Abstract:
A blast shield for underbody protection of vehicles is presented that combines energy absorption and deflection in order to provide occupant protection and increased survivability in the event of an underbody explosive blast, especially those caused by improvised explosive devices. Absorption of blast energy is accomplished by a dampening system comprising a plurality of spaced hydraulic dampers position on a hull that deflects forces outward from underneath the vehicle.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to an energy absorption device for installation under the body of a vehicle to protect the vehicle and occupants from explosive forces caused by the detonation of a bomb, such as an improvised explosive device (IED). Hydraulic dampers combined with a blast deflecting-shaped hull absorb and redirect blast energy absorb away from the vehicle. 
       BACKGROUND 
       [0002]    Improvised explosive devices (IEDs) may be bombs fabricated in an improvised manner from other explosive devices, such as an artillery shell. These devices may incorporate explosive materials, as well as fragmentation materials. IEDs may be remote controlled and/or triggered by infrared detectors, pressure bars, trip wires, and/or other suitable devices. Mines may be explosive devices placed on or in the ground. When in the ground, these mines may be referred to as land mines. These types of mines may be triggered by an operator and/or by the proximity of a vehicle, person, animal, and/or some other suitable object. The term IED may be inclusive of both improvised explosive devices as well as land mines. 
         [0003]    IEDs may target the underside of conventional ground vehicles and armored vehicles. Various counter-measures may be employed to reduce and/or eliminate threats from IEDs. Some counter-measures include electronic jamming devices that may prevent the ignition of remotely controlled IEDs. These electronic counter-measures, however, may be ineffective against IEDs that use trip wires or other non-wireless trigger mechanisms, such as pressure switches used in land mines. Chemical detection may in some cases be successful in locating an IED. Although these and other counter measures may be useful in preventing the triggering of IEDs and/or detecting IEDs, these explosive devices may still detonate regardless of the precautions in place. 
         [0004]    As a result, structures may be employed on the underside of vehicles to protect against pressures and forces generated when an IED explodes. These structures may take the form of blast plates. These blast plates can in some cases mitigate the effects of the explosive pressure and/or fragments to the occupants of a vehicle. These blast plates may be fabricated using armor similar to that used on the sides of armored personnel carriers and tanks. Likewise, it is known to design the plate with a V-shape in an attempt to redirect explosive forces outward and away from the underside of the vehicle. 
         [0005]    Another problem is that extra weight reduces the fuel efficiency of a vehicle and increases operating costs. Further, the weight may increase the strain on other components of the vehicle resulting in more maintenance being performed. The weight of the blast plates also may reduce the acceleration, maneuverability, and/or performance of the vehicle during travel. V plates with steep V shapes can greatly reduce the ground clearance of the vehicle, thus diminishing vehicle performance. As such, it would be advantageous to have a shallow V shape that performs as well as a steep V design while preserving as much of the original vehicle ground clearance as possible. 
         [0006]    Therefore, it would be advantageous to have a device that takes into account one or more of these issues, as well as possibly other issues. 
       SUMMARY 
       [0007]    The present invention combines energy absorption and deflection in order to provide ground vehicle occupant protection and increased survivability in the event of an underbody explosive blast, especially those caused by improvised explosive devices (IEDs). Energy adsorption is accomplished by the use of one or more dampening systems in combination with an energy deflecting V-shaped hull design. The blast shield of this invention can be installed on the underbody of a ground vehicle, for example, a Humvee. 
         [0008]    One advantageous embodiment of the present invention is a blast shield comprising a blast resistant panel, for example armor plating, having a left side edge, a right side edge, a front end, a rear end, a top surface and a bottom surface. An beam having a top and a bottom is connected to the top surface of the panel to form a V-shaped hull, preferably using a bolted connection and without using welds. A pair of dampers is positioned adjacent to and on either side of the beam with each damper having a bottom portion and a top portion. The bottom portion of the damper is in contact with the top surface of the panel and the top portion is adjacent to a channel cap connected to the top of the beam. The panel may also comprise two or more panels connected together without the use of welds to form the preferred V-shaped hull configuration. A preferred beam construction is one that has a cross-section in the shape of an “I,” sometimes referred to as an “I-beam,” however, beams having a different cross-section can be used. 
         [0009]    Yet another advantageous embodiment of the present invention comprises a blast shield that uses a V-shaped hull fabricated with only bolted and braced connections and no welds. The absence of welds allows each of the materials of construction to retain its full inherent mechanical strength. A dampening system is positioned mechanically in series between the armor plate and the support structure that defines the V-shaped hull. The rigid armor plate or plates deflect the blast energy while the dampening system simultaneously absorbs this energy by taking advantage of the inertia differential between the blast shield acting on one side and the vehicle weight acting on the opposite side, thus creating the required displacement in the dampers to absorb the blast energy. 
