US2243038A - Circuit interrupter - Google Patents

Description

May 20, 1941.

L. R LUDWIG CIRCUIT INTERRUPTER `Filed July'l, 1938 4 Sheets-Sheet 1 www 4 Sheets-Sheet 2 mf/a @my Filed July 1, 193B L. R LUDWIG IRcUIT NTERRUPTER Mgy zo, 1941.

May 20, 1941. L R, Upwlg 2,243,038

CIRCUIT INTERRUPTER.

Filed July 1, 1938 4 Sheets-Sheet 3 WITNESSE'S: INVENTOR ATTORNEY Patented May 20, 1941 UNITED sTATEs PATENT oFFicE Leon B. to l Westinghouse Electric a Manufacturing Company, East Pittsburgh,

' Pennsylvania Pa., a corporation of Application July 1, 1938, Serial No. 216,884

19Ciainis.

This invention relates to circuit interrupters,

and more particularly to arc extinguishers for circuit interrupters of the air break type. It is an object oi my invention to provide an air break circuit interruptcr which not only interrupts the circuit, but also restricts and deionines the arc gases so as to prevent the issuance of dame from the interrupting structure, thereby rendering the interrupter suitable for close mounting in metal cubicles or other' enclosed structure.

A further object of my invention is to increase the interrupting capacity f circuit interi-unters of the aforesaid type.

Another object of my invention remdes in the provision of an arc-extinguishing device for air.

circuit breakers of high interrupting capacity, which device is equally effective on alternating and direct-current circuits. A

A more specific object ot my invention is the provision of an arc-extinguishing device -for an air circuit breaker of the aforesaid type in which improved arc extinction is obtained by the use of spaced slotted plates of insulating material.

and in which. arc movement within the slots is obtained by a self-contained magnetic iield device thereby eliminating the necessity of a blowout coil or coils to secure arc movement.

Other objects and advautagesrelate to detalls of the interrupting structure such as the thickness of the interrupting plates, the spacing therebetweim, the shape of the arc receiving slots and the like. all of which will appear more fully in the following description when taken in connection with .the accompanying drawings, in which:

Figure 1 shows the circuit interrupter of my invention in side elevation, a portion oi .the arcextinguishing structure being broken away to reveal tlie position of the arc drawing contacts with respect to the arc-extinguishing device;

Fig. 2 is an enlarged side elevation view partially in section of the arc-extinguishing device group of plates forming Dart of the arc-extlnguishing device shown in the previous figures; Fig.6isanendelevationviewotamodiiled form of plate structure which may be used in the -arc-extinguishing device of my invention;

Fig. 'I is a fragmentary sectional view of the plate structure shown Ain Fig. 6. 4taken' along .the line VII-V11 thereof: g

Fig. 8 is a fragmentary sectional view showing a plate structure for an arc-extinguishing device similar to that shown in Fig. '7 except that the plates of magnetic material have been omitted;

Fig. 9 is a plan view showing a further form of plate structure capable oi use in the arc-extinguisher of my invention;

Fig. 10 is a sectional view o1' the plate structure shown in Fig. 9 taken along the line X-X thereof Fig. 1l is a sectional View of the plate structure shown in Fig. 10, taken along the line XI-XI thereof Fig. l2 is an elevation view showing still another arrangement of plate structure capable of use in the arc-extinguisher of my invention; and

Fig. 13 is a sectional view of the plate structure shown in Fig. 12, taken along the line XIII-m1 thereof.

In order to accomplish arc extinction without the issuance of ame exteriorly oi the arc-extinguishng structure,l numerous devices have heretofore been proposed. One form of ard-extinguishing structure which has proven to be successful commercially comprises a lplurality of spaced metallic plates having, aligned arc receiving slots therein. The arc to be extinguished is drawn within or at the entrance portion of the slots and is moved to the closed end of the slots, and nally into the metallic plates where it is caused to play as a series of short arcs between the plates. The metal plates in this instance quickly deionize 'the arc stream and bring about arc extinction without the issuance of ame from the vent passages between the plates. Although this type of circuit interrupter has proven to be effective in interrupting circuits carrying as high as 32,000 amperes at 15,000 volts, great diiilculty is encountered in causing currents of substantia-ily greater magnitude to properly transfer to the metallic delonizing plates.

