US2422569A

US2422569A - Circuit interrupter

Info

Publication number: US2422569A
Application number: US488847A
Authority: US
Inventors: Winthrop M Leeds
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1943-05-28
Filing date: 1943-05-28
Publication date: 1947-06-17
Anticipated expiration: 1964-06-17
Also published as: GB578422A; FR988420A; CH247849A

Description

June 17, 1947. w. M. LEEDS 2,422,569

CIRCUIT INTERRUPTER Filed May 28, 1943 5 SheetsSheet 1 insulation 017 Aer/e! 1 wrmzssas: INVENTOR w 8 46 Wmzfimp M Leeds.

Wit M June 17, 19470 w LEEDs 2,422,569

CIRCUIT INTERRUPTER Filed May 28, 1943 5 Sheets-Sheet 2 fig 2.

WITNESSES: INVENTOR Wily/270p fiZLeads.

WA. 630? v BY 4? 11 43 /iFM June 17, 1947. w, LEEDS 2,422,569

CIRCUIT INTERRUPTER Filed May 28,1943 5 Sheet-Sheet 3 WITNESSES:

4% Wink/Imp M Lead;

552% mZiaw June 17, 1947. w LEEDS CIRCUIT INTERRUPTER Filed May 28, 1943 5 Sheets-Sheet 5 INVENTOR h znzizrop M. Leeds.

BY I

Patented June 17, 1947 OIRGUIT INTERRUBTER Winthrop M. Leeds, Wilkinsburg,'Pa.,--assignor to Westinghouse Electric .Corporation, :East Pittsburgh, Fa, a corporation .of Pennsylvania Application May 28, 1943, Serial No. 488,847

20 Claims. 1

This invention relates to circuit interrupters and, more particularly, to are extinguishing structures therefor.

In arc extinguishing structures of the type which draw both a pressure generating arc and an interrupting arc, and which utilize the pressure created by the pressure generating arc to force fluid under pressure toward the interrupting arc to facilitate the latters extinction, the separation between the pressure generating contacts is largely determined by low current conditions. In other words, the pressure generated by the pressure generating arc is largely a function of the length of the pressure generating arc, and consequently durin low current interruption it is desirable to'have a considerable separation between the pressure generating contacts to generate adequate pressure to effect interruption of the interrupting arc.

I have found thatit is desirable to provide means to prevent-a lengthening of the pressure generating arc during high current interruption when the pressure is excessive, and my invention is concerned with the provision ofa circuit interrupter incorporating such means.

Ageneral object of my invention is to provide an improved circuit interrupter having an improved .arc extinguishing structure.

Another object .of my invention is to provide an improved circuit interrupter in which are disposed contact means for establishing and lengthening an arc. I-provide a valve means responsive to a predetermined pressure created in partby the arc to prevent further lengthening of the are by continued movement of the contact means.

Anotherobject is to providean improved circuit interrupter inwhich a pressure generating ar-c forces .fluid under pressure toward an interrupting arc to facilitate the latters extinction, and to provide suitable valve means responsive to a predetermined pressure created at leastin part by the pressure generating arc to prevent a lengthening of thepressure generating arc.

Another object is. to .provide' animproved circuit interrupter in which a pressure generating arc is establishedandto force fluid under pressure toward the pressuregeneratingarc during low current interruption to increase the presr sure formed thereat.

Another object is to provide an improved circuit interrupter in which both a pressure generating are and an-interrupting arcare established, and to provide means for-sending a supplementary blast of fluid toward both arcs simultaneously duringlow current interruption.

Further objects and advantages will readily become apparent upon a readingof the following specification taken in conjunction with the drawings, in which:

Figure 1 is an elevational view, partly in section, of .a circuit interrupter embodying my invention and shown in the closed circuit position;

Fig. '2 is an enlarged elevational view, in vertical section, taken through one of the arc extinguishing units of "Fig, 1, the parts being shown in the closed circuit position;

Fig. 3 is a'fragmentary vertical sectional view taken. along the line IIIIII.ofFig; '2;

'Fig. '4 is a view in section taken along the line IV-IV of Fig. 2;

Fig. 5 is a viewnsimilar to Fig. 2, but showing the disposition of the parts during high current interruption under high pressure conditions;

