Method and device for detecting a deterioration state in a suspension member arrangement for an elevator based on AC voltage measurements with suspension members being electrically short-circuited at their distal ends

Abstract

A method for detecting a deterioration state in an elevator suspension member including electrically conductive cords uses a multiplexing unit (MU) to apply first and second alternating voltages to proximal ends of first and second groups of the cords respectively and connect the proximal end of a third group of the cords to a voltage measurement arrangement connected to a reference potential. Distal ends of the groups are connected together. A first neutral point voltage between the third proximal end and the reference potential is determined. The MU is switched to apply the first alternating voltage to the second proximal end, apply the second alternating voltage to the third proximal end and determine a second neutral point voltage between the first proximal end and the reference potential. The deterioration state of the suspension member arrangement is determined based on the first and second neutral point voltages.

Claims

1. A method for detecting a deterioration state in a suspension member arrangement for an elevator, the suspension member arrangement including a suspension member having first, second and third groups of electrically conductive cords, the method comprising the steps of: proving a multiplexing unit for selectively connecting proximal ends of the cords in two of the first, second and third groups to an alternating voltage generator arrangement having a first voltage generator for applying a first alternating voltage and a second voltage generator for applying a second alternating voltage, and for selectively connecting proximal ends of the cords in a third of the first, second and third groups to a voltage measurement arrangement for determining voltages between the connected third proximal ends and an electrical reference potential; electrically connecting distal ends of the cords in the first, second and third groups to each other via a bridge interconnection; switching the multiplexing unit into a first configuration thereby applying the first alternating voltage to the proximal ends of the first group and applying the second alternating voltage to the proximal ends of the second group, and determining a first neutral point voltage between the proximal ends of the third group and the electrical reference potential; switching the multiplexing unit from the first configuration into a second configuration thereby applying the first alternating voltage to the proximal ends of the second group and applying the second alternating voltage to the proximal ends of the third group, and determining a second neutral point voltage between the proximal ends of the first group and the electrical reference potential; and detecting the deterioration state of the suspension member arrangement based on the first and second neutral point voltages.

2. The method according to claim 1 including switching the multiplexing unit multiple times into various configurations such that the first and second alternating voltages are applied at least once to each of the proximal ends of all of the groups and determining a neutral point voltage at least once between each of the proximal ends and the electrical reference potential respectively.

3. The method according to claim 1 wherein each of the groups includes several of the cords in the suspension member.

4. The method according to claim 1 wherein each of the groups includes several of the cords directly neighboring to each other.

5. The method according to claim 1 wherein several of the cords in each of the groups are electrically connected in parallel.

6. The method according to claim 1 wherein the first and second alternating voltages have same waveforms and a phase difference of 180°.

7. A detection device for detecting a deterioration state in a suspension member arrangement for an elevator, the suspension member arrangement including a suspension member having a first group, a second group and a third group of electrically conductive cords, wherein distal ends of the cords in the first, second and third groups are electrically connected to each other via a bridge interconnection, the detection device comprising: an alternating voltage generator arrangement including a first voltage generator for generating a first alternating voltage and a second voltage generator for generating a second alternating voltage; a voltage measurement arrangement for measuring neutral point voltages between proximal ends of the cords in each one of the first, second and third groups and an electrical reference potential; a multiplexing unit for selectively connecting the proximal ends of a first one of the first, second and third groups to the first voltage generator, the proximal ends of a second one of the first, second and third groups to the second voltage generator, and the proximal ends of a third one of the first, second and third groups to the voltage measurement arrangement; an evaluation unit for detecting the deterioration state of the suspension member arrangement based on the measured neutral point voltages; and wherein the detection device is adapted to perform the steps of switching the multiplexing unit into a first configuration thereby applying the first alternating voltage to the proximal ends of the first group and applying the second alternating voltage to the proximal ends of the second group, and determining a first neutral point voltage between the proximal ends of the third group and the electrical reference potential, switching the multiplexing unit from the first configuration into a second configuration thereby applying the first alternating voltage to the proximal ends of the second group and applying the second alternating voltage to the proximal ends of the third group, and determining a second neutral point voltage between the proximal ends of the first group and the electrical reference potential, and detecting the deterioration state of the suspension member arrangement based on the first and second neutral point voltages.

