Traction sheave elevator with drive member slippage control

Abstract

A traction sheave elevator includes a drive machine having an output shaft which is connected to the traction sheave via an endless drive member. An encoder is provided in connection with the traction sheave, and a motor speed detection device is provided. A monitoring unit is provided to which the output signal of the encoder and a speed signal of the motor speed detection device are fed. The monitoring unit includes a comparator which compares the output signal of the encoder with the speed signal of the motor speed detection device, and the monitoring unit initiates an emergency action if the result of the comparison exceeds a threshold value. The solution improves the safety in belt driven traction sheave elevators, particularly if only one belt is used for the transmission between drive machine and traction sheave.

Claims

1. Traction sheave elevator comprising a drive machine having an output shaft which is connected to the traction sheave via an endless drive member, whereby an encoder is provided in connection with the traction sheave so as to obtain a speed signal of the traction sheave, a motor speed detection device is provided, a monitoring unit is provided to which the output signal of the encoder and a speed signal of the motor speed detection device are fed, the monitoring unit comprises a comparator which compares the output signal of the encoder with the speed signal of the motor speed detection device, the monitoring unit initiates an emergency action if the result of the comparison exceeds a threshold value.

2. Traction sheave elevator according to claim 1, wherein the supply frequency of the motor drive is fed to the motor speed detection device.

3. Traction sheave elevator according to claim 1, wherein the monitoring unit is configured to open the safety chain of the elevator.

4. Traction sheave elevator according to claim 1, wherein only one drive member connects the drive machine with the traction sheave.

5. Traction sheave elevator according to claim 1, wherein the monitoring unit is integrated in the elevator control or in the motor drive.

6. Traction sheave elevator according to claim 1, wherein the motor speed detection device comprises an encoder in connection with a rotating part of the drive machine.

7. Traction sheave elevator according to claim 1, wherein the motor speed detection device is provided connection with an elevator control or a motor drive or with the drive machine.

8. Traction sheave elevator according to claim 1, wherein a wear detection unit is provided in the vicinity of the endless drive member, which wear detection unit is connected with the monitoring unit.

9. Traction sheave elevator according to claim 1, wherein at least one slip detector is provided in the vicinity of the endless drive member and of the output shaft and/or a drive pulley of the traction sheave shaft, which slip detector is connected with the monitoring unit.

10. Method for driving a traction sheave in a traction sheave elevator, in which elevator a drive machine drives the traction sheave via an endless drive member located between the output shaft of the drive machine and the shaft of the traction sheave, whereby the speed of the traction sheave is measured and compared to the speed of the drive machine and an emergency action is initiated if the result of the comparison exceeds a threshold value.

11. Method according to claim 10, wherein the speed of the drive machine is obtained from the supply voltage frequency of a motor drive.

12. Method according to claim 10, wherein the speed of the traction sheave is obtained with an encoder provided in connection with the traction sheave.

13. Method according to claim 10, wherein the threshold value is preset to a value between 0.05 m/s and 1 m/s of the velocity of the traction sheave rim.

14. Method according to claim 10, wherein in case of the threshold value being exceeded a safety chain of the elevator is opened.

15. Method according to claim 10, wherein in case of the threshold value being exceeded a gripping device of the elevator car is activated.

16. Method according to claim 10, wherein the threshold value is stored in a memory.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows a schematic illustration of a traction sheave elevator.

DETAILED DESCRIPTION

(2) FIG. 1 shows a traction sheave elevator 10 comprising a drive machine 12 with an output shaft 14 as well as a traction sheave 16 fixedly mounted on a rotating shaft 18. The shaft 18 of the traction sheave 16 is supported by bearings which are not shown in the drawing for clarity reasons. The output shaft 14 of the drive machine 12 and the shaft 18 of the traction sheave 16 are connected via an endless drive belt 20 running directly on the output shaft 14 and on a drive pulley 22 which is rotationally fixed to the shaft 18 of the traction sheave 16. The traction sheave 16 has on its outer rim 24 rope grooves or belt grooves on which hosting or suspension ropes/belts for driving an elevator car and optionally a counterweight are suspended. Two brakes 26, 28 are provided in connection with the traction sheave 16 which are located coaxially on both ends of the traction sheave. The two brakes 26, 28 serve to stop the traction sheave in case of an accident. The brakes 26, 28 are operated via an elevator control 30. The elevator control is connected to a motor drive 32, which comprises the components for the control of the drive machine 12, preferably also the power components as igbt transistors, thyristors, etc. The motor drive 32 is connected to the drive machine 12. The elevator control 30 is further connected to a remote monitoring or maintenance location 34 preferably via a telephone or internet connection. The elevator control 30 comprises a monitoring unit 36 which is provided to compare the speed of the drive machine with the speed of the traction sheave. The monitoring unit 36 comprises a memory 38 for reference values and threshold values. Further a motor speed detection device 35 is provided which is connected to the monitoring unit 36. The input of the speed detection device 35 is connected to the output 40 of the motor drive 32. By this connection, the motor speed detection device 35 obtains the frequency of the supply voltage to the drive machine which allows the calculation of the motor speed.

