Abstract:
A vehicle seat ( 1 ), in particular a motor vehicle seat, has at least one fitting ( 10 ) including two fitting components ( 11, 12 ) that can rotate relative to each other. At least one structural component ( 15 ) has at least one opening ( 16 ) for partially receiving the fitting ( 11, 12 ) and at least one mounting area ( 18 ) enclosing the opening ( 16 ) for mounting the fitting ( 10 ), by at least one weld seam ( 19 ) between the mounting area ( 18 ) and one of the two fitting components ( 11, 12 ). The mounting area ( 18 ) is reinforced by additional material relative to the other areas of the structural component ( 15 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a United States National Phase application of International Application PCT/PCT/EP2009/008797 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Applications DE 10 2009 005 130.9 filed Jan. 13, 2009 and DE 10 2009 031 581.0 filed Jun. 30, 2009, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a vehicle seat in particular motor vehicle seat, with at least one fitting which has two fitting parts which are rotatable relative to each other, and with at least one structural part which has at least one opening for partially receiving the fitting and at least one fastening region which surrounds the opening and is intended for fastening the fitting. 
       BACKGROUND OF THE INVENTION 
       [0003]    DE 101 05 282 B4 discloses a vehicle seat of this type, the fittings of which, which serve as backrest adjusters, are fastened to adapters as structural parts. A further vehicle seat of this type is known from DE 20 2005 007 198 U1, the upper end of the structural part of which, the structural part serving as a backrest side strut, having a lower material thickness which increases toward the lower end. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention is based on the object of improving a vehicle seat of the type mentioned at the beginning. This object is achieved according to the invention by a vehicle seat with at least one fitting which has two fitting parts which are rotatable relative to each other, and with at least one structural part which has at least one opening for partially receiving the fitting and at least one fastening region which surrounds the opening and is intended for fastening the fitting, in particular by means of at least one first weld seam between the fastening region and one of the two fitting parts. The fastening region is reinforced in relation to the other regions of the structural part by further material. 
         [0005]    The structural part to which the fitting can be fastened may be any component of the structure of the vehicle seat, for example a backrest side strut, a seat frame side part or an adapter which is designed specially for the connection of the structure to the fitting and is fastened to the structure. The fitting may be any adjuster of the vehicle seat, for example a backrest adjuster or a seat inclination adjuster, if appropriate even a seat height adjuster. However, the term “fitting” is also intended to include all other possible gearing and locking joints and other joints. With regard to the internal construction which is not of significance to the present invention, the fitting may be, for example, a geared fitting or a detent fitting. In order to rotate the two fitting parts relative to each other, the fitting is correspondingly driven or unlocked. The invention is suitable in particular whenever the external design of the fitting is a disk shape providing few fastening options. The fastening preferably takes place by means of a (first) weld seam, which is intended to be understood as meaning any geometries and types of welding, for example thin laser weld seams, thick MAG welding beads or individual resistance weld points. 
         [0006]    Since the fastening region is reinforced in relation to the other regions of the structural part by further material, the material thickness is increased only in a small area, namely in the fastening region. The strength is increased in comparison to a substantially constant, low material thickness and, in particular, higher torques can be transmitted, while weight and costs are saved in comparison to a high material thickness which is identical throughout, while strength properties are comparable. In particular in the event of a crash, the forces which are introduced by the fitting or are to be passed on into the fitting can be better absorbed and passed on. The further material is preferably a material which drops off during the formation of the opening, i.e. the opening is not punched out to the final geometry thereof but rather to a smaller size, wherein material remains for a collar or for segments. The fastening region is then preferably formed by deforming or folding over a collar region of this type or by folding over at least one segment, in which case the folded-over region or the folded-over segment can be fixed to that region of the structural part which is not folded over, in particular by means of a second weld seam, which is in turn intended to be understood as meaning any geometries and types of weld. However, the fixing may also take place by means of an interlocking connection. 
