Method and device in the press section of a paper machine for detaching the web from the face of the press roll

摘要

Method and device in the press section of a paper machine for detaching the web (W) from the smooth face (10') of a press roll (10). Within the area of the detaching point (R), a momentary and local heating effect is directed at the web (W) from outside the roll (10). In the method and in connection with the device, as the mantle or outer coating of the smooth-faced (10') roll (10), a material is used which is magnetically at least to some extent conductive. To the roll mantle, an induction heating effect of such a high frequency (f,fs) is applied free of contact that the depth of penetration ( delta ) of the heating effect remains sufficiently low in view of its local and momentary nature. By means of the heating effect, the water present between the web (W) and the roll face (10') is heated, as a rule vaporized, locally within the area of the detaching point (R) so as to detach the web (W) from the said roll face (10'). The electric frequency of the induction heating is within the range of f = 0.5 to 2 MHz, preferably within the range of f = 0.8 to 1.5 MHz.