US2958277A - Self-igniting incendiary devices - Google Patents

Description

w. o. SNELLING 2,958,277

SELF-IGNITING INCENDIARY DEVICES Filed May 9 1941 VIQZZer a fizzellz'qg.

2,958,277 SELF-IGNITHNG INCENDIARY DEVICES Walter 0. Snelling, Allentown, Pa., assignor to Trojan Powder Company, Allentown, Pa.

Filed May 9, 1941, Ser. No. 392,781

7 Claims. (Cl. 102-6) This invention relates to self-igniting incendiary devices and has for its primary object the provision of such a device which can be transported with reasonable safety as when carried in an airplane and which will delay action when dropped in surroundings which are temporarily unsuitable, as for example where the terrain is too damp or too cold or both, and which during such a delay is protected against inactivation.

A further object of the invention is to provide an incendiary device containing a self-igniting material. and a chemical heating composition which insures positive action when conditions are favorable for ignition.

A still further object of the present invention is to provide an envelope for any sort of incendiary device which will preserve the contents in active condition as long as the device is in damp or cool surroundings.

During the present war use has been made of incendiary devices doubtless including phosphorus which spontaneously takes fire as soon as the solute, usually carbon bisulfide, evaporates. An example of such incendiary devices is the so-called leaves which have been dropped on German forests and are utterly wasted if dropped during a rain or when reasonably heavy dew is on the foliage for under such circumstances the previously known incendiary devices will ignite quite independently of the wetness of the surrounding inflammable objects.

It the incendiary devices are water-wetted before dropping, it is recognized that these previously known devices will not be instantly acting. But the delay caused by simple surface wetting is not sufficient to prevent partial oxidation or slow smouldering over a long period of exposure. This premature action inactivates the device for subsequent proper functioning when the surroundings become favorable for ignition. I have found that surfaces coated with phosphorus from a carbon disulfide solution may not function at all if the coated surface is waterwetted before exposure, particularly if dropped in a cool or windy place. Slow oxidation does start and makes it self evident by the wisps of fumes given off, but in a cool or windy place the heat is dissipated as rapidly as it is liberated; and the temperature of the phosphorus coating will not rise high enough to actuate ignition.

Larger pieces of phosphorus likewise become inert or ineflicient when initially exposed to a cool or damp atmosphere. With the larger pieces, a new cause of the failure becomes evident. The oxidation, slowed down by unfavorable surrounding conditions, produces a deliquescent coating of phosphoric oxide and perhaps other which avidly combine with moisture to form a persistent, continually wet film of phosphoric acid. On subsequent exposure to sunlight, the rate of oxidation is further retarded in spite of the increased warmth, due partly to a coating of red phosphorus which results from the actinic exposure. Once these retarding coatings have formed, it is unlikely that the phosphorus will ever ignite unless the temperature of the surroundings rises to at least 34 centigrade or 90 Farenheit, the ignition temperature of phosphorus. In cool surroundings, a coated phosphorus does 2,958,277 Patented Nov. 1, 1960 not experience a sutficient temperature rise through its own oxidation to approach this ignition point.

My invention provides for a device which does not allow the self-igniting charge to begin to function until the surroundings are suitably dry, regardless of how many intervals of partial drying-out may be experienced. In one form of my invention a chemical heating compound provides for a sudden liberation of heat when the surroundings become dry, this heat raising the newly exposed phosphorus well above its ignition point and causing the de vice to function with positive action.

Since the ordinary incendiary device is incapable of both drying the material and igniting it, only relatively poor functioning of previous devices is possible under unfavorable conditions. It is a prime object of the invention to delay the action of the self-igniting incendiary device until such time as the surrounding objects may have dried out and therefore become inflammable when subjected to the flame of the present device.

