EP0774643B1 - Manufacturing method for an explosive ammunition element having a fragmentation/hull construction - Google Patents

Description

The present invention is in the field military, more particularly in that of explosive ordnance, projectiles, bombs, various devices for example, with controlled fragmentation (also called "predetermined" or "prepared"), in particular intended for anti-runway, anti-bunker or anti-vehicle operations (ships, tanks, tanks, etc.).

It relates more precisely to a new process for manufacture of an explosive ordnance item at controlled fragmentation with a load solid explosive contained in a metallic envelope internally coated by a sleeve provided indentations, dihedral for example, directed towards inside the ammunition, i.e. towards the loading.

The contact areas between the casing and the sleeve are therefore separated by cavities corresponding to the volume of indentations.

Patent FR 2 685 077 describes an element of ammunition explosive with controlled fragmentation allowing optimize the size of the chips produced by its fire depending on the target attacked.

The explosive charge is contained in a metal envelope consisting of 2 walls concentric, ferrule-shaped, separated by a clearance allowing them to be made mobile relative to the other according to a movement of rotation and / or translation, each wall being intended to be fragmented to produce shards whose mass individual is predetermined.

The relative mobility of the 2 walls in coincidence allows adjustment and programming, manual or automatic, the size of the flakes.

Patent FR 2 433 731 describes an element of ammunition explosive with controlled fragmentation comprising a thin-walled lining located between the envelope metal and the explosive charge and comprising indentations which are ribs directed towards the interior in the shape of a roof. The filling, made up by a thin sheath, provides an interior coating, total or partial, of the envelope.

According to a variant, the envelope is internally smooth and is covered with a metal trim or plastic material comprising ribs directed towards the interior in the shape of a roof.

When the trim is made of plastic, to make the explosive ordnance element, cover it, during the manufacture of the explosive charge by molding, the internal parts of the mold by a sheet plastic coated by front heating introduction of the explosive in a liquid or pasty state.

Closing the mold provided with projections causes the formation of roof-shaped ribs.

After cooling and opening the mold, removes the explosive charge coated by the lining.

This load and its trim must then be introduced in a metallic envelope with dimensions suitable for making the ammunition element.

Such a process by prior molding of the load explosive coated with the plastic sheath is long and very expensive at the industrial stage due to the multiple manufacturing operations (realization of suitable molds, non-stick surface treatment, pouring of the charge, solidification, demolding, insertion of the load obtained in the structure metallic) and precautions, for reasons security operators handling naked explosive charges.

In addition, the load quantities achievable simultaneously are limited by the number of molds available. The multiplication of molds makes very expensive industrial investment.

The object of the present invention is in particular to propose a much simpler and more economical process.

The proposed solution consists in carrying out prior, in particular using industrial techniques by simple and inexpensive molding well known from a person skilled in the art, a rigid enclosure-shaped sleeve provided with a single opening and provided with indentations directed inward, insert this sleeve into the metal structure of the ammunition and then proceed then to the classic casting and solidification of an explosive composition.

• L'opération dangereuse de démoulage et d'insertion du chargement explosif dans la structure est supprimée, d'où en résultent un gain de sécurité et une réduction du coût.
• Le moule nécessaire à la réalisation du manchon rigide est de conception beaucoup plus simple que celui nécessaire au moulage de l'explosif, notamment pour deux raisons. Tout d'abord, le problème de l'étanchéité est moins crucial, voire inexistant lorsqu'on utilise la technique bien connue des plasturgistes d'extrusion-soufflage des matières thermoplastiques.

The main advantages of this process are:

• The dangerous operation of demolding and inserting the explosive charge into the structure is eliminated, resulting in a gain in safety and a reduction in cost.
• The mold necessary for producing the rigid sleeve is much simpler in design than that necessary for molding the explosive, in particular for two reasons. First of all, the problem of sealing is less crucial, or even nonexistent when using the well-known technique of plastic extrusion blow-molding plastics manufacturers.

