Abstract:
A method and apparatus for fabrication of foam laminates suitable for use in the construction of furniture and case goods are provided. The panel has an upper surface formed from a thermoplastic sheet of material such as PVC. A cavity formed by the interior surfaces of the sheet have suspended therein attachment or mounting hardware which is subsequently encapsulated by an in situ structural foaming step.  
     The resulting laminated panel is useful as a table top, shelving, and as a structural component in a variety of case goods and furniture.

Description:
RELATED APPLICATIONS  
       [0001]    This is a divisional application of co-pending U.S. patent application Ser. No. 09/656,281, filed Sep. 6, 2000, and which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    In the manufacture of furniture such as tables, case goods, cabinetry, desks, shelves and related items, a wide variety of materials have been used. For instance, depending upon the desired market and price, furniture materials may range from low cost plastic molded units and particle board constructions to mid range wooden laminates to higher end premium wood or metal construction. Where a real wood or a high quality simulated wood appearance is sought, such products are difficult to find in durable, versatile furniture. Furniture constructed from particle board is extremely heavy, has poor strength characteristics, and suffers from a loss of integrity when exposed to moisture. Laminated wood products are easily damaged and are difficult to repair since the surface features and texture of the laminate covering are not shared with the underlying wood or particle board substrate.  
           [0003]    Accordingly, there is a need for improvements for providing finished furniture, case good products, and laminated panels which overcome the limitations of the prior art.  
         SUMMARY OF THE INVENTION  
         [0004]    It has now been discovered that a process and resulting product provides for a furniture grade, non-wood laminate which is useful in a variety of furniture constructions. The laminate comprises a thermoformable sheet which may be molded into a desired configuration. An interior cavity formed by curved edge walls formed in the thermoformable sheet is then used as part of a mold cavity into which a polyurethane foam is injected and cured. Following curing of the foam, the exposed foam surface may be covered with a decorative paper, vinyl, or fabric covering.  
           [0005]    Typically, the resulting laminate is interconnected to other laminate pieces or, in the example of a laminated table top, legs may be attached to the laminated top. Accordingly, appropriate mounting or attachment hardware may be suspended or placed within the cavity by appropriate jig(s). The jigs hold the mounting hardware in the desired three-dimensional spacial orientation during the foaming and curing step.  
           [0006]    Upon hardening of the structural foam, the mounting hardware is permanently attached to the laminate by the adhesive properties of the cured foam. The cured structural foam also imparts a great deal of rigidity to the resulting laminate, yet adds little additional weight. The thermoplastic molded sheet and the interior molded foam of the laminate are largely impervious to water, durable, and may be further milled, sawed, drilled or worked as needed for use as a laminate in general furniture making needs.  
           [0007]    The resulting laminates may be made of a wide range of thicknesses to accommodate various construction needs. The thermoformable materials may be selected from extruded sheets of pigmented and wood grained poly-vinyl chloride (PVC). PVC materials have an accepted appearance within the market place and may be provided in a number of color combinations. Further, various types of texture may be molded into the PVC sheet when thermoformed. Combined with the nearly indestructible properties of PVC along with the ease of repair of scratches and other blemishes, PVC has useful attributes as a laminate component. When used as part of a rigid foam laminate, a PVC sheet having a thickness of 2-3 mm provides a laminate having excellent strength and rigidity properties. However, other thermoformable sheet material may be used in place of the PVC.  
           [0008]    The use of a thermoplastic material, such as PVC, has advantages in that the surface of the laminate may be easily repaired by using various grades of sandpaper or steel wool and buffing with a rubbing compound to restore the surface of the damaged laminate to an attractive state. Conventional furniture laminates of pressed wood fibers or thin surface veneers are difficult to repair in a manner which restores an original appearance.  
           [0009]    The ability to position and mold in situ the attachment hardware simplifies assembly of a finished furniture article. Further, the assembled article is stronger than similar articles made from a compressed wood or whole wood since the material integrity is not compromised by conventional hardware installation techniques. Since no cutting, drilling, or other invasive action is applied to the substrate, the material integrity is maintained. This improvement is important given that failure or weakening of attachment sites and hardware is a common occurrence in traditionally constructed furniture.  
           [0010]    Hence, in one aspect, the invention resides in a method for making a laminate panel useful in furniture making. The laminate is formed by a process in which a sheet of a high impact wood grained PVC of about 2 mm in thickness is heated in an oven to a softening temperature. The heated PVC sheet is then stamped between a male and female mold into a form which, in one sample embodiment, may resemble a tray which defines a cavity area. The tray cavity is positioned within a foam molding station with the tray cavity being accessible to one or more jigs. The jigs are used to suspend inserts, such as mounting hardware and/or structural reinforcements, into the tray cavity area. The tray area is filled with a structural foam such as polyurethane using standard foam reagents and methods. Conventional polyurethane foam reagents and methods are well known within the art as set forth in U.S. Pat. Nos. 5,972,260 and 5,941,622 which are incorporated herein by reference.  
