BATTLEHEAD

Description

TECHNICAL FIELD

[0001] The present invention relates to a warhead comprising an outer casing and an inner shell, which delimits a central space for an explosive substance, in which the inner shell receives a series of preformed elements, which are arranged in contact with the outer side of the inner shell, and the inner shell is arranged for a controlled fragmentation upon a detonation of the explosive substance.PRIOR ART

[0002] Fragmenting warheads have long been known. Such warheads are often used in shells and other projectiles, but also in certain types of defence charges. The ways of triggering a detonation of the warheads vary and many different ways are known by the person skilled in the art, such as time fuses, percussion fuses, striking pins and electrical impulse currents.

[0003] Two main types of fragmentation are often mentioned, on the one hand splitting of the warhead itself, generally its casing, and on the other hand ejection of fragments which are configured and arranged in the warhead already during manufacture, so-called preformed fragments. Fragmentation of the casing can in turn be realized in two different ways, firstly by a random splitting of the casing upon detonation, and secondly by the casing having been provided with weakenings where a splitting is desired. The latter way is often referred to as controlled fragmentation.

[0004] One of many examples of preformed fragments is shown in US3974771A, in which ball-shaped fragments are arranged in spaces between an explosive charge and an outer casing. The fragments can be mutually identical or have different size and / or weight.

[0005] Examples of a fragmented casing are shown, inter alia, in US5040464A, in which a set of internally arranged grooves control the shape and mass of the fragments which are generated in a detonation.

[0006] Since the size, shape and mass of the fragments which are expelled upon a detonation of a warhead has a bearing on the effect which is achieved on the target, it is in certain cases interesting to combine preformed fragments with a controlled fragmentation in one and the same warhead. Such warheads are sometimes said to have a bimodal effect. Examples of such warheads are shown in WO2016 / 171794A1, which shows balls or other types of fragments which are arranged in grooves in a mortar shell.

[0007] Another way of achieving a bimodal effect is shown in WO2017 / 120684A1, in which two matrices of preformed elements, which are spherical and non-spherical respectively, are arranged in one and the same warhead. The two matrices are said in certain embodiments to come together into a single matrix.

[0008] The different existing warheads have different types of effect patterns and are usable for different types of targets or combinations of targets. Their effectiveness has been studied and, for targets or combinations of targets having different types of protection and weaknesses, different types of warheads having different effect patterns are suitable.

[0009] Document DE2557676A1 concerns a projectile containing fragments of depleted uranium alloy.

[0010] The projectile comprises a large number of preformed fragments embedded in the shell. These fragments are made of an alloy of depleted uranium and >=1 metal constituents. Preferably non-ferrous metal alloying constituents may be used, especially molybdenum, zirconium, cobalt, and / or tungsten. By incorporating depleted uranium in the form of fragments or "grape", the two advantages of uranium, i.e., its heavy weight and associated penetrating power and its pyrophoric action, are both rendered more effective than with a solid uranium block in the shell.

[0011] Document EP0616189A2 concerns a fragmentation body for fragmentation projectiles having structural fragments between an inner casing and an outer casing exists in a vacuum as a result of explosive forming. This fragmentation body is gas-tight as a result of welding of the inner casing and the outer casing in regions. The structural fragments are arranged uniformly distributed between the inner casing and the outer casing so that the internal and external ballistics of a fragmentation projectile which is provided with such a fragmentation body is not subject to any disturbance resulting from an unbalance or cracks in the outer casing.

[0012] Document EP0169585A1 concerns a fragmentation-type shell of the type constituted by a hollow cylindrical piece, a connecting ring and a quantity of fragments made of hard metal which are captive in a chamber provided in the hollow piece and / or the connecting ring, said hollow piece and the connecting ring being made integral with one another by means of a thread, characterized in that said thread is situated inside said hollow piece.PROBLEM DEFINITION

[0013] It is therefore wished to provide a warhead having an effect pattern which has maximum effect against a combination of semi-hard and soft targets. At the same time, the warhead must have sufficient strength to cope with stresses during transport and a possible firing.PROBLEM SOLUTION

[0014] The object underlying the invention is achieved if the warhead indicated in the introduction is given the characteristic that the preformed elements are arranged with a surface contact against the inner shell, as specified in claim 1. The warhead has a space between an inner shell and an outer casing that houses a filler material, which comprises pressed magnesium powder or pressed aluminium powder.

