HK1166771B - Electromagnetic safety trigger - Google Patents

Description

Electromagnetic safety equipment trigger

Technical Field

The present invention generally relates to electronic over-acceleration and over-speed protection systems for elevators.

Background

Elevators include safety systems to prevent the elevator from traveling at too high a speed in response to an elevator component breaking or otherwise becoming inoperative. Traditionally, elevator safety systems include a mechanical speed sensing device, typically referred to as a governor, and a safety device or clamping mechanism mounted to the elevator car frame to selectively clamp the elevator guide rails. If the hoist ropes break or other elevator operating member fails, causing the elevator car to travel at an excessive speed, the governor will trigger a safety device to slow or stop the car.

The safety device includes a brake pad mounted for movement with the governor rope and a brake housing mounted for movement with the elevator car. The brake housing is wedge shaped such that the brake pads are forced into frictional contact with the guide rail when the brake pads are moved in a direction opposite the brake housing. Eventually the brake pad becomes wedged between the guide rail and the brake housing so that there is no relative movement between the elevator car and the guide rail. To reset the safety system, the brake housing (i.e., the elevator car) must move upward while the governor rope is simultaneously released.

One drawback with this conventional safety system is that installation of the governor, including the governor sheave and tensioning sheave and governor rope, is very time consuming. Another disadvantage is that a large number of components are required to operate the system efficiently. The governor sheave assembly, governor rope, and tensioning sheave assembly are costly and take up a significant amount of space within the elevator hoistway, service pit, and machine room. Moreover, the operation of the governor rope and sheave assembly can produce a significant amount of noise, which is undesirable. In addition, the large number of components and moving parts can increase maintenance costs. Finally, in addition to being inconvenient, manually resetting the governor and safety equipment can be time consuming and costly. These drawbacks have an even greater impact on modern high-speed elevators.

Disclosure of Invention

An electromagnetic safety trigger for a safety device engaging a mass of an elevator system includes a link kinematically connected to the safety device, a linear actuator connected to the mass, an electromagnet connected to the linear actuator, and a spring connected between the link and the mass. The electromagnet is operable to release the link so as to allow the spring to move the link to engage the safety device.

Drawings

Fig. 1 shows a prior art elevator system employing a mechanical governor.

Fig. 2 is a schematic view of an elevator system including an electronic overspeed and over-acceleration protection system according to the present invention.

Fig. 3A-3C show a tachometer suitable for use in the electronic overspeed and overexposure protection system shown in fig. 2.

Fig. 4A and 4B are schematic illustrations of an electromagnetic safety trigger employed in an elevator system.

Fig. 5 is a cut-away plan view showing one implementation of an electromagnetic safety trigger mounted on an elevator car.

Fig. 6 is a flow chart of a method for detecting and handling over-acceleration and over-speed conditions of an elevator system mass according to the present invention.

Fig. 7 is a graph of an overspeed time period plotted as a function of the difference between the filtered speed of the elevator mass and a threshold speed that initially signals an overspeed condition.

Detailed Description

Fig. 1 shows a prior art elevator system 10 that includes a cable 12, a car frame 14, a car 16, a roller guide 18, a guide rail 20, a governor 22, a safety gear 24, a coupling 26, a lever 28, and a lift rod 30. The governor 22 includes a governor sheave 32, a rope loop 34, and a tensioning sheave 36. The cable 12 is connected to a car frame 14 and a counterweight (not shown in fig. 1) inside the elevator hoistway. A car 16 attached to the car frame 14 is moved up and down the elevator hoistway by the force transmitted by the cable 12 to the car frame 14 by an elevator drive (not shown) typically located in a machine room at the top of the elevator hoistway. Roller guides 18 are attached to the car frame 14 and guide the car frame 14 and car 16 along guide rails 20 up and down the elevator hoistway. A governor sheave 32 is mounted at an upper end of the elevator hoistway. A rope loop 34 is wrapped partially around the governor sheave 32 and partially around a tensioning sheave 36 (located at the bottom end of the elevator hoistway in this embodiment). The rope loop 34 is also connected to the elevator car 16 at the operating lever 28, ensuring that the angular velocity of the governor sheave 32 is directly related to the velocity of the elevator car 16.

