Abstract:
Polymeric plumbing fixtures such as sinks, lavatories and tubs are disclosed that comprise a thermoformed or molded interior shell having a top side with a relatively smooth, polymeric surface; a polymeric reinforcing layer bonded to the underside of the shell; and a thermoformed or polymeric cap nestably engageable with the underside of the reinforced shell. The cap cooperates with the shell to encapsulate the reinforcing layer and the reinforcing layer bonds the cap the shell to form a unitary structure. The polymeric cap thereby provides an attractive, finished surface on the underside of the resultant fixture. The structural configuration disclosed herein is particularly preferred for use in making kitchen sinks. A method for making the subject fixtures is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to plumbing fixtures and, more particularly, to fixtures such as sinks, lavatories and tubs having a polymeric shell with a relatively smooth polymeric top surface, a fiberglass or foamed polymeric reinforcing layer bonded to the underside of the shell, and a thermoformed polymeric cap bonded to the underside of the reinforcing layer to encapsulate the reinforcing layer between the underside of the shell and the cap. 
   2. Description of Related Art 
   Plumbing fixtures made of fiberglass and various other polymeric materials have become recognized and widely used in recent years as lower-cost alternatives to conventional fixtures made of cast iron, aluminum, porcelain, and the like. Such polymeric fixtures include showers, tubs, sinks and lavatories used in both residential and commercial construction and remodeling. Polymeric fixtures can comprise one or more polymeric materials including, for example, acrylics, polyesters, polyurethanes, other thermoplastic, cross-linked or thermosetting copolymers or terpolymers of resins and rubbers, such as acrylonitrile butadiene styrene (“ABS”), and other materials that are effective for use in particular applications or for achieving desired properties. Unlike cast metal fixtures, which generally have smooth undersides, polymeric fixtures often have rough, “chopped back” undersides. 
   Many plumbing fixtures, and particularly sinks, are made with a relatively smooth, top surface that is reinforced with a fiberglass backing comprising chopped fibers distributed throughout a polymeric resin matrix. Such backings are frequently applied using a “chop gun” that combines polymeric resin and a catalyst with chopped fiber roving that is sprayed through a nozzle onto a substrate. Catalysts such as organic peroxides are added to the polymeric materials to promote cross-linking, bonding, curing or hardening of the polymers. Such products are sometimes criticized by consumers and retailers because of the rough and unfinished look that is typically visible on the underside of sinks or other fixtures made in this manner. A new product configuration and method of manufacture are therefore needed that will enable polymeric plumbing fixtures such as sinks, lavatories and tubs to be made cost effectively and reliably, and with finished underlying surfaces that are strong but more attractive and easy to clean. 
   SUMMARY OF THE INVENTION 
   Polymeric plumbing fixtures such as sinks, lavatories and tubs are disclosed that comprise a thermoformed or molded interior shell having a top side with a relatively smooth, polymeric surface; a polymeric reinforcing layer bonded to the underside of the shell; and a thermoformed or molded polymeric cap nestably engageable with the underside of the reinforced shell, the reinforcing layer bonding the cap and the shell to form a unitary structure. The polymeric cap encapsulates the reinforcing layer and provides an attractive finish to the undersides of the fixtures. The outside of the cap is desirably provided with at least some surface texturing and a plurality of convex, radially extending ribs are around the drain opening of the cap. The ribs allow headspace for any gasses trapped between the shell and cap when the cap is nested over the shell and provide additional rigidity and strength to the finished fixture. 
   According to one preferred embodiment of the invention, a plumbing fixture is provided that comprises a thermoformed acrylic shell of desired shape and thickness, a reinforcing layer comprising chopped fibers dispersed in a crosslinked polyester matrix that is bonded to the back side of the sanitary surface layer, and a thermoformed acrylic cap layer fitted over the reinforcing layer and bonded to the reinforcing layer opposite the underside of the shell. The cap cooperates with the shell to encapsulate the reinforcing layer and form a finished surface on the underside of the resultant fixture. The structural configuration disclosed herein is particularly preferred for use in making kitchen sinks. 
   According to another preferred embodiment of the invention, a method is disclosed for making a polymeric plumbing fixture, most preferably a sink, that comprises the steps of providing a molded or thermoformed polymeric shell; inverting the shell so that its underside is facing upwardly, applying a reinforcing layer to the upwardly facing underside of the shell, providing a molded or thermoformed cap having a shape and size that generally conform to the dimensions of the shell in such manner that the shell can be nested inside the cap; coating the interior surface of the cap with a polymeric resin; inverting the cap and forcing it downward onto the inverted underside of the shell so that the reinforcing layer is encapsulated between the shell and the cap; and thereafter curing the reinforcing layer between the assembled shell and cap so that the shell and cap are bonded into a unitary fixture. 
