Abstract:
A locking pawl for a mechanism for blocking a belt retractor of a safety belt comprises a first locking pawl element made of a first material and adapted to block said belt retractor, and a second locking pawl element made of a second material and adapted to control a movement of said locking pawl. The first material is different from the second material.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a locking pawl for a mechanism for blocking a belt retractor of a safety belt.  
         BACKGROUND OF THE INVENTION  
         [0002]    Belt retractors serve to provide a vehicle occupant with safety belt webbing. Normally, the belt webbing can be withdrawn from the belt reel against the resistance of a spring element. In the blocked condition, belt webbing cannot be withdrawn.  
           [0003]    Disposed on such a belt retractor, as it is known for instance from German Utility Model 201 09 534, is at least one locking pawl which can be brought in engagement with locking teeth at a frame of the belt retractor, in order to non-rotatably block a belt reel. A mechanism for blocking the belt retractor allows to block the belt reel depending on the forces acting on the belt webbing or the acceleration forces acting on the vehicle. In both cases, the locking pawl is swiveled such that it engages in the locking teeth at the frame of the belt retractor. In the case of the belt-webbing-sensitive activation of the blocking mechanism, a coupling disc constituting an inertia disc, which is disposed at the belt reel so as to be rotatable relative to the same, lags behind the rotation of the belt reel due to its mass inertia. At the coupling disc, an actuating element is disposed, which effects a swivel movement of the locking pawl which thus engages in the locking teeth. The operation of such mechanism for blocking a belt retractor of a safety belt is described in detail in the above-mentioned Utility Model and will therefore not be represented in greater detail.  
           [0004]    Although such locking pawls for belt retractors generally perform their function very well, it is desired to improve the same even more, in order to for instance reduce the production of noise or decrease the weight of the locking pawl.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The invention provides a locking pawl for a mechanism for blocking a belt retractor of a safety belt, by means of which the production of noise is reduced distinctly. According to the invention, a locking pawl for a mechanism for blocking a belt retractor of a safety belt comprises a first locking pawl element made of a first material and adapted to block said belt retractor, and a second locking pawl element made of a second material and adapted to control a movement of said locking pawl. The first material is different from the second material. The first locking pawl element acts as load-bearing blocking element, the second locking pawl element acts as guide element. It is particularly advantageous if the first locking pawl element is made of a metal and the second locking pawl element is made of plastics. It is thus achieved that at several points there no longer occurs a metal-to-metal contact, as is usually the case, but that metal contacts plastics, which distinctly reduces the generation of noise. While the use of a locking pawl made of metal only requires a complex and expensive treatment of the metal surface, in order to achieve optimum sliding properties between the actuating element and the locking pawl, this is no longer required in the locking pawl of the invention, as the actuating element can cooperate with the second locking pawl element made of plastics. Moreover, the weight of the locking pawl is reduced distinctly.  
           [0006]    In an advantageous embodiment of the invention, the first locking pawl element is one from the group including stamped, sintered and cold extruded parts. The same can be produced at distinctly reduced costs as compared to the locking pawls used so far.  
           [0007]    In another advantageous embodiment of the invention, the second locking pawl element is an injection-molded plastic part which encloses the first locking pawl element. This may be effected for instance by simply attaching the second locking pawl element to the first locking pawl element by injection-molding, which provides for a particularly easy and inexpensive production of the locking pawl.  
           [0008]    Further advantageous aspects of the invention can be taken from the sub-claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 shows a belt retractor comprising a mechanism for blocking a belt retractor in a partial view with cut-out portions,  
         [0010]    [0010]FIG. 2 shows a perspective view of a first embodiment of the locking pawl according to the invention,  
         [0011]    [0011]FIG. 3 shows another perspective view of the first embodiment of the locking pawl according to the invention,  
         [0012]    [0012]FIG. 4 shows a perspective view of the first embodiment of an element of the locking pawl according to the invention,  
         [0013]    [0013]FIG. 5 shows another perspective view of the first embodiment of an element of the locking pawl according to the invention,  
         [0014]    [0014]FIG. 6 shows a perspective view of a second embodiment of the locking pawl according to the invention,  
         [0015]    [0015]FIG. 7 shows another perspective view of the second embodiment of the locking pawl according to the invention,  
         [0016]    [0016]FIG. 8 shows a perspective view of the second embodiment of an element of the locking pawl according to the invention, and  
         [0017]    [0017]FIG. 9 shows a perspective view of the second embodiment of another element of the locking pawl according to the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    The belt retractor shown in FIG. 1 has a frame  10  in which a belt reel (not represented) is rotatably mounted about an axis A. In the frame  10 , a circular opening is provided, at the edge of which locking teeth  12  are disposed across the entire periphery. On the belt reel, a schematically represented locking pawl  14  is pivotally mounted about an axis B. The locking pawl has a plurality of locking teeth  16  and can be brought in engagement with the locking teeth  12 . A coupling disc  18  is coaxially connected with the belt reel, so that it can be rotated relative to the same to a limited extent. The basic position of the coupling disc  18  with respect to the belt reel is determined by a spiral spring  20  which biases the coupling disc. An actuating element  22  firmly connected with the coupling disc engages in a control cam  24  which is provided in the locking pawl  14  and is composed of two recesses  24   a  and  24   b  disposed substantially at right angles to each other. In FIGS. 2, 4 and  5  the control cam  24  is represented on an enlarged scale.  
         [0019]    In FIGS. 2 and 3, the locking pawl  14  is shown in detail. The same consists of a first locking pawl element  26  with the locking tooth  16  and a second locking pawl element  28  with the control cam  24 .  
         [0020]    The first locking pawl element  26  is made of metal and has a first and a second main surface  26   a,    26   b  as well as an edge  26   c.  On the surface facing away from the second locking pawl element  28 , the first locking pawl element  26  has small recesses  30   a  and  30   b.  In the entire left-hand bottom region of the first locking pawl element  26  with respect to FIG. 3, a further recess  30   c  extends on the side facing away from the second locking pawl element  28  and is delimited by a step  32 . In the vicinity of the recess  30   c,  the first locking pawl element  26  has a through hole  34 .  
         [0021]    The second locking pawl element  28  is made of plastics and is composed of a base plate  36 , a control cam attachment  38 , three hook elements  40 , and a pin  42  (see also FIGS. 4 and 5). The base plate  36  has a first limiting surface  36   a  and a second limiting surface  36   b,  the two limiting surfaces being plane-parallel with respect to each other. Above the base plate  36  with respect to FIGS. 2 and 4, the control cam attachment  38  is provided, which is composed of a wall element  38   a  and a ceiling element  38   b,  as this is shown in particular in FIGS. 2 and 4. The wall element  38   a  is disposed so as to be vertical to the base plate  36 , the ceiling element  38   b  is parallel to the base plate  36 . In the ceiling element  38   b  of the control cam attachment  38 , the control cam  24  is recessed. The hook elements  40  each consist of an extension  40   a,  which extends substantially vertically from the base plate  36 , and a nose  40   b,  which at the end of the extension  40   a  is directly connected with the same.  
         [0022]    The first locking pawl element  26  and the second locking pawl element  28  are produced in independent working steps. The two locking pawl elements  26 ,  28  are then joined in a sandwich-like manner by snapping the second locking pawl element  28  onto the first locking pawl element  26 . To this end, the hook elements  40  must slightly be bent to the outside with respect to the base plate  36 , so that they can be pushed over the edge  26   c  of the first locking pawl element  26 . At the same time, the pin  42  engages in the through hole  34 , so that it protrudes on the side of the first locking pawl element facing away from the base plate  36 . Finally, the noses  40   b  of the hook elements  40  snap into the corresponding recesses  30   a - 30   c  of the first locking pawl element  26 . By the fourfold locking of the hook elements  40  and the pin  42  in the recesses  30  and the through hole  34 , respectively, it is achieved that the second locking pawl element  28  cannot inadvertently be withdrawn from the first locking pawl element  26 , and that the first locking pawl element and the second locking pawl element are secured against a lateral displacement with respect to each other. This provides for a simple, but particularly safe connection of the two locking pawl elements  26 ,  28 .  
         [0023]    In FIGS.  6  to  9  a second embodiment of the locking pawl is represented, in which the second locking pawl element  28  is an injection-molded plastic part which surrounds the first locking pawl element  26  made of metal.  
         [0024]    [0024]FIG. 6 shows the first locking pawl element  26  with the locking tooth  16 , which has the first and the second main surface  26   a,    26   b  (see also FIG. 8) as well as the edge  26   c.  There is furthermore shown a groove  44  as well as a first recess surface  46   a  and a second recess surface  46   b.  The first recess surface  46   a  is offset with respect to the main surface  26   b  by a step  32   a,  the second recess surface  46   b  is offset with respect to the first recess surface by a step  32   b.  At the edge  26   c,  a recess  30   d  is provided in the vicinity of the groove  44 . In the vicinity of the second step  32   b  between the two recess surfaces  46   a,    46   b,  the first locking pawl element  26  furthermore has the pin  42 . In the vicinity of the first recess surface  46   a,  there is provided the control cam  24  with the recesses  24   a  and  24   b.    
         [0025]    [0025]FIG. 7 shows the second locking pawl element  28  made of plastics with a frame  48  to which there is attached the control cam frame  50 , a pin cap  52  via a first connecting web  54  and a pawl edge portion  56  via a second connecting web  58  and a third connecting web  60 . On the main surface side facing away from the observer, the pin cap  52  is open. As can be better seen in FIG. 8, two pins  62  are disposed on the side of the control cam frame  50  facing away from the frame  48 . At its open end, the pin cap  52  furthermore is provided with a web  64  in the form of a semicircular arc, starting at the first connecting web  54 .  
         [0026]    [0026]FIGS. 8 and 9 show the locking pawl  14  with the first locking pawl element  26  and the second locking pawl element  28 . The second locking pawl element  28  is made such that it precisely fits together with the first locking pawl element  26 . Thus, the control cam frame  50  of the second locking pawl element  28  lies in the control cam  24  of the first locking pawl element  26  with the recesses  24   a  and  24   b.  The frame  48  of the second locking pawl element  28  is adapted to the profile of the step  32   a  of the first locking pawl element  26  and has a snug fit with the same. The pin cap  52  of the second locking pawl element  28  is adapted to the shape of the pin  42  of the first locking pawl element  26 , so that the pin is seated in the pin cap in a form-fitting manner. The second recess surface  46   b  of the first locking pawl element  26  accommodates the first connecting web  54  and the web  64 , whereas the groove  44  accommodates the second connecting web  58 . The pawl edge portion  56  of the second locking pawl element  28  lies in the recess  30   d  of the first locking pawl element  26  in a form-fitting manner.  
         [0027]    In the following, the production of the locking pawl will briefly be described. Upon producing the first locking pawl element  26 , the second locking pawl element is attached to the first locking pawl element by injection-molding. The connection between the first locking pawl element  26  and the second locking pawl element  28  is primarily effected by the annular connection of control cam frame  50 , third connecting web  60 , pawl edge portion  56  and second connecting web  58 , which in turn is connected with the frame  48 . To prevent that the control cam frame  50  can at least partly be withdrawn from the control cam  24 , the pins  62  are made such that they reach over the first locking pawl element  26  on the first main surface  26   a  (see FIG. 8). The frame  48  and the pin cap  52  furthermore prevent an at least partial lateral displacement of parts of the second locking pawl element with respect to the first locking pawl element. By means of few and simple measures there is thus achieved a good form-fitting connection between the first and second locking pawl elements.