Firestone Airstroke® Actuators
Airstroke® actuators are cylinders. They are different looking, and they do not work exactly like the well-known and accepted JIC cylinder. Functionally, however, air springs perform the same type of actuation tasks. Their primary use is as a short stroke, high force, single acting pneumatic actuator. Its unique capabilities make it ideal for friction free, leak free, flexible force applications. 80% of Firestone air springs used in industrial applications are used as actuators, or cylinders.
Most engineers are familiar with the design of a traditional hydraulic cylinder or pneumatic cylinder. Traditionally, a cylinder contains a piston sliding within a housing of circular cross section, connected to the work by a rod passing through one end of the device.
This common design calls for guides and seals which function to align and seal the sliding surfaces. These allow a pressurized, contained column of fluid to apply a force to the piston.
A Firestone Airstroke® actuator uses none of these components to contain and channel its column of fluid. The difference is the key to the air springs unique functionality, and the reason for its anonymity.
Firestone Airstroke® actuators have long been used in the industrial market as pneumatic actuators incorporated into new and innovative machinery designs as well as replacement actuators for existing applications that had previously used traditional pneumatic or hydraulic cylinders.
These replacement markets are created by the advantages of a flexible walled pneumatic actuator that is durable, operates well in corrosive and abrasive industrial environments, easily accepts misalignment, and has a high ratio of stroke to collapsed height. Each of these features give Firestone Airstroke® actuators the advantage over traditional hydraulic cylinders or pneumatic cylinders.
Why use an Airstroke® Actuator (rather than a pneumatic cylinder or hydraulic cylinder) for actuation?
Generally, initial cost is one-half or less than conventional pneumatic or hydraulic cylinders of the same force capabilities. This initial cost advantage is many times greater in the larger sizes.
Durable for Long Life
Airstroke® actuators are a further application of Firestone’s time proven Airide® springs for truck and bus suspensions. The long life and durability necessary for millions of miles of heavy-duty suspension use under adverse environmental conditions are also important factors in machine design.
No Maintenance or Lubrication Required
Unlike conventional pneumatic cylinders and hydraulic cylinders, Airstroke® actuators do not require periodic maintenance or lubrication. This reduces the long term cost of using an Airstroke® actuator as well as the labor needed for continued operation.
No Internal Rod or Piston
Airstroke® actuators have no internal rod, piston, or sliding seals as do conventional hydraulic or pneumatic cylinders. This allows for the design of Airstroke® actuators into any applications where dirt or grit would destroy the seals on conventional cylinders.
Friction Free for Immediate Response
Since Airstroke® actuators have no sliding seals, there is no breakaway friction as with conventional cylinders.
An Airstroke® actuator can do its work with either a liquid or gas. (Please see Design Guide, page 14 for acceptable media choices.)
An Airstroke® actuator possesses the unique capability of stroking through an arc without a clevis. Angular motion of up to 30 degrees is often possible, along with the design advantage of generally less complex linkages. The main restriction when stroking through an arc is to not exceed the maximum or minimum heights of the air spring on the outer sides of the air spring. When using an actuator with the mounting plates at an angle to each other, observe the following:
- Measure force at the height between the plate centers
- Measure maximum height at the side of the bead plate separated the furthest,
- Measure minimum height at the side of the bead plate collapsed the most
These measurements must fall within the guidelines for that particular part. Reversible sleeve type 1T parts may also stroke through an arc. In this case, care must be taken to prevent the bellows from rubbing (internally) against itself where it rolls over the piston.
Side Loading Capability
Airstroke® actuators, within certain limits, are not affected by side loads as are conventional cylinders. The upper and lower bead plate centers (or mounting plate centers in the case of a bead ring type attachment) may be out of line somewhat without injury to the bellows. A misalignment of 1 inch [25.4 mm] per convolution is generally allowable. Accordingly, a single convoluted air spring may be out of line by as much as 1 inch [25.4 mm], a double by 2 inches [51 mm], and a triple convoluted air spring by 3 inches [76 mm]. (Note: Smaller parts may return a shorter life than larger parts at the same alignment.) This misalignment capability eliminates potential rod bending, scoring, and excessive seal wear common to conventional cylinders.
Compact Starting Height
Airstroke® actuators have a low profile compared to conventional cylinders. Our smallest Airstroke® actuator is 2.3 inches [58 mm] in diameter and collapses to just 1.2 inches [31 mm] in height. Our largest triple convoluted Airstroke® actuator is 37 inches [940 mm] in diameter and will collapse to a very compact 5.5 inches [140 mm].
Wide Size Range
Airstroke® actuators are available in sizes ranging from 2.3 inches to 37 inches (58 mm to 940 mm) in diameter. The force capability is 100,000 pounds (445 kN). Strokes of up to 14 inches (365 mm) are possible with the standard parts catalogued in the Design Guide.