Method and device for checking the integrity of load bearing members of an elevator system

Abstract

A method for checking the integrity of a load bearing member of an elevator including tensile elements encapsulated in a case includes the steps of launching a source pulse through tensile elements of said load bearing member and comparing the feedback of said tensile elements with a comparator; tensile elements can be bridged to avoid a blind zone.

Claims

1. A method of testing at least one load bearing member of an elevator system, the at least one load bearing member including tensile elements of electrically conductive material encapsulated in a case, the method comprising: transmitting a first source pulse through a first one of the tensile elements and a second source pulse through a second one of the tensile elements, and determining a condition of the tensile elements based on a first feedback signal received via the first one of the tensile elements and a second feedback signal received via the second one of the tensile elements.

2. The method according to claim 1, wherein the determining a condition comprises: determining that the condition of one of the first one of the tensile elements and second one of the tensile elements is a damaged tensile element, if a difference between the first feedback signal and the second feedback signal is greater than a threshold.

3. The method according to claim 2, further comprising: determining which of the tensile elements is the damaged tensile element, if the difference is greater than the threshold, the determining which of the tensile elements is the damaged tensile element including, transmitting a third source pulse through a third one of the tensile elements, and determining which of the tensile elements is the damaged tensile element based on the first feedback signal, the second feedback signal and a third feedback signal, the third feedback signal being received via the third one of the tensile elements.

4. The method according to claim 1, further comprising: selecting the first one of the tensile elements and the second one of the tensile elements such that each of the tensile elements of a first load bearing member of the at least one bearing member are compared to the tensile elements of the first load bearing member and the tensile elements of a second load bearing member of the at least one bearing member according to a pattern.

5. The method according to claim 1, wherein the determining the condition of the tensile elements comprises: comparing one or more of transmission time differences, amplitude differences, and waveform differences between the first source pulse and the first feedback signal and between the second source pulse and the second feedback signal.

6. The method according to claim 1, wherein the first one of the tensile elements includes a first pair of bridged tensile elements connected via a first bridge connection, and the second one of the tensile elements includes a second pair of bridged tensile elements connected via a second bridge connection, and the method further comprises: transmitting a pulse from a first one of the first pair of bridged tensile elements to the first bridge connection; transmitting a pulse from a first one of the second pair of bridged tensile elements to the second bridge connection; transmitting a pulse from a second one of the first pair of bridged tensile element to the first bridge connection; and transmitting a pulse from a second one of the second pair of bridged tensile elements to the second bridge connection.

7. The method according to claim 1, wherein the first source pulse and the second source pulse are identical.

8. The method according to claim 1, wherein the transmitting transmits the first source pulse and the second source pulse simultaneously.

9. The method according to claim 1, wherein the transmitting transmits the first source pulse and the second source pulse such that a time duration of each of the first source pulse and the second source pulse is less than or equal to 100 nanoseconds.

10. The method according to claim 1, wherein the first source pulse and the second source pulse have an amplitude less than or equal to 50 V.

11. An elevator system comprising: at least one elevator car; at least one load-bearing member, the load bearing member including at least one tensile element made of electrically conductive material and encapsulated in a case; and a testing device configured to test an integrity of the load-bearing member, the testing device including, a pulse generator connected to at least the tensile elements of the load-bearing member, the pulse generator configured to transmit a first source pulse through a first one of the tensile elements and a second source pulse through a second one of the tensile elements, and a comparator configured to determine a condition of the tensile elements based on a first feedback signal received via the first one of the tensile elements and a second feedback signal received via the second one of the tensile elements.

12. The elevator system according to claim 11, wherein the testing device is configured to periodically test the integrity of the tensile elements.

13. An elevator system according claim 11, wherein the testing device is configured to test the integrity of the tensile elements, if a call of the elevator car is made when the elevator car is positioned at a lowest floor.

14. An elevator system according to claim 11, wherein the load-bearing member is a belt and the elevator car has no counterweight.

15. An elevator system comprising: at least one car; at least one load-bearing member connected to the at least one car, the load bearing member including tensile elements made of electrically conductive material and encapsulated in a case made of electrically resistive material; and a testing device configured to test an integrity of the at least one load-bearing member, the testing device including a pulse generator connected to the tensile elements of the at least one load-bearing member, the pulse generator configured to, transmit a first source pulse through a first one of the tensile elements and a second source pulse through a second one of the tensile elements, and determine a condition of the tensile elements based on a first feedback signal received via the first one of the tensile elements and a second feedback signal received via the second one of the tensile elements.

16. The method of claim 1, wherein the testing includes, testing the integrity of the tensile elements in response to a call on the elevator system occurring when a car of the elevator system is on a lowest floor.

