Ratchet
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(′rach·ət)
(design engineering) A wheel, usually toothed, operating with a catch or a pawl so as to rotate in only a single direction.
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A wheel, usually toothed, operating with a catch or a paw$$ so as to rotate in a single direction (see illustration). A ratchet and pawl mechanism locks a machine such as a hoisting winch so that it does not slip. The locking action may serve to produce rotation in a desired direction and to disengage in the undesired direction as in a drill brace. The catch or pawl may be of various shapes such as an eccentrically mounted disk or ball bearing. Gravity, a spring, or centrifugal force (with the catch mounted internal to the ratchet) are commonly used to hold the pawl against the ratchet. A ratchet and pawl provides an arresting action. See also Brake; Escapement; Pawl.
Ratchets. Toothed ratchet is driven by catch when arm moves to left; pawl holds ratchet during return stroke of catch. In roller ratchet, rollers become wedged between driver and follower when driver turns faster than follower in direction of arrow.
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McGraw-Hill Science & Technology Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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