Elevator safety arrangement for controlling elevator movement

Abstract

A method and a safety arrangement are provided for monitoring the movement of an elevator component, more particularly of an elevator car or of the automatic door of an elevator. In the method, a setup drive of an elevator component is run, and the speed and/or acceleration of the elevator component is measured during the setup drive, a threshold value for the speed and/or acceleration of the elevator component is formed on the basis of the measuring data obtained in the setup drive, the speed and/or acceleration of the elevator component is measured, and if the measured speed and/or acceleration exceeds the aforementioned threshold value, a monitoring signal for bringing the elevator to a safe state is formed.

Claims

1. A method for controlling the movement of an elevator component, said method comprising the steps of: running a setup drive of an elevator component, wherein the setup drive is an initialization of the elevator component where the elevator component performs a complete operational cycle, and measuring the speed and/or acceleration of the elevator component during the setup drive; forming a threshold value for the speed and/or acceleration of the elevator component on the basis of the measured speed and/or acceleration obtained in the setup drive; measuring the speed and/or acceleration of the elevator component after the setup drive, and if the measured speed and/or acceleration exceeds the threshold value, forming a monitoring signal that monitors the speed and/or acceleration of the elevator component; and based on the monitoring signal, controlling the operation of the elevator component to bring the elevator component to a stopped position.

2. The method according to claim 1, further comprising the steps of: forming a monitoring function for monitoring the movement of the elevator component; initializing the monitoring function into a state in which the monitoring function is not in use; determining one or more pass criteria for passing the setup drive; and taking the monitoring function into use after fulfilling the one or more pass criteria.

3. The method according to claim 1, further comprising the steps of: ascertaining the maximum value during the setup drive of the measured speed and/or acceleration of the elevator component; and forming the threshold value for the speed and/or acceleration of the elevator component on the basis of the maximum value during the setup drive.

4. The method according claim 1, further comprising the steps of: forming a speed reference for the elevator component for the setup drive; adjusting the speed of the elevator component with the motor drive to be according to the speed reference during the setup drive; forming a scaling factor, which connects the speed reference to the speed and/or acceleration during the setup drive; and forming a threshold value for the speed and/or acceleration of the elevator component as a function of the speed reference by means of the scaling factor.

5. The method according to claim 1, wherein the elevator component is an elevator car.

6. The method according to claim 5, further comprising the step of driving the setup drive by moving an elevator car from a terminal floor of the elevator hoistway and stopping at the opposite terminal floor.

7. The method according to claim 5, further comprising the step of starting an emergency stop of the elevator car on the basis of the monitoring signal.

8. The method according to claim 5, further comprising the steps of: forming two threshold values of different magnitudes for the speed of the elevator car on the basis of the measuring data obtained in the setup drive; if the measured speed of the elevator car exceeds the first threshold value, controlling the electric motor of the hoisting machine of the elevator and/or the machinery brakes of the hoisting machine for bringing the elevator car to the stopped position; and if the measured speed of the elevator car further exceeds the second, larger threshold value, activating a safety mechanism of the elevator car.

9. A safety arrangement of an elevator, comprising: an elevator component, a movement measuring sensor, which is connected to measure the movement of the elevator component; a motor drive for driving the elevator component; a safety controller, which is connected to the motor drive for bringing the elevator to a stopped position; and a data transfer channel formed between the motor drive, the movement measuring sensor and the safety controller, the safety controller comprising a processor and a memory, in which is a program to be executed by the processor, in which program the safety controller is configured: to receive from the movement measuring sensor measuring data about the speed and/or acceleration of the elevator component during the setup drive, wherein the setup drive is an initialization of the elevator component where the elevator component performs a complete operational cycle; to form a threshold value for the speed and/or acceleration of the elevator component on the basis of the aforementioned measuring data; to receive from the movement measuring sensor after the setup drive measuring data about the speed and/or acceleration of the elevator component, and if the measuring data being received in this case exceeds the threshold value; and to form a monitoring signal for bringing the elevator component to the stopped position.

10. The safety arrangement according to claim 9, wherein the elevator component is an elevator car.

11. The safety arrangement according to claim 10, wherein the safety controller is configured to start an emergency stop of the elevator car on the basis of the monitoring signal to be formed.

