Rock cracker cartridge and ignition capsule

Abstract

A rock cracker cartridge ( 1 ) contains a cracking powder charge ( 6 ) and an ignition capsule ( 30 ) with an ignition powder charge ( 29 ) in an ignition unit sleeve ( 31 ) which does not possess the mechanical strength that would be required for the ignition powder charge to be exploded in the open air when ignited. In the rock cracker cartridge there is also provided an ignition assembly sleeve ( 7 a ) which surrounds the ignition unit sleeve when the rock cracker cartridge is primed. In combination, the assembly which surrounds the cracking powder charge, and which comprises the ignition unit sleeve and the ignition assembly sleeve, has a sufficient strength for an adequate pressure to be developed in the assembly such that the ignition powder charge will explode and generate a flame of fire and the ignition unit sleeve as well as the ignition assembly sleeve be penetrated by the pressure and the flame of fire, said flame offire igniting the cracking powder charge.

1 - 22 . (canceled) 
     
     
         23 . A rock cracker cartridge comprising:
 a first, outer sleeve with an end wall in a first end and a central opening in a second end which in other respects is closed by a closure member;   a substantially cylindrical, second, inner sleeve which is coaxial with the first, outer sleeve and with said central opening and communicates with said central opening and is connected to and extends from said closure member in a main chamber in said first, outer sleeve; and   a rock cracker cartridge filling the space in the main chamber between said first and second sleeves and between the end wall in said first end and the closure member in the second end, wherein the primed rock cracker cartridge there is provided an ignition assembly comprising a first and a second ignition assembly member, said first ignition assembly member includes an ignition capsule with an ignition unit sleeve containing an ignition unit comprising an ignition initiator which can be activated electrically, and an ignition powder charge which can be ignited by the ignition initiator, and the ignition unit sleeve does not have the mechanical strength which would be required for an explosion of the ignition powder charge upon ignition of said ignition powder charge when the ignition capsule is in the open air, in which case the ignition unit sleeve only would be widened and possibly rupture and the ignition powder charge would burn without any explosive effect.   
     
     
         24 . The rock cracker cartridge according to  claim 23 , wherein the mechanical strength of the ignition unit sleeve, when the ignition capsule is inserted into the ignition assembly sleeve, which is surrounded by the cracking powder charge, in combination with the strength of the ignition assembly sleeve under support by the surrounding cracking powder charge, affords a sufficient mechanical strength to that assembly which comprises the ignition unit sleeve and the ignition assembly sleeve in order that, upon ignition of the ignition powder charge, an adequate pressure shall develop in the assembly and the ignition powder charge explode and generate a flame of fire, and the ignition unit sleeve and the ignition assembly sleeve be penetrated by the pressure and by the flame of fire which has a capacity to ignite the cracking powder charge. 
     
     
         25 . The rock cracker cartridge according to  claim 23 , wherein the ignition unit sleeve as well as the ignition assembly sleeve comprises a hard plastic material. 
     
     
         26 . The rock cracker cartridge according to  claim 23 , wherein the thickness of each of the ignition unit sleeve and of the ignition assembly sleeve amounts to at least 0.5 mm but not more than 2.0 mm, and that the combined thickness of the two sleeves amounts to at least 1.3 mm but not to more than 3 mm. 
     
     
         27 . The rock cracker cartridge according to  claim 23 , wherein the ignition unit sleeve comprises a one piece tube of plastic material, that said tubular sleeve of hard plastic material has a front end portion which is closed, and in the rear end a mouth portion with a rear opening, that the ignition initiator comprises an electrically activatable igniter with a socket to which ignition cables are connected, that the socket is provided in said mouth portion of the ignition unit sleeve, and that the igniter is provided in the ignition unit sleeve at a distance from the socket. 
     
     
         28 . The rock cracker cartridge according to  claim 23 , wherein the ignition unit sleeve is provided with external grooves which reduce the strength of the ignition unit sleeve in substantially the radial direction. 
     
     
         29 . The rock cracker cartridge according to  claim 28 , wherein said grooves extend from a position at a distance from said mouth portion in a direction towards the closed end of the ignition unit sleeve, and that said grooves has an extension within which at least the main portion of the ignition powder charge extends. 
     
