US3358600A

US3358600A - Self-destroying explosive cartridge for underwater seismic exploration

Info

Publication number: US3358600A
Application number: US520330A
Authority: US
Inventors: George L Griffith; William L K Schwoyer; Stephen L Mayer
Original assignee: Trojan Powder Co
Current assignee: BARCLAYS/AMERICAN/BUSINESS CREDIT Inc A CORP OF CT; Trojan Powder Co
Priority date: 1966-01-13
Filing date: 1966-01-13
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

1967 G L GRIFFITH ETAL 3,353,500

SELF-DESTROYING EXPLOSIVE CARTRIDGE FOR UNDERWATER SEISMIC EXPLORATION Filed Jan 13 1966 Iii-III- United States Patent 3,358,600 SELF-DESTROYING EXPLOSIVE CARTRIDGE FOR UNDERWATER SEISMIC EXPLORATION George L. Griflith, Coopersburg, and William L. K.

Schwoyer and Stephen L. Mayer, Allentown, Pa., as-

signors to Trojan Powder Company, Allentown, Pa., a

corporation of New York Filed Jan. 13, 1966, Ser. No. 520,330 14 Claims. (Cl. 102-24) ABSTRACT OF THE DISCLOSURE An explosive cartridge is provided comprising an explosive charge, and means to expose and dissipate the explosive charge in water, the cartridge containing a waterexpandible material which liberates a gas upon contact with water or which will expand in volume upon being contacted by water, such as polyvinyl alcohol, and so rupture the container in water.

This invention is directed to an explosive cartridge such as a primer or booster especially intended for use in underwater seismic exploration, and which is self-destroying after immersion in water, and to an explosive container useful for such cartridges.

A problem in underwater seismic testing or blasting is the booster, primer or other cartridge which for some reason does not detonate. An extremely hazardous situation sometimes occurs at the beachfront in coastal areas in the vicinity of intensive off-shore oil drilling and exploration. Seismic explosive charges which fail to detonate may eventually rise to the surface and be washed up on shore where they may be accidentally detonated, causing damage or injury. Hence, it has been necessary to recover such cartridges and manually deactivate them.

The present invention provides an explosive cartridge such as a primer or booster which avoids this problem by means incorporated therein automatically to permit deactivation and destruction thereof by water even if the cartridge charge does not detonate within a predetermined period of time.

The explosive container in accordance with the invention exposes an explosive charge contained therein to water, after immersion in water, and comprises, in combination, a first compartment for an explosive charge, which compartment is preferably Watertight, and a second compartment, not necessarily separated from the first, for a water expandible composition, which compartment is the site of the self-destroying action, a passage extending into the second compartment for flow of water thereinto when the cartridge is immersed in water, directional valve means in the passage to allow water to flow into the second compartment but substantially containing an increase in volume of material there, and means to expose an explosive charge in the first compartment to water, in a manner to permit distribution thereof in water, operable under pressure arising from an increase in volume in the second compartment. In this way, the explosive can be separated from the cartridge by Water-induced expansion of the expandible material in the second compartment, operating the explosive-exposing means, and so exposing the explosive to the deleterious and distributing action of the water. The invention also comprises a self-destroying explosive cartridge, comprising the said explosive container, containing an explosive charge in the first compartment and a water-expandible composition in the second compartment.

In a preferred embodiment of this cartridge, the passage is closed to prevent the accidental entry of moisture during storage, and is opened by the user just prior to the 3,358,600 Patented Dec. 19, 1967 ice cartridges being immersed in water or alternatively, shortly thereafter, by action of the water on the material closing off the passage, resulting in an automatic opening of the passage after a predetermined period of time has elapsed.

The water-expandible compositions suitable for destroying the explosive cartridge fall into two general classes. The first and preferred class includes compositions reactive with water to evolve a gas, and so increase the volume of gas in the compartment containing such composition. The second class includes solid materials capable of absorbing water in a sufiicient amount to increase substantially in volume, and so increase the volume of solid material in that compartment of the container. Thus, both classes of material are based on the same principle, waterexpandibility.

