EP1732836A2

EP1732836A2 - Method for detecting wear of the rope grooves of diverting pulleys and/or traction sheaves of an elevator, and elevator

Info

Publication number: EP1732836A2
Application number: EP05730721A
Authority: EP
Inventors: Petteri Valjus; Mikko Orava; Teuvo VÄNTÄNEN
Original assignee: Kone Corp
Current assignee: Kone Corp
Priority date: 2004-04-08
Filing date: 2005-04-05
Publication date: 2006-12-20
Anticipated expiration: 2025-04-05
Also published as: WO2005097651A3; FI20040522A; ES2400826T3; FI119766B; EP1732836B1; WO2005097651A2; FI20040522A0

Abstract

The invention relates to a method for detecting wear of the diverting and/or drive pulleys of an elevator, and to an elevator. In the method, a limit value is assigned to at least one of the following quantities: allowed displacement of the rope end against the spring force of a spring, allowed rope force of the rope, allowed tension of the rope, compression of the spring holding the rope, tension of the spring holding the rope, stress of the supporting structure adjacent to the rope fastening. During operation of the elevator, the displacement of an individual rope or another one of the above-mentioned quantities in relation to the corresponding quantity for the other ropes is detected from the sprung fastening arrangement of the rope ends. An alarm signal is generated if this quantity for an individual rope exceeds the predetermined limit value during operation of the elevator. An excess of the limit value is due to an increased rope force and indicates greater than normal wear of the rope groove of the diverting and/or drive pulley corresponding to the individual rope. To detect wear of the rope grooves (3) of the diverting and/or drive pulleys (4, 5), the elevator comprises a detector device (9) arranged in conjunction with the sprung fastening device (7).

Description

METHOD FOR DETECTING WEAR OF THE ROPE GROOVES OF DIVERTING PULLEYS AND/OR TRACTION SHEAVES OF AN ELEVATOR, AND ELEVATOR

FIELD OF THE INVENTION

The present invention relates to a method as defined in the preamble of claim 1. Moreover, the invention relates to an elevator as defined in the preamble of claim 8.

BACKGROUND OF THE INVENTION

The invention relates to traction sheave elevators which comprise an elevator car suspended with a number of ropes. The ropes are passed over diverting or drive pulleys provided with rope grooves, each rope being placed in a separate rope groove. The power moving the elevator car is transmitted to the ropes by the trac- tion sheave. At least one end of each rope is secured in a sprung manner to a fixed supporting structure by means of a sprung fastening device. The elevator may be provided with a counterweight or it may have no counterweight. Typically the sprung fastening device comprises a helical spring for each rope to hold the rope fast on the supporting structure in a sprung manner. One of the functions of the sprung fastening is usually to equalize the differences of tension between ropes arising from mutual differences of diameter of the rope grooves of the drive and diverting pulleys and/or differences between the ropes and/or different rope tensions remaining after installation.

The wear of one or more of the rope grooves of the drive and diverting pulleys of the elevator occurring during normal operation reduces the diameter of flexure of the rope, i.e. the radius of the rope groove. When the elevator is moving, i.e. when all the pulleys are rotating, the mutual circumferential lengths of the rope grooves change and become distance from each other due to wear of the pulley. The rope forces then begin to change during operation and become different due to groove friction, accelerating the wear of rope grooves exposed to a greater rope force. The phenome- non is contingent and becomes more and more probable with the lapse of time as the distance traveled by the elevator increases. Changes in the rope grooves of especially the traction sheave and the so-called "double-wrap" pulley give rise to considerable changes in rope force because the system is largely based on frictional grip.

To improve frictional grip and to reduce the wear of surface wires, the rope grooves of the drive and di- verting pulleys may be provided with an elastic coating against which the steel wire rope is pressed. When the coating is worn, the wear may at first be slow but it may continue ever faster and finally lead to a situation where the steel wire rope comes into contact with the metallic bottom of the rope groove of the pulley, with the result that a metal-to-metal contact occurs, which causes fast wear of the rope. Especially when thin steel wire ropes having a tensile strength 1.5 - 2 times higher than the tensile strength of con- ventional steel wire ropes are used, even slight wear of the rope weakens the rope proportionally more than in the case of a conventional rope. Therefore, the occurrence of metal -to-metal contact is to be avoided as effectively as possible. Furthermore, as it is consid- erably more expensive to replace the ropes than to re- place the drive and diverting pulleys, it is important to detect excessive wear of the rope grooves in time.

