INJECTION LIQUID PRESSURE CIRCUIT OF PRESSURE INCREASE TYPE DIE CASTING MACHINE

摘要

PURPOSE:To perform speed change and pressure increase operation in a short time by causing the self-closing of solenoid-operated selector valves simultaneously when the pump of a hydraulic source stops operation. CONSTITUTION:When the charging of molten metal by an injection plunger is completed, a single action piston 2 is prevented from advancement and enters the pressurizing stage when the pressure in a pressure chamber 10 is increased up to the pressure of an accumulator 21 and a pilot-operated check valve 33 for quick closing is closed quickly by the internal pressure. Here a solenoid-operated selector valve 48 is held energized simultaneously with a solenoid operated selector valve 45; a sequence valve 47 opens and a pilot-operated check valve B34 for quick opening opens, then the pressure oil in the accumulator 21 acts on the pressure chamber 35 of a pressure increase cylinder 3, thereby accomplishing the pressure increase operation. Molten metal solidifies upon lapse of a specified time and when a solenoid valve 43 is energized at this point of time, a pilot-operated check valve 40 opens, and the pressure oil passes through a pilot- operated check valve A30 for quick opening then through the valve 40, etc. and flows into the pressure chamber 10 of a single action cylinder 1, thereby advancing the piston 2 and pushing out the solidified metal.