Method and apparatus for pulsed pressure molding

Abstract

Method and apparatus for creating a molded product by first liquefying a metal in a crucible disposed in a crucible chamber and then applying a differential pressure level to the liquefied metal so as to force the liquefied metal into a mold. Once the liquefied metal is drawn into the mold, the pressure of the liquefied metal in the mold is raised to a solidification pressure in oscillating pressure steps. Once the pressure is raised to the solidification pressure, the liquefied metal is allowed to solidify.

What is claimed is: 
     
         1 . A method for pulsed pressure molding comprising:
 liquefying a metal in a crucible disposed in a crucible chamber;   applying a differential pressure level to the liquefied metal so as to force the liquefied metal into a mold;   raising the pressure of the liquefied metal in the mold to a solidification pressure in oscillating pressure steps; and   allowing the liquefied metal to solidify.   
     
     
         2 . The method of  claim 1  wherein applying a differential pressure to the liquefied metal comprises increasing the pressure in a crucible chamber. 
     
     
         3 . The method of  claim 1  wherein applying a differential pressure to the liquefied metal comprises decreasing the pressure in a mold chamber. 
     
     
         4 . The method of  claim 1  wherein raising the pressure of the liquefied metal in oscillating steps comprises:
 applying a gaseous pressure at a first level to the liquefied metal in the mold wherein the first pressure level is greater than the applied differential pressure; 
 reducing the gaseous pressure level to a level that is still greater than the applied differential pressure; and 
 increasing the gaseous pressure level to a second level that is greater than the first gaseous pressure level. 
 
     
     
         5 . The method of  claim 4  wherein applying a gaseous pressure comprises applying a gaseous pressure to either of the mold chamber or the crucible chamber. 
     
     
         6 . The method of  claim 1  wherein raising the pressure of the liquefied metal in oscillating steps comprises:
 isolating the liquefied metal in the crucible chamber from the liquefied metal in the mold; 
 applying a mechanical pressure at a first level to the liquefied metal in the mold wherein the first mechanical pressure level is greater than the applied differential pressure; 
 reducing the mechanical pressure level to a level that is still greater than the applied differential pressure; and 
 increasing the mechanical pressure level to a second level that is greater than the first mechanical pressure level. 
 
     
     
         7 . A pulsed pressure molding machine comprising:
 crucible disposed in a crucible chamber;   differential pressure unit for applying a differential pressure to a liquefied metal disposed in the crucible;   mold that receives the liquefied metal when a differential pressure is applied to the liquefied metal; and   pressure controller that controls the pressure unit so as to increase the pressure applied to the liquefied metal in increasing oscillating pressure steps.   
     
     
         8 . The molding machine of  claim 7  wherein the differential pressure unit comprises a pressure unit disposed to apply pressure to the crucible chamber. 
     
     
         9 . The molding machine of  claim 7  wherein mold is disposed in a mold chamber and the differential pressure unit comprises a vacuum unit disposed to apply a vacuum to the mold chamber. 
     
     
         10 . The molding machine of  claim 7  wherein the differential pressure unit comprises a gaseous pressure unit and the controller causes the differential pressure unit to:
 increase the applied differential pressure to a first increased level; 
 reduce the applied differential pressure to a level that is greater than the initially applied differential pressure; and 
 increase the applied differential pressure to a level that is greater that the first increased level. 
 
     
     
         11 . The molding machine of  claim 10  wherein the gaseous pressure unit is disposed to apply a positive pressure to the crucible chamber. 
     
     
         12 . The molding machine of  claim 10  further comprising a mold chamber for containing the mold and wherein the gaseous pressure unit is disposed to apply a positive pressure to the mold chamber. 
     
     
         13 . The molding machine of  claim 10  further comprising a mechanical pressure actuator for applying mechanical pressure to the liquefied metal and wherein the mechanical pressure actuator is disposed to isolate liquefied metal contained in the crucible chamber from the liquefied metal contained in the mold and wherein the pressure controller causes the mechanical pressure actuator to:
 apply work to the liquefied metal in the mold so as to cause an increase in pressure therein to a first level that is greater than the pressure applied to the liquefied metal by the differential pressure unit; 
 reduce the work applied to the liquefied metal in the mold so as to reduce the pressure therein to a level that is greater than the pressure applied to the liquefied metal by the differential pressure unit; and 
 apply work to the liquefied metal in the mold so as to cause an increase in pressure therein to a second level that is greater than the first pressure level applied to the liquefied metal by the mechanical actuator. 
 
     
     
         14 . The molding machine of  claim 10  further comprising a mechanical pressure actuator for applying mechanical pressure to the liquefied metal and an isolator gate and wherein the isolator gate is disposed to isolate liquefied metal contained in the crucible chamber from the liquefied metal contained in the mold and wherein the pressure controller causes the mechanical pressure actuator to:
 apply work to the liquefied metal in the mold so as to cause an increase in pressure therein to a first level that is greater than the pressure applied to the liquefied metal by the differential pressure unit; 
 reduce the work applied to the liquefied metal in the mold so as to reduce the pressure therein to a level that is greater than the pressure applied to the liquefied metal by the differential pressure unit; and 
 apply work to the liquefied metal in the mold so as to cause an increase in pressure therein to a second level that is greater than the first pressure level applied to the liquefied metal by the mechanical actuator. 
 
     
     
         15 . A molded product manufactured by a molding process that comprises:
 liquefying a metal;   applying a differential pressure level to the liquefied metal so as to force the liquefied metal into a mold;   raising the pressure of the liquefied metal in the mold to a solidification pressure in oscillating pressure steps; and   allowing the liquefied metal to solidify.