Patent application title: JOINT CEMENT-FREE DRYWALL JOINT CONSTRUCTION AND METHOD
Kurt Hamilton (Orange, CA, US)
IPC8 Class: AE04C234FI
Class name: Static structures (e.g., buildings) assembled in situ-type anchor or tie
Publication date: 2008-10-09
Patent application number: 20080245026
A drywall joint construction and method consisting essentially of abutting
drywall boards having a lengthwise crack therebetween and a joint
finishing system formed within the crack to complete the drywall joint
construction such that a flexible layer defines the joint's center-line
surface. Where the drywall boards are non-tapered, the resulting crack
therebetween may be filled with a flexible compound that also forms the
flexible layer and flushes the joint finishing system with the drywall
1. An interior drywall joint construction consisting essentially of:a
non-recessed first drywall board having a first lengthwise edge and an
outwardly-facing first planar surface, the first lengthwise edge being
substantially perpendicular to the first planar surface;a non-recessed
second drywall board having a second lengthwise edge and an
outwardly-facing second planar surface, the second lengthwise edge being
substantially perpendicular to the second planar surface, the second
drywall board being positioned substantially adjacent the first drywall
board such that the first and second lengthwise edges are brought into
substantially abutting contact so as to form a lengthwise crack between
the first and second planar surfaces, a center-line surface of the joint
construction being defined as the outwardly-facing surface directly over
the crack and exposed for surface treatment; anda flexible compound
filling the crack so as to form the center-line surface and flush the
joint construction with the first and second planar surfaces.
2. The construction of claim 1 wherein the flexible compound comprises:20 to 25 percent by weight filler;6 to 8 percent by weight lightweight filler;10 to 15 percent by weight glass bubbles;1 to 5 percent by weight methylcellulose;30 to 50 percent by weight resin; and10 to 20 percent by weight water.
3. The construction of claim 2 wherein the filler is selected from the group consisting of calcium carbonate and gypsum.
4. The construction of claim 2 wherein the lightweight filler is mica.
5. The construction of claim 2 wherein the glass bubbles have a Tg of greater than about -25.degree. C.
6. An interior drywall joint construction consisting essentially of:a support structure having an interior side;a non-recessed first drywall board having a first lengthwise edge and an outwardly-facing first planar surface, the first lengthwise edge being substantially perpendicular to the first planar surface, the first drywall board being installed on the interior side of the support structure;a non-recessed second drywall board having a second lengthwise edge and an outwardly-facing second planar surface, the second lengthwise edge being substantially perpendicular to the second planar surface, the second drywall board being installed on the interior side of the support structure substantially adjacent the first drywall board such that the first and second lengthwise edges are brought into substantially abutting contact so as to form a lengthwise crack between the first and second planar surfaces, a center-line surface of the joint construction being defined as the outwardly-facing surface directly over the crack and exposed for surface treatment; anda flexible compound filling the crack in a single coat so as to form the center-line surface and flush the joint construction with the first and second planar surfaces, the flexible compound comprising:20 to 25 percent by weight filler;6 to 8 percent by weight lightweight filler;10 to 15 percent by weight glass bubbles, the glass bubbles having a Tg of greater than about -25.degree. C.;1 to 5 percent by weight methylcellulose;30 to 50 percent by weight resin; and10 to 20 percent by weight water.
7. A method of forming a drywall joint consisting essentially of the steps of:installing a non-recessed first drywall board having a first lengthwise edge and an outwardly-facing first planar surface on an interior side of a support structure, the first lengthwise edge being substantially perpendicular to the first planar surface;installing a non-recessed second drywall board having a second lengthwise edge and an outwardly-facing second planar surface on the interior side of the support structure such that the second drywall board is substantially adjacent the first drywall board, the second lengthwise edge being substantially perpendicular to the second planar surface, such that the first and second lengthwise edges are brought into substantially abutting contact so as to form a lengthwise crack between the first and second planar surfaces, a center-line surface of the drywall joint being defined as the outwardly-facing surface directly over the crack and exposed for surface treatment; andfilling the crack with a flexible compound so as to form the center-line surface and flush the drywall joint with the first and second planar surfaces.
8. The method of claim 7 wherein the step of filling the crack with a flexible compound comprises a single coat.
This is a continuation-in-part application of a prior filed and currently pending application having Ser. No. 10/784,091 and a filing date of Feb. 23, 2004.
INCORPORATION BY REFERENCE
Applicant hereby incorporates herein by reference any and all U.S. patents and U.S. patent applications cited or referred to in this application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to interior drywall, and more particularly to drywall joint constructions and methods.
