Crank 1 rotates about fixed axis A. Slider 2 moves along fixed guide a. When crank 1 rotates about axis A, slider 2, carrying pawl 3 and flat spring 5, reciprocates. In the up- stroke of slider 2, pawl 3 comes out of perforation C of film 4 and slides along the film with its rounded tip b. In the down-stroke of slider 2, spring 5 inserts pawl 3 into perforation B of film 4 and the pawl advances the film downward.
$1655$SC,OC$