[0015] Further advantages are attained if the invention, moreover, is given one or more of the characteristics according to one or more of the subordinate patent claims.SUMMARY OF FIGURES OF THE DRAWING

[0016] The invention will now be described with reference to the appended drawings, in which: fig 1shows a direct side view of a warhead according to the invention; fig 2shows an axial sectional view of the warhead according to Fig 1; fig 3a and 3bshow radial sections through the warhead at two different points in its longitudinal direction; fig 4a and 4bshow a detailed view, directly from the side, of a portion of an inner casing in the warhead; and fig 5shows a detailed view of a cross section through a part of the outer wall of the warhead. PREFERRED EMBODIMENT

[0017] In Fig 1 is shown an exemplifying warhead 1, which is configured in accordance with the present invention. The outer side of the warhead 1 has a conventional design having a front and a rear body 2, 3 and an intervening middle section 4, at which the warhead 1 is dividable. The conventional outer side of the warhead 1 helps to make it suitable for use as a projectile in existing weapon systems without the need to make new procurements or adaptations of existing equipment.

[0018] The warhead 1 can be provided with further elements, such as a nose and / or tail in accordance with expert considerations. These elements can long be known, but can also be of newly developed types. The exact configuration of these elements lies outside the scope of the present invention and is in principle independent of the present invention.

[0019] In Fig 2, a section through the warhead 1 according to Figure 1 is shown. In the cross section can be seen a front 5 and a rear 6 chamber, for an explosive substance. The chambers 5, 6 are surrounded and outwardly delimited by an inner shell 7, which in turn is surrounded by an outer casing 8, which in the shown embodiment is also divided. On the outer side of the inner shell 7 are arranged a number of preformed elements 9. In the shown embodiment, the preformed elements 9 are spherical, but the invention is not limited to the case in which the elements 9 have precisely this shape.

[0020] The preformed elements 9 are recessed somewhat in the inner shell 7, preferably approximately corresponding to half its cross-sectional dimension. The recesses 10 have in the shown embodiment a cupped shape. The recess 10 is such that the inner shell 7 is in contact with the elements 9 over, broadly speaking, the whole of the recessed surface of the elements 9, which in the shown embodiment means approximately half of the total surface area of the preformed elements 9. The, relatively speaking, large contact surface between the elements 9 and the inner shell 7 results in the inner shell 7 acting as an effective sabot in order to give the preformed elements 9 a high acceleration when the warhead 1 detonates.

[0021] At the same time, the relatively large contact surface also provides a limitation in the pressure to which the preformed elements 9 are exposed when they are accelerated by the detonation, and reduces the risk of the preformed elements 9 being crushed or pulverized. Instead, they will only be slightly deformed and a high acceleration is given, resulting in a high penetrating capability in the target, for example a good penetration through armoured plate.

[0022] The preformed elements 9 are arranged one by one in the inner shell 7, without mutual contact with one another. The result of this is that they are not exposed to stresses from one another, neither during the firing phase nor upon the detonation. Since the preformed elements 9 are advantageously made of high-density heavy metal, for maximum penetrating capability, they would potentially be able to adversely affect one another in the event of mutual contact. An adverse effect of this kind could otherwise arise, for example, when the preformed elements 9 are exposed to forces from a large number of elements 9 in front of them.

