23, the bushing 265 completely insulates the cutter shaft from the bearings and the cutter shaft unit. Alternatively, the bushing could be designed to fit between the bearings 258 and support the member 263 . In any case, the cutter shaft remains firmly and symmetrically mounted so that it rotates freely on the bearings.

The charging plates 44 and 46 take the shape of a conductive cylinder having an inner diameter larger than that of the cutter shaft 42 . The barrels 44, 46 may be made of any suitable material such as brass tubing, copper tubing or the like. It will be appreciated that the size of the charging tubes 44, 46 can be selected to provide the desired capacitance to the shaft. In fact, the size of the charging tubes can be varied to provide different capacitances. For example, in the example shown in Figures 22 and 23, the charging tube 44 is longer than 46, so the highest capacitance is provided between the charging tube 44 and the knife shaft than between the charging tube 46 and the knife shaft. Alternatively, or in addition, the inner diameter of the charging plate can be varied to provide different capacitances depending on the different blade-charging plate spacing.

The charge tubes 44 , 46 are received in an electrically insulating support housing or tube 268 , which has an inner diameter to accommodate the charge tubes 44 , 46 . The insulating tube 268 may be made of suitable insulating material such as polycarbonate, nylon, PVC and the like. The insulating tube is used to prevent the charging tube from being grounded through the electric shaft unit, bearings, etc. An insulating tube 268 is positioned about the knife shaft 42 and is received in a bore 269 in the support member 263 . Bore 269 is coaxial with cutter shaft 42 . Thus, where the charging tubes 44, 46 are placed concentrically within the insulating tube, the charging tube inner diameter is automatically placed concentric or symmetrical to the knife axis by the insulating tube.

It will be appreciated that while the charging and insulating tubes in the example arrangement are cylindrical, other shapes could be used. For example, the insulating tube 268 has a short outer section while maintaining a circular inner section. Likewise, the charging tubes 44, 46 may have any suitable outer cross-section to match the inner shape of the insulating tubes. In any case, mounting the charging plate on the support member 263 ensures that the support sleeve remains in the correct position relative to the arbor regardless of movement of the arbor unit 250 .

In addition to electrical insulation to automatically position the charge tube, insulating tube 268 also serves to surround and protect the charge tube from damage and contact debris. In the exemplary arrangement, insulating tube 268 defines an aperture 270 disposed between charge tubes 44 and 46 to allow cables (not shown) to be soldered or attached to the charge tubes to carry signals from the detection circuitry of detection subsystem 22 . Another approach is to use two apertures, each placed above a charging tube.

Since the charging tubes cannot contact each other, the fit between the charging tube and the insulating tube is generally tight to frictionally prevent axial movement of the charging tube along the insulating tube. Alternatively, a protrusion or ring may be formed or placed on the inner diameter of the insulating tube between the charge tubes to prevent the charge tubes from touching each other. As a further modification, the aperture 270 can be used to apply filler, glue, epoxy or other substance between the charging tube and the insulating tube to prevent the charging tube from moving. Alternatively, one or more set bolts may pass through the insulating tube to support the charge tube.

Turning attention to Figures 24 and 25, there is illustrated an insulating tube, an alternative to a charging tube, for use with a contractor's style chainsaw. The insulating tube 268 includes a hollow opening with an outwardly beveled end for receiving the charging tubes 44,46. Each charging tube has an inner narrow rim. A cable (not shown) may be attached thereto (by electric welding or the like). The narrowness of the rim 271 allows the cables to be attached to the charging tube before it is inserted into the insulating tube. Usually the cable is fed through the hole 270.

The insulating tube 268 also includes a recessed area 272 for receiving a Hall Effect or similar sensor device 1000 . The sensor is used to detect the rotation of the saw blade/knife shaft. Sensor 1000 will be described in more detail in Section 10 below. The sensor is aligned with the aperture 273 in the charge tube 44 to sense the magnetic passage applied to the knife shaft (not shown). Alternatively, the sensor is aligned with aperture 273 in charge tube 46 . In some cases, for example, where charge tubes 44, 46 are identical, it may be preferable to place hole 273 in both charge tubes to reduce the number of different parts that must be produced.

Some example arrangements for capacitively coupling the charging plate to the knife shaft have been described. It will be appreciated that there are many suitable designs and that the invention is not limited to any one particular design. For example, if there is insufficient space between the bearing and the charging plate, one or more charging plates may be placed between the bearing and the pulley, or on the side of the pulley opposite the bearing.

It will be appreciated that one or more charging plates may be capacitively coupled to other portions of the running structure 12 than the saw blade 40 or arbor 42 . For example, the charging plates 44, 46 may be coupled to the arbor unit 250 that is electrically isolated from the machine 10 and the rest of the operating structure. In this design, the saw blade should be electrically coupled to the arbor unit. Therefore, the insulating sleeve between the saw blade and the cutter shaft or between the cutter shaft and the cutter shaft unit can be omitted. As another example, the charging plate could be coupled with a bearing pulley or the like.

It will be appreciated that the charging plates 44, 46 may be electrically coupled to other styles of cutting tools, including non-circular saw blades or cutters. For example, FIGS. 26 and 27 depict an example arrangement where a charging plate is capacitively coupled to the band saw 275 . Typically the band saw 275 includes a main housing housing a pair of vertically spaced wheels 277 . The outer rim of each wheel 277 is covered or wrapped with a high friction material such as rubber. A relatively thin continuous saw band loop 40 is tightened around the two wheels. The workpiece is cut by sending it towards the saw band 40 in the cutting area between the wheels 277. An upper saw band guide 279 and a lower saw band guide 280 maintain the circulating saw band on a steady path in the cutting area 278 . The workpiece is fed to the saw band on table 281 . The table forms the bottom of the cutting area.

The saw band should be electrically insulated from the main casing, which is normally grounded. Accordingly, saw band guides 279 and 280, which may include bearing guides and/or friction pads, etc., are made to electrically isolate the main housing from the saw band. Additionally, a high friction coating on the wheels 277 electrically insulates the saw band from the wheels. Alternatively, the wheels could be made of non-conductive material.

Depending on the application and space constraints within the main housing, the charging pads 44, 46 can be arranged in a variety of ways. Figure 26 illustrates two possible designs. In one design, the charging plates 44 , 46 are placed close to the saw band when the saw blade rides on the wheels 277 . The charging plate can be arc-shaped to match the outer edge of the wheel and maintain a fixed saw band-charging plate spacing. This is because the saw band is constrained to a fixed path against the outer edge of the wheel. The charging pad can be connected to the main housing by a non-conductive bracket to maintain electrical isolation from the housing.

Another one of many possible designs for a charging pad includes a charging pad unit 282 . The unit is designed to stretch along the saw band as it travels between the wheels 277 . As shown in detail in FIG. 27 , the charging pad unit includes charging pads 44 , 46 . In the depicted arrangement, the charging pad unit has a substantially C-shaped cross-section. It is sized to fit the side and rear (non-serrated) bands of the saw band. The charging plate unit is mounted on the main housing 276 and is resiliently biased toward moving the saw band by, for example, one or more springs 283 . Since the saw band 40 may tend to shift or drift in its path, the spring 283 ensures that the charging unit can move with the saw band. The charging pad unit 282 is typically made of a durable, non-conductive material such as ceramic, plastic, or the like. Charging pads 44, 46 are placed on or within the charging pad unit. Although the charging plate is illustrated as being positioned opposite the saw band 40, the charging plate could also be placed on the same side of the saw band. The self-aligning design of the charging plate unit ensures that the saw band-charging plate spacing is sufficiently fixed despite the movement of the saw band. In addition to band saws, the charging plate can also be capacitively coupled to machines with cylindrical cutting heads like jointers, planers, etc. The cutter head is usually mounted to rotate about the cutter axis. Accordingly, the charging plates 44, 46 may be capacitively coupled to the knife shaft or the flat end of the cutter head, etc. as described above.

Although an example system and method for detecting contact of a user's body with a saw blade is described herein. Many other systems and methods can also be used. For example, the detection system can sense the resistance of the user's body as it comes into contact with the saw blade. As shown in Figure 19, the sensor assembly of the detection subsystem 22 may include a contact brush 284 or similar sensor to make direct electrical contact with the saw blade. The contact brushes 284 may be mounted on, for example, the arbor unit 250 . Typically, the saw blade and contact brushes are electrically isolated from the arbor unit. Alternatively, as described in conjunction with the charging plates 44, 46, the contact brushes may be designed to couple directly to the cutter shaft or another portion of the running structure 12. In any event, contact of the user's body with the blade will act as a switch to form a conductive path that can be detected by appropriate circuitry in the detection subsystem 22 and/or control subsystem 26 . As a further alternative, the detection subsystem sensor assembly can be designed to detect contact by optical, electromagnetic or other non-electrical means.

As an alternative to detecting user contact with the saw blade, the detection subsystem may be designed to detect the approach of the user's body toward the saw blade by detecting contact of the user's body with a guard fence adjacent the saw blade. If the guardrail is placed in such a way that the user's body touches the guardrail before the saw blade, the saw blade is stopped before the user makes contact with it. It will be appreciated that this alternative detection system can be implemented in a variety of different designs and used with any of the machines 10 . As an example, FIG. 28 shows a saw 286 for a radial arm.

Typically, the radial arm saw 286 includes a horizontal base 287, a vertical support column 288 extending upwardly from the base 287, and a guide arm 289 extending upwardly from the column 288 and perpendicular to the base 287. A rail frame 290 is slidably combined with the lower side of the guide arm 298 . The bottom end of the rail frame is connected to the saw frame 291 and the motor assembly 16 to allow the saw blade 40 to be pulled through the base to cut a workpiece (not shown) supported by the base. A guard member 292 known in the art is positioned on at least one side of the saw blade 40 . The guard member 292 is positioned relative to the saw blade such that any part of the user's body that approaches the saw blade will first contact the guard member. Generally, guard member 292 is movably coupled to housing 291 to maintain its blade shielding position as the saw blade passes through a workpiece.

The guard member is electrically insulated from the housing 291 but is electrically coupled to a detection subsystem (not shown). Thus, any contact of the user's body with the protective member is detected. The detection subsystem is electrically coupled to the shielding member by any suitable means such as cables or the like (not shown). Alternatively, the detection subsystem is capacitively coupled to the shielding structure as described above via one or more charging pads positioned adjacent to the shielding structure.

Systems, methods and machines for detecting hazardous conditions may be described in the numbered paragraphs of the following declarations. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

2.1 A woodworking machine includes:

an excitation system for inducing electrical signals on the cutting tool;

a first capacitive coupling for electrically coupling the excitation system and the cutting tool;

A touch-sensing system for monitoring electrical signals induced on cutting tools;

and, a second capacitive coupling for electrically coupling the sensing system to the cutting tool;

2.2 A woodworking machine includes:

a motor;

an electrically isolated rotatable cutter shaft designed to be driven by a motor;

a circular saw blade;

an excitation system for generating electrical signals;

And a capacitive coupling for electrically coupling the excitation system and the knife shaft to transmit a portion of the electrical signal to the saw blade.

2.3 A woodworking machine includes:

a conductive cutting tool;

an excitation system for generating electrical signals;

A capacitive coupling connecting the excitation system and the cutting tool, where the capacitive coupling has a capacitance of at least 10 picofarads. Chapter 3: Retraction System

As briefly mentioned above, the reaction subsystem 24 can be designed with a retraction system to retract or remove the cutting tool from the point of accidental contact with the user. Removing the cutting tool from the point of accidental contact reduces the time the tool is in contact with the user, thereby minimizing injury to the user. Removing the cutting tool from the point of accidental contact also prevents any increased injury from the cutting tool moving towards the user. For example, the rotary blade on a miter saw has enough angular momentum to cause the blade to move down and toward the user when the detent pawl hits the blade. The rotating blade in a table saw also has enough angular momentum to move the blade up and toward the user when the detent pawl hits the blade. It depends on the position of the brake, the quality of the blade and the structure that supports the blade. Guarding against any such movement reduces potential injury to the user. A retraction system can replace or be shared with other safety systems.

Figures 29 and 30 show a cutaway view of a table saw with retraction system and brake mechanism. A saw blade 300 is installed on the cutter shaft 301 and rotates along the arrow 302 . A table 303 (not shown in Figure 30) defines the work plane of the table saw, adjacent to the saw blade. And the saw blade stretches out from the desktop. A support structure 304 may support the saw blade 300 and arbor 301 in any known manner, or as described in more detail in Section 13 below.

The saw blade 300 is designed to be rotatable up and down so that the user can extend the saw blade out of the tabletop as needed. The saw blade rotates about the pin 305 . The user can adjust its position by turning the saw blade. This is accomplished by turning a shaft 306 on which a worm gear is mounted. The worm gear is mounted on the shaft for rotation with the shaft. But as will be explained below, it can slide on the shaft when required. The worm gear 307 is mounted on the shaft 300 like a collar. The shaft extends along a longitudinal hole in the worm wheel. The worm gear is held in place by a spring clip 308 during normal operation of the saw. The spring clip is placed in a groove or channel 309 on the worm wheel and engages a detent or protrusion on the shaft 306 to hold the worm wheel in place. The worm gear is engaged with a bow 310 supporting a cutter shaft unit 311 which supports the cutter shaft 301 and the saw blade 300 in turn. Therefore, when the user turns the shaft 306, like turning a handle (not shown) attached to the shaft, the worm wheel 307 turns the cutter shaft unit 311 and the saw blade up and down in the direction of the worm wheel rotation.

A brake box 312 is mounted in the chainsaw adjacent to the saw blade 300 . The brake cartridge includes a pawl 314 that is biased toward the blade 300 by a spring 316 . The pawl is pulled away from the blade 300 by a release mechanism 318 . This has been described generally above and will be described in more detail in the following sections 4-5, and 7-8. As will be explained in Section 6 below, the detent box is designed so that the release mechanism releases the pawl into the saw blade when a detection signal is received.

The brake box 312 is placed on the axis of rotation of the saw blade so that the pawl 314 can rotate about the pin 305 . Thus, when the pawl 314 hits the saw blade, the angular momentum of the saw blade is transferred to the arbor unit. And saw blade, cutter shaft unit, frame and brake box try to retract or move down along the direction of arrow 320 . Alternatively, the brake cartridge could be placed on a different pin than pin 305, but only rotate with the blade.

The saw blade will move down as far as the bracket 310 and worm gear 307 allow. If the worm gear is fixed, the downward movement of the saw blade may snap off the teeth on the bracket and/or the worm gear and may prevent the saw from moving downward the necessary distance. In the example arrangement shown in Figs. 29, 30, the worm wheel is unjammed and moves onto the shaft 306 when the pawl hits the blade.

When the pawl hits the saw blade, the resulting angular momentum impact causes the spring clip 308 to snap loose allowing the worm wheel to slide off towards the end 322 of the shaft. The spring clips snapped loose. This is because the bracket moves down when the saw blade is stopped, and the bracket contacts the worm gear and forces the worm gear to move. The force of the bracket against the worm wheel causes the spring clip to snap loose. The worm wheel can be moved back from its shaft until the clip snaps onto the shaft to return the worm wheel to its original position.

The table saw shown in FIGS. 29 and 30 also includes a support frame 326 . The support frame 326 is designed with a base or area 328 in which a shock absorbing material 330 is placed. The bracket is placed under the arbor and the arbor unit so that the arbor unit hits the impact absorbing material 330 when the saw blade is retracted. The bracket 326 and the impact absorbing material 330 act as a barrier to stop the downward movement of the saw blade. The bracket is placed in a position where the saw blade 300 can be fully retracted. The impact absorbing material can be any one of rubber, foam, plastic, etc. used for seat cushions. One suitable material found to be available is available from AearoEAR, Indianapolis, Indiana under part numbers C--1002--06. Alternatively, the shock absorbing material 330 may be attached to the lower surface of the arbor unit instead of the bracket 326 . Additionally, bracket 326 may take many forms. In fact, the shaft 306 can be designed and mounted to provide a flat surface against downward movement of the saw blade.

Fig. 30 also shows a separator 335 which extends out of the table top behind the saw blade 300 to prevent backstroke. A saw blade guard may also substantially surround the saw blade 300 . Figure 30 further shows an enclosure 339 for the electronics and motor mounts associated with the security system. These two parts are not shown in FIG. 29 .

In the above configuration, the angular momentum of the saw blade causes the saw blade, arbor unit and cartridge to all move downward when the pawl strikes the saw blade. Therefore, the angular momentum of the saw blade causes retraction. The saw blade 300 is allowed to move downward a sufficient distance to fully retract the saw blade. The ability to retract the blade minimizes injury from accidental contact with the blade.

Figure 31 shows another example of a retraction system used with a brake pawl. The chainsaw 331 includes a saw blade 300 and a brake box 312 that accommodates a brake pawl 314 . The brake box and pawl are fixed on the chainsaw bracket by pins 332 . The pin is mounted on the chainsaw in such a way that it does not move up and down with the blade. When the blade hits the pawl, the blade climbs off the pawl or in other words, turns around the contact point of the pawl. The pawl does not rotate downwards with the blade, as shown in the example arrangement of Figs. 29, 30, because the pawl is fixed to the chainsaw frame. In this example device, the saw blade is retracted by "climbing off" the pawl.

Another example device for a retraction system includes a compressible bushing. Typically, in a table saw, miter saw or other machine the saw blade 300 is secured to the arbor by a bushing 333 as shown in FIG. 32 . A lock nut, washer and a shaft flange are used to secure the saw blade to the shaft. Bushing 333 may be made of a material soft enough to deform when the saw blade is suddenly stopped. For example, depending on the brake system used, a substantial radial shock load may be transmitted to the blade shaft upon activation of the blade brake. A variable row bushing can be used to absorb some of the shock and reduce the chance of damage to the arbor. Additionally, a combination of proper brake positioning and variable row bushings can be used to move the saw blade away from the user when the brake is activated. Where a plastic bushing is placed between the blade and the arbor, the substantial impact of braking the blade deforms the bushing almost immediately. Often the edge of the blade mounting hole will bite into the bushing as the blade tries to circle the pawl. Thus, if the pawl is mounted behind the saw blade, the saw blade will tend to move down towards the bushing and away from the user when the pawl engages the blade.

Figures 33, 34 show a miter saw equipped with a brake and retraction system. The miter saw is configured with a rotary motor assembly to allow the saw blade to move up and closer into the housing when the saw blade engages the brake pawl 348 . The motor assembly 350 is connected to the casing 352 by a pivot bolt 352 to allow the motor assembly to rotate about the bolt 354 in the direction of rotation of the saw blade. A spring 356 is compressed between the housing and a fixed pin 358 to bias the motor assembly in the direction of blade rotation. The motor assembly may include a raised lip 360 . It slides on the casing-flange to hold the bottom of the motor assembly in position against the rotating bolts on the casing.

The spring 356 maintains the rotation of the motor assembly in a normal position completely opposite to the direction of rotation of the saw blade during use of the chainsaw. However, once the pawl is released to engage the blade, the motor assembly and blade rotate upwardly against the biasing direction of the spring. In this example arrangement, the pawl is positioned in front of the blade so that the rotating bolt 354 is between the pawl and the knife shaft. This arrangement encourages the saw blade to move upwardly into the housing when blocked. The spring is selected to be of sufficient strength to hold the motor assembly in the down position while cutting into a workpiece. Yet it is compressible enough to allow the blade and motor assembly to move upward when the blade is blocked. Of course the saw blade and motor assembly can be designed in one of several ways so as to absorb at least a portion of the angular momentum of the saw blade.

Figure 35 shows an alternative arrangement for a miter saw. The miter saw is designed to be adapted to move away from accidental contact with the user by absorbing the angular momentum of the saw blade. In this design, the miter saw includes two swing arms 370 and 372 . One end 374 of each swing arm 370, 372 is connected to the base 376, and the opposite end of the swing arm is connected to the housing 380, saw blade, and/or motor assembly (not shown). The relative positions of the swing arms can be changed according to the desired swing arm movement. In FIG. 34 , swing arm 370 is attached to base 376 just below swing arm 372 . Typically, the motor assembly is securely attached to the end 378 of the swing arm 370 and the housing 380 is connected to rotate about the end 378 of the swing arm 370 . The end 378 of the swing arm 372 is only connected to the chassis. Alternatively, the motor assembly may be connected to rotate with the housing about the end 378 of the swing arm 370 .

The geometry of the design shown in Figure 35 causes the housing and/or motor assembly to rotate together as the swing arm twists. Notably, as the swing arm moves upward, the housing and/or motor assembly rotates in a direction opposite to the direction of rotation of the saw blade while cutting. As a result, when the pawl engages the blade and transfers blade angular momentum to the housing and/or motor assembly, the housing and/or motor assembly tends to rotate in the same direction as the blade. This causes the swing arm to twist upward, dragging the blade away from the workpiece and the user's body. Thus, the miter saw design shown in Figure 35 is adapted to absorb the angular momentum of the saw blade and convert the angular momentum into an upward force on the swing arm.

In either of the systems described above, a spring or other force may be used to urge the saw blade out of contact with the user. The spring can be released by a mechanism similar to releasing a pawl to strike a saw blade. Figures 36-38 show how a spring can be used to retract the blade in a table saw. A top view and a side view of an arbor unit 381 for driving a fixed arbor 382 of a saw blade (not shown) are shown in Figs. 36 and 37, 38, respectively. The cutter shaft 381 is fixed to the pin 383 so that the cutter shaft unit and the saw blade can be twisted up and down to adjust the position of the saw blade in the chainsaw.

Like the bracket 310 described above in conjunction with FIGS. 29 and 30, a fan 384 is also connected to the pin 383 and is connected to the arbor unit 381 to raise and lower the arbor in a manner to be described below. The gear sector 384 includes a side portion 385 substantially perpendicular to the plane of the cutter shaft unit 381 , and a top portion 386 above the cutter shaft unit 381 . The side portion 385 includes gear teeth 387 which mesh with the worm gear to raise and lower the arbor unit. The sides 385 and top 386 are interconnected and move together. The roof 386 covers the entire upper portion of the roof 386 as shown. The arbor unit is made to leave an area to accommodate the top 386 so that the top 386 does not extend substantially across the arbor unit. Otherwise, the ability of the arbor unit and saw blade to be twisted upwards if required, for example to contact the underside of the table top in a table saw, would be limited.

A container 388 is formed in the arbor unit 381 to accommodate the spring 389 . In the position shown in Figure 37, the spring 389 is compressed between the top 386 of the tooth sector 384 and the arbor unit 381 because the tooth sector and the arbor unit are coupled together.

The gear fan and the cutter shaft unit are connected together by a composite rod. As shown in FIG. 38, the composite rod has a first bracket connected at one end to the knife shaft unit and connected to a second bracket at the other end. A second bracket, in turn, is attached to the top 386 of the tooth sector 384 as shown. The first and second brackets are connected to each other by hinges, and are connected to the cutter shaft unit and the gear sector. The brackets are designed such that the spring force pushing the cutter shaft unit away from the top of the sector biases the first and second brackets in such a way that the brackets will move. A fusible member 392, which may take the form of a wire as described above, limits the movement of the stent. Of course, many different linkages could be used, and many styles and designs of fusible members or other release mechanisms could be used. The link can be chosen to provide enough mechanical advantage that the arbor unit and the top of the sector can be connected together with as thin a fusible member as possible so that the fuse member can be melted as easily as possible. Various similar composite linkages are described in Section 4 below. The fusible member is melted by a system as described above, or as described in more detail in Section 6 below. Composite linkages and fusible members are preferably designed such that they accommodate spring forces of 100 to 500 pounds or more.

When the fusible member is melted, the resultant link can move and the spring pushes the arbor unit 381 downwards, away from the top 386 of the tooth sector. As indicated by the dotted line in Figure 37, the saw blade is thus retracted. The stronger the spring; the faster the blade will retract. The tooth fan does not move. This is because it is connected by teeth 387 to the worm wheel or some other structure.

Retracting the blade by a spring or some other force can be considered direct retraction. A spring or other force can be used with some other retraction system to increase the speed of retraction of the cutting tool, or a spring or other force as a unique retraction method. The direct retract system described above can be used on a variety of machines, this includes table saws, miter saws and band saws.

Figure 39 is a schematic diagram of the band saw retraction system. Typically, a band saw includes a housing enclosing a pair of vertically spaced wheels. The perimeter of each wheel is wrapped or covered with a high friction material such as rubber. A relatively thin, continuous band ring tightly wraps around the two wheels. A workpiece is fed to the saw blade against the cutting area between the wheels and cut. The work is sent to the saw blade on the table. The table top forms the bottom surface of the cutting area.

The band saw shown in Figure 39 includes a roller 393 positioned adjacent the saw band. The rollers are designed to contact the saw band and push the saw band away from the point of accidental contact with the user. Additionally, the rollers can be designed to push the saw band away from the wheels, thus stopping the movement of the saw band. Fig. 40 is a top view of the roller pushing the saw band along the direction of the arrow. The rollers can be part of a brake box and can be released into the saw band like the release pawl described above. The rollers should have a diameter large enough that the rollers can roll over the teeth of the saw band.

Systems that directly retract the cutting tool can also be incorporated into hand-held circular saws, which typically include a base plate that contacts the work during cutting. The base plate supports the chainsaw on the workpiece. The base plate can be designed so that it is pressed down when the saw blade contacts the user. The result of this action is effectively retracting the saw blade as the base plate pushes the user away from the saw blade.

Retraction systems, methods and machines may be described in the numbered paragraphs declared below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

3.1 A woodworking machine includes:

a working part;

a detection system for detecting hazardous conditions between the person and the work part;

And, a retraction system associated with the detection system to retract the working part when a hazardous situation is detected.

3.1.1 The machine described in paragraph 3.1, where the working part is a rotating saw blade with angular momentum, where the retraction system is utilized at least in part to retract the saw blade using the angular momentum of the saw blade.

3.2 A table saw consisting of:

a working plane;

and, a rotatable saw blade that is raised and lowered relative to the work plane about a pivot point, where the rotation of the saw blade defines the direction in which the workpiece is fed into the saw, and, relative to the direction in which the workpiece is conveyed, the pivot point is at downstream of the saw blade.

3.3 A table saw consisting of:

a working plane;

a rotatable saw blade that is raised and lowered about a pivot point relative to the work plane;

a transmission system for raising and lowering the saw blade;

A release system in the drive train that allows the saw blade to drop relative to the work surface when certain events occur.

3.3.1 The table saw of paragraph 3.3, where the specific event refers to braking the saw blade.

3.3.2 The table saw of paragraph 3.3 further includes a stop that limits the fall of the saw blade.

3.4 A chainsaw consists of:

a rotatable saw blade that is raised and lowered about a pivot point relative to the work plane, where the saw blade is mounted on the knife shaft;

An arbor body for securing the arbor and further for retracting the arbor and blade when a specific event occurs.

3.4.1 The chainsaw of paragraph 3.4 comprises first and second parts that are fixed together until the occurrence of a specified event, and further comprises stored mechanical energy to move upon the occurrence of a specified event by releasing this energy First and second part.

3.5 A miter saw consisting of:

a base with sharp areas;

a saw blade;

a brake system for braking the saw blade;

A linkage between the blade and the base, where the linkage is designed to allow the blade to exit the cutting area when the brake system brakes the blade.

3.5.1 In the miter saw of paragraph 3.5, the linkage is designed so that when the brake system brakes the saw blade, the angular momentum of the saw blade causes the saw blade to withdraw from the cutting area.

3.6 A miter saw consisting of:

a base;

a chassis pivotally connected to the base;

a saw blade;

a mounting system for securing the saw blade in the housing;

Also, the braking system is adapted for braking the saw blade;

The mounting system is designed so that the blade rotates into the housing when the brake system brakes the blade.

3.7 A band saw consisting of:

A workplane with clipping with a cutout area;

a saw blade close to the cutting area;

a detection system for detecting dangerous conditions between the person and the saw blade;

and a retraction system associated with the detection system to push the saw blade away from the hazardous area when a hazardous condition is detected. Chapter 4: Spring Biased Braking Systems

From the above, the safety system 18 includes a braking mechanism 28 for stopping the cutting tool to prevent or reduce injury to the user. As also discussed above, the braking system may include at least one pawl 60 for engaging the cutting tool to stop rotation. Section 5 below illustrates a schematic example of a suitable pawl. For purposes of the following discussion, the cutting tool 14 will be described in the context of a saw blade 40 as in a table saw, miter saw, circular saw, or similar tool. It should be understood that the saw blade 40 may comprise a single saw blade like a glued or top carbon saw blade, or a combination saw blade like a tenoner.

As discussed further, pawl 60 may be urged toward saw blade 40 or other cutting tool by biasing mechanism 30 from its plugged or restricted position. In FIG. 2 , the biasing mechanism 30 includes a spring 66 . From its compressed position shown in FIG. 2 , spring 66 urges the pawl into engagement with saw blade 40 . FIG. 2 shows a limiting mechanism 32 limiting movement of pawl 60 toward the blade under the biasing force of spring 66 . However, when the restraint mechanism 32 is released, the pawl is no longer restrained in the plugged position. Like this, pawl enters engagement with saw blade rapidly under the active force of spring 66, just as shown in Figure 41. An example of a limiting mechanism acting as a release pawl is when a sufficiently high current is passed through the fusible member 70 . Other suitable release and restraint mechanisms are described in Section 6 below.

The particular implementation of spring 66 shown in Figure 2 is a helical compression spring. Here, spring 66 will be used to refer generally to any suitable spring, such as any suitable spring known here or elsewhere in the art. Here, specific spring types are referred to by specific reference numbers, such as helical compression spring 402 . Figures 2 and 41-59 show and illustrate various examples of spring-biased detent mechanisms and include various components, sub-components and possible variations. It should be understood that the spring biased detent mechanism may include any one or more of such elements, subelements and variations, regardless of whether those elements, subelements and variations are in opposite or different illustrations or descriptions.

The speed at which the pawls engage to brake the blade depends on the force of the spring on the pawls. Thus, the greater the force exerted by the spring on the pawl, the faster the pawl passes the distance from its constrained position to the blade. In tests, springs applying a force to the pawl in the range of 10 to 500 pounds have proven most effective, springs have been found to be most effective in the range of 50-200 pounds, and 100 pounds have proven particularly effective. However, it should be remembered that the restraining mechanism must not only counteract the force of the spring, but must also be able to release the pawl quickly from its blocked position. Therefore, there may be a tradeoff between increasing the spring force and increasing the complexity, strength and cost of a limiting mechanism capable of limiting the increased spring limiting force. And, if there is any mechanical advantage of replacing the associated structure with the spring should be taken into account.

The detent mechanism 28 utilizes additional springs 66 shown in FIGS. 42-44. In FIG. 42 , the spring 66 is in the form of a leaf spring 404 having a base 406 and a pawl engaging portion for engaging and urging the pawl 60 toward the saw blade 40 . The base 406 is secured to a suitable mounting assembly 410 . Mounting assembly 410 may employ any suitable structure for supporting the leaf spring base to bias pawl engaging portion 408 toward the pawl. As shown, the leaf spring 404 is a cantilevered leaf spring. FIG. 43 illustrates another example of a suitable mounting assembly 410 , where the mounting assembly includes a plurality of spaced apart brackets 411 .

In FIG. 44 , a torsion spring 412 is used to bias the pawl 60 into engagement with the blade 40 . The spring 412 includes a fixed end 414 , a biased end 416 for engaging the pawl 60 , and a central helical portion 418 . As shown, torsion spring 412 is mounted on the same pin or shaft 420 as pawl 60 . It will be appreciated that the spring 412 may be placed between the shaft and the pawl, affixed to the shaft adjacent or separate from the pawl, or to a structure different from the shaft 420 .

Figure 45 shows a pull spring. Unlike a compression spring, which resists an applied force, a tension spring resists it being extended from the center, or zero-load position. Thus, rather than pushing the pawl toward the blade, the pull spring 422 pulls the pawl toward the blade or other cutting tool. As shown, the tension spring 422 includes a biased end 424 connected to the pawl and a fixed end 426 connected to a suitable fixing assembly 410 . The fixed assembly faces toward the saw blade relative to the biased end portion. The fixed assembly to which fixed end 426 is attached may include a link, or bracket 428, attached to the end of the fixed assembly. Similarly, the biasing end 426 may be connected to the pawl or other structure that moves with the pawl by a strut or bracket 430 . Securement assembly 410 may include any suitable structure capable of supporting or securing end 426 without interfering with running structure 12 . For example, it can be fixed near the saw blade 40, connected to the saw blade shaft, fixed on a structure that tilts with the saw blade, moves up and down, etc. Alternatively, the tension spring 442 can act on a part of the pawl, or a strut connected thereto. That is, at the other end of the pawl torsion axis different from an engaging portion of the pawl saw blade. This design is represented by the dashed line in Figure 45. This design may be better. This is because the fixation assembly 410 is remote from the saw blade and is easier to locate.

Although only one spring 66 is shown in FIGS. 2 and 42-45, it should be understood that the detent mechanism 28 may include more than one spring. For example, in the illustrated device shown in FIG. 45, as in FIG. 46, a pair of pull springs 422 are used. When two or more springs are used, they may be of similar or different types and strengths.

In FIGS. 2 and 41-46, the spring 66 is shown engaging the pawl 60 directly. It should be appreciated that the spring may otherwise engage other structures in communication with the pawl. For example, spring 66 may engage one or more linkages. The biasing force of the springs through these linkages is transferred to the pawls. In this design, the restraint mechanism 32 can restrain either accommodating portion of the biasing mechanism and pawl assembly to prevent the pawl from coming into engagement with the saw blade or other cutting tool. For example, in the context of a restraint mechanism including a fusible member 70, the fusible element may be connected to the pawl 60, the spring 66, or one or more links connecting the spring and the pawl.

