Air shock absorbers and air springs (diapress, torpress or membranes) are the founding block of the air suspensions of vehicles and trailers, and they allow high perfomances in terms of comfort and safety.
The air spring is made up of a rubberized fabric flexible casing, containing compressed air, that is fixed to metal (or composite material) components.
A diapress (torpress or membrane) has the purpose of damping, just like any other normal spring.
The following picture adequately describes the main components of an air spring, down on the left, in particular of an air spring with membrane, metal bead plate and, down on the right, of a bellows air spring.
Before the introduction of air springs, only steel springs were used. Those springs need to be specifically manifactured, in order to obtain enough hardness, and so supporting the gross weight of the vehicle up to the heavy-weight truck loads. In any load distribution scenario, steel springs prove too stiff, providing an insufficient flexure for reducing vibrations and dampening impacts on the vehicle’s wheels and axles. This clear lack was resolved with the adoption of air springs, thanks to their variable elastic properties; in plain words, air springs allow variations of the spring rate or stiffness depending on the load. The spring compression is independent from the load distribution of the vehicle: for example, a vehicle with a light load will travel with a reduced air pressure in the diapress, while a fully-loaded vehicle will require a high air pressure. The change between low and high pressure in the air spring happens automatically, thanks to specific valves with level sensors.
In respect to steel springs, traditional leaf springs or modern light alloy springs, the installation of air sprigs involves the reduction of vibrations, the minimasation of damages to cab and body parts, increasing the lifetime of trucks and trailers. It also allows a constant ride height, and with this comes a more comfortable ride, reducing driver’s fatigue and enhancing safety. Here below are the properties and advantages that come from the installation o fair springs:
Regarding maintenance, it is necessary to service the compressed air system and the air spring constantly, for example:
compressed air pipings and devices, to avoid leaks;
air bellows support, to avoid damages;
correct functioning of the shock’s hermetic sealing;
correct tightening torque of nuts and bolts;
fixing and support system;
eventual sign of wear on the axle’s suspension, on the steering and on the crossbeams;
Servicing these components adequately it is possible to save a lot of money on maintenance costs.
There are three tupes of air springs: membrane-only, membrane with a metal bead plate and bellow air springs. Here below are more details for every kind of suspension.
Rubber membrane without metal elements, are present on the chassis as fixed parts, so they are not interchangeable. This type of diapress allows the regulation of the ride height.
Membrane air springs are easy to install, and thanks to their flexibility and elasticity, that allows a long stroke-excursion. This type of diapress has a metal bead plate, itself divided into two types:
conical fixing: the upper bead plate is inserted on the membrane via pressure. The metal bead plate can be re-used when the membrane is swapped;
The particular shape of this type of spring, allows a high spring stroke.
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