| 摘要 |
1,161,210. Coating conductors by extrusion. GENERAL CABLE CORP. 18 Oct., 1966 [20 Dec., 1965], No. 46442/66. Heading B5A. An electrical conductor core 10 is given a relatively thin conducting covering 14 at an extruder (12), Figs. 1 and 2 (not shown), and is then passed through a second extruder 16 to receive a relatively thick insulating covering 18 and simultaneously a further relatively thin conducting covering 20. The covering materials may be curable butyl rubber or ethylene-propylene polymers, but are preferably of cross-linkable polyethylene, the conducting layers being suitably loaded with carbon black. Extruder (12) has an exchangeable die (35) centred by screws (42). Extruder 16 is spaced downstream of extruder (12) to allow sufficient cooling of covering 14 before it passes through die 55. Covering 20 is derived from material 79 which is forced through conduit 76 to a peripheral channel 82, which promotes even flow, and is then bled to the interface between die 55 and insulating material 69 which forms covering 18. This form of feed gives to material 79 the action of a lubricant and it is stated that this material may be a compound, e.g. of polyethylene and butyl rubber. A curing chamber (22), Fig. 1 (not shown), preferably a catenary chamber, is provided downstream of extruder 16 and a further extruder (24) may provide a protective covering (23), Fig. 6 (not shown), applied before or after passage through chamber (22). All the extruders may incorporate screw impellers. Preferred thicknesses of the coverings are 15-20 mils for covering 14, 150-350 mils for covering 18 and 15-30 mils for covering 20.
|
