| 摘要 |
PURPOSE:To obtain the titled covered steel pipe, by blowing a hot air current against a melted plastic belt so that the melted plastic belt is forcibly united to the outer circumferential surface of a steel pipe that is rotatably fed, the bonding strength being stable even if the steel pipe has any stepped parts. CONSTITUTION:In case a steel pipe 4 is rotatably fed continuously, and a plastic belt 2 that is extruded from a T-die 1 and is in a melted or semimelted state is forcibly united onto the outer circumferential surface of the steel pipe 4 so that a plastic cover 6 may be formed, air 9 is dehumidified by a drier 10, is compressed by a pressure compensating circuit, and is heated by a heater 12 to obtain a high pressure hot current. The high pressure hot current is jetted from an air curtain nozzle 7 generally toward the axis of the steel pipe 4 so as to cause the plastic belt 2 to be forcibly and uniformly united to the outer circumferential surface of the steel pipe 4 so that the intended plastic-covered steel pipe may be obtained. |
