| 摘要 |
758,962. Magnetic structures; permanent magnet machines. PHILIPS ELECTRICAL INDUSTRIES, Ltd. April 8, 1954 [April 11, 1953], No. 10368/54. Classes 35 and 38 (2). [Also in Group V] A cylindrical anisotropic permanent magnet with poles distributed around its periphery, suitable for use in synchronous motors and bicycle dynamos, is made from a material consisting of non-cubic crystals of mixed oxides of iron and at least one of the metals Ba, Sr, and Pb, and if desired Ca, such as forms the subject of Specification 708,127, by a moulding process during which favourable directions for magnetization are produced, the body being subsequently sintered. Powdered material for forming a six-pole magnet is introduced with a liquid into space 12, in a mould and compressed by a ram 10, the liquid being expelled through holes 8 in the base 7 of the mould, which holes may be covered with filter paper. The mould comprises an outer casing 6 in which are fitted permanent magnets 1, 2, 3 separated by non- magnetic parts 5, and having non-magnetic inserts 4 to form the poles. The magnets may be formed of material similar to that used to make the cylindrical magnet, or of a Mn-Bi alloy. The magnetic flux produced by the permanent magnets 1, 2, 3 creates favourable directions for magnetism in the moulded magnet. The magnets 1, 2, 3 may be formed together in one piece, Fig. 3 (not shown), or each magnet may be in two pairs, separated if necessary by non-magnetic material, Fig. 4 (not shown). A projection 11 on the ram may pro. vide a spindle hole in the cylindrical magnet, and projections on the mould may mark the pole places. The grinding needed to the magnet owing to unequal shrinkage may be reduced by using a non-circular mould. Specification 747,724 also is referred to. |
