Abstract:
A body and any occupant of a land vehicle ( 10 ) is protected against effects of a landmine explosion, by conducting shock waves laterally outwardly by means of one or more shock wave guide members ( 16, 18 ) of a material having high acoustic velocity, and located proximate a ground engaging element ( 12 ) of the vehicle. The material may be glass, ceramic or the like having an acoustic velocity of about 6000 m/sec or more, i.e. higher than other materials of other components of the land vehicle. Shock waves encounter less resistance in high-acoustic velocity materials and are thus conducted laterally outwardly, i.e. away from the body. The shock wave guide members may be located immediately above bottom runs of tracks ( 12 ) and annularly within wells of bogey wheels ( 14 ) of track vehicles; and annularly around hubs or within tyres of wheels of wheeled vehicles.

Description:
TECHNICAL FIELD 
     This invention relates to a method of protecting a body or hull and any occupant of a land vehicle, such as an armoured vehicle, e.g. an armoured tank or car, against the effects of a landmine explosion, e.g. an anti-tank landmine explosion. It relates also to a land vehicle, and to a combination of a ground engaging element for a land vehicle and a shock wave guide member. 
     BACKGROUND OF THE INVENTION 
     When a vehicle sets off a landmine, generally the landmine explodes underneath a ground engaging element such as a wheel or track of the vehicle because of the ground pressure created by said ground engaging element on the landmine. 
     Japanese patent document having publication number 2002090095, discloses an apparatus for removing a mine buried under the ground surface. The apparatus includes a composite rotor having a plurality of generally coaxial rollers loosely located with lost motion in a radial direction over a fixed axis shaft mounted on, so as spatially to lead, a vehicle. The rollers can individually follow contours, hollows, humps, etc. to trigger landmines. Behind the rotor there is provided a protective plate screening the landmine blast and protecting the vehicle and an occupant. 
     Japanese Patent document having a publication number 2002340499, discloses a rotor including a plurality of blades. The rotor is rotated to cause the blades to cut into a ground surface to destroy mines. A curved safety cover is provided over the rotor to protect the vehicle and a driver from sand, mud and landmine fragments. A lower level grader-like blade deflects sand, mud and mine fragments laterally to provide a smooth running surface for the vehicle. It is notable that the vehicle is not intended to trigger landmines to explode, but to destroy landmines before explosion. The inventor thus did not anticipate landmine explosions and resulting shock waves. 
     U.S. Pat. No. 5,442,990 discloses a scarifying drum leading a track vehicle to explode landmines. A flap is provided over the drum to act as a shield. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the invention, there is provided a method of protecting a body or hull and any occupant of a land vehicle movable along a substrate on ground engaging elements against the effects of a landmine explosion, including conducting shock waves generated by the landmine explosion laterally outwardly by means of a shock wave guide member of a material having a relatively high acoustic speed and located proximate a ground engaging element of the vehicle. 
     For purposes of this specification, terms denoting direction, such as fore, rear, lateral, and the like should be interpreted with reference to a normal direction of forward travel of a land vehicle. The term “laterally outward” means “sideways away from (the land vehicle)”. 
     By “relatively high” acoustic speed is meant an acoustic speed higher than the acoustic speed of the metal used in components of the land vehicle. Such metal, e.g. steel, aluminum, and alloys thereof, generally have an acoustic speed of about 5000 m/sec. 
     The material of each shock wave guide member may be selected from materials including glass, a suitable ceramic such as an alumina, or the like, which have an acoustic speed of higher than about 6000 m/sec. Some ceramics may have acoustic speeds up to about 8000 m/sec. 
     When the vehicle is a track vehicle, the ground engaging elements being in the form of tracks, the guide member may be located in at least one of a well of a bogey wheel, i.e. an annular cavity surrounding a hub and radially inward of a rim of the bogey wheel; and immediately above a bottom run of a track intermediate bogey wheels. 
     When the vehicle is a wheeled vehicle, the ground engaging elements being in the form of wheels, the guide member may be located in a well of at least one of the wheels. The method may include absorbing energy by means of a liquid provided in a tyre of the vehicle, in the case that the wheels have tyres. 
     In accordance with a second aspect of the invention, there is provided a land vehicle movable along a substrate on ground engaging elements, which land vehicle is adapted or converted to protect its body or hull and any occupant against the effects of a landmine explosion, the land vehicle comprising a plurality of shock wave guide members proximate ground engaging elements thereof, the shock wave guide members being oriented to conduct shock waves laterally outwardly away from the body or hull. 
     When the land vehicle is in the form of a track vehicle, the ground engaging elements being in the form of tracks, the guide members may be positioned in wells of bogey wheels, as well as immediately above a bottom run of each track intermediate bogey wheels. Those guide members proximate tracks intermediate bogey wheels may have layers of low friction material, such as TEFLON, on their surfaces interfacing with the tracks. 
