Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Including product handling means
Patent
1998-01-06
1999-08-17
Tentoni, Leo B.
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Including product handling means
B29D 701
Patent
active
059391057
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for laying a plastic film on a roll, in particular for laying a polymer melt film on a chill roll.
In the production of plastic films, it is basically usual to press the melt film emerging from a slot dye onto a chill roll by means of a so-called air knife, whilst producing an adequate air velocity (dynamic pressure). In this case, the air knife extends in its longitudinal direction transversely over the width of the melt film, that is to say transversely to the take-off direction of the plastic film, air being able to emerge in the direction of the melt film via a continuous exit slot, generating a corresponding air velocity.
Since the melt film has a thicker edge, this must be pressed onto the chill roll with greater force. As a result, it is also necessary to pursue the objective of minimizing an inward step in the width of the film, that is to say to ensure that the width of the melt film remains as constant as possible during the plastic film production.
An apparatus forming the generic type has been disclosed by U.S. Pat. No. 4,255,365. The air knife disclosed by this apparatus has a multiplicity of air exit openings that are arranged in an offset manner in the longitudinal direction of the air knife and are directed onto the film web. This opens the possibility of producing different contact pressures over the length of the air knife, that is to say over the width of the plastic film web, in order ultimately to influence the thickness profile of the film.
However, in the case of this previously known apparatus, it is also necessary to use so-called "edge pipes" at the two edges of the film, in order to generate here in a deliberate way the higher contact pressure forces that are needed, matched to the respective film width. Finally, a design of this type is also only suitable for a specific width of a plastic film web.
It is therefore the object of the present invention to overcome the disadvantages according to the prior art, and to provide an apparatus improved in this regard for laying a plastic film on a roll, in particular for laying a polymer melt film on a chill roll.
SUMMARY OF THE INVENTION
According to the invention, it has been shown that, in particular in the case of higher take-off speeds, an offset, present in the take-off direction, of the effect lines of the exit openings of the air knife and of the means separately provided for blowing on the edge is disadvantageous. Such an offset of the effect lines of the means for blowing on the edge and of the blowing by the air knife has several disadvantages. It leads not only to distortion of the film, but also often causes markings on the film, especially in the edge region. As a result of the offset the effect lines in the prior art, it is often possible to detect blowing-in of the pressure air in the edge region between the roll and the film, as a result of which film edges that do not run quietly are produced, and the undesired turning up of the edges is possibly also favored. Finally, it is also possible to determine a mutual negative influence when adjusting the air knife and/or the means for blowing on the edge.
By contrast, according to the invention a joint, straight effect and laying line over the entire width of the film web, including the means for blowing on the edge, is made possible. As a result of this optimal, joint laying effect line, the risk present in the prior art of the occurrence of transverse markings on the film is reduced, and the risk of blowing in waste air in the edge region between roll and film is reduced. This also allows the most constant flat film edges to be achieved.
As an alternative, or in addition, provision is further made for the air knife to be adjustable in its longitudinal direction, that is to say with its effective width extending transversely to the plastic film web, that is to say in particular from the point of view of its effective air exit openings. This allows the laying-on width to be matched simply and precisely to the
REFERENCES:
patent: 3597515 (1971-08-01), Widiger
patent: 4255365 (1981-03-01), Heyer
patent: 5437546 (1995-08-01), Dupraz
Patent Abstract of Japan vol. 095, No. 002, Mar. 31, 1995 & JP 06 328464 A, Nov. 29, 1994.
Bruckner Maschinenbau GmbH
Tentoni Leo B.
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