EP0338874A1 - Explosive projectile producing explosions in a definite pattern - Google Patents

Abstract

The subject of the invention is a projectile generating a burst of splinters by operation controlled on a trajectory during a tense shot.

It comprises an explosive charge (1) contained in a metal casing (2), means for varying along its longitudinal axis x′x the ratio R of the radial thicknesses (e) of the explosive charge (1) and (E) of the 'metal casing (2) containing said load, so as to modulate along the longitudinal axis the speed of the flakes. The variation of the ratio R is obtained by modulation of the radial thickness (e) of the explosive charge (1). The ratio R is increasing from upstream to downstream, discontinuously according to several radial loading thicknesses or continuously to ensure dispersion of the chips. The load comprises a first section (5) of thickness equal to the internal diameter of the envelope (2), four tubular sections (6-9) of radial thickness increasing towards the base, a free space being provided within these wafers (6-9), in which is interposed a module (11) of shock wave damping material, and a wafer (10) disposed at the base, of thickness equal to the internal diameter of the envelope (2 ).

Application to military equipment.

Description

The technical sector of the present invention is that of explosive projectiles comprising a fragmentation envelope and an explosive charge, generating splinters during the explosion.

This type of projectile is well known to those skilled in the art and by way of example the patent FR-A-2 438 686. In all known projectiles, the aim is always to improve the fragmentation of the envelope metallic, the explosive charge occupying the internal space of the envelope. A zone of distribution of the fragments is obtained, the extent of which on the ground depends on the firing mode and the caliber. It follows that the scanning of a determined area of land with 30 to 40 mm caliber projectiles requires the use of a large number of these projectiles.

When we examine the intersection with the ground of the shrapnel of fragments of a projectile, after fusing operation during a tense shot and that we translate this intersection in terms of efficiency, we can define three zones:
- a central zone where the probability of being put out of action (Pk), the probability of being hit (Ph) and the density of flakes (De) are high,
- an upstream area where De is weak; the efficiency is therefore low,
- a downstream zone where Pk, Ph and De are reduced; the efficiency is average.

In the central area, Pk is high because the burst speeds are very high or even excess compared to an anti-personnel objective. Likewise, Ph is not optimized due to the excessive value of De, since several flakes can reach the same target.

To increase the effectiveness of such a projectile, various technical solutions are possible:
- increase the burst speed; but we are limited by the energy of the explosives,
- widen the downstream downstream area; this solution is of little interest, since the distance traveled by the flakes is increased; we therefore decrease their speed and consequently Pk.

The object of the present invention is therefore to provide a projectile generating a burst of splinters covering an area greater than that covered by known projectiles, which has the consequence of giving it greater efficiency. The invention also provides a projectile generating a focused burst of shrapnel.

The subject of the invention is therefore a projectile generating a burst of splinters by operation controlled on a trajectory during a tense shot, comprising an explosive charge contained in a metal envelope, characterized in that it comprises means for varying according to its longitudinal axis x′x the ratio R of the radial thicknesses (e) of the explosive charge and (E) of the metallic envelope containing said charge, so as to modulate along the longitudinal axis the speed of the fragments.

The variation of the ratio R can be obtained by modulating the radial thickness (e) of the explosive charge.

The ratio R can be increasing from upstream to downstream, discontinuously according to several radial loading thicknesses or continuously to ensure dispersion of the chips.

The load may comprise a first slice of thickness equal to the internal diameter of the envelope, four tubular slices of radial thickness increasing towards the base, a free space being provided within these slices, and a solid slice disposed at the level of the base, of thickness equal to the internal diameter of the envelope.

The load may consist of a first slice of diameter equal to the internal diameter of the envelope and of four solid slices of increasing thickness towards the base, a free space being provided between the metallic envelope and these four slices.

The ratio R can be decreasing from upstream to downstream, discontinuously according to several radial loading thicknesses or continuous to ensure focusing of the fragments.

