Abstract:
An assembly technique for closing a movable socket ( 10 ) without the need to deform or displace any portion of the socket housing ( 12 ), thereby allowing for the use of fully hardened socket housing materials. The internal components of the movable socket are installed within the housing through an opening ( 16 ), and a conical cover-plate ( 66 ) is positioned over the components, within the opening. An assembly tool ( 100 ) configured to exert pressure on the conical cover-plate is brought into engagement with the plate, and a downward load is applied, expanding the plate to seat within a circumferential groove ( 22 ) in the housing. The assembly tool includes a specifically contoured face ( 109 ) which alters the angle at which pressure is exerted against the expanding conical cover-plate as the plate deforms to a generally planar configuration, closing the opening in the housing. Once expanded, the cover-plate seats within the groove formed in the interior surface of the housing, thereby securing the internal components within the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE 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 closing one end of a movable socket without spinning, swaging, or welding, by means of an expanding cover-plate. While the invention is described in detail with respect to automotive applications, those skilled in the art will recognized 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 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, spun, swaged, or welded in place. Once secured in place, the cover-plate presses on the bearing member either directly or indirectly through a resilient rubber intermediate component. 
     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, sagging, or welding operations required to enclose the housing. Therefore, specialized heat treatment operations such as induction draw operations, or a reduction in the allowable hardness levels of the housing and bearing material surfaces must be employed when using traditional assembly methods. These options are utilized to prevent the housing from cracking during swaging or spinning operations. Welding is an alternative to swaging or spinning operations for securing the cover to the housing. However, welding hardened materials is a difficult and costly operation, and not commonly employed. 
     Accordingly, it is highly advantageous to develop an assembly method and associated components capable of enclosing a fully hardened housing without the need for specialized spinning, swaging, or welding operations. 
     BRIEF SUMMARY OF THE INVENTION 
     Among the several objects and advantages of the present invention are: 
     The provision of an assembly method for a movable socket employing an expanding cover-element to secure the socket components within a socket housing; 
     The provision of the aforementioned assembly method wherein the socket housing is fully hardened; 
     The provision of the aforementioned assembly method wherein the socket housing includes a counterbore adjacent the posterior opening, and an expanding cover-plate is seated on the counterbore prior to expansion; 
     The provision of the aforementioned assembly method wherein the expanding cover-element is expanded in-place by the application of direct pressure; 
     The provision of the aforementioned assembly method wherein direct pressure is applied to the expanding cover-element by means of a ram; 
     The provision of the aforementioned assembly method wherein the ram face is configured to alter the angle of applied pressure exerted on the expanding cover-element during the expansion process; 
     The provision of the aforementioned assembly method wherein the expanding cover-element deforms from a conic or convex shape to a generally planar configuration during the expansion process; and 
     The provision of the aforementioned assembly method wherein no deformation or displacement of the housing material is required during assembly, allowing for an increase in material hardness, extending the useful service life of the movable socket. 
     Briefly stated, the present invention features an assembly technique for closing a movable socket without the need to deform or displace the portion of the socket housing, thereby allowing for the use of fully hardened materials for the socket housing. During assembly, various internal components of the movable socket are installed within the housing through an opening, and a conical or convex cover-element, for example, is positioned over the components, within the opening. A ram or similar device configured to exert pressure on the cover-element is brought into engagement with the cover-element, and a downward force applied, expanding the element. A specifically contoured face on the ram alters the angle at which pressure is exerted against the expanding cover-element as the plate deforms to close the opening in the housing, ensuring a generally planar final configuration. Once expanded, the cover-element is retained within a groove formed in the interior surface of the housing, thereby securing the various internal components within the housing. 
     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 THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings which form part of the specification: 
     FIG. 1 is an exploded view of one illustrative embodiment of a movable socket assembly employing one embodiment of an expanding cover-plate of the present invention; 
     FIG. 2 is a partial sectional view of one illustrative embodiment of the ram of the present invention; 
     FIG. 3 is a sectional view of the face of a preferred embodiment of the ram, illustrating considerations in ram design; 
     FIG. 4 is a sectional view of an expanding cover-plate of FIG. 1 prior to installation; 
     FIG. 5 is a sectional view is a sectional view of the assembled component prior to the expansion of the cover-plate; 
     FIG.  6 A-FIG. 6I are sectional views of the ram face in contact with the expanding cover-plate at various points throughout the driving operation, illustrating the variable contact points between the two components; 
     FIG. 7 is a sectional view similar to FIG. 5, illustrating the expanded cover-plate in place; and 
     FIG. 8 is a section view similar to FIG. 5, of an alternate embodiment wherein the assembly tool incorporates a spring-loaded centering pin. 
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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 FIG. 1, the 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 including those having only one housing opening; to facilitate the description of the method and devices used in conjunction therewith, the preferred embodiment of present invention is described in reference to an exemplary 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 rubber cushion  64  are placed within central bore  14 , above hemispherical surface  56 , and secured therein by an expanding cover-plate  66  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 in and extends upward along 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 . Rubber cushion  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 includes an circumferential torus  74 , having an axial hole  76  formed in it through which the lubrication port  70  extends. Finally, cover-plate  66 , shown in an un-expanded conical configuration in FIG. 1, is placed above the rubber cushion  64  along 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 an outer diameter OD sized to fit within counter-bore  22 . 
     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 altered 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 below for installing the expanding cover-plate  66  is applicable to any movable socket wherein at least one end of the housing  12  must be enclosed to retain internal components in place. For example, a movable socket having only a single housing opening, through which the internal components are inserted and through which the stud lower portion  54  exits, may be enclosed by the method and device of the present invention, utilizing an expanding cover-ring disposed concentric to the stud, is considered within the scope of the invention. 
