Abstract:
A fastener for composite material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. The shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array.

Description:
BACKGROUND OF THE TECHNOLOGY 
       [0001]    This technology relates to fasteners which are employed for fastening composite material to a support structure. More particularly, the fasteners relate to deck screws employed for securing dense composite material. 
         [0002]    Numerous fasteners have been advanced for fastening deck members which are composed of composite material. Several of these such deck fasteners are directed to eliminating the volcanoing or mushrooming effect. As the technology of composite materials has advanced, the denseness of the composite members has increased. The increased denseness has had a significant impact on the effectiveness of conventional deck screws. Accordingly, many deck screws which were adapted to perform in earlier composite environments are significantly less effective in the more dense material. A significant issue resides in the difficulties of driving fasteners into very dense composite materials. 
       SUMMARY OF THE DISCLOSURE 
       [0003]    In one embodiment, a fastener for composite lumber comprises a head having a socket rotatably couplable for application of a torque and having a recessed underside with a lower rim. An elongated shank extends from the head and terminates at a distal tip. The shank has an upper portion with an enlarged diameter and a lower portion with a reduced diameter. The upper portion is traversed by a left hand thread. The lower portion has a tri-lobed configuration and is traversed by a right hand thread with the right hand thread having a plurality of notches. 
         [0004]    The right hand thread may extend substantially to the tip. At least one notch may be formed in the tip thread. In one embodiment, at least two notches are formed in the tip thread with at least two notches being out of phase. The notches form a spiral array. A land extends between the threads. The socket is preferably a square socket. The number of threads per inch of the left hand thread is less than the number of threads per inch of the right hand thread. The thread angle of the left hand thread is greater than the thread angle of the right hand thread. The left hand thread preferably has a minor diameter greater than the minor diameter of said right hand thread. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a longitudinal view, partly in phantom and partly in diagrammatic form, of a deck screw; 
           [0006]      FIG. 2  is an end view of a head portion of the deck screw of  FIG. 1 ; 
           [0007]      FIG. 2A  is an end view of an alternative embodiment of a head portion of the deck screw of  FIG. 1 ; 
           [0008]      FIG. 3  is an enlarged sectional view, partly in diagrammatic form, of a head and end portion of the deck screw of  FIG. 1  taken along the lines of A-A of  FIG. 2 ; 
           [0009]      FIG. 4  is a diagrammatic view illustrating a representative thread profile for a top portion of the deck screw of  FIG. 1 ; 
           [0010]      FIG. 5  is a diagrammatic view illustrating a representative thread profile for a bottom portion of the deck screw of  FIG. 1 ; 
           [0011]      FIG. 6  is a sectional view illustrating the deck screw of  FIG. 1  as employed for securing a composite material to a support structure; 
           [0012]      FIG. 7  is an enlarged longitudinal view of a medial portion of the deck screw of  FIG. 1 ; 
           [0013]      FIG. 8  is an enlarged cross-sectional view, partly in diagrammatic form, taken along the lines of B-B of  FIG. 7  and rotated 90°; 
           [0014]      FIG. 9  is an enlarged fragmentary view, partly in diagrammatic form, of a tip portion of the deck screw of  FIG. 1 ; 
           [0015]      FIG. 9A  is an enlarged fragmentary view, partly in diagrammatic form, of an alternative tip portion of the deck screw of  FIG. 1 ; 
           [0016]      FIG. 10  is a sectional view, partly in diagrammatic form, taken along the lines of C-C of  FIG. 9 ; 
           [0017]      FIG. 11  is a longitudinal side view, partly in diagrammatic form, illustrating a first stage workpiece stage for the deck screw of  FIG. 1 ; 
           [0018]      FIG. 12  is a longitudinal sectional view, partly in diagrammatic form, of a second stage workpiece for the deck screw of  FIG. 1 ; 
           [0019]      FIG. 13  is an end view of the workpiece of  FIG. 12 ; 
