PATENT ABSTRACT
A belt buckle feeder for a vehicle seat belt system includes a spindle drive and a belt buckle ( 12 ) mounted on a spindle ( 14 ) of the spindle drive, the belt buckle being movable in height via a spindle nut ( 28 ) located on the spindle ( 14 ). A safety mechanism comprising at least one locking element ( 44 ) is provided which is configured so that the locking element ( 44 ) enters into force fit and/or form fit with the spindle ( 14 ), when a predetermined force threshold is exceeded, and introduces force acting on the belt buckle ( 12 ) in the extending direction (R) of the spindle ( 14 ) into a mounting point fixed to the vehicle white bypassing the spindle drive.

PATENT DESCRIPTION
RELATED APPLICATIONS 
       [0001]    This application corresponds to PCT/EP2013/002246, filed Jul. 29, 2013, which claims the benefit of German Application No. 10 2012 016 211.1, filed Aug. 16, 2012, the subject matter, of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a belt buckle feeder for a vehicle seat belt system. 
         [0003]    Belt buckle feeders as they are called assist the buckling operation in passenger cars by moving the belt buckle along a defined distance from a home position into a feeding position in which the belt buckle can be better grasped by the vehicle occupant. After inserting the plug-in tongue into the belt buckle, the latter is moved back from the feeding position into the home position. 
         [0004]    Such system is intended to be as space-saving as possible and to be manufactured at low cost. At the same time, however, it has to be ensured that even when high forces are acting on the belt buckle, for example in the case of accident, the belt buckle cannot be removed from its home position. 
       SUMMARY OF THE INVENTION 
       [0005]    It is the object of the invention to provide a belt buckle feeder which meets these requirements. 
         [0006]    In accordance with the invention, this is achieved in a belt buckle feeder for a vehicle seat belt system including a spindle drive and a belt buckle secured to a spindle of the spindle drive and being movable in height via a spindle nut located on the spindle. A safety mechanism comprising at least one locking element is provided, wherein the safety mechanism is configured so that, when a predetermined force threshold is exceeded, the locking element enters into force fit and/or form fit with the spindle and introduces force acting in the extending direction of the spindle on the belt buckle into a mounting point fixed to the vehicle while bypassing the spindle drive. This configuration offers the option of avoiding to design the spindle drive and especially the spindle nut for the maximum forces acting during accident, thereby allowing to configure these components to be smaller, more light-weight and cost-effective. Merely the safety mechanism and the locking element have to be designed for absorbing the high forces; they are not necessarily part of the travel mechanism, however. 
         [0007]    According to the preferred embodiment it is provided that the safety mechanism is a movable mechanical bridge capable of adopting two positions. In a first position the safety mechanism does not enter into force and/or form fit with the spindle. In the second position such force and/or form fit with the spindle is provided, however. Moreover, the safety mechanism is always tightly hinged to a vehicle-side mounting point so that, when the bridge is deflected, the direct mechanical coupling from the spindle to the mounting point is provided. 
         [0008]    The safety mechanism preferably includes at least one deflecting member configured so that, when the force threshold is exceeded, it varies its position, thereby the locking element adopting an engaged position in which it contacts the spindle. The looking element can be a component separate from the deflecting member; however, the two components can also be tightly connected to each other. 
         [0009]    The change of position of the deflecting member upon the application of force can be effectuated by displacing, pivoting or deforming the deflecting member. This change of position performed by the deflecting member for moving the locking element corresponds to a short extending distance of the spindle in its direction of extension toward the feeding position. This distance preferably amounts to not more than few millimeters. 
         [0010]    The deflecting member is deflected, for example, by the spindle nut when the predetermined force is exceeded. The deflecting member can be a bearing of the spindle nub The bearing is a component constantly in contact with the spindle nut to which direct force transmission by the spindle not in the case of tensile force acting on the spindle is easily possible. The bearing of the spindle nut simultaneously can be the bearing of the spindle drive. 
         [0011]    When the predetermined force threshold is exceeded by force acting on the spindle nut, the deflecting member can deform or pivot by the force transmitted from the spindle nut to the deflecting member and thus can deflect the locking element into the engaged position. 
         [0012]    The locking element should be configured to be dimensionally stable even above the force threshold in the case of the forces usually occurring during an accident, advantageously also during a serious accident. 
         [0013]    There can be provided two looking elements which are preferably facing each other with the spindle being arranged there between. 
         [0014]    The predetermined force threshold preferably is approx. 7 to 9 kN. With forces of this order the deflecting member, i.e. for example the bearing of the spindle nut, then will advantageously yield. Of preference, the spindle nut itself and the connection of the spindle nut to the spindle thread are designed for forces ranging from 10 to 15 kN so as to form a safety margin. A breaking load of the locking element, on the other hand, preferably is more than 25 kN so as to ensure safe restraint of the vehicle occupant even in the event of serious accidents. 