2. Description of Related Art
In the interior drywall field, the conventional drywall joint is formed between drywall boards having tapered abutting edges so as to form an outwardly-facing recess along the joint that must be filled in. Conventional joint cement compound for filling the recess is formulated to be soft for easy sanding when finishing the joint. Unfortunately, as a result of this formulation, the typical conventional joint cement compound has little cohesion or adhesion to the underlying drywall boards, is weak and brittle, and is prone to cracking upon expansion or contraction of the drywall joint. Repair of such failed joints can be costly, particularly after the interior is completed and the building occupied.
Beyond these concerns relating to the structural integrity of the conventional drywall joint, the use of conventional joint cement compound also presents aesthetic problems for the finished joint, including the common problem of surface cracking. Because the joint cement is, again, soft and weak, when joint cement is at the surface of a drywall joint directly over the recess or crack between abutting drywall boards, center-line cracking along the recess often occurs as the joint is stressed and the drywall boards move relative to one another. Further, the conventional joint cement compound at the surface of the drywall joint also tends to absorb too much paint so as to leave different sheens on the wall or ceiling, commonly referred to in the art as flashing or photographing, and even allows for delamination between the drywall board, texture and paint.
Once a first coat of conventional joint cement compound is applied to the recess in the drywall joint, the typical drywall joint is completed by applying drywall tape or paper along the joint and then applying two top coats of conventional joint cement compound over the tape to flush the joint with the abutting drywall boards. Beyond the structural and aesthetic short-comings of this typical drywall joint, as explained previously, this joint finishing process creates other logistical and economic problems as well. First, the thick coats of conventional joint cement compound must be allowed to dry before the joint can be completed, requiring multiple trips to the work-site. And second, the number of coats of conventional joint cement compound adds further cost to the finished drywall joint both in terms of materials and labor.
The following art defines the present state of this field:
U.S. Pat. No. 2,323,963 to Ames is directed to a combined plastic and tape applicator which will combine the steps of applying plastic in the groove between adjacent wallboards and covering the plastic with tape for reinforcing purposes by first coating the tape with plastic and then applying it to the joint between two adjacent wallboard sections. This method of application not only combines two of the steps into one, but provides a more even distribution of the plastic that lies between the tape and the wallboard, thus increasing the adhesive contact between the plastic and the wallboard and thereby strengthening the entire joint.
U.S. Pat. No. 3,180,058 to Tillisch et al. is directed to a joint structure for plasterboard wherein there is provided plasterboard having a plurality of shallow, discontinuous indentations in multiple rows in at least one surface adjacent the edge thereof, and adapted to retain joint cement applied to such surface to insure a joint which is satisfactory and of pleasing appearance.
U.S. Pat. No. 3,708,935 to Kossuth et al. is directed to a predecorated wallboard for forming simulated monolithic predecorated wall construction composed of an elongated rectangular core panel including a set gypsum core enclosed on its two opposite sides and two longitudinal edges with a paper facing layer and having on its front side a flat central surface arranged between recessed marginal surfaces extending from the flat surface to the opposite longitudinal edges of the panel and tapering edgewise toward the rear side of the panel, and a decorative sheet including a cloth backing layer laminated only to the flat surface of the paper facing layer on the front side of the panel throughout the length of such front side and an outer polyvinyl chloride layer forming a decorative front wall surface, such sheet also including a narrower flap extending over one of the marginal surfaces but terminating flush with the adjacent longitudinal edge of the panel and a wider flap extending over the opposite marginal surface beyond the opposite longitudinal edge of the panel. Each wallboard is adapted to form a joint with an adjacent wallboard, such as a flat joint wherein the adjacent longitudinal edges of the panels are arranged in abutting relationship and the front sides thereof are flush, with the adjacent marginal surfaces thereof forming beneath adjacent narrower and wider flaps a shallow V-shaped recess or space to be filled to the level of the flat surfaces of the panels with a hardened joint cement layer to which the narrower and wider flaps are adhered as well as to each other in overlapping relationship over the marginal surface underlying the narrower flap, the joint being completed by cutting through the overlapping portions of both flaps, by removing the overlapping and overlapped marginal edge portions of the overlying and underlying flaps respectively to cause the narrow flap to terminate short of the adjacent longitudinal edge of the underlying panel, and by readhering the remainder of the overlying flap to cause the wider flap to extend into edge abutting and flush relationship with the narrower flap to form a practically invisible seam.
U.S. Pat. No. 4,122,222 to Parker is directed to a method and a preformed laminate useful in various forms for repairing holes and covering joints in drywall. The laminate comprises a sheet material backing having an overlay of plaster joint compound, or the like. The overlay has an outwardly tapered thickness. The laminate may be in circular, strip, or other form. The backing material is secured over the hole or joint, as the case may be, and a small amount of drywall joint compound is added around the perimeter to blend the patch into the wall surface.
