An elevator or lift (in British English) is a vertical transport vehicle that efficiently moves people or goods between floors of a building. They are generally powered by electric motors that either drive traction cables and counterweight systems, or pump hydraulic fluid to raise a cylindrical piston.

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A set of lifts in the lower level of a London Underground station in the United Kingdom. The arrows indicate each lift’s position and direction of travel. The lift on the right shows its doors on either side of the car to serve different floors.
This elevator to the Alexanderplatz U-Bahn station in Berlin is built with glass walls, exposing the inner workings.
Observation elevators at the 240 Sparks shopping center
An elevator in National University of Singapore
A wire-cage lift circa 1895

Languages other than English may have loanwords based on either elevator (e.g., Japanese) or lift (e.g., Cantonese).

Because of wheelchair access laws, elevators are often a legal requirement in new multi-story buildings, especially where wheelchair ramps would be impractical.

Design

Traction elevators.

Lifts began as simple rope or chain hoists. A lift is essentially a platform that is either pulled or pushed up by a mechanical means. A modern day lift consists of a cab (also called a “cage” or “car”) mounted on a platform within an enclosed space called a shaft or sometimes a “hoistway”. In the past, lift drive mechanisms were powered by steam and water hydraulic pistons. In a “traction” lift, 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 with a counterweight. Sometimes two lifts always move synchronously in opposite directions, and they are each other’s counterweight.

The friction between the ropes and the pulley furnishes the traction which gives this type of lift its name.
For more details on this topic, see #Hydraulic elevators.

Hydraulic lift use the principles of hydraulics (in the sense of hydraulic power) 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 cars. Recent innovations include permanent earth magnet motors, machine room-less rail mounted gearless machines, and microprocessor controls.

Which technology is used in new installations depends on a variety of factors. Hydraulic lifts are cheaper, but installing cylinders greater than a certain length becomes impractical for very high lift hoistways. For buildings of much over seven stories, traction lift must be employed instead. Hydraulic lifts are usually slower than traction lifts.

Lifts 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

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 configuration (potentially allowing wider entryways within limited space), the doors run on independent tracks so that while open, they are tucked behind one another, and while closed, they form cascading layers on one side.
Machine Room-less

All elevators, whether traction or hydraulic, require a machine room to store large electric motors (or hydraulic pumps) and a controller cabinet. This room is located above the hoistway (or below, for hydraulic elevators) and may contain machinery for a single or a group of elevators. Modern day traction motors boasting gearless and permanent magnet drive more compact and efficient; electronic microprocessors have replaced the mechanical relays. As a result, traction elevators can be built without a dedicated room above the shaft, saving valuable space in building planning.

The new lift design presents a departure from the traditional, looped over-the-top traction rope routing of traction elevators. The ends of the cables are fixed to the supporting structure, and the length of the cable are connected to the car and counterweight by means of a force-multiplying, energy saving compound pulley system. Machine Room-less elevators have become a welcome alternative to the older hydraulic elevator for low to medium rise buildings.
History
Elisha Otis’ elevator patent drawing, 15 January 1861.

The first reference to an elevator is in the works of the Roman architect Vitruvius, who reported that Archimedes built his first elevator, probably in 236 B.C. In some literary sources of later historical periods, elevators were mentioned as cabs on a hemp rope and powered by hand or by animals. It is supposed that elevators of this type were installed in the Sinai monastery of Egypt. In the 17th century the prototypes of elevators were located in the palace buildings of England and France.

In 1000, the Book of Secrets by Arab inventor Ibn Khalaf al-Muradi in Islamic Spain described the use of an elevator-like lifting device, in order to raise a large battering ram to destroy a fortress.

In 1793 Ivan Kulibin created an elevator with the screw lifting mechanism for the Winter Palace of Saint Petersburg. In 1816 an elevator was established in the main building of sub Moscow village called Arkhangelskoye. In 1823, an “ascending room” made its debut in London.

In the middle 1800’s, there were many types of crude elevators that carried freight. Most of them ran hydraulically. The first hydraulic elevators used a plunger below the car to raise or lower the elevator. A pump applied water pressure to a plunger, or steel column, inside a vertical cylinder. Increasing the pressure allowed the elevator to descend. The elevator also used a system of counter-balancing so that the plunger did not have to lift the entire weight of the elevator and its load. The plunger, however, was not practical for tall buildings, because it required a pit as deep below the building as the building was tall. Later a rope-geared elevator with multiple pulleys was developed.

Henry Waterman of New York is credited with inventing the “standing rope control” for an elevator in 1850.

In 1852, Elisha Otis introduced the safety elevator, which prevented the fall of the cab if the cable broke. The design of the Otis safety elevator is somewhat similar to one type still used today. A governor device engages knurled roller(s), locking the elevator to its guides should the elevator descend at excessive speed. He demonstrated it at the New York exposition in the Crystal Palace in 1854.

On March 23, 1857 the first Otis passenger 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 confident that a safe passenger elevator would soon be invented. The shaft was cylindrical 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 transport 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 was led by the need for movement of raw materials including coal and lumber from hillsides. The technology developed by these industries and the introduction of steel beam construction worked together to provide the passenger and freight elevators in use today.

