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