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.
The comb plate is the piece between the stationary landing and the moving step. It slants down slightly so that the comb teeth fit between the cleats on the steps. The front edges of the comb teeth are below the surface of the cleats.
The truss is the mechanical structure that bridges the space between the lower and upper landings. The truss is basically a hollow box made up of two side sections joined together with transverse braces across the bottom and just below the top. The ends of the truss rest on concrete or steel supports.
The track system is built into the truss to guide the step chain, which pulls the steps through an endless loop. There are two tracks: one for the front of the step (called the step-wheel track) and one for the trailer wheel of the step (called the trailer-wheel track). The relative position of these tracks causes the steps to appear from under the comb plate to form a staircase, and disappear back into the truss.
The reversal track at the upper landing rolls the steps around the top and starts them back in the opposite direction. An overhead track ensures that the trailer wheels remain in place as the step chain is turned back on itself.
Checking before calling What to do if the elevator is out of order? In some cases, fast and simple verification could be enough to put the elevator into service operation.
- Check if there is anything stuck inside the door sill (screws, coins...).
- Check the main power.
- Check the Stop push button inside the car (if existing).
- Check the independent button, reservation button, fire button (if existing).
- Check if there is anything (chewing gum, paper...) in front of the photoelectric eye.