Abstract:
A fastener assembly comprises a beveled flush nut shaped to fit flush to a surface of the first piece within a countersunk portion of a hole, a threaded rod sized to engage the beveled flush nut and to extend through the hole in the first piece and an aligned hole in the second piece. A first nut is sized to threadedly engage the distal end of the threaded rod. A second nut is sized to threadedly engage the proximal end of the threaded rod when extended through an aligned opening in a third piece positioned over the second piece. The threaded engagement at the beveled flush nut can be overcome by tightening the second nut against the third piece, thereby securing the first piece, second piece and third piece together.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/705,584, filed Sep. 25, 2012, which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    This application relates to fasteners, and in particular to a fastening arrangement or assembly suited to making repairs. 
         [0003]    In applications where fasteners are used to hold multiple components, parts or pieces together, it is sometimes necessary to make repairs. If the various pieces can be entirely disassembled all at one time without consequence, making repairs is straightforward. If, however, at least some pieces cannot be entirely disassembled without expensive, difficult and/or awkward preparations, then making repairs is complicated. 
         [0004]    For example, repairs to steel bridges can call for adding repair plates over damaged original components that are held in place with rivets or other fasteners. Simply adding a repair plate over the original components usually results in a gap between the repair and the underlying plate due to the heads of the existing rivets. Such a gap can cause moisture to collect and accelerate corrosion. 
         [0005]    A repair without gaps between the plates would require disassembling the connection. It is difficult to fully disassemble the connection, however, because the affected plate and fasteners are still carrying part of the bridge&#39;s load. To fully disassemble the plate in question may require temporarily supporting the bridge from below, which is time consuming and expensive, even if it is possible. 
       SUMMARY 
       [0006]    Described herein are approaches to a new fastener assembly that addresses these and other drawbacks in the prior art. 
         [0007]    According to one implementation, a fastener assembly for repairing a rivet connecting a first piece to a second piece comprises a beveled flush nut, a threaded rod, a first nut and a second nut. The beveled flush nut is shaped to fit flush to a surface of the first piece within a countersunk hole formed in the first piece at a location where a rivet has been removed. The threaded rod is sized to threadedly engage the beveled flush nut and has a proximal end positioned to extend proximally of the beveled flush nut, and a distal end sized to extend through the hole in the first piece and an aligned hole in the second piece. 
         [0008]    The first nut is sized to threadedly engage the distal end of the threaded rod, such that the threaded engagements between (1) the first nut and the threaded rod adjacent the second piece, and (2) the beveled flush nut and the threaded rod adjacent the first piece, are sufficient to secure the first and second pieces together. The second nut is sized to threadedly engage the proximal end of the threaded rod when extended through an aligned opening in a repair piece positioned over the second piece. 
         [0009]    The threaded engagement between the beveled flush nut and the threaded rod can be overcome by tightening the second nut against the repair piece. In this way, the first piece, second piece and repair piece are secured together by the threaded engagements between (1) the first nut and the threaded rod adjacent the second piece and (2) the second nut and the threaded rod adjacent the repair piece. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side elevation view of a conventional two-piece assembly to be repaired, shown together with a repair plate. 
           [0011]      FIG. 2  is a side elevation view in section of the two-piece assembly of  FIG. 1  after the repair has been initiated according to the new approach. 
           [0012]      FIG. 3  is side elevation view in section showing the two-piece assembly temporarily clamped together by the beveled flush nut, threaded rod and nut. 
           [0013]      FIG. 4  a side elevation view of the fastener assembly and repair plate as installed on a completed repair of the two-piece assembly. 
           [0014]      FIGS. 5 and 6  are side elevation views similar to  FIGS. 3 and 4 , respectively, except showing an embodiment where the threaded rod and one nut have been replaced by a bolt. 
           [0015]      FIGS. 7 ,  8  and  9  are side elevation views similar to  FIGS. 2-4 , respectively, except showing an embodiment where the beveled flush nut is welded to the threaded rod. 
           [0016]      FIG. 10  is a top plan view of a beveled flush nut. 
