Patent Publication Number: US-8117793-B2

Title: Suspended ceiling grid assembly with separation joints

Description:
CROSS REFERENCE TO RELATED APPLCATIONS 
     This application claims the benefit of the filing dates of U.S. Provisional Applications 61/017,437, filed Dec. 28, 2007, 61/078,492, filed Jul. 7, 2008, and 61/108,904, filed Oct. 28, 2008, the entire contents of each being incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Suspended ceiling systems are well-known in which a plurality of main runners extend parallel to each other, with cross members extending between the main runner at spaced intervals for supporting ceiling tiles or panels. The main runners and cross members, or cross tees, generally have an inverted T cross-sectional configuration, with a pair of oppositely-extending flanges connected by a web portion to a reinforcing bulb or bead. The cross members are typically connected to the main runners by a tongue that extends from the ends of the cross members and are received in an elongated slot in the web of the main runner. 
     It is also known to provide for a “fire rated” suspended ceiling system in which the connection between the main runners and the associated cross tees allows for limited expansion of the cross tees caused by an elevated temperature that would result from a fire without buckling the main runners. See, e.g., U.S. Pat. Nos. 4,601,153 and 4,677,802, both of which are incorporated herein by reference. 
     More recently, ceiling grid systems have been developed that allow for lateral movement of the cross members both into and away from the main runners, while maintaining the assembled relationship of the grid system, for use in geographical regions subject to earthquakes. Standards and requirements have been promulgated for ceiling suspension systems and areas requiring seismic restraint. Specifically, the International Building Code (“IBC”) requires the provision of a seismic separation joint for all ceiling areas exceeding 2,500 square feet. One method for providing for the separation joint is disclosed in U.S. Published Application US 2007/0180787, where joint clips are provided which attach to the grid at the points of intersection of the main runners and the cross-members. The clips support the reinforcing bulbs of the grid member so that the cross tees continue to be supported by the main runners upon separation. Consequently, an over-wide flange on the main runners is not required for support of the cross members. 
     By way of the present disclosure, an improved separation joint is provided. Specifically, the present disclosure provides for a seismic separation joint that does not require an additional clip member. 
     SUMMARY OF THE DISCLOSURE 
     A seismic separation joint for suspended ceiling grid system is provided in which the grid system comprises at least one main runner or tee and a pair of opposed cross tees that are secured to the main runner and extend in opposite directions therefrom. The tees each include a central web with a tongue or tab extending from the web. In the case of the cross tees, the tongues are slidably received in a slot in the web of the main runner. An elongated slot is formed in the web of the tees of a length corresponding to the amount of movement to be allowed for in the event of a seismic occurrence. Preferably, the elongated slot extends from the web of the tee into the tongue/tab associated therewith, such that the slots of the tees are aligned when a pair of tees are connected to each other. A fastener is received in a portion of the tongue/tab of at least one, and preferably both, of the tees distally of the slot and in the slot of the other tee, securing the tees to the to each other while providing for limited movement of the tees both into and away from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS AND PHOTOGRAPHS 
         FIG. 1  is a perspective view of a portion of a suspended ceiling grid system with at least one main runner and a plurality of cross tees secured thereto in accordance with the present disclosure. 
         FIG. 2  is a fragmentary perspective view of the end of a cross tee according to the present disclosure. 
         FIG. 3  is a side elevational view of the end of an assembled separation joint according to the present disclosure in its initial position. 
         FIG. 4  is a side elevational view of an assembled separation joint according to the present disclosure in its maximum compressed position. 
         FIG. 5  is a side elevational view of an assembled separation joint according to the present disclosure in its maximum extended position. 
         FIGS. 6 and 7  are exploded and assembled perspective views of a fastener assembly that may be advantageously used in combination the tees of the present disclosure. 
         FIG. 8  is a fragmentary side view of an alternative embodiment of a cross tee in accordance with the present disclosure. 
         FIG. 9  is a perspective view of an assembled separation joint connection for connecting two main runners end-to-end. 
         FIG. 10  is a perspective view of a cover that may be secured to the flanges of the runners. 
     
    
    
