Patent ID: 6485671
Filing Date: 2002-11-26
Classification: B29C

Abstract:
A method for creating an injection molded plastic article with a hollow chamber therein and utilizing an injection molding machine, a mold with a cavity, and a gas injection mechanism, the injection molding machine having a barrel with an injection end and a rotatable and longitudinally moveable screw positioned in the barrel, said method comprising the steps of:determining the volume of said mold cavity; determining the pressure necessary to fill said mold cavity with plastic material; determining the amounts by volume of plastic material and gas desired in said mold cavity, wherein the volume of gas is determined and fixed by said pressure; injecting said determined volume of plastic material into said mold cavity; and injecting said determined and fixed volume of gas into said plastic material in said mold cavity, while maintaining the pressure of said gas substantially constantly with the plastic pressure, said injection of said gas being delayed until sufficient plastic material has been injected into said mold cavity thereby preventing passage of said gas completely through said plastic material and causing blow-out.