I have discovered that an arc-extinguishing structure employing a plurality of spaced plates of insulating non-gas forming material having aligned arc-receiving slots therein is far more eilective than the known arc-extinguishing structure employing metallic plates, and is capable o! materially extending the upper limit of current capable of being interrupted. One embodiment of the interrupter which will be hereinafter described in detail, is capable oi producing complete circuit interruption oi v125.000 amper-es at 600 volts alternating current with only 1/2 cycle of arcing. When connected to a direct-current circuit the interrupter is capable of interrupting up to 80,000 ampere's or more at 750 volts.

The improved interrupting power of my arcextinguishing structure is based upon the magnetic blast theory and is explained as follows. If an arc is moved laterally in air by a suitable magnetic ileld against a non-gas-producing solid of such shape that no turbulent flow of gas is produced, the section of the are remains substantially unchanged and only a slight increase in pressure of the arc gas results. The arc voltage is increased somewhat due to the loss of ions and heat to the restricting walls of the solid. Now if slots or vent openings are placed along the restricting wall sothat the pressure is relieved, a strong blast of gas passes through the openings. The arc must, therefore, ionize fresh gas in considerable quantties'in order to maintain itself and the arc voltage is thereby greatly increased.

In other words, the eil'ect of the magnetic field is to move ions out of the arc stream. The force exerted by the magnetic fleld on the ions is transmitted to the gas surrounding the arc in collisions between the ions and the neutral gas mole.- cules. Thus, the moving ions cause un-ionized gas to be placed in motion so that a new supply of cool u1u-ionized gas is constantly being drawn past the arc. Of course, the ions which are moved into the venting slots will cause the arc to loop or bow somewhat into the slots since the arc attempts to follow the movement of the ions. However, the increasing flow of un-ionized gas into the arc increases the rate of deionization so that in case of alternating current, the arc path quickly becomes non-conducting following a current zero.A 'I'he rapidly escaping ions through the venting slots as well as the blast of unionized gas caused by the magnetic eld, produces a rapid rise in arc voltage so as to make the method of arc extinction equally effective on direct current. Arc extinction with the circuit interrupter of my invention is, therefore, accomplished in a manner different from that employed in liquid immersed breakers which subject the arc to a combined blast of arc extinguishing liquid and the products of decomposition of the arc. There is also a marked difference in the manner of arc extinction with my structure and that employed in air or gas blast breakers as heretofore used. Gas blast and air breakers of the prior art depend upon rapid lengthening of the arc by either magnetic or gas blast blowout means for extinguishing the arc. In my invention, there is substantially no lengthening of the arc as initially drawnnor is the arc split into a plurality of short serially related sections, as in metallic plate deionizing structures. The specific structure of one device with which I have accomplished my improved results will now be' described.

In Fig. 1 of the drawings, the reference numeral l5 designates a panel upon which the interrupter of my invention is mounted. 'I'he panel Il supports a frame i1 which carries a suitable operating mechanism generally indicated at I9.

.The operating mechanism I! is not specifically claimed herein and may be of any suitable arrangement, as for instance, that shown in Patent No. 2,177,014, issued October 24, 1939, to W. M. Austin, and assigned to the assignee of the instant application.

,The operating mechanism Il is adaptedI to actuate a pivoted contact carrying arm 2| hinged to a cross pin 23 to the frame I1. The contact arm 2| supports a main bridging contact 2l, the ends of which are adapted to normally engage the main line contacts 21 and 29. Connected to the main contact 21 is an arcing contact Il adapted to cooperate with a moving arcing contact Il carried by a suitable arm. 25 supported by the pivoted arm 2l. Inasmuch as the specific contact arrangement is not specifically claimed in the instant application, further details of Athe contact structure may be had 4by referring to Patent No. 2,214,471, issued September 10, 1940,

to L. R. Ludwig and M. E. Horne, and also assigned to the assignee of the instant application.

An arc established by the separation of the arcing contacts 3| and 33 is extinguished by an arc-extinguishing device 31 disposed in partially surrounding relation with respect to the arcing contacts. The arc-extinguishing device 31 is more specifically illustrated in Figs. 2 to 5 inclusive, and comprises a back support plate Il of insulating material and a front support plate 4l also of insulating material, between which are disposed a plurality of plates of insulating material spaced from each other by plates of magneticmaterial. The general shape and arrangement of these plates are more clearly shown in Fig. 5, which represents a group of plates disposed within the space indicated by the bracket at X in Fig. 2.

