Coextrusion apparatus and method using a rigid die for varying the outer

Abstract

Coextrusion apparatus for varying the outer profile of a generally tubular extrudate formed by merging inner and outer streams of elastomeric material by varying the size of the annular outer extrusion die opening by an axially moveable die ring which varies the flow of the outer stream of elastomeric material which is deposited on the outer surface of the tubular extrudate. The die ring is formed on the end of a hydraulically moveable piston and is axially slideably moved along and is located concentrically about the tubular extrudate. A first annular tapered surface of the die ring moves along a similar tapered surface of a fixed conical-shaped die pin to vary the size of the outer extrusion orifice formed therebetween. A second surface, oppositely tapered to that of the first tapered surface of the die ring and formed integrally therewith as a one-piece member, communicates with the flow channel of the outer elastomeric material stream and continuously compensates for a change in pressure within the outer flow stream caused by varying the flow volume of the outer stream at a location generally adjacent the application of the outer stream on the outer surface of the tubular extrudate. A reinforcing guide directs a plurality of fiber-type reinforcing elements into the tubular extrudate generally at the merger of the inner and outer streams of elastomeric material. A method for varying the outer profile of the tubular extrudate is also presented.