METHOD AND TESTING DEVICE FOR DETERMINING A STATE OF A SUSPENSION TRACTION APPARATUS OF AN ELEVATOR SYSTEM

Abstract

A method for determining a state of an elevator system suspension traction apparatus having at least one electrically conductive cord with a first end and an opposite second end, the cord having a wave impedance. A signal generator is electrically connected to the cord first end and a terminating resistor having a first resistance value matched to the wave impedance of the cord is electrically connected to the cord second end. The method includes the steps: inputting an, in particular alternating, electrical excitation signal of the signal generator into the cord first end; at least one of measuring a reflection signal of the excitation signal at the cord first end, and measuring a transmitted signal of the excitation signal at the cord second end; and determining the state of the suspension traction apparatus by comparing the excitation signal with at least one of the reflection signal and the transmitted signal.

Claims

1-15. (canceled)

16. A method for determining a state of a suspension traction apparatus of an elevator system, the suspension traction apparatus including at least one cord being electrically conductive and having a first end and an opposite second end, the cord having a wave impedance, wherein a signal generator is electrically connected to the first end of the cord and a terminating resistor having a first resistance value matched to the wave impedance of the cord is electrically connected to the second end of the cord, the method comprising the steps of: inputting an electrical excitation signal from the signal generator into the first end of the cord; at least one of measuring a reflection signal of the excitation signal at the first end of the cord, and measuring a transmitted signal of the excitation signal at the second end of the cord; determining a state of the suspension traction apparatus based on a comparison of the excitation signal with at least one of the reflection signal and the transmitted signal; and at least one of generating a warning signal and controlling operation of the elevator system in response the determined state of the suspension traction apparatus.

17. The method according to claim 16 wherein when the reflection signal is correlated or cross-correlated with the excitation signal, at least one of the warning signal is generated and the operation of the elevator system is stopped.

18. The method according to claim 17 wherein the reflection signal is considered as being correlated or cross-correlated with the excitation signal when a difference in frequency between the reflection signal and the excitation signal is less than 5%.

19. The method according to claim 16 wherein when the transmitted signal is uncorrelated with the excitation signal, at least one of the warning signal is generated and the operation of the elevator system is stopped.

20. The method according to claim 19 wherein the transmitted signal is considered as being uncorrelated with the excitation signal when a difference in frequency between the transmitted signal and the excitation signal is more than 1%.

21. The method according to claim 16 wherein the first resistance value of the terminating resistor is changed to a new second resistance value when at least one of conditions that the transmitted signal is uncorrelated with the excitation signal and that the reflection signal is correlated with the excitation signal is fulfilled, such that at least one of the reflection signal is uncorrelated with the excitation signal and the transmitted signal is correlated with the excitation signal.

22. The method according to claim 21 wherein when a difference between the first resistance value and the second resistance value exceeds a minimum difference value, at least one of the warning signal is generated and the operation of the elevator system is stopped.

23. The method according to claim 16 wherein at least one of the warning signal is generated and the operation of the elevator system is stopped when at least one of the reflection signal is correlated or cross-correlated with the excitation signal based upon a difference in amplitude between the reflection signal and the excitation signal being less than 5%, and the transmitted signal is uncorrelated with the excitation signal based upon a difference in amplitude between the transmitted signal and the excitation signal being more than 1%.

24. The method according to claim 16 wherein at least one of the warning signal is generated and the operation of the elevator system is stopped when the excitation signal has a peak width and the transmitted signal is uncorrelated with the excitation signal based upon a peak width of the transmitted signal deviates from the peak width of the excitation signal by more than 1%.

