Abstract:
A method for mounting PV modules to a deck includes selecting PV module layout pattern so that adjacent PV module edges are spaced apart. PV mounting and support assemblies are secured to the deck according to the layout pattern using fasteners extending into the deck. The PV modules are placed on the PV mounting and support assemblies. Retaining elements are located over and secured against the upper peripheral edge surfaces of the PV modules so to secure them to the deck with the peripheral edges of the PV modules spaced apart from the deck. In some examples a PV module mounting assembly, for use on a shingled deck, comprises flashing, a base mountable on the flashing, a deck-penetrating fastener engageable with the base and securable to the deck so to secure the flashing and the base to the shingled deck, and PV module mounting hardware securable to the base.

Description:
CROSS-REFERENCE TO OTHER APPLICATIONS 
     This application claims the benefit of provisional patent application No. 60/821,869 filed 9 Aug. 2006. 
    
    
     STATE SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with State of California support under California Commission Agreement Number 500-04-022. The Energy Commission has certain rights to this invention. 
    
    
     This application is related to U.S. application patent Ser. No. 11/776,272 filed on the same day as this application, entitled PV Module Mounting and Support Assembly and Installation. 
     BACKGROUND OF THE INVENTION 
     A typical method of securing PV modules to roofs using a wood deck is with a rack system including vertical stanchions and lateral rails. The vertical stanchions are often lag bolted into joists, which are typically on 24″ (61 cm) centers. Conical flashings, similar to the type used for ventilation pipes, are used to waterproof these penetrations. In some cases flashings are not used and “L” brackets or other mounting hardware is lag bolted directly through the roofing material, with the penetration caulked with sealant. Then lateral rails are attached to the stanchions, typically several inches off the roof to allow clearance for the flashings. PV modules are then attached to the rails. Reasons for using the vertical stanchions and a lateral rails approach include: PV modules are not typically designed in convenient widths relative to joist spacing, not all PV modules have geometries amenable to direct-deck mounting, and the racks are designed to accommodate generally any PV module. In most cases framed PV modules are mounted in this manner but methods to mount unframed PV modules to racks do exist. 
     In another method for securing PV modules to roofs, the PV modules are typically lag bolted into blocking members installed between rafters in the attic; other mounting hardware can also be used. Relatively large holes must often be pre-drilled through the roofing material to accommodate the mounting hardware. Because of the size of these larger holes and the configuration of the module, it is often difficult to tell if adequate waterproofing has been achieved. If blocking is used, the process of installing blocking involves extensive work in the attic which adds significantly to installation time. 
     A further method for securing PV modules to roofs uses a hold down device that can only be used with specially constructed PV modules having complementary hold down structure, such as laterally extending hold down pins. 
     BRIEF SUMMARY OF THE INVENTION 
     An example of a method for mounting first and second PV modules to a support structure, the support structure of the type comprising a deck, is carried out as follows. First and second PV modules are selected. Each PV module has upper and lower sides and edge segments defining a peripheral edge, the peripheral edge having upper and lower peripheral edge surfaces. A layout pattern for the first and second PV modules is selected so that a chosen edge segment of the first PV module will lie adjacent to but spaced apart from a chosen edge segment of the second PV module. A plurality of PV mounting and support assemblies are positioned at selected locations according to the layout pattern. Each PV mounting and support assembly comprises a base, a fastener and PV module mounting hardware. The base comprises a lower base surface and a PV module-support surface, the PV module-support surface located a chosen distance above the lower base surface. The fastener is engageable with the base and penetrable into the deck with the lower base surface facing the deck. The PV module mounting hardware is securable to the base. The PV module mounting hardware comprises a retaining element. Each PV mounting and support assembly is secured to the selected locations using the fasteners to engage the base and to extend into the deck with the lower base surface facing the deck. The first and second PV modules are positioned in the layout pattern and the first and second PV modules are placed on the PV module-support surfaces. Retaining elements are located over the upper peripheral edge surfaces of the first and second PV modules. The retaining elements are secured against the upper peripheral edge surfaces so to secure the first and second PV modules to the deck with the peripheral edges of the PV modules spaced apart from the deck. In some examples the layout pattern is selected without a need for the layout pattern to be aligned with any deck-supporting structure. 
