Abstract:
A ball socket for connection with a ball stud resists accidental pull-out of the ball stud. The ball socket includes arms that form a socket cup for retaining the ball stud. The arms allow relatively easy insertion of the stud head, yet greatly resist accidental pull-out. The ball socket may be used in connection with disengageable or conventional ball studs. The ball socket may be an in-line design, peanut-style, or some other design. One known effective application of the present invention is in automotive lamp assemblies. The in-line socket may include a centrally located mounting hole and an undercut which forms a chamber for trapping the head of a mounting screw to facilitate assembly to the reflector.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to pivot joints, and in particular to a pivot joint useful for connecting a headlamp adjuster to a reflector inside a headlamp assembly or an external reflector and lens headlamp assembly. The improved ball socket can be used effectively with disengageable ball stud or conventional spherical, semi-spherical or “eared” ball studs. 
     Pivotable spherical joints, commonly referred to as ball joints, include a ball stud 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. As seen in U.S. Pat. No. 5,707,133, the disclosure of which is incorporated herein by reference, 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. 
     In the automotive lamp assembly example, the support frame houses the reflector and the bulb on a pivotable mounting to allow the aim of the light to be adjusted using the adjuster. The lens seals the front of the assembly to protect it from the elements assailing the front end of the vehicle and provides an aerodynamic shape and attractive appearance. The reflector mounts inside the housing 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. Another type of automotive headlamp assembly that uses linear actuators is shown in U.S. Pat. No. 5,360,282. In this type of headlamp assembly the linear actuator is mounted to a bracket and the ball joint end supports a reflector, lens and light bulbs. This type of application requires a higher strength ball joint due to the additional weight being supported. In particular, pull-out strength of the ball joint needs to be greater to withstand vibration. 
     While one possible application of the present invention is in headlamp assemblies, other applications are possible and references to use in a headlamp assembly should not be deemed to limit the application of the present invention. Additionally, while the improved ball socket design described herein may be used with a disengageable ball stud, such as the one described in U.S. Pat. No. 6,113,301, the disclosure of which is incorporated by reference, it can also be used advantageously with ball studs having “ears” or engaging tabs or semi-spherical ball stud designs. Examples of such adjusters are disclosed in U.S. Pat. Nos. 4,689,725 and 5,186,531, an example of an “eared” ball stud is shown in FIG. 13, and an example of a semi-spherical ball stud is shown in FIG.  12 . 
     Conventional ball joints for use in automotive lamp assemblies typically include a ball stud with a spherical engagement head extending from an adjuster. The ball stud is moveable linearly in and out of the adjuster. Examples of such ball studs and corresponding sockets are shown in FIGS. 4 and 5 of U.S. Pat. No. 4,689,725; 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, several U.S. Patents disclose ball joints for use in headlamp adjusting mechanisms: 4,974,123, 5,047,904, and 5,063,481. 
     As is known in the art, ball studs interface with a plastic socket  20 , such as the one shown in FIGS. 1 and 2 and in U.S. Pat. No. 5,653,548. The sockets  20  are attached to the reflector such that movement of the ball stud effectuates movement of the reflector. For example, socket  20  is attached to a boss  30  with a fastener  31 . Boss  30  has an aperture  32  therein for receiving the fastener  31 . The interface between the ball stud (not shown) and the socket  20  is such that the head of the ball stud cannot be readily removed from the socket  20  once the head is disposed therein. This is because fingers or tabs  22  point inwardly toward socket cup  24  at approximately a forty-five degree angle to retain the head in socket  20 . The ball stud head cannot be allowed to slip from socket  20  once the adjuster is installed, or the adjuster will not be able to adjust the orientation of the reflector. When engaged in socket  20 , the ball stud head is free to pivot within the socket cup  24  of socket  20 . 
