Abstract:
A safety belt arrangement is provided that has a belt retractor that includes a force-limiting device. When triggered in a collision, the belt retractor is associated with limited belt release therefrom. Associated with the belt retractor is a tensioning device that is actuated subsequent to the primary collision and that eliminates slack in a belt that occurs when the force-limiting device is triggered during the primary collision.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a safety belt arrangement with a belt retractor comprising a force-limiting device that, when triggered in a collision, is associated with a limited release from the blocked retractor. 
     A generic safety belt arrangement is known from DE 43 31 027 A1. In it, the belt retractor is provided with a force-limiting device that in particular when cooperating with an airbag causes the intentional release of the belt in a controlled manner while simultaneously reducing the force peaks that occur during a collision. If subsequent to such a first collision (primary collision) there is a second collision, e.g. in a multi-vehicle collision, the slack in the belt created by the force-limiting device in the primary collision is disadvantageous because the triggered safety belt no longer holds the occupant wearing the safety belt securely enough. 
     The object of the invention is therefore to further develop a safety belt arrangement of the type specified in the foregoing so that the person wearing the safety belt is securely restrained even in a second collision subsequent to the primary collision. 
     SUMMARY OF THE INVENTION 
     This object is achieved, including advantageous embodiments and further developments of the invention, from the contents of the patent claims that follow this specification. 
     The main idea behind the invention is that associated with the belt retractor is a tautening or tensioning device that is actuated subsequent to the primary collision and that eliminates the slack in the belt that occurs when the force-limiting device is triggered during the primary collision. The invention is associated with the advantage that, despite the slack in the belt necessarily associated with the force-limiting process in a primary collision, the person wearing the belt is securely restrained if there is a second collision because the slack in the belt that is created during the primary collision is immediately eliminated by the additional tensioning apparatus provided in accordance with the invention. 
     In a first embodiment the invention provides that the tensioning device constitutes an energy accumulator that can be loaded by the rotation of the belt winding shaft in the direction of the belt&#39;s release while the force-limiting device is being triggered, whereby the loadable energy accumulator can especially constitute a tensible spring. Alternative energy accumulators, e.g. in the form of air compression, are also conceivable. This results in the advantage that an additional tensioning apparatus of this type is integrated into the retractor and simultaneously in particular false triggering is not possible because the energy to be stored in the tensioning apparatus is not built up until the force-limiting device is actuated. It can furthermore be provided that the untensed spring is connected to the belt winding shaft and its free spring end can be caused to engage with a stop attached to the housing when the force-limiting device is triggered so that the spring is tensed by the rotation of the belt winding shaft in the direction of the belt&#39;s release, said rotation occurring when a force is limited. 
     When in accordance with the generic DE 43 31 027 A1 the force-limiting device comprises a torsion bar that is blockably tensed on one side and that at the other end is joined to the winding shaft and the winding shaft is rotatable relative to the tensioning of the torsion bar while the force-limiting device is being triggered, the rotation of the winding shaft is advantageously used for tensing the spring constituting the tensioning device in that a lever arrangement is provided that is arranged between a shaft axis and the free spring end, that in its neutral position holds the spring end free, and that can be moved by the relative movement between the winding shaft and the tensioning of the torsion bar in an extended position that effects engagement of the spring end with the stop attached to the housing. 
     In a generic belt retractor, in which in the interior of the shaft body of the winding shaft is arranged a shaft casing that is joined on one side to the torsion bar and that can be fixed via the blocking system of the retractor and that encloses the torsion bar, such a lever arrangement can be arranged such that a first lever is borne on the shaft axis and is fixed to the shaft casing via a shearing pin and a second lever guiding the spring end is joined to the first lever and is deflectably arranged via a link guide embodied between the shaft body and the second lever radially outward until it engages the spring end held by the second lever at the stop attached to the housing. 
     If, in another embodiment of the safety belt arrangement, the force-limiting device comprises a torsion bar joined at its one end to the winding shaft and at its other end connected to a profiled head as carrier of the blocking member and the winding shaft is rotatable relative to the profiled head while the force-limiting device is being triggered, as an alternative to the lever arrangement an apparatus for tensing the spring can be provided that constitutes the tensioning apparatus in which apparatus the spring end is held at a gearwheel movably arranged via a control link at the torsion bar due to the relative movement between the winding shaft and the torsion bar until it engages in a toothed member attached to the housing, whereby the rotation of the winding shaft in the direction of the belt&#39;s release during the force-limiting process tenses the spring via rolling of the gearwheel on the toothed member attached to the housing. 
