Goteborg, Sweden-Each of today's main bearing types offers special qualities unique to the application at hand. For example:
Needle roller bearings are compact, but, unfortunately, they cannot function when the shaft is misaligned.
Spherical roller bearings accommodate misalignments and heavy loads, but are not able to handle axial displacement without causing friction.
Cylindrical roller bearings allow axial shaft displacement, but cannot function when misaligned.
A new design from SKF combines the key advantages of all three bearing types. Called CARB(TM), for Compact Aligning Roller Bearing, the design offers low friction and a high radial load-carrying capability. At the same time, it can accommodate misalignments and axial displacement of the shaft.
Key to CARB's success are its long, barrel-shaped rollers. A profile radius much larger than that of rollers in single- and double-row spherical roller bearings reduces friction without sacrificing the bearing's self-aligning capability. Additionally, locating the center of curvature of the outer ring raceway beyond the bearing axis allows: a wider bearing for favorable load distribution; greater possible axial displacement per given radial clearance; and designs with low section height. The only tradeoff is a reduction in axial load capability.
Field trials at the Braviken paper mill, just outside Norrkvping, Sweden, confirm the bearing's advantages. Installed in the plant's drying cylinders, the bearings must accommodate as much as 10 mm of thermal expansion in the thin-walled hollow cylinders.
SKF reports that the first CARB bearings will be available in outside diameters ranging from 310 to 500 mm.
Additional details, Europe...Contact SKF Group Public Affairs, S-415 50 Goteborg, Sweden, Tel: +46 31 372005, FAX: +46 31 372832.
Additional details, U.S...Contact SKF USA Inc., Box 1507, King of Prussia, PA 19406-0907, Tel: (610) 962-4300.