The load can comprise a first section of diameter equal to the internal diameter of the envelope, and four tubular sections of decreasing radial thickness towards the base, a free space being provided within these sections.

The load may comprise a first section of diameter equal to the internal diameter of the envelope, and four solid sections of decreasing thickness towards the base, a free space being provided between the metal casing and these four sections.

An inert shock-absorbing material can be interposed in the free space within the tubular sections.

An inert shock-absorbing material can be interposed in the free space between the envelope and the full wafers.

Loading can be achieved by stacking tablets.

An advantage of the present invention lies in the implementation of simple means for varying the speed of the fragments relative to the projectile, and it is surprisingly found that a small variation in this speed causes a variation in the resulting speed of the fragments relative to on the ground and therefore a great dispersion of the sheaf.

One can possibly obtain a focusing of the spray, while preserving a unique priming of the load.

• - la figure 1 illustre schématiquement la zone de répartition des éclats d'une gerbe,
• - la figure 2 représente une section partielle d'un projectile,
• - les figures 3 et 4 représentent des projectiles dans lesquels les vitesses d'éclats sont respectivement croissantes ou décroissantes d'amont en aval,
• - les figures 5 et 6 représentent une coupe d'un projectile selon deux modes de réalisation,
• - les figures 7 et 8 représentent une coupe d'un projectile selon deux autres modes de réalisation du projec­tile.

Other advantages of the invention will appear in the light of the additional description given below by way of indication in relation to a drawing in which:

• FIG. 1 schematically illustrates the area of distribution of the fragments of a sheaf,
• FIG. 2 represents a partial section of a projectile,
• FIGS. 3 and 4 represent projectiles in which the burst speeds are respectively increasing or decreasing from upstream to downstream,
• - Figures 5 and 6 show a section of a projectile according to two embodiments,
• - Figures 7 and 8 show a section of a projectile according to two other embodiments of the projectile.

FIG. 1 shows the combination of the static velocity vectors measured when the projectile is stopped in order to illustrate the zones of effectiveness of the fragments. The minimum speeds of the flakes V _{m are} measured, the maximum speeds of the flakes V _M for a known projectile of 35 mm caliber and these same speeds V ′ _m and V ′ _M for a projectile according to the invention of the same caliber. The speeds V _M and V _m of the fragments are communicated by the detonation of the explosive and are measured in a reference frame linked to the projectile. The speed V _R of the projectile is in both cases identical since it is the flight speed of the latter and it is measured relative to the ground.

The following results are obtained: KNOWN PROJECTILE PROJECTILE ACCORDING TO THE INVENTION V _R = 1000 m / s V _R = 1000 m / s V _M = 1700 m / s V ′ _M = 1700 m / s V _m = 1000 m / s V ′ _m = 700 m / s

The combination of the burst speed vectors with the flight speed delimits an area of efficiency on the ground. We see that the combination of the velocity vectors V _R and V _M or V ′ _M gives a resulting vector whose intersection with the ground gives the point A. The combination of the vectors V _R and V _m gives a resulting vector whose intersection with the ground gives the point B. The points A and B then delimit the zone P1 of effectiveness of the known projectile whose width is of the order of 3 m for a projectile initiated at 10 meters from the ground. The combination of the vectors V _R and V ′ _m gives a resulting vector whose intersection with the ground gives the point C. The points A and C then delimit the zone P2 of effectiveness of the projectile according to the invention which is of order of 5 m. It can be seen that the invention makes it possible to widen the zone of effectiveness of the projectile.

An opposite effect could be obtained by using the same means according to the invention for obtaining a focusing of the fragments. It suffices to modulate the minimum speed V _m of the flakes. It is also possible to provide focusing in two or more narrow zones by providing two or more minimum burst speeds.

In general, the vectors representing the speed of the bursts relative to the projectile are not normal to the lateral surface of the latter, but are inclined in the direction of propagation of the detonation wave inside the explosive charge .

