US2427074A - Arc chute - Google Patents

Description

Sept. 9, 1947. w. M. scorT, JR

ARC CHUTE Filed Jan. l2, 1945 99 INVENTOR.

M M .Scor-7; Je BY 0- O O O. .n O QQ\ Patented Sept. 9, 1947 UNITED STATES PATENT OFFICE ARC CHUTE William M. Scott, Jr., Bryn Mawr, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application January 12, 1945, Serial No. 572,554

3 Claims. 1

My present invention relates to circuit interrupters and more particularly to a novel arc quencher therefor comprising a plurality of spaced plates of insulating material arranged above and parallel to the arc, the said plates being intersected by a number of transverse metallic rods.

This application is a continuation in part of application Serial No. 550179, filed lAugust 19, 1944, and relates specifically to a special arrangement of the transverse metallic rods so that they are closer together at the upper portion of the arc chute and so that they are more closely spaced along the back and front regions of the arc chute. Thus, the distance between the transverse metallic rods is decreased as the distance from the point of initiation of the arc increases.

In the construction and operation of circuit interrupters, it is frequently necessary to provide means for extinguishing quickly the arc which is drawn between the contacts as they separate. Such circuit interrupters, which may be tripped open on the incidence of high currents, comprise a pair of main contacts (to carry the full current during normal operation), which are arranged to make after and break before a pair of parallel arcing contacts so that any arcing which may occur will not pit or otherwise destroy the contact surfaces of the main contacts.

The arc which is drawn between the arcing contacts when they separate under over-current conditions is blown upwardly by blow-out means, such as a magnetic blow-out or air blast (both well known in the art) into an are chute which is arranged to quench the arc by lengthening the same or cooling it, by a combination of these methods or in any other ways.

Arc chutes having spaced insulating plates to lengthen the arc or squeeze the arc into narrow slots are well known. Arc chutes which consist of spaced metallic plates or their equivalent which break the arc up into a number of small arcs in series and move the arc rapidly across cooling surfaces, are also well known.

My prior application Serial No, 550,179 contemplated as its essential function the provision of an arc chute which utilized both the principle of spaced insulating plates to lengthen and squeeze the arc, together with a series of metallic surfaces formed by a series of transverse pins, each of which extends through all of the insulating plates and which are so arranged that the arc is brought into contact therewith and broken up into a series of small arcs and cooled.

The specic improvement and object of my present invention is the arrangement of these transverse pins so that they will be progressively more closely spaced as the distance from the contacts between which the arc is initially drawn is increased.

A corollary object of my invention is the provision of means in connection with such a spaced plate transverse pin arc chute for moving the arc readily into the chute and then rapidly cooling and extinguishing the same.

Another object of my invention is the provision of novel arc chute extinguishing plates.

These and many other objects of my invention will become apparent in the following description and drawings in which:

Figure 1 is a cross-sectional View taken on line I-l of Figure 2 looking in the direction of the arrows.

Figure 2 is a front View of the elements of the arc quencher takenfrom line 2-2 of Figure 1.

Referring now to Figures l and 2, there is here shown an arc quencher 20 having generally the construction and operation of the arc quencher shown in my Patent No. 2,348,228, dated May 9, 1944, assigned to the assignee of the present invention. The arc chute 20 comprises a pair of side supporting plates 2l, 2| of insulating material, between which are mounted a number of spaced arc extinguishing plates 23, 24, 25, 2B, 2l, also of insulating material. The plates are integrated as a single unit by the transverse rivets 3D and 3| which are provided with insulating bushings 35.

Rivets 30 and 3l are also provided with individual insulating washers or spacers 31 to maintain the spacings between the insulating plates.

The side plates 2l, 2l also carry between them on the transverse bolt 44 the back arcing horn 45; and on the transverse bolts 40 and 4I the front arcing horn 42 and its extension 43.

Current enters the circuit breaker, which is here shown in fragmentary View, through the stud and passes to the main stationary contact 6l to the main movable contact 62 mounted on the movable contact arm 63. Appropriate means, such as pigtail connections or other members, may be utilized to carry the current from the main movable contact 62 into the opposite back connection stud, not shown.

The contact members are so arranged that the main movable contact 62 will separate from the main stationary contact 6l before the movable arcing contact 65 separates from the stationary arcing contact 66. When the main contacts 6l and 62 have separated, current flows from the stud 60 through the angle member 68 to the stamerma' 3 tionary arcing contact 06, which is situated at the lower end 69 of the back arcing horn 45, then to the movable arcing contact 65, which is carried by the movable contact arm B3, and then through a pigtail or other suitable connection to the opposite terminal, not shown.