12. The safety arrangement according to claim 9, wherein the elevator component is an automatic door of an elevator.

13. The safety arrangement according to claim 9, wherein the movement measuring sensor is a position sensor and/or a speed sensor and/or an acceleration sensor.

14. The method according to claim 2, further comprising the steps of: ascertaining the maximum value during the setup drive of the measured speed and/or acceleration of the elevator component; and forming a threshold value for the speed and/or acceleration of the elevator component on the basis of the maximum value during the setup drive.

15. The method according to claim 2, further comprising the steps of: forming a speed reference for an elevator component for the setup drive; adjusting the speed of the elevator component with a motor drive to be according to the speed reference during the setup drive; forming a scaling factor, which connects the speed reference to the speed and/or acceleration during the setup drive; and forming a threshold value for the speed and/or acceleration of the elevator component as a function of the speed reference by means of the scaling factor.

16. The method according to claim 3, further comprising the steps of: forming a speed reference of the elevator component for the setup drive; adjusting the speed of the elevator component with a motor drive to be according to the speed reference during the setup drive; forming a scaling factor, which connects the speed reference to the speed and/or acceleration during the setup drive; and forming a threshold value for the speed and/or acceleration of the elevator component as a function of the speed reference by means of the scaling factor.

17. The method according to claim 2, wherein the elevator component is an elevator car.

18. The method according to claim 3, wherein the elevator component is an elevator car.

19. The method according to claim 4, wherein the elevator component is an elevator car.

20. The method according to claim 6, further comprising the step of starting an emergency stop of the elevator car on the basis of the monitoring signal.

Description

BRIEF EXPLANTATION OF THE FIGURES

(1) FIG. 1 presents as a block diagram a safety arrangement of an elevator according to one embodiment.

(2) FIG. 2 presents as a block diagram a safety arrangement of an elevator according to a second embodiment.

(3) FIG. 3a illustrates a threshold value for speed according to the first or second embodiment.

(4) FIG. 3b illustrates a threshold value for acceleration according to the first or second embodiment.

MORE DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(5) For the sake of clarity, FIGS. 1-3 endeavors to present only the features that are essential from the viewpoint of understanding the invention. Consequently e.g. some generally known parts belonging to an elevator are not necessarily presented in the figures if the presentation of them is not significant from the viewpoint of understanding the invention.

(6) In the description the same reference numbers are always used for the same parts and functions.

(7) As a person skilled in the art can ascertain when becoming acquainted with the description, the terms “acceleration of an/the elevator car” or “acceleration of an/the automatic door” are used in the description in certain situations also to refer to the deceleration of an/the elevator car or to the deceleration of an/the automatic door, respectively.

(8) FIG. 1 presents a safety arrangement in an elevator, in which the elevator car 1 is driven in the elevator hoistway 1 with a motor drive in such a way that the elevator car 1 stops at the floors determined by service requests given by elevator passengers. The motor drive comprises a hoisting machine 8 of the elevator and also a frequency converter 16. The elevator car 1 is driven by pulling the hoisting roping 21 of the elevator with the traction sheave 19 of the hoisting machine 8. The traction sheave 19 is rotated by an electric motor 25 in the hoisting machine 8, by supplying current to the electric motor 25 from the electricity network 20 with a frequency converter 16. The electric motor 25 can be e.g. a permanent-magnet synchronous motor, an induction motor or a reluctance motor, or otherwise also a direct-current motor. The electric motor 25 is connected to the traction sheave 19 with a traction belt 24 in such a way that the axes of rotation of the electric motor 25 and of the traction sheave 29 are situated side by side. In some alternative solutions the electric motor 25 and the traction sheave 19 are situated consecutively on the same axis of rotation, in which case a traction belt 24 is not needed. In the solution of FIG. 1 the hoisting machine 8 is disposed in the top part of the elevator hoistway 7, but the hoisting machine could also be disposed e.g. at the side of the vertical path of movement of the elevator car 1 or in a pit below the elevator hoistway 7. On the other hand, the hoisting machine 8 can also be disposed in a separate machine room.

