US2372045A - Switch - Google Patents

Description

March 20, 1 G. c. ARMSTRONG SWITCH Filed Aug. 26, 1942 3 Sheets-Sheet l INVENTOR George 6. flr'mszroflg.

BY MLZJQW ATTORNEY March 20, 1945. e. c. ARMSTRONG SWITCH Filed Aug. 26, 1942 3 Sheets-Sheet 2 Wnussszs;

' INVENTOR Gaa ga 6. flrmszmng.

B QMMM ATTORNEY March 20, 1945.

G. c. ARMSTRONG 2,372,045

SWITCH Filed Aug. 26, 1942 3 Sheets-Sheet 3 'BY ME.

ATTORNEY Patented Mar. 20, 1945 SWITCH George 0. Armstrong, Wilkinsburg,

Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa.,

of Pennsylvania a corporation Application August 26, 1942, Serial No. 45.6,172

12 Claims.

The present invention relates to switches in general, and, more particularly, to improved constructional details of switches for eiiecting rapid extinction of arcs drawn therein.

A more specific object of the present invention is to provide an improved arc chute for an electric switch which will be rotatable to facilitate inspection of the switch structure.

Another object of the present invention is to provide arcing horns for the switch of improved construction to eiiect a rapid transfer of the are from the contacts to the arcing horns.

Another object of the present invention is to connect electrically the lower arcing horn of a switch to the movable contact to minimize subsidiary arcing.

Another object is to provide an improved arc chute construction in which the lower arcing horn is rotatable with the arc chute, and to provide an improved construction for electrically connecting the rotatable arcing horn to the movable contact.

Another object is to provide an improved arc chute susceptible of economy in manufacture which will effect a rapid extinction of the arc.

Another object is to provide a plate structure which. may be readily assembled or replaced to constitute an improved arc chute.

Another object is to provide an improved arc chute having a constricted slot into which the arc is moved, said constricted slot having widened equalization openings to minimize the back pressure tending to force the are out of said constricted slot.

Another object is to provide an improved arc chute comprising a plurality of suitably shaped insulating plates forming a constricted slot, into which the arc is magnetically moved and to provide novel venting means for assisting the motion of the are into said constricted slot and facilitating its extinction therein.

Another object is to provide an improved arc chute construction rotatable for quick inspection of the switch, said rotatable arc chute carrying one of the arcing horns and to provide a novel easily detachable finger construction for connecting the rotatable arcing horn with the moving contact of the switch.

Another object is to provide an improved switch in which the arcing horns have such a configuration as to facilitate venting of the arc gases and to rapidly efiect a lateral transfer of the interrupting are from the contacts into a constricted slot to efiect its rapid extinction therein,

A further object is to provide an improved switch, the parts of which are readily adapted to mass production and rapid assembly which will have improved electrical clearances and which will extinguish the are drawn more rapidly and more effectively than have electric switches heretofore manufactured.

Another object is to provide an arc rupturing structure which will be effective at relatively high voltages with a relatively small contact gap, and relatively slow speed of contact separation.

The principles of my invention are adapted to switches operating in gases, such as air, but merely for purposes of illustration, and not by way of limitation, I illustrate my invention as embodied in an oil-immersed switch.

Further objects and advantages will readily become apparent to one skilled in the art upon a reading of the following specification taken in conjunction with the drawings, in which:

Figure 1 is a sectional view of an oil-immersed switch embodying my invention with the blowout plate 3! and side plates 32, 33 broken away and with a section taken through the arc chute on the line II of Fig. 2 and shown in the open circuit position;

Fig. 2 is a top plan view of the switch shown in Fig. 1;

Fig. 3 is a fragmentary view in section taken on the line III-III of Fig. l

Fig. 4 is a fragmentary view incross-section taken on the line IVIV of Fig. 1;

Fig. 5 is a fragmentary view in cross-section taken on the line VV of Fig. 1;

Fig. 6 is a view of the electrical connector for the lower arcing horn taken on the line VIVI of Fig. 1;

Fig. 7 is a side elevational view of one of the side plates of the arc chute;

Fig. 8 is an end view of the plate shown in Fig. 7

Fig. 9 shows one of the insulating plates used in building up the arc chute;

Fig. 10 is an edge view of shown in Fig. 9;

Fig. 11 shows another insulating plate used in the arc chute;

Fig. 12 is an end view shown in Fig. 11;

Fig. 13 shows another insulating plate used in the arc chute;

Fig. 14 is an end view of shown in Fig. 13; and

Fig. 15 is a perspective view of the upper arcing horn l9.

