US2703828A - Circuit interrupter - Google Patents

Description

March 8, 1955 G, B, CUSH|NG 2,703,828

CIRCUIT INTERRUPTER Filed Jan. 25. 1950 2 Sheets-Sheet l Figi.

Figi. 3

WITNESSES: n INVENTOR I a`r George B. Cushing.

March 8, 1955 c. B. cUsHlNG l CIRCUIT INTERRUPTER 2 Sheets-Sheet 2 Filed Jan.v 25. 195o lNvENToR George B Cushlng BY' d 7z//Jw ATToRN 8 WITNESSES:

United States Patent CIRCUH INTERRUPTER George B. Cushing, Turtle Creek, Pa., assignor to Westmghouse Electric Corporation, East Pittsburgh, Pa., a y corporation of Pennsylvania Application January 25, 1950, Serial No. 140,491 21 Claims. (Cl. ZOU- 34) This invention relates to circuit interrupters in general,

and, more particularly, to contact operating structures therefor. A general object of my invention is to provide an improved high speed type of circuit interrupter in which improved means are utilized to provide the necessary contact pressure in the closed circuit position, yet providing extremely rapid opening separating motion or' the contact structure during the opening operation.

Another object is to provide an improved circuit interrupter utilizing improved movable dashpot means for providing the contact pressure in the closed circuit position and enabling extremely early separating motion between the contact structure to be achieved during the opening operation of the interrupter, without any time delay whatsoever.

Further objects and advantages will readily become apparent upon reading the following speciication taken in conjunction with the drawings, in which:

Figure 1 is a side elevational view, partially in vertical section, of an improved circuit interrupter embodying my invention and shown in the closed circuit position;

Fig'. 2 is an enlarged vertical sectional view through the left-hand arc extinguishing unit of Fig. l, the contact structure being shown in the closed circuit position;

Fig. 3 is a fragmentary vertical sectional view similar to that of Fig. 2, but indicating the disposition of the parts at the beginning of the opening operation;

' Fig. 4 is a fragmentary vertical sectional view, similar to that of Fig.' 3, but showing the disposition of the contact parts at the end'of the opening operation;

Fig. 5 is an enlarged vertical sectional view through my improved movable dashpot means;

Fig. 6 is an enlarged fragmentary view taken along the line VI-VI of Fig. 2;

Fig. 7 is an enlarged fragmentary view, in vertical section, of a modified type movable dashpot means;

Fig.. 8 is a view taken along the line VII--VIII of Fig. 7, looking in the direction of the arrows; and

Fig. 9 1s a diagrammatic view, in vertical section, of a modified type circuit interrupter incorporating my invention, the contact structure being shown in the closed position.

Referring to the drawings, and more particularly to Fig. l thereof, the reference numeral 1 designates a tank filled to the level 2 with a suitable arc extinguishing liquid 3, in this instance, circuit breaker oil. Depending from the cover 4 of the tank 1 is a pair of terminal bushings 5, 6, to the lower ends of which are appended identical arc extinguishing units, generally designated by the reference character 7.

The arc extinguishing units 7 are electrically interconnected in the closed circuit position of the interrupter as shown in Fig. l, by a conducting cross-bar or conducting movable member 8 actuated vertically in a reciprocal manner by an insulating lift rod 9. The lift rod 9 is connected to a suitable operating mechanism, not shown, which forms no part of my invention.

Referring to Fig. 2, which more clearly shows the internal construction of the arc extinguishing unit 7, it will be noted that I have provided suitable contact structure, generally designated by the reference character 10, and including a pressure-generating contact 11, an intermediate contact 12 and a lower movable interrupting contact 13. The movable interrupting contact 13 is carried at the extremity of the cross-bar or movable member 8.

The pressure-generating contact 11 is pivotally connected, as at 14, to a link.15, the latter being pivoted at a stationary pivot 16. The pivot pin 16 is journalled f"ice in the upper casting wall 17 of the pressure-generating chamber 18. The right-hand end of the pressure-generating contact 11 is bit'urcated, as shown, and forms two legs 19. The pin i4 passes through both legs 19.

