Music – Instruments – Stringed
Reexamination Certificate
2002-02-28
2004-08-10
Lockett, Kim (Department: 2837)
Music
Instruments
Stringed
Reexamination Certificate
active
06774292
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates to a stringed musical instrument and in particular to instrument components such as the neck and central body structure.
A few guitar builders and manufacturers have used carbon fiber with varying degrees of success. One such prior art design (U.S. Pat. No. 5,990,396) has a central T-shaped extruded stiffening bar preferably of graphite fibers which, alone, carries the load imposed by a plurality of strings, and the wood is not a structural element thereof. One other prior art design (U.S. Pat. No. 5,616,873) uses a fingerboard made of graphite fibers in the place of the traditional prior art fingerboard. This serves as the main structural element while using a wire to counteract the tension load imposed by a plurality of strings similar to another prior art design (U.S. Pat. No. 4,074,606). It specifies a soft wood, and the wood is not a structural element. Another prior art design (U.S. Pat. No. 4,951,542) using graphite, however, this patent pertains to the molding process, and does not relate to an engineered design, nor does it specify any particular orientation of the graphite fibers, also heat and pressure are used. One other prior art design (U.S. Pat. No. 6,087,568) using a graphite and glass composite to cast a complete neck assembly, of which wood is not a structural element.
Graphite, or carbon fiber (one and the same) is only rayon extruded under extreme heat and pressure. This changes its molecular structure on a subatomic level. It is a material that lends itself to highly engineered applications with its high strength and stiffness coefficient (it is six times stronger than chrome-moly steel). It is a composite material that offers excellent values of strength in compression as well as tension.
In order to capitalize on this attribute the structure must be designed, and the workmanship must be of such quality, so as to apply the fibers in a perfectly straight line with reference to the load being placed on it, carried by it, and distributed into other structures. When this is achieved, a minimal amount of graphite can be used. (The preferred embodiment of the invention uses approximately 60 cubic centimeters of material.)
Also, the magnitude of engineering should be considered. Many factors weigh into a design of this type. Such as string tension values, displaced tension fields, semi-tension fields, column loads, and load terminations, etc.
On the other hand arbitrary over use of graphite will produce a neck that will not resonate the desired tone, and be so stiff that any string orbit relief is impossible. The choice of a matrix strong enough to capture this material is paramount.
A true “composite” structure must be engineered and designed as a whole. This one is constructed from carbon fiber and wood. In the preferred embodiment it should be manufactured by hand, and not be extruded or mass produced, and it requires very skilled labor.
Some prior art designs place a number of small graphite rods in the node region of the structure (Center of Neck). This area is where the structure yields, or flexes the absolute least. In order to utilize this material best, and achieve a good strength to weight ratio the structural element (graphite) must be placed as far away from the node region as possible.
This instruments neck design is of composite sandwich/stressed skin truss type. It utilizes a high-density wooden core to bear against. From an engineering standpoint the wood's primary function is as an inter-laminar sheer and compression core. Which holds the graphite in its proper place so that it functions as designed, and transfers opposing loads in a semi-tension field from one point to another, and to withstand the crush loads imposed in the region between the compression spar and the tension spar.
From a musical standpoint the wood needs only to resonate the desired tone. It is still a crucial element to the structure.
BRIEF SUMMARY OF THE INVENTION
A composite structure, engineered using force vector controlled geometry, constructed around a high density structural wood core with an outer stressed skin truss structure made of carbon fiber cloth and epoxy resins, and containing therein compression and tension spar caps made of graphite.
I believe this is the first embodiment of this type technology applied to a stringed musical instrument, and with proper application of these materials there is little change in the relative mass to density ratio of the original wood. Therefore, tone and the natural resonance of the wood are preserved as much as possible, while tremendous gains in strength, stiffness, and stability are achieved.
Preliminary tests of the invention reveal that it is at least twelve times stiffer than a conventionally constructed (prior art) wooden neck. It has very little thermal creep and distortion in comparison to a (prior art) wooden neck, and although subjective, the tonal differences are insignificant.
REFERENCES:
patent: 4681009 (1987-07-01), Mouradian
patent: 4951542 (1990-08-01), Chen
patent: 5337644 (1994-08-01), Fishman et al.
patent: 5616873 (1997-04-01), Fishman et al.
patent: 6100458 (2000-08-01), Carrington et al.
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