Keyboard musical instrument having jacks changeable in escape speed between acoustic sound mode and silent mode

Abstract: A keyboard musical instrument selectively generates acoustic sounds and electronic sounds depending upon a mode selected by a player, and has a hammer stopper (320) for interrupting hammers (108) before strikes at strings (104) and an escape accelerator (340) for accelerating an escape of a jack (106e) from the hammer assembly (108) in the silent mode earlier than an escape in the acoustic sound mode, thereby preventing the hammer assembly (108) from capture between the jack (106e) and the hammer stopper (320) without deterioration of the piano key touch.

Description: This invention relates to a keyboard musical instrument and, more particularly, to a piano-like keyboard musical instrument equipped with jacks changeable in escape speed between an acoustic sound mode and a silent mode. DESCRIPTION OF THE RELATED ART The piano usually generates loud sounds, and the loud sounds may disturb neighbors. For this reason, a piano is equipped with a muting mechanism, and the muting mechanism softens the piano sounds. If the muting mechanism inserts a muffler between the strings and the hammer assemblies, the hammer heads strike the strings through the muffler, and the muffler rapidly absorbs the vibrations of the strings. As a result, the strings softly generate the sounds, and the muting mechanism prevents the neighbors from the loud sounds. U.S. Patent 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 the associated key action mechanisms: however, the key action mechanisms do not drive the hammer assemblies for rotation. 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 player's fingering on the keyboard. 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 the jacks do not drive the hammer assemblies. In detail, while a player is fingering on a keyboard, the depressed keys actuates the key action mechanisms only. Although the jacks behave as similar to the escape from the hammer butts or the hammer rollers, it is impossible to give the unique piano key touch, i.e., temporary heavy touch to the player. Player's finger 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. Serial 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. Serial No. 08/073,092, the U.S. Patent Application was patented, and U.S. Patent No. 5,374,775 was issued on December 20, 1994. The references cited in the patent prosecution are U.S. Patent documents 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. Patent 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. Patent 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. 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 rebound of the hammer shanks on the stopper. Although the escape point is variable depending upon the model of the piano, the standard escape point 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 installed between the hammer shanks and the strings, the hammer shanks are brought into contact with the stopper before the escape of the jacks from the hammer butts or the hammer rollers, and are caught between the stopper and the jacks. The regulating buttons are available for increasing the gaps between the escaping points and the strings. However, the player feels the key touch strange, because the jack escapes from the hammer butt/hammer roller earlier. Moreover, the jacks escaping earlier do not impart sufficient energy to the hammer butt/hammer roller, and the hammer head softly strikes the strings. As a result, the loudness is decreased, and the timbre is changed. Thus, there is a trade-off between the prevention of undesirable capture of the hammer shanks and the standard piano sounds. The prevention of the undesirable capture is required in a performance without an acoustic piano sound, and the standard piano sounds are expected in a performance through the acoustic piano sounds. For this reason, Japanese Utility Model Application No. 5-56462 proposes a keyboard musical instrument equipped with a kind of changing mechanism for changing a gap between the regulating button and the toe of the jack. If a player wants a performance without an acoustic sound, the changing mechanism inserts a spacer into the gap between the toe of the jack and the regulating button, and causes the jack to escape earlier. The hammer assembly rebounds after the escape of the jack, and the undesirable capture does not take place. On the other hand, when the player tries a performance through the acoustic sounds, the changing mechanism retracts the spacer, and the jack escapes at the standard point. Then, the jack can impart sufficient kinetic energy to the hammer assembly, and the hammer assembly strikes the strings as usual. Another solution is proposed in Japanese Utility Model Application No. 5-38463, and another type of changing mechanism is incorporated in the keyboard musical instrument disclosed therein. The