Abstract:
A roll formed sheet metal grid runner, and method of its manufacture, for a suspended ceiling grid having indexing tabs stamped from a central web of the runner profile, the tabs being effective to reliably locate ceiling panels and, when the grid runner is nested with other identical runners in a package, avoid marring of visible surfaces.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to suspended ceilings and, in particular, to improvements in grid runners. 
     PRIOR ART 
     Suspended ceiling grid runners are manufactured in a variety of cross sections to serve different functions and/or afford different appearances. Packaging of these grid runners for distribution may involve nesting them side-by-side with alternate runners being inverted. Such arrangements can minimize the size of a box in which the runners are packaged and the space taken up during transport and storage of the runners. While space may be conserved with a nested group of runners, the geometry of the runner cross section may allow the runner elements, visible in a finished installation, to be marred. Vibration during shipping and/or handling can cause parts of adjacent runners to mar the visible areas of a runner. 
     U.S. Pat. No. 4,679,375 shows a grid tee formed with tabs stamped out of a web. The tabs are intended to center tiles or panels in the grid spaces. The tabs reduce the risk that a panel can shift in the suspended grid space and slip off a flange. These prior art tabs, however, may be ineffective to restrain and center relatively thin panels of sheet metal or plastic. 
     SUMMARY OF THE INVENTION 
     The invention relates to a grid runner with an improved indexing tab construction. The inventive indexing tabs stamped from a central web of the grid runners, can protect nested grid runners from damage in transit. Once the grid runners are installed, the tabs, additionally, can restrain and center even relatively thin ceiling tiles in the grid spaces. 
     The indexing tab is especially adapted to be incorporated into a double reveal type grid runner. This runner type has a stepped flange which can be especially susceptible to marring when it is compactly nested in a package or box. 
     The indexing tab can be more readily implemented in certain types of grid runner constructions where the grid profile is made in two separate roll forming operations and when stamping is performed between these roll forming operations. In such runner constructions, the sheet metal area adjacent the lower margins of the web may not be folded in a preform state so that there is clearance for tooling to conventionally stamp the tabs at a level of the eventual flange. Locating the tabs at the flange level ensures that even thin panels can be restrained in the center of a grid space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a grid runner preform prior to final roll forming; 
         FIG. 2  is a fragmentary side elevational view of the grid runner preform of  FIG. 1 ; 
         FIG. 3  is a sectional view of the grid runner preform taken in the plane of the lines  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a finish rolled grid runner made in accordance with the invention; 
         FIG. 5  is a fragmentary side elevational view of the grid runner of  FIG. 4 ; 
         FIG. 6  is a diagrammatic end view of a package of grid runners in accordance with the invention; and 
         FIG. 7  is an enlarged fragmentary view of the package shown in  FIG. 6 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 4 and 5  illustrate an elongated grid runner  10  used to form a grid for a suspended ceiling. The illustrated grid runner  10  is of a style sometimes referred to as a double reveal profile. The profile is characterized with a two-level flange  11 . A central portion  12  of the flange  11  is dropped below laterally outward portions  13  of the flange. The grid runner also includes a central vertically extending web  14  above the flange  11  and a hollow reinforcing bulb  16  at the top of the web. In the illustrated case, the grid runner  10  is made of two roll formed sheet metal, typically steel, strips. A main body strip  17  forms an upper part of the flange  11 , the double walls of the web  14  and the reinforcing bulb  16 . A face sheet  18 , typically of lighter gauge than the main body strip  17 , forms the appearance or face side of the flange  11 . The face strip is retained on the main body strip by marginal longitudinally extending areas  19  folded over longitudinal edges of the main body strip  17  in the manner of a hem. The outer side of the face strip  18  can be pre-painted as is customary. 
     The grid runner  10 , as is conventional, can be provided as main runners and cross runners to form a rectangular grid that is suspended by wires. The flanges  11  serve to support ceiling tiles or panels in the grid spaces made by parallel and intersecting grid runners. The panels or tiles are typically carried on the upper sides of the laterally outward portions  13  of the flanges  11 . 
     In the illustrated case, the central flange portion  12  is somewhat narrower than the reinforcing bulb  16 . The illustrated grid runner  10  can be roll formed in two stages through a primary roll set and a secondary roll set. 
     When the strips  17 ,  18  exit the first roll set, they make up a grid runner preform  20  shown in  FIGS. 1 and 2 . The preform  20  has a generally conventional grid tee shape although the web  14  has a greater height than is normal. In the preform state, the material ultimately forming the two level flange  11  extends in a flat plane, apart from the marginal hem areas  19 , perpendicular to the web  14 . The grid runner preform  20  is received in a press where various details, including cross tee slots and end connectors are formed or, in the illustrated case, end connector pockets are formed for receiving end connectors. In this intermediate press station, indexing tabs  26  are stamped out of the web  14  by combination punch and die sets diagrammatically illustrated at  27 . The indexing tabs  26  are formed on both sides of the web  14 . Each tab  26  has a generally flat face  28  parallel to the web  14  and a free edge having sections  31 ,  32  generally lying in planes perpendicular to the web and to each other. The punch and die sets  27  on opposite sides of the preform  20  are complimentary to each such that the punch of one unit works with the die of the other and vice versa to form a pair of adjacent tabs during a stroke of the press. Alternatively, a simple die punch set can be used to form a single tab at a particular location along the length of the preform  20 . The material remaining at the web  14  where the cut edges  31 ,  32  are severed from the web proper are ordinarily supported by a die surface on the side of the web to which a tab is displaced. The spacing of the tab faces  28  from the web  14  or center of the finished grid runner  10  is selected to position a ceiling panel or tile in the center of a grid space. The tabs  26  whether in pairs on opposite sides of the web  14  or standing alone are made adjacent each end of the grid runner  10 . Additionally, main runners and long cross runners are formed with additional tabs on each side of the web along their lengths. 
     After the grid runner preform has been stamped with the tabs  26  and other features, it is passed through a secondary roll set. In this subsequent roll forming step, the flange  11  is finally shaped to the stepped configuration illustrated in  FIG. 4 .  FIGS. 4 and 7  illustrate that the tabs  26  extend vertically upwardly from the level of the outer flange portions  13 . More precisely, the lower edge  31  of a tab  26  is preferably less than about 0.010 in. above the upper surface of a hem  19  and can be at or below this surface. With this geometry, the tabs  26  can center ceiling panels of relatively thin gauge, e.g. 0.020 in. thick, without the risk that the panels can slip under the tabs and not be centered. 
     It is customary to nest grid runners side-by-side or laterally to minimize the size of a quantity of grid runners in a package for shipping and storage purposes.  FIGS. 6 and 7  illustrate a packaging arrangement for a number of grid runners  10  received in a box  36 , typically a cardboard container. It will be seen that alternate grid runners  10  are arranged with their adjacent upper flange portions  13  overlapped. Intervening grid runners  10  are inverted and their adjacent upper flange portions  13  are similarly overlapped. The tabs  26  of each grid runner abut the reinforcing bulbs  16  of adjacent grid runners. The tabs  26  are advantageously proportioned so that their width or lateral offset, measured from the center of the web  14 , combined with the width of a reinforcing bulb  16  is greater than the width of a flange  11  across its distal edges plus the width of the dropped central or mid-portion  12  of the flange. The foregoing described tab geometry prevents the distal flange edges, designated  34  of either alternate or intervening grid runners from contact with the dropped central flange portions  12  of adjacent runners. This situation is illustrated in  FIG. 7 . Contact of these elements during package handling and shipping could result in abrasion and marring of the visible surfaces of the drop central flange portion  12 . 
     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.