CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims benefit of copending U.S. Provisional Patent Application Ser. No. 62/026,268 entitled “CONNECTING KEY SYSTEM FOR MODULAR BUILDING UNITS,” filed with the U.S. Patent and Trademark Office on Jul. 18, 2014 by the inventor herein, the specification of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to modular building construction, and more particularly to a connecting system for joining wall panels of a modular building unit to a corner column. 
       BACKGROUND OF THE INVENTION 
       [0003]    Modular building units typically comprise a skeletal metal (e.g. steel) frame, a solid roof and floor, and wall panels that are inserted into the frame. The frame comprises an important structural element of the overall assembly, with the corner posts of the frame playing a primary support role for the remainder of the structure. In modular building configurations, it is desirable to maintain the corner posts as a principal support member to ensure proper support of the roof structure of the building unit, even if portions of the modular building unit other than the principal structural frame are to be replaced. 
         [0004]    The wall panels of the modular building units are often attached by providing a U-shaped profile bracket along the long vertical edges (such as by connecting such U-shaped profile to the structural corner posts of the frame) to receive a wall panel having a rectangular cross section. However, such fixed U-shaped profile brackets provide a fixed dimension capable of receiving a wall panel of a single thickness. Different installations may require or desire walls of differing thicknesses, but allowing the replacement of one wall panel with another, differently configured wall panel can be difficult, requiring replacement of such U-shaped brackets and possibly other structural elements in order to accommodate such a change. 
         [0005]    Thus, there remains a need in the art for a wall panel connecting system for a modular building unit capable of receiving panels of differing configurations, and more particularly for a wall panel connecting system that maintains the full skeletal support frame structure (including the corner support posts) of the modular building unit when reconfiguring the wall panel connections, and that allows reconfiguration of the wall panel connecting system without excessive effort or expense. 
       SUMMARY OF THE INVENTION 
       [0006]    Disclosed is a connecting system for connecting wall panels to the support frame, and more particularly to the rigid corner support posts of a support frame, of a modular building unit. The connecting system includes a modular bracket assembly and is configured so that two modular connecting brackets attach to each corner vertical support column, which modular brackets are configured to receive the vertical edge of a wall panel. The brackets themselves are configured for easy replacement and/or adjustment through minimal effort, and particularly without removing, altering, or otherwise disturbing the corner vertical support column of the frame of the modular building unit. 
         [0007]    In accordance with certain aspects of an embodiment of the invention, a wall panel connecting system is provided for a modular building unit, comprising: a modular building unit corner support post fixedly attached to a frame of said modular building unit, the corner support post having a first exterior face, a second exterior face, a first interior face, and a second interior face; a plurality of wall panels; and a modular wall panel connector configured for attachment to each of the first interior face and the second interior face of the corner support post, the modular wall panel connector further comprising an exterior portion detachably connectable to each of the first interior face and the second interior face of the corner support post and positioned to abut one of the wall panels at an exterior face of the wall panel, and an interior portion detachably connectable to the exterior portion and to each of the first interior face and the second interior face of the corner support post and positioned to abut the wall panel at an interior face of the wall panel. 
         [0008]    In accordance with further aspects of an embodiment of the invention, a wall panel connecting system is provided for a modular building unit, comprising: a rigid, fixed modular building unit frame having a plurality of corner support posts, a bottom rail extending between adjacent pairs of corner support posts, a top rail extending between adjacent pairs of corner support posts, and a plurality of wall panels extending between the corner support posts, the top rails, and the bottom rails, each corner support post having a first exterior face, a second exterior face, a first interior face, and a second interior face; and a modular wall panel connector attached to each of the first interior face and the second interior face of each corner support post, the modular wall panel connector further comprising an exterior portion detachably connected to each of the first interior face and the second interior face of the corner support post and abutting one of the wall panels at an exterior face of the wall panel, and an interior portion detachably connected to each of the exterior portions and to each of the first interior face and the second interior face of the corner support post and abutting one of the wall panels at an interior face of that wall panel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying drawings in which: 
           [0010]      FIG. 1  is a perspective view of a modular building unit in accordance with certain aspects of an embodiment of the invention. 
           [0011]      FIG. 2  is a top-down, sectional view of the modular building unit of  FIG. 1 . 
           [0012]      FIG. 3  is a close-up, top-down view of an exemplary modular wall panel bracket and corner support post for use with the modular building unit of  FIG. 1 . 
           [0013]      FIG. 4  is a close-up, top-down view of joined wall panels of  FIG. 2 . 