Thus, at some stage of wear, the drive pulleys and/or diverting pulleys have to be replaced. Usually the wear of drive and diverting pulleys is observed visually in connection with periodic maintenance. However, there is the problem that the wear of the rope grooves of the pulleys is very difficult to detect visually because the changes are of the order of fractions of a millimeter and there is no tool that could be used to access the pulleys for inspection, and because the elevator has a large number of pulleys and because they are located in inconvenient places in the eleva- tor shaft and on the elevator car.

OBJECT OF THE INVENTION

The object of the invention is to overcome the above- mentioned drawbacks.

A specific object of the invention is to disclose an economical method that will make it possible to detect excessive wear of the rope grooves of drive and/or diverting pulleys in time before any major and more ex- pensive damage occurs so that the need for maintenance and replacement can be determined.

BRIEF DESCRIPTION OF THE INVENTION

The method of the invention is characterized by what is disclosed in the characterization part of claim 1. Moreover, the elevator of the invention is characterized by what is disclosed in the characterization part of claim 8. Other embodiments of the invention are characterized by what is disclosed in the other claims. Inventive embodiments are also presented in the description part and drawings of the present application. The inventive content disclosed in the application can also be defined in other ways than is done in the claims below. The inventive content may also con- sist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or in respect of advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts. Within the framework of the basic concept of the invention, features of different embodiments of the invention can be applied in conjunction with other embodiments .

According to the invention, in the method at least one of the following quantities is assigned a limit value: allowed displacement of the rope end against the spring force of the spring, allowed rope force of the rope, allowed tension of the rope, compression of the spring holding the rope, tension of the spring holding the rope, stress of the supporting structure adjacent to the rope fastening. During operation of the elevator, the displacement, rope force, tension, spring compression, spring tension and/or stress of supporting structure of each individual rope in relation to the corresponding quantity for the other ropes is detected from the sprung fastening arrangement of the rope ends. An alarm signal is generated if the dis- placement, rope force, tension, spring compression, spring tension and/or stress of supporting structure of each individual rope in relation to the corresponding quantity for the other ropes exceeds the predetermined limit value during operation of the elevator. If the limit value is exceeded due to an increased rope force, this is an indication of greater than normal wear of the rope groove of the drive and/or diverting pulley corresponding to the aforesaid individual rope.

The elevator of the invention comprises an elevator car suspended with a number of ropes. The ropes are passed over diverting and drive pulleys provided with rope grooves. At least one end of each rope is secured in a sprung manner to a supporting structure by means of a sprung fastening device. The sprung fastening device comprises a spring for each rope to hold the rope fast on the supporting structure in a sprung manner.

According to the invention, to detect wear of the rope grooves of the drive and/or diverting pulleys, the elevator comprises a detector device arranged in conjunction with the sprung fastening device.

The central insight of the invention is to utilize the sprung fastenings of the ropes for the detection of the mutual difference of displacement/force of the rope ends and further for the detection of wear of the rope grooves of the drive and/or diverting pulleys. The invention has the advantage that an alarm regard- ing wear of the rope grooves can be obtained so that it will be detected at the right moment in order that the drive and/or diverting pulleys can be inspected and replaced if necessary.

In an embodiment of the method, based on the alarm signal, the degree of wear of the diverting and drive pulleys is checked and, if necessary, a worn drive and/or diverting pulley is replaced. In an embodiment of the method, the alarm signal is issued with a delay upon the lapse of a predetermined delay period after the excess of the limit value if the limit value continues to be exceeded after the aforesaid delay period.

In an embodiment of the method, the displacement difference between the ropes is observed during operation of the elevator, and an alarm signal is generated if the displacement difference is greater than the predetermined limit value.

In an embodiment of the method, the alarm signal is transmitted into the elevator's operation supervision system.

In an embodiment of the method, the elevator is stopped on the basis of the alarm signal.

In an embodiment of the method, excess of the limit value is detected by a mechanical, optical and/or electrical measuring method.

