Abstract:
An improved construction member or joist is disclosed that includes upper and lower chords connected by various members including first and second trimmable webs at either end thereof, which webs include end portions received in grooves in the upper and lower chords. Significantly, the profile of the end portions of the webs includes at least one notch or ridge that fits within a corresponding notch or ridge in the chord to provide a more secure attachment, even under unusual loading conditions. Supplemental webs are also provided that can be attached to the member at various locations to provide an additional degree of support only where needed.

Description:
This application claims the benefit of U.S. provisional patent application Ser. No. 60/238,021 filed Oct. 6, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed toward an improved construction member, and more specifically, toward a construction member such as a joist adapted to withstand stresses applied in several different directions as occur when the joist is used in a modular home being transported on a trailer. 
     BACKGROUND OF THE INVENTION 
     Joists and other construction members made of natural dimensional wood are becoming increasingly expensive and hard to obtain because the old growth wood of large diameter and high strength used for such members is itself becoming rare and expensive. Second growth lumber is not an acceptable substitute because of its limited size and strength. However it is desirable that second growth lumber be used whenever possible to minimize the use of larger, solid natural wood members. 
     The use of engineered construction members such as joists has increased in recent years to take advantage of the lower cost of second growth lumber. Such joists generally comprise upper and lower chords formed from second growth lumber or laminated veneer lumber connected by one of several means. One such joist uses a solid and continuous plywood or oriented strand board (OSB) web member running the length of the chords. Since OSB can be produced from wood that is unsuitable for many other structural uses, the lower cost of the materials used offsets much of the additional cost associated with manufacturing the member. Another type of engineered joist uses dimensional lumber chords joined by a combination of metal webs and vertical lumber webs attached to the top and bottom chords with metal plates. Still another uses wood struts attached between the upper and lower chords, some normal to the chords and others angled with respect thereto. These member may be finger jointed and glued to the top and bottom chords, for example. 
     Another advantage of engineered products over dimensional lumber is that these products can readily be made to any size and configuration required by industry, and can be made in a consistent manner so that they are uniformly straight and lightweight. It is also easier to control the strength and other properties of engineered lumber than natural lumber, and this allows manufacturers to provide products of consistent quality that are in high demand. The many through-openings between the upper and lower chords also makes the installation of wiring and plumbing in a structure much easier when engineered joists are used because the drilling required when dimensional lumber is used is reduced or eliminated. Engineered members are less expensive to install than dimensional lumber and can even be designed to provide specific load-bearing characteristics when necessary. And, when the ends of such construction members are provided with trimmable web sections between the upper and lower chords, these member can easily be trimmed at a work site to the exact dimensions needed, just like natural wood products. 
     While such engineered joist perform admirably, there are still problems that remain to be addressed. For example, when webs are added to the ends of such members to make them trimmable, it is generally necessary to glue the web to the upper and lower chords of the construction member and clamp the member while it dries. If the member is not clamped, the upper and lower chords may spread or the distance therebetween may not be consistent. Clamping adds to the time and cost required to make such a construction member. 
     Furthermore, certain applications require the joists to withstand forces that are applied in different directions or forces that are not applied uniformly along the length of the joist. One example of such problems is found in the engineered joists used to support a manufactured or “mobile” home. Such homes are generally constructed in one or two large sections and then transported by tractor trailer to a home site at which point they are placed on a fixed foundation. The modular homes are generally rectangular so that they will fit on a trailer. The joists that support the structure generally run the width of the home, which direction corresponds to the width direction of the trailer. However, joists are normally designed to be supported near their ends, such as when the home is placed on a foundation. On the trailer, however, the support comes at locations closer to the middle of the width of the structure. Supported in this manner, the joists and the manufactured homes are subject to flexure during the moving process, and this can lead to cracked interior walls and other problems when the home is transported. One method to address this problem would be to use over-manufactured joists that could withstand such stresses—however, as these stresses occur only for several hours of the many-year life span of a home, this method unnecessarily increases costs. It would therefore be desirable to provide an engineered joist that can be assembled without clamping, that provides additional support only in certain locations, and that resists the twisting and other unusual forces experienced by joists used in a manufactured home when the home is being transported. 
     SUMMARY OF THE INVENTION 
     These and other problems are addressed by the present invention which comprises an engineered construction member or joist comprising, in a first embodiment, top and bottom chords connected by a web, which web has non-linear, profiled end portions that are received in correspondingly shaped profiled grooves in the chords. Because these profiled end portions provide a mechanical connection between the chords and web, the need to clamp the upper and lower chords together when the web is glued to the chords is reduced or eliminated. It has also been found that these profiled end portions seem to provide greater strength and rigidity to the joists, especially when forces are applied in different directions when the joist and structure in which it is incorporated, is moved. While a primary use for such joists is envisioned to be in the manufactured home market, other applications where joist are subject to a forces in a variety of different directions can readily be imagined. 
