| 摘要 |
PURPOSE:To make high flatness maintainable on a suction surface even in use for years, by forming a groove magnetically dividing a face plate part into magnetic poles of a heterogeneous magnetic pole in an inner surface of the face plate, while making an outer surface of the face plate part into a flat surface through a simple member. CONSTITUTION:When an exciting coil is excited and a part corresponding to an outermost partition wall part 22 of a face plate part 20 is magnetized to an N pole, leakage flux between proximate heterogeneous magnetic pole parts is prevented from occurring at a time when a part corresponding to its inward partition wall part 24 is alternately magnetized to S and N. As a result, when the coil 14 is excited, an outer surface 20b of the face plate part is formed clearly with an annular heterogeneous magnetic pole part so that a work is surely clamped by dint of magnetic force acting on the outer surface 20b. Likewise, with a groove 28, the suction surface 20b is magnetically dividable into heterogeneous magnetic pole parts, and since the suction surface can be constituted of a single magnetic member, highly accurate flatness is securable on the suction surface 20b and, what is more, since there is no partial hardness difference due to a quality difference between materials used, no partial wear is produced, thus flatness for years is maintainable.
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