Abstract:
A module system including a frame, rack or mounting apparatus for mounting modules or panels, such as solar panels, is disclosed. The rack can maintain the modules in a module plane. The rack can be adjusted to alter the module plane. The frame can be constructed of purlins slid through a rotatable support beam.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a system for mounting and installing photovoltaic solar panels, and more particularly, to a mounting support system that can be rapidly constructed on a large scale. 
         [0003]    2. Description of the Related Art 
         [0004]    Solar photovoltaic (PV) cells convert light directly into electricity. By utilizing the most abundant, renewable energy available on the planet, namely the sun&#39;s rays, PV cells can provide a non-polluting source of electrical energy. As global energy consumption rises the need for clean, renewable sources of power has increased tremendously. This combined with the increased costs of conventional, fossil fuel based energy sources has led to a new era where solar PV systems can generate electricity at market competitive rates on a per kilowatt-hour basis. 
         [0005]    The rapid adoption, development and construction of PV based power plants has led to greater and greater market opportunities for companies producing PV modules. A PV module is an assembly of solar PV cells, typically in a glass laminate which is contained in a frame composed of aluminum or other metal. The PV module acts as an electrical component of a system of many such modules. Thousands of modules are strung together electrically to form commercial arrays for the generation of many thousands of kilowatts, or ‘megawatts’ of power. The greatly expanded market for PV modules combined with federal, state and local government incentive programs as well as huge investments in production capacity has created tremendous competition among PV module manufacturers. This competition has resulted in PV modules that now retail for as little as $1.00 per watt capacity at peak power output of the module. This compared to PV module prices of $4-$5 per watt just a few years ago. 
         [0006]    The rapid decrease in PV module costs in combination with the desire on the part of electrical utilities to own renewable energy assets has led to a renewed focus on so-called, ‘balance of system component’ costs. These components include DC-AC inverters, electrical connection components, and the racking systems used to hold the PV modules in place and exposed to the sun&#39;s rays. The racking systems must present the modules to the sun at a favorable degree of tilt while maintaining their structural capacity for 20 to 30 years which is the warranted energy production lifetime of the PV modules. 
         [0007]    The racking systems used for PV modules are often referred to as mounting structures. These systems are typically composed of metal, usually steel or aluminum. The systems have an element that is placed in the ground or attached to large ballast blocks typically of concrete. From this post or pier the system stands in the air supporting the PV modules at a height that is appropriate to prevent ground cover, encroaching weeds, or blown up topsoil from affecting the light exposure of the modules but not so tall as to require excess building materials. The primary structural load on these systems is created by wind forces acting on the PV modules themselves. The mounting systems present the modules to the wind in a manner not unlike a sail boat holds a sail—thus great amounts of wind load can be present in a typical PV system. 
         [0008]    As PV module mounting systems are deployed for larger and larger ground based systems the need to reduce the costs of the system through better engineering, reduction in total materials required and the innovative use of standardized commercial construction elements continues to rise. The costs and time associated with actual construction of the systems is also the subject of intense scrutiny as commercial building contractors look to be more and more competitive in the installation and commissioning of commercial and utility based PV power systems. 
         [0009]    The overall ease with which a PV mounting system can be delivered to the construction site, assembled, installed and finally commissioned is referred to in the PV power industry as ‘constructability’. There are many factors that play into good constructability, among them the reduction in labor hours required to assemble the system or the elimination of special trades and skills being required to complete the assembly. The elimination or reduction in special tools or expensive equipment needed is also a good step toward better constructability. Finally the ability to install the mounting systems in many differing climates, types of terrain, and in naturally occurring hazards such as wind, rain or snow can be the key to a suitable design for low cost, high value PV power systems. 
         [0010]    From these requirements for good constructability it can be understood that a PV mounting system which reduces the field labor hours required to build it and that eliminates costly, highly skilled trade workers would be desirable. A mounting system that can be assembled without the use of specialized tools or expensive and difficult to place equipment, such as cranes and hoists, would also be beneficial. Furthermore a system which can be sited on uneven terrain and made level through a series of minor adjustments, both to the height of the modules and the tile angle of the assembly, would allow for an assembly sequence with fewer steps. And lastly a PV mounting system that has at its core a utilization of readily available components that can take advantage of already high production quantities in industry would lead to lower costs for structural elements and thus be a substantial improvement over specialty componentry produced of expensive materials in small quantities unable to reach commercial market cost requirements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1   a  is a top view of a length of a variation of the frame at a tilt angle. 
