Coextrusion apparatus and method using an elastic die for varying the

Abstract

Coextrusion apparatus for varying the outer profile of a generally tubular extrudate formed by inner and outer streams of elastomeric material by varying the annular end opening of an elastic die ring which varies the size of an outer extrusion orifice and consequently the flow of the outer stream of elastomeric material which is deposited on the outer surface of the tubular extrudate. A hydraulically moveable piston is axially slideably mounted for engagement with the elastic die ring and has a wedge-shaped camming surface which moves along the outer surface of the elastic die ring to vary the size of the outer extrusion orifice and consequently the amount of elastomeric material extrudated therethrough. A linear motion detector is connected to the piston to detect the amount of linear axial movement of the piston to provide control signals for controlling the movement of the piston. The orifice for the inner stream of elastomeric material is located slightly upstream of the orifice for the outer stream of elastomeric material and is generally fixed. A reinforcing guide directs a plurality of fiber-type reinforcing elements into the tubular extrudte 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.