An elongated stabilizer bar for maintaining a pair of grid runners in parallel upright positions to support a panel on respective grid runner support surfaces, the stabilizer bar having a horizontal leg and a vertical leg, the horizontal leg having self-penetrating tabs arranged to pierce and thereby grip a core of the panel to fix the stabilizer bar to the panel, a vertical leg having a vertical slot at each end, the slot having an open bottom, the slot having a horizontal width adapted to receive and confine an upper reinforcing bulb of a respective one of the pair of grid runners to thereby restrain the respective grid runner against excessive bowing and twisting deflection.

BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to suspended ceiling construction and, in particular, to a device for stabilizing relatively long grid openings. 
       PRIOR ART 
       [0002]    Suspended ceiling grid design has evolved to arrangements where the grid modules or openings are commonly 2 foot by 4 foot or 2 foot by 2 foot (or metric equivalents). Accordingly, the grid members are designed with a geometry and material content to withstand the forces present in these now common grid module sizes. 
         [0003]    In recent times, there has developed a demand for larger panels than these common sizes. This presents a problem because the grid elements, typically tees, can bend and/or twist under the panel weight or other imposed loading. Deflection of a grid element for a given force is exponential with its unrestrained length and twisting is proportional to its length. It follows that a grid element having a standard construction but with an unusually long unrestrained length, can deflect and/or twist beyond normal limits. When a grid element deflects from its intended position, the associated edge of a panel can slip off the element. This results in an unsightly appearance or, worse, the panel can fall off the grid. 
         [0004]    Stabilizer bars have been available to maintain a pair of grid elements in their desired positions. An example of a prior art stabilizer bar is disclosed in U.S. Pat. No. 4,064,671. A typical prior art stabilizer bar in a completed ceiling installation cannot be ordinarily relocated to a functional position after an underlying panel has been raised to gain access to the plenum above the ceiling. There is no practical way of reinstalling stabilizer bars where the adjacent panels on both sides of the removed panel are in place. Accordingly, there has existed a need for a stabilizer bar arrangement that can be reinstalled after the panel beneath it is raised for access and then reset in a ceiling grid module. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides a stabilizer bar for a suspended ceiling grid that is reinstallable after its removal for access to the plenum above the ceiling. The stabilizer bar, in accordance with the invention, is rigidly affixed to the rear side of the ceiling panel and is arranged to engage a pair of parallel spaced grid runners when the panel is lowered into place. 
         [0006]    A hook structure at each end of the stabilizer bar is proportioned to laterally restrain an associated grid member. The hook structure engages opposite sides of a reinforcing bulb of a respective grid runner. As a result, the respective grid runner is restrained from excessive bowing and/or tilting which could otherwise result with an edge of an associated panel free to sag or drop from the grid. 
         [0007]    In the disclosed embodiment, the stabilizer bar is provided with integral tabs for penetrating and locking onto the body or core of an associated acoustical panel. Alternatively, the stabilizer bar has provisions for being fixed with screws or like fasteners to a wood or other dense composite panel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an isometric view of a stabilizer bar constructed in accordance with the invention; 
           [0009]      FIG. 2  is a plan view of a blank or stamping from which the stabilizer bar of  FIG. 1  is formed; 
           [0010]      FIG. 3  is an end view of the stabilizer bar; 
           [0011]      FIG. 4  is a fragmentary isometric view of the stabilizer bar showing the deployed positions of a stab tab, a capture tab, and a folded bulb hook; 
           [0012]      FIG. 5  is an elevational view of the stabilizer bar fixed as an assembly on a ceiling panel with the assembly installed on a pair of parallel grid runners; and 
           [0013]      FIG. 6  is a fragmentary isometric view of the stabilizer bar modified and fixed on a high density panel. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    A stabilizer bar  10  shown in  FIG. 1  is an elongated sheet metal body formed with a right angle cross-section. The stabilizer bar  10  can be made of a suitable malleable metal such as, for example, 21 gauge hot dipped galvanized steel. The stabilizer bar, for example, can have nominal lengths of 24 inches, 30 inches, and 48 inches or metric industry substitutes for these dimensions depending on the application. The stabilizer bar  10  is symmetrical about its mid-length. The stabilizer bar  10  includes a horizontal leg  11  and a vertical leg  12 , both of which are generally planar allowing a plurality of stabilizer bars to be nested for shipping purposes. The horizontal leg  11  has a pair of integral stab tabs  16  stamped or otherwise cut into its body at locations spaced from the leg ends along a free or distal longitudinal edge  17 . With particular reference to  FIG. 2 , showing the profile of the legs  11  and  12 , the tabs  16  are somewhat pointed adjacent the line of the distal edge  17 . A hole  18  in the leg  11  at the base of a tab  16  leaves two land areas  19  connecting the tab to the leg proper. The hole  18  forms a line of weakness  21  parallel to the length of the stabilizer bar  10 . At each end of the stabilizer bar  10 , the horizontal leg  11  is formed with an integral capture tab  23 . Preferably, the capture tab  23 , in the form of the stabilizer bar as it is shipped from the manufacturing site, has a proximal portion  24  in the plane of the horizontal leg  11  and a distal depending portion  25  in a plane at right angles to the plane of the horizontal leg. The distal portion  25  is in the form of a pair of truncated or blunted triangular barbs  26 . 
