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AssigneeInternationale Octrooi Maatschappij "Octropa" B.V.
InventorsFriedrich F. von und zu Aufsess, Gunter Huxhorn, Hans Pohl, Wolfgang Sasse
Estimating the term…
In an apparatus for the biaxial, simultaneous stretching of a flat film web from particularly polypropylene, the edges of the film web 1 are engaged by grippers 3, which in the stretching zone 9 are driven by divergent threaded spindles 5, and at least part of the stretching in longitudinal direction is effected, by means of a progressive pitch of the threaded spindles, simultaneously with part of the transverse stretching. Subsequent to the progressive pitch a thread with degressive pitch is provided, preferably at the end of the threaded spindles, effecting shrinkage of the previously stretched film web in longitudinal-direction, while preferably simultaneously the film web is further stretched in transverse direction. The shrinking of the film web takes place over about 5 to 10% of the spindle length at up to 10% of the previously produced longitudinal stretching, to the longitudinal stretching degree desired in the finished film.
In a process for the biaxial stretching of a flat film web from plastics material in a stretching apparatus in which the edges of the flat film web are retained by grippers driven by means of threaded spindles, and at least part of the stretching in longitudinal direction is being effects by means of a progressive pitch of threaded spindles simultaneously with at least part of the transverse stretching, the modification wherein the film is stretched in longitudinal direction at up to 10% in excess of the stretching degree desired in the finished film and, subsequently to the stretching in longitudinal direction, is shrunk to the desired stretching degree in longitudinal direction, while the film web is still being further stretched in transverse direction, by guiding the grippers in a degressive thread pitch.
In an apparatus for the biaxial stretching of a flat film web from a plastics material including grippers which engage the edges of the film web, and threaded spindles for driving the grippers, which have a progressive pitch over at least part of their length, adapted to permit at least part of the stretching in the longitudinal direction to be carried out simultaneously with at least part of the transverse stretching, the modification wherein at the run-off end of the threaded spindles, subsequent to the progressive pitch of the threaded spindles a thread of degressive pitch is provided for the further guiding of the grippers whereby the film can be shrunk in the longitudinal direction while the film web is still being stretched transversely.
Dependencies are inferred from the claim text.