Roller die extrusion apparatus for the co-extrusion of plastics

An apparatus (10) wherein extruded strips (98,116) of elastomeric material are fed separately over a cylindrical roller surface (20) at more than one angular position (126,128,130) relative to the roller (18) by a die head (12) to form predetermined cross-sectional areas of the co-extrusion (118). The channels (26,28,36,38) in the die head guide plate (32) connecting the extruders (14,16) and the orifices (30,40) at the roller surface (20) are provided by walls of a replaceable preformer insert (44) which are spaced from the walls of an opening (42) in the guide plate (32). Different sizes and configurations of the channels (26,28,36,38) can be obtained using different preformer inserts (44). The grooves (80,88,90,114,132,134,138,151,152,154) which guide the strips (98,116) of elastomeric material applied to the roller surface (20) are in replaceable finish dies (66,68) mounted in a slot (70) in the cylindrical surface (22) of the die head (12) so that the various laminations and configurations required can be obtained by inserting the desired finish dies (66,68). Different finish dies (66,68) have grooves (80,88,90,114,132,134,138,151,152,154) at different positions to provide the desired overlapping of the applied strips (98,116).