| 摘要 |
<p>The invention concerns a method and a device for impulse dewatering, in which method a paper or board web (10) is pressed in an extended press zone (I...IV) formed between a heatable backup roll (20) and a press shoe (18). Seen in the direction of progress of the web (10), the press zone (I...IV) first includes a first hydrodynamic area (I), which is followed by a hydrostatic area (II) and by a second, short hydrodynamic area (III). These three high-pressure areas (I...III) are followed in the press zone by a third hydrodynamic area (IV), which forms the final part of the press shoe (18). The length of this last area (IV) is at least one third of the total length of the press zone (I...IV), and its shape and/or loading is such that, in this area (IV) in the press zone, the pressure is first lowered to a level (p2) which is lower than the nip pressure (p1) proper but higher than the pressure in the environment, an the pressure remains then at this level substantially invariable substantially to the end of the area (IV).</p> |
