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Description  |
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FIELD OF THE INVENTION
This invention relates to a method and an apparatus designed primarily for
carrying out a preliminary tuning of a keyboard musical instrument, that
is, a rough tuning thereof performed prior to a fine, regular tuning
thereof.
BACKGROUND OF THE INVENTION
A conventional method for a regular and a preliminary tuning of a keyboard
musical instrument comprises the following steps of:
(1) vibrate a string;
(2) judge a tonal pitch from sonic vibrations thereof; and
(3) based on the judgment made in step (2), turn a tuning pin to carry out
the tuning operation.
Usually, tuning of a string by this method is so performed that the
above-listed tuning steps (1)--(3) are repeated several times to complete
the tuning.
According to the aforementioned conventional method, in the case of a piano
equipped with 230 strings, for example, it is necessary to individually
tune each string, as a result of which much time and labor is required to
tune a piano. Furthermore, when tuning step (1) is to be performed for a
key which actuates a plurality of strings in unison, it is necessary to
apply pieces of rubber, felt or the like to other strings so as to prevent
those strings from generating sound by vibration when the key is stricken
for tuning of a string other than those strings. This makes the tuning
operation very complex. In addition, since a string-exciting mechanism is
required in order to carry out tuning step (1), the tuning should be
performed in such a condition that an action mechanism has been
incorporated therein. This limits the freedom of selecting the sequence of
tuning steps. In tuning step (2), it is a general practice that, for
comparison, the reference string is vibrated simultaneously with the
string to be tuned and a tune pitch thereof is judged from the frequency
of a beat tone so generated, so that a comparatively high expertness in
the art is required to perform this step. Accordingly, in actuality all
tuning operations are almost exclusively performed by professional tuning
experts.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the foregoing problems
inherent in the conventional method.
In order to achieve this object, the first aspect of the present invention
is characterized by such an arrangement that, while a load of a preset
value or a load so applied as to produce a predetermined value of
displacement is being applied to a string, a tuning pin is turned until a
value of displacement of the string so produced or a reaction force
generated by a tension of the string so produced corresponds to a preset
displacement value or a preset load value, which is predetermined to give
a required frequency of vibration. The second aspect of the present
invention is characterized in that it comprises a load-applying means
which applies a load of a predetermined value to a string set up in place
or which is so adapted to apply a load to a string set up in place as to
produce a predetermined value of displacement of the string, a calculation
means which calculates a deviation between displacement value of the
string shown when the load-applying means is applied to the string and a
preset value of displacement predetermined to give a required frequency of
vibration or a deviation between a reaction force generated by a tension
of the string produced when the load-applying means is applied to the
string and a preset value of load predetermined to give a required
frequency of vibration, and a rotating means which turns a tuning pin
until the deviation calculated by the calculation means is reduced to
zero.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating the operation of the present
invention;
FIG. 2 is a block diagram illustrating a preferred embodiment of the
present invention for carrying out one of the tuning methods disclosed
herein;
FIG. 3 is a perspective view showing a load/measurement member and a moving
mechanism in accordance with the preferred embodiment of the invention;
FIG. 4 is a perspective view of a tuning pin rotation member in accordance
with the preferred embodiment of the invention;
FIG. 5 is a block diagram illustrating the important portions of another
preferred embodiment of the present invention; and
FIG. 6 is a perspective view of a load/measurement member in accordance
with the embodiment depicted in FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In general, the frequency f of vibration of a stretched string is
calculated by the equation:
##EQU1##
where L is the length of the string, T is the tension of the string, and
.tau. is the linear density of the string (weight per unit length).
Further, as shown in FIG. 1, there is a correlation between a load F
applied to the location D at which string 1 is struck and a displacement H
of the string 1 when load F is applied at location D, this correlation
being expressed by the equation:
##EQU2##
where G is a correction factor due to rigidity or the like of the string.
Therefore, a tension T.sub.s at a preset frequency f.sub.s of the string 1
having a length L and a linear density can be calculated by equation (1),
while a displacement H of the string 1 having a tension T.sub.s and a load
F applied thereto can be calculated by equation (2).
According to this invention, while applying by a load member 2a
predetermined load F to the location D at which the string 1 is struck, a
tuning pin 4 attached by screws to a frame 3 is turned by means of a
tuning pin rotation member 5 until a displacement H of string 1 at
position D corresponds to a predetermined displacement value H.sub.s
calculated by equation (2) for a preset frequency f.sub.s, whereby tuning
of string 1 is performed.
Instead of applying a predetermined load F.sub.s at location D of string 1,
such a load f as to produce a predetermined displacement H.sub.s may be
applied thereto and, while so doing, the tuning pin 4 is turned by means
of the tuning pin rotation member 5 until a reaction force generated by a
tension of the string 1 at location D corresponds to a predetermined load
F.sub.s calculated by equation (2) for a preset frequency f.sub.s, thereby
setting the frequency f of the string to the preset frequency f.sub.s.
