US2673271A - Electric circuit-breaker of the gas-blast type - Google Patents

Description

March 23, 1954 D. F. AMER ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Filed April 1, 1949 2 Sheets-Sheet l -5 mmnmum E3 E -5 H H y r 2 C c c c E c1 2 41 3 I J2 J p A3 J C2 0. C J2 1 J3 C, 2 J J3 D 1 A2 0 5: 1 I N 2 F3 5 F2 F a [44 l 3'6 L i: s

s L M :.;--S Inventor T A ttbrne y March 23, 1954 AMER 2,673,271

ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Filed April 1, 1949 2 Sheets-Sheet 2 rvB Q 9 Inventor A tiorney Patented Mar. 23, 1954 ELECTRIC CIRCUIT-BREAKER OF THE GAS-BLAST TYPE Donald Foster Amer, Newcastle-on-Tyne, England, assignor to A. Reyrolle &.Company Limited, Hebburn-on-Tyne, England, a company of Great Britain Application April 1, 1949, Serial No. 84,904

Claims priority, application Great Britain April 23, 1948 24 Claims. (01. 200-148) This invention relates to electric circuitbreakers of the gas-blast type in which the contacts separate within an arcing enclosure maintain'ed'filled with gas under a superatmospheric initial or filling pressure, a blast of deionising gas flowing from the enclosure to assist in extin'guishing the arc when the circuit-breaker is opened.

If, as in some arrangements, the blast of deionisin'ggas is produced by opening an exhaust valve so'that gas from the enclosure flows through a nozzle or vent adjacent to the separating contacts, the initial or filling pressure within the enclosure necessarily commences to'fall'from the initial valuefas soon as the exhaust valve opens. In order, therefore, to were the requisite blast during the separation of the contacts, a high initial pressure is desirable and the enclosure has to be mechanically designed to maintain and withstand such pressure. In conflict with this requirement is the fact that the higher the initial or filling gas pressure the greater the risk of moisture condensation within the circuit-breaker.

The invention has for its object to overcome these and other difficulties. I

In a circuit-breaker according to the invention, means are provided whereby the initial or filling gas pressure within the enclosure is supplemented during opening of the circuit-breaker. 7

Theinitial gas pressure may be supplemented by supplying to the enclosurev gas under a pressure exceeding the initial or filling pressure, or by applying pressure to the gas within the enclosure. 7 a

Preferably, the initial or filling gas pressure does not appreciably exceed that necessary for the optimum restriking gap between the open contacts to withstand full voltage, the said initial pressure being supplemented during opening of the circuit-breaker to provide the requisite gas blast. V In this way, under normal operating conditions, the contact enclosure only has to withstand and maintain the comparatively low filling pressure whilst, at the same time, adequate gas pressure is available to provide the requisite gas blast without any fall in pressure at the commencement of the contact separation. Moreover, since the gas pressure within the enclosure does not fall below the initial or filling value, the gap between the open contacts can be reduced to a value corresponding to that necessary for effective arc extinction. V M

The invention may becarried into practice in various ways but four con'structions, each embod'yi'ng the invention, are shown diagrammati- 2 cally, and by way of example, in Figures 1 to 4 respectively of the accompanying drawings, the apparatus being shown in longitudinal section in each figure. I

In the embodiment shown in Figural, the circuit-breaker comprises a hollow, and externally shedded, post insulator A mounted vertically on, and in open communication with, a metallic base B having incorporated 1 therein or I connected thereto a gas supply reservoir B in which a high gas pressure, say 250 pounds per square inch, is maintained. The reservoir B communicates with the interior of the post insulator A through a reducing valve B by which the gas is expanded and supplied at a pressure lower than that within the reservoir B For example this lower gas pressure, hereinafter referredto as the initial or filling pressure, may be of the order of '75 pounds per square inch. The-reservoir B communicates with the interior of the base B through a blast valve B controlled by an opening solenoid S whilst a relief valve B in the base B is controlled by a closing solenoid S the two solenoids S 8 constituting parts of a control circuit S for opening and closing the circuit-breaker.

