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BACKGROUND OF THE INVENTION
This invention relates generally to a musical instrument, and in particular
to an adjustable saddle for use with a stringed musical instrument such as
a guitar.
In a stringed musical instrument such as a guitar sound is produced by
causing one or more tightly stretched strings to vibrate, the frequency at
which the string vibrates, and thus the resultant sound output, being
dependent on a number of factors including string length, tension and
caliper (thickness). Variations in string caliper, tension and other
factors, in particular--the rod-like tendency of the string near its
contact points where little or no vibration is produced, make it desirable
that the vibrating string length be adjustable to give true intonation
wherein the instrument is tuned for producing properly pitched sounds when
played. While a number of devices are known for facilitating this
adjustment, none have proven altogether satisfactory, especially for
acoustic guitars.
Conventionally, one end of each string of a guitar is wound upon a shaft
associated with a tuning peg, the other end of the string being anchored
to a bridge. The bridge typically includes a saddle having a string
supporting surface fixing one end of the effective vibrating length of the
strings. The other end of the effective vibrating length of each string is
determined by the player when he manually engages or presses the strings
against the instrument frets or, when unengaged, by the location of a
string nut disposed near the guitar neck. In terms of adjusting the
instrument for proper intonation, it is the string length between the
saddle and the string nut which is critical and must be fixed for
compensating other string variables to produce a properly pitched
instrument.
Since the active length of a string may be determined at one end by either
the string nut or a fret, when tuning a guitar for proper intonation, the
saddle is normally used to effectuate the necessary string length
adjustment. Saddles for acoustic guitars conventionally comprise elongate
structures transversely disposed underlying the strings and having an
upstanding string supporting surface engaging the strings. Such saddles
are fixed in position in relation to the guitar sound board and thus
afford essentially no intonation adjustment capabilities although
sometimes slight adjustments are made by filing off small sections of the
saddle. Various saddles have also been developed, particularly for use
with solid body electric guitars, which comprise rather complex mechanical
structures including longitudinally movable string supporting elements
operated by adjustment screws or the like. These structures, however, are
relatively complex and expensive and, due to their excessive mass,
normally not suitable for use with acoustic guitars.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a new and
improved intonation adjustment mechanism for use with a stringed musical
instrument.
More particularly, it is an object of the invention to provide an improved
saddle mechanism operable for adjusting the effective vibrating length of
a musical instrument string without adversely affecting the sound
reproducing characteristics of the instrument.
In accordance with these and other useful objects an adjustable saddle
mechanism constructed according to the present invention comprises a
generally cylindrically shaped body portion rotatably received within a
similarly shaped aperture disposed diametrically underlying a guitar
string. An integrally formed coaxial head portion extends from the body
portion upwardly beyond the aperture and carries a generally semi-circular
shaped string supporting surface engaging the guitar string for defining,
in association with the guitar string nut or an engaged fret, the
effective vibrating length of the string. The semi-circular string
supporting surface is characterized by an axes offset from the axes of the
head portion and a diameter smaller than the extent of the head portion.
As a result, a "camming" action is produced wherein the effective
vibrating string length is adjustable by rotating the saddle and causing
the guitar string to be engaged at different points along the string
supporting surface.
BRIEF DESCRIPTION OF THE DRAWINGS
An illustrative embodiment of the invention will now be described in
conjunction with the accompanying drawings, wherein:
FIG. 1 is a top plan view of a guitar in accordance with the invention;
FIG. 2 is an enlarged top plan view of the bridge of the guitar seen in
FIG. 1;
FIG. 3 is a sectional view taken along the lines 3--3 of FIG. 2;
FIG. 4 is a pan view, partly in graphical form, of a saddle showing various
exemplary saddle orientations illustrating the principle of the invention;
and
FIG. 5 is a view similar to FIG. 3 showing a modification of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The guitar of FIG. 1 includes a body 10 and a neck 12. Rotatably mounted at
the distal end of neck 12 are a plurality of conventional tuning pegs 14.
Each peg 14 has a shaft associated with it, around which is wrapped one
end of one of the guitar strings 16. The other ends of the strings 16 are
anchored to a bridge 18 by a plurality of conventional bridge pins 20.
A plurality of saddle members 22 support or engage each of the strings 16
just in front of the bridge pins 20 in order to fix one end of the
effective vibrating lengths of the strings. The other end of the effective
vibrating length of each string is determined in the conventional manner
by the player, when he manually forces the strings against the frets 24,
or leaves them open. In the latter instance, the effective vibrating
length of the open string is determined by the location of the string nut
26.
