The present invention relates to a truss system used in the construction of commercial and residential buildings. More particularly, the present invention relates to a truss system using roll-formed light gauge metal truss members and fixtures.
In the construction field, structural members and fixtures are increasingly formed from light gauge metal due to the rising cost and declining quality of wood. Components formed from light gauge metal are preferred over wood in many applications because the metal components are lighter in weight, stronger, consistent in quality, not subject to shrinkage, and resistant to fire and insect infestation.
In producing the most economical light gauge metal truss system, it is desirable to roll form the elongated truss members with a cross-sectional configuration designed to achieve maximum strength of the member to meet the required structural codes while minimizing the weight of the metal used. A number of roll-formed light gauge metal truss chord members have been developed having different cross-sectional configurations. Typically such truss members have been formed with C-shaped or Z-shaped cross-sections which suffer from low strength-to-weight ratios. More recently, truss members have been formed with generally U-shaped cross-sections having a pair of substantially parallel legs extending from a base portion.
U.S. Pat. No. 4,986,051 to Meyer et al. dated Jan. 22, 1991; U.S. Pat. No. 5,417,028 to Meyer dated May 23, 1995; and U.S. Pat. No. 5,771,653 to Dolati et al. dated Jun. 30, 1998, each disclose an elongated truss chord member of light gauge metal having a generally U-shaped cross-section. The prior art chord members include in cross-section a pair of legs extending from a base portion. Each of the legs includes a recessed web attachment face so that the pair of web attachment faces are spaced apart a distance less than the width of the base portion. The legs terminate in an outwardly turned stiffening flange to improve the strength-to-weight ratio of the members. The outwardly turned stiffening flange also provides an outer face adjacent the distal end of each leg so that the cross-sectional width of the chord members at the base portion is substantially the same as the cross-sectional width of the chord member at the distal end of the legs to facilitate stacking and transport of the trusses, and engagement of the truss chord members with other structural members or fixture.
The prior art teaches the use of an inclined face in the portion of the chord member interconnecting the recessed web attachment face with the base. The inclined faces in each leg extend inward toward the opposite leg so that the web attachment faces are spaced apart a distance less than the width of the base. Truss chord members including inwardly extending inclined faces to interconnect the web attachment face and the base have several drawbacks. For example, it is desirable in a truss chord member to provide a wide web attachment face to thereby facilitate the attachment of the chord member to structural members received between the web attachment faces. In a member including an inwardly extending inclined face interconnecting the web attachment face and the base, the inclined face comprises a portion of the overall longitudinal width of the leg, thus the longitudinal width of the web attachment face relative to the overall longitudinal width of the leg is reduced.
Further by way of example, the angle of the inclined portion relative to the base may cause difficulties in engaging the chord member with truss clips and other fixtures.
A typical truss includes a plurality of truss web members interconnecting the truss chord members. A number of roll-formed light gauge metal truss web members have been developed having different cross-sectional configurations. Typically such web members have been formed with a C-shaped or H-shaped cross-section which suffer from low strength-to-weight ratios. Truss web members having a box-shaped cross section are favored because the box-shaped cross-sectional configuration eliminates two modes of failure of the members in compression compared to C-shaped or H-shaped members. However, box-shaped members are difficult to fabricate which adds to the expense of fabricating the truss and reduces the flexibility in providing trusses of differing dimensions.
It is known to fabricate a box-shaped member by nesting two C-shaped members. French Patent No. 939,599 dated Jan. 8, 1947, discloses an elongated member having a box-shaped cross section formed by nesting two elongated C-shaped members each having one longer flange and one shorter flange. The above-referenced French patent does not disclose or suggest structural members having sufficient size and strength to bear the loads subjected to a web member in a long span truss. Heretofore, such two-piece box-shaped members have not been made in such sizes or used as load bearing web members in trusses.
Accordingly, it is an object of the present invention to provide a novel truss system in which the structural members and fixtures are formed from light gauge metal.
It is another object of the present invention to provide a novel truss chord member which is easily roll formed having a cross-section that optimizes the strength of the member for the weight of the metal used.
It is another object of the invention to provide a truss system with truss chord members having wide web attachment faces.
It is still another object of the invention to provide a truss system with truss chord members which easily engage truss clips and other fixtures.
It is a further object of the invention to provide a truss system with truss chord members which are easily stacked and nested for efficient shipment.
It is yet another object of the present invention to provide a novel truss web member that is easily roll formed having a cross-section that optimizes the strength of the member for the weight of the metal used and provides flexibility in sizing for different size truss chord members.
It is still another object of the present invention to provide a novel truss web member having a box-shaped cross section that may be easily roll formed in different sizes.
Trusses are typically fabricated with upper and lower truss chord members and a plurality of interconnecting web members. Each of the web members having one end attached to an upper chord member and the other end attached to a lower chord member. The number and location of the web members is determined by the type of truss being fabricated and the structural requirements for the truss.
In the fabrication of trusses, the various members may be attached to each other by conventional means. Typically, the end portion of a web member is received between the web attachment faces of the chord member and attached thereto by self tapping screws or other conventional means. It is known to provide one or more pre-positioned holes along the length of structural members to facilitate the attachment of the members by screws or other conventional attachment means. U.S. Pat. No. 4,720,957 to Madray discloses a series of pre-positioned holes formed along the entire length of a C-shaped structural member. However, in the fabrication of trusses it is not necessary or desirable to pre-position holes along the entire length of the chord member. The pre-positioned holes need only be located along the portions of the chord member where a web member will be attached. Limiting the pre-positioned holes to one or more portions along the length of the chord member reduces the time and expense associated with forming the holes and provides an additional aid in properly positioning the web members.
Accordingly, it is an object of the present invention to provide a novel truss system and method of fabricating trusses which obviate the deficiencies of the known systems and methods.
It is another object of the present invention to provide a novel apparatus and method for positioning web members in a light gauge metal truss.
It is yet another object of the present invention to provide a novel apparatus and method for roll forming truss chord members from a blank of light gauge metal.
It is still another object of the present invention to provide a novel apparatus and method for forming the peak of a light gauge metal truss.
It is a further object of the present invention to provide a novel apparatus and method for securing a truss from uplifting forces.
It is yet a further object of the present invention to provide a novel apparatus and method for connecting one or more trusses together.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.
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