ratchet

/rach"it/, n.
1. a toothed bar with which a pawl engages.
2. (not in technical use) a pawl or the like used with a ratchet or ratchet wheel.
3. a mechanism consisting of such a bar or wheel with the pawl.
5. a steady progression up or down: the upward ratchet of oil prices.
v.t., v.i.
6. to move by degrees (often fol. by up or down): to ratchet prices up; Interest rates have been ratcheting downward.
[1650-60; alter. of F rochet; MF rocquet a blunt lance-head < Gmc]

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Mechanical device that transmits intermittent motion or permits a shaft to rotate in one direction but not in the opposite one.

Reversible ratchets are used on socket wrench handles and are convenient for tightening or loosening bolts in positions where a complete revolution of a wrench handle is impossible. They are used in mechanical jacks to lock the jack rod after each successive lift.

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▪ mechanical device
 mechanical device that transmits intermittent rotary motion or permits a shaft to rotate in one direction but not in the opposite one. In the Figure—> the arm A and the ratchet wheel B are both pivoted at O. The stem of the pawl P can slide in the arm and is kept in its lowest position by the spring S. If the arm oscillates through the angle α (alpha), the pawl rotates the wheel intermittently in a counterclockwise direction; if the arm rotates clockwise, the sloping side of the pawl rides over the teeth and has no turning effect on the wheel. If the pawl is rotated half a turn so that its sloping side is on the left, oscillation of the arm rotates the wheel in a clockwise direction only. Reversing ratchets of the type described are used on socket wrench handles and are convenient for tightening or loosening bolts in positions where a complete revolution of a wrench handle is impossible. They are also used to obtain an intermittent feeding motion (workpiece movement) on machine-tool worktables; the ratchet wheel is attached to the screw that moves the table, and the arm is driven by a crank, the throw of which can be varied to change α.

 On mechanisms that receive their power from a wound spring, such as watches and clocks, ratchets such as that shown at C in the Figure—> are used. The pawl Q pivots on a fixed axis and rides over the pointed teeth when the spring is being wound but prevents rotation of the wheel in a clockwise direction.

      Although ratchets with pawls and toothed wheels are the most common, other types are used. In one such type, an oscillating member works through a one-way clutch to rotate a wheel intermittently.

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Universalium. 2010.

Synonyms:

Look at other dictionaries:

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  • ratchet — ► NOUN ▪ a device consisting of a bar or wheel with a set of angled teeth in which a pawl, cog, or tooth engages, allowing motion in one direction only. ► VERB (ratcheted, ratcheting) 1) operate by means of a ratchet. 2) (ratchet up/down) cause… …   English terms dictionary

  • ratchet — [rach′it] n. [earlier rochet < Fr, lance head, distaff < It rocchetto, bobbin, spindle, dim. of rocca, distaff < Goth * rukka, akin to OHG roccho, spindle, distaff < IE base * ruk(k) , spun yarn] 1. a toothed wheel (in full ratchet… …   English World dictionary

  • Ratchet — A ratchet may refer to: * Ratchet (device), a mechanical device for controlling rotational motion * Socket wrench, a tool that makes use of the above mechanical device * A part of some forceps, to fix the blades of the forceps, such as in… …   Wikipedia

  • ratchet — ▪ I. ratchet ratch‧et 1 [ˈrætʆt] noun [countable] FINANCE an arrangement in which the value of someone s share in a company depends on how well the company performs. This is often done where company managers own a share in the company: • A… …   Financial and business terms

  • ratchet — [[t]ræ̱tʃɪt[/t]] ratchets, ratcheting, ratcheted 1) N COUNT In a tool or machine, a ratchet is a wheel or bar with sloping teeth, which can move only in one direction, because a piece of metal stops the teeth from moving backwards. The chair has… …   English dictionary

  • ratchet — {{11}}ratchet (n.) 1650s, from Fr. rochet bobbin, spindle, from It. rocchetto spool, ratchet, dim. of rocca distaff, possibly from a Germanic source (Cf. O.H.G. rocko distaff, O.N. rokkr), from P.Gmc. *rukka , from PIE root *rug to spin. Cf.… …   Etymology dictionary

  • ratchet — ratch|et1 [ˈrætʃıt] n [Date: 1600 1700; : French; Origin: rochet, from Old French rocquet point of a spear ] a machine part consisting of a wheel or bar with teeth on it, which allows movement in only one direction ratchet 2 ratchet2 v ratchet up …   Dictionary of contemporary English

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