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CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of U.S. Provisional Application No. 60/600,597 filed on Aug. 11, 2004, currently pending, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to the field of building construction and more particularly to a coated ceiling structure for the interior of a building and a method of forming the same.  
         [0003]     Industrial facilities and other buildings are often exposed to air that is laden with corrosive and otherwise harmful chemicals in the form of liquids, vapors, gases and solid particulate matter. The presence of such airborne contaminants, as well as extreme temperatures and humidity, can lead to the premature wear and eventual failure ofbuilding materials, including interior ceiling structures, made from materials such as steel, wood, concrete and masonry. Many factors contribute to the deterioration of such building materials, including chemical corrosion, water absorption, condensation, mold development, loss of strength, loss of thermal insulation efficiency and the like.  
         [0004]     Suspended or “drop” ceiling installations are well known in the building construction field. Suspended ceiling systems typically comprise a rigid grid or frame suspended from or attached to the interior surface of a roofing structure or the bottom side of a floor structure within a building. Rigid panels or tiles are then individually inserted into the openings in the grid. Each panel is supported on a ledge that extends around the perimeter of the respective opening of the grid.  
         [0005]     Suspended ceiling panels can be made of a wide variety of materials and serve numerous purposes such as providing thermal insulation and sound absorption and improving aesthetics. Moreover, by lowering the level of the ceiling within a building, suspended ceilings effectively reduce the air volume within the building that must be heated, cooled or filtered, thereby reducing equipment costs and energy consumption. A suspended ceiling may also offer protection to building materials and structures attached to the ceiling, such as air handling and electrical equipment. However, conventional suspended ceiling systems are not capable of withstanding long term exposure to the harsh environments that exist in many commercial and industrial buildings, such as described above, without degradation and eventual failure.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     According to the present invention, a method of forming a coated ceiling structure comprises the steps of: providing a base ceiling structure having an outer surface; applying a foam material in a fluid state to the outer surface of the base ceiling structure; and solidifying the foam material to form a rigid reinforcing layer on the base ceiling structure.  
         [0007]     According to a further aspect of the present invention, a method of forming a ceiling structure comprises the steps of: providing a base ceiling structure comprising a non-self-supporting material; and spraying a reinforcing material onto an outer surface of the base ceiling structure. The reinforcing material and the non-self-supporting material together form a self-supporting composite structure.  
         [0008]     According to a still further aspect of the present invention, A ceiling system comprises: a base ceiling structure for suspending from a structural member of a building; a substrate attached to the base ceiling structure; and a sprayable reinforcing material adhered to the substrate. The sprayable reinforcing material and the substrate together form a self-supporting composite material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a top perspective view of a portion of a suspended ceiling grid;  
         [0010]      FIG. 2  is a top perspective view of a portion of a suspended ceiling structure according a first example embodiment of the present invention;  
         [0011]      FIG. 3  is a sectional view of the suspended ceiling of  FIG. 2  taken along section line  3 - 3 ;  
         [0012]      FIG. 4  is a sectional view similar to  FIG. 3  of a suspended ceiling structure according to a second example embodiment of the present invention; and  
         [0013]      FIG. 5  is a sectional view similar to  FIG. 3  of a suspended ceiling structure according to a third example embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     As shown by way of example in  FIGS. 1-5 , the present invention provides a coated ceiling structure and a method of forming the same.  
         [0015]      FIG. 1  shows a known ceiling frame or grid structure  10  suspended from a building structure (not shown) by a plurality of wires  12 . The grid structure  10  comprises a plurality of longitudinally spaced frame members  14  connected at intervals by laterally spaced connecting members  16 . In the illustrated embodiments, the frame members  14  and connecting members  16  have an inverted T-shaped cross section, as best seen in  FIGS. 3-5 . Other suitable shapes and configurations can be used as desired. The spacing of the frame members  14  and the connecting members  16  is selected to provide openings  18  sized to each accommodate a tile or panel  20  to be inserted therein ( FIG. 2 ). For example, the size of the openings  18  and corresponding panels  20  may range from twelve inches by twelve inches to 48 inches by 96 inches. Other suitable dimensions can be used as determined by the requirements of the specific application.  
