Patent Publication Number: US-7581424-B2

Title: Method for the reinforcement of a wall region of a three-dimensional attachment

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a method for the reinforcement of a wall region of a three-dimensional attachment, especially car seat components for high torque loads, wherein a plate with a substantially evenly curved outer contour is cut out of a flat strip and, subsequently, the plate is formed and fine blanked into a pot-shaped body with projections and/or impressions and/or indentations and/or recesses and/or sinks and/or holes and/or pivots by means of a forming and fine blanking tool including die, counter-die, die plate, V-shaped projection and pressure plate, whereby a circular edge for a toothing is formed at the body. 
   Conventional seat adjustment components, for example, fixed and swiveling hinge parts of hinge attachments, are produced by forming, fine blanking or stamping with the necessary high dimensional accuracy for their final use (see, for example, EP 0 694 434 B1, DE 32 44 399 C2, DE 28 34 492 C2, DE 32 27 222 C1). 
   These known hinge parts substantially consist of a pot-shaped body with projections and/or impressions and/or indentations and/or recesses and/or sinks and/or holes and/or pivots. The body is provided with an evenly curved outer contour having a circular edge, into which is formed a toothing which is radially directed to the inner side thereof. This toothing has to functionally transmit very high rotational moments, so that the wall region between edge and body, i.e., the connection to the pot-shaped body, receives substantial loads, which often lead to fractures. This impairs the safety and reliability of the seat adjustment components. 
   In view of the aforementioned state of the art, it is an object of the invention to provide a method by which hinge attachments with a much higher safety with regard to fracture of the wall region between the edge with an inner toothing and the pot-shaped body of the hinge attachment can be produced in a cost-effective way. 
   SUMMARY OF THE INVENTION 
   This object is solved by a method of the kind discussed above, wherein a process according to the invention includes cutting a plate out of a flat strip with a substantially evenly curved outer contour and forming and fine blanking the plate into a pot-shaped body with a desired structural configuration including a surface formation, whereby at the body is formed a curved edge for a toothing. The thus formed pot-shaped body includes a wall region between the curved edge and a base thereof. By performing at least a two-staged cold-extrusion process in respectively opposite flow directions angular to a respective die movement prior to said step of forming to cause a purposeful material shifting in an area of the plate corresponding to the wall region to a degree that approximately equalizes runoff of the material caused by the subsequent forming, the wall region of the attachment is reinforced when formed. 
   In accordance with the hinge attachment produced according to the method of the invention, because the thickness of the wall region between the edge and the pot-shaped body of the attachment reaches a wall thickness approximately equal to the original wall thickness by a purposeful material shifting with at least a two-staged cold-extrusion process in respectively opposite flow directions angular to the die movement despite forming, a hinge attachment is formed without problems and withstands extremely high fracture loads. 
   The invention provides particular further advantage, in that high rotational moments can be transmitted without problems, so that hinge attachments are provided which are also suitable for special or defined load values, for example, for fixing a safety belt to the back of the seat of a car. 
   The shifting of material into the wall region of the connection provides additional advantage, in that the cutting becomes possible over the whole thickness of the material, so that the application of fine blanking becomes economically efficient, also, with complex and complicated three-dimensional multi-functional parts. 
   Further advantages and details will be understood from the following description with reference to the enclosed drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view through a hinge attachment according to the invention; 
       FIG. 2  is an enlarged view of a crack in the connection region between an edge and the pot-shaped body of the hinge attachment; 
       FIGS. 3   a  to  3   d  each is a schematic diagram of the sequences of the method according to the invention; and 
       FIG. 4  is a perspective view of a section through a three-dimensional hinge attachment produced according to the method of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In accordance with the method of the invention, three-dimensional multifunctional hinge attachments  1  for car seat components can be produced, which are fracture-proof at high loads, for example, up to 6000 N. 
     FIG. 1  shows a section through a circular hinge attachment  1 , which was produced out of a plate  2  of a flat steel strip with a thickness of for example 3 to 8 mm. It is noted, however, that hinge attachment  1  is not limited to such geometrical shape. 
   The plate  2  undergoes a combined forming and fine blanking process in the course of which the three-dimensional hinge attachment  1  is created. 
   The hinge attachment  1  comprises a pot-shaped body  3 , in which projections  4 , impressions  5 , a depression  6  and a hole  7  are formed by forming operations. The body  3  has a circular edge  8 , which is provided with a toothing  9  radially directed to the inner side. Depression  6  and edge  8  are connected by a wall region  10 . 
   The wall region  10  between the edge  8  and the indentation  6  of the pot-shaped body  3  is weakened during forming, i.e., a flow of material takes place from the wall region  10  in the direction of the indentation  6 . This, under load, leads to the crack R in the wall region  10 , shown in  FIG. 2 . 
     FIGS. 3   a  to  3   d  schematically show the sequence of operations of the method according to the invention. According to  FIG. 3   a , the plate  2  is firmly fixed between a pressure pad  11  and a die plate  12 . A die  13  controlled by the pressure pad  11  executes an upward movement in the direction SM of the die plate  12 . In the die plate  12  is provided a space  14 , which lies slightly offset in relation to the die axis A. 
   In the first step of the method according to this invention, the die  13  moves upward in the direction of die plate  12 , whereby a respective material volume V flows into the space  14  sideward of die  13  (see direction of arrow C). This material volume V fills the space  14  and thus at the side G of plate  2  opposite to die  13  occurs a material accumulation  15 . 
   The thus formed plate  2 , in the second step of the method according to the invention, additionally is fixed by a V-shaped projection  16  and the material accumulation  15  at the opposite side G by a counter-die  17  is shifted in a direction contrary to the direction of arrow C (see direction of arrow D), so that material flows into a space  18  sideward of die  17  and strengthens the wall region  10  between edge  8  and indentation  5  in the pot-shaped body  3  to the wall thickness s (see  FIGS. 3   c  and  3   d ), which, in this example, approximately corresponds with the material volume lost by flow during forming. 
   By dimensioning the spaces  14  and  18  the material volume V to be shifted can be determined, whereby it is possible to strengthen the wall thickness s of the wall region  10  to a value that is safe for a defined fracture load. Such a fracture-proof hinge part  1  is shown in  FIG. 4 . The dimensioning of spaces  14  and  18  results from the flow properties of the material of plate  2 , the hardness and stability under load of the dies  13  and  17 , the lubricant, the design of the tool as well as the necessary fracture load in the case of application. 
   Thus it becomes possible to reach fracture safeties much higher than the fracture load of these wall regions. 
   
