by Chris Woodford. Last updated: December 21, 2016.
Even when your house is clean, it's
absolutely filthy! That's because most of the dust and dirt in your house is way too small to
see. Fortunately, most of us can live without knowing this kind of truth about our homes;
a quick run around with the vacuum cleaner is enough to keep us happy.
Twenty-first century homes are packed with dozens of appliances and
gadgets, but vacuums are one of the few most of us simply couldn't live
without. We all know vacuums suck up dirt—but how exactly do they work?
And what makes a modern-style cyclonic cleaner different from an old-style bag cleaner?
Let's take a closer look!
Photo: Left: A Dyson cleaner, like this one, shows you just how much dirt it's picking up in its transparent bin. The dust and hair tends to swirl around thanks to the machine's "cyclonic" action. Other popular makes of vacuum cleaner (including Hoover, Miele, and Electrolux) also now make bagless cleaners, though they tend to work in a different way: they generally use internal filters to separate out dust and dirt, which is deposited in a plastic bin, while the air returns to the room through a grille in the back of the machine.
Vacuum cleaner or suction cleaner?
Photo: Not all floor sweepers use vacuums. This cordless Gtech SW01 sweeper has two rotating nylon brushes at the front that flip dust and hair into a slide-out plastic dirt bin (which I've opened up slightly, top right). Turn it over and you can see the main brush bar (with its purple bristles) and a smaller rotating brush (with black bristles) for cleaning edges (middle right). It weighs just 1.6kg and runs for 30–60 minutes on a full, 16-hour charge. All this machine has to do is spin the brushes, so it can get by with a tiny 7.2-volt electric motor (much smaller and less power-hungry than the motors in large vacuum cleaners, which, as we'll see below, also act as suction fans).
The name "vacuum cleaner" is a bit of a giveaway when it comes to
understanding how your machine works: vacuum cleaners work by suction.
("Suction cleaner" would be a better name than vacuum cleaner, in fact, because there's no actual
vacuum involved. There is a difference in air pressure, but nowhere is there is an absolute vacuum.)
If you've ever tried that cleaning trick with a tissue paper and a comb,
you'll know how effective suction can be for removing dirt. If not, try it now! Wrap a piece of tissue
paper around a comb. Breath out as far as you can and hold your breath.
Place the comb and paper against your mouth. Now lean against a dusty
armchair and press your mouth and the comb against it. Breath in
sharply so, effectively, you are breathing straight through the comb.
Take the comb away from your mouth and inspect the tissue paper. See how
dirty it is!
Now imagine what would happen if you could keep this trick up for hour upon hour, just
like a vacuum cleaner. Eventually, the dirt would build up on the tissue paper to such an
extent that air would no longer flow through it properly. Your ability to clean—as a
human vacuum cleaner—would be greatly impaired. This is a very important point: for
a vacuum cleaner to work effectively, it has to maintain powerful suction the whole time.
If its bag is full or its filters are clogged up, its suction will be dramatically reduced
and it won't pick up dust. This is a problem that plagues almost every type of vacuum
cleaner—even the bagless, cyclonic ones that are now so popular.
Vacuum cleaners with bags
Invented in 1901 by a British engineer, the first electric
vacuums were simple sucking machines with a brush and suction head at
the front, a motor in the middle, and a bag at the back. When you
switched them on, the motor whirred into action, sucking in air and
dirt and blowing them into the bag.
Think back to the "suck and filter" comb trick and you'll understand straight away how these old-style, bag vacuum cleaners work. In place of your
mouth, there's a powerful electric motor
attached to a fan that sucks in air. Instead of
a tissue paper and comb, there's a dirt bag (sometimes a disposable paper bag inside
a fabric bag), which catches the dust sucked in so you
can use the cleaner for some time without worrying about where all the
dirt is going. The bag isn't completely airtight, as you might think.
Air can pass out of it, though not dirt, so it effectively acts as a filter; the air is sucked
into the bag and then escapes through it, leaving the dirt behind inside it.
This diagram summarizes what's happening inside a conventional vacuum:
- Electricity outlet supplies energy to the cleaner's electric motor.
- In a typical cleaner, the electric motor is rated at about 500–1000 watts, so it
uses five to ten times as much energy as an old-style
- Rubber belt (blue) powered by electric motor turns brushes and beaters on the roller at the front of the machine.
