Abstract:
An array of photovoltaic panels is supported in rows and columns spaced from one another using a foldable bi-directional span of support members. The support members include a plurality of support joists and support rails braced at an incline. Each support rail is tubular and generally rectangular, having a lower wall section with a T-slot channel for acceptance of the head of a bolt for adjustable attachment with the support joist. Also, the support rail may have a C-slot channel for retaining electrical wires. Clips are used to secure each panel to upper wall portions of underlying support rails. Each clip has a generally U-shaped gasket and is retained to a corresponding support rail through a threaded hole in a top wall of the support rail that receives a bolt or similar threaded fastener.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a solar energy collection system, and more particularly to a support system for an array of photovoltaic panels and method of assembling the same. The invention includes a bi-directional span of support members, including a profiled support rail having a longitudinal T-slot channel adapted to receive the head of a bolt for adjustable attachment to a support joist, and the support rail may also include a longitudinal C-slot channel for retaining electrical wiring. 
       BACKGROUND OF THE INVENTION 
       [0002]    A standard photovoltaic panel array includes a plurality of solar panels optimally arranged for converting light incident upon the panels to electricity. Various support systems are used for attachment to roofs, free-field ground racks or tracking units. Typically, these support systems are costly, labor intensive to install, heavy, structurally inferior and mechanically complicated. For example, a support system generally includes off-the-shelf metal framing channels having a C-shaped cross-section, such as those sold under the trademarks UNISTRUT™ or BLIME™, improvised for use as vertical and horizontal support members. The photovoltaic panels are directly secured to the support members and held in place by clips. The clips serve as hold-down devices to secure the panel against the corresponding top support member in spaced-relationship. The clips are positioned and attached about the panel edges once each panel is arranged in place. 
         [0003]    For a free-field ground rack system as shown in  FIG. 1 , support elements, such as I-beams, are spaced and securely embedded vertically in the ground. Tilt brackets are installed at the top of each I-beam, and each tilt bracket is secured to the I-beam such that a tilt bracket flange extends above the I-beam at an angle as best seen in  FIG. 2A . As shown in this case, two UNISTRUT™ joists span the tilt brackets and are secured thereto. As seen in  FIG. 2B , UNISTRUT™ rails are positioned across and fastened to the horizontal joists. To secure each rail to the corresponding horizontal joists, a bolt through a bolt hole made in the rail sidewall attaches to a threaded opening in a transverse nut-like plate slideably mounted inside the channel of the UNISTRUT™ joist, so that the nut-like plate engages and tightly secures against the upper flange of the joist&#39;s C-channel as seen in  FIG. 2A . Importantly, the width of the plate is slightly less than the width of the channel, so that the plate can be slideably adjusted in the channel, without the plate rotating therein. 
         [0004]    Once the bi-directional span is assembled, each solar panel is positioned and top and bottom clips are secured to each rail about the perimeter of each panel, to hold the panel such that the center of each panel is between two rails. 
         [0005]    Another example of a support system is shown in U.S. Pat. No. 5,762,720, issued to Hanoka et al., which describes various mounting brackets used with a UNISTRUT™ channel. Notably, the Hanoka et al. patent uses a solar cell module having an integral mounting structure, i.e. a mounting bracket bonded directly to a surface of the backskin layer of a laminated solar cell module, which is then secured to the channel bracket by bolt or slidably engaging C-shaped members. Other examples are shown in U.S. Pat. No. 6,617,507, issued to Mapes et al., U.S. Pat. No. 6,370,828, issued to Genschorek, Pat. No. 4,966,631, issued to Matlin et al., and U.S. Pat. No. 7,012,188, issued to Erling. 