As shown in Fig. 5, the lowermost plate 43 is constructed of insulating material and preferably of refractory or other material that is substantially free from substance which gives off gas when acted upon by an arc such for example as asbestos board, quartz, soap stone or titanium oxide. Cold molded compositions as vfor instance a product known as artificial porcelain comprising 30% talc, 2% feldspar and 68% clay may also be used. In general all materials which are refractory in nature and have the requisite mechanical strength are suitable for this purpose. The preference for non-gas forming materials will be made known hereinafter. The plate 43 is provided with a notch or slot 45 extending from the lower end thereof inwardly and tapers from a relatively wide Width at the edge of the plate to a narrow slot-like portion at the closed end thereof. The outline of the slot 45 is perhaps more clearly shown in Fig. 3. Adjacent the plate 43 disposed on either side of the slot 45, is a pair of plates 41 of magnetic material, such as iron or steel, which serve as spacers between the insulating plate 43 and the next adjacent insulating plate 49. The iron plates 41 also serve to produce a magnetic field to facilitate arc movement upwardly in the slot 45, as will be explained more fully hereinafter.

The plate 49 is similar in construction to plate 43, with the exception that it is somewhat shorter and is adapted to support a transversely extending plate 5| of magnetic material across the upper end thereof, the purpose of which will also appear hereinafter. Two sets of plates 41 are also disposed between the plate 49 and a plate 5l, the latter plate being similar to plate 4I, with the exception that the entrance portion of its slot 45 has been extended and is of a smooth contour,

whereas the entrance portion of the slot 45 in plate 43 `is provided with two arcuate cutout portions, as shown at 55, for the purpose of accommodating the fixed arcing contact structure 3l.

With particular reference to Fig. 2 the insulating plates to the right of the portion indicated at X have identically the same slot contouras that shown by the plate 53 in Fig. 5. The insulating plates to the left of the portion indicated at X have the same slot contour as plate 43.

Each of the plates 43, 43 and 53 of insulating material, as well as the plates 41 of magnetic material, are provided with apertures l1 as shown in Figures 3 and 5. These apertures permit the assembly ofthe respective plates in the order shown upon four tubular members. 53 of insulating material. 'I'he stack of plates is firmly held together by bolts 5i passing through the two lowermost tubular members 53 and the respective front and back supports 33 and 4i. Either side of the plate assembly ls provided with a cover plate 53 secured to the respective front and back supports by screws 35, as shown. The plates 5i of magnetic material disposed in abutting relation with respect to the plates 43, are prevented from movement away from the plates 43 by means of bar members 51 secured to each of the side plates well as the cross-sectional area of the venting passage between the plates. In practice. I have found that the plates of insulating material may 33, and which register with the rectangular detents 53 provided in the plates 5i.

The front support 4i is also provided with al lwhich are anchored to suitablefastening means not shown, provided in the panel. The arc-extinguishing device 31 is positioned with respect to the fixed arcing contact 3| by means of a semicircular support 15 which forms part of the fixed arcing contact assembly and upon which `the back support plate 33 is adapted to rest. In order to properly center the arc-extinguishing device 31, the back support plate 33 is provided with a semi-circular notch or detent 11 as more clearly shown in Figs. 2 and 3. The support member 15 is adapted to register with the notch 11 when the arc-extinguishing structure 31 is in place. When Athus positioned and with movement of the arcing contact 33 to the open position, the path of movement of the contact 33 takes place centrally within the aligned slots 45 of the respective plates of insulating material.

