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BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to grid members of adjustable curvature for constructing curved drywall ceilings. 
       PRIOR ART 
       [0002]    Architects, interior designers, building owners and/or tenants from time to time specify curved ceilings for obtaining a desired look that distinguishes a room or space from the utilitarian appearance of a flat ceiling. The radii of curvature ordinarily varies from site to site and can even vary at a particular site. This variety makes it impractical for manufacturers to produce and inventory an array of grid tees that could correspond to the possible arched ceilings that might be specified. 
         [0003]    On site fabrication of framework for a curved drywall ceiling can require a high level of skill and extensive man hours making such ceiling construction relatively expensive. 
         [0004]    There is a need for manufactured grid members capable of reducing labor costs and required skill and that can be used for a full range of curvatures. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides a manufactured, field adjustable grid tee for use in constructing curved drywall ceilings. The tee can be formed in concave shapes to construct vaults or convex shapes to construct convex ceiling areas. The inventive tees can be arranged in parallel rows and be joined by conventional cross tees to form a non-planar grid to which drywall sheets can be attached. The invention can take various forms including versions that can be locked in an adjusted position with a screw fastener. Other configurations of the inventive tee can be permanently bent into a desired configuration. The stem or spine of the disclosed tees is provided with apertures to enable the tee to be suspended with hanger wires in the customary manner a flat ceiling grid is suspended. 
         [0006]    The tees are formed of sheet metal segments folded into a double layer stem and opposed flanges. The segments, which can be separate elements, initially joined elements or permanently joined elements, are arranged end-to-end. A curvature is imparted to the tee by causing the segments to become slightly angularly oriented to their adjacent segments. In some versions, the segments are assembled with a separate longitudinally continuous face strip, typically of sheet metal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a fragmentary side view of a first embodiment of the tee of the invention with a sheet of drywall attached thereto in a concave or vault configuration; 
           [0008]      FIG. 2  is a fragmentary view of the tee of  FIG. 1  in a convex configuration; 
           [0009]      FIG. 3  is a side view of a single segment of the tee of  FIG. 1 ; 
           [0010]      FIG. 4  is an end view of the segment of  FIG. 3 ; 
           [0011]      FIG. 5  is a fragmentary perspective view of the tee of  FIG. 1 ; 
           [0012]      FIG. 6  is a fragmentary side view of a modification of the tee of  FIG. 1 ; 
           [0013]      FIG. 7  is a plane view of an intermediate sheet metal blank from which the tee of  FIG. 6  is produced; 
           [0014]      FIG. 8  is a fragmentary perspective view of a second version of the inventive grid tee in a straight configuration; 
           [0015]      FIG. 9  is a fragmentary perspective view of a sheet metal blank with structural details of the tee of  FIG. 8 ; 
           [0016]      FIGS. 10A-D  illustrate different configurations of the tee of  FIG. 8 ; 
           [0017]      FIG. 11  is a fragmentary perspective view of a third embodiment of a grid tee of the invention; 
           [0018]      FIG. 12  is a fragmentary cross sectional view of the embodiment of  FIG. 11 ; and 
           [0019]      FIG. 13  is a fragmentary perspective view of a stamped metal sheet preform of segments of the tee of  FIG. 11 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The various tees described herein are manufactured from hot dipped galvanized sheet metal of, for example, between 28 and 22 gauge. The disclosed tees or runners are curvable in the sense that they are typically manufactured with a straight line configuration and are manually reconfigured into a desired curve in a vertical plane on the site where they are to be installed. The disclosed tees are analogous to conventional main tees used in suspended ceiling systems and can have a length of, for example, 10 feet. 
         [0021]    Referring now to  FIGS. 1-5 , a curvable tee  10  comprises a series of identical segments  11  joined end-to-end and an elongated face strip  12  assembled on the segments. The segments  11  are stamped with the illustrated edge profile. A segment  11  has the cross section of an inverted tee with a vertical stem  13  and horizontal flanges  14 . The stem  13  is formed with two layers  16  by bending the sheet stock through 180 degrees at an upper edge  17  of the stem  13 . At a lower edge of the stem  13 , each of its layers  16  is bent 90 degrees to form the flanges  14 . At their mid-lengths, each flange  14  has a tab  18  folded under the main part of the respective flange  14  in the manner of a hem to capture the face strip  12  against the flange  14 . The tabs  18  are sufficiently loose to allow local relative longitudinal sliding movement between the strip  12  and the segment  11 . Viewed from above, the segment  11  has rotation symmetry with one stem layer  16  having the semi-circular projection  19  while the other layer  16  has the projection  19  at the opposite end. 
         [0022]    The layer  16  not having the projection at the segment end has a semi-circular notch or cut-out  21  proportioned to receive a projection  19  of an adjoining segment  11 . 
         [0023]    The geometric center of a projection or tongue  19  at one end of a segment  11  is stamped into an integral rivet  22  which is received in a hole  23  punched into the geometric center of a projection  19  of an adjoining segment  11 . Once positioned in a receiving hole  23 , the rivet  22  can be upset to permanently couple the respective segments  11  together. 
         [0024]    The face strip  12  is longitudinally continuous along the full length of the tee  10  and is assembled within the tabs  18  of all of the segments  11 . Both layers  16  of the stem  13  are formed with aligned vertical slots  24  adapted to receive a pair of connectors of conventional drywall cross tees, one from each side of the tee  10 . Similarly, aligned holes  26  sufficiently large to receive a hanger wire are also formed in the stem layers  16  adjacent its upper edge, designated  27 . 
