US1924484A - Fuse - Google Patents

Description

Aug. 29, 1933. N. J. CONRAD FUSE Filed March l5 UNITED STATES PATENT orrica This invention relates to circuit interrupters .and more particularly to such interrupters as are particularly adapted for use on high voltage systems, although not limited to such systems. The 5 circuit interruptor of the present invention is of the fused type, that is it is one wherein the circuit is opened by the bl one of the objects of the vide a device of this character which is exceedingly rapid in its action cal in construction.

In the embodiment described for illustrative purposes the invention is incorporated in a lfuse of the well known type comprising Ia. glass tube tallic ferrules at its opposite ends for establishing a circuit through the fuse within. A movable terminal member is mounted within the contain-v er and adjacent one end thereof and a spring is provided for rapidly mo end upon the blowing o er is lled with an insulating liquid of high are extinguishing propertie drawn by the terminal member as it moves under the action of the spring, thereby quickly extinguishing the arc. This the Schweitzer & Conrad fuse and one torni thereof is shown in the United States patent to Edmond O. Schweitzer Number 1,135,548 issued April 13, 1915. however to be understood that the present invention is not limited to such fuse structures but is .of general application.

In the fuse herein shown the upper ferrule is provided with a shoulder upon which a bridge member rests, and the fuse is suspended from the bridge member by means of a point suspension to allow for a universal movement ofthe course understood that versal joint could be used if desired.

The movable system hich the fusefis conne is connected for supporting the same. A spring holder is mounted on the terminal and is provided with a helical groove coiled spring that pulls upwards on the lower ferr'ule. It is one of the objects of the present invention to provide a n for supporting the terminal and a novel means for connecting the spring to the terminal. Another feature of novelty of the present structure resides in the means for connection between the rule.

.Nicholas .3'. Conrad, Winnetim, Ill., assigner, by mesne assignments, to Schweitzer da (Conrad, Inc., Chicago, Ill., a corporation of Delaware Application March l5,- lllll.. Serial No. 436,@12 35 (lll. Ellie-117) within the fuse rises. owing of a fuse, and it is present invention proand simple and economi-s When an arc is quenched by an insulating lion uid, such as is here used, some of the liquid is voila- 'tilized by the heat of the arc. occupies a greater volume than i liquid from which it is genera or current flow bease of a very large c 1- rent new the amount of liquid volatilized may be of my 'invention herein or container having nieving it towards the other f the fuse. The contain- Vent CED s into which the arc is type of fuse is known as and Nicholas J. Conrad It is To prevent the li suncient to shatter the fuse unless sonrie ineens is providedA for permitting the escape of the vapor, For this reason a vent cap is provided, which vent cap blows when the pressure reaches c. predetermined value, that value being below that at which the glass' of the fuse would shatter.

Trie vent cap is sealed to the upper errule and it is one oi the objects of the present invention to provide an improved means for sealing the quid .within the iuse from creeping outward along the joint between the cap and the upper ferrule I provide a seal consisting of plastic baltelite or the like, and to prevent the entrance oi moisture into the iuse l provide an additional seal of asphaltum. bakelite constitutes the inner seal and the asphaltum the outer seal, whereby the prevents the liquid within the fuse from contacting with and attacking the asphaltum.

The attainment of the jects of the present invention will be apparent The barette above and further obirom the following specication taken in connec- Part thereof.

movable portion of the in the drawing! suspended parts. It is of any other form of uniline 2-2 of Figure 1;

comprises a terminal to the vent cap removed;

cted and to which a Wire for receiving the end of a line 5 5 of Figure l.

ovel-and improved means establishing the electrical fuse and the upperferfluid tight closure.

