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Having thus described the invention, what I desire to claim and secure by
Letters Patent is:
1. A tuning device for a stringed musical instrument comprising, in
combination:
a stringed musical instrument body having a set of strings extending
thereacross and including an anchor member having means to enable an end
of a string to be secured thereto;
means mounting the anchor member to the instrument body for movement to
vary tension of the string;
said anchor member being so constructed and arranged as to exhibit a strain
in a degree proportional to the tension of the string;
gage means on the anchor member for sensing the degree of strain of the
anchor member;
drive means for moving the anchor member selectively in a direction to
increase or decrease the tension of the string; and
control means operatively associated with the means for sensing for
operating the drive means in a direction and to an extent to vary the
tension in the string to that which will cause a predetermined amount of
strain on said anchor member.
2. A tuning device as set forth in claim 1 wherein said anchor member
comprises a lever member having finger means at one end for receiving said
end of the string.
3. A tuning device as set forth in claim 2 including base means forming a
fulcrum for the lever member with the other end of the lever member being
moved by said drive means to control string tension.
4. A tuning device as set forth in claim 1 wherein said drive means
includes motor means and gear means operated from said motor means and
having means for engaging said anchor member.
5. A tuning device as set forth in claim 4 wherein said gear means
comprises a first gear driven by said motor means and a second gear driven
by said first gear adapted to be controlled through a rotation of less
than 360.degree., said second gear having pin means for engaging with the
anchor member.
6. A tuning device as set forth in claim 5 wherein said first gear includes
a worm gear and said second gear includes a gear that has at least a
partial gear track, said pin means engaging with a hooked end of the
anchor member.
7. A tuning device as set forth in claim 1 wherein said strain gage means
is disposed fixed to a relatively elongated center portion of said anchor
member.
8. A tuning device as set forth in claim 1 wherein said control means
comprises a comparison means including means for establishing a fixed
signal corresponding to the desired tuned string tension, which fixed
signal is compared to the strain gage means signal.
9. A tuning device as set forth in claim 8 wherein said comparison means
comprises a bridge circuit with the strain gage means having elements
forming two branches of the bridge circuit and a fixed and variable
resistor forming the other two branches of the bridge circuit, the output
from said bridge being a signal of one of positive and negative polarity
coupled to said drive means.
10. A tuning device as set forth in claim 9 wherein said drive means
comprises at least a bi-directional motor, the signal from the bridge
circuit driving the motor in a direction dependent upon the polarity of
the bridge signal.
11. A tuning device as set forth in claim 10 including amplifier means
coupling between the bridge circuit and motor.
12. A tuning device as set forth in claim 1 including means for selectively
enabling the drive means including manually operated means.
13. A tuning device as set forth in claim 1 wherein the device is for
separately tuning a plurality of strings each having associated therewith
an anchor means, strain gage means, drive means and control means.
14. A tuning device for a stringed musical instrument comprising:
means for anchoring an end of a string, said anchor means being movable in
a manner to vary tension on the string;
means operatively associated with the anchor means for moving the anchor
means in a selected direction either to increase or decrease the tension
on the string;
means for sensing the tension on the string; and
control means for comparing the sensed tension of the string with that of a
predetermined tension, said control means being operatively associated
with the moving means to move the anchor means in a direction and to an
extent which will tension the string to a value corresponding to that
predetermined tension;
said means for sensing including switch means supported on said anchor
means and having at least two positions indicative of different stress
levels of the anchor means.
15. A tuning device as set forth in claim 14 wherein said means for sensing
senses strain of said anchor means which is in turn related to string
tension.
16. A tuning device as set forth in claim 14 wherein said control means
includes electrical null comparison means having said predetermined
tension represented by first manually controllable means for establishing
a first, desired tension, signal, and the actual string tension
represented by second means for establishing a second signal, compared
with the first signal.
17. A tuning device as set forth in claim 16 wherein said first and second
means define a bridge circuit the output of which has a signal of either
positive or negative polarity coupled to a bi-directional motor forming a
part of the moving means.