changing mechanism projects and retracts the regulating button per se , and changes the gap between a performance without an acoustic sound and a performance through acoustic sounds. The keyboard musical instrument achieves the same advantages as that disclosed in the former Japanese Utility Model Application. However, the keyboard musical instrument disclosed in the former Japanese Utility Model Application encounters a problem in that the changing mechanism is complex. Another problem is an unintentional small gap between the spacer and the regulating button, and the unintentional gap causes the load exerted on the jack twice. As a result, the player feels a change of load at the contact between the jack and the spacer and at the contact between the spacer and the regulating button. Yet another problem is an aged deterioration of the spacer, and it is hard to keep the escaping points constant over the service time of the keyboard musical instrument. The keyboard musical instrument disclosed in the latter Japanese Utility Model Application is free from the problems due to the spacer. However, a tuner is expected to appropriately regulate each of the regulating buttons in such a manner as to satisfy two escaping points, i.e., the escaping point for a performance without an acoustic sound and the escaping point for a performance through acoustic sounds. This tuning work is very difficult, and the tuning work is frequently required. Moreover, a serious problem is encountered in both keyboard musical instruments disclosed in the Japanese Utility Model Applications in that the key-touch is varied between the performance without an acoustic sound and the performance through acoustic sounds, because the jacks are brought into contact with the regulating button or the spacer at different timings. EP 0 675 480 A is a so-called intermediate document and forms prior art under Art. 54 (3) EPC. This document discloses a keyboard musical instrument comprising: a plurality of keys respectively assigned to 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. There appears to be disclosed some kind of escape accelerator which, however, exerts force on the foot portions of the jacks for accelerating the escape. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a keyboard musical instrument, a key touch of which is unchanged between a performance without an acoustic sound and a performance through acoustic sounds. To accomplish the object, the present invention proposes to accelerate an escape of a jack during a performance without an acoustic sound. In accordance with the present invention, there is provided a keyboard musical instrument as set forth in claim 1. Preferred embodiments of the invention may be gathered from the dependent claims. The keyboard musical instrument may further comprise an electronic system for generating electronic sounds instead of the acoustic sounds. 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 partially cross sectional side view showing an essential structure of a keyboard musical instrument according to the present invention in an acoustic sound mode; Fig. 2 is a partially cross sectional side view showing the essential structure of the keyboard musical instrument along a different section; Fig. 3 is a side view showing a cam portion formed on a rear surface of a jack; Fig. 4 is a front view showing a hammer stopper sub-system in a free position; Fig. 5 is a front view showing the hammer stopper sub-system in a blocking position; Fig. 6 is a front view showing a reaction generator in an inactive position; Fig. 7 is a front view showing the reaction generator in an active position; Figs. 8A and 8B are side views showing a behavior of a key action mechanism and a hammer assembly in a performance through acoustic sounds; Figs. 9A and 9B are side views showing a behavior of the key action mechanism, the hammer assembly and an escape accelerator in a performance without an acoustic sound; and Fig. 10 is a side view showing another escape accelerator incorporated in a keyboard musical instrument according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring first to figures 1 and 2 of the drawings, a keyboard musical instrument embodying the present invention largely comprises an acoustic piano 100, an electronic system 200 and a silent system 300, and has at least an acoustic sound mode for a performance through acoustic sounds and an electronic sound mode for a performance without an acoustic sound. In the following description, word "front" means a position closer to a player than word "rear", and directions "clockwise" and "counter clockwise" are determined on a sheet where a rotating part is illustrated. The acoustic piano 100 is an upright piano, and comprises a keyboard 101 provided over a key bed 103. Eighty-eight black and white keys 101a and 101b form the keyboard 101, and are turnable around balance pins (not shown). The black and white