US2416185A - Fluid blast circuit interrupter - Google Patents

Description

Feb. 18, 1947. w LEEDS FLUID BLAST CIRCUIT INTERRUPTER Filed Jan. 1. 1945 2 Sheets-Sheet 1 nsu/af/on INVENTOR Mh/bropfllleecz i.

BY 71/ i q 2 ATTORNEY;

WITNESSES Feb. 18, 1947. w LEEDS 2,416,185

FLUID BLAST CIRCUIT INTERRUPTER Filed Jan. 1, 1945 2 Sheets-Sheet 2 E59: 7. A g //A 3: 64 INVENTOR 35 M'flf/jrop/W. leads.

WlTNESSES:

64 4% wZfi- Patented Feb. 18, 1947 FLUID BLAST CIRCUIT INTERRUPTER Winthrop M. Leeds, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 1, 1945, Serial No. 570,820

19 Claims. 1

This invention relates to circuit interrupters in general, and, more particularly, to arc-extinguishing structures therefor.

In United States patent application, filed September 14, 1944, Serial No. 553,997, by Winthrop M. Leeds and assigned to the assignee of the instant application is shown and claimed a novel operating mechanism for a circuit interrupter. It is an object of my invention to provide an improved arc-extinguishing structure of the type described in the aforesaid application.

A general object of my invention is to provide an improved circuit interrupter which will more effectively interrupt the circuit therethrough in a novel manner.

More specifically, it is an object of my invention to provide an improved arc-extinguishing unit in which a bridging member adapted for rotation electrically connects two relatively stationary contacts. A plurality of inlet passages and vent passages communicate with an interrupting passage in which an interrupting arc is established by the separation between the bridging contact and one of the relatively stationary contacts. Preferably, the separation between the bridging contact and the other contact establishes a pressure-generating arc to force fluid through the inlet passages toward the interrupting arc to effect extinction thereof.

Further objects and advantages will readily become apparent upon a reading of 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 open circuit position;

Fig. 2 is an enlarged elevational view of the right-hand arc-extinguishing assemblage of Fig. 1 with a vertical sectional view taken through the upper arc-extinguishing um't substantially on the line II-II of Fig. 3, the parts being shown in the full open circuit position;

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

Figs. 4 and 5 show plate details used in the construction of the arc-extinguishing unit shown in section in Fig. 2;

Fig. 6 is an elevational view of a modified type of arc-extinguishing assemblage, the upper modifled arc-extinguishing unit being shown in vertical section taken substantially along the line VI-VI of Fig. 7, the parts being shown in the full open circuit position;

Fig. '7 is a sectional view taken along the line VII-VII of Fig. 6;

CJI

Figs. 8 and 9 show plate details used in the construction of the modified type of arc-extinguishing unit shown in Fig. 6; and

Fig. 10 is a vertical sectional view taken along the line X-X of Fig. 6.

Referring to the drawings and, more particularly, to Fig. 1 thereof, the reference numeral l designates a tank in which a suitable arc-extinguishing fiuid- 2, in this instance circuit breaker oil, is filled to the level 3. Depending from the cover 4 of the tank I are two insulating bushings 5, 6 through which extend terminal studs 1, 8. To the lower ends of the terminal studs 1, 8 are threadedly secured contact feet 9, I0 which fixedly support in position two identical arc-extinguishing assemblages generally designated by the reference numeral ll.

Each arc-extinguishing assemblage ll comprises a plurality of, in this instance two, arcextinguishing units generally designated by the reference numeral l2. Electrically interconnecting the two arc-extinguishing assemblages I l is a movable conducting bridging member I 3 which is reciprocably operated in a vertical direction by an insulating rod [4 actuated by suitable mechanism, not shown.

The upward or closing movement of the bridging member I3 causes the ends I 5 thereof toslide through disconnect fingers l6 striking crossmembers [1. At the ends of the cross-members I! are secured two insulating operating rods l8 extending longitudinally on opposite sides of each arc-extinguishing assemblage II. The operating rods I8 are pivotally connected at l9 to crank arms 20 which serve to rotate shafts 2| extending through the arc-extinguishing units l2.

