 |
|
When you want to move your arm, your brain sends a signal to a muscle that, upon receipt of that signal, retracts. That retraction pulls the arm in the direction required. To move the arm to other way, the brain signals another muscle to retract, and the arm moves that way. In both cases, the opposing muscles have been ordered to relax.
An air muscle works in a similar fashion.
If you have some tooling that is required to be moved a relatively small, but consistent distance, an air muscle can be used.
 |
In the drawing above you see a "typical" air muscle. On one end is a fitting port (some come with press in instant-type fittings) and on the other is a tooling mounting point. This could be a FNPT or similar.
When air is introduced to the air muscle, it contracts, as show in the drawing below.
 |
When contracting, the air muscle pulls the tooling, and does the work desired of it.
Air Muscles are single acting type actuators, meaning that they will require either an internal or external force to reset them, or revert them to their resting state. Air contracts them, and mechanical force, either in their design or by internal or external spring, extends them.
They are also a rodless type actuator as well.
They can be used horizontally or vertically. Some are used to hang tooling, using themselves as the tooling attachment to the machine.
There are, of course, limitations on the amount you can extend an air muscle, else it will get a sprain! :-)
By the same token, an air muscle has limitations on it's contraction force, this determined by its bore size.
Unlike typical linear actuators, the air muscle has it's greatest force when it begins pulling. The contraction also reduces the amount of surface area upon which the compressed air can work, thus self-limiting it's force. Ideal for self shock absorption.
As I mentioned, various companies offer a variety of bore lengths, some offer the air muscle in fixed lengths with connectors already attached, others (Festo) offers some of their air muscles in a tube form, that you cut to length and add the connectors you wish.
Given a non-changing load weight, the amount of air pressure you flow into it an air muscle will change it's contraction distance.
Think of it; for example, 50 PSI into an air muscle provides, say, 1/2" of travel, 100 PSI into the same air muscle results in 1" of travel. The same air pressure would generate the same amount of stroke, every single time in the same air muscle. Neat.
Want to move something very slowly? Supply air to the air muscle with an electric regulator that slowly increases pressure, and the air muscle will creep along.
When considering using an air muscle you have to think about the application to determine if this technology will suit. Here are some things to consider:
Some vendors will provide software into which you can load the specs of your application and the software will select the right unit for you.
Most vendors will provide CAD support drawings that you can use to drop into your circuit diagrams, if you are making them.
