Abstract:
A welded wire corner bead comprising at least one and preferably two continuous wires defining a periodic wave form extending from side to side of the bead, the bead being bent lengthwise along an axis.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to welded wire corner lath or beads.  
       BACKGROUND OF THE INVENTION  
       [0002]     Some building construction techniques involve the application of a coating such as stucco, plaster and the like to a building surface. This coating is the cladding or finish for such surfaces. In the following disclosure, the term stucco is used generally to apply to either cementitious or gypsum plasters as defined in applicable building codes.  
         [0003]     When applying a stucco coating, it is generally desirable to provide a lath on the surface. The lath provides reinforcement for the stucco and also attaches the stucco to the building surface. There are a number of different metal laths being used for stucco coatings. One common type is expanded metal lath. Another group of stucco laths is wire fabric laths. Within this group, there are woven wire laths and welded wire laths.  
         [0004]     The lath is attached to wood or metal framing by various fasteners, generally including nails, staples, self-tapping screws, or other mechanical fastening means.  
         [0005]     At the corners, a bead is normally provided since it is either required by building codes, or the builder or contractor will require the use of corner beads to obtain a superior result. These would be installed generally on external corners, either vertically or horizontally. Vertical corners are created by the wall intersections, and around columns and posts. Horizontal corners are created when architects and designers create build-outs or reveals, or when stucco is applied to bottoms of beams, or tops of wall sections.  
         [0006]     The most commonly used corner beads are bent into a Vee shape of approximately 70 degrees to 80 degrees. The flanges or legs of the Vee portions extend approximately 2 ½ inches. There are two general types of corner beads. The first is made from sheet metal and has expanded metal flanges and a solid metal nose that acts as the bead. The other general type is made from a grid of wires welded together, bent into a Vee shape with a continuous longitudinal wire at the nose to act as the guide to form the stucco corner.  
         [0007]     When the corner bead is installed correctly, it becomes the depth gage or screed that will regulate the depth of stucco or plaster at the corners. Various stucco systems require stucco in depths of ⅜ inch, ½ inch, ¾ inch or ⅞ inch. Therefore, different preformed angles are required in the corner bead to obtain the correct stucco depth. For stuccos in the ⅜ to ½ inch range, beads are formed with an 80-degree Vee, whereas for stucco in the ¾ to ⅞-inch range, beads are formed in the 70 degree range. Therefore consistency of angle forming and straightness are critical factors in obtaining correct stucco thickness.  
         [0008]     The prior art welded wire corner beads generally consist of a series of sinusoidal wires and a series of longitudinal wires resistance welded together at their intersections. Such wire beads of steel wire are generally known and are described in U.S. Pat. No. 2,645,930 by Raymond Stockton, in U.S. Pat. No. 3,175,330 by Henry Holsman, in U.S. Pat. No. 5,669,195 by Bekaert, as well as in other sources.  
         [0009]     The prior art wire corner beads may contain 3, 4 or 5 sinusoidal wires, with 6 or 8 longitudinal wires on the shoulders of the Vee, plus the nose wire on the tip of the Vee.  
         [0010]     The most common corner beads have 5 sinusoidal wires and 6 longitudinal wires plus the nose wire. The sinusoidal wires do not span the width of the corner bead, since they generally each have a width of 1¼ inches and a pitch of 2 inches. Therefore, a series of these sinusoidal wires is required to span the full width of the corner bead. Further, the sinusoids must be offset from each other by one-half pitch so that their points overlap to create intersections for welding. The sinusoidal wires alternate positions, with one above and the next one below across the width. The longitudinal wires can only be placed in the zones where there is a single wire thickness. The longitudinal wires must also alternate above and below the sinusoidal wires, in opposite steps from the sinusoids. This precludes all the longitudinal wires from being on one side of the product, preferably all on the surface facing outwards. To ensure that the sinusoidal wires overlay each other for welding purposes, additional wire must be used which is a waste of material. Further, the overlapping zone becomes greater which limits the positions of the longitudinal wires. These limitations and others will become more clear in the description of the drawings.  
