| 摘要 |
PURPOSE:To uniformly wind a thermoplastic synthetic resin sheet around the surface of a steel pipe even under environment where atmospheric temp. is low, by preheating the thermoplastic synthetic resin sheet to at least about room temp. prior to bringing said resin sheet into contact with the outer peripheral surface of the steel pipe to impart flexibility thereto. CONSTITUTION:A sheet preheating means 30 is arranged between a sheet supply means 10 and a sheet press bonding means 20 through a frame 13 and, when atmospheric temp. is low, the thermoplastic synthetic resin sheet 2 supplied from the sheet supply means 10 in a hard state is preheated to make it possible to impart flexibility to said resin sheet 2. A steel pipe 1 is fed in the pipe axis direction at a constant speed by a truck and the preheated thermoplastic synthetic resin sheet 2 supplied from the sheet supply means 10 is spirally wound around the outer peripheral surface of the steel pipe. For example, with due regard to weatherability, the thremoplastic synthetic resin sheet is formed from two-ply polyethylene consisting of a usual polyethylene outer layer and a modified polyethylene inner layer having adhesiveness and, for example, the modified polyethylene having adhesiveness to be used is pref. obtained by reacting high of low density polyethylene with maleic anhydride. |
