Abstract: An apparatus having a track for guiding a sheet therealong and means for feeding a sheet along the track. The feeding means includes a rotatable member having a shaft mounted for rotation, with the rotatable member having a driving periphery extending into the track. The feeding means also includes a coupling unit and means for rotatably mounting the coupling unit at the track, with the coupling unit having an expansible periphery. Also provided is a means including an endless coiled spring for selectively moving the expansible periphery between a first position in which the expansible periphery is uncoupled from the driving periphery and a second position in which the expansible periphery is expanded to form a driving coupling with the driving periphery of the rotatable member to feed a sheet positioned therebetween along the track when the rotatable member is rotated.