GB2210504A

GB2210504A - Switch operating mechanisms

Info

Publication number: GB2210504A
Application number: GB8723223A
Authority: GB
Inventors: Usko Uusipaikka; Reino Saarenmaki
Original assignee: Stromberg Oy AB
Current assignee: ABB Stromberg Oy
Priority date: 1986-05-08
Filing date: 1987-10-02
Publication date: 1989-06-07
Also published as: FR2622045A1; SE8701696L; DE3733916A1; SE8701696D0; FI74838C; GB8723223D0; FI74838B; FI861927A0

Description

0 4 A lock mechanism for the operating device of an electric switch The

invention relates to a lock mechanism for the operating device of an electric switch particularly amedium voltage switch. The operating device is typically a spring operating device. The lock mechanism comprises a first lever controlled by a control roller; a connecting link one end of which is connected to the first lever; and a second lever which is journalled on the other end of the connecting link adjacent to one end thereof and on a shaft adjacent to the other end thereof, the end of the second lever close to the connecting link being locked behind a turningwedge in the ON position of the switch when it is pivoted round the shaft.

The function of the spring operating device of an electric switch is to effect a rapid contact movement necessary for the contacts of the switch after having received the ON or OFF instruction. The movements of the spring operating device are effected by means of the energy stored in the springs.

The switch is kept in the ON position by means of a mechanical lock. Strains caused by the OFF connection springs are normally exerted on this lock. Another mechanical lock receives the forces caused by the ON connection spring. In practice. the latter lock is relatively easy to realize. The former, so called OFF side.lock is considerably more difficult to construct so as to function reliably. because it has to move rapidly and stop over a short distance at the locking stage. This often results in rebounding which in practice means that the lock does not function properly. In prior solutions of the above-described. type. attempts have been made to prevent rebounding by 1 2 means of various adjusting mechanisms and by the use of suitable damping materials in the limiters. The function of the limiter is to prevent an excessive movement of the end of the second lever to be locked behind the turning wedge, i.e. to prevent the end of the second lever from slipping beyond the dead point of the toggle joint.

The great spring forces of the connection springs of the switch are decreased by means of various lever transmissions and toggle joints to such an extent that the control of the switch can be effected by means of electric magnets having an attractive or repulsive force of a few tens of newtons. Since the toggle joints usually operate close to the dead point, the limiter has to be positioned very near the turning wedge. For this reason, even minor measuring errors and wear result in situations in which the toggle joint either does not move over a sufficient distance or it presses the limiter by force. In prior solutions, attempts have been made to solve such problems, too, by means of various adjustments.

The object of the present invention is to avoid the above problems and provide a lock mechanism of the type described in the beginning, in which minor measuring errors and wears do not affect the operation of the mechanism, and in which the rebounding can be prevented. This is achieved in such a manner that the first lever and the connecting link are interconnected by means of a resilient member, and that the mechanism comprises means for locking the normal movement of the first lever for effecting a resilient movement, the radius of the control roller being chosen so as to create movement beyond the locking point.

The basic idea of the invention is thus to 3 control the movement of the lock mechanism in a controlled and limited manner by means of the locking means, the control roller and the resilient member so that the effects of measuring errors are compensated by the resilient movement, and no limiter is needed for limiting the movement of the end of the lever to be locked behind the turning wedge.

By means of the solution according to the invention it is thus also possible to eliminate all the adjusting operations required by prior mechanisms.

In the following the invention will be described in more detail with reference to the examples of the attached drawings, wherein Figure 1 is a schematic view of a lock mechanism according to the invention when the switch is in the OFF position, Figure 2 illustrates the lock mechanism in a situation when the control movement has continued so far that the resilient movement has taken place, and Figure 3 illustrates a situation when the control carried out by the control roller has been completed and the switch is ready to be brought in the OFF position.

In Figure 1. an angular connecting link 2 is attached to a first lever 1, and the other end of the connecting link is journalled by means of a pin 6 near to one end 4a of a second lever 4. Adjacent to the other end thereof, the lever 4 is journalled on a shaft 14. The lever 1 and the connecting link 2 are interconnected by means of a spring 3, whereby the pin 6 is supported on a nS - tiplof the lever 1 between the connecting link 2 and the lever 4. The lever 1, the connecting link 2, the spring 3 and the lever 4 form a resilient toggle joint. The lever 1 is articulated to a third. nearly triangular lever 11 which is jour- 4 nalled on a shaft 13 and to which a OFF connection spring 15 is attached, one end of which spring 15 is positioned at a fixed point Pl. The lever 11 is kinematically connected to a contact 11a, as is shown schematically in the figure. The mechanism.further comprises a control roller 9 which rotates around a shaft 9a and which is shown in Figure 1 with an ON spring 10 tightened. The control roller 9 is locked by means of a latch 8 and a turning wedge 7. In addition, Figure 1 shows a turning wedge 16 and a return spring 17 thereof. The free end 4a of the lever 4 is locked behind the turning wedge 16 in the ON position of the switch lla in a manner described below.

