US2025549A - Operating mechanism for electric circuit breakers - Google Patents

Description

Dec. 24, 1935. D C, PRlNCE 2,025,549

OPERATING lAIICIUINISM FOR ELECTRIC CIRCUIT BREAKERS Filed Aug. 2,8, 1934 2 Sheets-Sheet 1 Fig. l.

Irivexnoom` f David C. Pfihce.

D. CQ PRINCE Dec. 24, 1935.

OPERATING MECHANISM FOR ELECTRIC) CIRCUIT BREAKERS 2 Sheets-Sheet 2 Filed Aug. 28, 1934 v Inventor" David C. Prnce,

His Attohng.

Patented Dec. 24,A 1935 UNITED STATES PATENT OFFICE OPERATING MECHANISM FOR ELECTRIC 1 CIRCUIT BREAKERS h David C. Prince, Swarthmore,a Pa., assignor to General Electric Company, a corporation of New York Application August 28, 1934, Serial No. 741,789

9 Claims.

the aforesaid type diiculties may be encountered, particularly in the interruption of short 10 circuit currents, where the breaker contacts are separated an appreciable distance. As is well known, the gas pressure produced by the action of an arc in an insulating liquid, as oil, is increased as the arc is lengthened. This increase in length is accompanied by increased deterioration in the dielectric strength of the oil, and an increased formation of gas and carbon. It is accordingly desirable to limit the length of the arc and theE resulting arc pressure to an extent consistent with eicient interruption by the oil jet.

Any increase in arc length over this value will produce unnecessary arc pressure and oil deterieration. In the event of severe short circuits,

, lthis unnecessary arc pressure may reach such values as to cause damage to the breaker.

Further, a, serious problem is encountered where the actuating means for the arc-extinguishing oil jet comprises a spring biased piston or the like. If high arc pressure exists during short circuit interruption, the piston may be either retarded or even forced backwards so as to greatly decrease the eect of or eliminate the oil jet, resulting in probable failure of the breaker. After the circuit has been interrupted it is desirable, especially in case of high voltage installations, to increase the distance between the contacts after interruption of the circuit in order that the contacts may be adequately insulated by the intervening oil. 40 A principal object of my invention is the provision of improved operating mechanism for electric circuit breakers of the aforesaid type which shall be eilicient and positive in operation at all valuesvof current within the rated capacity of the breaker.

In accordance with my invention, the circuit opening operation comprises quick separation of the contacts a. predetermined distance which is consistent with limitation of pressureand interruption of arcing between the contacts, and decelerating the contactsby dashpot action or the like while an o il jet is directed across the contacts by a spring biased piston or its equivalent. y

My invention will be more fully set forth in the following description referring to the accompanying drawings, andthe 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 more particularly to the drawings,A 5

Fig. 1 is an elevational View, partly in section, of an oil circuit breaker and operating mechanism in the closed circuit position embodying my invention; Fig. 2 is a view of the breaker and mechanism in the open circuit position prior to 1i)V resetting of the actuating means, and Fig. 3 is a similardview of the breaker and mechanism in the open circuit reset position in readiness for the subsequent closing and opening cycle.

The circuit breaker illustrated comprises a casl5 ing I containing an arc-extinguishing liquid 2, as oil, in which is immersed relatively movable contact structure, as a movable tubular contact 3, and a coacting stationary contact 4. The casing I is provided with a cylindrical portion 5 20 within which a piston 6 is movable for directing oil across the contacts upon separation thereof. The piston 6 is normally biased upwardly against a stop plate 'I by a spring 8, said spring being seated at its lower end on the stop plate l and at 25- its upper end on ange 9 carried by the piston rod I0. The lower end of the piston cylinder 5 is in communication, as at Il, with the main casing so that downward movement of the piston is effective to force oil into the main part'of 30 the casing.

Ihe flow of oil across the contacts is controlled by an insulating baie or partition l2 having a central aperture I3 for receiving the movable contact. The contact 3 which is tubular in 35 form and open at its lower end is provided with ports I4 positioned above the insulating partition I2. Accordingly, when the contact 3 is moved upwardly away from contact 4 to interrupt the. circuit, oil under pressure beneath the insu- 40 lating partition may escape into the upper part of the chamber only through the contact 3 and ports I4 which results in effective interruption of arcing.

The oil level in the casing is normally above the 45 insulating partition I2 as illustrated, the piston cylinder 5 being in communication at I5 with the oil above the partition. Within the cylinder 5 the stop plate I is provided with oil ports 'I' and the piston with similar ports 6 adapted to be 50 closed when the piston is depressed by a simple disk valve I 6 slidably mounted at the lower end of. the piston rod.

l'I'he casing of the circuit breaker may be constructedof metal so as to be in direct electrical u contact with the stationary contact and one breaker terminal Il. The other breaker terminal may be suitably connected at I8 to the mov able contact which is connected to an operating rod I9 and guided for vertical reciprocal movement within an insulating bushing 20 mounted, as at 2I in the upper wall of the breaker casing.

