| 摘要 |
PURPOSE:To provide a bent pipe having a small radius which makes as return part of a heat insulation pipe compact, improves building properties and renewal properties and is capable of contriving a cost reduction. CONSTITUTION:A flexible mandrel 2 is inserted into a pipe made of resin which is directly after extrusion forming and prior to crystallization, bending processing of the pipe 1 is performed so that bending radius becomes not exceeding three times as long as that of the same pipe 1, the flexible mandrel 2 is pulled out after crystallization of the same pipe 1 and the bent pipe 1 having a small radius to be formed is obtained. |
