The external fork type pneumatic actuator is also divided into double acting type and single acting type, which is composed of two split cylinders and has the characteristics of large output torque.
The structure of double acting external fork type pneumatic actuator is shown in Figure 1. When the air source pressure enters the air chamber at the a end of the cylinder from the air port a, the 2 piston and the piston rod assembly move synchronously to the right end of the cylinder. The air in the air chamber at the B end is discharged through the air port B. at the same time, the rotary shaft of the shift fork is synchronously driven by the two piston components to complete the action of 0 ° to 90 ° angular stroke. After the air exchange of the solenoid valve, when the air source pressure enters the air chamber at the B end of the cylinder from the air port B, the 2 piston and the piston rod assembly move to the left end of the cylinder, and the air in the air chamber at the a end is discharged through the air Port A. at the same time, the 2 piston assembly synchronously drives the fork shaft to rotate in the opposite direction to complete the angular stroke of 90 ° to 0 ° and realize the opening and closing of the ball valve. The output torque of double acting external fork type pneumatic actuator is a curve characteristic, as shown in Figure 2.
The structure of single acting external fork type pneumatic actuator is shown in Figure 3. When the air source pressure enters the air chamber at the a end of the cylinder from the air port a, the 2 piston and the piston rod assembly move synchronously to the right end of the cylinder, forcing the spring assembly to compress. At the same time, the 2 piston assembly drives the fork shaft to rotate synchronously, completing the action of 0 ° to 90 ° angular stroke. After the air exchange of the solenoid valve, the air source pressure is released from the air port A. under the elastic force of the spring, the 2 piston and piston rod assembly move to the left end of the cylinder. At the same time, the 2 piston assembly synchronously drives the fork shaft to rotate in the opposite direction to complete the angular stroke of 90 ° to 0 ° and realize the opening and closing of the ball valve. The output torque of single acting external fork type pneumatic actuator is also a curve characteristic, as shown in Figure 4.
