Note: Descriptions are shown in the official language in which they were submitted.
CA 02247831 1998-09-2
Rolling-contact bearing
Background of the Invention
Field of the Invention
The present invention relates to a rolling-contact
bearing, and more particularly it is intended to prevent
entrance of dust, snow, ice, and other foreign matter by
shutting off openings between inner and outer races at
opposite ends of the bearing with shields so as to be
applicable as the bearing for a bogie wheel of a snowmobile,
a pulley for auxiliary machines of an automotive engine,
etc.
Prior Art
As shown in Fig. 4, a snowmobile is designed to move
over snow or ice on a crawler or track 3 running endlessly
between a driving sprocket 1 and a driven sprocket 2.
Between the driving sprocket 1 and driven sprocket 2,
plural idler wheels 4 for guiding the track 3 are disposed.
The driven sprocket 2 and idler wheels 4 are collectively
called a bogie wheel.
The bogie wheel 5 is rotatably supported through a
rolling-contact bearing 10. That is, as shown in Fig. 5
and Fig. 6, an outer race 14 is press-fitted in a hole 5a
of the bogie wheel 5 and is positioned by a stop ring 5b,
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while an inner race 12 is press-fitted on to an outer
circumference 6a of a shaft 6, the shaft 6 and the inner
race 12 being fastened together between a washer 8 and a
frame 9 with a bolt 7. Reference numeral 7a denotes the
head of the bolt 7, and 7b a nut. Reference numeral 16
denotes a series of rolling elements, i.e., steel bolts in
this case, assembled between the inner and outer races 12
and 14 of the bearing 10. Reference numeral 17 denotes a
cage, and 18 a conventional seal fitted between the inner
and outer races 12 and 14.
Since the snowmobile is designed to travel on the snow,
the bogie wheel 5 in particular is used in severe
environments always exposed to snow and ice, and it is
subject to troubles such as deformation of the seals 18 due
to collision of pieces of ice and gravel, deterioration or
loss of packed grease due to entrance of water into the
bearing, rusting of inside of the bearing, and defective
rotation due to rust.
It is hence an object of the invention to extend the
life of the rolling-contact bearing by solving the problem
of short life due to entrance of foreign matter
Summary of the Invention
A rolling-contact bearing of the invention has a pair
of shields fitted to an inner race from both sides thereof
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in an axial direction, in which each of the shields is L-
shaped in a longitudinal section, and is composed of a
cylindrical portion for fitting on the outer circumference
thereof with the inner circumference of the inner race, and
a flange portion radially extending at an outer end of the
cylindrical portion.
Opposing ends of the cylindrical portions of the pair
of shields may come in contact with each other. However
the length of the cylindrical portions of the shields may
preferably so set that a clearance may be formed between
the opposing ends of the pair of shields in order to define
the width (axial dimension) of the bearing integrated with
the shields accurately without fluctuation. An outer edge
of the flange portion of the shield may preferably be
positioned in the vicinity of an inner circumference of the
outer races, which results in a kind of labyrinth formed
between the outer edge of the shield and an inner
circumference of the outer race, enhancing the shielding
effect.
An outer end surface of each of the shields may be
flush with, or spaced apart inward from an end surface of
the outer race as a result of reduction in the wall
thickness of the inner race by an amount corresponding to
the thickness of the shields. If the width of the inner
and outer races is set equal, the outer ends of the shields
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would protrude from the respective ends of the outer race,
causing water dropping from the ends of the outer race to
enter the bearing when the outer race is stopped. An
increase in weight due to addition of the shields may be
advantageously canceled as a result of reduction in the
wall thickness of the inner race by an amount corresponding
to the thickness of the shields.
The invention is also intended to extend the life of
the bearing by integrating the shields with the bearing for
a bogie wheel of a snowmobile, and preventing deformation
of seal due to collision of ice or gravel, deterioration or
loss of packed grease due to entrance of moisture into the
bearing, or rusting in the inside of the bearing.
That is, the invention relates to a rolling-contact
bearing for bogie wheel of snow mobile, comprising an inner
race forced on to a shaft, an outer race carried in the
bogie wheel, and a pair of seals for sealing, respectively,
openings between both ends of the inner and outer races,
wherein a shield for shutting off each of the openings is
further provided. With this shield, each of the openings
at both ends of the bearing is shut off nearly completely,
so that snow or ice can hardly enter the bearing, and
pieces of ice and gravel which come flying forward the
bearing is shut off by the shield, and therefore
deformation or damage of the seals can be prevented.
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In a preferred embodiment of the invention, a pair of
shields are fitted to the inner race from both sides
thereof in an axial direction. Each of the shields is L-
shaped in a longitudinal section, and is composed of a
cylindrical portion for attachment on the outer
circumference thereof to an inner circumference of the
inner race and a flange portion radially extending of an
outer end of the cylindrical portion.
The length of the cylindrical portions may
advantageously be so set that a clearance is formed between
opposing ends of the pair of shields. An outer edge of the
flange portion may advantageously be positioned in the
vicinity of an inner circumference of the outer race.
