US1157919A - Electric cut-off. - Google Patents

Description

W. C. ARSEM.

ELECTRIC CUT-OUT.

APPLICATION FILED FEB. 26. 1914.

Patented not. 26, 1915.

Inventor: William Ofi'rsem, y DZ MU; OF'TIGH.

Witnesse mdQ s @m W UNITED STATES FATE i WILLIAM C. ARSEM, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION QF NEW YORK.

ELECTRIC GUT-OUT.

1 157 919 Specification of Letters Patent. Patented Oct 26 1915,

I Application filed February 26, 1914. Serial No. 821,290.

To all whom it may concern: gree of heat which it may undergo in ordi- Be it known that I, VILLIAM C. AnsEM, a nary service, water of hydrated silicic acid citizen of the United States, residing at that is so held or combined and is liberated Schenectady, in the county of Schenectady, onlyat temperatures corresponding to the 5 State of New York have invented certaln blowing point of the fuse seems to be benenew and useful Improvements in Electric ficial in causing prompt blowing, absorbing Cut-Outs, of which the foll wing is a speciheat, and keeping the temperature within fication. reasonable limits.

My invention relates to electric cut-outs The silicic acid with which I have ob- 10 in which the opening of a circuit under contamed the best results is the hydrated acid ditions of excessive current flow is brought commercially known as Mercks silicic acid, about by overheating of a fusible conductor" pure, wet process (made, I believe, by addtraversed by the current. lng hydrochloric or other acid to a solution It is the. aim of my invention to secure suof sodium silicate or watenglass, washing perior functional and operating characteristhe precipitate, and drying it at a moderate 70 tics in such cut-outs by means of a special temperature) whose total water content as environment for their fuse conductors. found by heating at a relatively high tem- Among the advantages thus obtainable I perature until the weight becomes constant may mention special adaptation for high is about l l.l6%, corresponding to the forvoltages and small capacities; accuracy and mula 11 551 9 or 2810 1-1 0. As this ma- 7 reliability in the realization of intended caterial contalns an amount of very fine parpacities and circuit opening or blowing tlcles or dust sufficient to annoy those workcharacteristics; substantial uniformity of ing in the room Where the fuses are filled fuses constructed alike within the limits of with. it,, I usually prefer to prepare it for commercial conditions and methods of manuse by' shaking it thoroughly on a sieve of ufacture; delicacy as regards the percentage very fine bolting silk, re ecting all that difference between the current which the passes the sieve. fuse will carry. continuously and that on For the convenience of those desiring 'to which it will be sure to blow; and prompt, use my invention, I have hereinafter illus- I 30 quiet blowing when the fuse conductor melts trated and described several fuse structures or volatilizes. of the inclosed safety type in which silicic I. have found that the advantages which acid may be used by way of packing or filler I have mentioned and various others can about the fuse conductor, and I have given be secured when the fuse conductor means is dimensions and other data relating to their 5 surrounded with loose particles of silicic construction for particular capacities. It is so acid in a light, voluminous form, preferably to be understood, however, that this inforrather finely granulated or even powdered. mation is merely intended as an aid in the Dense, heavy silicic acid or silicic anhydesign of fuses according to the needs of drid-as flint sand or ground quartz, for eX- particular services, since the utility of silicic 4' ample,-is altogether unsuitable; for when acid about a fuse conductor does not in the a fuse conductor surrounded by such mateleast depend on the use of any particular rial is heated nearly or quite to its melting structure. a point by a progressively rising current, it In the accompanying drawings; Figure 1 will usually heat the surrounding material is a longitudinal sectional view of one form a5 enough to render the same conductive beof fuse structure that gives good results with fore it is itself ruptured, and the gradual a silicic acid filler such as above described.

growth and cumulatively increasing conduc- Fig. 2 is a Sl1l1llal.VlQW showing a modified tivity of the independent path thus formed construction.

for the current will result in an ultimate In Fig. 1 I have shown a simple construcrise thereof far beyond the intended maximum capacity of the fuse. While moisture not firmly held as water of crystallization or otherwise combined is undesirable as tending to cause the silicic acid to densify 55 or even coagulate or harden under the deof moderate capacities. As here shown, the fuse conductor means 1 is arranged within a cylindrical tube or shell 2 and is connected to ordinary terminal caps 3 by threaded parts 4 soldered thereto at 5 and in holes in 119 tion especially suitable for inclosed fuses v the caps at 6. Each of the caps 3 is removably secured in place by screws 7 that extend through it and through the walls of the tube 2 and are thfie aded into the ends of a U-shaped part 8 self threaded on the part 1 and held in place by a lock-nut 9. The Mercks hydrated silicic acid filler can be properly packed by merely pouring ltcln and slightly shaking or tapping the tubd12, care being taken to have the tube quite full when scaled up. The conductor means 1 of a fuse thus constructed and filled suitable for circuits of as high as 2400 volts and adapted to carry 30 amperes and blow within one minute on 50% overload may consist of a single strip or ribbon of commercial zinc 8 inches long, 3 mils thick, and 1 inch wide, with a short middle portion narrowc I as shown at 10 to inch, and the casing may be a fiber tube about 1 inch in externaldiameter, 1 to inch thick, and 12 inches long.

