US2292096A - Circuit-breaker operating system - Google Patents

Description

.Aug. 4,1942, c. THUMIM ETAL CIRCUIT-BREAKER OPERATING SYSTEM briginal Filed Feb. 6, 1940 2 Sheets-Sheet l CLOSE OPEN I /09 Inventors: Cari Thumim, Edward J. Frank Al xander C. Boisseau Their Afztwneg Aug. 4, 1942. c. THUMIM ETAL 2,292,096

' CIRCUIT-BREAKER OPERATING SYSTEM Or1g1na ".zled Feb. 6, 1940 2 Sheets-Sheet 2 "was" 90 i .1 g I L \l il I j 50 5.9 H r 77 umu v 79 inventmmsj Qari Thumim Edward J. Frank,

Patented Aug. 4, 1942 2,292,09 CIRCUIT-BREAKER orsaa'rmc SYSTEM Carl Thumim and Edward J. Frank, Yeadon, and

Alexander 0. Boisseau, Lansdowne, Pa, assignor to General Electric Company, a corporation of New York Original application February 6, 1940, Serial No. 317,564. Divided and this application April 4, 1941, Serial No. 386,920

7 Claims.

Our invention relates to circuit-breaker operating systems and more particularly to a tripfree fluid-actuated operating mechanism constructed so that the means to be actuated, such as the circuit breaker, can be released with respect to the fluid-actuated operating mechanism during the course of th closing stroke and prior to completion thereof.

This application is a division of our application Serial No. 317,564, filed February 6, 1940,

A further object of our invention is to provide a fluid-operated gas-blast circuit breaker in which trip-free operation is provided at any time during the operating cycle of the circuit breaker.

Further objects and advantages of our invention will become apparent as the following de scription proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of our invention, reference may be had to the accompanying drawings in which Fig. 1 is a partly diagrammatic layout of an operating system for a fluidoperated gas-blast circuit breaker embodying our invention, Fig. 2 is a cross-sectional view of the blast valve shown schematically in Fig. 1, and

.Fig, 3 is a sectional view of the blast valve taken on line 3-4 of Fig. 2.

Referring now to the drawings, we have illustrated our invention as applied to a fluid-operated circuit breaker III of the cross gas-blast type comprising a stationary contact ll and a, movable contactjl2 arranged to be operated so as to draw air-arc in an arc chute 13. The fixed contact II is connected to the line terminal ll while the movable contact i2 is connected to the line terminal IS. The fixed contact II is provided with spring pressed contact fingers Ha and longer arcing contact fingers I! while movable contact I2 is Provided with an arcing tip l2 so that, when the contacts separate, an arc therebetween occurs between arcing tips II' and I2. Immediately after separation of the contacts, one terminal of the arc isgtransierred by and air or gas-blast through conduit I6 from contact fingers II to the contact II" which is provided with a tip of arc-resistant metal. The air or gas blast from conduit l6 upon opening of the breaker drives the are into the arc chute l3 against the edges of a plurality of partitions I-l in the arc chute, which partitions are transverse to the arc gap and th ends of which extend close to the path of movement of the arcing tip [2 of the movable contact l2. The circuit breaker I0, illustrated by way of example in order to describe the operating system better, is not our invention but is described and claimed in United States Letters Patent 2,284,842, granted June 2, 1942, upon the joint application of David C. Prince, William K. Rankin, and Wilfred F. Skeats, and assigned to the same assignee as the present application.

In order to produce relative movement between contacts II and 12 by fluid pressure, we provide,

a fluid-operated motor comprising a cylinder l8 and a piston l9 operatively connected to movable contact l2 by means of connectin rod 20. This connecting rod 20 comprises two parts 20' and 20" joined with one another by a lost-motion connection 2| arranged to operate a tripping means 22 for releasing latch 23 which hold the circuit breaker III in the closed position. For high-speed opening of circuit breaker [0, it is desirable to release some form of energy-storage means to aid the fluid pressure in the opening operation. Latch 23 is provided in order to hold energy-storage means 24 comprising a spring in the charged condition. This energy-storage means or spring 24 is charged or compressed by fluid pressure during the closing movement of circuit breaker l0 and latch 23 cooperating with member. 25 restrains the circuit breaker and energy-storage means 24 in the closed and charged positions, respectively, until upward movement of piston i9 causes member 26 of lostmotion connection 2| to engage with tripping means 22 whereby latch 23 is released.

