A Brief History of Portable Air Compressors
There are many portable air compressors on the market today of varying sizes and power. And though they vary by size and power, they all work under the same basic principle and use just a couple of different technologies to generate air pressure. The basic idea is to put the air under so much pressure that when released the power is used to generate energy that is then used to for such things as operating power tools.
Though modern portable air compressors have only been around since the last century, the technology of compressed air has been in use for much longer. The original compressor is the human lung. When we breathe in deeply and then blow out, we are releasing air that has been under pressure. By blowing compressed air onto a fire, we can get it to burn hotter.
But the human lung did not compress enough to get much done, so before long the bellows was invented. Hand and foot bellows were the first portable air compressors widely used. Among other things, they were necessary to help fire burn hot enough for black smiths to do their jobs, from horse shoes to armor and weaponry (swords), bellows were a necessity.
Typically, these bellow had an outlet (often a nozzle) through which the air was pushed. The operator could control both the quantity and direction it was aimed. The bellows then had a separate inlet, so air entered through the inlet on one stroke and exits through the outlet on the opposing stroke.
The double action bellows was first used in ancient China, and later (about 1500 years later) was developed in Europe. The double action bellows was stronger and more efficient because it blew air out on both strokes of the handle. These bellows used a piston. When the piston was pushed, air entered from one side and flowed through the nozzle and then when the piston was pulled on the opposing stroke, air entered through the opposite side and would flow out through the same nozzle.
Pistons are still used in portable air compressors today. Though there are different technologies used in various compressors, most smaller compressors that are used in the home today use positive displacement and most compress air with a reciprocating piston.
In this modern era, our compressors are much more powerful and look quite different from the double acting piston bellows, but the basis for the technology is the same. A conventional piston compressor has a crankshaft, a connecting rod and piston, a cylinder and a valve head. The crankshaft is driven by either an electric motor or a gas engine.
At the top of the cylinder, there is a valve head that holds the inlet and discharge valves. Both are thin metal flaps, one mounted underneath and one mounted on top of the valve plate. As the piston moves down, a vacuum is created above it. This allows outside air to push open the inlet valve and fill the area above the piston. As the piston moves up, the air above it compresses, holds the inlet valve shut
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