| 摘要 |
PURPOSE:Title device wherein a precooling part is provided between the heating zone and the expansion zone to cool forcibly only the outer layer of plastic tubes, thereby preventing the sticking of tubes in the expansion zone to reduce the longitudinal expansion. CONSTITUTION:The whole part of plastic tube 5 is softened by heating with heater 7 in heating zone 1 and sent to precooling zone 2 where the tube is cooled only at the surface layer while the inner layer is kept at higher temperatures. Then tube 5 is sent to expansion zone 3 and the vacuum is applied to the surface layer to expand the tube 5 to the diameter of dice 13. At this time, as the surface is in solid state, the sticking of the tube to the wall of dice 13 is prevented and thus the longitudinal expansion can be avoided. |