Cooperating therewith, the cartridge container also includes means operated by pressure upon expansion in volume due to the water-expandible material in the second compartment, to expose the explosive material in the first compartment to the destructive action of water. As the volume of solid or gas in the compartment containing such material is increased, either by swelling of the solid or by evolution of the gas, the pressure required to operate such means is eventually reached, exposing the explosive preferably by opening up the container and allowing the explosive to pass out into the Water.

Such means to ensure exposure of explosive in the container under the desired condition can take any of a variety of forms. One preferred embodiment includes an inner container, serving as the first compartment, for an explosive charge, which container is removably fitted in the explosive container in a low friction or slip fit. Upon expansion of the water-expandible material, this inner container is gradually forced out of the container. Such an embodiment is shown in FIGURES 1 and 2 of the drawings.

Suitably, in this embodiment the container can be a tubular cartridge open at one end, into which end is fitted the separate container as the first compartment, and the open end of the cartridge is then closed off by a cap. Provision can be made for insertion of a blasting cap through the cap of the container. Both the cap and the container serving as the first compartment are held in place in a fit which is sufficiently tight to prevent entry of water under normal storage conditions, and to resist dislodgment, but which is desired to be ruptured by expansion of the Water-expandible material in such a manner as to force off at least the cap, and preferably force the first compartment container out of the explosive container as well. To facilitate such outward movement of the first compartment container, the outer walls of this container and/ or the inside walls of the explosive container, can be made of a relatively low friction or slippery material, such as, for example, a synthetic resin, for instance polyethylene, polypropylene, polyvinyl chloride or nylon, or they can be surfaced with a slippery material, such as any of the above, a water-soluble resin such as polyvinyl al cohol, or a modified water-soluble starch or a wax.

In a second embodiment, the means comprises a wall divider removably fitted in the container to separate the first and second compartments, and adapted to be dislodged upon expansion of the expandible material, so as to admit water from the second compartment into the first compartment. This embodiment is shown in FIG- URE 3.

In another embodiment, a container Wall or divider is provided that is weakened in one or more portions so that it can be ruptured by the water-expandible material upon increase in volume, and open the first compartment of the container to the entry of water. Such an embodiment is shown in FIGURES 4 and 5.

Other variations will be apparent to those skilled in the art from the above description.

The cartridge container can be made in any shape desired. Usually, however, explosive cartridge containers are tubes of generally cylindrical configuration, whose open ends are closed either by crimping, or by end caps. Other useful configurations include tubes that are polygonal, i.e., triangular, rectangular, pentagonal, tetrahedral, or hexahedral in cross-section. The cartridge container should be sufficiently strong to withstand normal wear and tear prior to use, and should be moistureresistant to prevent moisture from entering and deactivating the explosive prior to its being immersed in the water.

The passage in the cartridge container for conducting water to the compartment containing the water-expandible material opens through the cartridge container outer wall and leads water to the water-expandible material. The passage can be in the form of an orifice in the outer wall of the container, opening directly into the compartment containing such material.

Preferably, a one-way valve is included in the passage, allowing water to flow in, but preventing any material, whether solid, fluid, or gaseous, from passing out. The valve is unnecessary if the expanded material responsible for the increase in volume is a solid, and the passage is rather small in diameter.

The passage is preferably kept closed until the cartridge or booster is to be used by a plug or a film or strip or sealing material. This can be removed manually, before immersion, or it can be of a water-soluble material which will dissolve upon immersion in water, such as polyvinyl alcohol, a water-soluble gum, methyl cellulose, and like materials.

The container can be formed of any of the materials usually used for the manufacture of explosive cartridge containers. If plastic material be used, the container can be extruded to the desired shape, leaving an opening for filling, or it can be formed by rolling or folding a flat blank of the material to the desired shape. For example, a flat blank can be scored, cut and folded into a cube, cone, octahedron, tetrahedron, or any tubular shape desired.

In one common method for forming a cylindrical or tubular container, the blank is rolled on a mandrel to form a cylinder, and the ends are crimped or capped and sealed. Although a tubular cartridge can be formed with a single layer or wrapping, or with many layers of wrapping, it has been found preferable to form it from at least two complete layers, up 3 /2 layers, i.e., where up to one half of the circumference of the cylinder is formed of four layers. The methods of forming containers of different shapes are well known, and are not part of this mvention.