FIG. 47 shows an example detent mechanism 28 in which the spring engages the link directly instead of the pawl 60 . Within the detent structure there is a pair of pawls 60 for engaging the saw blade 40 . As shown, the pawl 60 includes a blade-engaging portion 434 for engaging the saw blade 40 , the pawl 60 twists about an axis or pin 436 and includes a distal end 438 connected to a link 440 . Link 440 is further connected to a spring-engaging link 442 . As shown, the linkage 442 includes an end 444 for moving toward the blade to draw the blade-engaging portion of the pawl into engagement with the blade. FIG. 47 illustrates a compression spring 402 engaged with a link 442 . However, any portion of the springs described herein may be used.

The spring 66 can also apply a biasing force to an engagement structure other than the pawl. In such an arrangement, instead of spring force acting on the upper portion of the pawl, the non-restraining mechanism 32 releases the engaging or biasing mechanism to urge the pawl into engagement with the saw blade or cutting tool of the machine 10. One advantage of the detent mechanism is that the biasing mechanism also applies force to the pawl until the pawl is pushed into engagement with the saw blade 40 . This may, but does not have to, enable pawl 60 to be selectively removed or replaced from the detent mechanism and need not inhibit biasing mechanism 30 .

Additionally, or alternatively, the biasing mechanism 30 may be its own module or cartridge so as to be selectively removable or replaceable from the detent mechanism. It may be used when a fusible element or other portion of the restraint mechanism 32 for overcoming the force of the spring 66 is mounted between the modules.

An example detent mechanism having an engagement mechanism 446 is shown schematically in FIG. 48 . As shown, the spring 66 acts on the engagement mechanism 466 . Engagement mechanism 466 is depicted as including a torsion plate 450 . Plate 450 selectively prevents the biasing force of the spring from acting on pawl 60 . As shown, the restraint mechanism 32 , such as the fusible member 70 , prevents the plate 450 from twisting about its axis 452 under the biasing force of the spring 66 . As a result, the pawl is not pushed towards the blade. A module or cartridge 448 is indicated by dashed lines and is a possible but not required element of the braking mechanism 28 . Module 448 is typically secured to a suitable bracket or receptacle on the machine, and may also include a link to a suitable mechanism to release restraint mechanism 32 . For example, the contact bracket may be in electrical connection with the release mechanism not forming part of the replaceable module.

A variation of this braking mechanism is shown in FIG. 49 . Engagement mechanism 446 is shown in the form of slidable member 454 to slide along track 456 toward or away from saw blade 40 . As shown, the fusible member 70 limits sliding movement of the slidable member 452 toward the saw blade. The spring is thus prevented from pushing the pawl 60 into contact with the saw blade 40 . FIG. 49 also shows a variation of this detent mechanism, where the fusible member 70 extends across the path of travel of the slidable member 454 to prevent movement of the member 454 under the force of the spring 66 . In fact, the fusible member 70 itself may form the engagement mechanism 446, as shown in FIG. The fusible member is shown extending across the path of the spring 66, thereby preventing the spring from pushing the saw blade or other cutting tool toward the pawl.

The fabrication mechanism shown in Figures 47-49 can also be understood to include a biasing mechanism 30 with a composite release mechanism. This is because less than one step is required to activate the braking mechanism and engage the pawl with the saw blade or other cutting tool. Unlike the detent mechanism shown in Figures 41-46, where the spring 66 is only required to release the restraint mechanism 32 to push the pawl 60 into the saw blade or other cutting tool. The detent mechanism shown in Figures 47-49 utilizes a combination release to engage the saw blade 40 and the pawl. For example, release of restraint mechanism 32 may allow a portion of biasing system 30 to move freely, for example to engage engagement mechanism 446 or a linkage. This in turn transmits this force to the pawl 60 .

FIG. 51 illustrates another example brake mechanism 28 with a combination release or combination release mechanism. Figure 51 shows a self-contained activation assembly schematic. Spring 66 is housed within a housing 458 as shown. A spring or a suitable spring-connected link can extend through an open end 460 when the restraint mechanism 32 is released. In the schematic arrangement shown in Figure 51, the muzzle end 460 is at least partially covered by a spanning member 462 between the spring and the pawl. Member 462 need not completely cover open end 460 . It should however prevent the spring 60 from passing through the port 460 and engaging the pawl 60 . Fusible member 70 , or another suitable means of restraining mechanism 32 , is connected to member 462 to prevent spring 66 from pushing the spanning member into contact with pawl 60 . As shown, member 70 passes through housing 458 and, in the arrangement shown, spring 66 . It should be understood that the housing 458 may be used with a detent mechanism 28 that does not include a combined release. In this case, the pawl 60 will pass through the open end of the adjacent casing.

Another example arrangement of a self-contained actuator assembly is shown in FIGS. 52,53. Here, the limiting mechanism 32 is releasably connected to the lever arm 464 . The lever arm 464 is in turn connected to an end 466 of a carrier 468 . Wooden lever, or torsion arm 464 rotates about a torsion axis defined by extension 465 on housing 458 . It should be remembered that arm 464 , carrier 468 and housing 458 (including extension 465 ) must be strong enough to withstand the force of spring 66 . The end 466 of the carrier 468 should be secured to the arm 464 so that it can be released relatively quickly when the restraint mechanism 32 is released and the arm 464 is initially twisted about the extension arm 465 . Alternatively, the lever arm 464 should be able to twist without hindrance until the pawl 60 is fully engaged with the saw blade 40 so that the twisting axis does not hinder the movement of the pawl 60 and increases the time required to brake the saw blade 40. In such a design where the arm 464 twists without restricting the movement of the pawl, the arm 464 need not be released from the carrier 468, instead the components can remain connected together.

Carrier 468 includes an elongated bracket 470 extending from housing 458 and further includes a pawl-release portion 472 for releasably receiving pawl 60 to allow selective removal and replacement of the pawl without disassembly or disassembly. The rest of the braking mechanism 28. As shown, the pawl-receiving portion 427 also forms a spanning member in which it prevents the spring from pushing the pawl into engagement with the blade 40 . In Figures 52, 53, member 472 and pawl 60 are of complementary design so that the pawl can be attached to a pawl-receiving portion without additional securing mechanisms. In the arrangement shown, the pawl can either be slid into the member 472 from one end, or alternatively the member 472 is briefly deflected outwardly as the pawl is inserted into its fixed position. It will be appreciated however that it may be necessary to use additional securing means such as screws, pins and other releasable fasteners. Since neither spring 66 nor fusible member 70 acts directly on the pawl or pawl-receiving part, the connection of these parts need not be strong. As a further modification, the pawl 60 may be fixedly mounted on or even integral to the carrier 468 or at least an engaging portion of the pawl.

A variation of a self-sustaining promoter is shown in FIG. 54 . Here, the length of the carrier 468 is selectively adjustable. Thus allowing the relative position of the pawl with respect to the saw blade 40 to also be adjustable. As shown, bracket 470 includes a buckle portion 474 that screws into pawl-receiving member 472 . The length of carrier 468 can be adjusted by rotating bracket 470, such as by a user-operable member 476, to increase or decrease the degree to which member 472 is received into pawl-receiving portion 472. In FIG. 54 , the pawl-receiving member 472 also includes a primary structure 478 to prevent the pawl from being placed into a position defined by the pawl-receiving member other than the primary structure 478 .

Figure 55 shows another spring bias mechanism arrangement. As shown, the lever arm 464 includes an end 480 connected to the housing 458 proximate the open end 460 . In the illustrated arrangement, end 480 is received in a cutout in the housing and includes a boss 482 . When the restraint mechanism 32 is released, the arm twists on the boss. Alternatively, the housing 458 may include a flange or extension on which the arm 464 rests. Preferably, when in the restrained position shown in FIG. 55, at least one end region 483 of the extension bracket 470 conforms to the inner diameter of the spring 66 to resist movement or tilting of the carrier.

As shown, bracket 470 includes an edge 471 extending generally parallel to and against spring 66 , and a generally opposite edge 473 extending through pawl-receiving portion 472 toward end 466 . FIG. 55 also shows another example of a pawl-engaging member 472 having a main bracket 478 . Edge 471 is on the side of bracket 470 away from torsion axis 464 to stabilize the carrier during installation and in a constrained position. Edge 473 is on the side of bracket 470 away from lever arm 464 to allow the bracket to be pushed by housing 458 to tilt when restraint mechanism 32 is released. This design of the carrier is an example of one that can be integrated with the detent 60, monolithic.

In the detent mechanism shown in FIGS. 52-55 , the portion of the fusible member 70 not connected to the torsion arm 464 may be secured to any suitable support structure to allow the fusible member to resist the force of the spring 66 . The support structure may form part of the braking mechanism shown in Figures 52-55. For example, the fusible member is secured to the housing 458 or the pawl-receiving part 472 . In such a design, the braking, biasing and limiting mechanisms shown in Figures 52-55 form part of a self-contained module or actuator.

Figure 56 shows a housing and torsion arm assembly assembly. In this arrangement, the distance between the torsion axis 484 of the arm 464 and the region of the arm 464 supporting the carrier 468 is reduced compared to the arrangement shown in FIGS. 42-54. As shown, arm 464 is torsionally connected to housing 458 by a pair of brackets 458 and includes a carrier-receiving portion 486 . In the device shown in FIG. 56, the arm 464 may have a generally planar design to allow the arm to extend against a portion of the end 487 of the housing. Upon release of the restraint mechanism, arm 464 twists relative to housing 458 and member 486 twists into the housing and releases the carrier under spring force to move. As shown, the end 487 of the housing 484 is sufficiently open to allow the member 486 to be twisted into the housing and release the carrier 468 . As shown, end 487 is also sufficiently blocked to prevent passage of spring 66 . FIG. 56 also illustrates an arrangement of bracket 470 . The brackets typically conform to the spring inner profile, thereby supporting the carrier 468 without axial tilting within the housing as the carrier passes through the housing. Another suitable design for bracket 470 is shown in phantom in FIG. 56 .

Figures 57 and 58 show another example of a spring-biased detent mechanism. The mechanism has a lever arm 464 that releases from an open end 460 of the housing 458 . As shown, the lever arm 464 is torsionally connected to the housing 458 by a pin 488 and includes a pair of clips that engage a spanning member 462 . As shown, span member 462 includes a cover 490 to cover open end 460 of housing 458 and includes protrusion 491 that is engaged by clip 489 . Alternatively, spanning member 462 may include any material sufficient to prevent passage of spring 66 before release of restraint mechanism 32, or to force another member to pass through end 460. Preferably, catch 489 when lever arm begins to twist upon release of restraint mechanism 32 Formed to release spanning member 462 .

Figure 59 shows another example of a spring-biased detent mechanism. As shown, when lever arm 464 is held in a vertical, or restrained, position by restraint mechanism 32 such as fusible member 70 . The lever arm and housing 458 serve to facilitate more uniform positioning of the carrier 468 and pawl 60 . Prior to attachment to fusible member 70 , lever arm 464 is twisted about edge 492 of housing 458 . Simultaneously, the lever arm is twisted into position as shown practically in FIG. 59 . In this interval, since the distance 293 between the edge 492 and the adjacent edge 494 of the carrier 468 is much smaller than the distance between the edge 492 and the fusible member 70, a mechanical advantage is achieved. However, to continue twisting the lever arm 464 downward, this mechanical advantage is lost. This is because the fulcrum at which the lever arm twists changes. This is reflected by distances 493' and 495'. As shown, the lever arm 464 is now twisted about the edge 496 of the extension 498 . The corresponding force for twisting the lever arm 464 can be used as an indication of whether the lever arm 464 is properly positioned. A fusible member can be attached to the anchor point. Of course, if the fusible member is a preform or is of a fixed length, accurate positioning of the lever arm 464 and pawl 60 can be achieved simply by attaching the fusible member.

The braking system and method are described in the numbered paragraphs declared below. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

4.1 A woodworking machine includes:

a working part;

a detection system for detecting hazardous conditions between persons and work parts;

And, a reaction system associated with the detection system to cause a predetermined action relative to the working part when a dangerous situation is detected, where the reaction system includes stored mechanical energy to cause the predetermined action to occur.

4.1.1 The woodworking machine of paragraph 4.1, where the reaction system comprises a spring like a container for stored mechanical energy.

4.1.2 The woodworking machine of paragraph 4.1, where the reaction system includes a brake and a spring to engage the brake with the working part.

4.2 A woodworking machine includes:

a cutting tool;

a detection system for detecting contact between a person and a cutting tool;

a brake pawl that stops the cutting tool when the detection system detects contact between a person and the cutting tool;

and the reserve mechanical energy to engage the brake pawls with the cutting tool.

4.2.1 The woodworking machine of paragraph 4.2, where the stored mechanical energy is a spring.

4.2.2 The woodworking machine of paragraph 4.2.1, where the spring pushes the brake pawl into contact with the cutting tool.

4.2.3 The woodworking machine of paragraph 4.2, where the stored mechanical energy is in a self-contained cartridge.

4.3 A woodworking machine includes:

a working part;

a detection system for detecting hazardous conditions between persons and work parts;

and a braking system for engaging and braking the working part when the detection system detects a dangerous situation, where the braking system includes a spring module for moving the brake pawl into the working part.

4.4 A brake cassette for a woodworking machine, the cassette containing:

a casing;

a brake pawl in the housing;

And, a spring module in the housing for selectively moving the brake pawl, where the biasing module is self-contained.

4.4.1 The brake cartridge of paragraph 4.4, wherein the spring module comprises a coil spring retracted by a mechanism. Chapter 5: Brake Mechanism

As noted above, the safety system 18 includes a braking mechanism 28 for stopping the cutting tool, thereby preventing or reducing injury to the user. As also previously described, the braking mechanism may include at least one pawl 60 for engaging the cutting tool to stop its rotation. For purposes of the following discussion, the cutting tool 14 will be described in the context of a saw blade 40 as on a table saw, miter saw, circular saw, or other similar tool. It should be understood that the saw blade 40 may comprise a single saw blade such as a glued blade or a carbonized tip saw blade, or a combination of several saw blades like a tenoner.

As discussed, the pawl 60 may be made of any suitable material capable of quickly stopping the saw blade or other cutting implement. The pawl should stop the blade within a desired time increment, say 5 milliseconds, preferably 3 milliseconds or less. The thermoplastic and metallic material examples above proved to be valid. Of course other materials may be used as long as they stop the saw blade within the desired time increment. Preferably, the pawl is made of a material that will not damage the machine. Even better, the pawl is made of a material that won't damage the cutting tool. The pawls may be formed by any suitable method, such as by cutting or casting the beard material into sheets. Similarly, the detents can be annealed to increase their strength.

It should be appreciated that the heavier the pawl, the greater the force required to push the pawl into contact with the saw blade or other cutting tool within the selected time increment, and the greater the force required by the restraint mechanism 32 to overcome the biasing mechanism. is also more restrictive. On the other hand, the pawl must be of sufficient mass and strength to withstand the force of the saw blade on the pawl. It should also be understood that the longer it takes for the pawl to engage the saw blade after the detection subsystem 22 detects a hazard, or a triggered condition, the longer the time it takes the saw blade to rotate and the risk of potentially cutting a user's hand or other body part. The longer the time. Therefore, it is best to keep this time to a minimum. Like by reducing the distance the pawl has to travel to engage the blade and increasing the speed at which the pawl travels over that distance. The speed of travel of the pawl is largely dependent on the weight of the pawl, the force of the biasing mechanism 30 pushing the pawl against the blade when the restraint mechanism 32 is released, and any friction in the mechanism.

There is no specific pawl size, geometry or weight suitable for stopping a saw blade or other cutting tool. Instead, size, geometry and weight can vary. This depends, for example, on the particular machine type and cutting mechanism with which the pawl is used, the pawl material or combination of materials, the corresponding configuration of the biasing mechanism 30 and restraint mechanism 32, and the like. Accordingly, the following discussion of materials, sizes and geometries and sizes is meant to provide some illustrative examples of suitable materials, geometries and sizes. Similarly, a detent may consist of one or more of the elements, sub-elements and possible variations discussed below, regardless of whether the elements, sub-elements and possible variations appear in the same drawing.

The thickness of the pawl can vary. Thicknesses in the range of about 1/2 to about 1 inch have proven effective, although thicknesses outside this range may be used as long as the pawl reliably stops the saw blade. When using a thick saw blade like a tenon saw blade, the pawl is more likely to have a thickness of more than an inch.

The pawl 60 engages the saw blade to quickly stop the rotation of the saw blade. The pawl 60 can have several different designs for engaging the saw blade, such as engaging the side of the saw blade or the teeth of the saw blade. As shown in FIG. 60, the pawl 60 is rotationally secured to a shaft 502 extending through a bore 504 of the pawl, and the pawl 60 is adapted to be twisted into the saw blade 40 under the influence of a biasing mechanism 30 like a spring 66. The sawtooth 506. It will be appreciated that the pivoting pawls described herein may alternatively twist with, rather than around, the axis of the fixed pawl. Other suitable biasing mechanisms are described in Section 4 above. Preferably, pawl 60 is adapted to be self-locking, ie to be drawn into tighter engagement with the teeth of saw blade 40 . This is due to the relative geometrical position of the pawl and blade when they are drawn together. For example, when the saw blade 40 is rotated in the direction shown in FIG. 60, when the saw blade contacts the pawl, the saw blade will pull the pawl into a tighter engagement of the saw blade.

The spacing of the pawl 60 to the blade 40 may vary when the pawl is in its restrained, or raised, position. For example, the spacing may vary depending on the design of a particular cutting tool, detection system, and/or braking system. Preferably, this distance is minimized to reduce the time necessary for the pawl to traverse this distance to engage the saw blade. It has been found that a pawl-to-blade spacing of 1/32-1/4 inch provides suitable results. A spacing of about 1/8 inch has proven particularly effective. Of course larger or smaller spacings can also be used. Since many cutting tools like saw blades do not have precise, uniform dimensions, position the pawl far enough from the blade to account for variations or irregularities in a particular saw blade such as those described in Section 8 below. Might be a must. Likewise, it may also be necessary to adjust the position of the pawl when changing blades to account for variations between particular blades. For example, for a circular saw blade with a normal diameter of 10 inches and a normal thickness of 0.125 inches, actual saw blades from different manufacturers or with different applications may be in the range of 9.5-10.5 inches in diameter and 0.075 inches in thickness. --Within 0.15 inches.

In the schematic arrangement of the pawl 60 shown in FIG. 60 , it can be seen that the pawl 60 includes a body 508 having a contact surface 510 for engagement with the saw blade 40 . The pawl 60 also includes an engagement member 512 that is engaged by the biasing mechanism 30 . As shown, the engagement member 512 forms a portion of a detent face 514 that generally faces away from the cutting tool. Engagement member 512 may also include a depression or protrusion on the body of the pawl. In the fixed position shown in FIG. 60 , the pawl 60 is twisted into the saw blade, such as when the safety system sends current to the fusible member 70 to release the restraint mechanism 32 . When the pawl is in contact with the blade, the contact surface generally extends along the blade and the teeth engage the pawl.

FIG. 61 shows another schematic example of a pawl 60 . As shown, the pawl is a little smaller than the one shown in Figure 60. The advantage of the smaller pawl is that it is lighter than a pawl made of the same material, so it does not require as much spring force as a heavier pawl to push the pawl into the blade at selected intervals . Alternatively, a smaller saw blade will tend, but not necessarily, to have a smaller contact surface 510 . In Figure 61, the pawl includes a blade-engaging shoulder 514. The shoulder is adapted to engage the saw blade ahead of the contact face, or at least a substantial portion of the contact face. Shoulder 514 may include a protrusion 516 . The protrusions extend outwardly from the pawl face 518, which generally faces the saw face. The shoulder 514 and/or protrusion 516 engages the saw blade prior to contact with the pawl surface, and this contact quickly twists the contact surface of the pawl into engagement with the saw blade. Essentially, the shoulder or protrusion reduces the time and/or spring force required to snap the pawl into a position that stops the saw blade. The braking is done by using the momentum of the saw blade transmitted by contact with the shoulder to pull the pawl into the saw blade. FIG. 61 also shows another arrangement of the engaging member 512 . As shown, the device includes a collar 520 extending from plane 514 and receiving a portion of the spring therein. Collar 520 has an inner diameter which is slightly larger than the diameter of the spring portion it receives. Collar 520 facilitates positioning of the spring or adjustment of the braking mechanism during assembly.

Figure 62 shows another schematic example of a suitable pawl. As shown, the pawl is slightly larger than previously illustrated and includes a contact surface 510 that generally conforms to the outside diameter of the saw blade. FIG. 62 also shows a securing assembly 522 for the restraint mechanism 32 . As shown, the fixation assembly 522 includes an aperture 524 . A portion of the restraint mechanism, such as a portion of the fusible member 70, protrudes from the void. The fusible member 70 may also be described as extending along a portion 526 of the pawl. Other suitable fusible members and restraint mechanisms are described in more detail in Section 6 below. To increase the gripping action of the pawl on the saw blade, the contact surface 510 of the pawl may be wrapped with a performance-enhancing material 527 . As shown in Figure 63. Performance - An example of a reinforcing material is a relatively high friction material. Like Kevar cloth or metal mesh, these materials "tangle" or get caught in the teeth of a saw blade or other cutting tool. Alternatively, the pawl could be made of a harder material than the blade and have a raised surface to "bite" into the blade. Alternatively, or in addition, the pawl may be configured with a gripping structure 529, such as a coating of high friction material, grooves, cutouts, holes, protrusions, etc., to further increase the gripping action of the pawl.

The pawl 60 may include one or more regions that are removed. These areas may take any suitable form, such as recesses that partially protrude from the pawl, or apertures or apertures that protrude fully from the pawl. FIG. 64 shows an example of a pawl employing recesses 530 with multiple removed regions. The removed area reduces the overall weight of the pawl, as compared to a similar but heavier pawl, thereby reducing the need for the biasing mechanism 30 to be added to the pawl during the selected time interval to move it into contact with the saw. The relative force of the sheet contact. The indentation, or groove 530, may also allow the sawtooth to bite deeply into the pawl to improve the pawl's grip on the sawtooth.

FIG. 64 also shows another example arrangement of the engagement member 514 . This means takes the form of a recess 532 extending into the pawl body 508, and a portion of the spring 66 extends therein. Recess 532 may be laterally open, or may include side walls 534, as shown by dashed lines. FIG. 64 also shows a mount 535 for attachment to the biasing mechanism 30 . As shown, retainer 535 takes the form of a protrusion around which a portion of a coil spring (similar to spring 66 in FIG. 61) extends. It should be appreciated that mount 535 may be used independently of recess 532 and/or sidewall 534 . FIG. 64 also shows another suitable means for securing assembly 522 of restraint mechanism 32 . As shown, the mount assembly includes a mount 536 for a link 538 . The link is connected to a fusible member that is not in physical contact with pawl 60 .

The pawl shown in FIG. 64 can also be described as having a body 508 of a blade-engaging portion 540 and at least one region of reduced thickness compared to the blade-engaging portion. For example, the previously described recess 543 has a reduced thickness compared to the blade-engaging portion 530 . Saw blade - The increased thickness of the engaging portion provides additional strength to that portion of the pawl, while the portion of reduced thickness reduces the overall mass of the pawl. The pawl 60 may also be described as including one or more reinforcing ribs, or brackets 542 . A bracket 542 generally extends between the aperture 504 and the blade engaging portion to reinforce the pawl.

FIG. 65 shows an example pawl having a plurality of removed regions 522 in the form of apertures 544. The aperture 544 reduces the comparable weight of the pawl compared to a similar pawl that does not include the aperture or other removed area. Aperture 544 also provides an area for the material forming pawl 60 to deform or flow in when the saw blade or other cutting tool strikes the pawl. These deformed areas reduce the stress on the pawl when engaging the saw blade. It should be understood that the size and positioning of the removed regions discussed herein are for illustrative purposes. And these areas can be positioned at any suitable location on the pawl, and have a variety of shapes, sizes and configurations.

Figure 66 shows a variation of the pawl of Figure 65. In FIG. 66 , the aperture 544 is filled with another material 546 . It should be appreciated that some or all of the apertures may be partially or completely filled with material 546 . For example, the body of the pawl 60 may be formed from one of the previously described materials. Instead the apertures are filled with another of the aforementioned materials or a material not mentioned above. As a specific example, the pawl body may be made of polycarbonate or ABS, with the aperture 544 filled with aluminum or another suitable metal.

Figure 67 shows another variation of the pawl of Figure 65. In FIG. 67 , the pawl 60 includes a plurality of apertures 544 . One or more cables 548 pass through these apertures. As shown, a single cable 548 surrounds the apertures and also extends through a portion of the interface 510 . Although, in Fig. 67, the number of cables or strands is roughly indicated, it may be desirable to have many strands, such as in the range of about 20 and 500 strands. It should be understood that a "strand" of wire means a length of cable extending through the pawl. Like transverse to the plane of a saw blade or other cutting tool, regardless of whether the strands are joined to or formed of the same uniform length as other strands. Alternatively, cables and strands may be threaded through one or more apertures without extending beyond the interface. An example of a suitable material for cable 546 is high tensile strength stainless steel. This stainless steel is available in a variety of different diameters. In experiments, a diameter of 0.01 inches proved effective, but cables 548 of larger or smaller diameters, as well as cables made of other materials, could be used.

Other forms of composite detents include detents formed from two or more regions of different materials. An example of such a composite pawl 60 is shown in FIG. 68 . In FIG. 68, the pawl body 508 includes a region 550 of a different material than the rest of the body. And the region 550 forms at least a part of the saw blade-engaging member 540 . It will be appreciated that region 550 may have a variety of different shapes, including layers of generally uniform thickness, such as shown in solid lines in FIG. 68 , or less uniform shapes, such as shown in dashed lines in FIG. 68 Strata 550 like that.

The detent 60 can also be made of a composite material, such as by layers of different materials or by infusing or embedding one specific construction material into another to increase ramping or enhance a desired characteristic. For example, a thermoplastic material may include a frame or diffuser fibers or other material. Figure 69 shows an example of a pawl made from this composite material. In Fig. 69, the pawl body is formed from a center material 552 into which filler material 554 has been added. The filler material 554 may take the form of particles, fibers, braided fibers, powder, and other similar forms.

The pawl 60 may also include a removable blade-engaging portion 540 . This allows the pawl to be replaced for reuse after the pawl has been used to brake the saw blade 60 and after the blade-engaging portion has been damaged by the saw blade. It will be understood that "removable" means that the blade-engaging portion can be selectively removed and reattached to the remainder of the pawl. Figure 70 shows an example of such a detent. In Fig. 70, the pawl includes a body 508 and a removable blade-engaging portion 540'. The saw blade-engagement portion 540 ′ can be made of the same or a different material or combination of materials as the body 508 . The blade-engaging portion 540' may be attached to the body 508 by any suitable attachment mechanism 556. The attachment mechanism 556 is only schematically illustrated in FIG. 70 . Examples of suitable attachment mechanisms 556 include interlocking portions on the body and the blade-engaging portion and/or mechanical linkages connecting the body and the blade-engaging portion.

In FIG. 71, the pawl 60 includes a housing or cover 558 covering at least the blade-engaging portion of the pawl. Housing 558 is constructed of a material that enhances the pawl's ability to brake saw blade 40 without damaging saw blade 40 . For example, the Shell 558 pack is made of Kevlar cloth. Similarly, such a material could be embedded into the thermoplastic or other material from which pawl 60 is formed. As schematically shown in Figure 69. As shown in FIG. 72, the housing 558 may extend fully or partially around the pawl, or may otherwise be partially embedded in the pawl. Still further, the Kelar cloth, or pieces of Kelar cloth, can be embedded in the thermoplastic or other material that makes up the pawl. As previously described with reference to Figure 69, it is not necessary to consider whether this material extends beyond the blade-engaging portion of the pawl.

FIG. 63 shows a pawl variation that includes housing 558. In Fig. 73, the body of the pawl defines a frame 560 comprising spaced apart side walls 562 and a channel 564 defining the interstices. Housing 558 extends through the channel and is positioned to engage and stop the saw blade when the pawl is pushed into the saw blade.

When the pawl 60 is secured for twisting into engagement with a saw blade or other cutting tool, the pawl may include more than one axis of rotation. Figures 74-76 show examples of this detent. In the illustration, the pawl is secured to a pair of torsion arms 566 . As shown, the pawl 60 has an elongated contact surface 510 to engage the majority of the blade. The torsion arms 566 may be of the same or different lengths and may be secured to pivotal attachment points (not shown) located either inside or outside the outer edge of the saw blade.

An advantage of a pawl with an elongated contact surface is that the force exerted by the pawl is distributed over a larger portion of the saw blade, thus allowing the saw blade to be braked more quickly. A longer contact surface can also be used to reduce the possibility of damaging the saw blade. This is because the braking force is distributed over the narrower teeth.

In FIG. 74, the torsion arm 566 is secured at a suitable location on the machine 10 relative to the pawl 60 away from the saw blade. In Fig. 75, however, the torsion arm is fixed close to the blade relative to pawl 60. In Fig. 76, one of the torsion arms extends to the top of the blade, while the other torsion arm extends closer to the blade relative to the pawl. One advantage of having the twist arm extended relative to the pawl, or close to the saw blade, is that the pawl cannot be twisted to a point after which the pawl would twist away instead of towards the saw blade. For example, in the pawl 60 arrangement shown in Figure 75, when the saw blade is rotated in the direction shown and strikes the pawl, the pawl will always be drawn into tighter engagement with the blade.

It should be appreciated that the previously described shaft 502 or other structure that secures the pawl may be fixed relative to the machine's housing. In machines where the position of the saw blade can be adjusted, it is preferred that the pawl is fixed in such a way that it moves with the saw blade as the position of the saw blade is adjusted. The latter placement ensures that the pawl maintains a predetermined position relative to the saw blade.

Alternatively, the pawl may be fixed at a machine location that is not adjusted with the blade, but in a fixed orientation suitable for use with the blade regardless of the mounting position of the blade. Figures 77 and 78 illustrate an example of such a "stationary" pawl. "Stationary" means that the position of the pawl does not move with the saw blade when the relative position of the saw blade moves. However, when the reaction subsystem is activated, the pawl 60 will still move into the engaged position with the saw blade. Alternatively, in machines with which the saw blade moves up and down as well as sideways, the pawl can be adapted to move with one adjustment, such as tilt with the blade, but remain with the other adjustment, such as the blade being raised and lowered and kept in a fixed position.

As shown in FIGS. 77 and 78 , when the saw blade is adjusted vertically, the pawl 60 is elongated, changing size and shape to extend along the perimeter 568 of the saw blade 40 . Similarly, the pawl 60 is sized to increase the width of the blade 40 bevel. As shown in Figures 77 and 78, pawl 60 is fixed in an orientation generally parallel to the vertical axis of travel of the saw blade and generally perpendicular to the tilt axis of the saw blade. As a result, the spacing of the saw blade from the contact surface 510 remains constant regardless of the position or orientation of the saw blade.

The upper end of the pawl is twist-attached to the upper twist arm 570 by twist pegs 572 . A twist peg 572 passes through one end of a twist arm 570 into the side of the pawl, and the other end of the twist arm 570 is torsionally attached by a twist peg 574 to one or more fixed points (not shown). The lower end of the pawl 60 is torsionally attached to the underlying torsion arm 576 by a torsion pin 578 . A twist pin 578 passes through one end of the twist arm 576 into the side of the pawl. The lower torsion arm is torsionally attached to a fixed point (not shown) by a torsion peg 580 . A biasing mechanism 30 such as one or more springs 66 is attached to the lower torsion arm of the torsion peg 580 on the side facing the torsion peg 577 . As such, the pawl 60 is designed to twist toward or away from the saw blade 40 . When the restraining mechanism 32, such as the fusible member 70, is released, the biasing mechanism pushes the upper end of the torsion arm 576 downward, thereby drawing the corresponding pawl end of the lower end of the torsion arm into engagement with the saw blade middle.

Torsion arms 570 and 576 are thus sized and oriented. The pawl 60 cannot be twisted upwardly to pass the blade without striking the edge of the blade. When the pawl strikes the saw blade while the blade is still rotating, the movement of the saw blade causes the pawl to continue to twist upward until the pawl is firmly inserted between the saw blade and the twist arm, stopping the saw blade. The contact surface 510 of the pawl may be structured, covered with a material, etc. to enhance the gripping action between the pawl and the blade.

The pawl 60 is biased upwardly by the biasing mechanism 30 to twist towards the blade. For example, the biasing mechanism 30 includes one or more springs 66 secured to a chainsaw twist frame or other suitable mounting structure. Thus, when the pawl is free to twist, the spring 66 drives the pawl to twist rapidly towards the blade. Similar to the example devices described above, the fusible member 70 may be associated with the pawl to hold it in position away from the saw blade. The fusible member is sized to hold the pawl slightly away from the edge of the saw blade. However, when a sufficient current is passed through the fusible member, the fusible member will melt causing the pawl to twist towards the blade under the force of the biasing mechanism 30 .

