Abstract:
A cornerbead for installation at a drywall outside corner, the cornerbead includes a substrate forming a nose and first and second elongated flanges. A first strip of perforated tape is adhered to the first flange at its exterior surface. The first strip of tape extends longitudinally of the first flange and a portion of the first strip of tape extends past the outer edge of the first flange. A second strip of perforated tape is adhered to the first elongated flange at its interior surface. The second strip of tape extends longitudinally of the first flange. The first strip has a coating of adhesive material on a side that faces towards the first flange and the second strip has a coating of adhesive material on a side that faces away from the first flange.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation-in-part of co-pending patent application Ser. No. 11/116,991 filed Apr. 27, 2005, the entire disclosure of which is hereby incorporated herein by reference for all purposes, and claims benefit of U.S. Provisional Application No. 60/565,904 filed on Apr. 27, 2004, the entire disclosure of which is hereby incorporated herein by reference for all purposes. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     In building construction, interior walls are generally formed by attaching preformed sheets of gypsum wallboard to a supporting frame. These sheets of wallboard are susceptible to damage, especially at outside corners. In order to protect an outside corner of a wall, a cornerbead is often installed on the corner prior to painting. A conventional cornerbead is typically a thin, elongate strip of metal or plastic with a right angle bend along the strip&#39;s longitudinal axis. The right angle bend forms a nose and two flanges extend from opposite sides of the nose. Holes are provided for nailing or screwing the cornerbead to the drywall.  
         [0003]     During the construction process an installer must place the cornerbead on the desired outside corner, hold the cornerbead in place with one hand and attach the cornerbead to the drywall using nails or screws with his or her other hand. Joint compound is then applied over the seam between the edge of the flanges and the wallboard to provide a smooth surface transition for painting. This process is very time consuming and must be repeated many times in a typical new construction project.  
         [0004]     Other techniques for attaching cornerbead to the drywall have been used. For example, U.S. Pat. No. 5,045,374 discloses a plastic cornerbead in which each flange is provided with a double-sided pressure sensitive adhesive tape strip adhering to the interior surface of the flange. The side of the strip that is inward relative to the flange, i.e. towards the drywall, is covered with a non-adhesive ribbon coated with a release agent. To install the cornerbead at a drywall outside corner, the ribbons are removed from the adhesive strips and the cornerbead is placed in position at the drywall outside corner. The adhesive strips hold the cornerbead in position without need for nails. The installer covers the flanges of the cornerbead and the adjacent drywall with joint compound, in conventional fashion. The adhesive tape strips prevent the joint compound from penetrating between the flanges and the drywall and accordingly the double-sided adhesive strips provide the permanent connection between the cornerbead and the drywall and the joint compound is simply a coating over the flange of the cornerbead and the adjacent drywall. Since the plastic cornerbead is flexible, and the adhesive strips allow limited movement of the flanges, significant movement of the flanges can occur in the event that the cornerbead is struck, for example when moving furniture. Accordingly, the joint compound, when dried, is prone to cracking along the outer edge of the flange.  
         [0005]     Cracking of drywall joint compound along the outer edge of the flange of a cornerbead is a significant problem for drywall installation and offsets many of the gains that have been made in use of alternative materials, such as plastic rather than metal, and alternative attachment techniques, such as adhesive rather than nails.  
         [0006]     What is needed is a cornerbead that is easier and faster to install than a conventional metal cornerbead yet does not result in cracking of the joint compound along the outer edge of the flange.  
       SUMMARY OF THE INVENTION  
       [0007]     In accordance with a first aspect of the invention there is provided a cornerbead for installation at a drywall outside corner, the cornerbead comprising a substrate forming a nose and first and second elongated flanges, each flange having an exterior surface and an interior surface, being formed with holes penetrating from the exterior surface to the interior surface, and having an inner edge and an opposing outer edge, each flange joining an opposing side of the nose at the flange&#39;s respective inner edge, a first strip of perforated tape adhered to the first elongated flange at the exterior surface thereof, the first strip of tape extending longitudinally of the first flange and a portion of the first strip of tape extending past the outer edge of the first flange, and a second strip of perforated tape adhered to the first elongated flange at the interior surface thereof, the second strip of tape extending longitudinally of the first flange, and wherein the first strip has a coating of adhesive material on a side that faces towards the first flange and the second strip has a coating of adhesive material on a side that faces away from the first flange.  
