METHOD AND DEVICE FOR CHANGING THE NATURAL FREQUENCY OF A NIP ROLL CONSTRUCTION IN A PAPER OR BOARD MACHINE

摘要

The invention concerns a method and a device for changing the natural frequency of a nip roll construction in a paper or board machine so that the rigidity of one or several loading elements, for example loading cylinder or loading beam, in the nip roll construction is varied. The loading cylinder with adjustable rigidity in accordance with the invention comprises a cylinder (11), into which two pistons (12, 13) have been fitted. The pistons (12, 13) have been attached each of them to a piston rod (14, 15) of its own, which piston rods have been passed through the end walls (11a, 11b) of the cylinder (11). Thus, in the cylinder (11), between the pistons (12, 13), a work pressure space (16) is formed, and at the opposite sides of the pistons (12, 13) counter-pressure spaces (18, 20) are formed. The pressure in and the volume of the work pressure space (16) are kept invariable, and the volumes of the counter-pressure spaces (18, 20) are varied, in which connection the cylinder (11) moves on the piston rods (14, 15), and the rigidity of the loading cylinder can be varied.