8. An elevator arrangement comprising: a suspension member arrangement including a suspension member having a first group, a second group and a third group of electrically conductive cords; and a detection device according to claim 7 for detecting a deterioration state in the suspension member arrangement.

9. The elevator arrangement according to claim 8 wherein distal ends of the first, second and third groups are electrically connected to each other via a bridge interconnector and wherein the proximal ends of the first, second and third groups are electrically connected to the multiplexer unit of the detection device.

10. The elevator arrangement according to claim 9 wherein the bridge interconnector includes a plurality of needle contacts introduced into the suspension member at closely neighboring positions to electrically contact the cords in the suspension member, the needle contacts being short-circuited with each other.

11. An elevator arrangement comprising: a suspension member arrangement including at least two suspension members, each of the at least two suspension members having only two groups of electrically conductive cords; wherein the cords in the two groups in each of the at least two suspension members are electrically short-circuited at distal ends thereof; wherein the distal ends of the cords in the at least two suspension members are electrically short-circuited; and a detection device including: an alternating voltage generator arrangement including a first voltage generator for generating a first alternating voltage and a second voltage generator for generating a second alternating voltage; a voltage measurement arrangement for measuring neutral point voltages between proximal ends of the cords in each of the groups and an electrical reference potential; a multiplexing unit for selectively connecting proximal ends of cords in a first of the groups to the first voltage generator, proximal ends of the cords in a second of the groups to the second voltage generator, and proximal ends of all other ones of the groups, as a third group, to the voltage measurement arrangement; and an evaluation unit for detecting the deterioration state of the suspension member arrangement based on the measured neutral point voltages; and wherein the detection device is adapted to perform the steps of switching the multiplexing unit into a first configuration thereby applying the first alternating voltage to the proximal ends of the first group and applying the second alternating voltage to the proximal ends of the second group, and determining a first neutral point voltage between the proximal ends of the third group and the electrical reference potential, switching the multiplexing unit from the first configuration into a second configuration thereby applying the first alternating voltage to the proximal ends of the second group and applying the second alternating voltage to the proximal ends of the third group, and determining a second neutral point voltage between the proximal ends of the first group and the electrical reference potential, and detecting the deterioration state of the suspension member arrangement based on the first and second neutral point voltages.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an elevator in which a method according to an embodiment of the invention may be applied.

(2) FIG. 2 shows a suspension member.

(3) FIG. 3 shows a measurement arrangement to be applied in a method for detecting the deterioration state in the suspension member arrangement according to an embodiment of the applicant's prior art.

(4) FIG. 4 shows major components of a measurement arrangement to be applied in a method for detecting the deterioration state in the suspension member arrangement according to an embodiment of the present invention.

(5) FIG. 5 very schematically shows another measurement arrangement to be applied in a method for detecting the deterioration state in the suspension member arrangement according to another embodiment of the present invention.

(6) FIG. 6 shows a bridge interconnector to be applied in an elevator arrangement according to an embodiment of the present invention.

(7) The figures are only schematic representations and are not to scale. Same reference signs refer to same or similar features throughout the figures.

DETAILED DESCRIPTION

(8) FIG. 1 shows an elevator 1 in which a method according to embodiments of the present invention may be implemented.

(9) 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 member arrangement 9. This suspension member arrangement 9 comprises one or more suspension members 11, sometimes also referred to a suspension traction media (STM). Such suspension members 11 may be for example ropes, belts, etc. In the arrangement shown in FIG. 1, end portions of the suspension members 11 are fixed to a supporting structure of the elevator 1 at a top of the elevator shaft 7. The suspension members 11 may be displaced using an elevator traction machine 13 driving a traction sheave 15. An operation of the elevator traction machine 13 may be controlled by a control device 18. For example at opposite end portions of the suspension member arrangement 9 components of a device 17 for detecting a deterioration state in the suspension member arrangement 9 may be provided.

(10) It may be noted that the elevator 1 and particularly its suspension member(s) 11 and its device 17 for detecting the deterioration may be configured and arranged in various other ways than those shown in FIG. 1.

(11) The suspension members 11 to be driven for example by the traction machine 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 traction machine 13.

