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FIELD OF THE INVENTION
This invention relates to a keyboard musical instrument and, more
particularly, to a keyboard musical instrument having a variable contact
point between a jack and a regulating button depending upon a mode of
operation.
DESCRIPTION OF THE RELATED ART
A piano is a typical example of the keyboard musical instrument. The piano
generates a loud sound through an impact of a hammer on a set of strings,
and the player is afraid that the loud sounds disturb the neighborhood.
For this reason, a piano is equipped with a muting/silent mechanism for
muting the loudness of the sounds.
A prior art muting mechanism is constituted by a cushion member and a
driving mechanism, and the driving mechanism moves the cushion member onto
the strings. While a player is performing a music, the hammer assemblies
rebound on the cushion member, and softly strike the sets of strings. The
cushion member rapidly takes up the vibrations of the strings, and the
strings generate soft sounds.
U.S. Pat. No. 2,250,065 discloses a prior art silent mechanism, and the
disclosed silent mechanism picks up the hammer assemblies so as to cut off
the functional relation between the key action mechanisms and the hammer
assemblies. Even if a player depresses the keys, the depressed keys
actuate only the associated key action mechanisms: however, the key action
mechanisms do not drive the hammer assemblies for rotation. Thus, the
strings are not struck by the hammer assemblies, and a sound is not
generated by the piano. If key sensors and/or hammer sensors are provided
for the piano equipped with the silent mechanism, a tone generator may
generate electronic sounds on the basis of the detected key/hammer
motions.
The prior art muting mechanism can not perfectly eliminate the sounds from
the piano, and the prior art silent mechanism changes the key-touch unique
to the acoustic piano, because an escape of the jack from the hammer
roller gives the unique key-touch to the player. Namely, while a player is
depressing a key, the jack is escaped from the hammer roller, and player's
finger suddenly feels light due to the elimination of the hammer weight.
Japanese Patent Application No. 4-174813 proposed a silent mechanism for an
acoustic piano, and U.S. Ser. No. 08/073,092 was filed claiming the
priority right on the basis of Japanese Patent Application No. 4-174813
together with other Japanese Patent Applications. Although several prior
arts opposed against U.S. Ser. No. 08/073,092, the U.S. Patent Application
was patented, and U.S. Pat. No. 5,374,775 was issued on Dec. 20, 1994. The
references cited in the patent prosecution are U.S. Patent documents U.S.
Pat. Nos. 2,250,065, 4,633,753, 4,704,931 , 4,744,281, 4,970,929,
5,115,705 and 5,247,129 and Foreign Patent documents 44782 (Germany),
68406 (Germany), 97885 (Germany), 3707591 (Germany) and 3707591C1
(Germany), To9-1U000077 (Italy), 51-67732 (Japan), 55-55880 (Japan),
62-32308 (Japan), 63-97997 (Japan) and 614303 (Switzerland).
The silent mechanism disclosed in U.S. Pat. No. 5,374,775 moves a stopper
into and out of the paths of the hammer shanks, and the hammer shank
rebounds on the stopper staying in the paths of the hammer shanks before
an impact on the strings.
However, the silent mechanism disclosed in U.S. Pat. No. 5,374,775 requires
a wide space between the strings and the hammer heads in the home
position, and is hardly installed in a small-sized piano and some kind of
piano with a narrow space between the hammers and the strings. In detail,
when deformation of a hammer shank and the stopper is taken into account,
the silent mechanism requires a gap ranging from 5 to 10 millimeters
between the hammer heads and the strings at the reboud of the hammer
shanks on the stopper so as to prevent the strings from the hammer heads.
On the other hand, although the escape point is variable depending upon
the notes assigned the strings, the escape point of a kind of piano is
regulated to 3 millimeters for low-pitched tones, 2.5 millimeters for
middle-pitched tones and 2 millimeters for high-pitched tones. If the
silent mechanism is effective, the hammer shanks are brought into contact
with the stopper before the escape of the jacks from the hammer rollers,
and are caught between the stopper and the jacks.
Japanese Patent Application No. 4-215400 discloses a regulating mechanism
for changing the escape point, and U.S. Ser. No. 08/174,179 and European
Patent Application No. 93120645.2 were filed claiming the priority rights
on the basis of Japanese Patent Application No. 4-215400 together with
other Japanese Patent Applications. The regulating mechanism disclosed in
Japanese Patent Application No. 4-215400 has a spacer insertable into a
gap between the toe of the jack and the regulating button, and the spacer
allows the jack to escape from the hammer butt (or the hammer roller)
earlier than the escap after the direct contact between the jack and
regulating button.