Mounted on top of the post insulator A is a cup-like or upwardly flaring metallic member A constituting the lowerportion of a contact en'- closure C which is completed by a cylindrical and externally shedded intermediate insulator A disposed on the said lower portion A and carrying an upper metallic portion or head A The lower metallic portion A? of the enclosure C is provided with an internal spider A which supports, in axial alignment with the hollow post insulator A, a rod-like fixed contact C which thus extends axially within the enclosure C. The upper wall or head A of the enclosure C has a downwardly extending metallic skirt D furnished at its lower end with a tubular shroud D of insulating material, the skirt D andshroud D thus extending downwards in the annular space between the cylindrical wall of the enclosure C and the fixed contact therein C Formed in the metallic skirt D adjacent to the upper or free end of the fixed contact C is an opening D through which extends a moving contact C operated by a piston C movable in a cylinder C extending laterally from the metallic head A of the enclosure C, the moving contact C cooperating with a brush contact C electrically connected to and lying within the said head A The contact piston C isprovided with a bleed passage C which establishes open communication between the enclosure C on one side of the piston C and the cylinder C on the opposite side thereof, for the purpose described below.

Formed in the upper wall of the metallic head A so as to be substantially coaxial with the fixed contact C, is a nozzle E flaring upwards into a cooling chamber E whose upper or outlet end has an exhaust port E controlled by an exhaust valve E mounted on a resilient diaphragm E (e. g. of rubber or springy metal) constituting part of the lower wall of an auxiliary chamber E in open comunication, through a bleed pipe E with the interior of the contact enclosure C.

With the circuit-breaker in the closed condition, as shown in Figure 1, the moving contact C extends through the opening D in the metallic skirt D into engagement with the upper end of the fixed contact C the circuit being thus completed from the lower metallic portion A of the enclosure constituting one pole X of the circuit-breaker, and through the fixed and movable contacts C C to the upper portion or head A constituting the second pole Y.

Both the blast valve B and the relief valve B in the metallic base B are now in their closed positions, but the interior of the enclosure C is maintained filled with gas at an initial or filling pressure of, say, '75 pounds per square inch, from the reservoir B through the reducing valve 13 The pressure being equalised, through the bleed passage C in the contact piston C on both sides thereof, the contacts 0 remain in the closed position. Further the gas pressure is insufficient to open the exhaust valve E and, apart from the gas being comparatively dry due to expansion by traversing the reducing valve 3, is sufficiently low to be readily maintained and withstood by the enclosure.

If it is desired to open the circuit-breaker, the opening solenoid S is energised thus opening the blast valve B so that the reservoir B is brought into open communication with the interior of the enclosure C. The excess pressure on the inner face of the contact piston C thus causes the moving contact C to be retracted from the fixed contact C thereby drawing an arc transversely within the metallic skirt D. The increased pressure within the enclosure C is transmitted through the bleed pipe E to the auxiliary chamber E so that the diaphragm E is flexed and the exhaust valve E opened. A blast of deionising gas, at the supplemented pressure, is thus caused to flow through the nozzle E so that the end of the arc rooted on the moving contact C is transferred first to the adjacent wall of the metallic skirt D and. then to, and through, the nozzle E whereby the are is extinguished. After a predetermined interval, the opening solenoid S is deenergised so that the blast valve B is closed and the pressure within the enclosure C returns to the initial or filling pressure, the exhaust valve E at the same time returning to the closed position due to the fall in pressure. The pressure being again equalised on opposite sides of the contact piston C the movable contact C remains in its open position.

The initial or filling pressure now obtaining in the enclosure 0, whilst inadequate to provide the requisite gas blast during opening of the circuitbreaker, is suflicient to withstand full voltage between the open contacts (3 C across a gap which does not exceed the optimum for efiective extinction by the gas blast produced by the increased pressure during opening of the circuitbreaker. In this respect it will be apparent that the filling gas pressure at the gap is maintained or increased except during the closing operation, now to be described.

In order to close the circuit-breaker, the closing solenoid S is energised so as to open the relief valve 13* in the base B. The sudden pressure drop on the contact side of the contactpiston C allows the initial-filling-pressure gas at the back of the piston C to cause it to move inwards thereby moving the movable contact C back through the opening D in the metallic skirt D and into engagement with the fixed contact C The relief valve B is then reclosed so that the pressure within the enclosure C is restored to the initial or filling value.