Referring more particularly to Fig. 2 it will be observed that the shaft 2| has a squared portion 22 which rotatably supports a bridging contact 23 which electrically interconnects two stationary contacts 24 and 25. The stationary contacts 24 and 25 are resiliently pivotally supported on pins 26, the latter being supported by the end insulating plates 21, 28 of the arc-extinguishing unit l2. v

Insulating means 29, in this instance comprising two circular plates 30, 3| are secured to and rotatable with the bridging contact 23. The insulating means 29 has formed thereon a plurality of surface irregularities 32, 33. More specifically,

the surface irregularities 32, 33 are in this instance formed by notching the two plates 30, 3|.

These notches serve to bring fresh liquid in contact with the are as the bridging contact 23 is rotated, thus aiding the arc-extinguishing action. Also the surface irregularities increase the creepage distance along the edge of the insulating means 29 immediately adjacent to the arc.

The plate structure for the arc-extinguishing unit l2 will now be described. The insulating plates forming the interrupting structure for the arc-extinguishing unit 52 are of four different types. The first type has a configuration such that it may be used to support a pin 25 and a leaf spring contact 35 secured in place by a terminal stud 35. The end insulating plates 21, 28 are of the first type. The second typemerely have apertures 35 extending therethrough through which the stationary contacts 24, 25 partially extend. The insulating plates 37!, 58 are of'the second type.

The third type has a configuration more clearly shown in Fig. l, the insulating plate shown being designated by the reference numeral 35. The insulating p ate 39 has four apertures 55 extending therethrough through which insulating tie rods 4| pass, cooperating with nuts 42 and sleeves '45 to maintain the several plates and the arc-extinguishing units l2 comprisingan assemblage H fixedly in place.

The insulating plate 39 has an enlarged portion 44 removed therefrom and a grooved portion '45 also formed therein. the purpose for which will appear more clearly hereinafter.

Immediately above the insulating plate 59 is an insulatin plate 46 of the fourth type. The plate 46 has a configuration more clearly shown in Fig. 5. The plate 46 has an enlarged portion 51 removed therefrom and a grooved port on 45 formed'therein. the purpose for which will appear more clearly hereinafter. Above the insulating plate 45 the plates 39. M alternatelyrepeat to the upper insulating plate 31.

It will be observed-from an inspection'of Figs. 2 and 3 that upon the assembling of the several plates 39, 55 a pressure chamber, generally designated by the reference numeral 59, is formed adjacent the contacts 25, 50 which cooperate to establish a pressureenerating are indicated by the dotted line 52 in Fig. 2. The pressure created at the pressure-generating are 52 forces fluid, in this instance oil, to flow toward the interrupting are 53 through a plurality, in this instance four, pairs of inlet passages, each of which is designated by the reference numeral 4. Theinlet passages 55 are formed by the grooved portions 55 formed in the plates 35.

The interrupting are 53 is established between the s ationary contact 25 and the movable contact 55 within an interrupting passage generally designated by the reference numeral 55. Fluid may exhaust out of the interrupting passage 55 through a plurality of in this instance three, pairs of vent passages, each of which is designated by the reference numeral 5'5. The vent passages 51 are formed by the grooved portion 58 formed in the insulating plates 45.

It will be observed that intermediate each inlet passage 54 and each vent passage 5'! is an .insulating portion (58 of plates 59, and 59 ofplates 4B) which cooperate with the surface irregularities -32 to establish a plurality of orifices, through which the interrupting arc 53 is drawn. Thus an orifice is formed between adjacently disposed inlet and vent passages. It will be observed that the vent passages 51! are positioned in pairs and the two vent passages 57 associated with each pair lead in substantially opposite directions out of the unit l2 on the lateral sides thereof.

