Molten metal injector system and method

Abstract

The molten metal injector system includes a holder furnace containing a supply of molten metal. A casting mold is supported above the holder furnace. The mold defines a mold cavity for receiving molten metal from the holder furnace. One or more molten metal injectors is supported from the bottom side of the mold. The injector is in fluid communication with the mold cavity and includes a reciprocating piston for pumping molten metal upward from the holder furnace and injecting the molten metal into the mold cavity. The injector is partially submerged in molten metal when the holder furnace contains molten metal. The injector includes a molten metal intake for receiving molten metal into the injector. The molten metal intake is located below the surface of the molten metal in the holder furnace.

We claim:  
     
         1 . A method of operating a molten metal injector in connection with a supply of molten metal and a casting mold having a mold cavity, comprising the steps of: 
 providing a casting mold defining a mold cavity;    supporting at least one molten metal injector from the bottom side of the casting mold, with the injector including a cylinder defining a piston cavity and a reciprocating piston located within the cylinder, with the cylinder including a molten metal intake for receiving molten metal into the piston cavity, and with the piston movable through a downstroke and a return stroke by a lifting mechanism operatively connected to the piston;    locating a supply of molten metal below the casting mold such that the cylinder and piston are at least partially submerged in the supply of molten metal and such that the molten metal intake lies submerged in the supply of molten metal, with the injector providing fluid communication between the supply of molten metal and mold cavity;    moving the piston through a downstroke with the lifting mechanism;    opening the molten metal intake during the downstroke of the piston to permit inflow of molten metal into the piston cavity from the supply of molten metal to at least partially fill the piston cavity with molten metal;    moving the piston through a return stroke with the lifting mechanism;    closing the molten metal intake to prevent further inflow of molten metal into the piston cavity from the supply of molten metal; and    injecting molten metal directly into the mold cavity with the injector.    
     
     
         2 . The method of  claim 1 , wherein the molten metal intake is a valve, with the valve operable between open and closed positions by a valve controller, and wherein the method further comprises the steps of: 
 opening the valve with the valve controller during the downstroke of the piston to permit inflow of molten metal into the piston cavity from the supply of molten metal; and    closing the valve with the valve controller during the return stroke of the piston to prevent further inflow of molten metal into the piston cavity from the supply of molten metal.    
     
     
         3 . The method of  claim 1 , further comprising the step of supplying inert gas to the piston cavity during the downstroke of the piston.  
     
     
         4 . The method of  claim 1 , further comprising the step of filtering the molten metal flowing into the piston cavity through the molten metal intake with a molten metal filter.  
     
     
         5 . The method of  claim 1 , further including the steps of: 
 providing and supporting a plurality of molten metal injectors from the bottom side of the casting mold, with each of the injectors providing fluid communication between the supply of molten metal and mold cavity; and    individually controlling the injectors to regulate the injection of molten metal into the mold cavity of the casting mold.    
     
     
         6 . An injector for injecting molten metal into a mold cavity of a casting mold, comprising: 
 a cylinder for at least partially submerging in a supply of molten metal, with the cylinder defining a piston cavity, and with the cylinder defining a fill conduit in fluid communication with the piston cavity and extending through a top wall of the cylinder;    a piston positioned within the piston cavity and movable through a downstroke and a return stroke, wherein the fill conduit extends along an axis substantially parallel to the piston over its entire length;    a lifting mechanism fixed to the cylinder and operatively connected to the piston for moving the piston through the downstroke and the return stroke; and    a valve connected to the cylinder for receiving molten metal into the piston cavity when the cylinder and piston are at least partially submerged in the supply of molten metal,    wherein the valve is configured to open during the downstroke of the piston permitting inflow of molten metal into the piston cavity when the cylinder and piston are at least partially submerged in the supply of molten metal, and    wherein the valve is configured to close during the return stroke of the piston preventing the inflow of molten metal into the piston cavity, and the piston is configured to pump the molten metal received in the piston cavity into the fill conduit for injection into the mold cavity when the cylinder and piston are at least partially submerged in the supply of molten metal.    
     
     
         7 . The injector of  claim 6 , further including a molten metal filter covering the inlet to the valve for filtering the molten metal flowing into the piston cavity through the valve during the downstroke of the piston.  
     
     
         8 . The injector of  claim 6 , wherein the piston and the cylinder are made of materials compatible with molten aluminum and aluminum alloys.  
     
     
         9 . The injector of  claim 6 , wherein the lifting mechanism is a rack and pinion.