Abstract:
In a panel ceiling, a grid that supports panels has main beams and cross beams. In assembly, the main beams are directly attached to an overhead structure and the cross beams and panels are assembled onto the main beams. Stepped slots in the main beams enable the cross beams to be locked to the main beams to keep the cross beams and panels aligned.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a panel ceiling having a grid framework that supports the panels. The grid is directly attached to an overhead structure such as an existing ceiling. 
     2. Background Art 
     The most common form of panel ceiling wherein a grid framework supports acoustical panels, is a suspended ceiling. Main beams of the grid are suspended on hanger wires anchored in an overhead structure. The grid, or a section thereof, of parallel main beams and interlocking, intersecting cross beams, is assembled, and hung, from the overhead structure, before the panels are inserted. In assembling the grid, the main beams can be separated and rotated as required to insert cross beam end connectors. 
     In such a ceiling, the hanger wires, in suspending the grid, create space between the overhead structure and the grid. This space is generally used, particularly in commercial construction, for utilities, such as air ducts and electrical conduits. 
     The space is also useful in connecting the cross beams to the main beams, and in placing panels into the assembled grid. 
     The main beams are hung by wires, and then the cross beams and main beams are maneuvered, using the space, to interlock the beams to assemble the grid. The main beams can be separated and rotated during the assembly. 
     In the assembled grid, the panels are inserted through the grid openings into the space above the grid, and then maneuvered into place on the grid. Sufficient space above the grid is required to so place the panels in a suspended ceiling. 
     A substantial body of prior art exists with respect to such suspended ceilings, since they possess many advantages and are extensively used. 
     A disadvantage of a suspended ceiling is that it consumes overhead space which is sometimes more needed below the ceiling than above the ceiling. 
     In another form of panel ceiling having a grid, the grid, through the main beams, is directly attached Go an overhead structure, eliminating the space between the overhead structure and the grid, and any use of hanger wires. Such a direct attachment is particularly desirable in residential structures where an old ceiling is being covered, in order to minimize loss of ceiling height. 
     In eliminating the space between the overhead structure and grid, however, other problems are created. 
     Whereas in the wire suspended grid, the main beams can be shifted during the installation of the cross beams, in direct attached grid, the main beams are first fixed in place, and then the cross beams are installed. The main beams cannot be shifted during a connection. Hence, the numerous different connections between the main beams and cross beams developed for suspended ceilings are not suitable for direct attached grid ceilings. 
     Another problem with direct attached grid ceilings, is the lack of space above the direct attached grid for placing panels. Again, this renders the extensive prior art relating to suspended ceilings inadequate to solve the problems of assembling grid, and placing panels, encountered in direct applied grid ceilings. 
     These problems encountered with direct applied grid have discouraged any wide spread use. 
     Attempts have been made to solve these problems. U. S. Pat. No. 4,920,719, incorporated herein by reference, creates space for placing panels and cross beams on the fixed main beams by the use of a stepped cross-section in the main beam which is directly attached to the ceiling. A panel is shifted into position using the space created by an upper stepped portion of such main beam, and a cross beam is then placed to help support the panel. 
     In the &#39;719 patent however, a cross beam, which must be placed after a panel is in place, does not positively lock into the main beams at a predetermined location, but rather the cross beam can slide along the main beam. An installer must use judgment in locating the panels and cross beams, to keep the panels and cross beams desirably aligned to present a uniform ceiling appearance. Such a procedure is time consuming and often the end result is unsatisfactory in that the panels are misaligned, and free to shift. 
     The prior art connections between the main and cross beams developed for suspended ceilings do not work with direct attached grid. As described above, prior art grid connections in suspended ceilings require space to assemble the connections, and require main beam movement during assembly. Both these requirements are lacking in direct attached grid. 
     SUMMARY OF THE PRESENT INVENTION 
     In a directly attached grid, directly attached main beams are slotted in such a way that connectors on the ends of the cross beams can be locked to the main beam at factory predetermined positions on the main beam. This aligns and secures the cross beams and panels in the ceiling in an orderly and uniform manner. A stepped slot enables the cross beams to be so locked. 
     The stepped slot has portions that necessarily extend in the web and in the adjacent step of the stepped main beam, and optionally in the riser adjacent to that step. 
     In assembling the grid on site, a cross beam is locked to a stepped main beam that is directly attached to an overhead structure. The cross beam is locked to the main beam, both along the main beam, as well as laterally of the main beam, at factory predetermined positions along the main beam. There is no judgment required of the installer in positioning the cross beams and panels after the main beams are aligned, spaced, and secured to the overhead structure. The end result is a uniform, secure, easily installed ceiling, with an interlocking grid. The panels are not free to shift. The ceiling face can be installed within one and one-half inches of an existing overhead structure. 