In order to operate piston i9, and, consequently, also movable contact i2 in response to fluid pressure, we provide a reserve fluid-pressure tank 21 which is connected to a fluid-pressure supply system through a nonretum valve. not shown, soils to trap suflicient fluid which, for example, may be air, at a suitable pressure to permit at least one operating cycle independent of the main fluid-pressure supply. Therefore, it the main fluid air supply should fail for any reason, one operating cycle of circuit breaker ll may still be obtained by virtue of the air or other fluid trapped in reserve tank 11. Reserve tank 21 is provided with a pressure switch, indicated schematically at 2| as comprising a sylphon bellows 29 connected to the reserve tank 21 and operatively connected to a suitable double-throw switch 3. cooperating with a plurality of contacts Ila and 30b which will be described hereinafter in greater detail.

Fluid-pressure tank 21 is connected by means of a conduit ii to a manifold 32 from which the fluidpressuremaybeadmittedtoeitherend of cylinder ll in accordance with the operation of either circuit breaker'opming valve 33 or circuit breaker clodng valve ll. Opming valve aisnormaliyheldinthepositimindioatedin Plg.i,closingoneendotmanitoldflagainst the fluidpressure tromconduit Ii bymeansol arelativelyhe'avyspring llactingonlever associated with opening valve 31' Valve is arrangedtobeoperatedbyopeningsoiaioid 31, which also operates its own seal-in switch a. Openin valve Ilinitsopmpositionisadapted to close escape port a through which fluid below piston I! may escape during the closing operation oi the circuit breaker ll.

Similarly, closing valve ll is normally held in the position indicated in Fig. 1, closing the other end '01 manifold 32 against the fluid pressure from conduit II by means of a relatively heavy spring ll acting on lever ll associated with closing valve ll. Lever ll, however, comprises two parts lid and lib, both mounted on a flxed pivot M, and, hence, diflers from lever ll associated with opening valve ll in a manner which will be described in greaterdetail hereinafter. Closing valve ll is arranged to be operated by closing solenoid l2 which also operates its own sealin switch l3. Closing valve ll in its open position is adapted to close escape port ll through which fluid above piston I! may escape during the opening operation of circuit breaker l0.

Trip-free operation of circuit breaker it is obtained by virtue of the fact that lever ll associated with closing valve ll and closing solenoid l! is constructed of two parts lia and lib which are held together as a single lever by means of latch l pivotally mounted on member lib and adapted to engage with an extension on member lia. A relatively light spring l6 is provided closing solenoid l! is still energized and holding lever lib downwardly against the tension of relatively light spring ll.

It is evident that the reversal of the direction 01' piston ll during the trip-free closing stroke can be greatly expedited ii the back pressure on the closing or upper end oi piston II is reduced instantaneously to a practicable minimum. Accordingly, we provide between the openings in cylinder II and the respective opening and closing valves 33 and ll a dumping valve l! which is arranged to provide a very large opening to atmosphere for the upper end of cylinder ll during the opening operation 01' circuit breaker II. This dumping valve ll comprises a relanectedtoapistoniloithesameorlargerdiameter, reciprocable in a cylinder 52 and normaliybiasedbymeansoispringlltohoiddumpingvalvememberilintheclosedposition. erativdywithpiston 8| isa second valvememberllassodatedwithescapeportll which is normally open when dumping valve munbcrllisclosedsoastoallowairoriiuiddr tromthelowerendotcylinder lltoeaeaps ainthesamemannerasportlland. inadditionthereto.duringtheclosingmovement arrangement, the upper end of cylinder II has to bias member lib in such a direction that latch l5 may engage the extension on member lia. It

will be understood, 01 course. that suitable spring means will be provided for latch l5 so as normally to tend to rotate itin a counterclockwise direction to engage-with the extension of member lla. By the arrangement just described, lever ll acts as a unitary member when clodng solenoid l2 is energized to open closing valve ll and, hence, to cause closing of the circuit breaker iii. If, however, during the closing operation of the circuit breaker, opening solenoid 31 should be energized through any cause, such, for example, as an abnormal current condition in the power circuits ll and i5, opening valve 33 will be operated. In order to obtain rapid closing the pressure therein instantaneously reduced so that rapid opening operation of circuit breaker ll may be obtained.