         [0025]    A sheet metal screw  28  is assembled in a hole  29  in the stem layer  16  forming the rivet  22 . The hole  29  is tangent to the circular edge of the mating projection  19  of the adjacent segment  11 . The tee  10  can be infinitely adjusted, between limits, to any desired curvature concave or convex with reference to the plane of the stems  13 . By way of example, the tee  10  (as well as other embodiments of the tee disclosed hereinbelow) can be placed against a pattern to obtain a desired arc. The tee  10  adjusts to a tangent with the desired curve by an angular displacement between each segment pair about the center of the respective rivet  22 . The segments  11  are locked in their desired positions by tightening the set screws  28 . After its curvature has been established the tee  10  can be suspended with wires assembled through the holes  26  provided in the stems  13 . The center location of the stem  13 , in the lateral direction of the tee  10 , improves the stability of the tee  10  when it is suspended and allows the use of conventional cross tees used in drywall ceilings. 
         [0026]      FIGS. 6 and 7  illustrate a curvable tee  30  that is a modification of the tee  10  illustrated in  FIGS. 1-5 . The same numerals for the same or essentially the same parts and/or function are used in this modification. The stem  13  and flanges  14  are stamped or otherwise formed from a single strip of sheet metal stock illustrated in  FIG. 7 . In an initial manufactured state adjacent segments  11  are joined in the upper region of their stems  13 . This condition can simplify manufacturing processes since individual segments  11  do not have to be individually positioned for assembly. A separate screw or rivet  32  can provide a pivot point for the segments  11  or an integral rivet  22  as described in the embodiment of  FIGS. 1-5  can be employed. The stem or spline  13  can be cut-out at a subsequent manufacturing step after a pivoted joint is established or can be field cut by the technician prior to installation of the tee  30  in a grid. If, rather than a simple cut, a small section of the top area of the adjoining stems  13  above the pivot center is removed, the tee  30  can be curved in a convex configuration. 
         [0027]      FIGS. 8-10  illustrate a second embodiment of the invention in which a curvable tee  40  has segments  41 . Stems  42  of the segments  41  are severed from one another while flanges  43  of the segments  41  remain longitudinally continuous from segment-to-segment. The tee  40  is made from a single sheet metal blank  44 , a short length of which is illustrated in  FIG. 9 . The blank  44  is formed with cross tee slots  45  and hanger holes  50 . The blank  44  is folded 180 degrees on itself at a longitudinal centerline  46  to establish a double layer segment stem  42 . The blank  44  is bent 90 degrees along lines  47  passing through longitudinally oriented slots  48  to create the oppositely extending flanges  43 . Arcuate slots  49  connect between the longitudinal slots  48  and rectangular holes  51  along the centerline  46 . The holes  51  separate adjacent segments  41 . 
         [0028]    The flange area in the blank  44  can be scored or notched transversely to the length of the blank  44  at lines  52  to assure that the tee  40  will bend along such lines when the tee  40  is bent in various configurations such as shown in  FIGS. 10A-10D . Holes  53  punched in the blank  44  accept sheet metal screws to fix a selected angular orientation between adjacent segments  41  to produce a desired curve or angular configuration. The tee  40  is ideal for use in construction of soffits and like structures where drywall panels are to be erected at angles including right angles. Where the desired angle, measured across the face of the tee  40  is greater than 180 degrees, parts of the stems  42  that project through the slots  48  are trimmed as indicated by the broken lines in  FIGS. 10A and 10B . 
         [0029]      FIGS. 11-13  illustrate a curvable tee  60  in a third embodiment of the invention. The tee  60  has segments  61  each with a stem  62  and flanges  63 . The segments  61  are unitary with one another. The tee  60 , additionally, includes a flange face strip  64 .  FIG. 13  illustrates a fractional length of a blank  66  stamped from a strip of sheet metal from which the stem  62  and flanges  63  are formed. The blank  66  includes hanger wire receiving holes  67  and cross tee connector slots  68 . The blank  66  is folded on itself at a centerline  69  to form the double layer segment stems  62  and bent at 90 degrees at the broken lines  71  to form opposed segmented flanges  63 . 
         [0030]    The flange face strip  64  extends continuously longitudinally along the full length of the tee  60 . As shown in  FIG. 12 , the longitudinal margins of the face strip  64  are folded around distal edges of the flanges  63  in the manner of a hem to hold the strip on the flanges while allowing relative local slip between a segment  61  and the strip while maintaining the segments in a common vertical plane. The angular orientation of adjacent segments  61  in the vertical plane is adjusted by applying sufficient manual force to permanently stretch an upper region of a bridge area  73  between two segments, desired concave curvature of the tee  60  can be obtained. Conversely, if a convex curvature is desired, a manual force is applied to elongate a lower portion of the bridge area  73 . 
         [0031]    Drywall sheets can be secured to any of the illustrated curvable tees in the manner illustrated in  FIG. 1 . The drywall sheet, designated  75  is flexed so that it is tangent to the segments and is attached to such segments with self-drilling drywall screws  76  that penetrate any face strip and flanges of the respective tee. 
         [0032]    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 curvable grid tee for suspending drywall capable of being configured vertically into convex or concave shapes comprising a series of identical web segments joined end-to-end, the segments being formed of sheet metal into a tee shaped cross section, the sheet metal of a segment being folded such that each segment has a vertical double layer stem with the stem layers joined at a common fold at upper edges thereof, the sheet metal at lower edges of each layer of the stem being bent outwardly to form a flange, a junction between adjacent segments permitting such adjacent segments to be angularly displaced relative to one another in a vertical plane such that the flanges are capable of supporting a drywall panel in a curved plane.