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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of and claims the benefit of priority under 35 U.S.C. §120 of U.S. application Ser. No. 13/278,980, filed Oct. 21, 2011, and claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/405,975, filed Oct. 22, 2010, and the entire contents of each of the above are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The embodiments discussed herein relate to a panel mounting system. More specifically, a system of extrusions for attaching panels to a building is described. 
     2. Description of the Related Art 
     Generally, a mounting system for mounting metal skin exterior panels on structural members of a building must have four basic characteristics: (1) load carrying capability to support the panels without substantial deformation; (2) adjustability to facilitate attachment of the panels to the structural members; (3) tight sealing to minimize infiltration of wind, rain, snow, hail and the like; and (4) removability to allow removal of any panel and/or seal member without disturbing others. However, it is known that the wall panels are widely used to create a finished, durable, and aesthetic appearance on building walls of all types, as well as for panels for truck bodies, shipping containers, and the like. The panels are typically formed as laminates of outer surface sheets bonded to inner core layer or layers that have structural strength and rigidity, yet are light-weight, flexible under building and environmental stresses, and attractive for the external or interior appearance of building walls. 
     The panels are mounted to building walls by various types of mounting devices. For example, one-piece channel-shaped extrusions of metal or rigid plastic are widely used to retain the panels at joints and corners. With conventional extrusion designs, installation proceeds progressively by first installing a corner or terminal extrusion, then a panel, then an “H” (straight, two-sided) extrusion, then another panel, and so on until another corner of termination is reached. Installers must be able to size the panels, position the mounting extrusions, and form joints that are properly aligned and cleanly formed. 
     However, conventional mounting systems using extruded devices have been rather inconvenient to use and expensive. With one-piece extrusions, installation proceeds in one direction along a building wall, and caulking the gaps between the panel edges and the extrusions must be done at the time of installation. If the panels are misaligned or a panel becomes damaged, the panels must be removed in sequence in the backward direction. An individual panel cannot be removed out of sequence. The already-installed caulking must be removed or it will detract from the clean appearance of the panels. With one-piece extrusions, the panel fitting and caulking must be done correctly when first installed. Installers may be tempted to leave out the caulking to facilitate panel repair or removal, but this can lead to panel and building failure due to water seepage through the gaps and into the building walls. 
     Additionally, extrusions in conventional mounting systems typically include a flange or extension that surrounds or overlaps the outer perimeter of the panel to retain and secure the panel to the building or other body to which the panel is mounted. For example, the outer perimeter of the panels may be inserted into a slot or groove of the extrusion so that one wall of the slot or groove is visible on the exterior of the mounted panel. The walls of the slot may be somewhat flexible and are typically spaced for the thickness of the panel. Another conventional mounting system includes multiple components, where the back of the panel is placed against a first component attached to the wall and then a second component snaps into the first component at a joint between adjacent panels. However, this second component includes an extension that overlaps the outer perimeter of the panel, such that a portion of the mounting system is again visible at the exterior edges of each panel section. 
     Thus, conventional mounting systems such as those described above do not provide a clean, planar surface for the exterior faces of the mounted panels because the flange or the extension securing the edge of the panels is raised from the panel edge and may be of a noticeably different color. 
     Furthermore, due to the variety of sill flashings, head flashings, and parapet flashings, which are often provided by the various door and window manufacturers, conventional mounting systems are not always compatible with the various flashings and can be troublesome for installers arriving at the jobsite with no directions on how to handle the intersection of two different building materials. 
     SUMMARY 
     One exemplary embodiment of the present invention provides a mounting apparatus for mounting a panel to a structure. The mounting apparatus includes one or more panel extrusions that attaches to a back side of the panel such that the panel extrusions are obscured behind the panel. A connector extrusion secures the panel extrusions to the structure. 
     Another exemplary embodiment of the present invention provides a mounting system for mounting panels to a structure. The mounting system includes an air and water barrier layer, a strip of foam tape disposed on the air and water barrier layer, and a panel assembly. The panel assembly includes a panel and one or more panel extrusions attached to a back side of the panel such that the panel extrusions are obscured behind the panel. A connector extrusion secures the panel assembly to the structure. The connector extrusion is disposed on the strip of foam tape to achieve leveling and seals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. However, the accompanying drawings and their exemplary depictions do not in any way limit the scope of the inventions embraced by this specification. The scope of the inventions embraced by the specification and drawings are defined by the words of the accompanying claims. 
