Review and summary

REVIEW AND SUMMARY

• In this chapter, the purpose, construction, operation, graphic symbols of various air control valves (i.e., pneumatic valves) and pneumatic actuators required for proper functioning of the pneumatic system have been discussed.

• Pneumatic valves are devices used to control pressure, flow direction, or flow rate in pneumatic circuits.

• Types of pneumatic (or air control) valves: Three basic types of air control valves, based on their function in the pneumatic system, are :

1. Directional control valves,

2. Non-return valves,

3. Pressure control valves, and

4. Flow control valves.

• The function of a directional control valve (DCV) is to control the direction of flow in a pneumatic circuit.

• The check valves are used to allow free flow of compressed air in only one direction, and to prevent any flow in the opposite direction.

• Shuttle valves, also known as double check valves, are used when control is required from more than one power source.

• Quick exhaust valve is used to exhaust the cylinder to the atmosphere quickly (to increase the piston speed of the cylinder).

• The pneumatic pressure regulator is used to supply a prescribed reduced outlet pressure in a pneumatic circuit and to maintain it at a constant value.

• Flow control valves, also known as volume-control valves, are used to regulate the volumetric flow of the compressed air to different parts of a pneumatic system.

• Pneumatic actuators are the devices used for converting the pressure energy of air (also called pneumatic energy) into mechanical energy to perform useful work.

• Types of pneumatic actuators :

1. Linear actuators (also called ‘pneumatic cylinders'), and

2. Rotary actuators (also called ‘air motors').

• The pneumatic cylinders are the devices for converting the air pressure into linear mechanical force and motion.

• The function of an air motor is to convert the pressure energy of the compressed air into rotary mechanical energy.

KEY TERMS ONE SHOULD REMEMBER

Pneumatic valves

Air control valves

Directional control valves

Non-return valves

Check valves 

Shuttle valves 

Double-check valves 

Quick exhaust valves 

Restrictor check valves 

Speed control valves 

Two-pressure-valves 

Pressure regulating valves

Flow control valves 

Volume control valves 

Pneumatic actuators 

Pneumatic cylinders

Single-acting cylinders 

Double-acting cylinders 

Cushion end cylinders 

Tandem cylinders 

Dual linear cylinders 

Double-rod cylinder 

Through rod cylinder

Telescoping cylinder 

Turn cylinder

Rotary cylinder

Rotating cylinder

Non-rotating cylinder

Air motors

Continuous rotary air motors

Gear motors

Vane motors

Pump motors

Limited rotation air motors