HK1020547B - Multimate project-switch lock-off mechanism - Google Patents

Description

Switch interrupt locking mechanism

The present invention relates to an interrupt lock mechanism for a switch, and more particularly, to an interrupt lock mechanism for selectively locking a power switch of an electric power tool.

In the field of power tools, it is generally desirable to prevent accidental activation of such tools until the user wishes to activate the tool. In a working environment, it is envisioned that in such power tools, a trigger switch is typically used, which may be accidentally activated to start the tool before the operator wants to activate the tool. In the case of cordless power tools, this phenomenon may consume energy, which the operator does not achieve. Such trigger switches may be accidentally activated when the operator picks up the tool and inadvertently grasps the trigger switch; alternatively, if the power tool is left unattended, the tool may be dropped or dropped onto the floor, which in turn activates the switch. This problem can be exacerbated when such power tools have a "click-on-click-off" mechanism, so that once the tool is turned on, it must be turned off intermittently.

In the past, many attempts have been made to solve this problem, for which purpose the trigger switch of the power tool is provided with an interrupt locking mechanism. The interrupt lock mechanism has a button in the area of the trigger switch that protrudes outward through the power tool body. The button securely engages the trigger switch within the tool to prevent the switch from being accidentally depressed. When the user wishes to use the tool, it is necessary to depress this button inwardly to disengage it from the trigger switch; the operator can then depress the trigger switch as needed. However, the disadvantage of this conventional trigger-type switch interrupt lock mechanism is that the placement of this button is awkward: if the operator wants to try and use the tool with one hand, he will loose his grip on the power tool, since he must first press the button with one extra finger before using the trigger switch; alternatively, if two hands are desired, one hand is necessary to depress the button, the second hand holds the tool and depresses the trigger switch. In the case where the power tool needs to be stably held during operation, for example, drilling or reciprocating sawing, there are disadvantages in that: when first turned on, the operator cannot maintain the stability of the tool because the hand typically used to hold the tool needs to disengage the interrupt lock mechanism.

Another example of an interrupt lock mechanism is disclosed in uk patent application No. 9718305.7.

It is therefore an object of the present invention to provide an interrupt lock mechanism for a switch which solves the above problems and allows the use of such a power tool to be improved.

According to the present invention, there is provided an interrupt lock mechanism for a power tool, comprising a longitudinally extending locking member having one end biased by a resilient force into engagement with a power switch to limit actuation of the switch; and an actuator member movable transversely relative to the locking member to engage the distal end of the locking member remote from said one end and to move the locking member out of engagement with the switch against its resilient biasing force. Using the longitudinally extending locking member in this manner, it is easy to place the actuator remote from the switch so that the user can operate the actuator with his second hand which is only used to stabilize the tool in a position where the user would normally use his hand to stabilize the power tool (e.g., in the area of the operating tool head).

Preferably, the locking member is pivotally mounted at a point between the one end and the point of engagement with the actuator such that when the locking member is engaged with the actuator, the one end can pivot out of engagement with the switch. Preferably, the locking member is pivotable in a first plane extending longitudinally along the axis of the locking member and perpendicular to the direction of transverse movement of the actuator. This plane generally bisects the power tool into two substantially symmetrical halves along its length.

For ease of manipulation of the mechanism, typically the locking element has a first axially inclined cam surface at its end opposite said one extremity; and the actuator has a cooperating second cam surface in cam engagement with the first cam surface. Thus, lateral movement of the actuator moves the locking member. Preferably, the actuator member is resiliently biased to move to an intermediate position relative to the locking member and is movable in either lateral direction. In this way, the first and second cam surfaces are cammed in engagement regardless of the direction of movement of the actuator. This has the advantage that either a left-handed person or a right-handed person can operate the mechanism; or the mechanism may be operated by the thumb or other finger of the hand on which the tool is supported, depending on the preference of the user; since the actuator may protrude from either side of the power tool and be accessible from both sides. In addition, depressing one button toward the interior of the power tool is more convenient than sliding movement of a corresponding one of the button devices. Preferably, the first cam surface has two surfaces that are anti-symmetric about the first plane; and the second cam surface has two anti-symmetrical surfaces that cooperate with the two surfaces of the first cam surface. Thus, one of the two cam surfaces includes a substantially V-shaped configuration; and the other cam surface defines an apex for alignment and cooperation with the one cam surface V-shaped structure.

