US2378270A - Switch operating mechanism - Google Patents

Description

June 12, 1945.

N. H. WESTERVELT SWITCH OPERATING MECHANISM Filed Nov. 29, 1943 Fi 4 I Inve n t or": Nelson H.Wester-ve!t,

b ivwajww His Attorney.

Patented June 12, 1945 SWITCH OPERATING MECHANISM Nelson H. Westervelt, Yeadon, Pa., assignor to General Electric Company, a corporation of New York Application November 29, 1943, Serial No. 512,185

3 Claims.

My invention relates to operating mechanisms for electric switches, and more particularly to operating mechanisms for power circuit breakers.

Electric switches, such as power circuit breakers, usually comprise a contact structure with actuating means to actuate the circuit breaker to the open or closed positions, or both. For high speed circuit breakers it has often been the practice to bias the contact structure to the open position by suitable spring means. In such an arrangement the actuating means for operating the circuit breaker, which might be a fluid motor, asolenoid, or the like, would, through a suitable operating mechanism, move the contact structure to the closed position against the biasing means, such as springs, thereby charging the springs during the circuit closing operation. It is obvious that suitable latching means must be provided to latch the circuit breaker or switch in the closed position. Opening of the circuit breaker" can then be initiated by releasing the latching means. It would be desirable to provide' an operating mechanism of the above mentioned type which would act as a force multiplying means near the end of the closing operation so as to take care of a greatly increased force as the energy storage means approaches the fully charged condition. It would further be desirable to provide an arrangement in which the latching means could be released by a very small force and yet wherein the operating mechanism was simple and compact in construction.

It is an object of my invention to provide a new and improved switch operating mechanism.

It is another object of my invention to provide an operating mechanism for an electric switch which is simple and compact in construction and which embodies the desirable features enumerated above.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of 'noyelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of. this specification.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1 diagrammatically illustrates an electric switch embodying the operating mechanism of my invention; and Fig. 2 is a perspective View of the operating mechanism shown in Fig, 1.

Although my invention is generally applicable to electric switches of the type in which the contact structure is biased to the open position and latched in the closed position against said biasing means, I have chosen to illustrate my invention as applied to a circuit breaker having a contact structure II] which is operated to the closed position through a suitable operating mechanism II by means of an actuating means comprising a fluid motor generally indicated at I2. The operating mechanism II, which will be described in greater detail hereinafter, includes a latching member or prop I4, which may be moved to its unlatching position by energization of its trip coil I5.

The circuit breaker comprising the contact structure III is schematically illustrated as a three-pole switch which is biased to the open circuit position by suitable means indicated as a spring I6. The contact structure I!) of the circuit breaker is arranged to control an electric circuit comprising conductors [1, I8 and I9.

The trip coil I5 of the operating mechanism I I embodying my invention is arranged to be energized to release the prop or latching means I4 in response to the operation of a protective relay 20, or a tripping control switch 2|. The protective relay 20 is illustrated simply as an over-current relay connected to be energized from a current transformer 22 in the circuit conductor I1. It will be understood, of course, that any number of relays may be employed in accordance with the art of circuit protection. Also as shown, the circuit of trip coil or winding I5, which includes 1 the conductors 23 and 24, may also include the contacts 25 of a circuit breaker a auxiliary switch which is closed when the circuit breaker is closed and open when the circuit breaker is open.

For actuating the operating mechanism II to close the contact structure IU of the circuit breaker, there is provided the fluid pressure actuated means or fluid motor I2 comprising a cylinder 26 Within which is reciprocally and slidably mounted a piston 21, carrying a piston rod 28. This. piston rod 28 is adapted to engage with the operating means I I as will be described hereinafter to move the circuit breaker to the closed position so that latching means I4 may become effective to hold the circuit breaker in closed position against the force of spring I6. While any suitable fluid may be provided to raise the piston 21 it is usual to use air under the desired pressure which may be contained in a suitable source or tank 29, from which it is supplied to cylinder 26 through control valve means 30. On the upstroke of the piston 21 suitable energy storing means, such as spring 3|, is compressed to effect the down or return stroke of the piston 21 to the lower posi tion shown. This down stroke operation follows the cutting off of the air supply by the control valve 30 so that the air in the cylinder 26 can be quickly exhausted to atmosphere through the medium of a dump valve 32 which uncovers exhaust ports 33. In order to avoid pressure above the piston 2'! on the up stroke and also to have it return freely under the bias of spring 3|, the cylinder 26 is provided with one or more suitably located ports 34. When the control valve 30 is open, air under pressure is admitted from source or tank 29 through the valve 30 to the back of the dump valve 32. This valve 32 moves to the left against the bias of a spring 35 and closes the exhaust ports 33. Coincidentally with the closing of the dump valve 32 the air under pressure opens an admission valve 36 mounted in the head of the dump valve 32 to uncover ports 31 therein for admission of air to the cylinder 26. The admission valve 36 is biased to the closed position by a spring 38 which becomes so compressed that when air is subsequently exhausted from the space 39 on the source side of dump valve 32 the valve 36 quickly closes the ports 31 whereby the dump valve 32 more effectively moves to uncover the ports 33. This construction of the dump valve is not my invention but is disclosed and claimed in a copening application, Serial No. 512,180, filed concurrently herewith upon an application of Thellwell R. Coggeshall, and assigned to the same assignee as the present application.

The control valve 33 may comprise any suitable form of electromagnetically actuated control valve but is preferably of the pilot differential type such as is disclosed in the copending Coggeshall application referred to above, or as is disclosed and claimed in Coggeshall application, Serial No. 512,17 9, filed concurrently herewith and assigned to the same assignee as the present application. In accordance with the last-mentioned Coggeshall application, electromagnetically actuated valve 30 includes an armature 40, a magnetic housing 4|, a pole piece 42 and a valve opening winding 43. The electromagnetic actuated means also includes two independent valve closing windings 44 and 45.

For closing the circuit breaker comprising contact structure 18, there is provided a closing control system for the valve opening winding 43. As shown, this circuit includes a closing control switch 46, the contacts 4! of a minimum pressure switch 48 which opens when the pressure in the tank 29 falls below a predetermined minimum value, a conductor 49, b auxiliary switch contacts 50 of the circuit breaker comprising contact structure l U, a conductor the contacts 52 of a short time delay circuit opening relay 53 whose winding 54 is energized upon closure of the closing control switch 46, a conductor 55, the valve opening winding 43, and a conductor 56. The opening of the circuit breaker closing control circuit by the slightly delayed contacts 52 of the relay 53 insures a positive opening of the control valve 30 in response to energization of its opening winding 43 and also prevents reclosure of the circuit break-- er as long as the control switch 46 is kept closed. In other words, with a single closure of the control switch 45, only one closure of the circuit breaker comprising contact structure It! can be efiected.

The valve closing winding 44 is provided for quickly returning the piston 21 to the down 'or normal position. The operating mechanism ll, although inherently trip-free as will become apparent hereinafter, cannot move to the open circuit position as long as air pressure below the piston Zlkeeps the piston rod 28 in other than its lowermost position. Valve closing winding 44 is so wound and connected to be energized that its polarity is opposite to the polarity of the valve opening winding 43 and is such as to neutralize the holding flux thereby to release the plunger or armature 40 for the valve closing movement. In order to insure the energization of the valve closing winding 44 at the proper moment, the circuit of this winding is controlled by a limit switch 58 which is actuated to the closed position in response to the movement of the piston 21 so as to close its contacts 59 in the circuit of the winding 44 when the circuit breaker is fully closed. As shown, the circuit of the valve closing winding 44 includes the contacts 59 of the cutoiT or limit switch 58, the conductor 60, the valve closing winding 44 and the conductor 6i.

