US2183729A

US2183729A - Fuse construction

Info

Publication number: US2183729A
Authority: US
Publication date: 1939-12-19
Anticipated expiration: 1956-12-19

Description

Dec. 19, 1939. H. A.'TR1P| ETT FUSE CONSTRUCTION Original Filed Aug. 13, 1938 3 Sheets-Sheet 1 ,fw ff,

m2 i M f w w 3 Sheets-Sheet 2 H. A. TRIPLETT FUSE CONSTRUCTION Original Filed Aug. 13,V 1938 Dec. 19, 1939.

Dec. 19, 1939. H. A.TR1P1 ETT FUSE CONSTRUCTION Original Filed Aug. 13, 1938 3 Sheets-Sheet 3 WMM Patented Dec. 19, 1939 UNITED STATES PATENT OFFICE FUSE CONSTRUCTION Original application August 13, 1938, Serial No. 224,696. Divided and this application May 8,

1939, Serial No. 272,341

(Cl. ZOO- 120) 28 Claims.

My invention relates, generally, to circuit interrupters. This application is a divisional application of my copending application Serial No. 224,696, led August 13, 19.38. It has particular relation to the renewable cartridge disclosed in said application, which is intended for use in a circuit interrupter having normal rated current carrying capacities of 400 to 1000 amperes at 7500 volts, and which are capable of interrupting l0 fault currents of 300 to 75000 amperes at this voltage.

The object of my invention, generally stated, is vto provide an improved form of cartridge for a heavy duty circuit interrupter that shall be simple and eilicient in operation and 'which may be readily andv economically manufactured and installed.

An object of my invention is to provide for opening a circuit operating at a relatively high voltage in which a relatively large current flows and at the same time employing the same apparatus for interrupting relatively small currents in the circuit.

A further object of my invention is to provide,

in a renewable fuse cartridge, for aligning it in proper relation to itsoperating mechanism.

Still another object of my invention is to provide for withstanding comparatively high operating stresses that are imposed on the movable terminal of a high ampere capacity circuit interrupter of the solid material type.

A still further object of my invention is to minimize the flow of the products of the arc, formed on blowing of a circuit interrupter of the solid arc extinguishing material type, back past its main terminal.

A further object of my invention is to minimize the ow of the products of the arcs, formed on blowing of a circuit interrupter of the solid extinguishing material type, back past its main and auxiliary rod-like terminals.

Another object of my invention is to substantially uniformly distribute tension stress among the auxiliary terminals of a circuit interrupter .13, of the solid arc extinguishing material type em- 'ploying av relatively large main rod-like terminal land a plurality of auxiliary rod-like terminals.

Other objects of my invention will, in part, be obvious and in part appear hereinafter.

:.0 My invention, accordingly, is disclosed in 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 :lo 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 my invention, reference may be had to the following detailed description, taken 5 in connection with the accompanying drawings, in which:

Figure l is a longitudinal sectional View of one embodiment of a replaceable fuse cartridge constructed in accordance with this invention; 10

Figure 2 is a detail sectional view taken along the line 2 2 of Figure 1;

Figure 3 is a bottom plan view of the fuse cartridge shown in Figure 1;

' Figure 4 is a longitudinal. sectional View of 15 another embodiment of the replaceable fuse cartridge;

Figure 5 is a top plan view of the fuse cartridge shown in Figure 4;

Figure 6 is a detail sectional view taken along 20 the line 6-6 of Fig. 4;

Figure '7 is a View, in side elevation, of one of the auxiliary terminals employed -in the fuse cartridge shown in Figure 4;

Figure 8 is a View, in front elevation, of the 25 auxiliary terminal shown in Figure 7 and Figure 9 is a detail sectional view taken along the line 9 9 of Figure 8.

In my copending application, referred to hereinbefore, I have disclosed how a replaceable fuse 30 cartridge per se can be mounted on one insulator and connected to one line terminal thereat. The other line terminal is mounted on another insulator spaced from the one insulator and this insulator carries an operating mechanism which 35 may be spring actuated and which is arranged to be mechanically connected to the movable terminal assembly of the fuse cartridge. An electrical connection is also provided between the movable terminal assembly and the other line 40 termina-l. The present invention is particularly directed to the features of construction of the various embodiments of the replaceable fuse cartridge shown and described in the application of which this application is a division.

