Patent Publication Number: US-2005123345-A1

Title: Method and apparatus for making a ball and socket joint and joint made by same

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates generally to the field of joint assemblies, and more particularly to movable joint assemblies, such as a ball joint. A molding-in-place technique is provided for molding a joint structure and surrounding linkage member in-place to form an integral, self-toleranced, self-retained, movable joint assembly for a desired application.  
      Existing joint assemblies typically comprises a ball and socket mechanism, which is formed by a multi-step process of forming a ball structure, forming a socket structure, and then assembling the ball structure and the socket structure. The ball structure is generally formed by a molding process or by molding a ball onto a stud or linkage. The socket structure is generally formed by a separate molding process, using the desired geometry of the ball structure as a basis for the geometry for the socket structure. Unfortunately, the multiple steps generally result in a poor fit between the ball and socket. For example, the dimensional variations between the ball and socket may result in a tighter or looser fit than desired.  
      There is a need, therefore, for an improved molding technique to improve the fit between the ball and socket and to prevent the problems caused by the dimensional variations between the ball and socket. Accordingly, it would be advantageous to mold the joint assembly in-place, thereby preventing the tolerance problems caused by the dimensional variations between the ball and socket.  
     SUMMARY OF THE INVENTION  
      The present technique provides a system and method for molding “in-place” a linkage structure about a joint structure. The technique uses a molding assembly having a plurality of centering and sealing structures for sealingly centering the linkage structure about the joint structure. A desired mold material is injected between the linkage structure and the joint structure “in-place” to provide a self-toleranced, self-retained, molded-in-place joint assembly.  
      In one aspect, the present technique provides a method of forming a mechanical joint. The method comprises molding a studded ball movably within a desired structure to form the mechanical joint. The studded ball is configured for coupling to a desired mechanical linkage.  
      In another aspect, the present technique provides a molding method for a mechanical joint. The method comprises injecting mold material into a cavity between a studded ball and a support structure for the studded ball. The method also comprises self-tolerancing the studded ball movably within the mold material.  
      In another aspect, the present technique provides a joint system. The system comprises a joint support structure and a studded joint member disposed within the joint support structure. The system also comprises a desired material molded-in-place about the studded joint member and internally retained within the joint support structure, wherein the studded joint member is movable and self-toleranced within the desired material.  
      In another aspect, the present technique provides a mold system for a ball joint assembly comprising a molding assembly configured to self-tolerance and mold-in-place the ball joint assembly. The molding assembly comprises a stud receptacle for a studded joint member, a first centering structure for the studded joint member, a second centering structure for a support structure disposed about the studded joint member, and a mold injection nozzle for injecting the desired mold material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:  
       FIG. 1  is a cross-sectional view of an exemplary molding assembly configured to form a molded-in-place joint assembly;  
       FIG. 2  is a flow chart of an exemplary molding process in accordance with the molding assembly illustrated in  FIG. 1 ;  
       FIG. 3  is a cross-sectional view of the molded-in-place joint assembly formed by the molding assembly illustrated in  FIG. 1 ;  
       FIG. 4  is a face view of the molded-in-place joint assembly illustrating gaps in the mold material caused by a centering mechanism of the molding assembly illustrated in  FIG. 1 ;  
       FIG. 5  is a cross-sectional view of the molded-in-place joint assembly having an internal retention feature for the mold material;  
       FIG. 6  is a cross-sectional view of the molded-in-place joint assembly having the internal retention feature and a double ended joint structure; and  
       FIG. 7  is a flow chart of an exemplary molding process illustrating formation of the joint structure and the molded-in-place joint assembly. 