Figure l is a longitudinal secti improved fuse structure;

Figure 2 is a sectional view taken along the Referring now more partie ing, the fuse shown compr ends oi' which fit into the rules 2 and 3 respectively, cured in position by a s which also serves as a pa tion with the accompanying drawing forming a onal view of my Figure 3 is a top view of the fuse structure with Figure 4 is a fragmentary sectional view taken along the line 1 -4 of Figure 2; and

Figure 5 is a sectional view taken along the ularly to the draw@ ises a glass tube 1 the upper and lower ierm the Ierrules being seuitable alloy filling 4 cking for producing a While the tube shown is cylindrical in shape and is formed of glass it Sill may, if desired, be made of any other suitable preventing 2 shape and likewise may be of any other preferred insulating material such as for example, ilber impregnated with bakelite or the like. The ferrules 2 and 3 are made of suitable conducting metal and constitute the terminals for making or breaking a circuit through the fuse. The upper and the lower ierrules are provided, on their inner side, with tapered or conical shoulders 6 forvcentering the tube 1 and for providing a minimum contacting area between the tube and the ferrules. The top of the upper ferrule 2 has a cylindrical bore Si 'formed therein and terminating in a shoulder Si. Beyond the bore 8 there is a cylindrical bore itl of reduced diameter, which bore terminates in e. shoulder il. The fuse mechanism as a whole is suspended within the tube i. by means of an upwardly arched bridge i3 that rests upon shoulder Q. The bridge nie-roher fits snugly within the cyiindrical bore d and provided at its opposite ends with a pair of upwardly extending projections lli-ifi which bear against the cylindrical wall of the bore ii, increasing the depth oi cooperation of the ends or the bridge member with the wall of the bore 8 and the bridge member from working up and out of its desired position in the bore 6. The projections 14 may ne made by merely stamping a small bulge in the bottom oi the bridge ,member at the ends thereof.

An inverted U-shaped bail member i6 extends through a central opening 17 in the bridge meinber and is supported by a bridge bar i8 which rests across the opening 17 in the bridge member 13 and which may be held in place by means of a wire cotter pin 20. A very short pin 21 is secured to the bridge bar 18 and constitutes a single point support for the bail member. A shallow spherical depression is formed in the bail member for providing a seat for the bail member on the pin 2l. The bail member has complete freedom of motion on the supporting pin 21. The bail member 16 constitutes a short length of copper tubing through which is passed a ilexible braided wire 25, of copper or the like, and a strain wire 26 of nichrome or the like, said wire having a high tensible strength and a rather high electrical resistance. The end of a fuse 'wire 27 is likewise extended into the copper tube. The tube is then flattened in a punchpress or the like to firmly secure the braided wire 25, the wire 26 and the fuse 27 in the tube. The fiattened tube is then bent to form an arch shape or U-shap'e member as shown in the drawing. A terminal assembly 30 is supported by the wire 26. The terminal 30 comprises an internally threaded sleeve 3l and a cable securing member 32 secured in the sleeve 31. The terminal 30 is made of brass or other suitable current conducting material. The sleeve 3l has a s et of longitudinally extending grooves 35l formed thereinl and has a hole 36 drilled therethrough near the end of the sleeve.

