Patent GB-581723-A (GB)
Title: Improvements in or relating to electric cables
IPC: H01B7/12
Filed: 1941-04-07
Abstract: 581,723. Electric cables. HENLEY'S TELEGRAPH WORKS CO., Ltd., W. T., and DAKER, H. H. April 7, 1941, No. 4628. [Class 36] In a buoyant electric cable having a heavy current conductor disposed about and supported on a flexible cellular core, the core includes a number of buoyancy elements each comprising a hollow cylindrical body containing gas under pressure and having one or both ends convex and of resilient material, and its circumferential wall of rigid material. In Fig. 1, the core comprises buoyancy elements 4 each with a resilient convex end wall 6 bearing against a rigid flat.end wall 5 of an adjacent element, soft rubber tapes 28 connecting the elements ; the stranded conductor 2 surrounds the core and is enclosed in rubber 3 or other flexible waterproof insulation. A continuous soft rubber sleeve may replace the tapes 28 and be formed by lapping or extrusion, and be vulcanised together with the outer cover 3. The rigid ends 5 may be concave. In another form, both ends of the elements 4 are convex and resilient, 'and solid disks, with flat or dished ends, are inserted at intervals between groups of elements 4. The resilient convex end walls may be of soft natural or synthetic rubber compositions, and the rigid circumferential or end walls of hard natural or synthetic rubber compositions, or of celluloid, plasticised synthetic resin composition or metal such as aluminium or an alloy thereof. The circumferential walls of the elements may be reinforced, as by inwardly extending webs or a moulded-in helix of brass &c. In Fig. 9, the element 4 comprises a body 20 of draw@ aluminium with circumferential beads 18 and a soft rubber cap 24 secured by screw &c. threads 19. Soft rubber ends may be secured to hard rubber bodies by vulcanising, either directly or with a junction layer, or by cementing 'or mechanical connection; a soft rubber sleeve may enclose the body and the edges of the ends. In Fig. 8, soft rubber caps 22 are connected to a moulded synthetic resin body by a threaded joint, the internal pressure causing the soft rubber flange to give a tight joint; cement may also be introduced between the threads, or the threads in the body may be formed on a moulded-in brass insert to which the threads on the caps 22 are vulcanised. Ends may be formed by cupping rubber sheet into recesses and holding the cups by suction while they are applied to the ends, preferably conical, of the body, the whole being then heated ; the body may also be formed by a similar cupping process and pressed to the ends before curing, acceleraters and retarding agents giving desired vulcanisation conditions. Bodies may also be extruded as a hollow tube and cut to the desired length before or after partial vulcanisation. Air or other gas under pressure may be entrapped between the parts of the elements as they are assembled, or substances such as water or ammonium nitrite may be introduced and decomposed during vulcanisation, or pressure medium may be introduced by a needle, preferably through a boss 29, Fig. 8. Adjacent elements of the core may be connected by snap action devices such as press studs 26, Fig. 7, which may be of metal or a moulded part of the end wall.