• L'opération elle-même de moulage est beaucoup plus économique car les problèmes liés à la sécurité pyrotechnique ne se posent plus. De plus, on peut réaliser les manchons rigides aux cadences élevées propres aux industries de la plasturgie.
• Il permet, contrairement au procédé connu précité par moulage simultané matière plastique/explosif, grâce au moulage préalable du manchon rigide, l'utilisation de matières plastiques supportant ou nécessitant des températures élevées de mise en forme qui seraient incompatibles avec les explosifs.
• La souplesse et l'élasticité de nombreuses matières plastiques ou élastomériques permettent la mise en oeuvre du procédé selon l'invention même lorsque le gabarit de l'ouverture de l'enveloppe métallique est inférieur au gabarit du manchon, ce qui n'est pas possible lorsqu'on opère par moulage simultané matière plastique/explosif.
• Il assure un meilleur contact d'ensemble entre l'enveloppe, le manchon et le chargement explosif, ce qui limite le risque de décollement intempestif pouvant se produire lorsque l'élément de munition subit de fortes accélérations, ou au contraire de fortes décélérations, par exemple lors de la pénétration dans une cible.

In addition, the use of plastics at high working temperatures allows the use of two-shell molds, taking advantage of their flexibility when hot and their thermal shrinkage (natural contraction), while the traditional molding of explosives or simultaneous plastic / explosive molding requires molds with a higher number of shells.

• The molding operation itself is much more economical since the problems associated with pyrotechnic safety no longer arise. In addition, rigid sleeves can be produced at high rates specific to the plastics industries.
• It allows, unlike the aforementioned known method by simultaneous plastic / explosive molding, thanks to the prior molding of the rigid sleeve, the use of plastic materials supporting or requiring high temperatures of shaping which would be incompatible with explosives.
• The flexibility and the elasticity of many plastic or elastomeric materials allow the implementation of the method according to the invention even when the size of the opening of the metal casing is less than the size of the sleeve, which is not possible. when operating by simultaneous plastic / explosive molding.
• It ensures better overall contact between the envelope, the sleeve and the explosive charge, which limits the risk of untimely detachment which can occur when the ammunition element undergoes strong accelerations, or on the contrary strong decelerations, by example when penetrating a target.

The present invention therefore relates to a new method of manufacturing a munition element explosive with controlled fragmentation comprising a solid explosive charge contained in an enclosure metallic whose inner wall is coated with a sleeve externally provided with indentations, it is say interior notches, grooves. Wall inside of the envelope and the outside surface of the sleeve are therefore in contact through protruding areas separated by voids corresponding to the volume of indentations.

The method according to the invention is characterized in that that we realize first of all, in general and preferably by molding, a rigid plastic sleeve or elastomeric, externally provided with indentations, and having an enclosure shape provided with a single opening, for example a form of case, bottle, warhead, cup or sock. Then we introduce the sleeve in a metal envelope comprising a opening and whose shape and dimensions are such that the sleeve can coat the inner wall of the envelope, the sleeve being introduced through the opening of the envelope the bottom first, that is to say so such that the opening of the sleeve is located opposite opening the envelope to make it accessible inside the sleeve through the opening of the envelope.

Then a composition is poured into the sleeve explosive pasty or liquid, then solidify the composition.

By plastic, we conventionally mean any synthetic material based on the use of macromolecules and capable of being shaped or molded, usually hot and pressurized.

By elastomeric material, we conventionally mean any polymeric material, natural or synthetic, having elastic properties and which can serve as rubber.

Generally, but not imperatively, the element of Explosive ordnance has an axis of symmetry. In a way preferred, it presents, in whole or in part, a cylindrical or ogival shape. The bottom can be flat, rounded, or of any shape. So that the sleeve can internally coat the envelope, when the munition element has a cylindrical shape, the inner diameter of the envelope is equal to the diameter outside of the sleeve and when the ammunition element has an ogival shape, the dimensions of the ogives delimited by the inner wall of the envelope and by the outer wall of the sleeve are identical.

The thickness of the wall of the sleeve is preferably constant or substantially constant, especially in the peripheral zone. The thickness of the bottom wall of the sleeve, i.e. the part of the sleeve opposite to its single opening can, for example, be slightly superior, in particular due to the technique of aforementioned blowing. The thickness of the sleeve wall can be any. It is however preferably significantly lower than that of the metal envelope, for example between 5% and 25% of the thickness of the envelope, preferably about 10%.

The indentations can have any form, but are preferably dihedral, roof-shaped, the dihedral edge being located towards the interior of the muff.

Dihedrons may have an opening angular in multi slope, for example in double slope, with respect to their plane of symmetry.

Preferably, the indentations, dihedral or no, are identical, and particularly preferred, when the sleeve has a shape cylindrical, they are distributed in the same crowns height with identical number of indentations identical, the indentations being regularly distributed on each crown and located alternately with the indentations of the upper crown and those of the lower crown. Along a generator, each indentation is thus located between two protruding areas not indented from the two crowns adjacent, and projecting surfaces in contact with the envelope, are identical, regularly spaced, in alternating from one crown to another, and represent approximately a chessboard drawing.

