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A method and associated apparatus for gas assisted injection molding wherein a quantity of fluid molding material is injected through a first injection flow path in a gas assisted injection molding nozzle into a mold cavity. The injection is then stopped by interrupting the flow of fluid through the

A method and associated apparatus for gas assisted injection molding wherein a quantity of fluid molding material is injected through a first injection flow path in a gas assisted injection molding nozzle into a mold cavity. The injection is then stopped by interrupting the flow of fluid through the first mold cavity, and introducing a time delay if desired. After any time delay, a quantity of pressurized gas or fluid at a first desired pressure is injected into the mold cavity through a second injection flow path which is isolated from the first injection flow path. The pressure is then reduced to a desired holding pressure, and the pressure is held in the mold while the part cools enough to be self supporting, at which time the pressure is vented from the mold cavity, and the part removed. The apparatus used, by isolating the molding material from the gas passages, is able to be of a simpler construction, avoid clogging of the passages, and use larger gas passages, all without the use of any check valves.

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A method of fluid assisted injection molding for producing a molded article, said method including the steps of: a) employing an injection nozzle for injection of fluid molding material from a supply of fluid molding material and a pressurized fluid from a supply of pressurized fluid into a mold cav

A method of fluid assisted injection molding for producing a molded article, said method including the steps of: a) employing an injection nozzle for injection of fluid molding material from a supply of fluid molding material and a pressurized fluid from a supply of pressurized fluid into a mold cavity, wherein said injection nozzle contains a rotatable valve containing a cylindrical barrel axially mounted within said injection nozzle, said cylindrical barrel having a separate first fluid molding material passageway and a separate second pressurized fluid passageway such that when said cylindrical barrel is in a first position said first passageway forms a portion of a first injection flow path and when said cylindrical barrel is in a second position said second passageway forms a portion of a second injection flow path, wherein said first and second injection flow paths form a common flow path from the end of the cylindrical barrel adjacent to the mold cavity to the end of the injection nozzle adjacent to the mold cavity, and wherein said first and second passageways at the end of said cylindrical barrel adjacent to the mold cavity are axially displaced from each other and from the center of the circle formed by said end of the cylindrical barrel; b) activating said rotatable valve to inject a quantity of fluid molding material from said supply of fluid molding material through said first injection flow path in said injection nozzle into said mold cavity, wherein said cylindrical barrel is rotated to said first position; c) activating the rotatable valve to stop said injection of fluid molding material through said first injection flow path by rotating said cylindrical barrel from said first position; d) activating the rotatable valve to inject a charge of pressurized fluid into said mold cavity through said second flow path in said injection nozzle to form a fluid containing cavity in said fluid molding material, wherein said cylindrical barrel is rotated to said second position and wherein said second flow path is isolated from said supply of fluid molding material; and e) containing said pressurized fluid within said mold cavity until said molded article has set in the mold cavity; and f) venting said pressurized fluid to ambient through said second flow path.