25. A testing device for determining a state of a suspension traction apparatus of an elevator system, wherein the suspension traction apparatus includes at least one cord being electrically conductive and having a first end and an opposite second end, the cord having a wave impedance, the testing device comprising: a signal generator generating an electrical excitation signal and being connected to the first end of the cord; a terminating resistor having a first resistance value matched to the wave impedance of the cord and being connected to the second end of the cord; at least one of a first detector for measuring a reflection signal of the excitation signal, wherein the first detector is connected to the first end of the cord, and a second detector for detecting a transmitted signal of the excitation signal, wherein the second detector is connected to the second end of the cord; and a control device for comparing the excitation signal with at least one of the reflection signal and the transmitted signal and for determining the state of the suspension traction apparatus based on the comparison of the excitation signal with at least one of the reflection signal and the transmitted signal, the control device at least one of generating a warning signal and controlling operation of the elevator system in response the determined state of the suspension traction apparatus.

26. The testing device according to claim 25 wherein the control device is adapted to at least one of generate the warning signal and stop operation of the elevator system when the reflection signal is correlated with the excitation signal.

27. The testing device according to claim 25 wherein the control device is adapted to at least one of generate the warning signal and stop operation of the elevator system when the transmitted signal is uncorrelated with the excitation signal.

28. The testing device according to claim 25 wherein the terminating resistor is a potentiometer for adjusting the first resistance value of the terminating resistor.

29. The testing device according to claim 28 wherein the control device changes the first resistance value of the potentiometer to a new second resistance value when at least one of the transmitted signal is uncorrelated with the excitation signal and the reflection signal is correlated with the excitation signal such that at least one of the reflection signal is uncorrelated with the excitation signal and the transmitted signal is correlated with the excitation signal.

30. An elevator system comprising: a car; at least one suspension traction apparatus for holding the car and moving the car, wherein the at least one suspension traction apparatus includes at least one cord being electrically conductive and having a first end and an opposite second end, wherein the at least one cord has a wave impedance; and a testing device according to claim 25 connected to the at least one cord.

Description

DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 shows a traction-type elevator in which the testing device according to an embodiment of the present invention may be used;

[0039] FIG. 2 shows a perspective view of the suspension transaction means of FIG. 1; and

[0040] FIG. 3 shows a schematic view of an embodiment of a testing device according to the present invention.

[0041] The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a traction-type elevator 1 in which the testing device according to an embodiment of the present invention may be used.

[0043] The elevator 1 comprises a car 3 and a counterweight 5 which may be displaced vertically within an elevator shaft 7. The car 3 and the counterweight 5 are suspended by a suspension traction means arrangement 9. This suspension traction means arrangement 9 comprises one or more suspension traction means or suspension traction apparatus 11. Such suspension traction means 11 may be for example ropes, belts, etc. in which cords are embedded in a jacket. In the arrangement shown in FIG. 1, end portions of the suspension traction means 11 are fixed to supporting structures 12 of the elevator 1 at a top of the elevator shaft 7.

[0044] The suspension traction means 11 may be displaced using a drive engine 13 driving a traction sheave 15. Therein, the suspension transaction means 11 may be wound around a traction surface of the traction sheave 15 and may furthermore be wound around pulleys 16 attached to the car 3. An operation of the drive engine 13 may be controlled by an elevator control device 17.

[0045] It may be noted that the elevator 1 and particularly its suspension traction means 11 may be configured and arranged in various other ways than those shown in FIG. 1.

[0046] The suspension traction means 11 to be driven for example by the drive engine 13 may utilize metal cords or ropes to support a suspended load such as the car 3 and/or the counterweight 5 that is moved by the drive engine 13.

[0047] FIG. 2 shows a perspective view of the suspension transaction means 11 of FIG. 1 being implemented as a belt 19. The belt 19 comprises a plurality of cords 23 which are arranged parallel to and spaced from each other. The cords 23 are enclosed in a jacket material 21 forming, inter alia, a jacket 25. Such jacket 25 may mechanically couple neighboring cords 23. Furthermore, the jacket 25 may protect the cords 23 against for example mechanical damages and/or corrosion. The jacket 25 may have a textured or profiled traction surface including longitudinal guiding grooves 27. The cords 23 may typically conventionally consist of or comprise multiple strands formed by wires made from a metal such as steel. The jacket material 21 may consist of or comprises a plastic or elastomeric material such as polyurethane.

