DEVICE AND METHOD FOR VENTILATING AN OFFSET POCKET SPACE IN A PAPERMAKING MACHINE

摘要

The device (10) and method are used for ventilating an offset pocket space (12) located in a drying section of a papermaking machine by injecting air from a t least one heated dry air supply inlet (11). The offset pocket space (12) is situat ed between three axially-parallel drying cylinders (20) over which consecutivel y runs a paper web (14). A first and a third of these cylinders (20) are vertically spaced from a second one. The paper web (14) is pressed against the first and the third cylinder (20) by a felt (16) which further runs around a felt roll (26) havi ng a rotation axis parallel to that of the cylinders (20). The felt roll (26) is disposed between the three cylinders (20) in an offset position which is closer to th e first cylinder (20) than the third cylinder (20). The device (10) comprises a first air outlet (50) where a first air stream i s directed into a cleft (30) defined where the felt (16) and the felt roll (26) join, a nd a second air outlet (52) where a second air stream is directed in close proximity of the felt (16) at a location which is upstream the cleft (30). The second air stream i s in a direction which is substantially opposite the running direction (R) of the felt (16). In use, the device (10) and the corresponding method allows the first air strea m to flow throughthe felt (16) and to lift the paper web (14) away from the felt (16) so as to reach the offset pocket space (12). The second air stream creates an a ir curtain to lower the pressure in a zone between the first (50) and the secon d (52) air outlet, thereby establishing a zone of reduced air pressure in close proximity of the felt (16) at a location which is immediately upstream the cleft (30).