The cross gas blast for arc-extinguishing purposes in arc chute I3 is also obtained from reserve fluid-pressure tank 21 through blast valve 58 and conduit ii. Blast valve 5 of the balanced pressure type, shown in detail in Figs. 2 and 3, is illustrated as mounted directly below reserve pressure tank 21 and comprises a streamlined valve member 51 which allows fluid pressure from tank 21 to pass through annular passageway ll to conduit ll leading to are chute ll. Conduit II is illustrated in Fig. 2 as mounted at an angle with respect to blast valve ll in order to provide additional space for illustrating the details of the control mechanism therefor. Valve member 51 cooperates with a replaceable valve seat 51' which is mounted in a casing ll enclosing a cylinder 6i within which piston ll operatively connected to valve member 51 reciprocates. Piston 60 is preferably flexibly connected with valve member 51 for the purpose of self-alignment and is provided with a valve guide 82 reciprocating in a sleevelike member I. A spring member Gl is placed between sleeve member 63 and valvev member 51 normally to tend to hold said valve member in the closed position. Cylinder 8|, sleevelike member 63, and

spring member 64 are supported centrally by radial ribs 65 bridging across annular air passage 58.

The upper end of cylinder 6| is closed by a plate 66 to which is fastened a metallic striking plate 61. plate 61 and plate 66 is a flexible buffer disk 68 to cushion the opening of blast valve 56. The.

Between the metallic striking for opening valve 51 as will beset forth in,

greater detail hereinafter. A small passage 16 is provided in piston -68 to interconnect th)e cylinder 6| on either side of piston 69 and, hence, to balance the pressures operating on the upper and lower surfaces under steady-state conditions. The area of piston 60 is relatively large compared to the area of valve member 51 so that a considerably, lower pressure operating on piston 60 may overcome a higher pressure operating on valve member 51.

In order to open blast valve 58, a pilot valve ll of relatively large diameter is opened, rapidly releasing the pressure on the upper side of piston 60, whereby an unbalance of the pressure on piston 60 is obtained and the fluid pressure operating against the under side of piston 60 is suflicient to overcome the forces holding valve member 5! closed, which comprise the fluid I pressure acting on the back of valve member 51 and spring means 64. Thereupon valve member 51 is forced open rapidly and piston .66 contacts with striking plate 61 whereupon check valve 12 closing port I3 in piston 60 is opened by virtue of the extension H thereon which engages with striking plate 61. The upper surface of piston 68 is recessed at so that fluid pressure either through small passage 19 or port 18 within which check valve 12 operates is dis- I decrease the volume of space 69 determined only by the clearance necessary for valve member 51. Furthermore, the area of pilot valve II has been made as large as practicable and this combinabolted at 19 and 80, respectively, to casing 59. Pilot valve H is held in the closed position by means 0 spring mechanism 8| supported by U-sha member 18 and including adjustable means 82 by which the closing force on pilot valve 1| may be adjusted to just overcome the normal fluid pressure in space 69 tending to open pilot valve 1|. Movement of pilot valve, 1| against the force of spring mechanism 8| is effected through a pair of levers 83. pivotally mounted at 84 to U-shaped member 11 and interconnected by block 85 provided with an opening 86 through which rod 81 for operating pilot valve H is connected. This opening 86 in block 85 is enlarged at either end thereof so 'as to prevent any binding action between rod- 81 and block 85 during the pivotal movement of levers 83. Pivotal movement of levers 83 is obtained either by the leftward pull of armature 88 of opening air-blast solenoid 89 or by the leftward thrust of armature 90 of closing airblast solenoid 9|. Pivotally mounted levers 83 are connected in clevislike fashion to armature 88 at 92 while an extension 93 provided with a roller 94 is connected to armature 90 of closing air-blast solenoid 9| so that movement of armature 99 may be transmitted through roller 94 and armature 88 to pivotally mounted members 83 for operating pilot valve H. Solenoids 89 and 9| are coaxially mounted and connected to one another by means of U-shaped plates 95. The entire apparatus including solenoids 89 and 9| is supported from casing 59 as a unitary,

structure by member 96. I

Pivotally mounted levers 83 are provided with a roller 91 which tends to hold a switch 98 in the open position whenever pilot valve 1| is closed. The contacts of switch 98,'however, are biased to the closed position by spring means 99 so that, whenever the opening air-blast solenoid 89 is energized, switch 98 is closed after which opening operation of the circuit breaker I0 is initiated. By this arrangement, switch 98 insures that the opening air blast for circuit breaker I0 is provided before opening of the circuit breaker may take place.

Certain features of our invention disclosed in 6 'this application relating to blast valve 56 per se tion has enabled us to obtain an operating speed I much higher than was possible heretofore.

