Patent Abstract:
A tensioner ( 10 ) for a vehicle safety device is provided with a tubular casing ( 12 ) in which a piston ( 18 ) is movably supported as well as with a closure member ( 26 ) closing the tubular casing ( 12 ) on the front face and forming a cable guide ( 38 ) for a tensioning cable ( 28 ) which may be connected to a belt buckle or an end fitting ( 34 ) and in which cable guide the tensioning cable ( 28 ) is deflected in arc shape. Further, the tensioner ( 10 ) comprises an inflator ( 24 ) accommodated in the closure member ( 28 ), wherein the tubular casing ( 12 ) includes a receiving area ( 14 ) for receiving the closure member ( 26 ) as well as a fastening portion ( 16 ) serving for fastening the tensioner ( 10 ) to a vehicle frame.

Full Description:
[0001]    This application corresponds to PCT/EP2015/000294, filed Feb. 11, 2015, which claims the benefit of German Application No. 10 2014 002 006.1, filed Feb. 17, 2014, the subject matter, of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a tensioner for a vehicle safety device, especially a belt buckle tensioner or an end fitting tensioner. 
         [0003]    Tensioners are used in versatile manners in vehicle safety devices. As a rule, they comprise a tubular casing in which a piston is movably supported, wherein an inflator is provided which in the case of release acts on the piston so that the piston is displaced in the tubular casing so that the tensioning cable is tensioned. Tensioning of the tensioning cable displacement of a belt buckle or end fitting arranged on the other end of the tensioning cable and tensioning of the seat belt. Moreover, the tensioners known from the state of the art include deflecting elements for the tensioning cable within the tensioner and the tubular casing, respectively. The tubular casing is further tightly dosed, with the exception of an aperture for passing through the tensioning cable, by a closing member in the form of a plug. Moreover, the tensioner or the tubular casing has to be adapted to be fastened on the vehicle side. For this purpose, typically a separate fastening portion in the form of a clamping piece by which the tensioner is fastened on the vehicle side is mounted on the tubular casing. In total, the tensioners known from the state of the art thus consist of plural individual components which, on the one hand, have to be assembled and, on the other hand, have to be carefully seated at the numerous contact points. This is connected with considerable mounting and cost expenditure. Further, such tensioners require increased space due to their numerous components. 
       SUMMARY OF THE INVENTION 
       [0004]    It is therefore the object of the invention to provide a tensioner which has reduced mounting effort while the quality is constantly high. 
         [0005]    In accordance with the invention, the object is achieved by a tensioner for a vehicle safety device comprising a tubular casing in which a piston is movably supported, a closure member closing the tubular casing on the front face which forms a cable guide for a tensioning cable that may be connected to a belt buckle or an end fitting and in which cable guide the tensioning cable is deflected in arc shape, an inflator accommodated in the closure member, wherein the tubular casing has a receiving portion for receiving the closure member as well as a fastening portion serving for fastening the tensioner to a vehicle frame. The basic idea of the Invention provides to facilitate assembly of the tensioner in that the tubular casing includes both a receiving area for the closure member and a fastening portion via which the tensioner can be fastened to the vehicle frame. In accordance with the invention, the tubular casing of the tensioner hence simultaneously fulfills plural functions, thus providing a compact tensioner that is easy to assemble. Furthermore, the closure member itself includes the cable guide for the tensioning cable defecting the tensioning cable in an arc shape, which causes the tensioning cable to be appropriately guided with low friction and separate components for cable guiding to be saved, which in turn reduces the mounting effort. 
         [0006]    In particular, the fastening portion is located in the receiving area. This allows achieving optimum support of the tensioner, as the fastening portion is arranged in the area of the tubular casing in which the largest mass is received. 
         [0007]    According to an aspect of the invention it is provided that the closure member and the tubular casing in the area of the fastening portion Include a recess through which a fastening means projects for fastening the tensioner on the vehicle side. The tubular casing thus may be fastened directly on the vehicle, wherein the closure member equally includes a recess via which the closure member can be mounted on the tubular casing. 
