BACKGROUND OF THE INVENTION

Field of the Invention (Technical Field) :

The present invention relates to a built-up playing court structure such as a granular structure, enabling a selected moisture content to b maintained within its surface layer, and a method for its construction. Description of the Related Art Including Information

Disclosed under 37 C.F.R. §§1.97-1.99 (Background Art) :

There are at present two basic types of surfaces used for playing courts, "hard" surfaces and "soft" surfaces. Hard surface courts generally have concrete and asphalt surfaces and, indoors, wood surfaces. Soft surface courts generally have lawn, clay and various composite built up surfaces. To effectively play court games, one is required to repeatedly turn and move with rapidity. One of the primary disadvantages of the use of hard surface courts is that the bones, muscles and connective tissues of players are stressed by repetitive activity on the hard surface. Conventional soft surface courts however also have disadvantages. Construction and maintenance costs are typically very high. Frequent cutting, rolling, smoothing and replenishing of the surface materials is required to keep the surface i a playable condition. Additionally, since most of these soft surface courts are constructed outdoors, and are porous, water retention following ambient rainfall may preclude play on the court surface due t puddles or a general muddy court surface having a slippery consistency.

Built-up playing courts consisting of gravel, sand, clay and vario bonding materials have been developed in the art as a more practical alternative to conventional clay courts. A clay or sand top surface layer is desirable, because such a layer makes a surface more playable by providing smoothness yet appropriate traction for the soles of players' shoes. However, there are several problems inherent in such conventional built-up surfaces. Loose sand or clay which is normally present at the uppermost surface layer over time washes down through t lower layer materials, such as gravel, due to rain or sprinkling; this

sand or clay is thus lost from the surface and has to be periodically replaced. Drainage of such courts presents a problem because the sand or clay tends to fill all of the void spaces between the lower surface materials (e.g. gravel). Thus, water will not drain laterally below the surface at a sufficiently fast rate. Hence, water drainage usually runs off over the top surface, gradually removing the surface materials. Even if the surface materials are not washed, away, they tend to be redistributed unevenly, causing smoothing problems. Furthermore, unless the surface is adequately sloped and almost perfectly uniform, there will be standing puddles of water following rains which will preclude use of the court until the water is removed by evaporation. Almost all conventional soft surface and hard surface courts have a slope in an attempt to prevent puddling. Another problem occurs in cold weather areas. Water trapped within the void spaces below the surf ce freezes. The expansion that takes place during freezing causes movement of the surface, thereby damaging it. Repair is necessary to smooth the damaged areas. Another problem is that wind tends to blow away or unevenly rearrange surface materials, especially when the surface is dry; again, requiring replacement or smoothing. This problem could be alleviated considerably by sprinkling the surface with water. However, during periods of winds or play, sprinkling is impractical. Another problem with wind is that the top surface tends to dry out, resulting in poor footing for the players and inconsistent ball bounce.

Since court games, particularly tennis, are played by millions of people, much time and energy has been devoted to solving such problems inherent in maintaining outdoor athletic courts. Examples of proposed solutions to some of the problems are disclosed in U.S. Patents No. 585,856, entitled Underground Irrigation, to Swanson; No. 1,222,648, entitled Growing Trough, to Marks; No. 1,690,020, entitled Pavement and Process of Laying Same, to Kirschbraun; No. 1,862,423, entitled Playing Court, to Otto; No. 1,958,850, entitled Tennis Court, to Foster; No. 2,024,158, entitled Playing Court, to Gallagher; No. 2,031,146, entitled Automatic Watering Device, to Dodge; No. 3,908,385, entitled Planted Surface Conditioning System, to Daniel et al; and No. 4,044,179, entitled Playing Surface for Athletic Games, to Haas, Jr.; German Patent No. 27 27 956, to Blank; and U.S. Patent No. 4,576,511, entitled Apparatus and Method of Creating and Controlling an Artificial Water Table, to Vidal, Jr.; No. 3,307,360, entitled Method of Subsurface

Irrigation and System Therefor, to Bailly; No. 3,625,010, entitled System and Method for Preventing Erosion, to Hakundy; No. 1,222,648, entitled Growing Trough, to Marks; No. 2,031,146, entitled Automatic Watering Device, to Dodge; Czechoslovakian Patent No. 111978 to Sramek; and Italian Patent No. 482615 to Ortensi. None of these patents teach the unique court surface structure of the present invention having a built-up court surface layer, a stabilizing subsurface layer, and means for selectively controlling moisture content in the built-up court surface layer. These patents are discussed in more detail below.

The '856, '360, '010, '648, and '146 patents and Czechoslovakian Patent No. 111978, disclose subsurface irrigation devices. The irrigation systems are used for providing water to a vegetative or natural soil surface cover. Italian Patent No. 482615 and German Paten No. 27 27 956 disclose a subsurface irrigation system for sports fields with granular surface covers. The '432 patent discloses a subsurface moisture barrier.

The '020, '158 and '179 patents disclose permanent, fixed surfaces. The '020 patent is directed to a combined bituminous and concrete pavement surface. The '158 patent teaches a playing court surface atop cork/sand gravel beds. The '179 patent discloses an artificial turf fabric surface which is intended to simulate grass.

