Apparatus for the injection molding of thermoplastics

A shut-off nozzle used in apparatus for the injection molding of fluidized thermoplastics, comprising:

• a nozzle body including a first bore for establishing a flow path for the fluid plastic, a first end of said nozzle body being adapted for fluid connection with a sprue of an associated mold body, and a second end thereof being adapted for fluid connection with an end of an associated injection molding machine, said nozzle body further comprising a second bore which communicates with said first bore and a third bore which communicates with said second bore;
• a needle valve adapted for reciprocating movement in said nozzle body second bore to control the flow of plastic through said nozzle body, said valve including a tip end, a base end, and a longitudinally extending bore open at one end through said tip end of said needle valve;
• an actuator bar adapted for extending through said nozzle body third bore, said needle valve being secured at said base end to said actuator bar, a fluid passage being provided in said actuator bar, said needle valve bore being in fluid communication with said actuator bar fluid passage;
• a source of pressurized fluid adapted to flow through said actuator bar fluid passage and said needle valve bore, said source being in fluid communication with said actuator bar fluid passage;
• an actuator mechanism for selectively moving said actuator bar and said needle valve to a closed position thereby preventing the flow of plastic through said nozzle body;
• a means for preventing the flow of plastic through said actuator bar fluid passage;
• and,
• a means for regulating the flow of pressurized fluid in both directions through said valve body fluid passage.

An apparatus for molding a plastic part comprising:

• an injection molding machine adapted for plasticizing and discharging thermoplastic materials;
• a mold body including a mold cavity adapted for receiving a flowable thermoplastic from said injection molding machine, said mold body including a sprue communicating with said mold body cavity;
• a nozzle body, secured between said mold body and said molding machine and including a first bore and a flow path means defined in said nozzle body for establishing a path for the flowable thermoplastic from said molding machine to said mold body sprue;
• a first valve means for controlling the flow of plastic through said nozzle body flow path means, said first valve means including a fluid passage having first and second ends, said first end being open to said mold body sprue, said first valve means being reciprocably mounted in said nozzle body first bore;
• a source of pressurized fluid which is adapted to be injected into said mold cavity through said second end of said first valve means fluid passage;
• actuator means for actuating said valve body to a closed position thereby preventing the flow of plastic through said nozzle body and into said mold body cavity but still allowing said pressurized fluid to flow into said mold body cavity;
• and
• regulating means for preventing the flow of the flowable thermoplastic through said valve means fluid passage and controlling the flow of pressurized fluid through said valve means fluid passage in both directions, said regulating means comprising:
• a first check valve having an upstream end;
• a second check valve spaced from the first check valve and having a downstream end, and
• a fluid pressure equalization line connecting the upstream end of said first check valve and the downstream end of said second check valve.