Abstract:
An inflatable body armor system has one or more body armor sections adapted to be worn by a user. Each body armor section includes (i) a inflatable flexible/sealable plenum, (ii) a ballistic armor fabric encasing the plenum, and (iii) a variety of lines, shaped objects and/or fabric sheets dispersed in the plenum to alter the trajectory of a projectile entering the plenum.

Description:
ORIGIN OF THE INVENTION 
     The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon. 
    
    
     CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This patent application is co-pending with one related patent application entitled “INFLATABLE TRAJECTORY ALTERING AND BLAST ENERGY ABSORPTION SYSTEM” (Navy Case No. 96127) by the same inventors as this patent application. 
     FIELD OF THE INVENTION 
     The invention relates generally to body armor, and more particularly to an inflatable body armor system that alters a projectile&#39;s trajectory as the projectile passes through an inflated plenum. 
     BACKGROUND OF THE INVENTION 
     In today&#39;s world, police and military forces frequently wear some form of body armor in order to reduce the threat of severe injury or death due to an incoming projectile. Current body armor technology utilizes layers of fabrics made from aramids (e.g., SPECTRA, KEVLAR, etc.), polypropylene, polyethylene, or high-performance P-phenylene benzobisoxazole (PBO) fibers. The fabric materials can be used alone or have ceramic panels positioned between material layers sewn into a vest type arrangement to surround the front and back of a person&#39;s upper torso. In the current art, the only methods used to increase body armor&#39;s ballistic protection involve (i) adding thick metal plates, ceramic plates, or other hard materials, or (ii) increasing the thread count and number of layers of fabric material. However, both methods increase the weight and cost of the body armor. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a body armor system that offers the wearer protection from an incoming projectile. 
     Another object of the present invention is to provide a lightweight body armor system. 
     Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings. 
     In accordance with the present invention, an inflatable body armor system includes at least one body armor section adapted to be worn by a user. Each body armor section includes a flexible/sealable plenum defined by spaced apart walls when the plenum is inflated, and a ballistic armor fabric encasing the plenum. Dispersed in the plenum are tensioned lines, shaped objects and/or ballistic fabric sheets for altering trajectory of a projectile entering the plenum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein: 
         FIG. 1  is a cross-sectional view of one embodiment of an inflatable trajectory altering system used in the inflatable body armor system of the present invention; 
         FIG. 2  depicts a view of the trajectory altering system of  FIG. 1  immediately after a projectile has punctured one wall thereof; 
         FIG. 3  is a cross-sectional view of another embodiment of the inflatable trajectory altering system that includes shaped objects therein; 
         FIG. 4  is a cross-sectional view of another embodiment of the inflatable trajectory altering system that includes the use of ballistic armor fabric sheets; 
         FIG. 5  is a cross-sectional view of another embodiment of the inflatable trajectory altering system that includes the use of a matrix of ballistic armor fabric sheets; 
         FIG. 6  is a cross-sectional view of another embodiment of the inflatable trajectory altering system that includes the use of a matrix of ballistic armor fabric sheets; 
         FIG. 7  is a cross-sectional view of another embodiment of the inflatable trajectory altering system that includes the use of shaped objects and a matrix of ballistic armor fabric sheets; and 
         FIG. 8  is a side, cross-sectional view of one embodiment of an inflatable body armor system in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Prior to describing the inflatable body armor system of the present invention, a novel inflatable trajectory altering system will first be described. The trajectory altering system forms the core element for the inflatable body armor system. 
     Referring now to the drawings, and more particularly to  FIG. 1 , one embodiment of an inflatable trajectory altering system of the present invention is shown in its inflated state and is referenced generally by numeral  10 . System  10  has an outer wall structure  12  made from a flexible and fluid-impermeable material that defines a plenum. More specifically, wall structure  12  has major opposing walls  12 A and  12 B that are spaced apart from one another when the interior volume defined by wall structure  12  is inflated with a lightweight fluid such as air. The means used to inflate wall structure  12  can be any compressed air (or other fluid) inflation system and is not a limitation of the present invention. Inflation of system  10  can occur just prior to use thereof or during the manufacture thereof without departing from the scope of the present invention. Also, the material used for wall structure  12  can be selected from a wide variety of well known flexible and fluid-impermeable materials and is, therefore, not a limitation of the present invention. 
     In general, the trajectory altering system of the present invention includes one or more types of material structures disposed within wall structure  12 . For the illustrated embodiment, flexible lines  14  are coupled to and span major opposing walls  12 A and  12 B such that lines  14  are placed in tension when wall structure  12  is inflated. Each of lines  14  can be made from a single fiber strand or multiple strands of fiber. In general, lines  14  should possess a high tensile strength and be abrasion resistant. Thus, a variety of polymer materials can be used for lines  14  with certain commercially-available products being preferred when system  10  is to be used to alter the trajectory of an incoming projectile. For example, lines  14  can be fibers made from the well-known polymeric strength materials SPECTRA available from Honeywell International Inc., KEVLAR available from E.I. du Pont de Nemours and Company, ZYLON available from Toyobo Company Ltd., TWARON available from Akzo Nobel, DYNEEMA available from Koninklijke DSM N.V., and nylon, just to name a few. 
