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RELATED APPLICATIONS  
       [0001]    This patent application claims the benefit of priority from co-pending U.S. Provisional Patent Application Serial No. 60/364,880 filed on Mar. 13, 2002. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to curtain walls used for building exteriors and, more particularly, but not by way of limitation, to the construction and assembly of sill and mullion sections of such curtain walls along with the curtain wall panels associated therewith.  
           [0004]    2. Description of the Related Art  
           [0005]    Curtain walls are typically constructed of extruded aluminum frame support members having generally U-shaped channels (although other shapes may apply) for supporting a plurality of panel members that serve as the exterior of a building. Such panel members are most often panes of glass, and often double pane glass sections, but other paneled building materials such as aluminum, granite, slate, or concrete are also utilized. Such panel members are often of identical size and shape. However, near doors, opening windows, or other access points into the building, panel members of different sizes and shapes may be utilized.  
           [0006]    More specifically, such curtain walls generally include a horizontal sill member having at least one portion forming a channel at the bottom of a wall section, a horizontal head member having a downwardly facing channel at the top of a wall section, and a plurality of vertical mullions running between the sill and head members. Panel members are supported by the channels of the sill member and the head member, and the vertical joints between adjacent panel members are formed at the mullions. In some designs, the mullions are disposed interiorly of the sill member, the head member, and the panel members so that only the joint between adjacent panel members, and not the mullions themselves, are visible from the exterior of the building. The designs do, however, vary, depending upon the desired aesthetics of the curtain wall construction.  
           [0007]    In another curtain wall construction, multiple panel members are typically arranged side-by-side and are secured and sealed between a sill member and a head member, with their vertical joints overlapping at a mullion. This vertical joint must then be sealed from both the interior and exterior of the building using both resilient gaskets, sealant tapes, sealant, and/or structural silicone, as described for reference purposes below.  
           [0008]    An existing solution is set forth and shown in U.S. Pat. No. 6,158,182 and assigned to the assignee of the present invention. Referring now to FIG. 1, a schematic, cross-sectional view of a sill member  10  of an exemplary curtain wall is shown. The sill member  10  secures a curtain wall to a structural support surface such as a concrete slab  12 . The concrete slab  12  may be at ground level or comprising a floor surface of a high rise building. Although not shown in FIG. 1, a head member similar to the sill member  10  secures the curtain wall to a concrete slab between floors of a building or other building structures, and a plurality of mullions span between the sill member  10  and the head member. The sill member  10  is typically formed as an integral aluminum extrusion. The sill member  10  also generally includes a channel section  14 , an anchoring section  16  disposed interiorly of a channel section  14 , and a cover  18 .  
           [0009]    Still referring to FIG. 1, the channel section  14  and the cover  18  cooperate to secure the panel member  20  to the sill member  10 . More specifically, the channel section  14  includes a base  14   a  and two legs  14   b  and  14   c  that form a upwardly facing U-shaped channel. A support member  22  rests on the top surface of the base  14   a . The exterior leg  14   b  has a groove  24  proximate the upper end of its interior surface facing the panel member  20 , and the interior leg  14   c  has a support surface  26  proximate the upper end of its interior surface. The cover  18  has a downward projecting leg  28  that engages a groove  30  on the exterior surface of the interior leg  14   c . The cover  18  also has two tongues  32 ,  49 , one proximate to each end of the cover  18 . The panel member  20  is placed within the channel section  14  on an upper surface of a setting block  34 . An exterior and interior gasket  36 ,  38  are located at the upper end of the exterior and interior legs  14   b ,  14   c . The gaskets  36 ,  38  operate to hold the panel member  20  in the channel section  14 . The setting block  34  is disposed on the top surface of the support member  22 . The exterior gasket  36  has a tongue  36   a  that engages the groove  24  of the exterior leg  14   b . The exterior gasket  36  is typically pre-installed in groove  24  of the exterior leg  14   b  during the manufacture of the sill member  10 . The interior gasket  38  has a groove  38   a  that engages the tongue  32  of the cover  18  and the support surface  26  of the interior leg  14   c . The channel section  14  further includes a plurality of support legs  40  below base  14   a.    
