Patent ID: 7713385

Claim:
Apparatus for treating a material web, comprising: at least one nip through which the material web is guided and which is formed between a first revolving heated surface and a second revolving surface; a box which bounds a space through which the material web is guided is arranged after the nip in the direction of movement of the material web; a first seal for sealing off the box with respect to the first surface; a second seal for sealing off the box with respect to the second surface; and a sensor connected to a blowing device, the sensor being configured to detect a relative humidity in the space, the blowing device being configured to convey fresh air into the space to control the relative humidity in the space, wherein the seals are configured to substantially seal at least one of steam, air or any combination thereof, wherein the first surface is heatable to approximately 120° C. and both surfaces in the nip have the same direction of movement as the material web, and the box comprises at least one wall having a heater, and wherein the box is substantially closed in a machine direction except for an inlet opening which is closed by a first wall arranged above the web in the direction of the force of gravity against the first surface and a second wall arranged below the web against the second surface, and an outlet opening through which the material web is guided to the outside, and the box is configured to be substantially closed from ambient atmosphere.