The bottom of the sleeve is generally smooth, devoid of indentations. This is also the case for the part of the sleeve located near the opening.

By way of illustration, in the case of a sleeve cylindrical, only the peripheral zone has indentations. The two sides, which can for example be approximately flat and parallel, constituting the bottom and the area in which the opening is located lack them.

The edges of the sleeve connecting the peripheral zone and the two flat faces can be rounded.

According to another preferred variant of the invention, the inner and outer walls of the envelope metallic are not weakened, i.e. that they are appreciably smooth, devoid of veins and / or grooves, crack initiators whose network predetermines future fragments.

This method of fragmentation controlled by weakening of the envelope is not always usable, especially for military heads intended to penetrate a target before operating ("penetrators"), or having to undergo strong accelerations (shells), the envelope being likely to be deteriorate before operation due to its too great fragility.

In this configuration, controlled fragmentation is only ensured by the cutting load effect due to the dihedral indentations of the sleeve.

In those situations for which he is not possible to weaken the envelope, it is well known to a person skilled in the art of carrying out an explosive charge with a multitude of dihedrons on its face peripheral in contact with the metal casing, but such ammunition can only be produced by integral molding prior to loading, with all the disadvantages that have been developed previously, or by molding followed by machining, which is still more expensive.

The present invention is therefore particularly interesting to implement in these situations.

According to another preferred variant of the invention, the plastic or elastomeric material constituting the rigid enclosure-shaped sleeve with a single opening is chosen from the group made up of polyalkylenes, natural elastomers and synthetic elastomers, preferably polyethylene low or high density.

The sleeve can be manufactured by any technique of molding or extrusion, but we prefer to use the extrusion blow molding technique, well known to plastics manufacturers, widely used for manufacturing plastic bottles, which is simple, little expensive and allows high rates.

The sleeve must be rigid enough to withstand the pressure of explosive compositions pasty or liquid when these are introduced.

When the sleeve is made of polyethylene, and so more general when it has flexibility and sufficient elasticity to be compressed without deterioration, we can introduce, by opening the envelope, a sleeve whose size is greater than envelope opening template.

To do this, simply compress the sleeve up to a template allowing its introduction in the envelope.

Once in the envelope, the sleeve resumes its shape and its original size and coated internally the envelope.

According to another variant of the invention, the flowable explosive composition consists of a binder organic polymerizable charged whose charge contains at least one organic nitro explosive, and we solidify the composition by polymerization of the binder. We obtain thus a charge of the composite explosive type (Cast explosive plastic bonded).

Pouring the explosive into the sleeve can be performed at atmospheric pressure or by injection under pressure, or by gravity under empty.

As examples of organic nitro explosives, we may include hexogen, octogen, pentrite, 5-oxo 3-nitro 1,2,4-triazole (ONTA), and mixtures of minus two of these compounds.

As examples of a polymerizable organic binder, can quote those allowing obtaining, after polymerization, for example by heating, of a matrix solid polymer filled with polyurethane type or polyester, possibly having groups energetic such as fluorinated, nitrated groups and / or azidae.

Polyurethane matrices are generally obtained by reaction of a prepolymer with hydroxyl endings with a polyisocyanate.

As examples of terminated prepolymers hydroxyls, there may be mentioned those whose skeleton is a polyisobutylene, a polybutadiene, a polyether, a polyester, a polysiloxane. Preferably a polybutadiene with hydroxyl endings.

As examples of polyisocyanates, mention may be made of isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), dicyclohexylmethylene diisocyanate (Hylene W), hexamethylene diisocyanate (HMDI), biuret trihexane isocyanate (BTHI), and their mixtures.

When the polymer matrix is a matrix polyester, it is generally obtained by reaction of a carboxyl-terminated prepolymer, preferably a carboxyl-terminated polybutadiene (PBCT) or a carboxyl-terminated polyester, with a polyepoxide, for example an epichlorohydrin condensate and glycerol, or a polyaziridine, for example the trimethylaziridinyl phosphine oxide (MAPO).

The polymerizable organic binder can optionally include a plasticizer, inert or active, such as those usually used in the implementation by flow of composite explosives.

In addition to the organic nitro explosive, the charge can possibly include for example a mineral oxidant such as ammonium perchlorate and / or a metal reducing agent such as aluminum.

According to another variant of the invention, the flowable explosive composition consists of a organic nitro explosive granular charge in suspension in a fusible explosive in the molten state, and the composition is solidified by lowering the temperature. One thus obtains a solid loading known as "melt-melt", consisting of an explosive matrix fuse, such as trinitrotoluene (TNT) which melts at 80 ° C, coating a granular explosive charge, such as hexogen, octogen or ONTA.

Explosive molten compositions, such as moreover in general, composite explosives aforementioned plastic binder used by casting, are well known to those skilled in the art.

According to another variant of the invention, the solid explosive charge is a bi-composition charge comprising a central coated composition by a peripheral composition.

Bi-composition explosive charges, and their processes for obtaining from explosive compositions flowable, pasty or liquid, are well known from the skilled person.

In the context of the present invention, it is preferred those for which the peripheral composition is less sensitive to the shock wave as the central composition, like those described for example in patents FR 2,668 146 and FR 2,678,262.

After inserting the sleeve into the envelope metallic, for example a removable pin is introduced in the sleeve then we sink, in the space between the pin and the inner wall of the sleeve, the composition liquid or pasty device. After solidification, we remove the spindle then we sink, in the space freed by the spindle, the liquid central composition or pasty which is then solidified.

Example 1

By carrying out the process according to the invention, a cylindrical element of ammunition explosive with controlled fragmentation comprising a loading with plastic binder composite explosive contained in a cylindrical steel casing, the inner wall is coated by a cylindrical sleeve plastic material externally provided indentations.

The steel casing, 10mm thick, has a 280mm outer diameter and an inner diameter of 260mm. Its height is 500mm. It has a background approximately flat and the face opposite the bottom is fully open (260mm circular opening of diameter). The envelope is not weakened. The walls interior and exterior are smooth.

The sleeve consists of a shaped enclosure case, cylindrical, made of high density polyethylene, with an approximately flat bottom and a opening on the approximately flat face opposite the background.

This sleeve has an outside diameter of 260mm and has 28 17mm high crowns including 52 identical indentations and regularly spaced by tower, in the form of dihedral grooves parallel to the axis of the sleeve and 6mm deep. The length of each groove is 17mm, i.e. the height of each crown, the edge of each dihedral is located at the inside of the sleeve and the angle of the dihedrons is 90 °. On each crown, the dihedral indentations are located alternately with the indentations of the upper crown and those of the lower crown. Each indentation is thus located between two zones in non-indented projection of the two adjacent crowns and projecting surfaces in contact with the envelope steel are identical, regularly spaced, in alternating from one crown to another, and represent approximately a checkerboard design approximately rectangular.

A rounding of 12mm radius connects the cylindrical part and the bottom. Another rounding of the same radius connects this same cylindrical part and the face, opposite the bottom, which includes an axial circular opening of diameter 90mm.

The thickness of the sleeve, more precisely the thickness of the constituent plastic, approximately constant, of the order of 1mm.

Depending on the area, it varies between 0.8mm and 1.2mm.

This sleeve, made of high density polyethylene, has everything first obtained by the extrusion blow molding technique from a mold adapted to the dimensions and the aforementioned configuration sought. The temperature in die outlet was 170 ° C.

Through the opening of the steel casing, we have then insert the sleeve into the envelope, the bottom of the sleeve being inserted first.

The opening of the sleeve is thus opposite the opening of the envelope, which makes it possible to accessible inside the sleeve through the opening of the envelope.

Given the shape and dimensions of the sleeve and the steel casing, the sleeve covers the wall inside of the envelope, the sleeve and the envelope being in contact through surfaces external protruding from the sleeve, as well as by the background.

Then poured into the sleeve, at 60 ° C, a explosive pasty composition consisting of 12% by weight octogen, 72% by weight of 5-oxo 3-nitro 1,2,4-triazole (ONTA) and 16% by weight of an organic binder polymerizable with polybutadiene with endings hydroxyls (PBHT) of mass around 2000 and isophorone diisocyanate.

The composition is solidified by polymerization of the binder by heating 7d at 60 ° C.

The loading was then started at using a plane wave generator (GOP) in diameter 90mm reinforced with a cylinder of the same diameter and height 45mm in composite explosive with plastic binder polyether with hydroxyl endings crosslinked by IPDI of octogenic weight composition 86%, crosslinked binder 14%.

After detonation of the explosive ordnance item and recovery of the fragments, there is a distribution quasi-Gaussian mass of these shards, perfectly centered on 20g.