European Patent App. No. 0,456,435 A1 to Retti is directed to an apparatus for taping joints between pieces of wallboard comprising a taping head, slidingly contactable with a wall, for substantially simultaneously applying a first layer of a joint compound to a joint between pieces of wallboard, embedding a wallboard tape in the first layer of the joint compound, and overcoating the embedded wallboard tape with at least one additional layer of the joint compound, a handle connected to the taping head, for supporting the taping head, the handle being manually graspable by an operator, the handle having a fluid conduit formed therein for passing joint compound to the taping head, a tape supply mounted on the handle for supplying wallboard tape to the taping head, a backpack, wearable by the operator, for supporting a supply of the joint compound and for producing a pressurized stream of the joint compound, and a flexible connecting means for fluidically interconnecting the backpack and the fluid conduit to pass the pressurized stream of the joint compound from the backpack to the fluid conduit.
U.S. Pat. No. 5,628,159 to Younts is directed to an improved joint strip for concealing a joint formed between two panels of adjacent wallboards formed of a flexible support strip capable of withstanding day-to-day wall vibrations and a rib adhered on one side of the support strip such that it extends the length of the support strip. The support strip may be formed from a variety of materials such as synthetic fibers, cellulose fibers, non-woven paper, plastic fibers, fiberglass, specially treated fabric, and mixtures thereof. The joint strip possesses superior strength and flexibility properties thus eliminating the need to use predecorated wallboard for forming a monolithic appearing wall.
U.S. Pat. No. 2,427,879 to Robertson et al. is directed to an improved surfacing material made from laminated sheets of fireproof sheet-like material particularly those formed from calcified gypsum. It particularly relates to a novel method of joining sheets of structural material together to form a proper type of weather barrier with a minimum of effort.
U.S. Pat. No. 3,749,692 to Scocos et al. is directed to a plasticized aqueous latex caulk containing solid filler through which paintability of the cured surface can be improved by using as about 60-80 weight percent of the plasticizer components a polybutene having an average molecular weight of about 400-500, viscosity of about 150-300 centistokes at 100° F., and pour point not substantially higher than about -20° F.
U.S. Pat. No. 6,884,830 to Hornaman is directed to a flexible setting type hydraulic joint compound and a method of forming flexible joints. The flexible joint compound of this invention primarily contains 2 to 20 parts by weight of an emulsion polymer having a Tg that is less than about -40° C., and 22 to 44 parts by weight of total water, based on 100 parts by weight calcium sulfate hemihydrate filler. It can be applied to joints between two adjacent sheets of gypsum board to form a flexible joint that is resistant to cracking.
U.S. Pat. No. 5,869,166 to Caldwell and U.S. Pat. No. 6,749,920 to Caldwell et al. are directed to using a combination of relatively coarse filler and latex binder, a high solids coating which has a minimum solids content of about 60% by volume, can be produced with a relatively low working viscosity. These very high solids coatings can be applied in thick single layers and oven cured without cracking. They maintain more than 80% of their original wet thickness. The resulting coating provides an extremely hard and durable surface, even on relatively soft mineral fiber board ceiling tiles or wall panels.
U.S. Pat. Nos. 4,743,475 and 4,820,754 to Negri et al. are directed to a paint made from a low cost, easily dispersible powder in which the pigment volume concentration is about 70% to about 75%, by which the unequal porosity and different textures of a drywall reinforced with joint tape and joint compound are concealed. A vinyl acetate/ethylene copolymer serves as the principle binder and a water soluble cellulose ether thickens the water dispersion of kaolin, attapulgus clay, mica, sodium potassium aluminum silicate and calcium carbonate.
U.S. Pat. No. 6,207,742 to Boldt is directed to a two-component aqueous composition for thick horizontal markings on roads or other traffic areas. One component includes a drying-accelerated binder, pigments, pulverulent fillers and additives, while the other component includes coarse fillers. The composition is very high solids and fast drying without the cracking, smearing, and dirt adhesion typical of thick film traffic markings.
U.S. Pat. No. 4,735,027 to Evans et al. is directed to a coating for a wallboard comprising silica sand, cement and a particulate, non-fibrous filler, where the ratio of the average sand diameter to the average filler diameter is within the range of from about 40:1 to about 20:1.
