Hydraulic cylinder It is the actuating element of a hydraulic transmission system, serving as an energy‑conversion device that transforms hydraulic energy into mechanical energy. Hydraulic motors produce continuous rotary motion, while hydraulic cylinders generate reciprocating motion.

　　Hydraulic cylinders come in three types: piston cylinders, plunger cylinders, and oscillating cylinders. Piston and plunger cylinders produce reciprocating linear motion, delivering linear velocity and thrust, while oscillating cylinders generate reciprocating rotary motion, providing angular velocity (rotational speed) and torque. In addition to being used individually, hydraulic cylinders can be combined in pairs or in larger groups, or integrated with other mechanisms, to perform specialized functions.

　　A single-acting hydraulic cylinder achieves motion in one direction by hydraulic pressure, while returning to its original position relies on external forces such as gravity or a spring. In this type of cylinder, only one chamber is supplied with fluid, whereas the other chamber is exposed to the atmosphere. A double-acting hydraulic cylinder, on the other hand, has fluid in both chambers, and motion in either direction is driven by hydraulic pressure.

　　Structural principle of a double-acting hydraulic cylinder: The actuating mechanism comprises the cylinder body, throttle valve cover, piston, piston rod, seals, and the bearing surfaces for the piston and piston rod. Typically, it can withstand pressures up to 20,000 kPa (continuous pressure) and is used across various industrial applications; for mixing and pressurization tasks, it can handle pressures as high as 55,000 kPa. Its stroke length can reach 3 meters, and the cylinder diameter can be as large as 20 centimeters, making it suitable for other specialized applications. According to the fundamental hydraulic relationship (Pascal’s law), the linear force generated by the hydraulic cylinder equals the system fluid pressure P multiplied by the effective piston area A, expressed as F = PA. Of course, friction and other real-world losses will reduce the actual force output.

　　The structure of a double-acting hydraulic cylinder actuator is that of a simple single‑acting hydraulic cylinder. With fluid applied to only one side of the piston, it generates output force and motion in a single direction. Alternatively, an external spring can return the piston to its initial position, allowing the fluid to flow back into the cylinder. When the piston rod extends forward, the double‑acting cylinder produces force or motion from fluid acting on both sides of the piston. The seal between the piston’s outer diameter and the cylinder’s inner diameter must reliably accommodate both pressure differentials and reciprocating motion. Additionally, double‑ended cylinders are available, with the piston rod extending through the rear cylinder cap to provide additional stroke.

　　Double-acting cylinders are a common type of hydraulic cylinder, providing output strokes in both directions. Industrial cylinder bodies also support tie rods to secure the cylinder barrel, cylinder head, and end caps. Today, industrial double-acting hydraulic cylinders have been further enhanced with sensor feedback and an electro‑hydraulic servo valve, enabling sophisticated high‑speed and displacement control. Their applications extend beyond production machinery and machine tools, as well as metalworking equipment, to include steel actuators, nuclear power plant controls, passenger elevators, and more.

　　That concludes our overview of key concepts related to hydraulic cylinders. We encourage you to study and thoroughly understand these topics, so you can select products and equipment that best meet your specific needs.