Fig. 6 is a view similar to Fig. 5 but showing the disposition of the parts during low current interruption under low'pressure conditions;

'Fig. '7 is an enlarged fragmentary view in vertical section taken along the line VIIVII of Fig. 5;

Fig.8 is a modified type are extinguishing unit embodying 'myinvention, :and showing the disposition of the parts during low current ,interruption under low pressure conditions;

Fig.9 is another modifiedtype arc extinguishing unit embodying my invention, and showing the disposition of the parts during low current interruption under low pressure conditions;

Fig. 10 is a fragmentary'enlarged view of still another modified type arc extinguishing unit embodying my invention, and showing the disposition of the parts during low current interruption under -low pressure conditions;

-'-Fig.-11 is a view in'section taken alon the line 'XI-'-XI of Fig; 10, and;

-Fig.--12 is a view in-section taken along the line XII-XE of Fig. '10.

'Referring; to the drawings, and in particular to Fig. 1, the reference-numeral I designates a tank filled to the level indicated witha suitable arcextinguishing fluid 2, in this instance oil.

Suspended from the cover' 3 of the tank I are insulating bushings. 4;5 which enclose terminal studs (not shown). :At the lower ends of the insulating bushingsq l, 5 and clamped to the .terminalstuds are contact feetG, I.

To the contact feet=6, 'l are securedarc extinguishing units generally designated by the reference numeral 8. The are extinguishing units 8 are electrically connected together in the closed circuit position of the interrupter, as shown in Fig. l, by a conducting cross-bar 3, which is reciprocally operated by an insulating operating rod l6, actuated by suitable operating mechanism (not shown). At the opposed outer ends of the conducting cross-bar 3 are movable contacts H, i2.

Referring more particularly to Fig. 2 it will be observed that I have provided a top dome casting i3 secured to the contact foot 6 having a gas escape valve l4 and forming a pressure chamber generally designated by the reference numeral [5.

Disposed within the pressure chamber (5 is a pressure generating contact l6 pivotally mounted at IT. An inspection plate I8 is provided to enable one to view the interior of the pressure chamber i5 without dissembling the arc extinguishing unit 8. A flexible shunt l9 electrically connects the dome casting I3 with the pressure generating contact [5. Cooperating with the pressure generating contact I6 is an intermediate contact 20 having a flange portion 2! which serves as a lower seat for a compression spring 22. Consequently, the intermediate contact is biased downwardly by the compression spring 22.

In the closed circuit position of the interrupter, as shown in Figs. 1 and 2, the electrical circuit therethrough comprises the left hand terminal stud (not shown), contact foot 6, top dome casting [3, flexible shunt l9, pressure generating contact l6, intermediate contact 29, movable contact H, conducting cross-bar 9, movable contact I2, through the right-hand arc extinguishing unit 8 in an identical manner, to the contact foot I and finally to the right-hand terminal stud (not shown).

An insulating operating rod 23 having a flange portion 24 is biased downwardly by a compression spring 25. At the upper end of the operating rod 23 is a slot 26, through which passes a pin 21, the latter also passing through the legs 28a of a bifurcated actuating member 28, which serves to actuate the pressure generating contact l6. Slots 29 are provided in the legs 28a to accommodate vertical movement of the operating rod 23.

A compression spring 30 having an upper seat in a bracket 3!, which in this instance is an integral portion of the contact foot 6, surrounds the upper portion of the operating rod 23, and has a lower seat upon the legs 28a, as more clearly shown in Figs. 5 and '7. It will, consequently, be apparent that the compression spring 30 biases the legs 28a downwardly to maintain the pin 2'! at the bottom of the slot 26 in the operating rod 23 as shown in Fig. '7.

An insulating valve disc 32 is rigidly secured to the operating rod 23. The operating rod 23 also has a flange portion 33. Disposed between the valve disc 32 and the flange portion 33, and slidable upon the operating rod 23, is a piston member 34 having apertures 35 formed therein. The piston member 34 is adapted to move in a piston chamber generally designated by the reference numeral 36.

The piston chamber 36 has an opening 31 at its lower end which is normally closed by a disc valve 38 slidable on the operating rod 23 and biased upwardly by a compression spring 39.

