| 摘要 |
1,083,895. Coating conductors by extrusion. STANDARD TELEPHONES & CABLES Ltd. Feb. 12, 1965 [Feb. 13, 1964], No. 6097/64. Heading B5A. In a method of coating an electrical conductor with insulating material the coated conductor is passed through a compression chamber 13-17 curved in conformity with the natural sag of the cable, attached directly to extrusion nozzle 7 and provided with a compressed air inlet 38 to maintain an air water interface 41 away from the nozzle. A liquid outlet 40 and bleed passage 39 are interconnected by means of a valve and pressure sensitive element (neither shown), to keep the position of interface 41 substantially constant. Generally a hawser (1), Fig. 1 (not shown), from reel (2) is heated by electrode wheels (11, 12) before and after passing through a drying chamber (3), the hawser is clad in copper strip (4), welded or box seamed in position at (6), thermoplastics insulating material such as polyethylene is extruded around the copper clad hawser at (7) and the electrical cable thereby formed is passed through a compression chamber (8), a modified form to that shown in Fig. 3, the pressure being applied to the cable by liquid at a value sufficient to prevent cavity formation in the insulant. The compression chamber (8) is fed with hot water under pressure from a tank (23) by a pump (24) and returned to the tank by pumps (34, 35). The pressure within the chamber is regulated by the provision of baffles (28) and (31), Fig. 2 (not shown), or a bleed pipe (not shown) between the baffles, the water being strained by gauzes (29, 32). Although hot water is used in chamber (8), its temperature is less than that of the insulant immediately after the latter leaves the extrusion die. More than one chamber (8) may be utilized. Drying chamber (3), Fig. 1 (not shown), is connected to a pump (10) and is kept below atmospheric pressure, liquid in the hawser interstices being vaporized therein as a result of heating by electrode wheels (11, 12). The insulant may surround a corrugated metal sheath rather than a hawser.
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