A combined reactive and passive armour

Abstract: Reactive armour elements each holding at least one reactive assembly (8;8′) of the kind in which an explosive layer (10; 10′) is sandwiched between two metal plates (11,12;11′,12′), which is paired with a passive assembly (9;9′) comprising a layer of swellable material (13;13′) sandwiched between two metal plates (14,15;14′,15′). In each such pair the reactive assembly is outermost. Various structural and geometrical con­ figurations are disclosed.

Description: The present invention concerns elements for making a protective reactive armour to be fitted on the outside of an enclosure liable to be exposed to attack by shaped-charge warheads and kinetic energy projectiles. Examples of enclosures protectable by a reactive armour made of elements according to the invention are armoured land vehicles such as battle tanks, armoured personnel carriers, armoured fighting vehicles, armoured, self-propelled guns and the like; armoured marine vessels; armoured static structures such as buildings, above-ground portions of bunkers, container tanks for the storage of fuel and chemicals and the like; etc. A reactive armour element according to the invention may be a basic type armour made integral with a conventional passive armour element, or alternatively of the add-on type. Warheads with shaped-charge munition, also known as hollow charge munition, are known to pierce armour and thereby destroy from within objects located inside an armoured enclosure. This capacity of a shaped charge results from the fact that upon detonation there forms an energy-rich jet also known as "thorn" or "spike" which advances at very high speed of several thousand metres per second and is thereby capable of piercing even relatively thick armour walls. In US-A-4,368,660 there is described an arrangement which purports to afford protection against the penetrating effect of an exploding shaped charge. According to that proposal there is provided a continuous wall structure having an explosive layer sandwiched between two wall members of an inert material, e.g. a metal, and being so arranged that the axis of an impinging projectile and of the jet formed upon detonation, includes with the surface of the wall structure an acute angle of say 45°. According to the said U.S. patent, when a jet of a hollow charge projectile penetrates the upper surface of such a protective arrangement it initiates the explosive layer and in consequence the walls thereof are thrown apart in opposite directions, both essentially normal to their surfaces. Thus one of the wall members moves in the direction of the protected substrate while the other moves away and in consequence and due to the acute angle included between the jet and the wall member surfaces, the jet is successively intersected by different portions of the moving wall members with the consequence that the mass and energy of the jet are rapidly consumed whereby the jet is attenuated. A similar arrangement is disclosed in GB-A-1,581,125 with the sole difference that in accordance with that disclosure the arrangement of the layer of explosive substance may optionally be covered only on one side by a layer of a non-combustible material. An improved protective armour is disclosed by the present Applicants in their US-A-4,741,244 and the corresponding EP-B1-0 161,390. This improved protective armour is of the add-on type and consists of a plurality of elements each comprising a cover member having suspended therefrom on the side that faces the substrate at least one explosive insert comprising an explosive layer sandwiched between two metal plates such that when the element is mounted on a substrate the explosive insert remains distant therefrom. W087/05994 (which is the closest prior art for claim 3) discloses a reactive armour wall structure for protection against hollow explosive charge jets and comprises one or more panel structures. Each panel has the form of a closed container and contains an explosive charge which can be initiated by the hollow explosive charge jet, and which when initiated generates detonation waves in the panel structure. The panel structure includes side walls which are highly reflective to the shockwaves generated in the panel structure, such as to reflect the shockwaves onto the hollow explosive charge jet and therewith degrade the jet. A plastic or rubber material having good shockwave-absorbing properties may be placed between the panel and the object to be protected. GB-A-2 191 277 (which is the closest prior art for claim 1) discloses a composite armour combining active and passive armour and comprising a homogenous metal armour plate and a plurality of reactive armour panels. Each panel comprises a forward layer, an intermediate layer of explosive material and a rearward layer of shock-attenuating material. The rearward layers of the panels are received in recesses in the armour plate. GB-A-2 200 437 (which is the closest prior art for claim 4) discloses an explosive package