           [0017]      FIG. 11  is a side view of a beveled flush nut. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In  FIG. 1 , a conventional assembly  10  of a first piece  12  connected to an overlapped second piece  14  by a rivet  16  extending through a through hole  20  ( FIG. 2 ) in both pieces is shown. As indicated at an area  15  in the example of  FIG. 1 , the first piece  12  is in need of repair, e.g., due to loss of material from corrosion. A preferred method of repair includes fitting the first piece  10  with an overlying piece to cover the area  15  and then secure the resulting assembly together. 
         [0019]    One form of a suitable overlying piece is a repair plate  18 . In  FIG. 1 , the repair plate  18  is shown aligned with and spaced away from the first piece  12 . The repair plate  18  is dimensioned at least as large as the area  15  and to extend to one or more adjacent holes for fastening. According to the conventional approach described above, the repair plate  18  would be attached to the first piece  12  with the gap between these two members remaining because of the presence of one or more of the rivets  16 . 
         [0020]    According to the new approach as shown in  FIGS. 2-4 , however, the repair plate  18  is installed adjacent the first piece  12  generally without a significant gap. As shown in  FIG. 2 , the conventional rivet  16  has been removed to expose a through hole  20  extending through the first piece  12  and the second piece  14 . In some examples, there are other rivets or connections between the first piece  12  and the second piece  14  (not shown) that hold these components together even after the rivet  16  is removed. Rivets establish a shear-type connection between the pieces. The through hole  20  has been drilled to define a recess, in this case a countersink  21 , to accommodate a threaded fastener, which in this case a beveled flush nut  22 . The beveled flush nut  22  has the general shape of an inverted truncated frustro-conical solid with an axial threaded bore. 
         [0021]    In  FIG. 3 , a length of threaded rod  24 , also called “allthread” has been threaded through the beveled flush nut and extends through the through hole  20  to the outer side of the second piece  14 , where it is secured with a nut  26 . Thus, as seen in  FIG. 3 , the first piece  12  and the second piece  14  are secured together, at least temporarily, by a clamping force exerted by threaded engagement between the beveled flush nut  22  and the threaded rod  24  at one end and the nut  26  and the threaded rod  24  at the other end. The components are preferably designed to have the capacity to replace the conventional rivet&#39;s shear capacity with a friction force applied by torqueing one of the nut  26 , the beveled flush nut  22  and the threaded rod  24  relative to the other two components. Because of the shape of the beveled flush nut  22 , it prevents lateral movement of the clamped assembly, which adds stability during the period before the repair plate  18  is installed. 
         [0022]    In some exemplary applications, the threaded rod  24  with the nut  26  attached is passed through the through hole  20  from the second piece side, and then the beveled flush nut  22  is rotated into its recessed position as shown. In other applications, the beveled flush nut  22  is installed first, and the threaded rod is installed from the first piece side of the through hole  20 . In typical applications, the connection of the beveled flush nut  22 , threaded rod  24  and nut  26  is tightened to a specified torque range, which is selected based upon component sizes, loads, materials, and/or surface treatments, as well as other factors. 
         [0023]    In  FIG. 4 , the repair plate  18  has been fitted over the first piece  12  to cover the area  15  and so that a hole in the repair plate  18  is passed over the protruding end of the threaded rod  24 . Because the beveled flush nut  22  is at least flush or even recessed relative to the first piece  12 , the repair plate  18  can lay flat against the first piece  12 . A nut  28  is threaded onto the protruding end of the threaded rod  24 . By torqueing the nut  28  (or the threaded rod  24 ), a clamping force is exerted between the beveled flush nut  22  and the nut  28  on the repair plate  18 . According to the approach described above, the beveled flush nut  22  or the threaded rod  24  in an intermediate section can be designed such that the force exerted by its threads is overcome by a greater force exerted by the nut  28  and the nut  26 . In this way, the greater force effectively strips the threads of the beveled flush nut  22  or the mating section of the threaded rod  24 , thereby allowing the threaded rod to pass relatively freely through the beveled flush nut  22  without having to be threaded or unthreaded. As a result, the force is exerted by the nut  26 , the threaded rod  24  and the nut  28  on the repair plate  18 , the second piece  14 , and the first piece  12  sandwiched therebetween. Stated differently, the stripping of the threads transfers the clamping force from being exerted by the beveled flush nut  22  and the nut  26  to being exerted by the nut  28  and the nut  26 . 
