US2247702A

US2247702A - Fuse construction

Info

Publication number: US2247702A
Application number: US304004A
Authority: US
Inventors: Ramsey Allan
Original assignee: Schweitzer & Conrad Inc
Current assignee: Schweitzer & Conrad Inc
Priority date: 1939-11-13
Filing date: 1939-11-13
Publication date: 1941-07-01
Anticipated expiration: 1958-07-01

Description

July 1, A R Y FUSE CONSTRUCTION Filed Nov. 13. 1939 4 Shets-Sheet 1 M g [I Q 15 g a s m S J/ July I, 1941. A. RAMSEY FUSE CONSTRUCTION Filed Nov. 13. 1939 4 Shasta-Sheet 2 Z9206)? far fiZZav fiwmrgy Ma, W

v I I'llllll V \p OWSQQAQQSQ 7 July 1, 1941. A Y 2,247,702

FUSE CONSTRUCTION Filed Nov. 13, 1939 4 Sheets-Sheet 4 Patented July 1,1941

Allan Ramsey;

Evanston,

Ill., asslgnor to Schweitzer & Conrad, Inc., Chicago, Ill., a corporation of Delaware Application November 13, 1939, Serial No. 304,004

46 Claims.

This invention relates, generally,to circuit interrupting apparatus and it has particular relation .to fuse devices.

An object of the invention is to reduce the pressure that is generated whena high current arc evolves an arc extinguishing medium from an arc extinguishing material.

Another object of the invention is to control the amount of arc extinguishing material that is exposed to the heat of an arc in accordance with the magnitude of the arc.

Still another object of the invention is to control the amount of arc extinguishingmaterial exposed to the heat of an are inversely in accordance with the magnitude of the arc.

A further object of the invention is to expose a relatively small amount of arc extinguishing material to the heat of a high current are and a relatively large amount of arc extinguishing material to the heat of a low current arc. I

Another object of the invention is to protect the inner surface of a circuit interrupter housing from the heat of the are that is drawn at the open end an arcing chamber which moves from one position to another within the housing to assist in extinguishing the arc.

A further object of the invention is to provide main and auxiliary bores in arc extinguishing material in a circuit interrupter of the moving chamber type in which the arc is first drawn in the auxiliary bore and subsequently in the main bore if it is not extinguished in the auxiliary bore.

Still another object of the invention is to restrain the movement of the moving arcing chamber by an arcing terminal which is connected by flexible conductor means to a line terminal.

A still further object of the invention is to provide for moving an arcing chamber within a fuse housing for elongating and extinguishing the are formed therein.

Another object of the invention is to dlrectl interconnect the arcing terminal which is movable with the arcing chamber and one line terminal of the fuse housing.

Still another object of the invention is to center the arcing'terminal with respect to the movable arcing chamber so that when the arcing chamber moves the arc is elongated axially oi it and of the fuse housing.

A further object of the invention is to incorporate in a replaceable unit a moving arcing chamber, a compression spring and a conductor including a rod-like section, a iusible'section and a flexible conducting section.

the line 5-5 of Figure 4;

Other objects'of the invention will, in part,

be obvious and in part appear hereinafter.

The invention, accordingly, is disclosed in the embodiments thereof shown in the accompanying drawings, and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of the invention, reference may "be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figures 1A and 1B constitute a longitudinal sectional view showing one embodiment oi the invention;

Figure 2 is a bottom plan view of the circuit interrupter shown in Figure 1;

Figures 3A and 3B constitute a longitudinal sectional view of another embodiment of the invention in which main andauxlliary bores are provided in solid arc extinguishing material; 2

Figure 4 is a. longitudinal sectional view of still another embodiment of the invention in which the movable arcing terminal restrains the movable arcing ohamber and is directly connected by flexible conductor means to one line terminal;

Figure 5 is a detail sectional view taken along Figure 6 is a longitudinal sectional view of still another embodiment of the invention and showing how it may be arranged for use in an enclosure such as a fuse box or housing;

Figure 7 is a longitudinal sectional view illustrating another embodiment of the invention; and

Figure 8 is a plan view of a detail of construction employed in the construction shown in Figure 7. l

Referring now particularly to Figures 1A and 1B of the drawings, it will be observed that the reference character l0 designates, generally, a

terminals II and I4 canbe so formed as to permit direct connection thereto of line conductors. Suitable gaskets l5 and ii are provided between the ends of the outer glass sleeve l2 and the adjacent surfaces of the line terminals [3 and i4. Snap rings I1 and I8 interflt with suitable registering grooves in the ends of the inner sleeves terminal 23 is deformed onto one end of strain and fusible elements 24 and 25 which may be formed respectively of high strength nickel chromium alloy and silver. The other ends of the strain and fusible elements 24 and 25 have deformed thereon one end of an arcing terminal 26 the other end of which is deformed onto a flexible conductor 21 which is of sufficient length to extend out of the lower end of the tubular insulating housing l0 and for connection to the lower line terminal H by means of a screw 28.

Mounted for longitudinal movement within the tubular insulating housing II is an arcing chamber that is shown generally at 31. The arcing chamber 3! has a longitudinally extending bore 32 within which the rod-like terminal 22 is telescoped, as shown. The bore 32 is formed in a mass 33 of solid arc extinguishing material which is capable of evolving an arc extinguishing medium due to the heat of an arc and it may comprise any suitable material such as magnesium borate, magnesium hydroxide, boric acid,

etc. The mass-33 of solid arc extinguishing material is contained within a sleeve 34 of suitable insulating material such as fiber and it is threaded at its upper end into a ferrule l! of metal. such as brass, which is provided with a centrally located aperture through which the rod-like terminal 22 extends.

The arcing chamber II is biased for movement within the tubular insulating housing II and along the rod-like terminal 22 by a coil compression spring 36. It will be observed that the coil compression spring 36 i interposed between the underside of the cap 2| and the upper side of the ferrule 35.

When an arc is drawn on blowing of the strain and; fusible elements 24 and 25, the intense heat thereof is likely to injure the inner surface of the inner sleeve ll of the tubular insulating housing. With a view to preventing such injury, a tubular arc chute 3! is threaded onto the lower end of the outer sleeve 34 of the tube or arcing chamber II and it extends downwardly and slightly out of the .lower line terminal l4. Preferably the arc chute 38 is formed of metal. It is provided with a shoulder 4| which is arranged to engage a ring 4| that is threaded into the lower end of the lower line terminal l4 for limiting the movement of the arcing chamber ti after it has been released for movement on drawing of the arc resulting from the blowing of the strain and fusible elements 24 and 2|.

