US3750527A

US3750527A - Fail-safe device for chemically armed mines

Info

Publication number: US3750527A
Application number: US00252168A
Authority: US
Inventors: R Heinemann
Original assignee: United States Department of the Army
Current assignee: United States Department of the Army
Priority date: 1972-05-11
Filing date: 1972-05-11
Publication date: 1973-08-07
Anticipated expiration: 1990-08-07

Abstract

A safety device is provided for inclusion into a dispenser for permeable chemically armed mines which are stored in a desensitized state by immersion in certain halocarbon liquids. A fluid which will permanently sterilize or deactivate the explosive composition of the mine is encapsulated in a sealed frangible container. The container is then partially enclosed in a polymeric material which has the property of swelling while under the influence of certain organic liquids and then forcefully contracting when this influence is absent, thereby breaking the container and permitting the encapsulated material to contact and permanently desensitize the explosive. For example, KOH encapsulated in a glass ampoule which is, in turn, enclosed in a tube of buna rubber. This device can be inserted in a dispenser loaded with chemically armed mines containing lead azide and RDX as the explosive, the dispenser is then filled with 1,1,2 trichloro- 1,2,2 trifluoro ethylene, to insure desensitization until activation is desired.

Description

lUted Stes atent 1 [111 3,750,527 Heinemann 1 Aug. 7, 1973 iFAlL-SAFE DEVICE FOR CHEMHCALLY [57] ABSTRAQT ARMED MINES [75] Inventor: Robert W. Heinernann, Dover, NJ.

[73] Assignee: The United States of America as represented by the Secretary 011 the Army, Washington, DC.

[22] Filed: May 11, 1972 [21] Appl. No.: 252,168

{58] Field of Search 86/1; 102/1, 57, 102/8 [56] References Cited UNITED STATES PATENTS 3,138,100 6/1964 Peschko 102/8 3,667,387 6/1972 Picard et al 102/57 Primary Examiner-Benjamin R. Padgett Attorney-Harry M. Saragovitz et a].

breaking the container and permitting the encapsulated material to contact and permanently desensitize the explosive.

For example, KOH encapsulated in a glass ampoule which is, in turn, enclosed in a tube of buna rubber. This device can be inserted in a dispenser loaded with chemically armed mines containing lead azide and RDX as the explosive, the dispenser is then filled with 1,1,2 trichloro- 1,2,2 trifluoro ethylene, to insure desensitization until activation is desired.

7 Claims, 3 Drawing Figures PAIENIE m". 7 I973 SHEET 2 [1F 2 FAIL-SAFE DEVICE FOR CHEMICALLY ARMED MINES The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION For certain battlefield applications, it is desirable to have a large number of packaged explosives, either mines or noisemaking devices or both, dispersed in preselected areas of the battlefield. An extremely advantageous method of accomplishing this is by aircraft deployment. This air dispersal necessitates the use of a large outer container, in which the smaller packages are disposed, prior to dispersal. Normally, after the small explosive packages are prepared, they are placed in the container at the point of preparation. The explosives or noisemakes are generally packed in small, vapor permeable, packages such as fabric bags or plastic film packets.

In the past, the practice has been to render these explosives safe by immersion in an environment of liquid halocarbon. The immersed explosives were then pack aged and shipped. These attempts to render the explosives safe by treatment with such an environment have not been completely satisfactory.

In addition to safety considerations, it was necessary to develop a system which would chemically desensitize the explosive for a pre-determined amount of time and then allow the explosive to arm itself. This, in essence, is a chemically-armed mine system. The large container used to disperse the small packages had to be capable of containing the explosives in both storage and battlefield conditions, in a desensitized, unarmed manner until they were deployed. This was especially difficult with a liquid halocarbon system because of the likelihood of solvent evaporation and premature arming of the explosive if the large container was pierced by rifle fire or shrapnel. In addition, if any leaks developed during shipping or storage through accident or rough handling, the explosive packages might arm prematurely and cause serious damage.

