Abstract:
An improved blast shield for use on a wheeled military vehicle. The blast shield has at least a portion responsive to a blast under the vehicle that reacts in response to the blast to block the door of the passenger compartment whereby the occupants of the compartment are protected from ejection from the vehicle for the duration of the blast effect.

Description:
GOVERNMENT INTEREST 
     The invention described here may be made, used and licensed by the United States Government for governmental purposes without paying me any royalty. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     In one aspect this invention relates to vehicle structures. In a further aspect this invention relates to military vehicles having blast protection devices. 
     2. Prior Art 
     When a ground vehicle passes over a land mine, the blast creates a large dynamic load on the vehicle structure which in turn frequently causes the vehicle latches to fail and the doors to fly open. Once the doors are open, the occupants can be easily stuck by blast forces, blast debris and possibly be ejected from the vehicle causing injury. Since land mines are relatively cheap, they have become ubiquitous in many parts of the world. Therefore, land mine encounters are becoming increasingly common as military troops take on peace keeping and other quasi-military missions in many parts of the world where they operate wheeled vehicles in unfamiliar and dangerous terrain. This has resulted in many injuries even where the vehicle has a blast shield disposed underneath the cab that will prevent the blast from collapsing the cab protecting the vehicle cab and preventing debris and shrapnel from entering the cab. 
     Present, solutions to the problem of sudden door opening due to blasts, consist of positive latching mechanisms such as sliding bolt type closures. Such closures have major disadvantages in that they require positive action to latch with the result that human error can result in the latch not being used. This is particularly true when the vehicle is being used under hostile conditions where speed is essential and the vehicle occupants are under stress. Further once latched, the doors require a positive operation to unlatch. This could create a safety condition should it be necessary to exit the vehicle rapidly; particularly if the latch has been jammed or there is some sort of misalignment as a result of a blast. 
     What is needed is a safety mechanism that deploys automatically to prevent unwanted door opening when needed to keep the doors closed and which does not interfere with the door&#39;s normal operation under normal conditions. 
     SUMMARY OF THE INVENTION 
     Briefly, the present invention comprises an improved blast shield protecting the passenger compartment of a wheeled military vehicle from land mine blast, the blast shield being adapted to interact with the doors to the compartment. The vehicle has a compartment for use by personnel, the compartment having a door hinged to the compartment that has a swing path that opens outward with respect to the compartment for ingress and egress. The ballistic blast shield is located on the under side of the vehicle and serves to protect the vehicle occupants in the event of a land mine detonation if the vehicle passes over a land mine. The improved blast shield of this invention has a reactive portion that responds to the force of a mine blast to move from a first ready position near the bottom edge of the door to a second blocking position. When the reactive portion is in the first ready position the door can be easily opened. When the reactive portion has moved to its second blocking position, it will prevent the door&#39;s movement along the swing path and retain the door in a closed position as long as there is a significant blast effect acting on the shield. The blocking action will protect the occupants from being ejected from the vehicle for the duration of the blast effect and keep the door closed to prevent debris from entering the passenger compartment. Depending upon blast force, the reactive portion may return to an unblocking position. Combat vehicles are also made with a roof exit so any crew and passengers can always exit even if the doors remain blocked. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the accompanying drawing: 
     FIG. 1 is a side view of one embodiment before a mine blast; 
     FIG. 2 is a side view of the embodiment of FIG. 1 during the a mine blast; 
     FIG. 3 is an enlarged view of a portion of FIG. 2; 
     FIG. 4 is a side view of a second embodiment before a mine blast; 
     FIG. 5 is a side view of the embodiment of FIG. 4 during a mine blast; and 
     FIG. 6 is a perspective view of a partial shield of the embodiment of FIG.  4 . 
    
    
     DETAILED DESCRIPTION 
     Referring to the accompanying drawing in which like numerals refer to like parts and initially to FIGS. 1-3, a vehicle  10  with a cab  12  is shown with two hinged doors  14  on one side designed to permit ingress and egress from the vehicle passenger compartment. The vehicle  10  shown in FIGS. 1-3 is a high mobility wheeled vehicle designed for various light duty uses both on and off road. 
