Belleville Spring Technical Notes
Belleville spring, disc spring, and conical compression washer are all names for the same type of spring. A Belleville spring is a conical shaped disc that will deflect (flatten) at a given rate. This spring rate is usually very high, allowing the spring to produce very large loads in a very small space.Belleville springs can be stacked in a variety of ways.
- Single, one spring
- Parallel, all springs stacked the same way
- Series, all springs stacked opposing each other
- Parallel-Series, a combination of parallel and series
A single Belleville spring has a specific load and deflection. Belleville springs in stacked arrangements provide increased load and/or deflection. Two springs stacked in parallel doubles the load of a single spring with no increase in deflection. Two springs stacked in series doubles the deflection of a spring with no increase in load. The parallel-series combination as shown below results in the load of two springs and the deflection of two springs.
Installation of Belleville SpringsBelleville springs must be utlized correctly in order to maximize their benefit. There are several important points when using Belleville springs in a bolting application.
- Be sure that the bolts are long enough to account for the thickness of the Belleville
- The OD of the spring should contact the surface of the joint
- The ID should contact the bolt head or nut
- If a tensioner is used to preload the bolts, the Bellevilles must be on the opposite side of the joint
Pre-Stressing Belleville SpringsMany Solon® Belleville Springs are pre-stressed (scragging) by deflecting them to flat as part of the manufacturing process. This flattening procedure results in residual stresses as the spring recovers height from the flat position. Most Belleville springs that are pre-stressed are optimized with the maximum possible load and deflection for any given spring geometry or material. The spring will no longer yield during subsequent loadings. The resultant residual stresses will also increase fatigue life and improve overall spring performance. Pre-stressing is also an excellent inspection method for maintaining the quality of springs. Because pre-stressing produces consistent spring free height, springs that do not meet free height tolerances are rejected.
Some standard springs are not pre-stressed for design considerations. If overall height (H) minus Thickness (T) is greater than Deflection (h) value, the part is most likely NOT preset. Consult Solon Manufacturing Co. for preset part information.
Note: Not all Belleville spring applications require the spring to be pre-stressed. For special applications, consult a Solon application engineer.