Patent GB-508036-A (GB)
Title: Improvements in or relating to electric cables
IPC: H02G15/24
Filed: 1937-12-24
Abstract: 508,036. Cable end - constructions ; joints. STANDARD TELEPHONES & CABLES, Ltd., SCOTT, T. R., MILDNER, R. C., and MENZIES, T. E. D. Dec. 24, 1937. No. 35757.. [Classes 36 and 38 (i)] A barrier joint or termination in an impregnated power cable is prepared by building up the insulation with fibrous tapes impregnated with polymerized material, basting the impregnated tapes with polymerizable material at intervals during the building up operation in order to cause adjacent tapes to adhere to one another and causing the impregnated fibrous tapes to overlap the protective sleeve of the cable. Such protective sleeve may be the cable sheath or an extension thereof, a joint sleeve, an end cap or an extension of an end cap. A termination in a single core cable is prepared by stripping back the sheath, entirely removing or partly removing and tapering the exposed insulation, securing a ferrule to the conductor and building up the insulation to overlap the sheath, the latter being first heated with monomer containing a little polymer. Before building up the insulation, the exposed part of the conductor may be wrapped with a tape formed of a mixture of rubber and partial polymer ; similar tapes may be applied over the ferrule and over the builtup insulation. Each end of the insulation may be covered with metal foil wrapped with copper. wires, or a metal sleeve may be used; a porcelain housing filled with oil, or a stress grading device, or both, may be provided over all. A joint may be similarly built up. As. shown in Fig. 1, a copper tape 5 is lapped over the uncovered insulation 2 and welded or sweated to the sheath, the insulation being then built up to overlap the tape ; a brass tube 7 is slipped over the conductor prior to connection of the ferrule 4. In the joint shown in Fig. 2, the conductors are connected by the ferrule 4, 11 being polymer-rubber tapes ; the insulation is built up to overlap the sheaths 1 to which the casing 12 is wiped. In the case of a belted multicore cable, a barrier is formed in the insulation directly surrounding the cores as described in Specification 504,720, a barrier being formed in the worming spaces by removing the wormings and filling the spaces with jute impregnated with or embedded in polymerized or partially polymerized materials, or with filaments or rods of the composition described in Specification 357,624; alternatively, the worming material may itself be impregnated with a polymer or partial polymer. The belt insulation is then built up to overlap the sheath. In the case of a screened multicore cable, a, belt of insulation is built up outside the screened cores to overlap the sheath, the barrier in the worming spaces being formed' of metal. Alternatively, preformed polymerized barrier sections may be assembled around the conductor or conductors and the insulation then built, up as described above the sections may be treated with monomer to effect adhesion. For instance, a joint in a belted cable may be formed by jointing the conductors by means of a ferrule having a central web, lapping on polymer impregnated paper, inserting preformed barrier sections and finally building up the belt insulation as above ; alternatively, the initial lappings may be omitted. The barrier sections may be built up of materials containing in addition to polymers other substances, e.g. of impregnated papers treated as in Specification 454,923, (Group VIII], or of a polymer-rubber composition or of a composition as described in Specification 507,323, [Group IV]. The preformed sections may be formed by pressing prepolymerized papers in a mould and basting with monomer or by the; use of monomer impregnated papers, polymerized after completion of the sections, or by lapping papers around pipes and cutting them to remove the sections from the pipes, or by the use of an extrudable composition ; the sections are preferably not completely polymerized in the factory. The polymer used may be polystyrol, alone or in admixture with polyethylene or polyisobutylene. In screened multi-core cables, the cores may be led through separate exit tubes in an end cap secured to the sheath and the individual core insulations built up as above; two such caps may be used to form a joint, a casing being provided. Such a termination, Fig. 3, may comprise a cap 24 wiped to the sheath 21 and exit pipes 27 through which are threaded the insulated conductors ; the latter are each provided with a lead sheath 28, 29 soldered to the exit pipes. Each sheath is then terminated as above described, the built-up insulation being extended over the ferrule and wires wound over the sleeve at 9. Specifications 429;611 and 492,331 also are referred to.