One of the weakest links in stamping, fabrication and materials handling machinery can be the seals in traditional cylinders used to actuate the equipment involved. This is critical in aggressive atmospheres laden with dust and waste, where such cylinders can clog up and wear prematurely over a lifetime of operation.
Air Springs Supply have a simple way to avoid this potential problem; by employing cylinders that lack such seals altogether, such as Firestone air spring actuators known as Airstrokes.
These highly engineered rubber and fabric air bags are flexible-wall, bellows-type air cylinders which are ideally suited to engineering of assemblies for high-repetition tasks, for which they are inflated and deflated rapidly to achieve their purpose.
“Traditional cylinder designs contain a piston sliding within a housing of circular cross-sections connected to the work by a rod passing through one end of the device. This design necessitates several guides and seals, which align and seal the sliding surfaces. These allow a pressurised, contained column of fluid to apply force to the piston," says Simon Agar, General Manager of Air Springs Supply.
“An air spring actuator uses none of these components to contain and channel its column of fluid. An air spring actuator contains its column of air in a fabric-reinforced rubber envelope, or bellows. The ends are sealed by bead plates, which are crimped around the bead of the bellows. These plates contain the attachment hardware for the part, normally a blind tapped hole called a blind nut. An air fitting, generally in one bead plate, allows fluid (air) to be introduced into the chamber. The fabric in the side wall of the bellows restricts radial expansion, so pressure is built up, causing axial extension.
Each style is, in essence, a heavy-duty balloon. Air spring actuators are available in a variety of styles, sporting differing components that control the shape and path of axial extension, but their basic design is the same,” says Agar.
In order to select the appropriate air spring actuator, it is important to know the force necessary, the required stroke and any special environmental concerns.
Airstroke actuators from Air Springs Supply, for example, give 40-40,000kg of pushing or lifting power. Offering power strokes of up to 350mm, Airstrokes are powered by simple, basic compressor equipment found in nearly every factory.
Australian and international uses for Airstroke air spring actuators have included:
- high speed metal stamping
- forming presses
- die strippers
- quench and pickling tank actuation
- conveyor line actuation (mining and manufacturing)
- conveyor stops and gravity gates
- pallet handling equipment
- web tensioning
- vibrating screens and compressor equipment
- high frequency stress testing of materials
- automotive metal press counterbalances
- belt takeup and roller friction brake on conveyor equipment.
Australian industrial plants also use these air spring actuators as:
- ram cylinders
- die cushions
- valve operators
- flexible connectors
- shock absorbers; and
The use of air spring actuators provide several cost benefits. Air spring actuators can be used instead of more expensive hydraulic systems when applying large forces. Sizes are available from fewer than 80mm to more than nearly 1000mm (3in to 38in) in diameter. The larger sizes allow force up to 40,000 kg each using only 7 bar (100psi) air pressure. The capital cost of an air spring actuator is normally less than half that of a pneumatic cylinder with equivalent capabilities.
Air spring actuators are also compact and easy to install. Flexible-wall air spring actuators operate by being compressed to their minimum height then extended when pressure is applied. In most cases, the minimum height is considerably less than the available stroke. As a result, air spring actuators can be put in a very compact space and extended to more than twice their starting height. This is ideal for floor mounted lifting devices and conveyors.
Air spring actuators also offer side load flexibility and simplified attachment. Thanks to the air spring actuators flexible, compliant bellows wall, instead of seals or guides, the bellows follows the path of least resistance. This means users do not have to worry about side loads caused by misalignment.
Since the bellows bends, bead plates do not have to remain parallel, this significantly simplifies attachment, especially when linkage is at an angle. As long as the bellows' side walls are not over-extended or over-compressed, users can stroke through an angle without clevises.
“We certainly don’t pretend air springs are the ideal actuator for all applications, but we do contend that they are the ultimate actuator for many applications for which they are not always considered,” says Agar.