Abstract:
A double row, angular contact ball bearing comprised of an integral inner race ring and an integral outer race ring, the outer race ring having at least one circumferential depressing between the rows of balls and the inner race ring having a circumferentially radially extending end member axially outside each row of balls. The present invention also relates to a method of manufacturing double row, angular contact ball bearings by shaping sheet metal or tubular work pieces to finished inner or outer race rings by rolling, pressing or deep drawing, introducing rows of balls between the race rings, shaping the race rings to final form by rolling or pressing, and rolling the rows of balls constantly about the circumferential periphery of the inner race ring during the rolling or pressing of the race rings.

Description:
This is a continuation of prior co-pending application Ser. No. 07/574,742 filed on Aug. 30, 1990 now U.S. Pat. No. 5,177,869 issued Jan. 12, 1993 which is a continuation of prior application Ser. No. 07/309,472 filed on Feb. 10, 1989, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention broadly relates to improvements in double row, angular contact ball bearings and methods for their manufacture. Specifically, the bearings of the present invention have an outer and inner race ring made of sheet metal material. 
     BACKGROUND OF THE INVENTION 
     Ball bearing assemblies with race rings made of sheet metal are not new per se. These known assemblies are simple and inexpensive to manufacture and are primarily employed where the demands for carrying capacity and precision are not too great. Typically, such bearing assemblies are manufactured with the outer and inner race rings pressed separately to their final, finished shape and then assembled in a known manner upon insertion of the balls. Various bearing types, such as deep groove or angular contact ball bearings, may be utilized. Because the race rings are initially shaped to final form prior to insertion of the balls, the bearing assemblies typically employ only a single row of balls. This allows for ease of assembly. However, double row bearings wherein the outer race ring is split so as to facilitate assembly are also known. For example, a bearing having a split outer race ring is disclosed in U.S. Pat. No. 3,732,606. Also, German Patent No. 25 18 129 describes a double row, angular contact ball bearings with race rings angularly adjustable relative to one another. 
     Bearing assemblies may be manufactured from a piece of sheet metal through a number of different methods. The most common method of manufacture involves pressing or rolling the race rings one at a time. However, the rings may also be shaped simultaneously during the process of assembling the bearing. U.S. Pat. No. 3,657,781  describes such a method of manufacturing a single row, deep groove ball bearing. Initially, two annular pieces of sheet metal are partially shaped by a known device, such as a shaping tool. In addition, a row of balls which are retained in position by means of shaping tool during the shaping process, also act to partially shape the race rings. But because of the demands placed upon the tool and its design, the method is complicated and expensive. A further drawback of this known method is that it can only be used to manufacture single row ball bearings. Insertion of a second row of balls is not possible because an additional raceway cannot be formed by means of the tool and balls. 
     SUMMARY OF THE INVENTION 
     With the foregoing in mind, it is an object of the present invention to manufacture double row, angular contact ball bearings from a sheet of metal in an inexpensive and relatively simple manner. Furthermore, bearings produced by the present invention will attain a certain level of quality, thereby achieving a wide range of use in industry. To this end, an important and novel feature of the present invention is the ability to adjust the clearance in the bearing assembly between the balls and the race rings during the assembly process. 
     By the present invention, it is possible to provide a double row, angular contact ball bearing having outer and inner race rings satisfying the above desiderata. Each ring is manufactured from a single sheet of metal. Furthermore, the outer race ring has at least one circumferential depression between the rows of balls while the inner race ring has a circumferentially radially bulging axial end member located outside each row of balls. 
     In a preferred embodiment of the present invention, it is advantageous to fold the axial ends of the outer race ring radially inward. Thereafter, reinforcing means such as ribs may be inserted in the depression of the outer race ring between the rows of balls and in the spaces formed at the folding of the edges of the outer race ring. The reinforcing means make the bearing assembly more rigid, thus providing for greater strength. 
     In a further embodiment of the invention, reinforcing means such as ribs may be inserted in the depression of the outer race ring between the rows of balls and in the spaces formed at the folding of the edges of the inner race ring. Such reinforcing means give the bearing assembly more rigidity, thereby increasing the strength of the assembly. 
     The invention also incorporates a method for manufacturing double row angular contact ball bearings starting form tubular or sheet metal formed work pieces. At the outset, on or both work pieces may be shaped to finished or semi-finished inner or outer race rings by rolling, pressing or deep drawing, where upon the balls are introduced between the race rings. The race rings then may finally be finish-shaped by rolling or pressing, wherein only the balls, which are kept constantly rolling, serve to counteract the pressure exerted upon the edges of the race rings during the rolling or pressing operation. 
