Cross Reference to Related Applications This is a continuation-in-part of U.S. Application No. 12/186,508, filed

August 5, 2008, which claims the benefit of U.S. Provisional Application No.

60/954,017, filed August 5, 2007. Each of the above-referenced applications is incorporated herein in its entirety. Background and Summary

Arrays of tiles are used for covering surfaces. These include arrays of paving stones, roof tiles, heat shield tiles, and armor tiles. Such arrays typically have plural tiles arranged edge-to-edge generally in a common plane. Each tile typically has two opposed broad faces that are generally flat or slightly curved or arcuate and has perimeter edge surfaces.

In some applications, it is best for such tiles to have edges that can overlap in such a way that no straight-through joints are present and such that the array is platelike with the thickness of the entire array not exceeding the thickness of a single tile. A straight- through joint, as discussed to herein, is a joint having a gap between two abutting tiles with at least a portion of the gap extending from one face of the array to the other face of the array that is normal to a face of the array. In the case of a curved array, a straight-through joint is a gap with at least a portion of the gap extending radially in a straight line between two abutting tiles at about 90° to a tangent where the tangent touches a curved face of the array.

Some approaches to avoiding straight- through joints have disadvantages. These include systems having tiles that overlap in the manner of fish scales and systems wherein seam sealers are placed over joints where tiles abut. Arrays made from such tiles cannot have a generally continuous outwardly facing surface because the outwardly facing surfaces of all the tiles are not in alignment. When tiles overlap in the manner of fish scales or seam sealers are used, there typically is excess weight, bulk, and added material expense to cover a given area. Example overlapping tile arrays having lap joints are shown in U.S. Patent No. 1,268,223 (Eimer) and U.S. Patent No. 6,35,777 (Neal). The weight penalty of such fish scale overlap designs can be 25% to 30%.

Monolithic tiles can be used when the coverage area is sufficiently small. But is impractical to cover a large area with a single tile, particularly if the tile is to be composed of a hard, brittle material such as a ceramic material. Such tiles are fragile and develop sharp, linear cracks propagating from the point of origin of a projectile hit through the thickness to the outer edges, so that a projectile hit typically damages the entire tile.

Tiles having edges with undercuts and/or groves sometimes have been used to address the straight-through joint gap problem, but are impractical to produce economically in high volume from hard materials. An example of tiles having undercut edges is shown in U.S. Patent No. 5,404,793 (Meyers). As used herein, the term "undercut" refers to any tile surface feature that makes it impossible to eject a part from a uniaxial die by simple linear displacement. An example of an undercut is a recess, groove, channel, or wall surface that extends radially inwardly from an edge of a part toward the axis of a punch of a die in which the part is formed and that blocks ejection of the part by simple linear displacement.

Described herein are tiles that have major and minor surface faces and edge surfaces that do not have undercuts relative to such an axis. In particular, such tiles do not have any recess, groove or channel that extends radially inwardly from an edge surface toward an axis that extends normal to at least one of the surface faces.

A chamfer is provided at each corner of the tile at the major surface face to permit a ledge of one tile to overlap a ledge of an abutting tile when placed in an array. Due to the presence of the chamfers, the perimeter of the major surface face generally is an irregular or regular octagon. The corners of the minor surface face need not be chamfered.

In particular, the major surface face is defined by an octagonal edge at the perimeter of the major surface face. The edge consists of eight edge portions extending between the corners of the octagonal edge. The edge portions at each corner extend at an internal angle of about 135° relative to each other. The minor surface face is square or otherwise rectangular and is defined by a rectangular edge that consists of four edge portions. Four edge surfaces extend between the four edge portions of the minor surface face and the perimeter of the major surface face. One or more of the edge surfaces and a portion of the major surface face define one or more laterally extending ledges.

Such tiles can be arranged in an array with the ledges of one tile overlapping ledges of abutting tiles to avoid straight-through joints. The edge surfaces are shaped such that the edge surface of the one tile generally conforms to the edge surface of the other tile when the pair of tiles is positioned edge-to-edge. The major and minor surface faces of the one tile generally align respectively with the minor and major surface faces of the other tile and with an edge surface of the one tile overlying an edge surface of the abutting tile, when viewed facing normal to surface faces of the tiles, with only a portion of the thickness of each tile overlapping so that the face-to-face thickness of the pair of tiles where they overlap is no greater than the distance between the major and minor surface faces of one of the tiles.

In some arrangements, all the tiles are identical in shape with abutting tiles inverted so their facing perimeter ledges mate when in an array. In other arrangements, arrays are built from two or more different styles of tiles that are not of identical shape but that have mating perimeter ledges.

