Description:FIELD OF THE INVENTION
[001] The present invention relates to bearings and more particularly to thrust bearings.

BACKGROUND OF THE INVENTION
[002] A bearing is a crucial component essentially required in many types of machinery which generally reduces the friction between two components. To improve efficiency of the machines, it is desired to reduce rotational torque loss by lowering the roller bearing's rotation resistance. With the said object, thrust needle roller bearings were developed.
[003] The needle bearings have a higher load capacity and stiffness and are also well suited for extreme situations which require the bearings to work with little lubrication and high-speed rotation. For instance, thrust bearings are widely used in vehicle’s automatic transmissions and air compressors. A thrust needle roller bearing is typically made up of a cage having pockets, bearing needle rollers, needles and raceway rings. The needles are arranged outwardly in a radial direction. The axial outer faces of the needle rollers are in sliding contact with respective walls of the pockets. The needle bearings are provided with retainers at the centre to hold or retain the needles within the pockets.
[004] It is known that the thrust needle bearings cage is provided with retainers disposed on the length side walls of the pockets. These retainers have end bent portions which retain the needle rollers inside the pockets. For a variety of reasons, it is preferable to have the bent portion extending into the cage pockets to keep the needles from falling apart. Owing to this structure, the needle rollers are easier to install inside the pockets and the lubricant is dispersed more uniformly. Further, this structure also improves the lubrication storage inside the bearings. The bent portions of the retainers are usually placed in the centre of the pockets, one on each side wall, thereby forming two points of contact between the needle and the pocket side wall
[005] Due to this two-point contact configuration of the retainers with the needle, the needles have been observed to get skewed in the pockets which results in increase of friction generated between the needles and the thrust bearing's raceway. The increased friction tends to increase the wear and tear of the needles. Further, it has been observed that in two-point retainer contact configuration of the prior art, the needles do not remain to be completely aligned radially with the centre of the needle during rotation and thus resulting in needle skewing. Furthermore, due to skewing movement, the needles have been observed to render surface contact with the pockets side wall generating friction and prevent the bearing from rotating smoothly. Therefore, the noise, vibration and harshness (NVH) of the bearing also increases and simultaneously, the uneven wear and tear reduces the bearing or needle life.
[006] Thus, there is a need in the art for a thrust bearing with improved needle retention inside the pockets and which addresses the aforementioned problems at least.

SUMMARY OF THE INVENTION
[007] In one aspect, the present invention is directed to a thrust bearing assembly. The bearing assembly comprises a plurality of needles and a set of retainers for each corresponding needle of the plurality of needles. The plurality of needles is arranged in an annular cage. The annular cage has a plurality of pockets adapted to support and rotatably hold the plurality of needles. The set of retainers retains the corresponding needle within a corresponding pocket. The set of retainers is provided as a set of protrusions on walls of the plurality of pockets. Each set of retainers restricting a movement of the corresponding needle within the corresponding pocket.
[008] In an embodiment of the invention, the movement of the corresponding needle is restricted with respect to the corresponding pocket and also about non-longitudinal axis of the corresponding needle.
[009] In another embodiment of the invention, each set of retainers has a first plurality of retainers and a second plurality of retainers. The first plurality of retainers is provided on a first wall and the second plurality of retainers is provided on a second wall of the plurality of pockets.
[010] In another embodiment of the invention, each of the first plurality and the second plurality of retainers includes two retainers located on each of the walls near longitudinal ends of the needles.
[011] In a further embodiment of the invention, each of the set of protrusions of retainers is wedge-shaped and has a triangular cross section. The protrusions restrict the movement of the needles by contacting the needles at at least one of surfaces of the protrusions.
[012] In a further embodiment of the invention, the protrusions extend in the circumferential direction with respect to the annular cage and below a surface of the annular cage. The protrusions have an inclined surface and a flat surface. The flat surface is parallel to and in a plane of the surface of the annular cage whereas the inclined surface enables restriction of the movement of the needle by contacting the needle.
[013] In another embodiment, the invention provides a thrust bearing assembly comprising a plurality of needles, an annular cage, and a set of retainers for each corresponding needle. The plurality of needles is arranged radially in the annular cage. The annular cage has a plurality of pockets. The plurality of pockets supports and rotatably holds the plurality of needles. Each set of retainers has four retainers provided as protrusions on length side walls of the plurality of pockets. The four retainers retain and restrict a movement of the corresponding needle within a corresponding pocket with respect to and about non-longitudinal axes of the corresponding needle. The protrusions are wedge-shaped and have a substantially triangular cross-section. The protrusions restrict the movement of the needles by contacting the needles at at least one of surfaces of the protrusions. The protrusions extend in the circumferential direction with respect to the thrust bearing and below a surface of the annular cage. The protrusions having a flat surface and an inclined surface. The flat surface is parallel to and in a plane of the surface of the annular cage. The inclined surface enables the restriction of the movement by contacting the needle.

