Elevator

A modern elevator has buttons to allow passengers to select the desired floor.

An elevator is a transportation device used to move goods or people vertically. In British English and other Commonwealth Englishes, elevators are known more commonly as lifts, although the word elevator is familiar from American movies and television shows.

See also Elevator (disambiguation) for other meanings of the word.

History

Elevator in a hospital

Elevators began as simple rope or chain hoists. An elevator is a hoist contained within an elevator well. An elevator consists of a cab (also "cage" or "car") or platform, the ropes or cables required to raise and lower it using pulleys, and machinery to move the rope. Later refinements included steam power and hydraulic power.

In 1853, Elisha Otis introduced the safety elevator, which prevented the fall of the cab if the cable broke, and on March 23, 1857 his first elevator was installed at 488 Broadway in New York City. The first elevator shaft preceded the first elevator by four years. Construction for Peter Cooper's Cooper Union building in New York began in 1853. An elevator shaft was included in the design for Cooper Union, because Cooper was utterly confident a safe passenger elevator would soon be invented: the shaft however was circular because Cooper felt it was the most efficient design. Later Otis designed a special elevator for the school. Today the Otis Elevator Company, now a subsidiary of United Technologies Corporation, is the world's largest manufacturer of vertical transportation systems.

The first electric elevator was built by Werner von Siemens in 1880. The safety and speed of electric elevators were significantly enhanced by Frank Sprague.

The development of elevators allowed easy access to the upper storeys of tall buildings and skyscrapers.

In some locations, the shaft and parts of the cab are made of transparent material. This allows riders to see outside the cab as they travel on an elevator. It allows people to watch the elevator cab as it travels between floors. Other locations have elevators that are located along the outside wall of buildings. This allows riders to see the outdoor environment as the cab runs along the side of the buildings.

Today, most elevators are computer-controlled. This allows the elevator system to place cabs where they are most needed, and allow for the smooth running of the system. It also permits greater access control to various floors of a building after hours and on weekends. Methods of access control include card readers, keys, and typing access codes into the control panel of the elevator.

Elevators are usually installed in a building during construction. Further renovations upgrade the cab instead of replacing it, but in a few cases the entire cab is replaced as well.

Types of elevators

In general, there are three types of elevators:

Traction type

Cable/traction Elevators - Operate using a counterweight that allows the elevator to easily be pulled up or down using cables attached to the roof of the elevator car.

Hydraulic type

Hydraulic Elevators - These are quite common for low and medium rise buildings. They use a hydraulically powered plunger to push the elevator upwards. On some, the hydraulic piston (plunger) consists of telescoping concentric tubes, allowing a shallow tube to contain the mechanism below the lowest floor. On others, the piston requires a deeper hole below the bottom landing, usually with a PVC casing for protection.

Paternoster

A special type of elevator is the paternoster, a constantly moving chain of boxes. A similar concept moves only a small platform, which the rider mounts while using a handhold and was once seen in multi-story industrial plants.

The Elevator Algorithm

The simple algorithm by which a single elevator can decide where to stop is:

Continue travelling in the same direction while there are remaining requests in that same direction.
If there are no further requests in that direction, then stop and become idle, or change direction if there are requests in the opposite direction.

The elevator algorithm has found an application in computer operating systems as an algorithm for scheduling hard disk requests.

Modern elevators use more complex heuristic algorithms to decide which request to service next.

Special operating modes

In areas with large populations of observant Jews, one may find a "Sabbath Elevator". In this mode, an elevator will stop automatically at every floor, allowing people to step on and off without having to press any buttons. Regenerative braking is also disabled if it is normally used, shunting energy collected from downward travel, and thus the gravitational potential energy of passengers, into a resistor network. This prevents violation of the Sabbath prohibition against doing useful work.

Floor numbering

In general, elevator call buttons are numbered one-by-one to indicate the floors or landings that they cause the car to move to. However, there are some conventions to be aware of. The most important are:

The difference between US and Commonwealth floor numbering.
There may be no designated "13th floor"; note that floor 14 is technically the thirteenth floor. East Asian countries may lack a '4th floor' for similar reasons.
The top level may be PH for Penthouse or, where applicable, R for Roof or O for Observation Deck.
The ground floor may be G for Ground, M for Main, L for Lobby, or 1. As an aid to the visually impaired, there is often an embossed * beside the button.
Below the ground floor is commonly B for Basement or P for Parking, sometimes LL for Lower Level.
Below the basement may be SB for Sub-Basement. Numbered levels below ground, such as B1 or P1, are also common; the numbers may run either way, but B2 is usually below B1.
Some buildings are just idiosyncratic; at one hotel in Toronto, the first six floors are labeled A, M, MM, C, H, and 1 (for Arcade, Main, Main Mezzanine, Convention, Health Club, and 1st floor).
Floor designations sometimes vary between different banks of elevators in a building (due to its layout), or even between buttons and indicators in the same elevator (due to careless installation).
Some elevators, especially in buildings with complex floor plans, have both front and rear doors that can open at the same floor; a second button with R appended to the floor abbreviation (e.g. GR or 2R) then requests a stop there with the rear door opening.
In Europe, floors below ground level may be simply labelled with negative numbers, i.e. -1 represents the first basement below ground, then -2, and so on.

The convention that higher floors have their buttons placed higher may help resolve ambiguities, but many elevators have enough buttons that they are grouped in rows of two or even three.

In order to comply with handicapped persons requirements, such as the American Disabilities Act (ADA), a secondary button panel may be installed which is located at a height that can be reached by a person in a wheelchair. In this case the buttons may be arranged in a horizontal fashion.

On the elevator's position indicator, you may see the letters EZ. This is used to represent an Express Zone which is a long section of travel where the elevator makes no stops. Typically these are found in elevators that serve the upper reaches of tall buildings, thus bypassing several of the lower floors on the way.

Dumb waiter

A small box elevator designed for the carriage of goods only is called a dumb waiter (or dumbwaiter). Often they are used in restaurants to bring food from the kitchen to the dining area, hence the name.

Material handling belts

A different kind of elevator is used to transport material. It generally consists of an inclined plane on which a conveyor belt runs. The conveyor often includes partitions to prevent the material from sliding backwards. These elevators are often used in industrial and agricultural applications.

When such mechanisms (or spiral screws or pneumatic transport) are used to elevate grain for storage in large vertical silos, the entire structure is called a grain elevator,

Elevator in the new city hall, Hannover

Sketch of the elevator at the new city hall, Hannover, showing the cabin both at the bottom and the top

View up the shaft of the elevator at the new city hall, Hannover

The elevator in the new city hall in Hannover is a technical rarity, and unique in Europe, as the elevator starts straight up, but then changes its angle by 15 degrees to follow the contour of the dome of the new city hall in Hannover. The cabin therefore tilts 15 degrees during the ride. The elevator travels a height of 43 meters. The new city hall was built in 1913. The elevator was destroyed in 1943 and rebuilt in 1954.