     In a second embodiment of the invention, a joist is provided with a two-piece web member that can be inserted at any needed location along the joist to provide additional support between the chords at the locations where a large load is to be supported. Advantageously, these web members can either be installed when the joist is manufactured or alternately, in the field when a structure incorporating the joist is being attached to another structure. For example, the web element can be placed where needed to provide additional support during the transport of a manufactured home, removed at the job site, and replaced with a second element at a different location along its length, such as under a load supporting wall, where needed. Since the web element is easy to install and remove, the element used during transport can be removed at the job site so as not to interfere with the placement of wiring and plumbing, etc. in the finished structure. And, when the vertical supports that surround the center chase of a joist are replaced with web members, it becomes possible to provide wider chases than has heretofore been feasible without unduly weakening the construction member. 
     It is therefore a primary object of the present invention to provide an improved constructional member with increased rigidity. 
     It is another object of the invention to provide an improved constructional member having chords connected by webs which are attached to the chords at profiled end portions. 
     It is yet another object of the invention to provide a construction member than can be assembled without clamping. 
     It is a further object of the invention to provide selectively insertable support webs for an engineered joist. 
     It is still another object of the invention to provide a method of selectively reinforcing a joist at a given location along its length. 
     It is still a further object of the invention to provide an engineered joist having a larger than normal central or other chases. 
     It is yet another object of the invention to provide an engineered joist with trimmable ends which include web portions with profiled end portions routed into upper and lower chords. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will become clear from a reading of the detailed description of the invention together with the following drawings of which: 
     FIG. 1 is a front elevational view of an improved joist according to the present invention being supported at its ends; 
     FIG. 2 is a front elevational view of the joist shown in FIG. 1 being supported at two points inward of its ends; 
     FIG. 3 is sectional elevational view taken through line III—III in FIG. 1; 
     FIG. 4 is a detail view of one of the supplemental joist supports shown in FIG. 1; 
     FIG. 5 is a sectional elevational view taken along line V—V in FIG. 4; 
     FIG. 6 is a sectional elevational view of a first alternate embodiment of a joist according to the present invention; 
     FIG. 7 is a sectional elevational view of a second alternate embodiment of a joist according to the present invention; and, 
     FIG. 8 is a side elevational view of a joist according to the present invention showing a modification that can be accommodated by such a joist. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein the showings are for purposes of illustrating preferred embodiments of the invention only, and not for the purpose of limiting same, FIG. 1 shows a construction member or joist  10  having a first end  12  and a second end  14  formed from an upper chord  16  having a top edge  18 , a bottom edge  20  and first and second side edges  22  and a lower chord  24  having a top edge  26 , a bottom edge  28  and first and second side edges  30 . The use of directional terms herein such as “top” and “bottom” refer to members oriented like the joist of FIG.  1 . Of course, these construction members do not have to be used as joists and can be inverted or used in a non-horizontal orientation; however, as such construction members are generally used in a vertical plane, they will be described in this orientation for simplicity. Upper chord  16  is connected to lower chord  24  by a plurality of angled braces  32  attached to the upper chord side edges  22  and lower chord  24  side edges  30  by metal plates  34  as known in the art, and one or more vertical braces  36 . Various arrangements of angled and vertical braces other than those shown in the figures are known in the prior art and can be used without departing from the scope of this invention. The joist also includes first and second end webs  40  which allow up to twenty four inches to be trimmed off the joist to provide a joist of a desired length, first and second supplemental webs  42 , and a wide center chase  44 . 
     The joist shown in FIG. 1 is supported at its ends  12 ,  14  by supports  46 . When the joist  10  is used in a manufactured home, for example, supports  46  would be the block foundation that supports the home. In FIG. 2, joist  10  is shown supported at two points inwardly of its ends by supports  48 . This configuration could occur in a variety of situation, including when the joist is used in the floor of a manufactured home that is being moved to a home site. In this case, supports  48  would be part of the trailer transporting the house. 
     Referring now to FIG. 3, the novel manner of mounting end webs  40  between the top and bottom chords is shown. Each of the ends webs  40  includes a central body portion  50  and first and second end portions  52  which extend from a shoulder  54  of the body portion. Each end portion  52  includes an end edge  56  having a cut  57  and connected to shoulder  54  by two side edges  58 ; each side edge  58  includes a notch  60 . Upper chord  16  includes a groove  62  in bottom edge  20  into which first end portion  52  of end web  40  is received. Groove  62  has chamfered edges  64 , an end wall  66  and two side walls  68  each of which includes a ridge  70  shaped and positioned to be received in notch  60  when the web is in place between the two chords. Cut  57  allows the end portion  52  to compress somewhat when it is inserted into groove  62 . 
