Extruder screw tip and associated flow channel

An extruder screw and flow channel head assembly comprising an extruder having a cylindrical barrel with a feed end and a discharge end, said discharge end being attached to a flow channel head containing a flow channel for carrying rubber from said extruder to a suitable die, a screw nose on said extruder screw positioned in a transition space at said discharge end of said barrel wherein said screw nose has a radially expanding upstream portion providing a conical surface of increasing diameter in the direction of flow of said rubber for maintaining said rubber in working engagement with said screw nose and the cylinder wall of said cylindrical barrel, whereby the pressure on said rubber is maintained in said transition space, said cylindrical barrel having a constant diameter, wherein said screw and screw nose rotate about a central axis without reciprocating movement in said cylindrical barrel as it moves said rubber from said feed end to said discharge end, further characterized by said screw nose having a downstream portion with a conical surface of decreasing diameter in the direction of flow of said rubber spaced from an opposing tapered wall of said flow channel head for maintaining working engagement of said rubber with said conical surface of said screw nose and said tapered wall of said flow channel whereby pressure on said rubber is maintained to prevent expansion of volatiles in said rubber.