Some people argue that home elevators began as simple rope or chain hoists. As a matter of fact, an elevator is essentially a platform that is either pulled or pushed up by a mechanical means. A modern-day elevator consists of a cab (also called a “cage”, “carriage” or “car”) mounted on a platform within an enclosed space called a shaft or sometimes a “hoistway”.
In the past, elevator drive mechanisms were powered by steam and water hydraulic pistons or by hand. In a “traction” elevator, cars are pulled up by means of rolling steel ropes over a deeply grooved pulley, commonly called a sheave in the industry. The weight of the car is balanced by a counterweight. Sometimes two elevators are built so that their cars can move synchronously in opposite directions. The friction between the ropes and the pulley furnishes the traction which gives this type of elevator its name.
Hydraulic elevators use the principles of hydraulics to pressurize an above ground or in-ground piston to raise and lower the car. Roped hydraulics use a combination of both ropes and hydraulic power to raise and lower the cars. Recent innovations include permanent magnet motors, machine room-less rail mounted gearless machines, and microprocessor controls.
The technology used in new installations depends on a variety of factors. Hydraulic elevators are cheaper, but installing cylinders greater than a certain length becomes impractical for very high lift hoistways. Therefore, for buildings of over seven floors, traction elevators must be employed instead. Hydraulic elevators are usually slower than traction elevators.
Elevators are a candidate for mass customization. There are economies to be made from mass production of the components, but each building comes with its own requirements like different number of floors, dimensions of the well and usage patterns.
Elevator doors protect riders from falling into the shaft. The most common configuration is to have two panels that meet in the middle, and slide open laterally. In a cascading telescopic configuration (potentially allowing wider entryways within limited space), the doors roll on independent tracks so that while open, they are tucked behind one another, and while closed, they form cascading layers on one side. This can be configured so that two sets of such cascading doors operate like the center opening doors described above, allowing for a very wide elevator cab. In less expensive installations, the elevator can also use one large “slab” door. Also, some buildings have elevators with the single door on the shaft way, and double cascading doors on the cab.