Abstract:
A pivot connection includes a ball stud head that creates strong anti-rotation characteristics while retaining substantially full pivotability. The ball stud head includes a mid-section that grips the interior of the socket so as to resist rotation. The improved ball stud head is useful in connection with quarter turn style ball sockets and quarter turn headlamp adjusters.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to ball studs used in ball joints, and in particular to an anti-rotation ball stud head particularly useful for connecting a headlamp adjuster to a socket on the reflector of a headlamp assembly. 
     Ball joints typically include a ball stud pivotally engaged in a socket. Such joints have a wide variety of applications where a pivotable connection between two parts is desirable. For example, they may be used in many types of linear actuators and have been found to be particularly useful in automotive lamp assemblies. Automotive lamp assemblies used as headlights typically comprise several basic parts: a support frame, a reflector, a lens, a bulb, and one or more adjusters. The support frame either completely houses the reflector and the bulb on a pivotable mounting to allow the aim of the light to be adjusted using the adjusters or provides a mounting surface for attaching a headlamp adjuster. The lens seals the front of either the support frame or directly to the reflector to protect it from the elements assailing the front end of the vehicle and provides an aerodynamic shape and attractive appearance. The reflector mounts on one fixed ball joint and is adjustable horizontally and vertically using adjusters that interface with the reflector through moving ball joints. The moving ball joints are moveable by actuating the adjusters connected to the moving ball joints by a ball stud having a head and a shaft. A socket is used to secure the pivotable engagement of the ball stud to the reflector. Ball joints are required because of the many possible adjustments that may be made to the orientation of the reflector. If ball joints are not used, the reflector into which the adjusters are fitted will not be sufficiently adjustable because the reflector will not be positionable in both the vertical and horizontal directions. Right angle adjusters are often used to allow the adjustment of the headlight from an adjusting position above the installed headlight. In other applications, motorized adjusters, straight adjusters, or other types of adjuster are used. 
     In many headlamp adjusters, the ball stud moves when a threaded nut rotates around a threaded shaft section of the ball stud. Because rotation of the ball stud is restrained when the threaded nut rotates around the threaded shaft section of the ball stud, the ball stud moves along its axis with respect to the adjuster thereby effectuating adjustment of the headlamp. In many headlamp adjusters, the ball stud will undesirably rotate unless it is prevented from doing so by structure on the head of the ball stud, e.g., engaging tabs (“ears”). Examples of such adjusters are disclosed in U.S. Pat. Nos. 4,689,725; 5,161,877; and 5,186,531. Sockets used in connection with such adjusters must coact with the ball stud to prevent rotation thereof in order for the adjuster to function because if the ball stud is allowed to rotate, then it will not move along its axis to effectuate adjustment. One drawback to the use of such ball stud and socket combinations is that the ears on the ball stud head must be aligned with receiving slots in the corresponding socket when the stud is installed in the socket. This complicates automated assembly. 
     In other headlamp adjusters, rotation of the ball stud is restrained by mechanism provided within the adjuster itself, e.g., the “anti-rotation insert” disclosed in U.S. Pat. No. 5,707,133. Examples of other such adjusters are disclosed in U.S. Pat. Nos. 4,796,494; 5,034,870; 5,079,676; 5,163,746; and 5,775,795. 
     In the various types of adjusters described above, a socket is used to make the pivotable connection between the ball stud and the reflector. Examples of ball stud and corresponding socket combinations are shown in FIGS. 4 and 5 of U.S. Pat. No. 4,689,725; FIG. 2 of U.S. Pat. No. 5,161,877; FIG. 1 of U.S. Pat. No. 5,673,992; FIG. 2 of U.S. Pat. No. 5,095,411; and FIGS. 10-14 of U.S. Pat. No. 5,186,532. Additionally, at least the following U.S. patents are specifically directed toward ball joints for use in connection with headlamp adjusting mechanisms: U.S. Pat. Nos. 4,974,123; 5,047,904; and 5,063,481. 
