Air springs contain a column of air in an elastomeric bellow or sleeve to provide suspension, isolation, or actuation. Commonly found in vehicle suspension systems, occasionally in conjunction with a coil spring, they are also used to insulate vibration in machinery and as linear or angular actuators.
Air Spring Operation
Air springs are employed through the use of an air compressor which fills and empties the pliable air bladder. The load is not distributed to the rubber liner, which only serves to contain the gas; the weight is attached to a piston or bead plate, which is directly supported by the air with very little deflection. A self-leveling mechanism is common to keep the air spring's load stable, and occasionally a separate coil spring is incorporated into the design. Also available are electronic air spring systems that can monitor air pressure, filter compressor air (preventing damage to the rubber bellows), and a lock to keep air inside of the spring in case of compressor or air line failure.
Air springs are most common in vehicle suspensions, but can also be used to keep vibrating/rotating machinery from affecting other components. Occasionally used as actuators, air springs can provide linear and angular translation.
Air Spring Composition
Convoluted air spring; Rolling lobe air spring. Image Credit: Firestone
Air fitting: A tapped hole allowing for the spring to be fed from the air compressor
Nut/bolt/mount: The method for attaching the air spring to the component. Some air springs incorporate a bolt and air fitting combination device.
Bead plate: Crimped metal plate enclosing the spring and allowing attachment. This is typically forged steel, cast zinc alloy or cast aluminum.
Bellows: The physical, multi-layer material withholding the compressed gas. Usually made of neoprene or rubber.
Girdle: Only found in air springs of convoluted design, separating the bellows chambers.
Bumper: An optional layer of padding protecting the piston from damage if the air spring fails.
Piston: The component attached to the machinery requiring suspension, which is in turn supported by the enclosed air. The piston housing is typically attached with further hardware.
Selecting Air Springs
Types of Air Springs
Outside of custom fabricated air springs, there are three available types of market-ready air springs.
Crimped, convoluted bellows, which attach the bellow to the bead plate by a permanent crimp in the plate. These provide good vibration isolation and linear/angular actuation, but are not for vehicle suspensions.
Sleeve bellows, which attach the bellows to the bead plate by an external clamp. This air spring type provides good vibration isolation, but only linear actuation. They are not typical in suspensions.
Rolling lobe bellows, which incorporate a piston at one end of the bellows, rather than a bead plate. This is most commonly found in vehicle suspensions, and is generally not recommended for vibration isolation.
Air Spring Specifications
Though they have comparable capabilities, air springs are much cheaper than pneumatic cylinders and other springs. When deflated, air springs have a small footprint, making them easy to manipulate and connect to machinery.
Air springs tend to have low maintenance routines and some manufacturers state their air springs are maintenance-free (set and forget). Air springs do not require lubrication, nor do they have seals or guides that may become misaligned or damaged like with other springs. Indeed, the bellows of air springs are prone to dry rot, though this could take years to develop. Air springs should be stored in dry, dark areas at room temperature.
Due to its durability and simplicity, air springs are good for most industrial and commercial applications. Rubber and neoprene are susceptible to dry rot, so dehumidified conditions could shorten the service life of an air spring. Both rubber and neoprene are suitable for use in high/low temperature applications, but have considerably less heat tolerance than metal spring options. While usable up to 65°C, neoprene should not be used below -40°C, and rubber shouldn't be used in sites below -60°C.
The name air spring is a bit of a misnomer, as the bellows of the spring can also accept other types of fluids such as nitrogen, carbon, water, and anti-freeze.
Air springs are widely utilized. Commonly as actuators in amusement park rides, packaging equipment, clutch systems, conveyor belts and scissor lifts, they also act as vibration insulators in centrifuges, commercial laundry machines, measuring and weighing machinery, and textile looms. While the air spring has impacted many industries like oil, logging, construction and manufacturing, it is most prominent in the automobile industry where the air spring is used in suspensions for vehicle brands like Lincoln, Cadillac, Hummer, and Jeep.
Air springs outlined in gray. Image credit: Jeep
JASO C613 - Air springs for trucks and buses.
NAVISTAR TMS 1070 - Air springs, suspension component.
Read user Insights about Air Springs
Related Products & Services
Compression springs are the most recognizable of spring and are intended to oppose compaction in the direction of the axis. The spring is extended at rest, shorten and store energy when a load is applied, and is one most efficient energy storage devices available. Traditionally, they are wound and uniform in pitch and diameter, but these traits vary considerably today.
Constant Force Springs
Constant force springs are a variety of extension spring. A strip of steel with a preset curvature is coiled tightly so that each turn of the strip rests on its inner neighbor. The spring is actuated in a pulling, liner motion with the deflection resistance originating from the material's stiffness and spring construction. Unlike other extension springs, a consistent degree of force is exerted despite the degree of deflection.
Die springs are a robust type of helical compression springs consisting of rectangular wire. For the same value deflection, die springs carry 30% more load. These springs are designed to carry very high compression loads in hostile environments. Made mainly for punch press to provide consistent and reliable resistance, die springs also find use in other industries.
Helically wound to oppose resistant forces, extension springs have consistent mechanical energy to return to its no-load, compressed position. The ends of the spring are attached to components intended to move apart, with the extension spring providing a reliable return force.
Flat springs are flat strips of material that, when deflected by an external load, store and release energy.
Gas springs provide controlled motion and speed for elements, such as lids and doors, that open and close.
Power Springs and Spring Motors
Power springs and spring motors are rotational-drive springs that are wound tightly and mounted on an arbor. They are used in applications such as retractable reels, tape measures, and retracting seat belts.
Preload Springs, Spacers, and Washers
Preload springs, spacers, and washers are meant to maintain tension in an assembly where some slack may be present. Their capabilities can eliminate rattle, compensate for expansion or contraction of the assembly materials, or absorb intermittent shock loads. These products are made of elastic deformable materials, most commonly convoluted ductile, high-strength metal alloys which come in machined, welded, and open-ring varieties.
Spring washers, sometimes called disc springs, lend their mechanical capabilities to the unique profile of the material: the irregularities of the washer compress with a proportionate resistance to return to their predeflected shape. Spring washers are employed in applications where assemblies need a part to take up play, maintain assembly tension, compensate for expansion or contraction in materials, or to absorb intermittent shock loads and provide a controlled reaction under dynamic loads.