FR2730558A1 - Fragmentation weapon with increased destructive power - Google Patents

Abstract

The fragmentation weapon consists of an explosive, a detonator and a fragmentation layer with inner (15) and outer (21) surfaces, fragmenting along pre-cut lines. The fragments are shaped so that their lateral surfaces (16, 19, 20) are oblique and angled alternately inwards and outwards. This ensures that the surfaces of adjacent fragments remain in contact in the initial moments after the charge has been exploded, providing a resistance to the explosive gases and giving the fragments increased energy and range.

Description

 This invention is in the field of military flash charges. It relates more particularly to the burst generator.

 A military burst charge mainly comprises a burst generator at least partially surrounding an explosive, the energy of which is used to propel the bursts. The energy tank constituted by the explosive is activated by a priming system.

 The shards generator is generally prefragmented in order to calibrate the shards in optimal size and mass guaranteeing the functional or structural destnjctjon of the target.

 Many means for prefragmenting the generator are known in the art. By way of example, mention will be made of the grooving of the generator, the external grooving of at least part of the explosive charge as described for example in patent FR 2,502,768 of the Applicant, or the grooving of a wedging material placed between the explosive and the generator as known from US Pat. No. 4,745,864, or else local weakening of the mechanical properties of the generator by electron bombardment. Generators can also be produced by a stack of notched rings or by winding around the explosive of a notched bar.

 Examples of embodiment of flash charges according to the prior art are shown in FIGS. 1, 2 and 3.

 These examples all relate to loads of revolution around a longitudinal axis. Such charges equip, for example surface-to-air or air-to-air missiles.

 In FIGS. 1 to 3, the elements having the same function bear the same reference numbers.

 Figure 1 includes Figures la, lb, and I c. These are military charges 10, represented in a longitudinal section, comprising a burst generator I constituted by a ferrule of revolution around the longitudinal axis XX of the charge. The ferrule has along the axis XX 'two ends 2, 3. At each end of the ferrule is fixed a flange 4, 5. The flanges 4, 5 and the ferrule 1 determine an internal volume 6 of the load. The interior volume 6 comprises an explosive 7 which fills the entire volume with the exception of a cylindrical central channel 8 centered on the axis XX. The central channel 8 houses in its middle a priming boost relay 9.

 Depending on the shape that we want to give to the sheaf of splinters, the splinter-generating shell 1 can have a cylindrical shape as shown in FIG. 1 a or concave or even convex as shown in FIG. 2b and 2c respectively.

 The chip generator can also, as shown in FIG. 2, be produced by a stack of notched rings II surrounding the explosive. Figure 2 includes Figures 2a and 2b.

 Figure 2a shows a longitudinal section of the load. FIG. 2b represents a top view of a ring 11. Each ring It has internal notches 12. The notches 12 and the height of the ring determine the size of the fragments to be obtained. The notches 12 are generally formed by grooves having a symmetry with respect to a local radial plane.

 Finally, the splinter generator can, as shown in FIG. 3, be produced by winding a notched bar around the explosive 7. FIG. 3, comprises FIGS. 3a, 3b and 3c.

 FIG. 3c represents a side view of a notched bar 13.

This bar has notches 12. When the bar 12 is wound around the explosive, these notches are traced according to local radial planes. Consisting of such a wound bar 13, the splinter generator 1 can of course have a cylindrical shape but also without difficulty in producing a convex or concave shape as shown in longitudinal sections of charges in Figures 3a and 3b respectively.

To the many advantages brought by the prefragmentation of the burst generator:
- precise calibration of the fragments;
repeatability of the characteristics of the burst of bursts in speed and angle;
- better directed effect; Added to this is the problem posed by the early rupture of the weakened generator and by the early leakage of the detonation gases generated by the explosive.

In general, and whatever the embrittlement process of the generator adopted, it is regrettable that, in the current solutions used, the mechanical rupture of the envelope is immediately accompanied by the leakage of the detonation gases from both others of the fragments generated. This effect has the direct consequence of limiting the modulus of the speed of expulsion of said fragments.

 This early escape is shown by arrows in Figure 4.

