Patent ID: 7352088

Claim:
A system comprising: a housing; a longitudinal shaft movably coupled to the housing to longitudinally and linearly reciprocate relative to the housing in the longitudinal direction of the shaft; a stator rigidly coupled to the housing, the stator shaped to define an inner space to receive a portion of the longitudinal shaft, the stator having stator poles extending inwardly with bore surfaces facing toward that portion of the longitudinal shaft received by the stator; windings wound around the stator poles; a mover affixed to the shaft, the mover; and magnetic material affixed to the mover, the magnetic material having bore surfaces facing outward in correspondence with the bore surfaces of the stator poles to define a gaseous gap between each of the correspondingly positioned ones of the bore surfaces of the magnetic material and the stator poles, portions of the bore surfaces of the stator poles being closer to the shaft than portions of the bore surfaces of the magnetic material, wherein the bore surface of at least a portion of the magnetic material affixed to the mover comprises a concave shape.