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS  
      Turning now to the drawings and referring first to  FIG. 1 , a molding system is illustrated in accordance with the present technique and designated generally by reference numeral  10 . The molding system  10  comprises an injection section  12  and a securement section  14  configured to generate a molded-in-place joint assembly  16 , which has a self-toleranced movable fit between the joint member and the mold material. The molding system  10  may be used to mold one or more materials (e.g., composite or layers) about the joint member and between the joint member and its support structure. The molding-in-place process can be performed on-site or off-site to generate the molded-in-place joint assembly  16  from a new or existing joint member and its support structure. For example, the system  10  can be applied to a fully or partially assembled or disassembled joint assembly, which may be fully or partially integrated or removed from the desired application.  
      As illustrated in  FIG. 1 , the molding system  10  comprises a variety of molding cavities and orientation members to mold a desired material uniformly around a joint member, such as a studded ball  18 . Although a variety of geometries and linkages may be used within the scope of the present technique, the studded ball  18  illustrated in  FIG. 1  has a ball member  20  coupled to a threaded stud  22 . The ball member  20  may have a spherical geometry, an oval geometry, a pin-shaped geometry, a dimple texture, a plurality of flat surfaces forming a generally ball shaped member, or any other suitable geometry for a joint member. Similarly, the threaded stud  22  may comprise any suitable linkage mechanisms, such as threads, lateral receptacles for pins or bolts, a second ball member, or any other desired structures.  
      As illustrated, the injection and securement sections  12  and  14  are configured to seal and align desired mold geometries about the ball member  20  and a substrate assembly  24 , which may have a variety of linkage and support structures for the molded-in-place joint assembly  16 . For example, the substrate assembly may embody a collar that is symmetrically disposed about the ball member  20 .  
      The injection section  12  has an injection cavity  26  for injecting an injection material  28  through a curved mold portion  30 . The injection material  28  may be any suitable mold material, such as a plastic or metallic substance. For example, a low friction material may be used to improve the bearing surface between the ball member  20  and the substrate assembly  24 . The injection section  12  also has a mold portion  32  to form a retention structure  34  for securing the mold structure  90  in place around the ball member  20 , as illustrated in  FIG. 3 . The mold portion  32  is disposed symmetrically about the substrate assembly  24  at an outer edge  36  of the substrate assembly  24 . Alternatively, the molding system  10  may provide an internal retention structure along an inner surface  38  of the substrate assembly  24  (e.g., see  FIGS. 5 and 6 ).  
      The injection section  12  also has orientation tabs  40  extending between the curved mold portion  30  and the mold portion  32 . Each of these orientation tabs  40  has a forward edge  42  configured to contact the outer edge  36  of the substrate assembly  24 . As the injection and securement sections  12  and  14  are disposed about the studded ball  18 , the forward edges  42  contact and align the substrate assembly  24  about the ball member  20  to ensure a uniform and properly aligned mold. Any suitable number of orientation tabs  40  may be used to facilitate alignment. For example, three orientation tabs  40  may be symmetrically disposed about the injection cavity  26  (i.e., at 120 degrees apart). Accordingly, as illustrated in  FIG. 1 , the upper orientation tab  40  may represent a single orientation tab, while the lower orientation tab  40  may represent two orientation tabs disposed 120 degrees apart from one another and from the upper orientation tab  40 .  
      The securement section  14  includes a central receptacle  44  for the studded ball  18  and a spring loaded collar(s)  46  disposed in a receptacle(s)  48  to provide a continuous seal between the substrate assembly  24  and the securement section  14 . A spring assembly  50  is disposed in the receptacle  48  to provide a spring force for the spring-loaded collar  46 , which may comprise a single symmetrical collar such as a ring-shaped collar. The spring-loaded collar  46  also accommodates any dimensional variations or tolerances in the substrate assembly  24  or various other components. The spring-loaded collar  46  is configured to contact an outer edge  52  of the substrate assembly  24  adjacent a mold portion  54 , which is provided in the securement section  14  to form a retention structure  56  opposite the retention structure  34 . As mentioned above, the molding system  10  may alternatively form an internal retention structure, such as along the internal surface  38  of the substrate assembly  24 . The securement section  14  also has an alignment structure  58  disposed adjacent the mold portion  54 . The alignment structure  58  is configured to contact the ball member  20  during molding and ensure proper alignment of the ball member  20  within the substrate assembly  24  and the injected material  28 . The alignment structure  58  also forms a sealed mold geometry for the injection material  28  as the pressure of the injection material  28  forces the ball member  20  against the alignment structure  58 . The molding system  10  also may utilize an alignment collar  60  on the studded ball  18  to facilitate alignment of the ball member  20  relative to the substrate assembly  38  and injection material  28 .  