It will be understood that the invention may be applied either to single-break or to multi-break circuit-breakers. Moreover, instead of the contacts being movable laterally with respect to the nozzle as described above, the movement of the contacts may be axial with respect to the nozzle or vent. One such construction is shown in Figure 2, in which the upper end of the hollow post insulator A carries a short intermediate cylindrical metallic member F having an internal spider F which supports a pneumatic cylinder F containing a vented piston F at the lower end of a rod-like movable contact F The contact enclosure G is completed by a plurality of short coaxial insulating tubes G mounted in axial alignment with, and on top of, the cylindrical metallic member F, each insulating tube G being constituted by two annular rings of insulating material arranged one within the other and radially spaced apart. The annular spaces C1 between the insulating rings G are in open communication with each other and, through a passage G3 in the wall of the intermediate cylindrical member F, with the pneumatic cylinder F on that side of the piston remote from the contact enclosure G.

Thus, for purposes of additional insulation, the supplementary annular space G in the insulating wall of the built-up contact enclosure G remains in open communication with the dry-gas space represented by the contact enclosure G and pneumatic cylinder F the gas trapped in this supplementary space also assisting the closing movement of the piston F when the pressure within the contact enclosure G is relieved or released to reclose the circuit-breaker as described below. The uppermost tube G is closed by a dome or head plate H having a central internal pin or rod H constituting the fixed contact in axial alignment with the movable con tact rod F The short insulating tubes G are axially spaced apart by a number of metallic rings J each of which has an exhaust pipe J extending radially from within the enclosure G and through the outer wall thereof. The exhaust pipes J are provided with transverse passages or vents J lying in alignment with the fixed and movable contacts H, F the outer end of each exhaust pipe J being closed by a spring-loaded exhaust valve J With the circuit-breaker in its closed condition, the interior of the enclosure G is filled with gas at the initial or filling pressure, this filling being maintained from the reservoir B through the reducing valve 13 as described above. The movable contact rod F is now in its uppermost position as shown in Figure 2, that is to say,

so that it extends through all the vents J in the aws em exhaust pipes J and into engagement with the fixed' contact H, the circuit being-established from the cylin'drical metallic member F, constituting one'pole X of the'circuit-breaker, and through the movable and fixed contacts-F H to the dome or-head H constituing the second'pole Y.

When-the'circuit-breaker is to Ice-opened, the blastvalve B isopened'by energising the opening solenoid S so that the initial-or filling pressure withinthe enclosure G is supplemented and the contact position F is moved downwards into its "cylinder F As the movable contact F is withdrawn from thevents J in the lateral exhaust'pipes J the exhaust valves J are automatically opened by the gas pressure and a blast of tdeionising gas is caused to flow through each vent J After a predetermined interval, the blast valve B3 is closed and the pressure within the-enclosure G reverts to the initial or filling valve whereupon the-exhaust valves -J -close due to the pressure drop.

For closing the circuit-breaker, the relief valve B 1in the base B of the circuit-breaker is opened so as to release the pressure within the enclosure G, the'excess pressure on the lower face of the vented contact piston F then moving the piston and movable contact F upwards into theclosed position. Having reclosed' the relief valve 13 the pressure within the enclosure G automatically returns to the initial or filling value.

For very high voltages it may prove practicable to provide only a closed reception space or expansion chamber for the exhaust gases, the pressure in the said reception space being relieved through a single valve ata predetermined intervalafter the circuit-breaker has been opened. In the arrangement shown in Figure 3, which may either be provided with an automatically operated exhaust valve as in the construction first described aboveor with a valve forevacuating the gases from a receptionspace, the axially movable contact rod F carries a piston F movable within a cylinder F under the gas pressure within the enclosure G The contact enclosure G comprises two coaxial insulating cylinders G 6? disposed one within the other and radially spaced apart, with the annular space G between them in open communication with the pneumatic cylinder F as in the second arrangement described above. In the closed condition of the circuit-breaker the movable contact rod F extends through or across a plurality of vents or nozzles K constituting the mouths of expansion chambers K K K disposed within the enclosure G When the circuit-breaker is opened by supplementing the gas pressure within the enclosure G the movable contact F is withdrawn from, so as to open, the vents or nozzles K and blasts of gas flow therethrough to assist in extinguishing the arc.