Because the ledge of one tile overlaps the ledge of an abutting tile, no grout or filler is required between mating edge surfaces. Such filler systems add cost, have maintenance issues, and can cause catastrophic system failures such as failure of the space shuttle Columbia heat shield tiles where grouting material between tiles came out and allowed heat penetration.

Arrays formed from tiles described herein can be held in place by attachment to a substrate by adhesives. Or tiles can be contained in fabric wraps to hold arrays in place.

Tile systems described herein will find application in many different fields including, but not limited to armor tiles for body armor, armor systems for non-body armor such as vehicles, airplanes helicopters and wherever ballistic and blast protection is needed, heat shields, patio floor tiles, bath tiles, cabinet tiles, roof tiles, building tiles, and in other architectural applications. For some applications, the entire major and/or minor surface face of a tile described herein can be slightly curved or arcuate, having a radius of curvature of 4 inches or more.

The major and/or minor surface faces can have texture, such as a series of curved or angular projections, to turn impinging projectiles to reduce or eliminate the effect of 90° projectile impacts, which have the greatest potential for penetration or cracking destruction of an armor tile.

The major and/or minor surface faces may be textured to provide a decorative effect.

Brief Description of the Drawings

In the drawings:

FIG. la is a front elevational view of a tile suitable for use in forming an array of tiles.

FIG. lb is a side elevational view of the tile shown in FIG. la.

FIG. 2a is a side elevational view of an array of two identical tiles, with the tiles shown aligned edge-to-edge with their respective major and minor surface faces facing in opposite directions.

FIG. 2b is an enlarged parital side elevational view of facing edge portions of the tiles shown in FIG. 2a.

FIG. 2c is an oblique view of an array of four of the tiles of FIG. 2a aligned edge-to-edge with immediately abutting tiles having their respective major and minor surface faces facing in opposite directions.

FIG. 3a is a side elevational view of an array of two of the tiles of FIG. la, with the tiles shown as being in reversed orientation relative to each other and aligned edge-to-edge.

FIG. 3 a is an enlarged parital side elevational view of edge portions of the tiles shown in FIG. 3 a.

FIG. 3c is an oblique view of an array of four of the tiles of FIG. la aligned edge-to-edge with immediately abutting tiles having their respective major and minor surface faces facing in opposite directions. FIG. 3d is a side elevational view of the tile of FIG. la.

FIG. 3e is a front elevational view of the tile of FIG. la.

FIG. 4a is a side elevational view of an array of two non-identical tiles with the tiles shown aligned edge-to-edge with their respective major and minor surface faces facing in opposite directions.

FIG. 4b is an enlarged parital side elevational view of facing edge portions of the tiles shown in FIG. 4a.

FIG. 4c is an oblique view of an array of two of each of the tiles shown in FIG. 4a aligned edge-to-edge with the two types of tiles having their respective major and minor surface faces facing in opposite directions.

FIG. 5 a is a side elevational view of an array of two non-identical tiles with the tiles shown aligned edge-to-edge with their respective major and minor surface faces facing in opposite directions.

FIG. 5b is an enlarged parital side elevational view of facing edge portions of the tiles shown in FIG. 5 a.

FIG. 5c is an oblique view of an array of two of each of the tiles shown in FIG. 5 a aligned edge-to-edge with the two types of tiles having their respective major and minor surface faces facing in opposite directions.

FIG. 6a is a side elevational view of an array of two non-identical tiles with the tiles shown aligned edge-to-edge with their respective major and minor surface faces facing in opposite directions.

FIG. 6b is an enlarged parital elevational view of facing edge portions of the tiles shown in FIG. 6a.

FIG. 6c is an oblique view of an array of two of each of the tiles shown in FIG. 6a aligned edge-to-edge with the two types of tiles having their respective major and minor surface faces facing in opposite directions.

FIG. 7 is an oblique view of an array of two non-identical tiles having curved faces, with the tiles aligned edge-to-edge with the two types of tiles having their respective major and minor surface faces facing in opposite directions.

FIG. 8 is an oblique view of a tile having textured major and minor surface faces. FIG. 9 is an oblique exploded view of a tile having the shape shown 1 with the tile being constructed from two separate pieces.

FIG. 10 is a side elevational view of a tile having curved faces. Detailed Description

Described herein are tiles that generally have the shape of a frustum of a pyramid. Each tile has major and minor bases or surface faces having perimeters that are generally rectangular, with the length of the sides of the rectangle being the same for both the major and minor surface faces, and four edge surfaces that are profiled to provide laterally extending perimeter ledges.