Referring to the drawings, and more particuthe insulating plate of the insulating plate the insulating plate ually operable crank, not shown,

larly to Fig. immersed type, the tank structure not being shown. The reference numeral I designates a suitable support to which plates 2 are rigidly secured. Plates 2 support an insulating operating bar 3 by brackets 3a and pins 33. The bar 3 is adapted for rotation about the pins 33 to effect the opening and closing of the switch. The operating bar 3 may be rotated either by a manor by a solenoid responsive to current conditions passing through the switch, not shown. Rotatable with the bar 3 is a bracket 4 carrying the movable contact structure. generally indicated bythe reference numeral 5. The bracket 4 has a horizontal extension 6 against which the movable contact 1 is biased by a compression spring 3, the other end of which is seated upon another portion 8 of the bracket 4. The bar 3 extends across the front of the switch panel to simultaneously operate the other poles of the switch.

Upon the rotation of the bar 3 in a counterclockwise direction, the bracket 4 will carry the movable contact 1 in a counter-clockwise direction to eflect engagement with the stationary contact l2, the compression spring 8 furnishing the desired contact pressure. Inserts 13 composed of a suitable electrically conductive arc resisting material may be imbedded in the coacting faces of the contacts 1, I2 to minimize pitting, burning or fusion of said contacts. A slot 14 provided in the movable contact 1 permits movement of the end of the horizontal extension 8 with respect to the movable contact 1 during the final portion of the closing operation. A fiexible conductor l electrically connects the movable contact 1 with the stud It, the latter being electrically connected to a line terminal of the switch.

A panel I1 mounted on plates 2 supports the stationary contact structure and blowout. coil assembly generally designated by the reference numeral l8. The arcing horn is for the stationary contact 12 comprises a member of channel configuration secured by a screw 20 to the stationary contact 12, the screw 20 also securing the stationary contact i2 to a conducting plate 2| imbedded in the panel I1. Each of the side portions 22 (see Fig. 3) of the arcing horn i3 is formed with a sharp apex 23 adjacent the stationary contact I2 to facilitate the transfer of the arc from the stationary contact l2 to the arcing horn it. The arcing horn I9 is preferably composed of magnetic material, in this instance steel, to magnetically assist in the transfer of the arc to the arcing horn l9. It will be noted that the channel configuration of the upper arcing horn l9 improves the venting for the arc gases and oil and also increases the ease of removal of the screw 20 in replacing the stationary contact l2, as Fig. 3 more clearly shows.

A blowout coil 24 surrounding a core 25 is attached by the screw 26 at one end to the conducting plate 2l. The other end of the blowout coil 24 is rigidly connected by the screw 21 to a conducting strip 28, which constitutes the other terminal of the switch. It will, therefore, be apparent that the electrical circuit through the switch comprises the conducting strip 28, screw 21, blowout coil 24, screw 26, conducting plate 2|, screw 20, stationary contact l2, movable contact 1, flexible conductor I6 and stud 16.

Referring to Fig. 2 it will be noted that the coil i4 serves as a bearing forthe rotational 1, the switch shown is of the oil-- movement of the arc chute structure, generally designated by the reference numeral 30. The rotatable arc chute structure 30 comprises the magnetic core 25, an insulating sleeve 250., two magnetic blowout plates 3|, two side plates 32 composed of refractory insulating material, two side plates 33 composed of insulating material;

in this instance fiber, and two support plates 34 formed of insulating material, in this instance fiber. The configuration of the support plates 34 is more clearly shown in Figs.'7 and 8. The support plates 34 have slots formed therein to support a plurality of suitably shaped insulating plates shown more clearly in Figs. 9 to 14, inclusive. It will be noted that the ends of the maznetic core 25 are machined down and threaded at 29. The nuts 23a hold the magnetic blowout plates 3! tightly against the magnetic core 25 to provide a good magnetic circuit and to avoid vibration.

