Abstract:
In a casing for a hinge attachment of a car seat and to a method for its manufacture, the height of a toothed element is significantly larger than the thickness of walls of the hinge parts and the hinge parts and the toothed element form a statically compact casing unit, which has a distinctly reduced weight and simultaneously has distinctive flexible assembling characteristics, high stability under load and high accuracy. The casing and toothed element are separately produced by fine blanking and both parts are connected through a material connection or an form-fit connection.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a casing for a hinge attachment of a car seat with a first hinge part firmly connectable to the frame of the back of the seat, a second hinge part firmly connectable to the frame of the seat, wherein the hinge parts, with respective perpendicularly bent off edges abutting each other at their front ends and symmetrically arranged with regard to the hinge axle with formed hollows, form the casing, a toothed element belonging to the casing, the toothing of which at least extends over one segment of the circle and is radially directed to the inner side, and a clamping ring holding together the edges of the hinge parts. 
     The invention further relates to a method for manufacturing a casing for hinge attachments of a car seat, wherein the hinge parts and a toothed element are largely brought into their final shape by fine blanking and forming, especially by hobbing and drawing, and matched according to dimensions thereof. 
     Conventional seat adjustment components, e.g. fixed and swivelling hinge parts of hinge attachments, are produced by forming and fine blanking or precision blanking with high dimensional accuracy regarding the finally intended use. These hinge parts have internal toothings or external toothings transmitting rotational movements, which are formed in one piece by ejection (see, for example, DE 32 44 399 C2, DE 28 34 492 C2, DE 32 27 222 C1). 
     The known state of the art according to DE 32 44 399 C2 attempts to control the minimum dimension of the effective toothed areas necessary for transmitting the rotational movement and the load from one hinge part to the other hinge part by using, for fine blanking, a bigger crimp area than necessary for the ejection area, so that the surplus material to be crimped serves for broadening the respective effective toothed area in excess of the thickness of the source material. This leads to a minor broadening of the teeth in excess of the source material but also to an attenuation of the material between crimped and ejected area. Therefore, fractures in the event of sudden loads cannot be excluded. 
     Moreover, no significant reductions of the effective thickness of the hinge parts can be achieved, because the crimped area always is limited to the toothed area. 
     Moreover, in the case of very fine toothings, as is necessary for a continuous and jerk-free adjustment of the back, fine blanking reaches its technological limits. 
     The limitations of fine blanking of portions with small corner radii in relation to the thickness of the sheet to be cut and to the quality of the material are well known. Based on experience, a fine blanking severity is defined which distinguishes the severity degrees S1 (easy), S2 (medium) and S3 (difficult) (see “Umformen und Feinschneiden”, in Handbuch für Verfahren, Werkstoffe, Teilegestaltung, pages 154 to 165, Verlag Hallwag AG, 1997, Switzerland). Thus the severity degree is essentially defined by the cutting path geometry and the thickness of the metal sheet. For this, the cutting path geometry is divided into simple geometric basic areas such as corner radii, hole diameters, groove and fin widths. From the ratio between a geometric dimension and the thickness of the metal sheet results the severity degree of fine blanking, which grows with growing metal sheet thickness. 
     This means that obtuse-angled corners with big radii are to be cut better than sharp-cornered with small radii. 
     Moreover, EP 0 694 434 B1 discloses a hinge for a car seat. This hinge includes a first flange and a second flange, wherein the first flange is firmly connectable to the frame of the back of the seat and the second flange is firmly connectable to the frame of the seat. Both flanges put together form a case clamped together by a ring. 
     Furthermore, the first flange is equipped with a toothed ring with the teeth directed to the inner side and on a circular slide way may freely rotate in relation to the flange. 
     Also this known hinge attachment is relatively material consuming and thus weighty and not very convenient to handle in the assembling process. 
     In view of the state of the art, it is an object of the invention to provide a casing of a hinge attachment and a method for manufacturing such an attachment, wherein the height of the toothed element is significantly bigger than the thickness of the walls of the hinge parts and the hinge parts and the toothed element form a statically compact casing unit, which has a distinctly reduced weight and simultaneously has distinctive flexible assembling characteristics, high stability under load and high accuracy. 
