GB1576211A - Actuating mechanisms for vacuum interrupters - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO ACTUATING MECHANISMS FOR VACUUM INTERRUPTERS (71) We, ASSOCIATED ELECTRIC AL INDUSTRIES LIMITED of 1, Stanhope Gate, London, W1A 1EH., a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to actuating mechanisms for vacuum interrupters, that is to say electrical devices incorporating within an air-evacuated envelope a pair of electrical contacts, one of which is movable into and out of engagement with the other, to make or break an electrical circuit. The movable contact is supported by an electrically conductive stem extending outwards through a flexible part of the envelope, commonly in the form of a diaphragm or bellows, the stem being coupled either directly or indirectly to a suitable actuating mechanism.

An object of this invention is to provide an actuating mechanism for such vacuum interrupters.

According to the present invention an actuating mechanism for a vacuum interrupter comprises a coupling member which, in use, is connected to the contact stem of the movable contact of a vacuum interrupter, and is displaceable into a first or a second position to cause the movable contact to move into and out of engagement respectively with the other contact of the interrupter when it is so connected, the mechanism comprising also a displacement member movable to displace the coupling member into the second position, and a level mechanism incorporating a pair of levers pivotally connected together, with one of the levers pivotally mounted on a support and the other lever pivotally connected to the displacement member, and the levers having an over-centre locking position in which they cause the displacement member to lock the coupling member in said second position, the mechanism further comprising biassing means acting on the levers to urge them into the locking position, and operating means operable against the biassing means to move the levers from the locking position and then to displace the coupling member towards and hold it in the first position, the biassing means being operable to return the levers to the locking position on release of the operating means.

Preferably the levers respectively comprise a first bell crank lever pivotally mounted on a support and having one limb acted upon by the spring means, and a second bell crank lever having a fulcrum located on the displacement member with one limb connected to the operating means, and the other limb pivotally coupled to the second limb of the first lever. The biassing means preferably comprises a spring.

The displacement member is preferably slidably supported on the contact stem of the vacuum interrupter or an extension thereof, and the stem or extension carries stop means against which the displacement member is urged to separate the movable contact of the vacuum interrupter from the fixed contact when the bell crank levers are moved into the locked position.

Then rotation of the first bell crank lever towards the locked position under the action of the spring means, when the operating means is released, produces a rapid movement of the displacement member towards the stop such that the initial opening movement of the contacts is effected by the member striking the stop means.

The striking of the stop by the moving displaceable member causes a sudden acceleration of the latter and consequently of the contact stem which ensures severance of weld spots on the contacts and a rapid acceleration of the movable contact to the open position.

Preferably a spring is interposed between the displaceable member and a member fixed to the contact stem or an extension thereof, such that when the operating means is operated to release the bell crank levers from their locked position and move the displaceable member away from the stop, the spring is compressed against the fixed member as the movable contact is moved into engagement with the fixed contact.

The springs will assist in providing stored energy for moving the displaceable member towards the stop when the operating means is released to allow the contacts to open.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation, partly in section, of an actuating mechanism in accordance with the invention; and Figure 2 is a side elevation similar to Figure 1 but showing the parts of the mechanism in a different operative position.

Referring to the drawings, the actuating mechanism is mounted on a framework 1 of non-ferrous metal which also forms a mounting for a vacuum interrupter 2 to be actuated by the mechanism. The vacuum interrupter 2 is secured to a limb 3 of the framework 1 by nuts 4 screwed on to threaded stems 5 projecting from an end plate 6 of the vacuum interrupter, so that the contact stem 7 which supports the movable contact 8 of the vacuum interrupter and is itself supported from the end plate 6 by means of bellows (not shown) to allow for opening and closing movement of the contact 8, projects through an aperture in the limb 3. A further limb 10 of the framework 1 is provided with holes to enable the framework 1 to be mounted on an electrical support insulator 12.

The actuating mechanism comprises a first bell crank lever 13 pivotally mounted on a spindle 14 secured to the framework 1 and having one arm 15 pivotally connected to a boss 39 fixed to one end of a shaft 16 which extends slidably through an opening in a support block 40 pivotally mounted on a spindle 17 secured to the framework 1. A powerful helical spring 18 is interposed between the spindle 17 and a flange 19 provided on the boss 39. A nut 20 screwed on a threaded end 21 of the shaft 16 enables the force exerted by the helical spring 18 on the boss 39 to be adjusted.

A second bell crank lever 22 is pivotally mounted on a spindle 23 secured to a displacement member in the form of a further block 35 slidably supported on one end of a rod 24 which is connected at its opposite end to the contact stem 7 of the vacuum interrupter 2. Rollers located on both ends of the spindle 23 extend into guide slots 25 provided on both sides of the framework 1 and extending parallel to the axis of the rod 24. One arm 26 of the bell crank lever 22 is pivotally connected to a switch operating member 27 by a spindle 28, while the other arm 29 is pivotally connected to the arm 30 of the bell crank lever 13 by a spindle 31. A helical spring 32 surrounding the rod 24 bears at one end against the block 35 and at the other end against a collar 36 which connects the rod 24 to the contact stem 7 of the vacuum interrupter and also provides a terminal for electrically connecting a conductor 37 to the movable contact 8 via the contact stem 7.

In Figure 1 the parts of the actuating mechanism are shown in positions in which the switch operating member 27 has not been operated and the movable contact 8 of the vacuum interrupter 2 is separated from the fixed contact 33. When the member 27 is unoperated, the linkage formed by the two bell crank levers 13 and 22 is urged by the helical spring 18 so that the arm 30 moves in an anti-clockwise direction and the arm 29 moves in a clockwise direction to a locked 'over-centre position. When the linkage is held in this locked position by the springs 18, the spindle 23 occupies the lefthand end of the guide slot 25 the block 35 bears against a nut 38 on the threaded outer end of the rod 24 and holds the movable contact 8 away from the fixed contact 33. A force applied to the rod 24 in the direction of the arrow 34, such as would normally cause the movable contact 8 to engage the fixed contact 33, will not unlock the locked linkage.

