Fire resistant ceiling construction
BACKGROUND OF THE INVENTION 
     This invention relates to fire resistant ceilings, and particularly to a fire resistant ceiling for a building in which steel structural members are utilized. In such building constructions it is important to protect the structural members from fire, since the high temperatures associated with the fire will quickly warp and destroy the structural members. 
     Heretofore, no direct means utilizing the ceiling structure itself has been provided to adequately protect these space trusses or structural members from the effects of fire, and accordingly, when a fire occurred, they were quickly damaged or destroyed by the high temperatures associated with the fire. In systems wherein means was provided to protect the structural members from the temperatures associated with a fire, the structure was either excessively expensive or was too complicated to be practical. 
     In accordance with the present invention, an exceptionally simple and economical system is provided for rendering a space grid ceiling construction fire resistant for a predetermined period of time, wherein the space grid ceiling construction includes a plurality of space trusses having bottom chords or base members with oppositely directed flanges on which ceiling panels are supported, and grid protecting fire resistant panels are secured to the space truss bottom chords beneath adjacent edges of the ceiling panels by means of economical and easy to use channel members. 
     Additionally, in accordance with the present invention, unique intersection covers are provided for covering the intersection between the longitudinally and transversely extending base members of the space trusses and perimeter channels are provided for protecting the space truss base members at the perimeter of the ceiling construction adjacent the side walls thereof. 
     Moreover, the unique intersection covers enable thermal expansion of the grid protection members or panels by allowing movement inside the intersection cover and the ceiling construction of the invention has an attractive appearance comprised of exposed white mineral fiberboard with black channels on each side and at the intersection cover. 
     Still further, the unique fire resistant ceiling construction of the invention allows assembly of the ceiling structure without requiring any separate fasteners and the like. 
     OBJECTS OF THE INVENTION 
     It is an object of this invention to provide a fire resistant ceiling construction for a building having a space grid construction comprised of a plurality of space trusses with bottom chords or space members on which ceiling panels are supported, and wherein unique grid protection means is provided for covering the exposed portions of the base members at adjacent edges of the ceiling panels to thus protect the space grid construction from the high temperatures associated with a fire at least for a predetermined period of time. 
     Another object of this invention is to provide a fire resistant ceiling construction which affords protection to metallic structural members in the ceiling for predetermined period of time, and wherein the ceiling construction utilizes fire resistant panels and fastening means which are quickly and easily clipped into position without requiring the use of separate fasteners and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective fragmentary view of a portion of a ceiling construction of the space grid type utilizing a plurality of space trusses. 
     FIG. 2 is a fragmentary exploded view in section showing the manner in which a grid protecting panel is placed in operative association with the bottom chords or base members of a space truss. 
     FIG. 3 is a view similar to FIG. 2 illustrating the manner in which the fastening clip or channel of the grid protecting panel is secured in position. 
     FIG. 4 is a fragmentary perspective view of the grid channel or clip for securing the grid protecting panel in place. 
     FIG. 5 is a bottom perspective view of the intersection cover of the invention. 
     FIG. 6 is an enlarged plan view of the intersection cover of FIG. 5. 
     FIG. 7 is an enlarged view in section with portions broken away of the intersection cover in FIG. 5. 
     FIG. 8 is an enlarged fragmentary view in section of a portion of a perimeter of a building construction showing the perimeter channel of the invention. 
     FIG. 9 is an enlarged, fragmentary, perspective view of the perimeter channel of FIG. 8. 
     FIG. 10 is a fragmentary view looking up toward a portion of a ceiling constructed in accordance with the invention, with the intersection covers omitted. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A portion of a building construction of the space grid type is indicated generally at 10 in FIG. 1 and comprises a plurality of space trusses 11 having roof supporting top chords 12 and ceiling supporting bottom chords 13. 
     As seen in FIGS. 2 and 3, the bottom chords or base members 13 have outwardly directed, horizontally extending flanges 14 thereon, on which suitable ceiling panels 15 are supported at their opposite edges. These ceiling panels are fire resistant. As seen clearly in FIGS. 2 and 3, the base members 13 between adjacent space trusses are spaced apart, thus leaving a space S therebetween through which fire and heat could readily pass to the space or area above the ceiling panels 15 and consequently damage or destroy the metal structural members or trusses. It should be noted that the longitudinally extending base members are designated as 13 and are shown in full lines in FIGS. 2 and 3, whereas the transversely extending base members have a configuration as indicated at 13&#39; in phantom lines in FIGS. 2 and 3. 
     Thus, with conventional constructions, it is readily apparent that when the ceiling panels 15 are positioned on the flanges 14 of the base members, the base members themselves are exposed to the effect of fire and would, therefore, be quickly damaged or destroyed by the high temperature associated with the fire. 
     Therefore, in accordance with the present invention, fire resistant grid protecting panels 16 are quickly and easily secured in position beneath the base members 13 by means of unique attaching clips or channels 17, thus covering the exposed structural base members with thermal protective material and contributing to the integrity of the fire protection provided by the ceiling components. 
     In a preferred construction, the grid protecting panels 16 comprise a white mineral fiberboard and all are approximately three inches wide, and panels 16a applied to the longitudinally extending base members 13 are approximately sixty inches long, and panels 16b as applied to the transversely extending base members 13&#39; are approximately fifty-seven inches long. Thus, as seen in FIG. 10, the shorter panels abut the longer panels and effectively shield the base members. 
     The channel clips or fasteners 17 preferably comprise 26 gauge steel prepainted black, and have an upwardly extending vertical flange or wall 18 approximately 5/8 of an inch high joined at its bottom to a horizontally extending flange or wall 19 approximately 9/16  of an inch wide, which is in turn joined with a downwardly extending wall 20 at an angle α of approximately 88°, the wall 20 having a width of about 3/4 of an inch. The wall 20 is in turn connected at its bottom edge with a second horizontally extending wall or bottom flange 21 at an angle β of 85° and the wall 21 is about 15/16  of an inch wide. The outer or free edge of bottom wall 21 is turned reversely upon itself at 22 for a distance of approximately 3/8 of an inch. With the clip as thus formed, the top and bottom walls 19 and 21 and the reversely extending portion 22 at the free edge of bottom wall 21 afford a resilient clamping action against the edge of the grid protecting panels 16 to securely clamp the panels 16 to the horizontally extending flanges 14 of the base members of the space trusses. 
     In assembling the ceiling construction of the invention, a clip or channel 17 is first applied or attached to one edge of a grid protecting panel 16, as seen in FIG. 2, and the channel and panel are then positioned with a flange 14 of one base member 13 received the top wall 19 and bottom wall 21 of the channel 17 and a second channel 17 is then inserted or positioned over the flange 14 and edge of panel 16 at the opposite side of the base member 13, as in FIG. 3. Ceiling panels 15 are subsequently positioned with their opposite edges lying on top of the top walls 19 of the channels 17 and their edges abutted against the upwardly extending flanges or walls 18 thereof. A spring clip C, having a pair of spaced, downwardly extending, yieldable legs and a horizontal tab, is positioned over the wall 18 to hold the panels 15 downwardly on the supports, as seen in FIG. 3. 
     A unique intersection cover 23 is provided at the intersection of the longitudinal and transverse base members, as seen in FIG. 5, to cover the joint at the intersection between the grid protecting panels 16a and 16b. The intersection cover 23 is substantially rectangular in configuration and has an upstanding integral tab 24 at each of the opposite corners thereof. The intersection cover has vertically offset center and corner portions 25 and 26, which not only reinforce the intersection cover, but impart an attractive appearance thereto. Each of the corner tabs 24 has a horizontally extending slot 27 therein which defines a weakened area between the ends of the tabs whereby the upper end 28 of the tab may be easily bent downwardly over the adjacent corner portions of the grid protecting panels 16 and the grid panel attaching channels 17. 
     In a preferred construction, the intersection covers 23 also comprise 26 gauge steel prepainted black and the tabs are approximately 1-13/16 inches long and 3/4 of an inch wide, and the cover is about four inches square. 
     In FIGS. 8 and 9, a perimeter channel 29 comprises a downwardly extending wall or flange 30, a horizontally extending wall or flange 31 and a vertically extending wall 32, with a horizontally offset portion 33 at its upper edge and a vertically extending flange 34. The perimeter channel 29 is utilized at the perimeter of a ceiling structure adjacent a wall W, and the horizontal and vertical flanges 33 and 34 are positioned over the flange 14 of a space truss base member 13 for receiving a ceiling panel 15, and the downwardly extending wall 30 of the perimeter channel 29 is received between a wall header angle 35, if one is provided, and a trim clip 36, which is attached to the wall with a suitable fastener means F. Suitable trim 37 is clipped or snap fitted to the trim clip 36 in a conventional manner. Thus, the perimeter channel 29 affords protection of the space truss base member 13 at the perimeter of the ceiling construction and also provides an attractive appearance or trim item at the perimeter of the ceiling. 
     The perimeter channel, in a preferred construction, also comprises 26 gauge steel prepainted black and is approximately 60 inches long, and the wall portion 31 is approximately 1-7/16 inches wide. 
     Thus by means of the present invention, a ceiling may be quickly and easily constructed and assembled which is both economical and fire resistant, and a ceiling constructed in accordance with the invention effective resists the effects of a fire for approximately one hour, thus affording ample time to control the fire before structural damage to the space trusses results. 
     As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is, therefore, illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims or that form their functional as well conjointly cooperative equivalents are, therefore, intended to be embraced by those claims.