How does an escalator work?

               In modern cities or towns we sometime see moving metal stairs operating in big high raised buildings or shops. They carry people up and down to different storeys. We call them escalators. People use them to avoid physical strains in climbing or descending stairs in such buildings. This moving staircase is also used for transportation of passengers in subways and other mass pedestrian areas in most modern cities. Do you know how does these mechanical stairs work?

               The basic mechanism of an escalator was first invented by Jess W. Reno of USA in 1881. It was used mainly for riding on masts of wooden or iron poles in ships to fasten ropes or belts in order to support a ship’s sails.

               The name “escalator” was applied to a moving stair-way in 1900 and was first shown in an exhibition held in Paris. Originally, the patent was with a company named “Otis Elevator Company”. Subsequently the word “Escalator” became popular through its use by public.

               Modern escalators are normally limited in size to about 60 feet (18 metres). Its floor to floor rise is about 12 feet (5 metres) apart. They are electrically powered and driven by an endless chain that goes round and round without stopping. A motor drives the chain connecting the steps together. At the end, its steps go underneath the escalator and back to the beginning. The steps of an escalator run on rails below the steps arranged beside each other so that the steps are raised one above or below the other like that of a staircase. Near the top and bottom, the steps level out in such a way that the users can walk on or off the escalator easily.

               An escalator generally rises at a rate of upto 120 feet (36 metres) per minute. Very large escalators have a capacity of 6,00C passengers per hour to transport.

               If a chain breaks or displaced somehow, the release of tension stops the escalator. Moreover, a safety switch in an escalator is so designed, that it halts the escalator immediately if the escalator develops some defects or disorders.