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Encyclopedia > Ratchet (device)
A ratchet lever hoist.
A ratchet lever hoist.

In mechanical engineering a ratchet is a device used to restrict motion in one direction. This sort of behaviour is useful in many areas, such as in turnstile, spanners (where rotation in confined surfaces can be achieved easily), winders, jacks, hoists and others. Image File history File linksMetadata Download high-resolution version (720x1400, 91 KB) Photo of a ratchet lever hoist (a. ... Image File history File linksMetadata Download high-resolution version (720x1400, 91 KB) Photo of a ratchet lever hoist (a. ... Mechanical engineering is an engineering discipline that involves the application of principles of physics for analysis, design, manufacturing, and maintenance of mechanical systems. ... Turnstiles at Alewife subway station in Cambridge, Massachusetts A turnstile, also called a baffle gate, is a form of gate which allows one person to pass at a time. ... A wrench or spanner is a tool used to turn bolts, nuts or other hard-to-turn items. ... Winder is a location in Georgia. ... Jackscrews are integral to one of the simplest kinds of car jacks still used. ... Builders hoist, with small petrol engine A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. ...


Rack and pawl

Ratchets work generally by having a form of gearwheel or rack (as in Rack_and_pinion) that, instead of having regular teeth, have teeth set off at an angle, and a stiff, thin protrusion called the pawl [1] (a) or the click that rests against the gearwheel (b). When the gearwheel is rotated in one direction, the protrusion raises and clicks back in place. Because of the shape of the gearwheel it is difficult to push the protrusion back and over the tooth of the gear. Alternatively, this gearwheel can be set in a molding shaped to admit rotation of this gearwheel in one direction only. If the gearwheel is rotated backwards the molding and the teeth will clash. Image File history File links Sperrklinke_Schema. ... Spur gears found on a piece of farm equipment A gear is a wheel with teeth around its circumference, the purpose of the teeth being to mesh with similar teeth on another mechanical device -- possibly another gear wheel -- so that force can be transmitted between the two devices in a... Rack and pinion animation A rack and pinion is a pair of gears which convert rotational motion into linear motion. ... Pawl was a Formula One constructor (Indy 500 only) in 1951, 1954 and 1955. ... Molding (US) or moulding (UK) can be: moulding or molding, a decorative feature used in interior design and architecture molding or moulding, a process used in manufacturing This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ...


See also

Freewheel mechanism In mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft. ...

External links

  • An animated display of ratchet mechanism

 
 

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