US2162910A - Explosive - Google Patents

Description

L. S. BYERS June 20, 1939.

EXPLOS IVE Filed NOV. 15, 1957 I YIME IIV w SECOND TIME secolvo INVENTOR.

LAUD 5. EYERS ?atented .iune 2Q 193$ massive Land 8. Byers, Glendale; Calii., assignor to Molex %xplosivcs, Ltd Manila, 1?. 1., a corporation of' Application November 15, 1937; sci-a1 No. 174,095

' l ignition through friction and shock and therefore of value as a general explosive. Other features and advantages of theinvention will appear in the following description. In the accompanying drawing: g 1

pressure curve as developed from the explosive omitting prepared cork as an ingredient.

Figure 2 is a similar graph as modified through the addition of specially prepared cork and 2 showing the clearly defined secondary pressure wave.

Before describing the invention in detail it is desired to call attention to the fact that for use infragmentation bombs the disrupting explosive must have special qualities and/or the bomb case must be especially designed to suit the pressure characteristics ofthe explosive, otherwise but a small proportion of the possible effectiveness of the bomb will be realized.

To be most efiective against personnel the fragmentation of a bomb must not result in case particles too fine nor too large, for such as are reduced below about a quarter of an inch across are found to have but little value except at very short range, while those greatly in excess of that sizerepresent just so much waste of valuable missile-forming material. With the above in mind, it will be evident that the use of an explosive in a bomb with .an extremely high brisance would reduce such a large proportion of the bomb caseto such inefiective sizes as to make the bombing a failure. On the other hand, an explosive of reducedinitial fractionating energy would result in larger case fragments but not be followed up with suflicient work energy or driving force to make them effective after the initial bursting shock. This is particularly so in small diameter cylindrical bombs wherein the storage space for the energy producing powder or explosive is limited. It has therefore been one 'of the objects of my invention to produce an explosive which will develop a suitable shattering force to split the bomb case into the largest number of effective size missile units and immediately follow this up with a secondary Figure 1 is a graph showing an approximate though powerful propulsion wave to hurl the ira ments outward.

Secondary pressure waves followlng'the initial shock have been observed with some explosives in tests with a Bichel gauge but have not been 5 sufiicient either in magnitude nor in time relation to the principal wave to be of any use, nor until my invention have they been studied and developed soas to be applicable to use in a fragmentation bomb or to blasting use where 10 a considerable work wave following the cracking or explosion wave would be valuable.

In the diagrams, Figure 1, the curve'shows at A the maximum pressure built up at the initial explosion over the time period as expressed in 18 1/1000 second intervals denoted on the .base. line, and B the point of maximum height and time position of the secondary wave. -The actual height of A will depend on the particular explosive or amount used and therefore the tons go pressure is not indicated on .the chart. This chart shows the generally negligible effect of the secondary wave as produced by my explosive composition when one of its ingredients is omitted, i. e. specially prepared cork.

In Figure 2 of the drawing which shows the modified'pressure curve obtained from an explosionofmy complete composition it will be noted that the peak of pressure A of the initial wave is more quickly .achieved,'and hence a so, sharper fractionating effect on the bomb case, and that this is much more quickly followed by" the crest B of the secondary or propulsion wave;

} also that the propulsion wave is many times the volume of wave B of Figure 1, as well as of great- 35 or pressure, thus providing a quick and powerful outward hurling force active on the bomb frag- 'ments an instant after the case has beendlsruptedn I As these charts represent the results of tests 40 made with a Bichel gauge they manifestly do not quite represent the pressure curves as where the confining-case is itself disrupted, as in a fragmentation bomb, and as to the precise effect no means has as yet been devisedfor recording, 45 but actual tests of the destructive effects pro- .duced by my improved explosive by exploding ,the bombs within a very large spaced sheet steel shielding container and examining the distribution and size of holes produced in the outer container with various explosives, proves that conditions with my improved explosive omposition' substantiate the graphof Figure 2,""though whether the time intervals are advanced by the 55 cases also with a sudden release of the confined gases isnot definitely known, though is considered likely.

In general, my explosive composition may be said to comprise an ammonium nitrate base fortified with a 'nitro body, sensitized with an easily oxidizable metal preferably in association with a fibrous refractory heat transmitter, and in some perchlorate, all controlled by especially prepared cork, the latter being principally involved in proper development of the secondary or propulsion wave.