     DETAILED DESCRIPTION 
     A description follows of specific embodiments shown in the accompanying drawings. However, this is for the purposes of illustration of the principles of the invention only, and not by way of limitation. 
     Turning to the drawings, there is seen a grid system for a suspended ceiling generally designated  10  comprising one or more main runners  12  generally extending the span of the grid system  10  and a plurality of cross members or cross tees  14  typically spanning between adjacent main runners  12 . 
     Both the main runners  12  and the cross tees  14  (both of which may be generally referred to as “tees”) have a similar, inverted T-shaped cross-sectional configuration, as is well known in the art and exemplified by the U.S. patents incorporated by reference above. Specifically, the runners  12  and cross tees  14  are formed of strips of sheet metal with a pair of opposed flanges  16 ,  16  defining the lower surface. The flanges are connected by a central web  18  to a reinforcing bulb or bead  20 . As is well known in the art, the flanges  16 ,  16  may be covered along their length on their bottom surfaces with an additional strip that is bent over the edges of the flanges. 
     The web  18  of the main runner  12  includes a plurality of vertically-oriented elongated openings or slots  22  at spaced intervals corresponding to the connection points for the cross tees  14  to the main runners. In order to connect the cross tees  14  to the main runners  12 , the webs  18  of the cross tees  14  are formed with tongues  24  that extend beyond the end surfaces of the bead and the flanges  16  and are adapted to be received in the slots  22  in the main runners  12 . The tongues  24  and the portions of the web  18  adjacent thereto may be embossed to provide additional strength and stiffness. Preferably, the tongue  24  is provided with an embossment or stitch  25  between the end of the slot  22  and the tip of the tongue  24  to enhance the rigidity of the tongue  24  and to prevent separation of the web. The end surfaces of the flanges  16 ,  16  of the cross tees include an edge portion  26  which is offset from the plane defined by the flanges  16 ,  16  by amount approximately equal to the thickness of the flanges so that, when the cross tees are installed in the ceiling grid, the offset edges  26  are positioned above the flanges  16 ,  16  of the main runners  12 , and the flanges of the main runners  12  and the cross tees  14  are in the same plane. 
     In keeping with the disclosure, a separation joint is provided between the tees of the grid system that permits a predetermined amount of longitudinal movement of the tees without compromising the structural integrity of the grid system. Specifically, the main runners and cross tees are inter-connected to form the grid system so that they are capable of limited movement both into and away from each other in response to, e.g., a seismic event. 
     To this end, the cross tees are formed with a generally horizontal slot  28  that extends generally equidistant into both the tongues  24  and the web  18  of the cross tee. When the tongues  24  of a pair of cross tees  14  are inserted into a slot  22  in the web  18  of a main runner  12 , the distal end of the tongue of each of the cross tees is slidably secured to the slot of the tongue of the other cross tee so that movement of the cross tees  14  relative to the main runner  12  along the length of the slot  28  both into the main runner ( FIG. 4 ) and away from the main runner ( FIG. 5 ) is accommodated without the cross tees  14  become disassociated from either each other or the main runner  12 . 
     The tongues  24  of the cross tees  14  may be secured in the slot  28  of the mating cross tee by any fastener  30  that permits slidable movement along the length of the slot. In the illustrated embodiment, the fastener  30  comprises a rivet  32  that is received in a sleeve  34  that expands when the rivet is inserted therein. However, a screw or bolt may also be used. In the illustrated embodiment, the fastener  30  is received in an aperture  36  on the distal end of the tongue  24  that is in generally axial alignment with the slot  28 . While two fasteners are used in the illustrated embodiments, a slip joint according to the present disclosure may also be assembled with a single fastener. The materials from which the fastener and runner are constructed may be advantageously selected so that a predetermined minimum force is required before either of the fastener or the slot/aperture that receives the fastener will fail. 
     In keeping with another aspect of the disclosure, the diameter of the shaft portion of the assembled fastener  30  may be slightly greater than the overall width of the slot, and the slot slightly oversized at a central portion of the slot (in general alignment with the ends of the bead and the flanges) to form a seat  38  that locates the fastener during the initial assembly and installation of the ceiling grid. Thus, to permit relative movement of the cross tees with respect to the main runner after initial installation, a force sufficient to slightly widen the slot  28  and/or deform the fastener  30  is required. The required deformation also provides a degree of internal friction in the sliding joint and a level of damping or energy dissipation during relative movement of the grid members. 
     Optionally, the reinforcing bead  20  of the cross tees  14  may be extended so that the beads  20  contact the reinforcing bead  20  of the main runner  12  when the grid  10  is in its initial, assembled condition (i.e., as shown in  FIG. 3 ). This aids in assembly of the grid  10 , as the seats  38  for the fasteners  30  are aligned with the apertures  36  in the tongues  24  when the reinforcing beads of the cross tees  14  contact the reinforcing bead of the main runner  12 . The extended portion of the bead is preferably weakened to allow the extension to deform, collapse, or be displaced to the side when subjected to an axial compressive force. The extended portion of the bead may be weakened by flattening and/or providing cutouts or notches, although other techniques will be apparent to those skilled in the art. 
     Also, the end of the tongue  24  may be narrowed in width to facilitate its insertion into the slots  22  in the main runner  12 . This may be accomplished by having a bevel  40  on the end of the tongue. Optionally, the end of the tongue  24  may have a second bevel  42  (best seen in  FIG. 8 ) for this same purpose. Also, with reference to  FIG. 8 , the tongue  24  may include a notch  44  in the bottom of the tongue  24  to facilitate centering the cross tee  14  relative to the main runner  12 , the notch  44  seating on the bottom of the slot  22 . The notch  44  is preferably trapezoidal in shape, but other shapes are also contemplated. 
     Turning to  FIG. 9 , the separation joint according to the present application is shown in the context of connecting two main runners in an end-to-end manner. The details as to the tongues, slots and fasteners are generally the same as that described above. As a consequence, the reference numerals used in connection with the embodiments shown in  FIGS. 1-8  are used for corresponding structure in the embodiment disclosed in  FIG. 9 . 
     When the separation joint of the present disclosure is used to connect two main runners end-to-end, a gap  46  between the ends of the flanges results. For aesthetic purposes, a cover  48  may be provided to close the gap  46 . The cover  48  permits slidable movement of the runners with respect to the cover  48 , as provided by the separation joint. With reference to  FIG. 10 , to facilitate installation, the outside edge  50  of the cover  48  is bent over so as to fit over a first edge of the flanges. The opposite, second edge  52  of the cover  48  includes at least one tab  54  (two such tabs being shown), such that when the first edge  50  of the cover  48  is located over the first edge of the flanges, the tab  54  may be bent back over the second edge of the flanges to secure the cover in place.