           [0012]      FIG. 1   b  is a top view of a length of a variation of the assembled system at a tilt angle. 
           [0013]      FIG. 2  is a first side view of a portion of a variation of the frame at a tilt angle. 
           [0014]      FIG. 3  is a second side view of a portion of a variation of the frame at a tilt angle. 
           [0015]      FIG. 4  is a bottom side perspective view of a variation of the frame at a tilt angle. 
           [0016]      FIG. 5  illustrates a variation of the post and post-to-support beam connector. 
           [0017]      FIGS. 6   a  and  6   b  illustrate side views of a variation of the module system in tilted and flat configurations, respectively. 
           [0018]      FIGS. 7 through 10  are perspective, end, top and side views, respectively, of a variation of the structural beam. 
           [0019]      FIGS. 11 through 14  are perspective, end, top and side views, respectively, of a variation of the support beam. 
           [0020]      FIGS. 15   a  through  15   c  are side views of a length of a variation of the structural beam inserted through a variation of the support beam. 
           [0021]      FIGS. 16 through 19  are perspective, top, side and top views, respectively, of a variation of the post-to-support beam connector. 
           [0022]      FIGS. 20 through 24  are perspective, top, front, side, and close-up side views, respectively, of a variation of the post. 
           [0023]      FIGS. 25 through 28  are perspective, top, rear and side views, respectively, of a variation of the tilt adjustment bracket. 
           [0024]      FIGS. 29 through 32  are perspective, top, side, and end views, respectively, of a variation of the thermal expansion joint. 
           [0025]      FIG. 33  illustrates a variation of the thermal expansion joint attached to structural beams. 
           [0026]      FIGS. 34 and 35  are perspective and top views, respectively of a variation of the tilt adjustment brace. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1   a  illustrates a frame  10  or racking structure can be used to support power-generating modules  12 , such as solar or photovoltaic (PV) modules, shown in  FIG. 1   b . The modules  12  can each have one or more solar cells. A group of modules  12  can form a panel, bay, or cluster of modules. For example a solar panel can be made from about 1 to 16 modules. The modules  12  can be used to generate electrical power from light power (i.e., photons). The modules  12  attached to the frame  10  can form a module system  14 . The module system  14  can have or be connected to electronics to capture, regulate, store, and route the electrical power to a destination such as a power grid. 
         [0028]    The frame  10  can be anchored to the ground and/or a foundation  16  (shown in  FIGS. 5 ,  6   a  and  6   b ). Frames  10  can be placed adjacent to each other, for example forming an extended, contiguous structure connected by expansion joints  18 , such as thermal expansion joints, having more than one anchor, such as posts or piles, and supporting a row of modules  12 . One or more module systems  14  or rows of module systems  14  can form a group of rows or a solar array. The frame  10  can support the modules  12  away from the ground or foundation  16 , such as with about 4 to 5 feet of vertical clearance below the bottom of the beams. The frame  10  can hold the modules  12  in a substantially flat plane. The frame  10  can alternately rotate the modules  12  and rotationally fix the modules  12 . 
         [0029]    The frame  10  can have a support beam  20 . The support beam  20  can extend in a lateral direction. The frame  10  can have first, second, third and fourth structural beams  22   a ,  22   b ,  22   c , and  22   d , respectively. The structural beams  22  can be purlins. The structural beams  22  can be attached to the support beam  20 . The structural beams  22  can extend in a longitudinal direction, perpendicular to the support beam  20 . The structural beams  22  can be positioned at a non-perpendicular angle with respect to the support beam  20 . All or some of the structural beams  22  can be parallel with the other structural beams  22 . All or some of the structural beams  22  can be positioned at non-parallel angles with respect to the other structural beams  22 . 
