Geometrical instruments – Straightedge type – Rules
Reexamination Certificate
2001-01-29
2003-01-14
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Straightedge type
Rules
C033S443000, C033S042000, C083S744000, C083S745000
Reexamination Certificate
active
06505411
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a portable saw guide and T-square and method of use where an accurate and straight saw cut is desirable when cutting raw construction materials. Specifically the invention is an improved T-Square which can be quickly and accurately secured to a work piece such as a sheet of plywood in order that a worker may use a guide edge of the T-square to accurately maneuver and guide a saw along a desired course. The portable saw guide securely clamps to the work piece and is capable of providing a flush linear contact between a surface of the workpiece and the saw guide to compensate for any non planar irregularities such as a bow, sag or warp in the work piece to facilitate continuous contact between the saw being guided and the guide edge of the T-square to produce a straight cut along the work piece.
BACKGROUND OF THE INVENTION
In the construction industry, raw materials, particularly lumber, specifically plywood and other rough cut wood materials which are used at a job site are rarely perfectly straight, square or planar as the case may be. The standard for cutting such materials at a job site is generally by use of a portable electric circular hand saw as is known in the industry. Access to a more functional table saw at a construction site is usually not available or inefficient in practice. The common practice in the construction industry is to cut lumber on a lumber pile or place lumber on saw horses in order to facilitate the cutting of a work piece with the electric circular saw. The nature of new lumber is to have slight warps or bends and the practice of using saw horses to support the lumber for cutting operations creates substantial difficulty in that the saw horses, which are linear supports, do not provide support along the entire planar surface of the lumber being cut. For instance where a common sheet of 4×8 ft. plywood is supported between a pair of saw horses, the plywood tends to bow or sag on either sides of the saw horses.
It is well known in the industry to snap a chalk line on the lumber and cut the plywood freehand solely using the saw's guide aligned with the chalk line. However, despite care of the user, the vibration of the circular saw together with any bow or sag in the lumber being cut, trying to guide the saw across the wood by following the chalk line leads to an inaccurate cut along the chalk line. This type of rough cut method is not adequate in most framing and construction projects, specifically when sheathing a wall or roof with plywood, any inconsistent cut in an initial or first sheet of plywood leads to a significantly exaggerated and increasing inconsistency as subsequent sheets are applied adjacent to the first.
To compensate for such freehand use a construction worker will use a make shift jig. This is where a material with a straight edge is fastened to the plywood so that the circular saw's fence is guided along the edge of the jig. The problem with this method is that due to its nature and dimensions plywood tends to warp and bow and a gap results between the plywood and the jig. As the saw is guided along the surface of the plywood it reaches the area of the gap created between the jig and the surface being cut and the saw slides into the gap between the jig's straight edge and the plywood precipitating an undesired and inaccurate cut.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a substantially immovable and secure saw guide for use with a circular saw to provide a straight cut of a raw construction material.
It is another object of the invention to provide a self securing device which provides such a guide for a circular saw with a minimum of manual intervention by a user.
It is a further object of the invention to compensate for any irregularities or a bow or sag in the material by providing the T-square saw guide with a flexible saw guide fence in intimate contact with the surface of the material being cut for mutually bowing or sagging with the material to facilitate a straight cut along the bowed or sagging material.
It is a still further object of the invention to provide a portable saw guide device which is inexpensive, light weight and may be quickly clamped and unclamped to a rough material being cut.
Another object of the invention is to provide a portable saw guide device which can retain appropriate lateral saw guiding stability while ensuring a longitudinally transverse flexibility for remaining in intimate contact with the surface being cut and which can withstand the working conditions of a construction site
REFERENCES:
patent: 515522 (1894-02-01), Frank
patent: 4281572 (1981-08-01), Stovall
patent: 4394800 (1983-07-01), Griset
patent: 4463644 (1984-08-01), Ferdinand et al.
patent: 5084977 (1992-02-01), Perkins
patent: 5459937 (1995-10-01), Albin et al.
Davis & Bujold P.L.L.C.
Fulton Christopher W.
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