     The ceiling can be disassembled, beginning at any point, and to any extent. Panels can be shifted above other panels for access to any point above the ceiling. The stepped slot of the invention further permits individual cross beams to be readily removed by vertical motion from a completed ceiling, and a given panel removed, without disturbing other panels in the ceiling. 
     The stepped slot of the invention exists in the main beam in a way that does no significantly reduce the strength of the main beam. The strength of the beam remains adequate to support the panels and cross beams. 
     The slot permits a cross beam to use the clearance created by the stepped beam to position and lock the cross beam to the main beam. 
     The stepped slot likewise permits the necessary clearance to unlock a cross beam from the main beam to permit an adjacent panel to be removed from a completed ceiling. 
     The horizontal portion of the stepped slot is critical to the invention, since it permits the connector on the cross beam to be shifted downward from its position above the step to hook onto the web. Main beam separation or twist is not necessary to achieve this connection. 
     The grid system of the invention can optionally be produced of metal, or of plastic. Where the grid is produced of plastic, the main and cross beam may be extruded to produce, for each, a uniform profile. The slots and the connectors are then formed by a cutting, in a stamping operation. The connectors are then offset, again in the stamping operation. Since the main beams are attached directly to an upper structure, the necessary rigidity of the grid is obtained from such upper structure. The stepped slot of the invention, wherein material is removed from the main beam, does not significantly detract from the strength obtained in the grid system by attaching the main beams directly to the overhead structure. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view from above the ceiling. 
     FIG. 2 is a vertical section taken on the line  2 — 2  of FIG.  1 . 
     FIG. 2A is an enlargement of the designated encircled portion of FIG.  2 . 
     FIG. 2B is an enlargement of the designated encircled portion of FIG.  2 . 
     FIG. 3 is a horizontal section taken on the line  3 — 3  in FIG.  2 A. 
     FIG. 4 is a vertical section taken on the line  4 — 4  in FIG.  1 . 
     FIG. 5 is a perspective view from below a ceiling showing a panel being inserted into position. 
     FIGS. 6,  7 , and  8  show the steps of a way to insert and lock a cross beam into the ceiling grid, particularly where the cross beam is confined on both sides by panels. 
     FIG. 6 shows the first step of the insertion of the cross beam, wherein the connector on one end of the beam is inserted into the slot to permit the cross beam to be rotated into position. 
     FIG. 7 shows the cross beam after it is shifted horizontally to where the hook in the connector at each end of the cross beam is vertically aligned with the web on the main beam. 
     FIG. 8 shows the cross beam locked in position to the cross beams, after the cross beam was moved vertically downward. 
     FIG. 9 is a perspective view taken from below a ceiling showing a panel being inserted into place between the main beams. 
     FIG. 10 in a vertical section taken on the line  10 — 10  of FIG.  9 . 
     FIG. 11 is a perspective view taken from below showing a panel about to be finally placed into position. 
     FIG. 12 is a vertical section taken on the line  12 — 12  in FIG.  11 . 
     FIG. 13 is a perspective view taken from below showing a panel in place between the main beams. 
     FIG. 14 is a vertical section taken on the line  14 — 14  of FIG.  13 . 
     FIG. 15 is an exploded perspective view taken from above showing a portion of the grid attached to an overhead structure. 
     FIG. 16 is a perspective view of a section of main beam showing the slot of the invention. 
     FIG. 17 is a vertical section showing a cross beam locked to a main beam. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The grid of the invention is attached to an existing overhead structure  10 . This can be, for instance, an existing ceiling  11 , as seen in FIGS. 1 through 14, or overhead wooden beams  12 , as seen in FIG.  15 . The only requirement of such overhead structure  10  is that it be strong enough to support the weight of the ceiling  15  of the invention, which includes a grid  20  of the main beams  21  and cross beams  22 , and ceiling panels  23 . 
     Main beam  21  can be of any suitable length, but a desirable length is 96 inches. Main beam  21  has a stepped cross-section as seen, for instance, in FIG.  16 . In beam  21 , flanges  24  and  25  extend horizontally from vertical web  26 . Web  26  has extending perpendicularly from the web, to one side thereof, in a horizontal plane, lower step  27 . Extending vertically upward from lower step  27  is riser  28 . Extending horizontally outward from riser  28  is upper step  30 . A space  29  is created by lower step  27 , which offsets riser  28 . 
     Suitable dimensions could be, for Instance, a combined flange width of 1″, a web height of ⅔″, a lower step width of ½″, a riser height of ¾″, and an upper step width of ⅝″. Where the beam is of extruded plastic of a stiff type, the wall thickness of the various elements in the cross-section of the beam could be {fraction (1/20)}″ thick. These dimensions are merely illustrative. 
