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[0001]    This application claims the benefit of priority from U.S. provisional application 61/524,372, filed Aug. 17, 2011. 
     
    
     BACKGROUND 
       [0002]    It is possible to join abutting substrates such as wooden boards in several ways. The substrates may be altered to create mortise and tenon or dovetail joints that allow the boards to interface and abut. These processes may require the use of special jigs or templates or a high degree of user skill and a large amount of time if created by hand. Additionally, it is necessary to start with at least one substrate piece longer than its desired final length, requiring an additional expenditure for materials. Moreover, users often strengthen these joints with other methods, as discussed below. 
         [0003]    In addition to machining the substrate to form a joint or in the alternative, adhesives may be used to bond one work surface to the other. Adhesives, such as wood glue, however, may seep beyond the boundaries of the joint and may require clean-up. It also often is necessary to clamp the substrates together and/or set the substrates aside for a period of time to allow the adhesive to set, adding time to the manufacture or assembly process. 
         [0004]    Mechanical fasteners also may be used to join substrates together. Traditional wood-type screw fasteners may be employed, and may provide much stronger holding power as compared to adhesives or other fasteners, but these often require pre-drilling a hole through at least one of the substrates, which adds additional time to the manufacturing process. This pre-drilling step also may result in the pieces being misaligned if one piece moved relative to the other during the pre-drilling step or if they are drilled separately and measurements are not precise. 
         [0005]    Alternatively, corrugated fasteners may be driven, e.g., using a pneumatic or powder-driven driving tool, into both substrates at the same time. These fasteners may span the joint between the substrates without requiring a separate pre-drilling step. Traditional corrugated fasteners, with or without the use of adhesives, may have significantly lower holding strengths than wood-type screw fasteners. In addition, they may lead to splitting of one or more of the substrates, particularly when driven in a direction generally aligned with the wood grain. 
         [0006]    In addition to the drawbacks described above, many of these methods may result in formation of a gap between the two substrates. Sometimes the gap allows for a portion of one substrate to abut the second substrate while another portion is spaced from the substrate, i.e., the joint is skewed. Other times, the gap may span substantially the entire joint, such as when a wood screw cannot embed completely in the second substrate. In either case, the presence of a gap not only is unsightly, but it may lead to a weakened joint between substrates. 
         [0007]    What is needed is a fastener that addresses the problems of the prior art. 
       SUMMARY 
       [0008]    The present disclosure is directed to a fastener for joining a plurality of substrates. In an embodiment, the fastener may include a bridge, a first rib extending outward from a first end of the bridge, and a second rib extending outward from a second end of the bridge, where at least one of the first and second ribs comprises a first flute and a second flute that converge at an apex. At least one, and preferably both, of the first and second flutes angle inwards towards a center of the fastener, preferably at substantially the same degree. In addition, the apex may be substantially centrally disposed width-wise on the fastener. Moreover, the fastener may have a height, a first end disposed outward from the first rib and a second end disposed outward from the second rib, wherein the bridge is disposed at a different location along the height than the first end and second ends, i.e., the bridge is offset from the ends when viewing the fastener from the side. Additionally, the bridge may be substantially planar. 
         [0009]    In another aspect, a fastener may include a bridge, which may be substantially planar, at least a first rib extending outward from a first end of the bridge and at least a second rib extending outward from a second end of the bridge. The fastener has a height, a first end disposed outward from the first rib and a second end disposed outward from the second rib, where the bridge is disposed at a different location along the height than the first and second ends. At least one of the first and second ribs may include a first flute and a second flute angled inwards towards a center of the fastener, e.g., between about 80 degrees and about 89 degrees. In addition, the first and second flutes may converge at a location generally equally spaced from the sides of the fastener. 
         [0010]    In still another aspect, a corrugated fastener may include a bridge and a plurality of ribs extending outward from opposing sides of the bridge along a length of the fastener. At least one rib on each of the opposing sides may include a plurality of flutes, which may angle inwardly towards a center of the fastener, and a remainder of the at least one rib also may angle inwardly towards a center of the fastener. The flutes and the remainder of the at least one rib may angle inwardly at substantially the same angle, e.g., between about 80 degrees and about 89 degrees. Moreover, the fastener may have a first end proximate a first plurality of ribs and a second end proximate a second plurality of ribs, the first and second ends having a first height. Similarly, the bridge may have a second height, which may be different from the first height of the first and second ends, and the fastener also may have at least one rib having the second height. 