The '385 patent discloses a system for irrigating and evacuating a playing field having a vegetative cover. This system incorporates a lattice of perforated pipes under the playing surface. The pipes are covered by a layer of sand followed by a layer of rooting media on whic the vegetative matter is grown. A pump attached to the pipe lattice allows a vacuum to be applied and accumulated surface water to be drawn down within the subsurface sand layer. Also incorporated into the system is a moisture sensor which allows automatic irrigation of the field.

The '423 patent discloses a soft surface court having a pervious surface layer which enhances drainage and moisture retention, depending upon ambient conditions. The '850 patent teaches the use of fine epidote as a top layer and coarser epidote as a lower layer for a tenni

court surface. Neither of these patents provide means for moisturizing the surface.

The '511 patent discloses means and an apparatus for maintaining a selected water level in a layered structure of particulate material.

SUMMARY OF THE INVENTION

(DISCLOSURE OF THE INVENTION)

The present invention relates to a built-up, moisture content controlling playing court structure comprising: a built-up court surface layer comprising fine aggregate materials; a barrier surface substantially impervious to moisture spaced beneath the built-up court surface layer; a containment wall positioned essentially peripherally about the built-up court surface layer and the barrier surface and extending upwardly from the barrier surface to about the level of the built-up court surface layer disposed thereabove; a subsurface bed of aggregate disposed atop the barrier surface and beneath the built-up court surface layer; the subsurface bed of aggregate being peripherally surrounded by the containment wall; a stabilizing layer of adhesive material applied atop the subsurface bed of aggregate; the stabilizing layer providing supportive stability to the subsurface bed of aggregate, and the layer of adhesive material comprising voids therein to provide adequate liquid conductivity between the subsurface bed of aggregate and the built-up court surface layer thereabove to substantially maintain the selected moisture content in the built-up court surface layer, and the built-up court surface layer of fine aggregate material disposed atop and in the voids of the adhesive coated stabilizing layer; and means for controllably introducing liquid to and draining liquid from the subsurface bed of aggregate and the built-up court surface layer to substantially maintain a selected moisture content in the built-up court surface layer. The built-up court surface layer is preferably essentially horizontal. This compares with conventional court surfaces which must be sloped in an attempt to prevent puddling.

The invention further comprises a method of constructing a built- up, moisture content controlling playing court structure comprising the following steps: a) obtaining a foundation for the playing court; b) providing a moisture barrier above the foundation;

c) providing a containment wall peripherally about the foundation; d) positioning above the moisture barrier means for introducing liquid to and draining liquid from the playing court structure to substantially maintain a selected moisture content in the playing court structure; e) providing a subsurface bed of coarse aggregate above th moisture barrier; and f) introducing fine aggregate into the voids of the coarse aggregate and on to its surface to provide a built-up, moisture content controlling playing court structure; and applying an adhesive material incompletely across the top of the subsurface bed of aggregate to add stability to the subsurface bed of aggregate.

The present invention also provides a unique built-up surface for a granular structure, such as a playing court, comprising a moisturized aggregate mixture, such as fine aggregate preferably comprising a mixture of granite, marble, quartzite, and limestone.

The present invention further comprises an improved surface for a granular structure comprising an aggregate layer in combination with an adhesive elastomeric layer, such as rubberized asphalt, polyurethane, and epoxy, with the adhesive elastomeric layer comprising voids for allowing fluids to freely pass therethrough and to and from the aggregate layer.

The present invention further comprises an improved surface for a granular structure comprising an upper fine aggregate layer in combination with an underlying mortar material layer.

The present invention further provides a method of constructing a surface for a built-up granular structure comprising the steps of providing a layer of aggregate, and providing an adhesive elastomer layer comprising voids for allowing fluids to freely pass therethrough and to and from the aggregate layer.

The invention also relates to a built-up, moisture content controlling granular structure and method of construction. The preferred structure comprises an upper surface layer comprising fine

aggregate material; a barrier surface substantially impervious to moisture spaced beneath the upper surface layer; a containment means positioned essentially peripherally around the structure; a subsurface reservoir bed disposed atop the barrier surface and beneath the upper surface layer, the subsurface reservoir bed being peripherally surrounded by the containment wall; and means for stabilizing the subsurface reservoir bed and for providing adequate fluid conductivity between the subsurface reservoir bed and the upper surface layer to substantially maintain the selected moisture content in the upper surface layer.

The present invention further provides a method of constructing a built-up, moisture content controlling granular structure comprising the following steps: a) obtaining a foundation for the granular structure; b) providing a moisture barrier above the foundation; c) providing a containment wall peripherally about the foundation; d) providing a subsurface reservoir bed above the moisture barrier; e) providing an upper surface layer comprising fine aggregate atop the subsurface reservoir bed; and f) providing means for stabilizing the subsurface reservoir bed and for providing adequate fluid conductivity between the subsurface reservoir bed and the upper surface layer to substantially maintain the selected moisture content in the upper surface layer.

