US3793603A - Fuse cartridges - Google Patents

Abstract

In an electrical fuse cartridge having a hollow insulating body enclosing the fusible element or elements and carrying the terminal heads of the cartridge, the said body is formed of a tubular mass of an insulating material in which a tube is embedded for circulation of a cooling fluid. The tube is preferably of non-metallic nature and it is coiled helically about the axis of the body. In a preferred embodiment the tubular mass is obtained by winding on a mandrel glass threads or ribbons impregnated with a uncured synthetic resin so as to form an inner layer on which the cooling tube may be coiled, then an intermediate layer which fills the helical space which separates the successive turns of the coiled tube, and an outer layer covering the intermediate layer and the tube, the unit thus obtained being thereafter treated to cure the resin in the three layers and to thus obtain a rigid one-piece body with the cooling tube embedded therein.

Description

United States Patent 1191 Fontaine Feb. 19, 1974 FUSE CARTRIDGES Primary Examiner-Gilheany Bernard A.

Assistant ExaminerF. E. Belli [75] Inventor' jg g Fontaine Eculny Attorney, Agent, or Firm-Alexander & Dowel] [73] Assignee: Societe Lucien Ferraz & Cie, [57] ABSTRACT Lyon/Rhone France In an electrical fuse cartridge having a hollow insulat- [22] Filed: July 17, 1972 ing body enclosing the fusible element or elements I and carrying the terminal heads of the cartridge, the 1 Appl' 272l60 said body is formed of a tubular mass of an insulating material in which a tube is embedded for circulation I52] U.S. Cl. 337/166, 174/15 R, 337/185 of a cooling fluid. The tube is preferably of non- [51 I Int. Cl. H0lh 85/04 metallic nature and it is coiled helically about the axis [5 F eld Of 5, 163; l6 of the body. In a preferred embodiment the tubular 174/ 15 R mass is obtained by winding on a mandrel glass threads or ribbons impregnated with a uncured syn- [5'6] References C ted thetic resin so as to form an inner layer on which the UNITED STATES PATENTS cooling tube may be coiled, then an intermediate layer 3,453,579 7 1969 Cinquin 337/166 ux which fills the helical Space which separates the 3,678,431 7/1972 Franklin 337/185 cessive turns the coiled tube and an outer layer 3,713,065 1 1973 Brichant.. 337 166 covering the intermediate layer and the tube, the unit 3,715,698 2/1973 Blewitt 337/185 thus obtained being thereafter treated to cure the 3,693,71 1 9/1972 Zygiel 165/164 resin in the three layers and to thus obtain a rigid one- 3,586,9l7 6/1971 Oates l74/l5 R piece body with thg COQIiEg tube embedded therein 2 Claims, 3 Drawing Figures FUSE CARTRIDGES The present invention relates to fuse cartridges which are used as protecting means against excessive currents and shortcircuits.

' These'cartridges comprise a generally tubular insulating body whose ends are closed by metallic heads which carry the contact members of the cartridge, these heads being connected with each other within the cartridge body by fusible elements (wires or strips) embedded in a mass of arc-quenching material (generally quartz sand).

Under the action of an excessive current or shortcircuit the fusible elements melt or volatilize and the are which appears between the heads is rapidly quenched by the sand or like material. But this are creates a sudden gaseous overpressure or pressure wave which is applied to the insulating body. The latter should therefore have a relatively high mechanical strength to withstand this bursting action. 'j The cartridge body should also evacuate the heat generated by the electric current in the fusible elements. Since the latter should melt under the action of an excessive current, it is unavoidable that under normal conditions they cause a slight voltage drop which is transformed into heat. This heat is'in part transferred to the arc-quenching material and therefrom to the cartridge body. Owing to the thermic conductivityof the fusible elements a noticeable portion of the heat thus generated is also transferred to the said body through the metallic heads of the cartridge.

lt has been proposed to cool the body of a fuse cartridge by means of an appropriate liquid (oil, demineralized water, etc...). For this purpose the cartridge body may be realized under flat form, liquid cooled metallic plates being applied against its sides. But of course such an arrangement is only effective for the outer surface ofthe body and since due to the required mechanical strength the latter should be relatively thick while being madeof an insulating material of low thermal conductivity the temperature gradient across the body wall is relatively important and limits the cooling possibilities. It has further been suggested to cool a fuse cartridge through its heads, but this is only effective in the case of cartridges of'short length.

