Blasting cartridge

Abstract

A cartridge ( 10 ) is provided having a receptacle ( 12 ) with propellant ( 14 ) therein and an open end with a stemming device ( 16 ) secured to the open end to form a substantially closed container. The stemming device ( 16 ) is operable to result in radial expansion thereof and has a static member ( 18 ) secured to the receptacle ( 12 ) and a piston ( 20 ) movable, at least partially within the container, relative to the static member ( 18 ) and the receptacle ( 12 ). The cartridge is configured such that ignition of the propellant ( 14 ) causes movement of the piston ( 20 ) to operate the stemming device ( 16 ) and cause radial expansion thereof before the receptacle ( 12 ) ruptures.

1 . A cartridge comprising a receptacle for holding a propellant therein and which has an open end, and a stemming device operable to result in radial expansion thereof having a piston movable relative to a static member, wherein the stemming device is secured to the open end of the receptacle to form a substantially closed container, with the static member secured to the receptacle and the piston movable at least partially within the container such that ignition of the propellant causes movement of the piston to operate the stemming device and cause radial expansion thereof before the receptacle ruptures. 
     
     
         2 . A cartridge as claimed in  claim 1  wherein the cartridge has an igniter secured within the stemming device with an operating cord extending therethrough. 
     
     
         3 . A cartridge as claimed in  claim 2  wherein the igniter is located in a socket in the piston. 
     
     
         4 . A cartridge as claimed in  claim 1  wherein the piston is partly located within the receptacle. 
     
     
         5 . A cartridge as claimed in  claim 4  wherein a nozzle extends from the end of the piston located within the receptacle. 
     
     
         6 . A cartridge as claimed in  claim 1  wherein the static member is secured over the open end of the receptacle. 
     
     
         7 . A cartridge as claimed in  claim 6  wherein the static member has a plurality of holes therein for receiving buttons on the receptacle. 
     
     
         8 . A cartridge as claimed in  claim 1  wherein the piston and static member have cooperating bearing surfaces, at least one of which is tapered such that relative movement causes radially outward expansion of either the static member or the piston. 
     
     
         9 . A cartridge as claimed in  claim 8  wherein the static member has a tapered bore and at least one longitudinal slit to permit radial expansion thereof. 
     
     
         10 . A cartridge as claimed in  claim 9  wherein the static member has a plurality of circumferentially spaced slits, each slit extending substantially the length of the tapered bore. 
     
     
         11 . A cartridge as claimed in  claim 1  wherein the static member of the stemming device has a tubular body with a number of ports therein and an anchor member associated with each port such that movement of the piston causes radially outward displacement of each anchor member. 
     
     
         12 . A cartridge as claimed in  claim 11  wherein each anchor member has a lug which extends centrally from one side of a panel, each lug providing a complementary fit within a port and the panels configured to extend over a part of the outer surface of the body, for the end of the piston engaging the lugs to be tapered, and for the free end of each lug to have a complementary taper to the piston. 
     
     
         13 . A cartridge as claimed in  claim 1  wherein a stemming device is secured to opposite ends of a tubular receptacle. 
     
     
         14 . A piston for a cartridge as claimed in  claim 1 , wherein the piston has a cylindrical section providing a sliding fit within a tubular receptacle and a tapered section which is movable within an expansion sleeve to cause radial expansion thereof, with a bore extending substantially axially through the piston and a nozzle extending from the end of the piston locatable within the receptacle.