Check valve I2 is provided so that pressure in space 69 may be built up rapidly when pilot valve 1| is closed so that valve member 51 is snapped shut in a minimum period of time. The extension ll on check valve 12 is sufliciently long so that check valve 12 is maintained in the open position for a reasonable length of time to prevent fluttering of the valve member 51.

It will be understood by those skilled in the art that operation of pilot valve ll requires considerably less operating force than would be required to open blast valve 51 directly. The pilot valve H and operating mechanism I6 therefor are mounted as a complete constructional unit in are described and claimed in a copending application, Serial No. 345,810,'filed July 16, 1940,

which application is a division of this application.

In order to control the operation of opening valve 33, closing valve 34, and blast valve 56, we provide anelectrical control system including a source of direct-current potential lflll. This source of control potential is connected to closing solenoid 42 through pressure switch 30, contacts 30a, closo" button NH, and mechanically operated cut-off switch. I82 which is arranged to be closed by cam member )3 when circuit breaker I0 is open and which opens at the end of the closing stroke ofcircuit breaker I0. Switch I02 for mechanically cutting ofi solenoid closing coil 42 is provided with a holding coil I04 for preventing pumping of the circuit breaker III in the event that it is closed upon an abnormal current condition and the operator fails to release close button |0|. At a predetermined point in the closing stroke of circuit breaker l0, switch I05 which is open in both the closed and open positions of the circuit breaker is closed by virtue of cam member I06 mounted on connecting rod 20 whereby closing air-blast solenoid 9| is energized for producing a blast of arc-extinguishing fluid in arc chute l8 by virtue of the movement oi. armature 88 which operates pilot valve II and, hence, also valve member 81 of blast valve 88. Mechanically operated switch I88 for controlling the closing air blast is closed before contacts II and I8 meet and opens after the contacts have engaged. As has been mentioned before. closing solenoid 88 is provided with a seal-in switch 88 i so that the operator may release "close button Ill prior to the completion of the closing operation.

Tripping operation of the circuit breaker may be initiated in one of three ways, either by manual operation of open" button I81, by automatic closure of protective relay I88 which is energized from current transformer I88 associated with power line l8 whenever an abnormal current condition occurs therein, or by the bridging of contacts 88b of pressure relay switch 88 in the event the pressure in reserve tank 81 falls below a predetermined minimum. All threeof these tripping means are connected in parallel with one another but, in any event, opening solenoid 31 cannot be energized until switch 88 has been closed which is accomplished by the operation of protective relay I88, manually operable open" button I81, or pressure relay 88 through the energization 08 opening airblast solenoid 88 through mechanically cut of! switch llli. This switch 8 opens during the opening stroke of the circuit breaker l8 by virtue of cam ill attached to connecting rod 88 and cuts off the opening air blast at the proper moment after the arc drawn has been extinguished. As soon as opening air-blast solenoid 88 is energized, switch is closed and opening solenoid 81. is energized through mechanical cutofl switch H8 which is closed at the beginning of the closing stroke by virtue of cam I88 mounted on connecting rod 88 and opens at the end of the opening stroke of circuit breaker I8. As was mentioned above, opening solenoid 81 is provided with a seal-in switch 88 to insure completion of the tripping operation even though "open" button I81, protective relay I88, or pressure responsive relay '88 bridging contacts 88b are immediately opened.

An auxiliary switch H8 is provided in series with signal means 8 which. for example, maycomprise a green light to indicate that the circuit breaker is in the open position. Switch H8 is closed when circuit breaker I8 is open and is opened mechanically by means of cam 8 on connecting rod 88 when circuit breaker I8 is in the closed position. A signal means 8 which. for example, may comprise a red light'is provided and is energized through opening air-blast solenoid 88 and mechanically operated cuteofl switch 8 for opening air-blast solenoid 88 when the circuit breaker I8 is in a closed position. It will be understood by thou skilled in the art that the resistance of signalmeans H8 issuchastoallowonlyaverysmallcurrent t flow through this circuit which is insumclent tocausesolenoidlltopullarmaturefltothe left and. hence. initiate tripping of circuit breaker l8. A signal means I" is also provided in series with relay switch 88 and contacts 880 to indicate the condition of the fluid pressure in reserve tank 81. If, for any reason, the pressure in reserve tank 81 should fall below a predetermined amount, sylphon bellows 88 will contract opening contacts 88a so that closing of the circuit breaker if it is in the open position is prevented. Furthermore, closing of contacts 881; will energize the opening air-blast coil 88 and initiate tripping operation of the circuit breaker in the event that it is in the closed position.