This figwe includes Figures 4a and 4b. Figure 4a is a cross section of a load made according to one of the models shown in Figure 1 to 3. Figure 4b is a partial longitudinal section. The flakes 14 are materialized by their projection perimeter. These flakes 14 are created from the lines of embrittlement obtained by the aforementioned means, from the start of the explosion, under the combined effect of the shock wave created by the explosion and the pressure of the decomposition gases. Each of these flakes has an internal face 15 facing the explosive, a side face 16 which includes all the surfaces which before the burst formed a body or were in contact with the rest of the flake generator.

 In the example shown in Figure 4, this lateral surface has four faces, two opposite faces 17, 18 located in planes perpendicular to the longitudinal axis XX 'of the load and two opposite faces 19, 20 located in radial planes of the charge. Each chip finally has an external face 21, opposite the internal face 15.

The acceleration of the flakes results, like their generation, from the shock wave and from the pressure of the gases exerted on their internal face 15. The arrows of FIG. 4 materialize the lines of flight of the gases. We see that as soon as the flakes begin their movement, they start to move away from each other, the gases of the explosion intrude into the interstices between the flakes. The pressures exerted on the lateral surfaces 16 of the flakes then tend to further separate the flakes from each other. This initial separation has two effects.

 On the one hand, the gas leakage rate between the flakes 14 increases rapidly, so that the pressure exerted on their internal face 15 also decreases rapidly. This helps to decrease the speed taken by the shards. On the other hand, the pressure exerted on the lateral faces from the start of the explosion contributes to giving the flakes a speed directed along the axis of the load and therefore to an axial dispersion of the flakes. This dispersion is not always desired.

 The present invention aims to increase the speed and therefore the energy of the flakes on the one hand and better control the spray of these flakes around a median transverse plane of the load.

 Structurally, the proposed improvement consists in extending the tightness of the generator after its mechanical failure by an appropriate definition of the prefragmentation characteristics of the chip generator.

The solutions proposed apply in the preferred modes to embrittlement by notching of rings or of wound bars, but they are also applicable to any generator of flakes.

 For all these purposes, the subject of the invention is a military charge comprising an explosive, firing means, and a burst generator, the generator having two faces, an inner face turned towards the explosive and an outer face turned towards the outside of the load, the distance between the internal face and the external face constituting the thickness of the flat generator, the load or the generator itself having means for creating from the generator, flakes having an internal face constituted by a part of the internal face of the generator, an external face constituted by a part of the external face of the generator, the distance between the internal and external faces of the chip constituting the thickness of the chip, a chip having a side face joining the internal and external faces of the load being characterized in that the means for creating the flakes are arranged so that two contiguous flakes A and B have for a first, A surface of internal surface sup higher than its outer face surface and for a second B an outer face surface greater than its inner face surface.

 When contiguous flakes have, as specified for the invention, internal surfaces which are alternatively larger then smaller than their external surfaces, this means that the lateral surface of one of the flakes widens from inside to outside whereas for the immediately contiguous shine, the lateral surface, on the contrary, widens from the outside towards the inside of the load.

 In general and in particular when the generator is constituted by a stack of notched rings or by winding a notched bar, the internal and external faces of the flakes have substantially rectangular shapes. In this case, according to a first embodiment of the invention, only the faces parallel to the axis of the load widen from the inside of the load towards the outside, and for a following burst from the outside. towards the inside.

 When it is said that the faces parallel to the axis of the load widen from the inside to the outside, we mean that the angular sector cut out on the internal and external faces is larger on the face outer than on the inner side. On the contrary, the angular sector cut out on the outer face is smaller when the faces parallel to the axis widen from the outside towards the inside.

 We know that the external surface of a burst generator is larger than its internal surface. As a result, in general, the external surface of a chip is larger than its internal surface, the ratio between the two being substantially equal to the ratio between the total external surface of the generator and its total internal surface. When we say that for a luster the external surface is larger than the internal surface it means that the ratio of the external surface of the luster to its internal surface is greater than the ratio due simply to the fact that the external surface of the generator is larger than its internal surface. In the first example of embodiment as in the second which will be explained below, there are shown perimeters of brightness cut constituted by straight line segments.