The strani wire 26 is inserted in thc grooves 35, the ends of the wire being passed through the opening 36 in crossed relationship land then again extending into the grooves 35 onthe opposite sides of the sleeve member, a similar groove 36' is formed for receiving the end of the fuse link 27. The sleeve is then compressed in a punch press so as to cause the walls of the grooves to come together and firmly grip the ends of the wire 26 and the end of the fuse link 27 in the sleeve mem'- ber 30.. A liquid director 40 is supported by the terminal 30 and for this purpose it has three holes, 120 apart, formed therein. Through these holes three pins or studs 42 are passed. These stds are freely movable within the holes in the sleeve member 31 and when they are fully lnserted within the sleeve the liquid director 40 may be passed over the sleeve. After the liquid director has been placed over the sleeve 3l a screw 44 is threaded into the bore of the sleeve 3l. The screw 44 is provided with a conical head 45 which forces the pins or studs Li2 outward. The liquid director 40 has a groove i6 formed therein and the rounded or spherical ends of the studs i2 enter this groove and thereby support the liquid director in spacedrelationship to the terminal. The cable terminal has an upper screw threaded portion 5o which. threads into the sleeve 3i. is thereby rigidly secured thereto and lower holiow portion into which a cable 53 oi material is rigidly secured. a. shoulder The portieri ci. the top of the sh r` 55 the lower Aostthread of the threaded portion flatteN ed surfaces 56 as may be seen in Figure 5, and the cable fastener has an opening of a similar As a result of this arrangement the spring fastener is held against rotation. There is a' loose ilt between the spring fastener 54 and the cable terminal 32, in order to permit a limited amount of side play between the two. Incase of deflection of the spring fastener 54 laterally against the tube l this play between the fastener 54 and the terminal member 32 will relieve the tube of the inertia of the terminal member 32, to which it would be subjected if the spring fastener and terminal 110 member were rigidly secured together. A helical groove is formed in the spring fastener 54 and said spring fastener is threaded into a helical coiled spring 60. The lower end of the spring 60 is threaded around a spring fastener 61 similar 115 to the spring fastener 54 and secured to or formed integral with a lower cable terminal 62. The lower ferrulev is provided with an inwardly extending boss which is bored and internally threaded to receive a threaded portion 66 on the 120 lower end of the cable terminal 62.

A washer 70 of bakelite or other suitable insulating material re'sts upon the shoulder 11 of the the cable tot upper ferrule and is provided with a central opening through which the upper terminal 30 extends. 125 The washer is of the split type and consists ofy two semi-circular halves which lie in the boro l0 and embrace the top of theterminal 30 after the terminal 30 has been assembled.

In assembling the fuse the spring 60 is first 130 threaded into the lower spring holder 61 and the upper spring holder 54 is then placed above the upper cable terminal 36 and is threaded into the top oi the spring 6G and then lowered onto the shoulder 55. Thereafter the assembly comprising the upper terminal 30 and the liquid director 40 are threaded onto the threaded portion 50. It is understood that at this time the spring is not under tension and therefore the two cable terminals are drawn rather closely together. The 14o bail 16 is provided with suitable depressions 72 and 'T3 formed therein for permitting the gripping of the bail memberby a tool whereby the same may be lowered into the tube 1. The mechanism is lowered until the threaded portion 66 145 on the lower cable terminal enters the bore in the boss 65 of the lower Ierrule. The threaded portion 66 is then threaded into the boss by means of a suitable tool. After this has been done the bail 16 is traised by means of the sep- 150 liti arate tool gripping the bail at the depressions 72 and 73, although other bail anchoring means may be employed and the bail is lifted until it extends through the opening 17 in the bridge member 13. After the tube is filled with a suitableyarc quenching liquid the split collar 'lll and the bridge bar 18 are then inserted into place and the bail 16 is thereafter lowered until it rests upon the bridge bar. The ilexiblebraided conductors 25 are previously inserted beneath the ends ofthe bridge 13 so that the flexible conductor rests upon the shoulder 9 and in turn is pressed ,downward by the bridge member 13 which seats thereon When the apparatus is in this position the spring is under a rather great tension and thereby exerts a considerable pressure upon the bridge member 13 which pressure is transmitted through the flexible conductorr25 to the shoulder `9 thereby maintaining a ilrrn electrical contact vbetween the flexible conductor -25 and the shoulder 9. .Due to the fact that the bridge member 13 ts rather snugly within the ferrule, as previously stated, any` tendency on the part of the bridge member to collapse dovmwardly under the action of thespring 60 will be resisted by the inner vertical wall-.of the ferrule and will result in an increase in the pressure of the bridge member against the inner vertical ferrule wall. It is to be noted the pin 2l and the bail, 16 provide a universal mounting for the terminal `member 30. The universal mounting support permits free movement of the terminal member 3o in all directions. It enables elimination ci guide prongs or the like and it eliminates possibility of lszinking of the fuse or strain wire such as might occur with a rigid anchor at the upper end.