     An example of a PV module mounting assembly, for use on a shingled support surface of the type having a deck on which shingles are mounted, comprises flashing, a base, a deck-penetrating fastener and PV module mounting hardware. The base is mountable to the flashing. The deck-penetrating fastener is engageable with the base and securable to the deck so to secure the flashing and the base to the shingled support surface. The PV module mounting hardware is securable to the base. In some examples a sealing layer is used between the upper flashing surface and the base. 
     An example of a PV module installation comprises an inclined shingled support surface, flashing, a base, a deck-penetrating fastener, means for sealing holes and PV module mounting hardware. The inclined shingled support surface comprises a deck on which upper and lower rows of shingles are mounted. The flashing has upper and lower flashing edges. The flashing is supported on the lower row of shingles with the upper flashing edge positioned beneath the upper row of shingles. The base is supported on the flashing. The deck-penetrating fastener passes through the flashing and into holes in the deck so to secure the flashing and base plate to the shingled support surface. Means are used to seal the holes in the deck. The PV module mounting hardware is securable to the base. 
     An advantage of the invention is that it is suitable for use with a number of different conventionally designed PV modules. The PV modules do not need any special hold down or attachment structures for use with various examples of this invention. In addition, the size of the modules does not depend on the spacing of the joists or other structure supporting the deck. Installation typically does not require access to an attic area for installation of blocking (which is not needed) or inspections. Some examples of the invention significantly reduce part count over conventional mounting systems, for example by eliminating the need for mounting rails, which reduces cost and installation complexity. In addition, some examples help to significantly reduce installation time, which also reduces cost. Additionally, some examples allow very low profile securement of the PV modules to the roof or other support structure. In some examples the PV modules can be mounted nearly flush to the support structure, consistent with proper airflow for cooling, which improves the aesthetics significantly. The region beneath the PV module can typically be fluidly coupled to the region above the module. Wind tunnel tests may be carried out to determine the parameters that would result in, for example, pressure equalization between the upper and lower surfaces, thus providing for reduced loads on the PV modules under different wind conditions. Wind loading on photovoltaic modules is discussed in more detail in U.S. patent application Ser. No. 10/922,117 filed Aug. 19, 2004 and entitled PV Wind Performance Enhancing Methods and Apparatus, US Patent Publication Number US-2005-0126621-A1 published Jun. 16, 2005. In some examples the mounting structure can incorporate both a hold down (mounting) function and an electrical grounding function to substantially eliminate the need for additional grounding structure. Some examples of the PV mounting and support assemblies permit adjacent PV modules to be placed relatively close to one another. This not only improves aesthetics but also increases the energy output for a given area of the roof or other support structure. By positioning deck-penetrating fasteners beneath the PV modules, uplift forces are essentially tension only; this is in contrast with some conventional PV module hold down structures in which the deck-penetrating fasteners are laterally offset from the PV modules resulting in both tension and bending forces on the fasteners. 
     Other features, aspects and advantages of the present invention can be seen on review of the figures, the detailed description, and the claims which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded isometric view of a PV mounting and support assembly with only a single deck-penetrating fastener shown for clarity; 
         FIG. 2  is an assembled isometric view of the assembly of  FIG. 1 ; 
         FIG. 3  is an enlarged partial side view of the clip of  FIG. 1 ; 
         FIG. 4  is an enlarged cross-sectional view of the assembly of  FIG. 2  shown securing adjacent PV assemblies to the deck of a support structure; 
         FIG. 5  is a simplified overall view of two adjacent PV assemblies secured to one another using the assembly  FIGS. 1-4 ; 
         FIG. 6  is a view similar to that of  FIG. 5  shown using surface-cushioning members engaging frameless PV modules; 
         FIG. 7  shows a layout tool used to properly position the assemblies of  FIG. 2  on the support structure; 
         FIG. 8  illustrates the layout tool of  FIG. 7  positioning two of the assemblies of  FIG. 2  and one of the internal PV mounting and support assemblies of  FIGS. 12-14 ; 
         FIG. 9  is a partially exploded isometric view of flashing and the assembly of  FIGS. 1 and 2  above a shingled support structure; 
         FIG. 10  shows the structure of  FIG. 9  with the PV mounting and support assembly secured to the flashing, the flashing supported on a lower row of shingles and extending beneath an upper row shingles; 
         FIG. 11  shows the assembly of  FIGS. 1 and 2  used at the periphery of a PV array with a spacer; 
         FIGS. 12 and 13  are exploded isometric and isometric views of an internal PV mounting and support assembly; 
         FIG. 14  is a cross-sectional view showing the assembly of  FIG. 13  secured to the internal lip of the frame of a PV assembly; 
         FIG. 15  is an isometric view of an example of a PV mounting assembly; and 
         FIG. 16  is an exploded isometric view of an example of a peripheral PV mounting assembly using a standoff between the clip and the base body. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description will typically be with reference to specific structural embodiments and methods. It is to be understood that there is no intention to limit the invention to the specifically disclosed embodiments and methods but that the invention may be practiced using other features, elements, methods and embodiments. Preferred embodiments are described to illustrate the present invention, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows. Like elements in various embodiments are commonly referred to with like reference numerals. 