Although we have described our invention as applied to a single-pole circuit breaker, it will be understood by those skilled in the art that it may equally well be applied to a multiple circuit breaker in which case blast valve 58 would be connected to a suitable manifold to distribute the fluid pressure to the different arc chutes of the multipole circuit breaker and connecting rod 88 would be adapted to operate a plurality of poles instead of only a single one.

The operation of our invention will be described with reference to Fig. 1 when the circuit breaker I8 is in the closed position as indicated. Tripping operation of the circuit breaker may be initiated in one of three ways; namely, if the operator manually depresses open" button I81, if an abnormal current condition occurs in power line l8 causing energization of protective relay I88, or if the pressure in reserve pressure tank 81 decreases sumciently so that pressure relay 88 causes switch 88 to bridge contacts 88b. If either of these three situations occur, opening blast solenoid 88 is energized from control circuit I88 through mechanical cutofl' switch H8. thus pulling armature 88 thereof to the left and opening pilot valve II as is evident from Fig. 2. The opening of pilot valve II will allow the pressure in space 88 to decrease rapidly so that the pressure balance on piston 68 is disturbed and valve 51 is opened, allowing a blast of fluid from tank 81 to pass through conduit i8 into arc chute I8.- This fluid blast occurs before the initiation of the opening operation of circuit breaker l8. As soon as opening blast solenoid 88 is energized and armature 88 is pulled to the left, switch 88 is closed, allowing opening valve solenoid 81 to be energized both to close its seal-in switch 88 and to open opening valve 88 while closing escape port 88. This allows fluid under pressure from tank 81 and manifold 88 to enter the lower end of cylinder 18. Furthermore, this fluid pressure moves piston ll ofdumping valve 88 upwardly to close escape port 88 and provide a very large opening to atmosphere at the upper end of cylinder l8 so that high-speed opening of circuit breaker i8 may take place. The initial upward movement of piston l8 by virtue of lost-motion connection 8| causes member 88 to engage tripping means .88, whereby latch 88 is released from member 88 and energy-storage means 84 is released to aid the fluid-pressure means in high-speed opening of circuit breaker l8. As the circuit breaker l8 reaches a predetermined podtlon in the opening stroke, cutoff switch 8 is opened. thereby deenergizing opening air-blast solenoid 88 whereby pilot valve II is closed by spring means 8| and check valve I8 allows fluid pressureto enter space 88 and cause valve member 81 to snap to the closed position. Further movement in the opening direction of connecting rod 88 causes cutofl switch H8 to open the energization circuit of solenoid 81, whereby Opening valve 88, is forced shut by relatively heavy spring 88. Auxiliary switch 8 is allowed to close and energize signal means III for indicating that the circuit breaker is in the open position.

To close the circuit breaker when it is in the open position. "close" button "I is operated and.iithepressureintank8'lissuiilcientlyhlgh so that pressure relay 28 allows switch 30 to bridge contacts 30a, closing solenoid 42 is energized through mechanically operated cutofl switch I02, which is in the closed position when circuit breaker I is open. The energization of closing solenoid 42 causes seal-in switch 43 to close and, furthermore, causes opening of closing valve 34 and closing of escape port 44 against the force of relatively heavy spring 40. This allows fluid under pressure from manifold 32 to enter the upper end of cylinder I8. Since the area of piston I is at least as large as that of valve member 50 of dumping valve 49, valve member 50 is maintained in the closed position by the force of spring 53 and piston I9 is forced downwardly, charging. energy-storage means 24 and moving circuit breaker ID to the closed position. Fluid underneath piston I9 is allowed to exit to atmosphere through escape ports 39 and 55. At a predetermined point prior to the meeting of contact tips II and I2, cutofl' switch I05 for closing air-blast solenoid 9| is closed, whereby armature 90 is moved to the left opening pilot valve II 'and operating blast valve 56 in the manner described above to produce a blast of gas or air transverse of contacts II and I2 prior to the closing thereof. .After contacts II and I2 have engaged one another, cutofi switch I05 is opened, deenergizing closing airblast solenoid 9| and, hence, allowing spring 4 means 8I to close pilot valve II, whereby blast means H4 and signal means H6 is energized through opening air-blast solenoid B9 and cutofl switch IIO therefor which has been closed as the circuit breaker reaches the closed position. The trip-free operation of the circuit breaker will be understood by those skilled in the art in view of the detailed description given above and will only be briefly mentioned hereinafter. If during the closing operation of the circuit breaker described in the preceding paragraph, protective relay I08 should initiate a tripping operation which it may do as soon as mechanical cutofi switch III! is closed, the tripping operation described above will be initiated and energization of opening solenoid 31 will occur,

whereby lever 35 causes rod 41 to engage projection 48 of latch 45 allowing member a to pivot and close closing valve 3,4 by virtue of relatively heavy spring 40 even though solenoid 42 is still energized. Hence, trip-free operation is obtained and rapid opening of circuit breaker I0 is accomplished.

