EP0063995B1 - Explosive projectile liberating preformed fragmentary elements, and manufacturing method therefor - Google Patents

Description

The present invention relates to anti-tank or anti-personnel explosive devices, and more particularly to explosive devices which comprise an envelope containing pre-fragmented fragments disposed around the explosive charge and launched forcefully in all directions during the explosion of that. -this.

For example, from document FR-A-2260774, devices are known in which the pre-fragmented fragments are steel balls projected during the explosion. Devices are also known in which the flakes are not completely fragmented before the explosion but consist of pieces of the envelope enclosing the explosive charge, envelope which has been previously deeply striated to ensure a division into small pieces launched into all directions.

• - soit d'utiliser des enveloppes minces pour enfermer la charge explosive, mais alors l'effet d'éclat additionnel de ces enveloppes minces est tout à fait négligeable alors qu'on souhaite que non seulement des éclats préfragmentés lourds soient lancés à grande vitesse, mais aussi que les morceaux d'enveloppe déchiquetée contribuent efficacement à l'effet recherché;
• - soit d'utiliser des enveloppes épaisses pour augmenter leur effet destructif lorsque l'enveloppe est déchiquetée, mais alors la perte d'énergie explosive qui en résulte pour effectuer la fragmentation de ces enveloppes devient trop importante.

The disadvantage of the existing devices currently comes from the fact that one must choose

• - either to use thin envelopes to enclose the explosive charge, but then the additional burst effect of these thin envelopes is completely negligible when it is desired that not only heavy pre-fragmented shrapnel be launched at high speed, but also that the pieces of shredded envelope effectively contribute to the desired effect;
• - or to use thick envelopes to increase their destructive effect when the envelope is shredded, but then the resulting loss of explosive energy to effect the fragmentation of these envelopes becomes too great.

The object of the present invention is to remedy these drawbacks by improving the speed of the pre-fragmented flakes housed in the envelope while increasing the effect of the additional fragments due to a thick envelope and not a thin envelope.

An improvement in the speed of the pre-fragmented flakes is obtained by making the contact between these flakes and the explosive much more intimate, and the effect of additional splinters of the thick wall is obtained by forming the explosive during its compression, forming making it possible to obtain between the pre-fragmented fragments annular fillers, hollow or dihedral, which are directed towards points of the thick wall to ensure its cutting.

More specifically, the explosive device of the invention comprises a charge of an explosive material inside a deformable waterproof thin sheath, and splinters distributed over a single thickness all around the thin sheath, and enclosed between this sheath thin and a relatively thick envelope, the thin sheath being deformed so as to be applied against the fragments and to allow an advance of explosive between two consecutive fragments; the flakes are distributed in non-contiguous annular layers, and between each group of two consecutive non-contiguous annular layers, the relatively thin sheath has, opposite and near the relatively thick envelope, but at a distance from the latter, a corresponding annular projection to an advance of the explosive charge towards it. The thin sheath preferably has, between two annular layers of consecutive flakes, a curved form of concavity facing outwards to form a portion of explosive charge comparable to a hollow charge facing the relatively thick envelope. It may also have substantially a dihedral shape to constitute a portion of explosive charge comparable to a dihedral charge, facing the relatively thick envelope.

The manufacturing method according to the invention consists in placing a thin, tight, deformable sheath in a relatively thick outer envelope, then inserting between the thin sheath and the envelope pre-fragmented fragments, then filling the thin sheath with explosive. and compressing this explosive by deforming the thin sheath until it is applied tightly against all the fragments and that it advances between two fragments towards the thick envelope; the fragments are in number such that they can be distributed between the thin sheath and the envelope in a single thickness and with between them intervals into which the sheath and the explosive which it contains can be introduced.

The prefragmented fragments can be spherical balls, which has the advantage of facilitating their distribution around the sheath.

The fragments are inserted into the thick envelope, around the thin sheath, by superimposing them in annular layers with a separation ring between each group of adjacent layers to keep the fragments spaced apart during the compression of the explosive and the deformation of the sheath, the separation rings being made of little compressible material and being able to be removed (for example by melting at low temperature, that is to say for example less than or equal to approximately 70 ° C.) after the operation of compression. In this process, it is preferable to provide that the rings have a toric shape to give the thin sheath and the explosive that it contains, between the pre-fragmented fragments, a concavity facing outwards, that is to say -significantly say a form of hollow charge facing the thick envelope. They can also have a polygonal section to give the sheath and the explosive that it contains a form of dihedral charge opposite the relatively thick envelope.