         [0030]    The frame  10  can have one or more expansion joints  18 . For example, the frame  10  can have one or more expansion joints  18  connecting a structural beam  22  to the respective structural beam first extension  22 ′ (e.g., from the first, second, third or fourth structural beams  22   a ,  22   b ,  22   c , or  22   d , respectively, to first, second, third or fourth structural beam extensions  22   a ′,  22   b ′,  22   c ′, or  22   d ′, respectively). Each structural beam extension  22 ′ can be collinear with the respective structural beam  22 . The frame  10  can have expansion joints  18  that can connect a structural beam first extension  22   a ′ to the respective structural beam second extension  22   a ″ (not shown), and ad infinitum. The expansion joint  18  can reduce or eliminate internal strain on the modules when a first structural beam (e.g., first structural beam  22   a ) and the adjacent structural beam extension (e.g., first structural beam extension  22   a ′) contract, as shown by arrows  23   a , and expand, as shown by arrows  23   b . For example, the thermal expansion coefficient of the modules  12  can be different than the thermal expansion coefficient of the structural beams  22 . During the course of a day or across seasons, the outdoor temperature will change. The modules  12  and structural beams  22  to which the modules  12  are attached can expand and contract in response to the change in temperature (or other external forces, such as wind) at different rates. The expansion joints  18  can allow additional expansion and contraction of the structural beams  22  to reduce the force exerted on the modules  12  by the attachments with the structural beams  22  when differential thermal expansion or contraction occurs. The expansion joints  18  can connect the structural beams  22  in a rigid yet expandable and contractable fashion along the long axis of each row of structural beam and structural beam extensions such that wind loads can be carried down the structure and dissipated over a longer beam length. For example, the structural beams  22  can each be about 20 feet to about 50 feet and about 10 can be connected in a row, for example (e.g., 40 feet, or up to about 200 feet to about 500 feet total for a single connected row, for example about 60 modules long or about 120 modules total). The frame  10  can have one or more posts  24  or piles. 
         [0031]      FIG. 1   b  illustrates that the modules  12  can be attached to the top of the structural beams  22  and/or the support beam  20 . The modules  12  can be positioned orthogonally on the frame  10 . For example, the modules  12  can be in a 2 (e.g., in the lateral direction) by 6 (e.g., in the longitudinal direction) grid on the frame  10 . The post  24  and support beam  20  can be positioned between two 2-by-6 grids of modules. The modules  12  can each have electrical junction boxes  26 , for example to connect to cables that draw electrical power from the module  12 . 
         [0032]      FIG. 2  illustrates that the frame can have a pile or post  24 . The post  24  can be a beam that can be inserted into ground, foundation  16  (e.g., concrete/cement/asphalt), or a combination thereof. The post  24  can be oriented vertically or at a non-perpendicular angle to the horizontal plane  28 . The post  24  can be attached directly or indirectly to the support beam  20 , for example at a perpendicular or a non-perpendicular angle. The support beam  20  can be configured to rotate or tilt with respect to the post  24 . 
         [0033]    The tilt angle  30  can be formed between the horizontal plane  28  and the long axis of the support beam  20  (which extends in the lateral direction of the frame  10 , as shown). The tilt angle  30  can be from about 0° to about 60°, more narrowly from about 20° to about 40° for example about 30°. The post  24  can be demarcated with indentations, ink, or other marks to indicate the appropriate location at which to position the tilt adjustment brace  32  and/or the tilt adjustment bracket  34  to result in a corresponding tilt angle  30 . The plane formed across the top surface of the structural beams  22  can lie at the tilt angle  30  with respect to the horizontal plane  28 . 
         [0034]    The post  24  can attach to the support beam  20  at one or more pivot bolts, such as the upper pivot bolt  36   a  and the lower pivot bolt  36   b , and at a tilt adjustment system  38 . 
         [0035]    One of the pivot bolts  36  can form a rotatable joint, hinge or pivot between the post  24  or an extension of the post (e.g., a post-to-support beam connector  40 ), and the support beam  20 . One of the pivot bolts can be removed and the other pivot bolt can be loosened to allow the support beam  20  to rotate with respect to the post  24  or an extension thereof. 
         [0036]    The tilt adjustment system  38  can have a tilt adjustment brace  32 , one, two or more tilt adjustment brace bolts  42  (which can be nuts), a tilt adjustment bracket  34 , a tilt adjustment strut  44 , a tilt adjustment bottom bolt  46 , a tilt adjustment top bolt  48 , or combinations thereof. The tilt adjustment system  38  can be configured to control the tilt angle  30 . 
         [0037]    The tilt adjustment brace  32  can be a U-bracket. The tile adjustment brace  32  can fit around the post  24 . The tilt adjustment brace  32  can be tightened to and loosed from the tilt adjustment bracket  34  with the tilt adjustment brace bolts  42 . The tilt adjustment brace  32  and tilt adjustment bracket  34  can be fixed with a friction fit to the post  24 , for example by tightening the tilt adjustment brace bolts  42 . 