     A “quarter turn” style ball socket that has been used in connection with headlamp adjusters (identified generally as  15 ) is shown in FIG.  1  and is identified generally as  20 . As shown in FIGS. 3A and 3B, the quarter turn socket  20  is used in connection with a reflector  22  having a boss  24  extending therefrom. The boss  24  has a hole into which the quarter turn socket  20  is inserted and typically also has ramp locks  26 . The quarter turn socket  20  has lugs  28  that protrude from the socket  20  which pass through the hole in the boss  24  when the socket  20  is inserted in the direction indicated by arrow  29  in FIG.  3 A. The socket  20  is usually already joined with a conventional ball stud  30  (FIG. 3) prior to being inserted into the boss  24 . After insertion, the socket  20  must be rotated a quarter turn to rotate the lugs  28  so that they will not be able to pass through the hole in the boss  24 . This rotation also locks the socket  20  into the boss  24 . In rotating the socket  20 , flexible wings  32  extending from the socket  20  flex and slide over the ramp locks  26  on the boss  24 . The wings  32  then snap down to prevent disengagement of the socket  20  from the boss  24  by further rotation of the socket  20  caused by rotational force imparted by the adjuster  15 . Of course, ramp locks  26  may not be necessary if an adjuster  15  with internal anti-rotation, e.g. the one disclosed in U.S. Pat. No. 5,707,133, is used because no rotational force is imparted by the ball stud on the socket  20 . When used in connection with a conventional ball stud  30  (FIG.  3 ), the quarter turn socket  20  cannot be installed to the boss  24  of the reflector  22  simply by rotating the ball stud  30 . This is because the smooth finish on the conventional ball stud  30  allows the ball stud  30  to slip within the socket  20  upon rotation (indicated by arrow  33  in FIG. 3B) of the ball stud  30 . Thus, a wrench or other tool that engages installation tabs  34  must be used to properly install the ball socket  20 . The necessity of a special tool to complete the installation of the socket complicates installation and adds to the total assembly time of the headlamp assembly. Additionally, it is highly desirable to provide a quarter turn style socket for use in connection with a headlamp adjuster that also mounts using a quarter turn because the entire assembly can then be easily and efficiently installed in the headlamp assembly. 
     Additionally, existing quarter turn style ball sockets retain the ball stud in the socket using an undercut type interference. This interference requires an even wall thickness around the entire circumference of the socket in order to maximize retention of the ball stud (pull out resistance) and maintain a uniform stress distribution around the socket to prevent cracking during assembly of the socket over the ball stud head. Existing quarter turn sockets have no slots for receiving “eared” ball studs or other means to restrict ball stud rotation and therefore can only be used in connection with adjusters having internal anti-rotation capabilities. 
     Unsuccessful attempts have been made to provide ear receiving slots in quarter turn sockets for the purpose of allowing the sockets to be used in connection with adjusters that require an external rotation restraint, Additionally, unsuccessful attempts have been made to provide ear receiving slots in quarter turn sockets for use with adjusters having internal anti-rotation capabilities for the purpose of facilitating installation of a quarter turn adjuster/socket combination. When ear-receiving slots are added to the quarter turn style socket, the pull out resistance is reduced and the non-uniform wall thicknesses results in a concentration of stress at the slots. 
     Because of these problems, even if the use of ear-receiving slots in the socket were a viable possibility, there are manufacturing complications when attempting to form both ears on the ball portion of the ball stud and anti-rotation grooves or flats on the threaded shaft portion of the ball stud. Thus, even in adjusters having internal anti-rotation, such as the one disclosed in U.S. Pat. No. 5,707,133, the use of an eared ball stud to cause rotation of the quarter turn socket would be problematic. 
     In attempts to insert conventional eared ball studs into internally smooth quarter turn ball sockets (i.e., no ear receiving slots), it has been found that the ears press against the smooth inside walls of the socket and the resulting interference generates some resistance to rotation. However, this combination does not generate a very high level of anti-rotation resistance and, when the interference is increased (by increasing the size of the ears), the entire socket expands and does not fit into the hole in a standard size boss on the reflector. Additionally, each incremental increase in the size of the ears greatly increases the concentration of stress at the ear-socket interface which results in a higher risk of socket cracking. Thus, the use of conventional eared ball studs with quarter turn sockets is not effective. 
     Accordingly, a need exists for a ball stud head that can be easily installed in a quarter turn socket preferably without the use of tools, that can be used in connection with adjusters having internal anti-rotation mechanism and adjusters requiring anti-rotation at the ball stud head, that exhibits high anti-rotation characteristics and allows full pivotability, and that is cost-effective and easily manufactured and installed. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an improved ball stud head configuration that is capable of being used in connection with quarter turn sockets and which solves the problems raised or not solved by existing ball stud head designs. While the present invention is particularly useful in connection with quarter turn style automotive ball sockets, it may also be used in connection with non-quarter turn automotive ball sockets and non-automotive lamp applications where similar performance capabilities and characteristics are required. 