- Vigorous beating and brushing loosens dirt from the carpet or rug.
- Fan attached to the electric motor sucks air and loosened dirt in through the front of the machine.
- Dirty air travels through to the back of the machine, cooling the electric motor as it passes by.
- Dirt is trapped in the bottom of the dirt bag (which may be a single fabric bag or a disposable paper bag fixed
inside a fabric bag).
- Relatively clean air emerges out of the back. Note that the outgoing air is much warmer than the incoming air
because it's picked up waste heat from the electric motor.
How does a bagless vacuum cleaner work?
Most modern vacuums have done away with bags and use easy-to-empty plastic bins instead. That means they need to use filters to separate the dust from the air (which is the job the bag used to do). Here's the setup in a typical modern, bagless Electrolux
cleaner. You'll notice that the airstream, which I've indicated with a large yellow arrow, is linear (a straight line) from
the hose at the front through to the grille at the back, just as it is in an old-style bag cleaner.
- Inlet: This attaches to the usual cleaning head and interchangeable tools (not shown).
- Dirt collecting bin: Normally this sits inside the cleaner at the front, but I've removed it and placed it on its side so
you can see things more clearly.
- HEPA filter: The filter is a cylinder of folded paper attached to the orange bit you can see at the base of the dirt bin. The air is sucked through the filter, leaving the dirt behind in the bin. You can see some photos of the actual filters from this machine in our article on HEPA filters.
- Motor unit: This cleaner has a very powerful 2000-watt motor, although it does need it to pull air through the HEPA filter. Motor ratings for cleaners with HEPA filters can be quite misleading: they don't necessarily give you more suction at the cleaning end, because
more of their power is used pulling air through the filter, which may clog frequently.
- Filter and outlet grille: This is a simple bit of sponge that you can remove and wash.
Cyclonic vacuum cleaners
Most vacuums used this "suck and bag the dirt" process until the late 1980s, when another British engineer named James Dyson felt it
was time to go one better.
The trouble with old-style vacuum cleaners is that they suck in
dirty air and blow it directly into the bag. The bag catches the dirt
and the relatively clean (but often still quite dusty) air drifts back into the room. The longer you
use a vacuum, the more the bag fills up. As the bag fills up, the
amount of empty air it can hold decreases, so its ability to suck in
more dirt is gradually diminished. The longer you go without emptying
your vacuum, the worse the problem becomes. But emptying the bag is
a real nuisance—and the dust can go everywhere!
Photo: Vacuum cleaners work just like the comb and paper trick using
two, sophisticated HEPA filters. Top: Lower filter: Take the
dust-collecting bin off a Dyson and you can see one of the two HEPA filters (beneath the circular grating).
This is actually the air outlet: clean air that has passed right through the machine passes through
this filter and returns to the room. Bottom: Upper filter: There's another, much more important filter at the top of the dust bin. This one cleans the air immediately after it has passed through the cyclone (after the bulk of the dust and dirt has already been removed).
Goodbye to the bag
Dyson decided to tackle this difficulty by doing away with the bag
altogether. By this time, he was already a successful inventor
manufacturing his own plastic garden equipment. His factory in
England's West Country was plagued with dust, so he designed a
"cyclonic" air filtering device to keep it clean. Using a powerful fan,
it sucked in dusty air and spun it around at high speed like a
centrifuge. Spinning the
dusty air was an effective way to separate the dust out of the air. In
a washing machine, the same
principle is used to
spin water from clothes at the end of the wash cycle. As the drum spins
at high speed, the clothes fling against the edge of the drum and the
water they contain is forced out through the drum's tiny holes. The
same idea proved just as effective in Dyson's air filter. Spinning the
dirty air separated out the heavy dust particles, which could be trapped and collected;
the cleaned air could then be piped
back into the room. Dyson's machine was so efficient and successful that he
wondered why vacuum cleaners didn't use the same idea. He resolved
to invent a cyclonic vacuum cleaner there and then.