It will be appreciated that many variations of the exemplary devices illustrated in Figures 77 and 78 are possible. For example, the pawl may be designed to twist towards the blade only under the force of gravity. Alternatively, the spring 66 could be a compression spring. The compression spring normally holds the pawl away from the blade until it is twisted upwards under the influence of the force of another spring, explosive, solenoid, gas pressure, etc. Still further, the pawl can be mounted on the opposite side of the blade to twist down into the blade under the influence of spring explosives, solenoid valves, gas pressure, etc.

Another example of a suitable pawl 60 is shown in FIG. 79 . As shown, pawl 60 includes a rear portion 582 that generally rears contact surface 510 . The rear portion 582 includes a plurality of track portions 584 . On a suitable fixed structure forming part of mechanism 12, track portion 584 cooperates with a corresponding plurality of track portions 587 to define track 590 on which roller 592 is located. The toothed roller 592 is rotatable within the track 590 . And when the saw blade strikes the pawl 60 , the translation of the pawl 60 towards the saw blade 40 is guided. The rollers also reduce friction against a sliding translational movement of the pawl under braking load. Preferably, the pawl 60 includes a guide pin 593 that runs within a track (not shown). The track defines a range of translational positions for the pawl 60 while maintaining contact of the rollers with the track.

FIG. 80 shows a schematic arrangement of another braking mechanism 28 . The device includes a pawl 60 which translates to engage the saw blade or other cutting tool as shown. The pawl 60 includes a contact surface which preferably but not necessarily conforms to the outer diameter of the saw blade 40 . The pawl 60 is restrained by the restraining mechanism 32 in its erect, or restrained, position. As shown, the restriction mechanism 32 includes one or more fusible members 70 . Preferably, the braking mechanism includes a guide mechanism 501 defining a track 503 . The pawl travels along the track 501 when the pawl is urged toward the saw blade or other cutting tool by the biasing mechanism 30 . Figure 80 shows an example of this guiding structure. In the figure, the guide structure includes a housing 505 . The pawl is at least partially received into the housing in its upright, or restrained, position. The pawl is at least partially protruded from the housing upon release of the restraint mechanism 32 . Much like a piston moving in a cylinder, driven by the biasing mechanism 60 , the pawl 60 moves on a translational path defined by the inner space of the casing 505 .

81 and 82 show other schematic examples of detent mechanisms 28 with translating pawls. In FIG. 81 , the guide structure 501 includes two or more guide-engagement members 507 protruding from the pawl 60 to engage with a corresponding number of guides 509 . The guide 509 is separate from the pawl and defines the path of translation of the pawl. In Fig. 82, the pawl 60 includes an internal guide-engagement member 507, such as one or more internal apertures 511 extending parallel to the pawl translation path. A corresponding number of guides 509 extend at least partially within the bore to define the path of travel of the pawl. In FIGS. 80-82, pawl 60 is pushed directly into blade 40 along a translational path. It should be appreciated that the pawl and/or guide structure may be inclined at an angle relative to the saw blade, such as to balance the angular momentum of the saw blade or to use braking force to draw the pawl more tightly to the saw blade.

Although the above illustrates an example device engaging the sawtooth in the range of a single brake pawl. The braking system may include a braking mechanism having two or more pawls that engage two or more locations around the blade periphery to reduce braking time and/or distribute braking effort. An example of such a braking mechanism is shown in FIG. 83. In the figure, the braking mechanism 28 includes pawls 60 for engaging the periphery of the saw blade 40 with two subdivisions 7d. The detent 60 is only schematically illustrated in FIG. 83 and may comprise any of the foregoing detents or a detent comprising one or more of the characteristic elements, subelements and variations described above. The pawls may be released from their erect or restrained position by a common release mechanism, or each pawl may have its own unique release mechanism. When the brake mechanism 28 includes a plurality of pawls, it is preferable to stand the pawls on opposite sides of the saw blade's rotating knife axis to reduce the force on the knife when the brake mechanism 28 is activated and the pawls 60 engage the saw blade. load on the shaft.

When the detent mechanism 28 includes a plurality of pawls, the pawls may also be constrained or interconnected to act together. An example of such a braking mechanism is shown in FIG. 84 , which includes a plurality of inline pawls 60 . As shown, each pawl 60 includes one or more toothed regions 513 having a plurality of serrations 515 . The area 513 adjacent to the saw blade 60 is interconnected by a toothed gear or link 517 which links the rotation of one pawl to the other so that the pawls move as a unit. It will be appreciated that one or more pawls or gears may be associated with a suitable biasing and limiting mechanism to bias the pawls into contact with the saw blade 40 and selectively restrict movement of the pawls until the safety system 18 until the reaction subsystem is started. In a variation of the brake mechanism shown in Fig. 84, the gear 517 may be omitted in favor of a link as the internal connection of the pawl.

As noted above, the pawl or pawls of the detent mechanism 28 may contact any suitable portion of the saw blade 40 or other cutting tool 14 . In the illustrative arrangement shown in Figure 2 and Figures 60-84, the pawl is mounted to engage the teeth or the outer edge of the saw blade. Another example of a suitable saw blade contact location is the side of the saw blade. In particular, the detent mechanism 28 may include two or more pawls for engaging the sides of the saw blade. Figure 85 shows an example of this braking mechanism. As shown, the pawls 60 are twistedly mounted on either side of the saw blade 40 . Each pawl includes a blade-engaging member 540 adjacent the blade, and a top 519 . The two pawls are torsionally fixed on the pin 521 . The pin 521 passes through a twist hole 523 in the pawl between the blade-engaging member and the top. A lever arm 525 is attached to the top 519 . Thus, when the lever arm of each pawl is twisted upward (as shown in Figure 85), the blade-engaging members approach each other. The pawls are fixed relative to the saw blade such that the contact surface is twisted towards the saw blade in the direction of travel of the saw blade. Once the pawls contact and grip the blade, they are pulled by the blade's downward motion to continue twisting. As a result, the saw blade is clamped tighter and tighter between the pawl contact surfaces 510 until the pawls cannot get any closer, at which point the saw blade is stopped between the pawls.

To ensure that both pawls are brought closer to the saw, a link 527 is attached to each end of the lever arm 525 . Link 529 is connected to a biasing mechanism (not shown). The biasing mechanism pushes the pawl into contact with the blade through the force exerted by link 527 and lever arm 525 .

It will be appreciated that the dual pawl system described above can be implemented in many variations. For example, the link could be actuated by any of the other actuation means described above. This includes explosives, solenoid valves, compressed gases and more. As another example, one or more pawls may be positioned to contact only one side of the blade. Additionally, the link could be omitted and each pawl actuated by a separate spring, explosive, solenoid, etc. Similarly, while a circular saw blade is used to illustrate a cutting tool for which the brake system can be used, the brake system is used for other shapes of saw blades, such as those used in seamers, shapers and band saws. piece.

For example, FIGS. 163, 164 depict an alternative arrangement for the braking mechanism 28 within the range of a band saw 594 . In this device, the braking system separates the saw band when a contact detection signal is received. By separating the saw band, the tension fit of the saw band on the wheel is released to allow the saw band to be stopped or removed without stopping the wheel.

As best seen in detail view 164 , the alternative braking mechanism 28 includes an explosive cable or bolt cutting device 596 . The device is placed near the saw blade 40 to separate the saw band upon receipt of the detection signal. Suitable cable cutters 596 are available from various sources, including those in New Jersey. The size and configuration of the cable cutting device 596 can be varied by the size and width of the saw band 40, band material, band speed, and the like. Typically, the cable cutting device 596 will be located immediately against the lower surface of the workbench to prevent the saw band from continuing to move downward after it has been detached. An electronics unit 597 similar to that described above is connected to the cable cutting device 596 so that an activation signal is sent to the device when the electronics unit detects contact of the user's body with the saw band. The device 596 then disengages the band almost instantaneously, and then releases the tension fit of the band around the wheel 595 . Once separated, the saw band essentially stops moving even though the wheels continue to turn. As noted above, the safety brake can optionally be designed to shut off the motor of the band saw 594, and disengage the saw band. Additionally, one or more pawls (not shown) may be designed to engage and stop the saw blade while at the same time, device 596 disengages the saw band, thus ensuring that the saw band does not continue to move after disengagement.

The braking system, components and methods may be described in the numbered paragraphs declared below. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

5.1 A woodworking machine includes:

a cutting tool for cutting a workpiece and comprising at least two cutting surfaces;

A brake system for stopping the cutting tool, where the brake system includes a thermoplastic pawl for engaging the cutting surface of the cutting tool.

5.1.1 The brake system of paragraph 5.1, wherein the pawl is self-locking when the pawl engages the cutting surface of the cutting tool.

5.1.2 The brake system of paragraph 5.1, where the pawl is pivotally mounted on the machine.

5.2 A brake system for braking circular saw blades with multiple teeth on the periphery consists of:

a first detent pawl for engaging the first saw tooth at a first position on the periphery of the saw blade;

a second detent pawl for engaging a second saw tooth at a position different from the first position on the periphery of the saw blade;

And, an activation mechanism for pushing both pawls into the blade.

5.3 A braking system for stopping a circular saw blade consists of:

a detent pawl having a region of saw blade contact, the detent pawl being shaped to simultaneously engage a region of the circular saw blade comprising at least 30 degrees of the blade circumference;

And, an actuation system adapted to selectively drive the brake pawl into the saw blade.

5.4 A woodworking machine includes:

a cutting tool adapted to cut a workpiece and having at least two cutting surfaces;

A braking system for stopping a cutting tool, wherein the braking system includes a pawl engaging a cutting surface of the cutting tool; and, the pawl is made of two materials having different physical properties.

5.4.1 The machine of paragraph 5.4, wherein at least one of the materials is a thermoplastic material.

5.4.2 The machine of paragraph 5.4, where at least one of the materials is metal.

5.5 A woodworking machine includes:

a cutting tool adapted to cut a workpiece and having at least two cutting surfaces;

A braking system adapted to stop the cutting tool, where the braking system includes a metal pawl adapted to engage a cutting surface of the cutting tool.

5.5.1 The machine of paragraph 5.5, where the pawl is primarily made of aluminium. Chapter 6: Launch Subsystem

In many security system 18 arrangements, a fusible member 70 such as that shown in FIG. 2 will be used to restrain some element or action. Pull the pawl away from the blade as explained earlier. Such a fusible member can take different forms, but is usually a wire which will melt after passing a certain electric current. This is also described above. Once the wire has melted, the brake or pawl is released to stop the blade.

When using the pawl as a brake, a fusible member may be attached to the pawl and a fixed point or bracket, such as contact bracket 72 shown in FIG. 2, to prevent the pawl from moving into engagement with the blade. In that arrangement, the pawl is biased toward the blade by a spring so that the pawl is always pulling on the fusible member. Therefore, the fusible member should have high tensile strength to withstand the continuous pull of the pawl and prevent the fusible member from breaking suddenly. In addition, the fusible member should have high tensile strength so that strength is maximized relative to the heat required to melt the member. Highly resistive fusible members are also best because heat builds up faster for a given current flow. It will be appreciated that the size of the fusible member will depend, at least in part, on the force required to restrain the spring. Generally, a higher spring force is desired to increase the speed and force with which the pawl contacts the blade. Where great pressure is required, a fusible member with a larger diameter is required and thus a higher current value is required to melt the fusible member. A larger current value in turn may require a transmission system with more expensive electronic components. Thus, a safety system that uses a fusible member to release a brake or pawl must take into account factors such as the amount of force applied to the fusible member and the size of the fusible member.

In the pawl and fusible member arrangement shown in FIG. 2 and previously described, the spring 66 biases the pawl toward the blade 40 with a specific force, and the fusible member 70 is of sufficient A cable of tensile strength so that the pawl resists the force of the spring. For example, the fusible member can be a 0.010 inch nickel wire or steel wire strand, and the spring can have a spring force in the range of about 5-25 pounds.

In FIG. 2 , the fusible member is generally shorter than about 1-3 inches and wraps around contact bracket 72 . Contact bracket 72 generally has a circular cross-section. Thus, it does not have any edges that might concentrate stress at a particular location of the fusible member. Alternatively, a contact bracket may include an edge to concentrate stress at a desired location of the fusible member. The contact bracket can take any form. It may be a pin or projection surrounded by a fusible member, it may be a screw with a circular hole through which the fusible member passes. In this way, the screw could just be rotated to wrap the fusible member around the screw, it could be a clip, or it could be some other structure.

In Fig. 72, the stent 72 includes a region or void that is about 0.010 to 0.5 inches (or less) split between the two halves of the stent. Electricity flows through one half of the stent, through the fusible member, and to the other half of the stent. Then, to the ground line. This short fracture area is beneficial for concentrating power to a small area to help melt the fusible member. The two halves of the stent can be considered as two closely spaced electrodes, where the electrodes also serve as a stent for the fusible member. While the electrodes also serve as supports, they must be strong enough to support the fusible member load.

Alternatively, the holder for fixing the fusible member may be separated from the electrode, and the electrode may simply be in contact with the fusible member. For example, in FIG. 2 , the contact bracket 72 may be a fixed point, and the electrode may be placed between the bracket 72 and the pawl 60 against the fusible member 70 .

It will be appreciated that the fusible member can be designed in many other ways. As an example, one coil could be attached to one contact pin and the opposite coil attached to the ground pin. If the middle of the coil is placed on the end of the spring adjacent to the pawl, when the coil melts, the spring will be released. In this design, the current to melt the fusible member flows only from the contact pin, through the fusible member, and into the ground pin.

In other arrangements, a cable of relatively low tensile strength may be used to secure the pawl against a large spring force. This can be accomplished by looping the cable such that different parts of the cable work together to secure the pawl. For example, a cable may be looped in the shape of a letter "M" or "VV" as shown in FIG. 86 . In this design, the fusible member 70 is tied at one end of the fixation point 600 . From there, the fusible member loops around the first leg 601 on one side of the pawl 60, then around the bracket 602, then around the second leg 603 on the other side of the pawl, after which the fusible member is tied at a second fixation point 604 superior. In this manner, the portions of the fusible member between fixation point 600 and strut 601 , strut 601 and bracket 602 , bracket 602 and strut 603 and strut 603 and fixation point 604 function as four separate strands. and together pull the pawl away from the blade. Thus, a fusible member with a tensile load of 30 pounds can pull a pawl that is biased toward the blade by a force of up to 120 pounds. In FIG. 86, the bracket 602 is designed to pass a surge current through a portion of the fusible member to melt the member. The fusible member then breaks off on bracket 602 and releases the pawl. This arrangement allows the use of a fusible member having a relatively small diameter so that it can be melted by a small current.

In some devices, a fusible member will be used to secure a two-stage linkage, clip or composite release. In turn, a link or synthetic release will limit some movement or fix some elements like a pawl. The fusible member effectively limits a movement or immobilizes an element by securing a link or composite release. Using a link or synthetic release offers a mechanical advantage. This advantage allows the system to use a fusible member with a smaller diameter and less tensile strength but capable of sustaining a force of several hundred pounds or more. This may allow a smaller fusible strand to be used so that it melts faster and/or with less current. The various linkages and synthetic releases are described in more detail in Section 4 above.

The fusible member can also be formed from a cable overpressed with end caps or flattened blocks to establish a given length. Overmolding to form end caps or flats provides an effective way to grip and secure cables. Figure 87 shows three such fusible members. The first fusible member, a cable 605, is closed at both ends. And both ends of the wire are fixed to the loop 606, which is a cast member, and the cable 605 is biased or knotted at its end 607 to prevent the cable from coming out of the coil. The wire loop 606 will typically be cast or molded at the end. The cable 605 can extend around the electrode and the wire loop 606 can extend to a pin on the pawl or a pin on the composite release.

The second fusible member shown in Figure 87 is similar to the first just described except that there is a loop at each end of the cable. As mentioned above, the cable ends are biased or knotted to secure the cable to the loop and prevent the cable from being pulled from the loop.

Figure 87 also shows the next cable 608. The cable has caps cast on its ends. The cap can be used to secure the cable to some devices.

Of course, those skilled in the art will appreciate that the fusible member can be designed in a variety of ways to secure the pawl or brake, and the particular arrangement described is merely illustrative of the possible ways. The fusible member itself can take different forms, like a cable or a film. In some installations it may be desirable to form the fusible member from a larger wire, sheet or strip. These profiles have a reduced waist portion of small size/width. In order to heat more intensively, a higher current density is obtained at the beam waist.

As explained above, the fusible member is connected to a firing system 76 which generates a sudden surge of current in response to the output signal from the contact detection system to melt the fusible member. In the example of a fusible member described above in connection with Figure 2, about 20-100 amps of current would be required to ensure safe or rapid melting. As those skilled in the art will appreciate, there are many suitable circuits for providing this current surge.

FIG. 88 schematically illustrates one arrangement of the launch system 76 . That example device includes one or more charge storage devices that discharge through the fusible member in response to a control subsystem output signal. (As mentioned above, the output signal from the control system depends on detecting contact between the user and the saw blade). The use of a charge storage device eliminates the need for the high current power supply necessary to melt the fusible member. It will be appreciated that, of course, a current source could be used instead of the charge storage means. Alternatively, other devices can be used to provide the required current, including a silicon rectifier or thyristor connected to the power line.

The transmitting system shown in FIG. 88 includes a pair of transistors 610 with relatively high current. The triode is connected to pass current stored in the memory device to the fusible member 70 . The transistor 610 is turned on by the output signal from the control subsystem 26 . As shown in FIG. 88, the output signal from the control subsystem 26 is connected to the gate of the transistor 610. Any suitable triode can be used. Like the IRFZ40 MOSFET triode known to those skilled in the art. The triode is connected in parallel between the charge storage device 611 and the fusible member 70 . In the example device, the charge storage device is in the form of a 75,000uF capacitive plate. A 100 ohm resistor 612 is connected to a 24 volt source to build and maintain the charge on the capacitive plates. When the control subsystem 26 output is high, the transistor 610 allows the charge stored on the capacitive plate to pass through the fusible member. The sudden release of the charge stored in the capacitive plates heats the fusible member to its melting point in about 1-5 milliseconds. Alternatively, one or more transistors can be replaced by other switching devices such as thyristors. One advantage of using stored charge to also melt the fusible member is that the firing system is not dependent on line power capacity or line voltage phase.

FIG. 89 shows another alternative arrangement for the launch system 76 . The alternative firing circuit comprises a fusible member 70 connected between a high voltage source HV and a thyristor 613 such as NTE5552. The thyristor gate is connected to the control subsystem 26 . The control subsystem 26 turns on the thyristor SCR 613 by supplying a current of about 40 mA, thus allowing the high voltage source HV to discharge through the fusible member 70 to ground. Once the thyristor is turned on, the thyristor will continue to conduct as long as the current through the fusible member 70 is above the holding current of about 40 mA, still allowing the current through the gate to be withdrawn. In this way, the thyristor will direct current through the fusible member until the fusible member is melted or the high voltage source is removed. The fact that the thyristor, once turned on, remains on allows it to react to even short pulses from the control system 26 . It should be noted that a high voltage (HV) capacitor provides high voltage pulses. Using high voltage capacitors results in a very high inrush current, so the fusible element melts much faster than using a low voltage system. It will be appreciated that the high voltage capacitor can be sized differently as necessary to provide the current necessary to melt the fusible member 70 .

FIG. 90 shows another arrangement of the launch system 76 . The device includes a fusible member 70 connected to a 390 microfarad capacitor, indicated at reference numeral 620, and a TYN410 thyristor, indicated at reference numeral 612. In a device like that shown in FIG. 90, capacitance 620 may vary from about 100 microfarads to 5000 microfarads. Capacitor 620 is connected between a high voltage charge line 622 (eg, from a jump boost charger) and ground. The high voltage charging cable charges the capacitor to about 180-200 volts. The thyristor gate is connected with the control subsystem 623 . A signal from the control subsystem 623 turns on the thyristor 621 to allow the capacitor to discharge through the fusible member 70 . In this device, the capacitor is believed to be capable of delivering a pulse of approximately 1000 to 1500 amperes. As explained above, once the thyristor is turned on, the thyristor will continue to conduct as long as the current through the fusible member remains above the holding current. In this way, the thyristor will pass current through the fusible member until the fusible member is melted or the high voltage source is removed. The firing system 76 also includes a 1K resistor connected between the SCR gate and ground to maintain the signal from 623 to ground until a signal from the control subsystem pulls it high. This way the transmitting system will not be triggered by noise. A sensing line 625 is connected between the thyristor 621 and the fusible member 70 . In this way the control system can monitor the charge on the capacitor 620 to ensure that the capacitor is charged and functioning. With respect to capacitance 620, connecting sensor 625 down from fusible member 70 allows the control system to check the capacitance through the fusible member. This means that the control system also checks that the fusible elements are complete and functioning properly. It should be noted that the sense wire can also be used to charge the capacitor.

Those versed in electrotechnical skills will understand that the above-described exemplary arrangements of transmission systems are but a few of the many designs that may be used. It will thus be understood that any suitable device or design may be used. The controllable system, power supply, sensing lines and devices used with or associated with the transmitting system are described in more detail in Sections 1, 2 and 3 above and Section 9 below.

FIG. 96 shows a launch system 76 assembled on a printed wiring board 630 . The transmitting system is similar to the circuit shown in FIG. 90 and includes a capacitor 620 and a thyristor 621 . A connector 631 is attached to the printed circuit board so that the circuit can be connected to the control system, sense lines and power supply. A contact support 632 formed by separate electrodes 634, 636 is secured to the printed circuit board. A fusible member also extends around the contact holder in use.

FIG. 92 shows a cross-sectional top view of the contact holder and electrodes 634 and 636 . And the fusible member 70 is wound on the electrode. As mentioned above, the electrodes are made with a small gap 640, and when current passes from one electrode through the fusible member to the other, the fusible member breaks or melts outside of this gap. Contact bracket 632 is designed to fit over a support plug and flange 642 to help secure the support to the plug.

FIG. 93 shows the printed wiring board 630 containing the capacitor 620 and the thyristor 621 installed in the cartridge 82 . The cartridge houses the pawl 60 , spring 66 and fusible member 70 . The fusible member 70 resists outward movement of the pawl by limiting the movement of the synthetic link 650 . The fusible member extends around contact bracket 632 . Sliding over the contact bracket 632 is a support plug that is part of the cartridge housing. When the firing system 76 on the printed circuit board 630 sends a surge current to the fusible member, the fusible member 70 melts. The combined link 650 and pawl 60 are then free to move, and the spring 66 quickly forces the pawl 60 outward. The cassette 82 can be designed for use with various types of power equipment, such as table saws, joint planers, and the like. In addition, the cartridge 82 can be "reloaded" and reloaded with a new detent and fusible member, and reused after launch from the launch system.

FIG. 94 shows a device in which a fusible member is mounted between a fixed point 652 and the pawl 60 . Two electrodes 653 and 654 are in contact with, but not supporting, the fusible member between the fixation point and the pawl. Electrodes 653 and 654 may take the form of conductive traces on a printed wiring board. The conductive traces are formed on the printed wiring board and extend slightly above the surface of the printed board so that the fusible member 70 can contact the two electrodes by extending across them. The printed wiring board is mounted in such a way that the electrodes 653 and 654 exert some pressure on the fusible member to ensure contact with the fusible member. Electrodes 653 and 654 are connected to a transmission system as described. Of course, the design and orientation of electrodes 653 and 654 can vary.

Figures 95 through 98 show data relating to the time required for a launch system to melt a cable for given factors. These given factors include things like launch system, cable size, load on the fusible member, etc. Figure 94 shows the approximate time taken to melt the wire under varying loads on the wire. The tested wires were stainless steel, ASTM 302/304, with 0.010 inch diameter temper springs, and were wound on brass electrodes at 0.044 inch spacing. The launch system uses a 390 microfarad capacitor charged to 163 volts to melt the cable. Approximate times for wire to melt for a given load are as follows: 231 microseconds for a 5-pound load, 98 microseconds for a 10-pound load, 6 microseconds for a 15-pound load, 48 microseconds for a 20-pound load, 39 microseconds for a 25-pound load, and 30 microseconds for a 30-pound load 33 microseconds, 22 microseconds for a 35-pound load, and 18 microseconds for a 40-pound load. These data show that as the load on the fusible member increases, the time required to melt the member decreases.

Figure 69 shows the approximate time required to melt the wire as the electrode spacing was varied. The cables tested were stainless steel, ASTM 302/304, 0.010 inch diameter tempered springs, wound on brass electrodes. The launch system uses a 390uF capacitor charged to 163 volts to melt the cable. The load on the cable is 20 lbs. The approximate times for the wire to melt for a specific electrode spacing are as follows: 70 microseconds for a 0.1 inch pitch, 47 microseconds for a 0.044 inch pitch, and 37 microseconds for a 0.013 inch pitch. The data show that as the electrode spacing decreases, the time to melt the fusible member decreases.

Figure 97 shows the approximate time it takes to melt a cable as a function of the voltage across the capacitor in the transmitting system. The tested wires were stainless steel, ASTM 302/304, tempered springs with a diameter of 0.010 inches, and were wound on brass electrodes at 0.044 inches apart. The transmit system uses a 390 microfarad capacitor. The approximate times for a wire to melt for a given voltage are as follows: 123 volts 296 microseconds, 133 volts 103 microseconds, 143 volts 81 microseconds, 153 volts 57 microseconds, 163 volts 47 microseconds, 173 volts 40 microseconds, and 183 volts Volts 39 µs. The cable will not melt when the voltage is only 103-113 volts. The data show that as the voltage increases, the time it takes to melt a fusible member decreases.

Figure 98 shows the approximate time taken to melt different size cables. The tested cables were all stainless steel, ASTM302/304, spring-flexible wire, and the cables were wound on brass electrodes at 0.044 inch spacing. The launch system uses a 390 microfarad capacitor charged to 163 volts. The cable has a 40 lb load. The approximate time it takes to melt a cable for a specific cable diameter is as follows: 18 microseconds for a 0.013 inch diameter, 39 microseconds for a 0.011 inch diameter, and 81 microseconds for a 0.012 inch diameter, a cable with a 0.013 inch diameter does not melt. The data shows that as the diameter of the cable decreases, the time it takes to melt the cable decreases.

These data show that in a system described above, a 25 to 200 pound load can be used in less than 200 microseconds, and preferably in less than 50 microseconds. Move the pawl toward one blade. Stainless steel is a good material for fusible components because of its high resistance, high strength and good corrosion resistance.

The firing system 76 can also be used to trigger actions other than melting a fusible member. For example, the firing system 76 can fire a small explosive charge to move the pawl. Figure 99 shows a relatively small, self-contained explosive charge 660. The explosive charge is in the form of a detonator or explosive that can be used to drive the pawl against the saw blade. An example of a suitable explosive charge available is M-100 explosive from Stresau, Laboratory, Inc; of Spooner, Wisconsin. The self-contained charge or detonator concentrates the explosive force in the direction of pawl movement. A trigger wire 662 emerges from the charge, which can interface with the delivery system 76 to trigger the detonation.

An explosive charge 660 is inserted between the pawl and a stationary block 664 adjacent to the charge to be used to move the pawl 60 . When the charge explodes, the pawl is pushed away from the block. A compression spring is placed between the block and the pawl to ensure that the pawl does not bounce off the blade when the charge explodes. The friction fit of the pawl against the block and the pawl is separated from the saw blade before exploding. However, the forces generated by the charge explosion are far more than sufficient to overcome the friction fit. Alternatively, the pawl could be separated from the blade in other ways. Like a breakable member, gravity, a spring between the pawl and the way, etc.

The launch system 76 may also trigger a DC solenoid valve. The solenoid valve can be overdriven by a rapid displacement caused by an inrush current, a compressed gas or cylinder supplying pressure in place of a spring or charge, or an electromagnet to push the pawl away from the blade or move the mounting The upper spring pawl releases towards the blade.

Launch and release systems and methods may be described in the numbered paragraphs of the following declarations. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

6.1 A mechanical release consists of:

an electrode system comprising a first electrode electrically connected to a current source, and a second electrode;

a fusible member electrically interconnecting the electrodes;

An electrical gating system interposed between the at least one electrode and the current source to selectively control the flow of current from the current source to the at least one electrode. Here, the fusible member is subjected to a tensile load of at least 10,000 psi between the electrodes.

6.1.1 The mechanical release of paragraph 6.1, wherein the fusible member has a tensile strength of at least 100,000 psi.

6.1.2 The mechanical release of paragraph 6.1, where the fusible member is made of a material selected from the group consisting of stainless steel and nickel.

6.1.3 The mechanical release of paragraph 6.1, where the fusible member is spring-flexible.

6.2 A woodworking machine includes:

a brake for stopping the cutting tool;

a biasing system adapted to push the brake from the waiting position to the braking position,

And, a release system for selectively holding the brake in the waiting position against the bias of the biasing mechanism.

6.2.1 The machine of paragraph 6.2, where the release mechanism is a single-purpose device.

6.2.2 The machine of paragraph 6.2.1, where the release mechanism comprises a fusible member.

6.2.1.1 The machine of paragraph 6.2.1.1, wherein the release mechanism includes first and second electrodes connected to a current source and a fusible member electrically connecting the electrodes to each other.

6.2.2 The machine of paragraph 6.2, where the release mechanism comprises an electromagnet.

6.3 A woodworking machine includes:

a cutting tool;

The brake is adapted to stop the cutting tool. At this time, the brake has an idle position and a brake position;

a brake for braking the cutting tool, where the brake has a waiting position and a braking position;

And, an actuation system for moving the brake from the waiting position to the braking position, where at least a part of the actuation system must be replaced after the brake is moved from the waiting position to the braking position.

6.3.1 The machine of paragraph 6.3, where the activation system includes an explosive device.

6.3.2 The machine of paragraph 6.3, where the activation system includes a fusible member. The fusible member is melted to allow the brake to move from the waiting position to the braking position.

6.3.3 The machine of paragraph 6.3, where the braking and at least part of the starting system are housed in a replaceable cartridge. Chapter 7: Replaceable brake cartridges

As explained above and depicted in FIG. 2 , a portion of the security system 18 may be housed in a replaceable cartridge 80 . 100-109 show various implementations of the cartridge 80. They have various elements, subelements and possible variations. It should be understood that the cartridge may comprise one or more of such elements, sub-elements and variations regardless of whether these elements, sub-elements and variations are shown in the same or different drawings and descriptions. Examples of suitable detent and bias mechanisms 28 and 30 including suitable pawls 60 that can be used with the cartridges described herein are described in Sections 4 and 5 above.

The cartridge 80 should include or be in communication with the operating portion of the release mechanism 34 . Release mechanism 34 is used to allow restraint mechanism 32 to release pawl 60 for engagement with a machine saw blade or other cutting tool. For example, in FIG. 2 , it can be seen that bracket 72 is in electrical communication with transmit subsystem 76 . Upon activation of detection subsystem 22 , such as upon detection of a hazard or trigger condition, firing subsystem 76 activates release mechanism 32 , such as by using the surge current stored in subsystem 76 to melt fusible member 70 . Examples of suitable restraint mechanisms 32 and launch subsystems 76 for use in cartridge 80 are described in Section 6 above.

Communication between the transmit subsystem and rack 72 may be established by any suitable electrical connection. Preferably, electrical communication between rack 72 and subsystem 76 is automatically established when cassette 80 is loaded into machine 10. For example, housing 82 may include contact points. These contacts engage corresponding contacts associated with the launch subsystem when the cartridge is seated in its installed position in the machine. Alternatively, a plug and socket assembly may be used to establish the electrical connection between the bracket 72 and the transmit subsystem 76 .

Cartridge 80 is removably mounted in machine 10 such that detent mechanism 28 and, in particular, pawl 60 are positioned adjacent the machine's saw blade or other cutting tool. Cartridge 80 may include a detent positioning system or other suitable mechanism for selectively adjusting the position of the pawl and/or the cartridge relative to blade 40 . For example, the position of the cartridge relative to the saw blade or other cutting tool may be adjusted by, for example, twisting or sliding the cartridge relative to one or more set bolts. In this case, the pawl-to-blade spacing can be determined indirectly by measuring the blade-to-cartridge spacing, if desired. Alternatively, the cartridge could be stationary and the pawl could be adjusted within the cartridge. As a further alternative, both the cartridge and the pawl can be adjusted. Similarly, the position of the mounting bracket can be adjusted relative to the saw blade. Examples of suitable brake positioning systems are described in Section 8 below.

As shown in Figure 100, the machine 10 includes a support structure 702 within the security system 18 for receiving the cartridge 80 and the handling portion of the cartridge. Support structure 702 may be mounted on or extend from any suitable structure of machine 10 . When the saw blade 40 is adjustable, it may be preferable to allow the cartridge 80 and/or support structure 702 to move with the saw blade so that the desired positioning of the pawl 60 and saw blade 40 is maintained. Alternatively, the cartridge may include a pawl 60 sized appropriately to accommodate adjustment of the blade position without corresponding adjustments to the cartridge and/or mounting structure.

Examples of suitable support structures include one or more brackets 704 . The cartridge is attached to the bracket 704 by any suitable releasable fixing means, such as bolts, pins or screws. The support structure 702 may additionally, or alternatively, include a shaft 706 on which one or more cartridges are mounted. For example, the pawl 60 shown in FIG. 100 is torsionally fixed on a shaft 706 . Shaft 706 passes through pawl 60 and through at least a portion of cartridge 80 . Also seen in FIG. 100 is a mounting bracket 704 that supports and positions the cartridge 80 relative to the saw blade 40 . Another example of a suitable support structure is a socket or other receptacle in machine 10 . Typically, the cartridge 80 will be supported in an appropriate orientation and/or position to maintain the intended installation position and orientation of the cartridge. The cartridge 80 and support structure 702 preferably includes a main structure 703 . The main structure 703 prevents the cartridge from being installed in the machine 10 in an inappropriate installation location. Figure 100 shows an example of a suitable master structure. In the figure, the housing of the cartridge 82 includes a beveled edge 705 matching the mounting bracket 704 . It should be appreciated that the primary structure 703 may comprise any suitable mechanism, including the relative size, shape and location of the cassette 80 and support structure 702 . This mechanism prevents the cartridge from being loaded where it should not be.

