US2694123A - Gas blast fuse - Google Patents

Description

Nov. 9, 1954 S. R. SMITH, JR

GAS BLAST FUSE Filed Sept. 2l, 1953 United States Patent O GAS BLAST FUSE Sidney- R. Smith, r., Stockbridge, Mass., assigner to GeneralA Electric Company, a corporation ofNeW York' Application September 21, 1953, Serial N0..381,2;72'

2 Claims. Cl. 20G-120) This invention relates to a fuse,- and' moreparticularly, to a. fuse having a blast of gas directed across the electrical arc.

Fuses having a blast of gas directed' against the electrical arc are well known in the art. One form of such a fusev comprises a fuseA tube closed' at one'endand: openI at the other end. Within the. fuse tube is positioned a fuse link having a fusible portion. Adjacent the closed end of thev fuse tube is positioned a cartridge of compressed gas. The interior walls of the fuse tube are constructed out of or' lined with a material which will evolve a gas when subjected to an electrical arc. When an overcurrent occurs in thev fuse link, the fusible portion will melt or rupture. The resultant electrical arc will cause the interior side walls of the fuse tube to evolve a gas which will aid in extinguishingV the electrical arc. Simultaneously', the electrical arc or the hea-t thereof will puncture the gas cartridge whereupon additional gas will be present in the fuse tube to extinguish the electrical arc. In such` a fuse the quantity of gas evolved by the interior side wal-ls of the fuse tube is very large and also very high pressures are built up within the fuse tube. Accordingly, the fuse tube must be constructed to withstand the4 forces of this large quantity of gas and its high pressures.

When a fuse of the type just described is used in a cutout, as the open type cutout wherein the fuse tube is` positioned adjacent to andv mounted on an elongated insulator, the gases produced within the fuse tube are expelled out of the open end of the fuse tube. This eXpulsive action of the gases out of the open end of the tube imposes high recoil forces upon the fuse tube and said recoil forces are transmitted to the insulator which carries. the fuse tube. Since the insulator has a limited strength and withstands recoil forces only of apredetermined value, the current interrupting ability of the cutout is accordingly limited.

It is an object of this invention to provide a gas blast fuse wherein the quantity of gas within the fuse tube and the pressures built up within the fuse tube can. be substantially predetermined and controlled.

My invention comprises a gas blast fuse having a fuse tube closed at one end thereof and open at the other end thereof, a fuse link having a fusible portion positioned within said fuse tube, a cartridge of compressed dielectric gas positioned within said fuse tube, the interior side walls of said fuse tube constructed out of a material which will evolve substantially no gases when subjected to an electrical arc whereby the quantity of gases within said fuse tube and the pressures within said fuse tube upon fusing of said fuse fusible portion can be substantially predetermined and controlled.

The invention will be better understood by considering the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. l is a side view, partly in section, of one form of my invention. Fig. 2 is a detailed side View, partly in section, of the upper portion of the fuse tube shown within Fig. 1. Fig. 3 is a detailed side view, partly in section, of an upper portion of a fuse tube illustrating another 'form of my invention. Like reference numerals throughout the various figures are used to indicate similar Darts.

L Referring now to the drawing and more particularly to Fig. l, shown therein is an open type cutout having an elongated porcelain or other insulating material member 1. The insulator 1 is carried by a pole line or the like from a support arm 2. Mounted adjacent the upper end portion 2,694,123 Patented Nov. 9, 1954 of the insulator 1 is terminal contact hardware comprising a U-shaped resilient latchcontact portion 3 and' a line terminal connecting portion 4. Connected adjacent the lower end portion of the insulator 1 terminali Contact hardware. comprising a hinge Contact portion 5 andi a line terminal connecting portion 6.