         [0006]    Notably, existing support systems require meticulous on-site assembly of multiple parts, performed by expensive field labor. Assembly is often performed in unfavorable working conditions, i.e. in harsh weather and over difficult terrain, without the benefit of quality control safeguards and precision tooling. Spacing of the photovoltaic panels is important to accommodate expansion and contraction due to the change of the weather. It is important, therefore, that the panels are properly spaced to maximum use of the bi-directional area of the span. Different spacing may be required on account of different temperature swings within various geographical areas. It is difficult, however, to precisely space the panels on-site using existing support structures without advanced technical assistance. For example, with the existing design described above (with reference to  FIGS. 2A and 2B ), until the rails are tightly secured to the horizontal joist, each rail is free to slide along the horizontal joists and, therefore, will need to be properly spaced and secured once mounted on-site. Further, since the distance between the two horizontal joists is fixed on account of the drilled bolt holes through the rails, it is preferred to drill the holes on-site, so that the horizontal joists can be aligned to attach through the pre-drilled attachment holes of the tilt bracket. 
         [0007]    A need exists, therefore, for a low-cost, uncomplicated, structurally strong support system and method, so as to optimally position and easily attach the plurality of photovoltaic panels, while meeting architectural and engineering requirements. 
         [0008]    To accomplish the foregoing and related objectives, this invention provides a support system that can be assembled off-site to precise engineering specifications, then folded and shipped to the installation site. At the site location, the support system is easily attached to the roof, rack or tracking unit, then unfolded, so that panels can be properly secured without waste of space, time or materials. Special gravity clips can be used to quickly and easily secure each panel in place, whereby the panel&#39;s own weight is used to hold it to the support system. 
       SUMMARY OF THE INVENTION 
       [0009]    An array of photovoltaic solar panels is supported in rows and possibly columns spaced from one another using a bi-directional span of support members. The support members include a plurality of horizontal support joists and vertical support rails to be braced at an incline. Each support rail is tubular, having a generally rectangular cross-section with an upper wall section having a thickness, and lower wall section having a longitudinal T-slot channel for acceptance of the head of a bolt for adjustable attachment with the respective support joist. Also, the support rail preferably includes a C-slot channel for retaining electrical wires. Gravity clips are preferably used to hold the panels to the support rails. The clips are either single-panel clips with a Z-shaped cross-section, or two-panel clips with a U-shaped cross-section, and are secured to a corresponding support rail through a threaded hole in a top wall of the support rail that receives a fastener, such as a self-threading screw or bolt. 
         [0010]    In accordance with one aspect of the invention, each support rail is attached to the support joists by bolts, wherein the head of each bolt can slide in the T-slot channel of the respective rail. The shank of the bolt passes through and is secured to the respective support joist using a nut or another fastener type to form the bi-directional span. Notably, with the bolts torqued tight, the bi-directional span can be easily folded to reduce space for shipping. Before folding, the gravity clips can be installed in the proper location by drilling and tapping threads in each opening to accept a threaded fastener. 
         [0011]    Preferably, solar panels are not shipped while attached to the support system, but they are easily installed once the support system is unfolded and secured in place at its final site location. The bolts securing the support joists and support rails are checked for tightness, and the solar panels are arranged and secured along their perimeters by the gravity clip members, i.e. between saw-tooth profiled gaskets to protect the panel surfaces. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    Having generally described the nature of the invention, reference will now be made to the accompanying drawings used to illustrate and describe the preferred embodiments thereof. Further, these and other advantages will become apparent to those skilled in the art from the following detailed description of the embodiments when considered in light of these drawings in which: 
           [0013]      FIG. 1  is a perspective view of an assembled conventional field ground rack support system for securing a plurality of solar panels; 
