Abstract:
The invention includes a support frame for producing a dental workpiece. The frame has a Z axis and comprising wall sections defining a hole that extends along the Z axis through the frame. At least one of the wall sections comprises an adhesive-directing surface extending along the Z axis in a non-parallel relationship. Such a configuration provides optimized methods for affixing a blank to the support frame and optimized properties of the blank after fixation to the support frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a U.S. National Phase Patent Application based on International Application Serial No. PCT/EP2008/000922 filed Feb. 7, 2008, the disclosure of which is hereby explicitly incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a device for assembling a first panel and a second, superposed panel, which device is intended to pass axially through a hole provided in each panel and comprises a hollow-shaped fixing base equipped with clipping means for clipping onto the first panel, and a captive locking member comprising an elongated body mounted in the fixing base and a retaining head for retaining the second panel. 
         [0004]    2. Description of the Related Art 
         [0005]    In many fields, particularly the automotive industry, it is necessary to assemble two parts together in an area where two panels, each integral to a respective one of the two parts, are superposed. Generally, the panels have through-holes that are intended to be aligned at the time of assembly. An assembly device is then inserted in the holes to accomplish the assembly of the two panels. Such assembly devices must be designed so that they lend themselves to fast, easy mounting in hard-to-access mechanical structures, often without visual guidance, and so that they can be counted on to hold the panels in place reliably. 
         [0006]    Prior-art devices, for example bolt and nut systems, are already capable of performing these functions. But this type of assembly device has always been hard to manipulate, since during the mounting operation it is necessary to hold the two panels against each other while at the same time inserting the bolt and screwing down the nut until tightness is obtained. The considerable mechanical complexity of this device makes it difficult to use in an automated production line. The operations of lining up the holes, holding the panels in place, and inserting and rotating the device are painstaking and laborious for a single operator to perform, which has the direct consequence of slowing assembly rates. 
         [0007]    The document EP0591186 describes a device for assembling two superposed panels, which device is composed of a fixing base and a captive locking member mounted in the fixing base. The device is intended to pass axially through a hole provided in each of the panels. The fixing base comprises clipping means for clipping it onto the first panel. A spring is disposed between the fixing base and the locking member in such a way as to naturally keep the retaining head, which retains said locking member, within the thickness of the second panel. The retaining head has two diametrically opposed lugs and the hole in the second panel is oblong in shape, with dimensions that are similar to those of the retaining head. In order to free the retaining head from the second panel and thus be able to rotate the locking member one quarter turn, manual pressure must be applied to the locking member to counter the force of the spring. After this rotation, the lugs serve to retain the second panel on both sides of its hole. 
         [0008]    Although it simplifies the operation of assembling the panels, such a device is not entirely satisfactory, since the rigidity that it imparts to the panel assembly is absolute, a fact that may, depending on the application, prove detrimental to safety. For instance, it is common for the first panel to be a suitable portion of an automobile chassis and the second panel a portion of a fender or the bumper of the automobile. In applications of this kind, the rigidity of the panel assembly is such that impact absorption by the fender or bumper is very poor. Meanwhile, government standards are placing increasing demands on automakers to improve safety in this respect. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a device for assembling two panels. 
         [0010]    The device according to the invention is characterized in that the locking member comprises a rupture zone interconnecting the retaining head and the elongated body of the locking member. 
         [0011]    Such a rupture zone, in practice, constitutes a cleavable, fusible region that tends to break under a predetermined external load on the device, especially when such a load is transmitted to the device by one of the two panels under the effect of an action external to the panels, such as an impact sustained by one of the panels. 
         [0012]    In one embodiment, the retaining head comprises a barrel having one end joined to the elongated body so as to prolong said elongated body, the rupture zone being comprised of a narrowing of the cross section of the barrel at the level of said end. 
         [0013]    In an advantageous manner, the retaining head comprises two diametrically opposed lugs projecting from the barrel. Such a retaining head is intended to engage in a similarly shaped hole in the second panel until the lugs are released and it thus becomes possible to rotate the locking member one quarter turn, so that the lugs come to retain the second panel on both sides of its hole. To ensure this manner of operation, the hole in the second panel thus is overall elongated, for example oblong, with a width that is slightly larger than the diameter of the barrel of the retaining head and, in any event, smaller than the distance between the ends of the lugs. A configuration of this kind results in retaining means for the second panel which, in addition to the fusibility described above, afford the possibility of relative translation between the two panels by sliding the barrel of the retaining head over the length of the hole in the second panel. 
