Lifts

Lifts may be worked by steam, gas, manual, or hydraulic power. A cage is arranged to be movable up or down a rectangular shaft, and in the case of non-hydraulic lifts is suspended by manilla or steel ropes or chains, which are passed over a grooved pulley at the top of the shaft, and support a weight which approximately balances the cage. The pulley may be rotated to raise the cage by means of belt or spur gearing from a countershaft driven by an engine, suitable mechanism being provided for reversing the motion for lowering or putting on the brake when the cage is stationary. In manual lifts a second rope, connected to the first by spur gearing, can be rotated by a long rope passed round it, by pulling which the gear can be driven in either direction. In some hydraulic lifts a long rod which supports the cage acts as the plunger of a eylinder sunk in the ground; water under pressure being admitted through a valve, the plunger is forced upwards, while a valve which allows the water to escape provides for the lowering of the cage. Owing to the difficulty of sinking the cylinder in a, pit, telescopic cylinders are sometimes used, or a short cylinder acts on a chain supporting the cage through pulleys so arranged that a small motion of the ram produces a relatively large motion of the cage. In all power lifts a rope which controls the gearing or valves hangs down inside the shaft, and is accessible from the cage.