Figure 101 shows another cartridge. Similar to the cartridge shown in FIGS. 2 and 100, cartridge 80 includes a housing 82, a detent mechanism 28 including pawl 60, a biasing mechanism 30 such as spring 66, and a fusible member 70 such as The limit mechanism 32 . Also shown is another example of a suitable support structure 703, namely, an irregularly shaped housing 82 and mounting brackets 704 to support the housing.

As shown, the pawl 60 includes an aperture or aperture 708 . A shaft or pin 706 may extend through the aperture within the machine 10 to support the pawl and cartridge. Also shown are apertures 710 in one or more side walls of the cartridge. A shaft 706 extends through the aperture. Alternatively, the cartridge 80 can be supported by a support structure 702 that does not directly support the pawl 60 . For example, pawl 60 is rotatable about an axis forming part of cartridge 80 . The cartridge 80 is supported by a support structure 702, such as a pin, a support frame or the like. However, it may be preferable to support the pawl 60 by at least one support structure 702 to increase the support force beyond that provided by the cartridge 80 . Similarly, this reduces the required strength of the cartridge 80 because most of the force exerted on the pawl as it engages the machine saw blade or other cutting tool is absorbed by the support structure 702 .

The pawl 60 should be restrained in its installed position within the cartridge 80 when the cartridge is not loaded into the machine. Figure 102 shows an example of a suitable linkage 714 between the pawl and the cartridge. In the figures, the aperture 710 through the cartridge 80 is larger than the corresponding aperture 708 through the pawl 60 . The pawl 60 includes an outwardly extending bushing, or bracket 716 . The bracket 716 extends at least partially from the side wall of the cartridge to position the pawl relative to the cartridge. It should be understood that this design could be reversed, with the pawl 60 having a larger aperture than the cartridge 80 and the cartridge having an inwardly extending bushing or bracket. The bracket passes at least partially through an aperture in the pawl 60 .

Figure 102 also details the opening 718 of the cartridge. When the restraint mechanism 32 is released, at least a portion of the pawl protrudes from the aperture. Although Fig. 102 shows the pawl 60 fully within the housing 82, it should be understood that at least a portion of the pawl may protrude from the housing 82 when the pawl is in its upright, or restrained, position. Opening 718 may include a cover 720 . Cover 720 seals the opening thereby preventing contaminants such as dust, particles, moisture, grease and the like from entering the cartridge and potentially interfering with operation therein. Although Figure 102 only shows It should be understood that the cover preferably completely covers the opening 718. The cover 720 may be made of any suitable material to prevent contamination from entering the cartridge through the aperture 718 while at the same time not interfering with the operation of the detent mechanism 28 . Suitable materials for the cover 720 include tape, thin steel, paper or plastic film. When the cover 720 is used to completely cover the opening 718, the entire cartridge is preferably, but not necessarily, enclosed to keep out contaminants. Cover 720 may be attached to the cartridge by any suitable structure, such as with glue 722 . In cartridge devices where the catch is not prevented from twisting or moving by the restraint mechanism 32, the cover 720 can also act as a catch-restraint mechanism to prevent the pawl from protruding through the opening 718 before the restraint mechanism releases the biasing mechanism 30. .

Returning briefly to FIG. 101 , it can be seen that the biasing mechanism 30 includes a spring 66 . The spring 66 is compressed between a spring-receiving portion 724 of the pawl and a bracket 726 forming part of the cartridge 80 . As shown, bracket 726 extends from the cartridge housing. Of course any suitable bracket may be used. This includes the end wall 728 of the cartridge, a bracket extending from the end wall and a bracket extending from at least one side wall 712 of the cartridge.

In the embodiment of the pawl 60 shown in FIG. A link 734 is torsionally connected to the housing 82 , and a link 736 internally connects the top portion 732 of the pawl 60 to the link 734 . As shown, when pawl 60 is in its upright and restrained position, both linkages are in compression. It should be understood that any suitable number and style of links may of course be used. Alternatively, the limiting mechanism 32 may directly secure the pawl, as shown in FIGS. A support on which mechanism 32 acts. The pawl is thus completely or relatively free from the bias of the spring 66 until the restraint mechanism 32 is released.

The fusible member 70 extends around the contact bracket 72 and at least a portion of a linkage to prevent the pawl 60 from twisting under the force of the biasing mechanism 32 . As shown, the top of the fusible member 70 is connected to the link. When the restraint mechanism 32 is released, as when a sufficiently large electric current flows through the fusible member 70 through the contact frame 72, the fusible member no longer fixes the link and pawl in the position shown, and the pawl The claw is twisted to its blade-engaged position shown in FIG. 103 .

The launch subsystem 76 may alternatively be placed within a cartridge 80 as illustrated in FIG. 104 . One advantage of locating the launch subsystem 76 within the cartridge 80 is that the launch subsystem can be replaced along with the rest of the cartridge. It also allows a means 742 for discharging the capacitance or other stored or generated current of the fusible member 70 to be positioned adjacent to the contact bracket 72 . This allows for a direct link rather than a cable connection to the contact frame. FIG. 104 also shows a plug 746 protruding from a port 748 of the housing 82 . Plug 746 is used to electrically connect reflection subsystem 76 to controller 50 or another suitable portion of control subsystem 26 . Alternatively, the contacts shown protrude from or form part of the housing 82 .

Figure 105 shows another example of a cartridge. As shown, the cartridge 80 includes the firing subsystem 76 of the release mechanism 34 . Figure 105 also shows another version of the links 734 and 736. Here link 734 is in tension rather than compression. Both the linkage assemblies shown in Figures 101 and 105 can be considered over center linkages. FIG. 105 shows fusible member 70 having a fixed length defined by top 752 . The top 752 is used to connect the contact frame 72 to the linkages 734 and 736, respectively. One advantage of a fixed length fusible member is that it provides simple cartridge assembly with consistent pawl positions.

Unlike in FIG. 101 , the bracket 726 supports the end of the spring remote from the pawl 60 . In FIG. 105, the cartridge 80 includes a removable bracket 754. In FIG. Bracket 754 is selectively removable from cartridge 80 to release or at least substantially reduce the biasing force of spring 66 on pawl 60 . For example, bracket 754 may be removed after activation of detent mechanism 28 to remove spring force for easy removal or replacement of the cartridge. One example of a suitable bracket 754 is a clip 756 extending from at least one side wall 712 of the cartridge. Clip 756 may be supported between two side walls of the cartridge. Alternatively, the cartridge 80 may include an inner bracket 758 for supporting the end 760 of the clip 756 . This is shown in Figure 106, where the pawl is in the blade-engagement position. Preferably the clip 756 or other bracket 754 can be removed from the cassette without first removing the cassette from the machine 10. For example, clip 756 may include a component 762 . As shown in Figure 107, member 762 extends to the outside of the cartridge 80 and can be grasped by a tool to withdraw the clip from the cartridge. A benefit of the device shown in FIG. 106 is that pulling the clip 756 releases the spring 66 . The spring 66 then breaks the fusible member 70 . The controller of the safety system can be designed to detect the breaking of the fusible member and react accordingly to the system failure.

Figure 104-06 shows the launch subsystem 76 housed in the cartridge 80. It should be understood that other elements of the security system electronics may also be located within the cartridge 80 . For example, the cartridge may include a sensing assembly to determine if the cartridge is properly loaded in the machine 10 . The machine is prevented from running until the safety system receives a signal that the cartridge is properly installed.

Placing most of the safety brake 30 within the cartridge allows the manufacturer to develop electronics with improved performance, additional functionality, etc., without requiring significant changes, if any, to the machine. As a further alternative, the security system 18 may include a plurality of cassettes, including at least one cassette containing the pawl 60 and at least one cassette containing such as an emission subsystem 76 and/or other electronic components of the security system. box. Figure 108 shows an example of such a cartridge assembly. As shown, a pair of cartridges 80 are represented by 80 ′ and 80 ″. Cartridges 80 ′ and 80 ″ can also be described as daughter cartridges or modules that are combined to form cartridge 80 . Cartridge 80' includes an electronics unit 764 such as launch subsystem 76 or control subsystem 26, and an electrical connector 766 connected to a cable 770 designed to operatively engage plug 768. The cable includes conductors that provide power to the electronics unit. The cable may also conduct output signals from the electronics unit, such as a cut-off signal to stop the motor assembly 16 , or a signal to the control subsystem 26 . These all depend on the particular electronics within the cartridge 80'. While the bung 768 and cable 770 are shown as freely movable, it will be appreciated that the bung 768 may be securely secured to the support surface to which the cartridge 80 is secured. Further, the plug 768 can be securely positioned to ensure that the cartridge is properly aligned and oriented when the plug is engaged with the plug. On the other hand, the cartridge 80" includes the pawl 60 and the biasing and limiting mechanism. These mechanisms are collectively shown as block 772 to indicate that the biasing and limiting mechanism can also form a card that can be selectively removed or replaced. Cartridges or Modules. Preferably, the cartridges communicate with each other, such as releasing the restraint mechanism in response to a signal from the electronics unit 764.

Alternatively, the cassette 80", or any cassette described, can be of different sizes and designs to accommodate different blade sizes. For example, a longer cassette version shown in Figure 109 could be used with a smaller Diameter saw blade 40. Further, different cartridges can be provided for different applications using different types of saw blades (eg, tenoning, crosscutting, stripping, plywood, etc.). For example, for the first type of saw blades can provide There is a first cartridge of the first type of pawl, and for a second different saw blade, a second cartridge with a second different pawl can be provided. Another way is that the electronics of a cartridge can be different from The electronics of the other cartridges allows for different applications (eg, cutting plastic instead of wood.) Furthermore, multiple cartridges can be used simultaneously to ensure that the safety brake reacts optimally to each material.

The brake cartridge and related machines and methods may be described in the numbered paragraphs declared below. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

7.1 A woodworking machine includes:

a machined part;

a detection system suitable for detecting hazardous conditions between persons and process components;

A brake system that brakes the machining part when the detection system detects a hazardous situation, where the brake system is housed in the cartridge.

7.1.1 The woodworking machine of paragraph 7.1, where the cartridge is designed to be replaced after the braking system brakes the machined part.

7.1.2 The woodworking machine of paragraph 7.1, where the cartridge houses a brake pawl for contacting the machined part, a biasing mechanism for moving the brake pawl into engagement with the machined part, and a biasing mechanism for releasing the Agency release agency.

7.1.2.1 The woodworking machine of paragraph 7.1.2, where the biasing mechanism includes a spring.

7.1.2.2 The woodworking machine of paragraph 7.1.2, where the biasing mechanism includes a spring and a mechanical linkage against the spring to restrain the brake pawl.

7.1.2.3 The woodworking machine of paragraph 7.1.2, where the release system includes a fusible member.

7.1.2.4 The woodworking machine of paragraph 7.1.2, wherein the release system includes a fusible member and a firing circuit for melting the fusible member.

7.1.2.5 The woodworking machine of paragraph 7.1.2, where the cassette is closed.

7.1.2.6 The woodworking machine of paragraph 7.1.2, where the cassette is made of plastic, the cassette includes an opening through which the brake pawl can pass, and the opening is covered until the brake pawl passes through it.

7.1.3 The woodworking machine of paragraph 7.1 further includes a work plane adjacent to the machining component, where the machining component is a saw blade designed to be raised and lowered relative to the work plane, and the cassette is mounted to follow the saw blade Lift together.

7.1.4 The woodworking machine of paragraph 7.1, where the cartridge is fixed on a rotating shaft of the machine.

7.2 A cassette for a carpentry machine, the cassette comprising:

A shell:

a brake pawl in the housing;

Move the brake pawl one mechanism. Chapter 8: Brake Positioning

A brake mechanism like that described above can be placed in different positions relative to the saw blade. For example, FIG. 110 shows an example brake positioning system 800 . Cartridge 80 and brake pawl 60 are generally torsionally mounted on a large shaft or pin 802 . The cartridge and pawl are held together until the brake is released. When the brake is released, the brake pawl is quickly pushed into the saw blade. The movement of the saw blade and the geometry of the pawl then cause the blade to advance deeply into the pawl to create a large deceleration motion. The pin 802 should be large enough, typically 0.75 inches, to absorb the deceleration hit without being damaged. The large diameter pin also reduces the likelihood of crushing the brake pawl 60 during braking. The twisted mounting of the cartridge on the pin allows the distance between the saw blade and the brake pawl face to be adjusted by turning the cartridge about the pin. The brake positioning system is used to establish and maintain the proper spacing between the pawl face and the outer edge of the saw blade 40 .

In its simplest form, the brake positioning system 800 includes a fixed pin 804 to position the cartridge 80 and thus the brake pawl 60 . This arrangement is generally sufficient if all saw blades used are of known size and the saw size is sufficiently fixed. Pin 804 is arranged parallel to pin 802 to allow cartridge 80 to be slid towards both pins simultaneously. A flexible sports clip bites the edge of the cartridge 80 to keep it in place on the pin. When the cartridge is removed, the clip is lifted from the cartridge and the cartridge slides off the pin. A clearance pin 808 is preferably mounted on a fixed radius of the arbor, such as a 51/10 inch radius, to ensure that no blades larger than those not in contact with the pawl can be loaded into the saw. The clearance pin is preferably located at a radial position from the knife radius that is only slightly smaller than the nearest portion of the pawl so that the saw blade will contact the pin first after contact with the pawl. Alternatively, the pin can be arc-shaped. The arc should be large enough to engage at least one saw blade tooth.

Figures 111-113 show an adjustable brake positioning system 800. The brake positioning system 800 includes a plurality of positioning teeth 812 formed on the rear of the cartridge 80 . A corresponding plurality of positioning teeth 814 are formed on the cartridge mounting surface 816 . The positioning teeth preferably have a tooth spacing of about 1/32 to 1/4 inch. The positioning teeth are spaced such that relatively small adjustments can be made by selecting where to engage the positioning teeth. A curved wall 818 is formed along a portion of the inner front edge of the cassette. The curved wall is positioned to engage the perimeter of the saw edge. This engagement occurs only before the positioning teeth engage each other when the cartridge is slid onto the pin 802 . This ensures that the pawl will remain at least as far from the blade as the curved wall projects forward from the pawl - typically 1/16 to 1/8 inch. Once the positioning teeth are engaged, the rotational position of the cartridge is fixed. The cartridge then slides the remaining distance toward the pin. Quick clips 806 hold the cartridge in place on the mounting surface and in place. A small protrusion 820 is formed on the edge of the cartridge and extends over the saw blade. This protrusion prevents the saw blade from being removed unless the cassette is partially removed and pivoted away from the saw blade. In this way, the protrusions ensure that the saw blade cannot be removed and replaced by a new saw blade without resetting the position of the cartridge. It can be seen that by twisting the cartridge on pin 802, adjusting the position of the brake pawl relative to the saw blade is simplified.

Due to the importance of establishing the correct pawl-to-blade spacing, it may be desirable to include a spacing detection system to ensure correct spacing. An example of such a system 824 is shown in FIG. 114 . System 824 includes an electrode located on the surface of the pawl adjacent to the blade. As described in Sections 1 and 2 above, in a contact detection system suitable for use with the present invention, an electrical signal is applied to the saw blade through a drive electrode. This signal can be picked up by electrodes 826 and monitored to ensure its amplitude is within a predetermined range. In particular, the amplitude detected by electrode 826 will drop off rapidly with distance from the saw blade. Therefore, by monitoring the detected amplitude, proper spacing can be verified. The system preferably prevents or disables the initial activation of the machine when the detected gap is outside the normal range. The user is then prompted to make the appropriate adjustments.

FIG. 115 shows another alternative brake positioning system 800 . The positioning system shown in Figure 115 utilizes a quick gripper 830 with only a beam 832 facing the cartridge. The gripper is mounted on the support surface 816 of the cartridge and is biased to abut against the cartridge. The end face of the cartridge includes a recess 834 for receiving the beam 832 . In use, the cartridge is slid towards the pin 802 as it is pivoted back from the saw blade. Once the cartridge is securely mounted on the pin, it is rotated forward until the beam is seated in the groove to prevent the cartridge from being vibrated off in the axial direction of the pin. Once the cartridge is fired, the user can lift the tab 838 to release the beam and allow the cartridge to rotate back. This reverse rotation can be used to release any remaining pressure from the cartridge activation spring.

FIG. 116 shows another brake positioning system 800 . In the system shown in Fig. 116, the cartridge 80 includes a groove 850 formed in one side. A spring pin 852 is positioned to engage the groove 850 when the cartridge 80 is rotated back from the saw blade, the spring pin positioned so that the pawl face is approximately 1/8 inch from the edge of the saw face. Of course, different pitches can also be used. The user can remove the cartridge by lifting the spring pin, rotating the cartridge forward until it clears the pin, and then sliding the cartridge off the pin 802. As described in more detail in Section 7 above, when the cartridge is fired, the pawl will normally snap into place on the blade and be biased towards the blade by the spring 66 . A release pin 756 is movable to release the rear of the spring and de-bias. This makes it easier to release the pawl from the blade and eliminates stress on the blade. Otherwise this pressure will make it more difficult to remove the saw blade.

Figure 117 shows a further brake positioning system 800. In this arrangement, pawl 60 and brake cartridge 80 are mounted on a support assembly 860 . This assembly 860 is selectively movable to adjust the position of the pawl and/or the cartridge. It will be appreciated that the support assembly 860 can be designed in a variety of different ways. In the example device shown in FIG. 117, assembly 860 includes a plurality of gears 862 having a toothed perimeter. Each gear includes a support post extending outwardly therefrom. Cassette 80 is mounted on assembly 860 so that the first support post passes through brake pawl 60 and the cassette, while the second support post passes only through the cassette. The pawl is adapted to twist about a first support post which supports the pawl and absorbs energy of the saw blade during braking. The second support post acts to angularly position the pawl relative to the saw blade and prevents rotation of the cartridge about each support post.

When the cartridge and pawl are mounted on the first and second support posts, the pawl can be properly positioned relative to the saw blade by the rotating gear 862 . Assembly 860 also includes a worm screw 866 or other suitable mechanism to rotate the gear. A handle or similar device can be fixed on the worm screw to facilitate turning. In this example arrangement, a worm screw 866 is used to engage both gears simultaneously so that the gears rotate simultaneously. As a result, the cassette 80 and brake pawl 60 maintain an angular position relative to the blade as the gear turns, however, as shown in Figure 117, the cassette pawl moves toward and away from the blade as the worm bolt rotates. This allows the brake to be positioned correctly for different sized saw blades. Further, this arrangement eliminates the need for different sized pawls and/or cartridges for different sized saw blades.

In another alternative, the gear 862 may be a different size to rotate a different angle as the worm bolt is turned. This may be useful where it is necessary to change the angular position of the pawl relative to the saw blade as the pawl is moved towards and away from the saw blade.

In the device shown in Figure 117, the pawl twist point is translated as the pawl moves closer and away from the saw blade, in a further alternative device the position of the pawl can be determined by simply twisting the pawl around the pawl twist post claws are adjusted. In such an arrangement, it may be desirable to have a relatively long pawl to accommodate saw blades of very different sizes.

The brake positioning system, method and related machinery may be described in the numbered paragraphs declared below. These paragraphs are for illustration and do not limit this disclosure or statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

8.1 A woodworking machine includes:

a machined part;

a cartridge including a brake pawl adapted to selectively engage and apply the brake;

And, a brake positioning system adapted to receive and adjustably position the brake cartridge relative to the cutting tool.

8.1.1 The woodworking machine of paragraph 8.1, wherein the brake positioning system is allowed to be adjusted to accommodate cutting tools of different sizes.

8.1.2 The woodworking machine of paragraph 8.1, where the brake positioning system includes a pivot shaft on which the cartridge is secured and the position of the brake cartridge relative to the cutting tool is adjusted by rotating the cartridge against the pivot shaft of.

8.2 A woodworking machine includes:

a cutting tool;

a motor suitable for driving the cutting tool;

An adjustable positioning brake near the cutting tool;

a sensor system adapted to sense the gap between the cutting tool and the brake;

a control system designed to control the operation of the motor and to receive a signal from a sensor system representative of the distance between the cutting tool and the brake, where the control system is further designed to selectively prevent the motor from operation.

8.2.1 The woodworking machine of paragraph 8.2, where the sensor system includes an electrode fixed to the brake pawl adjacent to the cutting tool, and the signal is dependent on the electrical connection of the electrode to the cutting tool. Chapter 9: Logic Control

Considering the logic controller 50 in more detail, it will be appreciated that the logic controller can be designed to perform a variety of functions depending on the particular type of machine 10 and/or utility. For example, the subgrade controller 50 can be designed to perform various self-checks to ensure that the detection subsystem 22 is functioning properly and to prevent accidental triggering of the reaction system 24 when the machine is turned on and off during machine operation. Additionally, the logic controller may be designed to control one or more devices to notify the user of the status of the machine 10 and security system 18 . Still further, the logic controller can be implemented in various ways. This includes one or more application-specific integrated circuits (ASICs), microprocessors, microcontrollers, digital logic circuits, and/or analog circuits, among others.

In an example device, the logic controller 50 is designed to perform the self-test logic sequence shown in FIG. 118 . The example sequence begins when the user initially powers the system, which is indicated at 901 . The logic system first checks to determine if the pawl-to-blade spacing is correct, which is indicated at 902 . The blade to pawl spacing may be measured by any suitable mechanism, as will be described in more detail below. If the spacing exceeds acceptable limits, the system responds with an error signal, which is indicated by 903 . The error signal can be an audible and/or visual signal or the like. In an arrangement which will be described in more detail below, the control subsystem includes a user panel adapted to display the status of the machine and to notify of any error conditions. Preferably, the logic system remains in an error state and prevents further operation of the machine until the correct blade-to-pawl spacing is detected.

If the blade-to-pawl spacing is acceptable, the logic system determines whether the input signal generated by the detection subsystem 22 on the charge plate 44 is detected to have a sufficient amplitude on the charge plate 46, which is determined by 904. sign. This step ensures that the reaction subsystem will not be falsely triggered at start-up due to errors in the detection subsystem grounding saw blades, incorrectly placed charging plate positions, etc. If the correct input signal is not detected, the logic controller 50 responds with an error signal 903 . It will be appreciated that each error condition may generate either the same or a different error signal.

If the correct input signal is detected, the logic controller further determines whether a fusible member is present, represented by step 905 . The presence of a fusible member may be determined by any suitable means, as described in more detail below. If no fusible member is present, logic controller 50 returns an error signal 903 . If a fusible member is detected, the logic controller then checks the stored charge of the firing subsystem 76 , which is represented by 906 . This step ensures that if a hazardous condition is detected, there will be sufficient charge to melt the fusible member. An example circuit for detecting sufficient charge is described in more detail below. If sufficient charge is not detected within a predetermined time, the logic controller responds with an error signal 903 .

In the sequence shown in Figure 118, the logic controller 50 allows the motor assembly 16 to be powered on after the predetermined checks are complete. This sign is at 907. It will be appreciated that the electrical sequence described above typically completes in no more than a few seconds if no errors are detected. Logic controller 50 may be designed to perform various checks during operation, other than the initial power-up procedure. For example, the rotation of the saw blade can be monitored by known mechanisms and the firing system stopped when the saw blade is not moving. This allows the user to access the saw blade without engaging the brake mechanism 28 when the saw blade is stopped. Example arrangements and implementations of various blade detection systems are described in Section 10 below.

It will be appreciated that many variations of the above logical sequence may be implemented. For example, some devices of the logic controller 50 may include a battery, a capacitor or other charge storage device to ensure that the detection and response subsystem will continue to function, at least temporarily, after machine power is turned off. As another example, power to the motor assembly may be turned off when an error occurs, which may not be a contact detection error like incorrect saw blade to charging plate spacing, insufficient charge on the charge storage, etc. As such, logic controller 50 may be implemented to provide any of a variety of safety and/or operational functions as desired.

In addition, since the reaction subsystem 24 is designed to stop the cutting tool 14 upon contact with the user's body, it may also be desirable to stop the motor assembly 16, or at least the portion of the motor adapted to drive the cutting tool, to prevent the motor from being driven while the drive is blocked. Damage to the motor while cutting the tool. However, because the machine 10 is generally designed to allow for the possibility that the cutting tool may stop due to galling or the like, it is usually sufficient to shut down the motor for a few seconds. This can be accomplished by simply cutting off power to the motor. For example, when machine 10 includes a magnetic contact switch 48, the logic controller may be used to interrupt the circuit that holds the magnetic switch closed to interrupt power to the motor. It will be appreciated that this step is optional, where interruption of power to the machine motor is neither necessary nor sufficient to prevent serious injury to the user should the user come into contact with the machine cutting tool. Therefore, the primary benefit of this step is to reduce the potential for damage to the motor assembly or drive system when the braking system prevents the cutting tool from turning or otherwise moving. It will be appreciated that there are many other suitable ways of stopping the motor assembly 12 . As an example, power to the motor assembly may be directly controlled by the safety brake 30 (ie, via a solid state on/off switch, etc.). This device has been described in detail in Section 1 above. It is also possible to simply let the existing overload circuit take over and shut down the blocked motor.

Since the contact detection subsystem described above relies on certain electrical characteristics of the human body, use of the safety system 18 when cutting certain materials, such as film-covered insulators, can cause the detection circuit to falsely detect contact with the user. Furthermore, as described in Section 1 above, very green wood may cause certain kinds of detection and false triggering of the system due to its relatively high dielectric constant. Accordingly, it is desirable to provide a manual bypass or override control to prevent brake operation during a particular cutting operation. A suitable override may include a mechanical switch between fusible member 70 and firing system 76 . Alternatively, the switch could be a single use switch. It is designed to reset itself after each use. As a further alternative, the safety system 18 may include sensors that operate in close proximity to detect the presence of film, green wood, etc., and automatically shut down the reactive subsystems. This alternative method saves the user from forgetting to stop and restart the brake system.

In any case, the override control can be designed in various ways depending on the application and the required level of security protection. For example, the override may be designed to pause (ie turn off) the machine if the user does not turn it on for a predetermined period of time (eg, 3, 5 or 10 seconds, etc.). This prevents the user from activating the override and subsequently getting confused and forgetting that the safety system has been disabled before starting to cut the workpiece. In some devices, it is desirable to allow the user to override errors caused by failed self-tests (eg, no fusible member, insufficient stored charge, missing or incorrect cartridge 80 installation, etc.). In other arrangements, the logic controller 50 may be designed to require the detection and response system to be operational before allowing the user to effect the override.

Generally, override controls are designed to reduce the possibility of user accidental activation. For example, an override switch may be located away from other operating switches and away from an area of machine 10 that a user may accidentally hit while using the machine. Alternatively or additionally, the override switch 48 may include a cover or similar obstacle that the user must remove or overcome before the switch is actuated. Those skilled in the art know such covered switches. As another additional safety consideration, the logic controller 50 can be designed to generate a visual and/or audible alarm or warning when the override is activated. Further, where the logic controller 50 is used to control the supply of power to the motor assembly 16, the logic controller can be designed to "pulse" the motor one or more times to warn the user that the blade is about to be shut off by the safety system. The case started. This will warn the user who mistakenly activates the override while in contact with the saw blade to move away from the saw blade quickly.

In consideration of the above, an alternative logic controller 50 device can be designed to implement the self-test and detection logic shown in Figures 119A-C. The main logical sequence, generally indicated at 910 in FIG. 119A , begins when machine 10 is connected to power source 20 for the first time, which is indicated at 912 . System integrity checks may include one or more of a variety of checks. These checks generally depend on the particular type and design of machine 10 . In this example arrangement, the system integrity check 912 includes testing the adequacy of the power source 20 (here a standard line power source) by any suitable means. Those skilled in the art know these ways. The system integrity check may also include driving a probe signal to the charging pad 44 and attempting to probe the signal on the charging pad 46 . Failure to detect the probe signal on the charging plate 46 can be indicative of several problems such as an electrical failure of the detection subsystem 22, a mislocated or grounded charging plate, a grounded saw blade, and the like. The example system integrity check 912 also includes a pawl-to-blade spacing check to ensure that the pawl 60 is properly positioned adjacent the blade 40 so that the pawl will engage and stop the blade when released. An example mechanism for detecting the correct blade-to-pawl spacing is described in more detail below. If any of the checks performed during the system integrity check 912 are negative, the logic controller turns off the motor assembly (if it is on), as shown at 913, and outputs an error signal to the user, as shown at 914 Show. This system integrity check will be repeated once the user corrects the error and resets the logic controller (e.g., by turning off and then back on power to the machine 10).

If the system integrity check is successful, the logic controller 50 proceeds forward to check the fusible member 70 and the charge stored in the firing subsystem 76 , indicated at 915 . If the fusible member or stored charge ratio check is negative, the logic controller shuts down the motor assembly, indicated at 913 , and then outputs an error signal, indicated at 914 . It may be desirable to repeat step 915 one or more times, or to provide a delay between steps 912 and 915 to ensure that the transmit subsystem 76 has sufficient time to build up charge.

If the checks of both the fusible member and the firing subsystem are successful, the logic controller continues with one of two operating cycles. This depends on whether the user-operable override switch has been activated, as indicated at 916. It will be appreciated that after the fusible member/charge storage check is performed, checking the user override signal prevents the user from overriding the security system 18 unless the security system is active. Thus, for example, if a contact detection occurs and the brake is triggered, the user cannot continue to operate the system until the fusible member, and/or the pawl; and/or the firing subsystem, etc. are replaced (usually by replacing the cartridge 80) . Alternatively, step 915 can be eliminated from the main operating loop. This will allow the machine 10 to be operated without regard to whether the safety system 18 is fully functional by implementing the override.

In any case, if an override is enabled, the logic controller 50 continues to operate in an override cycle, indicated at 917 and illustrated in more detail in FIG. 119B. Typically, the logic controller 50 first outputs a warning signal, as shown at 918 and described above. Next, at step 919, the logic controller checks the state of the "start" switch 48, which is user operable. to open the motor assembly 16. As noted above, the logic controller can be designed so that the "enable" switch reads the "on" state only if the switch is activated within a predetermined period after the override is activated. If, the "Start" switch is in the "OFF" state, the logic controller 50 turns off the motor assembly (if in the ON state), as shown at 920, and exits the override loop shown at 921. As shown in Figure 119A, the logic controller returns to the system integrity check at the end of the override loop. Thus, the logic controller will continue to perform system integrity checks and fusible member/stored charge tests until the "enable" switch is activated. This ensures that if a user initiates the override and then delays activation of the "Enable" switch, the system will not turn on if a fault occurs between the time the override is activated and the "Enable" switch is activated motor assembly.

If at step 919 the "start" switch is on, the logic controller proceeds to turn on the motor assembly 16 as shown at 922 . The motor assembly remains on until the "stop" switch 48 is activated by the user, which is indicated at 923 . Once the "Stop" switch is activated, the logic controller 50 turns off the motor assembly, as shown at 920 . And the override loop at 921 is exited. As described above, the logic controller returns to step 912 after exiting the override loop.

If the override has not been activated by the user in step 916 the logic controller 50 proceeds to the detection loop 925, which is illustrated in detail in FIG. 119C. In this example device, the detection loop 925 is depicted as consisting of two concurrently executing logic paths. In the first path 926 , the logic controller monitors the detection subsystem 22 while in the second path, the logic controller continues to recheck the fusible member and the stored charge of the emission subsystem 76 . This two-track operation ensures that the machine 10 is stopped if a fault occurs while the saw blade is running. Those skilled in the art will appreciate that this dual silicon operation can be accomplished in a variety of different ways, including using interrupts and the like. Alternatively, both paths can be implemented in a single sequence loop. However, since checking the stored charge can take milliseconds or even seconds in some devices, in those devices it is often desirable to perform both paths simultaneously so as not to require several milliseconds or longer between successive contact detection measurements. time.

Path 927 includes testing the charge stored by emitting subsystem 76 of fusible member 70 , indicated at 928 . This test is repeated continuously until either the fusible member test or the stored charge test fails. At this point the logic controller 50 turns off the motor assembly, indicated by 929 , and outputs an error signal, indicated by 930 . The logic controller also stops executing test 928 when it exits the probing loop or when an error occurs at path 926, which is described below. The testing of fusible member 70 and firing subsystem 76 may be the same as or different from the testing of the main loop at step 915 . In any event, the logic controller must be reset from step 930 as described above.

Path 926 is the contact detection path and includes the excessive resistive loading on the test saw blade, which is indicated by 931 . Step 931 ensures that power will not be supplied to the motor assembly if the capacitive loading on the blade is too high for the detection subsystem to detect contact between the user and the blade. This can happen for a variety of reasons. For example, if the blade is cutting a material with a high dielectric constant (such as green wood), the capacitive load on the blade will increase. This problem has been explained in detail in Section 1 above.

As another example, a user may accidentally actuate a "start" switch while in contact with the saw blade. Since some example detection subsystems rely on sudden changes in the signal (also not absolute voltage) on the charging plate 46, step 931 ensures that the safety system will not allow the saw blade to start spinning if the user is contact with the saw blade. In this arrangement, the logic controller is designed to set the excessive capacitive loading at a level approximately at least the amount of loading due to user contact with the saw blade. However, it will be appreciated that logic controller 50 may be designed to recognize that any desired amount of capacitive loading is excessive.

If the capacitive load on the saw blade is too high, the logic controller 50 outputs an error signal at 932 and turns off the motor assembly 16 (if it is on), which is represented by step 933 . The logic controller then exits the probing loop at 934 and returns to the system integrity check 912 in the main operating loop shown in FIG. 119A . It will be appreciated that the safety system 18 will not be activated during the few seconds that it stalls the saw blade. This is because the capacitive loading is too high to accurately detect contact with the user, and is likely to trigger even if no contact occurs. In an alternative arrangement, the logic controller may continue to monitor for contact detection during blade rotation and activate the firing system if contact is detected. Alternatively, the logic controller can be designed to activate the launch system if the load becomes too high.

If in step 931 the capacitive load on the saw blade is within the defined range, the logic controller proceeds forward to test the contact detection signal from the detection subsystem 22 , which is shown at 935 . If contact is detected, the logic controller determines whether the blade is rotating, as indicated by 936 . If the saw blade is spinning, the logic controller activates the firing subsystem at 937 , turns off the motor assembly 16 at 929 , and inputs an error signal at 930 . The logic controller must then be reset again as described above.

However, if the saw blade is not rotating at step 936, the logic controller outputs an error signal at step 932, turns off the motor assembly at 933 (if it was on), and exits the detection loop at 934. Thus, if a user touches the saw blade while it is rotating, the safety system will detect the contact but will not activate the firing subsystem. This allows the user to change or adjust the blade without activating the brakes. However, the user will typically cut off power to the machine 10 before adjusting or replacing the saw blade. In such a situation, neither safety system 18 nor motor assembly 16 will be operational.

If no contact is detected at step 935 , the logic controller 50 checks the state of the “start” switch 48 , which is shown at 938 . If the "stop" switch is activated, the logic controller turns off the motor assembly (if it is on), which is indicated by 939, and checks the rotation of the saw blade, which is indicated by 940. If the saw blade is rotating, the logic controller returns to step 931 so that contact detection remains enabled as long as the saw blade continues to rotate. Thus, if the user activates the "stop" switch and then touches the saw blade before it stalls, the safety system 18 will react to stop the saw blade. The logic controller exits the detection loop, indicated by 934, once the saw blade has stopped turning.

If at step 938 "stop" starts not being activated. The logic controller checks the state of the "start" switch 48, which is indicated by 941. If the "start" switch has been activated, the logic controller turns on the motor assembly (if it is off), and returns to contact detection, which is indicated by 942 . If the "start" switch is not activated, the logic controller turns off the motor assembly (if it is on), which is shown at 939, and checks at 940 for rotation of the saw blade. The logic controller continues to execute the detection loop until the saw blade stops, at which point the logic controller exits the detection loop, indicated by 934 . Thus, the logic controller is designed to continue to monitor contact detection as long as the saw blade is still rotating and the user has not initiated an override.

Those skilled in the art will appreciate that control subsystem 26 and logic controller 50 may be implemented in many different components and in different designs. Therefore, while the following two exemplary devices are described, it should be understood that other suitable embodiments may also be used.

Figure 120 shows a first example device. Logic controller 50 takes the form of a PIC16C63A--20/so controller available from Microchip Technology, Inc. of Chandler, Arizona. The logic controller is connected to the power supply 20, the contact detection subsystem 22, and a user interface board 178. The user panel may include any suitable mechanism for displaying signals to the user and allowing the user to input signals to the logic controller. Examples of suitable user plane mechanisms known to those skilled in the art then include lights, displays, buzzers, alarms, switches, buttons, handles and the like. In an example device shown in FIG. 121, the user panel 178 includes start, stop and override switches to allow the user to enter control commands, and includes a pair of LEDs to indicate system status. The LEDs can be used in various ways to indicate system status, such as by color, blinking, etc.

The logic controller is also connected to the launch subsystem 76 and to the motor control assembly 16 through a suitable motor control circuit 174 . This circuit is described in detail in Section 1 above. When the logic controller receives a signal from the detection subsystem 22 indicating that user contact with the saw blade has occurred, the logic controller activates the firing subsystem 76 and stops the motor assembly 16 . The sequence of operations and tests is implemented by stored software instructions and executed by a logic controller. It will be appreciated that software instructions may take a variety of different forms.

The exemplary implementation of the logic controller shown in Figure 120 is designed to perform various self-tests prior to activating power to the motor control 174 and whenever the saw blade is rotating. For example, the logic controller is designed to evaluate the line voltage provided by the power supply 20 and shut down the motor when the voltage drops below a minimum value sufficient to operate the safety system. The logic controller is also used to test the touch sense signal from the detection subsystem to ensure that the charging plate is positioned correctly, that the detection signal is properly coupled through the saw blade, and that the capacitive load on the blade is within limits, Further, the logic controller can also be connected to a saw blade rotation sensing element 177 . An example of a suitable mechanism for detecting blade rotation is described in Section 10 below.

In addition, the logic controller 50 can also be used to detect whether the firing subsystem 76 has sufficient stored charge to melt the fusible member 70 . It will be appreciated that sufficient storage of charge on the detect-emit subsystem can be achieved in a variety of different ways. These methods depend on the design of the launch system. In each of the embodiments described herein, transmit subsystem 76 includes a single 390 uF transmit capacitor 620 . The capacitor is designed to be discharged through the fusible member 70 by a suitable grounded thyristor SCR 621 . An example of the transmit subsystem 76 is described in detail in Section 6 above.

In the arrangement shown in Figure 120, the launch capacitor is charged and tested by a jump boost regulator 175. The skip boost regulator is shown in more detail in Figure 122. Skip boost regulator 175 includes a skip boost charger 183 that boosts a 32 volt supply input to 180 volts to charge the transmit capacitor. The logic controller 50 provides a 125KHz input to control the skip boost cycle of the charger. A voltage regulator circuit 184 monitors the voltage on the transmit capacitor and switches the charger 183 on and off as necessary to keep the charger near 180 volts. The regulator circuit 184 is made with a predetermined amount of hysteresis so that the charger will turn on when the transmitter circuit voltage drops below 175 volts, and turn off the charger when the voltage reaches 180 volts, which is determined by the voltage divider input and to set by the feedback from comparator 185.

The output of comparator 185 is sent to logic controller 50 . The logic controller monitors the time required for charging and the discharge time of the emission capacitor by the output state of the comparator 185 . In this way, the controller can verify that the emitter capacitor is functioning properly and storing an appropriate charge. If the launch capacitor cannot reach 180 volts quickly enough or discharge quickly enough, the logic controller determines that the launch capacitor or the charging system is faulty and programs appropriate action based on it.

It should be noted that the voltage stabilizing circuit 184 measures the voltage across the firing capacitor through the fusible member 70 . As a result, the voltage regulator circuit also tests the integrity of the fusible member. This is because a missing or failed fusible element will prevent the voltage regulator circuit from detecting the voltage on the transmit capacitor. While utilizing a single mechanism or test to check the charge of the firing capacitor and the fusible member clearly provides savings in process cycle time and component cost, the fusible member may additionally be tested separately from the firing capacitor voltage.

FIG. 123 schematically illustrates a second exemplary implementation of the logic controller 50 . Logic controller 50 was made from an 87C752 controller obtained from Philips Semiconductor of Sunnyvale, California. The logic controller of the second device is connected to the power supply 20, contact detection subsystem 22, transmitter subsystem 76, user panel 178, motor control 174, and blade rotation sensor 177 as described above for the first example device. Examples of suitable power supply 20, contact detection subsystem 22, and motor control 174 are described in Section 6 above. An example circuit and mechanism for sensing blade rotation is described in Section 10 below.

The launch capacitor charging circuit of the second device is regulated by the enable line from the logic controller 50 as shown in FIG. 124 . By stopping the charging circuit, the logic controller can monitor the capacitor voltage through an output of an analog-to-digital converter (A/D) going to it. When a capacitor is not charged, it will normally discharge at a relatively known rate through various paths to ground. By monitoring the rate of discharge, the controller can ensure that the capacitance of the capacitor is sufficient to melt the fusible member. Alternatively, the logic controller can be designed to measure the voltage across the firing capacitor over a complex number of discharge intervals to assess the integrity of the capacitor. In one arrangement, the logic controller measures the capacitor voltage at three defined intervals during the discharge cycle. These three intervals should correspond to 3%, 5% and 7% of the full charge voltage. The logic controller can be designed to interpret a low voltage as a failure during any discharge interval.

When used with the first example device described above, the logic controller is designed to test the emission capacitance through the fusible member 70, thereby simultaneously testing the fusible member. Alternatively or additionally, the logic controller may test the fusible member independently of the capacitance by monitoring the capacitance voltage during charging.

As mentioned above, the logic controller 50 can also be designed to monitor the pawl-to-blade spacing. It is well known in the art that many cutting tools, such as saw blades, do not have precisely consistent dimensions. As a result, when a new saw blade is installed in the chainsaw, the pawl may no longer be properly separated from the saw blade. An incorrectly positioned pawl can slow down the pawl's braking speed or prevent the pawl from stopping the blade. Therefore, it may be necessary to adjust the position of the pawl whenever the blade is renewed in order to ensure that the blade is braked at an even braking speed. Exemplary mechanisms and methods for automatically positioning the peace jaws have been described in Section 8 above. However, whether or not the pawl is automatically positioned, designing the controller 50 to detect incorrect blade-to-pawl spacing provides an additional level of assurance that protects the user from accidental contact with the saw blade.

It should be appreciated that there are many ways to detect incorrect spacing between the saw blade 40 and the pawl 60 . As an example, Figure 125 illustrates a pawl 945 with a capacitive system for detecting the correct pawl spacing. Similar to pawl 40 shown in FIG. 2, pawl 945 may include a member 946 that is beveled or otherwise shaped to quickly and completely engage the saw teeth of a cutting tool. Additionally, pawl 945 includes a pair of generally parallel, spaced apart cantilevered arms 947 . The cantilever extends through member 946 . The cantilever 947 is arranged to extend to either side of the saw blade without contacting the saw blade when the pawl is positioned adjacent to the saw blade. Each arm includes a capacitive plate 826 arranged on the inner surface of the arm adjacent the saw blade. Conductive wires 949 lead from each capacitive plate 826 to appropriate blade detector circuitry (not shown).

Capacitive plate 826 is positioned on cantilever 947 . Thus, when the distance between the pawls is within a desired range, the saw blade extends from between the two capacitor plates. It should be appreciated that the capacitance across the plates 826 will vary depending on whether the saw blade is positioned between the plates. The saw blade detector circuit is designed to drive an electrical signal through the conductive wire 947 and detect changes in capacitance between the plates.

Suitable circuitry for use with detent 945 is known to those skilled in the art. Figure 126, at 824, shows an example of a pawl-to-blade distance detection circuit. As described in Sections 1 and 2 above, an example contact detection system suitable for use with this patent applies an electrical signal to the saw blade through a driver board (not shown). The signal can be picked up by either or both plates 826 and monitored to ensure that the signal amplitude is within a predetermined range. In particular, the amplitude detected by the plate 826 will drop off rapidly with distance from the saw blade. Therefore, by monitoring the detected amplitude, proper spacing can be confirmed. If the proper signal is not detected, the circuit 824 transmits an error signal to the logic controller 50 to prevent operation of the machine 10 until the proper pawl-to-blade spacing is detected. Other examples include circuits similar to the example contact detection circuit described in Section 1.

Capacitive plate 826 can be selectively shaped to detect when the pawl is too close to the blade and when it is not close enough. Alternatively, two pairs of capacitive plates could be positioned on the pawl; one pair to detect if the pawl is too close to the blade; and another pair to detect if the pawl is too far away from the blade. In any case, the detection circuit is designed to send an error signal to the logic controller 50 . The controller then takes appropriate action.

While one example of an automatic pawl spacing detection system has been described above, it will be appreciated that many variations are possible. For example, both capacitive plates could be positioned on the same side of the saw blade rather than on opposite sides. The capacitive plate and/or the blade detection circuit may be separated by the pawl, in which case, for example, the capacitive plate and the detection circuit may be mounted on a separate circuit board associated with the pawl. Alternatively, the capacitive plate could be replaced by one or more LEDs and detectors, such that when the pawl is properly positioned, the saw blade blocks the light path between the diodes and detectors. Other methods for detecting the proximity of the saw blade and pawl are possible. As a further option, capacitive plates 826 may function as charging plates 44, 46 as well as pawl spacing detectors. Additionally, a detection plate may be mounted on the chamfered surface 946 of the pawl. The board can be used to detect drive input signals for contacts. The amplitude of the signal detected by the pole plate will be inversely proportional to the distance between the pole plate of the pole plate and the teeth of the saw blade. If this signal does not have an amplitude above a given threshold, the system interprets this as indicating that the pawl face is not close enough to the blade.

In installations where a portion of the security system 18 is installed in a replaceable cartridge 80, the logic controller may also be designed to detect whether the cartridge is properly connected to the remainder of the security system. One exemplary method of testing a viable connection to the cartridge is by inspecting a component mounted on the cartridge (eg, fusible link, charge stored by the launch system, etc.). Alternatively, a cable (not shown) connecting the cartridge 80 to the logic controller 50 may include a separate signal line. This signal line is grounded or biased when connected to the cartridge. In addition to detecting a viable connection to the cassette, the correct blade-to-pawl spacing can be detected by measuring the blade-to-cassette spacing. For example, capacitive plate 826 could be placed on cartridge housing 82 rather than on the pawl itself. Further, a failed blade-to-cassette distance test may also be used to detect an infeasible connection to the cassette.

The control system, method and associated machine may be described in the numbered paragraphs of the following declaration. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

9.1. A woodworking machine consists of:

a machined part;

A detection system suitable for detecting dangerous situations between the detection person and the processing part;

A response system associated with the detection system to cause a predetermined action to occur when a hazardous situation is detected;

And, a control system for operability of one or more process components, detection systems, and reaction systems.

9.1.1. The woodworking machine of paragraph 9.1, wherein the control system is used to control the one or more machining components, the detection system, and the response system operability by processing one or more data from the response system.

9.1.2. The woodworking machine of paragraph 9.1, where the control system is adapted to perform on-machine self-tests.

9.1.3. The woodworking machine of paragraph 9.1, where the control system is used to determine whether the detection system is operative.

9.1.4. The woodworking machine of paragraph 9.1, where the control system is used to determine whether the reaction system is operating.

9.1.5. The woodworking machine of paragraph 9.1, wherein the reaction system includes a capacitor, and wherein the control system is adapted to conduct a self-test to determine whether the capacitor is functioning.

9.1.6. The woodworking machine of paragraph 9.1, wherein the reaction system includes a fusible member, and wherein the control system is adapted to perform a self-test to determine whether the fusible member is functioning.

9.1.7. The woodworking machine of paragraph 9.1, where the detection system notifies the machining component of an electrical signal, and where the control system is adapted to effectively monitor that electrical signal.

9.1.8. The woodworking machine of paragraph 9.1, wherein the control system is adapted to prevent accidental triggering of the reaction system.

9.1.9. The woodworking machine of paragraph 9.1, where the control system is adapted to control the display device related to machine functions.

9.1.10. The woodworking machine of paragraph 9.1, wherein the machining member is driven by a motor, and wherein the control system is adapted to control the motor.

9.1.11. The woodworking machine of paragraph 9.1, where the machining member includes a saw blade, the response system includes a brake pawl for contacting the saw blade and positioned adjacent to the saw blade, and for monitoring the relative Control system for saw blade position.

9.1.12. The woodworking machine of paragraph 9.1 further includes a frame supporting a machining component, where the machining component includes a conductive cutting tool electrically insulated from the frame, a detection system for transmitting electrical signals to the conductive cutting tool, and a Monitors whether electrical signals are sent to the control system of the conductive cutting tool.

9.1.13. The woodworking machine of paragraph 9.1, where the reaction system includes a firing subsystem that triggers a predetermined action, the firing subsystem includes a fusible member, and the control system checks that the fusible member is in place.

9.1.14. The woodworking machine of paragraph 9.1, where the reaction system includes a firing subsystem that triggers a predetermined action, the firing subsystem is used to check the charge, and the control system checks whether the firing system is holding the charge.

9.1.15. The woodworking machine of paragraph 9.1, where the control system repeatedly checks the operability of one or more machining components, detection systems, and response systems while the machine is running.

9.1.16. The woodworking machine of paragraph 9.1, where the control system includes a microprocessor.

9.1.17. The woodworking machine of paragraph 9.1, where the control system allows the user to bypass the reaction system.

9.1.18. The woodworking machine of paragraph 9.1 further includes a frame supporting a machining component, where the machining component includes a conductive cutting tool electrically insulated from the frame, a detection system for transmitting electrical signals to the conductive cutting tool, and a A control system that monitors whether a transmitted signal within a certain range produces a detection signal.

9.2. A chainsaw consisting of:

a saw blade;

a detection system adapted to detect dangerous conditions between the person and the saw blade;

a response system associated with a detection system to cause a predetermined action to occur when a hazardous situation is detected;

and a control system adapted to monitor and control the detection and reaction system.

9.3. A method of controlling a chainsaw, wherein the chainsaw includes a saw blade driven by a motor, a system adapted to detect a dangerous condition between a person and the saw blade, and a response system associated with the detection system upon detecting The method of causing a predetermined action to occur when a hazardous situation occurs includes:

Check that the detection system works;

Check that the reaction system works;

And, if the detection and response system is active, the motor driving the saw blade is activated. Chapter 10: Motion Detection

As mentioned above, the safety system 18 may include a sensor or sensor assembly for detecting movement of the saw blade or cutting tool. The sensor assembly is typically connected to send a signal to the logic controller 50 indicating whether the saw blade is moving, which logic controller can be designed to react differently to the detected hazardous condition depending on whether the saw blade is moving. For example, a user of machine 10 often needs to access saw blade 40 in preparation for use of the machine and when installing or removing the saw blade. Typically, the user will disconnect all power sources to the machine 10 while performing such operations. However, in the event that the user neglects to disconnect the machine from the power source before contacting the saw blade, the logic controller 50 will receive a contact detection signal from the detection subsystem 22 . If the system 18 includes a blade motion sensor, the logic controller 50 can be programmed not to activate the firing subsystem 76 when the blade is not in motion. Instead, the logic controller may be programmed to take one or more other actions, which may be stopping the motor assembly 16, sounding an alarm, displaying an error, and the like. Alternatively, the logic controller can be designed to take no action when contact is detected when the saw blade is not moving.

In addition to detecting whether the saw blade is moving, the safety system 18 can also be designed to determine at which speed the saw blade is moving. This allows the logic controller to distinguish between fast blade motions that could cause injury to the user, and slow blade motions that would not normally cause injury to the user. For example, a user may manually move the saw blade without activating the firing subsystem 76 . In some arrangements, the logic controller 50 may be designed to analyze the signal from the blade motion sensor to determine the relative speed of the blade.

It will be appreciated that the blade speed at which injury is considered likely will vary depending on the type of machine 10 and blade 40 . For example, a 14" charred tooth blade on a table saw can cause more damage at low speed than a 5 3/8" glued blade on a chop saw. Thus, the arrangement of the safety system 18 used on a table saw can be designed to activate the firing subsystem only when the saw blade speed is above about 10, 25, 60 or 90 rpm. Yet another device for the safety system 18 on a chop saw can be designed to only activate when the blade speed is above about 40, 100 or 240 rpm.

Alternatively or additionally, the logic controller may be designed to only interpret saw blade rotation detected during or immediately after motor assembly 16 operation as dangerous, in other words, the saw blade motion detection will only be detected during The saw blade is driven by the motor assembly and is only active for a relatively brief period after the saw blade begins to stop turning. Any blade movement detected at other times will be ignored.

Safety system 18 may include any of a number of sensor assemblies to detect movement of the saw blade. Further, each sensor assembly may be modified as desired depending on the particular type of saw blade 40 and/or machine 10 design. Although several example sensor assemblies are described herein, it will be appreciated that various other methods and mechanisms may be adapted to automatically detect movement of the saw blade.

An example arrangement of the safety system 18 includes a magnetic sensing assembly 1000 designed to detect movement of the saw blade. It will be appreciated that movement of the saw blade may be detected by any other component of the safety system monitoring the movement of the saw blade or with the saw blade. These components include cutter shafts, bearings, motor assemblies, cutter shaft pulleys, etc. In the example device depicted in FIG. A coil can also be used to detect the magnetic field being rotated and deflected by the rotation. The magnet is fixed on the cutter shaft. The sensor 1001 is mounted and designed to detect the movement of the saw blade by detecting the movement of the magnet on the knife shaft. Sensor 1001 may be any suitable Hall effect sensor, such as, for example, the sensor available from Micron Intermatall of San Jose, California, product no. HAL114.

Hall effect sensor 1001 may be mounted in the vicinity of the tool axis by any suitable method. In the example device, the sensor is mounted in a recessed area 272 of an insulating tube 268 . The insulating tube also supports charging plates 44 and 46 . This is described in more detail in Section 2 above. The recessed area is aligned with the aperture 273 on the charging plate 44 . Alternatively, the recessed area can be aligned on the charging plate 46 with the aperture 273 . In any event, the magnets 1002 are aligned above the shaft 42 so that the magnets pass through adjacent apertures 273 as the shaft rotates in the insulating tube. Aperture 273 allows sensor 1001 to detect the magnetic field generated as it passes magnet 1002 . Sensor 1001 includes one or more connectors. These connectors allow the 1003 to connectably receive power from the logic controller and send signals to the logic controller.

The magnet 1002 may be mounted on the arbor in any suitable manner. Typically, the magnet is fixed to extend across the surface of the arbor. For example, the magnet may be press fit and/or glued to a recess on the shaft. Alternatively, one or more magnets may be fixed extending across the surface of the arbor. The size and number of magnets 1002 can be varied to control the signal generated by sensor 1001 . In an alternative arrangement, the magnet 1002 can be fixed at other locations, such as adjacent to the end of the shaft 42, or on the blade 40, etc. FIG.

Sensor 1001 may be connected to transmit signals to logic controller 50 through any suitable circuitry. For example, FIG. 128 shows an example rotation sensor circuit 177 suitable for coupling the signal from the sensor 1001 to the logic controller 50. Those skilled in the art will appreciate that circuit 177 may be modified as desired for a particular application.

Another example of a suitable method for detecting the movement of the saw blade is by electromagnetic field (EMF) measurement. As those of you who are technically savvy know, when power to a motor is cut off, the motor spins down and produces an EMF pulse on the incoming power line. Thus, where the saw blade 40 is driven by an electric motor assembly 16, as long as an EMF pulse is detected on the power supply line and power is supplied to the motor assembly, the saw blade can be considered to be rotating.

Thus, in another example arrangement shown in FIG. 129 , the security system 18 includes an EMF sensor 1005 . The sensor is designed to detect the movement of the saw blade. The sensor assembly 1005 includes an EMF detection circuit 1006 placed in the power supply path between the motor assembly 16 and the power supply 20 . Circuitry 1006 is adapted to monitor supply lines 1007 located on the power supply and motor assembly and to detect the presence of EMF pulses on the supply lines. Alternatively, the circuit 1006 may be placed at any suitable location for detecting EMF pulses from the motor assembly 16 . Circuit 1006 may be any circuit or mechanism for detecting EMF pulses, such as is known to those skilled in the art. The circuit 1006 is also connected to the logic controller 50 and is adapted to transmit a signal to the logic controller indicating whether an EMF pulse is present on the cable 1007 or not. Optionally, the circuit 1006 and/or the logic controller 50 may be adapted to analyze the detected EMF radiation and evaluate the speed of the saw blade 40 . In this case, the logic controller can be programmed to not activate the firing subsystem 76 at times when the blade speed is unlikely to cause serious injury to the user.

In another example arrangement, safety system 18 includes an electrical sensor assembly adapted to electrically detect movement of saw blade 40 . The safety system 18 can be designed to optically detect blade motion in a variety of ways. For example, a rotary optical encoder may be coupled to the shaft to detect rotation of the shaft. Any rotary encoder may be used, such as those available from Omron Electronics Inc. of Schaumburg, Illinois. Additionally, other optical sensor assemblies may also be used, as described below.

Typically, the optical sensor assembly will be at least partially covered to prevent sawdust or other debris from obstructing detection. An example arrangement of a light sensor assembly is shown at 1010 in FIG. 130 . The sensor assembly 1010 includes an optical sensor 1011 adapted to detect light from a light source 1012 . Alternatively, multiple light sources and/or optical sensors may be used. Those skilled in the art know that any of a variety of light sources can be used, including an incandescent or fluorescent, etc., light emitting diode (LED), laser diode, etc. Similarly, any of a variety of different optical detectors known to those skilled in the art may be used, including photodiodes, phototransistors, and the like.

In any case, the light source is arranged in such a way that the signal received by the light detector is different when the saw blade is rotating or not. For example, the light sources and detectors may be arranged to receive signals only when the saw blade is moving or only when the saw blade is stationary. Alternatively, the light source 1012 and detector 1011 may be arranged such that the amount of light radiation reaching the detector varies as the saw blade moves.

The device shown in Figure 130 utilizes this latter arrangement. The sensor assembly 1010 includes an LED 1012 fixed within the insulating tube 268 to emit light to the charging pad 44 or 46 through the aperture 273 . The light is reflected off the axis of the knife and detected by a photodiode 1011 also mounted within the insulating tube 268 near the aperture 273 . The knife axis includes one or more reflection reducing regions 1013 adapted to reduce the amount of light radiation reflected to the photodiode 1011. The area 1013 can be formed by covering the knife axis with a light absorbing film, making the knife axis rough to cause diffuse reflection of light, etc. In any event, the reduced reflection area produces a varying signal on the photodiode as the tool axis rotates. On the contrary, when the tool shaft is stationary, the photodiode produces a fixed signal.

The minimum spacing between the knife shaft 42 and the charging plates 44, 46 tends to maintain the knife shaft and photodiode/LED spacing so that debris does not obscure the signal. Alternatively, the insulating tube assembly may be enclosed within a protective enclosure (not shown).

In another alternative arrangement shown in FIGS. 131 and 132 , the light sensor assembly 1010 includes a blocking member 1014 fixed to the knife shaft and placed between the photodiode 1011 and the LED 1012 . Alternatively, the blocking member could be affixed anywhere on the cutting tool 14 or on the motor assembly 16 for rotation with the saw blade. The blocking member 1014 includes one or more light emitting regions or apertures 1015 . The aperture can take any desired form or size. The photodiode and light emitting diode LED are fixed in a support member 16 attached to the arbor unit 250 and placed on either side of the blocking member 1014 . The light emitting diodes are aligned to pass light through the aperture 1015 and likewise the photodiodes are aligned to detect light passing through the aperture 1015 . Thus, as the knife shaft 42 rotates, the light blocking member from the LED is alternately blocked and passed, thereby producing a changing signal on the photodiode.

The photodiode 1011 and light emitting diode LED 1012 may be connected to any suitable driving circuit. As known to those skilled in the art. Figure 133 shows an example circuit for generating a light signal at LED1012. Specific values of circuit elements and voltage sources may be selected for a particular application. In any event, the photodiode is connected to transmit a signal to the logic controller 50 indicating whether the saw blade 40 is moving.

In another example arrangement, the safety system 18 includes an electrical sensing assembly adapted to electrically detect movement of the saw blade 40 . There are numerous ways and mechanisms for electrically detecting saw blade motion. The particular method and/or mechanism chosen will generally depend on the particular type and design of machine 10 . For example, where the charging plate 46 is designed to capacitively detect a signal induced on the saw blade, any accidental saw blade thickness unevenness or saw blade rotation will cause the capacitance between the saw blade and the charging plate 46 to change between the saw blade and the saw blade. time-varying. As a result, the charging plate 46 will detect a varying signal amplitude as the saw blade rotates. Thus, a signal sensor can be designed to detect contact with the user as well as rotation of the saw blade. Preferably, occasional changes are not sufficient in magnitude and/or rate of change to trigger the response subsystem 24 .

Rather than relying on occasional uneven thicknesses, the safety system 18 may include an exemplary sensing assembly adapted to detect a signal change due to an engineered saw blade thickness or non-uniformity. Alternatively, the sensing assembly is adapted to detect signals from regions of the cutting tool 14 that are produced by thickness irregularities. These areas rotate with the saw blade and are electrically connected to the saw blade. Figure 134 shows an example arrangement of such a sensor assembly. The sensing assembly 1020 includes a detection electrode 1021 capacitively coupled to detect an electrical signal on the knife shaft 42 . Electrode 1021 may be secured in any suitable manner to provide electrical isolation from arbor 42 and other portions of cutting tool 14 and machine 10 . In this example arrangement, electrode 1021 is secured within insulating tube 268 and is arranged to extend to a point between charging plates 44 and 46 near the axis of the knife. Sensing assembly 1020 also includes one or more regions of uneven thickness 1022 . These regions are aligned on the axis of the blade and are sufficiently aligned with the electrode 1021 to pass the electrode as the axis of the blade rotates.

It will be appreciated that the uneven thickness region 1022 can be designed in any desired number, size, shape or form suitable for causing a change in the capacitance between the blade shaft and the electrode when the blade shaft rotates. In this example device, the non-uniform region 1022 takes the form of a groove formed in the surface of the arbor 42 . Thus the distance between the electrode and the knife axis is greater (and therefore less capacitive) when the inhomogeneous region is under the electrode than when it is not. Alternatively, the non-uniform region 1022 can take any form suitable for changing the capacitance between the blade axis and the electrode, including raised regions, dielectric pads, and the like. In any event, if an electrical signal is induced on the shaft (eg, by contacting the charge plate 44 of the detection subsystem 22), if the shaft is rotating, the electrode 1021 will detect a change in that signal. Conversely, if the shaft is stationary, the electrode will not detect signal changes.

Attention is now turned to FIG. 135 , which shows another example arrangement of an electrical sensing assembly 1020 . Here, the electrodes 1021 are placed close to the teeth 1023 of the saw blade 40 . Electrode 1021 may be fixed on arbor unit 250 or any other suitable location on machine 10 . In addition, the electrodes can be positioned on the side of the saw blade (as shown in Figure 134), or on the outer edge of the saw blade facing the axis of the knife. The size, shape and position of the electrodes vary depending on the position and size of the serrations 1023 . In any event, when the sawtooth 1023 passes over the electrode 1021, the capacitance between the saw blade and the electrode changes, thereby changing the magnitude of the signal detected by the electrode. Alternatively, a plurality of electrodes can be placed at different points around the saw teeth so that the positive function of the saw blade is detected by modulation of the relative signal amplitudes on the electrodes. Such an alternative detection mechanism may also be used with other sensing assembly 30 arrangements.

While some examples of magnetic, EMF, optical and electrical sensing assemblies for detecting blade motion have been described, it will be appreciated that many modifications and variations of these sensing assemblies are possible. Still further, the security system 18 may include other types of motion detection sensors such as mechanical sensors, acoustic or ultrasonic sensors, and the like. In any event, the invention provides an efficient and reliable method of distinguishing which conditions can and which are unlikely to cause injury to a user of a powered machine.

The motion detection system, method and related machine may be described in the numbered paragraphs of the following declaration. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

10.1. A woodworking machine consisting of:

a machined part adapted to work while in motion;

a detection system suitable for detecting hazardous situations between persons and working parts;

A response system associated with a detection system that causes a predetermined action to occur when a hazardous situation is detected;

And, a motion detection system adapted to detect movement of the processing part and to deactivate the reaction system when the processing part is not moving.

10.1.1. The woodworking machine of paragraph 10.1, wherein the machining component is a rotating saw blade, and wherein the motion detection system detects whether the saw blade is rotating.

10.1.2. The woodworking machine of paragraph 10.1, wherein the motion detection system detects the velocity of the motion and considers the saw blade to be not rotating if the rotational speed of the saw blade is below a threshold speed.

10.1.3. The woodworking machine of paragraph 10.1, where the motion detection system includes a sensor.

10.1.3.1. The woodworking machine of paragraph 10.1.3, where the sensor is a Hall effect sensor.

10.1.3.2. The woodworking machine of paragraph 10.1.3, where the sensor is an electromagnetic field sensor.

10.1.3.3. The woodworking machine of paragraph 10.1.3, where the sensor is an optical sensor.

10.1.3.4. The woodworking machine of paragraph 10.1.3, where the sensor is an electrical sensor.

10.2. A woodworking machine consisting of:

a machined part adapted to work while in motion;

a motor to drive the machining part;

a detection system adapted to detect dangerous conditions between the person and the saw blade;

and a reaction system associated with the detection system that causes a predetermined action upon detection of a dangerous situation, where the reaction system causes the predetermined action only when the motor is running or within a defined time after the motor has been running. Chapter 11: Translation Braking

In miter saws, chop saws, radial arm saws, and other powered equipment in which the cutting tool moves down toward or through the workpiece to cut the workpiece, the reaction subsystem 24 can include a mechanism that stops the cutting tool from continuing to move down or through the workpiece. system. Stopping the translational movement of the cutting tool minimizes injury caused by the user contacting the saw blade.