18. A tuning device as set forth in claim 14 wherein said switch means
comprises a pair of fixed contacts and means supporting the fixed contacts
in spaced relationship, and a deflectable contact and means supporting the
deflectable contact between the fixed contacts.
19. A tuning device as set forth in claim 18 including a tuning screw for
adjusting the position of the deflectable contact to a position
intermediate the two fixed contacts corresponding to a tuned position of
the associated string.
20. A tuning device as set forth in claim 18 wherein the control means
includes means responsive to one of a first signal corresponding to
closure of the deflectable contact with one of the fixed contacts to move
the anchor means in a first direction and a second signal corresponding to
closure of the deflectable contact with the other of the fixed contacts to
move the anchor means in an opposite direction.
21. A tuning device as set forth in claim 20 including indicator means for
displaying the first and second signals.
22. A tuning device as set forth in claim 19 including means for commonly
tuning all tuning screws associated with all strings in unison.
23. A tuning device as set forth in claim 22 wherein said means for
commonly tuning includes a slide member engageable with all tuning screws.
24. A tuning device as set forth in claim 14 including biasing means
operatively associated with the anchor means for compensating for tension
on the anchor means.
25. A tuning device as set forth in claim 24 wherein the means for moving
includes a motor disposed under an outer end of the anchor means.
26. A tuning device as set forth in claim 25 wherein the anchor means
comprises an elongated lever movable via the control means and having an
intermediate opening for receiving the biasing means.
27. A tuning device as set forth in claim 14 wherein the means for sensing
tension comprises pizzoelectric means.
28. A tuning device as set forth in claim 14 wherein the means for sensing
tension comprises capacitive sensing means.
29. A tuning device as set forth in claim 28 including a support means for
the capacitive sensing means whereby tension in the anchor means is a
function of the distance between capacitive plates forming the capacitive
sensing means.
30. A tuning device as set forth in claim 29 including circuit means
comprising tone generator means for driving the capacitive sensing means
and means responsive to the signal from the capacitive sensing means for
operating motor means bi-directionally as a function of the amplitude of
said signal.
31. A tuning device as set forth in claim 30 wherein the circuit means
further comprises rectifier means for providing a DC level corresponding
to capacitance and comparator means responsive to the DC level for
providing a motor control signal of one of two polarities.
32. A tuning device as set forth in claim 14 including logic circuit means
for providing opposite level signals corresponding to an open position of
the switch means and a closed position of the switch means.
33. A tuning device as set forth in claim 32 including a tune switch for
enabling the logic circuit means, said logic circuit means including logic
gate determination means.
34. A tuning device for a stringed musical instrument comprising:
means for anchoring an end of a string, said anchor means being movable in
a manner to vary tension on the string;
means operatively associated with the anchor means for moving the anchor
means in a selected direction either to increase or decrease the tension
on the string;
means for sensing the tension on the string; and
control means for comparing the sensed tension of the string with that of a
predetermined tension, said control means being operatively associated
with the moving means to move the anchor means in a direction and to an
extent which maintains the string at a constant frequency of vibration;
said anchor member comprising a somewhat elongated lever member having
front and back ends and an intermediate pivot,
said front end having means receiving the string and said back end having
means responsive to the moving means,
said lever member also having a bar portion the flexing of which is sensed,
said flexing occurring about the intermediate pivot.
35. A tuning device for a stringed musical instrument comprising:
an anchor member having means to enable an end of a string to be secured
thereto;
means mounting the anchor member for movement to vary tension of the
string;
said anchor member being so constructed and arranged as to exhibit a strain
in a degree proportional to the tension of the string;
strain sensing means associated with the anchor member for sensing the
degree of strain of the anchor member;
drive means for moving the anchor member selectively in a direction to
increase or decrease the tension of the string; and
control means operatively associated with the strain sensing means for
operating the drive means in a direction and to an extent to maintain the
string at a constant frequency of vibration;
said anchor member comprising a somewhat elongated lever member having
front and back ends and an intermediate pivot, said front end having means
receiving the string and said back end having means responsive to the
drive means;
said lever member having a bar portion the flexing of which is sensed, said
flexing occurring about the intermediate pivot.
