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BACKGROUND OF THE INVENTION 
   The present invention is directed to a drywall trimming element. More particularly, the present invention pertains to a drywall trimming element having a compound locking feature to enhance the bond between the element and the compound. 
   Drywall trimming elements are used at the intersection of drywall planes. For example, a drywall trimming element can be used at the intersection of two planes that define an outer corner. The trimming elements protect the edges and corners of the drywall from bumps, abrasions and damage. Trimming elements can also be used at inside corners (intersections that define an acute angle), to provide a smooth and visually appealing finish, as well as to protect the inside corner from damage. 
   Outside trimming elements are presently made, in one form, from metal. The metal corner bead includes an elongate corner, typically rolled or bent, and a pair of flanges or legs extending from the corner at about a 90 degree angle. To set these metal corner beads in place, the bead is fastened to the support behind the wall board (such as a wood stud) by screws, nails or the like through the legs. One or more layers of joint compound are applied over the bead, from the corner outwardly, over the legs, and smoothed to the wall surface (referred to as feathering), to eliminate any visual distinction from the corner to the wall surface. 
   While metal corner beads do in fact protect the drywall corners from damage, they too can be subject to damage, for example, when bumped or struck. In addition, the adhesion or bonding of the compound to the metal bead is limited. As such, with even a minor strike of the bead, the compound can separate from the bead resulting in a crack, crevasse or open spot at the corner bead. 
   Extruded plastic moldings have come into greater use (over metal) for a number of reasons. First, is their ease of use—they are easy to install, cut (when necessary) and fit to a corner. They are also much more “forgiving” and less subject to unwanted bending than metal when being stored and handled. Moreover, extruded materials will not discolor (e.g., rust) or corrode when subject to less than ideal or controlled environmental conditions. 
   It has also been found that extruded materials (moldings) can be formed into a wide variety of shapes and sizes. As such, extruded materials are used to form large radius corner elements, such as that disclosed in Koenig, Jr., et al., U.S. Pat. No. 6,691,477, crown moldings and crown-type moldings, as disclosed in Koenig, Jr., et al., U.S. Pat. No. 7,200,970, and archway moldings, as disclosed in Koenig, Jr., et al., U.S. Pat. No. 6,119,420, all of which are commonly assigned with the present application and all of which are incorporated herein by reference. 
   In order to secure the elements and moldings to the drywall, one or both of the legs of the elements and molding have openings therein. A fastener can be used to secure the element to the wall and one or more layers of joint compound are applied over the legs to create a smooth transition from the element to the wall surface. In some installations, the element is installed without the fastener, in which case a layer of joint compound is applied to the wall and the element is pressed into the wet joint compound. The openings in the element allow for the flow of joint compound therethrough which, when dried, hardens to secure the element to the wall. 
   Even though the hardened joint compound bonds well to and secures the element to the wall, it has been observed that when the element is struck a relatively hard blow, the compound will crack and the element can separate from the wall. While minor cracks can generally be readily fixed with sanding and applications of fresh compound (with intermediate sanding) and painting, if the element separates from the wall, repair is usually not so readily accomplished. That is, when the element separates from the wall, dried compound may fall from the wall or element and prevent the element from lying flush on the wall. This can result in the element bulging from the wall at locations where compound has collected between the element and the wall. It has also been observed that cracking and the like often occurs during settling of a wall/structure. 
   It has also been found that with substantial blows to the element, exterior compound can separate from the element. While this is readily repaired, the more cracking or chipping that occurs, the more repair that it required. 
   Accordingly, there is a need for a drywall trimming element that secures to a drywall with a high degree of integrity. Desirably, such an element permits being readily secured to the wall with compound such that the compound will not loosen from the element when struck. More desirably, such an element includes provisions to “lock” the compound to the element in such a manner as to withstand a substantial blow. 
   BRIEF SUMMARY OF THE INVENTION 
   A drywall trimming element is used for bridging two sections of drywall and is configured for securing to the drywall by joint compound. The element includes first and second opposing flanges each having an interior surface and an exterior surface. The interior surfaces are adapted to be positioned on or adjacent to a respective one of the drywall surfaces and the exterior surfaces are adapted for orienting away from the drywall surfaces. The interior and exterior surfaces each define respective surface planes. 