In the elevator system 10 shown in fig. 1, the governor 22, an electromechanical brake (not shown) located in the machine room, and the safety gear 24 act to stop the elevator car 16 in the event that the car 16 exceeds a set speed as it travels inside the elevator hoistway. If the car 16 reaches an overspeed condition, the governor 22 is initially triggered to engage a switch, which in turn cuts power to the elevator drive and drops a brake to prevent movement of the drive sheave and thus the car 16. However, if the cable 12 breaks or the car 16 otherwise experiences a free fall condition unaffected by the brake, the governor 22 may act to trigger the safety device 24 to prevent movement of the car 16. In addition to engaging the switch to drop the brake, governor 22 also releases the take-up device which grips governor rope 34. Governor rope 34 is connected to safety device 24 by mechanical linkage 26, lever 28, and lift rod 30. As the car 16 continues its descent unaffected by the brake, the governor rope 34, now blocked from movement by the actuated governor 22, pulls on the operating lever 28. Operating the operating lever 28 "sets" the safety device 24 by moving the link 26 connected to the lifting rod 30, which lifting rod 30 causes the safety device 24 to engage the guide rail 20 to stop the car 16.

As described above, there are many disadvantages to conventional elevator safety systems that include mechanical governors. Embodiments of the present invention thus include an electronic system: the electronic system is capable of triggering the inter-machine brake and releasing the electromagnetic safety trigger with low hysteresis and with minimal power requirements to engage the safety when a particular car overspeed and/or over-acceleration condition is detected. The electromagnetic trigger may be automatically reset and may be released to engage the safety device during the reset process. The overspeed and over-acceleration detection and processing system is configured to reduce response time and to reduce the occurrence of false triggers caused by conditions unrelated to passenger safety, such as passengers bouncing inside the elevator car.

Elevator over-acceleration and over-speed protection system

Fig. 2 is a schematic illustration of an elevator system 40 according to the present invention, the elevator system 40 including a car 16, a speed detector 42, an acceleration detector 44, an electromagnetic safety trigger 46, and a controller 48. The speed detector 42 is an electromechanical device configured to measure the speed of the car 16 as the car 16 travels inside the hoistway during operation of the elevator system 40 and to electronically communicate with the controller 48. For example, the speed detector 42 may be a tachometer, which may also be referred to as a generator. Generally, a tachometer is a device that measures the speed of a rotating member, for example, in Revolutions Per Minute (RPM). In embodiments of the present invention, the tachometer will either measure mechanical rotation electronically or will convert the mechanical measurements into electronic signals to be interpreted by the controller 48.

The acceleration detector 44 may be an electronic device configured to measure acceleration of the car 16. The acceleration detector 44 may be, for example, an accelerometer. One type of accelerometer that may be used is a micro-electromechanical system (MEMS), which is typically constructed from a cantilever beam with a proof mass (also referred to as a seismic mass). Under the influence of acceleration, the proof mass may deflect relative to its neutral position. The deflection of the proof mass may be measured by analog or digital methods. For example, the change in capacitance between a set of fixed beams and a set of beams attached to the proof mass may be measured.

The controller 48 may be, for example, a circuit board that includes a microprocessor 48A, an input/output (I/O) interface 48B, an indicator 48C (which may be, for example, a light emitting diode), and a safety chain switch 48D. The controller 48 is powered by a power source 50 and a battery backup 52.

As shown in fig. 2, a speed detector 42, an acceleration detector 44, an electromagnetic safety trigger 46, and a controller 48 are all coupled to the car 16. In fig. 2, a speed detector 42 is mounted to the top of the car 16 and an acceleration detector 44 may be mounted on a circuit board of a controller 48. In alternative embodiments, the speed detector 42 and the acceleration detector 44 may be mounted to the car 16 in various locations suitable for making speed/acceleration measurements. The controller 48 is configured to receive and interpret signals from the speed detector 42 and the acceleration detector 44, and to control the electromagnetic safety trigger 46.

