WO2007144456A1

WO2007144456A1 - Arrangement for detecting slack rope of an elevator

Info

Publication number: WO2007144456A1
Application number: PCT/FI2007/000171
Authority: WO
Inventors: Petteri Valjus; Teuvo VÄNTÄNEN; Alessandro Pilone; Marko Karppinen
Original assignee: Kone Corporation
Priority date: 2006-06-16
Filing date: 2007-06-15
Publication date: 2007-12-21
Also published as: FI20060596A0; FI20060596L

Abstract

The present invention relates to an arrangement for detecting slack rope in a traction sheave elevator, which elevator comprises at least a control unit (6), a hoisting machine (4) and a traction sheave (5) connected to it, as well as an elevator car (1) and a counterweight (3), which are fitted to travel backwards and forwards in an essentially vertical direction suspended on hoisting ropes (2) that are fixed at both their ends. The elevator is provided with at least one detector element (8, 11), which is fitted to detect slackening of the hoisting ropes (2) and to deliver information to the elevator system about the slackening.

Description

ARRANGEMENT FOR DETECTING SLACK ROPE OF AN ELEVATOR

The present invention relates to an arrangement for detecting the slack rope of an elevator as defined in the preamble of claim 1.

In traction sheave elevators the elevator car is moved by- means of a traction sheave and hoisting ropes. In order for movement of the elevator car to operate in the manner planned, there must be sufficient friction between the rope grooves of the traction sheave and the hoisting ropes, in which case the ropes do not slip on the traction sheave. A problem especially in elevators with counterweight is determining the correct friction in all loading situations. If the friction is not sufficiently large, slipping of the ropes may cause dangerous situations. For this reason the aim is often to increase the friction. However, friction that is too large can cause problems, especially when the hoisting machine is able to lift just the elevator car or the counterweight without the assistance of the other. These kinds of situations may occur e.g. in the following cases, if the friction is large: a) the elevator car starts moving upwards and for some reason the counterweight is jammed in place; b) the elevator car is moving upwards and for some reason the counterweight jams in place; c) the elevator car starts downwards and for some reason is itself jammed in place, but despite that the counterweight continues its movement upwards; d) the elevator car is moving downwards and for some reason suddenly jams in place, but despite that the counterweight continues its movement upwards; e) the elevator car drives to the limit switches in the upper part of the shaft as the result of a malfunction, and despite the counterweight being on the buffer, the elevator car can continue its movement upwards, in which case a problem is that the safety clearance in the upper end of the shaft is lost.

In situations a) - d) slack rope occurs on that side of the traction sheave on which the drive direction is downwards.

If the friction on the traction sheave is not lost immediately at the onset of the situation, the situation can become dangerous, since the friction is in any case lost for some time as a result of rope slackening. In this case either the elevator car or the counterweight falls freely downwards until the slackened ropes tighten.

So that the above-mentioned dangerous situations do not occur as a result of friction that is too great, elevator regulations stipulate that the danger of this kind of situation must be tested in connection with the safety test of an elevator such that an empty car is driven upwards when the counterweight is on the buffer. For the test to be passed satisfactorily, the elevator car cannot start moving. A problem is, however, that in certain conditions the requirements for passing the test may restrict the dimensioning of the hoisting system of the elevator or even make impossible in practice. In this case dimensioning of the elevator to be such that the above-mentioned test can be performed results in the elevator not operating sufficiently reliably and efficiently in normal use. Typically this can occur in e.g. the following elevator solutions: 1) in elevators in which there is no rope compensation and in which the car is relatively light, 2) in elevators in which there is no rope compensation and the lifting height of which as well as the unit mass of the hoisting ropes of which is great, in other words the safety factor of the ropes is greater than normal, 3) in elevators in which there are great friction requirements and in which e.g. so-called double-wrap roping is used and the traction sheave has semicircular rope grooves.

The purpose of this invention is to eliminate the aforementioned drawbacks and to achieve a reliable arrangement, in which sudden slack rope situations of the elevator do not cause dangerous situations. To enable this the purpose is to achieve a system for detecting slack rope of an elevator, so that the elevator would be safe to use and so that the elevator could easily be dimensioned to normal different operating situations without the special requirements of the slack rope test restricting the dimensioning of the elevator. The arrangement of the invention is characterized by what is disclosed in the characterization part of claim 1. Likewise other embodiments of the invention are characterized by what is disclosed in the other claims.