keys 101a and 101b extend in a fore-and-aft direction of the upright 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 figure 1. When the player depresses the black and white keys 101a and 101b, the black and white keys 101a and 101b are downwardly moved, and arrive at respective end positions. Notes of a scale are respectively assigned to the black and white keys 101a and 101b, respectively. The upright piano 100 further comprises a plurality of sets of strings 104 provided in front of a vertically extending frame (not shown) and stretched between tuning pins (not shown) and hitch pins (not shown). A center rail 105a laterally extends in front of the strings 104, and is shared between all of the sets of strings 104. The center rail 105a is positioned over the rear end portions of the black and white keys 101a and 101b, and is bolted to action brackets 105b at both ends and an intermediate point thereof. The upright piano 100 further comprises a plurality of key action mechanisms 106 functionally connected to the black and white keys 101a and 101b, a plurality of damper mechanisms 107 actuated by the key action mechanisms 106 and 101b for momentarily leaving the associated sets of strings 104 and a plurality of hammer assemblies 108 driven for rotation by the key action mechanisms 106. When the player depresses one of the black and white keys 101a and 101b, the depressed key 101a/101b causes the damper mechanism 107 to leave the set of strings 104, and actuates the key action mechanism 106 so as to rotate the hammer assembly 108. The hammer assembly 108 strikes the set of strings 104 in the acoustic sound mode, and the vibrating strings 104 generate an acoustic sound. When the player releases the key 101a/101b, the key action mechanism 106 and the hammer assembly 108 return to the initial positions or the home positions, and the damper mechanism 107 is brought into contact with the strings 104, thereby absorbing the vibrations of the strings 104. The key action mechanisms 106 are similar in arrangement to one another, and each key action mechanism 106 comprises a whippen flange 106a bolted to a lower end portion of the center rail 105a and a whippen assembly 106b rotatably connected to the whippen flange 106a. The whippen assembly 106b has a heel 106c held in contact with a capstan screw 101c implanted into the rear end portion of the black or white key 101a/101b. The key action mechanism 106 further comprises a jack flange 106d upright from a middle portion of the whippen assembly 106b, a jack 106e turnably supported by the jack flange 106d, a jack spring 106f inserted between the whippen assembly 106b and a toe 106g of the jack 106e and a regulating button sub-mechanism 106h opposed to the toe 106g. The jack 106e has an L-shape, and a swell 106i is formed in the upper portion of the toe 106g. The jack spring 106f urges the jack 106e in the counter clockwise direction at all times. While the black or white key 101a/101b is staying in the rest position, the whippen assembly 106b is horizontally maintained, and the swell 106i of the toe 106g is spaced from the regulating button sub-mechanism 106h. The regulating button sub-mechanism 106h has a regulating button 106j projectable toward and retractable from the swell 106i by turning a regulating screw 106k. If the gap between the swell portion 106i and the regulating button 106j is increased, the jack 106e escapes from the hammer assembly 108 later. On the other hand, if the gap is decreased, the jack 106e escapes earlier. When the toe 106g is brought into contact with the regulating button 106j, the reaction impedes the motion of the whippen assembly and, accordingly, the depressed key 101a/101b, and the player feels the key 101a/101b heavier than before. Thus, the jack 106e and the regulating button sub-mechanism 106h deeply concern a key-touch, and the position of the regulating button 106j defines the starting point of the escape of the jack 106e. As shown in figure 3 of the drawings, a cam member 310 is attached to the rear surface of the jack 106e, and a slope 310a bridges the surface 106n of the jack 106e and a surface 310b of the cam member 310. As will be described hereinlater, the cam member 310 forms a part of the silent system 300. Turning back to figures 1 and 2, the damper mechanisms 107 are similar in arrangement to one another, and comprises a damper lever flange 107a fixed to an upper surface of the center rail 105a, a damper lever 107b rotatably supported by the damper lever flange 107a, a damper spoon 107c implanted into the rear end portion of the whippen assembly 106b, a damper wire projecting from the damper lever 107b, a damper head 107e fixed to the damper wire 107d and a damper spring (not shown in figure 1) urging the damper lever 107b in the counter clockwise direction. While the black or white key 101a/ 101b is staying in the rest position, the damper spoon 107c does not push the damper lever 