           [0014]      FIG. 2A  is a side view of a tilt bracket mount with prior art C-shaped sectional channels secured back-to-back to form joists to which vertical rails of  FIG. 2B  are secured; 
           [0015]      FIG. 2B  is a side view of the prior art vertical rails, each with a C-shaped sectional channel; 
           [0016]      FIG. 3  is a perspective view of a support system of the instant invention showing solar panels arranged in a column and in spaced relationship thereon; 
           [0017]      FIG. 4A  is a top plan view of the bi-directional span of the assembly of the instant invention in the open position; 
           [0018]      FIG. 4B  is an end elevational view of the bi-directional span of the assembly shown in  FIG. 4A ; 
           [0019]      FIG. 5  is a top plan view illustrating the bi-directional span of the assembly in the folded position; 
           [0020]      FIG. 6  is a side elevation and partial sectional view that shows the horizontal support joists and tubular support rail with a single-panel clip; 
           [0021]      FIG. 7  is an end elevation and partial sectional view perpendicular to that shown in  FIG. 6 ; 
           [0022]      FIG. 8  is a cross-sectional perspective view of the module support rail; 
           [0023]      FIG. 9  is a cross-section of said support rail; 
           [0024]      FIG. 10  is a sectional elevation view showing a solar panel mounted between a two-panel clip and a single-panel clip; 
           [0025]      FIG. 11  is a sectional elevation view showing a panel being fitted within a gasket of the two-panel clip and arranged to be fitted into a single-panel clip gasket; and 
           [0026]      FIG. 12  is a sectional elevation view showing a panel fitted within the gasket of the two-panel clip, having rearmost retaining ribs, a fulcrum ridge and a saw-tooth profile. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    With reference to the drawings, a support system for a photovoltaic array of solar panels  12  known in the prior art includes a free ground rack structure having spaced vertical support elements  14  extending from the ground. The support system  10  of  FIG. 1  shows only two vertical support elements  14 , although multiple support elements may be used to accommodate a longer array of solar panels. Notably, the support system can also be mounted to a roof or tracking unit. Each of the support elements  14  for the free-field ground rack is preferably an I-beam securely embedded and vertically aligned in the ground, as is well known in the art. 
         [0028]    A pair of horizontal, C-shaped support joists  11 ,  13  is mounted at the upper ends of the support elements  14  by tilt bracket mounts  16 . Thus, the vertical support elements  14  are spanned by the joists  11 ,  13 . When there are additional arrays with additional support elements  14 , they can be spanned by multiple joists attached at their ends, or the joists  11 ,  13  can be longitudinally extended to span all of the support elements  14  in one, unbroken length. 
         [0029]    Vertical rails  15 , arranged perpendicular to the joists  11 ,  13 , are secured to the joists to produce a two-dimensional span, on which the panels are supported.  FIG. 2A  illustrates conventional joists  11 ,  13  secured to tilt bracket mounts  16  by back-to-back channels  17 ,  18 , with each channel having a C-shaped cross-section. Similarly, each conventional rail  15  is secured to the joists  11 ,  13  by bolts through a corresponding wall of its C-channel  19 , as best seen in  FIG. 2B . 
         [0030]    In accordance with a preferred embodiment of this invention,  FIG. 3  shows a support system  10  for a photovoltaic array of solar panels  12 , attached to the same, conventional vertical support elements  14 . The support system  10  in this case, however, includes a bi-directional span of horizontal joists  20  and vertical support rails  30 - 1  through  30 -n. Each support rail  30 -n in this design is preferably an aluminum extrusion, although, in the alternative, the rail may be made of roll-formed steel. Preferably, each support rail  30 -n has a tubular body  31  having a generally rectangular cross-section with an upper wall section  36  and lower wall section  32  defined between spaced side walls  35  as best seen in  FIGS. 8 and 9 . The upper wall section  36  has a flat top surface  37  and upper wall of varied thickness, preferably having its thickest portion  38  in the center. This thicker center portion  38  is for added strength when fastening the single-panel clips  100 ,  100 ′ and two-panel clip  120  (described below). Strength is also built into each support rail  30 -n using a thicker lower wall section  32 . The lower wall section  32  includes a longitudinal T-slot sectional channel  33  and, preferably, a longitudinal C-slot sectional channel  34 . 
