Stringed musical instrument

A light weight guitar neck construction and associated method of manufacture involves the use of a wood core with a strengthening layer, preferably of carbon fiber, and a finish layer, preferably a fiberglass sheet, both impregnated with a high temperature resin. A tensioning wire is provided in the neck, and is non-braided with a diameter of less than 0.100 inches.

FIELD OF THE INVENTION 
The present invention relates to a stringed musical instrument, and in 
particular to instrument components such as a neck for a guitar. 
BACKGROUND OF THE INVENTION 
Although attempts have been made to construct light-weight musical 
instruments, particularly guitars, these efforts have not been totally 
successful in constructing guitars of weights on the order of 5 pounds or 
less. Fabrication techniques have tended to be complex, time consuming, 
and in some instances cost prohibitive. U.S. Pat. Nos. 5,125,312 and 
5,189,235, which are assigned to the same assignee as the present 
invention, discuss light-weight musical instruments, and are hereby 
incorporated by reference. The neck of a guitar can add considerable 
weight to the instrument, so it would be desirable to make the neck 
lighter, while still producing a high quality instrument. 
SUMMARY OF THE INVENTION 
The present invention features a method of fabricating a light-weight 
component, such as a neck, for a musical instrument, and an instrument 
component, such as a neck. The instrument is fabricated with a solid wood 
core, preferably a light-weight soft wood. Disposed over the neck core is 
a strengthening layer and a finish layer which are preferably formed as a 
laminate to the outer surface of the core. The strengthening layer may be 
provided by one or more thin layers of carbon fiber while the finish layer 
preferably includes a thin layer of a fiberglass sheet. A high temperature 
resin material is preferably employed in the laminate, and heat is applied 
to cure the layers. Heat may be applied while subjecting the neck to a 
vacuum by disposing the neck in a vacuum bag. 
In accordance with another aspect of the invention, a light-weight neck has 
a wood core and a laminate including a strengthening layer and an outer 
finish layer. The strengthening layer preferably includes a layer of 
carbon fiber, and the finish layer preferably includes a thin layer of 
fiberglass sheet. The neck has a channel for holding a non-braided 
tensioning wire with a diameter of no more than about 0.100 inches, and 
preferably about 0.060 to 0.078 inches. This wire is substantially thinner 
and lighter than braided cables and rods that have previously been used. 
The wire has anti-rotation end pieces which are preferably swaged onto one 
end of the wire. The other end is accessible to a user with a tool for 
adjusting the tension. 
In another aspect, the invention features a resilient spring for providing 
an electrical connection, such as a ground path, between a cap that is on 
one side of a piezoelectric element and a conducting member that is on the 
other side of the element. The spring is preferably a corrugated strip of 
beryllium copper that is arranged in an annular region around the cap and 
the conductive member.

DETAILED DESCRIPTION 
Referring to FIG. 1, a guitar constructed in accordance with the present 
invention has a body 10 and a neck 12, which supports a fret board 14. 
Strings 16 are supported at the neck and at the body. At the neck, the 
strings may be supported in a conventional fashion with adjusting pegs 18. 
Strings 16 are supported at the body end at a bridge mechanism 20. 
In FIGS. 1-3, bridge mechanism 20 is illustrated as a tremelo bridge, 
however, the bridge mechanism may also be a fixed bridge type. Bridge 
mechanism 20 is partially received in a cavity 11 in the instrument body. 
For further details of parts of the bridge mechanism, refer to Fishman, 
U.S. Pat. No. 4,911,057, issued Mar. 27, 1990. 
The bridge mechanism 20 includes a holder 24, which in a fixed bridged 
construction would be held in a fixed position, although one might be 
adjustable. The bridge mechanism 20 also supports a circuit board 26 
supported in the cavity 11. As shown in FIG. 3, a lead wire 28 connects a 
piezoelectric transducer to circuit board 26. A jack 29 and a cable 30 are 
connected to an electronic device 32, which may an amplifier or 
synthesizer. Inside the guitar, circuit board 26 may have lines coupling 
to jack 29 so that signals from the piezoelectric crystals are coupled by 
cable 30 to device 32. 
