Abstract:
A wall stud includes a steel member having a generally rectangular cross-sectional shape and having at least first, second and third sides, the first and second sides being opposite one another. The wall stud also includes a first foam member having a generally rectangular cross-sectional shape. The first foam member is affixed to the first side of the steel member. The wall stud also includes a second foam member having a generally rectangular cross-sectional shape. The second foam member is affixed to the second side of the steel member. The wall stud also has a ridged cap affixed to a side of the first foam member opposite the steel member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Embodiments of the invention relate generally to steel construction systems and methods. More specifically, embodiments of the invention relate to construction systems and methods that employ steel and foam in place of wood, primarily for residential structures.  
         [0002]     The residential construction industry is heavily dependent on materials and techniques that have been in use for many years. The industry as a whole is resistant to change and is, therefore, ripe for improvements. For example, many have attempted to incorporate steel into residential construction as a replacement for wood framing. Unfortunately, however, many issues have prevented widespread acceptance of steel framing.  
         [0003]     Steel is generally more expensive than wood. Hence, a direct replacement of steel for wood, without regard to cost differences, would likely raise the price of a home to a unacceptable level given today&#39;s price differentials.  
         [0004]     Another problem is that steel conducts heat and cold much better than wood, thus making insulating a home much more difficult. Further, the temperature differential between a steel stud in an exterior wall and temperature of the inside of a home can cause visible artifacts to appear on the interior drywall at the studs.  
         [0005]     Yet another issue is that craft workers such as electricians and plumbers are less familiar with steel frame construction. As a result, their prices for working in such structures tend to be higher.  
         [0006]     For these and other reasons, improved steel frame construction techniques and systems are needed.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007]     Embodiments of the invention provide a wall stud. The wall stud has a steel member having a generally rectangular cross-sectional shape and having at least first, second and third sides, the first and second sides being opposite one another. The wall stud also includes a first foam member having a generally rectangular cross-sectional shape. The first foam member is affixed to the first side of the steel member. The wall stud also includes a second foam member having a generally rectangular cross-sectional shape. The second foam member is affixed to the second side of the steel member. The wall stud also has a ridged cap affixed to a side of the first foam member opposite the steel member.  
         [0008]     In some embodiments, the steel member is two-inch square tubular steel having a wall thickness in the range of 14 to 16 gauge. The first and second foam members may be two-inch square closed cell structural foam having a density in the range 6 to 8 pounds per cubic foot. The wall stud may include an adhesive material affixing the first foam member and the second foam member to the steel member. The ridged cap may include tabs that extend along opposite sides of the first foam member.  
         [0009]     Still other embodiments provide a wall panel. The wall panel includes a top plate having a generally rectangular cross-sectional shape, a bottom plate having a generally rectangular cross-sectional shape, and a plurality of studs affixed in a generally parallel configuration between the top plate and the bottom plate thereby forming a generally planer frame. Each stud, the top plate, and the bottom plate include a steel member having a generally rectangular cross-sectional shape and having at least first, second and third sides. The first and second sides are opposite one another. Each stud, the top plate, and the bottom plate also include a first foam member having a generally rectangular cross-sectional shape. The first foam member is affixed to the first side of the steel member. Each stud, the top plate, and the bottom plate also include a second foam member having a generally rectangular cross-sectional shape. The second foam member is affixed to the second side of the steel member. Each stud, the top plate, and the bottom plate also include a ridged cap affixed to a side of the first foam member opposite the steel member.  
         [0010]     In some embodiments, the steel members comprises two-inch square tubular steel having a wall thickness in the range of 14 to 16 gauge. The first and second foam members may be two-inch square closed cell structural foam having a density in the range 6 to 8 pounds per cubic foot. The wall panel may include an adhesive material affixing the first foam members and the second foam members to the steel members. The wall panel may include sheeting adjacent the second foam member of each stud, the top plate, and the bottom plate. The sheeting may be a closed-cell, structural foam material. The sheeting, the top plate, the bottom plate, and the plurality of studs may form one or more cavities, in which case the wall panel may include insulating foam disposed within the cavities. The insulating foam may be a closed cell, spray-on foam.  
