US2791178A

US2791178A - Incendiary device

Info

Publication number: US2791178A
Application number: US563352A
Authority: US
Inventors: Norman J Thompson
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-11-14
Filing date: 1944-11-14
Publication date: 1957-05-07
Anticipated expiration: 1974-05-07

Description

May 7 1957 N. J. THOMPSON INCENDIARY DEVICE Filed Nov` 14, 1944 INCENDIARY DEVICE Norman J. Thompson, Wellesley, Mass., assignor vto the United States of America as represented by the Secretary of War Application November 14, 1944, Serial No. 563,352

1 Claim. (Cl. 102-6) The invention described herein may be manufactured and used by or for the Government, for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to an incendiary device and a heater mixture therefor, and more particularly to an incendiary device and heater mixture which are particularly adaptable for use in the construction of an incendiary bomb.

One object of this invention is the provision of an incendiary device which is unusually safe in storage and in transport.

Another object of this invention is .the provision of an incendiary device which is not subject to evaporation or leakage.

A further object of this invention isthe provision of an incendiary which is extremely diicult to extinguish with ordinary agents since it will burn in the absence of oxygen from the surrounding atmosphere.

A still further object of this invention is the provision of an incendiary which is particularly effective since it combines the high temperature and radiation characteristics of the common magnesium bomb and the long reaching llames of the oil bomb.

A still further object of this invention is the provision of a heater mixture which is particularly adapted for use in the above indicated incendiary.

lFurther and additional objects will appear from the following description, the accompanying drawing and the appended claim.

In accordance with this invention, an incendiary device is provided which comprises preferably a fusible or combustible case (which may be reinforced with a strongnoncombustible case material such as steel), a body of substantially non-volatile combustible organic material of high calorific value within said case and a second body of heater mixture, also within said case, capable of selfsustained burning at a reaction temperature sufficient to melt or burn said case and to vaporize and crack said organic material. Organic materials having suitable physical and Vthermal properties are exemplified by fatty acids, fats, oils, and fatty esters, such as, stearic acid, oleic and tallow, and lard oil, but hydrocarbons and other mineralcarbonaceous materials which are readilyV available are preferred. The properties of high caloric value, high melting point, and high boiling point are important factors in the selection of these materials. For obtaining proper cracking, the heater mixture should give a localized heat of adequate intensity but should not burn too rapidly.

In accordance with one preferred embodiment of this invention, a non-volatile hydrocarbon mass is present in the form of a central core surrounded by the heater mixture and the whole Iis containedin a combustible or fusible case provided with suitable means for igniting the heater mixture. The heater mixture, during burning, fuses or ignites the case and at the same time volatlizes and cracks the hydrocarbon material to form vapors which nited States Patent are ignited. Thus the device possesses a high degree of effectiveness as an incendiary.

In accordance with one preferred embodiment of this invention, the heater mixture is placed in an annular space between the combustible or fusible case and the central hydrocarbon core. However, under certain conditions, it may be desired that the heater mixture be centrally located along the longitudinal axis of the device and surrounded by the non-volatile hydrocarbon material.

The hydrocarbon core may comprise a heavy hydrocarbon oil disposed Within an inner readily combustible receptacle, and to minimize the possibility of leakage, the oil may be practically solidified. This has been done effectively by providing a hydrocarbon-containing mass comprising cotton waste saturated with a heavy hydrocarbon oil and also by converting a heavy hydrocarbon oil to a solid mass by the use of suitable emulsifying agents. If desired, the hydrocarbon material may be a solid resinous or wax-like mass. In this event a separate receptacle will not be required for it.

The heater mixture for the device of this invention mayV with standard heater mixtures such as thermite or ther-v mate. Such a mixture comprises a heavy hydrocarbon oil, fine ake aluminum and sodium nitrate to which nely divided sulphur may be added to insure evenness of burning. The ingredients of the mixture may be proportioned to control the rate of burning and the total amount of heat liberated. The surface of the line flake aluminum permits the adsorption of large proportions of the hydrocarbon oil (having a high caloric value) without destroying the burning properties of the mixture. The larger proportion of oil at the same time provides a mixture insensitive to impact.