FIGS. 2-6 illustrate transducer assembly 34 secured in holder 24. 
Transducer assembly 34 includes a thin piezoelectric disk 36, a cap member 
38, a metallic member 40, and a dielectric member 42. The facing surfaces 
of the cap member and metallic support member have recesses such as the 
recess 41 (FIG. 5). These recesses partially accommodate piezoelectric 
disk 36. Metallic support member 40 has a terminal post 44 that is adapted 
to pass through hole 45 in dielectric base member 42. As shown in FIG. 4, 
terminal post 44 extends downwardly below the bottom surface of dielectric 
base member 42. A lead wire is soldered to the bottom end of terminal post 
44. Cap member 38 is of generally domed construction. Within the domed cap 
member a recess 47 is contiguous with a slot 48. Musical string 16, as 
shown in FIG. 3, is disposed in slot 48. 
To secure the piezoelectric crystal 36 in place between the cap member 38 
and the support member 40, a conductive adhesive layer 34 may be applied. 
This electrical layer couples the oppositely disposed upper and lower 
electrodes of the piezoelectric crystal to the respective cap member and 
metallic support member. Cap member 38 is electrically coupled by way of 
string 16 to other metallic parts of the guitar which may be considered as 
functioning as a ground. Non-conductive dielectric bonding 43 is provided 
to secure metallic support member 40 and dielectric member 42 as well 
dielectric member 42 and holder 24. A dielectric potting compound 49 is 
disposed about the transducer assembly. 
In the transducer assembly, cap member 38 is preferably constructed of a 
hard metal material such as of stainless steel. The piezoelectric disk is 
of a piezoelectric crystal material. The metallic support member may be 
constructed of a softer metal material, such as brass. The adhesive 
materials may be epoxy adhesives, either conductive or non-conductive as 
previously described. 
In one prior transducer construction, such as that illustrated in U.S. Pat. 
No. 4,774,867, the piezoelectric disk is bonded essentially only on one 
surface to increase output voltage. For this application, it is preferred 
to have the crystal bonded on both upper and lower faces with conductive 
epoxy 39. Bonding on both surfaces provides a more accurate output signal 
and better representative of the true mechanical string vibration. By 
essentially clamping both sides of the crystal a lower output voltage is 
provided. This means that the crystal is less sensitive to the compressive 
mode but is more sensitive to the rotational shear mode. This clamping 
better replicates the true mechanical string vibration. The hardness of 
potting compound 49 is instrumental and can be controlled so as to provide 
an accurate replication of the desired string vibration signal. Potting 
compound 49, in particular allows one to tune the shear mode, thus 
controlling the level of lateral clamping. The amount of clamping relates 
to the durometer hardness of the potting compound that is employed. 
The piezoelectric type of transducer of the present invention is an 
improvement over previously used magnetic transducers. These magnetic 
transducers, inter alia, are generally more cumbersome and require the use 
of ferrous strings. The piezoelectric transducer is more readily tunable 
and is constructed to desensitize the compressional mode. As such, the 
transducer is constructed to be less responsive to mechanical vibrations, 
such as those from the instrument body. 
With a piezoelectric transducer of this type, one can electronically add 
resonance to replicate a magnetic transducer. In this way a wide variety 
of sounds can be provided with piezoelectric transducers. Also, the 
piezoelectric type of transducer does not have To be used with ferrous 
strings but can be used with any type of string material. 