         [0008]     In accordance with a second aspect of the invention there is provided a method of manufacturing a self-adhering cornerbead, the method comprising the steps of forming an elongate substrate of uniform cross-section, said substrate including a nose, a first flange and a second flange, each flange having an exterior surface and an interior surface, being formed with holes penetrating from the exterior surface to the interior surface, and having an inner edge and an outer edge, each flange joining an opposing side of the nose at the flange&#39;s respective inner edge, and adhering a first strip of perforated tape longitudinally along the exterior surface of the first flange such that a portion of the first strip extends beyond the outer edge of the first flange, and adhering a second strip of perforated tape longitudinally along the interior surface of the first flange, and wherein the first strip has a coating of adhesive material on a side that faces towards the first flange and the second strip has a coating of adhesive material on a side that faces away from the first flange. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which  
         [0010]      FIG. 1  is a perspective view of a stage in the manufacture of a cornerbead embodying the present invention wherein strips of fiberglass mesh tape are being applied to the flanges of the cornerbead,  
         [0011]      FIG. 2  is a perspective view of a stage in the manufacture of a cornerbead embodying the present invention wherein a protective paper backing is being applied to the exposed portion of one of the strips of fiberglass mesh tape,  
         [0012]      FIG. 3  shows a cross-sectional view of a bullnose cornerbead embodying the present invention wherein a layer of coating material, which could be either polyurethane foam or paper, has been applied to the nose of the cornerbead,  
         [0013]      FIG. 4  is a cross-sectional view of a right-angle cornerbead embodying the present invention,  
         [0014]      FIG. 5  shows a cross-sectional view of a bullnose cornerbead embodying the present invention, and  
         [0015]      FIG. 6  shows a modification of the method described with reference to  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0016]     Referring to  FIG. 1 , the illustrated plastic cornerbead  20  is of uniform cross-section and is formed from a heated softened polymer extruded from a die (not shown). The cornerbead  20  includes a nose  22  and two perpendicular flanges  24 ,  26  joined by the nose  22 . Each flange  24 ,  26  has a thicker portion proximal to the nose  22 , a thinner portion distal to the nose  22 , an interior surface  27  and an exterior surface  28 . As the cornerbead  20  is extruded from the die, the flange  24  passes through a pair of rollers  30 A. A strip of fiberglass mesh tape  32 , from a tape supply roll (not shown), is fed through the pair of rollers  30 A. Thus the rollers  30 A apply the mesh tape  32  to the distal portion of the exterior side  28  of the flange  24 . The mesh tape  32  is positioned such that a portion  34  of the mesh tape  32  extends beyond an outer edge  36  of the flange  24 .  
         [0017]     In an embodiment of the invention, the mesh tape  32  is adhered to the flange  24  by a coating of adhesive material on an interior side  40  of the tape  32 .  
         [0018]     In another embodiment of the invention, the tape  32  is applied to the flange  24  before the softened polymer material is fully hardened, immediately after the cornerbead  20  is extruded from the die. Pressure from the set of rollers  30 A causes the tape to be embedded into the plastic and, as the plastic hardens, a bond is formed between the tape  32  and the flange  24 . An adhesive material is then applied to the interior side  40  of the exposed portion  34  of the tape  32 .  
         [0019]     Referring to  FIG. 2 , a protective paper backing  42  is removeably applied to the exposed portion  34  of the tape  32  to protect the adhesive material during shipping and storage. This may be accomplished immediately downstream of the station shown in  FIG. 1 , using a second pair of rollers  44 A in a manner similar to the application of the strip of fiberglass mesh tape shown in  FIG. 1 .  
         [0020]     A third pair of rollers  30 B, fed by a second tape supply roll (not shown), may apply a strip of fiberglass mesh tape  32  to the flange  26  in a manner similar to the one described above. Likewise, a fourth pair of rollers (not shown) may apply a protective paper backing to the strip of mesh tape  32  adhered to the flange  26  in a manner similar to the one described above.  
         [0021]     The cornerbead  20  is produced in indeterminate lengths, then cut into standard lengths for storage and shipping purposes. In use, an installer can cut the cornerbead  20  to any desired length.  
         [0022]     To install a cornerbead  20  embodying the present invention, an installer would remove the protective backing  42  from the exposed portions  34  of the tape  32  to expose the adhesive material and then place the cornerbead  20  into the desired position on a outside corner. Applying pressure along the length of the exposed portions  34  of the tape  32  will cause the cornerbead to adhere to the outside corner. The installer does not need to hold the cornerbead in place with one hand while securing it in position with nails or screws. Joint compound may then be applied to cover the tape  32  and provide a smooth transition surface from the drywall to the nose  22 .  
         [0023]     Referring to  FIG. 2 , in another embodiment of the invention, the flange  26  is formed with grooves  45  extending longitudinally along the interior surface  27  of the flange  26 . Holes  48  are punched through the flange  26  and open into the groove  45 . During installation joint compound applied to the cornerbead  20  will be forced through the holes  48  and will spread into the recess formed by the groove  45 . This creates an improved bond between the joint compound and the cornerbead  20 .  
