US3562691A

US3562691A - Fuse cartridges

Info

Publication number: US3562691A
Application number: US858283A
Authority: US
Inventors: Jean Pierre Cinquin
Original assignee: Lucien Ferraz et Cie SA
Current assignee: Lucien Ferraz et Cie SA
Priority date: 1968-09-27
Filing date: 1969-09-16
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09
Also published as: FR1589221A

Abstract

FUSE CARTRIDGES DEVICES COMPRISING RELATIVELY FLAT INSULATING BODY HAVING PARALLEL PERFORATIONS IN WHICH THE FUSIBLE STRIPS ARE DISPOSED, THESE STRIPS CONNECTING ELECTRICALLY TWO END PLATES DISPOSED AGAINST TWO OPPOSED SIDES OF THE INSULATING BODY TO FORM THE TERMINALS OF THE CARTRIDGE. COOLING PLATES ARE APPLIED AGAINST THE PREFERABLY METALLIZED MAJOR FACES OF THE BODY AND MEANS ARE PROVIDED TO DISSIPATE THE HEAT WHICH THE COOLING PLATES RECEIVE FROM THE INSULATING BODY. THESE HEAT-DISSIPATING MEANS MAY BE IN THE FORM OF WATER-COOLED COILS OR OF AIRCOOLED FINS. IN A MODIFICATION THE COOLING PLATES ARE IN HEAT-CONDUCTING CONTACT WITH ONE OF THE END PLATES, ADAPTED TO BE ITSELF APPLIED IN HEAT-CONDUCTING CONTACT AGAINST A COOLED CURRENT-CARRYING BAR.

Description

J. P. CINQUIN FUSE CARTRIDGES Feb. 9, 197-1 2 Sheets-Sheet 1 Filed Sept. 16, 1969 Feb. 9, 1971 J p. |NQU|N 3,562,691

FUSE CARTRIDGES Filed Sept. 16, 1969 2 Sheets-Sheet 2 WM bu Int. (:1. 110111 85/02 US. Cl. 337-185 9 Claims ABSTRACT OF THE DISCLOSURE Fuse cartridges devices comprising relatively flat insulating body having parallel perforations in which the fusible strips are disposed, these strips connecting electrically two end plates disposed against two opposed sides of the insulating body to form the terminals of the cartridge. Cooling plates are applied against the preferably metallized major faces of the body and means are provided to dissipate the heat which the cooling plates receive from the insulating body. These heat-dissipatting means may be in the form of water-cooled coils or of aircooled fins. In a modification the cooling plates are in heat-conducting cont-act with one of the end plates, adapted to be itself applied in heat-conducting contact against a cooled current-carrying bar.

The present invention relates to fuse cartridges used for the protection of electric circuits or apparatus.

Such fuses cartridges should support in continuous operation the full-load current of the apparatus which they protect and they should blow as soon as this apparatus is liable to be damaged by an overload. These conditions require in practice that the heat produced by the electric current which flows through the fusible element or elements of the cartridge may be easily dissipated. For this purpose it has already been proposed to realize the insulating body of the cartridge under a relatively flat rec-tan gular form, the fusible elements and the arc-quenching material associated therewith being disposed in parallel perforations extending between two opposed sides of the contour of the said body. With such an arrangement the heat flow from an element has only to pass through a limited thickness of arc-quenching material and through an insulating wall also of limited thickness before reaching the outer surface of the insulating body where it is dissipated by convection and by radiation. Experience however demonstrates that the cooling effect which is thus obtained is insufficient in many cases and more particularly when the apparatus to be protected is a semiconductor device provided with additional cooling means, because the heat-dissipating characteristics of such a device are too such different from those of a fuse cartridge of the kind mentioned.

It is an object of the present invention to provide a fuse cartridge wherein the heat generated by the electric current in the fusible elements may be dissipated more easily and more rapidly than heretofore.

Another object of this invention is to provide a fuse cartridge whose heat-dissipating characteristics are substantially similar to those of a cooled semi-conductor device protected by the said cartridge.

According to the present invention in a fuse cartridge comprising a substantially flat insulating body having parallel perforations extending between two opposed sides of the contour of the said body, fusible elements disposed in the said perforations together with arc-quenching material, and electrically conductive end plates disposed United States Patent 3,562,691 Patented Feb. 9, 1971 against the said opposed sides and electrically connected with each other by the said fusible elements, heat-conducting cooling plates are applied in heat-conducting contact against each of the major faces of the insulating body, means being provided for dissipating the heat which the said cooling plates receive from the said body, and one at least of the said end plates being spaced from the said cooling plates.

The heat dissipating means may be formed of tubes or passages associated with or provided in the cooling plates and through which a cooling fluid is circulated, or of aircooled fins carried by the said cooling plates. In the case of a fuse cartridge intended to be mounted on a cooled current-carrying bar, the cooling plates may be integral with the one of the end plates of the cartridge which is adapted to be applied against the bar, the said end plate playing the role of the said heat-dissipating means.