         [0007]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    In the drawings: 
           [0009]      FIG. 1  is a sectional view through a part of the first exemplary embodiment along the line I-I in  FIG. 5 ; 
           [0010]      FIG. 2  is an enlargement view showing the detail II in  FIG. 1 ; 
           [0011]      FIG. 3  is a sectional view through the structural part before the formation of the fastening region; 
           [0012]      FIG. 4  is a sectional view through the structural part after the formation of the fastening region; 
           [0013]      FIG. 5  is a side view of a part of the first exemplary embodiment; 
           [0014]      FIG. 6  is a perspective view of a part of the first exemplary embodiment; 
           [0015]      FIG. 7  is a schematic view of a vehicle seat according to the invention; 
           [0016]      FIG. 8  is a schematic view of part of a section (detail VIII in  FIG. 21 ) through a fitting with a structural part according to the second exemplary embodiment; 
           [0017]      FIG. 9  is part of a perspective view of a metal sheet serving as a structural part, in a first production step; 
           [0018]      FIG. 10  is an enlarged sectional view along the line X-X in  FIG. 9 ; 
           [0019]      FIG. 11  is part of a perspective view of the metal sheet from  FIG. 9 , in a second production step; 
           [0020]      FIG. 12  is an enlarged sectional view along the line XII-XII in  FIG. 11 ; 
           [0021]      FIG. 13  is part of a perspective view of the metal sheet from  FIG. 9 , in a third production step; 
           [0022]      FIG. 14  is an enlarged sectional view along the line XIV-XIV in  FIG. 13 ; 
           [0023]      FIG. 15  is part of a perspective view of the metal sheet from  FIG. 9 , in a fourth production step; 
           [0024]      FIG. 16  is an enlarged sectional view along the line XVI-XVI in  FIG. 15 ; 
           [0025]      FIG. 17  is part of a perspective view of the metal sheet from  FIG. 9 , in a fifth production step; 
           [0026]      FIG. 18  is an enlarged sectional view along the line XVIII-XVIII in  FIG. 17 ; 
           [0027]      FIG. 19  is part of a schematic sectional view after the fitting and the structural part have been put together and prior to welding; 
           [0028]      FIG. 20  is a top view of an end region of the structural part together with the fitting; 
           [0029]      FIG. 21  is a longitudinal sectional view along the line XXI-XXI in  FIG. 20 ; 
           [0030]      FIG. 22  is a top view of an end region of the structural part together with the fitting, said structural part and fitting being connected to each other by an alternative welding method; 
           [0031]      FIG. 23  is a longitudinal sectional view along the line XXIII-XXIII in  FIG. 22 ; 
           [0032]      FIG. 24  is a detailed view of the detail XXIV in  FIG. 23 ; 
           [0033]      FIG. 25  is a schematic side view of a vehicle seat according to the invention; 
           [0034]      FIG. 26  is a partial view of the third exemplary embodiment without the fitting; 
           [0035]      FIG. 27  is a sectional view along the line XXVII-XXVII in  FIG. 26  with the fitting; 
           [0036]      FIG. 28  is a side cutaway view showing the structural part of the third exemplary embodiment as a blank with a punched-out central region; 
           [0037]      FIG. 29  is a side cutaway view showing the structural part from  FIG. 28  with deployed segments after a first deformation step; 
           [0038]      FIG. 30  is a sectional view along the line XXX-XXX in  FIG. 29 ; 
           [0039]      FIG. 31  is a partial view of the fourth exemplary embodiment; 
           [0040]      FIG. 32  is a sectional view along the line XXXII-XXXII in  FIG. 31 ; 
           [0041]      FIG. 33  is a sectional view through the structural part of the fifth exemplary embodiment with deployed segments after a first deformation step; 
           [0042]      FIG. 34  is a sectional view corresponding to  FIG. 33  with folded-over segments; 
           [0043]      FIG. 35  is a sectional view corresponding to  FIGS. 33 and 34  with edges formed; 
           [0044]      FIG. 36  is a partial view of a modification to the third to fifth exemplary embodiments without the fitting; 
           [0045]      FIG. 37  is a sectional view along the line XXXVII-XXXVII in  FIG. 36  with the fitting; 
           [0046]      FIG. 38  is a partial view of the sixth exemplary embodiment without the fitting; 
           [0047]      FIG. 39  is a sectional view along the line XXXIX-XXXIX in  FIG. 38  with the fitting; 
           [0048]      FIG. 40  is a side cutaway view showing the structural part of the sixth exemplary embodiment as a blank with a punched-out central region; 
