US2443521A - Arc chute - Google Patents

Description

June 15, 1948. w. M. SCOTT, JR

ARC CHUTE 2 Sheets-Sheet 1 Filed Jan. 12, 1945 VINVENTOR.

M [0077 JR.

June 15, 1948' w. M. SCOTT, JR 2,443,521

ARC CHUTE Filed Jan. 12, 1945 2 Sheets-Sheet 2 2/ (own I] I; 25 y 2 26 27 INVEN TOR.

WVMJUTZ JR.

ATYWRNE).

Patented June 15, B48

ARC CHUTE William M. Scott, Jr., Bryn Mawr, Pa., aasignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application January 12, 1945, Serial No. 572,555 6 Claims. (Cl. 200-147) My present invention relates to circuit interrupters and more particularly to a novel are 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 staggered metallic strips or bars.

In my application Serial No. 550,179, filed August 19, 1944, I show a substantially similar arc chute having a plurality of insulating arc extinguishing plates arranged substantially parallel to the path of movement of the arc with a numbe;- of transverse metallic pins or rods intersecting and being supported by the insulating plates.

My present invention covers a construction in which the metallic members which intersect and are supported by the spaced insulated plates comprise a plurality of narrow copper strips or bars arranged with their narrow edges directed substantially toward the arc.

In the construction and operation of circuit interrupters, it is frequently necessary to provide means for extinguishing quickly the are 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 are which is drawn between the arcing contacts when they separate under overcurrent 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 arc chute which is arranged to quench the are by lengthening the same or cooling it, by a combination of these methods or in many other ways.

Arc chutes having spaced insulating plates to lengthen the arc or squeeze the are 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 are rapidly across cooling surfaces, are also well known.

My invention contemplates as its essential function the provision of an arc chute which utilizes both the principle of an arc chute which utilizes both the principle of spaced insulating plates to lengthen and squeeze the arc, together with a series of metallic surfaces with which the arc is brought into contact and broken up into a series of small arcs and cooled.

More specifically, my invention contemplates a plurality of spaced insulating plates extending in a direction parallel to the path of the are into which the arc is forced by blow-out means, the said spaced insulating plates being used in combination with a series of transverse metallic members which will break the are into a plurality of arcs in series and will also further cool the same.

Still more specifically, my invention contemplates that these metallic surfaces be formed by a series of transverse copper strips or bars, each of which extends through all of the insulating plates and each of which furnishes a conductive path between the various slots defined by the spaced insulating plates. These strips or bars are arranged so that their edges are substantially directed toward the are as it moves in its path through the chute.

Accordingly, the primary object of my invention is the formation of a novel are chute comprising spaced insulating plates together with spaced metallic members, the said plates and members extending in planes substantially normal to each other.

Another object of my invention is the provision of an arc chute having spaced insulating plates and extending in planes substantially parallel to that in which the arc is drawn, said plates being intersected by a plurality of transverse strips or bars of highly conductive material, the said strips or bars being so arranged that their edges are directed toward the arc as the arc moves along its path within the arc chute.

Another object of my invention is the mounting of the transverse strips or bars by means of insulating plates, where said strips or bars need not be supported by the side walls oi-the arc chute and may even be spaced therefrom and the mounting of the strips or bars so that they are closely adjacent to the arc.

Another object of my invention is the provision of novel blow-out means which includes the formation of certain of said strips or bars of ferrous material and arranging them so that they will co-act with ferrous plates on the sides of the arc chute to form a U-shaped magnetic path.

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

Figure 1 is a View in perspective partially broken away of my novel are chute.

Figure 2 is a. side view in perspective partially broken away showing the outside of my are ya chute.

Figure 3 is a front view of my novel are chute taken along line 3-3 of Figure 1.

Figure 4 is a longitudinal section through one of the special ferrous strips or bars of my novel are chute taken along line fl-l of Figure 3.

Figure 5 is a cross-sectional view taken on line 5-5 of Figure 4.

Figure 6 is a diagrammatic view of a slightly modified form of arc chute.

