Coaxial injector screw providing improved small shot metering
AssigneeMGS Mfg. Group, Inc.
InventorJohn Hahn
Life of this patent
Estimating the term…
Abstract
A screw for injection molding provides a coaxial piston that allows the effective cross-sectional area of the screw to be varied during the injection cycle permitting small shot metering with relatively large diameter injection molding screws.
Claims16
An injection screw for injection molding comprising:
- a screw for fitting within an injector barrel, the screw having outer threads to advance molten plastic toward a front of the barrel with rotation of the screw about an axis, the screw further having a central bore along the axis;
- and
- a piston slidably received within the central bore of the screw movable along the axis with respect to the screw;
- whereby a plastic shot may be controlled by movement of the piston within the screw.
An injection molding machine comprising:
- an injector barrel having a bore extending along an axis and terminating in a nozzle to abut a mold held by the injection molding machine;
- a screw for fitting within the injector barrel, the screw having outer threads to advance molten plastic through the bore toward the nozzle with rotation of the screw about an axis, the screw further having a central bore along the axis;
- a first actuator for rotating the screw about the axis;
- a piston slidably received within the central bore of the screw movable along the axis with respect to the screw;
- a second actuator providing relative movement between the piston and the screw.
A method of injection molding using an injection molding machine having an injector barrel having a bore extending along an axis and terminating in a nozzle to abut a mold held by the injection molding machine;
- a screw for fitting within the injector barrel, the screw having outer threads to advance molten plastic through the bore toward the nozzle with rotation of the screw about an axis, the screw further having a central bore along the axis;
- and a piston slidably received within the central bore of the screw movable along the axis with respect to the screw, the method comprising the steps of:
- (i) rotating the screw to fill the a front of the barrel with molten plastic while retracting the piston with respect to the screw away from the nozzle;
- and
- (ii) adjust a relative position of the screw and piston to eject molten plastic from the nozzle.
A program for use in a method of injection molding using an injection molding machine having an injector barrel having a bore extending along an axis and terminating in a nozzle to abut a mold held by the injection molding machine;
- a screw for fitting within the injector barrel, the screw having outer threads to advance molten plastic through the bore toward the nozzle with rotation of the screw about an axis, the screw further having a central bore along the axis;
- and a piston slidably received within the central bore of the screw movable along the axis with respect to the screw, the program executable on an electronic computer to:
- (i) rotate the screw to fill a front of the barrel with molten plastic;
- and
- (ii) move the screw relative to the piston to eject molten plastic from the nozzle.
Dependencies are inferred from the claim text.