Variable extrusion apparatus

976,845. Extruding tubes for blow moulding. CONTINENTAL CAN CO. Inc. May 28, 1963 [Aug. 13, 1962], No. 21359/63. Heading B5A. Apparatus for continuously extruding synthetic thermoplastic material as a tube having a controlled varied cross - section comprises an extrusion head 29 containing a die core 36 having a tapered tip 37 defining an annular orifice with the extrusion nozzle 33 which is varied in cross-section by vertical shifting of the core 36 during extrusion of the tube. The vertical shifting is effected by a pneumatic piston and cylinder unit 25 through a pivoted lever 56 connected by a pin 44 to the upper end of the core 36. The pin 44 is threaded into a fitting 65 carrying a pin 64 engaging in the forked end of the lever 56, and locked by a nut 66 in an axially adjustable position determining the initial cross - section of the extrusion orifice. The air supply to the unit 25 is regulated by solenoid valves controlled by a switch operated by cam mechanism driven in synchronism with the mechanism for opening and closing blow moulds (not shown) into which the tubing is fed.