elevator (of a building)


An elevator, also called a lift (UK), is a machine for raising and lowering passengers and freight from one level to another inside or outside buildings. Early elevators were driven by steam or hydraulic power. The first elevator was installed (1856) in a New York store by Elisha Otis, who had invented a safety system that incorporated rachets along the elevator shaft to ensure the body of the elevator could not drop accidentally. In 1889 the first electric elevator was installed in a New York building.


Hydraulic elevator
An hydraulic elevator of the nineteenth century uses pulleys. A pump (1 )pressurizes water to move the plunger (2). This movement is transmitted to the lower pair of pulleys (3) to raise or lower the elevator cage (4). In this way, the relatively small movement of the plunger is made to produce a large movement of the cage. The height and speed of the height are controlled from inside it by ropes (5); these are connected to the water pump.