Abstract:
A weather resistant, battery powered tripwire warning device includes a weather resistant housing, a battery mounted within the housing, an alarm mounted within the housing, at least one spotlight mounted on a side of the housing and configured to illuminate regions extending from the side of the housing, and at least one and preferably a pair of switches mounted on opposing sides of the housing and configured to close a circuit between the alarm and the battery when either switch is activated. Each switch is configured to be attached to a trip cord, such that a selected tension on the trip cord will activate the alarm. The tension required for activation of the switches is individually adjustable. The battery powered tripwire device may be employed for perimeter security of a military force or for training exercises.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to military early warning devices and outdoor alarm systems particularly those utilized to protect battlefield defensive perimeters.  
           [0003]    2. Description of the Related Art  
           [0004]    Throughout the years militaries have employed a variety of methods to ensure defensive security. During World Wars I and II, soldiers would emplace tin cans filled with rocks along concertina wire to provide early warning of enemy soldiers entering a perimeter. For obvious reasons, this tin can security system was neither effective nor easily employable. In later years, pyrotechnic tripwire devices were employed, which are still used today, to provide alert in the presence of intruders. These pyrotechnic devices are hazardous for soldiers to carry and store, and require significant technical knowledge to implement. In addition, some pyrotechnic tripwire devices are lethal by nature, which poses a problem for operations other than war.  
           [0005]    The great increase in non-combat military operations has left a gap in the ability of the military to provide a system that affords non-lethal battlefield security. During non-combat operations, civilians and combatants alike pose a variety of threats to the military. However, the use of lethal tripwire devices is extremely problematic. For example, such devices fail to distinguish between friendly and enemy. This problem has increased with United Nations Resolution 54/58 of 1 Dec. 1999, and other resolutions referring to the “Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects”, and in particular, the “amended Protocol on Prohibitions or Restrictions on the Use of Mines, Booby Traps and Other Devices” (Protocol II) implementing a ban on all lethal remote land mine and tripwire devices.  
           [0006]    Additionally, the military has a need for devices that may be used to train personnel in placement and detection of such equipment. It is not reasonable to assume that, because the US military has acknowledged and accepted the ban on such devices, hostile forces will accept the same limitations. Thus, it is essential that non-lethal devices be available for such training. Coupled with the inherent hazards and increased costs associated with known non-lethal pyrotechnic devices, the gap in military technology, and the need for a non-hazardous, easily deployable battlefield security device is evident. Such a device must be ergonomic, cost effective, simple to implement, adaptable to harsh environments, and be able to signal a security breech at a variety of distances.  
           [0007]    A known device employs a chemical light coupled with a spring-loaded hammer. When an intruder trips the device, the hammer is released to break a glass ampoule, allowing reactive chemicals to mix, which produces the chemical light. The device is safe to carry and simple to install. However, it has significant drawbacks. For example, the light produced is not easily visible in daylight. Even at night, the chemical response is not instantaneous, but may be delayed by several seconds, as the chemicals mix and begin to produce light. Thus, an intruder may be able to move away from the vicinity or disable the device before the intrusion is detected.  
           [0008]    More sophisticated electronic sensors, employing technologies common in building security systems, for example, such as laser sensors, infrared, and motion detectors, are not considered practical for a variety of reasons, including the level of training required to operate, the difficulty in preventing false alarms due to unpredictable environmental conditions, and the cost of such high-tech equipment.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    According to an embodiment of the invention, a tripwire device is provided as a training aid for military soldiers and as a non-lethal perimeter defense tool. The device is configured to be mounted in a housing that is adaptable to harsh outdoor environments and permits installation in a wide variety of outdoor locations. Ideally it utilizes both audio and visual means to indicate detection of movement at a variety of distances from an observation point.  