However, the jack early escaping from the hammer butt or the hammer roller
causes the player to feed the key-touch shallow. The shallow key-touch may
not be serious to a beginner. However, professional pianists hate the
shallow key-touch.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide a
keyboard musical instrument which is equipped with a mechanism increasing
a gap between a hammer head and strings at a finish of an escape without
change of a starting point of the escape for a key-touch unique to a
piano.
To accomplish the object, the present invention proposes to change a
contact point between a short portion of a jack and a regulating button
mechanism.
In accordance with the present invention, there is provided a keyboard
musical instrument comprising: a plurality of keys respectively assigned
notes of a scale, and selectively moved by a player; a plurality of string
means associated with the plurality of keys for generating acoustic tones
having the notes, respectively; a plurality of hammer assemblies
respectively associated with the plurality of string means for striking
the associated string means when the player selectively depresses the
plurality of keys, a plurality of key action mechanisms functionally
connected between the plurality of keys and the plurality of hammer
assemblies, respectively, and each including a whippen assembly rotated by
the associated key moved by the player, a regulating button mechanism, and
a jack having a long portion and a short portion merged with the long
portion at an intermediate portion rotatably supported by the whippen
assembly and brought into contact with the regulating button mechanism for
escaping from the associated hammer assembly; and a change-over means
associated with the regulating button mechanism for changing a contact
point between the short portion and the regulating button mechanism.
The keyboard musical instrument may further comprise a stopper for
preventing the plurality of string means from impacts of the hammer
assemblies and an electronic sound generating system for generating
electronic sounds in response to the keys depressed by the player.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the keyboard musical instrument according to
the present invention will be more clearly understood from the following
description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a cross sectional view showing the structure of a keyboard
musical instrument according to the present invention;
FIG. 2 is a side view showing a regulating button mechanism incorporated in
the keyboard musical instrument at a starting point of an escape according
to the present invention;
FIG. 3 is a cross sectional view showing a second regulating button
incorporated in the regulating button mechanism;
FIG. 4 is a front view showing second regulating buttons incorporated in
the keyboard musical instrument;
FIG. 5 is a front view showing a part of the second regulating buttons;
FIG. 6 is a graph showing relation between a key motion and a motion of
capstan button;
FIG. 7 is a graph showing relation between the key motion and a contact
point between a repetition lever and a hammer roller;
FIG. 8 is a graph showing relation between the key motion and a hammer
motion;
FIG. 9 is a perspective view showing a silent system incorporated in the
keyboard musical instrument;
FIG. 10 is a perspective view showing the silent system from another angle;
FIG. 11 is a block diagram showing the arrangement of an electronic sound
generating system incorporated in the keyboard musical instrument;
FIG. 12 is a side view showing a regulating button mechanism in a
silent/muting modes incorporated in another keyboard musical instrument at
a starting point of an escape according to the present invention;
FIG. 13 is a side view showing the regulating button mechanism at a
starting point of an escape in a standard acoustic sound mode;
FIG. 14 is a side view showing a regulating button mechanism incorporated
in yet another keyboard musical instrument at a starting point of an
escape according to the present invention;
FIG. 15 is a side view showing a regulating button mechanism at a starting
point of an escape in a silent/muting modes incorporated in still another
keyboard musical instrument according to the present invention;
FIG. 16 is a side view showing the regulating button mechanism at a
starting point of an escape in a standard acoustic sound mode;
FIG. 17 is a side view showing a jack and a regulating button mechanism
incorporated in a keyboard musical instrument according to the present
invention;
FIG. 18 is a side view showing a regulating button mechanism incorporated
in another keyboard musical instrument according to the present invention;
and
FIG. 19 is a side view showing a regulating button mechanism incorporated
in a keyboard musical instrument according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
Referring first to FIG. 1 of the drawings, a keyboard musical instrument
embodying the present invention largely comprises a grand piano 100, a
silent system 200 and an electronic sound generating system 300, and
selectively enters into at least a standard acoustic sound mode, a muting
mode and a silent mode. The grand piano is a standard type, and a piano
case (not shown) houses most of internal mechanisms of the grand piano
100. In the following description, a rotational direction is determined in
a figure to be referenced, and a player sits on the front side of the
keyboard musical instrument during a performance.
