Abstract:
An assembly technique and device for enclosing an open end of a movable socket ( 10 ) comprised of fully hardened materials with an expanding cover-plate ( 66 ) and for controlling the expansion of the cover-plate ( 66 ) to provide a central orifice ( 67 ) of predetermined dimensions to facilitate the installation of a grease fitting. During assembly, various internal components of the movable socket, including the pressure plate, are installed within a housing ( 12 ) through a posterior opening ( 16 ) with the cover-plate positioned over the components. A two-stage ram ( 100 ) having a contact surface and a concentric pivot punch ( 142, 158 ) is brought into engagement with the cover-plate. Pressure exerted by the two-stage ram is transferred to the cover-plate through the contact surface, expanding the cover-plate to conform to the contact surface and enclosing the internal components within the socket housing. The exerted pressure additionally results in the extension of the concentric pivot punch into the central orifice of the cover-plate, controlling the expansion of the cover-plate and establishing the central orifice to predetermined dimensions upon closure of the socket housing.

Description:
BACKGROUND OF INVENTION 
     This invention relates to the manufacturing and assembly of movable sockets, for example, ball-joints as used in automotive steering and suspension systems, and more particularly, to a method and device for performing dual operations of closing one end of a movable socket without spinning, swaging, or welding, by means of an expanding cover-plate, and for producing a centrally located orifice of predetermined size in the cover-plate. While the invention is described in detail with respect to automotive applications, those skilled in the art will recognize the broader applicability of the invention. 
     Conventional ball-joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets comprise a housing having a circular cylindrical internal surface, a ball stud with a ball head contained in the housing, and a synthetic resin, heat treated steel, or sintered alloy bearing member supporting the ball head within the housing. These components are installed into the housing through a posterior opening, with the ball stud extending outward through an axially disposed anterior opening of a smaller diameter than the ball head. Traditionally, the posterior opening is closed by means of a cover-plate, which is spun or swaged in place, as seen in FIGS. 1A-1D. Alternatively, the cover-plate may be welded into place. 
     Cover-plate elements are traditionally formed from a stamping process, whereby individual components having desired dimensions are stamped from metal sheets. Either during the stamping process or in a subsequent manufacturing step, a raised boss may be drawn or stamped into the cover-plate, and a centrally located hole of predetermined dimensions punched therein to receive a self-tapping or threaded grease fitting. 
     Once secured in place, the cover-plate presses on the bearing member either directly or indirectly through a resilient rubber intermediate component and a pressure plate. 
     Bearing components within the housing, against which the ball head or moveable component is articulated, perform best when the housing material is fully hardened, as it is better able to withstand the stresses and frictional wear associated with movement of the bearing components. Accordingly, the use of hardened materials greatly extends the useful life of the bearing components and the housing. However, hardened material surfaces greatly hinder traditional spinning, swaging, or welding operations required to enclose the housing. 
     As described in co-pending U.S. patent application Ser. No. 09/167,917 filed on Oct. 7, 1998 now U.S. Pat. No. 6,202,280, (herein incorporated by reference) a method and device for expanding a conical or convex cover-plate within the posterior opening may be employed to secure and enclose the socket components within the socket housing, allowing for closure of a fully hardened housing without the need for traditional spinning, swaging, or welding operations. 
     Alternatively, as is described in U.S. Pat. No. 6,125,541 to Parker, herein incorporated by reference, a two-stage ram having first and second contact surfaces may be utilized to first expand a conical or convex wear-indicator style cover-plate within the posterior opening of a housing, and then to further deform the cover-plate to a predetermined final position relative to the internal components of the socket to provide a predetermined wear indicator distance. Once assembled, movable sockets may be utilized as load carrying members in numerous mechanical systems, including automotive vehicle suspension and steering systems. Obviously, movable sockets or ball-joints employed in these applications are subjected to various operating conditions, and may be required to carry substantial loads. When wear develops, the performance of the movable socket or ball-joint degrades and, in the case of automotive applications, may result in erratic steering or excessive looseness and play in the vehicle suspension system. 
