Pneumatic actuators and common types

Pneumatic actuators use compressed air as power, converting the pressure energy of compressed air into mechanical energy to drive valves, dampers, and other components to complete opening, closing, or adjusting actions.

Common types of pneumatic actuators are as follows: Classified by movement type Linear motion type Ordinary cylinder: The piston has a rod, and the load is driven by the piston rod to achieve linear motion. The stroke range is from a few millimeters to tens of centimeters or even larger. The installation is relatively simple, but the larger the stroke, the larger the cylinder volume, and the higher the requirement for installation space. Rodless cylinder: There is no piston rod, and the external actuator is directly or indirectly connected to the piston to make it reciprocate linearly with the piston, saving a lot of installation space. Rotary motion type Swing cylinder: Also known as a rotary cylinder, the output shaft is restricted to reciprocate within a certain angle, which can drive the load to reciprocate or rotate a certain angle along a fixed axis. Pneumatic motor: Converts the pressure energy of compressed air into rotating mechanical energy, and can use a directional control valve to realize forward rotation, reverse rotation, and stop. It is characterized by light weight and no overload. Classified by acting force Single-acting cylinder: Only uses the thrust in one direction of the cylinder, and the retraction of the piston rod relies on the spring installed inside the cylinder or the external load. When the air supply is stopped, the cylinder will immediately return to its original position. Double-acting cylinder: The piston on both sides is driven by the pressure of compressed air to drive the piston rod or load to achieve reciprocating motion. It is the most commonly used type in automated production lines. Double piston rod cylinder: Both ends of the cylinder have piston rods at the front and rear ends, and both ends can simultaneously obtain two actions of forward and backward. Tandem cylinder: One type is to connect multiple pistons in series on the same piston rod, dividing the cylinder body into multiple inner chambers, and providing compressed air through multiple input ports to obtain double the acting force; the other type is to connect two cylinders independently in series, which can divide the required stroke of the load into sections and control the displacement in time. Classified by structural features Diaphragm type: The signal pressure acts on the diaphragm, causing it to deform and drive the push rod to move, thereby causing the valve core to displace and change the valve opening. It has a simple structure, low price, and convenient maintenance, but the stroke is small and can only directly drive the valve stem. It is suitable for occasions with small output and high precision. Piston type: The piston moves in the cylinder to generate thrust, and the output force is much greater than that of the diaphragm type. It is suitable for occasions with large output force, such as large-diameter, high-pressure drop control, or butterfly valve driving devices. Fork type: It has the characteristics of large torque, small space, and a torque curve that is more in line with the valve torque curve, but the appearance may not be very beautiful, and it is often used for valves with large torque. Rack and pinion type: Simple structure, stable and reliable operation, and explosion-proof safety. It is widely used in power plants, chemical industry, and petroleum refining where safety requirements are high.