US2447950A - Circuit interrupter - Google Patents

Description

? Aug. 24, 1948.

W. M. LEEDS ET AL CIRCUIT INTERRUPTER Filed April 3, 1945 3 Sheets-Sheet 1 M Z w d m 1 INVENTORS Winthrop ML eeds and M m. m v5 m w 7//////// mV///V/ w 0 W M J4 es /1. Cummzny. a/ 6K ATTORNEY Patented Aug. 24, 1948 UNITED STATES PATENT OFFICE CIRCUIT INTERRUPTER Winthrop M. Leeds, Forest Hills, and James M.

Cumming, Turtle Creek, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 3, 1945, Serial No. 586,354

15 Claims. 1 (Cl. 200150) This invention relates to circuit lnterrupters in general, and more particularly to circuit interrupters of the liquid-break type.

In a patent application filed February 1, 1945, Serial No. 575,589 by James M. Cumming and assigned to the assignee of the instant application, here is disclosed and claimed the concept of utilizing a difierential piston spring-biased in the operative direction, and of using a serially related arc to assist the spring means in forcing the differential piston in said direction. Our invention is concerned with various improvements relating to this type of structure.

A more specific object of this invention is to provide an improved circuit interrupter in which piston means carry an orifice through which is directed fluid, to facilitate in the extinction of the are drawn therein.

In United States patent application, Serial No. 465,244, filed November 11, 1942, now U. S. Patent 2,406,469, issued August 27, 1946, by Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker and assigned to the assignee of the instant application, there is disclosed and claimed a novel circuit-interrupting structure in which a plurality of jets of fluid are directed toward an arc at a plurality of spaced points along its length. The fluid is exhausted away from the are at a plurality of intermediate points. It is a further object of our invention to adapt such an interrupting structure to an interrupter of the type employing a pair of piston means, one piston means forcing fluid through such an interrupting structure and the other piston means being actuated by a serially related pressure-generating arc, to assist in moving the said one piston means.

Further objects and advantages will become apparent from a reading of the following specification, taken in conjunction with the drawings, in which:

Figure l is a circuit interrupter embodying our invention and shown in the closed circuit position;

Fig. 2 is an enlarged vertical sectional view through the right-hand arc-extinguishing unit of Fig. l, the parts being disposed in an intermediate position during the opening operation;

Fig. 3 is a sectional view, taken along the line III--III of Fig, 2;

Fig. 4 is a view similar to Fig. 2, but showing the disposition of the parts near the end of the opening operation;

Fig. 5 is a vertical sectional view of a modified type of arc-extinguishing unit embodying our invention taken substantially on the line V-V of Fig. 6, the disposition of the parts being taken at VI-VI of Fig. 5;

Fig. 7 is another modified type of arc-extinguishing unit embodying our invention, the parts being shown at an intermediate point in the opening operation;

Fig. 8 is a sectional view, taken along the line VIII-VIII of Fig. "I; and

Fig. 9 is a fragmentary vertical sectional view, taken along the line IXIX of Fi 7.

Referring to the drawings, and more particularly to Figure 1 thereof, the reference numeral l designates a tank in which a suitable arc-extinguishing fluid 2, in this instance oil, is contained, filling the tank I to the level 3. The tank I has a cover 4 from which depend two insulating terminal bushings 5, 6 through which extend terminal studs 1, 8.

Threadedly secured to the lower ends of the terminal studs 1, 8 are contact feet 9, l0 which support identical arc-extinguishing units generally designated by the reference numeral l I. Reciprocally operable in a vertical direction within the tank I is an insulating operating rod l2, at the lower end of which is secured a conducting bridging member l3 which serves, in the closed circuit position of the interrupter, to electrically connect the two arc-extinguishing units If.

Referring more particularly to Figs. 2 through 4-. inclusive, which show more clearly the construction of. the right-hand arc-extinguishing unit I l of Fig. 1, it will be observed that integrally formed with the contact foot I0 is a conducting cover member l4 having a vent opening l5 and secured by means (not shown) to a conducting casting member IS.