     When the web  40  is in place, shoulder  54  is spaced apart from chamfered edges  64 ; when an adhesive is used to bond the web to the chords, some will leak from groove  62 ; this gap receives the adhesive that leaks out and when that adhesive bonds between the edges  64  and shoulder  54  a stronger, more flexible bond results. The excess glue that surrounds the joint also helps provide a watertight seal and prevents water from leaking into the joint. The second end portion  52  of the end web  40  is identical to the first end and will not be described separately. This arrangement provides a more secure connection between the web and the chords, even when stresses are applied to the joist in various unusual directions, such as the sideways and other forces that such a joist might experience when used in a modular home being transported. 
     FIG. 6 shows an alternate embodiment of the end portion  50  wherein the web includes a ridge  73  while the groove sidewall  68  includes a notch  71  that receives the ridge. FIG. 7 shows yet another embodiment of the end portion  52  wherein protrusions  96  are provided near the end edge  56  in channels  98  of the end webs  40  and the side edges  58  are somewhat angled. This arrangement provides benefits similar to those discussed above, and, in addition, may make end portion easier to insert into groove  62 . Of course other arrangements of protrusions and openings, or multiple notches and ridges, could also be used without departing from the scope of this invention. 
     FIG. 8 shows a use of a construction member according to the present invention that takes advantage of the increased strength and rigidity provided by the profiled end edges of the end web members described above. FIG. 8 shows a construction member  100  used as a joist, which construction member includes a top chord  102 , a bottom chord  104  and an end web  106  installed below a floor  108 . A vertical end support  110  is attached to bottom chord  104  and to floor  108 ; diagonal supports  112  are also used between the upper and lower chords, one of which is installed adjacent to end web  106 . This arrangement provides sufficient strength that the end of top chord  102  can be removed and an opening  114  provided in the end web to allow wires or conduits to be installed near the end of a construction member. Furthermore, this open-top arrangement allows pipes or conduits to be dropped into opening  114  from above, before floor  108  is installed, thus greatly simplifying the installation process. Prior art construction members generally did not provide adequate strength to function properly with part of the top chord removed. 
     As seen in FIGS. 4 and 5, each supplemental web  42  comprises a first or upper portion  74  having a top edge  76  adjacent bottom edge  20  of upper chord  16 , first and second side edges  78  extending away from the upper chord, and a bottom edge  80  angled with respect to top edge  76  to give upper portion  74  the shape of a trapezoid. Bottom edge  80  of upper portion  74  also includes a channel  81  running between the side edges  78 . Supplemental web  42  further comprises a bottom portion  82  having a bottom edge  84  lying adjacent the top edge  26  of lower chord  24 , first and second side edges  86  extending away from the bottom chord, and a top edge  88  angled with respect to bottom edge  84  to give the lower portion  82  a trapezoidal shape. Top edge  88  includes a projecting tongue  90  extending between first and second side edges  86  which is shaped to be slidingly received by channel  81  of upper portion  74 . Upper portion  74  and lower portion  82  are connected by adhesive and/or screws  92  as will be described in more detail herein. 
     As will be appreciated from the foregoing description, one or more supplemental supports  42  can be placed at substantially any location along the joist between the end webs  40  by placing bottom portion  82  on the lower chord  24  and sliding upper portion  74  along upper chord  16  and against bottom portion  82  so that tongue  90  of the upper portion is received in channel  81  of the lower portion. As the two portions are forced against one another, angled bottom edge  80  of the upper portion and angled top edge  88  of the bottom portion slide against one another and force the top edge  76  of the upper portion against the upper chord and the bottom edge  84  of the lower portion against the lower chord  24 . An adhesive may be used to hold the two portions together and/or screws  92  can be driven thought the sides of the portions and through tongue  90  to hold the portions together. Thus, the supports may be placed as shown in FIG. 2 when the joists form the bottom of a manufactured home to provide additional support of the home on the bed of a trailer. These joists may be removed at the installation site if the additional support is no longer needed. Alternately, one or more of the supplemental support can be placed where extra support is needed—beneath a load-bearing wall, for example. Because the supplemental supports are easily installable on-site, they can be placed only where needed, leaving a maximum amount of room free for the running of wires, conduits, etc. and keeping the weight of the member to a minimum. And, because of the substantially increased support provided by such elements, the width of center chase  44  (or other chases) can be greater than is usually possible with conventional engineered lumber when the supplemental supports are placed adjacent the center opening. 
     The foregoing invention has been described in terms of preferred embodiments only. Obvious additions and modifications will occur to those skilled in the arts upon a reading and understanding of foregoing disclosure, and it is intended that all such obvious changes form part of this application to the extent that they are included within the scope of the several claims appended hereto.