           [0049]      FIG. 41  is a sectional view along the line XLI-XLI in  FIG. 40 ; 
           [0050]      FIG. 42  is a side cutaway view showing the structural part from  FIG. 40  with a deployed segment; 
           [0051]      FIG. 43  is a sectional view along the line XLIII-XLIII in  FIG. 42 ; 
           [0052]      FIG. 44  is a partial view of the seventh exemplary embodiment; 
           [0053]      FIG. 45  is a sectional view along the line XLV-XLV in  FIG. 44 ; 
           [0054]      FIG. 46  is a partial view of the eighth exemplary embodiment without the fitting; 
           [0055]      FIG. 47  is a view in the direction of the arrow XLVII-XLVII in  FIG. 46  without the fitting; 
           [0056]      FIG. 48  is a sectional view along the line XLVIII-XLVIII in  FIG. 46  with the fitting; 
           [0057]      FIG. 49  is a partial view of the ninth exemplary embodiment; and 
           [0058]      FIG. 50  is a sectional view along the line L-L in  FIG. 49 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0059]    Referring to the drawings in particular, a vehicle seat  1  for a motor vehicle has a seat part  3 , a backrest  4  which is attached by means of a respective fitting  10  on both sides of the vehicle seat to the seat part  3  and can be adjusted in inclination and/or freely pivoted relative thereto. In the present case, the fittings  10  are designed as detent fittings, the internal construction of which is described, for example, in WO 00/44582 A1 while said fittings, in respect of the external design thereof, have a disk shape, as described, for example, in U.S. Pat. No. 6,799,806 A. As an alternative, the fittings  10  are designed as geared fittings with an identical external design but with an internal construction as described, for example, in DE 44 36 101 A1 which discloses a self-locking eccentric epicyclic gearing. However, the internal construction of the fittings  10  may differ from said two known fittings. It is also possible to combine a single fitting  10  on one side of a vehicle seat with a joint on the other side of the vehicle seat. 
         [0060]    The two fittings  10  are in a geared connection to each other by means of a profiled transmission rod. The transmission rod is arranged horizontally and transversely with respect to the direction of travel and is rotatable about its own axis A. A hand lever (or hand wheel) which sits in a rotationally fixed manner on the transmission rod serves for the manual actuation of the fittings  10 . In the case of geared fittings, motorized actuation is also possible. The directional details below refer to the cylindrical coordinate system which is defined by the axis A. 
         [0061]    Each fitting  10  has a first fitting part  11  which is of approximately disk-shaped design and a second fitting part  12  which is likewise of approximately disk-shaped design. In order to hold together the two fitting parts  11  and  12  axially with insertion of the components arranged between said fitting parts, a clasping ring  13  is placed from the side of the first fitting part  11  onto the second fitting part  12  and, for example, is pressed onto and/or welded to same or flanged therearound. In this case, the first fitting part  11 , the second fitting part  12  and the clasping ring  13  form a disk-shaped (can-shaped) housing. The two fitting parts  11  and  12  support a driver  14  which interacts with the transmission rod, in particular is coupled thereto in a rotationally fixed manner or for carrying along therewith, and the rotation of which unlocks the fitting  10  (in the case of the latching fitting) or drives said fitting  10  (in the case of the geared fitting). The two fitting parts  11  and  12  are thus rotatable relative to each other. 
         [0062]    Although the disk shape affords the advantage of a compact constructional form, it is precisely for this reason, namely because of the small surfaces which are available, that particular challenges arise with regard to the technology for attaching the fitting to the structures of the seat part  3  and backrest  4 . For example, the attaching of the fitting  10  to a structural part  15  which is an integral subregion of the structure of the backrest  4  is described. An—at least approximately cylindrical—opening  16  is formed on the structural part  15 , said opening being surrounded annularly (or in an arcuate manner) by a fastening region  18  having edges  17 . The edges  17  which are arranged along two circular lines offset axially with respect to each other define the border of the opening  16 . The opening  16  may also have a different geometry, for example a star shape, or a different shape with cyclic symmetry with respect to the axis A. 