A primary object of the present invention is to regulate the moisture content in the surface of a granular structure, such as a soft- surface athletic playing court.

Another object of the invention is to provide a playing surface of consistent quality that can be uniformly level, if desired.

Another object of the present invention is to provide a unique surface for a granular structure possessing good traction, yet providing "slidability," to prevent injury.

Still another object of the present invention is to provide a surface which will not erode and yet provides good intrinsic drainage.

One advantage of this invention is that in accordance therewith, surface runoff during rain can be greatly reduced to essentially eliminate washing away and puddling of the surface.

Another advantage of the invention is that wind erosion is substantially reduced by providing moisture to the court surface at all times, including windy periods.

Yet another advantage of the invention is there is no need for costly, complicated moisturizing and drainage apparatus.

Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawing, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated into and form a part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention.

Fig. 1 is an isometric view of the built-up playing court structure of the invention;

Fig. 2 is a side view of one of the built-up court structure embodiments of the invention;

Fig. 3 is a side view of the Fig. 2 embodiment showing screening around each pipe;

Fig. 4 is a side view of another embodiment of the invention showing screening disposed above the pipes;

Fig. 5 schematically illustrates alternative control mechanisms for introducing liquid to and draining liquid from the playing court structure of the invention;

Fig. 6 is a side view of an alternative embodiment of the invention;

Fig. 7 is a cross-sectional view of a section of an alternative built-up granular structure of the invention;

Fig. 8 is a cross-sectional view of an alternative built-up granular structure of the invention;

Fig. 9 is a cross-sectional view of the preferred upper layer and subsurface layers of the surface of the invention;

Fig. 10 is a top view of the upper layer, shown by section A-A of Fig. 9; and

Fig. 11 is a cross-sectional view of an alternative embodiment of the subsurface layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION (BEST MODES FOR CARRYING OUT THE INVENTION)

The present invention relates to a built-up playing court structure, such as a granular structure, having a system for controlling the moisture content of the playing surface and the court structure. The invention can be utilized in the construction of new playing courts or to convert or retrofit existing playing courts. Fig. 1 shows a built- up playing court structure 10 in accordance with the present invention comprising a built-up court surface layer 12, a moisture barrier 14 spaced beneath the built-up court surface layer 12, a containment wall 16 on the periphery of the court 10, a subsurface bed 18 of aggregate material, and pipes 20 for controlling the moisture content in the subsurface bed of aggregate 18 and thereby surface layer 12.

Pipes 20 contains perforations or apertures 22 for introducing liquid to and draining liquid from the subsurface bed of aggregate 18 and, therethrough, the built-up court surface layer 12. The pipes 20 of the preferred embodiment, disposed generally horizontal, are substantially parallel to one another and spaced approximately three to six feet apart. Pipes 20 can be disposed directly above the moisture barrier 1 , or within the subsurface bed of aggregate 18. Although generally horizontal, the pipes 20 preferably slope slightly to enhance drainage, as shown in Fig. 2; but they can be disposed horizontally. If the pipes 20 slope slightly, moisture barrier surface 14 can also slope, as shown in Fig. 2. An existing hard court surface, which is converted to a built-up court in accordance with the invention, would most likely have such a slope. Whether or not the barrier surface 14 is sloped, the built-up court surface layer 12 can be horizontal because of the moisture content controlling capability of the invention which ensures proper drainage and moisturizing of the surface layer 12. This surface layer 12 preferably has a thickness above the gravel of between approximately 1/8 inch and 1/2 inch. In contrast, prior art playing surfaces are usually built having a slight slope in order to prevent puddling. Moisture barrier 14 can comprise, for example, a compacted surface covered with a waterproof membrane, such as a plastic sheet, or the surface of an existing hard court, preferably waterproofed or covered with a waterproof material.

For moisturizing the surface of the playing court in accordance with the invention, the moisture content of the built-up court structure 10 is preferably controlled by introducing liquid into the pipes 20. The liquid flows out of the apertures 22 into the playing court structure 10. For drainage, liquid passes from the playing court structure 10 through the apertures 22 and pipes 20. As mentioned previously, it is desirable to maintain a selected moisture content within the built-up court surface layer 12. The surface 12 should be kept somewhat moist, but not wet, to provide good footing, ball bounce, smoothness and firmness. Court surface 12 is also kept moist to eliminate dust during play and to eliminate the problem of wind depleting and redistributing the surface sand.

Although fresh, potable water will usually be the liquid used in accordance with the invention, other liquids may be utilized. For

example, salt water or other non-potable water sources which may be available can also be utilized. Additionally, when temperatures are below the freezing point, antifreeze can be introduced into the pipes 20 to prevent the fluid flowing into voids 30 between the pieces of aggregate material 18 from freezing and expanding, thereby causing damage to the court. Herbicides can also be added to the liquid to reduce or eliminate undesired vegetative growth on the built-up court surface. Likewise, surfactants, wetting agents, detergents,and other additives may be added to the liquid to enhance the movement of moisture upward by capilliarity from the liquid level within the pipes 20 to the surface layer 12.

