Jerk limiting in elevator rescue system

Abstract

An elevator rescue system allows an elevator car of an elevator to be moved in an emergency situation. The elevator includes an elevator motor acting on hoisting ropes by which the elevator car is suspended including at least one electro-mechanical brake and an encoder outputting a signal corresponding to its speed. The rescue system includes a back-up power source, a jerk monitoring circuit connected to the encoder and including a memory storing an upper threshold value for the derivative of car acceleration, a brake feed circuit controlled by the jerk monitoring circuit, and a release switch connected to the jerk monitoring circuit and/or to the brake feed circuit. The release switch activates the brake feed circuit to release the brake, and initiate the jerk monitoring circuit to compare the derivative of car acceleration derived from the encoder signal with the stored first upper threshold value, and forwards a control signal to the brake feed circuit to initiate/stop braking depending on the comparison result.

Claims

1. A rescue system for moving an elevator car of an elevator in an emergency situation, which elevator includes an elevator motor acting on hoisting ropes by which the elevator car is suspended and/or moved, which elevator motor comprises at least one electro-mechanical brake and an encoder outputting a signal corresponding to its speed, which system comprises: a back-up power source, a jerk monitoring circuit connected to the encoder and comprising a memory for at least one first upper threshold value for the time derivative of the car acceleration, a brake feed circuit which is controlled by the jerk monitoring circuit, at least one release switch which is connected to the jerk monitoring circuit and/or to the brake feed circuit, wherein the operation of the release switch activates the brake feed circuit to release the brake, and initiates the jerk monitoring circuit the jerk monitoring circuit comparing the derivative of the car acceleration derived from the encoder signal with the stored first upper threshold value so that when the derivative of acceleration exceeds the threshold the jerk monitoring circuit supplies, a control signal to the brake feed circuit to initiate/stop braking depending on the comparison result.

2. The system according to claim 1, comprising at least one car location indicator connected to the jerk monitoring circuit or to the brake feed circuit, wherein the control signal produced by the jerk monitoring circuit is supplied to the brake to stop the elevator car when the jerk monitoring circuit or the brake feed circuit receives a signal from the car location indicator, that the car has reached a floor area.

3. The system according to claim 1 or 2, wherein the brake comprises a spring biasing the brake into a gripping state and an electro-magnetic brake release to push the brake into a release state against the force of the spring.

4. The system according to claim 1, wherein the brake feed circuit includes a DC/DC voltage converter, which is connected to the backup power source.

5. The system according to claim 1, wherein the backup-power source is a battery or an accumulator.

6. The system according to claim 1, wherein the brake feed circuit comprises a semiconductor switch, which is connected to an output of the brake feed circuit, whereby the semiconductor switch is coupled to the jerk monitoring circuit.

7. The system according to claim 1, wherein the operation of the release switch activates the jerk monitoring circuit to forward the control signal to the brake feed circuit to release the brake.

8. The system according to claim 1, wherein the control signal is a binary signal which is high to release the brake and which is low to activate the brake.

9. The system according to claim 1, wherein the power for the operation of the brake feed circuit and/or of the jerk monitoring circuit is obtained from the back-up power source.

10. The system according to claim 1, wherein the car speed of the elevator is monitored by an overspeed governor.

11. The system according to claim 1, comprising a dynamic braking circuit short-circuiting the windings of the elevator motor, which dynamic braking circuit is powered by the back-up power source.

12. The system according to claim 11, wherein the dynamic braking circuit uses an inverter of the elevator motor drive including solid state switches for dynamic braking, whereby a dynamic braking control gets its operating supply voltage from a DC intermediate circuit of the inverter.

13. The elevator including the system according to claim 1.

14. A method of moving an elevator car of an elevator in an emergency situation, which elevator includes an elevator motor acting on hoisting ropes by which the elevator car is suspended and/or moved, which elevator motor comprises at least one electro-mechanical brake and an encoder outputting a signal corresponding to its speed, using a back-up power source, a brake feed circuit to operate the electro-mechanical brake, at least one release switch to initiate a rescue operation, the method comprising: releasing the brake in response to actuation of the release switch to move the elevator car in the direction of a floor, and monitoring acceleration of the elevator car and activating the brake when the derivative of acceleration exceeds an upper threshold value.

15. The method according to claim 14, further comprising using at least one car location indicator to monitor the level of the elevator car with respect to the floor level to which the elevator car approaches, said method allowing the car is to be moved until the car location indicator indicates arrival of the elevator car in a floor area, where current output to the brake is stopped to halt movement of the elevator car.