           [0011]    The foam cures into a rigid structure which surrounds the insert portions positioned within the cavity. The tray is then inverted so that the tray top may form the upward-facing surface of a table top, counter top, or similar article. Legs or other attachments may then be made using the inserts or mounting hardware previously foamed in place.  
           [0012]    In another aspect, the invention resides in the foregoing method and resulting product wherein the inserts are suspended partially within the cavity but do not make contact with the PVC molded article. The sequential foaming and curing steps thereby provide a layered structural foam between the sheet material and the insert. In accordance with this invention it has been found that by avoiding direct contact between a load bearing insert and the thermoformable sheet, a better distribution of forces occurs. As such, bulges or indentations which may otherwise occur from the transfer of forces between an insert and the laminate surface material are avoided.  
           [0013]    In yet another aspect of this invention, it has been found that the strength of conventional inserts used in the present laminated construction may be improved by increasing the surface area and/or orientation of the insert with respect to the foam substrate. For instance, the strength between the foam and a bracket may be increased by providing an angled bend to the bracket portion within the foam. The structural integrity of the foam laminate portion may be increased by altering the three-dimensional shape of the laminate as well. Further, the incorporation of structural members having a higher rigidity than the thermoplastic laminate may be used. Such structural members may be of wood, steel, or rigid plastic. These inserts may be placed in high stress areas and may be installed in a manner similar to various attachment hardware.  
           [0014]    These and other aspects of the invention will be described in greater detail in reference to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings.  
         [0016]    [0016]FIG. 1A is a perspective view of a table formed from a laminate of the present invention;  
         [0017]    [0017]FIG. 1B is a perspective view of a folding table constructed in accordance with the present invention;  
         [0018]    [0018]FIG. 2A is a perspective view illustrating various process steps and equipment used to form a laminate of the present invention;  
         [0019]    [0019]FIG. 2B is a perspective view similar to FIG. 2A setting forth additional steps of the laminate making process;  
         [0020]    [0020]FIG. 3A is a sectional view taken along line  3 - 3  of FIG. 2B;  
         [0021]    [0021]FIG. 3B is a sectional view showing additional details of construction of a table formed from a laminate of the present invention;  
         [0022]    FIGS.  4 A- 4 C set forth additional details of construction of a pedestal table according to the present invention; and  
         [0023]    [0023]FIG. 5 is a perspective view showing two laminate panels being joined together. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions.  
         [0025]    In describing the various figures herein, the same reference numbers are used throughout to describe the same apparatus or process pathway. To avoid redundancy, detailed descriptions of much of the apparatus once described in relation to a figure is not repeated in the descriptions of subsequent figures, although such apparatus or process is labeled with the same reference numbers.  
         [0026]    Referring first to FIG. 1A there is illustrated a work surface seen in the form of a table  10 . Table  10  has an upper work surface formed from a thermoplastic sheet of material such as PVC. The sheet has an exterior surface  22  seen here as the upper table surface and an interior surface best seen in reference to FIG. 2A. A curved edge  26  curves in a downward direction relative to an upper plane of surface  22  thereby forming an inverted tray-like configuration. As seen in reference to FIG. 2A, a cavity  28  is defined by the outer edge wall  26  and the interior surface  24  of the thermoplastic sheet  20 .  
         [0027]    As best seen in reference to FIG. 2A, a jig  35  is used to suspend a plurality of inserts  40  which are suspended at least in part within the cavity  28 . Preferably, the suspended inserts  40  make no direct contact with the thermoplastic sheet  20 . A structural foam  30 , such as a polyurethane foam available from Custom Rigid Formulation, is introduced through an injection gun or similar apparatus into the mold and allowed to cure. The polyurethane foam has a density of 11 pounds per cubic foot, with component A present at a ratio of 1 to 0.89 to component B and using water as an initiator and blowing agent. However, other structural foams may be used. While not separately illustrated, the foaming step is carried out in a foam molding unit, the upper mold half configured to accommodate the inserts and jigs while providing a platen surface which is pressed flat against the lower walls of edge  26  and the decorative layer  37 . If desired, the platen surface may be used to create depressions on other molded shapes within the surface of the cured form.  
         [0028]    As seen in FIG. 2B, following the foaming step, the cured rigid structural polyurethane  30  has filled in cavity  28  and is substantially flush with the outer edge walls  26 . Each insert  40  is at least partially embedded within the foam in the desired three-dimensional configuration initially established by the jigs  35 . If desired, a backing layer  37  may be attached to the exposed foam surface during the foam molding step using the foam as an adhesive. Backing  37  may be in the form of a decorative fabric, cardboard, or other covering and may be applied to the foam post-curing by use of a separate adhesive.  
