Claims:We Claim:
1.A method for manufacturing of a cage like structure, the method comprising:
obtaining a slotted strip;
introducing an angular cut at a pre-determined length on the slotted strip wherein the length is preferably between any two successive slots;
rolling the angularly cut strip to form a cylindrical structure; and
welding the cylindrical structure along the angularly cut positions to form a cage.
2.The method of claim 1, wherein the length is dependent on the final dimension of the cage formed.
3.The method of claim 1, wherein the angular cuts in the range of about 5o to about 60o.
4.The method according to claim 1, further wherein the angular cut is introduced either in the clockwise direction or anti-clockwise direction.
5.The method according to claim 1, wherein the rolled strip is removably retained in a fixture to:
retain the inner diameter of the cage; and
maintain edge planarity.
6.The method of claim 1, wherein the introduction of the angular cut eliminates skewed formation of cage.
7.The method of claim 1, wherein the welding is achieved by one selected from a list comprising of a laser welding, a plasmon welding.
8.A cage like structure as formed by the method of claims 1-6.
, Description:AN IMPROVED METHOD FOR MANUFACTURING A ROLLER BEARING CAGE

FIELD OF INVENTION
The invention generally relates to the field of mechanical engineering and particularly to a method of manufacturing a cylindrical cage for use as roller and/or needle bearing cage.

BACKGROUND
Needle roller bearings typically include a cage having slots with needles inserted into the slots. FIGs.1a, 1b and 1c, generally illustrates key stages in forming of a roller bearing cage known to exist in the art. The cage manufacturing generally includes the steps of slot generation on a roll of sheet blank metal. The roll is then cut into rectangular sheets of precise length to obtain a cylindrical shape. Subsequently, the cut edges of the cylindrical part are joined to form a cage. However, needle bearings require precision-made cages capable of exactly guiding the rolls on their assigned axial planes, i.e. in planes containing the general axis of the bearing.
The typical cage as formed by the method described herein before has the following disadvantages. The cutting is done by shearing along the middle of the slot and hence the dimension of cutting along the edge is uneven and varying. Further, the cutting is predominantly achieved by a separate press tool. The adoption of the press tool results in variation in the slot dimension at the strip. An additional disadvantage is the joining of the cuts which is preferably done by a resistance welding process, wherein the cut edges are pressed together and current is passed through to melt and fuse the ends. The process of resistance welding introduces skewing s (FIG1b) of rolls and burring r (FIG.1c) of the weld joints. Additionally the skew and the burr leads first to a reduced mechanical efficiency and then to breakage of the rolls. Further, the entire process as described above needs intervention by skilled personnel. Hence, there is a need for a method of formation of cage which is simple to perform and the cage obtained has the desired mechanical strength.

BRIEF DESCRIPTION OF DRAWINGS
So that the manner in which the recited features of the invention can be understood in detail, some of the embodiments are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG.1a illustrates the rectangular strip selected for manufacturing a cage known to exist in the art.
FIG.1b illustrates the skewness introduced in the welding process of a roller bearing cage known to exist in the art.
FIG.1c shows the burring of the welded joints a roller bearing cage known to exist in the art.
FIG.2a shows the step of selecting the width w in the slotted strip for introducing an angular cut for manufacturing of a cage like structure, according to an embodiment of the invention.
FIG.2b shows the angular cut obtained in the strip that is rolled into a cylindrical structure, according to an embodiment of the invention.
FIG.2c shows the laser welding of the angular cut in the cylindrical structure, according to an embodiment of the structure.
FIG.3a shows a perspective view of the overlap of the angular cut upon rolling of the slotted strip, according to an example of the invention.
FIG.3b shows a perspective view of the seamless welding achieved to form a cage like structure, according to an example of the invention.

SUMMARY OF THE INVENTION
One aspect of the invention provides a method for manufacturing a cage for needle roller bearing. The method includes obtaining a slotted strip, introducing an angular cut at a pre-determined length on the slotted strip wherein the cutis preferably between any two successive slots, rolling the angularly cut strip to form a cylindrical structure. The cylindrical structure formed is then welded to form a cage.
Another aspect of the invention in general provides for a method of manufacturing a cylindrical part of very accurate dimensions from roll of metal strip.

DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the invention provide a method for manufacturing a cage like structure. The method includes obtaining a strip. The means of obtaining the strip is not of concern and importance to the current invention. In one example of the invention, the strip 1 is a rectangular strip 1 with pre formed slots 3. Alternatively, the strip 1can is of any dimension that may be suitable to formation of the cage and all such dimensions are said to be included under the scope of this invention and as obvious to a person skilled in the art. Further, the strip can be either a slotted strip or a plain strip. In case of a slotted strip, the dimensions of the slot are dependent on the dimensions of the object to be retained in the slot. The strip 1 obtained can be either fed manually or automatically through a roller feed. A desired length of the strip is selected for manufacturing of the cage like structure, according to an embodiment of the invention. FIG.2a shows the step of selecting the width w in the slotted strip for introducing an angular cut for manufacturing of a cage like structure, according to an embodiment of the invention. Once the length is selected, an angular cut is done at the selected length on the slotted strip at a position preferably between any two successive slots. FIG.2b shows the angular cut obtained in the strip that is rolled into a cylindrical structure, according to an embodiment of the invention. The angular cut 5 performed is in different directions on either end of the strip 1. In one example of the invention, the angle of cut is about 12o with respect to the perpendicular of the strip on one side and on the other side the angle of cut is 17o from the perpendicular in the opposite direction. The angular cut 5 performed can be in a range of about 5o to about 60oon either in clockwise direction or anti-clockwise direction. In one example of the invention, the cut 5 is performed by a laser cutting machine. The angularly cut strip is then rolled to form a cylindrical structure.
In one example of the invention, the rolled strip 1 is removably retained in a fixture (not shown). The retaining of the cylindrical structure to the fixture allows the structure to retain the inner diameter of the cage. Further, the retaining of the cylindrical structure also allows to maintain the edge planarity. Additionally, the fixture is also provided with two C shaped slots (not shown) to maintain the exact inner diameter and overlap. FIG.2b also shows the overlap of the angular cut 5 upon rolling of the slotted strip 1, according to an embodiment of the invention. The overlapping ends of the rolled slotted strip is then welded to obtain a cage like structure.In one specific example of the invention the welding is achieved by laser welding. FIG.2c shows the laser welding of the angular cut in the cylindrical structure, according to an embodiment of the structure.
Alternatively other known techniques of precision welding can be adopted to achieve the welding of the structure and all such techniques are included in the scope of this invention and as obvious to a person skilled in the art. The overlapping structure created by the angular cut 5 eliminates skewed formation of the cage during welding.
In one specific example of the invention, the method as described herein above is adopted in the manufacturing of a roller bearing cage. The method includes obtaining a slotted strip. The means of obtaining the strip is not of concern and importance to the current invention. In one example of the invention, the strip 1 is a rectangular strip 1 with pre formed slots 3. Alternatively, the strip 1 can be of any dimension that may be suitable to formation of the cage and all such dimensions are said to be included under the scope of this invention and as obvious to a person skilled in the art. The strip 1 obtained can be either fed manually or automatically through a roller feed. A desired length of a slotted strip is selected for manufacturing of the cage like structure, according to an embodiment of the invention. Once the length is selected, an angular cut is done at the selected length on the slotted strip at a position preferably between any two successive slots. The angular cut obtained in the strip that is rolled into a cylindrical structure, according to an embodiment of the invention. The angular cut 5 performed is equal on either end of the strip 1. In one example of the invention, the angle of cut is about 12o with respect to position of the slot 3. The angular cut 5 performed can be in a range of about 5o to about 60o. In one example of the invention, the cut 5 is performed by a laser cutting machine. The angularly cut strip is then rolled to form a cylindrical structure.
In one example of the invention, the rolled strip 1 is removably retained in a fixture (not shown). The retaining of the cylindrical structure to the fixture allows the structure to retain the inner diameter of the cage. Further, the retaining of the cylindrical structure also allows to maintain the edge planarity. Additionally, the fixture is also provided with two C shaped slots (not shown) to maintain the exact inner diameter and overlap. FIG.3a shows a perspective view of the overlap of the angular cut upon rolling of the slotted strip, according to an example of the invention.
The overlapping ends of the rolled slotted strip are then welded to obtain a cage like structure.In one specific example of the invention the welding is achieved by laser welding. FIG.3b shows a perspective view of the seamless welding achieved to form a cage like structure, according to an example of the invention.
The invention, as described herein advantageously provides a method for formation of a roller bearing cage. One significant advantage of the method is the angular cut made between two successive slots rather than on the bridge of the slot. The angular cut allows overlap of the cut edges and the precision welding of the cut edges through laser eliminates the skew and burr of the cage formed, thereby increasing the mechanical strength of the cage. Additionally, the method as described herein does not involve intervention by skilled personnel and is easy to perform.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.