         [0011]    In yet another aspect, a fastener may include a bridge, a first plurality of ribs extending outward from a first end of the bridge and a second plurality of ribs extending outward from a second end of the bridge, the first plurality of ribs comprising a first rib and a second rib. The first rib comprises a first flute and a second flute that converge at an apex, where at least one of the flutes angle inwards towards a center of the fastener, and where the second rib comprises a first and second flute that are substantially aligned with one another. 
         [0012]    In a further aspect, a corrugated fastener may include a bridge and a plurality of ribs extending outward from opposing sides of the bridge along a length of the fastener. At least one rib on each of the opposing sides may include a plurality of flutes, the flutes angled inwardly towards a center of the fastener substantially symmetrically about an axis perpendicular to a direction of driving of the fastener. Conversely, at least one second rib on each of the opposing sides may include a second plurality of flutes that are substantially aligned with the direction of driving. In addition, at least one of a driving side, a first side, and a second side may include a ground edge. Moreover, each of the ribs on each side of the fastener may include a radius of curvature, where the radius of curvature of a rib proximate the bridge is larger than the radius of curvature of a rib on the opposite side of the first rib as the bridge. 
         [0013]    These and other features and advantages are evident from the following description, with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a top view of one embodiment of a fastener for securing a plurality of substrates together. 
           [0015]      FIGS. 2   a  and  2   b  (collectively “FIG.  2 ”) are side views of the fastener of  FIG. 1 . 
           [0016]      FIG. 3  is an end view of the fastener of  FIG. 1 . 
           [0017]      FIG. 4  is a side view of a plurality of fasteners embedded in a plurality of substrates. 
           [0018]      FIG. 5  is a perspective view of a second embodiment of a fastener embedded in a plurality of substrates. 
           [0019]      FIG. 6  is a top view of another embodiment of a fastener for securing a plurality of substrates together. 
           [0020]      FIG. 7  is a section view through line A-A in  FIG. 6 . 
           [0021]      FIG. 8  is a detail view of detail A in  FIG. 6 . 
           [0022]      FIG. 9  is a detail side view of the fastener of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring now to  FIGS. 1-3 , fastener  10  includes a plurality of ribs  12  separated by a bridge  14 . Ribs  12  may be disposed in a generally sinusoidal or wave-like fashion, such that fastener  10  may be considered a corrugated-type fastener. 
         [0024]    Fastener  10  may include a substantially identical number of ribs  12  on each side of bridge  14  such that fastener  10  is generally symmetrical about a widthwise centerline  32 . In the embodiment seen in  FIG. 2 , fastener  10  includes three ribs  12   a ,  12   b ,  12   c , spanning approximately 1½ periods of a wave, although more or fewer ribs may be used. Ribs  12   a ,  12   b ,  12   c  also may be substantially similarly spaced, although it is possible to alter converging angle  16  and/or diverging angle  18  to change spacing between ribs  12 . 
         [0025]    In addition, ribs  12   a ,  12   b ,  12   c  may have substantially similar amplitudes, although one or more ribs may be larger or smaller than the remaining ribs. In one aspect, ribs  12 —and fastener  10  generally—may be between about ⅛″ and about 1″ high, preferably between about ¼″ and about ¾″ high, and in one embodiment, about ½″high. In another aspect ribs  12  and fastener  10  may be between about 1/64″ and about ¼″ high, preferably between about 1/16″ and about ¼″ high, and in one embodiment, about 1/10″ high. 
         [0026]    Each rib  12  may comprise one or more curvilinear or partially cylindrical portions between converging angle  16  and diverging angle  18 . Whether seen as “hills” or “valleys,” depending on the angle from which fastener  10  is viewed, ribs  12  may have substantially similar radii of curvature, e.g., between about 1/32″ and about 1/16″ or, in one embodiment, about 0.035″ 
         [0027]    Each rib  12  may include a first flute  20  and second flute  22  that converge at clamping apex  24 . Apex  24  may be disposed at some point between first side  26  and second side  28 , which may distribute a clamping force of fastener  10  more evenly along a vertical plane of assembly, thereby increasing joint strength and minimizing gaps between substrates  2 ,  4 . 