           [0010]    According to a further embodiment of the invention, A tripwire warning device is provided, including a weather resistant housing, a battery mounted within the housing, an alarm mounted within the housing, a pair of switches mounted on opposing sides of the housing and configured to close a circuit between the alarm and the battery when activated, and further configured to be attached to trip cords, such that a selected tension on either of the trip cords will activate the alarm. According to an embodiment of the invention, the device includes a pair of spotlights mounted on opposing sides of the housing and configured to illuminate regions extending from the opposing sides of the housing when either of the switches is activated. The switches are individually adjustable for the tension required to activate the alarm function.  
           [0011]    According to another embodiment of the invention, a method of operation is provided.  
           [0012]    According to an additional embodiment of the invention, a training method is provided that utilizes a battery powered tripwire device formed in accordance with the foregoing embodiments. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 shows an isometric view of a battery powered tripwire device in use according to an embodiment of the invention;  
         [0014]    [0014]FIGS. 2 and 3 show partially exploded views of the device of FIG. 1;  
         [0015]    FIGS.  4 A- 4 C show a pull tab modified to adjust activation tension of the device of FIG. 1;  
         [0016]    [0016]FIG. 5 shows the device of FIG. 1 deployed in a battlefield;  
         [0017]    [0017]FIG. 6 shows the device being activated by an intruder; and  
         [0018]    [0018]FIG. 7 shows the device being activated by an intruder in darkness. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    According to an embodiment of the invention, a battery powered tripwire device is provided. One example of such a device is described with reference to FIGS.  1 - 3 .  
         [0020]    [0020]FIG. 1 shows the tripwire alarm for a defensive perimeter security  10 , while FIGS. 2 and 3 illustrate partially exploded views of the tripwire alarm  10  from opposite sides of the device. As shown in FIGS. 2 and 3, the tripwire alarm  10  consists generally of a cubical housing  11 , a back cover plate  20  of the housing, a battery cover  30 , a battery  40 , a unidirectional terminal separator and battery holder  50 , a negative power terminal  60 , a positive power terminal  70 , a positive contact plate  80 , a two variably sensitivity water resistant pull tabs  90  attached to trip cords  93  of a length suitable to be secured at locations 25-50 meters from the pull tabs  90 , and a high decibel siren  100 .  
         [0021]    As shown in FIGS. 2 and 3, the tripwire alarm  10  includes a generally cubical housing  11 . The housing is formed from high-density, impact resistant plastic. The rim  12  of the housing  11  mates with the rim  24  of the back cover plate  20  by means of waterproof cement such as dichloromethane, or by other conventional attachment means. Pull tab notches  13 , located on opposite sides of the housing  11 , are identical in size and are positioned in axial alignment with respect to each other. Alignment folds  73 ,  82  of the dual spring switch  72  and the positive contact plate  81  slide into the pull tab notches  13 . The notches  13  are large enough to allow the upper leaves  74  of the dual spring switch  72  to move freely, in such a way that the variably sensitive pull tabs  90  may be inserted between the respective upper leaf  74  and the positive contact plate  81 . The battery cover slip  14  is configured to cooperate with the slip  23  located on the back cover plate  20 . When the rim  12  of the housing  11  mates to the rim  24  of the back cover plate  20 , a generally rectangular slip is formed. This rectangular slip mates with the slot  32  of the battery cover  30  to form a weather resistant seal around the perimeter of the rectangular slip.  
         [0022]    Integrated into the generally cubical housing  11  are battery holder slots  15   a  and  15   b  that are configured to receive the battery holder  50 . The battery holder  50  slides into the battery holder slots  15   a  and  15   b  and is trapped therein when the back cover plate  20  is affixed to the housing  11 . The unidirectional terminal separator  54  may be formed as an integral part of the battery holder  50  or as an integral part of the cubical housing  11 .  
         [0023]    The cubical housing  11  includes the siren outlet  17 , and is configured to securely receive the siren  100  within the housing  11  and aligned with the outlet  17 . The siren outlet  17  permits the sound of the siren  100  to propagate from the housing  11  toward a defensive position.  
