Rock breaking

Abstract

A rock-breaking cartridge (10) includes a casing (16) of deformable material that forms an internal cavity (22) and a tapered part (82). A seal (90) extends around the outside of the tapered part (82) and a piston (92) inside the cavity (22) butts against the inside of the tapered part (82) to seal against the inside of the casing (16). A charge (46) is provided inside the cavity (22) on the side of the piston (92) that is opposite from a narrow end of the tapered part (82) and when the charge (46) is ignited, it causes the piston (92) to slide towards the narrow end and to force the tapered part (82) and seal (90) to expand. The expansion causes the seal (90) to seal against the inside of a hole in which the cartridge (10) has been placed and the seal (90), tapered part (82) and piston (92) form a sturdy plug to contain gasses generated by detonation of the charge (46).

1 . A rock breaking cartridge comprising:
 a casing of deformable material, said casing having a front end and a rear end, said casing forming an internal cavity and forming a tapered part in the vicinity of the rear end, with a narrow end of the tapered part being closer to the rear end than a wider end of the tapered part;   at least one deformable seal extending, at least in part, around the outside of the tapered part of the casing;   a piston disposed inside the internal cavity, said piston being dimensioned to but against the inside of the tapered part of the casing and to seal against the inside of the casing;   an end cap disposed at the front end of the casing and sealing the sealing the front end of the casing; and   a gas generating compound inside the internal cavity between the piston and the end cap.   
     
     
         2 . The rock breaking cartridge according to  claim 1 , wherein the tapered part of the casing is frusto-conical and tapers towards the narrow end. 
     
     
         3 . The rock breaking cartridge according to  claim 1 , wherein at least part of the piston has a frusto-conical shape. 
     
     
         4 . The rock breaking cartridge according to  claim 1 , wherein the piston includes a rounded head that buts sealingly against the inside of the tapered part of the casing, inside the seal. 
     
     
         5 . The rock breaking cartridge according to  claim 4 , wherein the piston includes a skirt that seals against the inside of the casing and the piston is at least partly hollow and defines an inside that is contiguous with the part of the cavity in which the gas generating compound is disposed. 
     
     
         6 . (canceled) 
     
     
         7 . The rock breaking cartridge according to  claim 1 , which includes grip formations that extend around the outside of the tapered part of the casing. 
     
     
         8 . The rock breaking cartridge according to  claim 7 , wherein the grip formations are integrally formed with the casing. 
     
     
         9 . The rock breaking cartridge according to  claim 1 , which includes an end cap that seals an end of the casing that is opposite from the tapered part. 
     
     
         10 . The rock breaking cartridge according to  claim 9 , wherein the cap is held on the casing by a retainer that is configured to release the cap from the casing upon a predetermined pressure being reached inside the internal cavity. 
     
     
         11 . A rock breaking cartridge comprising:
 a casing of deformable material, said casing having a front end and a rear end, wherein the casing has two tapered parts, at each of the opposing front end and rear end of the casing, with narrow ends of said tapered parts being directed towards the front end and rear end, respectively, and with wider ends of said tapered parts facing towards each other, said casing forming an internal cavity between the wider ends of the tapered parts;   at least two deformable seals, extending, at least in part, around the outsides of the tapered parts of the casing;   two pistons disposed inside the internal cavity, each of said pistons being dimensioned to but against the inside of one of the tapered parts of the casing and to seal against the inside of the casing; and   a gas generating compound inside the internal cavity between the two pistons.   
     
     
         12 . The rock breaking cartridge according to  claim 11 , wherein the casing comprises two sub-casings, each of said sub-casings has a tapered part, and the sub-casings are joined together in a sealing manner. 
     
     
         13 . The rock breaking cartridge according to  claim 2 , wherein at least part of the piston has a frusto-conical shape. 
     
     
         14 . The rock breaking cartridge according to  claim 2 , wherein the piston includes a rounded head that buts sealingly against the inside of the tapered part of the casing, inside the seal. 
     
     
         15 . The rock breaking cartridge according to  claim 2 , which includes grip formations that extend around the outside of the tapered part of the casing.