         [0028]    While apex may be located at any location along width of fastener  10 , apex  24  preferably is generally equally spaced between first side  26  and second side  28 , i.e., generally aligned with a lengthwise centerline  30  of fastener  10 . One or both of first and second flutes may be angled inward toward center  11  of fastener  10 . For example, if both first flute  20  and second flute  22  are angled inward, flutes may appear to form a chevron with apex  24  pointing toward center  11 . 
         [0029]    First flute  20  may form an angle, α, with first side  26 , and second flute  22  may form an angle, β, with second side  28 , where both angles are measured relative to the portion of first side  26  and second side  28  nearer center  11 . Preferably, α and β may be substantially similar angles, e.g., within the desired manufacturing tolerances, although different angles are possible. For example, one or both of α and β may be between about 75 degrees and about 89 degrees, preferably between about 80 degrees and about 89 degrees, still more preferably between about 85 degrees and about 89 degrees, and in one embodiment, about 87 degrees. 
         [0030]    Preferably, each first flute on each rib  12   a ,  12   b , and  12   c  includes a substantially equal angle, α, and each second flute on each rib  12   a ,  12   b , and  12   c  includes a substantially equal angle, β. In addition, angles α and β may continue past first flute  20  and second flute  22  and may apply to a remainder of rib  12 . 
         [0031]    First side  26  and second side  28  may be generally planar, which plane may be generally parallel to a plane including lengthwise centerline  30 . In the event that first side  26  and second side  28  are not generally parallel to that plane, angles α and β may be calculated relative to that plane, i.e., to a plane that is generally perpendicular to fastener and generally parallel to the plane including lengthwise centerline  30 . 
         [0032]    Moving inward, fastener  10  may include bridge  14  spanning a width between innermost ribs  12 . In one embodiment, as seen in  FIG. 5 , bridge  14  may be angled so as to form another chevron when viewed from the side or when sectioning fastener through a plane generally perpendicular to fastener and including lengthwise centerline  30 . Preferably, however, bridge  14  is generally planar along its length and width, as seen in  FIG. 2 . 
         [0033]    Staying with the side view of  FIG. 2 , it surprisingly was found that offsetting bridge  14  from first end  34  and/or second end  36  minimized wood splitting when fastener  10  was driven into wooden substrate  2 , particularly when driven in a direction generally parallel to the grain of substrate  2 . Bridge  14  may be offset from one or both of first end  34  and second end  36 . In this embodiment, bridge  14  may be substantially aligned with lower rib  12   b , while first end  34  and second end  36  may be substantially coincident with upper rib  12   c . In other embodiments, bridge may disposed higher or lower than lower rib  12   b , preferably while remaining misaligned with first end  34  and second end  36 . 
         [0034]    In still another embodiment, instead of being aligned with inner rib  12   a , first end  34  and second end  36  may be aligned with rib  12   b . In this embodiment, bridge  14  may not be substantially aligned with rib  12   b  but instead may be disposed at some other offset location. 
         [0035]    Similarly, first and second ends may be disposed at a height somewhere between rib  12   a  and rib  12   b . In that embodiment, bridge  14  preferably is disposed at a height substantially misaligned with first end  34  and second end  36 , which height may be greater or less than heights of ribs  12   a ,  12   b.    
         [0036]    It also was found that increasing a length of bridge increased joint strength when substrate  2  was joined to a second substrate  4 . As such, for use when joining wooden substrates  2 ,  4  such as ¾″×1⅕″ boards, bridge  14  may be between about ¼″and about ½″ long, preferably about ⅜″ long, and in one embodiment, about 0.36″ long. Bridge  14  may be longer or shorter, e.g., when joining substrates of different sizes. 
         [0037]    Alternatively, length of bridge  14  may be viewed in proportion to total length of fastener  10 . Bridge  14  may be between about 25% and about 50% of fastener length, preferably between about 30% and about 40%, and in one embodiment, about 39% of the fastener length. 
         [0038]    Fastener  10  also may have a thickness between first surface  38  and second surface  40 . In one embodiment, fastener  10  may be about 1/16″ thick, but fastener  10  is not limited to this thickness. 
         [0039]    Returning to  FIG. 1 , one or both of first end  36  and second end  38  may include an inwardly extending notch  42 . Notch may comprise a plurality of linear segments or a combination of a curved surface and one or more generally linear segments between curved surface and fastener ends. While notches  42  may assist in collating fasteners or guiding fasteners along a magazine within a fastener driving tool, notches may not be necessary. 
