US2441692A - Fuse - Google Patents

Description

May 18, 1948. R. H. EARLE Z-Mg? FUSE Filed June 5, 1944 4 Sheets-Sheet 3 IN VEN TOR. P/l/ f/ O9/ELE' KEY 25 mw A TTORNE y.

4 Sheets-Sheet A.

R. H. EARLE FUSE Filed June 5, 1944 n w Z W INVENTOR @au P/V Je( ma May 18, 1948.

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ATTORNEY.

Patented May 18, 1948 FUSE Ralph H. Earle, Wauwatosa, Wis.,v assigner to. vLine Material. Company, Milwaukee, Wls., a..

corporation. of .Delaware Application Junex, 1944, Serial No. .538,769

ldlai'ms.. (Cl. f3.llll---llllvv The invention herein disclosed relates yto irnprovenients in a f-.use for .an electric circuit;

-Electric power distribution systems 'are o oY casionally subject to abnormal fau-lt currents? which, if continued, will cause damage to` apparatus in the system. Therefore, so-calledeX- pulsion fuses and power fuses. are placed at advantageous positions in the. systems for inter rupting they flow of current when such fault currents occur and thus protect'. the apparatus against damage.

Fault currents may range froma slight flow of current in excess ofthe ratednormalcurrent of a distribution circuit. to .an abnormal value produced by a so-called dead short circuit, de pending upon thel impedance vof the.` circuit through which the fault current. flows.

The average distribution System is protected by fuses of conventional designs. adapted. tov

satisfactorily operate o ver the. .range of fault currents normally encountered andadaptedalso to be reoonditionedfor successive operationally. merely replacing an inexpensivel fuse llnlrtherein` As the power output of a distribution system is increased, it is found that thev values off the fault currents increase. Ultimately the poweroutput may reach a point where the possible "fault cur--4 rents are too high .to be handledlsafely or satis.- factorily by a conventional' fuse. Under such conditions fuses known as power fuses," are extra high rupt-uring capacity,v are-more expensive than the `conventional fuses, and are not.

generally suitable for more than one operation, whether or not the fault current interrupted thereby is of a relatively low value as compared to one of an excessively high value.

The primary object of this invention is to provide fuses which may be reconditioned after' each successive operation and which will' safely and satisdalctorilyv operate on fault currents of] higher Values than the conventional types of' use .of a comparatively short tube in each fuse,

- 30 used. These power fuses are designedfor anA thus freely venting the, gases produced by the arc and preventing the creation. of excessive pres sures which might burst the tube.

The fuse unit is further characterized by the fact that the arc produced in each fuse can be stretched to. the full length of the cartridge. When. the .arcs arothus stretched on relatively low fault currents, a maximum surface of the ber lining of the cartridges is exposed to the. arcs which as a result are quickly extinguished. Onthe other hand, when the arcs` are similarly elongated on high fault currents they oiler a snbstantia1 resistance to the flow of current, thusY limiting the Value to which the fault current canrrise. and the pressures tending to burstA the cartridges.

In the drawings which accompany this specification:

F'ig.Y 1 is a viewinside elevation, partly in vertical'section, illustrating a fuse unit embody'- ng -the invention herein disclosed.

Fig. 2V is a. view in side elevation, partly in vertical section, illustrating a modified form of* my invention.

Fig. 3g is an enlarged bottom View of` Figs. l and 2.

`Fig.y4s an enlarged fragmentary View in side elevation, showing the lower part of .the fuse units herein described and the position assumed thereby after interruption of an electric circuit.

Fig. 5 isa sectional fragmentary viewV in side elevation illustrating a modified` construction of an intermediateport-ion` of the fuse unit herein described.

