| 摘要 |
PURPOSE:To obtain synthetic resin spiral tube having pressure resistance, watertightness and flexibility by a method wherein continuous core material is loosely inserted in the inward of swollen-out part when band-like member, at the tip portion of the swollen-out part of which inwardly projecting rib is provided, is lap-wound and, after cooling, the continuous core material is taken out by cutting up the central part of the rib and finally the outer surface of the swollen-out part is covered by molten plastic. CONSTITUTION:A molten plastic band-like member 2, which is extruded from an extrusion machine, has a swollen-out part 3, which is continuous in extrusion direction and at the top part of which an inwardly projecting rib 5 or thick part is provided. When the band-like member 2 is lap-wound, a soft continuous core material for shape retaining is loosely or closely inserted in the inward of said swollen-out part 3. When the member practically cools down, the continuous core material is taken out by cutting up the swollen-out part 3 at the central part of the rib 5 or thick part. Next, another molten plastic flow is extruded to the cut-up part 6 or onto the outer surface of the swollen-out part 3 so as to provide a cap band 7 for covering the cut-up part. |
