Valve actuator having small isolated plunger

An electromagnetic actuator comprising:

• A) a stationary assembly that includes:
• i) a coil;
• ii) a pocket wall that includes a polymer and 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 defined by a chamber boundary;
• B) an incompressible fluid contained in the armature chamber, the incompressible fluid's molecular composition being such that the chamber boundary's materials are substantially impervious to molecular diffusion by said incompressible fluid;
• 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 forward and rear positions, 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.