The movable arcingchamber 3| is restrained in the positionshown in the drawings against the biasing forceof the coil compression spring 3| by means of a-lever 42 that is pivoted at 43 on the lower line terminal l4 and engages the lower end of the are chute 3!. The lever 42 is provided with a suitably shaped slotted openin 44, Figure 2, with which a conical fitting 4. deformed on the flexible lead 21, interflts.

on flow of fault current the strain and fusible elements 24 and II are blown and an arc is formed between the terminal 13 attached to the lower. end of the rod-like terminal 22 and the arcing terminal 24. This are is transferred from the terminal 28 to the metallic arc chute II as soon as the former moves downwardly sufficiently far because the latter is connected to the lower line terminal i4 through the ring 4!. The are then is confined within the metallic arc chute 3! and does not ordinarily follow the terminal 16 as it is swung outwardly at'the end of the flexible lead 21.

Since the arcing chamber II is no longer restrained it is moved downwardly under the biasing force of the spring 36. At the same time the lever 42 is rotated about its pivot because of the movement of the arc chute ll relative to the lower line terminal l4 and the arcing terminal 24 is withdrawn at a speed which is somewhat greater than the speed at which the arcing chamber 3i moves downwardly. This assists in rapidly elongating the arc and facilitates its extinction.

As is well understood the heat of the are thus formed evolves an arc extinguishing medium from the bore 32 in the solid are extinguishing material 33 which is of such character as to assist in extinguishing the arc. The amount of arc extinguishing medium that is evolved depends upon the magnitude of the arc current and also upon the amount of arc extinguishing material 33 that is exposed to the heat of the are. On flow of relatively heavy fault current through the arc and on the exposure thereto of a relatively large amount of the arc extingulshing material ll relatively great pressures are generated which in some cases result in destruction of the circuit interrupter by it being blown to pieces. Therefore, it is desirable to limit the amount of the arc extinguishing material 33 that is subjected to the heat of the are on flow of relatively high fault current so that these destructive pressures will not be generated. Obviously, it is desirable to have the amount of arc extinguishing material that is subjected to the heat of the are controlled automatically in accordance with the magnitude oi the arc current. It is for this purpose that the lower end of the bore 32 in the solid are extinguishing material 33 is flared outwardly as indicated at 46 and for this same. purpose that the arc chute 39 is provided with a flared out opening as indicated at 41. The flared out portions 4| and 4i provide a reaction area against which the arc extinguishing medium that is evolved by the heater the arc can react in a direction which obviously is opposite to the direction of the force exerted by the coil compression spring 36. Therefore, the movement of the arcing chamber II is controlled conjointly by the biasing force or the spring II acting in one direction and by the reaction force of the arc extinguishing medium on the flared portions and 41 acting in the opposite direction. The latter reaction will vary in accordance with the magnitude of the are which controls the amount of arc extinguishing medium that is evolved. Thus, the amount of arc extinguishing material 88 that is suhiected to the heat of the arc will vary inversely with its mag- Referring now to Figures 3A and 3B of the drawings, it will be observed that-the reference character 50 designates a tubular insulating housing that may be formed of any suitable insulating material, such as glass. Secured by a suitable alloy to the ends of the tubular insulating housing 59 are line terminals 5| and 52. It will be understood that the line terminals 5| and 52 are arranged to be mounted in fuse clips but that they may be arranged to be directly connected to the line conductors.

A rod-like terminal 53 extends through a suitable aperture in the line terminal 5| into the tubular insulating housing 56. A nut 54 is threaded, as shown, on to the upper end of the rod-like terminal 53 for engaging the under surface of the line terminal 5| against which it is held by a nut 55 that is threaded on to' the upper end of the rod-like terminal 53.

ble lead 13 through the lower line terminal 52 and is securely clamped thereto by a suitable With a view to protecting the inner surface of theiglass housing 50 from the heat of the are that is formed on blowing of the fusible and strain elements 61 and 68'an arc chute, shown generally at 15, is provided on the lower end of the movable arcing chamber 56. The are chute An arcing chamber, shown generally at 56, is 1 movably mounted within the tubular insulating housing 59 and it has alongitudinally extending main bore 51 which is telescoped with the rodlike terminal 53. The main bore 51 is formed in a mass 58 of solid arc extinguishing material which is capable of evolving an arc extinguishing medium under the heat of an are. It may comprise any suitable arc extinguishing material as previouslyindicated. The mass 58 of are ex tinguishing material is positioned within a sleeve 59 of suitable insulating material such as a phenolic condensation product to the upper end of which a metallic ferrule 60 is secured by any suitable means such as the pins 6|.

It will be observed that the lower end of the rod-like terminal 53 is tubular in construction and that it has positioned therein a liner 62 which may be formed of any-suitable insulating material, such as fiber, that is capable of evolving an arc extinguishing medium under the heat of ar arc-and which is provided with a longitudinaily extending auxiliary bore 63. It will be understood that the liner 62 is stationarily mounted with respect to the rod-like terminal 53 while the arcing chamber 56 is movable with respect thereto.

Spaced from the lower end of the rod-like terminal 53 is an arcing terminal 66 which is connected to the lower end of the rod-like terminal 53 by a fusible element 61, preferably in the form of a silver wire, and also by a strain element 68 one end of which is looped, as shown, over a pin 69 which extends transversely through the arcing terminal 66. The other end of the strain element 68 is looped over a pin 10 which extends transversely through the rod-like terminal 53 and also through the liner 62. The looped ends of the strain element 68 are so arranged-that a calibrated section 1| is provided between them, the current carrying capacity of which is of course less than at any other portion of the strain element. As a result of this construction the strainelement 68 fuses first at' the section 1| and the arc is formed adjacent the inner end of the auxiliary bore 63.

It will be observed that the pin 10, which ex-.

tends transversely through the rod-like terminal 53, extends into a slot 12 in the ferrule 66, thereby preventing relative rotary movement between the rod-like terminal 53 and the movable arcing chamber 56 as long as the fusible and strain

elements

61 and 68 remain intact.

