Constant-breadth cam 1 rotates about fixed axis A and is confined between the flat faces of the square yoke of follower 2 whose slot b slides along fixed pin B. Follower 2 has a toothed segment with claws a. When cam 1 rotates, claws a describe a complex curve in which they are inserted into perforations of the film, advance the film and are withdrawn from the perforations.
$3217$CmL,OC$