US2244061A

US2244061A - Arc quencher

Info

Publication number: US2244061A
Application number: US348717A
Authority: US
Inventors: Jr Herbert C Graves
Original assignee: ITE Circuit Breaker Co
Current assignee: ITE Circuit Breaker Co
Priority date: 1940-07-31
Filing date: 1940-07-31
Publication date: 1941-06-03
Anticipated expiration: 1958-06-03

Description

June 3, 1941 H. c. GRAVES, JR 1 ARC QUENCHER Filed July 31. 1940 2 Sheets-Sheet l INVENTOR Mal C. 51mm .lY 2 E &

ATTORNEY June 3, 1941.

H. c. GRAVES, JR 2,244,061

ARC QUENCHER Filed July 31, 1940 2 Sheets-Sheet 2 60 1, 554,-: 72 72a. 42a 53. L: 5/. 4- 73a 43;; -40b.

INVENTOR n Macaw it.

ATTORNEY Patented June 3, 1941 sac oomzcnaa Herbert G. Graves, 1r., West Chester, Pa., assignor to I. T. E. Circuit Breaker ()ompany, Philadelphia, Pa., a corporation Pennsylvania Application July 31, 1940, Serial No. 348,717

19 Claims.

This invention relates to switch gear and circuit interrupters and more particularly to are extinguishers therefor, the said are extinguishers being of the spaced plate type wherein a plurality of spaced metal plates of preferably magnetic material are utilized to quench the arc.

The spaced metal plates are arranged in substantially parallel relationship to each other, each of them being substantially at right angles to the path of the arc and having a series of registered notches therein through which the arc is initially drawn.

The flow of current in the arc produces a magnetic field surrounding the current path. Where plates of magnetic material embrace the are they form a path of low reluctance for this flux. The reaction of the flux on the current pulls the are into the notch and onto the metal plates. This breaks up the are into a plurality of short arcs in series, which the magnetic field continues to move along the plates at sufilcient speed so as to prevent the plates at the arc terminal from reaching excessive temperature. The breaking up of the are into a series of short arcs facilitates extinguishment and reduces the possibility of an alternating current are restriking after the current has passed through zero.

This action of the plates in moving the arc is augmented by the fact that the path of the current through the circuit breaker and the arc is in the form of a partial loop. A current flowing in such a path tends to enlarge its loop due to the concentration of fiux lines within the loop.

Heretofore, insulating sidewalls for supporting the plates have been molded into the necessary shape for supporting'the arc quenching plates either by molding notches therein or by inserting the plates during the molding operation or by other similar means.

The use of molded insulating sidewalls, however, necessitates a relatively thick material because of limitations in the molding operation itself and moreover there is a lack of flexibility in shaping these supporting walls to any suitable form.

I have discovered that by replacing molded insulating walls by thin bendable sheet material, I secure greater flexibility which enables me to bend the walls to any desired shape which may be suitable for supporting the arc quenching plates. Moreover, I may employ much thinner material for these side walls thus reserving a greater amount of space for the actual anc quenching plates.

This construction by increasing the plate area, increases the thermal capacity of the unit so that the temperature of the plates is raised less for each circuit interruption than is the case in prior arc quenching units.

An important object of the present invention,

therefore, is to provide in arc quenchers of the spaced plate type supporting side walls for the spaced plates of thin bendable sheet material.

Another important object of the present invention'is, in connection with the use of. such side walls of bendable sheet material, to provide a construction which increases the effective are interrupting plate area of the arc quencher without necessarily increasing the over-all dimensions or size of the unit.

A corollary object, therefore, is to provide a construction which inherently permits a greater interrupting plate area for a specific volume and hence increases the effectiveness of the arc quenching unit or makes possible a reduction in size, should that be desired.

The advantage flowing from this result is that when the arc quenching unit of the design of the present invention is used on a 600 volt circuit carrying a normal load of 600 amperes in a type of interrupter which normally in modern commercial design is expected to have a rated interrupting capacity of 20,000 amperes, the unit of the present invention, contained within the dimensions of the prior types of quenchers may be conservatively rated at 40,000 amperes and, in fact, has been able to interrupt 50,000 amperes or more without failure.