       FIG. 2  is an exemplary flow chart of a molding process afforded by the molding system  10  illustrated in  FIG. 1 . The operation of the molding system  10  is best illustrated with reference to the molding assembly illustrated in  FIG. 1 , the molding process illustrated in  FIG. 2 , and the molded-in-place joint assembly  16  illustrated in  FIG. 3 . As mentioned above, the molding system  10  may be utilized to mold-in-place a variety of joint mechanisms, including a ball joint, a pin joint, a bearing assembly with multiple joints, a socket assembly, or any other desired socket or bearing assembly. Accordingly, the molding system  10  may include configuring the mold assembly for the particular joint assembly (block  62  of  FIG. 2 ). For example, the geometry of the curved mold portion  30 , the mold portion  32 , the mold portion  54 , and the central receptacle  44  may be selected or modified for the geometry of the ball member  20  and the threaded stud  22 . Moreover, the positioning of the foregoing mold portions  32  and  54  and the spring-loaded collar  46  may be modified for a particular geometry of the studded ball  18  and the substrate assembly  24 . Further modifications also may be made for a different type of joint mechanism or socket assembly, as discussed above. After the suitable mold assembly has been selected, configured or designed, the molding system  10  may proceed to mold in place the desired joint mechanism or socket assembly.  
      The molding system  10  proceeds by selecting and preparing a mold material for the molding process (block  64  of  FIG. 2 ). The mold material may comprise a plastic, a metal, or any other desired material. Preparation of the mold material may comprise a variety of processes, such as mixing components, heating the material, and coupling a source of the mold material to the injection cavity  26  of the injection section  12 . In this exemplary embodiment of the molding system  10 , the ball joint may be heated to create a temperature differential between the ball joint and the substrate assembly (block  66 ). For example, the ball joint may be heated to 300 degrees Fahrenheit, while the substrate assembly remains at room temperature (e.g., 70 degrees Fahrenheit). As discussed below, this temperature differential facilitates heat transfer from the ball joint to the substrate assembly, thereby preventing the mold material from shrinking onto and sticking to the surface of the ball joint. It should be noted that the mold material may be different from the material comprising the substrate or ball, or these may be made of the same material.  
      After the mold material has been selected and prepared (block  64 ) and the ball joint has been sufficiently heated (block  66 ), the ball joint is inserted into a receptacle of the mold assembly (block  68 ). For example, as illustrated in  FIG. 1 , the threaded stud  22  of the studded ball  18  is inserted into the central receptacle  44  of the securement section  14  of the mold assembly. The substrate assembly is then positioned about the ball joint adjacent the mold assembly (block  70 ). For example, as illustrated in  FIG. 1 , the substrate assembly  24  may be disposed about the ball member  20  and seated adjacent the spring loaded collar  46  of the securement section  14 . The substrate assembly may embody an integral structure, such as a symmetrical or ring-shaped substrate assembly, or it may embody a plurality of substrate members to form a closed body about the ball joint. The molding system  10  then proceeds to close the mold assembly about the substrate assembly and the ball joint (block  70 ). For example, as illustrated in  FIG. 1 , the injection and securement sections  12  and  14  may be moved toward one another and seated against the outer edges  36  and  52  of the substrate assembly  24  to provide a sealed inner molding cavity for injection of the injection material  28  through the injection cavity  26  of the injection section  12 .  
