Abstract:
A mine has the ability to change from an armed state to a safe state without touching of the mine. The mine includes a case and an explosive charge in the case. Also included is a detonator located adjacent to the explosive charge. The firing of the detonator can set off an explosive chain for exploding the explosive charge. A movable firing pin in the case can strike and fire the detonator in response to pressure directed toward the case. The mine also includes a blocking member adapted to move from a retracted position to a blocking position between the detonator and the firing pin in order to prevent firing of the detonator by the firing pin. Also included is a driver for moving the blocking member from the retracted position to the blocking position without manual touching of the case.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mines, and in particular to devices for disabling a mine. 
     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. 
     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. The specification states that “remote communication may be performed with certain lines for activation and deactivation.” 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. 
     These references do not disclose any mechanisms for disabling a land mine. While electronics can be fabricated to perform a variety of sophisticated functions, the mechanical process of disabling the mine is extremely important. This mechanism must be highly reliable so that it does not run the risk of detonating the mine before it is placed. On the other hand, a mechanism must also be designed to (a) avoid premature disabling, and (b) reliably disable a mine when appropriate. Because of the dangerous nature of a mine, the mechanism must be made relatively simple and must have mechanisms that are unlikely to bind, jam, or otherwise fail. 
     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 show a movable element that is inserted into a blocking position to disable a land mine after it is armed. 
     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 does not disclose a blocking element that is inserted into a blocking position to disable the land mine after it is armed. 
     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 does not show a blocking element for disabling a land mine after it is armed. 
     See also U.S. Pat. Nos. 3,667,387 and 3,994,227. 
     Accordingly, there is a need for a mechanism for disabling a mine in a simple and highly reliable fashion. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a mine having the ability to change from an armed state to a safe state without touching of the mine. The mine includes a case and an explosive charge in the case. Also included is a detonator located adjacent to the explosive charge. The firing of the detonator can set off an explosive chain for exploding the explosive charge. The mine includes a movable firing pin mounted in the case for striking and firing the detonator in response to pressure directed toward the case. The mine also includes a blocking member adapted to move from a retracted position to a blocking position between the detonator and the firing pin in order to prevent firing of the detonator by the firing pin. Also included is a driver for moving the blocking member from the retracted position to the blocking position without manual touching of the case. 
     By employing the foregoing principles, an improved mine is achieved. In a preferred embodiment, a blocking member is slidably mounted in a mine and can move into a position between a firing pin and detonator to disable the mine. In one embodiment an electromagnet is energized with a polarity to repel a permanently magnetized element. If the electromagnet is disabled, the permanently magnetized element is drawn to the electromagnet to pull a flexible foam member in position between the firing pin and detonator. 
     This electromagnet can be disabled in a variety of ways. A circuit driving the electromagnet can have a timer that interrupts current to the electromagnet after a predetermined delay interval. Alternatively, a battery powering the electromagnet can simply run down. In some embodiments a radio receiver can detect and decode an encrypted command signal and then fire a firing cap to explode the mine. 
     In other embodiments, a spring loaded plunger can be biased to thrust a blocking member between the firing pin and detonator. A solenoid-like electromagnet, when energized, can pull the plunger and retract the blocking member to arm the mine. Again, interruption of the drive to the electromagnet will cause the blocking member to be thrust between the firing pin and detonator. In still other embodiments, a catch can hold a spring biased plunger in place until released by a separate releasing device. 
