Music – Instruments – Stringed
Reexamination Certificate
2001-02-07
2003-03-25
Hsieh, Shih-Yung (Department: 2837)
Music
Instruments
Stringed
C084S290000
Reexamination Certificate
active
06538183
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to methods of construction for acoustic and electrically amplified stringed musical instruments. The invention further relates to acoustic and electrically amplified stringed musical instruments comprising fiber-reinforced resin composite materials, where the instruments are provided with a frequency-damping interior coating.
2. Description of the Related Art
Stringed musical instruments, e.g., guitars, mandolins, lutes, violins, cellos, and the like, both acoustic and electrically amplified, have traditionally been constructed of wood. More recently, stringed instruments have been made from wood, molded plastics, molded composite materials, or a combination of wood, plastics and composite materials. The body of the stringed musical instrument may be solid, semi-hollow, or hollow. The neck is typically solid and may further include a truss rod for increased neck strength.
Stringed musical instruments constructed of wood typically have a pleasing resonance but lack the durability of instruments that are made from synthetic composite materials. When composite materials are used or wood and composite materials are combined in the construction of a stringed musical instrument, the durability and strength of the instrument are improved. However, the bulk density of the composite materials is much greater than the density of wood, and the sound-absorbing properties of the composite materials are quite different than those of wood. Hence the resonances of the instrument are changed so that it may produce unpleasing and unacceptable tone characteristics, sometimes described as “inny.”
Fiber-reinforced composites are appealing materials of construction for stringed instruments because such materials are light, stiff and far more resistant to environmental variables, particularly moisture and heat, than are the fine woods traditionally used. Composites are also mechanically stronger than other synthetic materials, e.g., molded plastics. For example, U.S. Pat. No. 4,290,336 describes a molded plastic guitar; this guitar has cost advantages but still requires ribs, a torsion rod, etc., to provide sufficient resistance to mechanical stresses. U.S. Pat. No. 4,313,362 discloses a molded plastic guitar; it features a reinforcement rod that runs from the butt end of the body to the upper portion of the peghead. U.S. Pat. No. 4,188,850 discloses a guitar made of metal and foamed plastic; the neck is formed of a metal body with plastic foamed around it. The neck of a stringed instrument is especially subject to warping because of the tension placed on it by the strings, which naturally varies across the strings from high to low. Thus, replacing all or part of the wood with a fiber-reinforced composite material has been a long-sought goal, especially for the neck of the instrument.
While the potential durability and strength of stringed instruments made in whole or in part of fiber-reinforced composite materials are well accepted, the tone qualities emitted by such instruments have not always been appreciated, nor have manufacturing methods that are simple and readily reproducible been available. Manufacturing methods for fiber-reinforced composite articles will preferably employ a minimum number of steps that require cutting, machining and joining. The resulting musical instruments will preferably emit pleasing tones.
The challenge of fabricating fiber-reinforced composite stringed musical instruments that produce pleasing sounds is appreciable. Composite materials, e.g., resins such as epoxy reinforced with fibers such as graphite, boron, or glass, differ greatly from wood in their acoustic damping properties. Wood is very “lossy”—heavily damping—in the sonic frequency range, especially in the high frequencies. While there has been extensive study of this topic, for example, Materials Research Society Symposium on Materials in Musical Instruments (1994), published in MRS Bulletin, XX, No. 3 (March 1995), the characteristics of pleasing sound quality are not readily quantified. The state of the art was summarized in quite an interesting way as follows (“Graphite Guitar Acoustics 101,” John A. Decker, Jr., Nov. 4, 1999, http://www.rainsong.com/acc101.htm): “There have been a number of experiments where people were asked to tell a Stradivarius violin, say, from a junk student fiddle or a Ramirez classical guitar from a junk guitar when they were played behind a curtain. Even “naïve” subjects—people off-the-street—can almost always differentiate the quality instrument from the junk one. However, if one tries to identify them by their frequency spectrum or mode structure, even musical-instrument acoustic physicists who have spent their entire careers working in this field can't tell which is which.”
The neck of a stringed musical instrument has been a focus of effort to strengthen and stiffen the instrument. U.S. Pat. No. 4,145,948 discloses a guitar neck constructed from graphite fiber reinforced plastic, in which the graphite fibers are oriented longitudinally to provide high stiffness in the direction of the strings. The neck components—the base of the neck, a top piece, and a fingerboard—are molded separately and then adhesively bonded together. No provision for sound frequency damping is disclosed. The inventor of the '948 patent, in a subsequent patent (U.S. Pat. No. 4,846,038), states that this hollow neck “requires an inordinate amount of machining and finishing.” The '038 patent discloses a solid guitar neck that has a graphite fiber reinforced composite T-bar in the neck body, and an attached fingerboard into which are spiked the frets. U.S. Pat. No. 4,846,039 discloses a solid guitar neck formed from alternating layers of epoxy and powdered carbon, fiber reinforced. This solid neck may be constructed with an integral fingerboard. U.S. Pat. No. 4,950,437 also discloses a fiber-reinforced composite neck that can be constructed with an integral fingerboard, by wrapping resin-impregnated fiber cloth around a neck insert, placing the wrapped insert in a mold, pressing the fingerboard down on the top surface of the wrapped insert, and curing the resin. The neck insert can be removed to produce a hollow neck. No provision is disclosed for damping of high frequencies to improve the quality of the sound emitted. U.S. Pat. No. 6,100,458 discloses a composite neck for a stringed instrument; the neck is molded with resin-impregnated fiber cloth around a foam core.
The soundboard of the stringed musical instrument has also attracted innovative materials approaches. In acoustical instruments, most of the sound quality arises from the soundboard. U.S. Pat. Nos. 4,873,907 and 4,969,381 disclose a fiber-reinforced composite soundboard, with a foam core. In order to avoid the “tinny” sound of soundboards made entirely of graphite-resin composites, a layer of acoustically dead fabric such as Kevlar® or Dacron® can be incorporated into the layers of graphite fiber weaves before curing. The resulting bulk density of the composite is 2-4 times that of wood; the composite is made thinner so that the areal density is approximately the same as wood. The soundboard, side and back are made separately, machined and joined. U.S. Pat. No. 5,333,527 discloses an acoustic guitar soundboard composed of compression molded, graphite-reinforced epoxy plastic. The soundboard can be provided with bracing ribs similar to a wooden soundboard in the molding process or afterwards; the sound quality is stated to be capable of being manipulated by forming the soundboard with various curved surfaces. U.S. Pat. No. 6,107,552 discloses a thin and light but strong soundboard fabricated of two outer layers of graphite reinforced sheet material sandwiched around a layer of low-density core material, such as rigid polyvinyl chloride.
A challenge of using synthetic composite materials is adapting the range of sound frequencies produced to be satisfactory to the ear. In some cases the goal is to simulate as closely as possible the sound of
Elliott Janet
Fuierer Marianne
Hsieh Shih-Yung
Hultquist Steven J.
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