     While functionally quite effective, there is at least one shortcoming to using ball studs in conventional “tabbed” sockets. This shortcoming is that the head  22  can be pulled out of socket  20  under certain conditions of operation, such as vibration while supporting heavier reflectors or in heavier headlamp assemblies like the one previously referenced in U.S. Pat. No. 5,360,282, leaving the adjuster non-operational. This unexpected pull-out generally occurs because tabs  22  are flexible. Tabs  22  must be flexible enough to allow the head to be inserted into socket  20 , while at the same time resist pull-out. Though pull-out of the ball stud is resisted to some degree of success, if enough pull-out force is applied, the tabs  22  deflect downward toward the socket cup  24  and the ball stud head “pops out.” Reducing the flexibility of tabs  22  is not an option because it would either be to difficult to insert the ball stud head into socket  20 , or the elasticity of the tabs  22  would be lessened to the degree that they would break off during insertion of the ball stud. 
     Accordingly, the need exists for an improved ball socket that securely retains a ball stud placed therein, can be effectively used in connection with disengageable or conventional ball studs, is cost effective, and resists accidental pull-out. The present invention relates to an improved ball joint which is capable of being used in automotive lamp assemblies and solves the problems raised or not solved by existing ball joints. Of course, the present invention may be used in a multitude of non-automotive lamp situations where similar performance capabilities are required. 
     SUMMARY OF THE INVENTION 
     The present invention provides a ball socket that is cost-effective, easily installed in the lamp, securely retains a ball stud placed therein, and can be effectively used in connection with disengageable or conventional ball studs. Further, ball studs can be selectively inserted and removed from the corresponding socket as desired, yet greatly resist accidental pull-out of the ball stud. 
     The ball socket for use with a ball stud and a mounting screw is generally constructed so that the socket has a face plate having an opening for receiving the ball stud, and a combination of support legs and arms extending from the face plate to form a socket cup for receiving the ball stud. The ball socket includes a socket body having a socket cup with an undercut portion defining a chamber. This chamber is designed to hold the head of a mounting screw. A mounting screw having a head may be placed in the chamber of the socket, yet still rotate for attachment purposes. The arms extend from the face plate to the opposite end of the socket, near the undercut portion. The arms have an upper portion, middle portion and a bottom portion. During insertion of the ball stud into the socket cup, at least the upper portion and middle portion of each arm deforms. 
     The ball socket may be used in a headlamp assembly. Generally, the headlamp assembly is composed of a reflector having a boss and a ball socket mounted to the boss by a mounting screw. The ball socket has an opening for receiving a ball stud into the adjacent socket cup having several arms. The headlamp adjuster has a ball stud extending therefrom, which is engaged in the ball socket. 
     The ball socket can accept different types of ball studs, either conventional or disengageable. The ability to use the socket with a wide variety of ball studs provides a significant benefit to headlamp assemblers because it allows the use of one style of socket with a number of types of ball stud. 
     While one possible application of the present invention is in headlamp assemblies, many other applications are possible and references to use in a headlamp assembly should not be deemed to limit the uses of the present invention. The terms “ball stud,” “engagement head,” or “head” as used herein should not be interpreted as being limited to spherical or semispherical shapes, rather, the engagement heads of ball studs in accordance with the present invention may have a wide variety of shapes and may include protrusions having semispherical or otherwise pivotably-shaped tips. The arms used in the socket can be a wide variety of shapes capable of selectively retaining the ball stud in the socket. These and other objects and advantages of the present invention will become apparent from the detailed description, claims, and accompanying drawings. 