107b, and the damper head 107e is held in contact with the set of strings 104. When the player depresses the black or white key 101a/101b from the rest position to the end position, the capstan screw 101c pushes up the whippen assembly 106b, and the whippen assembly 106b rotated in the counter clockwise direction causes the damper spoon 107c to rearwardly push the damper lever 107b. As a result, the damper lever 107b is rotated in the clockwise direction, and the damper head 107e leaves the set of strings 104. On the other hand, when the black or white key 101a/ 101b is released, the whippen assembly 106b is rotated in the clockwise direction, and the damper spoon 107c removes the pressure from the damper lever 107b. As a result, the damper spring (not shown in figure 1) urges the damper lever 107b in the counter clockwise direction, and the damper head 107e is brought into contact with the set of strings 104 again. The hammer assemblies 108 are also similar in arrangement to one another. Each of the hammer assemblies 108 comprises a hammer butt 108a turnably supported by a butt flange 108b fixed to the center rail 105a, a hammer shank 108c upwardly projecting from the hammer butt 108a, a hammer head 108d fixed to the leading end of the hammer shank 108c, a catcher 108e projecting from the hammer butt 108a, a back check 108f implanted into the front end portion of the whippen assembly 106b, a bridle tape 108g extending between the catcher 108e, a bridle wire 108h implanted into the front end portion of the whippen assembly 106b and a butt spring 108i urging the hammer butt 108a in the clockwise direction. While the black or white key 101a/101b is staying in the rest position, the top surface of the jack 106e is in contact with a butt skin 108j attached to a lower surface of the hammer butt 108a, and the hammer shank 108c is resting on a hammer rail cloth 108k attached to a hammer rail 108m. The hammer rail 108m is supported through hammer rail hinges 108n by the action brackets 105b, and the hammer rail hinges 108n are turnably connected to the action brackets 105b. Though not shown in figures 1 and 2, a soft pedal is connected to the hammer rail hinges 108n, and the angular position of the hammer rail 108m is changed by manipulating the soft pedal. On the other hand, the depressed key 101a/101b rotates the whippen assembly 106b and the jack 106e around the whippen flange 106a in the counter clockwise direction, and the jack 106e rotates the hammer assembly 108 in the counter clockwise direction. The swell portion 106i is brought into contact with the regulating button 106j in the acoustic sound mode. Then, the jack 106e is rotated in the clockwise direction, and escapes from the hammer butt 108a. The jack escaping from the hammer butt 108a kicks the hammer butt 108a, and the hammer assembly 108 is rotated toward the set of strings 104. The hammer head 108d rebounds on the strings 104 in the acoustic sound mode, and the vibrating strings 104 generate the acoustic sound. As described hereinbefore, when the swell portion 106i is brought into contact with the regulating button 106j, the jack 106e starts the escape. The escape is completed upon release of the hammer butt 108a from the jack 106e. When the jack 106e starts the escape, the friction between the top surface of the jack 106e and the butt skin 108 and the elastic force of the jack spring 106f, the player feels the depressed key heavier. When the hammer butt 108 is released, the player feels the key 101a/101b lighter, and the change of the load from the rest position to the end position is called as "key touch". The change of the load from the starting point of the escape to the completing point of the escape is called as "after touch", and strongly impresses the key touch on the player. On the other hand, after the strike of the strings, the hammer assembly is rotated in the clockwise direction. When the key 101a/101b reaches the end position, the catcher 108e is brought into contact with the back check 108f. At this time, the motion of the key/key action mechanism is temporarily stopped. Thereafter, the player leaves the finger from the key, and all the components return to the initial positions. Even though the catcher 108e rebounds, the bridle tape 108g links the whippen assembly 106b with the hammer assembly 108, and prevents the set of strings 104 from a double strike. Moreover, while the player is repeating the key, the bridle tape 108g accelerates the returning motion of the hammer assembly. The jack spring 106f urges the jack 106e so as to come into contact with the butt skin 108j again. The key action mechanisms 106, the damper mechanisms 107 and the hammer assemblies 108 are similar to those of a standard upright piano. The electronic system 200 comprises a plurality of key sensors 210 respectively provided under the black and white keys 101a and 101b for producing key position signals KP, a controlling unit 