Stock material or miscellaneous articles – Sheets or webs edge spliced or joined – Sheets or webs coplanar
Reexamination Certificate
2000-03-20
2002-07-02
Sells, James (Department: 1734)
Stock material or miscellaneous articles
Sheets or webs edge spliced or joined
Sheets or webs coplanar
C428S220000
Reexamination Certificate
active
06413606
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to drywall tapes for finishing drywall joints and, more specifically, to drywall tapes having non-uniform cross-sections, to drywall tape applicators and to methods of finishing drywall joints.
2. Brief Description of the Prior Art
In the field of building construction, wall surfaces are typically formed by flat sheets or panels of drywall affixed to underlying support or frame members. The drywall sheets are typically available in a limited assortment of standard sizes, such as 4 feet×8 feet; and, accordingly, a plurality of drywall sheets must be secured to the frame members in adjacent or abutting side-to-side, end-to-end and/or side-to-end relation in order to form a wall surface of larger dimension. Adjacent drywall sheets are placed as close as possible to one another and, preferably, in abutment with one another. Even though the adjacent drywall sheets are placed as close to one another as possible, a gap or groove is presented between adjacent or abutting side and/or end edges of the sheets. As a result, drywall joints are formed along the adjacent or abutting side and/or end edges of adjacent or abutting drywall sheets. Furthermore, the side edges of conventional drywall sheets are typically provided as “factory edges” in that outer surfaces of the drywall sheets, respectively, have non-sloping outer surface portions, respectively, and sloping outer surface portions, respectively, that slope inwardly from the non-sloping outer surface portions to the side edges. Accordingly, when the factory edge of a drywall sheet is adjacent or in abutment with the factory edge of another drywall sheet, the sloping outer surface portions cooperate to form a shallow depression along the thusly formed joint, the depression having a width extending between the non-sloping outer surfaces portions of the drywall sheets, respectively. An individual wall surface will typically have numerous joints, which interrupt the continuity of the wall surface and present an unattractive appearance. If left unfinished, the joints would be visible through the final wall finish, such as paint, wallpaper or other decorative coating, applied to the wall surface.
Conventional building construction techniques involve finishing the joints formed by adjacent or abutting drywall sheets so as to render the joints as invisible as possible after application of the final wall finish. The joints are finished conventionally using a paper drywall tape, such as Sheetrock® Joint Tape manufactured by U.S. Gypsum Company of Chicago, Ill., secured over the joints with joint compound or “mud”, an aqueous, cementitious adhesive. Conventional drywall tape is approximately 2 inches in width and is of uniform minimal thickness. The tape is supplied in rolls of various lengths ranging, for example, from 75 feet to 500 feet. According to conventional wall finishing techniques, an initial or bedding layer or coat of joint compound is applied over the joints, and the drywall tape is thereafter applied to the joints over the initial or bedding coat of joint compound. When applying the drywall tape, the width of the tape is centered or substantially centered over the corresponding joint so that the tape bridges the gap or groove thereof and is secured to the outer surfaces of the adjacent or abutting drywall sheets, respectively, forming the joint. The bedding coat of joint compound serves the purposes of filling the gaps of the drywall joints, filling the depressions formed at the joints by the sloping outer surface portions, i.e. the factory edges, of the adjacent or abutting drywall sheets and securing the drywall tape to the outer surfaces of the drywall sheets.
After the joint compound has dried, another layer or coat of joint compound is applied over the tape, in a step known as “blocking”, to smoothly blend or merge the tape with the non-sloping outer surface portions of the drywall sheets. Conventional “blocking” involves applying the layer or coat of joint compound as a band or stripe extending along the corresponding joint, the band or stripe being of greater width than the width of the drywall tape so that the joint compound serves to blend or merge side edges of the tape into the non-sloping outer surface portions of the drywall sheets. Usually, the band or stripe is applied so as to have a width of approximately 8 to 10 inches for drywall tape that is 2 inches wide, with the width of the band or stripe being centered or substantially centered over the width of the drywall tape. The joint compound is allowed to dry; and, thereafter, one or more additional layers or coats of joint compound is/are applied over the joints in a step known as “skimming” to render the joints as indistinguishable as possible from the non-sloping outer surface portions of the drywall sheets. The joint compound must typically be allowed to dry between application of the individual coats or layers; and, when dry, the individual coats or layers of joint compound must typically be sanded to obtain a smooth surface merging or blending imperceptively with the non-sloping outer surface portions of the drywall sheets. In addition, the joints usually must be cleaned between the application of individual coats or layers of joint compound in order to achieve the best results. For example, it is desirable that the joints be cleaned to remove dust or other surface debris, such as that generated by sanding.
Wall finishing in accordance with conventional procedures is costly and time consuming due to the materials and labor required. In particular, the need for several coats or layers of joint compound and the need for relatively wide bands of joint compound to “block” the joints adds to the cost of construction. Since the coats or layers of joint compound must be allowed to dry prior to sanding and/or the application of additional coats or layers thereover, it may take several days to finish a wall for painting, papering or other final wall finish. The time required for conventional wall finishing as well as the labor involved in executing the various wall finishing steps further increase the cost of construction.
In addition to the substantial time and cost required, conventional wall finishing techniques also require considerable skill and expertise. It is important, for example, that the tape lay uniformly or evenly as flush or flat as possible with the non-sloping outer surface portions of the drywall sheets and that the tape be sufficiently secured to the drywall sheets to prevent buckling or peeling of the tape. It is also important that the tape not be wrinkled and that there be no air bubbles under the tape. The finished drywall joints should not present abrupt variations in level but, rather, should be imperceptible after the application of paint, paper or other final wall finish. Additionally, the finished joints should not produce shadows or other visual irregularities under various lighting conditions. It is essential, therefore, that the right amount of joint compound be applied to the joints in the correct manner for each layer or coat. Furthermore, the drywall tape must be skillfully applied over the bedding coat of joint compound. In addition, the individual coats or layers of joint compound must be allowed the proper amount of time to dry prior to the application of additional coats or layers of joint compound and/or prior to sanding in order to ensure the aesthetic and structural integrity of the joints. Since application of the joint compound, particularly the “bedding coat”, to the joints is messy, care must be taken to avoid getting the joint compound on drywall surfaces other than those intended to have the joint compound applied thereon. Furthermore, the joints must be sanded with care. It is apparent, therefore, that the quality of finished drywall joints obtained with conventional wall finishing techniques is greatly dependent upon the skill and expertise of a particular wall finisher and is thusly subject to human differences.
Even where drywal
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