36. A tuning device for a stringed musical instrument comprising:
an anchor member having means to enable an end of a string to be secured
thereto;
means mounting the anchor member for movement to vary tension of the
string;
said anchor member being so constructed and arranged as to exhibit a strain
in a degree proportional to the tension of the string;
strain sensing means associated with the anchor member for sensing the
degree of strain of the anchor member;
drive means for moving the anchor member selectively in a direction to
increase or decrease the tension of the string and
control means operatively associated with the strain sensing means for
operating the drive means in a direction and to an extent to maintain the
string at a constant frequency of vibration;
said anchor member comprising a lever member having finger means at one end
for receiving an end of the string;
base means forming a fulcrum for the lever member with the other end of the
lever member being moved by said drive means to control string tension.
37. A tuning device for a stringed musical instrument comprising:
an anchor member having means to enable an end of a string to be secured
thereto;
means mounting the anchor member for movement to vary tension of the
string;
said anchor member being so constructed and arranged as to exhibit a strain
in a degree proportional to the tension of the string;
strain sensing means associated with the anchor member for sensing the
degree of strain of the anchor member;
switch means supported on said anchor member and having at least two
positions indicative of different stress levels of the anchor means,
visual indicator means responsive to said switch means for providing at
least two separate visually distinguishable signals corresponding to a
sharpness and flatness of the associated string;
and means for manually adjusting the string tension in a direction to
increase or decrease the tension corresponding to the visually
distinguishable signal to retune the string.
38. A tuning device as set forth in claim 37 wherein said means for
manually adjusting is for adjusting the position of the anchor member to
adjust string tension.
39. A tuning device as set forth in claim 37 wherein the visually
distinguishable signals are of differing colors.
40. A tuning device as set forth in claim 37 wherein the visual indicator
means includes a pair of light indicators.
41. A method of adjusting the tuning of at least one string of a stringed
musical instrument, comprising the steps of; sensing a tension associated
with a string, providing a switching action in response to sensed tension
and providing a visual indication corresponding to two different tension
levels corresponding to sharpness and flatness of the associated string,
and manually adjusting the string tension in a direction to increase or
decrease the tension and in accordance with the visually distinguishable
tension levels for retuning the string.
42. A method as set forth in claim 41 wherein the switching action is
mechanical switching.
43. A tuning device for a stringed musical instrument comprising:
a stringed musical instrument body having a set of strings extending
thereacross and having associated therewith, string fastening means
including means for anchoring an end of each string, said anchor means
being movable in a manner to vary tension on the string;
means mounting the anchor means to the instrument body;
means operatively associated with the anchor means for moving the anchor
means in a selected direction either to increase or decrease the tension
on the string;
means for sensing the tension on the string; and
control means for comparing the sensed tension of the string with that of a
predetermined tension, said control means being operatively associated
with the moving means to move the anchor means in a direction and to an
extent which will tension the string to a value corresponding to that
predetermined tension. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to an automatic tuning device preferably for
use with a stringed musical instrument such as an electronic guitar. The
tuning device is operable periodically to provide immediate, simultaneous
and automatic retuning of the strings of the instrument. While the device
of this invention may be used in association with any string musical
instrument, it is particularly suited for use with instruments which are
apt to go out of tune quite easily, such an an electric guitar.
The invention is useful particularly by professional musicians in concert,
where it is not uncommon for some or all of the strings to go out of tune
a number of times during a performance. This condition may result from a
number of causes, for example, from excessive heat from stage lights or
simply from the stresses that are imparted to the strings during the
concert. Usually, the player must take a few awkward minutes, possibly
interrupting the uniform flow of the performance, in order to retune.
Accordingly, it is one object of the present invention to provide an
automatic tuning device for a stringed instrument such as an electric
guitar.
Another object of the present invention is to provide an automatic tuning
device that permits easy and immediate retuning of the instrument upon
demand.
Still another object of the invention is to provide an automatic,
instantaneous returning device which may be operated during a performance,
even during the performance of a piece, without significant interruption.