    
    
     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 a mine in accordance with principles of the present invention; 
     FIG. 2 is a cross-sectional, elevational view of the mine of FIG. 1; 
     FIG. 3 is a cross-sectional, plan view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a detailed view of the electromagnet mechanism of FIG. 3; 
     FIG. 5 is a detailed view of the mechanism of FIG. 4 with the magnetized element drawn to the electromagnet; 
     FIG. 6 is a cross-sectional, plan view of a mine that is an alternate to that shown in FIG. 3; 
     FIG. 7 is a cross-sectional, elevational view of a mine that is an alternate to that shown in FIG. 2; 
     FIG. 8 is a cross-sectional, plan view taken along line  8 — 8  of FIG. 7; 
     FIG. 9 is a detailed view of the blocking mechanism of FIGS. 7 and 8; 
     FIG. 10 is a detailed view of a blocking mechanism that is an alternate to that of FIG. 9; and 
     FIG. 11 is a schematic block diagram of a receiver that may be employed in the foregoing embodiments. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-5, a case is shown with a hollow cylindrical housing  10  covered by a vertically reciprocatable cap  12 . Cap  12  is a circular disk with a dependent cylindrical apron  14 . A plunger  16  mounted concentrically on the underside of cap  12  and extends through a concentric hole  18  atop housing  10 . 
     A concentric cylindrical wall  20  is attached to the ceiling inside housing  10 . Fitted within an annular groove on the inside of wall  20  is a domed snap ring  22 . A firing pin  24  is shown attached concentrically in snap ring  22 . External pressure applied to cap  12  causes plunger  16  to descend and press against firing pin  24 . Eventually, snap ring  22  inverts its shape from upwardly convex (illustrated condition) to upwardly concave. The sudden change in shape drives firing pin  24  against concentrically-located detonator  26 . Detonator  26  is located above booster  28 , which is located on the floor of housing  10 . 
     The space inside housing  10  and outside wall  20  is filled with an explosive charge  30 . Charge  30  has essentially a cylindrical inner and outer surface and a flat bottom. The top of the explosive charge  30  is flat as well, except for a recess  32  containing components to be described presently. While recess  32  is shown as a pie-shaped sector with radially aligned side walls, in other embodiments a different shape can be used instead. 
     In this embodiment a blocking member is shown as a D-shaped, flexible material  34  made, for example from polyurethane foam. Member  34  is shown attached inside the curve of a C-shaped magnetized element  36 . Element  36  may be a horseshoe-type permanent magnet, although other types of magnets may be used instead. Blocking member  34 / 36  is slidably mounted atop shelf  38  and may be guided by appropriate guiding rails, guiding pins and the like (such guiding means not shown). 
     A driver is shown herein as an electromagnetic device in the form of a C-shaped magnetic core  40  encircled at its midsection by an electrical coil  42 . The driver also includes a circuit contained in a subsystem  44  for driving the electrical coil  42  through wires  45 . As described further hereinafter, subsystem  44  can have a timing means for controlling the time over which coil  42  is energized. Subsystem  44  will also include a battery for powering its internal circuit and the external coil  42 . 
     Essentially, the circuit in subsystem  44  can use coil  42  to magnetize core  40  and repel magnetized element  36  to drive it to the position shown in FIGS. 3 and 4. When coil  42  is not energized, core  40  does not apply a repulsive force and therefore, magnetized element  36  is attracted to core  40  and moves from the position shown in FIG. 4 to the position shown in FIG. 5, under circumstances to be described presently. 
     Subsystem  44  is shown with an antenna  47  projecting through an opening in the top of housing  10 . Antenna  47  lies primarily in a horizontal plane underneath cap  12 . A firing cap  49  is also shown occupying a cavity in charge  30 . Firing cap  49  connects to subsystem  44  and can be triggered under the circumstances described hereinafter. Subsystem  44  is shown with a key  46  acting as a manually operable projection for arming the mine in a manner to be described presently. 
     Referring to FIG. 6, previously mentioned housing  10  is shown with an internal cylindrical wall  48  that is similar to previously mentioned wall  20 , except that wall  48  is positioned in an off-centered location. Located inside wall  48  are components identical to those previously described in connection with FIGS. 2 and 3, and therefore these identical components bear reference numerals identical to those used previously. A pair of wires  50  is connected through cable  52  to a subsystem  54  that is identical to previously mentioned subsystem  44  (FIG.  2  and  3 ), except for the use of an external battery  56 , in contrast to the internal battery used in subsystem  44 . 
     In this embodiment explosive charge  58  is more compact and is essentially cylindrical except for the sector  60  and the volume occupied by walls  48 . 