         [0015]    A through slot  27  transverse to the length of the stabilizer bar  10  leaves a pair of spaced lands  28  joining the capture tab  23  to the horizontal leg proper and forms a transverse line of weakness  29  between the horizontal leg proper and the capture tab  23 . A plurality of through holes  32  are spaced along the length of the horizontal leg, preferably midway between the edge  17  and the vertical leg  12 . 
         [0016]    As shown in  FIG. 3 , the vertical leg  11  is stiffened at its upper edge by an integral offset formed by an oblique narrow band  33  and a vertical distal strip  34 . Each end of the vertical leg  12  includes a vertical slot  37  open at the bottom and forming an integral vertical depending hook  38 . A free end of the hook  38  has a beveled edge  39  leading to the slot  37 . A juncture of the hook  38  with the vertical leg proper is interrupted by a small through vertical slot  41  that leaves a pair of land areas  42  and forming a vertical line of weakness  43  in the juncture. 
         [0017]    The selected length of the stabilizer bar will correspond to the nominal spacing of a pair of main tees on which the stabilizer bar  10  is ultimately mounted. One or two stabilizer bars  10  can be used on a ceiling panel, depending on the length of the panel. Ordinarily, where one is used, it is located at mid-length of the panel; when two are used on longer panels, they are located from an end of the panel at ⅓ and ⅔ of the panel length. 
         [0018]    The stabilizer bar  10  can be fixed on the back side of an acoustical ceiling panel or tile of a low density type using the integral tabs  16  and  23 . The final position of a stabilizer bar on a panel is illustrated in  FIG. 3 , but their mutual assembly is accomplished before they are mounted on the ceiling grid. First, the stab tabs  16  are manually bent down 90 degrees to a vertical orientation, typically by the person installing a ceiling panel  44 . The land areas  19  bend at the line of weakness  21 . Thereafter, the stabilizer bar  10  is laterally symmetrically located on the panel  44  so that the slots  37  are both outward of long edges  46  of the panel  44  as shown in  FIG. 5 . Then, the stabilizer bar  10  is pressed downward to drive the stab tabs  16  into the core of the panel  44  until the lower face of the horizontal leg  11  abuts the backside of the panel  44 . Next, the capture tabs  23  are deployed by bending them so that the barbs  26  are driven into the vertical surfaces  46  of the respective edges of the panel  44 . The capture tab  23  hinges about the line  29  so that the proximal part  24  of the tab  23  can be folded tightly against the edge surface  46  while the barbs  26  are driven with a horizontal movement component into the core of the panel  44 . 
         [0019]    With the stab tabs  16  and capture tabs  23  deployed as described, the stabilizer bar  10  is fixed on the panel  44 . The assembly of the panel  44  and stabilizer bar  10  or stabilizer bars is ordinarily installed on a grid by first manipulating the assembly through a grid opening from below much the same way an ordinary panel without a stabilizer bar is manipulated. The suspended ceiling grid is represented by a pair of parallel spaced grid runners or tees  51  illustrated in  FIG. 5 . The grid runners  51  are spaced in parallel relation at, typically, the nominal dimensions recited above in the description of normally available stabilizer bars  10 . The panel and stabilizer bar assembly is aligned so that it overlies a grid module and is then lowered into place. 
         [0020]    The beveled edges  39  on the hooks  38  afford a centering action to bring the panel and stabilizer bar assembly into lateral registration with the grid tees  51 . As the assembly is lowered, reinforcing bulbs  52  of the grid runners  51  enter respective slots  37  in the stabilizer bar vertical leg  12 . The width of a slot  37  is dimensioned with a moderately loose fit relative to the width of a reinforcing bulb  52  to allow the bulb to freely slide into the slot but to not allow appreciable lateral movement of the bulb. The vertical dimension of the slot  37  is large in comparison to the height of the bulb  52 , in a normal range of panel thickness, so that a clearance will exist between the stabilizer bar and the top of the bulb. The hook  38  can be manually bent towards the associated bulb  52  at the line  43  to reduce interference with installation or removal of a panel in the adjacent grid module. 
         [0021]    With the panel  44  resting on flanges  53  of the grid runners  51 , the reinforcing bulbs  52  are constrained in both lateral directions by the sides of the respective slots  37 . Consequently, the grid runners  51  are restrained from significant lateral bowing and/or twisting about their longitudinal axii. Therefore, the risk that the edge of a panel  44  can slip off a flange  53 , deflected by the weight of a long panel or other force, is greatly reduced, if not eliminated. 
         [0022]    The inventive stabilizer bar has the advantage of allowing the panel  44  to which it is fixed to be lifted for access to the plenum above the grid and permits it to be reinstalled in the same manner as it was initially installed. 
         [0023]    The stabilizer bar can be modified by the technician installing it for use with wood or other dense core panels or tiles. A small reference notch  56  exists in the horizontal leg edge  17  adjacent each end of the leg  11 . A diagonal cut with a tin snips or the like is made from the notch  56  to the end of the horizontal leg  11  to sever the capture tab  23  from the stabilizer bar. The stab tabs  16  are not bent out of the plane of the horizontal leg  11 . As illustrated in  FIG. 6 , the stabilizer bar  10  is located on the back of a dense panel substantially as described above. Short screws  57  are assembled in the holes  32  and driven into the panel core to fix the modified stabilizer bar to the panel. 
         [0024]    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.