         [0011]     One disadvantage of the wire beads known in the prior art is that it is difficult to create a continuous series of sinusoidal shapes in multiple wires that are identical in pitch, to then offset them the correct one-half pitch, and then to position them correctly for welding. Variations as little as 1/16 inch in sinusoidal width or pitch can create production or quality problems. These variations result in high scrap rates in production because of either missed welds or quality control rejection because positioning variances exceed specifications. These variations in pitch can be the result of differences in tensile strengths between wires, slight differences in diameter, out of round variations of the wire, and differences in surface finish or lubricity of the surface. These types of differences are usually within the commercial tolerances of the wire suppliers and would be difficult and costly to tighten specifications. These variations in properties will affect the size and shape of the sinusoids, which in turn affects the phasing relationship. The other problem is in guiding these sinusoidal wires into the welding zone. The guiding system needs to have some clearance so that the wires do not bind. However, the sinusoids can then move back and forth within this clearance creating another product variance.  
         [0012]     Another disadvantage of the prior art wire corner beads is that the density of wires is very high at the nose area. This makes it difficult to fully imbed the wires in this region with stucco or plaster, leaving voids. These voids tend to create weak areas at the corners, as well as provide cavities for water to amass creating corrosion of the adjacent wires. This corrosion leads initially to rust staining of the stucco, and ultimately to complete loss of steel. This problem has resulted in some of the prior art having to add plastic nose pieces onto the corners, or produce products from more expensive materials such as stainless steel, or to provide secondary coatings such as epoxy coatings. Each of these solutions is a disadvantage in that it adds significant cost to the product.  
         [0013]     This high density of wires at the nose area is a greater disadvantage with the thinner stucco coatings. These thinner coatings, which are normally known as one coat systems, add glass or plastic fiber reinforcement to their stucco mix. The fibers make it more difficult to work the stucco around the wires with consequently more voids, which is more serious with the thinner stucco coatings.  
         [0014]     A further disadvantage of the prior art wire bead is that because of its configuration, it requires more steel material for its fabrication, than what is needed for the stucco attachment and the screeding function. This additional material is not only an economic factor, but also makes cutting the product in the field more difficult. Another disadvantage is that when an overlap must be made, there is a buildup of steel wire at the joint resulting in a step in the finished stucco finish. A further disadvantage is that larger cartons must be used to fit these bulkier beads resulting in higher packaging costs, higher shipping costs, and higher storage costs.  
         [0015]     Another disadvantage of the prior art wire bead is, that again because of its configuration, wire positions and wire sizes cannot be optimized for stucco needs.  
         [0016]     Hence, there is a need for an improved wire bead for stucco, plaster and the like.  
         [0017]     It is an object of this invention to provide a wire corner bead strip comprising multiple sinusoidal wires that span the full width of the strip and a series of longitudinal wires welded to the sinusoidal wires at each intersection, and in which the strip is bent at an angle around a central longitudinal wire to form a wire bead having a Vee shaped cross section.  
         [0018]     It is further an object of this invention to provide a wire corner bead with reduced wire density without sacrificing strength, straightness and rigidity, and provides superior stucco embedment.  
         [0019]     It is yet another object of this invention to provide a simplified wire corner bead design that is more tolerant of wire property variations and results in fewer production problems and quality rejects.  
       SUMMARY OF THE INVENTION  
       [0020]     In one aspect the invention comprised of welded wire corner bead comprising at least two continuous wires in overlapping periodic wave form, bent along a longitudinal axis of the bead and including at least three parallel longitudinal wires.  
         [0021]     In a more specific aspect, the invention comprises a welded wire corner bead being defined in two planes about longitudinal axis. The bead has a length and a lateral extent spanning the two planes. At least three parallel longitudinal wires are provided, with at least one of the longitudinal wires lying in each of the planes. At least two continuous wires are attached to each of the longitudinal wires and define a periodic waveform spanning the two planes across longitudinal axis.  
         [0022]     In another aspect, the invention comprises a welded wire corner bead defined in two planes about longitudinal axis so as to have contiguous inside faces and contiguous outside faces of the corner bead. The bead comprises at least three parallel longitudinal wires and at least one continuous wire attached to each of the longitudinal wires. The continuous wire defines a periodic waveform. All of the parallel longitudinal wires are disposed on the outside faces.  
