| 摘要 |
A magnetic grab has a pair of pole pieces each forming a downwardly directed pole and formed adjacent the respective poles with horizontally extending semicylindrical seats having approximately the same center of curvature and open concavely inward toward each other. One of the pieces has an upwardly directed upper surface to one side of the seats and the other piece has a lower surface directed downward at the upper surface and also to the one side of the seats. A rotor fitting in the seats is provided with a plurality of high-flux rotor magnets polarized about respective axes extending generally diametrically of the rotor axis. At least one low-flux permanent magnet having a vertical polarization axis between the upper and lower surfaces has its north pole engaging one of the surfaces and its south pole engaging the other surface. The rotor can be turned about its axis between an inactive position with the north poles of the rotor magnets turned toward the seat of the piece having the other surface and the south poles of the rotor magnets turned toward the seat of the piece having the one surface, and an active position with the north poles of the rotor magnets turned toward the seat of the piece having the one surface and the south poles of the rotor magnets turned toward the seat of the piece having the other surface.
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