US2038772A - Blasting charge - Google Patents

Description

Apr 28, 1936. .1. TAYLOR BLASTING CHARGE Filed Feb. 19, 1954 INVENTOR. Jah-LE 5 Talib? aillll'! ..11

Patented Apr. 28, 1936 UNITED AsTATlli-s PATENT OFFICE BLASTING CHARGE Application February 19, 1934, Serial No. 712,050 In Great Britain December 15, 1933 Claims.

Explosives of the non-detonating type, such as I blackpowder, cordite, and the like, undergo exotherinic decomposition on the application of flame or on exposure to high temperature. This 5 decomposition, as is well known, results in the formation of products at high temperatures such as arev capable of igniting methane-air and coal dust-air mixtures, and such explosives are not safe for use in fiery mines.

Accordingly devices havey been proposed for blasting, wherein such explosives as would be too dangerous to use in the ordinary manner are confined in a pressure-resisting shell having a. gas release means adapted to allow the gases to l5 escape when the internal pressure rises to a certain value. The amount of explosive placed Within the shell is insuiilcient of itself to operate the device, but a gas-producing substance or mixture of substances is also included in the shell,

for example ammonium nitrate or a mixture of ammonium nitrate and ammonium chloride or tities of gas, so that a comparatively large amount of heat is required and a correspondingly large amount of explosive or heating composition such as blackpowder.

I have found that mixtures of sodium nitrite or potassium nitrite with ammonium chloride or ammonium sulphate, in a range of widely varying proportions, provide self-sustaining gas producing mixtures which when conned in a rigid` vessel of the type having a member adapted to permit emission of the gases at a predetermined and considerable pressure are capable of eiect- 49 ing blasting with safety in ery or dusty mines. The mixtures used according to my invention, when initiated under ordinary pressure, do not exhibit explosive properties, but sustain their own decomposition. A small proportion of moisture of the o rder of 0.5% is desirable for the reaction mixtureto be easily initiated by the application of heat.

In putting my invention into effect, heat is supplied within the container to one portion of 50 the mixture, for instanceby lmeans. of a 3o grain powder fuse. Where loading is to take place in ery or dusty mines, it is of course desirable to use a safety igniter of a kind incapable of ignitingredamp-air mixture.

-It is far from necessary that the two materials` should be present in stoichiometrlcal proportions. 'I'he mixtures maybe used in powder form or may /be granular or compressed into cartridges and it is desirable that they be wrapped up in reproofed paper. They may, if desired, be loaded into the 5 container in the mine itself.

It will be understood that the invention is not limited to the case of coal mining, but it is of particularly g eat Value in that art since it not only provides a reliable method of blasting but 1o also facilitates the production of round coal.

The following is a description of a device embodyingrmy invention, which is illustrated in the appended drawing.

Into vone threaded endof a shouldered strong u;

. steel container (I) there is screwed a iiring head (2) separated frontil the container (I) by a sealing washer (9) of nbre or other suitable material such' that a. seal which is gas tight even at high pressures is ensured. The firing head (2) is pro- 20 vided with electrodes (1) and (8) of which one (8) is in metallic connection with the ring head (2) while the other (l) is insulated from the ring head. The mounting of the insulated electrode (1) is such as-to allow no gas leakage at 25 pressures up to about. 25 tons per sq. in. Terminais (I0) and (I I) are provided for the electrodes, which are used in initiating the cartridge elec-- trically. A protective steel cap (3) having an aperture (I4) for the leads to the terminals from 3Q the cable of the exploder or other suitable source -of electrical energy is screwed on the ring head (2) The blasting charge (I3) is introduced loqsely into the tube in therequisite amount.

On the shoulder of the container remote from the 35 iiring head (2). there is placed afibre or. like sealing washer (6), the'steel bursting disc (5) adapted, to be ruptured at a predetermined pressure being held in position between the said washei` and the hollow screwed-in cap (4) which 40 is pierced with suitable channels for the venting of the gases and the direction and distribution of the blast. An electric powder fuse or safety igniter (I2) containing for example 30 grains biackpowder is used. for ignition and provided with long leads from the electrodes and positioned as shown in the drawing so that the ash is directed towards th ring head and initiation occurs near the end of the charge adiacent to the cap (t) By so positioning the cap the tendency of the charge to be forced into a plug at the end nearest the cap (l) is overcome. Inblasting, the assembly is placed in the boreholel with the cap (4) as far in as possible, and the device (55'

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