INJECTION LIQUID PRESSURE CIRCUIT FOR PRESSURE INCREASE TYPE DIE CASTING MACHINE

摘要

PURPOSE:To change over smoothly a piston to a high speed and a pressure increase by constituting a titled circuit in such a way that the solenoid operated selector valve connecting to an accumulator closes of itself upon stopping of a hydraulic pump and a speed change and a pressure increase operation are accomplished simultaneously. CONSTITUTION:When a solenoid valve 32 is excited, the pressure oil in a pump 24 opens a check valve 28 to supply the pressure oil in an accumulator 21 to a solenoid operated selector valve 29. When the position Z of said valve is energized, the pressure oil acts on the side Z of a selector valve 48 and is supplied to selector valves 41, 44, 45. The pressure oil flows through check valves 50, 38 into a pressure chamber 3 and advances a piston 2 leftward at a low speed. When the valve 44 is energized, the pressure oil acts on a check valve A30 and opens the same in an extremely short time, then the pressure oil flows through a check valve 38 into a pressure chamber 3, thereby advancing the piston 2 leftward at a high speed. The advance of the piston 2 is prohibited when the charging of the molten metal is completed and since the pressure in the chamber 3 increases, the check valve 38 is closed in a short time. When the valve 45 is energized, a sequence valve 46 opens to open a check valve B55 in a short time. The oil pressure flows through said valve to a pressure chamber 39 and the pressure increase operation is accomplished.