Extrusion head for producing double-walled plastic pipes with cylindrical inner pipe and cross-corrugated outer pipe

摘要

1. Process for the production of double-walled PVC pipes with a substantially smooth inner wall and transversely corrugated outer wall, in which a plastics flow introduced from a single extruder into an extrusion head is split up in tubular manner at a point (6), in which the plastics flow is subsequently divided by a distributor (7) into two concentric plastics flows witch, after passing out of concentric nozzle orifices (14, 16), are joined together at a shaping and cooling means and in which during the extrusion of the tubes a first gas pressure is blown out between the outer and the inner orifice through which the outer tube is blown against a shaping arrangement and into the inner extruded tube is blown a second gas pressure which is lower than the first gas pressure, characterized in that the plastics flow from the distributor arranged in the vicinity of the point (6) passes uninterruptedly up to the orifices and that the temperature of the extruded tubes in the vicinity of the greatest transverse extension at least corresponds to the joining temperature of the extruded plastics flows.