Valve actuator position indicating system

Claim 1

A valve actuator for controlling and sensing the rotational position of a valve member comprising: an actuator motor for rotating an actuator shaft; an actuator arm coupled to said actuator shaft, the rotation of said actuator shaft causing rotation of said actuator arm through an angle exceeding 90°; a linkage connecting said actuator arm to said valve mechanism, the rotation of said actuator arm causing movement of said linkage and, in turn, rotation of said valve member; and a positional indicator means or sensing the angular position of said actuator shaft, said positional indicator means including: a positional indicator shaft coupled to said actuator shaft such that angular rotation of said actuator shaft causes a corresponding angular rotation of said positional indicator shaft; a rotor/stator assembly including a rotor coupled to a said indicator shaft whereby said rotor includes a magnetically active sector located about a portion of the peripheral surface of said rotor, and a magnetically inactive sector located about another portion of the peripheral surface of said rotor; and a stator comprising a first sensing pole piece partially surrounding said rotor, a second sensing pole piece partially surrounding said rotor, and a driving pole piece, said rotor being mounted for rotation with respect thereto, said rotor varying the inductive coupling in the stator; and a positional indicator circuit responsive to said rotor/stator assembly for generating an analog output signal which varies in accordance with the angular position of said rotor with respect to said stator and, therefore, in accordance with the angular position of said actuator shaft.