Referring now to Figures 1, 2 and 3, there is here shown an arc quencher it 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 are chute 26 comprises a pair of side supporting plates 2 I, 2! of insulating material, between which are mounted a number of spaced arc extinguishing plates 23, 2 3, 25, 26, 21, also of insulating material. The plates are integrated as a single unit by the transverse bolts 30, 31, 32, 33, which are provided with insulated bushings 35, 35.

Rivets 30 and Bi are also provided with individual insulating washers or spacers 3'1, 81 to maintain the spacing between the insulating plates at the front of the arc quencher. Bolts 32 and 33 carry a set of insulating spacers 38 between each pair of plates which serve to space the back ends of the plates from each other; the said spacers 38 also each having a hook-shaped extension 39 to engage a hook dd on the upper end of the arcing horn M, which is secured to the back panel 32 on which the circuit breaker is mounted. The plates 23-22 are accordingly insulated from each other and from the side plates 2!.

The side plates 2 i, 2i also carry between them on the transverse bolts tit and 65 the opposite arcing horn 36. The said arcing hornll has an extension il carrying a bolt 58 which may be secured to the stationary flange member all carried by the transverse insulating bridging support 50* in order to secure the arc chute in position. A conductive connection is made to the arcing horn at through the flange member 59 and the pigtail 52.

The are quencher 2b is particularly characterized by a large number of transverse copper strips or bars 60 which pass through slots in plates 23 through 27, as shown in Figures 1 and 8, and which are supported thereby.

The strips or bars 56 preferably do not contact the upper supporting insulating members or walls 2!, 2!. This will facilitate assembly and adjustment of the units, permits the strips or bars to be brought down to the contact which form the arcs, and removes the possibility of breakdown orcreepage along the supporting plates 2|, 2|. The remainder of the structure corresponds to the circuit breaker shown in my Patent No. 2,348,228 and in my application Serial No. 550,179.

Essentially the circuit breaker here shown comprises a lower back connection stud (not shown) to which the main movable contact 12 (on the contact arm 65) the arcing horn 46-61, and the arcing contact 18 are connected respectively by a pigtail (not shown), pigtail 52 and pigtail 6B. The circuit breaker also comprises an upper back connection stud 10 to which is secured the main stationary contact H, which engages the main movable contact 12 mounted on the contact arm 65 to complete a circuit from the upper to the lower connection studs.

When the main contacts H and 12 have separated, while the arcing contacts hereinafter described are engaged, current flows from the back connection stud Ill through the conductive bracket 13, to the lower end of the arcing horn M and to the stationary arcing contact 11, then to the movable arcing contact 78 mounted on the contact arm 55, and then through the pigtail 66 to the lower back connection stud.

As arcing contacts W and 18 separate, an arc is drawn therebetween. As the opening movement is completed, the root of the are at contact 11 is blown upwardly along the arcing horn fill while the root of the are at movable arcing contact 18 is transferred to arcing horn 38 and blown upwardly thereon. The blow-out means, hereinafter more specifically described, blows the center of the arc upwardly into the center of the plates 23 to 21. The plates 23 to 21 are longest in a vertical direction at plates 23 and 27; that is, the downwardly extending cusps 86 thereof extend further downwardly in the case of these plates. The center plate 25 has the shortest cusp 82. The intermediate plates 26 and 26 have cusps ti of intermediate length, as shown more particularly in Figure 2 and in dotted lines in Figure 1.

Thus in a transverse direction the plates of the arc chute present a V=shape which tends to guide the arc toward the center of the chute. The downwardlyextending cusps 8B, and 82 intercept the center of the arc and tend to guide the arc in its upward movement to squeeze into the confined space between the plates.

The arc in being driven upwardly tends to be squeezed into but one of the spaces; for instance, in. the space 85 between plates 26 and 25 or in the space 86 between plates 25 and 26. It is not necessarily confined to either or both Of these spaces but may be broken up into a plurality of parallel arcs in separate spaces.

