Patent ID: 6033205
Filing Date: 2000-03-07
Classification: B29C

Abstract:
A reciprocating screw for an injection molding machine, the machine including:a heating extruder barrel in which said reciprocating screw is mounted rotatably, the barrel having an extruder head, a tail portion and a longitudinal axis;a hopper coupled with the tail portion of the barrel for feeding plastic granules into the barrel via the hopper, said screw being capable of rotating in the barrel so as to move the plastic granules from the tail portion to the extruder head, thereby melting gradually the plastic granules in the barrel to form a molten plastic material in the extruder head, and extruding the molten plastic material from the extruder head; anda check valve disposed in the extruder head to prevent return flow of the molten plastic material in the extruder head;wherein the improvement comprises:said reciprocating screw being shaped as an eccentric screw which has a thread and a shank portion, said shank portion being eccentric from said thread and said longitudinal axis, said thread having a front end located in the extruder head of the barrel and a rear end located in the tail portion of the barrel, wherein an eccentric distance of said shank portion relative to said thread and said longitudinal axis increases gradually from the rear end to the front end.