The casting member 56 has an inwardly extending bracket H which supports a relatively stationary contact 18. A bolt l9 extends through the contact 18 and bracket IT. A compression spring 20 and a washer 2| are disposed on the bolt 19 between the bracket 11 and a nut 22. The compression spring 20 provides the requisite contact pressure between the stationary contact I8 and an intermediate contact 23. During the opening operation, a pressure-generating arc 28 is estab- Fished between the stationary contact l8 and the intermediate contact 23.

Attached to the casting member I6 is an insulating support 34 with a cylindrical member 24 which serves as a guide for the intermediate contact 23. A compression spring 25 disposed between the upper end of the cylindrical member '24 and a Shoulder 26 integrally formed with the intermediate contact 23 biases said contact in a downward direction.

The cylindrical member 24 also slidably guides a piston member 21 through which extends insulating return rods 29 which pass through suitable apertures 33 in the insulating support 34 fastened to the casting member 16;, A compression spring 31' and a, washer 32 are disposed on the return rods 29 between the support 34 and a nut 33. Consequently, it will be apparent that the compression spring 31 biases the piston member 21 to its upward or retracted position against the support 34.

member 31 forming the body of the. arc-extinguishing unit I I. Suitably secured'by means (not shown) to the casting member I6 is a conducting ring 38 which makes threaded engagement at 39 to the casing 31. The conducting ring 38- has a plurality of venting apertures 40 formed therein. An annular portion of the casing'31 is removed to form an annular passage at 41-, the purpose for whichwill appear more clearly hereinafter.

The sleeve 36 has formedtherein a. plurality of apertures 42 which permit a communication between the annular passage 41 and the region 43 within the sleeve 36. Threadedly secured at 44 to the lower end of the sleeve 38 is a casting member 45 constituting another'piston member which threadedly supports an insulatingorifice member 45. The lower end of the casting member 45 supports a movable contact 41 through a lost motion connection between shoulders 63 and 13.

Positioned on either side of the lower end of the movable contact 41 is a disconnect finger 50 which slidably engages the bridging member l3. A pin I passing through the lower end of the movable contact 41 and also the two disconnect fingers 50- also passes through slots 52 provided at the left-hand end of two lever members 53. These are pivotally mounted at 54 to a casting member 55 suitably secured by means (not shown) to a holding ring 58 threadedly secured at 5-1 to the lower end of the insulating casing 31. A pin 58 passes through both lever members 53 and pivotally supports the lower seat 59 of two accelerating compression springs 63 having their upper seats at GI integrally formed with the casting 55. The casting 55 supports a valve 62.

The operation of the arc-extinguishing unit I I will now be explained. In the closed circuit po sition of the interrupter, the electrical circuit passing through the arc-extinguishing unit I! comprises contact foot l0, cover member 14, bracket I1, stationary contact l8, intermediate contact 23, movable contact 41, disconnect fingers 50 through the bridging member I3, and through the left-hand arc-extinguishing unit II in an identical manner. When it is desired to open the electrical circuit passing through the interrupter, or in response to overload conditions existing in the circuit controlled by the interrupter, suitable operating mechanism (not shown) is actuated to cause downward motion of the operating rod I2. The downward motion of the operating rod I2 causes downward movement of the conducting bridging member I3 to permit the accelerating compression springs 60 to force the movable contact 41 in a downward direction.

There is permitted a slight opening travel of the movable contact 41 to take place before the shoulder 63 of contact 41 strikes the portion 64 of the casting 45. When this occurs the movable contact 41 and the casting 45 will move downwardly together as a unit, being biased downwardly by the accelerating compression springs The downward movement of the movable contact 41 permits downward motion of the intermediatecontact' 23 to cause a separation between the-contacts I8; 23 to establish a pressure-generating are 28 within a pressure-generating chambersgenerally designated by the reference numeral 65.

The pressure formed within the pressure-generating chamber 65 acts upon the piston member 21* to. force. thelatter downwardly into engagement w-ithithetshoulder 35 of the sleeve 35 to con sequent'ly drl've the'sleeve 38 and casting member 45. downwardly to thereby assist the accelerating compression springs 85. During this downward movement: of the casting member 45, the valve 62 closes, and oil withinthe region 53 is forced throughapertures 61. formed in the casting memher orpiston--and-upwardly through the throat 68 of the orifice member 46 toengage the main or interrupting are 69 drawn between the contacts 41 and 23.. The oil passing through the throat B8. enters the region 43 where it passes through the aperturesfl, through the annular passage 4| and out of the unit II through the apertures 43.