The arcing terminal 66 is connected by a flexi- 15 comprises preferably an outer sleeve 18 of metal, such as brass, and an inner sleeve or liner 11 of insulating material such as fiber. Pins 18 are provided for securing the arc chute 15 to the outer sleeve 59 of the movable arcing chamber 56. A shoulder 19 is formed by the outer sleeve 16 of the arc chute 15 and it is arranged to engage an inwardly extending flange 86 of a nut 8| that is threaded into the lower endof the lower line terminal 52 for limiting the movement of the movable arcing chamber 56 after the fusible and strain

elements

61 and 68 have blown. O a V a It will be observed that the flexible lead 13 extends through a suitable aperture in a centering element 82, preferably formed of suitablein sulating material such as'a phenolic condensation product, that interfits with the lower end of the arc chute 15. A metallic fitting 83, deformed on to the flexible lead 13 reacts against the underside of the centering element 82 and serves to restrain the movable arcing chamber 56 from movement as long as the fusible and strain

elements

61 and 68 remain intact. When they blow the arcing terminal 66 will be withdrawn from the rod-like terminal 53 substantially axially thereof thereby keeping the are centered with respect to the main and auxiliary bores 51 and 63. After the terminal 66 leaves the arc chute 15, the arc is transferred to the lower end of the outer metallic sleeve 16 and does not spread outwardly as would be the case if it were maintained from the terminal 66 as itswings from the flexible lead 13.

With a view to providing a reaction area on the movable arcing chamber 56 so that the movement thereof may be controlled mostly in accordance with the magnitude of the arc current, the lower end of the main bore 51 is flared outwardly as indicated at 84. This provides an area against which the arc extinguishing medium can react in a direction opposite to the biasing force of the coil compression spring 62.

Referring now particularly to Figure 4 of the drawings, it will be observed that the reference character 81 designates, generally, a tubular in- V sulating housing having an outer sleeve 88 formed preferably of a phenolic condensation product and an inner sleeve 89 formed preferably of fiber. Suitably secured to the ends of the housing 81 are line terminals 90 and 9|.

A nut 92 is threaded into the upper line terminal 96 and it carries a rod-like terminal 93 which, as shown, projects into the tubular insulating housing 81.

Movable mounted within the tubular insulating housing 81 is a movable arcing chamber 94 having a main bore 95 within which the lower end of the rod-like terminal 93 is telescoped and which is formed by a mass 96 of solid are extinguishing material. The mass 96 of solid arc extinguishing material may be formed of any of the materials mentioned hereinbefore. The mass 96 of solid arc extinguishing material is confined within a sleeve 91 that is secured to a metallic ferrule 98 at its upper end by suitable pins 99.

As shown more clearly in Figure 5 of the draw ings the upper portion of the rod-like terminal 93 is hexagonal in section and interfits with a correspondingly shaped aperture in the ferrule 98. This construction prevents relative rotary movement between the movable arcing chamber 94 and the rod-like terminal 93.

A coil compression spring I is interposed between the underside of the nut 92 and the upper side of the ferrule 98 for biasing the movable arcing chamber 94 downwardly.

It will be observed that the lower end of the rod-like terminal 93 is tubular in construction and that it has positioned therein a liner I02 of insulating material, such as fiber, which provides an auxiliary bore I03 from the surface of which an arc extinguishing medium is evolved due to the heat of an arc.

An arcing terminal I04 is spaced from the lower end of the rod-like terminal 93 and it is connected thereto by a fusible element I05, preferably in the form of a silver wire, and a strain element I06 which extends through the auxiliary bore I03. At its lower end the strain element I06 is looped over a pin I01 in the arcing terminal I04 and at its upper 'end it is looped over a pin I08 which extends transversely through the rod like terminal 93 and the fiber liner I02. The construction of the strain element I06 is such that a calibrated portion I09 is provided adjacent the upper end of the auxiliary bore I03, the current carrying capacity of which is less than any other portion. As a result when the strain element I06 blows, an arc will be formed within the auxiliary bore I03 adjacent the upper end.

It will be noted that the arcing terminal I04 has a spider IIO mounted thereon and that its arms are arranged to engage a suitable shoulder III formed in the outer sleeve 91 of the movable arcing chamber 94. As long as the fusible and strain elements I and I06 remain intact, the movable arcing chamber 94 is restrained from movement under the influence of the coil compression spring I00 by this construction.

A flexible lead H2 is connected, as shown, to

the arcing terminal I04 and is of suflicient length to extend out of the lower open end of the tubu lar insulating housing 81 where it is clamped to the lower line terminal 9| by any suitable means such as by a screw I I3. A cylindrical stop member II4, secured to the lower end of the tubular insulating housing 81 by pins II5 serves to limit the downward movement of the arcing chamber 94 after it has been released by blowing of the fusible and strain elements I05 and I06.

With a view to providing a reaction area for the arc extinguishing medium that is evolved on the blowing of the fusible and strain elements I05 and I06, the lower end of the main bore 95 is flared outwardly as indicated at H6. The reaction of the arc extinguishing medium on this area is in opposition to the biasing force of the coil, compression spring I00 and serves to control the movement of the arcing chamber 94 inversely in accordance with the magnitude of the are current.

Referring now particularly to Figure 6 of the drawings, it will be observed that the reference character I20 designates a tubular insulating housing having line terminals I2! and I22 at its ends. The line terminals I2I and I22 are provided, respectively, with contact fingers I23 and I24 which are arranged to engage suitable Stationary line terminals which may be carried on terminal I26 and which may be deformed on to one end of strain and fusible elements I29 and I30. The other ends of the strain and fusible ele ments I20 and I30 have deformed thereon an arcing terminal I3I. A sleeve I32, carried by the terminal I20, extends over the strain and fusible elements I29 and I30 and also telescopes with the arcing terminal I3I. The arcing terminal I3I is deformed on to a flexible conductor I44 which is of sufficient length to extend out of the lower end of the tubular insulating housing I20 and which is clamped to the lower line terminal I22 by any suitable means such as the screw I33.