The operation of the interrupter will now be explalned. In the closed-circuit position of the interrupter, not shown, the electrical circuit therethrough comprises terminal stud 8, contact foot Ill, conductor 65, terminal stud El, leaf spring contact 34, stationary contact 24, movable contact 55, bridging contact 23, movable contact 55, stationary contact 25, leaf spring contact 34, terminal stud 35, conductor 55 to terminal stud 5! through the lower arc-extinguishing unit 12 in an identical manner to the terminal stud 35 of the lower arc-extinguishing unit H2. The circuit then passes through a conductor 55 to the disconnect fingers l6 and thence through the bridging me ber 13 and through the left-hand arc-extinguishing assemblage I! in an identical manner to the left-hand terminal stud 1.

When it is desired to open the electrical circuit passing through the interrupter, or in response to overload conditions in the circuit controlled by the interrupter, suitable operating mechanism, not shown, is actuated to cause downward movement of the operating rod M. The downward movement of the operating rod i l causes downward movement of the ends i5 of the bridging member -I3 to permit downward movement of the cross-members l1 and insulating operating rods [8.

Considering only the right-hand arc-extinguishing assemblage II, it will be observed that opening or downward movement of the rods l3 will cause counterclockwise rotation of the shafts 2|. The rotation of the'shaft 21 will also cause a counterclockwise rotation of the bridging contact 23 to effect a simultaneous separation between the movable contacts 50, 55 and the stationary contacts '24, 25. The result is a simultaneous establishing of a pressure-generating are 52 and an interrupting are 53 within the arc-extinguishing unit l2. The pressure-generating are 52 established within the pressure chamber 59 generates pressure therein which forces oil to pass through the inlet passages 54 into the interrupting passage 56 toward the interrupting are 53. The oil strikes the interrupting arc 53 and passes through orifices defined by the portions 58, 59 and the surface irregularities 32 to exhaust out of the interrupting passage 56 through the several vent passages 51.

It will, from the foregoing description, be apparent that the interrupting are 53 is subjected to fresh streams of oil under pressure striking it at .a plurality of points along its length. Also fluid which has contacted the interrupting are 53 is permitted to exhaust out of the interrupting passage 5'5 at a plurality of intermediate points along the length of the are 55. The result is a rapid extinction of the interrupting are 53, and a consequent breaking of the electrical circuit passing through the interrupter.

When the movable contacts 55, 55 strike the plates 31, 38, respectively, the downward movement of the rods it! is .halted and the ends i5 of bridging member [3 separate from the disconnect fingers l 6 to introduce two isolating gaps into the circuit. Fresh oil may then fiow into the units 52 through the several vent passages 57 as the residual gases escape through the check valve 58. During the closing operation the upward. movement of the bridging member [3 causes the ends i5 thereof to strike the cross-members i1 thereby effecting an upward movement of the rods I 8. The upward movement of the rods H3 effects a suitable rotation of the shafts 2i and the bridging contacts 25 to cause a re-engagement between the stationary contacts 25, '25 and movable contacts 50, 55 to effect a completion of the electrical circuit through the interrupter.

Certain features of the interrupting structure comprising the inlet passages 54 and the vent passages 5? are disclosed and claimed in United States patent application Serial No. 465,244, filed November 11, 1942, by Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker, now U. S. Patent 2,406,469, issued August 27, 1946, and assigned to the assignee f the instant application.

Figs. 6 through 10 show a modified type of arcextinguishing assemblage II comprising modified types of arc-extinguishing units generally designated by the reference numeral 65. The modified type of arc-extinguishin unit 65 is generally similar in construction to the construction of the unit 12 previously described with the exception that the vent passages 66 formed in the modified vent plates 61 (Fig. 9) extend out the end of the unit 65. This arrangement tends to bias the arc outwardly against the orifice edges 58 and 59 which act as arc splitters. Other features of the unit 65 are identical in construction to the features previously described in connection with the arc-extinguishing unit l2; consequently, a minute description thereof is deemed unnecessary.