Referring now particularly to Figures l, 2 and 3 of the drawings, it will be observed that the reference character El designates, generally, a replaceable fuse cartridge or circuit interrupter that is arranged to be mounted on suitable support means and to be connected to an operating mechanism. The circuit interrupter or replaceable fuse cartridge Sl is somewhat similar in construction to that shown in my copending application, Serial No. 85,700, led June 17, 1936,

and assigned to the assignee of this application.

The circuit interrupter 61 is provided with a tubular housing or fuse tube 1|, having a ferrule or terminal 12 at its lower end. Since it is desirable to permit considerable latitude in positioning of the circuit interrupter 61 relative to the operating mechanism which is provided for opening the circuit, in order to avoid the requirement of accurate alignment therebetween insofar as the supports therefor are concerned, a ball and socket joint is provided for mounting the circuit interrupter 61 on its support member. The ball and socket joint is provided in part by an extension 13 depending from the ferrule or terminal 12, which constitutes the ball member and has a convex spherical surface 14 for engaging a correspondingly shaped surface on the support member (not shown). Suitable clamp means are provided for securing the extension 13 in place on the support means, as will be readily understood.

The circuit interrupter 61is provided with a movable terminal assembly, shown generally at 80. It comprises a main terminal 8|, the upper end of which is threaded as indicated at 82 to permit coupling to the operating mechanism (not shown), together with auxiliary terminals 83. 'I'he terminals 8| and 83 are rod-like in character. The auxiliary terminals 83 extend through a cross-member 84 that extends transversely through the main terminal 8| and they are adjustably secured by suitable nuts 85.

As previously indicated, the circuit interrupter G1 is provided with a tubular housing or fuse tube 1|. The fuse tube 1| is preferably formed of relatively rigid and strong insulating material such as a phenolic condensation product which is provided with a filling of solid arc extinguishing material, such as boric acid, which may be inserted as a single body or in several sections |06, as shown. At its upper end the fuse tube 1| is provided with a plug |01 of fiber o r the like that is held in position by suitable dowel pins |08 (Figure 2). At its llower end thev fuse tube 1I is provided with a retaining 'washer |09 and a sleeve ||0, both preferably formed of fiber, with the sleeve ||0 forming an arcing chamber with the lower end flared outwardly as indicated at |II. The lower end of the sleeve ||0 abuts a shoulder ||2 of the ferrule or terminal 12.

The solid arc extinguishing vmaterial |05, the plug |01, and the retaining washer |09 are provided with a centrally located main bore I3 and a pair of symmetrically disposed auxiliary bores I I4. The auxiliary bores I |4 are circular in crosssection, as shown in Figure 2, and are positioned on opposite sides of the main bore I I3. By providing two auxiliary bores ||4 and two auxiliary rod-like terminals 83, it is possible to provide a balanced construction in which the extremely high stresses imposed by a suitable retracting spring (not shown) may be resisted without permitting any binding action to take place while the terminal assembly is being withdrawn from the fuse tube 1 I. As shown in Figure 2, the main bore ||3 is generally oblong in shape for receiving a correspondingly shaped arcing terminal I5 which constitutes an extension of the main terminal 80.

In order to facilitate gripping the main terminal 80 and threading it into a retracting member (not shown), its opposite sides I I6 are slabbed off to receive the jaws of a wrench.

At its lower end the main arcing terminal IIS is provided with a plurality of fusible elements |20. The fusible elements |20 are preferably formed of silver wire and their size and number depends upon the rating of the circuit interrupter 61. For purposes of illustration I have shown four fusible elements |20. The lower end of the main arcing terminal ||5 is longitudinally drilled in order to receive one end of each of the fusible elements |20. The opposite sides of the lower end of the main arcing terminal ||5 are then forced inwardly, as at |2I, by a suitable tool, such as a punch, in order to hold the fusible elements |20 firmly in place in good electrical contact with the main arcing terminal ||5. The lower ends of each pair of fusible elements |20 are secured in terminal sleeves |23 which are deformed thereon to provide proper electrical and mechanical connection. The terminal sleeves |23 are provided with centrally located apertures through which screws |24 may be inserted for clamping them in position on the inner surface of the ferrule or terminal 12.

