DISC SPRINGS WITHOUT CONTACT FLATS
For disc springs without contact flats K4 = 1 and ho = lo – t. This applies to all disc springs in production groups 1 and 2, i.e. with a thickness of up to 6.0mm.

Because of the rectangular cross-section with rounded corners, as is specified for springs in groups 1 and 2, the application of load in practice always takes place via slightly shortened lever arms (see figure 4). Due to the h/H tolerance for the outer and inner diameters, the lever arms are shortened even further. This results in an increase in the spring load by the factor:

De – Di
De’ – Di’

in virtually all springs compared to the values calculated with formula 7.

These conditions take the standard DIN 2093 into consideration in that the thickness tolerances towards the minus side are clearly larger than towards the plus side. Therefore, we manufacture all springs with a slightly reduced disc thickness. This reduction in the lever arm length is also an explanation for the fact that the permissible deviations for the spring loads for groups 1 and 2 are considerably larger toward the plus than the minus side.