Abstract:
A ball stud system that provides a ball stud that will not loosen easily under the application of repetitive side loading on the ball portion of the stud. The ball stud is secured to the vehicle steering knuckle arm using the combination of a tapered nut and tapered washer. The tapered nut includes slots and the pin of the ball stud an aperture. A cotter pin may be placed through the slots and aperture in order to further prevent rotation of the nut.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Ball joints have been used for years within automobiles, particularly within automobile suspensions. As an example, a typical ball joint operatively connects a control arm to a steering knuckle within the automobile&#39;s steering system. The ball joint includes a ball stud and a socket. The ball stud gets attached to the steering knuckle. A pin portion of the ball stud is usually tapered in some manner and fits into a matching tapered hole in the steering knuckle. A distal end of the pin is typically threaded and a nut is attached thereto in order to hold the pin within the steering knuckle. The socket gets attached to the control arm. The socket fits over a spherical ball portion of the ball stud and permits relative universal rotation between the steering knuckle and control arm. Ball joints are also used in other areas of vehicle suspensions. 
         [0002]    In existing practice, many types of ball stud designs are used, including a small taper pin design and a large taper pin design. Taper angle is defined as the angle between the center line of the length of the stud and the tapered surface of the stud or washer used in combination with the stud. In the small taper design, the pin of the stud, where it fits into the steering knuckle has a slight, but consistent taper generally along its entire length. The stud is held in place using a nut with a flat bottom that fits against a flat face of the steering knuckle. When side loads are applied to the ball of the stud however, the tapered portion sinks deeper into the steering knuckle (as a result of friction and yielding of the material of the steering knuckle) as compared to its original position. This sinking results in a loss of torque in the nut that holds the stud in place. Once a certain amount of torque loss occurs, the joint is considered to have failed. In an extreme situation the nut will loosen to a point that it begins to rotate off of the stud. 
         [0003]    In a large taper design, a tapered washer is used in combination with a pin of generally consistent diameter. The tapered washer has a more severe taper that the pin within the small taper pin design, but the washer does not extend significantly into the steering knuckle. A common flat nut is again used on the opposite side of the steering knuckle in combination with the tapered washer. However, when a side load is applied at the center of the ball, the nut has a tendency to slip laterally along the flat face of the steering knuckle which it abuts. Due to this slipping motion, the nut has a tendency to loosen, and thus fail the joint again, and does not provide a superior connection to the steering knuckle. 
         [0004]    What is desired is a ball stud system wherein when mounted, and a side load is applied to the ball of the ball stud, the nut holding the stud in place will not lose torque or loosen. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    This object is achieved by the device of the present invention. 
         [0006]    The ball stud system of the present invention provides a ball stud that will not fail or loosen easily under the application of repetitive side loading on the ball portion of the ball stud. The ball stud is secured to a vehicle&#39;s steering knuckle or other suspension component using the combination of a tapered nut and tapered washer. The tapered nut includes slots and the pin of the ball stud an aperture. A cotter pin may additionally be placed through the slots and aperture in order to further prevent rotation of the nut. 
         [0007]    The present invention provides many benefits over the prior art. Because, under side loads, relative movement between the ball stud and suspension component is minimized, there is very little sinking of the ball stud into the suspension component. As a result the relative geometry of parts within the suspension, which is important to proper operation, is maintained. 
         [0008]    The ball stud system of the present invention is easier to disassemble than a small taper pin design which requires special tools. The small taper ball stud will self lock inside the tapered hole by friction. In this instance, once the securing nut is removed, a special tool must be used to press the stud out of the tapered hole. Such a tool is not required with the present invention. 
         [0009]    The ball stud of the present invention can be secured to a suspension component that is made of a relatively soft material, such as aluminum, because less surface contact pressure is required between the ball stud and the suspension component. The clamping load is generated by a combination of normal force (force applied perpendicular to the stud or taper surface and creates surface contact pressure) and friction force. The friction force is a fraction of the normal force and acts in a direction along the taper surface. In a small taper joint, friction force carries most of the clamp load. Normal force balances the clamp load. The same clamp load generates far less surface contact pressure in large taper joints than in small taper joints. 