In embodiments where the speed detector 42 is a tachometer, the tachometer may be mounted to an idler wheel on the top of the car 16. The idler sheave will rotate at a speed related to the speed of the car 16. The tachometer may thus be configured to measure the speed of the car indirectly by measuring the speed at which the idler wheel rotates. In an alternative embodiment employing a tachometer, such as in an elevator system having a 1: 1 roping (roping) arrangement that does not include an idler sheave on the car, static ropes may be suspended in the elevator hoistway adjacent to the car 16 and the tachometer may be connected to the ropes. For example, fig. 3A-3C show tachometer 54 including a mounting bracket 56, a generator 58, a drive sheave 60, and a tension sheave 62. Fig. 3A is a plan view of the tachometer 54. Fig. 3B and 3C are front and side elevation views, respectively, of the tachometer 54. The tachometer 54 may be connected to the car 16 by a mounting bracket 56. The generator 58, drive sheave 60 and tension sheave 62 are all connected to the mounting bracket 56. The drive sheave 60 is rotatably connected to the generator 58. The static roping suspended in the hoistway may extend upward from the bottom of the hoistway and wrap partially over the top of the tensioning sheave 62, under the drive sheave 60, and upward toward the top of the hoistway. As the car 16 moves up and down the hoistway, the action of the static rope on the tachometer 54 will rotate the drive sheave 60, which in turn will drive the generator 58. The output of the generator is a function of the speed at which the generator is driven and can be measured to provide an indication of the speed of the car 16. In yet another embodiment, the tachometer may be driven by engaging a fixed guide rail along which the car 16 is guided up and down the elevator hoistway.

The controller 48 receives inputs from the speed detector 42 and the acceleration detector 44 and provides an output to the electromagnetic safety trigger 46. The controller 48 also includes a safety chain switch 48D that forms a portion of a safety chain 64 of the elevator system 40. The safety chain 64 is a series of electromechanical devices distributed inside the elevator hoistway and connected to the elevator drive and brakes in the machine room.

An electromagnetic safety trigger 46 is disposed on the car 16 for connection to a car safety, which is not shown in fig. 2 for clarity, but which may be arranged and function similarly to the safety 24 described with reference to fig. 1. Fig. 1 shows the safety 24 disposed toward the bottom of the car 16, and an electromagnetic safety trigger 46 may also be mounted on the bottom of the car 16. An alternative embodiment includes an elevator system having a safety disposed toward the top of the car and an electromagnetic safety trigger 46.

During operation of the elevator system 40, the speed detector 42 and the acceleration detector 44 sense the speed and acceleration of the car 16 traveling inside the elevator hoistway. The controller 48 receives signals from the speed detector 42 and the acceleration detector 44 and interprets this information to determine whether an unsafe over-speed and/or over-acceleration condition has occurred. In the event that the car 16 experiences an unsafe overspeed and/or over-acceleration condition, the controller 48 first opens the safety chain switch 48D of the safety chain 64 of the elevator system 40. Opening switch 48D disconnects safety chain 64 to interrupt power to elevator drive 66 (typically in the machine room at the upper end of the elevator hoistway) and to activate or drop brake 68 on the drive sheave of elevator drive 66. In the event that movement of the car 16 is not affected by the falling inter-machine brake 68 (e.g., if the cable 12 connected to the car 16 fails), an overspeed or over-acceleration condition continues to be sensed and the controller 48 releases the electromagnetic safety trigger 46. Releasing the safety trigger 46 causes elevator safety (including, for example, the safety 24 shown in fig. 1) to be engaged to slow or stop the car 16. Embodiments of an electromagnetic safety device trigger and overspeed and over-acceleration detection and processing system according to the present invention will now be shown and described in greater detail.

Electromagnetic elevator safety equipment trigger

Fig. 4A and 4B are schematic illustrations of an electromagnetic safety trigger 46 employed in an elevator system including safety devices 70A and 70B in accordance with the present invention. The safety device trigger 46 includes a link 72, a linear actuator 74, an electromagnet 76, and a spring 78. Fig. 4A shows the trigger 46 in a ready state, waiting to be released to engage the safety devices 70A, 70B. Fig. 4B shows the trigger 46 released to engage the safety devices 70A, 70B. For simplicity, not all components of the elevator system are shown in fig. 4A and 4B. However, as noted above, generally the trigger 46 and components of the safety devices 70A, 70B will be mounted to the elevator system mass (including, for example, the car or counterweight) against which they protect against unsafe conditions. The safety devices 70A, 70B may be similar in arrangement and construction to the safety device 24 shown in fig. 1, or may be any other safety device capable of being mechanically engaged by the trigger 46 and slowing or stopping the elevator system mass in unsafe over-speed and/or over-acceleration conditions.