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art socket shown in relation to a mounting screw and mounting boss; 
     FIG. 2 is a cross-section of the prior art socket shown in FIG. 1 taken generally along the line  2 — 2 ; 
     FIG. 3 is a perspective view of one embodiment of a socket in accordance with the present invention; 
     FIG. 4 is an end elevation of the socket shown in FIG. 3; 
     FIG. 5 is a bottom cross-section of the socket shown in FIG. 3 taken generally along the line  5 — 5  in FIG. 4; 
     FIG. 6 is a side elevational view of the socket shown in FIG. 3; 
     FIG. 7 is a side cross-sectional view of the socket shown in FIG. 3 taken generally along the line  7 — 7  in FIG. 4; 
     FIG. 8 a  is a schematic side view of a ball stud prior to insertion into a socket in accordance with the invention as shown in FIG. 3; 
     FIG. 8 b  is a schematic side view of a ball stud during insertion into a socket in accordance with the invention as shown in FIG. 3; 
     FIG. 8 c  is a schematic side view of a ball stud after insertion into a socket in accordance with the invention as shown in FIG. 3; 
     FIG. 9 is a schematic diagram showing the forces exerted on the socket as a ball stud is pulled from a seated position within a socket in accordance with the present invention; 
     FIG. 10 is a perspective view of an alternative embodiment of the present invention having a peanut-style extension; 
     FIG. 11 is a perspective view of a disengagable ball stud; 
     FIG. 12 is a perspective view of a semi-spherical ball stud; 
     FIG. 13 is a perspective view of a ball stud with ears; and 
     FIG. 14 is a partial cross-section of an automotive lamp assembly having a socket constructed in accordance with one embodiment of the present invention installed to a reflector. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An improved ball socket  100  is shown in FIGS. 3-9. Socket  100  can be effectively used with conventional ball studs or disengageable ball studs. Referring to FIG. 7, socket  100  is preferably a one-piece design that includes a mounting screw  102  retained therewithin and extending through a mounting screw hole  104 . This allows the mounting point of socket  100  to be very close to the point where a ball stud is retained therein which results in reduced deflection of the part and more consistent aiming. However, it should be understood that the present improvement could be used with other prior art sockets that do not have a mounting screw  102  contained therein. One such embodiment is shown in FIG.  10  and described herein. 
     Socket  100  retains mounting screw  102  therein by providing an undercut portion  106  and a chamber  108  which secures head  110  of mounting screw  102  after being snap-fitted into socket  100 . The diameter of undercut portion  106  is smaller than the diameter of mounting screw head  110 . Thus, mounting screw  102  cannot be easily dislodged or separated from socket  100 , but is still allowed to rotate inside chamber  108  because chamber  108  is slightly larger than head  110 . The combined socket unit can be easily handled on an assembly line and installed using automated equipment, or more easily handled by hand. 
     As best seen in FIGS. 7 and 9, socket  100  has arms  112  that are capable of retaining a ball stud  114 . Arms  112  are the means by which a socket cup  126  is formed for retaining a ball stud. Arms  112  extend from the opening portion  116  of socket  100 , down to the base portion  118 , which is located next to chamber  108 . The function of the arms  112  is to provide improved resistance against accidental pull-out of the ball stud  114 . Thus, due to the construction of arms  112 , one must apply a greater linear force to pull ball stud  114  out of socket  100  than is required to push ball stud  114  into socket  100 . While the arms  112  work with a disengageable ball stud, the improved socket  100  may also be used with conventional ball studs. 
     For installation to a headlamp assembly (not shown), the mounting screw  102  is rotatable within the socket  100 . Alternative means for retaining the mounting screw  102  in the socket  100  could also be used, e.g., interference between the thread of the mounting screw  102  and the mounting screw hole  104 , and interference between the head  110  of the mounting screw  102  and the inside of the socket  100 . 
     As seen in FIG. 6, the improved socket  100  further may include support legs  120  extending from a face plate  122 . Support legs  120  provide additional structural stability to the socket and keep face plate  122  from moving substantially during insertion of the ball stud. As seen in FIG. 4, face plate  122  preferably includes flat edges or flats  124 . The interior portion of socket  110  where a ball stud is retained is referred to generally as the socket cup  126 . When a ball stud is inserted into socket  100  through opening  125  in face plate  122 , the ball is pivotally secured within the socket cup of  126  of socket  100  by arms  112 , and optionally, support legs  120 . Support legs  120  could be replaced with a contiguous body, but having separate support legs  120  is preferable to reduce weight and material costs. Also, while having four arms has been found to be an effective design, other numbers could be used. Likewise, while having four support legs  120  has been an effective design, other numbers could be used. 
     Arms  112  are generally curved to preferably conform to a substantially spherical shaped ball stud head. However, other curvatures could be used for different head shapes. Referring to FIGS. 3 and 4, it is also preferable that the upper portion  130  of arms  112  extends toward the center axis of socket  100  more than the upper portions  131  of support legs  120 . In this respect, the arms  112  substantially form socket cup  126 . Support legs  120  do riot operate to retain the ball stud in socket cup  126 . 
