Abstract:
A ball joint which uses spherical rollers to reduce the torque friction which tends to inhibit the rotation of the ball within a ball joint assembly. Two sets of spherical rollers are captivated between the ball and two liner rings in the ball joint housing. The ball has two annular raceways which act as the inner raceways for the spherical rollers. Two liner rings have internal diameters which match the configuration of the spherical rollers and which act as outer raceways for the spherical rollers. The two liner rings have external threads and are installed into the housing which has matching internal threads.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    1. Field of the Invention  
           [0004]    This invention relates in general to a ball joint and, more particularly, to a ball joint incorporating spherical roller elements.  
           [0005]    2. Description of Related Art  
           [0006]    Ball joints are used in applications where longitudinal displacement must be minimized, but where angular displacement must be tolerated. As such, the ball joint must be capable of sustaining longitudinal loads which are normally placed on the ball joint during operation. While there are many applications for ball joints, perhaps the most extensive use of ball joints is within the suspension and steering systems of automobiles.  
           [0007]    When used in an automotive application, the ball joint consists of four primary components: the ball, the pin, the lining, and the housing. The ball and pin are usually integral, with the ball being captivated by the lining which is encapsulated within the housing. When there is angular displacement of the pin, the lining allows the ball to move within the housing to allow the pin to move to its new angular position. When longitudinal thrust is place on the pin, the thrust is transferred through the pin and into the ball where the load is then transferred to the housing by the lining.  
           [0008]    While such ball joint designs provide the ability to allow the ball to swivel within the housing, such designs normally present high frictional torque when the ball and pin are rotated axially. This high frictional torque not only increases the effort needed to rotate the ball within the ball joint housing, but also contributes to the wear of the ball joint.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention overcomes these and other problems by providing a ball joint which reduces the friction torque and thereby reduces wear to the ball joint. More specifically, the present invention resides in a ball joint which incorporates spherical rollers to reduce the rotational friction torque in the ball joint and to assist in the transfer the loads on the ball and pin of the ball joint to the ball joint housing.  
           [0010]    In the present invention, the ball of the ball joint has at least one raceway on the exterior surface of the ball. Rolling elements in the form of spherical rollers travel upon the raceway on the ball. The liner rings of the ball joint are arcuate shaped to allow the spherical rolling elements to roll upon the surface of the liner rings. Thus, when assembled, the spherical rollers are located between the raceway of the ball and the arcuate surface of the liner rings and transfer the load placed on the ball to the housing while allowing the ball to rotate within the lining with reduced frictional torque.  
           [0011]    Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a sectional view of the ball joint with spherical roller bearings.  
         [0013]    [0013]FIG. 2 is a sectional view showing the ability of the present invention to sustain angular displacement of the pin. 
     
    
       [0014]    Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Referring now to the drawings, FIG. 1, an embodiment of a ball joint A is shown. The ball joint A includes a housing  1 , a first liner ring  2 , a second liner ring  3 , a ball and pin element  4 , and two sets of spherical rollers  5 , with each set forming a separate row.  
         [0016]    The housing  1  is cylindrical in shape, having a longitudinal axis X and a transverse axis Y. The housing  1  also has a front face  10 , a rear face  11 , an outside diameter  6 , and an inside diameter  7 , with the inside diameter having internal threads  8 . Three holes  9  are located in the housing  1  and are perpendicular to the outside diameter  6 . The three holes  9  are used to allow lubrication of the internal components of the ball joint A. The rear face  11  includes a flange  12  which projects inwardly from the outside diameter  6 , the flange  12  having a shoulder  13 .  
         [0017]    The first liner ring  2  has a set of exterior threads  14  which match the internal threads  8  of the housing  1 . The first liner ring  2  also has an arcuate interior surface  15  that lies within a spherical envelope having a radius R. An offset  16  is located at distal end of the first liner ring  2 , the offset being sized to match the dimensions of the shoulder  13  of the housing  1 . An annular groove  17  is located at the distal end of the first liner ring  2  and is dimensioned such that the radial surface  18  of the annular groove is in alignment with the rear face  11  of the housing  1  when the first liner ring  2  is installed in the housing  1 . The annular groove  17  provides a seat for a sealing device, such as a boot seal, to protect the ball joint A. The distal end of the first liner ring  2  also has three axial grooves  23 . The three axial grooves  23  have a radial length of about 8 degrees_and are radially located such that the center of each groove is spaced at 120 degree intervals around the axis X. The axial grooves provide a path for lubrication during change of lubricants in the ball joint A.  
