pulley

pulley
—pulleyless, adj.
/pool"ee/, n., pl. pulleys.
1. a wheel, with a grooved rim for carrying a line, that turns in a frame or block and serves to change the direction of or to transmit force, as when one end of the line is pulled to raise a weight at the other end: one of the simple machines.
2. a combination of such wheels in a block, or of such wheels or blocks in a tackle, to increase the force applied.
3. a wheel driven by or driving a belt or the like, used to deliver force to a machine, another belt, etc., at a certain speed and torque.
[1275-1325; ME poley, puly < MF polie MGk *polídion little pivot, equiv. to pól(os) POLE2 + -idion dim. suffix]

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In mechanics, a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim.

Pulleys are used singly or in combination to transmit energy and motion. In belt drives, pulleys are attached to shafts at their axes, and power is transmitted between the shafts by means of endless belts running over the pulleys. One or more independently rotating pulleys can be used to gain mechanical advantage, especially for lifting weights. The shafts around which the pulleys turn may attach them to frames or blocks, and a combination of pulleys, blocks, and rope is called a block and tackle. The pulley is considered one of the five simple machines.

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      in mechanics, a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. Pulleys are used singly or in combination to transmit energy and motion. Pulleys with grooved rims are called sheaves. In belt drive, pulleys are affixed to shafts at their axes, and power is transmitted between the shafts by means of endless (ends joined together) belts running over the pulleys. One or more independently rotating pulleys can be used to gain mechanical advantage, especially for lifting weights. The shafts about which the pulleys turn may affix them to frames or blocks, and a combination of pulleys, blocks, and rope or other flexible material is referred to as a block and tackle. Archimedes (3rd century BC) is reported to have used compound pulleys to pull a ship onto dry land. Together with the lever, wedge, wheel and axle, and screw, the pulley is considered one of the five simple machines. See also belt drive; block and tackle.

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Universalium. 2010.

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