U.S. Pat. No. 4,904,709 to Hermele is directed to a lightweight synthetic stucco composition which includes a mixture comprising a latex emulsion, water and titanium dioxide as well as a number of additives for adjusting the properties of the mixture and further including an admixture of hollow microspheres and macrospheres, with the microspheres having a diameter of about 10 to 150 microns and the macrospheres having a diameter of from 300 to 2000 microns, the admixture comprising between 30 and 60% of the finished composition. Utilizing a mixture of microspheres and macrospheres produces a substantial weight savings which makes the synthetic stucco composition easier to apply, less costly to transport and less demanding on the structure of the building. In addition, the particular combination of spherical structures provides a uniform tightly knit appearance free of pinholes and craters as the smaller particles fill the void spaces between the larger ones with the spherical shape of the particles allowing them to pack in a very tight arrangement. Where it is desired to have a more textured appearance, between 1 to 25% by weight coarse silica sand may be added to the admixture, with the coarse silica sand having a particle size from 1500 to 2000 microns.
U.S. Pat. No. 6,376,589 to Tanaka et al. is directed to a coating composition comprising a binder component consisting of (A') hydroxyl group-containing polyester resin having a number average molecular weight of 2,000-20,000, glass transition temperature of -40° C. to 30° C. and hydroxyl value of 5-95 mgKOH/g, (B) blocked polyisocyanate compound blocked with ε-caprolactam, and the equivalent ratio of the blocked isocyanate groups in said blocked polyisocyanate compound (B)/the hydroxyl groups in said polyester resin (A) being in the range of 0.7-1.2, and 0.5-30 parts by weight of said resin fine particles (C) with an average particle diameter of 8-70 μm, which do not completely melt at the time of coating film curing, per 100 parts by weight of said binder component. Said coating composition can form a coating film having excellent popping resistance, hardness, processibility, anti-tackiness, blocking resistance and curability by a high temperature short time baking.
U.S. Pat. No. 6,531,537 to Friel et al. is directed to methods of providing a paint line containing a latex polymeric binder. A range of paints can be formulated using sets of prepaints, at least one of which contains a latex polymeric binder. The paints may be applied as architectural coatings, industrial coatings, graphic arts coating, elastomeric coatings, and non-cementitious, aggregate finish coatings suitable for application on a wall directly or as a topcoat in exterior insulation finishing systems.
U.S. Pat. No. 5,308,397 to Whatcott is directed to a stucco coating for interior and exterior walls of buildings that provides increased bonding strength over the prior art.
U.S. Pat. No. 6,120,837 to Atsuyo et al. is directed to a method for priming an uneven surface of a blank using a novel "thermally expansible spray putty". This spray putty is prepared by mixing a priming paint for the blank with thermally expansible micro-capsules in amount of 0.5 to 10 weight % of the solid matter of the priming paint. The thermally expansible spray putty is preferably conditioned with an exclusive thinner to a high viscous state enabling it to be air-sprayed. Shell walls of the micro-capsules soften at a temperature below the setting temperature of a thermosetting paint to be used in finish painting of the blank. After the blank being treated by degreasing, drying and the like, the uneven surface of the blank is coated with the thermally expansible spray putty by spraying. After suitably setting the coated spray putty, it is dried by heating so as to expand the micro-capsules to obtain a substantially smooth surface of the blank. After simply grinding the surface, a smooth finish surface is obtained only by intercoating or finish painting it, which is sufficiently endurable to practical use.
U.S. Patent App. Pub. No. 20020108342 to Henits is directed to the preparation of a pair of abutting straight edges of a pair of wallboard panels for receiving spackle to provide smooth planar butt joints including the use of a rotary tool having a tool bit to form a channel extending on both sides of the butt joint after the wallboard panels have been installed. After the formation of the channel, spackling of the butt joint in a conventional manner results in a smooth planar finished surface.
U.S. Patent App. Pub. No. 20030084633 to Zuber et al. is directed to a construction assembly for interior works, comprising: prefabricated elements, preferably flat prefabricated elements e.g. gypsum fiberboards, cement fiberboards, gypsum wall boards or plaster boards, wherein said prefabricated elements comprise a coating layer formed of at least one skim coat deposited on said prefabricated elements by a coating device; and at least one jointing material, e.g. a sealing coat, joint coat and/or joint pointing coat, which joints adjacent said prefabricated elements to form a substantially plane outer surface comprising the visible surface of said at least one jointing material and the visible surface of the skim coated prefabricated elements, wherein said at least one jointing material and said at least one skim coat comprise a mineral filler, a binder and water; and wherein the composition of said at least one jointing material and said at least one skim coat are adapted to each other, whereby said at least one jointing material and said skim coat form, both in a dry state, a substantially homogeneous outer surface having over substantially all its surface at least one of the parameters comprised in the group consisting of coloration, reflectance factor and surface water absorbability which is substantially homogeneous over said surface; and whereby said outer surface is ready to be decorated. For instance, said at least one of the parameters differs by no more than 10%, preferably no more than 5%, at different parts of the overall surface, so that at least 90%, preferably at least 95%, homogeneity is achieved.