       FIG. 1  is an exploded isometric view of one example of a PV mounting and support assembly  2  made according to the invention. Assembly  2  includes a clip assembly  10  and a base  14 . Clip assembly  10  includes a clip  12  secured to base  14  by a bolt  16 . Base  14  includes a base body  18 , typically of extruded aluminum or some other appropriate material, and a sealant  20  secured to the lower surface  22  of base body  18 . Sealant  20  is typically in the form of a butyl tape about 3 mm thick. Base body  18  has a pair of raised portions  24  defining a gap  26  therebetween. Gap  26  extends down to a central region  28  of base body  18 , central region  28  having a threaded hole  30  formed therein for receipt of bolt  16  Central region  28  may include one or more clearance holes for additional screws  35 . Base body  18  also has a pair of flanges  32  having a number of mounting holes  34  used to secure base  14  to the deck  31  of a support structure  33 , such as a roof, with deck-penetrating fastener  35 . See  FIG. 4 . Bolt  16  passes through a central opening  36  in clip  12 , through a hole  38  formed in a spacer  40 , through gap  26 , and into a threaded hole  30 . Other types and configurations for base body  18 , such as a solid block without a gap  26  or flanges  34 , may also be used. 
       FIGS. 4 and 5  show clip assemblies  10  securing adjacent PV modules  50 , also called PV assemblies  50 , to base body  18 . Clip assemblies  10  are shown engaging adjacent PV assemblies  50  with screws  16  in the gap  58  between the PV assemblies. Assemblies  2  are commonly referred to as interior assemblies when used between adjacent PV assemblies. PV assemblies  50  include a peripheral frame  52  supporting a PV panel  54 . Frame  52  includes a lower peripheral edge surface  60  which is biased against the PV module support surface  62  of the base body  18  by virtue of clip  12  pressing against the upper peripheral edge surface  64  of frame  52 . The distance  65  between support surface  62  and a lower base surface  67  of base  14  is typically chosen by the desired distance between lower peripheral edge surface  60  and support structure  33 . Support structure  33  typically includes deck  31  covered by a weather barrier layer  66 . 
     In one embodiment deck-penetrating fasteners  35  are typically self tapping screws  35  between the size of #8 and #14 (M4-M6), and of sufficient length to fully engage with deck  31  and create penetrations or holes  68  therein. Deck  31  is typically 15/32″ (12 mm) thick oriented strand boards (OSB) or ½″ (12 mm) thick plywood or similar materials, on which shingles or other materials to create weather barrier layer  66  are mounted, formed or applied. It is preferably that holes  34  be situated on flange  32  such that the head of each screw  35  does not protrude above the top surface of flanges  32 . In one embodiment weatherproofed screws with sealing washers beneath the head are used in addition to sealant  20 . In some embodiments sealant  20  may be eliminated when other means for sealing the holes in deck  31  are used, such as a liquid sealant. In some embodiments screw  16  is a ¼″-20 (M6) stainless steel screw. A variety of clip or clamp devices, in addition to those described herein, may be used to secure PV assembly  50  to base  14 . 
     PV assembly  50  has a structural frame  52 , but may be an unframed PV laminate, or may be framed in a material that provides only protection of the edge of the PV laminate without significant structural function. This material may be nonconductive. An example of a frameless PV module  50  is shown in  FIG. 6 . PV mounting and support assembly  2  of  FIG. 6  differs from assembly  2  of  FIGS. 1-5  primarily by the use of surface-cushioning members  70  between clips  12  and upper peripheral edge surface  64  of PV assembly  50 . Such a surface-cushioning member could be supplemented by or replaced by a force-distributing plate or strip which may be secured to clip  12  or PV assembly  50  or simply located between the two. 