When an arc is established by the separation of contacts 3| and 33, the plates 41 of magnetic material cause the arc to be moved upwardly in the slots 45 towards the closed end thereof. The magnetic reaction is increased by the transversely extending plates 5I disposed in abutting relation with the plates of insulating material 43. It will also be observed that the transverse plates 5I of magnetic material are of the same thickness as the plates 43 of insulating material, so that the plates 41 of magnetic material provide a venting space or channel between adjacent plates of insulating material that is free and unobstructed. Thus as the arc is drawn between the. arcing contacts 3i and 33, and moves to the closed end of the slots 45 in accordance with the foregoing theory, it will be subjected to a strong blast of gas set up by the magnetic eld moving the arc upwardly. The use of gas-forming insulating material for the plates 43, 43 and 53 is undesirable in that the action of the arc upon such material produces gas in such quantities so as to act expulsively upon the arc which tends to blow the arc out of the slots 45 and in general hinders arc movement towards the closed ends of the slots. The arc is prevented from being moved or looped a substantial distance between the plates of in.

sulating material by the proper selection of thickness of the insulating plates. and also the spacing between the plates of insulating material, as

vary from $6" to V4 and the spacing between plates of insulating material may vary from Y." to M4". The plates of magnetic material 41 preferably have such a width that 'the space therebetween at the most constricted portion is from y. square inch to 3/4 square inch. I have found that if the cross-sectional area of the venting passages is too great, there is a marked tendency for the arc to elongate and be driven through the venting passages and out the open end thereof.

I have also discovered that the shape of the slot 45 is of importance in obtaining free and unimpeded movement of the arc, particularly of the higher current values upwardly towards the closed ends of the slots. For example, I have found that a slot that varies in width from at its apex to 1/3" .at a point two inches removed therefrom, has Substantially the proper taper at its upper or extremely narrow end. The lower portion of the slot, however, may increase in width more rapidly and so long as the sides thereof have a smooth contour and are of sumcient width to permit the moving arcing contact 33 to pass therethrough, no diiliculty is experienced in obtaining the requisite arc movement. In general, the shape of the slot 45 may be such that increases as l increases, where l is the distance measured along the axis of the slot from its apex and w is the width of the slot measured perpendicular to the axis. The taper or the rate at which the slot changes its width may also be expressed as halving in width in every longitudinal distance of from to 2 inches.

In order to prevent gases resulting from an arc within the slots 45 at the time of contact separation or shortly thereafter from being directed downwardly and against the circuit interrupter contact mechanism, I have provided two opposed deflecting members 13 disposed on either side of the path of movement of the contact 33, and respectively secured to the side cover members 83. The deflecting members 13 provide a throat or orifice-like passage in which moving contact 33 operates, and further provides a pocket immediately above the members, in which the gases are entrapped, deflected and caused to be directed upwardly in the event that the current being interrupted is suiliciently great to cause a blast of gas having a tendency for downward movement. This tendency for downward movement, however, persists only for a short interval of time and gives way to the effect of the magnetic field which drives the arc gases as well as considerable quantities of un-ionized gas upwardly of the slots and through the spaces between the plates of insulating material.

I have also discovered that effective arc extinction may be attained by .modifying the plate arrangement within the arc-extinguisher 31 as shown in Figs. 6 and '7. As shown `in these two figures, a plate 3l of insulating material, having a slot 33 therein, is placed on either side of a plate 35 of magnetic material having a slot 31 in Fig. '7 and assembled with spacing members 88 disposed therebetween so as to provide vent passages adjacent the arc and through which a blast of gas may be directed to aid in extinguishing the arc.

Although the plates of magnetic material prcduce superior performance, I have also discovered that a successful arc-extinguishing struc-n ture may be produced by the use of spaced plates of insulating material without plates of magnetic material or other magnetic means disposed there between, as shown in Fig. 8. In Fig. il the platesJ 8| correspond in shape to the plates 8| oi Fig. d, and are provided with spacers B9 without the use of magnetic material. The absence of iron or other suitable magnetic material in the arcextinguishing device as schematically illustrated in Fig, 8, permits a more rapid rise of arc volt age but also has the tendency of permitting the arc to be blown through the venting spaces between the plates of insulating material and appear exteriorly of the arc-extinguishing device before the arc is extinguished.l The addition of iron or other magnetic material to the arc-` extinguishing structure has a marked inductive effect and greatly reduces the transient voltage rise preceding current interruption, and .also limits the amount of movement of the arc into the venting spaces between the plates of insulating material, thereby lessening the danger of flame from appearing exteriorly of the arcextinguishing device. Therefore, a further advantage in the use of magnetic material in the arc-extinguishing structure resides in the provision of means for movingthe arc quickly towards the apex of the slots in the plates of insulating material without movement of the arc beyond the ends of the plates.