         [0014]    In one form thereof, the present invention provides a device for assembling a first panel and a second, superposed panel, the device being intended to pass axially through a hole provided in each panel and including a hollow-shaped fixing base equipped with clipping means for clipping onto the first panel, and a captive locking member including an elongated body mounted in the fixing base and a retaining head for retaining the second panel, characterized in that the locking member includes a rupture zone interconnecting the retaining head and the elongated body of the locking member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0016]      FIG. 1  is a front view of an exemplary assembly device according to the invention in an unmounted state; 
           [0017]      FIG. 2  is a front longitudinal sectional view of the device of  FIG. 1 ; 
           [0018]      FIG. 3  is a side longitudinal sectional view of the device of  FIG. 1 , taken in a section plane perpendicular to the section plane of  FIG. 2 ; 
           [0019]      FIG. 4  is a sectional view identical to that of  FIG. 2 , but in which the device is in a pre-nested state; 
           [0020]      FIG. 5  is a side view of the device in the pre-nested state after assembly with a panel; 
           [0021]      FIG. 6  is a view identical to that of  FIG. 5 , but after assembly with an additional panel; and 
           [0022]      FIG. 7  is a front view of the device in a nested state. 
       
    
    
       [0023]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. 
       DETAILED DESCRIPTION  
       [0024]    The exemplary assembly device depicted only in  FIGS. 1 to 4  comprises a fixing base  10  and a locking member  11  intended to be mounted captively in the fixing base  10 . 
         [0025]    The locking member  11  is chiefly composed of an elongated body  12  and a retaining head  13 . The end of elongated body  12  that is joined to retaining head  13  bears a rectangular-shaped first transverse plate  14 . The opposite end of elongated body  12  from retaining head  13  bears a circular peg  15  having two parallel faces. First transverse plate  14  and circular peg  15  are joined to each other by a central rib  16  equipped on each of its edges with a boss, respectively  17   a  and  17   b.  The central rib  16  is perpendicular to the face of circular peg  15  from which it extends, and coincides with one of its diameters. Central rib  16  is likewise perpendicular to first transverse plate  14 . The opposite face of circular peg  15  is equipped with a coupling member  18  capable of being joined to an external tool of the type of a hexagonal wrench or a cruciform, slot or star wrench. The external tool is capable of transmitting a rotational torque to locking member  11  through coupling member  18 . The circular peg  15  and the first transverse plate  14  are disposed coaxially, their common axis D defining the longitudinal direction in which locking member  11  and, in particular, elongated body  12  extend. 
         [0026]    As illustrated in  FIGS. 1 and 2 , two flexible detents  19   a  and  19   b  disposed one on each side of central rib  16  extend from circular peg  15  toward first transverse plate  14 . The flexible detents  19   a  and  19   b  are each joined at one of their ends to the face of circular peg  15  from which central rib  16  extends, and are flexible transversely, that is, toward central rib  16 . Each flexible detent  19   a,    19   b  has an inclined portion and a transverse portion. The transverse portion extends toward circular peg  15 , approaching longitudinal axis D. The transverse portion extends parallel to first transverse plate  14 , with a first axial offset e 1 , considered in the longitudinal direction. Flexible detents  19   a,    19   b  are coplanar in a plane perpendicular to central rib  16 . 
         [0027]    Circular peg  15  has, formed in its thickness, a peripheral shoulder  29  that axially confronts first transverse plate  14  and thus retaining head  13 . A chamfer  30  joins together said shoulder  29  and the face of circular peg  15  that bears coupling member  18 . 
         [0028]    Retaining head  13  comprises a cylindrically shaped barrel  20  having one end joined to elongated body  12  so as to prolong elongated body  12 . Otherwise stated, the axis of revolution of the barrel  20  coincides with axis D. The barrel  20  extends perpendicularly from the center of the opposite face of first transverse plate  14  from that which is joined to central rib  16 . Barrel  20  has a cross-sectional narrowing at the level of its end that is joined to first transverse plate  14 . The cross-sectional narrowing is in the form of an annular neck  21  formed in the outer face of barrel  20  in that region. Retaining head  13  also bears two diametrically opposed lugs  22   a  and  22   b  that project from the barrel  20 . The bottom transverse face of each of them extends parallel to first plate  14 , with a second axial offset e 2 , considered in the longitudinal direction. 
