The pneumatic actuators, also known as pneumatic cylinders, or air cylinders, are the devices that are applied for facilitating the motion, which is converted from the pneumatic energy, on the connected components of the mechanisms, and are necessary for driving entire devices where the mechanisms are on.
The pneumatic actuators can be presented as a variety of forms with different designs of the appearances, motion types, and operating methods. Through the transmission of the compressed air from the power source to the connected component, the related applications can receive sufficient kinetic energy for the device to be driven.
An actuator or a cylinder is vital for the smooth operation of a variety of applications, when the constant movements of the components are required. In other words, if there is no actuator for assisting the motion driving process, the devices cannot work as well as what they are supposed to.
The common design of an actuator is with a piston that moves along a rod inside the chamber of the body. The connected component moves due to the compressive force that is given from the piston and rod, and the piston moves with the rod because of the variation of the pressure of the compressed medium given from the power supply system inside the chamber. As this cycle keeps repeating, the result of the continuous motion transmission is able to be achieved.
While the comparisons between the pneumatic actuators and the hydraulic actuators often occurred, because they are equally common power sources in the realm of motion transmission. Apart from the similar operating principle, these two types of actuators actually have some variations that make the customers apply one rather than another.
First of all, the power sources of them are different. One uses compressed air or gas, and the other uses hydraulic fluids, which is usually oil instead. In addition, due to the limitation of the given pressure from the power sources, the pneumatic actuators are more suitable for low loads of energy transmission, while the hydraulic ones are capable of handling relatively heavier loads of the operation.
Since here we focus more on the pneumatic actuators, one of the reasons why the pneumatic type is chosen over its hydraulic counterpart is the problem of fluid leakage. The hydraulic actuators are operated as they receive hydraulic oil, so it is possible to have leakage occur if the actuators are not properly sealed. In contrast, there is no fluid in the pneumatic actuators, but the compressed air or gas as the alternatives. Therefore, there would not be the problem of medium leakage on the pneumatic type of actuators.
When it is necessary to transmit the pneumatic energy to be the motion driving source, the pneumatic actuators would undergo three procedures, including medium feeding, valve control, and pressure differentiating.
1. Medium feeding
This procedure is related to the supplying of the power source. For the pneumatic actuators, the power source is the compressed air or gas, which is provided from a compressor. Only when the compressor releases and delivers the medium, which is the compressed air or gas, then the motion transmission can be initiated.
2. Valve control
Between the compressor and the inlet port of the actuator, there is an air actuator valve that controls the delivering of the medium. As the compressed air is released from the compressor, the pressure would cause the valve to open, which allows the air to flow into the actuator.
3. Pressure differentiating
Once the compressed air or gas is given, the piston would move along the rod, and this can be derived from the pressure differentiating inside the chamber of the actuator body.
When the air or gas is delivered through the port of the actuator, the part that contains the medium has higher pressure, which thus pushes the piston to another part with lower pressure, so that the connected component can be driven afterwards.
A pneumatic actuator is used for the transmission of motion for the connected device. Depending on the requirements of different devices, the motion that this tool provides can be either rotary motion or linear motion, which own the same purpose but apply different principles during operation.
● Rotary motion transmission
The rotary motion transmission of a pneumatic actuator is achieved by the rack and pinion type of actuator, which is the most common among the pneumatic rotary actuators.
As the pressure causes the piston to move along the rod on the rack, then the pinion would be driven connecting parts between these two equipments, and it is the rotating of the pinion that drives the rotary part on the connected device to perform the rotary motion.
● Linear motion transmission
The linear motion transmission of the pneumatic actuators is straightforward and relatively simple than the rotary motion transmission, since only the first phase, which is the piston and rod movement should be applied, then the applications, which are connected directly to the rod of the actuators, would directly receive the linear motion accordingly.
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