US2598446A - Fluid actuated electric circuit breaker - Google Patents

Description

H. N. SCHNEIDER FLUID ACTUATED ELECTRIC CIRCUIT BREAKER Filed Dec. 30, 1948 pig. 3.

May 27, 952

/s I /a lrwverwtof: |-lar`c ci N.- Schneider,

ya V il V V Y Patented May 27, 1952 FLUD ACTUATED ELECTRIC CIRCUIT BREAKER Harold N. Schneider, Philadelphia, Pa., assignor to General Electric Company, a. corporation of New York Application December 30, 1948, Serial No. 68,318

9 Claims.

My invention relates to iluid actuated motivating mechanisms and more particularly to motivating mechanisms for supplying a force for operating electric circuit breakers and the like and Which varies during the operating cycle in a predetermined manner.

Electric circuit breakers frequently operate with a varying load throughout their working stroke, e. g., a high operating force is required during initial, intermediate, and final portions but not during certain other intervening portions of a circuit opening operation. Thus, the operating mechanism for such a circuit breaker preferably should produce an operating force which varies substantially in accordance with the load so that undue acceleration of the parts will not occur when the load is relatively light and so that adequate force is available where the load is known to be heavy.

A principal object of my invention is to provide a motivating mechanism which is capable of producing an operating force which varies over the operating cycle in a predetermined fashion.

Another object of my invention is the provision of an improved motivating mechanism which is relatively simple in construction and in operation and which is highly efficient as a source of intermittently applied power.

Still another object of my invention is to provide a circuit interrupting deviceand operating mechanism therefor having improved operating characteristics.

Further objects and advantages of my invention will become apparent as the following descripticn progresses and the features of novelty which characterize my invention Will be pointed out particularly in the claims forming a part of this specification.

My invention is an improvement on the operating mechanism disclosed and claimed in Patent 2,436,191 Timmerman, granted February 17, 1948, and assigned to the assignee of this application; and in certain respects is related to the metering pin device disclosed in Patent 2,296,071, granted to Thumim, September l5, 1942, vand assigned to the assignee of this application. In accordance with my invention, an auxiliary iiuid motor is provided to determine the operating characteristics of the mechanism during the initial portion of an operating cycle an-d a main fluid motor is used to supply the operating force during subsequent stages of an operating cycle, the main uid motor being controlled by meteringmeans responsive to the relative positions of the pistons of the main and auxiliary ,Huid motors during the operating cycle.

2 While I have illustrated my invention in conjunction with an electric circuit breaker, it will be understood that the invention is not limited thereto and that the invention is equally applicable to other types of apparatus wherein the requirements imposed on the mechanism by the load vary during the operating stroke; or Where perhaps, varying operating speeds are desired.

The circuit breaker which I have chosen as having a representative variable operating load is of the type wherein a pair of separable contacts are disposed Within a pressurized insulating casing and wherein an exhaust type blast valve is opened by the operating mechanism to reduce the pressure on one side of one of the contacts thereby to cause such contact to move automatically out of engagement with the other contact, which other contact is subsequently drawn by the operating mechanism away from its closed position a substantial distance following interruption of the arc so as to establish an adequate isolating gap between the separated contacts. `Such a circuit breaker imposes a relatively heavy load upon the operating mechanism during the first part of the operating stroke when the valve is being opened and a not-so-heavy load during a later portion of the operating stroke when the isolating action takes place. Very little operating force is necessary during certain intermediate no-load portions of the operating stroke, e. g., after the blast valve has been opened and while the interrupting action is being accomplished but before the isolating action takes place.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1 is a diagrammatic representation of a circuit breaker and its operating mechanism with the various elements shown in the positions which they occupy when the breaker is closed, Fig. 2 is a diagrammatic representation of the operating mechanism shown in Fig. l with the various parts shown in the positions which they occupy after the mechanism has completed a portion of an operating stroke while Fig. 3 is a diagramnfiaticv representation of the operating mechanism With the parts shown in the positions which they occupy upon completion of an operating stroke.

Referring now to Fig. l, I have illustrated a circuit breaker generally designated by the numeral l Which is operated by the motivating means generally designated by the numeral 2. The circuit breaker l is interrelated with the motivating means 2 through the agency of the force transmitting mechanism generally designated by the numeral 3.