     Preferably, socket  100  further includes leg extensions  133  to allow socket  100  to non-rotatably mount on a generally square boss  30 , such as that shown in phantom in FIG.  1 . This non-rotatable mounting is effectuated by the leg extensions  133  being placed on each side of such boss when the mounting screw  102  is threaded into a mounting hole, such as the mounting hole  32  seen in square boss  30 . This non-rotatable mounting allows the socket  100  to be effectively used with a disengageable ball stud because it ensures the proper orientation of the arms  112 . Of course, other shaped bosses could be used with the appropriate modification of the leg extensions of the socket to match the particular shape characteristics of the boss. Additionally, if a particular application allows rotation of the socket  100 , leg extensions  133  could be eliminated. 
     Installing the head  128  of a ball stud  114  into the corresponding, socket  100  of the present invention is quite simple. FIGS.  8 ( a )-( c ) shows how a conventional round ball stud is inserted. First, a positive linear force Fx is exerted on the ball stud  114  so that the head  128  is directed into the socket cup  126 . This direction is substantially parallel to the axis of mounting screw  102 , as show in FIG.  7 . Force Fx is great enough so that arms  112  undergo elastic deformation, as shown in FIG.  8 ( b ). This deformation results from the moment M applied to the upper segment  130  of arm  112 . Specifically, during deformation, face plate  122  remains substantially stationary in the radial direction thereof. The upper segment  130  of each arm  112  moves slightly into socket cup  126  due to moment force Fm, which results from the combined radial and tangential forces, Fr and Ft. The applied moment M moves the upper segment  130  of each arm  112 , and further causes each middle segment  132  to move in an outward direction with respect to socket cup  126 . The position of bottom segment  134  of arm  112 , located adjacent undercut portion  106  (not shown), remains substantially unchanged. As seen in FIG.  8 ( c ), the arms  112  return to their initial position once head  128  is contained within socket cup  126 . During insertion of a substantially spherical head  128 , head  128  “snaps” into the socket cup  126  just after the leading hemisphere of head  128  moves past the arm&#39;s upper segment  130  where the moment force is applied. Thus, the ball stud is inserted with a “snap fit.” 
     Removing a conventional ball stud  114  from the socket cup is not as simple as the insertion process. The reason that socket  100  resists ball stud pull-out is that the positive linear force Fx required to insert head  128  into socket  100  is less than the negative linear force Fx required to remove head  128  from socket  100 . Referring to FIG.  8 ( a ), the positive linear force Fx is translated to tangential and radial components, Ft and Fr respectively, at the spherical surface of head  128 . Likewise, in FIG. 9, the negative linear force Fx is translated into negative Fr and Ft components with respect to the surface of head  128 . The moment force Fm is perpendicular to the longitudinal axis  140  of upper segment  130 , and differs in direction from force Ft by an angle θ. Unlike the previous case when head  128  was inserted into socket  100 , upper segment  130  cannot easily move under the moment force Fm because it is restrained by arm  112 . Specifically, the bottom segment  134  of arm  112  is restrained so that arm  112  cannot move significantly in the negative Fx direction. Head  128  can only be removed by plastically deforming the upper segment  130  of arm  112 , by applying a hoop stress to faceplate  122  that is large enough to cause deformation thereof, or a combination of both. Thus, it is preferable that faceplate  122  is shaped to resist the hoop stress. 
     The increased pull-out force of the present invention has been demonstrated with pull-out and insertion force testing. It has been found that when a socket is made from a particular material, e.g., the plastic Zytel 103 Nylon, and in accordance with conventional designs such as the socket of FIGS. 1 and 2, the average pull-out force is significantly lower than that which results when the socket design is in accordance with the present invention. Even higher pull out resistance has been achieved using semi-spherical ball stud profiles as shown in FIG. 12 because the trailing edge  165  of the truncated sphere increases contact friction between the ball and socket which in-turn increases negative Fr and Ft component forces. 