The are extinguishing liquid is preferably inn troduced into the tube i before the split collar 'lo is set in place.

The liquid within the tube is of hielo arc quenching properties. Any suitable insulating liquid may be used. This insulating: liquid may comprise carbon tetra-chloride-or any of the in-n sulating liquids mentioned in the United States patent to Edmund 0. Schweitzer and Nicholas J. Conrad, No. 1,3ii19o7 of October 2o, lele, although any other preferred insulating liquid may be used.

il vent cap 3u is then mounted on. the top or? the upper ier'rule in order to close the top of the fuse. The cap ed is secured to the outside of the ierrule and is provided with an inclined shoulder 8i which overlies the ferrule. The can is seu cured to theV top oi the ferrule by a suitable ce ment which, although it may take other forms, preferably consists of a rim ot plastic bakelite the like interposed between the vent cover and the sides of the ferrule as indicated at e2. This substance prevents the egress of the insulating .liquid within the tube by creepage along the sides ci the lierrule. lin order to prevent the entrance of moisture into the tube there is further inter= posed between the vent .cap and the ierrulea loyer of suitable cement impenetrable to water. This cement .is indicated at 83 and may consist of esplialturn or the like.

The asphaltum is provided due to the i'act that moisture can creep into the fuse through the bakelite binder e2 if it were permitted to reach the beliebte. The bakelite 82 acts as an eective stop to prevent the liquid within the tube from reaching the asphaltum since the asphaltum is subject to attack by this liquid.

When an excessively large current flows through the fuse the i'use link 27 melts and substantially simultaneously therewith'thehigh resistance strain wire 26 likewise melts. Thev terminal 30 is then snapped downward by the spring 60 thereby drawing an are between the too oi the terminal and the remaining portion of the :fuse: link extending out of the bail mem ber lo. The liquid director 40 is spaced from the terminal member 31 and is drawn downwardly therewith during its descent. As may be seen from the drawing, the liquid director 40 is provided with a conical opening having its largest diameter bottommost. As the liquid director moves downwardly with the terminal 30` the liquid within the tube 1 squirts through the conical opening, past the space between the lithl uid director and the terminals, into the region or the arc. Thm `produces a violent agitation oi? the liquid in the region'of the are, constantly directing fresh, cool liquid into the arc to quickly extinguish it.

the circuit interruption a certain amount ci the liquid within the tube is voiatilised.

Since the gases that are formed by the volatilise.-s

tion of the liquid occupy a greater space than was occupied hy the liquid from which the gases were formed, it is apparent that the pressure within the tube l will increase. When the fuse functions to interrupt a very severe short-circuit amount oi ses generated becomes appreciable and unless means is provided for permitting the escape oi. the gas the resulting pressure will shatter the glass tube and splash the contents and the broken glass around everything. To avoid such an occurrence the cap il@ is not secured to the upper ierrule very tightly, so that when the pressure within the tube becomes excessive the cago will be blown oil, thus permitting the e escape of the gases generated. Thus the shatterexplosion chamber in the ferrule 2 above the split collar lo. Consequently the initial explosive eiieot upon blowing is substantially confined to the chamber above the collar 70 with the result on short-circuit or very heavy overload the vent cap blows off before any extensive pressure L can develop in theglass tube. When the arclng terminal is drawn down into the liquid the collar 7o is to rise and prevents any excessive pressure within the glass tube as the arcing ternitz nal .is wn down into the liquid. Even the initial ei; osive effect in the chamber above the collar lo 'm not transmitted through the ici-rule 5i and through the wall of the tube i, because in use the external shoulder ineens on the ferrule 2 is preferably seated against the iuse clip or an ad jacent shoulder and the explosive eiect through the ferrule is taken up by this seating engagen meut a d not transmitted to the wall of the tube.