A fuse tube 7 having` circuit interrupting means therein spans and electrically connects the upper terminal contact hardware and the lower terminal contact hardware. The fuse tube 7 is closed at its upper endl andi open at its lower end. Fuse tube 7 is pivoted at its lower end to the lower terminal contact hardware by a toggley mechanism comprisingl a clamping member 9- and a generally l.shaped contact 1li. Contact 10 ispivoted' at one of itsl ends tothe clamp 9 and pivoted atits other end' to the hinge element 5. Within the fuse tube 7 is positioned a fuse link 8 which extends out of the open lower end of fuse tube 7 and is tautly fastened to the contact 1G whereby the lower end of the fuse tubev 7 will abut the Contact As will be obvious to those skilledinthe art, when the fuse 11i-nk 8 is ruptured the fuse tube 7 will move downwardlyv and pivot away from the contact iti: Simultaneously, the contact 1i) will pivot away from the hinge S whereupon the fuse tube 7 will be unlatched from latch 3 for drop out movement;

Conventionally, the interior4 side walls of the fuse tube 7` have been constructed out of or lined with a material which will' produce a dielectric gas wheny subjected to an electrical are. Accordingly, when the Euse link 3 is ruptured and an electrical arc is drawn between the broken ends thereof, said electrical arc or the heat thereof will cause the interior Walls of the fuse tube 7 to evolve a gas. Said gas aids in extinguishing the electrical arc and is expelled out of the open bottoneA end of fuse tube 7i This expulsive action causes the fuse tube 7 to recoil axially upward. Therecoil forces imposed on fuse tube 7 are transmitted to insulator 1 through the upper and lower terminal contact hardware, and the recoil force imposed on the insulator 1 tend to fracture it thereby limiting the current interrupting capacity of the cutout.

Referringy now to Fig. 2, shown therein is a detailed side View of my gas blast fuse. in my invention the fuse tube 7 is constructed out of a refractory or inert material. That is, fuse tube 7 is constructed out of an insulating material which will produce substantially no gases when subjected to an electrical arc or the heat thereof. For in stance, fuse tube 7 can be constructed out of porcelain, micalex, steatite, or other like materials.

Positioned on the upper end of fuse tube '7 and c onnected thereto is a cylindrical Contact member 11. Member 1 1 has a central inner cylindrical flange 1 2 formed therein between itsy opposite ends. Contact member 11 can be fastened to the upper end of fuse tube 7V as by threads or the like whereby the flange 172v willv abut the uppermost edges of fuse tube 7. Within the upper end of fuse tube 7 is positioned a cylindrical gas cartridge support 13 carrying a cartridge 16 of compressed dielectric gas. Gas cartridge support 13 has a frusturn-like portion 14 at the lower end thereof and at its upper end support 13 has an outer flange 15. Flange 15 rests upon and is in electrical contact with liange 12. Gas cartridge 16 is supported and accurately positioned by support 13 as by a circumferential groove or indentation 17 in cartridge 16 and an internal circumferentially extending bead 18 whereby the gas within the cartridge 16 will be accurately blasted across the electrical arc.

The upper end of fuse tube 7 is closed by a contact cap 19 which threads down into the contact 11 to force the ange 15 into intimate electrical contact with flange 12 or contact 11. Fuse link 8 is connected to the frustum-like portion by a fuse link fusible portion 20 and strain wires 21. The lower or nipple end of the gas cartridge 16 is closed by a thin seal or disk 22 of fusible metal.

As will be obvious to those skilled in the art, when an overcurrent occurs in the fuse link 8 the fusible portion 20 and strain wires 21 will fuse or melt. Substantially simultaneously therewith the electrical arc or the heat thereof will cause the seal 22 of gas cartridge 16 to be punctured. Accordingly, the compressed gas with- 3 in gas cartridge 16 is now released to be blasted across the electrical arc within the fuse tube 7.

In my invention I prefer to use sulphur hexauoride gas within the gas cartridge 16. This is because sulphur hexafluoride has good dielectric and heat removal characteristics and will effectively cool and extinguish electrical arcs. However, it is obvious that other dielectric gases can be used within cartridge 16. For instance, carbon dioxide can be used as the gas employed to put out the arc.