   According to a particularly preferred embodiment of the invention, a plurality of adjustment rails are also provided during manufacture of the fixture for use in attaching the fixture to a cabinet, counter or wall structure. With the prior art “chopped back” construction, the base portions of adjustment rails were simply embedded in the fiberglass sprayed onto the underside of the deck around a sink. With the structure disclosed herein, the flange portions of the adjustment rails can now be inserted through slots in that part of the cap aligned with the deck, thereby providing additional support holding support for the rails while sandwiching the flange portion of the rails between the shell and the cap to promote better bonding. 
   Through use of the structure and method disclosed herein, manufacturing efficiencies are achievable that can speed up production as compared to conventional chopped-back fixtures. Furthermore, the use of a polymeric cap as disclosed herein can help reduce the quantity of volatile organic compounds that must be captured during production. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The apparatus of the invention is further described and explained in relation to the following figures of the drawings wherein: 
       FIG. 1  is a top plan view of an assembled sink made in accordance with a preferred embodiment of the invention; 
       FIG. 2  is a front elevation view of the sink of  FIG. 1 ; 
       FIG. 3  is a bottom plan view of the sink of  FIG. 1 ; 
       FIG. 4  is a cross-sectional elevation view taken along line  4 - 4  of  FIG. 1 ; 
       FIG. 5  is an exploded, cross-sectional side elevation view of a sink being made in accordance with the method of the invention; 
       FIG. 6  is a cross-sectional detail view taken along line  6 - 6  of  FIG. 2 ; 
       FIG. 7  is a perspective view of an adjustment rail that is attachable to a sink made according to a preferred embodiment of the invention for use in attaching the sink to a cabinet during installation; 
       FIG. 8  is a top plan view of the adjustment rail of  FIG. 7 ; 
       FIG. 9  is a front elevation view of the adjustment rail of  FIGS. 7 and 8 ; 
       FIG. 10  is a left side elevation view of the adjustment rail of  FIG. 9 ; and 
       FIG. 11  is a detail view of the rail as installed in the cap prior to assembly, taken from  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1-4 , plumbing fixture  20 , depicted in this embodiment as a kitchen sink  22 , preferably comprises three separate layers that are bonded together to form a unitary structure. The top layer is shell  24 , shown in  FIG. 1 , which includes all surfaces of sink  22  that are visible when sink  22  is viewed from above as installed. The bottom layer is cap  26 , shown in  FIG. 3 , which includes all surfaces of sink  22  that are visible when sink  22  is viewed from below as installed. Shell  24  and cap  26  are preferably formed of such size and shape that shell  24  can nest inside cap  26  with room therebetween for an intermediate layer  28 , as described below in relation to  FIGS. 4-6 . Intermediate layer  28  is disposed between shell  24  and cap  26 , and preferably comprises chopped fiberglass or a foamed polymeric material applied in such manner that it bonds shell  24  and cap  26  into a unitary fixture  20 . Such bonding can be achieved by selecting compatible polymeric materials and appropriate curing or cross-linking agents, or by the use of additional adhesive layers between intermediate layer  28  and the adjacent walls of shell  24  and cap  26 . 
   Shell  24  of sink  22  can be made with a single sink well but preferably comprises double sink wells  30 ,  32 , each having side walls  34 ,  36 , a bottom wall  38 ,  40 , and a drain hole  42 ,  44  respectively. Sink wells  30 ,  32  are preferably surrounded and separated by a substantially horizontal top deck  46  that is formed continuously with sink wells  30 ,  32  and comprises a plurality of apertures  48  adapted to receive such faucet and sprayer hardware, not shown, as may be desired. Drain holes  42 ,  44  and apertures  48  are preferably created in shell  24  by a bore saw or other similarly effective means following the bonding of shell  24  to cap  26 . Shell  24  is desirably thermoformed from an extruded or calendered sheet of a suitable polymeric material but can also be formed by other similarly effective means such as molding. A particularly preferred polymeric material for forming shell  24  is a continuous or cell-cast cross-linked acrylic that is heat cured to the desired degree of cross-linking. One such material is an acrylic polymer marketed under the trademark LUCITE® by Du Pont. LUCITE® polymers are reported to be acrylic resins consisting of a series of polymeric esters of methacrylic acid. When shell  24  is thermoformed from an acrylic sheet material, the thickness of the extruded sheet preferably ranges from about 0.080 to about 0.187 inches. In addition to the base polymer, it will be appreciated that other known polymeric additives such as coloring pigments and the like can also be incorporated into the polymeric sheet within the scope of the present invention. 