(9) A microprocessor is fitted in connection with the frequency converter 16, which microprocessor calculates the speed reference v.sub.ref of the elevator car 1, i.e. the target speed for movement of the elevator car 1 in the elevator hoistway 7. The frequency converter 16 measures the speed of rotation of the traction sheave 19 with a pulse encoder 22 and adjusts the measured speed of the traction sheave 19 towards the speed reference by adjusting the current of the electric motor 25 of the hoisting machine 8.

(10) The hoisting machine 8 also comprises two electromagnet machinery brakes 9. The machinery brakes 9 are kept open by supplying electric power with the brake control circuit 11 to the electromagnets of the machinery brakes 9, and the machinery brakes 9 are connected to mechanically brake the traction sheave 19 of the hoisting machine by disconnecting the electricity supply to the electromagnets of the machinery brakes 9.

(11) For avoiding an accident situation, an elevator car 1 has a safety mechanism 12 that stops the movement of a falling elevator car 1 by gripping hold of a guide rail of the elevator car 1. The safety mechanism 12 is designed in such a way that it is able to stop only a downward-moving elevator car 1. The safety mechanism 12 is activated by the overspeed governor 29. In the elevator of FIG. 1, the overspeed governor 29 is situated in the top part of the elevator hoistway 7. The overspeed governor 29 is connected to the safety mechanism 12 with a rope 28, which runs around the rope pulley 27 of the overspeed governor 29. The rope pulley 27 is able to rotate freely during normal operation of the elevator. The safety mechanism 12 is activated by stopping the movement of the rope pulley 27, in which case also the movement of the rope 28 stops. If the elevator car 1 moves downwards when the rope 28 stops, the safety mechanism 12 displaces into the gripping position and the elevator car 1 stops by gripping hold of a guide rail.

(12) The safety arrangement of FIG. 1 comprises positive opening safety contacts 23a, 23b, which are situated to monitor the safety of selected points in the elevator. With the safety contacts 23a, 23b e.g. the state of the entrances of the elevator hoistway 7 can be monitored, as can also: the extreme limits of permitted movement of the elevator car 1 in the elevator hoistway 7, the operation of the overspeed governor 29 of the elevator, the position of the car door of the elevator, the state of the end buffers of the elevator hoistway 7, temporary service spaces to be formed in the elevator hoistway 7, the state of the safety mechanism 12 to be activated with the overspeed governor 29, et cetera. The opening of a safety contact 23a, 23b indicates a functional nonconformance, such as endangerment of the safety of a monitored point.

(13) The safety arrangement also comprises an electronic safety controller 17. The safety controller 17 is an electronic programmable safety device that can comprise at least two microprocessors having their own memories, the softwares recorded in which the microprocessors execute independently of each other. The safety controller 17 is designed and programmed to follow the safety regulations in use in the field that are required of the safety devices of an elevator.

(14) The safety contacts 23a, 23b of the elevator are conducted to the electronic safety controller 17, and the electronic safety controller 17 is configured to read the state of the safety contacts 23a, 23b. Between the safety controller 17 and the frequency converter 16 is a data transfer bus 18, which data transfer bus 18 is also taken via a traveling cable onwards to the elevator car 1. On the elevator car 1 is a microcontroller 36, which reads the measuring signal of the acceleration sensor 13 of the elevator car and also calculates by integration the speed of the elevator car 1 and the distance traveled by the elevator car 1 from the acceleration data. The microcontroller 36 also reads the measuring data from the door zone sensor 14, which indicates the position of the elevator car 1 at the point of a hoistway door in the elevator hoistway 12 as well as information about which floor the elevator car 1 is situated at. In addition, the microcontroller 36 calculates from the data received from the door zone sensor 14 the speed of the elevator car 1 always when the elevator car 1 passes a hoistway door in the elevator hoistway. The solution described in e.g. patent publication WO 2011/042612 A1 can be used as a door zone sensor 14.

