WO2004080874A1

WO2004080874A1 - Overspeed governor

Info

Publication number: WO2004080874A1
Application number: PCT/FI2004/000125
Authority: WO
Inventors: Ilkka Lempiö; Esko Aulanko
Original assignee: Kone Corporation
Priority date: 2003-03-12
Filing date: 2004-03-09
Publication date: 2004-09-23
Also published as: FI20030367A; FI20030367A0; FI117092B

Abstract

The invention relates to an overspeed governor in conjunction with the rope wheel (2) of a triggering rope (1) connected to the emergency brake or safety gear of an elevator. According to the invention, the overspeed governor comprises a frame (3), and auxiliary frame (4) secured to the frame and turnable in relation to it, a braking element (5) secured to the auxiliary frame for braking the rotation of the rope wheel, magnetizing means (6) on the auxiliary frame for creating a magnetic field, a projecting part (7) of electrically conductive material mounted in conjunction with the rope wheel (2) and arranged to extend into the magnetic field and rotate with the rope wheel, and a holdback (8) extending into the magnetic field for determining the position of the auxiliary frame in relation to the frame.

Description

OVERSPEED GOVERNOR

The present invention relates to an overspeed governor mounted in conjunction with the rope wheel of a triggering rope connected to the emergency brake or safety gear of an elevator.

Traditionally, the operation of the emergency brake or safety gear of an elevator is based on the utilization of a centrifugal force, in other words, when the speed of rotation of a certain wheel in- creases beyond a given limit value, the centrifugal force will push a certain braking or gripping element to an operating position. This movement of the braking or gripping element caused by the centrifugal force is generally opposed by a mechanically operated spring device, which is used to determine the operating limits and sensitivity of the device.

Prior-art devices are in themselves simple in construction and reliable in operation, but they are difficult to adjust and the stability of adjustments made is insecure. This is because the devices are operated very seldom, if ever, and therefore the properties of mechanical springs and equivalent may change in the course of time.

The object of the present invention is to overcome the above-described drawbacks. A specific object of the invention is to disclose a new type of overspeed governor which is more reliable in operation, more versatile in regard of adjustability and more accurately adjustable and better able to preserve the accuracy than prior-art devices.

As for the features of the invention, reference is made to the claims.

The overspeed governor of the invention, which is designed for use in conjunction with the rope wheel of a triggering rope connected to the emergency brake or safety gear of an elevator, comprises a frame, an auxiliary frame secured to the frame and ro- tatable in relation to it and a brake element secured to the auxiliary frame for braking the rotation of the rope wheel. In addition, the auxiliary frame is provided with magnetizing means for creating a magnetic field and in conjunction with the rope wheel a projecting part made of electrically conductive material and arranged to extend into the magnetic field and rotate with the rope wheel . Further according to the invention, the overspeed governor comprises a holdback extending into the magnetic field for determining the position of the auxiliary frame relative to the frame. Thus, the overspeed governor of the invention is based on a projecting part of electrically conductive material moving in a magnetic field, wherein the eddy cur- rents generated in the projecting part produce a force acting on the magnetizing means and via these on the auxiliary frame and the braking element, said force triggering the overspeed governor into operation.

In an embodiment of the invention, the mag- netizing means consist of a pair of permanent magnets forming a gap in which the projecting part has been arranged to be movable. Although other types of magnetizing means are in themselves applicable, a permanent magnet is the best and most reliable device be- cause its operation and stability are independent of external factors and remain unchanged even in the long run.

In an embodiment of the invention, the projecting part consists of a disc-like plate or flange, e.g. a round and relatively thin aluminum plate, which is rigidly connected to the rope wheel so that it always rotates at the same speed with the rope wheel . Thus, the disc-like plate may be secured directly to the rope wheel or it may be mounted on the same shaft with the rope wheel so that it will rotate simultaneously with it . The holdback used in the overspeed governor is arranged to resist the motion of the magnetizing means caused by the forces produced by the eddy currents. The holdback is preferably secured to the frame of the overspeed governor. The material, position and shape of the holdback can be used as means of adjusting and controlling the operation of the overspeed governor.

In an embodiment of the invention, the hold- back consists of a plate or strip of ferromagnetic material extending into the gap formed by the magnetizing means. The holdback may also be so designed that it comprises at least two hold stations for holding the auxiliary frame in different rotational positions relative to the frame, depending on the magnitude of the force generated by the eddy currents.

In an embodiment of the invention, efficient braking is accomplished when the braking element comprises a brake pad implemented as a wedge-shaped body which, when the braking device is actuated, is thrust into a rope groove functioning as a braking surface.

The overspeed governor of the invention preferably comprises adjusting elements for adjustment of the air gap between the magnetizing means and the pro- jecting part, i.e. of the eddy currents produced. Likewise, the overspeed governor preferably comprises an adjusting device for adjustment of the air gap between the magnetizing means and the holdback. Thus, the force acting between the magnetizing means and the holdback can be adjusted by means of the distance between them, the shape of the holdback and/or the position of the holdback.

