Method and apparatus for manufacturing blow-moulded plastics pipes

摘要

A molten plastics material is first extruded in the form of a pipe from an extruder die (2) and the outer diameter of the extruded pipe is controlled and cooled by a cooling vessel (6) provided with a sizing sleeve (4) and positioned adjacent a gaseous phase vacuum section (7). The pipe (9) so formed is then brought to a temperature suitable for drawing by means of a temperature controller (10) i.e. an external heater, and preferably also a heater (20) inside the pipe, and is then blow-moulded by internal pressure within and also simultaneously axially drawn continuously by, a mould cavity defined between at least one pair of continuous strings of mould sections (15) which are positioned opposite each other to form a travelling mould, the strings each having a plurality of mould sections (15) arranged end to end on a driving chain (14) and being driven continuously to draw and carry the pipe (18) through the mould.