For a more complete understanding of this invention, reference is now made to the accompanying drawing wherein:

Fig. 1 is a broken sectional elevational View of an incendiary device constructed in accordance with one embodiment of this invention;

Fig. 2 is a fragmentary sectional view of the device shown in Fig. l taken along the line 2 2 thereof;

Fig. 3 is a broken sectional elevational View of a modified form of the incendiary device; and

Fig. 4 is a fragmentary sectional view of the device shown in Fig. 3 taken along the line 4 4 thereof.

Referring now more particularly to Fig. 1, the device there shown comprises an outer case 10 which may be constructed of a fusible or combustible material such as magnesium, aluminum, paper, nitrocellulose or other similar substance. This case is secured by suitable means to a base 12. A second case 14 is disposed within and spaced from the side walls of case 10. The case 14 is constructed of a readily combustible material such as paper, nitrocellulose or other readily combustible plastic. A non-volatile hydrocarbon core 15 is positioned within the inner case i4. This mass of material may comprise cellulose cotton waste saturated with a heavy hydrocarbon oil. However, it Will be apparent that the heavy hydrocarbon may be present in other physical forms if desired. The hydrocarbon material may be a solid, self-supporting wax-like or resinous mass, in which case the inner receptacle 14 may be dispensed with. One advantage of such a construction is that the device is more readily-assembled Gilsonite or other hydrocarbon resin,

wax, or emulsion has been found to be useful for this purpose. `One solid emulsion that has been found to be satisfactory for this purpose was prepared by cooking 87% by weight of #2 fuel oil and- 13% by weight ,of aluminum soaps of cocoanut-fatty 4acids together` for about 30 minutes at 212 F.

In the annular space between the side walls of the case and the case 14 is provided a heater mixture 16 which is capable of self-sustained burning and which will liberate sufficient heat to burn or fuse the combustible case 10 and to Volatilize and crack the hydrocarbon core. The heater mixture may comprise thermite, which is a mixture of iron oxide and aluminum powder in the ratio of about 3 to 1. Other thermite-like mixtures, such as thermate, may also be employed. A-typical thermate composition comprises 80% thermite and ,20% of a are mixture comprising:

Percent Barium nitrate 75 Aluminum flake 19 Sulphur 4.5 Castor oil 1.5

However, in accordance with one embodiment of this invention, a mixturercomprising suitable proportions of heavy hydrocarbon oil, tine ake aluminum and sodium nitrate may be used as the heater mixture. It has been found that the use of tine ake aluminum in mixtures of this character imparts properties to the resulting mixture that have been heretofore unobtainable. The tremendous surface area of the flaked aluminum will absorb a large amount of the heavy hydrocarbon oil (having a high caloric value) and will thus permit relatively large amounts of oil in the mixture without interfering with the burning characteristics. Moreover, the mixture is insensitive to impact when a larger proportion of hydrocarbon oil is used. Sulphur may be added to the mixture to insure evenness of burning if desired. A suitable mixture has been found to have the following composition:

Percent Motor oil (SAE-40) 15 Aluminum ake (through 200 M.) 35 Sulphur (through 100 M.) 2 Sodium nitrate (through 100 M.) 48

The relative proportions of the above indicated ingredients may be varied depending upon the desired burning rate and total heat output. This in turn may depend upon the characteristics of the fusible or combustible case. Lesser amounts of oil increases the burning rate and decreases the total heat output and vice versa. Also thermite or thermate may be incorporated into the above indicated mixture in order to control the burning properties thereof. Higher percentages of thermite or thermate tend to increase the local heat produced. In'the event that the fusible or combustible outer case 10 comprises magnesium then a suitable mixture has been found to be 50% standard thermate and 50% of the above indicated composition. In the event that nitrocellulose or other readily combustible material is used in the construction of the case 10, then the heater mixture may comprise smaller proportions of thermite or thermate and higher percentages of oil may be used.