         [0031]    In this embodiment, the length of each rail  30  is governed by the height of the individual solar panels  12  and the number of solar panels per column of panels. Each support rail  30 -/ through  30 -n is attached to the support joists  20  by bolts  40 , wherein the head  42  of each bolt is slidably accommodated in the corresponding T-slot channel  33  of the respective rail. The shank  43  of the bolt  40  passes through and is secured to the respective support joist  20  using a nut  45  or other type fastener to form the bi-directional span. Notably, with the nuts  45  and bolts  40  tightened securely, the bi-directional span can be folded to reduce space for shipping, as shown in  FIG. 5 . Each horizontal support joist  20  is separated from the corresponding vertical support rail  30 -n by nonconductive separation washers  24 , preferably made of nylon, in order to prevent galvanic interaction between unlike materials. The nylon washer  24  is preferably about ⅛ th  inch thick, although other materials and thicknesses may be used. 
         [0032]    Once the rails  30  are secured to the support joists  20 , the solar panels  12  are fastened to the rails using gravity clips  100 ,  100 ′,  120 . As shown in  FIGS. 3 ,  10 ,  11  and  12 , three types of clips are preferably used, i.e. end or single-panel clips  100 ,  100 ′ and an intermediate or two-panel clip  120 . The single-panel clips  100 ,  100 ′ have a generally Z-shaped profile with a base portion  110  and first wall  112 . Clip  100  has a first flange  114  and uses an unfulcrumed U-shaped gasket  130 . Clip  100 ′, on the other hand, has a first flange and gasket that substantially match that of flange  124  and gasket  131  described in detail below. 
         [0033]    The two-panel clip  120  is generally U-shaped having a first extended flange  114 , a second extended flange  124 , a first wall  112 , second wall  122  and a base portion  110 , and uses two different gaskets  130 ,  131 . Generally, both gaskets  130 ,  131  have a U-shaped cross-section with a fold  138 , upper and lower contact surfaces,  132 ,  134 , respectively, with a plurality of ribs  140 , i.e. saw-tooth profiles, and a back wall  136 . 
         [0034]    The fulcrumed U-shaped clip gasket  131  further includes resilient, rearmost retaining ribs  142 , designed to contact a top peripheral side  143  of the panel  12  to push and hold the panel downward into the clip below. Notably, there may be one retaining rib  142  extending from the upper contact surface  132  and one extending from the lower contact surface  134  (as shown in  FIGS. 10 through 12 ), or, in the alternative, there may be just one large rib extending from either the upper or lower contact surfaces. Still further, retaining rib  142  may extend from the back wall  136 , in which case the retaining rib  142  may be replaced with a spring to provide resiliency. 
         [0035]    The lower contact surface  134  of the fulcrumed gasket  131  further includes a fulcrum point  144 , i.e. an extended elongated ridge, which forces against the solar panel  12  toward the upper contact surface  132  and second clip flange  124 . 
         [0036]    In use, the bottom portion of the two-panel clip  120  holds the top peripheral edge of the lower solar panel  12  aligned with the other solar panels in the respective column of panels. As best seen in  FIGS. 10 and 11 , the bottom portion of clip  120  includes a second clip flange  124 , which is longer than the opposing first clip flange  114 , which holds the bottom of an uppermost solar panel  12  in the same column. The top or first clip flange  114  of the two-panel clip  120  is preferably the same length as that of the flange of the bottom mounted single-panel clip  100 , i.e. having the same U-shaped unfulcrumed clip gasket  130  used therewith. Preferably, the length of longer clip flange  124  is at least twice the length of the shorter first flange  114 , so that the solar panel  12  can be inserted first under flange  124 , pivoted on fulcrum point  144  and then inserted under flange  114 , whereby flanges  114 ,  124  and gravity hold the panel  12  firmly in place once set in position. 