The pipes 20 may be made of any suitable metal or plastic, or any other type of material usable in subsurface applications. The preferred pipe size is between approximately 1.5 inches and 2.5 inches outside diameter; however, other sizes can be utilized in accordance with the invention, as desired.

To prevent the aggregate material 18 from entering the pipes 20 through apertures 22, a layer of screening 24 may be provided. Screening 24 can be positioned as a layer within the subsurface bed of aggregate material 18, such as shown in Figs. 1, 4 and 6. In this embodiment, the aggregate material 18 surrounding the pipes should be of a size which is larger than the aperture size to deter the aggregate material 18 from entering the apertures 22. Alternatively, screening 24 can be wrapped around the pipes 20, as shown in Figs. 2 and 3. In this embodiment, the screen size should be smaller than the aggregate material 18 surrounding the pipes.

The containment wall 16 of the invention shown in the drawing is positioned peripherally about the built-up court surface layer 12 and the barrier surface 14 spaced therebelow. Wall 16 extends upwardly from the barrier surface 14 to about the level of the built-up court surface layer 12. The preferred height of the containment wall is 4 inches to 6 inches, but it can be any desired height.

Note in Figs. 2 and 3 that the subsurf ce bed of aggregate material 18 comprises essentially the same size material. Figs. 1, 4 and 6 illustrate embodiments with two subsurface layers, an upper layer

of smaller aggregate material 34 and a lower layer of larger aggregate material 36. For example, the upper layer of aggregate material 34 could be gravel having about a 0.5 inch average width and the lower layer of aggregate material 36 could be gravel having a about 0.75 inch average width. When two layers 34 and 36 of coarse aggregate material are used and screening 24 is present between the two layers 34 and 36, as shown in Figs. 1, 4 and 6, fine aggregate material, such as sand, should not be present in the voids 30 of the lower layer of aggregate material 36, as the fine aggregate material 28 could enter the apertures 22 of the pipes 20. A layer of rock chips or pea gravel 58,

(see Fig. 6) preferably having an average width of between approximately 1/8 inch and 1/4 inch, may be utilized to help support the screening 24. This particle size provides a faster moisturizing rate via wicking than the larger gravel, and a slower rate than the sand. As stated previously, no drain pipes are used in Fig. 6 as adequate lateral drainage is possible through the spaces between the gravel.

The Fig. 5 schematic illustrates a system for controlling the moisture content in the built-up court structure of the invention. The particular means used for achieving moisture and drainage control will depend on the climatic characteristics of the geographical location of the playing court, e.g. , desert, or tropics, and the seasons, e.g. , heavy rainfall, no rainfall, or high winds. The pipes 20 are shown in a substantially parallel configuration across the court. A pipe header 38 for filling the pipes 20 and another pipe header 40 for draining the pipes 20 are connected thereto. Conventional drain valves 42 can be provided on one or both ends of the drain pipe header 40 and the fill pipe header 38 (not shown) . If the pipes 20 are sloped, they will slope downward toward the drain pipe header 40 so that gravity aids drainage. The pipe headers 38 and 40 may be disposed within the containment walls 16, but are preferably positioned outside the containment wall 16 so that accessing valves 42 will not require an access hole in the court surface. In one embodiment, a conventional float valve device 44, which comprises a float disposed in a liquid containing tank. The liquid level therein is maintained through this float valve. A line via valve 45 connects from this tank to pipes 20 at approximately the same level as the liquid level in the pipes 20 in the subsurface bed of aggregate 18. When the liquid level in the subsurface bed 18 drops, the level in the tank drops the same amount. The float causes valve 44 to

open, replenishing water to the tank and to the subsurface bed 18. When the preset level is reached, valve 44 closes. Valves 45 and 46 are operated manually; in open position when valve 44 is in use, and closed when by-passed. In an alternative embodiment, shown by the dashed lines in Fig. 5, a moisture sensing instrument 48, is set to a desired moisture content. When moisturizing is needed, it causes a valve 50 to open, thereby allowing liquid present in a storage tank 52 to flow into the fill pipe header 38. The moisture sensor 48 may be positioned to detect moisture content at the pipe level or at the surface level. A water pump 54 or water pressure inducing device may be utilized to aid in filling the pipes 20. Additionally, valve 50 can be closed and liquids shunted through valve 55 and 57 through a choke, orifice or flow controller 56 to control the rate of flow of the liquid into the fill pipe header 38. Those skilled in the art will appreciate that the above described instruments may be controlled manually or automatically, as desired.