3 are disposed within the pressurized enclosure. i

As will appear more fully hereinafter, upward opening movement of the interrupting contact 8 occurs to draw an arc which is extinguished before the isolating contact 'l' moves an appreciable distance downwardly and subsequent downward movement of isolating contact l establishes an adequate insulating gap between the separated contacts. Contact 8 is shown tubular or nozzle-like in form and is provided with a flange 9 which extends aroundits `outer f periphery. A compressional spring Iilis interposed between the flange 9 and flange-like portion II of terminal cap 6. Compressional spring In biases contact 8 in a downward direction tcward its closed position. If desired a flexible conductor could be secured to the contact E and the terminal cap 6 to insure good electrical contact therebetween. Interrupting contact 8 is also provided with a nozzle opening I2 which cooperates with the upper end of the isolating contact l. Contact member l is mounted upon the reciprocating insulating contact rod I3 which is guided through a suitable spider I4 secured to the wall of the insulating casing E by .suitable means such as the screws I5. ings of the spider I4 aord free iiuid flow between the upper and lower portions of the pressurized enclosure. Isolating contact 'l is biased upwardly toward the circuit closed position by means of a suitable compressional spring interposed as shown between spider I and the shoulder of contact l. One of the breaker terminals is electrically connected to the contact by means of suitable wiping contact ngers I6. The circuit through the breaker comprises the terminal cap 6, separable contacts 'l' and the wiping contact fingers IS.

For the purpose of interrelating the isolating contact 'I with a motivating means located outside of the pressurized enclosure, a shaft Il' is journally supported in the crankcase 4 and an '"f internal crank arm I3 keyed to the shaft Il is connected through a link I3 to the contact rod I3. An external operating crank arm 2! is also keyed to the shaft I'I outside the enclosure 4. end of the operating crank arm 2B. Thus, it will be seen that an upward drive of roller 2l will causeA clockwise rotation of the offset crank comprising the arms I8 and 20 and will result in downward motion of the isolating contact 1.

For interrupting the circuit by causing the rapid separation of the interrupting contact 8 from the isolating contact 1, the normal sustained uid pressure inside the cap 6 above contact S is rapidly reduced so that the pressure fluid remaining below this contact in the casing 5 will cause quick upward motion of contact 3 against the bias of its reclosing spring I0. To this end, a down-stream blast valve is used for which an opening 22 is provided in a wall of the hollow terminal cap 6. The opening 22 is normally closed by the valve disc 23 normally biased to closed position by its compressional spring 24. Thus, when the valve disc 23 is opened downwardly, fluid entrapped within the exhaust The openy and ii i A roller 2l is mounted on the outer "i:

chamber formed by the walls of terminal cap e rapidly escapes to atmosphere through the exhaust opening 22 thereby drawing the interrupting contact 8 rapidly upward due to the pressure differential set up between the upper and lower surfaces of this contact. The arc drawn between the contacts I and due to movement of Contact 8 is blasted to extinction by the rapid enveloping ow of deionizing pressure nuid from the insulating casing 5 through the'interrupting nozzle constituted by the opening I2 in contact- 8.

For the purpose of controlling the operation of valve disc 23, a valve rod 25 is provided which is suitably connected to a rocker crank 26. Crank 26 is pivotally mounted at 2l and is provided with a cam roller 28. Thus, upward motion of cam roller 23 causes downward opening movement of the disc 23 of the downstream blast valve.

