US2433666A - Electric circuit interrupter - Google Patents

Description

Dec. 30, 1947. B, R, HERMANN 2,433,665

ELECTRIC CIRCUIT INTERRUPTER Filed April l5, 1944 Benjamin T2. Hermann,

His ttwney.'

Patented Dec. 30, 1947 .ELECTRIC CIRCUIT INTERRUPTER v'Benjamin R." Hermann, Lanesborough, Mass., assgnor to=GeneraliElectric Cmpany,a corporation Vf New 'York Application..April-15,` 1944, Serial No. 531,181

`2' Claims. (Cl. 20o- 114) .My invention relates to ,electric circuit interrupters, and more particularly to Yan expulsion type circuit interrupter such las a' fuse cutout, for use in distribution circuits, havinga much higher interrupting. capacity than similar.. interrupting devices used heretofore.

Fuse cutoutsof variousiformshave been .eXtensively used for protecting and controlling electric distribution circuits. Devices of thissortgenerally have a housingl provided witha frontopening with a coveror "doori hingedtofthehousing, for closing thisfront opening. Usually apair .otterminals, or contacts, `are Ymounted -withinthe housing and a fuse tubeis .mountedon thecoverand provided 4with .contactsto engage the contacts` or terminals vin the' housing when .the cover .is closed. Such cutouts are alsogenerally yprovided with means for indicating whether or not fthe circuit interrupting device. has operated.

My invention is. concerned with anelectric circuit interrupting device, 1or cutout, .havinga considerably higher. current .interrupting capacity than similar rdevices .used heretofore. fIn .the prior art circuit interrupters of .the expulsion type have been limited as kto cur-rent interrupting ability, first by inability to. preventrashoveri between ythe externally mounted. conductiveparts of .theexpu-lsion tube, second by inability to` withstand lthe re coil forces attendant upon theexpulsion action and third by mechanical.,ruptures-trength Aofthe fuse tube. It is an object of vmyinvention to provide a device. more nearly oronlylimitedias.to current .interrupting ability Aby 'the .mechanical strength of the vfuse tube whichcanbe constructed with great, resistance to mechanicalrupture.

It is another object of my invention.,=toprovide a new and improved circuit interrupting device with greatly increased interrupting4V capacity.

It is another object of my invention to provide a new and improved formof gas barrier for preventing4 arc -over` between`v conductivev .partsY or ,a circuit -interrupter incorporating a circuit .interrupting felement of the" expulsion type.

It fisanother-fobjectA ofmy invention toY provide anew and improved resilient mounting arrangement -for the covers or doors oiiuse'cutoutr housingsj so .asfto Y' eliminate any' dangerA of breakage thereof.

, Furtherv objects :andV advantages or my invention .will become-apparentes the 'following'de-f script-ion'proceeds and the features of novelty whichv characterize-my invention willwbe pointed out'. withf: particularity: iin .fthe-claims r`'annexed to and Viormingza..part yof this specification.

5 For a: better understanding fof my inventionA ref-v erence may be had to the accompanying drawing in which Fig. 1 is a side elevation, partly in section, of' an electric circuit interrupter of the fuse cutout type embodying my invention, Fig. 2 is a View taken on line 2--2 ofFig. 1, Fig. 3 is a View taken 0n line 3-3 of Fig. l, and Fig. 4 is a View taken online 4-4 of Fig. 1.

Referring now to the drawing, I0 indicates-a housing or casing of porcelain or similar weatherproof insulating material having an integrally formed electric creepage barrier I D which separates two stationary terminal assemblies generally indicated at II and I2, respectively,r mounted within housing ID. Lower terminal assembly II comprises a U-shaped terminal support I3 which isla'dapted to be cemented into'a pocket i4 in the lower vpart-oi housing IU. This pocket is preferablylled with a cementing material I5 which is pouredl hot into therecess I4. Terminal assembly II further includes a terminal I6 comprising a looped portion -Il into which a conductor maybe insertedand lirmly clamped into electrical engagement with terminal I6 by means of one or more clampingscrews I'I. VIn addition, lower terminal assembly I I includes a U-shaped contact clip I8 and a U-shaped spring backing means I9. The contact clip I8; the spring backing means I9, the terminal I6, and the U-shaped terminal support I3 comprising lower terminal assembly II, are assembled asclearly shown in Fig. 3 and joined as a unitary assembly by means ofsuitable fasteningv means such as rivets, orV asV indicated in Fig. 3 by bolts 2l). The various portions of lower terminal assembly II are assembled as a unit and then suitablycemented into recess I4, thecernent I5 substantially enveloping LU -shaped member I3.