Heretofore, it has been necessary to utilize additional insulating pieces to protect the legs of the arc quenching plates or to make the mold sufilciently thick so that the legs of the arc quenching plates may be embedded therein and thus protected from the direct effect of the are.

In the present invention I have found that the thin bendable insulating sheet material may be bent around the legs defining the notch of the arc quenching plates and thus afford a simple easily manufactured protection therefore.

An object of this invention'therefore is to provide a simplified means for protecting the legs defining the notches of the arc quenching plates from damage by the are when it is first drawn.

Since the walls which position the plates are of thin bendable sheet material, I have found it advantageous to brace and support the walls themselves; and for this purpose instead of using additional structure, I have found that the plates which are positioned by the thin insulating walls and the insulating walls themselves may interbrace each other to form a unitary whole.

Still a further object of this invention, therefore, is the provision in an. arc quenching unit of spaced arc quenching plates and insulating walls therefor which interbrace and support each other.

At the top of the stack of plates which frequently are arranged vertically, as shown in the drawings, that is, with their planes in a vertical position, there has been provided in the present invention a cover with vents through which the portion of Figure 1 and are gases'may escape. In the preferred modification, these vents are aligned with the apices of the notches in the plates, which notches are substantially centrally disposed within the plates themselves. v v

The location of the vents tends to cause the maximum gas velocity to occur in the central plane of the unit and hence along the notches. This action drives the are rapidly into the narrow part of the notches where heat is absorbed and then on to the plates when further cooling occurs.

These vents are not formed as a continuous slot but rather as a series of spaced holes preferably arranged so that they may be aligned with the plane of the apices of the notches.v

It is entirely probable, although it is difficult to ascertain, that these holes forming a discontinuous slot, contribute toward the quenching of the arc lay-permitting shunt paths of ionized gas to form over the top. Such shunt paths may cause instability of the are as the current approaches zero.

It is, therefore, a further object of the present invention to provide a series of spaced vents aligned with the apices of the notches in the spaced magnetizable plates.

Still another object of the invention is the provision of a simplified and novel type of arcing horn which may be integrally associated with the are quenching unit and connected into the arcing circuit in a simplified manner.

These and many other objects of this invention will in part be apparent and in part pointed out in the following description and drawings, in which:

Figure l is a view partly in cross-section showing a circuit interrupting apparatus with the arc quenching unit of the present invention in place.

Figure 2 is an exploded view in perspective showing the arc quenching unit and the means of mounting the same on the panel together with the meansfor connecting the arcing horn thereof into the circuit.

Figure 3 is a cross-sectional view of the arc quenching unit showing an enlargement of a taken on line 33 of Figure 4.

Figure 4 is an elevational view of the front of the are quenching unit taken along line 4-4 of Figure 3. v

Figure5isaplanviewofthebaseplate of the arc quenching unit for attaching the unit to the panel.

Figure 6 is aplan' view of a magnetizable plate.

Figures 7 and 8 are plan views of modified forms of top plates.

Referring now to Figure 1, thereis here shown a circuit interrupter having circuit connecting members Ill and I I which are secured in any suitable manner to portions of the circuit interrupter casing l2.

Current is led from the circuit connecting member to the connection strap I3 and thence to the stationary main contact H from which it passes to the movable main contact l5 and through the lead I to the terminal II which is appropriately connected to theconnecting member The contact I5 is mounted on a movable arm ated by the. handle 20 or by any suitable automatic tripping or closing apparatus.

A movable arcing contact 2| is also carried by the movable arm I! and is engageable with an appropriate stationary arcing contact 22 mounted on the plate I30 which is connected to the connection strap I3.