17. The method of claim 1, wherein the at least one load bearing member is a belt and a car on the elevator system does not include a counterweight.

18. The elevator system of claim 15, wherein the testing device is configured to test the integrity of the at least one load bearing member, if a call of the at least one car is made when the car is positioned at a lowest floor.

19. The elevator system of claim 15, wherein the at least one load-bearing member is a belt and the at least one car has no counterweight.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is a scheme of a first way of carrying out the inventive method, according to a first embodiment.

(2) FIG. 2 is a scheme of another way of carrying out the inventive method, according to a second embodiment with bridged tensile elements.

(3) FIG. 3 shows an example of pulse and feedback which denote a damage in a tensile element, according to the invention.

(4) FIG. 4 shows an example of a method of launching and receiving pulses, according to example embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) Referring to FIG. 1, the block 1 denotes a pulse generation unit, which may include one or more pulse generators, connected to tensile elements of a load-bearing member of an elevator. Said tensile elements are for example steel cords 2, 3. A comparator 4 is also electrically connected to said steel cords 2, 3.

(6) The unit 1 can launch a pulse through the steel cords 2, 3 while their feedback can be compared by means of the comparator 4.

(7) The method comprises preferably the following steps. A pulse generated by the unit 1 and having a known amplitude and duration, for example 50 V and 100 ns, is launched through steel cords 2, 3 via the input connections 5.

(8) In each cord 2 or 3, the pulse will normally travel the whole length of the cord. Depending on the cords being grounded or not, the cords 2, 3 are expected to give a certain feedback pulse or no feedback. However, a damage of the cord will result in a different feedback pulse, as elucidated for example in FIG. 3.

(9) Any feedback reaches the comparator 4 via connections 6. The output 7 of the comparator 4 is normally expected to be null or close to null; a non-null output 7, possibly over a certain threshold, may be interpreted as a damage of one of the cords 2, 3.

(10) FIG. 2 relates to a bridged embodiment of the invention.

(11) The steel cords 2, 3 and 8, 9 are bridged by means of bridge connections 10, 11 to form two pairs 12, 13.

(12) The method involves basically two steps. A source pulse is launched into one steel cord of each pair 12 and 13, for example cords 2 and 8, and the feedback pulse (received via connections 6) is checked by the comparator 4. Then, a source pulse is launched into the other steel cord of each pair, in the example the cords 3 and 9, and again the feedback pulses are analysed. This method avoids the blind zone since for example a damage undetected in the first step, being too close to the connection to pulse generator 1, will be revealed in the second step, or vice-versa.

(13) FIG. 3 shows the principle underlying the invention. A source pulse 100 having a known amplitude and duration is launched through a conductive tensile element, for example a steel cord (FIG. 3, A). Line 101 denotes the position of a damage of the cord, for example a location where the cord is worn and/or the cross section is reduced due to failure of some of the wires which compose the cord. The damage 101 will normally reflect at least partly the source pulse 100 (FIG. 3, B), thus generating an unexpected feedback 102 (FIG. 3, C) which can be interpreted as a symptom of a damage. Furthermore, knowing the speed of the source pulse and the length of the tensile cords, the system may calculate and show the location of the damage 101 along the cord.

(14) FIG. 4 shows an example of a method of launching and receiving pulses, according to example embodiments. In FIG. 4, the method may start at step S400. Beginning in step S410, a first pulse signal may be launched from the pulse generating unit 1 through the first cord 2. The first pulse signal may be, e.g., less than or equal to 50 V and last for less than or equal to 100 ns. Beginning in step S420, a second pulse signal may be launched from the pulse generating unit 2 through the second cord 3. The second pulse signal may be, e.g., less than or equal to 50 V and last for less than or equal to 100 ns. In step S430, a reflected signal of the first pulse signal may be received, as the first pulse signal travels down cord 2 and is reflected back. In step S440, a reflected signal of the second pulse may be received, as the second pulse signal travels down cord 3 and is reflected back. In step S450, the reflected first pulse signal and the reflected second pulse signal may be compared with the comparator 4. Based on a comparison of the first reflected pulse signal and the second reflected pulse signal, damage may be detected in any unexpected feedback signal, such as the unexpected feedback signal 102. If damage is detected, a determination of the cord affected and the damage location may be determined, for example by knowing a speed of the source pulse and a length of the cord in step S470. In step 480, the method may end.

(15) The invention is applicable to various load-bearing members of elevators. For example the load-bearing member may be a belt with steel cords in a polyurethane body, and each cord is composed of several steel tangled wires. The invention however may be applied to other embodiments including load-bearing members with non-metallic tensile elements.