From the foregoing description it will be apparent that I have provided an improved circuit interrupter in whichthe interrupting structure is of novel construction. Tests have clearly shown that the interrupting structure described above with its multi-orifice arrangement has been found to give highly eiiective arc interrupting action at current zero and yet to disturb the interrupting are 53 less at the current peak than straight cross blast devices, thus giving very low are energy. It will also be observed that in the foregoing construction by having the portions 58, 59 cooperate with the surface irregularities 32 to form the orifices between adjacent inlet and vent passages the resulting construction is more compact than the commercial device embodying the interrupting structure and disclosed in the aforesaid. patent by Leon R. Ludwig, Winthrop M. Leeds and Benjamin P. Baker.

Although I 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'sccpe of the appended claims.

I claim as my invention:

1. In a circuit interrupter, an arc-extinguish- 5 in unit, two relatively stationary contacts asscciated with the unit and disposed adjacent the end portions thereof, a bridging contact for electrically interconnecting the two stationary contacts in the closed circuit position, means pivotally mounting the bridging contact intermediate the ends thereof entirely within the unit, a pressure chamber disposed within the unit, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating are within the pressure chamber, an interrupting passage disposed within the unit, the bridging contact being separable from the other stationary contact to establish an interrupting are within the interruptin passage, and a plurality of inlet passages leading from the pressure chamber into th interrupting passage to permit fluid to flow toward the interrupting arc.

2. In a circuit interrupter, an arc-extinguish ing unit, two relatively stationary contacts associated with the unit and disposed adjacent the opposite ends thereof, a bridging contact positioned entirely within the unit for electrically interconnecting the two stationary contacts in the closed circuit position, a pressure chamber disposed within the unit, means pivotally mountin the bridging contact intermediate the ends thereof, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating are within the pressure chamber, an interrupting passage disposed withthe unit, the bridging contact being separable from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages leading from the pressure chamber into the interrupting passage to permit fluid to flow toward the interrupting arc, and a, plurality of vent passages leading away from the interrupting passage to permit the exhausting of fluid therefrom.

3. In a circuit interrupter, an arc-extinguish, ing unit, two relatively stationary contacts associated with the unit and positioned adjacent the opposite ends thereof, a bridging contact for electrically interconnecting the two stationary contacts in the closed circuit position and disposed wholly within the unit, a pressure chamber disposed within the unit along one side thereof, the bridging contact being separable from one of the stationary contacts to establish a pressuregenerating are within the pressure chamber, an interrupting passage disposed within the unit along the other side thereof, the bridging con tact being separable from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages leading from the pressure chamber into the interrupting passage on both sides of the bridging contact to permit fluid to flow toward the interrupting arc, means pivotally mounting'the bridging contact intermediate the ends thereof entirely within the unit, and means for effecting the rotation of the bridging contact wholly withinthe unit during the opening and closing operations of the interrupter.

4. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts associated with the unit and disposed adjacent theopposite ends thereof, a bridging contact for elec trically interconnecting the two stationary contacts in the closed circuit position and positioned wholly within the unit, a pressure chamber disposed within the unit along one side thereof. the bridging contact being separable from one of the stationary contacts to establish a pressuregenerating are within the pressure chamber, an interrupting passage disposed within the unit along the other side thereof, the bridging contact being separable from the other stationary contact I to establish an interrupting arc within the interrupting passage, a plurality of inlet passages straddling the bridging contact and leading from the pressure chamber into the interrupting passage to permit fluid to flow toward the interrupting are at different levels, a plurality of vent passages leading away from the interrupting passage at intermediate levels to permit the exhausting of fluid therefrom, means pivotally mounting the bridging contact intermediate the ends thereof within the unit, and means for effecting the rotation of the bridging contact during the opening and closing operations of the interrupter.