The predetermined displacement and load values should be in the range where
they are least affected by the rigidity characteristic of the string 1,
and should be determined by taking into consideration the measuring
accuracy of a displacement measuring sensor and the length of the string.
Tuning accuracy depends on whether these predetermined values are
appropriate or not.
According to the second aspect of the present invention, the
above-described string tuning operations are all carried out
automatically.
A preferred embodiment of the present invention will now be described with
reference to FIG. 2 which is a block diagram showing an apparatus wherein
a predetermined load is applied to a string.
Referring to FIG. 2, numeral 6 denotes a position control unit comprising:
(a) a tuning pin rotation member position control section 8 serving to
control an X-direction servo motor 7.sub.1, a Y-direction servo motor
7.sub.2 and Z-direction servo motor 7.sub.3 which are used to move the
tuning pin rotation member 5 up to the location of the tuning pin 4 so
that the rotation member 5 engages the tuning pin 4 screwed into the frame
3 placed in a predetermined location as shown in FIG. 1; (b) a load-use
weight moving servo motor 9 which is used to move the weight so as to set
up a load suitable for the length and tension of the string; (c) a
load/measurement member position control section 12 serving to control an
X-direction servo motor 11.sub.1, a Y-direction servo motor 11.sub.2 and a
Z-direction servo motor 11.sub.3 which are used to move a load/measurement
member, the load/measurement member being (represented by numeral 21 in
FIG. 3.) up to a location of the load member 2 used to apply a load to the
string 1 and measure a displacement of the string 1 from its stretched
condition; and (D) a tuning pin rotation control section 14 serving to
control a servo motor 13 which is used to rotate the tuning pin. All of
the control sections include a known servo circuit. Numeral 15 denotes a
sequencer which comprises a memory 16 and a programmer 17.
Stored in the memory 16 are X, Y and Z coordinates of a predetermined load
value, X, Y and Z coordinates of a load point location and a predetermined
displacement value. The programmer 17 feeds position control signals read
out from the memory 16, to the tuning pin rotation member position control
section 12 so as to operate them, which signals correspond respectively to
the tuning pin location, the predetermined load value and the load point
location. After the load/measurement member 21 has stopped at a position a
predetermined distance away from the predetermined load point location,
string locator sensor 18 is operated to find the location of the string 1.
This location is then fed back for controlling the load/measurement member
21 so that it is positioned at the center of the string 1. Thereafter,
control signals read out from the memory 16 which correspond to the
predetermined load value are inputted to the load-use weight position
control section 10. At the time when the predetermined load is applied to
the string 1, a deviation between the predetermined displacement value
read out from the memory 16 and a displacement value measured by a
displacement measuring sensor 19 is calculated so that the programmer 17
may continue to input operation signals to the tuning pin rotation control
section 14 until said deviation is reduced to zero.
In memory 16 only data for a predetermined type of piano are stored. When a
different type of piano is to be tuned, new data therefor are inputted
into memory 16 from a computer 20.
Likewise, when the predetermined displacement value or the like is to be
modified, the modified data should be newly inputted from the computer.
The above-described load/measurement member 21 is, for example, as shown in
FIG. 3, so constructed that it can freely move and adjust the load.
In FIG. 3, numeral 21A denotes a tubular-shaped tip of the load/measurement
member. Tip 21A has optical fibers 22 inserted therein. An optical sensor
23 that casts and receives light simultaneously is connected to these
fibers to form the string locator sensor 18. A displacement measuring
sensor 19, consisting of a dial gauge which outputs electrical signals
representing a displacement of the tip, is provided above the
tubular-shaped tip 21A. Further, attached to the load/measurement member
21 is a balance 26 whose one end is pivotally supported on a board member
24, on which is mounted the sensor 19, and whose other end has a load-use
weight 25 movably attached thereto. The load-use weight 25 is slidable by
the servo motor 9 so that a desired load may be applied to the string 1
through the tubular-shaped tip 21A. Tip 21A is freely adjustable in its
position by turning screw bolts 28.sub.1, 28.sub.2 and 28.sub.3
respectively by means of X-, Y- and Z-direction servo motors 11.sub.1,
11.sub.2 and 11.sub.3 (which are all mounted on a fixture member not
shown), these screw bolts being partially screwed into and thus held on a
block 27 fixedly attached to the board member 24.
In FIG. 3, reference numeral 29 denotes a damper for stopping oscillations
between the reaction force of the spring 1 and the load, and reference
numeral 30 represents a weight holder member which is used when moving the
load/measurement member 21.
