Patent ID: 7012495

Claim:
A switchable magnetic device, comprising a housing having a low magnetic reluctance path, a first permanent magnet, a second permanent magnet, and actuation means for causing relative rotation of the first and second permanent magnets, said first and second permanent magnets being diametrically polarised, to define a north and south pole regions of each permanent magnet extending throughout the length of each permanent magnet, said first and second permanent magnets being mounted within the housing such that the first and second permanent magnets are rotatable relative to each other to provide an active shunting arrangement, wherein said device presents a relatively strong external magnetic field when said first and second permanent magnets are positioned relative to each other such that a north and south poles of the first magnet are in substantial alignment with respective north and south poles of the second magnet, and the device presents a relatively weak external magnetic field when the first and second magnets are positioned relative to each other such that the north pole of the first magnet is in substantial alignment with the south pole of the second magnet and vice versa.