A further object of the present invention is to provide an automatic tuning
device for a stringed instrument which operates on the principle of
sensing the tension associated with each string, comparing the sensed
tension with a predetermined, preselected tension, and comparing the
sensed and predetermined tensions to make any necessary correction to the
actual string tension.
To accomplish the foregoing and other objects of this invention, there is
provided a tuning device preferably supported at the body of the
instrument adjacent the bridge and including individual means for
anchoring an end of each string of the instrument. The anchoring means is
movable in a manner to vary the tension on its associated string. Means
also are provided for sensing the tension associated with the string. Each
anchor means is associated with a drive means adapted to move the anchor
means in a selected direction, either to increase or decrease the tension
on the string. The tuning device also includes control means, preferably
in the form of an electrical bridge circuit, for providing a comparison
between the sensed tension of the string and a predetermined tension that
may be set to correspond with the tension that is desired in the string.
The control means is operatively associated with the drive means to cause
the drive means to move the anchor means in a direction and to an extent
which will tension the string to a value corresponding to the
predetermined desired tension.
In the disclosed embodiment, the control meas is operated periodically so
that the comparison and returning operation only occurs by way of manual
command from the player. The returning of all strings preferably occurs
with a single command when the player has determined that one or more of
the strings is out of tune.
In accordance with the preferred embodiment described herein, the anchor
means may be in a form of a pivotable lever having the string attached to
one end, the other end of the lever being movable by a drive means to
increase or decrease the tension in the string. The string tension is
sensed by a strain gage preferably attached to the lever member. In this
connection, the lever member preferably is at least partially flexible so
that the tension on the string is imparted to the lever member and thereby
sensed by the strain gage means. The control means comprises a bridge
circuit means which includes the strain gage windings as a part of the
bridge circuit.
In accordance with another embodiment of the present invention a
bi-directional sensing switch is provided instead of a strain gage
arrangement. This alternate embodiment includes a tuning adjust screw
associated with each string and common control means for the gage
adjustment of all tuning adjust screws. Still other version of the present
invention sense tensions by means of a peizoelectric transducer or
capacitive transducer.
DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages of the invention will be
appreciated more fully from the following further description thereof,
with reference to the accompanying drawings wherein:
FIG. 1 is a fragmentary top view of a portion of the body of a stringed
musical instrument depicting the device of this invention;
FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1 showing
the device in further detail;
FIG. 3 is a circuit schematic diagram showing the control circuitry in
accordance with the invention;
FIG. 4 is a fragmentary top view of a portion of a body of a stringed
musical instrument depicting another embodiment of the present invention;
FIG. 5 is a cross-sectional view taken along line 5--5 of a stringed
musical instrument depicting another embodiment of the present invention;
FIG. 6 is a circuit schematic diagram showing the control circuitry for the
embodiment of FIGS. 4 and 5;
FIG. 7 is a fragmentary top view of still another version of the present
invention;
FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 7 showing
further detail of this alternate version;
FIG. 9 is a fragmentary top view showing still another embodiment of the
present invention;
FIG. 10 is a fragmentary top view along line 10--10 of FIG. 9 showing
further detail of this embodiment employing peizoelectric sensing;
FIG. 11 is a cross-sectional view depicting still a further embodiment of
the present invention employing capacitive sensing;
FIG. 12 is a circuit diagram associated with the embodiment of FIG. 11;
FIG. 13 shows still a further embodiment of the present invention in a
cross-sectional view;
FIG. 14 is a logic diagram associated with the embodiment of FIG. 13;
FIG. 15 is a circuit schematic diagram showing the control circuitry for a
simplified version of the invention employing manual tuning with automatic
sensing; and
FIG. 16 is a fragmentary view showing the sensing switch and manual tuner.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 and 2 show the device as it might be mounted to the body 10 of an
electric guitar. In the drawings, only a portion of the body 10 of the
guitar is shown, it being understood that the instrument also has a neck
extending from the body and means on the neck for securing one end of each
of the strings. The device is secured to the guitar body 10 at a location
behind the bridge which is indicated generally by the reference character
12. The bridge preferably includes a plurality of low-friction rollers 14
which are grooved and which receive and support the strings 16. Each
string 16 is provided with an enlarged member, such as the ball 18, to
facilitate its attachment to the device, as will be described.