     Attachment of lines  14  to major opposing walls  12 A and  12 B is preferably accomplished by a method known as “drop stitching” which maintains the sealed and fluid-impermeable integrity of wall structure  12 . Drop stitching methods are known in the art of inflatable watercraft construction. See, for example, U.S. Pat. No. 6,074,261, the contents of which are hereby incorporated by reference. The lengths of lines  14  can be varied to shape the outer contours of wall structure  12  for a particular application. 
     The interior surfaces of wall structure  12  can be optionally coated or covered with a viscous polymeric sealing material layer  16  that serves to seal itself in the event of a small puncture. Examples of such sealing material constructions are disclosed in U.S. Pat. Nos. 4,501,035 and 5,295,525, the contents of which are hereby incorporated by reference. 
     The mechanism by which system  10  alters a projectile&#39;s trajectory will now be described with the aid of  FIG. 2  where a projectile  50  is shown after it pierces major wall  12 A but before it reaches major wall  12 B. For clarity of illustration, polymeric sealing material  16  has been omitted from  FIG. 2  and each of the other illustrated embodiments of the present invention that will be discussed later herein. Those of lines  14  that are in line with or immediately adjacent to the point of impact of projectile  50  tend to break or relax (within the region between dashed lines  18 ). However, due to the inflation of wall structure  12 , those of lines  14  surrounding relaxed region  18  experience a greater amount of tension as they are drawn towards region  18  and projectile  50 . As a result, forces F are applied to projectile  50  from circumferential points thereabout. 
     The action of circumferential forces F tends to alter the trajectory of projectile  50  thereby causing projectile  50  to encounter more of lines  14 . That is, forces F cause projectile  50  to experience yaw with respect to its original straightline course thereby making projectile  50  collide with more of lines  14 . Simultaneously, the change in projectile trajectory increases the projectile&#39;s force bearing area which reduces the projectile&#39;s localized pressure point to immediately reduce the projectile&#39;s penetration capability. Thus, more collisions translate to more projectile course alterations and increased projectile bearing area resulting in increased energy losses. 
     Trajectory alteration also dissipates large amounts of the projectile&#39;s kinetic energy in lines  14  as the larger projectile bearing area impinges on lines  14 . In addition, the subsequent movement of the impacted wall(s) absorb kinetic energy in a way not conducive to penetration thereby slowing the speed of projectile  50  and reducing its lethality. 
     In addition, the present invention mitigates the shock wave resulting from a blast event. For many battlefield situations, this type of shock wave typically lasts for less than 30 milliseconds. The impedance mismatch between major walls  12 A and  12 B combined with the ability of the plenum to deform upon shock wave arrival reduces the intensity of these short-lived blast-induced shock waves impinging on the wall structure. More specifically, the impedance mismatch and flexible plenum make the present invention respond to a short-lived shock wave in a non-frangible and flexible way. As a result, a short-lived blast-induced shock wave can be absorbed during its brief period of lethality. Still further, the two spaced apart walls of wall structure  12  will aid in the jet particulation of an exploded shaped charge warhead. 
     Projectile trajectory alteration and energy absorbing capabilities can be further enhanced by adding other material structures within wall structure  12 . Several examples will be described below with the aid of  FIGS. 3–7 . In  FIG. 3 , a plurality of small lightweight shaped objects  20  can partially or completely fill wall structure  12 . Objects  20  can be solid or hollow, and can be made from a hard lightweight material such as a ceramic material. Objects  20  can be shaped as spheres, cubes, pyramids, irregular shapes, or mixtures thereof, without departing from the scope of the present invention. For example, it is known that bi-modal distribution of small and large particles allows for more particles to be packed into a small volume thereby increasing resistance to penetration by a projectile. Thus, in general, the presence of objects  20  increases the amount of material available to absorb a projectile&#39;s energy and increases the surface area of the projectile due to mechanical damage as its trajectory is altered within wall structure  12 . Note that another embodiment could make use of a wall structure  12  partially or completely filled with objects  20  without the use of any lines  14 . 
       FIGS. 4–6  illustrate embodiments of the trajectory altering system that include the use of ballistic armor fabric sheets within wall structure  12 . As used herein, the term “ballistic armor fabric sheet” refers to any flexible but high-strength fabric that is accepted as having ballistic protection properties in the field of ballistic protection systems. Currently, such fabrics include the previously-mentioned SPECTRA, KEVLAR, TWARON and DYNEEMA. However, it is to be understood that the present invention could utilize other ballistic armor fabric sheets as such are developed. 
