Ratchet Mechanism

Ratchet Mechanism


a toothed mechanism for the conversion of reciprocating rotary motion into intermittent rotary motion in one direction.

As shown in Figure 1, a ratchet mechanism consists of a ratchet wheel (1), a driving pawl (2), an arm (3), a locking pawl (4), and a support (0). The driving pawl engages the teeth of the ratchet wheel under the action of a spring or of its own weight. When the arm moves counterclockwise, the driving pawl turns the ratchet wheel through a certain angle. When the arm moves clockwise, the catch slips past one or more teeth, but the locking pawl prevents the clockwise rotation of the ratchet wheel.

Figure 1. Diagram of a ratchet mechanism

Ratchet mechanisms are used in, for example, bicycles and machine tools. In load-lifting machines, ratchet mechanisms prevent the drum of the winch from moving backward under the weight of the load.

References in periodicals archive ?
It also has two cam clamps with a ratchet mechanism, with which you can disconnect the rear axle from the engine, and completely turn off the propshaft.
The handle was attached to a ratchet mechanism that made the same noise as an old football rattle.
To eliminate stretch wrap and banding to secure pallet loads, the reusable, rugged structural foam plastic enviroLid system features a unique, patented ratchet mechanism.
Once the Tecno Plug was hydraulically set and following the successful seal-integrity tests, the plug was locked in the set position with a ratchet mechanism, providing a further mechanical lock in place of the hydraulics to permanently set the plug, once abandoned in the pipeline.
Progressive withdrawal is allowed freely by the mechanism but once withdrawn to the desired negative volume, it is held at this negative pressure by the ratchet mechanism.
Ministers face key sticking points including finance for poor countries to cope with climate change, a long-term goal to bring greenhouse gas emissions to zero and a review and ratchet mechanism allowing countries to revisit their climate action plans and increase ambition.
That is why countries are rightly seeking to build an upwards ratchet mechanism into the agreement.
Caption: Kuhn Rikon: Sporting a ratchet mechanism rather than a pump or ripcord, Kuhn Rikon's Ratchet salad spinner is ergonomically designed, comes with a handy brake to stop the spinning, and has a 16-cup capacity.
Despite being faulty - the ratchet mechanism was not working - numerous bidders in the room competed with four telephones and countless Internet bidders, taking the price skywards.
He had the answer and he gives it to me: "Because when a bird lands Picture by Paul Norris on a tree there's a ratchet mechanism which makes the foot grip automatically.
Reliability in retrieving the plug is provided via the plug's robust ratchet mechanism, combined with the element being positioned above the slips.
Each ratchet mechanism is open to facilitate cleaning and can be easily reversed by simply flipping a lever in the tool head to make it easy to back off pressure when welding is finished.