Air Cylinders
Air cylinders, (i.e., compressed air pneumatic cylinders), function as actuators in pneumatic component systems. An actuator is any mechanism that supplies or transmits controlled energy in a reciprocating linear motion as part of a mechanical process. The energy generated via high-pressure compressed air is converted into kinetic energy that further drives a machine motor. In contrast to air or gas, a cylinder hydraulic actuator consists of a fluid motor that uses hydraulic power for mechanical operation.
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History of Air Cylinders
Pneumatic devices generate and utilize compressed air. The first pneumatic tool was a simple type of air compressor used by early smelters and blacksmiths for working metal and irons.
The first physicist and engineer to experiment and improve air compressors was Otto von Guericke during the 17th century. In 1650, Guericke invented the first air pump to produce a partial vacuum. He used the vacuum to learn about air in relation to combustion and respiration. It wasn’t until 1829 that a patent was made for the first stage or compound air compressor. This type of air compressor works through successive cylinders. A big improvement in efficiency was established in 1872 by using water jets to cool the cylinders known today as the water-jacketed cylinders.
How an Air Cylinder Works
Air cylinders function as actuators in pneumatic systems; an actuator is any mechanism that supplies or transmits controlled energy as part of a mechanical process. Many mechanical processes require access to an actuation method that is reliable, makes no use of harmful chemicals and that is available in many configurations. Different applications call for different air cylinder configurations. The single acting cylinder is able to perform an operating motion in one direction. Pressurized air is introduced on one side of a piston, which causes the piston to move. A spring on the other side of the piston supplies the return force after the pressurized air is released. 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 is capable of powered motion in two directions. 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. Within these two main configuration categories, there are many specialized configurations available.
Design of Pneumatic Air Cylinders
Every air cylinder is composed of a piston, end covers, and a cylinder barrel with at least one air inlet. As compressed air is directed into the cylinder, it pushes the piston along the cylinder’s length. The cylinder can be connected to a protruding rod or other structure, which is connected to the object that is intended to be moved.
Pneumatic cylinders will vary in appearance, size, and function. They generally fall into one of these categories: single acting cylinders (SAC’s), double acting cylinders (DAC’s), and other types. Valves control the flow of compressed air to the cylinder in both configurations.
SAC Design
SAC’s - Single acting (single stage) cylinders have a single inlet which allows compressed air in and moves the piston in one direction. A spring behind the piston pushes the piston back when the compressed air is evacuated. SAC’s require approximately half the amount of air used by a double acting cylinder for a single operating cycle. An example of an SAC would be a rotary screw air compressor. It has two interlocking helical rotors in a vessel or housing. Air comes in through an inlet valve and is taken into the space between the rotors. As the screws turn, they reduce the volume of the air, thus increasing the pressure.
DAC Design
DAC’s - Double acting (two-stage) cylinders are capable of powered motion in two directions. They have two inlets, one on either side of the piston, which allow compressed air in and out, pushing the piston back and forth. Here on IQS Directory, you can find a list of double acting cylinder manufacturers.
Although SAC’s and DAC’s are the most common types of pneumatic cylinders, there are numerous other types of pneumatic cylinders designed to fulfill specific and specialized functions.
Other Air Cylinder Designs
Cable cylinders have elongated housing, two rollers, and a cable that extends from one end of the cylinder to the other. The yoke, which is the load-bearing surface, is suspended by the cable and moves its attached load as the cable moves back and forth.
Rotary cylinders differ from typical air cylinders because they allow revolving motion instead of linear motion. They are typically housed in a circular enclosure in which impellers turn around an axis when pushed by a stream of compressed air. The load-bearing carriage is attached to the axis, which turns in circles both clockwise and counterclockwise.
Rodless cylinders are made of long barrels formed with a vertical slot that allows the piston to connect to a load-bearing carriage. They can use a mechanical or magnetic coupling to convey force, usually to a body that moves along the length of the cylinder. Each of these configurations varies in size and in a load-bearing capacity. The smallest varieties are used in the processing of very small electronics, and the largest is used in heavy-duty industrial processes. A cylinder’s composition also depends on its intended application. Stainless steel for example, is chosen for cylinders that will sustain heavy loads and be subject to harsh conditions.
