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  Tabletop for outdoor use reinforced with foam material and metal frameRelated Patent Categories: Horizontally Supported Planar Surfaces, MiscellaneousThe Patent Description & Claims data below is from USPTO Patent Application 20070227416. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation-in-part of U.S. application Ser. No. 10/968,502, filed Oct. 19, 2004, the entire contents of which is incorporated herein by reference. FIELD OF INVENTION [0002] The present invention relates generally to a tabletop, and more particularly to a tabletop for outdoor use that is reinforced with foam material and a metal frame. BACKGROUND OF THE INVENTION [0003] Tabletops are generally made of wood. However, wood tabletops are often subject to deterioration due to acidic, basic, air or water conditions over time. Therefore, tabletops, especially those for outdoor uses, are now made of other materials such as plastics, metals, or composite materials. [0004] Since plastic materials are light weight and can more readily withstand harsh environmental conditions, the majority of tabletops for outdoor use are currently made of plastic materials. However, tabletops made of bulky plastic materials are too heavy in weight, especially for portable tables. Consequently, tabletops with hollow supporting frames or with plastic or foam material supporting frames have been developed. The tables that include foam material supporting frames instead of a pure plastic framework greatly reduce the weight of a table top. Such table tops, by themselves, generally do not provide enough support strength for forming larger, heavier tables. Examples of larger tables might include rectangular or oval-shaped tables which may have diameters of 40 inches, 72 inches, or more. Tables of such large sizes are becoming more and more popular. Tables of such large sizes have been known to warp when the temperature is extremely high, or in tense sunlight, as the center of the tables may sink or become arched. The shape of the tables also contributes to this problem. Longer tables more easily warp in the center. [0005] The type of binder used for outdoor table tops may also be a factor in warping. Polyester resin is a frequently used binder due to its being relatively inexpensive. The drawback of polyester resin is its thermal expansion and contraction properties. The resin tends to expand significantly when the temperature goes up and contract when the temperature drops which causes it to change volume. If the frame does not provide sufficient supporting force to resist bending, the whole table will warp. If the deformation and temperature cycling is frequent, the table may even crack. Thus, there is a need for low cost tabletops with sufficient support strength to resist warping, and sufficiently light weight to be portable. [0006] U.S. Pat. No. 6,694,897 discloses a folding table that includes a shell filled with urethane foam that supports the table top. The table appears to be for indoor use and does not include a heavy stone top. There is no disclosure of a metal frame within the core which is surrounded by the foam material. [0007] U.S. Pat. No. 6,915,749 discloses a table top that includes a metal base, which includes a metal plate and a metal frame. The frame includes square metal tubes having dimensions of 10 mm. The metal plate has a thickness of 0.5-0.8 mm. This table is rather heavy, as it includes a metal frame and a metal plate. Also, the adhesion of such a table to binder, which is often unsaturated poly resin, is not very good. The adhesion between petroleum-based materials and metal is not as strong as adhesion between materials of the same base. There are several problems with the disclosed bonding. First, if there is some entrapped air between the support base frame and the binder layer, the air weakens the bonding and when the resin expands or contracts with temperature variation, the expansion or contraction force is uneven causing the base plate and binder to separate. Metal generally expands and contracts to a significantly lower extent than resin or plastic based materials. Second, the metal tubes are also susceptible to corrosion due to moisture in the environment, as well as to water and moisture used in polishing or finishing the table's stone surface. Corrosion or rusting of the frame causes it to crack and separate due to temperature changes. When the tabletop is ground, polished, and water-flushed, the water could penetrate deep through the resin layer and down to the metal base plate. Then enclosed metal may corrode and separate further from the resin layer later. When cut stone or similar material is used on the tabletops, and when resin is combined with the stone material, there may also be fine slits at stone-resin bonding face where the moisture and water may penetrate. SUMMARY OF THE INVENTION [0008] The invention relates to a tabletop for use on an outdoor table that includes a substantially flat sheet of fiberglass reinforced plastic and a supporting