     Turning now to FIG. 2, an assembly tool (ram) for use with expanding cover-plate  66  is shown generally at  100 . The assembly tool  100  comprises a cap portion  102  having a shaft  104  adapted for attachment to the driving member of a hydraulic or pneumatic press (not shown) and a base portion  106 . A removable stop-out plate  108  having a working face  109  is mounted to the base portion by a pair of threaded cap screws  110 A and  110 B. An axial bore  112  passes through the base portion and partially traverses the shaft, intersecting a radial bore  114  open to the exterior of the assembly tool. Included within stop-out plate  108  is an axial bore  116  aligned with axial bore  112 , such that a lubricant injected into radial bore  114  will exit the assembly tool adjacent the working face. A circular groove  118  disposed radially outward from axial bore  116  in the upper face  119  of the stop-out plate receives an O-ring seal  120 , preventing any lubricant escaping the intersection of axial bores  112  and  116  from reaching the threaded cap screws. 
     Turning to FIG. 3, the working face  109  of an alternate embodiment to stop-out plate  108  having an enlarged axial bore  116 A is shown. In the embodiment of FIG. 3, the working face  109  is defined by an outer surface  122  having a first portion  124  extending conically outward from a recessed area  125  adjacent assembly tool axis ATA, at an acute angle A relative to a plane P parallel to upper surface  119 . The first portion  124  smoothly transitions into a second portion  126  of the outer surface  122 , having a uniform curvature of radius RWF. In the embodiment shown in FIG. 3, angle A is 20°, and radius RWF is 0.500 inches, corresponding to the particular dimensions of one embodiment of expanding cover-plate  66  shown in FIG.  4 . 
     The preferred embodiment of the expanding cover-plate shown in FIG. 4 of the present invention is manufactured in the general form of a truncated hollow cone, having outer diameter OD as measured at base B. The expanding cover-plate  66  is open at base B, and has an opening  128  formed in it along an axis CPA, truncating the conical form. As with the working face  109 , the conical sides of the expanding cover-plate  66  comprises two distinct portions. A first portion  130 , adjacent the axial opening  128  is formed at a first acute angle A 1  with respect to base B. A second portion  132  is formed at a second acute angle A 2 , as measured with respect to base B, such that A 2  is less than A 1 . 
     The dimensions shown in FIGS. 3 and 4 are for the preferred embodiments of the expanding cover-plate  66  and the working face  109  of stop-out plate  108 , and form a matching set. Upon reading the following assembly method description, those skilled in the art will readily recognize that expanding cover-plates of a variety of sizes and shapes may be manufactured, including those with and without an axial opening  128 , and with more or fewer distinct conic surface portions, provided appropriate alterations are correspondingly made to working face  109 . For example, an expanding cover-ring (not shown) through which a stud exits may be utilized within the scope of the invention to enclose an open end of a housing (not shown) having only one opening through which all internal components are loaded. 
     Turing now to FIG.  5  through FIG. 7, the assembly operation of ball joint  10  utilizing assembly tool  100 , expanding cover-plate  66 , and the method of the present invention is described. The internal components of the ball joint  10 , including bearing  30 , stud  36 , pressure plate  62 , and rubber cushion  64  are stacked within housing  12 , and expanding cover-plate  66  is placed within posterior opening  16  on the shoulder of counterbore  22 , radially adjacent groove  24 . With all components axially aligned through their respective centerlines along vertical axis VA, assembly tool  100  is positioned such that working face  109  of the stop-out plate  108  contacts the upper surface of the expanding cover-plate (FIG.  5 ). 
     As shown in FIGS. 6A-6I, a load, preferably at least 7,500 pounds, is exerted on the expanding cover-plate  66  by the assembly tool  100 , flattening the generally conical form into a generally planar form, and expanding the cover-plate  66  beyond outer diameter OD. Due to the specific configuration and interaction between the working face  109  and the expanding covers-plate plate  66 , the circumferential contact region C between working face  109  and expanding cover-plate  66  shifts radially outward from vertical axis VA as the expanding cover-plate  66  deforms, continually transforming the vertical or axial load exerted by assembly tool  100  to an increasingly horizontal or radial expansion force, eliminating the tendency of the cover-plate  66  to cup or bow, and preventing excess vertical or axial loads on the internal components. Full expansion of the expanding cover-plate  66  is achieved when the working face  109  contacts lubrication port  70  of the pressure plate  62 , and circumferential rim  78  of the cover-plate  66  is seated within circumferential groove  24  of the housing  12  (FIG.  7 ). 
     Those skilled in the art will readily recognize that the load required to fully expand the cover-plate  66  will vary with the type, size, and thickness of the material employed in forming the cover-plate  66 , as will the specific angles shown in the preferred embodiment of FIGS. 6A-6I. Additional embodiments, such as shown in FIG. 8, may include an enlarged portion  134  in axial bore  116 , allowing for the placement of a centering pin  136 . Centering pin  136  is preferably seated against a shoulder  138  defined by portion  134  of the axial bore, and includes an centering shaft  140  extending external to the working face  109 . During assembly of the movable socket  10  and expansion of the cover-plate  66 , the centering shaft  140  seats within the axial opening of the lubrication port  70  in pressure plate  62 , ensuring the pressure plate remains centered within the housing  12  during the expansion operation. As the assembly tool  100  depresses and expands the cover-plate  66 , the tip of the centering shaft  140  will contact the hemispherical head  56  of the stud  36 , and compress a retaining spring  142 , allowing the centering pin  136  to retract within the assembly tool  100 . 
     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.