           [0014]      FIG. 5  is a front view of an exterior portion of a modular wall panel bracket of  FIG. 2 . 
           [0015]      FIG. 6  is a top-down, cross-sectional view of the exterior portion of the modular wall panel bracket of  FIG. 5 . 
           [0016]      FIG. 7  is a front view of an interior portion of a modular wall panel bracket of  FIG. 2 . 
           [0017]      FIG. 8  is a top-down, cross-sectional view of the interior portion of the modular wall panel bracket of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The following description is of a particular embodiment of the invention, set out to enable one to practice an implementation of the invention, and is not intended to limit the preferred embodiment, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
         [0019]      FIG. 1  provides a perspective view of a modular building unit  100  in accordance with certain aspects of an embodiment of the invention. Modular building unit  100  includes a skeletal frame formed by corner support posts  112 , bottom rails  114 , and top rails  116 . This skeletal frame provides the key structural integrity for the modular building unit. Positioned between corner support posts  112 , bottom rails  114 , and top rails  116  are wall panels  118  that form the wall structures spanning each side of the modular building unit. Other standard building features, such as doors  120  and windows  122 , may be provided and integrated with individual wall panels  118 . Also visible in  FIG. 1  is the exterior portion of a wall panel bracket  210  that mounts to corner support posts  112  and prevents wall panels  118  positioned adjacent to corner posts  112  from moving outward, and that covers any gap that might exist between wall panels  118  and their adjacent corner support posts  112 , all as discussed in greater detail below. 
         [0020]      FIG. 2  is a top down, sectional view of the modular building unit  100 . As shown in  FIG. 2 , a modular wall panel bracket  200  is provided at each corner support post  112  to join wall panels  118  to the frame of the modular building unit. With continued reference to  FIG. 2  and to the close-up, top down view of the modular wall panel bracket  200  and corner support post  112  of  FIG. 3 , each modular wall panel bracket  200  has an exterior portion  210 , an interior portion  230 , and preferably an interior corner trim piece  250 . As discussed in greater detail below, exterior portion  210  establishes an exterior flange that blocks wall panel  118  from outward movement, and interior portion  230  establishes an interior flange that blocks wall panel  118  from interior movement, while corner trim piece  250  covers the points at which exterior portion  210  and interior portion  230  connect to corner support posts  112 . 
         [0021]    With continued reference to  FIG. 3 , each corner support post  112  has a first outer wall  302  and a second outer wall  304 , both of which form the exterior corner of the modular building unit  100 . First outer wall  302  and second wall  304  may, for example, be configured at right angles to one another, although other angles, rounded corners, and the like may likewise by used as might be desirable to obtain a particular aesthetic or other benefit. A first interior wall  306  extends inward (toward the interior of modular building unit  100 ) from an end of exterior wall  302 , and a second interior wall  308  extends inward from an end of exterior wall  304 , thus forming a corner support post having at least four distinct sides. Interior walls  306  and  308  each have a length less than the lengths of the respective outer walls  302  and  304  to which they are attached in order to properly allow for connection of the modular wall panel bracket  200 , as discussed in greater detail below. 
         [0022]    A first connecting flange  307  extends from an end of first interior wall  306  toward an interior of support post  112 , and a second connecting flange  309  extends from an end of second interior wall  308  toward the interior of support post  112 , such that first connecting flange  307  is positioned generally perpendicular to second connecting flange  309 . Optionally, a first support rib  310  may be positioned on an interior face of first outer wall  302 , and a second support rib  312  may be positioned on an interior face of second outer wall  304 , each such support rib forming a right angle vertical member extending through corner support post  112 . An insulation sheet  314  may also optionally be provided on an interior of support post  112 , positioned to sit within opposing support ribs  310  and  312  on the interior of support post  112 . 
         [0023]    Modular wall panel brackets  200  join to support post  112  at first connecting flange  307  and second connecting flange  309 . More particularly, and as shown in  FIG. 3 , exterior portion  210  of wall panel bracket  200  and interior portion  230  of wall panel bracket  200  are each connected to each of first connecting flange  307  and second connecting flange  309  with a removable, threaded connector  316 , such as a screw, a bolt and nut assembly, or such other removable connector as will be known to those of ordinary skill in the art. While a first end of each of exterior portion  210  of wall panel bracket  200  and interior portion  230  of wall panel bracket  200  are brought together for connection to the respective connecting flange  307  or  309  of support post  112 , the opposite end of each of exterior portion  210  of wall panel bracket  200  and interior portion  230  of wall panel bracket  200  form a gap configured to receive the end of a wall panel  400 , such that the end of the wall panel  400  extends into the open space between the ends of exterior portion  210  and interior portion  230  of wall panel bracket  200 . Compressible foam gaskets  216  may be provided on the interior face of each of exterior portion  210  and interior portion  230  of wall panel bracket  200  and positioned to sit between each of exterior portion  210  and interior portion  230  of wall panel bracket  200  and the wall panel  400  positioned between them, thus providing a compressible seal against air and water infiltration into modular building unit  100 . 
