History of the Elevator
Primitive elevators were in use as
early as the 3rd century BC, operated by human, animal, or water wheel
power. From about the middle of the 19th century, power elevators, often
steam-operated, were used for conveying materials in factories, mines,
In 1853, American inventor Elisha
Otis demonstrated a freight elevator equipped with a safety device to prevent
falling in case a supporting cable should break. This increased public
confidence in such devices. Otis established a company for manufacturing
elevators and patented (1861) a steam elevator. In 1846, Sir William Armstrong
introduced the hydraulic crane, and in the early 1870s, hydraulic machines
began to replace the steam-powered elevator. The hydraulic elevator is
supported by a heavy piston, moving in a cylinder, and operated by the
water (or oil) pressure produced by pumps.
came into to use toward the end of the 19th century. The first one was built by the German inventor Werner von Siemens in 1880.
How Elevators Work
In a typical elevator, the car is
raised and lowered by six to eight motor-driven wire ropes that are attached
to the top of the car at one end, travel around a pair of sheaves, and
are again attached to a counterweight at the other end.
The counterweight adds accelerating
force when the elevator car is ascending and provides a retarding effort
when the car is descending so that less motor horsepower is required. The
counterweight is a collection of metal weights that is equal to the weight
of the car containing about 45% of its rated load. A set of chains are
looped from the bottom of the counterweight to the underside of the car
to help maintain balance by offsetting the weight of the suspension ropes.
Guide rails that run the length of
the shaft keep the car and counterweight from swaying or twisting during
their travel. Rollers are attached to the car and the counterweight to
provide smooth travel along the guide rails.
The traction to raise and lower the
car comes from the friction of the wire ropes against the grooved sheaves.
The main sheave is driven by an electric motor.
Most elevators use a direct current
motor because its speed can be precisely controlled to allow smooth acceleration
and deceleration. Motor-generator (M-G) sets typically provide to dc power
for the drive motor. Newer systems use a static drive control. The elevator
controls vary the motor's speed based on a set of feedback signals that
indicate the car's position in the shaftway. As the car approaches its
destination, a switch near the landing signals the controls to stop the
car at floor level. Additional shaftway limit switches are installed to
monitor overtravel conditions. more
Elisha Otis invented the "Improvement
in Hoisting Apparatus." Elisha Otis didn't actually invent the elevator,
he invented the brake used in modern elevators. His brakes made
skyscrapers a practical reality. (above illustration - patent drawing of
the Elisha Otis elevator)
Elisha Otis was inspired to design
what was then called the "safety elevator".
By 1850, steam and hydraulic elevators
had been introduced, but it was in 1852 that the landmark event in elevator
history occurred: the invention of the world's first safety elevator.
Rudimentary elevators, or hoists,
were in use during the Middle Ages and can be traced back to the third
century BC. They were operated by animal and human power or by water-driven
History of Elevators
A device for vertical transportation
of passengers or freight to different floors or levels, as in a building
or a mine. The term elevator generally denotes a unit with automatic safety
devices; the very earliest units were called hoists.
The question is often asked of those
within the elevator industry, "When and where was the elevator invented
and by whom?" This would elicit the same response if the question concerned
the birth of the ship, automobile, locomotive or aircraft. All such complex
machines are the brainchildren of countless innovators.
Alexander Miles patented an electric
elevator (U.S. pat#371,207) on October 11, 1887.
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