         [0011]     Still other embodiments provide a method of constructing a wall panel. The method includes assembling a generally planer steel frame. The frame includes a top plate having a generally rectangular cross-sectional shape and at least first, second, and third sides. The first and second sides may be opposite one another. The frame also includes a bottom plate having a generally rectangular cross-sectional shape and at least first, second, and third sides. The first and second sides being opposite one another and generally co-planer with the first and second sides of the top plate. The panel also includes a plurality of steel members affixed in a generally parallel configuration between the top plate and the bottom plate. Each steel member has a generally rectangular cross-sectional shape and at least first, second, and third sides. The first and second sides are opposite one another and co-planer with the first and second sides of the top plate and the bottom plate. The method also includes affixing first foam members having a generally rectangular cross-sectional shape to the first sides of the top plate, the bottom plate, and the steel members. The method further includes affixing second foam members having a generally rectangular cross-sectional shape to the second sides of the top plate, the bottom plate, and the steel members and affixing sheeting to the top plate, the bottom plate, and the steel members. The sheeting is disposed adjacent the second foam members to thereby form cavities together with the top plate, the bottom plate, the steel members, the first foam members, and the second foam members. The method further includes affixing a rigid cap to a side of each first foam member opposite each steel member to which each first foam member is affixed. The method also includes applying insulating foam into the cavities.  
         [0012]     In some embodiments, some operations take place at a first location and others take place at a second location. The first location may be a production facility and the second location may be a job site, in which case the method may include transporting the panel at least 0.25 miles between the production facility and the job site. The first location may include a controllable environment. Affixing first foam members may include using adhesive to affix the first foam member to the steel member. Affixing a rigid cap may include using fasteners to affix the ridged cap to the first foam member by penetrating the first foam member and anchoring the fastener into the steel member. The steel members may be two-inch square tubular steel having a wall thickness in the range of 14 to 16 gauge. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings wherein like reference numerals are used throughout the several drawings to refer to similar components. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.  
         [0014]      FIG. 1  illustrates an exploded view of a stud according to embodiments of the invention.  
         [0015]      FIG. 2  illustrates a wall panel according to embodiments of the invention, which panel incorporates studs as illustrated in  FIG. 1 .  
         [0016]      FIG. 3  illustrates a method of fabricating a wall panel such as the wall panel of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     Embodiments of the invention provide improved steel frame construction techniques and systems. Some embodiments provide wall studs having a combination of foam and steel that may be used in place of wood studs. Other embodiments employ such studs in pre-fabricated panels. Still other embodiments provide methods for constructing with steel and foam using a combination of off-site prefabrication and onsite installation.  
         [0018]     Although embodiments of the present invention will be described herein with respect to residential construction, those skilled in the art will appreciate that the embodiments described herein may be applied to commercial construction.  
         [0019]     Attention is directed to  FIG. 1 , which illustrates an exploded view of a stud  100  according to embodiments of the invention. The stud  100  includes a steel member  102  having an exterior foam member  104  fastened to one side and an interior foam member  106  fastened to the opposite side. The stud  100  may include an interior cap  108  and/or an exterior cap  110 . Either cap  108 ,  110  may be fastened to the stud with fasteners  112 . As will be described in greater detail below, the stud components may be fastened using other means such as tape, glue, and/or the like. In a specific embodiment, only the interior cap  110  is used.  
         [0020]     The steel member  102  may be any of a variety of steel products. In a specific embodiment, the steel member  102  is 16 gauge, two-inch square, tubular steel. Other embodiments employ different gauge steel (e.g., 14 gauge) and/or different size tube (e.g., 2″× 3 ″). Some embodiments employ “C-channel” and/or track steel instead of or in combination with tubular steel. In either case, the steel member  102  may be galvanized and/or otherwise coated. A coating system used in some embodiments is the GATORSHIELD® system, a product of the Mechanical Tube Division of Allied Tube and Conduit of Harvey, Ill. The steel member  102  may be specified to be oil free, which enhances the effectiveness of some adhesive fastening systems, as will be explained in more detail hereinafter.  