In order to reduce the resistance to the heat flow between the insulating body of the cartridge and the cooling plates, the major faces of the body are preferably metallized, the metallization terminating short of at least one of the opposed sides against which the end plates are applied, and the cooling plates are soldered to the metallized faces. The metal used for the metallization is preferably a fusible metal or alloy such as tin.

In the accompany drawings:

FIG. 1 is a side view of a twin fuse cartridge unit according to the invention, one of the elementary cartridges being illustrated in longitudinal section.

FIG. 2 is a front view thereof with parts in section.

FIG. 3 is a plan view of the unit illustrated in FIGS. 1 and 2.

FIG. 4 is a horizontal section of a modified metallic cooling plate.

FIG. 5 is a perspective view of the insulating body of a fuse cartridge before metallization of its major faces.

FIG. 6 is a longitudinal section of the insulating body with the cooling plates soldered to the metallized faces.

FIG. 7 is a longitudinal section of a cartridge body equipped with cooling plates having air-cooled fins.

FIG. 8 very diagrammatically illustrates the arrangement of the air-cooled fins in a twin fuse cartridge unit.

FIG. 9 is a side view of a fuse cartridge adapted to be carried by a cooled current-carrying bar.

FIG. 10 is a plan view thereof.

Referring to FIGS. 1 to 3, a twin fuse cartridge unit is formed of two elementary cartridges, generally referenced A and B, disposed above each other, and of three cooling devices C, D and E associated therewith.

Each elementary fuse cartridge comprises a heat-resistant insulating body 1 (preferably made of a ceramic material of high heat conductivity) having the form of a relatively thick rectangular plate provided with three parallel perforations 1a of elliptic cross-section which extend between two opposed sides of the rectangular contour of body 1, with the major axis of their cross-section parallel to the major faces of the said body. A fusible strip 2 is disposed in each perforation 1a, this strip being embedded in a mass 3 of a pulverulent arc-quenching material which fills the perforation. As illustrated strips 2 are folded in rectangular zig-Zag fashion, i.e. they comprise alternate upper and lower straight horizontal portions connected by short vertical portions. Each one of the ends of the strips is clamped between the corresponding side of body 1 and a metallic end plate 4 having a horizontally extending lug 5 adapted to form one of the terminals of the unit. As shown each end plate 4 extends horizontally across the full width of the unit and its height is such that it is common to the two elementary cartridges A and B. These end plates are suitably secured to body 1 of each elementary cartridge, as for instance by screws 6, body 1 being formed for this purpose with corresponding screw-threaded holes 1b (FIG. 1).

The above-mentioned cooling devices C, B and E are respectively mounted on the upper face of elementary cartridge A, between the lower face of cartridge A and the upper face of cartridge B, and against the lower face of cartridge B. Each device comprises two

copper cooling plates

7 and 8 between which is disposed a heat-dissipating copper tube folded on itself in the form of four parallel branches, the said tube being soldered to

plates

7 and 8.

The whole unit is clamped by means of bolts 10.

In operation a cooling fluid, such as water, is circulated through tubes 9 in order to evacuate heat collected by the copper plates which are in contact with the major faces of the elementary cartridges (or more exactly of the insulating bodies 1 thereof). Since the resistance to the heat flow between the fusible strips and the said faces is relatively low owing to the small thickness of arc-quenching material interposed between each horizontal portion of the strips and the adjacent wall of the perforations, and also to the small thickness of insulating material between this wall and the adjacent outer surface of body 1, the temperature of the strip does not rise dangerously in permanent operation under full nominal load. Moreover the heat-dissipating characteristics of the fuse cartridge unit may be similar to those of water-cooled semi-conductor devices with which such units may be associated FIG. 4 shows another embodiment of a cooling device for a fuse cartridge unit of the kind of FIGS. 1 to 3. This device comprises a thick copper plate 11 in the thickness of which a number of longitudinal passages 11a (three in the example shown) have been drilled, these passages being connected by transverse passages 11b. By obturating appropirate portions of these passages by plugs such as 12, it is possible to provide a single path for the flow of a cooling fluid between an inlet and an outlet.

It is of course important to realize a good heat-conducting contact between the major faces of the insulating body 1 of each elementary cartirdge A or B and the corresponding cooling plate such as 7, for instance. This is preferably obtained by metallizing the said faces, as for instance by spraying thereon molten metal droplets by means of a metallizing pistol. F or this purpose a protective covering 20 (FIG. 5) is first applied on each major face of body 1 in the vicinity of the sides thereof onto which the end plates 4 are ubsequently to be secured. This covering is conveniently realized by wrapping an adhesive strip on body 1, the width a of this strip corresponding to the safe distance which is to be maintained between each cooling plate such as 7 and the adjacent end plate 4 for avoiding short-circuits. The exposed portion of each major face is then cleaned by sand-blasting and tin or another similar easily fusible metal or alloy is sprayed thereon in order to realize a first metallic layer 21 (FIG. 6) firmly attached to the insulating material. A copper plate 7 which has been carefully cleaned as required, is then applied against each layer 21 and it is heated up to the melting point of the metallic layer 21. The plate 7 is thus soldered to the metallized face of the insulating body. The heating operation may be effected in an appropriate oven, plates 7 (together with tubes 9 and plates 8) being maintained against body 1 by appropriate springs. During this soldering operation, owing to the presence of the strip or covering 20, no molten metal can flow toward the sides of the insulating body which will thereafter receive the end plates 4. The strips or coverings 20 are then removed and the fuse cartridge may be mounted in the usual way.

It is obvious that the metallization could be performed by means of any desired metal, as for instance copper, the cooling plates being thereafter soldered to the metallic layer thus realized.

While FIG. 6 only shows a single fuse cartridge, it is obvious that the same procedure may be applied in the 4 case of multiple cartridge units, as for instance to the twin unit of FIGS. 1 to 3.

In the embodiment of FIG. 7 the cooling plates, here refrenced 22, are provided with air-cooled heat-dissipating fins 23 which may for instance be soldered to plates 22. In a modification each plate 22 may be cast together with the corresponding fins 23.

In the case of a multiple fuse cartridge unit the facing fins 23a of the elementary cartridges may be interdigitated, as shown in FIG. '8, their number being preferably reduced with respect to the fins 23 of the outer cooling plates of the unit, as illustrated. As in the construction of FIGS. 1 to 3 the unit preferably comprises a single pair of end plates for the insulating

bodies

1A and 1B of both elementary cartridges.

In FIGS. 9 and 10 the fuse cartridge is adapted to be mounted on a massive current-carrying bar 24 which is itself cooled in any appropriate manner, as for instance by inner water circulation as well-known in the art. The cooling plates 25 carried by the insulating body 1 of the cartridge are integral with one 26 of the end plates of the cartridge and this end plate is applied in heat-conducting contact against the current-carrying bar 24. In the example illustrated the end plate 26 carries two screwthreaded rods 27 which are passed through holes provided in bar 24, their protruding ends receiving clamping nuts 28.

It will be understood that the heat collected by cooling plates 25 flows towards end plate 26 and is transferred to bar 24 from which it is evacuated by the cooling agent.-

Of course cooling plates 25 and end plate 26 should be thick enough for offering no appreciable resistance to the heat flow. It is also ovious that the cooling plates 25 could be realized in the form of separate parts soldered to the end plate 26.

I claim:

1. A fuse cartridge comprising:

a substantially flat insulating body having two opposed sides and two major faces, said body 'being formed with substantially parallel perforations extending between said opposed sides;

electrically conductive end plates disposed against said opposed sides;

fusible elements disposed in said perforations to electrically connect said end plates with each other;

heat-conductive cooling plates applied in heat-conducting contact against said major faces of said insulating body, said cooling plates terminating short of one at least of said end plates;

and means to dissipate from said cooling plates the heat which they receive from said insulating body.

2. In a fuse cartridge as claimed in claim 1, said major face of said insulating body being metallized with the metallization terminating short of said one of said end plates, and said cooling plates being soldered to said metallized major faces.

3. In a fuse cartridge as claimed in claim 1, said heatdissipating means being in the form of fluid-cooled tubes in heat-conducting contact with each of said cooling plates.

4. In a fuse cartridge as claimed in claim 1, each of said cooling plates being formed with inner passages for a cooling fluid so as to form by itself said heat-dissipating means.

5. In a fuse cartridge as claimed in claim 1, said heatdissipating means being in the form of air-cooled fins carried by said cooling plates.

6. In a fuse cartridge as claimed in claim 1, each of said perforations containing a single fusible element, said element being in the form of a strip having successive pairs of folds substantially at right anges alternately in one and in the other direction so as to determine alternate upper and lower horizontal portions connected by vertical portions, and said strip beig emnbedded in a mass of arc-quenching material.

7. A fuse cartridge adapted to be mounted on a cooled current-carrying bar, said fuse cartridge comprising:

a substantially flat insulating body having two opposed sides and two major faces, said body being formed with substantially parallel perfortions extending-between said opposed sides;

a first and a second electrically conductive end plates disposed each against one of said opposed sides, with aid first end plate arranged to be applied in heatconducting contact against a cooled current-carrying bar;

fusible elements disposed in said perforations to electrically connect said first and second end plates with each other;

and heat conductive cooling plates applied in heat-conducting contact against said major faces of said in- 15 6 9. In a fuse cartridge as claimed in claim 7, said major faces of said insulating body being metallized with the metallization terminating short of said second end plate, and said cooling plates being soldered to said metallized. major faces.

References Cited UNITED STATES PATENTS 1,696,605 12/1928 Hollnagel 337280 2,326,257 8/ 1943 Schmidt 337166 2,871,314 1/1959 Swain 337--158 3,453,579 7/1969 Cinquin 337161 FOREIGN PATENTS 23,514 2/1913 Great Britain 337-222 HAROLD BROOME, Primary Examiner US. Cl. X.R.