   One or both of the interior and exterior surfaces have a plurality of upstanding longitudinally oriented ribs extending outwardly from the surface. The ribs extend away from their respective surfaces in a manner to define a void space between the surface adjacent to the ribs and an end of the ribs, such that a line extending outwardly from and normal to the surface of the flange adjacent to the ribs traverses through the void space and then subsequently contacts the ribs. 
   The void space is a region in which compound accumulates and sets around the rib, and from which the compound cannot be pulled directly away from the flange without contacting and moving the rib. The set joint compound is keyed into the void space and functions to lock the compound between the flange surface and the rib. 
   The ribs can be formed having a curved profile extending from the surface or a straight profile in which the ribs extend away from the flange at an angle other than 90 degrees to the surface of the flange. The ribs can also be formed having an enlarged head portion. 
   The ribs can be formed on the interior flange surfaces and/or the exterior flange surfaces, and can include openings or holes in one or both of the flanges. 
   The drywall trimming element can take the form of a corner element having a central curved or curvable portion between the flanges, a corner molding, an archway molding or any other drywall trimming element shape, configuration or functionality. 
   The trimming element can also be configured having one mounting flange having an interior surface adapted to be positioned on or adjacent to the drywall. The interior surface defines a surface plane and has a plurality of upstanding longitudinally oriented ribs extending outwardly from the surface. The ribs extends away from the surface to define a void space between the surface adjacent to the ribs and an end of the ribs, such that a line extending outwardly from and normal to the surface of the flange adjacent to the ribs traverses through the void space and then subsequently contacts the ribs. 
   Such an element can be configured to, for example, mount a chair rail or other architectural feature to dry wall. 
   These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
       FIG. 1  is a perspective view of one type of corner element (a bull nose element) having a compound locking feature embodying the principles of the present invention; 
       FIG. 2  is a cross-sectional view showing the corner element installed on a wall (outer) corner. 
       FIG. 3  is a sectional view or profile of the element of  FIG. 1  shown in a flat form and  FIG. 3A  is an enlarged partial view of the element; 
       FIG. 4  is a sectional view or profile of an alternate embodiment of the element shown in a flat form and  FIG. 4A  is an enlarged partial view of the element; 
       FIG. 5  is a perspective view of a section of crown molding having the present corner element; 
       FIG. 6  is cross-sectional view of the crown molding taken along line  6 - 6  in  FIG. 5 ; 
       FIG. 7  is a section of archway molding having the present compound locking feature; and 
       FIGS. 8 ,  8 A through  12 ,  12 A are sectional and enlarged partial views of alternate embodiments of the trimming element with compound locking feature. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. 
   It should be further understood that the title of this section of this specification, namely, “Detailed Description of the Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein. 
   Referring now to the figures, and in particular to  FIG. 1  there is shown an exemplary corner element  10  having a compound locking feature  12  embodying the principles of the present invention. The illustrated corner element  10  will be recognized by those skilled in the art as a bull nose corner element. The element  10  is so-named for its large radius rounded profile. 
   The element  10  has a pair of legs or flanges  14  extending outwardly from the radius portion  16 . The flanges  14  are offset rearwardly (as indicated at  18 ) from the periphery of the radius portion  20  and define a “mud leg” for the element  10 . As seen in  FIG. 2 , as indicated at  22 , this is the region that accommodates joint compound C to secure the element  10  to the drywall D. The flanges  14  define an inner or interior surface  24 , which is that surface that lies adjacent or facing the drywall D and an outer or exterior surface  26 , which is that surface that is oriented outward from the wall D. 
   The flanges  14  can include openings  28  therein to accommodate fasteners (e.g., screws, nails or the like), if it is desired to use fasteners. The openings  28  can also accommodate joint compound that is applied (or flows) between the exterior  26  and interior  24  surfaces of the flange. 
   The flanges  14  include a novel compound locking feature  12  that provides regions around which the compound C hardens to bond the element  10  and compound to one another and to the drywall D. In one embodiment, as seen in  FIGS. 3 and 3A , the flanges  14  include a plurality of ribs  30  that extend outwardly from the flange  14 . The ribs  30  are formed longitudinally on the flange  14 , traversing the length of the flange  14  (see  FIG. 1  for the longitudinal orientation of the ribs  30 ). 
   The ribs  30  extend out from the flange  14  a distance (or height) h 30  that is less than the distance d 18  from the exterior surface  26  to the outer surface of the radius portion  16  (less than the offset  18 ). In this manner, the ribs  30  remain below a surface defined by the outermost peripheral profile of the radius portion  16  to provide a smooth transition of joint compound C to the drywall D surface. 