It will now be apparent that in my invention the amount of gas generated within the fuse tube 7 and the gas pressures built up within the fuse tube 7 can be accurately predetermined and controlled. Substantially no gases are evolved by the interior side walls of the fuse tube 7 and the gases used to snuff out the electrical arc are contained solely within gas cartridge 16. Further, the gas cartridge 1.6 is accurately positioned within fuse tube 7 whereby the gases within cartridge 16 will be blasted substantially directly across the electrical arc within the fuse tube 7. With the volume of gas produced within fuse tube 7 and the gas pressure within fuse tube 7 substantially controlled, the fuse tube 7 need not be made as structurally strong as in conventional gas blast fuses. Accordingly, the costs of my fuse has been substantially reduced over the costs of conventional fuses. The amount of gas within cartridge 16 is preferably just suficient to scavenge the fuse tube 7 and snufl;` out the electrical arc therein. With a decrease in the volume of gas and the gas pressures employed to extinguish the electrical arc within the fuse tube, smaller recoil forces are imposed on the fuse tube 7. Consequently, smaller recoil forces are transmitted to and imposed upon the insulator 1 of Fig. 1 when my fuse is used in a cutout.

Therefore, cutouts employing my gas blast fuse can have a higher current interrupting capacity.

Referring now to Fig. 3, shown therein is another embodiment of my invention wherein the gas cartridge support means is less complicated than the gas cartridge support means of Fig. 2. In Fig. 3 the gas cartridge support means comprises a circular plate or disk 23 having a central opening and tabs 24 formed therein. The tabs 24 are disposed with respect to each other in a frusturn-like arrangement and the vertex of said frustumlike arrangement is directed towards the open bottom end of the fuse tube. The gas cartridge has a frustum-like lower end portion which is disposed within said frustrum-like arranged tabs 24. Otherwise, the construction and operation of the gas blast fuse of Fig. 3 is similar to the construction and operation of the gas blast fuse shown in detail in Fig. 2.

While there have been shown and described particular embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention and that it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

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

1. A fuse comprising a tube closed at one end thereof and open at the other end thereof, a fuse link having a fusible portion within said tube, said fusible portion fusing in response to an overcurrent in said fuse link whereby an electrical arc is established between fused ends of said fuse link, means for introducing a predetermined quantity of sulphur hexauoride gas at a predetermined pressure within said tube to extinguish said electrical arc, said means comprising a cartridge of sulphur hexafluoride gas within said tubular member, said gas releasable from said cartridge in response to establishment of said electrical arc Within said tube, said sulphur hexafluoride gas blasted across said electrical arc to extinguish said arc, the interior walls of said tube evolving substantially no gases when subjected to said electrical arc or the heat thereof.

2. A fuse comprising a dielectric non-gas evolving tube having a fuse link positioned therein; said fuse link consisting only of a flexible metallic conductor, at least one metallic strain wire and one metallic fusible portion, and a metallic cylindrical gas cartridge retaining member having an integral metallic frustum-like part at one endmost portion thereof and an integral metallic annular outer flange at the other endmost portion thereof; one end of said flexible conductor connected to said part by said strain wire and fusible portion, the other end of said flexible conductor extending out of one end of said tube, a metallic cylindrical internally threaded collar having an inner integral metallic annular shoulder therein approximately centrally thereof, the other end of said tube being externally threaded, said internally threaded collar threadably engaged at one end thereof with said externally threaded tube end whereby the endmost edge of said threaded tube end is in engagement with on side of said shoulder, an externally threaded metallic cylindrical closure cap closed at one end thereof threadably engaged at the other end thereof with another end of said internally threaded collar, said flange engaged with another side of said shoulder and clamped between said shoulder and the endmost edge of said closure cap other end, a closed metallic cylindrical cartridge of compressed sulphur hexauoride gas, said cartridge having a circumferentially extending indentation formed in a central portion thereof, said flange having a peripherally extending integral metallic bead formed along the inner perimeter thereof, said cartridge disposed within said retaining member and said bead engaged with said indentation, the end of said cartridge remote from said closure cap having a metallic nozzle-like integral part disposed concentrically within said frustum-like part, said nozzle-like part closed by fusible metal.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,952,734 Ten Brook Mar. 27, 1934 2,429,518 Kyle, Jr., et al. Oct. 2l, 1947

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