Geometrical instruments – Straightedge type – Rules
Reexamination Certificate
2002-06-11
2004-07-06
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Straightedge type
Rules
C033S042000, C033S640000
Reexamination Certificate
active
06757984
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to guides for cutting tools, and more particularly to a saw guide for accurately and efficiently cutting a sheet material to a particular dimension.
2. Description of the Background Art
Sheet material is commonly used to cover large areas of a structure at construction sites. Typical sheet materials include plywood, particleboard, oriented strand board (OSB), wallboard, and varieties of laminates. Plywood and OSB are typically used to form the outside walls, the roof, and the floors of a structure. Similarly, wallboard (e.g., drywall, paneling, etc.) is secured to the interior frame of the structure to define and cover inside walls. Finally, laminates provide decorative coverings for flat surfaces (e.g., floors, counters, etc.). Installation of the sheet materials generally requires a construction worker to make at least one large cut to size the sheet material appropriately for the application.
Preparing the sheet material for proper installation is a time consuming process. Sheet material is typically prepared at a cutting station centrally located at the construction site, and is cut with a handheld circular saw via the following process. First, the worker measures a predetermined distance from an end edge of the sheet material using a tape measure, and marks a “crows foot” reference mark on the sheet material near one side edge of the material. The worker then repeats the measuring and marking procedure to provide a second reference mark near the opposite side edge of the material. Next, the worker stretched a chalk line across the two reference marks, and snaps the chalk line to mark a cut line on the material parallel to the end edge of the sheet at the predetermined distance. The worker then cuts the sheet material along the chalk line to yield a piece of material the desired size. The several steps required to cut each piece of sheet material are time consuming, and result in high labor cost, even for experienced workers, to properly cut the sheet material.
Many prior art devices have attempted to make it easier to cut sheet material more accurately and efficiently. For example, frame guides attach to the sheet of material and either attach to or abut the hand saw, to ensure that the cut is straight. Typically, frame guides are bulky and sometimes completely stationary, thereby requiring additional labor time to manipulate the cutting tool and/or sheet material into the proper position to make accurate cuts. Further, frame guides do not eliminate the need to mark the cut location on the sheet of material.
Another type of guide, commonly known as a rip fence, engages a reference edge of the material and attaches to the saw to maintain the saw at a set distance from the reference edge during the cut. Rip fences can be difficult to manipulate and use, because the guide must be as long as the cut distance. Further, the edge of a rip fence hangs over the reference edge of the sheet material, and at long cut distances it is difficult for the user to slide the rip fence along the edge of the material in unison with the motion of the saw.
Yet another problem with known cutting guides is that it is difficult to make fine corrections in the cutting path during a cut. For example, a slight deviation between the angle of the saw blade and the straight edge of the guide can result in the side of the blade binding against the sheet material, or pushing the rip guide away from the reference edge of the sheet material. In particular, if the blade of a saw is not aligned exactly with the cut path defined by the blade, the saw will want to follow a slightly different (either toward or away from the guide) cut path. Because the path of the saw is fixed by the guide, the operator will not be able to correct for this problem.
What is needed, therefore, is a guide for a cutting tool that facilitates quick and accurate positioning of a blade of the cutting tool at any desired distance from a reference edge of a piece of sheet material. What is also needed is a guide that need not be as long as the cut that is being made. What is also needed is a guide that facilitates user correction of a cut path during a cut.
SUMMARY
The present invention overcomes the problems associated with the prior art by providing a simple to use guide for use with a cutting tool, that eliminates the need to make more than one measurement and/or to snap a cut line on the sheet material. In the disclosed embodiments, no part of the guide extends below the top surface of the sheet material when the cutting tool is positioned on the sheet material, and does not, therefore, interfere with the manipulation of the cutting tool over the sheet material.
In one embodiment, the guide has a set of alignment marks and a plurality of measurement scales associated with the alignment marks. Each measurement scale corresponds to at least one fiducial lines such that when one of the alignment marks is aligned with a particular fiducial line, the measurement scale corresponding to the particular fiducial line indicates the distance of the blade of the cutting tool from an edge of the sheet material. In a particular embodiment, the guide includes identifying indicia that correlate the measurements scales to the fiducial lines. Examples of identifying indicia include, but are not limited to, distinctive line patterns, distinctive colors, and distinctive reference characters.
The length of the measurement scales differs amongst the various embodiments. In one embodiment, the measurement scales are at least as long as, but not significantly longer, than the distance between adjacent fiducial lines. In another embodiment, the measurement scales are at least as long as, but not significantly longer, than one-half the distance between adjacent fiducial lines.
In some of the embodiments, at least two measurement scales corresponds to each fiducial line, and are both provided on the same line of the guide. One measurement scale indicates the distance of the cutting blade from a reference edge of the sheet material when the reference edge of the sheet material is disposed on a first side (e.g., the left side) of the cutting tool. The second measurement scale indicates the distance of the blade from the reference edge when the reference edge is on the other side (e.g., the right side) of the cutting tool. The relative disposition of the scales is indicative of which of the two scales is valid, depending on the orientation of the reference edge with respect to the cutting tool.
In an alternate embodiment, the guide includes a projection device coupled to the cutting tool. In a more particular embodiment, the projection device is a rotatable laser, elevated and rotatably coupled to the front of the cutting tool by a base portion. The guide has an annular portion that includes the measurement scales, alignment marks, and their associated distances. The alignment marks are aligned with the fiducial lines by aligning an alignment mark with a reference mark, and then positioning the cutting tool such that the projected beam impinges on the fiducial line.
In another alternate embodiment, the guide includes a base portion coupled to the cutting tool, and an alignment member slidably coupled to the base portion. The alignment member does not extend below the upper surface of the sheet material, so as not to allow the cutting tool to rest flat on the surface of the sheet material. The alignment marks and the measurement scale(s) are disposed on one of the base portion and the alignment member. The other of the base portion and the alignment member includes a reference mark. The alignment marks are aligned with a fiducial line by aligning the alignment mark with the reference mark, and aligning a predetermined portion (e.g., the distal end) of the alignment member with the fiducial line. In other words, aligning a distal end of the guide with a fiducial line, and aligning an alignment mark on the guide with a reference mark on the cutting tool positions the blade of the
Fulton Christopher W.
Henneman & Saunders
Henneman, Jr. Larry E.
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