Explosive package

[57] ABSTRACT

A thermoplastic film package containing a blasting explosive is provided having particular utility in secondary blasting operations. The package is especially suitable for aqueous slurry blasting agents which are filled through a self-closing valved opening. The package is also provided in the form of a train of detachably connected side-by-side packages.

Claims, 4 Drawing Figures

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PATENTED FEB 121974

3,791.297

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FIG. 4

3,791,297

EXPLOSIVE PACKAGE

This invention relates to a novel explosive package. More particularly, the invention relates to an improved package for explosives used in secondary blasting.

In secondary blasting, explosives are employed for the purpose of breaking up large pieces of rock in open pit operations or for the dislodgement of rock projections in underground workings and the like. Generally, in secondary blasting, an explosive charge is simply placed on the surface of the rock, jammed into a rock crevice or held against the rock by means of props or poles and thereafter detonated. In quarry operations, for example, a very large number of secondary blasts may be required to fragment boulders for subsequent crushing. Economy and convenience, therefore, are the principal requisites of any explosive used in secondary blasting.

In the past, it has been customary to prepare secondary blasting charges from one or several cartridges of conventional dynamite or to employ dynamite compositions packaged in small bags. This method is frequently both costly and inconvenient since charges of this type do not lend themselves to easy placement on or in the rock. It has been suggested by J.M.E. Romocki et al. in U.S. Pat. No. 3,534,685, granted on Oct. 20, 1970, to employ for secondary blasting charges a pulverized ammonium nitrate/fuel oil (AN/FO) blasting agent contained within a plastic bag, the bag being especially adapted for simplified priming. While this proposal goes far towards economizing secondary blasting operations, it has not solved all of the problems associated therewith. There remains a need for a yet further improved explosive package for secondary blasting, which package combines economy of production and use with safety, convenience and explosive effectiveness.

It is the object of the present invention to provide an improved explosive package suitable for use in secondary blasting.

It is a further object of the invention to provide a series of detachably connected explosive packages suitable for use in secondary explosive blasting.

Other objects of the invention will become apparent hereinafter.

The improved explosive package of the invention comprises a bag-like container of thermoplastic film and a blasting explosive composition contained within said container, said container being heat-sealed along at least two of its edges and having a valved filling opening for the introduction of blasting explosive therein.

The invention may be more fully understood by reference to the accompanying drawing wherein like numerals indicate like parts and wherein

FIG. 1 shows a view of a preferred embodiment of a package made in accordance with the present invention;

FIG. 2 shows a view of the package of FIG. 1 taken along line A—A thereof;

FIG. 3 shows an alternative form of package; and

FIG. 4 shows a train of the packages of FIG. 1 detachably connected together.

Referring to FIGS. 1 and 2 of the drawing, there is shown a valve bag 1 containing an explosive composition. Bag 1 which is of the general pillowcase type has a back wall 2 and a front wall made of partially overlap2 ping panels 3 and 4. Panels 3 and 4 are shown as integral with back wall 2 and thus form with the latter a length of tube which is closed at both ends by transverse seams 5 and 6. Except for a limited portion 7 extending transversely of the bag, panels 3 and 4 are united to each other in their common area of overlap by seams 8 and 9 extending from transverse seals 5 and 6 respectively to said portion 7. The portion 7 left unsealed in the common area of overlap between panels 3 and 4 constitutes a tubular valve opening suitable for insertion into the bag of filling spout 10. When the bag is filled with an explosive mixture, the edge of panel 3 acts as a valve which closes upon pressure exerted by the explosive mixture and prevents egress of the latter through the unsealed portion 7.

