US2442010A

US2442010A - Circuit interrupter

Info

Publication number: US2442010A
Application number: US515536A
Authority: US
Inventors: Winthrop M Leeds; Benjamin P Baker
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1943-12-24
Filing date: 1943-12-24
Publication date: 1948-05-25
Anticipated expiration: 1965-05-25

Description

May 25, 948 w. M. LEEDS ETAL 2,442,910

C IRCUIT I NTERRUPTER Filed Dec. 24, 1943 3 Sheets-Sheet 1 WITNESSES: 47 INVENTOR5 M nfhrap M Zeeas and g fier 'am/n p Bare/'1 May 25, 1948. w, M, LE D HAL 2,442,010

CIRCUIT INTERRUPTER Filed Dec. 24, 1945 3 Sheets-Sheet 3 g 6/ g g 6/ T 3 XI N 58 5 iii 1 WITNESSES: INVENTORS c Mhihrap/W. Leeds and I Ben am/n PEG/(6f:

Patented May 25, 1948 UNITED STATES PATENT OF FlCE CIRCUIT lNTEliRflFT-Eli Winthrop M. Leeds, Wilkinsliurg', and- Benjamin" P. Baker, Turtle Creek, Paaassignors t'o Westinghouse Electric Corporation; East Pittsburgh; Pa., a corporation of Pennsylvania Application December 24, 1943, Serial' No. 515,536

Claims; 1

Thisinvention relates to circuit interrupters, and, more particularly, to circuit interrupters-of the type having arc extinguishing structures in Whichfluid is forced into the are stream to effect rapid extinction of the are.

It wasfound in testing a circuit interrupter of the type having a nozzle-shaped stationary contact, from which a movable contact was withdrawn and having aplurality of laterally disposed inlet passages spaced along the path ofmovement of the movable contact, somewhat similar tothat shown in U. S. Patent 2,304,529 issued December 8, 1942, to Benjamin P. Baker, andassigned to the same assignee of this invention, that the greater proportion of the oil would flow through the inlet passage adjacent the vented-'nozzle-shaped contact. It was felt that this greater proportion of flow, which took place adjacent the stationary contact, could be attributed to the restriction of the lower inlet passages by the moving contact and the-back pressure from gasproduced by the arc. The disadvantage which resulted wasinadequate scavenging of the whole arc length by oil flow; It is desirable to have the arc extinguishing fluid traverse the entire arc space whatever the position of the moving contact. Furthermore, during a flushing operationtaken on no-load' operation of the interrupter, itis also desirableto have the flushing. oil pass throughthe entire arcing region.

It isageneral object of our invention to provide a solution for this problem.

Another object is to provide an improved circuit interrupter of'the type having a plurality of passages disposed along the path of move-- ment of the moving contact, and to provide valve means for controlling the flow of fluid through the plurality of passages. Preferably, it is desirable to provide valve means which are movable in responseto motion of the movable contact which successively opens the passages to permit the flow of fluid therethrough.

Another object is to provide an improved circuit interrupter of the type which causes a flow of fluid substantially transversely of the are at a level with a moving point in the arc. The moving point may move at a speed which is proportional to the speed of movement of the movable contact.

Another object is to provide an improved cir cuit interrupter of the type having separablecontact means to establish an are. We associate a chamber with the circuit interrupter havinga volume which is contract'able duringthe opening movement-of the movable contact means, and

2. which is expandable during the closingmovement thereof. We associate valve means with the chamber for causingunidirectional circulation of fiuid through the chamberduring a'complete operation of the interrupter.

Furtherfobiectswill become apparent upon a reading of the following specification taken in conjunction with the drawings, in which:

Figure 1' is acircuitinterrupter embodying our invention and showninthe closedcircuit position;

Fig. 2" is an enlarged .vertical sectional view through" one of the arc extinguishing units of Fig. 1, the contactsbeing shownin the partly open circuit position;

Fig. his; a View in sectiontaken-on the line 1II ;-;-III of Fi 2-;

Fig fl is a view in section taken on the line IV IV of Fig. 2'; a

Fig. 5 is a circuit interrupter embodying a modification of" our invention taken on the line V- V' of Fig. 6,-the"contacts beingshown in the partly open' circuit position;

Fig; 6 is a -view in section taken on the line VI -VI of' Fig.- 5;

Fig; 7 is'anotherinodification of our invention taken on"the-line--VIIVII'of Fig. 8, the contacts being shown in the partlyopen circuit position;

8-isa-view in-section taken on the line Fig. 9 is a view in section taken on'the line IX'IX- of Fig. 7;

Fig. -10-1s stillanotherembodiment of our invention; thecontacts again being shown in the partly open circuit position Fig. 11 isa view in section'taken on the line XI XI of-Fig. 10; and

Fig. 12 is 'a view in section taken on the line XII-XI} of Fig. 10'.

