GB921232A - Improvements in or relating to co-axial type cable and methods of manufacture thereof - Google Patents

Abstract

921,232. Air-spaced cables. STANDARD TELEPHONES & CABLES Ltd. Jan. 27, 1961 [Jan. 28, 1960], No. 3098/60. Class 36. [Also in Group V] In the manufacture of an air-spaced coaxial cable an insulating material such as polythene for holding the conductors apart is extruded as a strip 32 of the form shown in Fig. 13A. The strip is passed through a controlled temperature zone to heated rollers 36, 37 which mould it to the form shown in Fig. 1. After cooling, the strip is passed through slit rollers 44 which divide the central web 5 and trim the outer webs 4, and the central conductor 7 is introduced to the position shown in Fig. 13C. The two parts 14, 15 of the strip are rotated and slid into water-cooled blocks 48, Fig. 13D, through which cooling air is blown to the outer edges of the part-strips, while the conductor 7 passes through a hole in a heater 49 which also supplies radiant heat to the webs 4, 5 and to the edges of the internal integral webs 6 of the partstrips. The part-strips and the conductor are then passed through pressure-rollers 52 where the part-strips adhere to each other to form a tube surrounding and adhering to the conductor. After removal of the projecting joined webs a strip 56 of a high conductivity metal such as copper is formed around the tube to provide the outer conductor, the edges of this strip being corrugated, if desired, to prevent overlap of adjacent edges. The cable may be finished with helically wrapped steel tapes. Instead of dividing the central web 5 before the introduction of the conductor the surface-heated strip may be folded about its central web over the conductor and the parts united before trimming the projecting parts of the webs. In another embodiment, Fig. 8, the insulating material is moulded to form two arcuate channels connected by a central web 21 which forms part of the walls of the complete tube when the strip is folded about its inner webs. These are of alternate types 22 and 25 so that a web 22 can fit into a slot 28 in the co-operating web 25 of the other channel. The projecting portions of the joined outer webs 20 are removed as in the previous embodiments before the application of the outer conductor. In all embodiments it is possible to provide longitudinal ridges on the insulating tube which serve to space the outer conductor from the tube, some of the ridges being provided by only partially removing the projection portions of the joined webs.