GB430581A - Air space insulated strand for low capacity electric cable - Google Patents

Abstract

430,581. Cables. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Dec. 28, 1933, Nos. 36522 and 36526. Convention dates, May 29 and Aug. 17. [Class 36] An air-space insulated cable particularly for use as an aerial down-load comprises a conductor having an insulating sheath formed of an easily deformed plastic insulating material and of considerably greater internal diameter than the diameter of the conductor, the conductor being centrally supported within the insulating sheath by providing the sheath either with spaced annular constrictions or a continuous helical constriction. The plastic insulating material may consist of rubber, guttapercha, balata, cellulose derivatives, polystyrol, or a mixture of two or more of these .substances, with or without other materials. To facilitate constriction of the sheath, which may be effected by thin wires or threads, the plasticity of the sheath may be increased prior to or during the constricting operation, as by heating ; or the sheath may be formed of a rubber mixture which maintains its form in an unvulcanized condition so that the sheath may be formed with annular constrictions by a device similar to an iris diaphragm prior to vulcanization. Such a rubber mixture may comprise 32 per cent caoutchouc, 13 per cent bone-glue, 1 per cent sulphur, 0À3 per cent diphenylguanidine, 0À3 per cent aldol-alpha-naphthylamine or phenyl- #-naphthylamine, 5 per cent zinc oxide, 30 per cent kaolin, and 18À4 per cent chalk. The Figure shows an aerial down-lead comprising a conductor 11 surrounded by a rubber sheath 12 having annular constrictions 13 and over which is arranged a thin fibrous braiding 14, an electrostatic screen 15 formed of metal braiding, and an outer braiding 16 of impregnated fibrous material. The Specification as open to inspection under Sect. 91, comprises also constructions wherein the braiding 16 is coated with aluminium varnish and the electrostatic screen 15 is formed by one or more layers of helically wound tin foil or metallized paper tape, the tapes being applied in opposite directions and with open or closed turns when two layers are employed. Conductive wires may be either woven in the outer braiding 16 or helically wound directly of the screen 15. This subject-matter does not appear in the Specification as accepted.