Attempts have been made to solve this problem by incorporating gelling agents into the halocarbon system to prevent escape of this desensitizing liquid. While these attempts are practical, they are expensive, and mines which are exposed to the gelling agent have a tendency to leave trails of this material on foliage that has come in contact with them thereby eliminating the advantage of using this type of mine in certain heavily foliated areas. Additionally, the possiblity exists of a gel forming on the mine package, thus preventing evaporation of the halocarbon and subsequent arming of the mine. Under storage conditions quite a bit of time can pass before a leak in one of these canisters is observed and ifthe leak is large enough, the gel may not plug the hole and consequently the explosvie will arm. Further, these attempts have not added a positive method of completely desensitizing the mines if for any reason the halocarbon fluid is prematurely exhausted.

SUMMARY OF THE INENTION It is, therefore, an object of this invention to provide a safety device which will insure a positive and permanent desensitization of prematurely activated chemically-armed mines.

A further object is to provide a device which will insure the safety of chemically-armed mines without introducing the possibility of premature accidental deactivation.

Another object is to provide a more tactically advantageous method of deploying che'mically-anned mines in foliated areas.

Yet another object is to provide an economical means of insuring safety during storage, shipping and deployment of chemically-armed mines.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood by reference to the drawings and the following description, wherein it is shown that the above-mentioned objects are attained and the prior art deficiencies are overcome by the use of the device of my invention which includes a fluid which will permanently desensitize the explosive composition of the mine, encapsulated in a sealed frangible container which is, in turn, partially enclosed ina material that swells through contact with certain organic liquids and then forcefully contracts when this contact is removed thereby crushing the container and releasing the deactivating fluid, thus enabling this fluid to come in con tact with the explosive composition of the mine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a cross-sectional view of the item in which my invention may be used.

FIG. 2 is an enlarged cross-sectional view of the safety device shown in FIG. l in its intact, inactive state. I

FIG. 3 is an enlarged cross-sectional view of the safety device shown in FIG. 11 in its activated state.

Throughout the drawings the same numerals refer to the same items.

DESCRIPTION OF A PREFERRED EMBODIMENT My invention can best be shown in the context of the entire munition. As shown in FIG. 1, the safety device 10 is placed in the mine dispenser l2 and thus immersed in the desensitizing liquid 14. The mines 16, composed of a permeable plastic envelope 18, filled with explosive 20 are then disposed in the dispenser 12. The dispenser I2 is provided with an automatic ejection means 22 and a remotely controllable opening means 24 for use in deploying the mines 16 from aircraft. The safey device 10 while immersed in the desensitizing liquid M remains inactive. As shown in FIG. 2, the safety device It) is composed of a frangible container 24 which is filled with a sterilizing liquid or solution 26 and then sealed. The container 24 is then partially enclosed in a pre-treated swollen casing 28. The casing 28 is made of material specifically selected to swell under the influence of the desensitizing liquid 14.

The safety device 10 remains inactive so long as it is immersed in the desensitizing liquid 14. As shown in FIG. 3, if for any reason the desensitizing liquid 14 is exhausted, the casing 28 begins to contract, thus cracking the container 24 and permitting the sterilizing liquid 26 to contact the mines l6, permeate the envelopes l8 and permanently sterilize or deactivate the contained explosive 20. If the desensitizing liquid 14 is not exhausted before deployment, the safety device 10 is simply ejected with the mines 16 and will no longer be in a position to cause sterilization.

In operation, the encasing material selected is formed into a tube 28 having an internal diameter of 80 to 90 percent of the outer diameter of the frangible container 24 around which it is to be placed. The tube is cut into smaller cylindrical sections and immersed for 24 hours in the desensitizing liquid medium 14 in which it will be kept in its final use. The liquid 14 will usually be a halogenated aliphatic hydrocarbon. The encasing material is so selected and compounded that it expands by swelling action under the influence of the liquid 14 until the inner diameter of tube 28 is slightly larger than the outer diameter of the container 24 around which it is to be placed. The tube section is then slipped over the container 24, where it may be held in place by any convenient means. The container 24 is and casing 28 are from that time on maintained immersed in the desensitizing liquid 14. This same selected liquid 14 acts as the desensitizing liquid for mine explosives, which are activated by the lead azide used in various fuzing arrangements. Normally, should an accidental leak occur, the desensitizing liquid 14 would flow out of the container causing the explosive 20 to dry out and become sensitized, creating a hazardous condition. The presence of the safety device makes this eventuality much less hazardous. As the liquid 14 begins to evaporate, the encasing tube 28 around the container 24 shrinks in diameter as its dries, creating strong pressures around the container 24; this causes the container 24 to break, spilling the contents 26 onto the mines 16, thus initiating destruction and deactivation of the explosive 20.

