In mining and construction work and in particular mining operations holes are drilled into the stope face. Explosive charges are placed into the holes. For most effective use, the explosive charge should be ignited in a manner where an explosive container limits the space in which the explosion is contained. Many explosive containers have been suggested and used with varying degrees of successes.

It is an object of invention to provide an effective explosive container which is easy to use.

According to one aspect of the invention there is provided an explosion container comprising an elongated shank, a closure device at one end thereof which when the explosive container is homed is in close proximity to the explosive charge, and the retention means comprising the plurality of retention members that in use will be of greater dimensional diameter than the drilled hole, and are of a strength sufficient to deflect when the shank is being inserted into the drill hole but will have sufficient of strength to prevent or inhibit the explosive container from being moved outwardly of the drill hole when the explosive is detonated.

The retention members are preferably mounted on the shank. They are preferably disc-like in shape. The closure device is also preferably generally disc-like in shape but is preferably concave to fit more closely on to the explosive charge.

The retention members preferably have lines of weakness which facilitate the collapse of the members when the container is being inserted into the drill hole. Such lines of weakness being preferably a number, usually four, preferably radial slots extending inwardly from the periphery of disc. Another line of weakness may be provided by"V"-shaped radially extending recesses formed in the members.

A longitudinally extending conduit is preferably provided for the container to house detonator wires leading to the explosive charge in the drill hole. This conduit is preferably provided by enlarging the width of one set of aligned radial slots and preferably forming an aligned slot in the closure device.

The explosion container is preferably a plastic moulding. A bore preferably runs along the length of the shank.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings.

In the drawings : - Figure 1 is a perspective view of an explosion container of the invention ; Figures 2,3 and 4 are respectively side, front, and rear views of the explosion container; Figure 5 is a side view of an explosion container as used in a drill hole but with the detonator wires and withdrawal cable omitted in the interests of clarity, Figure 6 is a is a side view of the explosion container showing the location of the detonator wires and the withdrawal cable, and Figure 7 is a side view of a tamping rod for use with the explosion container of the invention.

Referring now to the drawings there is shown an explosion container 10 of invention. The explosion container 10 is a moulded monolithic plastic polyvinyl chloride member. It comprises an elongated shank 12 having a closure device 14 at one end and five retention members 16.

The shank 12 is of hollow circular section with an narrow bore 18 therethrough.

The closure device 14 comprises a dished member co-axially mounted on the end of the shank to present a concave face 20 to the explosive charge as will be described.

The diameter of the face 20 is sufficiently smaller than the diameter of the drill hole into which the explosion container 10 is to being inserted to permit it to pass down the drill hole. The bore 18 opens centrally through the face 20.

The retention members 16 are generally circular disc-like members which lie in planes radial to the shank 12 and covering the bulk of the length of the shank 12. They are sufficiently flexible to be distorted when the inserted into a drill hole of slightly smaller dimension to take up a conical shape as shown in Figure 5. Three narrow (possibly about 5 mm wide) radial slots 22 are provided in each member 16 extending inwardly from near the periphery 24 of the member, two 22.1 and 22.2 lying on a diameter of the members and a third 22.3 midway between the others. The slots 22 in the members 16 are aligned. A larger radial slot 26 (possibly about 10 mm wide) which is similar to the slots 22 is provided in each member 16 diametrically aligned with the slot 22.3. A further slot 28 is formed in the closure device 14 aligned with and of the same width of the slots 28, and extending from the periphery of the device 14.

A tamping rod 30 is provided. This is conveniently a steel or other metal rod having a handle 32 at one end and reduced diameter 34 at the other end.

The explosion container 10 is used as follows in mining operations (and as best shown in Figure 5). A drill hole 36 is drilled in a stope face, the diameter of which is slightly smaller than the diameter of the retention members 16. An explosive charge 38 is tamped into the drill hole 36 hard up against the base thereof and with the detonator wires 40 (see Figure 6) extending out of the drill hole 36. The wires 40 are fed through the channel formed by the slots 26 and 28 in the container 10. The explosion contain- er 10 is now pushed into the drill hole 36 by means of the tamping rod 30 with the reduced diameter end 34 engaging in the bore 18. As the explosion container 10 is pushed into the hole 36, the edges of the members 16 engage the wall of the drill hole 36 and are distorted into a conical shape (as shown in Figure 5). The explosion container 10 is pushed sufficiently deeply into the drill hole 36 that the closure device 16 engages the front end of the explosive charge 38. When the explosive charge 38 is detonated, the edges of the retention members 16 engage the side walls of the drill hole 36 and contain the explosion gases. The containment is necessary only in the initial phase of the explosion. This will cause the most effective use of the explosive.

In use, it will be desirable to attach a retraction cable 42 to the container. This cable 42 is attached between the front retention member 16 and the closure device 14.

The cable 42 is bent back on itself so that there are two lengths 44 and 46 which run along the edges of the retention members 16. Should the explosive device not detonate, the retraction cable will be pulled from outside the drill hole. This will cause the parts of the retention members which it engages to collapse. Consequently the container will now be relatively free of the sides of the drill hole and can be removed.

The invention is not limited to the precise constructional details hereinbefore described and illustrated in the drawings. For example the retention members may com- prise separate materials mounted on the shank. The shank may be generally of"U"- shape in section so that the electric wires can pass along the shank to the explosive charge. The containment device may comprise any other material and in particular any other suitable polymer such for polystyrene, low and high density polymers.