Dry end of a machine for the production of a fiber web

A dry end for a machine for manufacturing a paper web comprising:

• a plurality of dryer groups arranged one after the other along the path of the web through the dry end;
• each dryer group comprising:
• a single row of heatable drying cylinders;
• a reversal suction roll between each two drying cylinders in the group;
• an endless, web support belt which supports the web to travel together with the support belt through the dryer group;
• guide means in each dryer group for guiding the respective support belt in an endless loop through the respective dryer group;
• the support belt passes through the dryer group in a meander path so that the web on the support belt directly contacts one of the drying cylinders in the respective dryer group, the support belt then touches the next reversal roll in sequence and the web then touches the next drying cylinder in sequence so that the web comes into direct contact with the drying cylinders and the support belt comes into direct contact with the reversal suction rolls;
• the respective drying cylinders, suction reversal rolls and guide means of each of the dryer groups being so placed so as to define a respective separation place between each preceding dryer group and the succeeding dryer group thereafter in the path of the web through the dry end, and including means at the separation place for transferring the web from the preceding dryer group to the succeeding dryer group in the dry end;
• the drying cylinders and the reversal suction rolls in all of the plurality of the dryer groups are so placed that the drying cylinders are above the reversal suction rolls such that only the bottom side of the web contacts the drying cylinders.

A method for manufacturing a paper web with a machine including a dewatering press through which the web moves and a dry end following the dewatering press in the path of the web, the method including the steps of:

• providing in the dry end a plurality of dryer groups arranged one after the other along the path of the web through the dry end;
• a single row of heatable drying cylinders;
• a reversal suction roll between each two drying cylinders in the group;
• an endless, web support belt which supports the web to travel together with the support belt through the dryer group;
• guide means in each dryer ground for guiding the respective support belt in an endless loop through the respective dryer group;
• the support belt passing through the dryer group in a meander path so that the web on the support belt directly contacts one of the drying cylinders in the respective dryer group, the support belt then touches the next reversal roll in sequence and the web then touches the next drying cylinder in sequence so that the web comes into direct contact with the drying cylinders and the support belt comes into direct contact with the reversal suction rolls;
• the press being so placed and the drying cylinders, the suction reversal rolls and the support belt of the first dryer group after the press being so placed that there is a first, open separation place where the web travels free of support between the press and the first dryer group;
• the respective drying cylinders, suction reversal rolls and guide means of each of the dryer groups being so placed so as to define a respective separation place between each preceding dryer group and the succeeding dryer group thereafter in the path of the web through the dry end, and including means at the separation place for transferring the web from the preceding dryer group to the succeeding dryer group in the dry end;
• at least toward the terminal end region of the path of the web through the dry end, at least one of the separation places between a preceding and a succeeding drying group being developed as an open separation place where the web has a free unsupported path of travel from the respective preceding to the respective succeeding endless web support belt of the dryer groups;
• driving the press to move a web through the press to the first dryer group of the dry end;
• driving the drying cylinders in each of the dryer groups to rotate to move the web through the dryer group at a selectively variable and respective rotation speed and controlling the respective rotation speed of the drying cylinders of each of the dryer groups for enabling adjustment to produce a difference in rotation speeds between the drying cylinders of adjacent dryer groups;
• and
• setting the respective drive speed of the press and of the first dryer group following the press to achieve a positive speed difference at the first separation place, the positive speed difference meaning that the speed of the web through the first dryer group is greater than the speed of the web through the press, thereby relieving the tendency of the web to adhere to the surfaces of the drying cylinders of at least a first one of said plurality of dryer groups;
• setting the respective drive speed, in the dry end, at two of the dryer groups that are toward the terminal end of the path of the web away from the press, to a negative speed difference so that the support belt in the succeeding dryer group is moving the web slower than the support belt in the preceding dryer group is moving the web, thereby enabling attaining a paper web with extremely low moisture contact.