5. In a circuit interrupter, an arc-extinguish-' ing unit, two relatively stationary contacts asso ciated with the unit and disposed adjacent the opposite ends thereof, a "bridging contact positiohed wholly within the unit for electrically interconnecting ie two stationary contacts in the closed circuit position, a pressure chamber disposed within liillE unitalong one side thereof, the bridging contact being separable from one of the stationary contacts to establish apressure-generating are within the pressure chamber, an interrupting passage disposed within the unit along the other side thereof, the bridging contact being separable from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages on both sides of the bridging contact and leading from the pressure chamber into the interrupting passage to permit fluid to flow toward the interrup'ting arc, means pivotally-mounting the bridging'contact intermediate the ends thereof within the unit, means for effecting the rotation of the bridging contact during the opening and closing operations of the interrupter, and insulating means carried by and rotatable with the bridging contact for confining at least one ofthe arcs.

6. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts associated with the unit and disposed adjacent the opposite ends thereof, a bridging contact positioned wholly within the unit for electrically interconnecting the two stationary contacts in the closed circuit position, a pressure chamber disposed within the unit along one side thereof, the bridging contact being separable from one of the stationary contacts to establish a pressure generating are within the pressure chamber, an interrupting passage disposed within the unit along the other side thereof, the bridging contact being separable'from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages straddling the bridging contact and leading from the pressure chamber into the interrupting passage to permit fluid to now toward the interrupting arc, means pivotally mounting the bridging contact intermediate the ends thereof within the unit, means for effecting the rotation of the bridging contact during the opening and closing operations of the interrupter, and insulating means carried by and rotatable with the bridging contact, the insulating means having surface irregularities formed thereon for confining at least one of the arcs.

7. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts associated with-the unit and positioned adjacent the opposite ends thereof, a bridging contact disposed wholly within the unit for electrically interconnecting the two stationary contacts in the closed circuit position, a pressure chamber disposed within the unit along one side thereof, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating arc within the pressure chamber, an interrupting passage disposed within the unit alon the other side thereof, the bridging contact being separable from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages leading'from the pressure chamber into the interrupting passage at certain levels to permit fluid to flow toward the interrupting arc, a plurality of vent passages leading away from the interrupting passage at intermediate levels to permit the exhausting of fluid therefrom, means pivotally mounting the bridging contact intermediate the ends thereof wholly within the unit, means for 8 effecting therotationof thebridging contactrduning the opening and closing operations .of the interrupter, insulating means carried by and rotatable with the bridging contact for confining-at least one of the arcs, and the insulating means having surface irregularities formed thereon.

8. In a circuit interrupten an arc-extinguishing'unit, two relatively stationary contacts associated with :the unit and disposed adjacent the opposite ends thereof, a bridging contact disposed wholly within the unit for electrically interconnectingthe two stationary contactsin the closed circuit position, a pressure chamber disposed within the unit, the bridging contact being. separable from .one of the stationary contacts to establish a pressure-generating arc within the pressure chamber, :an interrupting passage .disposed within the unit, the bridging contact being separable from the other stationary contact to establish :an interrupting are within the interrupting passaga'a-plurality of inlet passages leading from the pressure chamber into the interrupting passage to permit fluid to flow toward the interrupting are, a plurality of vent passages leading away'f-rom :the interrupting passage to permit the exhausting of fluid therefrom, means pivotally mounting the bridging contact within the arc extinguishing unit intermediate the ends thereof, means for effecting the rotation of the bridging contact during the opening and closing operations of :the interrupter, insulating means carried by and rotatable with the bridging contact, the insulating means having surface irregularities formed thereon, and insulating means disposed along the interrupting passage having surface irregularities which cooperate with the irregularities formed on the insulating means rotatable with the bridging contact to provide a plurality of orifices through which the interrupting arc is drawn.

9. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts associated with the unit and disposed adjacent the opposite ends thereof, a bridging contact for electrically interconnecting the two stationary contacts in the closed circuit position, a pressure chamber disposed within the unit, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating are within the pressure chamber, an interrupting passage disposed within the unit, the bridging contact being separable from the other stationary contact to establish an interrupting are within the interrupting passage, a plurality of inlet passages leading from the pressure .chamher into the interrupting passage to permit fluid to fiow toward the interrupting are, a plurality of vent passages leading away from the interrupting passage to permit the-exhausting of fluid therefrom, means pivotally mounting the bridging contact intermediate the ends thereof wholly within the unit, means for effecting the rotation of the bridging contact during the opening and closing operations of the interrupter, insulating means carried by and rotatable with the bridging contact, the insulating means having surface irregularities formed thereon, and insulating means disposed along the interrupting passage having surface irregularities which cooperate with the irregularities formed on the insulating means rotatable with the bridging contact to provide a plurality of orifices through which the interrupting arcis drawn, an orifice being formed between :adjacently disposed inlet and .vent passages.

10. In a circuit interrupter, a stationary contact, a movable contact, means for pivotally mounting the movable contact, means effecting the rotation of the movable contact during the opening and closing operations of the interrupter, an interrupting passage, the movable contact separating from the stationary contact to establish an interrupting are within the interrupting passage, means forming a plurality of inlet passages leading toward the interrupting passage at certain levels, means forming a plurality of vent passages leading from the interrupting passage at intermediate levels, and insulating means carried by and rotatable with the movable contact to confine the interrupting arc.

11. In a circuit interrupter, a stationary contact, a movable contact, means for pivotally mounting the movable contact, means effecting the rotation of the movable contact during the opening and closing operations of the interrupter, an interrupting passage, the movable contact separating from the stationary contact to establish an interrupting are within the interrupting passage, means forming a plurality of inlet passages leading toward the interrupting passage at a plurality of levels, means forming a plurality of vent passages leading from the interrupting passage at a plurality of intermediate levels, and insulating means carried by and rotatable with the movable contact to confine the interrupting arc, the insulating means having surface irregularities.

12. In a circuit interrupter, a stationary con tact, a movable contact, means for pivotally mounting the movable contact, means effecting the rotation of the movable contact during the opening and closing operations of the interrupter, an interrupting passage, the movable contact separating from the stationary contact to establish an interrupting arc within the interrupting passage, means forming a plurality of inlet passages leading toward the interrupting passage at certain levels, means forming a plurality of vent passages leading from the interrupting passage at intermediate levels, insulating means carried by and rotatable with the movable contact to confine the interrupting arc, the insulating means having surface irregularities, and the interrupting passage being formed with a plurality of surface irregularities which cooperate with the aforementioned surface irregularities to provide a plurality of orifices through which the interrupting arc is drawn,

13. In a circuit interrupter, a stationary contact, a movable contact, means for pivotally mounting the movable contact, means effecting the rotation of the movable contact during the Opening and closing operations of the interrupter, an interrupting passage, the movable contact separating from the stationary contact to establish an interrupting are within the interrupting passage, means forming a plurality of inlet passages leadin toward the interrupting passage at certain levels, means forming a plurality of vent passages leading from the interrupting passage at intermediate levels, insulating means carried by and rotatable with the movable contact to confine the interrupting arc, the insulating means having surface irregularities, the interrupting passage being formed with a plurality of surface irregularities which cooperate with the aforementioned surface irregularities to provide a plurality of orifices through which the interrupting arc is drawn, and an orifice being formed between adjacently disposed inlet and vent passages.

14. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts as sociated with the unit and disposed adjacent the opposite ends thereof, a bridging contact disposed within the unit for electrically interconmeeting the two stationary contacts in the closed circuit position, means pivotally mounting the bridging contact intermediate the ends thereof, a pressure chamber disposed within the unit, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating arc within the pressure chamber, an interrupting passage disposed within the unit, the bridging contact being separable from the other stationary contact to establish an interrupting arc within the interrupting passage, a plurality of inlet passage leading from the pressure chamber into the interrupting passage at certain levels to permit fluid to flow toward the interrupting arc, a plurality of vent passages leading away from the interrupting passage at intermediate levels to permit the exhausting of fluid therefrom, and all the vent passages leading out one end of the unit.

