Disk 1 rotates about fixed axis A and has wedge-shaped groove a which is engaged by wedged segment 3. Segment 3 turns about axis B of lever 2 which turns freely about axis A. Working surface b of segment 3 is designed so that the segment jams in groove a when lever 2 is turned counterclockwise, and turns disk 1 in the same direction through the angle φ required for the feed movement. When lever 2 is returned to its initial position, segment 3 slides along groove a and clockwise rotation of disk 1 is prevented by segment 4 which turns about fixed axis C and has working surface d that jams in groove a.
$3391$SmF,Br$