Abstract:
A suspended ceiling grid assembly including parallel spaced main runners and pairs of cross runners on opposite sides of a main runner, the main runners having vertical slots spaced along their lengths, the cross runners having end connectors mutually inter-engaged in a common main runner slot, a brace stabilizing the pair of cross runners against relative hinge action in a vertical plane, the brace being a thin metal body having a cross section complimentary to a cross section of the cross runners, the brace abutting sides of the cross runners and being rigidly attached thereto.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to suspended ceiling construction and, in particular, to a grid runner accessory for supplementing the beam strength of a grid runner joint. 
     PRIOR ART 
     Island-type suspended ceilings use standard ceiling grid elements trimmed at the perimeter of the island with extruded or formed sheet metal vertically oriented moldings. It is desirable to locate overhead suspension wires inward from the perimeter so that they cannot be seen or are less conspicuous to an observer standing on the floor below. Set back of the suspension wires presents a problem where the grid runners have end joints that lie between the perimeter trim and the closest suspension wires. In these circumstances, a grid runner, bearing the weight of a portion of a tile or panel and part of the weight of the perimeter trim has a tendency to sag. It is also possible for this outlying weight to cause a grid runner or runners to pivot downwardly about the point where the suspension wire or wires are attached. This displacement at the ceiling perimeter can cause an inward section of the ceiling to rise above its intended plane. The foregoing explains a need for a practical solution for maintaining a suspension ceiling grid in its intended plane where the grid elements are cantilevered from their suspension wires. 
     SUMMARY OF THE INVENTION 
     The invention provides a brace for imparting beam strength to a joint between grid runner ends. The brace can eliminate objectionable sag of cantilevered grid runners and lift-up of inboard grid runners associated with cantilevered runners. 
     The disclosed brace is preferably made of sheet metal and is configured to closely abut the concealed part of a standard grid runner profile. The configuration of the brace makes the brace self-aligning to the grid runners to which it is attached. Additionally, the brace is configured to avoid interference with the grid runner end connectors forming a joint that the brace bridges across and strengthens. Still further, the brace maintains a narrow cross-sectional profile along its full length so that no significant interference with the installation or removal of a ceiling panel occurs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view looking down on a suspended grid, with perimeter trim exploded away, forming an island ceiling; 
         FIG. 2  is an isometric view of the brace of the invention; 
         FIG. 3  is a side view of the brace of the invention on a pair of end joined cross runners; and 
         FIG. 4  is an end view of the brace of the invention and a cross-section through a typical grid cross runner. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A grid system  10  for an island ceiling comprises main runners  11  and cross runners  12 . In the illustrated case, the runners  11 ,  12  have conventional inverted tee cross-sectional shapes. The grid runners  11 ,  12 , as shown in  FIGS. 3 and 4 , are, as is conventional, roll-formed sheet metal parts having an upper hollow reinforcing bulb  16 , a vertical central web  17 , and a lower flange  18  extending laterally to both sides of the web. The main runners  11 , as is customary, have vertical slots  19  in their webs  17  uniformly spaced along their lengths. The main runners  11  are connected directly end-to-end by end connectors such as disclosed in U.S. Pat. No. 7,703,258. The cross runners  12  are disposed on opposite sides of the main runners  11  and have end connectors joined through a common slot  19 . An example of a suitable end connector is disclosed in U.S. Pat. Nos. 5,517,796 and 5,761,868. 
     The suspended island ceiling grid  10  includes a perimeter trim  21  that conceals the ends of the grid runners  11 ,  12  and the edges of ceiling tiles or panels (not shown) carried on the grid. The trim  21 , which is at least several inches high, can be made of lengths  22  of aluminum or roll formed sheet metal. The trim lengths  22  are mounted on the grid runners  11 ,  12  with brackets  23  that are concealed when the trim lengths are installed. 
     Standard end connectors on the grid runners  11 ,  12  are primarily designed to provide high tensile resistance so that they do not readily pull apart. The end connectors, however, do not afford high bending moment resistance in a vertical plane. Consequently, where a grid runner  11 ,  12  is in a cantilever arrangement so that it has an end that is not supported by an overhead wire, another grid runner, or another element it can sag below the ceiling plane. This tendency to sag is greater when the weight of perimeter trim  21  and that of ceiling tiles is added onto the weight of the unsupported grid runner. 