(15) Since there can be an error in the speed data and position data integrated from the measuring signal of the acceleration sensor 13, the microcontroller 36 always corrects the integrated speed data and position data when it receives from a door zone sensor 14 information about the speed and position of the elevator car 1 when the elevator car 1 passes a hoistway door. The microcontroller 36 sends the processed measuring data for the acceleration, speed and position of the elevator car to the data transfer bus 18, and the safety controller 17 receives from the data transfer bus 18 the measuring data sent by the microcontroller 36. The safety controller 17 monitors the operation of the elevator from the safety contacts 23a, 23b and also on the basis of measuring data being received via the data transfer bus 18. The safety controller 17 brings the elevator to a safe state if the measuring data received indicates that the safety of the elevator is endangered.

(16) The data transfer bus 18 is preferably a serial interface bus, such as a CAN bus, LON bus, RS 485 bus, or corresponding. On the other hand the data transfer bus 18 can also be a wireless radio connection. Most preferably the data transfer channel 18 is implemented as a time-division protocol in such a way that the safety controller 17 receives measuring data from the data transfer bus at regular intervals.

(17) The safety controller 17 comprises a relay output for the safety signal 6. If necessary, the safety controller 17 brings the elevator to a safe state by disconnecting the aforementioned safety signal 6 by opening the contacts of a safety relay that is in the safety controller 17. When the safety signal 6 is disconnected, the machinery brakes 9 engage to brake the traction sheave 19 of the hoisting machine and the current supply to the electric motor 25 of the hoisting machine ceases.

(18) The safety controller 17 monitors that the movement of the elevator car 1 follows the desired movement. The safety controller 17 compares the measuring data of the speed and acceleration of the elevator car that it has received from the microcontroller 36 of the elevator car to the threshold value recorded in the memory of the safety controller 17. If the measured speed/acceleration of the elevator car 1 exceeds the threshold value recorded in memory, the safety controller 17 performs the necessary procedures for bringing the elevator to a safe state.

(19) In some embodiments two separate acceleration sensors 13 are fitted to the elevator car, and the safety controller 17 receives from the data transfer bus 18 acceleration measuring data from both acceleration sensors 13 separately. In this case a failure of an acceleration sensor 13 can be detected by comparing the measuring data being received from the different sensors 13.

(20) In some embodiments the speed/acceleration of the elevator car is measured with an encoder 15, which is connected to measure the movement of the rope pulley 27 of the overspeed governor 29.

(21) In some embodiments the speed/acceleration of the elevator car is measured with a magnetic strip suspended in the elevator hoistway 7. The absolute position, which is read by a reader that is on the elevator car 1, is coded into the strip.

(22) The safety controller 17 forms a threshold value for the monitoring of movement before the elevator is taken into normal operation. In normal operation the movement of the elevator car 1 is monitored by the safety controller 17, using the threshold value in the monitoring.

(23) Before the elevator is taken into normal operation, a setup drive is run with the elevator while subjected to monitoring by the safety controller 17. In the setup drive the elevator car 1 starts to move from a terminal floor of the elevator hoistway 7, drives at normal speed through the elevator hoistway 7, and stops at the opposite terminal floor.

(24) A microprocessor that is in connection with the frequency converter 16 calculates the speed reference v.sub.ref of the elevator car for the setup drive. The frequency converter 16 measures the speed of rotation of the traction sheave 19 with a pulse encoder 22 and adjusts the measured speed of the traction sheave 19 to be according to the speed reference v.sub.ref by adjusting the current of the electric motor 25 of the hoisting machine 8.

(25) The safety controller 17 during the setup drive regularly receives from the microcontroller 36 of the elevator car the processed measuring data of the acceleration sensor 13/door zone sensor 14 of the elevator car and it records the measuring data received as a set of samples in the memory of the safety controller 17. At the same time the safety controller 17 monitors the progress of the setup drive from the safety contacts 23a, 23b and by means of the data being received from the other sensors. If the safety controller 17 concludes there is a functional nonconformance, the safety controller 17 aborts the setup drive. This type of functional nonconformance can be e.g. the opening of a safety contact 23a, 23b of the elevator during the setup drive. The reason for this can be e.g. the activation of the overspeed governor 29 or the opening of a hoistway door. One reason for a functional nonconformance can also be an error detected by the frequency converter 16, such as a control error or overspeed of the traction sheave, et cetera. Taking the elevator into use is dependent on successfully passing the setup drive, so an aborted setup drive must be performed again.