     Accordingly, it is highly advantageous to develop a ram device capable of both expanding a conical or convex general-purpose cover-plate within a socket housing to enclose the housing without the need for specialized spinning, swaging, or welding operations. It is further highly advantageous to incorporate into the ram device, elements for establishing a desired cover-plate contour and a central orifice in the general-purpose cover-place of a predetermined size for the installation of a self-tapping grease fitting in a single machining operation. 
     SUMMARY OF INVENTION 
     Among the several objects and advantages of the present invention are: 
     The provision of an apparatus for expanding a conical or convex cover-plate to secure socket components within a socket housing and for establishing a central orifice in the cover-place of a predetermined size for the installation of a self-tapping grease fitting in a two-stage continuous operation; 
     The provision of the aforementioned apparatus wherein a contact surface expands the cover-plate within the housing, and an axially aligned pivot punch independently establishes a central orifice in the cover-place of a predetermined size for the installation of a self-tapping grease fitting; 
     The provision of the aforementioned apparatus wherein the contact surface is configured to expand the cover-plate within the housing and to produce a centrally located raised section or boss of predetermined height for clearance of internal socket components; 
     The provision of the aforementioned apparatus wherein the contact surface and the pivot punch are concentrically mounted within a ram housing; 
     The provision of the aforementioned apparatus wherein the pivot punch prevents the cover-plate from collapsing into a downward concave configuration during expansion; 
     The provision of the aforementioned apparatus wherein the pivot punch holds the cover-plate against the contact surface, forcing the cover-plate to conform to the surface configuration of the contact surface; 
     The provision of the aforementioned apparatus wherein the profile of the contact surface may be altered to numerous configurations ranging from flat to that which produces a centrally located raised section or boss in the cover-plate; 
     The provision of the aforementioned apparatus wherein the pivot punch includes an axial bore facilitating the injection of lubricant into the socket assembly in a single machining operation with the socket closing and orifice formation. 
     The provision of a method for use of the aforementioned apparatus wherein the cover-plate expansion operation and the cover-plate orifice establishing operation are integrated into a two-stage continuous pressing operation; The provision of the aforementioned method of use wherein the cover-plate expansion operation is a first stage operation, and the cover-plate orifice establishing operation is a second stage or sequential operation; and 
     The provision of the aforementioned apparatus and method which simplifies the assembly and manufacture of movable sockets to close tolerances while providing minimal unit-to-unit variations. 
     Briefly stated, the present invention features an assembly technique for enclosing an open end of a movable socket comprised of fully hardened materials with an expanding cover-plate and for establishing a central orifice in the cover-place of a predetermined size for the installation of a self-tapping grease fitting. During assembly, various internal components of the movable socket, including a pressure plate, are installed within a housing through a posterior opening and a conical or convex cover-plate is positioned over the components within the posterior opening. A ram of the present invention having a contact surface is brought into engagement with the cover-plate. Pressure exerted by the ram is transferred to the cover-plate through the contact surface, expanding the cover-plate. As the pressure is exerted by the ram, a coaxially located pivot punch is extended through a central bore in the contact surface, and engages an inner edge of the cover-plate. Continued engagement between the contact surface, pivot punch, and the cover-plate results in the cover-plate conforming to the contour of the contact surface during the expansion process, enclosing the internal components within the socket housing. As the cover-plate expands, the engagement between the pivot punch and the inner edge of the cover-plate established a central orifice in the cover-plate of a predetermined size. Additionally, lubricants may be injected into the now closed socket through a central bore in the pivot punch. 