TheV fuse unit illustrated in Fig. 1 is of the dropout type-wherein, upon rupture ofthe fusible elements, the fuse cartridge is released from the uppertermi-nal contacts and swings about its lower pivot to an inoperative position. The fuse cartridge C .comprises a pair of aligned tubes land 2 having. an inner surface from which are extinguishing gases may beevolved in the pres-- ence of an arc. The tubes are each provided with a ferrul'e 3 and 4, respectively, having an aperture. concentric with the bore of the tubes. A clamping sleeve 5 is rotatably-mounted by means of` the inwardly projecting ilange 6 upon the upper ferrule 3 and is threadedly engaged with the youterV periphery ofl the sleeve 4' to draw the ferrules` into clamping engagement with the fuse lini; buttons, as will more specically appear hereinafter.

vThe. cartridge-C isprovided with a mounting end of the tube 2 and pivotally secured at II to the lever I2 which in turn is provided with trunnions I3 rotatably carried by the hook-like bearings I4 on the terminal housing I5. The housing I5 is mounted fixedly on a supporting insulator I6 suitably secured to a base (not shown). A spring contact terminal I1 is secured to the housing in a suitable manner (not shown) and bears against the contact linger I8 on the lever I2. All of this structure is specifically disclosed in the patent to William O. Schultz, No. 2,378,109, issued June 12 1945, for Fuse construction.

The fuse link I9 within the tube 2 comprises Aa contact button 20 engaging the ferrule 4, a

fusible section 2I and a flexible section 22 which extends outwardly at the lower end of the tube and is clamped to the lever I2 by mechanism specically disclosed in the aforementioned William O. Schultz application. Briefly, this clamping mechanism, as may be seen in Fig. 3, comprises a movable clamping jaw 23 mounted on the lever I2 and co-operating with the gripping jaw 24 to normally bite the flexible section of the fuse link and hold it against withdrawal. A flipout lever 25 is pivoted at 26 on the lever I2 and is held against movement under the influence of the spring 2l by means of the exible section of the fuse link. A temporary latching lever 28 is mounted on the lever I2 for holding the clamping jaw 23 inoperative while the assembly is being re-iused.

The arm I6 embracing the lower end of the tube 2 has a projecting portion 29 which is adapted to receive a switch stick for lifting the cartridge C into and out of the hook-like bearing I4 when the cartridge is in the position shown in Fig. 4.

The upper tube I of the cartridge C is provided with a latching arrangement comprising sleeve 38 secured thereto by any suitable means such as setscrew 3l and having a pivot lug 32 and pull ring 32a integral therewith; a channeled latching lever 33 pivoted at 34 on the lug 32 and having lugs 35 for engagement with the contact prongs 36 at the notched portion 36a, the prongs being mounted on the insulator 3l which is secured to a base (not shown); and a flipout lever 38 pivoted at 38a on the upper end of the latching lever 33 and urged upwardly about the pivot 38 by means of spring 39.

Disposed in the upper tube I of the cartridge C is a fuse link 48 similar to the fuse link I9 and comprising a contact button 4| clamped between the ferrule 3 and the button 20 on the fuse link I3, a fusible section 42 and a flexible section 43 which extends from the upper end of the tube I and over the ipout lever 38 to the clamping nut 44. The clamping nut 44 is threaded on the stud bolt 45 on the latching lever 33 and secures the flexible section thereto.

A spring cap 46 may be loosely tted on the upper end oi the tube I and is adapted to prevent water from entering the tube. This cap will be blown from the tube by gases evolved and expanded therein when the fuse link 40 is ruptured under overload conditions.

The operation of the unit shown in Fig. 1 is as follows:

When the unit is in circuit as illustrated, current will flow between the upper and lower terminals 36 and Il, respectively, through the latching lever 33, fuse links 40 and I9, and the supporting lever I2. Under normal conditions in the circuit, the upper fuse link 40 holds the latching lever 33 against rotation counterclockwise on its pivot 34 4 and the fuse link I9 holds the supporting lever I2 against rotation clockwise on its pivot I3, thereby retaining the unit in the circuit closing position shown.

In the event the fuse link 4U is ruptured by reason of abnormal conditions in the circuit, the fusible section 42 will be severed. The flipout 38 will then be permitted to move counterclockwise under the influence of the spring 39 to widen the gap created by the severance of the fusible section, and the latching lever 33 will be permitted to rotate counterclockwise under the pressure of the upper terminal prongs 36 and gravity to disengage the lugs 35 from the notched portion 36a on the prongs 36. It will be observed that as the latching lever 33 moves counterclockwise it pulls the flexible section 43 from the tube I to further widen the gap in the fuse link and that, as the lever 33 so moves, the upper end of the cartridge swings clockwise about the pivot I3 and ultimately away from the upper prongs 36.