As shown in FIG. 4, if a string breaks, the ground path is interrupted. As 
this may be of concern, an embodiment of the invention such as that 
illustrated in FIG. 6 may then be employed. The transducer assembly has 
cap member 38, metallic support member 40, dielectric member 42, and 
piezoelectric disk 36, which are mounted in substantially the same way as 
described in connection with FIG. 4. A conductive epoxy adhesive is used 
for securing the piezoelectric disk. Between the top surface of the 
piezoelectric disk and cap member 38, conductive leaf 50 extends 
outwardly. Leads 51A and 51B are solder connected respectively to leaf 50 
and to terminal post 44. In an alternate arrangement, in place of the 
solder-connections illustrated in FIG. 6, a push on connector may be 
provided in place of the solder thus simplifying construction. With the 
arrangement of FIG. 6, should string 16 break, there is still an 
electrical connection to ground by way of lead 51A. 
An alternative arrangement to that shown in FIGS. 3 and 4 is shown in FIGS. 
35 and 36. A spring 200 that is preferably made from a strip of beryllium 
copper is provided around cap member 38 and provides an electrical path 
between cap member 38 and metallic member 40. The spring is preferably 
arranged in a corrugated manner to provide a conductive path while still 
being resilient to provide more accurate vibration detection. A compound 
149, similar to compound 49 in the embodiment of FIGS. 2 and 3, may be 
provided in the space along with the spring 200. As an alternative to the 
corrugated copper spring, stainless steel wool can be used since it too is 
conductive and also resilient. Since the wool is made from stainless 
steel, it does not rust like typical steel wool. 
FIGS. 7-12 illustrate details relating to the construction of the guitar 
invention. A body 52, a neck 53 and arms 54 have a basic wood core. Body 
52 and arms 54 may be cut from about 11/2 inch thick redwood material, 
while the neck 53 is preferably cut from about 1 inch Douglas fir or bass 
wood. The arms may be separate pieces, or body 52 and arms 54 may be 
integrally formed from a single integral block of wood. 
The wood core materials are preferably soft wood materials which are 
lighter in weight and are more well balanced tonally than hard woods that 
are typically used. Such woods are also less expensive, easier to cut and 
shape, and dimensionally stable than a hard wood core. With a soft wood 
core, rigidity and strength are provided with a laminate construction 
according to the present invention, in combination with a stiffening or 
tensioning cable. 
Referring to FIG. 9, a metal cable or rod, such as a stainless steel cable 
56, is received in an elongated recess 57 extending along the neck and 
into the body. A pair of anti-rotation pieces 58 are connected at each end 
of cable 56. A nut 59 is used to tighten and control the tension applied 
by cable 56. Filler pieces 60 are disposed over the cable and over the 
anti-rotation pieces to fill recess 57. 
As an alternative to cable 56, a non-braided, thin metal wire having a 
dimension of about 0.060" to about 0.078" can be used. An example is 
described in connection with FIG. 34 below. This smaller wire reduces the 
weight relative to the use of a thicker, braided cable. Furthermore, the 
non-braided cable is easier to swage. 
The cable may alternatively be secured from the opposite side, such as from 
the front side of the guitar, in which case the recess would be provided 
in the front surface. 
As indicated, the cable 56 is preferably installed and adjusted from the 
back of the instrument to provide a clean appearance from the front. The 
cable can be positioned very close to the back surface of the instrument 
where it has the most mechanical advantage. The cable adjusts in a place 
that is convenient in that there is no need to loosen strings or otherwise 
disturb the instrument to provide this adjustment. Also, since the cable 
is flexible, adjustment may be made nearly anywhere on the instrument, 
including at the neck end of the cable or at the body end. 
Referring to FIG. 10, after the body of the guitar has been contoured to 
the desired configuration, the neck is secured by gluing to the body, 
preferably using a high temperature epoxy. The glue joints may be angled 
to facilitate the shaping of the guitar without excess waste of material. 