The particular form of circuit interrupter contained within the casing l2 and the specific operation thereof forms no part of the present invention, but these members have been indicated in order to show a complete operative structure in which the arc quenching unit 30 of the present invention may be used. I

The are quenching unit 30 (see Figures 2, 3 and 4) comprises a pair of. insulating side walls 3| and 3|a of bendable sheet material, having a series of preferably rectangular perforations 32 to cooperate with lugs on the metal plates mounted between the walls.

The metal plates 40, each having the form shown in Figure 6, are preferably of magnetizable material. Each plate has a notch 4| and a pair of

legs

42 and 43 on each side of and beneath the notch. The walls of the notch 4| converge toward each other and terminate in the.

slot portion 44, the walls of which are substantially parallel.

Each plate is reversed with respect to its adjacent plate.

Each plate has a shoulder 45 projecting from the edge 46 midway between the top and the bottom thereof with a lug 41 projecting from the shoulder. Each plate also has extending from the opposite edge 49, the shoulder 54 near the top and the shoulder 5| near the bottom which carry respectively lugs 52 and 53. The top edge 55 of each plate also has a shoulder 58 near one end of the edge which carries a lug or extension 51. A comer of the plate adjacent the shoulder 58 and lug 51 is cut out at 58 to provide an additional passage for the flow of arc gases. Since adjacent plates are reversed, the passage is not continuous and thus an arc will not-restrike therethrough.

Plate 40a (Figures 3 and 4) is so positioned that shoulders 50a and 5|a-of edge 49a abut against the inner side of wall 3| and so that shoulder 45a of edge 46:: abuts against the inner side of wall ila: and the respective lugs 52a, 53a and 450 project through the perforations 32 in the walls. The cut-out 58a is arranged at th upper right corner.

Plate 40b is mounted in reversed position with respect to plate a so that the shoulders 50b and. Ilb abut against the inner surface of wall Ila and so that the lugs 52!: and 53!; project through perforations in the wall 3|a, while ll which is mounted on an insulated shaft I! contacts.- The insulated shaft ll may be oper-' each plate are displaced with respect to corre-' sponding-notches and slots in adjacent plates owing to the fact that the notches 4| and their associated and communicating slots 44 are slightly asymmetrically arranged or off-center with respect to a line drawn exactly between and parallel to edges 48 and 45. 7

Thus notch 4|a. of plate 40a and slot 440 of plate a are displaced with respect to notch lib and slot b of plate b (see Figure 4). The

- notch ll and slot ll of plate llc are arranged to exactly underly the corresponding notch and slot of plate a; While the notch H and slot H of plate 40d are arranged to register with those of plate 40b.

This prduces a narrow aligned notch 60 formed by the registering notches 4|, the said aligned notch being narrower than each of the notches 4|; and also produces an aligned slot "formed by the registering slots H, the aligned slot 5| being narrower than each of the slots 44.

By this means a more rugged die may be used to punch out the notches and their communicating slots while still making it possible to obtain a relatively narrow aligned notch and slot arrangement which will more readily restrict the increase the magnetic path for the formation of magnetic flux. Leg 2 is not necessary for the positioning of the side wall since a plurality of legs 43, by reason of the reversing of the plates, are aligned on each side of the arc path or notch and thus provide full support for the ends 12 and 12a walls 3| and Bla.

When the side walls and the plates are interlocked with the

lugs

41, 52, and 53 of the plates extending through perforation 32 of the walls and the ends of the walls hold in the slots III of the plates, then the parts may be permanently secu-red together by twisting, spreading, riveting over or otherwise deforming each lug so that an appropriate bearing surface will be formed thereby against the outer surface of the walls to prevent the lugs from slipping out of the perforations.

The back plate 80 having the form shown in Figure 5 is secured in the position shown in Figures 2, 3 and 4, bylugs BI and 82 of edge 83 and lug 84 of edge 85 which lugs extend through the perforations 32 in the side walls, and are appropriately deformed.

Plate 80 has a cutout 86 to register with the arcing horn 22 and a notch 81 communicating with the cutout 86 for engaging the locking member 88, Figure 2, in the manner hereinafter described.

