A new type of pneumatic actuator is fabricated of several molded plastic elements welded together in a sealed unit.
The Airomatic line of polyactuators from Firestone Industrial Products, Carmel, Ind. ( firestoneindustrial.com), requires just 0.6-in. clearance, provides strokes to 0.5 in., and handles loads to 100 lb at 35 psig. They can also be customized into specific sizes and shapes for a variety of applications.
The actuators have no pistons, rods, or sliding seals, so friction, bending, scoring, and wear that can hamper conventional air cylinders are not a concern. "They are as reliable as our larger air springs, so they're ideal for any industrial environment," says Tom Falk, manager of industrial and aftermarket distribution. Life tests have exceeded 5.7 million cycles with no loss of performance.
Originally designed for conveyor applications, the actuators assist in conveyor transfer sections and roller brakes, but can be used in almost any application requiring low pressure and short strokes. For instance, Automated Production Systems (APS), New Freedom, Pa., has turned to polyactuators to solve a process headache caused by traditional air cylinders on its APS Case Conveyor System, which handles packages ranging from plastic crates to corrugated boxes.
Air-operated parallel lift bars on each side of the conveyor belt manage package flow. As products emerge from a packer, filler, or other packaging machine, cases back up in a holding area before travelling to another machine or the palletizing area. When a case blocks a photo eye, actuators at 45 to 50 psi raise the lift bars, which prevents packages from moving with the conveyor belt. When the conveyor clears, the lift bars retract and packages continue along the line.
According to Jim Moffitt, an APS senior design engineer, the system had relied on air cylinders to raise the lift bars. However, unless cylinder motion was perfectly synchronized, the system would bind and halt production.
Airomatic polyactuators proved to be an ideal solution, says Moffitt. They require less space than air cylinders and have no side restraints to cause them to bind as they deflate. The plastic product also eliminates corrosion and deterioration worries, he says.