In preparing the instrument for the lamination process, a support caul 63 
is provided. The stiff caul screws to the fingerboard surface and extends 
to the body of the instrument. The laminate includes multiple layers 62 of 
unidirectional carbon fiber are impregnated with a high temperature epoxy 
resin, and a fiberglass cloth layer 64. Layer 64 is preferably applied 
with a 45.degree. bias as illustrated at 65. The 45.degree. bias cut 
enables the fiberglass to better conform to the curves of the core. Layer 
64 covers the back of both the body and the neck and can also covers the 
sides and front of the body as well. The fiberglass cloth is also 
impregnated with a high temperature epoxy resin. Each of these layers may 
be about 0.010 inch thick. The fiberglass cloth layer is bias cut and may 
have a thickness of about 0.003 inch. 
Caul 63 supports the neck and headstock in their correct alignment and 
insures good playability. The caul, which is first treated with a mold 
release, silicone material, provides a place for the extra laminating 
material to go and prevents the undesirable condition of excess laminating 
material being bonded to the fingerboard surface. 
After layers 62 and 64 have been impregnated, they are pressed onto the 
instrument and the laminate is then ready for curing. The guitar is 
disposed in a vacuum bag 67 (FIG. 11) and placed in an oven 66. The vacuum 
bag provides clamping pressure for the lamination. The curing occurs at a 
temperature of about 250.degree. F. for two hours. 
After the instrument is cured, the caul is removed and excess material is 
knifed off. The laminated edges are smoothed. The headstock and 
fingerboard surfaces are prepared. In this regard, FIG. 12 shows the 
instrument after being cured. Sharp edges may be radiused by sanding. 
Excess material such as illustrated at 69 in FIG. 12 may be trimmed off. 
Referring to FIGS. 13 and 14, the cross sectional views are taken at an 
intermediate step in the fabrication of the guitar. In both FIGS. 13 and 
14, caul 63 is still shown affixed to the wood core. FIGS. 13 and 14 also 
show tension cable 56, the filler piece 60, carbon fiber layer 62 
feathered at the edges, and fiberglass layer 64. These same layers are 
also illustrated in FIG. 14. FIG. 14 also illustrates the excess laminate 
being trimmed at 69. 
Reference is now made to FIGS. 15-18 for further details in the 
construction of the instrument fingerboard. In this regard, FIG. 15 shows 
a basic form 70 that is used to provide the proper contour for the 
fingerboard. On the top surface of the form 70, a release material, such 
as a gel, is preferably provided to enable the laminate components to be 
separated from the form. On top of the form, a uni-directional carbon 
fiber layer 72, and a bias cut fiberglass sheet 74 are provided. Both 
layer 72 and sheet 74 may be impregnated with a high temperature resin. 
The combination of the carbon fiber and the fiberglass on the form is 
subjected to high temperature in an oven. The arrangement illustrated in 
FIG. 11 with the use of a vacuum bag may be employed for heating and 
curing to form laminate 75 as illustrated in FIG. 16. 
FIG. 16 shows laminate 75 after having been formed by heating and after 
having also been trimmed to the proper size for a particular instrument. 
On the top surface of laminate 75, a mask is employed and the laminate is 
sandblasted using a mask to form roughened strips 77. These strips are 
disposed at positions corresponding to positions where the frets are to be 
secured. Frets 78 are cut to a proper length and partially curved to 
substantially match the curvature of laminate 75. The underside surface of 
the frets is also preferably sandblasted. The frets may be cut from a 
length of stainless steel material of cross-section as shown, for example, 
in FIG. 23. After sandblasting both the frets and the laminate, epoxy 
adhesive is applied to enable the frets to be secured onto the laminate. 
Thus, the frets are made of extremely hard wire, preferably stainless 
steel, in a construction that is tangless. 
As shown in FIG. 17, a fixture 80 has several locating pins 82 disposed at 
opposite ends of the fixture 80 for positioning the laminate board 
longitudinally. Locating pins 82 also locate frets 78. Rubber bands 84 
hold frets 78 securely against the laminate 75. With the laminate and 
frets in the position illustrated in FIG. 17, the assembly is baked. FIG. 
