Abstract:
A self-destruct accessory fits on a mine whose case has a cap that can be depressed to detonate the mine. The accessory has a cover that is sized to fit on the cap. The cover has a plurality of lines for securing the cover to the mine. An explosive charge is mounted upon the cover and a detonator is located adjacent to the explosive charge. A remotely controllable device coupled to the detonator can receive a detonation signal from a remote location to detonate the explosive charge and explosively depress the cap in order to detonate and destroy the mine.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mines, and in particular, to accessories that can be secured to a mine in order to destroy it. 
     2. Description of Related Art 
     Land mines are still considered a necessary part of warfare. Of course, a lingering problem is finding, and disabling or destroying the land mines after hostilities cease. While combatants may try to make maps indicating locations of land mines, these maps are often hastily made and inaccurate, or are lost in the destruction that is part of armed conflict. Oftentimes, there is simply not the resources available to devote the time needed for carefully tracking down, and extracting or detonating these mines. 
     There have been many proposals for disabling or destroying land mines after they are no longer needed. These designs have employed internal timing devices or remote controls for either disabling or detonating the mine. These features, however, are part of the original land mine as manufactured. Existing inventories of land mines cannot be simply modified to include these safety features. 
     For example, in U.S. Pat. No. 3,603,258 pin 106 punctures diaphragm 104 after a mine is armed. The punctured diaphragm allows piston 96 to slowly move and eventually operate a mechanism to self-destructively detonate the mine. This mechanism is internal and cannot be readily used to retrofit a mine to achieve self-destruction. See also U.S. Pat. No. 3,739,725 (hydroscopic material 18 gradually softens to withdraw pin 13, which causes a mine to self-destruct). 
     In U.S. Pat. No. 6,142,080 an electronic timer senses the cessation of spinning of a projectile to start a timer that eventually will electrically detonate the explosive charge. In U.S. Pat. No. 3,657,571 an electronic timer is used to self-destruct a land mine. In U.S. Pat. No. 6,244,184 a timer is started upon the launch of a projectile carrying submunition grenades. Capacitors in the timing circuits in each of the grenades self-destruct the grenades after a period of time. None of these technologies are readily implemented as a retrofit. See also U.S. Pat. No. 3,983,819. 
     Encoded signals have been used to trigger underwater devices designed to destroy underwater mines. In U.S. Pat. No. 4,369,709 an underwater device is armed after reaching a proper operating depth. The device can be detonated by coded signals received through a hydrophone. In U.S. Pat. No. 5,042,387 a device has an upper buoyant portion and a lower sinking portion, which are both able to attach to a mooring line of a mine. The upper and lower units detach and move toward the mine and the mine seat, respectively. A sonar signal from a surface ship detonates both devices to destroy the mine and to sever the mooring line. See also U.S. Pat. Nos. 4,696,234; 4,970,957; 5,771,833; and 6,308,633. These references concern highly specialized underwater equipment and do not teach techniques for simply retrofitting land mines in order to safely destroy or disable them. 
     In U.S. Pat. No. 5,415,103 an interrogation unit can program a land mine to set the conditions under which the land mine will detonate. See column 1, lines 16-17. The electrical firing circuit of U.S. Pat. No. 5,218,574 provides several operating modes for a land mine. In one mode, an electrolytic timing device can detonate the land mine after a predetermined delay. 
     In U.S. Pat. No. 4,856,431 a directional mine is armed by inserting firing unit 6, which is locked into place by pin 15. The mine can be detonated by firing the igniter 11. After a pre-programmed amount of time, however, an electromagnet retracts pin 15 to eject unit 17, thereby disarming the mine. This reference is relatively complicated and does not lend itself to a simple retrofit. 
     In U.S. Pat. No. 4,712,478 slider 30 has a passage that moves into position just before detonation to create a firing path. The land mine can be neutralized by an undefined circuit that fires detonator 44 before slider 30 is in the armed position. Alternatively, the battery that operates circuit 10 can run down and disable the land mine. This reference has no teachings that would allow a simple retrofit for existing land mines. 
     In U.S. Pat. No. 4,854,239 a munition is fired by two explosively powered pistons, if they are fired in a proper sequence before a third piston is fired. Premature firing of the third piston will fracture a component, which is then elevated to indicate the munition is disabled. Again, this complicated reference would not be suitable for a simple retrofit. 