The operation of the lock mechanism according to the invention will now be described with reference to all the figures 1 to 3 beginning from Figure 1.

As mentioned above, Figure 1 shows the switch in the OFF position with the ON spring 10 tightened. When the switch lla is controlled in the ON direction, the turning wedge 7 releases the latch 8, whereby the control rol1L9 starts to turn clockwise in the direction of the arrow A under the influence of the ON spring 10. While turning, the control roller 9 presses a roll 12 provided in the lever 1 so that the lock mechanism is forced to turn with respect to the shafts 13 and 14. At the same time the OFF spring 15 starts to tighten. When the control roller 9 turns, the mechanism is pressed downwards so that the centre of the roll 12 is displaced along the broken line B shown in Figure 3. and the centre of the pin 6 is displaced along the broken line C shown in Figure 1. A recess la is formed in the lever 1. the movement of an assumed point P2 Of the recess being indicated with the broken line D.

The normal movement of the mechanism in accord- 1 1 ance with the broken lines B and C continues freely until the recess la is displaced over the shaft 14 at a determined stage. Thereby the "upwardly" directed edge shape of the back portion of the recess la forces the lever 1 to be pivoted with respect to.the connecting link 2 when the control roller 9 presses'the mechanism further downwards, as a result of which the tip 5 of the lever 1 is released from the pin 6, and the spring 3 is stretched. This situation is shown in Figure 2 in which the recess la has been displaced over the shaft 14 and the pin 6 and the tip 5 of the lever 1 have been released from each other. thus stretching the spring 3. This situation is maintained until the control roller 9 is wholly passed by the roll 12. On reaching the position of Figure 2 as shown by the broken line C in Figure 1, the lever 4 has passed by the turning wedge 16, which now has plenty of time to pivot to the initial position thereof by means of the return spring 17.

The radius R of the control roller 9 is chosen so that it creates a more extensive movement than what is required for passing the lever 4 behind the turning wedge 16. This excess of movement as well as the locking effect of the recess creates and maintains a resilient movement; in other words, causes a gap to be formed between the tip 5 of the lever 1 and the pin 6. Accordingly, measuring errors and wear only change the size of the gap, i.e. the stretch of the spring, whereas they do not affect the operation of the lock mechanism itself.

Figure 3 further shows a situation in which the control roller 9 has already wholly turned from the position of Figure 2 past the roll 12. so that the spring 3 has drawn the pin 6 back to a position against the tip 5 of the lever 1 and the tip 4a of the 6 lever 4 to a position against the turning wedge 16. The switch lla is now ready to be passed in the OFF position.

The drawbacks of prior solutions, such as the risk of rebounding and the effects of measuring errors and the adjusting operations required thereby, can thus be eliminated by means of the above-described mechanism. Even though the invention has been described above with reference to the example of the attached drawings, it is obvious that the invention is not restricted thereto, but it can be modified within the inventive idea defined in the attached claims. Accordingly, the lever 1, for instance, need not necessarily get "locked" in the shaft 14, but it is as well possible to use a separate locking device or limiter for locking the normal movement of the lever 1 at a determined stage of the control movement of the control roller 9.

3 7

Claims

Claims:

1. A lock mechanism for the operating device of an electric switch, a medium voltage switch in particular, comprising - a first lever (1) controlled by a control roller (9), - a connecting link (2) one end of which is connected to the first lever (1), and - a second lever (4) journalled on the other end of the connecting link (2) adjacent to one end (4a) thereof and on a shaft (14) adjacent to the other end thereof, the end (4a) of the second lever (4) close to the connecting link (2) being locked behind a turning wedge (16) in the ON position of the switch when it is pivoted round the shaft (14), c h a ra c te r i z e d in that - the first lever (1) and the connecting link (2) are interconnected by means of a resilient member (3), and that - the mechanism comprises means (14, la) which lock the normal movement of the first lever (1) for effecting a resilient movement, - the radius (R) of the control roller (9) being chosen so as to create movement beyond the locking point.

2. A lock mechanism according to claim 1, c h a r a c t e r i z e d in that the resilient member is a spring (3).

3. A lock mechanism according to claim 2, c h a r a c t e r i z e d in that the locking means comprise a recess (1a) formed in the first lever (1), the recess being displaced over the shaft (14).

Published 1988 at The Patent 0mce. State House. 66 71 High Holborn. London WC1R 4TP. Further copies may be obtained from The Patent Office. Salles Branch. S, Mary Cray. c)rpington. Kent BR5 3RD. Printed by Multiplex techniques lid. St. Mary Cray. Kent. Con 1'87,