In an embodiment of the elevator, the detector device comprises: means for detecting displacement differences between the ropes, means for detecting rope force differences between the ropes, means for detecting rope tension differences between the ropes, means for detecting spring compression differences between the ropes; means for detecting differences of spring tension; and/or means for detecting stresses of a supporting structure adjacent to the rope fastenings.

In an embodiment of the elevator, the detector device is a mechanical, optical and/or electrical device. In an embodiment of the elevator, the detector device has been fitted to give an alarm signal with a delay upon the lapse of a predetermined delay period after excess of a predetermined limit value if the predetermined limit value continues to be exceeded after the aforesaid delay period.

In an embodiment of the elevator, the detector device comprises an electric circuit fitted to give an alarm signal when the displacement difference between the ropes is greater than the predetermined limit value.

In an embodiment of the elevator, the sprung fastening device comprises a frame secured to a fixed supporting structure. The frame is provided with a number of holes arranged in a row at a distance from each other and extending from a first side of the frame to a second side of the frame. Attached to each rope by means of a rope splice element is a draw bar. The draw bars go through the holes, extending from the first side of the frame to the second side. The part of each draw bar extending to the second side is provided with a thread extending to the end. Screwed on the thread of each draw bar is a nut. On the second side of the frame, between each nut and the frame is a compression spring.

In an embodiment of the elevator, the detector device comprises a conductor bar extending transversely relative to the direction of displacement of the ropes and fastened to one of the draw bars. Further, the detector device comprises a number of conductor loops or the like, each of which is fastened to the draw bars to form an array of loops through which the conductor bar extends . The conductor bar and loops have been fitted to form the aforesaid electric circuit, which is closed and produces an alarm signal when the conductor loop comes into electric contact with the con- ductor bar.

In an embodiment of the elevator, the size of the conductor loops has been selected to be suitable so that it corresponds to the limit value of allowed displace- ment of the rope.

In an embodiment of the elevator, the detector device comprises a flexible tube which is substantially straight when in an unstressed state and which is fas- tened to each draw bar substantially transversely relative to the direction of displacement of the ropes so that differences of displacement of the draw bars produce a bending of the tube. The diameter of the tube has been chosen to determine the limit value of allowed displacement, said tube having a first end and a second end and a radiation-absorbing inner surface. A radiation source is provided at the first end of the tube to direct radiation into the tube. A radiation detector is provided at the second end of the tube to detect radiation passing through the tube and to generate an alarm signal when the radiation detector stops detecting radiation.

In an embodiment of the elevator, the detector device comprises a microswitch, which comprises a switch frame; a flexural spring having a fastening end connecting the spring to the switch frame and a free end provided with a follower element, which spring can be bent against spring force from a free position to a bent position; and a switching element which is in a turn-on state in which the alarm circuit is in a turned-on state when the spring is in the bent position, and in a turn-off state in which the alarm circuit is in a turned-off state when the spring is in the free position. Furthermore, the detector device comprises a number of sheet metal parts, the number of which comprises to the number of ropes. Each sheet metal part is fastened to one rope or to some other part moving with the rope. Attached to one of the sheet metal parts is a microswitch. The other sheet metal parts comprise side edges oriented in the direction of rope displacement and provided with identical indentations fitted to receive the follower element into them. The sheet metal parts are set one upon the other as a pack with the side edges aligned with each other and mounted to be movable with respect to each other in the direction of displacement of the ropes. When there is no displacement difference between the ropes, all the indentations are mutually aligned and the follower element is inside all the indentations and the switching element is in the turn-off state. When a displacement difference occurs between the ropes, the indentation of at least one of the sheet metal parts has moved away from the aligned position with respect to the indentations of the other sheet metal parts and the follower element has risen out of the indentations against the side edge of the displaced sheet metal part. In this situation the switching element is in the turn-on state to give an alarm signal.

