Device for filling bore-holes formed in rock formation with particulate explosive

Feb. 23, 1965 s. h. alfredsson 3,170,366

DEVICE FOR FILLING BORE-HOLES FORMED IN ROCK

FORMATION WITH PARTICULATE EXPLOSIVE

Filed Dec. 15. 1961 2 Sheets-Sheet 1

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INVENTOR

SVEN HUGO ALFREDSSON ^BY Z ^C ATTORNEYS

Feb. 23, 1965 s. h. Alfredsson 3,170,366

DEVICE FOR FILLING BORE-HOLES FORMED IN ROCK

FORMATION WITH PARTICULATE. EXPLOSIVE

Filed Dec. 15. 1961 2 Sheets-Sheet 2

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Fig.7

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SVEN HUGO ALFREDSSON

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United States Patent Office

3,170,366

Patented Feb. 23, 1965

3,170,366

DEVICE FOR FILLING BORE-HOLES FORMED IN ROCK FORMATION WITH PARTICULATE EXPLOSIVE

Sven Hugo Alfredsson, Nasbypark, Sweden, assignor to Nitroglycerin Aktiebolaget, Gyttorp, Sweden, a corporation of Sweden

Filed Dec. 15, 1961, Ser. No. 159,628

Claims priority, application Sweden, Dec. 22,1960, 12,451/60

Claims. (CI. 86—20)

This invention relates to a device for filling bore-holes formed in rock formation with a particulate, namely a pulverulent or granular explosive which by means of a pressure fluid, such as compressed air, is conveyed into the holes through a loading tube, which has a smaller diameter than the boreholes and which preferably is constituted by a flexible hose.

It is known in prior art to recover explosive entrained by the returning flow of pressure fluid into the space between the tube and the wall of the bore-hole. For this purpose a sealing device is provided around the tube adjacent the mouth of the bore-hole from which sealing device another tube extends to a separator for the entrained explosive.

This known construction is relatively complicated in use.

It is one main object of the present invention to provide a device which simplifies the work and simultaneously permits a perfect separation of particles of explosive entrained with the return flow of pressure fluid while at the same time rendering the tubes easy to handle.

According to one main feature of the invention a grid or lattice work arranged externally on the tube is given such structure as to allow the returning pressure-fluid to pass between the tube and the wall of the hole while retaining particles of explosive following with said returning pressure fluid.

Further objects and advantages of the invention will become apparent from the following description, considered in connection with the accompanying drawings which form part of this specification and of which:

FIG. 1 is a diagrammatic partial view of a bore-hole formed in a rock formation and entered by a hose provided with a device constructed according to one embodiment of the invention.

FIG. 2 is a side elevation of the same embodiment which is enclosed in a hood or cover intended to facilitate the introduction of the hose into the bore-hole.

FIG. 3 is a perspective view of another embodiment of the invention.

FIG. 4 is a side elevation of a further embodiment with part of a brush-layer assumed to be cut away in order to obtain improved perspicuity.

FIG. 5 is a diagrammatic partial view of a bore-hole with a hose introduced thereinto and provided with a device constructed according to still another embodiment of the invention.

FIG. 6 is a top view following line VI—VI of FIG. 5.

FIG. 7 is a side elevation of still an alternative embodiment.

Referring to the drawings and in particular FIG. 1, reference numeral 10 denotes a bore-hole formed into rock formation and intended to be filled with explosive. Introduced into said hole is a tube which suitably is constituted by a flexible hose 12 and which is in connection with a source of pressure fluid, preferably compressed air, and suitably also with a storage container (not shown) for the explosive. The explosive is constituted by granules or a powder of a suitable explosive such as ammonium nitrate, for example, and is usually mixed with a smaller quantity of oil which causes the mass to become slightly sticky. The explosive deposits in the borehole while the hose 12 is retracted. The air required to convey the explosive into the bore-hole escapes into and through the space between the hole and the hose. According to the invention, the hose 12 is surrounded by a structure constituting a kind of grid or lattice work or filter which lets the returning air pass by but at the same time serves as a separator preventing particles of the explosive from becoming entrained with and conveyed out of the hole by the returning compressed air.