     In accordance with another feature of the present invention, the outer race ring and one axial end of the inner race ring may be initially shaped by rolling or pressing. The other axial end of the inner race ring may then be shaped by rolling after introduction of the balls. 
     It is an object of the present invention to finish-shape the inner race ring by rolling before shaping the outer race ring. The outer race ring can subsequently be shaped to final form after introduction of the balls, shaping of the outer race ring can be accomplished by depressing the ring between the rows of balls by means of a press roller. 
     Another object of the present invention is to manufacture double row, angular contact ball bearings where in the inner race ring is finish-shaped after the introduction of the balls. The inner race ring rotates upon a shaft and an axial and radial pressure is exerted upon the ends of the ring. Thus, the end of the race ring may be displaced axially upward to form a raceway. However, the inner race ring may also be shaped by axial pressure after introduction of the balls in a previously finish-shaped outer race ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the present invention and the various features and details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein: 
     FIG. 1 is a longitudinal sectional view of a ball bearing assembly; 
     FIG. 2 illustrates a method for manufacturing the bearing according to the present invention; 
     FIG. 3 shows an alternative method of manufacturing the bearing assembly; 
     FIG. 4 is a longitudinal sectional view similar to FIG. 1 showing a modified form of the bearing assembly in accordance with the present invention; 
     FIG. 5 shows a further embodiment of the bearing in accordance with the present invention; 
     FIG. 6 is a further embodiment of the bearing FIG. 1; 
     FIG. 7 is illustrated of a modified embodiment of a bearing assembly according to the invention; 
     FIG. 8 shows yet another modified embodiment of the bearing illustrated in FIG. 1; 
     FIG. 9 is an enlarged side elevational view of a two row angular contact ball bearing assembled in accordance with an additional method and with a portion broken away in sections to show additional details of construction; 
     FIG. 10 is an elevational view of the bearing shown in FIG. 9; 
     FIG. 11 is an enlarged fragmentary sectional elevational view showing schematically the first step in the assembly of the two row angular contact ball bearings shown in FIG. 9; 
     FIG. 12 is a view similar to FIG. 11 showing the second step in the assembly; 
     FIG. 13 is a view similar to FIGS. 11 and 12 showing the third step in assembly; 
     FIG. 14 is a fragmentary end elevational view taken on line 14--14 of FIG. 13; and 
     FIG. 15 is a view similar to FIGS. 11-13 showing the fourth and final step in assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and particularly to FIG. 1 thereof, there is shown a double row, angular contact ball bearing having an inner face ring (1), as outer race ring (2) and two rows of balls (3, 4) disposed between these race rings. The outer race ring (2) is provided with a circumferential depression (5) between the rows of balls, but is otherwise cylindrical. The inner race ring (1) is cylindrical in form, but has a circumferentially radially extending end member at its axial ends. The spaces formed by the circumferential depression (5) and the axial end members form a raceway for the rows of balls (3, 4). Thus, a two row, angular contact ball bearing is obtained. The bearing as shown in FIG. 1, has no retaining means for the balls (3, 4). Therefore, it incorporates a maximum number of balls. However, the invention is not limited to bearings without a retainer. 
     A stage during the manufacture of a bearing according to FIG. 1 is illustrated in FIG. 2. The outer race ring (2) is fabricated prior to the assembly of the bearing. Starting from a tubular sheet of metal, a circumferential depression (5) is rolled upon the ring (2). The inner race ring (1) is partially shaped before the assembly process and a radially extending edge (6) rolled at one axial end of a piece of tube. The opposite axial end (7) remains unshaped until after the balls (3, 4) have been introduced. By displacing the finished outer race ring (2) axially relative to the semi-finished inner race ring (1), the balls (3, 4) may be inserted into the raceways. The final stage in the manufacturing process is the clamping of the semi-finished bearing in a fixture and rolling the axial (7) of the inner race ring (1), as shown by the arrow in FIG. 2. To ensure that the raceways in the bearing are smooth and uniform, the balls (3, 4) must continuously rotate during the rolling of the axial end (7). To this end, either the inner ring (1) or the outer race ring (2) rotates during the rolling operation, thereby causing the balls (3, 4) to rotate. 
     By applying a carefully adapted pressure against the end (7) during the rolling operation, a bearing entirely free from play can be obtained. Normally, this objective is achieved by adjusting the clearance between the inner (1) and the outer (2) rings until a desired tolerance or no tolerance results. One advantage of the present invention is that this operation, which is both expensive and time consuming, can be entirely eliminated. 