The ledges are configured such that an array of tiles can be formed by aligning tiles edge-to-edge with abutting tiles having their respective major and minor surface faces facing in opposite directions. The edge surfaces are shaped so that the major and minor surface faces of one tile generally aligns respectively with the minor and major surface faces of an abutting tile and with an edge surface of the one tile overlying an edge surface of the abutting tile, when viewed facing normal to surface faces of the tiles, with only a portion of the thickness of each tile overlapping so that the face-to-face thickness of a pair of tiles positioned edge-to- edge is no greater than the distance between the major and minor surface faces of one of the tiles. The edge surfaces are shaped such that the edge surface of one tile generally conforms to the edge surface of another tile when the pair of tiles is positioned edge-to-edge with abutting tiles in inverted orientation such that the major and minor surface faces of the one tile generally are aligned respectively with the minor and major surface faces of the abutting tile.

An array of such tiles can have close fitting seams between the tiles.

Straight-through joints are avoided. And depending on how the tiles are secured in place, abutting tiles can tilt to some extent relative to each other so that an array can be somewhat flexible at joints between abutting tiles.

FIGS. 1 and 3a-3e illustrate an advantageous tile having certain

characteristics including:

a minor surface face 10

a minor surface width 15 a minor surface length 20

a minor surface depth 25

a minor surface perimeter 28

minor surface corners 30

a major surface face 35

a major surface width 40

a major surface length 45

a major surface depth 50

a major surface perimeter 53

chamfer surfaces 55

major surface face corners 59

a ledge 60

a vertical center line 65

a horizontal center lines 70

a total tile thickness 75

a ledge surface angle 80

a ledge surface thickness 85

Common Characteristics

All the tiles described herein have certain common characteristics, illustrated by the tile shown in FIGS, la, lb, and 3a-3e (and in other figures wherein like elements are designated by reference numbers wherein the last two digits are the same as those shown in shown in FIGS, la, lb, and 3a-3e), including the following.

The minor surface face 10 has a smaller area than the major surface face 35. Edge surfaces extend between the perimeter 28 of the minor surface face 10 and the perimeter 53 of the major surface face 35.

Edges of the minor surface perimeter 28 meet at each minor surface corner 30 at an internal angle about 90° as viewed facing normal to the minor surface face 10. The minor surface face perimeter 28 is rectangular or substantially rectangular and can be square or substantially square.

The major surface face perimeter 53 has four truncated corner or chamfer surfaces 55, one at each corner of the ledge 60. The chamfers permit the major surface perimeter 53 to fit alongside the corresponding minor surface face perimeter 25 of an abutting tile when the ledges of inverted abutting tiles overlie one another. Adjacent edges of the major surface perimeter 53 meet at an internal angle about at 135° as viewed facing normal to the major surface face 35. The major surface perimeter 53 thus is substantially octagonal, either an irregular octagon or a regular octagon. The octagon has eight edge portions with each pair of adjacent edge portions extending from a corner 59 at an internal angle of about 135° relative to each other.

As viewed facing normal to the minor surface face 10 as in FIG. la, each chamfer surface 55 is the hypotenuse of a right triangle. The lengths of the other two legs of the triangle are distances Di _, D ₂ , which are the distances from the major surface perimeter 53 to the minor surface face perimeter 28 measured along lines extending perpendicular to edge portions of the perimeter 28 viewed facing normal to the minor surface face 10 as shown in FIG. la. The distance Di is the difference between the minor surface face width 15 and the major surface width 40 divided by 2. The distance D _2, which is equal to the distance Di, is the difference between the minor surface face length 20 and the major surface length 45 divided by 2. In other words, as viewed facing normal to the minor surface face 10 as in FIG. la, the distance between a side edge portion 56 of the perimeter of the major surface face 35 and the nearest edge portion of the perimeter 28 of the minor surface face 10, as measured normal to the edge portions, is the same at each edge of the four side edge portions 56 of the perimeter of the major surface face.

Examples

FIGS. 1 and 3a-3e show a tile that is a body having a hexagonal base surface or major surface face 35 and a square apex surface or minor surface face 10 with the major and minor surface faces generally everywhere equidistant. Lateral faces or edge surfaces 58 extend from the minor surface face 10 to the major surface face 35, with the edge surfaces generally flaring progressively without any grooved or otherwise undercut portion.

A chamfer is provided at each corner of the tile at the major surface to permit a ledge of one tile to overlap a ledge of an abutting tile when placed in an array. Due to the presence of the chamfers, the perimeter of the major surface face is generally an irregular or regular octagon. The perimeter thus consists of eight edge portions. In particular, the tile of FIGS. 1 and 3a-3e has four side edge portions 56 and four chamfer edge portions 57, the side and chamfer edge portions alternate progressively around the perimeter with adjacent side and chamfer edge portions extending at an internal angle of about 135° relative to each other. In the illustrated tile, all the side edge portions 56 are of about the same length 40, 45 and the two pairs of facing side edge portions 56 extend at internal angles of about 90° relative to each other, so that the internal angle at each corner 54 of the perimeter of the minor surface face is about 90°.

