Patent ID: 7588002

Claim:
An electromagnetic actuator in which a rotor comprising permanent magnet means is rotatable in a stator which is magnetisable by causing an electric current to flow through at least one winding associated with the stator, wherein: the rotor is rotatable between stable rest positions; the rotor is connected to a rigid link by a mechanical linkage by which the rotational movement of the rotor is converted into substantially linear movement of the rigid link, the linkage having a mechanical advantage which varies in a predetermined manner during the rotation of the rotor; spring means store energy during part of the movement of the rotor and provide kinetic energy for accelerating the rotor during subsequent movement thereof away from rest at a first rest position towards another rest position; and a magnetic torque is exerted on the rotor when a current flows in said at least one winding which is sufficient to overcome the force(s) holding the rotor in the first rest position, to cause the rotor to rotate in a direction from the first rest position towards another rest position, wherein more than two stable rest positions are defined by spring forces acting on the rotor and/or magnetic forces exerted on the rotor by the stator, and the rotor is controllable by application of electric current pulses to the at least one stator winding to rotate from the first rest position to one of the other rest positions and back again, or through said other rest position to return to the first rest position while continuing to rotate in the same direction.