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US 4,341,474 AGranted
Extruder screw
OwnerNorton C. Wheeler, Jr., Waseem Rahiminventors
Life of this patent
Estimating the term…
Abstract
An extruder screw having a root, a helical primary flight on the root and a helical barrier flight on the root and forming with the primary flight a solids channel and a melt channel. The width of the solids channel gradually decreases and the width of the melt channel gradually increases along an upstream zone of the melting section. The width of the channels gradually changes in a downstream zone of the melting section but substantially less than in the upstream zone.
Claims7
An extruder screw having an inlet end and an outlet end comprising:
- (a) a root,
- (b) a helical primary flight extending about the root having a trailing edge and a leading edge, said flight and said root defining a feed section at the inlet end of the screw, a metering section at the outlet end of the screw and a melting section between the feed section and the metering section, and
- (c) a helical barrier flight on the root forming a solids channel with the trailing edge of the primary flight and a melt channel with the leading edge of the primary flight, the width of the solids channel gradually decreasing and the width of the melt channel gradually increasing in a downstream direction, said melting section being divided into at least two lengthwise zones, wherein the change in width of each of said channels is at a first constant rate in one of the zones and a second constant rate in the other of the zones, said rates being in accordance with the melting characteristics of the thermoplastic material in the screw.
Dependencies are inferred from the claim text.