Components of Air Cylinders
Carefully chosen air cylinders can be great assets for their users; they are effective, environmentally friendly, and available in enough configurations to suit the needs of most industries. Cylinders should be chosen for their ability to move the greatest load at the lowest acceptable velocity with the minimum available pressure. Air cylinders are safer than hydraulic in terms of reliability in performance and prevention of gas and fluid leaks.
ISO 6432-compliant cylinders all conform to the same dimensions from manufacturer to manufacturer, but not all air cylinder producers make compliant cylinders. Because so many of the processes in which air cylinders are used require extreme precision, every air cylinder must be carefully chosen to ensure proper and safe operation.
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. Cylinder mounting hardware which includes noses, blocks, pivots, and other equipment is chosen based on the size, force, and function of the cylinder.
Stainless steel and brass are among the most common construction materials. Nickel-plated brass is better for higher corrosion resistance than regular brass.
Air cylinders have a wide range available in sizes as small as 2.5 mm in diameter to 1,000 mm in diameter. Advanced equipment including compact cylinders, miniature air cylinders, and small air cylinders are gaining prominence among manufacturers as microtechnology development operations require access to them.
Applications for Air Cylinders
In many industrial applications, linear motion is part of the operating sequence. One of the most cost-effective and simplest ways to accomplish linear motion is with a pneumatic air cylinder. Air cylinders are used in food processing and packaging, metalworking, automotive manufacturing, mining, textile production and many other industries.
Flow Control System Operation in an Air Cylinder
A large number of industrial process machines that use compressed air as a source of energy include air cylinders, or to be more specific, pneumatic cylinders. Sometimes, pneumatic actuators are also used in industrial appliances to provide the energy to a manufacturing process. Compressed air is an inflammable and explosive gas that moves very fast from a high-pressure chamber to a low atmospheric pressure. The shift in the position of the air valve, the release of air or gas through the valve, and the movement of the cylinder piston and rod all occur very quickly.
Therefore, the speed of the piston, rod, and airflow are important aspects to measure and control during a process. Fast moving rods are impractical to measure, which is why air flow controller systems are used in many air cylinder designs. These mechanisms are usually installed in the air lines located between the valve and the cylinder. Oftentimes, these systems are installed in the cylinder port and also in the exhaust port. However, setting up the flow control mechanism in the exhaust port is not always a necessity.
While introducing an airflow controller system within a cylinder, it is important to notice the cylinder control reaction time. This majorly depends on the distance of the flow control system from the cylinder.
Another way to control the airflow is using needle valves. These valves regulate the flow of air inside and outside the cylinder. This trick can reduce the air flow significantly; however, air flow in either direction could create a problem in the heat or energy transfer of your process equipment.
Cylinder flow control systems, which look similar to a needle valve, include a needle bypass. This needle bypass enables the air to pass through the needle that finally controls the airflow.
The free flow of compressed air that passes through a cylinder’s flow control system allows the cylinder to have a full and desired supply of air. However, you will need to make sure that the flow control system has been installed properly. The system also ensures that the outflow of the air is also controlled to the necessary level, which ultimately helps achieve the desired cylinder speed.
If there is a need to introduce a second airflow control system, then also, the system will perform the same job.
Flow control systems control the airflow in and out of a cylinder port, and provide smooth and well-controlled movements of the cylinder piston. The smoother the piston movement, the more controlled your process equipment will perform. Without a throttling system, a piston moves at a very fast speed, uncontrollably. When a flow control system is hosted in the exhaust flow, it puts an end to the unregulated movement of the piston. In fact, the piston starts moving at the controlled and programmed rate. If you want this system to be installed in your process equipment’s compressed air unit, you will need to ensure that it has been installed correctly.
Most cylinder flow controls have a schematic on the side showing the flow paths to ensure that they are installed correctly. Proper installation will reduce waste while increasing the performance of the equipment.