The intonation of the guitar strings 16, i.e. their pitch producing
characteristics, is dependent on a variety of factors. Strings differ in
quality, even those intended to produce the same notes, and portions of
the very same string may differ in quality, for instance may be of
non-uniform thickness longitudinally thereof. Also, there may be
irregularities in the construction of the body of the instrument as well
as variations due to aging and the like. These factors may affect the
individual strings in different ways. To compensate for these factors, the
intonation of the strings 16 is adjustable to a degree by turning tuning
pegs 14 which increases or decreases string tension, as is well
understood. This method of adjustment is, however, incapable of effecting
active string length variations often needed to correct the instrument's
intonation. The present invention provides a saddle member operable for
individually adjusting the effective vibrating length of each of the
strings 16 to a high degree of precision to enable proper intonation to be
realized.
In accordance with the preferred embodiment of the invention, bridge 18
(see FIG. 2) includes a plurality of saddle receiving apertures 30, each
aperture 30 being disposed just in front of a corresponding bridge pin
receiving aperture 21. Strings 16 are anchored between the bridge pins 20
received within apertures 21 and tuning pegs 14 such that they pass
centrally or diametrically over saddle receiving apertures 30. While, in
the illustrated embodiment, apertures 30 are formed in bridge 18, other
methods of forming the apertures are also contemplated as being within the
scope of the invention. Thus, for example, apertures 30 may be formed
directly in the body of a solid-body electric guitar or the like.
Each aperture 30 (see FIG. 3) is configured for snugly but rotatably
receiving the cylindrically shaped body portion 32 of an individual one of
the saddle members 22. Saddle members 22 each further includes a head
portion 34 extending coaxially from one end of body portion 32 beyond
aperture 30, head portion 34 being secured to body portion 32 such that
the two portions are rotatable together. It will be observed that due to
the coaxial relationship between aperture 30, body portion 32 and head
portion 34, the strings 16 will diametrically pass over head portions 34
of saddles 22 as well as apertures 30 when tensioned between bridge pins
20 and tuning pegs 14. This condition is shown in FIG. 2 wherein each of
the illustrated strings 16 is anchored by a bridge pin 20 received within
an aperture 21 so that it diametrically passes over a head portion 34 of
an associated saddle member 22 dividing it into two equal sections.
Each of the head portions 34 of saddles 22 carries an annular raised
section 36 defining a generally semi-circular shaped string supporting
surface 38. String supporting surface 38 surmounts raised section 36 such
that a string 16 passing thereover will only contact one point of the
string supporting surface 38 of a particular saddle member 22. In
addition, it will be noted that the axes of string supporting surface 38,
as well as the axes of raised section 36, is offset with respect to the
axes of head portion 34 and that the extent or diameter of raised section
36 is smaller than the diameter of head portion 34. This allows raised
section 36 to be seated on head portion 34 with only a small section 40 of
its outer periphery being in common with the peripheral edge 42 of head
portion 34. As will be explained in further detail, this "off-center cam"
configuration of saddle member 22 conveniently allows for infinite
adjustment of the effective vibrating length of strings 16 within the
dimensional limits of the string supporting surface 38.
The operation of the adjustable saddle members of the invention is most
readily understood with reference to FIGS. 2 and 4. Initially, each saddle
22 is inserted in an aperture 30 with a string 16 passing over the center
44 of saddle head portion 34. Each string 16 will therefore engage or rest
upon a point along string supporting surface 38 dependent upon the
rotational orientation of saddle 22. Thus, in FIG. 2, string 16a engages
string supporting surface 38 of its associated saddle 22 at point a,
string 16b at point b, and string 16c at point c. The effective vibrating
length of each of the strings, which is individually adjustable by
rotating its associated saddle member 22 as explained below, is therefore
defined by string nut 26 at one end or, alternatively, by an engaged fret
24, points a, b and c respectively at the other end.
Referring now specifically to FIG. 4, assume initially that saddle member
22 is disposed in orientation A where string 16 passes over the center 44
of head portion 34, engages string supporting surface 38 at point P1 and
is anchored to bridge 18 by bridge pin 20. It will be observed that this
orientation of saddle 22 most nearly corresponds to that associated with
string 16b illustrated in FIG. 2. The effective vibrating length of string
16 can now be viewed as consisting of two sections; namely, a first
section extending from string nut 26 to the center 44 of head portion 34
and a second section extending from center 44 to point P1 of the string
supporting surface 38. Thus, with reference to saddle rotational
orientation A, the effective vibrating length of string 16 consists of the
length of string between string nut 26 and center 44 of head portion 34
plus the length of string extending radially from center 44 to point P1 of
string supporting surface 38.