     When the land vehicle is in the form of a wheeled vehicle, the ground engaging elements being in the form of wheels, the guide members may be positioned annularly in wells of at least some of the wheels e.g. at least fore wheels. When the wheels have hollow tyres around wheel rims, the guide members may be positioned annularly in the hollows of the tyres. By way of development, cavities within the tyres may be filled with a liquid for absorbing some of the energy of the explosion. The liquid may be selected to have an appropriate boiling point and coefficient of latent heat of evaporation. It may, for example, be water, glycerin, a mixture of water and glycerin, or the like. 
     The guide members may be of composite construction, each guide member comprising a plurality of oriented or directed laminates of a material having an acoustic speed of at least about 6000 m/sec. Such material may be a primary material, e.g. a glass or ceramic material. The guide member may be in laminated form comprising laminates of the primary material interposed by an interface material having an acoustic speed lower than that of steel, the laminates being directed generally in said laterally outward and upward, oblique direction. The interface material may be a synthetic polymeric material. Said interface material may have an acoustic speed lower than that of air. The laminates may thus be sandwiched in-between layers of material having a relatively low acoustic speed, lower than about 1000 m/sec, even lower than the acoustic speed of air. 
     The laminates may be oriented to extend obliquely laterally outwardly in use. 
     A respective guide member may be positioned annularly inward of a tread of the wheel. It may be annularly around a hub of the wheel. It is preferably acoustically well coupled to a wheel frame (colloquially referred to as a wheel rim). 
     The guide members may have surfaces which are profiled snugly to be received with little clearance, or even slight touching, on surfaces of the ground engaging elements. 
     In accordance with a third aspect of the invention, there is provided the combination of a ground engaging element for a land vehicle and a shock wave guide member of a material having an acoustic speed of higher than about 6000 m/sec, the guide member being locatable proximate a ground engaging surface of the ground engaging element. 
     When the ground engaging element is a track and bogey wheel arrangement for a track vehicle, the guide member may be adapted for location in one of a well of a bogey wheel, and immediately above a lower run of the track intermediate bogey wheels. 
     When the ground engaging element is a wheel for a wheeled vehicle, the guide member may be adapted for location within a well of the wheel. 
     When the ground engaging element is a wheel, having a hollow tyre, for a wheeled vehicle, the guide member may be adapted for location within the hollow of the tyre. 
     These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is now described by way of examples with reference to the accompanying diagrammatic drawings. In the drawings 
         FIG. 1  shows, in fragmentary side view, a track vehicle converted in accordance with the invention; 
         FIG. 2  shows, to a larger scale, fragmentarily, a bogey wheel of the track vehicle of  FIG. 1 , converted in accordance with the invention; 
         FIG. 3  shows, in diametrical section, the bogey wheel of  FIG. 2 ; 
         FIG. 4  shows, in cross section, to a larger scale, a guide member proximate a track of the track vehicle of  FIG. 1 ; 
         FIG. 5  shows, fragmentarily, in radial section, a first embodiment of a wheel for a wheeled vehicle in accordance with the invention; and 
         FIG. 6  shows, in a view corresponding to that of  FIG. 5 , a second embodiment of a wheel for a wheeled vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 to 4  of the drawings, a track vehicle in the form of an armoured tank is generally indicated by reference numeral  10 . The track vehicle  10  has a pair of tracks  12  guided along a lower run of each track on bogey wheels  14 . The track is shown fragmentarily only, and only one track  12  is shown, also fragmentarily. 
     In accordance with the invention, a first kind of guide member, generally indicated by reference numeral  16 , is located within wells of the bogey wheels  14 , i.e. annularly intermediate hubs  14 . 1  and rims  14 . 2  of the respective bogey wheels  14 . 
     In the event that the bogey wheel  14  has webs  14 . 3  at circumferentially spaced positions within said wells, the guide member  16  is in the form of a composite guide member comprising a plurality of segments  16 . 1  shown in  FIG. 2 . 
     As can best be seen in  FIG. 3 , each segment has a plurality of laminates  16 . 2  sandwiched in-between dividing layers  16 . 3  which may be of a yielding, even resilient, low acoustic speed material such as polyurethane, rubber or the like. The laminates  16 . 2  are oriented laterally outwardly. 
     In the event of a landmine explosion underneath the bogey wheel  14 , shock waves generated by the landmine explosion will propagate through the track  12 , through the rim  14 . 2  of the bogey wheel  14  immediately above the track  12  and will be “loaded into” the respective segment or segments  16 . 1 . The Applicant has realized that shock waves encounter resistance to propagation inversely proportional to the acoustic speed of a material. Thus, in a material having a high acoustic speed like glass, especially ceramics, such as that of the guide member  16 , the shock waves are guided effectively laterally outwardly in accordance with the orientation of the laminates. It is further to be appreciated that, should a component of the shock waves be conducted obliquely along such a laminate, when it reaches a dividing layer  16 . 3  having a low acoustic speed and thus offering high resistance to propagation of shock waves, the shock waves are deflected back into the high acoustic speed material which assists in guiding the shock waves laterally outwardly. 
