HOW ELEVATORS WORK
HOW ESCALATORS WORK
ELEVATOR SAFETY TIPS
ESCALATOR SAFETY TIPS
MACHINE-ROOM-LESS EVACUATION PROCEDURE
ELECTRIC ELEVATOR EVACUATION PROCEDURE
HYDRAULIC ELEVATOR EVACUATION PROCEDURE

In a geared or gearless traction system (used in mid-rise and high-rise installations, respectively), the elevator car is supported in a hoistway by several steel hoist ropes, usually two sheaves, and a counterweight. The weight of the car and counterweight provides sufficient traction between the sheaves and the hoist ropes so that the sheaves can grip the hoist ropes and move and hold the car without excessive slipping. The car and counterweights ride along vertical guide rails to keep them from swaying.

The machinery to drive the elevator is located in a machine room usually directly above the elevator hoistway. To feed electricity to the car and receive electrical signals from it, a multi-wire electrical cable connects the machine room to the car. The end attached to the car moves with it, so the cable is called the “traveling cable.”

A geared machine has a higher-speed motor, and the drive sheave is connected to the motor shaft through gears in a gear box, which reduce the rotational speed of the motor shaft to a lower drive-sheave speed. The gearless machine has a slow speed motor, and the drive sheave is connected directly to the motor shaft.

In a hydraulic system (used primarily in low-rise installations, where moderate car speed is acceptable), a car is connected to the top of a long piston that moves up and down in a cylinder. The car moves up when oil is pumped into the cylinder from a reservoir, raising the piston. The car is lowered when the oil returns to the reservoir.

The lifting action can be direct (piston connected to the car) or roped (piston attached to car via ropes). In both methods, the work done by the motor pump (kinetic energy) to lift the car to a higher elevation gives the car the ability to do work (potential energy). This energy transfer occurs each time the car is raised. When the car is lowered, the potential energy is used up, and the energy cycle is complete. The up and down motions of the elevator car are controlled by the hydraulic valve.