An arcing chamber I34 is movably mounted within the tubular insulating housing I20 and it telescopes with the rod-like terminal I26. It comprises an outer sleeve I35 of suitable insulating material such as a phenolic condensation product and an inner sleeve I36, preferably formed of flber.

A coil compression spring I31 reacts between the underside of a washer I30 which is threaded into the upper line terminal HI and the upper end of the movable arcing chamber I34 to bias the latter downwardly.

At its lower end the arcing chamber I34 is provided with a metallic sleeve I39 having a shoulder I40 which is arranged to abut a metallic bushing I4I that is secured to the lower end of the tubular insulating housing I20 by any Suitable means such as the pin I42 and the inwardly extending portion I43 of the lower line terminal I22. This construction serves to limit the downward movement of the arcing chamber I34 after the fuse link I21 has blown.

The movable arcing chamber I34 is restrained against the biasing force of the coil compression spring I31 in the position shown in the drawings by the flexible lead I44 which extends over one side of the lower projecting end of the movable arcing chamber I34. When the fuse link I21 blows, the arcing chamber I34 is no longer restrained and it is free to move downwardly under the influence of the coil compression spring I31. It will be understood that, after the arcing terminal It leaves the lower end of the arcing chamber I 34, the arc will be transferred to the metallic sleeve I39 rather than following the terminal I3I.

Referring now to Figure '7 of the drawings, it will be observed that a construction is illustrated which is similar to that shown in Figure 6 and described hereinbefore. The reference character I50 designates a tubular fuse housing that may be formed of any suitable insulating material. such as a phenolic condensation product. Line terminals I5I and I52 are provided at the ends of the housing I50 and they may be provided with contact fingers, such as the flexible contact flngers I53 and I54 for engaging suitable stationary line terminals. It will be noted that the housing I50 and line terminals I5I and I52 are generally of the same construction as shown in Ramsey Patent No. 2,091,452, issued August 31, 1937.

A flanged head I55 is secured by any suitable means, such as by threads as shown, to the upper line terminal I5I and it has depending therefrom a rod-like terminal I55. Telescoped'with I an inner tube or liner Ill of'ilber. The movable arcing chamber I51 is biased downwardly for movement relative to the rod-like terminal II! by means of a coil compression spring I60 that is interposed between the underside of the flanged head I55 and the upper end of the movable arcing chamber I51.

A renewable fuse link, shown generally at I55, is detachably secured to the lower end of the rod-.- like terminal I56. The fuse link I may be of the type shown in Ramsey Patent No. 2,144,707, issued January 24, 1939. It may comprise a relatively intusible terminal I that is provided with an extension !55 which may be threaded or otherwise secured to the lower end of the rodlike terminal I55. The lower end I! of the terminal I is tubular in shape and is deformed onto the upper ends of strain and fusible elements I51 and I 55. The lower ends 'of the strain and fusible elements I51 and I55 are secured by having the tubular upper end portion I" of a movable arcing terminal I15 deformed thereon. The lower end I of the movable arcing terminal I15 is deformed on to a flexible conductor I12 which extends out of the arcing chamber I51 and is of sufflcient length to extend out of the tubular housing III, as shown. A sleeve I13 of insulation, such as fiber, maybe secured to the upper terminal I and extends downwardly over the strain and fusible elements I81 and I and also over the movable arcing terminal I15. Y

With a view to holding the movable arcing I chamber I51 against the biasing force of the compression spring. I", a tubular fitting I14 having a conical lower end portion, as illustrated, is deformed on to the flexible lead I12 below the movable arcing terminal I10. The fitting I14 is arranged to fit into a slot I15 in a centering member I15 which, as shown in Figure 8 of the drawings, comprises a flat washer having a pcripheral recess I11 for interiitting with the lower end of the movable arcing chamber I51.- As long as the strain and fusible elements I61 and I68 remain intact, the movable arcing chamber I51 is restrained from movement downwardly under the influence of the coil compression spring I60. However, as soon as the strain and fusible elements blow on the occurrence of a predetermined overload, this restraining force is no longer present and the arcing chamber I51 moves downwardly carrying with it the movable arcing terminal I and elongating the are formed between it and the infusible terminal I64yat the lower end of the stationary rod-like terminal I56. The are is thus extended axially of the rodlike terminal I56 and of the movable arcing chamber I51 and of the housing I50, since the movable arcing terminal I'M is held substantially centrally of the movable arcing chamber I51. In some instances under extreme short circuit conditions sufficient pressure may be generated on blowing, of the strain and fusible elements I61 and I68 as to expel the arcing terminal I10 out of the housing I50 at a speed I, which is higher than it would otherwise be moved by the arcing chamber I51 under the influence of the coil compression spring I80.

The lower end of the flexible lead I" may be connected by any suitable means to the lower line terminal I52. For example, the clamp screw I threaded in a suitable boss integrally formed with the line terminal I52 may be used as shown.

It'is desirable to prevent the movable arcing chamber I51 from moving out of the housing I55. For this purpose the lower line terminal I52 may be provided with an extension I15 which projects into the bore of the housing I55 and into the path of the movable arcing chamber I51. When the latter engages the stop I15 further outward movement thereof is of course prevented.

It will be observed that the rod-like terminal I56, movable arcingchamber I51, coil compression spring I55 and removable fuse link I63 comprise a unit which is replaceable as such in the housing I 55. It will also be apparent that of this unit itis only necessary to renewthe fuse link I53 after it has blown in order to place it again in operating condition. 3

It will be understood that the heat of the are formed on blowing of the strain and fusible elements I51 and I 68 causes the evolution of an are extinguishing medium from the inner walls of the tube I13 of the fuse link I63 and also from the inner wall of the fiber liner I59. If desired the tube or sleeve I13 on the fuse link I63 may be omitted and reliance placed solely upon the arc extinguishing medium that is evolved from the fiber liner I59.

Since certain further changes may be made in the above constructions and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In a circuit interrupter, in combination, support means, a tubular arcing chamber biased for movement relative to said support means and other end and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, and means for drawing an are within the bore of said chamber adjacent its openend. said chamber being released for movement when the arc is drawn and movement thereof being controlled in accordancewith the resultant effect of two opposing forces, one being the force biasing the arcing chamber and the other being the reaction force of the arc extinguishing medium on the arcing chamber.