The right-hand ends of the legs 19 of the pressuregenerating contact 11 are pivotally connected to a pair of bosses 20, the latter jutnng outwardly from a piston 21. The piston 21 slides within a piston chamber 22, tormlng, collectively with the piston 21, a movable dashpot means, generally designated by the reference character 23. rl`he piston chamber 22 and the piston member 2l constitute a pair of relatively movable parts.

The upper end 24 of the movable dashpot means 23 has venting means 25 associated therewith including apertures or huid-inlet means 26 provided in the upper end wall 27 of the piston chamber 22. The apertures 26 are in communication with additional apertures 28 constituting a part of the venting means 25.

l provide valve means, generally designated by the reference character 29, associated with the venting means 25 and constituting a valve plate 30. l provide biasing means '31, in this instance including a compression spring, which biases the valve means 29 to its upper closed position over the apertures 26. rl`he compression spring 31 seats at its upper end upon the valve plate 30, and seats at its lower end upon a spider stop 32 integrally formed with the piston chamber 22. The movable piston chamber 22 is threadedly connected, as at 34 to an insulating operating member 35.

The insulating operating rod or member 35 is biased downwardly by an accelerating spring 36, the upper end of which seats against the lower plate 37 of the unit 7. The lower end ot the compression spring 36 seats against a cap 33 integrally formed with the side operating rod 35. lt will, therefore, be observed that the side operating rod 35 is biased downwardly into abutting engagement with the cross-bar 8, and is moved upwardly thereby duringthe closing operation in opposition to the biasing action exerted by the compression spring 36.

in the closed circuit position of the interrupter as shown by the full lines in Fig. l and also in Fig. 2, the electrical circuit therethrough includes terminal stud 39, clamp 40, top dome casting 41, flexible strap 42, pressure-generating contact 11, intermediate contact 12, lower movable interrupting contact 13 and through the conducting cross-bar 8 to the right-hand unit 7. The electrical circuit extends through the right-hand unit 7 in a similar manner to its passage through the left-hand uint 7.

During the opening operation, suitable mechanism, not shown, but which may be operated manually and which is responsive to overload conditions existing in the controlled circuit, operates to cause downward opening movement of the insualting lift rod 9. The downward opening motion of the litt rod 9 carries the crossbar 8 and lower movable interrupting contacts 13 therewith. The downward motion of cross-bar 8 permits the accelerating spring 36 to force the operating rod 35- downwardly with the cross-bar 8.

An important feature ol` my invention is the fact that during the initial portion of the opening operation the bosses 20, piston 21 and pressure contact 11 move immediately with the operating rod 35. In previous constructions, the contact biasing spring 43 was permitted to expand during the initial portion of the opening operation so that no opening movement whatsoever of the pressure-generating contact 11 took place until the wiping motion was taken up. In other words, in prior constructions, contact pressure between the several contacts was brought about by a compression spring 43 and a lost-motion connection between bosses 20 and the operating rod 35, so that at the end of the closing stroke theoperating rod 35 could move upwardly relative to the bosses 20 and pressure contact 11, thereby compressing the contact pressure spring 43 to bring about the desired contact pressure between the several contacts 1li, 12 and 13.

During the initial portion of the opening operation, in such prior art structures, the lost-motion between the bosses 20 and operating rod 35 would have to be taken up before the operating rod 35 caused downward motion of the legs 19 and hence clockwise rotative opening motion of the pressure contact 11 away from the intermediate contact 12 to draw a pressure arc therebetween. Consequently,v the dissipation of the lost-motion connection between the pressure-generating contact 11 and the side operating rod 35 caused a delay in the separation of the contacts 11,- 12, and this delay was undesirable for high speed operation. In my invention I eliminate any such delay, or time necessary to take up lost-motion between the legs 19 and the operating rod 35, by trapping oil within the upper end 24 of the movable dashpot means 23. This slug of oil trapped at the upper end of the movable dashpot means 23 causes the spring 43 to remain compressed at the initial portion of the opening operation so that the pressure contact 11 immediately separates from the intermediate contact 12 at the tirst instant of downward opening motion of the side operating rod 35, as permitted by downward opening motion of the cross-bar 8.