The minor surface face 10 and the major surface face 35 are substantially planar and extend substantially in parallel to one another. The tile thus has a total thickness 75 that is generally uniform as measured anywhere between the minor surface face 10 and major surface face 35 along a line normal to the surfaces. The minor surface face 10 has a smaller area than the major surface face 35 and is positioned such that the perimeter 28 of the minor surface face does not extend outwardly of the perimeter 53 of the major surface face when the body is viewed facing normal to the minor surface face.

The edge surfaces are not completely planer from the perimeter 53 of the major surface face 35 to the perimeter 28 of the minor surface face 10. In particular, the edge surfaces 58 are stair-stepped between the major and minor surface faces 35, 10, comprising plural planar surfaces that intersect at an angle other than 180°. The overall shape of the tile is that of a "step pyramid." In a step pyramid shape, the entirety of an edge surface does not lie in a single plane. Instead, at least one edge surface comprises a step that extends in parallel to a side edge portion 56 of a surface face.

The edge surfaces 58 have different portions or band surfaces 61, 62, 63, that have generally uniform widths 50, 25, 85 around the entire perimeter of the tile as shown in FIGS. 1 and 3a-3e. These include major and minor corner band surfaces 61, 62 extending from the perimeters of the major and minor surface faces 35, 10 respectively. Each corner band surface 61, 62 extends at an angle from its corresponding surface face 35, 10 such that the corner band surface and the surface face meet at a corner 71, 72. In the advantageous system of FIGS. 1 and 3a-3e, both the corner band surfaces 61, 62 extend generally perpendicularly to the surface faces 35, 10. Corner band surfaces are sometimes referred to herein as first and second surface portions.

For ease of reference, the tile can be considered to have a laterally extending ledge 60 that is defined by the band surface 63, the major corner band surface 61, and a portion of the major surface face 35. In general, the laterally extending portion(s) of an edge surface of a tile are sometimes referred to herein as a "ledge surface." Accordingly, in the tile of FIGS. 1 and 3a-3e, the band surface 63 is the ledge surface. The bridging band surface 63 is generally planar and extends diagonally, at an angle other than 90° to the surface faces, between the first and second corner band surfaces 61, 62.

The major and minor surface faces are centered relative to each other such that the perimeter 28 of the minor surface face is generally everywhere equidistant from the perimeter 53 of the major surface face, as measured along lines perpendicular to corner band surfaces 61, 62, when the body is viewed facing the minor surface face, as in FIG. 3e, that is, Di and D ₂ are equal distances on all four sides of the tile.

The tile of FIGS. 1 and 3a-3e is particularly advantageous because its edge surface is profiled such that the edge surfaces of any two abutting tiles conform to one another when the two identical tiles are positioned edge-to-edge with the surface faces of the two tiles facing in opposite directions, such that the major surface face of one tile faces in the same direction as the minor surface face of the abutting tile as illustrated in FIG. 3a-3c. Arrays made entirely from identical tiles that have such conforming edges are referred to herein as symmetric joint arrays.

Mating edge surfaces 58 do not have interlocking edge surfaces in the sense that abutting tiles can be tilted to some degree relative to one another in the manner of a hinge, if the tiles are suspended in the array in a manner that allows some movement.

FIGS. 3a-3c illustrate how several of such tiles can be assembled into an array with tiles positioned edge-to-edge with the surface faces of abutting tiles facing in opposite directions. In particular, the arrows appearing in FIG. 3c show how four tiles may be moved into position to assemble an array.

FIGS. 2a-2c show a different tile and illustrate that the angles between adjacent edge surfaces can differ. (The element numbers of similar elements in FIGS. 2a- 2c are the same as in FIGS. 1 and 3a-3e, but with the numbers incremented by 200.) In this tile, the ledge surface is a bridging band surface 263 that extends substantially parallel to the surface faces between the first and second corner band surfaces 261, 262. The tile has a laterally extending ledge 260 that is defined by the bridging band surface 263, the major corner band surface 261, and a portion of the major surface face 235. FIGS. 2a- 2c illustrate how several of such tiles can be assembled into an array with tiles positioned edge-to-edge with the surface faces of abutting tiles facing in opposite directions. In particular, the arrows appearing in FIG. 2c show how four tiles may be moved into position to assemble an array.