The container of the invention has at least two compartments, one for the water-expandible material and one for the explosive charge. In the case of primers, a booster charge compartment is also provided. Another compartment or well can be provided for a blasting cap, if desired. The relative positions of the compartments is unimportant, but the blasting cap compartment, if present, is always abutting or within the compartment containing the most readily initiated explosive charge.

The comparements can be separated by dividers or walls, which can be made by inserts fitted in the container from either end. Preferably, when the explosive charge is not precast or a bonded aggregate, the explosive charge compartment or compartments are formed of an inner container inserted in the main container in a manner to define in the remaining portion of the container a compartment for the water-expandible material. The various compartments are filled with explosive and water-expandible material, respectively, preferably so constituted as to form a solid mass in each compartment. Any openings are closed either by crimping the ends of the container material or by inserting end caps of known design.

The material used for forming the cartridge container is generally a strong and preferably water-resistant coated cardboard or heavy paper, such as kraft or manila of approximately sixty to one hundred forty pounds Weight. Other materials suitable for use in forming cartridge containers include polymeric synthetic resin materials such as Teflon, polyethylene, polypropylene, polyvinyl butyrate, cellulose acetate, cellulose acetate-butyrate, ethyl cellulose, polyvinyl chloride, vinyl chloride-vinyl acetate polymer, polyvinylidene chloride, polyacrylonitrile, ethylene glycol-terephthalic acid polymers, and nylon, as well as metal foils such as aluminum.

The inner surface of the container wall can be lined with a slippery or soluble resin which will prevent the explosive charge and/or explosive charge container from sticking to the container, and allow it to be pushed out.

Where the explosive cartridge is a booster, which is normally inserted into a wall in a main charge cartridge, it is preferred that the opening into the passage be placed at the top end of the booster, which would face out of the charge cartridge well. If the opening were placed at the sides or on the bottom of the cartridge, it may be obstructed by being pressed against the sides of the well.

The passage for entry of water to the Water-expandible material can be defined between the outer wall of the container and the wall of the internal compartment or compartments for the explosive charge. Valve means can be inserted in this passage. The passage can also take the form of an opening in the outer wall of the container, opening directly into the water-expandible material compartment; this can be formed in the sheet of Wrapping material before it is shaped into the cartridge. The oneway valve is then placed on the inside wall of the container, at the opening.

When the volume increase is due to solid material, the one-way valve can be a porous plug or plate, or a plug or plate having a small orifice therethrough. The openings in either case should be smaller than the expanded particles, to allow water to flow in, but retain the swollen particles.

In lieu of the above forms of valve means, there can be incorporated into the carriage a small check valve, for example, a ball valve of the type often used for pumps, which will allow the passage of water through the passage and into the interior of the container, but which will almost completely prevent the passage of any fluid in the reverse direction.

In the preferred tubular cartridge container, the container is filled with a cast explosive charge, and its open end closed by an end cap bonded thereto with a weak, and preferably a water-soluble or nonwater-resistant adhesive, such as animal glue, carboxymethyl cellulose, guar gum, or modified starch. Thus, after immersion in water the bond is destroyed, and when the internal pressure is increased by expansion of the material, the cap and also the charge will readily be pushed out, exposing the charge to water.

If, on the other hand, it is desired that the cartridge container itself be ruptured by the internal pressure exerted by the water-expandible material, a rupturable container can be used, of the type set forth in US. Patents Nos. 2,345,654 and 2,378,223. Rupturable containers can be used in place of or together with the weakly bonded end cap described above.

The time required for a cartridge to be destroyed or deactivated after immersion will usually be determined by the time required to open the passage if it is blocked by a water-soluble material which is determined by the amount and water resistance of the material used, the amount and type of the water-expandible composition, and the rate at which the water enters the cartridge. Generally, a fast-reacting gas-producing composition, rapidly increasing the internal pressure, will quickly expose the explosive charge to water, and deactivate the cartridge. A solidwhich will swell quickly and extensively upon contact with water can also deactivate the cartridge quickly.

