INJECTION MOLDING DEVICE FOR HOLLOW RESIN MOLDING

PURPOSE:To mold a hollow molded article having a stable quality by a method wherein a resin reservoir part connected to a cavity is provided on a parting face of a mold, a tip of a gas injection nozzle is so disposed as to face the resin reservoir part, and the resin reservoir part is changed in volume in accordance with a resin temperature. CONSTITUTION:A molten resin J is injected into a cavity 6. When the resin J is charged further into a resin reservoir part 10, the temperature of a sub- runner part 10a is detected by a temperature sensor 21. In accordance with the detected temperature, the volume of a thick-walled part 10b is changed, whereby the curing speed is made constant at the surface of the resin J in the thick-walled part 10b. In the stage that a cured shell layer is formed on the surface but the inner part is not cured, a pin part 15 of a gas injection nozzle 8 is projected to perforate the surface of the resin J. By retracting the pin part 15, a high-pressure gas in a gas flow path 16 flows into the resin through the hole of the surface layer of the resin J. At this time, the curing speed in the resin reservoir part 10 is always constant. Therefore, a trouble never occurs at the time of injecting the gas.