Windmoller Holscher

Gerhard Winkler

Hartmut Upmeier

Gerd Klinge

Fritz Achelpohl

Werner Josef Zimmermann

Jurgen Linkies

Helmut Helbig

Hermann Tupker

Ferdinand Loning

An extrusion die for a blow head for making blown plastic films comprises inner and outer rings, which are made of a ferrous material, particularly steel, and define between them an annular orifice. Those surfaces of the inner and outer rings which define the die orifice are covered by a layer consisting of a metallic material having a higher thermal conductivity than steel.

Extrusion die for a blow head for making blown plastic films

A nozzle ring of an extruder for blowing tubular plastics film is divided into cooling sectors provided with adjusting elements. The thicknesses of the blown film are measured over the circumference thereof and a number of film sectors of equal circumferential length corresponding to the number of cooling sectors is established from the measured thicknesses. Assuming that the film sector of maximum or minimum thickness has been extruded in the correct position for the purpose of determining the cooling sector associated with the film sector, the subsequent film sectors are in turn allocated to successive cooling sectors. From the measurements, the mean thickness distributions are determined over the individual film sectors. These values of mean thickness distribution define a measure for the correcting command for the adjusting elements of the cooling sectors that are associated with the respective film sectors.

Method of controlling the film thickness at a blown film installation

A nozzle ring of an extruder for blowing tubular plastics film is divided into cooling sectors provided with adjusting elements. The thicknesses of the blown film are measured over the circumference thereof and a number of film sectors of equal circumferential length corresponding to the number of cooling sectors is established. Assuming that the film sector of maximum or minimum thickness has been extruded in the correct position for the purpose of determining the cooling sector associated with the film sector, the subsequent film sectors are in turn allocated to successive cooling sectors. The mean thickness distributions are determined from the measurements over the individual film sectors. Those cooling sectors to which film sectors were allocated having thin or thick portions exceeding a respective thin or thick portion threshold value which is a fraction of the value of the film sector with the absolute minimum or maximum thickness, respectively, are cooled or heated until the film thicknesses are within the permissible tolerance range.

Method of controlling the film thickness at a blown film extruder

A nozzle ring of an extruder for blowing tubular plastics film is divided into correcting sectors provided with adjusting elements. The thicknesses of the blown film are measured over the circumference thereof and a number of film sectors of equal cross-sectional area corresponding to the number of correcting sectors is established from the measured thicknesses. Assuming that the film sector of maximum or minimum thickness has been extruded in the correct position for the purpose of determining the correcting sector associated with the film sector, the subsequent film sectors of equal cross-sectional area are in turn allocated to successive correcting sectors. The throughput and cross-sectional area or temperature of the respective correcting sector is adjusted until the circumferential lengths of the film sectors are equal.

In a film blowing plant comprising an extruder for the melt, a film blowhead, calibrating means for the blown tubular film, oscillatory take-off means for the film and a coiler for the flattened film, the output of the plant is set to an optimum figure by a process computer controlling the width and thickness of the film. The height of the line of solidification of the film above the blowhead is measured and, in response to a departure of this height from a given desired value, the output of the extruder is increased or reduced as the case may be.

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Lengerich, Germany

Gerhard Winkler