The device includes a base member 20 which is secured to the body 10 of the
guitar and which provides support for the other elements and components of
the device. The base member may be formed from a plate of sheet metal and
is formed to include a number of pairs of transversely spaced pivot lugs
22, 24 which extend upwardly from the base 20, at the forward end of the
base. The device is provided with one pair of such pivot lugs for each of
the strings of the instrument. Each of the lugs 22, 24 is formed to
include an opening 26. The openings 26 preferably are of a configuration
which tapers in a forward direction, defining a narrowed forward end 28
which serves as a bearing fulcrum surface, as described below.
Each pair of pivot lugs 22, 24 supports an anchor bar or lever, indicated
generally at 30, there being an anchor lever 30 associated with each of
the strings. In the illustrated embodiment, each of the levers 30 is
generally L-shaped, having a pair of upwardly extending fingers 32 at its
forward portion and a rearwardly extending main portion indicated at 34.
The strings 16 are attached to the upwardly extending forward portions of
the anchor bars 30 by inserting them between the fingers 32 so that the
restraining member such as the ball 18 is engaged as shown. Each of the
anchor bars 30 is pivotally mounted to a pair of pivot lugs 22, 24 by
means of a pair of transversely extending fingers 36, formed integrally
with each anchor bar 30. The fingers are dimensioned so that they will be
received in the openings 26 of the lugs 22, 24. The fingers 36 are formed
to include forward edges 38 which bear against the narrowed forward end 28
of the openings 26, thereby defining a transversely extending pivot axis
or fulcrum about which each of the anchor bars 30 may have independent
limited pivotal movement.
From the foregoing, it will be appreciated that the tension in each of the
strings 16, applied to its associated anchor bar 30, will tend to pivot
the anchor bar about the fulcrum 28, 38, tending to raise the rearwardly
extending main portion 34 of the anchor bar 30 (counterclockwise as seen
in FIG. 2). Means, described further below, are provided for engaging the
rearwardly extending portion 34 of the anchor bars 30 to balance and
resist the moment applied to the bars 30 by the tension of the strings 16.
Each of the anchor bars 30 is formed so that its main portion 34 is
comparatively long and will display a measurable amount of flexibility,
depending on the moment applied by the tension of the strings 16. The
degree of flexure of the anchor bar is proportional to the moment applied
by its associated string 16. Thus, the extent of flexure of the rearwardly
extending main portion 34 of the anchor bar 30 may be considered as being
a measure of the tension and, therefore, the pitch of the string 16. Means
are provided to sense the flexure of the main portion 34, including a
strain gage package 42 which is attached to each of the main portions 34,
preferably to their undersides as indicated in FIG. 2. The strain gage
package 42 will detect and provide an output signal corresponding to the
magnitude of the flexure of the anchor bar portion 34. The output from the
strain gage package 42 is used to control operation of a motor and gear
arrangement which is employed to pivot the anchor bar so that the string
16 will be tensioned properly as described herein.
Each of the anchor bars 30 is maintained in its position by an arrangement
which includes the rearwardly extending portion 34 of the anchor bar 30
which is maintained in engagement with a pin 46 which, in turn, extends
transversely from a segmented gear 48. The gear 48, in turn, is supported
by means of a shaft 50 and bearing members from the base member 20. The
gear 48 is driven by a worm gear 54 which, in turn, is driven by a motor
56, supported from a motor support 58. The arrangement of the bar 30, pin
46, gear 48, worm gear 54 and motor 56 insures that when the motor is not
operating (which is usually the case), the anchor lever 30 will be
maintained in a fixed position, resisting the moment applied by the
strings, and will maintain the strings 16 in tune. It will be appreciated
that the tension of the strings 16 continually biases the rearwardly
extending portion 34 of the anchor bar 30 into continuous engagement with
the pin 46.