In the general form of my invention, the body or container incorporates three separate functions: (1) to protect the self-igniting material from the atmosphere until the surroundings are suitably dry; (2) to disintegrate in part or entirety, as by shrinking or cracking after the surroundings have become dry, thus exposing the fresh selfigniting core to the atmosphere and causing it to function; and (3) to furnish additional combustible material for the incendiary device after the self-igniting material has functioned, thus intensifying its heat and flame.

This container body should have suflicient initial strength to withstand the impact from dropping a great distance, since these devices would be used principally by the flying service, and it should be sufficiently water-resistant initially to resist moisture penetration during long time storage under Water or in humidors. It may be pigmented, or painted or otherwise given a suitable drab color to minimize detection before it functions.

The shape and size of the body or container may vary widely, depending upon the ease of manufacture and assembly, as for example whether a pelleting machine or extrusion machine is used. If desired, the shape may be such as to increase air resistance and minimize the impact when dropped from a great height. The walls may be quite heavy, and serve as fuel; or quite thin and of comparatively negligible weight. The latter type makes a unit weighting considerably less than an ounce. These may be distributed in great quantities as an incendiary match for very combustible surroundings, or such lightweight units may be tightly fitted into perforated powder pellets which then furnish a more intense flame when they function. This particular arrangement has the same advantage as obtained in the well known practice of separating quantities of detonators from quantities of dynamite sticks or explosives cartridges through long storage, and not combining them until they are used.

In the drawings:

Figure 1 is a vertical section through a preferred form of my invention.

Figure 2 is an end view.

Figures 3 to 7 are sections through variant forms of my invention.

Figure 8 is an end view of the device of Figure 7.

Fig. 9 is a central cross-section through the device of Figure 4.

Fig. 10 is a simple and eflicient form of the invention.

The preferred form of self-ignited incendiary device is shown as the central element of Figure 1. This form is so simple and economical in construction, and can be made in such small sizes, that great numbers of them can be packed in a relatively small space, in suitably sealed humid cans which permit safe, easy transportation and distribution. In this type the non-breakable, preferably inflammable outer cover or container 31 has its open end or ends sealed by a layer of firm water-swelled substance 32 such as can be made from starch-paste, gelatin or glue gels, agar-agar, pectin, silica-gel, alumina-gel, bentonite or clay, viscose, or the like, or combinations of these; In the case of the starch-paste, which type is preferred, the'sealing material may 'bep'o'ufed'in'as a'cold fluid before the gel has set. The resulting plug serves as afirm, air-tight seal as long as the device remains in humid or vv'etsurroundings, but shrinks and exposes the contents in a dry and favorable atmosphere.

Because of its confinement, and the depth of the layer, this plug ordinarily will not dry out beforetlie surroundings do, but to insure that the seal remains intact until the surroundings are quite dry, I prefer to add avery small quantity of a hydroscopic agent such as glycerol, sorbitol, ammonium nitrate, calcium chloride, or the like, or suitable mixtures of thesewith the gel material, the amounts depending upon thewater content and thedsired rate of drying. The'resulting waterswelled plug insures that the surroundings are thoroughly dry before the self-igniting composition is exposed to the air which causes it to function.

The self-igniting composition 33 immediately inside the container and protected from exposure by the waterswelled plug, may consist of any material which is stable when kept wet by air-free water or other suitably inert volatile fluid, but which oxidizes'so rapidily on exposure to the atmosphere that it gives off a continually increasing amount of heat until ultimately it either bursts into flame itself or ignites the inflammable surrounding matter. Such self-igniting compositions may consist of a simple phosphorus pellet; or a loose absorbent having the desired wick effect, such as pulp, paper, cotton or nitrocotton, or starch nitrate powder, partly saturated with a solution of white phosphorus in carbon disulfide, or in benzene, ether, or other suitable phosphorus solvent; or it may consist of suitable inert absorbent'or inflammable absorbent contain ing spontaneously inflammable oil or oils such as triethyl phosphine, bismuth ethylchloride, cacodyl oxide, boron triethyl or the like; or it may consist of a highly inflammable composition mixed with a water-wet or alcohol-wet pyrophoric metal, such as amorphous zirconium, or black amorphous catalyst nickel, cobalt, iron, or the like, or pyrophoric lead, keeping such pyrohoric substances protected from exposure by a coating of air-free water or other volatile inertfluid, which in turn is confined by the water-swelled plug 32.

