US2276899A - Circuit interrupter - Google Patents

Description

March 17, 1-942 J. MfWALLACE CIRCUiT INTERRUPTER Filed Aug. s, 1938 Fig. 2

w l mm 7 y 3 s 8 Y m8 J m Km Q my .3 (WWII/ A WITNESSES: W W Wm 5m ATTORNEY Patented Mar. 17, 1942 James M. Wallace, North Braddock, Pal, signalto Westinghouse Electric a Manufacturing Company, East Pittsburgh, Pa a corporation of Pennsylvania Application August s, 1938, Serial No. 222,815 8 Claims. (on. 200417) This invention relates to circuit'interrupters, and more particularly, to fuse devices of the type embodying a. spring biased contact member normally held In closed circuit position by a Insible element and adapted, upon fusion of this elemeet, to draw an are into an axe-extinguishing chamber.

In the patent to H. H. Falmoe, llo. 2,095,736, issued Dctoloer 12, 1937, ls shown and described use structure of the aforesaid type in which. a rmg-blesed contact rod ls held in. current-com 1 of low sesisteuce and 2mvolee; or strep secured tolcw melt-leg; cc eolsler, one"; the om ctlon :cuce and sewes race;

eve she cellos. of the Yale-slag tube.

so proe'lcle is positive fuse operclzion .e occussence of e orcdetermlncd over is essential. she strep menisci-s sees me fusible joins so es no silvers the cur= borough the high resistance steam member which, clue to its lower current-coming copcclt'y, fuses a, relatively shortiutervel of time, therel zy pesmltting the sprlng hissing means to drew me concoct reel through the arc passage to esiasblish so are therein. As set forth in she aforesaid potent, positive seporation of the strap elemcms upon fuslom of the soldered joint slserebetweeu is obtained by constructing either of chase elements, or both, of bimetol' and arranging she elements with respect each other, so that when located by the load current, the two elements deflect away from each other. 7

The requlrmg biasing force to cause positive element separation mes. in accordance with the alcove pet-ens, also be obtained by making the strep elements or st least one of them, of spring m&l)lli&l, which places a predetermined bias upon the elements tending to cause separation.

2 have discovered that by constructing she strep elements of ordinary 'conduetlne; materiel. end. screw-loo" them in conjunction wlth the strain. member so that the letter causes she sprees biased contact coal to exert a smell but conslsenl: lateral closing force tending to move the elements egcsrt. metexielly improved results may be ob mined since the fusible solder 50ml; between the steep elements is iree 'ZIOlIl excessive mechanical slsmlu wl'lich may under certain conditions occur the lz-lmeiial construction to cause mocking cl lole is constant in that the biasing force ve contest; roe through J 10f; fiependeni; u con spring means mos are cee sclcleccsl losi'cle of the ljllbllial." member is c fuse refill quired to carry current and which may, due to the heating effect of the current, loose their tension otter longperlods of use.

It is an object of my invention to provide a use device having a fusible element which is more reliable in operation than devices heretofore known in the mt.

A further object of my invention is the provision of on improved fusible element for fiuse structures which is capable of being calibrated to wlshlc, closer limits than structures of the prior ell.

.t lcovher object of my lm entlon is the provision of e fusible element for fuse device, the structural arrangement of which pem'its use use of a, wide sense fusible metericls whereby better control oi she slowing cherccterlstlcs of sloe lose ole vlccs be obtained.

specif c object of invention device the time lime means emclcyecl so move con I will vise him 9. for drawing on ere therein she ,l w successively sllole connectors, the one so lose consisting of two main currentwerrying members joined by e. fusible metal end the one last to Ease serving as e stmin elementwhich is disposed out of alignment with the spring-closed conductor so as to orooluce a small but constant lolerel closing force for causing the two current seeming mcmcezrs to separate upon fusion of the lusllole motel.

@ther objects and edvantages relate to details of the fuse structure and will appear more lully' in one following description when read in con section with the eccompanylnc drawing, which:

Figure l is as side elevctlon view partially in secllom. cool with certain portions broken awsv of en expulslon fuse embodying my invention;

Flo. 2 is e cenlrel longitudinal sectional view oi. the unit of the fuse structure shown. in Fig. 1;

Fig. 3 is a perspective view of the fusible con Elections between the movable and the stationary lzermluel elements of my lose device; snol is as sectional View of the lower portion of the refill enlishovm in Fig. 2, showing the relative posltlom cl the fusible conneci'leus following "st siege oi the circuit interrupting operstloo.

m ll-igasre T. of the crowing, the reference numleer cleslgnezes e, tubular member of insulating such sat; eucl thereof for: the l-eceptlon of super cull lower metallic cop members '5 one; 5, r'espec lively. Betweee she cage members l and 9 is dis posed e sultelole weather-proof casing ll of porceloin or the Lilac. 'c-osed Within the lower pars se. of conductor by Elmo, having- & threeclezl portion more clearly shown in section in Fig. 2. The fuse refill unit I3 comprises a tubular casing II of insulating material, such as fibre, having a metallic ferrule member |1 screw threaded to the lower end thereof. The ferrule I1 is provided with an inwardly projecting flange |9 upon which an insulating cylinder 2| is disposed.