In 1874, J.W. Meaker patented a method which permitted elevator doors to open and close safely. U.S. Patent 147,853

In 1882, when hydraulic power was a well established technology, a company later named the London Hydraulic Power Company was formed. It constructed a network of high pressure mains on both sides of the Thames which, ultimately, extended to 184 miles and powered some 8,000 machines, predominantly lifts (elevators) and cranes.

In 1929, Clarence Conrad Crispen, with Inclinator Company of America, created the first residential elevator. Crispen also invented the first inclined stairlift.http://inclinator.com/about-inclinator.asp
Elevator safety
Pneumatic Vacuum Elevators

Pneumatic or “Vacuum” elevators operate without cables and can be installed more easily and quickly than their alternatives since their housing comprises prefabricated sections which are considerably narrower than conventional lift shafts. These sections are often transparent and afford the passenger a near 360° view. These elevators are strictly residential elevators and do not meet commercial compliance standards. This is the newest technology available for the residential market; the benefits are numerous. For example, the vacuum elevator does not require you to dig a pit, and can be simply placed on an existing finished floor, including carpet. There is no need to construct a hoistway because the cylinder acts as it’s own hoistway. Installation is usually 1-2 days, and there is very little pre-installation cost and prepratory work required. These features typically suggests that the price will be less than a traditional home elevator. Currently the pneumatic vacuum elevator is avaiable in 30″, 37″ and 52″ diameters, and they are available in three colors: navy grey, light grey and white. The structure is comprised of aluminum columns, steel doors, and tinted polycarbonate panels. Also, it requires the least amount of maintenance of all elevators. For more comprehensive information on how they work, videos and photos of these elevators, go to: “www.daytonaelevator.com”
Cable-borne elevators

Statistically speaking, elevators are extremely safe. Their safety record is unsurpassed by any other vehicle system. In 1998, it was estimated that approximately eight 100-millionths of one percent (10,000 in 120 billion) of elevator rides resulted in an anomaly, and the vast majority of these were minor things such as the doors failing to open. For all practical purposes, there are no cases of elevators simply free-falling and killing the passengers inside; of the 20 to 30 elevator-related deaths each year, most of them are maintenance-related – for example, technicians leaning too far into the shaft or getting caught between moving parts, and most of the rest are attributed to easily avoidable accidents, such as people stepping blindly through doors that open into empty shafts or being strangled by scarves caught in the doors. In fact, prior to the September 11th terrorist attacks, the only known free-fall incident in a modern cable-borne elevator happened in 1945 when a B-25 bomber struck the Empire State Building in fog, severing the cables of an elevator cab, which fell from the 75th floor all the way to the bottom of the building, seriously injuring (though not killing) the sole occupant – the female elevator operator. While it is possible (though extraordinarily unlikely) for an elevator’s cable to snap, all elevators in the modern era have been fitted with several safety devices which prevent the elevator from simply free-falling and crashing. An elevator cab is typically borne by six or eight hoist cables, each of which is capable on its own of supporting the full load of the elevator plus twenty-five per cent more weight. In addition, there is a device which detects whether the elevator is descending faster than its maximum designed speed; if this happens, the device causes bronze brake shoes to clamp down along the vertical rails in the shaft, stopping the elevator quickly, but not so abruptly as to cause injury. In addition, a hydraulic buffer is installed at the bottom of the shaft to cushion any impact somewhat.
Hydraulic elevators

Past problems with early hydraulic elevators meant those built prior to a code change in 1972 were subject to possible catastrophic failure. The code had previously required only single-bottom hydraulic cylinders. In the event of a cylinder breach, an uncontrolled fall of the elevator might result. Because it is impossible to verify the system completely without a pressurized casing (as described below), it is necessary to remove the piston to inspect it. The cost of removing the piston is such that it makes no economic sense to re-install the old cylinder; therefore it is necessary to replace the cylinder and install a new piston. Another solution to protect against a cylinder blowout is to install a “life jacket.” This is a device which, in the event of an excessive downward speed, clamps onto the cylinder and stops the car. This device is also known as a Rupture Valve in some parts of the world.

In addition to the safety concerns for older hydraulic elevators, there is risk of leaking hydraulic oil into the aquifer and causing potential environmental contamination. This has led to the introduction of PVC liners (casings) around hydraulic cylinders which can be monitored for integrity.

In the past decade, recent innovations in inverted hydraulic jacks have eliminated the costly process of drilling the ground to install a borehole jack. This also eliminates the threat of corrosion to the system and increases safety.
Mine-shaft elevators

Safety testing of mine shaft elevator cables is routinely undertaken. The method involves destructive testing of a segment of the cable. The ends of the segment are frayed, then set in conical zinc molds. Each end of the segment is then secured in a large, hydraulic stretching machine. The segment is then placed under increasing load to the point of failure. Data about elasticity, load, and other factors is compiled and a report is produced. The report is then analyzed to determine whether or not the entire cable is safe to use.