Non-coiled springs made from many different materials have been used since before the second century, with simple spring mechanisms evident in recorded designs from as far back as the Middle Ages. In 1250, for example, Villard de Honnecourt devised a ‘power’ saw which used a water wheel to push the saw blade in one direction, simultaneously bending a pole; as the pole returned to its unbent state, it pulled the saw blade in the opposite direction.
The coil spring has been an important element in industry since the early fifteenth century, when it was first documented. But it wasn’t until the Industrial Revolution that mass production techniques drove their popularity further within industry and manufacturing in general.
Though there have been many refinements to the traditional coiled spring, advances in recent decades have included the introduction of the crest-to-crest wave spring. Tooled using a single flat wire process, this component offers significant reductions in terms of axial and radial dimensions - particularly useful as machine envelopes continue to shrink.
A single crest-to-crest wave spring can replace a series of coil springs in applications such as mechanical seals. The reduced spring rate enhances the life of the seal face because the load differential at maximum and minimum work heights is greatly reduced. Longer seal life is achieved because the crest-to-crest configuration offers greater travel; essentially, the difference between the work heights is greatly increased.
Being a single component, the crest-to-crest wave spring offers more consistent parallel loading of the seal faces, resulting in greater compression. It also avoids the disadvantage of multi-coil spring seal configurations - namely ‘clogging’ - which often occurs between the turns when the seal is used in harsh duties, leading to leakage.
A single crest-to-crest wave spring is also brings benefits in terms of production tooling and ease of assembly. With pocketed coil springs, numerous beds have to be drilled for each coil spring element - clearly unnecessary when a single crest-to-crest wave spring is used instead.
A variety of forms
Wave springs come in a variety of forms, from single turn to triple interlaced, each offering an alternative to die stamped wave springs or disc springs. Die stamped products can traditionally require a longer lead time and incur expensive tooling costs, especially if the item in which the spring is to be used is subject to modification. This is not the case with crest-to-crest wave springs.
Flat wire (crest-to-crest) compression springs are often used in the construction of pressure relief valves, thanks to their ability to apply an exact load to the top sealing plate. They are also used in bearing pre-load arrangements where they are less likely to cause wear and bearing damage, while reducing noise and vibration. It is not uncommon to find crest-to-crest wave springs in the construction of mooring components that anchor oil rigs to the seabed or in the packers used for deep sea drilling.
Their versatility coupled with short lead times, plus the ability to offer prototype samples within three to four weeks or even sooner without resorting to expensive tooling costs, has provided a platform in industry and engineering that secures the spring’s future within industry for the foreseeable future.
- Brian Goode is technical director at TFC Europe