Ratchet wheel 1, rotating about fixed axis A, has ratchet teeth on both external and internal surfaces of the wheel. Lever 2 turns about fixed axis B. Connected by turning pairs D and C to lever 2 are pawls 3 and 4 which, when lever 2 is oscillated about axis B, alternately engage external and internal teeth of ratchet wheel 1, thereby turning it intermittently counterclockwise. To ensure proper engagement of pawls 3 and 4 with the teeth of wheel 1, the pawls are connected together by spring 5. Pawls 3 and 4 also serve as locks preventing reverse rotation of wheel 1. In one complete oscillation (back and forth) of lever 2, ratchet wheel 1 is turned through the angle α=360°/z₁+360°/z₂ where z₁=number of external teeth on wheel 1, z₂=number of internal teeth on wheel 1.
$1793$LR,4L$