   Referring to  FIGS. 2 ,  3  and  5 , cap  26  preferably comprises sink wells  50 ,  52  that are slightly larger than sink wells  30 ,  32 , respectively. Sink wells  50 ,  52  preferably further comprise side walls  54 ,  56 , bottom walls  58 ,  60 , and a continuously formed, substantially horizontal bottom deck  62  surrounding and separating sink wells  50 ,  52 . Bottom walls  58 ,  60  each comprise a drain hole  64 ,  66  that is cooperatively sized and alignable with drain holes  42 ,  44  of sink wells  30 ,  32 . A plurality of elongate slots  68  are preferably disposed in spaced-apart relation around the periphery of bottom deck  62  to permit the insertion of adjustment rails  70  through cap  26  prior to assembly of sink  22  as discussed below. Adjustment rails  70  are visible in  FIG. 2 , where they extend downward from the underside of bottom deck  62  around its perimeter to facilitate the attachment of sink  22  to a counter, cabinet or wall structure during the installation of sink  22 . Each adjustment rail preferably comprises at least one aperture, as discussed below, that is adapted to receive a fastener when installing sink  22 . 
   Like shell  24 , cap  26  is preferably thermoformed or molded from an extruded or calendered polymeric sheet. The thickness of the sheet used to form cap  26  preferably ranges from about 0.030 to about 0.125 inches, and most preferably from about 0.030 to about 0.080 inches. According to one preferred embodiment of the invention, cap  26  is made of a continuous or cell-cast, cross-linked acrylic sheet. The use of acrylic resins in making shell  24  and cap  26  is preferred because of their appearance, durability and proccessability, and because they bond well with the fiberglass material used in making the intermediate layer  28  between shell  24  and cap  26 . Another example of a polymeric material that can be used in making cap  26  is acrylonitrile-butadiene-styrene (“ABS”), a very durable polymer. ABS can be used alone or can be coextruded, for example, with a layer comprising an acrylic DR resin (containing butyl rubber). Other similarly effective polymeric sheet materials and laminates can likewise be used within the scope of the invention. 
   Referring to  FIGS. 4-6 , shell  24  is preferably thermoformed in a desired size and configuration from extruded acrylic sheet using conventional thermoforming equipment well known to those of skill in the art. After forming, shell  24  is desirably inverted to the position shown in  FIG. 5  for application of a fiberglass intermediate layer  28  before drain holes  42 ,  44  and apertures  48  are cut out of the shell. This prevents the fiberglass from being sprayed through the drain hole and apertures during application of intermediate layer  28 , thereby spoiling the smooth sanitary surface of shell  24 . Once shell  24  is inverted to the position shown in  FIG. 5 , intermediate layer  28  is desirably applied over the upwardly facing underside of the shell. Intermediate layer  28  is preferably applied using chop gun  79 , which sprays a mixture comprising three principal components onto shell  24 . According to a particularly preferred embodiment of the invention, intermediate layer  28  comprises a polyester resin, a cross-linking catalyst, and a reinforcing fiber such as chopped fiberglass gun roving. The polyester resin is desirably in the form of a sprayable liquid that provides a continuous matrix into which the glass fiber is dispersed during spraying. The cross-linking catalyst, preferably a compatible organic peroxide, causes the polyester resin to set up or harden more quickly, and also promotes bonding of the polyester resin to the surfaces of shell  24  and cap  26 . Instead of polyester resin, other similarly effective cross-linkable or thermosetting polymeric materials can also be used in forming intermediate layer  28  within the scope of the invention. Thus, for example, epoxy, polyurethane foam, and various combinations of foamed polymer and chopped fiber can also be used within the scope of the invention so long as the resultant intermediate layer  28  provides strength and rigidity to sink  22  or other fixture  20  and can also bond to both shell  24  and cap  26 . Other similarly effective filler materials can likewise be used within the scope of the invention. Referring to  FIG. 6 , where the principal material used in making intermediate layer  28  will not itself bond to shell  24  or cap  26 , another adhesive material  25 ,  27  can be used to pre-coat the contacting surfaces of both shell  24  and cap  26 , respectively, to achieve bonding. In such case it is important that the selected adhesive material also be capable of bonding to the principal material of intermediate layer  28  in order to achieve structural integrity between shell  24  and cap  26 . The materials used in forming intermediate layer  28  will desirably not adversely react with or otherwise degrade the properties of the polymers used to form shell  24  and cap  26 . Although  FIG. 5  only depicts a portion of inverted shell  24  being covered with intermediate layer  28 , it is understood that the entire exposed surface of shell  24  is desirably covered in like manner before assembling cap  26  to shell  24 . 
