Patent ID: 8663536

Claim:
An extruder unit ( 22 ) for an injection molding system ( 20 ), comprising a barrel ( 28 ) containing a screw ( 30 ); a piston housing ( 40 ), connected to and in communication with the barrel ( 28 ), the piston housing ( 40 ) defining a piston chamber ( 42 ); a piston ( 48 ), slidably located within the piston chamber ( 42 ), and movable between a retracted position and an extended position; the piston ( 48 ) further being adapted to rotatably mount the screw ( 30 ); a motor assembly ( 36 ), mounted to the piston housing ( 40 ) and operable to rotate the screw ( 30 ); and a hybrid injection actuator ( 38 ), the hybrid injection actuator ( 38 ) including: a drive unit ( 50 ), the drive unit ( 50 ) being one of electrically driven and hydraulically driven and being operable to move the piston ( 48 ) between the retracted position and the extended position; a gas pressure unit ( 93 ), coupled to the piston chamber ( 42 ) via a gas conduit ( 96 ), the gas pressure unit ( 93 ) being operable to provide a boosting force to the piston ( 48 ) to urge the piston ( 48 ) towards the extended position; and a lock valve ( 98 ) located between the gas pressure unit ( 93 ) and the piston chamber ( 42 ), the lock valve ( 98 ) being movable between an open position and a closed position to provide a selective communication between the gas pressure unit ( 93 ) and the piston chamber ( 42 ).