The above-described system (best shown in Figs. 1 and 5) has two modes, a draining mode and a moisturizing mode. The draining mode is used prior to or during rain or freezing weather. During the draining mode, liquid will flow through the aggregate materials, enter the pipe apertures 22, flow through the pipes 20, out the drain pipe header 40, and out drain valves 42. With the present invention, water drains through the surface, aggregate beds and pipes as fast as rain falls, thereby deterring lateral runoff from and erosion of the surface layer 12. The moisturizing mode is typically used in dry or windy weather conditions and any other time surface moisture evaporation is taking place. Various ways of controllably introducing liquid into the fill pipe header 38 were discussed above. Liquid from the fill pipe header 38 flows through the pipes 20, out of the apertures 22 and into the aggregate materials 18 to the preset level within the bed, then wicks by capillary action upward to the built-up court surface layer 12. The moisture barrier 14 prevents the liquid from flowing further downward out of the bed and also prevents settling or other movement of the foundation or base by retaining liquid from seeping out of the bed. As stated above, various types of liquids or additives may be used in the moisturizing mode to achieve desired results, such as killing vegetation, preventing freezing or merely to save on operating costs

e .g. , utilizing less expensive, non-potable water. Either or both modes can be used during play.

Fig. 6 illustrates an alternative embodiment of the invention. This embodiment does not use parallel pipes 20 as discussed above, but provides fill-drain pipes 60 for both providing liquid to and draining liquid from the built-up court structure 10. When additional moisture is required, liquid flows from the fill-drain pipes 60 into the subsurface bed of aggregate 18 to the preset level, and wicks therefrom upward to the built-up court surface layer 12. When drainage is required, liquid flows downward into the gravel bed and laterally outward into the fill-drain pipes 60. A coarse screen 62 is preferably provided over the open ends of the fill-drain pipes 60 to prevent the coarse aggregate material 36 from entering the fill-drain pipes 60. If a float-valve mechanism is utilized (not shown) , the liquid level in the built up bed will be the same as the level in the float valve tank. Overflow pipes 64 can be used above the liquid level but below the surface for draining during rain, without the need to open valves on pipes 60. With this arrangement the system is an automatic draining and moisturizing mode at all times.

Figs. 7 and 8 show other alternative built-up granular structured embodiments 10 in accordance with the present invention comprising an upper surface layer 12, a perforate adhesive layer 32 below the upper surface layer 12, a coarse aggregate reservoir bed which could be a reservoir layer 15 or a mortar material layer 33, an intermediate imperforate adhesive 17, a support layer 21, and a base 23. A containment wall 16, with drainage outlets 47 having screens 25, surrounds the periphery of court structure 10.

The reservoir layer 15 itself, in the embodiment shown in Fig. 7, comprises a mixture of coarse aggregate 26 and fine aggregate 28, such as sand and gravel. This layer provides a reservoir function; water percolates upwards and downwards between the upper layer 12 and this reservoir layer 15. Depending upon the desired moisture content of the upper layer 12, the fine aggregate 28 of the reservoir layer 15 allows for saturation of the reservoir layer 15. The uppermost coarse aggregate 26 particles in the reservoir layer 15 are secured together b the coating of adhesive elastomer 32, creating an adhesive foraminous

elastomeric layer or a web-like layer. The interstices or voids 31 between the coarse aggregate particles 26 in the reservoir layer 15 are filled with fine aggregate 28; the fine aggregate 28 is not coated with the adhesive elastomer 32, thus allowing the free percolation of water between the upper layer 12 and the reservoir layer 15. The voids 31 in the reservoir layer 15 containing the fine aggregate 28 are saturated with fluid, thus not only storing fluid, but providing supportive stability to the coarse aggregate 26 in this layer 15. The fluid moves upwardly by capillary or wicking action and downwardly by gravity. Obviously, the moisture content of the upper surface layer 12 can be controlled by maintaining a selected degree of liquid saturation in the reservoir layer 15. The reservoir layer 15 also provides support for the upper layer 12.

Several alternatives exist as to the exact composition of the reservoir layer 15. As noted previously, the coarse aggregate and fine aggregate mixture, discussed above, may be used. The reservoir layer 15 may be made of any thickness, depending on the need to more rapidly absorb excess water. The preferred thickness of the reservoir layer 15 is less than one inch.

In an alternative embodiment, shown in Fig. 8, the adhesive layer 17 and the sand-gravel aggregate, shown in Fig. 7, can be eliminated and replaced by a mortar mixture 33. This mortar mixture is preferably a weakly consolidated cement-sand-water mixture. The preferred mortar mixture comprises ten to twenty parts sand by volume to one part of Portland cement. All the heretofore described functions of the reservoir layer 15 of Fig. 7 would still accrue: reservoir layer stabilization, moisture retention, storage for a desired volume of moisturizing fluid for the upper layer, moisture transfer between the upper layer and reservoir, and support of the upper layer. One advantage to this mortar material 33 is that no perforate adhesive layer is required.

As shown in Figs. 7 and 8, underlying the reservoir layer 15 is an intermediate Imperforate moisture barrier 17. This moisture barrier 17 is shown in Fig. 7 as a solid adhesive layer 29 and as an impermeable sheet 37, such as a plastic sheet, in Fig. 8. If an adhesive elastomer is utilized as the moisture barrier 17, the preferred materials are

polyurethane, epoxy, rubberized asphalt, or a mixture thereof. Unlike the uppermost adhesive layer 32, shown in Fig. 7, however, this intermediate adhesive layer 17, also shown in Fig. 7, is applied to all of the aggregate, coarse aggregate and fine aggregate, in the next downward layer, the support layer 21. This intermediate adhesive layer 17 also stabilizes the underlying aggregate in the support layer 21 and is substantially impervious to moisture and free of voids. This moisture barrier 17 functions as a barrier to moisture between the base 23 and the reservoir layer 15 or mortar mixture layer 33. The moisture barrier 37 in the Fig. 8 configuration is optional and may be eliminated to simplify construction.

