GB2081031A

GB2081031A - Manufacturing Plug-in Fuses

Info

Publication number: GB2081031A
Application number: GB8122540A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-07-23
Filing date: 1981-07-22
Publication date: 1982-02-10
Also published as: GB2081031B

Abstract

To manufacture fuses as shown in the Fig., pairs of terminations 14, 16 are laid side-by-side on a conveyor which carries them through a welding station at which there is a welding jig 24. A length 26 of fuse wire extends from a leading termination 14 of a leading pair at the welding station to a winding drum (not shown) which maintains the wire taut. In a single welding operation, the wire is welded both to the trailing termination 16 of the leading pair and to the leading termination 14 of the adjacent pair. The wire breaks between the two pairs when heated by the welding operation and the leading pair, with its fuse element secured, becomes detached from the remaining length of wire. <IMAGE>

Description

SPECIFICATION Electrical Fuses This invention is concerned with the manufacture of so-called plug-in fuses.

A plug-in fuse comprises two electrically conductive terminations, usually in the form of pins or blades projecting from a casing, for connection of the fuse into an electrical circuit, 'the terminations being electrically connected by a fuse element.

There is described in U.S. Patent Specification -No. 3 909 767 a plug-in fuse in which blade terminations and the connecting fuse element are together provided by a single metal stamping, the metal stamping being mounted in a holder of an electrically insulating material. The metal stampings have to be carefully formed so that a bridging portion, between two blade portions and providing the fuse element, will have a required current-limiting performance.

U.K. Patent Specification No. 2 002 603A describes the construction of plug-in fuses by connecting a discrete fuse element in the form of a piece of fuse wire to discrete terminations in the form of blades. In some of the constructions described, end portions of the fuse wire are snap fitted into spring-clips of the blades. In other constructions, end portions of the fuse wire are connected to the two blades by soldering.

It is an object of this invention to provide a method of manufacturing plug-in fuses from discrete fuse and termination elements which enables such fuses to be produced rapidly, efficiently and economically.

The invention provides in one of its aspects a method of manufacturing plug-in fuses which each comprise a pair of terminations for connection of the fuse into an electrical circuit, the method comprising positioning a first pair of terminations adjacent one termination of a second pair with a free end portion of a length of fuse material welded to one termination of said first pair, and welding the length of fuse material simultaneously to the other termination of said first pair and to said one termination of the second pair, the length of fuse material between 'said other termination of said first pair and said one termination of said second pair being held taut in order that it breaks when heated by the welding operation.

In a preferred method, a plurality of pairs of terminations are laid side-by-side on a conveyor which is arranged to carry them step-by-step to, and past, a welding station at which there is a welding jig. The length of fuse material, which may be in the form of wire, is laid across the terminations, from a leading termination of a leading pair on the conveyor to a winding drum arranged to maintain the fuse material taut. In the welding operation, the length of fuse material is welded to the trailing termination of the leading pair and to the leading termination of the adjacent pair on the conveyor, and breaks between the two pairs. The conveyor is then advanced one step so that said adjacent pair (with the length of fuse material secured to its leading termination) and a next pair on the conveyor become positioned at the welding station for the next welding operation.Accordingly, upon each welding operation a short piece of the length of fuse material becomes the fuse element of the leading pair at the welding station, and the leading pair, with its fuse element secured, becomes detached from the remaining length of fuse material.

A plug-in fuse so manufactured may comprise a two-part casing of an electrically insulating material, one part of the casing carrying the terminations of the fuse on the conveyor and the other part being secured to first part after the welding operation.

There now follows a description, to be read with reference to the accompanying drawing, of a method of making plug-in fuses, which illustrates the invention by way of example.

The accompanying drawing is a diagrammatic perspective view illustrating the method.

