Patent GB-516869-A (GB)
Title: Improvements in and relating to blasting detonators or capped fuses
IPC: F42B3/195
Filed: 1938-06-11
Abstract: 516,869. Blasting detonators and fuzes. ROLFES, Ltd., and SCHNEIDER, E. June 11, 1938, No. 17422. [Class 9 (i)] Relates to blasting detonators or capped fuzes of the kind in which there is provided means whereby the fuze or electric cable of a detonator may be enclosed or protected, or part at least of its length enclosed or protected by a metal or other protective medium. According to the invention, such means comprises a metal or other protective tube or strip which is bent or capable of being bent and has or retains a uniform or substantially uniform cross-section, and which is adapted to be crimped or otherwise applied over the fuze cord or a plug containing the electric wires at bent parts thereof which would otherwise be exposed in a bore-hole and be liable to become cut or damaged during tamping of the blasting charge. Fig. 1 shows a construction in which the fuze 2 is enclosed in an S-shaped tube 3 which at its lower end is crimped by a ring 4 to the dead portion of a detonator 1 and at its upper end is crimped to the fuze by a ring 5. Constructions are also described, Figs. 2 and 4 (not shown), in which the invention is applied to an "inverted" detonator, the fuze or a rubber plug enclosing the electric wires being, protected along its outer side by a U-shaped metal strip secured to the dead portion of the detonator and to the fuze or rubber plug by crimped rings. If desired, such a strip may be combined with a piercing member, Fig. 6 (not shown) as described in Specification 521,014. Fig. 3 shows a modification in which the protective means consists of two S-shaped strips 9, 10 secured at their upper end to the fuze 2 by a crimped ring 11 and at their lower end to the dead portion of the detonator 1 by a crimped sheath 12. This sheath is formed with a clip 13 adapted to take a grip of the explosive stick when the detonator is inserted therein. Fig. 5 shows the invention applied to a delay-action electrical type of detonator in which the flexible fuze 18 is led outwards from the detonator shell 19 and has its remote end located adjacent an ignition pellet 20 adapted to be fired by current passing through the wires 21 enclosed in a rubber plug 22. The protective means comprises an aluminium tube 16 formed integral with a piercing member 17, the open end 23 of the tube being crimped on to the plug 22 after the shell 19, fuze 18 and pellet' 20 have been inserted therein. A beading or depressions 24 is or are made in the tube after insertion of the shell and fuze so as to locate the pellet 20 in correct relationship to the end of the fuze, the tube being finally bent to the curved shape shown. Fig. 7 shows a modification applied to a detonator 57 intended to be inserted into the side of the cartridge, the fuze 58 where it protrudes and would otherwise become chafed against the side of the borehole, being protected by the member 54 which is formed integral with a clip 55 and piercing member 56. Fig. 11 shows a further modification in which the detonator shell 62 and protective device 63 are formed initially of a single length of straight tubing and subsequently bent to the desired shape.