(12) FIG. 2 shows an example of a suspension member 11 which is embodied with 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 matrix material 21 forming, inter alia, a coating. Such coating may mechanically couple neighboring cords 23. The coating may have a textured or profiled surface including longitudinal guiding grooves. The cords 23 may typically consist of or comprise wires made from a metal such as steel. The matrix material 21 may consist of or comprises a plastic or elastomeric material. Accordingly, the cords 23 are typically electrically conductive such that an electric voltage may be applied to and/or an electric current may be fed through the cords without significant losses. Furthermore, the cords 23 are preferably electrically isolated from each other via the interposed electrically insulating matrix material 21 such that, as long as an integrity of the coating is not deteriorated, an electrical current or voltage between neighboring cords cannot be transmitted, i.e. no significant shunt current can flow from one cord 23 to another.

(13) Alternatively, suspension members 11 may have other shapes or configurations. For example, a belt may have several cords included into a body formed of matrix material, the body being non-profiled (i.e. flat) or having other shapes as those shown in FIG. 2. Alternatively, each cord may be enclosed by matrix material forming a kind of coating wherein the coated cords are separate from each other, i.e. not connected to each other via common matrix material. Generally, the suspension members 11 may be provided as coated steel suspension members.

(14) Typically, wires or cords of the suspension member 11 have a specified minimum strength to ensure an integrity of the suspension member arrangement 9 during its use in an application within an elevator 1. In certain suspension applications, such as for lifts or elevators, a factor-of-safety requirement for strength combined with other measures, such as protective coating of the cords 23 for example within the matrix material 21, may sustain an initial strength of a suspension member beyond an effective life of the protective measures employed to retain strength.

(15) Particularly in such cases, where the initial strength of the suspension member 11 is not expected to change during its useful life in an application, a simple electronic method may be employed and may be sufficient to detect an indication that for example initial physical properties of the suspension members have unexpectedly changed and trigger for example a replacement of the suspension member 11 or other counter-measures.

(16) FIG. 3 shows an exemplary embodiment of a device 17 as described in the “applicant's prior art”. Details on function principles of the device 17 and the deterioration detection method performed therewith may be obtained from the “applicant's prior art” and will not be repeated in detail herein for the sake of briefness.

(17) The device 17 is configured for detecting a deterioration state in a suspension member arrangement 9 for an elevator 1. Therein, the suspension member arrangement 9 may comprise one or more suspension members 11 such as for example belts as shown in FIG. 2 including a plurality of electrically conducting cords 23. In FIG. 3, the cords 23 are only indicated schematically as twelve elongate cords 23 being arranged parallel to each other. The multiplicity of cords 23 may be divided into two groups 24a, 24b of cords.

(18) In the “applicant's prior art” approach, a first group 24a of cords may comprise all odd numbered cords 23 whereas a second group 24b of cords may comprise all even numbered cords 23. Alternating voltages U.sub.1, U.sub.2 are applied from two voltage generators G.sub.1, G.sub.2 to a proximal end 25a of an uppermost cord (numbered “1”) of the first group 24a of cords and to a proximal end 25b of an adjacent cord (numbered “2”) of the second group 24b of cords. Distal ends 27a, 27b of these cords are then electrically connected to the next two cords (numbered “3” and “4”), respectively. Proximal ends 25a, 25b of these cords are again electrically connected to the next two cords (numbered “5” and “6”), and so on.

(19) However, with such series connections and intermittent arrangement of cords of the first and second groups 24a, 24b of cords, interconnecting the alternating cords 23 of the first and second groups, respectively, at their proximal and distal ends 25a, 25b, 27a, 27b requires precise alignment of any interconnectors and may therefore be complicated and prone to errors.

(20) In order to overcome interconnection issues, an alternative measurement arrangement as shown in FIG. 4 is proposed herein. In FIG. 4, only some relevant components and features of such measurement arrangement detection device 17 and a suspension member 11 are shown. Particularly, a voltage measurement arrangement 29 is represented only as a rough scheme and details of such voltage measurement arrangement 29 are omitted for the sake of simplicity of representation. Furthermore, features such as those described in the “applicant's prior art” may also be applied to the measurement arrangement of FIG. 4 but are not shown for the sake of simplicity of representation.

(21) Similarly to the approach shown in FIG. 3, an alternating voltage generator arrangement G comprises a first and a second voltage generators G.sub.1, G.sub.2 which generate first and second alternating voltages U.sub.1, U.sub.2 preferably having a same waveform, i.e. a same amplitude and same time profiles, but which are shifted by 180° with respect to each other.

