Renishaw Plc

Thomas John Stickland

James Reynolds Henshaw

Peter Geoffrey Holden

Joel Barnabas Chase

Rotary encoder apparatus is described that comprises an encoder scale or ring and an encoder scale reader. The encoder scale includes an incremental scale and one or more reference marks. The encoder scale reader comprises at least a first readhead and a second readhead that each produce a reference mark signal when passed over a reference mark of the encoder scale. The apparatus also comprises a reference position setter for determining, as the encoder scale reader is rotated relative to the encoder scale, at least one angularly repeatable reference position of the encoder scale relative to the encoder scale reader using a first reference mark signal produced by the first readhead and second reference mark signal subsequently produced by the second readhead.

Rotary encoder in which an absolute position is defined using reference mark signals produced by each of at least two readheads and method of operating the same

A rotary ring for use in scale reading apparatus has a scale on its outer circumference and is mounted on a rotary shaft To reduce error caused by the rotary ring not sitting concentrically on the rotary shaft the inner circumference of the rotary ring and the outer circumference of the shaft are both tapered. To compensate for eccentricity of the shaft, mounting screws are provided in holes on the rotary ring to adjust the position of the rotary ring until it is concentric with the axis of rotation of the shaft.

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Stonehouse, United Kingdom

Thomas John Stickland