Music – Instruments – Stringed
Reexamination Certificate
2000-01-27
2001-07-10
Nappi, Robert E. (Department: 2837)
Music
Instruments
Stringed
C084S267000
Reexamination Certificate
active
06259008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to truss rods for stringed instruments such as guitars and mandolins, and more specifically to an improved double-action truss rod enabling true two-way adjustment.
2. Description of the Prior Art
A truss rod (also known as an internal stiffener) may be installed into a channel in the neck of a stringed instrument to counteract forward warp or bow caused, e.g., by string tension. Prior art truss rods typically utilize parallel segments of square bar and round bar, welded together at one end, and fitted with a threaded nut on the other end of the round bar adjacent a fixed block on the other end of the square bar so that turning of the nut causes the relative length of one side of the truss to shorten, thereby bending the truss and therefore the neck of the instrument. However, in this structural arrangement, the truss rod bends in one direction only, thereby limiting the possible adjustments that can be made to the neck of the instrument.
SUMMARY OF THE INVENTION
The double-action truss rod for stringed instruments of this invention provides an improved truss rod for selectively bowing the neck of a stringed instrument. The inventive truss rod includes a segment of round stock having a pair of threaded ends, one set of threads in a first thread direction, and the other set of threads in the reverse thread direction. Complementary threaded blocks are threaded onto these threaded ends, and the blocks are welded or otherwise secured to a length of flat or square bar stock. A head bearing a socket is fixed to an end of the round stock, so that turning of the head turns the round stock. The reversed nature of the respective threaded ends causes the length of the portion of the round stock between the fixed blocks to either increase or decrease when the round stock is turned, which correspondingly causes the flat bar to bend either in or out.
The double-action truss rod of this invention thus provides an adjustable truss rod fabricated from metal inside the neck shaft of a stringed instrument. A small amount of give inside the instrument's neckshaft results in better playability with an adjustable truss rod that can be tightened and loosened to adjust and control the neck's response to string tension.
By incorporation of the right-hand threads on one end of the threaded rod, and left-hand threads on the other end, turning of the Allen socket causes the rod to either shorten or lengthen relative to the flat bar, thereby selectively bowing the bar (and thus the neck of the instrument) either inward or outward.
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patent: 5465642 (1995-11-01), Goto
patent: 5965830 (1999-10-01), Carlson
patent: 5973242 (1999-10-01), Spezia
Eddinger Darlene F.
Eddinger Steven W.
Johnson Larry D.
Johnson & Stainbrook LLP
Lockett Kim
Nappi Robert E.
Stainbrook Craig M.
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