           [0010]    The anchoring section  16  includes a base  16   a , an interior leg  16   b , and a plurality of support legs  42  below the base  16   a . The base  16   a  has a plurality of holes  44  spaced along its length for receiving fasteners  46  to secure the sill member  10  to the structural support surface  12 . The interior leg  16   b  has a groove  48  for receiving the tongue  49  of the cover  18 . The cover  18  stabilizes the interior gasket  38  that presses against the panel member  20  and also conceals the base  16   a  of the anchoring section  16  so that the fasteners  46  are not visible. A drawback of this example is that the panel member  20  cannot be installed until the cover  18  is placed over the fasteners, due to the fact that the cover  18  is needed to hold the interior gasket in place against the panel member  20 . Therefore, the entire structure must be inspected before the panel member  20  is installed as discussed in more detail below.  
           [0011]    The following technique is typically used to install the panel member  20  of such a curtain wall. First, the sill member  10  is laid on a shim  56  in the proper position on the concrete slab  12  and is used as a template to drill holes into the concrete slab  12  for each fastener  46 . One should note that the shim  56  does not run continuously along the length of the sill member  10 . Instead, the shim  56  is used at low points of the concrete slab  12  to level the sill member  10 , if necessary. The sill member  10  is removed from the shim  56 , and a hole  50  with a larger diameter is drilled in the place of each of the holes drilled using the sill member  10 . A structural insert  52  is secured within each of the holes  50  via epoxy or other conventional means. Each insert  52  has an internally threaded hole  54  for receiving fasteners  46 . The sill member  10  is repositioned on the shim  56  and secured to the concrete slab  12  using fasteners  46 . A sealant  58  is disposed continuously on the concrete slab  12  along both the exterior and interior sides of the shim  56 . A head member similar to the sill member  10  is secured to part of the building structure using the above-described techniques. Vertical mullions are secured between the sill member  10  and the head member at appropriate intervals along the curtain wall. The vertical mullions are attached at each side to sill members  10 . The support member  22  is disposed on the base  14   a  of the sill member  10 , and the setting block  34  is disposed on the support member  20 . The panel member  20  is then installed from the exterior of the building, typically first being tilted into the channel section of the head member, and then being dropped into the channel section  14  of the sill member  10 . The cover  18  is installed in the sill member  10 , and a glazing stop is installed in the head member of the curtain wall. The interior gasket  38  is disposed on the tongue  32  of the cover  18  of the sill member  10 , and a similar gasket is disposed on the tongue of the glazing stop of the head member.  
           [0012]    While such curtain walls, and other conventional curtain walls, have proved to be reliable commercial building systems, they suffer from several drawbacks. For example, installing the panel members at the building site also requires inspections during the process. These inspections must be performed by building code enforcement personnel, whose schedule may or may not be compatible with time schedules for the contractor erecting such curtain walls.  
           [0013]    Another solution is set forth and shown in U.S. patent application Ser. No. 10/099,070, assigned to the assignee of the present invention, and incorporated herein by reference. Referring now to FIG. 2, a side cross-sectional view a sill assembly  100  of the &#39;070 patent application is shown. By first installing a sill flashing  112  directly upon a support surface  155  such as a concrete slab, the remaining portions of the curtain wall may be assembled at the factory prior to delivery to the field for installation. An outside cap  108 , an interior cover  110 , and a sill member  106  are adapted for resting upon and mounting to the sill flashing  112 .  