U.S. Patent App. Pub. No. 20050072114 to Shiao et al. is directed to solar-reflective roofing granules having deep-tone colors formed by coating base mineral particles with a coating composition including an infrared-reflective pigment. Color is provided by colored infrared pigment, light-interference platelet pigment, or a metal oxide.
U.S. Patent App. Pub. No. 20050229519 to Colbert et al. is directed to coating and jointing material systems for wall construction. The coating is applied to drywall elements prior to installation and is compatible with the jointing materials such that a substantially homogeneous surface may be obtained after the drywall elements are assembled with jointing material and the jointing material is dried. Methods for the construction of interior walls and interior construction systems are provided.
Thus, the prior art described above teaches a combined plastic and tape applicator, a joint structure for plasterboard, a simulated monolithic predecorated wall construction, a laminate and method for drywall holes and joints, a wallboard taping process and apparatus therefor, a joint strip, method of forming a wall using the joint strip, and wall made therefrom, a structural product, an aqueous latex caulking composition, a flexible setting joint compound and method for making flexible joints, a high solids, low shrinkage coating, a drywall coating composition, a water-based marker material, a coating for wallboards, a textured exterior surface treatment, a coating composition capable of forming a thick coating film, prepaints and methods of preparing paints from the prepaints, base coat stucco mortars for coating and finishing interior and exterior walls of a building, a priming method for uneven surface, a wallboard butt joint preparation, a method, assembly and additional coat for the construction of interior works, colored roofing granules with increased solar heat reflectance, solar heat-reflective shingles, and process for producing same, and a system using a drywall board and a jointing compound, but does not teach an improved drywall joint construction and method that both altogether eliminates the conventional weak, chalky joint cement from the drywall joint, particularly at the joint surface, and provides a stronger, more attractive, and more economical joint. The present invention fulfills these needs and provides further related advantages as described in the following summary.
SUMMARY OF THE INVENTION
The present invention teaches certain benefits in construction and use which give rise to the objectives described below.
Aspects of the present invention are generally directed to a drywall joint construction and method consisting essentially of a first drywall board having a first lengthwise edge and an outwardly-facing first planar surface, a second drywall board having a second lengthwise edge and an outwardly-facing second planar surface, the second drywall board being positioned adjacent the first drywall board such that the first and second lengthwise edges are brought into substantially abutting contact so as to form a lengthwise crack between the first and second planar surfaces, and a joint finishing system formed within the crack to complete the drywall joint construction, as is generally known in the art. In the exemplary embodiment, the first and second lengthwise edges of the drywall boards are non-tapered so as to form the crack between the boards as a slit, wherein the joint finishing system is configured as a flexible compound forming the flexible layer and filling the slit so as to flush the joint finishing system with the drywall boards. As such, a flexible layer rather than joint cement is employed at the center-line surface of the drywall joint construction, yielding a stronger, more crack-resistant and more aesthetically-pleasing drywall joint construction.
A primary objective of the present invention is to provide a drywall joint construction and method of use of such construction that provides advantages not taught by the prior art.
Another objective is to provide such an invention capable of reducing the amount of joint compound in a drywall joint.
A further objective is to provide such an invention capable of eliminating the conventional joint cement from a drywall joint, particularly at the center-line surface.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the present invention. In such drawings:
FIG. 1 is a perspective view of an exemplary embodiment of a drywall joint of the present invention;
FIG. 2 is an enlarged cross-sectional view thereof taken along line 2-2 of FIG. 1; and
FIG. 3 is a cross-sectional view of a prior art drywall joint.
DETAILED DESCRIPTION OF THE INVENTION
The above described drawing figures illustrate the invention in at least one exemplary embodiment, which is further defined in detail in the following description.
Referring first to FIG. 1, the present invention is generally directed to a drywall joint construction 10 consisting essentially of a first drywall board 20 having a first lengthwise edge 22 and an outwardly-facing first planar surface 24, a second drywall board 30 having a second lengthwise edge 32 and an outwardly-facing second planar surface 34, the second drywall board 30 being positioned substantially adjacent the first drywall board 20 on a support structure 90 such that the first and second lengthwise edges 22, 32 are brought into substantially abutting contact so as to form a lengthwise crack 40 between the first and second planar surfaces 24, 34, and a joint finishing system 50 formed within the crack 40 to complete the drywall joint construction 10. As a threshold matter, it is noted that in the exemplary embodiment shown and described, no conventional joint cement of any kind is employed at the center-line surface 80 of the drywall joint construction 10. As will be appreciated by those skilled in the art, conventional joint cements are weak and chalky and are prone to cracking along the center-line surface 80 as the first and second drywall boards 20, 30 shift relative to one another, so that, as explained more fully below, by removing the conventional joint cement from the center-line surface 80, a stronger, more aesthetically-pleasing drywall joint construction 10 is obtained. Thus, center-line cracking in the joint cement of the conventional drywall joint is eliminated in the present invention by eliminating the joint cement from the critical center-line surface 80. Instead, a flexible layer 60, preferably of a flexible compound such as caulk, forms the center-line surface 80. Accordingly, it will be further appreciated that other related joint constructions, involving various drywall board configurations, compounds and flexible outer layers, are possible without departing from the spirit and scope of the present invention.
