Abstract:
An add-on armor adapted for protecting a belly of a vehicle, the add-on armor comprising a base plate and a plurality of energy absorbing modules fitted to the base plate. The arrangement is such that at least a majority of a surface of each energy absorbing module facing the base plate overlaps with the base plate at an area thereof constituting a module zone. The module zones are associated with different modules being spaced from one another by vacancy zones.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to add-on armors adapted for protecting a belly of a vehicle, in particular, add-on armors comprising energy absorbing mechanisms. 
       BACKGROUND OF THE INVENTION 
       [0002]    Vehicles, in particular military vehicles, require armor in order to protect them from incoming threats such as projectiles, bombs, missiles, mines etc. For this purpose, a variety of armors have been contemplated adapted for covering portions of the vehicle in order to provide the desired protection. 
         [0003]    In general, armor may be divided into two types—integral armor and add-on armor. The integral armor is integrally formed with the vehicle to be protected, while an add-on armor is usually attachable to the vehicle in a detachable manner, and may be mounted onto an existing vehicle and be removed therefrom if so desired. 
         [0004]    Specific add-on armors have been designed for specific portions of vehicles, e.g. door armor, hull armor, belly armor etc. One such example of a belly armor is disclosed in U.S. Pat. No. 5,905,225. 
       SUMMARY OF THE INVENTION 
       [0005]    According to the present invention there is provided an add-on armor adapted for protecting a belly of a vehicle, said add-on armor comprising a base plate and a plurality of energy absorbing modules fitted to said base plate so that at least a majority of a surface of each energy absorbing module facing said base plate overlaps with the base plate at an area thereof constituting a module zone, the module zones associated with different modules being spaced from one another by vacancy zones. 
         [0006]    According to a second aspect of the present invention there is provided an armored vehicle comprising a hull and an add-on armor of the first aspect of the present invention, said add-on armor being attached to the belly of the vehicle such that the energy absorbing modules are disposed between their respective module zoned and the belly of said vehicle. 
         [0007]    Said vehicle may be driven either by wheels (conventional vehicle) or by endless traction belt (e.g. tank, armored troop carrier). 
         [0008]    The add-on armor may be adapted to protect passengers located within the vehicle from an external force applied to the belly of the vehicle, e.g. a force caused by an explosion. Preferably, the add-on armor is adapted to absorb the majority of energy conveyed by the force of the explosion and the belly of the vehicle itself is adapted to absorb at least part of the remainder of said energy. 
         [0009]    It should be noted that the add-on armor is designed according to the specific shape and dimensions of the vehicle. Said vehicle may comprise a plurality of automotive components, e.g. drive shaft etc., some of which are externally located beneath the belly of the vehicle. The energy absorbing modules may be arranged along the base plate at predetermined locations such that when the add-on armor is mounted onto the belly of the vehicle, the energy absorbing modules are located between the automotive components. More specifically, the arrangement may be such that no automotive component of the vehicle is disposed between the energy absorbing module and the belly of the vehicle. 
         [0010]    Several advantages may arise from the above design, two of which are load distribution and automotive protection:
       load distribution—In the event of an explosion, loads applied by the explosion on the base plate at a local area (hereinafter ‘explosion zone’) may be distributed to all the energy absorbing modules located in the vicinity of the explosion zone. It is appreciated that in the absence of a base plate as described above, the only energy absorbing module/s to absorb the energy of the explosion would be those located at the explosion zone itself; and   automotive protection—since no automotive components are located between the energy absorbing module and the belly of the vehicle, and since most of the loads are taken on by the modules, in the event of an explosion the chances of an automotive component to take on loads is reduced, making it less prone to damage due to the explosion. It should also be noted that while local structural damage to the hull of the vehicle may be acceptable, damage to one of the automotive components may cause immobilization of the entire vehicle.       
 
         [0013]    It is appreciated that in the absence of a base plate as described above (i.e. in a design in which the energy absorbing modules are attached to the belly), the only energy absorbing modules to absorb the energy of the explosion would be those located at the explosion zone itself. 
