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BACKGROUND OF THE INVENTION 
     This invention relates generally to suspended ceiling systems and more particularly to a novel and improved system using ceiling panels that include a hinge allowing the ceiling panel to pivot downward so access to the area above the suspended ceiling system can obtained. 
     PRIOR ART 
     Suspended-ceiling systems typically include grid members that provide for oppositely extending ceiling panel support flanges. In these systems, the edges of the ceiling panels are installed by laying them in the panel opening created by the grid members. There are also suspended-ceiling systems that have grid members, which include channels designed to grip the vertically extending edges of metal ceiling panels. These ceiling panels are typically installed by snapping the flanges up into the grid member channel, and are generally referred to as “snap-up ceiling panels.” To access the area above the suspended-ceiling systems, the ceiling panels need to be completely removed from the grid and placed upon the floor or leaned against a wall where damage to the panel can result. The need to completely remove and install the panel each time access is needed above the grid system can be cumbersome and difficulty may arise when trying to realign the panel during installation especially for large 4 foot×4 foot panels. Prior art devices do not provide for a pan-style panel that allows easy access to the area directly above the suspension-ceiling system. 
     SUMMARY OF THE INVENTION 
     This invention may be described as a novel and improved suspension ceiling panel that includes a modified edge that acts similar to a hinge so that the panel can be pivoted downward allowing access to the area above the suspended ceiling. Once the panel is pivoted to the open position, the panel can be allowed to hang, supported by the hinge. The hinged ceiling panel is fabricated out of a single piece of metal, and does not require the use of fasteners for installation. The ceiling panel is formed of sheet metal having a planar surface surrounded by upwardly extending support flanges on three edges. The first edge of the ceiling panel includes an L-shaped hinge. Horizontal ribbing is formed in the upwardly extending support flanges to create a detent that snaps into the assembled grid to secure the panels. The ceiling panel is installed by inserting the L-shaped hinge into the channel at the bottom of the assembled grid first. Once the L-shaped hinge is properly in position, the panel can be pivoted upwardly so that the three support flanges can be snapped in to the channel in the grid. 
     The panels are formed by die-cutting a piece of sheet metal, which is relatively planar, into the correct size for the ceiling grid opening. While the panel is being cut, detents are simultaneously being formed on three of the edges of the panel. After the panel has been die cut, the three edges are die-bent upward to form the required flanges. The fourth edge is die-bent upward and inward to form the L-shaped hinge. 
    
    
     These and other aspects of this invention are illustrated in the accompanying drawings, and are more fully described in the following specification. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a hinged metal ceiling panel of the present invention attached to a ceiling grid system and hinged in the open position; 
     FIG. 2 is a cross section of FIG. 1 illustrating a hinge from one panel and a flange from another panel positioned within a channel of a grid member; 
     FIG. 3 is a cross section illustrating a hinge from one panel positioned within a channel of a grid member and a flange from another panel outside of the channel prior to installation; 
     FIG. 4 is a cross section illustrating a flange from one panel positioned within a channel of a grid member and a hinge from another panel outside of the channel in the proper position for installation; 
     FIG. 5 is a cross section a hinged panel using ghost lines to illustrate the movement of the hinge during the closing of the panel; 
     FIG. 6 is a cross section of FIG. 1 illustrating a hinged ceiling panel spanning from one grid member to another grid member using ghost lines to illustrate the panel in the open position. The panel is attached to the first grid member by use of a first flange and attached to the second grid member by use of a hinge; and 
     FIG. 7 is a cross section of FIG. 1 illustrating a hinged ceiling panel spanning from one grid member to another grid member with a second and a third flanges inserted into the grid channels. 
     FIG. 8 is a cross section of an alternative embodiment of a hinged panel. 
     FIG. 9 is a cross section of an alternative embodiment of a hinged panel. 
     FIG. 10 is a cross section of an alternative embodiment of a hinged panel. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention will be described fully hereinafter with reference to the accompanying drawings, in which a particular embodiment is shown, it is understood at the outset that persons skilled in the art may modify the invention herein described while still achieving the desired result of this invention. Accordingly, the description which follows is to be understood as a broad informative disclosure directed to persons skilled in the appropriate arts and not as limitations of the present invention. 
     FIG. 1 illustrates a portion of an assembled suspension ceiling incorporating hinged snap-up ceiling panels  10  in accordance with the present invention. In such a ceiling panel system, grid members  12  are interconnected to form a grid structure  13 . The grid members  12  are arranged to form openings  14  sized to receive the ceiling panels  10 . The grid members  12  are suspended from the building structure by wire hangers  16  or other supporting structures. 
