US2682221A - Priming device for liquid oxygen explosive cartridges - Google Patents

Description

June 29, 1954 H. SAUVAGE PRIMING DEVICE FOR LIQUID OXYGEN EXPLOSIVE CARTRIDGES Filed July 3, 1950 Inventor:

SAUVAG E HENRI AH or ney s Patented June 29, 1954 UNITED STATES PATENT OFFICE PRIMING DEVICE FOR LIQUID OXYGEN EXPLOSIVE CARTRIDGES France Application July 3, 1950, Serial No. 171,933

Claims priority, application France July 11, 1949 1 Claim. 1

My invention relates to a priming device for liquid oxygen explosive cartridges used in bore holes for blasting.

The evolution of the technique of mining by means of explosives makes it more and more necessary to fire in one single operation a large number of blasts, an operation termed large-volley blasting, in which electric primings are used with several timings, so as to spread out the shooting of the blasts. In such a blasting operation, the charging of the blast holes generally consists in the following steps: in each blast hole, explosive cartridges are successively introduced, the first one or the last one introduced being provided with a delayed electric priming; if a detonating fuse is used instead of this priming, the cartridges are placed against the fuse, which comes out of the blast hole; in both cases, tamping is effected in each blast hole, then, in case electric detonators are used, the electric wires issuing from all blast holes are connected together, then to an electric line and said electric line is tested. In case detonating fuses are used, the fuses from each blast hole are connected to a master fuse on which a priming is placed; then,

firing is effected. The time necessary for tamp ing and for setting up the connections between the electric wires of the fuses and for checking the electric line is relatively long as compared to the time necessary for introducing explosive cartridges in the holes; it is difiicult, at the present time, to shorten it sufficiently to allow, in the case of large-volley firing the use of liquid oxygen explosives because of the spontaneous evaporation of liquid oxygen, even if long life liquid oxygen cartridges are available. On the other hand, the delayed electric primings which are necessary do not always operate satisfactorily when they are cooled at low temperature.

The priming device according to my invention makes it possible to obviate the above mentioned drawbacks. It consists in an electric priming abutted against a detonating powder charge, characterized in that the detonating powder is completely or partly lining the face of the device in contact with the liquid oxygen cartridge.

The priming device makes it possible to apply large-volley firing to liquid oxygen explosives. To this effect, the loading of each one of the blast holes begins with the introduction of the above mentioned priming device, said device being held at the bottom of the blast hole by a support, for instance a socket or hollow sleeve so that the face provided with the detonating powder comes out towards the entrance to the blast hole; then connections are established between the electric wires of the primings together and also with the electric line; following this, a liquid oxygen cartridge is introduced in each hole until it rests on the face of the device provided with detonating powder; the contactbetween the detonating powder charge and the cartridge is thus very close and the transmission of the explosion wave is perfectly ensured; other cartridges may then be introduced and finally the usual tamping is effected in each hole.

Due to the fact that the priming device is placed separately and before the liquid oxygen cartridges, plenty of time is available first for introducing the priming devices, then for establishing and checking electrical connections and, after any time lapse, for the loading proper of said liquid oxygen cartridges, which loading, of course should be effected, as well as the tamping, as rapidly as possible. In the same manner, immediately after tamping, the shot should be fired by connecting the electric line to a current source. In this manner, there is obtained a saving, for the evaporation of the liquid oxygen, of all the time required for the introduction of the priming device and for the establishing and checking of electrical connections. In practice, for a blast hole 2 meters deep, the time necessary thus for the operations starting with the placing in position of the first cartridge until ignition, is half a minute whereas, in known methods, this time, which necessarily includes the placing in position of the priming devices and the establishing of electrical connections, is about three times longer.

Another advantage of the priming device thus used is that it is not necessary to use, in its manufacture, a special electrical priming designed for low temperatures. The electrical priming is not licked by cold gases evaporated from the cartridges and, consequently is subjected only to a very slight cooling.

In the above priming device, the charge of detonating powder may be placed in the form of an element of a detonating fuse wound in a spiral on the face of the device.

The figures in the appended drawing show, by way of example, types of embodiments of the present invention.

Figure 1 is relative to the priming device comprising an element of detonating fuse, and Figure 2 is relative to the priming device comprising a charge of detonating powder. In these two figures the device comprises a socket 4 having a diameter slightly smaller than that of the blast hole, which may be tight or not, and which is closed at its end facing the bottom of the hole by a plug 6; between said plug 6 and the socket 4 are passed the wires IU of the electric priming. In the vicinity of the axis of the socket is arranged the electrical priming 2, abutted in the known manner to the end of the detonating fuse- I in the case of Figure 1, and to the charge of detonating powder 8 in the case of Figure 2. Ac cording to Figure 1, the fuse is wound, at itsend, in the shape of a spiral bent against the bottom of the socket and held by a plate 5, of wood for instance, crimped inside the socket. According to Figure 2, the charge of .detonating powder 3 is enclosed in a cylinder formed by the bottom of the socket and a crosspiece 5 continued by an axial tube 1 extending down to the detonator. The first liquid oxygen explosive cartridge is placed against the bottom 3 of the socket.

In the case of an ascending blast hole, the device is preferably provided with a spring metal blade 9, of brass for example, for anchoring the device at the bottom of the blast hole and preventing it from falling back towards the hole entrance.

What I claim is:

In a detonator for liquid oxygen cartridges, a tubular shell having a closed upper end and an open lower end, a detonating fuse wound in the shape of a flat spiral the central portion of which extends as a rod at right angles with the plane of said fiat spiral, means adapted to hold the spirally wound portion of said fuse applied against the inner face of the shell closed end while allowing said rod to extend axially in said shell, thus forming a free insulating space between said rod-and the shell, an electric priming device with igniting wires, coupling means for connecting end to end said priming device to said axial rod, and a removable plug adapted to close the open end of the shell by clamping the igniting wires and allowing them to pass outside the shell.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 422,442 Peters Mar. 4, 1890 707,626 Norres Aug. 26, 1902 2,253,549 Barton Aug. 26, "1941 2,429,490 Scherrer Oct. 21, 1947 FOREIGN PATENTS Number Country Date 16,903 Great Britain o f1'912 24,137 Great Britain Oct. '15, 1914

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