Elevator

Invented by : Elisha Graves Otis

Invented in year : 1852

Elevator is a lifting device consisting of a platform or cage that is raised and lowered mechanically in a vertical shaft in order to move people or cargo from one floor to another in a building. They are also known as Lifts. Elevators are used to carry goods and supplies between floors of a building and other infrastructure facilities. Most modern elevators are powered by electric motors, with the aid of a counterweight, through a system of cables and sheaves (pulleys).

Components of a Typical Elevator

Metal Compartment known as 'Passenger Cars' which rise up and down.
Electric motor which lifts the cars up and down, including a braking system.
Strong metal cables and pulleys running between the cars and the motors.
Counterweights attached to the other side of the steel cable loops. These balance the cars.
Various safety systems like emergency brakes, guide rails, call boxes and shock absorbers. These are meant for the protection of the passengers if a cable breaks.
An electronic control system that directs the cars to the correct floors using a so-called "elevator algorithm" (a sophisticated kind of mathematical logic). It ensures large numbers of people are moved up and down in the quickest, most efficient way (particularly important in huge, busy skyscrapers at rush hour). Intelligent systems are programmed to carry many more people upward than downward at the beginning of the day and the reverse at the end of the day.

Working of an Elevator

• In an elevator system, the car is raised and lowered by traction steel ropes. These ropes are attached to the car, and looped around a wheel or roller with a groove along its edge for holding a belt, rope or cable.
• The wheel also known as Sheave, is connected to an electric motor . When the motor turns one way, the wheel raises the elevator; when the motor turns the other way, the sheave lowers the elevator. In gear-less elevators, the motor rotates the sheaves directly. In geared elevators, the motor turns a gear train that rotates the sheave.
• Typically, the sheave, the motor and the control system are all housed in a machine room above the elevator shaft.
• The ropes that lift the car are also connected to a counterweight which hang on the other side of the roller. The counterweight weigh about the same as the car filled to 40% capacity. In other words, when the car is 40% (an average amount), the counterweight and the car are perfectly balanced. This balance conserves energy as equal loads on each side of the sheave, takes only a a little bit of force to tip the balance one way or the other. Sometimes two lifts always move synchronously in opposite directions, and they are each other's counterweight.
• The motor is meant to overcome friction - the weight on the other side does most of the work. Simply, the balance maintains a near constant potential energy level in the system as a whole. Using up the potential energy in the elevator car (letting it descend to the ground) builds up the potential energy in the weight (the weight rises to the top of the shaft). The same thing happens in reverse when the elevator goes up. It is like a See-Saw having equal amount of weight on each end.
• Guide rails built along the sides of the elevator shaft enable the smooth sliding of the elevator car and the counterweight. The rails also prevent the counterweight from swaying back and forth. They also assist in the safety system of the car to stop it in an emergency.

History

Elevators have been in existence since 3rd century BC. But these were a far cry from the modern elevators. They were operated and powered by human force, animal force or water wheel power. These were essentially lifting platforms that used pulleys and capstans, or windlasses. Archimedes is considered to have built such a system during 236 BC. Similar systems with certain modifications have been mentioned in historic literature like the one's used in Sinai monastery of Egypt, Spain's 'Elevator-Like Lifting Device', 17th century elevators in the palace buildings of England and France. These ancient and medieval elevators used a 'Hoist Drive System'. During 1793, a much effective system was developed by Ivan Kulibin, it was known as 'Screw Drive Elevator'. It comprised of a 'Supporting Stand', a 'Power Unit', 'Screw Shaft' having an end unrotatablly fixed to the supporting stand and having an unfixed end, and a 'Nut' rotatably screwed on the screw shaft. It was installed first in Winter Palace, Russia. It was an important invention which led to the creation of modern passenger elevators. In 1823, an 'Ascending Room' made its début in London. In the middle 1800s, various Crude Elevators emerged. Those using hydraulic power were known as 'Hydraulic Elevators' or 'Steam Operated Elevator'. Hydraulic elevator systems lift a car using a hydraulic ram, a fluid-driven piston mounted inside a cylinder. A pump applied water pressure to a plunger, or steel column, inside a vertical cylinder. Increasing the pressure caused the elevator to ascend. The elevator also used a system of counter-balancing so that the plunger did not have to lift the entire weight of the elevator and its load. The plunger, however, was not practical for tall buildings, because it required a pit as deep below the building as the building was tall. In 1850, Henry Waterman built the 'First successful Non-Hydraulic Elevator' in New York City. It was installed in a Manhattan warehouse to hoist barrels to the upper floor. Waterman’s elevator was a crude platform lifted by a cable that wound around a cylindrical drum known as the windlass. The windlass was turned by steam power in one direction to lift the platform; then turned in the other direction to lower it. But these devices also limited the height of an elevator shaft, since the drum afforded only so much room to safely accept the winding rope. Because it utilised rope it was known as 'Standing Rope Control'.