(26) When the setup drive has been successfully passed, the safety controller 17 takes into use the movement monitoring function, according to the description, of the movement of the elevator car 1. The safety controller 17 forms the threshold values for the speed and acceleration of the elevator car that are needed in the monitoring function on the basis of the set of samples of the measuring data recorded in memory in the setup drive.

(27) In one embodiment the safety controller 17 ascertains from the set of samples recorded in memory the maximum values during the setup drive for the speed and acceleration of the elevator car 1. The safety controller 17 forms a threshold value for the speed of the elevator car in such a way that the threshold value is a constant value, which is 5 percent greater than the maximum value of the speed of the elevator car 1 measured by the microcontroller 36 of the elevator car during the setup drive. The safety controller also forms a threshold value for the acceleration of the elevator car in such a way that the threshold value for acceleration is a constant value, which is most preferably 25-50 percent greater than the maximum value of the acceleration of the elevator car 1 measured by the microcontroller 36 of the elevator car during the setup drive.

(28) In a further developed embodiment the frequency converter 16 sends to the safety controller 17 a speed reference v.sub.ref from the even speed run phase of the setup drive. The safety controller 17 ascertains the maximum value v.sub.max for the speed of the elevator car 1 from the set of samples recorded in memory from the even speed run phase. The safety controller 17 calculates the elevator-specific scaling factor k by means of the maximum value v.sub.max for speed and by means of the speed reference v.sub.ref:

(29) $k=\frac{v_{\mathrm{ma}x}}{v_{\mathrm{ref}}}.$
The safety controller determines the threshold value v.sub.lim, for speed in such a way that the threshold value is 5 percent greater than v.sub.max, in which case a description is obtained for the threshold value v.sub.lim as a function of the speed reference v.sub.ref, using the scaling factor k as an aid:
v.sub.lim=1.05*k*v.sub.ref

(30) The scaling factor k is an elevator-specific constant, which comprises elevator-specific information about, inter alia, a speed overrun causing a response of the speed regulator of the elevator car, fluctuation caused in the speed of the elevator car from the control of an open loop, scaling errors and offset errors of the speed/acceleration measuring apparatus, unit-specific variation of speed/acceleration sensors, et cetera. When the scaling factor k has been formed once, the equation above can after this always be used in the calculation of the threshold value v.sub.lim, so the threshold value in different drive modes (e.g. normal drive, service drive, rescue drive) for the different run speeds needed can be determined as a function of the speed reference v.sub.ref without separate setup drives. It must be noted that in the equation above the speed reference can also change as a function v.sub.ref(s) of the position s of the elevator car, in which case the threshold value v.sub.lim can be determined as a function of the position s of the elevator car:
v.sub.lim(s)=1.05*k*v.sub.ref(s)

(31) In a further developed embodiment the safety controller 17 regularly receives from the frequency converter 16 the instantaneous value of the speed reference v.sub.ref of the elevator car, which value is formed as a function of the position s. The safety controller 17 always also again determines a threshold value v.sub.lim when the speed reference v.sub.ref changes as the position s of the elevator car 1 changes.

(32) Also a corresponding scaling factor k.sub.2 can be formed for the acceleration of the elevator car, e.g. from the maximum acceleration a.sub.refmax of the speed reference as well as from the corresponding measured acceleration a.sub.max:

(33) $k_2=\frac{a_{\mathrm{ma}x}}{a_{\mathrm{ref}\mathrm{ma}x}}$

(34) In this case the threshold value a.sub.lim of acceleration can be formed by means of the speed reference and the scaling factor, using the following equation, wherein the threshold value a.sub.lim is 50 percent greater than the value calculated from the maximum acceleration a.sub.refmax of the speed reference:
a.sub.lim=1.5*k.sub.2*a.sub.ref max

(35) The maximum acceleration a.sub.refmax in the speed reference occurs at the start and at the end of a run, when the elevator car is accelerating in moving from the stopping floor and when braking at a stopping floor.

