| 摘要 |
PURPOSE:To revent the attracting force of a surface plate edge section of a permanent magnetic chuck from lowering, by using, as a frame member, a plastic magnet plate which is magnetized with the magnetizing direction being alternately reversed in the moving direction of a permanent magnet assembly in the thicknesswise direction of the plate and as well in correspondence to a permanent magnet. CONSTITUTION:A frame 20 made of a thicknesswise magnetized plastic magnetic plate whose magnetizing direction is alternately reversed so that the polar surfaces of different magnetic poles are alternately positioned in the longitudinal direction of the housing in correspondence to the arrangement of magnetic pole members 22, is disposed in a rectangular opening between a surface plate 18 and a bottom plate 16. With this arrangement, the leakage of magnetic flux between parts corresponding to the frame member 20 may be prevented between the magnetic pole members 22 on the surface plate 28 which are magnetized upon energization of the chuck such that they have different polarities, alternately, and the bottom plate 16. Accordingly, the attracting force in the surface plate edge section may be prevented from lowering.
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