lip-o: violent blowing ci the fuse, which results in removal oi the cop to, the upper terminal or the usejincluoling bridge i3, is freely expelled, inasmuch ss the release or" 'the terminal from the spring 'tension which held it in position releases the which it had upon. the inner walls ci. the ierrule. 'he fuse may be restored for service by unscrewing the sleeve 3o from the stud 50 and relu placing the same with a fresh unit, including new sleeve 3o, liquid. director 40, bridge i3 shuntina conductor 25, which are then readily dropped into place. The split washer '26, which liti likewise was expelled by is replaced by anew one. The liquid is replaced with a fresh charge and the device sealed.

While I have herein shown and described a preieri-ed embodiment of my invention it is to be understood that the invention is not limited tothe precise construction herein shown but is capable of various modications, the fuse here shown being merely illustrative oi the invention.

What I consider new and desire to secure Letters Patent is:

1. In a device oi! the class described, the combination ot a tubular casing, a terminal. ferrule on the casing, a movable terminal Within the casing, a coiled spring normally under 'tension and connected with the movable terminal, a fuse connected between the movable terminal and the ferrule and means for anchoring said movable terminal under the tension of said spring, said anchoring means having universal mounting on said Ierrule and including a bail member supported at a single point and in turn supporting the movable terminal and the fuse.

2. In combination, a trame, a terminal, a fuse connected between said terminal and said frame,

operation oi the fuse,

`a spring connected to said terminal and an anchor for said terminal including a bail member having universal. mounting on said frame and a strain wire supporting the terminal from said bail member.

3. A circuit interruptor comprising a casing, a terminal member supported within the casing by means including a universal mounting, a spring exerting a pull on the terminal, a severable connection including a fuse element disposed between the terminal Aand the universal mounting and a strain wire for relieving the fuse of the Spring tension.

4. A circuit interrupter comprising a casing, a bridge member supported in the casing, a terminal'member suspended from the bridge member by a sever-able connection including a strain wire and a single point suspension having freedom of motion in all directions, said strain wire being severed upon the operation of the device to interrupt the circuit, spring means for rapidly separating the terminal from the supporting bridge upon the severing of the circuit, arc quenching liquid within the'casing, and a liquid director carried by the terminal for directing the liquid .to the point of circuit interruption upon movement of the terminal under the action ci the spring. 1

5.' -A fuse having a terminal member. a sleeve into which the terminal member is threaded, a bridge member for `supporting the sleeve and thereby supporting the terminal member, a joint permitting universal movement of the sleeve with respect to the supporting bridge member, and a fusible element establishing an electrical connection between the terminal and the bridge member and located between them.

E. A fuse comprising a hollow supporting inember having embedded therein a connecting conductor, a fuse element,and a strain wire; and a terminal suspended from the supporting member by the strain wire, the other end of the fuse being connected to the terminal, thereby establishing a circuit between the terminal and the connecting conductor.

7. A fuse comprising a hollow supporting member having embedded therein a. connecting conductor, a fuse element, and a strain wire; a terminal suspended trom the, supporting member by the strain wire, the other end of the fuse element being connected to the terminal, thereby establishing a circuit between the terminal and the connecting conductor, and means for pulling the terminal member away from the supporting member.

8. A fuse comprising a hollow supporting member having embedded therein a connecting conductor, a ruse element, and a strain wire; a terminal suspended from the supporting member by the strain wire, the other end of the fuse element being connected to the terminal, thereby establishing a circuit between the terminal and the connecting conductor, means for pulling the terminal member away from the supporting member, and a point support for the supporting member whereby the same has a limited degree of universal motion.

9. A fuse comprising a hollow supporting member having embedded therein a connection conductor, a fuse element, and a strain wire; a terminal suspended from the supporting member by the strain wire, the other end of the fuse element being connected to the terminal, thereby establishing a circuit between the terminal and the connecting conductor, and a joint support for the supporting member whereby the same has a limited degree of universal motion.

l0. A fuse including a conducting cylinder having a groove therein, and a fuse wire embedded in the groove and rigidly held in place by compression of the sides of the grpove thereon.