While this type of are chute having only the spaced insulating plates 23 to 27 has been effective in use, it has been found that perhaps only one or two of the spaces, and usually only one, are actually eifective in extinguishing the arc. That is, the arc is forced up into but one of the four spaces which it may normally enter, is squeezed between the surfaces of the plates defining the space, and is extinguished therein,

The are in addition to being initially compressed in one or two of the slots or spaces between the plates is intercepted transversely by the plurality of metallic surfaces which define the strips or bars 60. These strips or bars 60 which are of highly conductive material, preferably copper, tend to break the are up in series among them. That is, should the arc be squeezed, say, into the slot 85, it will encounter a number of strips or bars 60, as shown by the dotted line 90, and will be broken up into a series of small arcs between these strips or bars.

In addition, as the arc'is driven upwardly, the initial small series arcs will go out and new arcs, as indicated at 9|, will be established across other strips or bars, which effect a new cooling action on the arc. As the arc moves still further upwardly, it will encounter still more strips and bars and be broken up into a larger number of small arcs in series. This continuous tearing of the roots of the small arcs from the lower strips or bars and re-establishing the small arcs above the small arcs which have been extinguished, will render the arcs unstable and lead to quick extinguishment.

The surfaces of the strips or bars 60 will tend further to cool the arc while the arc roots move along from strip to strip, and will result in quick extinguishment of the arc. Not only does this action take place within the principal slot (for instance, 85) into which the arc is first squeezed, but by reason of the fact that the strips or bars extend through all of the slots, arcs may be set up in adjacent slots. Thus, for instance, when a small series are is drawn between any two of the strips or bars, the current in that are may flow transversely through the chute (longitudinally through the strips or bars) into adjacent slots. The strips or bars are sufliciently close for the particular voltage for which the circuit breaker is rated so that at the substantial interrupting currents involved, new arcs may flash over between the adjacent strips or bars in other slots when the arc roots are torn away from the strips or bars in the original slot, thus transferring a portion of the arc to another and cooler slot and rendering the are as a whole even more unstable.

By this structure, therefore, the arc is first squeezed into one or more slots which extend parallel to the arc path and into which the are as a whole is squeezed between insulating plates. When squeezed into the slots between these insulating plates, the arc encounters a large number of spaced transverse strips or bars. These strips or bars break the are up into a series of small arcs between them and by reason of the rapid movement of the arc with respect to the surfaces of these strips or bars and upwardly from strip to strip, tend to cool the roots of the small series arcs. This tends quickly to extinguish the arc.

Furthermore, since each strip or bar extends through all of the slots, there is a tendency for the current to flow along the strips or bars and for a small arc to strike over between closely adjacent strips or bars or another slot when the arc roots are torn from the same strips or bars in the original slot, thus forming some of the series arcs in a cooler slot, again rendering the arcs highly unstable and tending quickly to extinguish them.

This combination of squeezing the are between insulating plates, intercepting the arc by metallic members or strips or bars, breaking the arc up into a plurality of small arcs in series with each other and causing some of the small arcs to strike over in adjacent slots, results in a very quick extinguishing action.

A great amount of back pressure often develops owing to the gases under high pressure which are confined in the narrow space. This back pressure has been to some extent alleviated by providing communicating holes between the plates.

I have found that, in addition to their primary function of breaking the arc into a series of small arcs, the metallic strips or bars Gil provide a conductive path between the spaces between the various plates, and aids materially in the extinw guishing of the arc.

As will be obvious from Figures 1 to 3, the insulating supporting plates .2! carry on their outer surfaces iron plates 95, 95. The are itself forms a half turned current loop, and the magnetic field thus created is reinforced by the iron plates 95, 85 to drive the arc upwardly with great rapidity. Thus, in appropriate cases, all of the strips or bars 60 may be of copper.

In Figures 3, 4 and 5, the formation of the strips or bars I00 in the upper two rows, of iron ing strips or bars I. The iron strips or bars rather than of copper, may reinforce the blowout effect. However, the arc chute may, in appropriate cases. comprise only copper strips or bars. Where only such copper strips or bars are used, then, if necessary, or desirable, a blowout magnet, such as that shown in my Patent No. 2,348,228, or in my application Serial No. 550,179 may be used.