In a completed form of the bomb the top of the case 10 may be provided with a suitable cover 17 and means for igniting the heater mixture. Such igniter means may comprise black powder whose burning may be initiated by a suitable firing mechanism.

Although the general design of the body, the closure, and fuze in the device may be varied, the drawing illustrates forms of bomb bodies provided with a standardized tail cup closure assembly and a standardized all-ways fuze assembly. The tail cup closure 17 is given a press t into a tail end extension of the bomb body and is l chromate.

crimped to the edge of this extension to make the tail cup more secure in place, also, to which it may be welded. The all-ways fuze is secured at its head plug 18 to an apertured hub 19 disposed centrally in the bottom of the tail cup 17 so that a iirst fire charge 20 at the base of the fuze assembly is surrounded by the heater mixture 16. Arming of the fuze is subject to a release band 21, which held in place as shown prevents the fuze from being armed so long as an adjacent bomb in a cluster holds theV band 21 in place. TheY tail cup hub 19 is encircled by a retaining ring 22 which may be used to secure the ends of cloth streamers (not shown) for stabilizing the bomb and regulating its speed in ight. Ring 22 also holds clip 23 in place as a catch forband 21.

The all-ways fuze assembly comprises a tubular fuze body 24 secured to head plug 18 and a base plug 25, with which the body 18 forms a hollow chamber having conical end surfaces. The ring mechanism inclosed in this hollow chamber is made up of a striker body 26 slidably coupled with a primer holder 27 and kept normally separated from a primer cap 28 in the primer holder by a safety pin 29 and by a coil spring 30. An larming pin 31 is passed through a central bore in the head plug 18 so that it projects into the striker 26, wherein the arming pin positions the safety pin 29 outwardly against a small coil spring 32 surrounding the safety pin to thereby lock Y the striker against movement. Ejection of the arming pin from the head plug 18 by spring 33, when the release band 21 no longer presses on the head of the arming pin, allows the safety pin 29 to become recessed within the striker 26 by the coil .spring 32 so that the coupled striker and primer holder are no longer fixed in position, and the striker-26 is free to move against coil spring 30 in the direction of a primer cap 28 within the primer holder 27. The tiringrmechanism assembly thus armed is free to gyrate in the hollow chamber with the outer ends of the striker and the primer holder sliding on the cam-like conical end surfaces of the chamber. When the tiring mechanism assembly is free to make such a movement, the striker 26 and primer holder 27 are forced together and upon impact of the bomb carrying the fuze, with sufficient set-back force, the striker 26 overcomes the resistance of coil spring 30 to drive tiring pin 41 into primer cap 28 seated in the primer holder 27. The armed firing mechanism is capable of functioning Vregardless of the position of the bomb on impact. The primer cap 28 is seated above a bore 34 extending through a primer holder 27. A flash back from the tired primer cap 28 passes through thisr bore and throughan aperture 40 in base plug 25 to ignite a tirst tire charge 20 attached to the base plug 25 by a combustible plastic cup 35.

A cotter pin36 through aligned drill holes in the head plug 18 and the head of the arming-pin 31 maintains the fuze unarmed until it is assembled to the bomb with the release band 21 in place on the clustered bomb. Spring band 37 is riveted to band 21 to assist in holding it in place. v

After a bomb cluster is dropped from air craft, the release band 21 unhinges from a bomb separated from the cluster and thereupon the arming pin 31 is ejected from the fuze to arm the tiring mechanism. When the bomb carrying the armed fuze receives adequate impact on hitting a target, the primer becomes ignited by percussion and tiashes back into the tirstptiring charge. lf desired a powder train delay element may be inserted into the bore 34 of the primer holder 27 Vor into the aperture 40 of the fuze base plug 25.