         [0010]    Another advantageous embodiment comprises a modular design with a fully bolted construction that allows ease of integration into retrofit kits for legacy vehicles and also can be integrated into clean sheet design for ground combat vehicles. This modular design includes the use of surface or connection bars that allow the blast shield to be fastened to the frame of the vehicle. The surface bars also provide rigid longitudinal support for the blast shield and are positioned along the right and left side edges of the panel. A crushable and compressible energy absorbing material can be sandwiched between the top surface of the panel and the bottom of the surface bar. Additionally, this deformable material can be used between truss ribs and the top surface of the panels and between end caps and the beam located on the centerline of the blast panel. 
         [0011]    Another advantageous feature of the present invention is that the dampening system can be tuned for a desired energy absorption taking into account the specifics of the vehicle and the expected types of IEDs. Tuning can be achieved by changing the configuration of the internal components of the dampers, including, for example, changing the number adjustable orifices, the orifice size, or the type of working fluid. The use of the dampening system is believed advantageous because blast energy will first be absorbed by the dampening system before absorption by the armor blast plates. 
         [0012]    Yet another advantageous embodiment of the blast shield of this invention includes the use of a plurality of truss ribs connected to the top surfaces of the panel and positioned to define a plurality of channels extending outward from the beam. Preferably, the channels house the dampening system of the present invention, where each channel can hold a damper contained between two adjacent ribs and covered by a channel cap, where the channel cap is connected to two adjacent truss ribs. The channel caps can be attached, preferably by screws or bolts, to the top of the beam. 
         [0013]    Another advantageous embodiment includes a dampening system comprising a plurality of hydraulic dampers having a slidable piston within a reservoir, where the reservoir is filled with a working fluid, preferably a viscous fluid, for example, grease. A hollow cylinder portion of the damper defines the reservoir within the cylinder wall. The top portion of the damper preferably comprises a deformable shock absorbing material that in a first state will securely contact the damper to the channel cap and in a second state will fragment and collapse in response to a blast event. The bottom portion of the damper can be wedged shaped and comprise the same or different deformable shock absorbing material used to form the top portion. The damper piston has one or more orifices to allow the working fluid to flow out of the reservoir when the cylinder and piston slide relative to each other. The piston can also be hollow defining a lower reservoir having a moveable seal that can be biased by a compression spring configured to keep the working fluid trapped within the lower reservoir and to allow the dampers to be filled with the working fluid. The orifices also allow the dampers to be bled to remove trapped air. The spring can be configured with enough compression force to return the movable seal to a starting position after compression. 
         [0014]    In yet another advantageous embodiment the blast shield comprises two end caps, one end cap is connected to the front end of the blast panel and the other end cap is connected to the rear end of the panel, where a deformable material is disposed between each end cap and the beam. 
         [0015]    Another advantageous embodiment of the present invention is the inclusion of a second dampening system where a second plurality of dampers are used to absorb blast energy that causes the side edges of the panel to pull inward towards the beam during an explosive evident. As the blast forces are directed upwards against the bottom side of the blast panel the panel is deformed into a so-called “gull wing” shape where the top surface on either side of the beam deflects upwards towards the vehicle causing each side of the panel to pull inwards toward the beam. To diminish the effect of this retraction of the side edges, the panel can include a longitudinal slot or opening along each edge. Further, each surface bar can include one or more downwardly extending lugs that project into openings or slots located intermittingly along the panel edges. A plurality of hydraulic dampers can be positioned in these slots and in contact with the lugs such that the dampers absorb the forces causing the inward movement of the panel edges These dampers can be the same or similar in design to the dampers described above. 
         [0016]    The present invention also includes a method of protecting the occupants of a vehicle from a blast event by providing a shield having one or more blast resistant panels connected to a beam where the top surface of the panel has opposing connection points, preferably along each side edge, for attaching the shield to the vehicle, preferably to the underneath of the vehicle and most preferably to the vehicle frame. The panel is connected to the panel to form a hull that directs blast forces away from the vehicle. A dampening system is coupled to the top surface of the panel(s) preferably such that at least a pair of dampers is positioned adjacent to and on either side of the beam. During a blast event the shield transforms from a pre-blast event state to a post-blast event state. This transformation caused to distance between the opposing connection points to move closer together. Stated differently, the opposing connection points are closer together in the post-blast state of the shield as compared to the pre-blast state. The method also results in one or more dampers moving from an uncompressed state to a compressed state when the shield transforms from a pre-blast event state to a post-blast event state. 