The tuning of the instrument by adjusting the effective vibrating string
length is accomplished by rotating saddle member 22 within its associated
aperture 30. Consider, for example, the effect of rotating saddle 22 in a
counterclockwise direction such that the saddle orientation changes from
that represented by A toward the orientation represented by B. It will be
observed that as saddle 22 is so rotated, the string 16 is shifted along
string supporting surface 38 from point P1 toward point P2. Due to the
off-center relationship between the string supporting surface 38 and the
center 44 of head portion 34, the length of string 16 between center 44
and string supporting surface 38 gradually and continuously increases in
response to the counterclockwise rotation of saddle 22. In particular,
during the rotation of saddle 22 from orientation A to orientation B, it
will be noted that the length of string 16 from center 44 to string
supporting surface 38 increases by an amount substantially equivalent to a
segment 50 of a radius drawn through center 44. Since the length of string
16 between string nut 26 and center 44 remains constant regardless of the
orientation of saddle 22, it will be seen that the overall effective
vibrating length of the string increases as saddle 22 is rotated in a
counterclockwise direction.
A similar effect is achieved when saddle member 22 is rotated in a
clockwise direction except that the change in string length is in a
decreasing direction. Thus, consider the effect of rotating saddle 22 in a
clockwise direction from orientation A to orientation C. This causes the
engagement point of string 16 with the string supporting surface 38 to be
shifted from point P1 toward point P3 which, as explained before,
continuously decreases the effective vibrating length of the string. In
particular, rotation of saddle 22 from orientation A to orientation C will
have reduced the overall vibrating length of string 16 by an amount
equivalent to the difference in length between string segments 54 and
segment 50.
In view of the foregoing, it will be appreciated that the effective
vibrating length of each string 16 is infinitely controllable within the
dimensional limits of string supporting surface 38 by rotation of the
saddle member. Thus, when rotated to an orientation wherein string 16
engages string supporting surface 38 at a point near the end 60 of raised
section 36, the effective vibrating length of the string is at a minimum.
On the other hand, when string 16 engages string supporting surface 38 at
a point near end 62 of raised section 36 the effective vibrating length of
the string is maximized. When string 16 engages string supporting surface
38 at any intermediate point, the effective vibrating length of the string
is adjusted to a corresponding length between its minimum and maximum
lengths.
The saddles illustrated in FIGS. 2 and 4 are shown in orientations such
that the strings coming from the tuning pegs 14 initially pass over the
center 44 of head portion 34 and then over string supporting surface 38 on
their way to bridge pins 20. The saddles may be individually adjusted by
180.degree. of rotation to effect string length changes while maintaining
this relationship. Defining the distance from string nut 26 to center 44
as L and the distance between center 44 and the points on string
supporting surfacd 38 at ends 60 and 63 of raised section 36 as X and Y,
the vibrating string length may therefore be adjusted between the limits
defined by the values for L+X and L+Y. A further degree of adjustment may
be achieved by orienting the saddles such that the strings coming from the
tuning pegs are caused to initially pass over string supporting surface 38
prior to passing over the center 44 of head portion 34. This condition is
illustrated in FIG. 2 by strings 16d and 16e. It will be noted that
180.degree. of rotation of saddle 22 under these circumstances allow for
the adjustment of the effective vibrating length of the strings between
the limits defined by the values for L-X and L-Y.
Although the extent or degree of vibrating string length adjustment
described above may be sufficient in certain cases, it may also be
desirable to extend the range of adjustment by providing other saddles
having interchangeable body portions but with differently configured
string supporting surfaces. Thus, saddles could be provided having
cylindrical body portions receivable within apertures 30 and carrying
elongate string supporting surfaces disposed across the saddle head
portion. Depending upon the position of the straight string supporting
surfaces, the effective vibrating length of string 16 would be adjustable
to nearly the entire diameter of the saddle head. Also, if desired, the
saddle receiving apertures 30 could be angled relative to bridge 18.
Referring to FIG. 5, the saddles 22 and apertures 30 can be formed having
cooperating external and internal threads 70 and 72 respectively. Each
saddle 22 may thereby be conveniently raised and lowered within its
aperture 30 for adjusting the height or action of the associated string 16
by suitably rotating the saddle. By rotating the saddles in multiples of
360.degree., the height adjustment may be effected without disturbing the
previously established string length adjustments.
The entire saddle 22 can be constructed of plastic, aluminum, brass or
other suitable hard material. In addition, head 34 may be of a hexagonal
shape to facilitate rotation or adjustment by a wrench or other suitable
tool under strained pressure.
While particular embodiments of the present invention have been shown and
described, it will be apparent that changes and modifications may be made
therein without departing from the invention in its broader aspects. The
aim of the appended claims, therefore, is to cover all such changes and
modifications as fall within the true spirit and scope of the invention.
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