A hydraulic cylinder is a hydraulic actuator that converts hydraulic energy into mechanical energy and performs linear reciprocating motion (or swinging motion). It has simple structure and reliable operation. When using it to achieve reciprocating motion, the reduction device can be omitted, and there is no transmission gap, and the movement is stable, so it is widely used in various mechanical hydraulic systems. The output force of the hydraulic cylinder is proportional to the effective area of the piston and the pressure difference on both sides; the hydraulic cylinder is basically composed of a cylinder barrel and a cylinder head, a piston and a piston rod, a sealing device, a buffer device and an exhaust device. Buffers and exhausts depend on the application, others are essential.