         [0015]    Forces above the predetermined force threshold can be introduced directly from the locking element into a mounting of the belt buckle feeder fixed to the vehicle and in this way virtually completely bypass the spindle drive including the spindle and the spindle nut. 
         [0016]    It is possible to pivot the locking element to the deflecting member and/or to a casing shell. For example, the locking element can be riveted to the casing shell. 
         [0017]    A pivoting motion of the locking element for moving the latter into the engaged position is advantageous, as a change of position of the deflecting member can be easily transformed into such pivoting motion, without the deflecting member having to cover large distances. 
         [0018]    The locking element preferably can be coupled to the spindle between the buckle head and the spindle nut. In this manner tensile forces can be directly transmitted from the belt buckle via the stable spindle to the locking element and to the vehicle body. 
         [0019]    The spindle nut preferably includes a stop which enters into contact with the deflecting member. Hence tensile force acting on the belt buckle is directly transmitted via the spindle nut to the deflecting member which changes its position when the tensile force exceeds the predetermined force threshold. 
         [0020]    The stop can be in the form of a peripheral shoulder on the spindle nut, for example. 
         [0021]    When the looking element is pivoted, a hinge point for pivoting can also be used as hinge point of the deflecting member. The deflecting member is thus enabled to both deform and pivot. 
         [0022]    In a preferred embodiment the looking element includes an eyelet extending through the spindle, wherein in the engaged position an inner edge of the eyelet engages in the outer periphery of the spindle. In this way both a force fit and a form fit are occurring, as the inner edge of the eyelet can dig into the spindle to a certain degree. In this way a safe force-transmitting connection is formed between the spindle and the locking element. 
         [0023]    It is sufficient to simply pivot the locking element by e.g. about 5° to 30° to incline the eyelet such that it enters into contact with the spindle. The displacement of the locking element in its engaged position thus can be caused by only a little change in position of the deflecting member. 
         [0024]    Advantageously, the flux of force extends from the spindle via the locking element and at least one casing shell to a fastening point of the casing shell on the vehicle. The casing shell can be an outer sheath of the belt buckle feeder and can also constitute the mounting thereof fixed to the vehicle. 
         [0025]    In a preferred embodiment the bearing, the spindle nut, the spindle and the entire spindle drive are enclosed by two casing shells. 
         [0026]    Since the spindle nut does not have to absorb high forces, it can be manufactured of plastic material, which reduces the weight of the belt buckle feeder. 
         [0027]    The spindle nut can be driven, for example, via a gearwheel, a worm gear or a bevel gear in a known manner. 
         [0028]    The spindle nut can be driven directly by an electric motor, but it is of advantage to connect the spindle nut to a flexible shaft and the latter to the electric motor or to any other suitable drive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Hereinafter the invention will be described in detail by way of an embodiment with reference to the enclosed drawings, in which: 
           [0030]      FIG. 1  shows a schematic perspective view of a belt buckle feeder according to the invention in its home position; 
           [0031]      FIG. 2  shows the belt buckle feeder of  FIG. 1  in its feeding position; 
           [0032]      FIG. 3  shows a schematic sectional view of the belt buckle feeder of  FIG. 1  in the home position; 
           [0033]      FIG. 4  shows a schematic sectional view of the belt buckle feeder of  FIG. 1  in the feeding position; 
           [0034]      FIG. 5  shows a schematic front view of the belt buckle feeder of  FIG. 1  in the home position; 
           [0035]      FIG. 6  shows a schematic front view of the belt buckle feeder of  FIG. 1  in the feeding position; 
           [0036]      FIG. 7  shows a schematic side view of the belt buckle feeder of  FIG. 1  in the home position; 
           [0037]      FIG. 8  shows a schematic side view of the belt buckle feeder of  FIG. 1  in the feeding position; 
           [0038]      FIG. 9  shows a schematic sectional view of the belt buckle feeder of  FIG. 1  upon application of force above the predetermined force threshold; 
           [0039]      FIG. 10  shows a schematic perspective view of the belt buckle feeder of  FIG. 9 ; 
           [0040]      FIG. 11  shows a schematic perspective view of a bevel-gear drive for the spindle drive of a belt buckle feeder according to the invention; 
           [0041]      FIG. 12  shows a schematic sectional view of the subassembly of  FIG. 11 ; 
           [0042]      FIG. 13  shows a schematic perspective view of a worm-gear drive for a spindle drive of a belt buckle feeder according to the invention; and 
           [0043]      FIG. 14  shows a schematic sectional view of the subassembly of  FIG. 13 . 