         [0023]     In yet another aspect, the invention comprises a method of manufacturing the corner bead wherein the longitudinal wires are disposed in opposed spaced relation to the longitudinal axis according to a predetermined thickness of stucco for which the bead is intended to be used. In yet another aspect, the invention comprises a method of manufacturing the corner bead comprising the steps of disposing the longitudinal wires away from points of overlapping intersection between the two continuous wires and welding the longitudinal wires to the continuous wires such that the thickness of the corner bead does not exceed two wire thickness throughout the weld points.  
         [0024]     The foregoing was intended as a broad summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]      FIG. 1  is a plan view of the typical configuration of welded wire corner beads according to the prior art.  
         [0026]      FIG. 2  is a cross sectional view of the wires in between welding wheels according to the prior art.  
         [0027]      FIG. 3  is a cross sectional view of the welded wire corner bead according to the prior art after it has been formed into the V-shape and installed on a building corner.  
         [0028]      FIG. 4  is a plan view of the improved welded wire corner bead in accordance with the preferred embodiment of the invention.  
         [0029]      FIG. 5  is a cross sectional view of the wires in between welding wheels in accordance with the invention.  
         [0030]      FIG. 6  is a cross sectional view of the welded wire corner bead in accordance with the preferred embodiment of the invention after it has been formed into the V-shape and installed on a building corner.  
         [0031]      FIG. 7  is a cross sectional view of two welded wire corners according to the prior art stacked together.  
         [0032]      FIG. 8  is a cross sectional view of two welded wire corners in accordance with the invention stacked together. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]     The relative positions of the components of the prior art welded wire corner bead are shown in  FIG. 1 . This configuration would represent a typical wire corner as used in the market today and as shown in Holsman U.S. Pat. No. 3,175,330. In this typical case, five sinusoidal wires ( 21 ) are arranged so that collectively, they span the width of the corner bead. Each laterally adjacent sinusoidal wire ( 21 ) is shifted by 90 degrees phase shift so that peaks of the adjacent sinusoids can overlap each other. This overlap provides intersections which are resistance welded together and which then holds the grid together.  
         [0034]     A series of longitudinal wires are also introduced and welded to the various sinusoidal wires ( 21 ). Starting at the outside edges, two edge wires ( 22 ) are welded to the outer sinusoidal wires near the outer peak. These edge wires ( 22 ) provide stiffness and rigidity to the formed corner bead. Further, these edge wires ( 22 ) are positioned to create nailing loops ( 10 ) for attachment of the corner bead to the building structure. Next are two other longitudinal wires ( 23 ) referred to as sighting wires. These are positioned so that the installer can sight along the wall and align these sighting wires ( 23 ) with the wall in both directions. This feature then results in the corner bead being installed so that the correct stucco depth is achieved when the nose wire ( 25 ) is used as a screed or depth gage. The next two longitudinal wires ( 24 ) are shoulder wires which provide strength to the corner during handling. These shoulder wires ( 24 ) also provide additional reinforcement of the stucco in the nose region, since the corner region is always the most vulnerable to physical damage from various impacts. The last longitudinal wire is the nose wire ( 25 ). This nose wire ( 25 ) defines the corner and provides a screeding edge to obtain a sharp, straight corner with proper stucco depth on both adjoining walls.  
         [0035]     Welded wire corner beads are normally fabricated from galvanized steel wire. The amount of zinc on the wires is classed as a ‘regular’ coating weight which is a low level of coating and which is not intended for prolonged exposure to a corrosive environment. The long term protection of the steel wire in both wire stucco laths and wire corners is the stucco itself. Stucco thickness of ⅛ inch or greater are adequate to repel majority of moisture that a wall of a building is exposed to and provide the long term life expected from these installations. However, as can be seen in  FIG. 3 , the nose wire ( 25 ) and the two shoulder wires ( 24 ) and the central sinusoidal wire ( 21   c ) are at the surface or very near the surface.  