         [0017]    The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0018]    The present invention will become more fully understood from the more detailed description presented below and the accompanying drawings which are presented by way of illustration only, and thus, are not limitations of the present invention, and wherein: 
           [0019]      FIG. 1  illustrates one possible advantageous embodiment of the present invention attached to the underbody of a ground vehicle; 
           [0020]      FIG. 2  schematically illustrates a perspective view of one advantageous embodiment of the blast shield of the present invention; and 
           [0021]      FIG. 3  presents a close up partial perspective view of the advantageous embodiment of the blast shield illustrated in  FIG. 2 ; 
           [0022]      FIG. 4  illustrates a perspective view of one embodiment of the damper of the present invention; 
           [0023]      FIG. 5  illustrates a cross-sectional perspective view of one embodiment of the damper of the present invention; 
           [0024]      FIG. 6  illustrates a close-up perspective of a side edge of one possible embodiment of the present invention using a second dampening system; and 
           [0025]      FIG. 7  illustrates a close-up perspective of a side edge of one possible embodiment of the present invention using a second dampening system viewed from the bottom of the blast shield. 
       
    
    
       [0026]    Corresponding parts are marked with the same reference symbols in all figures. 
       DETAILED DESCRIPTION 
       [0027]    Referring now to the drawings illustrating possible embodiments of the present invention,  FIG. 1  shows a blast shield  1  of the present invention connected to the underbody  101  of a ground vehicle  100 . Preferably, the blast shield system is bolted directly to the vehicle frame. 
         [0028]    Ground vehicle  100  may take various forms, for example, without limitation, it may be a high mobility multi-purpose ground vehicle, a tank, an armored personnel carrier, a car, a truck, or some other suitable type of ground vehicle. Although a ground vehicle is shown, different advantageous embodiments may be applied to other vehicles, such as winged or rotor aircraft, naval vehicles, or even prefabricated temporary buildings. 
         [0029]      FIG. 2  illustrates blast shield  1  as viewed from the top or looking downward from the vehicle underbody to which it is configured for attachment. A close-up cross sectional view of shield  1  is presented in  FIG. 3 . A blast plate or panel  2  is shown connected to beam  5 , illustrated as an I-beam, through connections  3 , preferably using bolts, screws, or other removable connectors. As alternative to the I-beam illustrated, beam  5  can have a different shape and cross-section, for example a hat-shaped beam, or can be any other structural support member that provides multiple attachment points for one or more panels  2 . Preferably, welded connections are not used in order to preserve the mechanical strength properties of the panel and to allow for a modular construction design. Panel  2  is preferably a single sheet of blast proof armor and may be comprised of any material suitable for deflecting and/or absorbing blast energy. For example, without limitation, blast panel  2  may be comprised of a metallic material, aluminum, titanium, steel, a steel alloy, a ceramic material, a composite material, and/or some other suitable material. The panel may have multiple layers of these mentioned materials, a single layer of a selected material, and/or some other suitable configuration. When a single panel is used it preferably has a non-planar shape design to direct blast forces outwardly away from the centerline of the panel where beam  5  is preferably connected. 
         [0030]    Panel  2  and beam  5  are connected through connectors  3  to form a V-shaped hull where the right and left sides of the panel project upwardly at angle Θ, which preferably is less than 90 degrees and more preferably in the range of from about 10 degrees to about 20 degrees upwardly from horizontal. (see  FIG. 2 ). In alternative embodiments of the present invention the right and left sides may comprise individual panels that are joined together through connection to I-beam  5 . Attached to the front and rear ends of panel  2  are end caps  7  connected through connectors  13 . Truss ribs  9  are connected to panel  2  through connector lugs  11  and can be interconnected to each other through cross supports  33 . Ribs  9  extend outwardly from beam  5  and are positioned in adjacent rows transverse to the beam  5  and the centerline  300 , preferably forming an approximate right angle with respect to the centerline, although the ribs may form non-right angles with respect to the centerline and still perform their intended function. Each pair of adjacent ribs forms a channel  9   a.  Channels  9   a  are partially covered with a channel cap  8  that is connected to the top of beam and to the adjacent ribs. The ribs are preferably fabricated to match the shape of panel  3 , preferably having angled bottom edges  9   b  matching angle Θ. 
         [0031]    Each side edge of panel  2  has connecting or surface bars  10  that allow blast shield  1  to connect through connectors  11  to the underbody  101  of vehicle  100 . Positioned between surface bars  10  and the edge of panel  2  is a destructible and deformable material  12 . The same or like deformable material  12  and  14  can also be positioned between the bottom edge  9   b  of ribs  9  and the top surface  2   a  and between end caps  7  and beam  5 , respectively. The destructible and deformable material can be selected from a group of materials that will crush in a blast event allowing displacement of the components on either side of the material, which also allows displacement of a dampener system. The dampening system comprises a plurality of dampers  30  that are configured to absorb additional blast energy at the same time as the deformable material. Preferably, the deformable material is stiff enough to allow rigid attachment of the armor structure to the vehicle, but soft or yielding enough to allow inertia to move the V-shaped hull relative to the center structure during a blast event. Suitable deformable materials could include polyurethanes, aluminum foam, or combinations of these or like materials. 
