GB2122432A - An improved electric cartridge fuse assembly - Google Patents

Abstract

Each electric fuse contact 21 of an electric cartridge fuse assembly comprises a single strip of resilient metal folded transversely of and approximately midway along its length and back upon itself to form a doubled strip and the doubled strip is folded transversely of its length intermediate of its ends to approximately L-shape. The limb 24 of the L-shaped doubled strip nearer the first transverse fold is detachably secured to the insulating base 31 of the cartridge fuse assembly by a conductor clamping screw 38 and the other limb 26 of the strip is adapted to resiliently grip a blade contact of a cartridge fuse or a separately formed supplementary contact to which a fuse terminal is electrically connected. Preferably, the single strip is of composite form and consists of a resilient steel strip and, overlying each major surface of the strip, a layer of copper. <IMAGE>

Description

SPECIFICATION An improved electric cartridge fuse assembly This invention relates to electric cartridge fuse assemblies ofthe kind comprising a base of electically insulating material on which are mounted two electric fuse contacts each of which has means for electrical connection to a conductor of a flexible electrical cable orto an electric busbar and, separately formed with respectto and detachably engageable with the base, a carrier of electrically insulating material on which an electric cartridge fuse is so supported that, when the carrier is detachably engaged with the base, the terminals ofthe cartridge fuse are in direct or indirect electrical connection with said electric fuse contacts of the base.Electric cartridge fuse assemblies ofthis kind witl hereinafter,forconvenience, be referred to as "of the kind described." In electric cartridge fuse assemblies of the kind described it is the general practice to employ, as each electricfuse contact, a contact assembly comprising a solid blockof brassorothermetal or metal alloy of high electrical conductivity to which a conductor of a flexible electric cable or an electric busbar can be electrically connected by a clam ping screw or other associated means, and a separately formed resilient strip of copper or other metal or metal alloy of high electrical conductivity which is electrically connected to the brass block and which is so shaped that a blade contact of a cartridge fuse, or a separately formed supplementary contact to which the fuse terminal is electrically connected, can be resiliently gripped between a limb ofthe copper strip and a side wall of the brass block or between two limbs of the copper strip. By virtue of their construction fuse contact assemblies ofthis kind aretedious to assemble and their cost represents a substantial proportion of the overall cost of a cartridge fuse assembly of the kind described.

It is an object ofthe present invention to provide an improved cartridge fuse assembly of the kind described in which the fuse contacts carried by the insulating base are simple in construction, easy to assemble and are less expensivethanfusecontact assemblies hitherto proposed and use.

According to the invention, in the improved electric cartridgefuseassemblyofthe kind described, each electricfuse contact ofthe insulating base comprises a single strip of resilient metal or metal alloy of high electrical conductivity, the strip being folded transversely of and at a position approximately midway along its length and back upon itselftoform a doubled strip and the doubled strip being folded transversely of its length at a position intermediate of its ends to approximately L-shape, the limb of the L-shaped doubled strip nearer the transverse fold in the strip being detachably secured to the insulating base of the cartridge fuse assembly by means for electrically connecting a conductor of a flexible electric cable or an electric busbarto the strip and the other limb of the L-shaped doubled strip being adapted to resiliently grip a blade contact of a cartridge fuse or a separately formed supplementary contact to which a fuse terminal is electrically connected. Preferably, the single strip is of composite form and consists of a resilient strip of steel or other metal or metal alloy and, overlying each major surface of the resilient strip, a layer of copper or other metal or metal alloy of high electrical conductivity.Alternatively the strip may be made of a metal or metal alloy which is a single material having adequate electrical conductivity and resilience such as brass and certain bronzes.

The insulating base of the cartridge fuse assembly preferably has an upstanding boundarywall around its periphery and the means for detachably securing to the insulating base the limb ofthe L-shaped doubled electrically conductive strip nearerthe transverse fold in the electrically conductive strip is preferably housed in a compartment which is bounded in part by the upstanding boundary wall ofthe base and in part by internal barrier walls of electrically insulating material, said limb ofthe L-shaped doubled electrical ly conductive strip being retained between the insulat ing base and the compartment and a hole being provided in the boundary wall ofthe insulating base for introduction into the compartment of a conductor of a flexible electric cable organ electric busbar.

The means for detachably securing to the insulating base the limb of the L-shaped doubled electrically conductive strip nearerthe transverse fold in the electrically conductive strip is preferably a clamping screwwhich passesthrough a metal washer housed in the compartment, screws into a tapped hole in the limb of the L-shaped doubled electrically conductive strip and engages in a recess in the insulating base of 1the cartridge fuse assembly.

