Thrust bearing

Details Thrust bearing Thrust bearing

2002-08-26

2004-06-22

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

Reexamination Certificate

active

06752535

ABSTRACT:

FIELD OF INVENTION
The invention relates to an improved thrust bearing preferably for extreme service applications partly through the use of a novel bearing cage assembly. Moreover, the invention allows for increased durability and useful life of both the thrust bearing and, when the thrust bearing is in use, a rotating shaft through the thrust bearing.
BACKGROUND OF THE INVENTION
Thrust bearings are commonly used In equipment with rotating shafts to absorb axial loads on the shafts and are usually comprised of a bearing cage assembly positioned between a dynamic race and a static race. The races are, for the most part, constructed of hardened steel, and the bearing cage assembly is normally constructed of brass, steel or polymer material.
A bearing cage assembly normally consists of a pair of annular cage portions having opposing upper and lower planar surfaces defining circumferentially spaced slots for receiving roller elements. The dimensions of the roller slots are such that radiused portions of the roller elements extend above the upper and lower planar surfaces which are then guided along a radial path when in contact with the race components.
The potential to obtaining maximum bearing capacity of a thrust bearing lies in the number, length and diameter of the roller elements. Generally, as the internal space in a bearing cage is increased to accommodate an increase in number and/or size of the rolling elements, the bearing's load capacity increases, Therefore, a maximum bearing capacity will be achieved with a bearing cage assembly design that allows for maximum utilization of the internal space which can be occupied by the rolling elements.
There are three equations that may be used to determine the performance of a cylindrical roller thrust bearing. First, the static capacity of a bearing is determined by:
 
C
oa
=32150
×ZL
we
D
we
Where,
C
oa
is the basic static load rating in pounds force,
Z is the number of rolling elements,
L
we
is the effective roller length in inches, and
D
we
is the effective roller diameter In inches.
Second, the dynamic capacity of a bearing is determined by:
C
a
=f
cm
L
we
7/9
Z
3/4
D
we
29/27
Where,
C
a
is the basic dynamic load rating in pounds force
f
cm
is a factor influenced by the pitch diameter of the rollers,
L
we
is the effective roller length in inches,
Z Is the number of rolling elements, and
D
we
is the effective roller diameter in inches.
Lastly, the basic rating life is determined by:
L
10
=(C
a
/P
a
)
10/3
×10
6
where,
L
10
is life associated with 90% reliability (in total revolutions),
C
a
is the basic dynamic load rating In pounds force,
P
a
is the applied load on the bearing in pounds force.
On the basis of the above-noted relationships, it is apparent that by increasing any one or more of the length of the roller elements, the number of the roller elements contained in the bearing cage, and the diameter of the roller elements, the basic static load capacity, the basic dynamic load capacity, and the basic rating life of the bearing substantially increases. For example, increasing the roller length by 10% can result in a 10% increase in static load capacity, an 8% increase in dynamic capacity, and a 37% increase in basic rating life.
Machined bearing cages made from brass or steel require thick cross-sections between the rolling element pockets to keep them sufficiently aligned, Rolling elements are placed in each of the pockets and a ring is secured around the outside diameter to hold the rolling elements in place. Other versions of the two-member steel cages also require thicker side cross-sections to hold the two halves together. This type of design severely limits the size and the quantity of the rolling elements, thus limiting the thrust bearing's capacity.
On the other hand, injection molded cages of polymer material allow extremely thin cross-sections between the rolling element pockets but still require thick peripheral inside and outside sidewalls of the bearing cage frame in order to secure the two halves together. Thick peripheral sidewalls limit the overall size of the rolling elements which can be accommodated by the bearing cage. Thus, similar to the metal bearing cage described above, bearing cages manufactured from polymer material also have limitations on the amount of load capacity that can be achieved as a result of their design, Moreover, the polymer materials easily degrade in high temperature applications and thus, are not the preferred material from which to manufacture bearing cages.
A common drawback associated with the aforementioned machined cages and injection molded cages is that solid dividers are employed to form roller pockets which severely limits the overall size and quantity of the roller elements contained within the bearing cage. In addition, these dividers provide a place for abrasive particles to become lodged and rub on the rolling elements within the bearing cage assembly, thus potentially reducing the life of the bearing. Although the bearings are immersed in lubricant, the latter has a limited ability to remove abrasive grit out from between the roller elements. Eventually, a build-up of abrasive grit occurs and one or more of the roller elements becomes jammed against the cage or is damaged by the grit thereby reducing the life of a thrust bearing.
To facilitate assembly of the bearing cage assembly with the roller elements, the bearing cages are generally formed of a pair of annular members which mate or interlock along an interface normal to the axis of the bearing cage assembly. In most instances, an interlocking engagement is used to secure the two halves of the bearing cage together after the pair of annular members and the roller elements are properly assembled. For example, in Canadian Patent Application No. 2,292,286, one of the cage members is formed with a radially outwardly projecting circumferential lip, while the other cage member is formed with a radially inwardly projecting circumferential lip adapted to interlock with the outwardly projecting lip to prevent axial separation of the cage members while permitting relative rotational movement thereof.
However, a disadvantage to using this type of engagement profile is that optimal thinness of the sidewall cannot be obtained which could otherwise allow for maximized roller fill (roller fill being the volume occupied by the rollers in the bearing cage) and, subsequently, increased bearing load capacity. There is a current need to increase the roller fill of a thrust bearing as well as to increase the service life of such bearing.
Equipment that is subjected to extreme service applications often experience vibrations that can result in contact between the rotating shaft and the bearing race edges. The inside edges of the bearing races are often quite sharp due to the grinding process used to dress the bearing race surfaces. This contact tends to cut sharp grooves into the rotating shaft. The sharp grooves can act as critical notch stress risers and lead to catastrophic failure of the shaft. There is a current need to reduce the risk of such an occurrence.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a bearing cage assembly component for an axial thrust bearing for a rotating shaft, the component comprising an annular bearing cage frame and a plurality of roller elements, The annular bearing cage frame comprises:
an inside sidewall and an outside sidewall, the inside sidewall having an exterior surface to be adjacent the rotating shaft, the exterior surface having a smoothly curved axial profile for reducing abrasion on the shaft;
a base extending between the respective sidewalls and including a plurality of first roller element slots; and
a top extending between the respective sidewalls and including a plurality of second roller element slots respectively aligned with the first roller element slots thereby providing pairs of aligned roller element slots in the base and top. The plurality of roller elements are respect

Affiliated with

Also associated with

Rating

Thrust bearing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Thrust bearing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thrust bearing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3335770