RATCHET AND PAWL Figure 2-12b shows a ratchet and pawl mechanism. The
arm pivots about the center of the toothed ratchet wheel and is moved back and forth to
index the wheel. The driving pawl rotates the ratchet wheel (or ratchet) in the counterclockwise
direction and does no work on the return (clockwise) trip. The locking pawl
prevents the ratchet from reversing direction while the driving pawl returns. Both pawls
are usually spring-loaded against the ratchet. This mechanism is widely used in devices
such as "ratchet" wrenches, winches, etc.
LINEAR GENEVA MECHANISM There is also a variation of the Geneva mechanism
which has linear translational output, as shown in Figure 2-12c. This mechanism is analogous
to an open Scotch yoke device with multiple yokes. It can be used as an intermittent
conveyor drive with the slots arranged along the conveyor chain or belt. It al 'r;an
be used with a reversing motor to get linear, reversing oscillation of a single slotte,
put slider.