In-Figs. 9 to 11, a modified plate structure is illustrated in which plates of insulating material ill are spaced from each other by narrow plates 93 of magnetic material disposed on either side of the arc-receiving slot 95. The magnetic eiect of the plates 93 of magnetic material is strengthened by the addition of a yoke 91, also of magnetic material, disposed about the upper end of the plate assembly. The arc-extinguishing operation, however, is performed in a manner as heretofore described. I

Figs. 12 and 13 illustrate a further possibility of plate structure which constitutes alternate plates of insulating material having a. slot |03 therein and plates |05 of magnetic material of inverted U-shape, as shown in Fig. 12. Thus the plates provide a spacing between the plates of insulating material and also -provide a strong magnetic field for moving the arc towards the closed end of the slot III. The plates |05 in this instance are of considerably greater length than the plates IDI so as to pro vide a suitable venting passage |01 between the adjacent plates of insulating material.

Although I have shown and described a specificil circuit interruptor and a number ofarc-cxtin guishing devices therefor, it is to be understood that the same is for the purpose of illustration 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 myinvention:

1. In a .circuit interrupter, means for establishing an arc, an arc-extinguishing structure for extinguishing said arc comprising means of insulating material having a. V-shaped slot therein decreasing progressively 'in width from t `ne side lil in which said are is adapted to play, said slot thereof to the other and terminating in a constricted closed end tip, said constricted tip decreasing in width from no greater than oneeighth inch at a point at least two inches from its apex to no greater than one-sixteenfth inch at its apex, said means of insulating material having venting passages therethrough communicating at spaced intervals with at least the constricted tip ci said slot, means for moving said arc into said constricted tip where it is adapted to play until extinguished, and means for subjecting said arc to a blast of uri-ionized gas while playing 1n said constricted tip.

2. In a circuit interrupter cf the air blast type. an arc extinguishing device comprising means of non-gas-forming insulating materia-.l having a tapered notch extending inwardly from one end thereof and a plurality of spaced venting passages leading from said tapered notch, means for establishing an arc within the larger portion of said notch, said tapered notch terminating in a. constricted tip which progressively decreases in width to the closed end thereof and which has a width, at its entrance portion to preclude alternating current arcs above a predetermined instantaneous current magnitude from entering therein, and means for moving said arc laterally within said notch and into said constricted tip following decay of the instantaneous current below said predetermined magnitude, said means causing a blast of 1in-ionized gas through the are stream and the venting es in said means of insulating material to assist in extinguishing the src.

3. In a circuit interruptor, means for establishing an arc. an arc-extinguishing structure for extinguishing said arc comprising a plurality of plates of insulating material having through venting spaces therebetween and slots of V-shape in which said arc is adapted to play, said slots decreasing progressively in width from one side thereof to the other and terminating in the constricted closed end tip, said constricted tip de.. creasing in width from no greater than one eighth inch at a point at leastI two inches from its apex to no greater than one-sixteenth inch at its apex, means for moving said arc into said constricted tips where it is adapted to play until extinguished, and means for subjecting said arc to a blast of un-ionized gas while playing in said constricted tip.

4. Ina circuit interrupter, an arc-extinguishing device. comprising a plurality of spaced plates of non-gas-formlng insulating material, said plates having substantially aligned tapered slots extending inwardly from one of their ends means for establishing an arc within the larger portion of said slots, said slots terminating in constricted tips which progressively decrease in width to the closed ends thereof and have a width wt their entrance portion to preclude alternating current arcs -above a predetermined instantaneous current magnitude from entering therein, and magnetic means for moving said arc laterally within said slots and into said constricted tips following decay of the instantaneous current below said predeterminedl magnitude, said magnetic means causing a blast of un-ionized gas through the arc stream and the spaces between the plates of insulating material to assist in extinguishing the arc.

