Constant-breadth cam 1 rotates about fixed axis A and is confined between the flat faces of yoke 4 on follower 2 which turns about axis B of slide 3. Slide 3 reciprocates along fixed guides b-b. Cam 1 carries pin D which slides along slot 1 of slide 3. When cam 1 rotates, claw a is inserted into a perforation of the film, advances the film and is withdrawn from the perforation.
$3207$CmL,OC$