         FIG. 1  is an external perspective view of an installed mounting system according to an exemplary embodiment of the invention; 
         FIG. 2  is a perspective view of the back side of a panel assembly according to an exemplary embodiment of the invention; 
         FIG. 3  is a perspective view of a cross-section of the mounting system according to an exemplary embodiment of the invention; 
         FIG. 4  is a perspective view of a panel extrusion according to an exemplary embodiment of the invention; 
         FIG. 5 a    is a perspective view of a connector extrusion according to an exemplary embodiment of the invention; 
         FIG. 5 b    is a perspective view of an end-of-run connector extrusion according to exemplary embodiment of the invention; 
         FIG. 6  is a cross-sectional view of two adjacent panel assemblies mounted to a structure according to an exemplary embodiment of the invention; 
         FIG. 7  is a cross-sectional view of an end run of a panel assembly mounted to a structure according to an exemplary embodiment of the invention; 
         FIG. 8  is a cross-sectional view of a v-groove cut in a panel according to an exemplary embodiment of the invention; 
         FIG. 9  is a perspective view of a spring clip according to an exemplary embodiment of the invention; 
         FIG. 10  is a perspective view of a spring clip inserted in a panel according to an exemplary embodiment of the invention; 
         FIG. 11  is another perspective view of a spring clip inserted in a panel according to an exemplary embodiment of the invention; 
         FIG. 12  is a perspective view of an insert strip with a spring clip in each side according to an exemplary embodiment of the invention; 
         FIG. 13  is perspective view of an insert strip with multiple spring clips in each side of the insert strip according to an exemplary embodiment of the invention; and 
         FIG. 14  is a perspective end view of an insert strip showing the ends of spring clips extending into the panel extrusions according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, the present advancement will be discussed by describing a preferred embodiment with reference to the accompanying drawings. However, those skilled in the art will realize other applications and modifications within the scope of the disclosure as defined in the enclosed claims. 
       FIG. 1  is a perspective view of a finished wall  10  with panels  12  mounted using the mounting system described herein. The panels  12  are typically mounted using only three specialized extrusions (not all shown in  FIG. 1 ). The panels  12  and insert strips  14  obscure the extrusions so there is a clean look to the finished wall  10 . In one non-limiting embodiment, it is preferable to use a panel having a corrugated core laminated between two metallic sheets (see  FIG. 8 ). When properly installed, the mounting system provides at least five seals that trap and drain water to the outside of the structure. The five seals are discussed in detail below. 
       FIG. 2  depicts a completed panel assembly  20  from the back side. A panel assembly includes the panel  12  and panel extrusions  30 . The panel extrusions  30  are visible from the back side of the panel assembly  20 , however, after installation, the panel  12  obscures the panel extrusions  30 , as discussed above. Once a panel assembly  20  is installed by securing it to a structure, insert strips  14  are placed adjacent to panel edges to obscure the connector extrusions  40  (see  FIG. 3 ). 
       FIG. 3  shows a perspective view of the junction between adjacent panel assemblies  20 . For clarity and to avoid obscuring the lines on the figure, the connector extrusion  40  is shown raised in the gutter space between the panel extrusions  30 . When installed, however, the connector extrusion  40  secures the panel extrusions  30  to the structure. As mentioned above, the insert strip  14  is disposed between the two panel extrusions  30  to hide the connector extrusion  40 . 
     A perspective view of a panel extrusion  30  is shown in  FIG. 4 . The following description of the features of the panel extrusion  30  is discussed in relation to the disposition of the panel extrusion as shown in  FIGS. 6 and 7 . The panel extrusion  30  is typically formed as a single extruded piece and then cut according to the required lengths. The panel extrusion  30  includes: an intermediate portion  33 , extensions  34 , a panel-side flange  31 , a structure-side flange  32 , and an insert strip flange  36 . 
     When the panel extrusion  30  is installed, the panel-side flange  31  is secured to the panel  12  in the panel assembly  20 , and the structure-side flange  32  is secured to the wall  100  of the structure. Although one of ordinary skill in the art will recognize that other shapes and positions may be used for the flanges  31  and  32 , in the non-limiting embodiment shown in  FIGS. 4, 6, and 7 , the flanges  31  and  32  are substantially flat and extend from respective extensions  34  in opposite directions. It is preferred that the structure-side flange  32  extends in a direction outward from the panel  12  so as to engage with the connector extrusion  40  and to be secured to the wall  100 . The extensions  34  extend from opposite ends of the intermediate portion  33  in opposite directions, thereby adjoining the flanges  31  and  32  to the intermediate portion  33 . 
     The panel extrusion  30  also includes an insert strip holding portion  35 . In one non-limiting embodiment, the insert strip holding portion  35  is a slot having an opening that is approximately the same width or smaller than the thickness of an insert strip  14 . The slot of the insert strip holding portion  35  is delimited by the insert support flange  36 , the extension  34 , and the intermediate portion  33 . In particular, the insert support flange  36  extends from the extension  34  adjacent to the intermediate portion  33  in a direction such that, when the panel extrusion  30  is installed, the insert strip holding portion  35  opens outward so as to receive an insert strip  14 . 