         [0024]    Integrated into the housing  11  are spot light outlets  18  that are configured to permit pre-focused spot lights  120  to slide from the interior cavity of the box  11  through the respective outlets  18  and expose the tips of the lenses of the spotlights  120  to the outside of the box  11 . The diameter of the spot light outlets  18  conforms to the shape of the spot lights  120 , and secures them inside the housing  11 . The spot light rims  122  may be coated with conventional sealant to prevent condensation inside the housing  11 . The pre-focused spot lights  120  may be conventional visible light spots or infrared spots, which produce a light that is invisible to the naked eye.  
         [0025]    Securing brackets  19  are located on either side of the housing  11 . The securing brackets  19  are formed integrally with the housing  11 . The securing brackets  19  permit the tripwire device  10  to be attached to an object, such as a tree  110  or post, etc., by means of a high strength chord, steel wire  111 , or nails.  
         [0026]    The back cover  20  consists of a generally planar surface with prominent rectangular out cropping. The back cover  20  is formed from high-density, impact resistant plastic. When the back cover  20  is mated to the housing  11 , the spot light securing post  21  pushes the negative spotlight power leaflets  62  against the negative contacts of the spotlights  120 , which in turn locks the spot lights  120  into the spot light outlets  18 . The tip  22  of the spot light securing post  21  further locks the negative power contact  60  into the housing  11  by pressing against a portion  63  of the contact  60  in the space separating the two negative spotlight power leaflets  62 .  
         [0027]    The battery cover  30  is generally rectangular in shape. The battery cover  30  may be formed from high-density rubber or plastic. The slots  32  of the battery cover  30  are configured to slide onto the slips  23  and  14  of the housing  11  and cover plate  20 , closing the battery port  13  in a water tight or water resistant closure. The housing  20  and battery cover  30  are sized and configured to push the positive battery terminal  42  of a conventional 9-volt battery  40  against the positive spring terminal  71  and the negative battery terminal  41  against the negative spring contact  61  when the cover  30  is in place on the housing  11 .  
         [0028]    The unidirectional terminal separator  54  is positioned in the housing  11  and defines two notches  52 ,  53 . A small notch  52  restrains the positive contact terminal  71  to the housing  11  when the battery holder  50  is locked into the cubical housing  11 . A large notch  53  restrains the negative contact terminal  61  to the housing  11  when the battery holder  50  is locked into the cubical housing  11 . The unidirectional terminal separator  54  is configured to correctly align the positive and negative terminals  42  and  41  of the battery  40  with the positive battery contact terminal  71  and the negative battery contact terminal  61 , respectively. If the battery is inadvertently reversed in the housing  11 , the terminals  42  and  41  of the battery  40  will be restrained from making reversed polarity contact, since the larger, negative battery terminal  41  is too large to fit into the small notch  52 . In such a situation, the battery  40  cannot be fully inserted into the battery port  13 , which, in turn, prevents the cover  30  from being closed. Thus, an operator is immediately made aware of the incorrect alignment of the battery.  
         [0029]    The negative power terminal  60  incorporates the negative battery contact terminal  61 , the negative spotlight power leaflets  62 , and negative siren contact  64 , and it is formed from a non-corroding and non-oxidizing conductive metal such as brass or aluminum. The negative battery contact terminal  61 , by the nature of its shape has a springing action. The negative battery terminal  41  is pressed into the negative battery contact  61  by the force of the battery  40  against the battery cover  30 . The negative spotlight power leaflets  62  are half circular in shape and configured to contact the negative terminals of the spotlights  120 . The distance between the negative spotlight power leaflets  62  is such that the tip  22  of the securing light post  21  forces the leaflets  62  against the negative terminals of the spotlights  120 , and locks the spotlights  120  to the housing  11 .  
