Patent ID: 8272622

Claim:
An electromagnetic actuator comprising a core, a ferromagnetic component movable in a gap in said core, a permanent magnet for attracting said component to one side of said gap, a solenoid for producing magnetic flux in said gap, a magnetic circuit of said solenoid being defined by part of said core, part of said gap and by a further gap between the ferromagnetic component and the core, and a demagnetiser having a magnetic circuit defined by another part of said core, another part of said gap and by said further gap, the demagnetiser being arranged to demagnetise the permanent magnet at least to the extent that the magnetic flux produced by the solenoid is diverted from said gap into said further gap and said movable component is movable away from the magnet under the magnetic force of the solenoid, a flux concentrator being arranged to concentrate the magnetic flux on said one side of the gap, and to maintain a net force, opposed to the force produced by the energised solenoid, keeping the ferromagnetic component on said one side of the gap.