Near the'end of the opening travel of the piston member: 45. after the arc has been interrupted, the-upper end 10 of the sleeve 35 separates from theportion 1| of the ring 38 to permit a venting of the pressure-generating chamber through the apertures 40. This venting of the pressuregenerating chamber relieves the pressure therein and permits the compression springs 3I toretrieve the piston member 21 to its upper or retracted position.

It will be apparent that the sleeve 36, the casting member 45- and the orifice member 46 together form. a piston member generally designated by the reference numeral 12, the continued downward operative travel of, which under the biasing action of the accelerating compression springs 59 serves to cause a continued flushing flow of oil from the region 66 upwardly through the throat 68.01- the oriiice 45. Since apertures 42 are sealed off, the. oil flow assists the upward retracting motion of piston 21, forcing gases and contaminated oil overthe edge 18 of sleeve 36 and out of the unit. I I through the apertures 43.

Fig. 4 shows the disposition of the parts following circuit interruption and after the piston member 12 has come to rest against the casting member 55. After this occurs, the bridging member I3 separates from the disconnect fingers 50 to introduce an isolating gap in the circuit. It will be observed in Fig. 4 that the compression springs 3| have retrieved the piston member 21 to its upper or retracted position, thus minimizing the closing load imposed on the closing mechanism of the interrupter. Gas may leave the pressure-generating chamber 65 through the vent opening I5, which alsopermits a circulation of oil to take place through the pressure-generating chamber 65 in the open circuit position of. the interrupter.

During the closing operation, the insulating rod I2 and the bridging member I3 move upwardly to cause an engagement between the bridging member I3 and the lower end of the movable contact 41. After the bridging member has picked up the movable contact 41, there is a slight travel of the movable contact 41 before the shoulder 13 thereof strikes the portion 64 of the casting member 45, at which time the casting member 45 and the movable contact 41 move upwardly together as a unit. The movable contact 41 then strikes the intermediate contact 23 raising the latter against the downward biasing action of the compression spring 25 to cause an engagement between the intermediate contact 23 and th relatively stationary contact I8, at which time the electrical circuit is closed through the interrupter. A subsequent opening operation is as previously described.

From the foregoing description, it is apparent that we have disclosed an interrupter which uses a movable orifice with the addition that the orifice is power-driven by a piston in a gas-generating chamber, this same piston returning to its original position after interruption has taken place, thus making the closing load imposed on the interrupter very small. Low currents which do not generate sufficient pressure within the pressuregenerating chamber 65 to operate the piston member 2 I quickly will be interrupted by the downward movement of the piston member 12 as caused by the accelerating compression springs 60.

It will, of course, be apparent that more complete follow-through by the driving piston 21 may be obtained if desired by delaying the opening of the vents 48 venting the pressure-generating chamber 55, and by making provision for greater travel of piston supports 29. During the closing operation, the valve 62 will open to permit the upward or retractive movement of the piston member 12 to draw fresh oil through the valve 62 and into the region 66 below this piston member 12.

Fig- 5 shows a modified type of arc-extinguishing unit generally designated by the reference numeral 18. Certain constructional features of this modified type of arc-extinguishing unit are identical to constructional features previously disclosed in connection with the interrupter of Fig. 2, consequently similar reference numerals have, where possible, been employed.

Secured to the cover member [4 by means (not shown) is a casting member 19 having a portion 89 threadedly secured at 8| to the upper end of an insulating casing 82. The casting member 19 resiliently supports a relatively stationary contact 83 having a portion 84 encircled by a compression spring 85, biasing the contact 83 downwardly with respect to the casting member 19. A conductor 86 electrically connects the contact 83 with the casting member "I9 and hence to the contact foot 19.

Integrally formed with the casting member 19 is an annular deflecting dome-shaped member 8 having a ring-shaped annular closed periphery designated by the reference numeral 88 which cooperates with a sleeve 89 to permit an opening and closing of a venting means generally designated by the reference numeral 90 and comprising apertures 9| integrally formed near the upper end of the casting member 19.