Further, according to the present invention, there is also provided an electric power tool including one of the above-described interrupt lock mechanisms; the power tool preferably further comprises a tool body and a removable tool head. The locking element is arranged on the tool body, and the actuating element is arranged on the tool head; thus, engagement of the tool body with the tool head will engage the actuator with the locking element. Typically, at least one of the first or second cam surfaces extends outwardly of the tool body or tool head respectively for engagement with the other of the first or second cam surfaces.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a front perspective view of a portion of a power tool body for receiving a removable tool tip;

FIG. 2 is a perspective view of FIG. 1 with the clamshell half removed;

FIG. 3 is a side view of the tool body of FIG. 1 with half of the clamshell housing removed;

FIG. 4 is a side view of a tool head coupling arrangement;

FIG. 5 is a side view of the tool body of FIG. 1 and the tool bit coupling arrangement of FIG. 4, after each has its clam shell halves or housings removed, when the tool body and tool bit are coupled together;

FIG. 6 is a perspective view of the tool head of a reciprocating saw with portions of the clamshell housing removed;

FIG. 7 is a side view of the power tool of FIG. 1 after attachment of the tool head attachment of the reciprocating saw of FIG. 6;

figure 8a is a perspective view of an actuator device from below;

figure 8b is a perspective view of the actuator device shown in figure 8a, seen from above.

Referring now to fig. 1, a power tool, generally designated by the numeral (2), includes a single body portion (4) which is generally formed of two halves of plastic clamshell housings (6, 8). The two clamshell halves fit together to enclose the internal mechanism of the power tool (described below). The basic design of the power tool is substantially described in corresponding uk patent application No. 9718312.3.

The body portion (4) forms a substantially D-shaped body, the rear end portion (10) of which forms a generally pistol grip which a user may grasp. A power switch in the form of a conventional trigger switch (12) projects inwardly from the rear portion (10), the power switch being operated by the index finger of the user in the usual manner in accordance with the design of the power tool. This pistol grip design is a common design and will not be described again in this embodiment. The front portion (14) of the D-shaped body has two functions: one is to provide protection to the user when grasping the pistol grip portion (10); and the other is to store two batteries (2b) as the power supply of the tool (2) (see figure 2). The two halves of the clamshell housing (6, 8) define an opening, generally indicated by reference numeral (16), which allows the battery to be inserted into the tool. The battery can be confined within the body portion and removed by a conventional means. It is known to those skilled in the art that the incorporation of removable batteries or battery packs into power tools is a well known method, and mechanisms for restraining and removing such battery packs are also well known. Since the battery is not per se part of the invention, it will not be described in more detail in the present invention.

The body portion (4) has an enlarged upper body portion (18) extending between the front and rear end portions (10, 14) for receiving a motor (20) of the power tool. The motor (20) used in this electric power tool is also a general motor, and will not be described in detail herein, except for the description of general functions. The upper body portion (18) further comprises a substantially cylindrical bore (22); the aperture is defined by the two half clamshell shells (6, 8) through which the output shaft (24) of the motor (20) is accessible.

The internal mechanism of the tool (2) will now be described in more detail with reference to fig. 2 and 3.

