How Vacuum Cleaners Work

In the last section, we saw that the suction created by a vacuum cleaner's rotating fan creates a flowing stream of air moving through the intake port and out the exhaust port. This stream of air acts just like a stream of water. The moving air particles rub against any loose dust or debris as they move, and if the debris is light enough and the suction is strong enough, the friction carries the material through the inside of the vacuum cleaner. This is the same principle that causes leaves and other debris to float down a stream. Some vacuum designs also have rotating brushes at the intake port, which kick dust and dirt loose from the carpet so it can be picked up by the air stream.

As the dirt-filled air makes its way to the exhaust port, it passes through the vacuum-cleaner bag. These bags are made of porous woven material (typically cloth or paper), which acts as an air filter. The tiny holes in the bag are large enough to let air particles pass by, but too small for most dirt particles to fit through. Thus, when the air current streams into the bag, all the air moves on through the material, but the dirt and debris collect in the bag.

You can put the vacuum-cleaner bag anywhere along the path between the intake tube and the exhaust port, as long as the air current flows through it. In upright vacuum cleaners, the bag is typically the last stop on the path: Immediately after it is filtered, the air flows back to the outside. In canister vacuums, the bag may be positioned before the fan, so the air is filtered as soon as it enters the vacuum.

Using this basic idea, designers create all sorts of vacuum cleaners, with a wide range of suction capacities. In the next section, we'll look at a few of the factors that determine suction power.

In the last section, we saw that vacuum cleaners pick up dirt by driving a stream of air through an air filter (the bag). The power of the vacuum cleaner's suction depends on a number of factors. Suction will be stronger or weaker depending on:

At the most basic level, this is all there is to a vacuum cleaner. Since the electric vacuum's invention a century ago, many innovative thinkers have expanded and modified this idea to create different sorts of vacuum systems.

So far, we have looked at the most typical types of vacuum cleaners: the upright and canister designs, both of which collect dirt in a porous bag. For most of the history of vacuum cleaners, these have been the most popular designs, but there are many other ways to configure the suction system. We'll look at some of these in the next section.

The first vacuum cleaners, dating from the mid 1800s, used hand-operated bellows to create suction. These came in all shapes and sizes, and were of minimal help in daily cleaning. The first electric vacuum cleaners showed up in the early 1900s, and were an immediate success (though for many decades they were sold only as a luxury item).

One very popular vacuum-cleaner design from this era is finding a resurgence in popularity today. This design, the central vacuum system, turns your whole house into a cleaner. A motorized fan in the basement or outside the house creates suction through a series of interconnected pipes in the walls. To use the cleaner, you turn on the fan motor and attach a hose to any of the various pipe outlets throughout the house. The dirt is sucked into the pipes and deposited in a large canister, which you empty only a few times a year. For more information, see How Central Vacuum Systems Work.

Wet/Dry Vacuums

For heavy-duty cleaning jobs, a lot of people use wet/dry vacuum cleaners, models that can pick up liquids as well as solids. Liquid material would soak paper or cloth filters, so these cleaners need a different sort of collection system.

The basic design is simple: On its way through the cleaner, the air stream passes through a wider area, which is positioned over a bucket. When it reaches this larger area, the air stream slows down, for the same reason that the air speeds up when flowing through a narrow attachment. This drop in speed effectively loosens the air's grip, so the liquid droplets and heavier dirt particles can fall out of the air stream and into the bucket. After you're done vacuuming, you simply dump out whatever has collected in this bucket.

Next, we'll look at two more innovations in vacuuming: the cyclone vacuum and the robotic vacuum.

One recent vacuum-cleaner variation is the so-called "cyclone vacuum." This machine, developed in the 1980s by James Dyson, doesn't have a traditional bag or filter system. Instead, the Dyson sends the air stream through one or more cylinders, along a high-speed spiral path. This motion works something like a clothes dryer, a roller coaster or a merry-go-round. As the air stream shoots around in a spiral, all of the dirt particles experience a powerful centrifugal force: They are whipped outward, away from the air stream. In this way, the dirt is extracted from the air without using any sort of filter. It simply collects at the bottom of the cylinder.

The cyclone system is a marked improvement on traditional vacuum cleaners -- there are no bags to replace and the suction doesn't decrease as you suck up more dirt.

Robotic Vacuums

Until recently, no matter how powerful the vacuum, someone still had to be there to push it around. Enter the robotic vacuum. These little gadgets clean all by themselves, thanks to a combination of motors, sensors and a navigation system. To explore one in more detail, check out How Robotic Vacuums Work.

In the future, we are sure to see even more improvements on the basic vacuum-cleaner design, with new suction mechanisms and collection systems. But the basic idea, using a moving air stream to pick up dirt and debris, is most likely here to stay for some time.

For more information on vacuum cleaners and related topics, check out the links on the next page.