• - la figure 1 est une coupe longitudinale d'une réalisation du dispositif explosif tel qu'un projectile au cours d'une étape de fabrication;
• - la figure 2 montre le dispositif explosif de la figure 1 au cours d'une étape ultérieure de fabrication;
• - la figure 3 montre le même dispositif explosif au cours d'une troisième étape de fabrication;
• - la figure 4 est une coupe transversale partielle suivant la ligne IV-IV de la figure 3;
• - la figure 5 est une coupe longitudinale agrandie correspondant à une partie de la figure 3;
• - la figure 6 montre une coupe longitudinale d'un dispositif explosif tel qu'un projectile selon une variante de réalisation de l'invention, au cours d'une première étape de fabrication;
• - la figure 7 représente une demi coupe longitudinale correspondant à la réalisation de la figure 6, au cours d'une seconde étape de fabrication;
• - la figure 8 montre une demi coupe longitudinale correspondant à une troisième étape de fabrication;
• - la figure 9 représente un détail agrandi de la figure 7;
• - et la figure 10 montre un détail agrandi correspondant à la figure 8.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows and which is given with reference to the appended drawings in which:

• - Figure 1 is a longitudinal section of an embodiment of the explosive device such as a projectile during a manufacturing step;
• - Figure 2 shows the explosive device of Figure 1 during a subsequent manufacturing step;
• - Figure 3 shows the same explosive device during a third manufacturing step;
• - Figure 4 is a partial cross section along the line IV-IV of Figure 3;
• - Figure 5 is an enlarged longitudinal section corresponding to a part of Figure 3;
• - Figure 6 shows a longitudinal section of an explosive device such as a projectile according to an alternative embodiment of the invention, during a first manufacturing step;
• - Figure 7 shows a longitudinal half section corresponding to the embodiment of Figure 6, during a second manufacturing step;
• - Figure 8 shows a longitudinal half section corresponding to a third manufacturing step;
• - Figure 9 shows an enlarged detail of Figure 7;
• FIG. 10 shows an enlarged detail corresponding to FIG. 8.

In FIG. 1, an explosive projectile body is seen which comprises a thick external envelope 10, for example of light metal, of cylindrical shape closed at one end and partially closed at the other end by a screwed ring 12 leaving in its center an opening through which an explosive material can be introduced into the body.

A thin inner sheath 14 is inserted into the opening of the annular ring 12 and penetrates to the bottom of the thick casing 10. This thin inner sheath can be made of aluminum, steel, copper, brass, plastic, natural rubber. or synthetic, etc., and it is waterproof so that an explosive material can be introduced into it which will be confined in this sheath.

The annular ring 12 allows the inner sheath 14 to be centered, leaving a free gap between this sheath and the inner wall of the thick casing 10. In this interval and before the final positioning of the annular ring 12, splinters are introduced. prefragmented 16, for example spherical steel balls, in a number such that a layer of a single thickness of flakes can be formed all around the thin sheath 14, leaving a small gap between two consecutive flakes 16. In Figure 1, there is shown the prefragmented flakes 16 piled on two thicknesses around the sheath 14, but they do not completely fill the gap between the sheath and the envelope 10, and they are intended to be then distributed all around sheath in a single thickness.

The next step in manufacturing the explosive body according to the invention is shown in FIG. 2: the sheath 14 is filled with an explosive material 24 which is compressed from above; this compression has the effect, taking into account the high deformation capacities that are given to the thin sheath 14, to push the latter radially in all directions to come into contact with the pre-fragmented flakes 16 which are thereby pushed back against the wall of the thick outer casing 10 and which are pressed against this wall in a single thickness, and distributed in superimposed annular layers, as can be seen in FIG. 2. It is understood that the sheath 14 is sufficiently thin to have a high coefficient of elongation under the effect of the radial pressure exerted during the compression of the explosive from above.

It will be noted that it is preferable to provide at the bottom of the thick casing 10 an inclined ramp 18 on which the prefragmented fragments 16 rest, this inclined ramp having the effect of facilitating the distribution of the fragments in a single layer during application. compression.

This compression and this deformation of the sheath have the effect of concentrating the explosive 24 all around each of the individually pre-fragmented flakes, and, therefore, during the explosion, this intimate contact communicates to the flakes 16 a much higher speed. only if they were separated from the explosive and its sheath.

