Method for heating a cylinder or roll with an electrically conductive ceramic outer layer

Abstract

Method and arrangement in a machine for the manufacture of paper or board, for heating an outer face of a cylinder or roll which is in direct contact with a web to be pressed thereagainst. The cylinder or roll face is heated from outside inductively by using a magnetic field, and by which a heating effect based on eddy currents is produced in the outer layer of the roll or cylinder. A relatively thin outer layer of an electrically conductive ceramic material is used as the cylinder or roll face, in which the resistive heating effect is concentrated. The depth of penetration of the heating effect in the radial direction of the roll of cylinder to be heated is restricted to a sufficiently low depth by choosing the thickness of the ceramic outer layer and/or the electric frequency of the induction heating. Additionally, on the basis of its electrical properties, the ceramic material of the outer layer is chosen so that the cylinder or roll face is provided with the necessary properties of strength, and is also chosen in view of the thermal shock of the heating effect.

Dependencies are inferred from the claim text.