         [0018]    The second liner ring  3  is exactly like the first liner ring  2  with the exception that the second liner ring  3  does not have an offset  16 . Instead, the external threads  14  are continuous on the outside of the second liner ring  3 . Similar to the first liner ring  2 , the second liner ring  3  also has three axial grooves  23 . The three axial grooves  23  of the second liner ring  3  also have a radial length of about 8 degrees and are radially located such that the center of each groove is spaced at 120 degrees intervals around the axis X. The axial grooves provide a path for lubrication during change of lubricants in the ball joint A.  
         [0019]    In a second embodiment of the present invention as shown in FIG. 2, the second liner ring  3  also has a shoulder  33  which projects outwardly from the X axis. The shoulder  33  is used when the second liner ring  3  is retained within the housing  1  by means of a rolled formed bead  30 . The roll formed bead  30  is created when the assembled components of the ball joint A are placed within a device which deforms a portion of the housing  1  to create the roll formed bead  30 . The roll bead  30  is continuous around the full circumference of the housing  1  and the second liner ring  3 .  
         [0020]    In the current embodiment, the first liner ring and the second liner ring are made of a material which reduces the friction between the liner rings  2  and  3  and the ball and pin element  4 . In other embodiments, the material of liner rings  2  and  3  may be of the same or similar material as the housing  1 .  
         [0021]    The ball and pin element  4  has a first pin  19 , a ball  20 , and a second pin  21 . In the current embodiment, the first pin  19 , the ball  20 , and the second pin  21  are integrated into a single ball and pin element  4 . It will be appreciated, however, that in other embodiments, these three parts may be separate or in any combination of integrated or connected parts.  
         [0022]    The ball  20  is spherical and has a radius of R′. The radius R′ is slightly smaller than the radius R of the first liner ring  2  and the second liner ring  3 . More specifically, R′ should be from about 0.002 to about 0.006 inches smaller than the diameter R. Alternatively, the radius R′ should be smaller than the radius R by an amount equal to about the elastic deformation range of the spherical rollers  5 . This difference in radii allows the spherical rollers to carry the loads under the designed loading conditions and also act to save the spherical rollers from catastrophic failure in the event of excessively high loads. Additionally, in another embodiment of the present invention, this difference in radii can eliminate the need for the axial grooves on the liner rings  2  and  3 , and on the ball  20 . The center of the ball  20  is in alignment with the Y axis of the housing  1 . The ball  20  has two oppositely inclined annular raceways  22 . The two annular raceways  22  are located longitudinally equidistant from the Y axis and have a cross sectional curvature conforming to the size and shape of the spherical rollers  5 . Each of the two annular raceways  22  lie between a first rib  31  and a second rib  32  which act to guide the spherical rollers  5  with the track of the raceways  22 . The ball  20  also has three axial grooves  24  which are located around the Y axis of the ball  20 , at equal circumferential intervals. The three axial grooves  24  have a radial length of about  18  degrees and are radially located such that the center of each groove is 120 degrees from the adjacent grooves and at their ends open through the faces of the ribs  31  and  32 . The axial grooves  24  provide a path to supply lubrication to the spherical rollers  5 .  
