| 摘要 |
<p>1370438 Multilayer pipes GINSA GENERAL INVENTORS SA 29 Nov 1971 [5 Dec 1970 13 Sept 1971] 55369/71 Heading B5A [Also in Divisions B2 and F2] Tubular plastics structures comprising an intermediate plastics layer, e.g. expanded polyurethane, with plastics reinforcing layers on each surface are made by forming the intermediate layer with at least one helical groove extending through the thickness thereof, and placing in the groove(s) plastics material which is then hardened to form helical reinforcing elements connecting the surface layers and bonded to or unified with them. The reinforcing plastics may be thermosetting. The constituent layers may all be deposited on to a rotating mandrel by spraying. After the intermediate layer has been deposited, at least one helical groove is cut therein to constitute spaces for the connecting elements; resin is then applied to fill the grooves and form the outer reinforcing layers. The cutter may be shaped to provide a groove of bevelled cross-section. Glass filamentary reinforcement may be provided in the groove by feeding therein continuous filaments which have been individually impregnated by passage through a bath containing resin. The rotating mandrel may be replaced by a stationary detachable cylindrical shell around which the means for depositing the layers and cutting the groove(s) rotates; this is particularly useful for the manufacture on site of vertical reservoir and tower walls. The process may be modified by winding a preformed strip of plastics material around the mandrel or shell to constitute the intermediate layer, the connecting elements being formed in spaces between the windings and/or by the juxtaposition of coatings on the edges of the strip; the internal and external surfaces of the product are then coated with resin, e.g. by spraying.</p> |
