Patent GB-499311-A (GB)
Title: Improvement in electrical cable
IPC: H01B7/22
Filed: 1937-07-19
Abstract: 499,311. Cables. GENERAL CABLE CORPORATION. July 19, 1937, No. 19954. Convention date, Aug. 8, 1936. [Class 36] A high tension cable comprises a conductor or conductors enveloped in porous insulating material, a thin flexible impervious integument enclosing the insulated conductor or conductors, an insulating compound which impregnates the porous insulating material and fills all interstices within the integument, an outer expansible and contractible sheath, and an elastic reinforcing element for the sheath applied or arranged in such a manner, dependent on the elastic properties of said element, so as to remain elastic when strained by expansion of the insulating compound under operating conditions yet resist said expansion sufficiently to maintain the insulating compound at a desired positive pressure. The impervious integument may consist of lead, or a non-metallic oil-resistant material such as Thiokol or that known under the Registered Trade Mark "Duprene," whilst the outer expansible and contractible sheath may be formed of a vulcanized rubber compound, the reinforcing element consisting of metal, fibrous, or rubber strands superimposed on or embedded in the sheath and helically applied, preferably as an open braid, with such a lay as to remain elastic under maximum expansion conditions of the sheath yet to store sufficient energy on expansion of the sheath to cause contraction of the sheath when the impregnating compound within the sheath contracts. In the construction shown in Figs. 1 and 2 conductors 21, each insulated with impregnated paper 22 and enclosed in a thin lead sheath 23 which is protected against wrinkling by an overlapping wrapping 24 of friction tape applied on a coating of a cement known under the Registered Trade Mark " Bakelite," are cabled together, with or without rubber fillers 25, and enclosed in a composite sheath comprising a wrapping 26 of rubberized cloth tape and inner and outer vulcanized rubber layers 27, 29, between which layers is disposed the elastic reinforcing element consisting of an open braiding 28 of cotton string applied under tension. In the modified construction of Fig. 4 the insulated conductors 31 are individually wrapped with metal tape 33 and are enclosed, together with fillers 35 in a triangular thin common lead sheath 38, protected against wrinkling and enclosed by a reinforced composite outer sheath as described with reference to Figs. 1 and 2, the inner rubber layer 40 of the composite sheath being formed with a circular outer periphery. In another construction, similar to that of Fig. 4, the thin common lead sheath is of circular section and the outer sheath comprises a single rubber layer reinforced by an external wrapping of wires. In a further construction the insulated conductors have a thin common circular lead sheath over which is applied a square sectioned reinforced composite outer sheath formed similarly to that shown in Figs. 1 and 2. Rubber fillers are disposed between the internal corners of the square sheath and the surface of the circular sheath. In any of the above constructions the thin lead sheath may be replaced by a sheath helically wrapped corrugated thin metal tapes 93, Fig. 10, the edges of adjacent tapes being soldered together. Specification 378,997 is referred to.