         [0024]    In the configuration shown in  FIG. 3 , wall panel  400  is positioned a distance away from support post  112 , creating a gap  318  between wall panel  400  and support post  112  (surrounded on its sides by exterior portion  210  and interior portion  230  of wall panel bracket  200 ). Optionally, insulation may be fitted within gap  318  to further aid in preventing air infiltration into and out from modular building unit  100 . 
         [0025]      FIG. 4  provides a close-up, top down view of joined wall panels  400  for use with the connecting system described herein. Each wall panel has a male connector edge  400   a  and a female connector edge  400   b  opposite male connector edge  400   a . Male connector edge  400   a  has an inwardly stepped section  402  so as to form a narrowed head along male connector edge  400   a . A connecting bracket  404  is provided along the exterior of male connecter edge  400   a , and has an outer most portion  406  that defines the maximum width of wall panel  400 , an inwardly turned step  407 , a connecting edge  408  extending from step  407  to the end of male connector edge  400   a , and a facing edge  410  extending between connecting edges  408  on either side of wall panel  400 . Facing edge  410  of male connector edge  400   a  abuts facing edge  420  of female connector edge  400   b  of an adjacent panel  400 , as discussed below. 
         [0026]    With continued reference to  FIG. 4 , female connector edge  400   b  includes a bracket  422  along the exterior of female connector edge  400   b , matching in width the outer most portion  406  of bracket  404  on male connector edge  400   a . Each bracket  422  forms a tongue engaging surface  424  sized to fit within step  407  of bracket  404  on male connector edge  400   a , thus enabling the joining of two adjacent wall panels in a tongue and groove connection allowing movement, separation, and replacement of wall panels on modular building unit  100  if and as desired. 
         [0027]      FIG. 5  provides a detail front view of exterior portion  210  of modular wall panel bracket  200 , and  FIG. 6  provides a top-down, cross-sectional view of such exterior portion  210 . As mentioned briefly above, exterior portion  210  of modular wall panel bracket  200  has an outer face  211  which forms an exterior surface of modular building unit  100  positioned between each corner support post  112  and an adjacent wall panel  400 , preventing movement of the wall panel toward the exterior of modular building unit  100 . A distal end of outer face  211  has a slightly inwardly bending flange  212 , thus preventing space between the interior of outer face  211  and the face of the wall panel  400  against which outer face  211  sits to accommodate a compressible gasket  216 . An interior column-facing arm  213  extends generally at a right angle from outer face  211 , which interior column-facing arm  213  is configured to abut first interior wall  306  of corner support post  112 . Interior column-facing arm  213  is preferably of smaller width than first interior wall  306  of corner support post  112 , so that outer face  211  of exterior portion  210  (and thus the wall panel  400  that exterior portion  210  restrains) sits slightly recessed from the outer walls  302  and  304  to corner support posts  112 , and from the outer faces of bottom rails  114  and top rails  116  of modular building unit  100 . A connecting arm  214  extends at generally a right angle from interior column-facing arm  213 , which connecting arm  214  is configured to abut connecting flanges  307  and  309  of corner support post  112 . A plurality of openings  215  are provided along the length of connecting arm  214  through which fasteners may be placed to join exterior portion  210  of modular wall bracket  200  to corner support post  112 . Such openings  215  may optionally be formed as elongate slots to allow vertical adjustment of exterior portion  210  of modular wall bracket  200  as may be necessary or desirable for varied installation environments. The particular position and configuration of openings  215  are symmetrical along connecting arm  214  so as to avoid requiring identification of right or left edges or top and bottom portions during installation, thus allowing exterior portion  210  of modular wall panel bracket  200  to be attached at either side of corner support posts  112 . 
         [0028]    As shown in  FIG. 5 , connecting arm  214  need not extend the full length of interior column-facing arm  213 , thus providing open space at the top and bottom of connecting flanges  307  and  309  on corner support posts  112 , which may be desirable to maintain access to the interior of corner supports posts  112  or other portions or components of modular building unit  100 . 