Cork in powdered form is not itself broadly newfin explosive mixtures, but heretofore it has been merely used either as an interstitial absorbent, or rather adsorbent, and densityv adjusting agent for liquid explosives, plastic explosive compounds such as blasting gelatine, or in the form of a colloid coated or impregnated filler for use in the dynamite type of explosive, or as precipitation nuclei for the building up thereon of explosive I compounds from non-explosive substances', but the peculiar properties of cork when ground within a certain range of fineness and baked to change the relation of its hydrogenoxygen to its carbon content, of controlling the pressure waves in an explosive composition appears to have been overlooked. Likewise, the eflect of a powdered, easily oxidiza'ble metal such as aluminum, agnesiur'n, aluminum zinc alloy, etc. as a sensitizer, while well known, appears not to have been studied in combination with a highly refractory fibrous agent such as finely fibered asbestos, a given weight of which (up to about 20% of the weight of the metal) may be used to replace twice said weight of the aluminum without impairing flame propagation, yet reducing undesirable or super-sensitiveness in the explosive, and at the same time considerably reducing' the cost of the explosive composition.

Some of the useful variations of an explosive composition in accordance with my invention may be set out as follows:

Percentage by weight I I1 Ill IV V Perchlorate oi potash 5.0 10. 20. 0 Nitrate of ammonia (preferably coated); 84. 0 85. 70.0 71. 6 60. 0 Powdered aluminum 7.0 4. 0 7. 0 6.0 5. 0 Asba=.tos, ilnely shredded l. 5 0. 5 1. 0 Cork, prepared 1.0 l. 0 3. 0 l. 0 5. 0 itro body 7.0 7. 0 7. 0 10.0 b. 0 carbonaceous combustible.: 7.0 3. 0 Antincid-carbonates oi Ca,

(optional) M g, etc l. 0 l. 0 l. 0 l. 0 l. 0

'Nitroglycerine, n'.onc-, di-, or tri-nitrotoluene or nitrobenzene rr nitro nspthalene, etc. The nitrotoiuencs are preferred for the purpose of this invention as giving the best results.

Compositions I and II are high-density, high velocity explosives, equivalent to a 70% dynamite in work energy produced. Composition II is,

equivalent to Composition I except that part of the aluminum asbestos.

Composition III is a low-density, medium velocity explosive, equivalent to a 60% dynamite in work energy produced.

Composition IV is a high density, medium velocity explosive, equivalent to a 60% dynamite in work energy produced.

Composition V is a medium density, medium velocity explosive, equivalent to a 50% dynamite in work energy produced. The three last coma less smothering effect.

monium nitrate grain to stand up longer in pro-' powder has been replaced by I v be noted, perchlorate of potash or other oxidizing salt to carry the increased carbon content to these formulas.

All of the variations of the explosive compositions shown contain ammonium nitrate as the principal ingredient, and I have found that a more satisfactory result is produced when the ammonium nitrate in granulated form is coated with calcium stearate, aluminum stearate or other insoluble stearate- (including metallic soaps, oleates, palmitatcs or mixtures thereof), a procedure which may be carried out'with finely powdered stearate added in amount of about to 5% to the nitrate in a revolving inclined coating bowl until the grains are well coated.

I am aware Ofammonium nitrate having been coated with petrolatum,

positions include, as will agents as parafiin, an undesirable desensitizing effect on the explosive reaction, and because of their high oxygen deficiencies, must be used sparingly if a good fume condition is to be maintained.

Furthermore, these coatings are used primarily for their moisture-proofing effect; however, such coatings have the tendency to suddenly break down when exposed to a combination of both hot climatic temperature and high humidity, allowing the quick solution of the ammonium nitrate grain.

Calcium stearate, my preferred coating material, has many advantages in the type of explosive composition to It is less de-sensitizing, thus permitting a lesser amount of other "sensitizing" ingredients to be used, and it reacts better in explosion, as it has It enables the amlonged exposures to high-humidity, high climatic temperature combinations.

The asbestos used in my explosive composition should be highly fibrous, of good quality, and reduced to a condition maintaining as many of the fibers intact preferably not exceeding about $5 of an inch in diameter and not over inch in length.

The great value of'the asbestos fiber, as previously indicated, is that it incandesces instantly and its incandescent fibers maintain and transmit the heat wave throughout the composition, thus permitting a considerable reduction in the quantity of and V where asbestos is used, it will be noted that in every instance it has replaced twice its weight of aluminum.

The preparation of the cork used in the explosive composition is importantboth in size 01 granule as well as in treatment. I have found that cork has a distinct value as a combustible in the types of explosive mixtures described herein due to the hydrogen, oxygen and carbon found in this material. In combustion, its action is as follows: Under the influence of sumcient heat, its high percentage of air contained in its myriads of microscopic air cells, expands o ing that whereas a sample of cork in its natural,

carbonaceous value of the cork-as an ingredient in an explosive mixture is increased by the simple expedient of baking or pre-heating the cork by slowly appliedheat long sustained, tests showstate contained 56.88% ofcarbon and 29.47% of oxygen, that baking this sample in granular form The mesh size of the prepared cork used inmy explosive composition is highly important as' there are some meshes at which explosion will fail to occur. The proper range of granulation is that which will pass a 10 mesh"- sieve and be retained on a 48 mesh sieve.