Referrin'g' to the drawings and, more particularly, to Fig-l 1, the reference'numeral I designates a tank filled to' the'level 2'with a suitable arc extinguishing: fluid, in this instance oil. Depending from the cover'3'of the tank I area pair of terminal bushings 4 which enclose a pair of terminal studs, not shown. Threaded to the lower end 'oftheterminal studs are a pair of apertured contact feet 5 which are clamped to the terminal studs by clamping studs 6. The contact feet 5 support a pair of arc extinguishing units, generally designated by the reference numeral 1; which arebridged in the'closed circuit position; as shown'inFigi' 1, by a conducting briclgin'g'bar'B; which is reciprocally operated in a vertical direction a by an insulating operating rod 9 to effect the opening and closing of the circuit through the interrupter. The full open-circuit position of the interrupter is shown by the dotted lines II) of Fig. 1. At the opposed outer ends of the bridging bar 8 are the movable contacts II of the interrupter. Since the two units 1 are identical, a description of only one will sutfice.

Bolts I3, which extend through the contact feet 5, secure a hollow stationary contact support I4 in place (see Fig. 2). Threadedly secured to the contact support I4 is an annular removable arc resisting stationary contact I5 having an aperture I6 therethrough for forming a vent. As shown in Fig. 2, insulating tie rods I1 and nuts I8 secure a grid structure, generally designated by the reference numeral I9, to the stationary contact support I4.

In this instance the grid structure I9 comprises two types of plates. The first type is herein called an insulating orifice plate and is designated by the reference numeral 20 in Fig. 2. The orifice plate 20 has an aperture 2I centrally formed therein through which moves the movable contact I I. The second type of plate comprises a plurality, in this instance four, segmental insulating plates 23 more clearly shown by the dotted lines in Fig. 4. The segmental insulating plates 23 are rigidly secured in place by the tie rods II and they form a plurality of inlet passages 24 between each pair of orifice plates 20.

The movable contact II separates from the stationary contact I5 to establish an are 25 as more clearly shown in Fig. 2. We provide movable valve means comprising a cylindrical slide valve or apertured member 26, the upper end of which is guided by a portion 21 integrally formed with the contact support I4. The lower end of the cylindrical slide valve 26 is threadedly secured at 28 to an ofistanding wall 29 integrally formed with the movable contact II. It will be observed that the cylindrical slide valve 26 and the wall 29 form a chamber, generally designated by the reference numeral 36 in Fig. 2. The movable contact I I has a passage 32 formed therein which connects the arcing region, generally designated by the reference numeral 33, with the chamber 36. -It will be observed that the are 25 has a fixed arc terminal at the stationary contact I5 and a movable arc terminal at the tip 31 or the movable contact II.

The cylindrical slide valve 26 and the offstanding wall 29 together form a piston member, generally designated by the reference numeral M, which moves in response to motion of the movable contact II within a piston chamber, generally designated by the reference numeral 42. The piston chamber 42 comprises an insulating cylinder 43, the upper end of which is threadedly secured at 44 to an offstanding flange 45 integrally formed with the stationary contact support I4. The lower end of the insulating cylinder 43 is threadedly secured to a bottom metallic plate 46 which also serves to guide the motion of the moving contact II.

In this instance four apertures 41 are provided in the cylindrical slide valve 26 to successively cause the opening of the inlet passages 24. It will be observed that the apertures 41 are positioned adjacent the tip 31 of the movable contact II. Consequently, as the contact I I moves downwardly one set of inlet passages 24 is sealed up and the next set of inlet passages 24 are opened up. Thus this arrangement permits a very effective use of the oil flow which must traverse the;

' against the offstanding wall 29.

entire arc space 33 whatever the position of the moving contact II. Furthermore, since oil flow is above the contact tip 31, being projected toward the point P, the clearance between the moving contact II and the grid plates may be reduced to a minimum. This means more restriction of the are 25 for a given size contact I5, and, therefore, more effective are interruption.

