the word pneumatics comes from the Greek Pneuma and means as much as “wind” and “breath”. It designates the employment of compressed air in science and technology. Compressed air becomes industrial as source of energy in Germany since approximately at the beginning 20. Century toDrive applied of hammers and drills. In the building of organs late 19. and early 20. Jh. the pneumatic Traktur was prevailing. For approximately 1960 pneumatics in the control plays - and automatic control engineering an important role.
Compressed air (become outdated: Compressed air) becomes by consolidating the ambient air in compressorsproduced. It can to the drive of pneumatic motors in tools such as z. B. Pneumatic hammers for riveting and compressed air screw drivers to be used. In control engineering mainly linear drives are used in the form of cylinders, z. B. to clamping and supplying workpieces in processing centers or to the catch of packing.
Each pneumatic plant consists of 3 subsystems: Compressed air supply - distribution of compressed air and compressed air preparation - control and actoric (“the part of the plant, that the work makes”)
table of contents
system for compressed air supply
the compressed air production and - supply is made by compressors. One calls these gas and steam pumps also compressor.The air compressor is a machine to the production of compressed air (compressed air becomes outdated).
system for the distribution of compressed air
of means of a tubing and a line system is then supplied provided compressed air to the application place. Here it, before it arrives into the construction units such as ski selector valves and drives, meets into one Service unit, where it is cleaned.
The line system is usually shifted as ring circuit, in order to place the supply surely also with repair or maintenance work. The lines are shifted usual way with a small downward gradient (about 1%), so that discharging of condensation is possible. Tolowest point of the ring circuit is a drain valve. One measures the compressed air of the top side of the ring circuit, so that the Kondesnwasser cannot run into the construction units.
The cross section of a line should be selected in such a way that a pressure loss is not exceeded by maximally 0.2 bar.
Valves application find
system for control for the controlling of compressed air. There are the following groups of construction units: 1. Ski selector valves 2. Non-return valves 3. Pressure control valves 4. Flow control valves 6. Special valves (z. B. ) [
number of switching positions
gives proportional valves to number of switching positions: They are enough from 2to 6. Mainly in the industrie and automatic control engineering because of the manufacturing costs only 2 or 3 switching positions are used. Whereby the valves with 2 switching positions are used with “normal” ski selector valves for switching from processes and these with 3 switching positions as valves with stop function, thus quasi asEmergency stop, to be used. (see 2. Non-return valve)
number of connections
the number of connections varies between two and seven connections. With 2/2-way valves only a normal finds passage from A to B instead of (expertly expressed of P (=Druckluftanschluss) after A (= power port)). With 3/2-way valvesfor example still another exhaust port is available beside the two mentioned above connections, which is able to air out the hoses or also the whole system. These 3/2-way valves apply z. B. during the control of single acting cylinders, in addition, to “de-energise” from “new ways”the pneumatic system.
During five connections one finds one compresser air bleed port (P), two power ports (A and B) and two exhaust ports (R and S). The 2 power ports are for example needed, in order to steer a double acting cylinder, whereby the cylinder on the side with compressed airsubjected (that it drives out) and it on the other side aired out (that this can drive out).
One finds four connections with 4/2-way valves. The function mode is the same as with the 5/2-way valves, however the two discharger UF connections were connected by an construction unit-internal drilling (a compresser air bleed port + two power ports+ an exhaust port = four connections).
Note: The P for the compresser air bleed port stands for “Pressure” (= " pressure”) and R with the discharger UF connection stands for “RESETs” (= " resetting”). According to new DIN - standards the compresser air bleed port P with “1” becomes, the power port A with “2” and/or. “4”, the exhaust portR and S with “3” and/or. “5” characterized.
actuation types application find actuation type in pneumatics. To divide these are into mechanical, electronic, pneumatic and manual operations.
Mechanical manipulation are tappet, feathers/springs, role, roller lever. Mechanical manipulation are operated by the machine. Drivesfor example the piston of a cylinder against the tappet of a valve, then is operated the valve (mechanical).
Electronic manipulation are z. B. Tracers, it function by electricity. A current pulse meets sent by a tracer in such a way these on one in the solenoid operated valveon electromagnets, the wave in the valve which ways closes and opens - tightens and thus a way for air opens and another locks.
Pneumatic manipulation: The valve is operated here by compressed air. For example becomes by the manual operationa valve the power port of the same opened and the pressure arrives at a further valve, which is operated by the compressed air. The evenly described wave is pressed here by compressed air into the desired position. The described example is called also “remote control “.