         [0014]    The energy absorbing module may have a thickness T measured between the face of the energy absorbing module facing the base plate and a face opposite thereto. Thus, the minimal distance required between the base plate and the belly of the vehicle when the add-on armor is mounted onto the belly, should be at least equal to the thickness T of the energy absorbing module. 
         [0015]    Said energy absorbing module may me adapted for undergoing progressive deformation under the application of the load of the explosion. By progressive deformation, a deformation is meant which, contrary to regular plastic deformation, does not lead to simultaneous crushing of the entire mechanism, but rather successively compresses it, such that uncompressed portions of the mechanism maintain their integrity until they are compressed. 
         [0016]    The arrangement may be such that under the application of the above mentioned force, the energy absorbing module is pressed upon from one side by the base plate and from the other side by the belly, applying a load to the module which entails its deformation. 
         [0017]    According to a third aspect of the present invention there is provided an add-on armor for a vehicle comprising a hull having sidewalls and a belly extending therebetween at a bottom side of said vehicle, said add-on armor comprising a base plate adapted for being externally mounted onto said belly and at least one energy absorbing module, which, when the base plate is mounted onto said belly is located between said base plate and belly said, wherein said energy absorbing module is adapted for undergoing progressive deformation under application of a load thereto. 
         [0018]    One advantage of an energy absorbing module which is adapted for undergoing progressive deformation is that during this deformation, loads applied to the energy absorbing module are not immediately transferred to the belly of the vehicle located above it. Thus, the energy absorbing module may absorb a considerable amount of energy before loads are transferred to the belly of the vehicle. 
         [0019]    The energy absorbing module may comprise at least any one of the following:
       a structure adapted for progressive deformation; and   at least one layer of energy absorbing material adapted for progressive deformation, e.g. metallic foam, for example, Aluminum foam.       
 
         [0022]    In the latter case, said energy absorbing module may comprise a plurality of layers, at least one of which is made of said energy absorbing material. In particular, said energy absorbing material may constitute an intermediate layer and be positioned between two cover layers. The cover layers and the energy absorbing material may be attached to one another to form the energy absorbing module by gluing, pressing and the like. 
         [0000]    1. The cover layers may be made of a material which is, on the one hand, adapted for undergoing local fracture under application of a predetermined load and on the other hand, is relatively light-weight and high durability to environmental conditions (wind, water etc.). Such a material may be chosen from a family of fibrous materials capable of undergoing deformation when a load is applied thereto, which is localized to an area essentially less than the area of said surface of the module, without influencing the remainder of the cover layer. Examples of such a material may be fiberglass or basalt sheets. It is noted that for the present invention, fibrous materials such as Aramid will not suffice due to their lack of durability to environmental conditions, and lack of ability to undergo localized deformation as defined above. 
         [0023]    The tendency of the energy absorbing material to undergo local deformation, demonstrates another advantage of the add-one armor, which is uniform application of load. More particularly, in the event of an explosion, in the absence of a base plate, the loads applied to the energy absorbing module may be very local, and thus entail only local deformation in the module, leading to a low absorption of energy. To the contrary, in the present invention, the explosion applies loads first to the base plate, which then uniformly transfers the loads through the module zone to the entire face of the energy absorbing module, thereby increasing its ability to absorb energy. 
         [0024]    The base plate may be formed with a plurality of attachment ports, associated with corresponding attachment ports of the belly of the vehicle. In particular, the base plate may have belly portions extending generally parallel to the belly of the vehicle and side portions extending generally parallel to the side walls of the vehicle such that the attachment ports located on the belly portions are associated with attachment ports located on the belly of the vehicle, and the attachment ports located on the side portions are associated with attachment ports located on the side walls of the vehicle. Attachment between the attachment ports of the base plate and the attachment ports of the belly may be performed by bolts, welding etc. 
         [0025]    The add-on armor may also comprise securing elements adapted for preventing the side portions of the base plate from detaching from the side walls of the vehicle under the impact of the force of the explosion on the belly portion of the base plate. Such securing elements may be adapted to be fitted between the base plate and the belly of the vehicle. According to a particular example, such a securing element may be a metal box having side faces attached to the vehicle belly and to a side portion and a belly portion of the base plate. 
