US2555898A

US2555898A - Fluid operating and braking system for circuit interrupters

Info

Publication number: US2555898A
Application number: US73376A
Authority: US
Inventors: Ira W Paterson; John F Chipman
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1949-01-28
Filing date: 1949-01-28
Publication date: 1951-06-05
Anticipated expiration: 1968-06-05

Description

June 5, 1951 l W PATIERSON ET Ax. 2,555,898

FLUID .OPEATING AND BRAKING SYSTEM FOR CIRCUIT INTERRUPTERS Filed Jan. 28, 1949 n.. Y Y n u [Lgs-1;, Ell fm2/m nz /35 32 me for Patented June 5, .1951

FLUID OPERATING AND BRAKIN G SYSTEM FOR CIRCUIT INTERRUPTERS Ira W. Paterson, Milton, and John F. Chipman,

South Weymouth, Mass assi gnors to Allis- Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application January 28, 1949, Serial No.` 73,376

This invention relates to electric switching devices of the type in which gas under pressure is utilized to operate a contact actuating means as Well as a brake and more particularly to means for controlling the dissipation of the kinetic energy of the actuating means and parts associated therewith.

In fluid operated electric switches where the movable switch contact and its associated actuating means have an appreciable amount of mass inertia, the kinetic energy of the switch and actuating means must be dissipated when the switch contact reaches one or the other end position thereof. In prior art braking systems such energy has been absorbed by suitable springs or by frictional brakes. Such frictional braking systems have applied a braking effort that is independent of the operating effort applied to the switch actuating means to operate the same, or the braking effort is not correlated with and proportional to the operating effort applied to the switch under variable operating conditions.

It is therefore one of the objects of the present invention to provide a new and improved control system for circuit breakers of the fiuid blast type.`

Another object of the present invention is to provide a new and improved fluid operated actuating and control system for switching devices in which the braking effort of a fluid operated brake mechanism is in a substantially constant ratio to the operating effort applied to the switch actuating means at any operation thereof.

A further object of the invention is to provide a new and improved fluid operated brake which rapidly supplies a predetermined braking effort arresting the operating movement of a fluid motor supplied at constant pressure and parts associated with and operated by it, and rapidly releases the fluid under pressure from the brake mechanism upon arresting the movement of the fluid motor and associated structure.

Objects and advantages other than those above set forth will be apparent from the following description when read inl connection lwith the accompanying'drawing in which:

14 Claims. (Cl. 20G-81.4)

` the exhaust valves of the embodiment illustrated in Fig. 1.

The present invention is shown as applied to a fluid operated polyphase circuit breaker of the gas blast type, of which only the elements of one phase are shown. As shown in the drawing, one phase of the circuit breaker consists essentially of a fixed arcing contact I and a movable contact 2 connected in series with disconnect contacts 3 and 4 in an electric circuit through terminals 5. The arcing contacts I and 2 are housed in a tubular insulator 6 of ceramic material of which porcelain is an example. A base member 1v supports tubular insulator 6 in any suitable manner.

A conductive annular member 8 made in two parts is mounted on and supported by insulator 6. An insulating tube II mounted within and axially aligned with insulator 6 is rigidly supported by base member 1. Tube II surrounds the cooperating arcing contacts I and 2 and cooperates with conductive annular member 8 to define an arcing chamber I2.

Contact I is secured to a tubular portion of base member I extending into insulating tube II. The cooperating movable contact 2 comprises an annular shaped arcing portion defina ing an orifice I4 and adapted to partially surround the top portionV of stationary contact I upon engagement therewith. Movable contact 2 further comprises a sleeve portion I5 and forms therewith a piston of `a fluid motor. Sleeve I5 is adapted to slide within guiding surfaces Which in turn, constitute downward extending portions IG and Il of the conductive annular or cylindrical member 8. The upward `stroke of sleeve I5 is limited by abutment of an annular projection thereof against a flange I8 backed by suitable shock absorbing material. The interior of sleeve I5 is insulated by a suitable material.

Arcing chamber I2 contains an auxiliary probe electrode I9. This electrode, which is secured to a cover 22 and in electrical contact with member 8, is usually axially aligned with sleeve I5.

