| 摘要 |
PURPOSE:To enable to eliminate and mitigate residual stress and bending stress of the inside of a polyethylene pipe, by so constituting the titled method that forming of the pipe is performed by extrusion molding, wound round a molding jig, the temperature is raised to the annealing temperature and the same is made to cool to the normal temperature after the lapse of a predetermined period of time. CONSTITUTION:After an end part of a polyethylene pipe 9 formed through extrusion molding has been fixed to a fixing fitment 6 of a molding jig 10 and the pipe 9 has been wound round a first roller 2, second roller 3 and third roller 4 in order while the pipe 9 is being pulled, the pipe 9 is fixed to a fixing fitment 7 and cut off. In addition to the above, when winding of the polyethylene pipe 9 round the molding jig 10 has been completed, the same is put in an annealing furnace; after the lapse of a predetermined period of time the same is left under the normal temperature as it is, it is cooled and cut off in a predetermined length. As the polyethylene pipe 9 is shrinked through heat shrinkage occuring on an annealing and cooling time, a deformation based on a warp and bend to be generated at the time of winding of the polyethylene pipe 9 round the molding jig 10 is eliminated and a product fitted to the molding jig 10 is obtained. |