Interphase barriers ll may be provided between adjacent poles which usually have individual are I chutes. Such interphase barriers will prevent any flash-over oi the are from one pole to the other. The are chute is supported at the front of the circuit breaker by the front lower edges of plates II which rest in the-slots O1, 9'! of the supporting bridge 5|. The back of the arc chute is supported by the hook 39 which engages the hook 40 of the arcing horn 4|.

The arc chute II is locked in place by the bolt 43 which engages the flange 4!. The arc chute may be readily removed for inspection and repair, or for replacement of other elements of the circuit breaker, simply by rotating bolt 48 so that it will disengage flange 4!. Upon such disengagement, the arc chute may simply be pulled forward and removed. The strips or bars 60 and plates 23 to 21 are preferably assembled together first as a unit and then assembled with the arc chute by placing the plate and strip or bar assembly between the plates 2| and passing the bolts 30 to 33 through aligned openings in the plates.

As shown in Figures 1 and 2, the transverse copper strips or bars may be arranged in planes parallel to each other but are preferably staggered with respect to each other in order that their edges may better intercept the arc. The plurality of transverse strips or bars 60 thus correspond to a multiplicity of transverse metallic arc extinguishing plates. The primary distinction, however, is that when the arc is broken up serially, then instead of the roots of the small series arcs moving continually over a single plate,,

the heat of which may be substantially increased by the arc, the roots of the small arcs are continually torn from one narrow plate or strip and transferred to another and cooler plate or strip. This combination of continual transference to successive cool plates, and the continual tearing of the roots of the small arcs from one plate and forcing the same over to other successive plates adds materially in the extinction of the arc.

While the arrangement of the strips or bars iii of Figures 1 and 2 is preferred, these strips or bars may be vantageously arranged in radiating form, as shown by the arrangement of the strips or bars ll of Figure 6. The advantage of the arrangement of Figures 1 and2 is that the arcing first encounters but one or two of the transverse strips or bars and is thus gradually broken first into a pair of arcs in series;

then into three or four arcs in series, and then into a multiplicity of arcs in series.

In the construction shown in Figure 6, the arc may initially be broken into a large number of arcs in series. This will introduce the cooling effect much more rapidly but may somewhat retard the initial rapid movement of the are into the chute.

In the construction shown more clearly in Figures 3 and 4, I have shown the upper two rows of strips or bars Ill as being made substantially of iron rather than of copper as are the remain- I have substantially the same cross section and arrangement as the copper strips or bars 60, but have an insulating sleeve or coating IOI over which is placed a copper sleeve or coating I02.

The copper sleeveor coating I02 extends across the arc chute for the same distance and in the same manner as the strips or bars 60 and thus preferably'does not come into contact with the side walls 2|, 2|.

The insulating coating IOI extends at I03, I03 beyond the end of the copper coating I02 and into the slots I04 in the insulatingv side walls 2| of the are chute. This prevents the iron portions I00 of the bars from being contacted by the arc. The iron portions I00 of the arc extend at I05, I05 beyond the ends of the insulating sleeve or coating I03 and into engagement with the inner surfaces of the ferrous plates 95 to form a complete U-shaped magnetic path 95l00-95 for which the arc constitutes a half turned current loop.

The inner surfaces of the plates 05, 95 may be provided with suitable grooves or through slots to receive the ends I05 of the iron strips or bars I00. The iron strips or bars I00 may be used without the insulating coating I03 or the conductive coating I02, and the conductive coating I02 may even be placed directly around the iron strip or bar I00 without the interpolated insulating coating I03. In this latter case, it would then 'be preferred that the iron strips or bars I00 should not extend up to or through the insulating side walls 2|, 2| and small air gaps would then exist between the ends of the bar I00 and the plates 95. The blow-out eifect would not be as great as that in the construction shown in Figures 3 and 4 but will be effective for circuit interrupters of low capacity.