         [0040]    Turning now to  FIGS. 6-9 , in another aspect, fastener  110  similarly may include a plurality of ribs  112  disposed in a generally sinusoidal or wave-like fashion and separated by a bridge  114 . 
         [0041]    Fastener  110  may include a substantially identical number of ribs  112  on each side of bridge  114  such that fastener  110  is generally symmetrical about a widthwise centerline  132 . As seen in  FIG. 7 , fastener  110  may include two ribs  112   a ,  112   b  on each side of bridge  114 , spanning approximately 1 period of a wave, although more or fewer ribs may be used. Ribs  112   a ,  112   b  may be substantially similarly spaced, although, as seen in  FIG. 7 , it is possible to alter converging angle  116  and/or diverging angle  118  to change spacing between ribs  112 . 
         [0042]    In addition, ribs  112   a ,  112   b  may have substantially similar amplitudes, although one or more ribs may be larger or smaller than the remaining ribs. In one embodiment, ribs  112 —and fastener  110  generally—may be between about 1/64″ and about ¼″ high, preferably between about 1/16″ and about ¼″ high, and in one embodiment, about 1/10″ high. 
         [0043]    Each rib  112  may comprise one or more curvilinear or partially cylindrical portions. Whether seen as “hills” or “valleys,” depending on the angle from which fastener  110  is viewed, ribs  112  may have substantially similar radii of curvature, e.g., between about 1/32″ and about 1/16″ or, in one embodiment, about 0.03.″ Alternatively, outermost ribs  112   b  may angle more severely or may include a generally linear or generally planar portion proximate ends  134 ,  136 , which may help increase clamping effect of fastener  110 . For example,  FIG. 7  illustrates that a radius of curvature between bridge  114  and rib  112   a  may be larger than a radius of curvature of rib  112   b , e.g., about 0.038″ as compared to about 0.03″, causing angle  116  to be larger than angle  118 . As such, rib  112   a  may have a longer wavelength than rib  112   b.    
         [0044]    As seen in  FIG. 7 , ribs  112   b  proximate ends  134 ,  136  may include a generally linear or generally planar portion  150 . Portion  150  may form an angle between about 45 degrees and about 80 degrees with respect to a plane along the length of fastener  110 , e.g., generally parallel to bridge  114 , preferably between about 50 degrees and about 75 degrees, and in one embodiment, about 65 degrees. 
         [0045]    As seen in  FIG. 6 , on each side of centerline  132 , rib  112   a  may include a first flute  120   a  and second flute  122   a  that converge at clamping apex  124   a , and rib  112   b  may include a first flute  120   b  and second flute  122   b  that converge at apex  124   b . Apexes  124  may be disposed at some point between first side  126  and second side  128 , which may distribute a clamping force of fastener  110  more evenly along a vertical plane of assembly, thereby increasing joint strength and minimizing gaps between substrates. 
         [0046]    While apexes may be located at any location along width of fastener  110 , apexes  124  preferably are generally equally spaced between first side  126  and second side  128 , i.e., generally aligned with a lengthwise centerline  130  of fastener  110 . 
         [0047]    With respect to rib  112   a , one or both of first and second flutes  120   a ,  122   a  may be angled inward toward center  111  of fastener  110 . For example, if both first flute  120  and second flute  122  are angled inward, flutes may appear to form a chevron with apex  124  pointing toward center  111 . Conversely, with respect to rib  112   b , one or both of flutes  120   b ,  122   b  may not be angled inward toward center  111 , such that flutes  120   b ,  122   b  may have collinear axes of curvature, which may be generally parallel to axis  132  or generally perpendicular to axis  130 . 
         [0048]    Turning back to rib  112   a , first flute  120   a  may form an angle, α, with first side  126 , and second flute  122   a  may form an angle, β, with second side  128 , where both angles are measured relative to the portion of first side  126  and second side  128  nearer center  111 . Preferably, α and β may be substantially similar angles, e.g., within the desired manufacturing tolerances, although different angles are possible. For example, one or both of α and β may be between about 75 degrees and about 89 degrees, preferably between about 80 degrees and about 89 degrees, still more preferably between about 85 degrees and about 89 degrees, and in one embodiment, about 88 degrees. 
