Electricity: electrothermally or thermally actuated switches – Electrothermally actuated switches – Fusible element actuated
Patent
1994-04-29
1996-01-16
Echols, P. W.
Electricity: electrothermally or thermally actuated switches
Electrothermally actuated switches
Fusible element actuated
29623, 29874, 140 71R, H01H 8504
Patent
active
054851378
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for manufacturing a fuse comprising a fuse element in the form of a wire and at least one terminal, the terminal having a larger cross section area than the fuse element.
BACKGROUND ART
A fuse comprises a fuse element, for example in the form of a wire, which at elevated current is heated and melts, the fuse blows, and the component that the fuse protects is disconnected.
In certain applications, such as fuses for protection of capacitor elements in power capacitors, the fuse comprises, in addition to fuse elements, also terminals which have a larger cross section area than the fuse element.
The fuse element usually consists of a wire, preferably a metal wire of copper, aluminium, silver, alloys based on these metals, as well as nickel silver, or any other material with a resistivity and melting point suitable for the application.
For a fuse element provided with terminals, the contacting, that is, the transition between terminal and fuse element, which with conventional technique is usually performed by means of soldering, welding or a mechanical pressure joint, is a critical step. The influence of heat from the soldering/welding or mechanical damage upon the contacting by means of the pressure joint weakens the fuse, preferably at the transition between terminal and fuse element. This has an adverse effect on the fuse and the protective function by the introduction of weakenings or other inhomogeneities in the fuse.
In connection with fuses in capacitor elements or in other components where the fuse is mounted "narrowly" and in close proximity to electrically loaded materials, all forms of mechanical pressure points must be avoided. For that reason, the transition between terminal and fuse element in fuses which make contact with or are mounted in close contact with electrically loaded materials, for example fuses mounted inside or adjacent to a capacitor element, must be of essentially the same dimension as the terminal, that is, no lumps of solder, welding material, mechanical clamps or the like, which exceed the dimensions of the terminal and create pressure points, can be allowed.
The invention aims to propose a method whereby a fuse, which comprises a fuse element in the form of a thin wire and at least one terminal, the terminal having a larger cross section area than the fuse element, can be manufactured in an economic and rational way while at the same time avoiding the above-mentioned problems arising in connection with the contacting or the transition between terminal and fuse element.
SUMMARY OF THE INVENTION
The invention relates to a method for manufacturing a fuse which comprises a fuse element in the form of a thin wire and at least one terminal, the terminal having a larger cross section area than the fuse element. The fuse element and the terminal are formed in one piece from the same wire while moving the wire, section-by-section, back and forth a number of times to form at least one ring or loop. The ring obtained is then twisted into a terminal in the form of a number of twisted-together wires, whereby one of the wires, included in part in the terminal, is formed also to partly constitute a fuse element. The method according to the invention simplifies the manufacture of fuses in relation to the known technique since no joining together of different components is required and all material, wire, is taken from the same roll.
According to a preferred embodiment of the method of the invention, fuses comprising two terminals and an intermediate fuse element are manufactured from the same wire. According to this embodiment, the wire is moved, section-by-section, back and forth a number of times to form at least one ring or loop. The ring thus formed is twisted to form a larger cross section area than the wire. Alternately with these sections of twisted wires, sections in the form of a single wire are arranged, whereupon the body formed from this wire, comprising sections in the form of a single wire, arranged alternately in t
REFERENCES:
patent: 550638 (1895-12-01), McCulloch
patent: 1867924 (1929-03-01), Roberts et al.
patent: 2000163 (1935-05-01), Clark
patent: 2659790 (1953-11-01), Jurgensen
Maleus Borje
Tjerngren Jan
Asea Brown Boveri AB
Echols P. W.
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