| 摘要 |
PURPOSE: To provide a method of producing a thick-walled plastic hollow bode free from residual stress that is normally caused in cast molding. CONSTITUTION: A cavity cooling core 9 is inserted into central cavity formed by a lower mold 2 and a lower mold 3, through a side portion by using a core moving device 21 having a rotational drive shaft 24 and a threaded portion. After the molten resin poured into the cavity is hardened by cooling it from inside and outside, the cavity cooling core 9 is drawn out and then the hollow product is separated from the molds. A reinforcing metal pipe is inserted into the hollow of the product, so that the hollow article becomes suitable for use as a long-size structural material. Since the hollow article has been sufficiently cooled from inside and outside so that no residual stress is present, the article is free from damages, such as cracking, which would otherwise be caused by temperature changes, even if it is used in an environment where the temperature remarkably changes. |