yFor producing the desired pause for eiecting extinguishment of the arc between the opening of the blast valve and the subsequent downward movement of isolating contact l, a raised cam 34 and a projecting arm 35 respectively may be .united in a common rotatable member 29, the cam and arm being spaced in the relative positions shown. This rotatable member 29 includes a driven arm 30 and is pivoted about a shaft 3|. The driven arm 3S is provided with a roller 32 arranged for engagement by the motivating mechanism 2 and a tensional return spring 33 is used for biasing the rotatable member 29 in a clockwise direction so that roller 32 engages the motivating means 2 in the breakerclosed position and during the opening stroke. Thus, a force exerted toward the right on roller 32 will cause the rotatable member 29 to rotate in a counterclockwise direction about the shaft 3l. When roller 28 rides over the raised cam portion 34 the valve disc 23 will open downwardly. A relatively large force is required to accomplish this downward motion of disc 23 against the action of biasing spring 24 and the pressure within the enclosure formed by the terminal cap y6 and parts associated therewith. As the rotatable member 29 continues its counterclockwise rotation, i. e., while the interrupting contact 8 opens and the arc is being extinguished, very little force is required for such rotation until the projecting arm S5 on rotatable member 29 engages the roller 2I. At this instant a second relatively heavy load is imposed on the mechanism as it picks up the drive to cause the isolating contact 'I to begin its downward isolating travel at the termination of which the various parts will ultimately occupy the breakeropen positions shown in dotted lines in Fig. 1. In this open position, a safe isolating gap has been established by the isolating contact l; the interrupting contact B meanwhile having been spring-returned to its down position coincident with the reclosing of the blast valve disk 23. Thus, the circuit breaker described above requires a relatively large operating force at the beginning and again at a point intermediate the circuit opening operation, but not during the intervening periods between these load peaks of suchan operation. Finally, a third virtual load peak arises at the stroke end, where a high `final force is probably required to prevent objectionable rebound of the moving mass.

A,In accordance with my invention, the motivating means generally indicated by the numeral 2 Vis constructed to supply an operating force which varies over the operating stroke in a predetermined fashion, and as illustrated is adapted to supply an operating force which varies in accordance with the load requirements of the circuit breaker described above. The motivating means 2 comprises the main cylinder 33, a kickoiT or auxiliary cylinder 31, their respective main and kick- off pistons 38 and 39, piston rod 49, eompressional piston return spring 4I and thrust regulating means comprising the metering pin 42 which is secured to and movable with the main piston 38. It will be observed that the metering pin 42 is provided with reduced portions 44 and 45 and that the resulting varying section of the metering pin cooperates with the internal throat or orifice portion 46 of the sleeve portion 41 of the kick-oir piston 39, thereby providing a variable pressure uid supply orifice at 46 for the main piston 38. The end of the kickoff piston sleeve 41 abuts the working face of the main piston 38 in driving relationship when the mechanism parts are in the breaker-closed positions shown in Fig. l.

Operating pressure is supplied to the cylinder 31 through the control valve 48 and its associated conduit from a source which is not shown. Valve 4S may be controlled by any suitable means such as solenoid 49 and armature 59. Solenoid 49 may be arranged to be energized in conventional manner from a current transformer 5l associated with the circuit 52 controlled by the circuit breaker l.

When a tripping impulse is received by the solenoid 49, the valve 48 is -opened and cornpressed air is supplied to the cylinder 31. Because the piston 39 is of a relatively large diameter, a high initial operating force is immediately developed by the kick-oir piston 39, and because the sleeve 41 is in driving engagement with the main piston 38, a large thrust is transmitted to the roller 32 by piston rod 40. This force is sufficient to overcome the high initial load imposed by the pressure on the valve disc 23 and the inertia of the moving parts associated therewith. This relatively heavy driving force will continue until the short stroke kickoff piston 39 is arrested by the right hand wall of its cylinder 31. The main piston 38 continues its movement to the right but with a reduced driving force, not only because of its smaller area, but also because its supply of pressure uid (which must pass through the orice 43) is throttled in accordance with the varying diameter of the metering pin 42.

Accordingly, full throttling occurs as the main piston 38 leaves the kick-off piston 39 because the large diameter portion 53 is virtually closing the supply orice 46. This low thrust part of the stroke corresponds to the low-load period when the blast valve roller 28 is riding upon the cam 34 and before the arm 35 has encountered the isolating contact roller 2l. As the instant of this encounter approaches and so that a greater opening force is'available, the metering pin has advanced to its least throttled relation with respect to the kick-off pistons sleeve 41, i. e. with the minimum section 45 of the metering pin passing through the orifice 43 as clearly shown in Fig. 2. Having now started the isolating contact 1 moving, the force necessary to continue it in downward motion may now be decreased; correspondingly the metering pins diameter is increased at 53al for producing an other throttled stroke portion, which is all that is necessary here for producing adequate force even though this downward movement now is compressing the isolating contacts return spring.