     As seen in  FIGS. 6 and 7 , the majority of the insert support flange  36  is substantially parallel to the intermediate portion  33 , however, it is understood that one of ordinary skill in the art could alter the position and/or shape of the insert support flange  36  to another angle, so long as the opening of the slot remains substantially the same width or smaller than the thickness of the insert strip  14 . Further, an end portion  37  of the insert support flange  36  may be angled so that it is not co-planar with the majority of the insert support flange  36 . Additionally, it is preferable that the end portion  37  of the insert support flange  36  is angled in a direction away from the intermediate portion  33 , which may ease insertion of the insert strip  14  into the insert strip holding portion  35 . 
     Furthermore, the panel extrusion  30  includes a raised ridge  38  that runs the length of the intermediate portion. Depending on the width of the insert strip  14 , the ridge  38  may assist in securing the insert strip  14  to the panel extrusion  30 , as shown in  FIG. 7 . 
     The following description of the features of the connector extrusion  40  is discussed in relation to the position of the connector extrusion as shown in  FIGS. 6 and 7 . There are two versions of the connector extrusion  40 , a connector extrusion  40  having two projection legs  44 , as seen in  FIGS. 5 a    and  6 , and a connector extrusion  40  having a single projection leg  44  (an end-of-run connector), as seen in  FIGS. 5 b    and  7 . The two versions, however, are otherwise substantially the same and therefore, the reference numerals used are the same for both versions. 
     Like the panel extrusion  30 , the connector extrusion  40  is also typically formed as single extruded piece and then cut according to the required lengths. The connector extrusion  40  includes: a groove  42  and at least one projection leg  44 . 
     The groove  42  of the connector extrusion  40  is delimited by side walls  42   a  and a junction wall  42   b  that adjoins the two side walls  42   a . In a non-limiting embodiment, it is preferred that a lower portion of each of the two side walls  42   a  extends past the junction wall  42   b . In the version of the connector extrusion  40  with only one projection leg  44 , the projection leg  44  extends from one of the two side walls  42   a  away from the groove  42 . In the version of the connector extrusion  40  with a projection leg  44  extending from each side wall  42   a , the two projection legs  44  extend in opposite directions away from the groove  42 . Preferably, in a non-limiting embodiment, the projection legs  44  are substantially perpendicular to the side walls  42   a  from which the projection legs  44  extend. 
     As shown in  FIGS. 6 and 7 , panel assemblies are mounted to a structure by engaging the structure-side flange  32  of the panel extrusion  30  with the projection leg(s)  44  of the connector extrusion  40 .  FIG. 6  shows a cross-sectional view of the junction between two adjacent mounted panel assemblies  20 . As mentioned above, a panel assembly  20  includes the panel  12  that is connected to a panel extrusion  30 . Typically, the panel  12  is prepared from a planar panel that has been cut with a v-groove  50  (see  FIG. 8 ) near each side edge and folded at the cut to make a return edge  12   a  and form a box shape. The preferred method of cutting the v-groove is described below. The return edge  12   a  of the panel  12  is typically  1 ″ in width, but may be wider or narrower depending on the needs of the particular job. The panel extrusions  30  are correspondingly sized and cut and are typically attached to the inside corners of the box-shaped panel  12 . Preferably, a fastener  24 , such as a screw for example, is used to fasten the panel  12  to the panel extrusion  30 . Additionally, a sealant  22  may be disposed between the panel extrusion  30  and the inside surface of the panel  12 . The sealant  22  is preferably a silicone sealant. 
     In another non-limiting embodiment, the mounting system further includes: an air and water barrier layer  102 , and a strip of foam tape  104 . The order of the assembled components is as follows. The air and water barrier layer is typically adhered to the surface of the wall  100  and then the strip of foam tape  104  is adhered to the surface of the air and water barrier layer  102 . The connector extrusion  40  is secured to the strip of foam tape  102  with a fastener  26  and engages the structure-side flange  32 , securing the structure-side flange  32  to the strip of foam tape  102  as well. Thus, the panel assemblies  20  are secured to the wall  100 . 
     The assembly shown in  FIG. 7  is substantially the same as described with respect to  FIG. 6 , however, as mentioned previously,  FIG. 7  depicts a single panel extrusion  30  and a connector extrusion  40  with only one projection leg  44 . In addition, the panel insert  14  is secured only on one side by the insert strip holding portion  35 . 
     As mentioned above, the complete installed mounting system  10  provides five seals that trap and drain water to the outside of the structure. The five seals are described below with reference to  FIG. 6 . The first seal is formed at the contact points of the outer surface of the insert strip  14  with the intermediate portion  33  of the panel extrusion  30 . The second seal is formed at the contact points of the inner surface of the insert strip  14  with the insert support flange  36  over the gutter space, which is between the insert strip  14  and the connector extrusion  40 . The third seal is formed at the contact point between the projection leg  44  of the connector extrusion  40  and the structure side flange  32  of the panel extrusion  30 . The fourth seal is formed between the strip of foam tape  104  and the structure side flange  32 . The fifth seal is formed between the strip of foam tape  104  and the air and water barrier layer  102 . Accordingly, when all of the above components are properly installed, the mounting system has five seals to prevent water from entering the structure to which the panels are mounted. 