         [0049]    First side  126  and second side  128  may be generally planar, which plane may be generally parallel to a plane including lengthwise centerline  130 . In the event that first side  126  and second side  128  are not generally parallel to that plane, angles α and β may be calculated relative to that plane, i.e., to a plane that is generally perpendicular to fastener and generally parallel to the plane including lengthwise centerline  130 . 
         [0050]    Turning to  FIG. 7 , in this aspect, bridge  114  may be substantially aligned with first end  134  and/or second end  136 . Preferably, bridge  114  and ends  134 ,  136  are centrally disposed along a height of fastener  110 . Alternatively, ends and bridge may be substantially aligned and may be disposed at a height other than generally along the midpoint of the height of fastener. 
         [0051]    Bridge  114  may be between about ¼″ and about ½″ long, preferably about ⅜″ long, and in one embodiment, about 0.3″ long. Bridge  114  may be longer or shorter, e.g., when joining substrates of different sizes. Alternatively, length of bridge  114  may be viewed in proportion to total length of fastener  110 . Bridge  114  may be between about 25% and about 50% of fastener length, preferably between about 30% and about 40%, and in one embodiment, about 39% of the fastener length. 
         [0052]    Fastener  110  also may have a thickness between first surface  138  and second surface  140 . In one embodiment, fastener  110  may be about 1/64″ thick, but fastener  110  is not limited to this thickness. 
         [0053]    One or both of first end  134  and second end  136  may include an inwardly extending notch (not shown), which may be similar to notch  42  described above. While notches may assist in collating fasteners or guiding fasteners along a magazine within a fastener driving tool, notches may not be necessary. 
         [0054]    At least one of ends  134 ,  136  and sides  126 ,  128  may include a ground edge  152 . As seen in  FIG. 6 , in one aspect, at least side  128  includes ground edge  152   c , where side  128  is the leading side that is driven into the substrates. Ground edge  152  may reduce thickness of material at side  128 . One or more grind geometries are possible, e.g., fastener  110  may include a grind on one or, as seen in  FIG. 9 , both of surfaces  138 ,  140 . Grind may terminate anywhere between, or including, surfaces  138 ,  140 . Edges may be ground substantially to a line contact, i.e., to where grinding planes substantially intersect in the case where both surfaces are ground or to where grinding plane intersects second surface  140  in the event that only surface  138  is ground. Preferably, however, edges may be ground so as to leave a flat  156  of side  128  remaining. Ground edges  152  may be angled downwardly from their respective surfaces an amount θ that may be between about 10 degrees and about 75 degrees, preferably between about 15 degrees and about 45 degrees. 
         [0055]    In the event that more than one edge is ground, grinds further may include a chamfer  154  between one or more ground edges  152 . 
         [0056]    Fastener  10  or  110  may be used when joining two substrates together, e.g., when joining two wooden pieces in a cabinet face frame assembly. In that application, the wooden members often are placed next to one another forming a butt joint between them, as seen in  FIG. 4 . The wood grain in the two members may be generally perpendicular to one another, which usually is the case when the members are joined generally perpendicularly. Alternatively, the members may be angled acutely or obtusely with respect to one another, but even then, the grain of one member usually remains offset from the other member. 
         [0057]    Regardless of relative grain orientations, members  2 ,  4  may be placed in an abutted relationship to one another, and fastener  10 ,  110  may be driven across joint. While fastener  10 ,  110  may be driven in any orientation across joint, preferably fastener is driven generally perpendicular to joint, without the need to pre-drill a pilot hole. Once engaged with members, clamping apex formed by first flute and second flute may direct clamping force toward center of fastener  10 ,  110 , drawing members  2 ,  4  together, preventing formation of gaps between members  2 ,  4 , and increasing joint strength. 
         [0058]    While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific exemplary embodiment and method herein. The invention should therefore not be limited by the above described embodiment and method, but by all embodiments and methods within the scope and spirit of the invention as claimed.

Summary:
A corrugated-typed fastener configured to couple a first substrate to a second substrate includes a bridge and a plurality of ribs, the ribs having a plurality of flutes. The flutes, and possibly the ribs, may be angled inwardly to form an apex disposed within the width of the fastener and pointing towards a center of the fastener. The ribs may extend outward from the bridge towards opposing ends of the fastener, and the ends may be at a different height than the bridge when viewing the fastener from the side. Alternatively, the ends may be at the same height as the bridge and also may be generally centered on the height of the fastener.