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Pneumatics (from Greekπνεῦμαpneuma 'wind, breath') is the use of gas orpressurized air in mechanical systems.
Pneumatic systems used inindustry are commonly powered bycompressed air or compressedinert gases. A centrally located and electrically-poweredcompressor powerscylinders,air motors,pneumatic actuators, and other pneumatic devices. A pneumatic system controlled through manual or automaticsolenoid valves is selected when it provides a lower cost, more flexible, or safer alternative toelectric motors, andhydraulic actuators.
Pneumatics also has applications indentistry,construction,mining, and other areas.
Although the early history of pneumatics is somewhat unclear,blowguns are often considered the earliest pneumatic device, being created independently by various indigenous groups around the world.Bellows are an early form of air compressor used primarily for smelting and forging.Ctesibius of Alexandria is often considered the father of pneumatics, "who worked in the early 3rd century BCE and invented a number of mechanical toys operated by air, water, and steam under pressure." Though no documents written by Ctesibius survive, he is thought to have heavily influencedPhilo of Byzantium while writing his work,Mechanical Syntaxis, as well asVitruvius inDe architectura.[1] In the first century BC, the ancient Greek mathematicianHero of Alexandria compiled recipes for dozens of contraptions in his workPneumatics. It has been speculated that much of this work can be attributed to Ctesibius.[2] The pneumatic experiments described in these ancient documents later inspired the Renaissance inventors of thethermoscope and theair thermometer, devices which relied upon the heating and cooling of air to move a column of water up and down a tube.[3]: 4–5
German physicistOtto von Guericke (1602–1686) invented the vacuum pump, a device that can draw out air or gas from the attached vessel. He demonstrated the vacuum pump to separate the pairs of copper hemispheres using air pressures.
Pneumatic systems in fixed installations, such as factories, use compressed air because a sustainable supply can be made by compressingatmospheric air.[4] The air usually has moisture removed, and a small quantity of oil is added at the compressor to prevent corrosion and lubricate mechanical components.
Factory-plumbed pneumatic-power users need not worry about poisonous leakage, as the gas is usually just air. Any compressed gas other than air is an asphyxiation hazard—including nitrogen, which makes up 78% of air. Compressedoxygen (approx. 21% of air) would not asphyxiate, but is not used in pneumatically-powered devices because it is a fire hazard, more expensive, and offers no performance advantage over air. Smaller or stand-alone systems can use other compressed gases that present an asphyxiation hazard, such as nitrogen—often referred to as OFN (oxygen-free nitrogen) when supplied in cylinders.
Portable pneumatic tools and small vehicles, such asRobot Wars machines and other hobbyist applications are often powered by compressedcarbon dioxide, because containers designed to hold it such asSodaStream canisters and fire extinguishers are readily available, and thephase change between liquid and gas makes it possible to obtain a larger volume of compressed gas from a lighter container than compressed air requires. Carbon dioxide is an asphyxiant and can be a freezing hazard if vented improperly.
Both pneumatics andhydraulics are applications offluid power. Pneumatics uses an easily compressible gas such as air or a suitable pure gas—while hydraulics uses relatively incompressible liquid media such as oil. Most industrial pneumatic applications use pressures of about 80 to 100 psi (550 to 690 kPa). Hydraulics applications commonly use from 1,000 to 5,000 psi (6.9 to 34.5 MPa), but specialized applications may exceed 50,000 psi (340 MPa).[5]
Pneumatic logic systems (sometimes called air logic control) are sometimes used for controlling industrial processes, consisting of primary logic units like:
Pneumatic logic is a reliable and functional control method for industrial processes. In recent years, these systems have largely been replaced by electronic control systems in new installations because of the smaller size, lower cost, greater precision, and more powerful features of digital controls. Pneumatic devices are still used where upgrade cost, or safety factors dominate.[6]
Another domain where pneumatic logic is beneficial is soft robotics. By introducing simpler pneumatic logic components into soft robotics, expensive, rigid components can be replaced or reduced, lowering the manufacturing costs of the contruction of soft robotic systems.[7]