     To create the grid structure  13 , a row of parallel evenly spaced grid members  12  are suspended by wire hangers  16 . Each row of the grid members  12  are spaced apart to accommodate the size of the hinged ceiling panels  10 . To accommodate a 4 foot by 4 foot ceiling panel, the grid members  12  would be spaced apart 4 feet on-center. The grid structure  13  also includes a second set of grid members  18  that are perpendicularly oriented in relation to the first set of grid members  12  to create the opening required for hanging the panels  10 . 
     The hinged snap-up ceiling panels  10  are normally rectangular, usually square in shape, and are typically made out of metal. Depending upon the ceiling design used, it may be desirable to shape the panels  10  into a rectangular shape but other shapes may be utilized. The hinged ceiling panels  10  include a bottom surface  20  and a top surface  22 . The panels  10  also include a hinge  24  along a first edge  25  and three flanges  26 ,  28  and  30  along second, third and fourth edges  27 ,  29 ,  31 . The hinged snap-up ceiling panel  10 , as shown in FIG. 1, is shown pivotally connected to the grid structure  13  by the hinge  24  creating an axis of rotation. When the ceiling panel  10  is pivoted to the open position, the weight of the ceiling panel  10  is completely supported by the interaction between the grid member  12  and the hinge  24 . Ghost lines  15  show the ceiling panel  10  transitioning from an open position to a closed position. It is beneficial to have the hinge  24  support the ceiling panel  10  because when all metal ceiling panels become as large as 4 feet by 4 feet, they become awkward to install and remove due to their relatively large size and weight. When working with a piece of sheet metal with such a large surface, any improper handling will result in damage to the overall finish of the ceiling panel  10 . Also, by using the hinge  24  that spans the length of the ceiling panel  10 , the weight of the panel is evenly distributed across the entire edge  24  of the panel  10 , preventing rippling that would be apparent in the bottom surface  20  of the panel  10 . Furthermore, once the ceiling panel  10  is connected to the grid members  12 , the ceiling panel  10  will automatically be in alignment to allow for easy closure by pivoting the ceiling panel  10  upward and snapping in the three other flanges  26 ,  28  and  30 . 
     FIG. 2 is a cross section of FIG. 1 taken along line  2 — 2  looking in the direction of the arrows and shows the grid member  12  and the hinge  24  along the first edge  25  of a first ceiling panel  10  and the flanged edge  26  of a second ceiling panel  10 . The grid member  12  is fabricated out of a single piece of die-formed sheet metal. The grid member  12  after fabrication includes a bulb portion  34 , a channel  36  and a double layer bridge portion  38  that connects the bulb portion  34  and the channel  36 . The overall shape of the grid member  12  is to give the member  12  strength to prevent flexing. Typically, apertures (not shown) are placed along the length of the bridge portion  38  so that wire hangers  16  can be threaded through and wrapped around the bulb portion  34 . Once the wire hanger  16 , as shown in FIG. 1, which can be in the form of a wire, is threaded through an aperture (not shown) and around the bulb portion  34 , the wire hanger  16  is wrapped around itself several times to prevent it from unraveling. The bridge portion  38  typically includes slots (not shown) that allow one grid member  12  to be connected to the second grid member  18  to form the grid structure  13 . The channel  36 , as shown in FIG. 2 is formed by bending the double layers of the bridge portion  38 , 90 degrees outward, 90 degrees downward and 90 degrees inward to form a boxed channel  36 . Bottom edges  42  are folded over to act as a detent surface for the flange  26  and a retaining surface for the hinge  24 . The hinge  24  is formed in the ceiling panel  10  by die-forming the hinge  24  90 degrees upward to create an upwardly extending leg  43  and then die-forming the edge 90 degrees inward to create an inward lip  44 . The inward lip  44  of the hinge  24  rests upon the bottom edge  42  in the channel  36  of the grid member  12 . The flange  26 , shown in FIG. 2, is formed by die-forming the edge  26  of the ceiling panel  10  upward 90 degrees to form a vertical member  45  and by forming a detent  48 . The ceiling panel  10  is retained to the grid structure  13  by forcing detent  48  past the bottom edge  42 . The detent  48  is properly positioned within the channel  36  when the detent  48  is resting upon the bottom edge  42 . The vertical member  45  biases the detent  48  to prevent the ceiling panel  10  from moving out of position. 