220 responsive to the key position signals KP for generating an audio signal AD and a headphone 230 for generating electronic sounds. The key sensors 210 and the controlling unit 220 are similar to those disclosed in U.S.P. 2,250,065, and no further description is incorporated hereinbelow for the sake of simplicity. The silent system 300 largely comprises a hammer stopper sub-system 320 and an escape accelerating sub-system 330, and the hammer stopper sub-system 320 is linked with the escape accelerating sub-system by means of a link sub-system 340 in this instance. Figures 4 and 5 illustrate the hammer stopper sub-system 320 in detail. The hammer stopper sub-system 320 includes a shaft member 320a rotatably supported by bearing units 320b (see figure 1) bolted to the action brackets 105b. The shaft member 320a horizontally extends in the lateral direction of the acoustic piano 100 between the strings 104 and the hammer shanks 108c at the home position. The hammer stopper sub-system 320 further includes cushion brackets 320c attached to the shaft member 320a at intervals and cushion members 320d respectively fixed to the cushion brackets 320c. The cushion brackets 320c are associated with the strings for high-pitch tones, the strings for middle-pitch tones and the strings for low-pitch tones so that the bearing units 320b rotatably support the shaft member 320a at the action brackets 105b. The hammer stopper sub-system 320 further includes a change-over mechanism 321 manipulative by the player for angularly moving the shaft member 320a, and the change -over mechanism 321 changes the hammer stopper sub-mechanism 320 between a free position and a blocking position. In detail, the change-over mechanism 321 has a lever 321a fixed to the shaft member 320a, a spring member 321b (see figure 1) urging the shaft member 320a in the clockwise direction, a flexible wire 321c engaged at one end thereof to the lever 321a and a nob 321d slidably supported by a bracket 321e fixed to the key bed 103 and connected to the other end of the flexible wire 321c. While no pulling force is exerted on the nob 321d, the spring 321b urges the shaft member 320a so as to direct the cushion members 320d downwardly as shown in figure 4, and the hammer stopper sub-system 320 allows the hammer heads 108d to strike the sets of strings 104 without an interruption with the cushion members 320d. The position allowing the hammer heads 108d to strike the strings 104 is referred to "free position FP". On the other hand, if the nob 321d is pulled, the flexible wire 321c rotates the lever 321a, and, accordingly, the shaft member 320a is rotated in the counter clock-wise direction against the elastic force of the spring 321b, and the cushion members 320d are opposed to the hammer shanks 108c. The position thus opposed to the hammer shanks 108c is referred to "blocking position BP". If the player depresses the key 101a/101b, the jack 106e of the key action mechanism 106 rotates the hammer butt 108a, and, thereafter, the jack 106e escapes from the hammer butt 108a. The hammer assemblies 108 rushes toward the strings 104. However, the hammer shanks 108c rebound on the cushion members 320d in the blocking position BP before an impact on the strings 104, and the set of strings 104 does not generate an acoustic sound. The jack 106e completes the escape from the hammer butt 108a at 6 to 8 millimeters between the hammer head 108d and the strings 104, and the hammer shank 108c rebounds on the cushion member 320d after the jack 106e completes the escape from the hammer butt 108a. The hammer stopper sub-system 320 further includes stopper rings 320e fixed to the shaft member 320a by means of pins 320f and protective sheets 320g attached to the opposite surfaces of the cushion brackets 320c. The stopper rings 320e set limits on the axial motion of the shaft member 320a, and the shaft member 320a can not axially move over the stopper ring 320e. The protective sheets 320g is formed of artificial leather, cloth or felt, and take up impact of the damper wires 107d. The escape accelerating sub-system 330 largely comprises the cam members 310 respectively attached to the jacks 106e and a reaction generator 331, and is changed between an active position and an inactive position. While the escape accelerating sub-system 330 is staying in the active position, the cam member 310 cooperates with the reaction generator 331 so as to convert a part of the force exerted on the whippen assembly 106b into a force exerted on the jack 106e for rotating it around the jack flange 106d. The reaction generator 331 includes a shaft member 332 split into two parts 332a and 332b, cushion sheets 333 respectively wrapping the two parts 332a and 332b and a connecting rod member 334 connecting the two parts 332a and 332b to one another. The connecting rod member 334 is bent twice, and is shaped into a U-configuration. Therefore, the connecting rod member 334 