Tuning apparatus for stringed musical instrument

A tuning apparatus for a stringed musical instrument includes a bridge base, a plurality of bridges, a plurality of anchor members of the same number as that of the bridges, and tuning bolts of the same number as that of the bridges or anchor members. The bridge base is fixed on a body. Each bridge is mounted on an upper surface of a front end portion of the bridge base and is movable along vertical and back-and-forth directions with respect to the body. Each bridge supports one end portion of a string at a top surface thereof. Each anchor member is mounted on an upper surface of a rear end portion of the bridge base and is movable along the back-and-forth direction. Each anchor member locks a bead coupled to one end of the string. Each tuning bolt is rotated to move the corresponding anchor member along the back-and-forth direction. The upper surface of the rear end portion of the bridge base is provided with a guide for guiding the corresponding anchor member, and the guide is inclined at the same angle as a holding angle at one end portion of the string.

BACKGROUND OF THE INVENTION 
The present invention relates to a simple tuning apparatus for a stringed 
musical instrument, wherein anchor members for tuning can be smoothly and 
easily moved and adjusted with a small operation force to improve 
operability. 
Various tuning apparatuses for stringed musical instruments such as guitars 
have been proposed. A typical example in which tuning operation is done at 
a tail side of the guitar is described in Japanese Patent Prepublication 
No. 59-15987. According to this tuning apparatus, a bead coupled at one 
end of a string is locked by an anchor member and the anchor member is 
moved back-and-forth by a tuning knob in a tuning block. In this case, 
since the bead is fitted in a recess formed in the anchor member to lock 
one end of the string, the string can be easily fitted to or replaced with 
a new one when it is broken. However, the bridges and the tuning block are 
separately provided, and the number of components is increased, resulting 
in cumbersome assembly. During assembly, the string is curved due to 
variations in components and positioning errors and the turning knob 
cannot be smoothly moved, resulting in inconvenience. A string portion 
between the bridge and the block is inclined at a proper angle (i.e., a 
holding angle) toward the body so as to define one end of the speaking 
length of the string, while the anchor member is substantially parallel to 
the surface of the body. Tension of the string exerts force on the anchor 
member so as to raise it up. As a result, knob movement becomes stiffer. 
SUMMARY OF THE INVENTION 
It is, therefore, a principal object of the present invention to provide a 
simple tuning apparatus for a stringed musical instrument, which has a 
small number of components and can be easily assembled. 
It is another object of the present invention to provide a tuning apparatus 
for a stringed musical instrument, wherein a tuning bolt can be operated 
with a small force. 
In order to achieve the above object of the present invention, there is 
provided a tuning apparatus for a stringed musical instrument, comprising: 
a bridge base fixed on a body; a bridge mounted on an upper surface of a 
front end portion of the bridge base and movable along vertical and 
back-and-forth directions, the bridge being arranged to support one end 
portion of a string at a top surface thereof; an anchor member mounted on 
an upper surface of a rear end portion of the bridge base and movable 
along the back-and-forth direction, the anchor member being arranged to 
lock a bead coupled to one end of the string; and a tuning bolt for moving 
the anchor member along the back-and-forth direction, the upper surface of 
the rear end portion of the bridge base being provided with a guide for 
guiding the anchor member, the guide being inclined at the same angle as a 
holding angle at one end portion of the string.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a plan view of a tuning apparatus for an electric guitar as a 
stringed musical instrument according to an embodiment of the present 
invention, FIG. 2 is a sectional view thereof taken along the line II--II 
of FIG. 1 together with a neck structure, and FIG. 3 is an enlarged 
sectional view showing the main part of the tuning apparatus of FIG. 1. 
Referring to FIGS. 1 to 3, a tuning apparatus 1 has a bridge base 4 fixed 
by a plurality of set screws 3 to a body 2. Bridges 6 and anchor members 8 
are mounted on the bridge base 4 in correspondence with strings 5 (5a to 
5d). Each bridge 6 supports one end of a corresponding one of the strings 
5 and each anchor member 8 locks a bead 7 fixed to one end of the 
corresponding string 5. This embodiment exemplifies a bass guitar with 
four strings. When the number of bridges 6 and anchor members 8 is 
increased, the present invention can be applied to a 6-string guitar. The 
other end of each string 5 is fixed through a nut 40 by a fixing mechanism 
43 at the distal end of a neck 41, as shown in FIG. 2. 
