- [Jared] Elevators
revolutionized the way we build and live in our cities. In this video, we'll be
exploring the different parts of an elevator, how it works,
and then the safety mechanisms which protect us as we ride
these amazing machines. (electricity crackling) (logo booms) In the 1800s, architects and engineers
were pushing the boundaries of how high we could build. As these buildings increased in height, there was somewhat of a limit. It was hard to utilize the upper floors because you had to walk
up a lot of stairs, and no one really wanted
to do that every day. The reason we started to build higher is because of elevators.
(elevator door dings) In many parts of the world,
it is referred to as a lift, but in this video, I'll
use the word elevator. The elevator is not a recent invention. The idea of using a machine
to lift things in the air, this is not a new idea. It can be traced back
to ancient civilizations over 2000 years ago. Various lifting devices such as hoists or cranes, these have been used in various places like factories and construction sites; but lifting people, that
usually wasn't done. If that rope snaps, there is nothing stopping you
from falling to the ground. In the early 1850s, Elisha Otis invented a safety mechanism that changed everything. Let's take a look. (gentle music) This is a simple lift that can be raised or lowered by the rope. The safety mechanism is
made up of a leaf spring, two pivot arms, and the
teeth on both sides. When the lift is being pulled upward, the pivot arms are rotated,
allowing the elevator to rise. But if the rope suddenly
loses tension for any reason, the leaf spring immediately
pushes the pivot arms down, which then comes in contact
with the metal teeth. This stops the elevator
from falling to the ground. Mr. Otis was so sure of his invention that he demonstrated
it to a crowd of people at the World's Fair. He lifted himself up on the elevator and then had someone cut
the supporting rope above. He only fell a few centimeters. This demonstration convinced the public that elevators could be safe
enough for people to ride. Elevators today have multiple
safety mechanisms in place, but it all started with Elisha Otis. Over the coming decades, elevator shafts became the
core of most buildings. This allowed for skyscrapers
to reach new heights and for the buildings
to be fully utilized. And of course, we have to
mention the revolving stairs, or more commonly known
today, the escalator, helpful for moving large amounts of people but only up a few floors. Once those buildings get really tall, the best solution? (elevator door dings)
The elevator. (lively music) (elevator door dings)
Ah, that music. But for this video, we'll pick up the pace just a little bit. (upbeat music) Let's go over some basic
parts of the elevator. Now, there's a lot of
different elevator companies and different ways to make elevators. Some of the mechanisms and names will be slightly
different depending on the elevator, so keep that in mind. This is called the shaft or the hoistway, the elevator pit at the very bottom, then we have the cab, which moves up or down inside the shaft, and these are the guide rails. The cab usually has
guide rollers to move it along the rails. There are two main types of elevators, hydraulic elevators
and traction elevators. In real simple terms, traction elevators lift the
cab from above using cables, and the hydraulic elevators
push the cab up from underneath. For most of this video, we're gonna look at traction elevators. These are the ones you'll find
in really tall skyscrapers. But first, let's at least get the basics of the hydraulic elevator. This uses a cylinder and a piston. These usually extend several
floors beneath the ground so there's enough length
to push the elevator up. Close by, you'll find a machine room with a pump unit filled with oil. When the elevator needs to go up, the oil is pumped through the
pipes and into the cylinder. The pressure pushes the piston up, which raises the elevator into the air. You'll find hydraulic
elevators in smaller buildings, usually not more than six stories tall. This is due to the length of the cylinder and the pressure involved
to push the piston up. (bright upbeat music) Okay, traction elevators. Are you ready? Traction elevators are most
common in taller buildings. In some places in the world, these elevators can service
more than 100 floors. Let's not get two carried away, though. I'm gonna demonstrate this
with just four floors. We'll keep things simple. At the very top is the machine room. This is where you'll
find the electric motor. The motor pulls the cables
by turning the sheave, which is basically a
special kind of pulley. On one side, the cables go
down and attach to the cab, and on the other side, it
attaches to the counterweight. The counterweight moves
opposite to the elevator cab. So why do we have this counterweight? Without the counterweight, the motor would have an
enormous amount of tension on only one side. It would have to work a lot
harder to lift or lower the cab. The counterweight makes it