Referring to Fig. 2 it will be observed that an abutting cylinder 40 is slidable in the cross-bar 9 and biased upwardly by a compression spring 4!, an aperture 42 being provided in the crossbar 9 to control the back-pressure on the cylinder do. The function of the cylinder 40 and compression spring 4| is to cushion the shock when the cross bar 9 picks up the operating rod 23, and to provide the requisite contact pressure for the interrupter in the closed circuit position.

The arc extinguishing unit 8 comprises a plurality of suitably shaped insulating plates held together by tie rods 43. Certain features of the arc extinguishing unit 8 are described and broadly claimed in a patent application by Leon R. Ludwig, Benjamin P. Baker and Winthrop M. Leeds, filed November 11, 1942, Serial No. 465,244, now U. S. Patent 2,406,469, issued August 27, 1946, entitled Circuit interrupters, and assigned to the assignee of the present application.

The insulating plates of the arc extinguishing unit 8 form vertical fiow passages generally designated by the reference numeral 44, which communicate at their upper end with the pressure chamber and at their lower end with a plurality of inlet passages 45, at the latter leading toward the interrupting are 48. After the oil has contacted the interrupting are 48 it passes out of ti e are extinguishin unit 8 through the exhaust passages 46 more clearly shown in Fig. 3.

The opening operation of the interrupter will now be described. When it is desired to open the electrical circuit passing through the interrupter, or when overload conditions exist in the electrical circuit controlled by the interrupter, suitable operating mechanism (not shown) moves the insulating operating rod l0 downwardly to result in a downward movement of both the conducting cross-bar 9 and th movable contacts H, 12.

During the interruption of low currents the operating rod 23 moves downwardly at the same rate of speed as the cross-bar 9, as shown in Fig. 6, to result in the pressure generating contact [6 rotating in a clockwise direction about the pivot point i! to draw a pressure generating are 41. Substantially simultaneously the movable Contact l l separates from the intermediate contact 20 to draw an interrupting arc 48. The valve disc 32, rigidly secured to the operating rod 23, moves therewith downwardly to close the apertures 35, pick up the piston member 34 and carry the piston member 34 downwardly in the piston chamber 36 to move the oil within the piston chamber 35. The oil, now under pressure within the piston chamber 36, opens the disc valve 38, against the upward biasing action of the compression spring 39, to permit oil to flow under pressure out of the piston chamber 36, through the opening 31 and passage toward the inlet passages 45, as indicated by the arrows in Fig. 6. This action occurs only during the interruption of low currents. After the pressure generating contact I6 has reached its maximum open circuit position, as shown in Fig. 6, the insulating operating rod 23 may continue to move downwardly because of the presence of the slot 23 in the rod 23. Thus the piston action is continued after the pressure generating contact 16 has stopped moving. It will, consequently, be apparent that during low current operation when the pressure produced by the pressure generating arc 41 is low that the piston member 34, biased downwardlyby compression spring 25, will serve to send a supplementary flow of oil under pressure through passage 60 toward the inlet passages 45 into engagement with the interrupting arc 48. The fully open circuit position of the interrupter is shown by the dotted lines of Fig, 1.

During the interruption of high current arcs -=the pressure created by the pressure generating arc 41 is sufficient to close the disc valve -38 against the opening 3! to-prevent oil 'leaving'the pistonchambertfi. The'trapped oil within the piston chamber under pressure prevents the down-ward movement of thepiston member 34; andthis, in turn, halts the downward movement of the operating rod 23. The'op'erating rod '23 then separates from the abutting cylinder ea as shown in Fig.5.

'It'will beobser'ved that when the insulating operating rod 23 is'halte'd in its downward movem'ent'by the'high pressure within the arc extinguishing unit '8, the pressur generating contact I6 cannot continue to rotate in a clockwise direction about the pivot point ll to further increase the length of the pressure generating are '41, and thus further increase the pressure in the chamber l5.