The lower arcing horn, for the movable contact 1, generally designated by the reference numeral 38, comprises a lurality of, in this instance three, closely spaced plates of magnetic material, in this instance steel. The spacing be- 7 tween the plates permits free venting for the two rivets 4i rigidly secure a are gases, and the use of magnetic material iacilitates transfer of the arc from the movable contact 1 to the lower arcing horn 36. A conductor strip 31 is interposed between two adjacently spaced magnetic plates 38, 39 of the group 33 (see Fig. 3) to electrically connect the lower arcing horn 36 to the movable contact 1. A resilient flexible finger construction generally designated by the reference numeral 40, and shown more clearly in Fig. 6, is provided to releasably receive the conducting strip 31 and to electrically connect the conducting strip 31 to the stud iii to which the flexible conductor I5 is also connected. Thus during the interruption process there is no subsidiary arcing between the lower arcing horn 36 and the movable contact 1.

Referring to Fig. 6, which shows more clearly the finger construction 40, it will be noted that resilient metallic strip 42 to the conducting strip 43 leading to the stud IS. A pin 44 riveted to the right hand end of the conducting strip 43, as viewed inFig. 6, serves to releasably hold the conducting strip 31 in place by passing through an aperture 45 in the strip 31. However. the conducting strip 31 may easily be disengaged from the finger construction 43 by merely separating the resilient metallic strip 42 from the conducting strip 43 to effect a withdrawal of the pin 44 from the aperture 45 provided in the lower end of the conducting strip 31. In other words, by a separation of the right-hand ends of the strips 42, 43 the pin 44, carried by the strip 43, will be removed from both the strip 42 and the conducting strip 31 to permit thereby a withdrawal of the conducting strip 31 from the finger construction ML' The bailie structure forming the arc extinguishing slot in the arc chute structure 33 will now be described. Referring to Figs. 11 and 12, an insulating plate 46 composed of insulating material, in this instance fiber, is shown having two projections 41 which may be inserted in the slots 35 of the support plates 34. It will be noted that the edge of the insulating plate 46 facing the contacts has a curved configuration 48. The top of the arc chute comprises a plurality, in this instance four, insulating plates 43 alternately disposed to form a plurality of alternately disposed pockets, designated by the reference numeral 43 in Fig. 1, into which the arc may be forced by the magnetic field to assume a zig-zag configuration. At the lower end of'the arc chute structure 30, also disposed in the slot 35 of the support plates 34, are a plurality, in this instance five, insulating plates 46 (see Fig. 11) alternately disposed to also form a plurality of alternately disposed pockets 49 into which the arc may be forced to assume a zig-zag configuration. Between the two sets of pockets 49 at the ends of the arc chute structure 30 is a portion, desig. nated by the reference'numeral 50 in Fig. 1, made up of insulating plates and 52 (see Figs, 9 and 13) alternately disposed to form a restricted slot generally designated by the reference nu-= mere! 53 in Fig. 1 into which the arc is forced.

Referring more particularly to Figs. 9 and it, it will be noted that the insulating plate 5i, in this instance composed of fiber, has projections 41 which seat into the slots 35 of the support plates 34, and a V-shaped slot 54 which narrows down at 55 to a small constriction. The constriction at 55 then widens at 58 into an equalization opening, the purpose for which will appear more 'fully hereinafter. The equalization opening 55 communicates with a narrow slot 5?.

The insulating plate 52 (see Fig. 13) also has projections 41 which may be slidably inserted in the slots 35 of the support plates 34, and an inward extending portion 58 which extends to a greater distance away from the contacts than does the narrow slot 51 in the insulating plate 5|, as Fig. 4 more clearly shows.

In the embodiment of my invention shown in Fig. 1 I provide a vent 53 between the two slots 35 in the support plates 34 to permit a ready escape of oil and gas as the arc enters the arc chute structure 30.

I have found it convenient and the manufacturing processes are accelerated by forming a subassembly of the arc chute structure 30 comprising the two support plates 34 between which are inserted theinsulating plates 46, 5|, 52 and the lower arcing horn 36. Tubular rivets 60 surrounded by insulating sleeves 6| compress the two support plates 34 together holding the several insulating plates within the slots 35 and securing the lower arcing horn 36 fixedly in position. By the use of tubular rivets 60 the subassembly may be inserted between the plates 33 (see Fig. 2) and held therein by two studs 52 and two nuts 63, the conducting strip 37 of the lower arcing horn 36 sliding between the connector 43 and the resilient metal strip 42 and being held in position by the pin 44.

