Static structures (e.g. – buildings) – Stepped; e.g. – stair – Risers connected to common stringer
Reexamination Certificate
1998-09-08
2001-01-16
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Stepped; e.g., stair
Risers connected to common stringer
C052S182000, C052S188000
Reexamination Certificate
active
06173540
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of Invention
Virtually all buildings having multiple floors are provided with a staircase to permit the occupants to move therebetween. In residential homes a staircase is constructed from so-called risers and stair treads of calculated dimensions based upon the ceiling height and staircase length.
Traditionally such risers and treads have been fabricated from boards of at least 12 inches in width which are clear of knots and are cut from hardwoods such as oak and other varieties. Because such select hardwood boards are dwindling in supply and extremely expensive when available, stair treads have recently been constructed from a plurality of boards which are more narrow and glued together along their adjacent edges. However, in such a construction process it is difficult to match the grains of the woods so that the glue joints are not visible which is undesirable aesthetically. Differences in the moisture content of the boards can also cause construction problems such as warping of the treads.
In a continuing effort to reduce building costs, plywood stair treads have been utilized in those instances where the stairs are to be carpeted. Modernly, engineered wood products such as particle board, chip board, and Oriented Strand Board (OSB) have been used in floor areas and wall and roof sheathing applications, but have been considered lacking in sufficient tensile strength to be used as stair treads.
Thus, the present invention has been developed to provide a stair tread fabricated from an engineered wood product such as Oriented Strand Board which has suitable mechanical and physical characteristics for use as a stair tread in residential construction.
SUMMARY OF THE INVENTION
After much study of the above described problems, the present invention has been developed to provide an improved stair tread manufactured from an engineered composite wood product. Unlike stair treads fabricated from solid wood, plywood, or particle board, the present stair tread is constructed from a structural board that is engineered for specific performance characteristics.
Precisely cut wood strips are mixed with phenolic resin binders or other newly developed binders and constructed in a four layer process including two core layers which lie perpendicular to the two surface layers. The composite board is then cured under intense heat and pressure to form an irreversible bond between the layered materials. This manufacturing process eliminates knot holes, voids, splits, and their related problems.
This combination of engineered design and manufacturing process gives the composite board its inherent strength, stiffness, durability and other desirable physical characteristics.
The present improved stair tread is constructed and graded to meet current industry standards—The Engineered Wood Association (APA) for stair treads and has become widely accepted in residential home construction.
In view of the above, it is an object of the present invention to provide an improved stair tread for use in residential home construction.
Another object of the present invention is to provide an improved stair tread construction from an engineered composite wood material having mechanical and physical properties suitable for this application.
Another object of the present invention is to provide an improved stair tread which meets or exceeds current industry standards for this product for use in commercial and residential construction.
Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings which are merely illustrate of such invention.
REFERENCES:
patent: 3393481 (1968-07-01), Meuret
patent: 3909997 (1975-10-01), Eickhof
patent: 4321293 (1982-03-01), Naka
patent: 4321294 (1982-03-01), Naka
patent: 4464870 (1984-08-01), Crepeau
patent: 4625266 (1986-11-01), Winter
patent: 5713166 (1998-02-01), Couture
Friedman Carl D.
Horton Yvonne M.
Mills Law Firm PLLC
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