In an embodiment of the elevator, the length of the indentation in the direction of the side edge has been selected to be suitable so that it corresponds to the limit value of allowed displacement of the rope. LIST OF FIGURES

In the following, the invention will be described in detail with reference to embodiment examples and the attached drawing, wherein

Fig. 1 presents an embodiment of the elevator of the invention,

Fig. 2 presents a sprung rope fastening device comprised in an embodiment of the elevator of the invention, provided with a first detector device detecting the difference of displacement of the ropes,

Fig. 3 presents the sprung fastening device of Fig. 2 in a situation where the detector device gives an alarm signal,

Fig. 4 presents a sprung rope fastening device comprised in an embodiment of the elevator of the invention, provided with a second detector device detecting the difference of displacement of the ropes,

Fig. 5 presents the sprung fastening device of Fig. 4 in a situation where the detector device gives an alarm signal,

Fig. 6 presents a sprung rope fastening device com- prised in an embodiment of the elevator of the invention, provided with a third detector device detecting the difference of displacement of the ropes, Fig. 7 presents the sprung fastening device of Fig. 6 in a situation where the detector device gives an alarm signal,

Fig. 8 presents an axonometric view of the detector device shown in figures 6 and 7, and

Fig. 9 presents an exploded view of the detector device in Fig. 8.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 is a diagrammatic view of a traction sheave elevator without the guide rails. The elevator comprises an elevator car 1 supported by a number of ropes 2, which are passed over diverting and drive pulleys 4, 5 provided with rope grooves 3. On each one of the diverting and drive pulleys 4,5, each rope 2 has a separate rope groove 3 in which the rope runs . One end of each rope is secured in a sprung manner to a supporting structure 6 by means of a sprung fastening device 7. The sprung fastening device 7 comprises a spring 8 for each rope 2. To detect wear of the rope grooves 3 of the drive and/or diverting pulleys 4, 5, the elevator comprises a detector device 9 arranged in conjunction with the sprung fastening device 7. The elevator is preferably an elevator without machine room, in which the drive machine is placed in the elevator shaft, although the invention is applicable for use even in elevators having a machine room. Although the elevator presented in Fig. 1 has a suspension ratio of 2:1, the invention is not restricted to the suspension arrangement illustrated in Fig. 1 or to any other given suspension ratio arrangement. In addition, although Fig. 1 presents an elevator car provided with a counterweight 24, the invention can be applied even in the case of elevators without counterweight .

The detector device 9 placed in conjunction with the sprung fastening device 7 to detect excessive wear of the rope grooves 3 may comprise e.g. means for detecting differences of displacement of the ropes 2. Such means are described in more detail in connection with figures 2 - 5.

An alternative to the detection of displacement differences may be that the detector device is provided with means for detecting differences of rope force of the ropes 2 or means for detecting tension differences of the ropes 2. Alternatively, it is possible to means for detecting differences of compression of the springs 8 or means for detecting differences of tension of the springs 8. A further alternative may be to provide means for detecting the stresses of a support- ing structure adjacent to the fastenings of the ropes 8, from which it is possible to draw indirect conclusions about the forces/stresses acting on different ropes. To measure the forces and stresses, it is possible to use force or stress sensors, such as strain gauges, suitably attached to the ropes, springs or supporting structure. The detector device 9 may be a mechanical, optical and/or electrical device.

When a detector device 9 is used, first a limit value is defined for at least one of the following quantities, depending on which quantity is to be measured: allowed displacement of the rope end against the spring force of the spring; allowed rope force of the rope; allowed tension of the rope; compression of the spring holding the rope; tension of the spring holding the rope; stress of the supporting structure adjacent to the rope fastening. Next, the elevator is operated in the normal manner. During operation of the elevator, the displacement, rope force, tension, spring compression, spring tension of each individual rope and/or the stress of the supporting structure in relation to the corresponding quantity for the other ropes is detected from the sprung fastening arrangement of the rope ends. An alarm signal is generated if during operation of the elevator the displacement, rope force, tension, spring compression, spring tension and/or stress of supporting structure of an individual rope in relation to the corresponding quantity for the other ropes exceeds the predetermined limit value. If the rope groove corresponding to one of the ropes on the drive and/or diverting pulleys is worn, the rope force will change, in other words, the rope in question begins to carry a force greater or smaller than the force of the other ropes. If the limit value of the observed quantity is exceeded due to a changed rope force, this indicates that the wear of the rope groove corresponding to the rope in question on the drive and/or diverting pulley is greater than allowed or that the other grooves have undergone simultaneous wear. Based on the alarm signal, which is preferably transmitted to the operation supervision system of the elevator, the diverting and drive pulleys are examined for wear and, if necessary, a worn diverting pulley and/or traction sheave is replaced. When necessary, the operation supervision system can immediately stop the operation of the elevator on the basis of the alarm signal .