         [0037]    The difference between single-panel clips  100  and  100 ′ is that clip  100 ′ is the first clip at the top of each support rail  30 -n; while clip  100  is the last clip, i.e. at the bottom of each support rail  30 -n. Since single-panel clip  100 ′ is the top clip of each support rail, it has a fulcrumed U-shaped gasket, identical to the fulcrumed gasket  131 , to accommodate its extended flange profile (identical to flange  124 ). This is necessary since the top single-panel clip  100 ′ forces against the top perimeter side  143  of the uppermost solar panel  12 , aligned with the other solar panels in the respective column of panels, to push the bottom edge of the panel  12  into the top portion of the two-panel clip  120  therebelow. Therefore, the profile of clip  100 ′ substantially matches that of the bottom portion of the two-panel clip  120  to fit and secure the top perimeter edge of each solar panel therein. 
         [0038]    Both of the clip gaskets  130 ,  131  include a T-shaped engagement protuberance  137  for slidable registration and attachment via a complementary, somewhat T-shaped retaining groove  117  formed between the walls  112 ,  122  and their respective flanges  114 ,  124 . Gaskets  130 ,  131  are used with each clip  100 ,  100 ′,  120  to protect the front and back edges  143  of each solar panel  12 . Each gasket  130 ,  132  is preferably extruded with the T-shaped mounting protuberance  137 . 
         [0039]    Preferably, the gaskets  130 ,  131  are made of a material which is physically and chemically stable, and preferably electrically nonconductive. Furthermore, the gaskets  130 ,  131  should be of an electrically resistant material and have good elasticity upon compression. Suitable materials, which can be employed include, but are not limited to, neoprene, butyl rubber, ethylene-propylene diene monomer (EPDM), chlorinated polyethylene (CPE) and a polytetrafluoroethylene (PTFE) material such as GORTEX® (a trademark of W.L. Gore &amp; Associates, Inc.), or TEFLON® (a trademark of E.I. DuPont de Nemours &amp; Company). 
         [0040]    This support system  10  allows for off-site assembly to precise engineering specifications, in that, once the support members are assembled, the bi-directional span can be folded, as shown with reference to  FIG. 5 , transported to the installation site, positioned and secured to the roof, rack or tracking unit via the tilt bracket  16  while still in the folded position, and unfolded to the position of  FIG. 3 . 
         [0041]    Specifically, the method of assembling this support system for an array of photovoltaic panels  12  in columns and rows, includes the steps of building the bi-directional span by attaching support members, i.e. support joists  20  and support rails  30 -n, using a plurality of attachment bolts  40  and nuts  45 . The top surface  37  of each rail  30 -n must be unobstructed for the solar panels to secure against. As previously described, each support rail  30 -n preferably has a substantial rectangular cross-section with an upper wall section  36  and lower wall section  32 . Each support system can be easily built and adjusted to various engineering specifications, in that the longitudinal 
         [0042]    T-shaped sectional channel  33  in the lower wall section  32  is adapted to adjustably receive the heads  42  of attachment bolts  40 . Bolts  40  attach each vertical support rail  30 -n, passing through one of the horizontal support joists  20 . The T-shaped slotted channel  33  permits the bolt  40  to be placed at any location along the length of the channel and through the horizontal support joist  20  as required. 
         [0043]    The perimeter, gravity clips  100 ,  100 ′,  120  can be pre-positioned and attached to the upper wall section  36  of the support rails  30  by a self-threading bolt  145  secured to thick portion  38  and whose head engages base portion  110  of the clip. The perimeter clips  100 ,  100 ′,  120  can be positioned and attached to the upper wall section  36  of the support rails  30  off-site to proper engineering specifications, so as to provide the necessary spacing for the columns and rows of the photovoltaic panels  12  of the array, without wasting space and time. 
         [0044]    Once the perimeter clips  100 ,  100 ′,  120  and rails  30 -n are attached to the support joists  20  as described above, the bi-directional span can be reduced in size by folding the support rails relative to the support joists  20 . The folded span can be easily shipped to the location for installation, then unfolded and secured to the roof, free-field ground rack or tracking unit for attachment of the photovoltaic panels  12  via the pre-positioned, attached and properly spaced perimeter clips  100 ,  100 ′,  120 . 
