US2977445A - Electrical fuse - Google Patents

Description

March 28, 1961 Filed 001:. 29, 1959 E. LANGE ELECTRICAL FUSE 2 Sheets-Sheet 1 March 28, 1961 E. LANGE ELECTRICAL FUSE 2 Sheets-Sheet 2 Filed Oct. 29, 1959 United States Patent ELECTRICAL FUSE Emil Lange, Ville dAvray, France, assignor to Aktieselskabet National Industri, Drammen, Norway Filed Oct. 29, 1959, Ser. No. 849,691

Claims priority, application Germany Jan. 5, 1959 4 Claims. (Cl. 200-120) This invention relates to electrical fuses. Electrical fuses are known wherein the extinguishing of the arc is effected by a flow of extinguishing medium produced by the arc itself; for this purpose in an extinguishing chamber there are two interruption gaps in parallel with one another, the first of which gaps is normally closed by a fusible wire, and there the pressure-producing arc occurs, upon fusing of the wire, but the second gap is constantly open, and the are occurring at the first gap is compelled to bridge the second gap and is extinguished there by the outflowing extinguishing medium.

The operation of such a fuse is quite advantageous, but for some uses of such fuses they must be small, but efficient and of good capacity.

It is often further advantageous if the noise of such fuses upon operating is substantially reduced.

The present invention is therefore intended to provide an improved fuse.

According to the invention there is provided an electrical fuse, comprising in combination an extinguishing chamber of insulating material containing extinguishing medium and provided with outlet apertures on opposite sides, connecting means secured on opposite sides of said extinguishing chamber, a fusible wire connected to said connecting means and passing through said extinguishing chamber, the two ends of said fusible wire being outside said extinguishing chamber and adjacent to a first pair of said outlet apertures and two electrodes secured inside said extinguishing chamber, said electrodes being arranged to form a gap through which said fusible wire passes substantially in a middle plane of said extinguishing chamber, each of said electrodes having an end remote from said gap adjacent to one of a second pair of said outlet apertures, the arrangement being such that upon the flow of excessive current said fusible wire melts and forms a first are extending between the one and the other of said first pair of outlet apertures and generating pressure in said extinguishing medium, a

second arc bridges said gap, and third and fourth arcs are formed one in each of said second pair of outlet apertures between said electrodes and said connecting means, said first and third and fourth arcs being subjected to the action of extinguishing medium flowing through said outlet apertures. Preferably the ends of saidfusible wire are at distances from said gap greater than the distances between said ends of said electrodes and said connecting means. In an advantageous construction said connecting means comprise contact blades and anchor rods secured to said contact blades, said fusible wire being secured to said anchor rods. The connecting means may comprise caps forming quietening spaces through which said extinguishing medium flows after leaving said outlet apertur'es.

Further and optional features of the invention appear from the following description and the accompanying drawing. I

By way of example'a fuse according to the invention is illustrated partly diagrammatically in the accompanying drawing, wherein,

Figure 1 is an elevation partly in section on the line II of Figure 2,

Figure 2 is an elevation partly in section on the line IIII of Figure 1, and

Figure 3 is a view in section on the line III--III of Figure 2.

The illustrated fuse comprises an extinguishing chamber 1 of insulating material in which are secured two electrodes 2 and 3 of which the parts 4 and 5 form a specific gap. These parts 4 and 5 and the gap are substantially in the middle horizontal plane of the extinguishing chamber 1, and the gap is between two outlet apertures 6 and 7 and is passed through by a fusible wire 8.

Ends 9 and 10 of the electrodes 2, 3 are adjacent to outlet apertures 11 and 12 of the extinguishing chamber 1.

The overall height of the two electrodes 2 and 3 together is equal to the internal height of the extinguishing chamber 1.

The fusible wire 8 is secured to anchor rods 13 and 14 with ends adjacent to the apertures 6 and 7. The rods 13 and 14 are secured in bores in connection pieces 15, 16.

So that the fusible wire 8 is introduced correctly into the extinguishing chamber 1- and the ends of the rods 13 and 14 are situated at the desired distances from the openings 6, 7, the rod 13 has an abutment head 17 and the bolt 14 has a' screw thread recess 18. By means of a guide pin (not shown) screwed into the recess 18 the fusible wire 8 is easily introduced into the extinguishing chamber 1 and it is located by the abutment head 17 in the correct position. After securing the rods 13, 14 the guide pin is removed.

In order to prevent welding of the rods 13, 14 in the bores of the connection pieces 15, 16, insulating tubes 19, 20 are provided.

The connection pieces 15 and 16 are advantageously integral with contact blades 21 and 22 respectively.

On the contact blades 21, 22 are secured caps 23, 24, which clamp the extinguishing chamber 1 by means of apertured plates 25 and 26.

