Heavy-Duty Pneumatic Cylinder

Utility through air power

Changes and improvements in the electric motor industry have produced linear motors making deep incursions in places where hydraulic cylinders formerly held sway. Hydraulic systems are great for brute force operations but are difficult to keep clean, and high pressures in some applications can pose a hazard for work crews. The working fluid is also toxic to the environment, so accidents can be costly to clean. On the other hand, electric motors can be precisely controlled but command a higher cost.

Now an alternative to both approaches is offered by Numatics, Franklin, TN, in the shape of their In Force cylinder line. The first member under that sobriquet is the ASP Series, designed to function in strenuous cylinder applications, such as packaging equipment, industrial furnaces, construction equipment, and automotive and motorcycle assembly lines. The steel cylinder is honed to a fine finish and then surface hardened by a Nitrotec process, which creates a thin (0.001-in.), uniform and extremely hard (64 to 71 Rc) iron nitride layer infused with a film of iron oxide. The result is a smooth, corrosion-free sealing surface and high abrasion resistance.

For added ruggedness, the ASP Series includes a graphite-filled, cast iron rod bushing made to a greater length than in standard cylinders. The use of cast iron provides maximum resistance against premature wear, while the added length adds improved alignment and support of the piston rod, as well as providing maximum load bearing support. The high-strength steel (100,000 psi min. yield) piston rod, in diameters from 5/8- to 3½-in., has a ground, polished and chrome-plated surface, which provides maximum life for both the rod bushing and the seals. The piston seal is carboxilated nitrile with Teflon compound for self-lubrication. The “T “ seal configuration with back-up rings prevents rolling, and seals at all pressures. All units in the ASP Series include a wear band, a stable lubricating strip located on the piston (the latter made of aluminum, the only non-steel component in the assembly). To maximize separation between load bearing points, the band was placed at the rear of the piston. The end caps are machined from precision square steel blocks and have a black oxide finish for corrosion protection. Additionally, a recess on both ends of the piston-mating surface enables the air to work on a larger piston area for effortless breakaway, even at low pressures.

The ASP Series of pneumatic cylinders has a nominal pressure rating of 250 psi, and is being offered initially in eleven bore sizes from 1.5- through 14.0-in. Standard operating temperatures are -10° to 165°F. There are 21 standard NFPA mounting options, all accomplished with one-piece mounts on units with bores up to 8.0 in.; i.e., there are no welded-on lugs. The NPTF ports have an enhanced design for a smooth flow path into and out of the cylinder. Options include stroke adjusters, high temperature rod boots and more.

—RM