In this embodiment of our invention, the casting member 45, sleeve 89 and orifice 45 together form a difierential piston member generally designated by the reference numeral 92.

The operation of this modified type of arcextinguishing unit will now be explained. In the closed circuit position of the interrupter (not shown), the electrical circuit therethrough comprises contact foot Ill, cover member l4, casting member 19, conductor 85, relatively stationary contact 83, movable contact 41, disconnect fingers 59 and conducting bridging member I3, through the left-hand arc-extinguishing unit 18 in an identical manner to the other contact foot 9 of the interrupter. During the opening operation, the bridging member I3 moves downwardly to permit the compression springs 60 to cause a slight downward travel of the movable contact 41 with respect to the casting member 45 before the shoulder 63 of the movable contact 41 strikes the portion 64 of the casting member 45, at which time the movable contact 41 and the casting member 45 move downwardly together as a unit under the biasing action of the compression springs 69. This causes separation between the movable contact 41 and the stationary contact 83 to establish an are 93 therebetween. During this initial opening movement, the sleeve 89 closes the venting means 90. When the arc 93 is drawn, it generates pressure within the region 43 and also within the region 66. Consequently, since the cylindrical member 94 integrally formed with the casting member 45 is moving out of the unit I8, the casting member 45, together with sleeve 89 and orifice member 46, acts as a differential piston. the arcing pressure thus assisting the compression spring 60 in driving the differential piston 92 downwardly to force oil to flow from the region 66, through the apertures 81, through the throat 58 and adjacent the arc 93 to effect the extinction thereof. Continued downward travel of the differential piston member 92 after the arc is extinguished causes the upper end 95 of the sleeve 89 to move below th periphery 88 of the domeshaped member 81 to cause an opening of the venting means 90. Consequently, the region 43 is vented through the venting means 90 into the region 96 which is freely vented by means of one or more venting apertures l5.

Continued downward travel of the piston member 92 causes a flushing flow of oil to pass from the region 66 through the throat 68 and out through the venting means 98 into the region 96 to flush contaminated oil out of the region 43.

When the differential piston member 92 strikes the casting member 55 following circuit interruption, the bridging member [3 separates from the disconnect fingers 59 to introduce an isolating gap into the circuit. It will be observed that the particular configuration of the annular deflecting dome-shaped member 81 is such as to deflect gas and oil downwardly into the region 43, and to effect a partial separation of the oil from the gas being vented through opening 99.

It will be observed from the foregoing description of this embodiment of our invention that we have disclosed a modified type of arc-extinguishing unit which uses the simple single-contact movable orifice principle, with the addition that a temporarily sealed exhaust chamber 43 is provided in which is developed pressure that acts on the orifice piston 92 helping to drive it downwardly. When the tubular valve 90 opens, after the arc is interrupted, the gas escapes and fresh oil flows into the unit from a reservoir above. During a subsequent closing operation, clean oil from the main body of the circuit breakers is drawn through valve 62 until valve 98 seals off. Thereafter, excess oil volume displaced by cylinder 89 may escape through openings 64.

Preferably the orifice constructions in Figs. 1-6 follow the teachings set forth and claimed in United States patent application filed March 23, 1945, Serial No. 584,413 by Thomas E. Browne, Jr., and assigned to the assignee of the instant application.

Figs. 7 through 9 show a modified type of arcextinguishing unit generally designated by the reference numeral 91. In some respects, this unit r 7 has features which are common to the unit H shown in Fig. 2. However, additional features are present which will appear more clearly in the following description.

The cover member I4 is secured by means (not shown) to a conducting plate 98 having a check valve 99 and supporting in a resilient manner a relatively stationary contact I00. An insulating supporting spider IOI is threadedly secured at I02 to the upper inner wall of the casing member I03. The spider IOI has apertures I04 through which extendinsulating retrieving rods I05 having heads I 06 at their upper ends to serve as upper seats for retrieving springs I01. The rods I05 are threadedly secured to a piston means I08.