Fig. 3 shows the relative position of the parts at the end of the initial portion of the opening operation when a shoulder 44 on the piston chamber 22 has struck a stop 45 formed by the casting 41. It will be noted that at this intermediate point in the opening operation still the slug of oil disposed in the region 46 above the piston 21 is trapped therein, causing the piston 2 1 to immediately move downwardly with the initial downward motion of the operating rod 35. A pressure-generating arc 47 is drawn between the pressuregenerating contact 11 and the intermediate contact 12 within the pressure-generating chamber 18.

Fig. 4 shows the conditionlater at the end of the opening operation when the slug of oil has had a chance to leak past the piston21 to the lower end of the piston chamber 22. It will ybe observed that the distance D in Fig. 4 is less than the distance D1 in Fig. 3 as a result of an extension of the contact compression spring 43 relative to its position in Figs. 2 and 3. As shown, the piston 21 moves upwardly to the stop provided by a spider 32.

The interrupting structure which utilizes the pressure generated at the pressure-generating arc 47 to create an oil ow to effect extinction of the interrupting arc, not shown, which is established between the intermediate and interrupting contacts 12, 13 forms no part of rnyl invention. Reference may be had for the details of the plate structure to U. S. Patent 2,467,760, issued April 19, 1949, to Leon R. Ludwig, Benjamin P. Baker and Winthrop M. Leeds and assigned to the assignee of the instant application. It suces to state that in the interrupting chamber 48 there are three types of plates used, an inlet plate 49 which permits the entrance of oil into the interrupting passage 48 from the vertical flow passages 50 leading to' the pressure-generating chamber 18'. The oil passing through pairs of inlet passages 51 passes through orifices 52 provided in orifice plates 5'3 and exhausts out of the unit 7 through laterally eX'- fending vent passages 54 formed by the lateral separation of two half plates 55, 5 6. For further details, reference may be had to' the foregoing patent, but as mentioned previously, such details form no part of my invention. it merely' being necessary' to know that I form two serially related arcs, a pressure-generating arc 47 between the contacts 11. 12 and an interrupting arc between the contacts 12, 13, and that oil is driven by the' pressure are 47 downwardly away from the pressure-generating chamber 18 through the two vertical flow passages 50 into the interrupting passage 48, against the interrupting arc, not shown, and out of the unit 7 by means of the vent passages 54.

In the fully open circuit position, as shown by the dotted lines 57 of Fig. 1, it will be observed that the cross-bar 8 withdraws the contacts 13 completely out of the units 7, and that also separation takes place between the cross-bar 8 and the caps 38 at the lower ends of the side operating rods 35.

During the closing operation the litt rod 9 moves the cross-bar 8 and contacts 13 upwardly. The contacts 13 enter the units 7, andthe cross-bar 8 strikes the caps 38 of operating rods 35 in abutting engagement to carry the latter upwardly therewith. At this time the piston 21 is at the upper end of the movable dashpot means 23 against the stop spider 32, as shown in Fig. 4 the contact compression spring 43 being extended.

The lower movable interrupting contact 13 strikes the intermediate contact 12 before the pressure-generating contact 11 strikes the intermediate contact'l2, raising the intermediate contact 12 slightly upwardly against the biasing actionof the compression spring 58. Further upward motion of the cross-bar 8, movable contact 13 and operating rod 35 takes place compressing the contact compression spring 43 and drawing oil within the chamber 46 past the valve means 29.

During this final portionof the closing operation, as mentioned, the compression spring 43 is compressed thereby providing the requisite contact presstir'e between the several contacts 11, 12 and 13 so that upon halting of the upward closing motion of the cross-bar 8 the the contact structure 10 and the movable dashpo't means 23 assume the position as shown in Figs. 2', 5 and 6. 'j'

From the foregoing description of an operation of my invention, it will be apparent that I have provided improved means for immediately causing separating ino'- tion between the contacts l11, 12 at the start of the down-l ward motion of the operatingl rod 35,` even before eittension of the contact pressure springv 43 oceiirs. This establishment of the pressure-generating arc 47 inA my improved interrupter before that of the prior rt'- structures lowers the interrupting time of the interrpter since the pressure-generating arc 47 is thereby established earlier than the pressure-'generating arc of the prior art structures. Furthermore,- I provide a Contact pressure spring 43 which functions in the same manner as in' prior art structures to provide the requisite contact pressare between the several contacts in the closed position. However, unlike the prior art structures, my invention operates to avoid any time delay, or the take up of lost-motion betweenthe operating rod 35 and pressuregenerating contact 11 at the beginning of the opening` operation.l

