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US 4,184,137 AGranted
Dual element fuse protector for electric circuits
AssigneeMcGraw-Edison Company
InventorsAldino J. Gaia, Angelo Urani
Life of this patent
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AssigneeMcGraw-Edison Company
InventorsAldino J. Gaia, Angelo Urani
Estimating the term…
The dual element fuse of the present invention has at least one fusible element and at least one mass of heat softenable material; and that fusible element will respond to a short circuit to fuse and thereby assure opening of the circuit, whereas that mass of heat softenable material will respond to a long-continued relatively-low potentially-hurtful overcurrent to soften and thereby initiate opening of the circuit. That dual element fuse has a shunt element which shunts the mass of heat softenable material and which will fuse after that mass of heat softenable material has initiated opening of the circuit; and hence that shunt element will minimize arcing as that mass of heat softenable material initiates opening of the circuit. That shunt element has a current rating which is larger than the current rating of the mass of heat softenable material, so it will not fuse until after that mass of heat softenable material has initiated opening of the circuit; and that shunt element has a current-interrupting characteristic which has the same shape as that of the current-interrupting characteristic of the fusible element, so its clearing time will be similar to the clearing time of that fusible element. Where the dual element fuse of the present invention has a plurality of fusible elements and a plurality of masses of heat softenable material, a connecting ring electrically interconnects one end of each of those fusible elements. In doing so, that connecting ring keeps any higher-than-normal-electrical-resistance connection between one of those fusible elements and an adjacent heat absorber from generating so much heat that it initiates premature softening of the mass of heat softenable material which is a part thereof.
An electric fuse which has first and second terminals, a chamber, a plurality of fusible elements disposed within said chamber, a plurality of electrical paths which connect a first end of each of said fusible elements to said first terminals, said electrical paths including spaced-apart discrete quantities of heat-softenable material which can respond to a long-continued potentially-hurtful relatively-low overcurrent to soften and thereby permit individual ones of said electrical paths to become open, a connecting ring disposed adjacent to and electrically interconnecting said first ends of said fusible elements, said connecting ring and said first ends of said fusible elements having interacting surfaces thereon which enable said connecting ring to fix the spacings between said first ends of said fusible elements, said second terminal electrically interconnecting second ends of each of said fusible elements, whereby said fusible elements are connected in parallel relation with each other between said second terminal and said connecting ring to provide a predetermined composite resistance that is independent of the resistance of said heat-softenable material, and whereby said connecting ring distributes the current, from said fusible elements within said chamber, to said plurality of spaced-apart discrete quantities of heat-softenable material inversely in accordance with resistances of said plurality of spaced-apart, discrete quantities of heat-softenable material.
Dependencies are inferred from the claim text.