| 摘要 |
PURPOSE:To keep both airtightness and watertightness between a synthetic-resin- coated steel pipe and a cap for a long time by surrounding an end part of the synthetic-resin-coated steel pipe with a molten synthetic resin and by cutting a constriction of the molten synthetic resin under a specified condition. CONSTITUTION:The figure (a) shows that a molten resin 6 is cylindrically extruded from a circular die 100 and is surrounding an end part 31 of a synthetic-resin- coated steel pipe 3. By closing a mold shown in the figure (b), fusion under heating by pressing an overlapping part 61 of the molten resin 6 faced to an end part 31 of the synthetic-resin-coated steel 3 against the layer 2 of the coated steel pipe 3, constriction and fusion under heating of the central part of the molten resin 6 by the upper end 111 of a mold 110, and cutting a constriction 62 of the molten resin 6, are carried out at the same time. As a result, the molten resin 6 is molded into a cap-shape and a steel 1 can be completely covered under an airtight and watertight condition with the cap-shaped molten resin 6 and the covered layer 2 of the synthetic resin covered steel pipe 3.
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