Ratchet Pawl Mechanism

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A Ratchet is a mechanical device that allows continuous or linear motion in only one direction while preventing motion in another direction. Ratchets are widely used in machinery and tools. A Ratchet mechanism is based on a wheel that has teeth cut out of it and a pawl that follows as the wheel turns and the pawl falls into the ‘dip’ between the teeth. The Ratchet wheel can only turn in one direction. When the teeth are moving in the unrestricted (i.e. forward) direction, the pawl easily slides up and over the gently sloped edges of the teeth, with a spring forcing it, (often with an audible ‘click’) into the depression between the teeth, as it passes the tip of each tooth. When the teeth move in the opposite (backward) direction, however, the pawl will catch against the steeply sloped edge of the first tooth, it encounters, thereby locking it against the tooth and preventing any further motion in that direction.