The operation of the embodiment of our invention shown in Figs. 1-4 will now be explained. In the closed circuit position of the interrupter as shown in Fig. l, the electrical circuit therethrough comprises left-hand terminal stud, not shown, left-hand contact foot 5, stationary contact support I4, stationary contact I5, movable contact II, conducting bridging bar 3 through the right-hand arc extinguishing unit I in an identical manner to the right-hand terminal stud not shown.

When it is desired to open the electrical circuit passing through the interrupter, or in response to overload conditions existing in the electrical circuit controlled by the interrupter, suitable operating mechanism, not shown, is actuated to cause downward movement of the insulating operating rod 9. The downward movement of the insulating operating rod 9 causes downward movement of both the movable contact II and downward movement of the piston member El within the piston chamber 42. The movement of the piston member 4I Within the piston chamber 42 forces oil to flow in the direction indicated by the arrows in Figs. 2 and 4. Also pressure formed by the arc 25 within the arcing region 33 will act through the passage 32 provided in the movable contact I I to communicate with the chamber 3i] and hence act against the wall 29 to speed up the downward movement of the movable contact II during high current interruption.

In other words, we provide a diiierential piston action caused by the arcing pressure acting through the passage 32. The arcing pressure acts through the inlet passages 24 and upwardly However, the arcing pressure also acts through the passage 32 and on top of the wall 29 and also on top of the contact II. The diilerential pressure which causes a net downward force to assist the opening operation of the movable contact II is the arcing pressure acting across an area equal to the cross-sectional area of the lower portion of the movable contact I I. During high current interruption this additional driving force speeds up the opening movement.

The downward movement of the piston member 4| within the piston chamber 42 causes oil to flow through the four apertures 41 provided in the cylindrical slide valve 26 and through the inlet passages 24 toward a point P, which in this instance moves at a speed equal to the speed or the movable contact II. The oil which enters the arcing region 33 at the level P must then traverse the entire arcing region 33 before it is permitted to vent through the aperture I6 provided in the stationary contact I5 as indicated by the arrows in Fig. 2.

It will, therefore, be apparent that we have provided an interrupter in which there are disposed a plurality of passages 24 which terminate at their inner end adjacent the are 25 and we provide movable valve means 26 movable in response to motion of the movable contact II for controlling the flow of fluid through the passages 24. 'As the movable contact II moves downward amaoro.

during. the opening operation, the. are 25. is lengthened and the apertures 41 provided in the cylindrical. Slide valve. ZILsuccessively open. the passages 24.-to permit the flow of oil therethrough.

It. will be noted that. the arrangement operatestopermit oil to flow through the particular passagesl twhichat a particular timeterminate adjacent the ti 3.! of themovable contact II. Theflow. of oil isv substantially transversely of thefarc 2'5 and is directed therein at a. level with the moving point P. inthearcing region 33, which point Pmoves at a. speed which in this instance is directly equal to the speed of. movement of the movablecontact II By making the speed of movement. ofv the movable. contact II different from the speed of movement of the movable cylindricalslide valve 25 by suitable means such as intermeshing gears, the speedof the point P could be different from the speed of. the movable contact II, For purposes of simplicity we felt it desirable to mechanically connect the slide valve 26 and the movable contact II so that the speed of. movement of the point P would be the same as the speed of movement of the movable contact II.

During the closing operationof the interrupter shown in Fig. 2, oil will be drawn upwardly through valve 35. and into chamber the latter then being expandedin volume. During the sub sequent opening stroke onno-load operation the volume of thechamber 42 diminishes and the fresh oil now disposed therein will move upwardly throughv the inlet passages 24 to flush carbonized products of decomposition disposed within the arcing region 33 upwardly and out through the aperture I6 provided in the stationary contact i5. Thus during no-load operation of the interrupter there is a complete flushing of the arcing region 33 because of this unidire tional fiow of fresh oil through chamber 42.

In the embodiment of ourinvention shown in Figs, 5 and 6 we provide a resiliently-mounted relatively. stationary contact 52 which cooperates with the movable contact I I to establish and lengthen an are 25. A ring-shaped plate 53, threaded to the. upper end of the cylindrical slide valve 26, forms a piston member which operates in apiston chamber 42. In this embodiment ofour invention the passage formed between the segmental insulating plates 23 form discharge .passages 54, which permit the discharge of oil from the arcing region 33. An offstanding portion 55 is integrally formed with contact H having. apertures 56 formed therein and is threadedly secured to the lower end of cylindrical slide valve 25. Apertures 51 are also formed in the top insulating plate member 580i the grid structure I9. The top insulating plate member 58 is threadedly secured at 59 to a guide 60 which guides the movement of the relativelyv stationary contact 52. Apertures BI are formed in the stationary contact support 62, The stationary contact support 62 may be secured to the contact feet 5 (see Fig.1) by bolts I3 which may be threadedly inserted into the contact support 62.