   The ribs  30  extend outwardly from the surface of the flange  14  at an acute angle α (as measured from the base  32  to an end  34  of the rib  30 ) relative to the plane P 14  of the flange  14 . This creates a void space  36  between the surface of the flange  14  and the rib  30 . The void space  36  is best seen by a line N extending from and normal to the flange  14  (or the plane P 14 ) that is spaced from the base  32  of the rib  30 . The line N, as it extends upward traverses through the void space  36  and contacts the rib  30  at some point along the line N, along the rib  30 . The void space  36  is a region in which compound C accumulates and sets (or hardens) around the rib  30 , and from which the compound C cannot be pulled directly away from the flange  14  without contacting and moving the rib  30 . Essentially, the set joint compound C is keyed into the void space  36  and functions to lock the compound C between the flange  14  and the rib  30 . 
   Viewed another way, the set joint compound C forms a wedge of hardened material that is not readily pulled out from under the rib  30  nor from the joint compound that is set over the outward side of the rib (as indicated at  38 ). As seen in  FIGS. 3 and 3A , the ribs  30  can be formed having a curved profile to create a larger void space  36  (compared to straight, angled ribs). 
   An alternate embodiment of the drywall element  110  having a compound locking feature  112  is illustrated in  FIGS. 4 and 4A . In this embodiment, the ribs  130  are formed relatively straight from the base  132  to the end  134  of the rib  130 , and with a bead  140  running longitudinally along the end  134  of the rib  130  (the bead  140  appears as a rounded shape in cross-section). The bead  140  creates a larger interference element in the set compound C, from which the rib  130  has to be pulled to dislodge the element  110 . 
   Although both embodiments of the element  10 ,  110  are shown with ribs  30 ,  130  extending from both the inner  24 ,  124  and outer  26 ,  126  surfaces of the flange  14 ,  114 , it will be appreciated that the elements  10 ,  110  could be formed with ribs  30 ,  130  extending from one or the other surface, as desired. It is also to be understood that the ribs  30 ,  130  on the outer surface  26 ,  126  bond to compound C that is applied to the outer surface  26 ,  126  or over the flange  14 ,  114 . In this configuration, loosening of the compound C on the outer surface  26 ,  126  will be lessened when the element  10 ,  110  is struck. 
   Conversely, ribs  30 ,  130  on the inner surface  24 ,  124  will establish a better bond among the element  10 ,  110  and compound C and drywall D. In this manner, in the event that the element  10 ,  110  is struck, there is less tendency for the element  10 ,  110  to separate from the drywall D. This is extremely advantageous in that if the element  10 ,  110  does not separate from the drywall D and if only cracks along the sides of the element  10 ,  110  occur, then repair is minimal. On the other hand, if the element  10 ,  110  separates from the drywall D, then the element  10 ,  110  may have to be removed, the underlying drywall D repaired and the element  10 ,  110  (or a new element) installed, which is a much more involved repair. 
   The trimming element  10 ,  110  can be formed as a wide variety of elements, for example, the traditionally recognized outside corner element  10 ,  110  shown in  FIGS. 1-4 . It will be appreciated that the trimming element can be formed as a crown molding  210 , such as that illustrated in  FIG. 5 . In this configuration, a flange  214  having the compound locking feature  212  can extend from an edge  242 , e.g., bottom, of the molding  210  for securing the molding  210  to a wall D. A lip or flange  244  can be positioned at an opposite end or edge of the molding  210  that is interior to the molding  212  and is thus in a non-visible location. The flange  214  having the ribs  230  thereon is positioned at a visible end of the molding  210 , and provides a surface that permits a smooth transition of joint compound C (feathering) between the molding  210  and the wall D. 
   Another embodiment of the trimming element  310  is illustrated in  FIG. 7  which shows an archway element that is suitable for archways around doors, windows and other arched architectural feature. The archway element  310  has a flat flange  314   a  (that flange that lies on a flat surface F) and the curved flange portion  314   b  (which is that portion that curves to form the arch). The curved flange portion  314   b  can be formed as a series of tabs  346  formed by slits  348  in the flange  314   b  that extend toward, but not into the corner (or nose) portion  316  of the element  310 . This permits readily bending the element  310 . 
   As can be seen in  FIG. 7 , the present compound locking feature or ribs  330  can be formed in the flat flange portion  314   a  and in the curved flange portion  314   b , on the exterior flange  326  surfaces and although not shown, on the interior flange surfaces. 
