Abstract:
A partition molding of a metal strip having a right angle cross-section with a vertical leg and a horizontal leg joined at a corner, the horizontal leg having a hem distal from the corner and projecting above a main part of the horizontal leg, the vertical leg having a series of regularly spaced holes for reception of drywall screws used to attach the molding to a wall whereby contact force between the molding and an overlying ceiling is concentrated at the hem and a reaction force can create a moment that serves to urge a lower edge of the vertical leg against a wall on which the molding is mounted.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to drywall construction and, in particular, to a molding for the intersection of a wall and an existing suspended ceiling. 
     PRIOR ART 
     Partition walls are often built after a suspended ceiling has been constructed, especially in remodeling or reconfiguration of existing spaces. Architects and interior designers prefer that the appearance at the upper edge of the partition wall being erected matches the wall angle trim of preexisting perimeter walls. 
     The prior art includes an extruded plastic angle molding intended for use with partition walls being constructed in spaces with existing suspended ceilings. This plastic molding has several disadvantages including an appearance that is distinguishable from standard wall angles. Once installed, the plastic trim is too resilient to be permanently bent to follow minor deviations in the ceiling and wall intersection from a true straight line. Small but discernable gaps between the plastic molding are, consequently, difficult to avoid. 
     The extruded thickness of the prior art plastic molding, used to impart some degree of stiffness, has the disadvantage of requiring a thick layer of joint compound to conceal its edges. Thus, in turn, the molding can require greater drying time for the joint compound. Typically, plastic molding is adhered or stapled to the wall. This leaves the molding vulnerable to moderate stress and strain causing the trim to separate from the wall even after it is finished with joint compound. Fastening with screws can be impractical because the plastic has a tendency to lift up in areas surrounding a screw. Since the described plastic molding is not regularly used, installers are not always familiar with techniques required to adequately install it. 
     To avoid using plastic trim, installers are known to use regular wall angle. This process is tedious since the upstanding vertical leg of the wall angle must be carefully notched to accommodate the ceiling grid elements. Additionally, a backer behind the drywall is commonly used to anchor the screws used to attach the wall angle. These backers are individually cut to fit between adjacent grid elements and are then screwed or otherwise fixed in position. 
     There remains a need for a molding for the described construction that is easy to install and, once installed, is resistant to separation from the wall and that can be permanently shaped to conform to local wall and ceiling run out from ideal straight conditions. 
     SUMMARY OF THE INVENTION 
     The invention provides a partition molding for use with existing suspended ceilings. The disclosed molding is made of a pre-painted strip of ductile sheet steel by conventional roll-forming techniques. The molding is characterized by a hem on a horizontal leg that matches the visible part of conventional suspended ceiling wall angle. When the molding is installed, the hem, additionally, can bias a lower edge of a vertical leg against the partition wall drywall. This and the relatively thin gauge of the metal strip can assure that the leg is concealed with a minimal thickness of drywall compound. A small reverse angle is provided at the corner of the molding to serve as a screed for guiding a taping trowel when burying the vertical leg with joint compound. The vertical leg is lanced to form holes for screws that attach the molding to a wall. Tabs displaced from the holes on the backside of the vertical leg have sharp edges that can bite into the paper cladding of the drywall enabling the molding to be temporarily held in a desired location with minimal finger force until it is fixed with fastening screws. The metal strip material has sufficient ductility to permit the molding to be permanently bent during installation so that the visible part is caused to more closely follow the line of the ceiling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective fragmentary view of a partition molding of the invention; 
         FIG. 2  is a fragmentary front side elevational view of the molding; 
         FIG. 3  is a cross-sectional view of the molding taken in the plane  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the molding taken in the plane  4 - 4  in  FIG. 2 ; and 
         FIG. 5  is a fragmentary cross-sectional view of an upper portion of a partition wall and a suspended ceiling. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, a partition molding  10  is an elongated sheet metal body in the general form of a right angle. The molding  10  is preferably a sheet metal strip roll formed into the illustrated shape. The molding  10  has a vertical leg  11  and a horizontal leg  12  joined at a corner  13 . A side of the strip is pre-painted before it is rolled into the angular shape and is otherwise processed to its final configuration. The painted side forms the bottom of the horizontal leg  12 . The corner  13  is formed as a small right angle oriented oppositely of the right angle of the molding proper. The sheet steel used to form the molding  10  can be, for example, type CS-B G-30 HDG (hot dipped galvanized) made within the standards of ASTM 653. This material has a ductility measured by an elongation in two inches of 20% or more. The horizontal leg  12  distal from the corner  13  includes an upturned and reverse-folded hem  14 , made at the margin of the strip, similar to that provided on conventional wall angle as is well known in the industry. The width of the horizontal leg, not including the reverse corner  13 , ideally matches that of conventional wall angles and is, for example, either 9/16 inch or ⅞ inch. The vertical leg, including the corner  13 , can measure 1.15 inch, for example. The molding can be supplied in lengths of 10 feet, for example. The gauge of the strip material of the molding  10  can be 0.019 inch, for example. Dimensions expressed in this disclosure are intended to include their industry metric equivalents. The offset of the sides of the reverse corner  13  from the main parts of the vertical and horizontal legs  11 ,  12  can, for example, be 0.090 inch or, about, 3/32 inch. 