It is desirable that no tension stress be applied to the fusible elements |20 in order that their time-current characteristics will be unaffected. 'Ihe stress that would otherwise be applied thereto in opposing the biasing action of a spring, not shown,` is transmitted through the auxiliary arcing terminals 83. At their lower ends, as indicated at |25, these auxiliary arcing terminals 83 are flattened onto strain elements |26 that may be formed of high strength wire such as nickel-chromium wire. The lower ends of the strain elements |26 are secured in the upper ends |21 of tubular terminals |28 that are flattened thereon. The lower ends |29 of the tubular terminals |28 are flattened at right angles to the upper portions |21 to provide for holding them in slotted openings |30 in inwardly extending pins |3 I. Flexible leads |32, formed preferably of insulated magnet wire, are secured in the deformed lower end portions |29 of the tubular terminals |28 and they extend considerable distances inside of the auxiliary bores II4. A disc |33, preferably formed of a suitable transparent material such as mica, serves to close th lower end of the ferrule or terminal 12.

On operation of the circuit interrupter 61, it will be understood that the fusible elements |20 are rst melted, since they carry the major portion of the current. The entire flow of current is then transferred to the strain elements |26, which immediately melt. Since the iiexible leads |32 extend into the auxiliary bores ||l| a considerable distance, and further, since they are provided with a slight insulating coating such as an enamel coating, an arc or arcs are first formed within the auxiliary bores ||4 and at some distance from their lower ends. In the event that the fault current is of comparatively low value, the arc or arcs may be extinguished within the auxiliary bores |I4. It will be understood that, as soon as the strain elements |26 are released, the terminal assembly 80 is no longer restrained and begins to move upwardly, thereby withdrawing the main arcing terminal ||5 and the auxiliary terminals 83 through their respective bores IIS and II4.

However, if the fault current is of such a value that it cannot be interrupted in the auxiliary bores I I4, then an arc is formed in the main bore H3 between the main arcing terminal ||5 and the ferrule or sleeve 12 or metal parts connected thereto. The large current arcs will then be extinguished in the main bore ||3 by the evolution of water vapor in the now well-known` manner.

The main bore I|3 is generally oblong or rectangular in cross-section in order to provide additional space for the auxiliary bores ||4 while still maintaining a suiiicient body of the solid arc extinguishing material |06. The cross-sectional area of the auxiliary bores can then be increased to increase the range of interrupting capacity thereof.

Another-embodiment of my invention is illustrated in Figures 4 through 9, to which reference will now be had.

It will be observed that the reference character |64 designates, generally, a replaceable fuse cartridge or circuit interrupter that contains certain features of construction not found in the circuit interrupter 61 shown in Figures 1, 2 and 3 and previously described. 'I'he circuit interrupter |64 is provided with a tubular housing or fuse tube |65 having at its lower end a ferrule or terminal |66. For the reasons set forth, it is desirable to mount the circuit interrupter |64 so that it will have some latitude of movement relative to its operating mechanism (not shown). For this purpose a ball and socket/supporting structure is provided which is similar to that illustrated, in part, in Figure 1 of the drawings and described hereinbeiore.

As shown, the ferrule or terminal |66 is provided with a ball member |61 the outer surface |68 of which is convex and spherical for engaging a correspondingly shaped surface on its support structure. Suitable clamp means are provided for securing the ball member |61 in place.

It will be observed that the tubular housing or fuse tube |65 constitutes a relatively thin shell. t is preferably formed of a phenolic condensation product and is provided with a liner 204 that may be formed of fiber.` Inside theliner 204 a lling of a solid arc extinguishing material, such as boric acid, is provided in a plurality of sections 205. A plug 206, preferably formed of ber, is threaded into the ber liner 204, as shown, at the upper end of the housing. A retaining ring 201. also preferably formed of fiber, is provided below the lower section 205 of the solid arc extinguishing material for holding it in place. The sections of solid arc extinguishing material 205, the plug 20G, and the retaining ring 201 are provided with a centrally located main bore 208 and a pair of auxiliary bores 209 for receiving the main and auxiliary terminals |16 and |11, respectively. The main and auxiliary terminals |16 and |11 are rod-like in character and circular in cross-section. The diameters of their

respective bores

208 and 209 are such that only sufficient clearance is provided to permit the terminals to be freely withdrawn therethrough. In other words, the main and auxiliary terminals |16 and |11 substantially fill their respective bores 208 and 200 so that relatively little, ii any, of the products of the arc or arcs formed on operation of the circuit interrupter |64 are permitted to flow back therethrough past the terminals 416 and |11.

