GB1289553A - - Google Patents

Abstract

1289553 Cables SUPERIOR CONTINENTAL CORP 17 Nov 1969 [22 Nov 1968] 56134/69 Heading H1A In a telecommunication cable a metal foil electrical shield 15, 15<SP>1</SP>, 15<SP>11</SP>, Fig. 12, or 15, Fig. 16, or 15, Fig. 17, is provided between groups of insulated conductors 14, 16 transmitting signals in opposite directions. The metal foil, e.g. of aluminium may be coated on one or both sides with plastic insulating material, e.g. polyethylene, polypropylene or polyethylene terephthalate, or completely surrounded, i.e. also at the edges, by plastic insulating material. Where the foil is uncoated, and possibly also where the foil is coated, conductor regions are filled with a polyethylene grease-like material serving both as dielectric insulation and as a moisture barrier. The shielding foil may be longitudinally or helically wrapped around the conductors and may be corrugated to increase its mechanical strength. As shown in Fig. 12 the shield is composed of three overlapping helically disposed tapes 151, 15<SP>11</SP>, 15<SP>111</SP>. The composite core formed by the conductor groups 14, 16 is surrounded by a polyethylene terephthalate tape 17, a corrugated longitudinally folded or wrapped armour tape 18 which may be bonded on one or both sides to a layer of polyethylene, and a polyethylene sheath 19 which may be filled with carbon black. The metal foil may have a thickness of 0.0254 to 0.1270 mm. and may be twice the thickness of the dielectric coating. The polyethylene grease-like material has an average molecular weight below 10,000 and a density below 0.91 grms./ml, at 25‹ C. Rotating wire twisting apparatus and dies for applying a plastic-coated metal foil shield between groups of conductors are diagrammatically illustrated (Figs. 18, 19), the die plates having rows of radially spaced holes and slots for the conductors and foil shield.