         [0016]     The frame members  14  and connecting members  16  of the grid structure  10  may be made from any suitable material(s), including solid and cellular plastics, other polymers, steel, aluminum, wood, composite materials and the like. The cross-sectional dimensions of the frame members  14  and connecting members  16  are selected in accordance with strength and other requirements of a particular application. The wires  12  that suspend the grid structure  10  from the building structure may be made of any suitable material and are selected to have an appropriate strength, thickness and spacing between wires, depending upon factors such as load, regulatory requirements and other applicable requirements for a particular application.  
         [0017]     As best shown in  FIG. 2 , a plurality of self-supporting panels  20  are inserted into the openings  18  in the grid structure  10  so that the peripheral edges  22  of the self-supporting panels  20  rest on surrounding ledges or flanges  24  provided by the inverted T-shaped profile of the frame members  14  and connecting members  16 . As used herein, the term “self-supporting” refers to a material that is rigid, strong and/or resilient enough to withstand its own weight without deforming when the material is not supported by an additional structure. Further, as also used herein, the term “non-self-supporting” refers to materials that will substantially deform under their own weight when not supported by and/or attached to an additional supporting structure. The self-supporting panels  20  shown in  FIG. 2  can be made of any suitable self-supporting material, including single or multiple layers of solid or cellular plastics, aluminum, steel, gypsum board, cement board, fiberboard, paper, cardboard, plywood, particle board, hardboard, oriented strand board, fiberglass products of various thickness, density and shapes, and other materials that meet the requirements for a particular application. Further, it should be appreciated that the grid structure  10  of the disclosed embodiments comprises frame members  14  and connecting members  16  that are self-supporting.  
         [0018]     According to a first example embodiment of the present invention, as shown in  FIGS. 2 and 3 , a base ceiling structure  25  comprising the grid structure  10  and panels  20 , or other suitable base ceiling structure is installed in a building structure. Then, a layer of foam material  26  is sprayed onto a substrate, namely the underside or exposed outer surface of the base ceiling structure  25 . Once the foam material  26  solidifies or sets, it forms a seamless, rigid reinforcing layer. One or more additional layers of materials may be sprayed over the foam material to form a protective and/or aesthetic outer coating  28  on the foam material  26 . The outer coating  28  may be used to improve the appearance of the foam material  26  and/or to provide further performance characteristics in addition to those provided to the foam material  26 , depending upon the requirements of a particular installation. The foam material  26  and/or the outer coating  28  acts to strengthen or otherwise reinforce self-supporting materials such as the panels  20  of the present embodiment. The combined coated ceiling structure  30  exhibits particular desired performance characteristics including thermal insulation, moisture resistance, chemical resistance, impact resistance, washability, rigidity, strength, light weight, and the like.  
         [0019]     By applying the foam material  26  and/or the outer coating  28 , according to the present invention, it may be possible to use materials for constructing a suspended ceiling structure that would not by themselves meet strength and other engineering and/or regulatory requirements. For example, certain geographic areas, such as California, have state-mandated strength requirements for resisting seismic activity. In this example, less expensive materials that do not meet the seismic requirements could be used to construct a suspended ceiling structure, which would then be sufficiently reinforced according to the present invention to meet the seismic requirements. Other examples of regulatory requirements include national standards promulgated by the American Society for Testing Materials (ASTM), such as ASTM C 635, ASTM C 636, ASTM E 580, ASTM E 1264, which are incorporated by reference herein.  
         [0020]     In the first example embodiment of  FIGS. 2 and 3 , the foam material  26  is a polyurethane foam and is sprayed onto the base ceiling structure  25  in a liquid or fluid state. Once the polyurethane foam material solidifies to form a rigid polyurethane foam insulation layer, an additional material, such as a protective topcoat of fire-resistant, unsaturated polyester liquid polymer may be sprayed or otherwise applied over the foam material  26  as the outer coating  28 . Other suitable sprayable foams and other coatings may be applied to the base ceiling structure  25 , depending upon the desired performance characteristics and the particular application. As used herein, “sprayable” refers to a material that can be sprayed, pumped or otherwise applied to a substrate by being dispersed in a mass or jet of droplets or droplet-like particles. Examples of sprayable materials include, for example, cellular or solid thermoset plastics and thermoplastics, other polymers, cementitious materials, fibrous materials, plaster materials, mastics, other composite materials, cellulose, commercially available sound absorbing material and insulating materials, paints, and the like. Such sprayable materials can be applied as a base coating, in place of the foam material  26 , or as the outer coating  28 .  