2. In a circuit interrupter, in combination, support means, a tubular arcing chamber biased for movement relative to said support means and substantially closed at one end and open at the other end and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, spring means biasing said chamber for said movement, and

means for drawing an arc withinthe bore of formed by material capable of evolving an arc extinguishing medium due to the heat of an arc,

ans biasing said chamber for moveconductor means extending through aid chamber and substantially filling preventing said relative movement torccnnecting said line terminals, said -ns including a rod-like terminal am one line terminal, an infusible iinal connected to the other line terminal, and fusible means interconnecting said rod-like and infusible terminals; said chamber being released for movement on blowing of said fusible means resulting in the formation of an are between said rod-like and arcing terminals and its movement being controlled conjointly by the biasing force of said spring means acting in one direction and the reaction force due to piessure generated by the arc blast acting in th opposite direction.

4. In a circuit interrupter, in combination, support means, a tubular arcing chamber biased for movement relative to said support means and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, a rod-like terminal extending into the bore of said chamber and substantially filling the same, and means for drawing an arc from the end of said rod-like terminal within said bore, said chamber being released for movement when the arc is drawn and the movement thereof being controlled in accordance with the opposing actions of the force biasing it and the reaction force due to the evolution of the are extinguishing medium whereby the quantity of said material subjected to the heat of the arc varies inversely with the magnitude of the arc.

5. In a circuit interrupter, in combination, an axially movable arcing chamber substantially closed at one end and having a relatively large reaction area at the other end, support means for said arcing chamber, means biasing said arcing chamber for movement in the direction in which said reaction area faces, and means whereby an arc is formed adjacent said other end of said arcing chamber and the same is released for movement at a speed which depends upon the force of said biasing means acting in one direction and the pressure due to the arc blast acting on said reaction area in the opposite direction.

6. In a circuit interrupter, in combination, a tubular arcing chamber, means movably mounting said arcing chamber, rod-like terminal means extending into the bore of said chamber from one end, the other end of said chamber being flared outwardly, means biasing said chamber for movement relative to said rod-like terminal means, and means for drawing an arc from said rod-like terminal means adjacent the flared out and of said chamber and for releasing said chamber for movement the speed of which is governed by.

the force of said biasing means acting in one direction and the pressure due to the arc blast acting on the surface of said flared out end of said chamber acting in the opposite direction.

7. In a circuit interrupter, in combination, a

tubular arcing chamber having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of any arc,

means movably mounting said arcing chamber,-

terminal means adjacent the flared out end of said chamber and for releasing said chamber for movement at a speed which is governed by the force of said biasing means acting in one direction and the pressure due to the evolution of arc extinguishing medium acting on the surface of said flared out end of said chamber acting in the opposite direction whereby the quantity of said material subjected to the heat of the arc varies inversely with its magnitude.

8. A replaceable circuit interrupter unit for interconnecting a pair of line terminals comprising, in combination, a rod-like terminal having a flanged head at one end adapted to be clamped to one line terminal, an arcing chamber telescoped with said rod-like terminal, a coil compression spring reacting between said flanged head and one end of said arcing chamber for biasing the latter for movement relative to said rodlike terminal, the other end of said arcing cham-' ber being flared outwardly to provide a reaction area, an arcing terminal spaced from said rodlike terminal and connected thereto by fusible means, means interconnecting said arcing chamber and said fusible means whereby movement of the former is restrained as long as the latter remains intact, and flexible conductor means connected to said arcing terminal and adapted to be connected to the other line terminal of said housing, the pressure generated by the arc blast acting between said flanged head and one end of said arcing chamber for biasing the latter for movement relative to said rod-like terminal, the other end of said arcing chamber being flared outwardly to provide a reaction area, an arcing terminal spaced from said rod-like terminal and connected thereto by fusible means, a. centering member interiltting with said arcing chamber for holding said arcing terminal centrally thereof and restraining said arcing chamber from movement and for causing said'arclngterminal to .be withdrawn substantially axially of said rod-like terminal on blowing of said fusible means, and flexible conductor means connected to said areing terminal and adapted to be connected to the other line terminal of said housing, the pressure generated by the arc blast on blowing of said fusible means acting against said reaction area and opp sing the movement of said arcing chamher by said spring,

10. In a circuit interrupter, in combination, a tubular housing of insulating material having line terminals at its ends, a tubular arcing chamber biased for movement within said housing, means whereby an arc is drawn at one end of said arcing chamber and the same is released for movement, and a shield carried by said arcing chamber at said one end thereof for protecting the inner surface of said housing from the heat of the arc.

11. In a circuit interrupter, in combination, a

tubular housing of insulating material having line terminals at its ends, a tubular arcing chamber biased for movement within said housing, means whereby an arc is drawn at one end of said arcing chamber and the same is released for movement, and a metallic arc chute carried by said arcing chamber at said one end thereof for protecting the inner surface of said housing from the heat of the arc.

12. In a circuit interrupter, in combination, a tubular housing of insulating material having line terminals at its ends. a tubular arcing chamber biased for movement .within said housing; means including a movable arcing terminal,

whereby an arc-is drawn at one end of said arcing chamber and the same is released for movement, and an arc chute including a metallic section electrically connected to one line terminal and carried by said arcing chamber at said one end thereof for protecting the inner surface of said housing from the heat of the arc and to which said arc is transferred when said arcing terminal reaches a predetermined position with respect thereto. a

13. In a circuit interrupter, in combination, a tubular housing of insulating material closed at one end and open at the other andv having line terminals at its ends, a rod-like terminal extending from the line terminal at the closed end of said housing, an arcing chamber telescoped with said rod-like terminal and biased for movement relative thereto in the direction of the open end of said housing, means whereby an arc is drawn from said rod-like terminal at one end of said arcing chamber and the same is released for movement toward the open end of said housing, and an arc chute carried by said arcing chamber at said one end thereof for protecting the inner surface of said housing from the heat of the arc.

14. In a circuit interrupter, in combination, a tubular housing of insulating material closed at one end and open at the other and having line terminals at its ends, a rod-like terminal extending from the line terminal at the closed end of said housing, an arcing chamber telescoped with said rod-like terminal and biased for movement relative thereto'in the direction of the open end of said housing, means whereby an arc is'drawn from said rod-like terminal at one end of said arcing chamber and the same is released for movement toward the open end of said housing, and an arc chute carried by said arcing chamber at said one end thereof and extending to said open end of said housing and movable out of the same for protecting the inner surface of said housing from the heat of the arc.

