GB471935A - Improvements in or relating to the manufacture of electric cables or other insulated conductors - Google Patents

Abstract

471,935. Power and heating cables. SOC. ALSACIENNE DE CONSTRUCTIONS MECANIQUES. Dec. 11, 1935, Nos. 34355 and 34356. Convention dates, Dec. 12, 1934 and Oct. 25, 1935. [Class 36] [Also in Group XI] In a process for the manufacture of power or heating cables of the kind comprising one or more cores insulated from an outer sheath by pulverulent mineral insulation such as magnesia or steatite, and wherein the cable is formed from a work-piece (comprising a metal sheath surrounding insulation and a core or cores) which is subjected to a drawing, rolling, or other metallurgical treatment to bring it to its final dimensions, the insulation is completely dehydrated by heat before the work-piece is subjected to the metallurgical treatment. The insulation material is preferably dehydrated before its introduction into the sheath, the material being heated, in the case of magnesia, to a temperature of at least 600‹ C., and preferably about 800‹ C., for three hours. The insulation material may be introduced into the sheath in powder form by tamping, or in the form of compressed blocks, and is preferably compressed to its density limit as described in Specification 472,159. For the manufacture of heating cables, the core of the work-piece is a thin resistance wire, the insulation is applied in block form, and the metallurgical treatment consists of a swaging or shrinking treatment to reduce the blocks to powder form followed by a few drawing stages insufficient to bring the thin core to its breaking condition. Specification 259,552, [Class 36], also is referred to.