           [0014]    The curtain wall as set forth in the &#39;070 patent application is assembled by first temporarily fastening, with a fastener  153 , the sill flashing  112  to the support surface  155  of a building at the job site. The sill member  106  is mounted to two vertical mullions (not shown) at opposite ends of the sill member  106 . An outside cap  108  is secured to the sill member  106  and provides a groove for attaching an exterior gasket  151 . The exterior gasket  151  presses against the exterior of the panel member  150  to secure the panel member  150  set on the top surface of a setting block  200  placed in a channel of the sill member  106 . The sill member  106 , outside cap  108 , panel member  150 , and setting block  200  may be preassembled at a factory prior to being shipped to the job site. However, the sill flashing  112  must be temporarily secured at the job site prior to fastening the sill member  106  and other components permanently to the support surface  155 . After the sill flashing  112  has been temporarily secured to the support surface  150  and the sill member  106 , outside cap  108 , panel member  150 , exterior gasket  151 , and setting block  200  have been assembled at the factory and shipped to the job site, then the sill member  106  is permanently secured to the sill flashing  112  and the support surface  155  with at least one fastener  152 . Building code enforcement personnel then inspect the securement of the sill assembly  100 . Once approved, then the interior cover  110  is secured to the sill flashing  112  and the sill member  106 .  
           [0015]    The &#39;070 patent application allows for some pre-assembly to occur at the factory, however, the sill assembly must to be split into two pieces, namely the sill member  106  and the sill flashing  112 , in order to allow the pre-assembly of the sill member  106  with other components.  
           [0016]    For this reason, it would be greatly advantageous to provide a curtain wall system construction that maximizes the ability for pre-assembly without sacrificing the structural integrity of the overall curtain wall system.  
         SUMMARY OF THE INVENTION  
         [0017]    The present invention relates to curtain walls used for building exteriors and the assembly of a building curtain wall with a sill and mullion assembly permitting the substantially flush mounted panel members therewith. More particularly, one aspect of the present invention relates to a curtain wall system including a first vertical mullion operable to attach to a first sill member and a second vertical mullion operable to interlock with the first vertical mullion. The present invention also relates to a mullion cap for attaching to a bottom surface of a vertical mullion. The mullion cap includes a substantially planar bottom plate having an upper surface, a lower surface, a front edge, and a back edge. The mullion cap further includes an attachment face located on the upper surface of the substantially planar bottom plate. The attachment face is operable to attach to the vertical mullion.  
           [0018]    In another aspect, the present invention includes a curtain wall system comprising a first vertical mullion operable to attach to a first sill member, and a second vertical mullion operable to interlock with the first vertical mullion. The first vertical mullion may also include a protrusion and the second vertical mullion may include a groove for interlocking with the protrusion. In one aspect, the first sill member attaches to the first vertical mullion via at least one screw spline and screw. The second vertical mullion may also be further operable to attach to a second sill member, while the first sill member may be formed as a single extrusion. The curtain wall system may also include a mullion cap for attaching to a bottom surface of at least one of the first and second vertical mullions. In one aspect, the mullion cap attaches to the first vertical mullion. The vertical mullions may also include a securement clip for attaching the vertical mullions to one another. The securement clip may be fastened to an interior surface of a second vertical mullion. The securement clip includes an extension that abuts a securement face located on an interior surface of the first vertical mullion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    For a more complete understanding of the present invention, and for further objects and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings in which:  
         [0020]    [0020]FIG. 1 (Prior Art) illustrates a side cross-sectional schematic view of a sill member of a conventional curtain wall;  
         [0021]    [0021]FIG. 2 illustrates a side cross-sectional view of a sill assembly of a curtain wall system;  
         [0022]    [0022]FIG. 3 illustrates a perspective view of a sill and mullion assembly according to an embodiment of the present invention;  
         [0023]    [0023]FIG. 4 illustrates an enlarged perspective view of a mullion cap as shown in accordance with an alternate embodiment of the present invention;  
         [0024]    [0024]FIG. 5 illustrates an enlarged top view of the vertical mullion and mullion cap as shown in FIG. 4,  
         [0025]    [0025]FIG. 6 illustrates a bottom view of the mullion cap as shown in FIG. 4;  
