Patent ID: 6988821
Filing Date: 2006-01-24
Classification: B29B,B29C

Abstract:
1. An improved screw of the type that rotates within a heated containment barrel for conveying and melting plastic material, the screw comprising: a shaft having an upstream end and a downstream end; a primary flight secured to the surface of the shaft and extending helically in successive turns around the circumference of the shaft; a secondary flight secured to the surface of the shaft downstream of the primary flight, wherein a primary channel is defined between the primary flight and secondary flight; the primary and secondary flights defining a feed section at the upstream end of the shaft, a metering section at the downstream end of the shaft, and a melting section intermediate the feed and metering sections; each of the primary and secondary flights having a lead that varies along the length of the screw and the leads being selected so that the primary channel increases in width through at least the melting section.