A plurality of rigid interconnecting conductors 23 disclosed and claimed in U. S. Patent 2,533,545, of ChesterD. Ainsworth and Gustav Jansson issued December l2, 1950 and assignedto the assignee of this application, electrically connect movable contact 2 to member 8 and in turn terminal element 5V which is vsecured to member 8.

Each rigid interconnecting conductor 23 is in the form of a rocking contact lever which is in permanent contact with the conductive annular member 8 and sleeve I5 at all times. A plurality of spring means 24 provide a contact pressure between interconnecting conductors 23 and member 6 and sleeve I5, thus providing an electrical .circuit connection therebetween. These springs have a dual function and additionally effect resetting or reclosing of contact 2 upon decrease of fluid pressure at movable contact 2.

Base member 1 is connected to a reservoir 21, constituting a source of arc extinguishing uid under pressure. The fluidis supplied to the inlet portion of the arcing chamber I2 upstream of movable contact 2 for the purpose of directing a blast of arc extinguishing uid under pressure between the arcing contacts and through the arcing chamber. The arc extinguishing fluid under pressure may be a suitable inert gas, but it will be assumed herein that the iluid is airV -under pressure of the order of 100 or more pounds per square inch.

The compressed air for operating the system is derived from a storage tank or compression system (not shown) and ows through a reducing valve 25 and a pipe line `26 toa blast manifold or reservoir 21. The a-ir under pressure in reservoir 21 is intended to produce the arc extinguishing blast across the gaps -formed between the pair of cooperating arcing contacts upon separation thereof. The arc extinguishing blast from reservoir 21 to the arcing contacts I and 2' is controlled by a blast valve 28 through a pipe line 29 interconnecting the blast valve 28 and the base member 1 which in turn communicates with the arcing chamber I2. i

Blast valve 28 comprises uid motors 3| and 32 for controlling a blast inlet port 44. Motor 3| comprises a cylinder 33, a piston 34, a piston return spring 35, a piston rod36, and an .inlet port 31. Motor 32 comprises a cylinder 4I, a piston 4'2, a return spring 43 for piston 42, an exhaust port 45, anda valve 46 for closing exhaust port 45 under the action of a spring 41.

Piston rod 36, when actuated by piston 34, opens valve 46 against the action of spring 41. As long as port 45remains closed, air under pressure supplied from reservoir 21 to the space below piston 42 through a hole drilled in the piston cooperates with spring 43 to maintain the piston in the position shown.

A fluid pressure tank or reservoir 48 connected to the source of supply through reducing valve 25 is provided for supplying fluid under pressure to a uid operated motor means I and a iiuid operated brake mechanism 52. The motor and the brake control the movable disconnect contact of the circuit breaker. In order to prevent a backflow of compressed air from reservoir 48 into pipe line 26 upon decrease of pressure in pipe line 26 due to the reduction of pressure in reservoir '21 after the occurrence of an arc extinguishing blast of air through blast valve 28, a check valve 53 -is provided between pipe line 26 and reservoir48. Check valve "53 is of the commercial type having a small bleed hole permitting tank 48 to bleed gradually into pipe system 2'6 if the pressure remains lower in system 26 than in tank 48 for a considerable period of time. The purpose 'of this'bleed hole is to cause pressure lockout means to make any operation by air derived from tank v48 impossible in casethe pressure in manifold 21 drops permanently below the safe limit required for interruption of the circuit byair blast.

Acontact 3.

Fluid motor 5I comprises a cylinder 54 and a piston 56. Piston 56 is mounted on a piston rod 51 which is axially aligned with cylinder 54 and extends through the cylinder covers. A slide valve port 59 in piston rod 51 of motor 5I acts to vent closing air in breaker closed position to aid fast reversal of piston 56. Cylinder 54 provides ports 58 and 62 for intake and exhaust purposes. Port 6| is provided for blast valve reset control.

Brake 52 comprises brake shoes 63 provided with a brake lining 64 acting on a drum 65 connected to a shaft 66 which actuates disconnect When air under pressure is fed to brake cylinder 61, a piston 68 actuates brake shoes 63 and they tighten about the drum 65, thus arresting movement of shaft 66.

ISlide or control means such as valves 1| and 12 are provided for admitting compressed air from reservoir 48 to fluid brake 52 and comprise cylinder 13 and 14, pistons 15 and 16, piston rods 11 and 16, and inlet and outlet p orts 8|, 82, and 83, 84, respectively. Slide valves 1I and 12 are operated by means of a crank mechanism secured to piston rods 11 and 18 which comprises a pair of slotted arms or links and 86, each having a lost motion connection with the operating shaft 66 of the disconnect switch contact 3. Shaft 66 is operated by the disconnect contact operating fluid motor 5|.