Each plug-in fuse being manufactured comprises a two-part, electrically insulating, moulded plastics casing, comprising an upper part 10 and a lower part 12 (as shown in the drawing), the lower part 12 providing two parallel channels to accomodate a pair of terminations in the form of two conductor blades 14 and 1 6 which project from the casing and enable the fuse to be connected into an elctrical circuit. Each of the upper and lower parts of the casing comprises two integrally moulded studs 1 8 which project, through apertures in the blades, into recesses in the other of the casing parts, for positive location of the blades in the casing parts. The casing parts 10 and 12 are, in the finished fuse, welded together. The casing is of a clear plastics material.

Before assembly of the casing, a fuse element 20 has first to be secured to connect electrically the two blades 14 and 16. Opposed cut-outs 22 in the blades are arranged to increase the distance between the blades where the fuse element 20 goes across, to provide clearance from the fuse element and increase the operative length of the element. The upper casing part 10 is formed with a transversely-extending groove (not shown) to accommodate the fuse element 20.

For securement of the fuse element 20, a plurality of lower casing parts 1 2 carrying blades 1 4 and 1 6 in position (hereinafter referred to as fuse bodies) are located side-by-side on a conveyor arranged to move the bodies stepwise to, and past, a welding station at which there is an electrical resistance welding jig 24. (The direction of movement of the conveyor is indicated in the drawing by an arrow.) A length 26 of fuse wire is laid across the pairs of blades of the fuse bodies on the last conveyor, and is maintained taut by a winding drum (not shown); in continuous performance of the method the free end of the wire is always secured (as to 28) to the leading blade 14 (i.e. further from the winding drum) of a leading fuse body at the welding station, as will become apparent hereinafter.

The welding operation is performed as follows.

The conveyor is arranged to stop, between advances, with the welding jig 24 astride two fuse bodies at the welding station, so that the welding jig operate to weld the wire 26 simultaneously to the trailing blade 1 6 of the leading fuse body (as at 30) and to the leading blade 14 of the adjacent body (as at 32). Upon performance of the welding operation, the taut wire 26 extending between the two fuse bodies at the welding station becomes heated and breaks.

The conveyor is next advanced one step to bring the trailing blade 1 6 of the second fuse body into position opposite the welding jig, and further welding operation is performed, and so on. At each welding operation, securement of a fuse element 20 is completed on the leading fuse body at the welding station and initiated on the adjacent body, and the continuous wire 26 becomes severed between the bodies. The upper casing part 10 can be secured to the lower casing part 12 to complete the plug-in fuse. The completed fuse may then be discharged immediately from the conveyor, or other operations (e.g. electrical checking) may be effected before discharge.

Claims

1. A method of manufacturing plug-in fuses which each comprise a pair of terminations for connection of the fuse into an electrical circuit, the method comprising positioning a first pair of terminations adjacent one termination of a second pair with a free end portion of a length of fuse material welded to one termination of said first pair, and welding the length of fuse material simultaneously to the other termination of said first pair and to said one termination of the second pair, the length of fuse material between said other termination of said first pair and said one termination of said second pair being held taut in order that it breaks when heated by the welding operation.

2. A method according to claim 1 in which pairs of terminations are laid side-by-side on a, conveyor which carries then step-by-step to, and past, a welding station at which there is a welding jig arranged to perform said welding operation:

3. A method according to claim 2 in which the length of fuse material extends from the leading termination of a leading pair of terminations on the conveyor ot a winding drum arranged to maintain the fuse material taut during said welding operation.

4. A method occurring to either of claims 2 and 3 in which one part of a two-part casing of a fuse being manufactured carries each pair of terminations on the conveyor, the other part of the casing being secured to said one part after the welding operation.

5. A method according to any one of the preceding claims in which the fuse material is in the form of wire.

6. A method of manufacturing plug-in fuses which is substantially as hereinbefore described with reference to the accompanying drawing.

7. A plug-in fuse manufactured by a method according to any one of claims 1 to 6.

8. A plug-in fuse substantially as hereinbefore described with reference to the accompanying drawing.