11. A fuse including a conducting cylinder having a longitudinal groove therein extending up to the end ci the cylinder, and a fuse wire embedded in the groove and rigidly held in place by compression of the sides of the groove thereon.

12. In combination, a terminal having a plurality of grooves therein, wire supporting means for the terminal extending into at least one of the grooves, and a fuse wire extending into another one of the grooves, said fuse wire and said wire supporting means being secured in place by compression of the terminal to force the side walls of the grooves together.

13. A fuse comprising a casing, a fusible element in the casing, a cap for the casing extending over the outer periphery of the casing, said cap being adapted to be blown oi! ot the casing upon an abnormal blowing of the fuse, and an air tight seal between the cap and the outer periphery of the casing, said seal comprising a plastic compound to prevent the leakage of the contents o! the tube and a dissimilar compound to prevent the entrance 'oi moisture into the tube.

i4. A fuse comprising a casing, a fusible element in the casing, a cap for the casing, said cap being adapted to be blown otr of the casing by an abnormal blowing of the i'use, a body of arc quenching liquid within the casing for extinguishing the are of the fuse, and a seal between the cap and the casing for sealing the same, said seal comprising a compound impervious to the action of the are quenching liquid on the inner side of y the seal for preventing the outward creepage of 1U) the liquid, and a compound impervious to moisture on the outer side of the seal for preventing the entrance o! moisture into the casing.

i5. A ruse comprising a casing, a fusible element in the casing, a cap for the casing, said cap being adapted to be blown oil.' of the casing by an abnormal blowing of the fuse, a body of arc` quenching liquid within the casing for extinguishng the arc of the fuse, and a seal between the cap and the casing for sealing the same. said 150 the outward creepage of the liquid, and an asphal-= tum compound impervious seal comprising a phenol condensation compound impervious to the action of the arc quenching liquid on the inner side of the seal for preventing to moisture on the outer side of the seal for preventing the entrance of moisture into the casing.

18. A terminal member comprising, ceiving portion,

having a central opening therethrough, a bridge bar extending across said opening, and a terminal' suspended from the bridge bar by a single point suspension having freedom of "motion in. all ditablishing the rections.

i8. fuse device having a retraction spring and a universal su port for anchoring said spring and a bail member resting thereon.

is. A fuse comprising a 'tubular member hav= ing contact ferrules at its upper and lower ends, means including a fuse link for maintaining an electrical connection between the ferrules, spring the connection, electrical contact with the upper ferrule for es` tablishing the electrical circuit between the fuse link and the upper ferrule, said last named means including a conductor electrically connected to the fuse link, and a transverse member extendresting on the conductor within the `ici-rule and maintaining the pressure contact between the conductor andthe ierrule through the action of said spring.

\ 20. A fuse comprising a tubular member naving contact ferrules at its upper and lower ends, maintaining an electrical connection between the ferrules, spring means normally under tension and. released upon gap in the connection, said upper ferrule having a shoulder therein, and means making a pressure electrical contact with the upper ferrule for es-1 electrical circuit between tlie fuse link and the upper ferrule, said last named means including a conductor electrically connected to the fuse link, and a transverse member extend= ing across and resting on the shoulder Within the ferrule and maintaining the pressure contact between the conductor and the fel-rule through the action of said spring, said fuse link and spring being supported from the transverse member.

vleased upon blowing of the iuse link and the upper ferrule, said last named means including a transverse including a transverse member extending across and resting Within the icrrule and maintaining the pressure contact through the action of said spring, said fuse and spring means being supported from said transverse member by means including a universal mounting.

