Patent ID: 6596213
Filing Date: 2003-07-22
Classification: B29B,B29C,B29K,Y10T

Abstract:
A method for co-extruding multiple polymer plastic materials as for injecting through a gate region into a mold cavity to produce a molded article, that comprises, co-extrusively flowing streams of polymer plastic materials with at least one interior stream that is to serve as an interior core of a resulting molded plastic article within inner and outer streams of plastic material that serve as covering wall plastic material layers for the core; forcing the flowing streams to flow along concentric annular flow paths within and along a longitudinally extending tubular extruder nozzle to the cavity gate region; adjusting the flow streams initially to cause the core stream to start to flow at a region of substantially zero gradient in the transverse flow velocity profile of the extrusion; thereupon varying the relative volumetric flow ratio of the inner and outer layer streams after the zero-gradient flow of the core layer has started, in order to offset the core layer flow from the zero gradient and to shift the core layer closer to one of the inner or outer annular flow boundaries, thereby to produce a molded article wherein the major portion of the core layer is closer to one of the inner or outer article walls than the other.