A suspended metal ceiling system having a grid of support members suspended from a structural ceiling and a plurality of ceiling panels positioned on the grid of the support members having a locking mechanism for connecting the ceiling panels to the grid actuatable from a side wall of the ceiling panels.

CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to U.S. Provisional Application No. 61/325,159 filed Apr. 16, 2010, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a suspended metal ceiling system, and more particularly to a metal ceiling system having locking panels without visible access holes. 
     Suspended ceiling systems are known in which metal ceiling panels are supported by inverted T-shaped support and frame members which are suspended from the structural ceiling of a room or building. Prior suspended ceiling systems include ceiling panels that are placed on horizontal base portions of the inverted T-shaped support members resulting in the T-shaped members being exposed. For particular applications, it is desired that the T-shaped support members be concealed. In such applications the individual ceiling panels must be attached to the support structure in a manner which conceals the support structure. For such configurations it is desirable that the ceiling panels be secured to the support structure so that they cannot become dislodged for any reason. This is particularly problematic when ceiling systems are used for outdoor applications which are subject to environmental conditions such as the wind. In such applications, it is desirable to provide a locking mechanism for the individual ceiling panels to be secured to the support structure. In locking applications, it is necessary to be able to easily unlock the panels to gain access above the suspended metal ceiling, however for aesthetic reasons holes should not be positioned on a visible surface of the ceiling panel in order to access the locking mechanism. Consequently a need exists for a new suspended metal ceiling system having locking panels without visible access holes. 
     SUMMARY OF THE INVENTION 
     The present invention is a suspended metal ceiling system having individual metal panels having a locking mechanism for rigidly securing the ceiling panels to the support structure without having access holes for the locking mechanism on a visible surface. In particular, the present invention provides a suspended ceiling system which comprises a plurality of inverted T-shaped support members suspended from the structure ceiling of the room or application, each T-shaped member having a horizontal base portion. The ceiling system further includes a grid of T-shaped support members including rows of horizontally extending support members and laterally extending support members forming the grid. A plurality of metal ceiling panels are positioned over each opening formed in the horizontally and laterally spaced openings in the grid. Each of the laterally spaced T-shaped support members are also referred to as a main tee member and each of the horizontally positioned T-shaped members are also referred to as a cross tee member. 
     The metal ceiling panels are attached to the main tee members by having a torsion spring attachment on either side of the panel. The ceiling panels are locked to the main tee members by having a slide clip arrangement positioned on either end of the ceiling panel on both sides of the panel creating four points of locking attachment. Each slide clip is positioned on either end of a panel stiffener located along each side of the ceiling panel. Each slide clip includes a spring for engagement and exterior loading. Each slide clip includes a screw shaft which extends through an opening on a side wall of the panel which can be engaged by a bladed tool to operate the slide clip to lock and unlock the ceiling panel. 
     These and other aspects of the present invention can be more fully understood with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a single ceiling panel as attached to the support structure of the present invention; 
         FIG. 2  is an exploded perspective view of the ceiling panel of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of two adjacent ceiling panels taken along the main tee member of the support structure of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view of two adjacent ceiling panel members taken through the slide clips of  FIG. 1 ; 
         FIG. 5  is a detail view of the slide clips of  FIG. 1 ; 
         FIG. 6  is a side view of the slide clip in the locked position; and 
         FIG. 7  is a side view of the slide clip in an unlocked position. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-4 , a suspended metal ceiling system  10  of the present invention is illustrated. The suspended metal ceiling system  10  includes a plurality of laterally spaced apart rows of T-shaped support members  12  also referred to as main tee members. As with all the T-shaped support members for the ceiling system, main tee  12  includes a horizontal base portion  14  and a vertical portion  16 . Vertical portion  16  includes a plurality of spaced apart holes  18  in which is positioned a fastener to connect the main tee member to a T-shaped hanger  20  which extends from a ceiling or other overhead structure. The vertical portion  16  of main tee member  12  is attached to the hanger  20  on its base portion  22  which also has holes  24  aligned with holes  18 . Intersecting, and connected to main tee members  22  are a plurality of spaced apart T-shaped horizontal support members  26  also referred to as cross tee members. Cross tee members  26  also have a horizontal base portion  28  and a vertical portion  30 . The rows of main tee members and cross tee members intersect and are connected to form a patterned array and rigid support structure. The horizontal base portions of the main tee members and the cross tee members are rigidly connected to one another at the intersection by rivets or other suitable fasteners  32 . 
