What is a Pneumatic Cylinder? – Principles, Types, Applications

Pneumatic Cylinder

  A pneumatic cylinder is a special type device that uses the energy created by compressed gas to create a force for alternating linear motion. Since that “pneuma” is the Greek word for air, a pneumatic cylinder may also be called an air cylinder.

         A force is applied into the piston, pushing it in the desired direction, very much like hydraulic cylinders. A disc or a cylinder serves as the pneumatic cylinder’s piston. The piston rod transfers the developed force to the object that has to be moved. Due to its cleanliness, silence, and need for little fluid storage space, a small percentage of engineers like this system.

Characteristics of Pneumatic cylinder

Pneumatic cylinder general characteristics include:

• Stroke length of 1 mm to 2 m
• Available force of 2 KN to 30 KN
• Piston speed of 0.02 mm to 2 m/s.

Cylinder Construction

         There are several minor parts as well, including seals, bearings, guiding bands, permanent magnets, and pistons and piston rods. The main parts are the cylinder barrel, bearing cap, end cap, piston, and piston rod.

         All of these components are part of the aforementioned five components that constitute a conventional cylinder.

Cylinder Barrels

         They were originally “simply” tubes. Nonetheless, the majority of cylinders today use extruded profiles rather than tubes. The benefit is that a profile can be utilized for extra purposes.

• Installing the sensors.
• The ability to mount attachment pieces
• Pressurizing double-acting cylinders just one way

Piston Rods

• The component that conveys the force and movement of the cylinder to the outside is the piston rod.
• For the purpose of connecting to other customer components, the piston rod tip typically features a thread.

Pistons

• The actual movement in the cylinder is accomplished by the piston, which is attached to the piston rod.
• The piston must perform more than just a movement, though. Between the front and back cylinder chambers, it creates a seal.
• The piston also needs to transform the kinetic remaining energy in the final position. Moreover, the bearing and end caps are important.

Bearing Caps

• The bearing cap serves as both a bearing and a sealing point for the piston rod while also closing the cylinder (cylinder barrel) on one side.
• Usually, the bearing cap houses one of the air connectors.

End caps

• The end cap secures the other side of the cylinder (Cylinder Barrel).
• The end cap is often where the second air connection is found.

Different Forms of Pneumatic Cylinder

• The cylinders’ size, shape, and composition vary according to the use for which they are intended. Pneumatic cylinders can be made from a variety of materials, including stainless steel, steel, nickel-plated brass, and aluminum.
• The selection of materials for the devices involves considering a variety of factors, including the quantity of loads, a particular stroke length, temperature, and humidity. The devices are also available in a variety of body designs.

Different forms of body constructions offered depending on the job specification

• Flanged-type cylinders cylinder have fixed flanges on the ends. The most prevalent type of cylinder structure is a tie rod cylinder, which is used to support a wide range of weights. They have also been shown to be the safest form to use.
  • Threaded end cylinders have a tendency to have the ends attached to the tube body.
  • One-piece welded cylinders, which are crimped or welded to the tube at the ends.

General Types of Pneumatic cylinder

The basic types of pneumatic cylinders are

• Single-acting cylinders
• Double-acting cylinders
• Telescoping cylinders

Single-acting cylinders

• Single-acting cylinders (SAC) operate under pressure created by compressed air.
• SAC cylinders typically have relatively little extension because of how much room the compressed spring occupies.

Double-acting cylinders

• Air pressure is used by double-acting cylinders (DAC) to retract strokes and change range. This cylinder is composed of two air-intake ports.
• Each has an outstroke and an instroke.

Telescopic Cylinder

• Single-acting and double-acting telescoping cylinders are also referred to as telescopic cylinders.
• They are frequently used for applications where the piston must experience little side loading since their designs enable substantially longer strokes.

Single, Double & Reverse Acting Cylinder

         Cylinders come in single acting, double acting, and reverse acting varieties. Double acting is the most typical, followed by single acting. Reverse-acting gets employed very rarely.

Operating Modes of Pneumatic Cylinder

Types of Cylinder

The pneumatic cylinders are further classified into following types.