In fig. 4A and 4B, the link 72 is kinematically connected to the safety devices 70A, 70B through pivot points 80A, 80B and safety device lifting bars 82A, 82B, respectively. In alternative embodiments, the link 72 may be connected to the safety devices 70A, 70B by a simpler or more complex motion mechanism in any arrangement that causes the safety devices 70A, 70B to be engaged when the link 72 is moved. Additionally, there may be more than one electromagnetic safety trigger 46 employed in the elevator system. For example, rather than one trigger 46 engaging both security devices 70A, 70B as shown in fig. 4A and 4B, alternative embodiments may include a trigger 46 for each security device 70. A linear actuator 74 is connected to one side of the elevator car 16. An electromagnet 76 is connected to the linear actuator 74 and magnetically connected to the linkage 72. A spring 78 is connected between the coupler 72 and the car 16.

The electromagnetic safety trigger 46 is operable to engage the safety devices 70, 70B in the event of an unsafe overspeed or over-acceleration condition being detected for the car 16 during elevator operation. As shown in fig. 4B, the trigger 46 is configured to break the magnetic connection between the electromagnet 76 and the linkage 72 by actuating the electromagnet 76 when an over-speed or over-acceleration condition occurs. When the electromagnet 76 is actuated, the link 72 is allowed to move away from the electromagnet 76, which releases the energy stored in the compressed spring 78 to decompress the spring 78. Decompressing the spring 78 in turn moves the link 72 to raise the lift rods 82A, 82B and thus engage the safeties 70A, 70B to slow or stop the car 16.

The trigger 46 may be automatically reset after the safety condition of the car 16 has been resolved. The linear actuator 74 is configured to extend to position the electromagnet 76 to grasp the link 72, i.e., reestablish the magnetic connection, after the link 72 has moved to engage the safety device 70, 70B. The linear actuator 74 may then retract the electromagnet 76, the electromagnet 76 magnetically connected to the link 72 to compress the spring 78 and disconnect the safety device 70, 70B. Finally, the trigger 46 may engage the safety devices 70, 70B during a reset operation by causing the electromagnet 76 to release the link 72 when the linear actuator 74 is retracted.

Fig. 5 is a cross-sectional plan view showing one implementation of an electromagnetic safety trigger 86 according to the present invention mounted toward the bottom of the elevator car 16 adjacent a safety lifting bar 90. The trigger 86 includes a link 92, a linear actuator 94, an electromagnet 96, and a coil spring 98. In fig. 5, one end of a link 92 is connected to the lifting rod 90. The opposite end of the link 92 is connected to a coil spring 98 and magnetically connected to the electromagnet 96. Between the ends, the link 92 is pivotally connected to the car 88 at pivot point 100. The linear actuator 94 is connected to an electromagnet 96. A coil spring 98 is connected to the car 88. Trigger 86 is shown in a ready state with coil spring 98 fully compressed and electromagnet 96 magnetically connected to link 92.

The electromagnet 96 is configured to be magnetized when in a de-energized state and demagnetized when in an energized state. Thus, during normal safe operation of the car 88, the electromagnet 96 retains the link 92 and the compressed coil spring 98 without the need for a continuous supply of electricity. When an unsafe over-speed or over-acceleration condition is detected, the trigger 86 may be released to engage a safety device connected to the lift bar 90 by: an electrical pulse is sent to the electromagnet 96 to remove the magnetic connection to the link 92, thereby releasing the energy stored in the compressed spring 98 to decompress the spring 98. Decompressing the spring 98 in turn moves the link 92 to move the lifting rod 90 and thus engage the safety device to slow or stop the car 88.

The linear actuator 94 is an electrical actuator that includes an electric motor 94a operatively connected to a drive shaft 94 b. The motor 94a may employ, for example, a ball screw or worm drive system to convert rotational motion of the motor 94a into linear motion of the shaft 94 b. In any case, the motor 94a may be non-back drivable to make the trigger 86 more energy efficient and less complex. The non-backdrivable actuator may be set to a specific position, such as an extended or retracted position of the shaft 94b, and held there without a continuous supply of electrical power to the actuator. The drive shaft 94b will only move during the reset operation, first being connected to the electromagnet 96 and then moving the safety mechanism back to its reset position.