for use in a reactive armour construction. Said package comprises an explosive material embedded between layers of resilient material which are contained between upper and lower rigid plates in a sandwich structure. The explosive material, preferably plastic bonded, may be contained in a waterproof jacket, e.g., a plastic bag. The layers are preferably of soft rubber, e.g., silicone rubber. The plates may be of metal, e.g., armour steel, but may alternatively comprise a composite fabric/ceramic composite. The glacis of an armoured vehicle may be covered with a spaced array of such packages. FR-Patent 865464 discloses a passive armour comprising one or more rubber layers sandwiched between two or more metal plates. The assembly serves for the attenuation of kinetic energy projectiles. Prior art reactive armours have the drawback that due to the intrinsic inertia of the reactive system and the high velocity of the jet head, a front portion of an oncoming jet manages to penetrate and reach the main armour practically without any attenuation, and although such a head portion accounts only for a fraction of the energy and mass liberated by a shaped detonating charge, it is nevertheless liable to cause damage. A further drawback of known reactive armours of the kind specified is due to the fact that in operation the innermost metal plate of the two plates between which the explosive charge is sandwiched, i.e. that plate that is closest to the main, passive armour, is hurled against the latter and the resulting impact may cause internal damage such as spalls and mechanical deformation, and also undesired shocks and vibration. In case of deformation of the inner side of a wall portion in an armoured vehicle, operative parts such as the engine, the communication system, the weaponry and the like are liable to be damaged. Similar damage is liable to occur in consequence of spalling in which case, moreover, personnel is liable to be injured by inwardly hurled spalls and hydraulic, electric and fuel systems are liable to be damaged. It is the object of the present invention to provide a new, improved reactive armour element for making a protective reactive armour free of the above deficiencies. This object is solved with the features of the claims. SUMMARY OF THE INVENTION In accordance with the present invention there is provided an element for making a reactive armour effective against shaped charge warheads and kinetic energy projectiles, comprising a casing holding at least one reactive mass and energy consuming assembly of the kind in which an explosive layer is sandwiched between two metal plates, characterized in that each of said reactor mass and energy consuming assemblies is paired with a passive mass and energy consuming assembly comprising a layer of swellable material sandwiched between two metal plates, the reactive mass and energy consuming assembly of each pair being outermost. In accordance with one embodiment of the invention the said paired assemblies are spaced from each other. In accordance with another embodiment the paired assemblies are coupled together and have a common intermediary metal plate. By a modification of such an embodiment the intermediary metal plate is removed and the layer of swellable material is applied directly to the explosive layer. A reactive armour element according to the invention may be integral with a basic armour element or be of the add-on type. The invention further provides an enclosure fitted with a reactive armour comprising elements of the kind specified. Enclosures included within the scope of the present invention comprise armoured land vehicles such as battle tanks, armoured personnel carriers, armoured fighting vehicles, armoured, self-propelled guns; armoured marine vessels; armoured container tanks for holding fuel and chemicals; armoured buildings; and the like. Where in operation a reactive armour element according to the invention is hit by a jet generated by an oncoming shaped charge warhead and forming an acute angle with the protective assemblies, the explosive charge of the reactive assembly is initiated whereupon that assembly functions as a conventional reactive armour with the two metal plates between which the explosive charge was sandwiched being thrown apart in directions normal to their surfaces. The head portion of the jet which, due to its high speed and the inertia of the reactive assembly, as a rule penetrates therethrough without any significant attenuation, is intercepted by the passive assembly in which the metal plates are driven apart by the swellable material and the mass and energy of the head portion of the jet are partly consumed whereby such head portion is attenuated. In consequence, the likelihood of any damaging perforation of the main, passive armour of the protected enclosure is significantly reduced. The main and tailing portions of the jet are then attenuated by a mass and energy consuming abrasion mechanism as explained in detail in US-A-4,741,244 and EP-B1-0161390 