Patent ID: 6229422
Filing Date: 2001-05-08
Classification: H01F

Abstract:
A switchable holding magnet system comprising:a central pole piece providing a central pole face;a magnetically permeable frame providing a peripheral pole face at least on either side of said central pole face and a backing plate bridging said central pole piece;between said backing plate and said central pole piece,a first, switchable permanent magnet and,beside said first permanent magnet, a second permanent magnet having an energy (Hc) which is substantially higher than that of said first permanent magnet; anda coil surrounding both said first and second permanent magnets inside of said peripheral pole face;whereby energization of said coil in one direction can reverse the polarization of said first magnet and thereby effectively short circuit flux produced by said second magnet and terminate holding while energization of said coil in the opposite direction can polarize said first magnet in parallel with said second magnet thereby to effect holding.