Tham khảo tài liệu 'the design of rolling bearing mountings (fag bearing co) episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 98 Two-bearing screen with straight-line motion Basically a two-bearing screen with straight-line motion consists of two contra-rotating synchronous circular throw systems. Operating data Screen box weight G 33 kN imbalance weight G1 kN amplitude r m speed n 900 min-1 number of bearings z 4 acceleration due to gravity g m s2. Bearing dimensioning The bearing loads of a linear motion screen vary twice between the maximum value Frmax and the minimum value Frmin during one revolution of the eccentric shafts. For calculation of these loads the distance R between the centres of gravity of imbalance weight and the pertinent bearing axes is required. Weights G and G1 amplitude of linear vibration r and distance R have the following relationship G r G1 R - r In this example R m When the centrifugal forces act perpendicular to the direction of vibration the maximum radial load F J imax is calculated as follows F 1 z .G1 . g _ R n n 30 2 _ 1 4 900 30 2 73 kN The radial load is at its minimum Frmin when the directions of centrifugal forces and vibration coincide. The radial load is then Frmin 1 4 G1 g R - r n n 30 2 1 4 900 30 2 kN Since the radial load varies between the maximum and minimum according to a sinusoidal pattern the equivalent dynamic loadP with the supplementary factor fz is thus P . . Frmax Frmin 73 kN With the index of dynamic stressing fL Lh 11 000 h selected for vibrating screens and the speed factor fn n 900 min-1 the required dynamic load rating C fL fn P kN The spherical roller bearing FAG with a dynamic load rating of 655 kN is chosen. Machining tolerances The locating bearings of the two eccentric shafts are at the gear end the floatingbearings at the drive end. The inner rings point load are have loose fits i. e. the shaft is machined to g6 or f6. The outer rings are circumferentially loaded and tightly