[0023] In Fig 3a and 3b, two sections through the warhead 1 are shown. The cross sections are taken at different places in the longitudinal direction of the warhead 1 at two different diametral dimensions. In the cross sections can be seen how the preformed elements 9 are arranged at a distance apart in the cupped recesses 10 in the inner shell 7 also in the circumferential direction. In the shown embodiment, the preformed elements 9 are arranged with the same number of elements 9 per layer, which means that the elements 9 are arranged somewhat more sparsely in Fig 3a, in which the diameter of the warhead 1 is greater than in Fig 3b.

[0024] In Fig 4a is shown a smaller portion of some rows of the preformed elements 9, which are recessed in the inner shell 7. In this figure, it can be seen especially well that the preformed elements 9 are arranged at a distance apart, so that they are not exposed to stresses from one another, for example when the warhead 1 is fired. The distances between the preformed elements 9 also provide good opportunities to adjust the weight of the warhead 1 with high precision. In particular, opportunities are given to limit the total weight of the warhead 1, since the preformed elements 9 do not need to be stacked one upon another in order to fill a certain volume, but rather are placed in recesses in precisely that number and formation which is required to attain the intended effect in the target.

[0025] The interspaces between the preformed elements 9 are constituted by the inner shell 7 in those regions in which the cupped recesses 10 are not arranged. The material in these regions together forms a framework structure, which gives a good strength to the warhead 1 as a whole before and during the firing. The warhead 1 must withstand the loads which arise during both transport and storage and upon a possible firing.

[0026] When the warhead 1 detonates, the inner shell 7 will by contrast be split into smaller parts which are accelerated at the same time as the preformed elements 9 are accelerated, and the outer casing 8 is splintered. The detonation forces herein act from inside on the inner shell 7, the preformed elements 9 and the outer casing 8. It is an object of the invention that the shape and size of the smaller parts of the inner shell 7 are controllable, so that the desired effect on the target is obtained, primarily as regards soft targets. The inner shell 7 will be broken up in the cupped recesses 10, since the material in the inner shell 7 is at its thinnest there. Fracture will also occur in the direction transversely to those portions of the inner shell 7 which have full thickness. Through the arrangement of the cupped recesses 10 in a systematic pattern over the whole of the surface of the inner casing or of the inner shell 7, a deliberate, controlled fragmentation of the inner shell 7 is achieved.

[0027] In Figure 4b, the approximate appearance of a fragment 11 which is the result of the controlled fragmentation is sketched. Further fragments 11 with broadly corresponding appearance and mass will be obtained, since the cupped recesses 10, and the material weakenings which they bring about, are arranged in a pattern which is repeated over the whole of the inner shell 7. At the same time, the cupped recesses 10 have a parallel function in that they help to hold the preformed elements 9 in place prior to the detonation and to accelerate them gently in connection with the detonation.

[0028] The fragments 11 which are the result of the controlled fragmentation therefore have a size and mass which is effective against semi-hard targets. The preformed elements 9 act primarily against hard targets, such as armoured plate, whilst the splinter from the outer casing 8 acts primarily against soft targets. In certain embodiments, the outer casing 8 is also configured with a controlled fragmentation, which in certain cases resembles the controlled fragmentation of the inner shell 7, but in other cases is configured according to the prior art in the field.

[0029] The cupped recesses 10 in the inner shell 7, which is often made of steel, are achieved with any suitable production technology, such as machine cutting, powder metallurgy technology, casting or additive technology, etc. The thickness of the inner shell 7 at the bottom of the cupped recesses 10 is in an advantageous embodiment 0.4-0.5 times the characteristic length of the preformed elements 9, since the inner shell 7 is made of steel and the preformed elements 9 are made of heavy metal. In other materials and combinations of materials, other mutual size relationships can apply. Should the preformed elements 9 be spherical, the characteristic length is the diameter thereof.

[0030] In a practical illustrative embodiment, the diameter of the spherical heavy metal elements 9 is 10 mm, and the thickness of the steel inner shell 7 at the thinnest point is about 5 mm. The recesses 10 have a depth which corresponds to approximately half the characteristic length, which results in the thickness of the inner shell 7 at the thickest point being in this case about 10 mm.

