Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-10-17
2004-06-01
Footland, Lenard A (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S513000, C384S516000, C029S898061
Reexamination Certificate
active
06742933
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to a bearing and a method of assembling the bearing and, more particularly, this invention relates to an integral shaft bearing (whose typical usage is for a water pump) and a method of assembling the bearing.
A typical water pump used for circulating coolant water for an automobile engine comprises a cylindrical housing with an installation flange on the side nearest the engine and fastened to the cylinder block of the engine by way of the installation flange. Provided on the radial inside of the housing is a rolling element bearing. A typical rolling element bearing is shown in FIG.
7
. The typical rolling element bearing generally designated by the numeral
10
comprises a ring forming an outer race
12
having a pair of first and second outer raceways
14
,
16
, a rotating spindle or shaft
18
forming an inner race and having a pair of first and second inner raceways
20
,
22
opposed to the first and second outer raceways
14
,
16
, respectively. A pulley (not shown) driven by a belt which, in turn, is driven by the crankshaft of the engine is mounted on one end of the shaft, as may be a fan, and an impeller (not shown) is mounted on the other end of the shaft
18
. The end
24
of the shaft
18
on which the pulley is mounted has a larger diameter than the other end
26
of the shaft
18
. A plurality of balls
28
,
29
rides in each of the spaces defined by the first and second inner and outer raceways, respectively. Cages
30
,
32
are used to maintain the spacing of the balls
28
,
29
. Seals
34
,
36
may be provided between the ends of the ring
12
and the spindle
18
to prevent the grease filled inside the bearing
10
(when prelubricated with grease) from leaking out, as well as prevent foreign matter such as dirt or steam on the outside from getting inside the unit.
When the drive belt is mounted on the pulley which is fixed to the shaft and on a pulley fixed to the engine driveshaft, the belt is under tension, thereby creating an overhung, or moment, load on the pulley end of the shaft. This leads to various stresses which, in turn, lead to premature wear and shorter life of the bearing. U.S. Pat. No. 5,462,489 to Kan, et al., which is incorporated herein by reference in its entirety, teaches one such problem involving possible breakage of the shaft and its solution, but this patent does not address other stress-related problems.
U.S. Pat. No. 6,168,316 to Paling, et al., which is incorporated herein by reference in its entirety, teaches lengthening the life of the unit by using a full complement of balls in mutual contact, and no cage, in the raceways nearer the pulley end of the unit, with spaced-apart balls held in place by a cage in the raceways nearer the impeller end of the unit.
Japanese unexamined utility model application (Jitsukai) No. Sho 53-97701 to Koyo Seiko K. K., which is incorporated herein by reference in its entirety, teaches a bearing assembly which can use either balls or rollers in both raceways, or balls in the raceways at the pulley end of the shaft and rollers in the raceways at the impeller end of the shaft. The construction of JP 53-97701 uses a shaft having a smaller diameter at the pulley end and balls which are larger in diameter mounted in the raceways at the fan end, thereby reducing the stresses caused at the ball/raceway contact by the drive belt, but increasing the bending stresses within the shaft, causing a greater propensity for the problems outlined in the Kan, et al.
U.S. Pat. No. 6,231,242 to Yano, et al., which is incorporated herein by reference in its entirety, teaches a bearing wherein the pulley end of the shaft is larger in diameter than the impeller end, but has a counterbore portion in the outer raceway at the pulley end of the unit, thereby allowing for a full complement of balls in the raceways at that end, but spaced-apart balls in the raceways at the impeller end of the unit. Both sets of balls are the same size and both are held in place by cages. The diameter of the balls is 22-25% of the outside diameter of the outer race or 25-28% of the diameter of the outer raceway at the pulley end of the unit, i.e., the outer raceway which is counterbored.
Regardless of the measures taken to reduce stress, all the prior art bearings are subject to premature failure.
Japanese laid-open (Kokai) patent application No. 2000-314428, which is incorporated herein by reference in its entirety, teaches a method of assembling a prior art bearing. Referring to
FIGS. 8A-8
D, in assembling a ball bearing, the first plurality of balls
28
to be placed in the first inner raceway
20
at the pulley end of the unit
10
are first inserted into a first cage
30
to form a first balls-and-cage assembly
38
. The first-balls-and cage assembly
38
is slid over the shaft
18
at its pulley end
24
until the balls seat in the first inner raceway
20
. The thus-assembled shaft and first ball-and-cage Assembly
40
is then slid, impeller end first, into the outer race
12
through the pulley end of the outer race, until the balls seat in the first outer raceway
14
and the first inner raceway
20
and first outer raceway
14
are lined up. The impeller end of the shaft is then displaced in a direction perpendicular to its axial centerline within the outer race as shown in FIG.
8
D. After that, the second plurality of balls
29
is inserted onto the shaft within the outer race at its second outer raceway end, and the second cage
32
is inserted over the shaft and within the outer race to surround the second plurality of balls.
The major disadvantage of the prior art method of assembly is the first set of balls and their cage had to be assembled onto the shaft before being inserted into the housing. This exposed the balls to possible damage and contamination
It is, therefore, an object of the present invention to provide a bearing for an apparatus, such as a water pump, having a rotating shaft with a driving element such as a pulley at one end and a driven element such as an impeller at the other end which is free of the aforementioned and other such disadvantages.
It is another object of the present invention to provide a bearing for an apparatus having a rotating shaft with a driving element such as a pulley at one end and a driven element such as an impeller at the other end which reduces the maximum stress and is therefore less susceptible to failure at the end of the shaft opposite the driving element.
It is still another object of the present invention to provide an improved bearing for a water pump.
It is yet another object of the present invention to provide a method of assembling the inventive bearing which is easy and economical to practice.
These and other objects are accomplished by providing a bearing for a water pump or the like having a stepped shaft and a counterbored raceway at the fan or pulley end which allows for use of a larger number of balls in the raceway at the fan or pulley end, and which allows for using larger balls at the impeller end.
While the invention is described by reference to the preferred embodiment of use in a water pump, it is equally useful in any apparatus having an integral shaft driven at one end and driving a device at the other end. Non-limiting examples of such applications are supercharger driveshaft, fan support, idler, and various agricultural uses such as planter wheel, furrowing disk, seed meter, etc. In addition, the inventive bearing could be used in a dentist's drill or other small device application. The inventive bearing could also be used in an electric motor drive.
The inventive method of assembly of the bearing includes inserting the first ball and cage assembly into the outer race at its pulley end, then sliding the shaft, impeller end first, into the outer race through the pulley end such that the first inner raceway and the first balls align with the first outer raceway. The shaft is then displaced in a direction perpendicular to its axial centerline within the outer race. A second plurality of ba
Crowell & Moring LLP
Footland Lenard A
NSK Corporation
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