         [0029]    As seen in reference to FIG. 3A, the foam  30  fills the cavity defined between edges  26  and interior sheet surface  24 . Insert  40 , suspended a set distance from any wall surface of sheet  20 , is surrounded in part by the rigid foam. As best seen in reference to FIG. 3B, insert  40  may serve as an attachment point for additional accessories such as a table leg  42 . While insert  40  is illustrated as an L-shaped bracket defining a plurality of apertures, insert  40  may be provided by any conventional connectors or hardware. For example, hardware such as a folding bracket, height adjustment mechanisms, or tilt top mechanisms, may be used and secured as described above.  
         [0030]    Additional inserts  40  may be provided in the form of reinforcing members which may be added within the cavity in high stress areas prior to foaming. Further, in some applications, it may be useful to add wooden blocks or board members within the foamed cavity. The wooden structural member may thereafter be used as an attachment area for various connectors such as screws or nails. For instance, where the laminate of the present invention is provided in the form of a rectangular countertop, a wood member may be placed within the foamed cavity. The wood member may thereafter be used to anchor traditional screws or lag bolts which position the countertop to a lower support frame.  
         [0031]    An additional embodiment in the invention may be seen in reference to FIG. 1B which illustrates a table with four folding legs. In this embodiment, each table leg  42  is attached to conventional folding hinges seen here as insert  40 . Such folding hinges are conventionally used in the construction of folding tables and card tables. A portion of each hinge insert  40  is anchored within the rigid foam  30 . Each hinge insert  40  and attached leg  42  are adjacent a corresponding depression  32  defined within the surface of the adjacent foam  30 . Each depression  32  is preferably formed during the molding process by an appropriate shaped mold cover template associated with the molding platen and conformed to the dimensions which permits the hinge to close and thereby place the associated table leg within the confines of the depression  32 . The molded depressions may be milled following the curing of the rigid foam.  
         [0032]    The folded table as seen in FIG. 1B offers substantial advantages in terms of strength, weight, and durability compared to conventional folding tables. For instance, a standard card table lacks strength and rigidity for supporting heaving loads. Conventional folding tables of a sturdier construction typically have a particle board construction and/or a steel support frame which increases the table&#39;s weight. A table constructed according to the present invention has the combination of high strength along with light weight which facilitates commercial shipping as well as the end use of the table.  
         [0033]    An additional embodiment of a work surface is seen in reference to FIGS.  4 A- 4 C. As seen in FIG. 4C, a pedestal mounted table  110  may be provided which is secured on a pedestal mount  142 . As seen in FIG. 4A, insert  140  is in the form of a mounting bracket having a threaded bolt for the mated engagement of a pedestal leg  142 . As seen in reference to FIG. 4B, a portion of insert  140  is positioned above the outer foam surface while other portions are encapsulated by the foam. As seen in reference to FIGS. 4A and 4B, it is useful to provide insert extensions  146  which are integral with or otherwise attached to and form a part of insert  140 . Such extensions  146  increase the surface area and hence the bond strength between the foam and the inserts  140 . Further, the extensions  146  help distribute forces throughout the laminate.  
         [0034]    The extensions  146  may be integral with the insert  140  or may be separately attached to a conventional insert  140  using some form of permanent attachment. In either case, the extension  146  provides for an increased surface area and hence increased strength and force distribution between the insert and the structural foam.  
         [0035]    It has further been found advantageous to suspend load bearing inserts during the foaming process so that direct contact between the insert and the thermoplastic sheet are avoided. In this manner, forces will not transfer directly from the insert to the sheet material where, if in intimate contact, distortions or buckling of the surrounding sheet material may occur.  
         [0036]    As seen in reference to FIG. 5, the present laminates may be used to provide component parts for furniture construction. For instance, article  10 A may be the upper surface of a shelf, cabinet, or dresser. Laminate  10 B is a corresponding side panel of the above-referenced structure. A connector  46 , seen here in the form of a threaded bolt, may be used to secure laminate  10 A to laminate  10 B via the corresponding inserts  40 .  
         [0037]    Panels such as those seen in FIG. 5 may be provided and used in place of particle board and wooden board for consumer assembled furniture. Connective hardware may be provided at precise locations within the rigid foam. Traditional connectors such as locking cams, dowels, bolts, support clips, brackets, and other conventional hardware may be used to secure the assembled components. Further, the laminated panels of the present invention are resistant to moisture, are lightweight, have excellent strength and load-bearing characteristics, and may be easily disassembled and reassembled numerous times. Further, the rigid panels resist warping and flexing under heavy loads.  
         [0038]    The present laminates have the exterior surface securely bonded to the inner foam core. As such, separation of the exterior surface from the lower surface is prevented. In conventional wood or plastic laminated furniture, the upper decorative or work surface will often separate from the underlying substrate. Such flaws are unsightly, and promote rapid deterioration of the laminated structure as moisture penetrates and contributes to the delamination process. Such delamination is of particular concern in the restaurant industry where separations between a laminate and the lower core material may constitute a violation of local health codes. The present laminate structure eliminates such problems. The surface of the laminate may be easily repaired by using various grades of abrasive paper or wool, along with various rubbing compounds.  
         [0039]    Although various embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged, both in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.