Abstract: The sprocket assembly for periodic advancement of film in a film projector is supported axially between rotated members and is corotative with the members upon increase in axial force therebetween. One of the members is axially restrained and the second member supported for minute axial movement. Force giving rise to the corotation of the members and sprocket assembly is applied to the second member by selective energization of an electromagnet.

Abstract: Apparatus of the type wherein a desired length of adhesive strip is fixed to an edge of a stack of sheets with heat and pressure includes automatic means for reliably providing the desired length of strip from a roll of adhesive strip. The automatic means include a pair of rollers which engage and feed strip, one of the rollers being mounted for free rotation and the other of the rollers being coupled to a shaft by a one-way clutch. Means rotate the shaft from a start-of-feed position a selectable amount in one direction, with said other roller and clutch engaged, to feed the desired length of strip and, thereafter, a spring counter rotates the shaft to the start-of-feed position, said position being determined by an abutment which limits rotation of a gear coupled to the shaft. A flywheel frictionally coupled to the shaft prevents bounce when the abutment limits rotation of the gear, thereby preventing rotation of the shaft in said one direction and, consequently, unmetered feeding of adhesive strip.