GB735992A - Improvements in the manufacture of insulating tubes - Google Patents

Abstract

735,992. Tubes of fibrous material. VIAL, P., and SIBILLE, R. Oct. 14, 1953 [Oct. 28, 1952], No. 28293/53. Class 99 (2). [Also in Group XVI] An electrical insulating tube is formed by winding a layer of pulp of cellulosic fibres onto a mandrel, e.g. a rubber-covered and expansible mandrel (see Group XVI), and subjecting the tube thus obtained to an outwardly-directed, radial compression while the tube is partially moist. Subsequently the tube may be impregnated with an insulating composition which fills the spaces between the fibres. As shown, paper pulp flows from a distributer 1 to a trough 3 and is deposited on an endless wire cloth 4 passing over a number of suction boxes 5 which draw most of the water from the pulp. The layer of pulp is wound onto the mandrel 6 resting on the cloth 4 and rotatably supported by oscillatable arms 7. The mandrel carrying the still moist tube may be disposed within a casing, e.g. a two-part block, and then expanded so that the tube is compressed against the casing; alternatively, the casing is formed by a metal tube, a sheet-iron plate wound onto the tube and held in place by a coiled wire, a tube of wire cloth, or wire cloth wound around the tube. The tube may be partially dried before compression, or wholly dried after compression, and while still mounted on the mandrel; alternatively the tube is submitted to a drying operation when removed from the mandrel and, if necessary, with the aid of a further support. When the casing comprises a wire cloth, drying of the tube is carried out with the casing in position. If the tube is subjected to a limited degree of compression the outer periphery of the tube is dried to form a hard outer layer and compression takes place without the use of a casing.