Two batteries (26) (only one battery is shown in fig. 2) are fitted into the front end portion (14) of the body portion (4) through the battery opening (16) and electrically engaged with the connection terminals (28). The battery (26) is restrained within the tool body (4) by a detent mechanism (30) which is manually operated to facilitate removal of the battery. Such a mechanism is a common mechanism in the field of removable battery packs and will therefore not be described. The electrical connection (28) is electrically connected to the motor (20) by the trigger (12) in the usual manner (note that for clarity of the drawing, the electrical connection is not shown, but includes insulated wire connections of the usual design). When the trigger (12) is actuated, a user may selectively connect the motor (20) to the battery (26) to energize the motor (20); the motor then rotates the output shaft (24) to form a high speed rotary drive output. As can be seen in fig. 1 and 3, the motor shaft (24) has a male gear (32) for engaging a female gear of a drive mechanism on a power tool head, which will be described later.

As is common in modern power tools, the motor (20) is provided with a forward/reverse switch (34), which switch (34) is operable to reverse the connection between the battery (26) and the motor (20) (via switch 12) and thereby reverse the direction of rotation of the motor output shaft as desired by the user. Such a mechanism is also a common mechanism in the field of power tools.

Referring now also to fig. 2, the power tool (2) is shown with one of the clamshell housings (8) removed to show the internal working mechanisms of the tool in perspective view. As can be seen, the motor is supported by ribs (generally indicated at (36)) of the conventional clamshell housing, which are symmetrical to corresponding ribs on the clamshell housing (8) to confine the motor within the clamshell housing. The foremost one of these ribs (36a) (fig. 3) forms a forwardly extending plate (38), which plate 38 together with a corresponding forwardly extending plate on the removed clamshell housing portion (8) substantially closes off the front end (40) of the motor, leaving only a circular opening (42) through which the motor shaft (24) passes. The circular hole (42) is coaxial with the motor shaft axis (49). The two clamshell halves (6, 8) further include two semicircular plates (44) disposed in front of the front extension plate (38) and substantially parallel to the plate (38) to form a second outwardly extending plate (46). The second extension plate (46) also has a circular aperture (48) to provide easy access to the motor shaft (24). The two bores (42 and 48) are coaxial on an axis (49). As can be seen in fig. 3, the two extension plates (38, 46) form a cavity (47) around the motor axis (49). The chamber (47) is accessible from the outside through a hole (48), the chamber (47) being substantially intended to receive a gear wheel (32) on the motor shaft.

In addition, the outer extending plate (46) is itself recessed within the cylindrical bore (22) such that a substantially cylindrical cavity is formed between the bore (22) and the plate (46) so that the gear (32) of the motor shaft does not protrude outside the body portion (4).

The power tool (2) includes a plurality of interchangeable tool head attachments which are secured to the body portion (4) to form a particular form of power tool having the intended function. Various embodiments of the tool head include, among other things, a typical drill bit holder, a reciprocating saw drive mechanism, and a parts sander. Each tool bit attachment has a drive mechanism which engages the motor shaft gear (32) so that the motor (20) can drive the drive mechanism of each tool bit.

Referring now to fig. 4, it can be seen that each tool head attachment, generally indicated at (50), has a common connection means (52), indicated in solid lines in fig. 4. The tool head coupling arrangement (52) includes a substantially cylindrical outer body portion (54). The body portion (54) is ergonomically designed to match the outer contour of the body portion (4) when the attachment is attached. The overall design of the tool head is a function of the different types of tool head attachments, and in general, the tool head can have different profile shapes according to the specific functions of the power tool. However, the design shown in figure 4 is common to all tool heads and may be functionally connected to the tool head as indicated by reference numeral (55).

A substantially cylindrical plug (56) extends rearwardly from the outer body portion (54) and is shaped to closely fit the cylindrical bore (22) of the body portion (4). As shown in fig. 1, the cylindrical bore (22) of the body portion is formed by a plurality of inwardly directed ribs (23) forming a substantially cylindrical cavity. The cylindrical plug (56) has a substantially flat circular rear wall (58) about a tool head axis (60). A second plug (62), also substantially cylindrical and hollow, projects rearwardly from the rear wall (58) and extends coaxially with the axis (60). The second plug has a diameter substantially smaller than the diameter of the plug (56). The hollow plug (62) has a plurality of external cylindrical shoulders (64) forming an external cylindrical recess (66). In addition, the plug (62) has an outer diameter which is gradually increased as viewed in the left-to-right direction in fig. 4, and this outer diameter is constituted by a number of chamfered steps indicated by reference numerals (68). The chamfer steps are inclined radially outwardly from the axis (60). The chamfered steps (68) form a plurality of angled guide shoulders on the spigot (62) to provide a taper to the spigot. In addition, the plug (56) also has a chamfered step (70) forming an inclined guide surface.