In Figure 3, there is shown the end of the compression operation: not only the inner sheath 14 is deformed by applying tightly against the flakes 16, put still it separates them by penetrating between the consecutive flakes, and in particular between the consecutive annular layers which it thus separates, and thereby causing a part of explosive 24 to penetrate between these fragments and in particular between the annular layers. Of course, the chips were previously inserted in a number such that this spacing is possible, leaving only a thickness of chips between the inner sheath 14 and the thick envelope 10.

Figures 4 and 5 show, in cross section and in longitudinal section respectively, enlarged and partial views of the explosive device of the invention at the end of the compression operation. It can be seen that each of the pre-fragmented flakes 16 (preferably spherical balls) is tightly clamped between the inner sheath 14 and the outer casing 10, and moreover that a portion of explosive 24 projects directly opposite and near the inner wall of the envelope 10, but at a distance therefrom, between each group of two adjacent flakes 16 and in particular between two consecutive annular layers.

During the explosion of the load, two effects combine to reinforce its efficiency: on the one hand, the load parts projecting directly opposite the casing 10 cause the casing 10 to be cut at level of these projections, and on the other hand the parts of explosive charge 24 closely molded around the pre-fragmented fragments 16 communicate to the latter a maximum speed during the explosion.

This is possible even with a thick casing 10 thanks to the fact that the explosive projections 24 are located directly opposite the outer casing 10 and close to it, and the explosion of the charge 24 causes both a deep penetration of multiple target structures (thanks to heavy splinters 16) and significant tearing of target surfaces thanks to larger fragments constituted by the envelope fragments 10 having undergone a controlled cutting.

It is important that not only the inner sheath 14 is highly deformable under the effect of a compression exerted in the radial direction, but also that it does not undergo any prefragmentation and is not crossed by any crack even after the compression operation. In particular, the sheath must have sufficient tightness with respect to the hot gases from the launcher.

An alternative embodiment of the invention has been described with reference to FIGS. 6 to 10, in which the essential difference lies in the way in which the pre-fragmented flakes are distributed around the inner sheath 14 during the manufacturing operation.

Unlike the first embodiment described, the prefragmented flakes 16 are not piled up in several thicknesses at the start of manufacture, but they are initially, that is to say before any operation for compressing the explosive material and even before introduction thereof, distributed in superimposed annular layers spaced from one another and over a single thickness around the sheath 14.

This distribution is carried out for example by placing a first layer of pre-fragmented flakes (spherical balls in particular) at the bottom of the casing 10 around the sheath 14, then a separation ring 20 above this first layer of flakes 16, then a new layer of splinters 16, and a new separation ring etc. to the top. The initial dimension of the internal sheath 14 relative to the internal diameter of the thick casing 10 is such that a single thickness of splinters can find its place between the sheath and the casing 10.

The separation rings 20 are preferably toric and the dimensions of their section relative to the dimensions of the pre-fragmented flakes 16 are such that the layers of pre-fragmented flakes are perfectly separated from each other during the first manufacturing phase.

The second manufacturing phase consists in introducing the explosive material 24 inside the sheath 14 and in compressing it by the upper opening in the annular ring 12 which closes the envelope 10 while preventing the pre-fragmented fragments from coming out upwards. . The compression also has the effect of strongly deforming the sheath 14 by applying tightly against the prefragmented flakes 16 which therefore come to be wedged between this sheath and the thick outer envelope 10. This intimate contact will also have the effect of increasing the speed of expulsion of pre-fragmented fragments during the explosion. In addition, the deformable sheath 14 is inserted into the space between two layers of prefragmented flakes maintained separated by a separation ring 20. The explosive 24 also comes to lodge in this interval. The sheath takes, at each separation ring 20 a shape closely adapted to the shape of the separation ring and the explosive therefore takes on this level a concave shape of concavity turned radially outward, that is i.e. towards the wall of the thick casing 10.

FIG. 9 represents a detail of FIG. 7, showing the shape taken by the deformable sheath 14 and the explosive inside this sheath at the level of a separation ring 20 and at the level of two adjacent pre-fragmented flakes 16.

The next manufacturing step is shown in Figure 8; it consists in eliminating the separation rings 20, that is to say removing them from their location between the prefragmented flakes 16. A process which can be used to effect this elimination is fusion, and provision is made for this. effect that the separation rings are made of a fusible material at low temperature, that is to say at a temperature low enough not to generate a risk of explosion of the explosive material, and, for example less than or equal to 70 ° C approximately; it is for example possible to achieve for this purpose the rings 20 of alloy with low melting point, in particular based on gallium, and / or indium, cadmium, tin, bismuth, etc., or use waxes such as paraffin. Heating can be done externally. The molten material is then housed, for example, in a cavity 22 at the bottom of the envelope 10.

