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Claims  |
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We claim:
1. A bridge assembly for a stringed musical instrument, the instrument
including a body, a neck extending from said body, and one or more
strings, each of which extends over said body and said neck, and each of
which is stretched between two anchor points, said bridge assembly being
located between said anchor points, said bridge assembly comprising:
a base having a bottom surface for attachment to a surface of said
instrument;
saddle means against which said one or more strings are held; and
means attached to said base for holding said strings against said saddle
means by changing the direction of said strings as said strings pass said
saddle, each of said strings having a first point of contact and a last
point of contact with said bridge assembly, said string being the same
vertical distance from said bottom surface of said base at said first
point of contact and said last point of contact.
2. A bridge assembly as recited in claim 1 wherein said saddle means
comprises one or more first vertical surfaces extending from said base,
and said means for holding said strings against said saddle means
comprises one or more second vertical surfaces extending from said base,
said second vertical surfaces being offset from said first vertical
surfaces with respect to the lines between said anchor points whereby said
strings are held against said saddle means and change direction as said
strings pass said saddle means.
3. A bridge assembly as recited in claim 2 wherein said vertical surfaces
are the surfaces of pins extending from said base.
4. A bridge assembly as recited in claim 1, wherein said saddle means
comprises a member extending from said base, and wherein said means for
holding said strings comprises a plurality of slots defined in said
member, said slots being at an angle with respect to the lines between
said anchor points.
5. A bridge assembly as recited in claim 1 wherein said saddle means
comprises:
a first surface parallel to said bottom surface of said base, said first
surface being located on lines between said anchor points of said strings;
and
a second surface parallel to said bottom surface of said base, spaced from
said first surface and at the same distance from the bottom of said base
as said first surface,
wherein said means for holding said strings against said saddle comprises:
means attached to said base and located between said first and second
surfaces for pressing said strings onto said first and second surfaces.
6. A bridge assembly as recited in claim 5 wherein said means for pressing
said strings onto said first and second surfaces comprises a surface of an
aperture in a member attached to said base and located between said first
and second surfaces, said member comprising an intermediate hold down.
7. A bridge assembly as recited in claim 1 wherein said means for holding
said strings against said saddle comprises a member attached to said base
and spaced from said saddle, said member having one or more apertures
therein, said strings passing through said apertures, a first surface of
each of said apertures supporting a string at a distance from the bottom
surface of said base the same as said string is supported from the bottom
surface of said base by said saddle, and a second surface of said aperture
supporting said string closer to the bottom surface of said base than said
string is supported by said saddle.
8. A stringed musical instrument comprising:
an instrument body, said body having a top;
a neck extending from said body;
a bridge attached to said top of said body; and
a plurality of strings stretched over said body and said neck, said strings
being anchored at one end to said body and at a second end to an end of
said neck remote from said body, each individual string engaging said
bridge at at least two contact points, said string applying a force to
said bridge at said contact points so that intimate contact is maintained
therebetween, wherein the forces applied by said strings are resisted and
carried by said bridge, and are not transferred to said top of said body.
9. The musical instrument of claim 8, wherein said forces applied to said
bridge are vertical forces.
10. The musical instrument of claim 8 wherein said forces applied to said
bridge are lateral forces.
11. The musical instrument of claim 8 wherein for every force applied to
said bridge by said strings, there is an equal and opposite force applied
by said strings, the forces applied thereby being balanced so that there
is no net force applied to said bridge and no pressure applied by said
bridge to said top of said body.
12. The stringed musical instrument of claim 8 wherein said bridge
comprises:
a base, said base having a lower surface attached to said body top; and
a saddle extending from said base, wherein at least one of said at least
two contact points is defined on said saddle.
13. The musical instrument of claim 12 wherein the vertical distance
between each individual string and said lower surface of said base does
not vary as said string passes over said base.
14. The musical instrument of claim 13 wherein said saddle comprises a
plurality of saddle pins extending from said base, said bridge further
comprising a plurality of pressure pins extending from said base, one each
of said plurality of pressure pins corresponding to one each of said
plurality of saddle pins and being laterally offset therefrom, said at
least two contact points comprising:
a first contact point between said string and said saddle pin and a second
contact point between said string and said corresponding pressure pin.
15. The musical instrument of claim 13 wherein said saddle comprises a
member extending from said base, said member having a plurality of
openings defined therein, and wherein one each of said plurality of
strings passes through one each of said plurality of openings, said at
least two contact points being defined by said opening.
16. The musical instrument of claim 15, wherein said openings comprise
angled slots defined in said member extending from said base.
17. The musical instrument of claim 15, wherein said openings comprise
holes defined in said member, said holes being vertically in line with the
undeflected string path of the strings passing therethrough.