         [0026]    The base plate itself may be in the form of ballistic armor (referred herein as ‘belly armor’), e.g. having a construction and/or made of a material providing ballistic protection against the expected force of the explosion against which protection of the passengers of the vehicle is sought. 
         [0027]    According to a particular example, the belly armor may extend generally parallel to the belly of the vehicle and adapted for providing additional ballistic protection to the belly of the vehicle. The belly armor may be made of a material providing ballistic protection, e.g. steel. 
         [0028]    In order to increase its ballistic protection, the belly armor may have a special anti-ballistic design, for example, a V-shaped design. The base plate may be mounted onto the vehicle such that the apex of the V shape is the most remote point of the belly armor from the belly of the vehicle. Hereinafter, the term ‘central portion’ will refer to the area of the apex of the belly armor, while the term ‘peripheral portion’ will refer to areas of the belly armor surrounding the central portion. Such a V-shaped design may be adapted for diverting the energy of an explosion from the central portion towards the peripheral portion of the belly armor, and consequently towards the portions of the belly of the vehicle adjacent the side walls thereof. 
         [0029]    The belly armor may be designed so as to have an increased ballistic protection at the central portion thereof than at the peripheral portion. Such an increase may be provided, for example, by the belly armor having an increased thickness at the central portion. According to a particular design, the central portion may be provided with an auxiliary armor sheet attached thereto at an external side thereof, i.e. such that, when the add-on armor is mounted onto the belly, the belly armor is disposed between the auxiliary sheet and the vehicle belly. 
         [0030]    The auxiliary armor sheet may be made of a material similar to the material of the belly armor in its ballistic characteristics. According to a particular example, the belly armor and the auxiliary armor sheet may be separated therebetween by an intermediate layer adapted for interrupting energy dissipation between the auxiliary armor sheet and the belly armor itself. Such a material may be, for example, ballistic fabric, fiberglass, basalt sheet etc. 
         [0031]    The belly armor may further be fitted with an internal energy absorbing member which is attached to an inner side of the belly armor and extending along the ridge formed by the V-shaped design of the base plate. Such an energy absorbing member may be generally similar in construction to the previously described energy absorbing module, i.e. it may also be adapted for performing progressive deformation. However, it should be noted that it is not restricted to the exact construction previously described, i.e. an intermediate layer and two cover layers. 
         [0032]    The above described arrangement and manner of operation may allow the majority of energy of the explosion to be absorbed by the add-on armor (i.e. the belly armor and the energy absorbing modules), leaving only a minor amount of energy to be absorbed by the belly of the vehicle itself. Thus, passengers located within the vehicle are not subjected to considerable loads due to an explosion and remain generally protected. 
         [0033]    The add-on armor according to the present invention may be particularly useful for vehicles having a low ground clearance. By ‘ground clearance’ a vertical distance is meant which, when the vehicle is positioned on a reference surface, is measured between the lowermost point of the belly of the vehicle and the reference surface. In general, for energy conveyed by the same explosion, an armor of a vehicle having a low ground clearance will require to absorb substantially more energy than an armor of a vehicle with high ground clearance for providing a similar level of protection to the vehicle. The term ‘low’ with respect to ground clearance refers to a ground clearance which is not greater than 50 mm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0035]      FIG. 1  is a schematic cross-sectional view of a vehicle adapted for mounting thereon the add-on armor of the present invention, the cross-section being taken along a plane extending between side walls of the vehicle; 
           [0036]      FIG. 2A  is a schematic front isometric view of an add-on armor according to the present invention; 
           [0037]      FIG. 2B  is a schematic cross-section view of the add-on armor shown in  FIG. 2A , taken along a plane perpendicular to a base plate of the add-on armor as shown by line I-I  FIG. 2A ; 
           [0038]      FIG. 2C  is a schematic enlarged view of the detail A shown in  FIG. 2B ; 
           [0039]      FIG. 2D  is a schematic rear isometric view of the add-on armor shown in  FIG. 2A ; 
           [0040]      FIG. 2E  is a schematic bottom isometric view of the add-on armor shown in  FIG. 2A ; and 
           [0041]      FIG. 3  is a schematic isometric view of an energy absorbing module used in the add-on armor shown in  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0042]    With reference to  FIG. 1 , a vehicle, generally designated as  1  is shown comprising a hull having side walls  2  extending in a generally vertical direction and a belly  3  extending between the side walls  2  at the bottom of the vehicle  1  (i.e. generally parallel to the ground). The vehicle  1  further comprises a wheel base having an axle  4  with two wheels  5  mounted thereon. Inside the hull of the vehicle there are positioned two seats  6 . 