Among the suitable gas-producing compositions are mixtures of sodium bicarbonate or other water-soluble bicarbonates with a solid acid or acid salt which in the presence of water will react with the bicarbonate to produce carbon dioxide gas. Such solid acids or acid salts include tartaric acid, citric acid, sodium tartrate, oxalic acid, lactic acid, the polyphosphoric acids, and boric acid.

Among the materials which will swell upon being contacted with water are polyvinyl alcohol, gelatin, the alginates, agar-agar, and silica gel.

The amount of water-expandible composition and the size of the second compartment will be determined by the internal force or pressure necessary to open the cartridge. This pressure will be determined by the material and manner of construction of the container, and by the external water pressure at the depth to which the cartridge will be immersed.

This cartridge can be used with any type of explosive charge. A primer will be filled with a high explosive charge. Any high explosive can be used, such as TNT sensitized ammonium nitrate type slurry high explosives, smokeless powder sensitized ammonium nitrate type slurry high explosives; nitro-starch sensitized ammonium nitrate type slurry high explosives; TNTammonium nitrate pellet form solid high explosives and nitrostarch sensitized ammonium nitrate type semi-solid high explosives, nitroglycerine dynamites, such as semi-gelatins, ammonia gelatins and ammonia dynamites. The specific gravity is not critical, but should be greater than one by a sufficient amount to ensure that the cartridge will not float, and will preferably be at least 1.1.

A primer cartridge can include a booster explosive in close juxtaposition to the high explosive. A booster cartridge will contain a booster explosive. Any booster eX- plosive can be used, such as pentolite (a mixture of 1:1 pentaerythritol tetranitrate (PETN) and trinitrotoluene), ammonium dynamite, nitroglycerine dynamite, nitroglycerine, semi-gelatin and gelatin dynamites, composition B, RDX (Cyclonite or cyclotrimethylenetrinitramine) and pentaerythritol tetranitrate.

In the preferred cartridge, the water-expandible material is preferably packed into the bottom of the container, beneath the explosive.

The explosive charge can be placed into the container in a liquid form, as molten or as a slurry, and then al lowed to harden. This is especially useful when the charge is contained in a separate container or sack. Otherwise, it can be placed into the container in particulate form, and then tamped carefully to ensure that it is firmly packed. If the charge is not put in a separate internal container or sack, it is important that the charge be firmly packed, so that upon increase in pressure due to expansion of the expandible material, the pressure can be immediately transformed into internal pressure to operate the means for exposing the explosive to water, rather than merely to pack the charge together.

The following drawings show preferred embodiments of cartridges falling within the scope of this invention.

FIGURE 1 is an elevation view in cross-section of a tubular cartridge having a water-entry passage opening through the top end cap, and the explosive charge in an internal container;

FIGURE 2 is a top view of the tubular cartridge container of FIGURE 1;

FIGURE 3 is an elevational view in cross-section of a tubular cartridge wherein the water-entry passage opens through the lower end cap, and the explosive charge compartment is separated from the water-expandible material compartment by an internal divider.

FIGURE 4 is an elevation view in cross-section of a tubular cartridge in which the explosive charge compartment and the water-expandible material have no separating divider or wall; and

FIGURE 5 is an elevation view in cross-section of a tubular cartridge container wherein the passage is in the form of an opening located in a wall of the Water-expandible material compartment.

In FIGURES 1 and 2, the cartridge container is formed from rigid propylene polymer tubing extruded in the usual manner. The deeply recessed bottom end cap 3, of like material, is bonded to the side walls 2 of the tube by heat and pressure, forming an open-ended container.

At the bottom of the container 1 is a layer of a gasproducing composition 10 formed of a mixture of sodium bicarbonate (5 g.) and citric acid (5 g.). Resting on this lower layer of gas-producing composition is an inner container 5 of rigid polyethylene tubing, containing a cast in situ explosive booster charge 8. The explosive charge had the following formulation:

Ingredients: Parts by weight Nitrostarch M 75 Ethylene glycol 5 Ammonium nitrate 10 The water inlet passage 9 is fonmed between the side wall 2 of the container 1 and the side wall 6 of inner container 5, from the top of the container, and opening into the recess 7 of the cap 3, where the gas-producing composition 10 is placed.