The grand piano 100 comprises a keyboard 101 supported by a key frame 102
mounted on a key bed 103. Eighty-eight black and white keys 101a and 101b
form the keyboard 101, and are turnable with respect to balance pins 104.
The black and white keys 101a and 101b extend in a fore-and-aft direction
of the grand piano, and front end portions of the black and white keys
101a and 101b are exposed to a player. While a force is not being exerted
by the player, the black and white keys 101a and 101b are staying in
respective rest positions as shown in FIG. 1. When the player depresses
the black and white keys 101a and 101b, the black and white keys 101a and
101b are moved as indicated by arrow A, and arrive at respective end
positions. Notes of a scale are respectively assigned to the black and
white keys 101a and 101b, respectively.
The grand piano 101 further comprises a plurality of sets of strings 104
horizontally stretched between tuning pins (not shown) and hitch pins (not
shown) over the keyboard 101, a whippen rail 105 laterally extending over
the rear end portions of the black and white keys 101a and 101b, a
plurality of key action mechanisms 106 supported by the whippen rail 105
and a plurality of hammer assemblies 107 turnably supported by a hammer
shank rail 109. Action brackets support the whippen rail 105 and the shank
flange rail 109. The action brackets 108, the black and white keys
101a/101b and the key frame 102 are laterally movable by means of a shift
pedal (not shown), and cause the hammer assemblies 107 to strike the
strings fewer than the normal number for lessening the softening the
timbre and prolonging the tones. The sets of strings 104 respectively
vibrate, and generate acoustic tones with the notes of the scale assigned
to the black and white keys 101a and 101b, respectively.
The plurality of key action mechanisms 106 are similar in structure to one
another, and are functionally connected to the black and white keys 101a
and 101b by means of capstan screws 110. When the black and white keys
101a and 101b are depressed, the associated key action mechanisms 106 are
actuated by the capstan screws 110, and rotate the associated hammer
assemblies 107 toward the sets of strings 104. The hammer assemblies 107
rebound on the sets of strings 104, and return to respective home
positions shown in FIG. 1.
The grand piano 100 further comprises a plurality of damper mechanisms 111
movably supported by a damper lever rail 112. The damper mechanisms 111
are respectively held in contact with the sets of strings 104 while the
black and white keys 101a and 101b are staying in the rest positions, and
do not allow the strings 104 to vibrate. The damper mechanisms 111 is
respectively actuated by the rear end portions of the black and white keys
101a and 101b, and are separated from the sets of strings 104. Then, the
strings 104 are allowed to vibrate, and generate the acoustic tones,
respectively.
Each of the key action mechanisms 106 comprises a whippen flange 106a fixed
to the whippen rail 105, an whippen assembly 106b turnably supported by
the whippen flange 106a, a repetition lever flange 106c fixed to an
intermediate portion of the whippen assembly 106b, a repetition lever 106d
turnably supported by the repetition lever flange 106c, a jack 106e
turnably supported by a front end portion of the whippen assembly 106b, a
repetition spring 106f urging the repetition lever 106d and the jack 106e
in the counter clockwise direction and a regulating button mechanism 106g
supported by the hammer shank rail 109.
The hammer assemblies 107 are also similar to one another, and each hammer
assembly 107 comprises a hammer shank flange 107a fixed to the hammer
shank rail 109, a hammer shank 107b turnably connected to the hammer shank
flange 107b, a hammer roller 107c fixed to the hammer shank 107b and a
hammer head 107d fixed to the leading end of the hammer shank 107b.
The jack 106e has an L-shape, and is broken down into a long portion 106h
and a short portion 106i. The long portion 106h passes through an aperture
formed in the repetition lever 106d, and the hammer assembly 107 at the
home position causes the hammer roller 107c to stay on the top surface of
the long portion 106h of the jack 106e. On the other hand, the short
portion 106i is opposed to the regulating button mechanism 106g while the
black/white key 101a/101b is resting. The repetition spring 106f urges the
jack 106e in the counter clockwise direction at all times, and a jack
button 106j backwardly projects from the long portion 106h is pressed
against a jack stop spoon 106k fixed to the whippen assembly 106b while
the short portion 106i is spaced from the regulating button mechanism
106g.
The repetition lever 106d is urged in the counter clockwise direction at
all times, and a repetition lever button 106m is pressed against the rear
end portion of the whippen assembly 106b.
