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About Air Cylinders
Air cylinders are the final component in a pneumatic
or compressed air control or power system. Air cylinders, or pneumatic
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. The choices for cylinder housing styles include the following:
tie-rod, smooth body, pancake, rectangular, multiple bore, stainless
steel, rodless,
compact, miniature/microcylinder,
clean profile and twin-rod cylinder.
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. A single acting air cylinder 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. Other types of cylinders include rotary
cylinders, impact cylinders and multiple- position, or opposed-thrust, cylinders.
Pneumatic systems produce large linear movement and consist of an input, a process
and an output. The input is compressed air from the compressor or hand pump.
The process is a valve that directs the air to the rod end or base of the cylinder,
and the output is an extending or retracting piston rod. Use of pneumatic systems
is advantageous because they can be connected with hoses, pipe or tubing without
difficulty. Air is inexpensive and plentiful and can be easily compressed and
stored in tanks. Exhaust air is relatively environmentally friendly and can be
returned to the atmosphere. Pneumatic systems are used to push, pull, lift and
open/close doors in material handling and processing. They can also hold, remove
and position materials or pieces for manufacturing.
Air cylinder manufacturers produce many different cylinder designs for a variety
of applications in different industries. Choosing an air cylinder for a pneumatic
system can be a daunting 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. In 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.
Featured
Articles
http://www.wisegeek.com/what-is-an-air-cylinder.htm
http://www.inmotiononline.com.au/feature_article/article.asp?item=404
Types of Air Cylinders
- have
adjustable stops at one or both ends to restrict the amount of piston
travel.
- 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.
- ,
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.
- convert power from compressed air into
mechanical power.
- 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.
- have
one piston, and the piston rod extends from both ends of the cylinder.
- , 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, are easy to install, 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.
- have
two or more boxes and pistons combined or stacked in the same cylinder.
- are 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.
- are
cylinders in which the piston rod, ram or plunger and the relative
rotation of the cylinder housing and piston are set.
- have
shorter lengths and larger diameters than other cylinders.
- are comprised of a piston, a lower and upper
port and an expansion chamber.
- are 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.
- 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.
- are
cylinders in which the cylinder body encases the piston.
- are
encased in a rectangular, box-shaped frame.
- have an extruded anodized aluminum barrel
that is formed with a longitudinal slot, permitting the connection
of the piston to the mounting carriage. A hardened stainless steel
band pneumatically seals the cylinder, while a second stainless
steel 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.
- have
only one piston, and the piston rod extends from only one end.
- are 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.
- consist
of two or more cylinders with linked piston assemblies.
- are
held together by exterior tie rods and are usually in a rectangular
bolt pattern.
- 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.
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