which explanation is herewith incorporated by reference. Upon the initiation of the reactive, mass and energy consuming assembly, the innermost metal plate thereof is thrown in direction of the main, passive armour. In its flight the plate is intercepted by the associated passive mass and energy consuming assembly and in this way the likelihood of spalling, deformation, shocks and vibrations resulting from the impact of the said innermost metal plate of the reactive assembly on the main armour is in accordance with the invention significantly reduced. It has been found in accordance with the present invention that a reactive armour made of elements of the kind specified, is also effective against armour-piercing kinetic energy projectiles such as, for example, sub-calibre projectiles and armour piercing bullets even when such projectiles do not initiate the reactive armour. In such a situation the metal plates of an associated pair of protective assemblies produce an augmented spaced armour effect which is an aggregate of the effects produced by the plates of the two assemblies and is significantly larger than in conventional reactive armour where a similar effect is produced by only one or two plates. Thus, in this way the impact of a kinetic energy projectile is also mitigated in accordance with the invention, which is a significant improvement over conventional reactive armour which is designed not to be initiated by kinetic energy projectiles. Preferably the reactive and passive mass and energy consuming assemblies that together constitute a pair of associated assemblies in accordance with the invention, are parallel to each other. They may, moreover, be either parallel to the outer wall of the casing or be mounted askew with respect thereto. Where the pair constituting associated reactive and passive assemblies are parallel to the outer wall of the casing, the reactive assembly may be attached to the inner face of the outer wall or be distanced therefrom. In the former case, the outer wall may serve as the outermost plate of the reactive mass and energy consuming assembly. The invention also provides a method of protecting an enclosure against shaped charge warheads and kinetic energy projectiles, comprising fitting such enclosure on the outside with a reactive armour made of elements of the kind specified. DESCRIPTION OF THE DRAWINGS Some specific embodiments of the invention will now be described, by way of illustration only, with reference to the annexed drawings in which: Fig. 1 is a diagrammatic longitudinal section showing elements in accordance with an embodiment according to the invention mounted on a main, passive armour; and Figs. 2 to 8 are diagrammatic longitudinal sections of further embodiments of elements according to the invention. The elements 1 according to the invention shown in Fig. 1, of which one is shown in full while only fractions are shown of the two contiguous ones are of the add-on type. Each element 1 comprises a casing 2 having an outer wall 3 and inner wall 4 and side walls 5 and is mounted on a main passive armour plate 6 by means of suitable members 7. Mounted within casing 2 are two pairs of energy and mass consuming units (the details of the mounting are not shown), consisting each of spaced reactive and passive assemblies 8, 9 and 8', 9', respectively. The two assemblies 8, 9 and 8', 9' are shown to form two, essentially parallel V-shaped configurations. Assemblies 8 and 8' are conventional reactive armour assemblies and they comprise a layer of explosive material 10, 10'sandwiched between metal plates 11, 12 and 11', 12', respectively. The passive assemblies 9 comprise each a layer of a swellable, passive energy and mass consuming material 13, 13', e.g. of rubber, sandwiched between metal plates 14, 15 and 14', 15', respectively. In Fig. 1, arrow A signifies a jet generated by an oncoming shaped charge warhead. The jet is shown to arrive normal to the outer wall 3 of casing 2 and as it penetrates therethrough it hits one of the reactive assemblies - assembly 8 in the case shown in Fig. 1 - which then functions in the conventional way as described in US-A-4,741,244 and EP-B1-0 161,390. The head portion of jet A which remains essentially unattenuated is intercepted by the associated passive assembly 9 together with the main, attenuated portion of the jet. By this interception the swellable material 13 of assembly 9 is caused to swell whereby plates 14 and 15 are pushed apart which generates a mass and energy consuming effect similar to that generated by the moving plates 11 and 12 of the reactive assembly 8. In this way the head portion of jet A is attenuated and the attenuation of the main portion of jet A achieved by operation of the reactive attenuating assembly 8 is amplified, with the overall consequence that the so attenuated jet is no longer capable of perforating the main armour 6. Due to the augmented attenuation achieved by a reactive armour according to the invention it becomes possible to reduce