     When the shock waves reach the surface of the guide member, and preferably it should do so at approximately right angles, the shock waves, when they encounter the neighbouring air, which has a low acoustic speed, cause spalling of the material which results in a fragment or fragments of material to be liberated and to be projected generally in the direction of spalling i.e. laterally outwardly. 
     In this regard, the Applicant has realized that a blast effect generated by the landmine explosion and following the shock waves in time, generally follows the path or route of least resistance. In this regard, the Applicant has further appreciated that the shock waves crack and pulverize the material of the guide member, but at a propagation speed substantially lower than the acoustic speed. Thus, the guide member remains intact fully to propagate the shock waves, but immediately behind the shock waves, cracks and pulverizes to facilitate being displaced or blown away by the blast effect. Thus, a route of lesser resistance is created in the direction in which the shock waves were guided. Furthermore, the effect of spalling and of a fragment being projected from the outer surface creates a region of low pressure which is followed by the blast effect. 
     Thus, the Applicant has realized that managing or guiding of the shock waves in a predetermined direction away from a body of the track vehicle not only protects the body against the effect of the shock waves, but also that the blast effect tends to follow the leader shock waves and that the body of the track vehicle is thus also protected against the effects of the blast. 
     Similarly, with reference to  FIG. 4 , a guide member  18  comprises a plurality of laminates  18 . 2  sandwiched by dividing layers  18 . 3  of polyurethane, rubber, or the like. By way of development, the guide member  18  is profiled at its interface with the track  12 , to fit snugly over the track  12 , and even to rub against the track  12 . To mitigate such rubbing, a rubbing surface  20  of a low friction material such as Teflon is provided at the interface. 
     The mechanism of guiding of the shock waves in the case of the guide member  18  is exactly the same as that of the guide member  16  and also the creation of a route of lesser resistance is similar. 
     The Applicant believes that the invention provides a simple, elegant and relatively inexpensive method of managing shock waves by directing or guiding the shock waves in a desired direction, and furthermore that such guiding of the shock waves creates a route of lesser resistance which is followed by the blast in preference thus also protecting vulnerable and valuable parts of the vehicle against the effect not only of the shock waves, but also of the blast. 
     With reference to  FIG. 5  of the drawings, a wheel in accordance with the invention is generally indicated by reference numeral  110 . The wheel  110  is a solid wheel, i.e. not a neumatic wheel or inflatable wheel. It is generally of sturdy construction and suitable for use in traversing a minefield to detonate anti-personnel mines. It is to be understood that it will be mounted to a vehicle. In accordance with the invention, the wheel  110  is suitable to protect a body or hull of the vehicle and thus also an occupant of the vehicle against the effect of a powerful landmine, such as an anti-tank mine, which may be encountered in a field of generally anti-personnel mines. 
     The wheel  110  comprises a wheel frame  112  having a hub  114  defining a hub volume  115  via which the wheel  110  is mounted to the vehicle in any appropriate fashion. The wheel frame  112  comprises, at an outer periphery thereof, a peripheral flange  116 . A tread  118  in the form of a hoop of an appropriate grade of steel is mounted via the peripheral flange  16  to the wheel frame  112 . 
     In accordance with the invention, in an annular space radially within the tread  118 , there is provided a guide member  120  which is conveniently a composite member comprising a plurality of segments, together forming an annular construction. 
     Each section of the guide member  120  is of generally triangular cross-section comprising a plurality of laminates  122  with layers of dividing material in the form of dividers  124  being sandwiched in-between adjacent laminates  122 . The laminates  122  and the dividers  124  form a parallel directed structure pointing radially inwardly and laterally outwardly. If a bottom segment of the wheel  110  is viewed, the laminates  122  and dividers  124  are directed obliquely upwardly and laterally outwardly. It is to be appreciated that the side of the wheel  110  having the wheel frame  112  will be proximate a body or hull of a vehicle to which the wheel  110  is mounted. That side, indicated by reference numeral  140 , will be referred to as the protected side, as the body or hull, and the occupant of the vehicle are to be protected against the effects of a landmine explosion taking place underneath the tread  118 . 
     The laminates  122  are of a material having a high acoustic speed, whereas the dividers  124  are of a yielding, even resilient, material having a low acoustic speed, such as a synthetic polymeric material, for example polyurethaine, rubber, or the like. 