18. The musical instrument of claim 12, wherein said at least two contact
points comprise a first contact point, an intermediate contact point and a
last contact point, said first contact point and said last contact point
being spaced vertically upward an equal distance from said lower surface
of said base, said intermediate contact point being spaced vertically
upward from said lower surface of said base a distance less than said
distance from said lower surface of said base to said first and last
contact points, said first and last contact points being the same vertical
distance from the lower surface of said base as the undeflected string
path.
19. The musical instrument of claim 18 wherein said saddle further
comprises:
a front saddle extending from said base, said front saddle having a saddle
top, said first contact points being defined on said front saddle top;
a rear saddle extending from said base, said rear saddle having a saddle
top, said last contact points being defined on said rear saddle top; and
an intermediate hold down projecting from said base between said front and
rear saddles, said intermediate contact points being defined by a
plurality of apertures in said intermediate hold down, said intermediate
hold down having one each of said apertures for each string, said
apertures being positioned below said saddle tops, wherein said strings
pass through said apertures and said apertures press said strings onto
said saddle tops. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
In order to illustrate the principles of the present invention, it is
described herein in connection with an acoustic guitar, but it will be
understood that the principles disclosed are applicable to other stringed
acoustic instruments as, for example, mandolins etc.
The modern acoustic guitar has been in use for many years, relatively
unchanged. Even though the traditional design of guitars is generally
satisfactory, there are several deficiencies which persist uncorrected.
One of these is that the guitar top requires substantial bracing to resist
the downward and lateral forces resulting from string tension acting on
the top of the bridge and on the tailpiece. (Note, as convenient
nomenclature, the terms "downward" and "vertical" are used to denote a
direction normal to the surface of the guitar top, and "lateral" is used
to denote a direction parallel to the top surface.)
Another deficiency in conventional prior art guitars is the lack of
intonation and action adjustments. It is often desirable to make changes
in these parameters after manufacture of the instrument is completed, but
this is not possible in prior art instruments.
One object of the present invention, therefore, is to provide a "stress
free" bridge system which does not have the downward and lateral forces on
the instrument top due to string tension.
Another object of the present invention is to provide convenient intonation
and action adjustments for a stringed musical instrument.
SUMMARY OF THE INVENTION
In order to achieve intimate contact between the strings of an acoustic
guitar and the bridge, the top of the bridge in prior art guitars is not
placed in line with the front and rear string anchors, but rather, is
raised somewhat. The strings therefore press down on the bridge achieving
the desired intimate contact. However, the bridge then presses down on the
guitar top, resulting in an undesired force on the top, which must be
resisted by bracing. In addition, the rear anchor for the strings on most
guitars is fastened to the guitar top itself, which results in an
undesired lateral force on the top. Means are provided in the present
invention for avoiding such lateral forces.
In the present invention, outside of the bridge assembly itself, the
strings extend in a straight line (at least in the vertical direction)
between the front and rear string anchors. With this construction, there
is no resultant force pressing the bridge assembly to the guitar top. The
desired intimate contact between the strings and the bridge is achieved in
the same manner as in the prior art, i.e., by causing the strings to
change direction at the point of connection between the strings and the
bridge saddle. However, the forces created by this change in direction of
the strings are resisted within the bridge assembly itself instead of
being resisted by the top of the guitar as in the prior art. The change in
direction of the strings can be either vertical (perpendicular to the top
surface of the guitar), lateral (parallel to the top surface of the
guitar), or in any arbitrary direction. Whatever is the path of the
strings through the bridge assembly, the point of exit of the strings from
the rear of the bridge assembly is made to be the same distance from the
bottom surface of the bridge assembly as is the point of entry of the
strings at the front of the bridge assembly. In those embodiments where
the strings exit the bridge assembly at a different horizontal position
(which would result in a lateral force or couple on the instrument top),
it is preferred that the strings be paired, the lateral forces or couples
resulting from the strings in each pair cancelling each other.
Action, by which is meant the distance between the strings and the
fingerboard of the guitar, is adjusted by tilting the neck of the guitar
with respect to the guitar body. In the presently preferred embodiment of
the invention, a neck which extends through the body and terminates near
the tail of the guitar is used, and the neck is tilted about an axis near
the front of the guitar where the neck joins the body. The adjustment is
accomplished by inserting an appropriate shim between the neck extension
and a fixed block at the tail. Intonation changes, changes which result
from changes in the lengths of the strings, may be made by adjusting the
amount the neck projects from the instrument, using a set screw bearing
against the end of the neck extension at the tail of the guitar.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectioned side view of a guitar embodying the principles
of the present invention showing, in particular, a neck construction
including intonation and action adjustments. Only a portion of the neck is
shown, and the portion shown is partially sectioned and broken to more
clearly show the construction of the instrument.
