Three-lobe constant-breadth cam I and round eccentric cam 3 are rigidly attached together and rotate about fixed axis A. The contour of cam 1 is enclosed by the square opening of follower 4 which has slot b sliding along fixed pin 2. Cam 3 acts on flat surface d of rocker arm (follower) 5 which oscillates about fixed axis D of pin 2. Follower 4 has two claws a and rocker arm 5 has claw e. When cams 1 and 3 rotate, follower 4 has a complex motion in which claws a are inserted into perforations of the film, advance the film and are withdrawn from the perforations. After the film has been advanced, claw e of rocker arm 5 is inserted into a perforation to hold the film stationary until its next movement. Surface d of rocker arm 5 is held in contact with cam 3 by flat spring 6.
$3109$SmC,OC$