BRIEF DESCRIPTION OF THE DRAWINGS
[014] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a plan view of a thrust bearing assembly, in accordance with an embodiment of the invention.
Figure 2 illustrates a top view of a cut-section of the thrust bearing assembly, in accordance with an embodiment of the invention.
Figure 3 illustrates a top view of the pocket having a set of retainers, in accordance with an embodiment of the invention.
Figure 4 illustrates a cross-sectional view of the thrust bearing assembly along a plane perpendicular to a longitudinal axis of a needle, in accordance with an embodiment of the invention.
Figure 5 illustrates a perspective view of the pocket of the thrust bearing assembly, in accordance with an embodiment of the invention.
Figure 6 illustrates a perspective view of the thrust bearing assembly, in accordance with an embodiment of the invention.
Figure 7 illustrates an exploded view of the thrust bearing assembly, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[015] The present invention is directed to a thrust bearing assembly having a plurality of needles. The plurality of needles are arranged radially in an annular cage. The annular cage has a plurality of pockets for supporting and rotatably holding the plurality of needles. The thrust bearing assembly has a set of retainers for each corresponding needle of the plurality of needles. The set of retainers are provided to retain the corresponding needle within a corresponding pocket. The set of retainers are provided as a set of protrusions on walls of the plurality of pockets. Each set of retainers retains and restricts a movement of the corresponding needle within the corresponding pocket.
[016] Figure 1 illustrates a plan view of a thrust bearing assembly (10), in accordance with an embodiment of the invention. The thrust bearing assembly (10) comprises an annular cage (11) having plurality of pockets (12) adapted to hold and rotatably support needles 15 (shown in Figure 2). The pockets (12) are arranged radially on the annular cage (11) and positioned spaced apart from each other in a radial way with a constant pitch.
[017] Figure 2 illustrates a top view of a cut-section of the thrust bearing assembly (10), in accordance with an embodiment of the invention. The pocket (12) supports and rotatably holds the needle (15) (i.e. needle being represented by dotted lines in the figure 2) within the pocket (12). In this embodiment, the length of the needle (15) is shorter than the pocket length providing a sufficient clearance to have a smooth rotation of the needle (15) and further enabling easy flow of the lubricant through the pocket (12).
[018] In one embodiment, the thrust bearing assembly (10) has retainers (13) being provided for each corresponding needle (15). The retainers (13) retaining the corresponding needle (15) within a corresponding pocket (12). The retainers (13) restrict the movement of the corresponding needle (15) within the corresponding pocket (12).
[019] As shown in Figure 2, the pocket (12) is a formed as a cavity inside the annular cage (11). The pocket (12) has four walls adjoining each other surrounding the cavity whereas the needle (15) is positioned between two length-side walls extending along longitudinal ends of the needle (15). The shape of the pocket (12) corresponds to the shape of the needle (15).
[020] Figure 3 illustrates a top view of the pocket (12) having a set of retainers (13) formed on both the length-side walls of the pocket (12). The thrust bearing assembly (10) having a set of retainers (13a, 13b) provided for each corresponding needle (15).
[021] Figure 4 illustrates a cross-sectional view of the thrust bearing assembly (10) along a plane perpendicular to a longitudinal axis of the needle (15), in accordance with an embodiment of the invention. As shown, the thrust bearing assembly (10) has the set of retainers (13) provided for each corresponding needle (15). The set of retainers (13) are provided as a set of protrusions (14a, 14b) formed on the walls (12a, 12b) of the pocket. Each set of retainers (13) has a first plurality of retainers (13a) and a second plurality of retainers (13b). The first plurality of retainers (13a) are formed on a first wall (12a) of the pocket (12) whereas the second plurality of retainers (13b) are formed on a second wall (12b) of the pocket (12). The first and second walls (12a,b) are the length-side walls of the pockets (12).
[022] In one embodiment, each of the plurality of retainers (13a, 13b) is located on each of the wall (12a, 12b) of the pocket near longitudinal ends of the needles (15). The plurality of retainers (13a, 13b) having protrusions (14a, 14b) to restrict the movement of the needle (15) by contacting with the surface of the needle (15). The protrusions (14a, 14b) extend in the circumferential direction of the needle (15) to retain the needle (15).
[023] In one embodiment, the protrusions (14a, 14b) are having a flat surface and an inclined surface formed below the flat surface. The inclined surface extends slantwise away from the walls (12a, 12b) of the pocket. The flat surface being parallel to and in a plane of the surface of the annular cage (11). The inclined surface enabling restriction of the movement by contacting the needle (15).
[024] In another embodiment, the set of protrusions (14a, 14b) comprise at least two protrusions formed on wall of the pocket and at least two protrusions are formed on another wall of the pocket. These four protrusions collectively form a four-point contact configuration between the needle (15) and the wall of the pocket. The four-point configuration of the protrusions (14a, 14b) allow the needle (15) to stay aligned with the pivotal axis of the needle (15) during rotation and thus prevents the skewing of the needle (15).