It will be apparent to those skilled'in the art that our invention is not limited to ,the particular construction shown but that changes and modifications may be made without departing from .the spirit and scope of our invention and we aim in the appended claims to cover all such changes and modifications.

What we claim as new and desire tosecure by Letters Patent of the United States is:

1. In an operating system for an electric circuit breaker comprising aplurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, means for connecting said source of fluid with said fluid motor for closing said circuit breaker, means for opening said circuit breaker, and means interposed between said fluid motor and said first-mentioned means operable during the opening movement of said circuit breaker for instantaneously reducing the back pressure against said fluid motor so that high-speed opening operation of said circuit breaker may be obtained.

2. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a source .of fluid under pressure, means operable by said fluid under pressure for producing relative movement between said contacts, a plurality of solenoid-operated valves for selectively connecting said source of fluid with said last-mentioned means for closing and opening said circuit breaker, and means interposed between said means operable by said fluid under pressure and said plurality of solenoidoperated valves operable during the opening movement of said circuit breaker for instantaneously reducing the back pressure against said means operable by said fluid pressure to a practicable minimum.

3. In an operating system for an electric circuit breaker comprising a plurality of relative- 1y movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, valve means for connecting said source of fluid with said fluid motor for closing said circuit breaker, means for opening said circuit breaker, and a dumping valve of relatively large diameter interposed between said valve means and said fluid motor operable during the opening movement of said circuit breaker for very rapidly reducing the back pressure against said fluid motor that high-speed opening operation of said circuit breaker may be obtained, said dumping valve being so constructed and arranged as to remain closed during the closing operation of said circuit breaker.

4. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, a first valve for connecting said source of fluid with said fluid motor for closing said circuit breaker, a second valve for connecting said source of fluid with said fluid motor for opening said circuit breaken'said valves being so con-. structed and arranged as to control exhaust ports associated with said fluid motor, solenoid means for operating each of said valves, a dumping valve of relatively large diameter including operating means comprising a spring-biased piston interposed between said fluid motor and said first and second valves, said piston being operable by said source of fluid for holding said dumping valve in a closed position during the closing operation of said circuit breaker but arranged to open said dumping valve during the opening movement of said circuit breaker for instantaneously reducing the back pressure against said fluid motor Whereby high-speed opening operation of .said circuit breaker may be obtained, and means associated with said dumping valve to prevent opening thereof during the closing operation of said circuit breaker.

5. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, means for connecting said source of fluid with said fluid motor for operating said circuit breaker, and means interposed between said fluid motor and said first-mentioned means for substantially instantaneously relieving the fluid pressure tending to retard the reversal of said fluid motor comprising means including a dumping valve operable to theopen position in response to the force exerted thereon by the fluid under pressure which causes reversal of said fluid motor.

6. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a fluid motor comprising a cylinder and piston for producing relative movement between said contacts, a source of fluid under pressure for operating said motor, means for connecting said source of fluid with said motm for closing said circuit breaker, and means interposed between said fluid motor and said flrstmentioned means ior rapidly relieving the fluid pressure tending to retard the reversal of said fluid motor to open said circuit breaker including a dumping valve operable in response to the force exerted thereon by the fluid under pressure causing reversal of said fluid motor to open a large escape port between said cylinder and'atmosphere.

'I. In an operating system for an electric circuit breaker comprising a plurality of relatively movable contacts, a source or fluid under pressure, a fluid motor comprising a cylinder and piston arranged to be connected to said source,-

means operatively relating said piston to said circuit breaker, a large valve in said cylinder arranged tovent quickly to atmosphere the fluid pressure acting to move said piston in one direction. fault-responsive means for initiating the opening of said circuit breaker, and means for opening said large valve immediately after the operation of said fault-responsive means to permit trip-free operation of said circuit breaker and high-speed opening thereof.

CARL THUMIM.

EDWARD J. FRANK.

ALEXANDER C. BOISSEAU.

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