A suitable first tire charge which does not burn explosively comprises 25% magnesium and 75% barium To vent gases from the bomb when the heater mixture begins to burn, a smallrvent hole may be made in the upper part ofthe bomb body and a small blowout plug may be normally fitted in this hole.V *In* operation, theheater mixture burns downwardly from the upper regions of the case 10 causing the case to fuse or burn as the mixture burns down. When the mixture has burned down as far as the hydrocarbon core, the latter is caused to vaporize and the hydrocarbon is cracked. The cracked vapors are ignited and a very intense burning is produced. The incendiary is almost impossible to extingui-sh by ordinary agents because of the presence of oxidizing agents (iron oxide and NaNOa) in the heater mixture which provide the necessary oxygen for combustion.

A modified form of the incendiary device is shown in Figs. 3 and 4. This modified form comprises a hydrocarbon core 1S and a heater mixture 16 similar to the device shown in Figs. 1 and 2. The outer case, however, comprises a layer of nitrocellulose reinforced with a perforated steel sleeve 39. This sleeve serves to reinforce the case so that the device when used as a bomb will not be deformed on impact. Other noncombustible reinforcing agents such as expanded metal, Wire screen, or other foraminous sheet material may be employed if desired. However, the use of a perforated steel sleeve is preferred for the reason that, as the contents of th-e case are being bur-ned, jets of llame Will be projected through the perforations thus setting fire to any combustible object that happens to be positioned near the burning incendiary. In actual production the nitrocellulose layer may be molded directly inside of and into the perforated steel case whereby the perfor-ations ane lled with the nitrocellulose.

It will thus be seen that an incendiary device has been disclosed herein which may be readily and cheaply prepared. By having its charge in a substantially solid and non-volatile condition, the device is not subject to evaporation or leakage, during storage or handling, yet when functioning, gives lthe effects of long aming jets of gas. It is diicult to extinguish and the mixture contained therein is not sensitive to impact, thus rendering lthe dcvice safe to transport. The ingredients of the heater mixture may be proportioned to provide any desired burning rate and heat liberation that may be required for effectiveness against any Igiven target.

While in the foregoing several specific embodiments of this invention have been specifically disclosed it is not intended that the invention should be limited strictly thereto. It will be apparent to one skilled in the art that many modifications may be made and it is therefore intended that this invention be limited only by the scope of the appended claim.

I claim:

An incendiary bomb including means for cracking oil within said bomb and being charged with heavy lhydrocarbon oil adapted to be cracked by said means in said bomb, said means comprising a bomb casing having a nitrocellulose wall portion and a surrounding, reinforcing steel sleeve provided with a plurality of perforated portions through which jets of arne are outwardly and forcibly directed through said sleeve for igniting combustibles in the vicinity of said bomb, said casing containing an inner core of cotton impregnated with heavy hydrocarbon oil, a beater composition in which said core is imbedded and held apart from said wall portion consisting essentially of an admixture of a volatile hydrocarbon oil, ther-mite, and a are mixture, said tiare mixture consisting by weight of from about 19% to about 35% of line aluminum flakes providing, in aggregate, a surface area highly adapted to absorb a large quantity of heavy hydrocarbon oil, 4from about 48% to 75% of fine particles of a readily oxidizable nitrate selected from the group of nitrates consisting of sodium nitrate and barium nitrate and from about 1% to about 2% of sulfur in the form of line particles adapted to make said composition burn more evenly.

References Cited in the le of this patent UNITED STATES PATENTS 1,174,925 Arndt Mar. 7, 1916 1,306,747 Chanard June 17, 1919 1,313,068 Chanard Aug. 12, 1919 1,484,190 Ray Feb. 19, 1924 1,877,232 Duncan Sept. 13, 1932 2,035,509 Schladt Mar. 31, 1936 2,318,994 Helmbold May 11, 1943 2,445,311 Cook et al July 20, 1948 FOREIGN PATENTS 17,788 Great Britain of 1908 449,193 Great Britain June 22, 1936 453,795 Great Britain Sept. 18, 1936 OTHER REFERENCES Colliers Magazine (article: Wing Talk), March 8, 1940 (page 6).