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9 INTERNAL SELF-ALIGNING BALL & ROLLER BEARING UNITS

SPHERICAL ROLLER BEARINGS SELF ALIGNING BALL BEARINGS
Spherical roller bearings consist of an outer ring having a The outer ring raceway of self-aligning ball bearings forms a
continuous spherical raceway within which two rows of barrel- spherical surface whose centre is common to the bearing
shaped rollers are guided by an inner ring with two raceways centre. The inner ring of the bearing has two raceways. The
separated by a centre rib. balls, cage, and inner ring of these bearings are capable of a
shifting in order to compensate for a certain degree of misalign-
ment with the outer rings. As a result, the bearing is able to
align itself and compensate for unevenness in the shaft/housing
finish, bearing fitting errors, and other sources of misalignment.
However, since axial load capacity is limited, self-aligning ball
bearing are not suitable for applications with heavy axial
loads.
The use of an adaptor on the tapered bore of the inner diameter
makes installation and disassembly much simpler, and for this
reason adaptors are often used on equipment with drive shafts.

This bearing has self-aligning properties, and is therefore suited
for use in situations where misalignment between the inner and
outer rings occurs due to housing installation error or shaft
flexure.

Spherical roller bearings have a large capacity for radial loads,
axial loads in either direction, and complex loads. They are also
suited to applications where vibration and shock loads are
encountered. When operating under axial loads however, it is
best to maintain conditions so that Fa/Fr 2e to prevent the
VII
occurrence of a sliding movement along the row of rollers not
receiving the axial load. (For the value of e refer to dimension Allowable misalignment
tables.)
Listed below are the allowable misalignment angles for
Both cylindrical and tapered bore bearings are available. bearings with self aligning characteristics when place under
Bearings with a tapered bore are specified by attaching the normal load conditions. This degree of allowable misalignment
suffix ‘K’ to the end of the bearing’s basic number. The standard may be limited by the design of structures around the bearing.
tapered ratio is 1:12 for bearings with a ‘K’ suffix. In bearing
series 240 and 241, the suffix ‘K30’ indicates that the taper ratio Allowable misalignment under normal loads (loads equivalent
for those bearings is 1:30. Most tapered bore bearings to 0.09C r): 0.07rad (4.0 )
O
incorporate the use of adapters and withdrawal sleeves for
shaft mounting.
Allowable misalignment
O
Normal load (loads equivalent to 0.09C r)......0.009rad (0.5 )
O
Light load ......................................................0.035rad (2.0 )

SPACER RINGS
In the cylindrical bore type housings the bearing seat is wider than the bearing to allow
lateral movement of the shaft. Spacer rings are provided with each pair of housings and
are used to locate one bearing per shaft. The outer bearing will not be located, but will
be free to move laterally if shaft expansion or deflection takes place.

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