When the pressure subsides within the are extinguishing unit 8 the oil under pressure within the piston chamber 36 will then be able to open the disc valve-38 and flow out of the piston cham- *ber 36, through the opening 31 and passage 69 toward the inlet passages "45 to fiush the region where the interrupting arc 48 was extinguished. This flushing action raises the dielectric strength in the region where the interrupting are 48 has been extinguished and prevents delayed rcstriking of the interruptingarc 36, which would prolong the arcing time of the interrupter. It also prevents premature breakdown of the contact gap duringa closing operation.

It will therefore be apparent that my invention is operative to produce a supplementary oil flow by piston action during the interruption of low currents. It is also apparent that during high current interruption my invention is operative to prevent a further lengthening of the pressure generating arc'di. During such high current interruption my invention is operative to send a flushing stream of uncontaminated'oil toward the region where the interrupting are 48 was extinand after the pressure has completely subsided withinthe arc'extinguishing unit 8, the gas escape valve l4 opens to permit accumulated gas within the pressure chamber [5 to flow out of the unit 8.

During the closing operation the piston member 34 is picked up by the flange portibn 33. This opens the apertures 35 to permit oil of high dielectric strength to rapidly fill the piston chamber '36. Consequently the closing operation is not opposed by suction behind the piston member 34.

It will be apparent that when the interrupter is operated under no load conditons, that is, with no current flowing through the interrupter, my invention provides a means for completely flushing the arc extinguishing unit 8 with oil brought in through the piston chamber36.

In the embodiment or my invention shown in Cir Fig. -8 I'provide a modified type arc extinguishing unit -generally designated by th reference-hm "mera1 50. It willbe noted that a modified contact foot 5| is utilized to form the piston chamber'36 at the upper end of the arc extinguishing unit'50.

'In this embodiment of my invention a-bracket58,

integrally formed with the top dome casting 52, serves'as a lower seat for the compression spring 'tewhich-biases the disc valve 38 upwardly to close the conduit 53.

The operationof the operating rod 23 is identical to the operation of the operating rod 23 used in the embodiment of my invention shown in Figs.

interruption, wh'en the pressure produced at the pressure generating arc4'l is small, the pressure of the oil in the piston chamber is sufficient to force the disc valve 38 downwardly against the biasing action of the compression spring 39 and to send a supplementary oil flow through the conduit 53-toward the pressure generating 'arc Al.

Thus, oil is forced into the pressure chamber 55 from the piston chamber 36 to cause fresh oil to contact the pressure generating arc -41 to increase thepressure formed'atthe pressure generating-arc 4i. Also some of the oil'from the piston chamber 35 passes through-the vertical flow passages Mi and through the inlet passages 45 to help extinguish the interrupting arc 48.

Fig. 8 shows the disposition of the parts during low current interruption when the disc valve has been opened by the pressure of the oil in the piston chamber 36. The directionof flow is-indicated by the arrows.

During the interruption of high currents the pressure formed at the pressure generating are 41 within the pressure chamber l5 will be sufficient to maintain the disc valve 38 closed against the conduit 53. As previously explained this halts the downward movement of the operating rod 23 to preventa further lengthening of the pressure generating are 41. Howeven'when the pressur has subsided within the pressure chamber l5, after the interruption of the high current arcs, the pressure of the oil within the piston chamber 36 will then be suificient to open the disc valve 38 and send a fresh quantity of oil through the conduit 53 into the pressure chamber 15 to flush out the contaminated oil within the arc extinguishing unit 50.

-It will, therefore, be evident that in the embodiment of my invention shown in Fig. 8 I position the piston chamber 36 at the upper end of the unit to force fresh oil against the pressure generating arcdl during low current interruption to increase the pressure formed therein; and during high current interruption the piston chamber 35 is operative to flush out the entire unit 50'aftera circuit opening operation.

In the embodiment of my invention shown in Fig. 9 I provide a modified stationary intermediate "contact'54 which has a longitudinal passage extending axially therethrough. The longitu- -dinal passage 55 intersects a lateral passage 55,

which communicates with the passage 51 leading from the piston chamber 36. It will be apparent that in the operation of this embodiment of my inventionduring low current interruption the piston member 34 will be operative to send a quantity 'of-freshoil through the openings", through th -pa's-sage 5l-and through the intermediate contact 54, to contact both the pressure generating are 4'! and also the interrupting are 48. The fresh oil which passes through the intermediate contact 54 to engage the pressure generating arc 47 will increase the pressure formed thereat. The fresh oil which passes through the intermediate contact 54 and engages the interrupting arc 48 serves to facilitate the extinction of the interrupting are 48. It will, therefore, be apparent that in the embodiment of my invention shown in Fig. 9 I utilize a novel construction of intermediate contact 54 to utilize more effectively the supplementary oil blast forced out of the piston chamber 36 during low current interruption.