Like the reservoir layer 15 or mortar mixture layer 33, the suppor layer 21 also preferably comprises coarse aggregate 26 and fine aggregate 28, and also supports the overlying layers. Unlike the reservoir layer 15 or mortar mixture layer 33, however, the support layer 21 is dry throughout because of the moisture barrier 17. The dry fine aggregate 28 stabilizes the coarse aggregate 26. The preferred fine aggregate 28 may be sand, although other fine aggregate materials may be utilized in accordance with the invention. Likewise, the preferred coarse aggregate 26 is gravel or pebbles, but other coarse aggregate materials may be utilized in accordance with the invention. The coarse aggregate 26 is preferably three-quarter inch to one inch i diameter. This support layer 21 rests directly upon the base 23 which may be an existing structure, soil, or any other firm, preferably (but not necessarily) level surface. While desirably so, base 23 need not level inasmuch as support layer 21 will compensate for any unevenness therein. No sealant or impermeable layer is required between this base 23 and the support layer 21, since this function is performed by support layer 21 and moisture barrier 17.

The thickness of the layers or beds and the coarseness of the aggregate can be varied, depending on moisturization and stability factors. The invention is not limited to the particular beds represented in the drawings.

Containment walls 16 are disposed about the periphery of the layer structure, preferably four inches to six inches high, but they could b of any desired height. Also placed in the containment are drainage

outlets 47 to directly remove fluid surplus at the upper layer 12. These drainage outlets 47 can also be used as inlets to introduce water to the structure by flooding the upper layer 12. As many outlets/inlets 47 as deemed necessary are provided; they may be screened to prevent aggregate from entering. Such screens 25 should be of finer mesh than the finest aggregate of the upper layer 12.

Moisturization of the structure 10 can be accomplished by utilizing natural rain in combination with the reservoir layer 15 or mortar material layer 33. The reservoir layer 15 or mortar material layer 33 becomes saturated with the water for use in moisturizing the upper layer 12 by wicking action, over an extended period, such as a day or more. Excess water is drained through the outlets 47. In dry climates or periods, watering or moisturization can be achieved by sprinkling, either manual or automatic, of the upper layer 12, by flooding the upper layer 12 through the outlets 47 (which also serve as inlets) , by sunken hoses in the upper layer 12 (particularly useful in windy conditions) , or other means, common to the art, for providing moisturization to surfaces. In this structure, too, other fluids, such as weed killer and antifreeze, can be utilized to not only moisturize the surface, but provide other functions.

In yet another alternative embodiment, not shown, a permeable layer could replace the moisture barrier 17 shown in Figs. 7 and 8. In such an embodiment, an alternative moisture barrier would need to be disposed beneath the aggregate, such as atop the base 23. This embodiment is useful when a thicker aggregate bed is needed for drainage. The preferred additional permeable layer is an adhesive elastomer layer, such as discussed above, to allow fluid conductivity between beds, yet stabilize the coarse aggregate.

The invention further comprises a method for constructing a built- up, moisture content controlling granular structure comprising the steps of obtaining a foundation for the granular structure; providing a moisture barrier above the foundation; providing a containment wall peripherally about the foundation; providing a subsurface reservoir bed above the moisture barrier; providing an upper surface layer comprising fine aggregate atop the subsurface reservoir bed; and providing means for stabilizing the subsurface reservoir bed and for providing adequate

fluid conductivity between the subsurface reservoir bed and the upper surface layer to substantially maintain the selected moisture content in the upper surface layer. Maintenance of the upper layer 12 is accomplished by wide drag brooming or other means, common to the art, for maintaining granular surfaces.

Figs. 9-11 show a preferred surface of the invention comprising an upper layer 12, a subsurface reservoir layer 19 and an intermediate adhesive elastomeric layer 32. This surface is useful in all of the court embodiments discussed herein. As seen therein, the upper layer 12 comprises a compacted, moisturized fine aggregate 28, such as crushed rock or stone. Coarse aggregate 26, such as gravel or pebbles, mixed with fine aggregate 28, makes up the preferred subsurface reservoir layer 19. Preferably, the coarse aggregate 26 is disposed to permit edges of the coarse aggregate to substantially touch to provide an adequate support layer. The upper layer 12 is stabilized by applying the adhesive elastomer material 32 atop the bed of coarse aggregate 26 to prevent the coarse aggregate materials from shifting, and to eliminate extensive maintenance, such as rolling. This adhesive elastomer material 32 does not form a solid layer separating the upper layer 12 from the subsurface layer 19. As best illustrated in Fig. 10, which is a top view of the surface shown as Sec. A-A of Fig. 9, only the tops of the grains of the coarse aggregate 26 are coated with the adhesive elastomer 32 to provide voids or interstices 31 for liquid and fine aggregate 28 to flow or pass between the upper layer 12 and the subsurface bed 19. Fine aggregate 28 fills the interstices 31 in the adhesive elastomer layer 32 and the spaces between the grains of coarse aggregate 26 in the subsurface layer. The upper layer 12, comprising the fine crushed aggregate 28, is spread to a depth of preferably less than one inch and most preferably between approximately 1/4 inch and 1/2 inch above the adhesive elastomer layer 32. The surface may then b rolled, compacted, and moisturized, thereby compressing the layer 12 an forcing the fine aggregate 28 downward into the interstices 31 in the adhesive elastomer layer 32 and between the coarse aggregate 26.