Turning to FIG. 2, in the exemplary embodiment of the drywall joint construction 10 of the present invention, the first and second drywall boards 20, 30 are shown installed in a substantially co-planar, abutting relationship, as when drywall is installed on an interior wall or ceiling of a building. Specifically, in the exemplary embodiment the drywall boards 20, 30 are installed on support structure 90 such as framing studs or the like as are now known or later developed in the art. Preferably, as will be better appreciated from the following more detailed description, the drywall boards 20, 30 are installed on the inside or interior side of the support structure 90, or on the side of the support structure 90 designed to be covered by a roof (not shown) and enclosed away from the outside and the elements; i.e., on that part of the building structure opposite the exterior. The drywall boards 20, 30 are "non-tapered" or "non-recessed," such that the abutting first and second lengthwise edges 22, 32 are substantially perpendicular to the respective first and second planar surfaces 24, 34 and the crack 40 between the abutting boards 20, 30 is configured as an outwardly-opening slit. The joint finishing system 50 comprises a flexible compound 52 defining the flexible layer 60 (FIG. 1) and filling the crack 40 so as to flush the joint finishing system 50 with the first and second planar drywall surfaces 24, 34. So as to more readily flush the flexible compound 52 with the drywall surfaces 24, 34, it is preferred that the flexible compound 52 be of a non-shrink formulation such as a caulk or a compound including 20-25% filler such as calcium carbonate or gypsum, 6-8% lightweight filler such as mica, 10-15% 3M® glass bubble, 1-5% methylcellulose, 30-50% resin and 10-20% water by weight, though, again, a number of flexible compounds now known or later developed will suffice. Preferably, in any such flexible compound, any polymers or the like included in the formulation, such as the 3M® glass bubbles, will have a glass transition temperature (Tg) that is greater than about -25° C., rendering the resulting flexible compound relatively sandable and finishable. It will be appreciated by those skilled in the art that by using a flexible compound that is non-shrinking, time and material costs may be saved, while the structural integrity of the finished joint is yet improved. Again, the exemplary embodiment shown in FIGS. 1 and 2 also has the critical advantage over prior joint systems of employing a flexible layer 60 (FIG. 1), here the flexible compound 52, at the center-line surface 80 over the crack 40 between abutting drywall boards 20, 30, rather than weak, chalky joint cement, so as to produce a joint construction 10 that is stronger, more crack-resistant and more attractive. As will again be appreciated by those skilled in the art, and as the test data below confirms, a finished drywall joint construction 10 having a flexible compound 60 rather than weak, chalky joint cement compound at the center-line surface 80 over the crack 40 between abutting drywall boards 20, 30 produces a joint that is stronger and more crack-resistant. As such, the joint will also be more attractive. By comparison, the conventional joint cement formulation includes 20-25% filler such as calcium carbonate or gypsum, 6-8% lightweight filler such as mica, 5-15% attapulgite or bentonite clay, 1-5% methylcellulose, 5-8% resin and 50-60% water by weight. It will be appreciated by those skilled in the art that the relatively smaller amount of water by percent weight in the exemplary non-shrink formulation results in a flexible compound 52 that shrinks relatively less when setting.
Samples both of the exemplary drywall joint construction of the present invention shown in FIGS. 1 and 2 and of the conventional drywall joint construction shown in FIG. 3 were evaluated for crack-resistance under the test explained below. The conventional joint construction 110, again as shown in FIG. 3, includes abutting drywall boards 120, 130 having tapered first and second lengthwise edges 122, 132 so as to form a channel 140 that is partially filled in by a first taping coat 152. A drywall tape 160 is applied over the taping coat 152, and then the joint is flushed by one or more topping coats 170 of joint cement over the tape 160. Thus, it is clear that in the typical prior art drywall joint, joint cement forms the center-line surface 180 directly over the channel 140. While one topping coat 170 is shown, it is often the case that two or more topping coats are required to flush the joint, further weakening and adding more labor and material costs to the conventional drywall joint.