In addition, there exists for a given projectile a maximum speed and a minimum speed of the fragments, this difference in speed being due both to the geometry of the projectile and to the distance between the initiation of the explosive charge and the considered section of the shell of the projectile. The angle between the maximum and minimum velocities and the normal to the projectile envelope is one of the factors which determines the opening of the burst of splinters and is of the order of 3 to 10 ° for a medium caliber projectile. .

In FIG. 1, in order to illustrate the zones of effectiveness of the splinters, the combination of these speed vectors has been shown in the case of an initiation by a warhead rocket (vectors inclined downstream of the projectile). For the sake of simplification, all the speed vectors are represented with a common origin which corresponds to the theoretical point called the operating point of the explosive projectile and only the directions of flakes oriented towards the ground have been represented. In reality, there is a set of velocity vectors which presents a symmetry of revolution around the axis of the projectile (if the initiation of the explosive charge is symmetrical).

In Figure 2, there is shown a partial section of a projectile of axis X′X where we see the explosive 1 thick (e) and the metal casing 2 thick (E). The thickness of the explosive will more generally be defined as being the half-difference of the external and internal diameters (when the latter exists) of the section of explosive considered. rée. In Figure 2, it is a full slice. It is well known that the speed Vx of the fragments at the level of a section of the envelope of a given explosive projectile is a function of the nature of the explosive (NatExpl), of the density thereof (Dexpl ), of the density of the envelope (Denv), of the distance of the envelope section considered at the initiation of the explosive (x), and of the ratio of the thicknesses e and E (R = e / E) .

We will write:
Vx = F (NatExpl, Dexpl, Denv, x, R)

It is also known that the speed Vx will vary like the ratio R, therefore that a low value of this ratio will cause a reduced speed and vice versa.

The ballistics of the ammunition being fixed, it becomes very difficult to vary the metal casing itself and the mass of the projectile. On the other hand, the distribution of matter, expressed by the moments of inertia and the position of the center of gravity, conditions the stability of the projectile. As a result, it is difficult to vary the three preceding factors simultaneously. Therefore, according to the invention, the ratio R is varied.

Thus, the invention proposes to modulate the speeds of the flakes along the longitudinal axis of the projectile by playing on the values of the ratio R along this same axis. Depending on the characteristics desired for the projectile (efficiency, therefore width of area covered by the fragments at a given operating height), it will be possible to define a minimum speed of the fragments (the maximum speed being that corresponding to the maximum loading of the 'envelope).

These minimum and maximum speeds will correspond to minimum and maximum values of the ratio R. The ratio R between these two extreme values will be varied continuously or discontinuously, as a function of the progressiveness desired for the variation of the burst speeds along the axis of the projectile, that is to say as a function of the homogeneity desired for the distribution on the ground of these fragments.

When the minimum value of the ratio R is incompatible with the transmission of the detonation, this theoretical value will be replaced by the minimum value actually compatible with this transmission, we will indeed play on the characteristics of the damping material.

Figure 1 shows the burst velocity vectors with a common origin located at the point of operation. In reality, for a given section of the projectile, the speed vectors have their origin at the level of said section.

FIGS. 3 and 4 show more precisely the distribution of the speed vectors along the envelope of the projectile, always in the case of a priming by warhead rocket (vectors inclined downstream of the projectile).

FIG. 3 represents a projectile in which the burst velocities have an increasing value from upstream to downstream (projectile according to the variant embodiments of FIGS. 5 and 6), this value being able to increase continuously or else in stages. The result is a scattering of the chips.

FIG. 4 represents a projectile in which the burst speeds have a decreasing value from upstream to downstream (projectile according to the variant embodiments of FIGS. 7 and 8). We then see that there is a zone of focalization of the fragments at the level of the point Ω, or rather, due to the symmetry of revolution of the projectile and the initiation, a focusing ring passing through Ω and whose axis is the axis of the projectile.

Thus, it is possible thanks to the invention to define a speed distribution of shards which ensures a concentration or focusing of the latter at a known distance from the projectile. This will be particularly interesting in the case of projectiles intended to hit aerial targets such as missiles.

