Introduction to Pneumatic Units

Power Actuators, Motors and Shock Absorbers

Actuators convert fluid energy into useful work.

Fluid-power actuators are available in a number of forms to provide specific types of action. Cylinders work through linear extension; motors impart continuous rotary motion to objects; rotary actuators twist an object through only a partial arc.

Generally, all types of actuators are available for pneumatic or hydraulic operation. Often, the same cylinder can be used for either air or low-pressure oil operation. Air and hydraulic motors, though similar, are usually not interchangeable.

 

 

Cylinders

When fluid is pumped into a cylinder, piston and rod are forced to move in or out against a load. Movement can be all at once, or in increments; the piston may even rotate or carry fluid. It can be returned by gravity, springs, or reversed flow.

Single-acting cylinders, the simplest type, power a stroke in only one direction. When the fluid is allowed to drain from the cylinder, some external force must push the piston back to its starting position. This low-cost cylinder can be used for any job -- like a lift against gravity -- that provides a returning force.

Cushioned cylinders are single-acting cylinders with a built-in shock absorber. Where the function of the cushion is to reduce shock or hammering against the cylinder head, cushions are usually nonadjustable. But adjustable cushions are available for applications where precise cylinder speed is important.

Ram cylinders are usually single-acting types with a rod at or near full-piston diameter. The large-diameter ram is favored when column loads are extremely high or when the rod overhang in a horizontal cylinder could cause sagging. Ram cylinders are frequently used for large press applications and for jacking.

Spring-return cylinders are similar to the low-cost single-acting types, but with a spring added to return the piston to its starting point. This type is widely used in both pneumatic and hydraulic service, but is not always suitable for hydraulic service; if the spring is heavy enough for speedy piston return, it may require too much force to compress. The cylinder must be about twice as long as the required stroke to include space for the spring. Some cylinders are spring loaded in the opposite direction, so they extend with spring action and retract pneumatically or hydraulically.

Double-acting cylinders contain two fluid chambers so that pressure can be used to both extend and retract the rod. Sealing devices work in both directions. This type of cylinder is by far the most common, and can be used in nearly all types of applications. Effective working area of the rod side of the piston is less than that of the other side, so double-acting cylinders retract faster than they extend, and exert less force on the retraction stroke.

Double-end rod cylinders are double-acting types with a rod extending from each side of the piston. A chief advantage of this type is that working areas of both piston sides are equal. So the piston moves at the same rate and delivers equal forces in each direction. Double-end rod cylinders are available with a hollow rod, so that fluid or another machine element can be passed through the cylinder. In a design variation often used on planers, the hollow piston rod is restrained and the cylinder body is forced back and forth to shift the moving table.

Tie-rod cylinders, the oldest and most common, are typically used in industrial jobs. The cylinder body is held together by four or more tie rods that extend the full length of the body and pass through the end caps or mounting plate. In operation, they may perform any of the common cylinder functions except telescoping.

One-piece cylinders are most often used on mobile equipment and farm machinery. The body is either cast integrally, or head and body may be welded together. This is the least expensive type of cylinder; it is compact and simple. But it cannot be repaired when damaged or worn.

Threaded-head cylinders offer a compromise between tie-rod and one-piece units. Threaded units are relatively compact and streamlined, yet can be disassembled for repair by unthreading either or both ends from the cylinder body.

Telescoping cylinders provide a long stroke from a short body. Total stroke length may be as much as four times as long as the collapsed length of the cylinder. Available in either single or double-acting models, telescoping cylinders are widely used for vehicle applications; a typical job is lifting the bed of a dump truck. Force output varies with rod extension: highest at the beginning, when full piston area is used; lowest at the end of the stroke, when only the area of the final stage can be used to transmit force.

Diaphragm cylinders are used in either hydraulic or pneumatic service for applications that require low friction, no leakage across the piston, or extremely sensitive response to small pressure variations. They are frequently used as pneumatic actuators in food and drug industries because they require no lubrication and do not exhaust a contaminating oil mist. Spring-return models should not be pressurized in the reverse direction because reversals can pleat the diaphragm and shorten its life. Double-acting actuators with twin diaphragms are available for applications requiring pressure reversal.