When it is desired to inspect the contacts or to make any adjustment whatsoever the entire arc chute structure 30 consisting of the core 25,

sleeve 25a, the two magnetic blowout plates 3|,

the two insulating plates 32, the two insulating plates 33 and the two support plates 34 with the plate structure interposed therebetween and the lower arcing horn 36 may be rotated as a unit in a counter-clockwise direction, as viewed in Fig. 1, about the coil 24 as a bearing, the conducting strip 31 of the lower arcing horn 36 being detached from the pin 44 of the connector 43. It will, therefore, be apparent that I have provided a chute structure which may be readily rotated about the axis of the blowout coil to permit ready accessibility to the contacts and to the upper arcing horn I3.

Furthermore, by the formation of a sub-assembly consisting of the two support plates 34, the insulating plates disposed therebetween, and

the lower arcing horn 38 and by the provision of the two studs 82 which releasably hold the sub-assembly between the insulating plates 33 and 32 (see Fig. 2) it is very easy to replace the part of the arc chute structure 30 with little inconvenience following burning of the restricted slot after a long operational life of the switch. Since in operation the insulating plates 32 and 33 are little afiected by the arc their replacement is notnecessary. The only part of the arc chute structure 30 which is burned and may need replacement is the sub-assembly enclosed by the support plates 34, and as stated above, this replacement is very easily effected by removal of the two studs 62.

It will be noted that the sub-assembly is with out bolts or other conducting members other than the two rivets 6D. This construction simplifies the problem of insulation and the electrical clearance between the top and bottom of the arc chute is thereby increased. In some instances it is desirable to mount the insulating plates 46, 5! and 52 in the slots 35 of the support plates 3d rather loosely so that excessive pressure created by arcing will force adjacent insulating plates apart to permit some venting between successive lplates. Consequently, the creepage surfaces between the plates are broken up and restriking of the are effectively prevented. It will also be observed that the blowout plates 3| and all metallic parts connected to or near the upper pontact l2 are electrically isolated from the lower arcing horn 36 and the movable contact I. The construction also facilitates manufacturing by minimizing the number of pieces which must be held inposition while riveting. As pointed out above the disassembly and replacement of the arc chute parts is facilitated.

The operation of the switch will now be described. Assume that the switch is closed with movable contact 1 engaging stationary contact i2. Upon the rotation of the operating bar 3, effective by external operating mechanism, not shown, the movable contact I will be drawn downward away from the stationary contact i2 to draw an are 65 therebetween. At least two forces will come into play to efiect a rapid lateral transfer to the right, as viewed in Fig. l, of the are 65 from the stationary contact l2 and movable contact 7 to the respective arcing horns l9 and 36. One of these forces will be the strong transverse magnetic field set up by the blowout coil 24, and the other force will be the use of the arcing horns of the configuration described and their being composed of magnetic material.

In moving outward along the face of a contact an are drawn at any point on the face tends to move toward the side edges of the contact because of the directional effect of the magnetic field set up :by currents in the body of the contact. In the upper arc horn IS the sides 22 of the arc horn l9 are so located that they are adjacent to the side edges of stationary contact [2, and hence are in the best position to receive an arc as it moves along the contact l2. The are horn l9 and contact l2, being electrically connected, are at the same potential. The surfaces being discontinuous, the arc terminal will not move readily directly from a hot crater on the contact l2 to a new cold terminal on the arc horn I 9. To aid in transfer of the arc terminal from the contact I2 to the arc horn IS, the horn I9 is preferably made of magnetic material and the sides 22 have relatively sharp corners 23 so located as to facilitate arc transfer.

' tively Transfer of the arc to the corner 23 results from two facts. First, the arc in moving around the adjacent corner of the contact l2 near the side 22. of the horn l9 tends to stop at the corner of contact l2, thus causing ionized vapor from the arc crater to be physically directed at the corner 23 of the horn I9, creating there a highly ionized region which aids are transfer from the contact |2 to the side 22 of arc horn I9. I

Second, if the arc terminal does not stop at the corner of the contact |2 nearest the corner 23 of the horn I9, but starts to move down the back of the contact |2, as shown in Fig. 1, the potential drop between the arc terminal and the point in the arc stream forced against the corner 25 of the horn i9 will cause transfer. Deionization of the arc stream 65 at the constriction of the are 55 as it bends around the relatively sharp corner 23 also raises the arc voltage at this point aiding transfer of the are 65 from the contact I. to the side 22 of the upper horn IS. The channel in the center of the are born I9, as defined by the side portions 22, provides an outlet for gas pressure and oil, to minimize back pressure which would retard arc movement. I

The forming of the side portions 22 with relasharp corners 23 is important to constrict the arc stream 55 and hence to raise the arc voltage at this point, thus facilitating transfer of the are 55 from contact |2 to arcing horn IS.