         [0026]    [0026]FIG. 7 illustrates a bottom exploded view of a sill and mullion assembly including the mullion cap of FIG. 4 according to an alternate embodiment of the present invention;  
         [0027]    [0027]FIG. 8 illustrates a bottom perspective view of the sill and mullion assembly including the mullion cap of FIG. 5;  
         [0028]    [0028]FIG. 9A illustrates a top view of a securement clip of the mullion assembly of an alternate embodiment of the present invention;  
         [0029]    [0029]FIG. 9B illustrates a perspective view of a securement clip of the mullion assembly of FIG. 9A,  
         [0030]    [0030]FIG. 10A illustrates a top view of the engaged securement clip of the mullion assembly of FIG. 9A;  
         [0031]    [0031]FIG. 10B illustrates a perspective view of the engaged securement clip of the mullion assembly of FIG. 10A;  
         [0032]    [0032]FIG. 11 illustrates a perspective view of the sill and mullion assembly according to an alternate embodiment of the present invention; and  
         [0033]    [0033]FIG. 12 illustrates a side cross-sectional view of the sill and mullion assembly including the mullion cap of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    In the present embodiment, as shown in FIG. 3, a curtain wall assembly  250  of a preferred embodiment of the present invention is illustrated. Vertical mullions  300 ,  302  are extruded in a shape permitting direct interengagement one with the other. One of the vertical mullions  300  is formed to provide a groove  304  on its rearward face for receiving a protrusion  306  of another of the vertical mullions  302 . The groove  304  and protrusion  306  are arranged so that the vertical mullions  300 ,  302  are angled with respect to each other and then rotated until the rearward faces of both vertical mullions  300 ,  302  are aligned in a planar fashion as described in more detail in FIGS. 7 and 8. Although the preferred embodiment of the present invention describes the interlocking mechanism of the vertical mullions as a groove  304  and protrusion  306 , any means of interlocking the two vertical mullions  300 ,  302  together may be used. For example, a male and female snap arrangement may be employed, as well as two protrusions from the rearward faces of the vertical mullions  300 ,  302  which may be secured together with additional fasteners. The interlocking vertical mullions  300 ,  302  permit a restricted amount of movement to allow for thermal expansion and contraction while preventing failure under extreme stresses that may be exhibited by a hurricane or other natural disasters.  
         [0035]    Sill members  308  are constructed as a single extrusion for direct engagement with the vertical mullions  300 ,  302  via screw splines  310 . The sill members  308  are further constructed to provide a channel  312  for receiving a panel member (not shown) such as glass, granite, or other building material. The sill members  308  are fastened to the vertical mullions  300 ,  302  which are then interlocked. The sill members  308  also provide various other grooves within the channel  312  for receiving components used to stabilize or secure the panel member. In the preferred embodiment, the interior surface of a forward leg  312   a  of the channel  312  includes two grooves  314 ,  316  while the interior surface of an intermediate leg  312   b  includes a groove  318 , a support leg  320 , and an upper protrusion  322 . These grooves  314 ,  316 ,  318 , the support leg  320 , and the upper protrusion  322  may be oriented in a variety of ways to aid in the securement of various components placed in the channel  312 . In an alternate embodiment, the grooves  314 ,  316 ,  318 , support leg  320 , and upper protrusion  322  are eliminated and the components may be placed directly on the upper surface of a base  312   c  of the channel  312 . The face opposite the groove  318  and support leg  320  of the intermediate leg  312   b  includes a groove  324  in addition to a groove  326  disposed on the interior surface of a rearward leg  328 . In the preferred embodiment, the screw splines  310  are oriented between the intermediate and rearward legs  312   b  and  328 .  
         [0036]    Referring now to FIGS.  4 - 6 , a mullion cap  400  may be used with the curtain wall assembly  250  of the present invention. The mullion cap  400  may also be eliminated in an embodiment of the present invention. The mullion cap  400  includes a bottom plate  402  that is substantially planar and substantially rectangular in shape, however, other orientations may be used depending on the configuration of the vertical mullions  300 ,  302  and the sill members  308 . On an upper surface of the bottom plate  402 , an attachment face  404  is located approximately near the center of the bottom plate  402 . In the preferred embodiment, sides of the attachment face  404  do not extend to the outside edges of the bottom plate  402 . In alternate embodiments, the attachment face  404  may be located at a position other that near the center of the bottom plate  402  and may also have sides that extend to or beyond the edges of the bottom plate  402 . Also in the preferred embodiment, the attachment face  404  includes an aperture  406  for securement to at least one of the vertical mullions  300 ,  302 . A lower surface of the bottom plate  402  is substantially planar as illustrated in FIG. 6, although other orientations are possible.  