     In  FIG. 4 , a plurality of ballistic armor fabric sheets  22  are arranged within wall structure  12  in a spaced-apart and substantially parallel fashion to form an angular relationship with lines  14  when lines  14  are in tension. Ends of sheets  22  can be coupled to wall structure  12  in a variety of ways. For example, the ends of sheets  22  can be adhered to wall structure  12  with an adhesive and then stitched in place when lines  14  are stitched in. Lines  14  are passed through sheets  22  during the stitching process. The presence of sheets  22  aids in altering a projectile&#39;s trajectory and absorbs energy from the projectile. Specifically, when an incoming projectile impinges on a sheet  22 , the sheet deflects to absorb energy and defines an angular path for the projectile to follow. If/when a projectile passes through one of sheets  22 , the projectile encounters another sheet  22  where its trajectory is again altered and its energy is absorbed. 
     In  FIG. 5 , sheets  22  are tethered to one another by ballistic armor fabric sheets  24  that are angularly disposed with respect to lines  14  and sheets  22 . As a result, sheets  22  and  24  form a matrix of sheets that lie on different angles for trajectory alteration.  FIG. 6  depicts a similar concept with sheets  26  (only one sheet  26  is shown for clarity of illustration) being interspersed with sheets  22  and substantially parallel to major opposing walls  12 A and  12 B. 
     Each of the embodiments shown in  FIGS. 4–6  could further include shaped objects partially or completely filling the interior of the wall structure. For example,  FIG. 7  illustrates the  FIG. 5  embodiment and further includes shaped objects  20  within wall structure  12 . Furthermore, each of the embodiments depicted in  FIGS. 4–7  could be implemented without the use of lines  14 . 
     One or more of the above-described inflatable trajectory altering systems can be utilized in the construction of an inflatable body armor system in accordance with the present invention. The body armor system can be constructed to fit any portion of one&#39;s body, although it is typically constructed as a vest as will be described herein by way of example. Accordingly, it is to be understood that the inflatable body armor vest described herein is simply a representative example and is not a limitation of the present invention. 
     Referring now to  FIG. 8 , an inflatable body armor vest in accordance with the present invention is shown and is referenced generally by numeral  100 . In the illustrated embodiment, body armor vest  100  includes a front  101 A and a rear  101 B held together by straps  102  that would drape over and rest on a user&#39;s shoulders. The inflatable portion of front  101 A and rear  101 B is constructed from one of the above-described inflatable trajectory altering systems. 
     By way of example, body armor vest  100  is shown using the inflatable trajectory altering system shown in  FIG. 1  (without polymeric sealing material  16  for simplicity of illustration) with common reference numerals being used to describe the common elements thereof. For on-demand inflation, a compressed gas source  30  (e.g., a CO 2  cartridge) is coupled to wall structure  12  by a valve  32 . In cases where vest  100  is also serving as a flotation device, gas source  30  could be a water-actuated pressurized gas release device that (preferably) would also include manual means of inflation. One such device is disclosed in U.S. Pat. No. 5,311,394. 
     To provide inflation integrity in the event of a leak in wall structure  12 , the interior portion of wall structure  12  can be divided into individual sealed chambers separated by chamber walls  12 C. As would be well understood in the art, each of chamber walls  12 C can incorporate a “one way valve” (not shown) to permit system inflation from a single gas source  30 . 
     Each wall structure  12  is encased by fabric  40  having ballistic armor qualities. Currently, the preferred materials for fabric  40  are SPECTRA and KEVLAR. Panels of fabric  40  can be stitched to encase each wall structure  12 . Fabric  40  can also be used to define pockets  42  designed to receive conventional rigid armor plates  44  (e.g., metal, ceramic, etc.). 
     The portion of fabric  40  that will come into contact with a user can be quilted or dimpled at  40 A to define a three-dimensional surface that creates air gaps between fabric  40  and the user&#39;s body. The air gaps will keep a user cool during an extended wearing of vest  100 . 
     The advantages of the present invention are numerous. The inflatable body armor system provides ballistic protection as tensioned flexible members (e.g., lines and/or fabric sheets) dispersed in the body armor&#39;s inflated plenum serve to alter an incoming projectile&#39;s trajectory while simultaneously absorbing the kinetic energy thereof. The inflated nature of the body armor makes it lightweight and buoyant. By dividing the inflated plenum into individual chambers, the body armor will not be compromised by a single point failure. In addition, the present invention mitigates shock resulting from a blast event. 
     The present invention provides the means to build body armor panels of relatively great thickness and relatively low weight. Armor thickness is of great importance as it is the only means available to overcome the basic thermodynamic limitation imposed by the fact that it takes time to transfer/absorb energy/work. Thus, a thicker armor provides the time necessary to effect energy transfer/absorption of a projectile or blast energy. 
     Although the invention has been described relative to a specific embodiment thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.