     An outer face (with reference to an installed orientation) of the vertical leg  11  is knurled with small square indentations to improve adhesion of joint compound. At regularly spaced locations of 2 inches, for example, the vertical leg  11  is lanced to form a rectangular hole  17  and a rectangular tab  18  of material from the hole. The hole  17  is cut on three sides and the tab  18  is folded back at a 4th side. The hole can measure 0.16 inch square, for example, enabling it to receive a number  6  drywall screw without interference with the thread crests and to prevent passage of its head. 
     For reference purposes and by way of example, the height of the hem above a lower face of the horizontal leg  12  can be 0.078 inch or about 5/64 inch. 
       FIG. 5  shows an example of an installation of the inventive molding  10  on a drywall partition wall  26 . The illustrated wall  26  is constructed directly and symmetrically below a grid tee or runner  27  of a grid of a pre-existing suspended ceiling  28 . Attachment clips  29 , with an inverted tee configuration, are assembled over the grid tee  27  at spaced locations above the space where the wall  26  is to be situated. An inverted U-shaped sheet metal stud track  31  is attached to flanges of the clip  29  with screws  32 . The stud track, of known construction, receives upper ends of sheet metal studs  33  (only one is illustrated in  FIG. 5 ) serving as a plate to connect the studs on, for example, 16 inch or 24 inch centers. Alternatively, the wall framing can be wood. Sheets of drywall  34  are attached to opposite sides of the studs  33  and track  31 . 
     With the drywall sheets  34  in place, the molding  10  is located on the drywall so that the hem  14  is at the plane of the ceiling  28  represented by a lower surface  36  of a ceiling tile  37 . The angle between the molding legs  11 ,  12  can be manufactured to be slightly greater than 90 degrees, i.e. nominally 92 degrees. 
     The lanced tabs  18 , as shown in  FIG. 4 , project out of the plane of the vertical leg  11  enabling horizontal sharp edges  41  ( FIG. 3 ) to bite or grip into the paper covering of the drywall  34  with relatively little hand pressure applied to the molding  10 . Once the molding  10  is determined to be in a correct position, light hand pressure will lock it in position against gravity until fastened by a screw  42 . A screw  42  inserted in a proximal hole  17  is driven through the drywall sheet  34 , a depending flange of the track  31  and, in some instances, a flange of a stud  33 . Preferably, the head of the screw locally pulls the sheet metal of the molding leg  11  into the drywall so that the head is substantially flush or countersunk below the outer surface of the leg  11 . Where, as shown, a stud track  31  or other member serving as a plate, is available at the inner top of a wall, the molding  10  requires no additional backing for securement by screws. 
     Since the upper part of the hem  14  is higher than remaining parts of the horizontal leg, a reaction force from contact with parts of the ceiling will tend to rotate the molding in a direction which will bias a lower edge  43  of the vertical leg against the drywall sheet  34 . This can occur where a tab  18  serves as a fulcrum for the pivoting movement or where finger pressure is applied against the vertical leg  11  in both vertically upward and horizontally inward directions. 
     After being fixed to the wall  26  with screws  42 , the vertical leg  11  can be concealed with joint compound. The vertical offset of the reverse corner  13  serves as a screed for a taping knife or trowel. Joint compound applied in one or more coats tapers inwardly from the reverse corner  13  to a vanishing line several inches below the reverse corner. The joint compound conceals the vertical leg including its lower edge  43  and heads of the screws  42 . If desired, joint tape can be applied over the vertical leg to improve the resistance of the joint compound to cracking. The thin gauge 0.019 inch of the molding  10  requires only a minor average thickness of the tapered layer of joint compound to conceal the molding  10  particularly at its lower edge  43 . This reduced volume of joint compound can reduce drying time. 
     The described molding is somewhat malleable or ductile so that it can be manually bent up or down especially along the free or distal edge of the horizontal leg  12  to conform this leg to the ceiling where the ceiling  28  or wall  26  are not perfectly flat, for instance. Where the wall  28  deviates from a flat plane and the vertical leg is drawn against it, the horizontal leg has a tendency to be drawn up or down in a buckling mode. This deflection can be corrected manually by permanently bending the horizontal leg  12  up or down as needed. Plastic moldings are too resilient to permit this type of adjustment. Where an end of the molding  10  intersects an existing wall angle, the molding can be trimmed by cutting the horizontal leg  12  at a 45 degree angle and by positioning it under the existing wall angle to create a faux miter joint. This is not practical with a plastic molding because of the necessary thickness used to obtain stiffness in the plastic molding. 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.