     The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In the accompanying drawings which form part of the specification: 
     FIG. 1A is a sectional view of a prior art apparatus for spin and swagging closure of a socket assembly; 
     FIG. 1B is sectional view of the prior art apparatus of FIG. 1A compressing the components of a socket assembly; 
     FIG. 1C is a sectional view of the prior art apparatus of FIG. 1A engaging and swaging the housing material of the socket assembly to entrap the cover-plate; 
     FIG. 1D is a sectional view of the prior art apparatus of FIG. 1A upon completion of the socket closing procedure; 
     FIG. 2 is an exploded view of one illustrative embodiment of a movable socket assembly employing the expanding cover-plate of the present invention; 
     FIG. 3 is a partial view illustrating the movable socket of FIG. 2, with the upper end components in-place, prior to expansion of the cover-plate; 
     FIG. 4 is a sectional view of the two-stage assembly tool of the present invention; 
     FIG. 5 is a section view similar to FIG. 4, illustrating the contact surface of a removable stop-out plate and a pivot punch in engagement with an unexpanded cover-plate of a ball-joint housing assembly; 
     FIG. 6A is an enlarged sectional view of the engagement region in FIG. 5 between the contact surface, pivot punch, and unexpanded cover-plate; 
     FIG. 6B is a view of FIG. 6A as pressure is exerted against the cover-plate by the contact surface, resulting in engagement between the cover-plate inner edge and the pivot punch; 
     FIG. 6C is a view of FIG. 6A as continued pressure is exerted against the cover-plate by the contact surface, and the engagement between the pivot punch and the inner surface of the cover-plate conforms the cover-plate to the contact surface and into engagement with the housing while establishing a central orifice of predetermine dimensions; and 
     FIG. 6D is a view similar to FIG. 6A, illustrating the closed housing assembly following expansion of the cover-plate and establishment of a central orifice of predetermined dimensions by the tool and method of the present invention. 
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
     DETAILED DESCRIPTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what we presently believe is the best mode of carrying out the invention. 
     Referring generally to FIGS. 2 and 3 the two-stage expanding cover-plate assembly method of the present invention may be used to enclose a movable socket, such as the ball-joint shown at  10 , within a housing  12  without the need for spinning, swaging, or welding. Those skilled in the art will readily recognize the applicability of the following method to the assembly of a variety of different movable sockets; to facilitate the description of the method and devices used in conjunction therewith, the preferred embodiment of present invention is described in reference to a ball-joint  10 , but is not limited to use therewith. 
     Housing  12 , within which the various internal components of the ball-joint are enclosed, is generally cylindrical, with a central bore  14  of non-uniform radius having a posterior opening  16  and an anterior opening  18 . The radius R of central bore  14  decreases to define a curved surface  20  at the base of the housing, adjacent anterior opening  18 . A counterbore  22  having a circumferential groove  24  is formed in bore  14 , adjacent the posterior opening  16 . The exterior surface  26  of housing  12  may follow the general contour of the central bore  14 . In the embodiment illustrated, the surface  26  has an expanded ridge  28  formed in it. The ridge  28  is used for attachment of ball-joint  10  to other components (not shown). As may be appreciated, the ridge  28  also may be adapted for other specific kinds of installations employing threads or other connectors (not shown). 
     To assemble ball-joint  10 , a bearing  30  sized to fit within central bore  14  is seated within housing  12 . The bearing  30  includes a central bore  32  axially aligned with a vertical axis VA of the housing, and a curved outer surface  34  of bearing  30  is designed to correspond to the curvature of surface  20  in housing  12 . 
     Next, a stud  36  having a generally cylindrical body  38  and an enlarged head portion  40  with a circumferential flange  42  is passed through central bores  32  and  14 , such that the underside  44  of flange  42  rests on an upper surface  46  of the bearing seated within the housing. The body  38  includes a uniform diameter upper portion  50  adjacent flange  42 , a tapered central portion  52 , and a lower portion  54  of a narrow uniform diameter. The upper portion  50  is sized to fit within the central bore  32  of bearing  30 , with the central portion  52  and lower portion  54  extending through the anterior opening  18 , externally of housing  12 . The head portion  40  includes a hemispherical surface  56  with a radius Rh greater than that of upper portion  50 , but less than radius R of the housing  12 . When assembled, the hemispherical surface  56  and the curved outer surface  34  define a generally spherical unit within housing  12 , allowing for conical movement of stud  36 . Those skilled in the art will readily recognize that numerous shapes and configurations for stud  36  and bearing  30  are possible. For example, the stud  36  may include a generally spherical head, eliminating the need for bearing  30 , or the cylindrical body may include threads (not shown), bores as at  58 , or grooves as at  60 , for attachment of external components (not shown). 