It is an object of the present invention to avoid the above-mentioned limitations and to provide a liquid cooled fuse cartridge having an insulating body of high mechanical strength with a high heat dissipating capacity.

In accordance with the present invention a hollow body for a liquid cooled electrical fuse cartridge comprises a cooling tube embedded in a tubular mass of an insulating material.

In 'a preferredembodiment the cooling tube, which is conveniently made of a plastic or synthetic material, is coiled helically co-axially to the cartridge body, the tubular mass in which it is embedded being formed of a hardened synthetic resin re-inforced by a fibrous material with fibres extending substantially circularly about the aforesaid axis. The fibrous material used comprises preferably glass fibres.

The invention further concerns a process for the manufacture of acartridge body by winding on a mandrel three layers of a textile material with longitudinallyextending fibres, impregnated with a synthetic resin in the non-hardened state, namely an inner layer on which the cooling tube is coiled, an intermediate layer which 7 fills the spaces between the successive turns of the helically coiled cooling tube, and an outer layer which covers the said tube, the mass thus obtained being thereafter treated so as to harden the synthetic resin and to obtain a one-piece rigid hollow body in which the cooling tube isembedded.

In the annexed drawings:

FIG. 1 is a side view with fragmental section of a fuse cartridge comprising an insulating body according to the invention.

FIG. 2 is a transverse section thereof.

FIG. 3 is a fragmental longitudinal section of a cartridge body according to the invention obtained by winding appropriately impregnated glass threads or ribbons.

. The cartridge illustrated in FIGS. 1 and 2 comprises a tubular insulating body 1 the ends of which are closed by two metallic heads 2, each being in one with a contact blade 3. These heads 2 are secured to the body 1 by any appropriate means not shown. They may be formed for this purpose with an inner portion of reduced diameter which fits into the corresponding end of body 1. Heads 2 are electrically connected with each other by means of a fusible strip 4 which is pleated in accordion fashion within body 1, this strip being embedded in a mass 5 of an appropriate arc-quenching material, such as for instance quartz sand.

In the embodiment illustrated the cartridge body 1 has a more or less elliptical transvers profile and strip 4 is so arranged that the ends of its successive folds may come into contact with the inner surface of the said body. Such an arrangement reduces to a minimum the average thickness of the material 5 which separates the strip from the body wall and enhances heat'transfer between the strip and the said body.

As above indicated the cartridge body 1 includes a coiled tube 6 which is embedded in the thickness of the wall thereof, this tube having outwardly extending ends 7 and 8 through which it may be connected with an appropriate system of cooling liquid. Tube 6 may be made of metal, more particularly in the case of low voltage circuits, but it seems preferable to use a tube made of an appropriate plastic or synthetic material in order to avoid the presence of an electrically conductive member which may cause superficial electrical leaks or facilitate the formation of an outer are between the cartridge heads under the action of the voltage surge which generally appears when the fusible element melts under a heavy current.

The cartridge body may be made of any insulating 'material capable of being moulded or otherwise disposed around the coiled tube. It may more particularly be realized in an appropriate plastic or synthetic material by injection moulding within a mould provided with means for retaining the coiled tube at the proper position in the moulding cavity. In such a case, if the tube is itself made of a plastic or synthetic material, the latter should of course be of such a'nature as to withstand the injection temperature without being damaged, which may be difficult in some cases. Furthermore a hollow body made of an injected material does not generally possess a very high mechanical strength against bursting. ltseems therefore preferable to realize body 1 in the following manner:

