Gas Spring Design

Gas Spring Design

Gas springs consist of a shaft connected to a piston head that moves in a cylinder. High pressure gas contained within that chamber absorbs much of the energy from unwanted shocks, thus protecting adjacent equipment and components. Gas spring design is important because gas springs must provide reliable and controllable damping. Unlike leaf or coil springs, a properly calibrated gas spring can provide near constant force through the entire stroke. Likewise, when force is removed the compressed spring extends at an even pace rather than snapping back as many alternative damping mechanisms might. This control makes gas or air springs popular in a number of industries including automotive, marine, aerospace, food processing, medical and manufacturing applications. Specific uses vary as gas springs are commonly found in engine hoods, luggage compartments, hatches, positioning fixtures, adjustable beds and chairs, awnings, conveyors and even landing gear. With such variability the design of these seemingly complex devices often requires the use of CAD software operated by skilled engineers. Physical considerations include cylinder diameter, maximum width, mounting and rod diameter. As gas spring design requires accuracy and precision, manufacturers and engineers often assist in the selection of application specific devices.

In more detail the gas spring body is a sealed, tubular cylinder most often made of steel, stainless steel, aluminum or durable thermoplastics. While the exterior is often of less concern, both the inner and outer surfaces must be precision finished for high smoothness to reduce unnecessary friction and allow for the insertion of a tight fitting piston. Elastomeric or metal seals and o-rings are placed around the piston head, which transects the cylinder to divide it into two airtight compartments. A rod is attached to the piston head on one end and protrudes out of the cylinder allowing the other to connect to the working mechanism. High pressure gas is contained within the cylinder in precise amounts. The high pressure gas must also be suited to specific applications for the safety of workers and optimal functioning of the product. Nitrogen and carbon gas springs are popular choices as these gases, even under pressure are safe to use in a number of environments. Cold-rolling, drawing and stamping are popular manufacturing techniques for the many components of a gas spring, which is most commonly assembled using CNC machining, welding or threading. Gas spring designers must consider both physical and performance specifications in order to ensure the functionality of the mechanism. Performance concerns include working temperatures, absorber stroke, compressed and extended lengths, maximum force, maximum cycles per minute and load capacity.