Central Vacuum Systems and Wet/Dry Vacs
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.
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.