In testing the various drywall joint constructions, 12''×13'' pieces of drywall boards were abutted along their finished edges and the joints between the boards were completed according to the exemplary joint construction 10 of the present invention and the conventional drywall joint 110 now used in the art. Each such assembly was laid horizontally on a workstation such that the joint itself was positioned directly over a vertical piston. While the edges of the respective boards opposite the joint were held in place, the piston was caused to gradually force the center of the assembly, or the joint, vertically upward so as to effectively flex or bend the assembly about the joint. Such movement of the piston was allowed to continue until a crack visibly appeared on the surface of the joint. The crack resistance of each joint was then quantified as the change in position of the piston from the joint at rest to the joint at failure, when a crack was observed. Under this test, the conventional drywall joint 110 (FIG. 3) failed, or a crack was observed on the joint, at between 4.5 and 5.0 mm. Comparatively, in the exemplary joint construction 10 of the present invention (FIG. 2), no crack was seen until the joint was flexed to between 210.0 and 220.0 mm from its unflexed starting position, indicating that eliminating the joint cement by replacing the conventional tapered drywall boards 120, 130 (FIG. 3) with non-tapered boards 20, 30, and thus constituting more of the joint system 50 with drywall board rather than with joint cement, further improved the strength and crack-resistance of the joint. Thus, as in the exemplary joint construction 10 wherein no joint cement is used at all (FIGS. 1 and 2), it is clear from this testing that ridding the joint construction 10 of joint cement altogether and instead comprising the joint of relatively more board material, so as to reduce cost by requiring less filler material in the joint, and of a flexible compound in filling the crack between the boards and smoothing or flushing the surface, produces the relatively strongest, most crack-resistant joint. While no joint should be expected to see in normal use the kind of movement or flexure indicated, this testing still provides a striking comparison of the crack-resistance of the joint construction 10 of the present invention relative to a conventional drywall joint 110. The testing proves that in the exemplary embodiment of the present invention wherein the joint cement is not only eliminated from the center-line surface of the joint, but also from the entire joint, significant improvements in crack-resistance over the conventional prior art drywall joint 110 were achieved.
It follows that by removing the conventional joint cement from the center-line surface 80 of the drywall joint construction 10 according to aspects of the present invention, a stronger, more crack-resistant joint is achieved. Generally, drywall board is over 300% stronger than the typical joint cement, and flexible compounds such as caulks can be even stronger. Thus, though it has generally always been thought in the art that the joint cement is the strongest part of the joint system, this is simply not the case, as the above test data indicates. In fact, the typical joint cement is actually designed to be weak and chalky so that it can be easily sanded down to bring it flush with the abutting drywall boards. These same attributes cause the joint cement to be prone to cracking. The present invention takes advantage of a correct understanding of the relative strengths of the components of the typical drywall joint to beneficially remove the joint cement from the joint construction, and particularly the center-line surface of the joint, so as to produce an improved, stronger and more crack-resistant drywall joint construction.
Moreover, the problem of surface cracking, which makes a drywall joint unsightly and costly to repair, is effectively eliminated by the joint construction 10 of the present invention. While having the soft and weak joint cement at the surface of a drywall joint directly over the recess or crack between abutting drywall boards allows center-line cracking to often occur along the recess as the joint is stressed and the drywall boards move relative to one another, the joint construction 10 of the present invention is stronger and greatly reduces the risk of such surface cracking by entirely removing the joint cement from the center-line surface 80. Further, as is known in the art, the conventional joint cement at the surface of the typical drywall joint 110 also tends to absorb too much paint so as to leave different sheens on the wall or ceiling, commonly referred to as flashing or photographing. The joint constructions 10 of the present invention eliminates this problem as well, again, by entirely removing the absorptive joint cement from the center-line surface 80. The risk of delamination between the drywall board, texture and paint possible in the conventional drywall joint 110 employing joint cement 170 at the surface 180 is also effectively eliminated in the joint constructions 10 of the present invention. And regarding the aesthetics of the drywall joint, it is preferred, though not necessary in practicing the present invention, that an elastomeric paint (not shown) be employed in covering the joint that has a crack resistance equal to or exceeding that of the joint, or that has a flexibility or elongation meeting or exceeding that of the joint construction. In this way, the paint would be unlikely to crack before the joint ever would.
Beyond these structural and aesthetic considerations, those skilled in the art will appreciate that the joint construction 10 of the present invention also provides economic benefits over the conventional drywall joint 110. As seen, when non-tapered drywall boards 20, 30 are employed, the space 40 to be filled in is reduced, thereby reducing the materials required and, accordingly, the labor needed to install the materials. In the exemplary joint construction 10, the elimination of the drywall tape and drywall joint cement altogether provides even further savings in terms of both materials and labor.
