GB191114803A - Improvements in Fusible Cut-outs for Controlling Electric Circuits. - Google Patents

Abstract

14,803. Hope, V. June 26. Fusible cut-outs.-A bi-metallic fusible cut-out is made up of a metal having a relatively high fnsing-point, and preferably a comparatively high electrical couductivity, and a metal having a relatively low melting-point, one enclosing the other. A core C, Fig. 1, of copper or like metal is enclosed in a sheath S of tin-lead alloy or like metal. An excess current melts the alloy at a relatively low temperature, whereupon the whole excess current is carried by the copper, the cross-sectional area of which is such that it is quickly fused by this current. The copper core may be of multiple wires stranded or separated, and the sheathing may be provided with radiating fins S1, Fig. 3. Several copper cores C2, Fig. 4, may be embedded in a sheathing of tin or tin alloy. The core may be of tin &c. and the sheathing of copper, in which case the copper may be deposited electrolytically in a granular state with interstices for the escape of the core when it melts; or fine copper wires may be loosely woven, braided, or twisted on to the core. An enclosed handle-type of fuse is shown in Fig. 9, in which the bi-metallic fuse-wires F are gripped between the flanges A, B in connexion with the contacts K1. In some cases, a third metal having characteristics between the other two may be employed, so that the three metals fuse in succession. The presence of melted tin indicates that the fuse is on the point of blowing or has already blown.