Patent Publication Number: US-7914069-B2

Title: Protection device for vehicle floor pan

Description:
The present application is based on International Application PCT/JP2005/003025, filed Dec. 5, 2005, which claims priority to French Application No. 0413619, Filed Dec. 21, 2004, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The technical scope of the invention is that of devices to ensure the protection against mines of the floor pan of a land vehicle. 
     To protect the floor pan of a land vehicle it is known to affix armour under it that enables the energy produced by the mine blast to be absorbed. Known armour comprises one or several metallic or composite layers and possibly deflection means. Patent WO03/102489 thus describes convex add-on armour ensuring the protection of the mechanical transmission means of the vehicle. 
     Known armours are not adapted for the protection of vehicles having low ground clearance, typically about 400 to 500 mm. These vehicles are particularly vulnerable to mines and namely to blast-effect antitank and antipersonnel mines. 
     BRIEF SUMMARY OF THE INVENTION 
     The aim of the invention is to propose a protection device able to ensure, with a relatively reduced total thickness, effective protection for the floor pans of vehicles against the effects of mines, and namely blast-effect mines. 
     Thus, the invention relates to a device to protect the floor pan of a land vehicle against mines, a device which incorporates at least one layer of deformable reinforcement parts positioned between a plane front plate and a plane rear plate, the surface density of the front plate being greater than that of the reinforcement. 
     The ratio of the reinforcement surface density to the surface density of the front plate will advantageously be less than 0.7. 
     The reinforcements may be constituted by at least one row of at least two tubes. 
     According to one embodiment, the device incorporates at least two reinforcement parts in contact with one another and arranged at a substantially median part of the front plate. 
     The device may incorporate at least one row of reinforcement parts in side-by-side contact with one another and spaced over substantially the entire area of the floor pan. 
     The front plate may be rectangular and the reinforcements may have their axes parallel with one length of the front plate. 
     Or, the front plate may be rectangular and the reinforcements may have axes parallel with one width of the front plate. 
     The rear plate may be constituted by the floor pan of the vehicle itself. 
     The rear plate may advantageously be integral with the front plate and the reinforcements thus forming a protective casing adaptable to the floor pan of a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will become more apparent from the following description of different embodiments, such description being made with reference to the appended drawings, in which: 
         FIG. 1  schematically shows a vehicle passing over a mine, such vehicle equipped with a floor pan protection device according to the invention. 
         FIG. 2  shows a first embodiment of a protection device according to the invention. 
         FIGS. 3 ,  4  and  5  show other embodiments of the device according too the invention. 
         FIG. 6  is a top view of the protection device according to  FIG. 5 . 
         FIG. 7  is a top view of a variant protection device according too the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a vehicle  1  incorporates a cab  2  carried by wheels  3  connected to the cab by an axle  4 .  FIG. 1  shows a blast-effect mine  5  positioned on the ground  6 . During its ignition, this mine generates high pressure (represented by arrows p) on the floor pan  7  of the vehicle  1 . 
     In accordance with the invention, to enable the floor pan  7  to withstand the blast effects, a protection device  8  is affixed to it. 
     Even though the vehicle has low ground clearance, the vehicle equipped with the device  8  has residual ground clearance G greater than 300 mm. 
       FIG. 2  shows a first embodiment of such a device  8 . This protection device  8  incorporates a plane front plate  9  made of a material having high mechanical strength, as well as a layer of deformable reinforcement parts  10 . 
     Here, the deformable reinforcement parts are tubes made of a material having high mechanical properties. 
     The tubes  10  are thus placed between the front plate  9  and a rear plate which here is the floor pan  7  of the vehicle. 
     To facilitate assembly of the device, a case  11 , for example, of bent sheet metal, receives the front plate  9  and the reinforcement parts  10  and incorporates lugs  12  enabling it to be fastened to the floor pan  7  of the vehicle  1 . 
     According to another characteristic of the invention, the surface density of the front plate  9  is greater than that of the reinforcements  10 . Thus, a ratio of surface density of the reinforcements to the surface density of the plate will advantageously be chosen to be less than or equal to 0.7. 
     By surface density we mean the ratio of the mass of the element in question to the surface of the floor pan  7  covered by said element. 
     The rectangular floor pan of width  1  and length L is covered. For the embodiment in  FIG. 2  where the tubes  10  cover substantially all the width  1  of the floor pan, it suffices that the mass of the front plate  9  is greater than that of the reinforcement parts  10 . 
     All the tubes here have the same diameter and are in side-by-side contact. The same level of protection is thus ensured over the entire surface of the floor pan  7 . The tubes are fastened to the front plate  9  by static retention means, for example, bonding, flanges, spot welding, and the like. 
     The device according to the invention operates as follows. 
     When the mine  5  is ignited, pressure is exerted on the front plate  9  which is sufficiently resistant to consume part of the mine&#39;s energy, and to stop splinters and projections. The dimensions of the front plate  9  enable it to be given sufficient rigidity enabling part of the energy received to be communicated to the tubular reinforcement parts  10 . 
     These reinforcement parts are dimensioned to be able to deform in flexion and compression in a relatively localized manner thus enabling, with a reduced volume, part of the energy produced by the blast of the mine  5  to be consumed. Moreover, they have the property of having a bending inertia moment that is sufficient to participate in the stiffness of the floor pan for protection perpendicular to the mine. 