As shown in FIG. 4, the above-described tuning pin rotation member 5 is so
arranged as to be rotated through a clutch 31 by a servo motor 13 for
turning the tuning pin 4. The position of tuning pin rotation member 5 can
be freely adjusted by rotating screw bolts 33.sub.1, 33.sub.2 and 33.sub.3
respectively by means of X-, Y- and Z-direction servo motors 7.sub.1,
7.sub.2 and 7.sub.3 (all of which are mounted on a fixture member not
shown), these screw bolts being partially screwed into and held on a block
32 which supports the servo motor 13.
The above-described tuning apparatus in accordance with the preferred
embodiment of the invention can be used to carry out a string tuning
method in accordance with the invention. The tuning pin rotation member 5
is moved by servo motors 7.sub.1, 7.sub.2 and 7.sub.3 to be set onto the
tuning pin 4 at a location corresponding to the position identification
signals outputted by the programmer 17. The load/measurement member 21 is
moved by means of servo motors 11.sub.1, 11.sub.2 and 11.sub.3 so as to
start the string-locating operation from a location at a predetermined
distance (within the range not to result in an erroneous location of a
neighboring string) short of the position at which the string is struck
and, having located the string, stop at the center of the string.
Moved by the servo motor 9, the load-use weight 25 is also set at the same
time to a position at which the predetermined load is produced. Next, the
load is applied to the string 1 through the tubular-shaped tip 21A of the
load/measurement member 21. In this case, the tubular tip 21A constitutes
the load point. The displacement measuring sensor 19 detects a flexure
amount of the string 1 and inputs it to the programmer 17 of the sequencer
15. Since the programmer 17 continues to output operation instruction
signals until such time when a deviation between the predetermined
displacement value read from the memory 16 and a flexure or deflection
amount, that is, a displacement of the string 1 measured by the sensor 19,
is reduced to zero, the servo motor 13 continues to rotate the tuning pin
4. The tuning pin 4 is always rotated first in such a rotational direction
and to such an extent that a tension of the string 1 becomes higher than
the preset value and then in the return direction until said deviation is
reduced to zero. As the tuning pin completes the above operation, the
tuning pin rotation member 5 is disengaged from the tuning pin 4, and the
load/measurement member 21 is also disengaged from the string 1.
FIG. 5 is a block diagram illustrating important portions (excluding the
position control unit and the servo motors) of a second preferred
embodiment of the invention in which the load is applied to the string 1
so that a predetermined displacement thereof is produced, the
load/measurement member 21' being constructed as shown in FIG. 6.
According to this second embodiment, a load-cell pressure measuring sensor
34 is employed in place of the displacement measuring sensor 19; the
programmer 17 supplies position signals corresponding to the tuning pin
location and the load position, respectively to the tuning pin rotation
member position control section 8 and the load/measurement member position
control section 12. These position signals are read out from memory 16, so
as to respectively operate control sections. Since it is necessary for the
tubular-shaped tip 21A of the load/measurement member to be positioned at
the center of the string 1 after the load/measurement member 21' has
stopped at the predetermined load position, the string locator sensor 18
is operated to locate the string correctly and feed back the correct
location thereof so as to control the load/measurement member 21'. Next,
the position identification signals corresponding to the predetermined
displacement value of the string 1, which value is read from the memory
16, and signals for the pressure (load)-string location measured by the
pressure measuring sensor 34 are supplied to the load/measurement member
position control section 12 so as to adjust a displacement of the string 1
to the predetermined displacement value. A deviation between a value of
the pressure to be inputted of the string 1 measured by the pressure
measuring sensor 34 and the preset pressure value read from the memory 16
is calculated so that operation signals may be supplied to the tuning pin
rotation control section 14 until said deviation is reduced to zero.
In accordance with the string tuning method using an apparatus in
accordance with the second preferred embodiment, the sequencer 15 is
operated to set the tuning pin rotation member 5 to the selected tuning
pin 4. The load/measurement member 21 is first moved to a location
slightly off the load measuring point and thereafter moved in the
horizontal direction to a center of the string 1 located by the string
locator sensor 18, where it remains. Next, while the string 1 is kept
pressed for the predetermined displacement thereof, the servo motor 13 for
rotation of the tuning pin is operated to turn the tuning pin 4 until the
pressure of the string 1 detected by the pressure measuring sensor 34
corresponds to the predetermined load value stored in the memory 16.
The other operations are the same as in the method described in connection
with the first preferred embodiment.
As described in the foregoing, according to the present invention, when
each string of a keyboard musical instrument in which a plurality of
strings are struck in unison in response to actuation of a key, it is not
necessary to apply rubber pieces or other means to strings not being tuned
in order to prevent those strings from vibrating to generate sound, as is
required in accordance with the conventional tuning method. Thus it is
very easy to carry out the tuning operation. Moreover, according to the
present invention, tuning of each string can be carried out when the
product is in a semi-complete condition such as before being combined with
an action mechanism therefor, so that more operational freedom for the
tuning operation is assured for a higher work efficiency.
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