Patent ID: 7208706

Claim:
A shrinking arrangement for a tool holder ( 3 ) which retains a rotary tool with a press fit in a central accommodating opening ( 11 ), said arrangement comprising: an induction-heating arrangement ( 15 , 18 ) for thermally expanding the tool holder ( 3 ) in the region of the accommodating opening ( 11 ), wherein the induction-heating arrangement ( 15 , 18 ) includes an induction-coil unit ( 15 ) with an induction coil ( 21 ), which can be positioned essentially concentrically on the region of the accommodating opening ( 11 ) of the tool holder ( 3 ) for thermal-expansion purposes, and also has a yoke arrangement ( 101 ) which is made of ferromagnetic material and extends axially along the outer circumference of the induction coil ( 21 ) and radially along at least one of the two axial end surfaces of the induction coil ( 21 ), those regions of the yoke arrangement ( 10 ) which are adjacent to the tool-insertion end and/or remote from the tool-insertion end having a plurality of yoke elements ( 109 ) which are made of ferromagnetic material, project radially inward beyond the inner circumference of the induction coil ( 21 ), are guided such that they can move relative to one another and of which the radial projection beyond the inner circumference of the induction coil ( 21 ) can be changed for operational purposes, wherein the yoke elements ( 109 ) are guided such that they can be pivoted relative to one another.