   In preparation for bonding of cap  26  to intermediate layer  28  on shell  24 , cap  26  is preferably thermoformed, trimmed, bored for drain holes  64 ,  66 , and then coated lightly with a mixture of the polyester resin and cross-linking catalyst. Boring drain holes  64 ,  66  prior to assembly of cap  26  to shell  24  facilitates venting most of the air that might otherwise be trapped between the two parts. Adjustment rails  70  are also desirably pre-installed in cap  26  prior to placement over shell  24  and intermediate layer  28 . Referring to FIGS.  5  and  7 - 11 , adjustment rails  70  preferably comprise elongate, L-shaped metal brackets having a base portion  80  and a flange portion  82  that are mutually perpendicular and joined along one edge. Flange portion  82  is desirably inserted through one of elongate slots  68  and base portion  80  is preferably seated flush against deck  62 . Removable tape strips  78  or other similarly effective means can be used to hold adjustment rails  70  in this position temporarily until cap  26  is installed in place over shell  24 . Base portion  80  preferably comprises a plurality of longitudinally spaced apertures  84  that provide a better interlock with the material used to make intermediate layer  28  when shell  24  and cap  26  are assembled. Flange portion  82  preferably comprises at least one elongate slot  86  or a plurality of spaced apertures, not shown, to receive and facilitate adjustment in positioning of a fastener during installation of sink  22 . Finally, spraying the interior surfaces of sink wells  50 ,  52  with the same resin and cross-linking agent used for forming intermediate layer  28 , but without the chopped fiber, just prior to assembly will facilitate bonding of cap  26  to intermediate layer  28 . 
   Soon after application of intermediate layer  28  to the inverted bottom, side walls and deck of shell  24 , preformed and pre-coated cap  26  is desirably inverted in alignment with shell  24  and placed downwardly over coated shell  24 , pressing cap  26  into place to seat cap  26  in contacting engagement with intermediate layer  28  and promote bonding between intermediate layer  28  and the interior surfaces of cap  26 . The interval between the time that intermediate layer  28  is applied to the upwardly facing underside of shell  24  and the time that inverted cap is installed downwardly over shell  24  is preferably short so that intermediate layer  28  will not have cured, hardened or set up to the point where it will not bond with cap  26 . 
   Referring to  FIGS. 3-5 , according to a particularly preferred embodiment of the invention, bottom walls  58 ,  60  of sink wells  50 ,  52  each further comprise a plurality of thermoformed or molded ribs  72 ,  74  that are spaced apart from and extend radially outward from drain holes  64 ,  66 , respectively. Ribs  72 ,  74  protrude outwardly and create elongate concave spaces on the opposite side of bottom walls  58 ,  60  between shell  24  and cap  26  of assembled sink  22  in which any remaining entrapped air or volatile gases rising from the intermediate layer can be captured when cap  26  is applied over shell  24  during and after assembly of sink  22 . 
   Referring to  FIGS. 2 and 6 , surface texturing such as dimples  76  or other desired shapes can optionally be formed into cap  26  when sink  22  or other fixture  20  is formed, thereby enhancing the visual appearance of the outside surface of cap  26  and simultaneously providing greater bonding surface and a stronger interlock between cap  26  and intermediate layer  28 . 
   Once shell  24  and cap  26  are joined as described above, they are desirably allowed to set or cure under ambient conditions for approximately 45 minutes prior to further handling. It should be understood that the time required for curing will vary according to factors such as the materials used, the thickness of intermediate layer  28 , and the ambient temperature. Where the ambient temperature is below about 50° F., it may be desirable to expose the assembled sinks  22  or other fixtures  20  to radiant heaters, heat lamps or other similarly effective means for a few minutes to promote cross-linking or bonding. 
   It will be apparent to those of ordinary skill in the art upon reading this disclosure that other similarly effective polymeric materials can also be used in forming shell  24  and cap  26  of the invention in place of the preferred acrylics disclosed herein. In this respect, the present invention resides in the fact that a preformed polymeric shell is coated on its underside with one or more materials that will form an intermediate layer that is then covered with a preformed cap made to nest over the shell, thereby capturing and encapsulating the intermediate layer therebetween, except where apertures are provided for ancillary hardware, etc. In the finished product, both shell  24  and cap  26  are desirably bonded to the intermediate layer to form a unitary sink  22  or other fixture  20 . 
   Although not shown in the drawings, it should also be understood that shell  24  can comprise excess material around the perimeter of deck  46  that is trimmed away following the application of intermediate layer  28  and assembly to cap  26 . Such trimming is conveniently done at or about the time that drain holes  42 ,  44  and apertures  48  are cut out of shell  24  of sink  22 . 
   Other alterations and modifications of the invention will likewise become apparent to those of ordinary skill in the art upon reading the present disclosure, and it is intended that the scope of the invention disclosed herein be limited only by the broadest interpretation of the appended claims to which the inventor is legally entitled.