         [0043]    The vehicle  1  may be a military vehicle, in which case protection thereof against various threats may be sought. For this purpose, attention is drawn to  FIGS. 2A to 2E  in which an add-on armor generally designated  10  is shown comprising a base plate  20  and six energy absorbing modules  30 . 
         [0044]    The energy absorbing modules  30  are disposed along predetermined locations of the base plate  20  (hereinafter referred to as ‘module zones’ MZ) leaving vacant spaces between the modules  30  (hereinafter referred to as ‘vacant zones’ VZ). The modules  30  are oriented so with respect to the base plate  20  that a face thereof facing the base plate  20  is almost fully covered by it. 
         [0045]    In assembly, the add-on armor  10  is adapted to be mounted onto the belly  3  of the vehicle  1  as seen in  FIG. 2B . The add-on armor is adapted to protect passengers located within the vehicle  1  (e.g. sitting on the seats  6 ) from an external force applied to the belly  3  of the vehicle  1 , e.g. a force caused by an explosion. The add-on armor  10  is designed to absorb the majority of energy conveyed by the force of the explosion so that the belly  3  of the vehicle  1  itself absorbs only a part of the remainder of this energy. 
         [0046]    It should be noted that the add-on armor  10  is designed according to the specific shape and dimensions of the vehicle  1 . Thus, the module zones MZ are chosen such that when the add-on armor  10  is mounted onto the vehicle  1 , no automotive components of the vehicle  1 , e.g. the axle  4 , are disposed between the energy absorbing modules  30  and the belly  3 , i.e. passing only above the vacant zones VZ of the base plate  20 . 
         [0047]    Several advantages may arise from the above design, two of which are load distribution and automotive protection:
       load distribution—In the event of an explosion, loads applied by the explosion on the base plate  20  at a local area (hereinafter ‘explosion zone’ EZ) will be distributed to all the energy absorbing modules  30  located in the vicinity of the explosion zone EZ. It is appreciated that in the absence of a base plate  20  as described above, the only energy absorbing modules  30  to absorb the energy of the explosion would be those located at the explosion zone itself; and   automotive protection—since no automotive components are located between the energy absorbing module  30  and the belly  3  of the vehicle  1 , and since most of the loads are taken on by the modules  30 , in the event of an explosion the chances of the automotive component/s to take on loads is reduced, making it less prone to damage. It should also be noted that while local structural damage to the hull of the vehicle  1  may be acceptable, damage to one of the automotive components may cause immobilization of the entire vehicle  1 .       
 
         [0050]    The energy absorbing module  30  has a thickness T measured between the face of the energy absorbing module  30  facing the base plate  20  and a face opposite thereto. Thus, the minimal distance required between the base plate  20  and the belly  3  of the vehicle  1  when the add-on armor  10  is mounted onto the belly  3 , should be at least equal to the thickness T of the energy absorbing module  30 . 
         [0051]    The energy absorbing module  30  is adapted for undergoing progressive deformation under the application of the load of the explosion. By progressive deformation, a deformation is meant which, contrary to regular plastic deformation, does not lead to simultaneous crushing of the entire mechanism, but rather successively compresses it, such that uncompressed portions of the mechanism maintain their integrity until they are compressed. 
         [0052]    The arrangement is such that under the application of the above mentioned force, the energy absorbing module  30  is pressed upon from one side by the base plate  20  and from the other side by the belly  3 , applying a load to the module  30  which entails its deformation. 