A second pair of

slide valves

81 and 88 which, for example, may comprise a common body member 9| and a. pair of

pistons

92 and 93 are connected to slide valves 1| and 12, respectively, to serve the purpose of dumping or exhausting compressed air from the brake mechanism 52 upon dissipation of the kinetic energy of the disconnecting switch mechanism. Piston 92 is relatively small in diameter as compared to piston 93. This is intended to provide a trip predominating feature in case contradictory operating impulses are being supplied to slide valves 1| and 12. Cylinder body member 9| provides an inlet port for piston 93 and an inlet port 96 for piston 92.

Pistons

92 and 93 are provided with a common spring 94 which positions them in the position shown in the absence of air pressure in

ports

95 and 96.

Exhaust ports

91 and 98 provided in member 9| for

pistons

93 and 92, respectively, are connected to a pair of exhaust ports |0| and |02 of slide valves 12 and 1|, respectively.

A pair of piston valves |63 and |04 provide interlocking means for effecting proper sequential operation -of the opening of the blast valve 28, the initiation of the opening operation of the disconnecting switch contact 3, and the reclosing of the blast valve 2'8. Piston valves |63 and |04 comprise cylinders |05 and |06, pistons |01 and |08, and return springs II| and ||2, respectively.

A pair of opening and closing valve means |I4 and I I5 control the actuating means for the circuit breaker. Valve means II4, I|5 may be of any suitable known type and are diagrammatically shown as valves of the magnetic type comprising casings I|6 and ||1, valve elements |I8, I2I, armatures |22, |23 and coils |24 and |25, respectively.

The circuit breaker illustrated in the drawing is shown with the disconnect contacts in the open circuit position and the pneumatic control system in the corresponding position. A closing operation is initiated by energization of the closing solenoid Valve I I5, thereby permitting air under pressure from reservoir 48 to pass through a pipe line |26 to and through valve |5, through a pipe line |21 and inlet port 62 to iiuid motor Part of the air flow through pipe line |21 passes through the pipe line |28 to the inlet port 8| of slide valve 1|. As long as piston 15 of slide valve 1| is in the position illustrated in the drawing inlet port 8| is closed. Operation of solenoid valve ||5 results in moving piston 56 of motor 5| from right to left to actuate shaft 66 and thereby close the disconnect contacts. After a predetermined travel of piston 56, shaft 66 actuates slotted arm 85, piston rod 11 and piston 15. The latter then opens inlet port 8| of slide valve 1|. Air under pressure thenflows from pipe line |28 through slide valve 1|, outlet port 82, through a pipe line |29 to the fluid brake 52.

The brake Adecelerates shaft 66 by absorbing the kinetic energy of the shaft and of contact 3. Simultaneously with rotation of shaft 66, piston 16 of valve 12 is caused to move to the left by the action of the reset spring behind it, thereby closing

ports

84 and 83 and preventing exhausting of live air through lines |09, |51 and |56.

,A port |02 in cylinder 13 of slide valve 1| is connected to slide valve 81 and more particularly port 98 thereof through pipe line |34. The pressure impulse initiated through opening of solenoid valve l5, however is also transmitted to port 96 and results in moving slide dumping valve 81 and more particularly piston or valve 92thereof to the closed position or that position where port 98 is closed. Exhaust of air from pipe lines |28, |29 to atmosphere through ports 98, |35 is thereby prevented.

Upon return of solenoid valve |5 to the position shown, pressure in pipe line |28 decays by leakage of air past the movable elements connected in line |28 and by venting to atmosphere through port |30 of valve ||5. Slide valve port 59vacts to Vent closing air when the breaker reaches closing position, thereby rapidly dropping the pressure in pipelines |21, |28. When -the pressure has decayed in pipe lines |21 and |28 to a predetermined value, dumping or. slide valve 81 is reset by the action of spring 84, resulting in immediate dumping or exhausting of .huid under pressure from iluid brake 52 through exhaust port |35 of valve 81.