Finally, at the completion of the opening stroke, when the isolating contacts return spring is being fully compressed and when rebound of the moving parts is undesirable, the oriiice 46 is again unthrottled by the second reduced section 44 of the metering pin 42 as is best shown in Fig. 3. At this point the control valve 48 is caused to reclose, thus terminating the opening cycle.

It will be understood that, during the downward isolating movement of the slower moving contact 1 of the pair, the interrupting nozzle contact 8 returned automatically back to its own position by virtue of the reclosing of the blast valve 23 coincident with the roller 28 termin nating its dwell up on the cam surface 34.

For the purpose of holding the contact 1 in its downward or isolating position against the upward urge of its closing spring, a suitable hold-open latch 54 is provided. Latch 54 is pivotally mounted at 55 and is biased in the counterclockwise direction about pivot 55 by its cornpressional return spring 56 against the stop 51. Thus, when rotatable member 29 and parts associated therewith are moved to the breakeropen position shown by the dotted lines of Fig. 1, the roller 32 has brushed aside the latch 54 which instantly returns under the roller 32 as shown so that rotatable member 29 and contact 1 are securely held in the breaker-open position.

The mechanism may be released to effect a breaker-closing stroke by manually rotating the latch 54 in a clockwise direction by means of the handle 58. This closing operation merely requires that the isolating contact 1 move upward under the force of its closing spring to meet the interrupting contact 8, which is now in its down position as already explained, whereby to reestablish current ow through the line 52.

Thus, by my invention, it is possible to obtain, within limits, any desired force Variation throughout the operating stroke by simply providing diierent cross-sectional areas along the length of the metering pin 42 so as to vary the amount of uid available to the working face of the main piston 38. From the above detailed explanation it will be clear that the metering pin is generally designed so that its longitudinal contour anticipates the loading conditions to be encountered along the mechanism stroke; i. e. Where heavy loading occurs, the pin da. is decreased and conversely, for light load portions of the stroke, the dia. of the pin is increased to produce appropriate throttling of the pressure fluid supply orifice. Furthermore, it will be ohvious that the initial piston 39 could be made of a smaller diameter than the piston 3S in order to provide for a low initial force if desired.

It will be apparent to those skilled in the art that my invention is not limited to the particular construction shown but that changes and modincations may be made without departing from the spirit and scope oi the invention and I intend in the appended claims to cover all such changes and modifications.

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

l. A fluid actuated mechanism for supplying operating force to a load which varies in a predetermined fashion during an operating cycle comprising, a main motivating means, an auxiliary motivating means, means including a source of iiuid under pressure and a valve ior supplying pressure fluid to said auxiliary motivating means during the initial portion of an loperating cycle of said mechanism to impart a predetermined operating force to the load, and regulating means including an orifice in said auxiliary motivating means and a metering pin movable relative to said orifice in response to relative movement between sai-:l main and said auxiliary motivating means for controlling the llow of uid to said main motivating means from said source of fluid under pressure in accordance with the relative positions of said main and said auxiliary motivating vmeans during subsequent portions of an operating cyclel 2. A fluid actuated mechanism for supplying operating force to a load which varies in a predetermined fashion `during an operating cycle comprising, a main motivating means, an auxiliary motivating means, means including a source of fluid runder pressure and a valve for supplying pressure fluid to said auxiliary motivating means during he initial portion of an operating cycle of said mechanism to impart a predetermined operating force to the load, and regulating means including an orifice in said auxiliary motivating means and a metering pin movable relative to said orilice in response to relative movement between saidmain and said auxiliary motivatinD- means, said metering pin having a cross-sectional which varies along its length, said orice and said metering pin being operable to control the amount of pressure fluid supplied to said main motivating means from said source of lluid under pressure in accordance with the relative positions of said main and said auxiliary motivating means during subsequent portions of an operating cycle.