23. .fi fuse comprising a tubular member having contact ierrules at its upper and lower ends, means including a fuse iinl for maintaining an electrical connection between the ferrules, spring means normally under tension and released upon blowing ci the fuse link to produce an extended gap in the connection, said upper ferrule having a shoulder therein, and means making a pressure electrical 'contact with the upper ierrule for establishing the electrical circuit between the fuse linlr and the upper ferrule, said last named means including a transverse member extended across and resting on the shoulder within the ferrule and maintaining the pressure contact through the action of said spring, said transverse member extending upwardly from the shoulder and bearing against the inner side Walls of the upper fer rule, said fuse and spring means being supported from said transverse member by means including a universal mounting.

24. ./-l fuse comprising a tubular member hav ing a contact ferrule at its upper end, a fuse linie, spring means normally under tension and relink to produce an extended gap in the circuit through the fuse, and means making a pressure electrical contact with the ierrule ior establishing an electric circuit between the fuse lint". and the ferrule, said last means including a transverse member eiatencling across and resting upon a shoulder with in the ierrule maintaining the pressure conn tact through the action of said spring, said transverse member making e. snug t within the fer rule and being arci-led upwardly from said snoula der with the fuse and spring means located below the transverse member and supported therefrom and pulling the same against the shoulder.

25. i fuse comprising al tubular member liavlfing a contact ierrule at its upper end, a fuse iinlsz, spring means normally under tension and re leased uponblowing oi the fuse'link to produce an extended gap in the circuit through the fuse, and means making a pressure electrical contact with the ferrule for establishing an electric oir cuit between the fuse link and. `the ferrule, said last named means including a transverse mientol ber extending across and resting upon a shoulder within the ierrule and maintaining the pressure Contact through the action of said spring, said izo transverse member extending upwardly from said shoulder with the fuse and spring means located below the transverse member and supported therefrom by means including a universal mounting.

26. A fuse including a casing having a ferrule at its upper end, a bridge member supported on the inner side of the ferrule, a fuse link, a movable terminal, means supporting said. movable terminal from said bridge member, spring means pulling said movable terminal away from the bridge member and pulling said bridge member inward of the fuse casing, and a conductor extending a circuit between the 'fuse and the ierrule, said bridge member bearing on the end of said conductor and through the action of the spring exerting a clamping action to clamp the conductor against the ferrule.

27. A fuse including a casing having a ferrule at its upper end, a bridge member supported on the inner side of the ferrule, a fuse link, a movable terminal, means supporting said movable terminal from said bridge member, said bridge member being upwardly arched from its support- A ed ends andsaid terminal being suspended from the crown of the arched portion, spring means pulling said movable terminal inwardly of the casing and away from the bridge member, and a conductor extending a circuit between the fuse and the Ierrule, said bridge member bearing on the end of said conductor and through the action of the spring exerting a clamping action to clamp the conductor against the ferrule.

28. A fuse Iincluding a casing having a ierrule at its upper end, a bridge member extending across the open end of the errule and supported on the inside thereof with its ends against the inner vertical peripheral wall of the ferrule, means for drawing a gap in the circuit extending through the casing, said means including a spring held under tension and a fuse link for eiecting the release of the spring, said spring exerting a pull on the bridge member, and a conductor for extending a circuit from the fuse link to the ferrule, the two ends of the conductor being interposed between the wall of the Ierrule and the opposite ends of the bridge member, whereby the pull of the spring on the bridge' member produces a pressure contact between the conductor and the ferrule.

29. A fuse including a casing having an open ferrule at its upper end, an upwardly arched bridge member extending across 'the open end of the rei-rule and supported on the inside thereof, and means for drawing a gap in the circuit through the casing, said means including a spring held under tension and a fuse link for effecting the release of the spring, said spring exerting its pull at the crown of the arched portion of the bridge and in a direction inward of the casing, the ends of the bridge member bearing against the inner side .of the vertical peripheral waii ci the Ierrule whereby the ferrule holds the bridge member against being iiattened by the action oi' the spring.