         [0063]    The structural part  15  may also be an integral subregion of the structure of the seat part  3  or a separate adapter which is connected to the structure of the backrest  4  or of the seat part  3 . The use of the invention is not limited to the connection of a fitting  10  to a seat part  3  and backrest  4 . On the contrary, said invention can be used in all cases of connecting fittings and components to structural components known to a person skilled in the art. For example, a fitting for a seat height adjuster can be attached in the same manner as described in DE 10 20009 008 576 A1 which is a subsequent publication. 
         [0064]    The fitting  10  is fitted to the structural part  15  by an end side having a shoulder  10   a , in the present case by that end side of the first fitting part  11  which faces away from the second fitting part  12 , wherein the shoulder  10   a  is inserted into the opening  16  until the fitting  10  bears against the fastening region  18 . The opening  16  then preferably receives the shoulder  10   a  in an interlocking manner. The fitting  10  fitted in this manner is connected, preferably welded, fixedly (i.e. nondetachably) to the structural part  15 , for example by means of one or more first weld seams  19  which are preferably produced by laser welding. The first weld seams  19  may also be produced by different types of welding, such as MAG welding. They may be circular, circular-arc-shaped, in the form of points or of a different geometry. The opening  16  is aligned with the axis A. The annular shape (or arc shape) of the fastening region  18  defines a radial width b (for example 4 mm) which is significantly smaller than the diameter d (for example 52 mm) of the opening  16 . The fastening region  18  may optionally be fixed by one or more second weld seams  20 . The second weld seam  20  may optionally be of a depth such that it reaches as far as the fitting  10  and therefore, in addition to (or instead of the) first weld seam  19 , fastens the fitting  10  to the structural part  15 . The second weld seams  20  may likewise be circular, circular-arc-shaped, in the form of points or of a different geometry and may be produced by laser welding, MAG welding or a different welding process. Instead of or in addition to a second weld seam  20 , the fastening region  18  may also be fixed by means of clinching, which can be integrated into the punching process and may optionally be supplemented later by additional second weld seams  20 . 
         [0065]    To produce an optimized connection between the structural part  15  and the first fitting part  11 , further material in relation to the remaining regions of the structural part  15  is accumulated in the fastening region  18  in order to reinforce the structural part  15  in the local surroundings of the fitting  10 . The additional material preferably originates from the spatial region which is now occupied by the opening  16 , i.e. slopes away during the formation of the opening  16 , and would normally be punched out as waste. For this purpose, starting from a metal sheet, in a preparatory step, a blank for the structural part  15  is punched out and the outer border  15   a  of the structural part  15  is optionally produced, for example a border which is bent over by approx. 90°—if appropriate in the same working step. At the same time or in a later step, a central region is punched out within a substantially planar, circular region which can be raised (by, for example, two material thicknesses) in the same direction as the outer border  15   a.    
         [0066]    The exemplary embodiments below differ with regard to the further machining of the structural part  15  and of the fastening region  18  produced. The method steps do not have to take place in individual manufacturing steps or molds. Depending on the mold concept, a plurality of method steps can be realized in one manufacturing step or one mold. 
         [0067]    In the first exemplary embodiment ( FIGS. 1 to 6 ), in order to produce the fastening region  18 , a collar is first of all produced from the material around the central, punched-out region ( FIG. 3 ), wherein the opening  16  with the diameter d thereof is also produced. The material of the axially protruding collar is subsequently deformed (by axial compression and radial pushing) in such a manner that the fastening region  18  is produced. The edges  17  are formed by further machining ( FIG. 4 ). 
         [0068]    The fastening region  18  is a part of the structural part  15  that is formed completely integrally with the other regions of the structural part  15 . Whereas the other regions of the structural part  15  are formed with a substantially constant, average material thickness x 1  (in the present case 1.2 mm), the fastening region  18 , by contrast, has an increased (enlarged) material thickness which increases continuously in the radial direction from the average material thickness x 1 —at the transition to the other regions of the structural part  15 —to a maximum material thickness x 2  (in the present case 1.5 mm)—at the border of the opening  16 , specifically, in the present case, of concave design in profile with a radius R (in the present case approximately 27 mm). 