5. In a circuit interruptor, an arc-extinguishing device comprising a stack of plates of insulating material. means spacing said pistes a preventing passages, said plates being substantially.

determined distance from each other to provide free from maiterials which give off gas when acted upon by an arc and having elongated tapered notches therein, said tapered notches decreasing progressively in width from the open to the closed ends thereof and having a constricted portion of at least two inches in length adjacent the closed ends thereof of width to prevent entry thereinto of valternating current arcs of a predetermined instantaneous current magnitude, means for establishing an arc within said notches, and means for moving the arc into the constricted portion of said notches following decay of the instantaneous value of the arc current below a predetermined magnitude where it is cooled and extinguished. i

6. In a circuit interrupter, an arc-extinguishing device comprising a stack of plates of insuiating material, means spacing said platea a predetermined distance from each other to provide vent passages therebetween, said plates being substantially free from materials which give oi! gas when acted upon by an arc and having aligned elongated tapered notches therein, means for establishing an arc within said aligned notches, and plate means of magnetic material disposed within said stack adjacent the closed ends of said aligned notches to provide an intense magnetic field for moving the arc against the closed end oi' said aligned notches where it plays until extinguished, said plate means of magnetic material being placed in abutting relation with and across the outer edges of a plurality of plates of insulating material so as not to restrict the venting passages between said plates of insulating material.

7. In a circuit interrupter,` an arc-extinguishing device comprising a stack of plates of insulating material, means spacing said plates a predetermined distance from each other to provide vent passages through the stack, said plates being of refractory material and having elongated tapered notches therein which terminate in a constricted tip decreasing progressively in width from no greater than one-eighth inch at a point at least two inches from the closed end of the notches to no greater than one-sixteenth inch at the closed end, means for establishing an arc within said aligned notches, and plates o! magnetic material disposed at spaced intervals in the stack of plates of insulating material to provide an intense magnetic field for moving the arc into the constricted tips of said notches where it plays until extinguished.

8. In a circuit interrupter, an arc-extinguishing device comprising means of insulating material substantially free from material which gives of! gas when acted upon by an arc, said means of insulating material denning an elongated V-shaped notch and a plurality of spaced venting passages therethrough communicating at least with the closed end of said notch, means for establishing an arc within said notch, and means ofxnagnetic material embedded in said means of insulating material but disposed outside said venting passages for producing a magnetic field to move the are toward the closed end of said notch where it isadapted to play without substantial looping into said venting passages.

9. In a circuit interrupter, an arc-extinguishing device comprising a stack of plates of insulating material, said plates being substantially free from materials which give oi! more than a small quantity of gas when acted upon by an arc and having elongated tapered notches extending inwardly from one end thereof', means spacing said plates from each other to provide venting passages therebetween in alignment with the longitudinal axes of said notches, means for establishing an arc within said notches, and plate means of magnetic material disposed at intervals in the stack but disposedoutside said venting passages for producing a magnetic ileld to move the arc toward the closed end of said notches i and a blast of gas through the arc to aid in extinguishing the arc, said plates of insulating material being spaced from each other a distance to prevent substantial movement of the arc therebetween.

l0. In a circuit interrupter, an arc-extinguishing device comprising a stack of plates oi' insulating material, said plates of insulating material being substantially free from materials which give of! gas when acted upon by an arc and having slots of V-shape therein, plates of magnetic material disposed between said plates of insulating material on either side of said slots and extending longitudinally of said plates of insulating material to provide vent passages of predetermined cross-sectional area in alignment with said lots, means for drawing an arc within said slots, said plates of magnetic material providing a magnetic ileld for moving the arc toward the closed ends of said slots, and additional plates of. magnetic material disposed transversely of said longitudinally disposed plates of magnetic material for strengthening the magnetic reaction for moving said arc, said plates of insulating material being spaced from each other a distance to prevent substantial movement of the arc therebetween.

l1. In a circuit interrupter, an arc-extinguishing device comprising a stack of plates of insulating material, said plates of insulating material being substantially free from materials which give of! gas when acted upon by an arc and having aligned slots of V-shape therein, plates of magnetic material disposed between said plates of insulating material on either side of said aligned slots and extending longitudinally of said plates of insulating material to provide vent passages of predetermined cross-sectional area in alignment with said slots, means for drawing an arc within said aligned slots, said plates of magnetic material providing a magnetic ileld for moving the arc against the closed ends of said aligned slots where it is adapted to play until extinguished, and additional plates of magnetic material disposed transversely of said longitudinally disposed plates of magnetic material for strengthening the magnetic reaction for moving said arc, said additional plates of magnetic material being disposed in abutting relation to said plates of insulating material and having sub-4 stantially the same thickness so as to prevent obstructing the vent passages between said plates of magnetic material opposite said notches to strengthen the magnetic field set up by the arc within said plates of magnetic material.