         [0036]     There are two problems associated with this aspect of the prior art. First, there is a high risk of corrosion and rusting, especially in wetter climates, since these wires are at or near the surface and do not have an adequate covering of stucco protection. In an attempt to address this problem, efforts have been made to protect the nose wire by enclosing it in a plastic strip as disclosed in Holsman U.S. Pat. No. 3,175,330. These efforts have not been successful since the plastic tube is not bonded to the nose wire and water can be trapped within the tube and accelerating the corrosion problem.  
         [0037]     Secondly, the plastic tube provides no protection for the shoulder wires ( 24 ) and the central sinusoidal wire ( 21   c ). The other problem with this solution is that the stucco does not adhere to the plastic portion. Therefore, the stucco terminates in very thin sections on either side of the plastic tube, and becomes even more vulnerable to physical damage. Consequently, Looverie U.S. Pat. No. 5,669,195 discloses a triangular or shaped wire at the nose (or apex) for better adhesion of the stucco. However, this solution has not improved the corner vulnerability and still has the drawback of the surface wires being vulnerable to corrosion.  
         [0038]     As can be seen in  FIG. 1 , the grid of wires is held together by welding together the overlaps of the sinusoidal wires ( 21 ). If the sinusoidal amplitude or pitch changes or varies between the five sinusoidal wires ( 21 ), there is the risk that the peaks of adjacent sinusoids may drift out of the desired phase relationship. If this happens, then the overlap is lost, welding cannot occur and the product is no longer held together. This results in lost material (scrap) and loss of productivity while the repair is made. Some of the factors that can cause variations in formation of the sinusoids is varying wire tensile strengths, varying wire sizes, varying wire backtension, and varying surface lubricity of the wire. It is difficult for the wire manufacturers to further improve on these characteristics, since there will always be a tolerance range that these wire manufacturers require.  
         [0039]     A similar problem may arise if the sinusoidal wires drift sideways. As a result of the possible variations in sinusoid amplitude, the guides for spacing the individual sinusoidal wires are usually enlarged to cope with these variations. However, the consequence is that the sinusoidal wires can then drift sideways over a larger range. Therefore, again there is the risk that the overlap may be lost and hence the weld. Similarly, at the edge wires ( 22 ), there is the risk of the nailing loops becoming too small, or too big. There is also a potential of the edge wire ( 22 ) missing the sinusoid peak altogether and not welding.  
         [0040]     To minimize the effects of these problems, the solution in the prior art has been to increase the amplitude of the sinusoidal wires. This has the negative result of increasing wire usage without any net benefit to the product. It also has the negative result that with the increased wire mass, it is more difficult for the applicator to force the stucco through this wire mass. This results in voids around the wires and a poor stucco job subject to cracking and subject to water intrusion. This solution has a further negative impact by decreasing the gap between adjacent sinusoidal peaks and this further limits placement options for the various longitudinal wires.  
         [0041]     In  FIG. 2 , the cross sectional view shows the positioning configuration of all the wires. The wires pass between two welding wheels, upper welding wheel  31  and lower welding wheel  32 . The wheels are driven which pulls the wires through the space between the wheels. The wheels are energized so that an electrical current passes through the various intersections of the wires in the pinch point. The upper wheel is usually spring loaded to provide a squeezing force on the wire intersections.  
         [0042]     As can be seen in  FIG. 2 , the wheels are smooth and the gap is even across the width. Therefore, the combinations of wires and wire thicknesses must be consistent across this width. Otherwise, welding can not occur at the joints where there is inadequate squeezing force, or in worst case, no squeezing force at all.  
         [0043]     To achieve these even pressures, the sinusoidal wires ( 21 ) must alternate above and below each other to achieve even thickness of sinusoidal overlaps. The longitudinal wires ( 22 ,  23 ,  24 , and  25 ) must then alternate in the gaps created, and must be of the same diameter as the sinusoidal wires ( 21 ) to maintain this even thickness.  
