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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     The invention relates to suspended ceiling systems and, in particular, to components of such systems that facilitate access to the space above a ceiling. 
     PRIOR ART 
     U.S. Pat. No. 4,535,580 discloses a screw slot runner for a suspended ceiling grid and U.S. Pat. No. 4,696,142 discloses a snap-up panel useful with the screw slot style grid runner. U.S. Pat. No. 6,467,228 discloses edge configurations for snap-up panels that serve as hinges to enable the panels to be folded downwardly for access to the space or plenum above the ceiling while remaining supported on the grid. 
     Panels of the type disclosed in these referenced patents are typically made of metal or rigid plastic sheet stock. Besides affording a distinctive look, this type of panel is quite durable thus making it a good choice where access to the plenum is anticipated to be necessary, especially when it is expected to be relatively frequent. Where the grid spacing and panels are nominally 2′×2′ or other standard module size, it is difficult for a technician or tradesman to work or climb through the available opening of a single panel and grid module. Frequently, a grid runner will be damaged by a person operating or passing through the space of an open panel. The damage often is difficult to repair and persons unfamiliar with the nature of the grid connections in an attempt to remove a damaged grid runner can damage other runners to which it is connected, thus compounding the problem. 
     SUMMARY OF THE INVENTION 
     The invention provides a convenient, low skill level manner to afford a double size opening in snap-up panel suspended ceiling systems. The system utilizes a special grid cross runner at the location or locations in a ceiling where it is anticipated access will be required. The special runner can be used to replace an original runner anytime after the original ceiling construction is completed. 
     The specialized grid runner can take various forms, each preferably characterized by a locating feature capable of resisting both up and down forces to facilitate panel installation and removal and to contribute to support an adjustment of a pair of adjacent panels. In alternative embodiments of the invention, the snap-up panels are provided with unique edge formations that provide a faux slot and eliminate the need for a special removable grid runner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a somewhat schematic elevational view of a suspended ceiling system incorporating the invention; 
         FIG. 2  is a fragmentary perspective view of a first form of a specialized cross runner of the invention; 
         FIG. 2A  is a side elevational view of one end of the cross runner of  FIG. 2 ; 
         FIG. 3  is a fragmentary perspective view of a second form of a specialized cross runner; 
         FIG. 3A  is a side elevational view of one end of the cross runner of  FIG. 3 ; 
         FIG. 4  is a fragmentary perspective view of a third form of a specialized cross runner; 
         FIG. 4A  is a side elevational view of one of the cross runner of  FIG. 4 ; 
         FIG. 5  is a somewhat schematic fragmentary plan view of a suspended ceiling system with snap-up panels having asymmetric edges; 
         FIG. 6  is a schematic cross-sectional elevational view of the suspended ceiling system of  FIG. 5  taken in the plane  6 - 6  in  FIG. 5 ; and 
         FIG. 7  is a fragmentary isometric view of a ceiling panel used in the embodiment of  FIGS. 5 and 6 ; and 
         FIG. 8  is a fragmentary isometric view of a ceiling panel in accordance with a further embodiment of the invention; and 
         FIG. 9  is a fragmentary elevational view of a suspended ceiling employing the panel of  FIG. 8 . 
     
    
    
     In various figures, the cross-sectional size of the runners and edge detail of the panels is exaggerated for visual clarity. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIGS. 1 ,  2  and  2 A, there is shown a portion of a suspended ceiling grid system  10 . The system  10  includes main runners  11 , cross runners  12 , and hinge snap-up panels  13 . The aforementioned U.S. Pat. Nos. 4,535,580, 4,696,142, and 6,467,228, incorporated herein by reference, disclose various details and aspects of these components. A common manner of constructing a ceiling grid is to use main tees or runners  11 , typically 10′ or 12′ long and joined end-to-end. The main tees  11  are suspended, from overhead superstructure by wires for example, so that they are parallel to one another and are spaced on 4′ centers. Dimensions given herein can have metric equivalents depending on the country of origin or use. Nominal 4′ long cross runners  12  are assembled in regularly spaced main runner slots. Typically, the 4′ cross runners will be spaced on 2′ centers. Extending between the 4′ long grid runners  12  are nominally 2′ long cross runners at least some of which are of the types disclosed hereinafter. 
     The suspended grid described immediately above is characterized by modular panel spaces of nominal 2′×2′ dimension, i.e. their dimensions in the plane of the ceiling. It will be understood that the invention can be used with other standard module sizes. 
     The standard runners  11 ,  12  with which the specialized cross runners of the invention to be described are employed, have a central slot or opening  15  on their lower faces formed by opposed C-shaped flanges  16 , each terminating at an edge  17 . 
     The rectangular panels  13 , preferably made of sheet material such as aluminum or other metal or rigid plastic such as polycarbonate, are pan shaped with vertical sidewalls  18  on their four sides or edges. One sidewall  19  can be incorporated that has an in-turned flange  21  that develops a hinge function explained below. The three other sidewalls  18  have inwardly projecting detent surfaces  22  that releasably catch on the associated edge  17  of a slot or opening  15  of an overlying grid runner  11 ,  12  or  26 . 