During and after this fusion, the pre-fragmented flakes 16 remain in position, and are held in place, no longer by the separation rings then melted, but by the compressed explosive 24 and the sheath 14.

Figure 10 shows a detail of Figure 8 on which we see the final result which is that the sheath 14 and the explosive take a particular shape which is both intimate contact around each of the pre-fragmented flakes 16 and also a shape concave facing the wall of the outer casing 10, this concave shape advancing between the flakes 16 adjacent to the wall 10, facing the latter and up to but close to the latter, but at a distance therefrom .

The concave shape thus produced ensures a cutting of the wall 10 at this interval between two flakes and this cutting is even better than that which was carried out in the first embodiment by the simple projection of explosive between two flakes, because now there is a hollow charge effect to cut the thick envelope 10 around the pre-fragmented flakes 16.

The shape of the sheath and explosive part between the pre-fragmented flakes is not necessarily exactly that of a hollow charge; it can also be that of a dihedral load if the separation rings 20 are not toric but of polygonal section. In any case, provision can be made for the projections to be formed by small charges formed according to the cutting effect that one seeks to obtain.

Claims (11)

1. An explosive device incorporating an explosive charge (24) inside a thin leakproof deformable sheath (14) and shrapnel (16) distributed in a single thickness, all around the thin sheath (14) and enclosed between this thin sheath and a relatively thick casing (10), the thin sheath (14) being deformed so as to be applied against the shrapnel (16) and to permit a forward movement of the explosive between two consecutive shrapnel members, characterised in that the shrapnel (16) is distributed in noncontiguous annular layers and in that, between each group of two consecutive noncontiguous annular layers, the relatively thin sheath (14) has, facing and close to the relatively thick casing (10), but at a distance from the latter, an annular projection corresponding to a projection of the explosive charge (24) towards the latter.

2. A device according to Claim 1, characterised in that the relatively thin sheath (14) has, between two consecutive annular layers of shrapnel (16), a curved shape with a cavity turned towards the relatively thick casing (10) to form an explosive charge portion (24) comparable to a hollow charge turned towards the relatively thick casing (10).

3. A device according to Claim 1, characterised in that the relatively thin sheath (14) has, between two consecutive annular layers of shrapnel (16), a dihedral shape to form an explosive charge portion (24) comparable to a dihedral charge facing the relatively thick casing (10).

4. A device according to one of Claims 1 to 3, characterised in that the prefragmented shrapnel is spherical balls (16).

5. A process for the manufacture of an explosive device according to one of Claims 1 to 4, consisting in placing a thin, leakproof deformable sheath (14) in a relatively thick outer casing (10), inserting prefragmented shrapnel (16) between the thin sheath and the casing, filling the thin sheath (14) with explosive (24), compressing the explosive while deforming the main sheath until the sheath is applied closely against all the shrapnel (16) and until it moves forward between two consecutive shrapnel members towards the thick casing (10), the shrapnel being such in number that it can distribute itself between the thin sheath (14) and the casing (10) in a single thickness, characterised in that the shrapnel (16) is inserted in the thick casing (10) around the thin sheath (14), being superposed in annular layers with a separating ring (20) between each group of two successive layers, to keep the shrapnel (16) separated during the compression of the explosive (24) and the deformation of the sheath (14), the separating rings (20) being made of a material with low compressibility and being suitable for being removed after the compression operation, and in that the rings (20) are removed after the compression operation.

6. A process according to Claim 5, characterised in that the prefragmented shrapnel is spherical balls (16).

7. A process according to Claim 6, characterised in that the rings (20) are made of a material capable of melting at a sufficiently low temperature not to give rise to a risk of explosion of the explosive (24), so that they can be removed by melting at this temperature after the compression operation.

8. A process according to Claim 7, characterised in that the said temperature is at most equal to approximately 70°C.

9. A process according to either of Claims 7 and 8, characterised in that the rings (20) are made of a low-melting alloy, particularly based on gallium.

10. A process according to any one of Claims 5 to 9, characterised in that the rings (20) are toric in shape to give the sheath (14) and the explosive (24) which it contains, between the prefragmented shrapnel (16), a shape of a hollow charge turned towards the relatively thick casing (10).

11. A process according to one of Claims 5 to 9, characterised in that the rings have a polygonal cross-section to give the sheath (14) and the explosive (24) which it contains, between the prefragmented shrapnel (16), a shape of a dihedral charge facing the relatively thick casing (10).

Images