         [0024]     Referring to  FIG. 3 , in another embodiment of the invention, wherein the cornerbead  20  is formed from a polymer such as vinyl, a thin layer of closed-cell polyurethane foam  48  is applied to the exterior surface of the nose  22  and any portions of the flanges  24 ,  26  not covered by the mesh tape  32 . The foam&#39;s surface is then subjected to abrasion, for instance via sandblasting, to provide improved bonding characteristics with paint or other finishing products likely to be applied after installation.  
         [0025]     Fiberglass mesh tape provides a good bonding surface for joint compound. The fiberglass mesh tape comprises a plurality of longitudinal and transverse strands that intersect to define an array of apertures. When the cornerbead is installed, these apertures allow joint compound to bond with the tape as well as the surface of the wallboard beneath the tape thus reinforcing the joint compound as well as providing a smooth surface for painting.  
         [0026]      FIG. 5  illustrates another embodiment of the invention.  FIG. 5  not only shows that the invention is applicable to other configurations of cornerbead than right angle cornerbead and is applicable in particular to bullnose cornerbead, but also shows that the fiberglass mesh tape  32  may be attached to the interior surfaces  27  of the flanges  24 ,  26  in addition to the exterior surfaces  28  thereof. In the event that it is desired to attach the mesh tape to the interior surfaces of the flanges, as shown in  FIG. 5 , a coating of an adhesive that will bond to both the cornerbead material and the mesh tape is applied to the interior surfaces of the flanges after the extruded cornerbead has hardened and the mesh tape is applied to the adhesive-coated flanges using rollers in a manner similar to that described with reference to  FIG. 1 . The strip of mesh tape that is applied to a flange has a coating of adhesive on its interior surface (the surface remote from the flange), and this adhesive coating is covered with the protective backing  42 . When the protective backing  42  is removed and the cornerbead is applied to a drywall outside corner, the adhesive material on the interior surface of the mesh tape provides a bond between the interior surface of the flange and the drywall. The  FIG. 5  structure has the advantage that the cornerbead is secured more firmly to the gypsum wallboard and is therefore less likely to be accidentally dislodged or disturbed. Alternatively, the inner strip of mesh tape may be applied to the interior surface  27  of the flange  24  before the softened polymer material is fully hardened. Pressure from a set of rollers causes the tape to be embedded into the still soft plastic and, as the plastic hardens, a bond is formed between the tape and the flange&#39;s interior surface in a manner similar to that described with reference to  FIG. 1 .  
         [0027]     Referring again to  FIG. 3 , in another embodiment of the invention, wherein the cornerbead  20  is formed from a polymer such as acrylic and fiberglass mesh tape has been attached to both the interior surfaces of the flanges  24 ,  26  and the exterior surfaces thereof, a thin sheet of paper  48  is adhered to the exterior surface of the nose  22 .  
         [0028]      FIG. 4  illustrates another embodiment of the present invention that is the result of the manufacturing process shown in  FIG. 2 .  
         [0029]      FIG. 6  shows a modification of the method described with reference to  FIG. 2 . In accordance with this modification, the protective paper backing tape  42  is not applied to the interior surface of the mesh tape  32  adhering to the exterior surfaces of the flanges, but an adhesive that will bond to both the cornerbead and fiberglass mesh tape is applied to the interior surfaces of the flanges of the cornerbead, a second strip of fiberglass mesh tape is applied (adhesive side inward) to the adhesive on the interior surface of each flange, as described with reference to  FIG. 5 , and a paper backing tape (not shown) is applied over the interior surface of the second strip of fiberglass mesh tape, as also described with reference to  FIG. 5 . Such a construction ensures that the cornerbead will be held in place after being positioned over the gypsum wallboard but nevertheless permits the cornerbead to be removed and repositioned should adjustment be necessary. When the installer is satisfied with the position of the cornerbead, the installer applies joint compound over the flanges and the adjacent wallboard, in conventional fashion. The joint compound penetrates through the apertures in the mesh tape and the holes  48  in the flanges and spreads between the flanges and the drywall in the grooves  45 . When the joint compound has dried, the mesh tape is firmly integrated into the joint compound and the joint compound provides a firm permanent bond between the cornerbead and the wallboard. The mesh tape reinforces the joint compound and virtually eliminates the danger that the joint compound will crack under normal circumstances.  
         [0030]     It will be appreciated that the invention is not restricted to the particular embodiment that has been described, and that variations may be made therein without departing from the scope of the invention as defined in the appended claims and equivalents thereof. For example, although it is preferred that strips of apertured tape be attached to both the exterior surface and the interior surface of the flange, it is not essential to the invention to employ a strip of apertured tape at the interior surface of the flange. In particular, it would be possible to apply a film of adhesive to the interior surface of the flange. The holes in the flange would still allow the joint compound to penetrate the flange and bond the cornerbead to the drywall. Unless the context indicates otherwise, a reference in a claim to the number of instances of an element, be it a reference to one instance or more than one instance, requires at least the stated number of instances but is not intended to exclude from the scope of the claim a structure having more instances of that element than stated.