To unlock the linkage and cause the movable contact 8 to engage the fixed contact 33 pressure is applied to the switch operation member 27 to move it to the right as seen in the Figures, so that the arm 29 moves in an anticlockwise direction and the arm 30 moves in a clockwise direction from the over-centre position. The spring 18 is compressed and the block 35 is moved along the rod 24 towards the right guided by the guide slot 25, this compressing the spring 32 against the collar 36 and urging movable contact 8 into engagement with the fixed contact 33 as shown in Figure 2. The movable contact 8 may be moved away from the fixed contact 33 by removing the pressure from the operating member 27 so that the linkage returns to the locked position urged by the spring 18. The action of the spring 18 when the operating member 27 is released results in the block 35 moving rapidly towards the nut 38 assisted by the spring 32, the arrangement providing a stored energy pick-up of the movable contact assembly which ensures severance of any weld spots on the contacts 8,13 and assists in providing a rapid acceleration of the movable contact 8 to the open position.

WHAT WE CLAIM IS:- 1. An actuating mechanism for a vacuum interrupter comprising a coupling member which, in use, is connected to the contact stem of the movable contact of a vacuum interrupter, and is displaceable into a first or a second position to cause the movable contact to move into and out of engagement respectively with the other contact of the interrupter when it is so connected, the mechanism comprising also a displacement member movable to displace the coupling member into the second position, and a level mechanism incorporating a pair of levers pivotally connected together, with one of the levers pivotally mounted on a support and the other lever pivotally connected to the displacement member, and the levers having an over-centre locking position in which they cause the displacement member to lock the coupling member in said second position, the mechanism further comprising biassing means acting on the levers to urge them into the locking position, and operating means operable against the biassing means to move the levers from the locking position and then to displace the coupling member towards and hold it in the first position, the biassing means being operable to return the levers to the locking position on release of the operating means.

2. An actuating mechanism according to Claim 1 in which said first lever is a bell crank lever pivotally mounted on a support and having one limb acted upon by the biassing means, and said second lever is also a bell crank lever, the fulcrum of which is located on the displacement member with one limb connected to said operating means and the other limb pivotally connected to the second limb of the first lever.

3. An actuating mechanism according to Claim 2 wherein the displacement member is slidably supported on the contact stem of the vacuum interrupter or an extension thereof, and the stem or extension carries a stop against which the displacement member is urged to separate the movable contact of the vacuum interrupter from the fixed contact when the bell crank levers are moved into the locked position.

4. An actuating mechanism according to Claim 3 wherein rotation of the first bell crank lever towards the locked position under the action of the biassing means, when the operating means is released, produces a rapid movement of the displacement member towards the stop such that the initial opening movement of the contacts is affected by the member striking the stop.

5. An actuating mechanism according to Claim 4 wherein a spring is interposed between the displaceable member and a member fixed to the contact stem or an extension thereof, such that when the operating means is operated to release the bell crank levers from their locked position and move the displaceable member away from the stop, the spring is compressed against the fixed member as the movable contact is moved into engagement with the fixed contact.

6. An actuating mechanism according to any preceding claim wherein said biassing means comprises a spring.

7. An actuating mechansim for a vacuum interrupter substantially as shown in and as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. the movable contact 8 to the open position. WHAT WE CLAIM IS:-

1. An actuating mechanism for a vacuum interrupter comprising a coupling member which, in use, is connected to the contact stem of the movable contact of a vacuum interrupter, and is displaceable into a first or a second position to cause the movable contact to move into and out of engagement respectively with the other contact of the interrupter when it is so connected, the mechanism comprising also a displacement member movable to displace the coupling member into the second position, and a level mechanism incorporating a pair of levers pivotally connected together, with one of the levers pivotally mounted on a support and the other lever pivotally connected to the displacement member, and the levers having an over-centre locking position in which they cause the displacement member to lock the coupling member in said second position, the mechanism further comprising biassing means acting on the levers to urge them into the locking position, and operating means operable against the biassing means to move the levers from the locking position and then to displace the coupling member towards and hold it in the first position, the biassing means being operable to return the levers to the locking position on release of the operating means.

2. An actuating mechanism according to Claim 1 in which said first lever is a bell crank lever pivotally mounted on a support and having one limb acted upon by the biassing means, and said second lever is also a bell crank lever, the fulcrum of which is located on the displacement member with one limb connected to said operating means and the other limb pivotally connected to the second limb of the first lever.

3. An actuating mechanism according to Claim 2 wherein the displacement member is slidably supported on the contact stem of the vacuum interrupter or an extension thereof, and the stem or extension carries a stop against which the displacement member is urged to separate the movable contact of the vacuum interrupter from the fixed contact when the bell crank levers are moved into the locked position.

4. An actuating mechanism according to Claim 3 wherein rotation of the first bell crank lever towards the locked position under the action of the biassing means, when the operating means is released, produces a rapid movement of the displacement member towards the stop such that the initial opening movement of the contacts is affected by the member striking the stop.

5. An actuating mechanism according to Claim 4 wherein a spring is interposed between the displaceable member and a member fixed to the contact stem or an extension thereof, such that when the operating means is operated to release the bell crank levers from their locked position and move the displaceable member away from the stop, the spring is compressed against the fixed member as the movable contact is moved into engagement with the fixed contact.

6. An actuating mechanism according to any preceding claim wherein said biassing means comprises a spring.

7. An actuating mechansim for a vacuum interrupter substantially as shown in and as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.