         [0045]    Specifically, the preferred method to assemble the bi-directional span is to align the first horizontal support joist  20  and insert a bolt  40  in spaced, pre-drilled holes  44  passing through the support joist  20  with the bolt head  42  at the top of the joist and a hex nut  45  at the bottom. The separation washer  24  is included near the bolt head. The process is repeated for the second horizontal support joist  20 . 
         [0046]    Next, a single vertical support rail  30 -/ is aligned with the head  42  of the first bolt  40  located in position along the first horizontal support joist  20 . The bolt head  42  is lifted, separated from the separation washer  24 , and slid into the T-slot channel  33  in the vertical support rail  30 . This step is then repeated for the second horizontal support joist  20 . The end of the first vertical rail  30 - 1  is then aligned with a side wall of the first horizontal joist  20 , and the hex nuts  45  are torqued snug. Using a machinist square, the horizontal support joist  20  is made perpendicular to the vertical support rails  30 - 1 . The other vertical rails  30 - 2  through  30 -n are assembled and secured in like fashion. 
         [0047]    As previously stated, bolts  40  and hex nuts  45  are used to securely fasten the horizontal support joists  20  to the corresponding vertical support rails  30 - 1  through  30 -n. Preferably, each hex nut  45  has a nylon insert. The nylon insert retains torque pressure of the fastener during shipping and prevents the support rails  30 -n from loosening from the support joists  20  when folded and unfolded. Notably, on account of the separation washers  24  and the nylon hex nuts  45 , the rails  30 -n can pivot relative to the horizontal support joists  20  without any significant loosening. Grasping the ends of both horizontal joists, the first horizontal joist  20  is pushed away relative to the second horizontal joist  20 , permitting the assembly to fold into a condensed, folded form for shipping. 
         [0048]    It is important to note for assembly and shipping purposes, that the tubular body form  31 , varied wall thickness  38 , and channels  31 ,  32  substantially reduces the weight of the module rails  30 -n, and, therefore, the overall weight of the assembled system (in comparison to the prior art). Yet, the structural strength is enhanced. After shipping the assembly to the field for installation, it is unpackaged, and the bottom-most horizontal support joist  20  is mounted and secured to the vertical support element  14  via the tilt bracket mounts  16 . Then, grasping the end of top-most horizontal support joist  20 , it is pushed to unfold and realign mutually parallel to the other support joist, and perpendicular to the vertical support rails  30 . The space between the horizontal support joists  20 , can be adjusted (if needed) by sliding the joists along the rails (via their T-slot channels), so that the spacing of the joists  20  precisely align with and attach to the tilt bracket mounts  16 . In contrast, it is not possible to easily space the joists  11 ,  13  in the conventional design shown in  FIGS. 2A and 2B  along its several conventional rails  15 , since the spacing therebetween is fixed by the drilled bolt holes made in rails  15  through the side wall of channels  19 . 
         [0049]    Once the assembly of this invention is unfolded, the top-most horizontal support joist  20  is secured to the tilt bracket mounts  16 . Then, using a machinist square or similar setup fixture, the spacing and perpendicular relationship of the vertical support rails  30  are checked relative to the side wall of the bottom horizontal support joist  20  and adjusted (if needed). The hex nuts  45  are also checked to assure that they continue to be snug after shipping and installation. And finally, with the expanded bi-directional span properly positioned and secured to the support elements  14 , each solar panel  12  is fixed in place by inserting the top of the panel into its top perimeter clips  100 ′ or  120 , then pivoted about the respective gasket fulcrums  144 , to fit the panel&#39;s bottom edge into corresponding bottom perimeter gravity clips  100 ,  120 , as best seen in  FIGS. 10 through 12 . To finish the installation, wires are tucked away in the corresponding C-shaped slotted channels  34 . 
         [0050]    While the invention has been particularly shown and described with reference to the specific preferred embodiments, it should be understood by those skilled in the art that various exchanges in form and detail may be made therein without department from the spirit and scope of the invention as defined by the appended claims.