Apparatus for refining polymeric material

Abstract

An extruder apparatus for working polymeric material having a feed screw with dual flight defining a primary channel and a secondary channel. The primary channel progressively decreases in cross-sectional area while maintaining a constant width in cooperation with the secondary channel that increases in cross-sectional area to accommodate all the melt as it changes from a solid phase to a fluent phase. The secondary flight's height is such as to accommodate the melt as it is formed in the primary channel.

I claim: 
     
       1. In a machine for processing polymeric material comprising a cylinder; said cylinder having die means at one end thereof; a feed screw rotatably mounted in said cylinder and extending longitudinally therethrough for moving plastic material therethrough to progressively change said plastic material from the solid phase to a fluent phase for extrusion therefrom; said feed screw having first means for operatively exerting continuous pressure on said plastic material for moving said plastic material; second means integral with said feed screw for continuously leading off the fluent phase progressively from said first means as the plastic material is changed from the solid phase by contact with said cylinder, said fluent phase being directed away from and not through the remaining solid phase; .[.and.]. said first means defines a groove having a constant axial width with decreasing radial depth in the direction of said die means providing a constant amount of surface area exposed to said cylinder for material carried by said groove; .Iadd.and said second means defines a second groove having an increasing axial width with increasing radial depth in the direction of said die means. .Iaddend. 
     
     
       2. In a machine for processing polymeric material as set forth in claim 1 wherein said .Iadd.groove of said .Iaddend.second means .[.has a groove which.]. progressively increases in cross-sectional dimension toward said die means. 
     
     
       3. In a machine for processing polymeric material comprising a cylinder; said cylinder having a die means at one end thereof; a feed screw rotatably mounted in said cylinder for moving plastic material therethrough to progressively change said plastic material from the solid phase to a fluent phase for extrusion therefrom; said feed screw having first means for operatively exerting continuous pressure on said moving plastic material; second means integral with said feed screw for continuously leading off the fluent phase progressively changed from the solid phase by contact with said cylinder, said fluent phase being directed away from and not through the remaining solid phase; said first means defines a groove having a constant axial width to maintain a constant amount of the solid phase of the moving plastic material to contact said cylinder; said second means has a groove .Iadd.of increasing axial width and increasing radial depth to provide a groove .Iaddend.which progressively increases in cross-sectional dimension toward said die means; said groove of said first means is defined by the leading face of a primary flight and the trailing face of a secondary flight; and said primary flight having a greater clearance between the uppermost edge portion of said primary flight and .[.said barrel.]. .Iadd.the interior wall of said cylinder .Iaddend.than the uppermost edge portion of said secondary flight. 
     
     
       4. In a machine for processing polymeric material as set forth in claim 3 wherein the bottom surface of said groove of said first means merges with said uppermost edge portion of said primary flight to provide a clearance space that is equal to said clearance space provided between said uppermost edge portion of said primary flight and said barrel. 
     
     
       5. In a machine for processing polymeric material as set forth in claim 3 wherein the bottom surface of said groove of said first means defines a terminal portion that provides a clearance space closely adjacent to the merging of said first means with said second means at the terminal upstream end thereof that is approximately equal to the clearance space between said uppermost edge portion of said primary flight and .[.said barrel.]. .Iadd.the interior wall of said cylinder.Iaddend. . 
     
     
       6. In a machine for processing polymeric material as set forth in claim 5 wherein clearance space defined by said terminal portion of said first means in cooperation with .[.the.].  .Iadd.said .Iaddend.interior wall of said .[.barrel.].  .Iadd.cylinder .Iaddend.is constant for a portion of said groove of said first means.