Caged roller assembly and reduction gear unit using the same

Bearings – Rotary bearing – Antifriction bearing

Reexamination Certificate

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Reexamination Certificate

active

06513987

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a caged roller assembly having a high load bearing capacity within a limited space and a planetary reduction gear unit using such caged roller assembly.
2. Description of the Prior Art
It is known that caged roller assemblies or caged roller assemblies are used in planetary reduction gear unit employed in various applications including, for example, construction machines. This type of caged roller assemblies has long been and is currently desired to have an increased load bearing capacity. While a full type roller assembly without a roller retainer is currently available as a bearing capable of exhibiting a maximum load bearing capacity within a limited space, it has been recognized that the full type roller assembly has a handling problem, specifically difficulty in assemblage and overhauling, and often involves a potential functional problem in that some of the rollers tend to skew during the use of the bearing. To alleviate these problems recognized in the art, various caged roller assemblies have been suggested.
For example, there exists a well known caged roller bearing which comprises a plurality of rollers and a circumferentially extending annular roller retainer having pockets spaced an equal distance from each other in a direction circumferentially of the roller retainer to accommodate the rollers, and the roller retainer has the pillars that extend from a radially inner side to a radially outer side of the roller retainer. Each pillar is formed in, for example, V-shape and provided with radially outer and inner roller stoppers to retain the roller in position. With this structure, since the pillar extending radially is disposed between the neighboring rollers, it is difficult to decrease a circumferential space between such rollers to thereby increase the number of rollers employed therein.
FIGS. 8A and 8B
illustrate another prior art caged roller assembly designed to increase the number of rollers employed therein. The caged roller assembly shown therein comprises a circumferentially extending annular roller retainer
51
having opposite ends formed with annular collars
51
b
, and a plurality of rollers
52
rotatably accommodated within respective pockets
53
defined in the roller retainer
51
so as to be spaced an equal distance from each other in a direction circumferentially of the roller retainer
51
and as to leave a pillar
57
between the neighboring pockets
53
. Where the number of the rollers
52
is increased, each of the pillars
57
has no way other than to be reduced in width, resulting in such a shape as shown in FIG.
8
B.
Prior to the caged roller assembly of
FIGS. 8A and 8B
being mounted in, for example, a machine or a reduction gear unit, the prior art caged roller assembly is in such a condition that the rollers
52
is highly susceptible to separation or fall from the associated pockets in a direction radially inwardly of the roller retainer
51
although separation or fall of the rollers
52
in a direction radially outwardly of the roller retainer
51
is effectively refrained. Considering the ease to mount the caged roller assembly in a machine or reduction gear unit, means is necessitated to prevent the rollers
52
from inadvertently separating or falling out of the associated pockets
53
radially inwardly as well as radially outwardly by the time the caged roller assembly is ready to be mounted in the machine or reduction gear unit.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been devised to provide an improved caged roller assembly capable of exhibiting a high load bearing capacity even within a limited space substantially without some or all of the rollers being skewed during use thereof, and in which roller assembly prior to the caged roller assembly being mounted in a machine or reduction gear unit, separation or fall of some or all of the rollers out from the pockets in both directions radially inwardly and outwardly of the roller retainer is effectively prevented to facilitate a quick mounting or installation of the caged roller assembly in the machine or reduction gear unit.
A further important object of the present invention is to provide the improved caged roller assembly of the type referred to above, wherein means is provided to minimize depletion of a lubricant oil from a rolling surface to thereby prevent the roller retainer from being worn in frictional contact with the rollers.
The present invention has additional objects and features which would become apparent from the detailed description of preferred embodiments thereof that is herein set fort.
In order to accomplish these and other objects of the present invention, the present invention in accordance with one aspect thereof provides a caged roller assembly which includes a roller retainer including a large-diameter circumferential ring body having ends opposite to each other and a pair of annular flanks extending radially inwardly from the respective ends of the circumferential ring body, and a plurality of rollers rotatably carried by the roller retainer. The circumferential ring body has a plurality of circumferentially spaced pockets defined therein and the rollers are rotatably positioned within the respective pockets. Each of said rollers has opposite end faces each formed with an axially inwardly extending bearing recess defined therein. Bearing bosses are formed in each of the annular flanks in a circular row one for each of the pockets, the circular row of the bearing bosses in each annular flank being aligned with a pitch circle that is defined by respective axes of rotation of the rollers. The bearing bosses in the annular flanks are rotatably engaged in the bearing recesses on the opposite end faces of the associated rollers, said circumferential ring body having a diameter greater than the pitch circle of the rollers.
According to the structure described above, prior to the caged roller assembly of the present invention being mounted in a machine or reduction gear unit, not only is any possible separation of the rollers in a direction radially outwardly from the roller retainer prevented by opposite side edges of the pockets, but also any possible separation of the rollers in a direction radially inwardly from the roller retainer is prevented by the bearing bosses rotatably engaged in the bearing recesses at the opposite end faces of the rollers. Since each of the pillars of the roller retainer situated between the neighboring pockets is provided only on a radially outer side of the roller retainer, as compared with the roller retainer having the pillars that extend from a radially inner side to a radially outer side of the roller retainer such as in the prior art caged roller assembly, the roller retainer used in the present invention can have a simplified shape and be easy to manufacture, allowing to expand the limit to which each pillar situated between the neighboring pockets can be reduced in width. Accordingly, the number of the rollers that can be employed within a predetermined space available in the caged roller assembly can advantageously be increased to thereby increase the load bearing capacity of the resultant caged roller assembly. The bearing recesses defined in the opposite end faces of each of the rollers, in which the corresponding bearing bosses rigid or fast with the annular flanks engage also serve as oil sumps and, therefore, the frictional wear of respective portions of the annular flanks that are held in sliding contact with the end faces of the rollers can advantageously be minimized.
The manner in which the rollers are guided by the roller retainer can be classified into two types depending on the dimensional relationship. Where a gap between each roller and the adjacent side face of each pillar between the neighboring pockets is small relative to the size of a radial gap (play) between the bearing recess in each end face of the rollers and the associated bearing boss of the roller retainer that is engage

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