In the construction shown in Figure 4-, the re ception or expansion chamber and the enclosure together constitute a self-contained and enclosed gas circuit. The movable contact L moves relatively to the fixed contact rod M in a direction transverse to the axis of the associated nozzle N, as in the construction first described above, the cylinder L of the contact piston L on that side thereof remote from the enclosure, being in open communication through a bleed passage L with a reception chamber N on the low pressure side of the nozzle N. The contact enclosure 0 on the high pressure side of the nozzle N is in open communication with a reservoir P formed in the base of the circuit-breaker, and pressure control pistons Q are movable in a cylinder Q whose upper and lower ends are respectivelyin open communicationswith the reception chamber N on the low pressure side of the nozzle N and the contact enclosure 0 on thehigh-pressure'side of the nozzle N. The rod-Q of the pressure-control pistons Q carries'at its lower end an actuating piston P movable in a cylinder P disposed within thereservoir P and having 'anassociated closing valve P and. opening valve P When the circuit-breaker is in the closed condition, the pressure-control pistons Q are in their uppermost positions and the gas pressure, throughoutthe gas circuit, including the reservoir P, contact enclosure 0 and reception chamber N1, is at the initial or filling value, 1. e.the pressure within the reservoir P. To-open thecircuitbreaker, the opening valve P is operated'so that the pressure-control pistons Q move downwards and thus apply pressure to the gas in the enclosure 0 whilst at the same time reducing the pressure in the reception chamber N The increased pressure in the contact enclosureoassisted bythe reduced pressure in the reception chamber N moves the contact piston L and therefore the moving contact L, outwards away from the fixed contact M. The increased gas pressure on the high pressure side of the nozzle N accompaniedby the simultaneous reduction in pressure on the low pressure side of the nozzle provides the necessary gas blast through the nozzle N for extinguishing the arc.

For closing the circuit-breaker, the closing valveP is operated so that the pressure-control pistons Q move upwards, thereby decreasing the pressure within the enclosure 0 so that the movable contaot piston L assisted now by the increased pressure in'the reception chamber N moves into engagement with the fixed contact rod M. The pressure then equalises throughout the system at the initial or filling value.

B suitably proportioning the gas spaces on the high and low pressure sides of the nozzle N respectively, a normally maintained initial or filling gas pressure of, say, four atmospheres can be converted, by operation of the pressure control piston Q, to a pressure of eight atmospheres on the high pressure side of the nozzle N and a pressure of one atmosphere on the low pressure side, thereby producing an adequate gas blast through the nozzle N during opening of the circuit-breaker.

When the exhaust valve is live, as in known superatmospheric-filled open-type circuit-breakers, the valve has to be operated by some form of non-conducting mechanical coupling or independent pneumatic means. The invention, however, permits operation of the exhaust valve Without such independent operating means. Further, since the gap between the open contacts lies in an atmosphere of gas at a pressure not less than the superatmosph'eric filling pressure throughout the opening movement and while the circuit-breaker remains open, the said gap can be reduced to a value which, while short enough to satisfy requirements of arc extinction, is yet sufiiciently long to meet requirements of isolation without the provision of additional seriesbreak isolating means, since, for usual gap "configuration, the curve of dielectric break-down strength plotted against air-pressure rises steep- 1y at its origin. In the latter respect, the initial or filling gas pressure maintained in the contact enclosure while the contacts are open need not exceed that necessary to ensure that a normal gap will withstand full voltage. For example.

the initial pressure may be about one third of that to which the gas pressure is raised during arc quenching.

What I claim as my invention and desire to secure by Letters Patent is:

1. A gas-blast electric circuit-breaker comprising an arcing enclosure, a restricted nozzle leading from such enclosure, two relatively movable cooperating contacts adjacent to the nozzle within the enclosure, means whereby the enclosure is maintained filled with gas under a superatmospheric initial or filling pressure, means whereby ablast of deionising gas is caused to flow from the enclosure past the contacts and through the nozzle in timed relation with the separating movement thereof so as to assist in extinguishing the are drawn between the separating contacts, and means whereby the pressure within the enclosure is reinforced during the flow of the said blast thereby preventing reduction of the pressure within the enclosure below the said initial or filling value.