The motors 56 may be operated upon demand by the user, in a direction which
will drive the segmented gears 48 in either direction as indicated by the
arrows in FIG. 2. Thus, motors 56 may be employed either to increase the
tension or decrease the tension on their strings 16, thereby varyng their
pitch. To this end, the motors 56 preferably are of the conventional high
speed DC reversible variety, which are commercially available from a
number of sources.
Thus, the angular pivot attitude of the anchor bar 30 about the fulcrum 28,
38 is controlled by operating the motor 56 to rotate the gear 48 and the
pin 46 between its range of positions. It is noted that the gears 48 are
segmented and do not rotate through 360.degree.. Rather, they rotate
through an angle of approximately 120.degree., to limit the extent to
which the anchor lever 30 may be pivoted. As shown in FIG. 2, rotation of
the gear in a counterclockwise direction causes the bar 30 to pivot
clockwise, thus increasing the tension and pitch of the string.
Conversely, rotation of the gear 48 in a clockwise direction causes the
bar 30 to pivot counterclockwise, decreasing the tension and pitch of the
string 16.
As shown in FIG. 1, each strain gage package 42 includes strain gage
resistance elements 60, 62, which are also shown, schematically in FIG. 3.
It will be appreciated that when the motor 56 is operated to increase the
pitch of the string 16, there will be an increase in the flexure of the
anchor lever 30 with a correspondingly modified output signal from its
associated strain gage package 42. Conversely, if the motor 56 is operated
to decrease the string pitch, there is a corresponding decrease in the
flexure of the portion 34 of the lever 30 which results in a
correspondingly opposite output signal from the strain gage package 42.
The strain gage package 42 may be selected from any one of a variety of
commercially available packages which typically include strain gage
resistance elements 60, 62. These elements are provided in a package and
are usually adhered to the member to be measured in a perpendicular
configuration as suggested in FIG. 1. The strain gage elements are shown
in their physical position in FIGS. 1 and 2 but are shown in FIG. 3 as
being connected in a bridge circuit which is of a common Wheatstone bridge
configuration. As shown in FIG. 3, the other legs of the bridge include a
fixed value resistor 64 and a variable resistor 66 which is adjustable to
correspond to the proper intended pitch for the particular string. The
variable resistor may be in the form of a simple potentiometer having a
control knob which may be mounted at any suitable location on the body of
the instrument. There are, of course, a plurality of such potentiometers
and control knobs as well as a corresponding plurality of motors 56 and
associated gear mechanisms associated with each string of the instrument.
FIG. 3 is a schematic circuit diagram of a preferred form of control
circuit for each string. As previously indicated, this control circuit
includes a bridge circuit comprised of the strain gage resistive elements
60, 62 and the fixed resistor 64 and variable resistor 66. The two
resistors 64, 66 are selected to be compatible with the resistive elements
60 and 62. The bridge circuit, as well as the operational amplifier 70 are
powered by a battery B which couples by way of the "tune" switch 72 to the
input of the bridge circuit. The output from the bridge circuit couples to
the input of the operation amplifier which also receives operating voltage
from the battery B, either directly or by way of the tune switch 72. The
output from the operational amplifier couples to the DC motor 56. The
switch 72 is a momentary switch which preferably operates all bridge
circuits in a ganged fashion and may be mounted to the instrument at any
convenient location.
In operation, the instrument is tuned initially in its usual manner, by
tuning pegs or the like. It is not necessary that the tuning be precise.
Final tuning is effected by operating switch 72 to close the bridge
circuit and by adjusting each of the variable resistances 66. Thus, for
each string, its associated control knob 66 is rotated thereby providing
either a positive or negative control signal to the operational amplifier
depending upon the value of the variable resistor. The DC motor 56 thus is
operated to either increase or decrease the tension on the string 16 until
a null condition is reached corresponding to the intended pitch of that
string. At that point, the variable resistor is maintained in a fixed
position corresponding to the proper tension of the string 16. The same
procedure is used with the other strings until all of the strings have
been tuned.