FIGS. 4a-4c show tiles 411a, 411b that are not identical to one another but that have mating edge surfaces. (The element numbers of similar elements in FIGS. 4a-4c are the same as in FIGS. 1 and 3a-3e, but with the numbers incremented by 400.) The major corner band surface 461a of tile 411a extends generally perpendicularly to the major surface face 435a. The minor corner band surface 462a of tile 41 la flares from the minor surface face 410a as shown in FIGS. 4a-4b. The major corner band surface 461b of tile 41 lb tapers from the major surface face 435b as shown in FIGS. 4a-4b. The minor corner band surface 462b of tile 411b extends generally perpendicularly to the minor surface face 410b. In these tiles, the ledge surfaces are bridging band surfaces 463a, 463b that extend substantially parallel to the surface faces respectively between the first and second corner band surfaces 461a, 462a and 461b, 462b. The tile 41 la has a laterally extending ledge 460a that is defined by the bridging band surface 463a, the major corner band surface 461a, and a portion of the major surface face 435a. And the tile 41 lb has a laterally extending ledge 460b that is defined by the bridging band surface 463b, the major corner band surface 461b, and a portion of the major surface face 435b. FIG. 4a-4c illustrate how several of such tiles can be assembled into an array with tiles positioned edge-to-edge with the surface faces of abutting tiles facing in opposite directions. In particular, the arrows appearing in FIG. 4c show how four tiles may be moved into position to assemble an array.

FIGS. 5a-5c show tiles 511a, 511b that are not identical to one another but that have mating edge surfaces. (The element numbers of similar elements in FIGS. 5a-5c are the same as in FIGS. 1 and 3a-3e, but with the numbers incremented by 500.) Tiles 51 la, 51 lb have no bridging band surfaces, only major corner band surfaces 561a, 561b and minor corner band surfaces 562a, 562b respectively. The major corner band surface 561a of tile 511a tapers from the major surface face 535a as shown in FIGS. 5a-5b. The minor corner band surface 562a of tile 511a extends generally perpendicularly to the minor surface face 510a. The major corner band surface 561b of tile 511b extends generally perpendicularly to the major surface face 535b. And the minor corner band surface 562b of tile 51 lb flares from the minor surface face 510b as shown in FIGS. 5a-5b. The tile 511a has a laterally extending ledge 560a that is defined the major corner band surface 561a and a portion of the major surface face 535a. And the tile 51 lb has a laterally extending ledge 560b that is defined by the minor corner band surface 562b, the major corner band surface 561b, and a portion of the major surface face 535b. In these tiles, the ledge surfaces thus are the surfaces 561a, 562b. FIGS. 6a-6c illustrate how several of such tiles can be assembled into an array with tiles positioned edge-to-edge with the surface faces of abutting tiles facing in opposite directions. In particular, the arrows appearing in FIG. 6c show how four tiles may be moved into position to assemble an array.

FIGS. 6a-6c show tiles 611a, 611b that are not identical to one another but that have mating edge surfaces. (The element numbers of similar elements in FIGS. 6a-6c are the same as in FIGS. 1 and 3a-3e, but with the numbers incremented by 600.) Tiles 61 la, 61 lb have no bridging band surfaces, only major corner band surfaces 661a, 661b and minor corner band surfaces 662a, 662b respectively.

Notably, in these tiles, the band surfaces 661a, 662b have a curved profile, as shown best at FIG. 6b. In particular, the band surfaces 661a, 662b have a cross section that is a portion of a circle so that the band surfaces 661a, 662b are portions of cylindars. (A portion of each band surface 661a, 662b could be considered to be a "bridging band surface." In particular, portions nearest the band surfaces 661b, 662a might be considered to be "bridging band surfaces" because the curved band surfaces 661a, 662b might be considered to comprise plural surfaces.) The major corner band surface 661a of tile 61 la tapers from the major surface face 635a as shown in FIGS. 6a-6b. The minor corner band surface 662a of tile 61 la extends generally perpendicularly to the minor surface face 610a. The major corner band surface 661b of tile 61 lb extends generally perpendicularly to the major surface face 635b. And the minor corner band surface 662b of tile 611b flares from the minor surface face 610b as shown in FIGS. 6a-6b. The tile 61 la has a laterally extending ledge 660a that is defined the major corner band surface 661a and a portion of the major surface face 635a. And the tile 611b has a laterally extending ledge 660b that is defined by the minor corner band surface 662b, the major corner band surface 661b, and a portion of the major surface face 635b. In these tiles, the ledge surfaces thus are the surfaces 661a, 662b.

General Considerations

As discussed above, the major surface faces of the various tiles have perimeters that are octagons. This is because tiles having rectangular major surface face perimeters experience corner interference. Corner interference prevents tiles from fitting closely together with tight seams. The corners of the tile ledges thus are chamfered to avoid interference. Each tile shape has corner interference conditions which dictate the extent of truncation required. The corners of the minor surface face need not be chamfered in order to avoid corner interference.