As a result, my inventionhas all the advantages of the prior art structures in providing a contact compression spring 43, which is compressed during the final portion of the closing operation, but my invention does not have the disadvantage of necessitating the taking up of lost-motion between the pressure contact 11vand the side operating rod 3510 delay the formation of the pressure-generating arc 47. With my vinvention immediate establishment of the pressure arc 47 results upon initial downward motion of the operating Arod 3S by the use of the movable dashpot means 23A which I have provided. The result is a tast high speed interr'upter in which the pressure and interrupting arcs are. established immediately upon initial downward motion of the cross-bar 8 andoperatingrod 35.

In certain instances, it may be desirable to interchange the pressure-generating and interruptingarcs, so that instead of the` pressure-generating arc 47 being established at the contacts 11, 12, it may be established between the contacts 12, I3. In such event, the interrupting arc might be established between the contacts 11, 12', the order merely being inverted. Naturally, m invention .is applicable to su'ch an arrangement in w ich it ijs desirable to establish the interrupting arc at the top of the unit 7 between the contacts 11, 12 rather than at the lower end of the unit 7, as shown in the foregoing embodiment of. my; invention.

Figs. 7 and 8' collectively show a modified form of movable dashpot means, generallyl designated by thereference character 59 and including a piston 60 and a pis'- ton chamber 61. The operating rod 35 is threadedly connected, as at 34, to lthe piston 60. The legs 19 of the bifurcated pressure-generatingContact 11 are pivotally mounted upon vbosses 62 integrally formed with the piston chamberol. A Contact ycompression spring 63 isy disposed at' the upper end of the piston chamber61,fasA showman'd biases the piston 60 downwardly. I provide valve means, generally designated by'thereference character 64, controlling the eiiit of liquid, in this instance', oil, out of the region 65 above the piston' 60.

The valve means 46 4 includes a ball v'alv'e 66 closing an aperture 67 provided centrally throngh thepis'tojn 60 and communicating with a passage 68 drilled throiigti the' extension 69 of the piston 6p. A second passage 1411's formed Within the extension 71. the latte'= b'eig thede'd to the upper end of the operating rod 35.

It willA Be noted that the piston chamber 61 is substam s, tiallyV completely enclosed, there being no necessity for 'cil .entering or: leaving the piston chamber 61- sine the diameter of the extension 69 is the same as the diameter of the extension 71 and operating rod 35. c

The operation of this form of my invention will now be described. The modified movable dashpot means 59 1s shown in Figs. 7 and 8 in the closed circuit position of the interrupter (see Fig. 2) with the contact compression spring 63 providing the contact pressure between the several contacts 11, 12 and 13. Oil completely lls the dashpot means 59, and the ball valve 66 closes the aperture 67 as shown.

During the opening operation of the interrupter, at the iirst instant of downward opening motion of the operating rod 35, as permitted by lowering of the contact member 8, the entire movable dashpot means 59 immediately moves downwardly with the operating rod 35. This results because of the oil trapped within the region 72 at the lower end of the piston chamber 61. As a result, the initial downward opening motion of the operating rod 35 causes instant downward motion of the piston chamber 61 immediately causing opening rotative motion of the pressure-generating Contact 11. Consequently, a pressure-generating arc 47 is immediately established. lnterruption follows in a manner previously described and leakage of oil around the periphery of the piston 60 permits the contact compression spring 63 to force the piston chamber 61 upwardly relative to the operating rod, 35, which at this time has been halted, and the result is slight closing motion of the pressure-generating contact 1I t0 the distance D, as shown in Fig. 4. The interrupter now is in the fully open circuit disconnect position, as shown by the dotted lines 57 of Fig. l.