     Clip  12  is a generally U-shaped structure having a central portion  42 , through which central opening  36  is formed, and a pair of upstanding arms  44 . Arms  44  and central portion  42  define an access region  45 . Access region  45  is accessible from above to provide clear access to screw  16  thus facilitating the use of clip assembly  10 . Arms  44  include extensions  46  having downwardly extending teeth  48 . As shown in  FIG. 3 , clip assembly  10  is used with PV assemblies  50  of the type having electrically conductive frames  52  surrounding PV panels  54 . As can be seen in  FIGS. 2 and 3 , the head of screw  16  is located completely within access region  45  and is located below the top surface of frame  52  of PV assembly  50 . In addition, the generally T-shaped configuration of arms  44  with downwardly facing teeth  48  provide for a low profile structure. This low profile structure creates a cleaner, less cluttered appearance and also minimizes shading of PV panel  54 . 
     Frames  52  have an upper, circumferentially extending edge  56  which are engaged by teeth  48  of clip  12 . Frame  52  is typically anodized aluminum and thus has a non-conductive outer surface. Frame  52  may also have other types of non-conductive outer surfaces, such as a painted outer surface. To ensure good electrical contact between clip  12  and frame  52 , teeth  48  act as surface-disrupting elements. The serrated teeth or other structure cuts through any nonconductive material on frame  52  thereby creating a positive electrical connection with clip  12 , and via screw  16 , to base  14 . This helps to ensure good grounding between frames  52  of adjacent PV assemblies  50  through clip  12 . Other surface-disrupting methods could also be used, such as causing clip  12  to slide against and score a portion of frame  52  or through the use of other types of surface-disrupting structures or procedures. 
     In the example of  FIGS. 1-5 , three teeth  48  are used at each extension  46  of arms  44 . The use of a number of points  44  at each extension  46  allows some adjustment in the position of clip  12  relative to frame  52 , thus facilitating installation. Teeth  48  are oriented to be generally parallel to a line connecting extensions  46  of each arm  44  and thus generally perpendicular to the adjacent frame  52 . 
     Arms  44  are preferably not perpendicular to central portion  42 . In the disclosed example, arms  44  extend inwardly over central portion  42  to define an included angle  53 , see  FIG. 3 . Included angle  53  is an acute angle and typically ranges from 80-88°, and is about 83° in the disclosed example. This helps to strengthen clip  12  because arms  44  will tend to straighten out under load. Another advantage with the angulation of arms  44  is that doing so results in more of a point contact by teeth  48  with frame  52 . This can be for two primary reasons. The first reason is that teeth  48 , for practical purposes, do not narrow down to a true point but rather to a line or edge, the length of which is as long as clip  12  is thick. Therefore, by angling arms  44 , the ends of teeth  48  first engage frame  52  to provide more of a point contact than a line contact. The second reason is based upon the fact that manufacturing constraints limit how sharp of an edge teeth  48  will exhibit. In some examples, teeth  48  will exhibit a rounded edge so that if arms  44  were perpendicular to central portion  42 , teeth  48  would provide a generally cylindrical surface against frame  52 . 
     Clip  12  also secures frame  52  to base  14  by capturing the frame between arms  44  of clip  12  and support surface  62  of raised portions  24  of base body  18 . Spacer  40 , as suggested in  FIG. 3 , helps to ensure adjacent PV assemblies  50  are located in a proper distance from one another. Spacer  40  is typically made of rubber or some other material including, for example, metal or cardboard, sized to be larger than the width of central portion  42 , illustrated in  FIG. 3 . The size of spacer  40  is chosen so that when PV assemblies  50  expand during hot weather, or otherwise, PV assemblies  50  have room to expand before contacting clip  12 . This helps to prevent damage to PV panels  54 , which could occur if PV assemblies  50  were to press directly against clip  12  during such thermal expansion. The use of spacer  40  simplifies installation and by eliminating the need to use a special tool to ensure proper spacing of PV assemblies during installation. Although the primary grounding created by clip  12  is from frame  52  of one PV assembly  50  to frame  52  of an adjacent PV assembly, clip assembly  10  can also be used to provide grounding between PV assembly frames  52  and base  14 . Although not presently preferred because it may require a specially designed frame  52 , in some examples clip  12  may be attached to or an integral portion of frame  52 . 