16. The method according to claim 14 or 15, wherein after activation of the brake after exceeding the upper threshold value the brake is opened again after the car speed has dropped to a lower threshold value.

17. The method according to claim 14 wherein the operation of the release switch starts the jerk monitoring unit to control dynamic braking of the elevator motor via a dynamic braking circuit.

18. The method according to claim 14 whereby an overspeed governor is used to monitor the elevator car speed.

19. The method according to claim 14 wherein the method is performed by a system a jerk monitoring circuit connected to the encoder and comprising a memory for at least one first upper threshold value for the car acceleration and/or its time derivative; and a brake feed circuit which is controlled by the jerk monitoring circuit; wherein the release switch is controlled by the jerk monitoring circuit; wherein the releasing the brake activates the brake feed circuit to release the brake, and initiates the jerk monitoring circuit by comparing the derivative of car acceleration as derived from the encoder signal with the stored first upper threshold value, and forwarding a control signal to the brake feed circuit to initiate/stop braking depending on the comparison result.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described hereinafter by means of the enclosed drawing. This shows an inventive elevator rescue system with a jerk monitoring circuit and a dynamic braking circuit.

(2) FIG. 1 shows a schematic diagram of an inventive safety system with a jerk monitoring unit, a brake feed circuit and a dynamic braking circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) FIG. 1 shows an inventive elevator rescue system 10 for performing a safe and comfortable rescue drive of an elevator car with trapped passengers to the next floor. The figure shows a traction sheave 12 which drives hoisting ropes on which an elevator car is suspended. The hoisting ropes and the car are not shown in the figure for clarity purposes. In the rim area of the traction sheave 12 two electro-mechanical brakes 14a, 14b are provided which are controlled by a brake feed circuit 16. The traction sheave 12 is connected with the rotor of an elevator motor, whereby the rotor of the elevator motor and the traction sheave can optionally be integrated in one part, which is the case in the embodiment. In connection with the traction sheave 12 or motor an encoder 18 is arranged which is connected via a first signal line 20 to a jerk monitoring circuit (or rescue control circuit) 22. The jerk monitoring circuit 22 is connected with a release switch 24 which is preferably embodied as a push button and located in a maintenance panel which is accessible either from a floor or from a machine room. The jerk monitoring circuit is furthermore connected to a dynamic braking circuit 26. The output 27 of the dynamic braking circuit is connected to the motor windings. Thus the dynamic braking circuit 26 is able to short-circuit the windings of the elevator motor dependent on a control signal of the jerk monitoring circuit 22. The dynamic braking circuit also may comprise braking resistors so that either by connecting the motor windings via the braking resistors or by short circuiting them two different dynamic deceleration forces can be applied to the motor. The jerk monitoring circuit 22 further comprises a memory 28 having a first memory section 30a with a first upper and lower threshold value and a second memory section 30b with a second upper and lower threshold section. The rescue system 10 further comprises a car location indicator 32 which is a simple indicating means and/or which is a signal giving means connected via a second signal line 34 to the jerk monitoring circuit 22.

(4) The invention further comprises a back-up power source 36 which is connected with the brake feed circuit 16. The back-up power source is for example an accumulator or a battery. The back-up power source 36 also provides all the components of the inventive elevator rescue system 10 with the required electric power.

(5) The inventive rescue system works as follows: If an emergency situation comes up where people are trapped in an elevator car during a car ride, a comparably unskilled person as for example a housekeeper may open a control cabinet of the elevator and push the release button 24 which starts the jerk monitoring circuit 22. Upon activation the jerk monitoring circuit 22 initiates the brake feed circuit 16 to provide current to the electro-mechanical brakes 14a, 14b which releases the brakes and initiates the elevator car to start running. The encoder 18 gives a speed signal to the jerk monitoring circuit 22 from which speed signal the jerk monitoring circuit calculates the acceleration and/or its derivation in time. If the acceleration and/or its deviation in time - which means the increase of the accelerationexceeds a certain first upper threshold value stored in the first section 30a of the memory 28, the brake feed circuit 16 is controlled to shut down in which case the electro-mechanical brakes 14a, 14b start gripping the traction sheave until the actual acceleration value achieves a first lower threshold value, e.g. a certain decrease of the acceleration, in which case the jerk monitoring circuit 22 again activates the brake feed circuit 16 to feed current to the electro-mechanical brakes 14a, 14b to release them. Via this means the car acceleration is kept below the first threshold value. This car movement monitored by the jerk monitoring circuit 22 ensures that the elevator car approaches the next floor without the acceleration or the rise of the acceleration exceeding a certain threshold value. Therefore, the subjective safety feeling of the trapped passengers is enhanced and the ride of the elevator car to the next floor to free the trapped passengers is more comfortable than in a system where the velocity of the elevator car is monitored.