the thickness and weight of the main passive armour 6. In the course of operation, the innermost plate 12 or 12' of a reactive assembly 8 or 8' is thrown in the direction of wall 4 and would normally penetrate therethrough and hit the main armour 6. However, in accordance with the present invention the innermost plate 12 or 12' of a reactive assembly 8 or 8' is intercepted by the associated passive assembly 9 or 9' and in this way deformations, spalling, shock and vibration normally caused by the impact of the innermost metal plate of a reactive armour element, are significantly mitigated. A reactive armour according to the invention is also effective against armour piercing kinetic energy projectiles. Such projectiles will, as a rule, not initiate the explosive layer of the reactive mass and energy absorbing assemblies 8, 8'. This is so because in accordance with the present state of the art the layers 10 and 10' are, for reasons of safety, constituted by an explosive with a high initiation threshold. However the metal plates 11, 12, 14 and 15 and 11', 12', 14' and 15' produce a spaced armour effect which may further be enhanced by swelling of the swellable material 13, 13' and in this way the penetration capability of a kinetic energy projectile is significantly attenuated. In Figs. 2 to 8 constituent parts analogous to those in Fig 1 are designated with the same numerals. Turning first to Fig. 2 which also shows an add-on embodiment, the reactive and passive assemblies are combined into two units 15"and 15"'. Unit 15" comprises a layer of explosive material 16 sandwiched between metal plates 17 and 18 and a layer of a swellable passive energy attenuating material 19 sandwiched between metal plates 18 and 20, metal plate 18 thus being common to the reactive and passive assemblies. The structure of unit 15"' is analogous with the various components being designated 16', 17', 18', 19' and 20', respectively. Similar as assemblies 8,8';9,9' in Fig. 1, units 15" and 15"' are arranged in V-shaped configuration. In the add-on embodiment of Fig. 3, units 21, 21' are again arranged in V-shaped configuration and each holds a reactive and a passive assembly in combination. However, as distinct from the embodiment of Fig. 2, in this case the explosive and swelling layers are contiguous. Thus, in unit 21 an explosive layer 22 and a layer 23 of swellable material bear on each other and they are jointly sandwiched between metal plates 24 and 25. The second unit 21' is of similar design with the components being designated 22', 23', 24' and 25', respectively. In the embodiment of Fig. 4, the reactive armour elements 1 are integral with the basic armour 6, and the reactive and passive assemblies are spaced from each other and extend in parallel to the outer wall of the casing. Thus, the reactive assembly 26 extends in parallel to the outer wall 3 at a distance therefrom and comprises an explosive layer 28 sandwiched between metal plates 29 and 30. The passive assembly 27 is spaced therefrom and bears directly on the basic armour 6, thus forming the inner wall of the casing. Assembly 27 comprises a layer of swellable material 31 sandwiched between metal plates 32 and 33. The embodiment of Fig. 5 is again of the add-on type and comprises reactive and passive assemblies 34 and 35 extending across casing 2 in spaced relationship and in parallel to the outer and inner walls 3 and 4. The reactive assembly 34 comprises an explosive layer 36 sandwiched between metal plates 37 and 38 and the passive assembly 35 comprises a layer of swellable material 39 sandwiched between metal plates 40 and 41. In the add-on embodiment of Fig. 6 the reactive and passive assemblies are associated with respectively the outer and inner walls of casing 2. However, whereas the reactive assembly 42 is attached to an existing outer wall 3 of the casing, the passive assembly 43 constitutes the inner wall of the casing. As shown, the reactive assembly 42 comprises an explosive layer 44 sandwiched between an outer metal plate 45 that bears on the outer wall 3 of the casing and an inner metal plate 46. The passive assembly 43 which constitutes the inner wall of casing 2, comprises a layer of swellable material 47 sandwiched between metal plates 48 and 49. The add-on embodiment of Fig. 7 is essentially similar to that of Fig. 6 and the various components are designated with the same numerals. However, in this case the outermost plate 45 of the reactive assembly 42 constitutes the outer wall of the casing and the additional outer wall 3 is absent. In the add-on embodiment of Fig. 8, the reactive and passive assemblies are askew with respect to the outer and inner walls 3 and 4 and extend across the casing in parallel to each other. It comprises a reactive assembly 50 and a passive assembly 51. Assembly 50 comprises a layer of explosive material 52 sandwiched between metal plates 53 and 54 and the passive assembly 51 comprises a layer of swellable material 55 sandwiched between metal plate 56 and 57.