     Referring to FIGS. 7,  8  and  9 , housing  10  contains an explosive charge  30  identical to that shown in FIGS. 2 and 3. Consequently, charge  30  has an identical recess  32 . Cylindrical walls  60  are concentrically located inside housing  10  and circumscribe previously mentioned booster  28 , detonator  26  and firing pin  24 , which are all located in the same position as previously described. 
     An alternate blocking member is shown as a paddle  62  made of a flexible material such as a plastic foam, and is attached to the end of shaft  64 . Shaft  64  has a central flange  65  separating distal end  64 A from proximal end  64 B. Proximal end  64 B is encircled by a compression spring  68  acting as a bias member that is part of a driver. Spring  68  together with shaft  64  slidably fit in a socket  71  mounted on an inside wall of housing  10 . Proximal end  64 B extends outside housing  10  to form a manually operable projection that can be manipulated for the reasons to be described presently. 
     A releaseable catch is shown as an L-shaped bar  70  pivotally mounted on trunnions  72 . The end  74  of bar  70  is shown engaging the distal face of flange  65 . The opposite end of bar  70  is shown attached to a tension spring  76  tending to rotate bar  70  and release end  74  from flange  65 . This releasing motion of bar  74  is restrained by fuse wire  78  which prevents spring  76  from causing rotation of bar  70  beyond the position shown in FIG. 9, but does allow rotation in opposition to spring  76 . As described further hereinafter, a pulse of current applied to fuse wire  78  will rupture the wire, thereby enabling tension spring  76  to rotate bar  70  and move end  74  away from flange  65 . 
     A subsystem  75  (FIG. 7) is shown mounted above shaft  64  to rotatably fin support previously mentioned bar  70 . Subsystem  75  also contains the previously mentioned circuit, including a battery and an optional timing means. Previously mentioned antenna  47  is shown connected to subsystem  75  through an upper opening in housing  10 . 
     Referring to FIG. 10, an alternate driver is shown with a paddle  80  made of a flexible material such as a plastic foam, and attached to a shaft  82 . Shaft  82  is slidably mounted inside solenoid coil  86 . Compression spring  84  encircles shaft  82  between paddle  80  and solenoid coil  86  in order to urge shaft  82  out of coil  86 . Solenoid coil  86  is an electromagnetic device that can be energized through wires  88  to magnetically attract and pull shaft  82  into the position shown in FIG. 10, thereby compressing spring  84 . To facilitate the magnetic attraction, shaft  82  may be made of two parts with the portion to the right made of plastic or other non-magnetic material so that the bulk of the ferromagnetic material is contained inside solenoid coil  86  when energized as shown in FIG.  10 . 
     Referring to FIG. 11, radio receiver  90  detects a radio signal from antenna  47  and applies the detected signal to decoder  92 . Receiver  90  can detect AM or FM signals modulated in a variety of fashions, especially pulse code modulation. The signal from receiver  90  is a series of encrypted bits that are sent to decoder  92  for decoding. If a self-destruct code is received, decoder  92  sends a signal to a firing cap, for example cap  49  of FIG.  2 . If a disable code is received, decoder  92  operates switch  94  to disconnect battery  96  from device  98 . Device  98  may be coil  42  of FIG. 3, fuse wire  78  of FIG. 9, or solenoid coil  86  of FIG.  10 . 
     The system of FIG. 11 can also disable itself through a timing means  100 . This timer  100  may be a clock driving a counter until a predetermined count is reached, at which time switch  94  is operated. Alternatively, a charging device can be slowly charged until it reaches a threshold voltage, at which time switch  94  may be operated. In all of these arrangements, battery  96  will have a limited life. When battery  96  runs down, power can no longer be supplied through switch  94  to device  98 . With the schemes described above (except for FIG.  9 ), the absence of power will result in disabling of the mine. Furthermore, the previously mentioned key (for example key  46  of FIG. 1) can be manipulated to set the state of switch  94 . 
