Method for eddy current heating a roll in a paper machine
AssigneeValmet Corporation
InventorJaakko Riihinen
Life of this patent
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Abstract
A method and apparatus for the inductive heating of a roll used in the manufacture of paper by means of eddy currents, such as the inductive heating of a calender roll. In the apparatus, pole shoe devices provided with electromagnetic coils are used, by means of which the eddy-current heating is applied only to the surface layer of the roll, the surface layer being constituted of ferromagnetic material, solely from outside the roll. The apparatus comprises several iron cores placed side by side and provided with magnetizing coils. Into each coil, a magnetizing current is passed, the magnetizing current being of adjustable intensity and/or frequency to control the temperature profile of the roll in the axial direction thereof.
Claims7
A method for heating a roll in the production of paper, which comprises applying eddy current heating to only an outer surface layer of the roll, and exclusively applying the eddy current heating from outside the roll, to inductively heat the roll, comprising the steps of:
- providing the roll with an outer surface formed of ferromagnetic material,
- disposing the outer layer of the roll about a heat insulation layer of magnetically non-conductive material, to confine the eddy current heating to substantially within the outer layer from exclusively outside the roll,
- disposing means for applying the eddy current heating outside the roll proximate to the outer surface layer thereof,
- conducting magnetizing current through the means to generate magnetic flux from the means to pass only through the outer surface layer, and
- adjusting at least one of intensity and frequency of the magnetizing current, to control temperature profile along an axial direction of the roll.
Dependencies are inferred from the claim text.