Stone working – Sawing – Rotary
Reexamination Certificate
1999-10-01
2001-07-10
Morgan, Eileen P. (Department: 3723)
Stone working
Sawing
Rotary
C125S001000, C125S012000, C073S001790, C073S001810
Reexamination Certificate
active
06257225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is apparatus and a method for cutting or sawing a slab of stone or similar material.
2. The Prior Art
A substantial number of patents are concerned with apparatus for cutting slabs of stone, concrete or the like. These include: British Patent No. 1,058,958 of Wholton et al.; U.S. Pat. Nos. 2,736,311 of Coates; 5,442,984 of Tate; 3,207,016 of Huff, 4,998,775 of Hollifield; 5,398,458 of Henriksen et al.; and 2,619,081 of Johnson.
In these patents, the slab of stone remains fixed and the cutter is mounted on a carriage that is moved along a set of parallel rails that are spaced above the slab. In some instances, such as Wholton et al., Huff, and Tate, the rails are mounted on a table-like structure, while in other instances the rails are part of a large and heavy installation.
In order to provide an open space to accommodate the slab and to permit free passage of the cutting tool, it is common practice to support the rails at their ends only. The desirability of being able to make lengthy cuts is well recognized. As a result, the rails in the prior art devices were lengthy compared to the cross sectional size of the rails.
The difficulty of making these extended rails rigid can be readily appreciated. Pure sagging of the rails in a vertical direction was tolerable since it affected mainly the depth of the cut. However, several other factors were at work.
First, the carriage that was moved along the rails was not balanced, with the result that the carriage applied more weight to one of the rails than to the other. The more heavily loaded rail sagged more, thereby causing the top of the cutting blade to tilt laterally toward the more heavily loaded side.
A second source of inaccuracy was caused by the manner in which the carriage was pushed along the rails. Ordinarily, the carriage was pushed by the user, and no special precautions were taken to assure that the applied force, which often included a downward component, was equally distributed between the two rails. Depending on the location of the handgrip relative to the rails, it was not unusual for one of the rails to be loaded more heavily than the other, again resulting in a tilting of the cutter blade.
The typical reaction of prior art designers to these causes of inaccuracy was to make the rails and their supporting structures less flexible. In most instances this resulted in a much heavier structure, which therefore was much less portable. It was generally thought that lightweight apparatus could not produce accurate cuts, and if accurate cuts were to be achieved, a large, heavy, and therefore non-portable machine was required.
Thus, conventional design philosophy, starting with the assumption that the rails must be spaced above the workpiece, led to the conclusion that accurate cutting could only be achieved with large, heavy, fixed installations and that lightweight portable equipment could not produce cuts of satisfactory accuracy.
The present inventor has devised a totally different design approach that runs counter to the conventional design philosophy and that permits remarkable accuracy to be achieved with lightweight portable equipment.
SUMMARY OF THE INVENTION
As an experienced stone fabricator, the present inventor was aware of the fact that a very high percentage of the stone cutting that is done is performed on slabs of stone that have already been prefinished so that their surfaces are relatively flat. These slabs are typically used for kitchen and bathroom counters, and the required cutting is for the purpose of trimming the slabs to a desired size.
The gist of the present invention is as follows. Instead of using rails suspended and spaced above the workpiece as in the prior art, the present inventor took the unprecedented step of laying the rails directly on top of the workpiece, in contact with it.
By this single bold stroke, problems resulting from deformation of the rails were completely overcome. It was no longer necessary to use rails heavy enough to support a moving carriage that typically weighed several hundred pounds, because in the new approach, the workpiece itself, a slab of granite, undergirds the rails and prevents them from sagging. This permits the rails to be made much lighter, which permits, in one embodiment, tracks twelve feet long that weigh only 24.5 pounds each.
Portability is extremely important, because it enables the cutting to be done onsite. This eliminates the need to transport the slabs to a cutting facility along with templates made at the job site, and then returning the cut slabs to the job site.
In carrying out his radical design approach, the present inventor uses rails that are hollow tubes of rectangular cross section in a preferred embodiment. As a practical matter, he found it advantageous to apply a long strip of a soft rubber to the underside of the rails, which bears against the slab. This rubber strip prevents movement of the rails with respect to the workpiece once the rails have been manually positioned on it.
Because the lateral location of the cutting blade is not at the center of the carriage, the rails will not be positioned symmetrically with respect to the marked cut line. To facilitate proper positioning of the unconnected rails with respect to the marked cut line (and to assure that the rails are parallel), the inventor has devised a calibration tool that greatly reduces set-up time.
In an alternative embodiment that is more attractive when shorter rails can be used or when portability is not a factor, the rails are connected to each other but continue to be laid directly onto the slab in accordance with the present invention.
The novel features which are believed to be characteristic of the invention, both as to structure and method of use, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which several embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.
REFERENCES:
patent: 5056272 (1991-10-01), Battaglia
patent: 5545079 (1996-08-01), Larsson et al.
patent: 5941227 (1999-08-01), Bearden
patent: 6073621 (2000-06-01), Cetrangolo
McKown Daniel C.
Morgan Eileen P.
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