GB311774A - - Google Patents

Abstract

311,774. Telefonaktiebolaget L. M. Ericsson, (Assignees of Sieverts Fabriks Aktiebolag, M.). May 16, 1928, [Convention date]. Cables; arrangement and disposition of parts of; with pressure controlling means for oil filling; laying; armouring. - In order to prevent the formation of voids in a leadsheathed high-tension cable, the insulating material is placed under pressure, and the lead sheath is covered with cement or concrete which may be reinforced, or is enclosed in tubes. In the construction shown in Fig. 1, a central oil cavity is formed in a conductor 1 which is covered with oil-impregnated paper insulation 2. A lead sheath 3 surrounds the insulation 2 and is enclosed in a layer 4 of impregnated fabric or paper. The cable thus formed is cast into concrete which forms a covering 5. Armouring 6, preferably helical wire concentrically disposed in the covering 5 is provided. When cables are laid out side by side, they may be cast in the same concrete, which may be of triangular section. In a modified construction, the outer covering is formed by a metal tube of steel, copper or brass, applied over the lead sheath of a rubber-insulated cable. Fig. 5 shows a method of laying down the cable, which is preferably divided into hermetically sealed sections 13, 14, the sections being united by sleeves 15. 'The cable ends may be mounted on poles 16, 17 and formed with end sleeves 18, 19 from which the conductor projects through insulators 20, 21. Fig. 6 shows a cable 22 formed with an expansion reservoir 23 communicating through a junction box 24 with the cable interior. A bottle 25 containing highpressure gas such as carbon dioxide is connected to the reservoir 23 to maintain the pressure. The bottle 25 may be cut off by a cock 26, and used only occasionally to compensate for leakage from the reservoir 23. In a modified apparatus, constant pressure is maintained within the cable by a pump which is adapted to pump oil from a reservoir into the cable through an end box when the cable is cooling. When the cable is heated, the oil is allowed to pass back to the reservoir through an automatic valve. The pump may be operated automatically under control of the pressure in the cable. The Specification as open to inspection under Sect. 91 (3) (a) describes also a rubber-insulated cable having metal tubes disposed directly on the insulation. This subject-matter does not appear in the Specification as accepted.