         [0029]    Turning now to fixing base  10 , it is hollow-shaped and is composed of a cylindrical bushing  23  internally delimiting a bore  24  that comes out at one end of the bushing  23 . Bushing  23  is intended to receive elongated body  12  as described hereinafter. A second transverse plate  25  of rectangular shape and of smaller thickness than first axial offset e 1  extends from the other end of cylindrical bushing  23 . Second plate  25  is pierced by a circular opening  26  that is centered axially with respect to the bore  24 . The elongated body  12  of locking member  11  is mounted in the fixing base  10  by engaging the circular peg  15  (followed by the rest of elongated body  12 ) through the circular opening  26 . During this operation, the chamfer  30  facilitates the engagement of circular peg  15  in circular opening  26 . Consequently, after this mounting operation, axis D coincides with the axis of revolution of the cylindrical bushing  23 . Axis D therefore defines the longitudinal direction in which locking member  11 , fixing base  10  and, more generally, the assembly device as a whole extend. 
         [0030]    In practice, second transverse plate  25  constitutes an axial stop operating in the direction of axis D, arranged transversely around cylindrical bushing  23 . In addition, at least one maintaining fin, here two of them, labeled  27   a  and  27   b,  made of elastically deformable material, projects from the outer face of cylindrical bushing  23 , with an inclined portion and a transverse portion. The inclined portion extends toward second transverse plate  25 , drawing away from axis D. The transverse portion extends parallel to second plate  25 , with a third axial offset e 3 , considered in the longitudinal direction. Maintaining fins  27   a,    27   b  are elastically deformable transversely, that is, toward the bore  24 , perpendicularly to the longitudinal direction. 
         [0031]    Circular opening  26  also comprises two diametrically opposed, rectangular notches  28   a,    28   b.  The shape and dimensions of each notch  28   a,    28   b  are complementary to those of the bosses  17   a,    17   b  of elongated body  12 , such that bosses  17   a,    17   b  are able to engage in notches  28   a,    28   b.    
         [0032]      FIGS. 1 to 3  illustrate the assembly device immediately after production, during which the fixing base  10  and the locking member  11  are manufactured in one piece by injecting a plastic into a suitable mold. From the bottom of chamfer  30  on down, circular peg  15  is joined over its thickness to the contour of the circular opening  26  in the fixing base  10  by a cleavable joint. This joint is formed by a film of very thin material, so that it breaks easily. This way of fabricating the assembly device facilitates the design of the injection mold and eliminates the need to perform an extra assembly operation on a special machine. The assembly device is in an unmounted state at this point. 
         [0033]    In a subsequent step, prior to any assembly with a panel, the locking member  11  is inserted partway into the cylindrical bushing  23  of fixing base  10  by forcibly engaging the chamfer  30  of elongated body  12 , followed by the peripheral shoulder  29 , in circular opening  26 . In the course of this operation, the cleavable joint which had united fixing base  10  and locking member  11  until now is broken, and the two parts become independent of each other. To be able to engage locking member  11  in circular opening  26 , the user must also take care to line up the bosses  17   a,    17   b  with the notches  28   a,    28   b  of circular opening  26 . In an initial phase, locking member  11  must be inserted far enough into cylindrical bushing  23  so that the peripheral shoulder  29  of circular peg  15  extends longitudinally beyond circular opening  26 . The diameter of circular opening  26  is larger than the overall diameter of circular peg  15  but slightly smaller than the outer perimeter of peripheral shoulder  29 ; this is why the engagement of elongated body  12  must be done forcibly. After the foregoing engagement, the contour of the circular opening  26  of fixing base  10  is, moreover, interposed between the peripheral shoulder  29  and the flexible detents  19   a,    19   b  of elongated body  12 , an arrangement that ensures the longitudinal retention of fixing base  10 . In addition, the bosses  17   a,    17   b  are longitudinally positioned on the edges of central rib  16  in such a way that after engagement, the bosses  17   a,    17   b  are seated in the notches  28   a,    28   b  of circular opening  26 . Relative rotation between the fixing base  10  and the locking member  11  is consequently blocked after the engagement described above. The assembly device is then in a pre-nested state, depicted in  FIG. 4 . 