Figures 2 - 5 present embodiments in which the mutual motion of the ends of the ropes 2, i.e. the displace- ment difference between the ropes 2 is observed during operation of the elevator, and an alarm signal is generated if the displacement difference is greater than the predetermined limit value.

In the embodiment presented in Fig. 2 and 3, the detector device 9 comprises an electric circuit 10, which has been fitted to output an alarm signal when the displacement difference between the ropes 2 is greater than the predetermined limit value. In the embodiment in Fig. 4 and 5, the displacement difference between the ropes 2 is observed optically to detect an excess of the predetermined limit value.

Figures 1 - 5 show the structure of the sprung fastening device 7. It comprises a frame 11, which is secured to a fixed supporting structure 6 and which is provided with a number of holes 12 arranged in a line at a distance from each other and extending from the first side I of the frame to the second side II of the frame. A number of draw bars 13 are each secured by means of a rope splice element 14 to a rope 2. The draw bars 13 extend through the holes 12 from the first side I of the frame to the second side II. The end of each draw bar 13 extending to the second side II is provided with a thread 15 extending to the end of the draw bar. Screwed on the thread of each draw bar 13 is a nut 16, which serves as an end stop for the helical spring used as a compression spring 8, which has been fitted on the second side II of the frame 11 to act between the frame 11 and the nut 16. The draw bar 13 is inside the helix of the spring. As the rope force of the rope 2 varies, the spring 8 springs and its compression changes. To allow the invention to be utilized, springs 8 of a stiffness selected to suit the rope and its length are required, as elevators traditionally have had. The stiffness of the spring 8 is so chosen that the spring 8 will not bottom out in normal operation with a suitable extra rope force. When one of the ropes begins to bear a load greater than that of the others, e.g. when the elevator is run from one end of the shaft to the other, a sufficient movement of the spring 8 is ob- tained and the displacement can be detected by the device of the invention. Wear of the rope groove can be detected before any one of the rope grooves has been worn out too much, and that the safety factor of the rope will not fall to a level too low. The safety fac- tor allowed (according to EN81-1 1998 Annex N) in a certain type of elevator may easily fall too low, depending on the K+Q+T. If the spring constant of the selected spring is k=43 N/mπv i.e. 4*d4 mm, then the maximum K+Q+T for the example elevator type is about 1500 kg, in which case a rope force of

(9,81*1500/(5*4) = 735 N) will lead to a safety factor of 19.6. If the extra force is not allowed to drop the safety factor below 15, then the extra force obtained is 225 N, which will lead to a spring compression of 5.2 mm. This can already be clearly detected by the detector device of the invention.

The detector device 9 in Fig. 2 and 3 comprises a conductor bar 17 which extends transversely in relation to the direction of displacement of the ropes 2 and is fastened to one of the draw bars 13. Further, the detector device 9 comprises a number of conductor loops 18 or the like, which are fastened to the draw bars 13 to form a row of loops through which the conductor bar 17 extends. In Fig. 3, the rope force acting in one of the ropes is greater than in the other ropes, which has led to a situation where the conductor bar 17 and the conductor loop 18 of the rope bearing the greatest load close the circuit 10 generating an alarm signal. The size of the conductor loops 18 has been suitably chosen so that it corresponds to the limit value of allowed displacement of the rope.

Figures 4 and 5 show an optical detector device 9 comprising a flexible tube 19, which in the situation of Fig. 4 is substantially straight. The tube 19 is fastened to each draw bar 13 substantially transversely relative to the direction of displacement of the ropes 2. Thus, as can be seen from Fig. 5, a displacement difference between the draw bars 13 produces a bend in tube 19. The diameter of the tube 19 has been chosen to determine the limit value of allowed displacement. The inner surface of the tube 19 is light-absorbing so that the radiation is not reflected from the inner surface. A radiation source 22 is disposed at the first end 20 of the tube to direct radiation into the tube 19. A radiation detector 23 is disposed at the second end 21 of the tube 19 to detect radiation passing through the tube and to generate an alarm signal when the radiation detector 23 stops detecting radiation.

