Gear 1 rotates about fixed axis A and meshes with composite rack 2. When gear 1 rotates clockwise, rack 2 travels in a straight line to the left. As soon as pin a of the rack passes the edge of wedge 3, the wedge automatically closes off the straight guide. As a result, pin b moves along arc d-d even before pin a reaches apex A of triangle ABC. Owing to the action of springs (not shown), wedges 3, 4 and 5 always close off the circular guides. Therefore, when pin b has passed along arc d-d, it travels along straight portion e-e. As soon as pin b passes the edge of wedge 4, the wedge automatically closes off the straight guide, and pin a moves along the circular guide even before pin b reaches point B. This sequence of motions continues around the triangle.
$2528$LrG,GI$