Calender to polish paper web surfaces has an additional nip in front of the roller stack with soft rollers to give an initial surface polish and prevent oscillations and vibrations which could form visible bars in the paper

摘要

To process a paper web, the surface is polished be passing through a number of nips in a calender formed by a stack of paired calender rollers. The web surface is polished before passing through the calender nips, using a roller nip without slippage, where the two rollers have soft mantles. For polishing the paper web surface, both the calender rollers in the additional leading nip are powered, and both sides of the web are treated identically. The additional roller nip is outside the plane of the nips formed by the paired calender rollers. An Independent claim is included for a calender assembly, with an additional roller nip outside the stack (2) of calender rollers. It is formed by two powered soft rollers (24, 25) with identical surface characteristics. The rollers are rotated at a surface speed which matches the web (21) speed of travel.