[025] Figure 5 illustrates a perspective view of the pocket (12) of the thrust bearing assembly (10), in accordance with an embodiment of the invention. Each of the set of protrusions (14a, 14b) is wedge-shaped and has a triangular cross section. The triangular cross section of the protrusion is formed by adjoining the flat surface with the inclined surface being extended from the walls of the pocket.
[026] Figure 6 illustrates a perspective view of the thrust bearing assembly (10), in accordance with an embodiment of the invention. The annular cage (11) has a plurality of needles (15) being holded and rotatably supported inside the pocket (12) via. retainers (13).
[027] Figure 7 illustrates an exploded view of the thrust bearing assembly (10), in accordance with an embodiment of the invention. The needles (15) are shown in an unassembled state just before assembly with the cage (11) being outside the annular cage (11). The needles (15) are in the form of a cylindrical roller.
[028] In another exemplary embodiment, the invention provides a thrust bearing assembly comprising a plurality of needles (15), an annular cage (11), and a set of retainers (13) for each corresponding needle (15). Each of the plurality of needles (15) is in the form of a cylindrical roller and are arranged radially in the annular cage (11). The annular cage (11) has a plurality of pockets (12). The plurality of pockets (12) supports and rotatably holds the plurality of needles (15). Each set of retainers (13) has four retainers provided as protrusions (14a,b) on length-side walls (12a, 12b) of the plurality of pockets (12). The four retainers provide a four-point contact to retain and restrict a movement of the corresponding needle (15) within a corresponding pocket (12) with respect to and about non-longitudinal axes of the corresponding needle (15).
[029] In the exemplary embodiment, the protrusions (14) are wedge-shaped and have a substantially triangular cross-section. The protrusions (14) extend in the circumferential direction with respect to the thrust bearing (10) and below a surface of the annular cage (11). The protrusions have a flat surface and an inclined surface. The flat surface is parallel to and in a plane of the surface of the annular cage (11). The protrusions (14) restrict the movement of the needles (15) by contacting the needles (15) at at least one of surfaces of the protrusions (14). The inclined surface enables the restriction of the movement by contacting the needle (15).
[030] Advantageously, the thrust bearing assembly of the present invention provides a bearing assembly having a four-point contact configuration between the needle and walls of the pocket. In comparison to the conventional two-point retainer configuration of the thrust bearing, the four-point configuration of the present invention increases the stability and balance of the needles whilst being rotated inside the pocket. The four-point configuration secures the needle to stay aligned with the pivotal axis of the needle which decreases the friction between the retainers and the surface of the needle and thus provide a smooth rotation thereto. The four-point retainer structure of the invention provides a better hold and retention of the needles in the cage. As a result, the skewing movement of the needles is restricted and minimised and the needles remain substantially parallel to the length side walls of the pockets. Hence, the noise, vibration, and harshness of the bearing reduces which further increases the life of the bearing assembly as well as the efficiency.
[031] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims. , Claims:We Claim:
1. A thrust bearing assembly (10), the trust bearing assembly (10) comprising a plurality of needles (15), an annular cage (11), and a set of retainers (13) for each corresponding needle (15);
a. the plurality of needles (15) being arranged radially in the annular cage (11), the annular cage (11) having a plurality of pockets (12), the plurality of pockets (12) supporting and rotatably holding the plurality of needles (15); and
b. each set of retainers (13) retaining and restricting a movement of the corresponding needle within a corresponding pocket, the set of retainers being provided as a set of protrusions (14a,b) on walls (12a, 12b) of the plurality of pockets (12).