In the illustrated tiles, for example the tile shown in FIG. la, to avoid corner interference, each side edge portion 56 of the perimeter of the major surface face 35 is the same length as and extends in parallel to the nearest edge portion of the perimeter edge 28 of the minor surface face 10. Also, the ends of each side edge portion 56, which are located at the corners 59 of the perimeter of the major surface face 35, are aligned respectively with edge portion ends, which are located at the corners 59 of the perimeter of the minor surface face 10, along a line that are collinear with an edge portion of the perimeter of the minor surface as viewed facing normal to the minor surface face. As mentioned above, the major surface face 35 is defined by an octagonal edge 53 at the perimeter of the major surface face. The edge 53 consists of eight edge portions extending between the corners 59 of the octagonal edge. The two edge portions at each corner 59 extend at an internal angle of about 135° relative to each other. The minor surface face 10 is defined by a rectangular edge 28 that consists of four edge portions. And the distance from the minor surface face perimeter to the major surface face perimeter is uniform around the perimeter of the minor surface face 10 where the distance Di, D ₂ is measured along lines, such as lines 65, 70, extending perpendicular to the side edge portions 56 of the major surface face 35 as viewed facing normal to the minor surface face.

It should be appreciated that angles, distances, and geometric relationships mentioned herein can vary to some extent without significantly affecting the performance of a tile array. The amount of allowable variation will depend on the needs and requirements of the application and on the thickness and other dimensions of the tiles and may be determined empirically or by mathematical calculation. As an example, the corner angles of the tile shown in FIGS, la, lb, and 3a-3e can vary slightly. The extent of the allowable variation will depend on the width Di, D ₂ of the ledge or, in other words, will depend on the ratios of the dimensions 15, 40, and 20, 45 of the major and minor surface faces. Although it is ideal for adjacent edges of the major surface perimeter meet at an internal angle of 135°, good results can be achieved with corners 59 having internal angles of 135° plus or minus 4°. And for some configurations, the internal angles could be 135° plus or minus 10° without creating a 90° straight-through gap. And as a general matter, it typically is not practical to mass produce tiles of the type described herein to have perfect dimensions. Such variations are applicable to all the tiles described herein.

In an array, tiles are positioned edge-to-edge and meet at joints. The tiles have mating edges of one of two types, "symmetric" and "asymmetric." Tiles having symmetric edges are shown in FIGS. 1, 2a- 2c, and 3a-3e. Such tiles can be "turned over" and fit to abutting tiles. The edges have a profile such that, when two such tiles are inverted relative to each other and placed edge-to-edge, the facing edges are complimentary and mate as shown in FIG. 3c such that an array can be built using only tiles of this configuration. Advantageously, in symmetric edge tiles the minor surface depth 25 and the major surface depth 50 will be substantially equal as shown in FIGS. 1 and 3a-3e. All aspects of the manufacture and use of tiles described herein are simplified by the use of symmetric types. Asymmetric edge tiles do not conveniently invert and require at least two types of tiles used in pairs to fit together to form an edge-to-edge array of tiles. But asymmetric type tiles can have edge profiles that are advantageous for forming tile arrays to be used for certain applications. Tiles having asymmetric edges are shown in FIGS. 4a-4c, 5a-5c, and 6a-6c.

In the symmetric-edged tile of FIGS. 1 and 3a-3e, the major- to-minor surface connecting ledge surface 63 is at an angle other than than 90° to the horizontal axis 70 extending from the bottom of the minor surface depth 25 to the top edge of the major surface such that the minor surface depth 25 and the major surface depth 50 are approximately equal.

As shown in FIG. la and FIG. lb, the ledge surface angle 80 is such that the minor surface depth 25 and the major surface depth 50 are substantially equal. The angle can be calculated with normal mathematical equations. The angle will depend on the minor surface depth 25, the major surface depth 50, the total thickness of the tile 75, and the relative sizes of the minor surface face 10 and major surface face 35, which determine the distances Di and D ₂ .

As previously observed, the tiles of FIGS. 1 and 3a-3e and the tiles of FIGS. 2a- 2c have and major and minor surface faces with perimeters that respectively are octagonal and square. Tiles having minor surface face perimeters that are

"rectangles" other than squares can have similar symmetric-edge profiles.