frame. The supporting frame includes a layer of fiberglass reinforced plastic including substantially U-shaped cross-members extending laterally with respect to the flat sheet. The layer of fiberglass reinforced plastic underlies the flat sheet and forms an enclosed space between the sheet and the U-shaped cross-members. The supporting frame also includes a metal frame within the enclosed space and a foam material substantially filling the enclosed space and surrounding the metal frame. For the purposes of this invention, U-shape merely means any shape open at one end, capable of receiving a metal frame, and capable of being enclosed by the sheet and filled with foam material. [0009] The invention further relates to a tabletop for use on an outdoor table that includes a substantially flat sheet of fiberglass reinforced plastic, a fiberglass reinforced plastic supporting frame including substantially U-shaped cross-members extending laterally within the supporting frame, a metal frame, and a foam material. The supporting frame underlies the flat sheet and forms an enclosed space between the sheet and the U-shaped cross-members of the supporting frame. The metal frame is within the enclosed space and is surrounded by foam material which substantially fills the enclosed space. [0010] The tabletop may further include a coloring layer that resembles stone and may be formed of one or more of stone, marble, clay, slate, granite, tile, ceramic, or porcelain. The coloring layer is attached to the plate by an adhesive layer that may be formed of a resin of one or more of an unsaturated polyester resin, a vinyl ester resin, or an epoxy resin. An optional mesh may be included within the adhesive material. The flat sheet and the supporting frame may be formed of fiberglass reinforced plastic, the foam may be formed of expandable polystyrene, expandable polyurethane, etc., and the metal frame may be formed of one or more of aluminum, iron, or steel. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The invention will be better understood in relation to the attached drawings illustrating preferred embodiments, wherein: [0012] FIG. 1 is a perspective view of a tabletop of the present invention; [0013] FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1; [0014] FIG. 3 is a cross-sectional view of an alternate embodiment according to the invention; and [0015] FIG. 4 is a perspective view of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0016] The present invention provides a tabletop for outdoor use that is light weight and yet maintains support strength. The tabletop has sufficient strength to resist deformation or warping. Further, the tabletop is resistant to common outdoor environmental conditions, such as acidic, basic, air, and wet conditions. [0017] Referring to FIG. 1, a perspective view of a tabletop 1 of the present invention is illustrated. As shown, the tabletop 1 comprises a sheet of plastic 10 and a plastic supporting frame 20. The plastic supporting frame 20 is covered by and attached to the sheet of plastic 10. The sheet of plastic 10 and the plastic supporting frame 20 may both be formed of fiberglass reinforced plastic (FRP) or similar material, the mat and resin layers of which may incidentally merge into a single multi-layered FRP structure. FRP has the additional advantages of being corrosion resistant and low weight. [0018] The plastic supporting frame 20 preferably comprises cross-members 21 and a circular rim 22. The circular rim 22 surrounds the cross-members 21 and defines the shape of the tabletop 1. The cross-members 21 extend from points on the circular rim 22 in a chord to a corresponding point across from the starting point. Further, additional cross-members 21 may extend perpendicularly to the first set of cross-members 21 to form right angles within the circular rim 22. While the arrangement of cross-members 21 is shown in FIG. 1 as being at right angles with respect to each other, the arrangement is not so limited. The cross-members 21 may be arranged in any manner, so long as they provide sufficient support for the FRP sheet 10. Rim 22 may be of any shape desired for the perimeter of tabletop 1, described here as circular for convenience. Spaces between cross members 21 and rim 22 may be open, as shown in FIG. 1, filled as shown in FIG. 4 and discussed below, or may comprise some other desired structure. Although any number of cross-members 21 may be used within the scope of the present invention, typically at least three cross-members 21 in each direction are used, with two cross-members 21 crossing the diameter of the circular rim 22 and intersecting in approximately the center of the tabletop. This configuration permits the various components of the table to be fit together securely to prevent discontinuities therein. In this way, the table is better able to maintain its rigidity, as well as keep moisture from penetrating the interior parts of the table, such as the metal frame 60 discussed below. Continue reading... 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