In Fig. 2 I have shown an ordinary and simpler construction suitable for inclosed fuses of relatively small capacities. Except in the case of very small fuses, I usually prefer to make the fuse conductor 11 in the form of a very thin ribbon, just as in the fuse shown in Fig. 1, since I find that if the conductor 11 is thin enough in proportion to its width the very material deformation toward a cylindrical form that it suffers as the result of capillary force or surface tension when it melts causes it to blow more promptly and sharply than would otherwise be the case. Contrary to what might, perhaps, be expected, the silicic acid fillerdoes not seem to interfere with this capillary effect, but rather tends to break the molten ribbon by its presence and hasten the blow- For rated capacities not exceeding about -10 amperes, superior results can be obtained by making the fuse conductor 11 of metallic cadmium. Such a fuse conductor to carry 4. amperes and blow almost instantly on overload, suitable for 500-volt circuits or for lower voltages,; can be made of ribbon of commercial cadmium 2 mils thick, mils wide, and 4?; inches long. The casing for this conductor may be a fiber tube about 5 inch in external diameter and 1 g inch thick,

the filler of prepared silicic acid such as above mentioned being packed as in the case of the fuse of Fig. 1 and with the same precautions. For 250-volt circuits and a blowing point of thesame percentage overload, a 2 ampere fuse can be made of about 1% inches of 2 mil ribbon 26. mils wide, the fiber tube casing being aboutfg, inch to inch in external diameter and inch or more thick, and the filler being unsieved hydrated silicic acid to the amount'of about 0.78 gram. Agaim'for circuits of about 250 volts or less, a fuse tocarry 0.4 ampere and blow almost atended to at instantly on 0.55 ampere can be made with cadmium wire 22 mils in diameter and about 11 inches long, the casing being of the same fiber tubing as that of the 2 ampere fuse, and the filler being likewise unsieved hydrated silicic acid.

The uniformity and the action of fuses such as illustrated in Figs. 1 and 2 are improved by careful centering ofthe fuse conductor means in the casing, by uniform packing of the filler, by not using too much filler or packing it too tight (the more or the tighter the filler, the longer the blowing time of the fuse), and by otherwise taking care that the heat capacity and heat insulation shall be uniform both all around the conductor and throughout its length,as well as, also, in different fuses. If these points are all, it will be found that the silicic acid filler will not form an independent conductive path f-or the current under any circumstances,not even, for example, in fuses of as high as 100 amperes capacity for direct current circuits of Voltages as high as 1800,and that when the fuse blows this filler acts to diffuse the liquid or va orous metal and so counteracts any explosive tendency.

From the foregoing description it will be evident that besides afiording various functional and practical advantages such as above set forth, my invention greatly enlarges the field of usefulness for ordinary fuses; for whereas with fillers such as were previously used, fuses for direct current circuits were practically limited to voltages not exceeding 1200, and were found more or less unsatisfactory even for this voltage, with my silicic acid filler such fuses can readily be used on direct current circuits of double this voltage. Incidentally, it may be remarked that with a silicic acid filler and a cadmium fuse conductor a reliable, delicate fuse of as low as 0.4; ampere rated capacity can readily be made, as already described; whereas formerly, with'other fillers and fuse conductor metals, the so-called one ampere fuse, deemed the smallest practicable, might when new carry anywhere from its rated blowing current of 19 amp'eres up to 3 amperes 'or over without blowing, and after being several times subjected for a few seconds to currents approaching its initial blowing current might even stand five amperes or 2. An electricifuse having its fuse condue clrated s1l1c1c form.

5 tor surrounded by 100 d hydrated subs tion of one molecule of and in a light,

Gopies of this 1:

tor surrounded by loose particles of hyacid in a light, voluminous dry p voluminous form.

s a packing or filler for electric fuses,

atent may be obtained for five cents each, '0 Washington, D. Q

In Witness Wh hydrateci silicic acid in t a ticles, light this 25th day Witnesses ereof I have form o1 loose, it) and high ly voluminous. hereunto set my of February 1914.

WILLIAM G. ARSEM F. CASPER ZAPF,

aLEN ORFORD.

y addressing th e Commissioner of Eateuts

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