     
       
         
             
           
             
                 
             
             
               List of drawing references 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
          
             
                 
               hinge attachment 
               1 
             
             
                 
               plate 
               2 
             
             
                 
               body of 1 
               3 
             
             
                 
               projections 
               4 
             
             
                 
               impressions 
               5 
             
             
                 
               depression 
               6 
             
             
                 
               hole 
               7 
             
             
                 
               edge 
               8 
             
             
                 
               toothing 
               9 
             
             
                 
               wall region between 8 and 6 
               10 
             
             
                 
               pressure pad 
               11 
             
             
                 
               die plate 
               12 
             
             
                 
               die 
               13 
             
             
                 
               space in 12 
               14 
             
             
                 
               material accumulation 
               15 
             
             
                 
               V-shaped projection 
               16 
             
             
                 
               counter-die 
               17 
             
             
                 
               space in pressure pad 
               18 
             
             
                 
               die axis 
               A 
             
             
                 
               direction of arrow in flow direction 
               C 
             
             
                 
               direction of arrow contrary to flow direction 
               D 
             
             
                 
               opposite side of 2 
               G 
             
             
                 
               crack in 10 
               R 
             
             
                 
               direction of die 13 
               SM 
             
             
                 
               wall thickness of 10 
               s 
             
             
                 
               material volume 
               V