The symmetric-edge tile shown in FIGS. 2a and 2b is configured such that a single tile can be inverted to form an array in all directions which has no 90° through joints. The chamfers 255 extending from the major surface face allow the ledges 260 of abutting tiles to overlap and thus not increase the thickness of the entire array beyond the total thickness of an individual tile. The minor surface depth 225 and the major surface depth 250 are equal in order to have the surfaces of abutting inverted tiles align. The depth could be somewhat unequal, if surface mismatch is not an important issue. The minor to major surface connecting ledge surface 263 is at 90° to the vertical center line extending from the bottom of the minor surface depth 225 to the top edge of the major surface 250 parallel to the minor and major surfaces, in the horizontal axis. Tile arrays having asymmetric joints can be seen as being formed from alternating "A" and "B" configuration tiles. The use of A and B tiles is best in certain applications, for example to allow different thicknesses and connecting ledges to be used for the minor surface depth and perimeter and the major service depth and perimeter. Asymmetric tiles employ the same type of corner chamfer as the symmetric configuration tiles allowing ledges to overlap with tiles aligned in a common plane. Any of several angles and/or radii can be used for the edge band surfaces of asymmetric tiles so long as the edge profiles are matched so that the facing edges of abutting A and B tiles mate.

Curved arrays can be formed from the tiles described herein and are particularly useful for better fit in situations where the surface to be covered is not flat.

Such curved arrays can be formed from flat tiles by setting abutting tiles at an angle to one another to form an arcuate array. With such arrays, there will be small gaps between the tiles at a convex surface of the array. But such arrangements are workable for certain applications because even with a small gap at the convex surface, the array will not have a 90° gap through to the opposite concave surface.

The gap at the convex surface of adjacent tiles can be substantially reduced and for certain large radii be effectively eliminated by the use of tiles having curved surface faces, with one of the surface faces being at least partially concave and the other of the surface faxes being at least partially convex. FIG. 7 shows example tiles having curved surface faces 710a, 735b, in particular, surface faces that are portions of cylinders that are concentric. For most applications in which curvature is helpful, both the major surface face and minor surface face of the tiles is a curved surface having a radius of at least 4 inches.

The radii that can be used to form the desired curvature can easily be calculated by well understood geometric engineering principles. The size of the tile can be varied to meet desired curvature and acceptable surface gaps. The variations are many. By way of illustration, but without limiting the size of tile or radius: a. A tangent circle radius of 10 inches using a curved tile 2 inches square will result in a convex surface gap of .0151 inches and the same curvature made with angled flat tiles of the same size will result in a convex surface gap of .0564 inches, or 3.75 times greater.

b. If the size of the tile is reduce to 1 inch, the convex surface gap for a 10 inch tangent circle radius will be approximately 50% smaller or .0075 inches.

c. If the size of the tile is made 4 inches, the convex surface gap is increased by about 2 times to about .0304 inches.

d. A tangent circle radius of 60 inches made with 2 inch curved tiles will result in a convex surface gap of .0025, as a practical matter very small.

e. In all cases, because of the overlap edges of adjacent tiles the convex surface gap is only on the surface, decreases as it moves to the center of the tile, and in no case is a 90° through gap to the minor surface created.

The tiles shown in FIG. 7 have major surface faces and minor surface faces that generally are portions of cylinders and that are concentric. The tile has a total thickness that is generally uniform as measured anywhere along radii of the cylindrical surfaces. Curved- surface tiles having surfaces that are portions of cylinders are the most practical to manufacture in quantity. But tile surfaces could be portions of spheres or could have even more complex curvatures.

Any of the tiles described herein may have a textured surface face. For example, the tile shown in FIG. 8 has both the minor and major surface faces 810, 835 that are textured. The textured surface can have ridges and/or peaks formed by the appropriate placement of triangles (pyramids), squares (cubes), rectangles, and/or curved radii ridges (waves) where the depth of any depression is not more than 60% of the distance between peaks or ridges.

Tiles of a unitary construction, where the entire tile is a formed as a single piece having a uniform composition throughout, is the most efficient for most applications. However, any of the tiles described herein can be made in more than one part, which can be advantageous in some applications. For example, FIG. 9 shows a tile of the shape shown in FIGS. 1, 2a-2c, and 3a-3e. Only the tile of FIG. 9 differs in that it is a sandwich arrangement where parallelepiped portion defined by the minor surface face 910 and the minor corner band surface 962 is formed separately from the remainder of the tile. The tile portions can be bonded together by any of several conventional methods including but not limited to adhesives, brazing, tape, welding, and glue with or without heat. Separate tile portions also may be held in place, without bonding, by envelopment within a matrix material, such as by wrapping with fabric, positioning in pockets formed in fabric, or the like.

The tiles described herein are configured to allow construction from very hard materials such as the various ceramics currently used in the manufacture of tiles. Ceramic tiles, particularly those used for ballistics applications, will have a hardness of at least 1000 Vickers.

Tiles of hard materials are best are formed by processes using mechanical or hydraulic presses and using dies with outer configurations and/or top and or bottom punches and/or cavities that will produce a green body for an entire tile of a desired shape. The green body is cured by heat or some other method to complete formation of the tile.

The edge design may be applied without regard to the size, large or small, with the limitation being dependant on the capacity of the equipment used to make or form the tile.

