Gas venting arrangement in high speed injection molding apparatus and

Abstract

A gas venting arrangement in a high speed injection molding apparatus such as a high speed die casting machine. The gas venting arrangement includes a gas vent control valve which is closable at an optimum timing and at high speed. This valve closure is achievable by providing an improved combination of a control circuit and a valve driving mechanism. The control circuit is connected to a molten metal sensor and sends a high voltage output drive signal to the valve driving mechanism when the sensor detects a first molten metal or a metal splash. The valve driving mechanism includes an electromagnetic valve connected to a pneumatic source and a pneumatically operated valve connected between the electromagnetic valve and the gas vent control valve. The pneumatically operated valve is also connected to the pneumatic source. The electromagnetic valve performs prompt change-over operation upon receiving the drive signal, and supplies driving pneumatic pressure to the pneumatically operated valve. The pneumatically operated valve performs prompt change-over operation upon receiving the driving pneumatic pressure for promptly applying pneumatic pressure to the gas vent control valve, to thereby close the same at high speed and at optimum timing without delay.