         [0038]    A lower end of the tilt adjustment strut  44  can rotatably attach to and extend from the tilt adjustment bracket  34 . The lower end of the tilt adjustment strut  44  can be hingedly attached to the tilt adjustment bracket  34  by the tilt adjustment bottom bolt  46 . An upper end of the tilt adjustment strut  44  can rotatably attach to and extend from an attachment point with the support beam  20 , for example at a drilled hole in the support beam  20 . The upper end of the tilt adjustment strut  44  can be hingedly attached to the support beam  20  by the tilt adjustment top bolt  48 . 
         [0039]    The tilt adjustment brace bolts  42  can be loosened, releasing the friction fit of the tilt adjustment brace  32  and tilt adjustment bracket  34  from the post  24 . The tilt adjustment brace  32  and tilt adjustment bracket  34  can be slid up and/or down the post  24 , for example, aligning the tilt adjustment brace  32  and tilt adjustment bracket  34  with a demarcation indicating a desired tilt angle  30  shown on the post  24 , or until a visual or measured inspection of the tilt angle  30  is achieved. The tilt adjustment brace bolts  42  can then be tightened, friction fitting and fixing the tilt adjustment brace  32  and tilt adjustment bracket  34  to the post  24 , and fixing the tilt angle  30 . 
         [0040]    The tilt adjustment strut  44  can have multiple sections that can be lockably and unlockably extendable and contractable with each other, extending and contracting the length of the tilt adjustment strut  44 . The tilt angle  30  can be adjusted by extending or contracting the length of the tilt adjustment strut  44 . 
         [0041]    The structural beams  22  can be slid through beam slots on the support beam  20 . The structural beams  22  can fix to the support beam  20  with structural cross-brackets  50  (e.g., L-brackets). The structural cross-brackets  50  can be fixed, such as by screwing (e.g., at structural cross-bracket screw holes using Tek screws or similar, self-drilling, metal fasteners), crimping, welding, with epoxy, or a combination thereof, to the structural beam  22  and the support beam  20 . 
         [0042]      FIGS. 3 and 4  illustrate that the upper end of the post  24  can attach to the lower end of a post-to-support beam connector  40 . The upper end of the post-to-support beam connector  40  can attach to the support beam  20 . The post-to-support beam connector  40  can be configured to adjust vertically, as shown by arrows, with respect to the post  24  (as shown) and/or the support beam, adjusting the height of the support beam  20  from the ground or foundation  16 . The height of the support beam  20  can be adjusted, for example from about 0 in. to about 6 in., more narrowly from about 0 in. to about 3 in., yet more narrowly from about 0 in. to about 2 in., for example, about 0 in., about 2 in., or about 3 in. 
         [0043]    The post-to-support beam connector  40  can have upper and lower beam connector or height adjustment slots  52   a  and  52   b , respectively. Upper and/or lower height adjustment or beam connector bolts  54   a  and  54   b , respectively, can be inserted through the upper and lower height adjustment slots  52   a  and  52   b , respectively, and through the post  24 . The upper and/or lower height adjustment bolts  54   a  and  54   b  can be fixed to the post  24  in the direction of the long axis of the post  24 . The upper and lower height adjustment bolts  54   a  and  54   b  can be loosened, for example to release a friction fit fixing the beam connector  40  to the post  24 . The beam connector  40  can be translated with respect to the post  24 . The upper and lower height adjustment bolts  54   a  and  54   b  can then be tightened to friction fit the beam connector  40  to the post  24 , fixing the height of the support beam  20 . 
         [0044]    The first, second, third, and fourth structural beams  22   a ,  22   b ,  22   c  and  22   d  can be attached, respectively, to first, second, third and fourth structural beam extensions  22   a ′,  22   b ′,  22   c ′ and  22   d ′ by the expansion joints  18 . Any of the extended structural beams  22  can extend along a row of module systems. 