         [0010]    The ball stud system of the present invention also provides a better sealing structure for the ball socket area as the seal used therein rests on a large tapered washer. The tapered washer is attached to the stud and seal prior to assembly with the suspension component (e.g. steering knuckle), whereas in a device not using such a washer, the seal connection is made with the vehicle component upon assembly. In addition, the washer surface is typically better machined than the vehicle component (e.g. steering knuckle) surface, thus, allowing the formation of a better seal. 
         [0011]    These and other aspects of the invention are herein described in particularized detail with reference to the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention is explained in more detail by way of the subsequent Figures, wherein: 
           [0013]      FIG. 1  shows a perspective view of a vehicle suspension system including a ball stud system according to the invention; 
           [0014]      FIG. 2  shows a close up view of the ball stud system (mostly in phantom lines) within a ball joint in the vehicle suspension system; 
           [0015]      FIG. 3  shows a cross sectional view of the ball stud system attached to the vehicle suspension component; and 
           [0016]      FIG. 4  shows an exploded view of the ball stud system of the ball joint as well as a portion of the vehicle suspension component. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Schematically, and in a very simplified manner,  FIGS. 1-4  show an exemplary embodiment of a ball stud system  10  according to the present invention for use within a vehicle ball joint  12 . The ball stud  14  is not easily loosened during normal operation of the vehicle, i.e. torque within the nut securing the ball stud in place is not lost easily. The ball stud system  10  includes a ball stud  14 , tapered washer  16  and tapered nut  18 . 
         [0018]    Referring to  FIG. 4 , the ball stud  14  is preferably formed from steel and includes, from the bottom up, a ball  20 , a tapered neck  22 , a shoulder  24 , and a pin  26 , all integrally formed. The preferred material of construction for the washer  16  and nut  18  is also steel. The ball  20  has a known generally spherical shape which merges at its top into an adjacent neck  22 . At the bottom of the ball  20 , the spherical shape, preferably, is truncated. The neck  22  is a truncated cone with a proximal end  28 , adjacent the ball  20 , having a smaller diameter than the distal end  30  opposite the ball  20 . The shoulder  24  is located adjacent to the distal end  30  of the neck  22  and is shorter than the neck  22 . The shoulder  24  has a generally unchanging diameter along its height. This diameter is generally equivalent to the largest diameter of the neck  22 . 
         [0019]    The pin  26  of the ball stud  14  is adjacent to the shoulder  24  and includes a proximal end  34  and a distal end  36 . Along its length, the pin  26  has, in general, a consistent diameter. The pin  26  is threaded from its distal end  36  to approximately the halfway point of the pin&#39;s length. From the threaded portion to a point  37  that is about one third of the length of the non-threaded section from the shoulder, the pin has a diameter that is approximately equivalent to that of the outer radius of the threads. From this point  37  to the shoulder  24 , the pin  26  has a slightly larger diameter. The surface of the non-threaded portion of the pin  26  is generally smooth. Adjacent to the distal end  36 , an aperture  38  passes through the entire thickness of the pin  26 . 
         [0020]    The tapered washer  16  includes a proximal end  40  and a distal end  42  and tapers linearly from the proximal end  40  to the distal end  42 . When in place within the ball stud system  10 , the proximal end  40  of the tapered washer  16  has a greater diameter than the distal end  42 . An aperture  44  passes axially through the center of the tapered washer  16 . The aperture  44  is countersunk slightly at the proximal end  40  of the washer  16 . The countersink provides clearance between the washer  16  and ball stud  14  in the fillet area where the stud shape changes from large diameter to small diameter. 
