Extrusion die with rotating components

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 through 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 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;
• wherein the first cylindrical surface is formed on a tip portion that is mounted for rotation within the bore, said tip portion including a tip drive connector system extending externally of the bore for operative connection to a tip drive motor;
• wherein the second cylindrical surface is formed on a die element that is mounted for rotation within the second module, said die element including a die drive connector system extending externally of the die assembly for operative connection to a die drive motor;
• and
• wherein the tip drive motor and the die drive motor are separate and independently controlled by the computer controller;
• wherein the die element is rotatably mounted on the die holder by a support system including a series of bearings positioned at an interface of said die element and said die holder, 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 die member, and said chamber having means, mounted on the die member for circulating the oil within said bath;
• and
• a combination of radial and thrust bearings mounted in said bearing compartments to support said die member for rotation.

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 through 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 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;
• wherein the flow passage further comprises:
• a pair of supply channels constructed in said die body, connecting with the inlet and extending through said die body towards opposite sides of said die body;
• a distribution groove having upstream and downstream edges, constructed an interface between said die body and said die holder, connecting with the supply channels and extending in a plane transverse to the direction of flow;
• and
• a conical extrusion passage communicating with the downstream edge of said distribution groove and extending downstream to connect with the extended cylindrical exit channel, wherein the distribution groove receives flowing plastic from the supply channels and distributes said flow in a balanced manner about its downstream edge to supply a balanced flow of plastic to the extrusion passage and the cylindrical exit channel.