         [0045]      FIG. 5  illustrates the post-to-support beam connector  40  can attach to the upper end of the post  24 . The long axis of the post  24  can be aligned and parallel with the long axis of the beam connector  40 . The lower end of the beam connector  40  can have a beam connector upper slot  52   a  and a beam connector lower slot  52   b , as shown in  FIGS. 16 through 19 . The upper end of the beam connector  40  can have upper and lower pivot bolt holes  56   a  and  56   b , respectively. The upper and/or lower pivot bolts  36   a  and  36   b  can be inserted through the upper and lower pivot bolt holes  56   a  and  56   b , respectively, and through the support beam  20 , as described herein. 
         [0046]      FIG. 6   a  illustrates that the when the top surface of the modules  12  can be at the same tilt angle  30  as the support beam  20 . The tilt angle  30  can be fixed at a non-zero tilt angle, for example after installation and assembly of the module system  14  and during collection of light energy. 
         [0047]      FIG. 6   b  illustrates that the tilt adjustment strut  44  can be disconnected and detached from the tilt adjustment bracket  34  (as shown) and/or from the support beam  20 . The upper pivot bolt  36   a  and/or lower pivot bolt  36   b  can be tightened to the beam connector  40  and the support beam  20 , for example, to fix the tilt angle  30 . The tilt angle  30  can be about 0°, for example, during assembly, replacement or maintenance of the module system  14 . 
         [0048]      FIGS. 7 through 10  illustrate that the structural beam  22  can be a Z purlin beam. The structural beam  22  can have a structural beam body  58 . The structural beam  22  can have a structural beam upper flange  60  perpendicular to the structural beam body  58  and an upper flange neck  62  extending at an angle (e.g., from about 30° to about 90°, for example about 45°) from the upper flange  60 . The structural beam  22  can have a lower flange  64  perpendicular to the structural beam body  58 , for example extending in a different lateral direction than the upper flange  60 , and a lower flange neck  66  extending at an angle (e.g., from about 30° to about 90°, for example about 45°) from the lower flange  64 . 
         [0049]    The structural beam  22  can have one or more connection ports  68  configured to connect to the modules  14 . For example, the structural beam  22  can have a connection port  68  at each end and two connection ports  68  near the middle of the length of the structural beam  22  configured to attach to two modules  14 . The connection ports  68  can be elongated to allow the modules  14  to be adjusted along the long axis of the structural beam  22  during attachment and to allow translation during differential thermal expansion or mechanically-induced (e.g., by wind) translation between the module  14  and the structural beam  22 . 
         [0050]    The structural beam  22  can have one, two, three or more expansion connector ports  70  at each end of the structural beam  22 , configured to attach to expansion joints  18 . 
         [0051]      FIGS. 11 through 14  illustrate that the support beam  20  can have one, two, three, four or more beam slots  72 . The beam slots  72  can be open ports extending through the entire thickness of the body of the support beam  20 . The circumference of the beam slot  72  can be a closed shape entirely within the support beam  20 . 
         [0052]    The support beam  20  can have upper and lower pivot slots  74   a  and  74   b . The upper and lower pivot bolts  36   a  and  36   b  can be inserted through the upper and lower pivot slots  74   a  and  74   b , respectively. The upper and lower pivot slots  74   a  and  74   b  can be placed at an angle to the long axis of the support beam  20  (e.g., from about 15° to about 60°, for example about 30°). 
         [0053]    The support beam  20  can have upper and lower flanges extending perpendicularly from the support beam body. 
         [0054]    The support beam  20  can have pass-through holes  76 . Cables (not shown) for carrying electrical power generated by the modules  14 , sending control and/or monitoring data, or otherwise, can be bundled if desired, and pass through the pass-through holes  76 . The pass-through holes  76  can be used as handles to grip the support beams  20  during installation or maintenance. 
         [0055]    The support beam  20  can have structural cross-bracket screw holes  78 . The structural cross-bracket screw holes  78  can directly or indirectly (e.g., via screws) fixedly attach to the structural cross-brackets  50 . The structural cross-brackets  50  can directly or indirectly fixedly attach to the structural beams  22 . One, two or more structural cross-bracket screw holes  78  can be adjacent (e.g., within about 4 in., more narrowly within about 2 in.) to each beam slot  72 . 
         [0056]      FIGS. 15   a  through  15   c  illustrate that the beam slot  72  can have a beam slot width  80  from about 0.10 in. to about 0.75 in., for example about 0.40 in. The structural beam  22  can have a structural beam thickness  82  from about 0.050 in. to about 0.175 in., for example about 0.07 in. The structural beam  22  can be slid through the beam slot  72 . The beam slot  72  can be shaped substantially identically to the structural beam cross-section. 