         [0069]    The diameter of the projection having the shoulder  10   a  on the fitting  10  is somewhat smaller than the diameter d of the opening  16 , and therefore an annular gap with the gap width g is produced between the fastening region  18  and shoulder  10   a . The axial size of the gap is defined by the maximum material thickness x 2  of the fastening region  18 . The gap width g (for example 1.5 mm) can correspond approximately to the maximum material thickness x 2 , thus producing an at least approximately square cross section. However, a gap which is as small as possible, i.e. g&lt;&lt;x 1 , x 2 , b is preferred. The shoulder  10   a  then bears—at least approximately—flush against the fastening region  18  or the edges  17 . When the fitting  10  is inserted into the opening  16 , the first weld seam  19  is subsequently provided, for example by four welding beads which are arranged in the circumferential direction of the opening  16  and partially fill the gap, if present. For a laser weld seam as the first weld seam  19 , a very small, imperceptibly, small gap width g is preferred. 
         [0070]    In the second exemplary embodiment ( FIGS. 8 to 24 ), the fastening region  18  is produced from a circular-ring-shaped region  21   a  of the structural part  15 , which region is arranged around the central, punched-out region ( FIGS. 9 ,  10 ). Approximately the inner half of the circular-ring-shaped region  21   a  is bent outward through approx. 90° to form a collar region  21   b  ( FIGS. 11 ,  12 ), wherein the bending direction corresponds to that of the outer border  15   a . In a further step, said collar region  21   b  is bent outward further, i.e. is flanged forward, as illustrated in  FIGS. 13 and 14 , but this step may be omitted given suitable materials, material thicknesses and/or collar widths. In a subsequent step, the collar region  21   b  is flanged over to form a circular-ring-shaped, folded-over border region  21   c , i.e. that surface of the circular-ring-shaped region  21   a  which faces the direction of the outer border  15   a  and has not been bent over bears against that surface of the circular-ring-shaped, folded-over border region  21   c  which has been bent over by 180° ( FIGS. 15 ,  15 ). That part of the circular-ring-shaped region  21   a  which has not been bent over and the circular-ring-shaped, folded-over border region  21   c  together form the fastening region  18  (x 2 =2·x 1 ) which is preferably fixed by the second weld seam  20 , i.e. by a nondetachable connection of the regions  21   a  and  21   c . Depending on the dimensional accuracy of the deformation operation, in a subsequent step, further finishing with correction of the inside diameter of the remaining circular opening  16  and the formation of the edges  17  can take place, for example by means of a further deformation operation, but if appropriate also with cutting ( FIGS. 17 ,  18 ). The fitting  10  is subsequently fastened to the finished structural part  15 . 
         [0071]    In the third to fifth exemplary embodiments ( FIGS. 26 to 35 ), a star is punched out as the central region ( FIG. 28 ). This results in the production in the circumferential direction of a plurality of segments  31  next to one another which have, for example, a trapezoidal or rectangular form and are separated from one another by gaps. The segments  31  are deployed like a collar by 90° with respect to the non-deformed region of the structural part  15  ( FIGS. 29 ,  30 ,  33 ), i.e. they point in the axial direction. The segments  31  are subsequently folded over (crimped) further radially outward such that they rest on the adjacent region of the structural part  15  in the form of a doubling of the material (x 2 =2·x 1 ) ( FIG. 34 ). The annular region which is doubled at some point forms the fastening region  18 . The folded-over segments  31  are fixed to that region of the structural part  15  which is not folded over, and are preferably connected thereto by means of a respective second weld seam  20  (preferably laser weld seam) ( FIGS. 26 ,  27 ,  31 ,  32 ). By means of appropriate punch geometries and calibrating operations, the material at the bending edge on the outside is shaped as far as possible without bending radii and, instead, the edges  17  are formed by further processing of said transition region between the region which is not folded over and the region which is folded over ( FIG. 35 ). This permits improved welding later on to the fitting  10 . 
         [0072]    In the third exemplary embodiment ( FIGS. 26 to 30 ), the segments  31  are spaced apart from one another by a spacing similar to the width thereof, i.e. the distance between the segments  31  and the width of the segments  31  are approximately identical in the circumferential direction. For example, six segments  31  are produced with a width of approximately 30° on average, with gaps in between which likewise have a width of approximately 30° on average. Said segments  31  are, for example, all folded over in the same direction, namely from the plane of that region of the structural part  15  which is not folded over onto that side of the structural part  15  which faces away from the fitting  10 . When the edges  17  are formed, the region between the segments  31  is preferably deformed in such a manner that a small part thereof lands on the side of the folded-over segments  31 . 