Manual operationsare tracers, pushbuttons, levers and pedals. These are operated with muscle power. If a lever is operated, then the wave addressed into “electronic manipulation” is shifted in the desired direction and thus another switching position is taken.
Beside the form of the remote control already explained, valves can also stillbecome servo-controlled. First the example of use: With small switching force a large flow rate is to be de-energised. If Kraft of the z. B. pneumatic manipulation to be sufficient around a valve to switching would not bring (like it for example with a pneumatic sensor the case is) must this small switching force large switching force head for, able is the valve to be steered.
the non-return valve
these valves let through air only in a direction, this is done via check valves and also with valves with check function. Over application andalso meaning of these valves to make clear, here now some everyday examples are to be described.
1. Check valve: the check valve is essential with the supply of air. If one blows for example a Schwimmring up, then supplied air would escape with the inhalation of air. The sameis essential also when inflating a motor-car tire, because by this valve withdrawing air is prevented. A further example is the gas bottle. If one throttled the withdrawal quantity of the gas and one ignites this gas on too much, then the quantity of the gas is not enoughfrom the flame “alive to receive”. Then the danger exists that the flame spreads the inside the gas bottle, if not the penetration of air into the bottle is prevented.
The check valve consists of a funnel and of a ball. Pressure of that comesSide from the these is desired (z. B. Hineinpumpen of air into a tire), then squeezes it out the ball from the funnel and air can ungehindet by the construction unit flow. However if air pressure from the side comes, where it is unwanted, then that causesAir pressure that the ball is pressed into the funnel, thus does not come air by this construction unit.
2. Kind of the non-return valves are the valves with stop function. These valves are normal ski selector valves, which have 3 switching positions, 2 working positions and a mid-position closed, those by feathers/springs at bothSides with Nichtbetätigung of the valve always one takes. There are different kinds of valves with stop function, some leaves in central position no air through (emergency stop), others guarantees escaping air that z. B. the doubly working cylinder is still aired out.
the flow control valve
Flow control valves affect the flow rate of compressed air by the valve. A representative of this group are throttle valve for the connection in doubly working cylinders retract resistor check valves for exhaust air are used. The controlling of the exhaust air causes a speed control independently of the cylinder load. They affect the flow rate. Uses of flow control valvesit is if one wants to realize that the cylinder is to drive out slowly (the throttle valve ensures for the fact that the piston area fills only slowly with compressed air), in addition, with time-delayed switching actions (by the throttle valve a large air space, also as pneumatic memory well-known, fills - everafter attitude of the valve - something and/or. badly more slowly than without throttling. Only if in the pneumatic memory a sufficiently high pressure collected, the valve, which is time-delayed, becomes (pneumatically) operates).
the pressure control valve
of pressure control valves, like the 3/2-way valve with pressure-dependent change-over andthe sequence valve (pressure pressure sequence valve), open only after reaching a certain pressure, which the pneumatic manipulation exerts. This realized by an adjustable feather/spring, which harder and/or. more softly to be adjusted can. Effected by one the feather/spring continuing to press together or to be eased being able. A feather/spring, those alreadysomething is pressed together, can only with much Kraft be pressed together further. Thus the pneumatic manipulation must apply enough pressure, in order to bring the valve to switching.
- the cylinder for straight-line movements (z. B. to Spans)
- the cylinder with transmission for lagging
- the pneumatic motor for rotary movements
of advantages pneumatics:
- Forces and speeds of the cylinders are steplessly adjustably
- cylinders and pneumatic motors achieve high speeds and numbers of revolutions
- of pneumatic equipment can without damage up to stood still to be overloaded
- compressed air are storable in receivers
- large piston force are not attainable, there the operating pressure usually under 10bar are
- homogeneous piston speeds are not possible
- without stops no exact positions possible
- leaking out compressed air cause for noise
- P. Croser, F. Ebel: Pneumatics, basic level, FESTO didactic GmbH & cost.Kg. Esslingen 2003, ISBN 3-540-00022-4
- G. Prede, D. Scholz: Electropneumatics, basic level, FESTO didactic GmbH & cost. Kg. Esslingen 2001, ISBN 3-540-41446-0
- G. Bird, E. Mühlberger: Fascination pneumatics, bird book publishing house 2001, ISBN 3-8023-1886-2
on the left of
- FESTO didactic - FESTO didactic - applicationsand tools