     In the event of a landmine explosion underneath the tread  118 , shock waves generated by the landmine explosion will propagate through the tread  118  and will be “loaded” into the guide member  120  via a surface  126  thereof proximate the tread  118 . The applicant has realized that shock waves encounter resistance to propagation inversely proportional to the acoustic speed of a material. Thus in a material having a high acoustic speed like glass, or especially ceramic, such as that of the laminates  122 , the shock waves are propagated well along such high acoustic speed material. It is further to be appreciated that the dividers  124  are of a material having a very low acoustic speed and thus offering very high resistance to propagation. In fact, a combination of a high acoustic speed material backed by a low acoustic speed material acts as a mirror for shock waves, thus deflecting or reflecting the shock wave back into the high acoustic speed material. In the embodiment illustrated, it is expected that shock waves traveling generally directly upwardly through the tread  118  into the respective laminates  122 , will be guided obliquely laterally outwardly generally along the laminates  122  as deflection or reflection takes place at each interface between the respective laminates and their backing dividers  124 . It is furthermore to be appreciated that the laminate  122  at the extremity is flanked by air, which also has a low acoustic velocity and deflecting will thus also take place along the extreme laminate  122 . 
     Thus, it is expected that shock waves will be propagated obliquely upwardly and laterally outwardly from the surface  126  to a lateral surface  128  along an annular side of the guide member  120  and thus toward an outside, indicated by reference numeral  142  of the vehicle. 
     When the shock waves reach the surface  128  of the guide member  120 , the shock waves, when they encounter the neighboring air, which has a low acoustic speed, cause spalling of the material which results in a fragment or fragments of material to be liberated and to be projected generally in the direction of spalling, i.e. generally laterally outwardly, to create a route of lesser resistance and thus to induce the blast effect generated by the landmine explosion and following the shock waves in time, generally to follow the path or route of lesser resistance, as described above. 
     With reference to  FIG. 6 , a further, developed embodiment of a wheel in accordance with the invention is generally indicated by reference numeral  210 . In many respects, the wheel  210  resembles the wheel  110  and its construction and operation are not fully described again. 
     The wheel  210  includes a wheel frame  212  having an outer peripheral rim  216  seating an inflatable tyre  219  having side walls  219 . 1  and a tread  219 . 2 . A steel tread  218  in the form of a hoop and of an appropriately durable material such as steel which is resistant to explosions of anti-personnel mines, could be used. The steel tread  218  has, along side edges thereof, laterally inwardly directed flanges  218 . 1  for seating over the tyre tread  219 . 2  and thus to prevent the steel tread  218  from unseating. It is to be appreciated that the steel tread  218  will be positioned over the tyre  219  when the tyre is deflated. 
     Within the tyre  219 , there is provided a guide member  220  similar to the guide member  120  of  FIG. 5 . The guide member  220  may be secured to the rim  216  in any convenient and appropriate fashion, for example by means of an annular, frame-like securing member  230  which is shown schematically. The guide member  220  has laminates  222  interposed by dividers  224  of materials similar to those described with reference to  FIG. 5 . 
     The mechanism of guiding of shock waves in the wheel  210  is similar to that described with reference to  FIGS. 1 to 5  and it is thus not repeated. 
     By way of development, the volume within the tyre  219  is advantageously filled by means of a liquid  232 . The liquid  232  is selected to be effective in absorbing energy associated with the landmine explosion. The liquid may have a relatively low boiling point and its latent heat of evaporation will be selected to absorb energy in the form of heat. A layer of liquid between the steel tread  218 , and the face  226 , will promote acoustic coupling and thus “loading” of the shock waves into the guide member  220 . 
     It is to be appreciated that the wheel  210  of  FIG. 6  has the advantage that it has some resilience providing a suspension effect and is thus expected to allow a vehicle to travel faster than a vehicle rolling along wheels of the kind of  FIG. 5 . 
     The invention has the advantage that a vehicle shod with wheels for traversing a minefield to detonate anti-personnel mines in the minefield, is protected against the effects of any high powered landmine, such as an anti-tank landmine, which may be laid in the minefield being cleared. 
     The invention is applicable in principle also in other kinds of wheels, for example, an annular guide member as described may be positioned 
     within a well of a wheel frame having a “soft” tyre, i.e. a pneumatic tyre, a solid moulded tyre of rubber, polyurethane, or the like, whether or not such a wheel has an outer hoop of steel or other explosion resistant material; 
     within a pneumatic tyre (tubed or tubeless) when the wheel does not have the outer hoop as in  FIG. 6 ; 
     moulded within a moulded solid tyre of rubber, polyurethane or the like, whether or not such a wheel has an outer hoop of steel or other explosion resistant material. 
     It should be apparent that the foregoing relates only to the preferred embodiments of the present application and that numerous changes and modifications may be made herein without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.