Patent ID: 6932316

Claim:
An electromagnetic actuator comprising: A) a stationary assembly that includes: i) a coil; ii) a pocket wall that defines an armature pocket that has front and rear pocket ends and is closed except for a mouth at the front end thereof; and iii) a flexible diaphragm that closes the mouth of the armature pocket and thereby forms with the pocket wall a substantially fluid-tight armature chamber; B) an incompressible fluid contained in the armature chamber; and C) an armature that includes high-magnetic-permeability material, has front and rear armature ends, cooperates with the incompressible fluid to fill the armature chamber, and is disposed in the armature chamber for movement, in directions in which it can be urged by magnetic force resulting from current flow through the coil, between a forward position, in which the armature leaves a relatively large space in the armature chamber behind the armature, and a rear position, in which the armature leaves less space in the armature chamber behind the armature, the front end of the armature so engaging the diaphragm when the armature is in its forward position that the diaphragm assumes a shape that extends farther forward than the shape assumed by the diaphragm when the armature is in its rear position, the armature forming an internal fluid-flow passage therethrough in which, as the armature moves toward and away from the rear end of the armature pocket, the incompressible fluid flowing between the portion of the armature chamber behind the armature and other portions thereof experiences less flow resistance than does incompressible fluid flowing therebetween outside the armature.