 However, it is not excluded that the junction surface between the inner and outer faces of a chip such as it results from a prefragmentation is a curved surface. The important thing is that the lateral surfaces of flakes thus created in the thickness of the generator cut out for consecutive flakes internal and external surfaces which are altematively larger and smaller than their external and internal surfaces respectively.

 In a second embodiment, only the faces opposite one another along the axis of the load go for adjoining splinters alternately flaring or converging from the outside to the inside.

 In the preferred embodiment, the flakes include both the features of the first and second embodiments. The fragments are then formed by pyramid trunks with substantially rectangular bases, the large faces of which are alternately the inner faces then the outer faces.

Explanations as to the mode of operation of the invention and various embodiments will be given with reference to the appended drawings in which:
- Figures 1 to 4, with commentaries representative of the prior art, are intended to illustrate some known embodiments of generators of pre-fragmented flakes (Figures 1 to 3) and their mode of operation at the start of the explosion (Figure 4).

 - Figure 5 is intended to illustrate the mode of operation of the invention.

- Figure 6 illustrates a first embodiment of the invention;
- Figure 7 illustrates a second embodiment of the invention;
- Figure 8 illustrates a third embodiment of the invention;
- Figure 9 shows a longitudinal section of a load with a splinter generator consisting of a stack of rings;
- Figure 10 shows a top view of a conventional ring produced according to the prior art to equip the load shown in Figure 8;
- Figure II shows a top view of a ring produced according to the invention;
- Figure 12 shows comparative curves between the burst speeds obtained with the load of Figure 9 equipped with rings according to the prior art and the same load equipped with rings according to the invention.

 Figure 5 includes Figures 5a and 5b. FIG. 5a represents a view in an axial direction of a part of a splinter generator according to the invention.

 In FIG. 5a, the generator is shown at the instant to at which the shock wave caused the generator to break along the prefragmentation lines. The fragments although separated from each other from this moment are still in contact with each other by their lateral surfaces 16. The fracture lines have separated the fragments into fragments A and fragments B. The surface of these latter has been shown hatched. The pressure coming from the detonation gases of the explosive is exerted on the internal faces 15 of the fragments. A flake A alteme with a flake B. The flakes A have an internal face surface 15 which is greater than that which this same internal surface would have if it resulted from an interception by an angular sector equal to the angular sector intercepted by the face ext 21.

 The flakes B have an internal surface 15 which is less than the surface that this same internal surface would have if it resulted from an interception by an angular sector equal to the angular sector intercepted by the external face 21 of the flake B. The flakes A are therefore subjected to a stronger acceleration than that of the flakes B.

 At the instant to + At shown in FIG. 5b the flake A has traveled a greater radial distance than that of the flake B and it exerted on the lateral faces 19 of each of the contiguous flakes B, a pressure continuing to maintain l 'tightness between the different flakes whose meeting constituted before the explosion a ring. In an embodiment intended to validate the concept of the charge and which will be discussed later, the flakes A also had a mass less than that of the flakes B so as to increase the ratio between the acceleration of the flakes A and that flakes B.

 FIG. 6 represents a top view of a ring, of a flash charge according to the first embodiment of the invention.

 The burst generator is produced by a stack of rings II similar to that shown in FIG. 2b. Compared to the ring shown in Figure 2b, only the orientations of the notching lines change. The notching lines are not radial. A first notch line 22 made with a radial, passing through the point where the notch line 22 crosses the inner surface of the ring at a positive angle. Each notching line 22 is contiguous to two notching lines 23 which, with the radial passing through the point where the notching line 23 crosses the internal surface of the ring, a negative angle. Thus, this first version of the invention consists in delaying the leaks of detonation gas appearing between the adjacent fragments of the same circumference by a particular orientation of the notch.

 The detonation of the explosive charge, followed by the inflation of the generator, then its mechanical rupture initiated at the bottom of the notch, generates two types of so-called A and B decasts, of the same efficiency, but whose positioning relative to the start of the explosion favors the sealing for a few additional moments during which the transfer of internal energy into kinetic energy continues.

 The flake A is characterized by an apparent surface facing the detonation products, greater on which the thrust force relative to the mass of the flake is increased. In addition, the mass of this chip is preferably slightly lower than that of a chip B, which causes a reduction in the inertia on expulsion. it follows a radial displacement of the flakes, specific to their type, favoring a relative sliding of the contiguous flakes almost sealed in the equatorial plane of the military charge.