     FIG. 3 is a cross section of a ceiling system as in FIG. 2 that shows the grid member  12  and the hinge  24  of a first ceiling panel  10  and a disengaged flange  26  of a second ceiling panel  10 . When a panel is released from the grid structure  13 , as shown by the second panel in FIG. 3, enough downward force is applied to the ceiling panel  10  to force the detent  48  of the flanges  26 ,  28  and  30  from the bottom edge  42  of the grid members  12 . The spacing  43  between the bottom edges  42  is wide enough to allow the flange  26  to be released from the channel  36  of the grid member  12  without interfering with the hinge  24 . 
     FIG. 4 illustrates a cross section of a ceiling system as in FIG. 2 that shows the grid member  12  and a disengaged position of the hinge  24  of a first ceiling panel  10  and the flange  26  of a second ceiling panel  10 . The flange  26  is biased against the bottom edge  42  within the channel  36  of the grid member  12 . The disengaged hinge  24  is shown in the proper position for insertion into the channel  36  so the first ceiling panel  10  can be properly installed. The spacing  43  between the bottom edges  42  is wide enough to permit the installation of the hinge  24  without interfering with the flange  26 . 
     FIG. 5 is a cross section of a ceiling system as in FIG. 2 that shows a grid member  12  and the hinging movement of the hinge  24  of a first ceiling panel  10  and the flange  26  of a second ceiling panel  10 . Ghost lines  45  illustrate the movement of the hinge  24  during the closing of the first ceiling panel  10 . The inward lip  44  of the hinge  24  maintains contact with the bottom edge  42  during the opening and closing of the ceiling panel  10 . The hinge  24  is sized so that it does not contact the flange  26  of the second ceiling panel  10  during the opening and closing of the first ceiling panel  10 . 
     FIG. 6 is a cross section of the ceiling system of FIG. 1 taken along line  6 — 6  looking in the direction of the arrows and shows a pair of parallel grid members  12  and a ceiling panel  10  that includes a flange  26  and a hinge  24 . The ceiling panel  10  position is maintained between the parallel grid members  12  by the biasing of the flange  26  against the bottom edge  42  of the grid member  12 . The ghost lines  53  illustrate the movement of the ceiling panel  10  as it is lowered from a closed position to an open position. As the ceiling panel  10  opens, it is pivoted about the hinge  24  at a point where the inward lip  44  contacts the bottom edge  42 . The opening of the ceiling panel  10  does not disturb the other ceiling panels  10  in the grid structure  13 . 
     FIG. 7 is a cross section of the ceiling system of FIG. 1 taken along line  7 — 7  looking in the direction of the arrows and shows the flange  28  and the flange  30  of a ceiling panel  10  installed between two parallel grid members  18 . The flanges  28  and  30  are designed so that that the vertical members  45  are biased against the bottom edges  42  of the grid members  18 . Upon the opening of the ceiling panel  10 , as in FIG. 6, both flanges  28  and  30 , along with transverse flange  26 , will be released from their respective channels  36 . 
     FIGS. 8-10 are cross sections of a ceiling system as in FIG. 2 that show the grid member  12  and an alternate embodiment of the hinge  24  of a first ceiling panel  10 . The hinge  24  includes dimples  50 , evenly spaced along the length of the hinge  24 , which aid in guiding the hinge  24  into the proper location within the channel  36 . The dimples  50  also prevent unwanted vertical movement of the panel  10  when it is in the closed position, as shown in FIG. 10. A continuous longitudinal dimple or projection is yet another alternative configuration. 
     The hinged snap-up ceiling panels  10  are designed so that an individual can open and close a 4-foot×4-foot ceiling panel  10  without the aid of other workers. Since the hinge  24  maintains contact with the bottom edge  42  of the grid member  12  during the opening and closing of the ceiling panel  10 , the alignment of the ceiling panel  10  with respect to the opening  14  in the grid structure  13  is maintained. 
     Various features of the invention have been particularly shown and described in connection with the illustrated embodiment of the invention, however, it must be understood that these particular arrangements merely illustrate, and that the invention is to be given its fullest interpretation within the terms of the appended claims.

Summary:
The invention is directed to a hinged ceiling panel, which is pivotally attached to a suspended ceiling grid structure to provide for a hinged ceiling panel that pivots to allow access to the area above the grid. The hinged ceiling panel includes a hinge located on a first edge and grid-releasable flanges located on the remaining edges of the panel. The hinged ceiling panel is designed so that a single person can easily release the panel from the grid system and pivot it downwards whereby the hinge supports it. The hinged ceiling panel is also designed so that an individual can also reposition the panel within the grid structure without the aid of others.