US1940255A - Explosive - Google Patents

Description

i5 Dynamites which Patented Dec. 19, 1933 EXPLOSIVE Norman G. Johnson,

to E. I.

Woodbury, du Pont de Nemours &

N. J., asslgnor Company, Wilmington, Del., a corporation oi Delaware No Drawing. Application July 8, 1931 Serial No. 549,578

10 Claims.

My invention relates particularly to improved nongelatinous dynamite compositions and more especially to dynamite compositions of a pulverulent or granular nature which will flow or 5 pour freely.

Explosives of the dynamite type are commonly termed high explosives in distinction from explosives such as black powder, which are designated as low explosives, the difference in 10 terminology between high and low explosives coming from the differing velocities of combustion. Whereas, explosives such as black powder burn at velocities in the neighborhood of 300 m/sec. for columns of explosives approximately 1%" in diameter, high explosives such as dynamites are consumed so rapidly that the decomposition is termed detonation, the velocity of detonation in the case of dynamites ranging from 1200 to 6000 m/sec. for 1%" cartridges. The high velocity of dynamites is due commonly to the presence of nitroglycerin in the formula.

Black blasting powder has ordinarily been used in the past in granular form, in which form the powder could be loaded into the borehole simply by pouring. Dynamites, on the other hand, have-customarily been put up in much different form. The usual method of packaging dynamites has been to punch the material tightly into the paper shells of the cartridges. These shells have then been folded over or crimped at the two ends. When thus packed, the dynamite has usualLv been shot directly in the wrapper, the paper container being considered an ingredient of the dynamite. With such a method of use of dynamites the possession of good pouring or free flowing properties was obviously of no advantage.

Occasions frequently arise, however, where it is very desirable to be able to pour the dynamite into the bore-hole, as is the case when granular black powder is used. In order to do this it is necessary that the dynamite be removed from the cartridge, either by direct removal of the entire shell or by the unfolding of one end of the cartridge, so that the dynamite may be poured out. The more convenient method 01' using high explosives which are to be loaded in such a manner is to use an explosive which has been packed in bags in the first place, rather sothan in cartridges. Because of the physical properties of the usual dynamite compositions,

these explosives are not adapted to such a method of use and have the property of flowing freely to a very slight extent, if at all.

can' be loaded by pouring in the bore-hole are frequently desired in quarrying work. It is often advantageous to use small diameter holes, not more than 2 inches in diameter for example, because of the saving in drill- 0 ing costs. In such cases it is the practice often (Cl. 521l) to chamber the holes, that is to-say, to set off successive shots in the bottom of the hole until this part has been enlarged to a considerably increased volume. In blasting such chambered holes, the use of free-running explosives is particularly advantageous, since such explosives will fill the enlarged portion of the hole almost completely.

The high explosives used in such work prior to the present invention have ordinarily contained a large amount of sodium nitrate in their compositions, together with ammonium nitrate usually, and carbonaceous combustible materials, while small percentages of nitroglycerin have customarily been used as sensitizing agent and explosive ingredient. Sodium nitrate has frequently been used in such explosives in amounts up to -60 per cent by weight of the entire explosive composition. Whereas the explosives of such nature heretofore in use have given satisfactory results in generaltheir properties have not been all that could be desired with respect to their ability to pour freely into the bore-hole.

The object of my invention is to produce a new and. improved explosive composition for such use, which possesses all the advantages in explosive properties of the dynamite previously used and which has in addition the property of flowing freely to an unusual degree. Further objects will be apparent as the description of my invention proceeds.

I have discovered that this desirable result is obtained by the use of an improved form of sodium nitrate or other metallic nitrate in place 01 the common form previously used. Whereas the nitrate in general use in such explosives has consisted of very finely ground material of either natural or synthetic origin, or of material of varying forms and crystal size, I find it desirable to use a metallic nitrate in the form of small spherical pellets. While the nitrate used will preferably be sodium nitrate, because of its advantages from the economic point of view, and from the point of view of oxidizing properties, I do not intend to be limited in my invention to this material. Potassium nitrate, calcium nitrate and other metallic nitrates in the form of pellets are intended to be included within the scope of my invention. Also, a mixture of these nitrates may be used for this purpose.