15, In a circuit interrupter, in combination, a tubular housing of insulating material closed at one end and open at the other and having line terminals at its ends, a rod-like terminal extending from the line terminal at the closed end of said housing, an arcing chamber telescoped with said rod-like terminal and biased for movement relative thereto in the direction of the open end of said housing, an arcing terminal spaced from said rod-like terminal and connected thereto by fusible means, an arc chute carried by said arcing chamber for protecting the inner surface of said housing from the heat of the are formed on blowing of said fusible means, flexible conductor means interconnecting said arcing terminal and the other line terminal, and means cooperating with said are chute for holding said arcing terminal centrally thereof and restraining said arcing chamber from movement and for causing said arcing terminal to be withdrawn substantially axially of said rod-like terminal when said fusible means blows.

16. In a circuit interrupter, in combination, a tubular insulating housing, a tubular arcing chamber within said housing biased for movement relative thereto and substantially closed at one end and open at the other and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, means for drawing an' arc within the bore of said chamber adjacent its open end, said chamber being released for movement when the arc is drawn and movement thereof being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing the arcing chamber and the otherbeing the reaction force of the arc extinguishing medium on the arcing chamber, and a shield carried by said arcing chamber at the end where the arc is drawn for protecting tneirmer surface of said housing from the heat of the arc.

'17. In a circuit interrupter, in combination, a tubular insulating housing, a tubular arcing chamber within said housing biased for movement relative thereto and substantially closed at one end and open at the other and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, spring means biasing said chamber for movement relative to said housing, means for drawing an arc within the bore of said chamber adjacent its open end, said chamber being released for movement when the arc is drawn and said movement being controlled in accordance with the opposing actions'of said spring means and of the arc blast, and a metallic arc chute carried by said arcing chamber at the end where the arc is drawn for protecting the inner surface of said housing from the heat of the arc.

, 18. In a circuit interrupter, in combination, a

tubular insulating housing, a pair of line terminals for said housing, a tubular arcing chamber within said housing having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, spring means biasing said chamber for movement relative to said housing; conductor means extending through the bore of said chamber and substantially filling the same for preventing said relative movement and for interconnecting said line terminals, said conductor means including a rod-like terminal extending from one line terminal, an arcing terminal connected to the other line terminal, and fusible means interconnecting said rod-like and infusible terminals; said chamber being released for movement on blowing of said fusible means resulting in the formation of an are between said rod-like'and arcing terminals and its movement being controlled conjointly by the biasing force ofsaid spring means actingin one direction and the reaction force due to pressure generated by the are blast acting in the opposite direction; and an arc chute carried by said arcing chamber at the end where the arc is formed between said rod-like and arcing terminals for protecting the inner surface of said housing from the heat of the arc.

19. In a circuit interrupter, in combination, a tubular insulating housing, a pair of line terminals for said housing, a tubular arcing chamber within said housing having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, spring means biasing said chamber for movement relativeito said housing; conductor means extending through the bore of said chamber and substantially filling the same for interconnecting said line terminals, said conductor means including a rod-lilac terminal extending from one line terminal, arcing terminal connected to the other line terminal, and fusible means interconnecting said rod=lilze and infusible terminals; and a lever pivoted on said housing and operatively connected to said arcing terminal and cooperating with said arcing chamber for holding the same in place as long as said fusible means remains intact, said chamber being released by said lever for movement on blowing of said fusible means resulting in the formation of an are between said rod-like and arcing terminals and its movement being controlled coniointly by the biasing force of said spring means acting in one direction and the reaction force due to pressure generated by the arc blast acting in the opposite direction.

20. In a circuit interrupter, in combination, a tubular insulating housing, a tubular arcing chamber within said housing biased for movement relative thereto and substantially closed at one end and open at the other and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, means for drawing an are within the bore of said chamber adjacent its open end, said chamber being released for movement when the arc is drawn and movement thereof being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing the arcing chamber and the other being the reaction force of the arc extinguishing medium on the arcing chamber, and a shield carried by said arcing chamber atthe end where the arc is drawn for protecting the inner surface of said housing from the heat of the are, said shield comprising an outer tube of metal having a liner of insulating material.

21. In a circuit interrupter, in combination, a tubular insulating housing, a. tubular arcing chamber within said housing biased for movement relative thereto and substantially closed at one end and open at the other and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc, means for drawing an arc within the bore of said chamber adjacent its open end, said chamber being released for movement when the arc is drawn and movement thereof being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing the arcing chamber and the other being the reaction force of the arc extinguishing medium on the arcing chamber, and a shield carried by said arcing chamber at the end where the arc is drawn for protecting the inner surface of said housing from the heat of the are, said shield comprising an outer tube of metal having a liner of material capable of evolving an arc extinguishing medium due to the heat of the arc and providing a bore from which the medium is evolved.

22. In a. circuit interrupter, in combination,

in the auxiliary bore is not extinguished, the

portion of said arc extinguishing material providing said main bore being biased for movement with respect to said support means and released for such movement when the arc is drawn in said auxiliary bore.

23. In a circuit interrupter, in combination, support means, solid arc extinguishing material providing main and auxiliary bores from the surfaces of which an arc extinguishing medium is evolved due to the heat of an arc, and means for drawing an arc first in said auxiliary bore and subsequently in said main bore if the arc in the auxiliary bore is not extinguished, the portion of said are extinguishing material providing said main bore being biased for movement with respect to said support means and released for such movement when the arc is drawn in said auxiliary bore, said movement being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing said portion of the arc extinguishing material providing said main bore and the other being the reaction force thereon of the arc extinguishing medium.

24. In a circuit interrupter, in combination, support means, solid arc extinguishing material providing main and auxiliary bores from the surfaces of which an arc extinguishing medium is evolved due to the heat of an arc,'one end of said main bore being iiared outwardly thereby providing a reaction area, means for drawing an are first in said auxiliary bore and subsequently in said main bore if the arc in the auxiliary bore is not extinguished, and means biasing the portion of said are extinguishing material providing said main bore for movement with respect to said support means in the direction faced by said reaction area and the same being released for such movement when the arc is drawn in said auxiliary bore, said movement being controlled in accordance with the resultant effect of two opposing forces, one being the iorce biasing said portion of the arc extinguishing material providing said main bore and the other being the force exerted on said reactionarea by the arc extinguishing medium.