While the hammer assembly 107 is staying at the home position, the hammer
roller 107c rests on a top surface of the long portion 106h of the jack
106e, and the hammer shank stop felt 106n is fixed to the rear end portion
of the whippen assembly 106b. A drop screw 107e downwardly projects from
the hammer shank flange 107a, and regulates the amount of return distance
from the closest point when a player softly depressing the associated key.
As will be better seen in FIGS. 2 and 3 of the drawings, first and second
semi-spherical portions 106o and 106p are formed on the short portion 106i
of the jack 106e, and the first semi-spherical portion 106o is usually
called as "toe".
The regulating button mechanism 106g associated with each jack 106e
comprises a first regulating screw 106q inserted into a first regulating
rail 113 screwed into the hammer shank rail 109, a first regulating button
106r fixed to the first regulating screw 106q, a second regulating button
106s engageable with the second semi-spherical portion 106p and a
change-over sub-mechanism 106t shared with other second regulating buttons
106s. In this instance, the distance between the rotational axis of the
jack 106e and the first semi-spherical portion 106o is twice as long as
the distance between the rotational axis of the jack 106e and the second
semi-spherical portion 106p.
Assuming now that the key 101a/101b is depressed at a certain speed, the
jack 106e brought into contact with the second regulating button 106s at
the second semi-spherical portion 106p gives a smaller force to the hammer
assembly 107 than the jack 106e brought into contact with the regulating
button 106r at the first semi-spherical portion 106o. Moreover, the
transmitting time period of the former is shorter than the transmitting
time period of the latter. As a result, the hammer assembly 107 associated
with the former slowly turns around the shank flange 107a, and gently
rebounds on the strings for producing a soft acoustic tone.
However, the starting point of escape is not changed between the first
regulating button 106r and the second regulating button 106s, and the
key-touch unique to the grand piano is given to the player in all of the
modes of operation.
As will be better seen from FIGS. 4 and 5, each of the second regulating
buttons 106s is associated with one of the plurality of groups of key
action mechanisms 106, and, accordingly, the key action mechanisms 106 of
each group share the second regulating buttons 106s.
The change-over sub-mechanism 106t comprises a second regulating rail
bracket 106u bolted to the hammer shank rail 109 and a rod member 106v
rotatably supported by means of bearing units 106w on the second
regulating rail bracket 106u, and the second regulating buttons 106s are
split into a plurality of sections respectively corresponding to the
groups of the key action mechanisms 106. Cloth members 106wa are inserted
between the inner surfaces of the bearing units 106w and the rod member
106v, and allow the rod member 106v to be smoothly rotated.
Each second regulating button 106s comprises a threaded stem portion 106x
screwed into each of bush members 106va inserted into through holes formed
in the rod member 106v at intervals, a bracket 106y fixed to the leading
end of the threaded stem portion 106x, cloth punchings 106za and 106zb
inserted between the bracket 106y and the head portion of the threaded
stem portion 106x and a cloth member 106zc attached to the lower surface
of the bracket 106y. The bracket 106y is split into two peaces, and the
threaded stem portion 106x is rotatable in the bracket 106y. A cubic head
106xa is formed at the opposite end of the threaded stem portion 106x, and
a tuner can rotate the threaded stem portion 106x with a wrench.
Therefore, the gap between the second semi-spherical portion 106p and the
cloth member 106zc is regulatable by turning the threaded stem portion
106x. The rod member 106v is shared between all of the second regulating
buttons 106s, and a manipulating grip 116 is connected through a flexible
wire 117 to connecting rods 118 implanted into the rod member 106v. The
manipulating grip 116 is slidable in a case 119 attached to the key bed
103.
Though not shown in the drawings, a spring urges the connecting rods 118 in
the counter clockwise direction, and the second regulating buttons 106s
are changed to an idling position indicated by dots-and-dash line in FIG.
2. While the keyboard musical instrument is being performed in the
standard acoustic sound mode, the spring maintains the second regulating
buttons 106s in the idling position. 0n the other hand, when the keyboard
musical instrument enters into the muting mode or the silent mode, the
manipulating grip 116 is pulled toward the front side, and the connecting
rods 118 rotate the rod member 106v in the clockwise direction against the
elastic force of the spring (not shown). Then, the second regulating
buttons 106s is changed to an active position, and the cloth members 106zc
are opposed to the second semi-spherical portions 106p.
