Wall framing systems consisting of glass or metal panels supported by aluminum framing elements are well known. The framing elements of such systems (e.g. mullions, sills, jambs, etc.) are often provided in two sections: an interior or "gutter" section and an exterior or "face" section. These two sections are joined conventionally by one or more connector clips that, together with the interior and exterior framing sections, support the metal or glass panels.
A common problem with such wall framing systems is water that seeps into, condenses within or otherwise infiltrates the core of the framing elements. The potenital damage presented by such water is well known, and its disposal is widely recognized as necessary to the successful maintenance of the wall framing system. Water that has infiltrated an exterior section of a framing element is easily disposed of through weep holes and the like that discharge such water to the exterior of the building. However, water that has infiltrated the interior section of a framing element is a much more difficult problem. Disposal of this water must be accomplished without any discharge or leakage into the interior of the building. Instead, this water must be directed from the interior framing element section to the corresponding exterior framing element section for disposal therefrom.
Various arrangements have been provided in the prior art purporting to solve this problem. For example, U.S. Pat. No. 4,055,923 discloses a Z-shaped flashing member mounted within the core of the horizontal mullions for diverting water from the interior mullion section to the exterior mullion section. The flashing member is mounted by screws, rivets or adhesives. Internal bridge pieces are provided at the crossings of the vertical and horizontal mullions that extend through the vertical mullions so as to connect the water diverter in one horizontal mullion to the water diverter in another.
As a further example, U.S. Pat. No. 4,448,001 discloses a moisture control dam system wherein certain mullion walls are provided with thickened ribs on their inside surfaces to seal around the edges of the outside faces of the panels. A pair of vertical grooves are formed within each such rib. Vertical dams made of a sheet material are inserted into these grooves to dam up any accumulated moisture and prevent its discharge out the end of a frame element.
As a yet further example, U.S. Pat. No. 4,428,171 discloses a store-front system for buildings including a plurality of support clips located at the intersections of the horizontal and vertical mullions. A drip shield is provided. The inner edge portion of the drip shield is arranged to be supported by an ear formed integrally with and projecting downwardly of the support clip.
Several problems exist with the above and other such prior art arrangements. For example, many such framing systems require a differently sized flashing member when panels of different thicknesses are mounted within the framing elements. Because panel thickness often varies (even within the same framing system), an additional inventory of flashing members must be kept on site or otherwise available so that the correct flashing member may be provided when needed. The use of bridges or other like members to extend across the intersection of a vertical mullion and a horizontal mullion compounds this problem. Where such bridge pieces are used, an inventory of both flashing members and bridges must also be kept on site or readily available. When used in a wall framing system employing panels of differing thicknesses, additional inventories of appropriately sized flashing members and flashing members and bridges must be maintained. Not only do such additional inventories of flashing members and bridges increase the costs associated with building supplies, the very existance of differently sized flashing members and bridges pieces provides the opportunity for dealer and installer error.
Yet another problem with such prior art arrangements is that of their relative complexity. As noted above, separate bridge members have been provided in addition to the dam or flashing member. Furthermore, prior art dam members are often mounted by screws or bolts secured to the interior mullion section. Other arrangements provide for the flashing member to be mounted upon the clip that connects an interior mullion section to an exterior mullion section. While not only requiring connectors to mount the dam or flashing member, these arrangements fail to consider the small size of the mullion core within which the dam member, the mounting bolts and screws, and the connecting clips must be manipulated and secured. These difficulties are complicated by the fact that the installer must often work in a cramped space that may be several hundred feet off the ground.
Yet another problem with prior art systems is that the fitting of the dam or flashing member within the horizontal mullion must be done entirely by the installer. In such framing systems, the installer must estimate the appropriate length and width of the dam member to insure a proper fit within the mullion. The installer then notches or cuts the dam member to fit within the frame element. Because it is often done without any predetermined measuring devices, such field fitting operations enhance the potential for installation error. Because precise fitting is imperative for system performance, such field fitting operations can result in system failure.