During the closing operation, the upward closing movement of the contact member 8 picks up the operating rod 35 in a manner previously described and causes reclosure of the contacts 11, 12 and 13 with the piston 60 freely moving upwardly within the piston chamber 61 by the opening of the valve means 64 and a consequent rapid passing of oil through the passage 68, aperture 67 and through the second passage 70 to the region 72 within the piston chamber 61. pression spring 63 is easily compressed with the free passage of oil past the valve means 64 and the breaker is in the closed position, with the requisite contact pressure being provided between the several contacts 11, 12 and 13 bythe compression of the contact compression spring The foregoing modification, as illustrated in Figs. 7 and 8, shows how I have interchanged the parts so that instead of the pressure-generating contact 11 being connected to the piston 21, it is connected to the piston chamber 61. Instead of the operating rod 35 being connected to a piston chamber 22, it is connected to the piston 6i). A complete interchange of the dashpot parts relative to the pressure contact 1l and the operating rod 35 has consequently been made in the embodiment of my invention shown in Figs. 7 and 8.

Fig. 9 shows a modified type of arc extinguishing unit generally designated by the reference character 74. In this embodiment, the pressure-generating arc is established between a lower movable pressure contact 75 and a rigidly stationary intermediate contact 76. The interrupting arc is established between the rigidly stationary intermediate contact 76 and an upper movable interrupting contact 77. The interrupting chamber 48 is vented by means of the plurality of vents 79 extending out of the unit 74, and the passage of oil during an interrupting operation is as indicated by the arrows of Fig. 9.

The side operating rod 35 may be connected by a movable dashpot means 23 to a rotatable lever S0, the lefthand end of which is pivotali'y connected, as at 81, to an actuating lever 82. The actuating lever S2 is pivotally connected, as at 83, to the upper end of the movable interrupting contact 77 The left-hand end of the actuating lever 82, as viewed in Fig. 9, is connected to a roller 84 which slides in a stationary raceway 85. The lever 80 is pivotally connected at 86 to a stationary pivot as provided by a stationary bracket 37.

The lower movable pressure-generating contact 75 is pivotally connected, as at 88, to an actuating arm 89, the right-hand end of which is pivotally connected, as at 90, to a link 91, the upper end of which is pivotallyconnected at a stationary pivot 92. The actuating arm 89 is pivotally connected, as at 62, to a movable dashpot means 59.

As a result, the contact com- The operating rod 35 is biased downwardly, as in Fig. 2, by an accelerating compression spring 36. ln the closed circuit position, as shown in Fig. 9, the contact pressure between the contacts 76 and 75 is provided by the contact compression spring 63 within the movable dashpot means 59. The contact pressure between the contacts 76, 77

is provided by the contact compression spring 43 dis-l intermediate contact 76 to draw an interrupting arc, not.

shown. At the same time, the lower movable pressure generating contact 75 moves downwardly away from the rigidly mounted intermediate contact 76 to establish a pressure-generating arc 47. Liquid ow takes place as indicated by the arrows of Fig. 9, and extinction of the interrupting arc takes place. Subsequently, the contact member 8 separates from the conducting cap 94 to provide a disconnect gap into the circuit. Following extinction of the arc, the contact compression springs 43, 63 ot' the dashpots 23, 59, respectively, extend to slightly shorten the pressure-generating and interrupting gaps in a manner previously described.

During the closing operation, the contact member 8 moves upwardly, picks up the conducting cap 94 and hence the operating rod 35, to move the contact structure to the closed position, the contact pressure being provided by the Contact compression springs 43, 63 of the movable dashpot means 23, 59, respectively.

This embodiment, as shown in Fig. 9, describes the flexibility and interchangeability of the movable dashpot means 23, 59. It shows that wherever a contact compression is desired with immediate opening motion.

of the contact with the initial opening movement of the contact operating mechanism, in such a case my im-l slight clearance, the piston chamber and the piston con-` stituting a pair of relatively movable parts, means at all time connecting one of the contacts with one of the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the other of said parts, and valve means associated with the movable dashpot means to trap liquid within the movable piston chamber so that during the initial portion of the opening operation the movable piston chamber and the piston move together as a unit in the same direction.

