| 摘要 |
PURPOSE:To obtain a pipe made of polyethylene where a recessed part is not generated even if a connecting protrusion is shaped on an end part, by a method wherein post- hitting of blowing-in jigs having almost the same diameter as the inside diameter of the pipe into parison is performed on both end part sides of the parison, the inside of the pipe is made smooth and the pipe connecting protrusions are shaped on the outsides of both end parts of the pipe. CONSTITUTION:Parison 2 comprised of polyethylene resin extruded through a die 1 of an extruding machine is placed between necessary molds 3, 4 for manufacture of a pipe having connecting protrusions on end parts. Post-hitting of blowing-in jigs 7, 8 having almost the same diameter as the inside diameter of a pipe which is to be manufactured and air blowing-in holes 5, 6 in the central part into the parison 2 are performed from both sides of an introduction direction of the parison into the mold and the reverse direction at a time. Air is blown in through the blowing-in holes 5, 6 and a pipe 11 made of polyethylene, on the outsides of end parts of the pipe of which the connecting protrusions 10 are shaped is molded. The parison 2 is pressed against a space among the blowing jigs 7, 8 and molds 3, 4, the connecting protrusions 9, 10 are shaped precisely and the inside of the pipe becomes smooth. |
