Method and device for manufacturing a sheath aerated in an insulating material around a conductor, and coaxial cable provided with such a sheath

摘要

The annular passage (34, 35) in the extruding head (3), surrounding the core conductor (20) guide (2), contains viscous insulant, eg. ethylene-propylene fluoride, under pressure. Following a conical reducing section (22, 32), this passage divides into eg. 4 or 5 equally spaced T-section apertures, the T cross-bars forming a divided outer annulus connected by the T legs to a complete inner annulus surrounding the guide. After drawing out and cooling, the cross-bar material unites, forming the tubular outer part of the core insulation, that emerging from the legs forming partitions between longitudinal air-filled voids. Opt., by extruding in a gas-chamber, other fillings are possible. A draw-down ratio of 25 or more is achieved by delaying conductor-insulant contact.