     Assemblies  2  are typically secured to deck  31  of support structure  33  based upon a layout pattern for PV assemblies  50 . After the layout pattern has been chosen, assemblies  2  are located at selected locations according to the layout pattern so that the assemblies are properly positioned to engage the edges of one or more PV assemblies  50 . Although this could be carried out using PV assemblies  50  as a positioning fixture, it is preferably carried out with the aid of a layout tool, such as layout tool  72  shown in  FIGS. 7 and 8 . Layout tool  72  has appropriately located openings  74  size to properly position assemblies  2 , see  FIG. 8 , at appropriate orientations and spacing. Layout tool  72  helps to accurately position assemblies  2  in two axes. In some examples layout tools may be used to locate guide holes or mounting holes for the proper location of assemblies  2 . 
       FIGS. 9 and 10  illustrate mounting PV mounting and support assembly  2  on top of a shingled support structure  76  with flashing  78  between assembly  2  and shingled support structure  76 . Flashing  78  has upper and lower edges  79 ,  80  with upper edge  79  extending beneath an upper row  81  of shingles and lower edge  80  extending past the lower edge  83  of a lower row  82  of shingles. Flashing  78  is used to waterproof penetrations  68  into deck  31 . The use of flashing  78  in this manner is advantageous because it provides a smooth and consistent surface for the typically elastomeric sealing material of sealant  20  to seal against. Because flashing  78  covers a relatively large area, 1 square foot (929 cm 2 ) in one example, and is fastened tightly to the support structure  33 , it discourages water infiltration to the area of penetrations  68 , especially by wind-driven rain, and facilitates the shedding of water downwardly. Flashing  78  may be used in conjunction with liquid-applied roofing sealants to further protect penetrations  68  from any water infiltration. Flashing  78  may not be needed when the water shedding layer of support structure  33  is of a type, such as a metal roof, that waterproofing the deck screw penetrations can be made without the use of flashing. For example, with metal roofs sealant  20  may provide sufficient waterproofing. With an asphalt or composition shingle roof, base body  18  may be mounted directly to the shingled weather barrier layer  66  with penetrations  68  sealed using an appropriate sealing composition, alone or in combination with sealant  20 , between the base plate and the shingle surface. In one example flashing  78  is galvanized or Galvalume coated steel. Flashing  78  may be any suitable sheet metal material or fabricated from plastic, composite or elastomeric materials. Flashings  78  may be pre-attached to base  14  rather than field-installed. In some examples shims, not shown, may be used to correct for undulations in support structure  33  so that the PV assemblies  50  remain generally coplanar. 
     Clip assembly  10  of  FIGS. 1 and 2  can be used at the periphery by using, for example, a spacer  100  located between the otherwise unused extensions  46  of clip  12 , see  FIG. 11 , and the base  14 . Spacer  100  is used to ensure that the force exerted by clip  12  is straight down on PV assembly  50  and to keep clip  12  properly engaged with the PV assembly. Spacer  100  has a periphery  102  configured to accommodate frames  52  having different heights. Other types of variable-height of spacers, including threaded, telescoping spacers and spacers consisting of stacks of individual spacer elements, can also be used. 
       FIGS. 12-14  illustrate an internal photovoltaic mounting and support assembly  104  including an internal clip assembly  106  designed as a modification of clip assembly  10  of  FIGS. 1 and 2 . Clip assembly  106  includes a clip  108  and pieces of electrically insulating adhesive-backed tape  110 ,  112 . Tape  110  is secured to raised portions  24  of base body  18  to cover support surface  62 . Tape  112  is adhered to clip  108  as shown in  FIGS. 12 and 13  to lie above gap  26 . A gap  113  is formed between clip  108  and support surface  62 . Screw  16  is tightened onto base body  18  and then PV assembly  50  is secured to clip assembly  106  by sliding an internal lip  116  of frame  52  into gap  113  between clip  108  and base body  18  and between insulating tape  110 ,  112 . This is possible because of the open region  118  defined by PV panel  54  and peripheral frame  52 . Tape  110 ,  112  helps to ensure the snug engagement of lip  116  between clip  108  and base body  18  and also helps to reduce marring of the surface of lip  116 . The size of gap  113 , the thickness of internal lip  116 , and the thickness and physical characteristics of tape  110 ,  112  are chosen to permit the internal lip to slide into and out of gap  113  while snugly engaging the internal lip. 
