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[0001]    The invention relates to suspended ceiling constructions and, in particular, to systems in which ceiling panels are downwardly removable from a suspended grid. 
       BACKGROUND OF THE INVENTION 
       [0002]    Suspended ceilings ordinarily comprise a rectangular metal grid and panels or tiles that are set in the grid spaces from the plenum above the plane of the grid. While this installation technique allows the grid elements and panels to take simple forms, it requires some minimum overhead clearance and usually leaves the lower face of the grid elements fully exposed. These characteristics can limit the places where these ordinary systems can be used as well as the aesthetics of such installations. 
       SUMMARY OF THE INVENTION 
       [0003]    The invention provides grid and panel components for suspended ceilings that allow the panel to be installed and removed from the grid by movement through the space below the ceiling. The invention relies on laterally resilient elements disposed where the edges of the panels are supported by the surfaces of the grid members. In some embodiments of the invention, the resilient elements are situated on the grid members while in other embodiments the resilient elements are situated on the panel. The resilient elements are preferably located at two opposite edges, at least, of each panel. One or both of the interengaging surfaces of the grid and panel edge can be configured to develop a camming action to produce lateral movement of the resilient element and thereby enable installation or removal of the panel on or off the grid when the panel is forced upwardly or downwardly. In some disclosed arrangements, the configuration produces a camming action during both upward panel installation movement and downward panel removal movement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a fragmentary cross-sectional view of a novel grid tee and ceiling panel construction for a suspended ceiling capable of downward access; 
           [0005]      FIG. 2  is a view similar to  FIG. 1  of a modified ceiling panel; 
           [0006]      FIG. 3  is a view similar to  FIG. 1  of yet another modification of a ceiling panel and a grid tee; 
           [0007]      FIG. 4  is a cross-sectional view of a grid tee and ceiling panel construction of a still further modification; 
           [0008]      FIG. 5  is an isometric view of a variant of the grid tee illustrated in  FIG. 4 ; 
           [0009]      FIG. 6  is a fragmentary cross-sectional view of a still further grid tee and ceiling panel constructed in accordance with the invention; 
           [0010]      FIG. 7  is an isometric view of a variant of the grid tee illustrated in  FIG. 6 ; 
           [0011]      FIG. 7A  is an isometric view of still another variant of the grid tee illustrated in  FIG. 6 ; 
           [0012]      FIG. 8  is a cross-sectional view of a grid tee constructed in accordance with the invention; 
           [0013]      FIG. 9  is an isometric view of a grid tee clip; 
           [0014]      FIG. 10  is a cross-sectional view of the clip of  FIG. 9  shown in an installed position on a supporting grid tee of complementary configuration; 
           [0015]      FIG. 11  is a cross-sectional view of a grid tee and a novel ceiling panel; 
           [0016]      FIG. 12  is a cross-sectional view of the edge detail of a grid tee in a still further variation of a ceiling panel; 
           [0017]      FIG. 13  is a cross-sectional view of the edge detail of a modified form of ceiling panel similar to that shown in  FIG. 12 ; and 
           [0018]      FIG. 14  is a fragmentary cross-sectional view of a grid tee and a ceiling panel of unique construction embodying the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The grid members described herein will be typically formed of rolled sheet metal strips of steel or aluminum as is customary in the industry. The grid members, commonly, have the general cross-sectional shape of an inverted T with the bottom having a panel supporting flange and the top having a hollow reinforcing bulb. The grid members or tees, in a customary manner, are arranged in a rectangular grid, ordinarily using long main runners and short cross runners. The grid module, for example, can be 2′×2′ or 2′×4′, or metric equivalent, as well as other desired sizes. It will be well understood that the various tees disclosed herein can be used in only one direction, with conventional tee shapes in the other direction, so that a rectangular panel is supported on two opposite edges or, alternatively, can be used in both directions so that the panel is supported on all four edges. The ceiling panels described herein are typically rectangular (which term includes square) composite boards having desired mechanical and acoustic properties and are of known composition. In all of the disclosed embodiments, at least two opposite edges of a panel have a special form for cooperating with resilient elements on the adjacent grid members or themselves constitute or integrate the resilient elements. 
