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An escalator is a moving staircase – a conveyor transport device for carrying people between floors of a building. The device consists of a motor-driven chain of individual, linked steps that move up or down on tracks, allowing the step treads to remain horizontal.
Escalators are used around the world to move pedestrian traffic in places where elevators would be impractical. Principal areas of usage include department stores, shopping malls, airports, transit systems, convention centers, hotels, arenas, stadiums and public buildings.
Escalators have the capacity to move large numbers of people, and they can be placed in the same physical space as one might install a staircase. They have no waiting interval (except during very heavy traffic), they can be used to guide people toward main exits or special exhibits, and they may be weatherproofed for outdoor use. A non-functioning escalator can function as a normal staircase, whereas many other conveyances become useless when they break down.
Escalators, like moving walkways, are often powered by constant-speed alternating current motors and move at approximately 1–2 feet (0.3–0.6 m) per second. The typical angle of inclination of an escalator to the horizontal floor level is 30 degrees with a standard rise[clarification needed] up to about 60 feet (18 m). Modern escalators have single-piece aluminum or stainless steel steps that move on a system of tracks in a continuous loop.
Escalators have three typical configuration options: parallel (up and down escalators side by side or separated by a distance, seen often in metro stations and multilevel motion picture theaters), crisscross (minimizes space requirements by "stacking" escalators that go in one direction, frequently used in department stores or shopping centers), and multiple parallel (two or more escalators together that travel in one direction next to one or two escalators in the same bank that travel in the other direction).
Escalators are required to have moving handrails that keep pace with the movement of the steps. This helps riders steady themselves, especially when stepping onto the moving stairs. Occasionally, a handrail will move at a slightly different speed from the steps, causing it to "creep" slowly forward or backward relative to the steps. Riders may find this effect disconcerting and this problem should be fixed.
The direction of escalator movement (up or down) can be permanently set, or be controlled by personnel according to the predominant flow of the crowd, or be controlled automatically. In some setups, direction is controlled automatically by whoever arrives first, whether at the bottom or at the top (the system is programmed so that the direction is not reversed while a passenger is on the escalator).
A number of factors affect escalator design, including physical requirements, location, traffic patterns, safety considerations, and aesthetic preferences. Foremost, physical factors like the vertical and horizontal distance to be spanned must be considered. These factors will determine the length and pitch of the escalator. The building infrastructure must be able to support the heavy components. The escalator should be located where it can be easily seen by the general public. In department stores, customers should be able to view the merchandise easily. Furthermore, up and down escalator traffic should be physically separated and should not lead into confined spaces.
Traffic patterns must also be anticipated. In some buildings, the objective is simply to move people from one floor to another, but in others there may be a more specific requirement, such as funneling visitors towards a main exit or exhibit. The escalators must be designed to carry the required number of passengers. For example, a single-width escalator traveling at about 1.5 feet (0.5 m) per second can move about 2000 people per hour. The carrying capacity of an escalator system must match the expected peak traffic demand, presuming that passengers ride single file. This is crucial if there are sudden increases in the number of riders. For example, escalators at stations must be designed to cater for the peak traffic flow discharged from a train, without causing excessive bunching at the escalator entrance.
In this regard, escalators help in controlling the flow of people. For example, an escalator to an exit effectively discourages most people from using it as an entrance[clarification needed], and may reduce security concerns. Similarly, escalators often are used as the exit from airport security checkpoints. Such an egress point would still generally be staffed to prevent its use as an entrance during times of light pedestrian traffic.
It is preferred that staircases be located adjacent to the escalator if the escalator is the primary means of transport between floors. It may also be necessary to provide an elevator lift near the escalator for wheelchairs and disabled people. Finally, consideration should be given to the aesthetics of the escalator.
|Size||Width (between balustrade panels)||Single-step capacity||Applications||Power consumption|
|Very small||400 mm (16 in)||One passenger, with feet together||A rare historic design found mostly in older department stores||3.7 kW (5 hp)|
|Small||600 mm (24 in)||One passenger||Low-volume sites, uppermost levels of department stores, when space is limited||3.7 kW (5 hp)|
|Medium||800 mm (31 in)||One passenger + one package or one piece of luggage||Shopping malls, department stores, smaller airports||7.5 kW (10 hp)|
|Large||1,000 mm (39 in)||Two passengers – one may walk past another||Mainstay of metro systems, larger airports, train stations, some retail usage||7.5 kW (10 hp)|
Safety is also major concern in escalator design. In India, where women wear saris, there are heavy chances of getting the pallu entangled in the escalator. As a result, a special sari guard is built into most escalators.
There is a risk of foot injuries for children wearing footwear such as Crocs and flip-flops that might get caught in escalator mechanisms. This was due to the softness of the shoe's material combined with the smaller size of children's feet.
