 | Hydraulic organ
Storage and suppression of pulsation
The first deliberate exploitation of energy in the air is handed down to us by the Greek Ktesibios (ca. 285 to 222 BC). He built a hydraulic organ and used compressed air for the storage and reduction of vibration.
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Fig. 1.3: The catapult of Ktesibios | Catapult
Storage of energy
Ktesibios used another property of compressed air, stored energy, for his catapult. With the aid of air compressed in a cylinder, the Greek’s catapult generated enough tension to propel missiles.
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Fig. 1.4: The temple doors of Heron | Temple doors
Expansion and the performance of work
Heron, an engineer living in Alexandria in the first century BC, found a way to open the doors of a temple automatically by keeping the flame at the altar inside the building permanently alight. The secret was to use the expansion of hot air to force water out of one container and into another. Heron recognised, even if unwittingly, that it was possible to perform work by changing the condition of air.
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Fig. 1.5: Compressed air to increase energy | Pascal's law
Increasing energy
It was only in the 17th century that a series of learned people began to study the physical laws applicable to compressed air. In 1663 Blaise Pascal published an essay on increasing energy by using liquids (hydraulics), that was also valid for the technology of compressed air. He found that the energy exerted by one man at one end of a closed container of water was equivalent to the energy exerted by 100 men at another end.
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Fig. 1.6: Compressed air as a means of transport | Transporting objects through pipes
Pneumatic conveyance
Taking up where Heron left off, the French physicist Denis Papin described in 1667 a method of transporting objects through pipes. He exploited the slight difference in pressure inside a pipe. In doing so he found out that energy was generated at an object inside the pipe. This was recognition of the advantage of the high work speeds obtainable by using air. Papin thus laid the foundation stone for pneumatic conveyance.
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Fig. 1.7: Pneumatic brakes in a train ca. 1870 | Pneumatic brakes
Power transmission
As early as around 1810, trains were being powered by compressed air. In 1869 Westinghouse introduced his pneumatic brake. His brake motor followed three years later. In this system the brakes were applied by over-pressure i.e., the full braking effect is obtained if there is a drop in pressure e.g., by the bursting of a hose. This was the first use of a fail-safe system.
Brake systems based on this principle are still used in HGVs today.
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| Pneumatic post
Conveyance by compressed air
The idea of trains powered by compressed air was not forgotten. In 1863, Latimer Clark together with an engineer named Rammel built a pneumatic conveyance system in London. It featured small trolleys moving completely inside conveyor tubes and was designed to transport postal bags and parcels. This system was much more flexible than the heavy, atmospheric railways of 1810, and led eventually to the introduction of pneumatic post.
Pneumatic post networks soon sprung up in Berlin, New York and Paris. The Paris network reached its peak length of 437 km in 1934. Even today, pneumatic post systems are still used in large industrial operations.
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Fig. 1.8: Pneumatic drills in tunnel construction | Pneumatic tools
Transporting energy
When the tunnel through Mont Cenis was being built in 1857, the new technology was used in a pneumatically-powered hammer drill to cut through the rock. From 1861 they used pneumatically-powered percussion drills, these being supplied with compressed air from compressors at both ends of the tunnel. In both cases the compressed air was transported over long distances.
When in 1871 the breakthrough in the tunnel was achieved, there were over 7 000 m of pipelines on both sides. Thus, for the first time, the transportability of energy was demonstrated and made known to a wide public as one of the advantages of compressed air. And from here on, pneumatic tools of even greater performance and versatility were developed.
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Fig. 1.9: Compressed air station in Paris 1888 | Pneumatic networks
Central generation of compressed air and signal transmission
The experience gained using networks of pneumatic lines and the development of more powerful compressors led to a pneumatic network being installed in the sewage canals of Paris. It was put into commission in 1888 with a central compressor output of 1 500 kW. By 1891 its output rating had already reached 18 000 kW.
The all-round success of the pneumatic network was underlined by the invention of a clock, the minute hand of which was moved on every sixty seconds by an impulse from the compressor station. People had not only seen the possibility of transporting energy, but also of moving signals over great distances through a pneumatic network.
The pneumatic network in Paris is unique to this day, and is still in use.
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Fig. 1.10: Four-stage adding device with wall
radiation elements | Signal processing
Compressed air for the transmission and processing of signals
In the 1950s in the USA the high flow speed of compressed air was first used for the transmission and processing of signals. Low-pressure pneumatics, also known as fluidics or pneumonics (pneumatic logic), allow the integration of logical switching functions in the form of fluidic elements in a very small area at pressures of 1.001 to 1.1 bar.
The high operating precision of the fluidic logic elements under extreme conditions allowed them to be used in the space and defence programmes of the USA and the USSR. Immunity to electromagnetic radiation from exploding nuclear weapons gives fluidics a special advantage in several sensitive areas.
Even so, over the course of time fluidics has largely been superseded by electrical and microelectronic technology in the fields of signal and information processing. |