     An alternative embodiment of the invention has as its subject a tensioning apparatus arranged outside the retractor, in which tensioning apparatus a drive energy for the secondary tensioning apparatus is to be maintained. In a corresponding exemplary embodiment of the invention it is provided that the retractor is fastened to a movable slide member on a track attached to the vehicle and the tensioning device is embodied as a drive apparatus that acts on the slide member and that eliminates the slack in the belt caused when the slide is displaced with the retractor during a primary collision and that is triggerable subsequent to the primary collision. Depending on the strength of the tensioning apparatus, in addition to eliminating the slack in the belt, the body of an occupant who is, e.g., bent forward can be returned. In accordance with exemplary embodiments of the invention, the drive apparatus can be embodied as pre-tensed compression springs that drive the slide member when triggered or alternatively as a drive apparatus that acts pyrotechnically on the slide member. 
     Finally, the retractor used in the safety belt arrangement, in addition to being joined to the force-limiting device, can also be joined to a tensioning apparatus for the primary collision, as described in the generic DE 43 31 027, so that two tensioning devices are available in such an embodiment of the invention, and these are one tensioning device for the primary collision and one tensioning device for the secondary collision that is activated by the force-limiting function. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Exemplary embodiments are illustrated in the drawings and described in more detail in the following. 
     FIG. 1 is an exploded view of the arrangement of the winding shaft of a safety belt with a tautening device, in the form of a winding spring effective when putting a safety belt on and off, coupled to the winding shaft that is actuated prior to a primary collision and a force-limiting device and associated tensioning apparatus that is actuated following a primary collision; 
     FIG. 2 is a detailed illustration of an end view of the winding shaft with a spring constituting the tensioning apparatus in its neutral position; 
     FIG. 2 a  is the subject of FIG. 2 with a coupled spring; 
     FIG. 3 is another exemplary embodiment with a spring constituting the tensioning apparatus corresponding to FIG. 2; 
     FIG. 3 a  is the subject of FIG. 3 with a coupled spring end; 
     FIG. 4 a  is a side elevation of another exemplary embodiment with a gearwheel for a drive for tensing the spring that constitutes the tensioning apparatus; 
     FIG. 4 b  is an end view of the subject of FIG. 4 a  with the spring in the neutral position; 
     FIG. 4 c  illustrates the subject of FIG. 4 b  while the spring is tensed; 
     FIG. 5 is a partial cut-away of another embodiment with an externally arranged tensioning apparatus that acts on the retractor; 
     FIG. 5 a  is an exploded perspective view of the embodiment shown in FIG.  5  and showing, in particular, details of the retractor; and 
     FIG. 5 b  is a partial sectional view of a modification of the embodiment shown in FIG.  5  and showing a pyrotechnic drive device with a corresponding housing, from which a piston is withdrawable with this piston being connected with the slide so that the belt roller can be correspondingly moved. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 illustrates the individual components of a winding shaft  9  in which arranged on a shaft axis  10  is a torsion bar  13  that is joined at its one end in a positive fit to a shaft casing  12  fitted over the torsion bar  13  and that is joined at its other end in a positive fit to a shaft body  11  fitted over the shaft casing  12 , on which shaft body  1  the safety belt (not shown) is wound. At its end that forms the connection to the torsion bar  13 , the shaft casing  12  forms a blocking side  14  for connecting to the blocking system (not shown) of the safety belt retractor. 
     Borne on the side on the shaft axis  10  facing away from the blocking side  14  is a first lever  15  that is loosely joined to a second lever  16 ; in addition to the lever arrangement  15 ,  16 , fitted on the shaft axis  10  is a spring  17  for a secondary tensioning apparatus that is fixed at its inner end in a slot  19  in the shaft axis  10  and the outer spring end  18  of which terminates in a crook. As can be seen from FIGS. 2 and 2 a , the lever  16  has a guiding function for the spring end  18 . The lever  16  has a first pin  26  that engages the spring end  18 , that guides it [the spring end], and that is axially spaced from the shaft axis  10 . On its opposing side, the lever  16  is guided in an associated slot  28  of the shaft body  11  via a second axial pin  27 . In order to maintain the secondary tensioning apparatus in the form of the spring  17  in the neutral position during normal operation of the retractor, the first lever  15  is fixed by means of a recess  22  embodied thereon to a shearing pin  21  that is arranged on the shaft casing  12  and that extends through the shaft body  11  into an associated guide slot  29 . 