         [0021]     Polyurethane foam is particularly suitable for spraying onto a ceiling structure according to the present invention, since it is capable of being sprayed as a foam. Once set, polyurethane foam produces a layer or membrane having a relatively high strength to weight ratio and a relatively high insulation value. However, other materials, such as intumescent paints or coatings, having suitable properties may be used according to the present invention in place of, or in addition to, polyurethane foam.  
         [0022]     Further, the foam material  26  can vary in formulation to produce a variety of achievements. For example, the density of the foam material  26  can be varied to adjust a reaction time of the material. The term “reaction time” as used herein refers to the average amount of time it takes for a sprayed material to form a cellular foam once it is sprayed or otherwise applied to the base ceiling structure  25 . By adjusting the amount of certain chemical additives in a polyurethane material, for example, the density of the resulting foam material  26  can be adjusted within a range, typically from 0.5 lb/ft 3  to 3 lb/ft 3  having a reaction time typically between one second and one minute, more or less. The density and reaction time of a particular material affects certain physical properties of the resulting foam material, including weight and strength.  
         [0023]     Additionally, the contact pressure of the foam material  26  as it is sprayed onto the base ceiling structure  25  may be varied as necessary to produce a sufficiently strong and lightweight layer or membrane of foam material that solidifies or sets quickly enough. For example, the contact pressure of the foam material must be properly set to prevent the weight of the material to cause it to deform too greatly or even fall off of the base ceiling structure  25  before it can set. Contact pressure can be adjusted, as is known in the art, by varying such factors as the formula of the material, the particular equipment used to spray the material, and pressure and other settings of the spraying equipment.  
         [0024]     The seamless nature of the spray-applied layers of the present invention, such as the foam material  26  and/or outer coating  28 , provides a monolithic, aesthetically pleasing and protective membrane that protects the underlying base ceiling structure  25  from moisture, chemicals, heat, fire and/or other environmental conditions detrimental to their long term performance and use in many applications. Moreover, the spray-applied materials can add substantial strength and rigidity to the base ceiling structure  25  enabling thinner, less strong and less costly grids, panels and non self-supporting materials to be used.  
         [0025]     In the following example embodiments of the present invention shown in  FIGS. 4 and 5 , to the extent that the structures illustrated therein correspond to the structures shown in  FIGS. 1-3 , the same reference characters will be used.  
         [0026]     According to a second example embodiment of the present invention,  FIG. 4  shows a grid structure  10  having a layer of non-self-supporting material  32  attached to the underside of the grid structure  10 . The second example embodiment differs from the first example embodiment in that the self-supporting panels  20  of the first example embodiment have been eliminated. As with the first example embodiment, a foam material  26  and/or an outer coating  28 , as described in detail above, is sprayed or otherwise applied onto a substrate, namely the non-self-supporting material  32 . The foam material  26  adheres to the non-self-supporting material  32  such that, after the foam material  26  sets or solidifies, the combination of the non-self-supporting material  32  and the foam material  26  forms a self-supporting composite ceiling structure  33 .  