         [0044]     As can be seen, the prior art product design has to a large extent been dictated by the manufacturing process and there has been little ability to improve the product to be better adapted for stucco application. For example, using various wire sizes across the grid would allow the product design to be optimized by providing more size and mass where it was best required and less mass where it wasn&#39;t needed. Secondly, since the longitudinal wires must be within the gaps created by two adjacent sinusoidal wires, the ability to change longitudinal wire positions sideways is limited.  
         [0045]     As can be seen in  FIG. 3 , a further disadvantage of the prior art is that the sighting wires ( 23 ) are on the backside of the corner bead. Again this is the result of the manufacturing restrictions. It would be an advantage to have all the longitudinal wires on the outside of the corner bead, since this would improve the strength of the corner and provide less resistance to achieve full embedment of the corner with stucco.  
         [0046]     In  FIG. 4 , a preferred embodiment of welded wire corner bead  40  in accordance with the present invention is shown. The welded wire corner bead of the present invention includes, generally, the same components as prior art welded wire corner beads; namely a series of sinusoidal wires and a series of longitudinal wires, but arranged in a different manner.  
         [0047]     The significant difference of the present invention is that each sinusoidal wire spans the full width of the corner bead. In the exemplary embodiment of  FIG. 4 , the welded wire corner bead comprises three transverse sinusoidal wires  41 ,  42  and  43 . In other embodiments, there may be a lesser or greater number of transverse sinusoidal wires. The number could be as low as two or up to five or more. By changing the number of sinusoidal wires, the density of the grid can be altered to achieve greater strength if desired. By welding the sinusoidal wires  41 ,  42  and  43  together at their intersections, by welding these sinusoidal wires  41 ,  42  and  43  to the longitudinal wires  44 ,  45 ,  46  and  47 , and by forming this grid into a Vee shape, a truss structure is created. This truss structure provides strength and rigidity to the improved corner. This is important during handling and during installation on the job site to ensure that the wire corner is not distorted, and that a straight stucco corner is achieved.  
         [0048]     Although these transverse wires  41 ,  42  and  43  are described as sinusoidal, they may be fashioned into other shapes. As shown in  FIG. 4 , the transverse wires  41 ,  42  and  43  are fashioned with straight sections as they traverse at a diagonal across the width of the corner bead  40 . Conversely, these wires could traverse along arcs or curved paths.  
         [0049]     A feature of the preferred embodiment of the invention is that the transverse wires will always cross with the previously placed transverse wire. The advantage is that with variations in wire properties or placement of these transverse wires, there will always be a crossing point or intersection. Therefore, a weld can always be made to join the wire grid together. This will eliminate the problem associated with the configuration of the prior art wire corner bead.  
         [0050]     Another advantage of the preferred embodiment is that there is more efficient utilization of the transverse wires. Since the wires are essentially in a straight line path, wire usage is reduced which is an economical advantage over the prior art. Further, the wire density is reduced since the overlap areas are eliminated. This has an advantage for the applicator to be able to fully embed the corner with stucco to achieve better quality stucco corners.  
         [0051]     As shown in  FIG. 4 , the welded wire corner bead may have a series of longitudinal wires attached to the transverse wires. At the outer edges, edge wires  44   a  and  44   b  may be provided to form nailing loops  48 . At some distance from the edges, sighting wires  45   a  and  45   b  may be provided. At the mid area, two shoulder wires  46   a  and  46   b  may be provided as well as the nose or apex wire  47 . All of these longitudinal wires are placed on only one side of the transverse wires, and do not alternate as in the prior art. As shown in  FIG. 6 , the placement of these longitudinal wires will be such that they will face the outside surface when formed into a V-shape and placed on an external corner.  
         [0052]     In the preferred embodiment, the locations of the sighting wires and the shoulder wires may be repositioned to achieve preferred locations, and no longer be limited to spaces between loops. For example, the position of the sighting wires needs to be altered for different stucco thickness designs. This has not been possible with the prior art but can be easily achieved with this embodiment.  
         [0053]     A further advantage with the invention is that varying wire sizes may now be incorporated. This possibility is the result of the orientation of the transverse wires on one face and the longitudinal wires on the other face, and the elimination of the overlapping loops. The welding wheels will then be able to follow the various changes in wire thickness and create sound welds.  
         [0054]     In  FIG. 5 , the relationship of the welding wheels  51 ,  52  and the position of the wires for the present invention is shown. The welding wheels  51 ,  52  are smooth and the gap is even across the width, similar to the prior art. However, since the intersections pass through the welding zone in a sequential manner rather than a simultaneous manner as in the prior art, there are fewer intersections in the weld zone at any given point along the new corner. This is a key difference in achieving the ability to vary the combinations of wire sizes or shapes. Since there are fewer weld intersections in the weld zone, the upper welding wheel  51  can move up and down and compensate for varying thicknesses at sequential weld points and still achieve consistent welding.  
         [0055]     A further advantage with this invention is the possibility of utilizing shaped wires. There is an advantage to use flattened wires since these wires function as scrapers and assist in pulling the stucco from the trowel and forcing it into the corner cavity. In the prior art, flattened wires could not economically be utilized since they would have to be of the same thickness as all other wires. This would then result in heavier longitudinal wires which would not be economical. However, with this invention, varying wire thickness can be incorporated and flattened wires may be utilized for some or all of the longitudinal wires.  
         [0056]     Another benefit of utilizing flattened longitudinal wires is that the individual corners can be stacked tighter with less space in between each corner. In  FIG. 7 , the prior art corner is shown stacked with another similar corner. The nose wires  25  cannot contact the adjacent sinusoidal wire  21  resulting in a spacing X of approximately 0.25 inches between corners. This has a major disadvantage when these corners are overlapped on a building corner. The installer must force or distort the overlapping corner to reduce this gap. This is difficult to achieve properly and usually results in an undesirable step in the finished stucco. The other disadvantage is that more space is required for packaging and warehousing. Presently, wire corners are packaged 40 pieces into a 10 inch carton.  
         [0057]     In  FIG. 8 , the improved wire corner  40  is shown with flattened longitudinal wires  44 ,  45 , and  46  and is shown stacked with another similar corner. In this case the nose wire  47  is much closer to sinusoidal wires  41 ,  42 ,  43  resulting in a tighter stack. The resulting space Y between corners is approximately 0.15 inches. This results in an improved stucco corner with virtually no noticeable step at overlapping joints. Further, it will allow significant savings in packaging and warehousing costs since 50 individual corners will now be packed in the same 10 inch carton.  
         [0058]     The same packaging and warehousing saving can be achieved with round longitudinal wires as well, since the stacking height with round wires will be approximately 0.20 inches and 50 corners will fit into the same carton.  
         [0059]     There are other wire shapes that also could be utilized, such as spiral or helical wire. These wires would provide greater strength for a given weight or wire size. Therefore, a stronger corner may be fabricated with the use of shaped wires with the configuration of the preferred embodiment.  
         [0060]     To enhance the corrosion resistance, it is a further feature of the preferred embodiment to provide a chromate conversion coating of the galvanized wires after the product is fabricated. Stucco corners are usually packaged in groups of 10 per bundle. To make chromate conversion coating economically viable, it is desirable to be able to batch coat the wire corners in groups of 10. With the reduced wire density of the improved wire corner of this invention, it is now possible to achieve a successful chromate coating of the wire corners. The other advantage of chromate conversion after fabrication is that the weld points, where zinc has been burned off during welding, are now provided with some corrosion protection.  
         [0061]     In the embodiment of  FIG. 4 , the transverse wire sizes and longitudinal wire sizes may range from 16 ga to 20 ga. In the preferred embodiment, the transverse wires would be 17½ ga and the longitudinal wires would be 17 ga, except for the nose wire which would be 16 ga.  
         [0062]     The amplitude of each transverse wire could range from 3 inches to 6 inches. The preferred embodiment would have an amplitude of 5 inches. The pitch of each transverse wire could range from 2 inches to 8 inches. The preferred embodiment would have a pitch of 6 inches. In the case of 3 transverse wires as shown in  FIG. 4 , nailing loops  48  would be formed every S inches, in this case every 2 inches.  
         [0063]     It will be appreciated by those skilled in the art that the preferred and alternative embodiments have been described in some detail but that certain modifications may be practiced without departing from the principles of the invention.