      The substrate assembly is then centered relative to the ball joint to ensure the desired mold thickness and orientation of the substrate assembly relative to the ball joint (block  72 ). For example, as illustrated in  FIG. 1 , the orientation tabs  40  interact with the outer edges  36  of the substrate assembly  24  to facilitate desired positioning of the substrate assembly  24 . The spring-loaded collar  46  accommodates any dimensional variation in the substrate assembly  24  and other components of the molding system  10  to ensure a continuous seal between the molding assembly and the substrate assembly. Moreover, the alignment collar  60 , fitted within receptacle  44 , and the alignment structure  58  ensure proper alignment of the studded ball  18  and ball member  20 . The injection and securement sections  12  and  14  also may be coupled to ensure that the foregoing alignment mechanisms cooperate to provide an overall alignment between the ball member  20  and the substrate assembly  24 .  
      The molding system  10  then proceeds to inject mold material about the ball joint (block  76 ). For example, the injection material  28  may be injected through the injection cavity  26  and into the mold cavity between the substrate assembly  24  and the ball member  20 . As illustrated in  FIG. 1 , the injection material  28  is injected toward the ball member  20  on an opposite side from the threaded stud  22 , which is disposed in the central receptacle  44  of the securement section  14 . The injection material  28  also may facilitate alignment as it pushes the ball member  20  against the alignment structure  58 . The pressure of the injection material  28  preferably forces the ball member  20  against surface  58 , thereby automatically sealing the mold cavity. Alternatively, the studded ball  18  may be pulled into the central receptacle  44  prior to injection of the injection material  28  to facilitate alignment against the alignment structure  58 . In either case, the molding system  10  maintains the centering during mold injection to provide a uniform mold thickness (block  78 ). The mold material is injected into the mold cavity until the entire cavity is full, which may be determined by a volume or pressure sensor. If desired, the molding system  10  may then retract the centering mechanism to fully inject mold material about the ball joint (block  80 ). For example, the orientation tabs  40  illustrated in  FIG. 1  may be backed away from the substrate assembly  24  to allow mold material to fill the gaps caused by the orientation tabs  40  (e.g., the gaps illustrated in  FIG. 4 ).  
      The mold material may then be solidified between the substrate assembly and the ball joint (block  80 ). For example, the mold material may be allowed to solidify at room temperature, a coolant or cooler environment may be applied to the structure to accelerate cooling, or any other solidification step may be utilized within the scope of the molding system  10 . It also should be noted that the temperature differential between the ball joint and the substrate assembly, as discussed above, facilitates solidification of the mold material. For example, the act of heating the ball joint ensures that the mold material solidifies from the substrate assembly inwardly toward the ball joint, thereby forming an insulative structure that keeps the mold material from contracting onto and sticking to the ball joint. In this manner, the substrate assembly essentially acts as a heat sink for the heated ball joint. Thus, the present technique helps reduce shrinkage of the mold material and it controls the tightness of the fit between the mold material and the ball joint. The result is a self-toleranced molded-in-place joint assembly, such as the molded-in-place joint assembly  16  illustrated in  FIG. 3 .  
      The molding system  10  then proceeds to remove the molded-in-place ball joint from the mold assembly (block  80 ). The molded-in-place ball joint may be further modified and refined or it may be immediately incorporated into a desired assembly (block  86 ). For example, the molded-in-place ball joint may be incorporated into a suspension system of a vehicle or any other movable joint application.  
