Apparatus for hot runner injection moulding

Claim 1

Apparatus for hot runner injection moulding including a die assembly, a die cavity defined within said die assembly, an inlet port in said die assembly communicating with said die cavity, molten synthetic resin material being injected, in use, through said inlet port into said die cavity, an injector device for delivering molten synthetic resin material to said die cavity through said inlet port, said injector device including an injection nozzle having an open end communicating with said inlet port and an elongated plunger means disposed in said bore in said injector device, said plunger being reciprocably mounted in said bore for movement between an inoperative position wherein one end of said plunger means extends into and closes the open end of said injection nozzle to prevent flow of the molten synthetic resin through said injection nozzle into said inlet port and an operative position wherein said one end of said plunger means is withdrawn from said injection nozzle and said plunger allows molten synthetic resin material to flow through said injection nozzle into said inlet port, and a thermally insulating sleeve positioned around said injection nozzle and having a corresponding hole therethrough so as to provide thermally insulating material between said die assembly and the whole of that portion of said injection nozzle adjacent thereto, said hole in said sleeve communicating with said inlet port so that said sleeve is spaced from said die cavity by a portion of said die assembly and so that when said plunger means is in said operative position, the molten synthetic resin material can flow from said injection nozzle through said hole in said sleeve and through said inlet port to said die cavity, and when said plunger means is in said inoperative position said one end of said plunger means further extending through said injection nozzle and said hole in said sleeve into said inlet port.