When the solenoid trip valve ||4 is energized, compressed air ows from reservoir 48 through trip valve ||4, a pipe line |36, and inlet port |31 into piston valve |03. An outlet port |38 of piston valve |03 transmits the pressure impulse through a pipe line |4| to the inlet port 31 of blast valve 28 and of the blast valves of the other phases of the circuit breaker. The piston 34 of motor 3| moves under the action of the pressure impulse to open exhaust port 45, thus reducing the pressure in the space below piston 42. This 'permits air from reservoir 21, communicating with air blast valve 28 through a pipe line |42 and in inlet port |43, to move piston 42 of fluid motor 32 against the action of spring 43. The

` movement of piston 42 under the air pressure vfrom reservoir 21 opens the inlet port 44 and -permits an air blast to move through a pipe line 29 to arcing contacts and 2 of the circuit breaker. The air blast causes separation of the arcing contacts and 2 and extinguishment of the arc occurring therewith.

The travel of piston 56 of fluid motor 5| from leftto right results, through the movement of piston rod 18 Aof slide valve 12, in the opening of inlet port 83 and outlet port 84. At the same time, link allows resetting of piston 15 of

seal ports

82 and 8| of valve 1| thereby preventing exhausting of live air being fed to line |29 through port S4 from inlet port 83 and line |56. A pressure impulse is thus permitted to iioW from piston valve |03, through a pipe line |56, inlet port 83, outlet port 84, pipe line |29 to iiuid brake 52. This results in operation of fluid brake 52 upon a predetermined travel of the movable disconnect contact 3. Any pressure impulse in pipe line |56 acts upon slide valve 88, through a pipe line |51 and port 95. Piston 83 of slide Valve 88 is then moved against the action of spring 94 and closes normally open ports 81 and I6! of valve 88 which are provided for dumping or exhausting air from the fluid brake 52 through an exhaust port |0| of slide valve 12 and a pipe line |09.

Upon reclosure of blast valve 28 and the resetting of piston valve |03 due to the reduction or decay of pressure in pipe line |46, port |48 of piston valve |03 is closed. Reduction of the pressure in pipe line |56 as a result of leakage of air i past the movable elements such as pistons |01 and 56 connected therewith results in resetting of slide valve 88 under the action of spring means 84 and permits dumping of air under pressure from the fluid brake 52 through the exhaust port |0| in slide valve 12, pipe line |09 and exhaust port |6I.

If closing and opening pressure impulses are substantially simultaneously initiated by solenoid valves |55 and ||4, respectively, the trip pre- .dominating feature of slide valves 88 will permit only the completion of the opening cycle of the circuit breaker. Thus, when the closing impulse is initiated by valve ||5, a pressure impulse is transmitted from reservoir 48 through valve ||5, pipe line |21, pipe line |28 and inlet port 96 of slide valve 81. This pressure impulse moves piston 92, which closes port 98 of slide valve 81. The

.pressure in pipe line |21 moves piston 56 of motor 5| from right to left, and piston 56 in turn moves piston 15 of slide valve 1| from left to right and piston 16 of slide valve 12 from right to left. The movement of piston 15 from left to right opens inlet port 8| of slide valve 1| and permits air to ow through pipe line |29 to the iluid brake 52, and the movement of piston 16 from right to left closes

ports

83 and 84.

If, however, a contradictory trip impulse was initiated by valve |4 shortly after or at the same .time as the breaker closing impulse, air under pressure flows through trip valve I I4, pipe line |36, inlet port |31 of valve |03, outlet port |38 of valve |93, pipe line |4| and inlet port 31 of air blast valve 28. The air blast valve is actuated, permitting opening of the arcing contacts I and 2. Part of the air passing through blast valve 28 is transmitted through a pipe line |46 to valve |93 and moves piston |01 thereof from right to left. This movement of piston H11 opens outlet port |48 of valve |03 and permits air under pressure to now through pipe line |56 to the inlet port 95 of slide valve 88. Because the diameter of piston 93 is greater than the diameter of piston 92, piston 93 moves from left to right and moves piston 92 of slide valve 81 against the pressure of pipe line |28, urging it from left to right. Upon movement from left to right of piston 92 of slide valve 81 ports 98 and |35 are opened, thus permitting exhausting brake 52. Ports 98, |35 also exhaust the air being admitted to the right side of piston 56 through valve ||'5, thereby permitting a complete opening cycle of the circuit breaker to occur. A slide valve port 59 in piston rod 51 of motor 5| also acts to vent closing air in breaker closed position to aid fast reversal of piston G.

