Injection mechanism for molding plastics

A mechanism for injecting plastics from an injection molding machine into one or more mold cavities via one or more gates in said one or more mold cavities, said mechanism comprising:

• an injection bushing for receiving molten plastic from said injection molding machine;
• more than one injection nozzle for injecting molten plastic into said one or more mold cavities, each of said nozzles having one or more nozzle conduits therethrough for passage of molten plastic, each said nozzle conduit terminating in a nozzle aperture positioned immediately opposite one of said mold cavity gates;
• a distributor block for providing flow paths for the molten plastic between said receiving bushing and said injection nozzles, said distributor block including distributor channel means communicating with said nozzle conduits, said injection nozzles being connected to said distributor block;
• means for maintaining the molten plastic at an adjusted temperature;
• means for injecting the molten plastic from said injection bushing through said distributor channel means and said nozzle conduits into said mold cavity gates;
• a needle valve positioned in each of said nozzle conduits for closing each respective mold cavity gate when moved longitudinally outwardly from said nozzle aperture;
• a guide bushing slideably mounted for longitudinal movement in said distributor block opposite each said nozzle conduit, each said guide bushing having the end of one of said needle valves remote from said nozzle aperture fixedly mounted therein, each said guide bushing also having a surface area exposed to the molten plastic being injected through said distributor block whereby the pressure of the molten plastic when being injected by said injection means tends to move said guide bushing away from said nozzle aperture thereby moving said needle valve longitudinally and opening said mold cavity gate;
• a chamber in said distributor block;
• and,
• one plunger slideably mounted in said distributor block chamber and connected to several of said guide bushings and thereby to their respective needle valves for moving said needle valves longitudinally outwardly to close their respective mold cavity gates, said plunger being actuated by fluid pressure and being adapted for longitudinal movement in the same direction as said needle valve to which said plunger is connected.