During high current. interruption, after the pressure has subsided within the unit, the piston chamber 35 will be operative to send a fresh flow of oil through the opening 31, through the passage 51, through the passage 55 in the intermediate contact 54 and toward both regions where the two arcs were extinguished. This raises the dielectric strength in these two regions to prevent reignition, and also prevents premature breakdown during a rapid reclosing operation.

In the embodiment of my invention shown in Figs. through 12 the constructional features are somewhat similar to the arrangement shown in Fig. 8. Therefore, similar reference numerals have been used where possible. However in this embodiment of my invention I provide a modified type dome casting 63 in which are disposed a plurality of insulating plates to form a plurality of jets of oil which contact the pressure generating are 4'! during low current interruption, when the pressure formed at the pressure generating arc 4'! may be small.

The insulating plates are of three kinds. The first kind is herein called an insulating inlet plate and is designated by the reference numeral 64, and shown more clearly in Figs. 10 and 11. The insulating inlet plate 64 has an inlet passage 65 formed therein, as shown more clearly in Fig. 11. The second kind of plate is designated by the reference numeral 66 and is shown more clearly in Figs. 10 and 12. The third kind of insulating plate is herein called an insulating pocket plate and is designated by the reference numeral 57. The configuration of the insulating pocket plate 61 is more clearly shown in Figs. 10 and 12. The insulating pocket plate 67 has formed therein a pocket 68 which serves to retain a quantity of fresh oil adjacent the path of movement of the pressure generating contact it.

All of the insulating

plates

64, 66 and 67 are provided with cut out portions 69, which, when assembled, form a vertical flow passage generally designated by the reference numeral 10. The flow passage 13 communicates with the conduit 53 leading toward the piston chamber 36.

At the lower end of the dome casting 63 is an insulating plate designated by the reference numeral l i, which has an orifice 12 formed therein accommodating the movement of the pressure generating contact i6.

The operation of the embodiment of my invention shown in Figs. 10 through 12 will now be explained. During the interruption of low currents, when the pressure formed at the pressure generating are 4? is small, the pressure of the oil within the piston chamber 36 will open the disc valve 38 to force under pressure a fresh quantity of oil out of the piston chamber 36, through the conduit 53, through the vertical flow passage 10 and toward the pressure generating are 41 through the inlet passages 65. This fresh oil strikes the pressure generating arc 41 as the latter lengthens to increase the pressure formed thereat. This pressure acts through the orifice 12 in the insulating plate H to act downwardly through the vertical flow passages 44, through the inlet passages 45 and toward the interrupting are 48 not shown.

As the pressure generatin contact l6 rotates in a clockwise direction about pivot IT, the pressure generating are 41 is drawn past the pockets 68 provided in the insulating pocket plates 61. Consequently, the pressure generating arc 41 is not only drawn past the pockets 68 containing fresh oil, but also the pressure generating are 41 is drawn adjacent the inlet passages 65, through which fresh oil from the piston chamber 36 passes toward the pressure generating are 41. This raises the pressure within the pressure chamber l5 and facilitates the interruption of the interrupting are 48.

During the interruption of high currents when th pressure formed by the pressure generatin are 4'! in the pressure chamber [5 is sufiiciently high to maintain the disc valve 38 closed, the operating rod 23 is halted to prevent a len thening of the pressure generating are 41. After the interruption of the high current arcs, the pressure subsides within the pressure chamber [5 to permit the piston 34 to move downwardly in the piston chamber 36 to send a flushing stream of oil through the conduit 53, through the vertical flow passage 10 and into the pressure chamber I5. This cleans out the contaminated oil within the pressure chamber 15 and raises the dielectric strength within the entire arc extinguishing unit.