       
    
    
     DESCRIPTION 
       [0044]      FIG. 1  illustrates a belt buckle feeder  10  including a belt buckle  12  the lower end of which is tightly secured to a spindle  14 . The spindle  14  is pan of a spindle drive described further below which in the example illustrated here is driven by means of a flexible shaft  16  coupled to an electric motor  18 . 
         [0045]    The spindle  14  can be moved in height via the spindle drive (see arrow R) so that the belt buckle  12  can adopt a home position in which the spindle  14  is most retracted and a feeding position in which the spindle  14  is most extended (see  FIGS. 1 and 2 , for example). The belt buckle  12  is moved into the feeding position only in driving situations related to buckling and unbuckling so that it is more convenient for a vehicle occupant to grasp the belt buckle  12 . In all other driving situations the belt buckle  12  is provided in the home position ( FIG. 1 ). 
         [0046]    The belt buckle  12  is connected to the spindle  14  so that also high forces occurring during accident, for instance, can be transmitted from the belt buckle  12  to the spindle  14 . The belt buckle  12  can be secured to the spindle  14  either rigidly or pivotally relative to the latter. 
         [0047]    The belt buckle feeder  10  includes two casing shells  20 ,  22  being arranged to face each other and enclosing the spindle  14  as well as the spindle drive. Each of the two casing shells  20 ,  22  is bent of a sheet metal part. At a lower end the two casing shells  20 ,  22  converge and form a mounting portion  24  provided with an eyelet for fixedly mounting the entire belt buckle feeder  10  on the vehicle. 
         [0048]    In the direction of the belt buckle  12  the two casing shells  20 ,  22  expand in the transverse direction so as to provide a compartment for the spindle drive arranged there between. 
         [0049]      FIG. 3  illustrates the belt buckle feeder  10  including the belt buckle  12  in the home position, while  FIG. 4  shows the belt buckle feeder  10  including the belt buckle  12  (not shown here) in the feeding position. 
         [0050]    The spindle drive illustrated in detail in  FIGS. 3 and 4  includes a spindle nut  26  which is screwed onto the spindle  14 . The spindle  14  has an appropriate thread (not shown) along its entire height-movable length. 
         [0051]    A drive gearwheel  28  engaged in an external tooth system (not shown) of the spindle nut  26  which is equally located between the casing shells  20 ,  22  is arranged in parallel to the spindle nut  26 . The drive gear wheel  28  is connected to the flexible shaft  16  and is rotated by the same. The rotation of the drive gearwheel  28  is transmitted to the spindle nut  26 , whereupon the spindle  14  is moved in the longitudinal direction through the spindle nut  26  so that its extended length and thus the position of the belt buckle  12  can be varied. 
         [0052]    In order to prevent co-rotation of the spindle  14  a locking device  30  which is disposed in a guide  32  formed in either of the casing shells  20 ,  22  is arranged at the lower end of the spindle  14 . This is illustrated in  FIG. 4 . 
         [0053]    The spindle out  26  is supported in a bearing  34  to be stationary but rotatable, the bearing  34  being split (with respect to the Figures) into upper and lower bearing blocks  36 ,  38 . The lower bearing block  38  is tightly fixed between the casing shells  20 ,  22 . The two upper bearing blocks  36  are arranged on opposite sides of the spindle  14  and rest on the lower bearing block  38 . 
         [0054]    Each of the two upper bearing blocks  36  includes an opening  40  through which a securing pin  42  is passed by which the two casing shells  20 ,  22  are riveted to each other. 
         [0055]    Each of the securing pins  42  moreover connects a locking element  44  to the casing shells  20 ,  22  by the securing pin  42  reaching through openings in the looking element  44  that are aligned with the openings  40 . 
         [0056]    The two locking elements  44  are arranged at the belt buckle-side end of the casing shells  20 ,  22  and thus are located between the belt buckle  12  and the spindle nut  26 . 
         [0057]    Both locking elements  44  are bent in one piece of a sheet metal and, apart from two securing tabs  46  including the openings through which the securing pins  42  are projecting, include a tab comprising an eyelet  48  through which the spindle  14  extends. The locking elements  44  are mirror-inverted and are arranged above the upper bearing blocks  36 . 
         [0058]    In normal vehicle operation the locking elements  44  and the eyelets  48  are in the position shown in  FIGS. 1 to 8  in which the eyelet  48  extends perpendicularly to the spindle  14  and during height adjustment the spindle  14  moves through the eyelets  48  without contacting the inner edge thereof. The entire bearing  34 , i.e. both the lower bearing block  38  and the upper bearing blocks  36  are constantly maintained in the same shape and position. This is also applicable to the normal driving operation, when tensile forces F acting on the belt buckle  12  which are not excessively high in the direction R of the feeding position attempt to pull the spindle  14  upwards out of the casing shells  20 ,  22 . Those tensile forces acting on the belt buckle  12  are transmitted via the spindle nut  26  to the bearing  34  and from there into the casing shells  20 ,  22  and into the vehicle. 