In the event the fuse link I9 is ruptured under abnormal conditions, the fusible section 2I will be severed and the supporting lever I2 will be released for clockwise movement about the pivot I3. In so moving, the lever I2 will carry the pivot II downwardly and'permit the cartridge C to withdraw the lugs 35 from the notches 36a on the prongs 36, and thereby permit the cartridge to swing in a clockwise direction about the pivots II and I3.

As the supporting lever I2 moves to release the cartridge, the flipout lever 25 will also move downwardly under the inuence of the spring 2l. Thus the flexible section 22 of the fuse link I9 will be drawn axially downwardly from the tube 2 by the combined action of the supporting lever I2 and flipout 25, thereby lengthening the gap in the severed portion of the fuse link.

From the foregoing it will be apparent that if either or both of the fuse links .I9 and 40 are ruptured, the cartridge will be released for movement to open circuit position.

In Fig. 1, I have shown the tubes I and 2 of substantially the same internal diameter, but the lower tube 2 is slightly shorter than the upper tube I. Assuming that the tubes are of the same material, such as iiber, and of the same bore and length, and that the fuse links I9 and 40 are of the substantially same calibration, then for all practical purposes the rupturing capacity of both portions of the cartridge may be considered as the same and will, in the event of the occurrence of abnormal conditions in a circuit to which the fuse links are responsive, operate simultaneously to interrupt the circuit by introducing a gap in each fuse link. This, in effect, introduces two gaps in series in the electric circuit and affords superior circuit interrupting operations over that attainable in a fuse unit embodying a single fuse link.

I am not prepared at this time to state positively why two fuses in series relation exhibit an improved operation over a single fuse. However, `in general, the arc in each fuse appears to exhibitwa current limiting effect on a fault current and when two or more such fuses are placed in series relation, each apparently co-operates with the other or others to limit the ilow of current therethrough and thus reduces the rupturing load to which each is subjected and, consequently, lowering of the value of the fault current below that which might otherwise be present during circuit interrupting operations.

It is common practice to provide expulsion agences fuses; mitin-diner lined. cartridges. Whenythese:

fusessare-rdesignednfor1a.50il0:voltz:circuit; the car tridges/willLzbe approximatelyV .5?" long and arev adequate.- for interrupting small. faint` currents'.

oi'ianv average. value. Howeverl desirable .lit may bethat suclrcartridges.belonger-where the smallestifault. currents. are encountered', this is not practical. because .the longer cartridgesv .cause higher pressures to :build` up and increase thedangers.oifburstingV onz'heavy fault-currents. `Ac

cordlngly; the length Vof' the cartridges Yinl-con.-k

I 'have provided a. fuse. unit which secures-thel desirable: 1chenac'teristicsV of" a. cartridge which will extinguish. arcs: producedY by `very small fault currentsfa-nd one which will` not burst on lvery heavy fault currents'. By connecting twoy 5000 volt cartridges in series, keach of` which is. 5" long, I` secure: the advantage of a single arc 10" long` andldo-not sacrifice the advantage of the freer venting of a 5 cartridge. I secure an advantage iny that each of the arcs produces a 'resistance' to the flow of current and thereby materially reduce the fault current to a safe value.

Another exam-ple which` will? illustrate the advantages of my invention -is inthe use of this device -in v a 15,'0001volt circuit. A conventional fuse designed for use in this circuit would usually7 haves. cartridgeA long and if closed at one ends-would burst on extremely-high fault currents. However, if the fuse unit of my inventionv is used, theI cartridges mayeacl'r be only T1/2" long. Thus the totallength ofthetwo arcs will be 1'5" long, but 'due' tothe shorter lengthv ofA each cartridge, the venting will :be -freer and much larger fault currentsv willfbehandled without bursting the cartridges.

Furthermore,y

'-In- Fig. 2 there is shown another embodiment off-my invention, which differs from the device otFig. I only with respect to its upper contact structure andi theV fusible` link in the lower tube. *Phe-'upper contact structure of Fig; 2 `has a ferrule 41 which is secured to the upper'vend' of the-'fusel tube by means of the pins 48. At the upper end of `the .ferrule 4.1 and integral therewith is a laterally projecting portion 49 having a. threaded aperture receivingV a ,bolt 50. which is secured therein and which :clamps thev flexible `leader 43 of the fuse link 4-to the portion 49.