[0048] FIG. 3 shows a schematic view of an embodiment of a testing device 10 according to the present invention. The testing device 10 comprises a signal generator 30, a potentiometer 40, a control device 70 and a first detector 50 and/or a second detector 60. The testing device 10 is adapted for testing a cord 23 of a suspension traction means 11 or several cords 23 of one or several suspension traction means 11 of an elevator system, i.e., the cord which carries the car. The cords 23 can be encapsulated, in particular together with other cords 23. The cord(s) 23 can be encapsulated in a belt made of polyurethane. The cord 23 is tested by the testing device 10 in situ, i.e., after the cord 23 has been installed (and has been used). The testing device 10 tests the status of the cord 23, and, thus, of the suspension traction means 11 during the operation of the elevator system. The testing can be done while the car of the elevator system is not moved. Alternatively, the cord 23 can be tested before being installed in the elevator system and/or after they have been removed from the elevator system.

[0049] The testing of the cord 23 can be done in intervals with pauses in between or continuously.

[0050] The signal generator 30 is (electrically) connected to a first end 80 of the cord 23. The first end 80 of the cord 23 can also enclose a small region which is very close to the physical first end/tip of the cord 23. The first detector 50 is also connected to the first end 80 of the cord 23. The second detector 60 is connected (electrically) to the second end 85 of the cord 23, wherein the second end 85 of the cord 23 is opposite to the first end 80 of the cord 23. The second end 85 of the cord 23 can also enclose a small region which is very close to the physical second end/tip of the cord 23. The potentiometer 40 is (electrically) connected to the second end 85 of the cord 23. The potentiometer 40 is connected in parallel to an electrical connection leading directly from the second end 85 of the cord 23 to the second detector 60.

[0051] The control device 70 is (electrically) connected to the signal generator 30, the first detector 50, the second detector 60 and the potentiometer 40. The control device 70 controls the signal generator 30, the first detector 50, the second detector 60 and the potentiometer 40.

[0052] The signal generator 30 generates an excitation signal. The excitation signal can be a high-frequency signal. The frequency can be set to a set value (e.g., 5 MHz) or can be changed during the testing. For example, the excitation signal can be a rectangular signal with a set frequency. Other kinds of excitation signals (sinus, triangular etc.) are possible.

[0053] The resistance value of the potentiometer 40 (which is the terminating resistor) is adjusted such that the resistance value of the potentiometer 40 is essentially the same as the wave impedance of the cord 23. Thus, the second end 85 of the cord 23 seems to be nonexistent for the excitation signal but the cord 23 seems to be indefinitely long for the excitation signal. Therefore, if the (first) resistance value of the potentiometer 40 is matched to the wave impedance value of the cord 23, no reflection of the signal should occur and the signal should be transmitted essentially without attenuation to the second detector 60. The wave impedance value and the resistance value are the respective values for the frequency of the excitation signal.

[0054] The excitation signal is input into the cord 23 at the first end 80 of the cord 23. If the resistance value of the potentiometer 40 is matched to the wave impedance value of the cord 23, the first detector 50 should detect no reflection signal. Thus, if a reflection signal is detected or measured by the first detector 50, wherein the reflection signal is correlated with or similar to the excitation signal (essentially the same form and/or essentially the same frequency), the wave impedance value of the cord 23 is different from the resistance value (or wave impedance value) of the potentiometer 40. Hence, the original wave impedance value of the cord 23 has changed. This indicates a change of the status/in the status of the cord 23 and, thus, of the suspension traction means 11, i.e., the cord 23 deteriorated and/or a tear/rip of the cord 23 or parts thereof has occurred. The control device 70 compares the measured reflection signal with the excitation signal.

[0055] If the reflection signal is correlated with or similar to the excitation signal (in particular has a similar form), a warning signal can be generated/issued by the control device 70 to a warning device 90. This warning signal can produce an optical or acoustic warning signal from the warning device 90 within the car 3 of the elevator system and/or at the central control of the elevator system. Also, the warning signal can lead to a stop of the operation of the elevator system by the elevator control device 17. The operation of the elevator system can be stopped, by moving the car to the next possible stop, opening the doors and requesting the passengers to leave the car (via optical and/or acoustic indicators/signals).

