HYBRID EXPLOSIVE UNIT

Abstract: A hybrid explosive unit which is intended for artillery shells or anti-tank mines and which comprises a casing (2), an explosive charge (1) in the casing defining, at the upper end thereof, an upwardly facing hollow, a dished element (5) lining said hollow, a metal cylinder (4) embedded in said charge (1) and extending through the middle of said dished element (5), a sheath (8) of inert material surrounding said cylinder (4), said cylinder (4) and said sheath (8) being adapted together to form a first projectile of high penetrating power, and a member of inert material (3) embedded in said charge (1) across the lower end of said cylinder (4) and of said sheath (8) and adapted, upon the unit being fired, to act as an attenuator and diffractor of the resulting direct detonation wave, said member (3) and said dished element (5) being adapted together to form a second projectile of high penetrating power which travels behind the first upon the unit being fired.

Description: Hybrid explosive unit The present invention relates to a hybrid explosive unit, i.e. comprising a detonating explosive and inert material. Known explosive units used in ventral action anti-tank mines require, in orde to function satisfactorily, an auxiliary charge which, prior to detonation of the main charge, displaces the earth covering the embedded mine. In addition, the constituent parts of the mine in the blast zone of the hollow charge dis¬ rupt the formation of the blast and cancel out the penetrating effect. In ac¬ tual practice, providing an auxiliary charge presents numerous problems, amongst others the setting of the delay time for the detonation of the main charge with respect to the auxiliary charge and the force of the auxiliary charge. Other problems are of an external nature and are caused by different types of terrain in which mines may be embedded, ranging from the extreme mobility of sandy terrain to the extreme hardness of frozen terrain. In British Specification 2,039,008A there is disclosed an explosive unit in particular intended for use in anti-tank projectiles, comprising at least two hollow tandem charges of unequal power operating in cascade, one charge being fired first and constituting the exciter charge disposed behind the main charge, a single priming device in the form of a frusto-conical annular body for firing both charges. The blast of the exciter charge is adapted to pass through an axial opening and thus penetrate into the main charge. The system is fired by means of a single priming unit excited by a detonator. A screen disposed between the priming unit and the exciter charge has the effect that the detonation wave produced by the exciter charge is transmitted to the main charge by means of a pyrotechnical relay which functions either as an "acce- OV?I ls Swiss Specification 475,543 relates to a hollow charge for anti-tank land mines. The explosive charge is housed in a casing which is closed by a conica insert which displays an angle of substantially 90° and which is disposed ove the hollow charge, the apex of the conical insert being cut off and replaced by a cone of inert material. In German Specification 1901 472 C there is described an explosive head for combating tanks, comprising two hollow charges (primary and secondary) which are activated one after the other. The casing containing the hollow charge i closed at its lower extremity by a disc held in position by a retaining ring. An element is located in an axial hole formed in the disc and a point in the middle of a transmission plate extends into the said element. The rear surfa of the primary charge defines a caving adapted to receive a two part deflect constructed of inert material. It is an object of the present invention to provide a hybrid explosive unit, in particular for anti-tank mines having a ventral action, able to penetrate the armour plating of the underside of tanks, even when the mines are embedd and covered by a layer of earth 10 to 20 cms. thick. The projectile that issues from the explosive unit provided by the present invention, is actuate by the interaction of detonation waves with appropriate inert materials. It capable of maintaining its penetrating capacity consistently over a distance of several metres from the point of detonation of the explosive charge, even if it is necessary for the projectile to traverse layers of earth several decimetres in thickness when the unit is exploded. According to the present invention therefore, there is provided a hybrid ex¬ plosive unit comprising a casing, an explosive charge in the casing defining at the upper end thereof, an upwardly facing hollow, a shaped element linin said hollow, a metal cylinder embedded in said charge and extending through the middle of said shaped element, a sheath of inert material surrounding s cylinder, said cylinder and said sheath being adapted together to form a fi projectile of high penetrating power, and a member of inert material embedd in said charge across the lower end of said cylinder and of said sheath and adapted, upon the unit being fired, to act as an attenuator and diffractor the resulting direct detonation wave, said member and said shaped element being adapted together to form a second projectile of high penetrating powe which travels behind the first upon the unit being fired. The expressions "upper" and "lower" refer to the directions when the mine i embedded in use. Two embodiments of a hybrid explosive unit according to the present inventi will now be described with reference to the accompanying drawings in which:- Fig, 1 is an axial cross-section of the first embodiment; Fig. 2 is an axial cross-section of the second embodiment. The units shown in Figs. 1 and 2 have each a hollow explosive charge 1 (e.g. trinitrotoluene (TNT) or cyclonite ( T4) , shown in dotted form, a casing 2 having an open upper end, a plate 3 of inert material, for example plastic, ceramic or metal, a tubular metal cylinder 4 embedded in the charge 1 and surrounded by a sheath of inert material 8, e.g. resting on the plate 3, a dished metal element 5 lining the hollow in the charge and a cover 6, pre¬ ferably of synthetic material, closing off the top end of the casing. The metal cylinder 4 may be of such a length, as with the embodiment shown in Fig.1, that its upper extremity lies flush with the dished element 5 or, as with the embodiment shown in Fig. 2, extends above the dished element 5 depending on the desired length of the blast. All parts in the illustrated O P units, when viewed from above, have a circular cross-section. The function of the plate 3 is two-fold: firstly it functions as an attenua of the resulting shock waves and secondly as a diffraction lens. Considering the first function of the plate 3. The latter is traversed by a shock wave generated by interaction with a direct detonation wave 0 rfir itse generated at 7 (firing point) and propagated with a velocity Vd. dependent the explosive material employed. As it passes through the plate 3, the shoc wave is attenuated and is capable of causing an explosion under the plate which is of greater diameter than the metal cylinder 4, thereby generating detonation, low power, wave O , which is propagated in the explosive mater of the hollow charge 1, in the immediate vicinity of the metal cylinder 4, a velocity Vd , less than Vd.. The metal cylinder 4 has the tendency, unde the influence of the detonation wave of velocity d , of being compressed a of creating a direct high velocity blast along the line of the axis X-X. in order to achieve optimal penetration into the object to be destroyed, t blast must have both stable dimensions and stable velocity. To achieve the best possible stability, it is essential that the velocity of propagation the detonation wave in the metal cylinder 4 be somewhat less than or at mo equal to the speed of sound in the material composing cylinder 4. It is for this reason that the metal cylinder 4 is surrounded by a sheath of ine material 8. The drop in the velocity Vd 2 in the metal cylinder 4 is naturally dependen the nature of the material used for the sheath 8 and its thickness. This s ath may be cylindrical as shown in Figs. 1 and 2 or it may be frusto-conic in form with its narrow end adjacent to cover 6. By reducing the velocity Vd, to a value Vd,, less than the critical veloci are created for the generation of a stable blast, that is to say a blast th does not lengthen or disperse during propagation. The length of the blast i practically equal to the height of the metal cylinder 4, while its velocity VB, directed along the axis X-X, is substantially equal to twice Vd 3 , Vd 3 being equal to the velocity of propagation of the explosion wave in the met cylinder 4. The part of the metal cylinder 4 which is flush with the upper face of the dished metal element 5 or which extends above the latter (Fig. 2) „ behaves, the formation of the first projectile, in the same way as the portion immer in the explosive. This part, which is subjected to the stresses imposed by dished element 5 and projected under the impulsive force of the detonating mass, continues to feed the mass of the projectile already in motion. The second function of the plate 3 is that of acting as a diffraction lens. The direct detonation wave 0 * - , surrounding the inert plate 3, imparts to diffraction wave 0^ an appropriate shape before acting with the dished me element 5, to constitute a second projectile which travels behind the first projectile formed by the metal cylinder 4 surrounded by the sheath of inert material 8. With this arrangement, there is created, already within the explosive unit, stable high velocity projectile, which does not lengthen or disperse over a distance of several metres and is not affected by disturbances caused by po sible thicknesses of the terrain covering the explosive unit or other mate¬ rials covering the hollow explosive charge 1. The hybrid explosive unit provided by the present invention is also suited f use in artillery shells, inter alia.

