pneumatic linear actuators (pneumatic cylinders)

PNEUMATIC LINEAR ACTUATORS (PNEUMATIC CYLINDERS)

1. What are Pneumatic Cylinders ?

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

• The pneumatic cylinders are basically used for single-purpose applications such as clamping, stamping, transferring, branching, allocating, ejecting, metering, tilting, bending, turning and many other applications.

2. Types of Pneumatic Cylinders

The different classification scheme of the pneumatic cylinders are given below:

1. Based on the applications for which air cylinders are used:

(i) Light duty air cylinders,

(ii) Medium duty air cylinders, and

(iii) Heavy duty air cylinders.

2. Based on the cylinder action :

(i) Single-acting cylinders, and

(ii) Double-acting cylinders.

3. Based on the cylinder's movement : 

(i) Rotating type air cylinders, and 

(ii) Non-rotating type air cylinders.

4. Based on the cylinder's design:

(i) Through rod cylinders, 

(ii) Cushion end cylinders,

(iii) Tandem cylinders,

(iv) Double rod cylinders,

(v) Telescoping cylinders, etc.

3. Single- and Double-Acting Air Cylinders

• As the name suggests, the single-acting air cylinders can deliver a force in only one direction. In these types, air only moves or pushes the piston in one direction and the piston is returned by means of an external spring or by gravity.

• In the double-acting air cylinders, air pressure can be applied to either side of the piston, thereby providing a pneumatic force in both directions.

• The construction, working principle, graphic symbol, merits and demerits of single- and double-acting air cylinders are very much similar to that of the hydraulic cylinders. For more details, refer Sections 5.3 and 5.4, Chapter 5.

4. Other Pneumatic Cylinders

Some of the basic pneumatic cylinder types and their brief descriptions are presented in Table 12.2.

Table 12.2. Some basic types of pneumatic cylinders

5. Rotating- and Non-Rotating Type Air Cylinders

• Rotating-type air cylinders are used in applications requiring that the cylinder body can be connected to a rotating member while the air connections to the cylinder be in a stationary housing. Such cylinders are used on lathes, grinders, spinning machines and other machines with rotating spindles.

• Non-rotating type air cylinders are more widely used than rotating cylinders. Because the great majority of applications do not involve a rotating member.