     See also U.S. Pat. Nos. 3,115,834; 3,447,461; 3,667,387; 4,058,061; 4,712,480; 4,854,239; 5,511,482; and 6,112,668, cited in the pending U.S. patent application Ser. No. 09/578,096, filed May 25, 2000 by the same inventor. See also U.S. Pat. Nos. 3,667,387 and 3,994,227. 
     Accordingly, there is a need for a self-destruct accessory that can be installed on a land mine in a simple and reliable fashion. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a self-destruct accessory for a mine whose case has a cap that can be depressed to detonate the mine. The accessory includes a cover sized to fit on the cap and has a plurality of lines for securing the cover to the mine. Also included is an explosive charge mounted upon the cover and a detonator located adjacent to the explosive charge. Firing of the detonator can cause the explosive charge to explode. The explosive charge can explosively depress the cap when the cover is mounted on the cap. The accessory also includes a remotely controllable device coupled to the detonator for firing it. 
     According to another aspect of the invention a method employing an explosive cover can destroy a mine whose case has a cap that can be depressed to detonate the mine. The method includes the step of fitting on the cap the explosive cover. The cover holds an explosive charge and a detonator. Another step is securing the cover to the mine with a plurality of lines. The method also includes the step of sending a detonation signal to the detonator from a remote location to detonate the explosive charge and explosively depress the cap in order to detonate and destroy the mine. 
     By employing the foregoing principles, an improved technique is achieved for destroying a mine with a self-destruct accessory. In one preferred embodiment, a cover is designed to fit closely over the cap of a land mine. Preferably, a number of straps extend from the edge of the cover and are used to secure the cover to the land mine. The ends of the straps can be fastened together using various connectors or buckles. Alternatively, the straps can extend from the side of the cover and attach to a fastener on the opposite side of the cover. In any event, the cover is installed in such a way that the land mine can be deployed in the usual fashion and will explode when pressure is applied to be cover to depress the cap of the land mine. 
     In a preferred embodiment an explosive charge can be mounted atop a supporting plate of the cover. When the land mine is no longer needed, an encoded signal can be sent to a remotely controlled detonator in the cover. This detonator can ignite a primer that in turn detonates the main explosive charge. The main explosive charge produces a pressure wave that depresses the cap of the land mine so it explodes safely. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is perspective view of an accessory about to be installed on a mine in accordance with principles of the present invention; 
     FIG. 2 is a perspective view of the accessory of FIG. 1 installed on the land mine; 
     FIG. 3 is a detailed, fragmentary view of the connection between the lines on the underside of the land mine of FIG. 2; 
     FIG. 4 is plan view of the underside of the cover of FIG. 1 with a portion of its supporting plate broken away to show the contents of the cover; 
     FIG. 5 is an elevational, cross-sectional view of the cover of FIG. 4; 
     FIG. 6 is a cross-sectional view of a cover that is an alternate to that shown in FIG. 5; 
     FIG. 7 is a cross-sectional, elevational view of a cover that is an alternate to that shown in FIG. 5 with a portion broken away for illustrative purposes; 
     FIG. 8 is a detailed, cross-sectional view of a fastener that is an alternate to that shown in FIG. 5; and 
     FIG. 9 is a schematic block diagram of a receiver and transmitter that may be employed in the foregoing embodiments. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-5, a self-destruct accessory is shown as a cover  10  with two female mating lines  12  and two male mating lines  14 . Preferably, the proximal ends of lines  12  and  14  are integrally molded to the edge of cover  10 . Lines  12  are shown secured to the edge of cover  10  at the three and six o&#39;clock positions, while lines  14  are at the nine and twelve o&#39;clock positions. Other embodiments may have a different number of lines located at different positions that are not necessarily equidistantly spaced. 
     The distal ends of the female mating lines  12  each have a ratchet clasp  12 A in the form of a hollow box that is open at two opposite ends. The ratchet clasp  12 A contains an inclined tooth  12 B, one such tooth being visible through the distal opening shown in FIG.  1 . Clasp  12 A is designed to receive the male mating line  14 , which may be inserted in only one direction, retraction being prevented by the inclined tooth  12 B. Ratchet clasp  12 A may be a conventional type of clasp, often referred to as a zip tie. 