One of the pair of shields may be disposed between a
shoulder of the shaft and an end of the inner race, the
other being disposed between a washer and a bolt head.
Brief Description of the Drawings
Fig. lA is a longitudinal sectional view of a rolling-
contact bearing with shields; Fig. lB is a longitudinal
sectional view similar to Fig. lA with the shields
dismantled;
Fig. 2 is a longitudinal sectional view showing a
modified embodiment;
Fig. 3 is a longitudinal sectional view showing a
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different embodiment;
Fig. 4 is a perspective view of a snowmobile;
Fig. 5 is a longitudinal sectional view of a bearing
portion of a bogie wheel; and
Fig. 6 is an enlarged view in part of the bearing shown
in Fig. 5.
Description of the Preferred Embodiments
Fig. 1 shows an embodiment in which a pair of shields
for shutting off both sides of a rolling-contact bearing 10
are integrated with the bearing 10. This bearing 10 is of
an outer race rotation type in which an outer race 14
rotates while an inner race 12 is fixed.
The bearing 10 is composed of the inner race 12, the
outer race 14, a series of rolling element 16, a cage 17,
and a pair of seals 18. The inner race 12 is smaller in
width (axial dimension) than the outer race 14 so that when
the shields 20 are fitted, the dimension between the outer
ends of the shields 20 may be nearly equal to the width of
the outer race 14. The width of the inner and outer races
12 and 14 may be set equal; in that case, however, the
outer ends of the shields 20 protrude from the respective
ends of the outer race 14, causing water dropping from the
ends of the outer race 14 to enter the bearing when the
outer race 14 is stopped. The inner circumference at both
CA 02247831 1998-09-2~
ends of the outer race 14 is gradually expanded from inside
to outside in the axial direction. The seal 18 has its
outer edge fitted in an annular recess formed in the inner
circumference of the outer race 14, an annular seal lip
formed in the inner edge of the seal 18 coming in a
slidable contact with the inner race 12.
Each shield 20 is an annular member of an L-shaped, or
an inverted L-shaped section, press-formed from a steel
plate blank, and is composed of a cylindrical portion 22
for attachment at the outer circumference thereof to the
inner circumference 12a of the inner race 12, and a flange
portion 24 radially extending at an end of the cylindrical
portion 22. The length of the cylindrical portion 22 is so
set that a proper gap may be formed between the opposing
ends 23 when the pair of shields 20 are in position in the
bearing 10. An outer end 25 of the flange portion 24 of
the shield 20 is positioned in the vicinity of the inner
circumference of the outer race 14.
The pair of shields 20 are installed in the inner race
12 of the bearing 10 from both sides thereof in the axial
direction, and the bearing 10 together with the shields 20
is mounted on the shaft 6. Therefore, the inner
circumference of the cylindrical portions 22 of the shields
20 is the fitting surface with the outer circumference of
the shaft. Both ends 23 of the cylindrical portions 22 may
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come in contact with each other. Alternatively, the length
of the cylindrical portions 22 may be such as to form a
clearance between the ends 23, which is advantageous in
that the width (axial dimension) of the bearing 10
integrated with the shields 20 may be set accurately
without fluctuation.
The flange portion 24 of the shield 20 extends in the
immediate vicinity of the inner circumference of the outer
race 14 to shut off the opening at both ends of the bearing
10 almost completely. Therefore, snow or ice can hardly
enter the bearing. Pieces of ice or gravel which come
flying forward the bearing are shut off by the shields 20,
so that any deformation or damage of the seals 18 can be
prevented. Thus, an increase in the life of the bearing 10
is ensured. Moreover, the inner circumference at both ends
of the outer race 14 is expanded from inside to outside in
the axial direction, so that as the outer race 14 rotates,
water and other foreign matter near the end of the outer
race 15 are scattered about by the action of centrifugal
force.
In a modified embodiment shown in Fig. 2 two shields
30a and 30b are used, in which one shield 30a is disposed
between a shoulder 6b of the shaft 6 and an end of the
inner race 12, and the other shield 30b is disposed between
a washer 8 and the head 7a of a bolt 7. The shield 30b may
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be disposed between the washer 8 and the end of the inner
race 12.
Fig. 3 shows a different embodiment of the invention in
which an iron plate pulley 40 is fitted to the outer race
14 of the Fig. 1 bearing 10 with shields 20. As mentioned
previously in relation to Fig. 1, entrance of foreign
matter from outside can be securely prevented by the
combined sealing action of the seals 18 and the shields 20,
it is applicable to the field where decrease in the life of
the bearing is caused by entrance of dust, such as
auxiliary machine pulley of an automotive engine.
According to the invention, therefore, by preventing
deformation or damage due to collision of ice or gravel to
the seal of the bearing, deterioration or loss of packed
grease due to entrance of moisture into the bearing, or
rusting inside of the bearing, the life of the bearing can
be increased.