With a view to further preventing the backward flow of the products of the arcs past the` main terminal |16, a packing is provided at the upper end of the bore 208. As illustrated, the bore 208 is enlarged as indicated at 2|0 for receiving several layers of chevron packing 2|| which may be positioned on top of a spreader ring 2|2. A compression ring 2|3 is positioned on top of the upper layer of packing 2|| and a gland 2|4, preferably formed of a phenolic condensation product, is threaded into the threaded upper end of the enlarged recess 2|0 in the ber plug 206. The gland 2|4 is screwed downwardly suiciently far to compress the layers of packing 2|| and to move them into pressure-tight engagement with the cylindrical main terminal |16. However, it is only tightened sufficiently far to provide this pressure-tight relation without substantially preventing the main terminal |16 from being freely withdrawn through the main bore 208.

It will be observed that the layers of chevron packing 2|| are so disposed that opposition to the flow of gas in the directionof movement of the terminal |16 increases as the gas pressure in the main bore 208 increases. While this tends to retard the movement of the terminal |15 somewhat, it will be understood that it is permissible since, under such conditions, a relatively great pressure is exerted on the lower end of the terminal |16 by the gases evolved under heavy overload conditions. If desired, the auxiliary terminals 11 may be provided with chevron packing as is the main terminal |16, for the same purpose. -oweveig it will not ordinarily be necesfary to provide this additional packing.

With a View to facilitating the outward flow of the products of the arc or arcs, the lower ends of the main and auxiliary bores 208 and 269 are flared outwardly as shown at 2|8 and 2|9, respectively.

The main terminal |16 is provided at its lower end with a plurality of fusible elements 220. Preferably, the fusible elements 220 are formed of a silver wire and, as previously indicated, their number and size will depend upon the rating of the circuit interrupter |64. For illustrative purposes, four fusible elements 220 have been shown. The lower ends of the fusible elements 220 are secured in a terminal sleeve 223 that is deformed thereon. The terminal sleeve 223 is provided with a suitable aperture through which a screw 224 may be placed for securing it in good contact engagement with the inner surface of the ferrule or terminal |66.

Strain elements 225, preferably formed of nickel-chromium alloy, are provided fo. restraining the auxiliary terminals |11 and for relieving the fusible element 220 of stress that would otherwise be imposed thereon. As shown more clearly in Figures 7, 8 and 9 of the drawings, the ends 226 of the strain element 225 are corrugated to facilitate holding of the same. The lower end of the auxiliary terminal |11 is provided with a suitable longitudinally extending aperture into which the upper end 226 of the strain element 225 may be inserted. As indicated at 221, the lower end of the auxiliary terminal i 11 is deformed onto the upper end 226 of the strain elen ment 225 so that it is mechanically held in place and, at the same time, good electrical contact is provided Itherewith. The upper end of the auxiliary terminal |11 is attened as indicated at 228 andhif provided with an aperture 229 through which the screw |80 may be placed. The lower end of the strain element 225 is positioned in the upper end 230 of a sleeve 23|. The

All

end 230 is then deformed onto the corrugated lower end 226 for providing mechanical and electrical connection thereto. The lower end 232 of the sleeve 23l is deformed at right angles to the other end 239 for positioning across a slotted opening 233 in a pin 234, Figure 4, which extends inwardly from 'the ferrule or terminal |66. It will be noted that two pins 234 are provided, one for each of the auxiliary terminals l'l'l. After the upper end portions 230 of the sleeves 23! have been positioned in the slots 233 in the pins 234, the ends thereof are closed to prevent disengagement thereof.

The lower end of the ferrule or terminal 5S is closed by a disc 235 that is preferably formed of transparent material such as mica.

It will be noted that the upper end of the main terminal |16 is threaded at 238 for insertion in a Suitable threaded boss of the operating means (not shown). A lock nut 239 is provided for holding the main terminal H6 in position once it has been set in place. The opposite sides of the main terminal ITB are slabbed oi, as indicated at 240, to facilitate the engagement of the jaws of a wrench for turning it into place.