     The vehicle  10  has a blast shield  16  disposed across the lower forward portion of the vehicle, a majority of the shield being hidden from view. The basic structure and installation of such blast shields are known in the art and further detailed description will be omitted in the interest of brevity. The blast shield  16  is located slightly behind the foremost wheels  18  and is contoured so as to cover the underside of the front portion of cab  12  which contains the passenger-operator area of vehicle  10 . The foremost portion of the blast shield  16  located nearest the front wheels  18  has an associated reactive portion shown as a reactive arm  20  attached to the blast shield which extends longitudinally along vehicle  10  towards the rear wheels  22 , the reactive arm having a first end  24  mounted to the vehicle. The first end  24  of the reactive arm  20  is attached so that the deforming effect of a mine blast on the blast shield  16  will cause the reactive arm to move. In its first, normal undeployed position shown in FIG. 1, the reactive arm  20  extends parallel and juxtaposed to the lower edge  26  of door  14 . The reactive arm  20  as shown in its normal, undeployed state, is also located slightly outside the plane of the outer surface of door  14  so it can move freely in a plane parallel to and slightly outside the door&#39;s outer surface. The reactive arm  20  has a second free end  28  opposite first end  24  which is free to move upwards towards the lower edge  26  of the door  14  outside the plane of the door to a blocking position where second end  28  of arm  20  prevents the door from moving on its hinges  30  to an open position. 
     The reactive arm  20  has a cam surface  32  on the second, free end  28  which contacts and is adapted to interact with a complimentary fixed cam surface  34  formed on a reaction plate  36  rigidly mounted on vehicle  10 . The reaction plate  36  is firmly mounted to the vehicle  10  and when the reactive arm  20  moves rearward under the blast influence, will interact with the cam portion  32  of the reactive arm to move free end  28  across the swing path of door  14 . 
     The functioning of reactive arm  20  of this embodiment in response to a blast is shown best in FIGS. 2 and 3. In these Figures, a blast (not shown) has occurred near the front wheels  18  of the vehicle  10 . The blast acting rearward and upward on the shield  16  under the front portion of passenger compartment  12  has moved the reactive arm  20  towards the rear of vehicle  10  which in turn causes cam surface  32  of the reactive arm  20  to move over the mating reactive surface  34  of reaction plate  36  causing the, reactive arm to move to a point where it covers a portion of the front door  14  preventing the door from opening outward. This will protect the vehicle passengers from being ejected and the incursion of debris. This variant of the invention is particularly adapted for use where the front wheels are mounted ahead of the passenger compartment and therefore the wheels  18  will cause the detonation so the blast is in front of the passenger compartment. 
     Certain families of military vehicles are manufactured as a cab forward design where the foremost wheels are actually located behind the passenger compartment and thus the effects of a blast will be directed to the rear portion of the passenger compartment. A second embodiment of the present invention is shown in FIGS. 4 to  6  to address this cab configuration and blast pattern. In these Figures a cab forward design is shown where there are front steering wheels  46  located physically behind a cab  48  and a mine blast acting upward is most probable near one of these front steering wheels. 
     In this embodiment, a blast shield  50  is formed so it extends laterally across the rear portion of cab  48 . The shield  50  is attached to the truck frame (not shown) using a flange  51  and a plurality of fasteners (not shown) which pass through a plurality of apertures  53 . The blast shield  50  shown has a single flange  51  but obviously multiple flanges could be used to mount the inboard side of the blast shield. The blast shield  50  as formed and mounted surrounds the lower and back portion of the cab  48  and as attached to the vehicle frame, at one edge forms a cantilevered structure. Mounting the blast shield  50  with its innermost portion attached to the vehicle frame leaves a leading free edge  54  to move or rotate about the attachment axis at the frame to a position where the free edge  54  can block the door  56  from swinging open on its hinged edge  58 . As shown in FIG. 3, the blast shield  50  in its normal position forms a part of a normal construction for cab forward design. The upper edge  60  of shield  50  lies juxtaposed the lower edge of the door  56  of the cab  48 . The blast shield  50  is formed with a relatively larger inclined face  62  which will receive the greater portion of any blast effect, the orientation of the face  62  receiving the blast force being inclined at an angle which causes the shield  50  to move upward and forward from its normal position. The vectors of the blast force will move at least a portion of the shield  50  to the position shown in FIG.  5 . In this position, the front edge  64  has rotated and/or translated to a position where it covers a portion of the door&#39;s lower edge to forestall opening in response to a blast. Generally in using a blast shield of this structure, there will be two longitudinal beams forming a major portion of the frame. A blast shield  50  in a right and left-hand version, the left-hand version being shown in FIG. 6, will be mounted on each side of the frame with a shaped center blast resistant section disposed between the beams. 
     Various alterations and modifications will become apparent to those skilled in the art without departing from the scope and spirit of this invention and it is understood this invention is limited only by the following claims.