Claims: C L A I M S 1. A hybrid explosive unit comprising a casing, an explosive charge in casing defining, at the upper end thereof, an upwardly facing hollow, a dis element lining said hollow, a metal cylinder embedded in said charge and extending through the middle of said dished element, a sheath of inert material surrounding said cylinder, said cylinder and said sheath being adapted together to form a first projectile of high penetrating power, and member of inert material embedded in said charge across the lower end of sa cylinder and of said sheath and adapted, upon the unit being fired, to act an.attenuator and diffractor of the resulting direct detonation wave, said member and said dished element being adapted together to form a second projectile of high penetrating power which travels behind the first upon th unit being fired. 2. ' A hybrid explosive unit as in claim 1, wherein the lower end of the said cylinder bears on said member and the upper end of said cylinder is fl with the front surface of said domed element. 3. A hybrid explosive unit as in claim 1, wherein the lower end of sai cylinder bears on said member and the upper end of said cylinder protrudes beyond the front surface of said domed element. 4. A hybrid explosive unit as in any one of claims 1 to 3, wherein sai sheath is cylindrical. 5. A hybrid explosive unit as in any one of claims 1 to 3, wherein sai sheath is frusto-conical with its narrow end nearest said cover. 6. A hybrid explosive unit substantially as hereinbefore described, wi particular reference to the accompanying drawings, one of claims 1 to 6. i-ϊ∑ OMPI IPO

Inventors: MARER JOSEPH GEORGES CAMILLE, MARER, JOSEPH, GEORGES, CAMILLE
Applicants: BRIND ANSTALT IND, BRIND ANSTALT FUER INDUSTRIE PATENTE
Application year: 1984
Main classification: F42B1
IPC codes: F42B1, F42B23