The back plate also has a .portion 89 extended beyond the top of the arc quenching unit, this extension having a notch 90 which may be engaged by the head of a suitable screw 9| (Figure 2) for completing the securement of the unit to the panel in the manner hereinafter described.

It should now be noted that the

legs

42 and 43 of the plates 40 provide not merely a means for positioning ends II of the side walls, but also furnish additional areas of magnetic material which increase the cross-sectional area of the path for the magnetic flux and thus accelerate the upward movement of the arc. The aligned notches ll with their communicating slots 44 provide a means for first compressing the arc and cooling it. The arc is then broken into a series of short arcs as it travels onto the metal plates.

As previously described, the flow of current in the arc produces a magnetic field surroundin the current path. The plates of magnetizable material form a low reluctance path for the flux. The are is pulled into theplates where it-is broken rinto a series of short arcs and moved along the .plates at suflicient speed to prevent the plates from reaching an excessive temperature. Extinguishment is thus facilitated, and possibility of a restriking of the arc is reduced.

, Since a bendable insulating sheet which embraces portions of the plates is used, a greater area is posible for each of the plates within standard over-all dimensions for the arc quencher as a whole, thus increasing the strength of the magnetic field and causing greater and more rapid movement of the arc.

In previous arc chutes designed for interrupting high values of current, it was found advisable to protect the ends of the legs of the magnetic plates from the arc. This was done by making the side walls of an insulating material which when in a plastic condition, could be pressed in a mold to the required shape and then caused to harden as by the setting-of a cement or binder. Due to the nature of the process and the physical characteristics of the resulting material, these parts required a minimum thickness of a quarter of an inch or more. The construction shown in the present application provides superior protection for the legs of the plate and permits the use of a thin bendable inexpensive material. The material now used is less than a sixteenth of an inch thick. Thus, instead of requiring one half inch of width for both the side plates, less than one eighth of an inch is used with a corresponding increase in plate width. The width of the plates in an arc quencher having an outside width of 2 is, therefore, increased from 1 to 2" or 25.6% for the same overall width of the assembly. In addition to this, the use of thin sheet material as hereinafter described over the top of the arc chute permits longer. metal plates to be used. The increase in area of the-plates that may be thus obtained, is 45.2%. The added height increases the distance from the top of the slot to the top edge of the plate by one quarter of an inch, thus giving a greater cooling surface.

As is seen more particularly in Figure 2, a top plate I00 is secured to the arc chute by the lugs 51 which pass through appropriate perforations therein. These lugs 51 are also twisted or deformed in the same manner as are

lugs

41, 52 and 53 in order to secure the top plate I00 in position. Each side of the plate I" is supported by lugs 51, the lugs 51 in adjacent plates being staggered with respect to each other owing to the reversal of adjacent plates.

Vents are provided in the top plate I. These vents consist primarily of circular openings or perforations of substantial size along the center line of the plate. These vents III are so arranged that they are above the apices of the notches 4| and their slots 44 and thus provide for a vent along the line or area of greatest speed of the discharged gases.

The location of the vents tends to cause the maximum gas velocity to occur in the central plane of the unit and hence along the slots. This action drives the are rapidly into the narrow part of the notches. where the heat is absorbed, and so on to the plates.

Instead of using a continuous slot oreven an open space along the. top wall the vents Ill have closed areas III between them. This has been found to be more eflicient apparently for the reason that a series of short shunt arcs are probably produced from vent to vent around the spaces III, thus making the are even more unstable. The reason for the berzeficial result obtained is not quite clear. And yet, using atop plate I h'aving vents IIO separated by short intervals III in connection with an arc chute of the type herein described, it has been possible to obtain an interrupting capacity on a 600 volt circuii; normally carrying a maximum of 600 amperes oi as high as 50,000 amperes without failure by using an arc chute, the over-all dimensions of which are no greater than those of arc chutes previously usable at interrupting capacities of only 20,000 amperes or thereabouts;

It should be noted that the top plate I00 is cut out at I13 so that these cutouts may register with slight extensions III of the insulating side walls 3| and 3Ia to help position the top plate I00 and correspondingly the longitudinal extensions In of the top plate I00 register between the extensions III--III on the side walls in order further accurately to position the top plate I00 and to interbrace the structure and prevent skewing thereof.

