Head assembly for blow-extruding a tubular plastic foil

Abstract

An apparatus for blow extruding a tubular plastic foil has a nozzle having an upwardly open annular mouth generally centered on a longitudinal axis for upwardly extruding a tubular plastic strand and an inner tube extending upward from the nozzle within the mouth thereof, having an upper end spaced axially from the mouth, and formed between the upper end and the mouth with at least one radially throughgoing hole. A stabilizer head carried on the inner-tube upper end is formed with passages having inner ends opening into the inner tube at the upper end thereof and outwardly directed outer ends. An outer tube surrounding the inner tube defines an inner longitudinal passage therewith, extends upward from the nozzle within the mouth thereof, and has an upper end above the hole and below the inner-tube upper end. A partition extends crosswise across the inner tube immediately below the hole and subdivides the inner tube into a lower tube section and an upper tube section and a blocking element engaged between the outer-tube upper end and the inner tube above the hole closes the upper-tube upper end. A guide sleeve between the head and the outer tube has a foraminous upper portion, an imperforate lower portion. One or more radially extending conduits below the partition between the inner and outer tubes form a flow path between an outer passage between the strand and the outer tube and an interior of the lower inner-tube section.