Patent GB-198044-A (GB)
Title: New or improved methods of loading submarine cables
IPC: H02G15/14
Filed: 1922-02-23
Abstract: 198,044. Pernot, F. E., and Rich, L. J. Feb. 23, 1922. Inductances.-Lumped or concentrated electric inductances for loading submarine cables are arranged so that the hydrostatic pressure is communicated equally to all parts of the loading structure in order to prevent forces tending to changed the shape of the structure, the loading coils being preferably impregnated with and surrounded by a fluid or practically incompressible material such as gutta percha or caoutchouc. Coils of toroidal form may be used to avoid interference from external metal bodies or external magnetic fields. The coil 17 may be wound on a solid toroidal core 16, Fig. 6, of impregnated wood, gutta percha, vitrified clay, or stone or of a material containing iron, the winding filling the central aperture of the core. The coil 17 is positioned in an inner sealed tank 19 by perforated supports 20 and a perforated protecting layer 18 of insulation, the tank 19 having corrugated or other flexible ends 21 and being filled with an incompressible material or fluid such as tar or oil, preferably introduced into the tank in a vacuum chamber to exclude air. The tank 19 is surrounded by an outer tank 31 perforated so that the water has access to the exterior and flexible ends of the tank 19, the hydrostatic pressures being communicated to the fluid in the tank 19 and to every part of the loading coil. The cable conductor 25 is passed through the ends 21 of the tank 19 through seals 26 or through stuffing boxes 28, Fig. 9, with packing compressed by a screw 30. The cable is passed through a central aperture of the head 32 of the tank 31, and the sheathing wires 36 may be held by a screw clamp 37 and are passed through apertures in the head 32 and spliced back into the cable. In a modification, the space between the tanks 19, 31 is filled with gutta percha, Chatterton's compound, tar or other material protecting the tank 19 from the action of the sea but communicating the pressure. In a further modification, the windings 17 are impregnated with and surrounded by a protective incompressible material which does not remain liquid, such as gutta percha, balata or vulcanized rubber, and are enclosed in a perforated closelyfitting container through one end of which a twincore cable is introduced, the insulation of the cable being connected to the protective material around the coil so that the conductor is completely enclosed from the cable to the coil. In order to avoid sharp bends in the cable, at the point of entry to the loading structure, the cable may be introduced to the tank containing the loading coils by a ball-and-socket joint comprising socket 64, Fig. 8, formed in the tank and engaging a ball 61 through which the cable is passed and to which the wire sheathing is secured by a screw clamp 62. The ball 61 may have a hood to prevent its entry into the tank when the cable is not under tension. For convenience of manufacture, the loading coil core may be in two' or more sections wound separately, and, in order to allow access to the centre of the core of the fluid by which the coil is surrounded, may be hollow and perforated. In the form shown in Fig. 4, the coil is in two parts held together by wires 14 over a protective strip 13, the two halves of the hollow perforated core 9 being connected by internal members 12. Specification 195,815 is referred to. The Provisional Specification describes loading coils of flat strip conductors of the width of the coil separated by strip insulation.