Upper terminal assembly I2, except for the contact clip andV spring backing means, is kidentical inV every respect with lower terminal assembly II and the correspondingjparts'thereof are designatedby the same reference numerals. The contact clip of upper terminal assembly I2 is designated by the referencenumeral IS' and diners from lower terminal assembly I8 mainly in being somewhat' longer, the purposeof which will'become apparent as the followingfdescription proceeds. Similarly, the spring backing means of upper terminal assembly I2 vdesignated'as I9 is very similar to spring backing means I9 of lower terminal assembly II differing mainly in the length thereof. The terminals IB of the upper and lower terminal assemblies may, if "desired, be constructed in the manner of the terminal disclosed in #my-prior copending applicatiom- Serial No.

3 422,901, filed December 13, 1941, now Patent No. 2,393,163 issued January 15, 1946, and assigned to the same assignee as the present application.

To the back of housing or casing lil there is secured a mounting bar 2| 'for attachment of the cutout to a suitable supporting structure (not shown). This mounting bar 2| is preferably cemented into an external recess 22 in the housing I9 in the same manner that the U-shaped ter minal supports |3 are cemented into position.

In addition to terminal supports i3 and mcunting bar 2|, in the embodiment as shown, a pair of hinge supports 23 are cemented into recesses 24 in the lower portion of the housing i3, one on either side of the housing. These hinge sup ports 23, best shown in Fig. 2, comprise hinge pin portions 23 one extending into housing i3 from either side thereof in diametrically oppose-d relationship. The remaining portion of each hinge support 23 is preferably enlarged and knurled in order to insure rm support as by cementing within its associated recess 24.

In order to provide a closure for housing lo I provide a cover or door 25, preferably made of a molded, insulating compound or the like, which includes an integral handle or eye 25 which may be either grasped manually or engaged by a suitable form of switch stick to open and close the cover 25 with respect to housing I9. The cover 25 is provided with a barrier 2'! arranged in opposed relationship with respect to creepage barrier I9', as will be described in greater detail hereinafter. Barrier 21 has an opening 28 therein which only affords sufficient clearance to accommodate a tube 29 or similar housing for a suitable expulsion type circuit interrupting device. Barrier 21 and opening 28 cooperate with tube 29 to provide a relatively long, close fitting joint which to all intents and purposes is gas-tight, when subjected to suddenly increased pressure on one side of the barrier. A suitable sealing means may be employed if desired. I have chosen to illustrate the member 29 as a fuse tube which may be of conventional construction but preferably having greater strength against forces which would cause rupture. A pair of terminals or contacts 30 and 3| are mounted thereon one adjacent either end thereof. The upper terminal or contact 39 threadedly mounted on the upper end of expulsion tube 29 is adapted to be electrically engaged by the contact clips I8 of upper terminal assembly I2, while the lower Contact 3| is adapted to be electrically engaged by the contact clips i8 of lower terminal assembly The fuse tube 29 preferably includes at least a lining 32, see Figs. 3 and 4, of gas evolving insulating material such as horn fiber or the like, which emits large quantities of arc extinguishing gases when subjected to the heat of an electric arc. These gases are expelled from the open lower end of fuse tube 29.

Mounted within fuse tube 29 is the conventional so-.called universal fuse link, of the button head type, which is held in position by cap 33 screwed to upper terminal 39. As will be understood by those skilled in the art, the fuse link mounted within fuse tube 29 includes a fusible element which may or may not be paralleled by a strain wire. The fusible element and parallel arranged strain wire, if one is provided, are usually connected to a flexible conductor adapted to extend out of the open lower end of fuse tube 29. In the drawings only the flexible conductor 34 of the fuse link is visible. In the event of an excess current condition, the fusible element of the fuse link ruptures and the arc drawn is eXtDgllShed tube 29.

on the expulsion principle to interrupt the circuit between terminals I6.

The lower contact 3| associated with fuse tube 29 comprises an enlarged rectangular portion 3| including an opening having suflicient clearance to accommodate fuse tube 29. A U-shaped hinge member 35, best shown in Fig. 3 and comprising hook-shaped ends 36 for engaging the hinge pins 23', is securely fastened as by screws 31 to the rectangular portion 3|' of lower Contact 3| of fuse Fuse tube 29, which is inserted in an opening in lower Contact 3|, is fastened thereto by means of a pin 38 extending both through hinge member 35 and the rectangular portion 3| of lower contact 3|. The exterior of fuse tube 29, as is best shown in Fig. 3, is provided with a slot or recess 39 so that pin 38 acts as a key to securely fasten lower contact 3| to fuse tube 29.