Industrial air cylinders can be customized according to plant or application requirements by working with a manufacturer or supplier. In addition, liquid and solid carbon dioxide in a variety of cylinders, vessels, and containers can be customized to fit precise application needs.
Types of Air Cylinders
Brass Cylinders
Pneumatic actuators built of specific copper alloys that resist corrosion and wear and allow use in a number of harsh industrial environments.
Cable Cylinders
Pneumatic devices that utilize pressure differentials to convert compressed air energy into mechanical energy in order to facilitate lateral movement of a cable or wire and all attached loads.Clean profile cylinders are flat barrels with round edges and T-slots for sensors along the entire length of the barrel on three sides. Clean profile cylinders are used in applications that require ease of cleaning and good hygiene as the clean, square line design prevents the collection of dust and dirt.
Compact Cylinders
Also called “short stroke cylinders,” are cylinders whose overall dimensions at zero stroke are minute compared to the typical cushioned cylinders. These low-profile cylinders are used in applications in which there is not enough space for a standard length cylinder, as they can lock or move short distances, even in limited spaces.
Compressed Air Cylinders
Convert power from compressed air into mechanical power.
Double Acting Cylinders
Have air lines that provide pressure to both ends of the cylinder, supplying motion in two directions. The flow of compressed air is controlled by valves.
Double Rod Cylinders
Have one piston, and the piston rod extends from both ends of the cylinder.
High-Pressure Air Cylinders
The most powerful compressed air units. High-pressure cylinders can be used to perform extensive tasks, while having low space requirements due to their tiny and well-designed structure.
Miniature Air Cylinders
Also called “microcylinders,” are small, rectangular, single-acting air cylinders in which the springs are housed inside enlarged piston rods. Miniature air cylinders operate in reverse motion and are easy to install. They offer a range of interchangeable mounting brackets, which attach to the cylinder ends to provide versatility and adaptability and can be powered by plant air.
Multiple Bore Cylinders
Have two or more boxes and pistons combined or stacked in the same cylinder.
Multiple-Position Cylinders
Double-acting cylinders that consist of two cylinders with the same diameter. Multiple-position cylinders provide three or more end positions, as opposed to the normal two provided by other double-acting cylinders.
Non-rotating Cylinders
Cylinders in which the piston rod, ram or plunger and the relative rotation of the cylinder housing and piston are set.
Pancake Cylinders
Have shorter lengths and larger diameters than other cylinders.
Pneumatic Cylinders
Consist of a piston, a lower and upper port and an expansion chamber.
Reverse Single Acting Air Cylinders
Similar to single acting air cylinders, but the port is located on the opposite end in order to provide power on the retraction (or “pull”) stroke.
Rectangular Cylinders
Encased in a rectangular, box-shaped frame.
Rodless Cylinders
Have a barrel that is formed with a longitudinal slot, permitting the connection of the piston to the mounting carriage. A hardened band pneumatically seals the cylinder, while a second band on the exterior closes the slot and prevents contamination to the interior of the cylinder; a system of slide rails divides the two bands in the pressure-free zone between the two piston seals, which allows movement of the mounting carriage.
Rotary Cylinders
Pneumatic actuators that utilize pressure differentials, converting compressed air energy into mechanical energy, which is manipulated to facilitate rotational movement. Single rod cylinders have only one piston, and the piston rod extends from only one end.
Single Acting Cylinders
Have air pressure that supplies motion and force from one side of the piston flange and a spring that provides the return force after pressure release. Single-acting air cylinders utilize about half the amount of compressed air, which is controlled by valves, required by double-acting air cylinders for a single operating motion.
Small Air Cylinders
Compact pneumatic actuators precision-built to maximize productivity within a limited amount of space. Smooth body cylinders are cylinders in which the cylinder body encases the piston.
Stainless Steel Cylinders
Suitable for harsh environments in which they will be rigorously cleaned for hygienic reasons or exposed to corrosive forces. Stainless steel cylinders are often referred to as “throwaway,” as they are irreparable, and therefore, the cheapest of all cylinders.