(22) In contrast to the approach shown in FIG. 3, the cords 23 in the suspension member 11 are not only divided into two groups but into three groups 24a, 24b, 24c. It shall be noted that the three groups of cords are not necessarily included in a single suspension member 11 but may be included in 2 or 3 suspension members 11 of a suspension member arrangement 9. Furthermore, more than three groups of cords may be comprised in the suspension member arrangement and may be distributed among one or a plurality of suspension members, such that each suspension member comprises one, two or more groups of cords.

(23) Furthermore, in contrast to the approach shown in FIG. 3, each of the groups 24a, 24b, 24c comprises cords 23 directly neighboring each other. In the example shown, four cords 23 are included in each one of the groups 24a, 24b, 24c.

(24) Therein, the cords 23 of one of the groups 24a, 24b, 24c are electrically connected in parallel. For such purpose, a parallel connector 26 may electrically connect proximal ends 25a, 25b, 25c of each of the groups 24a, 24b, 24c, respectively. Distal ends 27a, 27b, 27c of each of the groups 24a, 24b, 24c are also electrically connected in parallel. Furthermore, the groups 24a, 24b, 24c are short-circuited, i.e. electrically interconnected with each other, at their distal ends 27a, 27b, 27c. For such purpose, a short-circuit connector 28 may interconnect all of the cords 23 of all of the groups 24a, 24b, 24c.

(25) In contrast to the approach shown in FIG. 3, the voltage generator arrangement G is not statically electrically connected to the three groups 24a, 24b, 24c of cords 23 in the suspension member 11. Instead, the detection device 17 comprises a multiplexing unit 30. This multiplexing unit 30 may connect each of the two voltage generators G.sub.1, G.sub.2 to the proximal ends 25a, 25b, 25c of one of the groups 24a, 24b, 24c of cords 23. Furthermore, the multiplexing unit 30 may selectively connect the voltage measurement arrangement 29 to the proximal ends 25a, 25b, 25c of one of the groups 24a, 24b, 24c of cords 23.

(26) For such purpose, the multiplexing unit 30 comprises internal switches for selectively connecting electrical connections 31, 32 to the voltage generators G.sub.1, G.sub.2 and an electrical connection 33 to the voltage measurement arrangement 29, on the one hand, to electrical connections 38 to the proximal ends 25a, 25b, 25c of one of the groups 24a, 24b, 24c of cords 23.

(27) In the example shown in FIG. 4, the multiplexer unit 30 is shown in a configuration, in which the first voltage generator G.sub.1 is connected to the proximal ends 25a of the first group 24a of cords, the second voltage generator G.sub.2 is connected to the proximal ends 25b of the second group 24b of cords and the voltage measurement arrangement 29 is connected to the proximal ends 25c of the third group 24c of cords. In such configuration, the first and second alternating voltages U.sub.1, U.sub.2 will be transmitted through the cords 23 of the first group 24a and of the second group 24b, respectively. As distal ends 27a, 27b of both groups 24a, 24b are electrically interconnected, a neutral point voltage U.sub.n applies at the interconnection of these distal ends.

(28) As long as both groups 24a, 24b of cords 23 are substantially identical with respect to their electrical characteristics, particularly with respect to their electrical resistances, such neutral point voltage U.sub.n will have substantially no AC component as the applied first and second alternating voltages U.sub.1, U.sub.2 have identical waveforms and include a phase shift of 180°. However, upon any changes to the electrical characteristics occurring in one of the groups 24a, 24b of cords, such balanced situation is modified such that the neutral point voltage U.sub.n generally includes an AC component. As such changes in the electrical characteristics typically result from deteriorations of the cords 23 in the suspension members 11, the presence and/or characteristics of such AC component may be interpreted as indicating such deteriorations.

(29) In order to be able to measure the neutral point voltage U.sub.n by electrically contacting the suspension member 11 at its proximal end, the short-circuited interconnector 28 not only interconnects the first and second groups 24a, 24b of cords but also establishes a bridge interconnection to the distal end 27c of the third group 24c of cords. Accordingly, the neutral point voltage U.sub.n is further transmitted towards the proximal end 25c of this third group 24c of cords. This proximal end 25c is then connected via the multiplexer unit 30 to the voltage measurement arrangement 29 and such that the neutral point voltage U.sub.n may be measured by the voltmeter 35 comprised therein with respect to a reference potential 34 such as a ground potential.