The regulating rail 113 is split into a plurality of regulating rail
sections, and the regulating rail sections are corresponding to a
plurality of groups of action mechanisms. The first regulating button 106r
is opposed to the first semi-spherical portion 106o, and the gap d between
the first semi-spherical portion 106o and the first regulating button 106r
is regulatable by turning the first regulating button 106r. A starting
point of escape of the jack 106e is determined by the gap d, and is
usually regulated in such a manner that the hammer head 107d reaches 2-3
millimeters from the associated set of strings 104. If the gap d is
decreased, the starting point of escape becomes early. On the other hand,
if the gap d is increased, the starting point of escape becomes late.
Turning back to FIG. 1, while a black/white key 101a/101b is traveling from
the rest position to the end position, the capstan button 110 upwardly
pushes the whippen assembly 106b, and the whippen assembly 106b and the
jack 106e turn around the whippen flange 106a in the counter clockwise
direction. The jack 106e turning around the whippen flange 106a causes the
hammer assembly 106d to turn around the shank flange 107a in the clockwise
direction. When one of the first and second semi-spherical portions 106o
and 106p is brought into contact with the first or second regulating
button, the whippen assembly 106b still turning around the whippen flange
106a causes the jack 106e to turn around a pin PN in the clockwise
direction against the elastic force of the repetition spring 106f. Then,
the jack 106e escapes from the hammer roller 107c, and the hammer assembly
107 rushes toward the set of strings 104.
The hammer head 107d rebounds on the set of strings 104, and the hammer
roller 107c is brought into contact with the repetition lever 106d. The
hammer roller 107c impacts on the repetition lever 106d, and the
repetition lever 106d turns around the repetition flange 106c in the
clockwise direction against the elastic force of the repetition spring
106f. The hammer assembly 107 is finally received by a back-check 114. On
the other hand, when the black/white key 101a/101b is slightly lifted from
the end position, the hammer head 107d is released from the back check
114, and the repetition spring 106f rotates the repetition lever 106d in
the counter clockwise direction. As a result, the hammer assembly 107
turns in the clockwise direction over a small angle, and the jack 106e
comes into contact with the hammer roller 107c.
The damper mechanism 111 comprises a damper lever flange 111a fixed to the
damper lever rail 112, a damper lever 111b turnably supported by the
damper lever flange 111a, a damper block 111c functionally connected to
the leading end of the damper lever 111b, a damper wire 111d upwardly
projecting from the damper block 111c and a damper head 111e connected to
the leading end of the damper wire 111d. While the black/white key
101a/101b is resting, the rear end portion of the key 101a/101b is
downwardly spaced from the leading end of the damper lever 111b, and the
damper head 111e is held in contact with the set of strings 104 by the
self-weight.
When the player depresses the key 101a/101b, the rear end of the depressed
key 101a/101b upwardly pushes the damper lever 111b, and the damper lever
111b turns around the damper lever flange 111a in the counter clockwise
direction. A damper guide rail 115 guides the damper wire 111d, and the
damper wire 111d causes the damper head 111e to leave the set of strings
104. The set of strings 104 is allowed to vibrate, and generates the
acoustic tone upon impact of the hammer head 107d.
When the player releases the key 101a/101b, the rear end portion sinks, and
allows the damper lever 111b to turn around the damper lever flange 111a
in the clockwise direction. The damper head 111e is brought into contact
with the set of strings 104, and the vibrations of the strings 104 is
taken up by the damper head 111e.
The key action mechanisms 106, the hammer assemblies 107 and the damper
mechanisms 111 behave as similar to those of a standard grand piano except
for the regulating button mechanisms 106g.
The behavior of the key action mechanism 106 is hereinbelow analyzed in
detail. Assuming that the jack 106e escapes from the hammer roller 107c
after a contact of the second semi-spherical portion 106p with the second
regulating button 106s, the distance between the point of application and
the fulcrum, i.e., between the second semi-spherical portion 106p and a
pin member PN is decreased to a half of the distance between the first
semi-spherical portion 106p and the pin PN, and the angular velocity of
the jack 106e and the angle of the rotation are increased to the twice of
those of the jack 106e escaping through the contact between the first
semi-spherical portion 106o and the first regulating button 106r. When
paying attention to the top surface of the long portion 106h, the
horizontal component force is rather large than the vertical component
force due to the increased angular velocity, and allows the jack 106e to
escape from the hammer roller 107c earlier than the escape through the
contact between the first semi-spherical portion 106o and the first
regulating button 106r. Thus, the jack 106e escapes from the hammer roller
107c at a longer distance between the hammer head 107d and the strings
104.