Some inventive embodiments are also discussed in the descriptive section of the present application. The inventive content of the application can also be defined differently than in the claims presented below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of expressions or implicit sub-tasks or from the point of view of advantages or categories 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. Likewise the different details presented in connection with each embodiment of the invention can also be applied in other embodiments.

One advantage of the solution according to the invention is that the elevator is safe for users in all operating situations. A further advantage is that dimensioning of the elevator is freer, in which case dimensioning of the elevator does not need to be restricted so that the elevator also passes a slack rope test. A further advantage is the simplicity, dependability and operational reliability of the solution.

The invention will be described in the following in more detail by the aid of two examples of its embodiments with reference to the attached drawings, wherein

Fig. 1 presents a simplified and diagrammatic side view of an elevator solution, in which one embodiment according to the invention is used.

Fig. 2 presents a simplified and diagrammatic side view of a mechanical detector element according to the invention used to detect slack rope,

Fig. 3 presents a simplified and diagrammatic side view of a detection element according to Fig. 2 in a slack rope situation and

Fig. 4 presents a simplified and diagrammatic side view of an elevator solution, in which a second embodiment according to the invention is used.

Fig. 1 presents a simplified and diagrammatic side view of a typical traction sheave elevator, in which one embodiment according to the invention is used. The elevator is preferably an elevator provided with a control unit 6, in which the elevator car 1, the hoisting roping formed of parallel hoisting ropes 2, the counterweight 3 and the hoisting machine 4 with its traction sheave 5 are disposed in the elevator shaft. The hoisting machine 4 with its traction sheave can also be outside the shaft. The elevator receives its lifting force from the hoisting machine 4 as a result of the friction between the traction sheave 5 and the hoisting ropes 2.

In the roping solution presented in Fig. 1 each hoisting rope 2 is fixed at its first end to a fixed point in the upper part of the elevator shaft via a first detector element 8 that measures the rope force of the hoisting ropes 2. From their fixing points the hoisting ropes 2 are led to pass to one or more diverting pulleys 9 on the elevator car, after passing around the bottom of which the hoisting ropes 2 are led upwards to the traction sheave 5 of the hoisting machine 4, after passing around the top of which the hoisting ropes 2 are further led via possibly one or more diverting pulleys 7 under one or more diverting pulleys 10 on the counterweight 3 and then further upwards to the fixing point of the second end, to which the hoisting ropes 2 are fixed via the second detector element 8 that measures the rope force of the hoisting ropes 2.

Figs. 2 and 3 present one mechanical detector element 8, which is applicable for use in an arrangement according to the invention. In the situation presented in Fig. 2 the hoisting ropes 2 are taut in a normal situation owing to the rope force caused by the elevator car 1 or the counterweight 3, and correspondingly in the situation presented in Fig. 3 the hoisting ropes 2 have slackened so much that the detector element 8 has activated the limit switch 19.

The detector element 8 comprises at least a frame part 14, which is securely fixed in place in connection with the fixing points of the hoisting ropes 2. A transmission element 13, which is e.g. a plate-like part suited to the purpose, is fitted to be supported on the top surface of the frame part 14. The ends of each parallel hoisting rope 2 of the hoisting roping are fixed to the fixing wedge 16, which for its part is fixed to the vertical fixing arm 17, which fixing arm is fitted to pass through the transmission element 13 of the frame part 14 from the bottom upwards and on the upper end of which fixing arm 17 is a part provided with a screw thread for the fixing nut 18, which fixing nut 18 is fitted to rest on the top surface of the transmission element 13 under the effect of the rope force exerted by the hoisting ropes. By means of the fixing nut 18 also the tightening of the hoisting ropes can be individually adjusted. A spring element 15 or corresponding actuator acting against the rope force of the hoisting ropes 2, which is fitted to push the transmission element 13 off the frame part 14, is disposed inside the frame part 14. At a suitable distance above the transmission element 13 is a limit switch 19, the triggering element 20 of which is situated to be activated by means of the transmission element 13 when the transmission element 13 rises by a certain distance off the top surface of the frame part 14. The direction of the rope force of the hoisting ropes 2 is shown in Figs. 2 and 3 with an arrow 21.

