Coextrusion apparatus for varying the inner and/or outer profile of a

Abstract

Coextrusion apparatus for varying the inner profile of a generally tubular extrudate formed by a first stream of elastomeric material by an axially movable inner die ring which varies the size of an orifice and consequently the flow of a second stream of elastomeric material which is deposited on the inner surface of the tubular extrudate. A compensating ring is axially slidably mounted within the inner die ring and moves generally in an opposite direction to the movement of the die ring to compensate for pressure changes within the second stream of material caused by varying the size of the orifice, to provide an accurately controlled initiation and termination of the material. Pistons are formed integrally on the inner die ring and compensating ring and are located within annular fluid pressure chambers whereby the flow of fluid into the chambers will coordinate the movement of the die ring and compensating ring. A reinforcing guide directs the plurality of fiber reinforcing elements into the tubular extrudate prior to depositing the variable stream of elastomeric material on the inner surface of the extrudate. In another embodiment, a generally constant outer layer of a different elastomeric material may be applied to the outer surface of the tubular extrudate simultaneously with the varying of the inner profile thereof.