The Design of Rolling Bearing Mountings

Vibrating machinesVibrating screens are used for conveying and gradingbulk material. They operate in mines, quarries, stonecrushing plants and foundries, in the foodstuff andchemical industries, and in many other preparationand processing plants.The main vibrating screen types are: two-bearingscreens with circle throw, two-bearing screens withstraight-line motion, and four-bearing screens.Vibrator motors and vibrating road rollers also comeunder the category of vibrating machines.Selection of bearing type and bearing designRolling bearings in vibrating screens are stressed byhigh, mostly shock-type loads. To compound matters,the bearings, while rotating about their own axis, performa circular, elliptical or linear vibrating motion.This results in high radial accelerations (up to 7 g)which additionally stress the bearings, and especiallythe cages. High operating speeds, usually with inaccuratelyaligned bearing locations, and pronounced shaftdeflections are additional requirements which are bestmet by spherical roller bearings.For these adverse operating conditions FAG sphericalroller bearings with reduced bore and outside diametertolerances and an increased radial clearance are used:The FAG standard design E.T41A is used for shaft diametersof 40...150 mm. The centrifugal forces of theunloaded rollers are accommodated by two pressedsteel,window-type cages and radially supported by acage guiding ring in the outer ring.Shafts with diameters of 160 mm and more are supportedon vibrating screen bearings A.MA.T41A.These bearings have a fixed centre lip on the inner ringand retaining lips on both sides. The split machinedbrass cage is of the outer-ring riding type.Bearing dimensioningVibrating screen bearings which are comparable withfield-proven bearings can be dimensioned on the basisof the index of dynamic stressing f L , provided that theboundary conditions are comparable as well. f L valuesbetween 2.5 and 3 are ideal.FAG 138