Integral with the ferrule 4l are a pull ring 5I and-a pair of contact arms-52 projecting oat--4 wa'rdly inv opposite directions. from the ferrule These contact-arms are engaged by the 4downwardly urged spring arms `53 at the latchingffpcrtions `lliathe springarms being mounted on'the insulator $31. which Yis secured to. a base (-not shown).

The fuse link 54 in the lower tubular member 2 has a fusible section 55 of lower amperage than the fusible section 42 in the upper tubular member l. A lower amperage fuse is provided in the lower tubular member 2 so that the lower fuse link 54 will ordinarily blow before the upper does.

The operation of the lower tubular member 2 upon the blowing of its fuse is the same as that described for the lower tubular member of Fig. 1. In the upper tubular member, however, the operation is different. The fusible section 42 will melt under heavy overload or short circuit conaanname-.thefsaseseyolvediwill tenerne; serine can;4 AAl* from. the cartridge: cleat;

unharmed nortionfcfftheiusezalink.

Under-:ordinary".orerload cond cnsftheflowerfuse Willzblowsnrst. It' is: possible that the upper;

fuse: will never blow, 4but itsrpresence insures. protection4 runder abnormal; conditions.: 'when suchy conditions are present, :both hiresl `mayblow. simultaneously or :in series.A

.5 shows a modified construction: foizthe; intermediate portion of1 the fuse; units. hereinr before described. It is; adaptable; 'coweither ci? the-devices illustrated ,in Figs; 1;;and12. j-IfIerer the. clamping: sleeve (5? cf'fFigs. 1` and1.2;.`s replaced-1 by acast ttingi into/which'. are threadedzxthe;

tubularmemberstandl'.

Fitting; 5E has Itwo. arms 5.1; andrzcontaining. acutelyrangular passageways4 5B :and Bib. titre/tri-L ed internally at (il: and.i: 2r to.- receive` .p lugsyi' and .fiil-y and; hayingshoulders 6.5 and: .66.` `unen.

whichV are `seated'. the. `buttcnhead terminals; il and. til.Y flianiti'on 8.9- is: positioned` between the acutely angularv passageways to prevent: prospective arcs .from-bridging the gap between-the- 1 cartridges, vlatching means-at` each end. of said;

unit conjointly releasably Aengaging `Vthe `upper cartridge with saidiupper. terminal` said latching means: being movable, relative to said unitair@ permit withdrawal; from/said' upper"tierminal,.zand.

, a pair of fuse links eachk located in onefof said' cartridges: vand serially connected, said leaching; means: being controlled byV each of'said.-fuseflinksy through` the con-joint action of said means.

2. In a fuse structure including upper and. lower relatively spaced insulated:r terminals, a fuse unitl bridging said terminals.. and comprisY ing va pair of` fuse cartridges in. endy to endizzrela.- tion-andi each open for expulsion cfwgasesl there.- ini at its. opposite. end, means. connecting fthe ad jacent .ends of' said! cartridges andi forming :a closure, a fuse link-in each of'saidcartridges: electrically connected in. seriesito .the other :bysaid means, and latching meanssat each'end'r of.' said unitconjointly holding said unit electriv cally connected to said; terminals, said` latch.-` ingl umeans being operatively controlled" by each. offsaid fuse links -through the conjoint action of saidflatchingmeans.

3'. In -a lfuse. structure including upper and. lower relatively spaced insulated terminals, a fuse uni-t pi-votallymounted.l onr said 'lower `:terminal andlatchedto said upper'terminal',fsaiduunit being open at oppositegends for .the expulsionot gases therein and 'being closed' intermediatefits. end-s. tolform separate-arcing chambers, saidunit. having a pivot mountingA comprising afsuprrerting lever pivoted on said unit and on said lo'wer terminal and having a latching lever pivoted on said unit adjacent said upper terminal for latching engagement therewith, a first fuse link in one of said chambers restraining said support ing lever, and a second fuse link in the other of said chambers restraining said latching lever.