     To insert a disengagable style ball stud  150 , such as that shown in FIG. 11, the indents or flats  152  on the head  154  are oriented toward the arms  112  on the socket  100 , and the rounded portions  156  of the head  154  are oriented toward the relief areas  158 , as seen in FIG.  4 . The head  128  is inserted into the socket  100 . The head is then rotated to engage the rounded portions  156  of head  154  with the arms  112  of the socket  100 . Alternatively, head  154  of ball stud  150  can be inserted into the socket  100  in a manner similar to how a conventional ball stud  150  is inserted into a socket  100 , that is, by snapping the head  154  past the arms  112 , as previously described herein. If removal of the adjuster from the lamp assembly is desired, ball stud  150  can be disengaged from the socket  100  by rotating the ball stud  150  such that the arms  112  of the socket  100  no longer engage the round portions  156  of ball stud  150 , and the rounded portions  156  of ball stud  150  are oriented toward the relief areas  158 . Ball stud  150  can thus freely pass from the socket  100  because flats  152  on ball stud  150  can pass by arms  112  on socket  100 , and rounded portions  156  can pass through relief areas  158 . 
     In an additional embodiment, as shown in FIG. 13, the improved socket  100  may be used with “eared” ball studs  160  to prevent rotation of the ball stud. FIG. 13 show the ears  162  on an eared ball stud  160 . In this embodiment, the improved socket  100  provides ear slots  164  in between the support legs  120  and arms  112  as shown in FIG.  4 . When an eared ball stud  160  is fitted into the socket  100 , the ears  162  slide into the ear slots  164 . Because the ears  162  are engaged in ear slots  164 , eared ball stud  160  cannot rotate with respect to the socket  100 . As previously described, the leg extensions  133  are provided to allow the socket  100  to non-rotatably mount on a square boss. This non-rotatable mounting allows the socket  100  to be effectively used with a conventional eared ball stud  160  because it ensures proper orientation of the ear slots  164  and prevents rotation of the socket  100 . In addition to being most effective with an eared ball stud  160 , the improved socket  100  with ear slots  164  can also be used with a disengageable or a conventional ball stud. The ability to use the socket  100  with a wide variety of ball studs provides a significant benefit to headlamp assemblers because it allows the use of one style of socket with a number of types of ball stud. 
     In yet an additional embodiment of the present invention shown in FIG. 10, the improvements of socket  100  may incorporated into a conventional “peanut style” socket  170 . The difference between this socket and socket  100  is the extension  172  of face place  122 , the optional ridged edges  173  to resist moment forces applied to extension  172 , and the lack of a chamber for mounting a screw. Extension  172  has an aperture  174  therein for mounting purposes, as is known in the art. 
     The improved socket  100  is preferably manufactured using conventional injection molding technology. The mounting screw  102  can also be manufactured using conventional methods. Prior to shipment to the headlamp assembler, each socket  100  is preferably snap-fitted with a mounting screw  102  using automated or hand means. Of course, other process and methods could be used to manufacture pieces and assemble the assembly. 
     FIG. 14 shows an improved socket  100  installed in a lamp assembly  180  shown in phantom. The lamp assembly  180  includes a support frame  182 , a reflector  184 , a lens  186 , a bulb (not shown), and one or more adjusters  190 . The support frame  182  houses the reflector  184  and the bulb on a pivotable mounting to allow the aim of the lamp to be adjusted using the adjuster  190 . The lens  186  seals the front of the assembly to protect it from the elements assailing the front end of the vehicle and provide an aerodynamic shape and attractive appearance. In such a lamp assembly  180 , the reflector  184  mounts inside the housing one fixed ball joint  192  and is adjustable horizontally and vertically using adjusters  190  (only one shown in FIG. 14) that interface with the reflector  184  by moving ball joint  194 . FIG. 14 shows the improved socket  100  secured to a square boss  200  extending from the reflector  184 . The leg extensions  133  of the socket  100  interface with the sides  202  of the square boss  200  to non-rotatably engage the socket  100  with the boss  200 . 
     The socket of the present invention has many other applications aside from use in a lamp assembly. Thus, 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.