Escalator


An escalator is a moving staircase which carries people between floors of a building or structure. It consists of a motor-driven chain of individually linked steps on a track which cycle on a pair of tracks which keep the step tread horizontal.
Escalators are often used around the world in places where lifts would be impractical, or they can be used in conjunction with them. 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. They have no waiting interval. They can be used to guide people toward main exits or special exhibits and may be weatherproofed for outdoor use. A non-functional escalator can function as a normal staircase, whereas many other methods of transport become useless when they break down or lose power.

History

Inventors and manufacturers

, a patent attorney from Saugus, Massachusetts, is credited with patenting the first "escalator" in 1859, even though 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. The suggested motive power was either manual or hydraulic. "The object of the invention is to enable persons to ascend and descend from one story of a building to another" according to his 1859 patent, while also indicating that they can be "used in the ordinary way, when desired." It is implied that the normal way is identical to that of a stationary staircase.
In 1889, Leamon Souder successfully patented the "stairway", an analogous 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.
On March 15, 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 that was built by the Otis Elevator Company in 1899. Reno, a graduate of Lehigh University, produced the first working escalator 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 degree 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 he had sold his patents. Some wooden Reno-type escalators were still being used at Downtown Crossing 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 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 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. It won first prize at the 1900 Paris Exposition Universelle. 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 the French manufacturers Hallé and Piat.
Piat installed its "stepless" escalator in Harrods Knightsbridge store, which was unveiled 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, while Westinghouse called their model an Electric Stairway. The Toledo-based Haughton Elevator company referred to their product as simply Moving Stairs. The Otis trademark is no longer in effect.
Kone and Schindler introduced their first escalator models several decades after the Otis Elevator Co., but grew to dominate the field over time. Today, Mitsubishi and ThyssenKrupp are Otis's primary rivals. 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 of the "big four" manufacturers to emerge onto the global market, Kone first acquired the Montgomery Elevator company, then took control of Germany's Orenstein & Koppel Rolltreppen.
In the twenty-first century Schindler became 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 the Haughton Elevator company. A decade later, Schindler assumed control of the North American escalator/elevator operations of Westinghouse, forming Schindler's American division.

Extant historic escalator models

Notable examples of historic escalators still in operation include:
Authors and historians have offered multiple interpretations of the source of the word "escalator", and some degree of misinformation then proliferated. For reference, contradictory citations by seven separate individuals, including the Otis Elevator Company itself, are provided below.
Seeberger trademarked 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. As evidenced in Seeberger's handwritten documents, 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 . By 1906, Seeberger noted that the public had instead come to pronounce it .
"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 the singular form of the plural noun "scalae", which can denote any of: "a flight of steps or stairs, a staircase; a ladder, 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, and he specifies that "any other form and character of type may be employed... without altering in any essential manner the character of trade-mark." Otis Elevator Co. advertisements so frequently capitalized all of the letters in the word.
In 1950, the landmark case Haughton Elevator Co. v. Seeberger precipitated the end of Otis's exclusive reign over 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 Otis’ 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 Otis had "used the term as a generic descriptive term... in a number of patents which 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.

Design

Design factors include innovative technology, physical requirements, location, traffic patterns, safety considerations, and aesthetics. Physical factors such as the distance to be spanned determine the length and pitch of the escalator, while factors such as the infrastructure's ability to provide support and power must be considered. How upward and downward traffic is separated and load/unload areas are other important considerations.
Temporal traffic patterns must be anticipated. Some escalators need only to move people from one floor to another, but others may have specific requirements, such as funneling visitors towards exits or exhibits. The visibility and accessibility of the escalator to traffic is relevant. Designers need to account for the projected traffic volumes. For example, a single-width escalator traveling at about can move about 2000 people per hour, assuming that passengers ride single file. The carrying capacity of an escalator system is typically matched to the expected peak traffic demand. For example, escalators at transit stations must be designed to cater for the peak traffic flow discharged from a train, without excessive bunching at the escalator entrance. In this regard, escalators help manage the flow of people. For example, at many airports an unpaired escalator delivers passengers to an exit, with no means for anyone entering at the exit to access the concourse.
Escalators are often built next to or around staircases that allow alternative travel between the same two floors. Elevators are necessary for disability access to floors serviced by escalators.
Escalators typically rise at an angle of 30 or 35 degrees from the ground. They move at, like moving walkways, and may traverse vertical distances in excess of. Most modern escalators have single-piece aluminum or stainless steel steps that move on a system of tracks in a continuous loop.
Different types of escalator planning include:
  • Parallel ;
  • Multiple parallel ;
  • Crisscross.
Most countries require escalators to have moving handrails that keep pace with the movement of the steps as a safety measure. This helps riders steady themselves, especially when stepping onto the moving stairs. Occasionally a handrail moves at a slightly different speed from the steps, causing it to "creep" slowly forward or backward relative to the steps; it is only slippage and normal wear that causes such losses of synchronicity, and is not by design. An updated drive wheel system was patented by John P. Spriggs and James F. Evans in 1995, which some escalators use today. These are often used in conjunction with the escalator, but reduce the risk of creep.
The direction of escalator movement can be permanently set, controlled manually depending on the predominant flow of the crowd, or controlled automatically. In some setups, the direction is controlled by whoever arrives first.