         [0053]    One advantage of such an energy absorbing module is that loads applied to the energy absorbing module  30  are not immediately transferred to the belly  3  of the vehicle  1  located above it. Rather, the energy absorbing module  30  absorbs a considerable amount of energy before loads are transferred to the belly  3  of the vehicle  1 . 
         [0054]    With particular reference to  FIG. 3 , the energy absorbing module  30  comprises an intermediate layer  32  and two cover layers  34  confining the intermediate layer  32  from opposite sides thereof. The cover layers  34  and the intermediate layer  32  can be attached to one another by any conventional means such as gluing, pressing and the like. Reverting momentarily to  FIGS. 2A to 2E , the modules  30  are mounted on the base plate  20  such that one cover layer  34  faces the base plate  20  and the other cover layer  34  faces the belly  3  of the vehicle  1 . Due to a curved shape of the base plate  20 , the energy absorbing module  30  is provided with a support  36  located between a bottom cover layer  34  thereof and the base plate  20 , adapted for firmer positioning thereof on the base plate  20 . 
         [0055]    The intermediate layer is made of a material adapted for performing progressive deformation, e.g. Aluminum foam. Such a material is adapted, under the application of a load, to become compressed (on account of its porous structure) and thereby absorb energy. Upon complete compression thereof, the material continues to absorb energy in a manner similar to regular metal (in this case Aluminum). 
         [0056]    The cover layers  34  may be made of fibrous brittle materials, having the advantage, on the one hand, of being adapted for undergoing local fracture under application of a predetermined load and on the other hand, being light-weight and high durability to external conditions (wind, water etc.). In the present example, the cover layers are made of fiberglass. However, other materials chosen from a family of fibrous brittle materials may be used as cover layers, e.g. basalt sheet. 
         [0057]    The tendency of the energy absorbing material to undergo local deformation, demonstrates another advantage of the add-one armor  10 , which is uniform application of load. More particularly, in the event of an explosion, in the absence of a base plate  20 , the loads applied to the energy absorbing module  30  may be very local, and thus entail only local deformation in the module, leading to a low absorption of energy. To the contrary, when using a base plate  20 , the explosion applies loads first to the base plate  20 , which then uniformly transfers the loads through the module zone MZ to the entire face (cover layer  34 ) of the energy absorbing module  30 , thereby increasing its ability to absorb energy. 
         [0058]    The base plate  20  has a central portion  22  and two peripheral portions  24 , arranged such that when mounted onto the vehicle  1 , the portions  22 ,  24  extend along the longitudinal direction of the vehicle  1 , i.e. between a front end thereof and a rear end thereof. Each portion  22 ,  24  has a respective top face  22 T,  24 T and a respective bottom face  22 B,  24 B, such that the energy absorbing modules  30  are mounted on the top faces  22 T,  24 T, and when the add-on armor  10  is mounted onto the vehicle  1 , the top faces  22 T,  24 T face the belly  3  of the vehicle  1  and the bottom faces  22 B,  24 B face the ground (assuming the vehicle  1  is positioned on the ground it in its upright position). Thus, the energy absorbing modules  30  are confined between the top faces  22 T,  24 T of the base plate  20  and the belly  3  of the vehicle  1 . 
         [0059]    The central portion  22  of the base plate  20  is formed with several attachment ports  26  adapted for attachment of the add-on armor  10  to the belly  3  of the vehicle  1 . In addition, the peripheral portions  24  of the base plate  20  are each fitted with three side extensions  40  and the central portion is fitted at one side thereof with a rear extension. The extensions  40 ,  50  are each formed with a respective base portion  42 ,  52  adapted for attachment to their respective central/peripheral portion  22 ,  24  (e.g. by welding), and a respective vehicle portion  44 ,  54  extending generally perpendicular to the base portion  43 ,  52  and formed with respective attachment ports  46 ,  56  adapted for attachment to the side walls  2  and rear wall (not shown) of the vehicle  1 . 
         [0060]    The base plate  20  is further fitted with six structural integrity devices  60  located on the peripheral portions  24  of the base plate  20  adjacent the side extensions  40 . Each structural integrity device  60  comprises a bottom face  62  attached to the base portion  42  of the extension  40 , a side face extending perpendicularly thereto, and a top face  66  extending along the belly  3  of the vehicle  1 . The purpose of the structural integrity devices  60  will be explained in detail later with respect to the operation of the add-on armor  10 . 
