Pressure casting machine having a hydraulically loadable shot unit

Claim 1

A PRESSURE CASTING DEVICE COMPRISING, MEANS DEFINING A MOLD, A BUSHING CONNECTED TO SAID MOLD FOR FILLING THE MOLD WITH A CHARGE OF MATERIAL TO BE CAST, A SHOT PISTON DISPLACEABLE IN SAID BUSHING FOR DIRECTING THE CHARGE OF MATERIAL INTO THE MOLD UNDER PRESSURE, A PRESSURE CYLINDER, A PRESSURE PISTON SLIDABLE IN SAID PRESSURE CYLINDER AND CONNECTED TO SAID SHOT PISTON FOR DISPLACING SAID SHOT PISTON IN SAID BUSHING, MEANS FOR DIRECTING FLUID UNDER PRESSURE TO SAID PRESSURE CYLINDER INCLUDING A PUMP CONNECTED TO SAID PRESSURE CYLINDER FOR DIRECTING AN INITIAL FLOW OF RELATIVELY LOW FLUID PRESSURE BEHIND SAID PRESSURE PISTON DURING THE INITIAL MOVEMENT OF SAID SHOT PISTON FOR INJECTING A MATERIAL TO BE CAST INTO SAID MOLD AND A FLUID PRESSURE ACCUMULATOR CONNECTED TO SAID PRESSURE CYLINDER AND LOCATED IN CLOSE PROXIMITY TO SAID PRESSURE CYLINDER FOR SUPPLYING FLUID UNDER HIGHER PRESSURE THAN SAID PUMP, A SHORT CONDUIT CONNECTING SAID ACCUMULATOR TO SAID PRESSURE CYLINDER FOR DIRECTING PRESSURE TO EFFECT RAPID MOVEMENT OF SAID SHOT PISTON AFTER AN INITIAL MOVEMENT HAS TAKEN PLACE, AT LEAST SAID SHOT PISTON BEING MADE OF A RELATIVELY LIGHT MATERIAL SO THAT THE KINETIC ENERGY IMPARTED THERETO DURING MOVEMENT WILL BE RELATIVELY SMALL, SAID ACCUMULATOR HAVING A PISTON SLIDABLE THEREIN AND DIVIDING SAID CHAMBER INTO A GAS CHAMBER AND A LIQUID CHAMBER, AND MEANS FOR CHARGING SAID GAS CHAMBER WITH A PRESSURIZED GAS, SAID LIQUID CHAMBER BEING CONNECTED TO SAID PRESSURE PISTON.