Fig. 2 illustrates a modified structure combining the brake control valves 1| and 12 with the pressure responsive exhaust valves 81 Aand 88 in a single self-sustained structural unit.

Although but tWo embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein Without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. An electric circuit interrupter comprising a pair of relatively movable cooperating contacts, reciprocating motor means for relatively moving said contacts, a fluid operated brake mechanism of the frictional type lor arresting relative movement of said contacts, a source of fluid under pressure, valve means distinct from said motor means for admitting fluid under pressure from said source to said brake mechanism, and a linkage operated by said motor means for operating said valve means upon a predetermined contact operating movement of said motor means.

2. An electric circuit interrupter comprising a pair of relatively movable cooperating contacts, a rocking shaft for relatively moving said contacts, reciprocating motor means for rocking said shaft, a fluid operated brake mechanisin for arresting the rocking motion of said shaft, said brake mechanism including a brake drum iixedly mounted on said shaft and friction elements adapted to cooperate with said drum, a source of fluid under pressure, a brake Valve distinct from said motor means for admitting fluid under pressure from said source to said brake mechanism, a mechanism including a lost motion connection operated by said shaft for actuating said brake valve upon a predetermined contact operating movement or" said motor means, and valve means for relieving pressure in said brake mechanism after cessation of the rocking motion of said shaft.

3. An electric circuit interrupter comprising a pair of relatively movable cooperating contacts, uid operated motor means for relatively moving said contacts, a fluid operated brake mechanism of the frictional type for arresting the relative movement of said contacts, a main source of fluid under pressure, an auxiliary source of fluid under pressure, a pressure responsive valve permitting substantially unidirectional fluid flow from said main source to said auxiliary source and precluding substantial reverse flow of fluid under pressure, first valve means distinct from said motor means for admitting fluid under pressure from said auxiliary source to said Ibrake mechanism, a second valve means for admitting uid under pressure from said auxiliary source to said motor means, and a linkage operated by said motor means for operating said rst valve means upon a predetermined contact operating movement of said motor means.

4. An electric circuit interrupter comprising a pair of relatively movable cooperating contacts, a iiuid motor of the reciprocatory type for relatively moving said contacts, a fluid operated brake mechanism of the frictional type for arresting relative movement of said contacts, a source of fluid under pressure, a pair of brake valves for alternatingly admitting fluid under pressure from said source to said brake mechanism, and a rocking lever supported by a shaft and operated by said uid motor for operating said pair of brake valves, said rocking lever having a pair of arms situated on different sides of said shaft and forming part of a linkage for opening either of said pair of brake valves and closing simultaneously the other of said pair of brake valves, said linkage including a pair of lost motion connections for opening either of said pair of brake valves upon a predetermined contact operating movement of said motor means.

5. An electric circuit interrupter comprising a pair of relatively movable cooperating contacts, a fluid motor of the reciprocatory type for relatively moving said contacts, a uid operated brake mechanism of the frictional type for arresting relative movement of said contacts, a source of fluid under pressure, a pair of brake valves for alternatingly admitting fluid under pressure from said source to said brake mechanism, a rocking lever supported by a shaft and operated by said fluid motor for operating said pair of brake valves, said rocking lever having a pair of arms situated on different sides of said shaft and forming part of a linkage for opening either of said pair of brake valves and closing simultaneously the other of said pair of brake valves, said linkage including a pair of lost motion connections for opening either of said pair of brake valves upon a predetermined contact operating movement of said motor means, and a pair of valve lmeans for relieving the pressure in said brake mechanism after cessation of the movement of said contacts, each of said pair of valve means being associated With one of said pair of brake valves and adapted to relieve the pressure in said brake mechanism through the brake valve with which it is associated.

6. In an electric switching device the combination of a fluid motor comprising a cylinder and a piston operatively arranged therein, a uid operated brake mechanism for arresting the stroke of said piston at either end of said cylinder, a source of lluid under pressure, a pair of valve means for admitting uid under pressure from said source selectively to either end of said cylinder, motor fluid supply conduits and brake fluid supply conduits for dividing the flow of fluid under pressure issuing from each of said pair of valve means into a motor supply flow and a separate brake supply now, a pair of brake valves one in each of said brake iluid supply conduits, and a crank mechanism operated by said fluid motor for operating said pair of brake valves, said crank mechanism comprising a pair of lost motion connections adapted to open either of said pair of brake valves upon a predetermined contact operating movement of said motor means.

