Counter-piston central injection die casting

Abstract

A die casting system can employ a counter piston to make central injection of large parts or multiple cavity parts possible. The die casting system can include a shot piston disposed on an injection side and a counter piston disposed on an ejector side. The counter piston can move between a sealing position to seal a liquid in the shot sleeve during pouring and slow injection phases, and an opening position to allow the liquid into the casting cavity during cavity injection phase.

What is claimed is: 
     
         1 . A die casting machine having an ejector side and an injection side, comprising:
 a counter piston disposed on the ejector side;   a shot piston disposed on the injection side; and   a shot sleeve configured to receive the shot piston and a liquid.   
     
     
         2 . The die casting machine of  claim 1 , wherein the counter piston is movable between a first position and a second position. 
     
     
         3 . The die casting machine of  claim 2 , wherein when the counter piston is in the first position, the liquid is allowed to flow from the shot sleeve to a casting cavity. 
     
     
         4 . The die casting machine of  claim 2 , wherein when the counter piston is in the second position, the liquid is prevented from flowing from the shot sleeve to a casting cavity. 
     
     
         5 . The die casting machine of  claim 2 , wherein when the counter piston is in the second position, the shot sleeve is sealed off by the counter piston from a casting cavity. 
     
     
         6 . The die casting machine of  claim 5 , wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. 
     
     
         7 . The die casting machine of  claim 1 , wherein the counter piston has a non-uniform surface facing the shot sleeve, the non-uniform surface configured to form a corresponding non-uniform surface on a casting part. 
     
     
         8 . The die casting machine of  claim 2 , wherein the counter piston is further movable to a third position. 
     
     
         9 . The die casting machine of  claim 8 , wherein when the counter piston is in the third position, the counter piston is out of a counter piston sleeve for cleaning and lubrication. 
     
     
         10 . The die casting machine of  claim 1 , wherein the shot sleeve comprises a pour hole configured to allow the liquid to enter the shot sleeve. 
     
     
         11 . The die casting machine of  claim 1 , wherein the shot sleeve comprises a vent port configured to allow air to leave the shot sleeve. 
     
     
         12 . The die casting machine of  claim 1 , wherein the counter piston is connected to a driving cylinder, the driving cylinder configured to control motion of the counter piston. 
     
     
         13 . A die casting process employing a counter piston, the process comprising:
 moving the counter piston to at least partially contact a shot sleeve so as to prevent a liquid from flowing from through the shot sleeve to a casting cavity;   sliding a shot piston inside the shot sleeve so as to remove air from inside the shot sleeve; and   moving the counter piston away from the shot sleeve so as to allow the liquid to enter the casting cavity.   
     
     
         14 . The die casting machine of  claim 13 , further comprising moving the counter piston out of a counter piston sleeve for cleaning and lubrication. 
     
     
         15 . The die casting machine of  claim 13 , further comprising pouring the liquid into the shot sleeve through a pour hole on the shot sleeve. 
     
     
         16 . The die casting machine of  claim 13 , wherein removing air from inside the shot sleeve comprises removing air from the shot sleeve from a vent port on the shot sleeve. 
     
     
         17 . A die casting machine configured to control a flow of molten metal into a casting cavity during a third phase, comprising:
 a housing;   a shot sleeve slidingly disposed in the housing and forming a receptacle, the receptacle being configured to receive the molten metal and a gas during a first phase;   a shot piston configured to slide in the shot sleeve so as to remove the gas from the receptacle during a second phase leaving the molten metal; and   a counter piston slidingly disposed in the housing so as to prevent the molten metal from entering the casting cavity during the first and second phases while allowing the molten metal to enter the casting cavity during the third phase.   
     
     
         18 . The die casting machine of  claim 17 , wherein the counter piston comprises a tapered edge on a side facing the shot sleeve to create a pressing seal with a tapered edge of the shot sleeve on a side facing the counter piston. 
     
     
         19 . The die casting machine of  claim 17 , wherein the counter piston has a non-uniform surface facing the shot sleeve, the non-uniform surface configured to form a corresponding non-uniform surface on a casting part. 
     
     
         20 . The die casting machine of  claim 17 , wherein the counter piston is connected to a driving cylinder, the driving cylinder configured to control motion of the counter piston.