In Figure 5, there is shown in section a projectile 3 which can be a medium caliber shell, of longitudinal axis x′x. It includes a head rocket 4 and a metal casing 2 made of steel. The envelope contains the explosive charge 1 consisting of six 5-10 sections of explosive. The envelope 1 can be weakened beforehand according to the method taught in the French patent cited above.

The maximum loading thickness corresponds to the case of full loading. The minimum thickness is conditioned either by the calculation of the effectiveness of the projectile, or by the value of the critical thickness of the explosive allowing the transmission of the shock wave. Depending on the desired result, the ratio R is modulated continuously or discontinuously. In the invention, examples have been described for illustrative purposes in which the ratio R is discontinuous. The wafer 5 has a thickness equal to the internal diameter of the casing 1 and the other four wafers 6 to 9 are in the form of tubular elements of decreasing thickness towards the base of the projectile. The heights of these different sections are determined so as to obtain a uniform distribution over the area to be covered. A solid slice 10 is disposed at the level of the projectile base.

The number and the height of the sections is a function of the progressiveness which one wishes to adopt between the speeds V _m and V _M. Thus, the ratio R of the thickness of the load 1 and of the casing 2 is varied increasing along the axis x′x towards the base. The speed of the flakes generated at each slice is therefore increasing in the same direction, which makes it possible to distribute the flakes more widely over the upstream and downstream zones mentioned above. In the free space within sections 6 to 9, a module 11 is placed in inert material, both in terms of detonation and that of fragmentation. Its density is equivalent to that of the explosive. As an indication, a pulverulent or compressed material similar to the ballast used in the exercise shells is used.

In Figure 5, there is shown a load 1 consisting of a cast block; one could use a load consisting of a stack of tablets corresponding to sections 5-10. These can be obtained by compression.

In order to compare the performance of a projectile according to the invention to that of a conventional projectile, a certain number of shots are taken.

A 35 mm explosive projectile according to the state of the art, the general external shape of which is that shown in FIG. 5, comprising a prefragmented envelope, for example by electronic bombardment, (see French patent cited above), is initiated at a distance from the ground of the order of 10 meters while being animated with a speed of the order of 910 m / s. The fragments are then distributed in a global zone, along the axis of fire, of the axis of fire, of the order of 3.20 meters.

The average density of shards, along the axis of fire, is then approximately 5.41.

A projectile according to the invention and more particularly in accordance with that shown in FIG. 5, provided with a module of the same density as the explosive, whose R varies between 1 and 4 gives the following results:
width of zone: 5.50 meters,
average chip density: 3.34.

There is thus a decrease in the average density of the flakes and a widening of their distribution area; which is explained by the fact that the initial velocities of the fragments relative to the projectile have decreased in the areas of lesser thickness of explosive. This leads to an increase in the opening angle of the burst of splinters. Indeed, the absolute initial speed of each burst is obtained by composition of its relative speed (decreased) with the speed of the projectile (unchanged), hence the angle of the spray is modified.

The absolute speeds of the flakes only decrease by a maximum of 20%, which nevertheless leads to an increase in the angle of the spray of 50%, the reduced reduction in speed ensures good anti-personnel efficiency over a notably larger area, hence a higher overall efficiency, the reduced density obtained (3.34) being still large enough for the probability of attack to be maximum.

Simulations have shown that this increase in the effectiveness of the projectile makes it possible to reduce the bursts of 10 shots to approximately 6 shots, which ensures an economy in ammunition.

In Figure 6, there is shown an alternative embodiment of the load 1. This load 1 consists of five sections of explosive 12-16. The thickness of these slices which are in the form of solid elements aligned on the axis x′x, increases towards the base. A damping material 17 is placed between the casing 2 and the charge 1. The role of this material is to absorb part of the energy of the explosive, which makes it possible to obtain a reduced burst speed with a greater thickness of explosive. This solution makes it possible to use the invention in the case of an explosive with a large critical thickness for the transmission of the detonation or when it is impossible to achieve a charge of small thickness. A dispersion of the same order as that of the projectile according to FIG. 5 is ensured.

