Overrunning Clutch

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overrunning clutch

[′ō·və‚rən·iŋ ′kləch]
(mechanical engineering)
A clutch that allows the driven shaft to turn freely only under certain conditions; for example, a clutch in an engine starter that allows the crank to turn freely when the engine attempts to run.

Overrunning Clutch


(also freewheeling clutch), a device used to connect two coaxial shafts or a shaft to a freely moving part that is seated on the shaft. An overrunning clutch transmits rotary motion and torque from a driving member to a driven member in one direction only. There are overrunning versions of positive clutches, including adaptations of the ratchet and jaw types; there are also overrunning friction clutches, with circular cylindrical and eccentric rollers and with self-tensioning helical springs (Figure 1).

Figure 1. Overrunning clutches: (a) ratchet clutch; (b) jaw clutch; (c) friction clutch with cylindrical rollers; (d) friction clutch with self tensioning helical spring; (1) element transmitting rotary motion and torque in the direction indicated by the arrow; (2) element to which rotary motion and torque are transmitted

Overrunning clutches are used to prevent a reverse transmission of motion in a kinematic loop, such as motion from the driving wheel of a bicycle to the pedals. They are used to convert a rocking motion to a rotary motion, for instance, in the pulse type of continuously variable transmissions, or to impart to a slowly rotating shaft a faster rotation in the same direction, as, for example, in mechanisms for high-speed shifting in metal-cutting machines. Other applications include winding mechanisms and arresting devices, where reverse shaft rotation must be prevented.

References in periodicals archive ?
He remembers when Formsprag first sold overrunning clutches to Bell Helicopter for the Hueys they supplied to the Army throughout the Vietnam War.
The ST3Ox and the ST25 gear drive models use a transmission driven PTO protected by an overrunning clutch. The ST30 with the hydro transmission features a live PTO.
The Russelectric TriPower in particular consists of the replacement of the pony motor starting motor with an automatic overrunning clutch and engine.
Stieber is the world's market leader for overrunning clutches and backstops, with a world-wide service network which includes over 1,000 stocking distributors and technical centres.
Overrunning clutches would allow coupling or decoupling of the engines either automatically or at the pilot's discretion.
"Driven by one of the cart's ground wheels, this drive delivers a 1.6:1 speed ratio, is completely enclosed, and incorporates overrunning clutches and a series of links which adjust easily to provide the desired feed and seed rate.