Adjustable extrusion die

Abstract From the Canadian patent

An extruder die head for extruding profiles particularly, plastic pipes. The die head includes an inner mandrel and an outer sleeve, between which is defined a flow channel. Adjacent the outlet of the die head the flow channel defines, an outlet flow zone that tapers inwardly toward the axis of the die head to define a converging flow passage and at a point, upstream of the outlet flow zone the flow passage diverges outwardly in the direction of material flow to provide a, pressure balance zone whereby the axial pressures acting on the outer sleeve are in opposite directions to substantially offset each other. The outer sleeve is axially movable relative to the mandrel by means of an …