         [0034]    In the subsequent course of its use, the assembly device in the pre-nested state is intended, first, to be mated with a first panel P 1  and a second, superposed panel P 2 , so that the panels can be rigidly assembled in another subsequent step. More precisely, the panels P 1  and P 2  are intended to be assembled with the fixing base  10  and the locking member  11 , respectively, in the manner described below. Panels P 1  and P 2  are generally each integral to a respective part, said parts (not shown) being intended to be assembled together in an area where panels P 1  and P 2  are superposed. More than one assembly device can be used to assemble the parts. 
         [0035]    The second panel P 2  ( FIG. 5 ), whose thickness is slightly smaller than the second axial offset e 2  between the lugs  22   a,    22   b  and first transverse plate  14 , comprises an overall elongated through-hole  31  having a rectangular or oblong shape, for example, with a width that is slightly larger than the diameter of barrel  20  and retaining head  13  and, in any event, smaller than the distance between the ends of the lugs  22   a,    22   b.  The length of hole  31 , on the other hand, is greater than the distance between the ends of lugs  22   a,    22   b.  Hole  31  is therefore similar in shape to retaining head  13 , with slightly larger dimensions to create mounting play. 
         [0036]    To assemble second plate P 2  on locking member  11 , retaining head  13  is engaged longitudinally in hole  31  until lugs  22   a,    22   b  attain a released position in which panel P 2  is situated longitudinally between first transverse plate  14  and lugs  22   a,    22   b.  The user then manipulates the retaining head  13  by hand to cause the locking member  11  to rotate one quarter turn. Since the bosses  17   a,    17   b  are seated in the notches  28   a,    28   b  of circular opening  26  during the rotation of locking member  11 , this movement of locking member  11  is accompanied by a corresponding movement of fixing base  10 . After rotation ( FIG. 5 ), the lugs  22   a,    22   b  serve to retain second panel P 2  on both sides of its hole  31 . The assembly of second panel P 2  is complete. A configuration of this kind results in retaining means for retaining second panel P 2  that ensure the possibility of relative translation between second panel P 2  and the assembly device by sliding the barrel  20  of retaining head  13  over the length of the hole  31  in the second panel P 2 . 
         [0037]    First panel P 1  ( FIG. 6 ), whose thickness is slightly smaller than the third axial offset e 3  between second transverse plate  25  and the transverse portions of the maintaining fins  27   a,    27   b,  comprises a through-hole  32  having a circular shape of slightly larger diameter than the outer diameter of the cylindrical bushing  23 . This configuration makes it possible to introduce the bushing  23  into the hole  32 . As first panel P 1  slides along bushing  23 , the maintaining fins  27   a,    27   b  bend in the transverse direction, while the contour of hole  32  slides along the inclined portions of the fins  27   a,    27   b  until said inclined portions, and thus the fins  27   a,    27   b,  are released. The maintaining fins  27   a,    27   b  then return by elastic rebound to their natural configuration, such that their transverse portions come into contact with one of the faces of first panel P 1 . The other face of first panel P 1  is in contact with second plate  25 , which can be provided for this purpose with a plurality of distributed bulges  33 . The first panel P 1  thus is clamped between the second plate  25  and the maintaining fins  27   a,    27   b,  and the assembly of first panel P 1  is complete ( FIG. 6 ). Maintaining fins  27   a,    27   b  and second transverse plate  25  constitute clipping means for clipping first panel P 1  to fixing base  10 . 
         [0038]    In this state, the rotation of fixing base  10  relative to first panel P 1  is impossible because of the clipping means. As explained previously, the rotation of locking member  11  relative to fixing base  10  is also impossible. Since the panels P 1  and P 2  are superposed and are fixed in rotation relative to each other, the rotation of retaining head  13  relative to second panel P 2  is impossible, thus safety-locking the assembly. In addition, in the absence of an external axial load, the flexible detents  19   a,    19   b  of elongated body  12  prevent the free translation of locking member  11  relative to fixing base  10 . 
