Static structures (e.g. – buildings) – Inclined top cover – Rafter tie-in at horizontal-type support
Reexamination Certificate
1998-05-15
2001-04-24
Safavi, Michael (Department: 3635)
Static structures (e.g., buildings)
Inclined top cover
Rafter tie-in at horizontal-type support
C052S092300, C052S093100, C052S712000
Reexamination Certificate
active
06219975
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to trusses and more particularly, to a truss having an integral hold down strap.
BACKGROUND OF THE INVENTION
Structures which are occasionally subject to sustained high winds, such as structures located in regions subject to hurricanes, preferably have substantial connections between components of the structure to increase the strength of the structure and prevent damage in high winds. Building codes in these regions require that there be additional connections between trusses. in the roof, joists in the floor and the walls to anchor the roof and floor. For instance, it may be required to anchor each end of a truss or floor joist to the adjacent wall with a hold down strap.
It is well known to provide flexible metal straps for the purpose of connecting the roof truss (or floor joist) to a stud in an adjacent wall. An example of such a strap is shown in U.S. Pat. No. 3,861,094 (Jureit et al.). The Jureit et al. strap is an elongate piece of sheet metal formed at either end with teeth projecting outwardly from the sheet metal. Small, spaced apart sections are erupted from the sheet metal as by punching to define the teeth. The ends of the strap are driven into the truss and into a stud in the wall, respectively, to secure one to the other.
Toothed hold down straps can be hammered into the truss (or joist) and adjacent wall by laborers at the construction site. However, this is a time consuming process and often requires the laborers to get into precarious positions high up on the structure near the edge of the roof to secure the hold down straps to the wall. Moreover, the hold down straps must be stored by the laborers and then located when needed for securing the truss. It is known to secure one end of a toothed strap to the truss at a plant where the truss is assembled so that the strap is integrated with the truss prior to erecting the truss on the wall of the structure. The end of the toothed hold down strap can be pressed into the truss by the same press used to drive other nailing plates into adjoining wooden elements forming the truss. At the construction site, the laborer need only secure the other end of the strap to an adjacent stud.
The sheet metal must be sufficiently strong so that the teeth formed can be driven into the wooden elements of the truss or joist and the wall. There must be enough thickness in the sheet material so that teeth punched from the sheet material will not simply bend over rather than penetrating the wood of the truss components when pressed against them. Sheet material having this thickness (e.g., 22 gauge sheet metal) is thicker than needed to adequately secure the truss to the wall. Thus, the cost of the straps is high because the sheet metal must be quite heavy so that teeth formed are of sufficient strength. Further, the formation of the teeth in the hold down straps is an additional step in the construction process, whether the hold down straps are secured to the truss at the construction site or at the assembly plant. The tooth formation step, which is in addition to the step of stamping out the hold down straps from a web of sheet metal, also adds to the cost of the truss. Thus, it would be desirable to have a truss assembly with an integral hold down strap that is easily fastened to a wall and is inexpensive to manufacture.
SUMMARY OF THE INVENTION
These and other objects may be obtained by a truss, having an integral hold down strap, which is used with other structural components, such as wall studs and the like, to form a structure. The truss contains an upper and lower chord and typically contains web members that extend between the upper and lower chords to provide strength and rigidity. The web members and the chords are connected to each other by nailing plates. The lower and upper chord converge at the heel of the truss and are connected by at least one nailing plate. A web member, such as a polygonal block, may be located between the upper and lower chord at the heel of the truss.
The hold down strap in one embodiment is an elongate piece of sheet metal which is smooth and free of teeth. The strap has a first portion which contains two opposing flanges that are bent such that the first portion has a generally U-shaped cross section. The hold down strap also has a second portion sized to extend from the first portion and into engagement with one of the other structural components, such as a stud or a wall top plate. The first portion of the hold down strap is sized to engage the end surface of the lower chord with the two opposing flanges engaging the side surfaces of the lower chord. The hold down strap is attached to the lower chord with a nailing plate, typically with the same nailing plate that connects the lower chord to the upper chord or the lower chord to the polygonal block web member.
The hold down strap is free of integrally formed teeth which eliminates the fabrication step of punching out the teeth. Typically, for integrally formed teeth to be effective and not bend during installation, the teeth must be formed from thick metal, usually at least 22 gauge. Because the hold down strap is free of integral teeth, the strap may be fabricated from thinner sheet metal. The use of thinner steel, typically 26 gauge, reduces cost. Also, the use of 26 gauge steel promotes quick and easy attachment to the truss by the same nailing plate that is used to connect the lower and top chords because the integrally formed teeth of the nailing plate can easily penetrate the thin sheet metal of the brace.
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MiTek Holdings, Inc.
Safavi Michael
Senniger Powers Leavitt & Roedel
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