Patent ID: 7292028

Claim:
An apparatus for sensing the absolute value of the rotational position of a shaft, said apparatus comprising: a) a first single-turn rotary encoder arranged at one end of the shaft and configured to sense the shaft's rotational position within a single revolution thereof, said first single-turn rotary encoder being circumscribed by an outer periphery; b) a second rotary encoder unit for sensing the number of revolutions of said shaft, said second rotary encoder unit comprising: i) a reduction gear linkage drivable by the shaft and being arranged annularly around a portion of the shaft, said reduction gear linkage having an output element, driving motion applied by the shaft ( 14 ) to the reduction gear linkage ( 18 ) translating into a motion coaxial with motion of the shaft; ii) a rotary element connected to said output element, said rotary element being located beyond said one end of the shaft but along a common axis therewith; iii) a second single-turn rotary encoder configured to sense the rotational position of said rotary element within a single revolution thereof; iv) an essentially U-shaped yoke connecting member for drivingly connecting said output element of the reduction gear linkage to said rotary element, said connecting member extending around the outer periphery of the first single-turn rotary encoder.