Tandem Cylinders
Consist of two or more cylinders with linked piston assemblies.
Telescoping Air Cylinders
Can work in single as well as double action cylinders. These smart motors can be tuned according to the specific needs of the manufacturing applications and, therefore, are usually more expensive than the previously discussed cylinders.
Tie-Rod Cylinders
Held together by exterior tie rods and are usually in a rectangular bolt pattern.
Twin Rod Cylinders
Consist of a series of twin-cylinder slide units and feature side-by-side twin cylinders in one body and two piston rods connected with a mounting plate. This design guarantees precise guiding compared to a typical cylinder and applies double the force of a cylinder of the same height.
Proper Care for Air Cylinders
Proper care must be taken for air cylinders because there isn’t any lubrication inside the air cylinder as there is with oil lubricated cylinders. Some condensation is formed when the compressor is used. It is important to look for corrosion formation on non-stainless-steel elements. This corrosion can cause problems during use if not maintained correctly. It might go unnoticed while in use, however when idle for any length of time, the corrosion can be problematic over time.
A few things to keep in mind while maintaining air cylinders:
- Air compressors must have a properly fitted water safety device. When a fitter water safety device isn’t available, stop the water supply a few minutes before stopping the air compressor, and then allow the compressor to run unloaded. This makes it possible for the condensation to drain out.
- Air compressor cylinders should be run for at least 30 minutes every week. Do not keep the air compressor idle for long durations.
- At least monthly cleaning is required for unloading piston in the suction valve cover. Applying a thin layer of grease or silicone will help avoid sticking.
It is very important that the air cleaner element is kept clean at all times. Cleaning should be done every 500 working hours from inside out.
Things to Consider When Purchasing an Air Cylinder
Air cylinders, also known as pneumatic cylinders, are industrial devices that apply mechanical engineering principles to produce force and movement. The force and movement are driven by high-pressure compressed air, which actually can be labeled as the source of energy that regulates the performance or production of process equipment. The energy generated via high-pressure compressed air is converted into kinetic energy that further drives a machine motor.
To attain a desired machine speed and overall process quality, it is crucial to use a machine that is appropriate for your unique process. In the following paragraphs, we discuss points to consider when selecting the most appropriate air cylinder for your manufacturing process.
Air Cylinder Machine Weight
When you begin the process of selecting an air cylinder for your process equipment, it is important to keep the weight of the machine in which the air cylinder will be used in mind. The machine consumes the energy released by the cylinder, and its performance depends on the pressure generated by the compressed air. Therefore, the weight of the motor, typically the starter motor, should be kept in mind when selecting the fuel cylinder. Ideally, you should choose a compression cylinder that is suitable for a machine that has 25% more weight than your machine. This is a safe margin that most manufacturing businesses apply.
Cylinder Rotation Diameter
If you want an object to move four inches, then the ideal size of the cylinder’s rod should be at least four inches. However, you can select a longer cylinder size. Most importantly, the size of the object as well as the size of the rod or piston within the cylinder need to be taken into consideration.
Correct Cylinder Installation
Before selecting an air cylinder, check with your air or pneumatic cylinder supplier to ensure that they provide installation service. Make sure that the cylinder has been installed properly to promote safety and efficiency. The cylinder should be installed depending on its size and type. There are different installation procedures that should be followed to assure the proper functioning of the application. Additionally, air cylinders come with several design options that ease their installation. Some of the frequent options are rod-cap thread, rear-cap thread, rear tang, mount, threaded holes that you can use to tighten the bolts, etc. Proper installation can bear the load that the pressure of the compressed air cylinder is trying to move.
Cylinder Type
There are many types of air cylinders, such as reusable cylinders, non-reusable or repairable cylinders, NFPA cylinders (these are approved as per government standards), rod based cylinders, and metal (steel, aluminum, etc.) cylinders. Before deciding which type of cylinder will be suitable for your application, take into consideration the conditions in which it will be used and the application type. You can seek more suggestions on selecting the correct type of cylinder from your supplier or process engineers.