When the water-swelled plug dries out, the volatile phosphorus solvent evaporates through the exposure, and the wick action of the absorbent during this evaporation produces a tendency for the phosphorus to accumulate on the evaporating surface, where its oxidation is intensified and ignition'insured. As long as the water-swelled plug 32 is kept from drying out and shrinking, either by close confinement or by humidification in the storage containers, the seal remains intact and the carbon disulfide cannot evaporate, so the self-igniting layer cannot function, nor can it deteriorate. When it falls to a place having suitably dry conditions, the water in the starch-paste or similar gel evaporates, causing the plug to shrink and break away from the wall of the container. The carbon disulfide evaporates through 'thisopening, causing white phosphorus to accumulate nearby. In this fresh and finely divided condition the phosphorus starts to oxidize as soon as the heavy solvent fumes escape and allow the entrance of air; the heat of oxidation soon raises the phosphorus to the kindling point and this in turn ignites the inflammable case and the very inflammable'absorbent'next to the main body of combustible material.

The main body of combustible'material 34 is preferably made of a mixture of starch nitrate and an'oxidizing agent, but could suitably be made of any highly inflame mable combination of combustible and oxidizing agent, respectively, such as sugar and potassium chlorate; or

charcoal, sulfur, and sodium nitrate; or aluminum and barium nitrate. The main body of material 34- may be separated from the self-igniting layer 33 by a pyroxylin washer 35, or film of col'lodion, or both, to prevent diffusion of the phosphorus solvent or pyrophoric wetting agent, or other action during a long period of storage. Using the preferred mixture of starch nitrate and oxidizing agent, I have found it convenient after pressing this into the container to apply a few drops of acetone or other volatile starch nitrate solvent, which readily evaporates and leaves a hardened surface suflicient for this purpose. A small quantity of startch nitrate is placed on top of this, and then a few drops of solution containing about l050%, preferably around 30%, white phosphorus in carbon disulfide. This is quickly covered over with a layer of suitable starch-paste or similar hydrophile which on standing sets to a firm gel. These units are then stored by close confinement in a humid container, preferably filled under slight pressure by an inert gas such as carbon arenas or 'nitro gen.

I havemad'e'units of this 'type so small that they weigh considerably less than an ounce, and many thousands of them" some beca'rried'in an averageaircraft load. While the size and duration of flame resulting from one of these units is more than enough to ignite readily combustible matter, the intensity can be greatly increased by the use of perforated powder pellets36' of any size or shape desired, into' which these small units would be tightly inserted just before distribution. The perforated pellet 36 could'suitably be made of the same combination of a combustible and oxidizing agent as described for the main body 34, or even a less sensitive incendiary charge, for example, it may advantageously be made of a thermite composition such as aluminum and iron oxide, as the smallunits having the main body filled with my preferred mixture will readily ignite thermite.

Figure 3'shows another form of my invention, in which the inflammable body 37 is made so thick that it serves the same purpose as the pellet 36 shown in Figure l, intensifying the heat and flame of the combustion. The water-swelled plug 38 and the self-igniting mixture 39 may be the same as before, and in this case no outside shell is needed as a separate container and no main body of filler is required as the heavy container body 37 itself furnishes the main quantity of incendiary material. The conventional pattern illustrated with a single opening can readily be formed by pelleting but when formed by extrusion the body would have the central cavity completely thru as in Figure 4, thus requiring two plugs 38. This insures proper functioning in case the device lands with one opening imbedded against the ground. In either form, as in the device of Figures 1 and 2, the container body 37 is made of an unbreakable, very inflammable plastic such as is made from nitrated cotton or nitrated starch or similar material properly plasticized.