2. A circuit interrupter including a pressure-generating contact, an intermediate contact and a movable in` terrupting contact, the pressure-generating contact and the intermediate contact being cooperable to establish a pressure-generating arc, the intermediate contact and the movable interrupting contact being cooperable to establish a serially related interrupting arc, a movable member which carries the movable interrupting contact, an operating member making abutting engagement with the movable member at least near the end of the closing operation, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting the pressure-generating contact with,

one of the parts, means connecting the operating mem.-

ber with the other of said parts, and valve means associated with the movable dashpot means to trap liquid within the movable piston chamber so that during the initial portion of the opening operation the movable` piston chamber and the piston move together as a unit in the same direction.

.3.; A. circuitvtinterrupter.including :a pressurevgeneratingcontact,J an -intermediate contact and iav movable. m-

terrupting contact, the pressureggenerating .contactand thel lintermediate .contact .being cooperable to )esablish a pressuregeneratingfarc, the .intermediate contact and the movable v.interrupting contactfbeing cooperable to establishna :serially related interrupting arc, .a movable member which carries the -movable interrupting contact, an operatingvmember.;making abutting engagementwith the movablemember :at leastnearthe end-of the closing .operation, movable dashpot Ymeans including. av movable piston chamber and a piston movable therein with only slight .clearancqthe piston chamber and -the piston constituting ,a pair of yrelatively movable parts, .means at alltimesonnecting the .pressure-generating contact with oneof the parts, lmeans connecting the operat'ingmemberl with the other of said parts, means biasing the piston toward one .end of the piston chamber, huid-.inlet means-for .thepiston chamber :adjacent said one end of the piston chamber, `vand valve means associated with the movable dashpotmeansto trap liquid Within the movable ,pistonchamber so that during theinitial portion lof the .opening operation the-.movable .piston chamber and.

the .pistonmove together asaunit inthe same direction.

'4. A circuit interrupter including a fpressure-'generating contact, an intermediate contact and a movable interrupting contact, the pressure-generating contact and the intermediate contact being cooperable to establish a pressure-generating arc, the intermediate contact and the .movable interrupting contact being cooperable to establish a serially related. interrupting arc, a movable member which carries the movable interrupting contact, an-operating membermaking abutting engagement with the movable member at least near the end of the closing operation, .movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the Vpiston constituting a pair of relatively movable parts, means interconnecting at .all times the pressurefgenerating contact with one of the parts, means Vconnecting the operating member with the other of said parts, means biasing the piston toward one .end of the piston chamber, `lluidinlet means for the piston chamber vadjacent said `one end of the piston chamber, .and valvemeans controlling sai'duid-inlet means.

5. A circuit @interrupter Yincluding .contact structure comprising a pair of relativelymovable cooperable contacts, movable dashpot means including a movablepiston .chamber and a piston :movable .therein -with only slight clearance, means at all times connecting 'one .of the contacts `with .the `movable piston chamber, an operating member Vfor .opening and closing the contact structure. and means at all Atimes connecting the operating member with .the piston.

k6. A circuit interrupter including contact structure comprising apair of relatively movable cooperablecontacts, movable dashpotmeans includinga movablepiston vchamber and a piston movable therein with k only slight clearance. .means at all times connecting one .of the 'contacts with the movable piston chamber, an `operating .member Afor opening andclosing the contact structure, means at all times connecting theoperating member with the piston, and means biasing the piston toward one end ofthe pistonchamber. '7. A circuit interrupter including a pressure-generating contact, an intermediate contact and a movable 'interrupting contact, the pressure-generating contact and the Lintermediate contact being .cooperable to establish a pressure-generating.arc,.the intermediate contact and the movablesinterrupting ,contact being cooperable to establish aserially.related'interrupting arc, a movable membei'. Which.,carries the `.movable interrupting contact, an operating member making abutting engagement with the movable member-at least near the end of thetclosing operation, movable 'dashpot .means including amovable piston lchamber andV a `piston movable therein with only slight-"clearance, means .at .all `times .connecting vthe pressurefgenerating contact with vthe .movable pistonA chamber, `and means at all times connecting the 'operating member with .the ,pi ston.

l8'. A circuit .interrnpter including :contact structure comprising a pair of .relativelymovable cooperable contacts, movable dashpotmeans including a .movable pis.- ton' vchamber 'and a piston movable therein, .the-,piston necting the operating memberv with the other yof .said

parts, vmeans biasingone of saidipairof relatively movableuparts ina-direction tending to close the contacts under pressure, and one-way acting valve means .hlndermg motion of thefpiston within the piston chamber Vin theopposite direction.