The alternative form of the invention illustrated in FIG. 3 shows a package generally similar to that of FIG. 1 and 2 with the exception that it comprises a bag having two ply walls. The back wall 2 is comprised of plies 2A and 2B and the panels 3 and 4 of the front wall are comprised of plies 3A and 3B and plies 4A and 4B respectively. Panel 3 which, in the area of overlap with panel 4 is located inwardly of the bag with respect to said panel 4, is characterized in that the free edge of its inner ply 3A projects somewhat beyond the free edge of its outer ply 3B. Except for the above differences, the bag which the package of FIG. 3 is made of is similar to that shown in FIGS. 1 and 2. In the package construction of FIG. 3, the edges of plies 3A and 3B act as dual valves which close the unsealed portion 7 upon pressure of the explosive mixture contained in the bag.

FIG. 4 shows a series or train of explosive-filled bags such as illustrated in FIGS. 1 and 2 or FIG. 3, interconnected by webs 11 of the film material which the bags are made of. Webs 11 have perforations 12 therein to aid in detaching one package from the adjacent one when desired.

While AN/FO explosives may be used in the explosive package of the invention, the preferred explosive for use is an aqueous slurry mixture comprising a thickened mixture of oxidizer salts and fuels dispersed in an aqueous solution of the salts.. Such a composition is economic to manufacture and safe to use and is ideally suited to the aforedescribed container since it results in a package which is kneadable and which can be wedged into rock fissures or conformed to rock irregularities. Slurry explosives may also be packaged in the described container by simple extrusion methods thus to provide a package of high density. The resultant package resembles somewhat a small pillow.

The thermoplastic film employed in the container preferably has a thickness of about 4 mils and doubleply film of 2 mils in each ply has been used to manufacture superior packages. Double ply containers exhibit improved tear resistance over single ply containers. A number of flexible plastic materials combining high tensile and tear strength are known which may be used in the construction of the container and which will suggest themselves to those skilled in the art. A preferred material of construction is polyethylene having a wall thickness of from about 2 to about 8 mils.

A shown in FIG. 3, the explosive package of the invention may be provided in a detachable train form.

Such a configuration permits the blaster to choose one, two or more packages as may suit the needs of the blasting to be undertaken. The connected packages for

3,791,297 multiple use can be simply pleated together in accordion fashion to provide larger charges. Single containers may be simply detached by tearing along the perforated or weakened connecting web.

It will be obvious to those skilled in the art that a number of so called “valved” containers may be suitably employed in the explosive package of this invention; the principal requirements for such a container being economy, ease of filling, durability and, especially, satisfactory retention of the explosive contents. While the valve container described herein has been shown to be excellent for the purpose intended, other similar known containers could doubtlessly be adapted for the purpose. A container of the type herein described is more fully disclosed by P. T. Jennings et al. in Canadian Pat. No. 709,244, granted on May 11, 1965.

In use in the field at the blasting site for secondary blasting, the blaster will prepare an initiation means, for example, a loop of detonating cord or a detonating cap and fuse or a small primer charge and place it in contact with the outside wall of the explosive package. The choice of initiator will depend on the sensitivity of the secondary blasting explosive used. Such an initiator may be secured in place by, for example, an adhesive tape strip. The thus assembled charge is then placed on the rock or obstruction to be blasted and the charge initiated. Generally, charges for secondary blasting will range from about 1 to 20 pounds or more in weight.

The following Example illustrates the improved explosive package of the invention but it is in no manner to be limited to the embodiment described.

EXAMPLE

In an underground gold mine at a 3,100 foot level draw point, a series of 12 secondary blasts were fired using 1 lb. and 2½ lb. explosive packages of the invention where a TNT-containing aqueous ammonium nitrate slurry comprised the explosive composition. Each explosive package was primed by means of a wrap of a 25 grains/foot detonating cord and strategically placed against the boulder or the “hang-up rock projection to be blasted. The detonating cord primers were initiated by means of blasting caps and safety fuse. Excellent fragmentation was obtained on all boulders and hang-ups. It was noted by mine personnel that the priming and placing of the packages were simple and speedy and provided excellent contact with the rock. Because of the nature of the explosive used, the period required for smoke clearance after blasting was much reduced as compared to conventional dynamite or AN/FO explosives formerly used in secondary blasting.