Although the trigger 86 shown in fig. 5 employs a coil spring 98, alternative embodiments may include different mechanical springs or other resilient members. For example, the trigger 86 may employ a torsion spring connected to the link 92 at a pivot point 100. The torsion spring may be arranged to remain in compression when the actuator 94 is retracted and the electromagnet 96 is magnetically connected to the link 92.

Over-acceleration and over-speed detection and processing system

Generally, elevator systems are designed to detect and engage elevator safety equipment in runaway and free fall conditions. An out of control condition is when the elevator machine room brake is unable to hold the car while the car is traveling in either direction, producing a threshold maximum acceleration. The free fall condition is that the elevator travels down at 1 g. Activation of the safety device usually means that the disconnection of the drive system and the dropping of the inter-machine brake has failed or is not expected to prevent the elevator car from traveling at an unsafe speed and/or acceleration.

Elevator regulations specify such maximum speeds: at this maximum speed, a safety device is required to apply a stopping force to the elevator. Some jurisdictions also specify two speed settings, one to drop the brake and disconnect the drive system and one to apply the safety device.

Passengers in the elevator can create disturbances in a short period of time, which will make the system appear to be over-speeding and/or over-accelerating. The elevator safety device should not react to these disturbances. Examples of passenger disturbances that do not create unsafe conditions include jumps in the car or jumps that cause the car to oscillate. The passenger may cause an oscillation of 2 to 4 hertz with, for example, an amplitude of 0.4m/s (1.3 ft/s). Nor should the safety device be erroneously engaged in the event of an emergency brake or bumper impact. The speed signal is typically obtained by some form of traction encoder or transmitter, including, for example, the tachometer arrangement described above. These devices may experience momentary false readings due to loss of traction. Embodiments of over-acceleration and over-speed detection and processing systems according to the present invention detect elevator system runaway and free-fall conditions by distinguishing over-acceleration and over-speed caused by conditions unrelated to passenger safety from over-acceleration and over-speed caused by unsafe conditions. Upon detection of an actual runaway and/or free fall condition, the system electronically activates the inter-machine brake and, when appropriate, triggers the safety device.

The over-acceleration and over-speed detection and processing system includes electromechanical speed and acceleration detectors connected to and configured to send signals to the controller described with reference to fig. 2 and shown in fig. 2. The controller may include a microprocessor and associated circuitry. The velocity and acceleration detection and processing algorithm(s) included in the system may be implemented in implanted software or may be stored in memory for use by the microprocessor. The on-board memory may include, for example, flash memory.

Fig. 6 is a flow chart of a method 120 for detecting and handling over-acceleration and over-speed conditions of an elevator system mass, such as a car or counterweight, according to the present invention. As described above, the method 120 may be implemented as one or more software or hardware based algorithms executed by the controller. The method 120 includes receiving a sensed velocity of the mass from the velocity detector (step 122) and receiving a sensed acceleration of the mass from the acceleration detector (step 124). A filtered velocity of the mass is calculated as a function of the sensed velocity and the sensed acceleration (step 126). The filtered speed is compared to a threshold speed to determine if the mass has reached an overspeed condition (step 128).

The raw speed signal captured by the speed detector may be affected by various errors, most typically slippage of a tachometer used as the speed detector, for example. To reduce the impact of such errors on the system, the sensed velocity may be combined with the sensed acceleration in a manner that results in a combined (filtered) velocity with an overall smaller error. The filtered speed may be calculated using, for example, a proportional Plus Integral (PI) filter (step 126), and the measured acceleration is fed into the loop to adjust for error conditions, including, for example, slippage of the speed detector.

The filtered velocity may be calculated as a function of the sensed velocity and the sensed acceleration by initially multiplying the velocity error by a gain to determine a proportional velocity error (step 126). The velocity error is also integrated and the integrated velocity error is multiplied by a gain to determine an integrated proportional velocity error. The proportional velocity error, the integral proportional velocity error, and the measured acceleration are added to determine a filtered acceleration. The filtered acceleration is integrated to determine a filtered velocity. The calculation of the filtered speed may be accomplished in a continuous loop, where the speed error is equal to the sensed speed minus the filtered speed calculated by the controller through the loop in the previous cycle. The effect of the PI filtering is: causing the acceleration information to dominate at higher frequencies where the acceleration detector exhibits greater accuracy than the velocity detector; and causing the velocity information to dominate at lower frequencies where the velocity detector exhibits greater accuracy than the acceleration detector.

