| 摘要 |
PURPOSE:To improve the lifting-up capacity by an apparatus wherein an auxiliary pole is provided between an outer pole having cup-like section and a cylindrical inner pole, main and auxiliary coils are respectively wound between the adjacent poles, and the main coil is protected by a ferromagnetic plate. CONSTITUTION:A column-like inner pole 12 made of a ferromagnetic substance is fixed to the inner bottom surface of a cylindrical outer pole 11 having the bottom and made of a ferromagnetic substance, and a cylindrical auxiliary pole 13 made of a ferromagnetic substance is fixed to the inner bottom surface of the outer pole 11 between the outer and inner poles. A main coil 14 is inserted between the inner pole 12 and the auxiliary pole 13, while an auxiliary coil 15 is inserted between the auxiliary pole 13 and the outer pole 11. Then, a protective plate 16 made of a ferromagnetic substance is mounted to protect the pole surfaces of both inner pole 12 and auxiliary pole 13 as well as the outer surface of the main coil 14. An opening between the auxiliary 14 and the outer pole 11 is closed by an an annular protective plate 17 made of a nonmagnetic substance. By so doing, the density of magnetic flux just below the inner pole 12 becomes higher and has a substantially constant size over the area up to the auxiliary pole 13. |