         [0073]    In the fourth exemplary embodiment ( FIGS. 31 ,  32 ), the segments  31  are of significantly smaller width and are spaced apart from one another at an even smaller distance, for example are of a width of on average 10° with an average distance therebetween of 5°. The individual segments  31  are, for example, all folded over onto that side of the structural part  15  which faces away from the fitting  10  and are secured by a respective second weld seam  20 . 
         [0074]    In the fifth exemplary embodiment ( FIGS. 33 to 35 ), the segments  31  are folded over in an alternating manner on different sides of that region of the structural part  15  which is not folded over. Every second segment  31  is folded over onto the side facing away from the fitting  10 , and every second segment  31  which is offset thereto is folded over onto the side facing the fitting  10 . This results overall in triple the material thickness (x 2 =3·x 1 ) for the fastening region  18 , but only at some points in the circumferential direction and not over the full circumference. 
         [0075]    In a modification ( FIGS. 36 ,  37 ) to the three abovementioned exemplary embodiments, only every second segment  31  is folded over and fastened by means of a second weld seam  20 . The segments  31  which are not folded over project radially inward into the opening  16  and, when the fitting  10  is connected, come to lie on the end side thereof. 
         [0076]    In the sixth exemplary embodiment ( FIGS. 38 to 43 ), the punched-out segment  31  has a lunar shape (arc shape) with a connecting web  45  to the (upper) border of the opening  16  which is otherwise punched out to be circular ( FIGS. 40 ,  41 ). The connecting web  45  is first of all folded once in the center thereof by 90° ( FIGS. 42 ,  43 ) and then once again by 90° such that the segment  31  comes to lie on the (upper) border of the opening  16  on the structural part  15 . By means of a second weld seam  20 , which also includes the weld points, the segment  31  is connected to that region of the structural part  15  which is not folded over, thus resulting in the fastening region  18 . In contrast to the three previous exemplary embodiments, the fastening region  18  is not completely distributed over the circumference of the opening  16  but rather is present merely in an arcuate manner on the upper border which is subjected to a higher load. In order to form the edge  17 , the connecting web  45  is cut, for example punched, to size, as a result of which the opening  16  reaches the final size thereof ( FIGS. 38 ,  39 ). 
         [0077]    The seventh exemplary embodiment ( FIGS. 44 ,  45 ) is a modification of the second exemplary embodiment. As there, a collar region is produced, of which, however, only one part, for example, only approximately half of the axial length thereof, is bent back obliquely and placed on the circular-ring-shaped region  21   a , it is preferably also fixed there by the second weld seam  20 . This results in a triangular profile. 
         [0078]    In the eighth exemplary embodiment ( FIGS. 46 to 48 ), an axial widening (x 2 &gt;x 1 ) is achieved by a fastening region  18  which is wave-shaped in the axial direction (and circumferential direction), without additional material being required. 
         [0079]    In the ninth exemplary embodiment ( FIGS. 49 ,  50 ), the additional material of the fastening region  18  originates from an additional part  55  which is punched out separately with an opening  56 . The opening  56  of the additional part  55  preferably has the same geometry as the opening  16  of the structural part  15 . The additional part  55  is fitted to the structural part  15  in such a manner that the openings  16  and  56  are aligned, and is subsequently welded to the structural part  15  by means of the second weld seam  20 . The resultant fastening region  18  then has twice the material thickness as the structural part  15  (x 2 =2·x 1 ). The additional part  55  may be of annular design, or it has a drop shape, the pointed end pointing upward and reinforcing that part of the fastening region  18  which is subjected to a higher load. The fitting  10  is then fitted to the structural part  15  by, for example, the first fitting part  11  being inserted by the shoulder  10   a  into the openings  16  and  56 . The fitting  10  and the structural part  15  are subsequently welded to each other by means of the first weld seam  19 . In a modified embodiment, the opening  56  has a smaller diameter than the opening  16  such that the fitting  10  is inserted until it bears against the additional part  55 . 
         [0080]    Further reinforcement possibilities are also conceivable. Furthermore, a reinforced fastening region  18  can be produced by hardening, for example of a boron steel. 
         [0081]    While specific embodiments of the invention have been described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.