| 摘要 |
A permanent magnet energized holding device for holding of, or onto, ferromagnetic objects and readily switchable between "on" and "off" positions, has outer and inner cup-shaped pole shoe members of good magnetically conductive material concentrically nested in spaced apart relation one inside the other with their rim edges or pole faces lying in a common plane. A ring-shaped stationary permanent magnet is fixed in the space between the peripheral side walls of the cup members, and the cup members and stationary magnet are correspondingly divided magnetically into two portions at the same points therearound by non-magnetic mediums. A rotatable permanent magnet sandwiched between the base end walls of the cup members is rotatable therebetween by an operating shaft or other actuating means to switch the holding device between its "on" and "off" positions. The two magnets are magnetized in the direction of their smallest dimension or thickness, with portions of each having opposite magnetic polarity. The magnetically divided portions of the stationary magnet are arranged to magnetize the pole portions of the cup members with opposite polarity. In one rotative position of the rotatable magnet, the magnetic polarity thereof coincides with that of the stationary magnet and reinforces the magnetic force thereof so as to increase the magnetic flux in the respective pole shoe members, while in another rotative position its magnetic polarity is in opposition to the magnetic polarity of the stationary magnet and reduces the magnetic flux in the pole shoe members of the device.
|