25. In a circuit interrupter, in combination, a

tubular insulating housing, solid arc extinguishing material within said housing providing main and auxiliary bores from the surfaces of which an arc extinguishing medium is evolved due to the heat of an arc, one end of said main bore being flared outwardly thereby providing a reaction area, means for drawing an are first in said auxiliary bore and subsequently in said main bore if the arc in the auxiliary bore is not extinguished, means biasing the portion of arc extinguishing material providing said main bore for movement with respect to said housing in the direction faced by said reaction area and the same being released for such movement when the arc is drawn in said auxiliary bore, said movement being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing said portion of the arc extinguishing material providing said main bore and the other being the force exerted on said reaction area by the arc extinguishing medium, and a shield movable with said main bore for protecting the inner surface of said housing from the heat of the arc.

28. In a circuit interrupter, in combination, line terminals in insulated spaced relation, solid arc extinguishing material providing main and auxiliary bores from the surfaces of which an arc extinguishing medium is evolved due to the heat of an arc, a rod-like terminal extending from one line terminal into said main bore, and an arcing terminal connected to the other line terminal and spaced from said rod-like terminal and connected thereto by fusible means arranged on blowing to draw an arc first in said auxiliary bore and subsequently in said main bore if the arc in the auxiliary boreis not extinguished, the portion of said are extinguishing materialproviding said main bore being biased for movement along said rod-like terminal toward said other line terminal and released for such movement when the arc is drawn in said auxiliary bore.

27. In a circuit interrupter, in combination, line terminals in insulated spaced relation, solid arc extinguishing'material providing main and auxiliary bores from the surfaces of which an arc extinguishing medium is evolved due to the heat of an are, a rod-like terminal extending from one lineterminal into said main bore, and an arcing terminal. connected to the other line terminal and spaced from said rod-like terminal and connected thereto'by fusible means arranged .on

blowing to draw an arc first in said auxiliary bore and subsequently in said main bore if the arc in the auxiliary bore is not extinguished, the portion of said are extinguishing material providing said main bore being biased for movement along said rod-like terminal toward said other line terminal and released for such movement when the arc is drawn in said auxiliary bore, said movement being controlled in accordance with the resultant effect of two opposing forces, one being the force biasing saidpor'tion of the arc extinguishing material providing said main bore and the other being the reaction force there on of the arc extinguishing medium.

28. In a circuit interrupter, in combination, a pair of line terminals in insulated spaced relation, a rod-like terminal extending from one line terminal, a tubular arcing chamber movably mounted on said rodlike terminal, spring means biasing said arcing chamber to effect movement ihereof, arcing terminal means spaced from said rod-like terminal and connected thereto by fusible means and reacting against said arcing chamber to hold the same against the biasing force of said spring means, and flexible conductor means interconnecting said arcing terminal and the other line terminal.

29. In a circuit interrupter, in combination, a pair of line terminals in insulated spaced rela; iion, a rod-like terminal extending from one line terminal, a tubular arcing chamber movably mounted on said rod-like terminal and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of an arc and a reaction area against which the arc extinguishing medium can react, spring means biasing said arcing chamber to efiect movement thereof, arcing terminal means spaced from said rod-like terminal and connected thereto by fusible means and reacting against said arcing chamber to hold the same against the biasing force of said spring means, and flexible conductor means interconnecting said arcing terminal and the other line terminal, said arcing chamber being released for movement on blowing of said fusible means and said movement being controlled in accordance with the resultant effect of two opposing forces, one being the force of said spring means biasing said arcing chamber in one direction and the other being the reaction force of said are extinguishing medium on said reaction area acting in the opposite direction whereby the amount of said material exposed to the heat of the arc varies inversely with the magnitude of the arc.

30. A circuit interrupter comprising, in combination, a tubular insulating housing, an arcing chamber wholly within said housing and biased for movement relative thereto, means for drawing an are within said chamber adjacent its open end, said chamber being released for movement when the arc is drawn, and means for limiting the movement of said chamber after the arc is drawn to prevent it from moving substantially out of said housing;

31, -A circuit interrupter comprising, in combination, a tubular insulating housing, an arcing chamber having its inner surface formed by material capable of evolving an arc extinguishing medium due to the heat of an are wholly within said, housing and biased for movement relative thereto, means for drawing an are within said chamber adjacent its open end, said chamber being released for movement when the arc is drawn, and means for limiting the movement of said chamber after the arc is drawn to prevent it from moving substantially out of said housing.

32. A circuit interrupter comprising, in com bination, a tubular insulating housing, a rod-like terminal extending inwardly from one end of said housing, a tubular arcing chamber wholly within said housing and telescoped with said rod-like terminal and biased for movement relative thereto, means cooperating with said rod-like terminal for restraining said movement of said arcing chamber, the restraint being terminated on the drawing of an are between said rod iike terminal and said means, and means for limiting the movement of said chamber after the are is drawn to prevent it from moving substantially out of said housing.

33, A circuit interrupter comprising, in combination, a tubular insulating housing, a rod-like terminal extending inwardly from one end of said housing, a tubular arcing chamber wholly within said housing and telescoped with said rod-like terminal, a compression spring surrounding said rod-like terminal and biasing said tubular arcing chamber for movement relative thereto, means cooperating with said rod-like terminal for restraining said movement of said arcing chamber, the restraint being terminated on the drawing of an are between said rod-like terminal and said means, and means for limiting the movement of said chamber after the arc is drawn to prevent it from moving substantially out of said housing.

34. A circuit interrupter comprising, in combination, a, tubular insulating housing, a rod-like terminal extending inwardly from one end of said housing, a tubular arcing chamber wholly within said housing and telescoped with said rodlike terminal and biased for movement relative thereto toward the other end of said housing, means cooperating with said rod-like terminal for restrainingsaid movement of said arcing chamber, the restraint being terminated on the drawing of an are between said rod-like terminal and said means, and means at said other end of said housing disposed to cooperate with the end of said arcing chamber adjacent thereto for limiting the movement of said arcing chamber after the arc is drawn.