           [0020]      FIG. 14  is a longitudinal view, partly in diagrammatic form, and partly in phantom, of a third stage workpiece for the deck screw of  FIG. 1 ; and 
           [0021]      FIG. 15  is an enlarged sectional view, partly in phantom and partly in diagrammatic form, taken along the lines D-D of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    With reference to the drawings wherein like numerals represent like parts throughout the several views, a deck screw is generally designated by the numeral  10 . Deck screw  10  is especially adapted for securing elongated deck members  20  to a support member  22  wherein the composite material is a highly dense material such as, for example, Trex™ deck material, Timber Tech™ deck planks, etc. As illustrated in  FIG. 6 , the deck screw  10  functions to be driven through the composite member  20  into the support structure  22  to a depth wherein the head is below the upper surface of the material and forms a cylindrical counterbore above the head. The deck screw  10  can be driven without volcanoing or mushrooming of the material around the head and can be relatively easily driven without intense resistance to the application of torque during the driving process. 
         [0023]    With reference to  FIG. 1  the deck screw  10  includes a head  30  and an elongated shank  40  which extends from the head and has a generally bifurcated form. In one embodiment, the screw length l 1  is 2.75 ins with a head diameter d 1  of 0.285 ins. The shank  40  has an upper portion  42  of length l 2  of enlarged nominal diameter and a lower portion  44  of length l 3  of reduced nominal diameter which has a distal tip  46 . The tip terminates in a well-defined vertex point  48  which in the preferred form has a vertex angle of 25 degrees. The tip  46  functions as a drill point. 
         [0024]    With additional reference to  FIGS. 2 and 3 , the head  30  includes a recess  32  which at an upper portion is defined by a #1 square socket  34  and is adapted for coupling with a torque driver bit (not illustrated). Socket  34  preferably has a minimum depth of 0.075 ins and preferably a depth from 0.075 ins to 0.095 ins. If the socket depth is too shallow, the head will disengage during driving. If the head is too deep, the structural integrity of the head is jeopardized. The corners of the socket  34  may be rounded (not illustrated). 
         [0025]    With reference to  FIG. 2A , an alternative socket  34 A is defined by 8 radial slots and is adapted for coupling with a torque driver (not illustrated). The coupling socket  34 A may be similar in form and function to that described co-pending U.S. patent application Ser. No. 11/185,377 filed Jul. 20, 2005 which is assigned to the applicant of the present invention and the disclosure of which is incorporated by reference. The eight point torque driving engagement provides an efficient coupling engagement to facilitate torqueing of the deck screw and mitigate against disengagement of the tool during the driving process. 
         [0026]    The head  30  includes a tapered skirt-like periphery  36  which includes a recessed underside  38  and a lower cutting rim  39 . In one form, the angle of the underside flaring is on the order of 39 degrees as illustrated in  FIG. 3 . The head socket  34  is adapted to efficiently couple with the driver. The underside  38  of the head is configured to prevent composite material from being displaced past the head during the driving process and for capturing the composite material and trapping same at its underside. The cutting rim  39  is adapted to provide a clean, circular opening in the composite material and to present a pleased, finished setting of the deck screw in the drive bore so that the top surface of the head is below the surface of the dense composite material ( FIG. 6 ). 
         [0027]    The shank  40  has an upper portion  42  proximate the head which has a larger diameter than that of the lower portion  44 . In one embodiment, the upper portion  42  includes a left hand thread  52  which extends a length l 7  or approximately 0.750 inches and is 9 threads per inch. Thread  52  has a thread angle of 48 degrees as illustrated in  FIG. 4 . In a preferred embodiment of thread  52 , the minor thread diameter is 0.133 inches and the major thread diameter is 0.210 inches. 
         [0028]    Various approximate dimensions for one embodiment are summarized in Table I. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE I 
               
