US 4,425,489 AGranted

Electromagnetic heating system for calender rolls or the like

AssigneeKleinewefers GmbH

InventorsJosef Pav, H. J. Lauschner, Peter J. Gaede

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Abstract

A calender roll whose shell consists of ferromagnetic material is heated by several groups of electromagnets which are mounted within the shell on a stationary carrier and whose pole shoes are adjacent to the internal surface of the shell. The temperature of the external surface of the shell is monitored at several locations as considered in the axial direction of the roll, and the resulting signals are compared with reference signals denoting the optimum or desired temperatures at such locations. Signals denoting the differences between the actual temperature signals and desired temperature signals are used to regulate the characteristics of electric current which is supplied to the windings of the electromagnets. Each electromagnet of each group can be regulated independently of all other electromagnets. Alternatively, two or more electromagnets of each group or entire groups of electromagnets may be regulated simultaneously. Additional electromagnets are provided to heat the end portions of the shell. Alternatively, such end portions can be heated by the rotors of electric motors which rotate the shell. The characteristics of current which is supplied to the windings of certain electromagnets can be influenced by signals which denote the magnitude of flexural stresses upon selected portions of the shell so that the corresponding electromagnets oppose deformation of adjacent portions of the shell.

Claims17

Dependent claims

A roll, particularly a calender roll, comprising a rotary hollow cylindrical shell consisting of ferromagnetic material and having an external surface and an internal surface;

and heating means for said shell, including a plurality of groups of electromagnets adjacent to at least one of said surfaces, surrounding the axis of said roll and with the axis of said shell, at least a portion of the external surface of said shell being unobstructed by said electromagnets and each of said groups comprising a plurality of discrete neighboring electromagnets and the neighboring electromagnets of said groups having different polarities and being distributed in the circumferential direction of said shell, each of said electromagnets having a winding and being arranged to induce a magnetic flux in the respective portion of said shell, a source of d-c current for the windings of said electromagnets, adjustable means for regulating the magnetic flux which is induced by the electromagnets of at least some of said groups independently of the magnetic flux induced by the other groups, said regulating means including means for varying the intensity of current which is supplied to said windings, signal generating monitoring means for ascertaining the temperature of a plurality of locations along said external surface, as considered in the axial direction of said shell, and control means having input means connected with said monitoring means and arranged to adjust said regulating means so as to maintain a predetermined pattern of temperature along said external surface.

Dependencies are inferred from the claim text.