Those skilled in the art will appreciate that there are a number of reasons why even available flexible compounds and non-recessed or non-tapered drywall boards known in the art have heretofore not been combined or employed as taught herein to arrive at an improved, joint cement-free drywall joint construction and methodology. First, regarding prior art flexible joint systems such as that disclosed in U.S. Pat. No. 6,884,830 to Hornaman, there is a specific call-out that the compounds include an emulsion polymer having a glass transition temperature (Tg) of "less than about -40° C.; preferably less than about -45° C." However, it will be appreciated that the use of such emulsion polymers renders the resulting compound relatively gummy and so difficult to sand and finish as needed. As such, the use of such a compound in forming a flexible drywall joint system has not gained commercial acceptance. Moreover, it will be further appreciated that in the Hornaman system there is called for a relatively more expensive compound material, as compared with conventional joint cements and even alternative flexible compound formulations, without any decrease in the amount of material, as the use of non-recessed drywall boards is not suggested, resulting in an increase in total material cost (i.e., the Hornaman system essentially entails the same volume of material as used in a prior art joint at a higher material cost per unit volume). This aspect has likely further led to non-acceptance of the Hornaman system in the field. Regarding the use of non-recessed or non-tapered boards, current industry thinking about the suggested applications for such, in view of the general and pervasive industry teachings of preparing a drywall joint as shown in FIG. 3, further teaches away from the present invention. Specifically, it is well known in the industry to employ non-recessed drywall boards only in three scenarios: (1) as backing board for paneling or the like; (2) in interior drywall applications where the finishing step will entail wallpaper, very heavy texture, or the like and, expressly, not conventional paint; or (3) in exterior applications. Thus, currently, the use of non-recessed or non-tapered drywall boards has been taught away from for conventional interior drywall applications wherein a typical texture and surface paint are anticipated being applied over the outside surfaces of the drywall boards. And those skilled in the art will appreciate the reason for such teaching: heretofore there has not been shown or taught in the art a system as in the present invention whereby non-recessed drywall boards can be employed in an interior joint without a bulge or hump at the center-line surface of the joint that results in shadows or the appearance of different color tones, which is a type of flashing or photographing. That is, the use of non-recessed drywall boards, though reducing the total amount of material needed to finish the joint, under current joint finishing techniques yet results in a so-called "humped joint" by virtue of the top coat of joint cement and/or the drywall tape over the joint and so is not practiced. Again, those skilled in the art will appreciate that such joint cement and tape are eliminated in the joint construction and method of the present invention, thereby enabling or facilitating the use of non-recessed drywall boards even in conventional interior drywall applications in conjunction with the present invention.
To sum up regarding the features and advantages of the improved drywall joint construction and method of the present invention, it will be appreciated that tremendous cost savings are achieved in the form of less material by volume and less labor. Specifically, material costs are greatly reduced in the present system due to only filling a relatively small crack between abutting, non-recessed drywall boards rather than a larger space between recessed or tapered drywall boards as in the current industry practice. Moreover, in the prior art, to fill such a relatively large space often multiple coats are required to flush the joint, leading to increased labor costs, both for each application, as well as relatedly due to the longer dry times for each coat and the delays between each. By comparison, the application as in the present invention of a flexible, relatively non-shrinking compound in a crack between non-recessed drywall boards allows a single coat to effectively flush the joint, greatly reducing the labor costs associated with the drywall finishing step. It will be particularly appreciated that even prior art flexible joint systems as disclosed, for example, by Homaman, simply do not provide the same cost savings and advantages as the joint construction and method of the present invention, in that Hornaman involves a relatively higher cost material per unit volume, making it more expensive at the outset and further more expensive in that more material by volume is required as compared to the present system. Thus, those skilled in the art will appreciate that the present joint cement-free drywall joint construction and method greatly improves the art of interior drywall installation and finishing by tremendously reducing material and labor costs. With these kinds of advantages, clearly such a system would be known and used in the art were it obvious. But the art has not employed such a system for the reasons described, but has instead actually taught away from the use of non-recessed drywall boards for most interior drywall applications, whereby the system and method of present invention has solved a problem not heretofore solved and so has satisfied a long felt and as yet unmet need of reducing material and labor costs in the widespread general art of interior construction using drywall or gypsum boards.
Therefore, the present invention of an improved drywall joint construction and method both altogether eliminates the conventional weak, chalky joint cement from the drywall joint, particularly at the joint surface where cracking is most likely and most detrimental, and provides a stronger, more attractive, and more economical joint. While the invention has been described with reference to at least one exemplary embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims and it is made clear, here, that the inventor believes that the claimed subject matter is the invention.
Patent applications by Kurt Hamilton, Orange, CA US
Patent applications in class ASSEMBLED IN SITU-TYPE ANCHOR OR TIE
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