         [0024]      FIGS. 5 and 6  illustrate an embodiment where the nut  26  and the threaded rod  24  are replaced by a bolt. For example, as shown in  FIG. 5 , the bolt  50  can be inserted from the second piece side, threaded through the beveled flush nut  22  and have its threaded shaft  52  extend beyond the first piece  12 . In this way, the repair plate  18  can be installed over the first piece  12  and secured with the nut  28  as shown in  FIG. 6 . Using a bolt instead of the threaded rod and one of the nuts reduces the number of components and can provide for easier handling and assembly in some circumstances. 
         [0025]      FIGS. 7 ,  8  and  9  illustrate an embodiment where the threaded rod and the beveled flush nut are joined together by a permanent connection. For example, the beveled flush nut  22  can be included as a portion of the one-piece threaded rod assembly  60 . In  FIG. 7 , the threaded rod assembly  60  is inserted through the through hole  20  until the beveled flush nut portion is against the countersink and with the remaining length of the threaded rod assembly  60  extending beyond the second piece  14 . As shown in  FIG. 8 , the first piece  12  and the second piece  14  are secured together, at least temporarily, by a clamping force exerted by the beveled flush nut portion bearing against the countersink at one end and the threaded connection between the threaded rod assembly  60  and the nut  26  at the other end. 
         [0026]    In  FIG. 9 , the repair plate  18  is installed to lie flat against the first piece  12  and the nut  28  is threaded onto the threaded rod assembly  60 . The nut  28  is torqued to a predetermined specification. In some implementations, the torque is selected not to cause the beveled flush portion to separate from the remainder of its threaded rod assembly  60 , but rather to lift slightly out of the countersink, which similarly results in transferring the clamping force to the connections at the nut  26  and the nut  28 . 
         [0027]      FIGS. 10 and 11  are detailed views showing the geometry of the beveled flush nut  22 . According to one specific implementation, the beveled flush nut is made of a  4140  steel that is heat treated, and is dimensioned to be received within ⅜″ thick steel plate and with ¾″ threads. Any acceptable bevel angle can be used, such as about 40 degrees. Of course, the dimensions of the various components can be sized to suit the operating requirements of the particular application. The intersection of the first piece  12  and the repair plate  18 , as well as other exposed surfaces, can be sealed or treated as appropriate for the conditions, e.g., such as with zinc-rich paint as appropriate. 
         [0028]    Thus, the beveled flush nut  22  can be used in at least two modes: (1) as a threaded fastener capable of exerting a clamping force, even if temporary; and (2) as a passive component that passes freely over the threaded rod  24  tensioned at other locations but still allowing adjacent pieces to fit close together. In many applications, the described assembly offers advantages because it allows for step-wise repair of damaged load-bearing connections that otherwise would require separate support. In addition, the repair plate or component can be fit against the original piece requiring repair without gaps. 
         [0029]    Although not shown in figures, a conventional flat washer can be provided adjacent the nut  26  and/or adjacent the nut  28 . Although the examples above describe two nuts  26  and  28 , it would also be possible in some applications to have the nut  28  and the threaded rod  24  replaced by a bolt threaded through the second piece  14 , the first piece  12  and the beveled flush nut  22 . 
         [0030]    In many applications, it is not necessary to take any measures to prevent the beveled flush nut  22  from rotating when not intended. If avoiding such unintended rotation is required, the beveled flush nut  22  can be installed with a thread locking compound or its edge can be set with a punch. Although the described examples highlight the assembly&#39;s use in making repairs, the assembly can be used in other applications where multiple pieces are fit closely together, and is particularly suited to holding two or more pieces together until final steps are completed.