CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Japanese Application No. 2005-165264 filed Jun. 6, 2005, incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     Pin and grommet fasteners for joining panels and/or for mounting various types of members on panels are well known. See, for example, Unexamined Japanese Utility Model Application Publication No. 1-85509 (Patent Document 1), U.S. patent application Publication No. US2005/0062263 (Patent Document 2), Unexamined Japanese Patent Application Publication No. 2000-240624 (Patent Document 3), and U.S. patent application Publication No. US2004/0247410 (Patent Document 4). For certain applications, for example attaching a curtain shield airbag to a body panel of a vehicle, it is desirable that such fasteners be strong enough to resist detachment forces in both vertical and horizontal directions with respect to workpieces.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0003]     The present invention provides an improved pin and grommet fastener that can be fastened to workpieces, such as panels, with high enough fastening strength to resist both vertical and horizontal detachment forces. The invention provides a fastener (clip) that can provide high fastening strength to a thin panel and that can effectively prevent deformation of the thin panel. More particularly, the invention can provide secure attachment of a curtain shield airbag to a body panel of a vehicle.  
         [0004]     In a preferred embodiment, a fastener of the invention comprises a pin having a head and a plurality of legs depending from the head, and a grommet having a flange and a shank depending from the flange. In use, the pin is pushed into the grommet. The shank of the grommet has longitudinal slots for receiving respective legs of the pin when the pin is pushed into the grommet, and has resilient pawls for engaging corresponding regions near edges of a mounting hole in a workpiece (e.g., a car body panel) when the grommet shank is inserted into the mounting hole. The grommet shank has a strong central axial column, the cross-section of which occupies most of the cross-section of the grommet shank. When the pin is fully inserted into the grommet shank, legs of the pin engage the axial column of the grommet and also engage respective resilient pawls of the grommet to prevent the pawls from being moved inwardly of the grommet shank. The legs also fill out portions of the grommet shank cross-section not occupied by the axial column. When the grommet shank has a polygonal cross-sectional profile, for example, and is inserted into a matching hole, the cross-section of the grommet shank matches the profile of the hole. By virtue of the invention, high fastening strength is achieved that strongly resists axial and transverse detachment forces applied to the fastener. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     The invention will be further described in conjunction with the accompanying drawings, which illustrate a preferred (best mode) embodiment, and wherein:  
         [0006]      FIG. 1  is a plan view of a pin of a fastener in accordance with the invention;  
         [0007]      FIG. 2  is a front elevation view of the pin of  FIG. 1 ;  
         [0008]      FIG. 3  is a cross-sectional view taken along line A-A in  FIG. 2 ;  
         [0009]      FIG. 4  is a plan view of a grommet of a fastener in accordance with the invention;  
         [0010]      FIG. 5  is a front elevation view of the grommet of  FIG. 4 ;  
         [0011]      FIG. 6  is a side elevation view of the grommet of  FIG. 4 ;  
         [0012]      FIG. 7  is a cross-sectional view of the grommet taken along line B-B in  FIG. 5 ;  
         [0013]      FIG. 8  is a side elevation view of a fastener of the invention in which the pin is partially inserted into the grommet;  
         [0014]      FIG. 9  is a front elevation view of the fastener in which the pin is fully inserted into the grommet;  
         [0015]      FIG. 10  is a cross-sectional view taken along line C-C in  FIG. 9 ;  
         [0016]      FIG. 11  is a somewhat diagrammatic view showing a fastener of the invention initially engaged with an attachment member of a curtain shield airbag;  
         [0017]      FIG. 12  is a view similar to  FIG. 11  showing a fastener of the invention initially engaged with an attachment member of a curtain shield airbag and a body panel of a vehicle; and  
         [0018]      FIG. 13  is a view similar to  FIG. 12  showing a fastener of the invention mounting an attachment member of a curtain shield airbag on a body panel of a vehicle.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     A fastener  3  in accordance with the invention comprises a pin  1  shown in  FIGS. 1-3  and a grommet shown in  FIGS. 4-7 . Each of the pin and the grommet may be an integral plastic molding. The pin has a head  7  of plate-like form and a plurality of depending legs  9 . In the embodiment shown, a depression is provided in a top surface of the head  7  of the pin that may be engaged by a fingertip to facilitate pushing the pin into the grommet (as later described). In the embodiment, legs  9  have a T-shaped cross-section. Although two oppositely disposed legs are employed in the embodiment, the invention is not so limited.  
         [0020]     The grommet  2  comprises a plate-like flange  10  with a shank  11  depending from the flange. In the embodiment, the shank is polygonal in cross-section, more particularly, generally rectangular. The shank has a strong axial column  13 , which in the embodiment is generally rectangular (e.g., square) in cross-section, and a plurality of resilient pawls  14  (e.g., four). In the embodiment, the pawls  14  are fan-shaped in cross-section. In the embodiment, the pawls  14  are hinged to the shank  11  at ends remote from the flange  10  and are separated from the axial column  13  by slots  17 , so that the pawls may flex toward and away from the column  13 . The ends of the pawls closest to the flange  10  have shoulders  15 , which are closely spaced from the flange  10 . As later described, the distance between the shoulders  15  and the flange  10  is designed so that an attachment member of a curtain shield airbag (with or without a reinforcement plate) and a body panel of a vehicle can be sandwiched between the shoulders  15  and the flange  10 .  
         [0021]     Except for the slots  17 , the axial column  13  takes up nearly the entire cross-section of shank  11 , to fill up most of the profile of a corresponding hole or holes in workpieces. The legs  9  of the pin take up portions of the cross-section of the shank  11  that are not filled by the axial column  13 . This provides high rigidity and high shearing force resistance. In the embodiment, the slots  17  are T-shaped in cross-section to complement the T-shaped cross-section of the legs  9  of the pin. See  FIGS. 4 and 7 . The flange  10  has holes therethrough that are extensions of the slots  17 , so that the legs  9  of the pin can be passed through the flange  10  into the slots  17  in the grommet shank.  