Example 2

By carrying out the process according to the invention the same cylindrical element of ammunition explosive with controlled fragmentation only for example 1, except on the one hand that the explosive charge is a composite explosive with bi-composition plastic binder including the peripheral layer is less sensitive to the wave of shock than the central layer, and secondly that the diameter of the opening of the polyethylene sleeve is 200mm instead of 90mm.

For this example 2, we operate strictly as for Example 1 up to the step, not included, of casting the explosive pasty composition in the sleeve.

After inserting the sleeve into the envelope, positioned in the sleeve, axially and resting on its bottom, a removable cylindrical pin of diameter 130mm and height 500mm, then we sink in space located between the spindle and the inner part of the sleeve, 60 ° C, a pasty explosive composition consisting of 51% by weight of ammonium perchlorate, 17% by weight octogen, 20% by weight of aluminum and 12% by weight a polymerizable organic binder based on polybutadiene with approximately hydroxyl-terminated mass 2000 and isophorone diisocyanate.

The composition is solidified by polymerization of the binder by heating 7d at 60 ° C.

After removing the spindle, we pour in the central space thus freed, at 60 ° C, a composition explosive pasty consisting of 50% by weight of octogen, 24% by weight of ammonium perchlorate, 12% by weight aluminum and 14% by weight of an organic binder polymerizable with polybutadiene with endings hydroxyls of mass around 2000 and isophorone diisocyanate.

The composition is solidified by polymerization of the binder by heating 7d at 60 ° C.

The priming of the bi-composition loading was then carried out using a reinforced 50mm diameter GOP of a cylinder of the same diameter and height 35mm in same composite explosive as that used for the example 1.

After detonation of the explosive ordnance item and recovery of the fragments, we note, as for Example 1, a quasi-Gaussian distribution of the mass of these chips, perfectly centered on 20g.

Claims (12)

1. Process for manufacturing an explosive ammunition element of controlled fragmentation comprising a solid explosive charge contained in a metal casing, the internal wall of which is covered by a rigid sleeve, of plastics or elastomer material, externally provided with indentations, characterized in that:

   a rigid sleeve, of plastics or elastomer material, externally provided with indentations and having an enclosure shape equipped with a single opening, is first of all produced,

   the sleeve is then introduced into a metal casing comprising an opening and the shape and dimensions of which are such that the sleeve may cover the internal wall of the casing, the sleeve being introduced through the opening of the casing in a manner such that the opening of the sleeve is located opposite the opening of the casing to render the interior of the sleeve accessible through the opening of the casing,

   a pasty or liquid explosive composition is then poured into the sleeve, then the composition is solidified.
2. Manufacturing process according to Claim 1, characterized in that the ammunition element has a cylindrical shape and in that the internal diameter of the casing is equal to the external diameter of the sleeve.
3. Manufacturing process according to Claim 1, characterized in that the ammunition element has an ogival shape and in that the dimensions of the ogives delimited by the internal wall of the casing and by the external wall of the sleeve, are identical.
4. Manufacturing process according to Claim 1, characterized in that the indentations are in the shape of dihedrals.
5. Manufacturing process according to Claim 2, characterized in that the sleeve is provided with crowns comprising an identical number of identical indentations, the indentations being regularly distributed over each crown and located alternately with the indentations of the upper crown and those of the lower crown.
6. Manufacturing process according to Claim 1, characterized in that the external and internal walls of the metal casing are not embrittled.
7. Manufacturing process according to Claim 1, characterized in that the sleeve comprises a wall of a thickness which is substantially constant and between 5% and 25% inclusive of the thickness of the metal casing.
8. Manufacturing process according to Claim 1, characterized in that the plastics or elastomer material is selected from the group constituted by the polyalkylenes, the natural elastomers and the synthetic elastomers.
9. Manufacturing process according to Claim 8, characterized in that the plastics material is a polyethylene.
10. Manufacturing process according to Claim 1, characterized in that the size of the opening of the casing is less than the size of the sleeve, and in that the sleeve has sufficient flexibility and elasticity for it to be able to be compressed without damage then introduced into the opening of the casing.
11. Manufacturing process according to Claim 1, characterized in that the pourable explosive composition is constituted by a charged polymerizable organic binder, the charge of which contains at least one organic nitrated explosive, and in that the composition is solidified by polymerization of the binder.
12. Manufacturing process according to Claim 1, characterized in that the pourable explosive composition is constituted by an organic nitrated granular explosive charge in suspension in a fusible explosive in the molten state, and in that the composition is solidified by lowering of the temperature.