Importance

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Abstract

A detented encoder, employed for sensing a rotation of a wheel by a user between detent position, and suited for use in a pointing device or other user input device. The detented encoder includes a light emitter, a pair of photodetectors, and a codewheel. Interruption of light emitted by the light emitter and received by the photodetectors is processed by a logic circuit to produce a quadrature signal indicative of the detent position of the wheel. The codewheel is integral to a shaft that is supported at one end by a support bracket connected to the lower case of the device. The wheel rotates the shaft when turned by a user. The shaft includes a plurality of evenly-spaced, longitudinally extending spline teeth. A biasing member or opto spacer is operatively coupled to the lower case and includes a base portion on which the light emitter and photodetector are mounted. The biasing member includes a cantilever portion. A U-shaped slot in the cantilever portion includes a protrusion that engages the spline teeth on the shaft. The protrusion is biased against the splined portion of the shaft, so that as the shaft is rotated, the protrusion moves in and out of spline wells defined between adjacent spline teeth, thereby creating a detent action. The detented encoder also includes a microswitch that is activated by the shaft when a user depresses the wheel. A logic device processes the signal produced by the photodetector to determine the transitions between the detent positions as the wheel is turned.

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First Claim