An intermediate contact I09 is provided which extends through the spider I5 and also through the piston member I03. A lower movable contact I I is supported at the end of the conducting bridging member I3 and serves to make electrical engagement with the intermediate contact I09 in the closed circuit position of the interrupter not shown).

The piston member I08 engages, during the opening operation, a shoulder II I provided on a piston means II2 biased downwardly in the operatlve direction by an accelerating compression spring II 3 disposed between the piston member I I2 and the piston member I08.

Disposed below the unit 91 is a plate member I I 4 having an aperture II5 centrally-positioned therein and having four insulating upstanding rods threaded therein which extend through apertures I I1 provided at the lower end of the casing I03. At the upper ends of the rods IE6 areshoulders I I8 which prevent the rods I. I0 from passing completely out of the apertures II1.

From the foregoing, it will be apparent that during the closing operation the enlarged portion H9 of the lower movable contact IIO engages the aperture II5 to move the rods IIB upwardly to move the piston means I I2 upwardly to the retract-ed position thereby charging the accelerating compression spring I I3. Also, engagement is made between the movable contact I I0 and the intermediate contact I09, the latter being raised to engage the relatively stationary contact I00, thus completing the electrical circuit through the unit 91.

The structure which we provide for effecting I the interruption of the interrupting arc I20 drawn between the movable contact H0 and the intermediate contact I00 is disclosed and broadly claimed in a patent application filed November 11, 1942, Serial No, 465,244, now U. S. Patent 2,406,469, issued August 27, 1946, by Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker, and assigned to the assignee of the instant application. Briefly, it comprises an interrupting structure generally designated by the reference numeral I2I. The interrupting structure I2I forms two vertical flowpassages generally designated by the reference numeral I22 which communicate through apertures I23 to the region I24 below the piston means I I2. Communicating with the vertical flow-passages I22 are a plurality of inlet passages I25, in this instance six, which effect a communication between the two vertical flow-passages I22 and the interrupting arc I20. This flow engages the interrupting arc I20 and passes through orifices I26 to exhaust through a plurality of exhaust passages I21, in this instance four, as more clearlyshown in Figs. 8 and 9. The exhaust passages I21 communicate with twovertical exhaust passages I28, as more clearly shown in Fig. 9. As shown in Fig. 9, the exhaust passages communicate with the region exterior of the unit 91.

The operation of the unit 91 will now be ex,- plained. In the closed circuit position thereof, the electrical circuit comprises contact foot 10, cover member I4, conducting plate 98, conductors I29, stationary contact I00, intermediate contact I 09 through lower movable contact II 0 to the bridging member I3. During the opening operation, the bridging member I3 moves downwardly, thus first causing a separation between the contacts I00, I09 to draw a pressure-generating arc I30 within the pressure-generating chamber I3I'. Continued downward travel of the movable contact IIO causes a separation between the contacts I09, IIO to establish an interrupting are I 20. During this time, the accelerating compression spring I I3 moves the piston means I I2 downwardly in its operative direction. Also, the pressure Within the pressure-generating chamber I3I acts through the spider member IM to force the piston means I08 downwardly against the upward biasing action exerted by the retrieving springs I01. The piston means I08 strikes the shoulder II I of the piston means II2 to drive the latter downwardly, thereby assisting the accelerating compression spring H3. The downward operative movement of the piston means II2 forces oil from the region I24. through the apertures I23, through the vertical flow-passages I22 and through the inlet passages I25 to strike the interrupting arc I20, thereby deionizing the same. This fluid exhausts through the exhaust passages I21, and through the vertical exhaust passages I28 to the region exterior of the arc-extinguishing unit 91.

Extinction of the interrupting arc I20 soon follows and the circuit through the interrupter is broken. The continued downward travel of the piston means IIZ causes a flushing flow of fluid to pass toward the interrupting arc and out of the unit 91 through the vertical exhaust passages I28. Upon a release of the pressure within the pressure-generating chamber I3I, the check valve 09 opens to let out residual gas and let fresh oil enter the pressure-generating chamber I3I. During the closing operation, as previously de-v scribed, the upward movement of the contact H0 effects a reengagement of the several contacts and moves the piston means II'2 upwardly to its retracted position, thereby charging the accelerating compression spring I I3. The unit 91 is then in readiness for the next opening operation.

