Abstract:
An apparatus for forming acrylic sheet for use in manufacturing a structural member wherein the acrylic sheet forms the outer surface of the structural member and a composite material is formed within the formed sheet to provide a decorative appearance, utilizes a movable linear heating element positioned adjacent the sheet to heat a region of the sheet and a bending tool to bend the sheet along the heated portion such that a the acrylic is permanently deformed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to the field of simulated marble and stone structural members such as countertops, shower enclosures, vanity tops, and the like. In even greater particularity the present invention relates to such structural members wherein the outer layer is an acrylic layer.  
         [0002]     The inventor herein has previously devised improved structural members using the teachings of the co-owned U.S. Pat. No. 5,948,333, the teachings of which are incorporated by reference. The products produced in accordance with the teachings of the &#39;333 patent have proven the efficacy of manufacturing faux marble or stone using a light weight backing, however, there is a demand for such product which have a more resistant surface than the gel coat used in those products. Further, those products require molds for the formation of the structural shape. A material that provides a strong and resistant outer surface is acrylic and some manufacturers have attempted to use acrylic as the outer surface by heating sheets of acrylic and vacuum forming the sheets about a prefabricated mold. Such a process requires a large vacuum head as well as a mold to shape the acrylic. Accordingly, such a process is very expensive and had limited applications.  
       SUMMARY OF THE PRESENT INVENTION  
       [0003]     It is an object of the present invention to provide decorative structural members such as shower surrounds, counter tops, and the like which are easy to manufacture and handle and which provide a tough stain resistant outer surface.  
         [0004]     Yet another object of the invention is to provide such decorative members which can be custom fitted to a particular area without the use of molds.  
         [0005]     Still another object of the invention is to provide a cost effective faux marble or stone structural member without the use of costly machinery and techniques.  
         [0006]     These and other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     An apparatus for making structural members in accordance with the present invention is depicted in the accompanying drawings which form a portion of this disclosure and wherein:  
         [0008]      FIG. 1  is perspective view of a forming table with a heating element at one end thereof;  
         [0009]      FIG. 2  is a partial side sectional view along the midline of a forming table with a sheet of acrylic thereon, with the heating element and bending frame positioned about the acrylic for forming the acrylic;  
         [0010]      FIG. 3  is an end elevational view of the bending frame of the present invention; and,  
         [0011]      FIG. 4  is a sectional view of a product made in accordance with this invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]     Referring to the  FIGS. 1-4  for a clearer understanding of the invention, it may be seen that the preferred embodiment of the invention contemplates an acrylic outer shell A which serves as a mold for the structure as well as the tough and lustrous outer layer of the product. A table  10  for holding a sheet of acrylic A is provided as a work area to begin building the product. The dimensions of the product and its various corners bends and transitions are studied to devise a plan to turn the sheet of acrylic into the outer shell of the product. Suspended over table  10  is a rod  12  made from an electrically resistive material such that passing an electric current through the rod generates radiant heat. It will be appreciated that the rod my have an ceramic insulator extending lengthwise and partially annularly about it so that heat from the rod is transmitted only toward the acrylic sheet. Preferably, rod  12  is suspended beneath a gantry, not shown, that can be used to position the rod precisely over any area of table  10  and acrylic sheet A thereon. Alternatively rod  12  may be mounted on a movable frame  15  for positioning adjacent the sheet along the edges of the table. It will be understood that the frame illustrated is integrated to the table frame  11 , however, a floor mounted frame, supported on a set of wheels or a gantry as mentioned may be used to position rod  12  relative to table  10 . Rod  12  needs to be able to raise the temperature of the acrylic sheet as high as about 325° F. in a region along the length of the rod. At about 325° F. an acrylic sheet becomes pliable and will deform, for example by gravity or vacuum forming. Thus, if a region along rod  12  is heated and one side or the other of the sheet adjacent the rod is not supported the acrylic sheet will droop and bend along the heated portion such that when the sheet cools it will retain the orientation it adopted during the droop.  
         [0013]     To utilize the pliability of the heated area to form corners a movable breaking tool  12  is associated with the table. Breaking tool  13  includes a hinge and a forming plate  16 . Although the term plate is used it is to be understood that plate includes any planar extension which may have apertures therein such as a web or the like and may be of any suitable dimension in accordance with the sheet of acrylic being formed or the portion thereof being formed. Associated with movable frame  15  is a locking handle clamp  17  or similar device that will affix the acrylic sheet to the underlying table frame  11  to avoid any relative movement between the breaking tool and the acrylic sheet during the forming operation. As may be seen breaking tool  12  includes a locking plate  14  which is shown affixed to table frame  11 , however, breaking tool  12  may also be mounted to a floor mounted movable frame  15   a  such that rod  12  and breaking tool  13  are positioned as a unit relative to acrylic sheet A. Associated with forming plate  16  is a positioning handle  18  which allows the operator to control the inclination of forming plate  16  relative to the plane of the acrylic sheet mounted to the table. It is to be understood that in some embodiments locking element  14  may be affixed to the table at an orientation which is not coplanar to the acrylic sheet. For example the locking element may be affixed to a vertical edge of table  12  with a clamp  17  engaging the sheet. In such an arrangement forming plate  16  may be subjacent a portion of the sheet extending beyond the table and may be moved up or down about the horizontal hinge axis to form the acrylic sheet.  