35. A circuit interrupter comprising, in combination, a tubular insulating housing having line terminals at its ends; conducting means within said housing interconnecting said line terminals and including a rod-like section connected to one line terminal, a flexible conducting section connected to the other line terminal, and a fusible section interconnecting said sections; a tubular arcing chamber telescoped with said rod-like section for movement relative thereto toward said other line terminal, and means interconnecting inwardly of said housing from one of said ing said conducting means and said arcing chamline terminals, a tubular arcing chamber teleber for restraining the latter from movement as scoped with said rod-like terminal, compression long as said fusible section remains intact. spring means biasing said arcing chamber away 36. A circuit interrupter comprising, in comfrom said one line terminal toward the other line bination, a tubular insulating housing having line terminal, an arcing terminal spaced from said terminals at its ends; conducting means within rod-like terminal and connected thereto by fusisaid housing interconnecting said line terminals ble means, flexible conductor means interconand including a rod-like section connected to necting said arcing terminal and said other line one line terminal, a flexible conducting section terminal, and means centering said arcing terconnected to the other line terminal,- and a fusible minal with respect to said arcing chamber and section interconnecting said sections; a tubular interconnecting them whereby movement of id arcing chamber telescoped with said rod-like arcing chamber is restrained as long as said fusisection for movement relative thereto toward said ble means remains intact and on blowing thereof other line terminal, and means interconnecting said arcing terminal is. moved axially outwardly said conducting means and said arcing chamber of said housing.

for restraining the latter from movement as long 41. A replaceable circuit interrupter unit for as i iol section remains intact, said intermounting in. a tubular housing having a lin terccnnecting means also serv ng to move said flexminal at each end comprising, in combination, ible conduc g section re e to said insulating a rod-like terminal having a flanged head at one housing c: movement of said 1- J g chamber. end adapted to be clamped to one line terminal,

interrupter comprising, in coman'arcing chamber telescoped with said rod-like insulating ho ing having terminal, a coil compression spring reacting bes conducting tween said flanged head and said arcing chamber *'"*-terccnnectmg d line to lasing the later for movement relative to c section consaid rod-like terminal, an arcing terminal spaced "e coneuctfrom said rod-like terminal and connected thereby fusible means interconnecting said arcing chamber and said fusible means whereby movement of the former res ained as long as atter remains intact, and EXlble conductor ted to arcir terminal and connected the other line tert hulahou end ccmpri in combination. head at one :1 one line terminal, with said rcdsion spring reacting en said flange head and said arcing charmthe latter for movement relative to said rod-ilk terminal, an arcing terminal ,15 3; ha b r 3x73 spaced from said rod-like terminal and connected g -5e inward t her thereto by fusible means, a centering member terminal spaced 5 interiitting with said arcing chamber for hold 21 connected the g by itsing said arcing terminal centrally thereof and ibie means, fie. ale con uctor means intercon- TBS-training Said arcing Chamber fro movement necting said arcing terminal and said other line so and Causing Said arcing al to be Withterminal, and means interconnecting said arcing drawn substantially a l y of said rod-like terchamber and said fusible means whereby move- IIliml-l bIQWiIlg Of Said fusible ans, nd fieX- merit of the former is restrained as long as the ible conductor means connected to said arcing latter remains intact. terminal and adapted to be connected to the 39. A circuit interrupter comprising, in comother line terminal of said housing.

hination, a tubular insulating housing having line 43. A replaceable circuit interrupter unit for terminals at ends; conduc n 11192115 W thin mounting in a tubular housing having a line tersaid housing interconnecting said line terminals minal t each end comprising, in combination, and including a rod-like section connected to one a md 1ike terminal having a flanged head at one line terminal, a flexible conducting section con- 50 end adapted to be clamped to one line terminal nected to the other line terminal, and a fusible an arcing chamber telescoped with Said rodmke' aggression? tt iiiffgthi ermine a we section for movement relative thereto toward said Ey ai ig gfig g figggi f fgix g other line terminal, and a centering member in- 0' tcrfitting with the end of said arcing chamber J said md'nke terminal; a renewable fuse link adjacent said other line terminal and cooperat- Guiding coupling member e vably coupled ing with said conducting means for restraining to the other end of Said Tod-like terminal, said arcing chamber as long as said fusible sec- P terminal: fusible means inter 00111190151118 tion remains intact and for'lengthening the are said coupling member and Said arcing tenninal. formed on blowing of said fusible section substanand flexible conductor mwns extending ro said tially axially of said arcing chamber arcing terminal for connection to the other line 40. A circuit interrupter comprising, in comal of aid housing; and means interconbination, a tubular insulating housing having line necting said arcing chamber and said flexible conterminals at its ends, a rod-like terminal extend- 7 duct-or means whereby movementof the former is restrained as long as said fusible means remains intact.

44. In a circuit interrupter, in combination, support means, a tubular arcing chamber biased for movement relative to said support means and releasably held in place, said chamber being substantially closed at one end and open at the other end and having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of the arc, and mean for drawing'an are within the bore of said 0 amber adjacent its open end, the movement of said chamber after its release being controlled in accordance with the resultant of two opposing forces, one being the force biasing. the arcing chamber and the other being the reaction force of the arc extinguishing medium on the arcing chamber.

45. In a circuit interrupter, in combination, support means, a tubular arcing chamber biased for movement relative to said support means and releasably held in place, said chamber being substantially closed at one end and open at the other end having its bore formed by material capable of evolving an arc extinguishing medium due to the heat of the arc, spring means biasing said chamber for said movement, and means for drawing an are within the bore of said chamber adjacent its open end. the movement of said chamber after its release being controlled in accordance with the opposing actions of said spring means and 01' the arc blast.

.46. In a circuit interrupter, in combination, support means, a tubular arcing chamberbiased for movement relative to said support means and releasably held in place, the bore oi said chamber being formed by material capable of evolving an arc extinguishing medium due to the heat oi an are, a rod-like terminal extending into the bore of said chamber and substantially filling the same, and means for drawing an'arc from the end oi said rod-like terminal within said bore. the movement of said chamber after its release being controlled in accordance with the opposing actions or the force biasing it and the reaction ALLAN RAMSEY.