         [0057]      FIG. 15   a  illustrates that the structural beam  22  can have a cross-section in a Z-shape. 
         [0058]      FIG. 15   b  illustrates that the structural beam  22  can have a cross-section in a C-shape. 
         [0059]      FIG. 15   c  illustrates that the structural beam  22  can have a cross-section in an I-shape. 
         [0060]      FIGS. 16 through 19  illustrate that the post-to-support beam connector  40  can have the height adjustment or beam connector upper and lower slots  52   a  and  52   b  and the upper and lower pivot bolt holes  56   a  and  56   b , as described herein. 
         [0061]      FIGS. 20 through 24  illustrate that the post  24  can be an I-beam. The upper end of the post  24  can have a post upper hole  84   a  and a post lower hole  84   b . The height adjustment or beam connector upper and lower bolts  54   a  and  54   b  can pass through the beam connector upper and lower slots  52   a  and  52   b , respectively, and through the post upper and lower holes  84   a  and  84   b , respectively, for example to attach the beam connector  40  to the post  24 . 
         [0062]      FIGS. 25 through 28  illustrate that the tilt adjustment bracket  34  can have a tilt adjustment bracket base  86 . The tilt adjustment bracket  34  can have a tilt adjustment bracket flange  88  that can extend perpendicularly and at an upward angle from the tilt adjustment bracket base  86 . The tilt adjustment bracket base  86  can have brace slots  90  for attachment to the tilt adjustment brace bolts  42  (or for the tilt adjustment brace  32  to extend through and attach to nuts). The tilt adjustment bracket flange  88  can have a strut hole  92  for the tilt adjustment bottom bolt  46  to attach to the tilt adjustment bracket  34 . 
         [0063]      FIGS. 29 through 33  illustrate that the thermal expansion joint  18  can have one, two three or more joint holes  94  at a first end of the joint  18 , and one, two, three or more joint slots  96  at the second end of the joint  18 , opposite to the first end. Expansion joint screws or bolts  98  can be inserted through joint slots  96  and joint holes  94  and through the underlying expansion connector ports  70  on the structural beams  22 . The expansion joint scews or bolts  98  can be, for example, #12 SMS screws. The expansion joint bolts  98  can be affixed with fastening nuts placed on top of sliding washers (e.g. stainless steel or plated bushings). The expansion joint bolts  98  inserted through the joint holes  94  can longitudinally fix the expansion joint  18  to the structural beam  22 . The expansion joint bolts  98  inserted through the joint slots  96  can allow longitudinal translation along the length of the slot between the expansion joint  18  and the structural beam extension  22 ′, and thus between the structural beam  22  and the structural beam extension  22 ′. 
         [0064]    The joint slots  96  can be from about 0.5 in. long to about 3.0 in. long, for example about 1.875 in. long. 
         [0065]    The space between the structural beam  22  and the respective structural beam extension  22 ′ can be a joint gap  100 . The joint gap can vary due to external factors, such as variations in temperature, wind loads, weight loading, or combinations thereof. The joint gap can be from about 0.25 in. to about 4.0 in., for example about 1.0 in. 
         [0066]      FIGS. 34 and 35  illustrate that the tilt adjustment brace  32  can be a U-bracket. The tilt adjustment brace  32  can have threaded attachment sections  102 , for example at one or both terminal ends of the tilt adjustment brace  32 . The tilt adjustment brace bolts  42  can be nuts that can attach to the threaded attachment sections  102 . 
         [0067]    Any or all bolts described herein can be used with washers (e.g., on one or both sides of the surface being bolted to or through) and nuts (e.g., on the opposite site of the surface being bolted to or through). 
         [0068]    Any or all of the elements of the frame described herein can be made from a rigid material such as wood, metal, plastic, or combinations thereof. For example, any or all of the elements can be made from steel (e.g., stainless steel), aluminum, polyvinyl chloride (PVC), or combinations thereof. 
         [0069]    Any elements described herein as singular can be pluralized (i.e., anything described as “one” can be more than one), and plural elements can be used individually. Any species element of a genus element can have the characteristics or elements of any other species element of that genus. The term “comprising” is not meant to be limiting. The above-described configurations, elements or complete assemblies and methods and their elements for carrying out the invention, and variations of aspects of the invention can be combined and modified with each other in any combination.