         [0032]    The dampening system of the present invention can comprise two separate systems. On system comprising a plurality of dampers  30  located in the channels  9   a  formed by adjacent ribs  9  and located underneath channel caps  8 . The second dampening system, as discussed in more detail below, comprises a plurality of dampers  60  positioned in a slot  36  on the side edges of panel  2 .  FIG. 3  shows a pair of dampers  30  arranged adjacent to beam  5  and positioned on either side of the beam. Multiple dampers can be positioned along the length of the centerline  300 , preferably having a damper in each channel  9   a  and on each side of the beam  5 .  FIGS. 4 and 5  illustrate a preferred damper design. Piston  34  is slidable within cylinder  33 . The top portion  32  of the damper is a cushion, preferably comprising a soft material, such as plastic, that isolates the rigid cylinder  33  from extreme shock loads, e.g., a metal on metal contact during a blast event. Although the exemplified dampers described here and shown in the figures are hydraulic dampers, other damper designs could be used, for example, those based on one or more springs, compressible materials, frangible materials, or designs that may incorporate a combination of such materials with hydraulic and/or spring features. 
         [0033]      FIG. 5  shows the internals of a preferred damper design. A reservoir  35  is defined by the upper surface of the cylinder  33 , the cylinder walls and top surface  37  of piston  34 . Grease or other viscous working fluid  50  is contained in reservoir  35 . The top  37  of piston  34  may have one or more adjustable orifices  36  having orifice channels  38 . The adjustable orifices can allow the working fluid to flow from the reservoir  35  to a lower reservoir  39  upon compression of damper  30  during a blast event. This restricted flow of the working fluid provides the energy absorbing dampening effect of the dampening systems of the present invention. The adjustable orifices  36  can be configured to allow the dampening system to be tuned during the manufacturing process to allow the blast shield  1  to be used for different structures on different vehicles. Seals  45 , for example, piston rings, allow piston  34  to slide relative to cylinder  33  while preventing the working fluid  50  from leaking out of reservoir  35 . A return spring  40  can be used in conjunction with bladder umbrella seal  41  to trap any of the working fluid passing through orifices  36 . This combination of spring and bladder seal can allow the dampers to be filled and bled and/or to return the working fluid into reservoir  35  after compression. 
         [0034]    In a preferred arrangement, each dampener  30  is provided with a bottom portion  15  made of the same cushion material as the top portion  31  or of the deformable material  32 . The bottom portion can be directly connected to the dampener  30  or be a separate component that is position on the top surface  2   a  of panel  2  directly under the damper  30 . In ether case it is preferred that the bottom portion  15  is wedge shaped matching angle Θ. This allows the damper to be positioned vertically plum relative to the horizontal. 
         [0035]    Referring again to  FIGS. 2 and 3 , during an explosive event that occurs underneath the blast shield  1 , blast energy is directed upward against the bottom surface  2   b  of panel  2  causing the right and left sides of the panel to bow or deflect upwards in the direction shown by arrows  20   a  and  20   b.  This deflection of the panel causes a gull wing shape because the rigid beam  5  resists upward movement. As the right and left portions of panel  2  move upwards, the sides of the panel are simultaneously pulled inwards towards the centerline  300  in the direction shown by arrows  21   a  and  21   b.  To minimize the effect of this inward pulling and the strain placed on connecting bars  10  and underbody  101 , a second dampening system can be used. 
         [0036]    The optional second dampening system is shown in  FIGS. 6 and 7  where one side edge of panel  2  is shown having a slot or opening  76 .  FIG. 7  shows a view from looking up from the ground at the bottom side of panel  2 . One of a plurality of cut outs  90  in the blast panel is shown along with a plurality of connection points or holes  11   a  that are shaped to allow lateral movement of the blast shield in the direction of arrow  77  relative to the vehicle body and connectors  11 . Surface bar  10  has a lug  75  extending downward into slot  36  of cut out  90  and has an inner wall  54  and outer wall  53  that is tapered to provide support for the second dampening system. The optional second dampening system can comprise a plurality of dampers  60  that are positioned in space  52  formed between inner wall  54  and wall  55  of panel  2 . As panel  2  is pulled in the direction shown by arrow  77  during a blast event the dampers  60  will compress as space  52  decreases and will absorb and dampen the blast energy. Dampers  60  are preferably of the same design as those described above for dampers  30 . 
         [0037]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various application such specific embodiments without departing from the generic concept, and therefore such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation.