An escalator is a continuous moving stairway with handrails, used to carry people from one level to another. The word "Escalator" was originally a trademark of the Otis Elevator Company, but wide public usage has made it a generic term.
Escalators carry streams of people from level to level with safety, comfort, and convenience, provide service without waiting and without an operator, and handle heavy continuous traffic to heights of several stories.
An escalator can carry from 5,000 to 10,000 persons per hour, depending on passenger-way width, speed, and density of loading. Standard U.S. widths are 32 and 48 inches (81.3 and 121.9 cm) and speeds are 90 and 120 feet (27.4 and 36.6 meters) per minute. Escalators can handle loads that vary from floor to floor or moment to moment, and are readily reversed in direction to cope with changing traffic flow.
Escalators have always had special appeal for department stores, since passengers can often see the merchandise as they move from floor to floor. Shopping centers and air, rail, and bus terminals depend heavily on escalators to move crowds of people and cope with traffic peaks. In hotels and office buildings, escalators impart main-floor accessibility to frequently used facilities on upper and lower floors. Suburban office buildings of moderate height increasingly rely on escalators as the principal means of vertical transportation. Museums, art galleries, schools, hospitals, concert halls, grandstands, and sport arenas are using more and more escalators. There were about 12,000 in the United States in 1971.
One of the shortest escalators has a rise of only 5.5 feet (1.7 meters), between lobby levels in a Florida motel. North America's highest-rising escalator in the early 1970's lifted people 68 feet (20.7 meters) in the Man and His World exposition at Montreal. This height is exceeded in England by the 85-foot (25.9-meter) rise of escalators at both ends of a pedestrian tunnel under the Tyne River.
In an escalator a series of steps is connected by step axles to two endless chains and supported by rubber- or nylon-tired wheels on endless steel tracks. The chains are guided by the tracks in such a way that the steps level out at the top and bottom landings. The chains and the steps connected to them are led over two sprockets at the upper end of the escalator and returned, with the steps in flat formation, to the lower landing where they turn back into the carrying path. The angle of the path is 30° from the horizontal. An electric motor in the upper landing drives the chains and steps through reduction gearing and chain-and-sprocket linkage.
Handrails on both sides of the escalator are driven by chain and sprocket from the main drive to move at the same speed as the steps. Balus-trading and panels support the handrails and protect passengers from internal moving parts.
Passengers are also protected by many safety features, such as a device to stop the system should the step-chain break, the system become overloaded, or an object be caught between the edge of a moving step and the stationary skirt.
The entire escalator is contained in a steel frame or truss rigidly connected at the upper and lower landings to the building framework.
History of the Escalator
The first U.S. patent on an escalator was issued in 1859, but it was not used. Jesse W. Reno and Charles D. Seeberger independently invented two types of practical escalator about 1890. The Otis Elevator Company in time acquired rights to both. The first escalators were built and operated in 1899 at the Otis factory in Yonkers, N. Y. One remained in the plant as a demonstration unit until 1902, when it was installed in a Chicago department store. The second was the earliest one used by the public- first at the Paris Exposition of 1900, then from 1901 to 1939 at Gimbels, a department store in Philadelphia. Other early escalators were in New York City- in the subway system and at Bloomingdale's, another department store.
Early escalators had shunts at the upper landing, a safety provision to ease passengers off to one side. In 1920 the present type of comb plate was incorporated, with a gentle ramplike action safely lifting the passenger's feet off the moving treads should he fail to step off at the landing.
Standardization of escalators, begun extensively in the late 1940's, helped reduce relative cost and contributed to wider use in a growing variety of building types.