In lieu of the sealed frangible container, a different type of container may be used, which has one or more openings capable of being closed by a rubber stopper. The container may be filled with the sterilizing liquid or solution and tightly stoppered with stoppers which were manufactured from the same selected rubber compound used for the encasing material and which had been immersed for the necessary swelling time in the liquid to be used as the desensitizer. The container can be so placed inside the mine-containing canister that the sterilizing liquid will leak out should the stoppers be withdrawn. If the canister is now opened and the desensitizing liquid is withdrawn or permittedv to evaporate, then the rubber stoppers will shrink and permit the contents to leak out onto the explosive; thus desensitizing it.

The choice ofdesensitizing liquid is governed by criteria of non-reactivity with the explosive and an evaporation rate that will permit practical arming or drying times for theitems. Any liquid which will meet these criteria can be used, for example 1,1,2 trichloro-, 1,2,2 trifluoroethane; l,l,2,2 tetrachloro-, 1,2 'd'it'luoroethane; l,l,2,2 tetrafluoro- 1,2 dibromoethane; carbon tetrachloride and tetrachloroethylene. It has been found that halocarbons of a chain length of one or two carbon atoms containing at least one halogen substituent are preferred, such as perchloroethylene. These halocarbons preferably have a boiling point between about 30 C to 120 C.

The sterilizing liquid must be capable of permanently deactivating the explosive with which it comes in contact. Choice ofliquid or solution will ultimately depend on the type of explosive used. For example, an aqueous solution of a strong base, such as sodium or potassium hydroxide works well with lead azide containing explosives as it destroys the azide. Additionally, the aqueous portion of the solution deactivates any secondary explosives contained. The amount to be used depends, of course, on the amount of explosive to be sterilized.

The explosive mixtures that may be permanently sterilized by the sterilizing liquid compose two major classes. First, impact sensitive pyrotechnic or noisemaking compositions. This class is usually made up of sensitive explosives, such as mixture of red phosphorous, potassium chlorate or perchlorate and ground glass. Any combination of a mixture of a strong oxidizer, abrasive agent and pyrotechnic fuel can be used to form the pressure sensitive mines. Second, explosive mixtures composed of secondary explosives, such as RDX, and primary explosives, such as lead styphnate or lead azide, may be used. The choice of secondary explosive is largely governed by reliability for example, PETN or HMX, may be used advantageously as well as any common secondary explosive.

The permeable envelope material used for the mine is selected for its nonreactivity and its permeability towards both the desensitizing liquid and the sterilizing liquid. For example, cotton duck may be used as well as certain films which are permeable to these liquids, such as Alathon or .Tyvek polyethylene film (both names are registered trademarks of E. l. DuPont de Nemours & Co.). The thickness of the film may be varied to achieve diverse permeation rates.

The encasing material is selected for its ability to swell under the influence of the desensitizing liquid used and to forcefully contract in the absence of such fluid. The thickness of this material will partially govern the forcefulness of its contraction. l have found that materials of choice for the encasing material are compounds such as isoprene, butadiene-styrene, isobutylene-isoprene and silicones. Many rubber-like compounds or materials, as described in Army Material Command Publication AMCP-706, formerly Ordnance Corps Pamphlet ORDP 20-3l0 entitled Ordnance Materials Handbook Rubber and Rubber-like Materials, dated December, 1956, mayalso be selected, using the above-mentioned criteria.

The frangible container may be fabricated from glass or plastic or any material which is non reactive with both the desensitizing liquid-and the sterilization liquid. Additionally, this material must be frangible to be eas-' ily broken by the encasing material.

l have found by the use of my invention thata standard canister or dispenser can be completely sterilized within a few hours after exhaustion of the desensitizing liquid. v

Summarizing, the safety device of my invention employs a frangible container filled with a fluid capable of permanently sterilizing or deactivating a selected explosive. This frangible container is partially encased in a material which has the capability of swelling under the influence of selected liquids and contracting forcefully, after swelling, in the absence of these liquids. My invention is particularly useful in the case of chemically-armed mines which are stored and dispensed in a reversibly desensitized state by the use of a desensitizing liquid which liquid also has the capacity to swell the aforementioned encasing material.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of my invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of my invention.