   Other configurations of ribs and rib patterns are illustrated in  FIGS. 8-12 .  FIGS. 8 and 8A  illustrate an embodiment  410  of the element in which the ribs  430  extend generally normal to the surface  424 ,  426  of the flange  414 , but include an enlarged head portion  440  that creates a void space  436  under the head  440 , between the head  440  and the surface  424 ,  426 . That is, the enlarged head  440  increases the region or space between the surface  424 ,  426  and the head  440  in which compound accumulates and sets around the rib  430 . The heads  440  are flattened to further increase their width w 440 , and thus increase the size or width of the void space  436 . 
     FIGS. 9 and 9A  illustrate an embodiment  510  in which the ribs  530  extend straight, e.g., linearly, but at an angle β to the surface  524 ,  526 . The ribs  530  are formed generally parallel to one another. Again the ribs  530  are formed with a head portion  540  to better establish the void space  536 . In this configuration, the heads  540  are rounded. 
     FIGS. 10 and 10A  illustrate an embodiment  610  in which the ribs  630  extend straight (again, linearly), but at opposing angles γ to the surface  624 ,  626 . The ribs  630   a  at a positive angle γ are formed generally parallel to one another and the ribs  630   b  at a negative angle γ are formed parallel to one another. Here, the ribs  630  are formed with a flattened head portion  640 . 
     FIGS. 11 and 11A  illustrate an embodiment  710  in which the ribs  730  extend straight (again, linearly), but at opposing angles δ to the surface  724 ,  726 . The ribs  730   a  at a positive angle δ are formed generally parallel to one another and the ribs  730   b  at a negative angle δ are formed parallel to one another. Here, the ribs  730  are formed with a rounded head portion  740 . 
     FIGS. 12 and 12A  illustrate an embodiment  810  similar to  FIGS. 11 and 11A  in which the ribs  830  extend straight (again, linearly), but at opposing angles δ to the surface  824 ,  826 . The ribs  830   a  at a positive angle δ are formed generally parallel to one another and the ribs  830   b  at a negative angle δ are formed parallel to one another. Here, too, the ribs  830  are formed with a rounded head portion  840 . 
   In this embodiment, the ribs  830  extend from the surface  824  of the flange  814  at offset transverse plane locations (see, e.g., P 830aa  and P 830bb ), compared, for example, to the ribs  730  illustrated in  FIG. 11A , in which the ribs  730  extend from the same transverse plane P 730ab . That is, in this embodiment  810 , the ribs  830  are staggered from one another. In addition, as is seen in  FIG. 12 , the ribs  830  can be formed in groups or sets  850   a ,  850   b  along the width of the flange  814 , rather than in a continuous arrangement along the width. 
   It will be appreciated that numerous other shapes and elements and configurations and orientations of trimming elements, as well as the present compound locking feature can be used to affix or apply trimming elements to drywall, and that such other shapes and elements and configurations and orientations are within the scope and spirit of the present invention. 
   It will also be appreciated that although the trimming element is discussed as covering or trimming a corner or the like where two separate sections of drywall meet, it will be appreciated that the present trimming element with compound licking feature can be used on single drywall panel to, for example, provide an architectural detail such as a chair rail. It will be understood that such a trimming element can be affixed to a drywall panel, as a decorative feature and not intended to cove a corner. In such an application, the trimming element can include two flanges, but can also be configured having a single flange. Again, it will be understood that the trimming element spans, extends over or bridges two sections of drywall only insofar as there is drywall on either side of the element. This is not intended to limit the use or application of the trimming element, and the scope of the present invention, as to installations in which two separate drywall sections are bridged. 
   All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure. 
   In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
   From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Summary:
A drywall trimming element for bridging two sections of drywall is an extruded element having first and second opposing flanges each having an interior surface and an exterior surface. The element is secured to the drywall by joint compound. The interior surfaces are adapted to be positioned on or adjacent to a respective one of the drywall surfaces. The interior and exterior surfaces each define respective surface planes. One or both of the interior and exterior surfaces have a plurality of upstanding longitudinally oriented ribs extending outwardly from the surface. The ribs extend away from their respective surfaces and define a void space between the surface adjacent to the ribs and an end of the ribs, such that a line extending outwardly from and normal to the surface of the flange adjacent to the ribs traverses through the void space and then subsequently contacts the ribs. The void space serves to provide a joint compound locking feature for the trimming element.