         [0020]    Referring now to  FIG. 1 , there is shown, in cross-section, a grid runner or tee  10  and a pair of ceiling panels  11 . The grid tee  10  has a hollow reinforcing bulb  12  running along its upper edge and oppositely extending panel supporting flanges  13  along its lower edge or bottom. Web or stem layers  14  extend generally vertically between the bulb  12  and flanges  13 . In the illustrated example, the flanges are in the form of U-shaped channels with the bight of the U distal from its associated web  14 . Edges  16  of the panels  11  have grooves or pockets  17  that receive respective flanges  13 . The tee  10  is roll-formed or otherwise fabricated such that in its free state, as shown in  FIG. 1 , the web layers  14  diverge from one another, their spacing increasing with increasing distance from the bulb  12 . The panels or tiles  11  can be released from the grid formed by the tees  10  by squeezing the tees to bring the web layers  14  together so that at least one of the flanges  13  is withdrawn from its respective groove  17  and the associated panel  11  is allowed to drop vertically downwardly for access to the plenum above the plane of the ceiling. 
         [0021]      FIG. 2  illustrates a grid tee, which can be of the same configuration as the tee disclosed in  FIG. 1  and ceiling panels  21  of a modified edge profile from that illustrated in  FIG. 1 . Edges  22  of the panel include grooves  23  for receiving the tee flanges  13 . Above the grooves  23  the edges are angled or beveled at  24 . This angled construction allows the surfaces  24  to cam their respective flanges  13  inwardly when the panels are pushed upwardly during the installation process. That is, the panels  21  can be installed on the tees  10  from below by a push-up motion in which the bevels  24  operate to resiliently deflect a flange and associated web layer  14  until the panel  21  is in its vertical installed position and the flange  13  can snap into the groove  23 . Small holes or slots  26  can be provided in the vicinity of the juncture between the flanges  13  and their respective web layers  14  to enable a tool to be inserted therein from below the ceiling and through a gap between the adjacent panels  21  to deflect a web layer  14  towards its opposite web layer to release the flange  13  from the groove  23  and, therefore, the panel  21  from the tee  10 . 
         [0022]    Referencing  FIG. 3 , a grid tee  30  differs from that shown in  FIGS. 1 and 2  in that its flanges  31  are more bulbous or rounded than that previously shown. Ceiling panels  32  have edges  33  with V-shaped grooves or pockets  34  and a beveled or chamfered upper zone  36 . An inclined surface  38  of a lower part of the flange  31  engages the surface of the bevel  36  when a panel  32  is pushed upwardly during installation with the result that flange  31  and web  35  are deflected inwardly until the flange snaps into the groove  34  for installation of the panel from the space below the grid tee. An inclined surface  39  of the groove  34  bears against an inclined surface  41  on the upper part of the flange  31  to cam the flange and web  35  inwardly to displace the flange from the groove when the panel  32  is pulled downwardly and is thereby released from the installed position. 
         [0023]    At  FIG. 4 , a grid tee  45  is shown having the hollow reinforcing bulb  46  at its top and a panel supporting flange  47  at its bottom. Disposed between the bulb  46  and flange  47  is a double wall or layer web  48 . The flange  47  has symmetrical sections to the right and left of the web as viewed in  FIG. 4 . Each of the flange sections has a horizontal portion  49  extending from the web  48  and an upturned portion  51  distal from the web. The upturned portion  51  is convex relative to a corresponding ceiling panel  52  by virtue of an outwardly inclined section  53  and an inwardly inclined section  54 . The grid tee  45  is illustrated in its free state or essentially in its free state. A ceiling panel  52  has an edge configuration which is complementary to the corresponding section of the flange  47 . In particular, an edge  56  includes an outwardly flared or directed surface  57  and an inwardly flared or directed surface  58 . The surfaces  57 ,  58  form a shallow groove or pocket for receiving the tee flange portion  51 . The material of the grid tee  45  is sufficiently resilient to enable the sides of the flange  47  to flex inwardly to enable the panel  52  to be pushed into place for installation from below the plane of the ceiling and be pulled downwardly for access to the plenum above the ceiling. During installation, the outwardly inclined flange section  53  serves as a cam when engaged by a corner  59  of the panel  52  to force the flange portion  51  inwardly for installation of the panel  52 . For dismounting or removal of the panel  52 , the flared panel surface  57  working as a cam against the flange surface  54  forces the flange section  51  laterally inwardly to permit the panel to be pulled off the grid tee  45 . The flange  47  can be slit, notched, or otherwise weakened at points  61 , for example, to assure that the flange will flex for installation or removal of a panel  52  without excessive compressive forces being applied against the panel which could otherwise damage it. 
