GB482649A - Improvements in or relating to resistors - Google Patents

Abstract

482,649. Resistances ; couplings. INTERNATIONAL RESISTANCE CO. July 1, 1936, No. 18305. Convention date, July 19, 1935. [Classes 37 and 38 (i)] An electric resistance unit comprises a resistance strip which includes an electric current conducting element having separate terminals connected thereto and completely encased and hermetically sealed in and in direct contact with a block of moulded insulating material composed of a phenolic condensation product, a metallic heat distributing strip being attached to or embedded in the insulating block and extending substantially throughout the length and width of the resistance strip. The resistance may be a wire 11, Fig. 4, wound round a strip 10 of fibrous material and terminals 12 are connected to the wire by wrapping the end 17 round the wire and doubling back the part 15, so as to clamp the section 16 firmly in contact with the resistance. The insulating block 18 is moulded round and in contact with the resistance, being preferably of rectangular shape and with a shelf portion 21 which serves to support the part 13a of the terminal. A metallic strip 22 separated from the resistance by a fibrous insulating strip 26 and by the insulating material of the block 18 surrounds and extends along the length of the resistance and serves to equalize the temperature throughout the wire. Alternatively, the metallic strip may form part of the resistance core, being separated from the wire by a fibrous layer. Two metallic strips, 49, 50, Fig. 6, may be provided, one above and one below the resistance 45 and extending beyond the ends of the block of moulded material. A top cover plate 20, Fig. 4, of metal may be provided and is bent down at its ends and secured to a metallic supporting plate 43. These plates 20, 43 serve to radiate heat generated in the resistance and in the form shown in Fig. 6 the heat distributing plates 49, 50 extend beyond the insulating block 48 and are connected to the top and bottom plates 51, 54 as shown. In a modification, the resistance block is encased on all four sides in a metal casing which is attached to a supporting metal plate and is provided with recesses through which the terminals pass. Specification 472,408 is referred to.