     Most of the length of such lines  12  and  14  are plastic straps with the male straps  14  having a series of ratchet teeth  14 A on one side. The ratchet clasp  12 A is integrally molded with the length of the rest of the line. In other embodiments, the clasp may be a plate with two parallel slots through which the mating strap  14  can be threaded. Various other types of buckles and fasteners may be used as well. In simplified embodiments, the lines may work without any fastener and may simply be tied together. 
     Cover  10  is designed to fit over the cap  16  that is mounted atop case  18  of the land mine  20 . This land mine  20  is a conventional mine that detonates when downward pressure depresses cap  16 . In this embodiment cover  10  has a circular outline in order to fit onto cap  16 , but in other embodiments the cover may have a different outline designed to fit over another specific land mine with a different outline. 
     Cover  10  has a top plate  22  with an integral annular sidewall  24  designed to encompass cap  16 . Mounted concentrically inside sidewall  24  is an internal annular wall  26  that extends over 300°, leaving an opening into which a booster charge  28  protrudes. Mounted under plate  22  between walls  24  and  26  is an annular explosive charge  30  that extends 360° and lies against booster  28 . Circular bottom plate  32  fits closely inside the annular wall  24  and encloses the space under top plate  22 . 
     An antenna  34  runs along the inside of wall  26  and connects to remotely controllable device  36 , which has the receiver  36 A and decoder  36 B shown in FIG.  9 . As explained further hereinafter, device  36  is able to ignite booster charge  28  in response to encoded signals received by antenna  34 . Antenna  34 , device  36 , and booster charge  28  fit between plates  22  and  32 , and are herein collectively referred to as a detonator. 
     Referring to the alternative embodiment of FIG. 6, components identical to those previously described in connection with FIGS. 1-5 bear the same reference numeral, while components that are only similar are identified with the same reference numeral but marked with a prime (′). Cover  10 ′ has an upper plate  22 ′ surrounded by an integral annular sidewall  24 ′. Plate  22 ′ has a central chamber partially encompassed by internal wall  38  to hold a central explosive charge  30 ′. In this embodiment, explosive charge  30 ′ has a cylindrical shape. Fitting in a gap in internal wall  38  is a booster charge  28 ′, which can be ignited by detonator device  36 ′. Booster charge  28 ′ is located between explosive charge  30 ′ and detonator device  36 ′. 
     As before, explosive device  36 ′ is connected to an antenna (not shown) for receiving encoded signals. In this embodiment, the components involved in the explosive chain are all centrally located inside cover  10 ′, in contrast to the distributed, annular explosive charge  30  of FIG.  4 . 
     Referring to FIG. 7, alternative cover  40  has a base plate  42  with an integral annular sidewall  44 . Cover  40  also has mounted atop plate  42  an inverted annular channel  46  containing an annular explosive charge  48 . Also mounted atop plate  42  to the inside of channel  46  is a detonator  36  that is identical to the one previously mentioned in connection with FIG.  4 . As before, detonator  36  cooperates with an antenna and a booster charge (not shown). The booster charge fits in a gap in channel  46  (similar to the gap shown in wall  26  of FIG. 4) and can be ignited by detonator  36  to explode explosive charge  48 . Detonator  36  is covered by an upper plate  50  that fits onto an annular outside ledge on the upper inside corner of channel  46 . 
     Integrally molded on the bottom edge of annular sidewall  44  are two lines, one such line  52  being shown in FIG.  7 . Two mating fasteners  54  (one visible in this view) are mounted on the side of annular sidewall  44 . Fastener  54  is in the form of a tunnel through which line  52  can be threaded. An inclined tooth  54 A inside fastener  54  allows insertion of line  52  in one direction (upwardly through fastener  54  in this view). Teeth (not shown) on the inside face of line  52  engage tooth  54 A to ensure this unidirectional insertion. Fastener  54  operates in a manner similar to that associated with fastener  12 A of FIG.  1 . 
     Referring to FIG. 8, an alternative fastener is shown that can replace fastener  54  of FIG.  7 . This fastener has an eccentric barrel  58  pivotally mounted on pin  60  between a pair of embossments  62  (one visible in this view) on annular sidewall  44 ′ (corresponding to sidewall  44  of FIG.  7 ). The lever  64  mounted on eccentric barrel  58  can be used to manually rotate barrel  58  to change the spacing between sidewall  44 ′ and barrel  58 . By rotating lever  64  in the direction indicated by the arrow  65 , the gap between barrel  58  and sidewall  44 ′ is reduced so that a line (such as line  52  of FIG. 7) can be gripped between elements  58  and  44 ′. 