In the embodiment in Fig. 6 - 9, the sprung fastening device 7 is of a type corresponding to that in Fig. 1 - 5. This embodiment differs from the embodiment in Fig. 1 - 5 in respect of the detector device 9. In the embodiment in Fig. 6 - 9, the detector device 9 is im- plemented using a simple, commercially available ad- vantageous electric switching component, a microswitch 25.

In this embodiment, the detector device comprises a microswitch 25, which comprises a switch frame 26 and a flexural spring 27 having a fastening end 28 connecting the spring to the switch frame 26 and a free end 29 provided with a follower roller 30. The spring 27 can be bent against its spring force from a free position A (see Fig. 6) to a bent position B (see Fig. 7) . The microswitch 25 comprises a switching element 31, which is in a turn-on state I in which the alarm circuit 10 is in a turned-on state when the spring 27 is in the bent position B, and in a turn-off state II in which the alarm circuit 10 is in a turned-off state when the spring is in the free position A.

The detector device 9 in Fig. 6 - 9 further comprises a number of sheet metal parts 32, 33, 34, 35, the now corresponds to the number of ropes 2. Each sheet metal part is fastened to one rope or to some other part moving with the rope. For the sake of clarity, the diagrams in Fig. 6 and 7 present a case where the detector device is fastened directly to the ropes 2, but it is obvious that it can be fastened e.g. to the draw bars, to the rope splice elements 14 or to any element that moves in the same way as the ropes.

The microswitch 25 is secured to one 35 of the sheet metal parts. The other sheet metal parts 32, 33, 34 comprise side edges 36, 37, 38 oriented in the direction of rope displacement and provided with identical indentations 39, 40, 41 fitted to receive the follower element 30 into them. The length of the indentations 39, 40, 41 in the direction of the side edges 26, 37, 38 has been suitably selected so that it corresponds to the limit value of the allowed displacement of the ropes 2. As can be best seen from Fig. 8, the sheet metal parts 32, 33, 34, 35 are set one upon the other to form a pack with the side edges 36, 37, 38 aligned and flush with each other.

As can be best seen from Fig. 9, the sheet metal parts

32, 33, 34, 35 are mounted so as to be movable with respect to each other in the direction of displacement of the ropes 2, i.e. in the vertical direction, with a guide arrangement which comprises a vertical flange 42 formed in the sheet metal part 35 provided with a microswitch 25 and vertical elongated and identical slots 43, 44, 45 formed in the other sheet metal parts 36, 37, 38 and aligned with each other, said flange 42 extending through each slot. The sheet metal parts 32,

33, 34, 35 are held as a pack by a holding element 46 fastened to the flange 42.

When no displacement difference exceeding the allowed limit value exists between the ropes 2, all the indentations 39, 40, 41 are mutually aligned and the follower element 30 remains inside all these indenta- tions, so the switching element 31 is in the turn-off state II. Fig. 6 corresponds to such a situation.

When a displacement difference greater than the allowed limit value appears between the ropes 2, indi- eating wear of a rope groove on a diverting pulley and/or traction sheave, the indentation 40 of the sheet metal part corresponding to the rope in question, in Fig. 7 sheet metal part 33 by way of example, moves away from the aligned position relative to the indentations 39 and 41 of the other sheet metal parts 36 and 38 and the follower element 30 rises away from the indentations against the side edge 37 of the displaced sheet metal part 33. The switching element 31 of the microswitch is now brought into the turn-on state I, causing generation of an alarm signal. The issue of an alarm signal can be delayed to eliminate unnecessary alarms originated by causes other than wear of the diverting and/or drive pulleys. An alarm signal is preferably only issued if an excess of the limit value of allowed displacement is found to persist after a given delay period.

The invention is not limited to the embodiment examples described above; instead, many variations are possible within the scope of the inventive concept defined in the claims.