         [0037]    As shown in the top view of FIG. 5, a fastener  500  is utilized to secure the attachment face  404  of the mullion cap  400  to a vertical face  502  of the vertical mullion  302 . The attachment face  404  may also be oriented in another direction to facilitate securement to another face of the vertical mullion  302 . As shown, the bottom plate  402  abuts the lower surface of the vertical mullion  302  and extends on both sides of the vertical face  502 . The bottom plate  402  may also be fabricated to be flush with the vertical face  502  instead of extending past the vertical face  502 .  
         [0038]    [0038]FIGS. 7 and 8 illustrate the process of interlocking the vertical mullions  300 ,  302  together, as well as the securement of the mullion cap  400  to the bottom surface of the vertical mullions  300 ,  302 . The vertical mullions  300 ,  302  are angled with respect to each other and sealant  700  is placed on bottom edges of the vertical mullions  300 ,  302 , as well as an upper surface of the mullion cap  400 . The mullion cap  400  is secured to the bottom surface of the vertical mullions  300 , 302 . An end dam  702  may also be utilized in the preferred embodiment and attached to the vertical mullion  300  that is not secured to the mullion cap  400 . The end dam  702  is secured to a vertical face of the vertical mullion  300  in a similar fashion to that of the mullion cap  400 . The sealant  700  placed on the upper surface of the mullion cap  400  marries the end dam  702  to the mullion cap  400 , thereby providing a water tight seal. As shown in FIG. 8, the groove  304  may be placed over the protrusion  306  and rotated into position. In an alternate embodiment, the vertical mullions  300 ,  302  may be rotated into position and then the sealant  700  may be applied. Then the mullion cap  400  may be secured to the bottom surface of the vertical mullions  300 ,  302 .  
         [0039]    Now referring to FIGS. 9A and 9B, a securement clip  900  according to an alternate embodiment of the present invention is described. To further enhance the structural integrity of the interlocking vertical mullions  300 ,  302  during negative pressure loading, a securement clip  900  may be added to an internal face of the vertical mullion  300  including the groove  304 . In a first embodiment of the securement clip  900 , the securement clip  900  is formed of a single aluminum extrusion and is fashioned with an extension  904  at one end of the securement clip  900 . Although in the preferred embodiment a single aluminum extrusion is utilized, other configurations and material may be used to form the securement clip  900 . Other configurations may include multiple pieces and may span only a portion of the interior face. The securement clip may also be integrally formed with the vertical mullion  300 . The securement clip  900  abuts the internal face of the vertical mullion  300  from a side  906  of the groove  304  to a leg  908  oriented at or near a corner  910  of the vertical mullion  300 . The leg  908  abuts at least a portion of the extension  904 . The extension  904  includes a curved end portion for fastening against a securement face  902  of the opposite vertical mullion  302  with the protrusion  306 . The securement face  902  protrudes from an interior surface at or near a corner  912  of the vertical mullion  302 . The extension  904  of the securement clip  900  is operable to contact the securement face  902  as shown in FIGS. 10A and 10B.  
         [0040]    As illustrated in FIGS. 10A and 10B, the curved end portion of the extension  904  abuts the securement face  902  to further secure the vertical mullions  300 ,  302 . When the vertical mullions  300 ,  302  are interlocked, the respective corners  910 ,  912  are oriented near each other to facilitate engagement between the extension  904  and the securement face  902 . As shown, the leg  908  is oriented to protrude rearward of the corners  910 ,  912  of the vertical mullions  300 ,  302  and supports the extension  904  of the securement clip  900 . When the securement clip  900  is engaged, the leg  908  may rest on the interior surface of the vertical mullion  302  near the securement face  902 .  
