How do elevators or lifts work ?

Seriously, what would have happen if there were no elevators & if people were to walk up &  down a 50 or 100 storey building everyday in cities like NY ! I can’t even imagine the fatigue.

Well, keeping our thought aside, let us see how do elevators work ?

Elevators :-
Ok, as everyone knows what is an elevator, we will see what will it be called by those crazy physicists & engineers in their technical language. They would say – An elevator is a machine which lets us increase or decrease our potential energy. And yes it does that. Suppose you are on floor 1 & you need to  go on floor 10, what you need to do is just increase your potential energy, since P.E is directly proportional to height of object raised from the ground. This is an example of law of conservation of energy. You really do have higher P.E on the top floor even if you don’t feel  energetic(the feel after having a Red Bull).

so how do they work ?
The car is connected to a pulley system through steel or metal cables. The electric motor drives the pulley which pulls up or down the car(now we will see changes in the design as it was just rough idea).
We will see one by one parts of a lift (called in British language) along with their contributions in working.

lift

The basic main parts of an Elevator.

Counterweight :-
You must have observed this one. You can see this thing on ground floor whenever an elevator is at the top floor. When the lift starts coming down, the counterweight starts moving upside & vice versa. But why do we need it ?
Imagine the lift has to go up on 10th floor now being on ground floor & it will require 1000 KJ of energy. What these smartass’s have done – they have joined a counterweight on the other end of the cables. Now what happens, the electric motor above require less energy to lift you because our friend – Mr Counterweight is already helping us by pulling us up. Which means instead of 1000 KJ, this time you would need less amount of energy like 500 KJ thereby consuming less power.  There you go.

The counterweight makes it easier for the motor to raise and lower the car just as sitting on a see-saw makes it much easier to lift someone’s weight compared to lifting them in your arms. Also a heavy loaded elevator car would be hard to pull up but will race down to the ground while coming down. All thanks to counterweight, which makes it easier to control the car. A counterweight weighs almost half of a fully loaded car.

Doors :-
The automatic doors of the car are essential & are very convenient to handicapped people. A typical automatic door systems consist of a motor which is connected to an arm which is again connected to a long metal arm which is attached to the door. The door then can slide back & forth on the metal rail.
When the motor turns the wheel, it rotates the first arm which results in rotation of second long metal arm too which closes or opens the door.The door is made up of two panels which close in on when the door opens & extend when they close. You can visit this link to see the animation.
Also many elevators have a motion or ultrasonic sensor which keeps the doors from closing if somebody is between them. Source

Electronic systems :-
Basically what they call is the “elevator algorithm” is fed into the lift’s computer system – to stop at floors to which the buttons represent, alarms etc.

Safety :-
Making the cables from steel strands doesn’t assure a 100% guarantee of safety. So Otis elevator(Otis -the one who designed it) had a ratchet system as a backup. Each car ran between two vertical guides with sturdy teeth all the way to the top. If the cables broke, a spring loaded mechanism with hooks sprung outside engaging into the metal teeth. So now you are somewhere stuck in between the floors but you are SAFE. These mechanisms were used on Otis elevators & only few of them have it today.

otis-elevator-patent

Black colored teeth pointing upwards in Otis Elevator.

What if the teeth or hook breaks or bends & the car doesn’t stop ?
So, as a second backup, there are giant hydraulics or gas spring buffer located at the bottom to absorb the impact of collision. So don’t worry you are safe.

Some quick facts :-

  • The first safety elevator was designed by Elisha Graves Otis.
  • The Taipei 101 tower in Taipei, Taiwan has the fastest elevator having a stunning & mind-boggling speed of 60 km/hr(37.7 mph) !!!!! The elevators even has pressurized cylinders to prevent ear popping !

&  now you are free to think what would have happen if there were no elevators & if people were to climb up & down a 50 storey building everyday 😛 !

sources:-
https://en.wikipedia.org/wiki/Elevator
http://www.explainthatstuff.com/how-elevators-work.html

 

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