• Cylinders with piston rod
• Diaphragm & Rolling Diaphragm Cylinders
• Double ended piston Rod
• Rod-less Cylinders (linear drives)
• Telescopic Cylinder
• Tandem Cylinder
• Multi-position Cylinders
• Impact Cylinders
• Rotary Cylinder

Cylinders with piston Rod

Cylinders with piston rods can be further classified according to two different functions.

• Single-acting cylinders
• Double-acting cylinders

Single-acting cylinders

• Single-acting cylinders only apply compressed air to one side of the piston face, leaving the other side exposed to the atmosphere.
• Only one direction of work can be produced by the cylinder.
• A built-in spring controls the piston’s return movement.
• The built-in spring’s spring force is intended to return the piston to its starting position at a sufficiently high speed when there is no load.
• The natural length of the spring serves as a stroke limiter for single-acting cylinders with built-in springs.
• Because of this, single-acting cylinders are only offered with stroke lengths of up to about 80 mm.

Working of Single Acting Cylinder

         The piston is moved in one direction by the compressed air coming in, and this direction is also where the cylinder force is built up. The air is simply released from the cylinder in the event that the piston needs to return to its starting position.

         The piston is pushed back to its starting position by the mechanical spring. The ventilation/exhaust hole in this component ensures that no high or low pressure is produced as a result of the piston movement in the second cylinder chamber.

Single Acting Cylinder Push & Pull Type

Single-acting Cylinder Push Type

• To force the piston out of the cylinder, compressed air is introduced.
• When the pressure is released, the spring automatically retracts the piston to its starting position.

Single-acting Cylinder Pull type

• To move the piston inside of the cylinder, compressed air is introduced.
• The piston in the cylinder began retracting as soon as the compressed air flowed through the port.
• At the cylinder end is where the pressure port is situated.

Advantages of Single Acting Cylinder

• Simple actuation via a 3-way valve
• Defined position in the event of a power outage
• Reduced air usage

Disadvantages of Single Acting Cylinder

• Force can only be built up in one direction
• Cylinder has a longer construction length
• Maximum stroke length is limited by the spring force
• Spring force reduces force.

Applications of Single Acting Cylinder

• Transferring
• Converging
• Branching
• Allocating
• Clamping
• Ejecting
• Pressing

Single acting cylinder are available in various design as

• Diaphragm Cylinder
• Rolling Diaphragm Cylinder

Diaphragm Cylinder

• It is known as a clamping cylinder.
• The function of the piston is carried out by an integrated diaphragm consisting of rubber, plastic, or even metal.
• The center of the diaphragm is where the piston rod is fastened.
• The tensile stress of the diaphragm results in friction rather than a sliding seal.
• They are employed in short stroke applications, including the production of tools and fixtures, riveting, embossing, lifting, and press clamping.
• They typically work in the food sector.

Rolling Diaphragm Cylinder

They do not exhibit sliding friction and function with 0% leakage when compressed air is introduced to the port, moving the piston rod outward as the diaphragm rolls along the cylinder’s inner walls

Double Acting Cylinder

• The compressed air’s force causes the piston to move in two different directions.
• The maximum stroke length is 2 metres.
• The forward and return strokes have distinct forces and speeds.
• The single-acting cylinder’s building basis is identical to that of a double-acting cylinder.
• The two ports are used alternately as supply and exhaust ports, however there is no return spring.
• The ability to perform work in both directions of motion is a benefit of the double-acting cylinder.
• The cross-sectional area of the piston rod reduces the effective piston surface on the piston rod side.

Different position of Double Acting Cylinder when applying pressure

Advantages of Double Acting Cylinder

• Force increases in all directions of motion
• Constant force (depending on stroke) Possible stroke lengths of several meters

Disadvantages of Double Acting Cylinder

• Every movement requires compressed air
• In the case of a compressed air failure, there is no designated position

Application of Double Acting Cylinder

• Manufacturing of Knife,Doors
• Warehouse Conveyors
• Silk screening, and powder coating

Cylinder With End Position Cushioning

• For protection against heavy impact and damage, cushioning is employed in the final position.
• A cushioning piston obstructs the air’s straight path to the outside before it reaches the end position.