2. A gas-blast electric circuit-breaker comprising an arcing enclosure, a restricted nozzle leading from such enclosure, means whereby the enclosure is maintained filled with gas at a superatmospheric initial. or filling pressure, two coopcrating contacts adjacent to the nozzle within the enclosure, at least one of said contacts being movable, a cylinder, a piston within the cylinder and operatively connected to the movable contact, said piston being exposed to the gas pressure within the enclosure, and means whereby the gas pressure within the enclosure is supplemented so as to move said piston and separate the contacts whilst at the same time causing a blast of deionising gas to flow from theenclosure past the separating contacts and through the nozzle to assist in extinguishing the are drawn between them, the said supplementation of the pressure preventing reduction of the pressure within the enclosure below the initial or filling value during the flow of the said blast.

3. A gas-blast electric circuit-breaker comprising an arcing enclosure having a restricted discharge nozzle or vent, two cooperating contacts within the enclosure on the high pressure side of the vent, at least one of said contacts being movable, an exhaust valve opening to atmosphere on the low pressure side of the vent, means whereby the enclosure is maintained filled with gas at a superatmospheric initial or filling pressure, means whereby the exhaust valve is opened to cause a blast of deionising gas to fiow from the enclosure and past the contacts through the nozzle, and means whereby the gas pressure within the enclosure is reinforced during the flow of the blast thereby preventing reduction of the pressure within the enclosure to a value less than the initial or filling pressure.

4. A gas-blast electric circuit-breaker comprising an arcing enclosure, an exhaust valve controlling the discharge of gas from the enclosure, two relatively movable cooperating contacts within the enclosure, means whereby the exhaust valve and the contacts are opened in timed relation, means whereby gas under pressure is supplied to the enclosure so as to maintain the enclosure filled with gas under a superatmospheric initial or filling pressure while the exhaust valve is in the closed position, and means whereby the supply of gas under pressure to the enclosure is supplemented when the exhaust valve is opened, so that, though opening of the exhaust valve causes a blast of deionising gas to flow from the enclosure and past the separating contacts to assist in extinguishing the are drawn between them, reduction of the gas pressure within the enclosure below the initial or filling value is prevented by the supplementary gas supply.

5. A gas-blast electric circuit-breaker comprising an arcing enclosure, an exhaust valve controlling the discharge of gas from the enclosure, two relatively movable cooperating contacts within the enclosure, means whereby gas under pressure is supplied to the enclosure so as to maintain the enclosure filled with gas under a superatmospheric initial or filling pressure while the exhaust valve is in the closed position, means whereby the exhaust valve and the contacts are opened in timed relation by a gas pressure within the enclosure above the said initial or filling value, and means whereby the supply of gas to the en-- closure is supplemented to open the exhaust valve and the contacts so that, though opening of the exhaust valve causes a blast of deionising gas to fiow from the enclosure and past the separating contacts so as to assist in extinguishing the are drawn between them, reduction of the gas pressure within the enclosure below the initial or filling value is prevented by the supplementary gas supply.

6. A gas-blast electric circuit-breaker comprising an arcing enclosure, an exhaust valve controlling the discharge of gas from the enclosure, two relatively movable cooperating contacts within the enclosure, means whereby gas under pressure is supplied to the enclosure so as to maintain the enclosure filled with gas under a superatmospheric initial or filling pressure while the exhaust valve is in the closed position, means whereby the exhaust valve and the contacts are opened in timed relation by a gas pressure within enclosure above the said initial or filling value, means whereby the supply of gas to the enclosure is supplemented to open the contacts and exhaust valve, so that though opening of the exhaust valve causes a blast of deionising gas to fiow from the enclosure and past the separating contacts so as to assist in extinguishing the are drawn between them, reduction of the gas pressure within the enclosure below the initial or filling value is prevented by the supplementary gas supply, and a relief valve which, when opened, releases the pressure within the enclosure thus closing the exhaust valve and the contacts.

'7. A gas-blast electric circuit-breaker compris ing an arcing enclosure having a restricted discharge nozzle or vent, an exhaust valve on the low pressure side of the vent and controlling the discharge of gas from the enclosure through the vent, a valve-control chamber the pressure in which operates the exhaust valve, a bleed conduit interconnecting said chamber and the enclosure on the high pressure side of the vent, two cooperating contacts within the enclosure, at least one of said contacts being movable, a cylinder in open communication with the enclosure, a vented piston movable within the cylinder and operatively connected to the movable contact, means whereby gas under pressure is supplied to the enclosure so as to maintain the enclosure filled with gas under a superatmospheric initial or filling pressure while the exhaust valve is in the closed position, the gas pressure within the enclosure necessary to operate the exhaust valve and piston exceeding the said when the circuit-breaker is to be opened, the

aevaan supply of gas under pressureto the enclosure-is supplemented to raise the pressure therein to' a value exceeding the initial or filling pressure thereby opening the exhaust valve and operatingthepiston toseparate the contacts, so that though opening of the exhaust valve causes a blastof deionising gas to flow from the enclosure past the separating contacts andthrough the vent so as to assist in extinguishing-thearc drawnbetween the contacts, reduction of the gas pressure within the enclosure below the initial or fill ing valueis prevented by thesupplementarygas supply:

8; Agas-blast electric circuit-breaker comprising an arcing enclosure having a restricted di"- charge nozzle or vent, an exhaust valve on-the low pressure side of the vent and controlling the discharge of gas from the enclosure through-the vent, a valve-control'chamberthepressure-in' which operates the exhaustvalve, a bleed condui-t-interconnecting' said chamber and-the enclosure on the high pressure side of the vent; two

cooperating contacts within the enclosure, at least one of said'contacts-being movable a cylinder in open communication with the enclosure, a piston movable within the cylinder and operatively connected to the movable contact, means whereby gas under pressure is supplied to the enclosure so as to maintain the enclosure filled with gas'undera superatmospheric initial or filling pressure while the exhaust valve is in the closed position, thegas pressure within the en'- closure; necessaryto operate the exhaust valve and piston exceeding the initial or filling pressure, means whereby, when thecircuit-breaker is.

to-be opened, theisupplyyof gas under pressure within the enclosureis supplemented to raise the pressure therein to a value exceeding the initial.

or filling pressure thereby opening, the exhaust valve andoperating the piston. to separate the contacts, so that though openingof the exhaust valve causes a blast of deionising gas to flow from.

the enclosure past the separating contacts and through the vent. so as to assist in extinguishing the are drawn between the contacts,'reducti'on of the gas pressure within the enclosure below the initial or fillingvalueis prevented by the supplementary gas supply, and a relief valve which, when opened, releases the pressure within the enclosure thus causing the exhaust valve and movable contact to reclose.

9.3 A gas-blast electric circuit-breaker comprising an arcing enclosure, an exhaust valve controllingthe dischargeof gas from the enclosure, two; relatively movable cooperating contacts within the enclosure, means whereby the exhaust valve and contacts are opened in timed relation, a reservoir containing gasvunder superatmospheric pressure, a primary gas supplycon-v duit connecting the reservoir to the enclosure, a,

reducingvalve determining, the supply of gas through the primary conduit to the enclosure which is thus maintained filled with gas at a superatmospheric initial or filling, pressure, as determined bythe reducing valve, while the exhaust valve ,is, in the closed position, a supple mentary gas suppl conduit connecting the reservoir to the enclosure, anda blast valve control lingsa-id supplementary conduit, the blast valve being opened when the exhaust valve is opened so that, though opening of the exhaust valve causes a blast of deionising gas to fiow'from the enclosure and past the separating contacts to assist in extinguishing the arc -drawn'between them, reduction of the gas pressure within the 10.3 enclosure below the initial or filling value is preventedby the supplementary gas supply.

10. A gas-blast electric circuit-breaker as claimed in claims, in which the exhaust valve and the contacts are opened by a gas pressure prising'an arcing' enclosure having a restricted:

discharge nozzle or: vent; an exhaust valveon the lowpressure side ofthe vent and controlling.

the discharge of gas from the enclosure through the-vent, a valve-control chamber the pressure in which operates the exhaust valve a bleed conduit interconnecting said chamber and theenclosure on the high pressure side of the vent;

two cooperating contacts within the enclosure,

at least one of said contacts being movable, a

cylinder in open communication with-the enclosure on the high pressure side of the vent, .a:

vented piston movablewithin said cylinder and operatively connected to 1 the movable contact, a reservoir containing gas under superatmospheric pressure, a primary gas supply conduitconnecting the reservoir to the enclosure, a reducing valve determining the supply of gas through the primary conduit to the enclosure which is thus maintained filled with gas atasuperatmospheric initial or fillingpressure, as