The circuit breaker so far described is of the well known impulse type and is described and claimed in my Patent No. 1,922,862, granted August 15, 1933, for Electrical switching apparatus.

The operating means for the circuit breaker comprises a common actuating means as compression spring 22, a motor 23 for charging said spring, tripping means 24 for releasing the energy of said spring, and retarding means 25 for decelerating the movable contact.

With the mechanism in the closed circuit position shown, the spring 22 is under compression and is maintained in such position by the tripping means 2li. T he linkage structure operatively interconnecting the aforesaid elements comprises a main lever 26 pivotally supported as at 27 and connected as at 28 to the compression spring 22.

At the end of the lever 26, at 29, a oating lever' 30 is pivotally carried, one end of the floating lever having a pin or roller 3I adapted to be en- -gaged by the pivoted latch 32 of the tripping .3d which is pivotally mounted at 35. The floating over-current device.

lever 30 is likewise provided with a pin 36 operable within a slot 31 formed in an extension of the piston rod Il).

It will, therefore, be apparent that the bias of spring 22 tends to rotate the floating lever 3ll` in a counter-clockwise dir ection about the pin 3| which serves as the fulcrum, with the result that the contact rod I9 is forced downwardly to make firm contact engagement between contacts 3 and it.

- The contact retarding means 25 is connectedto the contact operating lever 34 through'a link 38 which is connected through a lost motion connection to the dashpot lever 39. The aforesaid lost motion connection comprises a pin Il at the end of the lever 39 operable in a slot ll at the lower end of link 38. The retarding means per se forms .no part of the ,present invention and may comprise ka simple dashpot or shock-absorbing device as a piston 42 having a through-bore 43 operable within a cylinder I4 containing oil or liquid of y' suitable viscosity. The actuating lever 39 which trolled in any suitable manner as bythe usual 'Y Such means, as a tripping solenoid, is indicated at 46 for coacting with the tripping latch 32. When the tripping .solenoid 46 is actuated by excess current, the plunger thereof strikes the extension 32' of the-latch and rotates the' same clockwise vagainst the bias of latch spring 41 so that the latch no longer restrains'pin 3l of the floating lever 30. This pin, therefore, no longer functions as a fulcrum, with the result that the fulcrum is instantly shifted from the pin 36 to the pin 3T. A momentary fulthis point it will be noted that the retarding device l0 I 25 comes into action opposing further rapid separation of the contacts.

At the point where the lost motion connection with the retarding device is taken up the fulcrum of the floating lever 30 may be considered 15 as having shifted to the pin 33'. 'I'hat is, the pin 33 may be considered a yielding fulcrum due to the dashpot resistance so that the spring 22 now acts through the oating lever 36 and pin 36 to f drive the piston rod Ill downwardly. 'I'he piston 20 6 accordingly drives oil across the separating contacts at a high rate and the movable contact is decelerated in moving to its final open circuit position whichis illustrated by Fig. 2.

It will be noted that although the main force 25 of the spring 22 is not applied to the piston until after initial separation of the contacts, the pin 36 functions as a fulcrum during this initial separation so that a downward force is exerted on the piston .rod I0 from the instant of tripping.

The circuit breaker and mechanism in Fig. 2 are in the open circuit position, the contacts 3 and 4 being insulated with respect to each other by the oil 2 and the piston 6 being at the lower end of its stroke. The resetting of the mecha- 35 nism, including recharging of the compression spring 22,*is effected in the following manner.

The motor 23 is energized through suitable main cam gear 58 in clockwise direction as indicated. The cam gear 56 which is suitably connected to the motor through a reduction gearing, indicated at 5I, is provided with an arcuate slot 52 concentric with respect to the cam shaft sa. A roller connected at sa to a pitman 55 is 45 positioned in the slot 52. The opposite end of the pitman 55 is pivotally connected, as at 55, to the floating lever 38. The pitman'connection '56, is so located With respect to the main lever connection 29 that elevation of the pitman tends. to rotate the floating lever clockwise about 29 asa center.

Elevation of the pitman is accomplished by energization of motor 23."It will be noted that rotation of the cam gear 50 causes the cam to 55 pick up the roller 55 at the end of the slot at 52 within nearly a half revolution. Continued rotation 'of the cam carries the pitman to the high dead-center position of the cam illustrated by Fig. 3 at which point the motor 23 is suitably deenergized as-by a limit switch for example. During rotation ofthe cam 50 in elevating the pitman, the floating lever 301s restrained at its end 33'A with respect to clockwise rotation since 65 the circuit breaker is open, the movable contact being at its upper limiting position. Accordingly, the cam force is applied directly at the endY of the main lever'29 to cause counter-clockwise rotation thereof and compression of spring v22. 70 During this operation the pin and slot connection 36-31 between the floatingl lever and piston rod ,permits the floating lever to move`independently of the piston rod. v

Referring to Fig. 3, at the end of the spring charging operation the roller 3| of the oati'ng lever is opposite and somewhat beyond the coacting end of latch 32, the mechanism being held 'in such position by the cam 50. The piston 6 is separately returned to its upper position by its spring 8, the floating lever pin 36 in this position Y being at the upper end of. the slot 31. The mechanism is now in its open circuit reset position.