         [0027]     The non-self-supporting material  32  can be attached to the underside of the grid structure  10  by mechanical fasteners  34 , such as nails, screws, bolts, brads, staples, rivets or other suitable fasteners. A continuous sheet of the non-self-supporting material  32  can be used to cover the underside of an entire grid structure  10 . In this embodiment, the grid  10  and the non-self-supporting material  32  forms a base ceiling structure  25 ′ onto which the foam material  26  and/or other layers is applied in accordance with the present invention. Alternatively, panel-like sections (not shown) of the non-self-supporting material  32  can be used, each section covering one or more of the openings  18  in the grid structure  10 . Seams between the sections of non-self-supporting material  32  are not apparent since, once the foam material  26  is applied, a seamless composite ceiling structure  33  is formed. Suitable non-self-supporting materials  32  include, for example, single or multiple layers of various materials such as heat shrinkable or non-heat shrinkable plastic films and sheets, open mesh and tightly knit fabrics, felt, wire mesh, and the like. Alternatively, the self-supporting materials described with reference to the first example embodiment and shown in  FIGS. 2 and 3  can also be attached to the underside of the grid structure by the mechanical fasteners  34 .  
         [0028]     A third example embodiment of the present invention, as shown in  FIG. 5 , is substantially identical to the second example embodiment shown in  FIG. 4 , except that a layer of adhesive material  36  is used instead of the mechanical fasteners  34 . In the third example embodiment, layers of the adhesive material  36 , such as glue, are provided between the non-self-supporting material  32  and the grid structure  10 . The adhesive material  36  can be provided on substantially all of the bottom surfaces of the grid structure that face the non-self-supporting material  32 . Alternatively, the adhesive material  36  can be provided as a bead or strip and/or can be provided at spaced apart intervals, so that less adhesive material  36  is required. Other configurations of adhesive material  36  can be provided as desired.  
         [0029]     Although the specific example embodiments of the present invention that are described herein are directed to materials that are sprayed onto a base ceiling structure  25 , other suitable techniques can be used to apply the foam material  26  or other materials used to coat the underside of the base ceiling structure  25 . For example, the foam material  26  or other suitable coating material could be applied on the underside of the base ceiling structure  25  by pumping or otherwise extruding the foam material  26  from a suitable nozzle or applicator so that it flows directly onto the base ceiling structure  25 . Other possible methods of applying the coating material include rolling, brushing, troweling, sponging, hand rubbing/packing, air spraying, airless spraying, and other known techniques for applying coating materials.  
         [0030]     Further, although the specific example embodiments of the present invention that are described herein are directed to applying coating materials to a suspended base ceiling structure  25  comprising a grid structure  10 , the present invention contemplates the application of coating materials to other ceiling structures, including grid-less and/or non-suspended ceiling structures. As used herein, the term “non-suspended” refers to ceiling structures that are directly and/or rigidly attached to a building structure or underlying ceiling structure of a building, such that there is little or no space or gap therebetween. Further, as also used herein, the term “grid-less” refers to ceiling structures that do not include a separate supporting grid or frame to support the material to which the inventive coating(s) is/are applied. One example of a grid-less ceiling structure, not illustrated herein, comprises a plurality of interlocking tiles being suspended from or attached directly to a building structure. Another example of a grid-less ceiling structure, not illustrated herein, is a web of non-self-supporting material that is suspended under tension from surrounding wall structures. Other suitable materials and structures may be used according to the present invention.  
         [0031]     The suspended base ceiling structure  25  described in the disclosed example embodiments are shown and described as being suspended from a building structure by a plurality of wires  12 . However, other structures for suspending a base ceiling structure  25 , in place of the plurality of wires  12 , are contemplated to be within the scope of the present invention. Examples of alternatives to the plurality of wires  12  including metallic and nonmetallic ropes and cables, flexible or rigid strips or rods, blocks, joists, trusses, and the like.  
         [0032]     It should be evident that this disclosure is by way of example and that various changes maybe made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.

Summary:
A ceiling system including a base ceiling structure for suspending from a structural member of a building, a substrate attached to the base ceiling structure, and a sprayable reinforcing material adhered to the substrate. The sprayable reinforcing material and the substrate together form a self-supporting composite material. A method of forming the coated ceiling structure includes the steps of providing a base ceiling structure having an outer surface, applying a foam material in a fluid state to the outer surface of the base ceiling structure, and solidifying the foam material to form a rigid reinforcing layer on the base ceiling structure. Alternatively, the base ceiling structure is a non-self-supporting material, and a reinforcing material is sprayed onto an outer surface of the base ceiling structure. The reinforcing material and the non-self-supporting material together form a self-supporting composite structure.