13. In a circuit interrupter oi' the air break type, arc extinguishing means comprising a plurality of plates of insulating material, said plates being substantially free of material which gives off a gas when acted upon by an arc and having elongated tapered slots extending therein from one edge thereof, means for establishing an arc within said slots, said slots havinor a constricted portion which decreases progressively in 'width to the closed end thereof and is so narrow that alternating current arcs of relatively high instantaneous current magnitude will not enter therein but will permit entry only of arcs of less than a predetermined instantaneous current magnitude, and magnetic means for moving the arc laterally toward the closed ends of said slots, said arc playing outside said constricted portion until the instantaneous current has been reduced to said predetermined value whereupon it is moved by said magnetic means into said constricted portion where it is quickly cooled and extinguished- 14. In a circuit interrupter, arc-extinguishing means of insulating -material comprising a plurality of plate portions, spaced from one-eighth inch to one-fourth inch apart, said plate portions being free from large quantities of materials which give off a gas when acted upon by an arc and having a thickness from one-eighth inch to one-fourth inch, said plate portions having slots extending therein from one edge thereof, means for establishing an arc within said slots, and members of magnetic material to assist movement of the arc against the closed end of said slots, the magnetic ileld produced by said magnetic members also `causing a blast of cool un-ionized gas to be moved through the arc as it plays against the closed end of said slots.

g 15. In a circuit interrupter, arc-extinguishing means comprising a plurality of plates of insulating material, spaced from one-eighth inch to oriefourth inch apart, said plates being substantially free from materials which give off a gas when acted upon by an arc and having a thickness from vone-eighth inch to -one-fourth inch, said plates having aligned slots extending therein from one edge thereof, means for establishing an arc within said slots, and members of magnetic material disposed between said plates of insulating material longitudinally thereof on either side of said slots to assist movement of the arc against the closed end of said slots, said members of magnetic material serving to space said plates of insulating material apart and be` ing displaced laterally from each other so as t provide a venting space betweenadiacent plates of insulating material having a cross-sectional area 'of from one-eighth square inch to threefourths square inch, the thickness of said plates of insulating material. the spacing betweensaid plates and the cross-sectional area of said venting spaces cooperating to prevent substantial lengthening of the arc and movement thereof between said plates of insulating material.

ld. In .a circuit interrupter, arc-extinguishing means comprising a plurality of spaced plates of insulating material, said plates of insulating material being of substantially refractory material and having elongated tapered notches therein aligned at least at the open ends thereof, a pair of contacts at least one of which is adapted to be moved within said aligned notches to establish an arc therein, and means disposed on either side of the path of movement of said movable contact adjacent the open ends of said aligned notches and arranged toclose the open ends of said notches except for the space required for contact movement to cause the gas produced by said arc upon separation of said contacts to expand laterally and in a direction away from said contacts so as to prevent said gas from being blown out of the open end of said notches.

1'7. In a circuitI interrupter, arc extinguishing means comprising means of insulating material having an elongated V-shaped groove extending inwardly from one end thereof, said means of insulating material having spaced venting passages therethrough communicating With said groove, contact means separable within the open end of said groove for establishing an arc, and lining members disposed laterally of said contact means and arranged to close in part the open end of said groove to prevent arc gases from being blown out of said groove in the direction of said contact means.

18. In -a circuit interrupter, arc extinguishing means comprising a plurality of plates of insulating material each of said plates having an elongated V-shaped slot extending inwardly from one end thereof, means spacing said plates from each other to provide venting passages therebetween, con'tact'means separable within the open ends of said slots for establishing an arc, and deiiecting members of insulating material disposed laterally of said contact means adjacent the ends of said plates to substantially close the spaces between said plates on each side of said slots, said deecting members extending inwardly with respect to the open ends of said slots to provide a constricted entrance passage to saidslots for preventing arc gases from being blown out of said slots in the direction of said contact means.

19. In a circuit interrupter, arc extinguishing means comprising a plurality of plates of insulating material having elongated V-shaped slots extending inwardly from .one end thereof, means for establishing an arc withiny said slots, andplates of U-shaped magnetic material disposed between said plates of insulating material having the legs of the U on opposite sides of said slots for moving said arc towards the closed ends of said slots, the transverse portion of said plates of magnetic material extending beyond the plates LEON n. LUDWIG.

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