In another form of my invention, shown in Figure 4, there is no water-swelled plug as the container 41 itself is so made that it disintegrates by cracking or shrinking or warping on drying out, thus exposing the self-igniting mixture. This container 41 is made from unplasticized non-breakable inflammable plastic material mixed with a volatile solvent or solvent-blend which evaporates in suitably dry surroundings and causes the protective container to break open, mainly by cracking. If desired, specific lines of weakness, 45, may be molded or cut in, to'insure that the container breaks in the manner desired, on drying out, but a properly made composition will crack as desired without such weakness. A suitable composition may be very low viscosity nitrocellulose, or preferably starch nitrate, without any plasticizer but colloided with a volatile solvent such as butyl acetate. Amyl acetate and butyl propionate are also suitable solvents, although they evaporate more slowly and thus cause slower cracking of the container. Ethyl acetate is faster in its functioning but is too water-soluble for long underwater storage. For this reason I prefer butyl acetate, and make a colloid with starch nitrate containing from about 15% to 25% of this solvent, which gives the mixture a consistency resembling that of stiff pie dough. However, the solvent ratio and therefore the consistency of the colloid may be widely varied, depending upon whether it is extruded or pelleted, for example. While true plasticizers must be avoided, small quantities of waterproofing agents such as butyl stearate or paraifin oil or the like may be added. These swea to the surface and improve the water resistance for long periods of storage under water.

Since no water-swelled plug is required for this type, the ends may be tightly sealed by a waterproof film 42 such as collodion or nitrocellulose or ethyl cellulose, and the contents inside kept quite protected from water even though the unit may be totally immersed in water for storage. Under these circumstances, and the somewhat slower rate of exposure due to the shrinking of the case 41, I have found it suitable to use more active self-igniting mixtures 43 which are decomposed by water and therefore cannot be used successfully in proximity with a waterswelled plug. Thus other spontaneously inflammable metal-alkyls such as zinc dimethyl or zinc diethyl may be used here, besides the water-stable types such as boron triethyl and the pyrophoric metals previously mentioned. I have also found it desirable, when using this water-tight closure 42, to augment the action of the self-igniting core by employing a chemical heating compound which does not react until it is exposed to air or moisture. For example, an acid anhydride such as phosphoric anhydride or arsenic anhydride or selenic anhydride may be intimately mixed under an inert solvent such as petroleum ether or benzene with a dry base such as calcium hydroxide or magnesium hydroxide or the like. I prefer to use a mixture of phosphoric anhydride and calcium hydroxide, mixed to a pasty solid with pertoleum ether. The phosphoric anhydride must not be in excess, but should be in approximately molecular proportions with the base, or less; otherwise when it starts to react it may form a surface syrup or a glaze, either of which will prevent proper functioning. Small pieces of phosphorus 44 may be directly incorporated into this pasty solid 43. Such a mixture is catalysed to reaction by a small amount of absorbed water-vapor, and the intense heat of reaction is more than enough to raise the exposed phosphorous to its kindling point, thus igniting the incendiary device. Nevertheless I have found this mixture to be quite inert as long as it is protected from moisture by the petroleum ether and the confinement of the colloided case 41. The small pellets of phosphorus 44 may vary considerably in size, but must be quite free from water; they may be distributed through the heating compound, as shown in Figure 4, which illustrates an extruded container, or the phosphorus may be concentrated in one lump at the inner end if a pelleted or molded container such as shown in Figure 3 is used.

Figure 5 illustrates the same type of incendiary device functioning through disintegration of the container, but

in this form the moisture-sensitive contents 47 are protected by a thicker piece 48 at one or both the end closures, depending on whether "or not the central well extends entirely through the body or only part-way. This end closure is made of the same colloided material as the main body 46, and may be cemented to it either with a suitable solvent or with a collodion mixture or similar cement 49.