In FIG. 7, other means have been shown making it possible to vary the ratio R. The load 1 comprises five sections 18-22 all being in the form of cylindrical elements, stacked on the axis x′x. Section 18 is full while sections 19-22 are annular. An inert material 23 is placed in the free space within the wafers and its role is to dampen the transmission of the shock wave as it passes. This damping increases with the thickness of the material 23 when one goes towards the base. In this embodiment, the variation of the ratio R leads to a focusing of the fragments.

In FIG. 8, another alternative embodiment is shown showing five sections of explosive. The slice 24 is identical to the slice 18 of the previous embodiment, while the slices 25-28 are formed by solid cylindrical elements aligned on the axis x′x. As before, a material 29 can be provided in the form of a single piece as shown on the left part of the figure when a single piece load is used. We can also proceed by superimposing tablets rimmed with inert materials as shown in the right part of the figure. As in the previous embodiment, a focusing of the fragments is obtained.

In the case of the interposition of a damping material, the flaking of the metal casing at the interface between the casing and the explosive is avoided. Thus, for a load of given size, the mass of the small fragments is reduced (less than 0.1 g) which represents nearly 50% of the total mass of the envelope. The number of effective shards is therefore increased.

In the previous examples, the number and the height of each section is a function of the progressiveness which it is desired to adopt between the speeds V _m and V _M.

Claims (11)

1 - Projectile generating a burst of splinters by operation controlled on a trajectory during a tense shot, comprising an explosive charge (1) contained in a metal envelope (2), characterized in that it comprises means for varying according to its longitudinal axis x′x the ratio R of the radial thicknesses (e) of the explosive charge (1) and (E) of the metal casing (2) containing said charge, so as to modulate along the longitudinal axis the speed shards. 2 - Projectile according to claim 1, characterized in that the variation of the ratio R is obtained by modulation of the radial thickness (e) of the explosive charge (1). 3 - Projectile according to claim 2, characterized in that the ratio R is increasing from upstream to downstream, discontinuously according to several radial thicknesses of loading or continuous to ensure dispersion of the fragments. 4 - Projectile according to claim 3, characterized in that the load comprises a first section (5) of thickness equal to the internal diameter of the envelope (2), four tubular sections (6-9) of radial thickness increasing towards the base, a free space being provided within these sections (6-9), and a section (10) arranged at the base, of thickness equal to the internal diameter of the envelope (2). 5 - Projectile according to claim 3, characterized in that the charge (1) consists of a first section (12) of diameter equal to the internal diameter of the envelope (2) and four solid sections (13-16) increasing in thickness towards the base, a free space being provided between the metal casing and these four sections. 6 - Projectile according to claim 2, characterized in that the ratio R is decreasing from upstream to downstream, discontinuously according to several radial thicknesses of loading or continuous to ensure focusing of the shards. 7 - Projectile according to claim 6, characterized in that the load comprises a first section (18) of diameter equal to the internal diameter of the envelope (2), and four tubular sections (19-22) of radial thickness decreasing towards the base, a free space being provided within these sections (19-22). 8 - Projectile according to claim 6, characterized in that the load (1) comprises a first section (24) of diameter equal to the internal diameter of the envelope (2), and four solid sections (25-28) of thickness decreasing towards the base, a free space being provided between the metal casing (2) and these four sections. 9 - Projectile according to claim 4 or 7, characterized in that an inert material (11, 23) shock wave damper is interposed in the free space within the tubular sections (6-9, 19-22) . 10 - Projectile according to claim 5 or 8, characterized in that an inert material (17, 29) shock wave damper is interposed in the free space between the envelope (2) and the full wafers (13- 16, 25-28). 11 - Projectile according to any one of claims 4 to 10, characterized in that the loading (1) is carried out by stacking of tablets.

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