Pneumatic Cylinders and pneumatic motors are the actuating elements of pneumatic transmission systems. They convert the pressure energy of compressed air into mechanical energy. Pneumatic Cylinders are used to achieve linear reciprocating motion or swinging, while pneumatic motors are used to achieve continuous rotary motion.
1. Classification of Pneumatic Cylinders
According to different standards, Pneumatic Cylinders can be classified in the following ways.
(1) According to the direction in which the compressed air acts on the end face of the piston, Pneumatic Cylinders can be classified into single-acting Pneumatic Cylinders and double-acting Pneumatic Cylinders. The movement of a single-acting Pneumatic Cylinder in only one direction is driven by air pressure, and the reset of the piston is achieved by the force of the spring or gravity. The reciprocating motion of the piston in a double-acting Pneumatic Cylinder is all accomplished by compressed air.
(2) According to structural features, they can be classified into piston Pneumatic Cylinders, vane Pneumatic Cylinders, diaphragm Pneumatic Cylinders and gas-liquid damping Pneumatic Cylinders.
(3) According to the functions of the Pneumatic Cylinders, they can be classified into ordinary Pneumatic Cylinders and special Pneumatic Cylinders. Common Pneumatic Cylinders mainly refer to piston single-acting Pneumatic Cylinders and double-acting Pneumatic Cylinders. Special Pneumatic Cylinders include gas-liquid damping Pneumatic Cylinders, diaphragm Pneumatic Cylinders, impact Pneumatic Cylinders, booster Pneumatic Cylinders, stepping Pneumatic Cylinders, rotary Pneumatic Cylinders, etc.
2. Single-acting Pneumatic Cylinder
A single-acting Pneumatic Cylinder refers to a type of Pneumatic Cylinder where compressed air only takes in air at one end and drives the piston to move. The return of the piston is assisted by other external forces (such as gravity, spring force, etc.). Its structural principle is shown in Figure .
Figure : Structural Principle of Single-acting Pneumatic Cylinder
Characteristics of single-acting piston Pneumatic Cylinders
(1) Due to single-sided air intake, the structure is simple and the air consumption is low.
(2) Due to the use of spring reset, a portion of the energy of the compressed air is utilized to overcome the reaction force of the spring, thereby reducing the output thrust of the piston rod.
(3) Short effective travel distance;
(4) The thrust and movement speed of the piston rod vary during the stroke. Therefore, single-acting piston Pneumatic Cylinders are mostly used in short-stroke scenarios where the thrust and movement speed of the piston rod are not highly demanded, such as in positioning and clamping devices.
3. Double-acting linear Pneumatic Cylinder
In a double-acting Pneumatic Cylinder, the reciprocating motion of the piston is all driven by compressed air. The single-rod double-acting Pneumatic Cylinder is the most widely used type of common Pneumatic Cylinder, and its structure is shown in Figure 1-3. Both end covers of the Pneumatic Cylinder are equipped with intake and exhaust ports. When intake is made from the air port on the rodless side end cover, the piston rod is pushed to extend; conversely, when intake is made from the air port on the rod side end, the piston rod is pushed to retract. Double-acting Pneumatic Cylinders have the advantages of simple structure, stable output force and stroke that can be selected as needed. However, since they achieve the extension and retraction movement by alternately acting compressed air on the piston, the effective action area of the compressed air during retraction is relatively small, so the force generated is less than the thrust generated when extending. It is generally used on packaging machinery, food machinery, processing machinery and other equipment.
Figure Single-rod double-acting Pneumatic Cylinder
4. Thin Pneumatic Cylinder
The thin type Pneumatic Cylinder, also known as the diaphragm type Pneumatic Cylinder, has a structure shown in Figure 1-4. It uses compressed air to push the piston to reciprocate through a diaphragm. It has the advantages of compact structure, simplicity, easy manufacturing, low cost, convenient maintenance, long service life, low leakage and high efficiency. It is suitable for pneumatic fixtures, automatic control valves and short-stroke applications. It is mainly composed of parts such as the Pneumatic Cylinder body, diaphragm and piston rod, and can be either single-acting or double-acting.
Figure Diaphragm Pneumatic Cylinder
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