Method of making ball bearing retainer or cage

Abstract: To form a ball bearing retainer (10) or cage, material is first formed into a flat ring. Ball receiving pockets (12) are formed in the flat ring leaving bridge material (14) between adjacent pockets. The bridge material between adjacent pockets is flattened such that the bridge material spreads to meet the adjacent bearing balls (30), thereby locking the retainer within a ball bearing assembly. The resulting substantially flat bridge (42) between adjacent reconfigured ball pockets (34) is then crimped such that ends of the bridge are moved slightly towards each other and pressure of the reconfigured ball pockets against the bearing balls is reduced. Forming of a separate bearing retainer or cage is also disclosed.

Description: This invention relates to a method of making a ball bearing retainer or cage and more particularly to a one-piece ball bearing retainer with a crimped configuration providing ball retention. Many types of ball bearing retainers and cages are known. One of the major types includes welded metal retainers where two halves are welded together. These welded two-piece retainers have fair wrap-around and conformity to the ball shape. Operating temperature is limited by the lubricant and not by the retainer. However, it is difficult to ensure 100 percent good welds with a welded two-piece retainer design. Riveted two-piece metal retainers are similar to welded two-piece metal retainers except the two halves are riveted together rather than welded. That type retainer requires many small rivets that are difficult to insert. Visual inspection is more accurate than with welded retainers; however, poor riveting may occur. Similarly, mechanically interlocked retainers also require two halves and may be difficult to fasten together. Spring finger-type retainers offer a one-piece design but are difficult to make with sufficient ball contacting surface or wrap-around. Spring finger-type retainers usually require special heat treating. Polymer retainers offer one-piece design and have good wrap-around and ball conformity. However, polymer retainers are generally limited to lower temperature and low strength applications. One proposed metal retainer is formed as one-piece by fashioning a sheet metal ring into an undulatory form with open ball pockets spaced apart by U-shaped connecting portions. After balls are placed into the pockets, the U-shaped connecting portions are upset, causing the sides of the U-shaped connecting portions to spread and partially conform to the contour of the balls. However, that proposed design fails to provide sufficient ball retention without gripping the balls too tightly, (see e.g. GB-A-591 747). From DE-A-2 659 432 there is known a method of making a ball bearing retainer according to the preamble of claim 1 and a method of producing a ball bearing assembly according to the preamble of claim 4. According to one aspect of the present invention there is provided a method of making a ball bearing retainer or bearing cage, comprising the steps of: forming material into a ring; pressing the ring, thereby forming ball receiving pockets in the ring and leaving bridge material between adjacent ball receiving pockets; inserting a bearing ball or a ball which may be only a portion of a sphere into each ball receiving pocket; and flattening the bridge material between adjacent ball receiving pockets such that the bridge material spreads to meet the adjacent bearing balls or balls and forms a substantially flat brigde, thereby retaining the bearing balls or balls within reconfigured ball pockets, the respective reconfigured ball pockets having a depth greater than one-half the diameter of the bearing balls or balls, the bridge material forming a substantially flat bridge between adjacent reconfigured ball pockets; characterised in that the method further comprises the step of crimping the substantially flat bridge between adjacent reconfigured ball pockets such that ends of said bridge are moved slightly towards each other and pressure of the reconfigured ball pockets against the bearing balls or is reduced. According to another aspect of the present invention there is provided a method of producing a ball bearing assembly, comprising the steps of: forming material into a ring; pressing the ring, thereby forming ball receiving pockets in the ring and leaving bridge material between adjacent pockets, the resulting structure being a partially formed bearing retainer; positioning a plurality of bearing balls within an annular space between an outer bearing ring and an inner bearing ring; inserting the partially formed bearing retainer within the annular space between the outer bearing ring and the inner bearing ring such that a said bearing ball is received in each ball receiving pocket; and flattening the bridge material between adjacent ball receiving pockets such that the bridge material spreads to meet the adjacent bearing balls and forms a substantially flat bridge, thereby locking the partially formed bearing retainer to the bearing balls, the bearing balls being retained within reconfigured ball pockets, the reconfigured ball pockets having a depth greater than one-half the diameter of the bearing balls, the bridge material forming a substantially flat bridge between adjacent reconfigured ball pockets; characterised in that the method further comprises the step of crimping the substantially flat bridge between adjacent reconfigured ball pockets such that ends of said bridge are moved slightly towards each other and pressure of the reconfigured ball pockets against the bearing balls is reduced. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Fig. 1 is a cross-sectional view illustrating a portion of a partially formed first embodiment of one-piece ball bearing retainer; Figs. 2 and 3 are cross-sectional views illustrating an intermediate step in the forming of the one-piece ball bearing retainer embodiment of Fig. 1 and, in addition, illustrating tooling that may be used to partially form the retainer; Fig. 4 is a cross-sectional view illustrating a portion of the completed one-piece ball bearing retainer embodiment of Fig. 1; and Fig. 5 is a cross-sectional view illustrating a portion of a partially formed second embodiment of one-piece ball bearing retainer. In this specification, identical elements in different embodiments are given identical reference characters. Figure 1 illustrates a portion of a partially formed one-piece ball bearing retainer 10. The ball bearing retainer 10 is used to retain balls of an antifriction bearing as described below. To form the ball bearing retainer 10, metal is first formed into the shape of a flat ring, using any known forming method. In one such method, the ring is punched as a "washer" from a wide strip or sheet of flat metal. In another method, the flat ring is formed from a narrow flat strip of metal which is coiled edge-wise ("the hard way") into a split ring. The ends of the split ring may be left unjoined or may be welded or mechanically linked by a puzzle-like cut or other means to form a continuous band. Overlapping ends, for example, may be joined by a lap weld, coined to an even thickness, and trimmed to size. Next, multiple ball receiving pockets 12 are pressed into the flat ring. When the ball receiving pockets 12 are formed, bridge material 14 is left between adjacent ball receiving pockets 12. In the preferred embodiment of Figure 1, bridge material 14 is formed into an initial "tent" shape, having a peak 16 and sloping side portions 18 and 20. This "tent" shape facilitates the subsequent forming steps, described below. However, other initial shapes of bridge material 14 can be used with similar effect. The ball receiving pockets 12 each have a rounded bottom portion 22 and substantially parallel straight side portions 24 and 26, extending above the centreline 28 of bearing balls 30 to be positioned within ball receiving pockets. The parallel, straight side portions 24 and 26 join sloping side portions 18 and 20, respectively. Thus, ball receiving pockets 12 have a depth greater than one-half the diameter of the bearing balls 30. Spherically concave ball seats 32 may be pressed into the flat ring, either concurrently with the forming of ball receiving pockets 12 or as a separate, subsequent step, to achieve the same basic cross-section as two-piece retainers. During the forming of the ball receiving pockets 12, material of the ring is gathered together, thereby reducing the diameter of the ring to the desired pitch diameter of the bearing balls 30. Significantly, the sloping side portions 18 and 20 of bridge material 14 and the straight side portions 24 and 26 of ball receiving pockets 12 provide an open pocket without side relief, thereby facilitating release of the ball bearing retainer 10 from the forming tooling. The rounded bottom portion 22 of the ball receiving pockets 12 has a diameter slightly greater than that of the bearing balls 30 to provide a clearance fit. An alternative method for forming the ball bearing retainer 10 is to coil a flat strip of metal edge-wise ("the hard way") and cut off more than a 360 degree arc, or length. The length is selected such that progressive forming of the ball receiving pockets 12 absorbs the arc in excess of 360 degrees. As a result, after final forming, the ends of the coiled flat strip just meet and are available for welding or mechanical forming, if desired. Or, the ends may overlap slightly at final forming to permit lap welding, coining and trimming, as stated above. Figures 2 and 3 illustrate a subsequent step in which the bridge material 14 is pressed downward and spreads circumferentially to meet adjacent bearing balls 30, thereby retaining the bearing balls 30 within the reconfigured ball pockets 34. Dimensions of bridge material 14 are selected such that straight side portions 24 and 26 conform to the bearing balls 30 as arcuate portions 36 and 38, respectively. The reconfigured ball pockets 34 have a depth greater than one-half the diameter of the bearing balls 30 such that arcuate portions 36 and 38 partially close the pockets; that is, the chordal length of the opening is smaller than the diameter of the balls to provide ball retention. The reshaping of the partially formed ball bearing retainer 10 is indicated as reconfigured ball retainer 40, having a substantially flat bridge 42 between adjacent reconfigured ball pockets 34. Due to the spreading of bridge material 14 against the bearing balls 30, the reconfigured ball pockets 34 initially provide a tight fit with the bearing balls 30. Depending upon the resiliency of the material used, some clearance may result from "spring back" of the reconfigured ball retainer 40 after it is removed from the tooling, thereby facilitating desired rotation of