How Do Vacuum Cleaners Create Suction?

[Inquiring_Mike]

I was watching my mother vacuum the floor today. How do they work? What produces the suction?

 

[Doc]

Vacuum tubes.

Nah, just kidding. It is produced by a fan.

 

[zoobyshoe]

Taking apart an old vacuum cleaner
is something I would recommend
everyone do at least once in their
life.

The powerful motor drives a fan
as doc said, but the fan is speci-
ally engineered. It is two thin
plates of sheet metal and the
blades are curved pieces of metal
that separate the two plates.
There is a large hole in one of
the plates. When the motor spins
the fan air is thrown out radially
from between the plates. This
causes more air to be sucked into
the hole.

The air is blown into the dust bag
where the dust is trapped and the
"filtered" air is squeezed back
out into the atmosphere through
the pores in the bag and its cover.

The motor also drives a revolving
brush via a belt which loosens
dirt fron the carpet and helps
throw it up into the fan blade.
When you suck up a penny or screw
the machine will complain. This is
the object encountering the fan.
Some less well engineered vacuums
have plastic fan blades that you
can break if you suck up anything
of substance. Some vacuums are
rigged so that everything coming
in actually bypasses the fan. The
one I had like this wasn't as
powerful as the other type.