The open end of the passage 9 is closed by a plug of a water-soluble resin 11, in this case guar gum. A one-way valve 13 is located immediately below the plug of guar gum, and just above the gas-producing composition 7. The valve 13 will allow water to flow through passage 9 into the compartment 7, but will prevent any water or gas from escaping from compartment 7 through the passage.

The container shown in FIGURES 1 and 2 is filled as follows: After the recessed end cap 3 has been bonded to the tube 1, the water-expandible composition is filled into the recess. Next, the container 5 is filled with granular explosive, and the blasting cap well 17 is inserted. The container then is placed in the open space above the water-expandible composition, substantially filling the container, except for passage 9, from the top of the cap to the upper end of the tube 1. Then, the end cap 15 is placed across the open end of container 1, with its central aperture 19 across the open end of the well 17, thus clolsing off both the sack and the container, but not the we 1.

The end cap 15 is then sealed to the plastic container 1 by a water-soluble adhesive, in this case animal glue, and the plug 11 is inserted in the mouth of passage 9, closing it off to the entry of water.

When the self-deactivating booster of FIGURES 1 and 2 is immersed in water, i.e., salt water or fresh water, the guar gum plug 11 dissolves, allowing Water to pass down the passage 9 and through the one-way valve 13 into contact with the gas-producing composition 10. Carbon dioxide is promptly vigorously evolved by the gasproducing composition 4, and, since the check valve 13 prevents any gas from escaping through the passage 9, exerts pressure on the bottom of container 5 and the interior walls of the container. The water-soluble adhesive holding the end cap 15 to the container 1 is slowly dissolved, and the cap becomes free, ready to be pushed out. When the internal pressure in the container below container 5 becomes sufficiently greater than the external water pressure, the container 5 is pushed against the end cap 15, and the end cap 15 is pushed out and away from the end of

containers

15 and 5. The now open container and its explosive charge will be forced out from the container 1 and is exposed to the water, which can thereby deactivate the charge. The cap and charge can pop out from the container, much as a cork is discharged from a pop gun.

In the booster of FIGURE 3 the container 25 is also an extruded cellulose acetate butyrate tube, open at both ends.

A movable spacer member 28 loosely fitted in the tube 25 divides the container into two compartments, 29 and The inner walls 27 of the cartridge container are covered with a coating of Teflon, to ensure that the hardened explosive charge will not stick to them, thereby allowing the charge to slide easily out of the cartridge.

Cellulose acetate-butyrate end cap 26 is bonded across one open end of the container 25 by ultrasonic bonding. Water entry into compartment 29 is provided by tube 31, formed integral with the lower end cap 26, and extending into the container. A tape 38 is placed over the end of tube 31, to close it'off. Perforated plate 39 in the tube 31 serves as a valve, to allow water to pass into the lower compartment 29 of the container when the tube is open, but to prevent any solid material within the compartment from escaping through the tube. A water-expandible material 32 such as gelatin or polyvinyl alcohol is in the compartment 29, and a cast explosive charge 33, such as pentolite, is in the compartment 30. End cap 35 with blasting cap well 37 attached is inserted into, and closes off the other end of, the container 25, and is attached thereto in substantially the same manner as in the cartridge of FIGURES 1 and 2.

This booster cartridge is filled as follows: First, the water-expandible material is filled in compartment 29, and then the spacer 28 is placed loosely on top, but not bonded to, the side walls of the tube. The molten explosive charge is then poured into the container '25, upon the separator member 28, and the end cap 35 is inserted. The molten charge is allowed to harden, forming the cast charge 33.