1 claim:

1. The combination of a plurality of liquidpermeable, reversibly-desensitized, chemically-armed mines immersed in a liquid desensitizing medium, with a safety device comprising:

able, reversibly desensitized, chemically-armed mines immersed in a liquid desensitizing medium, with a safety device comprising: 2

a sterilization liquid capable of permanently deactivating said mines;

frangible means, immersed in said liquid desensitizing medium, for containing said sterilization liquid in close proximity to said mines;

means for opening said containing means and releas ing said sterilization liquid to permeate and deactivate said mines, said opening means comprising a member that expands in contact with said liquid desensitizing medium and shrinks in the absence of said medium.

3. The combination as defined in claim 2 wherein said sterilization liquid is an aqueous solution ofa sterilizing agent being, said sterilizing agent capable of re acting with the explosive contained in said mines and thereby deactivating said explosive.

4. The combination as defined in claim 3 wherein said sterilizing agent is an aqueous solution of a strong base.

5. The combination as defined in claim 4 wherein said sterilizing agent is an aqueous solution of a compound selected from the group consisting of sodium hydroxide and potassium hydroxide.

6. The combination as defined in claim 2 wherein said opening means is a polymeric material partially encasing said containing means, said polymeric material selected from the group consisting of silicone rubber, buna rubber and styrene rubber.

7. The combination of a plurality of liquid permeable, reversibly desensitized, chemically-armed mines immersed in a liquid desensitizing medium, with a safety device comprising:

a frangible sealed glass ampoule immersed in said liquid desensitizing medium in close proximity to said mines;

a sterilization liquid capable of permanently deactivating said mines contained in said ampoule, said sterilization liquid being selected from the group consisting of a 10% by weight. aqueous solution of potassium hydroxide and a 10 percent by weight aqueous solution of sodium hydroxide;

means for breaking said ampoule and releasing said liquids, said means responding to the absence of said liquid medium with a contractile force sufficient to break said ampoule, said means comprising a tubular casing mounted on and partially enveloping said ampoule, said casing being fabricated from a polymeric material selected from the group consisting of isoprene, silicone, butadiene-styrene and isobutylene-styrene.

Claims

2. The combination of a plurality of liquid permeable, reversibly desensitized, chemically-armed mines immersed in a liquid desensiTizing medium, with a safety device comprising: a sterilization liquid capable of permanently deactivating said mines; frangible means, immersed in said liquid desensitizing medium, for containing said sterilization liquid in close proximity to said mines; means for opening said containing means and releasing said sterilization liquid to permeate and deactivate said mines, said opening means comprising a member that expands in contact with said liquid desensitizing medium and shrinks in the absence of said medium.
3. The combination as defined in claim 2 wherein said sterilization liquid is an aqueous solution of a sterilizing agent being, said sterilizing agent capable of reacting with the explosive contained in said mines and thereby deactivating said explosive.
4. The combination as defined in claim 3 wherein said sterilizing agent is an aqueous solution of a strong base.
5. The combination as defined in claim 4 wherein said sterilizing agent is an aqueous solution of a compound selected from the group consisting of sodium hydroxide and potassium hydroxide.
6. The combination as defined in claim 2 wherein said opening means is a polymeric material partially encasing said containing means, said polymeric material selected from the group consisting of silicone rubber, buna rubber and styrene rubber.
7. The combination of a plurality of liquid permeable, reversibly desensitized, chemically-armed mines immersed in a liquid desensitizing medium, with a safety device comprising: a frangible sealed glass ampoule immersed in said liquid desensitizing medium in close proximity to said mines; a sterilization liquid capable of permanently deactivating said mines contained in said ampoule, said sterilization liquid being selected from the group consisting of a 10% by weight aqueous solution of potassium hydroxide and a 10 percent by weight aqueous solution of sodium hydroxide; means for breaking said ampoule and releasing said liquids, said means responding to the absence of said liquid medium with a contractile force sufficient to break said ampoule, said means comprising a tubular casing mounted on and partially enveloping said ampoule, said casing being fabricated from a polymeric material selected from the group consisting of isoprene, silicone, butadiene-styrene and isobutylene-styrene.