         [0030]    The positive power terminal  70  incorporates the positive battery contact  71  and the upper leaves  74  of the dual spring switch  72 , and it is formed from non-corroding and non-oxidizing conductive metal such as brass or aluminum. The positive battery contact  71 , by the nature of its shape, has a springing action. The positive battery terminal  42  is pressed into the positive battery contact  71  by the force of the battery  40  against the waterproof battery cover  30 . The prominent feature of the positive power terminal  70  is the dual spring switch  72 . The upper leaves  74  of the dual spring switch  72  move freely, in such a way that the variably sensitive water resistant pull tabs  90  can be inserted, and when removed, the upper leaves  74  naturally expand to contact the positive contact plate  81 . The spring alignment folds  73  of the upper leaves  74  engage respective contact plate notches  13 , keeping the positive power terminal  70  locked in the housing  11 , while permitting motion of the upper leaves  74 .  
         [0031]    The positive contact node  80  incorporates a positive contact plate  81 , positive light contacts and holders  83 , and a positive power supply point  84 , formed from non-corroding and non-oxidizing conductive metal such as brass or aluminum. The generally planar, positive contact plate  81  is contacted by the spring action of the upper leaves  74  of the dual spring switch  72  when either of two variably-sensitive water resistant pull tabs  90  are removed. The plate alignment folds  82 , located on the sides of the contact plate  81 , engage respective contact plate notches  13 , locking the positive contact node  80  to the housing  11 . The spotlights  110  are further locked into the housing by the positive light contacts and holders  83 , which have a semi-cylindrical shape to hold the spotlights  120 . The light contacts and holders  83  supply positive power from the battery  40  when the circuit is completed by the removal of either variably sensitive water resistant pull tabs  90 . Positive power is supplied to the siren  100  via a connection soldered to the positive power supply point  84 .  
         [0032]    The variably-sensitive water resistant pull tab  90  is formed from high density, impact resistant plastic. The trip cord  93  is attached to a cord attachment point  91 . A waterproof seal  92  is formed from a soft synthetic or natural rubber material and is attached to the pull tab  90  by a non-water soluble adhesive. The thin waterproof seal  92  aligns in such a way that the alignment folds  82  and  73  are completely sealed from the outside environment when the pull tab  90  is installed. When installed, a blade  94  of the pull tab is positioned between an upper leaf  74  of the dual spring switch  72  and the positive contact plate  81 , insulating the one from the other. The variably-sensitive water resistant pull tab  90  has three sensitivity settings, as Illustrated in FIGS.  4 A- 4 C. FIG. 4A illustrates the least sensitive setting. Increasing the sensitivity of the pull tab  90  is achieved by breaking off and discarding a single triangular piece of the blade  94  along a scored line  95 , as shown in FIG. 4B. For even greater sensitivity, a second triangular piece can be broken off along a scored line  95 , as illustrated in FIG. 4C. The variable sensitivity is achieved by reducing the surface area contacting both the positive contact plate  81  and the upper leaf  74  of the dual spring switch  72 .  
         [0033]    A water resistant audio siren  100  consists of a siren  101  coupled to a control circuit  104 . The control circuit  104  is configured to supply an appropriate signal to cause the siren  101  to emit a high decibel sound, when a supply voltage is present across a positive and negative wires  108 ,  109 . The control circuit  104  and siren  101  are constructed from materials chosen for maximum resistance to water and corrosion. The positive wire  108  is soldered or otherwise electrically connected to the positive power supply point  84 , while the negative wire  109  is soldered or otherwise electrically connected to the negative contact plate  60  at the solder point  64 .  
         [0034]    According to the embodiment described, the negative power terminal  60 , the positive power terminal  70 , and the positive contact node  80  may each be manufactured from a single flat piece of material, cut and folded into the appropriate shape. This affords significant economy to the manufacture of the device. However, other embodiments of the invention include more complex configurations. For example, one of ordinary skill in the art can easily design a device configured to have the spotlights  120  and the siren  100  on separate circuits to allow selective activation. In another embodiment, the dual spring switch  72  is separated into two independent switches. In an additional embodiment, a different type of switch is employed. In one embodiment, only one switch and tripwire are incorporated into the device.  