     As can be seen in detail in FIG. 2, during normal operation of the retractor the shaft body  11  carries the lever arrangement  15 ,  16  with it via the shearing pin  21 , so that the shaft body  11  rotates freely when the spring  17  is relaxed. When the safety belt retractor is blocked, the profile head  14  is fixed with the shaft casing  12  and the shearing pin  21  seated thereon via the engagement of the blocking member (not shown) so that due to the pull on the safety belt wound on the shaft body  11  and due to the connection that exists at the end opposing the profiled head  14  between the shaft body  11  and the torsion bar  13  there is a further counterclockwise rotation of the shaft body  11  and thus the shaft body  11  rotates relative to the shaft casing  12 . 
     Due to the pin/slot connection  27 ,  28 , the relative rotation between the shearing pin  21  and the shaft body  11  via the pin  27  conducts and deflects the second lever  16  outward radially such that it carries via its first pin  26  the spring end  18  of the spring  17 . Once the spring end  18  projects far enough over the exterior diameter of the shaft body  11 , during the further rotational movement of the shaft body  11  it [the spring end] catches on one of the stops  24  that is attached to the housing. During the further rotation of the shaft body  11  relative to the shaft casing  12 , the shearing rod  21  shears off once it has reached its final position in the slot  29  so that the spring  17  is tensed via the continuing rotation of the shaft body  11  during the force-limiting process. This means that a drive energy for the return rotation of the winding shaft  9  is available after the primary collision for eliminating the slack in the belt that resulted due to the actuation of the force-limiting device. 
     The exemplary embodiment illustrated in FIGS. 3 and 3 a  is distinguished from the exemplary embodiment described in the foregoing (FIGS. 2,  2   a ) in terms of construction and function in that the pin  26  is omitted and the spring end  18  is guided by means of a peg  36  seated thereon in a longitudinal slot  23  arranged in the lever  16  so that the radial movement of the lever  16  leads to a linear expulsion of the spring end  18  over the circumference of the shaft body  11  until it engages at the stop  24  attached to the housing. 
     In the exemplary embodiment illustrated in FIGS. 4 a  through  4   c , the secondary tensioning apparatus is arranged in the form of the spring  17  between the profiled head  14  and the shaft body  11  so that in this embodiment there is no shaft casing  12 . 
     As can be seen in detail from FIG. 4 a , the spring  17  is arranged between the end face of the shaft body  11  and the profiled head  14 , whereby for adjusting the normal operation the shaft body  11  and the profiled head  14  are joined via the associated shearing pin  21 . A shaft  41  carrying a gearwheel  42  is movably mounted in the guide slots  40  that are arranged mutually opposing on the profiled head  14  and on the end of the shaft body  11  and that are disposed radially outward in mutual opposition. 
     In the neutral position, which can be seen in FIG. 4 b , the gearwheel  42  is situated inside the contour of the shaft body  11 , so that the shaft body  11  can rotate in both directions of rotation without the spring  17  being tensed. Once the profile head  14  has been blocked by the blocking member (not shown) and by the shearing rod  21  having been sheared off, the relative rotation between the shaft body  11 , which continues to rotate while the force-limiting device is effective, and the fixed profiled head  14  causes the gearwheel  42  to move radially outward until it engages in the toothed member  43  fixed to the housing. As the shaft body  11  continues to rotate relative to the profiled head  14 , the end of the shaft  41  situated in the profiled head  14  is sheared off so that the further rolling of the gearwheel  42  on the toothed member  43  fixed to the housing causes the spring  17  to tense via the further rotation of the shaft body. 
     FIG. 5 illustrates another embodiment of the invention in which the secondary tensioning apparatus is arranged outside the safety belt retractor. A safety belt retractor  30  is affixed to a slide  31  that is movable on a track  32  that is attached to the vehicle. Associated with the slide  32  is a tensed compression spring  33  as a drive apparatus; it can be triggered subsequent to a primary collision via a suitable control. The compression spring  33  acts on the slide  31  so that the retractor  30  is locked by the accelerated movement of the retractor and the belt strap  35  is tautened and the slack in the belt that occurs during the course of the primary collision is thus eliminated. Subsequent to this tautening or tensioning movement the slide  31  locks with the track  32  attached to the vehicle by means of a provided catch  34  (nose, recesses  36 ). 
     It is also possible to provide a pyrotechnic drive apparatus as an alternative to the pre-tensed compression spring  33  (not further illustrated). 
     The features of the subject of this document that are disclosed in the foregoing specification, in the patent claims, and in the abstract and drawings can be essential individually and in any desired combination for realizing the invention in its various embodiments. 
     The specification incorporates by reference the disclosure of German priority document 197 32 453.3 of Jul. 29, 1997 and European priority document PCT/EP98/04458 filed Jul. 17, 1998. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.