,The circuit closing ope'ration is accomplishedl by releasing Dart of the stor'ed energy in spring 22. This is effected simply by energizing the motor 23 so as to move the pitman 55 beyond the dead-center position. Upon release, the spring 22 acting on the floating lever 30 at 29 causes roller 3| to engage latch 32. The floating lever 30 is` thereupon rotated in a counterclockwise direction about the roller 3| to cause downward circuit closing movement of the movable contact rod I9, thus returning the circuit breaker and mechanism to the position illustrated by Fig. 1.` It will be noted that the contacts are protected ,against excessive closing force by the dashpot action of the retarding means 25, the retarding means therefore functioning usefully during both the circuit opening and closing operations. 'I'he mechanism is, therefore, effective to limit the arc pressure within the circuit breaker and to establish an oil jet for effectively interrupting the arc at the upper limit of the breaker capacity. The mechanism is likewise trip-free in action since opening of latch 32 during the circuit closing operation would cause the breaker to assume the open circuit position illustrated by Fig. 2. f

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

WhatLI claim as new and desire to secure by Letters Patent ofthe United States is:

1. In an electric circuit breaker including separable contacts and a piston for directing an arcextinguishing liquid between said contacts upon separation thereof, operating means for effecting. separation of said contacts anda working stroke of said piston common thereto, and a retarding device for decelerating said contacts after predetermined separation thereof independently of the working stroke of said'piston.

2. In an electriccircuit breaker including separable contacts and a piston for directing an arcextinguishing liquid between said contacts upon separation thereof, an operating spring for efv fecting separation of said contacts and a work-` ing stroke of said piston, and a retarding device for decelerating said contacts after predetermined separation thereof, said spring completing the Working stroke of said piston independently of/ said retarding device.

y3. Operating mechanism for electric circuit breakers' having separable contacts and a piston forv directing an arc-extinguishing liquid between and means for directing a jet of arc-extinguishing liquid between said contacts upon separation thereof, comprising actuating means common to said liquid directing means and contacts, retarding means, and means operatively interconnecting said actuating means, contacts and retarding means so that quick separation and subsequent deceleration of said contacts are accompanied by a high velocity jet of arc-extinguishing liquid. f

5. Operating mechanism for electric circuit breakers of the type including separable contacts and a piston for directing an arc-extinguishing liquid between said contacts upon separation thereof, comprising energy storing means common to said piston and contacts, retarding means, means including a lost motion connection interconnecting one of said contacts and said retarding means, means operatively interconnecting said Aenergy storing means, piston and contact,

vand tripping means associated with said lastbreakers of the type including separable contacts and a piston for directing arc-extinguishing liqt uid between said contacts upon separation thereof, comprising a main actuating spring, retarding means connected through Aa lost motion connection to one of said contacts, means interconnecting said spring, contact and piston, and tripping means for said interconnecting means, said interconnecting means arranged so that upon acltuation of said tripping means said spring is effective to separate said contacts a predetermined distance independently of said retarding means 4o and to eect a working stroke of said piston duringxdeceleration of' said contact by said retardingmeans.

7. Operating mechanism for electric circuit breakers of the type including separable contacts and a piston for directing an arc-extinguishing liquid between said contacts upon separation thereof, comprising a main actuating spring common to said piston and the movable contact, linkagev structure operatively interconnecting said spring, movable contact and piston, said linkage structure having a lost motion connection with said piston, retarding means operatively connected through a lost motion connection to said linkage structure, and tripping means coacting with said linkage structure. maintaining said spring in charged position, actuation of said tripping means causing initial opening movement of said movable contact independently of said retarding means, said movable contact being subsequently decelerated by sa'id retarding means, said nection to'said movable "Contact, and means including a, second lost'motion connection operatively connecting saidjlfrloating lever and piston, actuation of said tripping means causing said v7spring initially to'actuate said floating lever to cause quick opening movement of said movable contact for a predetermined distance followed by deceleration thereof, said spring acting on said piston to cause an arc-extinguishing ow of liquid. o n

9. Operating mechanism for electric circuit breakers of the type including separable contacts and a. piston for directing an arc-extinguishing .liquid between said contacts upon separation fthereof, comprising a main actuating spring, a .lever operatively connected to said Ispring, a oating lever pivotally carried by said rst lever, tripping means for coacting with said oating lever, said floating lever being likewise operatively con@ nected to the movable contact and to said piston, retarding means operatively connected through a lost motion connection to said movable contact, and motor actuating means operatively connected to said oating lever for storing energy in said spring, actuation of said tripping means effecting release of said energy for actuating said 1 DAVID C. PRINCE.

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