Rotating cylinders impart linear motion to a rotating device. They are often used to actuate rotating chucks on turret lathes. Fluid is ported to the rotating cylinder through a stationary distributor. Rotating cylinders are available both with solid and hollow pistons.

Nonrotating cylinders are used in applications that demand both accurate linear position and precise angular orientation. Special guides can be added to standard cylinders to prevent rod rotation, but this is often expensive and unwieldy. More often, twin-rod or rectangular cylinders are used.

 

More Information on Compressed Air Amplifiers

Compressed air amplifiers (sometimes called vortex tubes) are often used in blow-off and cooling applications. Compressed air input into the air amplifier uses the coanda effect to create a large flow of surrounding air. Amplification ratios of 25 - 40 times are common.

 

More Information on Compressed Air Logic

Compressed Air Logic systems use air valves to control cylinder sequencing. Air logic systems use only air signals and no electrical signals. Air logic systems are particularly useful in applications requiring explosion-proof automation.

 

More Information on Compressed Air Tanks

Air Tanks (also called receivers, or air reservoirs) are used to store compressed air. Most systems have a main air tank at the air compressor to store the output of the compressor and to dampen any fluctuations within the compressed air system. Air tanks are also used at the point of application where its main function is to ensure that the application always has a steady, ample supply of compressed air at a consistent pressure.

 

More Information on Compressed Air Blow Guns

Compressed air blow-guns are a hand-operated air valve that allows the user to direct and control a blast of compressed air. Applications include machine blow-off and liquid agitation. Most blow-guns are designed to comply with OSHA regulations.

 

More Information on Quick-disconnect Couplings

Quick-disconnect couplings are used to join components within a system that routinely need to be disconnected. Quick-disconnect couplings are often used to connect compressed air tools to air supply hoses. Couplings are available in brass, steel, stainless steel, aluminum and plastic (acetal). Couplings consist of two components, the plug (or the nipple) and the socket (which can sometimes come with a sleeve-lock). The Industrial Interchange is a standard sized coupling that is produced by all coupling manufacturers.

 

More Information on Automatic Drain Valves

Automatic drain valves are used at key locations within a compressed air system to drain water and other contaminants from the system. Automatic drain valves use a timer to open the valve for a specific and programmable duration of time. The length of time between valve openings is also programmable.

 

More Information on Electrical Connectors for Solenoid Valves and Air Cylinders

DIN connectors and quick-disconnect connectors are used to connect solenoid valves, valve manifolds, air cylinder limit switches, or proximity sensors.

 

More Information on Exhaust Mufflers for Compressed Air

Exhaust mufflers (also called silencers) are important components within a quiet and safe compressed air system. Exhaust air exiting an air valve can create noise levels that are unacceptable to OSHA and other governing bodies. Exhaust mufflers reduce the noise generated by air exhaust. The overall size of an exhaust muffler will determine the amount of pressure-drop created by the muffler. Clearly, a lower pressure drop with a high noise reduction is the ideal solution. Exhaust mufflers are available in many different materials including; sintered bronze, sintered stainless steel, fiber canister, and plastic.

 

More Information on Compressed Air Fittings

There are many different types of compressed air fittings that are used depending on what type of tubing or pipe is used and what the system pressure is.

 

 

More Information on Barbed Fittings for Compressed Air

Barbed fittings are mostly used for low-pressure applications and often require a tube clamp sleeve be inserted over the tubing to secure it to the fitting. Barbed fittings are available in brass, steel, stainless steel and plastic (polysulfone).

 

More Information on Compression Fittings for Compressed Air

Compression fittings consist of three components; the fitting body, a sleeve (or ferrule), and a nut. For softer tubing, an insert is used inside the tubing for additional support. Compression fittings are designed for use on aluminum, copper or plastic tubing.

 

 

More Information on Pipe Fittings for Compressed Air

Pipe fittings consist of many different configurations, each threaded with pipe thread (NPT). Pipe fittings are used in hard-piped systems, or as adapters in tubing or hose systems. Configurations of pipe fittings available include; reducers, bushings, tees, nipples, unions, couplings, elbows and street elbows.