The granulated cork, upon treatment as explained above. serves a dual purpose, one of which is to form an intergranular cushion against friction and impact, rendering the explosive powder much safer in handling and using, but most important is its capacity to bring about a pause or delay in the explosive reaction of certain types of explosive mixtures such as are described herein. This pause or delay, after the first pressure peak which, even though such as might be almost a imperceptible in time, has importance in certain uses, such as in the shattering of a metallic consecondary propulsion wave is of highest importance. The energy of most military explosives is expended in one sudden burst and, unless the walls of the metallic container are of tough metallic material, proportionately heavy to this sudden burst, the container is apt to be broken into 50 small fragments, too small for effective use as missiles. v

I have proved that, with this pause after the initial shock, and powerful secondary wave as herein described, a less tough, less expensive me- 5 tallic case may be used, and yet produce fragments equally as eifective as to size and efflciency. Furthermore, I am able to produce efiicient results with smaller metallic cases than hereto- 4 ognized as basic in the formulation of coal mining permissibles.

(2) The entrance of the residual-carbon from v the cork into the reaction. Carbon dioxide is formed from these elements (heat of formation +94;385 kilogram calories).

When Action (1) has taken place, the heat works up to the second stage, causingAction (2) to take place. The delay is the time interval between-the initiation Stage (1) and Stage (2).

Instead of the special heat treatment of the round cork to increase its carbon content as described, it is possible to use raw cork and add powdered carbon to raise it to the value of. that in the baked cork set out, but in such case the intimate distribution of the carbon throughout the substance of the cork particles as obtained by the slow baking process could not be realized, nor would the chemical reaction upon explosion be as efiective.

- In considering the above description of my improved explosive composition, it will be noted that I prefer ammonium nitrate as a base. and also prefer aluminum as the heating and sensitizing element, modified by potassium perchlo rate in the formulas as shown, as I have found the materials and proportions given to yield the most eiTectiv e explosion characteristic and secondary propulsion wave. I do not limit myself to these specific materials, as it is possible to modify the action of the explosive composition by combining or substituting in part other alkali nitrates besides ammonium nitrate, such as those of sodium, potassium, etc. and perchlorates, as well as other metallic powders in combination with fibrous asbestos, without departing from the spirit of my invention, as above generally set out and as sought to be included in my appended claims.

-I claim:

1. Inan explosive composition of the character described, the combination of a powdered readily oxidizable metal with finely shredded asbestos.

2. In an explosive composition of the character described, the combination of powdered aluminum and finely shredded asbestos.

3. An explosive composition comprising an in timate mixture of an alkali nitrate, an explosive nitric ester, a powdered readily oxidizable metal, and ground baked cork.

- 4. An explosive composition comprising an intimate mixture of ammonium nitrate coated with a metallic soap, a nitrotoluene, a powdered readily oxidizable metal, and ground baked cork.

5. An explosive composition comprising an intimate mixture of ammonium nitrate, an explosive nitric ester, a powdered readily oxidizable metal, and ground baked cork.

6. Ah explosive composition comprising an intimate mixture of an alkali nitrate as the major ingredient, an explosive nitric ester, a powdered readily oxidizable metal, ground baked cork, and fibrous asbestos in finely divided condition.

'7. An explosive composition comprising an intimate mixture of an alkali nitrate, an alkali perchlorate, a nitrotoluene, a-powdered readily oxidizable metal, and ground baked cork.

8. In an explosive composition, a brisance controlling material comprising ground baked cork.

LAUD B. BYERS.

v I JQERTI-FIGATE OF gomcw'io'ng rmnud. 2,162,9 0... A uh-2o, 19 9';

p muns Ems, y 1;- is hereb certified' t at the place of m mmn or the assighee i'n' izh ab'ove numbered patent was erronoualy 'decribd and. speoifi-ed as 4 whe rega said plaqe of incorporation ahouldiave been dscribed and specified a; Hong Kong, 1; Shown by the record of assignments in thig I office; ind thatthe' aai d Lei itera Patent should be readwith this correction 1' therein 'fih a t'the same maycon fiorm to th record bfthe case in the Patent I Office. I I I j-. 5 Q 4 s ri'a a sealed 1:111; 7th dayof libvmbe'r, A. D. 19 9. q

v I HenrfVem Az sdale, 7 (3 Acting Commissiqner 01f Patents.

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