Though there were many inventors who can be credited with the invention of the first elevator but the one invention which revolutionised and led to the development of further advanced elevator system was created by Elisha Graves Otis. In 1852, invented a safety device that prevented elevators from falling if the hoisting cable broke. His elevator brake system gave him the honour of being the 'Father of the passenger elevator' and eventually the inventor of Elevator. He worked on his system while living in Yonkers, New York. Otis’s elevator was a simple platform that moved between two guide rails, with a steam-powered windlass at the top of the shaft to raise or lower the cable. The innovation was a safety device that could stop the fall of the elevator in the event the cable broke. The simple device consisted of two metal hooks and a spring, attached to the cable where it met the platform. If tension in the hoist rope was relaxed, in the event of a cable break, for instance, the hooks immediately sprang to a horizontal position, where their ends would catch in teeth cut into the guide rails and stop the elevator’s descent. He demonstrated his elevator at the New York exposition in the Crystal Palace in 1854. On March 23, 1857 the first Otis passenger elevator was installed at 488 Broadway in New York City.

Development in the Invention of Elevator

In 1861, Elisha Otis patented a steam elevator and also established an elevator company.

In 1874, J.W Meaker patented a method of opening and closing elevator doors safety. He was inspired by safety concerns of people who were reluctant or had doubts.

In 1880, Werner Von Siemens of Germany invented the Electric Elevator and the first of it's type was used at the end of the 19th century. Frank Sprague contributed in increasing the safety and speed of the electric elevators.

In 1887, American Inventor, Alexander Miles of Duluth, Minnesota patented an elevator with automatic doors that would close off the elevator shaft.

In 1894, the Push-Button Elevator was introduced in 1894. It was more reliable and cheaper to operate than the hand-operated manned elevator

In 1895, the Englishmen Frost and Strutt invented a device called the Teagle. It was a marked improvement over the windlass. Instead of a drum at the top of the shaft, the teagle employed a pulley wheel and counterweight; with the cable pressed so tightly against the wheel that it turned with the pulley. The teagle eliminated the cable-length limitations of the earlier windlass elevators, now buildings could rise toward the sky.

In 1904 a “gearless” feature was added by attaching the drive sheave directly to the armature of the electric motor, making speed virtually unlimited.

With increased building heights, elevator speeds increased to 1,200 feet (365 metres) per minute in such express installations as those for the upper levels of the Empire State Building (1931) and reached 1,800 feet (549 metres) per minute in the John Hancock Center, Chicago, in 1970.

In 1915, Automatic Leveling mechanism was developed. It allowed the car to rest precisely at floor level.

Automatic operation, widely popular in hospitals and apartment buildings because of its economy, was improved by the introduction of collective operation, by which an elevator or group of elevators answered calls in sequence from top to bottom or vice versa. The basic safety feature of all elevator installations was the hoist-way door interlock that required the outer (shaft) door to be closed and locked before the car could move. By 1950 automatic group-supervisory systems were in service, eliminating the need for elevator operators and starters.

Role of the Invention of Elevator in the development of Human Life

• The use of the safety brake system invented by Elisha Otis is still part of the modern elevator design.

• Elevators are essential for making offices and apartments accessible to handicapped people.

• Elevators facilitated residence and commercial activities to be conducted above ground. Large amounts of weight needed to be transported to higher elevation was possible and easy.

• The hydraulic elevator is still used in some warehouses and parking garages.

• The invention of elevators lead to the development and invention of escalators.