| 摘要 |
PCT No. PCT/SE88/00237 Sec. 371 Date Dec. 26, 1989 Sec. 102(e) Date Dec. 26, 1989 PCT Filed May 5, 1988 PCT Pub. No. WO88/09106 PCT Pub. Date Nov. 17, 1988.A device for heating a workpiece includes a coil arrangement connected to a voltage source for generating a magnetic field. The coil arrangement is positioned around a core of electric steel sheeting having two poles spaced apart to form an air gap for accommodating a central portion of a workpiece. One of the poles is movable wherein the poles engage the workpiece which bridges the air gap or engage each other by extending through the center of an annular workpiece. The coil arrangement includes first and second coils, each positioned about one of the poles, generating a magnetic field inside and outside the core. The magnetic field concentrated in the core heats the central portion of the workpiece while outer magnetic field heats peripheral portions of the workpiece to achieve a rapid and uniform heating of the workpiece. At least one of the coils can be moved with respect to the associated pole to control the heating of the workpiece. A third coil can be positioned around the air gap and connected in series with the first and second coils. |