         [0021]     The interior foam member  106  and the exterior foam member  104  are two square-inch, six-pound, closed cell, structural foam strips in some embodiments. In other embodiments, eight-pound structural foam is used. In a specific embodiment the foam is LAST-A-FOAM® foam, a product of the General Plastics Manufacturing Company of Tacoma, Wash. The foam may be cut into strips from larger sheets. Other types and sizes of foam may be used. In some embodiments, the foam members  104 ,  106  are made of a fireproof or fire resistant material. Either or both the interior foam member  106  and the exterior foam member  104  may be notched as shown. Notches  114  may be spaced at intervals such as 24″ to thereby improve the efficiency with which utilities may be installed in the final structure.  
         [0022]     The exterior cap  110  (if used) and interior cap  108  are 25 gauge steel sheeting (i.e., sheet metal), which may be galvanized and specified to be oil free. Other sizes, generally in the range of 22-25 gauge, may be used. Other materials may be used, such as wood, fiberglass, and other, generally ridged materials. The caps  108 ,  110  may be bent such that a tab  116  extends on either side of the foam members  104 ,  106 . The tabs  116  may be, for example, three-eights inches, three-quarter inches, or the like. The tabs  116  provide a fastening point for utility items such as electrical boxes while the cap itself serves as a secure attachment point for dry wall, foam, OSD, or other interior or exterior sheeting.  
         [0023]     The foam members  104 ,  106  may be attached to the steel member  102  using tape, glue, or any acceptable adhesive (not shown) in some embodiments. In a specific embodiment, the foam members  104 ,  106  are fastened to the steel member  102  using an adhesive transfer tape, such as 3M™ 6035. The caps  108 ,  110  may be attached to the foam members  104 ,  106  using a similar product. In some embodiments, fasteners  112  are used to secure the caps  108 ,  110  to the steel member  102 . The fasteners  112  penetrate the foam members  104 ,  106  and penetrate the steel member  102 , thereby securing the entire assembly. The fasteners may be, for example, grade  5  or better, galvanized, self-taping screws.  
         [0024]     It should be appreciated that steel studs according to other embodiments do not necessarily include all the components illustrated and described here, as will be appreciated by those skilled in the art. Further, the stud  102  need not be fully assembled as shown before being integrated with other building materials as will become clear from the ensuing description of a wall panel  200  made using a plurality of steel studs such as the stud  102 .  
         [0025]     As will be described in more detail hereinafter, exterior sheeting  118  may be applied to the completed stud.  
         [0026]     Having described a stud  102  according to embodiments of the invention, attention is directed to  FIGS. 2 and 3  which together illustrate and describe a wall panel  200  and a method of constructing one. The wall panel incorporates steel studs according to embodiments of the invention. For purposes of this description, the studs comprised by the wall panel  200  are the studs  102 , although other embodiments of panels according to the present invention may incorporate different steel stud embodiments.  
         [0027]      FIG. 3  depicts a method  300  of constructing a wall panel and incorporating it into a structure according to embodiments of the invention. Those skilled in the art will appreciate that other embodiments of methods according to the present invention may include more, few, or different steps than those illustrated and described here. Further, the steps illustrated and described here may be traversed in different orders than depicted here.  
         [0028]     The method  300  begins at block  302  at which point a steel frame  202  is assembled. Typically, steel members  204  are welded on two-foot centers to top  206  and bottom  208  plates of the same tubular steel material. Window openings  210  and doorway openings  212  are framed at this time. In some embodiments, this step takes place at a pre-fabrication facility in a controlled environment. To accommodate this construction methodology, the panel  200  is sized appropriately for transportation to the job site.  
         [0029]     At block  304 , exterior foam members ( 104  from  FIG. 1 ) are fastened to the steel members  204  using an adhesive system as previously described. The adhesive system may be glue, double-stick tape, and/or the like. In a specific embodiment, the adhesive is applied from a carrier that is rolled like tape. As the carrier is unrolled, a sticky surface is exposed that is applied to one of the surfaces (e.g., the steel members  204 ). Thereafter, the carrier is removed, thus exposing the second sticky surface to which the other surface (e.g., a foam member  104 ) is adhered. Having specified the steel components to be oil free improves the adherence properties of such adhesive systems. In some embodiments, pressure is mechanically applied to the assembly to improve the adherence of the foam members to the steel members  204 . The foam members typically are fastened to both vertical and horizontal steel members  204 .  