On operation of the circuit interrupter l64, the fusible elements 220 (Figure 4) are rst melted, whereupon the entire flow of current is tran:- ferred to the strain elements 225, which melt and form an arc or arcs between the auxiliary terminals |11 and the corresponding portions 23?) of the sleeves 23|. If the fault current is comparatively slight, the arc or arcs formed will be drawn and entirely extinguished in one or both of the auxiliary bores 209. However, if the fault current to be interrupted is outside of the range of the auxiliary bores 209, then an varc will strike between the main terminal |16 and the terminal or ferrule |66, or some of its inwardly projecting parts, and will be drawn into the main bore 20d on continued movement of the main terminal |16 therethrough, where it will be extinguished due to the evolution of water vapor from the walls thereof.

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

I claim as my invention:

1. In a circuit interrupter, in combination, arc extinguishing material providing a main bore and a plurality of auxiliary bores, the cross sectional area of said main bore being relatively large and the cross sectional area of each auxiliary bore being relatively small, a stationary terminal at one end of said bores, and main and auxiliary relatively infusible terminals in said main and auxiliary bores, respectively, substantially lling the same and adapted on being moved away from said stationary terminal to draw an arc first in one or more of the auxiliary bores and subsequently in thev main bore if the arc in the auxiliary bore or bores is not extinguished.

2. In a circuit interrupter, in combination, arc extinguishing material providing a main bore and a plurality of auxiliary bores, said bores being parallel to each other and the cross-sectional area of said main bore being relatively large and the cross sectional area of each auxiliary bore being relatively small, a stationary terminal at one end of said bores, and main and auxiliary relatively infusible terminals in said main and auxiliary bores, respectively, substantially filling the same and adapted to be simultaneously moved away from said stationary terminal to draw an arc rst in one or more of the auxiliary bores and subsequently in the main bore if the are in the auxiliary bore or bores is not extinguished.

3. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores respectively, and fusible means interconnecting said main and auxiliary arcing terminals and said arcing terminal carried by said housing.

4. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and a. plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, fusible means interconnecting said main arcing terminal and said arcing terminal carried by said housing, and strain means interconnecting said auxiliary arcing terminals and said arcing terminal carried by said housing, said fusible means being adapted to blow before said strain means on operation of the cartridge, said strain means relieving said fusible means of stress otherwise imposed thereon.

5. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and an auxiliary bore, a main arcing terminal and an auxiliary arcing terminal in said main and auxiliary bores, respectively, a fuse wire secured at one end to said main arcing terminal, a relatively infusible terminal secured to the other end of said fuse wire, means securing said relatively infusible terminal to said arcing terminal carried by said housing, and a strain Wire interconnecting said auxiliary terminal to said arcing terminal carried by said housing.

6. In a circuit interrupter, in combination, a housing. an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, a plurality of pairs of fuse wires secured at one end to said main arcing terminal, a relatively infusible terminal secured to the other end of each pair of fuse wires, means individually securing each relatively infusible terminal to said arcing terminal carried by said housing, and a plurality of strain wires interconnecting said auxiliary arcing terminals and said arcing terminal carried by said housing for relieving said fusible means of stress otherwise imposed thereon.

'7. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, means operatively interconnecting said main and auxiliary arcing terminals for movement as a unit, and fusible and strain means interconnecting said main and auxiliary arcing terminals, respectively, and said arcing terminal carried by said housing.

8. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality oi auxiliary arcing terminals in said main and auxiliary bores, respectively, means operatively interconnecting said main and auxiliary arcing terminals for movement as a unit, fusible and strain means interconnecting said main and auxiliary arcing terminals, respectively, and said arcing terminal carried by said housing, and exible conducting means connected to said arcing terminal carried by said housing and extending into each of said auxiliary bores for causing arcs to be drawn therein.

9. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and an auxiliary bore, a main rod-like arcing terminal and an auxiliary rod-like arcing terminal in said main .and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rod-like arcing terminals being suchas to substantially ll their respective bores, and fusible means interconnecting said main and auxiliary arcing terminals and said arcing terminal carried by said housing. v

10. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a iilling of solid arc extinguishing material in said housing having a main bore and an auxiliare bore, a main rod-like arcing terminal and an auxiliary rod-like arcing terminal in said main and auxiliary bores, respectively, the cross-sectional areas of said mainand auxiliary rod-like arcing terminals being such as to substantially iill their respective bores, fusible means interconnecting said main arcingl terminal carried by said housing, and strain-means interconnecting said auxiliary arcing` terminal and said arcing terminal carried by said housing, said fusible means being adapted to blow before said strain means on operation of the interrupter, the arc produced on blowing of said strain means being formed between said arcing terminal carried by said housing and the adjacent end of said auxiliary arcing terminal. f

11. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and an auxiliary bore, a main rod-like arcing terminal and an auxiliary rod-like arcing terminal in said main and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rodlike arcing terminals being such as to substantially ll their respective bores, fusible means interconnecting said main arcing terminal and said arcing terminal carried by said housing, strain means interconnecting said auxiliary arcing terminal and said arcing terminal carried by said housing, said fusible means being adapted to blow before said strain means on operation of the interrupter, the arc produced on blowing of said strain means being formed between said chamber being flared outwardly in the direction of said arcing terminal carried by said housing to facilitate the iiow of the products of the arcs formed on blowing of said fusible and strain means.

l2. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main rod-like arcing terminal and a plurality of auxiliary rod-like arcing terminals in said main and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rod-like arcing terminals be- `ing such as to substantially fill their respective bores, and fusible means interconnecting saidmain and auxiliary arcing terminals and said arcing terminal carried by said housing.

i3. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a liing of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main rod-like arcing terminal and a plurality of auxiliary rod-like arcing terminals in said main and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rod-like arcing terminals being such as to substantially fill their respective bores, fusible means interconnecting said main arcing terminal and said arcing terminal carried by said housing, and strain means interconnecting said auxiliary arcing terminals and said arcing terminal carried by said housing, said fusible means being adapted 'to blow before said strain means on operation of the interrupter, the arc or arcs produced on blowing of said strain means being formed between said arcing terminal carried -by said housing and the adjacent ends of said auxiliary arcing terminals.

lll. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a. plurality of auxiliary bores, a main rod-like arcing terminal and a plurality of auxiliary rod-like arcing terminals in said main and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rod-like arcing terminals .being such as to substantially ll their respective bores, fusible means interconnecting said main arcing terminal and said arcing terminal carried by said housing, strain means interconnecting said auxiliary arcing terminals and said arcing terminal carried by said housing, and an arcing chamber individual to each of said main and auxiliary arcing terminals, each arcing chamber being flared outwardly in the direction of said arcing terminal carried by said housing to facilitate the iiow of the products ofl the arcs formed on blowing of said fusible and strain means.

15. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a bore extending therethrough, a rod-like arcing terminal movable through said bore between which and said arcing terminal carried by said housing an arc is formed on operation of the interrupter, and packing means in said bore cooperating with said rod-like arcing terminal for substantially preventing the passage therepast of the products produced by said arc.

16. In a circuit interruptor, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and an auxiliary bore, a main rod-like arcing terminal and an auxiliary rod-like arcing terminal in said main and auxiliary bores, respectively, fusible means interconnecting said main and auxiliary arcing terminals and said arcing terminal carried by said housing, and packing means in said main bore cooperating With said main rod-like arcing terminal for substantially preventing the passage therepast of the products of the arc produced in said main bore on operation of the interrupter.

17. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and an auxiliary bore, a main rod-like arcing terminal and an auxiliary rod-like arcing terminal in said main and auxiliary bores, respectively, the cross sectional areas of said main and auxiliary rodlike arcing terminals being such as to substantially fill their respective bores, fusible means interconnecting said main and auxiliary arcing terminals and said arcing terminal carried by said housing, and packing; means in said main bore cooperating with said main rod-like arcing terminal for substantially preventing the passage therepast of the products of the arc produced in said main bore on operation of the interrupter.

18. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main rod-like arcing terminal and a plurality of auxiliary rodlike arcing terminals in said main and auxiliary bores, respectively, the cross-sectional areas of said main and auxiliary rod-like arcing terminals being such as to substantially fill their respective bores, fusible means interconnecting said main and auxiliary arcing terminals and said arcing terminal carried by Said housing, and packing means in said main bore cooperating with said main rod-like arcing terminal for substantially preventing the passage therepast of the products of the arc produced in said main bore on operation of the interrupter.

19. Areplaceable fuse cartridge for mounting on support means for interconnecting a pair of line terminals and disposed to be tensioned by `external spring means comprising, in combination, a tubular housing, a pair of arcing terminals between Which an arc is adapted to be formed, one being stationarily mounted with respect to said tubular housing and adapted to be connected to one line terminal, and the other being movable and adapted to be connected to the other line terminal, fusible means interconnect- Ving said arcing terminals, and means on said 'housing for mounting the same on said support means and automatically aligning the housing with said support means.