After the coarse aggregate material 26 is stabilized, as discussed above, the fine aggregate material 28 is applied to the surface and washed down into the bed to fill the voids 31 between the coarse aggregate material 26 and to form the upper surface layer 12. The

presence of the fine aggregate material 28 in the surface layer 12 and in the voids 31 of the subsurface bed of aggregate 19 keeps the court structure 10 permeable so that liquid can be drained from or added to the court structure 10. The smoothness of the top surface can then be easily established and maintained with conventional wide drag brooms. Essentially, upper layer 12 provides a simple yet effective surface of fine aggregate, as discussed previously herein. Both drainage and moisturization of this improved upper surface layer are accomplished by controllably introducing fluid directly at this surface either manually, by automatic sprinklers, or by any other direct surface watering means, or by subsurface watering means. The upper layer may be level so drainage takes place at the periphery of the upper surface layer. The relative size proportions of fine aggregate in the upper surface layer provide a bonding effect when moisturized, resulting in a court surface having increased "playability." Nevertheless, the high retained moisture content of the surface also provides a safety margin in that safe footing is provided, decreasing the possibility of knee and ankle injuries. Any desired thickness may be used to accomplish the desired moisture content of upper layer 12, although it is preferably between approximately 1/4 inch and 1/2 inch thick.

The preferred surface materials for both the upper layer 12 and subsurface layer 19 are crushed stone or rock, such as volcanic or igneous, metamorphic, sedimentary, or synthetic rocks. The invention is not limited to any particular materials. The upper layer 12 should include a finer aggregate material than the subsurf ce layer 19. The fine aggregate 28, which forms the upper layer 12 and is disposed in the interstices 31 in the adhesive elastomer layer 32 as well as between the coarse aggregate 26 of the subsurface layer 19, preferably comprises weathered granite, limestone, quartzite, and marble, or mixtures thereof, but may be other suitable materials, such as basalt, felsite, rhyolite, augite, olivine, biotite, silica, obsidian, tuff, volcanic ash and dust, agglomerates, latite, monzanite, dacite, granodiorite, andresite, dorite, dolomite, marble, mica, feldspar, quartz, calcite, gabbro, syenite, diorite, gneiss, schist, synthetic rocks, or mixtures thereof. The sizing of this fine aggregate 28 is preferably between approximately 9% and 26% by weight +4 mesh, between approximately 11% and 34% by weight +10 mesh, between approximately 17% and 50% by weight +40 mesh, and the balance -200 mesh; and most preferably between

approximately 15% and 20% by weight +4 mesh, between approximately 20% and 25% by weight +10 mesh, between approximately 30% and 35% by weight +40 mesh, between approximately 20% and 25% by weight +200 mesh, and th balance -200 mesh. Care, however, should be taken to avoid the introduction of substantial clay minerals and fines, at -200 mesh, sinc a high amount of fines might deleteriously produce a "muddy" court. Th preferred fine aggregate mixture, the granite, marble, quartzite, and limestone mixture, is a significant improvement over prior court aggregate surface materials in that it is not adversely affected by under saturation or over saturation from the coarse aggregate reservoir layer 19. Other top dressing materials are more sensitive to moisture content and have a comparatively more narrow range of maximum and minimum moisture content for good playability. With the wider range of moisture content permitted by this material, playability will be good when the moisture supplying reservoir is super saturated or only partially saturated, in high or low humidity conditions, in hot sunny weather or cloudy cooler weather, or in windy or calm weather. Thus, n adjustments are necessary in changing weather conditions.

The coarse aggregate subsurface or reservoir layer 19 preferably comprises larger aggregate than the upper surface layer 12, such as gravel, pebbles, and the like, or mixtures thereof. The diameter of th coarse aggregate 26 is preferably between approximately 1/4 inch and 1 inch, and most preferably between approximately 1/4 inch and 3/8 inch Fine aggregate 28, such as sand or tuff, may also be disposed in the subsurface layer 19. The fine aggregate 28 allows for saturation of th subsurface layer 19 and allows liquid to flow down from or wick up to the upper layer 12. Thus, the subsurface layer 19 acts as a "reservoir layer.

