US2286023A - Pneumatic operating mechanism for circuit breakers - Google Patents

Description

June 9,4 1942. H. E. sTRANG 2,286,023

runuurc ormwma uncxunsu Fon Blaauw BREAKERS v Filed July 11, 1940 ro oPEN c/Rcu/r /20 l BAEAKER PoslrloN 20:

g. swlrcH ITNCTYLOT: Harold E. Strang,

Patented June 9, 1942 PNEUMATIC OPERATING MECHANISM CIRCUIT BREAKERS FOR Harold E. Strang, Ardmore, Pa., assigner to General Electric Company, a corporation of New York '- Application July 11, 1940, Serial No. 344,965

(Cl. 20o-82) 6 Claims.

My invention relates to pneumatic operating mechanisms having particular application to circuit breakers, and has particular reference to mechanisms of the trip-free type where the means to be actuated, such as a circuit breaker, can be released with respect to the actuating or closing means during the course of the closing stroke and prior to completion thereof.

Heretofore, circuit breaker operating mecha nisms of the trip-free type have generally included a collapsible linkage arrangement or the like involving a more or less complicated design of toggles, levers and latches. Since the tripfree type mechanism is required to be very rapid in action due to the fact that immediate tripiree operation of the circuit breaker is essential when the circuit breaker is closed on a fault current,V mechanical arrangements have been preferred to known pneumatic types in view of the high speeds of operation that have been obtained with certain mechanical mechanisms.

A principal object of the present invention is the provision of an `improved and simplified trip-free mechanism of the pneumatic or iluid operating type that is efficient, positive and rapid in operation, rugged and compact in design and composed of comparatively few essential operating elements. I

lMy invention will be more fully set forth in the following description referring to the accomlpanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, the single figure thereof is a diagrammatic view, partly in section, of a pneumatic operating mechanism for an electric circuit breaker embodying the present invention.

The pneumatic mechanism illustrated by way of example comprises essentially a source of operating iluid pressure indicated at I, a duid motor or actuating means 2 and the means to be actuated comprising in the present instance the operating means 3 of an electric circuit breaker (not shown). preferably compressed air, although it should be understood that any suitable uid medium, preferably elastic, under pressure can be employed. The iiuid motor 2 comprises an operating piston 4 disposed for reciprocal movement in a cylinder 5 that is arranged to be in communication with the source I through a control valve 6. The piston I is provided with a plunger 1 operatively related to a lever' 8 that is ypivotally The source of fluid pressure is mounted at 9 and connected at III to the circuit breaker rod II. The piston plunger is arranged to engage a roller I2 carried by the lever 8 and to rotate the lever counterclpckwise to cause closing movement of the breaker rod II.

In the closed circuit position shown, the breaker rod is latched in position by a latch member I 3. The latch I3 is normally biased at I4 toward latching position against a limiting stop I5 to be engaged by a roller I6 carried by the breaker rod. The breaker is normally biased toward open position by the usual breaker springs (not shown) so that when the latch I3 is rotated clockwise about its pivot I3' to release the roller I6, the breaker rod II drops rapidly to its open circuit position.

Let it now be assumed that the circuit breaker is to be tripped open in response to a fault condition. The coil I1 of the fault responsive relay indicated at Il is energized in response to a fault condition to close the contacts at Il by downward movement of the relay coil plunger I9. The tripping control circuit is thereupon energized from the control source 20 through the relay contacts I 8, the latch tripping coil 2| and the contacts 22 of the so-called auxiliary aswitch. Upon energization of the trip coil 2 I the plunger 2 I is projected toward the left to cause clockwise rotation of a lever 23 and corresponding rotation of the latch I3 thereby causing release of the breaker rod II and opening of the breaker. The lever 23 is co-pivotally mounted at I3 with the latch I3 and is disengageably related thereto by an oiset portion 23 arranged to engage an extension I3" of the latch. The breaker is now open and the roller I2 of the lever 8 rests on the upper end of the plunger 'I.

'The breaker closing operation is performed in the following manner.` Assuming now that no fault condition exists, the relay I1 due to its spring bias at II closes the closing circuit contacts at 24 so that when the closing button is pressed bylthe operator to close the contacts at 25 the operating coil 26 of the valve 6 is enervgized from the control source 20 through the contacts 24 and 25, the pressure indicating aux-V iliary switch 21 and the contacts of the limit switch 2B. When the plunger 2l' of the valve solenoid is moved toward the right, it completes a holding circuit at the contacts 26" so that the closing operation can be completed notwithstanding but momentary closure of the closing button. Simultaneously the slide valve member 29, which is reciprocally operable within the valve housing I0 and is normally biased at II toward closed position, is moved to uncover the port 32 thereby establishing fluid connection between the source I and the cylinder I. Admission of iiuid under pressure to the working` face of the piston l results in upward movement of the piston and corresponding closing movement of the lever 3 and breaker rod .I I.

' This closing movement constitutes a strong high speed closing thrust that is effective to close the circuit breaker against the usual spring and contact resistance, at which time the latch I3 is snapped by its spring ilbeneath the breaker rod roller II to hold the breaker in the closed position. It will be noted that when the-piston l is lnear the upper limit of its travel, it engages the is coveredv by 4the left-hand portion of the valve member. i

In the operation so far described, it has been assumed that no fault condition existed that required trip-free operation during the closing stroke. Let it nowbe assumed that the fault condition which caused the initial tripping and open-el ing of the circuit breaker has not been corrected and that the operative attempts to close the circuit breaker while the fault condition exists. The closing operation is initiated in the manner above described. However, when the breakeinears the end of the closing stroke as the breaker contacts first engage (the a switch now being closed), the fault responsive relay I1 will cause actuation of the tripping solenoid 2| and clockwise movement of the lever 23. This lever, it will be noted, not only causes rotation of the latch Il to a nonlatching position but also engages the extension 33' of a dump valve 33 to cause immediate venting of the cylinder 5 to atmosphere through a comparatively large port 34.

It will therefore be observed that when the dump valve 33 fis open the piston I is no longer acted upon by a closing force since the operating K pressure is practically instantly dissipated even though the valve 8 still be open. In fact, the piston l can move to its initial position notwithstanding the continued flow of fluid from the source I by reason ci' the free venting at the dump valve.l With this 'arrangement'. the mechanism is completely trip-free during the closing operation and the trip-free operation is `moreover'` instantly responsive to the fault condition for permitting the circuit breaker immediately to return to its open circuit position. The dump valve 33 is spring biased at 35 toward `its normally closed position as shown. I

It should be understood that my invention'is4 not limited to specific details of construction and arrangement thereof herein illustrated. and that changes and modifications may occur te one skilled in ,the art without departingl from the spirit of my invention. Y

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

1. A fluid pressure operating mechanism of the,y trip-free type for an electricl circuit breaker comprising a source of iiuid pressure, a iluid motor including a piston and cylinder, means disengageably relating said piston to said' circuit breaker for closing said breaker, a latch for holding said circuit breaker in closed position independently of said piston so that said piston canv return to its initial open position whereby said circuit breaker-'is normally free to tripopen at high speed independently of said piston, a dump valve for venting said cylinder to atmosphere at the working face of said piston whereby said piston can also return to its initialposition during a closing operation, and fault responsive means for releasing said latch to cause opening movement of said breaker and for also opening said dump valve for causing trip-free operation.

2. A pneumatic operating mechanism of the trip-free type for an electric circuit breaker comprising a source of compressed air, an operating cylinder and piston arranged to be' connected through a control valve to said source,lmeans disengageably relating said piston to said circuit breaker including a linkage, a latch for holding said linkage in closed circuit position, a dump valve for venting at high speed the pressure in said cylinder on the working side of said piston, an'actuating member common to said latch and said dump valve, and fault responsive means operatively related to said common actuating member for causing substantially simultaneous release of said latch and opening of said .dump valve for trip-free operation.

3. Apneumatic operating mechanism of the trip-free type for an electric circuit breaker comprising a source of compressed gas, a iluid motor including a piston and cylinder, a control valve between said source and cylinder, said valve being` arranged to admit gas under pressure from said source to said cylinder and also directly to vent said cylinder to atmosphere, means operatively relating said piston to said circuit breaker for closing said breaker, a latch for holding said ciropening movement oi' said breaker and for also opening said dump valve for causing trip-free operation.

4. A pneumatic operating mechanism of the trip-free type for an electric circuit breaker comprising asource of compressed gas, an operating cylinder and piston arranged to be connected through a control valve to said source. a lever arranged to be disengageablyv engaged by said piston for closing said circuit breaker, a latch for holding said lever in closed circuit position whereby said piston can return to its initial position after closing said breaker, a dump valve for venting at high speed the pressure in said cylinder on the working side of said piston notwithstanding continued fiowp'f gas from said source, actuating means commonsaid latch and said dump valve, and fault responsive means oper-.- `atively related to said common actuating means for causing trip-free operationz'by substantially simultaneous release of said latch and opening of said dump valve.

'5. A fluid pressure operating mechanism of the trip-free type for an electric circuit breaker comprising a sourceof fluid pressure, a fiuidmotor arranged to be connected to said source, means operatively relating said motor to saidA circuit breaker for closing said breaker, a latch for holding closed said breaker, a dump valvefor instantly venting said ,uid motor to permit high speed reversal thereof, said dump valve and latch being Vmechanically interrelated, and a tripping solenoid operative both to release said latch and to open said dump valve for tripfree operation of said breaker.

ducing a closing operation of said breaker, a

source of fluid under pressure for operating said motor, a control valve forconnecting said source of fluid with said iluid motor for closing said circuit breaker, a latch for holding closed saisi-y breaker, and a dump valve directly connected to said fluid motor apart from the connection to said pressure source operable upon the opening movement of said circuit breaker for instantaneously reducing the back pressure against said uid motor so that high-speed-opening operation of said circuit breaker may be obtained. HAROLD E. STRANG.

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