 

Plastic Fittings for Compressed Air
 

More Information on Plastic Fittings for Compressed Air

Plastic fittings are available in anti-static, cleam-room, and food-grade configurations. Depending on the application requirements, the fitting can be made of phenolic, acetal, PBT, or some other plastic. Plastic fitting also offer the added bonus of being corrosion resistant.

 

More Information on Push-In Fittings for Compressed Air

Push-in fittings (sometimes called push-on fittings) are the simplest fittings to use and are very popular on automation equipment. A collet retains the tubing solidly within the fitting. The collet is pushed back to remove the tubing from the fitting. Push-in fittings are often made of nickel-plated brass, but they are also available in plastic.

 

 

More Information on Compressed Air Flow Meters

Compressed air flow meters consist of a piston held-down by a spring, mounted in a tapered, transparent tube. As the flow increases through the flow meter, the piston will move towards the larger end of the tube in order to allow more air to flow. The edge of the piston is clearly visible through the transparent tube and by comparing the location of the piston to gradations on the tube, the compressed air flow is clearly seen.

 

More Information on Compressed Air Hose

Hose used in compressed air applications is usually made of a synthetic rubber tube with a spiral-braided reinforcement and a synthetic rubber jacket. The rubber construction of the hose makes it very resistant to oils and other contaminants often found in compressed air systems. Hose, although more expensive and bulkier than plastic tubing is much tougher and is often used on hand-held air tools. Barbed-fittings are used almost exclusively on hose.

 

More Information on Hose Reels for Compressed Air

Unlike a plain storage hose reel, live hose reels are available that use a swivel joint to allow the hose to be used without first removing it completely from the reel. The swivel joint inside the reel allows the hose to be attached to the air supply and held pressurized while on the reel, and while being unwound from the reel. Live cable reels are also available for electrical cable storage.

 

 

More Information on Compressed Air Manifolds

Compressed air manifolds are a convenient way of connecting many outlets to a single compressed air supply. Manifolds are usually a long rectangular block of anodized aluminum. Ports are drilled along the sides of the manifold and also into the ends. Generally, the ports on the ends are one-size larger than the side ports. A manifold can also be assembled using banjo fittings. Banjo fittings are fittings with a male thread on one side and a female thread on the other so that they may be ganged together. Most banjo fittings include push-in connections for plastic tubing.

 

 

More Information on Precision Orifices

Ruby and sapphire precision orifices are used in orifice nozzles and restrictors. Precision orifices are used in applications that require precision flow rates. The most critical factor in obtaining a precise rate of flow and coefficient of discharge (CD) is maintaining a precision orifice. The inside diameter, the roundness, the length of the orifice throat as well as the condition of the orifice edges are all factors that affect the flow through the orifice. High precision orifice tolerances are maintained through the use of laser drilling and wire lapping. Ruby and sapphire are almost as hard as diamond, have five-times the abrasion resistance of carbide, and are chemically inert. Applications that use precision orifices include; O2 analyzers, ink jet printing, high pressure jetting, micro metering, leak detection and chemical spray.

 

 

More Information on Pressure Gauges

Pressure gauges consist of a thin, formed spiral tube called a bourdon tube. As pressure is applied to the tube, it straightens out, causing the precision movement that is attached to the centre of the spiral to shift upward. The shifting of the movement causes the needle to rotate within the housing, which indicates the input pressure. Pressure gauges are a very useful tool in every compressed air system and not only give a snapshot of current conditions of the system, but also over time, can help to diagnose the long-term health of the system. Pressure gauges are available in pressure ranges to suit any application, and depending on the accuracy required, units ranging from 0.5% to 3.0% accuracy are available.

 

 

More Information on Pressure Switches for Compressed Air

Pressure switches are useful for monitoring pressure levels in compressed air systems. Most pressure switches consist of a diaphragm attached to an adjustable spring and a micro-switch. System pressure is applied to the side of the diaphragm opposite the spring. Once system pressure exceeds the force generated by the tension of the adjustable spring, the micro-switch is activated. The pressure setting can be adjusted by adjusting the spring tension. Often the micro-switch is a dry-contact switch that will accept any voltage.