         [0061]    The base plate  20  is designed to function as a ballistic armor, and as such, has a construction and/or is made of a material providing ballistic protection against the expected force of the explosion against which protection of the passengers of the vehicle is sought. 
         [0062]    In particular, both central portion  22  and peripheral portion  24  of the base plate  20  are made of High Hardness (HH) steel about 10 mm thick, thus being adapted to protect the belly of the vehicle against various ballistic threats. In addition, the central portion  22  of the base plate  20  has a V-shaped, such that the apex  27  of the V-shape is the remote most point from the belly  3  when the add-on armor  10  is mounted onto the vehicle  1 . Such a V-shaped design is adapted for diverting the energy of an explosion from the central portion  22  towards the peripheral portions  24  of the base plate  20 , and consequently towards portions of the belly  3  of the vehicle  1  adjacent the side walls  2  thereof. 
         [0063]    The central portion  22  of the base plate  20  is formed fitted with an auxiliary sheet  70  adapted to provide the central portion with increased thickness, and consequently with increased ballistic characteristics. The auxiliary sheet  70  is made of HH steel about 8 mm thick. The auxiliary sheet  70  may be attached to the central portion  22  by bolts  73 . The auxiliary sheet  70  is separated from the central portion  22  by a buffer sheet  72  adapted for interrupting energy dissipation between the auxiliary sheet  70  and the central portion  22 . It is appreciated that were the auxiliary sheet  70  be attached directly to the central portion  22 , the energy dissipation therethrough would be almost equivalent to dissipation through 18 mm of steel. The buffer sheet  72  is made of fiberglass material and is about 5 mm thick. 
         [0064]    In addition, the central portion  22  is fitted with an internal energy absorbing member  76  attached to the top face  22 T of the central portion  22  and extending along the ridge formed by the V-shaped of the central portion  22 . The energy absorbing member  76  is also adapted for progressive deformation, and is also made of Aluminum foam adapted for progressive deformation. The energy absorbing member  76  is held in place by a curved frame  74  attached to the central portion  22  on both sides  75  of the member  76 . The energy absorbing member is adapted to further absorb energy in the event of an explosion as will now be described. 
         [0065]    In operation of the add-on armor  10 , in the event of an explosion in the vicinity of the belly of the vehicle, the energy of the explosion will first be absorbed by the base plate  20 , in particular by the central portion  22  thereof. Such absorption may cause deformation of the central portion  22  towards the belly  3  of the vehicle  1 . In this case, upward deformation of the central portion  22  will urge the V-shape to straighten, entailing pressing on the energy absorbing member  76  by the central portion  22  on one side and by the curved frame  74  on the other side. The energy absorbing member  76  will then progressively deform, absorbing some of the energy of the explosion. 
         [0066]    Simultaneously, energy is diverted by the V-shape design of the central portion  22  to the peripheral portions  24 , also urging them to deform in an upward direction towards the belly  3  of the vehicle  1 . 
         [0067]    Upon sufficient deformation of the central portion  22  and peripheral portions  24 , i.e. when the they reach a distance from the belly  3  of the vehicle  1  which is equal to thickness T of the energy absorbing module  30 , a load will be applied to the energy absorbing module  30 , due to it being pressed upon by the belly  3  of the vehicle  1  on one side and by the base plate  20  on the other side. Due to this load, the intermediate layer  32  of the energy absorbing module  30 , will begin to progressively deform, thereby absorbing and additional amount of energy of the explosion. 
         [0068]    It should be understood that the upwards deformation of the central portion  22  of the base plate  20  causes a moment M to be applied to the vehicle portions  44  of the extensions  40 , causing them to detach from the side walls  2  of the vehicle  1 . However, due to the presence of the integrity devices  60 , the vehicle portion  44  of the extension  40  is prevented from detaching from the side wall  2  of the vehicle  1 . 
         [0069]    Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations, and modification can be made without departing from the scope of the invention, mutatis mutandis.