3. A fluid actuated mechanism for supplying operating force to a load which varies in magnitude in a predetermined fashion during an operating cycle comprising, a main piston, an auxiliary piston, a cylinder for each of said pistons, means including a source of fluid under pressure and a valve for supplying pressure fluid to said auxiliary piston to impart a predetermined operating force to the load during the initial portion of an operating cycle of said mechanism, and regulating means for the remainder of the operating cycle comprising a throat in said auxiliary piston and a cooperating metering pin movable with said main piston controlling the amount of pressure huid supplied to said main piston from said source of fluid under pressure.

li. A iiuid actuated mechanism for supplying operating force which varies in magnitude in a predetermined fashion during an operating stroke comprising, a main piston, an auxiliary piston movable with respect to said main piston, a cylinder for each of pistons, said cylinders being coaxially disposed, means including a source of fluid under pressure and a valve for supplying pressure fluid to said auxiliary piston during the initial portion of an operating stroke of said mechanism to impart a predetermined operating force to said main piston, and regulating means comprising a throat in said auxiliary piston and a cooperating metering pin secured to said main piston and movable through said throat for controlling the amount of pressure fluid supplied to said main piston from said source of iluid under pressure in accordance with the relative positions of said main and said auxiliary pistons during subsequent portions of an operating stroke.

5. A fluid. actuated mechanism for supplying operating force which varies in magnitude vin a predetermined fashion during an operating stroke comprising, a main piston, an auxiliary piston movable with respect to said main piston, a cylinder for each of said pistons, said cylinders being coaxially disposed, means including a source of fluid under pressure and a Valve for supplying pressure fluid to said auxiliary piston to impart a predetermined operating force to said main piston during the initial portion of an operating stroke of said mechanism, and regulating means operable during the remainder of the operative stroke comprising a throat in said auxiliary piston and a cooperating metering pin secured to said main piston and movable through said throat for controlling the amount of pressure lluid supplied to said main piston from said source of fluid under pressure, said metering pin having a crosssectional area which varies in a predetermined fashion along its length.

6. A circuit interrupting device comprising a pressurized casing, an interrupting contact and an isolating contact disposed in said casing and respectively movable to draw an arc to be interrupted and to establish an isolating gap between said contacts, valve means in said casing, means responsive to opening of said valve means for moving said interrupting contact out of engagement with said isolating contact, auxiliary motivating means for opening said valve means to cause opening of said interrupting contact, main motivating means for operating said isolating contact after operation of said interrupting contact, and means for regulating the operating force developed by said main motivating means in accordance with the relative positions of said main and said auxiliary motivating means.

'7. A circuit interrupting device comprising casing containing fluid under pressure, normally closed valve means in a wall of said casing, a pair of relatively movable contacts within said casing, means responsive to an opening of said valve means for moving one of said contacts o-ut of engagementwith the other of said contacts and for establishing a blast of fluid for interrupting the arc drawn between said contacts, auxiliary motivating means for opening said valve means, main motivating means for moving said other contact to establish an isolating gap between said contacts, and means for regulating the operating force developed by said main motivating means in accordance with the relative positions of said main and said auxiliary motivating means.

8. A circuit interrupting device comprising a casing containing fluid under pressure, normally closed Valve means in a wall of said casing, a pair of relatively movable contacts within Said casing, means responsive'to an opening of said valve means for moving one of said contacts out of engagement With the other of said contacts and for establishing a blast or fluid for interrupting the arc drawn between said contacts, an auxiliary lluid motor for opening said valve means, a main uid motor for moving said other Contact to establish an isolating gap between said contacts, and regulating means for controlling the operation of said main motivating means in accordance with the relative positions of said main and said auxiliary motors.

9. A circuit interrupting device comprising a casing containing fluid under pressure, normally closed valve means in a wall of said casing, a pair of relatively movable contacts within said casing, means responsive to an opening of said valve means for moving one of said contacts out of engagement with the other of said contacts and for establishing a. blast of fluid for interrupting the arc drawn between said contacts, an auxiliary piston for operating said valve means, a main piston for moving said other contact to establish an isolating gap between said contacts, an ori'ce in said auxiliary piston, and a metering pin movable with said main piston and cooperating with said orice to regulate the operation of said main piston.

HAROLD N. SCHNEIDER.

REFERENCES CITED The following references are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Logan Oct. 30, 1906 Whitsell Sept. 13, 1932 Dewey Sept. 29, 1936 Biermanns June 22, 1937 Gruber Feb. 28, 1939 Trencham Apr. 4, 1939 Prince Apr. 15, 1941 Thumim Sept. 15, 1942 Gollmer Sept. 7, 1943 Bassett et a1 Feb. 11, 1947 Cousino Nov. 16, 1948

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