15. In a circuit interrupter, an arc-extinguishing unit, two relatively stationary contacts associated with the unit and disposed adjacent the opposite ends thereof, a bridging contact disposed within the unit for electrically interconnecting the two stationary contacts in the closed circuit position, means pivotally mounting the bridging contact intermediate the ends thereof within the unit, a pressure chamber disposed within the unit, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating are within the pressure chamber, an interrupting passage disposed Within the unit, the bridging contact being separable from the other stationary contact to establish an interrupting arc within the interrupting passage, a plurality of inlet passages leading from the pressure chamber into the interrupting passage at a plurality of levels to permit fluid to flow toward the interrupting arc, a plurality of vent passages leading away from the interrupting passage at a plurality of intermediate levels to permit the exhausting of fluid therefrom, the vent passages being positioned in pairs, and the two vent passages associated with a pair leading in substantially opposite directions out of the unit on the lateral side thereof.

16. In a circuit interrupter of the liquid break type, an arc extinguishing unit, two relatively stationary contacts disposed adjacent the end portions of the unit, a bridging contact disposed interiorly of the unit for electrically interconnecting the-two stationary contacts in the closed circuit position, means pivotally mounting the bridging contact intermediate the ends thereof interiorly within the arc extinguishing unit, and a substantially circular plate member composed of insulating material secured to and rotatable with the bridging contact.

17. In a circuit interrupter of the liquid break type, means including a plurality of contiguously disposed insulating plates for forming an arc extinguishing unit, a pair of relatively stationary contacts disposed at opposed ends of the unit, some of the plates having openings formed therein to provide a pressure-generating chamber laterally along one side of the unit interiorly thereof, some of the plates having openings therein for forming an interrupting chamber extending laterally along one side of the unit interiorly thereof, a bridging contact disposed entirely within the unit for electrically interconnecting the two stationary contacts in the closed circuit position, means pivotally mounting the bridging contact intermediate the ends thereof wholly within the unit, the bridging contact being separable from one of the stationary contacts to establish a pressure-generating are within the pressure-generating chamber, the bridging contact also being separable from the other sta tionary contact to establish an interrupting are within the interrupting chamber, and a substantially circular plate member fixed to and. rotatable with the bridging contact.

18., The combination in a circuit interrupter having a, rotatable bridging contact electrically interconnecting two relatively stationary contacts, of an arc, extinguishing unit including a plurality of contiguously disposed insulating plates, the stationary contacts being disposed at opposite ends of the unit, the bridging contact being disposed wholly within the unit, means pivotally mounting the bridging contact intermediate the ends thereof within the unit, some of the plates having openings formed therein to provide a pressure-generating chamber disposed interiorly within the unit along one side thereof, some of the plates having openings therein which upon alignment form an interrupting chamber extending along the other side of the are extinguishing unit, the bridging contact being separable from one stationary contact to estab- 12 lish a pressure-generating. are within, the pressure generating chamber, and the bridging contact also being separable from the other stationary contact to establish an interrupting are within the interrupting chamber.

19. In a circuit interrupter of the liquid break type, an arc extinguishing unit, two relatively stationary contacts associated with the unit and disposed adjacent the end portions thereof, a bridging contact for electrically interconnecting the two stationary contacts in the closed circuit position and disposed wholly within the unit, means pivotally mounting the bridging contact intermediate the ends thereof entirely within the unit, means defining a pressure-generating chamber disposed laterally along one side of the unit interiorly thereof, means defining an interrupting chamber disposed laterally along the other side of the unit interiorly thereof, and a plurality of separate passages interconnecting the pressure-generating chamber with the interrupting chamber.

WINTHROP M. LEEDS.

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

UNITED STATES PATENTS 0 Number Name Date 1,934,454 Spurgeon Nov. 7, 1933 2,100,753 Schofield et a1 Nov. 30, 1937 2,156,450 Cole e May 2, 1939

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