FIELD OF THE INVENTION
The present invention generally relates to a bearing assembly for large rating A.C.
Induction motor to arrest high axial load from driven equipment. More particularly, the
present invention relates to an improved bearing arrangement mounted at drive end
side of large rating A.C. induction motor, to eliminate damages of the bearings from
high axial load from driven equipment.
BACKGROUND OF THE INVENTION
A.C. Induction motor of large rating say 1700 KW, acts as a prime mover and drives
high pressure roller press for grinding of clicker into fine particles for the production of
the cement. Induction motors having standard bearing assembly as per prior art does
not sustain very heavy thrust load in the axial direction and expected life of bearing also
may get reduced to large extent. In such type of standard bearing arrangement, ball
bearing of 2 series has to bear load in axial direction, which is used in combination with
2 series cylindrical roller bearing at the drive end side of motor. As the level of axial
load increases on ball bearing from driven equipment, which is coupled with motor
shaft using flexible coupling and universal shaft (intermediate shaft), standard bearing
assembly definitely needs reinforcement at drive end side of motor. Such heavy thrust
load (7.5 tons) generated from roller press, is of alternating nature with unpredictable
frequency, is transmitted to motor through universal shaft.

OBJECTS OF THE INVENTION
It is therefore an object of the invention, to propose an improved bearing arrangement
mounted at drive end side of large rating A.C. induction motor, to eliminate damages of
the bearings from high axial load from driven equipment.
It is also an object of the invention to propose a suitable roller and ball bearing and
other bearing assembly components for motor, which could perform satisfactorily
without damage, during occurrence of intermittent but very high axial loads.
Another object of the invention is to propose an improved bearing arrangement
mounted at drive end side of large rating A.C. induction motor, to eliminate damages of
the bearings from high axial load from driven equipment, which can be selected from
roller bearings, ball bearings or other types of known bearings applicable to cement
industries.
SUMMARY OF THE INVENTION
According to the invention there is provided an improved bearing arrangement mounted
at drive end side of large rating A.C. induction motor, to eliminate damages of the
bearings from high axial load from driven equipment. The large rating A.C. Induction
motor, in particular are 4 pole motors having rigid rotors and rotates on anti-friction
bearings. The invention proposes use of four point contact ball bearing of 3 series in
combination with a 3 series cylindrical roller bearing, mounted inside a housing (made
of cast iron) and supported by inner bearing cap (made of steel) from inside and grease
flinger (cast iron) from outside. Number and size of hex bolts are also increased from 4

to 8 and from size M12 to size M16, in order to provide extra support to the proposed
system. The purpose of strengthening the bolts is to secure both the bearings in
position and to sustain large amount of axial load from both directions, without fail.
Also size of the bearing housing has been enlarged in order to accommodate 3 series of
four point contact ball bearing and cylindrical roller bearing, which are wider in width
and larger in diameter than the prior art 2 series deep grove ball bearing and cylindrical
roller bearing. However, shape of the housing is retained identical as per prior art.
The present invention also proposes use of inner bearing cap made of fabricated steel
in place of cast iron as per prior art, since steel is having better tensile strength to
counter heavy forces than cast iron. However, shape of the inner bearing cap is also
retained identical according to prior art.
The proposed bearing arrangement can be used in variety of A.C. Induction motors,
with either CACA (closed air circuit air cooled) or TETV (totally enclosed tube ventilated)
enclosure, having rigid rotors. These motors can further be used as a prime mover for
high pressure roller press and mills for grinding of clinker in cement industries.
The newly invented bearing assembly is unique and capable of enhancing bearing life to
large extent and can avoid premature damage to bearings. In this way, very less
maintenance of bearing components will be required and could bring machine down
time drastically and in turn shall increase production of cement.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG-1 Section arrangement of large rating A.C. Induction motor with CACA enclosure for
which new bearing assembly is proposed.
FIG-2 Shows schematic of an A.C. Induction motor coupled with universal shaft using
flexible coupling.
FIG-3 Shows details of magnitude of various forces, and their point of application on
motor shaft extension.
FIG-4 Schematic of a typical bearing housing made of cast iron as per prior art.
FIG-5 Schematic of a typical inner cap made of cast iron as per prior art.
FIG-6 Section arrangement of a bearing assembly as per prior art.
FIG-7 Schematic of proposed larger bearing housing made of cast iron as per new art.
FIG-8 Schematic of a proposed inner bearing cap made of steel as per new art.
FIG-9 Section arrangement of a newly invented bearing assembly as per new art.

