Method for the control of the nip-pressure profile in a paper making machine

摘要

A method and apparatus in the press section of a paper machine for regulating the axial linear-load profiles in its nip or nips (N.sub.1, N. sub.2,N.sub.3). The axial temperature profile(s) of the outer mantle(s) of a press roll or rolls (11, 13, 16, 17) is/are regulated. Thereby, the distribution of the diameter of the press roll in the axial direction is controlled on the basis of thermal expansion. Also thereby, the distribution in the transverse direction of the machine of the linear load in the press nip or nips (N.sub.1,N.sub.2,N.sub.3) formed by the press roll or rolls (11, 13, 16, 17) is affected. The temperature profile of the outer mantle(s) (11', 13',17') of the press roll or rolls (11, 13, 17) is regulated by a press felt or felts (10, 14, 18) running through the press nip or nips (N.sub.1, N2, N3) formed by the roll applying a heating/cooling effect whose profile in the axial direction of the roll is regulated, and/or by applying a set of water jets (F) directly onto the outer mantle(s) of the press roll or rolls, the jets' quantity distribution (F.sub.1 . . . FN) and/or temperature distribution (T.sub.1 . . . TN) being regulated so as to obtain the desired distribution of np- pressure profile.