There is first prepared a mandrel having the dimensions desired for the inside of the said body. Threads or ribbons of an appropriate material under fibrous form, preferably glass, are then would on this mandrel while being impregnated with a thermosettable synthetic resin in the unhardened state until there is obtained a layer having a thickness a (FIG. 3) equal to the distance desired between the coiled cooling tube and the inner surface of the cartridge body. The cooling tube 6 is then wound on this first layer. If required the tube may be heated at such a temperature that it may be sufficiently deformable for the winding operation. Also care must be taken that it should not flatten, as this is well known in the art. The coiled tube thus realized is then maintained on the mandrel and appropriately impregnated strips of glass threads or ribbons are wound in the helical spaces which separate the successive turns of the tube until the said spaces are wholly filled, which corresponds to the thickness b in FIG. 3. Finally an outer layer of impregnated glass threads or ribbons is wound on the smooth cylindrical surface thus realized so as to form an outer layer having the thickness c which is desired for the insulating material covering the coiled tube.

After treatment of the resin and removal of the mandrel, there is thus obtained a one-piece tubular body of considerable mechanical strength against inner pressure waves and in which the coiled cooling tube is wholly embedded.

Whatever may be the method used for the manufacture of the cartridge bod'y according to the invention, this body may be cooled in a region close to its inner surface, i. e., with a much lower temperature gradient than by means of the known outer cooling plates. If the cooling tube is made of a plastic or synthetic material,

the cartridge body comprises no electrically conduct- .ing part which could lead to the formation of an arc when the fusible element volatilizes under the action of an excessive current or of a short-circuit.

It is to be noted that the cooling tube could be coiled in zig-zag formationincluding straight portions parallel to the cartridge axis and connected with each other in V series by semi-circular portions. In some cases the cooling system could comprise a number of longitudinal tubes connected in parallel between two headers. Of course with non-helical formations the spaces between the coils or sections'can no more be filled by winding threads or ribbons of a fibrous material such as glass, and it is therefore necessary to provide a moulding operation at least'for the thickness b of FIG. 3.

I claim:

1. A process for the manufacture ofa cartridge body,

comprising the following steps:

a. winding on a mandrel a first textile material with longitudinally extending fibers to form an inner layer on said mandrel, said first material being impregnated with an uncured synthetic resin;

b. winding helically a cooling tube on said inner layer with the successive turns being separated from each other by a helical intermediate space;

c. winding helically on said inner layer and in said helical intermediate space a second textile material with longitudinally extending fibers to form a helical intermediate layer which completely fills said space and realizes on said mandrel a substantially smooth peripheral surface, said second textile material being impregnated with an uncured synthetic resin;

d. winding on said smooth surface a third textile material with longitudinally extending fibers, to form an outer layer which covers said intermediatelayer and said tube, said third textile material being impregnated with an uncured synthetic resin;

e. treating the tubular mass thus obtained on said mandrel to cure the synthetic resin in said'inner, intermediate and outer layers and to thus form a one-piece rigid hollow body.

2. In a process as claimed in claim 1, one at least of said first, second and third textile materials comprising glass fibers.

Claims (2)

1. A process for the manufacture of a cartridge body, comprising the following steps: a. winding on a mandrel a first textile material with longitudinally extending fibers to form an inner layer on said mandrel, said first material being impregnated with an uncured synthetic resin; b. winding helically a cooling tube on said inner layer with the successive turns being separated from each other by a helical intermediate space; c. winding helically on said inner layer and in said helical intermediate space a second textile material with longitudinally extending fibers to form a helical intermediate layer which completely fills said space and realizes on said mandrel a substantially smooth peripheral surface, said second textile material being impregnated with an uncured synthetic resin; d. winding on said smooth surface a third textile material with longitudinally extending fibers, to form an outer layer which covers said intermediate layer and said tube, said third textile material being impregnated with an uncured synthetic resin; e. treating the tubular mass thus obtained on said mandrel to cure the synthetic resin in said inner, intermediate and Outer layers and to thus form a one-piece rigid hollow body.

2. In a process as claimed in claim 1, one at least of said first, second and third textile materials comprising glass fibers.

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