Escalators are a common sight in stores, malls, and business buildings. These moving stairways get their name from a combination of the words “elevator” and “scala,” which is Latin for “steps.” Escalators provide a quick and efficient way to move many people between floors. Elevators can only carry ten to twenty people at a time, and require several minutes per trip. Escalators, on the other hand, can carry thousands of people per hour. The invention in its modern form is credited to Charles D. Seeberger in conjunction with the Otis Elevator Company, and was first seen by the public when it won first prize at the Paris Exhibition in 1900.
A large truss forms the box that houses the escalator’s machinery. This hollow area extends from one floor of the building to the next, and has metal sides slanting upwards with braces at the top and bottom. This structure provides the support and framework for the escalator. The ends of the truss are held up by steel or concrete and hold the escalator in place. The truss bridges the area between the top and bottom of the escalator and supports it.
Escalators are actually specialized conveyor belts, and work in much the same way. Electric motors power most escalators, moving a drive gear and causing the attached conveyor belt to turn. The conveyor belt, in this case, is really a chain. The steps are attached to the chain and are pulled around the loop as the drive gear pulls the chain. The drive wheel also is connected with a belt to another gear that pulls the handrail along at the same speed as the steps. The handrail is really a second small conveyer belt that is positioned a bit higher than the main belt that carries the steps.
Two special problems had to be solved before the escalator could become as useful as it is today. The conveyor belt had to keep passengers on level footing though the conveyor chain had to be inclined. Also, the inventors had to develop a means to fold the steps up at the top and bottom of the machine so riders had a safe and convenient way to enter and exit at the top and bottom of the conveyor.
To solve the problem of level footing, the escalator has a number of separate steps that are attached to the drive chain. Each step has a wheel on the bottom running in a track that follows nearly the same path as the chain, but lower. The steps balance on their bottom wheel in the track. The tracks are inclined for the majority of the distance between the top and bottom of the escalator and a steady distance between the upper and lower tracks is maintained. However, if this arrangement were kept at the top and bottom of the escalator, the individual steps would go around the end of the track and start back down the other side, all the while keeping their stair-step arrangement. The escalator would need a hole at the top and bottom a foot or more wide to allow the steps to travel around the end of the track and to reappear at the other end. Such a gap would be quite hazardous to passengers, and would make entering and exiting unacceptably risky.
The tracks guiding the individual steps get closer together as the conveyer belt approaches the top and bottom ends of the escalator. This levels the steps out into a sort of landing and allows the rider to step on or off a level platform instead of trying to move onto or off of an individual step. After the steps leave the level platform, the distance between the tracks expands outward, causing the steps to slide into their step formation. When the steps approach the other end of the escalator, the upper and lower tracks again come closer together and cause the steps to flatten into the landing for easy boarding and exiting.
Each step also has a comb-like edge that meshes neatly with combs on a plate in the floor. The combs cause the folded step to slide beneath the plate without scraping or bumping. These combs also allow the individual steps to slide up and down beside one another as the steps fold and unfold near the top and bottom of the machine. This mechanism eliminates many of the cracks and places where clothing, strings, or other things could get caught between the parts of the machine as people ride it.
Escalators are marvelous in their simplicity, operating with a simple conveyor belt system. They are a safe and efficient way to move people between floors. No wonder they are chosen as the method to make different levels accessible in many stores and businesses.
