US2408352A - Gas cooling arrangement for circuit interrupters - Google Patents

Description

Sept. 24, 1946. H, mus 2,408,352

GAS COOLING ARRANGEMENT FOR CIRCUIT INTERRUPTERS Filed March 24, 1944 Inventor: JJ' 3 Charles H. Titu /9 y My His Attoffiy.

Patented Sept. 24, 1946 GAS COOLING ARRANGEMENT FOR CIRCUIT INTERRUPTERS Charles H. Titus, Philadelphia, Pa., assignor to General Electric Company, a corporation of New York Application March 24, 1944, Serial No. 527,912

1 My invention relates to electric circuit interrupters and more particularly to air circuit interrupters, and has for its principal object the provision of an improved circuit interrupter which is particularly effective in suppressing flame emission from the arc extinguishing structure of the circuit interrupter by rapidly cooling the arc gases.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is a front view, partly in section, of an electric circuit breaker embodying my invention; Fig. 2 is an exploded view in perspective of the arc extinguishing structure for one pole of the electric circuit interrupter shown in Fig. 1, including the means for suppressing flame emission; Fig. 3 is an enlarged sectional view taken on line 33 of Fig. 1, and Fig. 4 is a sectional view taken on line 4--4 of Fig. 3.

Although my improved means for suppressing flame emission from an arc chute may be applied to any are chute, I have specifically illustrated it as applied to a multiple slot arc chute of the type disclosed and claimed in the co-pending application of Joseph W. Seaman, Serial No. 527,913, filed concurrently herewith and assigned tothe same assignee as the present application.

Referring now to the drawing, I have illustrated an electric circuit interrupter generally indicated at I0, which might be a single-pole or multiple-pole circuit interrupter. In Fig. 1 a three-pole circuit interrupter is indicated comprising an insulating casing II with three upper terminals I2, and three lower terminals [3 mounted on the casing. Although each pole of the circuit interrupter I may include one, two, or more contacts in multiple, I have specifically illustrated an arrangement in which two contacts are provided in multiple. These contacts are not visible in Fig. 1 but the supporting rods I4 for the movable contacts are clearly visible in Fig. l as well as in Fig. 3. With the slots of the arc chute designed for optimum current interruption as will be described hereinafter, it has been found that two contacts in parallel are satisfactory for a IOU-ampere breaker, while three contacts in parallel might be desirable for a 200- ampere breaker, and four contacts in parallel might be desirable for a GOO-ampere breaker, it being understood that each pole of the circuit breaker is provided with such multiple contacts.

The operating mechanism and certain other features of the circuit breaker disclosed in Fig. 1 are not my invention, but are disclosed and claimed in the copending application of John A.

6 Claims. (Cl. 200-444) Favre, Serial No. 555,630, filed September 25,

1944, and assigned to the same assignee as the present application.

Mounted in the upper part of casing II of circuit interrupter ID are a plurality of arc extinguishing structures or are chutes I5, one for each pole of the circuit interiupter. Each of these arc chutes, best shown in Figs. 2 and 3, preferably comprises a structure which may be removed as a unit if desired. Furthermore, these are chutes are formed of an insulating material and preferably a bonded asbestos compound which might comprise a phosphoric asbestos compound which could be molded to the desired shape. The are chutes might also be made from asbestos board machined to the proper shape. Each arc chute or are extinguishing structure comprises a pair of outer walls It and I! which are adapted to be arranged in spaced parallel relationship. The arc extinguishing structure is divided into a plurality of narrow slots such as 18, by one or more insulating barriers I9. Since only two multiple contacts for each pole are illustrated, only a single insulating barrier I9 is required. Each of the members 16 and I1 is provided with an extension 20 at one edge thereof which cooperates with an extension 2| of insulating barrier or wall I9 to determine the spacing between the members I6, I1 and I9. The edge of barrier I9 opposite the edge upon which extension 2| is mounted is adapted to fit within a slot formed by cutaway portions of members I6 and IT. The arc chute is held together as a unitary structure by any suitable means, which is indicated in the drawing as pins 22', one of which passes through the extensions 2!] and 2| and the other of which passes through openings 23, 24 and 25 in members I6, H and I9, respectively.