Claims: An add-on type element for making a reactive armour effective against shaped charge warheads and kinetic energy projectiles, comprising (a) at least one reactive, mass and energy consuming assembly (8,8') of the kind in which an explosive layer (10;10') is sandwiched between two metal plates (11,11'), and (b) at least a passive, energy consuming assembly (9,9') comprising a layer of swellable material (13,13') sandwiched between two metal plates (14,14'), (c) wherein said passive assembly is, with respect of the direction of the jet, downstream of and paired with said reactive, mass and energy consuming assembly (8,8'), (d) wherein there is a spacing between the reactive assembly and the passive assembly, and (e) wherein said swellable material is adapted to swell when hit by the jet of a shaped charge whereby the metal plate (14,14') of the passive assembly (9,9') is moved out of its original position, whereby mass and energy are consumed (Figs. 1, 4 to 8). An add-on type element according to claim 1, wherein there is a spacing between the passive assembly and the main armour. An add-on type element for making a reactive armour effective against shaped charge warheads and kinetic energy projectiles, comprising (a) at least one reactive, mass and energy consuming assembly of the kind in which an explosive layer (16;16') is sandwiched between two metal plates (17,18;17',18'), and (b) at least a passive, energy consuming assembly comprising a layer of swellable material (19,19') sandwiched between two metal plates (20,18;20',18') (c) wherein said passive assembly is, with respect to the direction of the jet, downstream of and paired with said reactive, mass and energy consuming assembly, (d) wherein there is a spacing between the passive assembly and the main armour (6), and the paired assemblies are coupled together to form a unit of paired assemblies having a common intermediary metal plate (18,18'), and (e) wherein said swellable material is adapted to swell when hit by the jet of a shaped charge whereby the metal plate (20,20') of the passive assembly (9,9') is moved out of its original position, whereby mass and energy are consumed (Fig. 2). An add-on type element for making a reactive armour effective against shaped charge warheads and kinetic energy projectiles, comprising (a) at least one reactive, mass and energy consuming assembly (21,21') of the kind in which an explosive layer (22,22') is directly in contact and parallel with a metal plate (24,24'), which is, with respect to the direction of the jet, upstream of the explosive layer (22,22'), and (b) at least a passive, energy consuming assembly comprising a layer of swellable material (23,23') which is upstream of and directly in contact and parallel with another metal plate (25,25'), (c) wherein said passive assembly is, with respect of the direction of the jet, downstream of and paired with said reactive, mass and energy consuming assembly, (d) wherein there is a spacing between the passive assembly and the main armour (6), and the paired assemblies are coupled together so that the layer of swellable material (23,23') is applied directly to the explosive layer (22,22'), and (e) wherein said swellable material is adapted to swell when hit by the jet of a shaped charge whereby the metal plate (25,25') of the passive assembly is moved out of its original position, whereby mass and energy are consumed (Fig. 3). An element according to any one of claims 1 to 4, being integral with a basic armour element (6). An element according to any one of claims 1 to 5, comprising a casing (2) with an outer wall (3), an inner wall (4) and side walls (5). An element according to claim 1 or 2, wherein the paired assemblies (8,9;8',9') are parallel to each other. An element according to any one of claims 1 to 7, wherein the paired assemblies (26,27) (34,35) (42,43) are parallel to the outer wall (3) of the casing (2). An element according to claim 8, wherein the reactive assembly (42) of a pair is attached to the inner face of the outer wall (3) of the casing (2). An element according to Claim 9, wherein the outermost plate (45) of the reactive assembly (42) serves as the outer wall of the casing (2). An element according to any one of claim 6 to 10, wherein the paired assemblies (8,9; 8',9') (50,51) are askew with respect to the outer wall of the casing. An element according to Claim 11 comprising a single pair (50,51) of reactive and passive assemblies extending across the casing (2). An element according to Claim 11 comprising two pairs (8,9; 8',9') (15,15') (21,21') of reactive and passive assemblies forming together two essentially parallel, V-shaped configurations. An enclosure fitted with a reactive armour comprising elements according to any one of Claims 1 to 13. An enclosure according to Claim 14 being an armoured land vehicle. An armoured land vehicle according to Claim 15 being a battle tank. An armoured land vehicle according to Claim 15 being selected from the group of armoured personnel carriers and armoured fighting vehicles. An armoured land vehicle according to Claim 16 being an armoured, self-propelled gun. An enclosure according to Claim 14 being an armoured marine vessel. An enclosure according to Claim 14 being an armoured container. An enclosure according to Claim 14 being an armoured building. A method of protecting an enclosure against shaped charge warheads and kinetic energy projectiles, comprising fitting such enclosure on the outside with a reactive armour made of elements according to any one of Claims 1 to 13.

Inventors: BENYAMI MOSHE, ERLICH YOAV, FRILING SAMUEL, PARTOM YEHUDA, ROSENBERG GIDEON, SHEVACH HAIM, BENYAMI, MOSHE, ERLICH, YOAV, FRILING, SAMUEL, PARTOM, YEHUDA, ROSENBERG, GIDEON, SHEVACH, HAIM
Applicants: ISRAEL STATE, THE STATE OF ISRAEL MINISTRY OF DEFENCE RAFAEL ARMAMENT DEVELOPMENT AUTHORITY
Application year: 1990
Main classification: F41H5
IPC codes: F41H5