The hydraulic cylinder is a hydraulic actuator that transforms the hydraulic energy into mechanical energy and is used for linear reciprocating movement (or swinging motion). It is simple in structure and reliable in work. It is used to realize reciprocating movement, can be removed from the deceleration device, and there is no transmission clearance, smooth movement, so in a variety of mechanical hydraulic system has been widely used. 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 usually consists of the rear cover, the cylinder, the piston rod, the piston assembly, the front cover and other main parts, to prevent leakage of oil from the hydraulic cylinder or from the high-pressure cavity to the low-pressure cavity, in the cylinder and end cap, piston and piston rod, piston and cylinder, piston rod and the front cover are equipped with a sealing device, the front cover outside, also installed dustproof device, In order to prevent the piston from rapidly returning to the stroke terminal, the cylinder head is also provided with a buffer device, sometimes the exhaust device is also needed.