bearing balls 30. Figures 2 and 3 also illustrate a forming press 44 which may be used to press the bridge material 14 so as to form the substantially flat bridge 42. Upper portion 46 of a die set includes fingers 48 which mate with lower portion 50 of the die set to form the substantially flat bridge 42, as described below. The lower portion 50 may include spherically concave recesses 52 for receiving the ball seats 32 and bearing balls 30. As illustrated in Figure 3, forming of the reconfigured ball retainer 40 may be done after the bearing balls 30 are positioned between inner and outer bearing races 54 and 56, respectively, and the ball bearing retainer 10 is inserted. The "tent" shape of the bridge material 14 facilitates guiding of the bearing balls 30 into ball receiving pockets 12, and rounded bottom portion 22 provides final circumferential spacing of the bearing balls 30. Flattening of the bridge material 14 to form substantially the flat bridge 42 provides a unique locking effect to prevent removal of the reconfigured ball retainer 40 from the resulting bearing assembly. Preferably, support is provided during the flattening of the bridge material 14 to prevent the retainer from skidding radially outwardly. Without such support, the pitch diameter of the retainer would tend to increase. For example, as shown in Figure 3, the retainer may be forced against the bearing balls 30 by clamping between the lower portion 50 of the die set and stop surface 58 of fixture 60. The bearing balls 30 are retained radially by the outer race 56, thereby preventing an undesired increase of pitch diameter of the reconfigured ball retainer 40 during forming. However, it is not necessary to position the retainer 10 between the bearing races when producing the reconfigured ball retainer 40, provided that the retainer is sufficiently restrained against radially outward movement. The present method may also be employed to produce a subassembly with only the bearing retainer and bearing balls. Such a bearing retainer, which retains the bearing balls in all directions without aid of bearing races, is referred to herein as a bearing "cage". In order to ensure that sufficient clearance is provided between ball pockets and bearing balls 30, the substantially flat bridge 42 is reconfigured as "crimped" bridge 62, as shown in Figure 4. This crimping operation results in slight "overbending", either upward or downward, to move ends of the bridge 62 slightly closer together, drawing the reconfigured ball pockets 34 back slightly from the bearing balls 30. A clearance fit is thus provided between the balls and completed ball pockets 64 of the completed ball retainer 66. The crimped bridge 62 may have a V-shape with central crease 68, or may have other shapes resulting in the desired foreshortening. The crimping tooling may be separate from the tooling used to form the substantially flat bridge 42. Alternatively, flattening and crimping may be accomplished by a single set of tooling, for example, that of Figure 2. The upper and lower portions 46 and 50 of the die set have wedge and concave configurations, respectively, which first provide flattening (Figure 2) and, upon further closing of the die set, provide crimping to form the crimped retainer 66 (Figure 4). The ball bearing retainer is preferably made of steel or brass, depending upon the desired application, although other materials could also be used. Notches or other weakening of the bridge material 14 may be employed to facilitate desired bending at the peak 16 and/or at the juncture between the sloping side portions 18, 20 and straight side portions 24, 26. The bridge material 14 may have other shapes in addition to the "tent" shape of Figure 1; for example, an arched bridge 70 of partially formed ball bearing retainer 72 may be used, as shown in Figure 5. The present method allows visual inspection of a bearing assembly or bearing cage to determine if the bearing balls 30 are properly secured. The crimped bridge 62 is easily visible, even when installed between the inner and outer bearing races 54 and 56. The assembled bearing has annular openings between the bearing races after the bearing assembly is removed from the forming press 44, as is apparent from Figure 3. In contrast, welds and rivets of known two-piece bearing retainers are not easily inspected for proper fastening. The present method may also be employed to form a separate retainer or cage to be snapped over bearing balls when the separate retainer or cage is installed in a bearing assembly. This separate retainer or cage may be formed about a first set of balls, as described above, and those balls would later be removed as a final step in forming the separate retainer or cage. To facilitate removal of this first set of balls, those " balls" may be only portions of spheres and may be integrated in tooling that rotates them for removal. From the above, it will be apparent that the present method provides a low cost method of making a ball bearing retainer that has good wrap-around and ball conformity in combination with high temperature limits. Because the resulting retainer is a one-piece design, manufacturing costs and assembly problems relating to assembling two halves together are eliminated. Also, the present method provides a method of making a bearing cage with similar features suitable for use as a subassembly for insertion in ball bearing assemblies.