Fire protection of an escalator may be provided by adding automatic fire detection and suppression systems inside the dust collection and engineer pit, in addition to any water sprinkler system installed in the ceiling. To limit the danger caused by overheating, ventilation for the spaces that contain the motors and gears must be provided, and small targeted clean agent automatic extinguishing systems can be installed in these areas. Fire protection of an escalator floor opening may be provided by adding automatic sprinklers or fireproof shutters to the opening, or by installing the escalator in an enclosed fire-protected hall.
In the official inquiry that followed, the Fennell Report, it was determined that the fire started slowly, smoldered virtually undetected for a time, then exploded into the ticketing hall above in a phenomenon known as the “trench effect.” In the escalators’ undercarriage, approximately 8,800 kilograms (19,400 lb) of accumulated detritus acted as a wick to a neglected buildup of interior lubricants; wood veneers, paper and plastic advertisements, solvent-based paint, plywood in the ticket hall, and melamine combustion added to the impact of the calamity.
As a result of the report, older wooden escalators were removed from service in the London Underground. Additionally, sections of the London Underground that were actually below ground were made nonsmoking; eventually the whole system became a smoke-free zone.
Despite their considerable scope, two Congressional Acts, the Rehabilitation Act of 1973 and the Americans with Disabilities Act of 1990 (ADA), did not directly affect escalators or their public installations. Since Section 504 of the Rehabilitation Act included public transportation systems, for a few years, the United States Department of Transportation considered designs to retrofit existing escalators for wheelchair access. Nonetheless, Foster-Miller Associates’ 1980 plan, Escalator Modification for the Handicapped was ultimately ignored in favor of increased elevator installations in subway systems. Likewise, the ADA provided more accessibility options, but expressly excluded escalators as “accessible means of egress,” advocating neither their removal nor retention in public structures.
In the United States and Canada, new escalators must abide by ASME A17.1 standards, and old/historic escalators must conform to the safety guidelines of ASME A17.3. In Europe, the escalator safety code is EN115.
Nathan Ames, a patent solicitor from Saugus, Massachusetts, is credited with patenting the first "escalator" in 1859, despite the fact that no working model of his design was ever built. His invention, the "revolving stairs", is largely speculative and the patent specifications indicate that he had no preference for materials or potential use (he noted that steps could be upholstered or made of wood, and suggested that the units might benefit the infirm within a household use), though the mechanization was suggested to run either by manual or hydraulic power.
In 1889, Leamon Souder successfully patented the "stairway", an escalator-type device that featured a "series of steps and links jointed to each other". No model was ever built. This was the first of at least four escalator-style patents issued to Souder, including two for spiral designs (U. S. Patent Nos. 723,325 and 792,623).
In 1892, Jesse W. Reno patented the "Endless Conveyor or Elevator." A few months after Reno's patent was approved, George A. Wheeler patented his ideas for a more recognizable moving staircase, though it was never built. Wheeler’s patents were bought by Charles Seeberger; some features of Wheeler’s designs were incorporated in Seeberger’s prototype built by the Otis Elevator Company in 1899.
Reno, a graduate of Lehigh University, produced the first working escalator (he actually called it the "inclined elevator") and installed it alongside the Old Iron Pier at Coney Island, New York City in 1896. This particular device was little more than an inclined belt with cast-iron slats or cleats on the surface for traction, and traveled along a 25° incline. A few months later, the same prototype was used for a month long trial period on the Manhattan side of the Brooklyn Bridge. Reno eventually joined forces with Otis, and retired once his patents were purchased outright. Some Reno-type escalators were still being used in the Boston subway until construction for the Big Dig precipitated their removal. The Smithsonian Institution considered re-assembling one of these historic units from 1914 in their collection of Americana, but "logistics and reassembly costs won out over nostalgia", and the project was discarded.
Around May 1895, Charles Seeberger began drawings on a form of escalator similar to those patented by Wheeler in 1892. This device actually consisted of flat, moving stairs, not unlike the escalators of today, except for one important detail: the step surface was smooth, with no comb effect to safely guide the rider's feet off at the ends. Instead, the passenger had to step off sideways. To facilitate this, at the top or bottom of the escalator the steps continued moving horizontally beyond the end of the handrail (like a miniature moving sidewalk) until they disappeared under a triangular "divider" which guided the passenger to either side. Seeberger teamed with Otis in 1899, and together they produced the first commercial escalator which won the first prize at the Paris 1900 Exposition Universelle in France. Also on display at the Exposition were Reno's inclined elevator, a similar model by James M. Dodge and the Link Belt Machinery Co., and two different devices by French manufacturers Hallé and Piat.
Piat installed its "stepless" escalator in Harrods Knightsbridge store on Wednesday, November 16, 1898, though the company relinquished its patent rights to the department store. Noted by Bill Lancaster in The Department Store: a Social History, "customers unnerved by the experience were revived by shopmen dispensing free smelling salts and cognac." The Harrods unit was a continuous leather belt made of "224 pieces . . . strongly linked together traveling in an upward direction," and was the first "moving staircase" in England.
Hocquardt received European patent rights for the Fahrtreppe in 1906. After the Exposition, Hallé continued to sell its escalator device in Europe, but was eventually eclipsed in sales by other major manufacturers.
In the first half of the twentieth century, several manufacturers developed their own escalator products, though they had to market their devices under different names, due to Otis’ hold on the trademark rights to the word “escalator.” New York-based Peelle Company called their models the Motorstair, and Westinghouse called their model an Electric Stairway. The Toledo-based Haughton Elevator company referred to their product as simply Moving Stairs.
Kone and Schindler introduced their first escalator models several decades after the Otis Elevator Co., but grew to dominance in the field over time. Today, they, Mitsubishi, and ThyssenKrupp are Otis' primary rivals.
Schindler now stands as the largest maker of escalators and second largest maker of elevators in the world, though their first escalator installation did not occur until 1936. In 1979, the company entered the United States market by purchasing Haughton Elevator; nine years later, Schindler assumed control of the North American escalator/elevator operations of Westinghouse.
Kone expanded internationally by acquisition in the 1970s, buying out Swedish elevator manufacturer Asea-Graham, and purchasing other minor French, German, and Austrian elevator makers before assuming control of Westinghouse’s European elevator business. As the last "big four" manufacturers held on to the escalator market, KONE first acquired Montgomery Elevator Company, then took control of Germany’s Orenstein & Koppel Rolltreppen.
Jesse Reno's escalators did not resemble modern escalators too closely. Passengers' feet tilted upward at an angle, and the treads consisted of cleated metal (initially) or wood (later models). Reno worked on his own for several years, gaining success with installations from Toronto to Cape Town, South Africa. Similar units of the day by other manufacturers resembled conveyor belts more than moving staircases. For a time, Otis Elevator sold Reno's escalators as their own "cleat-type" escalators.
Seeberger's model, bought by Otis, clearly became the first "step-type" escalator, so called after its visual likeness to steps on a regular staircase. The company later combined the best aspects of both inventions (guiding slats and flat steps) and in 1921 produced an escalator similar to the type used today: they called it the "L-type" escalator. It was succeeded by the "M-type", the "O-type", and current models by Otis such as the "NCE-type" escalator.
Jese Reno, in addition to being known for the first “practical” escalator in public use, also designed the first escalators installed in any underground subway system – a single "spiral" escalator at Holloway Road tube station in London in 1906, which was actually a helical escalator. The experimental device never saw public use, and was forgotten for several decades. The remains of this are now in the London Transport Museum's depot in Acton.
Also the first fully operational "spiral" escalator, Reno’s design was nonetheless only one in a series of several similar proposed contraptions. Souder patented two helical designs (see above), Wheeler drafted helical stairway plans in 1905, Seeberger devised at least two different helical units between 1906 and 1911 (including an unrealized arrangement for the London Underground), and Gilbert Luna obtained West German, Japanese, and United States patents for his version of a "spiral" escalator by 1973. When interviewed for the Los Angeles Times that year, Luna was in the process of soliciting “major firms” for acquisition of his patents and company, but statistics are unclear on the outcome of his endeavors in that regard.
The Mitsubishi Electric Corporation was most successful in its development of "spiral" (more helical than true spiral) escalators, and has sold them exclusively since the mid-1980s. The world's first "practical" "spiral" escalator—a Mitsubishi model—was installed in Osaka, Japan, in 1985.
In use, a major planning advantage presented by "spiral" escalators is that they take up much less horizontal floor space than traditional units, which frequently house large machine rooms underneath the truss.
Helixator, an experimental "spiral" escalator design which currently exists as a prototype scale model, could further reduce the floor space. The design has several innovations that offer the possibility of a continuous helix. Driven by a linear motor instead of a chain system, the Helixator spreads the force evenly along the escalator path, avoiding excessive force on the top chain links and removing geometry, length and height limits.
Several authors and historians have contributed their own differing interpretations of the source of the word “escalator”, and some degree of misinformation has heretofore proliferated on the Internet. For reference, contradictory citations by seven separate individuals, including the Otis Elevator Company itself, are provided below.