         [0024]      FIG. 5  illustrates a grid tee  62  similar in function to that of the tee  45  illustrated in  FIG. 4 . In this instance, flange sections  63  are L-shaped having a horizontal portion  64  and a vertical portion  65 . Spaced longitudinally along the vertical flange portion  65  are a series of regularly spaced projections  66  stamped from the plane of the vertical portion. The projections have inclined surfaces  67 ,  68  which function as the corresponding surfaces  53 ,  54  of the grid tee  45  of  FIG. 4 . The grid tee  62  can be used with the panel  52  shown in  FIG. 4  and mounting and dismounting of the panel can be accomplished in the manner described in connection with  FIG. 4 . 
         [0025]      FIG. 6  illustrates a variation of a grid tee  70 . Flange sections  71  of the grid tee  70  are inverted from the orientation of the flange sections described in connection with  FIG. 4 . The flange sections  71  include a horizontal portion  72  and a vertical portion  73  depending from the horizontal portion. The vertical portion  73  is convex in relation to ceiling panels  74  by virtue of an outwardly extending portion  76  and an inwardly extending portion  77 . The ceiling panels  74  have their edges shaped to conform to the profile of the flange sections  71 . Specifically, an edge  78  of a panel  74  has a V-shaped groove  79  proportioned to fit against the outward and inward section  76 ,  77  of the vertical flange portion  73 . A panel  74  can be installed or removed from the grid tee  70  by pushing it into place or pulling it from its installed position in the same way as described in connection with the grid tee  45  and panel  52  shown in  FIG. 4 . 
         [0026]      FIG. 7  illustrates a grid tee  80  analogous to the grid tee  62  of  FIG. 5 . The grid tee  80  has flange sections  81  which include a horizontal portion  82  and a vertical portion  83  depending from the horizontal portion and distal from the grid tee web  84 . Projections  86  are stamped out of the vertical portions  83 . The projections are spaced along the length of the grid tee  80  and have a profile when the tee is viewed endwise similar to that of  FIG. 6 . The grid tee  80  can be used with the ceiling panel  74  of  FIG. 6  or panel  52  of  FIG. 4  in the manner of installation and removal described in connection with those figures. 
         [0027]      FIG. 7A  illustrates a modified grid tee  85  similar to the tee  80  of  FIG. 7 . Flange sections  87  include horizontal portions  88  and vertical portions  89 . Resilient grips  95  are integrally formed on the vertical portions  89  at spaced locations along the length of the grid tee  85 . The grips  95 , being cut out of the vertical portion  89  on three sides to leave an integral hinge  96 , are relatively long compared to their vertical dimension, including the vertical length of the hinge. The short vertical length of the hinge  96  and the relatively long distance from a bulbous free end  98  of the grip  95  results in a relatively soft spring, i.e. a low force required for deflection of the grip. The resulting soft action of the grips  95  permits them to readily deflect when a panel such as illustrated in  FIG. 6  is pushed up for installation and pulled down for dismounting, thereby avoiding excessive force and possible damage to the panel. 
         [0028]      FIG. 8  illustrates a modified form of grid tee  90 . Flange section  91  includes horizontal portions  92  and vertical portions  93 . Spaced along the length of the grid tee  90  are sheet metal spring clips  94  disposed in associated elongated slots stamped in the upper region of the vertical flange parts  93 . A portion of the clip  94  outside of the flange section  91  serves the purpose of the projections  86  of the grid tee  80  ( FIG. 7 ) to accept and retain a panel  52 ,  74  such as shown in  FIGS. 4 and 6 . Within the flange sections  91  a clip  94  has an integral arm  97 . The arm  97  can be manipulated with a tool inserted between adjacent panels to release a panel by causing the part of the clip  94  external of the flange section  91  to flatten against the vertical flange part  93 . 
         [0029]      FIGS. 9 and 10  illustrate a twist-on clip  100  for suspending ceiling panels  101 . The clip  100  is proportioned to be mounted on the lower face of standard grid tees, typically having a face width of 15/16′. The clip  10  can be stamped from steel sheet stock and hardened before or after stamping so as to have a spring-like character. The clip  100  includes a pair of opposed grips  102  on diagonally opposite corners and a pair of stops  103  on its other diagonally opposite corners. Depending from the original plane of the body of the clip  100  are a pair of opposed legs  104 . The legs  104  each have a projection  106  that extends laterally with respect to a plane of its associated leg  104  which, when installed on a grid tee is parallel to a plane of a web  107  of a tee  108  on which it is installed ( FIG. 10 ). A panel  101  has a roll-formed metal molding, of light gauge steel  109 , or an extrusion of plastic such as polyvinylchloride (PVC) affixed to its edge and extending upwardly above the upper side of the panel  101 . 