It will be apparent that the arc 25 has a fixed arc terminal atthe stationary contact 52 and a movable arc terminal at the tip 31 of the movable contact II. During the. opening operation the. movable contact Il moves downwardly together with the cylindrical slide valve 25 and piston .member 53, The downward movement of piston. member 53 within piston chamber 42 causes a flowof oil out of piston-chamber 42 stance moves at the samespeed as themove 10. ment of the movable arc terminal; The direction of flow is indicated by the-arrows in Figs. Sand 6.

It. will be observed that in Figs. 2, 5'andl0 .that the vertical lengths of the apertures 41. is sub-.

: stantiallyequalto twice the widthofthe plates 2Q, 23; Consequently, at notime is theentrance or discharge of oil from the. arcing region 33.-

entirely prohibited, there always being atleast oneiull width of. discharge or. entrancepassage 5s, 24 through which the oil may-pass.

It will be apparent. from theabove descriptionv that in the embodiment of our-invention shown in Figs. 5 and 6, wehave providedvalve-means- 25 responsive tomotionof the movable contact: I I for directing-a flow'of oil adjacent the. fixed are terminal, through the arcingregion 33 and dis.-

charging out of the. arcing region 331adjacent the movable arc terminal at a level P which moves inthis instance at a speed directly equal-to the 1 speedof the movablelcontact I I. As mentionedin. connection with Fig. 2 intermeshing gears oriother means could be-provided'tohave the speed-oi movementof the point PinFig. 5 different from the speed of-movement of the movable arc. terminal.

Again the valve causes a unidirectional-flow of oil through the piston chamber 42 during a complete. operation of -.-the interrupter.

In the embodiment of our inventionshown in Figs. 7 through 9, we provide acircuitinterrupter oi modified construction having a. piston. chams b-er generally. designatedby thereferencenw.

meral "H. Thepiston chamber II has. an enlarged portion Hand a-smaller -closedportion .753. An insulating cup-shaped member I41 is threadedly securedlat '55 to the .oifstanding sup port portion 55 of the movable contact III The ofistanding support portion 55 again has aperturesv 56 .formed therein.

5 ...enlarged portion I2 is threadedly secured to'an apertured support plate It which may be secured to the contact feet f Fig. l' by any suitable means suchas the bolts l3 shown in Fig: 1. Again the valve 35 causes unidirectional. flow of oil through the piston chamber II during each @complete operation of the interrupter.

In Fig. '7 the grid structure I9 is movable-with the movable contact I l beingsecured to the cupshaped member M bythe insulating tie rods I1. During the opening operation themovable contact ll, cup-shaped member 'I Land-grid-structure 59 move downwardly as a unit from the/enlarged portion I2 into thesmallerclosed portion 'IEIofthe piston chamber 1|. Thiscauses anupward flow of oil radially inwardly toward the movable arc terminal, upwardly within the arcing region 33 and outwardly through the discharge passages 54 at a level P which, in thisinstance, is adjacent the stationary arc terminal. It-will be apparent that the gridstructure I9 coacts with theashoulder I! to permit-the discharge of oil through the discharge passages 54 only ata level adjacent the fixed arc terminal It will benoted thatthe discharge passages 54 are uncovered successively'as theylare brought below the-stationary The. upper end of the 7. contact tip, while the outer openings of these discharge passages 54 are successively sealed off as they move below the shoulder 11 integrally formed with the piston chamber 1 I.

It is also to be observed that the pressure in the exhaust chamber, generally designated by the reference numeral 18, in Fig. 7, tends to accelerate the moving contact II by acting downwardly on the moving grid [9. The size of the apertures 1 6a determines the magnitude of the pressure in the exhaust chamber.

In the embodiment of our invention shown in Figs. 10-12, we disclose an arrangement similar to that shown in Fig. 5. However, we provide a passage 32 through the movable contact H to permit differential piston action to accelerate the opening movement of the movable contact ll during high current interruption. In other words, the arcing pressure acts upwardly on the ringshaped piston 53, but also acts downwardly on the support portion 55 by actin through the passage 32. The differential piston area is, therefore, the area of the support portion 55 minus the area of the ring-shaped piston member 53, and the arcing pressure acting on this differential piston area tends to accelerate the movement of the moving contact H during high current interruption.