Certain aspects of increasing the pressure created at a pressure generating arc to facilitate rapid interruption of one or more interrupting arcs are described and broadly claimed in a patent application by Benjamin P. Baker, S. N. 471,847, filed January 9, 1943, now U. S. Patent 2,412,857, issued December 17, 1946, and assigned to the assignee of this application.

It will be observed that in each embodiment of my invention the piston chamber 36 is operative during the closing operation to draw fresh oil into the piston chamber 36, which fresh oil is subsequently used during the next opening operation of the interrupter. Consequently, it will be apparent that the piston chamber 36 is operative to send oil in unidirectional path through the arc extinguishing unit. It will be apparent that during low current interruption my invention is operative to send a supplementary oil flow toward one or both of the established arcs. Durin high current interruption my invention is operative to flush out the entire unit to prevent restriking and also to prevent premature breakdown during rapid reclosing.

The broad concept of forcing fluid under pressure both toward the pressure generatin arc and the interrupting arc is disclosed and broadly claimed in a patent application by Roswell C. Van Sickle, Robert E. Freidrick and Francis J. Fry, filed May 27, 1943, Serial No. 488,624, entitled Circuit interrupters, and assigned to the assignee of the instant application.

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

I claim as my invention:

1; Ina. circuit interrupter, meansfor establishing. and lengthening. a. pressure. generating arc; means for. establishing. an interrupting. arc, the-pressure. generating. are forcing fluid under pressure toward the. interrupting arc to facilitate the latters extinction, a piston Chamber, and valve-means disposed'at the entrance to the piston-chamber and responsive to a predetermined pressure" created in part by the pressure generating arc to prevent the first-mentioned means from lengthening the pressure generating arc.

2. In a circuit interrupter, a pressure generating-contactcooperable with an intermediate contacttoestablish and lengthena pressure gen eratingarc, a movablecontact cooperable with the-intermediate contact to establish an. interrupting arc, operating means movable in response to motionof the movable contact for actuating the'pressure generating contact, apiston chember, piston-means disposed-in the pisto-ncharnber and-'operated-by the operating means, and valve means disposed at the entrance to'the piston chamber tohalt the motion ofthe operating meanswhenthepressure createdat least in part by the pressure generating arc exceeds a predetermined pressure.

3; In a circuit interrupter, means for estab" lishing and lengthening an arc, apiston chamber containing fluid, piston means operative within thechamber to assist in .circuitinterruption, and valve means disposed at the entrance to the piston chamber andoperative at a predetermined pressure created in part by the arc to close the entrance to the piston chamber and stop the operation oi-the pistonmeans and also toprevent afurthenlengthening of the are by said firstmentioned means.

4; ma circuitinterrupter, afirstcontact coop erable with a secondcontact to establish and lengthen an arc, a piston chamber, operating lishing an interrupting arc, means for utilizing the pressure created at the pressure generating arc to force fluid under pressure toward the interrupting arc to facilitate the latters extinction, and piston means operable only during low current interruption for forcing fluid toward the pressure generating arc and the interrupting are simultaneously.

6. In a circuit interrupter, a pressure generating contact cooperab-le with an intermediate con tact to establish a pressure generating are, a mom able contact cooperacle with the intermediate contact to establish an interrupting arc, the intermediate contact having a fluid conducting passage formed therein, and means for forcing fluid through the passage toward both arcs only during low current interruption.

7. In a circuit interrupter, a pressure generating contact cooperable with an intermediate contact to establish a pressure generating arc, a movable contact cooperable with the intermediate contact to establish an interrupting arc, the intermediate contact having a fluid conducting passage formed therein, and piston means onerable only during low current interruption ier 1'0 forcing fiuidthrough the passage. towardboth arcs.

8.. In a circuitinterrupter, a pressruegenerah.

ing. contact. cooperable with an intermediate. c011. tact to establish a pressure generating arc, a movable contact cooperable. with the intermediate. contact to establishan interruptingarc, the-intermediate contact having a fluid conducting passage extending axially. therethrough, and. means for forcing fluid through the. passage toward both arcs to effect their-extinction.