so that there is less strain on the motor. All it has to do is tip the balance so the elevator moves up or down. The counterweight will
weigh as much as the cab when it's about halfway filled up. Ideally, the system will work best if it's perfectly balanced, but this won't always be the case. The weight of the elevator
cab will frequently change. This is the controller box. It's like the brains of the elevator, safely moving it up and down. Not all traction elevators
are going to have a dedicated machine room. They're able to fit the
motor and other components at the very top of the elevator shaft. They refer to this as a machine
room less elevator, or MRL. We won't go into detail about these, but I at least wanna mention them so you know that they exist. Elevators have many
safety features built in to protect the passengers
riding in the cab. First, you have the machine brake. This is used to stop the
spinning of the motor and hold the cab steady. There are usually at least
four cables holding up the cab, sometimes as many as eight cables. Each of these cables is strong
enough to hold the weight of a fully-loaded elevator. The likelihood of all of these cables
snapping is very small, but if it did happen,
you would still be safe. Let me show you. Do you remember Mr. Otis' safety mechanism at the beginning of this video? The modern version of this
is a little different, but the main idea is still the same. At the bottom of the elevator
cab is the emergency brake. There are two clamps, and these are located on
both sides of the guide rail. Normally, they don't touch so the elevator is allowed
to move up and down. But if the lever is pulled, then they move in and grip the guide rail which stops the elevator from falling. The lever is connected to a cable, and this is a separate cable from the ones that lift the cab. This cable attaches to
another wheel at the top. Let's take a look. Back up here in the machine room, this device is called
the overspeed governor. Normally, this spins along
with the elevator cab as it moves up and down. Inside is a mechanism with two flyweights. Let's say, for whatever reason, that the cab starts to
move downward too quickly. The overspeed governor will spin faster. It spins too fast, these
flyweights will move outward and catch the gear teeth on the side. This will stop the spinning,
which stops the cable, and the weight of the cab now
causes the lever to go up, and there's clamps on both
sides of the elevator, which firmly hold it in place. Now, if you do happen to
get stuck in an elevator, don't try and force
the door and climb out. Press the emergency call button to get connected with
someone who can send help. Let's talk about that door mechanism. (elevator door dings) There are essentially
two doors on an elevator. On each floor, you'll find a door. These are usually called
the hoistway doors. And then on the elevator cab itself, you'll find the cab door. So when these are together, we have the cab door
and the hoistway door. We don't want either door to open unless the cab has come to a complete stop at the correct floor.
(elevator door dings) These doors also have
sensors so they won't close if something is in the way, and the elevator won't start moving until the doors are completely closed. Let's look at just the cab for a minute. The door operator is located at the top. This turns some gears,
which pulls on the lever, which slides the door open. Notice how each of the hoistway
doors does not have a way to open by themselves. The doors can only be
opened by the door operator on top of the cab. When this opens, it will pull
the hoistway door with it. Each of the hoistway
doors has an interlock. This ensures that it won't open until the cab is right behind it. Let's look at the mechanism. Each hoistway door has a beak. When this is down, the door won't open. Push up on this bar, and the beak goes up. This allows the door to open. Down below, you'll find
two black pickup rollers. Push the one on the left, and it rotates, which pushes up on the bar,
which unlocks the door. So how does this get unlocked then? Well, I'm glad you asked. On the cab door, there's
a piece called the clutch. As the cab moves up and down, the clutch moves right around the rollers. When the cab stops,
the cab door will open. The clutch will push on the pickup roller, which will unlock the mechanism. Both doors can now slide open together. In a rescue situation, or
maybe even for maintenance, the workers can use a special
key to unlock the door, even if the cab isn't right behind it. Now, a key like this should only be used by authorized personnel who have a good reason
to be opening the door. And of course, be safe around elevators. Please don't be fooling around. Be responsible and use these machines as they are intended to be used. (uplifting music) My name's Jared. I create 3D animations to show
and explain how things work. Click the cards to watch another video, or click here to subscribe. Thanks for watching, and
I'll see you next time. (uplifting music)
