Rock Bolt

Abstract

The present invention relates to rock bolts which may be used in mining applications. The rock bolt of this invention includes a mechanical anchoring arrangement to facilitate retaining the rock bolt in a borehole, and also a drill bit to enable self drilling of the rock bolt. Rotation of the rock bolt about an axis of the rock bolt in a first direction causes the drill bit to drill into rock and to create a borehole to receive the rock bolt. Subsequently, rotation in the opposite direction actuates a mechanical anchoring arrangement to anchor rock bolt.

The invention claimed is: 
     
         1 . A self drilling rock bolt comprising:
 an elongated hollow shank having a threaded portion at a head end;   a mechanical anchoring arrangement including an expansion assembly having an expansion shell and a cooperating chuck threaded to the threaded portion of the hollow shank, the chuck having an extension portion having a central hole into which the threaded portion of the hollow shank is received; and   a drill bit coupled to a periphery of the extension portion of the chuck, the drill bit positioned radially outward from the central hole of the extension portion,   wherein the chuck is arranged to rotate together with the expansion shell whereby rotation of the rock bolt in one direction provides a drilling action with the expansion shell rotating together with the hollow shank whereas rotation of said bolt in an opposite direction provides axial movement of the chuck relative to the hollow shank and the expansion shell to mechanically secure the rock bolt.   
     
     
         2 . A self drilling rock bolt as defined in  claim 1 , wherein the head end of the hollow shank is arranged to move into the central hole to facilitate tightening of the bolt against a surface without leaving any tail of the bolt protruding from the surface. 
     
     
         3 . A self drilling rock bolt as defined in  claim 1 , wherein the chuck includes surfaces in sliding keyed engagement with corresponding surfaces on the expansion shell for conjoined rotation of the chuck and the expansion shell. 
     
     
         4 . A self drilling rock bolt as defined in  claim 1 , wherein the expansion shell and the cooperating chuck have cooperating surfaces arranged to slide over each other resulting in expansion of the expansion shell so that walls of the expansion shell abut walls of a borehole thereby mechanically securing the rock bolt to a borehole wall. 
     
     
         5 . A self drilling rock bolt as defined in  claim 1 , further comprising a drive end portion connected to a tail end of the hollow shank and being adapted for engagement by a drill rig for drilling in said one direction and mechanically securing in the opposite direction. 
     
     
         6 . A self drilling rock bolt as defined in  claim 1 , wherein a stop is provided on the end of the hollow shank which, in use, prevents the chuck from moving off the rock bolt during drilling. 
     
     
         7 . A self drilling rock bolt as defined in  claim 1 , wherein the outer walls of the expansion shell include protrusions to aid mechanical interference with borehole walls. 
     
     
         8 . A self drilling rock bolt as defined in  claim 7 , wherein the protrusions are arranged in spiral formation to facilitate fluid and leavings flow during drilling.