     Referring to FIG. 9, radio receiver  36 A detects a radio signal from antenna  34  and applies the detected signal to decoder  36 B. Receiver  36 A can detect AM or FM signals modulated in a variety of fashions, especially pulse code modulation. The signal from receiver  36 A is a series of encrypted bits that are sent to decoder  36 B for decoding. If a self-destruct code is received, decoder  36 B sends an ignition signal to a booster charge, for example booster charge  28  of FIG.  4 . This encoded signal is produced by encoder  68  that modulates transmitter  66  to transmit an encoded signal through antenna  70 . 
     To facilitate an understanding of the principles associated with the foregoing apparatus, its operation will be briefly described in connection with the embodiment of FIGS. 1-5 and  9 . Land mine  20  is a conventional mine that an armed force may already have in inventory. Mine  20  lacks the ability to be destroyed by a remote control. For this reason, mine  20  is retrofitted with cover  10 . Cover  10  is placed over cap  16  with sidewall  24  encircling cap  16  as shown in FIG.  5 . 
     Cover  10  is secured in place by joining together each of the lines  14  with a mating line  12  on the opposite side of cover  10 . As shown in FIG. 3 line  14  is inserted through the opening in fastener  12 A. Teeth  14 A ratchet over the inclined tooth  12 B (FIG.  1 ). Tooth  12 B is inclined to allow insertion of line  14  in one direction so that lines  12  and  14  can be tightened around mine  20  and will not loosen. Once lines  12  and  14  have been tightened they form two transverse bindings around mine  20  as shown in FIG.  2 . Lines  12  and  14  are not tightened so much as to depress cap  16 . Depression of cap  16  by tightening lines  12  and  14  is unlikely since normally about 35 pounds of force must be applied to depress cap  16  in order to detonate mine  20 . 
     Mine  20  with the newly installed cover  10  can be returned to inventory or can immediately be used in combat. Mine  20  can be laid in the usual fashion at a theater of operations. Personnel or vehicles that cross over mine  20  will depress cap  16  in the usual fashion to detonate the mine. 
     After hostilities cease land mine  20  may still remain in place unexploded. Finding and exploding/disabling land mine  20  in the conventional manner is obviously extremely dangerous. This danger is augmented by the fact that the exact location of land mines may not be known because they were scattered randomly or because the map of their location was destroyed in the preceding conflict. 
     With the present accessory  10  land mine  20  can be exploded at a safe distance by field personnel. When appropriate, transmitter  66  (FIG. 9) can send over antenna  70  an encoded signal generated by encoder  68 . This radiated signal is received by antenna  34  and detected by receiver  36 A. Depending upon the transmitted code, decoder  36 B can issue a signal to fire the booster charge  28  (FIG.  4 ). 
     Once ignited, booster charge  28  quickly explodes explosive charge  30 . Cover  10  then explodes sending an upward pressure wave, but more importantly, a downward pressure wave. This downward pressure wave depresses cap  16  and explodes land mine  20 . 
     It will be appreciated that the embodiment of FIG. 6 will operate in substantially the same fashion, except that the explosive chain will start from the side and propagate into the central explosive charge  30 ′. The embodiments of FIGS. 7 and 8 will operate in a manner similar to that of FIGS. 1-5; it is just that the manner of fastening the accessory to the land mine is different. 
     It is appreciated that various modifications may be implemented with respect to the above described, preferred embodiment. For example, the mine need not have a circular perimeter and may have a perimeter that is square, rectangular, polygonal, elliptical or shaped otherwise. The structure of the cover is may be made of a different number of components than illustrated herein. Also, the structural components of the cover may all be made of a similar material; or different components may be made from different materials, including plastics, metals, ceramics, composite materials, etc. Moreover, the explosive and booster charge can be made of a variety of materials of various shapes that may be positioned in any one of a number of different locations. Also, the encoded signal may be transmitted by radio frequency waves, visible light, infrared energy, acoustic waves, etc. In addition, the disclosed electrical circuit can be modified to include fewer or more features and may be fabricated from discrete electrical components, integrated circuits, etc. Also, the various components can have different sizes and shapes depending upon the desired volume, strength, thermal stability, etc. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.