Lower contact 3| is also provided with a rearwardly extending rectangular portion 49 which is adapted to be electrically engaged by contact clips I8 of lower contact assembly Because of this rearwardly extending portion contact clips |8 may be shorter than contact clips I8. The rearwardly extending portion 49 also provides a means for electrically connecting the cable portion 34 of the fuse link extending from the lower open end oi fuse tube 29 to contact 3| and includes a clamping or snubbing device very similar to the one disclosed and claimed in United States Letters Patent 2,267,393, Bennett, granted December 23, 1941, and assigned to the same assignee as the present application.

This rearwardly extending portion 49 includes a trough or recess 4| which at the extreme rear of portion 40 is generally V-shaped, as indicated at 42, the apex of which is open toward the bottom. Pivotally mounted within recess 4| is an operating tongue 43. In securing fuse link cable 34 to the clamping device just described, the cable 34 is looped around the tongue 43 and behind the upwardly extending portion 44 thereof, as best shown in Fig. 3, with the ends of the loop extending out of the open apex of the V-shaped portion 42 of extension 40. The loop of the cable is then drawn as tight as possible around tongue 43. The tension applied to the cable 34 by the fuse link pull-out means to be described hereinafter pulls tongue 43 down into recess 4| so as tightly to clamp the loop of the cable between the edges of the tongue and the V-shaped portion 42 of recess 4|. The greater the tension on the fuse link the more tightly is the cable 34 clamped in the clamp.. ing means described above. With this clamping device it is possible to secure the cable 34 to lower contact 3| very quickly and easily without the aid of any tools.

In order to provide prompt fuse link terminal separation upon rupture of fusible elements, particularly in that range of fault currents where there is not sufficient expulsion action caused by the arc in fuse tube 29, I have provided an articulated fuse link pull-out means which takes up a very small amount of space and yet which provides for a wide separation between the fuse link terminals. This articulated fuse link pull-out means, which is essentially the same as that disclosed and claimed in my prior copending application referred to above, comprises a pair of rigid members or arms l5 and 4G, most clearly shown in phantom in the extended position (Fig. 1). Arm 45 is preferably constructed as a U-shaped member with the base of the U pivotally mounted to U-shaped hinge member 35, as indicated at 41. A suitable coiled spring 48 associated with pivotal .tated'in a clockwise direction aboutpivot 41 with reference toFig. 1. vThe vsprings .48 and 5i! therefore applytension to theiuselinkcable 34 toopverate the clamping means described above. Upon rupture -of the 'fusible .element the articulated fuse link pull-out means is released to pull the lower portion offthe.fuseelinkfrom the end of the fuse tube with high speed. This pull-out means assumes the position indicated by dotted ,lines in Eig. v1 upon rupture of the .fusible element and consequently also functionsas Va suitable indicating means to indicate the condition of the cutout. It 'should bernoted -that the arm 46 includes-a curved portion fltwhich substantially protects the spring 50 from the hot gases-expelled from the fuse tube 2S during the arc extinguishlng operation.

I have found that when fuse cutouts are used to interrupt relatively high currents, the recoil force incident to fuse interruption becomes so great as to cause breakage of the doors or covers 25 which are generally constructed of relatively brittle material as compared to the mechanical strength that can be provided in other parts of the cutout such as tube 29. Heretofore, such cover members have generally been rigidly fastened to the fuse tube or hinge support, The recoil forces due to expulsion action drive the fuse tube 29 upwardly with respect to the hinge pin 23. Since the axis of the fuse tube is not in line with the hinge pins 23 the fuse tube tends to bow which in turn would put a transverse or bowing stress on the cover 25, which being relatively brittle might be broken if means for relieving the stress were not provided. In accordance with my invention, I permit the relatively strong fuse tube 25 to receive the recoil shocks directly from the hinge supports and fasten the door to the hinge supports by means which will relieve the door from the bowing stress. Accordingly, I have illustrated the U-shaped member as b-eing fastened to the lower portion of door or cover 25 by means of screws 5I. I also provide a plurality of coiled springs 52 mounted in recesses 53 in cover 25 for engaging the base of the U-shaped member 35. These springs, three being shown in the drawings arranged like the legs of a tripod with their axes perpendicular to the inner face of cover 25, are maintained in compression by bolts 5I and provide a resilient connection between the door or cover 25 and fuse tube 25 permitting the tube 29 to bow without bowing the door 25.

