Belleville washer

A Belleville washer, also known as a coned-disc spring,conical spring washer,disc spring, Belleville spring or cupped spring washer, is a conical shell which can be loaded along its axis either statically or dynamically. A Belleville washer is, then, a type of spring shaped like a washer. It is the frusto-conical shape that gives the washer a spring characteristic.

The "Belleville" name comes from the inventor who in Dunkerque, France, in 1867 patented a spring design which already contained the principle of the disc spring.

The real inventor of Belleville washers is, then, unknown.

Through the years, a lot of different profiles for disc springs have been developed. At today the most used are the profiles with or without contact flats, while some other profiles, like disc springs with trapezoidal cross-section, have lost importance.

Through the years, the request of an always greater precision in calibrations process, the availability of new materials and new and more accurate calculation methods, led to the introduction of the disc spring into all areas of technology and now disc springs are used in a lot of industries: automotive, building, defense and so on. In the different fields, if they are used as springs or to apply a pre-load of flexible quality to a bolted joint or bearing, Belleville washers can be used as a single spring or as a stack. In a springs stack, disc springs can be stacked in the same or in an alternating direction and of course it possible to stack packets of multiple springs stacked in the same direction.

Disc springs has a number of advantageous properties compared to other types of springs:

As said, thanks to these advantageous properties, Belleville washers are today used in a large number of fields, some examples are listed in the following.

In the army industry, Belleville springs are used, for instance, in a number of landmines e.g. the American M19, M15, M14, M1 and the Swedish Tret-Mi.59. The target (a person or vehicle) exerts pressure on the belleville spring, causing it to exceed a trigger threshold and flip the adjacent firing pin downwards into a stab detonator, firing both it and the surrounding booster charge and main explosive filling.

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Wikipedia