When the tool head attachment (50) is engaged with the body portion (4), the coupling device (52) is inserted into the cylindrical bore (22) of the body portion (4) such that the axis (60) of the tool head attachment is substantially coaxial with the motor shaft axis (49). When the attachment means (52) is received in the cylindrical bore (22), the chamfered leading edge (70) may bear against the rib (23) to maintain the tool head attachment (50) in alignment with the motor shaft axis (49). In this way, the guide edge (70) acts as a guide surface. Further insertion of the coupling device (52) into the bore (22) causes the hollow cylindrical plug (62) to pass through the hole (48) in the outwardly extending plate (46) to surround the gear (32) of the motor shaft.

As can be seen in fig. 5, which shows the attachment of the tool head attachment (50) to the body portion (4), the diameter of the inner bore (42) of the front end extension plate (38) is smaller than the diameter of the bore (48) of the outer extension plate (46). Additionally, the diameter of the distal end (72) of the plug (62) substantially matches the diameter of the bore (42); and the outer diameter of the spigot (62) corresponds to the diameter of the bore (48). Thus, when the tapered plug (62) is inserted into the body portion (4), the plug (62) fits complementarily with the holes (42 and 48), as shown in FIG. 5. Thus, the front extension plate (38) and the outer extension plate (46) can securely receive the plug of the coupling device (52) to limit axial movement of the coupling device within the body portion (4) of the power tool. The axial support of the connection device is facilitated by the close fit of the plug (56) around the cylindrical bore (22). A shoulder (74) is formed between the outer body portion (54) and the plug (56) for abutting against an outer rib (76) of the clamshell housing to limit further axial movement of the connection means (fig. 5).

In order to restrain the tool head attachment (50) relative to the body portion (4), the body portion (4) is further provided with a resiliently biased locking means (defined between the front end extension plate (38) and the outer extension plate (46) as shown in figure 3) within the cavity (47). This locking device (not shown in the drawings) comprises a resilient mechanism; the mechanism further includes two resiliently biased spring wires symmetrically disposed about the axis (60) across the apertures (42 and 48) such that when the connector (52) is passed through the aperture (48), the chamfered step (68) of the spigot (62) engages the biased spring wires to bias the spring wires out of the path of the cylindrical spigot (56). The plug (62) is then inserted further into the body portion (4) so that the resiliently biased spring wires encounter the cylindrical recess (66) on the plug (56). By returning to its resiliently biased position, the spring wires snap into engagement with the recess (66) to restrict further axial movement of the connector (52). In addition, the locking means is provided with a push button (not shown) which passes through an aperture (78) in the body portion (4) and which is pushed to push the two spring wires apart from engagement with the cylindrical recess (66) of the connecting means (52) so that the attachment head (50) of the tool can be removed when required.

The power tool (2) is also provided with an intelligent interrupt locking mechanism. The mechanism prevents actuation of the trigger switch (12) when no tool head attachment (50) is attached to the body portion (4). This interrupt lock mechanism has two functions: one is to prevent the power tool from being accidentally turned on to consume energy (battery); and as a safety mechanism, when no tool head is connected, the electric tool can be prevented from being switched on, because the rotating speed of a motor shaft gear (32) of the electric tool is very high (up to 15000 r/min), and an injury accident can be caused if the motor shaft gear accidentally contacts the motor shaft.