As the arcing contacts 66 and 65 separate, an are is drawn therebetween and is transferred to the arcing horns 45 and 42 by suitable blow-out means, preferably magnetic, which are wellknown in the art. are so well known, they are not here shown but may comprise the blow-out means shown in my application Serial No. 550,179' or in my Patent When the arc is blown up on the arcing horns 45 and 42, the current path is from'the stud 60 through the angle member 68, the lower end 69 of the arc horn 45 to the are horn 45, then across the arc to the arc horn 42 through the extension 43` of the arc horn 42 to the connecting member l0, to which a pigtail '1| is connected, in order to permit current to flow to the opposite terminal of the circuit breaker.

The are extinguishing plates 23 through 2l are here shown as substantially V-shaped plates, the lateral edges t of which substantially parallel the principal portions ofthe arcing horns 45 and 42, and the lower ends 8| of which arel convexly rounded at the region first presented to the arc. The plates 23' to 21 are not directly in contact with the arcing horns but a small space' 82 is left between the edges oi the plates andthe arcing horns on each side.

The arc quencher 20 is particularly characterized by a large number of transverse copper pins |00, |00 which pass through perforations in the plates 23 through 2l, as shown in FigureslV and 2, and which are supported by' the plates 23 through 2l. The pins preferably do not contact the opposite supporting insulating members Zl-ZI. This will facilitate assembly and adjustment of the unit, permits the pins to be brought down close to the contacts which form the arc, removes the possibilityl of breakdown or creepage along the supporting plates 2|, 2 The remainder of the structure shown corresponds to the circuit breaker shown in my Patent No. 2,348,228.

The particular advantages of the transverse copper pins I 00 have been specifically described in my application Serial No. 550,179 above referred to, and my theory o1" the specific operation of these pins to obtain extremely fast arc extinguishment has also been set forth therein.

The specific contribution of the present invention, apart from the novel extinguishing plate shown is the staggering of the pins |00. Thus, pins |00d are relatively widely spaced from each other. Pin leila is arranged at the very center of the lowest portion of the arc chute in order to intercept the arc and break it serially into two substantially equal arcs. As the arc moves up to the position indicated by the dotted line A, pins lilllaZ and |0903 will also intercept the arc, and the arc at this instant should be broken serially into substantially four arcs in series.

As the arc is moved up once more, one of the four series arcs of arc A will move into engagement with one ol the pins |001?. The arc will then have the approximate form shown by the dashed line B of Figure 1. As the arc moves upwardly, arc B may then pass from the arc horn 42 to the pin |00a3, to the pin |00b1, to the pin |00a2, to the arc horn 45,`

Since such blow-out meansv As the are is blown up still more, it may intercept still other pins and thus in a third position assume the condition shown by line C. In this case, the small arc between pins |001)1 and |00?)2 has been intercepted by pin |00c2 and the small arc between pin |00a3 and arc horn 42 has been intercepted by pin |00172 so that the arc C now passes from the arc horn 42 to pin |00b2, then from pin |0002, then to pin |00b1, and so on, as shown in the figure.

As the arc moves upwardly again to the position shown, for instance, at D, more pins are intercepted and the short series arc are much smaller. The short arcs are at all times subject tothe blow-out which causes the arc as a whole to rise. But, it will be seen that the shorter arc may tend to resist further upward movement, since that would require undue lengthening thereof. Accordingly, the upper pins |00d are much more closely spaced than the lower pins |00a and the spacing of the pins is progressively lessened, as noted, `so that the top-most pins |00e are separated by much less than half the distance between the pins |00a. By this means, therefore, as the number of the arcs in series is increased and as the length of these arcs becomes relatively smaller, the spaces between the pins is progressively decreased so that a greater number of pins is introduced in series with the arcs, the number of arcs is increased, and the cooling effect described in application` Serial No. 550,179 is greatly' enhanced.

Not only arethe upperV pins Illllel progressively more closely spaced than the' lower pins, but also I have found that a lateral progressive spacing is closer spacing of the pins adjacent the arcing horns permits this upwardly arched position of the arc `to be assumed; that is, the portions-of theA are at position E, which are adjacent to the arcing horns 42 and 45, are downwardly directed,

and the close positioning of the' pins adjacent to' the arcing horns 42 and 45 permits the spacing of the pins to be somewhat similar with respect to arc E at the portions of the arc adjacent-the arcinghorns 42 and 45'.

By' this structure, therefore, the are is first squeezed into one or more slots which extendparallel to the are path and into which the arc as a whole is squeezedbetween insulating plates. When squeezed into the slots" between these insulating plates, the arc encounters a large number of spacedltransverse pins. These pins break the are up into a series of small arcs between them and, by reason of the rapid movement of the ar'c with respect to the surfaces of these pins and upwardly from `pin to pin, tend to` cool` the roots of the small series arcs. This tends quickly to extinguish the arc:

Furthermore, since each pin extends through-

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