30. A fuse including a casing having an open ierrule at its upper end, an upwardlr,7 arched bridge member extending across the open end ci 'the ferrule and supported on the inside thereof,

means for drawing a gap in the circuit through the casing, said means including a spring held under tension and a fuse link for effecting the release of the spring, said spring exerting its pali at the crown ci' the arched portion ci 4the bridge and in a direction inward or the casing, the ends Vcontact Ierrules at its of the bridge member bearing' against the inner side of the vertical peripheral wall of the ferrule whereby the ierrule holds the bridge -member against being flattened by the action of the spring, and a closure for the open` end of the ferrule subject to be opened by internal pressure.

31. A fuse comprising a tubular member having a contact ferrule at one end, a conductor within the ierrule, means for establishing an electric connection between the conductor and the ferrule, said means including a transverse member extending across and resting within the ferrule with its opposite ends upon both ends of the conductor and pressing said conductor against the ierrule, a tension spring within the tubular member mechanically connected to the transverse member by means including a severable connection and exerting the pressure for pressing the conductor against the errule, said severable connection between the spring and the transverse member including a fuse connected to the conductor whereby upon blowing o! the fuse the spring is retracted from the transverse member.

32. A fuse including a tube of insulation having contact ferrules at its opposite ends, a iilling of arc quenching liquid within the tube, the upper ferrule having a shoulder therein at its upper end with the wall of the ferrule extending upward from said shoulder, a bridge member extending across the errule and resting against the shoulder with the ends o! the bridge member held in position by the upward extending portion of the wall of the ferrule, means establishing an electrical connection between the ferrules, said means including a connecting device suspended from the bridge member by a severable connection including a fuse link, a tension spring secured at one end to the lower ferrule and at its other end to the connecting device and exerting a pull on said device, the pull of the spring being transmitted through the severable connection and the bridge member to the shoulder on the upper ferrule, said connection'being severed upon blowing of the fuse, thereby permitting a retraction of the spring to produce an extended gap through the arc quenching liquid to promptly interrupt the circuit between the ferrules.

33. A fuse including a tube of insulation having opposite ends, a filling ot arc quenching liquid within the tube, the upper fel-rule having a shoulder therein at its upper end with the-wall of the ferrule extending upward from said shoulder, a bridge member extending across the ferrule and resting against the shoulder with the ends of the bridge member held in position by the upward extending portion of the wall of the tei-rule, means establishing an elec trical connection between the ferrules, said means including a connecting device suspended :from the bridge member by a severable connection including a fuse link, a tension spring secured at one end to the lower ierrule and at its other end to the connecting device and exerting a pull on said device, the pull of the spring being transmitted through the severable connection and the bridge member to the shoulder on the upper ferrule, a conductor interposed between the bridge member and the errule and pressed into ilrm contact with the ferrule by the pull of the Spring on the bridge member, said conductor being electrically connected with the fuse link. said severable connection being severed upon blowing oi' the Jfuse, thereby permitting a retraction of the spring quenching liquid to promptly interrupt the'circuit between the ferrules.

34. In combination, a fuse housing having a metal lerrule with a longitudinal opening provided with an open end adapted to be releasably closed, a terminal member extending across the longitudinal opening of the ferrule and being' supported by engagement with the walls thereof, e fuse under tension connected to the central part of said member, and a low resistance conductor connected at one point to the adjacent end of Vthe fuse, said conductor having an enti which is pressed by the terminal bar into goed electricel contact with the fermle to .form e. shtml;

bar and be expelled from the Ierabout. said terminal bar, said terminal conductor being free to rule on violent blowing of the fuse.

35. A replacement unit for :reconditioning a fuse, comprisngan arched terminal bar with a. :fuse link connected to the central part thereof, slmnting connections ci low resistence connected centrally to the adjacent end of the fuse and extending under the ends of the terminal bnr, and e, terminal member connected to the opposite' end of the fuse and lowing a, coupling portion for ready connection to or disconnection from n,

tension spring. y

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