     At strategic locations in the expanse of a suspended ceiling or, if necessary or desirable, generally throughout the ceiling expanse, a pair of hinged snap-up panels  13  can be assembled on the ceiling grid with their relative orientations illustrated in  FIG. 1 . Where the hinged snap-up panels  13  are not expected to be required, more standard snap-up panels can be used where the panel sidewalls on all four edges of the panel are like the sidewalls  18  illustrated in  FIG. 1 . The hinge sides  19  of each pair of panels  13  are arranged remote and parallel to one another. The panel sides  18  opposite the respective hinge flanges  21  are adjacent one another and commonly share a cross-runner embodying principles of the invention. 
     The various specialized cross-runners disclosed herein can have a nominal length of 2′, but other nominal dimensions are contemplated. Referring to a specialized cross runner  26  depicted in  FIGS. 1 ,  2  and  2 A, the removable cross runner has a U-shaped cross-section. In its installed orientation, the runner  26  has an upper horizontal web  27 , parallel spaced vertical sidewalls  28  depending from the web, and in-turned narrow flanges or lips  29  at the lower or distal edges of each sidewall. Preferably, the geometry of the flanges  29  simulates that of the C-shaped flanges  16  forming the slot  15  of the runners  11 ,  12 . Both ends of the cross runner  26  are modified from a plain C-shaped channel to create pairs of connectors  31  that include tabs  30  proportioned to index into holes or openings  33  in the web of the transverse runners  11 ,  12 . The connectors can be fashioned from the original sidewalls of the channel stock from which the runner  26  is made. The connectors  31  are proportioned to closely fit between upper reinforcing bulbs  32  of the main or cross runners  11 ,  12  and their lower C-shaped flange  16  so that 
     the flanges or lips  29  lie in the same plane as the lower part of the C-shaped flange  16  of the runners  11 ,  12 . In assembled position, the connectors  31 , being restrained by the bulb  32  and flange  16  of the runners  12 , vertically index the cross runner  26  and prevent it from moving significantly vertically upwardly or downwardly. 
     The cross runner  26  functions in the same manner as a conventional slot style runner  11 ,  12  in vertically supporting and horizontally constraining the flange or sidewall  18  of a panel  13 . The detent surface  22  in the form of a re-entrant rib or other element snaps over the lip  29  so as to allow the lip to vertically support the panel  13 . The vertical force required to snap the detent  22  over the lip  29  is sustained by the connectors  31  bearing against the reinforcing bulb  32  of the transverse runner  12 . When the second of the pair of panels  13  sharing the cross runner  26  is snapped in place, the pair of panels  13  will be properly horizontally located. 
     By snapping the pair of panels  13  down so that they swing about their respective hinge-like flanges  21 , access to the plenum above the ceiling  10  is provided. The cross runner  26  can be removed by rotating it slightly about a vertical axis so that an end connector  31  is free of vertical constraint of one of the bulbs  32  of the transverse runner  12  thereby permitting the runner to be lifted or lowered out of the ceiling area. Alternatively, the runner  26  can be slid horizontally towards one of the hinged sides of one of the panels  13 . Removal or re-positioning of the cross runner  26  essentially doubles the size of an access opening from what would be available when a cross runner is left in place. Thus, when the panels are nominally 2′×2′, a nominal 2′×4′ opening is available. This larger opening can make it much easier for a person to work or pass through the opening in the grid. 
     Referring to  FIGS. 3 and 3A , another form of a removable cross runner  36  is illustrated. In the various figures, parts that have the same or comparable features or functions are identified by the same numeral as a general rule. The cross runner  36  has the cross-section of a conventional slot-style runner including lips  37  defining a slot  38 . The cross runner  36  has a length suitable to fit between a pair of transverse runners spaced 2′ apart or some other specified nominal distance. An end connector  39  is formed on a web  40  of the cross runner  36  at each of its ends. The end connector  39  includes a first section  41  proportioned to fit closely vertically between the top of the flange  16  and the underside of the bulb  32  of a transverse runner  12  and a second section  42  proportioned to fit in the conventional connector receiving slot  43  in the web of the transverse runner. The length of the connector second section  42 , in the longitudinal direction of the runner  36 , projecting from the first section  41  is small, preferably being about 0.3 inch, for example. While in the illustrated form, the end connector  39  is formed of the same sheet metal stock as the cross runner  36 , it will be understood that the end connector can be fabricated from a separate piece of metal and permanently rigidly affixed to the respective end of the cross runner. 