The interrupt lock mechanism (80) includes a rotatable lever switch member (82) pivotally mounted on a pin (84); the pin is integrally moulded with the right shell housing (6). The switch member (82) is essentially an elongate plastics pin having a downwardly projecting portion (86) at its innermost end which is biased downwardly (by means of a conventional coil spring, not shown) to the position shown in figures 2 and 3, against the trigger switch (12). The trigger switch (12) includes an upstanding tab (88) which is a rearwardly facing shoulder that engages the fulcrum pin lever tab (86) when the interrupt lock mechanism (80) is in the unactuated position (fig. 2).

In order to activate the trigger switch (12), the user must depress the trigger switch (12) with their index finger, i.e.: when viewed in fig. 3, the switch (12) is moved from right to left. However, the trigger projection (88) abuts against the projection (86) of the interrupt lock mechanism, which restricts the trigger switch (12) from moving in this manner.

The opposite end of the switch member (82) has an outwardly facing cam surface (90) which is inclined to a substantially wedge-shaped profile, as shown in figure 2.

Referring now also to fig. 1, it can be seen that the two clamshell halves (6 and 8) form, in the region of the cylindrical bore (22), a channel (92) of substantially rectangular cross-section extending downwardly from the circumference of the cylindrical bore (22) and designated by the reference numeral (92). The cam surface (90) is located within this channel (92), exposed on the outside of the body portion (4) (fig. 1).

Referring now also to fig. 4, it can be seen that the tool head attachment (50) has an additional projecting portion (93) which is substantially rectangular in cross section forming a cam ramp (96) which slopes radially outwardly from the axis (60) in a direction away from the spigot (62). The cross-sectional profile of this projection (94) matches the rectangular channel (92) of the body portion (4) in which it can be placed. This protruding portion (94) has two functions: (i) acting as an orientation mechanism; it enables the tool head to be correctly oriented about its axis (60) relative to the body portion (4) so that the projecting portion (94) is disposed within the oblong channel (92) (enabling a predetermined alignment of the tool head relative to the body portion); (ii) the cam surface (96) is cooperable with the cam surface (90) of the interrupt lock mechanism (80) such that continued movement of the tool head attachment (50) towards the body portion (4) causes camming engagement between the cam surfaces (96 and 90). This cam engagement causes pivoting deflection of the switch member (82) about the pin (84) (against the resilient biasing force of a coil spring, not shown); and moves the projection (86) upwardly (to the start position shown in figure 3) so that the projection (86) disengages from the trigger projection (88) and the user can move the trigger (12) as desired to turn on the power tool. Access to the tool bit may automatically deactivate or disable the interrupt lock mechanism.

However, in some instances, it may be desirable for the tool head to include a manual stop for engaging the cam surface (90) of the interrupt lock mechanism (80). In particular, in some forms of power tools, it is desirable that the interrupt lock mechanism remain engaged with the trigger switch (12) even when the tool head is attached to the body portion. Thus, the interrupt lock mechanism (80) requires manual manipulation. In this manner, the power tool itself will not be accidentally turned on by accidentally depressing the switch (12) when the tool bit is attached. This requires that the power tool have a means to stop the interrupt lock mechanism manually, rather than automatically. It should be understood that this additional feature is optional for different tool heads. This feature is not normally used in electric sanding machines; this feature is also optional for drill bit attachments. However, in recent years, it has been desirable to incorporate a manual break-lock mechanism into reciprocating saws because accidental activation of such saws can cause serious injury if the user is not ready.

A manual operating mechanism for the interrupt lock mechanism (80) will now be described, by way of example only, in connection with a reciprocating saw head attachment for a power tool. However, it should be understood that such a mechanism could be used in any power tool head attachment.