The valve closing winding 45 is provided in order to insure a fast or early opening of the con tact structure l0 when it is closed during an abnormal circuit condition. Means are provided for simultaneously tripping the circuit breaker and effecting the closing of the valve means 30. Valve closing winding 45 is independent of valve closing winding 44 and it is wound and connected to be energized so as to release the armature 40 to close the valve 30. A parallel trip circuit comprising the trip coil l5 of the operating mechanism H is also provided. The circuit for the valve opening winding 45 includes the contacts of protective relay 20 and the trip switch 2| in parallel, the conductor 23, the circuit breaker a auxiliary switch contacts 25, a conductor 52, the valve closing or neutralizing winding 45 and a conductor 53.

The control arrangement described thus far is not my invention but is disclosed and claimed in the above mentioned Coggeshall application, Serial No. 512,179.

In accordance with my invention the operating mechanism II, also shown in perspective in Fig. 2, comprises an output bell crank 10 pivotally mounted about a fixed pivot H. Crank l0 actually comprises two levers 10a and 10b spaced apart from one another but united to form a single member. At one end of crank 10 there is mounted a roller 12 which is inserted between the levers 10a and 10b. A circuit breaker operating rod 13 is suitably fastened between the members 10a and 10b at the other end of crank 10. Circuit breaker operating rod 13 is directly connected to the contact structure IU of the circuit breaker for closing the same.

Instead of transmitting the force from piston rod 28 directly to the roller 72 fastened to crank 10, I provide an independently pivoted lever 14 having one end thereof pivoted about a fixed pivot 15. Th other end of lever 14 is provided with a pair of rollers 16 and 11. As best shown in Fig. 2 the lever 14 is actually a U-shaped member with the rollers 16 and H rotatably. mounted within the open end of the U. The roller 16 transmits force from piston rod 28 to roller 12. The lever 14 is so arranged with reference to piston 28 and crank 10 as to effectively form a toggle arranged to act as a force-multiplying means. The effective toggle so formed comprises the link 14 as one link thereof while the rollers 12 and 11, which maintain the distance between the pivots about which these rollers rotate constant, form the other link of the effective toggle. Actually the pivots of rollers 12 and 11 might be interconnected by a link and the rollers 12 and 11 dispensed with, in which case an actual toggle would be provided. By providing the rollers 12 and 11 the eifectiveness of the arrangement which acts as an effective toggle is not impaired and friction is greatly reduced. With this arrangement it is obvious that as the contact structure In of the circuit breaker approaches the closed position as indicated in Fig. 1, when the greatest closing force is required, the lever I4 and the roller I2 of crank I and the roller I1 as mentioned above effectively provide a force-multiplying toggle arrangement which for a given force from plunger or piston rod 28 produces a much larger force on circuit breaker operating rod I3 at the end of the closing stroke when it is most needed. During this closing operation the roller I6 directly engages the roller 12 associated With crank I0.

When, during a closing stroke of a circuit breaker, the operating mechanism II approaches the position indicated in Fig. 1 the latching means or prop I4 biased to rotate in a clockwise direction by virtue of spring means I8 engages the roller 1! to hold the contact structure I0 of the circuit breaker in a closed position after the piston 21 returns to its normal position shown in Fig. 1. It will be observed that with the arrangement shown in Fig. l a comparatively small force is exerted on latching means or prop I4 and the bulk of the energy stored in spring I 6 in the form of back force exerted through circuit breaker operating rod 13 is counteracted by lever I4. Furthermore, by providing a separate roller IT for the latching means I4 friction is greatly reduced and a much smaller tripping force for latch I4 is required. It will be obvious from Figs. 1 and 2 that the operating mechanism II is free to collapse upon a predetermined counterclockwise movement of the latching mean or prop I4 and thereby to allow the opening of the circuit breaker providing there is no support or force against the roller I6 to hold it in the illustrated position when the prop I4 is moved out of holding engagement with roller 11.