The pelleted material described above will be strikingly diiferent from the ordinary sodium nitrate as used in explosives. The material previously available has ordinarily been ground to a definite degree of fineness but the particles are present in a variety of different shapes and forms. Improved pelleted material, on the other hand, exists in the form of smallballs of such size that they should ordinarily pass an 8-mesh sieve and be held on 30-mesh. The process by which said pellets may be obtained may vary within wide limits. One process consists of having a molten material sprayed through small openings into a cooling gaseous mixture where the material will immediately harden to small spherical pellets, usually somewhat hollow in nature. Various other methods of forming the pellets are available also.

1am aware that ammonium nitrate in the form of coarse grains and of hollow spherical granules has been used in explosive compositions. Such forms of this material for use in dynamites are described in U. S. Patent 1,113,- 275 (Woodbury) and in U. S. Patent 1,613,335 (Symmes). However, the use of pelleted ammonium nitrate is not suitable to accomplish the objects of the present invention. Ammonium nitrate in the form of hollow granules was used by the foregoing investigators for the purpose of obtaining a low density dynamite. Explosives containing such granules of ammonium nitrate could not be, or remain, free-running because of the great hygroscopicity of the compound, which would tend to cause it to cake.

By the use of sodium nitrate or other solid metallic nitrate, in the desired pelleted form in dynamite compositions, I obtain a high explosive of extraordinary properties, which is perfectly adapted to the desired use where a free-running explosive is wanted. An explosive containing such pellets may be poured into a borehole in such manner as to fill completely all the crevices of the bore-hole, without need of tamping.

While various compositions of ingredients may be used according to my invention in the manufacture of free-running explosives, the following will illustrate one satisfactory composition:

While I have described specifically the use of sodium nitrate in pelleted form in the above illustration, it should be understood that any solid metallic nitrate in pelleted form may be used in place of it. I may prefer also to use only a portion of the sodium nitrate or other metallic nitrate present in the explosive in the form of pelleted material, a suflicient percentage of pelleted nitrate being present to give the desired free-running properties to the explosive.

From the foregoing description of my invention it will be apparent that I do not intend to be limited except as indicated in the following patent claims:

I claim:

1. A non-gelatinous dynamite composition. containing as an ingredient a solid metallic nitrate in the form of spherical pellets.

2. A non-gelatinous dynamite composition, containing as an ingredient an alkali metal nitrate in the form of spherical pellets.

3. A non-gelatinous dynamite composition, containing as an ingredient sodium nitrate in the form of spherical pellets.

'4. A free-flowing non-gelatinous dynamite composition, containing as an ingredient a solid metallic nitrate in the form of spherical pellets.

5. A free-flowing non-gelatinous dynamite composition, containing as an ingredient an alkali metal nitrate in the form of spherical pellets.

6. A free-flowing non-gelatinous composition, containing as an ingredient sodium nitrate in the form of spherical pellets.

7. A free-flowing non-gelatinous composition, containing as an ingredient potassium nitrate in the form of spherical pellets.

8. A free-flowing non-gelatinous composition,

containing as an ingredient calcium nitrate in the form of spherical pellets.

9. A free-flowing non-gelatinous composition, containing as an ingredient sodium nitrate in the form of spherical pellets, of such size that they will pass a sieve having 8 meshes to the inch and will be held on a sieve having 30 meshes to the inch.

10. A free-flowing non-gelatinous dynamite, comprising 3 to 20 per cent nitroglycerin, 20 to '70 per cent spherical pelleted sodium nitrate, 5 to 20 per cent carbonaceous combustible material, and an antacid.

NORMAN G. JOHNSON.