For interrupting low currents of values not sufficient to generate sufficient pressure within the pressure-generating chamber I3I to cause downward travel of the piston member I08, reliance may be had upon compression spring I I3 to cause the downward travel of the piston means II2 to produce the desired oil flow through the passages of the interrupting structure I2I.

From the foregoing description, it will be apparent that we have provided an improved circuit interrupter involving two piston means of novel construction, in which one of the piston means is utilized to force fluid through a suitable inter-. rupting structure toward the interrupting arc, and in which the other piston means is. actuated by a pressure-generating arc to assist the motion of the said one piston means. It will also be apparent that we have improved the interrupting structure set forth in the aforesaid patent of Leon R. Ludwig, Winthrop M. Leeds and Benjamin 9 Baker, in a manner such that a serially related pressure-generating arc is employed to force fluid by piston means through an interrupting structure of the type set forth in the aforesaid patent.

Although we have shown and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, means for establishing an arc, piston means movable in an operative direction to force fluid toward the arc to facilitate the extinction thereof, means biasing the piston means in said operative direction, means defining an orifice carried by the piston means through which the arc is drawn, means for establishing a second arc, and means responsive to the pressure created by the second arc to assist in moving the piston means in the operative direction.

2. In a circuit interrupter, means for establishing an arc, piston means to facilitate the extinction of the arc, means defining an orifice carried by the piston means through which the arc is drawn, means for establishing a second arc, and means responsive to the pressure created by the second arc to assist in moving the piston means in said operative direction.

3. In a circuit interrupter, means for establishing an interrupting arc, piston means for facilitating the extinction of the interrupting arc, means venting the non-working side of the piston means, means for establishing a pressuregenerating arc, and another independently movable piston means operated by pressure from the pressure-generating arc to assist the motion of the first said piston means.

4. In a circuit interrupter, means for establishing an interrupting arc, piston means for facilitating the extinction of the interrupting arc, means defining an. orifice carried by the piston means, the interrupting are being drawn adjacent to the orifice to receive the blast of fluid passing therethrough, means for establishing a pressuregenerating arc, and another separately movable piston means operated by pressure from the pressure-generating arc to assist the motion of the first said piston means.

5. In a circuit interrupter, an arc-extinguishing unit, a piston member movable within the unit, means biasing the piston member to move in the operative direction, a movable contact carried by the piston member, an intermediate contact, a relatively stationary contact cooperable with the intermediate contact to establish a pressure-generating arc, the intermediate contact being cooperable with the movable contact to establish an interrupting arc, the piston member forcing fluid toward the interrupting arc to effect the extinction thereof, and means responsive to the pressure of the pressure-generating arc to assist the working motion of the piston member 6. In a circuit interrupter, an arc-extinguishing unit, a piston member movable within the unit, means biasing the piston member to move in the operative direction, a movable contact carried by the piston member, an intermediate contact, a relatively stationary contact cooperable with the intermediate contact to establish a pressuregenerating arc, the intermediate contact being cooperable with the movable contact to establish an interrupting arc, the piston member forcing fluid toward the interrupting arc to effect the extinction thereof, and another piston member operated by pressure created at the pressure-generating arc to assist the opening motion of the first piston member.

'7. In a circuit interrupter, an arc-extinguishing unit, a piston member movable within the unit, means biasing the piston member to move in the operative direction, a movable contact carried by the piston member, an intermediate contact, a relatively stationary contact cooperable with the intermediate contact to establish a pressuregenerating arc, the intermediate contact being cooperable with the movable contact to establish an interrupting arc, the piston member forcing fluid toward the interrupting arc to effect the extinction thereof, another piston member operated by pressure created at the pressure-generating arc to assist the opening motion of the first said piston member, and venting means to relieve the pressure created at the pressure-generating arc operated by working motion of the said other piston member.

8. In a circuit interrupter, an arc-extinguishing unit, a piston member movable within the unit, means biasing the piston member to move in its operative direction, a movable contact carried by the piston member, an intermediate contact, a relatively stationary contact cooperable'with the intermediate contact to establish a pressuregenerating arc, the intermediate contact being cooperable with the movable contact to establish an interrupting arc, another piston member operated by pressure created at the pressure-generating arc to assist the operative motion of the first said piston member, venting means to relieve the pressure created at the pressure-generating arc actuated by the operative motion of the said other piston member, and means biasing the said other piston member to its retracted position.

