| 摘要 |
A permanent magnet energized holding device, which has a maximum holding power for a given volume of magnetic material, can be readily switched on and off with a minimum of force. At least two pairs of plate-shaped poleplates are provided with a permanent magnet arrangement sandwiched in between. Each pair of poleplates are separated by a non-magnetic medium. The permanent magnet arrangement consists of a fixed magnet, having a circular opening, and a disc shaped magnet rotatable in the opening. The two magnets are magnetized in the direction of their smallest dimension with portions of each having opposite magnetic polarity. The portions of the stationary magnet are arranged to magnetize the pole plates with opposite magnetic polarity. The disc shaped magnet, in one position, has magnetic polarity which coincides with that of the stationary magnet and reinforces its magnetic force and in another position, has magnetic polarity in opposition to the magnetic polarity of the fixed magnet whereby to oppose and reduce the flux in the poleplates.
|