determined by=the-reducing valve, while the ex haust valve is in the closed position, a supplementary gas supply conduit connecting the reservoir to the enclosure, a blast valve controlling the supply of gas-through the supplementary conduit, and a relief valve which, when opened; relieves the pressure within the enclosure and thus "causes the exhaustvalve and contacts to reclose, so'that when the circuit-breaker is to be opened, the blast valve is openedwhereby'the exhaust valve and the movable contact are moved into their open positions and, though a blast of deionising gas is thus caused to fiow from the enclosure and past the separating contacts to the vent, thus assisting in extinguishing the arc drawn between the contacts, reduction of'the' pressure within the enclosure to a value below the initial or filling pressure is prevented by the supplementary gas supply,and when the circuitbreaker is to be closed, the'relief valve is opened" so that the exhaust valve and the movable contact are'restored-to their closed'positions;

13. A gas-blast electric circuit-breakercomprising an arcing enclosure having at least one discharge nozzle or vent, a gas-expansion cham ber communicating with said vent, two cooperating contacts within the enclosure, at least one of said contacts being movable and, when in its closed position, extending into, so as to close,

the vent, a cylinder, a vented'piston operatively" connected to the movable contact and slidable within said cylinder-which is in open communication with the enclosure through the vent in the piston, means wherebygas underpressure is supplied to the enclosure so that the enclosure is maintained filled with gas at a superatmospheric initial or filling pressure, and means whereby the supply of gas under pressure to the enclosure can be supplemented, thereby operating the piston and withdrawing the movable contact from the vent so that, though a blast of deionising gas is thus caused to flow through the vent and past the separating contacts to the expansion chamber, thus assisting in extinguishing the are drawn between them, reduction of the pressure within the enclosure below the initial or filling value is prevented by the supplementary gas supply.

14. A gas-blast circuit-breaker as claimed in claim 13, in which the discharge of gas from the gas-expansion chamber is controlled by a springloaded exhaust valve.

15. A gas-blast electric circuit-breaker as claimed in claim 13, having a relief valve which, when opened, relieves the pressure within the enclosure so that the pressure within the cylinder predominates and restores the movable contact to its closed position.

16. A gas-blast electric circuit-breaker comprising an arcing enclosure having at least one discharge nozzle or vent, a gas-expansion chamber, communicating with said vent, two cooperating contacts within the enclosure, at least one of said contacts being movable and, when in its closed position, extending into, so as to close, the vent, a cylinder, a vented piston operatively connected to the movable contact and slidable within said cylinder which is in open communication with the enclosure through the vent in the piston, a reservoir filled with gas under super atmospheric pressure, a primary gas-supply conduit connecting the reservoir to the enclosure, a reducing valve determining the supply of gas through the primary conduit to the enclosure, so

that the enclosure is maintained filled with gas at a superatmospheric initial or filling pressure, a supplementary gas supply conduit connecting the reservoir to the enclosure, and a blast valve controlling the supply of gas under pressure through the supplementary conduit to the enclosure, opening of the blast valve causing the gas pressure within the enclosure to be supplemented whereby the piston is operated to withdraw the movable contact from the vent so that, though a blast of deionising gas is thus caused to flow from the enclosure, past the separating contacts and through the vent to the expansion chamber, thereby assisting in extinguishing the are drawn between the contacts, reduction of the pressure within the enclosure to a value below the initial or filling pressure is prevented by the supplementary gas supply.

1'7. A gas-blast circuit-breaker as claimed in claim 16, having a relief valve which, when opened, relieves the pressure within the enclosure so that the pressure within the cylinder predominates and restores the movable contact to its closed position.

18. A gas-blast electric circuit-breaker comprising an arcing enclosure having at least one discharge nozzle or vent, a gas-expansion chamber communicating with said vent, two cooperating contacts within the enclosure, at least one of said contacts being movable and, when in its closed position, extending into, so as to close, the vent, a cylinder, a vented piston operatively connected to the movable contact and slidable within said cylinder which is in open communication with the enclosure through the vent in the piston, an exhaust valve controlling the discharge of gas from the enclosure, a valvecontrol chamber the pressure in which operates the exhaust valve, a bleed conduit communicating between the enclosure and said valve-control chamber, means whereby gas under pressure is supplied to the enclosure so that the enclosure is maintained filled with gas at a superatmospheric initial or filling pressure, and means whereby the supply of gas under pressure to the enclosure can be supplemented, thereby operating the piston to withdraw the movable contact from the vent so that, though a blast of deionising gas is thus caused to flow through the vent and past the cooperating contacts to the expansion chamber and past the exhaust valve, thus assisting in' extinguishing the are drawn between the contacts, reduction of the pressure within the enclosure below the initial or filling value is prevented by the supplementary gas supply.