The reciprocating saw tool head (200) (fig. 6) includes a clamshell profile that matches the clamshell profile of the tool body. The tool head (200) includes a drive spindle (not shown) having a free end connected to a female gear member (204) which engages the male gear (32) of the motor output shaft (24) (fig. 2). It will be appreciated that when the tool head attachment (200) is connected to the body portion (4), the male gear of the motor shaft (24) and the female gear of the drive shaft (102) automatically mesh together, so that activation of the motor (20) causes the tool head drive spindle to simultaneously rotate, thereby forming the rotary drive means of the tool head drive mechanism (only generally described herein). The tool head drive spindle is connected to an internal drive wheel (not shown) which is used to drive a conventional planetary gear reduction mechanism (indicated by reference numeral (212)). It is known to those skilled in the art that the use of a planetary gear reduction mechanism is a standard practice and will not be described in detail herein, but it is to be understood that the planetary gear reduction mechanism can reduce the output speed of the motor typically used in such power tools by about 80%. As with conventional designs, the exact gear reduction ratio is dependent upon the number of teeth of the gears used in such gear sets. The gear reduction mechanism (212) has a rotary output device coupled to a drive conversion mechanism (232) for converting the rotary output of the gear reduction mechanism to linear motion for driving the saw blade (234) in a linear reciprocating motion, as indicated by arrow (236). As can be seen in fig. 6, this reciprocating motion is not parallel to the tool bit drive axis (249); this is only a preference for the ergonomic design of this particular tool head. If desired, the reciprocating motion may also be made parallel to the tool head axis (249) (and thus the motor drive axis (49)). The tool head (200) itself is a common design for reciprocating saws that have a base plate (238) that contacts the surface to be cut to stabilize the tool if desired. The profile of the tool head when coupled to the tool body is also selected according to ergonomic requirements, as shown in fig. 7.

The drive conversion mechanism (232) utilizes a conventional reciprocating space crank, which is well known to those skilled in the art and will not be described in detail herein. However, it should be understood that other methods of converting rotational motion to linear motion may be used. However, the output of the drive mechanism (232) includes a pin member (234) that engages a slot in a plate member (250). The plate member (250) is free to move only in the direction (236) of saw blade reciprocation by the use of guides in the clamshell body. The free end of the plate (250) is secured to a blade locking device (262) for engaging a conventional saw blade (234) in a standard manner.

For this reciprocating saw head (200), the connecting means (52) does not comprise the further protruding portion (94) previously described for general connecting means. Instead, the clamshell housing of the tool head (200) defines a substantially rectangular opening (280) from which extends a substantially V-shaped cam member (300) (fig. 8a and 8 b). The cam member (300) is shaped and oriented such that when the saw head (200) is secured to the tool body (4), the cam surface (90) of the break-lock mechanism is contained within the angled V-shaped configuration of the cam member (300) without requiring a force on the cam member (90) to stop the break-lock mechanism.

Referring now to fig. 8a and 8b, it can be seen that the cam member (300) is connected by a leg (301) to the middle of a plastics moulded, longitudinally extending rod (302) to form an actuating member (350). When mounted on the tool head, the rod (302) extends substantially perpendicular to the axis (249) of the tool head (and also perpendicular to the motor axis (49) of the tool bar), so that each free end (306) of the rod (302) projects laterally from the opposite side of the tool head (fig. 7) to form two external buttons. In addition, the lever (302) includes two integrally formed resiliently deflectable spring members (310), each of which engages an adjacent side wall of the inner surface of the clamshell housing when the lever (302) is inserted into the tool head clamshell housing, substantially maintaining the lever centrally within the clamshell housing, so that the cam surface (300) remains substantially centered when the lever projects outwardly to the rear of the tool head.

Forces acting on either surface (306) of the lever (302) projecting outwardly of the tool head overcome the spring force of one of the spring members (310) to move the surface (302) inwardly towards the tool head. This movement of the lever member produces a greater movement of the cam member (300). It will therefore be appreciated that the cam member (300) is movable in a rearward direction perpendicular to the tool head axis, depending on which of the two surfaces (306) is depressed. In addition, when the external force is removed from the surface (306), the biasing force of the spring member (310) elastically deformed may return the lever member (302) to its original center position. For convenience, the cam and lever members (300 and 302) form a one-piece molded plastic component with two molded spring members (310).

