| 摘要 |
<p>1299490 Extruding magnets PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 25 June 1970 [28 June 1969] 30875/70 Heading B6A [Also in Division H1] The anisotropy of a permanent magnet, extruded from a mixture of powdered magnetic material and binder through a rectangular nozzle outlet 3 which is surrounded by a device which produces an orienting magnetic field, is improved by causing the mixture to flow between a plurality of shear orienting partitions 4 extending across and along the extrusion passage 2 and in planes substantially perpendicular to the direction of the magnetic field and terminate prior to the nozzle outlet. The permanent magnetic material may be alloys or mixtures e.g. manganese, bismuth, but preferably is a hexa-ferrite BaO, 6Fe2 03, in which the barium may partially or completely be replaced by strontium, calcium or lead, and the plate shaped particles are oriented by the shear effects of passage between the partitions 4 to align the easy axis of magnetization thereof, extending perpendicularly to the planes of the particles, with the orienting magnetic field. In the described embodiment, the permanent magnetic material is obtained by grinding the sintered product of barium carbonate or iron oxide. The orientating magnetic field comprises a D.C. magnetic field of 3 to 10 KOe which is applied through the length of the brass nozzle 1 by permanent magnetic devices, or by a device comprising spaced coils 7, soft-magnetic pole shoes 8, and a soft-magnetic frame 9 closing the magnetic circuit around the nozzle 1. The partitions 4 may comprise magnetic, or non- magnetic material e.g. bronze or brass, and in the described embodiment both the spacing between adjacent partitions 4 and the section of the passage 2 of the nozzle 1 in which they are located decreases in the direction of extrusion. The partitions 4 are of progressively decreasing length transversely from the axis of passage 2, and they taper from their centres to knife edges at their rearward, and desirably also at their forward edges. The extruded magnets may comprise synthetic resin or rubber binder which hardens after extrusion, or may be compressed and sintered after extrusion.</p> |