4. In a fuse structure including upper and lower relatively spaced insulated terminals, a fuse unit pivotally mounted on said lower terminal and latched to said upper terminal, Said unit being open at opposite ends for the expulsion of gases therein and being closed intermediate its ends to form separate arcing chambers,

7 said unit having a pivot mounting comprising' a supporting lever pivoted on said unit and on said lower terminal, a first fuse link in one of said chambers restraining said supporting lever, and a second fuse link in the other of Vsaid chambers electrically connected with said upper terminal.

"5. In a fuse structure including upper and lower relatively spaced insulated terminals, a fuse unit pivotally mounted on said lower terminal and latched to said upper terminal, said unit being open at. opposite ends for the expulsion f gases therein and being closed intermediate 'its ends to form separate arcing chambers, said unit having pivot means affording movement relative to said lower terminal to withdraw the latched end of said unit from said upper vterminal in a direction longitudinally of said unit, 'a first fuse link in one of said chambers restraining said unit against said movement, and a second fuse link in the other of said chambers electrically connected to said upper terminal.

6. In'a fuse structure including upper and lower relatively spaced insulated terminals, a fuse unit pivotally mounted on said lower terminal and latched to said upper terminal, said unit being open at opposite ends for the expulsion of gases therein and being closed intermediate its ends to form separate arcing chambers, said unit having pivot means affording movement relative to said lower terminal to withdraw the latched end of said unit from said upper terminal in a direction longitudinally of said unit and said unit having a movable latching member mounted thereon adjacent said upper terminal for engagement therewith, a first fuse link in one of said chambers restraining said unit against said movement, and a second fuse link in the other of said chambers restraining said latching member.

' 7. In a fuse structure including a pair of spaced insulated terminals, a fuse unit bridging said terminals and comprising a cartridge having a plurality of arcing chambers and a plurality of fuse links each respectively located in one of said chambers and connected in series with each other, each 'of said fuse links having a buttonhead terminal, said buttonhead terminals forming a closure for each of said arcing chambers, means joining-said arcing chambers and holding sai-d buttonhead terminals in a contiguous relation- Ship, a lower supporting and contact structure including a flipout mechanism for said fuse cartridge, an upper latching and contact structure including a flipout mechanism for said fuse cartridge.

8 In a fuse, a pair of spaced fixed terminals, a'cartridge open at both ends normally bridging said terminals and pivotally supported at its lower end, said cartridge being movable on its pivotal support and comprising an upper and a lower tube, a fuse link in each of said tubes, one of said fuse links being of a lower ampere rating than the other of said fuse links, each-of said fuse links having a buttonhead terminal, means joining said upper and lower tube and holding said buttonhead terminals in end to end electrical contact, said fuse links including each a exible leader projecting out of opposite ends of said cartridge, means disposed respectively at the ends of said cartridge for anchoring said leaders individually, a latching means controlled by the fuse link in said upper tube carried by said cartridge at its upper end for releasably engaging a contiguous xed terminal and maintaining said cartridge in latched engagement with one of said contiguous xed terminal, the fuse link in said mally bridging said terminals and operative tor drop out of bridging relation thereto, said cartridge being open at both ends and comprising a pair of arcing chambers, each of said arcing chambers containing a fuse link, each of said fuse links having a buttonhead terminal forming closure for each of said arcing chambers at the intermediate section of said cartridge, a clamp-y ing sleeve joining said arcing chambers and holding said buttonhead terminals in a contiguous relationship, said fuse cartridge having a lipout mechanism at each of its opposite ends, whereby two distinct fuse units, each having an independ-l ent means of operation, are comprised in a single fuse structure.

10. A fuse unit for bridging spaced insulated terminals, said unit comprising a pair of expulsion tubes in end to end relation and reach having a contact at its open end, a pair of fuse links each located in one of said tubes and having a buttonhead contacting the other buttonhead and a flexible lea-der connected with one of said contacts, said -buttonheads jointly forming a closure for adjacent ends of said tubes, and a clamping sleeve joining said adjacent ends of said tubes and holding said buttonheads in contacting engagement.

RALPH H. EARLEL REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Schultz Dec. 12. 1944

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