GB1371823A - Coaxial cables - Google Patents

Abstract

1371823 Coaxial cables GENERAL CABLE CORP 8 June 1972 26890/72 Heading H1A An air spaced coaxial cable wherein the inner and outer conductors 11, 17 (Fig. 1) respectively are spaced by polar polyethylene discs 12 such that when these discs are heat bonded therein, watertight compartments are formed to improve cable reliability. The cable is manufactured, Fig. 1, by moulding discs 12 to inner conductor 11 at 16, shaping and enclosing discs 12 with outer conductor 10 by dies 18, 19, welding conductor 10 at 20, drawing through dies 21, to make diameter of 10 correspond to diameter of discs 12, by means of haul off device 22, and heating at 23 to bond discs 12 to inside of outer conductor 40. In the embodiment shown in Fig. 4, attenuation properties of the cable are improved by interspersing electromagnetically lossy adhesive polar polyethylene discs 32<SP>1</SP> with low loss non-polar polyethylene discs 32<SP>11</SP>, which do not form a watertight bond with the inner and outer conductors, but which enhance the attenuation properties of the cable. In a further embodiment, Fig. 5 (not shown), a thin walled tube (35) of bondable dielectric material is interposed between discs 32<SP>1</SP>, 32<SP>11</SP> and outer conductor 33. In another embodiment, Fig. 6 (not shown), when a plastics sheath is applied over the outer conductor, an intermediate layer of bondable dielectric material is interposed therebetween to improve the heat bonding process. In yet another embodiment (not shown) the local surfaces of the inner and outer conductors may be pre-treated with adhesive polar-polyethylene before the bonding of the spacer discs thereto. A table is given showing comparative attenuation factors between a cable according to the present invention, and that with foam dielectric.