Supported from the back wall of casing II in such a manner as to extend within the slots I8 of the arc chute 15 are stationary contacts 26 (Fig. 3) which are connected in parallel or multiple by flexible copper conductors 21 suitably connected to terminal I2. In order to prevent any magnetic forces produced by virtue of the current flowing through flexible conductors 21 t0 the bottom of stationary contacts 26 from causing the arc to move downwardly on contacts 26 rather than upwardly, a magnetic shield 28 is provided which may comprise copper plated steel, or the like. This magnetic shield is mounted between flexible conductors 2'1 and contacts 26. A rivet 29 holds the shield 28 and flexible Conductors 2'! and the terminals I2 in proper alinement as a unitary assembly. This arrangement of the stationary contacts is not my invention, but is disclosed in the above mentioned Favre application.

Cooperating movable contacts 33 are adapted to be supported on movable conducting supporting rods id so as to move within the narrow slots I8 of the arc chutes #5. The movable contacts I 33 so are arranged that the entire motion there.

of is within narrow slots l8. Thus the arc is always drawn at the place where itis to be interrupted and no additional means are required to force the are into the arc chute, as was the case in prior art constructions. The open position of movable contacts 3 is indicated by dotted lines in Fig. 3.

Upon separation of stationary contacts 25 and movable contacts 33 an arc will be drawn. Due to slight mechanical difierences between the contacts, this are will always be drawn at one set of contacts and means must be provided to immediately transfer this are to all of the multiple contacts arranged in parallel since the ability for one slot to interrupt current is limited. To this end I provide the wall or barrier l9 between the slots l8 with a plurality of openings 32 to provide uniform distribution of the gases and consequently to produce parallel arcs, one in each slot with the current shared substantially equally between the arcs in the respective slots; Although the openings 32 have been indicated as circular openings, it should be understood that this is not essential and any other means for obtaining distribution of the arc gases between the slots [8,

such as irregular shaped openings, can of course i be used.

The arc chute was designed by varying the size thereof, the slot spacing and the arrangement of the holes 32 for optimum current interruption. The greater the current to be carried by each contact in each slot, the wider the slot and. the larger the openings between slots. I have found a slot width of less than inch to be very desirable, An are chute having a inch slot Width with the openings 32 being inch in diameter spaced on A9, inch centers with alternate rows of holes filling the intervening space appeared to yield the best results for the range of short circuit currents involved.

The are chutes I5 are open at the top, as best shown in Fig. 4, in order to provide a passageway 33 to atmosphere. In order to cool the arc gases and suppress flame emission from the arc chute during the circuit interrupting operation, there is provided in accordance with my invention a mufiler or gas cooling arrangement arranged in passageway 33 immediately above barrier l9 which does not extend to the top of the arc chute, as is clearly shown in Fig. 4. This mufiler preferably comprises a serie of U-shaped members 34 and 35. The U-shaped members 34 and 35 have a length dependent upon the spacing between the members I5 and ii. The U-shaped members 34 may be supported from member it as by being molded into member E5, or by being cemented into recesses or slots formed in member [5. Similarly, the U-shaped members 35 may be molded or cemented into member H. Members 34 and 35 might be positioned in slots in members and I? and held in position by rivets, such as 22 holding members 16 and H in position. These U-shaped members are nested together when the arc chute is completely assembled, as best shown in Fig. 4, with the U- shaped members being in the upright position as far as the U is concerned, while the U- shaped members 34 are in the inverted position. When nested together or spaced and interleaved as shown, the respectively inverted and erect members 34 and 35 form a discontinuous sinu soidal member to provide a plurality of sinuous escape openings for the hot exhaust gases. Preferably these U-shaped members nest together so that the adjacent ends of two inverted U-shaped members 34 extend within one of the U-shaped members 35 andvice versa. The U-shaped members at the front and the back of the arc chute may not be entirely complete, as is clearly shown .in Fig. 4, and particularly at the back the U- shaped members .34 and 35' are incomplete in order to provide room for the stationary contact assembly. Preferably, the U-shaped members 34 and .35 are constructed of magnetic material such as copper plated steel, or the like so as to cause the arc to spread out within the slots to the best advantage for are interruption purposes. The copper plating is provided purely as a protective coating to prevent corrosion. By making the parts of the muflier arrangement discontinuous, an adequate creepage path is provided, The hot arc gases contact the rounded bases of the upright U-shaped members 35 and in view of the smooth surfaces which they engage, little erosion of the metallic members 35 occurs and the gases are rapidly cooled. If desired, the inverted U- shaped member 34 may be provided with perforations 35 either on the sides thereof or as illustrated in the drawing, over the entire surface thereof. With this arrangement additional venting of the exhaust gases is provided.