The bridge base 4 comprises a plate member. Front and rear walls 9 and 10 
are integrally formed at the front and rear ends of the bridge base 4, 
respectively. The front and rear walls 9 and 10 extend upward and 
constitute bolt mounting portions. Vertically elongated horizontal through 
holes 11 respectively corresponding to the bridges 6 are formed in the 
front wall 9. Similarly, tuning bolt through holes 12 respectively 
corresponding to the anchor members 8 are formed in the rear wall 10. A 
front 1/3 portion 4A of the bridge base 4 is thin and flat. A pair of 
right and left guide grooves 14 for each bridge 6 are formed on the flat 
portion of the bridge base 4, so that a total of eight guide grooves 14 
extend along the extension direction of the strings 5. The pair of right 
and left guide grooves 14 are parallel with each other and substantially 
symmetrical about the corresponding string. A remaining rear portion 4B of 
the bridge base 4 is inclined downward from the rear end of the front 
portion 4A and reaches the rear wall 10. The longitudinal section of the 
rear portion 4B constitutes substantially a right-angled triangle. The 
upper surface of the rear portion 4B constitutes an inclined surface 15 
whose extended surface crosses the upper surface of the body 2 at a proper 
angle .theta.. Guides 16 for the anchor members .theta. are integrally 
formed in the front portion of the inclined surface 15 as parallel to the 
surface 15, respectively. The guides 16 are also inclined with the same 
angle 8 as the inclined surface 15. The guide 16 guides the corresponding 
anchor member 8 along the back-and-forth direction. The guide 16 has a 
substantially T-shaped cross section as shown in FIG. 3 and extends along 
the extension direction of the string 5. Since a height difference 
.DELTA.H between the first or fourth string 5a or 5d and the second or 
third string 5b or 5c is present due to a curved central portion of a 
fingerboard 20 on the neck 41, the height of the guides 16 for the second 
and third strings 5b and 5c is different from that of the guides 16 for 
the first and fourth strings 5a and 5d. More specifically, a height H1 of 
the inner guides 16 for the second and third strings 5b and 5c is higher 
by the difference .DELTA.H than a height H0 of the end guides 16 for the 
first and fourth strings 5a and 5d (See FIG. 3). 
The bridge 6 is formed in a prism shape and is disposed on the front 
portion 4A of the bridge base 4. A substantially inverted V-shaped groove 
21 is formed in the upper surface of the bridge 6, so that a string seat 
projection 22 is formed at the top of the bridge 6. One end portion of the 
corresponding string 5 is supported by the top of the string seat 
projection 22. A pair of vertical screw holes 23 vertically extending 
through each bridge 6 are formed at two ends thereof. Height adjusting 
screws 24 are threadably engaged with the holes 23, respectively. The 
lower ends of the screws 24 are engaged in the corresponding pair of guide 
grooves 14 formed in the front portion 4A of the bridge base 4 and are 
urged downward by the string pressure. When the height adjusting screws 24 
are selectively rotated by a screwdriver or the like, the corresponding 
bridge 6 is vertically moved and the height of the string 5 is adjusted. 
The bridges 6 are coupled to the front walls 9 of the bridge base 4 
through corresponding pitch bolts 26. Each pitch bolt 26 is threadably 
engaged with a screw hole 25 of the corresponding bridge 6 through a bolt 
insertion hole 11 of the wall 9. When the bolt 26 is rotated, the bridge 6 
is moved in the back-and-forth direction to adjust the octave pitch of the 
corresponding string 5. During this operation, the height adjusting screws 
24 are moved along the corresponding guide grooves 14. 
The anchor members 8 extend along the longitudinal direction of the body. 
