Patent ID: 6725569
Filing Date: 2004-04-27
Classification: D21F

Abstract:
A method for ventilating an offset pocket space located in a drying section of a papermaking machine, the offset pocket space being situated between three axially-parallel drying cylinders over which consecutively runs a paper web, a first and a third of these cylinders being vertically spaced from a second of the cylinders, the paper web being pressed against the first and the third cylinder by a felt which further runs over a felt roll having a rotation axis parallel to that of the cylinders, the felt roll being disposed between the three cylinders in an offset position which is closer to the first cylinder than the third cylinder, the offset pocket space being delimited by a first cleft defined where the felt and the paper web separate, a first draw of the paper web from the first cleft to the second cylinder, a free portion of the second cylinder, a second draw of the paper web from the second cylinder to a second cleft defined where the felt and the paper web rejoin, and the felt between the first cleft and the second cleft, the method comprising:directing a first air stream, at least partially following a curved path, from a first air outlet into a third cleft defined where the felt rejoins the felt roll, the first air stream flowing through the felt and lifting the paper web away from the felt to reach the offset pocket space; directing a second air stream from a second air outlet in close proximity to the felt, the second air stream being supplied at a location which is upstream of the third cleft and in a direction which is substantially opposite the running direction of the felt so as to create an air curtain which lowers the pressure in a zone between the first and the second outlet, thereby maintaining the paper web on the felt for as long as possible; restricting air coming from the offset pocket space from reentering the third cleft by flowing over a free portion of the felt roll; and restricting air coming from the first outlet from entering the lower pressure zone between the first and the second air outlet.