[0056] The second detector 60 measures/detects the transmitted signal of the excitation signal, i.e., the portion of the excitation signal which is transmitted. If the resistance value of the potentiometer 40 (the terminating resistor) is essentially the same as the wave impedance value of the cord 23 (for the excitation signal/the frequency of the excitation signal), the transmitted signal should be very similar to the excitation signal, i.e., having the same form with no or only minor attenuation and/or the same frequency. The control device 70 compares the transmitted signal with the excitation signal.

[0057] If the transmitted signal is uncorrelated with or non-similar to the excitation signal (frequency is different, form is different and/or amplitude is very different), a warning signal can be generated/issued by the control device 70 to the warning device 90. This warning signal can produce an optical or acoustic warning signal within the car of the elevator system and/or at the central control of the elevator system. Also, the warning signal can lead to a stop of the operation of the elevator system by the elevator control device 17. The operation of the elevator system can be stopped, by moving the car to the next possible stop, opening the doors and requesting the passengers to leave the car (via optical and/or acoustic indicators/signals).

[0058] Changes in the reflection signal and/or in the transmitted signal indicate a change of status of the cord 23 and, thus, in the status of the suspension traction means 11.

[0059] It is also possible, that the control device 70 tests or monitors several cords 23 of one suspension transaction means 11 or of several suspension transaction means 11 of an elevator system 1, e.g., ten suspension cords 23 or ten cables. Each cord 23 or cable can have a signal generator 30, a potentiometer 40 and a first detector 50 and/or second detector 60. Alternatively, several cords 23 or cables share a signal generator 30 and/or a first detector 50 and/or second detector 60. If a change of/in status is detected in only one or a few cables or cords 23, e.g., 2 or 3, no action needs to be taken normally, since there is a large enough safety buffer, i.e., the rest of the cables or cords 23 (e.g., 6 or 7) can carry the car 3 safely, even if one or more cable or cord 23 rip/tear. If more than a set number or set percentage of the cords 23 change status, a warning signal is generated and/or the operation of the elevator system 1 is stopped (as described in detail above).

[0060] If the control device 70 detects that the transmitted signal is not similar to the excitation signal and/or that the reflection signal is similar to the excitation signal, the control device 70 can adjust the resistance value of the potentiometer 40/terminating resistor such that the reflection signal is non-similar to the excitation signal and/or such that the transmitted signal is similar to the excitation signal. Thus, the resistance value of the potentiometer 40 is changed from a first resistance value (which is equal to the original wave impedance of the cord 23) to a new second resistance value (which is equal to the current wave impedance of the cord 23 for the excitation signal). If the difference between the first and second resistance value is small, i.e., smaller than a set minimum difference value (for example 2 ohm) or a set minimum percentage of the original resistance value (e.g., 10%), no current danger is present. No tear/rip of the cord 23 is immanent. If the difference between the first and second resistance value is equal or larger than the minimum difference value or the minimum difference percentage value, a warning signal can be issued and/or the operation of the elevator system can be stopped. Large changes in the status of the cord 23 indicate a possible rip/tear in the near future.

[0061] After adjusting the resistance value of the terminating resistor via the potentiometer 40, the monitoring/testing of the suspension traction means 11 can continue.

[0062] The warning signal can be transmitted to a central elevator system monitoring server. This can alert maintenance staff to further inspect the relevant suspension traction means 11. This further inspection can be done with x-rays or similar nondestructive testing method. Also, the changes in the resistance value of the terminating resistor/potentiometer 40 can be saved locally or sent to a central server where they can be used and/or saved.

[0063] The control device 70 can further analyze the reflection signal and/or the transmitted signal. In particular, the control device 70 can do a Fourier analysis of the reflection signal and/or the transmitted signal. Also, the amount of difference between the first resistance value and the second resistance value can be take into account by the control device 70.

[0064] Finally, it should be noted that the term comprising does not exclude other elements or steps and the a or an does not exclude a plurality. Also elements described in association with different embodiments may be combined.

[0065] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.