In some embodiments, acceleration errors and speed errors may be monitored during normal elevator operation to detect faults in the speed detector or acceleration detector. The acceleration error and the velocity error may be passed through a low pass filter and a detector error may be declared if the acceleration error or the velocity error exceeds a threshold error level.

In addition to calculating the filtered velocity (step 126), the method 120 includes comparing the filtered velocity to a threshold velocity to determine whether the mass has reached an overspeed condition (step 128). The initial over-speed detection point typically occurs when the speed of the elevator mass exceeds an over-speed threshold, which is often specified by industry regulatory authorities. When the threshold overspeed is exceeded, the drive and brake system are de-energized. However, if an overspeed condition is detected without additional conditions, the system will be sensitive to a variety of disturbances, including for example a person jumping in the car. To mitigate these disturbances, a variety of processing techniques may be used, including, for example, signaling an overspeed condition only when the velocity of the mass exceeds the threshold velocity for a continuous period of time ("overspeed period").

The over-speed period may be a fixed value, including, for example, 1 second. Alternatively, the over-speed period may be calculated as a function of the amount by which the filtered speed exceeds the threshold speed. For example, fig. 7 is a graph of the over-speed time period as a function of the difference between the filtered speed of the elevator mass and the threshold speed that begins to signal a possible over-speed condition. Curve 130 in fig. 7 represents one way to achieve an additional condition of overspeed time before signaling the elevator mass as an overspeed condition. As shown in fig. 7, the overspeed time is related to the amount by which the filtered speed exceeds the threshold speed in an exponentially inversely proportional (expondiallyoverlyselect). Thus, when the filtered speed of the elevator mass exceeds the threshold speed by an ever increasing amount, the overspeed time (i.e., the time the mass must dwell at the speed exceeding the threshold before signaling an overspeed condition) decreases exponentially. After comparing the filtered speed to the threshold speed to determine whether the mass has reached an overspeed condition (step 128), which may include determining whether the filtered speed of the mass is greater than the threshold for an overspeed time, the method 120 may also include dropping the drive sheave mechanical brake.

As described above, in some situations, dropping the drive sheave brake will fail to stop the elevator mass, signaling an out of control condition. The method 120 may thus include the steps of: when the mass stays in an overspeed condition after the drive sheave mechanical brake has dropped, the electromechanical safety trigger is released,to engage the elevator safety equipment. The trip (trip) point at which the signal indicates an out-of-control condition may be a speed V_TAt a speed V_TAt a set rate A, the mass accelerating will take a set amount of time T_sTo reach the speed V required by the regulation_cTo apply the stopping force of the safety device. As an example, a 1 meter/second (m/sec) elevator accelerating at an acceleration of 0.26g may travel in 145 milliseconds from an initial overspeed threshold of 1.057m/s to a regulatory required speed V of 1.43m/s_c. It takes 25 milliseconds to activate and engage the security device. Thus, the trip speed V_T1.35m/s, which is the speed at 120 milliseconds (145-25) from 1.057 m/s. This trip speed allows the necessary time (25 milliseconds) to activate the safety equipment before reaching the speed required by the regulations.

In addition to an out-of-control condition, a separate unsafe condition known as free fall must be considered in the elevator safety system. As the name implies, a free-falling elevator system mass falls without being prevented by any brake or safety device activation. Mathematically, the free fall condition occurs when the mass travels down at 1 g. Because the free-falling mass is not impeded by the brake or safety device, it will travel from the initial overspeed threshold to the point: at this point the safety device must begin to apply the stopping force in a shorter period of time than if it were uncontrolled. For example, an elevator at 1 m/s in free fall may travel from an overspeed threshold of 1.057m/s to the trip point required by regulations in 45 milliseconds. If the elevator safety system uses only the speed of the mass, the actuation of the safety device will have to start at a lower speed, so that disturbances associated with a non-safety situation (i.e. not associated with a safety situation) will result in more false trips. The filtered acceleration defined by the velocity can be used to remove interference and allow for faster reaction times.