         [0014]     In operation, the operator determines the number and location of the breaks to be present in the finished product. For example, a counter top may have a first vertical surface on the outer edge of the counter and a transition to the horizontal top of the counter with the transition constituting the first break. A second transition at the back of the counter top to a vertical back splash constitutes a second break and a third transition to a horizontal top of the backsplash constitutes the third break. Utilizing the present invention a sheet of acrylic of appropriate dimension would be positioned on the table with a portion of the sheet corresponding to the front of the countertop and first transition extending beyond the table. Locking clamp  17  would be engaged to secure the sheet relative to forming plate  16  and bar  12  would be positioned above the transition region to apply heat to the sheet. Positioning handle  18  may then be used to urge forming plate  16  and the portion of the sheet adjacent handle  18  to a position offset from the table top. When the portion of the sheet being displaced is at the selected inclination, plate  16  is stopped and heating rod  12  is removed or de-energized allowing the acrylic to cool and solidify. It will be appreciated that the radius of curvature of the transition can be controlled by the relative position of the hinge line to the application of pressure by the forming plate. Additionally mandrels formed from a non-plastic material that will not bind to the heated may be used to precisely form a radius in each transition. The forming process is repeated until each transition is formed.  
         [0015]     The acrylic sheet A as formed is then positioned to serve as the outer shell of the structural member and has an outer surface  21  and an inner surface  22 . Inner surface  22  is coated with a layer  23  which may form a decorative pattern. For example to achieve a cultured marble appearance a pattern of swirls and veins may be formed using printer&#39;s ink create the illusion of the depth achieved by lines and curves within the base color of natural marble. The swirls and veins are applied in a random manner thereby creating a more realistic marble appearance. However, unlike the method for creating cultured marble which requires one to use color for the veins and swirls throughout the matrix which defines the object, the color used to create the veins and swirls in the present method is only used in the thin second layer thereby creating the same effect with less material and ink. Of course any other pattern or visual presentation may be applied to the inner surface of acrylic sheet and will be visible on the structure. For example, pebbling, printing, or texturing may be achieved in this manner. A preferable thickness of layer  23  is between 10 and 20 mils.  
         [0016]     Thereafter, a second layer  24  is applied over the decorative layer. Layer  24  may comprise calcium carbonate or other suitable filler material with polyester resin and pigment for the purpose of providing a base color on which the decorative layer appears. A base color layer of calcium carbonate has a cure time between 15 to 20 minutes at a temperature about 77° F. and would have a thickness of about 20 to 30 mils. The acrylic sheet A, decorative layer  23  if desired, and base color layer  24  form an overall exterior for the structural member. Subsequently, a fill layer  26  is added to fill the inside of the object with polyurethane foam, which has a density substantially less than that of the matrix of conventional cultured marble. The polyurethane foam consists of equal parts of polymeric diphenylethane diisocyanate and polyol tertiaryamine. Blending of the aforementioned components produces a chemical reaction causing expansion of the components for the purpose of filling the mold thereby defining the fixture as is well known. Unlike the eight hour cure time required for cultured marble, the cure time for the chemical reaction of the polyurethane mixture is between 30 to 35 minutes. Therefore, in addition to being much lighter, the polyurethane foam used to fill the imitation marble object is also a much more time and cost efficient component.  
         [0017]     As will be understood, the acrylic surfaced fixture or structural member does not need to be demolded or substantially cleaned for use since the acrylic serves as the mold for the in inner layer. Any excess polyurethane is removed from the back of the product to obtain a smooth backing, for attaching to wall surfaces by an ordinary cutting implement and provides a much cleaner surface than the limestone matrix of cultured marble, which must be removed with a specialized tool. Accordingly, in addition to the aforementioned advantages, the polyurethane filling is also easier to remove than excess cultured marble. Moreover, the final product has a weight approximately 20 percent of the weight of cultured marble or other stone materials.  
         [0018]     It will be understood from the above that in as much as no mold are required, fixtures and structural members may be custom made for any location by measuring the space available for the unit and then appropriately forming the acrylic sheet in accordance with the measurements. Thus, the invention may be used to provide fixtures for locations that cannot be serviced by standard size or shaped fixtures or structural members.  
         [0019]     It is to be understood that the form of the invention shown is a preferred embodiment thereof and that various changes and modifications may be made therein without departing from the spirit of the invention or scope as defined in the following claims.