Induction Coil Unit

An induction coil unit for heating a component which is rotationally symmetrical relative to an axis and is composed of electrically conductive material, in particular a sleeve part, which holds an elongated object with an interference fit in a retaining opening which is central with respect to the axis, preferably for heating the sleeve part of a tool holder which holds a shank of a rotating tool, in particular a drilling and milling tool, with an interference fit in its retaining opening which is central with respect to the rotation axis, comprising:

• a retaining area which is central with respect to the axis for the component;
• a number, in particular an even number, of pole pieces which are arranged distributed at equal angular intervals around the axis and are composed of a material with soft-magnetic characteristics, guiding magnetic flux;
• a plurality of coils which can be fed with alternating current, to produce magnetic fluxes in the pole pieces such that the magnetic flux is in the opposite direction in the circumferential direction of adjacent pole pieces wherein the pole pieces have end surfaces which radially face the axis and can be brought into touching contact, in the form of a line or an area, or virtually such a touching contact, with the outer circumferential surface of the component over the majority of their axial height in a first area along the generatrix of an outer circumferential surface of the component, and in that a second area is adjacent to the first area axially on at least one side of the first area, at least one of the end surfaces, in particular each of the end surfaces, in which second area the end surface runs at a greater radial distance from the generatrix of the outer circumferential surface than in the first area.