What is a single acting pneumatic air cylinder?

Pneumatic air cylinder design:

In a single acting pneumatic cylinder, air is supplied to one side of the piston through a port, causing the piston rod to extend in one direction to complete tasks such as lifting objects. The other side releases air into the environment. The movement in the opposite direction most commonly occurs through mechanical springs, which cause the piston rod to return to its original or base position. Some single acting cylinders use gravity, weight, mechanical motion, or externally installed springs to drive the return stroke, although these designs are less common. In contrast, the double acting cylinder has two ports that provide compressed air for the extension and retraction of the piston rod. Double acting design is more typical in the entire industry, with an estimated 95% of applications using this cylinder style. However, in some applications, single acting cylinders are the most cost-effective and suitable solution.

In a single acting cylinder, the design can be a "base position reduction" with spring reset or a "base state addition" with elastic extension. This depends on whether the compressed air is used to provide power for the output stroke or the input stroke. Another way to consider these two options is to push and pull. In push design, air pressure generates thrust and pushes the piston. Adopting a tension design, air pressure generates thrust to pull the piston. The most widely specified type is the pressure extension type, which uses internal springs to return the piston to its base position when air is expelled. One advantage of single acting design is that in the event of power or pressure loss, the piston will automatically return to its basic position. The disadvantage of this style is that due to the opposite spring force, the output force is somewhat inconsistent throughout the entire stroke. The travel length is also limited by the space required for compressing the spring and the available spring length.