The explosive charge 33 in the cartridge of FIGURE 3 has the formulation:

Ingredients: Parts by weight PET'N (200 mesh) 50 TNT 50 In use, the tape '38 is removed by hand before the cartridge is immersed in water. Then, when water flows into the tube 31, it contacts the polyvinyl alcohol, which swells, applying an internal pressure against the divider 28 beneath the cast explosive charge 33. This pushes the explosive charge against the top end cap 35. Since the top end cap is bonded to the container 25 with a watersoluble adhesive, this is dissolved 'by water after immersion, which frees the cap. After the polyvinyl alcohol has expanded sufiiciently, the charge 33 is eventually pushed out by the internal pressure, exposing the charge to the deleterious dispersing action of water.

In the booster of FIGURE 4, the cartridge container 40 is formed from a rolled sheet of water impermeable Teflon-coated 140 weight kraft paper. The cartridge container has two

undivided compartments

41, 42. An end cap 44 of aluminum metal is permanently bonded across one open end of the container by a non-water soluble epoxy cement. A gas-producing composition comprising parts sodium bicarbonate and 5 parts sodium hydrogen tartrate, approximately parts per hundred parts of explosive composition, is placed in compartment 42. An explosive charge 46 precast in a mold is then placed in compartment 41, over the gas-producing composition; blasting cap well 47 is cast into the explosive charge 46. The charge has the following formulation:

Ingredients: Parts by weight Nitrostarch 85 Dinitrotoluene End cap 50 is attached across the end of the container after it is filled with explosive charge 46, and is bonded to the container by a water-soluble adhesive, such as sodium carboxymethylcellulose.

An orifice 52 is formed in the side wall of the container 40, and a tube 53 having a flange 51 is bonded thereto with epoxy cement. In the tube 53 is placed a sintered metal plate 54, over which is applied a watersoluble film, in this case polyvinyl alcohol. When the cartridge is immersed in water, the water will dissolve away the film, and pass through the sintered plate into compartment 42 of the cartridge. Upon contacting the composition 45, gas will be evolved, which cannot readily escape outwardly through the sintered metal plate, since it is covered with water, but will exert a pressure against the cast charge, thereby eventually pushing it and the end cap 50 off from and out of the cartridge container, deactivating the cartridge.

The cartridge container 58 of FIGURE 5 is of the readily rupturable type, disclosed in US. Patent No. 2,345,654, wherein'the outer side wall of the container is formed of a sheet of coated heavy weight kraft paper wrapped on a mandrel to form a cylindrical tube. The sheet of paper is previously weakened at

points

66, 67, so as to be rupturable there, by a sufficient internal pressure. The container is designed as a primer cartridge, and has three compartments, 70, 71, 72, of which two, '70 and 71, are separated by a sheet divider 73 from the compartment 72. The end cap 59 is bonded to one end of the container by a nonwater-soluble epoxy cement.

Compartment 70 contains an explosive booster charge 77, such as granular pentaerythritol tetran-itrate, and directly below is a primer charge 75 of a pelleted primer explosive, such as pentolite, or composition B. Compartment 72 contains the gas-producing material 63. End cap 65 closes ofi the other open end of the tube, and is bonded to the container 58 by a water-soluble sodium carboxyinethylcellulose adhesive.

The top portion of the container, down to the member 73, is coated with Teflon on both the inner and the outer walls.

In the wall of the container end cap 59 is an opening 68, closed oif by polyvinyl alcohol tape 69, and a porous plate 62. When the cartridge is immersed in water, the polyvinyl alcohol tape and the sodium carboxymethylcellulose adhesive will 'be dissolved away, allowing water to pass into the container through opening '68, and contact the gas-producing material as. The gas so produced is prevented from escaping by the water-filled plate 62 and pressure thus created is exerted against the divider 74 and the side walls of the container, either forcing the charge out of the container after dislodging the cap 65, or bursting the container in the

portions

66, 67, in either event dispersing the charge into the body of liquid and thereby deactivating the booster.

Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. An explosive container that, after immersion in water, exposes an explosive charge contained therein to water in a manner to distribute the explosive therein, comprising a container having a first compartment for an explosive charge and a second compartment for a waterexpandible material, a passage leading from outside the cartridge container into the second compartment for flow of water thereinto when the cartridge is immersed in water, but capable of substantially containing an increase of volume of material in the second compartment, and means to expose an explosive charge in the first compartment to water, operable under pressure arising from an increase in volume in the second compartment, including an inner receptacle for an explosive charge defining the first compartment and forming a barrier separating the first compartment from the second compartment, and adapted to be pushed out of the container under pressure arising from an increase in volume in the second compartment.