18 shows the final fret board including the laminate with the individual 
frets attached after the ends of the frets are cut and finishing work is 
done. 
Reference is now made to FIGS. 19-23 for further details of the fingerboard 
construction. FIG. 22 in particular shows a prior art tanged fret 
construction. FIG. 22 shows a conventional fret 85 having a tang 87. These 
individual frets are constructed of a relatively soft material and are 
hammered into a slot in the fret board. After the fret has been inserted 
into the fret board it must then be reformed. The formation of a fret 
board in this manner is quite time consuming and costly. Because a 
relatively soft metal is employed, the fret board has to be reworked in 
the future. On the other hand, according the present invention, the frets 
are of a hard metal. Rather than inserting these frets into a slot in the 
fret board, they are adhesively secured to the surface of the fret board. 
The fret construction of the present invention requires little or no 
reworking after the frets are applied. 
FIG. 19 is a perspective view showing the fingerboard attached to the 
guitar neck. The fingerboard may be secured to the instrument neck using, 
for example, a thin film adhesive. This may be provided in a relatively 
thin film on the order of 0.002 inch thick. Films of this type are 
preferred over the use of an applied liquid because the films are 
dimensionally stable and provide an accurate adhesive layer. One thin film 
adhesive that has been employed is a thermal plastic film adhesive that 
can be applied and provides sealing by application of heat. Also, one can 
employ an unsupported acrylic film adhesive. This does not require the 
application of heat. The adhesive that uses the application of heat may be 
preferred in that this will make it easier to remove and replace the 
fingerboard, simply by the application of heat. 
Frets 23 may be bonded to the fret board laminate itself using instead a 
methylacrylate. Layer 88 for securing fret 78 to the laminate (FIG. 23). 
FIG. 23 also shows a thin film adhesive 90 for bonding the fingerboard 
structure to the guitar neck. 
To secure the frets on the fingerboard, a material such as methylacrylate 
is particularly advantageous. Since it is an anarobic adhesive in which 
the cross-linking occurs in the absence of oxygen, only the concealed 
adhesive will harden and adhesive that is exposed to oxygen will not 
harden. This means that it will be easier to remove excess adhesive. 
Reference is now made to FIG. 25 which is a longitudinal cross-sectional 
view taking along line 24--24 of FIG. 19. In FIG. 24, tensioning cable 56, 
which may be a stainless steel cable, is adapted to flex around any 
corners or curves. The ends of the cable are supported by anti-rotation 
devices 58. There is also a tension adjusting nut accessible from the hole 
91. A portion of the fingerboard 75 is shown with the frets 78. The top 
surface 92 can be painted or may also be coated with at least fiberglass 
and perhaps also the carbon fiber. With the use of at least fiberglass 
coat there is a harder surface provided. FIG. 24 also shows the use of 
several wood filler strips 60. The underside surface is shown with its 
carbon fiber layer 62 and fiberglass layer 64. A heavy primer may be used 
to fill the rough surface of the fiberglass and then the instrument may be 
painted. 
Referring to FIGS. 25-27, in an alternate embodiment of the invention, 
circuit runs are provided individually from each fret. When a fret is 
engaged with a finger such as that shown in FIG. 26, the conductivity 
between the string and the fret can be sensed by one of the circuit runs. 
Such a signal can be coupled by way of cable 30 to electronic device 32. 
In this way, one can electronically sense the particular fret that is 
being engaged when in fact the string causes conductivity with the 
particular fret. 
FIG. 25 shows the series of frets 78, as well as strings 16 and circuit 
runs 94. As illustrated in FIG. 26, a conductive epoxy dab 95 completes 
the electrical conductivity from fret 78 to circuit run 94. 