(36) Of course, threshold values of different magnitudes for different drive modes/run speeds could also be determined by driving separate setup drives at different run speeds and by again determining in connection with each setup drive the threshold values in the setup drive on the basis of the measuring data for movement of the elevator car 1 received from the microcontroller 36 of the elevator car.

(37) FIG. 3a presents a graph 4 of the speed of the elevator car 1 as a function of the position s of the elevator car, when the elevator car 1 starts to move from a terminal floor and stops at the opposite terminal floor. The threshold value 2 for the speed of the elevator car is formed in such a way that the threshold value 2 (continuous line) is a constant value that is 5 percent greater than the maximum speed 4 of the elevator car measured by the microcontroller 36 of the elevator car during the setup drive. In addition, FIG. 3a presents as a dashed line 2′ the threshold value that is formed as a function of the speed reference v.sub.ref in such a way that the threshold value 2′ changes as the speed reference changes in the proximity of the end zone of the elevator hoistway.

(38) FIG. 3b correspondingly presents the graph of the acceleration 5 of the elevator car 1 during a setup drive, as a function of the position s of the elevator car 1. The threshold value 3 for the acceleration of the elevator car is formed in such a way that the threshold value 3 is 50 percent percent greater than the maximum acceleration of the elevator car 1 measured by the microcontroller 36 of the elevator car during the setup drive.

(39) As stated in the preceding description, the safety controller 17 monitors the movement of the elevator car 1 by comparing the measuring data of the speed 4 and acceleration 5 of the elevator car being received from the microcontroller 36 of the elevator car to the set threshold values 2, 3, and if the measured speed 4/acceleration 5 of the elevator car 1 exceeds a threshold value 2, 3, the safety controller 17 performs the necessary procedures for bringing the elevator to a safe state. In one embodiment the safety controller 17 in this case disconnects the safety signal 6, in which case the machinery brakes 9 engage, the power supply to the electric motor 25 of the hoisting machine ceases and the elevator car 1 stops. After stopping the elevator car 1 returns to the stopping floor by driving with the hoisting machine 8 at a reduced speed. If the overspeed monitoring activates a number of times within a certain time, the safety controller 17 removes the elevator from use.

(40) In another embodiment when the threshold value is exceeded the safety controller 17 sends a speed limiting command via the data transfer bus 18 to the frequency converter 16, on the basis of which command the frequency converter 16 drops the speed of the elevator car 1 but continues the run onwards to the original destination floor.

(41) In a further developed embodiment the safety controller 17 forms two threshold values of different magnitudes for the speed of the elevator car 1. If the measured speed of the elevator car 1 exceeds the first of the threshold values, the safety controller disconnects the safety signal 6, and if the speed of the elevator car 1 further continues increasing also to the second larger threshold value, the safety controller 17 also activates the safety mechanism 12 of the elevator car. For this purpose a solenoid is fitted in connection with the rope pulley 27 of the overspeed governor 29, which solenoid is controlled with a control signal of the safety controller 17. The solenoid is configured to stop the movement of the rope pulley 27 with the control of the safety controller 17.

(42) In FIG. 1 the frequency converter 16 as well as the contactors in the main circuit of the machinery brakes 9 are controlled with a safety signal 6. The control could also be implemented in other ways; the safety signal 6 could be e.g. connected to control electronics of the frequency converter 16 and also of the brake control circuit 11 in such a way that when disconnecting the safety signal 16 the passage of control pulses to the IGBT transistors of the frequency converter 16 as well as to the MOSFET transistors of the brake control circuit 11 ceases, in which case also the electricity supply to the electric motor 25 of the hoisting machine ceases and both machinery brakes 9 engage to brake the traction sheave 19.

(43) FIG. 2 presents an automatic door of an elevator, said door comprising a safety arrangement according to the description that monitors the movement of the door panels 10. The door operator of the elevator car comprises an electric motor, preferably a brushless direct-current motor, which drives a traction sheave 30, which is connected to a traction belt 34. The door panels 10 are fixed to a traction belt 34 in such a way that the door panels 10 move, according to the direction of rotation of the traction sheave 30, either towards each other or away from each other, in which case the doors open or close.