       FIG. 8  is a cross-sectional view of a v-groove  50  cut in a panel  12  to form the box shape. The v-groove  50  may be formed by any of a variety of ways known to those skilled in the art. In a non-limiting embodiment using a laminated panel  12 , it is preferable that the v-groove  50  pass through one of the outer metallic sheets, all the way through the corrugated core, and then begin to cut away a small amount of the inner surface of the opposing metallic sheet. It is preferred to cut the v-groove  50  in the above-described manner so that the panel  12  bends easier and straighter, and does not leave a mark on and/or penetrate the outer surface of the opposing metallic sheet, which would ruin the panel  12 . 
     A spring clip  60  is depicted in  FIG. 9 . The spring clip  60  is used to hold in place narrow insert strips, which would otherwise rest so that the insert strip does not entirely cover the intermediate space between adjacent installed panel assemblies  20 . The spring clip  60  is typically formed as a cylindrical thin rod and then bent to the desired shape, discussed herein. Preferably, the spring clip is an elastic metal, however, other elastic materials may be suitable. In one non-limiting embodiment shown in  FIGS. 9-13 , the spring clip  60  includes: an arm extension  61 , a first bend  62 , a first extension  63 , a second bend  64 , a second extension  65 , a third bend  66 , an third extension  67 , and a fourth bend  68 . 
     The arm extension  61  of the spring clip  60  extends away from the first extension  63  such that the first bend  62  is an angle between approximately 90 and 150 degrees, and preferably approximately 120 degrees. The second bend  64  connects the second extension  65  and the first extension  63 . The second bend  64  forms a loop which allows the first extension  63  and the second extension  65  to be substantially parallel, however the second extension  65  extends from the second bend  64  in a plane that is distinct from the plane along which the first extension  63  extends. The third bend  66  forms a loop which allows the second extension  65  and the third extension  67  to be substantially parallel. Additionally, the third extension  67  may extend from the second bend  64  in substantially the same plane along which the second member  63  extends. The fourth bend  68 , located at the end of the arm extension  61 , prevents the spring clip from digging into the panel once the insert strip is installed. 
       FIGS. 10 and 11  show the spring clip  60  inserted into the side of an insert strip in two different positions, such that in the position shown in  FIG. 10 , the arm extension  61  extends in a first angled direction and in the position shown in  FIG. 11 , the arm extension  61  extends in a second angled direction. Further, in  FIG. 10 , the third extension  67  remains against the exterior surface of the insert strip such that only the first and second extensions  63  and  65  are inserted into the core of the insert strip. In  FIG. 11 , however, the third extension  67  is inserted into the core of the insert strip beside the first and second extensions  63  and  65 .  FIG. 12  further illustrates the positions shown in  FIGS. 10 and 11 , as the spring clips  60   a  and  60   b  are inserted into opposite sides of the same insert strip  14 . Once inserted into the insert strip  14 , the arm extensions  61  typically extend at approximately a 45° angle with respect to the edge of the insert strip  14  where the spring clips  60   a  and  60   b  are inserted. 
     The two different positions of insertion of the spring clips  60   a  and  60   b , as shown in  FIG. 12 , cause the arm extensions  61  to hold specific positions with respect to the insert strip  14 . Specifically, the arm extension  61  of spring clip  60   a  lies in the plane of the panel surface of the insert strip  14 , at a position of 45° from the cut longitudinal edge of the insert strip  14 . The arm extension  61  of spring clip  60   b  is positioned 45° away from the plane of the panel surface of the insert strip  14 , and 45° away from the plane of the cut longitudinal edge of the insert strip  14 , which is perpendicular to the plane of the panel surface of the insert strip  14 . 
       FIG. 13  shows an insert strip in position to be inserted between panel assemblies  20 . The insert strip in  FIG. 13  includes two spring clips  60  on each side. 
     As depicted in the cross-sectional view in  FIG. 14 , the insert strip  14  is inserted into the junction area between two panel assemblies  20 . The arm extensions  61  of the spring clips  60  extend from the sides of the insert strip  14  and abut the panel extrusion  30  to place the insert strip between the two panel assemblies  20 , thereby concealing the mounted connector extrusion  40 . 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Summary:
A mounting apparatus for mounting a panel to a structure. The mounting apparatus includes a panel extrusion that attaches to a back side of the panel such that the panel extrusion is obscured behind the panel in order to show a clean surface look. A connector extrusion secures the panel extrusion to the structure for simple construction.