Patent ID: 6139179
Filing Date: 2000-10-31
Classification: B29C

Abstract:
An axially elongated extruder screw having a screw body including an axially extending extruding portion defined by a feed section at an inlet end of said screw, a metering section at an outlet end of said screw and a barrier section between said feed and metering sections, said extruder screw further comprising:a first helical primary flight having a first advancing surface, and a first retreating surface, extending continuously about and coaxial with said screw body substantially along the entire length of said extruder screw;a second helical primary flight extending continuously at least part-way along said feed section to said outlet end of said extruder screw and having a second advancing surface and a second retreating surface;said screw body defining a first helical surface of revolution between said first advancing and second retreating surfaces, and cooperating therewith to define a first solids channel;said screw body defining a second helical surface of revolution between said second advancing and first retreating surfaces, and cooperating therewith to define a second solids channel;said barrier section including;a first barrier flight having a third advancing and a third retreating surface, extending about and coaxial with said screw body along said barrier section, said first barrier flight being positioned between said first advancing and second retreating surfaces thereby causing said first helical surface of revolution to be redefined between said third advancing and second retreating surfaces;said screw body defining a third helical surface of revolution between said first advancing and third retreating surfaces and cooperating therewith to form a first melt channel extending along said barrier section;a second barrier flight having a fourth advancing and a fourth retreating surface, extending about and coaxial with said screw body along said barrier section, said second barrier flight being positioned between said second advancing surface and said first retreating surface thereby causing said second helical surface of revolution to be redefined between said fourth advancing and first retreating surfaces; andsaid screw body defining a fourth helical surface of revolution between said second advancing and fourth retreating surfaces and cooperating therewith to form a second melt channel extending along said barrier section.