Abstract:
A fastening device to be fitted into a support part ( 22 ) has a cover plate ( 1 ) and two clamping arms ( 6, 7 ). Each clamping arm ( 6, 7 ) has an inner leg ( 5 ) and an outer leg ( 10 ) which has a bracing structure on its end facing the cover plate ( 1 ). The bracing structure of each clamping arm ( 6 ) is provided with two flat side cheeks ( 15, 16 ) that are joined to mutually opposite side margins ( 13, 14 ) of the respective outer leg ( 10 ) and extend toward the other clamping arm ( 6, 7 ). Each side cheek ( 15, 16 ) has an end face ( 17 ) that is oriented at an angle to the cover plate ( 1 ) and falls away toward the respective outer leg ( 10 ) from the end remote from that outer leg ( 10 ). The fastening device according to the invention can consequently be used in the presence of relatively high extraction forces with support parts that vary in thickness over a relatively large range.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a U.S. National Phase patent application based on International Application Serial No. PCT/EP2007/002784 filed Mar. 29, 2007, the disclosure of which is hereby explicitly incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is directed to a fastening device. 
         [0004]    2. Description of the Related Art 
         [0005]    One known fastening device is disclosed in DE 35 24 651 A1. The prior fastening device for fastening an add-on part to a support part comprises a cover plate and two clamping arms disposed on mutually opposite sides of the cover plate. Each clamping arm has an inner leg, which is joined to the cover plate, and an outer leg, a flat tongue portion of a bracing structure being formed on the outer leg, on its end face proximate the cover plate. The tongue portion engages in a receiving opening configured in the inner leg and closely surrounding said tongue portion, it being provided that in the installed state, the tongue portions brace themselves against the back side of the support part, i.e., the opposite side from the add-on part, in substantially parallel alignment with the cover plate. 
         [0006]    Although very high extraction forces are achieved with such a fastening device, it is disadvantageous that the fastening device has to be matched to the thickness of the support part within relatively close tolerances. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a fastening device that can be used in the presence of relatively high extraction forces with support parts that vary in thickness over a relatively large range. 
         [0008]    Due to the fact that in the inventive device, the bracing structure comprises side cheeks formed on side margins of the outer leg and having beveled end faces, the clamping arms automatically adapt to the thickness of the particular support part by virtue of the side cheeks inserting themselves more or less deeply into the receiving opening. 
         [0009]    In one form thereof, the present invention provides a fastening device to be fitted into a support part, and including a cover plate and two clamping arms joined to the cover plate on opposite marginal sides and disposed opposite each other on one side of the cover plate, each clamping arm including an inner leg proximate the other clamping arm and an outer leg that is remote from the other clamping arm and is connected by a tie portion to the end of the inner leg remote from the cover plate and includes a bracing structure at its end proximate the cover plate, the bracing structure of each clamping arm being configured with two flat side cheeks, which are joined to mutually opposite side margins of the respective outer leg and extend toward the other clamping arm, and each side cheek having an end face that is oriented at an angle to the cover plate and falls away toward the respective outer leg from the end remote from the outer leg, characterized in that configured in each inner leg is a receiving opening in which the side cheeks joined to the respective opposite outer leg engage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a perspective view of an exemplary embodiment of a fastening device according to the invention; 
           [0012]      FIG. 2  is a sectional view of the exemplary embodiment according to  FIG. 1  in an installed state; 
           [0013]      FIG. 3  is a perspective view of another exemplary embodiment of a device according to the invention; 
           [0014]      FIG. 4  is a sectional view of the exemplary embodiment according to  FIG. 3 ; 
           [0015]      FIG. 5  is a sectional view of another exemplary embodiment of a fastening device according to the invention, with clamping arms locked together at their free ends; and 
           [0016]      FIG. 6  is a sectional view of another exemplary embodiment of a fastening device according to the invention, with expansion tongues extending into a screw receiving space configured between clamping arms. 
       
    
    
       [0017]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. 
       DETAILED DESCRIPTION 
       [0018]      FIG. 1  is a perspective view of an exemplary embodiment of a device according to the invention, which is made of stamped and bent sheet metal and is provided to be fitted into a support part not illustrated in  FIG. 1 , and which comprises a substantially rectangular cover plate  1 . Joined to opposite long sides of the cover plate  1  are support tongues  2  that extend outwardly away from the cover plate  1  and in the exemplary embodiment according to  FIG. 1  are each bent stepwise at their end remote from the cover plate  1 . 
         [0019]    Present in the center of the cover plate  1  is a thread structure  3 , for example in the form of a stamped thread, into which a screw (not shown in  FIG. 1 ) can be screwed in order to fasten an add-on part to the support part. 
         [0020]    Configured on both sides of each support tongue  2  is a tie portion  4  by means of which an inner leg  5  of each clamping arm  6 ,  7  is joined to the cover plate  1 . The inner legs  5  each have a receiving opening  8  in their regions adjacent cover plate  1 , and extend toward each other on one respective side of the cover plate  1 , in such a way that the ends of clamping arms  6 ,  7  remote from cover plate  1  preferably rest against or at least are closely adjacent to each other. 
         [0021]    At the ends remote from cover plate  1 , clamping arms  6 ,  7  each comprise a bent-back portion  9  that is bent back approximately 180 degrees and is joined to the respective inner leg  5 , and onto each of which is further formed a respective outer leg  10 . Each outer leg  10  extends from bent-back portion  9  approximately parallel to the inwardly opposite inner leg  5  toward the cover plate  1  and terminates by its end face  11  which is proximate the cover plate  1 , and which is narrower than the width of the outer leg  10  in the region of transition to bent-back portion  9 , at a distance from cover plate  1  that is greater than the thickness of the support part that can be used with the inventive fastening device. To increase the rigidity of the outer leg  10  and to reduce the mounting force of the inventive device according to  FIG. 1 , formed into each outer leg  10  is an outwardly convex swaged portion  12  that extends in the longitudinal direction of said outer leg  10 . 
         [0022]    Formed at the side margins  13 ,  14  of the outer legs  10  are wing-like side cheeks  15 ,  16 , which abut the respective end face  11  and are bent back, from an arrangement originally in the plane of the outer leg  10 , substantially at right angles in the direction of the opposite clamping arm  6 ,  7 , and which are disposed opposite each other in pairs. The length by which each side cheek  15 ,  16  protrudes beyond the respective outer leg  10  is smaller than or at most equal to the distance between the inner legs  5  in the region of side cheeks  15 ,  16 , such that the outer legs  10  are able to deflect until contact is made with the inner legs  5 . In the exemplary embodiment according to  FIG. 1 , each side cheek  15 ,  16  engages in the receiving opening  8  of the respective inner leg  5 . 
         [0023]    It can further be seen from  FIG. 1  that the side cheeks  15 ,  16  are configured on their end faces  17  proximate the cover plate  1  with a step structure  18  composed of elevations and depressions. Present as a terminating elevation at the end of each side cheek  15 ,  16  directed away from the respective outer leg  10  is a blocking shoulder  19  that rises from the end face  17  in the direction of cover plate  1 . A slanted back side  20  extends from the end of each side cheek  15 ,  16  remote from said outer leg  10  toward the respective outer leg  10 , with the result that the dimension of each side cheek  15 ,  16  in the longitudinal direction decreases continuously from outer leg  10  to the end remote from outer leg  10 . 
         [0024]      FIG. 2  is a sectional view of the exemplary embodiment according to  FIG. 1  in an installed state in a support part  22  configured with an insertion opening  21 . It can be seen from  FIG. 2  that once the clamping arms  6 ,  7  have been guided through the insertion opening  21 , the outer legs  10  are caused to spring outward until the end faces  17  of side cheeks  15 ,  16  rest against the rim of the insertion opening  21 , the degree to which said outer legs  10  spring outward depending on the thickness of the particular support part  22 . The step structures  18 , by digging into the rim of the insertion opening  21 , serve to keep the outer legs  10  from inadvertently being pressed in toward the inner legs  5  when a screw is screwed in and the ends of clamping arms  6 ,  7  remote from cover plate  1  spread apart, while the blocking shoulders  19  prevent the outer legs  10  from springing outward all the way, down to a given minimum thickness of support part  22 . 
         [0025]      FIG. 3  is a perspective view of another exemplary embodiment of a device according to the invention, it being noted that elements that are at least functionally similar in the exemplary embodiments according to  FIGS. 1 and 2  and  FIG. 3  are provided with the same reference characters and are not described in more detail below. It can be seen from  FIG. 3  that in this exemplary embodiment, the widths of the inner legs  5  and the outer legs  10  are substantially the same, such that the inner legs  5  are disposed between the side cheeks  15 ,  16 . 
         [0026]      FIG. 4  shows the exemplary embodiment according to  FIG. 3  in a sectional view in the longitudinal direction. It can be appreciated from  FIG. 4  that in this exemplary embodiment the end faces  17  of side cheeks  15 ,  16  are configured as smooth-surfaced, whereas the blocking shoulders  19  are each configured with, as a depression, a respective tool application recess  23  that is open toward the outer leg  10 . 
         [0027]    The exemplary embodiment according to  FIGS. 3 and 4 , which is configured without a thread structure for receiving a screw, is inserted in an insertion opening of a support part, the clamping action being achieved solely by the springing outward of outer legs  10 . By the insertion of a detaching tool (not shown in  FIGS. 3 and 4 ) in the tool application recesses  23 , the outer legs  10  can be moved toward the inner legs  5  until the end faces  11  of the outer legs  10  are within the rim of the insertion opening and the inventive device can thus be withdrawn again from the support part. This demountability is furthered by the smooth-surfaced end faces  17  of the side cheeks  15 ,  16 , since there is no pronounced digging into the margin of the insertion opening. 
         [0028]      FIG. 5  is a sectional view in the longitudinal direction of another exemplary embodiment of a device according to the invention, it being noted that elements that are similar in the exemplary embodiments according to  FIGS. 1 to 4  and  FIG. 5  are provided with the same reference characters and are not described in more detail below. In the exemplary embodiment according to  FIG. 5 , configured on each inner leg  5  in the region of the respective tie portion  9  are a rear-engagement web  24  that extends in the transverse direction and a rear-engagement tongue  25  which is bent back toward the cover plate  1  and extends toward the other inner leg  5 , and which penetratingly engages in a penetrating-engagement opening  26  provided in the tie portion  9  of the other clamping arm  6 ,  7  and engages behind the rear-engagement web  24  of the other inner leg  5 . The clamping arms  6  are thus locked together at their ends remote from the cover plate  1  to prevent them from spreading apart, which is advantageous particularly in the case of one-sided loading, to prevent a clamping arm  6 ,  7  from bending away under a one-sided load. 
         [0029]    It can further be appreciated from  FIG. 5  that configured on side cheeks  15 ,  16 , on the sides remote from cover plate  1 , are back sides  27  oriented preferably approximately at right angles to the longitudinal direction of the clamping arms  6 ,  7  and disposed opposite bracing projections  28 , illustrated by their marginal edges in  FIG. 5 , which enter into the receiving openings  8 . The fastening device according to the exemplary embodiment of  FIG. 5  is thereby stabilized against a tensile load, since the back sides  27  brace themselves against the bracing projections  28  when a tensile load is applied. 
         [0030]      FIG. 6  is a sectional view in the longitudinal direction of another exemplary embodiment of a device according to the invention, it being noted that elements that are similar in the exemplary embodiments according to  FIGS. 1 to 5  and  FIG. 6  are provided with the same reference characters and are not described in more detail below. In the exemplary embodiment according to  FIG. 6 , formed on the outer leg  10  of each clamping arm  6 ,  7  is an expansion tongue  29  which extends toward the other clamping arm  6 ,  7 , and which engages through a clearance  30  provided in the opposite inner leg  9  and enters into a screw receiving space  31  configured between the clamping arms  6 ,  7 . Each expansion tongue  29  is bent back, by a flat end portion  32  located at its free end remote from the respective outer leg  10 , toward bent-back portions  9 , said end portions  32  being oriented roughly parallel to each other and being disposed spacedly opposite each other in the center of screw receiving space  31 , considered in the longitudinal direction. 
         [0031]    In the exemplary embodiment according to  FIG. 6 , formed on cover plate  1  is a threaded bushing  33  having a fine internal thread and projecting into screw receiving space  31 , and into which can be screwed a screw (not shown in  FIG. 6 ) having a fine external thread that mates with the fine internal thread. Due to the fact of end portions  32  being arranged roughly in the center of screw receiving space  31 , the clamping arms  6 ,  7  come to be locked in place at a very early stage, initially as a result of the spreading of the outer legs  10  and also by means of the bent-back portions  9  of inner legs  5 . 
         [0032]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.