Resting upon the cylinder 2| of insulating material is a tubularllning member 23, preferably formed of compressed boric acid or other suitable gas evolving substance. The tubular lining member 23 is held in position within the casing I! by means of a plug 25 of insulating'material screw threaded into-the upper end of the casing. Disposed within the bore of the tubular lining member 23 is a metallic contact rod 21, the lower end of which terminates slightly above the lower end of the lining member 23 and is provided with two connecting conductors 29 and 3|. 'These connecting members are more clearly shown in Fig. 3 and are adapted to be connectedat their upper end to the contact rod 21 and are preferably disposed in a slot 33 provided in the end of the rod 21 and secured thereto by solder and a rivet 35. The lower ends of the connectors 29 and 3| are secured by means of a screw 31 to the ferrule l1.

The connecting conductor 29 comprises two strap-like members 39 and 4| of conducting and relatively stiff material, such as copper or bronze. The member 39 is substantially straight and forms an extension to the contact rod 21, whereas the member is angular in shape, as shown,

having a portion 43 lying substantially parallel with the member 39. The portion 43 is adapted to be secured to the member 39 by means of low melting point solder shown at 45.

The angular m'ember 4| is provided with a slot 41 through which the connector 3| may pass so as to permit the connector 3| to act as a strain member serving to withstand the longitudinal stress placed upon the contact rod 21 when the refill unit |3 is placed within the fuse device. Although the strain connector 3| is preferably constructed of relatively high resistance material such as Nichrome, comprising about 78% nickel and {20% chromium, other suitable materials may be used.

When disposed within the fuse casing, the upper edge of the ferrule H of the refill unit l3 engages an inwardly projecting shoulder 43 of the lower cap member 9 and is clamped in position by a collar 49 screw threaded into the lower end of the lower cap member 9, which collar in turn engages the lower end of the ferrule H. The upper and screw threaded end of contact rod 21 is connected to a spring support block to which a tensioning spring 33 is attached at its lower and and which spring is secured at its upper end to the upper terminal cap 1, thereby placing the contact rod 21'and the two fusible connections 29 and 3| under tension. Details of the connections between the refill unit l3 and the upper cap terminal 1 are more clearly set forth in the patent to H. L. Rawlins, No. 1,976,- 634, issued October 9, 1934.

Insofar as the instant application is concerned, it will be sufllcient to state that the upper cap terminal Tmakes electrical connection with the spring support member 5| by means of a'flexible shunt 55. Thus, the electrical circuit through the fuse devicejas shown in Fig. l, proceeds from the upper cap terminal 1 through the flexible shunt 55, member 5|, conductor rod 21, fusible connections 29 and 3|, ferrule l1, and terminates with the lower cap member 9.

21 is of somewhat smaller diameter than the bore through the lining member 23, so as to permit a predetermined amount of lateral movement within the lining member. The connecting members 39 and 4| when in the Joined condition, are so disposed with respect to the strain connection 3| and the contact rod 21 that the latter is maintained adjacent the right side of the bore in the lining member 23, as viewed in Fig. 4.

It will thus be apparent that since the strain connector 3| is disposed out of alignment with the contact rod 21 and the biasing spring 33 exerts a force longitudinally of the contact rod 21, there will exist a component of. force upon the conductor 39 at right angles to the force tending to move the contact rod 21 through the bore of the lining member 23. When the current through the fuse device exceeds a predetermined value, the conducting members 39 and 4| become heated so as to melt the fusible joint 49 between these members, thereby permitting them to separate and assume the position as shown in Fig. 4, due to the lateral biasing component produced by the biasing spring 33 and the strain connector 3|.

Upon separationof the members 39 and 4| in the manner aforesaid, current through the'device is diverted through the strain'member 3|, which due to its higher resistance and relatively low current-carrying capacity, fuses to permit the biasing spring 53 to draw the contact rod 21 upwardly through the core of the tubular lining member 23 and to establish an arc therein. The action of the arc upon the side walls of the lining member 23 produces large quantities of gas, which cause the arc to be-extinguished by expulsive action, which is well understood in the art.

From the foregoing, it is apparent that the arrangement of the fusible connecting members I 39, 4| and 3| is such that a small but constant The contact rod lateral biasing force supplied by the main spring 53 is placed upon the member 39 to cause it to separate from the cooperating member 4|. The fact that this biasing force is small and is of constant magnitude throughout the life of .the fuse device, makes it possible to select a soldering material for joining the connectors 39 and 4| which will give the most desirable operating characteristic. In other words, the fusible solder Joint need not withstand as high a mechanical strain as is in some instances encountered when the members 39 and 4| are constructed of bimetal or of spring material.

Although I have shown and described a specific fuse structure, it is to be understood that the same is for the purpose of illustration and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, a pair of relatively rigid conducting members normally secured together and separable upon the occurrence of predetermined conditions, biasing means for applying a force to move one of said conducting members longitudinally, and means cooperating with said biasing means to cause said biasing means to move said conducting members laterally apart prior to substantial movement of said one member longitudinally, and said conducting members being rigid with respect to the force exerted by said biasing means in a direction to move said conducting members laterally apart.

2. In a circuit interrupter, a pair of conduc-

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