     A metal panel  34  is positioned over each opening formed by the main tee members and the cross tee members. As seen best in  FIG. 2  the metal panel  34  comprises a horizontal surface  36  and vertical side walls  38  positioned around the perimeter of the horizontal surface  36 . The edge of vertical side walls  38  is folded over to provide a top horizontal surface  40 . A c-shaped panel stiffener  42  is positioned on opposite inside surfaces of the vertical side walls of the metal ceiling panel adjacent the main tee members  12  and extend along the side of the metal ceiling panels below the horizontal base member of the main tee members. 
     The metal ceiling panels are attached to the main tee members  12  by a torsion spring  44  which extends through slots  46  in the panel stiffener, the vertical side walls  38  and top horizontal surface  40  in the metal ceiling panel, and in the horizontal base portion  14  of the main tee member. There are separate torsion spring attachment locations, generally referred to as reference number  48  in  FIG. 1  on either side of the metal ceiling panel. 
     The metal ceiling panels are locked into place to the main tee members by a c-shaped slide clip  50  positioned at each end of the panel stiffener  42  on either side of the ceiling panel. The slide clip  50  is positioned within the channel of the panel stiffeners as seen best in  FIG. 4  and includes a flange  52  extending from an upper surface of the slide clip. Flange  52  extends through a slot  54  in the end of the panel stiffener and a slot  56  in the horizontal base portion  14  of main tee member  12 . The top horizontal surface  40  is cut away at its end to accommodate travel of the flange  52 . As seen best in  FIG. 5  flange  52  slides within slot  56  to an end of the slot so that it engages the horizontal base portion to lock the metal ceiling panel to the main tee member. The slide clip  50  includes a screw  58  which has a shaft  60  which extends through a slot  62  in the side wall of the panel stiffener and a slot  64  in the vertical side wall  38  of the metal ceiling panel as seen best in  FIG. 6 . As shown in  FIG. 7  to disengage flange  52  from the main tee member to unlock the ceiling panel, a bladed tool  66  is slid between adjacent ceiling panels along vertical side walls  38  to engage the end of the shaft  60  and slide the shaft within the slot  64  to disengage the flange from the base of the main tee member. As shown best in  FIG. 5  the slide clip includes a torsion spring  68  which is attached between the slide clip  50  and the end of the panel stiffener  42 . The torsion spring  58  biases the slide clip and the flange in the locked position. As the stud moves the slide clip out of disengagement, the spring expands and when the stud is released the spring pulls the slide clip back into a locking engagement. 
     As shown in  FIG. 1  the locking slid clip arrangement, generally shown as reference  70  is positioned in each corner of the metal ceiling panel. As can be appreciated, the metal ceiling panel of the present invention has been designed to provide a locking engagement without visible access holes by incorporating the locking feature with its means for engaging and disengaging on a side surface between individual panels and not visible from a viewing orientation of the ceiling panels. 
     The components of the present invention are made of metal, for example aluminum, however other materials are contemplated by the present invention. Further by way of example a typical ceiling panel can have a 30×30 inch dimension. However, other sizes are contemplated herein. The ceiling panels further can include acoustical design considerations and can have a plurality of finishes including metal or wood laminates. 
     Although the present invention has been described and illustrated with respect to a preferred embodiment thereof, it is to be understood that changes and modifications can be made therein which are within the full intended scope of this invention as hereinafter claimed.