singlepawl

Single-pawl, also written as single pawl, refers to a simple ratchet mechanism that uses a single pawl to engage a toothed wheel to permit motion in one direction and block it in the opposite direction. The pawl is a lever pivoted on a fixed axis and typically biased by a spring toward the ratchet. When the ratchet wheel turns forward, the pawl rides over the tooth flanks, allowing rotation; when rotation reverses, the pawl drops into a tooth, preventing backward movement.

In a single-pawl design, all load transmission and wear concentrate on one contact point between the pawl and the ratchet teeth. This simplicity keeps the mechanism compact and cost-effective, but it can limit torque capacity and increase wear on the single engagement point compared with multi-pawl systems. Tooth geometry, pawl shape, and spring force are important to prevent slipping and to ensure reliable engagement under load.

The arrangement is common in small, manually operated devices such as hand winches, clamps, lever hoists, and ratchet straps, where a compact, inexpensive unidirectional stop is desirable. It is less common in high-load or high-cycle applications, where double- or multi-pawl designs distribute load and tolerance better.

Maintenance considerations include inspecting pawl and teeth for wear, ensuring the spring maintains adequate bias, and lubricating contact surfaces to reduce wear. If the single pawl becomes worn or the spring weakens, the mechanism can fail to engage or slip. See also: ratchet, pawl, escapement.