Rocker arm 6 of four-bar linkage DCBA turns about fixed axis A and is connected by turning pair E to pawl 4. Levers 1 and 2 turn about fixed axes G and F. Lever 2 has pins a and b. Pawl 4 engages ratchet wheel 3, turning it intermittently counterclockwise. Pin a on lever 2 prevents reverse rotation of ratchet wheel 3. When lever 1 is turned clockwise, pin a is disengaged from wheel 3 and pin b turns pawl 4 also disengaging it from ratchet wheel 3.
$1834$LR,ML$