Blasting-cartridge case

This invention relates to methods of and containers for igniting explosives especially ammonium nitrate and fuel oil (AN/FO).

AN/FO is commonly required to be used in bore holes in the ground in water bearing strata and for this reason it is usual to contain the AN/FO in polythene bags. These may be as long as the hole e.g. 30 feet. However, these tend to float due to air in the bags which introduces difficulties and may collapse so as not to guarantee adequate contact with the primary explosives needed to initiate ignition of the AN/FO which for safety reasons must be lowered into the hole first. Moreover, polythene bags tend to develop static electricity which is a danger factor when the normal method of filling polythene bags on a shot site is followed. Hitherto it has only been practicable to use the much more costly gelignite or a slurry of AN/FO mixed with gums to make a kind of gel.

According to the present invention I provide a substantially rigid tube of plastics material, a closure at each end of the tube, said tube having a recess in its wall between its ends to receive a detonating cartridge.

The tube is preferably provided with means for holding a detonating line along the pipe. The tube will be filled with AN/FO.

Also preferably the tube may carry projecting means capable of permitting movement of the tube down the bore holes and engaging the walls of the hole to prevent it from floating up the hole. This ring may be toothed or serrated.

The effect of the projecting means coupled with the fact that each container is fired with its own individual charge at the same instant as all the other containers in the hole ensures that the explosion takes place where it should be, i.e. down the hole. It also reduces air over pressure, a major complaint and also reduces the chances of flyrock dramatically. Also the fact that the containers can be filled the day prior to use and stored in magazines, allows any static electricity generated to dissipate and so eliminate the danger of accidentally firing detonators. The containers cannot float up in a water filled bore hole.

As the bore and recess is completely separate from the space for the AN/FO there is no possibility of water reaching the AN/FO which would neutralize the explosive.

The invention will be further described by way of example with reference to the accompanying diagrammatic drawings wherein:-

• FIGURE 1 is an elevational view of a container made in accordance with the invention;
• FIGURE 2 is a plan view thereof;
• FIGURE 3 is a cross-sectional view thereof on the plane 3-3 on Figure 1;
• FIGURE 4 is a longitudinal section of the container;
• FIGURE 5 is an elevational view of a modified form of container;
• FIGURE 6 is a view thereof in the direction of the arrow 6 on Figure 5; and
• FIGURES 7 and 8 are part sectional views on the planes 7-7 and 8-8 on Figure.5.

The container 10 is made of plastics material which is rigid and may be about 3-5 mm thick. A bore 11 is made throughout its wall and a recess 12 is provided about midway between its ends. This recess divides the bore but does not penetrate the interior of the container. The bore 11 is provided in a rib 17 formed longitudinally on the inside of the tubular container 10. The container has an integral end wall 13 and its other end is provided with a screw cap 14.

Around the container and fixed to it is a serrated collar 15 having its teeth directed towards one end of the container. This collar may be held in position by slipping it over the neck of the container and by screwing the container cap 14 down on to it.

Two or more containers may be placed in a hole in axial alignment with the bores 11 in alignment. Detonating cartridges located in the recesses 12 will be connected together by a detonating cord which extends through all the bores 11 and alongside the detonating cartridges to form a continuous line.

In Figures 5 to 8 the container 18 is a rigid circular extruded tube of plastics material about 3-5mm wall thickness. Its ends are closed by caps 19,20 of plastics material which have a tight push on fit on the container. Midway between the ends of the tube it is formed with a recess 21. Extending over the recess 21 is a resilient clip 22 which is made of plastics material and is fixed by welding or adhesive to the container 18 and this serves to hold the detonating cartridge (primer) 25 in position.

Aligned with the recess on either side of it are clips 26,27,29,30 also made of plastics material and fixed to the container. These serve to hold the detonating cord 28 in position alongside the primer 25.

Similarly attached to the container 18 are several projections 32,33,34. These are of plastics material and are in the form of bifurcated strips all projecting at an angle of about 45° from the container with the furcations all pointing in the same axial direction.

The containers can be rapidly pushed down a bore hole with a plastics rod with the projections pointing up so that they will slide easily down the hole but will jau on the wall of the hole and prevent them from floating u When a sufficient number are placed in the hole with the "Cordtex" or like detonating cord held in the clips, the hole is filled in with rock or earth and upon ignition all the charges will ignite simultaneously and will blow the rock face out laterally without blowing upwards out of the hole. The plastics containers will completely disintegrate.

Instead of using a detonating cord, it is possible to provide an electrically operated detonator with each primer cartridge and these detonators will be all connected electrically in series so that they can be ignited by current from an electric battery.