More Information on Pressure Transducers for Compressed Air

Pressure transducers (or pressure transmitters) consist of a solid-state pressure sensitive chip that outputs an electrical signal proportional to the input pressure. The output electrical signal is usually 4-20 mA or 0-10 VDC with adjustments for zero-level, and span. The output electrical signal can be transmitted to a PLC to control another device, or transmitted to a panel to display the pressure on a digital meter. They are often referred to as P/I or P/E transducers.

 

 

More Information on Proximity Sensors

Proximity sensors (sometimes called proximity switches) are used on automation equipment to detect the presence of products or equipment. Inductive sensors are non-contact proximity sensors designed to detect the presence of a ferrous material. Capacitive proximity sensors are able to detect both metallic and non-metallic materials.

 

More Information on Rotary Unions for Compressed Air

Rotary unions are installed in rotary equipment to transmit compressed air and other media from a stationary header or piping, to rotating equipment. Rotary unions must be capable of containing high pressures while rotating at high speeds. Sealing surfaces must rotate smoothly, with minimum friction to assure a long leak-free life.

 

More Information on Seals for Compressed Air

Seals are the most important part of any compressed air system. Buna-N (Nitrile) is the most popular seal material used in pneumatic systems. In high temperature applications, Viton (also called Fluorocarbon) is used. Urethane is also used in certain sealing applications. Most cylinders use a pressure-energized and wear-compensated lip-seal for both the piston seal and the rod seal. O-ring seals are used as static seals and in some cylinders in place of the lip-seal.

 

 

More Information on Pneumatic Timers & Pneumatic Counters

Pneumatic timers are an air-logic device used that provides a time-delay in a pneumatic system. A pneumatic counter is used to count a specific event and provide an output when a preset count is reached. Pneumatic timers and counters are useful in applications that do not have existing electrical control (such as a PLC), or explosion-proof and intrinsically-safe applications.

 

More Information on Tubing for Compressed Air

Plastic tubing is a very attractive alternative to traditional piping. Polyurethane, polyethylene, and nylon are the most popular types of tubing available for compressed air applications. When used with push-in style fittings, plastic tubing becomes a very economical option for compressed air systems.


More Information on Compressed Air Hose

Hose used in compressed air applications is usually made of a synthetic rubber tube with a spiral-braided reinforcement and a synthetic rubber jacket. The rubber construction of the hose makes it very resistant to oils and other contaminants often found in compressed air systems. Hose, although more expensive and bulkier than plastic tubing is much tougher and is often used on hand-held air tools. Barbed-fittings are used almost exclusively on hose.

 

 

More Information on Two-Hand Anti-Tie Down Controls

Two-hand anti-tie down controls are used in applications that for safety reasons require both of the operators hands to be kept clear of the machine. Two normally-closed spring-return push button valves are connected to the two inputs of the anti-tie down valve. The output of the anti-tie down is used to actuate a control valve. The two-hand anti-tie down protects the operator by requiring that the two push buttons be actuated within a small period of time. This prevents an operator from 'tying down' one of the push button valves and using the other to initiate the process. Presses, stamping machines, and machines with automatic clamping fixtures are typical applications that use two-hand anti-tie down valves.

 

 

 

Air Cylinders

Air cylinders are used in applications ranging from crust breakers in the steel industry to wafer processing in the semiconductor industry. For this reason, manufacturers have developed many different styles of cylinders with many different operating characteristics, some of which are highlighted below.

Stainless Steel Air Cylinders  

 

Stainless body air cylinders are sometimes referred to as "throwaway" cylinders, due to the fact that they are non-repairable. Generally these cylinders are the least expensive option.

These cylinders are available in both imperial and metric. The metric cylinders generally conform to the ISO 6342 standard. For the imperial cylinders, there is no official industry standard, but most manufacturers' cylinders are interchangeable.

Generally these cylinders have anodized aluminum heads, a stainless tube, and a stainless steel piston rod.

Tie-Rod Air Cylinders  

 

 

"Tie-rod cylinder" is a generic term for an air cylinder with a square head and cap, and 4 bolts (tie-rods) holding the cylinder together.

There are 2 different standards that fall under the "tie-rod" category. The NFPA cylinder is the North American standard, ISO 6431 is the European standard.

Some companies also make tie-rod cylinders that do not conform to either standard.