         [0059]    The connection of the spindle nut  28  to the thread of the spindle  14  is configured so that it can easily withstand forces occurring during normal vehicle operation approximately corresponding to forces having an upper limit of 7 to 9 kN. 
         [0060]    If a higher tensile force F is applied, for example during accident when force is exerted via the vehicle occupant on the webbing and thus on the belt buckle  12 , the spindle  14  and consequently the spindle nut  26  are pulled upwards (in the Figures) in the feeding direction R. The spindle nut  26  includes a stop  50  in the form of a peripheral radial shoulder opposing a stop face  51  on the lower side of the upper bearing blocks  38  (see  FIGS. 4 and 9 , resp.). 
         [0061]    During normal operation the stop  50  does not contact the stop face  51 . Only when the predetermined force threshold of about 7 to 9 kN is exceeded, the stop  50  on the spindle nut  26  is pulled so as to contact the stop face  51  of the upper bearing blocks  36  so that the latter, too, are loaded in the direction of the tensile force F. 
         [0062]    A deflecting member  52  which in the illustrated example is identical to either of the two upper bearing blocks  36  is assigned to each of the locking elements  44  (see  FIG. 9 ). Upon application of force above the predetermined force threshold the deflecting member  52  starts deforming, pivoting and/or moving in the direction of the tensile force F. Accordingly, the respective deflecting member  52  urges against the superimposed locking element  44  and exerts force directed upwards (in the Figures) on the same. 
         [0063]    Since the locking elements  44  are pivotally hinged to the casing shells  20 ,  22  via the mounting pins  42 , a movement of the two deflecting members  52  results in pivoting of the two locking elements  44 . As a result, the tabs of the locking elements  44  including the eyelets  48  are tilted with respect to the cross-section of the spindle  14 . Thus an inner edge  54  of the eyelet  48  in portions contacts the peripheral surface of the spindle  14 . 
         [0064]    This situation is illustrated in  FIGS. 9 and 10 . 
         [0065]    The shape and the material of the locking elements  44 , especially of the edge of the eyelets  48 , are selected so that the inner edge  54  of the eyelet  48  cuts into the outer periphery of the spindle  14  and somewhat digs into the material of the spindle  14  or at least wedges between two windings of the thread. 
         [0066]    When the extension force F is increased, the edge  43  of the eyelet  48  is increasingly cut into the spindle  14  so that constantly improving force and form fit occurs between the looking element  44  and the spindle  14 . 
         [0067]    As soon as the locking element  44  contacts the spindle  14 , the flux of force is no longer effectuated via the spindle  14 , the spindle nut  26 , the bearing  34  and the casing shells  20 ,  22  but via the spindle  14 , the locking elements  44 , the mounting pins  42  and the casing shells  20 ,  22  through the mounting portion  24  directly into a component fixed to the vehicle. Only these components have to be designed for absorbing the high forces in the range of up to approx. 25 kN acting in the case of accident. 
         [0068]    Therefore, in the present example the spindle nut  26  is made of plastic material. It is loaded at no time beyond its breaking load of approx. 10 to 15 kN, as the flux of force is guided via the locking elements  44  already in the case of lower forces. 
         [0069]    Therefore the entire spindle drive can also be dimensioned to be smaller, for merely the casing shells  20 ,  22 , the locking elements  44  and the spindle  14  have to be designed as load-bearing components. This permits a very slender design of the entire belt buckle feeder  10  which therefore is perfectly suited also for use with the front seats, for example. 
         [0070]    The locking elements  44  and the two casing shells  20 ,  22  are made of sheet steel in this case. 
         [0071]      FIGS. 11 and 12  illustrate a drive variant in which the spindle nut  26  is not driven via a parallel gearwheel but via a bevel gear  60 . In this case an electric motor  18  is provided directly on the belt buckle feeder  10 , but the bevel gear could as well be connected, as described in the previous example, to the electric motor  18  via a flexible shaft. 
         [0072]    In  FIGS. 13 and 14  a drive of the spindle nut  26  via a worm gear is illustrated in which a worm  70  connected to an electric motor  18  drives a worm wheel  72  which in turn is engaged in an external tooth system on the spindle not  26  and is adapted to rotate the latter. 
         [0073]    The worm  70  could as well directly drive the spindle nut  26 ; in this case the external tooth system thereof is in the form of a worm wheel. 
         [0074]    In this case, too, the electric motor  18  can be arranged directly on the belt buckle feeder or can be connected to the worm  70  via a flexible shaft. 
         [0075]    In these examples the locking elements  44  are not shown, however the drive shown in  FIGS. 11 and 12  and, resp., in  FIGS. 13 and 14  can be employed instead of the spindle drive shown in  FIGS. 1 to 10 , as a matter of course.