      As illustrated in  FIG. 3 , the molded-in-place joint assembly  16  comprises an integral mold-linkage structure  88  formed by the molding system  10 . As illustrated, the integral mold linkage structure  88  includes the substrate assembly  24  molded into and retained by a mold structure  90 , which may embody a substantially symmetrical or uniform molded-in-place shell about the ball member  20 . As mentioned above, the orientation tabs  40  and the alignment structure  58  ensure that the ball member  20  is centered within the substrate assembly  24  to provide a substantially symmetrical or uniform molded-in-place structure (i.e., the mold structure  90 ) about the ball member  20 . The mold structure  90  also may have gaps caused by the orientation tabs  40  of the injection section  12 . In a front view of the molded-in-place joint assembly  16 ,  FIG. 4  illustrates such gaps corresponding to a set of three orientation tabs  92  disposed symmetrically at 120 degrees apart. The molded-in-place joint assembly  16  also may have a lateral linkage member  94  coupled to the threaded stud  22 , as illustrated in FIG.  4 . However, as discussed above, the studded ball  18  may have any desired connection mechanism and ball joint geometry. The substrate assembly  24  and retention mechanism for the mold structure  90  also may vary depending on the desired application and the type of joint member, which may be a ball, a pin, a bearing assembly, or any other desired structure.  
      The mold structure  90  also may comprise one or more materials, which are molded onto the ball member  20  as a composite mold or as a multi-layered mold. For example, the mold structure  90  may be formed in multiple molding steps, which progressively build layers of low friction materials, heat resistant materials, corrosion resistant materials, impermeable materials, durable materials, and various other functional material layers. The final mold layer would then secure, or self-retain, the ball member  20  within the substrate assembly  24 .  
      In the embodiment illustrated in  FIGS. 1, 3  and  4 , the molded-in-place joint assembly  16  has retention structures  32  and  56  disposed at outer edges  36  and  52  of the substrate assembly  24 . Alternate embodiments are illustrated in  FIGS. 5 and 6 . As illustrated in  FIGS. 5 and 6 , the substrate assembly  24  includes an internal retention cavity  96  for securing the mold structure  90  in place relative to the substrate assembly  24 . Any suitable geometry may be utilized for this internal retention cavity  96 . As illustrated in  FIG. 6 , the molded-in-place joint assembly  16  also may be formed from a double-ended studded ball  18 . For example, the studded ball  18  may have threaded studs  22  on opposite sides of the ball member  20 . Accordingly, the injection and securement sections  12  and  14  may be modified to accommodate the extra threaded stud  22 . For example, the securement section  14  illustrated in  FIG. 1  may be used for both threaded studs  22  illustrated in  FIG. 6 , while an injection section may be incorporated into one of the securement sections  14  or into the substrate assembly  24 . In either case, the mold structure  90  is molded-in-place about the ball member  20  to form the molded-in-place joint assembly  16 .  
      The molding system  10  is further illustrated with reference to  FIG. 7 , which is a flow chart illustrating manufacturing of the molded-in-place joint assembly  16  according to certain aspects of the present technique. As illustrated, the molding process is initiated (block  98 ) to form the molded-in-place joint assembly  16  in an essentially two-step process comprising formation of a ball stud and formation of the molded-in-place ball joint. In process  100 , the molding system  10  proceeds to configure a ball stud mold assembly (block  102 ), which is then used to mold a ball material  104  onto a stud  106  to form a ball stud (block  108 ). The stud  106  may comprise any desired material and linkage structure, such as a metallic threaded stud. Similarly, the ball material  104  may comprise any desired material, such as a metal, a ceramic, a plastic, or any other suitable material or combination of materials. The ball stud mold assembly may be configured to make a spherical ball, a multi-surfaced ball, an oval ball, an elongated ball or pin, a dimpled texture, or any other desired structure. Accordingly, the molding system  10  then proceeds with process  110  to form the molded-in-place ball joint. The process  110  may proceed similar to the process illustrated in  FIG. 2 . As illustrated, the process  110  proceeds by configuring a socket mold assembly (block  112 ), such as the injection and securement sections  12  and  14  illustrated in  FIG. 1 . The ball stud is then positioned into the socket mold assembly (block  114 ). A substrate/link  116  and a socket material  118  are also provided for molding with the ball stud. The process  110  then proceeds by simultaneously molding the socket material onto the ball stud and into the substrate/link (block  120 ). The socket mold assembly is then separated to obtain a molded-in-place ball joint (block  122 ).  
      While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.