The limb ofthe L-shaped doubled electrically :conductive strip in which a blade contact of a cartridge ,fuse, or a separately formed supplementary contact to Iwhich a fuse terminal is electrically connected, can be :resiliently gripped preferably is housed between the upstanding boundary wall ofthe insulating base ofthe cartridge fuse assembly and the barrierwall of the compartment housing the clamping screw and, preferably, the free end of one or each part of said limb of the L-shaped doubled electrically conductive strip is transversely folded outwardly and is so shaped asto bearagainstthe boundary wall ofthe insulating base orthe barrierwall ofthecompartmentand so facilitate resilient gripping of the blade contact or separately formed supplementary contact.

The invention also includes, for use in an improved cartridge fuse assembly of the kind described, an improved fuse contact as hereinbefore described.

The invention is further illustrated by a description, by way of example, of two preferred forms of fuse contact for use in cartridge fuse assemblies of the kind described with reference to the accompanying draw ing, in which: Figure 1 is an isometric view ofthe first preferred fuse contact; Figure 2 is a fragmental plan view of the insulating base of a cartridge fuse assembly, with the fuse The drawing originally filed was informal and the print here reproduced is taken from a later filed formal copy.

contact shown in Figure 1 mounted therein; Figure 3 is a sectional end view ofthe insulating base taken on the line Ill-Ill in Figure 2; Figure 4 is an isometric view of the second preferred fuse contact; Figure 5 is a fragmental plan view of the insulating base of a cartridge fuse assembly with the fuse contact as shown in Figure 4 mounted therein, and Figure 6 is a sectional end view ofthe insulating basetaken on the lineVI-VI in FigureS.

Thefirst preferred fuse contact shown in Figure 1 comprises a single strip 1 of composite form and consisting of a resilient strip of steel and, overlying each majorsurface of the resilient strip, a layer of copper. The composite strip 1 is folded transversely of and art a position 2 approximately mid-way along its length and back upon itselftoform a doubled strip and the doubled strip is folded transversely of its lenth at a position 3 intermediate of its ends to approximately L-shape. The limb 4 ofthe L-shaped doubled strip 1 nearerthetransversefold 2 inthe strip hasatapped hole 5 extending through the adjacent parts ofthe strip constituting this limb.The extreme ends 7 of the parts ofthe strip 1 constituting the other limb 6 of the fuse contact are each flared outwardly to facilitate introduction between these parts of the limb of a blade contact of a cartridge fuse or a separately formed supplementary contact to which a fuse terminal is electrically connected.

Aswill be seen on referring to Figures 2 and 3,the insulating base 11 of the cartridge fuse assembly has an upstanding boundarywall 12 extending around its periphery and has, at each of its ends (ofwhich one only is shown) a compartment 14which is bounded in part by the upstanding boundary wall 12 and in part by internal barrierwalls 16and 17 of electrically insulating material.When an electric fuse contact as shown in Figure 1 is supported on the insulating base 11, the limb 4 ofthe L-shaped doubled electrically conductive strip 1 is retained between the insulting base and the compartment14anda clamping screw 18 passes through a square metal washer 15 housed in the compartment and screws into the tapped hole 5 in the limb 4 and engages in a recess 19 in the insulating base. The other limb 6 of the fuse contact 1 is located between the boundarywall 12 and the barrier wall 17.

A hole (notshown) is provided in the boundarywall 12 ofthe insulating base for introduction of a conductor of a flexible electric cable or an electric busbar into the compartment 14for electrical connection to the fuse contact 1 by the clamping screw 18.

The electric fuse contact shown in Figure 4 comprises a single strip 21 of composite form consisting of a resilient strip of steel and, overlying each major surface of the resilient strip, a layer of copper. The strip 21its folded transversely of and at a position 22 approximatey mid-way along its length and that upon itselftoform a doubled strip and the doubled strip is folded transversely of its length at a position intermediate of its ends to approximately L-shape. One limb 24 ofthe L-shaped doubled strip 21 nearerthe transverse fold 22 has atapped hole 25 extending through both parts of the strip constituting that limb.

End portions 27 of the parts of the strip 1 constituting the other limb 26 of the L-shaped doubled strip are eachtransverselyfolded outwardlytoform an end portion of substantially inverted U-shape.