It, after a period of time, the tension in the string 16 either increases
or decreases, then the switch 72 can later be momentarily closed to retune
the strings. Switch 72 is a momentary switch that is normally open thus
providing no signals to the operational amplifier and DC motor 56. When
the player decides that retuning is necessary, the momentary switch 72 is
closed, thereby powering all bridge circuits and, in turn, operating the
associated DC motors where necessary. The DC motor 56 is preferably of the
type that operates quite rapidly which results in substantially immediate
retuning. Depending on whether there has been a relaxtation or an increase
in tension of the string 16 there will be either a positive or negative
voltage coupled to the operational amplifier and the output from this
amplifier will be of a polarity to rapidly drive the DC motor 56 in the
proper direction to change the tension in string 16 to again cause a
balanced condition in the bridge circuit. It should be noted that some,
but not necessarily all, of the strings may be out of tune. As to those
strings which are not out of tune, there is essentially no signal coupled
to the operational amplifier and the DC motor 56 operates in neither
direction, instead simply maintaining the tension in the string 16
imparted by the anchor bar 30. Although FIG. 3 shows control associated
with only one string, it is understood that the correct tension for each
string is set by setting the variable reference resistor in each bridge
circuit associated with individual strings.
FIGS. 4-14 depict other versions of the present invention all embodying the
basic principles described herein for providing immediate and automatic
retuning of the strings of a stringed musical instrument. In these further
versions of the invention, like reference characters will be used as
previously assigned in the preferred embodiment of FIGS. 1--3.
FIGS. 4-6 show one alternate version of the present invention employing a
bi-directional switching element for controlling an associated drive
motor. The device of this invention is secured to the guitar body 10 in a
manner and at a position as previously described in FIGS. 1 and 2. The
string 16 extend over the bridge and each string is provided with an
enlarged member, such as the ball 18, which facilitates the strings'
attachment to the device. The device includes a base member 20 which is
secured to the body 10 of the guitar in some suitable manner. The member
20 provides support for the other elements and components of the device.
The base member 20 may be formed from a plate of sheet metal and has a
turned end 21 as clearly depicted in FIG. 5. The end 21 effectively forms
a fulcrum point and may accommodate wings or lugs 35 on the lever 30 in an
manner similar to the arrangement previously described in connection with
FIGS. 1 and 2.
Each of the levers 30 is generally L-shaped having a pair of upwardly
extending fingers 32 at its forward end for receiving the string 16 and a
rearwardly extending main portion 34.
Each of the anchor bars or levers 30 is controlled by virtue of the portion
34 which is maintained in engagement with a pin 46 which, in turn, extends
transversely from a segmented gear 48. The gear 48 is supported by means
of a shaft 50 and bearing members from a base member 20. The gear 48 is
driven by a worm gear 54 which is driven by a motor 56 supported from a
motor support 58.
A contact lead 76 has one end fixed to the top surface of lever 34 and has
another end that is free supporting contact 78. The contact 78 along with
contacts 80 and 82 are preferably gold plated contacts. The contacts 80
and 82 are supported on facing ends of the U-shaped contact support 84.
The screw 86 is an adjustment screw for the separation of the contacts 80
and 82. FIG. 5 shows leads extending from each of the contacts 78, 80 and
82. Reference is also made hereinafter to FIG. 6 which depicts the contact
arrangement.
The device also includes a tuning adjustment screw 88 which is received by
an internally threaded insert 90 supported in the contact lead 76. The
member 84 and the lever 34 are preferably of a heavy gage steel whereas
the contact lead 76 is of a relatively thin gage steel. In FIG. 5 the
contact lead 76 is shown in its intermediate position with its associated
contact 78 disposed intermediate the contact 80 and 82 but contacting
neither of these contacts. This is the proper position of the contact lead
when the associated string is properly tuned. In this regard, the guitar
or other instrument may be initially tuned in a conventional manner, then
the on-off switch 94 is turned on followed by an initial adjustment by
means of the adjusting screw 80 until the center contact 78 is not
touching either of the other contacts 80 or 82. This tuning operation is
performed for each and all of the strings. Preferably, a flexible seal 99
is provided around the contacts as depicted in FIG. 5.
