| 摘要 |
1,212,255. Coating cores by extrusion. BRITISH INSULATED CALLENDER'S CABLES Ltd. 27 Feb., 1969 [28 Feb., 1968], No. 9672/68. Heading B5A. In the coating of a core 1 with rubber or a rubber-like composition the core is passed through an extruder 4 to receive a degasified rubber mix as coating, a vacuum being applied between the core and coating in the die head, and the coated core is passed substantially horizontally through a curing bath 6 open to the atmosphere such that the pressure difference across the wall of the coating is due substantially entirely to atmospheric pressure. As shown, bath 6 contains a liquid, heated by heaters 7, which preferably comprises a mixture of alkali metal nitrates and or/nitrates, e.g., a eutectic mixture of potassium and sodium nitrate and sodium nitrate and sodium nitrite. Rollers or a stainless steel belt may guide the coated wire through the bath and a detector 12 may regulate a tensioning unit 11. Also provided are a wash bath 8 and a drier 9. Instead of the liquid bath, a fluidized bed may be employed comprising small glass beads, sand or talc. The bed is preferably electrically heated with air being the preferred fluidizing gas. The extruder comprises a screw whose pitch and/or root diameter provide a precompression zone (13), Fig. 2 (not shown), a decompression zone (15) associated with a vacuum line (16) and breaker plate (14), and an output zone (17) of intermediate screw pitch to passage area ratio. Fig. 3 (not reproduced), shows a crosshead having a resilient inlet seal (23) and a vacuum port (24). The core may be a bare or previously coated wire, a group of wires, or one or more strands. The coating materials specifically mentioned are natural rubber, neoprene (poly. chloroprene), butyl rubber, silicone rubber and styrene butadiene rubber. |
