Ex-stock Belleville spring washers in 300 series stainless steel

These compact and high-performance spring washers found early application in firearms and now are widely found in aerospace, automation, building industry and elsewhere because of their ability to support very large loads with minimal use of space and to provide variable performance characteristics by varying their assembly format.

Belleville washers are a type of spring shaped like a washer - named after Julien Belleville who in 1867 patented the design on which these modern versions are based. They are also commonly referred to as a coned-disc spring, conical spring washers, disc spring, Belleville spring or cupped spring washers.

By stacking Belleville Washers in various configurations, additional load flexibility can be achieved in four different ways:

• Single: One washer
• Parallel: All washers stacked the same way
• Series: All washers stacked opposite each other
• Series-Parallel: A combination of the two

A single Belleville Spring Washer has a specific load for a given deflection. Two washers stacked in parallel will yield double the load of a single washer for the same deflection; three washers will yield triple the load; four washers will yield four times the load, etc.

Alternatively, two washers stacked in series will yield double the deflection of a single washer for the same load; three washers will yield triple the deflection; four washers will yield four times the deflection, etc.

Various series-parallel combinations therefore can provide a wide variety of combined results of load versus deflection for the stack. Consequently, depending upon the application, the designer can:

• Stack in "parallel" to increase load
• Stack in "series" to increase deflection
• Adjust the load and deflection of a washer stack by adding or removing individual washers and/or the sequence in which they are used, whether in series or parallel

Stacks of washers can thereby provide a significant damping action in parallel stack configuration by reason of friction induced hysteresis which dissipates unwanted energy for example in architectural systems. They offer the ability to provide further adjustment by swapping out varying thicknesses in a stack to tune the force or compression range - also by mixing and matching of parallel/series spring discs.

Belleville spring washers are similar in operation to wave washers as an anti-vibration device when installed with machine screws - but offering much higher load capability and can be useful to offer a visual indication of any relaxation taking place in a joint over time or under adverse conditions.

Lee Spring Belleville washers made in 300 series stainless steel are passivated in accordance with ASTM A967 and are available in sizes from 4.8mm to 95mm OD with load ratings from 25N to 58000N. Further information on Lee Spring products can be found on their website at www.leespring.co.uk.