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If you have an application that requires virtually immediate response of your linear actuator, the diaphragm or rolling lobe air cylinder can provide it.
Where there is a need for minute, hesitation free movement; perhaps in web tensioning, diaphragm or rolling lobe air cylinders are the perfect solution.
The rolling-lobe type cylinder is ideal for use with electronic regulators that use an electrical signal to alter the pressure to the cylinder to vary the cylinder force, responding very quickly in providing greater or lesser rod end force as the electronic regulator increases or decreases the air pressure to the cylinder ports.
What is a diaphragm or rolling lobe air cylinder then? Please have a look at the simple drawing below.
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Instead of the piston-to-barrel bushings and seals in a traditional linear air cylinder, the piston in the diaphragm or rolling lobe cylinder is attached to a diaphragm which is attached to the end cap.
The rolling lobe is depicted in blue in the drawing.
A single acting style is shown in the drawing. They are available in spring extend, spring return and also in double acting formats.
Since there is no “sticktion” between the cylinder piston and the cylinder barrel as compressed air enters the cylinder, the piston and the rod start to move almost instantly. Movement is free, effortless-almost frictionless.
As the piston travels the length of the cylinder barrel, the diaphragm unrolls (it is a rolling lobe, after all) to allow the piston to travel. Upon the return stroke, the diaphragm re-rolls to it’s former shape.
This type of cylinder is unmatched in low breakaway force, and repeatability of stroke.
This type of cylinder requires no external lubrication source.
The diaphragm, rolling-lobe type cylinder offers a number of mounting styles but the norm is through four threaded mounting holes on each cylinder cap. Clevis brackets or foot mounts are available as well.
Like other types of air actuators, you will need to know the following to help select a diaphragm cylinder for your application:
