Introduction
Disc springs are conically shaped annular discs which, when loaded in the axial direction, change shape.
As a close approximation, it can be assumed that the rectangular cross-section of the disc spring rotates about it's theoretical mid- point. This assumption is the basis for the Almen and László #) equations for disc spring loads and material stresses.
The disc spring calculations which are contained in the DIN 2092 are derived from this same hypothesis. In practice, it has been found to be adequate for its intended purpose and is now generally accepted. In comparison to other types of springs, disc springs produce small spring deflections under high loads. The ability to assemble disc springs into disc spring stacks overcomes this particular limitation. When disc springs are arranged in parallel (or nested), the load increases proportionate to the number of springs in parallel, while when disc springs are arranged in series (alternately) the travel will increase in proportion to the number of springs serially arranged. These assembly methods may be combined in use.
One special feature of the disc spring is, undoubtedly, the fact that the load/deflection characteristic curve can be designed to produce a wide variety of possibilities. In addition to practically linear load/deflection characteristic curves, regressive characteristics can be achieved and even disc springs which exhibit increasing spring deflection while the corresponding disc spring load is decreasing are readily available.
Many disc springs are manufactu red with load-bearing surfaces; for the most part, these are larger disc springs which already require allover machining processes during production. For these particular disc springs, modified calculations must be used. Loadbearing surfaces greatly improve the disc spring's performance, particularly when they are used in disc spring stacks.
In some disc spring applications, the guide elements themselves may interfere with the proper functioning of the disc spring stack. Some solutions to this particular problem by means of self-centering disc springs have been included in this handbook.
Slotted disc springs present a completely different case. Slotting changes the load/deflection characteristic of the single disc spring, providing larger spring deflections for greatly reduced loads. The slotted part is actually functioning as a series of miniature cantilever arms.
Normal, standard disc springs are manufactured from materials defined in the DIN 2093. However, numerous other raw materials for special disc spring applications exist. The most common of these special materials and their relevant characteristics for disc springs have been described in the tables.
Corrosion affects both the basic raw material as well as the finished disc spring.
Please note that the disc spring manufacturing program is not limited to the hundreds of disc springs discussed in this site but, indeed, encompasses many thousands more custom made and special disc springs for numerous applications.
For the technical assistance which is required for the design and production of such special parts, our Technical Department is ready and willing to assist in every manner possible.
#) Almen, J.O. e Lŕszlň, A.: ?The Uniform-Section Disk Spring? Trans. ASME 58 (1936), pp.305-314