Method of fastening a guard rail by means of a guard rail bolt, the guard rail bolt and the tool for fastening the guard rail bolt

Abstract

A self-expanding and self-undercutting guard rail bolt includes a dowel having a guard rail fastening end and a ring. The fastening end is configured to be driven in rotation, and the ring is configured to rigidly connect to a first screwing end of the dowel by an incipient fracture portion. The self-expanding and self-undercutting guard rail bolt further includes a counter-dowel screwed to the dowel by a second screwing end. The counter-dowel includes an expansion cone, and an anti-rotation head having at least one edge which projects beyond a periphery of the dowel to prevent rotation of the counter-dowel about an axis of the guard rail bolt.

1 . Method of fastening a guard rail to a concrete slab by means of a self-expanding and self-undercutting bolt comprising a dowel having expanding lugs and an expansion core, the method comprising a phase consisting in drilling a hole in the slab, a phase consisting in driving the bolt in to a desired depth independent of the depth of the hole, a dynamic tightening phase resulting in the formation of the undercut and a static tightening phase of the guard rail. 
     
     
         2 . Method according to  claim 1 , in which the dynamic tightening is carried out by relative screwing of the dowel and the expansion core to a given depth. 
     
     
         3 . Method according to  claim 2 , in which the dowel is screwed on to the expansion core until the fracture of incipient fracture means. 
     
     
         4 . Self-expanding and self-undercutting guard rail bolt for carrying out the method of  claim 1 , comprising a dowel and a counter-dowel screwed together by means of their screwing ends, the dowel comprising at its fastening end a guard rail fastening head designed to be driven in rotation and rigidly connected at its screwing end by means of incipient fracture means to a ring provided with expansion lugs, the counter-dowel comprising at its other expansion end an expansion cone and anti-rotation means, the expansion lugs comprising means for forming an undercut. 
     
     
         5 . Tool for fastening a guard rail bolt, comprising means for driving it in rotation and complementary means for controlling the driving depth of the bolt. 
     
     
         6 . Tool according to  claim 5 , provided with a spindle fixed in rotation with a cylindrical drive sleeve designed to drive the bolt in rotation. 
     
     
         7 . Tool according to  claim 6 , in which the sleeve is guided in translation by a stop guide and is returned by the action of a spring to a pin for driving the bolt in rotation. 
     
     
         8 . Tool according to  claim 7 , in which the length of the sleeve is equal to the length of the spindle increased by the length t of the pin, but reduced by the minimum length of the spring. 
     
     
         9 . Tool according to  claim 7 , in which the length of the lower end of the stop guide is a function of the thickness of the fastening nut.