         [0039]    To complete the assembly of panels P 1  and P 2 , locking member  11  is inserted all the way into fixing base  10  by forcibly engaging elongated body  12  in cylindrical bushing  23  (in its bore  24 ). As the second transverse plate  25  of the base  10  slides along the elongated body  12 , the flexible detents  19   a,    19   b  bend in the transverse direction, while the contour of the circular opening  26  slides along the inclined portions of the detents  19   a,    19   b  until said inclined portions, and thus the detents  19   a,    19   b,  are released. The detents  19   a,    19   b  then return by elastic rebound to their natural configuration, such that their transverse portions come into contact with one of the faces of second plate  25 . The other face of second plate  25  is in contact with first plate  14 . Second plate  25  is therefore held in place between first plate  14  and the flexible detents  19   a,    19   b . The assembly of the first and second panels P 1  and P 2  is complete ( FIG. 7 ), and the panels P 1  and P 2  are braced by the superposition of the two transverse plates  14  and  25 . The assembly device is now in the nested state, and the shapes of the parts to which panels P 1  and P 2  are integral are such that the possibility of movement of the second panel P 2  relative to the assembly device (and thus relative to the first panel P 1 , via the clipping means) is eliminated. 
         [0040]    When the assembly device is in the nested state, the circular neck  21  of the barrel  20  of retaining head  13  constitutes a rupture zone interconnecting the retaining head  13  and the elongated body  12  of locking member  11 . Such a rupture zone, in practice, constitutes a cleavable, fusible region that tends to break under a predetermined external load applied to the assembly device, especially when such a load is transmitted to the device by one of the two panels P 1 , P 2  under the effect of an action external to the panels P 1 , P 2 , such as an impact sustained by one of the panels P 1 , P 2 . 
         [0041]    Any other equivalent means of creating such a rupture zone can be used, for example a region in which the material is locally different and more fragile, a region having a dotted-line-type discontinuous joint, a region containing a plurality of longitudinal support webs, etc. 
         [0042]    The assembly device described hereinabove further makes it possible to disassemble the panels P 1  and P 2 . With the device in the nested state, the user introduces an external tool into the bore  24  of cylindrical bushing  23 , from the open end thereof, until it is inserted in the coupling member  18  of circular peg  15 . The user then transmits a rotational torque to the locking member  11  so as to rotate it one quarter turn relative to the fixing base  10  (and thus relative to second panel P 2 ). The retaining head  13  is then guided by the hole  31  in second panel P 2 , and second panel P 2  can be removed from the assembly device, which, for its part, remains clipped to the first panel P 1 . 
         [0043]    A second effect of this relative rotation between the locking member  11  and the fixing base  10  is that the flexible detents  19   a,    19   b  of elongated body  12  are brought into registration with the notches  28   a,    28   b  of circular opening  26 . This disengagement of the flexible detents permits a longitudinal translation of locking member  11  in relation to fixing base  10  that tends to move the first and second transverse plates  14  and  25  away from each other. This translation is limited by the bosses  17   a,    17   b  coming into contact with the second transverse plate  25  of fixing base  10 , enabling locking member  11  to rotate freely again. Another quarter-turn rotation causes the bosses  17   a,    17   b  to be seated back in the notches  28   a,    28   b,  and the peripheral shoulder  29  to come into contact with the second transverse plate  25 . The locking member  11  is captive and can be used for a subsequent assembly. 
         [0044]    The possibility of relative movement of the second panel P 2  with respect to the assembly device as long as the device is not in the nested state is particularly advantageous when the first panel P 1  is a portion of an automobile chassis and the second panel P 2  is a fender portion of the automobile. With such a pair of panels P 1  and P 2 , the system constituted by the panels P 1  and P 2  assembled on the assembly devices and by the devices all in the pre-nested state is to be processed in a cataphoresis-type processing oven before all the devices are placed in the nested state. During this operation, the high temperatures to which the second panel P 2  (the fender) is exposed induce dimensional deformations of panel P 2 , and the possibility of relative movement of the second panel P 2  relative to the assembly devices permits the transverse displacements of second panel P 2  during its deformation. 
         [0045]    When the second panel P 2  is an automobile fender portion or bumper portion, the rupture zone interposed between the retaining head  13  and the elongated body  12  clearly serves to improve the safety of the prior-art devices by making it possible to release the fender or the bumper, respectively, in the event of an accident, thus creating an impact energy absorption zone. 
         [0046]    It goes without saying that the step of assembling the second panel P 2  with the aid of the retaining head  13  can be performed after the step of assembling the first panel P 1  with the aid of the clipping means without departing from the scope of the invention. Nor is the invention limited to the previously described shape of the retaining head  13 . In particular, a retaining head  13  that is placed in retention mode by rotating it one quarter turn is not exclusive; in this regard, it is possible to contemplate a retaining head that automatically goes into retention mode, for example a circular retaining head. 
         [0047]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.