     It is therefore an object of the present invention to provide a ball stud head that can be easily installed in a socket. It is another object of the present invention to provide a ball stud head that can be used in connection with headlamp adjusters having an internal anti-rotation mechanism and adjusters requiring anti-rotation at the ball stud head. It is an additional object of the present invention to provide a ball stud head that exhibits high anti-rotation characteristics and allows full pivotability when inserted into a socket. It is a further object of the present invention to provide a ball stud head that is cost-effective and easily manufactured and installed. The ball stud of the present invention provides the above identified and many additional objects. As described in more detail below and shown in the accompanying drawings, the head of the ball stud of the present invention includes a toothed portion such that the head, when inserted into a ball socket, is pivotable within the socket but is substantially non-rotatable within the socket. 
     An important aspect of the invention is the provision of an area on the head of the ball stud that engages the interior walls of the ball socket when assembled. The resulting engagement substantially restricts rotation of the ball stud with respect to the socket but allows substantially the same pivotability of the head within the socket as with a conventional smooth-head ball stud. The interface between the provided area and the interior of the socket results in relatively even distribution of stress levels circumferentially around the walls of the socket. The provided area can be a toothed or knurled portion around the mid-section of the head of the ball stud. If exceptionally high anti-rotation is desired or if a plastic ball stud is used, internal teeth can be molded into the socket that mate and engage with the teeth on the ball stud head to further increase anti-rotation resistance. Additionally, the teeth on the head can be formed with extensions to further grip the interior of the socket and provide still more anti-rotation. 
     Teeth can be formed on the ball stud head by first producing a generally spherical ball stud head using conventional cold-heading or machining techniques. After this operation, the teeth can be roll formed into the mid-section of the head using knurling roll dies or trimmed in a multi-station or secondary cold-heading process. 
     Installing the improved ball stud head of the present invention into a conventional socket is quite simple. The anti-rotation ball stud head is snapped into the socket where the head is retained within the socket by an undercut interference. In one embodiment, as the head is inserted, the multiple teeth encounter the interior of the socket and displace material. The engagement between the multiple teeth and the interior of the socket provides a substantially non-rotational engagement between the head and the socket while allowing pivotability substantially the same as with conventional ball stud heads. Once the ball stud head is installed in the socket, the socket is installed in the reflector of the headlamp assembly. If the socket is a quarter turn socket, this installation is accomplished by turning the ball stud a quarter turn. When the present invention is used in connection with a quarter turn socket and a quarter turn mounted headlamp adjuster, the installation into the lamp assembly can be accomplished by a simple quarter turn without using tools. 
     While the present invention is particularly useful in headlamp assemblies, other applications are possible and references to use in a headlamp assembly should not be deemed to limit the uses of the present invention. Rather, the present invention may be adapted for use where a pivot joint is desired but rotation of the ball stud with respect to the socket is not desired. These and other objects and advantages of the present invention will become apparent from the detailed description, claims, and accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWING 
     FIG. 1 is a partially exploded perspective view of an anti-rotation ball stud head in accordance with one embodiment of the present invention shown extending from a quarter turn headlamp adjuster and a conventional quarter turn socket; 
     FIG. 2 is a perspective view of an anti-rotation ball stud head in accordance with one embodiment of the present invention; 
     FIG. 3 is a perspective view of the head of a prior art smooth-headed ball stud; 
     FIG. 3A is a perspective view of a prior art ball stud in a quarter turn socket that has been inserted in the direction indicated by arrow  29  into a boss protruding from a reflector; 
     FIG. 3B is a perspective view of a prior art ball stud in a quarter turn socket that has been inserted into a boss protruding from a reflector, the ball stud being rotated as indicated by the arrow  33 ; 
     FIG. 4A is a perspective view of an anti-rotation ball stud head in accordance with one embodiment of the present invention engaged in a quarter turn socket that has been inserted in the direction indicated by arrow  35  into a boss protruding from a reflector; 
     FIG. 4B is a perspective view of an anti-rotation ball stud head in accordance with one embodiment of the present invention engaged in a quarter turn socket that has been inserted into a boss protruding from a reflector, the ball stud being rotated as indicated by arrow  37 ; 
     FIG. 5 is a partial cross-section of an anti-rotation ball stud head in accordance with the present invention inserted into a conventional quarter turn socket; 
     FIG. 6 is a perspective view of a ball stud head in accordance with an additional embodiment of the present invention shown during a step of the manufacture thereof; 
     FIG. 7 is a perspective view of the ball stud head of FIG. 6 after the completion of the manufacture thereof; and 
     FIG. 8 is a partial cross-section of an alternative embodiment of an anti-rotation apparatus in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, one embodiment of the present invention is advantageously used in connection with a headlamp adjuster  15  and a socket  20 . While the socket shown in FIG. 1 is known as a quarter turn style socket  20  because of the manner in which the socket is retained in the reflector, the invention may be used in other types of sockets where a non-rotating pivot connection is desired. As best seen in FIG. 2, the head  38  of the ball stud (identified generally as  40 ) of the present invention includes a toothed portion  42  such that the head  38 , when inserted into the ball socket  20 , is pivotable within the socket  20  but is substantially non-rotatable within the socket  20 . 