         [0022]      FIG. 8  shows the pin  1  partially inserted into the grommet  2 . In this position, it is preferred that the pin be temporarily fastened to the grommet, so that the fastener may be easily handled and transported without inadvertent separation of its parts. Such temporary fastening of the pin to the grommet can be achieved, for example, as disclosed in Patent Document 2 by providing internal resilient pawls near the base of the flange  10  that engage grooves in the legs  9  of the pin near their tips. As further disclosed in Patent Document 2, such internal pawls can engage shoulders midway of the legs  9  when the pin is fully inserted into the grommet to a permanent fastening position, so that the pin is held against withdrawal from the grommet.  
         [0023]     When the pin and the grommet are arranged as shown in  FIG. 8 , and the head  7  of the pin is pressed toward the flange  10  of the grommet, legs  9  of the pin enter the slots  17  in the shank of the grommet, so that a side of each leg  9  makes contact with the axial column  13  and two sides of each leg make contact with corresponding two sides of two adjacent resilient pawls  14 , as shown in  FIG. 10 . This provides a very stable, rigid assembly of the pin and the grommet, in which the pawls  14  are held against movement inward of the grommet shank.  
         [0024]      FIG. 11  shows a fastener  3  of the invention temporarily fastened to an attachment member  5  of a curtain shield airbag  18 . In such use, the shank  11  of the grommet  2  is inserted in a mounting hole in the attachment member  5 , having a profile that matches the cross-sectional profile of the grommet shank. A reinforcement plate  19  can be provided against the attachment member  5 , as shown in  FIG. 11 , in which case the reinforcement plate will have a hole aligned with the hole in member  5 . The thickness of the reinforcement plate  19  can be selected to ensure that a gap between the flange  10  of the grommet  2  and the shoulders  15  of the pawls  14  will be filled when an airbag attachment member  5 , a reinforcement plate  19 , and a vehicle body panel  6  are sandwiched between the flange  10  and the shoulders  15  of the pawls  14 .  
         [0025]     With a grommet shank cross-section that is polygonal, a corresponding polygonal hole will be provided in the attachment member  5 , the reinforcement plate  19 , and the body panel. When the grommet shank  11  is inserted in such holes, the pawls  14  are resiliently flexed inwardly of the shank  11  to permit the shank to be passed through the holes.  
         [0026]     By virtue of the temporary attachment arrangement shown in  FIG. 11 , an assembly comprising a curtain shield airbag with a plurality of fasteners of the invention inserted in corresponding holes of an airbag attachment member and reinforcement plate can be handled as a unit and delivered to a vehicle assembly line for mounting on a body panel, as will now be described.  
         [0027]      FIG. 12  shows a fastener  3  in accordance with the invention temporarily fastened to an airbag attachment member  5 , a reinforcement plate  19 , and a vehicle body panel  6 . The shank  11  of the grommet  2  is passed through a hole in the body panel  6  aligned with the holes in members  5  and  19 . The pawls  14 , after being flexed inwardly of the shank  11  for insertion through the aligned holes, then rebound so that the shoulders  15  are disposed to engage regions of the body panel  6  adjacent to the hole through the body panel. If now the pin  1  is pressed in the direction of arrow  21  in  FIG. 13  to insert the legs  9  of the pin into the slots  17  in the grommet shank  11  until the head  7  of the pin abuts the flange  10  of the grommet, the attachment member  5 , the reinforcement plate  19 , and the panel  6  will be permanently sandwiched between the flange  10  and the shoulders  15  of the pawls  14 . In the embodiment, the shoulders  15  of the pawls  14  will abut regions of the body panel adjacent to corners of a polygonal hole through the body panel  6 . Opposite sides of the axial column  13  will be disposed to engage corresponding edges of the aligned holes and opposite sides of the legs  9  of the pin will be disposed to engage corresponding edges in the aligned holes. With the aligned holes filled up, and pawls  14  prevented from movement inwardly of the grommet shank, very stable and secure attachment of the airbag to the body panel is achieved.  
         [0028]     While a preferred embodiment of the invention has been shown and described, changes can be made without departing from the principles and spirit of the invention, the scope of which is defined in the claims which follow. For example, the cross-sectional configuration of the grommet shank and the mounting holes can vary from the rectangular cross-section in the embodiment shown and described. Other polygonal cross-sections can be used, or even rounded cross-sections. The number and positions of resilient pawls and the number and configuration of pin legs can vary appropriately. In any case, it is essential that an axial column of the grommet remain highly rigid and have sufficient strength to withstand both horizontal and vertical detachment forces. When a curtain shield airbag is mounted on a body panel with fasteners of the invention, the fastener must have sufficient strength to withstand strong horizontal shearing force, so that the curtain shield airbag does not come off of the body panel when the airbag is rapidly deployed. Although the fastener embodiment of the invention has been shown and described for use in mounting an airbag on a body panel, other applications of the fasteners are of course possible. For example, fasteners of the invention can be used to replace nuts and bolts or rivets in various fastening applications.
A pin and grommet fastener provides high enough fastening strength to resist both longitudinal and transverse detachment forces tending to separate the fastener from workpieces. The pin has a head with depending legs, and the grommet has a shank with slots to receive respective legs passed through holes in a flange of the grommet. The shank has a strong axial column. Pawls on the grommet shank are held against movement inward of the shank by engagement with respective legs of the pin. The fastener can be used to mount a curtain shield airbag on a car body panel, for example.