As in Fig. 2, we have a chamber 30 which is expandable during the opening operation and contractable during closing operation. The slide valve action of cylindrical slide valve 26 is the same as in Fig. 5. Therefore, a further description concerning this feature is not necessary for a full understanding of this embodiment of our invention. It will be noted that in Fig. 10 the discharge of oil takes place through the discharge passages 54 at a level P, which level moves at the same speed as the movable contact ll. As previously mentioned, a different speed ratio could be obtained by means permitting relative movement of the contact I l with cylindrical slide valve 26, such as intermeshing gears or other suitable means well known in the art.

Although we have illustrated our invention as adapted to particularly desirable forms of circuit interrupters which use a suitable are extinguishing liquid such as oil, it is to be clearly understood that some aspects of our invention are not limited to these particular types of interrupters but are adapted to the use of any fluid which need not be oil but could be a gas or even air. Also separate sources of pressure to drive such fluids as gases or liquids could be used instead of relying on piston action of the moving parts.

Although we 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 appended claims.

We claim as our invention:

1. In a circuit interrupter, means for establishing an arc, means defining a plurality of stationary passages terminating at one end closely adjacent to the arc, and a cylindrical slide valve substantially surrounding the are for controlling the flow of fluid through the plurality of passages.

2. In a circuit interrupter, movable means for establishing and lengthening an arc, means delining a plurality of stationary passages terminating at one end closely adjacent to the arc, and a cylindrical slide valve substantially surrounding the are responsive to motion of the first- 8. mentioned means for controlling the flow of fluid through the plurality of passages.

3. In a circuit interrupter, an annular stationary contact, a movable contact cooperable with the stationary contact to establish an arc, stationary means partly of insulating material for forming a plurality of inlet passages tenninating adjacent the path of movement of the movable contact, a piston chamber containing fluid, a piston member secured to and movable with the movable contact within the piston chamber, the piston member having an aperture formed therein to successively open the inlet passages while meanwhile closing others and thus permit fluid forced under pressure from opening movement of the piston member to successively pass through the inlet passages to the arc, and at least part of the fluid discharging through the annular stationary contact.

4. In a circuit interrupter, a stationary con tact, a movable contact cooperable with the stationary contact to establish an arc, stationary means partly of insulating material forming a plurality of discharge passages leading away from the path of movement of the movable contact, a piston member secured to and movable with the movable contact, the piston member having an aperture formed therein to successively open the discharge passages during the opening operation while meanwhileclosing others, the piston member forcing the fluid adjacent the stationary contact toward the arc and at least part of the fluid discharging away from the are through the discharge passages upon the opening thereof.

5. In a circuit interrupter, a stationary contact, a movable tubular contact cooperable with the stationary contact to establish an arc, stationary means partly of insulating material forming a plurality of discharge passages leading away from the path of movement of the movable tubular contact, a difierential piston member secured to and movable with the movable contact, the differential piston member having an aperture formed therein to successively open the discharge passages during the opening operation while meanwhile closing others, the differential piston member being driven by arcing pressure acting through the movable tubular contact to force fluid adjacent the stationary contact toward the arc, and at least part of the fluid discharging away from the arc through the discharge passages upon the opening thereof.

6. In a circuit interrupter, a piston chamber having an enlarged portion and a smaller closed portion, a stationary contact and a movable contact both disposed within the piston chamber and cooper-able to establish an are, a grid structure partly of insulating material and secured to and movable with the movable contact from the enlarged portion of the piston chamber to the smaller closed portion thereof, the grid structure operating as a piston within the piston chamber to force fluid adjacent the movable contact and into the arc, the grid structure forming a plurality of discharge passages for the discharge of fluid from said arc, the discharge passages being successively closed upon opening movement of the grid structure into the smaller portion of the piston chamber.

7. In a circuit interrupter, means at least partially of insulating material forming an arc passage, means for establishing an arc within the arc passage, the'first-mentioned means also providing a plurality of fluid passages disposed axially along the arc passage whereby fluid may flow 9 through the fluid passages, and means for successively openingth'e fluid passages one by one While at the same time successively closing others of said fluid passages so that fluid may pass only through the fluid passages which are opened by said last-mentioned means.