         [0030]    The molding  109  is mechanically attached to the panel by an appropriate fastening technique such as creating barbs in the body of the molding, use of separate staples, and/or use of adhesive. It will be understood that the panel  101  can be assembled on the clip  100  and its associated grid tee  108  by pushing it in place to cause the legs  104  to be cammed inwardly by contact of the upper corner of the molding  109  and the lower part of the projection  106 . The legs  104  snap into the pocket formed by the outward flare of the molding  109 . Conversely, the panel  101  can be dismounted from the installed position illustrated in  FIG. 10  by pulling the panel downwardly to cause the upper part of the projection  106  to cam the leg  104  inwardly and thereby release the panel  101 . During removal of a particular panel  101 , the adjacent panel can be lifted above its normal resting position shown in  FIG. 10  to provide a finger or tool hold of the panel being removed. 
         [0031]    With reference to  FIG. 11 , there is shown conventional grid tees  108  and a novel ceiling panel  109 . The base of the panel  109  is made of conventional ceiling panel stock. The edge of the panel  109  is rabbeted such that it includes a vertical surface  111  recessed from the outwardmost edge  112  of the panel. Affixed to the rabbet surface  111  is a resilient foam edge  113 . The rabbeted edges of the panel  109  and the resilient foam edges  113  are proportioned such that the panel can be pushed up between a pair of regularly spaced parallel grid tees  108 . During this push-up installation motion, the resilient foam edge  113  is resiliently compressed so that it can pass through the space between the flanges of the grid tees  108 . When the panel  109  abuts the lower face of the grid tee  108 , the resilient foam edge expands to its free state such that it overlies the adjacent part of the grid tee flange and thereby holds the panel in place. The resilient foam edge  113  can be an extrusion or a molded part either formed in place on the panel  109  or adhered to the panel with a suitable adhesive. 
         [0032]      FIG. 12  illustrates an alternative to the design illustrated in  FIG. 11 . The panel  109  has a clip  114  secured to its vertical surface  111 . The clip  114  can be a suitable extruded plastic such as PVC or like material having resilient properties enabling it to work as a spring. The plastic strip  114  can be continuous along the length of the associated panel  109  and is adhesively or mechanically attached to the vertical surface  111  of the rabbeted edge of the panel  109 . The strip or clip  114  is provided on at least two opposite edges of the panel  109 . The assembly of the panel  109  and clips  114  can be installed on a suspended grid from below the plane of the grid in the manner described in connection with  FIG. 11 . 
         [0033]    Referring now to  FIG. 13 , a ceiling panel  109  has a light gauge metal spring  117  attached to its vertical surface  111 . The spring  117  which can run continuously along the vertical surface  111  or can be provided in spaced segments is mechanically attached to the panel  109  with integral barbs, staples, or adhesive, as desired. The metal spring  117  has a shape when viewed along the direction that the vertical surface extends analogous to the shape of the plastic strip  114  disclosed in  FIG. 12 . This enables the assembly of the panel  109  and spring  117  to be used in the same manner as described in connection with  FIGS. 11 and 12  such that the panel  109  can be assembled from below the plane of the grid. 
         [0034]    With reference to  FIG. 14 , a ceiling panel  120  is clad with a light gauge metal sheet  121 . The metal sheet  121  has an inverted pan shape. The periphery of the cladding sheet  121  is formed with a vertical flange  122 . The flange  122  is bent inwardly to form a rib or bead  123 . The flange  122  and its bead  123  are proportioned to releasably catch on a slot edge  124  of a conventional slot type grid tee  125 . 
         [0035]    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 system comprising metal grid members and rectangular composite acoustical panels, the panels having edges at their peripheries, the grid members having a cross section generally like an inverted T such that they provide oppositely extending flanges adapted to support the panels at their edges, a resilient element at a juncture between a support on the grid member flanges and at least one edge of each panel, the resilient element being arranged to temporarily deflect to permit a panel to be raised from below the grid member into an installed position and to extend itself to hold such panel in position on the grid.