Patent Publication Number: US-4545165-A

Title: Modular monolithic ceiling grid system

Description:
DESCRIPTION 
     1. Technical Field 
     This invention relates to the field of sub-ceiling structures in which modular panels are supported by a framework of rails suspended from the building structure overhead. 
     More particularly, this invention relates to such sub-ceiling structures wherein the panels display a grid pattern formed from intersecting louvers defining open cells, the louvers being of a thick or beam shape as distinguished from a thin or blade shape. 
     Still more particularly, this invention relates to the special category of grid panel sub-ceilings wherein the support rails and panel boundaries are visually integrated to blend unobtrusively into the louver grid patterns of the panels, presenting the appearance of a monolithic grid over the entire finished sub-ceiling area, as distinguished from the more common category of grid panel sub-ceilings wherein the support rails and panel boundaries are revealed or even accentuated architecturally. 
     Of critical importance for sub-ceilings within the field of this invention are the ease and economy of installing the sub-ceilings originally, the resistance of the panels to damage in handling, and the ease of removal and re-installation of the panels for cleaning, lamp replacement or access to the space above. 
     2. Background Art 
     U.S. Pat. No. 3,378,980 discloses panels with a grid pattern of intersecting louvers, supported by rails resembling the louvers, wherein some of the louver ends extend beyond the support rails, abutting, overlapping or in close proximity to corresponding shortened louver ends of adjacent panels: the support rails are made to blend with the louvers to attain the desired overall monolithic appearance. However, the exposed louver end joinings, being susceptable to bending distortion and dimensional tolerances, tend to be difficult to conceal. 
     U.S. Pat. No. 4,034,534 discloses panels with a grid pattern of intersecting thick louvers having a U-shaped cross section and having hooked end tabs fitting downwardly into slots in U-shaped support rails. 
     Both U.S. Pat. No. 3,378,980 and U.S. Pat. No. 4,034,534 are capable of providing a monolithic grid appearance; however, installation and removal of panels tend to be difficult due to the problem of aligning the numerous mating slots around the edge of the panels simultaneously; therefore structures of the type taught by these two inventions fail to provide the ease of panel installation and removal sought as an object of the present invention. 
     U.S. Pat. No. 3,768,224 discloses a framework of support rails having an inverted T cross-sectional shape, capable of supporting panels of various materials and textures; however, prior to the present invention, there has been no availability or knowledge of modular louvered grid panel structures capable of combination with the inverted T support rails to achieve the required overall monolithic grid appearance. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, modular panels, formed from intersecting louvers of U-shaped cross-section defining open cells in a grid pattern, have perimeter strips attached to the ends of the louvers. The perimeter strips are dimensioned and positioned such that when the panels are set into place into a framework of inverted T support rails, such as those disclosed by U.S. Pat. No. 3,768,224, the vertical surfaces of the perimeter strips align and blend with the flanges of the support rails to simulate the appearance of the louvers; thus the desired overall monolithic appearance is accomplished along with the extreme ease of panel installation and removal provided by the inverted T support rail structure. 
     Subordinate features include (1) the utilization of louvers wherein the bottom of the &#34;U&#34; of the U-shaped louvers has a width substantially equal to the width of the cross-bar of the inverted T-shaped support bars; and (2) the perimeter strips are of L-shaped cross-section and the base of the &#34;L&#34; is raised relative to the bottom of the U-shaped panel louvers to make the bottom of the panels lie in the same plane as the bottom of the inverted T-shaped supports. 
     In accordance with a broad aspect of this invention, conventional T-bar sub-ceiling supports may be employed to produce an apparently continuous egg-crate or cross-louvered construction. This is accomplished by using thick louvers having a bottom configuration substantially the same as the bottom configuration of the T-bar supports. 
     In accordance with an additional aspect of the invention, the thick louvers are formed into rectangular panels, and support arrangements are provided on all four sides of each panel to rest on the T-bar supports with the lower surface of each panel preferably at the same elevation as the lower surfaces of the T-bar supports. 
     Further, these support arrangements may include light baffles extending upward from the outer edges of the support rails so that the T-bars with the adjacent support arrangements have substantially the same appearance as the thick louvers making up the body of each panel. 
     This arrangement has the advantages of both (1) an apparently infinite continuous sub-ceiling; while also (2) providing the ease of quick panel removal for access to lights or other structure located above the sub-ceiling. 
     Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description, and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The details of this invention will be described in connection with the accompanying drawings, in which; 
     FIG. 1 is a perspective view of a sub-ceiling illustrating the principles of the invention, having one of the modular panels removed; 
     FIG. 2 perspective view showing the louvers and perimeter strips of a corner portion of a panel prior to assembly; and 
     FIG. 3 is a cross-sectional view of an inverted T rail, supporting L-shaped perimeter strips at the ends of U-shaped louvers forming the modular panel. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, FIG. 1 shows a sub-ceiling constructed according to this invention, having a framework of latitudinal support rails lA and longitudinal support rails lB, suspended from the structure of a building by wire hangers 2. The support rails have an inverted T cross-sectional shape as shown in FIG. 2 and FIG. 3, with flanges 3 at the bottom as shown, including optional upturned rims 4 at the outer edges of the flanges. 
