Patent ID: 6598658
Filing Date: 2003-07-29
Classification: B22D

Abstract:
The method of pressure casting a lead article comprising the steps of:increasing the pressure of a source of molten lead sufficiently to force the molten lead to flow in a liquid state into a mold cavity; maintaining the mold cavity at a sufficiently low temperature so that when molten lead is injected therein the molten lead solidifies therein; closing a runner to said mold cavity while maintaining said molten lead in a closed system to prevent entrapment of air in the molten lead as a fresh charge of molten lead is introduced into the closed system; and removing a solidified casting from said mold cavity, wherein the closing of the runner includes the step of driving a piston into said mold to thereby shut off the supply of molten lead to the mold cavity and to simultaneously increase the internal pressure of the molten lead solidifying therein to thereby reduce the volume occupied by air in said solidified casting.