(44) The traction sheave 30 is rotated by supplying current to the electric motor with a frequency converter 32. The control unit 33 of the door of the elevator calculates a speed reference for the door panels, and the frequency converter 32 measures the speed of rotation of the traction sheave 30 with a pulse encoder 31 and adjusts the measured speed of the traction sheave 30 towards the speed reference by adjusting the current of the electric motor rotating the traction sheave 30.

(45) The safety arrangement also comprises an electronic safety controller 17. Between the safety controller 17 and the frequency converter 32 is a data transfer bus 35, via which the safety controller 17 at regular intervals receives from the frequency converter 32 information on the measuring data of the encoder 31.

(46) The safety controller 17 comprises a relay output for the safety signal 6. If necessary, the safety controller 17 brings the elevator to a safe state by disconnecting the aforementioned safety signal 6 by opening the contacts of a safety relay that is in the safety controller 17. When the safety signal 6 disconnects, the power semiconductors of the frequency converter 32 cease to conduct and the current supply to the electric motor rotating the traction sheave 30 ceases.

(47) The safety controller 17 monitors that the movement of the traction sheave 30 follows the desired movement. The safety controller 17 compares the measuring data of the encoder 31 to the threshold value recorded in the memory of the safety controller 17. If the speed/acceleration of the traction sheave 30 indicated by the measuring data of the encoder 31 exceeds the threshold value recorded in memory, the safety controller 17 disconnects the safety signal 6.

(48) The safety controller 17 forms the aforementioned threshold value in all essential respects in the same manner as was presented when describing the embodiment of FIG. 1. Consequently, before the elevator is taken into normal operation, a setup drive is run with the door operator of the elevator while subjected to monitoring by the safety controller 17. In the setup drive the door panels are driven in such a way that the doors are both opened and closed. The speed and acceleration of the door panels 10 during the setup drive can be according to FIGS. 3a and 3b.

(49) The safety controller 17 also regularly receives from the data transfer bus 18 during the setup drive the measuring data of the encoder 31 and it records the measuring data received as a set of samples in the memory of the safety controller 17, in the same manner as has been described above. Taking the elevator into use is dependent on successfully passing the setup drive, i.e. the door panels have opened and closed normally, so an aborted setup drive must be performed again.

(50) When the setup drive has been passed, the safety controller 17 takes into use the movement monitoring function according to the description. The safety controller 17 forms the threshold values needed in the monitoring function on the basis of the measuring data of the encoder 31 received in the setup drive.

(51) The safety controller 17 sets the threshold value v.sub.lim for speed to be 5 percent greater than the maximum value v.sub.max of speed measured in the setup drive and the threshold value a.sub.lim for acceleration to be 50 percent greater than the maximum value a.sub.max of acceleration measured in the setup drive.

(52) In a further developed embodiment the control unit 33 of the door sends to the safety controller 17 the value of the speed reference v.sub.ref from the even speed (maximum speed) run phase of the setup drive. The safety controller 17 calculates the scaling factor k specific to the door operator by means of the maximum value v.sub.max for speed and by means of the speed reference v.sub.ref:

(53) $k=\frac{v_{\mathrm{ma}x}}{v_{\mathrm{ref}}}.$
The safety controller determines the threshold value v.sub.lim for speed in such a way that the threshold value is 5 percent greater than v.sub.max, in which case a description is obtained for the threshold value v.sub.lim as a function of the speed reference v.sub.ref, using the scaling factor k as an aid:
v.sub.lim=1.05*k*v.sub.ref

(54) The speed reference changes as a function v.sub.ref(s) of the position s of the door panels 10, in which case also the threshold value v.sub.lim can also be determined as a function of position s. This occurs in such a way that the safety controller 17 regularly receives from the control unit 33 the instantaneous value of the speed reference v.sub.ref(s). The safety controller 17 always also again determines a threshold value v.sub.lim when the speed reference v.sub.ref changes as a function of the position s of the door panels 10.

(55) The invention is described above by the aid of a few examples of its embodiment. It is obvious to the person skilled in the art that the invention is not limited to the embodiments described above, but that many other applications are possible within the scope of the inventive concept defined by the claims presented below.

(56) The safety controller 17 is not necessarily a separate unit, but instead it could also be integrated into e.g. a frequency converter 16, 32.