20. In a circuit interrupter, in combination, arc extinguishing material providing a main bore and a plurality of auxiliary bores, a stationary arcing terminal at one end of said bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, adapted to be tensioned for moving the same away from said stationary arcing terminal to draw an arc between said stationary arcing terminal and one end of said main and auxiliary arcing terminals, rst in one or more of the auxiliary bores and nally in the main bore if the arc in the auxiliary bore or bores -is not extinguished, and means interconnecting the other ends of said main and auxiliary arcing terminals in such manner that tension stress applied to said main arcing terminal is substantially uniformly .distributed among said auxiliary arcing terminals.

21. In a circuit interrupter, in combination, arc extinguishing material providing a main bore and a plurality of auxiliary bores, a stationary arcing terminal at one end of said bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, adapted to be tensioned for moving the same away from said stationary arcing terminal to draw an arc between said stationary arcing terminal and one end of said main and auxiliary arcing terminals, rst in one or more of the auxiliary bores and nally in the main bore if the arc in the auxiliary bore or bores is not extinguished, and evener means interconnecting the other ends of said main and auxiliary arcing terminals to substantially uniformly distribute tension stress applied thereto among said auxiliary arcing terminals.

22. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, fusible means connecting one end of each of said main and auxiliary arcing terminals and said arcing terminal carried by said housing, and means interconnecting the other ends of said main and auxiliary arcing terminals in such manner that tension stress applied to said main arcing terminal is substantially uniformly distributed among said auxiliary arcing terminals.

23. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, fusible means connecting one end of each of said main and auxiliary arcing terminals and said arcing terminal carried by said housing, and evener means interconnecting the other ends of said main and auxiliary arcing terminals to substantially uniformly distribute tension stress applied thereto among said auxiliary arcing terminals.

24. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a main bore and a plurality of auxiliary bores, a main arcing terminal and a plurality of auxiliary arcing terminals in said main and auxiliary bores, respectively, fusible means connecting one end of each of said main and auxiliary arcing terminals and said arcing terminal carried by said housing, means mechanically and electrically interconnecting the other ends of said main and auxiliary arcing terminals, and manually operable means for adjusting the interconnecting means to effect desired distribution of tension stress among said auxiliary arcing terminals.

25. In a circuit interrupter, in combination, a tubular housing, a terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a central main bore and a pair of auxiliary bores on opposite sides of the main bore, the main bore having a generally rectangular and relatively large cross section and the auxiliary bores having relatively small cross sections, main and auxiliary terminals in said main and auxiliary bores, said main terminal conforming to and substantially filling said main bore, and fusible means interconnecting said main and auxiliary terminals and said terminal carried by said housing.

26. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a bore extending therethrough, a rod-like arcing terminal movable through said bore between which and said arcing terminal carried by said housing an arc is formed on operation of the interrupter, and packing means in said bore cooperating with said rodlike arcing terminal for substantially preventing the passage therepast of the products produced by said arc, said packing means being arranged and adapted to increase its resistance to the iiow of said products as the pressure thereof increases.

27. In a circuit interrupter, in combination, a housing, an arcing terminal carried by said housing, a lling of solid arc extinguishing material in said housing having a bore extending therethrough, a rod-like arcing terminal movable through said bore between which and said arcing terminal carried by said housing an arc is formed on operation of the interrupter, and packing means in said bore cooperating with said rod-like arcing terminal for substantially preventing the passage therepast of the products produced by said arc, said packing means including one or more V-shaped rings substantially concentric with said rod-like arcing terminal with the tip of the V pointing in the direction of movement thereof away from said arcing terminal.

28. A replaceable fuse cartridge for mounting on support means for interconnecting a pair of line terminals and disposed to be tensioned by external spring means, in combination, a tubular housing, an arcing terminal carried by said housing, a filling of solid arc extinguishing material in said housing having a bore extending therethrough, a rod-like arcing terminal movable through said bore between which and said arcing terminal carried by said housing an arc is formed, fusible means interconnecting said arcing terminals, packing means in said bore cooperating with said rod-like arcing terminal for substantially preventing the passage therepast of the products produced by said arc, and means on said housing for mounting the same on said support means and automatically aligning the housing with said support means.

HUGH A. TRIPLE'I'I'.