A circuit interrupter including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means including `amovable piston chamber .and .a -piston movable therein with only slight clearance, the piston chamberand thepiston constituting apair of relativelymovable parts, `means at all times connecting one `of Athe ,contacts with one of .the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the otherof said parts, a spring biasing the .piston toward one end of .the piston chamber, and 'valve means associated with the movable das'hpot means to trap liquid within the movable vpiston chamber so that .during the initialportionio'f the opening operationthe movable piston chamber and .the pistonmove together as a unit in the same direction.

.10. A circuit interrupter including contact .structure comprising a pair .of relativelymovable cooperable contacts, movable dashpot meansincluding a movable piston chamber and a--piston movable therein with only slight clearance, the piston chamber and the .pistonconstituting a pair of vrelatively movable parts,.means at allztimes connecting .one of the contacts with one of theparts, an operating member for opening and closing thecontact structure, meansmovably connecting theoperating member with the other of said parts, a .spring biasing the piston toward one endof the piston chamber, andoneway acting valveineans permitting relatively free motion of the piston toward one endof the piston chamber but hindering. motionot the. piston toward the opposite `end of thepiston chamber.

1l. A circuit .interrupter .including :Contact vstructure comprising va pair ofrelatively ,movable cooperable-contacts, movable dashpot means includinga movablefpiston chamber and a piston movable therein withl only slight clearance, the piston chamber and the piston constituting a pair of relatively movableparts, means at all times connecting .one of the contacts with one of the parts, lan operating member for opening and closing-the contact structure, means .movably connecting the operating member with the other of said parts., a spring biasing the piston .towardone end of the piston chamber, vfluid-.inlet meansfor'thepiston chamber disposed adjacent said end of. the piston chamber, and valve means associated with the movable dashpot means to trap liquid Within the movable piston chamber so that during the. initialportion ofthe .opening operation the movable piston chamber and the piston move together as a unit inthe same direction.

V12. .A circuit interrupter including contact structure comprising a pair of relatively movable cooperable .con-V tacts,.movable dashpot means including a movable piston chamber and a piston movable therein with only vslight clearance, the piston chamber and the piston constituting a pair of relatively movable parts,.means at .alltimcs connecting .one of the .contacts with one of the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the other of said parts, a spring biasing the piston 'toward one end of the piston chamber, fluid-inlet means for the piston chamber disposed adjacent said end of the piston chamber, and one-Way-acting valve means controlling said fluid-inlet means.

13. A circuit interrupter including contact structure comprisinga `pair of relatively movable cooperable contacts, movable dashpot means including-amovable piston.

connectingone ot the contacts with one oi` the parts, au`

operating member for 'opening and closing the contact structure,.meansmovably connecting the operating .mem-..

berv with the other of said parts, ,fluid-.inlet means.: for

the piston chamber disposed adjacent one end fof-:the

piston chamber, and valve means associated with the movable dashpot means to trap liquid within the movable piston chamber so that during the initial portion of the opening operation the movable piston chamber and the piston move together as a unit in the same direction.

14. A circuit interrupter including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means includingI a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting one of the contacts with one of the parts, an

operating member for opening and closing the contact` structure, means movably connecting the operating member with the other of said parts, fluid-inlet means for the piston chamber disposed adjacent one end of the piston chamber, and one-way-acting valve means controlling said uid-inlet means.

l5. A circuit interruptor including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting one of the contacts with one of the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the other of said parts, a spring biasing the piston toward one end of the piston chamber, iiuid-inlet means for the piston chamber disposed adjacent said end of the piston chamber, one-way-acting valve means controlling said fluid-inlet means, and means biasing the one-Way-acting valve means to the closed position over the fluid-inlet means, and valve means associated with the movable dashpot means to trap liquid within the movable piston chamber so that during the initial portion of the opening operation the movable piston chamber and the piston move together as a unit in the same direction.

