Stacking Disc Springs in Series
Single disc springs are assembled 'opposed to each other' to form a spring column. This 'in series' formation is a means of multiplying the deflection of a single disc spring, the force element remains as that for a single spring.
E.G. A disc spring that requires a force of 5000N to deflect 1mm, when assembled to form a column of 10 disc springs in series, will require a force of 5000N to deflect 10mm.
The cumulative effect of bearing point friction of large numbers of disc springs stacked in series, can result in the disc springs at each end of the stack deflecting more than those in the centre. In extreme cases this may result in over-compression and premature failure of the end springs. A 'rule of thumb' is that the length of the stacked disc springs should not exceed a length approximately equal to 3 times the outside diameter of the disc spring.
Normally, disc springs stacked in 'series' formation are of identical dimensions, however, it is feasible to stack numbers of disc springs of increasing thickness in order to achieve 'stepped' and progressive characteristics. With such arrangements, it is necessary to provide some form of compression limiting device for the 'lighter' disc springs, to avoid over-compression whilst the 'heavier' springs are still in process of deflection.