         [0030]     At block  306 , exterior sheeting ( 118  from  FIG. 1 ) is fastened to the panel  200 . The exterior sheeting may be OSB, hardboard, structural foam, DENSGLASS™, or other appropriate material. In a specific embodiment, the exterior sheeting is ten-pound, closed cell, foam and may be either structural or not. In some embodiments, the exterior sheeting is fireproof or fire resistant. The exterior sheeting may be glued, taped, or the like, and/or secured with mechanical fasteners (not shown). The sheeting may be installed without removing portions for doorway  212  and/or window openings  210 .  
         [0031]     In some embodiments, insulating foam  218  is applied to the panel cavities  220  at block  308 . In addition to providing greater structural support, the foam enhances the insulating properties of the wall panel. For example, some embodiments have an R-8 per square inch rating and 3# density. The insulating foam  218  may be, for example, a two-part polyurethane foam such as those distributed by USCS of Phoenix, Ariz., or other appropriate foam material. In some embodiments, the insulating foam  218  is fireproof or fire resistant. The insulating foam  218  need not completely fill the panel cavities  220 . In some embodiments, the insulating foam  218  is not applied until the panel  200  is further along in the assembly process and, in some cases, is not applied until the panel  200  is erected at the job site.  
         [0032]     In some embodiments, adhesive (not shown), if used, is applied to the interior side of the steel members  204  at block  310 . In other embodiments, this operation is not performed until the panel  200  is erected at the job site.  
         [0033]     At block  312 , the panel  200  is shipped to the job site. Typically, several panels are shipped simultaneously. At block  314 , the panel is used along with other panels to assemble a structure. Panels  200  may be fastened together using screws, bolts or other mechanical fasteners. In some embodiments, the panels are welded together to form the structure. As is apparent, the panels may be assembled at other points in the process.  
         [0034]     At block  316 , notched, interior foam members ( 106  from  FIG. 1 ) are attached to the steel members  204 . The interior foam members may be attached as previously described using glue, tape, or other appropriate adhesive material. In embodiments wherein an adhesive material was applied at block  310 , a backing may be removed so that the interior foam members may be attached. The interior foam members typically are attached to both horizontal and vertical steel members  204 .  
         [0035]     At block  318 , interior steel caps ( 108  from  FIG. 1 ) are attached to the interior foam members. The interior steel caps may be attached using tape, glue, and/or other appropriate adhesive. In some embodiments, the caps are also or alternatively fastened using fasteners ( 112  from  FIG. 1 ) that penetrate the interior foam members  220  and screw into the steel members  204 .  
         [0036]     It should be noted that blocks  316  and  318  may be iteratively completed. In other words, it is not necessary that all interior foam members  220  be fastened to the panel  200  before any caps  222  are attached. In fact, as previously mentioned, the steps illustrated and described here may be completed in any of a variety of orders.  
         [0037]     Is should also be noted that the insulating foam may be applied at any point in the process, either before or after the panel is shipped to the job site. Likewise, the sheeting covering the window openings  210  and doorways  212  may be removed at most any time, either before or after the panel  200  is shipped to the job site.  
         [0038]     It should also be noted that the references to “interior” and “exterior” herein need not import meaning into the final orientation of the panel with respect to the inside and outside of a structure. In some embodiments, the side referred to herein as “interior” may in fact be oriented toward the exterior of the structure. Likewise with the term “exterior.” Further, a panel may be used on the interior of a structure, in which case the terms have no relevance to the finale orientation of the panel with respect to the interior and exterior of the structure.  
         [0039]     The panels  200  may be placed on any appropriate foundation material, including concrete, structural foam footings, OSB floor sheeting, and/or the like. In some embodiments, steel floor and/or roof truss systems are employed to complete a structure that is essentially free of wood products. In some embodiments, similar panels are used in basement wall applications. In such applications, portions of the panel, especially buried exterior portions, may be coated with a material that prevents moisture intrusion. An exemplary coating is NITROCOAT 2595, a two-part coating product from UCSC or Phoenix, Ariz. Further still, in some embodiments, panels may include an orthogonal member for placement below grade to serve as a footing.  
         [0040]     Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention, which is defined in the following claims.