While the circular vents III) are preferred, other types of vents such as those seen in the views of Figures 7 and 8 may be utilized. Thus, in Figure 7, the vents 2I0 in the top plate 200 the lead I21 (Figures 2 and 1) to the arcing horn. The lead I21 connects the arcing horn I20 with the terminal I'I.

Stationary arcing contact 22 is mounted on plate I30 which is secured in any suitable manner to the connection strap I3. Plate I30 is separated by an insulating strip I3I from the con nection strap I3 but the extension I32 of the plate I30 forms a base for the stationary contact I4. This extension I32 is also in contact with the connection strap l3 thus providing. a suitable may be slots transversely arranged and slightly diagonal; or as in Figure 8, a double row of slots may be used. This increases the area of the top plate through which gases may play and may permit shunt arcs to play over a greater portion of the top surface.

In each case the vents are so arranged that they flt in with the patternof the staggered stakes or lugs 51 and thus do not interfere with securement of the top plate to the arc quenching structure.

The top plate has also a structural p p se, since its interlocking with the side walls and its securement to the plates prevents any skewing or the plates with respect to the side walls.

An arcing horn I20, Figures 1 and 3, is provided in conjunction. with the arc chute, the said arcing horn being mounted on the front plate I2I. The front plate I 2I is not secured to the side walls 3I and 3Ia but instead is mounted on the plate 40a by means of rivets I22, I22 having insulating bushings I23 and washers which effectively insulate the plate I2I from the plate 40a.

The arcing horn is connected to the lower terminal oi the circuit breaker so that during arcing, the arc maybe transferred to this horn, shunting out the moving contact. The are horn plate is spaced from thesides and the top of the housing. This is done so that when the circuit breaker is opened, there will be full voltage between the upper terminal and the lower terminal, Since the outer arcing horn is connected to the lower terminal, there will be full voltage between the outer arcing horn and "the back, or supporting plate of the arc chute. By providing the construction shown, the possibility oi leakage along the fibre housing is greatly reduced.

The arcing horn I20, as seen in Figures 1 and 3, projects into the arcing path formed by the registering notches ll of the aligned parallel plates 40. The arcing -horn I20 and the plate I2I aredrilled and threaded at I25 in order to receive the screw I26 (Figure 2) which attaches path for the current from the connecting member I0 through the strap I3 to the stationary main contacts I4 and the stationary arcing contact 22.

The stationary arcing contact 22 is adjacent the securing member which also serves in part as a stationary arcing horn since it is aligned with the arcing path produced by the aligned slots in the magnetic plates.

The arc quencher as a unit may be secured to the plate I30 by means 01 the notch 81 in the base plate 80, see Figure 5, which is engageable around the post I40 which cooperates to support the member 80, while the portion HI 0! the member 80 projects beyond the notch 81 in order to engage the opposite or inner surface of the base plate 00.

The screws Si is passed through the notch of the base plate 30 into the threaded opening I00 in the plate I30, thus completing the attachment of the arc quenching unit.

Subsequently, the arcing horn I20 is connected into the circuit by placing the end I5I of the lead I21 (Figure 2) over the opening I25 (Figure 3) in the arcing horn I20 and passing the screw I26 through the perforation I53 in the end I5I of the lead and into the threaded opening I20.

The are quenching unit after the completion 'of'this operationis ready for use in the circuit interrupter.

The edges I00IOI of the insulating side walls 3 I and 3Ia (see Figures 2 and 3) extend beyond the base plate 80 and abut the insulating sheet III on either side of the plate I30, thus further serving toposition the arc quenching unit in place and also providing for further interphase insulation.