         [0035]    It will be recognized that there are many possible variations possible while remaining within the scope of the invention. For example, a microchip may be used to control the activation of the siren and lights. Such a chip would eliminate the need for discreet components of the control circuit. A microchip could also be employed to deactivate the spotlights or siren, in accordance with a pre-programmed time schedule, or in response to a photoelectric cell. In this way, the tripwire device could be configured to respond to intruders by sounding the siren during daylight hours and by illuminating the vicinity during nighttime hours. Additionally, infrared spotlights would be visible to observers using night vision aids, while an intruder might remain unaware of having triggered an alarm.  
         [0036]    According to an embodiment of the invention, an infrared sensor is used to detect activation of the tripwire alarm.  
         [0037]    Other embodiments of the invention include variations in size of the tripwire alarm device, alternative materials used to manufacture the device, etc. According to an embodiment of the invention, the siren is programmable to produce one of a variety of distinctive tone patterns, enabling an observer or sentry to differentiate between several devices deployed along a perimeter, thus providing information as to the location of an intrusion. In another embodiment, the tripwire alarm is configured to respond with a first tone pattern if a first one of the pull tabs is removed, and a second tone pattern if the second pull tab is removed.  
         [0038]    [0038]FIGS. 1 and 5 illustrate a typical installation of the tripwire alarm, according to an embodiment of the invention. The tripwire alarm  10  is attached to a tree  110 , using a piece of wire  111 . String or cord, fishing line, nails, and cable ties are some of the alternative means that may be employed to affix the tripwire alarm  10  in place. The tripwire alarm  10  may be attached to any suitable object or surface, such as a post, a stake driven into the ground for the purpose, or a section of a building. The tripwire alarm  10  may include a pressure sensitive adhesive strip on one side, for mounting the tripwire alarm  10  on a smooth surface. In such a case, the operator peels a protective cover from the strip to expose the adhesive and presses the tripwire alarm against a selected surface to affix the device thereto, with the exposed adhesive between the device and the surface.  
         [0039]    The trip cords  93  are attached at one end to a respective one of the pull tabs  90 , and at the other end to a convenient object, such as another tree, post, stake, etc. The trip cord  93  may be 50 meters or more in length, and may be placed 6-24 inches above the ground.  
         [0040]    To install the tripwire alarm  10 , an operator first ensures that the battery  40  is removed from the tripwire alarm to ensure the device does not activate during set up. While holding the waterproof housing  11  firmly against a tree  110  or other such object, the high strength chord or steel wire  111  is passed through one of the securing brackets  19 , around the tree  110 , then through the other securing bracket. Ends of the wire may then be tied together, or they may each be tied to one of the securing brackets  19 .  
         [0041]    With the battery  40  removed, the operator removes one of the two pull tabs  90 . The trip cord  93  is then tied or otherwise attached to the pull tab  90  through the cord attachment point  91 . The operator setting up the tripwire alarm  10  has-three sensitivity settings to choose from, as illustrated in FIGS.  4 A- 4 C. The sensitivity setting is selected based upon the terrain, vegetation and possible avenues of approach, such at paths and roads. The operator breaks the blade  94  of the pull tab  90  as previously described in accordance with the desired sensitivity setting. The operator then slides the pull tab  90  into the pull tab notch  13 , between the upper leaf  74  of the dual spring switch  72  and the positive contact plate  81  and continues to push until the waterproof seal  92  mates up with the side of the housing  11  to ensure the contact point is water resistant. The trip cord  93  is then extended to the side of the device along the desired perimeter from 5 to about 50 meters, and at a height of about 18 inches from the ground. The trip cord  93  is then firmly attached to the secondary attachment point  112  using sufficient tension to prevent the trip cord from significant sagging and to not pull the pull tab  90  from the pull tab notch  13 . The second trip cord  93  is deployed in a direction roughly opposite that of the first trip cord  93 , following the procedure previously described. The operator rechecks the pull tabs  90  to ensure that the seals  92  remain in contact with the housing.  