     As shown in partial cross-section in FIG. 5, a toothed portion  42  on the head  38  of the ball stud  40  to engage the interior  44  of the ball socket  20 . During assembly, the teeth of the toothed portion  42  displace material within the interior  44  of the socket  20 . The resulting engagement substantially restricts rotation of the ball stud  40  with respect to the socket  20  but allows pivotability of the head  38  within the socket  20 . The interface between the many teeth of the toothed portion  42  and the interior  44  of the socket  20  results stress levels distributed substantially evenly around the circumference of the interior  44  of the socket  20 . As shown in FIG. 8, if exceptionally high anti-rotation is desired or if a plastic ball stud is used, internal teeth  41  can be molded into the socket  20  that mate and engage with the teeth on the ball stud head  40  to further increase anti-rotation resistance. Additionally, as shown in FIG. 7, the toothed portion  42  on the head  38  can be formed with extensions  46  to further grip the interior  44  of the socket  20  and provide additional anti-rotation. 
     The toothed portion  42  on the ball stud head  38  can be formed by first producing a generally spherical ball stud head  38  using conventional cold-heading or machining techniques. After this operation, the toothed portion  42  can be roll-formed into the mid-section of the head  38  using knurling roll dies or trimmed in a multi-station or secondary cold-heading process. This is generally believed to be the easiest and most cost efficient manufacturing method, however, it is possible that the toothed portion could alternatively be formed or trimmed in the cold-heading process. In manufacturing the embodiment shown in FIG. 7, a generally spherical ball stud head  38  with a ridge  48  is produced using conventional cold-heading or machining techniques (FIG.  6 ). Then, the toothed portion  42  is roll-formed into the mid-section of the head  38  over the ridge  48  to produce the extensions  46  shown in FIG.  7 . If a plastic ball stud  40  is used, it can be manufactured, including the toothed portion  42 , by injection molding. 
     As best shown in FIG. 5, when installing the ball stud head  38  of the present invention into a conventional quarter turn style socket  20 , the anti-rotation ball stud head is snapped into the socket  20  and the head  38  is retained within the socket  20  by undercut interference. As the head  38  is inserted, the toothed portion  42  encounters the interior  44  of the socket  20  and displaces material. The engagement between the toothed portion  42  and the interior  44  of the socket  20  results in non-rotational engagement between the head  38  and the socket  20  while allowing pivotability of the head  38  within the socket  20 . Once the ball stud head  38  is installed, the socket  20  may be installed in the reflector  22  of the headlamp assembly. If the socket  20  is a quarter turn style, this installation is accomplished by turning the ball stud  40  a quarter turn. The ball stud head  38  of the present invention the invention is preferably used in connection with a quarter turn socket  20  and a quarter turn mounted headlamp adjuster  15  (FIG.  1 ), thereby further facilitating installation into the lamp assembly because the socket  20  and the adjuster  15  can be installed in the lamp assembly with a simple quarter turn without using tools. 
     Ball studs in accordance with the present invention may be made from a variety of materials depending on the particular application. Ball studs used in headlamp adjusters are generally manufactured from hard metal or plastic, typically steel, zinc, brass, or nylon. Sockets used in connection with the ball stud of the present invention are preferably formed from injection molded plastic. In the present invention, in order for the toothed portion  42  to be able to create the anti-rotation engagement with the interior  44  of the socket  20 , the ball stud  40  is manufactured from a material having a hardness substantially the same as or greater than the socket  20 . 
     As illustrated by the foregoing description and shown in the Figures, the present invention is suitable as an anti-rotation ball stud for use in connecting a headlamp adjuster to a reflector. The present invention overcomes the limitations and disadvantages of existing ball studs by utilizing an effective design whereby the head can be pivotably but non-rotatably engaged in the corresponding socket, is easily installed, and is cost effective. Of course, the anti-rotation ball stud of the present invention may be used in other non-headlamp assembly applications. 
     Although the invention has been herein shown and described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims.