A ceiling system having a primary grid network which includes a plurality of grid members that are in generally perpendicular relation and form points of intersection. The ceiling system includes one or more joint clips, each of which is attached to the grid network at a point of intersection. Each joint clip partitions the primary grid network into smaller networks, which move independently of one another. At the same time, the appearance of an overall primary grid network is preserved.

CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 60/536,427, filed Jan. 14, 2004, entitled “Suspended Ceiling System Utilizing Seismic Separation Joint Clips”. 


   BACKGROUND 
   The invention relates to a suspended ceiling grid network which utilizes clips to connect a primary grid member to a secondary or cross grid member in generally perpendicular relationship. More specifically, the invention relates to a grid network having a clip which permits lateral movement of the cross grid member relative the primary grid member in at least two horizontal directions with respect to the ceiling plane, while maintaining the assembled relationship of the primary and cross grid members. 
   Clips for securing two grid members in generally perpendicular relation to one another in order to form a ceiling grid network are widely known in the art. In geographical regions subject to earthquakes, steel buildings are designed with lateral force resisting (seismic) systems to resist the effects of earthquake forces. Seismic systems make a building stiffer against horizontal forces, thus minimizing the amount of relative lateral movement and resultant damage. Although the buildings may be designed structurally to provide seismic resistance to lateral forces, suspension ceiling systems remain very susceptible to displacement under seismic conditions. 
   ASTM E 580-02 provides a standard practice for “Application of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Requiring Seismic Restraint.” This standard practice covers acoustical ceiling suspension systems and their additional requirement for application both in areas subject to light to moderate seismic disturbance such as Uniform Building Code (UBC) Seismic Zone 2, and areas subject to moderate to severe seismic disturbance such as UBC Seismic Zones 3 and 4. The intent of this standard practice is to provide an unrestrained ceiling system designed to accommodate the horizontal movement of the grid network when loads are applied laterally to a ceiling surface, such as during a seismic event. ASTM E 580-02 requires, in areas subject to light to moderate seismic disturbance, that the primary and cross grid members of the ceiling system, including their splices, connectors and expansion devices be designed and built to carry an average test load of 60 lbs. in tension with a 5 degree misalignment of the primary and cross grid members in any direction. 
   Typically, a ceiling system having a ceiling area of less than 2500 square feet, is attached to the wall via wall angles on two adjacent sides. On the other two sides, wall angles with 2 inch horizontal legs are used along with spacer bars and hanger wires. Thus, during a seismic event, the grid members abutting the wall can move laterally away from the wall, i.e. float on the 2 inch perimeter wall angle. The 2 inch wall angles provide the 5 degree misalignment of the primary and cross runners in the direction of the horizontal ceiling plane as required by ASTM E 580-02. 
   In order to comply with ASTM E 580-02 at an interior ceiling location, one solution that has been contemplated by those skilled in the art is to utilize primary and cross grid members having four inch horizontal flanges, in other words, two inch flanges on either side of the vertical web. This solution effectively provides the same effect as the 2 inch wall angles at an interior ceiling location. However, from an aesthetic standpoint, it is undesirable to use grid members having such wide flanges. 
   Additionally, the 2000 International Building Code specifies that “for ceiling areas exceeding 2,500 square feet a seismic separation joint or full height partition shall be provided.” Essentially, this requires a large ceiling area to be segmented into independent smaller areas to prevent the ceiling from completely collapsing during a seismic event. 
   In order to comply with both ASTM E 580-02 and the 2000 International Building Code, a grid network is needed which eliminates for primary grid members having 4 inch lower flanges and which partitions a single ceiling area into smaller independent ceiling areas. 
   SUMMARY 
   The present invention is a ceiling system having a primary grid network which has a plurality of grid members disposed in generally perpendicular relation forming a plurality of intersection points. The primary grid network is partitioned into more than one grid network by attaching the joint clip of the invention at points of intersection of the grid members. 
   Each clip, which can be formed from a single piece of resilient sheet metal, secures first and second cross grid members to the primary grid member. The clip has a first resilient fastening portion extends in the longitudinal direction of the primary grid member and attaches to the primary grid member. The clip also has a second resilient fastening portion which extends from the first fastening portion at a right angle. The clip further includes a third resilient fastening portion which extends from the first fastening portion at a right angle on the side of the first fastening portion opposite the second fastening portion. 
   The joint clip of the invention partitions the primary grid network into smaller networks, or islands. Each smaller grid network is capable of moving independently of neighboring grid networks, while at the same time, preserving the aesthetic appeal of the overall grid network. The clip adds structural strength to the overall grid framework to prevent twisting and withdrawal of the cross grid members from the primary grid member. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a fragmentary perspective view of the ceiling system illustrating the joint portion of the system to which an example embodiment of a clip of the invention is shown mounted. 
       FIG. 2  is a plan view of the example embodiment of the clip shown in  FIG. 1  prior to being bent into shape. 
       FIG. 3  is an elevation view of cross grid member inserted into the clip of  FIG. 1 . 
       FIG. 4  is a fragmentary perspective view of the ceiling system illustrating the joint portion of the system to which an alternate embodiment of the clip of the invention is shown mounted. 
       FIG. 5  is a perspective view of a cross member support portion of the clip shown in  FIG. 4 . 
       FIG. 6  is a perspective view of a main body portion of the clip shown in  FIG. 4 . 
       FIG. 7  is a perspective view of the first fastener portion of the clip of  FIG. 1 . 
   


   DETAILED DESCRIPTION OF THE INVENTION 
   The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. Those skilled in the relevant art will recognize that many changes can be made to the embodiments described while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and may even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof, since the scope of the present invention is defined by the claims. 
   The ceiling grid network of the invention includes a plurality of primary and cross grid members. The grid members shown throughout the drawings are of a generally inverted T-cross section, which are well known in the art. However, it should be noted that other grid members could be used in the grid network of the invention. The primary and cross grid members are typically spaced in perpendicular relation to accommodate ceiling panels and other suspended ceiling equipment, such as light fixtures. The grid network formed can be suspended from a stationary fixed ceiling. 
   Referring now to  FIGS. 1-3  and  7 , the intersection of a primary grid member and a cross grid member is shown. As shown in  FIG. 1 , the cross grid member  12  is disposed in generally perpendicular relation to the primary grid member  10 . Each of the grid members  10 , 12  comprise a web  14  extending generally vertically and flange  18  extending horizontally from both sides of the vertical web  14 . The vertical web  14  may include a bulb portion  16  at an end of the vertical web  14  opposite the horizontal flange  18 . Although the bulb portion  16  is shown throughout the drawings as having a rectilinear cross section, the bulb can have several different configurations, such as a generally circular cross shape. 
   A joint clip  20  is attached to the grid network at an intersecting point of the primary  10  and cross grid members  12 . In the example embodiment shown in  FIG. 1 , the clip  20  is formed of a single flat piece of generally resilient yet flexible material, such as spring steel material. The material may be stamped using mass production techniques well known in the art.  FIG. 2  shows the clip  20  of  FIG. 1  in its unbent form. When bent into its finished shape, the clip, when viewed from the top, is of general cross shape. 
   A first resilient fastener portion  22  of clip  20  is attached to a primary grid member  10 . As best seen in  FIG. 7 , the first resilient fastener portion  22  has two opposing leg  32 ,  34  which form a downwardly opening channel  36  for straddling the vertical web  14  of a primary grid member  10 . Preferably, the first fastener portion  22  is configured so that its opposed legs  32 ,  34  follow the geometry of the vertical web  14  of the primary grid member  10 , including any bulb portion  16 . If the primary grid member  10  has a bulb  16 , the first fastener portion  22  can be snap-fastened to the primary grid member  10  by forcing it down over the bulb  16 . The opposing legs  32 ,  34  can be slightly spread at the bottom to form an inverted-V channel  37  to allow easier attachment of the clip onto the primary grid member  10  having a bulb  16 . The bulb  16  of different grid members  10  can vary somewhat but are typically of similar width so that a single size of downwardly opening V-shaped channel  37  should be suitable for use with most grid members. 
   When inserted into channel  36 , the primary grid member  10  is slidably secured therein by the crimping of the resilient opposing leg portions  32 , 34  about the vertical web  14  of the primary grid member. The clip  20  is prevented from moving upwardly away from assembled relation by the engagement of the leg portions  32 , 34  with the underside of the bulb  16  of the primary grid member  10 . The apex of the inverted-V channel  37  should be sufficiently tight to provide support for the underside of the bulb  16  of the vertical web  14 . 
   Each leg portion  32 ,  34  may include one or more inwardly detents  38  stamped inwardly in a direction toward the opposing leg. The detents  38  further assist in engaging the vertical web  16  of the primary grid member  10  in a generally snug, gripping relationship in channel  36 , thereby further resisting longitudinal movement of the primary grid member  10  in channel  36 . However, during seismic activity, the primary grid member is able to move within channel  36  in a direction shown by Arrow L despite this resistance. 
   Each clip  20  further includes second and third resilient fastener portions,  24  and  25  respectively, also referred to as “cross grid member supports”, extending from, and integrally connected to, the first resilient fastener portion  22  in generally perpendicular relation. The second resilient fastener portion  24  effectively attaches a first cross grid member  12  to the primary grid member  10 . Likewise, the third resilient fastener  25  portion effectively attaches a second cross grid member  12  to the primary grid member  10 . 
   Each resilient fastener  24 ,  25  has two opposing clip webs  40 ,  42  which generally follow the geometry of the web  14  (and bulb  16 ) of a secondary grid member  12 . In this embodiment, the top of each cross tee support is open forming a channel  44  having generally a Y-shaped cross section.  FIG. 3  shows cross grid member  12  received in the channel  44  of resilient fastener  24 . As shown, the clip webs  40 ,  42  contour to the shape of the vertical web  14  and are spaced so as to provide a snug fit about the grid member  12 . The grid member  12  is secured in channel  44  by the crimping of the clip webs  40 ,  42  about the vertical web  14 . 
   In a conventional configuration, a cross grid member  12  it typically supported by a lower horizontal flange  18  of the primary grid member  10 . Here, support for the cross grid member  12  by the primary grid member is not required as the clip webs are contoured to the underside of the bulb  16  of the secondary grid member  12 . Thus, resilient fastener  24  alone can support the secondary grid member  12 . This is particularly important during a seismic disturbance when cross grid member  12  is displaced in the directions shown by arrow M in  FIG. 1 . A clip web length of at least 2 inches is preferable in order to safely comply with ASTM E 580-02. 
   Each clip web  40 ,  42  may also include one or more detents  38  stamped inwardly in a direction toward the opposing leg. The detents  38  assist in engaging the vertical web  16  of the secondary grid member  12  in a generally snug, gripping relationship, to resist any withdrawal movement of the secondary grid member  12  from fastener portions  24  and  25 . Despite this resistance, during seismic activity, the secondary grid member  12  is able to move in channel  44  in the directions indicated by Arrow M. 
   Since the direction of the motion of the independent ceiling areas during an earthquake is unpredictable it may be possible that two ceiling areas, and therefore their respective cross beams, on either side of a separating primary grid member move in opposite directions lengthwise along the primary grid member, i.e. in opposite directions of the horizontal directions indicated by Arrows P and X in  FIG. 4 . 
   The example embodiment of the joint clip shown in  FIGS. 4-6  permits independent motion of the secondary grid members  12  in the four horizontal directions. The key is that each cross member moves independent of one another and is not dependent on the sliding engagement of the first fastener portion to the primary grid member. In other words, the first fastener portion can be fixedly attached to the primary grid member. It should be noted that the fastening portions illustrated in the second alternative embodiment are individual components and are attached to one another to form the joint clip. 
   In this configuration, each opposing leg  32 , 34  of the first fastener portion  22  has a clip carrier  52  which is defined by a carrying slot  54  stamped in the leg of the first fastener portion  22 . The second and third fastener portions  24 ,  25  of the first embodiment are modified to include a face plate  56 . The face plate  56  integrally extends from the top of the clip webs  40 , 42  in a downward direction but is spaced from the side edge of the clip webs. The face plate  56  contains one or more downwardly extending planar tabs  58  stamped out of the face plate  56  with the top of the tabs  58  integrally attached to the face plate  56 . The tabs  58  engage carrying slot  54  bf the first fastener portion  22 . When engaged, the second or third fastener portion  24 , 25 , and, thus, a cross grid support member  12  attached thereto, can slide along the clip carrier or track  52  in carrying slot  54 , in the directions indicated by Arrows P and X in  FIG. 4 . As before, the cross grid member  12  retains its freedom of horizontal motion in channel  44 , i.e. in a direction perpendicular to the primary grid member  10  as indicated by Arrow M.