EXPLOSIVE DEVICE

Abstract: An arrangement in explosive devices, e.g. shells, mines, bombs or the like, including a fuse (3), a main charge (1) and an auxiliary charge (4) which is disposed between the fuse and the main charge and effective in detonating the main charge. The main charge (1) is encapsulated in a safety casing and separated from the auxiliary charge (4) by different mechanical obstruc­ tions. In accordance with the invention, the auxiliary charge (4) comprises a charge having directed explosive action of the type which on being detonated produces a mass jet of high-order energy and high velocity. The auxiliary charge is oriented such that after penetrating an intermediate mechanical obstruction the jet will penetrate into the main charge, therewith detonating the main charge. To this end, the auxiliary charge (4) is spaced from the mechanical obstruction (11) by a dis­ tance sufficient to enable the jet to develop to the extent required, before meeting the obstruction.

Description: The present invention relates to an improvement in explosive devices, e.g. shells, mines, bombs or like devices, which include a fuse, a main charge and an auxiliary charge arranged between the fuse and the main charge and effective in detonating the main charge, which is encapsulated and separated from the auxiliary charge with the aid of mechanical obstacles. The main charge of an explosive device constructed in accordance with the above is usually placed in a strong casing. The casing is utilized, inter alia, for reasons of safety, e.g. as protection during transport and storage. Its purpose is, inter alia, to protect against blows and knocks and other extraneous effects. Moreover, the casing is normally required to be impervious, such as to allow the explosive device to be stored for long periods under hard conditions. In order to achieve reliable detonation of the main charge in spite of the presence of its safety casing, there have been previously used different types of arming safety means or moveable mechanical parts, e.g. for rotating an opening in the casing into register with an auxiliary detonating charge, see for instance US-A-4. 430.938. Alternatively, a casing which incorporates weakened portions can be used, although this will also present certain drawbacks. Apart from a decrease in safety, means of the kind mentioned above also result in extra costs and design restrictions. In the detonation of such encased main charges, normally an auxiliary charge, a so-called BOOSTER, is used as a connecting link in the explosive chain between fuse and main charge. Depending on the size of the main charge, this BOOSTER can assume large dimensions, e.g. 1-1.5 kg. If an additional barrier is located between the BOOSTER and the main charge, e.g. in the form of a sheet metal plate, a plastics plate, water or some other material, or combinations therebetween, the size of the BOOSTER must be increased in order for it to perform its task of detonating the main charge. The main object of the present invention is to provide an arrangement which will permit simple and reliable detonation of an encased main charge without utilizing arming safety means or other mechanical parts or weakened portions, while using a considerably smaller charge than has been required previously. The invention is based on the knowledge that the above-mentioned object can be achieved with the aid of an auxiliary charge which has a directed explosive action of the type which on detonation achieves a mass jet of high energy and high velocity. Such charges, known as "shaped charges" or "hollow charges", are utilized today mainly for providing greater penetrative power, primarily against armour plating. It has also been proposed to utilize small charges of this kind in different fuse systems, but never for solving the specific problems encountered in conjunction with detonating encased main charges. Civil applications are also to be found. AT-B-251 462 discloses an arrangement in explosive devices, including a fuse, a main charge and an auxiliary charge which is arranged between the fuse and the main charge and effective in detonating the main charge, the main charge being separated by mechanical obstruction from the auxiliary charge. This prior art arrangement is used for the detonation of a main charge in the form of a bulk explosive material placed in a blast hole. The detonation is initiated by means of the main shock wave from the auxiliary charge which is in the form of a so called hollow charge and preferably placed in direct contact with the explosive material. In the case of encased main charges as in the present invention much smaller charges can be used when conventional BOOSTER charges are replaced by shaped or hollow charges. As a result of the large penetrative power of such charges, the encasement and configuration of the main charge can be decided upon essentially without regard to detonation problems, since the jet generated by such a shaped or hollow charge will penetrate far into the main charqe in any case. However, it is necessary to position the shaped charge at a given distance from the main charge, so that the jet has time to develop to the extent necessary to penetrate the main charge. An inventive device of the kind mentioned in the introduction is further characterized in that the auxiliary charge comprises a charge which has a directed explosive action and of the type which on being detonated produces a mass jet of high-order energy and high velocity; the auxiliary charge is oriented such that said jet penetrates into the main charge after penetrating intermediate mechanical obstruction; the auxiliary charge is spaced from said mechanical obstruction such that the jet is able to develop to the extent required before meeting said obstruction; the auxiliary charge is fixed in the outer end of a tubular element, the inner end of which is closed off and attached to a protective casing encapsulating the main charge; the tubular element projects out through an opening in the protective casing enclosing the main charge; and the inner end of the tubular element is provided with a flange which is connected to the part of the inner surface of the protective casing surrounding the opening. A sealing element is suitably arranged between the flange and the inner surface of the protective casing. When the auxiliary charge includes a charge with a metal lined cavity which expands conically in the jet direction, it is preferred that the distance between the auxiliary charge and the mechanical obstruction substantially corresponds to the largest diameter of the auxiliary charge cavity. The jet path should be free from every element which can affect the development of the jet, and said path is preferably represented by an enclosed space filled with air but otherwise empty. This will ensure that the jet has time to develop, such as to obtain the required penetrative power. The invention will now be described in more detail with reference to the accompanying drawing, the single Figure of which schematically illustrates a section through a part of a main charge to which there is connected an auxiliary charge having a detonator. The numeral 1 denotes the main charge itself, which can be moulded or pressed and comprises a commercially avaible explosive, such as HEXOTOL, OKTOL, HEXOTONAL and OKTONAL, plsatically bonded explosives, etc. The main charge 1 is enclosed in a strong protective casing 2, which protects the charge against external forces. Further mechanical obstruction may be present between the casing and the charge. The numeral 3 denotes a conventional fuse which is disposed for detonating an auxiliary charge 4 having directed explosive action and having the form of a hollow or shaped charge. The hollow or shaped charge 4 includes an explosive 5 which can be detonated by the fuse 3, the explosive being provided with a cavity 6 widening in a direction towards the main charge 1, this cavity being lined with a metal lining 7, suitably a copper lining. The sleeve-shaped hollow charge is fixed in the outer end of a tubular connector 8, which extends through an opening in the protective casing 2. The inward end 11 of the tubular connector 8 is closed off and provided with a flange 9, which is connected to the protective casing on the surfaces surrounding the opening, e.g. with the aid of screws 10. A sealing element (not shown) is preferably applied between the flange 9 and the interior surface of the casing 2. As a result of the closed off end 11 of the tubular connector 8, the main charge can be kept encapsulated in a protective casing without weakened portions or moveable parts which are to be moved relative each other. The closed end 11 presents a mechanical obstacle which is penetrated by the mass jet from the shaped or hollow charge when the charge is detonated, the jet then penetrating deeply into the main charge and therewith effects satisfactory detonation of the charge. The shaped or hollow charge is arranged with given spacing from the closed end 11, this spacing being sufficiently great to enable the jet to develop to the required extent, before it reaches the mechanical obstruction represented by the end 11. It has been found that this spacing should be of the same order of magnitude as the calibre of the shaped or hollow charge, i.e. a distance substantially corresponding to the largest diameter of the cavity 6. By utilizing a closed tubular connector in accordance with the illustrated embodiment, there is achieved the advantage of intact encapsulation of the main charge while, at the same time, ensuring that the shaped or hollow charge will be correctly oriented relative the main charge and fixed at a pre-determined distance from the first true mechanical obstruction. Moreover, the jet path between the shaped or hollow charge and the mechanical obstruction will be free from other elements which can affect the development of the jet. As a result of rotational symmetric compression of the metal insert 7 of the shaped or hollow charge when the auxiliary charge is detonated, the jet will take the form of a short pulse consisting of metal from the insert 7. As mentioned above, the metal insert will punch through the end enclosure 11 and penetrate deeply into the main charge 1, such as to detonate the charge. This will occur irrespective of whether there is further mechanical obstruction between the end closure and the main charge or not. The invention thus permits the main charge to be configured and enclosed solely on the basis of the demands placed on such an enclosure without regard to detonation problems, since the latter can be solved in accordance with the present invention and essentially quite independently of the configuration and encapsulation of the main charge. The above described embodiment of an arrangement according to the invention may, of course, be modified in several respects within the scope of the claims. This applies, for example, to the configuration or design of the auxiliary charge and the manner in which the charge is connected to the protective casing of the main charge.

