Elevator

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.
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

An elevator (or lift) is a vertical transport equipment that efficiently moves people or goods between floors (levels, decks) of a building, vessel or other structure. Elevators are generally powered by electric motors that either drive traction cables and counterweight systems, or pump hydraulic fluid to raise a cylindrical piston.

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

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

Contents

Design

Some argue that lifts began as simple rope or chain hoists (see Traction elevators below). 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.

Hydraulic lifts 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 (see Hydraulic elevators below). Roped hydraulics use a combination of both ropes and hydraulic power to raise and lower 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 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 lifts 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. 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: a single panel door the width of the doorway that opens to the left or right laterally.

Machine room-less

General

All elevators, whether traction or hydraulic, have required 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.

Machine room-less elevators are designed so that most of its components fit within the shaft containing the elevator car; and a small cabinet houses the elevator computer. The traction rope is configured for force multiplication in a complex pulley system. In this configuration, the traction motor moves more rope per distance traveled, but works half as hard due to force multiplication factors of the pulley system.

This new design was first developed by KONE in 1996.

Benefits

Facts

---national and local building codes did not address elevators without machine rooms

Elevator modernization

Most elevators are built to provide 15 to 25 years of service, as long as service intervals specified by the manufacturer are followed. As the elevator ages and certain components become increasingly difficult to replace, a complete overhaul of the elevator may be suggested to the building owners.

History

Elevator design by the German engineer Konrad Kyeser (1405)

The first reference to an elevator is in the works of the Roman architect Vitruvius, who reported that Archimedes (c. 287 BC – c. 212 BC) built his first elevator probably in 236. 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 1000, the Book of Secrets by 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.[1] In the 17th century the prototypes of elevators were located in the palace buildings of England and France.

The ancient and medieval elevators used the drive system based on hoist. The invention of another system. based on the screw drive, was perhaps the most important step in elevator technology since ancient times, which finally led to the creation of modern passenger elevators. The first screw drive elevator was built by Ivan Kulibin and installed in Winter Palace in 1793, while several years later another Kulibin's elevator was installed in Arkhangelskoye near Moscow. In 1823, an "ascending room" made its debut in London.[2]

Elisha Otis' elevator patent drawing, 15 January 1861.

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.[3]

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.[3]

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.[4] The shaft was cylindrical because Cooper felt it was the most efficient design.[5] 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.[6] 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.[7]

In 1929, Clarence Conrad Crispen, with Inclinator Company of America, created the first residential elevator. Crispen also invented the first inclined stairlift.[8]

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.

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 (1 in 12 million) 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,[9] 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.[9] 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.[10] However, there was an incident in 2007 at a Seattle children's hospital, where a ThyssenKrupp ISIS machine room-less elevator free-fell until the safety brakes were engaged. This was due to a flaw in the design where the cables were connected at one common point, and the kevlar ropes had a tendency to overheat and cause slipping (or, in this case, a free-fall). 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 percent 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 copper brake shoes to clamp down along the vertical rails in the shaft, stopping the elevator quickly, but not so abruptly as to cause injury. This device is called the governor, and was invented by Elisha Graves Otis.[10] In addition, a hydraulic buffer is installed at the bottom of the shaft to cushion any impact somewhat.[9]

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. A device known as a rupture valve is often attached to the hydraulic inlet/outlet of the piston and can be adjusted for a maximum flow rate. If a pipe or hose were to break (rupture), the flow rate of the rupture valve would increase and surpass a set limit and mechanically stop the outlet flow of hydraulic fluid, thus stopping the piston and the car in the down direction.

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 rails 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 rail is safe to use.

Uses of elevators

A residential elevator in Singapore.

Passenger service

A passenger elevator is designed to move people between a building's floors.

Passenger elevators capacity is related to the available floor space. Generally passenger elevators are available in capacities from 1,000 to 6,000 pounds (450–2,700 kg) in 500 lb (230 kg) increments. Generally passenger elevators in buildings eight floors or less are hydraulic or electric, which can reach speeds up to 200 ft/min (1.0 m/s) hydraulic and up to 500 ft/min electric. In buildings up to ten floors, electric and gearless elevators are likely to have speeds up to 500 ft/min (2.5 m/s), and above ten floors speeds begin at 500 ft/min (2.5 m/s) up to 2000 ft/min (10 m/s).

Sometimes passenger elevators are used as a city transport along with funiculars. For example, there is a 3-station underground public elevator in Yalta, Ukraine, which takes passengers from the top of a hill above the Black Sea on which hotels are perched, to a tunnel located on the beach below. At Casco Viejo station in the Bilbao Metro, the elevator that provides access to the station from a hilltop neighborhood doubles as city transportation: the station's ticket barriers are set up in such a way that passengers can pay to reach the elevator from the entrance in the lower city, or vice versa. See also the Elevators for urban transport section.