Rodless Air Cylinders  

 

 

Rodless cylinders are a space-saving alternative to standard rod-style air cylinders.

There are several different styles of rodless cylinder:

กค  Band Cylinders - the carriage rides along the length of the cylinder body. The carriage is connected to the piston through a slot along the top of the cylinder. This slot is sealed with stainless or plastic bands.

กค  Cable Cylinders - the yoke is connected to the piston by 2 cables that run along the cylinder, around a pulley and into the end of the cylinder caps. Through the use of pulleys, the effective stroke of the cylinder can be doubled. Also by wrapping the cable around an external pulley, rotary motion can be created.

กค  Magnetically-Coupled Cylinders - the carriage is connected to the piston through a strong magnet. This design does not allow contamination to enter the cylinder, but loading is limited by the strength of the magnet.

Compact Air Cylinders  

Many manufacturers make a low-profile cylinder for applications where there is not enough space for a standard length cylinder.

Generally, compact cylinders have very little tolerance for side-loading due to their design.

There is no standard for the dimensions of compact cylinders, but just as in the stainless body cylinders, several manufacturers make an interchangeable design.

 

More Information on Pneumatic Air Springs

Air springs are a fabric-reinforced rubber donut with a metal end plate at the top and bottom. As the air spring is pressurized the unit expands and the end plates move apart. As the air spring is vented, the end plates move towards each other. The flexibility of the rubber donut allows the air spring to actuate in an arc, and also allows for end-plate misalignment. The compact size of the air spring allows them to be used in low-clearance lifting applications. Air spring applications include: transfer conveyor actuation, scissor lifts, vehicle suspension systems, and vibration isolation.

 

 

More Information on Compressed Air Booster Cylinders

Booster cylinders use shop compressed air to power an air-over-oil system used in punching, notching, and stamping applications. For efficiency, most booster cylinders use a low pressure (LP) advance stroke to advance the tool towards the work piece. Once the tool is staged at the advanced position, the high pressure (HP) power stroke is started. The advancing air cylinder piston drives the much smaller diameter piston of the hydraulic ram. The ratio between the area of the air cylinder piston and the area of the hydraulic ram is the factor by which the oil pressure is increased.

 

More Information on Braking Air Cylinders and Locking Air Cylinders

A locking cylinder uses a spring-loaded lock that clamps into a groove within the rod and holds the cylinder in position even if air pressure is lost. Air is applied to unlock the clamp. Braking cylinders use a spring-loaded friction brake that locks onto the piston rod. More flexible than locking cylinders, the braking cylinder allows the cylinder to hold at any position throughout the stroke. The brake is spring-activated and air-deactivated.

More Information on Compact Air Cylinders

Compact air cylinders offer the same force output as larger cylinders while taking up less space. Their small size and flexible mounting options make compact air cylinders ideal for small automation equipment. Some low-profile cylinders are available with flat machined sides and threaded-hole mounts for easy, accurate mounting. Despite their small size, compact air cylinders are still able to have magnetic position sensing switches mounted to them.

 

 

More Information on Air Cylinder Hardware

Air cylinder hardware consists of all of the components required to mount air cylinders. In North America, and other countries that use the NFPA cylinder standard, the main parts included in this category include: clevises, rod eyes, rod-end alignment couplers, spherical rod eyes, clevis brackets, eye brackets, air cylinder flanges, trunnions, trunnion brackets, clevis pins, and jam nuts. In Europe and other countries that use the ISO and CETOP standard cylinders, air cylinder hardware includes: female hinges, male hinges, square joints, narrow female hinges for articulated heads, narrow male hinges with articulated heads, square joints with articulated heads, pedestals, pivots, pins, air cylinder flanges, intermediate hinges, front female hinges, clevises, clevis brackets, standard feet, internal and external feet.

 

More Information on Air Cylinder Limit Switches

Air cylinder magnetic limit switches usually come in two varieties. Magnetic reed switches use a tiny micro-switch that is actuated by the magnet within the cylinder's piston. Hall-effect switches are solid-state and sense the magnetic field electronically. Hall-effect switches are available as either NPN or PNP.

