The built-in fork type pneumatic actuator (Fig. 1) replaces the gear rack of the traditional rack pneumatic actuator with the fork assembly, which is also divided into double action and single action. Compared with the rack and pinion type, the cylinder diameter of the built-in fork type pneumatic actuator only needs to be 300 mm under the same structure and output torque. Compared with the rack and pinion type, the built-in fork type has the advantages of long service life, small volume, easy installation, energy saving, environmental protection and fast working speed.
(1) long service life
The traditional transmission mode of rack and pinion actuator is sliding friction between the piston of aluminum alloy and the shaft of steel. The friction coefficient is large and the motion pair is worn. Under extreme working conditions, tooth breakage is easy to occur, which brings potential safety hazards to the operation. The built-in fork actuator adopts the bearing like structure, and the transmission mode is the rolling friction between the alloy steel ball and the alloy steel fork, which reduces the friction coefficient and the internal dynamic wear. The smooth and wear-resistant shaft sleeve and multi-point guide seal can improve the sealing performance and greatly reduce the friction, and play the role of supporting and fixing the piston. It can make the piston and fork more stable in the process of movement, and the service life can reach more than 1 million times.
(2) Small size
The rack thickness of the rack and pinion pneumatic actuator virtually increases the inner diameter of the cylinder, and cannot increase the effective arm length. When the same opening and closing torque is generated, the embedded structure of the built-in fork pneumatic actuator can make more effective use of the internal space of the cylinder, and only needs a smaller cylinder diameter. In addition, the weight of the fork piston is lighter than that of the rack piston, which greatly reduces the volume and mass of the actuator by 40%, and is easy to install.
(3) Energy saving and environmental protection
Compared with the rack and pinion type, the built-in fork type pneumatic actuator can reduce the air consumption, reduce the workload of the compressor, save electricity, and can choose smaller compressor. Under the condition of the same torque, the fork type pneumatic actuator can meet the environmental protection requirements of the equipment because of its smaller air consumption.
(4) work faster
Compared with the rack and pinion type pneumatic actuator with the same torque, the cylinder block with the built-in fork type pneumatic actuator is smaller and the working response speed is faster.
The working principle of the built-in fork type pneumatic actuator is the same as that of the rack and pinion type. However, due to the difference of the internal transmission mechanism, the output torque characteristics of the built-in fork type pneumatic actuator are very different from those of the rack and pinion type, and are similar to those of the external fork type. The output torque characteristics of the built-in fork type pneumatic actuator are shown in Figure 2.