In fact, when the first semi-spherical portion 106o was brought into
contact with the first regulating button 118, the jack 106e escaped from
the hammer roller 107c at the distance of 3 millimeter. On the other hand,
the contact between the second semi-spherical portion 106p and the second
regulating button 106s caused the jack 106e to escape from the hammer
roller 107c at the distance of about 5 millimeters, and the difference was
about 2 millimeters.
The increased angular velocity makes the vertical component force
decreased, and completes the escape early. The jack 106e transmits the
vertical force over a shorter time, and slowly rotates the hammer assembly
107. The hammer assembly gently strikes the strings 104, and the stings
104 generate a soft acoustic tone through weak vibrations. Even though the
distance between the hammer head and the strings becomes wider at the
escape, the second semi-spherical portion 106p is brought into contact
with the second regulating button 106s at the same timing as the contact
between the first semi-spherical portion 106p and the first regulating
button 118, and the key touch is not changed among the standard acoustic
sound mode, the muting mode and the silent mode.
The ratio of the angular is variable together with the position of the
second semi-spherical portion 106p on the short portion 106i, and affects
the hammer motion as described hereinbefore. However, if the second
semi-spherical portion 106p is too close to the pin PN, the angle of
rotation of the long portion 106h is excessively increased, and is
violently brought into collision against the inner wall of the repetition
lever 106d. The collision may break the key action mechanism 106. On the
other hand, if the second semi-spherical portion 106p is too close to the
first semi-spherical portion 106o, the distance of the hammer head cloest
to the strings is unchanged among the standard acoustic sound mode, the
muting mode and the silent mode, and the hammer shank 107b may get between
the jack 106e and a shank stopper which is described hereinlater. The
present inventors took these problems into account, and decided the second
semi-spherical portion 106p at the intermediate point of the short portion
106i.
FIGS. 6 to 8 illustrate motions of the key action mechanism 106, and each
abscissa is indicative of a distance of the key 101a/101b from the rest
position. The jack 106e starts the escape at point S, and the key
101a/101b reaches the end position at point B. While a player is slowly
depressing the key 101a/101b from the rest position to the end position,
the capstan button 110 roughly traces linear line L1 as shown in FIG. 4,
and the contact point between the hammer roller 107c and the repetition
lever 106d also roughly traces linear line L2 until point S (see FIG. 7).
When the jack 106e starts the escape, the repetition lever is brought into
contact with the drop screw 107e. After the contact with the drop screw
107e, the capstan button 110 still rises, and rotates the repetition lever
106d in the clockwise direction in FIG. 1 between point S and point B. As
a result, the contact point between the hammer roller 107c and the
repetition lever 106d gently rises. The rise h is about 0.4 millimeter.
The hammer assembly 107 traces real line L3 in the standard acoustic sound
mode (see FIG. 8), and broken line L4 in the muting/silent mode. In the
muting/silent modes, the jack completes the escape at point A', and the
finishing point of escape A' is earlier than the finishing point of escape
B in the standard acoustic sound mode. Point C is indicative of the
maximum height of the hammer when the key 101a/101b is gently depressed.
Point C is spaced from the strings 104 by 3 millimeters. The jack 106e
supports the hammer roller 107c along path S-C-B and or S-C'-A', and
directly transfers the force due to the key motion to the hammer roller
107c. In the muting and silent mode, the repetition lever 106d supports
the hammer roller 107c along path A'-B, and the hammer roller 107c gently
rises together with the repetition lever 106d. For this reason, the force
due to the key motion is indirectly transferred through the repetition
lever 106d to the hammer roller 107c. The hammer assembly 107 rises seven
to eight times wider than the hammer roller 107c, and the gradient of the
path between point A' and B is also seven to eight times larger than the
height of the repetition lever 106d between point S and point B. While the
key 101a/101b is being gently depressed, the key-touch like a click is
given between the path S-C-B or S-C'-A' due to the friction force between
the jack 106e and the hammer roller 107c.