Air Cylinder Manufacturers and Suppliers
IQS Directory provides a detailed list of air cylinder manufacturers and suppliers. Find companies that can design, engineer, and manufacture air cylinders to your specifications. Peruse our website to review and discover top air cylinder manufacturers with roll over ads and complete product descriptions.
Connect with the air cylinder companies through our hassle-free and efficient request for quote form. We have provided company profiles, website links, locations, phone numbers, product videos, and product information for your reference.
Read reviews and stay informed with product new articles. When looking for a reputable air cylinder manufacturer for every type of air cylinder, IQS is the premier source for you.
Air Cylinder Terms
Actuator
A device that converts fluid power into mechanical power. An actuator may be a cylinder or a fluid motor.
Air Consumption
The amount of compressed air that is consumed by a pneumatic cylinder. The energy of the air is converted into power output and exhausted into the atmosphere on the reversal of the piston stroke.
Air Compressor
Device used in a pneumatic power system to supply the compressed air.
Bellows
A circumferentially corrugated cylinder that is flexible and thin-walled and may have integral ends that axially contract or expand when under changing pressure.
Bore
The inside diameter of the cylinder tube.
Bubble Tight
A term referring to a tightly closing valve seat that prevents the leakage of visible gas bubbles.
Clearance
On the working side of the piston, the maximum volume of the cylinder from which the piston displacement volume per stroke is subtracted. Typically, clearance is expressed as a percentage of the displacement volume.
Clevis
A cylinder mounting device.
Compressed Air
Air that is at any level of pressure greater than the prevailing atmospheric pressure.
Crosshead Assembly
The connecting assembly used to translate circular motion to linear motion from the crankcase and connecting rod to the cylinder head and piston rod.
Cushion Cylinder
A device in a cylinder that enables the control of movement by restricting the flow at the outlet, stopping the movement of the piston rod.
Cylinder
Also referred to as a “linear motor,” it is a device that converts pneumatic power into linear (in a line) or reciprocating (back-and-forth) motion.
Cylinder Thrust
The driving force (i.e. the piston power) generated in the cylinder that is a function of the piston diameter, the working air pressure and resistance caused by friction.
Directional Control Valve
A valve that controls the flow of air in a particular direction.
Drag
A situation in which the valve remains partially open after popping until the pressure further decreases.
Filter
A device through which air is passed in order to separate suspended contaminants. The life of cylinders and valves is lengthened by using filters.
Fluid
A liquid or gas.
Fluid Power
Power conveyed and maintained by the use of a pressurized fluid.
Foot
A mounting device for cylinders.
Gag
A device that, when attached to a safety or safety relief valve, prohibits its opening at the set pressure.
Linear Actuator
A device that creates mechanical force in a linear manner.
N.C. (Normally Closed)
A designation describing the position of a valve when it is resting (non-activated).
N.O. (Normally Open)
A designation describing the resting position (non-activated) of a valve.
Piston
The sliding piece that is put into motion by pneumatic pressure. Typically, pistons consist of a short cylinder fitted inside a cylindrical tube in which it moves in and out.
Piston Velocity
Determined by opposing forces, operating pressure, inside diameter, length of air line between control valve and cylinder and size of control valve. The piston velocity may also be affected by the installation of any quick-exhaust or throttle valve.
Pneumatic System
The use of a gas, usually air, to transmit, convert or store power.
Port
The external or internal terminus of the valve on an air cylinder.
Power Factor
The relationship between the surface area of a piston and air pressure of an air cylinder.
PSIA (Pounds Per Square Inch, Absolute)
The sum of gauge and atmospheric pressures, which will vary with altitude.
Regulator
A device that provides control of the operating pressure of the compressed air system. Regulators allow working pressure of the system to be adjusted from the minimum to the maximum at the prop.
Reservoir
A storage area for air that, when located near the prop, prevents air starvation.
Solenoid
A coil of wire, usually in cylindrical form, that is used as a switch or control for the valve of an air cylinder. When solenoids carry a current, they act like a magnet, drawing a moveable core into the coil as the current flows.
Valve
A device that controls the flow of air in an air cylinder.
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