Patent ID: 6926509

Claim:
An extruder apparatus for producing a length of hollow tubing, said apparatus comprising an extruder barrel for containing a material to be extruded, a extrusion head having a die face, means to move the material from said extruder barrel through said extrusion head and outwardly through said die face, said extrusion head having a central mandrel and having an outer die surrounding said central mandrel and forming a space between said central mandrel and said outer die for passage of the material though said extrusion head to form a hollow extruded tubing having inner dimensions determined by the outer dimensions of said mandrel, means to vary the outer dimensions of said mandrel so as to vary the inner dimensions of a tubing extruded from said extrusion head, said extruder apparatus further including a pressure means to provide a predetermined pressure within the tubing as it is extruded from said extrusion head, and a pressure controller adapted to control the level of pressure provided within the tubing to maintain the inner dimension of the tubing and prevent the tubing from collapsing.