Abstract:
A motor vehicle seat with a belt that can be stretched across the lower back portion of the seat. The belt can be tightened to varying degrees, and serves as a lordotic support. One end of the belt winds onto a belt drum that can be activated by a hand-operated wheel.

Description:
FIELD OF THE INVENTION 
     The invention relates to a motor vehicle seat with a belt that is embodied as a lumbar support. 
     BACKGROUND OF THE INVENTION 
     In the case of a motor vehicle seat of the known type (EP 05 77 696 B 1), a belt, which is led at one end in such a way that its position may be shifted, extends between the lateral capping pieces of a backrest. A curved element that is capable of being pivoted, as a result of whose repositioning the belt may be tightened to varying degrees, engages a cut-out of the belt or a slide that is connected to it by means of a cable. As a result of the cut-out, the belt is considerably weakened in terms of its sturdiness. Even the provision of a cable that transfers the tightening force is problematical. Furthermore, the range for repositioning the known belt is rather limited. 
     SUMMARY OF THE INVENTION 
     Taking this state of the art as a point of departure, it is the underlying task of the invention to embody a motor vehicle seat, of the type that may be presumed to be known, in such a way that the tension of the belt that constitutes the lumbar support may be repositioned across a wide area, and that the tensioning member can engage the belt without weakening it. 
     The resolution of this task is accomplished with the characteristics of a motor vehicle seat with a belt that is embodied as a lumbar support. 
     The lumbar support can be repositioned in an area whose size is practically arbitrary. The repositioning device saves space and is sturdy, and it can be housed in any ordinary backrest. The tensioning force is introduced to the belt uniformly across the entire cross-section of the belt so that the belt cannot be over-burdened at the point of engagement. 
     In what follows, a preferred embodiment form of the invention is described in detail by virtue of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the front view of a backrest with a lumbar support; 
     FIG. 2 shows an enlarged cut-out of the backrest with the repositioning device for the lumbar support according to FIG. 1 in the slackened state; 
     FIG. 3 shows a cross-section through the backrest according to FIG. 1 with a completely slackened lumbar support in keeping with FIG. 2; 
     FIG. 4 shows a cut-out of the backrest according to FIG. 1 that is in keeping with FIG. 2, when the lumbar support is tightened; 
     FIG. 5 shows a cross-section through the backrest according to FIG. 1 with a lumbar support in keeping with FIG. 4 that is maximally tightened. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Only the frame of a backrest  1  of a motor vehicle seat, with lateral capping pieces  1   a  and  1   b,  is depicted in the drawings. In the region of the seat user&#39;s lumbar region, a belt  2  is stretched horizontally, as a lumbar support, from one lateral capping piece  1   a  to the capping piece that lies opposite it,  1   b.  One end of belt  2  is attached to the lateral capping piece  1   a , whilst the other end is wound onto a belt drum  3 . The belt drum  3  is seated so as to be capable of rotation around a winding axis  3   a,  likewise on lateral capping piece  1   a.    
     On the lateral capping piece  1   a,  a flange  4   a  is provided in which a gear shaft  5   a,  with a horizontal axis which belongs to a set of gears  5  that is embodied as an angular gear that is attached by means of a flange to the lateral capping piece  1   a,  is seated so as to be capable of rotation. On the gear shaft  5   a,  a hand-operated wheel  4  is attached parallel to a lateral surface of the rest  1   c.  By way of the set of angular gears  5 , the belt drum  3  is turned by the hand-operated wheel  4  around its winding axis  3   a,  which runs vertically. In the process, depending upon the direction of rotation, belt  2  is either wound onto belt drum  3  or is unwound off it. 
     One end of a draw rope  9 , which passes through the flange  4   a  in a bore hole  4   b,  is attached to the circumference of the gear shaft  5   a.  A spring  10 , which is attached so as to hang onto lateral capping piece  1   a,  engages at the other end of draw rope  9 . On the draw rope  9 , a stop  8 , which lies against an opposing stop  4   b  of the flange  4   a  grips when the draw rope  9  is wound up onto gear shaft  5   a.    
     According to FIG. 3, the belt  2  follows a course with a first portion of a conveyor  2   a  from a point of attachment on the lateral capping piece  1   a  to a deflection roller  6 , and with a second portion of a conveyor  2   b,  from this deflection roller  6  to belt drum  3 . The deflection roller  6  is seated on lateral capping piece  1   b  in such a way that it is capable of rotation by means of a strap  7   a.  In addition, a guide roller  7 , which is capable of rotation around an axis that is parallel to the axis of the deflection roller  6 , is also borne by the strap  7   a.  The guide roller  7  maintains contact between the first portion of the conveyor  2   a  and the portion of the conveyor that runs in the opposite direction,  2   b.    
     In the depiction of FIG. 1, half of belt  2  is wound onto belt drum  3 . The belt  2  runs in a position of medium tension. The draw rope  9  is completely unwound from gear shaft  5   a,  and spring  10  is, in large measure, relaxed. The hand-operated wheel  4  can be repositioned in either direction of rotation such that belt  2  is either unwound or wound up, depending upon the direction of rotation. 
     In FIGS. 2 and 3, belt  2  is depicted in the relaxed state. The hand-operated wheel  4  is turned in the counterclockwise direction. The draw rope  9  is wound onto gear shaft  5   a,  and spring  10  has been stretched. Belt  2  has completely unwound itself from belt drum  3 . Due to the pressure exerted upon the belt by the seat&#39;s user and by the upholstery, the length of belt  2 , which has become unwound from belt drum  3 , has run so far around deflection roller  6  that one portion of conveyor  2   a  makes contact with the portion of the conveyor  2   b  connected to belt drum  3 . 
     FIGS. 4 and 5 depict belt  2  in its tightened position. Belt  2  is wound up by means of hand-operated wheel  4  onto belt drum  3  in excess of the length that forms the underlying assumption of FIG.  1 . Draw rope  9  is unwound off the coil that is depicted in FIG. 2, until it reaches that which is depicted in FIG. 1, and wrapped in the opposite direction, that is, clockwise, onto gear shaft  5   a  until contact is made once more between stop  8  and the opposing stop  4   b  of the flange  4   a  . In the process, belt  2  has been drawn by belt drum  3 , by way of deflection roller  6  and guide roller  7 . 
     In the desired position of tension of belt  2 , depending on the case, the belt drum  3  is held fast by means of a catching of the hand-operated wheel  4 , or by means of self-inhibition in the set of gears  5 . The catching or self-inhibition, respectively, cannot be overcome as a result of the spring  10 , either. 
     The foregoing description of the invention illustrates and describes the present invention. Additionally, the disclosure shows and describes only the preferred embodiments of the invention but, as mentioned above, it is to be understood that the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with the various modifications required by the particular applications or uses of the invention. Accordingly, the description is not intended to limit the invention to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.