DETAIL DESCRIPTION OF THE INVENTION
FIGURE-1 shows a typical cross sectional layout of a large capacity, for example a
1700kw A.C. Induction motor in CACA (closed air circuit air cooled) construction. This
motor rotates on anti-friction bearings. Rotor geometry including core and shaft results
in rigid operation of the rotor. The figure also shows mounting of newly invented
bearing assembly, at the drive end side of motor.
FIGURE-2 shows an outline of TETV type of A.C. Inductor motor. The figure also
displays how motor is coupled with carden shaft through flexible coupling and universal
joint. Also location of various axial and tangential forces acting on motor shaft is
explicitly shown.
FIGURE-3 shows location, distances and magnitude of axial and tangential forces acting
over shaft extension of motor. Maximum axial force exerted by driven equipment
through carden shaft is approximately 7.5 tons.
FIGURE-4 shows bearing housing (06) suitable to house 2 series cylindrical roller
bearing (04) and deep grove ball bearing (05), as per prior art.
FIGURE-5 show inner bearing cap (01) made of cast iron as per prior art.
FIGURE-6 shows section arrangement of drive end bearing assembly as per prior art.
In this arrangement 2 series cylindrical roller bearing (05) and deep groove ball bearing
(04) are conjointly used. These bearings are housed inside bearing housing (06), Inner
bearing cap (01), outer bearing cap (11) and grease flinger (09). Hex bolt (07) and

spring washer (08) are used to tighten Inner bearing cap (01) with bearing housing
(06).
FIGURE-7 shows large bearing housing (6A) as per new art, however its shape has
been retained as per prior art. Same is required to house 3 series cylindrical roller
bearing (5A) and four point contact ball bearing (4A).
FIGURE-8 shows large size inner bearing cap (1A) made of steel in place of cast iron, as
per new art. However, its shape has been retained as per prior art. Newly designed
inner bearing cap (1A) having 8 tapped holes for fixing with housing as against 4
tapped holes in the prior art.
FIGURE-9 shows section arrangement of newly developed bearing assembly. In this
novel arrangement 3 series cylindrical roller bearing (5A) and 3 series four point contact
ball bearing (4A) are housed inside large bearing housing (6A), inner bearing cap (1A)
grease flinger (9A), and outer bearing cap (11A). 8 nos. M16 hex bolts (7A) and 8 nos.
spring washers (8A) are used to tighten inner bearing cap (1A) and housing (6A). In the
new art, in order to withstand large axial forces generated by carden shaft, size and no.
of hex bolts are changed to M16 and 8 nos. from M12 and 4 nos. respectively. Large
size grease flinger (9A), and outer bearing cap (11A) are also used to suit new
combination of 3 series cylindrical roller bearing and four point contact ball bearing
(4A), however their shapes are also retained as per prior art.

WE CLAIM :
1. An improved bearing assembly for large rating A.C. Induction motor to withstand
high axial load from driven equipment and enhance bearing life, the
improvement is characterized by following steps :-
providing 3 series cylindrical roller bearing (5A) in combination of four point
contact ball bearing (4A) for stiffening of bearing assembly;
assembly the cylindrical roller bearings (5A) and four point contact ball bearings
(4A), conjointly in a housing (6A) to enhance bearing life more than 40,000
operating hours, while experiencing axial force of 7.5 tons from both directions;
locating an inner bearing cap (1A), an outer bearing cap (11A), made of steel,
the inner bearing cap (1A) having at least 8 tapped holes for fixing the bearing
housing (6A); and
fixing the inner cap (1A) by using at least M16 hex bolts (7A), eight spring
washers (8A), and grease fingers (9A) on the housing (6A).