Method for discharging gas out of metal molds and apparatus therefor

摘要

A method and apparatus capable of continuously discharging contaminated gas out of metal molds, the gas being generated prior to the casting step and including moisture. A gas vent valve is provided at a gas vent passage in communication with a mold cavity. A suction unit and a vacuum pump are selectively connected to the gas vent valve. After closure of the metal molds, the suction unit is connected to the gas vent valve to perform sucking interior of the mold cavity. By this suction, an external air is introduced into the metal molds through a pouring port of a shot sleeve. Thus, contaminated gas in the cavity is replaced with a clean air. During injection molding, the gas vent valve is connected to the vacuum pump for decompressing the mold cavity. Vapor explosion is avoidable since moisture content is removed from the mold cavity even if the molten metal is introduced into the cavity.