Pinion 1 rotates about fixed axis A. Link 2 reciprocates along axis c-c in fixed guides B-B and has duplex rack a. The teeth of pinion 1 are arranged along one half of its pitch circle. When pinion 1 rotates continuously in one direction its teeth alternately engage the two sides of rack a imparting a sliding motion to link 2 in the left and right directions. Link 2 has dwells at its extreme end positions.
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