Ordnance – Shields – Shape or composition
Reexamination Certificate
2001-06-22
2004-04-13
Johnson, Stephen M. (Department: 3641)
Ordnance
Shields
Shape or composition
C089S036050, C089S036080, C002S002500
Reexamination Certificate
active
06718861
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of apparatus and systems for shielding personnel and other objects from hostile activity, including objects or projectiles fired from a gun or resulting from explosions. More particularly, this invention relates to an armoring system which operates to trap ballistic projectiles using a combination of layered components, including plugs.
BACKGROUND OF THE INVENTION
Many different approaches to the protection of personnel from life-threatening attacks exist. Examples include bullet-proof glass, concrete and steel building structures, armored cars, bullet-resistant jackets, and others. The particular avenue taken depends on whether the person to be protected is stationary, located in a vehicle, located within a building, or is required to maintain mobility outside the confines of any specific stationary structure.
For example, light-weight armor relies primarily on the strength and preferred placement of materials to defeat bullets or other projectiles. Thus, armor made of fabric material, such as nylon, aramids, or polyethylene, is designed to defeat lead-filled bullets, often called ball rounds. The conventional “bullet-proof” vest, however, cannot stop bullets that have hard cores. These types of bullets are often referred to as armor-piercing (AP) bullets. Currently, to defeat AP bullets, a layered structure element comprising a hard front face (e.g., ceramic) bonded to a metal or composite substrate element, is used. This combination of plates is inserted into pockets sewn into vests for body armor application. Alternatively, the combination of plates can consist of an integral element that has a shape somewhat conformable to the body. Such plates can also be attached to vehicles and other structures for protection of personnel.
Using the conventional multi-plate approach, material geometries and spacing between armor elements may be adjusted to induce ballistic projectiles to fracture and rotate about the incoming velocity vector. For example, one concept involves placing a multiplicity of holes within an armor element configuration. Given proper spacing between elements, the probability is great that an incoming projectile will strike the edge of a hole in the primary or first element, causing it to rotate before impacting the secondary or backup armor element. This approach requires a robust primary element so as to initiate rotation, and adequate air space between the primary and secondary elements to enable the projectile to rotate sufficiently before the second impact. Although effective as a system, it is difficult to decrease the weight of the primary element (while retaining performance), and a large air space is necessary between the primary element and the secondary element.
Lighter ceramics and improved substrate performance allow the production of reduced areal density elements, such that lighter armor can be produced to protect against a given threat. However, over the past twenty years, the decrease in areal density required to defeat AP threats has been incremental at best. New materials have resulted in small improvements in armor weight (i.e., areal density). To substantially reduce the weight of armor, including that worn by personnel, requires a significant decrease in areal density—much larger than that obtained to date.
SUMMARY OF THE INVENTION
As described above, some armor systems are designed to use the primary armor layer to initiate rotation, or “tumbling” about the incoming velocity vector of the projectile. Rotation of the ballistic projectile relies on the use of asymmetric force to initiate turning, and requires space between the initiating element and some type of backup element to provide time for the projectile to rotate. This “tumbling” action serves to increase the surface area of the projectile encountered by the backup armor element. In other armor systems, a ceramic-faced armor operates to blunt the point and shorten the length of an AP bullet through erosion, but it does not increase the overall presented area of the bullet.
The momentum trap ballistic armor system of the present invention makes use of a new mechanism to reduce the armor weight required to defeat AP threats and other ballistic projectiles. The system effectively increases the presented area of the projectile, which in turn increases the effectiveness of the secondary armor layer (or layers). In use, the system operates to combine an armor element with the projectile, effectively “trapping” the momentum of the bullet. The combination of the armor element and the projectile moves forward as a unit to encounter the secondary armor layer. The armor element carried along with the projectile is called a “plug.” The secondary armor element is typically ballistic fabric, which is used to stop the bullet-plug combination.
Thus, the invention includes a momentum trap ballistic armor system which comprises an accelerating layer (typically ceramic) and a plug layer adjacent to the accelerating layer. The plug layer, in turn, includes at least one opening, with a plug maintained therein. Typically, a multiplicity of such openings and plugs are included in the plug layer. An energy absorbing layer (typically ballistic fabric) adjacent to the plug layer may also be included as part of the system.
The plug layer may be metallic, or make use of a composite. Plugs are usually maintained within the opening using an interference fit, adhesive, or some type of machined connection.
In an alternative embodiment, the momentum trap ballistic armor system comprises an accelerating layer, a plug layer adjacent to the accelerating layer, and an energy absorbing layer adjacent to the plug layer. In this case, the plug layer includes an opening and an attachment means for a releasable attachment of the plug from the opening. The attachment means may include an interference fit, adhesive, a grooved or machined fit, or some type of machined connection. As mentioned above, the energy absorbing layer may be some type of ballistic cloth, and the plug layer typically includes a multiplicity of openings wherein the attachment means is used for a releasable attachment of a corresponding multiplicity of plugs.
In another embodiment, the momentum trap ballistic armor system in the present invention may also be described as an accelerating layer, a plug layer adjacent to the accelerating layer, and an energy absorbing layer adjacent to the plug layer wherein the plug (included in the plug layer) accelerates to a speed approximately equal to the speed of a projectile upon impact. The acceleration of the plug is completed before the projectile perforates the plug so that a projectile-plug combination can be formed and captured by the energy absorbing layer. Typically, a portion of the accelerating layer is encapsulated by the plug at about the same time the projectile-plug combination is formed. The surface area of the plug is substantially the same as the surface area of the opening within the plug layer where it is maintained, and the plug surface area is usually substantially greater than the cross-sectional area of the projectile.
Finally, the momentum trap ballistic armor system may comprise an accelerating layer (typically ceramic) and a plug layer adjacent to the accelerating layer. The plug layer, in turn, includes a multiplicity of plugs attached or bonded to the accelerating layer. Each one of the multiplicity of plugs may also be bonded or attached to at least one other of the multiplicity of plugs. An energy absorbing layer (typically ballistic fabric) adjacent to the plug layer may also be included as part of the system.
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Anderson, Jr. Charles E.
Johnson Gordon R.
Orphal Dennis L.
Baker & Botts L.L.P.
Johnson Stephen M.
Southwest Research Institute
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