Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-05-19
2001-03-20
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S911000, C089S036020, C089S036040
Reexamination Certificate
active
06203908
ABSTRACT:
The present invention relates to a composite armor panel. More particularly, the invention provides improved ceramic bodies for use in armored panels providing lightweight ballistic protection which may be worn by the user, and for protecting mobile equipment and land, air and amphibious vehicles against high-speed fire-arm projectiles or fragments. The invention also includes a composite armor and ballistic armor containing said bodies.
There are three main considerations concerning protective armor panels. The first consideration is weight. Protective armor for heavy but mobile military equipment, such as tanks and large ships, is known. Such armor usually comprises a thick layer of alloy steel, which is intended to provide protection against heavy and explosive projectiles. Due to its weight, such armor is quite unsuitable for light vehicles such as automobiles, jeeps, light boats, or aircraft, whose performance is compromised by steel panels having a thickness of more than a few millimeters.
Armor for vehicles, including land, airborne and amphibious vehicles, is expected to prevent penetration of bullets of any weight, even when impacting at a speed in the range of 700 to 1000 meters per second. The maximum armor weight which is acceptable for use on light vehicles varies with the type of vehicle, but generally falls in the range of 40 to 100 kg/m
2
.
A second consideration is cost. Overly complex armor arrangements, particularly those depending entirely on synthetic fibers, can be responsible for a notable proportion of the total vehicle cost, and can make its manufacture non-profitable.
Fairly recent examples of armor systems are described in U.S. Pat. No. 4,836,084, disclosing an armor plate composite including a supporting plate consisting of an open honeycomb structure of aluminium; and U.S. Pat. No. 4,868,040, disclosing an antiballistic composite armor including a shock-absorbing layer. Also of interest is U.S. Pat. No. 4,529,640, disclosing spaced armor including a hexagonal honeycomb core member.
Ceramic materials are nonmetallic, inorganic solids having a crystalline or glassy structure, and have many useful physical properties, including resistance to heat, abrasion and compression, high rigidity, low weight in comparison with steel, and outstanding chemical stability.
Such properties have long drawn the attention of armor designers, and solid ceramic plates, in thicknesses ranging from 3 mm. for personal protection to 50 mm. for heavy military vehicles, are commercially available for such use.
Much research has been devoted to improving the low tensile and low flexible strength and poor fracture toughness of ceramic materials; however, these remain the major drawbacks to the use of ceramic plates and other large components which can crack and/or shatter in response to the shock of an incoming projectile.
Light-weight, flexible armored articles of clothing have also been used for many decades, for personal protection against fire-arm projectiles and projectile splinters. Examples of this type of armor are found in U.S. Pat. No. 4,090,005. Such clothing is certainly valuable against low-energy projectiles, such as those fired from a distance of several hundred meters, but fails to protect the wearer against high-velocity projectiles originating at closer range. If made to provide such protection, the weight and/or cost of such clothing discourages its use. A further known problem with such clothing is that even when it succeeds in stopping a projectile the user may suffer injury due to indentation of the vest into the body, caused by too small a body area being impacted and required to absorb the energy of a bullet.
A common problem with prior art ceramic armor concerns damage inflicted on the armor structure by a first projectile, whether stopped or penetrating. Such damage weakens the armor panel, and so allows penetration of a following projectile, impacting within a few centimeters of the first.
The present invention is therefore intended to obviate the disadvantages of prior art ceramic armor, and to provide ceramic bodies for deployment in composite armor panels which are effective against armor-piercing, high-velocity, small-caliber fire-arm projectiles, yet which are of light weight and therefore can be incorporated in a composite panel having a weight of less than 45 kg/m
2
, which is equivalent to about 9 lbs/ft
2
when used in personal armor and light vehicles and which can be of greater weight when used in heavier vehicles and/or in armor against heavier ammunition.
In the field of armor material, the terms “surface mass” and “weight” are often used interchangeably, as will be done in the present specification. Another way of expressing the above concept is to relate to “a surface weight which does not exceed 450 Neuton/m
2
.”
A further object of the invention is to provide an armor panel which is particularly effective in arresting a plurality of projectiles impacting upon the same general area of the panel.
Thus, according to the present invention there is now provided a ceramic body for deployment in composite armor, said body being substantially cylindrical in shape, with at least one convexly curved end face, wherein the ratio D/R between the diameter D of said cylindrical body and the radius R of curvature of said at least one convexly curved end face is at least 0.64:1.
In preferred embodiments of the present invention, the ratio D/R between the diameter D of said cylindrical body and the radius R of curvature of said at least one convexly curved end face is at least 0.85:1.
In especially preferred embodiments of the present invention the ratio D/R between the diameter D of said cylindrical body and the radius R of curvature of said at least one convexly curved end face is between about 0.85:1 and 1.28:1.
In further preferred embodiments of the present invention the ratio D/R between the diameter D of said cylindrical body and the radius R of curvature of said at least one convexly curved end face is at least 1.28:1.
U.S. Pat. No. 4,665,794 discloses the use of ceramic pieces of tubular of spherical shape in a composite armor environment. U.S. Pat. Nos. 4,179,979; 3,705,558; and 4,945,814 disclose the use of ceramic spheres in a composite armor arrangement. None of said patents, however, teach or suggest the specific shapes of ceramic bodies as defined herein, and the surprisingly superior properties thereof as shown in comparative Example A hereinafter.
The armor plates described in U.S. Pat. No. 5,763,813 and U.S. application Ser. No. 09/048,628 are made using ceramic pellets made substantially entirely of aluminum oxide. In U.S. application Ser. No. 08/944,343 the ceramic bodies are of substantially cylindrical shape having at least one convexly-curved end-face, and are preferably made of aluminium oxide.
Obviously, other ceramic materials having a specific gravity equal to or below that of aluminium oxide, e.g., boron carbide with a specific gravity of 2.45, silicon carbide with a specific gravity of 3.2 and silicon aluminum oxynitride with a specific gravity of about 3.2 can be used in place of aluminum oxide in the composite armor of the present invention.
Thus, oxides, nitrides, carbides and borides of magnesium, zirconium, tungsten, molybdium, titanium and silica can be used and especially preferred for use in the present invention are pellets selected from the group consisting of boron carbide, titanium diboride, silicon carbide, magnesium oxide, silicon aluminum oxynitride in both its alpha and beta forms and mixtures thereof.
Ceramic bodies which are substantially cylindrical in shape and which have at least one convexly curved end face are known and are manufactured by various companies in Israel, Italy, India, Germany and the United States as a grinding media. These ceramic bodies, however, have been found to be inferior in properties for use in a composite armor panel, as described in comparative Example 1 hereinafter, in that these bodies prepared with a height H of 7.5 mm and a diameter D of 12.8 mm have been found to shatter
Fulbright & Jaworski L.L.P.
Loney Donald J.
LandOfFree
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