The method 120 may therefore further comprise the steps of: the filtered acceleration is compared to a threshold acceleration, and how long the mass has been in an over-speed condition is measured. A filtered acceleration is calculated as part of calculating the filtered velocity of the mass (step 126), and is equal to the sum of the proportional velocity error, the integral proportional velocity error, and the measured acceleration. In the event that the filtered acceleration and over-speed time exceed set thresholds, the method 120 can further include dropping the drive sheave brake and simultaneously engaging elevator safety equipment. For example, if the filtered acceleration exceeds 0.5g and the elevator mass continues to travel down for 10 milliseconds at a speed greater than the overspeed threshold, the inter-machine brake and safety device may be actuated. Requiring a smaller duration of time above the speed threshold avoids tripping under impact conditions (e.g., a person impacting a platform while jumping). Defining the acceleration with the velocity information prevents tripping during other events, including, for example, emergency stops and bumper impacts.

The method 120 may also include filtering the raw acceleration measurements at one or more frequencies to reduce the effects of external interference. Filtering the measured acceleration may include filtering the measured acceleration through one or more of a low pass filter and a band stop filter in a range of hoistway resonances. For example, the measured acceleration may be first advanced through a low pass filter to remove high frequency disturbances. Next, the acceleration may be advanced through a band-stop filter to remove effects from oscillations associated with unsafe conditions, including, for example, human bouncing in the car and system excitation during an emergency stop. The goal of the band reject filter is to reduce the effect of hoistway resonance, which may include, for example, a 10db reduction at frequencies of 2.5Hz to 6 Hz.

Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention, which is defined by the appended claims.

Claims (20)

1. An apparatus configured to engage a safety device of an elevator system mass, the apparatus comprising:

a link kinematically connected to the safety device;

a linear actuator connected to the elevator system mass;

a spring connected between the link and the elevator system mass; and

an electromagnet connected to the linear actuator and magnetically connected to the linkage and operable to release the linkage, thereby allowing the spring to move the linkage to engage the safety device.

2. The apparatus of claim 1, wherein the electromagnet is configured to retain the link when de-energized and release the link when energized.

3. The device of claim 1, wherein the linear actuator comprises an electric motor.

4. The apparatus of claim 3, wherein the linear actuator comprises one of a ball screw and a worm screw.

5. The device of claim 3, wherein the linear actuator is non-back drivable.

6. The apparatus of claim 1, wherein the linear actuator is configured to extend to a position where the electromagnet grasps the link after the link has moved to engage the safety device.

7. The apparatus of claim 6, wherein the linear actuator is configured to retract an electromagnet magnetically connected to the link to compress the spring and disconnect the safety device.

8. The apparatus of claim 7, wherein the electromagnet is configured to release the link to engage the safety device while the linear actuator is retracted.

9. The device of claim 1, wherein the spring comprises one of a coil spring and a torsion spring.

10. The apparatus of claim 1, wherein the coupling comprises:

a first end connected to the security device;

a second end magnetically connected to the electromagnet; and

a pivot connection connected to the mass between the first end and the second end.

11. An elevator, comprising:

a car;

balancing weight;

a safety device connected to one of the car and the counterweight and configured to prevent movement thereof; and

a device configured to engage the safety apparatus, the device comprising:

a link kinematically connected to the safety device;

a linear actuator connected to said one of said car and said counterweight;

a spring connected to the link; and

an electromagnet connected to the linear actuator and magnetically connected to the linkage and operable to release the linkage, thereby allowing the spring to move the linkage to engage the safety device.

12. The elevator of claim 11, wherein the electromagnet is configured to retain the link when de-energized and release the link when energized.

13. The elevator of claim 11, wherein the linear actuator comprises an electric motor.

14. The elevator of claim 13, wherein the linear actuator comprises one of a ball screw and a worm.

15. The elevator of claim 13, wherein the linear actuator is non-back drivable.

16. The elevator of claim 11, wherein the linear actuator is configured to extend to a position where the electromagnet grasps the link after the link has moved to engage the safety device.

17. The elevator of claim 16, wherein the linear actuator is configured to retract an electromagnet magnetically connected to the link to compress the spring and disconnect the safety device.

18. The elevator of claim 17, wherein the electromagnet is configured to release the link to engage the safety device while the linear actuator is retracting.

19. The elevator of claim 11, wherein the spring comprises one of a coil spring and a torsion spring.

20. The elevator of claim 11, wherein the coupler comprises:

a first end connected to the security device;

a second end magnetically connected to the electromagnet; and

a pivotal connection between the first end and the second end connected to the one of the car and the counterweight.