Expandable Bolt with Shielded Tip

Abstract

The present invention includes a rock bolt having a longitudinally expandable tube. The tube includes a longitudinally extending depression that defines a temporary enclosed longitudinal passageway. The rock bolt further includes a shielded distal end to prevent debris from entering the temporary enclosed longitudinal passageway. The distal end is shielded using a cover which may be a plug or a cap and may provide a rounded tip for the rock bolt. The plug may be spherical. The cap may be attached such that its proximal end abuts the distal end of the rock bolt, is inserted into the distal end of the rock bolt, or extends beyond the distal end and along the sidewall of the rock bolt. The present invention also includes a method of making such a rock bolt and a method of using such a rock bolt.

The invention claimed is: 
     
         1 . A rock bolt comprising:
 an expandable tube that is partially collapsed upon itself so as to form a longitudinally extending depression between two longitudinally extending interior passageways, wherein the longitudinally extending depression forms a temporary main passageway at a distal end of the expandable tube, wherein the two longitudinally extending interior passageways form the interior of the tube upon expansion, wherein the temporary main passageway is open at the distal end of the expandable tube, wherein the two longitudinally extending interior passageways are closed at the distal end of the expandable tube, and wherein a pressurized fluid may be delivered into the two interior passageways to force the depression outward to thereby expand the expandable tube and compress the expandable tube against surrounding rock;   an end fitting attached to the distal end of the expandable tube, the end fitting having a sidewall and two open ends, a first of the open ends extending longitudinally beyond the closed distal ends of the interior passageways; and   a cover covering the first open end of the end fitting.   
     
     
         2 . The rock bold according to  claim 1 , wherein the cover provides a rounded tip for the rock bolt. 
     
     
         3 . The rock bolt according to  claim 1 , wherein the cover is a plug. 
     
     
         4 . The rock bolt according to  claim 1 , wherein the cover is a cap. 
     
     
         5 . The rock bolt according to  claim 4 , wherein the proximal end of the cap abuts the distal end of the rock bolt. 
     
     
         6 . The rock bolt according to  claim 4 , wherein the cap comprises a closed distal end, an open proximal end, and a sidewall extending from the distal end to the open proximal end that creates an inner cavity, and wherein the cap is placed over the distal end of the rock bolt such that the distal end of the rock bolt extends into the inner cavity of the cap. 
     
     
         7 . The rock bolt according to  claim 4 , wherein the cap comprises a closed, distal end, an open proximal end, and a sidewall extending from the distal end to the open proximal end that creates an inner cavity, and wherein the cap is placed into the distal end of the rock bolt such that the proximal end of the cap extends into the temporary longitudinal passageway of the rock bolt. 
     
     
         8 . The rock bolt according to  claim 1 , wherein a central portion of the cover extends longitudinally from the first open end of the end fitting a greater distance than a peripheral portion of the cover extends longitudinally from the first open end of the end fitting to facilitate centering the rock bolt within a borehole. 
     
     
         9 . A method of manufacturing a rock bolt comprising:
 partially collapsing a tube upon itself so as to form a longitudinally extending depression between two longitudinally extending interior passageways, wherein the longitudinally extending depression forms a temporary main passageway at a distal end of the expandable tube;   attaching an end fitting to the distal end of the expandable tube, the end fitting having a sidewall and two open ends, a first of the open ends extending longitudinally beyond the closed distal ends of the interior passageways;   closing the two longitudinally extending interior passageways at the distal end of the expandable tube; and   covering the first open end of the end fitting by affixing a cover to the end fitting.   
     
     
         10 . The method according to  claim 9 , wherein the cover provides a rounded tip for the rock bolt. 
     
     
         11 . The method according to  claim 9 , wherein the cover is a plug. 
     
     
         12 . The method according to  claim 9 , wherein the cover is a cap. 
     
     
         13 . The method according to  claim 9 , further comprising placing a stiffening tube on a proximal end of the expandable member, wherein the stiffening tube surrounds the proximal end of the expandable member and has an opening that aligns with a corresponding opening in the expandable tube, thereby providing fluid communication to an interior of the expandable tube. 
     
     
         14 . The method according to  claim 9 , wherein a central portion of the cover extends longitudinally from the distal end of the first open end of the end fitting a greater distance than a peripheral portion of the cover extends longitudinally from the first open end of the end fitting to facilitate centering the rock bolt within a borehole. 
     
     
         15 . A method of using a rock bolt comprising:
 providing a rock bolt comprising:   an expandable tube that is partially collapsed upon itself so as to form a longitudinally extending depression between two longitudinally extending interior passageways, wherein the longitudinally extending depression forms a temporary main passageway at a distal end of the expandable tube, wherein the two longitudinally extending interior passageways form the interior of the tube upon expansion, wherein the temporary main passageway is open at the distal end of the expandable tube, and wherein the two longitudinally extending interior passageways are closed at the distal end of the expandable tube;   an end fitting attached to the distal end of the expandable tube, the end fitting having a sidewall and two open ends, a first of the open ends extending longitudinally beyond the closed distal ends of the interior passageways; and   a cover covering the first open end of the end fitting;   drilling a borehole in rock;   placing the rock bolt in the borehole;   expanding the tube by providing pressurized fluid to the two interior passageways of the expandable tube, thereby providing frictional engagement between an exterior of the tube and an interior of the borehole; and   draining the fluid from the interior of the tube.   
     
     
         16 . The method according to  claim 15 , wherein the cover provides a rounded tip for the rock bolt. 
     
     
         17 . The method according to  claim 15 , wherein the cover is a plug. 
     
     
         18 . The method according to  claim 15 , wherein the cover is a cap. 
     
     
         19 . The method according to  claim 15 , wherein a central portion of the cover extends longitudinally from the distal end of the first open end of the end fitting a greater distance than a peripheral portion of the cover extends longitudinally from the first open end of the end fitting to facilitate centering the rock bolt within a borehole.