FIG. 136 shows an example apparatus for a system that stops translation of a cutting tool incorporating a radial arm saw 1100 . Generally, the radial arm saw 1100 includes a horizontal base 1102 , a vertical post 1104 extending upwardly from the base 1102 , and a guide arm 1106 extending vertically away from the base 1102 from the post 1104 . A cartridge 1108 is slidably connected to the lower edge of the guide arm 1106 . The bottom of cassette 1108 is coupled to saw housing 1110 and motor assembly 1112 to allow saw blade 1114 to be pulled through the base to cut a workpiece (not shown) supported by the base. The radial arm saw 1106 is preferably equipped with the system described above to stop the rotation of the saw blade. The system includes a brake pawl within the cartridge 82 .

In use, a user grasps the handle 1116 on the chainsaw and pulls the chainsaw and blade through a workpiece on the base 1102 . While doing this, the user may accidentally pull the chainsaw with a misplaced finger or other part of his body. When contact occurs, the brake pawl 60 works to brake the rotation of the saw blade, but since the user is still pulling the chainsaw toward his or her own body when the contact is detected. The chainsaw may continue to move toward the user even though the pawl 60 has stopped the saw blade. This continued motion may cause the stopped saw blade to be driven onto the user's body (eg, the user's hand) causing further injury. A system that stops the movement of the cartridge and saw along the guide arm when contact of the saw blade with the user's body is detected would solve this problem.

It will be appreciated that there are many ways to stop the sliding of the bracket 1108 along the guide arm 1106 . Figure 136 shows two examples. One example includes a pivoting wedge assembly 1118 . Assembly 1118 includes a wedge or pawl 1120 pivotally connected to guide bracket 1108 . An actuator 1122 secured to bracket 1108 is operably connected to the control and detection subsystems associated with brake pawl 60 and cassette 82 . Activator 1122 engages pawl 1120 when pawl 62 is released. However, once contact between the saw blade and the user's body is detected, the detection system sends an activation signal to the actuator 1122 . The signal sent to the actuator 1122 may be the same signal used to trigger the release of the brake pawl 60, or it may be a different signal. In any event, upon receipt of an activation signal, the actuator drives wedge 1120, causing it to pivot into the guide arm to prevent further movement of the guide bracket forward of the guide arm. The wedge can be covered with or made of a high friction material like rubber. And/or it can be designed with tooth profile etc. to increase its braking effect.

Another example brake design shown in FIG. 136 includes a lockable spool assembly 1124 . Assembly 1124 may be used instead of, or in conjunction with, wedge 1118 . In any event, the lockable spool assembly includes a spring-loaded spool 1126 secured to support post 1104 . A rope or cable 1138 is attached to guide bracket 1108 at one end and wound around drum 1126 at the other end. When the user pulls the chainsaw across the base, the reel unwinds to allow the cord to extend. The spring loaded drum ensures that the drum can maintain a little tension on the cord and retrieve the cord wound on the drum as the user pushes the chainsaw back towards the support post. Assembly 1124 also includes a spool brake, such as pawl 1130 . The brake is operatively connected to the control and detection subsystem associated with the brake pawl 60 . Thus when blade contact with the user's body is detected, an activation signal is sent to the drum brake, causing the drum to lock. Once the reel is locked, the cord will prevent further movement of the chainsaw away from the support post 1104 . In an exemplary arrangement of a spool assembly 1124 not shown in FIG. In this case, the rope will be turned back from the drum to the support post 1104 .

It will be appreciated that there are many alternative methods and designs for stopping the guide bracket and chainsaw from running along the guide arm. Any one or more of these alternatives may be used in place of, or in conjunction with, the brake design shown in Figure 136 and described above.

FIG. 137 shows an example arrangement of a system for stopping translation of a cutting tool involving a miter or chop saw 1150 . It will be appreciated that miter saw 1150 may be any type of miter saw. This includes a simple miter saw, combination miter saw, sliding combination miter saw, etc. Typically, miter saw 1150 includes a base or stand 1152 for securing the compartment being cut. A swing arm 1154 is pivotally connected to the base 1152 to allow the swing arm to pivot downward toward the base. Attached to swing arm 1154 is a housing 1156 adapted to at least partially house saw blade 1158 . A motor assembly 1112 is coupled to the housing and includes a rotating arbor 1160 to which the saw blade is secured. The motor assembly 1112 includes a handle 1162 having a trigger switch operable to operate the chainsaw. An optional blade guard (not shown) can extend from the bottom of the enclosure 1156 to cover any portion of the blade exposed from the enclosure. When using the miter saw 1150, the user pulls up the saw, places a workpiece on the base 1152, and then drives the saw down toward the workpiece to cut the workpiece.

Miter saw 1150 also preferably includes a brake pawl 60 within cartridge 82 designed to stop rotation of the saw blade as shown above. A saw blade spinning at a few thousand revolutions per minute has a considerable angular momentum. Therefore, when the brake pawl engages and stops the saw blade, angular momentum must be transferred to the brake. Since the swing arm of a miter saw is free to pivot in the direction of blade rotation, when the blade is stopped suddenly, the angular momentum of the blade can be transferred to the swing arm, causing the swing arm to swing downward . This sudden and forceful downward movement of the swing arm could injure the user if part of the user's body is under the saw blade.

There are many suitable methods for preventing sudden downward movement of the swing arm. For example, the pivotal connection between the swing arm and the base could be electrically locked. For example, use an electromagnetic plate brake to prevent pivoting of the swing arm. The signal to lock the connection can be provided by the detection system. Alternatively, a shock absorber such as a gas-filled cylinder can be connected between the swing arm and the base to limit the speed at which the swing arm can pivot relative to the base, shown at 1180 in FIG. 137 . This arrangement can also limit how far the saw blade can move between the moment contact between the saw blade and the user is detected and the moment the saw blade is braked by the pawl. While there are many other ways of connecting the swing arm to the base to prevent sudden movement of the swing arm toward the base, most such designs transfer angular momentum to the swing arm/base assembly. Depending on the weight and balance of the saw, this angular momentum may be sufficient to cause the entire saw to topple. Therefore, it is necessary to fix the base on a stable surface with clamps, bolts, etc.

Figure 137 shows a method for preventing the swing arm 1154 from moving downward suddenly. Swing arm 1154 includes a cam portion 1170 having a cam surface 1172 . Cam portion 1170 may be integral with swing arm and housing 1156 . A detent pawl 1174 is secured to vertical post 1104 adjacent cam surface 1172 and an actuator 1176 is positioned adjacent pawl 1174 . The actuator 1176 is operatively connected to the control and detection system associated with the brake pawl 60 and the cartridge 82 so that the actuator 1176 engages the pawl 1174 when the pawl 62 is released. During normal operation, the activator 1176 maintains the disengagement of the pawl from the cam surface. However, once contact between the saw blade and the user is detected, the detection system sends an activation signal to the actuator, which may or may not be the same as the signal that triggers the release of the brake pawl 60 . In any event, when an activation signal is received, the actuator actuates pawl 1174, causing it to pivot into cam surface 1172 to prevent further rotation of the swing arm. The pawl 1174 may be made of or covered with a high friction material such as rubber and/or be designed with teeth or the like to enhance its braking action. The cam portion 1170 can be modified to extend as far outward as possible from its pivot point to provide as strong a moment arm as possible to help stop the downward movement of the swing arm.

The miter saw in FIG. 137 also includes a piston/cylinder 1180 connected between the swing arm and the base 1152. The piston/cylinder limits the pivoting speed of the swing arm relative to the base and can also be used to stop or limit the movement of the saw blade when sudden contact with the saw blade is detected.

There are many alternative methods, designs and designs for stopping the downward movement of the swing arm. Any one or more of these alternatives may be used instead, or in addition. The pawl, cam design shown in Figure 137 and described above. The most important thing is to provide a mechanical stop that stops the downward movement of the swing arm when the saw blade contacts the user.

Figure 138 shows an alternative translation brake mechanism installed in a pneumatic upper shredder. The shredder 1181 includes a saw blade 40 secured to a pivoting knife shaft unit 1182 . The saw blade and/or some saw-related components are electrically isolated and connected to a detection system as described in Sections 1 and 2 above. This arrangement allows the detection of contact of the saw blade with the user as described in those cases.

The knife shaft unit is pivoted upward by a pneumatic cylinder 1183 to the position shown in dashed lines. The cylinder can be activated by the user. Like by stepping on a foot switch, or by an electronic controller. In either case, a solenoid valve (not shown) is typically provided to control gas delivery to the cylinders. A blade guard 1184 is provided to cover the saw blade as it protrudes from the top of the table. In many cases, the blade guard moves down when the saw is started to act as a grip for the material being cut. A metal strip 1885 along the bottom of the blade guard can thus be electrically insulated and used as an electrode to detect contact with the user as described above. Since the blade guard does not rotate, it may not be necessary to use capacitive coupling to detect contact, and any suitable system may be used. In any event, the detection system monitors the contact of the bottom of the blade guard with the user. Although not required, it is preferred that the control subsystem only treat the detected contact as a dangerous condition and trigger the reaction system during actual activation of the chainsaw. Otherwise, accidental contact while the user is placing the material to be cut could cause a false trigger where no hazard exists. However, if the bottom of the blade guard hits the user during the start cycle of the chainsaw, the reaction system should be activated. Since the user's hands can be covered with gloves or can be placed under the tabletop, in most cases a blade guard alone is not sufficient for contact detection. Conversely, contact of the saw blade with the user (when the saw blade cuts through the glove) can also be monitored and trigger a reaction system. Alternatively, the glove could be made of, or use a conductive material.

As an alternative or in addition to monitoring contact with the saw blade, an area of the chainsaw tabletop adjacent to the blade opening can be isolated and used to monitor contact with the user, as with a saw blade guard. For example, a 2 cm wide metal strip with a slit for the saw blade to pass through can be fitted with an insulating material on the table top where the saw blade protrudes. This strip-shaped area can be used as a contact detection electrode. Therefore, if the user's hand touches the electrodes on the tabletop, that is, within 1 cm of the saw blade on the tabletop, the reaction system can be triggered when the chainsaw is activated. Of course similar systems can be used on many other types of woodworking machines, such as in the material feeding section of a planer, to detect dangerous situations.

The saw 1181 includes a reaction system 24 . The system is designed to interrupt the upward movement of the saw if contact with the user is detected by the guardrail/table top or saw blade. The reaction system 24 includes a first link 1186a extending between the arbor unit 1182 and an end of a lever link 1186b. The lever link rotates around a pivot point 1187, and its other end is connected to a second link 1186c. The pivot point is positioned such that the second link travels much farther than the first link during activation of the saw. A spring 1188 is connected to the free end of the second link to tension the entire linkage against upward movement of the saw body. This tension, although not required, helps to ensure that any play in the linkage has been tensioned when the brake is activated, as will be described below, thereby minimizing upward movement after activation.

The reaction system also includes a brake mechanism 28 in the form of a pawl 1189 . The pawl is fixed on a pivot 1190 and is biased towards the second link by a biasing mechanism 30 in the form of a belleville spring stack 1191 . The spring is preferably positioned to urge the pawl in the opposite direction of its rotation. This minimizes any upward play or free distance when the pawl face contacts the second link. Again, this will reduce the upward movement of the saw blade after the brake is triggered. A restraining mechanism in the form of an electromagnet 1192 is magnetically coupled to the upper edge of the pawl to maintain the pawl position against the biasing mechanism. Typically, the pawl is made of a hard magnetic material and provides serrations on the front face to grip or bite into the link when engaged. The pawl may also be provided with an electromagnetic plate attached to the upper part to engage the electromagnet. A sliding surface 1193 guides the second link against the pawl and provides a support for the second link as the pawl pushes the link. A limiter 1194 holds the second link against the sliding surface so that when the pawl is actuated, there is no play and ensures that the link does not accidentally contact the pawl prior to release. Preferably the pawl face is fixed or so: it travels very close together, preferably between 0.1mm and 2mm, to minimize the time necessary to engage the link.

Under normal conditions, an electric current is driven through the electromagnet to hold the pawl. When the reaction system is activated, the resistance is interrupted and preferably a reverse current is provided for a short time to rapidly release the pawl which is urged by a spring into contact with the second link. The pawl then immediately engages the second link to prevent further upward movement of the saw blade. At the same time, the pneumatic cylinder is reversed to begin retracting the saw blade. Simple cylinder reversal with a standard solenoid valve is not fast enough. It cannot stop the upward motion quickly enough to prevent serious injury. However, the detent brake can stop the upward movement within 1-5 milliseconds and restrict the pneumatic cylinder until the solenoid valve can be reversed to retract the saw blade. Optimally, the retraction begins in substantially less than 100 milliseconds so that the user does not have time to react and jerk their hand through the still-rotating blade and cause more serious injury.

After the brake pawl is released, a projection 1195 on the second link is positioned to resist the electromagnet to reset the pawl when the saw is fully lowered. When the saw blade is lowered, the protrusion pushes the lower edge of the pawl to bring the pawl back into contact with the electromagnet. This resets the system ready to be used again. It should be appreciated that electromagnet release could be used alternately with the fusible member components described above. Fusible members are generally cheaper to install, but have the disadvantage that they are only good for one use.

FIG. 139 shows an alternative reaction system similar to the one in FIG. 138 designed to stop translational motion. The system in FIG. 139 includes only one extension arm 1199 connected to the arbor unit 1182 . The extension arm provides some mechanical advantage, similar to the lever linkage of FIG. 138 . When the reaction system is activated, the pawl 1189 grabs the linkage 1186 as previously described to stop the upward movement of the saw blade. As before, the spring 1188 maintains a tension on the link to tighten any play that may exist or develop in the mechanism. It should be appreciated that the systems of Figures 138 and 139 can be used together to create additional mechanical advantages in translational braking mechanisms.

Figure 140 shows another reaction system similar to that shown in Figures 138,139. In the reaction system of FIG. 140, the brake is fixed on the cartridge 1196 and the cartridge slides along the link 1186 on the bushing 1197. The cartridge is secured to a bracket 1198 which is connected to the arbor unit 1182 and rotates about it. When the cutter shaft unit is turned upward, the cartridge is driven along the link. When contact is detected, the pawl is released to grip the face of the link and stop the upward movement of the saw. As noted above, springs 1188 and 1191 are positioned to eliminate any play in the translational detent mechanism. It should be noted that different cut-off saws have different mechanisms like cams, eccentrics etc. to lift and lower the saw blade and the translational brakes and variations described above can also be applied to these different mechanisms.

The translational brakes described above can also be used with various brake or brake retraction systems for combined benefits. For example, the saw blade may be braked while the translation brake is engaged to further minimize the chance of serious injury. Alternatively, or in addition, a retraction mechanism may be provided to rapidly retract the saw blade.

The system, method and machine for stopping translational motion can be described in the numbered paragraphs proclaimed below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

11.1. A woodworking machine consisting of:

a cutting member, where the cutting member is adapted to translate relative to the workpiece being cut;

A detection system suitable for detecting a dangerous situation between a person and a defined part of the machine;

and a response system for translation of the workpiece adapted to interrupt cutting when the detection system detects a dangerous situation between a person and a portion of the machine.

11.1.1. The woodworking machine of paragraph 11.1, where the defined part of the machine is the cutting element.

11.1.2. The woodworking machine of paragraph 11.1, where the defined part of the machine is a guardrail.

11.1.3. The woodworking machine of paragraph 11.1, wherein the reaction system is adapted to interrupt the translation of the cutting member by stopping its translational movement.

11.1.4. The woodworking machine of paragraph 11.1, wherein the reaction system interrupts the translation of the interrupting cutting member by reversing its translational movement.

11.1.5. The woodworking machine of paragraph 11.1 further includes a brake system that stops the movement of the cutting member when the detection system detects a hazardous situation.

11.1.6. The woodworking machine of paragraph 11.1, where the defined part is a cutting part and where the hazardous situation is the contact between a person and the cutting part.

11.1.7. The woodworking machine of paragraph 11.1, where the defined part is a cutting part and where the hazardous situation is the approach between a person and the cutting part.

11.2. A radial arm saw consisting of:

a guiding arm;

a saw blade secured to slide along the guide arm;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

And a reaction system adapted to interrupt the sliding of the saw blade when the detection system detects a dangerous situation between the person and the saw blade.

11.2.1. The chainsaw of paragraph 11.2, where the reaction system includes a member designed to contact and engage the guide arm.

11.2.1.1. The chainsaw of paragraph 11.2.1, where the member is a pawl.

11.2.2. The chainsaw of paragraph 11.2, where the saw blade is mounted on a guide arm that slides along a support structure, where the reaction system includes a thread between the support structure and the knife shaft, and where the The leads are used to stop the saw blade from sliding on the guide arm when a dangerous situation is detected.

11.2.2.1. The chainsaw of paragraph 11.2.2, where the cord is unwound as the saw blade slides on the guide arm.

11.2.2.2. The chainsaw of paragraph 11.2.2, wherein the cord is looped around a cylinder and where the cylinder is locked to prevent the cord from being released if a hazardous situation is detected.

11.3. A miter saw consisting of:

a base;

臂：A base supported by a base and adapted to pivot toward the workpiece being cut

arm:

a saw blade fixed to move with the swing arm to contact the workpiece as the swing arm rotates toward the workpiece;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

臂运动的反应系统。and a sensor suitable for interrupting the saw blade and

Response system to arm movement.

11.3.1. The miter saw of paragraph 11.3, where the reaction system includes an electric lock designed to prevent rotation of the swing arm.

11.3.2. The miter saw of paragraph 11.3 further includes a piston/cylinder for limiting the rotational speed of the swing arm.

11.3.3. The miter saw of paragraph 11.3, wherein the swing arm includes a cam portion, and further comprising a pawl for engaging the cam portion to stop pivoting of the swing arm when a hazardous condition is detected.

11.4. A machine safety system, the safety system comprising:

a detection system suitable for detecting a dangerous situation between a person and a processing part of a machine, where the processing part is in motion;

and a reaction system associated with the detection system. The reaction system interrupts the movement of the working part when the detection system detects a dangerous situation between a person and the machined part.

11.4.1. The safety system of paragraph 11.4, where a hazardous situation refers to human contact with a machined part, and where a detection system is used to capacitively transfer an electrical charge to the processed part and to detect when the charge drops.

11.4.2. The safety system of paragraph 11.4, where the movement of the processing part is translation and the reaction system stops that translation movement.

11.4.3. The safety system of paragraph 11.4, where the reaction system interrupts the movement of the processing part within 25 milliseconds of detecting a dangerous situation.

11.5. A chopping saw consisting of:

a saw blade secured to the pivoting arbor unit and adapted to pivot into contact with the workpiece to cut the workpiece;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

A reaction system for interrupting the movement of the saw blade and the pivoting knife shaft unit when the detection system detects a dangerous situation between a person and the saw blade.

11.5.1.. The chop saw of paragraph 11.5 further comprising a pneumatic cylinder that pivots the saw blade and pivots the knife shaft unit.

11.5.2. The chopping saw of paragraph 11.5, where the detection system detects a dangerous situation between the person and the saw blade.

11.5.3. The chop saw of paragraph 11.5 further comprising a blade guard, and the detection system detects a dangerous situation between a person and the saw guard.

11.5.4. The chop saw of paragraph 11.5 further comprising a work surface through which the saw blade extends to cut the workpiece, and where the detection system detects human contact with at least a portion of the work surface.

11.5.5. The chopping saw of paragraph 11.5, where the reaction system includes a brake mechanism and a link between the pivoting knife shaft unit and a fixed point, where the link includes at least one The part that moves when the knife shaft unit turns, and a brake mechanism is used to limit the movement of the link to stop the movement of the pivoting knife shaft unit.

11.5.6. The chopping saw of paragraph 11.5, where the reaction system includes:

a link having a lever for pivoting around a pivot point, the lever has two ends, and the pivot point is closer to one end, a first lever is connected to the pivoting knife shaft unit and, closer to the pivot between that end of the pivot point, and a second lever connected to the other end of the lever, where movement of the pivoting knife-axis unit causes movement of the first lever, which in turn causes the lever to pivot about and a brake mechanism for stopping the movement of the second lever, and the braking of the second lever then stops the movement of the pivoting knife shaft unit.

11.5.6.1. The chop saw of paragraph 11.5.6, wherein the reaction system further includes a spring connecting the second lever to a predetermined point.

11.5.7. a member fixed to and extending from the pivoting arbor unit and which member moves with the pivoting arbor unit;

a link attached to one end of the member, where the link moves with the member;

and a braking mechanism adapted to stop movement of the link, where the link then stops movement of the pivoting knife-axis unit.

11.5.7.1. The chop saw of paragraph 11.5.7, wherein the reaction system further includes a connecting lever and a spring at a predetermined point.

11.5.8. The chopping saw of paragraph 11.5, where the reaction system includes:

a strut secured to the pivoting arbor unit and adapted to move with the pivoting arbor unit;

a connecting rod associated with the strut;

a cartridge secured to the strut and adapted to slide on the linkage as the strut moves;

and a braking mechanism adapted to stop movement of the cartridge, where the cartridge then stops movement of the strut and pivoting knife shaft unit.

11.5.8.1. The chop saw of paragraph 11.5.8, wherein the reaction system further includes a connecting link and a spring at a predetermined point.

11.5.9. The chopping saw of paragraph 11.5, where the reaction system includes a brake mechanism and a link between the pivoting knife shaft unit and a fixed point, where the link includes at least one The part that moves when the arbor unit turns, and the brake mechanism is used to limit the movement of the link to stop the movement of the pivoting arbor unit, where the brake mechanism is used to limit the movement of the link to stop the pivoting arbor movement of the unit, where the brake mechanism includes a brake pawl, and the brake mechanism includes an electromagnet for maintaining the brake pawl in a non-brake position until a dangerous situation is detected.

11.5.9.1. The chop saw of paragraph 11.5.9 further includes a member designed to engage the brake pawl and move the brake pawl into contact with the electromagnet to set the brake in the non-brake position. Chapter 12: Deactivating Cutting Tools

In many of the devices described above, the reaction subsystem 24 is designed to stop and/or retract the saw blade. However, alternative arrangements of the reaction system 24 may be designed to prevent injury to the user in other ways. For example, Fig. 141 shows an arrangement for a reaction system suitable for disabling dangerous parts of a cutting tool. In the apparatus of Fig. 141, the cutting tool is generally a cylindrical cutter head. The cutter head has one or more elongated saw blades secured to the reverse surface of the head. Such cutters are used on joint planers such as the joint planer 1200 and planers. During operation, the cutter head rotates about its cylindrical center. As the work passes across the cutter head, the saw blade makes a wide kerf in the adjacent surface of the workpiece. As with machines using circular saw blades described above, machines using cylindrical blades can cause serious injury if the saw blade comes into contact with the user's body. The reaction subsystem shown in Figure 14124 is designed to prevent or enable this damage is minimized. As a clarification, many elements of the safety system 18 are not shown in Figure 141 because they are similar to elements in the other cutting machines described above.

The seam saw 1200 includes a generally cylindrical cutter head 1202 fixed to and rotatable about a knife shaft 1204 . The arbor is typically fixed in one or more bearing assemblies (not shown) and is rotationally driven by a motor assembly. The motor assembly is connected to the cutter shaft either directly or systematically by means of a belt pulley. The cutter head is fixed in a main frame structure 1206 and extends upwardly in the space between the infeed table 1208 and the outfeed table 1210 . A workpiece is cut by sliding through the cutter head along the infeed table 1208 and into the outfeed table 1210 . Typically, the vertical positions of the infeed table 1208 and outfeed table 1210 are independently adjustable in order to control the depth of the cut into the workpiece and align with the top surface of the cutter head.

The cutter head is usually made of a metal material such as steel, and generally includes three blades 1212 fixed to the surface of the cutter head and extending beyond the surface of the cutter head. It should be understood that more or fewer blades may be used and that the use of the safety system 18 of the present invention is not limited to the number of blades on the head 1201 . One or more bushings 1214 of non-conductive material are placed between the bit and the shaft to insulate the bit and blades from the frame 1206 . Charging boards 46 and 46 may be placed adjacent to the tool head to couple signals generated by the detection subsystem across the tool head. In Fig. 141, the charging plate (indicated by dashed lines) is mounted on one flat end near the cutter head. Alternatively, the arbor could be insulated from the frame and a charging plate could be placed around the arbor, as described in Section 2 above.

Due to the relatively small number of blades, the first contact of the user's body with the blade may occur on one of these blades or on the surface of the blade itself. However, the blade is electrically connected to the head so that any contact with the user's body is detected whether it is on the blade or not. Once contact is detected, the reaction system is activated to quickly stop the rotation of the cutter head 1202 and/or disable the blades.

In the device depicted in Figure 141, the safety system 18 includes a reaction system 24 designed to cover the blades to prevent them from injuring the user. In particular, the reaction system in FIG. 141 includes a flexible sheet 1120. Such as plastic, rubber, metal foil, metal mesh, braid, etc., used to cover the blade. A particularly desirable material is 0.005-0.050 inch thick stainless steel sheet. Sheet 1220 includes a hook 1222 positioned at one end to engage either blade. The hook is preferably integral with the sheet and forms a short flap for gripping the blade. Alternatively, the hook can be separated and integrated with the sheet. When the hook 1222 is pushed against the bit 1202, the next passing blade grabs the hook causing the sheet 1220 to wrap around the bit as the bit rotates. In this way, the blade is covered by the sheet 1220 to protect the user from serious injury. Typically, the outer surface of the hook 1222 is rounded or not beveled to prevent injury to the user when the hook is pulled around the cutter head.

The sheet preferably extends across the entire width of the blade and is preferably longer than 2/3 of the circumference of the blade to allow it to cover all three blades simultaneously. Preferably, the sheet should be longer than the circumference of the cutter head to wrap more than one turn around the cutter head. The sheet is typically shaped to curl inwardly. The curl reduces the tendency of the sheet to bounce off the cutter head. The free end of the sheet is stored on a roll 1124. The spool may include a torsion spring or other device to limit the number of revolutions the spool can turn to pull the cutter head toward a stop. Alternatively, the end of the sheet material 1220 opposite the hook can be secured so that the bit stops the bit after it completes a full revolution. Additionally or alternatively, the motor assembly of the joint cutter may be turned off to stop rotation of the cutter head.

The hook is moved into contact with the cutter head by being secured to the front of the drive plate 1226 or other high speed activation assembly. The hooks can be clicked or glued to the sheet, secured with soft rivets, or provided with holes through which protrusions on the sheet can be pushed through. This method of attachment is necessary to hold the hook firmly in place during normal use, yet allow it to separate from the sheet when it is grasped by the blade. The drive plate is preferably as wide as the hook to provide sufficient rigidity to ensure that the entire hook engages the blade simultaneously.

Figures 142-144 show an alternative saw blade cover system for machines using circular saw blades. The reaction system in Figure 142 includes a strap 1230 constructed of a flexible material. The tape is used to wrap around the teeth of the saw blade 40 . Strap 1230 includes a loop formed at the leading end. The ring is hooked to a pair of torsion springs 1234 and held in an upright position by a guide structure (not shown) fixed to the saw frame, as described in the above section 4406. . When the springs are released, they pull the ring 1232 down into the gullets 1236 of one saw blade 40 . The gullets grab the leading edge of the ring and pull the ring off the spring and pull the strap forward as shown by the dashed lines in FIG. 142 . The width of the ring forms a shock absorbing structure to absorb part of the impact caused by the cogs grabbing the ring. It is also possible to provide a compressible material at the leading end of the ring to act as a shock absorbing system to reduce shock loads.

As shown in Figure 143, the tail of the strap is shaped to fold over the teeth of the blade. The tail of the tape is stored on a reel 1238. The C-belt unwinds as it is wound on the reel. The strap is preferably made of a spring flexible material. It returns to an unbiased C-shape when bent to fit the circumference of the saw blade. , such as spring flexible stainless steel 0.005 to 0.050 inches thick.

The leading end of the strap is preferably positioned as close as possible to where the blade emerges from the guardrail or saw housing. This includes that the strap will reach the user's location as quickly as possible to minimize injury. The motor of the saw will preferably be disengaged as soon as the reaction system is activated. In addition, the reaction system of Figures 142-144 is also preferably used with a braking system such as that described in Section 11 above, or with a retraction system such as that described in Section 3 above to further Minimize damage.

Figure 145 shows another alternative reaction system. In this system, the cutter is blocked when the reaction system is activated. In particular, a pawl 1240 is pushed into contact with the saw blade teeth when the reaction system is activated. The pawl is preferably made of a plastic material such as polycarbonate. The material forms bends 1242 in the gullets 1236 between the teeth when cut by the saw teeth. The bend blocks the sharp edges of the teeth to prevent the teeth from cutting into the user. The pawl can also be made of a softer material than polycarbonate, such as Ultra High Molecular Weight Polyethylene (OHMWPE) to reduce the braking effect on the blade when the bend is formed. The saw blade should preferably have gullets shaped with relatively parallel tooth edges to minimize the tendency for the bend to slip out. As with the band saw described above, the pawl is preferably placed as close as possible to where the blade emerges from the guardrail or housing to minimize the number of unobstructed teeth exposed to the user. Of course, with appropriate modifications, the same principles can be applied to other cutting tools, such as a joint router, or former.

Figure 146 shows another alternative setup for the reaction system. In this device, the teeth on the cutter are broken or moved. A pawl 1244 is provided for selectively engaging the teeth of the saw blade 40 . The pawl is made of a material hard enough to dislodge or break the carbide insert 1246 on the saw tooth on contact. Suitable materials include carbide and hardened steel. The pawl is activated by the mechanism described above for the brake pawl 60 . When activated, the pawl moves into the path of the saw blade teeth as shown in FIG. 146 . The pawl moves into contact with a support structure 1248 . The bracket structure is adapted and positioned to support the sawtooth of the pawl. The support structure may be of any suitable form including a pin, strut, bracket etc. In any case the carbon insert is crushed by the impact from the striking pawl. This reactive system is best used with a translation braking system or a retraction system, and is primarily used to create sufficient user-blade clearance to give the translation or retraction system more time to operate.

147 and 148 show another arrangement of a reaction system. In this arrangement a cutting tool is wrapped around a covering. A forming machine having a work plane 1264 guard rail 1264 and cutter head 1266 is shown at 1260 . A workpiece slides past the cutting tool along the guardrail on the work plane. The cutting tool shapes the workpiece as it moves past. The safety system on the forming machine 1260 includes a pair of shafts 1268 that are vertically spaced apart and rotate about pins 1270 . The shank 1268 is biased by the spring 66 against the cutting head 1266 . This is as described above in connection with other devices. A fusible member 70 limits the rotation of the shank 1268 toward the cutting head. The security system also includes a cover 1272 . The cover is in the form of a plate and is fixed between two long handles as shown in Fig. 148 . The cover is secured to two bags 1274 and 1276 made of material. The handles slide into the bag so that the cover jumps over the area between the two handles. The bag extends along the upper and lower sides of the cover on the end adjacent the handle. The cover extends away from the long handle and is wound on a roll 1278 . When the system detects accidental contact with the bit 1266, the fusible member 70 is melted and the handle 1268 is released and rotated towards the bit due to the spring 66 as described above in connection with the other devices. As the handle 1268 moves toward the cutter head, the cover contacts the cutter head and the cutter head grabs or bites into the cover and pulls the cover away from the handle 1268 and shaft 1278 until the cover wraps around the cutter head. The cover can be any material that is strong enough to absorb sudden accelerations when it hits the cutter head, yet must be flexible enough to grip the cutter head and wrap around it. Possible materials include Kevlar fabric, stainless steel wire mesh, natural or synthetic fabrics, etc. The shroud can be used with an internal brake to slow the movement of the cutter head more rapidly, or power to the motor can be disengaged to stop the cutter head.

The various devices described above for covering, blocking or neutralizing cutting tools are particularly suitable for use on relatively light machines such as portable circular and miter saws or on jointers such as joint planers, shapers and planers and other machines with heavy cutting tools.

The system, method and machine for disabling and securing cutting tools may be described in the numbered paragraphs declared below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

12.1. A machine consists of

a cutting element;

a motor adapted to drive the cutting element;

a detection system suitable for detecting hazardous situations;

and a response system adapted to at least partially shield the cutting element in response to the detected hazardous condition.

12.1.1. The chopping saw of paragraph 12.1, wherein the cutting element is circular and has cutting edges distributed along the circumference of the circle, and the reaction system includes a web for wrapping around the circumference of the cutting element.

12.2. A machine consists of:

a cutting element having one or more cutting edges;

a motor adapted to drive the cutting element;

a detection system suitable for detecting hazardous situations;

and a reaction system adapted to stop the cutting edge when the detection system detects a dangerous situation.

12.2.1. The machine of paragraph 12.2, wherein the reaction system separates the cutting edge from the cutting element.

12.3. A machine consists of:

a cutting element having one or more cutting edges;

a motor adapted to drive the cutting element;

a detection system adapted to detect hazardous situations associated with cutting edges;

and a reaction system adapted to arrest the cutting edge in response to a detected hazardous situation. Chapter 13: Table Saw

It will be appreciated that the safety system 18 can be designed for use with a table saw in a variety of ways. Figure 149 shows a type of table saw 1400 often referred to as a contractor saw. It includes a table top from which a saw blade 1402 extends. The desktop and saw blade are supported by a casing 1403 and table legs 1403 . The housing 1403 houses the mechanical structure that supports, positions and drives the saw blade. A motor that drives the saw blade can be located inside or outside the housing. A switch 1405 turns the saw on and off, causing the saw blade 1402 to rotate. Handles, such as handle 1406, are used to adjust the position of the saw blade relative to the tabletop, for example, how far the blade sticks out of the tabletop or how the blade is tilted relative to the top of the table . Of course, table saws come in many different designs, from large saws for industrial use to small saws that can be placed on a workbench or frame, and table saws with various types of table tops and cases. Basically, a table saw is a saw with a flat workspace or "table top" and a cutting blade extending upward through the table top. A user places a workpiece on a table and slides it over the saw blade to cut the workpiece.

