Device and method for generating a negative pressure in a film machine

A film machine for the production of a plastic film, wherein the film machine comprises a transport for transporting film material and an outlet device, wherein the film material is guidable out of the outlet device in form of a melt strip through the transport wherein

• at least one main chamber is provided for the generation of a first negative pressure in a first influence area and at least one auxiliary chamber for the generation of a second negative pressure in a second influence area wherein the first influence area is assignable to at least one main area of the melt strip and the second influence area to at least one edge area of the melt strip adjacent to the main area and wherein the first negative pressure differs from the second negative pressure in order to effect a stabilization of the melt strip, and
• wherein
• at least the first negative pressure or the second negative pressure are at least automatically or controllably varied,
• extensions of the at least one auxiliary chamber in a width direction are configured in such a way that the second influence area of the auxiliary chamber amounts to between 2% to 10% of a whole influence area or of the first influence area of the main chamber, and
• at least a sealing element or a wall are configured adjustably for the separation of the main chamber from the auxiliary chamber, wherein the sealing element comprises a curved form adjusted to the transport at the side facing the melt strip.

A device for the generation of a negative pressure for stabilizing a melt strip in the area of a transport of a film machine comprising:

• at least one main chamber for generating a first negative pressure in a first influence area, and
• at least one auxiliary chamber for generating a second negative pressure in a second influence area, wherein
• the first influence area is assignable to at least one main area of the melt strip and the second influence area is assignable to at least one edge area of the melt strip adjacent to the main area, and
• wherein
• the first negative pressure differs from the second negative pressure in order to effect a stabilization of the melt strip,
• at least the first negative pressure or the second negative pressure are at least automatically or controllably varied,
• the main chamber is separated fluidically from the auxiliary chamber,
• at least a sealing element or a wall are configured adjustably for the separation of the main chamber from the auxiliary chamber, wherein the sealing element comprises a curved form adjusted to the transport at the side facing the melt strip, and
• the sealing element contacts to the transport.

A method for the production of a film, wherein the film material is guided out of an outlet device in form of a melt strip through a transport, and by at least one main chamber a first negative pressure is generated in a first influence area and by at least one auxiliary chamber a second negative pressure is generated in a second influence area, wherein the first influence area is assigned to at least one main area of the melt strip and the second influence area to at least one edge area of the melt strip adjacent to the main area and wherein the first negative pressure differs from the second negative pressure, whereby a stabilization of the melt strip is effected, and

• wherein
• at least the first negative pressure or the second negative pressure are at least automatically or controllably varied,
• extensions of the at least one auxiliary chamber in a width direction are configured in such a way that the second influence area of the auxiliary chamber amounts to between 2% to 10% of a whole influence area or of the first influence area of the main chamber, and
• at least a sealing element or a wall are configured adjustably for the separation of the main chamber from the auxiliary chamber, wherein the sealing element comprises a curved form adjusted to the transport at the side facing the melt strip.