Patent ID: 8400036

Claim:
An electromagnetic actuator having a magnetic material stator and a magnetic material thrust disk separated from each other by a gap and sharing an axis of symmetry, wherein the stator comprises an inner pole having an extension, an outer pole having a diffuser portion and a back face having ends joined to the inner and outer poles at transition regions so as to define a coil cavity bounded by the thrust disk, and is sized and configured so as to have a flux path cross-sectional area that first decreases from a reference cross-sectional area (A ref ) in a region of the inner pole adjacent the gap, then increases in an immediately adjacent region in a direction toward the back force and then increases even more along a back face inner pole extension with the flux path extending substantially along a direction of the axis of symmetry, whereupon the flux path curves around from the inner pole to the back face in a direction substantially transverse to the axis of symmetry in one of the transition regions upon which the flux path cross-sectional area then decreases monotonically until reaching another of the transition region at the outer pole where the flux path is again substantially along the axial direction and the cross-section area is slightly greater than the reference cross-sectional area (A ref ) and then decreases to approximately the value of the reference cross-sectional area whereupon it decreases gradually to a value below the reference cross-sectional area (A ref ), and finally the flux path cross-section area gradually increases in a transition region between the outer pole and the diffuser portion to a value below the reference cross-sectional area (A ref ) whereupon in the diffuser portion the flux path cross-sectional area increases to a point at the gap substantially above the reference cross-sectional area (A ref ).