     In this example internal PV mounting and support assembly  104  acts to secure PV assembly  50  in place but does not necessarily provide a grounding function. In other examples internal clip assembly  106  could be configured to provide a grounding function as well as a mounting function by, for example, causing a spike to pierce the surface of lip  116  when the lip is inserted between clip  108  and base body  18 . Although tape  110 ,  112  is in this example electrically insulating, it need not be. 
     Internal PV mounting and support assembly  104  may be used in conjunction with PV mounting and support assembly  2  to secure one edge of PV assembly  50  to support structure  33  in less time than if all edges were secured to the support structure using assemblies  2 . The positioning of two assemblies  2  and one assembly  104  is shown in  FIG. 8 . 
       FIG. 15  illustrates a PV mounting assembly  120  typically used with the flashing  78  of  FIGS. 9 and 10 . Assembly  120  includes a base body  122  that does not have a PV module support surface  62  as do the above-described examples. Rather, separate structure is used to raise PV assemblies  50  above support structure  33  if it is desired to do so. An appropriate sealing mechanism, such as sealant  20 , is used with or as a part of assembly  120 .  FIG. 16  illustrates a peripheral PV mounting assembly  124  similar to that of  FIG. 15  but including a peripheral mounting clip  126  having arms  44  extending to one side only. In addition, assembly  120  of  FIG. 16  uses a standoff  128  between clip  126  and base body  122  to provide stability for assembly  121  when clip  126  is secured against a peripheral edge of a PV assembly  50 . 
     The size of PV modules  50  that can be supported using PV support and mounting assemblies  2 ,  104  and PV mounting assemblies  120 ,  124  is dependent on the expected wind speed and exposure conditions as well as the construction of the underlying support structure. The disclosed examples can typically be used with PV modules  50  having a plan area of up to, for example, about 18 sq ft (1.67 m 2 ) for roofs and other support structures  33  constructed using conventional techniques. PV modules having larger plan areas may be accommodated but in some cases may require an adjustment of conventional construction practices and strengthening of the various mounting components. 
     Other contemplated implementations of this invention include the use screws made from other materials, or fasteners other than screws to secure base  14  to support structure  33 . Countersunk fasteners can be used to avoid interference between frame  52  and the fasteners. Instead of a screw  16  engaging threaded hole  30 , a different type of fastening device, such as a threaded stud, friction based connection, bayonet or twist-lock connection, push-on connector, ratchet fastener, or other similar device may be used. Instead of a butyl tape type of sealant  20 , other materials for sealant  20  can be used; examples include an adhered rubber foot, a mechanically fastened rubber foot, foam tape, spray foam, butyl tape, cork, liquid adhesive or sealant, and a gasket. Base body  18  may be made by a variety of methods, including casting, molding, or machining and may be made from any suitable metal, plastic, composite, wood, or elastomeric material. In some examples base  14  may be integrated directly into the PV module  50  so that the bases and modules ship to site and are installed as a unit. In some examples base  14  may be integrated such that PV module frame  52  itself acts as the base and is secured directly to the roof deck. PV modules with bases integrated with the module frame may be constructed such that the frame design promotes airflow beneath the module even with the module fastened directly to the roof. 
     During installation mounting screw  16  may be torqued such that the threaded member and the clip are pre-loaded above the maximum code wind load plus an appropriate safety factor. This ensures a secure mechanical and electrical connection in all field conditions and excludes moisture from the ground bond area at teeth  48  by creating a high pressure connection zone around each point. 
     The use of threaded connections has been emphasized. However, other types of connections, such as a ratchet-type of connections and connections using spring fingers, may also be used. 
     The above descriptions may have used terms such as above, below, top, bottom, over, under, et cetera. These terms are used to aid understanding of the invention are not used in a limiting sense. 
     While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims. Any and all patents, patent applications and printed publications referred to above are incorporated by reference.