The inclusion of slots on either the inner or outer diameter creates a lever which works on the unslotted portion of the spring. This has the effect of reducing the spring load and increasing the deflection (figure 39).

The resulting spring has a softer characteristic with a large deflection and in proportion to the outside diameter smaller spring loads. It is most important with this type of spring that the permissible stresses in the annular portion are not exceeded and, if necessary, the outside diameter must be increased to compensate.

Figure 39 – click to enlarge

Taking these limitations and a few design features into account, this type of spring has many possible applications. The classic example is the automotive clutch spring. Notable are the slotted ball bearing preload springs which give extremely low loads.

The first approximation for the calculation of slotted disc springs can be achieved by considering the lever arm and the formula on page ‘Equations for calculations‘.

The loads generated depend to a large extent on the shape of the slots or the corresponding fingers. The deflection of the fingers is only a small percentage of the total deflection and can be ignored. If you need to consider the use of slotted disc springs please contact us so the design and manufacture may be discussed.