     
         30 . The rock cracker cartridge according to  claim 29 , wherein the igniter is accommodated in the ignition powder charge, that the main portion of the ignition powder charge is provided between the igniter and the closed end portion of the ignition unit sleeve, and that said external grooves extend from at level with the outer end of the igniter along the cylindrical wall of ignition unit sleeve to the closed end portion of the ignition unit sleeve. 
     
     
         31 . The rock cracker cartridge according to any of  claims 28 , wherein the ignition unit sleeve has an outwardly directed flange in the region of the mouth, and that the outer surface of the ignition unit sleeve is cylindrical and smooth in the region between said flange and said grooves, and that said outer surface is cylindrical and smooth also between said grooves all along the length of said grooves. 
     
     
         32 . The rock cracker cartridge according to  claim 23 , wherein the end portion of the ignition unit sleeve is cupped and is located at least partly in or border the nose portion of the ignition assembly sleeve. 
     
     
         33 . The rock cracker cartridge according to  claim 32 , wherein between the ignition assembly sleeve and the ignition unit sleeve is a gap, the width of which has no significant importance for the strength of the ignition assembly but allows the ignition capsule, in connection with priming of the cracker cartridge, to be entered into the ignition assembly sleeve without jamming, and that a constriction is provided on the inside of the ignition assembly sleeve in a zone adjacent to the tip of the ignition assembly sleeve, said constriction having a radial extension which is larger than the width of said gap, in order to fix the ignition capsule in its primed position through friction between the ignition assembly sleeve and the ignition unit sleeve in the region of the constriction. 
     
     
         34 . The rock cracker cartridge according to  claim 23 , wherein one or more, in the axial direction protruding members are provided on said closure member, and that there is at least one free space between the protruding members, which form spacers when the rock cracker cartridge is placed upside-down in a bore with the protruding member/members resting on the bottom of the bore, such that the ignition cables may run through said free space/spaces without being damaged. 
     
     
         35 . An ignition capsule comprising:
 an ignition unit sleeve in the form of a tube, which has mouth and a mouth portion in one end, is closed in the opposite end, and contains an ignition unit, wherein the ignition unit sleeve comprises a hard plastic material, that the ignition unit comprises an ignition initiator which can be activated electrically, and an ignition powder charge which can be ignited by the ignition initiator, and that the ignition unit sleeve does not have the mechanical strength which would be required for an explosion of the ignition powder charge upon ignition of said ignition powder charge when the ignition capsule is in the open air, in which case the ignition unit sleeve only would be widened and possibly rupture and the ignition powder charge would burn without any explosive effect.   
     
     
         36 . The ignition capsule according to  claim 35 , wherein the ignition intitiator comprises an electrically activatable igniter with a socket to which ignition cables are connected, and that the socket is provided in said mouth portion of the ignition unit sleeve. 
     
     
         37 . The ignition capsule according to  claim 35 , wherein the ignition unit sleeve is provided with external grooves which reduce the rupture strength of the ignition unit sleeve in substantially the radial direction thereof. 
     
     
         38 . The ignition capsule according to  claim 37 , wherein said grooves extend from a position at a distance from said mouth portion towards the closed end of the ignition unit sleeve, and that said grooves have an extension within which at least the main part of the ignition powder charge extends. 
     
     
         39 . The ignition capsule according to  claim 37 , wherein the grooves have a depth corresponding to at least half the wall thickness of the ignition unit sleeve. 
     
     
         40 . The ignition capsule according to  claim 39 , wherein the mean width of the grooves is of the same order as the wall thickness of the ignition unit sleeve. 
     
     
         41 . The ignition capsule according to  claim 35 , wherein the igniter is accommodated in the ignition powder charge, that the main portion of the ignition powder charge is provided between the igniter and the closed end portion of the ignition unit sleeve, and that said external grooves extend from at level with the outer end of the igniter along the cylindrical wall of ignition unit sleeve to the closed end portion of the ignition unit sleeve. 
     
     
         42 . The ignition capsule according to  claim 43 , wherein the ignition unit sleeve has an outwardly directed flange in the region of the mouth, and that the outer surface of the ignition unit sleeve is cylindrical and smooth in the region between said flange and said grooves, and that said outer surface is cylindrical and smooth also between said grooves all along the length of said grooves. 
     
     
         43 . The ignition capsule according to  claim 35 , wherein the end portion of the ignition unit sleeve is cupped. 
     
     
         44 . The ignition capsule according to  claim 35 , wherein the ignition powder charge comprises nitro powder.