In the embodiment shown in FIG. 1 the hose 12 is externally and at a minor distance from its outlet end located within the hole 10 provided with a crown of filaments or bristles 14 secured to the hose by means of an annular member 16, said filaments or bristles preferably radiating outwardly in a slightly distorted manner. The filaments or bristles 14 may be disposed in one layer or in several layers which are slightly distorted helically. They are preferably made of a non-metallic material such as Piassava, palm oil or a synthetic plastic material or similar substances. It is essential that they have such mutual spacing as surely to catch and retain particles of the explosive following the return air escaping between the hose and the wall of the hole but without at the same time producing any appreciable resistance against the passage of said air. Granules of the explosive thus depositing on the brush formed by the filaments may further improve the desired filtering effect. The deposits may be removed at suitable intervals either outside or inside of the bore-hole, in which latter case they are directly utilized in the filling of the bore-hole.

The filaments or bristles 14 project from their zone of attachment in the annular member 16 in an oblique direction towards the outlet end of the hose. They are slightly resilient. In order to facilitate their introduction into the bore-hole the bristles may be enclosed in a manner shown in FIG. 2 by a hood or cover 18 made of preferably resilient plastic or other similar material. Said hood is automatically drawn off when the compressed air is let in into the hose.

In the embodiment shown in FIG. 3 a sleeve 20 carries knobs 22 projecting radially or substantially radially outwards. The knobs are suitably disposed in several layers displaced peripherally relative one another so as to eliminate direct straight passages for the returning air. The knobs 22 which are dimensioned so as to bridge the space between the hose and the wall of the hole may be made integrally with the sleeve 20 for example by being moulded together with said sleeve in some suitably synthetic or natural plastic material. The sleeve is forced onto the hose 12 or united therewith by some other suitable means.

In the embodiment shown in FIG. 4, filaments 24 of a resilient non-metallic material are helically disposed between two fastening rings 26, 28. The filaments extend in mutually parallel relationship and project with their middle portion outwardly to reach a maximum radius equalling or surpassing that of the bore-hole so as completely to bridge the spacing between the hose and the wall of the hole. An inner assembly of filaments 33 may be attached with both ends to annular members 32, 34. In this inner assembly the filaments extend helically but in an opposite direction relative to the filaments 24. The hose 12 or a separate tubular member extends between or past the annular members 32, 34 as is indicated at 35. The granular explosive is entrained by the air-current out at the hose and the returning air is filtered when passing through the outer and/or the inner assembly of filaments.

3,170,366

According to FIGS. 5 and 6, the end 35 of the hose is formed with annular flanges 38 of some suitable flexible material. Said annular flanges have a larger diameter than the bore-hole 16 and consequently abut against the wall of said hole. The flanges 38 are provided with mutu- 5 ally peripherally displaced perforations 46 dimensioned so as to form passages for the air streaming therethrough and simultaneously separators for entrained particles of explosive.

According to FIG. 7 the hose is provided with one 10 single annular flange 38 the outer diameter of which largely surpasses that of the bore-hole 10, into which the flange is introduced with the hose end 36. In FIG. 5 the hose is assumed to be advanced inwards within the bore-hole 10, the flanges 38 consequently having been 15 bent rearwards. In FIG. 7 it is assumed that the borehole is being filled with explosive while the hose is retracted out of the hole.

The lattice work may be constituted by foamed plastic material or some other foamed porous material. It may 20 also be constituted by a wire gauze or strainer screen or screen plate fitting to the contour of the hole. The flanges 38 may be slotted radially if desired.

While several more or less specific embodiments of the invention have been shown and described, it is to be un- 25 derstood that this is for the purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.