Patent ID: 6957953
Filing Date: 2005-10-25
Classification: B29C

Abstract:
1. An extruder for extruding extrudate, comprising: a generally cylindrical barrel portion having a longitudinal axis and an end face; a screw conveyor rotatably arranged coaxially within the barrel portion, the screw conveyor having a downstream end, the screw conveyor having helical flights that define a first flow path within the barrel for the extrudate; an adapter arranged on the end face of the barrel portion, said adapter having an opening with varying diameters that defines a second flow path for the extrudate where a downstream end of the opening defines an exit portion of the extruder, the opening of the adapter having a first diameter that tapers toward the longitudinal axis to a narrower second diameter, and a third diameter that tapers from a downstream end of the narrower second diameter outwardly from the longitudinal axis, and the cross-sectional flow of extrudate between an upper edge of the first diameter opening and a side of the screw tip is approximately equal to the cross-sectional flow of extrudate between the third diameter opening and a lower edge of the screw tip; and a screw tip secured to the downstream end of the screw conveyor and extending into the adapter where the screw tip reduces dead space in a cross-sectional flow area of the second flow path so that the cross-sectional flow of extrudate in the first and second flow paths remain approximately constant whereby the volume of extrudate flowing through the first flow path is relatively constant with the volume of extrudate exiting the extruder.