Types of passenger elevators

The former World Trade Center's twin towers used skylobbies, located on the 44th and 78th floors of each tower.

Passenger elevators may be specialized for the service they perform, including: hospital emergency (Code blue), front and rear entrances, double decker, and other uses. Cars may be ornate in their interior appearance, may have audio visual advertising, and may be provided with specialized recorded voice instructions.

An express elevator does not serve all floors. For example, it moves between the ground floor and a skylobby, or it moves from the ground floor or a skylobby to a range of floors, skipping floors in between. These are especially popular in eastern Asia.

Capacity

Residential elevators may be small enough to only accommodate one person while some are large enough for more than a dozen. Wheelchair, or platform lifts, a specialized type of elevator designed to move a wheelchair 6 ft (1.8 m) or less, often can accommodate just one person in a wheelchair at a time with a load of 1000 lb (450 kg).

Freight elevators

A specialized elevator from 1905 for lifting narrow gauge railroad cars between a railroad freight house and the Chicago Tunnel Company tracks below.

A freight elevator, or goods lift, is an elevator designed to carry goods, rather than passengers. Freight elevators are generally required to display a written notice in the car that the use by passengers is prohibited (though not necessarily illegal), though certain freight elevators allow dual use through the use of an inconspicuous riser. Freight elevators are typically larger and capable of carrying heavier loads than a passenger elevator, generally from 2,300 to 4,500 kg. Freight elevators may have manually operated doors, and often have rugged interior finishes to prevent damage while loading and unloading. Although hydraulic freight elevators exist, electric elevators are more energy efficient for the work of freight lifting.

Stage lifts

Stage and orchestra lifts are specialized lifts, typically powered by hydraulics, that are used to lift entire sections of a theater stage. For example, Radio City Music Hall has four such lifts, an "orchestra lift" that covers a large area of the stage, and three smaller lifts near the rear of the stage. In this case, the orchestra lift is powerful enough to raise an entire orchestra, or an entire cast of performers (including live elephants) up to stage level from below.

Local jurisdictions may govern their use, installation and testing; however they are often left out of local code enforcement provisions due to their infrequent installation.

Vehicle elevators

Vehicular elevators are used within buildings or areas with limited space (in lieu of ramps), typically to move cars into the parking garage or manufacturer's storage. Geared hydraulic chains (not unlike bicycle chains) generate lift for the platform and there are no counterweights. To accommodate building designs and improve accessibility, the platform may rotate so that the driver only has to drive forward. Most vehicle elevators have a weight capacity of 2 tons.

Rare examples of extra-heavy elevators for 20-ton lorries, and even for railcars (like one that was used at Dnipro Station of the Kiev Metro) also occur.

Boat elevators

In some smaller canals, boats and small ships can pass between different levels of a canal with a boat lift rather than through a canal lock.

Aircraft elevators

An F/A-18C on an aircraft elevator of the USS Kitty Hawk

On aircraft carriers, elevators carry aircraft between the flight deck and the hangar deck for operations or repairs. These elevators are designed for much greater capacity than other elevators, up to 200,000 pounds (90 tonnes) of aircraft and equipment. Smaller elevators lift munitions to the flight deck from magazines deep inside the ship.

On some passenger double-deck aircraft such as the Boeing 747, Lockheed L-1011 or other widebody aircraft, lifts transport flight attendants and food and beverage trolleys from lower deck galleys to upper passenger carrying decks.

Residential elevator

The residential elevator is often permitted to be of lower cost and complexity than full commercial elevators. They may have unique design characteristics suited for home furnishings, such as hinged wooden shaft-access doors rather than the typical metal sliding doors of commercial elevators. Construction may be less robust than in commercial designs with shorter maintenance periods, but safety systems such as locks on shaft access doors, fall arrestors, and emergency phones must still be present in the event of malfunction.

Limited Use / Limited Application

The limited-use, limited-application (LU/LA) elevator is a special purpose passenger elevator used infrequently, and which is exempt from many commercial regulations and accommodations. For example, a LU/LA is primarily meant to be handicapped accessible, and there might only be room for a single wheelchair and a standing passenger.

Dumbwaiter

Dumbwaiters are small freight elevators that are intended to carry food rather than passengers. They often link kitchens with rooms on other floors.

Paternoster

A paternoster in Berlin, Germany

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

Scissor lift

The scissor lift is yet another type of lift. As most of these lifts are self-contained, these lifts can be easily moved to where they are needed.

Rack-and-pinion lift

The rack-and-pinion lift is another type of lift. This lifts are simpler in construction, but noisy and slow. They are nonetheless the most used type of lift for buildings under construction (to move materials and tools up and down).

Material handling belts and belt elevators

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.

There have occasionally been lift belts for humans; these typically have steps about every seven feet along the length of the belt, which moves vertically, so that the passenger can stand on one step and hold on to the one above. These belts are sometimes used, for example, to carry the employees of parking garages, but are considered too dangerous for public use.

Types of hoist mechanisms

There are at least four means of moving an elevator:

Traction elevators

Geared traction machines are driven by AC or DC electric motors. Geared machines use worm gears to control mechanical movement of elevator cars by "rolling" steel hoist ropes over a drive sheave which is attached to a gearbox driven by a high speed motor. These machines are generally the best option for basement or overhead traction use for speeds up to 500 ft/min (2.5 m/s).

Gearless traction machines are low speed (low RPM), high torque electric motors powered either by AC or DC. In this case, the drive sheave is directly attached to the end of the motor. Gearless traction elevators can reach speeds of up to 2,000 ft/min (10 m/s), or even higher. A brake is mounted between the motor and drive sheave (or gearbox) to hold the elevator stationary at a floor. This brake is usually an external drum type and is actuated by spring force and held open electrically; a power failure will cause the brake to engage and prevent the elevator from falling (see inherent safety and safety engineering).

In each case, cables are attached to a hitch plate on top of the cab or may be "underslung" below a cab, and then looped over the drive sheave to a counterweight attached to the opposite end of the cables which reduces the amount of power needed to move the cab. The counterweight is located in the hoist-way and rides a separate railway system; as the car goes up, the counterweight goes down, and vice versa. This action is powered by the traction machine which is directed by the controller, typically a relay logic or computerized device that directs starting, acceleration, deceleration and stopping of the elevator cab. The weight of the counterweight is typically equal to the weight of the elevator cab plus 40-50% of the capacity of the elevator. The grooves in the drive sheave are specially designed to prevent the cables from slipping. "Traction" is provided to the ropes by the grip of the grooves in the sheave, thereby the name. As the ropes age and the traction grooves wear, some traction is lost and the ropes must be replaced and the sheave repaired or replaced. Sheave and rope wear may be significantly reduced by ensuring that all ropes have equal tension, thus sharing the load evenly. Rope tension equalisation may be achieved using a rope tension gauge, and is a simple way to extend the lifetime of the sheaves and ropes.

Elevators with more than 100' (30 m) of travel have a system called compensation. This is a separate set of cables or a chain attached to the bottom of the counterweight and the bottom of the elevator cab. This makes it easier to control the elevator, as it compensates for the differing weight of cable between the hoist and the cab. If the elevator cab is at the top of the hoist-way, there is a short length of hoist cable above the car and a long length of compensating cable below the car and vice versa for the counterweight. If the compensation system uses cables, there will be an additional sheave in the pit below the elevator, to guide the cables. If the compensation system uses chains, the chain is guided by a bar mounted between the counterweight railway lines.

Hydraulic elevators

Climbing elevator

A climbing elevator is a self-ascending elevator with its own propulsion. The propulsion can be done by an electric or a combustion engine. Climbing elevators are used in guyed masts or towers, in order to make easy access to parts of these constructions, such as flight safety lamps for maintenance. An example would be the Moonlight towers in Austin, Texas, where the elevator holds only one person and equipment for maintenance.

Elevator air conditioning

Concept

Elevator air conditioning is fast becoming a popular concept around the world. The primary reason for installing an elevator air conditioner is the comfort that it provides while traveling in the elevator. It stabilizes the condition of the air inside the lift car. Some elevator air conditioners can be used in countries with cold climates if a thermostat is used to reverse the refrigeration cycle to warm the lift car.

Health

One of the many benefits of installing an elevator air conditioner is the clean air that it provides.

Air is sucked from the elevator’s hoist way straight into the car using a motorized fan. The air sucked into the hoist way may be filled with dust mites, germs and bacteria.

With an elevator air conditioner, air provided is much cleaner because the cold air is the same air that comes from the car itself. Not only that, the cold air that is produced from the air conditioner also goes through a layer of filter. This filtration removes particles that are harmful to the human body.

A poorly maintained air-conditioning system may promote the growth and spread of microorganisms, but as long as the air conditioner is kept clean these health hazards can be avoided.

Energy

Elevator airflow diagram

Elevator lobby air conditioning constantly leaks into the elevator shaft due to elevator movements and elevator shaft ventilation requirements, resulting in wasted energy. By using elevator air conditioners, less energy is used because the air conditioner is able to cool the inside of the elevator more effectively.

Drawbacks

Heat generated from the cooling process is rejected into the hoistway. The elevator cab (or car) is not air-tight, and some of this heat will reenter the car and reduce the overall cooling effect, which may be less than ideal.