Relation among points A', B, C, C' and S is expressed as C>B>C'>A'>S. In
the muting/silent modes, jack 106e approaches the hammer roller 107c to
the strings 104 by the distance between the point C' and the strings 104;
however, the distance of the hammer head closest to the strings h2 is 5
millimeters at the point B. Dots-and-dash line is representative of the
motion of the hammer 107 pressed by the repetition lever 106d only, i.e.,
without the jack 106e, and the path of the hammer 107 is matched partially
with the real line until point S and partially with the broken line L4
between A' and B.
In this instance, the distance between the hammer head 107d and the strings
104 is regulated as shown in the following table. The interrupt point with
the shanks stopper 210 is further shown in the table. In the table,
"distance" means the distance between the hammer head and the associated
strings.
TABLE
______________________________________
high tone
intermediate
middle tone
low tone
Distance
range tone range range range
______________________________________
Standard
1.5 2.0 2.5 3
acoustic
sound
mode
Silent 3.5 4.0 4.5 5.0
mode
Inter- 3.0 3.0 4.0 5.0
ruption
______________________________________
Referring to FIGS. 9 and 10 concurrently with FIG. 1, the silent system 200
comprises a shank stopper 210 changeable between a free position FP and a
blocking position BP and a change-over mechanism 230 connected to the
shank stopper 210. The shank stopper 210 is provided in a space between
the strings 104 and the hammer shanks 107b at the home position, and is
split into two stopper sections (see FIG. 10). One of the stopper sections
is provided for the sets of strings assigned to low-pitched tones, and the
other stopper section is provided for the sets of strings assigned to
middle-pitched tones and high-pitched tones.
The shank stopper 210 comprises a rod member 211 split into two sections
211a and 211b, cushion brackets 212a and 212b respectively attached to the
two sections 211a and 211b, lower cushion members 213a and 213b attached
to the cushion brackets 212a and 212b, upper cushion members 214a and 214b
fixed to the lower cushion members 213a and 213b and protective skins 215a
and 215b fixed to the upper cushion members 214a and 214b. The lower
cushion members 213a and 213b, the upper cushion members 214a and 214b and
the protective skins 215a and 215b form a cushion unit 216.
The section of the shank stopper 210 for the strings 104 assigned to the
low-pitched tones is rotatably supported at one end thereof by a bearing
unit (not shown) attached to an inner surface of a side board 217 and at
the other end thereof by a bearing unit 218a attached to a board 219 by
means of a bracket 220. Though not shown in FIGS. 9 and 10, the section of
the shank stopper 210 for the strings 104 assigned to the low-pitch tones
is further supported at an intermediate portion by a bearing unit.
The section of the shank stopper 210 for the strings 104 assigned to the
middle-pitched/high-pitched tones is rotatably supported at one end
thereof by a bearing unit 218b fixed to the bracket 220 and at the other
end thereof by a bearing unit 218c fixed through a bracket 221 to an inner
surface of the side board 217. The intermediate portion is also rotatably
supported by a bearing unit (not shown).
The cushion brackets 212a and 212b are formed of wood, aluminum alloy or
iron, and the upper cushion members 214a and 214b are different in the
modulus of elasitisity from the lower cushion members 213a and 213b. The
protective skins 215a and 215b are formed of leather or synthetic resin.
The change-over mechanism 230 comprises a grip 231 manipulated by a player,
a case 232 slidably supporting the grip 231, transmitting cords 233a and
233b connected to the grip 231, bracket 234 fixed to the inner surfaces of
the side board 217 and arm members 235 fixed to the sections 211a/211b of
the rod member 211. Each of the transmitting cords 233a and 233b is formed
by a stationary flexible tube 233c and a flexible wire 233d. The flexible
tube 233c is fixed between the bracket 234 and the case 232, and the
movable flexible wire 233d is slidably inserted into the flexible tube
233c. The movable flexible wire 233d has a ball 233e fixed to the leading
end of the flexible wire 233d, and is engaged with the bracket member 235.
If the player pulls the grip 231, the flexible wires 233d slides in the
flexible tubes 233c, and pulls down the arm members 235. Then, the shank
stopper 210 is changed from the free position FP to the blocking position
BP, and the cushion unit 216 is opposed to the hammer shanks 107b. While
the shank stopper 210 is resting in the free position FP, the hammer heads
107d rebound on the associated sets of strings 104 without an interruption
of the shank stopper 210 . However, the shank stopper 210 in the blocking
position BP causes the hammer shanks 107b to rebound thereon without an
impact on the strings 104. The shank stopper 210 enters into the blocking
position BP in the silent mode, and rests in the free position FP in the
standard acoustic sound m | | |
