Lifts. Under this term are included numerous contrivances for raising weights. Such machines have various names: hoists—usually hand-worked and for lifting light goods in warehouses; elevators—chiefly used for taking passengers or their luggage, &c. to the upper floors of large hotels, business premises, &c.—and so on. There are also special Elevators (q.v.) for grain. Lifts are often on a large scale, such, for example, as occur on certain canals in place of locks at changes of level—where practically a section of the canal is alternately raised and lowered; and again on underground railways to bring passengers to the surface level (there are notable examples at the Mersey Tunnel).
Lifts consist primarily of a cage for the people or goods raised, a shaft in which this cage works, and the necessary machinery for raising or lowering the cage. There are two chief methods in use for this latter purpose; in the one the cage has attached to its top ropes or chains which are wound up on a barrel or drum; in the other the cage is lifted by hydraulic pressure applied directly, or through the intervention of chains and ropes.
The ropes in use are, for light work, hempen; for heavy work, steel-wire ropes or chains. It is usual to counterbalance the dead-weight—i.e. the weight of the cage; in this case the rope attached to the top of the cage is generally not the lifting rope. The cage-robe is simply carried up to the top of the shaft, over a pulley there, and has suspended at its other end the counterbalance; the working rope operates the shaft of this pulley, and so lifts the cage. This saves a good deal of waste work, since the load lifted each time is only the net load, passengers and goods.
Hoists all require to be provided with some automatic clutch arrangements in case the chains or ropes break, water leaks off, the rams or pistons fracture, &c., otherwise the cages would run down with destructive velocity. These clutches are usually some form of catch kept clear of the side guides in ordinary working, but set in action by compressed springs when an accident happens. They should always be regularly tested to see if they are in working order.