While I much prefer a plug to a film, the latter has definite possibilities either with or without an enveloping glass case. In the form illustrated in Figure 6 the body 50 has a central well 51 extending partly or all the way through the body to house the potentially spontaneous igniting agent as before, for example, an absorbent material saturated with phosphorus. In this modification the body and its contents is completely inclosed in an envelope or cover 52, preferably of thin sheet material which shrinks upon drying and therefore will become ruptured when fully dry, thus admitting air to the self-igniting agent or mixture held by the absorbent material in the well 51.

The pellet 50 is preferably made of a mixture of starch nitrate with an oxidizing agent but could almost as well be made of any highly inflammable mixture such as po tassium chlorate and sugar; or a mixture of sodium nitrate, sulfur and charcoal; or a mixture of barium nitrate and aluminum powder or flakes, or other mixture of a combustible agent with an oxygen-carrying salt. As stated, I prefer a mixture of starch nitrate with an oxidizing agent and press this mixture into the annular disk of the shape shown.

The protective covering 52 having the delay action might be a mere coating of any lacquer or paint that would crack or disintegrate upon drying, a mixture of glue and water, or a material such as agar-agar in water and if desired, loaded with finely divided clay or bentonite. A reasonably thin viscose cellulose sheet shrinks to a great extent upon drying and by being made both thin and weak it ruptures when shrunk by exposure to dryness. The film or envelope could be of a substance that will disintegrate by loss of volatile solvent. The best material tried so far is starch nitrate. The time of rupture of the envelope can be controlled to a chosen degree of dryness depending upon conditons upon which it is used, as for example, by incorporating into the envelope a hygroscopic substance ;or a combination of such substances. As one typical example, I mix ammonium nitrate with the viscose solution before making it into sheets and when this material forms the coating the drying of the envelope will be delayed until after the air has dried out the ammonium nitrate solution, thus preventing premature action of the self-igniting agent and delaying the flame projection until the degree of dryness in the surrounding atmosphere is more favorable to the effectiveness of the incendiary device.

Inasmuch as these self-igniting incendiary devices are to be used principally in the flying service it is essential that they should be insured against premature action, not only in transit but after the device has been dropped from the airplane and has landed on the ground. If these devices fall in a damp place the humidity will prevent any shrinking of the outer envelope and nothing will happen for a time. If, however, the dampness in the vicinity of the device is only temporary, the envelope 52 will dry after the surrounding material has dried and with the cracking of the envelope the dry air will enter and will ignite the phosphorus which in turn will kindle the pyrotechnic composition forming the body 50 and this, by throwing a great flame, will ignite the nowdry inflammable material in the vicinity.

Figures 7 and 8 show an incendiary device which is a combination of two diiferent waterproof, inflammable solv-ated plastics forming the two halves 59 and 60 of the container body. Both halves initially contain approximately equal quantities of volatile solvent, but one half dries to a considerably stronger material than the other. Thus as the solvent evaporates from both surfaces of the two different halves of plastic, the contracting force on the surface of the stronger plastic 59 causes it to buckle or break away from the weaker half 60, thus causing the weaker half (or the joint) to break and expose the inclosed self-igniting composition 62. The two halves may be cemented together with a mutual solvent or with collodion or suitable material 61 after placing in either half a quantity of the self-igniting composition, preferably the pasty solid containing small pellets or chips of phosphorus 44 and a heating mixture consisting of phosphoric anhydride and calcium or magnesium hydroxide, mixed in petroleum ether.

While in Figures 7 and 8 the device is shown with its axial dimensions less than the diameter, the body of this cylindrical incendiary may be elongated as in Figure 4 inwhich case each; ofnthe two halves will be shaped like thetcontainersi of Figures 3 and 5 withv their open-ends facing each iother thus employing no plug as both ends are solid for the central well is partly in each-half asin Figure 7, orequally obviously the hollow cylindrical bodyAl-mffigure 4 maybe intwo longitudinal halves asin the case :of'the. commonlead pencil, save that the two halves areo-f-unequal strength.

