Method and apparatus for molding of plastic tubing, including an elongate nozzle receiving an extrudate of an expandible plastic material under pressure from an extrusion head and a coaxial mandrel with air supply and evacuating passages communicating with a vortex generation tube for cooling air before...http://www.google.es/patents/US4545751?utm_source=gb-gplus-sharePatente US4545751 - Apparatus for molding of plastic tubing