FIG. 6 shows a schematic diagram depicting the circuitry for controlling
the motor 56. In FIG. 6 only two stages are shown including two
bi-directional switches 100. Each of these bi-directional switches is
shown schematically as including the contacts 78, 80, 82. The contacts 80
and 82 receive respective positive and negative voltage levels by way of
the on-off switch 94. The movable contact 78 may be in an intermediate
position between the contacts 80 and 82 or may couple signals from either
one of these contacts but of course not from both contacts at the same
time. The movable contact 78 fixed to the contact lead 76 couples to an
input of the DC amplifier 102. Power to each of the amplifiers 102 is
coupled from the positive and negative voltage terminals by way of the
tune switch 104. In the open position of the tune switch 104, power is not
coupled to any one of the amplifiers 102 and thus in that position there
is no possibility of a control signal from the output of the amplifier to
the DC motor 56. The signal line 105 that couples to the input of the
amplifier 102 also has a connection by way of resistor R to the payer of
light emitting diodes L1 and L2. The diode L1 may illuminate a red
condition while the diode L2 illuminates a green condition. These diodes
will be illuminated under proper conditions even when the switch 104 is
open. The red or green indication at the light emitting diodes indicates
that the string is sharp or flat respectively. When either of these
conditions is indicated, then the tune switch 104 may be closed with
either a positive or negative signal being coupled to the DC amplifier
with the output of the amplifier then driving the DC motor 56 in the
appropriate direction. Thus, for example, if the contacts 78 and 80 are
closed, then the LED L2 is illuminated and there is a positive output
voltage level from the amplifier 102 causing the motor 56 to operate in
the opposite direction causing a tightening of the string. If the movable
contact 78 is in the position shown in FIG. 6 then upon closure of the
tune switch 104 there is no output signal from the amplifier 102 to drive
the DC motor in either direction.
To initially set up the device of this invention the guitar is tuned in a
conventional manner. Once this has been accomplished, then the individual
tuning screws 88 are operated so as to center the contact lead 76 thus
extinguishing any of the indicators that may be illuminated. Then, at a
later time, if any one of the indicators becomes illuminated to indicate
either a loosening or tightening of a string the tune button 104 may be
closed to provide automatic retuning of that string by operation of the DC
motor 56 in the appropriate direction.
The embodiment shown in FIGS. 4 and 5 is also provided with another feature
which provides for the ganged tuning of all tuning screws 88 so as to tune
all strings to either a slightly higher or slightly lower than normally
tuned pitch. This feature is embodied in the form of a shroud 107 having a
lower leg supported from the base member 20. This shroud extends over all
of the tuning screws but leaving an edge of each tuning screw accessible
through an opening in the shroud 107. The shroud 107 includes a plate 108
which may be integral with the shroud and which supports a slide member
110. The slide member 110 is of elongated shape as depicted in FIG. 4
having a toothed surface 112 adapted to engage with an outer toothed
periphery of the head 114 of the tuning screw 88. In the position shown in
FIG. 4 the tab 116 of the slide member 108 is at its intermediate position
with the slide member 110 essentially out of contact with the tuning
screws. The tab 116 may then be moved into the slide channel in the shroud
into engagement with all of the tuning screws whereby the slide member 110
may be moved in either direction for rotating all of the tuning screws in
unison either clockwise or counterclockwise depending upon whether the
operator wishes to increase or decrease the pitch of all strings in
unison.
FIGS. 7 and 8 show another embodiment of the present invention using much
of the identical structure shown in FIGS. 4 and 5. The device depicted in
the embodiment of FIGS. 7 and 8 includes a base member 20 from which is
supported the lever member 30. The string 16 is supported in the same way
as previously indicated by means of the fingers 32. In the embodiment of
FIGS. 7 and 8 the lever member 30 is somewhat longer being provided with
an opening 120 for receiving one end of an auxilliary biasing spring 122.
The other end of spring 122 is securely fixed to the member 20. The
bi-directional | | |
