Ultrasonic rotary shaft position encoder

Abstract

A device and method for monitoring the angular displacement of a rotating shaft provides an ultrasonic transceiver reflecting pulses off of a reflecting edge of a vane of a rotor affixed to the shaft. The reflecting edge is configured in the profile of an involute curve so that changes in the time delay between transmission and reception of each reflected pulse, which correspond to changes in the distance between the transceiver and the reflecting edge, are linearly related to changes in the angular displacement of the shaft, and arranged such that the reflecting edge is normal to the probe axis so that the energy is reflected back to the probe. A circular disc may be associated with the vane to provide a reference reflected pulse, which eliminates errors which might occur due to wobbling of the shaft.

Dependencies are inferred from the claim text.