FIG. 2 is a fragmented side sectional view of a guitar according to the
present invention showing an adjustable height tailpiece
FIG. 3 is a fragmented section taken at 3--3 of FIG. 2.
FIG. 4 is a fragmented section taken at 4--4 of FIG. 2.
FIGS. 5, 6, 6A, 7 and 8 are perspective views of five different embodiments
of a bridge assembly for the guitar of FIGS. 1-4. FIGS. 7 and 8 are
sectioned for clarity.
DETAILED DESCRIPTION OF THE INVENTION
The general constructional details of a guitar embodying the principles of
the present invention can be seen by reference to FIG. 1, where a cross
sectional side view of a guitar embodying such principles is illustrated.
The body of the guitar shown in FIG. 1 can be seen to have a bottom 10, a
heel block 11, a tail block 12, and a top 13. A neck 14, which extends out
of the front of the guitar, is shown broken, the unseen portion to the
right of the break being of conventional construction, i.e., including
means for anchoring the front ends of the strings and for adjusting their
tensions. A fingerboard 15 is located on the top surface of the neck. One
embodiment of a "stress free" bridge assembly 16 is shown mounted on the
top 13 ahead of the rear string anchor (tailpiece 17). The strings 18 are
stretched between the head (located at the remote end of the neck) and
tailpiece 17. A fret which is located at the head (the "nut", not shown),
and the bridge assembly, define the free length of the strings, i.e., the
vibrating portion. Intimate contact between the strings and their end
supports (the nut, and/or the frets along the fingerboard, and the bridge
assembly) is essential to assure fixed free lengths and consistent end
conditions for the vibrating strings.
Constructional details of five embodiments of the invented bridge assembly
are shown in FIGS. 5-8. The invented bridge assembly provides the desired
fixed free length and consistent end conditions without putting stress on
the guitar top. In each of these figures, for clarity and convenience,
only two strings are shown. Guitars normally have six strings, of course,
but illustrating two strings is believed adequate to convey the principles
involved in the invention.
In FIG. 5, a bridge assembly is shown having a base 51 which is intended to
be glued or otherwise attached to the guitar top. The strings 18 (18-1 and
18-2 being shown) stretch between the nut and the tailpiece, and pass
around pins 52 (the saddle pin) and 53 (the pressure pin). As can be seen,
pins 52 and 53 are not set in line with the path of the strings, but are
offset such that the strings partially bend around the pins. Also, the
pins are set such that the string 18-1 bends in the opposite direction as
compared to string 18-2. This is done so as to balance out at least most
of the horizontal forces and couples created by the bends. In a guitar
having six strings, three would bend in one direction, and the other three
in the other direction. Since there is no vertical change in direction of
the strings through the bridge assembly, there is no vertical component of
force to be resisted. The location of the strings vertically on the pins
is in the straight line between the tailpiece and the nut. As shown, the
strings will naturally assume their position as described. If desired,
however, either pins 52 or 53, or both may be provided with a
circumferential groove in which the strings rest, and the pins threaded
into the base 51 so that groove height can be adjusted as appropriate.
A modification of this embodiment of the bridge assembly (not illustrated)
includes three pins in each set, two being in line with the undeflected
path of the string between the nut and the tailpiece, and the third
located between the first two, but offset so as to create a partial bend
of the string around all three pins. With this arrangement, there would be
no net force or couple which requires balancing.
FIG. 6 illustrates a second embodiment of a bridge assembly. The brige
assembly of this embodiment has a base 61 and a slotted saddle 62. The
strings 18-1 and 18-2 in this embodiment are shown passing through angled
slots 63-1 and 63-2. The slots are angled sufficiently that the strings
are in intimate contact with one side of the slot as they enter the
saddle, and the other side as they leave the saddle. Again, half of the
slots are angled in one direction, and half in the other direction,
balancing out substantially all of the horizontal forces and couples. If
preferred, the slots, instead of being straight, as illustrated, could
have a "vee" shape as they pass through the saddle 62. Such a construction
would avoid any horizontal force or couple. Another variation of this
embodiment involves the use of holes 64 instead of the slots 63. In this
variation, the holes are angled through the saddle in the same way as are
the slots illustrated in FIG. 6. The holes preferably pass through the
saddle horizontally, i.e., both ends of the holes are at the same height
above the bottom surface of the base 61, and are in line (vertically) with
the undeflected path of the strings.