'7. In an electric switching device the combination of a fluid motor comprising a cylinder and a piston operatvely arranged therein, a fluid operated brake mechanism for arresting the stroke of said piston at either end of said cylinder, a source of fluid under pressure, a pair of valve means for admitting fluid under pressure from said source selectively to either end of said cylinder, motor fluid supply conduits and brake fluid supply conduits for dividing the flow of fluid under pressure issuing from each of said pair of valve means into a motor supply flow and a separate brake supply flow, a pair of brake valves one in each of said brake supply conduits, a crank mechanism operated by said fluid motor for operating said pair of brake valves, said crank mechanism comprising apair of lost motion connections adapted to open either of said pair of brake valves upon a predetermined contact operating movement of said motor means, and a pair of pressure responsive exhaust valves for relieving the pressure in said brake mechanism alternatingly through one of said brake valves after cessation of the relative movement of said piston and cylinder.

8. In an electric switching device the combination of a fluid motor comprising a cylinder and a piston operatively arranged therein, a fluid operated brake mechanism for arresting the stroke of said piston at either end of said cylinder, a source of fluid under pressure, a pair of valve means for admitting lluid under pressure from said source selectively to either end of said cylinder, motor fluid supply conduits and brake fluid supply conduits for dividing the flow of fluid under pressure issuing from each of said pair of valve means into a motor supply flow and a separate brake supply flow, a pair of brake valves one in each of said brake supply conduits, a crank mechanism operated by said iluid motor for operating said pair of brake valves, said crank mechanism comprising a pair of lost motion connections adapted to open either of said pair of brake valves upon a predetermined contact operating movement of said motorl means, a pair of exahaust ports one in each of said brake valves, said exhaust ports being open and closed upon a predetermined movement of said crank mechanism, and a pair of pressure responsive exhaust valves for relieving the pressure in said brake mechanism through said exhaust ports in response to a predetermined pressure condition in said brake supply conduits.

9. In an electric switching device the combination of a fluid motor comprising a cylinder and a piston operatively arranged therein, a iluid operated brake mechanism for arresting the stroke `of said piston at either end of said cylinder, a source of fluid under pressure, a pair of valve means for admitting fluid under pressure from said source selectively to either end of said cylinder, motor fluid supply conduits and brake fluid supply conduits for dividing the flow of iluid under pressure issuing from each of said pair of valve means into a motor supply ilow and a separate brake supply flow, a pair of brake valves one in each of said brake supply conduits, a crank mechanism opearted by said iluid motor for operating Said pair f brake valves, said crank I0 'mechanism' comprising Aa pair.v of lost motion connections adapted to' open either of said pair of brake valves upon a predetermined-contact operating movement of said motor means, and a pair of pressure-responsive exhaust valves for relieving vthe pressure in said brake mechanism alternatingly through one ofsaid brake valves after cessation of the relative movement of said piston and cylinder, said pairof brake valves and said pair of pressure. responsive exhaust valves being combined in a single self-sustained structural unit.

10. In an electric switching device the combination of a fluid motor 'comprising a cylinder and a piston operatively arrangedtherein, a fluid operated brake mechanism for arresting the stroke of said piston at either end of said cylinder, a source of fluid under pressure, a pair of valve means for admitting fluid under pressure to said source selectively to either end of said cylinder, motor fluid supply conduits and brake iluidsupply conduits for dividing the ilow of fluid under pressure issuing from each of said pair of valve means into a motor supply ilow and a separate brake supply ow, a pair vol brake valves one in each of said brake supply conduits, a crank mechanism operated by said fluid motor for operating said pair of brake valves, said crank mechanism comprising a pair of lost motion connections adapted to open either of said pair of brake valves upon a predetermined contact operating movement of said motor means, and a pair of pressure responsive exhaust valves for relieving the pressure in said brake mechanism alternatingly through one of said'brake valves after cessation of the relative movement of said piston and cylinder and comprising a cylinder, al pair of axially aligned relatively movable pistons arranged within said' cylinder, a common resilient means mounted between and axially aligned with said pistons for biasing said pistons to valve open position, and means for actuating said pistons against the biasing action of said resilient means to valve closed position, lone of said pistons having a larger diameter than the other so as to actuate the other of said pistons to valve open 4position when both pistons are actuated simultaneously by said actuating means.

