METHOD AND DEVICE FOR SUPPLYING GAS INTO HOLLOW SPACE OF INJECTION MOLDING DIE FOR MANUFACTURE OF HOLLOW SYNTHETIC SUBSTANCE BODY

摘要

PURPOSE: To produce a hollow body having a good surface and optimally uniform wall thickness by heating at least a part of a gas discharge port by molten plastic flowing in the cavity of a mold and subsequently supplying a predetermined amt. of a gas into the cavity of the mold through a gas injection nozzle. CONSTITUTION: Molten plastic is injected into the cavity of a mold through the injection duck of an injection mold. During the injection of the molten plastic, the front end part 17 of a gas injection nozzle 8 advances into the cavity 3 of the mold by the gas discharge opening 18 of the nozzle 8 and at least a part of the end part 17 of the gas injection nozzle 8 present in the almost central part of the cavity 3 of the mold is surrounded by the molten plastic flowing in the mold to be heated by the molten plastic. Next, a predetermined amt. of the gas is supplied into the cavity 3 of the mold under predetermined pressure through the gas injection nozzle 8. The plastic is pressed to the wall of the cavity of the mold in uniform thickness. By this constitution, a damage- free smooth film uniform in wall thickness is obtained.