In operation of the arc quencher, the aligned notches form the path of the arc.

When the movable contactcarrylng arm I8 is caused to move toward the open circuit position wherein the contacts are separated, normally the movable contacts I4 and I0 are separated first so that the arc is drawn between the movable arcing contact 2| and the stationary arcing contact 22.

During the opening movement of the arcing contacts an arc is initiated at the final point of separation, which is at the uppermost points of the stationary and moving elements. Thus the initial point of gas' generation, which is substantially explosive in action, occurs at a point above the edges I0 of the return bend of the side walls. The intense heat generation in the initial arc produces a high gas pressure and hence radial velocity of gas. The downward flow of gas is prevented in the center, by the contacts themselves, particularly at, and shortly after the initial separation and, at the sides, by the return bends oi the side walls. An influence is, therefore, produced to increase the lateral and vertical velocities of the gas. This action tends to drive the are more rapidly up through the notches and onto the plates, hence contributing to quick extinguishment' of the arc.

The end of the arc is transferredfrom the movable arcing contact 2| to the stationary arc-' ing horn I20 mounted on the plate III.

The end of the are which plays upon the, stationary arcing contact 22 is also transferred by the magnetic held onto the member II which becomes a stationary arcing horn.

When the arc enters the plates, it is broken into a series of short arcs and quenched. In the event that it moves beyond the upper edges of the plates, then the arc gases may vent through the openings III in the top plate (or the openings II. in top plate I, or openings 3|. in top plate 3") and short shunt arcs may be established from opening to opening, thus rendering the are even more unstable so that it may readily be quenched.

The plate ill is cut out at I50 where a portion of it would be registered with and aligned with the opposite arcing born 88, thus making it even more dimcult for the arc to play between these members. This opening also served as a vent to relieve the gas pressure incident to current interruption and thus reduces the possibility of hot gases being blown down toward the breaker mechanism.

Since the insulating side walls are of bendable sheet material which embraces portions of the plates and these permit increased plate area, the arc quenching action is enhanced.

The

legs

43 and 42 of the plates which extend into the bent-around portions of the side walls enhance the magnetic effect by an additional area while the other portions of the plates by reason of their greater area can have the effect above noted.

The are quenching unit is simple in construction and readily attachable to the unit. Thus during the manufacture bent ends I2 of the walls may be inserted in the aligned slots III and the perforations in the side walls may engage the lugs of the plates. The lugs are twisted or otherwise deformed to make the engagement permanent. The top'wall is then mounted in place and the lugs also twisted or otherwise deformed. The bottom wall may be mounted in place at the same time as the plates are mounted. The plate "a may have the front member Ill secured thereto before the said plate 400 is secured in the stack.

There has here been described a physical form v and actual embodiment of an arc quencher whichby comparison with other units of the same over-all dimensions has more than twice the interrupting capacity of such other units. The actual reason for this vastly increased interrupting capacity may lie in any one of the elements hereinabove described or may actually inhere in only the combination thereof or in only a combination of certain portions of said elements. The action of the are when it is being quenched is so rapid as to make it, at the very least, difficult to determine the above described are quencher, should move more than %."4" apart to interrupt high currents in a very short arcing time.

In each of the foregoing portions of the de-' scrlption there has been described the, preferred embodiment which actually hasbeen found to be successful at for instance currents of 600 volts carrying a normal load of 600 amperes where its interrupting capacity was as high as 50,000 ameach of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher, said plates being each normal to and supported by said side walls at the outer edges of said plates; said side walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches,

and means on said plates for securing said bent portions of said side walls in bent position.

2. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs'defining each.notch; corresponding legs on corresponding sides of the plates being aligned with each other;

opposed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from; the outer edges of said plates extending through said side walls and securing said plates and side walls together, said side walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches, and means on said plates for securing said bent portions of said side walls in bent position.

3. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each otherpopposed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from the outer edges of said plates extending through said side walls and securing said plates and side walls together, and said extensions having shoulders at their bases for spacing the outer edges of the plates from the side walls, said side walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches, and means on said plates for securing said bent portions of said side walls in bent podtion. I l

4. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned-to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said arc quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from the outer edges of said plates extending through said side walls and securing said plates and side walls together, said extensions from opposite edges of the plates being staggered with respect to each other; said plates being arranged so that adjacent plates are reversed with respect to each other whereby extensions through each side wall are staggered, a top plate secured to the ends of said notched plates and engaging said side walls; said top plate, notched plates and side walls interbracing and supporting each other.

5. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher; said plates being each normal to and supportedby said side walls at the outeredges of said plates; said side-walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches, certain of the legs on each side of the arcing path defined by the aligned notches having a slot on the inner notch-defining boundary thereof engaging the free end of the bent around portion of the side wall.

6. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; said side walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches, one leg of each plate having a slot on the inner notch-defining boundary thereof engaging the free end of the bent around portion of the side wall, adjacent plates being reversed with respect to each other whereby the free end of each side wall is engaged by certain of said slots.

'7. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates;

. said side walls being of bendable insulating sheet material, the ends of said side walls extending beyond said legs being bent around the ends of said legs and into the entrances to said notches, and means on said plates for securing said bent portions of said side walls in bent position, each notch in each plate being asymmetric with respect to the center line of the plate which runs through the notch, adjoining plates being reversed with respect to each other, a restricted portion of each notch being aligned with restricted portions of each of the other notches.

8. In an arc quenching structure, having a plurality of spaced plates, 9. housing therefor comprising a side wall of bendable sheet insulating material, means for securing said spaced plates to said side wall, an end of said side wall being re-entrantly bent into a U-shaped reinforcing channel, and means for securing said end of said Side wall in said U-shaped reinforcing position.

9. In an arc quenching structure, having a plurality of spaced plates, 9. housing therefor comprising a side wall of bendable sheet insulating material, means for securing said spaced plates to said side wall, an end of said side wall being re-entrantly bent into a U-shaped reinforcing channel, and means on said spaced plates engaging said end of said side wall and secur ing said end in said U-shaped reinforcing position.

10. In an arc quenching structure, a plurality of spaced substantially rectangular plates, each plate having a notch extending from one edge thereof defined by legs, said notches being substantially aligned and defining an arcing path; housing means for positioning said plates in spaced relationship, said housing means enclosing the unnotched edges of said plates and embracing the ends of said legs; and an opening in a wall of said housing, said opening being substantially aligned with and intersecting the plane of the axis of said notches through the apices thereof.

11. In an arc quenching structure, a plurality of spaced substantially rectangular plates, each plate having a notch extending from one edge thereof, said notches being substantially aligned and defining an arcing path; housing means for supporting said plates in spaced relationship and enclosing the unnotched edges of said plates;

'said housing comprising a. pair of opposed side walls and a top wall, each of insulating material and ach secured to said plates, the said top wall being interlocked with said side walls, and an opening in a wall of said housing, said opening being substantially aligned with and intersecting the plane of the axis of said notches through the apices thereof.

12. In an arc quenching structure, a plurality of spaced substantially rectangular plates, each plate having a notch extending from one edge thereof defined by legs, said notches being substantially aligned and defining an arcing path; housing means for positioning said plates in spaced relationship, said housing means enclosing the unnotched edges of said plates and em: bracing the ends of said legs and a plurality of openings in a wall of said housing for egress of arc gases, said openings being substantially aligned with and intersecting th plane of the axis of said notches through the apices thereof,

said notch and defining a projection of said plate,

said projection extending in the plane-of said plate toward the edge of said plate with winch said notch communicates; the center line of said housing means for positioning said plates in spaced relationship, said housing means enclosing the imnotched edges of said plates; integral extensions-of said housing embracing the ends of said legs; and an opening in a wall of said housmg, said opening being substantially aligned with and intersecting the plane of the axis of said notches through the apices thereof.

