Plastic composite deck screw

Abstract

A deck screw for use with plastic and plastic composite deck materials has a shank with a lower segment having a right hand thread and an upper segment having a left hand thread. The upper left hand threaded section has a major diameter which is the same as or slightly less than the major diameter of the lower right hand threaded section. The deck screw evacuates and eject loose material cut out from the deck material as the screw penetrates the deck material, preventing undesirable unsightly deformation of the deck upper surface.

1 . A deck screw for fastening a workpiece to a base member, comprising: 
 a shank having a lower segment having a right hand thread and an upper segment having a left hand thread, said right hand thread of said lower segment having a right hand thread major diameter, said right hand thread and said left hand thread being adjacent each other without a substantial gap therebetween, said left hand thread of said upper segment having a left hand thread major diameter, said left hand thread major diameter being equal to or slightly less than said right hand thread major diameter; and    a head having means for engagement by a fastener driving tool.    
   
   
       2 . The deck screw of  claim 1  wherein said left hand thread major diameter is slightly less than said right hand thread major diameter.  
   
   
       3 . The deck screw of  claim 2  wherein said left hand thread major diameter is 0.10 mm or less smaller than said right hand thread major diameter.  
   
   
       4 . The deck screw of  claim 2  wherein said right hand thread of said lower segment and said left hand thread of said upper segment are adjacent each other and provide a length of the threaded portions of the shank, and wherein said right hand thread of said lower segment comprises from about 45 percent to about 80 percent of the length of the threaded portions of the shank.  
   
   
       5 . The deck screw of  claim 4  wherein said right hand thread of said lower segment and said left hand thread of said upper segment are adjacent each other and provide a length of the threaded portions of the shank, and wherein said right hand thread of said lower segment comprises from about 60 percent to about 70 percent of the length of the threaded portions of the shank.  
   
   
       6 . The deck screw of  claim 4  wherein said screw has a total length of about 70 mm, and said left hand thread of said upper segment has a length of between 15-17 mm, and said right hand thread of said lower segment has a length of the between 43-46 mm.  
   
   
       7 . The deck screw of  claim 1  wherein said head has a lower surface with an annular channel surrounding said shank.  
   
   
       8 . The deck screw of  claim 1  wherein said left hand thread has a left hand thread angle and the right hand thread has a right hand thread angle, and the left hand thread angle is greater than the right hand thread angle.  
   
   
       9 . The deck screw of  claim 8  wherein said left hand thread has a left hand thread angle of between about 30° to about 45° and said right hand thread has a right hand thread angle of between about 25° to about 40°.  
   
   
       10 . The deck screw of  claim 8  wherein said left hand thread has a left hand thread angle of about 40° and said right hand thread has a right hand thread angle of about 30°.  
   
   
       11 . The deck screw of  claim 1  wherein said left hand thread has a left hand thread pitch and the right hand thread has a right hand thread pitch, and the right hand thread pitch is larger than the right hand thread pitch.  
   
   
       12 . The deck screw of  claim 11  wherein said left hand thread pitch has a left hand thread pitch of between about 1.8 mm to about 2.8 mm and said right hand thread has a right hand thread pitch of between about 2.3 mm to about 3.2 mm.  
   
   
       13 . The deck screw of  claim 12  wherein said left hand thread pitch has a left hand thread pitch of about 2.3 mm and said right hand thread has a right hand thread pitch of about 2.8 mm.  
   
