method and device for extruding a length of its different wall strength broken rohrfoermigen between product from thermoplastic plastic

摘要

874,056. Extruding tubes for blow-moulding. METAL BOX CO. Ltd. Dec. 7, 1959 [March 5, 1959], No. 7757/59. Class 87(2). A method of making a tube of varying wall thickness for use in a blow-moulding operation, comprises varying the amount of material delivered to an extrusion nozzle and moving the extruded tube away from the nozzle at a constant linear speed. The amount of material M, e.g. polyethylene, p.v.c., polystyrene or cellulose esters, delivered to the nozzle 2 is varied by axial movement of a valve member 31 operated against a spring 32 by a hydraulic cylinder and the extruded tube is gripped by pivoted arms 8, 9 mounted on a mounting 10 and normally held in the non-gripping position by a spring 12. During extrusion an air cylinder 28 moves down a rod 27 which firstly rocks a lever 23 to force a frusto-conical member 13 between the arms 8, 9 forcing them to grip the tube 3, and then moves down, at a constant speed, the mounting 10 and gripped tube 3 whilst the amount of material fed to the nozzle 2 is varied by the valve 31. An electrical control circuit Fig. 6, (not shown) and safety devices are provided.