Now it's very important to point out that Dyson did not invent the idea of
using a cyclone to remove dust from air. In fact, if you look at his original patent
(Vacuum cleaner appliances,
dated 1983), you'll find he references quite a number of earlier inventions ("prior art"),
the first of which is Bert M. Kent's
Vacuum Creating and dust-separating machine
developed 70 years before, in 1913, and patented in 1917. Kent clearly states that one of his objects "is to
provide a machine... in which the 'cyclone' principle of dust separation is employed and the use of screens
avoided." Dyson's genius, however, was to apply this principle to a relatively compact, household vacuum cleaner and persuade
people that it was more effective than the vacuum cleaners they'd become used to; it was as much about
marketing as anything else—which is true of all great inventions.
Perfecting the invention
Between the late 1970s and the mid 1980s, Dyson built no fewer than
5,127 prototypes of his cyclonic cleaner. By the late 1980s, he was
selling a bright pink cyclonic cleaner called the
in Japan. It was large, clumsy, and expensive, but it earned him enough money to
develop a more compact, affordable cyclonic vacuum called the DC01.
During the mid-1990s, this new machine won countless design awards and
soon became Britain's biggest selling vacuum cleaner—and machines based on this design are
now sold worldwide.
Its secret is simple: because there is no bag to clog up with dust and
dirt, the machine always sucks with exactly the same power.
You still have to empty the dirt bin every so often, but the cyclonic
action means a Dyson with a full dirt bin works equally as well as one that's
just been emptied.
All this goes to show that, no matter how good an invention appears
to be, someone can always make it better!
(Talking of improvements, have you seen robotic vacuum cleaners
that clean your home automatically?)
Key parts of a Dyson vacuum
So how does a Dyson actually work. First, let's quickly run through the key parts you'll find on one of the classic early models: the Dyson DC04 upright:
- Brush bar and air intake: The rotating brush under this bar loosens dirt in the rug so the vacuum's suction can pull it in. This is much the same as in a conventional vacuum.
- Height adjustment: Allows you to use the cleaner on hard floors, rugs, and other surfaces. When the vacuum is upright, the rotating
brush is switched off. Air sucks in through an extension hose at the top of the machine instead.
- Powerful electric motor: This is effectively a giant fan that sucks in air and pulls it through the machine's cyclone and filters. As you've probably noticed, the motor in a vacuum cleaner gets quite hot after a few minutes; that's why the cool air it sucks in emerges from the machine somewhat hotter. On this Dyson, the air outlet is at the bottom, just underneath the dirt bin. Put your hand there and you'll feel warm air blowing out.
- Transparent plastic dust collection bin. The bin on this cleaner is absolutely full. One interesting thing worth noting on Dysons is the way their centrifugal, spinning action sorts dust particles into bands of different sizes, much like a centrifuge. You can just about see in this photo that there's a band of grit at the bottom of the bin, followed by a darker band of bigger dirt particles, with lighter fluff sitting on top.
- Cyclone: The cyclone is a large yellow plastic cone that points down into the dust bin:
The cyclone is the most important part of a Dyson. You can see from this photo that it's a tapering,
cone-shaped piece of plastic with small holes in the top. The electric motor sucks dirty air into the top of the
cyclone, where it whirls around at high speed. While the air is drawn through the cone, the dust spins around, drops down, and collects in the clear plastic bin beneath ready for disposal.
Just above the cyclone is the upper dust filter (it's inside the gray cylinder, above the yellow cyclone, in the photo of the HEPA filters up above). There's one filter immediately above the dust collection bin and a second one at the bottom of the machine. The air passes through this second filter, for an extra clean, just before it returns to the room.
- Air hose: The electric motor sucks air through the Dyson along a network of tubes. The air is piped to the top of the machine, pulled and whirled through the cyclone, before returning through this pipe to the bottom of the machine. You can see the actual airflow through the machine in the photo down below.
How does a cyclonic vacuum cleaner work?
Now we've seen the parts, how do they all work? Here's a rough guide to what everything does as the air flows through a typical multiple-cyclone vacuum cleaner. In this model:
- Air enters through the brush bar at the bottom.
- The air enters the first stage tangentially (perpendicular to the cylindrical dirt bin) and spins around the cyclone in the middle. The dirt particles swirl to the edge, fall downward, and collect at the bottom while the air is drawn up through holes in the cyclone itself.
- The somewhat cleaner air passes into the second, upper stage.
- Here, a similar process happens only with a number of smaller cyclones that remove much finer dirt particles.
- The relatively clean air passes through a HEPA filter. Since most of the dirt has already been removed,
this filter doesn't really impede the flow of air through the machine.
