A vacuum pump moves air, powders, fluids etc, by creating a vacuum.
When air is removed from a sealed space, it creates a pressure deficit which allows the product to flow into that space. In other words, the product moves from a place of higher pressure to a place of lower pressure.
The first vacuum pump was created in approximately 1650, but it is likely that suction pumps have been in existence for thousands of years, because a bamboo reed used as a straw would qualify as a primitive, man-powered suction pump.
Vacuum pumps are usually classified in one of three basic categories: positive displacement, entrapment or momentum transfer, also known as molecular.
Positive displacement pumps use a mechanism in which they alternate the expansion and sealing off of a cavity. They are used mainly for lower vacuums and can also be paired off with momentum transfer pumps. In the case of pairing, the positive displacement pump starts the momentum and the momentum transfer pump continues the momentum with the higher vacuum.
Molecular or momentum transfer pumps remove air from a chamber by using blades that rotate at a high speed. They work best for higher vacuums.
Entrapment pumps actually solidify gases with ionisation, chemicals or very low temperatures before moving them. Consequently, they are normally used for very high vacuums.
Vacuum pumps can be used for flight instruments in older aircraft, moulding of composite plastic, electric lamps, vacuum tubes, CRT’s, uranium enrichment, medical processes, mass spectrometers, analytical instruments, milking machines, freeze drying, sewage systems and air conditioners.