When crank 1 of four-bar linkage ABCD rotates about fixed axis A, the tip of claw, or hook, E , mounted on connecting rod 2 , describes a connecting-rod curve. At portion b-b of this curve, claw E engages a perforation of the film which it moves. At another portion of the connecting-rod curve, claw E is withdrawn from the perforation. Pin C of connecting rod 2 slides along arc-shaped guide a-a whose centre is at point D.
$777$LW,OC$