Patent ID: 7150308

Claim:
An injection molding method, comprising: providing solid metal into a melt furnace; melting the solid metal into a liquid state in the melt furnace; providing the liquid metal from the melt furnace through a first metal inlet into a metal supply system located in the melt furnace; pumping the liquid metal from the metal supply system through a second metal inlet into a vertical injection mechanism; and injecting the liquid metal from the vertical injection mechanism into a mold located above the vertical injection mechanism; wherein: the metal supply system comprises a conduit; a metering plunger located in a sleeve and operatively attached to the conduit pumps the liquid metal; the liquid metal is provided into the sleeve when the metering plunger retracts to draw in liquid metal into the sleeve by suction from the melt furnace through the first metal inlet; the liquid metal is provided into the vertical injection mechanism when the metering plunger advances to provide liquid metal from the conduit through the second metal inlet; the sleeve contains a first opening to the melt furnace located between a maximum retracted and a maximum advanced position of the metering plunger; the metering plunger is retracted above the first opening to draw in liquid metal into the sleeve; and the metering plunger is advanced below the first opening to provide liquid metal through the second metal inlet; further comprising: vertically moving a three way valve located across the conduit to a first position to allow liquid metal to flow from the melt furnace into the sleeve; vertically moving the three way valve to a second position to allow liquid metal to flow from the metering plunger toward the second metal inlet after the step of retracting the metering plunger above the opening; and vertically moving the three way valve to a third position to allow liquid metal to flow from the vertical injection mechanism to a drain.