Process for extruding a thermoplastic sheath in the form of a tubular film provided with perforations and device for carrying out the process
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United States of America Patent
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-
Dec 1, 1981
Grant Date -
N/A
app pub date -
Dec 28, 1979
filing date -
Dec 28, 1979
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
The present invention relates to a process for extruding a thermoplastic sheath in the form of a tubular film provided with perforations and to a device for carrying out the process, according to which the extruded film passes over a skirt through which are blown jets of hot air provoking the perforation and formation of openings in the film; in the areas where the film is not to be perforated, air jets are also blown through channels of smaller width, therefore with a reduced pressure, so that the jets do not provoke the perforation of the film but form an air-cushion facilitating the flow of the film on the skirt; the channels are supplied from a pneumatic chamber with interposition of a rotary distributor formed by a ring made of graphite or self-lubricating material. The invention is applicable to the manufacture of partially perforated tubular films with a view to making packings.
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