- The air blows back into the room after passing through a second HEPA filter.
The motor unit (not shown on this drawing) and fan is located at the base of the machine in between the two back wheels.
Please note that this drawing is not an exact representation of what happens in a Dyson (or any other, similar machine): it's just designed to give you a very general idea of what's happening in a cyclonic cleaner. In a Dyson DC04, like the one photographed up above, the air flow is actually like this:
I've removed the cyclone and dustbin, moved it to the side, and turned it backwards so you can see clearly what's happening. The red line shows the airflow up to the point at which it enters the cyclone. The orange line shows the airflow after the air exits the cyclone. The air enters through the brush bar, passes up a pipe at the side of the machine to the top, where it enters the cyclone, spins around, passes through the upper HEPA filter, then leaves through a second pipe also near the top of the machine, before traveling back down another pipe to the fan and the lower HEPA filter and finally exiting just underneath the dirt bin.
If you'd like to know more, please refer to one of the patents in the reading list down below, where you'll find complete technical drawings and a detailed explanation of how everything works in an actual machine.
When it comes to suction, conventional vacuum cleaners tend to... suck, for want of a better word. Bulging bags and clogged filters progressively reduce the airflow and the suction, making it impossible for them to pick up more dirt effectively. Without filters, however, they blow quite a lot of the finer dust (the harmful particles known as PM10s, smaller than 10 microns) back into your room; so, instead of "vacuum cleaning", they are simply "dust rearranging": sucking in dirt and blowing it back out so it settles somewhere else. That's a particular problem for people with asthma or dust allergies.
Artwork: A simplified water vacuum cleaner.
What's the solution? One option is to use a water vacuum, which uses a tank of water to trap the dirt instead of a bag or conventional dirt bin. The dusty incoming air fires into the water tank, where the dirt is held in solution. The moist air that leaves the tank is then spun around to remove the water (a bit like in a Dyson), producing clean air that flows back into the room.
Here's how a typical water vacuum works:
- Air is sucked in through the brush bar in the usual way.
- A powerful motor (not shown) pulls the air through a water tank, where most of the dirt is trapped.
- The moist air continues through the tank, spiraling past plastic plates, which help to separate out the water droplets from the air that carries them. The water drips back down into the tank.
- Clean, dry air exits through an outlet on top of the machine.
Find out more
On this website
- Electrical Appliance Manual by Graham Dixon. Haynes, 2000. Basic maintenance and repair guidance for common vacuums and other domestic appliances.
Artwork: One of Hoover's original vacuum cleaner patents. This one dates from around World War II and was filed by William D. Sellers and Alfred G. Gross in 1939. All the basic features are in place—the rotating brush bar at the front (red), the fan (center), the belt drive (green), and the bag outlet at the back (yellow)—in a design that would remain largely unchanged until Dyson's innovations appeared in the 1980s. For more details, see US Patent: 2343227: Suction Cleaner. Artwork courtesy of US Patent and Trademark Office.
There are dozens of patents covering cyclonic and other types of vacuum cleaners, including many filed by
James Dyson and his associates. Here are a few worth looking at if you want to study cyclonic vacuum cleaner design in more detail:
- Vacuum Creating and dust-separating machine by Bert M. Kent. US Patent #1,220,641. This is the earliest cyclonic dust separator I've found.
- Vacuum cleaning system by Norman Davis. US Patent #3,425,192. This multi-cyclone design, assigned to the John E. Mitchell Company, bears a strong visual similarity to Dyson's later, multi-cyclone designs.
- Vacuum cleaner appliances by James Dyson. US Patent #4,373,288. I believe this is Dyson's original cyclonic vacuum cleaner patent, filed April 15, 1980 and granted February 15, 1983.
- Cyclonic separating apparatus including upstream and downstream cyclone units by Peter David Gammack et al. US Patent #6,994,740. A more sophisticated Dyson cleaner design from 2006.
- Cyclone dust separating apparatus and vacuum cleaner having the same by Jang-keun Oh et al. US Patent 7,361,200. An alternative, more compact cyclonic design from Samsung.
For a detailed look at a typical water vacuum, try:
If you liked this article...
You might like my new book, Atoms Under the Floorboards: The Surprising Science Hidden in Your Home, published worldwide by Bloomsbury.
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