 In the second embodiment of the invention, the splinter generator 1 is constituted by a stack of rings of two types, rings C and rings D. This embodiment of the invention is shown in FIG. 7, the surface of the internal face of a ring C is larger than its external surface.

 On the other hand, for each ring D immediately adjacent to a ring C, it is the external surface of the ring which is greater than that of the internal surface.

 Figure 7 includes Figures 7a, 7b, 7c. FIG. 7a represents an exploded longitudinal section of part of a flat generator 1 constituted by a stack of notched rings. In the case shown, these are type C 24 rings all similar to each other and type D25 rings also similar to each other. With the possible exception of the end rings in contact with the flanges 4, 5 (not shown in FIG. 7), each ring has symmetry with respect to a plane perpendicular to the longitudinal axis XX '. The rings C have an inner face 26 and an outer face 27. They also have two opposite faces 30, 31 symmetrical with respect to a plane perpendicular to the axis XX. This last provision is not obligatory; it constitutes only an ease of realization. The rings D25 have an inner face 28 and an outer face 29. they also have two opposite faces 32, 33 symmetrical with respect to a plane perpendicular to the axis XX '. The rings C altement with rings D. The rings C have an axial length, measured parallel to the axis XX ', which decreases from their inner face 26 to their outer face 27. The rings D have an axial length which goes decreasing from their outer face 29 to their inner face 28. The opposite faces 30, 31 of a ring C located between two rings D are in contact respectively with the faces 33 of the first contiguous ring D and 32 of the second contiguous ring D. If ron defines for the axial line X) C, a front direction and a rear direction, this means that the rear face of a ring C is parallel to the front face of a ring D and that the front face of a ring C is parallel to the rear face of a ring D.

 The rings C and D can be notched as in the prior art shown in Figure 2b. They will preferably be notched according to the first embodiment of the invention, as shown in FIG. 6.

 The mode of operation of the second embodiment of the invention will now be explained with reference to FIGS. 7b and 7c.

 FIG. 7b represents a section through an axial plane of three flakes cut out of three successive rings, a central ring C and two rings D contiguous to this ring C. The central flap bears the reference 34 and the other two the references 35 and 36 respectively. The ring 34 has an inner face 37 which is a part of the inner face 26 of the ring C to which the chip 34 belongs. It has an external face 38, a front face 39 and a rear face 40. Similarly, the rings 34 and 36 each have an internal face 41 an external face 42, a front face 43 and a rear face 44.

 FIG. 7b represents the flakes 34 to 36 at the instant to of their formation.

 Figure 7c shows them a short time after the start of the explosion. The surface 37 of the internal face of the flake 34 is greater than the surface of the external face 38. For the flakes 35 and 36, it is the opposite, the surfaces of the internal faces 41 are smaller than the external surfaces 42.

The chip 34 is therefore subject to a stronger acceleration than the adjacent chips 35 and 36.

 The front 39 and rear 40 faces of the chip 34 slide along the rear faces 44 of the front chip 36 and the front 43 of the rear chip 35. This contact ensures prolonged sealing. This seal can in principle be maintained until the inner face 37 of the chip 34 arrives at the outer faces 42 of the chips 35 and 36.

 It will be noted that the same effect can be obtained with two notched bars profiled alternatively to present the profile of a developed ring C then D or D then C. The two bars are wound simultaneously.

 This embodiment is illustrated in Figure 8. This figure includes Figures 8a and 8b.

 FIG. 8a represents a perspective view of two pieces of bar used to make a spark gap.

 FIG. 8b represents a perspective view of a half-section of a splinter generator 1 produced according to this design.

 The generator 1 according to the invention is in this embodiment produced by simultaneous winding of two bars C and D designated in FIG. 8a by the references 45 and 46. Only pieces of these bars have been shown, the length of the bars must be sufficient to cover the area provided for the spark gap. The bar 45 extends along a longitudinal axial line YT and the bar 46 along an axial line ZZ. The axial line is a line passing through the geometric center of a cross section of the bar and substantially parallel to the surfaces delimiting the bar longitudinally.

 In the example shown in FIG. 8a, these are four flat faces whose cross section is a surface in the shape of a truncated triangle.