     Since the raceways have been rolled at the same time the balls are rotating, a surface smoothness in the tracks almost as high as the surface smoothness for ground rings is achieved. In addition, the frictional resistance of the present bearing is almost as low as a corresponding bearing having ground rings. Furthermore, the rolling of the end (7) in the inner race ring (1) by applying a pressure is accomplished with only the balls (3) counteracting the applied pressure. Therefore, it is not necessary to use any external pressure means other than the balls or to use any other device for maintaining the balls in position during the rolling operation. This is a considerable improvement over earlier known methods. 
     Another method of manufacturing a bearing according to the present invention is shown in FIG. 3. The inner race ring (1) is finish-shaped prior to assembly. The outer race ring (2), which was initially tube-shaped, is circumferentially depressed between the rows of balls (3, 4) by means of a press roller (8). The outer race ring (2) continuously rotates while the depression (5) of the ring (2) is formed by the press roller (8) resulting in a bearing having the same properties as the bearing embodied in FIG. 2. It is possible to use a finished inner ring having at least a pair of finished raceways and an unfinished outer ring, and then pressing the outer ring in the region midway between the inner raceways to finish form the outer raceways. 
     FIG. 4 illustrates a bearing according to the present invention having the same inner race ring (1) as in the earlier figures, but wherein the two axial ends (9, 10) of the outer race ring (1) have been rolled radially inward. These rolled axial ends (9, 10) form a protective edge to keep out particles such as dust or dirt which may inhibit the functioning of the assembly. 
     A further embodiment of the present invention can be seen with reference to FIG. 5. FIG. 5 shows a bearing assembly wherein a cover (11) has been introduced to protect the bearing. Because the outer race ring (2) has a larger axial length than the inner race ring (1), the cover (11) may be arranged in the space formed by the outer axial ends of the race rings. 
     Another modification of the bearing according to the present invention is shown in FIG. 6. The inner race ring (1), which was initially tube-shaped, has a larger axial length than the inner ring of FIG. 1. Therefore, the bearing assembly has an inner race ring (1) projecting outside the outer race ring (2). This modified bearing is less susceptible to external axial forces because of the increased surface area of the inner ring (1). Another advantage of the modified bearing is that the axial edges of the inner race ring (1) may be folded and reinforcing means such as ribs may be inserted in the spaces formed by the folding to make the bearing more rigid. Likewise, reinforcing means may be positioned in the circumferential depression (5) in the outer race ring (2) to further increase the rigidity of the bearing. The increased rigidity of the bearing assembly provides greater strength. 
     In accordance with another feature of the present invention, a sealing member (12) may be inserted in the spaces formed by the axial ends of the race rings. As shown in FIG. 7, the sealing member protects the bearing assembly from foreign particles, such as dust, dirt or liquids, which may be introduced during operation of the assembly. 
     FIG. 8 shows yet another embodiment of a bearing according to the present invention. The race rings have a larger axial length than the rings illustrated in FIGS. 1-7, and the outer race ring (2) is equipped with two circumferential depressions (13). The increased axial length of the race rings allows them to withstand greater axial forces which may be placed upon the assembly, during normal operating procedures. 
     There is illustrated in FIGS. 9-15 another embodiment of a method for forming a double row angular, contact ball bearing in accordance with the present invention. As illustrated therein, a finished outer ring 10a is inserted in a suitable manner axially into an assembly position in the support of an assembly machine or the like 10b. A tubular member, 11a, is inserted axially into the ring 10a to a position concentrically aligned with the outer ring 10a. A complement of balls 12a are then inserted in the annular space between the ring members 10a and 11a from both axially ends. The outer ends 14a of the inner ring 11a are then bent to form a finished inner ring by means of two rotatable forming members inserted from both ends into the inner ring 11a. During this bending operation, the inner ring, 11a, is rotated by means of the rotatable members. This rotation causes the balls 12a to rotate. The outer ring 10a is held against rotation by means of clamping jaws 13a. When the ends 14a are bent to a predetermined degree, a preload between the inner and outer rings 11a, 10a respectively is created which causes the outer ring 10a to begin rotating. Rotation of the outer ring 10a is a signal that the formation of the bearing is completed. The amount of preload may be adjusted in the bearing to a predetermined desired preload simply by adjusting the tension applied by the clamping jaws 13a. 
     While particular embodiments of the present invention have been illustrated and described herein, it is not intended to limit the invention, and changes and modifications may be made therein with the scope of the following claims. Many different variations of the present invention may be produced by the methods of manufacture disclosed herein. Despite the inexpensive method of manufacture, bearing assemblies fabricated from the methods illustrated and described herein are of the highest precision and quality.