9-. In a circuit. interrupter, means. for. estab lishing a pressure generatingv arc, means for establishing an interrupting arc, meansfor-utilizing the pressure. created adjacent the pressuregenerating arc to force. fluidtoward thev interrupting arc to effect the latters extinction, andmeans.

for directing a pluralityofjetsof fluid into the pressure generating arc asthe latter. islengthened to increase the pressure. formed thereat.

10; In a circuit interrupter, an arc. extinguishing unit, means. for establishing a pressure..gen-. erating are at a first end of they unit, means forv establishing an interrupting. are adjacent the other end of. the unit, and; pistonmeans dis-.

posed adjacent the firstendof theunitand 0p.-

erative. at apredetermined low pressure to send a jet of fluid toward the pressure generating are.

11. In a. circuit. interrupter, meansfor. estabe li-shing and lengthening apressure generating,

arc, means for. establishing! an interrupting. arc, the. pressure. generating. are. forcing. fluid: under pressure. toward the. interrupting arc to facilitate the latters. extinction, andzvalvemeans respone sive to apredeterminedpressure, created in part,

by the pressure generating arc. to preventthe first-mentioned means fromi lengthening the. pressure generating are.

12; In acircuit interrupter, at pressuregener ating contact cooperable with an intermediate. contact to, essablishand lengthenapressure generating arc, a ,movable contact cooperable with,

the intermediate contact to establish an interrupting arc, operating means movable in response to motion of the movable contact for actuating the pressure generating contact, piston means operated by the operating means, and valve means to halt the motion of the operating means when the pressure created at least in part by the pressure generating arc exceeds a predetermined pressure.

13. In a circuit interrupter, means for establishing and lengthening an arc, a piston chamber containing fluid, piston means operative within the chamber to assist in circuit interruption, and valve means operative at a predetermined pressure created in part by the arc to stop the operation of the piston means and also to prevent a further lengthening of the arc by said first-mentioned means.

14. In a circuit interrupter, a first contact cooperable with a second contact to establish and lengthen an arc, a piston chamber, operating means for the first contact extending through the piston chamber, and valve means associated with the piston chamber and responsive to a predetermined pressure created at least in part by the arc to stop the operation of the operating means and hence to prevent a further lengthening of the are.

15. In a circuit interrupter, means for establishing a pressure generating are, means for establishing an interrupting arc, means for utilzing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, and mean including a plurality of insulating plates disposed in contiguous relationship for directing a plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat.

16. In a circuit interrupter, means for establishing a pressure generating arc, means for establishing an interrupting are, means for utilizing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, and piston means for directing a. plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat.

17. In a circuit interrupter, means for establishing a pressure generating are, means for establishing an interrupting arc, means for utilizing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, and piston means operable only during low current interruption for directing a plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat.

18. In a circuit interrupter, means for establishing a pressure generating are, means for establishing an interrupting arc, means for utilizing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, plate structure for directing a plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat, and piston means for forcing fluid through the plate structure to strike the pressure generating arc in a plurality of jets as the latter is lengthened.

19. In a circuit interrupter, means for establishing a pressure generating are, means for establishing an interrupting are, means for utilizing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, plate structure for directing a plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat, and piston means operable only during low current interruption for forcing fluid through the plate structure to strike the pressure generating arc in a plurality of jets as the latter is lengthened.

20. In a circuit interrupter, a pressure generating contact cooperable with an intermediate contact to establish a pressure generating arc, a movable contact cooperable with the intermediate contact to establish an interrupting arc, means for utilizing the pressure created adjacent the pressure generating arc to force fluid toward the interrupting arc to effect the latters extinction, an insulating plate having an orifice therethrough through which the pressure generating arc is drawn, and means for directing a plurality of jets of fluid into the pressure generating are as the latter is lengthened to increase the pressure formed thereat.

WINTHROP M. LEEDS.

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

UNITED STATES PATENTS Number Name Date 2,292,547 Sadler Aug. 11, 1942 2,147,497 Prince et al Feb. 14, 1939 2,258,226 Skeats Oct. 7, 1941 1,992,109 Whitehead Feb. 19, 1935 2,095,441 Howe Oct. 12, 1937 1,814,847 Paul July 14, 1931 2,077,338 Lingal et al Apr. 13, 1937 715,291 Potter Dec. 9, 1902 2,075,749 Paul Mar. 30, 1937