Fastener for sheet material

Abstract

The invention relates to a system of fastening sheet material cladding onto substrates with hammer driven fasteners. The fasteners are cylindrical and have a first diameter at a tip end which is larger than a second diameter at a head end. When the fastener is driven through sheet material a hole is produced which is larger in diameter than the portion of the fastener adjacent the head. The sheet material is free to move laterally relative to the fastener because of the oversized hole that is produced by the oversized tip of the fastener. Additionally, deformation or dimpling is avoided because the small-diameter portion of the fastener does not produce axial frictional forces on the sheet material as it passes through the sheet material.

1 . A fastener comprising: 
 a cylindrical shaft comprising an insertion tip formed at a first end of the shaft and a head formed at a second end of the shaft;    the shaft comprising at least two cylindrical members of different diameters;    a first cylindrical member with a first diameter D 1  being contiguous with the first end of the shaft;    a second cylindrical member with a second diameter D 2  being contiguous with the second end; and    the second diameter D 2  being smaller than the first diameter D 1 .    
   
   
       2 . The fastener of  claim 1  wherein an axial length of the fastener is no greater than about 10 to 20 times the diameter D 2  of the second cylindrical member.  
   
   
       3 . The fastener of  claim 1  wherein the head is planar and is oriented orthogonally to the axis of the cylindrical member.  
   
   
       4 . The fastener of  claim 1  wherein the fastener is comprised of aluminum.  
   
   
       5 . The fastener of  claim 1  wherein: 
 the cylindrical member  40  has a diameter D 2  at least as large as about 1/16″ to about ⅛″;    the fastener has an overall length that is about 10 to 20 times as great as the diameter D 2 ;    the diameter D 1  of the first cylindrical member  36  is no greater than about 2 to 3 times the diameter D 2 ; and    an axial length of the first cylindrical member  36  is no greater than about 10 to 25% of the axial length of the second cylindrical member.    
   
   
       6 . A method for attaching sheet material to a substrate comprising the steps of: 
 supporting the sheet material adjacent the substrate;    driving a cylindrical fastener, having first diameter D 1  along a first portion of its length and a second smaller diameter D 2  along a second portion of its length, through the sheet material and into the substrate to produce a hole in the sheet material that is as large as the first diameter; and    driving the fastener further into the substrate to position the second portion of the fastener into alignment with the sheet material.    
   
   
       7 . The method of  claim 6  wherein the fastener is driven only far enough into the substrate to retain the sheet material in close proximity to the substrate but sufficiently distant from the substrate so that the sheet material is free to move laterally under a head of the fastener.  
   
   
       8 . The methods of  claim 6  wherein: 
 the sheet material are fastened with a plurality of the fasteners with a spacing between the fasteners; and    the spacing between fasteners when combined with a difference between the first and second diameters of the fasteners is suitable to permit thermal expansion of the sheet material without being constrained by the fasteners.    
   
   
       9 . The method of  claim 8  wherein: 
 L 1  is a distance between fasteners;    L 2  is a distance between holes produced by the fasteners at a mean temperature;    L 3  is a distance between the holes at a temperature extreme higher than the mean;    L 4  is a distance between the holes at a temperature extreme lower than the mean; and 
 the diameter D 1  and the diameter D 2  are interrelated in accordance with a relationship D 1 −D 2 ≧(L 3 −L 4 )/2.