(30) The neutral point voltage U.sub.n may then be evaluated in the evaluation unit 36. For example, the evaluation unit 36 may detect whether or not the neutral point voltage U.sub.n comprises an AC component and may, optionally, analyze a magnitude and/or type of the AC component. Particularly, the evaluation unit 36 may evaluate neutral point voltages U.sub.n1, U.sub.n2 measured in various configurations of the multiplexing unit 30, i.e. upon the alternating voltages U.sub.1, U.sub.2 being applied to various ones of the groups of cords. Based on such evaluation, a signal may be issued indicating the deterioration state of the suspension member arrangement 11. For example, such signal may be transmitted to a remote monitoring center.

(31) FIG. 5 schematically represents another example of a measurement arrangement comprising a detection device 17 and the suspension member arrangement 9. Therein, the suspension member arrangement 9 comprises three suspension members 11. Each of the suspension members 11 comprises two groups 24a-f of cords 23. Each of the groups 24a-f comprises four cords 23. The cords 23 are connected in parallel by parallel connectors 26 connecting their proximal ends 25a-f and by the bridge interconnectors 28 connecting their distal ends 27a-f. Therein, while the parallel connectors 26 connect only the cords 23 of one of the groups 24a-f, the bridge interconnector 28 connects the cords 23 of all cords 23 comprised in both groups comprised in a single suspension member 11.

(32) Furthermore, in the suspension member arrangement 9 comprising several suspension members 11, the suspension members 11 are interconnected at their distal ends with an overall interconnector 39. Such overall interconnector 39 may be e.g. a cable electrically interconnecting the bridge interconnectors 28 at the distal ends of each of the suspension members 11.

(33) In the exemplary configuration shown in FIG. 5, the multiplexer unit 30 (not shown in this figure) is temporarily configured such that the first alternating voltage U.sub.1 is applied to the first group 24a of cords including half of the cords 23 comprised in the first suspension member 11 whereas the second alternating voltage U.sub.2 is applied to the fourth group 24d of cords including half of the cords 23 comprised in the second suspension member 11. In such configuration, all other groups 24b, 24c, 24e, 24f of cords to which presently no alternating voltage is applied may be used as electrical back connections through which the neutral point voltage U.sub.n may be supplied to the voltage measurement unit (not shown in this figure) of the detection device 17.

(34) FIG. 6 shows an example of a bridge interconnector 28 for electrically interconnecting the cords 23 comprised in a belt 19 forming a suspension member 11. The bridge interconnector 28 comprises a base body 40 and several needle contacts 37. The base body 40 electrically interconnects the needle contacts 37. For example, the base body 40 and/or the needle contacts 37 may be made from metal and, optionally, may form an integral device. The needle contacts 37 may extend in parallel directions and may be spaced from each other by distances being equal to or smaller than lateral distances between neighboring cords 23 in the belt 19. Furthermore, the needle contacts 37 may have a length sufficient for reliably contacting the cords 23 in the belt 19 upon the bridge interconnector 28 being pressed onto the distal end 27 of the belt 19.

(35) Finally, it should be noted that terms such as “comprising” do not exclude other elements or steps and that terms such as “a” or “an” do not exclude a plurality. Also elements described in association with different embodiments may be combined.

(36) 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.

LIST OF REFERENCE SIGNS

(37) 1 elevator 3 car 5 counterweight 7 elevator shaft 9 suspension member arrangement 11 suspension member 13 traction machine 15 traction sheave 17 detection device for detecting deterioration states 18 control device 19 belt 21 matrix material 23 cords 24a first group of cords 24b second group of cords 24c third group of cords 25a proximal end of first group of cords 25b proximal end of second group of cords 25c proximal end of third group of cords 26 parallel interconnector 27a distal end of first group of cords 27b distal end of second group of cords 27c distal end of third group of cords 28 bridge interconnector 29 voltage measurement arrangement 30 multiplexing unit 31 electrical connection to first voltage generator 32 electrical connection to second voltage generator 33 electrical connection to voltage measurement arrangement 34 reference potential 35 voltmeter 36 evaluation unit 37 contact needles of bridge interconnector 38 electrical connection to group of cords 39 overall interconnector 40 base body of bridge interconnector U.sub.1 first alternating voltage U.sub.2 second alternating voltage U.sub.n neutral point voltage G alternating voltage generator arrangement G.sub.1 first alternating voltage generator G.sub.2 second alternating voltage generator