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The history of power elevators in the U. ... In these early elevators, a steam engine was connected by belt and gears to a revolving drum on which the hoisting rope was wound. ... Electric Elevators The electric motor was introduced in elevator construction in 1880 by the German inventor Werner von Siemens. ... Within the next 12 years, electric elevators with worm gearing connecting the motor and drum came into general use except in tall buildings. ... Since the introduction of electric motive power for elevators, various improvements have been made in motors and methods of control. ... Computing equipment was developed for compiling automatically information that vastly improved the operational efficiency of elevators in large buildings. ... The use of automatic programming equipment eventually eliminated the need for starters at the ground level of large commercial buildings, and thus the operation of elevators became completely automatic. Automatic elevators are now generally employed in all types of buildings. The World Trade Center in New York City, with its two 110-story towers, had 244 elevators with carrying capacities of up to 4536 kg (10,000 lb) and speeds of up to 488 m (1600 ft) per min The 110-story Sears-Roebuck Building in Chicago has 109 elevators with speeds of up to 549 m (1800 ft) per min.
Approximate Word count = 885
Approximate Pages = 3.5
(250 words per page double spaced)
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