The cylinder is composed of a cylinder barrel, an end cover, a piston, a piston rod and a seal. Its internal structure consists of:
1) Cylinder barrel
Cylinder The inner diameter of the cylinder represents the output force of the cylinder. The piston must reciprocate smoothly in the cylinder, and the surface roughness of the inner surface of the cylinder should reach Ra0.8μm.
SMC and CM2 cylinder pistons use combined sealing rings to achieve two-way sealing, and the piston and piston rod are connected by riveting without nuts.
2) End cover
The end cover is equipped with intake and exhaust ports, and some also have a buffer mechanism inside the end cover. The rod side end cover is equipped with a sealing ring and a dust ring to prevent air leakage from the piston rod and external dust from mixing into the cylinder. There is a guide sleeve on the rod side end cover to improve the cylinder's guidance accuracy, bear a small amount of lateral load on the piston rod, reduce the amount of downward bending of the piston rod when it extends, and extend the service life of the cylinder. Guide sleeves are usually made of sintered oil-containing alloy, forward-inclined copper castings. In the past, malleable iron was commonly used for end caps. In order to reduce weight and prevent rust, aluminum alloy die-casting was often used, and brass materials were sometimes used for micro cylinders.
3) Piston
The piston is a pressure-bearing part in the cylinder. In order to prevent the left and right chambers of the piston from channeling air, a piston sealing ring is provided. The wear-resistant ring on the piston can improve the guidance of the cylinder, reduce the wear of the piston seal ring, and reduce friction resistance. The wear-resistant ring length uses materials such as polyurethane, polytetrafluoroethylene, cloth-filled synthetic resin, etc. The width of the piston is determined by the size of the sealing ring and the necessary length of the sliding section. The sliding part is too short, which can easily cause early wear and jamming. The materials of piston are commonly aluminum alloy and cast iron, and the piston of small cylinder is made of brass.
4) Piston rod
The piston rod is the most important force-bearing part in the cylinder. Usually high carbon steel is used, with hard chromium plating on the surface, or stainless steel is used to prevent corrosion and improve the wear resistance of the sealing ring.
5) Seal ring
The seal of the rotating or reciprocating parts is called a dynamic seal, and the seal of the stationary part is called a static seal.
The main methods of connecting the cylinder barrel and the end cover are as follows:
Integral type, riveted type, threaded connection type, flange type, tie rod type.
6) When the cylinder is working, it relies on the oil mist in the compressed air to lubricate the piston. There are also a small number of lubrication-free cylinders.