GB654958A - Improvements in and relating to blasting cartridges - Google Patents

Abstract

654,958. Blasting cartridges. CARDOX (GREAT BRITAIN), Ltd., LORING, E. A., SHIMMIN, T. A., and BRAY, N. Dec. 20, 1948, No. 32876. [Class 9 (i)] A blasting cartridge has a pressureresistant steel casing in two screwconnected sections 1, 2 providing front and rear chambers 3, 4 separated by a partition 5. The partition 5 is a rupturable steel disc with a restricted aperture 7 through which the front chamber 3 is filled with liquid carbon dioxide. The front section 1 has a shoulder 11 on which is seated a rupturable closure disc 13 held in position by a discharge head 54 as in Specification 517, 417. Screwed into the section 2 is a firing head 6 as described in the aforementioned Specification. In the rear chamber 4 is an initiator 14 comprising a paper container 15 filled with a heating or gas-producing composition 16 with a matchhead 17 embedded therein as described in Specification 617,417. The composition is preferably as described in Specifications 617,136 and/or 480,330. The rear chamber may also contain liquid CO 2 . The cartridge is charged with liquid CO 2 as described in Specification 387,068, the liquid flowing through a passage 18 in the firing head into the rear chamber and thence into the forward chamber. The partition 5 may be imperforate, a byepass passage in the casings connecting the chambers 3, 4 or the chambers may be filled independently. If the initiator is filled with a heat-producing composition, on firing the liquid CO 2 is converted into gas and the increased pressure ruptures the partition 5 propelling the charge in the front chamber into the borehole, while in a liquid state, to produce fissures; the liquid expanding into gas in the fissures completes the blasting action. With a gas-producing initiator, the liquid CO 2 in the initiator chamber may be omitted. The partition separating the charge chamber from the initiator chamber may form a unitary structure with the initiator. In one arrangement the initiator chamber is within the firing head.