     Once stud  36  and bearing  30  are seated within the housing, a pressure plate  62  and a rubber cushion preload device  64  are placed within central bore  14 , above hemispherical surface  56 , and secured therein by an expanding cover-plate  66  having an axial bore  67  as described below. The pressure plate  62  sits on top of stud  36 , and includes a curved indentation  68  having a radius of curvature corresponding to Rh. In the preferred embodiment, a lubrication port  70  is formed at the center of the pressure plate  62 . Port  70  permits the injection of a lubricant into the interior spaces of the assembled ball-joint  10 . The rubber cushion preload device  64  sits, in turn, on an upper surface  72  of pressure plate  62 , and serves to hold the pressure plate  62  in place against the stud  36  while simultaneously permitting small movements in response to the conical movement of the stud. The rubber cushion preload device comprises a cylindrical body  74 , having an axial passage  76  formed in it. Finally, cover-plate  66 , shown in an un-expanded conical configuration in FIG. 2, is placed above the rubber cushion  64  adjacent counter-bore  22 , for vertical compression and lateral expansion as will be described, to seat within circumferential groove  24  and enclose the various components within housing  12 . To facilitate the insertion of the cover-plate  66  within the posterior opening of housing  12 , the cover-plate  66  includes a circumferential rim  78  having and outer diameter OD sized to fit within counter-bore  22 . FIG. 3 illustrates the arrangement of the ball-joint  10  upper components  36 ,  62 ,  64 , and  66  prior to the expansion of the cover-plate  66 . 
     As indicated above, those skilled in the art will recognize that the various internal components of the moveable socket secured within the housing  12  by the cover-plate  66  may be varied in size and shape depending upon the particular application for which the movable socket is designed, and accordingly, the above described ball-joint  10  is merely exemplary of one embodiment. The assembly method described co-pending U.S. patent application Ser. No. 09/167,917 for installing the expanding cover-plate  66  is applicable to any movable socket wherein one end of the housing  12  must be enclosed to retain internal components in place. 
     Turning now to FIG.  4  and FIG. 5, an improved two-stage assembly tool or ram for use with the expanding cover-plate  66  is shown generally at  100 . The two-stage assembly tool  100  comprises a cylindrical housing  102  having a central axis CA, mounted concentric to a housing adapter  104 . Housing adapter  104  includes an axially aligned lubrication injection passage  105 , surrounded by an O-ring seal  105 A and is secured to a head adapter  106  by a number of retaining bolts  108  circumferentially spaced about the axis CA. Each retaining bolt  108  is secured to a threaded recess  109  in the housing adapter  104  through a threaded bore  110  in a circumferential flange  112  of the spin head adapter  106 . In the preferred embodiment shown in FIGS. 4 and 5, the head adapter  106  is configured with an external surface  114  for attachment to the driving member of a hydraulic or pneumatic press (not shown), and the housing adapter  104  is secured to the spin head adapter  106  by three equidistantly spaced identical retaining bolts  108 . The head adapter  106  further includes a lubrication injection port  107  aligned to delivery a lubricant flow to the axially aligned lubrication injection passage  105  in the housing adapter  104 . 
     The cylindrical housing  102  of the two-stage assembly tool  100  includes a bore  116  concentric with the central axis CA and an inwardly-protruding circumferential shoulder  118  adjacent a posterior end  120  of bore  116 . When assembled, the shoulder  118  seats against a circumferential flange  122  on the housing adapter  104 , thereby retaining the housing portion  102  on the spin head adapter  106 . The anterior end  124  of the housing  102  is enclosed by a mounting plate  126  secured to the housing portion  102  by a number of identical countersunk cap screws  128  threaded into recesses  129 . In the preferred embodiment, a total of six socket-head cap screws  128  are equidistantly spaced about the circumference of the anterior end  124 . 
     The mounting plate  126  comprises a torus body  127  having a rectangular cross-section, and is configured with a number of flanges for attachment of various components. First, an outer circumferential flange  130  extends radially outward from the body  127  to seat on the anterior end  124  of the housing  102 . The flange  130  includes a number of identical countersunk threaded bores  132  through which the identical cap screws  128  pass into the housing  102 . Those skilled in the art will recognize that the number of bores  132  corresponds to the number of cap screws  128  utilized in retaining the mounting plate  126  to the housing  102 . Extending radially inward from the body  127 , an inner circumferential flange  134  defines an axial passage  136  through the mounting plate  126 . Additionally included within the body  127  are a number of ports  137 , for the equalization of air-pressure within the two-stage assembly tool  100  and for the introduction of a lubricant thereto as required. Finally, a cylindrical flange  138  on the anterior surface of the body  127  defines a recessed mount  140  into which a removable stop-out plate  142  is secured. 