[0031] In Fig 5, a portion of the inner shell 7, the preformed elements 9 and the outer casing 8 are shown in detail in a cross section. The space 12 between the inner shell 7 and the preformed elements 9 on the one hand, and the outer casing 8 on the other hand, are filled with a filler material 12, which holds the preformed elements 9 in place. The filler material 12 also seals against gases from the detonation, for an effective acceleration of the preformed elements 9 and the fragments 11 from the controlled fragmentation.

[0032] The filler material 12 has low density, such as plastic, epoxy, pressed magnesium powder or pressed aluminium powder, etc. The total mass for the warhead 1 can thus be kept down to reasonable levels, despite the fact that the preformed elements 9 are often made of heavy metal. A limitation of the mass facilitates the general handling of the warhead 1, but also has the advantage that the warhead 1 acts together with existing weapon systems without these needing to be adapted to any major extent.ALTERNATIVE EMBODIMENTS

[0033] In the above description and the drawing, the warhead 1 has been shown as a dividable projectile. The dividability is not a precondition for the invention being able to function according to the above description, but rather it can very well be made non-dividable according to the principles for producing warheads which are known to the person skilled in the art in the field. Nor is the invention limited to just projectiles, but is usable in any permitted form of warhead.

[0034] As has also been mentioned in the description above, the invention is not limited to preformed elements 9 which are spherical, but rather any other shape which the person skilled in the art, through routine tests, finds gives the aspired result, is conceivable as an alternative.

[0035] Also the shape of the fragments 11 which is the result of the controlled fragmentation is variable by varying the size of and distance between the cupped recesses 10. The mutual position thereof also affects the size and shape of the fragments 11. As an alternative to the rings of recesses 10 which are shown in the drawings, the recesses 10, for example, can be arranged in rows which are substantially parallel with the longitudinal axis of the warhead, in spiral pattern, etc. In a further alternative embodiment, the recesses 10 are arranged in different configurations on different parts of the inner shell 7 in order to achieve different kinds of directivity. A further alternative is that the recesses 10 are arranged so that the strength of the warhead 1 is affected, preferably in the positive direction. One way of achieving this is to arrange the recesses 10 at greater distance apart where the stresses can be assumed to be greatest, for example at the base of a shell which is to be fired from a barrel.

Claims

1. Warhead (1) comprising an outer casing (8) and an inner shell (7), which delimits a central space (5, 6) for an explosive substance, in which the inner shell (7) receives a series of preformed elements (9), which are arranged in contact with the outer side of the inner shell (7), and the inner shell (7) is arranged for a controlled fragmentation upon a detonation of the explosive substance, wherein the preformed elements (9) are arranged with a surface contact against the inner shell (7), wherein the preformed elements (9) are arranged without mutual contact with one another, at a distance apart in circumferential direction; wherein the outer casing (8) is configured with a controlled fragmentation upon the detonation of the explosive substance; wherein the preformed elements (9) act primarily against hard targets, such as armoured plate, whilst the splinter from the outer casing (8) acts primarily against soft targets; wherein a space between the inner shell (7) and the outer casing (8) houses a filler material (12), characterized in that the filler material comprises pressed magnesium powder or pressed aluminium powder.

2. Warhead (1) according to Claim 1, characterized in that the inner shell (7) comprises recesses (10), which are arranged to distribute the force from the detonation amongst the preformed elements (9), and wherein the preformed elements (9) are recessed.

3. Warhead (1) according to Claim 2, characterized in that the recesses (10) in the inner shell (7) are arranged to act as weak links upon the detonation, for the controlled fragmentation of the inner shell (7).

4. Warhead (1) according to any one of Claims 1 to 3, characterized in that the thickness of the inner shell (7) is of the same order of magnitude as the preformed elements (9).

5. Warhead according to Claim 1, characterized in that the density of the filler material (12) is lower than the density of the inner shell (7) and the preformed elements (9) respectively.

6. Warhead according to Claim 1, characterized in that the filler material (12) bears against the preformed elements (9).