For actuating the latching means or prop I4 in the tripping direction as illustrated, a suitable tripping solenoid including the trip coil I and a plunger 19, is provided. Whenever trip coil I 5 is energized by virtue of operation of protective relay 28 or actuation of manual trip switch 2I, plunger I9 engages with a lever 80 mounted on the shaft 8| also supporting latching means I4. A suitable stop 82 limits the clockwise rotation of lever 80 and prop I4.

In view of the detailed description given above, the operation of the operating mechanism embodying my invention will be more or less obvious to those skilled in the art. Whenever protective relay 20 is energized or the control switch 2I is actuated, trip coil I5 is energized to move latching means or prop I4 to the releasing position. By virtue of the separate roller I1 and the arrangement of lever I4 a very small force is required to release latching means I4. The circuit breaker comprising contact structure III is then opened by the bias of spring I6 and is of course free to open without opposition from the piston 21 which returned to its lower position at the end of the preceding closing operation. At the same time the trip coil I5 is energized, the valve closing winding 45 of valve 30 is also energized but since valve 30 is already closed nothing happens as a consequence of this energization.

Upon the opening of the circuit breaker the auxiliary switch contacts 25 are opened and the auxiliary switch contacts 50 are closed. When it is desired to close the circuit breaker the closing control switch 46 is moved to the closed position and if the pressure in tank 29 is sufiicient, then the valve opening winding 43 is completed and will be maintained until a short time delay circuit opening relay 53 opens its contact 52. The energization of winding 43 opens valve 30 and the released pressure gas causes the piston 21 to move upwardly to move the operating mechanism I I to the position indicated in Fig. 1 whereupon the latch I4 is caused under the bias of spring 18 to move under roller I1 and maintain the circuit breaker in the closed position. As soon as the piston 21 reaches the end of its up stroke with the breaker fully closed, the limit switch 58 closes its contacts 59 thereby energizing the valve closing or neutralizing winding 44 to cause immediate closing of valve 30 which permits the quick return of piston 21 by virtue of the operation of dump valve 32. In the event that the circuit breaker is closed upon a fault, the operation of the protective relay 20 is immediately efiective to cause the opening of the circuit breaker through energization of the valve closing winding 45. I

It will be observed that I have provided an op erating mechanism which is simple and compact and yet which provides a greatly increased force at the end of the closing stroke when increased force is desired. Furthermore, with my improved arrangement a minimum tripping force is required for releasing the operating mechanism.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made Without departing from my invention and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a switch operating mechanism, a reciprocally movable actuating means, means to be actuated comprising a lever pivoted about a fixed pivot and having a roller at one end thereof, an independent force transmitting member mounted on a fixed pivot and having a roller mounted on the free end thereof adapted to transmit force between said actuating means and said roller on said means to be actauted, said independent member and said lever roller effectively forming a toggle arranged to act as a force-multiplying means and rovide a greatly increased force near the end of the closing operation of said switch mechanism.

2. In a switch operating mechanism, a reciprocally movable actuating means, means to be actuated comprising a lever pivoted about a fixed pivot and having a roller at one end thereof, an independent force transmitting member mounted on a fixed pivot and adapted to transmit force between said actuating means and said roller on said means to be actuated, said independent member and said lever roller effectively forming a toggle arranged to act as a force-multiplying means and provide a greatly increased force near the end of the closing operation of said switch mechanism.

3. In a switch operating mechanism, a reciprocally movable actuating means, means to be actuated comprising a lever pivoted about a fixed pivot and having a roller at one end thereof, an independent force transmitting member mounted provide a greatly increased force near the end of the closing operation of said switch mechanism, and a latch engaging the other of said pair of rollers for holding said mechanism in a predeter- 5 mined position.

NELSON H. WESTERVELT.

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