| 摘要 |
A position retention device includes a pivot member having a mounting axle, a cylindrical seat, a cylindrical housing and an annular member. A cylindrical seat is mounted co-axially on the mounting axle of the pivot member, and has pluralities of circumferentially formed and alternately disposed north and south pole sectors. A cylindrical housing is mounted co-axially and rotatably on the mounting axle of the pivot member. An annular member is disposed within the annular receiving chamber in the cylindrical housing for simultaneous rotation with the cylindrical housing. The annular member has pluralities of circumferentially formed and alternately disposed north and south pole sectors. Position of the cylindrical housing is retained stationarily with respect to the cylindrical seat by virtue of attraction between adjacent two of the north or south pole sectors of the cylindrical seat and the annular member.
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