 

 

More Information on Rod Boots for Air Cylinders

Rod boots (sometimes called bellows) provide protection against cylinder rod scoring from abrasive particles, chips and other potentially damaging debris. Rod boots are often manufactured of neoprene coated nylon fabric and are an accordion design that expands and contracts with the extension and retraction of the cylinder.

 

More Information on Air Cylinder Rod Locks

Air cylinder rod locks are added to the rod-end of cylinders. In order to incorporate the rod lock, the cylinder must have an extended piston rod. The lock is essentially a friction brake that is applied by spring-force, and removed with an air pressure signal. Because the rod lock applies a friction brake to the rod, it can be applied at any position within the stroke of the air cylinder.

 

More Information on Air Cylinder Slides

Air cylinder slides consist of an air cylinder with external guide shafting. The cylinder and the shafting are connected through a tooling plate. Cylinder slides offer a substantial side-load rating increase over plain cylinders due to the addition of the guide shafting. The most common type of bushings that are available in cylinder slides are bronze bushing, composite bushing, and ball bearing.

 

More Information on Diaphragm Air Cylinders

A diaphragm cylinder uses a rubber diaphragm in place of a piston. Without the friction of a standard piston with seals, diaphragm cylinders are ideal for applications that require a low-friction actuator. To further reduce friction, diaphragm cylinders are often built as a single-acting cylinder with the rod bushing replaced with a linear bearing.

 

More Information on ISO Air Cylinders

ISO cylinders meet both the ISO 6431 and VDMA 24562 standards. ISO cylinders are metric and are generally available in bore sizes ranging from 32mm (1-1/4") to 100mm (4"). ISO cylinders are a medium-duty cylinder and are repairable. ISO cylinders are very popular in Europe. They are not as popular in North America, but they are available from many manufacturers.

 

Standard        
Pneumatic fluid power; single rod cylinders, 1000 kPa (10 bar) series, with detachable mountings, bores from 32 mm to 320 mm; mounting dimensions
Document Number: ISO 6431
International Organization for Standardization
01-May-1992
11 pages

 

Description: Establishes a metric series of mounting dimensions (basic dimensions, nominal stroke and tolerances, bore sizes, mounting styles, piston rod characteristics) required for interchangeability of commonly used pneumatic cylinders.

Keywords: bores; dimensions; interchangeability; mounting dimensions; pneumatic cylinders; pneumatic equipment; pneumatic fluid power; single rod cylinders


Note: This is a withdrawn item.

More Information on Other Air Cylinders

There are many air cylinders that have been developed for specific applications and do not necessarily fit into a specific category. These include threaded body air cylinders, pencil air cylinders, belly dump air cylinders for dump trailers, air cylinders with hydraulic feed check, and others.

 

More Information on Rodless Air Cylinders

Rodless cylinders are a compact alternative to standard rod-style cylinders. The stroke of a rodless cylinder is contained within it's body length which makes rodless cylinders about half the length of conventional cylinders. Rodless cylinders are generally used in long-stroke shuttle applications, but they have many applications. Band cylinders have a carriage that rides along the outside of a tube with a longitudinal split in it. The piston rides inside the tube and is attached to the carriage through the tube's split. A band covers the split to seal the tube. As the carriage moves along the tube, the band is unseated and then reseated as the carriage passes. The band is not able to create a perfect seal, therefore there is always a very slight leak from band cylinders. Cable cylinders use a piston with aircraft cable attached to both ends of it. The cable travels from the end of the piston, through a gland seal in the cylinder's end cap, around a pulley, and connects to a yoke that travels along the length of the cylinder. As air is input into the left end of a cable cylinder, the piston travels to the right which pulls the yoke to the left. Magnetically coupled cylinders use a piston that has very strong, rare earth magnets attached to it. The carriage that travels outside the tube is magnetically coupled to the piston inside the tube. As the piston travels back and forth within the cylinder tube, the carriage travels with it. Magnetically coupled cylinders are leak-free since there are no leak points. In tough applications, the limiting load capacity of the cylinder can be the strength of the magnet.

