Optimised profile shapes for track rollers
For many installation situations, the critical factor is not the load rating of the bearing arrangement within a track or yoke type track roller, but the insufficient wear resistance in the contact area between the outer ring and the rolling partner (rail). The outer rings, which are usually thick-walled, can lead to premature wear on the rolling partner and thus to failure of the entire units if the profile shape is selected incorrectly.
Track rollers are often designed with a spherical or straight profile of the outer-ring running surface. Cylindrical rollers with a straight profile can transmit high loads, but they do not have a high tilt-angle tolerance and therefore place very high demands on the accuracy of the connection geometries (Fig. 1).
Track rollers with a spherical profile are therefore often used to avoid the problem of low tilt-angle tolerance, as this profile shape also tolerates higher misalignments. However, this leads to a significant increase in contact pressure (Fig. 2).
The combination of the two basic shapes, such as cylindrical-spherical profiles, counteract these effects, but they can only be used with sufficiently wide track rollers (e.g.: yoke type track rollers for multi-rolling mills).
Company Artur Küpper has therefore developed and successfully tested an optimised profile shape for track rollers. By using outer rings with optimally profiled shell surfaces, we are able to adapt the contact situation to your needs:
With the K-Opt profile shape, we found an alternative to the spherical profile. The contact pressure has significantly been reduced, whereby tilt angles within the permissible misalignments of the inner bearing continue to be transmitted safely.
The L-Opt profile shape approaches the ideal of line contact for transmitting high loads without the risk of high stresses caused by edge runners that can occur with the smallest misalignments of the outer ring.
With the design tools that we have developed, we can create a specific profile shape for your special task. When designing, we take into account possible misalignments from adjacent constructions, the material of the rail or counter roller, and the ambient conditions.
In summary, the adjustment of the profile of the outer-ring running surface leads:
- to lower contact stresses
- to less wear on both rolling partners
- to a lower heat development
- to a longer service life
Thus, it leads to increased plant availability while simultaneously reducing maintenance costs.