Charles Seeberger created the word "escalator" in 1900, to coincide with his device’s debut at the Exposition Universelle. According to his own account, in 1895, his legal counsel advised him to name his new invention, and he then set out to devise a title for it on his own. As evidenced in Seeberger's own handwritten documents, archived at the Otis Elevator Company headquarters in Farmington, Connecticut, the inventor consulted "a Latin lexicon" and "adopted as the root of the new word, 'Scala'; as a prefix, 'E' and as a suffix, 'Tor.'" His own rough translation of the word thus created was "means of traversing from", and he intended for the word to be pronounced, "es‧ʹkæl‧ə‧tər" (es-CAL-a-tor).
"Escalator" was not a combination of other French or Greek words, and was never a derivative of "elevator" in the original sense, which means "one who raises up, a deliverer" in Latin. Similarly, the root word "scala" does not mean "a flight of steps", but is defined by Lewis and Short’s A Latin Dictionary as the singular form of the plural noun "scalae", which denotes any of the following: "a flight of steps or stairs, a staircase; a ladder, [or] a scaling-ladder."
The alleged intended capitalization of "escalator" is likewise a topic of debate. Seeberger’s trademark application lists the word not only with the "E" but also with all of the letters capitalized (in two different instances), and he specifies that, "any other form and character of type may be employed . . . without altering in any essential manner the character of [the] trade-mark." That his initial specifications are ostensibly inconsistent, and since Otis Elevator Co. advertisements so frequently capitalized all of the letters in the word, suppositions about the "capital ‘e’" are difficult to formulate.
The verb "escalate" originated in 1922, and has two uses, the primary: "to climb or reach by means of an escalator" or "to travel on an escalator", and the secondary: "to increase or develop by successive stages; spec. to develop from 'conventional' warfare into nuclear warfare." The latter definition was first printed in the Manchester Guardian in 1959, but grew to prominent use during the late 1960s and early 1970s.
In 1950, the landmark case Haughton Elevator Co. v. Seeberger precipitated the end of Otis's reign over exclusive use of the word "escalator", and simultaneously created a cautionary study for companies and individuals interested in trademark retention. Confirming the contention of the Examiner of Trademark Interferences, Assistant Commissioner of Patents Murphy’s decision rejected the Otis Elevator Company’s appeal to keep their trademark intact, and noted that "the term 'escalator' is recognized by the general public as the name for a moving stairway and not the source thereof", observing that the Otis Elevator Co. had "used the term as a generic descriptive term…in a number of patents which [had] been issued to them and…in their advertising matter." All trademark protections were removed from the word "escalator", the term was officially genericized, and it fell into the public domain.
As noted above, a few escalator types were installed in major department stores (including Harrods) before the Expo. Escalators proved instrumental in the layout and design of shopping venues in the twentieth century.
By 1898, the first of Reno’s "inclined elevators" were incorporated into the Bloomingdale Bros. store at Third Avenue and 59th Street. This was the first retail application of the devices in the US, and no small coincidence, considering that Reno's primary financier was Lyman Bloomingdale, co-owner of the department store with brother Joseph Bloomingdale.
The first "standard" escalator installed on the London Underground was a Seeberger model at Earls Court. Noted above, London's Underground installed a rare spiral escalator designed by Reno, William Henry Aston and Scott Kietzman for the Holloway Road Underground station in 1906; it was run for a short time but was taken out of service the same day it debuted. The older lines of the London Underground had many escalators with wooden treads (ca. 1930s) until they were rapidly replaced following the King's Cross fire, noted above.
In 1905, the American Woolen Company’s Wood Mill in Lawrence, Massachusetts (then "the largest single worsted mill in the world") utilized Otis' Seeberger-type "reversible" escalators to carry its workers between floors four times a day. The machines did not run all day: rather, escalators ran solely to transport employees to/from midday meals and in/out of the mill. In its advertising, Otis Elevator Company hailed this unconventional use for its unique benefits to both workers and owners: "The profitable and practicable feature of the Escalator, from the viewpoint of the owner, is the increased efficiency of each operator due to the elimination of stair climbing."
In San Francisco, an escalator at Hunters Point Naval Shipyard was used to convey personnel between the first and third floors. At the time of its construction in 1948, it was touted thus: "[it has the] highest lift of any industrial building in the world. It rises 42 feet (12.8 meters)."
A few notable examples of historic escalators still in operation include:
Several metro or subway systems in Central and Eastern Europe feature very long escalators.
On some busy systems, such as those in the UK, US, Germany, Taiwan and Hong Kong, there is a de facto standard policy of standing on the right. Often, this informal standard is reinforced by official regulations, though official enforcement is rarely required. In most of Japan including Tokyo, the policy is to stand on the left; however in Osaka they stand on the right. Either way, the open side of the escalators is reserved for those riders walking and overtaking.
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