Functions of the main components of a hydraulic cylinder:

 (1) Cylinder body: The cylinder body is welded from the cylinder barrel, flange, exhaust valve seat, and oil port. It is the main body of the hydraulic cylinder. The surface roughness Ra value of the inner bore is generally required to reach 0.16~0.32μm so that the piston and its seals and supports can slide within it and ensure the sealing effect, reducing wear. The cylinder body must withstand a large liquid pressure, so it is required to have sufficient strength and rigidity. The flange is welded to its end to connect the end cap. The oil port and exhaust valve seat are welded to both ends of the outer circle of the cylinder body and communicate with the inner bore to allow the pressure oil to enter and exit and the air to be discharged.

(2) Piston: The piston is the main component of the hydraulic cylinder that converts hydraulic energy into mechanical energy. The size of the effective area of ​​its two end faces determines the magnitude of the thrust and pull. There are sealing rings between the piston body and the piston rod to ensure that no internal leakage occurs in the hydraulic cylinder.

(3) Piston rod: The piston rod is an important component that transmits the mechanical energy generated by the piston to the load. One end is connected to the piston, and the other end is connected to the load (through parts such as lugs). To output the force generated by the hydraulic cylinder, sufficient strength and rigidity are essential; therefore, calculating the strength of the piston rod is crucial. Since it slides reciprocally within the guide sleeve, its outer surface must be wear-resistant and rust-resistant. Therefore, the outer surface of the piston rod is generally chrome-plated. At one end, there is a journal for fixing the piston and a buffer plunger, requiring all outer surfaces to be concentric.

(4) Support Seat: The support seat is the transition part between the cylinder end and the guide sleeve, ensuring the coaxiality of the guide sleeve and the inner bore of the cylinder. Some hydraulic cylinders, to reduce the number of parts, have the guide hole directly made on the support seat. Sealing rings are installed on its outer diameter and end face to prevent leakage of pressurized oil.

(5) Guide Sleeve: The guide sleeve is designed to ensure the linearity of the reciprocating sliding motion of the piston rod. It is generally made of aluminum-tin bronze, which has good wear resistance and a low coefficient of friction. The inner bore surface has annular and straight oil grooves to facilitate oil entry into the sliding pair, reduce friction, and extend service life. (6) End Cap: The end cap is the "sealing point" of the hydraulic cylinder. It can be connected to the cylinder body via welding, threading, bolting, etc. Its inner surface has a sealing ring to prevent pressure oil leakage and a dustproof ring to scrape away dirt from the piston rod and prevent dust from entering the hydraulic cylinder.

(7) Cylinder Bottom: The cylinder bottom is the "sealing point" at the bottom of the hydraulic cylinder. It can also be connected to the cylinder body in various ways. To simplify the structure, an oil port, exhaust valve hole, and buffer chamber can be directly installed on it.

(8) Nylon Support Ring: Due to the long-term sliding friction between the piston and the inner surface of the cylinder bore, the smooth inner wall of the cylinder can easily be scratched. To avoid this, nylon (polyamide) or polytetrafluoroethylene (PTFE) is used to make a support ring that fits onto the piston, separating the piston from the inner wall of the cylinder. This improves lubrication performance and avoids the possibility of cylinder scoring. (9) Air release valve: Air often remains or enters the hydraulic cylinder and hydraulic lines. Since air is compressible, if not removed, it will cause piston creep and vibration. Therefore, air should be released when using the hydraulic cylinder. The air release valve is designed to remove air. After venting, close the air release valve, and the hydraulic cylinder can work normally.

(10) The functions of parts such as oil ports, retaining keys, retaining key caps, spring retaining rings, oil cups, bushings, and sealing rings are quite obvious. Their selection must be based on the specific conditions of the hydraulic cylinder.