     It is desirable that suspension wires  27  supporting the island ceiling grid system  10  are spaced inwardly away from the perimeter so that they are not readily seen by a person standing below the ceiling. Consequently, in these circumstances, cross runners  12  intersecting the perimeter of the system  10  are typically not supported directly by a wire  27 . Additionally, a perimeter trim length  22  may not be capable of supporting its weight as well as the weight of intersecting cross runners  12  and panels mounted on them. The cross runners at the perimeter are, therefore, typically, in a cantilevered condition. A cantilevered grid runner, in accordance with the invention, can be supported by a brace  31  that bridges a joint with an associated grid runner to impart additional beam strength to the cantilevered grid runner. 
     The brace  31  is an elongated metal strip having a cross-section complimentary to the external cross-section of a grid runner  11 ,  12  above its flange  18 . In the illustrated case, the brace  31  is a sheet metal element with its cross-section shape and with its side profile formed in a stamping die or dies. The cross-section of the brace  31  is illustrated in  FIG. 4  and its side profile is illustrated in  FIG. 3 . By way of example, the brace  31  can be stamped of hot-dipped galvanized steel of 0.03 inch thickness. 
     With reference to  FIG. 3 , it will be seen that the brace  31  is an elongated body symmetrical about the center of its length. At the center of its length, the brace  31  has a generally rectangular cut out  32  with a central upwardly extending notch  33 . On a lower half, and preferably on a lower ⅓ of its height, the wall of the brace  31  has a step  34 , with a horizontal component, extending the full length of the brace. From the step  34 , the brace has a lower wall portion  36  that extends vertically downwardly, and an upper wall portion  37  that extends vertically upwardly. At an upper edge  38 , the upper wall portion  37  has an integral flange  39  bent obtusely so that it is inclined downwardly from its attachment with the wall proper. Preferably, the height of the brace  31  exceeds twice the height of the grid runners with which it is used. A pair of spaced holes  41  are provided on each half length of the brace  31 . One of the holes  41  is adjacent the cut out  32  and the other hole  41  is adjacent an end of the brace  31 . Notches  42  in the lower wall portion  36  from a lower edge  43  are spaced from the central cut out  32 . 
       FIGS. 3 and 4  illustrate the brace  31  installed on two end connected cross runners  12  on opposite sides of a main runner  11 . The lower wall portion  36  of the brace  31  fits closely in the pocket between the cross runner flange  17  and the cross runner reinforcing bulb  16  in both the cantilevered cross runner  12  and the runner  12  to which the cantilevered runner is connected. The lower edge  43  of the lower wall portion  36  rests on top of the flange  18  and an upper edge of the lower wall portion at the offset or step  34  contacts a lower face  44  of the reinforcing bulb  16 . Suitable fasteners such as self-drilling screws  46  are assembled through the holes  41  and are driven through the web  17  of the associated cross runner  12  to fix the brace  31  and cross runners  12  together. The vertical distance of the holes  41  above the lower edge  43  and adjacency to the step or offset  34  assures that the upper wall portion  37  will be drawn adjacent the reinforcing bulb  16  and the assembly of the brace  31  to the respective cross runner  12  will be rigid and stable. 
     As shown in  FIG. 3 , the cut out  32  is larger than the area occupied by the end connectors  26  so that regardless of the side of the cross runners  12  the brace  31  abuts interference with the connectors is avoided.  FIG. 3  also reveals that the notch  33  at the mid-length of the brace  31  avoids interference with a main runner  11  which provides the slot in which the cross runner end connectors  26  are joined. When the brace  31  is installed, its flange  39  is situated over the cross runner reinforcing bulb  16  and, preferably, does not extend laterally beyond the bulb more than the thickness of the brace material so that it does not interfere with placement or removal of a ceiling panel. 
     The brace  31  transfers the bending moment on a cantilevered cross runner  12  to the associated cross runner to which the cantilevered cross runner is connected. The associated cross runner, in turn, transfers this moment to the interior of the grid system  10  where it can be sustained. 
     The weight of the perimeter trim  21  supported on cross runners using the point of attachment of a nearby suspension wire  27  as a fulcrum may tend to lift an inboard portion of the ceiling system  10  where the ceiling grid can “hinge” at a joint between grid runner ends. To eliminate this hinge action, the brace  31  can be attached to the involved cross runners  12  in the manner described above. This is illustrated by the middle row of braces  31  in  FIG. 1 . 
     The notches  42  in the lower wall portion  36  can accommodate tile centering projections (not shown) on the web of the host grid runner  12 . 
     The disclosed brace  31  can be used in essentially the same manner as described above on main runners  11 . On shorter cross runners  12 , when the screws  46  are assembled in the holes  41 , the lower wall portion  36  is trapped snuggly in the pocket between the cross runner flange  18  and cross runner bulb  16  of the respective cross runners making a rigid assembly of the connected pair of cross runners and brace  31 . 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.