The are will rapidly move from the contacts to the arcing horns and will be forced into the V-shaped slot 54 of the insulating plates While the arc is moved into the slots 54 considerable gas will be evolved not only from a disintegrat-ion of the surrounding oil medium but also from the fiber. plates themselves. In the arc chute construction shown, the venting of this ionized gas is greatly facilitated by the gas passing upward between the side portions 22 of the upper arcing horn i9, through the central vent 59, and between the magnetic plates comprising the lower arcing horn 35.

By the provision of the equalization openings 55 in the insulating plates 5| I have equalized the arc pressure surrounding the are after it has entered the equalization openings 55 to prevent it from being forced back toward the contacts and out of the chute structure by the back pressure of the gas formed. The plurality of openings 55 collectively establish a continuous elongated widened equalization region in the arc chute to prevent back pressure from forcing the arc back out of the chute. Consequently, the arc chute comprises a plurality of insulating plates 5|, each of which has a restricted slot 55 formed therein which suddenly widens into the equalization opening 56. By such a construction, the plurality of plates align to form a relatively restricted continuous elongated arc passage 53 (see Fig. 1) which communicates with a relatively enlarged continuous elongated equalization passage formed by the alignment of the openings 55 provided in the several plates 5|. .Alternately disposed between the several plates 5| are the insulating spacer plates 52. In the assembled form of the arc chute, the spacer plates 52 are disposed just beyond the elongated equalization passage formed by the alignment of the openings 56. The are will be forced to the right, as viewed in Fig. 1, so that ultimately the ends of the arc will assume a zig-zag configuration caused by the portions 49 at the ends of the arc chute, and the center of the arc will be forced against the corrugated sur- 2,372,045 I faces created by the adjacently disposed insulating plates 5|, 52, during which time a blast of gas passes through the vent 59 to assist in cutting the arc and aiding in its extinction. Extinction soon follows, and the venting permits a ready replacement of oil through the chute structure 30 of high dielectric strength for the next operation of the switch.

By the use of arcing horns-of the shape shown in Fig. 1 the length of the arc is rapidly increased as it moves out along the horns, and the venting of ionized gas particles is also greatly facilitated by the construction shown.

Although the particular embodiment of my invention shown inFig. 1 is an oil-immersedcontactor, the construction of my switch is such that it may be readily operated in air with equal effectiveness. It will be noted in this connection that by th use of insulating plates formed of flber which evolves arc extinguishing gas when being contacted by an arc, sufllcient are extinguishing gas would readily be available if the switch shown embodying my invention were operated in air. Naturally, the constructional details of the arcing horns, the particular design of the plates. and the method of assembly do not depend upon the use of oil for their effectiveness. Merely for purposes of illustration, and not by way of limitation, I have shown my invention as embodied in an oilimmersed switch.

The switch of the particular construction shown has been successfully tested up to 40,000 kva. at 4600 volts and up to 25,000 kva. at 2300 volts. However, by increased proportions the switch obviously may be used at higher currents and at higher voltages.

It will be observed that by the novel venting means which I have used, ionized gas and liquid particles will not be driven back toward the region of the contacts to lower the dielectric strength therebetween and to increase the risk of restriking. By the provision of the venting means described the ionized gas and liquid particles are forced away from the region of the contacts, and naturally such a venting of the ionized gas and liquid particles away from the contacts encourages a circulation of fresh.oil of high dielectric strength into the region between the contacts to effectively prevent reignition of the are. It will be observed that by connecting the lower arcing horn 35 directly to the same stud l5 to which the conductor i5 is attached, the lower arcing horn is directly electrically connected to the movable contact I to consequently prevent any subsidiary arcing between the movable contact I and the lower arcing horn 35 after the arc has transferred to the lower arcing horn 55.

From the above description it will be readily appparent that I have provided an improved arc chute structure easy to manufacture and readily assembled which serves to'prevent the are from being forced out of the arc chute due to the back pressure of the arcing gases by an equalization of the arc gas forces acting on the arc column and which compels the ends of the are to assume a zig-zag configuration intimately engaging the fiber plates to consequently evolve additional arc extinguishing gas. The use of such an improved arc chute in conjunction with the improved design of arcing horns composed of magnetic material results in a switch capable ofinterrupting high current at high voltage with a minimum of space. The particular construction described permits easy accessibility to the contacts because of the fact that the are chute may be rotated as a unit about the blowout coil as a bearing. A previously described the portion of the arc chute which is susceptible to burning and wearing is capable of easy replacement by merely removing two studs. The interruption of the arc is very efiectively accomplished in the arc chute structure described, and reignition of the arc is effectively prevented by the proper circulation of the oil and by the improved venting means used.