         [0008]    Especially the recesses of the fastening portion and of the closure member are aligned with each other. The fastening means which fastens the tubular casing to the vehicle may simultaneously fix the closure member on the fastening portion, thus the mounting effort also being further reduced, as only one fastening means is required. 
         [0009]    According to another aspect of the invention, the closure member is provided to be formed in one piece. The closure member that guides the tensioning cable and receives the inflator thus is in the form of an integral subassembly, wherein the closure member at the same time tightly closes the tubular casing on one axial end. The closure member thus fulfills at least three functions. By the integral design the mounting expenditure and, respectively, the mounting effort in turn can be reduced. 
         [0010]    Another aspect of the invention provides a pressure chamber which is partly delimited by the tubular casing to be formed between the closure member and the piston. Since the tubular casing constitutes part of the pressure chamber wall, it is especially easy to manufacture. A separate pressure chamber casing need not be introduced into the tensioner and be fastened. The pressure built up in the pressure chamber acts on the piston so as to displace the same inside the tubular casing. 
         [0011]    In particular, the tubular casing includes a lateral opening for the tensioning cable, wherein the tensioning cable is continuously guided in the tubular casing up to the opening or the tensioning cable in portions sticks out of the tubular casing on the side opposed to the opening. The guideway ensures that the tensioning cable extends in the area of the piston coaxially thereto so that there is no angular offset which might have a negative effect during later tensioning. The fact that the tensioning cable in portions sticks out of the tubular casing allows for a larger bending radius of the tensioning cable inside the cable guide, thus causing appropriate running properties of the tensioning cable along the cable guide to be achieved. 
         [0012]    According to another aspect of the invention it is provided that a cable inlet member mounted on the closure member through which the tensioning cable is passed and in which the tensioning cable is deflected is provided between the closure member and the piston. The cable Inlet member ensures that inside the tensioner the tensioning cable is guided to the piston so that no excessively small bending radii occur which might negatively affect the tensioning behavior of the tensioning cable. 
         [0013]    Especially the closure member and the cable inlet member can be attached to each other. The modular structure helps to achieve that different cable inlet members can be combined with different closure members, thus allowing different combinations to be formed for different types of tensioners or tensioning cables, respectively. 
         [0014]    According to another aspect of the invention, a pressure chamber connected to the inflator is provided in the closure member. The gas generated by the inflator is transmitted via the pressure chamber to the piston which is appropriately displaced within the tubular casing. The closure member thus also adopts the function of a gas or pressure line. 
         [0015]    The closure member in particular includes a peripheral annular groove including a sealing arranged thereon which contacts the inner side of the tubular casing. The sealing can be formed on the closure member itself or on the cable inlet member. This ensures that the pressure chamber is sealed toward the open axial end of the tubular casing and that the closure member tightly seals the tubular casing on the front end. 
         [0016]    Another aspect of the invention provides that the closure member is a plastic injection-molded part, especially a multi-component injection-molded part. In this way, an especially inexpensive closure member possibly including an injection-molded seal can be manufactured, wherein based on the injection-molding technique complicated geometries can be realized so that even micro-tensioners including micro-inflators can be easily incorporated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0017]    Further advantages and aspects of the invention are resulting from the following description and the drawings that are referred to. The drawings illustrate in: 
           [0018]      FIG. 1  a perspective exploded view of a tensioner according to the invention in accordance with a first embodiment, 
           [0019]      FIG. 2  a sectional view across the assembled tensioner according to  FIG. 1 , 
           [0020]      FIG. 3  a perspective view of the assembled tensioner of  FIGS. 1 and 2 , 
           [0021]      FIG. 4  a perspective exploded view of a tensioner according to the invention in accordance with a second embodiment, 
           [0022]      FIG. 5  a sectional view across the tensioner of  FIG. 4  in the assembled state, and 
           [0023]      FIG. 6  a perspective view of the tensioner according to  FIGS. 4 and 5  in the assembled state. 
       
    
    
     DESCRIPTION 
       [0024]    In  FIGS. 1 to 3  a tensioner  10  according to a first embodiment in the form of a buckle or end fitting tensioner is illustrated. 
         [0025]    The tensioner  10  comprises a tubular casing  12  including a receiving area  14  on an axial front end  12   a.  The tubular casing  12  moreover includes a fastening portion  16  provided in the receiving area  14 . 
         [0026]    In the tubular casing  12  furthermore a piston  18  is movably supported, wherein the piston  18  includes a bushing portion  20  and an actuating portion  22  which are formed in one piece. The piston  18  interacts with an inflator  24  provided inside a closure member  28  (cf.  FIG. 2 ) which is put into the receiving area  14  of the tubular casing  12 . The closure member  28  in the assembled state closes the tubular casing  12  on its front end  12   a.    
         [0027]    After being ignited, the inflator  24  acts on the actuating portion  22  of the piston  18  via a pressure chamber  27  partly present in the closure member  26  (cf.  FIG. 2 ) so as to axially displace the piston  18  inside the tubular casing  12 . Thus the piston  18  is displaced or urged, respectively, toward the end  12   b  of the tubular casing  12  opposed to the front end  12   a.    
         [0028]    The pressure chamber  27  is configured so that the tubular casing  12  is part of the chamber wall. 
         [0029]    The piston  18  moreover is connected to a tensioning cable  28  via its bushing portion  20  so that displacement of the piston  18  within the tubular casing  12  results in tensioning of the tensioning cable  28 . For this purpose, the piston  18  is coupled, more exactly clamped, to a damping portion  32  of the tensioning cable  28  arranged on a first end  30  of the tensioning cable  28 . 
         [0030]    When the tensioning cable  28  is tensioned via its clamping portion  32  by the piston  18  and the inflator  24 , resp., such tensioning is transmitted to a fitting  34  arranged on the other end  38  of the tensioning cable  28 . In this way, a belt buckle or an end fitting, for example, is tensioned so that a vehicle occupant is restrained. 
         [0031]    The tensioning cable  28  extends partly inside the tubular casing  12 , wherein the tensioning cable  23  is deflected by the closure member  26 . For this purpose, the closure member  26  includes a cable guide  38  in the form of a groove-type recess extending in the form of a pitch circle so that the tensioning cable  28  with a deflecting portion  40  may lay around the cable guide  38  and is guided along the latter (of.  FIG. 2 ). Due to this configuration of the cable guide  38 , low-frictional running of the tensioning cable  28  along the cable guide  38  is guaranteed. 
         [0032]    In the area of the cable guide  38  the tensioning cable  28  moreover includes a guide sleeve  42  (cf.  FIG. 2 ) which serves for guiding the tensioning cable  28  with low friction to the piston  18  in the area of the cable guide  38  and behind the deflection portion  40  of the tensioning cable  28 . 
         [0033]    In the shown embodiment, starting from its clamping portion  32  at the first end  30  the tensioning cable  28  extends continuously inside the tubular casing  12  until it leaves the tubular casing  12  laterally at an opening  44 . At the opening  44  again a guide sleeve  46  is arranged which serves for supporting the tensioning cable  28  even outside the tubular casing  12  so as to prevent the tensioning cable  28  from bending shortly behind the opening  44 . 
         [0034]    As already mentioned in the beginning, the tubular casing  12  includes, next to the receiving area  14 , the fastening portion  16  by which the tubular casing  12  is fastened on the vehicle side. 
         [0035]    In the shown embodiment, the fastening portion  16  is formed by a continuous recess  48  interacting with a fastening means  50  (in this case a stud bolt) so that the tubular casing  12  can be fastened to a vehicle frame via its fastening portion  16 . 
         [0036]    The closure member  26  equally comprises a recess  52  which in the assembled state is aligned with the recess  48  of the fastening portion  16  (cf.  FIG. 2 ) so that the fastening means  50  projects both through the recess  48  of the fastening portion  16  and through the recess  46  inside the closure member  26 . 
         [0037]    Hence, via the one fastening means  50  the closure member  26  can be fastened to the tubular casing  12  and to the receiving area  14 , resp., and at the same time the casing tube  12  can be fastened to a vehicle. 
         [0038]    The closure member  26  moreover includes a groove having a sealing  64  arranged thereon so as to tightly close the open axial end  12   a  of the tubular casing  12 . The sealing  54  arranged in this way is located between the closure member  26  and the inner wall of the tubular casing  12  (cf.  FIG. 2 ). 
         [0039]    Moreover, further sealing rings  56 ,  58 ,  60  are provided for sealing the tubular casing  12  and, respectively, the individual areas. The sealing ring  56  seals, for example, the inlet area of the tensioning cable  28  into the piston  18 , whereas the sealing rings  58 ,  60  are associated with the piston  18  and the tubular casing  12 . 
         [0040]    Furthermore, balls  62  running on a conical surface of the piston  18  and indenting into the tubular casing  12  after tensioning are provided so that the piston  18  cannot be withdrawn anymore inside the tubular casing  12 . 
         [0041]      FIG. 3  illustrates the assembled tensioner  10  according to the first embodiment in the assembled state. 
         [0042]    In  FIGS. 4 to 6  a tensioner  10  according to a second embodiment is illustrated. The differences between the second embodiment and the first embodiment will be explained hereinafter, wherein equal or equally functioning components are provided with equal reference numerals. 
         [0043]    The tensioner  10  according to the second embodiment differs from the tensioner  10  of the first embodiment to the effect that the tubular casing  12  includes a recess  64  facing the opening  44  of the tubular casing  12 . 
         [0044]    Thanks to the recess  64  the tensioning cable  28  may stick out of the tubular casing  12  in portions in the area of the deflecting portion  40  and of the cable guide  38  of the closure member  26 , respectively ( FIG. 5 ). In this way it is achieved that the tensioning cable  28  may cover a larger bending radius in its deflecting portion  40  than in the first embodiment, thus allowing the tensioning cable  28  to be guided more easily inside the tubular casing  12  and the tensioner  10 , respectively. 
         [0045]    In addition, the closure member  28  in the second embodiment is structured so that it interacts with a cable inlet member  66  which can be attached to the closure member  28 . 
         [0046]    The cable inlet member  66  ensures that the tensioning cable  28  is deflected behind the cable guide  38  so that it extends in parallel to the axial orientation of the tubular casing  12  into the piston  18  and the bushing portion  20  of the piston  18 , respectively. This helps to prevent shear forces that might impair the functioning of the tensioner  10 . The tensioning cable  28  thus is arranged in the area of the piston  13  coaxially to the latter and to the tubular casing  12 . 
         [0047]    The cable inlet member  66  inter alia replaces the guide sleeve  42  from the first embodiment. 
         [0048]    The cable inlet member  66  further includes a pressure guiding duct  68  which, starting from the pressure chamber  27 , leads to the actuating portion  22  of the piston  18  so that the pressure generated by the inflator  24  acts on the actuating portion  22  of the piston  18 . 
         [0049]    Furthermore, the cable inlet member  66  includes two sealing rings  70 ,  72  which interact with the closure member  26  and the piston  18  so that, on the one hand, the transition area between the pressure chamber  27  and the pressure guiding duct  68  and, on the other hand, the transition area between the cable inlet member  66  and the tubular casing  12  are sealed. 
         [0050]    In  FIG. 6  the tensioner  10  according to the second embodiment is illustrated in the assembled state. 
         [0051]    In total, the parts required for assembling a tensioner  10  were minimized so that the entire tensioner  10  can be assembled with as little mounting expenditure as possible, with the tensioner  10  moreover exhibiting a compactor design. 
         [0052]    In all embodiments the tensioning cable  28  is continuously guided inside the tubular casing up to the opening  44  in the non-actuated home position. 
         [0053]    The closure member  28  especially is a plastic injection-molded part, in particular a multi-component injection-molded part. The sealing  54  and/or the guiding sleeve  42  may be attached by injection-molding.

Technology Classification (CPC): 1