15. In an arc quenching structure a plurality of spaced notched plates, the said notches being substantially aligned to form an arcing path, each of said plates having a pair of legs defining each notch; corresponding legs on corresp nding sides of the plates being aligned with each other; opposed side wall for said are quencher: said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from the outer edges of said plates extending through said side walls and securing said plates and side walls together, said extensions from opposite edges of the plates being staggered with respect to each other: said plates being arranged so that adjacent plates are reversed with respect to each other whereby extensions through each side wall are staggered, said extensions having shoulders at their bases for spacing the outer edges of the plates from said side walls, a top plate secured to the ends of said notched plates and enga in said side walls; said top plate, notched plates and side walls interbracing and supporting each other.

18. In a circuit interrupter having a stationary contact and a complementary contact movable between positions of disengagement and ent with said stationary contact, an are 4 quenching structure comprising spaced notched a metal plates, one end plate of said structure electrically-and mechanically connected to said stationai'ycontact. a metallic arcing horn secured to the other end plate in closely spaced relation with said movable contact when in said disengaged position, said arcing horn being electrically connected to said movable contact, the notches in said plates being substantially aligned, each .of said plates havinga pair of legs deilningeach notch; corresponding legs on corresponding sides.

of the 'plat'es'being aligned with each other; op-

posed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from the outer edgu of said plates extending through said side-walls and securing said plates terminal structure and extending from a surface thereof, an extension of said stationary contact in spaced relation to said surface of said ter- 'minal structure, an arc quenching structure comprising spaced notched metal plates, an end plate of said quenching structure in contact with said terminal structure and positioned by the cooperation of its notch with said stationary contact and the extension thereof, a plurality of said plates having notches substantially aligned,

each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; extensions from the outer edges of said plates extending through said side walls and securing said plates and side walls together, said extensions from opposite edges of the plates being staggered with respect to each other; said plates being arranged so that adjacent plates are reversed with respect to each other whereby extensions through each side wall are staggered, a top plate secured'to the ends of said notched plates and engaging said side walls; said top plate, notched plates and side walls interbracing and supporting each other. c

"18. In'a circuit interrupter having a stationary contact and a complementary contact movable between positions of disengagement and engagement with said stationa'ry contact, an arc quenching structure comprising spaced notched metal plates, one end plate of said structure electrically and mechanically connected to said stationarycontact, a metallic arcing horn secured to the other end plate in closely spaced relation with said movable contact when in said disengaged position. said arcing horn being electrically connected to said movable contact, the notches in said plates being substantially aligned, each of said plates having a pair of legs defining each notch: corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said arc quencher; said plates being each normal to and supported by said side walls at the outer edges of said plates; is top plate secured to the ends of said notched plates and engaging said side walls; said top in spaced relation to said surface of said terand side walls together, said extensions from opposite edgesof the plates being staggered with respect to each other: said plates being arranged so that adjacent plates are reversed with respect to each other whereby extensions through each side wall are staggered,- a top plate secured to the ends, of said notched plates and said sick walls: said top plate, notched plates and zigserwalls interbracing and, supporting each ""l'!*.*In-a;circuit interrupter having terminal structure, a stationary contact moimted on said plate, notched plates and side walls interbracing and supporting each other.

19. In a circuit interrupter having terminal structure, a stationary contact moimted on said terminalstructure and extending from a surface thereof, an extensionof said stationary contact minal structure, an arc quenching structure comprising spaced notched metal plates, an end plate of said quenching structure in contact with said terminal structure and positioned by the cooperation of its notch with said stationary contact and the extension thereof, a plurality of said plates having notches substantially aligned, each of said plates having a pair of legs defining each notch; corresponding legs on corresponding sides of the plates being aligned with each other; opposed side walls for said are quencher: said plates being each normal to and supported by said side walls at the outer edges of said plates: a top plate secured to the ends of said notched plates and engaging said side walls: said top plate, notched plates, and side walls interbracing and supporting each other.

= C. GRAVES, Ja.