The three-stage pneumatic actuator is a special specification actuator that provides three position operation modes of 0°, 45°, 90°, and 180°. The neutral position is achieved by a mechanical brake created by the movement of the two auxiliary pistons. The middle position can be adjusted. For example, a 90° travel actuator is available with 20°, 30°, 50°, 70°, etc. Action form of three-stage pneumatic actuator: single-acting and double-acting.
A three-stage pneumatic actuator is an actuator that uses air pressure to drive a valve to open, close, or adjust. It is also called a pneumatic actuator or a pneumatic device but is usually called a pneumatic head. Sometimes pneumatic actuators are equipped with some auxiliary devices. Commonly used valve positioners and handwheel mechanisms. The function of the valve positioner is to use the feedback principle to improve the performance of the actuator so that the actuator can achieve precise positioning according to the control signal of the controller. The function of the handwheel mechanism is to directly operate the control valve to maintain normal production when the control system is powered off, the gas stops, the controller has no output or the actuator fails. Three-stage pneumatic actuator When the compressed air enters the pneumatic actuator from the nozzle of the pipe, the gas pushes the double piston to move linearly to both ends (the cylinder head end). The rack on the piston drives the gear on the shaft 90 degrees counterclockwise and the valve opens. At this time, the gas at both ends of the pneumatic actuator valve is discharged through nozzle B. On the contrary, when the compressed air enters the two ends of the pneumatic actuator from the nozzle B, the gas pushes the double plug to move linearly in the middle, and the rack on the piston drives the gear on the shaft to rotate 90 degrees clockwise, and the valve closes. At this time, the gas in the middle of the pneumatic actuator is discharged through the nozzle. The above is the standard transmission principle. According to the user's requirements, the installation of the pneumatic actuator can adopt the opposite transmission principle to the standard type, that is, select the right shaft to turn clockwise to open the valve, and counterclockwise to close the valve. Single-acting (spring return) pneumatic actuator nozzle a is the intake port, and nozzle B is the exhaust port (nozzle B should be equipped with a muffler). The inlet to the nozzle is an open valve. When the air is cut off, the valve is closed by spring force.
The adjustment mechanism type and structure of the three-stage pneumatic actuator are basically the same, mainly because the actuator is different. Therefore, the introduction of pneumatic actuators is divided into two parts: actuators and control valves. A pneumatic actuator consists of an actuator and control valve. According to the size of the control signal, the corresponding thrust is generated to push the control valve to act. The regulating valve is the regulating part of the pneumatic actuator. Under the thrust of the actuator, the control valve produces a certain displacement or angle to directly adjust the fluid flow.