Frusto-pyramidal tiles, as described herein, are particularly well suited for efficient, high rate production by such standard pressing processes because there are no undercuts in the edge surfaces. Such tiles most efficiently can be of unitary construction, which is to say not constructed from plural laminated parts.

To form such tiles efficiently, the edge surfaces must not grooved or otherwise undercut. This permits efficient production by the use of rapid-rate closed-die manufacturing methods.

For example, to form armor tiles having appropriate properties, a powder is pressed into a die to form a green compact. The green compact is ejected from the die and then heated to sinter the powder to complete the tile. Rapid and repeated reuse of dies is essential to success.

The use of dies can be made highly efficient by forming tiles in the presently claimed configurations, where the edges of the tiles are without undercuts. A tile having an undercut cannot be formed in a simple uniaxial die.

The issue of undercuts is discussed in Powder Metallurgy Science, second edition, Randall M. German, 1994, ISBN 1-878954-42-3, page 234. That publication states that to achieve compact integrity and dimensional control, the tooling should be kept as simple as possible along the axis of pressing. The shape must allow for easy powder flow into the die cavity and easy ejection. Thus, certain shapes are not possible for uniaxial pressing and require methods such as isostatic pressing or dies which can be disassembled on each pressing cycle.

A tile with an undercut portion is an example of such a shape that is not possible for uniaxial pressing.

A uniaxial die has a straight-sided wall and upper and lower punches that conform to the shape of the die wall. One or both punches travel along an axis to compact a loaded compactible material charge. This is the most efficient tool for mass production of hard parts such as armor tiles.

For example, U.S. Patent No. 6,318,986, titled Undercut Split Die, col. 1, lines 17-19, states: "In some cases, the compacted part has an undercut which prevents removal of the part or blank from the dies by linear or axial displacement." As noted in German, "certain shapes are not possible for uniaxial pressing and require methods such as cold isostatic pressing or dies which can be disassembled on each pressing cycle." Such "not possible" shapes include parts with undercuts. And, although parts with undercuts can be formed using "isostatic pressing or dies which can be disassembled on each pressing cycle," such elaborate processes are not efficient for making tiles in high volume.

The inefficiency of dies which must be disassembled is shown by publications such as U.S. Patents Nos. 5,102,607; 5,503,795; 5,698,149; 5,772,748; and 6,318,986. These patents show and describe just how elaborate dies must be to deal with the problem of undercuts.

Isostatic pressing can be used to form green bodies to be used for making hard parts having undercut portions by powder metallurgy, but isostatic pressing is highly inefficient such that hard tiles having undercut portions still cannot be made economically.

Tiles of the shapes described herein, without undercuts, can be made without the need for such costly, wear-prone, and relatively slow-cycling dies or isostatic pressing. For example, a tile of the type shown in FIGS. 1 and 3a-3e can be formed in a uniaxial die having a central pressing axis that extends normal to the minor and major surface faces 10, 35, coincident with the line 79 shown in FIG. 3d, because the edges of such a tile have no recess, groove, channel, or wall surface that extends radially inwardly toward the central pressing axis so as to prevent linear

displacement of the part from the die by only simple axial movement of the punches.

Curved tiles of the type shown in FIG. 7 also can be formed using uniaxial dies, which permits efficient high volume production. Here again there must be no undercut edges so that the tiles can be pressed and ejected from a simple die. This can be accomplished efficiently by making tiles having edge surface portions that do not extend radially but that, for example, instead extend parallel to the axis of the die used during the forming process. FIG. 10, for example, shows a tile having edge surface portions 1061, 1062 that extend in parallel to a centerline 1065, which in turn extends in parallel to the pressing axis of a die best suited for forming such a tile. For the tile of FIG. 10, the pressing axis of the die thus is normal to a line 1046 that is tangential to the center of major surface face 1035.

In some instances, in addition to the tiles described herein, an array could include some tiles having undercuts. Although it is not practical to make numerous hard tiles having undercuts, non-uniaxial dies or isostatic pressing could be used to make some such tiles in low volume for use in limited areas to make an overall array more effective. Such tile shapes also could be formed from a meltable material by die casting. Or a body of a ceramic material could be machined to form a tile having such a shape.

In the illustrated tiles, the major and minor surface faces generally are everywhere equidistant. Although the major and minor surface faces best are substantially continuous, one or both of the surface faces may define a cavity for the purpose of weight reduction or may have a surface texture shaped to deflect an incident projectile. And for some applications, it is not necessary for the face surfaces of abutting tiles in an array to be aligned precisely; but an array could instead have a surface with a cross-sectional profile in the nature of a square wave with the surface faces of abutting tiles at somewhat different elevations.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated tiles are only examples and should not be taken as limiting the scope of the invention.