Figures 150 and 151 show side views of the internal mechanism of a table saw designed with the safety system described above. Figure 152 shows a bottom view of the same saw, and Figure 153 shows a projected view. In the saw, the saw blade 1402 is secured to the arbor 1407 by a nut (not shown). The arbor rotates the saw blade in the direction of arrow 1409 . Table top 1401 (not shown in Fig. 151), defines the work plane of the table saw and is adjacent to the saw blade. The saw blade extends above the table top.

An arbor unit 1410 supports the arbor 1407 and holds the arbor in bearings to allow the arbor to rotate. The cutter shaft is connected to a motor (not shown). As is well known in the art, by a drive belt over the knife shaft pulley and the slide shaft of the motor drive shaft. The motor may be mounted on a motor plate 1411 as shown in FIG. 150 .

The arbor unit 1410 is also fixed on a pin 1412 and is rotatable about the pin. The pin 1412 is then secured to a support member 1413 . This support member, together with another support member 1414, forms at least a portion of the table saw support frame. The support frame is attached to the cabinet, table legs, and/or table body.

The saw blade 1402 is designed to rotate up and down so that the user can position the saw blade higher than the table top as necessary. The saw blade rotates about pin 1412 . The user can rotate the saw blade to adjust its position by turning a shaft 1415 to which a worm wheel 1416 is secured. The worm gear is fixed to the shaft for rotation therewith, but it can also slide on the shaft if necessary, as will be explained below. The worm gear 1416 is mounted like a bushing on the shaft 1415, and the shaft extends through a longitudinal aperture in the worm gear. The worm wheel is held during normal operation of the saw by a spring clip 1417 which is positioned in a groove or channel on the worm wheel and engages a pin or groove on the shaft 1415 to hold the worm wheel in place. . The worm gear meshes with a rack or tooth sector that is connected to or is part of the arbor unit 1410 . Thus, when the user turns the shaft 1415, such as by turning a handle or knob attached to the shaft like handle 1406 in FIG. The saw blade moves up and down.

Most table saws are also designed to allow the saw blade 1402 to be tilted from side to side relative to the table top 1401 . This is accomplished by a system similar to the shaft 1415, worm gear 1416 and rack 1418, but the system is normally turned perpendicular to the plane of the saw card. Support members 1413 and 1414 may be used as part of the system, for example, support member 1414 may consist of a toothed sector or rack similar to rack 1418 . The fabrication member includes arcuate protrusions 1440 . The protrusion cooperates with an arcuate groove or slides on a mount unit (not shown) to allow the support member to rotate. The fixing unit is fixed on the table top of the table saw.

A brake cartridge 1419 is secured to the table saw adjacent to the blade 1402 (the cartridge is open in Figures 150 and 152 and has a cover in Figure 153). The cartridge can be designed as described in Sections 7 and 8 above. The pawl is pulled away from the blade 1402 by a release mechanism 1422 described in Section 4 above. As explained in detail in Section 6 above, the cartridge is designed so that upon receipt of a detection signal, the release mechanism releases the pawl into the saw blade. The detection signal causing release of the pawl and the system for generating this signal have been described in more detail in Sections 1 and 2 above. Enclosed in a housing 1423 secured to the arbor unit 1410 are electronics forming at least part of the detection of user contact with the saw blade, and subsequent signaling to release the brake pawl. The enclosure should be closed to prevent sawdust and other particles from entering the enclosure and potentially damaging electronic equipment contained therein.

When the pawl is released, the pawl rapidly strikes the teeth of the saw blade. The teeth bite into the pawl, stopping the blade. The saw described above can stop the saw blade within 2 to 10 milliseconds, thereby mitigating the extent of injury caused by accidental contact with the saw blade.

The brake cartridge 1419 is positioned on the pivot axis of the saw blade so that the pawl 1420 can move around the pin 1417. Thus, when the pawl 1420 strikes the saw blade, the angular momentum of the blade is transferred to the arbor and the blade, arbor, frame and cassette tend to retract or move downward in the direction of arrow 1424. If the worm gear is fixed in place, the downward movement of the blade can dislodge the teeth on the frame and/or the worm gear, and prevent downward movement of the blade if desired. In the particular arrangement shown in Figures 150 and 151, the worm gear is adapted to disengage quickly and move onto the shaft 1415 when the saw blade strikes the pawl.

When the saw blade strikes the pawl, the force of the impact causes the spring clip 1417 to release quickly, allowing the worm wheel to slide down the shaft toward the shaft end 1425 . The spring clip releases quickly because the frame is pushed down as soon as the saw blade stops, and the frame contacts the worm wheel and forces the worm wheel to move. The force of the shelf against the worm wheel causes the spring clip to release quickly. The worm then moves into a receiver 1426 formed around the end of the shaft. The worm gear is put back into place simply by lifting the arbor to pivot the blade upward, which causes the frame to move up and the worm wheel to slide back along the shaft 1415 until the spring clip snaps into position on the shaft.

The table saw shown in FIGS. 150 and 151 also includes a stand 1427 . The brace is designed with a base or region 1428 into which an impact absorbing material 1429 (shown in FIGS. 150 and 151 , but not in FIG. 153 ) is placed. The bracket is positioned under the arbor and arbor unit so that the arbor unit hits the impact absorbing material 1429 when the saw blade is retracted. The bracket 1427 and impact absorbing material 1429 act like a stop to stop the downward movement of the saw blade. The bracket is positioned in such a way that the saw blade 1402 can be retracted a sufficient distance. The shock-absorbing material can be one of many shock-absorbing materials, such as rubber, foam, plastic, and the like. One material found to be suitable is available from AearoEAR of Indianapolis, Indiana under part number C-1002-06. Alternatively, the shock absorbing material 1429 may be attached to the lower surface of the arbor unit instead of the bracket 1427 . Furthermore, bracket 1427 may take many forms. In fact, the shaft 1415 is designed and placed such that it provides a plane on which to stop the downward movement of the saw blade.

In the configuration described above, the angular momentum of the saw blade causes the saw blade, frame and cartridge to all move downward when the pawl strikes the saw blade. In this way, the angular momentum of the saw blade causes retraction, and the saw blade 1402 is allowed to move down a sufficient distance so that the saw blade is fully retracted. The retractability of the saw blade minimizes injury from accidental contact with the saw blade and at the same time works in conjunction with the braking system described above. The retractability of the saw blade is due in part to the fact that the point of rotation of the saw blade relative to the direction of rotation of the saw blade can be described as what can be thought of as now the "back" of the table saw. The brake cartridge can also be fixed on this "back" and can be arranged to pivot with the blade as described above, or it can be fixedly mounted on the frame of the saw so that it does not interfere with the blade. turn together and that way, when the pawl engages the blade, the blade climbs off the pawl. Other designs that can be used alone or with the specific devices described here are described in Section 3 above.

Figure 151 also shows a breakaway device 1430 extending over the table top 1401 behind the saw blade 1402 to prevent kickback. A blade guard may also substantially surround the blade 1402 and prevent accidental contact with the blade.

Those table saws described above can include logic controllers to test that the saw and its safety system are working properly. For example, the logic controller can verify that the brake pawl is in the vicinity of the blade and that the firing system is ready to release the pawl into the blade upon detection of accidental user contact with the blade. The saw may also include various signals, lights, etc., to inform the user of the status and operating characteristics of the table saw. Self-test, logic control and user interface have been described in chapters 9 and 10 above.

Figure 161 shows another example of a safety system in the context of a typical table saw. The saw blade 40 is mounted for rotation about a knife shaft 42 . The knife shaft extends outwardly from a swing arm 1432 (as seen in FIG. 161 ) which rotates about an axis 1434 to raise and lower the saw blade. A worm gear 1436 engages an arcuate bracket on the swing arm to rotate the swing arm about the axis. Safety system 18 includes a bracket 1438 attached to the swing arm by, for example, one or more bolts extending through the bracket. Resting on stationary bracket 1438 are charging pads 44 and 46 . The charging plate is placed parallel to and slightly spaced from the saw blade 40 to create a capacitive bypass between the plates. The mounting bracket may be made of an electrically insulating material or include electrical insulation between the bracket and the charging pad.

The fixing bracket 1438 extends from the end of the swing arm 1432 to the edge of the saw blade 40 . A pawl 60 is pivotally mounted on a bolt extending from the bracket. The free end of the pawl is biased by a compression spring 66 towards the edge of the saw blade. The spring is held in a compressed state between the pawl and a spring unit 1444 . The spring unit protrudes from the bracket. A fusible member 70 is secured to a pair of contact bolts 1446 . The fusible member is connected to the pawl and biases it away from the edge of the saw blade against the bias of the spring.

An electronic device 1448 includes a contact detector like the detection subsystem 22 described above. Shielded wires extend from the electronic device to charging pads 44 and 46, respectively. Electronics 1448 also includes a current generator, such as transmit subsystem 76 described above. The current generator is connected to the contact bolt 1446 . A power line 1450 extends from the electronics 1448 to a suitable power source (not shown). When the contact detector detects contact between the user's body and the saw blade, the transmitting circuit melts the fusible member, thereby releasing the pawl. The pawl engages and stops the saw blade abruptly.

It should be noted that by placing the pawl and charge plate on the bracket 1438 attached to the swing arm, the pawl and charge plate move with the saw blade as it is adjusted. This eliminates the need to reposition the pawl and/or charging plate each time the saw blade is moved. Further, the specific arrangement of the safety system 18 depicted in FIG. 161 is suitable for simple installation or retrofitting of existing table saws that do not currently have a safety brake. The only requirement for retrofitting an existing table saw is to make a hole or holes in the end of the swing arm to receive the bolt 1440 . The exact location of the bracket 1438 can be adjusted as desired, such as extending down to fit within a particular table saw frame.

The table saws described above are designed to absorb the impact of the brake pawl braking the saw blade. However, on some table saws, such as small table saws, it is desirable to manufacture these saws that would be damaged if the brake pawl stopped the saw blade, perhaps by bending the arbor or other support structure. In fact, the saw can be specially made to absorb the energy of stopping the blade by destroying or damaging a part of the saw. Such saws may be considered disposable, they are only used until an accident occurs that requires the brake pawl to stop the saw blade. A disposable saw may be less expensive to manufacture, and the reduced injury to the user in the event of an accident would justify the cost of the entire saw.

A table saw equipped with the disclosed system and method can be described in the numbered paragraphs declared below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

13.1. A table saw consisting of:

working plane;

A rotatable saw blade adapted to extend upward through the work plane.

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

and a brake system adapted to stop the rotation of the saw blade when the detection system detects a dangerous situation.

13.1.1. The table saw of paragraph 13.1, wherein the blade is electrically isolated from the rest of the saw, and the detection system is adapted to transmit an electrical signal to the blade capacitance and detect the occurrence of a predetermined change in the signal.

13.1.2. The table saw of paragraph 13.1, where the blade is fixed to the shaft and where the blade is electrically insulated from the rest of the saw and the detection system is adapted to capacitively transmit an electrical voltage to the blade and shaft. signal and detects the occurrence of a predetermined change in that signal.

13.1.3. Table saws of paragraph 13.1, where a hazardous situation is defined as contact between a person and the saw blade.

13.1.4. The table saw of paragraph 13.1, where a hazardous situation refers to the approach between a person and the saw blade.

13.1.5. The table saw of paragraph 13.1, where the brake system includes a brake pawl for you to engage the saw blade.

13.1.5.1. The table saw of paragraph 13.1.5, where the brake pawl is part of the replaceable cartridge.

13.1.5.2. The table saw of paragraph 13.1.5, wherein a spring biases the brake pawl toward the blade.

13.1.5.3. The table saw of paragraph 13.1.5, wherein a fusible member limits engagement of the brake pawl with the fusible member.

13.1.5.3.1. The table saw of paragraph 13.5.3, wherein the brake system includes a linkage between the brake pawl and the fusible member.

13.1.6. The table saw of any of paragraphs 13.1 further comprising a firing system that activates the braking system when a hazardous situation is detected.

13.1.6.1. The table saw of paragraph 13.1.6, where the emission system includes a capacitor.

13.1.7. The table saw of paragraph 13.1 further includes a frame supporting the saw blade, wherein the saw blade is raised and lowered relative to the frame, and the braking system is designed to be raised and lowered with the saw blade.

13.1.8. The table saw of paragraph 13.1 further comprising a frame supporting the blade, wherein the blade is tilted relative to the frame, and the braking system is designed to tilt with the blade.

13.2. A table saw consisting of:

a working plane;

A rotatable saw blade adapted to extend upwards through the work plane;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

and a launch system adapted to activate the braking system when the detection system detects a dangerous situation.

13.2.1. The table saw of paragraph 13.2, where the braking system includes a pawl that is biased toward the blade, the firing system includes a fusible member that restrains the pawl from contact with the blade, and The firing system fuses the fusible member to release the brake pawl into the saw blade.

13.2.2. The table saw of paragraph 13.2 further includes a test system for testing the operability of the launch system.

13.2. A safety system for a table saw, where the table saw includes a rotatable saw blade, the safety system includes:

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

and a brake system adapted to stop the rotation of the saw blade when the detection system detects a dangerous situation. Chapter 14: Miter Saw

Turning now to FIGS. 154 and 155 . An example embodiment of machine 10 in the context of miter saw 1510 is shown. The miter saw is also commonly referred to as a chop saw. It will be appreciated that the miter saw 1510 can be any style of miter saw, including a simple miter saw, a combination miter saw, a sliding combination miter saw, and the like. Typically, miter saw 1510 includes a base or stand 1512 adapted to hold a workpiece being cut. A swing arm 1514 is pivotally connected to the base 1512 to allow the swing arm to pivot downwardly towards the base. Attached to the swing arm 1514 is a housing 1516 adapted to at least partially enclose a circular saw blade 40 . A motor assembly 16 is connected to the housing and includes a rotating arbor 42 to which the saw blade is secured. The motor assembly 16 includes a handle having a trigger 1520 operable to operate the saw. Saw blade 40 is rotated downward toward base 1512 . An optional blade guard (not shown) may extend from the bottom of the housing 1516 to cover any portion of the blade exposed outside the housing. When using the miter saw 1510, the user places the workpiece on the base 1512, under the raised blade, and then moves the saw blade upwards through the swing arm 1514 to cut the workpiece. It should be understood that various specific arrangements of miter saws with improved safety systems are discussed herein and include various elements, subelements, features, and variations thereof. The miter saw may include any one or more of the elements, subelements, features and variations disclosed herein, regardless of whether particular elements, subelements, features and variations are described or shown together in the figures.

The portion of saw 1510 where sensors 44 and 46 detect contact with the user should be electrically isolated from ground and the rest of saw 1510 to allow an input signal to be capacitively coupled from one plate to the other. For example, saw blade 40 may be electrically insulated from the rest of the saw by a plastic or other non-conductive bushing, such as shown outside 1570 in FIG. 160 . Alternatively, the blade and arbor assembly can be electrically isolated. Also shown in FIG. 160 is an insulating spacer 1572 for insulating the saw blade 40 from the arbor flange 1576 and the arbor spacer 1578 . The insulating spacer should be thick enough to create only negligible capacitance between the saw blade and the grounded arbor flange and spacer. A typical thickness is about 1/8 inch, although thinner or thicker shims may be used. Additionally, some or all of the arbor components may be made of a non-conductive material, such as ceramic, to reduce or eliminate the need for bushing 1570 .

An arbor nut 1580 secures the entire saw blade assembly to the arbor 42 . The friction created by tightening the arbor nut causes torque from the arbor to be transferred to the blade. Although not required, it is desirable that the blade be able to slide slightly on the arbor in the event of sudden braking to reduce the mass that must be braked and to reduce damage to the blade, arbor and/or Other elements in the drive system of the saw. Alternatively, a collapsible arbor bolt can be used in place of the nut 1580 . The arbor bolt has a collared shaft. The shaft is threaded into the arbor 40 and the arbor head holds the blade assembly on the arbor.

Still further, it may be desirable to make the bushing from a softer material. The bushing should be soft enough that it deforms when the blade is stopped suddenly. For example, depending on the type of brake system used, a sufficient radial shock load can be transferred to the arbor when the brakes are activated, a deformable bushing can be used to absorb part of the shock and reduce damage to the arbor Opportunity. Additionally, the combination of proper brake positioning and a deformable bushing can be used to move the saw blade away from the user when the brake is activated, as will be discussed further below.

In an alternative embodiment, the arbor and/or part of its supporting frame is electrically isolated from ground and also does not insulate the saw blade from the arbor. One benefit of this arrangement is that if the saw blade is electrically connected to the arbor, the arbor itself can be used to capacitively couple the input signal between the charging plates 44-46. An example of this design has been described in Section 2 above.

Any of the various designs and arrangements of safety system 18 described above may be incorporated into miter saw 1510. In an exemplary arrangement shown in FIGS. 154 and 155, safety system 18 is a cartridge type system. In addition to charging plates 44 and 46 , brake mechanism 28 and detection subsystem 22 are housed in cartridge 80 . Examples of suitable cartridges 80 are described in Sections 7 and 8 above. The cartridge is designed to be secured to the inner front surface of the housing 1516 by any suitable securing mechanism 1527, such as by one or more bolts 1524. The enclosure may include a removable panel or door 1526 to allow access to the cartridges. Alternatively, a cartridge 80 may be inserted in a port or opening of the housing with a pawl 60 secured in the cartridge and positionable in front of the saw blade. Examples of suitable pawl and brake mechanisms using a similar approach are described in Sections 4 and 5. It should be appreciated that the cassette 80 is not required for all miter saw devices disclosed herein, and that the miter saw 1510 can be made without a cassette. Instead, the brake mechanism of the safety system can be mounted in any suitable operative position relative to the saw blade 40 and need not be placed in a cartridge.

Charging pads 44 and 46 are attached to the inner wall of housing 1516 by one or more mounts 1528 . The mount may be attached to the housing by any suitable fastening mechanism 1522, such as by bolts 1532. The mount is also designed to position the charging plate parallel to, and very close to, the saw blade 40 . As shown in Figure 155, the distance between the charging plate and the saw blade is preferably smaller than the distance between the charging plate and the housing to minimize any parasitic capacitance that exists between the charging plate and the housing. Alternatively, the housing can be made of a non-conductive material.

Cables 1534 and 1536 connect the charging plate to the security system electronics, which may be housed in a cassette or elsewhere on the miter saw. Power to the security system 18 is provided by any suitable power source, such as a cable extending from the motor assembly 16 . In addition to activating engagement of the pawl with the blade, the electronics in the cartridge 80 may also be designed to interrupt power to the motor assembly 16 when contact between the user's body and the blade is detected.

A circular saw blade rotating at several thousand revolutions per minute has a sufficient value for angular momentum. Thus, when the pawl engages a circular saw blade like that found in a miter saw and stops the blade within a few milliseconds, this angular momentum must be transferred to the brake mechanism, including the pawl. Since the swing arm of the miter saw is free to rotate in the direction of blade rotation, the angular momentum of the saw blade can be transferred to the swing arm to cause the swing arm to swing downward when the saw blade is suddenly stopped. This sudden and forceful downward movement of the swing arm could injure the user if part of the user's body is under the saw blade. Therefore, another alternative arrangement for the miter saw 1510 includes a means of preventing the swing arm from moving downward when the saw blade is stopped. In addition, the pawl is typically secured to the front of the miter saw so that when the pawl engages the blade, it pushes the blade up and away from the user (that is, deforms the plastic bushing).

It will be appreciated that there are many suitable ways to prevent sudden downward swing of the swing arm. For example, a pivoting link between the swing arm and the base of the miter saw can be electrically locked. For example, an electromagnetic leaf brake is used to prevent the swing arm from rotating. The signal to lock the linkage can be provided by a detection system. An example of a miter saw with a lockable swing arm is shown in Figure 156. An electromagnetic leaf shutter is shown schematically at 1537 in the figure. Alternatively, or in addition, a shock absorber may be connected between the swing arm and the base to limit the rapidity with which the swing arm can rotate relative to the base. This arrangement also serves to limit the distance the saw blade can move in the time between detection of the saw blade and user contact and stopping of the saw blade by the pawl. An example miter saw is shown in FIG. 157 and has shock absorbers 1539 extending between the base and the miter saw swing arm. While there are many other ways of connecting the swing arm to the base to prevent sudden movement of the swing arm towards the base, most of these arrangements transfer angular momentum to the swing arm/base assembly. Depending on the weight and balance of the saw, this angular momentum may be sufficient to cause the entire saw to topple. Therefore, it is desirable to secure the base to a stable surface with clips, screws, etc.

Alternatively, the miter saw could be designed to absorb any angular momentum without moving the swing arm downward. For example, the example device shown in Figures 154 and 155 is designed with a rotary motor assembly to move the saw blade up into the housing when engaged with the pawl. The motor assembly 16 is connected to the housing 1516 by a pivot bolt, or shaft 1540, and allows the motor assembly to rotate about the bolt 1540 in the direction of blade rotation. A spring 1542 is compressed between the housing and a fixed point 1544 to bias the motor assembly in the direction of blade rotation. The motor assembly may include a lip 1546 . The lip slides against flange 1548 on the housing to hold the end of the motor assembly opposite the pivot bolt on the housing.

During use of the saw, the spring 1542 maintains the motor assembly in a normal position completely opposite to the direction of rotation of the saw blade. However, once the pawl is released to engage the blade, the motor assembly and blade rotate upward against the bias of the spring. In this arrangement, the pawl is positioned in front of the blade so that the pivot bolt is between the pawl and the knife shaft. This arrangement allows the saw blade to move upwards into the housing when braked. The selected spring should be strong enough to hold the motor assembly down when cutting through a workpiece, yet sufficiently compressible to allow the blade and motor assembly to move upward when the blade is stopped.

Although one example arrangement of the safety system 18 has been described in the context of a miter saw, the invention should not be considered limited to any one particular arrangement. This is because the design and arrangement of the safety system 18 can vary among miter saws and applications. For example, the design of the pivot motor assembly may also be combined with one or more of the other systems described above for preventing sudden rotation of the swing arm toward the base. Still further, it should be appreciated that the saw blade and motor assembly can be designed in one of a number of different ways to at least partially absorb the angular momentum of the saw blade.

FIG. 158 shows an alternative arrangement for a miter saw 1510 . The miter saw is designed to be adapted to move away from accidental contact with the user by absorbing the angular momentum of the saw blade. In this design, the miter saw includes two swing arms 1550 and 1552 . One end 1154 of each swing arm is connected to the base 1512, and the opposite end of the swing arm is connected to the housing 1516, saw blade 40, and/or a motor assembly (not shown). The relative positions of the swing arms can be changed according to the desired swing arm movement. In FIG. 158, the farm 5c arm 1550 is attached to the base 1512 just below the swing arm 1552. Typically, the motor assembly is securely attached to end 1556 of swing arm 1152 , while housing 1516 is connected to rotate about end 1556 of swing arm 1550 . The end 1556 of the swing arm 1552 is only connected to the chassis. This arrangement mimics the movement and triggering of the motor assembly that can be found in many conventional miter saws. Alternatively, the motor assembly may be connected to rotate with the housing about the end 1556 of the swing arm 1550 .

The geometry of the design shown in Figure 158 causes the housing and/or motor assembly to rotate together as the swing arm twists. Notably, as the swing arm moves upward, the housing and/or motor assembly rotates in a direction opposite to the direction of rotation of the saw blade while cutting. As a result, when the pawl engages the blade and transfers blade angular momentum to the housing and/or motor assembly, the housing and/or motor assembly tends to rotate in the same direction as the blade. This causes the swing arm to twist upward, dragging the blade away from the workpiece and the user's body. Thus, the miter saw design shown in Figure 158 is adapted to absorb the angular momentum of the saw blade and convert the angular momentum into an upward force on the swing arm.

The design shown in FIG. 158 and described above illustrates a further alternative arrangement for a miter saw with safety system 18. In particular, the safety system may be designed to rapidly remove the blade of the cutting tool from the user upon detection of contact with the user's body, in addition to, or in addition to, stopping the blade. This alternative arrangement can be implemented in the context of any of the cutting tools described herein. For example, a table saw with safety system 18 may include an arm that is adapted to pivot downwards, the swinging arm being in contact with the blade when a hazard or trigger condition is detected, such as when the blade is turning. To make contact, pull the blade down under the upper surface of the saw. A spring (not shown) may be attached to the swing arm to increase the speed at which the swing arm falls. It should be understood that a similar arrangement could be designed in the context of any of the saws described herein. In the case of a miter saw, an electromagnetic leaf brake can be used to stop the movement of the swing arm upon contact with a user. Additionally, the restraint system can be used to release a spring to push the swing arm up when the saw blade comes into contact with the user. With this situation, it may not be necessary to stop the saw blade suddenly to avoid injury.

FIG. 159 shows any example of a miter saw 1510 . As shown, saw 1510 shows another mechanism that stops sudden downward movement of swing arm 1514 when safety system 18 is activated and pawl 60 engages saw blade 40 . Swing arm 1154 includes a cam portion 1560 having a cam surface 15622 . Cam portion 1560 may be integral with swing arm and housing 1516 . A detent pawl 1564 is secured to vertical post 1566 adjacent cam surface 1562 and an actuator 1568 is positioned adjacent pawl 1564 . The actuator 1568 is operatively connected to the control and detection system associated with the brake pawl 60 and the cartridge 80 so that the actuator 1568 engages the pawl 1564 when the pawl 60 is released. During normal operation, the activator 1568 maintains the disengagement of the pawl from the cam surface. However, once contact between the saw blade and the user is detected, the detection system sends an activation signal to the actuator 1568, which may be the same as or different from the signal that triggers the release of the brake pawl 60. In any event, when an activation signal is received, the actuator actuates pawl 1564, causing it to pivot into cam surface 1562 to prevent further rotation of the swing arm. The pawl 1564 may be made of or covered with a high friction material such as rubber and/or be designed with teeth or the like to enhance its braking action. The cam portion 1560 can be modified to extend as far outward as possible from its pivot point to provide as strong a moment arm as possible to help stop the downward movement of the swing arm.

The safety system 22 can also protect the user from injury by wrapping a protective surface around the saw blade when a hazard or trigger condition is detected. Alternatively, or in addition, the system 22 may protect the user by a square that breaks the saw blade. Examples of these means of the security system 22 are described in Section 12 above.

A miter saw equipped with the disclosed system and method can be described in the numbered paragraphs declared below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

14.1. A miter saw consisting of:

a base;

a saw blade supported by a base;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

A reaction system associated with a detection system to cause a predetermined action to occur when a hazardous situation is detected;

14.1.1. The miter saw of paragraph 14.1, where the reaction system includes a brake system that brakes the saw blade.

14.1.2. The miter saw of paragraph 14.1, where the reaction system includes a mechanism for retracting the saw blade.

14.1.3. The miter saw of paragraph 14.1, where the reaction system includes a mechanism that covers the saw blade.

14.2. A miter saw consisting of:

a base;

a swing arm supported by the base and adapted to pivot toward the workpiece being cut;

a saw blade fixed to move with the swing arm to contact the workpiece as the swing arm rotates toward the workpiece;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

And a reaction system adapted to interrupt the movement of the saw blade and the swing arm when the detection system detects a dangerous situation between the person and the saw blade. Chapter 15: Circular Saw

Figure 162 shows the implementation of the safety system 18 by means of a circular saw 1500 held in one hand. Generally, circular saw 1500 includes a housing 1502 that houses a motor assembly (not shown), a guide plate 1504 , and a retractable blade guard 1506 . Saw blade 40 is connected to the motor assembly by arbor 42 . Safety system 18 may be implemented on saw 1500 in any of the arrangements and designs described above. In the example device shown in Figure 162, the security system is shown as a cartridge-based system. Cartridge 1508 includes a pawl 60 and is attached to housing 1502 so that the pawl can engage the saw blade. A charging plate (not shown) may be affixed to the inside surface of the housing adjacent the saw blade or at any location suitable for capacitively coupling an input signal across the saw blade and detecting contact. The cassette and pawl are shown secured adjacent the front of the blade to avoid interference with the blade guard 1506 . Alternatively, the pawl and cartridge can be secured anywhere adjacent the saw blade.

From the above, the safety system 18 can be implemented on a circular saw with a brake pawl engaging and stopping the saw blade. Alternatively, or in addition, safety system 18 may be designed to take other actions to prevent serious injury to the user. As an example, safety system 18 may include a quick action actuator, such as a spring, for rapidly pushing guide plate 1504 downward. By retracting the saw blade over the guide plate. This serves to push the user's hand or body away from the saw blade.

A circular saw equipped with the disclosed system and method can be described in the numbered paragraphs declared below. These paragraphs are intended to illustrate and not to limit the disclosure statement in any way. Changes and modifications may be made to the following description without departing from the scope of the present disclosure.

15.1. A circular saw consisting of:

a saw blade supported by a housing;

a detection system suitable for detecting a dangerous situation between a person and the saw blade;

A reaction system associated with a detection system to cause a predetermined action to occur when a hazardous situation is detected;

15.1.1. The circular saw of paragraph 15.1, where the reaction system includes a brake system that brakes the saw blade.

15.1.2. The circular saw of paragraph 15.1, where the reaction system includes a mechanism for retracting the saw blade.

15.1.3. The circular saw of paragraph 15.1, where the reaction system includes a mechanism that covers the saw blade.

Industrial applicability

The invention finds application in power equipment, and particularly in woodworking equipment such as table saws, miter saws, chop saws, band saws, circular saws, joint planers and the like.

It is believed that the disclosure set forth above encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its best form, the specific particular devices disclosed and shown here should not be considered in a limiting sense, since there may be many variation. The subject matter of the invention includes all recent and nonobvious combinations and subcombinations of the various elements, capabilities, functions, and/or properties disclosed herein. No single property, function, element or characteristic of a particular disclosed device is essential to all disclosed inventions.

Claims (214)

1. carpenter's machine comprises:

An electrical conduction cutting tool;

One in order to survey the detection system of the contact between user and the cutting tool; And, the engagement and stop cutting tool when detection system detects contact between user and the cutting tool of a brake system, this brake system.

2. according to the described machine of claim 1, further comprise a support cutting tool and with the framework of cutting tool electric insulation.

3. according to claim 1 or 2 described machines, wherein, cutting tool comprises a saw blade.

4. according to claim 1 or 2 described machines, wherein, detection system capacitively gives cutting tool a signal of telecommunication, and surveys the variation whether this signal is scheduled to.

5. according to the described machine of claim 1, wherein, brake system comprises that one is biased into engagement at least a portion cutting tool to stop the brake pawl of cutting tool.

6. according to the described machine of claim 5, wherein, brake system comprises that a design makes the brake pawl move into the spring of cutting tool.

7. according to the described machine of claim 5, wherein, brake system comprises a relieving mechanism, and this relieving mechanism optionally limits the brake pawl and meshed cutting tool before detection system is found the user and cutting tool is contacted.

8. according to the described machine of claim 7, wherein, relieving mechanism comprise one detecting contact is the fuse that melts between user and the cutting tool.

9. according to the described machine of claim 5-8, wherein, minimum a part of brake system is accommodated in the removable cartridge.

10. according to the described machine of claim 1, wherein, in the time of brake system engagement cutting tool, brake system is used to make cutting tool to withdraw from from the user.

11. according to the described machine of claim 1, wherein, detection system and cutting tool Capacitance Coupled.

12. according to the described machine of claim 11, wherein, the electric capacity between detection system and the cutting tool connects and comprises a drive electrode and a sensing electrode.

13. according to the described machine of claim 1, wherein, detection system is used for surveying the contact between user and the cutting tool in the scope of 100 microseconds that cutting tool contacts with the user.

14. according to the described machine of claim 1, wherein, brake system is used for stopping cutting tool in 10 milliseconds of scopes that cutting tool contacts with the user.

15. according to the described machine of claim 14, wherein, brake system is used for stopping cutting tool in 5 milliseconds of scopes that cutting tool contacts with the user.

16. according to the described machine of claim 5, wherein, when brake pawl and cutting tool engagement, this brake pawl is from locking on the cutting tool.

17. according to claim 5 or 16 described machines, wherein, minimum part brake pawl is made by thermoplastic.

18. according to claim 5 or 16 described machines, wherein, minimum part brake pawl is made by aluminum.

19. according to the described machine of claim 1, wherein, brake system comprises that at least two brake pawls are to be used to mesh cutting tool.

20., further comprise a control system, and the activation of control brake system with the supervision detection system according to the described machine of claim 1.

21. according to the described machine of claim 20, further comprise the motor of a driving cutting tool, and wherein, the operation of control system control motor.

22. according to the described machine of claim 20, wherein, control system is used to check to the small part brake system can be moved to the small part brake system confirming.

23. according to the described machine of claim 21, wherein, control system is used for checking at least that partly brake system can move to the small part brake system confirming before activating motor.

24. according to the described machine of claim 22, wherein, brake system comprises a capacitor, and test comprises the voltage of checking on the capacitor.

25. according to the described machine of claim 22, wherein, brake system comprises a capacitor, and test comprises the electric capacity of checking on the capacitor.

26. according to the described machine of claim 21, wherein, when the contact between user and the cutting tool was detected, control system was used to close motor.

27. according to the described machine of claim 20, wherein, only when cutting tool moved, control system just triggered brake system.

