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Real-lifeapplications prove successful Example 1: Inflatable actua-tors serve as automatic door seals for environmental chambers, process- ing vessels, sterilizers, and flood bar- riers. Typically, Figure 1, the door slides into place along a track; then the bladder actuators, mounted to the side and arranged to match the outline of the door, expand to press it later- ally and seat all the seals. With a sin- gle pressurization, the inexpensive actuators exert a surprisingly high, uniform force all around the door. Example 2: In a web-type glass-cutting machine, an inflatable bladder serves as a soft brake that holds the web in place when needed, Figure 2. The machine builder reworked the brake design mainly for gentleness and reliability. Earlier mechanical brakes jerked the belt to a stop, result- ing in excessive scrap rates and serv- ice calls for the machine as a whole, not just the brakes. The inflatable- bladder brake also saved about $500 per machine. Example 3: Bladder actuators openand close high-pressure control valves in extremely large filtration equipment, where maintenance ac-

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AUTOMATE WITH AIR

By R. Paugh and K. Sterry, Pawling Engineered Products

Soft Actuators Serve Hard Applications - 7327 SOFT ACTUATORSSERVE HARD APPLICATIONS

â—� contamination resistance â—� â—� generation of force over a large area simplicity â—� â—� light weight flexibility to fit in tight locations(It’s not unusual to be able to squeeze a bladder into a space where no cylin- der or stepper motor would fit.) â—� no metal parts, thus no corrosion â—� modest cost

Simple but versatile inflatable bladders cansolve a variety of design challenges.

â—� â—� minimal maintenance.Those are some of the reasons whyinflatable bladder-type actuators are being found as workholders, parts positioners, expanding mandrels, and clamps, as well as soft brakes on belt conveyors. the economy and reliability ofpneumatics, and

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any designers overlook the po-tential of inflatable bladders foractuation applications, but thanks to improved elastomeric materials and new cross-sections, the niche for bladder-type actuators is expanding. Today’s inflatable actuators deliver longer strokes — up to 2.5 in. — and many can exert uniform force over their entire stroke. For the right appli- cation — typically single-acting, repetitive, short strokes, where posi- tional precision is not required — other advantages include:
Figure 1. When the blue door slides intoplace, four inflatable actuators — arranged in a rectangular pattern — expand to seal the door in place. cess is limited. Low air pressure translates into very high forces for re- liable operation even under extreme process pressures. In tests, the bladder actuator operated the mechanism against process pressures that actually deformed the valve gate. Plus, there are no loose, moving parts to fail in the actuator mechanism. These examples illustrate how in-flatable bladders can solve certain ac- tuation challenges. All three applica- tions require a force distributed uniformly over a wide area and in-