| 摘要 |
1517387 Magnetization; permanent magnets RCA CORPORATION 9 Sept 1975 [10 Sept 1974] 37064/75 Heading H1P [Also in Division H2] A ring 21, attached to a turntable in a synchronous video disc drive assembly (Division H2), is permanently magnetized to have poles of alternate polarity along its periphery by locating the ring 21 in an annular gap defined between an outer upstanding wall of a silicon steel housing 30 and arcuate surfaces 35 of magnetic shoes 32 supported from a base of housing 30 by legs 34 around which are located windings (37), Figs. 4, 6 (not shown). A control circuit, Fig. 6, supplies a D.C. pulse of a predetermined adjustable duration and predetermined amplitude to windings (37) for establishing a unidirectional flux at each of shoes 32, the flux directions being as indicated in Fig. 5. |