         [0023]    The first pin  19  and the second pin  21  are configured to allow connection of the pins to other machine components which incorporate the present invention. In the embodiment described herein, the first pin  19  has a circumferential shoulder  25  and a groove  26  whereby the pin  19  can be inserted into an opening of a machine component which can then be held captive by the installation of a snap ring (not shown) into the groove  26 . The second pin  21  has a different method of attachment which utilizes a chamfered shoulder  27  and a mounting hole  28 . The second pin  21  is installed into another opening of a machine component by inserting the neck  29  of the second pin  21  into the opening and then captivating the machine component by installing a fastener such as a bolt (not shown) into the mounting hole  28 . This method of attaching the first pin  19  and the second pin  21  to a machine component are only examples of the type of connections which may be used to attached the present invention to a machine component. For example, the pins may be attached to the machine component by riveting, welding, gluing, shrink-fitting, interference fitting, or by use of other retaining mechanisms such as locknuts, jam nuts, and clamping devices. It is understood that the attachment method may be modified as needed for each application without going beyond the scope of the present invention.  
         [0024]    The spherical rollers  5  are configured to match the two oppositely inclined annular raceways  22  of the ball  20 , as well as the radius R of the first liner ring  2  and the second liner ring  3  such that the outwardly presented faces of the spherical rollers  5  lie within a spherical envelope that is slightly larger than diameter than diameter of the surface of the ball  20 . When assembled, the spherical rollers  5  are positioned between, and travel upon, the two annular raceways  22  of the ball  21 , and the arcuate interior surfaces  15  of the first liner ring  2  and the second liner ring  3 . Thus, the arcuate interior surfaces  15  of the first liner ring  2  and the second liner ring  3  act as the outer raceways for the spherical rollers  5 . The spherical rollers may be separated and held into position on the annular raceways  22  of the ball  21  by a cage (not shown).  
         [0025]    To assemble the ball joint A, the first liner ring  2  is installed into the housing  1  by screwing the first liner ring  2  into the housing  1 . The first liner ring  2  is installed into the housing  1  until the shoulder  13  comes into contact with the flange  12  of the housing  1 . A first set of spherical rollers  5  is placed onto the annular raceway  22  of the ball  21 , and the ball and pin element  4  is then inserted through the inner opening of the first liner ring  2  until the spherical rollers  5  contact the arcuate inside surface  15  of the first liner ring  1 . A second set of spherical rollers  5  is placed on the second annular raceway  22  and the second liner ring  3  is then installed into the housing  1  by screwing the second liner ring  2  into the housing  1  until the inside arcuate surface  15  of the second liner ring  3  contacts the spherical rollers  5 . While the current embodiment utilizes liner rings, these rings may be omitted from other embodiments such that the ball  20  of the ball and pin element  4  are in direct contact with the interior surface of the housing which is configured to be an arcuate surface having the radius R. Once assembled, the ball joint A can then be connected with other machine components by attaching the first pin  19 , the second pin  21 , and the housing  1  to the machine components wherein the ball joint A is to be used.  
         [0026]    It must be noted that the description of the current embodiment show the use of threads in the housing  1 , the first liner ring  2 , and the second liner ring  3 . However, the present invention is not isolated to embodiments which only use threads to engage these three elements, In fact, there are a number of other types of interconnecting methods which can be used and still stay within the scope of the present invention. For example, as shown in FIG. 2, the internal components can be retained within the housing  1  by inserting those components into the housing and then rolling over or otherwise deforming a portion of the front face  10  of the housing  1  such that a roll bead  30  is generated which covers a portion of the second liner ring  3 , thus holding the second retainer ring  3  and the other internal components within the housing  1 . Other forms of retention such as retaining rings, end plates with fasteners, welding, bonding, and wedging, or a combination of these methods, may also be used to retain the first liner ring  2  or the second liner ring  3  to the housing  1 , thereby retaining the internal components of the ball joint within the housing.  
         [0027]    When assembled, ball joint A allows for the ball and pin element  4  in FIG. 2 to rotate axially and to allow angular displacement of the ball and pin element  4  within the ball joint A. The lower portion of FIG. 2 illustrates this type of angular displacement by indicating the two positions B and C of the housing  1  in relation to the ball and joint element  4 .  
         [0028]    While the above description describes various embodiments of the present invention, it will be clear that the present invention may be otherwise easily adapted to create other embodiments to fit any configuration where a ball joint with reduced frictional torque may be utilized. As such, the present invention, the embodiments described herein, and other embodiments which may be suggested by the present disclosure are useful where ball joints having reduced frictional torque are indicated.  
         [0029]    In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.