9. In a circuit interrupter, an arc-extinguishing unit, means for establishing a pressure-generating arc and an interrupting arc, a piston means for forcing a plurality of jets of fluid at the interrupting arc, exhaust means for permitting the exhaust of fluid from the interrupting are at a plurality of points, and another piston means operated by the pressure created at the pressuregenerating are for assisting the working movement of the first said piston means.

10. In a circuit interrupter, means for establishing an arc, a differential piston member, an orifice operatively associated with the differential piston member, means biasing the differential piston member to move in a direction to force fluid through the orifice, the are being established adjacent to the orifice to receive the blast of fluid passing therethrough, and the diiferential piston member having unequal surface areas exposed to the arcing pressure with the greater surface area acting under the arcing pressure tending to move the differential piston member in said direction.

11. In a circuit interrupter, means defining a substantially enclosed arc extinguishing unit, means for establishing an are within the unit, a differential piston member movable within the unit, an orifice operatively associated with the differential piston member, means biasing the differential piston member to move in a direction to force fluid through the orifice, the arc being established adjacent to the orifice to receive the blast of fluid passing therethrough, the differential piston member having unequal surface areas exposed to the arcing pressure with the greater '11 surface area acting under the arcing pressure tending to move 'the differential piston member in said direction, venting means for the unit to relieve the pressure therein, and opening means for the venting means actuated upon a predetermined travel of the differential piston member.

12. In a circuit interrupter, a differential piston member, means defining an orifice member carried by and movable with the differential piston member, means for establishing an arc within the orifice, means biasing the differential piston member to move in a direction to force liquid through the Orifice and adjacent to the arc, and the differential piston member having unequal surface areasexposed .to. the arcing pressure with the greater surface area acting under the arcing pressure tending to move "the differential piston member in said direction.

13. In a circuit interrupter, anarc extinguishing unit, a relatively stationary contact disposed within the .unit, a .difierential piston member, means defining .an orifice member movablewith the differential piston member, a .movable contactseparablefrom the stationary contact to establish an are within the orifice, a lost-motion connection between the movable contact and the differential piston member, means biasing the movable contact toward the open circuit position, the biasing means also acting upon the .differen-- tial piston member after the lost motion is taken up to move it in a direction to force liquid through the orifice and adjacent to the arc, and the differential piston member having unequal surface areas exposed to the arcing pressure with the greater surface-area, acting under the arcing pressure tending tomove the differential piston .-memher in said direction.

14. In a circuit interrupter of the liquid, break type, a body of arcextinguishing liquid, a substantially enclosed arc extinguishing unit immersed in the liquid, a piston member movable within the unit, an orifice member-carried by the. piston member, a movable contact, a lost-motion connection between the movable contact and the-piston member, the movable contact moving with the piston member after the taking up of the lost motion, another contact cooperab-le with the aforesaid movable contact to establish an are within the orifice member, the piston member forcing liquid through the orifice member into engagement with the arc to effect the extinction thereof, and means biasing the movable contact toward the open circuit position,

15. In a circuit interrupter of the liquid break type, a body of arc extinguishing liquid, a substantially enclosed arc extinguishing unit immersed in the liquid, a piston member movable within the unit, an orificemember carried by the piston member, a movable contact, a lost-motion connection between the movable contact and the piston member, the movable contact moving with the piston member after the taking up of the lost motion, another contact cooperable with the aforesaid movable contact to establish an are. within the orifice member, the piston member forcing liquid through the orifice member into engagement with the arc to effect the extinction thereof, means biasing the movable contact toward the open circuit position, adisconnect con tact, means electrically connecting the disconnect contact in series with the movable contact, and a movable actuating disconnect contact separable from said disconnect contact and during the closing operation making engagement therewith to cause closing motion of the movable contact and charging of the biasing means.

WINTI-IROP M. LEEDS. JAMES M. CUMMING.

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

UNITED STATES PATENTS

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