Condensation

Air conditioning poses a problem to elevators because of the condensation that occurs. The condensed water produced has to be disposed of; otherwise, it would create flooding in the elevator car and hoistway.

Ways to remove condensed water

There are at least four ways to remove condensed water from the air conditioner. However, each solution has its pros and cons.

Atomizing

Atomizing, also known as misting the condensed water, is another way to dispose of the condensed water. Spraying ultra fine water droplets on to the hot coils of the air conditioner would ensure the condensed water evaporates quickly.

Though this is one of the best methods to dispose of the condensed water, it is also one of the costliest because the nozzle that atomizes the water easily gets choked. The majority of the cost goes to maintaining the entire atomizing system.

Boiling

Disposing of condensed water works by firstly collecting the condensed water and then heating it to above boiling point. The condensed water would eventually be evaporated thereby disposing it.

Consumers are reluctant to employ this system because of the high rate of energy used just to dispose of this water.

Cascading

The cascading method works by flowing the condensed water directly onto the hot coils of the air conditioner. This would eventually evaporate the condensed water.

The downside of this technology is that the coils have to be at extremely high temperature for the condensed water to be evaporated. There is a chance that the water might not evaporate entirely and that would cause water to overflow on to the exterior of the car.

Drainage system

Drainage system works by creating a sump to collect the condensed water and using a pump to dispose it off through using a drainage system.

It is an efficient method, but it comes at a heavy price because the cost of building the sump, and maintaining the pump to make sure it operates, is very expensive. Moreover, the pipes used for drainage would look ugly on the exterior. This system also cannot be implemented on a built project.

Controlling elevators

General controls

Typical freight elevator control station
A modern internal control panel

A typical modern passenger elevator will have:

Some elevators may have one or more of the following:

Other controls, which are generally inaccessible to the public (either because they are key switches, or because they are kept behind a locked panel), include:

Controls in early elevators

Manual pushbutton elevator controls.
Otis 1920s controller, operational in NYC apartment building.

External controls

An external control panel

Elevators are typically controlled from the outside by up and down buttons at each stop. When pressed at a certain floor, the elevator arrives to pick up more passengers. If the particular elevator is currently serving traffic in a certain direction, it will only answer hall calls in the same direction unless there are no more calls beyond that floor.

In a group of two or more elevators, the call buttons may be linked to a central dispatch computer, such that they illuminate and cancel together. This is done to ensure that only one car is called at one time.

Key switches may be installed on the ground floor so that the elevator can be remotely switched on or off from the outside.

In sky lobby elevator systems, one would select the intended destination floor (in lieu of pressing "up") and be notified which elevator is to serve that request.

Floor numbering

Elevator buttons showing the missing 13th floor

The elevator algorithm

The elevator algorithm, a simple algorithm by which a single elevator can decide where to stop, is summarized as follows:

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. An introduction to these algorithms can be found in the "Elevator traffic handbook: theory and practice" given in the references below.

Destination Control System

Some skyscraper buildings feature a destination operating panel where a passenger would register their floor calls before entering the car. The system would let them know which car to wait for, instead of everyone boarding the next car. In this way, travel time is reduced as the elevator makes fewer stops for individual passengers, and the computer distributes adjacent stops to different cars in the bank.

It can also improve accessibility, as a mobility-impaired passenger can move to his or her designated car in advance.

Inside the elevator there is no call button to push, or the buttons are there but they cannot be pushed – they only indicate stopping floors.

The system was first pioneered by Schindler Elevator as the Miconic 10. Manufacturers of such systems claim that average traveling time can be reduced by up to 30%.[11]

There are some problems with the system, though, and it is subject to gaming. Sometimes, one person enters the destination for a large group of people going to the same floor. The dispatching algorithm is usually unable to completely cater for the variation, and late comers may find the elevator they are assigned to is already full. Also, occasionally, one person may press the floor multiple times. This is common with up/down buttons when people believe this to be an effective way to hurry elevators. However, this will make the computer think multiple people are waiting and will allocate empty cars to serve this one person.

The same destination scheduling concept can also be applied to public transit such as in group rapid transit.

References

Special operating modes

Anti-Crime Protection (ACP)

Anti-Crime Protection will force each car to stop at a pre-defined landing and open its doors. This allows a security guard or a receptionist at the landing to visually inspect the passengers. The car stops at this landing as it passes to serve further demand.

Up peak (MIT)

During Up Peak mode (also called Moderate Incoming Traffic), elevator cars in a group are recalled to the lobby to provide expeditious service to passengers arriving at the building, most typically in the morning as people arrive for work or at the conclusion of a lunch-time period. Elevators are dispatched one-by-one when they reach a pre-determined passenger load, or when they have had their doors opened for a certain period of time. The next elevator to be dispatched usually has its hall lantern or a "this car leaving next" sign illuminated to encourage passengers to make maximum use of the available elevator system capacity.