     The cross beams  22  have a cross-section with flanges  31  and  32 , and a web  33 . A rib  35  extends along the top of cross beam  30 . 
     A connector  36  is formed at the end by cutting out part of the web  33  and rib  35  at  37 . Also part of flanges  31  and  32 , and web  33 , are cut out at the end at  38 . The remaining part of web  33  at the end of the connector is formed into a hook  40 . Also, the end is slightly offset at  41  to permit opposing connectors  36  to remain in line, when connected to a main beam  21 , as explained below. 
     The cross beams  22  are desirably of a  24  inch length between hooks  40  at the ends of a connector  36 , to support a 24 inch ceiling panel  23 . 
     A main beam  21  has spaced at, for instance,  24  inch intervals along the length, a stepped access slot  50 . The slot  50  has a portion  53  that extends in the vertical web  26  through a portion  52  that extends in the horizontal lower step  27  and optionally through a portion  51  that extends in the vertical riser  28 . Portion  51  may be connected to portion  52 , or it may be isolated from portion  52 , but in either case, it will be aligned with portion  52 . However, it is only essential to the invention that the slot  50  extends in the vertical web  26  and through step  27 , since the cross beams  22  can be maneuvered into place without passing the connector  36  through the slot  50  in riser  28 . 
     Portion  51  of stepped slot  50  in the vertical riser  28  extends about a vertical center line from the bottom of the riser  28  to near the top, suitably having a peak at the top of the slot  50 . The slot  50  can be, for instance, of a width slightly greater than the ½″ of the flanges on the cross beam  22  to permit the connector  36  to be inserted through the slot  50  when inserting the cross beam  22  into place, as explained below. The height of the slot  50  portion in the riser  28  can be, for instance, {fraction (6/10)}″ to permit the connector  36  to pass into the slot  50  without interference. 
     Portion  52  of stepped slot  50  optionally extends entirely across lower step  27 , with the same width, that is slightly greater than ½″, for instance, as that of slot portion  51 . 
     Portion  52  of stepped slot  50  continues into the vertical web  26 , at slot portion  53 . It is critical to the invention that portions  52  and  53  be continuous, so that connector  36  can pass downward to connect onto web  26 . The slot portion  53  narrows from the width of the slot at the top, which conforms to the width of the slot in lower step  27 . The slot portion in the web tapers at a 45° angle to a tail portion at  54 . 
     The ceiling  15  of the invention uses a perimeter strip  55 , as best seen in FIGS. 2 and 2B. The strip is in a U shape, having legs  56  and  57  extending from base  58 . A spacer rib  60  extends from leg  57  to position a ceiling panel  23 . Legs  56  and  57  extend horizontally when the strip  55  is in position, and spacer rib  60  extends vertically. Alternatively, upper leg  56  may be omitted. 
     In assembling the ceiling  15  of the invention, the main beams  21  are affixed to the overhead structure  10  in a parallel relationship, desirably 24″ apart. The structure  10  can be appropriately marked, as by chalk lines, to indicate where the main beams are to be attached, working from the center outward. The perimeter strip  55  is affixed to the edge of the structure  10  entirely around the room perimeter with fasteners  61 , either through leg  56 , or base  58 . Main beams  21  are spliced at their ends by a suitable insert  85  that aligns the beams by slipping into groove  86  formed by ridges  87  and  88  formed in flange  25  and lower step  27  by, for instance, extruding, where the main beam itself is of extruded plastic. A bump  90  keeps the insert in place in the groove. 
     Main beams  21  are longitudinally positioned so that slots  50  line up laterally of the beams, and extend across the ceiling in a line that extends perpendicularly to the length of the parallel main beams, at 24″ intervals. 
     The main beams  21  are affixed to the existing ceiling  10  or overhead structure  11  with screws  61  or other suitable fasteners. 
     The upper step  30  of each of the main beams  21  extends, as viewed, for instance, in FIG. 2, in the same direction. In FIG. 2, the upper steps  30  are shown extending to the right, but permissibly, the steps may all extend to the left. The procedure to be described would be performed in mirror image fashion with left extending upper steps  30 . 
     After the main beams  21  and perimeter strip  55  have been affixed to the overhead structure  10 , the panels  23  and cross beams  22  are inserted. Beginning at one end of a row  78  between main beams  21 , a first panel  23  will be inserted between the main beams  21  as seen, for instance, in FIGS. 9 through 14. A panel  23  is first shifted diagonally in a direction shown by arrow  65  into a space at  29  created by the lower step  27 . the panel  23  is now free to be rotated in the direction shown by the arrow  66  to the positions shown in FIGS. 11 and 12. The panel is then shifted in the direction of arrows  67  and  68  into the position shown in FIGS. 13 and 14, where it rests on flanges  24  and  25 . 
