A vacuum cleaning machine is a surprisingly complicated piece of equipment.  The many engineering formula, materials science, and human ergonomics brought together in a single machine is quite impressive.  All of these engineering disciplines circle around a single fundamental principle. That principle is the establishing of an air pressure vacuum on demand and wherever an operator chooses.  The air pressure vacuum is then used to  perform a useful task of transporting other loose materials from a resting state to an agitated state and then back to a resting state.

Let’s look at the air pressure vacuum first and then how it applies to a cleaning machine.

What is a vacuum: A vacuum is a measure of lower air pressure as it relates to normal (ambient) atmospheric air pressure around the Earth. The ambient atmospheric air pressure at sea level around the globe is approximately 14.7 pounds per square inch (PSI). A vacuum air pressure would be any measured pressure less than 14.7 psi. Air pressure is understood to be the force applied per square inch by atmospheric compounds.

Gravity is constantly pulling atmospheric compounds (air) towards the earth. Thus, the weight of air exerts a force measured in pounds. The closer airs get to the earth the more gravity exerts an attractive force pulling it towards the earth. The farther air is from the earth the less gravity exerts an attractive force and the less it weighs.

So, as one measures air pressure at sea level ( a level that is constant around the globe 14.7 psi) and then again at the top of Mt. Everest, there is less air pressure at the top of the mountain (10 psi).

One can say that there is a 4.7 psi vacuum present at the top of Mt. Everest compared to sea level ambient air pressure of 14.7 psi. The mathematical formulae would look something like this:

Ambient pressure at sea level (14.7psi) – Ambient pressure at Mt. Everest (10 psi) gives a 4.7 psi difference in air pressure) [14.7psi – 10psi = 4.7psi]

What difference does this make? – A lot!

If we were to box up 1 cubic foot of air from the top of Mt. Everest and a 1 cubic foot of air at sea level and place the boxes side by side with a perfect seal around the common side between the two, we would have one box with low air pressure and another with high air pressure. If we then were to drill a hole from one box through to the other, there would be a sudden breeze and maybe a whistle sound as air from the high pressure box moved rapidly to the low air pressure box. Once the pressure equalized in each box, the breeze would stop and the two boxes would have the same air pressure.

[ENGINEERING NOTE] => This example follows the second law of thermodynamics where the total energy of two systems (entropy) is not lost, but is transferred from unequal states (high air pressure and low air pressure) to a common state (equal air pressure).

If we wanted to maintain a constant breeze (airflow) through the hole between the two boxes it would be necessary to maintain an air pressure imbalance between the two boxes.   One box would need to be at a lower air pressure than the other box.  This condition would maintain an airflow from the higher pressure box to the lower pressure box.

The basic operating principle behind a vacuum cleaning machine is to create an air pressure vacuum by mechanical means, thereby establishing an airflow to equalize the air pressure differential.  This is accomplished through the use of a power plant.  The power plant is typically an electric motor with a fan assembly attached.  The fan assembly, when it spins, creates an air pressure vacuum.  The air pressure vacuum and associated airflow is used to transport loose materials from one point to another.

Engineers use the airflow in various ways, manipulating the speed and volume of air to suit their needs.  There are many ways by which a manufacturer can manipulate airflow to meet different physical designs of their equipment.  By reducing the diameter of hoses the airflow speed can be increased, but the volume decreased.  By increasing the pressure differential so there is more vacuum generated by the power plant, the manufacturer can increase volume of airflow.

In the diagram here airflow is proceeding through a hose and into the torpedo shaped vacuum.   Here it is entering a filtration wast canister and then passing through the fan assembly and power plant finally exiting the machine at the rear.

[ENGINEERING NOTE] =>  This style machine becomes increasingly less able to introduce floor dirt into an air stream due to the impedance of the airflow as the waste container becomes full of floor dirt.  The airflow must pass through the filtration bag (waste container).  More dirt means less airflow.  The problem with this style is that as the filter bag becomes full, the power plant motor overheats due to lack of airflow necessary to cool it.

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