Air Cylinders Industry Information

Air cylinders are the final component in a pneumatic or compressed air control or power system. They are used in the food processing and packaging, metal working, automotive, mining, textile, and forest industries. Also referred to as compressed air cylinders or pneumatic cylinders, air cylinders are devices that convert compressed air power into mechanical energy. This mechanical energy produces linear or rotary motion. In this way, the air cylinder functions as the actuator in the pneumatic system, so it is also known as a pneumatic linear actuator. The air cylinder consists of a steel or stainless steel piston, a piston rod, a cylinder barrel and end covers. As compressed air moves into a cylinder, it pushes the piston along the length of the cylinder. Compressed air or a spring, located at the rod end of the cylinder, pushes the piston back. Valves control the flow of compressed air to the cylinder. There are two basic types of air cylinders-double acting cylinders, which are able to perform an operating motion in two directions and single acting cylinders, which are able to perform in one. Other types include rotary cylinders, cable cylinders and rodless cylinders. They are housed in different styles and named accordingly. These include stainless steel cylinders, brass cylinders, compact cylinders, miniature air cylinders and small air cylinders.

Air cylinder manufacturers produce two basic types of air cylinders: single acting and double acting. The single acting cylinder is able to perform an operating motion in only one direction. It has air pressure on one side of a piston flange, supplying force and motion, and a spring supplying the return force after pressure release. Single acting cylinders require approximately half the amount of air used by a double acting cylinder for a single operating cycle. A double acting pneumatic cylinder has powered motion in two directions, with pressure on both sides. When a cylinder is pushed out in one direction, compressed air moves it back in the other direction. Air lines running into both ends of the cylinder supply the compressed air. The flow of compressed air is controlled with valves for both single and double acting cylinders. Cable cylinders have elongated housing, 2 rollers and a cable that extends from one end to the other. Rotary cylinders differ from typical air cylinders because they provide the ability to move machine tooling in a revolving motion, instead of linear. Rodless cylinders are made of long, aluminum barrels formed with a vertical slot which allows the piston to connect to the mounting carriage. They are actuators that use a mechanical or magnetic coupling to convey force, usually to a body that moves along the length of the cylinder, but doesn't extend beyond it. Cable cylinders are rodless, but don't use the same type of sealing method and have a cable attaching either sides of the piston instead of a rod.

Every pneumatic air cylinder has specific components, although different versions vary somewhat. A typical cylinder consists of a rod, which is a linear actuator kept inside the cylinder, a port, which is a hole in the cylinder that the compressed air (media) is conveyed to attain linear movement, piston seals, anodized heads, wrench flats and mounting cylinders for installation. Housings for air cylinders come in a wide variety. Those made out of brass and stainless steel are suitable for harsh environments, where they will be thoroughly and hygienically cleaned, or exposed to corrosive forces. Miniature and small air cylinders are single-acting and disposable. Their springs are housed inside enlarged piston rods and they operate in reverse motion. Compact cylinders' overall dimensions are much smaller than other cushioned cylinders. Therefore, they are used where space is very limited.  

Manufacturers of air cylinders produce many different cylinder designs for a variety of applications in different industries. Choosing an air cylinder for a pneumatic system can be a difficult task. Air cylinder manufacturers can customize units with a special stroke, a custom mounting style or unusual seal material. Although custom air cylinders have the advantage of exactly suiting the application, it is recommended to look for an off-the-shelf solution first, as standard air cylinders cost less and are available for quick delivery. With sizing cylinders, focus on the load, velocity and air pressure. The cylinder should be sized to move the greatest load at the lowest acceptable velocity with the minimum available pressure. Determine the stroke length, the spring force (for a single-acting cylinder) and the overall dimensions of the cylinder. The mounting style-the options for which include nose, block, universal, pivot and trunnion-is determined by the size, force and function of the cylinder. Optional components that help to improve cylinder performance or prevent problems include cushions, bumpers, stop tubes, dual pistons, flow controls, position-sensing switches and position feedback sensors. Environmental factors have a huge impact on cylinder operation, so choose seals, beatings, lubricants, materials and finishes that will help counteract any negative effects.