(3) Furthermore, the input of the motor speed detection device 35 is connected with a motor encoder 42 which co-acts with markings 44 on the output shaft 14 of the drive machine 12 to obtain a speed signal of the drive machine.

(4) The monitoring unit 36 is further connected with a traction sheave encoder 46 which is provided in connection with the shaft 18 of the traction sheave 16 thereby reading markings 48 on the circumference of the shaft 18 so as to obtain a speed signal of the traction sheave. Furthermore, the monitoring unit 36 is connected with a wear detection unit 50 which is located adjacent or in connection with the endless belt 20. Furthermore, the monitoring unit 36 is functionally connected with a switch 52 of the safety chain 54 of the elevator.

(5) At the contact point of the drive belt 20 with the drive pulley a first slip detector 56 is provided and at the contact point of the drive belt 20 with the output shaft 14 a second slip detector 58 is provided. Both detectors 56, 58 are connected wirelessly with the monitoring unit 36. They may of course also be connected via normal wiring, e.g. a serial bus. The wear detection unit 50 as well as the slip detectors 56, 58 are optional units. In the embodiment, the monitoring unit 36 is part of the elevator control 30. This is however not necessary.

(6) The invention works as follows:

(7) During normal operation, the speed signal obtained from the motor encoder 42 or from the output 40 of the motor drive 32 has a certain relationship to the output signal of the traction sheave encoder 46. This fixed relationship depends on the transmission ratio of the endless belt 20 between the output shaft 14 of the drive machine 12 and the drive pulley 22 of the traction sheave 16. Anyway, during normal operation, a comparison of these signals corresponds to a reference value stored in the memory 38.

(8) In case of a break of the endless drive belt 20 or an undue slip of the endless drive belt 20 on the output shaft 14 of the drive machine 12 or on the drive pulley 22 of the traction sheave 16, the comparison between the output signal of the traction sheave encoder 46 on one hand and the speed signal of the motor encoder 42 and/or of the output signal from the motor drive 32 deviates from the reference value by a threshold value also stored in the memory 38. In this case the monitoring unit 36 opens the switch 52 of the elevator safety chain 54 which leads to immediate stop of the drive machine 12 and via the elevator control to the activation of the traction sheave brakes 26 and 28 (by deenergizing them). Furthermore, the monitoring unit initiates via the elevator control 30 an emergency call to a remote monitoring or maintenance location 34 which is connected with the elevator control 30 via a telephoneor internet connection.

(9) Via this measure, the operation safety of the traction sheave elevator can be maintained although only one single endless drive member in form of the endless drive belt 20 is provided between the drive machine 12 and the traction sheave 16.

(10) The monitoring unit is in the illustrated embodiment also connected with wear detection unit 50 which optically scans the surface of the endless drive belt 20. The monitoring unit 36 compares the signals from the wear detection unit 50 with reference values stored in the memory 38 and issues a maintenance signal to the remote monitoring or maintenance location 34 which leads to a replacement of the endless drive belt 20 before it breaks. Further slip detectors 56, 58 are provided to detect slipping of the belt 20 on the drive pulley 22 or on the output shaft 14. These slip detectors 56, 58 may also be provided together with the wear detection unit 50 via one and the same sensors. The slip detectors and the wear unit are preferably fixed on a support in the close vicinity of the rotating parts. The slip detectors issue a slip signal to the monitoring unit 36 comprising information about the speed difference between the belt on one hand and the drive pulley 22 or the output shaft 14 on the other hand, respectively. If the speed difference deviates from a reference value stored in the non-volatile memory 38 by a also stored second threshold value a maintenance signal is issued to the remote monitoring or maintenance location 34 indicating due maintenance.

(11) In some embodiments the wear detection can be done without additional slip detectors because the increasing difference between motor speed and traction sheave speed also indicates increasing slip and therefore wear of drive belt.

(12) In the above embodiment, the speed signal of the motor speed detection device is obtained from the motor drive 32 as well as from the motor encoder 42. It is clear that the invention can be realized with only one of these two detection systems. Furthermore, it is clear to the skilled person that the motor speed detection device 35, the monitoring unit 36 as well as the elevator control 30 do not have to be provided as integrated units but can also be provided on separate locations. Of course, these components can also be provided as software components in a control program implemented in the elevator control 30.

(13) Furthermore, it is clear that the motor encoder 42 can be located in connection with any other rotated part of the drive machine 12, e.g. in connection with the rotor of the drive machine 12. On this behalf, the motor encoder 42 could be located within the casing of the drive machine 12. In the same way it is clear that the traction sheave encoder 46 can be located in connection with any other rotatable part, e.g. in connection with the traction sheave 16 itself or with the drive pulley 22.

(14) Of course the drive belt 20 could also be coupled directly to the traction sheave (instead of axis 22) in parallel with the elevator ropes.

(15) It shall further be understood that the length of the output shaft 14 of the drive machine 12 as well as the length of the shaft 18 of the traction sheave 16 are exaggerated. The exaggerated lengths of the shafts have been chosen to illustrate the function of the invention. In reality, the shafts are much shorter.

(16) It should be noted that the different embodiments mentioned in the description can be combined with each other. The invention can be varied within the scope of the appended patent claims.