Claims: An explosive device, including a fuse (3), a main charge (1) and an auxiliary charge (4) which is arranged between the fuse and the main charge and effective in detonating the main charge, said main charge being encapsulated and separated by mechanical obstruction from the auxiliary charge, wherein the auxiliary charge (4) comprises a charge which has directed explosive action and of the type which on being detonated produces a mass jet of high-order energy and high velocity; the auxiliary charge (4) is oriented such that said jet penetrates into the main charge (1) after penetrating intermediate mechanical obstruction (11); the auxiliary charge is spaced from said mechanical obstruction such that the jet is able to develop to the extent required before meeting said obstruction; the auxiliary charge (4) is fixed in the outer end of a tubular element (8), the inner end of which is closed off and attached to a protective casing (2) encapsulating the main charge (1); the tubular element (8) projects out through an opening in the protective casing (2) enclosing the main charge (1); and the inner end (11) of the tubular element (8) is provided with a flange (9) which is connected to the part of the inner surface of the protective casing (2) surrounding the opening. A device as claimed in claim 1, wherein a sealing element is mounted between said flange (9) and the inner surface of the protective casing (2). A device as claimed in claims 1 or 2, wherein the auxiliary charge includes a charge (5) with a metal lined cavity (6) which expands conically in the direction of the jet, and the spacing between the auxiliary charge (4) and said mechanical obstruction (11) corresponds essentially to the largest diameter of the auxiliary charge cavity (6). A device as claimed in any claims 1-3, wherein the jet path between the auxiliary charge (4) and said mechanical obstruction (11) is substantially free from any element which can affect the development of the mass jet. A device as claimed in claim 4, wherein said jet path is represented by an enclosed space, filled with air but otherwise empty.

Inventors: HALLSTROEM, STIG, Hallström, Stig
Applicants: AB BOFORS
Application year: 1989
Main classification: F42B3
IPC codes: F42C19