Electromagnetic force motor having adjustable magnetic saturation

Claim 1

In an electromagnetic force motor having a pair of pole pieces spaced apart to provide an air gap therebetween; an armature positioned with a portion thereof in said air gap, said armature being adapted to move in said air gap from a neutral position thereby more closely approaching one of said pole pieces; a magnetic circuit in said motor including said pole pieces, said armature and a permanent magnet meanS, said permanent magnet means providing polarizing flux; electrical signal receiving means operatively associated with said magnetic circuit to establish magnetic flux therein of a strength proportional to a received electrical signal; the improvement of apparatus for enabling adjustment of force versus input signal characteristic, comprising: and at least one region of magnetically saturable material disposed in the flux path of said magnetic circuit, said region defining a magnetic saturation path thereat; a discrete member of magnetically permeable material; said region defining means for receiving said discrete member thereat to thereby vary the length or cross-sectional area of said saturation path; said permanent magnet polarizing flux and signal receiving means magnetic flux being sufficient to magnetically saturate said region at a selected armature position within said air gap in the absence of said discrete member, but being insufficient to magnetically saturate those portions of said region that are occupied by said discrete member at that armature position.