   
       14 . A deck screw for fastening a workpiece to a base member, comprising: 
 a shank having a lower segment having a right hand thread and an upper segment having a left hand thread, said right hand thread of said lower segment having a right hand thread major diameter, said right hand thread and said left hand thread being positioned to form a continuous thread pattern, said left hand thread of said upper segment having a left hand thread major diameter, said left hand thread major diameter being slightly less than said right hand thread major diameter;    said right hand thread of said lower segment and said left hand thread of said upper segment provide a length of the threaded portions of the shank, and wherein said right hand thread of said lower segment comprises from about 45 percent to about 80 percent of the length of the threaded portions of the shank;    said left hand thread having a left hand thread pitch and the right hand thread having a right hand thread pitch, said right hand thread pitch being larger than said right hand thread pitch;    said left hand thread having a left hand thread angle and the right hand thread having a right hand thread angle, said left hand thread angle being greater than said right hand thread angle; and    a head having means for engagement by a fastener driving tool having a lower surface with an annular channel surrounding said shank.    
   
   
       15 . The deck screw of  claim 14  wherein said left hand thread major diameter is 0.25 mm or less smaller than said right hand thread major diameter.  
   
   
       16 . The deck screw of  claim 15  wherein said left hand thread major diameter is 0.10 mm or less smaller than said right hand thread major diameter.  
   
   
       17 . The deck screw of  claim 16  wherein said right hand thread of said lower segment comprises from about 60 percent to about 70 percent of the length of the threaded portions of the shank.  
   
   
       18 . The deck screw of  claim 17  wherein said left hand thread pitch has a left hand thread pitch of between about 1.8 mm to about 2.8 mm and said right hand thread has a right hand thread pitch of between about 2.3 mm to about 3.2 mm.  
   
   
       19 . The deck screw of  claim 18  wherein said left hand thread pitch has a left hand thread pitch of about 2.3 mm and said right hand thread has a right hand thread pitch of about 2.8 mm.  
   
   
       20 . The deck screw of  claim 18  wherein said left hand thread has a left hand thread angle of between about 30° to about 45° and said right hand thread has a right hand thread angle of between about 25° to about 40°.  
   
   
       21 . The deck screw of  claim 20  wherein said left hand thread has a left hand thread angle of about 40° and said right hand thread has a right hand thread angle of about 30°.  
   
   
       22 . The deck screw of  claim 1  wherein said right hand thread and said left hand thread are positioned to form a continuous thread pattern.  
   
   
       23 . A method of mounting a plastic or plastic composite board to a base member, using a deck screw having a shank having a lower segment having a right hand thread and an upper segment having a left hand thread, said right hand thread of said lower segment having a right hand thread major diameter, said right hand thread and said left hand thread being adjacent each other without a substantial gap therebetween, said left hand thread of said upper segment having a left hand thread major diameter, said left hand thread major diameter being equal to or slightly less than said right hand thread major diameter, said screw having a head having means for engagement by a fastener driving tool, comprising the steps of: 
 engaging said means for engagement with a fastener driving tool;    rotating said deck screw in a clockwise direction to drive said deck screw into said board by engagement of said right hand thread of said lower segment with said board and subsequently with said base member, thereby forming loose material in said board, said left hand thread of said upper section evacuating and ejecting at least a portion of said loose material; and    said screw head being drawn down into and seated in said board until a screw upper surface is substantially flush with an upper surface of said board and said upper surface of said board is not substantially deformed.    
   
   
       24 . A method of mounting a plastic or plastic composite board to a base member, using a deck screw having a shank having a lower segment having a right hand thread and an upper segment having a left hand thread, said right hand thread of said lower segment having a right hand thread major diameter, said right hand thread and said left hand thread being adjacent each other without a substantial gap therebetween, said left hand thread of said upper segment having a left hand thread major diameter, said left hand thread major diameter being slightly less than said right hand thread major diameter, said deck screw having a head having means for engagement by a fastener driving tool, comprising the steps of: 
 engaging said means for engagement with a fastener driving tool;    rotating said deck screw in a clockwise direction to drive said deck screw into said board by engagement of said right hand thread of said lower segment with said board and subsequently with said base member, thereby forming loose material in said board, said left hand thread of said upper section evacuating and ejecting at least a portion of said loose material; and    an upper surface of said board being not substantially deformed when said screw is driven into said work member and seated in said board.