         [0029]    Likewise,  FIG. 7  provides a detail front view of interior portion  230  of modular wall panel bracket  200 , and  FIG. 8  provides a top-down, cross-sectional view of such interior portion  230 . As mentioned briefly above, interior portion  230  of modular wall panel bracket  200  has an interior face  231  which forms an interior surface of modular building unit  100  positioned between each corner support post  112  and an adjacent wall panel  400 , preventing movement of the wall panel toward the interior of modular building unit  100 . A distal end of interior face  231  may be provided a connection hook  232  that is positioned to receive interior corner trim  250 , as discussed further below. An interior wall stop arm  233  extends generally at a right angle from interior face  231 , which interior wall stop arm  213  is configured to abut the end of a wall panel  400 . Wall stop arm  233  is positioned with respect to interior walls  306  and  308  of corner support posts  112  to create gaps  318 , which as mentioned above may be used to position insulation within the corner joints of modular building unit  100 . A connecting arm  234  extends at generally a right angle from interior wall stop arm  233 , which connecting arm  234  is configured to abut interior column-facing arms  213  on exterior portion  210  of bracket  200  and in alignment with connecting flanges  307  and  309  of corner support post  112 . A plurality of openings  235  are provided along the length of connecting arm  234  through which fasteners may be placed to join interior portion  230  of modular wall bracket  200  to corner support post  112 . Such openings  235  may optionally be formed as elongate slots to allow vertical adjustment of interior portion  230  of modular wall bracket  200  as may be necessary or desirable for varied installation environments. Likewise, as noted above with respect to  FIG. 5 , the particular position and configuration of openings  235  are symmetrical along connecting arm  234  so as to avoid requiring identification of right or left edges or top and bottom portions during installation, thus allowing interior portion  230  of modular wall panel bracket  200  to be attached at either side of corner support posts  112 . 
         [0030]    As shown in  FIG. 7 , connecting arm  234  need not extend the full length of interior wall stop arm  233 , thus providing open space at the top and bottom of connecting flanges  307  and  309  on corner support posts  112 , which may be desirable to maintain access to the interior of corner supports posts  112  or other portions or components of modular building unit  100 . 
         [0031]    As mentioned above, connection hook  232  may be provided at the distal end of interior face  231  of interior portion  230 . With reference again to  FIG. 3 , connection hook  232  may have preferably two or more openings to receive threaded connectors  316 , which threaded connectors may be used to attached outer edges of an elongate corner trim piece  250  to interior portion  230  of wall panel bracket  200 , thus providing a clean and finished appearance to the interior corner joints of modular building unit  100 . Elongate corner piece  250  may likewise be joined to interior portion  230  with hook-and-loop fastening material, non-permanent adhesive, or such other non-permanent attachment mechanisms as may occur to those of ordinary skill in the art. 
         [0032]    With this assembly, those skilled in the art will recognize that modification of wall panels is easily managed, including replacing wall panels of a certain thickness with wall panels of a differing thickness, as may be desirable to, for example, reduce material costs in environments with lower environmental stress concerns. Specifically, by simply removing corner trim piece  250  and changing only the interior portion  230  of modular bracket  200  (i.e., changing the length of interior wall stop arm  233 ), wall panels  400  of varying thicknesses may be easily and quickly accommodated. While interior portion  230  of wall panel bracket  200  may be provided with different dimensions of wall stop arm  233 , interior wall stop arm  233  may alternatively be adjustable (in any of multiple manners as will be apparent to those skilled in the art) to allow a single set of components to be used with modular building unit configurations having varied wall thicknesses. 
         [0033]    Also, those of ordinary skill in the art will recognize that the components described herein may be modified from the specific examples presented without departing from the spirit and scope of the invention. For instance, the elements of modular wall bracket  200  may be comprised steel, but may likewise be comprised of, for example, PVC or other materials, for example to improve thermal insulation. 
         [0034]    Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.
Disclosed is a connecting system for connecting wall panels to the support frame, and more particularly to the rigid corner support posts of a support frame, of a modular building unit. The connecting system includes a modular bracket assembly and is configured so that two modular connecting brackets attach to each corner vertical support column, which modular brackets are configured to receive the vertical edge of a wall panel. The brackets themselves are configured for easy replacement and/or adjustment through minimal effort, are fully symmetrical to allow use of bracket elements at varied locations, and may be replaced or adjusted particularly without removing, altering, or otherwise disturbing the corner vertical support column of the frame of the modular building unit.