The adhesive elastomeric layer 32, disposed between the upper layer 12 and subsurface layer 19, presents, after curing, an interstitial sheet-like, web-like, or foraminous structure comprising voids that provide passages for liquid to freely flow or percolate between the upper layer 12 and the subsurface or reservoir layer 19. Similarly, fine aggregate 28 can pass through the adhesive elastomeric layer 32 between the upper layer 12 and subsurface layer 19. Moisture control of the surface is thus achieved by allowing this fluid flow between layers 12 and 19. The adhesive elastomeric layer 32 prevents

the coarse aggregate materials 26 from shifting, resulting in decreased maintenance. The preferred adhesive elastomeric material 32 comprises rubberized asphalt, polyurethane, epoxy, or mixtures thereof. The adhesive material 32 is selected to remain resilient after curing. The adhesive elastomer layer can be used beneath the upper fine aggregate layer (see Figs. 7-9 and 11) and also as an intermediate layer between aggregate beds (see Fig. 8). The web-like nature of the adhesive elastomer layer provides stabilization of the underlying layer, while allowing fluid to flow between layers. Thus, the term "surface," as used throughout the specification and claims, is not only intended to cover upper layers of a structure, but also intermediate layers.

Fig. 11 shows an alternative embodiment wherein a low-strength, weakly consolidated, high porosity, or high permeability mortar material 33, such as a cement mixture, is used instead of the adhesive elastomer layer 32 and loose coarse aggregate layer 19, shown in Fig. 9. This mortar material 33 provides fluid flow to and from the upper layer 12. A preferred mortar mixture is a mixture of Portland cement, sand, and water. Preferably one part by volume Portland cement is mixed with 10-20 parts by volume of coarse sand (with a preferred grain size of approximately .005 to .025 inch). This alternative embodiment has sufficient resiliency to keep the surface moisturized, to prevent cracking of the surface, and to retain the "softness" of a granular court surface. Coarse aggregate 26, such as shown in Fig. 9, is preferably mixed with the mortar material 33, although the subsurface layer 19 may comprise only the mortar mixture 33. The mortar material 33 locks or stabilizes the coarse aggregate 26.

The invention further comprises a method for constructing a surface for a built-up granular structure. The method comprises the steps of providing a subsurface reservoir layer comprising coarse aggregate; applying an adhesive elastomer web atop the subsurface reservoir layer; providing a layer of fine aggregate atop the adhesive elastomer layer; compacting the surface, such as by rolling; and thereafter periodically moisturizing the surface. These various layers are discussed, in detail, above.

The adhesive elastomer material is preferably applied atop the bed of coarse aggregate by spraying, but other means common to the art for

applying adhesive materials may also be used in accordance with the invention. The application of adhesive elastomer should provide for the creation of voids within the elastomer layer to allow fluid to pass freely therethrough. After the coarse aggregate is stabilized with the adhesive elastomer, the fine aggregate is washed down into the subsurface bed to fill the voids or interstices in the adhesive elastomer layer and between the coarse aggregate. Additional fine aggregate is applied to form the upper layer.

There is further provided, in accordance with the invention, an alternative method of constructing a surface for a built-up granular structure. The method comprises the steps of providing a subsurface reservoir layer of coarse aggregate and a high permeability or high porosity mortar material, such as a Portland cement, sand, and water mixture; providing an upper layer of fine aggregate; compacting the surface, such as by rolling; and thereafter periodically moisturizing the surface.

The presence of the fine aggregate in the upper layer keeps the surface permeable so that fluid can be drained from or added to the surface structure. Good drainage is inherently provided by the granular structure of the upper layer, without the need for sloping.

Moisturizing of the surface may be accomplished by subsurface or surface irrigation means or by direct application of water to the upper surface layer or subsurface layers. Moisturizing tends to further compact the surface by cementing or bonding the finer particles together. This, in turn, is believed to provide good traction while allowing "slidability," thus preventing injury. Moisturizing may be provided as often as required to maintain desired conditions in the surface. The smoothness of the upper surface layer can be easily established and maintained with conventional wide drag brooms or other means, common to the playing court art, for maintaining clay or granular courts.

In addition to providing a surface which is tractive and relatively safe, the instant invention also provides a playing court surface offering excellent ball bounce.

INDUSTRIAL APPLICABILITY The invention is further illustrated by the following non-limiting examples.

EXAMPLE 1 An upper aggregate surface layer was made by mixing decomposed

(weathered) granite, limestone, quartzite, and marble, with no plastic ingredients, such as clay. The aggregate size was 17.45% by weight +4 mesh, 22.85% by weight +10 mesh, 33.30% by weight +40 mesh, 22.73% by weight +200 mesh, and the balance of -200 mesh. The hardness was approximately 3-5 on the Mohs scale. This fine aggregate was disposed atop an elastomer layer and a coarse aggregate material layer.

EXAMPLE 2 An upper aggregate surface layer was made with a volcanic (igneous) conglomerate. The conglomerate was made chiefly of granite type rocks composed mainly of rounded, subangular fine grain (4 mm) . The composition of the volcanic conglomerate was specifically basalt, diorite, gabbro, felsite, rhyolite, and tuff with traces of latite, dacite and andresite. The composition was badly decomposed volcanic and powder-like material. This fine aggregate was disposed atop an elastomer layer and resulted in good playability in a wide range of moisture content of the top surface dressing.

Although the invention has been described with reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents.