What is Air Cylinder?

Figure 1: Air Cylinder.
(Go to Okmarts and pick the Air Cylinder you need)

1. Definition

The Air Cylinder is a cavity ( in which the piston is placed ) on the block of the internal combustion engine. It is the track of piston movement in which gas burns and expands. The cylinder wall can also dissipate part of the explosive waste heat transmitted by the gas to keep the engine at normal working temperature. The types of cylinder include integral type and single cast type. Single cast type is divided into dry type and wet type. When the cylinder and the block are cast into a whole, it is called an integral cylinder. A single cast cylinder barrel is called a cylinder liner. The cylinder liner in direct contact with the cooling water is called wet cylinder liner; Those that do not come into direct contact with cooling water are called dry cylinder liners.

2. Structure

The air cylinder is composed of cylinder barrel, end cover, piston, piston rod and seal

2.1 Cylinder Barrel

Figure 2: Cylinder barrel.

The inner diameter of the cylinder barrel represents the output force of the cylinder. The piston make smooth reciprocating sliding in the cylinder barrel. The surface roughness of the cylinder barrel should reach Ra0.8 μ m.

2.2 End Cap

Figure 3: End cap.

The end cap have a port for intake and exhaust, and some are provided with a buffer mechanism. The rod side end cap is provided with a sealing ring and a dust ring to prevent air leakage from the piston rod and prevent external dust from mixing into the cylinder. And there is also a guide sleeve to improve the guide accuracy of the cylinder, bear a small amount of transverse load on the piston rod, reduce the downward bending amount when the piston rod extends and prolong the service life of the cylinder.

The guide sleeve usually uses sintered oil-bearing alloy and copper castings. In the past, malleable cast iron was commonly used for end caps. In order to reduce weight and prevent rust, aluminum alloy die casting was often used. And brass was used for micro cylinders.

2.3 Piston

Figure 4: Piston.

The piston is the pressurized part in the cylinder. It has a sealing ring to prevent gas channeling between the left and right cavities of the piston. The wear ring on the piston can improve the guidance of the cylinder, reduce the wear of the sealing ring and reduce the friction resistance. The wear ring is made of polyurethane, polytetrafluoroethylene, cloth sandwiched synthetic resin and other materials. The width of the piston is determined by the size of the sealing ring and the length of the sliding part. The material of piston is usually aluminum alloy and cast iron. The piston of small cylinder is usually made of brass.

2.4 Piston Rod

Figure 5: Piston rods.

The piston rod is the most important stressed part in the cylinder. It is usually made of high carbon steel with hard chromium plated surface or stainless steel to prevent corrosion and improve the wear resistance of the sealing ring.

2.5 Sealing Ring

The seal of the rotary or reciprocating motion is called dynamic seal, and the seal of the stationary part is called static seal.

3. Classification

Cylinders for reciprocating linear motion are as follow:

① Single acting cylinder: there is only a piston rod at the end which supplies air from one side of the piston and gathers energy to generate air pressure. The air pressure pushes the piston to generate thrust and extend. It will return by spring or self weight.

② Double acting cylinder: supply air alternately from both sides of the piston and output force in one or two directions.

Figure 6: Single acting cylinder ( left ) and double acting cylinder ( right ).

③ Diaphragm cylinder: replace the piston with diaphragm, output force only in one direction and return with spring. It has good sealing performance.

④ Impact cylinder: This is a new type of component. It converts the pressure energy of the compressed gas into the kinetic energy of the high-speed (10 ~ 20 m / s) movement of the piston to do work.

The cylinder for reciprocating swing is called swing cylinder, including rotary cylinder, gas-liquid damping cylinder and stepping cylinder.

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