               
                   
                   
               
             
             
               
                   
                 d1 
                 0.285 ins  
               
               
                   
                 l1 
                 2.75 ins 
               
               
                   
                 l2 
                 0.80 ins 
               
               
                   
                 l3 
                 1.75 ins 
               
               
                   
                 l4 
                 0.02 ins 
               
               
                   
                 l5 
                 0.10 ins 
               
               
                   
                 l6 
                 0.12 ins 
               
               
                   
                 l7 
                 0.75 ins 
               
               
                   
                   
               
             
          
         
       
     
         [0029]    In another embodiment l 7  is approximately 0.45 ins. and l 3  is approximately 1.675 ins. 
         [0030]    As will be further described, the lower shank portion  44  also has a tri-lobe configuration as best illustrated in  FIG. 15 . The lower shank portion  44  is traversed by a right hand thread  54  which is 12 threads per inch and has an included thread angle of 30 degrees as illustrated by the profile of  FIG. 5 . A preferred embodiment of thread  54  has a minor diameter md of 0.123 inches and a major diameter Md of 0.190 to 0.196 inches. 
         [0031]    With reference to  FIGS. 1 and 7 , the thread  54  for a length l 8  of approximately 0.5 to 0.9 inches is traversed by a spiral array of notches  60 . As best illustrated in  FIG. 8 , the spiral array  60  subtends an angle of approximately 90 degrees about the shank axis with the depth of each notch being approximately the minor diameter. The notch width nw 1  is approximately 0.10 inches. The spiral array  60  extends approximately 1 revolution per 1.5 inches in length. 
         [0032]    With reference to  FIG. 9 , the shank terminates in the tip  46  which continues the spiral thread  54 . A notch  62  is shown in section the width nw 2  may be longer for notch  62 . In some embodiments, only one notch may be employed for the tip. If two notches are employed, the second notch  64  is slightly out of phase to create a split point. The notches  62 ,  64  may extend to a depth slightly into the minor diameter at the tip as illustrated in  FIG. 10 . The depth wd 2  of the notch is 0.12 inches. Another tip  46 A having a blunt point with notches  62 A and  64 A is illustrated in  FIG. 9A . 
         [0033]    Representative dimensions for lower portion  44  for a preferred embodiment are set forth in Table II. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE II 
               
               
                   
                   
               
             
             
               
                   
                 l8 
                 0.5 to 0.9 
                 ins 
               
               
                   
                 nw1 
                 0.10 
                 ins 
               
               
                   
                 nd2 
                 0.12 
                 ins 
               
               
                   
                 md 
                 0.123 
                 ins 
               
               
                   
                 Md 
                 0.190 to 0.196 
                 ins 
               
               
                   
                   
               
             
          
         
       
     
         [0034]    The manufacturing process for the deck screw  10  is best illustrated in the  FIGS. 11-15 . The initial work piece cut off shown as  10 A in  FIG. 11  has a workpiece diameter wd 1  of 0.15 ins and a workpiece length wl 1  of 2.70 ins. The first blow shown in  FIG. 12  produces workpiece  10 B which forms the bifurcated shank portions  425 ,  44 B and the head  30 B with workpiece lengths wl 2  of 2.68 ins and wl 3  of 0.125 ins and workpiece head diameter wd 2  of 0.250 ins. The coupling recess  32  is then punched into the head portion to form the final head detail as shown in  FIG. 3 . 
         [0035]      FIG. 14  shows the tri-lobe formed shank portion  44 A for the workpiece  10 C. The dimensions for workpieces  10 A,  10 B and  10 C are given in Table III for a screw  10  having a final length l 1  of 2.75 ins. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE III 
               
               
                   
                   
               
             
             
               
                   
                 l1 
                  2.75 ins 
               
               
                   
                 Wd3 
                 0.137 ins 
               
               
                   
                 wl1 
                  2.70 ins 
               
               
                   
                 wd1 
                  0.15 ins 
               
               
                   
                 wl2 
                  2.68 ins 
               
               
                   
                 wd2 
                 0.250 ins 
               
               
                   
                 wl3 
                 0.125 ins 
               
               
                   
                 wl4 
                  2.69 ins 
               
               
                   
                 wl5 
                 1.715 ins 
               
               
                   
                 wl6 
                 0.875 ins 
               
               
                   
                 wl7 
                 0.115 ins 
               
               
                   
                   
               
             
          
         
       
     
         [0036]    The threads  52 ,  54  are then rolled onto the workpiece  10 C. The notches  60  and  62  are then punched into the workpiece. Alternately, the notches may be formed during the thread forming process.