Naturally and as already explained above, these surfaces could be curved surfaces. The bar 45 has two opposite faces 47, 48. The surface of an element of length of the face 47 is smaller than the surface of the same length of the face 48. The bar 46 has two opposite faces 49, 50. The surface of an element of length of the face 50 is smaller than the surface of the same length of the face 49. The faces 47 and 49 of the bars 45 and 46 each form after winding part of the internal surface 55 of the spark gap. The opposite faces 48 and 50 of the bars 45 and 46 respectively each form a part of the outer surface 56 of the spark gap 1. Two other faces 51, 52 and 53, 54 for the bars 45 and 46 respectively join the opposite faces 47, 48 for the bar 45 and 49, 50 for the bar 46. During the winding to make the spark gap, the faces, for example 52 of the bar 45 and 53 of the bar 46, come into contact with one of the wall. After a first helical winding turn of the two bars, it is the face 54 of the bar 46 which comes into contact with the face 51 of the bar 45.

 The two bars 45 and 46 are prefragmented by embrittlement obtained by any known means, for example with notches which can be either in planes perpendicular to the axial line, or alternatively and preferably in planes forming with local planes perpendicular to the axial line of the alternatively positive then negative angle bars.

 The spark gap 1 obtained by such a helical winding of the two bars 45 and 46 is shown in FIG. 8b. This winding is carried out around an axial line X) of the spark gap. The internal face 55 of the spark gap is formed by the addition of the surfaces of the small face 47 of the bar 45 and the large face 49 of the bar 46. The external face 56 of the spark gap is formed by the addition of the surfaces of the surfaces 50 of the small face of the bar 46 and 48 of the large face of the bar 45. In the rolled position the opposite faces 51 and 52 of the bar 45 converge towards each other, the line of convergence of the plane of these two faces while remaining tangent to a helix-shaped convergence curve parallel to the helix-shaped curve described by the axial line of the bar 45. Similarly, the opposite faces 53, 54 of the bar 46 converge rune towards the other, the line of convergence of the plane of these two faces turns while remaining tangent to a curve of convergence in the form of helix parallel to the curve in form of helix described by the axial line of the bar 46. The convergence curve of the faces 51, 52 is closer to the axial line XX ' of the spark gap as is the convergence curve of the faces 53, 54 of the bar 46 which converge them towards the outside of the spark gap.

 In the preferred embodiment the rings or notched bars forming the generator have both the characteristics shown in Figure 6 and Figure 7b so as to extend the seal both in equatorial planes and along the axis XX '.

 The tests carried out and which will be discussed below with the aid of FIGS. 9 to 12 show that there is, for a load carried out with a burst generator according to the invention, improvement in the kinetic energy communicated to the bursts by compared to the same charge produced with a burst generator according to the prior art.

 FIG. 9 represents a longitudinal section of a load used to carry out the tests, the results of which will be discussed below. It is a cylindrical charge 10, without a central channel comprising priming means 9, composed of a detonator and a relay. The charge contains an explosive 7. This explosive is surrounded by a burst generator 1 constituted by a stack of rings 11. Fiasques 5, 4 close the charge 10 at its ends 3, 2.

 The burst generator 1 is further maintained by a ferrule 55 intended to ensure structural rigidity of the load, rigidity required due to the carrying conditions provided for this load. This configuration, with ferrule 55, is a priori less favorable for verifying the expected results of the invention than a configuration which would not include a ferrule.

 Without changing anything either in the explosive or in the means of ignition, in the number of rings or in their external shape, this charge was tested with two modes of notching the rings. In a first configuration shown in FIG. 10 seen from above, the rings 11 have been notched according to radial notches 12.

 In a second configuration shown in FIG. 11 seen from above, the rings II have been notched with notches 22, 23 like those shown in FIG. 6 and described above during the description of this figure.

 The average of the results obtained is represented by the curves f, g, h, in FIG. 12.

 These curves represent the average speed of the flakes expressed in hundreds of meters per second as a function of their longitudinal position in the load of figure 9. The middle of the load is marked 0.

