Pneumatic cylinders, also known as pneumatic air cylinders or air cylinders, are devices that change the power exerted by compressed air into mechanical energy. This energy is then harnessed to generate rotary or linear motion in pneumatic systems. Generally, these systems exist for one of two reasons. They either: open and close, lift and push and pull doors in material handling and material processing applications, or position, hold and remove pieces or materials for manufacturing.
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Design of Pneumatic Cylinders
The basic configuration of pneumatic cylinders is one that consists of a piston, a piston rod, a cylinder barrel and end covers. The shape of the cylinder body, or housing, itself may be one of any number of common styles, which include: twin-rod cylinder, rodless, tie-rod, miniature/microcylinder, compact, rectangular, multiple bore, pancake, clean profile and smooth body. Typically, these parts are made either of steel, stainless steel, nickel-plated brass or aluminum. To work, compressed air, controlled by valves, is sent into the cylinder, where it forces the piston to move through the length of the cylinder. Once it reaches the end of the cylinder, the piston is pushed back into its original position either by a spring or additional compressed air. To assist in these operations, specifically by increasing their production of linear energy, pneumatic cylinders can be joined with tubing, pipes or hoses.
Pneumatic cylinders are typically available in sizes ranging from approximately 2.5 mm (0.10 in) and 1,000 mm (39 in). In addition to type and size, they are ordered according to their air consumption, speed and mounting configuration, or how they are attached to adjacent machinery.
Materials Used in Pneumatic Cylinders
The most commonly available materials for pneumatic cylinder construction include: steel, stainless steel, nickel-plated brass and aluminum. In addition, they may be configured with a variety of different mount ends. These include: plain, flanged, threaded, foot, clevis, trunnion, eye or torque, clevis and bracket-single or bracket-double.
Types of Pneumatic Cylinders
There are a variety of different pneumatic cylinder types, including impact cylinders, rotary cylinders, opposed-thrust cylinders, cushion end cylinders, tandem cylinders, telescopic cylinders, multiple-position cylinders, rodless cylinders, through rod air cylinders, tie rod cylinders, flanged-type cylinders, one-piece welded cylinders and threaded end cylinders.
- Tie Rod Cylinders
- Able to work with many, many different types of applications, tie rod cylinders are the most secure, the safest and likely the most heavily used type of pneumatic cylinder.
- Flanged-Type Cylinders
- Following tie rod cylinders, flanged-type cylinders are those pneumatic cylinders with fixed flanges, consisting of protruding collars and ribs or flat rims, attached to their ends.
- One-Piece Welded Cylinders
- Have ends that are welded or crimped to the tube. They are valued as inexpensive to produce and quite secure. However, some of their value is detracted when one factors in the fact that their end cannot be removed, and therefore the space in between the end and the tube cannot be serviced.
- Threaded End Cylinders
- Cylinders with ends screwed onto their tube body. On the one hand, the threaded ends of threaded end cylinders are a great idea, because they help create secure bonds with other ends. However, on the other hand, they can be a risk, because the material reduction involved in their formation can weaken the tube and cause issues later down the line, such as problems with thread concentricity.
- Single and Double Acting Cylinders
- None of the above pneumatic cylinders, however, are as popular or common types as single acting cylinders and double acting cylinders. The difference between the two is, in short, that a single acting cylinder can direct motion in one direction only, while a double acting cylinder can direct motion in two directions. Single acting cylinders use air pressure one side to generate force and motion and return the piston using a spring that activates after pressure release. They use about half the energy required to power double acting cylinders, which have air lines running at both ends in order to provide compressed air-inspired motion in multiple directions.
Things to Consider When Purchasing Pneumatic Cylinders
For guidance, customers are advised to seek out experienced manufacturers, who will take into consideration variables like load levels, application location, projected temperatures and humidity and intended stroke lengths. Pneumatic cylinders are cleaner, quieter and require less space for fluid than hydraulic cylinders. Provided they make the right feature selections for their application, customers will find that pneumatic cylinders are inexpensive and accessible, easily installed and environmentally friendly.