8. In a circuit interrupter, stationary means at least artially of insulating material forming an arc passage, means for establishing an arc within the arc passage, the first-mentioned means also providing a plurality of fluid passages spaced axially along the are passage whereby fluid may flow through the fluid passages, and valve means including a movable apertured member for successively opening the fluid passages one by one while at the same time successively closing others of said fluid passages so that fluid may pass only through the fluid passages which are opened by said valve means.

9. In a circuit interrupter, stationary means at least artially of insulating material forming an arc passage, means venting the are passage only adjacent one end thereof, means for establishing an are within the arc passage, the firstmentioned means also providing a plurality of fluid passages disposed axially along the arc passage whereby fluid may flow through the fluid passages into the arc passage, and valve means including a movable apertured member for successively opening the fluid passages one by one while at the same time successively closing others of said fluid passages so that fluid may enter the arc passage only through the fluid passages which are opened by said valve means.

10. In a circuit interrupter, stationary means at least partially of insulating material forming an arc passage, means for forcing fluid into the arc passage adjacent one end thereof, means for establishin an are within the arc passage, the first-mentioned means also providing a plurality of spaced fluid passages extending axially along the arc passage whereby fluid may exhaust out of the arc passage through the fluid passages, and valve means including a movable apertured member for successively opening the fluid passages one by one while at the same time successively closing others of said fluid passages so that fluid may exhaust out of the arc passage only through the fluid passages which are opened by said valve means.

11. In a circuit interrupter, means at least partially of insulating material forming an arc passage, means for establishing an are within the arc passage, the first-mentioned means also providing a plurality of pairs of fluid passages spaced axially along the arc passage whereby fluid may pass through each pair to strike at least opposite sides of the are within the arc passage, and means for successively opening the pairs of fluid passages one by one while at the same time successively closing others of said pairs of fluid passages so that fluid may pass only through the pairs of fluid passages which are opened by said last-mentioned means.

12. In a circuit interrupter, relatively stationary means at least partially of insulating material forming an arc passage, means for establishing an are within the arc passage, the first-mentioned means also providing a plurality of pairs of fluid passages spaced axially along the arc pas- 70 2,293,833

sage whereby fluid may pass through each pair to strike at least opposite sides of the are within the arc passage, and valve means including a movable apertured member for successively opening the pairs of fluid passages'one by one while at the same time successively closing others of said pairs of fluid passages so that fluid may pass only through the pairs of fluid passages which are opened by said last mentioned means.

13. In a circuit interrupter, stationary means at least partially-of insulating material forming an arc passage, means venting the arc passage only adjacent one end thereof, means for establishing an are within the arc passage, the firstmentioned means also providing a plurality of fluid inlet passages disposed axially along the arc passage whereby fluid may flow through the fluid passages into the are passage, and means for successively opening the fluid passages one by one while at the same time successively closing others of said fluid inlet passages so that fluid may pass only through the fluid inlet passages which are opened by said last-mentioned means and exhaust out said venting means.

14. In a circuit interrupter, means at least partially of insulating material forming an arc passage, means forcing fluid into the arc passage adjacent one end thereof, means for establishing an are within the are passage, the first-mentioned means also providing a plurality of fluid exhaust passages disposed axially along the arc passage whereby fluid may exhaust away from the arc passage out through the fluid exhaust passages, and valve means for successively opening the fluid exhaust passages one by one while at the same time successively closing others of said fluid exhaust passages so that fluid may exhaust out of the arc passage only through the fluid exhaust passages which are opened by said last-mentioned means.

15. In a circuit interrupter, relatively stationary means at least partially of insulating material forming an arc passage, means for establishing an are within the arc passage, the first-mentioned means also providing a plurality of pairs of fluid exhaust passages spaced axially along the arc passage whereby fluid may exhaust out of the arc passage through the fluid exhaust passages, and valve means for successively opening the pairs of fluid passages one by one while at the same time successively closing others of said pairs of fluid passages so that fluid may exhaust out of the arc passage only through the pairs of fluid exhaust passages which are opened by said lastmentioned means.

WINTHROP M. LEEDS. BENJAMIN P. BAKER.

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

UNITED STATES PATENTS Number Name Date 1.955,215 Whitney et al Apr. 17, 1934 2,067,643 Reher Jan. 12, 1937 2,111,416 Balachowsky Mar. 15, 1938 2,158,846 Balach'owsky May. 16, 1939 2,262,516 Prince Nov. 11, 1941 Paxton Oct. 13, 1942