     Furthermore, by positioning at least two profiled reinforcement parts in contact with one another, the level of protection is improved for a minimal protection mass. Indeed, the deformation of the front plate  9  is attenuated because of the proximity of the reinforcement parts and by the increase in stiffness resulting from their mutual contact. Two reinforcement parts in contact have an overall stiffness effect which is improved with respect to that of the same two parts positioned at a distance from one another. 
     By proposing to position these reinforcement parts on the area of floor pan which is sought to be protected, the invention thereby enables a better trade-off between a reduced protection mass and an optimal level of protection. 
     It is thus possible for effective protection to be provided for the floor pan  7  of the vehicle at a relatively low thickness of protection, for example, E less than 200 mm, thereby enabling the protection of the floor pans of vehicles with low ground clearance. 
     Moreover, the reinforcement parts  10  enable the floor pan  7  of the vehicle to be rigidified and thus its deformation further to the explosion of a mine to be limited. 
     In other embodiments, other types of deformable reinforcement parts may be used, for example profiled parts with a different section, for example, polygonal or elliptical, or bracket-shaped profiled parts or T-sectioned beams may be used. 
     However, the cylindrical shape is that which ensures the best trade-off between the deformation capability, the bending inertia moment and the reduced volume. 
     Someone skilled in the art will easily dimension the tubes, which may vary in type of material, length and thickness, and the front plate according to the protection characteristics required for a given vehicle. 
       FIG. 3  shows a protection device according to another embodiment which only differs from the previous one in the presence of a rear plate  13  integral with the reinforcement parts and acting merely to hold the tubes. 
     The two plates  9  and  13  as well as the reinforcement parts  10  are made integral with a case  11  forming a protection casing able to be adapted to a vehicle floor pan, for example using fastening lugs  12 . 
     In this embodiment, the reinforcement parts  10  are deformed between the two plates  9  and  13 . The casing  8  is thus autonomous and it is possible for it to be fastened at a distance from the vehicle&#39;s floor pan  7 . 
     It is thus possible for a vehicle in which the transmission mechanisms  14  are positioned below the floor pan  7  to be protected. 
     According to the embodiment shown in  FIG. 4 , the reinforcement parts  10  do not cover all the surface of the floor pan. 
     A row  15  of three tubular reinforcement parts  10  is thus arranged at a median part M of the front plate  9 . 
     Separate reinforcement parts  10   a  and  10   b  are arranged at a distance on both sides of this median row  15 . 
     This embodiment enables the mass of the protection device to be reduced. It is, in fact, essential for the median part of the floor pan to be protected since it is here that the pressure generated by the ignition of a blast-effect mine is at its highest. 
     The peripheral reinforcement parts  10   a  and  10   b  improve the distribution of the stresses communicated by the front plate  9 . 
     It is naturally possible to position the reinforcement parts  10  only at the median part M.  FIGS. 5 and 6  thus show such an embodiment in which the median row  15  incorporates five reinforcement parts  10 . 
     According to this embodiment, the reinforcement parts  10  of the median row are made integral with the front plate  9  using flanges  16  of sheet metal, welded to the front plate  9 . Also see  FIG. 6 . 
     The assembly will be fastened to the vehicle floor pan by any suitable means, for example, fastening lugs  12 . 
     It is also possible for the previous embodiments to be combined, for example for a device to be made that is analogous to that in  FIG. 4  but which does not have a rear plate  12 . In this case, the tubular reinforcement parts will be fastened to the front plate  9 , for example by sheet metal collars. The assembly will then be applied against a floor pan  7  of the vehicle. 
     In all the embodiments described up to now, the front plate  9  is substantially rectangular with a width  1  and length L which are substantially those of the floor pan of the vehicle to be protected. Furthermore, the tubular reinforcements  10  have their axes  17  parallel to the vehicle&#39;s longitudinal axis, shown here by the length L of the front plate  9 . See  FIG. 6 . 
     It is possible for tubular reinforcements  10  to be positioned which have a different orientation. 
       FIG. 7  thus shows a protection device in which the tubular reinforcements  10  have their axes  17  perpendicular to the vehicle&#39;s longitudinal axis, and thus parallel to the width  1  of the front plate  9 . 
     A first row  18  of reinforcement parts  10  arranged next to each other, two-by-two, is positioned near the rear part AR of the device here, positioned to the rear of the vehicle&#39;s floor pan  7 . Other separate reinforcement parts  10  are arranged towards the front part AV of the device. The reinforcements  10  are preferably positioned in the most vulnerable zones, namely, the cab. 
     Such an arrangement also enables the device to be made lighter. The tubular reinforcements are more numerous to the rear of the vehicle since it is here, near the cab, that maximal protection must be ensured, and thus where the energy absorbing capacity must be the greatest. The number of tubes may be reduced for the less vulnerable zones, like the drive train, for example. 
     Once again, the reinforcement parts are made integral with the base plate using flanges  19 . 
     The previous figures show reinforcement parts  10  of a length substantially equal to the length L or width  1  of the front plate  9 . 
     It is also possible for the protection device to be made with reinforcement parts of a smaller length. When defining the protection device, the reinforcements will be concentrated on the zone which most needs to be protected.