Plate cam 1 rotates about fixed axis A. Follower 5 reciprocates in fixed guides B-B and carries roller 4 which rolls along the contour of cam 1. Follower 5 is connected by turning pair D to segment gear 2 which meshes with fixed rack 3. When cam 1 rotates, segment gear 2 rolls along rack 3 and its point a travels along path q which is a portion of a prolate cycloid. In the extreme position, when point a reaches point a', the mechanism becomes locked and segment gear 2 is indexed in this position. The mechanism is brought out of the indexed position by pushing follower 5 to the left and compressing spring 6.
$3334$GrC,I$