The spring force of the spring element 15 of the detector element 8 is dimensioned such that the transmission element 13 rests in a normal situation on the top surface of the frame part 14 pulled by the rope force of the hoisting ropes 2 as long as the hoisting ropes are taut and a sufficiently great rope force is exerted on the detector element 8. If the hoisting ropes slacken as a result of any of the above- mentioned fault situations, the spring force of the spring element 15 is sufficient to press the transmission element 13 off the top surface of the frame part 14 and to touch the triggering element 20 of the limit switch 19, in which case the limit switch 19 connected to the control unit 6 or other suitable place in the elevator system cause the elevator car to stop in position e.g. by means of the brake of the elevator before free fall has time to start. After this the elevator is released for service via manual freeing.

Instead of mechanical detector elements 8 also electrical detector elements can be used at the ends of the hoisting ropes 2 or at another suitable location on the hoisting rope 2 , which electrical detector elements measure the changing of the rope force of the hoisting ropes 2, e.g. with force sensors implemented with strain gauges or similar means, the resistance of which changes in relation to a changing of the rope force. The force sensors are connected to the elevator system essentially in the same manner as the above-mentioned switch 19 and bring about in connection with a slackening of the hoisting ropes 2 stopping of the elevator car 1 as quickly as possible.

Fig. 4 presents an elevator solution, in which a second embodiment according to the invention is used for detecting slack roping. In this solution the hoisting ropes 2 are fixed at their ends directly to an essentially secure fixing point 12 and instead of slackening detection occurring at the ends of the hoisting ropes 2 slackening of the roping is detected electrically from the hoisting machine by means of an electrical detector element 11. In this case e.g. a change in the current of the hoisting motor is measured and based on it a change in the torque that is caused by a sudden slackening of the roping is detected. A change in torque can be detected also from the fixing of the hoisting machine 2 e.g. by means of the force sensors referred to earlier. The information about a change in torque is led to the drive system of the elevator in order to stop the elevator car in the same manner as referred to earlier.

It is obvious to the person skilled in the art that the invention is not limited solely to the examples described above, but that it may be varied within the scope of the claims presented below. Thus e.g. the element detecting a change in rope force can also be some other type of element than what is described above. The idea however is a function that detects a sudden change in rope force, which after observing a change sends information to the elevator system and in which elevator system is the ability and means to stop the elevator car after receiving said information.

It is also obvious to the person skilled in the art that the invention can be used also just as well with other rope suspensions than with the 2:1 suspension presented in the figures. With greater suspension ratios the solution works just as well and also with a suspension ratio of 1:1 the solution works even though a connection to the drive system from the moving elevator car and counterweight must be formed when measuring the rope force at the ends of the hoisting ropes.

Claims

1. Arrangement for detecting slack rope in a traction sheave elevator, which elevator comprises at least a control unit (6), a hoisting machine (4) and a traction sheave (5) connected to it, as well as an elevator car (1) and a counterweight (3), which are fitted to travel backwards and forwards in an essentially vertical direction, suspended on hoisting ropes (2) that are fixed at both their ends, which is provided with at least one detector element (8, 11), which is fitted to detect slackening of the hoisting ropes

(2) and to deliver information to the elevator system about the slackening, characterized in that the detector element

(8) is disposed at both ends of the hoisting ropes (2) .

2. Arrangement according to claim 1 or 2 , characterized in that both ends of each hoisting rope (2) are suspended via the flexible element of the detector element (8), such as a spring element (15), such that the spring force of the spring element (15) is arranged to be exerted in essentially the opposite direction to the rope force of the hoisting ropes (2) .

3. Arrangement according to claim 1, 2 or 3, characterized in that the detector element (8) contains at least a frame part (14) essentially fixed in its position and a transmission element (13) fitted to move with respect to the frame part (14), which transmission element (13) is fitted to rest on the frame part (14) owing to the rope force and to move away from the frame part (14) owing to the spring force of the spring element (15) of the frame part (14) .

4. Arrangement according to any of the preceding claims, characterized in that the detector element (8) contains a switch (19), which is fitted to send information to the elevator system about the slackening of a rope when the transmission element (13) detaches from the frame part (14) as it is pushed by the spring element (15) .

5. Arrangement according to any of the preceding claims, characterized in that the switch (19) is connected to at least the control unit (6) of the elevator.

6. Arrangement according to claim 1, characterized in that the detector element (8, 11) is an element that measures rope force or torque, which is fitted to react electrically to a change in force and/or torque.

7. Arrangement according to claim 1, characterized in that the detector element (11) is an element that measures torque, which is fitted to measure torque based on a change in the current of the motor of the hoisting machine (4) .

8. Arrangement according to any of the preceding claims, characterized in that the spring-action detector element (8) and the detector element (8, 11) that electrically measures force or torque are fitted to operate together.