The working principle of hydraulic cylinders is based on Pascal's principle, which means that the pressure on a sealed liquid can be transmitted in all directions with a constant magnitude. Hydraulic cylinders use oil as the working medium to transmit motion through changes in sealing volume, and transmit power through the pressure inside the oil. The specific process is as follows:
Power section: Convert the mechanical energy of the prime mover (such as an electric motor or engine) into hydraulic pressure energy.
Execution part: Convert the hydraulic pressure input by the hydraulic pump into mechanical energy to drive the working mechanism. In hydraulic cylinders, hydraulic pressure pushes the piston rod to extend or retract, thus completing linear reciprocating motion.
Control part: used to control and regulate the pressure, flow rate, and flow direction of the oil, in order to achieve precise control of the movement of the hydraulic cylinder.
Auxiliary parts: including oil tank, filter, accumulator, seals, pipelines, etc., used for oil storage, filtration, measurement, and sealing to ensure the normal operation of the hydraulic system.

The hydraulic cylinder is mainly composed of the following parts:
Cylinder barrel and cylinder head: The cylinder barrel is the main part of the hydraulic cylinder, which bears the hydraulic pressure. Connect the cylinder head to the cylinder barrel, seal one end of the cylinder barrel, and install a piston rod sealing device.
Piston and piston rod: The piston is located inside the cylinder, separating the cylinder into two chambers. The piston rod is connected to the piston, transmitting the movement of the piston to the outside.
Sealing device: including piston seal, rod seal, etc., used to prevent oil leakage and ensure the normal operation of hydraulic cylinders.
Buffer device: used to reduce the impact of piston rod movement to the terminal, protect hydraulic cylinders and mechanical equipment.
Exhaust device: used to remove air from the cylinder and prevent cavitation.
Classification
Hydraulic cylinders can be classified according to different classification methods:
Divided by exercise mode:
Linear reciprocating motion type: The piston rod performs linear reciprocating motion, which is the most common type of hydraulic cylinder.
Rotary swing type: outputting torque to achieve reciprocating swing, commonly used in situations where swinging motion is required.
According to the effect of hydraulic pressure:
Single acting: There is only one hydraulic chamber, and the piston rod can only move in one direction. The movement in the other direction requires external force or spring assistance.
Double acting: There are two hydraulic chambers, and the piston rod can move in two directions, driven by the hydraulic pressure of the two chambers.
Divided by structural form:
Piston type: The piston and piston rod are connected together, and the piston moves back and forth in the cylinder.
Piston type: The plunger is not in contact with the cylinder, and motion and power are transmitted through the change in sealing volume formed by the plunger head and cylinder head.
Multi level telescopic sleeve type: composed of multiple cylinder sleeves stacked together, it can achieve multi-level telescopic and increase stroke.

Hydraulic cylinders have the advantages of simple structure, reliable operation, smooth movement, high force, and adjustable speed, and are applied in various mechanical equipment, such as:
Construction machinery: excavators, loaders, bulldozers, rollers, etc.
Metallurgical equipment: rolling mills, continuous casting machines, blast furnace top equipment, etc.
Ship field: servos, cranes, cable tensioners, etc.
Aerospace: landing gear, cabin doors, control surfaces, etc.
Agricultural machinery: combine harvesters, tractors, etc.

When selecting hydraulic cylinders, the following factors need to be considered:
Use pressure: Select the working pressure level of the hydraulic cylinder based on the system's working pressure.
Speed: Calculate the movement speed of the hydraulic cylinder based on the system's flow rate and the effective area of the piston.
Travel: Determine the travel of the hydraulic cylinder according to work requirements.
Operating conditions: Consider factors such as working environment, load characteristics, installation method, etc., and select the appropriate type and structure of hydraulic cylinder.
Brand and Quality: Choose branded hydraulic cylinders to ensure product quality and performance.
In addition, when using hydraulic cylinders, the following points should be noted:
Maintain oil cleanliness: Regularly replace hydraulic oil to prevent impurities from entering the hydraulic system and damaging seals and hydraulic components.
Reasonable lubrication: lubricate moving parts such as piston rods to reduce friction and wear.
Regular inspection: Regularly check the operating status of hydraulic cylinders, promptly detect and handle faults.
Correct installation: Install according to the installation requirements of the hydraulic cylinder to ensure installation quality and reliability.