When the tool head (200) is mounted on the tool body (4), the cam surface (90) of the interrupt lock mechanism is located within the V-shaped formation of the cam surface (300) and interengages with the formation. As shown in FIG. 1, the cam surface (90) has a substantially convex shape extending along its longitudinal axis with two symmetrical cam surfaces located on each side of a vertical plane extending along the central axis of the part (80). The cam surface (300) has a corresponding concave cam shape with two symmetrical cam surfaces in opposite directions to the two surfaces of the cam (90) for abutting engagement of the two cam surfaces. When the tool head (200) is secured to the tool body in this manner, the concave cam surface (300) receives the convex cam surface (90) and they mate with one another. Therefore, the interrupt lock mechanism is not stopped by an undue force acting on the cam surface (90) from the cam surface (300). At this time, the interrupt lock mechanism remains engaged with the switch (12), thereby preventing the electric tool from operating; this also prevents the power saw from being switched on accidentally.

When the saw is desired to be operated, the user places one hand on the pistol grip (10), presses the switch (12) with the index finger, and holds the tool head attachment (200) with the second hand in the usual manner to operate the reciprocating saw. In use, the second hand is used to hold the saw steady. The user engages an adjacent one of the two projecting surfaces (306) of the actuator (350) with a finger or thumb of the user's second hand to hold the power tool. When the operator wishes to start using the tool, he depresses one of the two surfaces (306) with his thumb or index finger, causing the cam surface (300) to move laterally relative to the tool head axis (249) causing a ramp (320) of the convex surface (300) to move sideways into engagement with one of the convex ramps of the cam surface (90); thereby effectively moving the cam member (90) downwardly relative to the tool body (4), operating the interrupt lock mechanism (80) in the same manner as previously described for automatically disabling the interrupt lock mechanism.

When the operator releases the surface (306), the cam surface (300) returns to its central position out of engagement with the cam surface (90) under the resilient biasing force of the spring member (310). However, because the trigger switch (12) is held in the actuated position, the interrupt lock (80) cannot be reengaged with the switch (12) until the switch (12) is released. Thus, when one of the actuator (350) buttons (306) on the tool head is depressed, the power tool is free to be used before the switch (12) is released, and when the switch (12) is released, if the user wishes to resume operation, he must depress one of the buttons (306) to again disable the interrupt lock mechanism.

This particular arrangement has a number of advantages: first, with this particular form of tool head, the interrupt lock mechanism is manually deactivated. Furthermore, the interrupt lock mechanism may be manually deactivated in areas where the user wishes to grasp the power tool in order to always keep the tool stable. In this way, the user can place the saw in the position he wants to use and hold the tool steady, while using his hand to hold the tool to release the interrupt lock mechanism before activating the tool. In this way, when the user deactivates a conventional interrupt lock mechanism with his second hand in the region of the trigger switch (12), there is no need to move the tool away from the region to be cut.

Another advantage of this mechanism is that people who are accustomed to doing things with the right hand or people who are accustomed to doing things with the left hand can easily use the tool; since the manual actuator (350) is accessible from either side of the tool head.

Although the present invention is described in connection with a power tool that includes a removable tool head, it should be understood that the interrupt lock mechanism can be used in a typical power tool where the cam surfaces (300 and 90) can be placed in the body of the power tool. However, the protruding surface (306) may remain in the corresponding area shown in fig. 7. It should also be understood that the cam surface shapes (92 and 300) can be readily reversed, i.e.: providing the interrupt lock mechanism (80) with a substantially V-shaped cam surface; and the tool body includes a substantially concave cam surface. An important factor in the relationship between the cam surfaces is that each cam surface is angled relative to the other to translate the transitional motion of the actuator (350) in the transverse direction into a substantially vertical movement of the cam surface (90) of the interrupt lock mechanism (80).

