| 摘要 |
1,139,961. Flexible tubing. GENERAL CABLE CORP. 19 Jan., 1966 [1 Feb., 1965], No. 2469/66. Heading F2P. [Also in Division H1] A flexible duct comprising a metallic strip 14, folded into tubular form with no internal support and with its edges 18, 18 free for relative movement, is prevented from collapsing inwardly when a jacket 36 of plastics material, e.g. polyethylene, is extruded over it, allowed to cool and contract, by initially coating the strip 14 with a thin layer 24 of highly adhesive polyethylene containing reactive carboxyl groups which forms a chemical bond with the metal, the relatively thicker outer jacket 36 being firmly bonded to the inner layer 24 so as to prevent relative movement between the outer jacket 36 and the folded strip 14 and between the strip edges 18, 18. In this way the plastics material is unable to slip relative to the metallic strip 14 shrinkage being able to take place only by radial contraction i.e. by reduction of thickness. As shown, a transversely corrugated aluminium strip 22, which is coated on one, 24, and preferably the other side, 26 with a thin layer, or layers, e.g. of a copolymer of polyethylene and acrylic groups, before it is fed, e.g. from a storage roll, not shown, to pinch rollers 16, is advanced in the direction 12 past a supporting roll 46 and a heater 40 to an extruder 32 to receive the plastics jacket 36, e.g. of polyethylene, the thin layer 24 becoming activated by the hot jacketing material 34 to develop a firm bond with the jacket 36. The thin inner layer 26 is preferably formed to protect the interior surface of the duct, e.g. from corrosion. The duct encloses a loose cable core 10. Alternatively, the duct may be employed to carry a gas. The longitudinal edges of the strip (14) may be slightly spaced, Fig. 3 (not shown), or be arranged in overlapping relationship, Fig. 4 (not shown). As shown, the strip is 0À008 inch, the layers 24, 26 0À001-0À003 inch, and the jacket 0À06-0À08 inch thick. |