Although I have shown and described a particular structure, it is to be understood that the same was for illustrative purposes and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

' I claim as my invention:

1. In a switch, a contact, an arcing horn for said contact, said arcing horn being of channel configuration and having two side portions, at least one of the side portions of said arcing horn terminating in a sharp apex adjacent said contact to facilitate arc transfer from said contact to said arcing horn.

2. In a switch, relatively movable contacts for establishing an are, a, pivotally mounted arc chute, an arcing horn arranged to move with said arc chute, detachable latching connecting means for electrically connecting the arcing horn to one of the contacts, and the detachable latching connecting means also servin to latch the arc chute in it operative position.

3. In a switch, relatively movable contacts for establishing an arc, a pivotally mounted arc chute, an arcing horn secured to said are chute and arranged to rotate therewith, a connector for said arcing horn and secured thereto, and relatively fixed latching connecting means for said connector, the latching connecting means serving to latch the arc chute in its operative position.

4. In a switch, a pivotally mounted arc chute, an arcing horn fixed to said arcing chute and ro tatable therewith, a metallic strip member secured to said arcing horn, and relatively fixed latching connecting means for resiliently electrically engaging said metallic strip member in latched engagement when said are chute is rotated to an extrem position,

5. In a switch, a pivotally mounted arc chute, said are chute comprising insulating side plates having one or more slots formed therein, a plurality of abutting insulating plate members inserted in said one or more slots for forming said are chute, the plate members being loosely held so as to separate under high arcing pressure conditions.

6. In a switch, an arc chute, side plates for said are chute, slots provided in said side plates, and a plurality of abutting insulating plates insertable in said slots for constituting said are chute, the plates separating from each other dur ing high arcing pressure.

7. In a switch, an arc chute, said chute having walls of insulating material defining a slot therebetween, said slot being open on one side to permit lateral movement of the arc thereinto, and

' an arc chute into which said are having a constricted portion adjacent the open side thereof, a widened portion into which the arc may move from said constricted portion and extending continuously for a major part or the length of the slot for the equalization of arcing pressure, and a second constricted portion on the other side of the widened portion opposite the first said constricted portion.

8. In a switch, means for establishing an arc, an arc chute into which said are is moved, one portion along the length of said are chute having walls defining a slot which is restricted in width at one part thereof and widened therebeyond, said slot being continuously open for a major part of its length to permit lateral movement of the arc therein from the restricted part into the widened part, a second portion along the length of said are chute having walls defining a zig-zag slot portion compelling the arc to assume a zigzag configuration as it is moved thereinto.

9. In a switch, means for establishing an arc,

is moved to effect its extinction, said are chute having a slot one part of which is constricted in width and another part of which is widened to form an equalization opening, said constricted part or the slot and said equalization opening each being continuous for a major part of the length thereof and opening one into the other to permit movement of the are from the constricted part of the slot into the equalization opening, and venting means for the arc gases beyond said equalization opening.

10. In a switch, means for establishing an are, an arc chute into which said are is moved to effect its extinction, a center portion of said are chute, said center portion containing a slot into which said are is moved, the slot having a widened equalization opening extending continuously along a major part of the length of the center portion of the arc chute to equalize the effect of the arc gases upon said are during the time it is in said equalization opening, venting means for the arc gases in said center portion, end portions for said are chute, at least one of said end portions having a slot wavy in cross-section for causing the arc to assume a wavy configuration as it moves thereinto.

11. In a switch, relatively movable contacts for establishing an are, an arcing horn of channel configuration and having at least'a side portion terminating in a sharp apex adjacent one of the contacts, a second arcing horn comprising a plurality of closely spaced metallic plates, an arc chute into which said are is moved, said are chute comprising a plurality of adjacently positioned insulatin plates.

12. In a circuit interrupter, a blowout coil, a magnetic core disposed within the blowout coil, a magnetic blowout plate making abutting engagement with the core and fixedly secured thereto, the core and the blowout plate being adapted to rotate together using the inside of the blowout coil as a bearing.

GEORGE C. ARMSTRONG.

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