Holes 30 and notches 31 are formed in the upper surfaces of the front ends 
of the anchor members 8, respectively. Each hole 30 is a portion for 
locking the corresponding bead 7 coupled to one end of the corresponding 
string 5. Each notch 31 communicates with the corresponding hole 30 and 
extends forward therefrom. The width of each notch 31 is smaller than a 
diameter of the corresponding bead 7 but is slightly larger than a 
diameter (i.e., a diameter of an ornamental string portion 32) of an end 
portion of the string which is locked at the bead 7. The ornamental string 
is wound by the string 5 itself after the string is inserted in the 
corresponding bead 7. More particularly, the ornamental string portion 32 
is inserted in the corresponding notch 31 from the top to prevent rotation 
of the string 5 itself and removal of the bead 7. In this case, the bead 7 
is vertically inserted in the hole 30 and prevented from slipping out of 
the notch 31. 
Substantially T-shaped recesses 35 as shown in FIG. 3 are formed at the 
front lower portions of the anchor members 8, respectively. The guides 16 
are fitted in the recesses 35, respectively, so that the anchor members 8 
can be moved along the back-and-forth direction as guided by the guides 
16. Transverse and upward movement of the anchor members 8 is prevented by 
guiding by means of the guides 16 and the recesses 35. The anchor members 
8 are inclined at the same angle as that (.theta.) of the inclined surface 
15. In this case, the inclined angle .theta. of the inclined surface 15 is 
the same (.theta.=.theta.1) as an angle (i.e., an angle of about 7.degree. 
at which a string portion A between the string seat projection 22 and the 
bead 7 is inclined with respect to an effective vibration string portion) 
of the string portion A. 
The anchor members 8 are coupled to the rear wall 10 by tuning bolts 37. 
The tuning bolts 37 are respectively inserted in bolt insertion holes 12 
formed in the rear wall 10 and are threadably engaged with screw holes 38 
formed in the rear portions of the anchor members 8. The tuning bolts 8 
are integrally formed at the rear end portions with operation knobs 39, 
respectively. When each operation knob 39 is rotated by hand, the 
corresponding anchor member 8 is guided by the guide 16 and moved along 
the back-and-forth direction, thereby adjusting the tension force of the 
string 5. A central axis line of the tuning bolt 37 and the center axis of 
the string portion A of the corresponding string 5 are aligned in line by 
adjusting the height of the bridge 6. This construction is very important 
to prevent the anchor member 8 from receiving rotational force from the 
tension of the string 5. Since the inclined angle .theta. of the inclined 
guide 16 is substantially the same as that .theta.1 of the string 5, the 
inclined angle of the string 5 is not changed even if the corresponding 
anchor member 8 is moved in the back-and-forth direction. The anchor 
member 8 is thus free from the rotational force. An excessive force will 
not act on the anchor member 8, and the tuning bolt 37 will not locally 
contact the corresponding bolt through hole 12. As a result, the operation 
knob 39 can be smoothly rotated. 
The rear wall 10 is preferably formed to be perpendicular to the tuning 
bolts 37. 
In the above embodiment, the hole 30 is used as the locking portion of the 
bead 7. However, the locking portion is not limited to the hole. A 
projection for mounting the bead 7 may be used in place of the hole 30. In 
this case, the projection prevents rotational movement of the bead 7, so 
that the notch 31 can be omitted. 
In the above embodiment, the central portion of the upper surface of the 
fingerboard 20 is curved, as described with reference to FIG. 4. However, 
the upper surface of the fingerboard 20 may be flattened. In this case, 
the heights of the guides 16 are identical. 
In the tuning apparatus for a stringed musical instrument according to the 
present invention, bridges each supporting one end portion of each of the 
strings and anchor members each locking one of the beads of the strings 
are disposed on the bridge base. Unlike in the conventional tuning 
apparatus having separate bridges and the tuning block disposed anchor 
members, the number of components can be decreased, and the tuning block 
and bridges need not be separately positioned, thereby simplifying the 
assembly operation and preventing misalignment of the bridges with the 
tuning block and bending of the strings. 
The inclined surface of the anchor members of the bridge base has the same 
angle as the holding angle of the string. At the same time, the center 
axis of each tuning bolt for adjusting the corresponding anchor member is 
aligned with the center axis of the string portion bent at the holding 
angle. An excessive tension force will not act on the anchor members and 
tuning bolts, and thus the tuning bolts can be smoothly rotated, thereby 
facilitating tuning operation. Furthermore, since the anchor members are 
slidably fitted on the guides disposed on the inclined surface, undesired 
transverse and upward movement of the anchor members is prevented, thus 
providing many industrial advantages.