Blown film extruder thickness error corrector - comprises elastically deformable annular die lip acted upon by piezoelectric elements

摘要

Blown film extruder for producing synthetic thermoplastic film has a blowing head to which an annular gap nozzle is attached comprising a metallic inner and/or outer annular gap nozzle lip forming a complete circle for extruding the film and a device for inflating the blown film. The thickness of the film in the vicinity of the gap nozzle is subjected to thickness error correction in conformity with measured thickness readings using at least one elastically deformable annular gap nozzle lip which is prestressed by at least one set of peripherally distributed, radially acting setting elements, the lip being elastical deformed by the elements to effect the correction.