Ratchet, << RACH iht, >> is a wheel or bar that can move in only one direction. It often consists of a notched wheel and a pawl (metal bar hung from a pivot). The pawl is attached to a lever. As the lever is moved, the free end of the pawl locks into a tooth of the wheel, causing the wheel to rotate. A second pawl may be used to prevent the wheel from turning backwards while the lever is being returned to begin another stroke.
A mechanical counter is a simple device that uses the ratchet-and-pawl combination. A ratchet-and-pawl mechanism locks a machine such as a hoisting winch so that it does not slip.