     SUMMARY OF THE INVENTION 
     This object is fulfilled through a casing of a hinge attachment of the kind discussed above with a first hinge part connectable to a frame of a back of the seat and a second hinge part connectable to a frame of the seat. The hinge parts include respective perpendicular edges which extend in a direction of a hinge axis, and which abut each other at front ends thereof and thereby, being symmetrically formed with hollows therein, collectively define the casing. A toothed element produced by fine blanking having a generally encircling shape is receivable within the casing, and includes toothing which extends over at least one segment of the generally encircling shape and which is radially directed to an inner side thereof. A clamping ring holds together the edges of the hinge parts, with radially inner sides of the perpendicular edges of the first and second hinge parts being formed as an inner abutment for the toothed element, the toothed element being secured at a bottom face of said toothed element by a seating of each of the first and second hinge parts lying adjacent to the perpendicular edge thereof which is formed into the wall of one of the hinge parts. An outer side of the toothed element is fixed to the perpendicular edge through a connection peripherally extending approximately alongside a central plane of the toothed element at an inner corner of the perpendicular edge of the hinge part or by press-fit engagement and at least one form-fit connection, which substantially secures the toothed element in the direction of the hinge axis and/or prevents twisting about the hinge axis. 
     The solution according to this invention provides a compact casing of a hinge attachment, the toothed element of which has a thickness at least 1.7-fold bigger than the thickness of the material of the hinge parts. The toothed element gets an internal toothing with small radii, so as to create a large plane of action, which makes it possible to continuously transmit rotating movements in a jerk-free manner, but also big moments without problems. Of special advantage in this connection is that the toothed elements can be used with different heights and widths, so that hinge attachments can be provided, which are appropriate for special or determined loads. 
     Additionally, teeth width as well as diameter of the toothed element according to the field of application may be respectively varied. The toothed element with an outer surface thereof is supported by the bent off edge of the first hinge part and the edge of the inner surface lies in a seating, so that the toothed element in the direction of the x-axis is secured at its bottom. In the y-axis the toothed element is circularly connected to the edge of the first hinge part, wherein the material connection exists approximately in the middle of the teeth height. 
     The material connection between toothed element and first hinge part advantageously is carried out by laser welding, but may be realized by any other suitable material connection, such as another welding method or even by an adhesive joint. 
     Because the toothed element also carries out a supporting function, the thickness of the walls of the hinge parts can be significantly reduced, so that fine blanking and forming of the hinge parts can be realized with more simple and cost-effective tools. The use of multistage, more expensive production processes, is minimized. 
     Compared with the significantly more complex fine blanking combined with cold flow forming, the hinge parts are produced in simple fine blanking processes and manufactured to finished hinge attachments by a highly effective method. 
     Further advantages and details will be understood from the following description with reference to the applied figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective exploded view of a hinge part with a toothed element produced by fine blanking and cold forming; 
         FIG. 2  is a perspective cross-sectional view of a hinge part with an inserted toothed element; 
         FIG. 3  is a cross-sectional view of a casing of a hinge attachment assembled of a first and a second hinge part; 
         FIG. 4  is a perspective view of a form-fit assembled hinge attachment; and 
         FIGS. 5   a  to  5   d  depict possible variants of form-fit connections. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an exploded view of a first hinge part  1  as one half of a casing and a toothed element  2  with common hinge axis A. In the depicted example, the The first hinge part  1  was produced of a blank (not shown) with a thickness d of 4 mm, by fine blanking and forming. While depicted as circular in the example, the first hinge part is not limited to such geometrical shape. The finished part has a circular edge  3 , a central hole  4  for inserting a hinge axle (not shown) along a hinge axis A, a circular plane seating  5  for the toothed element  2  directly adjacent to the inner side of edge  3 , a depression  6  disposed concentric with regard to the hinge axis A for forming a circular inner edge, and four ejected recesses  7 , which serve for the fixing of the back of the seat to the frame by welding. 
     The second hinge part  8  has a substantially convergent design as the first hinge part  1 , and forms the second half of the casing. 
     The toothed element  2  has an outer diameter corresponding to the inner diameter of the edge  3 . Fine teeth  10  with a radius of for instance 0.3 mm are cut in the inner side  9  of the toothed element  2 , which extend over the entire height H of the toothed element  2  and at least over one segment of the circle of element  2 . Of course also the whole toothed element  2  may be equipped with teeth throughout an inner side thereof. 
     The toothed element  2  in this preferred embodiment, in comparison with the thickness d of the first hinge part  1 , has a height which is approximately 1.7-fold bigger, and thus is dimensioned significantly stronger. Depending on the height and the width of the toothed element, respective high moments can be received and transmitted. With the use of various toothed elements  2  with different heights and widths, it becomes possible to manufacture hinge attachments with different load limits. 