LIST OF REFERENCE NUMBERS

elevator car (1) rope (2) rope groove (3) diverting pulley (4) drive pulley (5) supporting structure (6) sprung fastening device (7) spring (8) detector device (9) electric alarm circuit (10) frame (11) hole (12) first side (I) of frame second side (II) of frame draw bar (13) rope splice element (14) threads (15) nut (16) conductor bar (17) conductor loop (18) tube (19) - first end (20) - second end (21) radiation source (22) radiation detector (23) counterweight (24) microswitch (25) switch frame (26) flexural spring (27) - fastening end (28) - free end (29) follower element (30) free position (A) bent position (B) switching element (31) turn-on state (I) turn-off state (II) sheet metal parts (32, 33, 34, 35) side edge (36, 37, 38) indentation (39, 40, 41) flange (42)

Claims

1. A method for detecting wear of the diverting and/or drive pulleys of an elevator, said elevator comprising an elevator car supported by a number of ropes, which are passed over diverting and drive pulleys to achieve a desired transmission ratio, at least one end of each rope being secured in a sprung manner to a supporting structure, characteri zed in that - at least one of the following quantities is assigned a limit value: + allowed displacement of the rope end against the spring force of a spring, + allowed rope force of the rope, + allowed tension of the rope, + compression of the spring holding the rope, + tension of the spring holding the rope, + stress of the supporting structure adjacent to the rope fastening, - the elevator is operated,

- during operation of the elevator, the displacement, rope force, tension, spring compression, spring tension and/or stress of the supporting structure of each individual rope in relation to the corresponding quan- tity for the other ropes is detected from the sprung fastening arrangement of the rope ends, and

- an alarm signal is generated if the displacement, rope force, tension, spring compression, spring tension and/or stress of the supporting structure of each individual rope in relation to the corresponding quantity for the other ropes exceeds the predetermined limit value during operation of the elevator, an excess of the limit value due to an increased rope force being an indication of greater than normal wear of the rope groove of the drive and/or diverting pulley corresponding to the aforesaid individual rope.

2. A method according to claim 1, character i zed in that, based on the alarm signal, the degree of wear of the diverting and drive pulleys is checked and, if necessary, a worn drive and/or diverting pulley is replaced.

3. A method according to claim 1 or 2, charac teri zed in that the alarm signal is issued with a delay upon the lapse of a predetermined delay period after the excess of the limit value if the limit value continues to be exceeded after the aforesaid delay period.

4. A method according to any one of claims 1 - 3, characteri zed in that the displacement difference between the ropes is observed during operation of the elevator, and an alarm signal is generated if the displacement difference is greater than the predeter- mined limit value.

5. A method according to any one of claims 1 - 4, characteri zed in that the alarm signal is transmitted to the elevator's operation supervision system.

6. A method according to any one of claims 1 - 5, characteri zed in that the elevator is stopped on the basis of the alarm signal .

7. A method according to any one of claims 1 - 6, characteri zed in that excess of the limit value is detected by a mechanical, optical and/or electrical measuring method.

8. An elevator, comprising an elevator car (1) supported by a number of ropes (2) which are passed over diverting and drive pulleys (4, 5), at least one end of each rope being secured in a sprung manner to a supporting structure (6) by means of a sprung fastening device (7) , said sprung fastening device comprising a spring (8) for each rope for sprung attachment of the rope, characteri zed in that, to detect wear of the rope grooves (3) of the diverting and/or drive pulleys (4, 5), the elevator comprises a detector device (9) arranged in conjunction with the sprung fastening device (7) .

9. An elevator according to claim 8, character - i z e d in that the detector device (9) comprises at least one of the following: means for detecting displacement differences between the ropes (2), - means for detecting rope force differences between the ropes (2), - means for detecting rope tension differences between the ropes (2) , - means for detecting compression differences between the springs (8) , - means for detecting tension differences between the springs (8), and/or - means for detecting stresses of a supporting structure adjacent to the rope (8) fastenings.

10. An elevator according to claim 8 or 9, charac teri zed in that the detector device (9) is a mechanical, optical and/or electrical device.

11. An elevator according to any one of claims 8 - 10, characteri zed in that the detector device (9) has been fitted to give an alarm signal with a delay upon the lapse of a predetermined delay period after excess of a predetermined limit value if the predetermined limit value continues to be exceeded after the aforesaid delay period.

