DE2558780

Multiple extrusion head extrusion-blow moulding apparatus, preferably using a common continuously operating extrusion conveyor, in which apparatus the various extrusion heads have their accumulator pistons driven for identical and simultaneous movement during the extrusion strokes either by means of a common drive means or by separate drive means each controlled from a common control means. Common control may also be exercised over the charging stroke of the accumulator piston. Closed loop control over the wall thickness in dependence upon the final length of the parison, as well as open loop control over the wall thickness in response to a desired program may be imposed simultaneously on the extrusion orifice gap width.