Patent ID: 6669458
Filing Date: 2003-12-30
Classification: B29C,B29L

Abstract:
An extrusion die assembly, constructed of a plurality of axially aligned modules, for extruding plastic into tubular products, said plastic flowing through the die assembly from upstream to downstream, said assembly comprising:a flow passage extending through the die assembly, constructed to provide a balanced flow of plastic from an upstream inlet to a conical extrusion channel to a cylindrical exit channel; a die body having an axial bore and a first passage forming at least an upstream portion of said flow passage; a die holder, constructed to be assembled adjacent to the die body, said die holder having an axial bore constructed to cooperate with said axial bore of said die body and form a continuous axial bore therewith; said die holder further having a second passage means constructed to form at least a downstream portion of the flow passage connecting with the upstream portion; cooperating elements mounted for independent rotation in said die body and said die holder to form said cylindrical exit channel connecting with said flow passage to receive flowing plastic from said conical extrusion channel; said elements including first and second concentric cylindrical surfaces, said first surface displaced radially from said second surface to form said exit channel; drive motors operatively connected to the cooperating elements to independently rotate said elements to provide a rotating motion between said first and second surfaces relative to each other; and a computer controller operatively connected to the drive motors to control the relative rotation of the elements, to impart, in said plastic being extruded, a spiral orientation to enhance the strength of the tubular product; and further wherein said cooperating elements are rotatably mounted by a support system including a series of bearings positioned at an interface of said cooperating elements and said extrusion die assembly, said support system comprising: a closed oil bath including multiple bearing compartments and a chamber having oil contained therein, said chamber extending in a substantially annular configuration at the periphery of the cooperating elements, and said chamber having means, mounted on said cooperating elements for circulating the oil within said bath; and wherein, said series of bearings comprises a combination of radial and thrust bearings mounted in said bearing compartments to support said cooperating elements for rotation.