As compared with prior art, the overspeed governor of the invention has significant advantages. The overspeed governor is very reliable in operation and independent of external influences and disturbances. It can be easily adapted for use in different applications by only making mechanical adjustments, i.e. by using different air gap sizes. The adjustments remain unchanged and stable even over long periods of time. In the following, the invention will be described in detail with reference to the attached drawing, wherein

Fig. 1 presents a diagrammatic partially sectioned view of an overspeed governor according to the invention, and

Fig. 2 presents a diagrammatic side view of the overspeed governor in Fig. 1.

An overspeed governor according to the invention as presented in the drawing comprises a fixed frame 3 in conjunction with the rope wheel 2 of a triggering rope 1 connected to the emergency brake or safety gear of an elevator, the rope wheel 2 being ro- tatably mounted in relation to said fixed frame. Secured to the frame 3 is an auxiliary frame 4, which is turnable in relation to it. The free turning movement of the auxiliary frame 4 relative to the frame 3 can be controlled or limited e.g. by means of a suitable spring or by gravity. Secured to the auxiliary frame 4 is a braking element 5 for braking the rotation of the rope wheel 2. The braking element 5 is provided with a wedge-shaped brake pad 11, which has been fitted to brake the rope wheel by the wedge-shaped rope groove 10 of the wheel.

In addition, the overspeed governor comprises magnetizing means 6 secured to the auxiliary frame 4 and consisting of a pair of permanent magnets, which form a gap 9 between them. Mounted on the same shaft with the rope wheel 2 is a projecting part 7, i.e. a round aluminum plate extending into the gap 9 formed by the pair of permanent magnets between them, so that it rotates simultaneously with the rope wheel . Ar- ranged to extend into the same gap is also a holdback 8, i.e. a thin band-like steel strip.

The overspeed governor of the invention presented in the drawing works as follows. At normal op- erating speeds, the aluminum plate 7 rotates in the gap 9 so that the eddy currents produced are insignificant and do not generate any forces that would cause operation of the device. On the other hand, in exceptional conditions when the rope wheel for some reason rotates at an excessive speed, the aluminum plate is rotating at a corresponding speed, in other words, moving at this speed in the gap 9. In this situation, due to the strong eddy currents set up in the aluminum disc, a sufficiently strong force is gen- erated between the aluminum disc and the permanent magnet, causing the auxiliary frame 4 and together with it the braking element 5 to turn. Thus the brake pad 11 gets wedged into the rope groove 10 of the rope wheel 2 and stops the rope wheel and therefore the triggering rope 1, which again leads to the final action, such as operation of the safety gear.

In the foregoing, the invention has been described by way of example with reference to the attached drawing while different embodiments of the in- vention are possible within the scope of the inventive concept defined in the claims .

Claims

1. An overspeed governor in conjunction with the rope wheel (2) of a triggering rope (1) connected to the emergency brake or safety gear of an elevator, characterized in that the overspeed governor comprises a frame (3) , an auxiliary frame (4) secured to the frame and turnable in relation to it, - a braking element (5) secured to the auxiliary frame for braking the rotation of the rope wheel, magnetizing means (6) on the auxiliary frame for creating a magnetic field, a projecting part (7) of electrically conductive material mounted in conjunction with the rope wheel (2) and arranged to extend into the magnetic field and rotate with the rope wheel , and a holdback (8) extending into the magnetic field for determining the position of the auxiliary frame in relation to the frame.

2. An overspeed governor according to claim 1, characterized in that the magnetizing means (6) consist of a pair of permanent magnets forming a gap (9) in which the projecting part (7) has been ar- ranged to be movable.

3. An overspeed governor according to claim 1 or 2, characterized in that the projecting part (7) consists of a disc-like plate or flange, e.g. an aluminum plate .

4. An overspeed governor according to claim 3, characterized in that the disc-like plate (7) is mounted on the same shaft with the rope wheel (2) so that it rotates simultaneously with the rope wheel .

5. An overspeed governor according to claim 1, characterized in that the holdback (8) is secured to the frame (3) .

6. An overspeed governor according to claim 2 , characterized in that the holdback (8) consists of a plate or strip of ferromagnetic material extending into the gap (9) formed by the magnetizing means (6) .

7. An overspeed governor according to claim 1, characteri zed in that the holdback (8) comprises at least two hold stations for holding the auxiliary frame (4) in different rotational positions relative to the frame (3) .

8. An overspeed governor according to claim 1, charac t eri zed in that the braking element (5) comprises a brake pad (11) fitted to the rope groove (10) of the rope wheel (2) to brake it.

9. An overspeed governor according to any one of claims 1 - 8, characteri zed in that the overspeed governor comprises adjusting elements for adjustment of the air gap between the magnetizing means (6) and the projecting part (7) .

10. An overspeed governor according to any one of claims 1- 9, characteri zed in that the overspeed governor comprises an adjusting device for adjusting the air gap between the magnetizing means (6) and the holdback (8) .