In the embodiment of the invention illustrated in FIGS. 25-27, on top of 
the wood core there is directly provided a printed circuit board including 
dielectric substrate 96 which carries the circuit runs 94. An adhesive 97 
secures the printed circuit board substrate. FIG. 27 also shows circuit 
run 94 as well as conductive epoxy dab 95. A non-conductive epoxy layer 78 
is employed over the substrate to isolate the circuit runs. Also, there is 
an epoxy layer 99 or alternatively a methylacrylate adhesive is provided 
to secure the frets. 
FIGS. 29-34 illustrate a method for making an instrument component, with a 
guitar neck shown as an example of one such component. A light-weight 
guitar neck 100 includes a wood core 153 which may be a soft wood, a 
flexible wire 180, filler pieces 160, and one or more layers 162 of 
unidirectional carbon fiber, each of which may be about 0.010 inch thick. 
The layers of carbon fiber, two of which are illustrated, are impregnated 
with a high temperature epoxy resin. A pre-impregnated (prepreg) material 
can also be used. To prepare the neck for lamination, a stiff support caul 
163 is provided to support the neck and the headstock in selected 
alignment, to provide a place for the extra laminating material to go, and 
to prevent excess laminating material from being bonded to the finger 
board surface. The caul is first treated with a silicone mold release 
material. 
A fiberglass cloth layer 164 is applied over the carbon fiber layers 162 
with a 45.degree. bias, as illustrated at 165, to enable the fiberglass to 
conform to the curves of the neck. Layer 164 is about 0.003 inches thick 
and is preferably impregnated with a high temperature epoxy resin. 
After carbon fiber layers 162 and fiberglass layer 164 are impregnated with 
resin, they are pressed onto the neck core for curing. Referring to FIG. 
30, the neck is placed in a vacuum bag 167 to provide clamping pressure 
for the lamination. The curing occurs in an oven 166 at a temperature of 
about 250.degree. F. for about two hours. 
After the neck is cured, the caul is removed, excess material is removed 
with a knife, and the laminated edges are smoothed. The headstock and 
fingerboard surfaces are then prepared. Sharp edges may be radiused by 
sanding, and excess material is trimmed. 
The light-weight neck may be secured to the body by a variety of methods, 
one of which is shown in FIGS. 31-34. Referring to FIG. 31, a series of 
threaded inserts 100 are disposed in core 153 at an end 102 of the neck. 
Referring to FIG. 32, fingerboard 175 with attached frets 178 is shown 
just prior to attachment of the fingerboard to the neck core 153. 
Referring to FIG. 33, a half-lap joint 104 is constructed to join a planar 
surface of the guitar body and a planar surface at end 102 of light-weight 
neck core 153. A number of machine screws 106 are fed into screw holes the 
back of the guitar body and engage the threaded inserts in the neck. Other 
fitted joints, such as mortise and tenon joints can be constructed to 
engage respective surfaces of the guitar neck and guitar body. The neck 
and body may also be glued together. The fitted joints are typically used 
in conjunction with the glue. 
Referring to FIG. 34, since the neck is formed as a separate piece, a 
tension wire 180 is provided completely within the neck. Wire 180 is 
preferably about 0.060 inches to about 0.078 inches and is preferably 
non-braided music wire. At the body end of the neck, a washer 190 is 
pressed against the opening for the wire, and a cap 192 is swaged over the 
end of the wire. Unlike some cables, since the wire is not braided, it is 
easier to swage. At the headstock end, an internally threaded 
anti-rotation fitting 194 is swaged onto the end of the wire. A washer 
198, which is preferably made from metal, is placed over a screw 196 which 
is screwed into fitting 194. The tension adjusting screw is accessible 
through an opening 184 in the neck, and allows adjustment with an allen 
wrench, a screwdriver, a Torx wrench, or some other device that mates with 
screw head 182. Fitting 194 prevents rotation by having a rectangular 
shape and by being disposed in a slot that is also rectangular. 
Having now described a number of embodiments of the present invention, it 
should now be apparent to those skilled in the art that numerous other 
embodiments and modifications thereof are contemplated as falling within 
the scope of the present invention as defined by the appended claims.