As mentioned above, the above description is of a preferred embodiment only. However, it should be understood by those skilled in the art that various changes in this basic design may be made without departing from the basic concept of the invention. In particular, this particular example illustrates an interrupt lock mechanism (80) that pivots in a plane that is substantially vertical through the power tool. However, converting this pivoting motion to motion in a plane substantially perpendicular to the vertical plane allows the stop (86) to pivot substantially side-to-side into and out of engagement with the trigger switch (12) which is a more convenient engineering change. In this case, the end cam surface (90) shown would be replaced by a substantially tapered apex; the latter has vertically inclined cam surfaces which are received in substantially V-shaped cam surfaces of the actuator of the tool head so that lateral movement of the actuator in either direction pivots the actuator about a fulcrum to activate/deactivate the interrupt lock mechanism (80) as required.

As a further variation on the concept of the present invention, it is contemplated that the pivoting design of the interrupt lock mechanism (80) may be replaced by a simple sliding lever mechanism that is longitudinally engaged with the trigger switch (12) by a spring bias within a channel. In this case, the rod may include an aperture having cam surfaces therein for receiving an actuator extending transversely therethrough; the actuator member has a cam surface in reciprocating engagement with the cam surface of the lever member to translate transverse movement of the actuator member into longitudinal movement of the lever member against the biasing force of the spring in a known manner.

Furthermore, although the preferred embodiment describes an actuator accessible from either side of the tool head; it should be understood that the actuator may be accessible on only one side of the power tool, if desired.

Claims (13)

1. An interrupt lock mechanism for a power tool including a longitudinally extending locking member having one end resiliently biased into engagement with a power switch to limit actuation of the switch; and an actuator member movable transversely relative to the locking member and engaging the locking member at a location remote from the one end thereof to move the locking member out of engagement with the switch against its resilient bias.

2. The interrupt lock mechanism of claim 1 wherein the locking member is pivotally mounted at a point between said one end and a point of engagement with the actuator; so that when the locking member is engaged with the actuating member, the one end can be pivoted to disengage the switch.

3. The interrupt lock mechanism of claim 2 wherein the locking element pivots in a first plane extending longitudinally along the locking element axis and perpendicular to the direction of transverse movement of the actuator.

4. An interrupt lock mechanism as claimed in any one of the preceding claims wherein the locking element has a first axially inclined cam surface at the opposite end; and said actuating member has a cooperating second cam surface for camming engagement with said first cam surface to cause said locking member to be cammed.

5. The interrupt lock mechanism of claim 4 wherein the actuating member is resiliently biased to an intermediate position relative to the locking member and is movable in either lateral direction; such that there is cam surface engagement between the first and second cam surfaces regardless of the direction of movement of the actuator.

6. The interrupt locking mechanism of claim 5 derived from claim 3 wherein the first cam surface has two symmetrical surfaces about the first plane; and said second cam surface has two anti-symmetrical surfaces for cooperative engagement with said two surfaces of said first cam surface.

7. An interrupt lock mechanism as claimed in any one of the preceding claims in which the actuator projects outwardly of the tool body to form an actuator button.

8. The interrupt locking mechanism of claim 7 derived from claim 5 wherein the actuating members project from opposite sides of the power tool to form two opposed actuating buttons.

9. The interrupt lock mechanism of claim 8 wherein said push button is located remotely from said switch.

10. A power tool comprising an interrupt lock mechanism as claimed in any one of the preceding claims.

11. The power tool of claim 10 including a tool body and a removable tool head, wherein said locking element is disposed on said tool body and said actuating element is disposed on said tool head; whereby engagement of the tool body with the tool head causes engagement of the actuating member with the locking member.

12. A power tool according to claim 11, when dependent on claim 4, wherein at least one of said first or second cam surfaces extends outwardly of the tool body or tool head respectively to engage with the other of said first or second cam surfaces.

13. A power tool according to any one of claims 10 to 12 when dependent on claim 9 wherein said power tool has a handle portion including the power switch and a body portion; the button projects from the body portion.