The commencement of Up Peak may be triggered by a time clock, by the departure of a certain number of fully loaded cars leaving the lobby within a given time period, or by a switch manually operated by a building attendant.

Down peak

During Down Peak mode, elevator cars in a group are sent away from the lobby towards the highest floor served, after which they commence running down the floors in response to hall calls placed by passengers wishing to leave the building. This allows the elevator system to provide maximum passenger handling capacity for people leaving the building.

The commencement of Down Peak may be triggered by a time clock, by the arrival of a certain number of fully loaded cars at the lobby within a given time period, or by a switch manually operated by a building attendant.

Sabbath service (SHO)

In areas with large populations of observant Jews or in facilities catering to 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. This prevents violation of the Sabbath prohibition against operating electrical devices when Sabbath is in effect for those who observe this ritual.[12]

However, Sabbath mode has the side effect of wasting considerable amounts of energy, needlessly running the elevator car sequentially up and down every floor of a building, repeatedly servicing floors where it is not needed. For a tall building with many floors, the car must move on a frequent enough basis so as to not cause undue delay for potential users that will not touch the controls as it opens the doors on every floor up the building.

Independent service (ISC)

Independent service is a special service mode found on most elevators. It is activated by a key switch either inside the elevator itself or on a centralized control panel in the lobby. When an elevator is placed on independent service, it will no longer respond to hall calls. (In a bank of elevators, traffic would be rerouted to the other elevators, while in a single elevator, the hall buttons will be disabled). The elevator will remain parked on a floor with its doors open until a floor is selected and the door close button is held until the elevator starts to travel. Independent service is useful when transporting large goods or moving groups of people between certain floors.

Inspection service (INS)

Inspection service is designed to provide access to the hoistway and car top for inspection and maintenance purposes by qualified elevator mechanics. It is first activated by a key switch on the car operating panel usually labeled 'Inspection', 'Car Top', 'Access Enable' or 'HWENAB'. When this switch is activated the elevator will come to a stop if moving, car calls will be canceled (and the buttons disabled), and hall calls will be assigned to other elevator cars in the group (or canceled in a single elevator configuration). The elevator can now only be moved by the corresponding 'Access' key switches, usually located at the top-most (to access the top of the car) and bottom-most (to access the elevator pit) landings. The access key switches will bypass the door lock circuit for the floor it is located on and allow the car to move at reduced inspection speed with the hoistway door open. This speed can range from anywhere up to 60% of normal operating speed on most controllers, and is usually defined by local safety codes.

Elevators have a car top inspection station that allows the car to be operated by a mechanic in order to move it through the hoistway. Generally, there are three buttons - UP, RUN, and DOWN. Both the RUN and a direction button must be held to move the car in that direction, and the elevator will stop moving as soon as the buttons are released. Most other elevators have an up/down toggle switch and a RUN button. The inspection panel also has standard power outlets for work lamps and powered tools.

Fire service mode (EFS)

Depending on the location of the elevator, fire service code will vary state to state and country to country. Fire service is usually split up into two modes: Phase One and Phase Two. These are separate modes that the elevator can go into.

Phase one mode is activated by a corresponding smoke sensor or heat sensor in the building. Once an alarm has been activated, the elevator will automatically go into phase one. The elevator will wait an amount of time, then proceed to go into nudging mode to tell everyone the elevator is leaving the floor. Once the elevator has left the floor, depending on where the alarm was set off, the elevator will go to the Fire Recall Floor. However, if the alarm was activated on the fire recall floor the elevator will have an alternate floor to recall to. When the elevator is recalled, it proceeds to the recall floor and stops with its doors open. The elevator will no longer respond to calls or move in any direction. Located on the fire recall floor is a fire service key switch. The fire service key switch has the ability to turn fire service off, turn fire service on or to bypass fire service. The only way to return the elevator to normal service is to switch it to bypass after the alarms have reset.

Phase two mode can only be activated by a key switch located inside the elevator on the centralized control panel. This mode was created for firefighters so that they may rescue people from a burning building. The phase two key switch located on the COP has three positions: off, on, and hold. By turning phase two on, the firefighter enables the car to move. However, like independent service mode, the car will not respond to a car call unless the firefighter manually pushes and holds the door close button. Once the elevator gets to the desired floor it will not open its doors unless the firefighter holds the door open button. This is in case the floor is burning and the firefighter can feel the heat and knows not to open the door. The firefighter must hold door open until the door is completely opened. If for any reason the firefighter wishes to leave the elevator, they will use the hold position on the key switch to make sure the elevator remains at that floor. If the firefighter wishes to return to the recall floor, they simply turn the key off and close the doors.