In the caps 23, 24 are tubular inserts 27, 28, forming quietening spaces 29, 30 and 31, 32 which are in connection through holes 33, 34, respectively. p

The quietening spaces 29, 30 have openings 35, 36 forming connections to atmosphere.

Due to the arrangement of the spaces 29, 30 and 30, 31 the pressure extinguishing medium issuing from the extinguishing chamber 1 cannot flow away immediately into atmosphere, but is bafiled and quietened.

The caps 23, 24 are held together by a cylinder 37 of insulating material.

The illustrated fuse operates as follows upon the passage of excessive current.

On the melting of the fuse wire 8 a first are burns between the rods 13 and 14 and produces a very great rise of pressure in the extinguishing medium in the chamber 1. This first arc gives rise to a second are which bridges the gap between the parts 4 and 5 of the electrodes 2, 3 while a third are is formed in the outlet aperture 11 be tween the end 9 and the plate 25 and a fourth arc is formed in the outlet aperture 12 between the end 10 and the plate 26.

Thus firstly a great pressurerrise is produced by the long first arc, which pressure rise immediately brings about a fiow of extinguishing medium through the first pair of apertures 6, 7 and the second pair of apertures 11, 12. v

The roots of the first are on the rods 13, 14 are exposed to the flow of extinguishing medium through the first pair of outlet apertures 6 and 7; and thus the long first arc is quickly quenched, but due to the form of the electrodes 2, 3 only the short second are now burns in the extinguishing chamber 1 between the parts 4, and produces a small additional rise of pressure. Since the spacing of the ends 9, 10 from the plates 25, 26 is very small, and since these plates 25 and 26 are at the same potentials as the rods 13 and 14 respectively, arcs now burn only in the outflow apertures 11, 12 and in the gap between the parts 4, 5.

The short third and fourth arcs are easily extinguished by the outflowing pressure extinguishing medium and thus the current is etficiently broken.

Thus by the described arrangement the arcs are subjected to a very eflective flow of pressure extinguishing medium first on the rods 13, 14 and then at the extinguishing points 9, 25 and 10, 26. Thus four streams of extinguishing medium are directed on to the arcs from the beginning of the quenching action.

The outflowing pressure extinguishing medium passes first into the quietening spaces 31, 32 and then flows through the holes 33, 34 into the quietening spaces 29,

30, in order then to pass to atmosphere through the holes 35, 36. The noise of operation of the fuse is very greatly damped by this guidance of the outfiowing extinguishing medium.

The top of the abutment head 17 can be covered with appropriate colour to indicate the nominal current-cart ing capacity of the fusible wire 8.

Air or other gas or an inert powder or liquid can be used as, extinguishing medium,iwith conventional means for retaining the medium in the chamber 1 as necessary.

I claim:

1. An electrical fuse, comprising in combination an extinguishing chamber of insulating material containing extinguishing medium and provided with a plurality of outlet apertures in each of two opposite sides, connecting means secured on said two opposite sides of said extinguishing chamber, a fusible wire connected to said connecting means and passing through a first pair of said outlet apertures and extending rectilinearly through said extinguishing chamber, the two ends of said fusible wire being outside said extinguishing chamber and adjacent one to each of said outlet apertures constituting said first pair of said outlet apertures, and two electrodes secured inside said extinguishing chamber, said electrodes having parts which terminate opposite one another on opposite sides of said fusible wire substantially in a middle plane of said extinguishing chamber perpendicular to said fusible wire so that said parts form in said middle plane a gap through which said fusible wire extends spaced from said parts, each of said electrodes having an end remote from said gap adjacent to one of a second pair of said outlet apertures, the arrangement being such that upon the flow of excessive current said fusible wire melts and forms a first arc extending between the one and the other of said first pair of outlet apertures and generating pressure in said extinguishing medium, a second arc bridges said gap, and third and fourth arcs are formed one in each of said second pair of outlet apertures between said electrodes and said connecting means, said first and third and fourth arcs being subjected to the action of extinguishing medium flowing through said outlet apertures. I

2. An electrical fuse as claimed in claim 1, said connecting means comprising contact blades and anchor rods secured to said contact blades, said fusible wire being secured to said anchor rods, one of said anchor rods comprising an abutment head facilitating correct positioning of said fusible wire and the other of said anchor rods being provided with a screw-threaded recess to receive a guide-rod facilitating insertion of said anchor rods and fusible wire.

3. An electrical fuse as claimed in claim 1, said connecting means comprising caps forming quietening spaces through which said extinguishing medium flows after leaving said outlet apertures.

4. An electrical fuse as claimed in claim 1, the ends of said fusible wire being at distances from said gap References Cited in the file of this patent UNITED STATES PATENTS 2,854,551 Lange Sept, 30, 1 958 FOREIGN PATENTS 1,095,668 France necrzz, 1954

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