16. A circuit interrupter including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting one of the contacts with one of the parts, an operating member ttor opening and closing the contact structure, means movably connecting the operating member with the other of said parts, spring means biasing one of said pair of relatively movable parts with respect to the other of said pair of relatively movable parts, means for actuating the operating member to cause closure of the contact structure, said spring means tending in the closed circuit position of the interruptor to maintain the contacts closed under spring pressure, and valve means associated with the movable dashpot means to trap liquid Within the movable piston chamber so that during the initial portion of the opening operation the movable piston chamber and the piston move together as a unit in the same direction.

17. A circuit interruptor including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting one of the contacts with one of the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the other of said parts, spring means biasing one of said pair of relatively movable parts with respect to the other of said pair of relatively movable parts, means for actuating the operating member to cause closure of the contact structure, said spring means tending in the closed circuit position of the interruptor to maintain the contacts closed under spring pressure, fluid-inlet means for the piston chamber disposed adjacent one end of the piston chamber, and valve means associated with the movable dashpot means to trap liquid within the movable piston chamber so that during the initial portion of the opening operation the movable piston chamber and the piston move together as a unit in the same direction.

18. A circuit interrupter including contact structure comprising a pair of relatively movable cooperable contacts, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting one of the contacts with one or the parts, an operating member for opening and closing the contact structure, means movably connecting the operating member with the other of said parts, and the piston and piston chamber moving together during the initial portion of the opening operation to separate the contact structure.

19. A circuit interrupter including a pressure-generating contact, an intermediate contact and a movable interrupting contact, the pressure-generating contact and the intermediate contact being cooperable to establish a pressure-generating arc, the intermediate contact and the movable interrupting contact being cooperable to establish a serially related interrupting arc, a movable member which carries the movable interrupting contact, an operating member making abutting engagement with the movable member at least near the end of the closing operation, movable dashpot means including a movable piston t chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting the pressure-generating contact with one of the parts, means connecting the operating member with the other of said parts, and the piston and piston chamber moving together during the initial portion of the opening operation to separate the pressure-generating and intermediate contacts.

20. A circuit interrupter including a pressure-generating contact, an intermediate contact and a movable interrupting contact, the pressure-generating contact and the intermediate contact being cooperable to establish a pressuregenerating arc, the intermediate contact and the movable interrupting contact being cooperable to establish a serially related interrupting arc, a movable member which carries the movable interrupting contact, an operating member making abutting engagement with the movable member at least near the end of the closing operation, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means at all times connecting the pressure-generating contact with one of the parts, means connecting the operating member with the other of said parts, means biasing the piston toward one end of the piston chamber, fluid-inlet means for the piston chamber adjacent said one end of the piston chamber, and the piston and piston chamber moving together during the initial portion of the opening operation to separate the pressure-generating and intermediate contacts.

21. A circuit interrupter including a pressure-generating contact, an intermediate contact and a movable interrupting contact, the pressure-generating contact and the intermediate contact being cooperable to establish a pressure-generating arc, the intermediate contact and the movable interrupting contact being cooperable to establish a serially related interrupting arc, a movable member which carries the movable interrupting contact, an operating member making abutting engagement with the movable member at least near the end of the closing operation, movable dashpot means including a movable piston chamber and a piston movable therein with only slight clearance, the piston chamber and the piston constituting a pair of relatively movable parts, means interconnecting at all times the pressure-generating contact with one of the parts, means connecting the operating member with the other of said parts, means biasing the piston toward one end of the piston chamber, fluid-inlet means for the piston chamber adjacent said one end of the piston chamber, valve means controlling said fluid-inlet means, and the piston and piston chamber moving together during the initial portion of the opening operation to separate the pressuregenerating and intermediate contacts.

References Cited in the file of this patent UNITED STATES PATENTS 2,422,569 Leeds June 17, 1947 2,530,952 Fry Nov. 2l, 1950 FOREIGN PATENTS 486,050 Great Britain May 30, 1938 640,009 Germany Dec. 2l, 1936

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