The end opposite to the priming is marked -100. The priming end is marked +100. The generator flakes shown immediately after fracturing in Figure 10 all had a mass of 2.9 grams. The generator flakes shown immediately after fracturing in figure II had a mass of 2.9 grams for the A flakes and a mass of 3.2 grams for the B flakes, the total mass of the flakes being the same in both cases.

 The average measured speed of the bursts of the generator according to the prior art, as shown in FIG. 10, is the subject of curve h.

 During the test of the improved prototype represented in FIG. 11, two families of flakes differentiated in speed and individual mass were obtained.

 The first family which corresponds to the fragments A is the object of the curve.

 The second family is the subject of curve g.

 The inventor believes that a single mass of splinters could be easily obtained, if this is specified, by a simple adjustment of position of the notches without affecting the overall performance of the load.

 The measurement of the speeds respectively obtained during the two tests makes it possible to evaluate at around 10% the gain in kinetic energy MV2 of the flakes impacting the target and this by simple evolution of the orientation of the notching of the rings This gain results from the invention carried out according to the first mode only.

Claims (7)

 1. Military charge (10) comprising an explosive (7), firing means (9), and a decay generator (1), the generator having two faces, an internal face facing towards the explosive and an external face towards the outside of the load, the distance between the internal face and the external face constituting the thickness of the flat generator, the load (10) or the generator (1) itself having means (12) to create at from the generator (1) of the flakes (14) having an internal face (15) constituted by a part of the internal face of the generator (1), an external face (21) constituted by a part of the external face of the generator (1 ), the distance between the internal and external faces of a chip (14) constituting the thickness of the chip, The piece (14) having a lateral face (16) joining the internal (15) and external (21) faces, the load being characterized in that the means for creating the pieces (14) are such that two contiguous pieces A and B have for a first A, an inner face surface (15) greater than its outer face surface (21) and for a second B an outer face surface (21) greater than its inner face surface.  2. Military charge (10) according to claim 1, in which the burst generator (1) consists of a stack of rings (11), the means for creating the bursts being constituted by notches (22, 23) load (10) characterized in that the notches (22, 23) make with a local radial plane of the ring (11), alternatively a positive angle then a negative angle.  3. Military charge (10) according to claim 1, in which the burst generator (1) consists of a helically wound bar, the means for creating the bursts being constituted by notches (22, 23), charge characterized in that that the notches make with a local radial plane of the propeller, alternatively a positive angle then a negative angle.  4. Military charge according to claim 1, in which the burst generator consists of an alternative stack along a longitudinal axis of the charge, of notched rings of type D (25) and of type C (24) each ring having a front face (31, 32) and a rear face (30, 33), load characterized in that for a D-type ring (25) the front face (32) has a frustoconical surface, the apex of the cone defining this surface being located behind this face (32) on the longitudinal axis, the rear face (33) has a frustoconical surface, the apex of the cone defining that rear face (33) being located in front of this face on the longitudinal axis and in that the rear face (30) of a contiguous ring of type C situated in front of this first ring is parallel to the front face (32) of the first ring (25) and in that the front face (31) a contiguous type C ring located behind this first ring (25) is parallel to the rear face (33) of the first ring (25).  5. Military charge (10) according to claim 4, characterized in that the notches (22, 23) of the rings (24, 25) form with a local radial plane of the ring (24, 25) alternately a positive angle then a negative angle.  6. Military load (10) according to claim 1 in which the declination generator is constituted by two pre-fragmented bars having a longitudinal line, wound helically around a longitudinal axial line of the load, a first bar C (45) and a second bar D (46) each of the bars (45, 46) having four faces (47, 48, 51, 52; 49, 50, 53, 54) of which two faces, a first (47, 49) and a second (48, 50 ) constitute parts of the internal and external surfaces of the spark gap and of which two other faces of each bar, a third (51, 53) and a fourth (52, 54) are parts of surfaces converging together towards a line of convergence substantially parallel to the longitudinal line of each bar, the line of convergence of the first bar (45) being closer to the axial line of the load than the longitudinal line of this first bar and the line of convergence of the second bar (46 ) being further from the longitudinal line of the load than is the longitudinal line of this second bar (46).  7. Military charge according to claim 6, characterized in that the preframentation lines of the bars (45, 46) form with a local radial plane of the bar (45, 46) alternatively a positive angle then a negative angle.