Claims: A method of making a ball bearing retainer (10) or bearing cage, comprising the steps of: forming material into a ring; pressing the ring, thereby forming ball receiving pockets (12) in the ring and leaving bridge material (14) between adjacent ball receiving pockets; inserting a bearing ball (30) or a ball which may be only a portion of a sphere into each ball receiving pocket (12); and flattening the bridge material (14) between adjacent ball receiving pockets such that the bridge material spreads to meet the adjacent bearing balls or balls and forms a substantially flat bridge, thereby retaining the bearing balls or balls within reconfigured ball pockets (34), the respective reconfigured ball pockets having a depth greater than one-half the diameter of the bearing balls or balls, the bridge material forming a substantially flat bridge (42) between adjacent reconfigured ball pockets; characterised in that the method further comprises the step of crimping the substantially flat bridge between adjacent reconfigured ball pockets such that ends of said bridge are moved slightly towards each other and pressure of the reconfigured ball pockets against the bearing balls or balls is reduced. A method according to claim 1, further comprising the step of positioning the ring, with the ball receiving pockets formed therein, between inner and outer bearing races (54, 56) before the step of flattening the bridge material to retain the bearing balls within the reconfigured ball pockets. A method according to claim 1 or 2 and further comprising the step of removing the balls to provide a separate retainer or cage. A method of producing a ball bearing assembly, comprising the steps of: forming material into a ring; pressing the ring, thereby forming ball receiving pockets (12) in the ring and leaving bridge material (14) between adjacent pockets, the resulting structure being a partially formed bearing retainer (40); positioning a plurality of bearing balls (30) within an annular space between an outer bearing ring and an inner bearing ring (54, 56); inserting the partially formed bearing retainer within the annular space between the outer bearing ring and the inner bearing ring such that a said bearing ball (30) is received in each ball receiving pocket; and flattening the bridge material (62) between adjacent ball receiving pockets such that the bridge material spreads to meet the adjacent bearing balls and forms a substantially flat bridge, thereby locking the partially formed bearing retainer to the bearing balls, the bearing balls being retained within reconfigured ball pockets, the reconfigured ball pockets having a depth greater than one-half the diameter of the bearing balls, the bridge material forming a substantially flat bridge between adjacent reconfigured ball pockets; characterised in that the method further comprises the step of crimping the substantially flat bridge between adjacent reconfigured ball pockets such that ends of said bridge are moved slightly towards each other and pressure of the reconfigured ball pockets against the bearing balls is reduced. A method according to claim 4, wherein the step of inserting the partially formed bearing retainer within the annular space between the outer bearing ring and the inner bearing ring provides a desired final spacing of the bearing balls. A method according to claim 4 or 5, wherein the step of flattening the bridge material between adjacent ball receiving pockets comprises pressing the partially formed bearing retainer against the bearing balls, the bearing balls being restrained by at least one of the inner bearing ring (54) and the outer bearing ring (56), such that radially outward movement of the partially formed bearing retainer is limited during the flattening step. A method according to any one of the preceding claims, wherein the pressing of the ring forms the ball receiving pockets with a rounded bottom portion (22) and substantially parallel straight side portions (24, 26), the side portions extending above the centreline of the bearing balls or balls. A method according to any one of the preceding claims and further comprising the step of pressing the ball receiving pockets, thereby forming ball seats with spherical surfaces. A method according to any one of the preceding claims, wherein the bridge material between adjacent pockets initially has a "tent" shape. A method according to any one of claims 1 to 8, wherein the bridge material between adjacent pockets initially has an arch shape. A method according to any one of the preceding claims, wherein the crimping of the substantially flat bridge between adjacent reconfigured ball pockets is a slight overbending past the flat condition to an inverted "tent" or arch shape. A method according to any one of the preceding claims, wherein the step of forming material into a ring comprises coiling a narrow strip of metal edge-wise and joining ends to form a flat washer-like ring. A method according to any one of the preceding claims, wherein the step of pressing the ring to form ball pockets in the ring results in reducing the diameter of the ring to match a desired pitch diameter of the bearing balls. A method according to any one of claims 1 to 10, wherein the step of forming material into a ring comprises coiling a narrow strip of metal edge-wise and cutting the coiled narrow strip to provide overlapping ends, and wherein the step of pressing the ring to form ball pockets comprises progressive forming such that the overlapping of the ends is reduced.

Inventors: ALLING RICHARD L, BENSON JEFFREY P, ALLING, RICHARD L., BENSON, JEFFREY P.
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY
Application year: 1993
Main classification: F16C33
IPC codes: F16C33, B21D53