Abstract:
A truss incorporates metallic webs of differing gages, and in protected positions between chord members, to enable its use as a floor joist.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the construction of lightweight trusses adapted for use in commercial and residential environments. More specifically, the invention concerns simplifications and economies in the construction and fabrication of such trusses particularly useful as floor joists. 
     Prior to this invention, trusses and trussed joists of the type referred to were constructed of all wooden members, or with diagonal metallic webs of different lengths interconnecting non-parallel upper and lower members. See for example U.S. Pat. No. 3,748,809. 
     No way was known to construct a less expensive yet satisfactorily sturdy truss using metallic diagonal webs of equal length, to achieve economies and simplifications in truss construction, and in the manner to be described. 
     SUMMARY OF THE INVENTION 
     It has been found that an extremely lightweight and easily fabricated truss, useful as a floor joist, may be formed by interconnecting parallel upper and lower chord members with equal length metallic webs of differing thickness, or gage. Basically, the truss comprises 
     (a) upper and lower longitudinally extending generally parallel chord members which are vertically spaced apart, 
     (c) multiple upright blocks which are longitudinally spaced apart along the length of said chord members and located therebetween, said blocks interconnecting the chord members, 
     (c) and multiple load carrying metallic webs in spaces between the blocks, each web having flat ends, one of which is located between the upper end of a block and the lower side of the upper chord member, and the other of which is located between the lower end of another block and the upper side of the lower chord member, said other end located closer to the center of the truss than said one end, 
     (d) successive webs in a direction away from the center of the truss having increasing thickness. 
     As will be seen, the metallic webs may typically have angled main extents between their opposite ends; the interconnection of the web ends and chords may be quickly accomplished by driving nails through the chords and web flat ends and then into the ends of the blocks, which may consist of wood; and the approximately equal length steel webs may, successively, have thicknesses which increase by about 2 gage in directions away from the center of the truss. Further, strength of the truss is optimized, while the webs remain protectively confined between the chord members, by increasing the overall width of each web main extent to bear a ratio to the chord width which lies between 0.75 and 1.00. In this manner, an extremely lightweight truss is achieved, with maximum strength; the chord members and certain blocks may comprise wooden two by fours; equal length webs and equal distance separation of the blocks may be employed; and rapid fabrication achieved. If desired, a strength increasing metallic strip may be protectively attached to the lower chord member, as will be seen. 
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which: 
    
    
     DRAWING DESCRIPTION 
     FIG. 1 is a side elevation of a truss incorporating the invention; 
     FIG. 2 is a perspective view of a portion of the FIG. 1 truss; 
     FIG. 3 is a fragmentary elevation showing a modified construction; 
     FIG. 4 is an enlarged section on lines 4--4 of FIG. 5; 
     FIG. 5 is a perspective view of a metallic web as employed in the truss of FIGS. 1 and 2; and 
     FIG. 6 shows nailing details. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows upper and lower longitudinally elongated chord members 10 and 11 extending in the same generally horizontal direction and spaced apart vertically. Such members are typically parallel, may advantageously consist of wood, and they have inner sides at 10a and 11a. They may for example comprise wooden two by fours. 
     Means is provided to interconnect the members 10 and 11, such means typically including non-metallic (as for example wooden) upright blocks 12a-12g which are longitudinally spaced apart and located between members 10 and 11. The vertical dimensions of the blocks are typically equal; however the end wooden blocks 12a typically comprise two side-by-side two-by-fours, whereas blocks 12b-12g comprise single wooden two-by-fours. Fasteners such as nails 13 connect the chords to the ends of the blocks, as represented in FIG. 1 and in the FIG. 6 nailing detail. In addition, blocks 12a to 12g may be glued to the upper chord members inner side 10a and to a metallic strap 15 extending flatly along the inner side 11a of the lower chord member. Strip 15 may be glued to side 11a; it may have 22 gage, and it has width about the same as that of the lower chord member. (See FIG. 2). Nails 13 project through the reinforcement strip 15, as shown. 
     The upper and lower chord members and blocks are also interconnected by multiple load carrying metallic webs 18-23 located in the spaces between the blocks, such webs extending diagonally between the chord members, as shown. Each web has flat ends, as at 21a and 21b, in FIG. 5, one of which (21a, for example) is located between the upper end of a block (see block 12c, for example) and the lower side 10a of the upper chord member; and the other end (21b for example) is located between the lower end of another block (block 12d for example) and the upper side 11a of the reinforcement strap 15. In each case, the web lower or other end is located closer to the center 100 of the truss than the web upper or one end, as referred to. 
     Further, it will be noted the successive webs in a direction away from the center of the truss have increasing thickness (i.e. decreasing gage). In the example, web 19 has 26 gage; web 20 has 24 gage; web 21 has 20 gage; web 22 has 18 gage and web 23 has 16 gage. Web 18 has 26 gage, as shown. 
     This construction enables the webs to be alike in length and width, which enables the like blocks to be spaced apart longitudinally at equal intervals, while at the same time the strength of the truss increases, outwardly or away from center 100. FIG. 4 shows the webs to have angled cross sections throughout their main extents, between the flat ends. 
     More specifically, the overall width W 1  of each web is the same as or only slightly less than the overall width W 2  of each chord member. Thus, for example, the ratio W 1  /W 2  is between 3/4 and 1, and preferably is about 7/8. As an example, if the chord members consist of two-by-fours, their widths are about 31/2 inches, and the overall width of each web is about 33/8 inches. Again, uniformity of spacing of the blocks and webs is thereby enabled, while the webs are protectively located between the chord members, and at the same time the truss strength increases in an outward direction. 
     In FIG. 3, the flat metallic strap is omitted adjacent the side 11a of chord member 11. 
     In FIGS. 1-3, the blocks 12a comprise two side-by-side wooden two-by-fours, and the blocks 12b-12g may comprise wooden two-by-fours. Note that the flat ends of the webs, as at 21a and 21b, extend beyond the ends of the blocks; see for example overhang 21b&#39; in FIG. 3. Finally, FIGS. 1 and 6 show that increasingly more nails are employed to connect the chords and blocks, in direction toward the ends of the truss. 
     In the above, the chord members may be spliced, if desired. Also, as seen in FIG. 2, the end portion 23a&#39; of the flat end 23a of web 23 is folded up and nailed to the end of the upper chord member 10. FIG. 2 additionally shows shorter nails at 40 extending through the web flatened portion 23b&#39; that projects beyond block 12b. It will be seen that each web has a similar flatened portion that projects beyond its associated block, and that short inserts (as for example 11/2&#34; nails) project therethrough and into the adjacent chord member. FIG. 6 shows the nailing details with numbers (3-8) in squares also referenced in FIG. 1. Accordingly, extreme strength is achieved, together with ease of fabrication.