Gear 1 rotates about fixed axis A and is rigidly attached to lever a which is connected by turning pairs C and D to two identical members 3. Members 3 carry rollers 4 which roll along the inside surface of fixed drum 5. Gear 6 rotates about fixed axis B, meshes with gear 1 and is rigidly attached to cam 2. When gear 1 rotates and a roller 4 reaches recess b, it is pushed into the recess by cam 2 and held there until member 3 is swivelled about axis C or D. In this way, each member 3 is swivelled through 180° once in each revolution about axis A.
$3307$GrC,ML$