2. An explosive container that, after immersion in water, exposes an explosive charge contained therein to water in a manner to distribute the explosive therein, comprising a container having a first compartment for an explosive charge and a second compartment for a waterexpandible material, a passage leading from outside the cartridge container into the second compartment for flow of water thereinto when the cartridge is immersed in Water, but capable of substantially containing an increase of volume of material in the second compartment, and means to expose an explosive charge in the first compartment to water, operable under pressure arising from an increase in volume in the second compartment including an inner receptacle for an explosive charge, defining the first compartment and forming a barrier separating the first compartment from the second compartment, and adapted to be pushed out of the container under pressure arising from an increase in volume in the second compartment, said means for exposing the explosive charge to water comprising a weakened wall of the first compartment, rupturable under pressure arising from an increase in volume from the second compartment.

3. An explosive container that, after immersion in water, exposes an explosive charge contained therein to water in a manner to distribute the explosive therein, comprising a container having an open end and having a first compartment for an explosive charge and a second compartment for a water-expandible material, a passage leading from outside the cartridge container into the second compartment for flow of water thereinto when the cartridge is immersed in water, but substantially containing an increase in volume of material in the second compartment, and means to expose an explosive charge in the first compartment to water, operable under pressure arising from an increase in volume in the second compartment, said means for exposing the explosive charge to water comprising a cap closing off the open end, the cap being removably attached to the container, and being adapted to be pushed out of position under pressure arising from an increase in volume from the second compartment.

4. An explosive cartridge that, after immersion in water, is self-destroying by exposure of explosive contained therein to water in a manner to distribute the same in water, comprising a container having a first compartment and a second compartment, an explosive charge in the first compartment, a water-expandible material in the second compartment, a passage leading from outside the cartridge container into the second compartment for flow of water thereinto when the cartridge is immersed in water, but substantially containing an increase in volume of material in the second compartment, and means to dissipate an explosive charge in the first compartment from the container into water surrounding the container, operable under pressure arising from an increase in volume in the second compartment.

5. An explosive cartridge in accordance with claim 4 having closure means closing off the passage for entry of water, to keep the cartridge watertight until used.

6. An explosive cartridge in accordance with claim 4, wherein the closure means is removable manually prior to immersion of the cartridge in water.

7. An explosive cartridge in accordance with claim 4, wherein the closure means is removably by action of water after immersion of the cartridge in water.

8. An explosive cartridge in accordance with claim 4, wherein the explosive charge is a booster charge.

9. An explosive cartridge in accordance with claim 4, having a directional valve means in the passage allowing water to flow into the second compartment but substantially containing an increase in volume of material in the second compartment.

10. An explosive cartridge in accordance with claim 4, wherein the explosive charge is pentolite.

11. An explosive cartridge in accordance with claim 4, wherein the water-expandible material is a material which liberates a gas upon contact with water.

12. An explosive cartridge in accordance with claim 11, wherein the water-expandible material comprises a water-soluble carbonate.

13. An explosive cartridge in accordance with claim 4, wherein the water-expandible material is a material which itself increases in volume upon contact with water.

14. An explosive cartridge in accordance with claim 13, in which the water-expandible material is polyvinyl alcohol.

References Cited UNITED STATES PATENTS 601,604 3/1898 Walsh. 2,759,417 8/1956 ONeill 102-28 X 3,279,372 10/1966 Patterson 10228 BENJAMIN A. BORCHELT, Primary Examiner. V. R. PENDEGRASS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,358,600 December 19, 1967 George L. Griffith et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 64, for "comparements" read compartments column 4, line 44, for "carriage" read cartridge column 10, line 16, for "removably" read removable Signed and sealed this 22nd day of April 1969.

ISEAL) Ittest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Lttesting Officer Commissioner of Patents