Press section with an equalizing nip in a paper machine

A method for pressing a web in a press section of a paper machine, comprising the steps of:

• forming an extended nip between first and second press rolls, said first press roll having a flexible mantle, said second press roll having a rigid mantle,
• passing the web on support of a press felt or fabric through said extended nip whereby the web is dewatered in said extended nip,
• forming an equalizing nip between a third press roll and said second press roll, said third press roll comprising a rotatable smooth-faced equalizing-press roll directly contacting the web,
• passing the web through said equalizing nip after said extended nip to stretch the web in order to equalize asymmetry of roughness formed in the web at least in said extended nip before said equalizing nip,
• arranging a rotatable guide roll between said equalizing-press roll and an initial drying cylinder of a dryer section arranged after the press section and between said equalizing-press roll and an initial drying wire guide roll over which a drying wire runs before carrying the web thereon such that the web has an open draw from said equalizing-press roll to said guide roll, and
• rotating said guide roll such that the web has a different running speed about said guide roll than in said equalizing nip to compensate for the stretching of the web taking place in said equalizing nip and to tension the web.

In a press section of a paper machine in which a paper web is pressed including extended-nip means for forming an extended nip, said extended-nip means comprising a first press roll having a flexible mantle and a second press roll having a rigid mantle arranged in nip-defining relationship with said first press roll, a press felt or fabric for carrying the web through said extended nip whereby the web is dewatered in said extended nip, the improvement comprising

• a third press roll arranged in nip-defining relationship with said second press roll to form an equalizing nip through which the web passes after said extended nip, said third press roll comprising a smooth-faced equalizing-press roll structured and arranged to directly contact the web, the web being stretched in said equalizing-nip zone to equalize asymmetry of roughness formed in the web in said extended nip,
• a stretchable transfer belt running over said second press roll and through said extended nip, said transfer belt running through said equalizing nip and in a substantially straight run after said equalizing nip in which the web is carried forward, and
• compensation means for compensating for the elongation of the web in said equalizing nip by providing the web with a different running speed after the equalizing nip than before said equalizing nip, said compensation means comprising means for stretching said substantially straight run of said transfer belt.

In a paper machine having a forming section in which a paper web is formed, a press section in which the web is pressed and a dryer section in which the web is dried, the dryer section including an initial drying cylinder over which the web first runs in the dryer section, the press section including extended-nip means for forming an extended nip, said extended-nip means comprising a first press roll having a flexible mantle and a second press roll having a rigid mantle arranged in nip-defining relationship with said first press roll, a press felt or fabric for carrying the web through said extended nip whereby the web is dewatered in said extended nip, a method for pressing the web in the press section comprising the steps of;

• passing the web through an equalizing nip after said extended nip to stretch the web and equalize asymmetry of roughness formed in the web in said extended nip, said equalizing nip being defined in part by a third press roll,
• transferring the web to a smooth-faced, stretchable transfer belt in said equalizing nip, said transfer belt running in a loop over said third press roll through said equalizing nip and in direct contact with the web,
• rotating a drive roll arranged in the loop of said transfer belt to stretch said transfer belt after said third press roll in order to compensate for the stretching of the web taking place in said equalizing nip and tension the web, said drive roll being rotated such that the web has a different running speed after said equalizing nip than before said equalizing nip, and then
• transferring the web from said transfer belt after the stretching of said transfer belt into direct contact with the initial drying cylinder in the dryer section of the paper machine.