Inasmuch .as of. these self-igniting incendiary-idevices are tobe usedprincipally in' 'the flying service it is essential that =theyshould be insured against premature action, not only when the device has landed in damp or cold surroundings, butalso before and-during transit. The small compact incendiary devices described as the central element of Figure 1 readilyqadapt themselves to close-packing, in humid containers, preferably air-tight containers inwhich the air. is displaced by an inert gas such as carbondioxide or nitrogenunder slight pressure, such containers would be made to open immediately be-- fore discharging the devices from the plane, or immediately after dropping from the plane by a delay-action spring device or pressure generator or any 'similardevice which breaks ?the container with sufficient force to scatter the units without damagi-ng'them. Any of my incendiary devices may be packed in thismanner.

However, as in Figure 6 each incendiary unit may be separately enclosed in a frangible envelope or complete cover 55 such as'thin glass, which is shattered by the impact when the'device hits the ground. As long as this frangible envelope remains intact, as in transit or long storage, the film 52, the water-swelled plug 32 or 38, or the solvent-wet container which disintegrates on drying, remain unchanged and keep the self-igniting composition eifectively-sealed. The efficiency of either type is increased by'the autogenous sealing of the device in the frangible container filled with carbon dioxide, nitrogen, or otheninert-gas, preferably under slight pressure with respect to that of the atmosphere.

What I claimis:

1. An incendiary device comprising a self-igniting agent of the type which rapidly increases in temperature tothe kindling point-when exposed to the air, an enclosing casing initiallyprotecting the agent from the atmosphere but composed at least in part of a material slowly deformable when exposed to warm -dry air to admit air to the agent toinitiate ignitiomin which the casing is a water-proof container having a deep central well, and a water swelled plug closing said well.

2. An incendiary device comprising a self-igniting agent of the type which rapidly increases in temperature to the kindling point when XPOSed to the air, an enclosing casing initially protecting the agent from theatrnosphere but composed at least in part of a material slowly deformable when exposed to warm dry air to admit air to the agent to initiate ignition, in which the casing is a hollow container in which the agent is;,sealed at one end with a plug which shrinks to form cracks when dried.

3. Th me h t=mak n s ti it e in e dia y device which consistsdn forming acontainer with a central cayity,;partly filling the cavity with a mixture of a com-bustibleand an oxidizing-agent, applying to the packed mixture a solvent ;for the combustible agent to form a hardened surface, then packing in the cavity an absorbent, saturating the absorbent-with a solution of white phosphorus in carbonbisulfid and then sealing the packed cavity with a hydrophile paste which sets on standing to a firm gel.

4. An incendiary device comprising a pellet of inflammable -material 'having therein a central well whose diameter is a small fpaction of the diameter of the pellet, a test-tube shaped inflammable container fitting said-well, a selfigniting agent in the container, and a plug closure .of water-swelled material to preventaccess of air to the agent, said closure shrinking-in a dry atmosphere to expose the agent forrapid kindling.

5. Thedevice of claim 4 in which a body of combustible material; fills themajor portion of the container, the agent-isbetween said body and the plug, and {the pellet is of less sensitive incendiary material than the body'ofpornbustible material in the container.

6.'T.he device of claim 5 in which the pellet is of a thermite composition.

7. Thedevice of claim 2 in which the casing is an elongated tube closed at the endopposite the plug.

References Cited in the file of this patent UNITED STATES PATENTS 2,558,726 Barker July 3, 1951 FOREIGN PATENTS 24,275 Great Britain 1914

Claims (1)

1. 4. AN INCENDIARY DEVICE COMPRISING A PELLET OF INFLAMMABLE MATERIAL HAVING THEREIN A CENTRAL WELL WHOSE DIAMETER IS A SMALL FRACTION OF THE DIAMETER OF THE PELLET, A TEST-TUBE SHAPED INFLAMMABLE CONTAINER FITTING SAID WELL, A SELF-IGNITING AGENT IN THE CONTAINER, AND A

Images