     As described in the co-pending U.S. patent application Ser. No. 09/167,917, stop-out plate  142 , best shown in FIG. 4, and FIGS. 6A-6D includes a working face  144  configured to deform a conical or convex cover-plate  66  into a desired configuration and an enlarged axial bore  145 . The stop-out plate  142  is secured within the recessed mount  140  by a number of identical cap screws  146 , each threaded through identical radial bores  148  in the cylindrical flange  138  and into a receiving channel  150 . In the preferred embodiment, a total of three cap screws  146  are equidistantly space about the central axis CA to retain the stop-out plate  142  within the recessed mount  140 , however, one skilled in the art will recognized that greater or fewer numbers of cap screws may be employed within the scope of this invention, and that the receiving channel  150  may be replaced by a number of circumferentially disposed receiving recesses (not shown). 
     Axially disposed within the bore  116  is a pivot punch  158  having a cylindrical body  160  and a longitudinal bore  162  axially aligned with the central axis CA. A posterior end  164  of the body  160  is configured to contact the housing adapter  104 , such that the axial passage  162  is aligned with the axial passage  105  in the housing adapter  104 . An anterior end  166  of body  160 , has a tapered exterior surface, and is configured to extend through the mounting plate axial passage  136  and partially into the enlarged axial bore  145  of stop-out plate  142 . 
     To provide for a compressive force acting on the pivot punch  158 , a die spring  174  is placed concentrically around the body  160  in the bore  116 , between the posterior end  164  and the body  127  of the mounting plate  126 . When installed within the housing  102 , the die spring  174  seats between the mounting plate  126  and an O-ring adapter  167  is seated about the posterior end  164  of the body  160  of pivot punch  158 . In the preferred embodiment, the die spring  174  is provided with an 846 lb preload between the O-ring adapter  167  and the mounting plate  126 , to maintain the pivot punch  158  in a withdrawn position. 
     One skilled in the art will recognize that alternate types of compressible spring members, such as helically wound springs may be employed within the scope of the invention, provided the loading requirements are met. By slightly compressing or preloading the die spring  174 , an expansion force is directed coaxially along the central axis CA, urging the housing adapter  104  and mounting plate  126  in opposite directions. As is readily apparent from examination of FIGS. 4 an  5 , the mounting plate  126  is secured to the cylindrical housing  102 , which is in turn seated against a surface of the housing adapter  104 . The load on the posterior surface  156  of the mounting plate  126  is transferred to the housing  102  through the countersunk cap screws  128 , causing the shoulder  118  of the housing  102  to seat securely against the circumferential flange  122  of the housing adapter  104 . The expansion force thereby is seen to hold the housing  102  and associated components against the housing adapter  104 . 
     Continuing to refer to FIGS. 4 and 5, assembly of the two-stage stop-out two-stage assembly tool  100  of the present invention begins with the cylindrical housing  102  and the housing adapter  104 . The housing adapter  104  is placed within the housing  102 , adjacent the posterior end, such that the circumferential flange  122  on the housing adapter seats against the should  118  of the housing  102 . Next, the pivot punch  158  and its associated O-ring washer  167  are seated within bore  116 , concentric with the axis CA. The die spring  174  is then placed within the housing bore  116 , about the pivot punch  158 , such that one end of the die spring  174  seats against the O-ring washer  167 . 
     To enclose the housing  102 , the mounting plate  126  is axially aligned with the central axis CA and positioned against the anterior end  124  of the housing  102 , compressing the die spring  174  to the predetermined preload. Countersunk cap screws  128  are then threaded into the housing  102  through the mounting plate bores  132 , securing the mounting plate in a fixed relationship with the housing and retaining the pivot punch  158  within the housing bore  116  in such a manner to allow for a small degree of axial movement of the pivot punch. All axial movement of the pivot punch  158  is restrained by the die spring  174 . 
