Properties and Construction

The spring characteristic curve is a representation of the force - deflection behaviour of the spring. Depending upon the dimensional ratios, the characteristic curve of a disc spring is more or less digressive up to the flat position (Fig. A). In special cases disc springs can be designed so that deflection beyond the flat position is possible.

Fig. A: Typical characteristic curves

As a rule disc springs are used as modular components. Disc springs stacked facing the same way are called a spring pack. Single springs or packs stacked facing alternate ways are described as a spring stack (Fig. B/C). When the springs are stacked facing the same way, the deflection of the pack is equal to that of a single spring. The load at a given deflection is proportional to the number of single springs used in the pack. When the springs are stacked facing alternate ways, the deflections of the individual springs are added together.

Fig. B: Disc spring pack consisting of four single discs
Fig. C: Disc spring stack consisting of four single discs

The load on the stack is equal to the load on the individual spring. When calculating the spring deflection and load capacity of a stack composed of single springs or packs, one must proceed accordingly (Fig. D).

Fig. D: Various spring disc combinations

(a) spring pack of 3 single discs: 3-fold force
(b) spring stack of 4 single discs: 4-fold force
(c) spring stack of 3 packs of 2 single springs each: 3-fold deflection, 3-fold force

It is possible to generate progressive characteristic curves by combining spring packs containing different numbers of disc springs or single disc springs of varying thickness to form a stack. In these cases the packs or single discs with the lower load capacity do not contribute to the deflection of the stack after reaching the flat position or their upper stroke limits, with the result that the total spring rate of the stack rise (Fig. E).

Fig. E: Spring combination to obtain a progressive characteristic line