Method and arrangement for computing and regulating the distribution of a linear load in a multi-nip calender and a multi-nip calender

In a method for computing and regulating the distribution of linear load in a multi-nip calender in which a material web is passed through the nips, the nips being defined by a set of rolls arranged in a substantially vertical position and including a variable-crown upper roll, a variable-crown lower roll, the variable-crown upper roll and variable-crown lower roll being structured and arranged to selectively apply a load to at least two intermediate rolls arranged between the upper roll and the lower roll, said at least two intermediate rolls being provided with support cylinders, all of the rolls in the set of rolls being supported such that, when in nip-defining relationship, the rolls have bending lines which are curved downward, the improvement comprising the steps of:

• assigning a value to at least one variable representing a physical property affecting the bending of each of said at least two intermediate rolls;
• applying a first force to said at least two intermediate rolls by means of said variable-crown upper roll;
• applying a second force to said at least two intermediate rolls by means of said variable-crown lower roll;
• applying a support force to each one of said at least two intermediate rolls by means of said support cylinders;
• adjusting at least one of the following to place the set of rolls in a state of equilibrium and a predetermined state of deflection:
• the first force, the second force, at least one of the support forces and at least one of weight forces exerted on each of said at least two intermediate rolls;
• and
• wherein the step of assigning a value to at least one variable representing a physical property affecting the bending of each of said at least two intermediate rolls comprises the step of assigning a value to bending rigidity, mass, shape, and material of each of said at least two intermediate rolls;
• and
• further comprising computerized modeling using all essential elements of the multi-nip calender including all physical properties of the set of rolls and selecting a type and a position of each roll in the set of rolls;
• determining of regulation parameters based on the computerized modeling;
• regulating of the multi-nip calender assembled based on the computerized model assembled with the type and the position of each roll in the set of rolls.