     The two-stage assembly tool  100  is next secured to the head adapter  106  by retaining bolts  108  threaded through bore  110  in the flange  112  of the head adapter and into the housing adapter  104 . Once secured to the head adapter  106 , the axial bore  105  aligns with a corresponding bore in the spin head adapter, permitting the injection of a lubricant through the axial bore  105 , and into the axial bore  162  of the pivot punch  158 . The final step in assembly the tool  100  is the selection and attachment of the removable stop-out plate  142 . As is described in the co-pending U.S. patent application Ser. No. 09/167,917, the removable stop-out plate includes the working face  144  configured to deform a conical or convex cover-plate  66 , and accordingly is selected to correspond to the size and shape of the cover-plate. The removable stop-out plate  142  is positioned axially within the recessed mount  140  on the mounting plate  126 , and secured thereto by the placement of cap screws  146  threaded through the flange  138  of the mounting plate  126  and into the receiving channel  150  of the stop-out plate  142 . 
     Turning to FIGS. 6A through 6D, the two-stage assembly tool  100  as described above is utilized in the closure operations of a ball-joint  10  as follows. First, the internal components of the ball-joint  10  are stacked within the ball-joint housing  12  as described in the co-pending U.S. patent application Ser. No. 09/167,917, and positioned in axial alignment beneath the two-stage assembly tool  100 , previously secured to a hydraulic or pneumatic press (not shown) by the head adapter  106 . The initial operation of the two-stage assembly tool is to close the ball-joint as described in the co-pending application. A downward force is exerted by the hydraulic or pneumatic press, moving the working face  144  of the removable stop-out plate  142  into contact with the expanding cover-plate  66 . A continued exertion of downward force by the hydraulic or pneumatic press shifts the housing adapter  104  in an axially downward direction relative to the cylindrical housing  102  of the two-stage assembly tool  100 , compressing the die spring  174  until the housing adapter  104  contacts the mounting plate  126 . The downward force exerted by the press is now transferred directly to the working face  144 , and continues until such time as closure of the ball-joint  10  by expansion of the cover-plate  66  is completed as described in the co-pending application. Simultaneously with the exertion of the compression/expansion force on the cover-plate  66 , the pivot punch  158  is driven downward by the compression force through the axial bore  145  in the working face, and extends into the central opening  67  of the cover-plate  66 . 
     As best seen in FIGS. 6B-6D, as the cover-plate  66  begins to deform under the compression load from the working face  144 , the inner surface of the cover plate central opening  67  contacts the exterior cylindrical surface  166  of the pivot punch. The result is an increased radial load on the cover-plate, causing the cover-plate  66  to deform in such a manner as to conform to the working face  144 . Simultaneously, the exterior cylindrical surface  166  of the pivot punch ensures that the central opening  67  in the cover-plate  66  is sized to predetermined dimensions corresponding to those of the pivot punch  158 . As seen in FIG. 6C, upon full expansion of the cover-plate  66  and the closure of the ball-joint  10 , the working face  144  contacts the upper surface of the counterbore  22  in the ball-joint housing  10 , and is blocked from further downward movement. At this point, it is desirable to inject a quantity of lubricant into the closed ball-joint  10  through the axial bore  162  of the pivot punch  158 . The lubricant exits the pivot punch  158  at anterior end, adjacent the cylindrical surface  166 , below the now closed cover-plate  66 . 
     Upon completion of the deformation of the expanded cover-plate  66  by the pivot punch  158 , and the injection of the lubricant, the load is withdrawn from the two-stage assembly tool  100 , permitting die spring  174  to axially retract the pivot punch  158  within the cylindrical housing  102 , and the removal of the two-stage assembly tool  100 . 
     Those skilled in the art will recognize that the die spring load requirements, the final deformation shape of the expanded cover-plate  66 , and the sizing of the cove-plate central bore  67  to receive a self-tapping or threaded grease fitting may be adjusted as required to achieve alternative deformations of the cover-plate  66  factoring material composition and component sizes. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. 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.