By the construction here shown, however, every one of the transverse strips or bars 60 and I00 has a cooling efiect, and, in fact, the cooling effect of the upper strips or bars I00 is enhanced since the copper coating I02 has a somewhat greater surface than the surface of the copper strips or bars 60. The strips or bars 60 constitute in effect a multiplicity of small transverse plates supported by a plurality of insulating members and provide a greater surface and a greater cooling effect than has been possible in the case of the continuous transverse plates of the prior art.

In the foregoing, l. have described my invention in connection only with specific preferred embodiments thereof. Many modifications and variations of my invention within the limitations of the foregoing disclosures should now be obvious to those skilled in the art. Accordinglyfl prefer to be bound not by the specific disclosures herein but only by the appended claims.

I claim:

1. An are chute comprising means for drawing an arc, means for moving the arc into the chute, and are extinguishing means within the arc chute; said are extinguishing means comprising a plurality of plates of uniformly spaced insulating material mounted so that their planes are longitudinal to the arc path and a plurality of metallic plates of rectangular cross-section, each of said metallic plates extending through the plates of insulating material and the spaces therebetween in the path of and transverse to said are path as it enters said are chute.

2. An arc chute comprising means for drawing an arc, means for moving the are into the chute, and are extinguishing means within the arc chute; said are extinguishing means comprising a plurality of uniformly spaced plates of insulating material and a plurality of metallic plates, each of said metallic plates extending through the plates of insulating material and the spaces therebetween transverse to said are path; the said metallic plates being of rectangular cross-section and substantially parallel to each other with their edges disposed substantially toward said arc, the plurality of said insulating plates being transverse to the metallic plates and in the spaces intermediate the ends of said metallic plates.

3. An arc chute comprising means for drawing an arc, means for moving the arc into the chute, and are extinguishing means within the are chute; said are extinguishing means comprising a plurality of uniformly spaced plates of insulating material and a plurality of metallic plates, each of said metallic plates having a rectangular cross-section and extending through the plates of insulating material and the spaces therebetween transverse to said are path; said metallic plates being arranged in a plurality of rows and having their edges directed toward the arc; the plurality of said insulating plates being transverse to the metallic plates and in the spaces intermediate the ends of said metallic plates.

4. An arc chute comprising means for drawing an are, means for moving the are into the chute, and are extinguishing means within the arc chute; said arc extinguishing means comprising a plurality of uniformly spaced plates of insulating material and a plurality of metallic plates, each of said metallic plates extending through the plates of insulating material and the spaces therebetween transverse to said are path; said metallic plates having a rectangular crosssection and being arranged in a plurality of rows and having their edges directed toward the are;

the plates in any one row being staggered with respect to the plates in an adjacent row, the plurality of said insulating plates being transverse to the metallic plates and in the spaces intermediate the ends of said metallic plates.

5. An arc chute comprising means for drawing an are, means for moving the are into the chute, and are extinguishing means within the arc chute; said are extinguishing means comprising a plurality of uniformly spaced plates of insulating material and a plurality of metallic plates, each of said metallic plates extending through the plates of insulating material and the spaces therebetween transverse to said are path; said metallic plates having a rectangular cross-section and being arranged in a plurality of rows and having their edges directed toward the arc; the plates in any one row being staggered with respect to the plates in an adjacent row; the surfaces of said plates extending in planes substantially radiating from the point of initiation of the arc, the plurality of said insulating plates being transverse to the metallic plates and in the spaces intermediate the ends of said metallic plates.

6. An arc chute comprising means for drawing an arc, means for moving the are into the chute, and are extinguishing means within the arc chute; said are extinguishing means comprising a plurality of uniformly spaced plates of insulating material and a plurality of metallic plates, each of said metallic plates extending through the plates of insulating material and the spaces therebetween transverse to said are path;

9 said metafiic plates having a rectangular crosssection an arranged in a plurality 01' rows and having thflr edges directed toward the arc;

the plates in any one row being staggered with lic plates.

WILLIAM M. 50011, JR.

10 ammcns 0mm The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Traver Jan. '7, 1930 Baker Sept. 5,1933 Jennings Sept. 24, 1935 Baker Feb. 14, 1939 Pokorny Feb. 23, 1943

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