(6) Furthermore, the jerk monitoring circuit controls a dynamic braking circuit 26 depending on the exceeding of second upper and lower threshold values stored in the second section 30b of the memory 28. Preferably, these second threshold values are the derivation of the acceleration so that the jerk monitoring circuit 22 only triggers the dynamic braking circuit 26 to start dynamic braking, i.e. short-circuiting of the motor windings, when the rise of the acceleration, that means the derivation of the acceleration in time, exceeds a certain second upper threshold value. By this means, it can be ensured that in case of an essential imbalance of the elevator system (loaded elevator car minus counterweight), the increase of the acceleration is reduced by starting dynamic braking which then may avoid the triggering of the electro-mechanical brakes 14a, 14b by the jerk monitoring unit 22. Therefore, the control of the elevator safety travel under use of the braking circuit 26 enables a smoother car drive than in case of a control only via the brakes 14a,b. Preferably the first upper and lower threshold values are acceleration values, whereas the second upper and lower threshold values are preferably the derivation values of the acceleration, i.e. the rise or fall of the acceleration over time.

(7) Of course also the integral of acceleration can be used to control dynamic braking. Therefore, the second threshold values in the second memory section 30b also may comprise these integral values (velocities) to keep the car velocity within a defined range.

(8) The control of the brake feed circuit 16 via the jerk monitoring circuit 22 is preferably performed in that the brake feed circuit 16 comprises a DC/DC voltage converter converting the DC voltage of the back-up power source 36 (e.g. 24 V) to the DC voltage necessary to activate the electromagnets of the brakes 14a, 14b (e.g. 250 V). The output of the brake feed circuit 16 is preferably connected with a semiconductor switch and the output of the jerk monitoring circuit 22 preferably is connected with the control gate or connector of the semiconductor switch in the brake feed circuit. The semiconductor switch may be a transistor, preferably an IGBT or MOSFET.

(9) The aforementioned operation of the elevator car towards the next floor can be ensured by holding the release switch 24 pressed until the car location indicator 32 indicates the approach of a floor area in which the trapped passengers can escape. In this case, the release switch has to be manually pushed until the car location indicator 32 lights up. In another embodiment of the invention, the car location indicator 32 is a signal giving device which is connected via a second signal line 34 with to jerk monitoring circuit 22. In this case the car location indicator 24 issues via the second signal line 34 a stop signal to the jerk monitoring unit 22, whereafter the jerk monitoring unit controls the brake feed circuit 16 to stop the car. In this case the car may approach the next floor area automatically. Thus, the release switch, i.e. push button, has only to be pressed once at the beginning and the elevator starts moving automatically whereby the acceleration of the elevator car is monitored by the jerk monitoring circuit 22. After the elevator car reaches a floor area, the car location indicator 32 gives a signal via the second signal line 34 to the jerk monitoring circuit 22 which initiates the jerk monitoring circuit 22 to shut down the brake feed circuit so that the electro-mechanical brakes 14a, 14b grip the circumference of the traction sheave 12 and stop the elevator car in the approached floor area without any manual interaction of the person who has pushed the release switch. This embodiment has the advantage that the freeing of the passengers can be performed automatically by only pushing the push button 24 once whereafter the jerk monitoring circuit 22 automatically drives the elevator car to the next floor area. This allows totally unskilled persons to free trapped passengers.

(10) The invention is not restricted to the above embodiments but may be varied within the scope of the appended patent claims.

(11) It shall be understood that components mentioned in the invention may be provided once or as several, e.g. distributed parts. Thus, the numbers of brakes may vary between one and four according to the size of the elevator. Furthermore, the jerk monitoring circuit as well as the brake feed circuit as well as the dynamic braking circuit do not necessarily to be separated units but can be integrated as one or several units in another combination or configuration, which may optionally be integrated as a module of an elevator control.

LIST OF REFERENCE NUMBERS

(12) 10 elevator safety system 12 traction sheave 14a,b electro-mechanical elevator brake 16 brake feed circuit 18 encoder 20 first signal line 22 jerk monitoring circuit 24 release switch (push button) 26 dynamic braking circuit 27 output of dynamic braking circuit 28 memory 30a,b first/second memory section 32 car location indicator 34 second signal line 36 back-up power source (battery or accumulator)