The arcs drawn within the arc chute l5 are always extinguished before they engage the metallic cooling plates 34 and 35 and only the hot arc gases impinge against these plates, which gases are rapidly cooled thereby effectively eliminating any flame emission from the arc chute which is due to incandescent gas arcing.

It will be noted that with the labyrinthian construction of the mufiler comprising metallic cooling plates 34 and 35 the hot gases are forced to impinge upon both the lower and upper surfaces of the plates so that greater cooling is obtained. Thi is possible by virtue of the fact that the hot gases are generated for only a short period of time and because of their relatively high velocity when they impinge against the cooling plates the depth of heat penetration is small. Thus even though the cooling plates are of thin material, both sides thereof can be used as cooling surfaces in accordance with my invention.

While I have shOWn and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber having a passageway through which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across said passageway with the outer side of the'bight of the erect members and the inner side of the bight of the inverted members toward the base of the passageway thereby forming a plurality of sinuous escape openings for the outfiowing hot exhaust gases of an are formed in said chamber.

2. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber, a passageway comprising two walls between which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across the opening between the walls of said passageway to provide a plurality of sinuous escape openings for the outfiowing hot exhaust gases of an arc formed in said chamber, the outer side of the bight of the erect U-shaped members being toward the outfiowing hot exhaust gases.

3. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber, a passageway comprising two walls between which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across the opening between the walls of said passagewa r with the outer side of the bight of the erect members and the inner side of the bight of the inverted members toward the base of the passageway thereby forming a plurality of sinuous escape openings for the outfiowing hot exhaust gases of an arc formed in said chamber, certain of said members being perforated to provide additional venting for the arc exhaust gases.

4. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber, a passageway comprising two walls between which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across the opening between the walls of said passageway to provide a plurality of sinuous 6 escape openings for the outfiowing hot exhaust gases of an arc formed in said chamber, said erect U-shaped members being supported by one of said walls and said inverted U-shaped members being supported by the other of said walls.

5. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber, a passageway comprising two walls between which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across the opening between the walls of said passageway to provide a plurality of sinuous escape openings for the outfiowing hot exhaust gases of an are formed in said chamber, the outer side of the bight of the erect U-shaped members being toward the outfiowing hot exhaust gases and the inverted U-shaped members being perforated to provide additional venting means for said exhaust gases.

6. In arc extinguishing means for an electric circuit interrupter, an arc extinguishing chamber, a passageway comprising two walls between which exhaust gases may leave said chamber, and a gas cooling arrangement comprising a series of alternately erect and inverted U-shaped metallic members interleaved and spaced in parallel relation across the opening between the walls of said passageway to provide a plurality of sinuous escape openings for the outfiowing hot exhaust gases of an are formed in said chamber, the outer side of the bight of the erect U-shaped members being toward the outfiowing hot exhaust gases and the inverted U-shaped members being periorated to provide additional venting means for said exhaust gases, and means supporting the erect U-shaped members from one of said walls and the inverted U-shaped members from the other of said walls.

CHARLES H. TI'IUS.

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