(From:CMB-CETA Editor)
Vibratory machines are playing an increasingly important role in the construction industry. They permit the replacement of conventional, time-consuming and environmentally harmful work methods with new, much more effective and eco-friendlier techniques. Vibrating motors that can, for instance be attached to assemblies in order to convey or separate materials by means of vibration, are one example in this context. Vibrating screens, used mainly in the processing and recycling sectors, work according to a similar principle.
A very important product group is comprised of vibratory rollers. There is hardly a construction site today where these machines are not needed. New vibratory compaction methods are more and more often replacing conventional equipment, such as static rollers. A second, less well-known product group includes vibratory pile drivers and deep vibrators. Vibratory pile drivers are used in the installation of sheet pile walls or tubes, while deep vibrators are deployed for generating pile foundations by compacting loose ground.
High loads, harsh conditions
The rolling bearing supports incorporated in all these machines have to meet very high demands: shock loads as well as high speeds, accelerations and centrifugal forces combined with vibration and oscillation require bearings of extremely high performance capacity. For example, they must be able to withstand centrifugal acceleration of up to 550 m/s², resist harsh environmental conditions, such as high temperature differences and cope with shaft misalignments that further stress the machine and thus the rolling bearing supports.
To ensure the reliable, long-standing and economical operation of vibratory equipment, it is crucial to know precisely what demands will be placed on the application in question. In addition, in-depth product expertise together with state-of-the-art bearing selection and design tools must be relied upon. INA cylindrical roller bearings have proven their particular worth in such machines. Their special features include low friction and smooth operation as well as high dynamic and static load capacities.
Example 1: Bearing support for an unbalance shaft in a vibratory roller
LSL cylindrical roller bearings feature a distinctive brass disk cage. Due to its special design as a plane disk, the mass of the cage itself and thus that of the bearing has been reduced. The cage also ensures lower friction, since the rolling elements outside the load zone are decelerated less. Another advantage is that the bearing can accommodate a larger number of rolling elements. This results in significantly increased basic dynamic load rating and calculated life compared with conventional cylindrical roller bearings. Having up to 50 percent lower friction than full complement cylindrical roller bearings, LSL bearings operate at lower temperatures, require lower input power and produce lower noise emissions, all of which make a significant contribution to longer bearing life. Shaft misalignment is reliably accommodated by the inner ring raceways which feature a special profile.
Example 2: Bearing support for the unbalance adjustment device in a vibratory pile driver
This application also uses the unbalance shaft bearing supports described in Example 1. They ensure that extreme centrifugal accelerations of up to 550m/s² can be coped with reliably. However, the unbalance adjustment device features a special bearing support. In the past, plain bushes were used for this position, but these were characterized by high friction and heavy wear and also led to long adjustment times in imbalance positioning. Thanks to new calculation possibilities and detailed application expertise, Schaeffler Group Industrial developed a specific bearing support using RNA needle roller bearings, which reduces friction and adjustment times by up to 40 percent. The shaft and housing have also been redesigned. Here, too, a smaller drive can now be used for generating the swivel motion. This means that the conversion from plain bearings to rolling bearings has brought about clear advantages in terms of (energy) efficiency.
