hoist(redirected from Ratchet lever hoist)
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mechanical device for hauling or lifting consisting essentially of a movable drum around which a cable is wound so that rotation of the drum produces a drawing force at the end of the cable.
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a cyclical or continuous-operation machine for lifting freight and passengers in special carrying devices that move along rigid vertical (sometimes inclined) guides or rails. A distinction is made among cable, chain, rack, screw, and plunger hoists, depending on the way in which the driving force is transmitted to the carriers.
A predominant position is occupied by cable hoists, in which the carrier is lifted on steel cables that pass around cable sheaves or are wound around the drums of hoisting winches. In hoists with cable sheaves, which transmit the tractive force by friction, the carrier (a cab, cage, skip, platform, trolley, or car) is balanced by another similar carrier or by a counterweight that also moves along guides. In drum hoists a counterweight reduces the load on the drive. When additional load-lifting equipment is used for balancing, the efficiency of the hoist is increased. Hoists usually have an electric drive, and sometimes a hydraulic drive.
The diversity of designs and types of hoisting machinery results from the broad sphere of application of such devices. Elevators, escalators, and occasionally paternosters have become commonplace in residential, public, administrative, and industrial buildings. Funiculars, or passenger cable hoists that operate cyclically, are used to lift passengers in cars along an inclined railway on mountains, steep banks, and other natural eminences.
Skip hoists are used to raise useful minerals and barren rock to the surface in mines, pits, and quarries, and also to charge blast furnaces. In underground mining, cage hoists are installed to raise and lower personnel, equipment, and materials. Buildings are erected with the aid of pillar, cable, and shaft construction hoists; the pressure (delivery) pipes for high-mountain hydroelectric power plants are assembled by special trolley hoists. Various types of hoists are used in maintenance plants (for example, automobile lifts) and for the servicing and minor repair of buildings, gas holders, and other high structures (for example, cherry pickers). (The Russian term, pod”emnik, is also applied to the equipment for lifting ships traveling through canals having different water levels.)
REFERENCESKifer, L. G., and I. I. Abramovich. Gruzopod”emnye mashiny, vol. 2. Moscow, 1949.
Pod”emniki. Moscow, 1957.
Fedorova, Z. M., and I. F. Lukin. Pod”emniki: Konstruirovanie i raschet elementovpod”emnika. Kharkov, 1971.
N. A. LOBOV