28. according to the described machine of claim 2, wherein, cutting tool is installed on the axostylus axostyle of rotation, detection system and axostylus axostyle Capacitance Coupled, and, axostylus axostyle and framework electric insulation, but and cutting tool electric coupling.

29. according to the described machine of claim 1, wherein, machine is a table saw.

30. according to the described machine of claim 1, wherein, machine is a mitre saw.

31. according to the described machine of claim 1, wherein, machine is a round arm saw.

32. according to the described machine of claim 1, wherein, machine is an annular saw.

33. according to the described machine of claim 1, wherein, machine is a seam planing tool.

34. according to the described machine of claim 1, wherein, machine is a band saw.

35. according to the described machine of claim 1, further comprise a motion detection system, wherein, this motion detection system makes brake system lose ability when cutting tool does not move.

36. according to the described machine of claim 1, further comprise the framework of a support cutting tool, wherein, the cutting tool quilt is with respect to the framework lifting, and brake system is designed to the cutting tool lifting.

37. according to the described machine of claim 1, further comprise the framework of a support cutting tool, wherein, cutting tool is tilted with respect to framework, and brake system is designed to tilt with cutting tool.

38. carpenter's machine comprises:

The cutting tool of a conduction;

A contact detection system that is used to survey between people and the cutting tool, wherein, detection system is used for capacitive character and gives cutting tool a signal of telecommunication, and surveys the variation whether this signal is scheduled on cutting tool.

And a reaction system relevant with detection system and cutting tool, here, reaction system is used for causing preconcerted operations with respect to cutting tool when detection system detects contact between people and the cutting tool.

39. according to the described machine of claim 38, wherein, reaction system comprises a brake that is used to mesh and stop cutting tool.

40. according to the described machine of claim 38, wherein, reaction comprises the retraction system of a withdrawal cutting tool.

41. according to the described machine of claim 38, wherein, reaction system covers cutting tool.

42. according to the described machine of claim 38, wherein, reaction system stops the translational motion of cutting tool.

43. the security system of a machine, this security system comprises:

The detection system of the contact between part that is used to survey people and machine works, wherein, detection system is used for capacitively giving working portion a signal of telecommunication, and surveys when electric charge descends; And, a reaction system relevant with detection system.This reaction system causes the generation with respect to a predetermined action of working portion when detection system detects contact between people and the working portion.

44. one is used to handle workpiece and comprises that the machine that contacts detection system comprises:

A conduction sensor that is arranged in machine potential danger position, wherein sensor can contact with workpiece or user;

One contacts detection system to receive signal therefrom with sensor couples together, wherein, the contact detection system be designed to according to the rate of change of signal when the contact distinguish contacting of sensor and workpiece and with the contacting of user.

45. carpenter's machine comprises:

A cutting tool that is used for cut workpiece;

One be used to provide have first amplitude and period the signal of telecommunication activating system, the coupling of this signal of telecommunication and cutting tool is to bring out the corresponding signal of telecommunication of second amplitude on cutting tool;

And sensing contact system that is used to respond to the signal of telecommunication that brings out on the cutting tool, here, the sensing contact system surveys contact between user and the cutting tool according to being detected the variation of the signal of telecommunication during surveying, here, during the detection between 5 to 150 microseconds, and minimum be the twice in signal of telecommunication cycle.

46. according to the described machine of claim 45, wherein, activating system is adjusted first amplitude according to the characteristic of the signal of telecommunication that is detected.

47. according to the described machine of claim 46, wherein, activating system is to be used to adjust first amplitude to keep the second predetermined amplitude.

48. according to the described machine of claim 46, wherein, the regulation of first amplitude is less than every millisecond 10%.

49. carpenter's machine comprises:

A cutting tool that is used for cut workpiece:

Activating system with the electricity output that is used to bring out the first amplitude signal of telecommunication is arranged on cutting tool, wherein, as long as in the scope of the electric loading on the cutting tool in certain boundary line, activating system just can be used to adjust the amplitude of electricity output to keep first enough fixing amplitude.

50. according to the described workpiece system of claim 49, wherein, this boundary line comprises the rate of change of the maximum of electric loading.

51. a contact detection system comprises:

A sensor;

One is used to produce the activating system that drives signal, wherein, drives signal and links to each other with sensor to bring out corresponding induced signal on sensor, and here, the ratio of drive signal amplitude and induced signal amplitude changes according to the distance of object apart from sensor;

And a control system that is used to adjust drive signal amplitude is to keep the fixing amplitude of a substance when the sensor at various objects.

52. carpenter's machine comprises:

A conduction cutting tool;

An activating system that is used on cutting tool, bringing out the signal of telecommunication;

First Capacitance Coupled that is used to electrically connect activating system and cutting tool;

A contiguous sense system that is used to monitor the signal of telecommunication that on cutting tool, brings out;

And, second Capacitance Coupled that is used to electrically connect sensor-based system and cutting tool;

53. carpenter's machine comprises:

A motor;

The next rotatable cutter shaft of electric insulation that is driven by motor of design;

A saw blade;

An activating system that is used to produce the signal of telecommunication;

And one be used for electric coupling activating system and cutter shaft to transmit the Capacitance Coupled of a part of signal of telecommunication to saw blade.

54. carpenter's machine comprises:

A conduction cutting tool;

An activating system that is used to produce the signal of telecommunication;

A Capacitance Coupled that connects activating system and cutting tool, wherein, Capacitance Coupled has the capacitance of 10 picofarads at least.

55. carpenter's machine comprises:

A working portion;

A detection system that is used to survey the unsafe conditions between people and the working portion;

And a retraction system relevant with detection system partly bounces back to make work when dangerous situation is detected.

56. according to the described machine of claim 46, wherein, working portion is a rotating saw blade with angular momentum,

The system that wherein bounces back is utilized the saw blade angular momentum saw blade that bounces back at least in part.

57. a table saw comprises:

A working face;

And one here, the rotation of saw blade defines the direction that workpiece is sent to electric saw with respect to the rotatable saw blade of working face around a pivotal point lifting, and with respect to the direction of conveying workpieces, pivotal point is in the downstream of saw blade.

58. a table saw comprises:

A working face;

One with respect to the rotatable saw blade of working face around a pivotal point lifting;

A transmission system that is used for the lifting saw blade;

Delivery system in transmission system, this delivery system allow saw blade to fall with respect to working face when particular event takes place.

59. according to the table saw of claim 58, wherein, this particular event is meant the braking saw blade.

60., further comprise stopping that a restriction saw blade falls according to the table saw of claim 58.

61. an electric saw comprises:

One with respect to the rotatable saw blade of working face around a pivotal point lifting, and here, saw blade is installed on the cutter shaft;

A cutter shaft body that is used for fixing cutter shaft, and further be used for when a particular event takes place retraction cutter shaft and saw blade.

62. electric saw according to claim 61, comprise first and second parts that all are fixed together before the generation up to particular event, and the mechanical energy that further comprises deposit is to move first and second parts to discharge this energy when the generation of particular event.

63. a mitre saw comprises:

Pedestal with sharp keen zone;

A saw blade;

A brake system that is used to brake saw blade;

Connecting rod at saw blade and pedestal, wherein, connecting rod is designed to when brake system braking saw blade saw blade be withdrawed from from cutting zone.

64. according to the mitre saw of claim 63, connecting rod is designed to that the saw blade angular momentum makes saw blade withdraw from from cutting zone when brake system braking saw blade.

65. a mitre saw comprises:

A pedestal;

A casing that is pivotally connected to pedestal;

A saw blade;

The fixing installation system of saw blade in casing;

And brake system has adapted in order to check saw blade;

This installation system is designed in brake system braking saw blade, and saw blade rotates into casing.

66. a band saw comprises:

The working face that cutting is arranged with cutting zone;

Saw blade near cutting zone;

A detection system that is used to survey the unsafe conditions between people and the saw blade;

And a retraction system relevant with detection system is to push saw blade open when detecting unsafe conditions from the deathtrap.

67. carpenter's machine comprises:

A working portion;

A detection system that is used to survey the unsafe conditions between people and working portion;

And a reaction system relevant with detection system is to cause the generation of a predetermined actions with respect to working portion when detecting unsafe condition, and wherein, reaction system comprises that the mechanical energy of deposit is to cause the generation of predetermined action.

68. according to carpenter's machine of claim 67, wherein, reaction system comprises a spring that likes the container of deposit mechanical energy.

69. according to carpenter's machine of claim 67, wherein, reaction system comprise a brake and spring with

Make brake and working portion engagement.

70. carpenter's machine comprises:

A cutting tool;

One is used to survey the detection system that contacts between people and the cutting tool;

A brake pawl that when detection system detects between people and the cutting tool contact, stops cutting tool; And the deposit mechanical energy that makes brake pawl engagement cutting tool.

71. according to carpenter's machine of claim 70, wherein, what lay in mechanical energy is a spring.

72. according to carpenter's machine of claim 71, wherein, spring handle brake pawl pushes and the contacting of cutting tool.

73. according to carpenter's machine of claim 73, wherein, the mechanical energy of deposit is in a self-holding cartridge.

74. carpenter's machine comprises:

A working portion;

A detection system that is used to survey the unsafe conditions between people and working portion;

And a brake system that when detection system detects unsafe condition, is used to mesh and brake working portion, wherein, brake system comprises a spring module that is used for the brake pawl is moved into working portion.

75. the braking cartridge of carpenter's machine, cartridge comprises:

A casing;

A brake pawl in the casing;

And one in the casing is used for the optionally spring module of travelling brake pawl, and here, the bias voltage module is controlled oneself.

76. according to the braking cartridge of claim 75, wherein, spring module comprises a helical spring of being shunk back by a mechanism.

77. carpenter's machine comprises:

A cutting tool that is used for cut workpiece and comprises at least two cutting surfaces;

A brake system that is used to stop cutting tool, wherein, brake system comprises a thermoplastic pawl that is used to mesh the cutting surface of cutting tool.

78. according to the brake system of claim 77, wherein, pawl is self-locking when the cutting surface engaged of pawl and cutting tool.

79. according to the brake system of claim 77, wherein, pawl is pivoted on the machine.

80. one is used to brake at periphery and has the brake system of the saw blade of plural sawtooth to comprise:

A first brake pawl that is used for meshing first sawtooth in saw blade periphery primary importance;

A second brake pawl that is used for being different from engagement second sawtooth of primary importance at the saw blade periphery;

And, an activation mechanism that is used for two pawls are pushed saw blade.

81. a brake system that is used to stop saw blade comprising:

Brake pawl with the zone that contacts with saw blade, this brake pawl are shaped as can be simultaneously and a zone engages of the saw blade that comprises at least 30 degree saw blade girths;

And one is suitable for optionally ordering about the activation system that the brake pawl enters saw blade.

82. carpenter's machine comprises:

A cutting element that is suitable for cutting workpiece and has at least two cutting surfaces;

A brake system that is used to stop cutting element, wherein, brake system comprises a pawl with the engagement of the cutting surface of cutting element; And this pawl is to make with two kinds of materials with different physical characteristics.

83. 2 machine according to Claim 8, wherein, at least a material is a thermoplastic.

84. 2 machine according to Claim 8, wherein, at least a material is a metal.

85. carpenter's machine comprises:

A cutting element that is suitable for cutting workpiece and has at least two cutting surfaces;

A brake system that is suitable for stopping cutting element, wherein, brake system comprises a metal pawl that is suitable for meshing the cutting surface of cutting element.

86. 2 machine according to Claim 8, wherein, pawl mainly is made of aluminum.

87. a machinery discharges and comprises:

One comprise be electrically connected to a current source comprise first, and the electrode system of second electrode;

The fusible member that electrode is electrically connected mutually;

An electric gate system that is placed between at least one electrode and the current source flows at least one electrode from current source optionally to control electric current.Wherein, between fusible member sustaining electrode at least 10, the tensile load of 000psi.

88. 7 machinery discharges according to Claim 8, wherein, fusible member has at least 100, the tension intensity of 000psi.

89. 7 machinery discharges according to Claim 8, wherein, a kind of material of selecting in one group of material that fusible member is made up of stainless steel and nickel is made.

90. 7 machinery discharges according to Claim 8, wherein, fusible member has the spring flexibility.

91. carpenter's machine comprises:

A brake that is used to stop cutting element;

One is suitable for pushing brake the bias system of normal danger to from holding fix,

And, the delivery system that can optionally brake be remained on holding fix that is used to resist the bias voltage of bias mechanism.

92. according to the machine of claim 91, wherein, relieving mechanism is a special purpose device.

93. according to the machine of claim 92, wherein, relieving mechanism comprises a fusible member.

94. according to the machine of claim 93, wherein, relieving mechanism comprises the fusible member that is connected to first on the current source and second electrode and electrode is electrically connected mutually.

95. according to the machine of claim 91, wherein, relieving mechanism comprises an electromagnet.

96. carpenter's machine comprises:

A cutting element;

Brake has adapted in order to stop cutting tool, and at this moment, brake has the position of free and the position of brake;

A brake that is used to brake cutting element, wherein, brake has a holding fix and a normal danger;

And one is used for brake is moved on to the start-up system of application position from holding fix, and wherein, the part of start-up system must be replaced after moving on to this position of stopping from holding fix will braking at least.

97. according to the machine of claim 96, wherein, start-up system comprises a destructor.

98. according to the machine of claim 96, wherein, start-up system comprises a fusible member.This fusible member is melted to allow brake to move on to normal danger from holding fix.

99. according to the machine of claim 96, wherein, the brake and at least the part of activation system be contained in the replaceable cartridge.

100. carpenter's machine comprises:

A processing component;

A detection system that is suitable for surveying the condition of the danger between people and the processing component;

The brake system of a braking processing component when detection system detects dangerous situation, wherein, brake system is accommodated in the cartridge.

101. according to carpenter's machine of claim 100, wherein, cartridge is designed to be replaced behind brake system braking processing component.

102. according to carpenter's machine of claim 100, wherein, cartridge is held a brake pawl that is used to contact processing component, one is used for the brake pawl is moved into the bias mechanism that meshes with processing component, and a relieving mechanism that is used to discharge bias mechanism.

103. according to carpenter's machine of claim 102, wherein, bias mechanism comprises a spring.

104. according to carpenter's machine of claim 102, wherein, bias mechanism comprises that a spring and an antagonism spring are to limit the mechanical linkage of brake pawl.

105. according to carpenter's machine of claim 102, wherein, delivery system comprises a fusible member.

106. according to carpenter's machine of claim 102, wherein, delivery system comprises a fusible member and a radiating circuit that is used to melt this fusible member.

107. according to carpenter's machine of claim 102, wherein, cartridge is closed.

108. according to carpenter's machine of claim 102, wherein, cartridge is made of plastics, cartridge comprises the perforate that a brake pawl can pass through, and perforate is covered with by lining before it at the brake pawl.

109. according to carpenter's machine of claim 102, further comprise a working face that is close in processing component, wherein, processing component is a saw blade, saw blade is designed to respect to the working face lifting, and cartridge is installed into saw blade one lifting.

110. according to carpenter's machine of claim 102, wherein, cartridge is fixed in the rotating shaft of machine.

111. a cartridge of carpenter's machine, this cartridge comprises:

A shell;

A brake pawl in the shell;

A mechanism of travelling brake pawl.

112. carpenter's machine comprises:

A processing component;

A cartridge that comprises the brake pawl that is applicable to optionally engagement and braking brake;

And, one be suitable for receiving and adjustable ground position brake cartridge with respect to the brake navigation system of position of cutting tool.

113. according to carpenter's machine of claim 102, wherein, the brake navigation system allows to be adjusted to hold the cutting element of different sizes.

114. according to carpenter's machine of claim 102, wherein, the brake navigation system comprises a pivotal axis that cartridge is fixed thereon, and the brake cartridge is that the rotation cartridge that leans against on the pivotal axis is regulated with respect to the position of cutting element.

115. carpenter's machine comprises:

A cutting element;

A motor that is suitable for driving cutting element;

Brake near the location regulated of cutting element;

A sensing system that is suitable for responding to the interval between cutting element and brake;

Design with control motor operated and received from the representative of sensing system cutting element and braked between the control system of signal of spacing, wherein, control system further is designed to optionally prevent the running of motor according to what receive from the signal of sensor.

116. according to carpenter's machine of claim 115, wherein, sensing system comprises an electrode that is fixed on close cutting element on the brake pawl, and signal depends on the electrical connection of electrode and cutting element.

117. carpenter's machine comprises:

A processing component;

A detection system that is suitable for surveying the dangerous situation between people and processing component;

A reaction system relevant with detection system takes place to cause preconcerted operations when detecting dangerous situation;

And one is suitable for one or more processing components, detection system, and the control system of reaction system operability.

118. according to carpenter's machine of claim 117, wherein, by handling one or more data from reaction system, control system is used to control one or more processing components, detection system, and reaction system operability.

119. according to carpenter's machine of claim 117, wherein, control system is suitable for carrying out the self check on the machine.

120. according to carpenter's machine of claim 117, wherein, control system is used to determine whether detection system works.

121. according to carpenter's machine of claim 117, wherein, control system is used to determine whether reaction system works.

122. according to carpenter's machine of claim 117, wherein, reaction system comprises a capacitor, and is suitable for carrying out self check to determine whether capacitor works in this control system.

123. according to carpenter's machine of claim 117, wherein, reaction system comprises a fusible member, and wherein control system is suitable for carrying out self check to determine whether fusible member works.

124. according to carpenter's machine of claim 117, wherein, detection system is notified processing component the signal of telecommunication, and wherein control system is suitable for monitoring effectively that signal of telecommunication.

125. according to carpenter's machine of claim 117, wherein, control system is suitable for preventing the triggering of reaction system chance.

126. according to carpenter's machine of claim 117, wherein, control system be suitable for controlling about with the display unit of machine function.

127. according to carpenter's machine of claim 117, wherein, processing component is driven by motor, and wherein control system is suitable for controlling motor.

128. carpenter's machine according to claim 117, wherein, processing component comprises a saw blade, and reaction system comprises that one is used for contacting saw blade and is positioned near the brake pawl of saw blade, and is used to monitor the control system of brake pawl with respect to the saw blade position.

129. carpenter's machine according to claim 117, further comprise a framework that supports processing component, wherein, processing component comprises a conduction cutting instrument with the framework electric insulation, one is transmitted the detection system of the signal of telecommunication to the conduction cutting instrument, and one is used for the control system whether monitor electrical signal is sent to the conduction cutting instrument.

130. according to carpenter's machine of claim 117, wherein, reaction system comprises an emission subsystem that triggers predetermined action, the emission subsystem comprises a fusible member, and control system checks whether fusible member puts in place.

131. according to carpenter's machine of claim 117, wherein, reaction system comprises an emission subsystem that triggers predetermined action, the emission subsystem is used to check electric charge, and control system checks whether emission system maintains electric charge.

132. according to carpenter's machine of claim 117, wherein, control system is checked one or more processing components, the operability of detection system and reaction system repeatedly when machine run.

133. according to carpenter's machine of claim 117, wherein, control system comprises microprocessor.

134. according to carpenter's machine of claim 117, wherein, control system allows user's bypass reaction system.

135. carpenter's machine according to claim 117, further comprise a framework that supports processing component, wherein, processing component comprises a conduction cutting instrument with the framework electric insulation, one is transmitted the detection system of the signal of telecommunication to the conduction cutting instrument, and whether signal that is used to monitor within the specific limits and is transmitted produces the control system of a detectable signal.

136. an electric saw comprises:

A saw blade;

A detection system that is suitable for surveying the condition of the danger between people and the saw blade;

A reaction system relevant with detection system is to cause the generation of a predetermined action when detecting dangerous situation;

And control system that is suitable for monitoring and controlling detection and reaction system.

137. the method for a control electric saw, wherein, electric saw comprises the saw blade that is driven by a motor, a condition that is suitable for surveying the danger between people and the saw blade, and reaction system relevant with detection system causes the generation of a predetermined action when detecting dangerous situation, and this method comprises:

Check whether detection system works;

Check whether reaction system works;

And, just start to drive the motor of saw blade if detection and reaction system work.

138. carpenter's machine comprises:

A processing component that when mobile, is suitable for work;

The detection system of dangerous situation between parts that are suitable for surveying people and work;

The reaction system of the generation that when detecting dangerous situation causes a predetermined action relevant with detection system;

And one is suitable for surveying the motion detection system that processing component moves and stop reaction system when processing component does not move.

139. according to carpenter's machine of claim 138, wherein, processing component is a rotating saw blade, and wherein whether motion detection system surveys saw blade in rotation.

140. according to carpenter's machine of claim 138, wherein, motion detection system is surveyed the speed of motion, and if the saw blade rotating speed think that when a critical value speed is following saw blade is not rotating.

141. according to carpenter's machine of claim 138, wherein, motion detection system comprises a sensor.

142. according to carpenter's machine of claim 141, wherein, sensor is a hall effect sensor.

143. according to carpenter's machine of claim 141, wherein, sensor is an electromagnetic field wild throw sensor.

144. according to carpenter's machine of claim 141, wherein, sensor is the sensor of an optics.

145. according to carpenter's machine of claim 141, wherein, sensor is an electric transducer.

146. carpenter's machine comprises:

A processing component that when mobile, is suitable for work;

A motor that drives processing component;

A detection system that is suitable for surveying the condition of the danger between people and the saw blade;

And the reaction system of the generation that when detecting dangerous situation causes a predetermined action relevant with detection system, wherein reaction system only just causes these preconcerted operations at motor running or in the definite time after motor turns round.

147. carpenter's machine comprises:

A cutting part, wherein cutting part is suitable for doing translation with respect to the workpiece that is cut;

A detection system that is suitable for surveying the dangerous situation between people and the machine one definite position;

And the reaction system that interrupts the workpiece translational motion of cutting during a dangerous situation that is suitable between a detection system finder and a machine part.

148. according to carpenter's machine of claim 147, wherein, the determining section of machine is a cutting part.

149. according to carpenter's machine of claim 147, wherein, the determining section of machine is a guardrail.

150. according to carpenter's machine of claim 147, wherein, reaction system is suitable for interrupting the translation of cutting part by stopping its translational motion.

151. according to carpenter's machine of claim 147, wherein, reaction system interrupts the translation of cutting part by putting upside down its translational motion.

152., further comprise a brake system that when detection system detects dangerous situation, stops the cutting part motion according to carpenter's machine of claim 147.

153. according to carpenter's machine of claim 147, wherein, determining section is cutting parts, and wherein dangerous situation is meant the contact between people and the cutting part.

154. according to carpenter's machine of claim 147, wherein, determining section is cutting parts, and wherein dangerous situation is meant close between people and the cutting part.

155. a line-bar resaw comprises:

A guid arm;

A saw blade that is fixed and slides with along guid arm;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And interrupt the reaction system that saw blade slides during a dangerous situation that is suitable between detection system finder and saw blade.

156. according to the electric saw of claim 155, wherein, reaction system comprises that a design contacts and embed the member of guid arm.

157. according to the electric saw of claim 156, wherein, this member is a pawl.

158. electric saw according to claim 155, wherein, saw blade is installed in along the guid arm of supporting structure and slides, wherein, reaction system comprises a clue between supporting construction and cutter shaft, and wherein this clue is used for stopping saw blade and slides on guid arm when detecting dangerous situation.

159. according to the electric saw of claim 155, wherein, this rope is released when saw blade slides on guid arm.

160. according to the electric saw of claim 155, wherein, this rope is enclosed on a cylinder, and wherein cylinder locked to stop this rope when detecting dangerous situation, to be emitted.

161. a mitre saw comprises:

A pedestal;

One by base supports and be suitable for pivoting to the workpiece that is cut swing arm;

One is fixed when workpiece rotates with the saw blade of swing arm campaign with contact workpiece when swing arm;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And the reaction system that interrupts saw blade and swing arm campaign during a dangerous situation that is suitable between detection system finder and saw blade.

162. according to the mitre saw of claim 161, wherein, reaction system comprises that a design prevents the electric lock of swing arm rotation.

163., further comprise one in order to limit the piston of swing arm rotary speed according to the mitre saw of claim 161.

164. according to the mitre saw of claim 161, wherein, swing arm comprises a cam portion, and comprises that further one is used for the engagement with cams part to stop the pawl that swing arm pivots when detecting dangerous situation.

165. the security system of a machine, this security system comprises:

A detection system that is suitable for surveying the dangerous situation between people and the machining parts, wherein, processing component moves;

And reaction system relevant with detection system.The motion at interruption of work position when this reaction system detects unsafe condition between people and processing component in detection system.

166. according to the security system of claim 165, wherein, dangerous situation is meant contacting of people and machining parts, and wherein detection system is used to capacitively transmit electric charge and survey when the quantity of electric charge descends to processing component.

167. according to the security system of claim 165, wherein, the motion of processing component is translation, and reaction system stops that translational motion.

168., wherein, interrupt the motion of processing component in reaction system 25 milliseconds after finding dangerous situation according to the security system of claim 165.

169. a chopping saw comprises:

One be fixed on the pivot cutter shaft unit and be suitable for pivoting and enter the saw blade that contacts with workpiece with cut workpiece;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

A reaction system that is used for when detection system detects unsafe condition between people and saw blade, interrupting saw blade and pivot cutter shaft unit motion.

170., further comprise the pneumatic cylinders of a pivot saw blade and pivot cutter shaft unit according to the chopping saw of claim 169.

171. according to the chopping saw of claim 169, wherein, detection system is surveyed the dangerous situation between people and saw blade.

172. the chopping saw according to claim 169 further comprise a saw blade guardrail, and detection system detects the dangerous situation between people and saw blade guardrail.

173. according to the chopping of claim 169 saw, further comprise a working face, cut workpiece is come on saw blade this plane of extending, and wherein detection system is surveyed contacting of people and at least a portion working face.

174. according to the chopping saw of claim 169, wherein, reaction system comprises a braking mechanism and Jie

Connecting rod between pivot cutter shaft unit and fixing point, wherein, connecting rod comprises the part that at least one moves when pivot cutter shaft unit rotational, and the motion that braking mechanism is used to limiting rod is with the motion of the cutter shaft unit that stops to pivot.

175. according to the chopping saw of claim 169, wherein, reaction system comprises:

One has and is used for the connecting rod of the lever that pivots around a pivotal point, this lever has two ends, and pivotal point is nearer apart from an end, one first lever be connected in pivot cutter shaft unit with, near between that end of pivotal point, and second lever that is connected with the lever other end, wherein, the motion of pivot cutter shaft unit causes the motion of first lever, and the motion of first lever then drawing and play lever and pivot around pivotal point, and the pivot of lever causes the motion of second lever; And a braking mechanism that is used to stop second lever motion, and the braking of second lever connects the motion of the cutter shaft unit that stops to pivot.

176. according to the chopping saw of claim 175, wherein, reaction system further comprises a spring that connects second lever and a predetermined point.

177. one is fixed to and pivots certainly the member that the cutter shaft unit extends, and this member moves with pivot cutter shaft unit;

A connecting rod that is attached to this member one end, wherein, this connecting rod moves with member;

And a braking mechanism that is suitable for stopping link motion, wherein, connecting rod then stop the to pivot motion of cutter shaft unit.

178. according to the chopping saw of claim 177, wherein, reaction system further comprises a spring that connects a lever and a predetermined point.

179. according to the chopping saw of claim 169, wherein, reaction system comprises:

A pillar that is fixed on the pivot cutter shaft unit and is suitable for moving with pivot cutter shaft unit;

A connecting rod relevant with pillar;

A cartridge that is fixed on the pillar and is suitable for when pillar moves, on connecting rod, sliding;

And a braking mechanism that is suitable for stopping the cartridge motion, wherein, cartridge then stops the motion of pillar and pivot cutter shaft unit.

180. according to the chopping saw of claim 179, wherein, reaction system further comprises a spring that connects a connecting rod and a predetermined point.

181. chopping saw according to claim 169, wherein, reaction system comprises a braking mechanism and the connecting rod between a pivot cutter shaft unit and a fixing point, wherein, connecting rod comprises the part that at least one moves when pivot cutter shaft unit rotational, and, the motion that braking mechanism is used to limiting rod is with the motion of the cutter shaft unit that stops to pivot, wherein, the motion that braking mechanism is used to limiting rod is with the motion of the cutter shaft unit that stops to pivot, wherein, braking mechanism comprises a brake pawl, and braking mechanism comprises that one is used for the brake pawl is remained on a non-braking position up to the electromagnet that detects dangerous situation.

182., comprise that further one is designed to make it to enter the member that contacts and then brake is arranged on non-normal danger with electromagnet with engagement of brake pawl and travelling brake pawl according to the chopping saw of claim 181.

183. a machine comprises:

A cutter assembly;

A motor that is suitable for driving this cutter assembly;

A detection system that is suitable for surveying dangerous situation;

And reaction system that is suitable for the dangerous situation that arrives in echo probe up to small part shielding cutter assembly.

184. according to the chopping of claim 183 saw, wherein, cutter assembly is circular and prolongs round girth distribution cutting edge that reaction system comprises that one is used for twining the band of cutter assembly periphery.

185. a machine comprises:

Cutter assembly with one or more cutting edges;

A motor that is suitable for driving this cutter assembly;

A detection system that is suitable for surveying dangerous situation;

And reaction system that is suitable for when detection system detects dangerous situation, stopping cutting edge.

186. according to the machine of claim 185, wherein, reaction system separates cutting edge with cutter assembly.

187. a machine comprises:

Cutter assembly with one or more cutting edges;

A motor that is suitable for driving this cutter assembly;

A detection system that is suitable for surveying the dangerous situation relevant with cutting edge;

And reaction system that is suitable for when the dangerous situation that echo probe is arrived, stoping cutting edge.

188. a table saw comprises:

Working face;

One is suitable for by the upwardly extending rotatable saw blade of working face;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And brake system that is suitable for when detection system detects dangerous situation, stopping the saw blade rotation.

189. according to the table saw of claim 188, wherein, saw blade and electric saw other parts electric insulation, and detection system is suitable for to signal of telecommunication of saw blade electric capacity transmission, and survey the generation of a predetermined variation of this signal.

190. table saw according to claim 188, wherein, saw blade is fixed on the cutter shaft, and wherein saw blade and electric saw other parts electric insulation, and detection system is suitable for transmitting a signal of telecommunication to saw blade and cutter shaft electric capacity, and surveys the generation of a predetermined variation of this signal.

191. according to the table saw of claim 188, wherein, dangerous situation is meant the contact between people and the saw blade.

192. according to the table saw of claim 188, wherein, dangerous situation is meant approaching between people and the saw blade.

193. according to the table saw of claim 188, wherein, brake system comprises a brake pawl that is suitable for meshing saw blade.

194. according to the table saw of claim 193, wherein, the brake pawl is the part of replaceable cartridge.

195. according to the table saw of claim 193, wherein, a spring will brake the pawl bias voltage to saw blade.

196. according to the table saw of claim 193, wherein, a fusible member restriction brake pawl and the engagement of fusible member.

197. according to the table saw of claim 196, wherein, brake system comprises a connecting rod between brake pawl and fusible member.

198. any one further comprises an emission system that triggers brake system when detecting dangerous situation according to the table saw of claim 188.

199. according to the table saw of claim 198, wherein, emission system comprises an electric capacity.

200. according to the table saw of claim 188, further comprise a framework that supports saw blade, wherein saw blade is with respect to framework and by lifting, and brake system is designed to the saw blade lifting.

201. the table saw according to claim 188 further comprises a framework that supports saw blade, wherein saw blade is tilted with respect to framework, and brake system is designed to tilt with saw blade.

202. a table saw comprises:

A working face;

One is suitable for by the upwardly extending rotatable saw blade of working face;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And emission system that is suitable for when detection system detects dangerous situation, triggering brake system.

203. table saw according to claim 202, wherein, brake system comprises a brake pawl that is biased to saw blade, and emission system comprises a fusible member that limits the brake pawl and make it not contact with saw blade, and this fusible member of emission system fusing is discharged into saw blade with the pawl that will brake.

204. the table saw according to claim 202 further comprises a test macro that is used to test the emission system operability.

205. a security system of table saw, wherein, the table saw comprises a rotatable saw blade, and security system comprises:

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And brake system that is suitable for when detection system detects dangerous situation, stopping the saw blade rotation.

206. a mitre saw comprises:

A pedestal;

One by the saw blade of base supports;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

Take place when detecting dangerous situation, to cause preconcerted operations with a reaction system relevant with detection system;

207. according to the mitre saw of claim 206, wherein, reaction system comprises the brake system of a braking saw blade.

208. according to the mitre saw of claim 206, wherein, reaction system comprises the mechanism of a retraction saw blade.

209. according to the mitre saw of claim 206, wherein, reaction system comprises that one covers the mechanism of saw blade.

210. a mitre saw comprises:

A pedestal;

One by base supports and be suitable for pivoting to the workpiece that is cut swing arm;

One is fixed when workpiece rotates with the saw blade of swing arm campaign with contact workpiece when swing arm;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

And the reaction system that interrupts saw blade and swing arm campaign during a dangerous situation that is suitable between detection system finder and saw blade.

211. an annular saw comprises:

A saw blade that is supported by a shell;

A detection system that is suitable for surveying the dangerous situation between people and the saw blade;

Take place when detecting dangerous situation, to cause preconcerted operations with a reaction system relevant with detection system;

212. according to the annular saw of claim 211, wherein, reaction system comprises the brake system of a braking saw blade.

213. according to the annular saw of claim 211, wherein, reaction system comprises the mechanism of a retraction saw blade.

214. according to the annular saw of claim 211, wherein, reaction system comprises a mechanism that covers saw blade.

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