| 摘要 |
<p>In the switchable magnet system disclosed herein, a central pole piece (29) is backed by at least two permanent magnets (33, 35) having substantially different energies so that one of the magnets (33, 35) is relatively switchable or reversible and the other (35, 33) is not. A magnetically permeable frame (17) provides a peripheral pole face (21, 23) at least on either side of the central pole face (29) and a backing plate (15) bridging the central pole piece (29) over the permanent magnets (33, 35). A coil (41) surrounds the first and second permanent magnets (33, 35) inside of the peripheral pole face (21, 23). Accordingly, energization of the coil (41) in one direction can reverse the polarization of the first magnet (33), thereby effectively short circuiting flux produced by the second magnet (35) and terminating holding, while energization of the coil (41) in the opposite direction can polarize the first magnet (33) in parallel with the second magnet (35), thereby to effect holding.</p> |
