Fasteners for composite material

Abstract

A fastener has a shaft, a head at a first end of the shaft, and a point at the other end of the shaft. A first portion of the shaft adjacent the point is threaded. The first portion typically extends about one-half the total length of the shaft. A second portion of the shaft (adjacent the head) is not threaded, but has a plurality of spaced rings. A knurled portion can be provided between the first and second portions, if desired. Conventional symmetrical or asymmetrical thread can be used in the threaded portion, or a three lobe thread can be used.

What is claimed is:  
     
         1 . A fastener comprising: 
 a shaft,    a head at a first end of the shaft, and    a point at the other end of the shaft,    a first portion of the shaft adjacent the point being threaded, and extending about one-half the total length of the shaft, and    a second portion of the shaft adjacent the head not being threaded, said second portion having a plurality of spaced rings.    
     
     
         2 . The fastener of  claim 1  comprising a knurled portion between said first and second portions.  
     
     
         3 . The fastener of  claim 1  wherein said first portion has asymmetrical threads.  
     
     
         4 . The fastener of  claim 1  wherein said first portion has threads having three radial lobes.  
     
     
         5 . The fastener of  claim 1  comprising three said rings, wherein said rings are unequally spaced with respect to each other.  
     
     
         6 . The fastener of  claim 1  wherein said shaft has a total length TL from an inside surface of said head to said point, the fastener comprising three of said rings, a first of said rings being located about 0.23 TL from said inside surface, a second of said rings being located about 0.16 TL from said inside surface, and a third of said rings being located about 0.07 TL from said inside surface.  
     
     
         7 . The fastener of  claim 1  comprising three said rings, wherein said rings are equally spaced with respect to each other.  
     
     
         8 . The fastener of  claim 1  wherein said shaft has a total length TL from an inside surface of said head to said point, the fastener comprising three of said rings, a first of said rings being located about 0.13 TL from said inside surface, a second of said rings being located about 0.08 TL from said inside surface, and a third of said rings being located about 0.04 TL from said inside surface.