In FIG. 7, a bridge assembly is shown with a base 71, a front saddle 72,
and a rear hold down 73. The strings pass over the top of the front saddle
and through holes 74-1 and 74-2 in the rear hold down. The holes 74 are
angled downward through the hold down 73 such that the bottom surface of
the holes at the rear of the rear hold down is the same distance from the
bottom of base 71 as is the top of front saddle 72, and the top surface of
the holes at the front of hold down 73 is below the top surface of saddle
72. The top surface of saddle 72 and the bottom surface of the hole 74 as
it emerges from the rear of hold down 73 should be substantially in line
with the undeflected path of the string between the nut and the tailpiece.
In this embodiment, there are no horizontal forces or couples to be
balanced out.
A final illustrative embodiment of the invented stress free bridge is shown
in FIG. 8. In this embodiment, a front saddle 82 and a rear saddle 83,
having the same height, project from base 81. As before, the saddle tops
should be in line with the undeflected string path between the nut and the
tailpiece. An intermediate hold down 84 projects from the base 81 between
the front and rear saddles. Holes 85 which deflect the strings downward
are formed in the hold down 84. Also slots 86 are provided to allow the
strings to be put in place without the necessity of threading them through
the holes 85. The top surface of holes 85 are below the line between the
tops of the front and rear saddles so that the strings are pressed down
onto the saddles.
Refer now back to FIG. 1 which illustrates the intonation and action
adjustments of the present invention. The neck 14, to which retaining
plate 20 is screwed, is fastened to the guitar body by bolt 19. The hole
in plate 20 through which bolt 19 passes is elongated in the direction of
the neck major axis, which allows the neck length to be varied as will be
explained below. The neck, instead of ending near its point of connection
with the front of the guitar as is conventional in the guitar art, extends
through the guitar, and is fastened to the tail block 12 by bolt 21. A
shim 22 is located between the tail block and the rear end of the neck 14,
allowing adjustment of the vertical location of the rear end of the neck
with respect to the guitar body. Varying the thickness of the shim 22
causes the neck to pivot about the front of the body where it is clamped
by bolt 19. Pivoting the neck in this manner changes the spacing between
the strings and the fingerboard 15, thereby providing an adjustment of the
action of the guitar.
The position of the neck 14 in a lengthwise direction can be adjusted by
screw 24. Turning screw 24 in (after loosening bolts 19 and 21) moves the
head away from the bridge, increasing the length of the strings and
thereby causing changes in intonation. A removable access plate 23
provides access to screw 24 and bolt 21 when adjustments are to be made.
In order to remove all stresses from the guitar top, not only should the
bridge assembly not exert forces on the top, but the rear string anchor
(tailpiece 17) should be mounted on something other than the guitar top.
As shown in FIG. 1, tailpiece 17 is mounted to tail block 12 under access
plate 23. The tailpiece is preferably made so that it can pivot vertically
at its point of connection with the tail of the guitar (at 17'). With this
construction, a plane including the pivot line 17' and the top of the nut
will include the strings (except for the portions of the strings within
the bridge).
FIGS. 2-4 illustrate a second tailpiece construction which, for the most
part, is contained within the body of the guitar, and which has the added
advantage of being adjustable in height. The tails of the strings 18 are
anchored in tail anchor block 31, which is attached to an anchor strut 32.
Anchor strut 32 projects through an opening in the guitar top, and is held
by two tension screws 33-1 and 33-2, which, in turn are held to heel block
35 by nuts 34-1 and 34-2. The strut 32 preferably has the form of a "U"
channel, but could have other constructions, if desired. The couple
arising from the tension in the strings 18 and the resisting force of
tension screws 33 results in a force which is resisted by set screw
36.which, in turn, bears against cross member 32-1 of strut 32. The
tension screws 33 are made small enough in diameter, and are attached
solidly to the strut 32, so that when set screw 36 is adjusted, the
tension screws 33 bend, rather than the joint between them and strut 33
twisting. Hence, adjusting set screw 36 in or out will cause the height of
tail anchor 31, and consequently the heights of the string tails, to vary.
Screws 37, which are threaded into cross piece 32-1 are used to tighten
the strut 32 against set screw 36 after the adjustment, and thereby secure
the assembly.
For reasons of clarity, no neck extension is shown in FIGS. 2-4. If an
extended neck is used with the tailpiece construction of FIGS. 2-4, the
neck extension would most conveniently pass through an opening made in
strut 32.
What has been described is a novel stringed musical instrument including a
"stress free" bridge and intonation and action adjustments, among other
features. Various modifications and adaptations of the invention will no
doubt occur to persons skilled in the art, and these modifications and
adaptions are intended to be covered by the attached claims.
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Description |
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