Fire Service is for emergency use only, although fire service keys can be purchased on eBay, and other websites. Only trained responders should use this feature, and it is by no means a safe way to escape from a burning building.

Medical emergency/'Code Blue' service (EHS)

Commonly found in hospitals, Code Blue service allows an elevator to be summoned to any floor for use in an emergency situation. Each floor will have a 'Code Blue' recall key switch, and when activated, the elevator system will immediately select the elevator car that can respond the fastest, regardless of direction of travel and passenger load. Passengers inside the elevator will be notified with an alarm and indicator light to exit the elevator when the doors open.

Once the elevator arrives at the floor, it will park with its doors open and the car buttons will be disabled to prevent a passenger from taking control of the elevator. Medical personnel must then activate the Code Blue key switch inside the car, select their floor and close the doors with the door close button. The elevator will then travel non-stop to the selected floor, and will remain in Code Blue service until switched off in the car. Some hospital elevators will feature a 'hold' position on the Code Blue key switch (similar to fire service) which allows the elevator to remain at a floor locked out of service until Code Blue is deactivated.

Emergency power operation (EPR)

Many elevator installations now feature emergency power systems which allow elevator use in blackout situations and prevent people from becoming trapped in elevators.

Traction elevators

When power is lost in a traction elevator system, all elevators will initially come to a halt. One by one, each car in the group will return to the lobby floor, open its doors and shut down. People in the remaining elevators may see an indicator light or hear a voice announcement informing them that the elevator will return to the lobby shortly. Once all cars have successfully returned, the system will then automatically select one or more cars to be used for normal operations and these cars will return to service. The car(s) selected to run under emergency power can be manually overridden by a key or strip switch in the lobby. In order to help prevent entrapment, when the system detects that it is running low on power, it will bring the running cars to the lobby or nearest floor, open the doors and shut down.

Hydraulic elevators

In hydraulic elevator systems, emergency power will lower the elevators to the lowest landing and open the doors to allow passengers to exit. The doors then close after an adjustable time period and the car remains unusable until reset, usually by cycling the elevator main power switch. Typically, due to the high current draw when starting the pump motor, hydraulic elevators aren't run using standard emergency power systems. Buildings like hospitals and nursing homes usually size their emergency generators to accommodate this draw. However, the increasing use of current limiting motor starters, commonly known as "Soft-Start" contactors, avoid much of this problem and the current draw of the pump motor is less of a limiting concern.

Elevator convenience features

Elevator floor indicator

Elevators may feature talking devices as an accessibility aid for the blind. In addition to floor arrival notifications, the computer announces the direction of travel, and notifies the passengers before the doors are to close.

In addition to the call buttons, elevators usually have floor indicators (often illuminated by LED) and direction lanterns. The former are almost universal in cab interiors with more than two stops and may be found outside the elevators as well on one or more of the floors. Floor indicators can consist of a dial with a rotating needle, but the most common types are those with successively illuminated floor indications or LCDs. Likewise, a change of floors or an arrival at a floor is indicated by a sound, depending on the elevator.

Direction lanterns are also found both inside and outside elevator cars, but they should always be visible from outside because their primary purpose is to help people decide whether or not to get on the elevator. If somebody waiting for the elevator wants to go up, but a car comes first that indicates that it is going down, then the person may decide not to get on the elevator. If the person waits, then one will still stop going up. Direction indicators are sometimes etched with arrows or shaped like arrows and/or use the convention that one that lights up red means "down" and green means "up". Since the color convention is often undermined or overrided by systems that do not invoke it, it is usually used only in conjunction with other differentiating factors. An example of a place whose elevators use only the color convention to differentiate between directions is the Museum of Contemporary Art in Chicago, where a single circle can be made to light up green for "up" and red for "down." Sometimes directions must be inferred by the position of the indicators relative to one another.

In addition to lanterns, most elevators have a chime to indicate if the elevator is going up or down either before or after the doors open, usually in conjunction with the lanterns lighting up. Universally, one chime is for up, two is for down, and none indicates an elevator that is 'free'.

Observatory service elevators often convey other facts of interest, including elevator speed, stopwatch, and current position (altitude), as with the case for Taipei 101's service elevators.

Standards

The mechanical and electrical design of elevators is dictated according to various standards (aka elevator codes), which may be international, national, state, regional or city based. Whereas once many standards were prescriptive, specifying exact criteria which must be complied with, there has recently been a shift towards more performance-based standards where the onus falls on the designer to ensure that the elevator meets or exceeds the standard.