         [0021]    The tapered nut  18  also includes a proximal end  45  and a distal end  46 , with flats  48  of the nut located adjacent the distal end  46 . A middle section  50  is located therebetween. The nut  18  tapers outwardly from the proximal end  45  into the middle section  50 . The taper is linear. After reaching a point of greatest diameter  52  within the middle section  50 , the tapered nut  18  then tapers inwardly until reaching the flats  48  on the tapered nut  18 . The flats  48  are of a type known in the art, namely six flat portions around the circumference of the nut  18 . The flats  48  are provided with vertical notches  54 . The notches  54  are located at the center of each flat  48  and extend from the distal end  46  of the nut  18  downward to a point approximately half way along the height of the flat  48 . The nut  18  includes an aperture  56  passing axially through the center of the nut  18 . Approximately, two thirds of nut adjacent to the aperture  56  is threaded, beginning at the distal end  46 . This amount of threading allows the nut  18  to be effectively secured to the ball stud  14 , but does not significantly reduce the stretch length of the ball stud  14 . A significant reduction in the ball stud&#39;s stretch length would make the ball stud more susceptible to allowing a reduction of torque in the nut  18  when side forces were applied to the ball stud  14 . 
         [0022]    Referring to  FIGS. 1-4 , the vehicle includes a mount  60  that is preferably the steering knuckle, but may be any vehicle component if the ball stud system  10  is used elsewhere within the suspension or another part of the vehicle. 
         [0023]    Referring to  FIGS. 3 and 4 , the tapered washer  16  is placed over and around the pin  26  of the ball stud  14  and moved downwards until the tapered washer  16  rests on the shoulder  24  of the ball stud  14 . The washer  16  surrounds the non-threaded portion of the pin  26  having a slightly larger diameter. The ball stud  14  is then moved into place on the mount  60 . The tapered portion of the washer  16  fits into a mating tapered portion  62  formed in the mount  60 . A portion of the tapered washer  16  does not fully fit into the mount  60 , but protrudes slightly at the proximal end  40  of the tapered washer. The tapered nut  18  is then threaded onto the threaded portion of the pin  26 . The tapered portion of the tapered nut  18  fits into a mating tapered portion  64  formed in the mount  60 . A portion of the tapered nut  18  does not fully fit into the mount  60 , but protrudes slightly at the point of greatest diameter  52  of the tapered washer. 
         [0024]    The loading capacity of the ball joint determines the size of the nut and washer as well as the taper angle of each and how far they penetrate into the mount. 
         [0025]    Referring to  FIG. 2 , the ball portion  20  of the ball stud  14  functions as a normal ball, as is known in ball joints within the art, namely a socket  70  mates with the ball  20  in such a way that universal directional movement is provided between the ball  20  and socket  70 . The neck  22  of the ball stud  14  spaces the socket  70  which fits over the ball  20  from the mount  60  into which the pin  26  fits. The shoulder  24  of the ball stud  14  provides a seat for the proximal end of the tapered washer  16 . Force is transferred through the ball stud  14  to the tapered washer  16 . 
         [0026]    Referring to  FIGS. 2 and 3 , the pin  26  acts as a means for securing elements on both sides of the mount  60  (for example, a steering knuckle). The aperture  38  within the distal end of the pin  26  permits a cotter pin or the equivalent to be placed therethrough. The tapered nut  18  secures the ball stud  14  in place. The nut is tightened until an appropriate torque is measured. The cotter pin engages the slots  54  within the tapered nut  18  to act as an additional means of preventing unwanted rotation of the tapered nut  18 . 
         [0027]    As opposed to the generally spherical shape of the ball  20 , other known shapes may be used such as a truncated cone. The neck  22  may be straight as opposed to being frusto-conical. The slots may also be omitted from the tapered nut. 
         [0028]    Although the invention has been shown and described with reference to certain preferred and alternate embodiments, the invention is not limited to these specific embodiments. Minor variations and insubstantial differences in the various combinations of materials and methods of application may occur to those of ordinary skill in the art while remaining within the scope of the invention as claimed and equivalents.