In order to further cushion door or cover 25 which by action of the recoil forces tends to be slammed closed, I provide resilient inserts 54 and 55, best shown in Figs. 1, 2 and 3. These resilient inserts, which may be sponge rubber or the like, are suitably cemented to the edge of the cover within suitable recesses formed therein. The resilient member 54 is fastened to the upper edge of cover 25, while two resilient members 55 fiO 6 are::provided-oneither sideioficover; 25v near. .the lower portion.;thereof. .y These resilient Imembers 5.4 and u55 `rcushion the door vorrcover 25w with :respect togv housing ILD. vIphave found Lthat with .the above-,arrangement breakage-of door ort-.cover member 25 on cutouts used for interrupting high curren-ts'is substantially eliminated.

lIn accordance withmyfinvention I provldea substantially gasetight 4barrier between upper and lower terminal assemblies I2 and I I,'respec tively, toprevent hot gases expelled from the circuit-interruptingxdevice from bridging these terminalv assemblies and `causing Afailure of Athe .circuit interruptingidevice. The use of barriers or dams for this purposehas been employedhere.- tofore yaszdsclosed and claimedin UnitedStates LettersPatent, Newton et al.,1,694,9'19, granted December 11, 1928, and assigned to the same assignee asfthe present; application. However, such prior use `has depended entirely upon Athe formation .ofa circuitcus or-:restricted ipath Ato prevent thehot ionized gases from: bridging the contacts. Myexperiments proved conclusively that'such circuitous*V or restricted paths are not suiicientto prevent the gases from bridging` the contacts when very large currents are interrupted such. as are permittedwith the high'rupture :strengthzit ispra'ctical -to1louild'into a'fwell constructed tube 29. :Therefore vin order tozapproach even a fair percentage of the interrupting ability of suche fuse tube rLhave found :it :necessary to providea sealingmeansfsuchas va gas-,tight barrier between the upper and lower terminal assemblies I2 and II respectively, thereby dividing the housing into a plurality of chambers between which gas cannot be interchanged upon the application of a suddenly applied pressure. In addition, I have found it necessary to construct the sealing means so as to prevent any electromagnetic radiations, such as ultra violet light, from the arc gases 4or other short wave length emissions from the arc from rendering conducting the air path between the upper and lower terminal assemblies I2 and I I respectively, and thereby causing a ilashover external to the tube 29 with the attendant destruction of the circuit interrupting device, To this end the barrier 21 formed integrally with door 25, is provided with a circumferential groove 51 within which is placed a resilient sealing member 58. This sealing member may comprise sponge rubber or the like and may be of the same material as resilient members 54 and 55, described above. Resilient member 58 is suitably fastened as by cementing or the like in recess 51 so that when door or cover 25 is closed resilient sealing member 58 is in sealing engagement with creepage barrier Ill as best shown in Fig. 4, to eiectively isolate the upper and lower terminal assemblies by a gas tight and light tight barrier and thereby effectively prevent arc-over between conductive parts of the circuit interrupting device. A resilient sealing member 59 which may be made of the same material as resilient members 54, 55 and 51 may be provided as shown in Fig. 2 to insure light tightness between barrier 21 and fuse tube 29. By the expression light tight as used in this specification and claims is meant that the barrier prevents the transmission of short wave length emissions or electromagnetic radiations whether in the visible spectrum or not.

From the above description it will be obvious that the spring-backed contact clips I8 eiTectively latch the fuse tube and consequently cover 25 in the closed position, as well as electrically connect upper terminal I6 with upper contact 30. Door or cover 25 may be rotated about hinge pins 23' and when the cover is sufiiciently opened it may be completely removed from housing l to facilitate replacement of the fuse link associated therewith.

The operation of the Circuit interrupting device of my invention will be obvious in view of the detailed description included above.

While I have shown and described what I at present consider the preferred embodiment of my invention, it will be understood by those skilled in the art that various changes and modications may be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A circuit interrupting device having a housing, a pair of terminal assemblies located in spaced relationship in said housing and each provided with means for receiving a contact of a circuit interrupting device, a tubular casing, means for pivotally mounting said casing in said housing, and a door for closing an open side of said housing, means for preventing shocks incident to operation of said circuit interrupting device rom being transmitted from said tubular casing to said door comprising resilient means including a spring interposed between said door and said means for pivotally mounting said ca-sing in said housing, said spring being arranged to have its axis substantially perpendicular to said door.

2. A circuit interrupting device having a housing, a pair of terminal assemblies located in spaced relationship in said housing and each provided with means for receiving a contact of a circuit interrupting device, a tubular casing, means for pivotally mounting said casing in said housing, and a door for closing an open side of said housing, means for preventing shocks incident to operation of said circuit interrupting device from being transmitted from said tubular casing to said door comprising a first resilient means interposed between said door and said means for pivotally mounting said casing in said housing, and a second resilient means for cushioning said door in its engagement with said housing.

BENJAMIN R. HERMANN.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,684,518 Sandin Sept. 18, 1928 1,900,687 Bash Mar. 7, 1933 2,066,172 Bennett Dec. 29, 1936

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