Some of the national elevator standards include:

Because an elevator is part of a building, it must also comply with standards relating to earthquake resilience, fire standards, electrical wiring rules and so forth.

The American National Elevator Standards Group (ANESG) sets an elevator weight standard to be 2200 lbs.

Additional requirements relating to access by disabled persons, may be mandated by laws or regulations such as the Americans with Disabilities Act.

US and Canadian elevator standard specifics

A typical elevator style (Dover/ThyssenKrupp Impulse fixtures) found in many modern residential and small commercial buildings.

In most US and Canadian jurisdictions, passenger elevators are required to conform to the American Society of Mechanical Engineers' Standard A17.1, Safety Code for Elevators and Escalators. In Canada the document is the CAN/CSA B44 Safety Standard, which was harmonized with the US version in the 2000 edition. In addition, passenger elevators may be required to conform to the requirements of A17.3 for existing elevators where referenced by the local jurisdiction. Passenger elevators are tested using the ASME A17.2 Standard. The frequency of these tests is mandated by the local jurisdiction, which may be a town, city, state or provincial standard.

Passenger elevators must also conform to many ancillary building codes including the Local or State building code, National Fire Protection Association standards for Electrical, Fire Sprinklers and Fire Alarms, Plumbing codes, and HVAC codes. Also, passenger elevators are required to conform to the Americans with Disabilities Act and other State and Federal civil rights legislation regarding accessibility.

Residential elevators are required to conform to ASME A17.1. Platform and Wheelchair lifts are required to comply with ASME A18.1 in most US jurisdictions.

Most elevators have a location in which the permit for the building owner to operate the elevator is displayed. While some jurisdictions require the permit to be displayed in the elevator cab, other jurisdictions allow for the operating permit to be kept on file elsewhere – such as the maintenance office – and to be made available for inspection on demand. In such cases instead of the permit being displayed in the elevator cab, often a notice is posted in its place informing riders of where the actual permits are kept.

Unique elevator installations

World statistics

Country Number of elevators installed
Italy 850,000
United States 700,000
People's Republic of China > 1,010,000 [2]

As of January 2008, Italy is the nation with the most elevators installed in the world, with 850,000 elevators installed[13] that run more than one hundred million lifts every day, followed by United States with 700,000 elevators installed and People's Republic of China with 610,000 elevators installed since 1949[14]. The world's largest market for elevators is Italy with more than 1,629 million euros of sales and 1,224 million euros of internal market.

Eiffel Tower

An elevator pulley in the Eiffel Tower.

The Eiffel Tower has Otis double-deck elevators built into the legs of the tower, serving the ground level to the first and second levels. Even though the shaft runs diagonally upwards with the contour of the tower, both the upper and lower cars remain horizontally level. The offset distance of the two cars changes throughout the journey.

There are four elevator cars of the traditional design that run from the second level to the third level. The cars are connected to their opposite pairs (opposite in the elevator landing/hall) and use each other as the counterweight. As one car ascends from level 2, the other descends from level 3. The operations of these elevators are synchronized by a light signal in the car.

Taipei 101

The observation deck elevator floor indicator in the Taipei 101.

Double deck elevators are used in the Taipei 101 office tower. Tenants of even-numbered floors first take an escalator (or an elevator from the parking garage) to the 2nd level, where they will enter the upper deck and arrive at their floors. The lower deck is turned off during low-volume hours, and the upper deck can act as a single-level elevator stopping at all adjacent floors. For example, the 85th floor restaurants can be accessed from the 60th floor sky-lobby. Restaurant customers must clear their reservations at the reception counter on the 2nd floor. A bank of express elevators stop only on the sky lobby levels (36 and 60, upper deck car), where tenants can transfer to "local" elevators.

The high speed observation deck elevators accelerate to a world-record certified speed of 1010 meters per minute (60.6 km/h) in 16 seconds, and then it slows down for arrival with subtle air pressure sensations. The door opens after 37 seconds from the 5th floor. Special features include aerodynamic car and counterweights, and cabin pressure control to help passengers adapt smoothly to pressure changes. The downwards journey is completed at a reduced speed of 600 meters per minute, with the doors opening at the 52nd second.

The Gateway Arch

The interior of one of the Gateway Arch tramway cars

The Gateway Arch in St. Louis, Missouri has a unique elevator system which carries passengers from the visitors' center underneath the Arch to the observation deck at the top of the structure.

Called a tram or tramway, people enter this unique tramway much as one would enter an ordinary elevator, through double doors. Passing through the doors the passengers in small groups enter a horizontal cylindrical compartment containing seats on each side and a flat floor. A number of these compartments are linked to form a train. These compartments each individually retain an appropriate level orientation by tilting while the entire train follows curved tracks up one leg of the arch.

