Patent ID: 8201500

Claim:
A rock cracking assembly comprising a powder charged rock cracker cartridge and a detonator which can be triggered electrically and comprising an igniting powder charge, the rock cracker cartridge comprising: a substantially cylindrical outer sleeve comprising a plastic material with an end wall in a first end; a plug comprising plastic material which, enclosing said outer sleeve, is inserted into and secured in an opposite second end of the outer sleeve; a main chamber in the outer sleeve between said end wall and said plug, which main chamber is filled with a blasting powder charge, an end of the plug pressed against the blasting powder charge; a substantially cylindrical inner sleeve, which is coaxial with the outer sleeve and, connected to said plug, extends and is pressed into the blasting powder charge, the amount of the blasting powder charge being adapted to the space which accommodates the powder such that the blasting powder charge is compacted to some degree, and a central through hole in said plug which communicates with the inner sleeve, which is closed in its inner end, which is inserted into the blasting powder charge, wherein the hole in the plug and the inner sleeve in combination form a priming chamber having a shape corresponding to the outer shape of the detonator, and wherein, in the assembled rock cracking assembly; an inner portion of the priming chamber, corresponding to the region of the inner sleeve, defining an ignition chamber, accommodates that portion of the detonator which contains the igniting powder charge; and the inner sleeve comprising a plastic material, the thickness of the inner sleeve being selected such that the inner sleeve in less than 25 ms (milliseconds) is penetrated by the pressure and the flame of fire which are formed when the detonator is ignited, thereby igniting the blasting powder charge.