19. A gas-blast electric circuit-breaker as claimed in claim 18, having a relief valve which, when opened, relieves the pressure within the enclosure so that the pressure within the cylinder predominates and restores the movable contact to its closed position.

20. A gas-blast electric circuit-breaker comprising an arcing enclosure having at least one discharge nozzle or vent, a gas expansion chamber communicating with said vent, two cooperating contacts within the enclosure, at least one of said contacts being movable and, when in its closed position, extending into, so as to close, the vent, a cylinder, a vented piston operatively connected to the movable contact and slidable within said cylinder, an exhaust valve controlling the discharge of gas from the enclosure and expansion chamber, a valve-control chamber the pressure in which operates the exhaust valve, a bleed passage communicating between the said chamber and the enclosure, a reservoir filled with gas under superatmospheric pressure, a primary gas-supply conduit connecting the reservoir to the enclosure, a reducing valve determining the supply of gas through the primary conduit to the enclosure, so that the enclosure is maintained filled with gas at a superatmospheric initial or filling pressure, a supplementary gassupply conduit connecting the reservoir to the enclosure, and a blast valve controlling the supply of gas under pressure through the supplementary conduit to the enclosure, opening of the blast valve causing the gas pressure within the enclosure to be supplemented whereby the piston is operated to withdraw the movable contact from the vent so that, though a blast of deionising gas is caused to flow from the enclosure, past the separating contacts and past the exhaust valve from the vent and expansion chamber, thereby assisting in extinguishing the are drawn between the contacts, reduction of the pressure within the enclosure to a value below the initial or filling pressure is prevented by the supplementary gas pp y.

21. A gas-blast electric circuit-breaker as claimed in claim 20, having a relief valve which, when opened, relieves the pressure within the enclosure so that the pressure within the cylinder predominates to restore the movable contact to its closed position, the predominating atmospheric pressure at the same time predominating over that in the valve-control chamber to restore the exhaust valve to its closed position.

22. A gas-blast electric circuit-breaker comprising an arcing enclosure having a discharge vent or nozzle, an expansion chamber communi eating with the low pressure side of the nozzle, a pressure chamber communicating with the enclosure on the high pressure side of the nozzle, two cooperating contacts within the enclosure on the high pressure side of the nozzle, at least one of said contacts being movable under the gas pressure within the enclosure, a cylinder communicating at opposite ends respectively with the expansion chamber and. pressure chamber, a piston slidable within said cylinder, means whereby the enclosure is maintained filled with gas under a superatmospheric initial or filling pressure, means whereby the piston is operated in one direction to supplement the pressure in the enclosure and reduce the pressure in the expansion chamber thus moving the movable contact towards the open position and causing a blast of deionising gas to flow from the enclosure and past the separating contacts to the nozzle, thereby assisting in extinguishing the are drawn between the contacts whilst preventing reduction of the gas pressure within the enclosure below the initial or filling pressure, and means whereby the piston is operated in the reverse direction to reduce the pressure in the enclosure thereby restoring the movable contact to the closed position.

23. A gas-blast circuit-breaker as claimed in claim 22, in which the enclosure and the cylinder are in permanent open communication with a reservoir containing gas under the initial or filling gas pressure.

24. A gas-blast circuit-breaker as claimed in claim 22, in which the movable contact is operatively connected to a piston movable in a cylinder one end of which is in open communication with the arcing enclosure on the high pressure side of the nozzle whilst the other end of the cylinder is in open communication with the expansion chamber on the low pressure side of the nozzle.

DONALD FOSTER AMER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,375,983 Thomson Apr. 26, 1921 1,937,482 Ruppel Nov. 28, 1933 2,280,321 Thommen Apr. 21, 1942 2,367,934 Flurscheim Jan. 23, 1945 2,382,274 Trencham Aug. 14, 1945 2,392,647 Cox Jan. 8, 1946 2,459,600 Strom Jan. 18, 1949 2,500,429 Nijland Mar. 14, 1950 2,531,617 Forwald. Nov. 28, 1950

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