GB1249741A - Improvements in or relating to apparatus for making coaxial cable - Google Patents

Abstract

1,249,741. Insulating conductors by extrusion. PHELPS DODGE COPPER PRODUCTS CORP. 28 July, 1969, No. 37844/69. Heading B5A. [Also in Division H1] A concentric layer 14 of insulating material disposed about a tubular centre conductor 11 carries a helical web 16 of insulating material which supports an outer conductor (not shown). A thin aluminium or copper tape is passed through a forming die 70 which has a passage 71 whose cross-section varies continuously from rectangular at the input end to substantially annular at the output end and wraps the tape into a tube with overlapping edges. The tube is passed over a central supporting rod to an extrusion die 38. A plasticized resinous material, e.g. polyethylene, polysulphone, P.T.F.E. is fed into the extrusion apparatus by a screw 36 and is forced into the die orifice through an annular cavity 34. The die 38 has a radial suborifice 42 intersecting a circular orifice 40 of larger diameter than the centre conductor 11. The die 38 is rotated in a carrier 44 by a motor 53, as the centre conductor 11 is pulled through the die 38 thus forming the helical web 16 and insulating layer 14. The die 38 is rotated in the same direction as the direction in which the outer edge of the centre conductor overlaps the inner edge. To produce an insulating layer of uniform thickness the speed of the conductor 11 through the apparatus 22, the speed of rotation of the die 38 and the rate of feed of the plastics insulating material are co-related by control unit (30, Fig. 3, not shown). The relationship may be varied to change the pitch of the helical web, either manually or automatically.