     The cross runner  36  is installed by assembling the second section  42  at each end in the corresponding connector slot or opening  43 . The connector first section  41  is proportioned to fit between the flange  16  and bulb  32  of the transverse runner  11 . The panels  13  work with the cross runner  36  in essentially the same manner as that described with the cross runner  26  of  FIGS. 2 and 2A . When the panels  13  are lowered about their hinge sides  19 , the cross runner  36  can be removed. To enable such removal, a transverse runner  12  at one end of the cross runner is rotated about a horizontal axis so that the bulb  32  is forced away from the cross runner and the second connector section  42  is released from the slot  43 . At this point, the cross runner can be rotated about a vertical axis or lifted out of position and thereby removed. After the cross runner  36  has been removed access to the plenum has been facilitated. The cross runner  36  can be re-installed by reversing the described removal process and the panels can be raised back into their installed positions. 
       FIGS. 4 and 4A  illustrate modified cross runner  46  having a cross-section like that of the regular slot style grid runner. A retractable connector or clip  47  is disposed on at least one end of the cross runner  46 . The connector  47  is captured on a rivet or pin  48  permanently attached to the web of the cross runner  46  and disposed in a slot  49  formed in the connector. The slot  49  enables the connector  47  to be moved longitudinally of the cross runner  46  a limited distance. A finger grip  51  formed as a part of the connector  47  facilitates this action. A forward end section  52  of the connector  47  is proportioned to fit in the connector slot  43  to index the cross runner  46  to a proper center. The forward end section  52  is proportioned to vertically index the cross runner  46  to the transverse runner  12  by fitting closely with the slot  43 . 
     Of the various versions of the removable cross runner, the unit illustrated in  FIGS. 4 and 4A  is expected to be the most intuitive for those persons unfamiliar with a ceiling system. 
     Referring to  FIGS. 5-7  a pair of panels  56  are installed on a grid of runners which are diagrammatically shown as main runners  11  and cross runners  12  of the slot type. The panels  56  are asymmetrical by virtue of having a sidewall  59  with an integral inverted channel  61  extending along substantially half of the length of the sidewall. The sidewalls  18  along the other edges of the panel  56  are of a standard shape having longitudinally extending detent ribs  22  or hinge side  19 . The panels  56  compliment one another when arranged side-by-side and one is orientated a half turn about a vertical axis relative to the other. In this orientation, the half length channels  61  are additive and extend completely along the joint line formed between the panels  56 . 
     As depicted in  FIG. 6 , the channel  61  is proportioned so that when two panels are inter-engaged, the apparent space, designated  64 , between the panels when viewed from below, is the same as a gap between two panels with standard sidewall configurations. The side of the channel  61  remote from its associated panel  56  has an in-turned lip  67  that serves the function of a lip or edge  17  of a standard grid runner  11 ,  12 . 
       FIG. 8  illustrates still another embodiment of the invention in the form of a modified snap-up panel  71 . The panel  71  like the other panels described herein is nominally a 2′×2′ unit having the characteristic pan shape of a snap-up panel. The panel  71  includes three sidewalls  18 ,  19  with the sidewall  19  having a hinge functioning flange  21 . 
       FIG. 9  is a schematic elevational fragmentary view of a ceiling system utilizing the panel of  FIG. 8 . One sidewall  72  of the panel  71  has an inverted channel  73  extending across substantially its full length. The illustrated channel  73  is integral with the remainder of the sidewall  72  and is located on a side  74  remote from the hinge flange  21 . The channel  73 , at an outer wall  75 , has an in-turned flange  76  that mimics the function of the lip or edge  17  of a standard runner. Similar to the panel  56  and associated inverted channel  61 , the panel  71  and its inverted channel  73  are proportioned to produce a space  77  between the panel edge and adjacent panel  13  that when viewed from below has the same width as a gap between two other panels  13  of standard or hinge design. 
     Regarding the arrangement of  FIGS. 5-7 , the panels  56  can be hinged downwardly or removed to provide an opening of roughly 2′×4′. Regarding the arrangement of  FIGS. 8 and 9 , when the specialized panel  71  and a mating hinged panel  13  are swung downwardly about their respective hinge functioning flanges  21 , an opening of about 2′×4′ is made available. It will be understood that in all of the embodiments of the invention, the panels surrounding the pairs of displaced panels can remain in place and are not required to be removed to release one of the disclosed removable cross runners. This includes those panels adjacent the ends of the removable cross runners; this is true even in the case of the embodiment of  FIGS. 3 and 3A  because the deflection of the intersection runner  12  required for removal of the cross runner  36  is minimal. 
     While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.

Summary:
A suspended ceiling comprising a grid formed of intersecting grid runners and snap-up panels supported on the grid runners, the grid runners dividing a ceiling area into standard modules, the pans being formed of sheet material and each having its sides sized to cover the module size while leaving a space at visible faces thereof between adjacent panels when in an installed position on the grid, at least one adjacent pair of panels being displaceable from their installed positions, the gap between a pair of displaceable panels being closed by a removable runner or the displaceable panels so that when the displaceable panels are displaced from their installed position and any removable runner is removed, an access opening of twice the standard module is made available for accessing the area above the ceiling while adjacent panels at longitudinal ends of the gap between the displaceable panels can remain in respective installed positions.