11. An electric circuit interrupter comprising a pair of relatively movable cooperating arcing contacts, a pair of relatively movable cooperating disconnect contacts, means for relatively moving said arcing contacts, iluid operated motor means for relatively moving said disconnect contacts, a uid operated brake mechanism of the frictional type for arresting the relative movement of said disconnect contacts, a main source of fluid under pressure, a first auxiliary source of fluid under pressure connected to said main source for providing a blast of fluid adjacent said arcing contacts upon separation thereof, a second auxiliary source of fluid under pressure connected to said main source independently of said ilrst auxiliary source, a pressure responsive valve providing for unidirectional fluid flow from said main source to said second auxiliary source and precluding substantial reverse flow of fluid under pressure, and means for supplying fluid under pressure from said second auxiliary source at substantially the same pressure to both said motor means and said brake mechanism.

12. An electric circuit interrupter comprising a -pair of relatively movable cooperating arcing contacts, a pair of relatively movable cooperating disconnect contacts, means for relatively moving said arcing contacts, uid -operatedrnotor means for relatively moving said disconnect contacts, a iluid operated brake mechanism of the frictional type for arresting the relative movement of said disconnect contacts, a main source of fluid under pressure., a rst auxiliary source of fluid under pressure connected to said main source for providing a blast of uid adjacent said arcing contacts upon separation thereof, a second auxiliary source of fluid under pressure connectied to said main source independently .of said rst auxiliary source, a pressure responsive valve providing for unidirectional uid flow from said main source to :said second auxiliary vsource and precluding substantial reverse 11o-W Vof Iluid under pressure, means for supplying uid under pressure from said second auxiliary source at substantially the same pressure to both said motor means and said brake mechanism, and valve means for relieving the pressure in said brake mechanism after arresting the movement of said disconnect contacts.

13. electric circuit interrupter of the fluid blast type comprising a pair of cooperating :arcing contacts, a second pair of relatively movable cooperating contacts in series with said Lrst mentioned contacts, a main source of fluid under pressure, a first auxiliary source of fluid under pressure connected to said main source, means for establishing an arc extinguishing duid blast from said first auxiliary lsource adjacent said arcing contacts, a second auxiliary source of fluid under pressure connected to said main source in dependently of `said ii-rst auxiliary source, a valve interconnecting said lauxiliary vsources providing for substantially unidirectional dow of uid from said rst `auxiliary source to said second auxiliary source and precluding substantial reverse .flow fof fluid upon decrease in pressure of said rst auxiliary source, a fluid operated motor for relatively moving :said second pair of contacts, a uid operated brake mechanism yof the frictional type for arresting the relative movement of said 'second pair of contacts, and means for supplying iaO nuid under pressure from said second auxiliary source at substantially the same pressure to both said .iluid operated motor and said brake mechanism.

14. An electric circuit interrupter comprising a pair of relatively movable cooperating arcing lcontacts, a pair of relatively movable cooperating disconnect contacts, means for actuating said arcing contacts, fluid operated motor means for relatively moving said disconnect contacts, .a fluid operated brake mechanism of the frictional type for arresting relative movement of said disconnect contacts, a main source of iluid under pressure, a rst auxiliary source of fluid under pressure connected to said main source for providing a blast of fluid adjacent said arcing contacts upon separation thereof, a second auxiliary source of fluid under pressure, a distribution system for uid under pressure supplied from said main source through a reducing valve to said second auxiliary source, said distribution system providing for unidirectional oW from said distribution system to said second auxiliary source and precluding a substantial reverse ow of uid under pressure, and means for supplying fluid under pressure from said second auxiliary source to both said motor means and said brake mechanism.

IRA W. PATERSON. JOHN F. CHIPMAN.

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

UNITED STATES PATENTS Number Name Date 2,248,593 Thumim July 8, 1941 2,316,944 Ernst Apr. 20, 1943 2,320,763 Trautman June 1, 1943 2,420,441 Paterson May 31, 1947 2,430,128 Lerstrup Nov. 4, 1947 2,437,086 Frank et al Mar. 2, 1948