• Instead, a tiny, frequently changeable escape aperture is left open.
• In the cylinder’s last section, compressed air is produced.
• The built-in throttle return valves tiny escape apertures are used to release the excess pressure that results.
• Energy is changed by the necessary compression work.
• The piston advances gradually to its final position.

Rod Less Cylinder

• In a Rod Less cylinder, the load moves next to the piston.
• The key benefits of doing this are having the same stroke length in a smaller space, delivering the same force in both directions, and preventing rod buckling under heavy loads or long strokes.
• The cylinder barrel’s internal piston is propelled by compressed air.
• The piston moves throughout the length of the cylinder in either direction depending on the air pressure on each port.

Advantages of Rod Less cylinder

• In contrast to conventional cylinders, rodless cylinders offer a number of benefits.
• They are perfect for applications with limited space because of their smaller footprint for a similar stroke length.
• Improved capacity to withstand large loads and moment forces.
• Since there is no rod, they are protected against rod bending and buckling.
• Identical force in both directions.

Disadvantages of Rod Less Cylinder

• Dust and dirt from the environment are a threat.
• The movement of the load is fixed to the cylinder’s length.
• When they stretch, inner and outer bands may deteriorate over time.
• Loss of air pressure may occur as a result of air leaks caused by band deterioration.

Application of Rod Less Cylinder

• Material handling
• Loading & lifting
• Web cutting

Rod Less cylinders have two different functional principles

• Mechanically coupled slide
• Magnetically coupled slide

Tandem Cylinder

• The tandem cylinder combines the advantages of two double acting cylinders into a single structure.
• The force on the piston rod is almost doubled by this configuration and the simultaneous loading of both pistons.
• This design is appropriate for applications where a significant amount of force is needed but the cylinder diameter is constrained.

Multi Position Cylinder

• It is made up of a pair or more double acting cylinders.
• The individual cylinders exit based on the applied pressure.
• There will be four places when two cylinders with differing stroke lengths are used.
• Used to fill shelves with products from a conveyor, lever, sorting machine, etc.

Impact Cylinder

• The impact cylinder is the cylinder that has a high kinetic energy.
• Develops a 7.5 to 10 m/s stroke velocity.
• Utilized for pressing, flanging, riveting, punching, etc.

Cable Cylinder

• This cylinder has two active surfaces.
• Each side of the piston has a cable that is fastened to it and run across rollers.
• Small size devices producing long stroke lengths are utilized in door operation.

Telescopic Cylinder

• A special type actuator called a telescopic cylinder can extend far greater than a conventional rod-style cylinder can.
• Two or more tubes that are nestled inside of one another are used to create telescopic cylinders; these tubes serve as both the rod and the barrel.

Application of Telescopic cylinder

• Considering hydraulic cylinders may be used in dump truck bodies. To empty the vehicle, we must lift the dump body 60 degrees.
• Due to the length of the single-stage traditional hydraulic cylinder, dump body cannot return to complete horizontal rest position, making this operation difficult. Telescopic hydraulic cylinders solved design engineer’s challenge.
• Telescopic Cylinder Internal Schematic and Application

Advantages of Telescopic cylinder

• The ability to create single acting, double acting, or a single / double acting combination telescopic hydraulic cylinders.

Disadvantages of Telescopic cylinder

• The telescoping hydraulic cylinder has more expensive and sophisticated design flaws.

Rotary Cylinder

• The piston rod drives the gear wheel using a gear tooth profile. Depending on the direction of the stroke, linear motion is subsequently translated to rotary motion.
• The swivel range is 45, 90, 180, 270, and 360 degrees.
• Pressure, piston area, and ratio all affect torque.

Application of Rotary Cylinder

• Used for regulating air conditioning systems
• Bending metal tools
• Rotating work items, among other things.

Rotary Vane Cylinder

• Has a tiny rotational angle.
• It is rarely larger than 300 degrees.
• It is used for lesser torques.