12. An elevator according to any one of claims 8 - 11, characteri zed in that the detector device (9) comprises an electric alarm circuit (10) fitted to give an alarm signal when the displacement difference between the ropes (2) is greater than the predetermined limit value.

13. An elevator according to any one of claims 8 - 12, characteri zed in that the sprung fastening device (7) comprises a frame secured to a fixed supporting structure (6) , said frame being provided with a number of holes (12) which are arranged in a line at a dis- tance from each other and extend from a first side (I) of the frame to a second side (II) of the frame, - a number of draw bars (13) , each of which is fastened to a rope (2) by means of a rope splice element (14) , said draw bars going through the holes and extending from the first side (I) of the frame to the second side (II), the part of each draw bar extending to the second side being provided with a thread (15) extending to the end, - a number of nuts (16) , each of which is screwed on the thread of a draw bar, and - a number of springs (8) , each of which has been fitted on the second side (II) of the frame to act between the frame (11) and the nut (16) .

14. An elevator according to any one of claims 8 - 12, characteri zed in that the detector device (9) comprises - a conductor bar (17) extending transversely relative to the direction of displacement of the ropes (2) and fastened to one of the draw bars (13), and a number of conductor loops (18) or the like, each of which is fastened to the draw bars (13) to form an array of loops through which the conductor bar extends, the conductor bar and loops being fitted to form the aforesaid electric circuit (10) , which is closed and produces an alarm signal when the conductor loop comes into electric contact with the conductor bar.

15. An elevator according to claim 14, charac teri zed in that the size of the conductor loops (18) has been selected to be suitable so that it cor- responds to the limit value of allowed rope displacement .

16. An elevator according to any one of claims 8 - 13, characteri zed in that the detector device (9) comprises - a flexible tube (19) which is substantially straight when in an unstressed state and which is fastened to each draw bar (13) substantially transversely relative to the direction of displacement of the ropes (2) so that differences of displacement of the draw bars produce a bending of the tube, the diameter of which tube has been chosen to determine the limit value of allowed displacement, said tube having a first end (20) and a second end (21) and a radiation- absorbing inner surface, a radiation source (22) disposed at the first end (20) of the tube to direct radiation into the tube, and - a radiation detector (23) disposed at the second end (21) of the tube to detect radiation passing through the tube and to generate an alarm signal when the radiation detector stops detecting radiation.

17. An elevator according to claim 13, charac - teri zed in that the detector device (9) comprises - a microswitch (25) , which comprises -- a switch frame (26) -- a flexural spring (27) having a fastening end (28) connecting the spring to the switch frame (26) and a free end (29) provided with a follower element (30) , which spring can be bent against spring force from a free position (A) to a bent position (B) , -- a switching element (31), which is in a turn-on state (I) in which the alarm circuit (10) is in a turned-on state when the spring is in the bent position (B) , and in a turn-off state (II) in which the alarm circuit (10) is in a turned-off state when the spring is in the free position (A) , - a number of sheet metal parts (32, 33, 34, 35) , the number of which comprises to the number of ropes (2) , each one of said sheet metal parts being fastened to one rope or to some other part moving with the rope, the aforesaid microswitch (25) being attached to one (35) of the sheet metal parts while the other sheet metal parts (32, 33, 34) comprise side edges (36, 37, 38) oriented in the direction of rope displacement and provided with identical indentations (39, 40, 41) fitted to receive the follower element (30) into them, which sheet metal parts (32, 33, 34, 35) have been set one upon the other as a pack with the side edges in alignment with each other and mounted to be movable with respect to each other in the direction of displacement of the ropes, so that when there is no displacement difference be- tween the ropes (2), all the indentations (39, 40, 41) are mutually aligned and the follower element (30) is inside all the indentations and the switching element (31) is in the turn-off state (II), and when a displacement difference exists between the ropes, the in- dentation of at least one of the sheet metal parts has moved away from the aligned position with respect to the indentations of the other sheet metal parts and the follower element has risen out of the indentations against the side edge of the displaced sheet metal part, in which situation the switching element is in the turn-on state (I) to give an alarm signal.

18. An elevator according to claim 17, charac teri zed in that the length of the indentation (39, 40, 41) in the direction of the side edge (36, 37, 38) has been selected to be suitable so that it corresponds to the limit value of allowed displacement of the rope (2) .