Prodn. of high bursting strength plastic tube - by extruding material into revolving barrel contg. centre core to form spiral, cooling in situ opening barrel end and expressing product

Plastic tube is produced by heat-softening the material and feeding at least one length into the space between a mould core and a concentric outer cylinder mould tool, forming the material into the tube and then cooling it. The soft material is fed in at a fixed point on the circumference and the outer mould tool is continuously rotated; the material is thus formed into spiral; this is compressed axially, its turns are fused together and finally solidified by cooling. More specificallt the metal barrier and inner core tool from the annular space; the barrel rotates liquid-tight in a mounting and is turned by a drive. The mounting can swivel about the axis from one filling position to one final position. An extruder discharges the softened polymer through the point into the space between core and barrel while the assembly is horizontal. ADVANTAGE - Produces tubes with higher bursting strength than hitherto but using more material than previously.