2. The thrust bearing assembly (10) as claimed in claim 1, wherein the set of retainers (13) restrict the movement of the plurality of needles (15) with respect to the corresponding pocket (12) about non-longitudinal axes of the corresponding needle.

3. The thrust bearing assembly (10) as claimed in claim 1, wherein the each set of retainers (13) has a first plurality of retainers (13a) and a second plurality of retainers (13b), the first plurality of retainers (13a) being provided on a first wall (12a) and the second plurality of retainers (13b) being provided on a second wall (12b) of the plurality of pockets (12).

4. The thrust bearing assembly (10) as claimed in claim 3, wherein each of the first plurality of retainers (13a) and the second plurality of retainers (13b) includes two retainers, the two retainers being located on each of corresponding walls (12a, 12b) near longitudinal ends of the needles (15).

5. The thrust bearing assembly (10) claimed in claim 1, wherein each of the set of protrusions (14) is wedge-shaped and has a substantially triangular cross-section, the protrusions (14) restricting the movement of the needles (15) by contacting the needles (15) at at least one of surfaces of the protrusions.

6. The thrust bearing assembly (10) claimed in claim 5, wherein the protrusions extend in the circumferential direction with respect to the thrust bearing (10) and below a surface of the annular cage (11), the protrusion having a flat surface and an inclined surface, the flat surface being parallel to and in a plane of the surface of the annular cage (11), the inclined surface enabling restriction of the movement by contacting the needle (15).

7. A thrust bearing assembly (10), the trust bearing assembly (10) comprising a plurality of needles (15), an annular cage (11), and a set of retainers (13) for each corresponding needle (15);
a. the plurality of needles (15) being arranged radially in the annular cage (11), the annular cage (11) having a plurality of pockets (12), the plurality of pockets (12) supporting and rotatably holding the plurality of needles (15); and
b. each set of retainers (13) having four retainers, the four retainers being provided as protrusions (14a,b) on length side walls (12a, 12b) of the plurality of pockets (12), the four retainers retaining and restricting a movement of the corresponding needle (15) within a corresponding pocket (12) with respect to and about non-longitudinal axes of the corresponding needle (15).

8. The thrust bearing assembly (10) as claimed in claim 7, wherein the protrusions (14) are wedge-shaped and have a substantially triangular cross-section, the protrusions (14) restricting the movement of the needles (15) by contacting the needles (15) at at least one of surfaces of the protrusions (14).

9. The thrust bearing assembly (10) as claimed in claim 7, wherein the protrusions (14) extend in the circumferential direction with respect to the thrust bearing (10) and below a surface of the annular cage (11), the protrusion having a flat surface and an inclined surface, the flat surface being parallel to and in a plane of the surface of the annular cage (11), the inclined surface enabling restriction of the movement by contacting the needle (15).

Dated this 25th Day of July 2022
NRB Industrial Bearings Ltd
By their Agent & Attorney

(Nikhil Ranjan)
Agent for the Applicants
Reg No IN/PA-1471