     A cross beam is then inserted onto a pair of main beams  21 . One way is to point a cross beam  22  diagonally upward to the left of a row  78  as orientated in FIG. 2, and hook the left end of the cross beam  22  onto the left main beam  21  in the row. The connector is hooked through a stepped slot  50 . The right downward end of the cross beam  22  is brought toward the installer, away from the installed panel until the right end clears the flange on the right main beam in the row. The right end is then moved vertically upward into the space created by stepped portion  29 , above slot  50 . 
     The hook on the right end of the cross beam  22  is then moved vertically downward, through slot  50 , to hook onto web  26 . 
     During the insertion of cross beam  22  as described, in order to clear the panel  23  which is in place, it is necessary to slightly lift the panel corner. 
     Alternatively, a cross beam  22  can be inserted as shown in FIGS. 6 through 8. A connector  36  at one end of the cross beam  22  is inserted through slot portion  51  in the riser  28 , in the direction of arrow  71 . The connector  36  at the opposite end of the cross beam  21  at  73 , is rotated upward, as shown by arrow  75 . The cross beam is then shifted horizontally, as shown in FIG. 7, by arrows  76 , and then moved downward as shown by arrow  77  in FIG.  6 . Hooks  40  are locked to web  26  so that the cross beam  22  is locked laterally and longitudinally to the main beams  21 . 
     In many instances, it may be desirable to move a panel already in the ceiling, out of the way before installing a cross beam. A panel can be lifted and shifted into the horizontal space created by space  29  and slid over adjacent panels and cross beams. Such a procedure would be necessary to place the last remaining cross beam in a ceiling row. Panels can be shifted back after the cross beams are in place. 
     The ability to so shift panels into the horizontal space created by space  29  is of importance. It permits simpler cross beam application, especially in placing the last cross beam in a row. It will enable access to any place above the ceiling. Further, it permits the disassembly of any portion of the ceiling. 
     In the event the invention is practiced without a slot portion in the riser  28 , the cross beam will be only shifted into the space created by the lower step  27 , and the opposite connector at the left as seen in FIG. 14 will be maneuvered into place by movement in a plane parallel to the plane of the suspended ceiling  15 . 
     When cross beam  22  is in place, panel  23  will be uniformly and securely positioned and supported in place. 
     The panels are inserted throughout the ceiling in the full rows  78  where the span between main beams is 24″. The rows  81  which lie at the sides of the ceiling  15 , having a main beam  21  at the left, and a perimeter strip  55  at the right, as seen in FIG. 2, will virtually always be less than 24″. As described above, the rows are preferably laid out from the middle of the ceiling outward, so that it would be entirely coincidental if the edge rows were 24 inches, in which case the procedure described above for the rows  78  between main beams would be followed. The panel and connector  36  at the end of the cross beam  22  would be shifted into space  82 , as seen in FIG. 2B in the perimeter strip. The connector would be hooked onto spacer rib  60  in the manner that the connector is hooked onto the web of a main beam  21 . 
     In virtually all cases, however, where the ceiling is laid out from the middle outwards, row  81 , as seen in FIGS. 2 and 2B, will be less than 24″. To lay the panels and cross beams in such a row, a panel will be cut to the width of the row, as will the cross beams. A cross beam  22  will be cut only at the end that engages the perimeter strip  55 , and will simply be cut squarely at the desired length, as seen in FIGS. 2 and 2B. The space  59  in the perimeter strip  55  can be used to insert the cut cross beam  22 , as well as the panel  23 , in the same manner as space  29  created by lower step  27  is used in a main beam. The cut cross beam simply lies on the leg  57 , as shown in FIG. 2B, slightly short of spacer rib  60 , and does not lock onto the spacer rib  60 . The cut cross beam, however, does lock into the stepped slot  50  at the end opposite the cut, so that, again, the panel  23  and cross beam  22  are uniformly positioned without judgment on behalf of the installer. 
     At the end of the row opposite the start of the row, a panel  23  is cut to accommodate the last space left when inserting a row, and the panel  23  simply rests on the leg  57  of the perimeter strip  55 , slightly short of the spacer rib  60 . Rib  60  will prevent a panel from shifting off of the main beam flange  25 , on which it is supported. 
     A panel, or panels, can be removed anywhere in the ceiling by simply reversing the steps set forth above. The panels, as well as the cross beams that are removed, can be stored in the ceiling by sliding the panels into the space above the adjacent panels that are already in place. This allows access to the overhead structure, for instance for repair, after which the stored panels and cross beams can be put back in place.