       FIG. 2  shows the toothed element  2  inserted into the first hinge part  1 . The bottom side of the toothed element  2  lies in the horizontal plane seating  5 , directly adjacent to the inner side  11  of edge  3  of the first hinge part  1 , and the outer side is supported by the inner side  11  of edge  3 , so that the toothed element  2  is secured perpendicular to the hinge axis A. The bent off circular edge  3  thus effectively forms an abutment  12  for the toothed element  2 . Because the toothed element  2  in comparison to the wall thickness d of the first hinge part  1  is dimensioned significantly stronger, the edge  3  ends approximately in the central plane ME of the toothed element  2 . The edge  3  then lies at a height of the toothed element  2 , which corresponds to about 45% of the height of the latter. 
     Along the central plane ME, the inner line  13  (inner corner) of the edge  3  is materially connected to the toothed element  2  by laser welding. Of course also other welded connections or adhesive connection are suitable. The circular welding connection  14  at the outer line  13  secures the toothed element  2  against detachment in the Y-direction or in the direction of the hinge axis A. 
       FIG. 3  shows the casing  15  comprised of the first hinge part  1  with a joint created by welding toothed element  2  and the second hinge part  8 . The second hinge part  8  of similar design with its outer edge  3  abuts on the edge of the first hinge part  1 . The edges  3  of both casing parts are encompassed by a clamp ring  16 , which fixes both parts at each other by clamping. 
       FIG. 4  shows a form-fit connection between toothed element  2  and the abutment  12  of the hinge part  1 . At the inner side of the abutment  12  extends the seating  5 , which is dimensioned to provide an interference fit when toothed element  2  is inserted. To prevent twisting of the toothed element  2  in relation to the abutment  12  at the vertical wall of abutment  12 , beads  18  are formed in regular distances concentrically to the hinge axis A, which when joined form-fit, lie in recesses  19  respectively placed on the outer perimeter of the toothed element  2 . 
       FIGS. 5   a  to  d  show possible versions of the form-fit connection between abutment  12  and toothed element  2 , wherein in  FIG. 5   a  the arrangement of bead  18  at the toothed element  2  and the respective recess  19  in abutment  12  is shown, in  FIG. 5   b  the version of  FIG. 4 , in  FIG. 5   c  is shown the alternating arrangement of form-fit connections  20  at the perimeter of abutment  12  and of toothed element  2  is shown, and in  FIG. 5   d  the arrangement of to aligned with each other recesses  19  forming a room  22  for inserting a lock pin  21  is shown. 
     When assembled and under load, the toothed element  2  respectively supports against the inner wall  11  of edge  3  of the first hinge part  1  and the second hinge part  8 . During transmission of the load the force is applied to the toothed element  2 , so that in case of a welded connection  14  the latter is not subject to shearing forces. 
     Where an interference fit between toothed element  2  and abutment  12  occurs, an equal division of the applied forces is applied to the form-fit connections regularly placed on the perimeter, so that a detachment of the interference fit is safely excluded. 
     With the method according to the invention, a casing  15  for a hinge attachment of a car seat with a wall thickness d of  4  mm is manufacturable. At first, the basic parts  1  and  8  are made from a blanking strip or sheet by conventional fine cutting and forming. Separately, the production of the toothed element  2  is carried out also by fine blanking. The components are produced in simple fine blanking tools, which are all known and the description of which can be omitted herein. 
     By virtue of inserting the toothed element  2  into the hinge part  1  tailored to the dimensions of the toothed element and welding the same with the toothed element  2  or pressing the toothed element  2  into the seating  5  of the hinge part  1 , an assembly suitable for hinge attachments is developed. By choosing a definite height and width of the toothed element  2  a casing  15 , a hinge attachment of a car seat can be manufactured for a definite load moment. 
     LIST OF DRAWING REFERENCES 
     
         
         first hinge part  1   
         toothed element  2   
         edge of  1  and  8   3   
         hole  4   
         seating  5   
         depression  6   
         recess  7   
         second hinge part  8   
         inner side of  39   
         fine toothing  10   
         wall of  1   11   
         abutment  12   
         inner line of  3   13   
         welded connection  14   
         casing  15   
         clamp ring  16   
         interference fit  17   
         bead  18   
         recess  19   
         form-fit connection  20   
         lock pin  21   
         insertion room  22   
         hinge axle A 
         bottom FE 
         height of  2  H 
         central plane ME