Design Information for Urelast Springs

Rubber & Urelast spring design information including springs and sheets outlining tolerances, and how to calculate stroke rate and space requirements. 

Installation Information

Elastomer springs can be used in single, parallel or row arrangement. Their force-distance behaviour corresponds to the familiar laws governing spring behaviour. For optimum application of elastomer springs, the following installation information must be complied with:

Guidance

Guidance and centering of the springs is ideally achieved with guide bolts (DIN ISO 10069-1). They are required for unfavourable spring geometry and in order to avoid buckling of the spring stacks.

Space Requirements

EFFBE elastomer materials are incompressible. Consequently, for installation dimensions, clearences, such as distances for the bulging out of the springs must be taken into account. The crucial factor is the spring stroke; simplified, the bulging percentage equals the compression percentage. A safety margin must also be provided (See Diagram 7).

Stacking

For greater spring strokes, elastomer springs are stacked in rows; in this regard the geometry must be complied with (See Diagram 8). The Individual springs must be seperated from each other by spring washers. AAt equal spring forces, the individual spring strokes are added together. The spring stacks must always be guided.

Contact Faces

The contact faces of the spring should be R_z 25 to R_Z 40 in accordance with DIN ISO 10069-1. They can be flat, elevated or in a recess. When mounted at a raised level, the diameter must at least be equal the dimention of the spring collar. If mounted in a recess, the clearence must be adapted to the bulge factor (See Diagram 7).

Stroke Rate

For dynamic continuous use, the stroke rate in conjunction with the deformation must always be considered. If the limit values are underranged the service life increases due to lower self-warming (See Diagram 6).

Tolerances

Dimensional tolerances in accordance with DIN ISO 3302-1 M3 apply at a reference temperature of +20⁰C.

Hardness tolerences in accordance with DIN ISO 10069-1 apply with the tolerance of ±3 Shore A.

Commissioning

Prior to the final dynamic stress, the springs should be loaded and unloaded several times (up to 10 times, Diagram 5). All subsequent diagrams present the 10th load change of quasistatic deformation. They correspond to DIN ISO 10069-1.

Tolerance Table

Permissible dimensional deviations in accordance with DIN ISO 3302-1 M3:

F= Fixed Dimension

C= Closure Dimension

Spring Stroke (S)

The values of the table apply as maximum spring stroke based on the original height (L) of the spring, dependant on the stroke rate.

Settling Distance(S_s)

In addition to the type of deformation, its size and the temperature, the spring material determines the settling distance. The information is based on values recorded in practice that are reached in dynamic application after 10³ load changes at 90% (See Diagram 4).

The intial drop in force can be compensated through and increase in the force specification by FV. At high dynamic stress the practical increase values for quality are:

• EFFBE 295 CR70 - By approx. 10% (factor 1,1, i.e. nominal load x 1,1)    
• EFFBE Urelast UN80 - by approx. 20% (factor 1,2, i.e. nominal load x 1,2)
• EFFBE Urelast U90 - by approx. 30% (factor 1,3, i.e. nominal load x 1,3)                  

Preload (S_v)

The preload deflection must be selected greater than the settling distance (See Diagram 3) due to the bottoming tendency and to ensure positive-locking spring application.