| 摘要 |
PURPOSE:To reduce or eliminate the influence of the magnetic field of a magnet to the outside by constructing a magnetic seal with a plurality of magnets having different directions of magnetization. CONSTITUTION:A magnetic seal magnet which constitutes a source of the magnetic field consists of a plurality of permanent magnets 32 and 33 having different directions of magnetization, so that in a zone at the upper end of a central stationary shaft 8, which is sufficiently remove from the magnetic seal section (i.e., in the neighborhood of an upper cylinder 1, rotary transformer ferrites 13 and 14 and head 6), the effect of the magnetizing action of the permanent magnets 32 and 33 is weak, and this zone is magnetically neutral. In other words, the magnetizing action of the magnetic fluxes 37 and 38 cancel each other, thus eliminating the effect of the magnetic field upon the upper cylinder 1 or the like. |