         [0041]    [0041]FIG. 11 illustrates the curtain wall assembly  250  once the vertical mullions  300 ,  302  have been rotated into place and the mullion cap  400  has been secured to the vertical face  502  of the vertical mullion  302  and a bottom surface of the end dam  702 . Once rotated into position, the rear faces of both vertical mullions  300 ,  302  are substantially planar. Depending on the interlocking mechanism utilized, one of the rear faces may be slightly inset with respect to the other rear face. As shown and discussed with reference to FIG. 5, in the preferred embodiment, the bottom plate  402  of the mullion cap  400  substantially covers the lower surface of the curtain wall assembly  250  from the edge of the sill member  308  attached to one vertical mullion  302  to the edge of a second sill member  308  attached to the other vertical mullion  300  that is interlocked with the first vertical mullion  302 . The mullion cap  400 , as installed, creates a water tight seal for the vertical mullions  300 ,  302 . The interlocking vertical mullions  300 ,  302  also provide addition structural support and do not pull apart when loaded with extreme stresses such as those experienced during natural disasters.  
         [0042]    Referring now to FIG. 12, a curtain wall assembly  250  including a panel member  1000  secured in the channel  312  of the sill member  308  is illustrated. A setting chair  1002  may be fashioned with two legs  1004 ,  1006  operable to sit in the grooves  316 ,  318  of the forward leg  312   a  and the intermediate leg  312   b , respectively. A setting block  1008  rests on an upper surface of the setting chair  1002 . The panel member  1000  has a lower surface that rests on the upper surface of the setting block  1008 . As noted above, the setting block  1008  may also rest on an upper surface of the base  312   c  of the channel  312 . An exterior gasket  1010  attaches to the forward leg  312   a  via the groove  314 . The exterior gasket  1010  aids in the stabilization and securement of the panel member  1000  in the channel  312 . On the interior side of the panel member  1000 , a plug  1012  is supported by the support leg  320  of the intermediate leg  312   b . On the upper face of the plug  1012 , structural silicone  1014  is utilized to create a water tight and structural seal between the panel member  1000  and the intermediate leg  312   b . In an alternate embodiment, in place of the plug  1012  and the structural silicone  1014 , a gasket similar to the exterior gasket  1010  may be utilized. The panel member  1000  is stabilized and secured via the exterior gasket  1010 , the setting chair  1002 , the setting block  1008 , the plug  1012 , and the structural silicone  1014 . The assembly of the panel member  1000  within the channel  312  may take place at the factory or other alternate site.  
         [0043]    The curtain wall assembly  250  may be assembled at the factory and then shipped to the job site. The assembly required at the job site is the attachment of the sill member  308  to a support structure  1016  of the building via at least one fastener  1018 . The fastener  1018  secures the bottom surface of the sill member  308  to the support structure  1016 . Once the sill member  308  is secured, an assembly cover  1020  is placed over the exposed portion of the sill member  308 . Preferably, the assembly cover  1020  includes two legs  1022 ,  1024 , one disposed at each end of the assembly cover  1020 . The forward leg  1022  is operable to fit in the groove  324  located on the intermediate leg  312   b  and the rearward leg  1024  is operable to fit in the groove  326  located on the rearward leg  328 . The assembly cover  1020  may also be fastened to the sill member  308  by other securement means such as fasteners or snaps. By allowing direct access to the fully assembled and secured curtain wall assembly  250 , an inspector may easily view the securement of the sill member  308  to the support structure  1016 . Once viewed, the assembly cover  1020  may be secured to the sill member.  
         [0044]    It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. While the curtain wall assembly shown and described have been characterized as being preferred it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

Summary:
Disclosed is a curtain wall assembly used for building exteriors. The curtain wall system includes a first vertical mullion operable to attach to a first sill member and a second vertical mullion operable to interlock with the first vertical mullion. A mullion cap may be attached to a bottom surface of at least one of the vertical mullions. The mullion cap includes a substantially planar bottom plate having an upper surface, a lower surface, a front edge, and a back edge. The mullion cap further includes an attachment face located on the upper surface of the substantially planar bottom plate. The attachment face is operable to attach to the vertical mullion.