More Information on Stainless Steel Air Cylinders

Stainless body cylinders are a very popular low-duty, low-cost cylinder. They consist of a stainless steel tube crimped to anodized aluminum end-caps. As the end-caps are crimped to the tube, these cylinders are not repairable. There is no official standard for these cylinders, but most manufacturers make an interchangeable model. The ISO 6432 standard determines the dimension of stainless body cylinders in Europe. The European model is not interchangeable with the North American version. Stainless body cylinders are known under many different names such as; disposable cylinders, throw-away cylinders, original line cylinders, industrial interchange cylinders, and roundline cylinders.

More Information on Telescopic Air Cylinders

Telescopic air cylinders are used in applications that require a collapsed (retracted) length that is much shorter than the required stroke. Telescopic cylinders consist of several stages of equal stroke length, each having a successively smaller diameter than the stage that precedes it. When the cylinder is in the retracted position, the stages are nested within one another. As the cylinder is extended, each nested stage emerges from it's neighbor and extends to it's full length. There are very few applications for telescopic air cylinders, and only a few manufacturers make a telescopic air cylinder. Most applications using telescopic cylinders are hydraulic.

More Information on Tie-rod Air Cylinders

Most tie-rod cylinders are NFPA interchangeable. The NFPA standard controls the major outside dimensions of tie-rod cylinders, making cylinders built by different manufacturers interchangeable. Tie-rod cylinders got their name from the fact that tie-rods are used to hold the cylinder together. The tie-rods extend from one end cap to the other and are either threaded into the end cap or pass through the end cap with a nut on the opposite side. Most cylinders have four tie-rods, but large, heavy-duty tie-rod cylinders can have many more. Heavy-duty tie-rod cylinders have a steel barrel and steel end caps. Medium duty tie-rod cylinders generally have an aluminum cylinder barrel and anodized aluminum end caps.

More Information on Escapements for Parts Feeding

An escapement is a specialized actuator with two inter-connected cylinders in a single housing. The mechanism that connects the two cylinders forces the extension and retraction of the two cylinders in a specific sequence. Escapements are used in parts feed systems and are designed to isolate and release a single part.

More Information on Pneumatic Multi-Motion Actuators

A multi-motion actuator is a single actuator that combines both linear motion and rotary motion, or perhaps linear motion in two separate planes. Multi-motion actuators offer users a simple alternative to purchasing separate components and fabricating transition plates to mount them together. 

More Information on Air Motors

Air motors use compressed air to produce a continuous rotary motion. Air motors are compact, easily reversible, they can be overloaded or stalled for long periods of time without incurring damage, and they can be used in locations where electric motors are not permitted such as hazardous environments. The different styles of air motors available are: vane, radial piston, axial piston, gerotor, impulse turbine, and reactive turbine air motors. Air motor applications include: dentist drills, hoists, mixing, vehicle drive systems, and pneumatic tools.

More Information on Rotary Index Tables

Rotary index tables use an air cylinder to drive a rack and pinion system. The pinion is attached to the lower end of a toothed ratchet. A pawl engages the ratchet once the required rotation angle has been reached, and prevents the index table from rotating further. Standard rotation angles are 90 degrees (4-stations), 60 degrees (6-stations), 45 degrees (8-stations), 30 degrees (12-stations) and 15 degrees (24-stations).

More Information on Indexing Rotary Actuators

Indexing actuators are rotary actuators that rotate in only one direction. A one-way clutch allows the actuator output shaft to rotate in one direction only and prevents it from rotating backwards as the actuator rotates back in the opposite direction.  

More Information on Pneumatic Rotary Actuators

Rotary actuators move through an arc when a compressed air signal is applied. Vane rotary actuators use a rubber or plastic sealed vane that rotates within a housing, and are available in single-vane and double-vane varieties. In rack and pinion rotary actuators, a compressed air cylinder drives the rack that powers the pinion. Double rack units increase the torque output. Scotch yoke rotary actuators are also available. A scotch yoke is a mechanism used to convert linear motion into a rotary motion.

More Information on Valve Actuators

Valve actuators are a specialized type of rotary actuator used to operate large process valves. Plug valves, butterfly valves and ball valves, as well as dampers and other 90?turn devices use actuators. Rack and pinion and scotch yoke actuators are usually used on rotary valves while diaphragm actuators are often used on linear-actuated valves. Valve actuators are often packaged with built-in sensors and position indicators. 

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