Pneumatic drive

In general terms, the transmission of energy in the pneumatic drive is as follows:

1. Drive motor ^{[ clarify ]} transfers the torque to the compressor shaft, which delivers energy to the working gas.
2. Working gas after special preparation in pneumatic lines through regulating equipment enters the air motor, where the pneumatic energy is converted into mechanical.
3. After that, the working gas is released into the environment, in contrast to the hydraulic drive , in which the working fluid in the hydrolines is returned either to the hydraulic tank or directly to the pump .

Many pneumatic machines have their own design counterparts among volumetric hydraulic machines . In particular, axial-piston pneumatic motors and compressors , gear and lamellar pneumatic motors, pneumatic cylinders are widely used ...

Air enters the pneumatic system through the air intake .

The filter cleans the air in order to prevent damage to the drive elements and reduce their wear.

The compressor compresses the air.

Since, according to Charles's law , the air compressed in the compressor has a high temperature, before the air is supplied to consumers (as a rule, air motors), the air is cooled in a heat exchanger (in a refrigerator).

To prevent icing of air motors due to the expansion of air in them, as well as to reduce the corrosion of parts, a moisture separator is installed in the pneumatic system .

The receiver is used to create a supply of compressed air, as well as to smooth the pressure pulsations in the pneumatic system. These pulsations are due to the principle of operation of volumetric compressors (for example, piston compressors) that supply air to the system in batches.

In the atomizer , lubricant is added to the compressed air , which reduces friction between the moving parts of the pneumatic actuator and prevents them from seizing.

In the pneumatic actuator, a pressure reducing valve is installed, which provides compressed air to the pneumatic motors at constant pressure.

The distributor controls the movement of the output links of the air motor.

In a pneumatic motor ( pneumatic motor or pneumatic cylinder ), the energy of compressed air is converted into mechanical energy.

Virtues

• unlike the hydraulic drive, there is no need to return the working fluid (air) back to the compressor;
• less weight of the working fluid compared to the hydraulic actuator (relevant for rocket production);
• the smaller weight of executive devices in comparison with electric;
• the ability to simplify the system by using a cylinder with compressed gas as an energy source, such systems are sometimes used instead of squibs , there are systems where the pressure in the cylinder reaches 500 MPa;
• simplicity and efficiency, due to the low cost of the working gas;
• speed of operation and high speeds of pneumatic motors (up to several tens of thousands of revolutions per minute);
• fire safety and neutrality of the working environment, which makes it possible to use a pneumatic drive in mines and in chemical production;
• in comparison with a hydraulic actuator - the ability to transmit pneumatic energy over long distances (up to several kilometers), which allows the use of a pneumatic actuator as a main in mines and mines ;
• unlike the hydraulic actuator , the pneumatic actuator is less sensitive to changes in the ambient temperature due to a lower efficiency dependence on the working medium (working gas) leaks; therefore, the change in the gaps between the pneumatic components and the viscosity of the operating medium do not seriously affect the pneumatic actuator parameters; This makes the pneumatic drive convenient for use in the hot shops of metallurgical enterprises.

disadvantages

• heating and cooling of the working gas during compression in compressors and expansion in pneumatic motors; This disadvantage is due to the laws of thermodynamics, and leads to the following problems:
  • the possibility of freezing of pneumatic systems;
  • condensation of water vapor from the working gas, and therefore the need to drain it;
• the high cost of pneumatic energy compared to electric (about 3-4 times), which is important, for example, when using a pneumatic actuator in the mines;
• even lower efficiency than the hydraulic drive;
• low response accuracy and smoothness;
• the possibility of explosive rupture of pipelines or industrial injuries, due to which small industrial gas pressures are used in industrial pneumatic drives (usually pressure in pneumatic systems does not exceed 1 MPa, although pneumatic systems with operating pressures up to 7 MPa are known - for example, at nuclear power plants ), and consequence, the efforts on the working bodies are much smaller in comparison with the hydraulic actuator ). Where there is no such problem (on rockets and airplanes) or the size of the systems is small, pressures can reach 20 MPa and even higher.
• To regulate the magnitude of the rotation of the actuator stem, it is necessary to use expensive positioning devices.

By the nature of the impact on the working body of the pneumatic actuators with the progressive movement are:

• two-position , moving the working body between the two extreme positions;
• multi-position , moving the working body in different positions.

According to the principle of action, pneumatic actuators with progressive movement are:

• unilateral action ; return of the drive to the initial position is carried out by a mechanical spring;
• two-way action , moving the working body of the drive is compressed air.

According to the design pneumatic actuators with the progressive movement are divided into:

• piston , which is a cylinder in which the piston moves under the influence of compressed air or a spring (two versions are possible: in single-sided piston pneumatic actuators, the working stroke is carried out by compressed air and idle by a spring; in two-sided, both working and idling moves due to compressed air);
• membrane , representing a sealed chamber, divided by a membrane into two cavities; in this case, the cylinder is connected to the rigid center of the membrane, on the whole area of ​​which compressed air produces the action (as well as the piston ones, they are made in two forms — one-sided or two-sided).
• Bellows are used less frequently. Almost always one-sided action: the force of return can be created both by the elasticity of the bellows itself, and with the use of an additional spring.

In special cases (when increased speed is required) a special type of pneumatic actuators is used - a vibratory pneumatic actuator of the relay type .

• Pneumatic actuator valves
• Pneumatic mail
• Air muscles
• Airguns
• Pneumatic computer

One of the applications of pneumatic actuators is their use as power actuators on pneumatic simulators .

Pneumatic brake actuator

The pneumatic drive of brakes is used on trucks, tractors and railway transport.

Pneumatic tool

Air motors are used to drive various tools : drills , wrenches , jackhammers , grinding heads. Also pneumatic press .

Such a tool ensures the safety of work in explosive areas (with gas accumulation, coal dust), in an environment with a high moisture content .

• Pneumatic battery
• Receiver (vessel)

• Vacuum drive
• Hydraulic drive
• Electric drive

• Basta TM Hydraulic and hydropneumatic automation. - Moscow: Mechanical Engineering, 1972. - p. 320.

• Skhirtladze A.G., Ivanov V.I., Kareev V.N. Hydraulic and pneumatic systems. - Moscow: ITs MSTU "Stankin", "Janus-K", 2003. - p. 544.
• V. Levin. Muscles from the air // Science and Life: Journal. - M .: True, 1989. - № 5 . - p . 41-45 . - ISSN 0028-1263 .

• Pneumatic drive