As will be seen on referring to Figures 5 and 6, the insulating base 31 of the cartridge fuse assembly has an upstanding boundarywall 32 extending around its periphery and has, at each of its ends (which one only is shown) a compartment 34which is bounded in partbytheupstanding boundarywall32andinpartby internal barrier walls 36 and 37 electrically insulating material. Whenthefuse contact shown in Figure4 is supported on the insulating base 11, the limb 24 of the L-shaped double electrically conductive strip is retained between the insulating base and the compa rtment 34 and a clamping screw 38 passes through a square metal washer 35 housed in the compartment and screws into the tapped hole 35 in the limb 34 and engages in a recess 39 in the insulating base. The other limb 36 of the L-shaped double electrically conductive strip 21 is located between the boundary wall 12 and the barrierwall 37 and the outwardly folded end parts 27 ofthefuse contact bearagainstthe boundary wall and this barrierwall and so facilitate resilient gripping of the blade contact or separately formed supplementary contact of a cartridge fuse. A hole (not shown) is provided in the boundary wall 32 oftheinsulating base 31 for introduction of a conductor of a flexible electric cable or an electric busbar into the compartment 34 for electrical connec tiontothefuse contact bythe clamping screw 38.

Claims (10)

1. An electric cartridge fuse assembly of the kind described, wherein each electric fuse contact ofthe insulating base comprises a single strip of resilient metal or metal alloy of high electrical conductivity, the strip being folded transversely of and at a position approximately midway along its length and back upon itselfto form a doubled strip and the doubled strip being folded transversely of its length at a position intermediate of its ends to approximately L-shape,the limb ofthe L-shaped doubled strip nearerthetrans- versefold in the strip being detachably secured to the insulating base ofthe cartridge fuse assembly by means for electrically connecting a conductor of a flexible electric cable or an electric busbarto the strip and the other limb ofthe L-shaped doubled strip being adapted to resiliently grip a blade contact of a cartridge fuse or a separately formed supplementary contact to which afuseterminal is electrically connected.

2. A electric cartridge fuse assembly as claimed in Claim 1,wherein the single strip of each electric fuse contact is of composite form and consists of a resilient strip of steel or other metal or metal alloy and, overlying each major surface of the resilient strip, a layer of copper or other metal or metal alloy of high electrical conductivity.

3. An electric cartridgefuse assembly as claimed in Claim 1 or 2, wherein the insulating base ofthe assembly has an upstanding boundarywall around its periphery and the means for detachably securing to the insulating base the limb of the L-shaped doubled electrically conductive strip nearerthetransversefold in the electrically conductive strip is housed in a compartment which is bounded in part by the upstanding boundary wall of the base and in part by internal baFrierwalls of electrically insulating material, said limb ofthe L-shaped doubled electrically conductive strip being retained between the insulating base and the compartment and a hole being provided in the boundary wall of the insulating base for introduction into the compartment of a conductor of a flexible electric cable or an electricbusbar.

4. An electriccartridgefuse assembly as claimed in Claim 3, wherein the means for detachably securing to the insulating base the limb of the L-shaped doubledelectricallyconductivestripnearerthetrans- versefold in the electrically conductive strip is a clamping screw which passes through a metal washer housed in the compartment, screws into a tapped hole in the limb ofthe L-shaped doubled electrically conductive strip and engages in a recess in the insulating base of the cartridge fuse assembly.

5. An electric cartridge fuse assembly as claimed in Claim 3 or 4, wherein the limb of the L-shaped doubled electrically conductive strip in which a blade contact of a cartridge fuse, or a separately formed supplementary contact to which a fuse terminal is electrically connected, can be resiliently gripped is housed between the upstanding boundary wall of the insulating base of the cartridge fuse assembly and the barrierwall ofthe compartment housing the clamping screw.

6. An electriccartridgefuse assembly as claimed in Claim 5, wherein thefree end of one or each part of a limb in which a blade contact of a cartridge fuse, or a separately formed supplementary contact to which a fuse terminal is electrically connected, can be resi lientlygripped is transversely folded outwardly and is so shaped asto bearagainstthe boundary wall ofthe insulating base orthe barrier wall ofthe compartment and so facilitate resilient gripping of the blade contact or separately formed supplementary contact.

7. An electric cartridge fuse assembly substantial.

ly as hereinbefore described with reference to and as shown in Figures 2 and 3 ofthe accompanying drawing.

8. An electric cartridge fuse assemblysubstantially as hereinbefore described with reference to and as shown in Figures 5 and 6 of the accompanying drawing.

9. For use in an electric cartridge fuse assembly of the kind described, an electric fuse contact comprising a single strip of resilient metal or metal alloy of high electrical conductivity, the strip being folded transverely of and at a position appoximately midway long its length and back upon itself to form a doubled strip and the doubled strip being folded transversely of its length at a position intermediate of its ends to approximately L-shape,the limb of the L-shaped doubled strip nearer the transverse fold in the strip having a tapped hole extending therethrough and the other limb of the L-shaped double strip being adapted to resiliently grip a blade contact of a cartridge fuse or a separately formed supplementary contact to which a fuse terminal is electrically connected.

10. For use in an electric cartridge fuse assembly of the kind described, an electric fuse contact substantially as hereinbefore described with reference to and as shown in Figure 1 or Figure 4 of the accompanying drawing.