     Incidentally, for convenience in the present description, the adjectives &#34;latitudinal&#34; and &#34;longitudinal&#34; are employed to designate substantially perpendicular sets of rails or louvers. 
     Modular panels, typified by panel 5, shown removed in FIG. 1, are set into place from above into rectangular cell openings provided by the intersecting support rails 1. Each panel 5 comprises intersecting latitudinal louvers 6A and longitudinal louvers 6B, having a U-shaped cross-section as shown in FIG. 2. The louver ends are assembled to perimeter strips 7 which have an L-shaped cross-section with the foot portion resting on top of the flange rims 4 of the support rails 1, as shown in FIG. 3. It will be noted that the outer edges of the flanges of support rails 1 are in alignment with the vertical surfaces of the perimeter strips 7, and the bottom surfaces of the louvers 6 are co-planar with the bottom surfaces of the support rail flanges 3. The width of the flanges 3 is made equal to the thickness of the louvers 6, thus the exposed portions of the support rail flanges 3 and the perimeter strips 7 blend to simulate the appearance of the louvers 6 to disguise the support rails 1 by integrating them into the required overall monolithic grid ceiling appearance. 
     The intersections of latitudinal louvers 6A with longitudinal louvers 6B and the fastening of the louvers 6 to the perimeter strips 7 are accomplished through the use of mating half-slots as shown in FIG. 2. It may be noted that the bottom of the &#34;U&#34; must be cut away to form the half-slot construction 8 which mates with the simpler pair of half slots 9 as shown in FIG. 2. Once the panels 5 are assembled, there is never any need to dissemble any of the slot joinings afterwards, therefore the slots may be dimensioned to fit each other tightly to avoid rattles and light leaks. In systems which depend on half-height slots to carry the panels on the support rails, a compromise is required between a loose fit to permit panel removal and a tight fit to avoid rattles and light leaks. 
     In the preferred embodiment of this invention, the support rails are spaced 24&#34; by 48&#34; on centers, a common standard size facilitating the optional installation of standard size fluorescent lighting troffers and other modular ceiling utilities. For mounting smaller light troffers or other appliances into a louvered panel, holes may be provided in the louvers at concealed locations within the intersections to accomodate wire hangers for additional support. 
     In the preferred embodiment of this invention, the louvers are spaced 4&#34; on centers, the support rail flange width and the louver thickness are 1/2&#34;, and the louvers are 21/8 high. The louvers are formed from sheet aluminum, approximately 0.024&#34; thick. The rims 4, flanges 3, and the web of the support rails 1 are made approximately 1/16&#34; thick in the preferred embodiment of this invention, where the support rails are extruded from aluminum. Alternatively, the rails may be roll-formed from sheet steel or aluminum, and may be formed with an enlarged tubular shape along the upper edge of the rail for stiffening. The shape and dimensions of the web portion of the support rails may be modified as desired for strucural purposes without affecting the monolithic appearance of the ceiling, since that portion of the rails is concealed by the panel perimeter strips 7. 
     In the preferred embodiment of this invention, the exposed lower flange portion of the support rails is finished or painted to match the finish or paint on the louvers of the panels. Alternatively, the support rail flanges may be designed to be enclosed by a metal wrap-around cap, suitably finished or painted. 
     The height of the support rail outer flange edges is made 3/16&#34; in the preferred embodiment: this dimension may be modified at the designer&#39;s discretion, or the flange rim 4 may be omitted to use a plain flange such as is disclosed in U.S. Pat. No. 3,768,224. 
     The position of the perimeter strips 7 with respect to the louver ends in co-operation with the height of the outer edges of the support rail flanges aligns the lower surfaces of the support rails 1 in coplanar relationship with the lower surfaces of the louvers 6. 
     The principles taught by this invention are applicable to numerous variations in addition to the completely monolithic ceiling grid pattern disclosed: architecturally desirable patterns may be created by concealing some of the support rails as described while allowing other support rails to be revealed or accentuated. For example, in a structure like that shown in FIG. 1, the longitudinal rails 1A, spaced 24&#34; on centers, may be concealed by locating their bottom surfaces at the same elevation as the louver bottoms, while accentuating the latitudinal rails 1B, spaced 48&#34; on centers, by extending their bottom surfaces further downward to a lower elevation than the other rail and louver bottoms. The effect thus created is that of 48&#34; wide monolithic grid panels running the full length or width of a room, demarked by the prominent latitudinal rails lB which may be finished distinctively to provide further contrast. As in the preferred embodiment, this configuration also readily accepts standard sized lighting troffers and other ceiling utilities in the standard 24&#34; by 48&#34; support rail openings. 
     This invention is susceptable of many variations in dimensions and proportions, and may be fabricated from a variety of materials by those skilled in the art, without departing from the intent and spirit of the invention. In addition to the alternatives mentioned in the preceeding paragraph, instead of using L-shaped perimeter strips, the ends of the U-shaped thick louvers may be partially cut vertically, and bent into a horizontal plane to rest on the T-bar supports with the bottom of the louvers co-planar with the bottom of the T-bar supports. The present invention encompasses all such variations and alternatives.