| 摘要 |
The appts. includes a travelling mould with a cavity having a corrugated section sepd. by bell sections. Single wall bells are formed in a double wall thermoplastics pipe by moulding an outer wall to provide corrugated sections sepd. by bell sections and extruding a smooth inner wall into the outer wall. The inner wall is not subjected to the action of an internal presser and is removed wholly or in part from the bell section after the pipe is fromed. As the pipe cools, the air pressure in the chamber between the outer and inner walls reduces considerably tending to collapse the outer wall.
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