The high rise buildings which are tearing the vertical limits are made possible only because of elevators. Stepping onto the first floor by using stairs is possible but stepping on the hundredth floor is really a sweaty task. Therefore, a machine is needed to move from floor to floor. That machine is an elevator; just hit the floor number button on the elevator and you will be there in just few seconds. Today’s elevator has a speed of 64 km/h or 3,500 ft/minute. Moreover, an elevator has the capacity to take you into space and NASA already started working on an elevator that could carry us from earth to outer space. In this article let us know how these elevators work.
What is elevator?
Elevator also called as LIFT is a machine which vertically transports or lifts the people, materials, etc. from one floor to another of a building in a very controlled manner. Now-a-days every building is installed with elevators it’s like it became mandatory. Elevators are generally enclosed so usually the working components are not visible. But the major components of elevator are:
1. Elevator Car – The metal boxes or the platform which moves up and down.
2. Control Unit – The control system that directs the elevator car to the desired floors, and moves the passengers up and down efficiently, etc.
3. Electric motor – which lifts and lowers the elevator cars using steel ropes or metal cables.
4. Counterweight – the elevator car and the weight moves in opposite direction to reduce the strain on the motor and to balance the car.
5. Safety system – protects the passenger in situation like if the ropes or cable breaks, if power supply goes off, etc.
How elevators work
The most safe and efficient elevators are the Cable Elevators or Roped elevators. The steel cables are used to lift up and lower down the elevator car. These cables are attached to the car on the one side and counterweight on the other side. As the lift rises the counterweight descends. The counterweight weighs nearly the same as the elevator car when it is half full. Means, when the elevator car is half or 50% full with the passengers then it equals the counterweight.
The cables carrying elevator car and counterweight on the either sides are looped around a sheave. A sheave is nothing but a pulley with grooves used to hold the cables, as the sheave rotates the cable also moves. To rotate the sheave and external force is required, so an electric motor is installed and the sheave is connected to that electric motor. When the motor turns in clockwise direction, the sheave lifts up the elevator car and lowers it when the motor turns in anti-clockwise direction.
The electric motor uses very small amount of energy because almost all the work is done by the counterweight. It works as a see-saw, when the weight on the one end is heavy it becomes easy to lift the one on the other end and to lift the heavy load on the one end an extra force is required on the other end and that extra force is given by electric motor. On the Guide Rails, the elevator car and the counterweight move. The electric motor with sheave and the control system are installed at the top of the elevator shaft.
The Cable or Roped elevators are considered to be the safest elevators but how the safety system of elevators works and how they protect us from falling from heights if the cable breaks.
Each elevator is supported by multiple cables. But how many cables could break without the lift plummeting to the ground. If the elevator is mounted with six steel cables and five of them are cutoff then the one that is left over will hold your elevator up. Flat steel belts are being tested to replace the more conventional cables, just 3 mm thick these belts are strongest traditional cables that take less space, weighs 20% less and last three times as long.
Attached to each elevator is a governor rope which doesn’t carry any load but moves with the elevator car. This governor rope runs over its own wheel (the sheave) at the top of the shaft. If the governor starts spinning too fast showing that the elevator car is out of control then the sheave automatically stops. This stops the governor rope which in turn pulls down the brake bringing the elevator car to halt. If there is some more chance of brake fails there is a heavy duty shock absorber at the bottom of the shaft. It works like a giant buffer cushioning the elevator car.
In modern elevators, there are devices to ensure comfort and safety. An automatic elevator doors have an infra-red beam which sits inside the doorway.
If the beam is broken as the door closes, the door stops from getting closed and reopens so you don’t get squashed. These automatic doors open when the floor is arrived and closes it before the elevator car starts moving and runs on electric motor.
An electric motor is mounted on the top of the elevator car to which a long metal arm is attached. The metal arm is attached to the two doors – inner door and the outer door. As the metal arm moves both the doors move towards another end until the door is completely closed and vice-versa to open. These doors completely rely on the control system or the computer elevator which is embedded with the elevator algorithm.
Types of elevators
1. Passenger elevators:
• Size – Can accommodate from one person to more than a dozen
• Speed – 200 to 2000 ft/min
• Performance – specialized for the service they perform
• Uses – Hospital emergency, front and rear doors, double-Decker
2. Freight elevators
• Size – can carry from 2,300 to 4,500 kg of weight
• Speed – 50 to 100 ft/min
• Performance – large and can carry heavy loads
• Uses – used in industries, during high-rise construction buildings to carry material, instruments, etc
3. Sidewalk elevators
• Size – available in different sizes based on requirement
• Speed – up to 150 ft/min
• Performance – Controlled via external switch, consist of automatic doors
• Uses – used to move materials from basement to ground level
4. Stage Lift elevators
• Size – can lift up the entire stage with the performers
• Speed – manually operated
• Performance – powerful enough to lift an entire orchestra
• Uses – music halls, orchestra, theater stage, etc.
5. Vehicle elevators
• Size – can lift the weights more than 20 tons
• Speed – slow and steady
• Performance – improved accessibility, rotational elevator car
• Uses – used to lift Lorries, rail cars, heavy duty vehicles, etc.
6. Aircraft elevators
• Size – can lift up to 91,000 kg
• Speed – slow
• Performance – lifts fighter planes, aircraft’s, etc.
• Uses – to lift aircraft’s and also used within the aircraft’s such as in Boeing 747 to carry food from lower deck to upper deck
7. Residential elevators
• Size – depends upon the capacity of the residential building
• Speed – depends upon number of floors of building
• Performance – good safety system and design
• Uses – used in residential and commercial buildings
Across the globe elevators move more than two billion people a day. Before the elevators came into existence only five storeys were possible but now the record breaking skyscraper with 163 floors is made possible only because of elevators. It’s really a remarkable and the most essential machine.