| 摘要 |
Apparatus for applying overpressure to a moving web path (3, 16, 17), com prising at least: a surface (1a, 2a) against which the web path is pressed b y the effect of negative pressure; a pressure box (19) which is placed on th e opposite side of the web path with respect to said surface (1a, 2a) and th rough which the overpressure is effective on the web path travelling past sa id surface (1a, 2a), The pressure box comprises at least an overpressure cha mber (22) restricting the overpressure area (24) subjected to the overpressu re, wherein the overpressure chamber has the shape of a tapering or narrowin g throat (23), having an air gap (28) between its narrow end and the web pat h and a channel (29) at its wide end, via which channel air is capable of be ing discharged from the overpressure chamber. In one example the pressure bo x (19) also comprises at least one overflow chamber (30) restricting the are a (X2) subjected to the pressure of the overflow chamber, wherein both said channel (29) and said air gap (28) lead from said overpressure chamber to th e overflow chamber.
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