         [0042]    The battery  40  is then inserted into the housing  11 , ensuring that the positive and negative terminals  42 ,  41  are correctly aligned with the unidirectional terminal separator  54  to maintain correct polarity of the battery  40 . The waterproof battery cover  30  is installed in such a way that the slots  32  engage the slips  23 ,  14  of the housing  11 , pushing the positive and negative battery terminals  42 ,  41  against the positive and negative battery contact terminals  71  and  61 .  
         [0043]    According to one embodiment, the tripwire alarm is used in training exercises to train personnel in handling and placing the devices, and defending perimeters therewith. According to another embodiment, the tripwire alarm is used to train personnel in the avoidance or detection of such devices. In another application of the principles of the invention, the tripwire alarm is used in hazardous or combat situations to defend a perimeter.  
         [0044]    Depending upon the application, the tripwire alarm may be emplaced in a variety of configurations. FIG. 5 illustrates a configuration in which the tripwire alarm  10  is affixed to a tree  110  and the trip cords  93  are stretched, parallel to the ground, to nearby trees  112 . Such emplacements may be made with a plurality of tripwire alarms to completely cover a boundary or section. In such an application, for example, the secondary attachment point of a first tripwire alarm, to the left of the first alarm may also be used as the secondary attachment point of a second tripwire alarm, to the right of the second alarm. If each of the trip cords is extended about 50 meters from a tripwire alarm to the respective secondary attachment points, each alarm may be used to cover a perimeter section of 100 meters. Thus, a one kilometer section of perimeter would require only ten tripwire alarms. Additionally, for tactical reasons it may be desirable to use layers of defense, in which case additional tripwire alarms would be emplaced roughly parallel to each other.  
         [0045]    In another application, the tripwire alarm may be used to train personnel in the detection of lethal tripwire devices. In such an application, the tripwire alarm is configured to mimic the behavior of such a lethal device. Accordingly, the trip cord  93  is extended from the housing only to the extent of the kill radius of a typical lethal device, and it is strategically placed, such as along a path or natural passage. It would not generally have a second trip cord deployed inasmuch as such devices usually employ only one tripwire.  
         [0046]    In one application, it may be desirable for activation of the tripwire alarm to be undetected by an intruder, especially in nighttime conditions. In such a case, infrared spotlights may be used in the device, which are clearly visible to night vision equipped personnel but invisible to the naked eye. Additionally, the alarm might be configured to be activated indirectly. For example, the housing of the alarm might be attached to a tree at a higher level than previously described, while the trip cord is attached to a limb of the same or a neighboring tree, preferably above the head of an intruder, in such a way that movement of an individual past the limb will cause the alarm to be activated. In this way, the intruder will not notice the existence of the cord, and thus may remain unaware of the alarm. If the tripwire alarm is positioned within line of sight of a defensive position, an infrared sensor, similar to the type used to control home electronics, may be used to detect properly modulated infrared emissions from the alarm, even during daylight hours, permitting silent monitoring during daylight hours, as well. Other possible configurations will be evident to those skilled in the art.  
         [0047]    [0047]FIGS. 6 and 7 illustrate the tripwire alarm in use. The defensive position and sentry  120  is located about 50 to 300 meters from the tripwire device  10 . The adversary  114  inadvertently pulls the flexible line  93 . Due to the force exerted by the adversary  114 , the pull tab  90  is removed from the pull tab notch  13 . The upper leaf  74  of the dual spring switch  72  expands naturally and contacts the positive contact plate  81 . This in turn provides power to the siren  100  and the pre-focused spot lights  120 . In response to the siren  100 , the sentry  113  is alerted to the adversary  114  and may take appropriate action.  
         [0048]    [0048]FIG. 6 illustrates a daylight condition, while FIG. 7 shows the activation of the alarm during night or dark conditions. Under dark conditions, activation of the pre-focused spot light  120  illuminates the region around the alarm to permit visual acquisition of the target for identification. Alternatively, the alarm may incorporate infrared lights, which operate in the non-visible spectrum, which would allow the usage of night vision goggles for the sentry  113  to permit visual acquisition of the target for identification.  
         [0049]    All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.  
         [0050]    From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.