     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  11 . When the mine is shipped from the factory blocking member  34  is in the position shown in FIG.  5 . When the mine is placed in the field, key  46  is manipulated to close switch  94  (FIG.  11 ). Consequently, coil  42  is energized to produce a magnetic force that repels magnetized element  36 . As a result, element  36  is driven away to the position shown in FIG.  4 . 
     This resulting condition shown in FIGS. 2 and 3 arms the mine. Consequently, pressure applied to cap  12  can depress plunger  16  to push firing pin  24 . If pushed sufficiently, domed ring  22  will invert and snap firing pin  24  down against detonator  26 . Consequently, detonator  26  will start off an explosive chain, and will fire booster  28 . Booster  28  will fire explosive charge  30  to complete the explosion. 
     The mine can however, be disabled. In the simplest case, battery  96  (FIG. 11) in subsystem  44  (FIGS. 2 and 3) can run down. As a result, current no longer flows through wire  45 , so that coil  42  is disabled. Consequently, no magnetic repulsive forces are generated through core  40 . In response, magnetized element  36  is now attracted to core  40  and will move from the position shown in FIG. 4 to that shown in FIG.  5 . Once positioned as shown in FIG. 5, firing pin  24  is isolated from detonator  26 . Therefore, even if cap  12  is depressed and firing pin  24  descends, it strikes foam material  34  without further effect. 
     In some cases field personnel may wish to disable the mine before the battery runs down. In this case transmitter  102  (FIG. 11) can send an encoded signal over antenna  104 , which is received by antenna  47  and detected by receiver  90 . Depending upon the transmitted code, decoder  92  can either issue a signal to fire the firing cap or can operate switch  94 . If switch  94  is operated, then battery  96  can no longer supply current to device  98 , which is in this embodiment, coil  42 . Therefore blocking element  34  will return to the position shown in FIG. 5 for the reasons previously given. 
     Alternatively, the closure of switch  94  (FIG. 11) can supply power to timer  100 . After a predetermined time elapses, timer  100  provides an overriding signal to open switch  94  and disable device  98  to bring about the condition shown in FIG.  5 . 
     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 an offcenter position. 
     Also, the embodiment of FIGS. 7-9 will operate in a similar fashion with some exceptions. The mine will be shipped from the factory with the blocking member  62  in the position  63  shown in phantom in FIG.  7 . When placed in the field, the operator will withdraw the exposed end  64 B of shaft  64  to bring blocking member  62  to the position shown in full in FIG.  7 . To accomplish this, flange  65  will push, lift, and pass the beveled face of bar end  74 . To do this, bar  70  will rotate about trunnions  72  to stretch tension spring  76  and lift bar  70  off fuse wire  78 . 
     Once flange  65  passes bar end  74 , tension spring  76  rotates bar  70  back to rest on fuse wire  78 . This produces the condition shown in FIG. 9 where spring  68  pushes flange  65  against bar end  74 . Bar end  74  continues to fly restrain flange  65  and shaft  64  since bar  70  cannot rotate past fuse wire  78 . 
     In this embodiment, current must be supplied through fuse wire  78  (FIG. 9) in order to release shaft  64  and blocking member  62 . Accordingly, this embodiment requires a source of electrical current in order to disable the mine. An arrangement of this type may be appropriate where a high-energy electromagnetic pulse is issued near the mine. 
     For the embodiment of FIG. 10, the circuit of FIG. 11 will operate in the above described manner to supply or remove current from wires  88 . Upon removal of current from wires  88 , blocking member  80  will be deployed to prevent firing pin  24  from reaching detonator  26  (FIG.  7 ). 
     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. While the blocking member is shown having a rectangular shape, in other embodiments this member can be cylindrical or shaped otherwise. This member may in some cases be formed from a number of separate components. Also a variety of firing pins can be used that are positioned in a number of different locations and supported by a variety of mechanisms. Furthermore, the blocking member can be moved by a variety of mechanisms deriving energy from sources such as torsion springs, elastomers, gravity, electrical charges, magnetic fields, etc. Moreover, the blocking member need not slide linearly, and may rotate or follow a curved path, in other embodiments. 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.