There are two tramways within the Arch, one at the north end, and the other at the south end. The entry doors have windows, so people traveling within the Arch are able to see the interior structure of the Arch during the ride to and from the observation deck. At the beginning of the trip the cars hang from the drive cables, but as the angle of the shaft changes, they end up beside and then on top of the cables.

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

New City Hall, Hanover, Germany

Elevator in the new city hall, Hannover, Germany, showing the cabin at the bottom and the top

The elevator in the New City Hall in Hanover, Germany 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 hall. 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.

Luxor Inclinator Elevator

In Las Vegas, Nevada, at the Luxor Hotel, is the Inclinator. The shape of this casino is a pyramid. Therefore, the elevator travels up the side of the pyramid at a 39 degree angle. Although people refer to this "inclined elevator" as an inclinator, this is incorrect.

Twilight Zone Tower of Terror

The Twilight Zone Tower of Terror is the common name for a series of elevator attractions at the Disney's Hollywood Studios park in Orlando, the Disney's California Adventure park in Anaheim, the Walt Disney Studios Park in Paris and the Tokyo DisneySea park in Tokyo. The central element of this attraction is a simulated free-fall achieved through the use of a high-speed elevator system. For safety reasons, passengers are seated and secured in their seats rather than standing. Unlike most traction elevators, the elevator car and counterweight are joined using a rail system in a continuous loop running through both the top and the bottom of the drop shaft. This allows the drive motor to pull down on the elevator car from underneath, resulting in downward acceleration greater than that of normal gravity. The high-speed drive motor is used to rapidly lift the elevator as well.

The passenger cabs are mechanically separated from the lift mechanism, thus allowing the elevator shafts to be used continuously while passengers board and embark from the cabs. Multiple elevator shafts are used to further improve passenger throughput. The doorways of the top few "floors" of the attraction are open to the outdoor environment, thus allowing passengers to look out from the top of the structure.

"Top of the Rock" elevators

Guests ascending to the 67th, 69th, and 70th level observation decks (dubbed "Top of the Rock") atop the GE Building at Rockefeller Center in New York City ride a high-speed glass-top elevator. When entering the cab, it appears to be any normal elevator ride. However, once the cab begins moving, the interior lights turn off and a special blue light above the cab turns on. This lights the entire shaft, so riders can see the moving cab through its glass ceiling as it rises and lowers through the shaft. Music plays and various animations are also displayed on the ceiling. The entire ride takes about 60 seconds.

Disneyland, Anaheim, California

Part of the Haunted Mansion attraction at Disneyland in Anaheim, California, takes place on an elevator. The "stretching room" on the ride is actually an elevator that travels downwards, giving access to a short underground tunnel which leads to the rest of the attraction. The elevator has no ceiling and its shaft is decorated to look like walls of a mansion. Because there is no roof, passengers are able to see the walls of the shaft by looking up, which gives the illusion of the room stretching.

Elevators for urban transport

In some towns, where terrain is difficult enough to justify, elevators are used as part of the urban transport systems. Examples:

See also

  • Building transportation systems
  • Escalator
  • Grain elevator
  • Elevator consultant
  • Elevator inspector
  • Elevator mechanic
  • Elevator operator
  • Elevator paradox
  • Space elevator
  • Elevator surfing
  • Funicular
  • Double-deck elevator
  • Paternoster

Notes

  1. ↑ The Book of Secrets - Kitab al Asrar of al-Muradi - part 1 of 2 at YouTube
  2. ↑ Conveyor technology: Elevator at conveyor-tech.com
  3. ↑ 3.0 3.1 The Elevator Museum, timeline
  4. ↑ http://www.cooper.edu/facilities/library/archive/symbol/symbol5.html
  5. ↑ http://www.ringwoodmanor.com/peo/ch/pc/pc.htm
  6. ↑ The History of the Elevator - Elisha Otis
  7. ↑ Ralph Turvey, London Lifts and Hydraulic Power, Transactions of the Newcomen Society, Vol. 65, 1993-94, PP.147-164
  8. ↑ [1]
  9. ↑ 9.0 9.1 9.2 http://www.windypundit.com/archives/2008/04/elevator_of_deathnot_really.html
  10. ↑ 10.0 10.1 http://www.newyorker.com/reporting/2008/04/21/080421fa_fact_paumgarten?currentPage=all
  11. ↑ http://www6.schindler.com/SEC/websecen.nsf/pages/elev-MHR-Mic10-01
  12. ↑ http://ohr.edu/ask_db/ask_main.php/39/Q1/
  13. ↑ source: ANIE Federazione (Federazione Nazionale Industrie Elettrotecniche ed Elettroniche
  14. ↑ source: China's elevator market study, 2005-2006, Publisher "Research in China"

References

External links