forms a gap 335 between the two parts 332a and 332b, and the gap 335 allows the action bracket 105b provided at an intermediate portion of the center rail 105a to be without an interference with the reaction generator 331. The reaction generator 331 further includes a plurality of rod members 336 fixed to the shaft member 332 at intervals and a plurality of bearing units 337 attached to the center rail 105a. The rod members 336 has a straight portions extending in parallel to the shaft member 332, and the straight portions of the rod members 336 are turnably supported by the bearing units 337. For this reason, the shaft member 332 is angularly movable around the bearing units 337, and the cushion sheets 333 becomes closer to or spaced from the rear surface of the jacks 106e. The reaction generator 331 is linked with the hammer stopper sub-system 320 by means of the link sub-system 340 as described hereinbefore. The link sub-system 340 includes a bracket member 340a fixed to the center rail 105a, an inverted L-shaped arm member 340b turnably supported by the bracket member 340a, a connecting rod 340c inserted into a slot formed in one end portion of the inverted L-shaped arm member 340b and an adjusting mechanism 340d provided between the other end portion of the inverted L-shaped arm member 340b and the lever 321a. When the spring member 321b urges the lever 321a in the clockwise direction, the elastic force of the spring member 321b is transferred through the adjusting mechanism 340d to the inverted L-shaped arm member 340b, and the inverted L-shaped arm member 340b is rotated in the clockwise direction around the bracket 340a. As a result, the cushion sheets 333 is spaced from the rear surfaces of the jacks 106e, and the reaction generator 330 remains in the inactive position. On the other hand, if the nob 321d is pulled, the flexible wire 321c rotates the lever 321a in the counter clockwise direction, and the rotation of the lever 321a is transferred through the adjusting mechanism 340d to the inverted L-shaped arm member 340b. As a result, the inverted L-shaped arm member 340b is rotated in the counter clockwise direction, and the shaft member 332 and the cushion sheets 333 become closer to the rear surfaces of the jacks 106e. As a result, the reaction generator 330 causes the escape accelerating sub-system 330 to enter into the active position. The adjusting mechanism 340d includes connecting bolt members 340e and 340f turnably connected to the inverted L-shaped arm member 340b and the lever 321a and a bracket member 340g formed with female threaded portions engaged with the connecting bolt members 340e and 340f, respectively. If the bracket member 340g turns in one direction, the connecting bolt members 340e and 340f are inserted into the bracket members, and the gap between the lever 321a and the inverted L-shaped arm member 340b is decreased. This means that the cushion sheets 333 become slightly spaced from the rear surfaces of the jacks 106e. On the other hand, if the bracket member 340g turns in the opposite direction, the gap is increased, and the cushion sheets 333 are slightly closer to the rear surfaces of the jacks 106e. Thus, the adjusting mechanism 340d appropriately regulates the reaction generator 331 at the active position. Description is hereinbelow made on behaviors of the keyboard musical instrument in the acoustic sound mode and the silent mode. First, a player is assumed to perform a music through the acoustic sounds. The player does not manipulate the nob 321d, and the spring 321b pulls down the lever 321a. As a result, the hammer stopper sub-system 320 and the escape accelerating sub-system 330 remain in the free position FP and the inactive position, respectively, and the keyboard musical instrument is in the acoustic sound mode. Figures 8A and 8B illustrate the key action mechanism 106 and the hammer assembly 108 in the acoustic sound mode. When the player depresses the white key 101b in the performance, the capstan button 101c pushes up the whippen assembly 106b, and the whippen assembly 106b and the jack 106e is rotated around the whippen flange 106a in the counter clockwise direction. The jack 106e is not rotated around the jack flange 106d until the swell portion 106i is brought into contact with the regulating button 106j. As a result, the jack 106e rotates the hammer assembly 108 in the counter clockwise direction. When the swell portion 106i is brought into contact with the regulating button 106j as shown in figure 8A, the rotation of the whippen assembly 106b causes the jack 106e to rotate in the clockwise direction around the jack flange 106d against the jack spring 106f, and the jack 106e escapes from the hammer butt 108a. Thus, the jack 106e starts the escape at the contact with the regulating button 106j, and completes the escape from the hammer butt 108a. At this time, the escape accelerating sub-system 330 in the inactive position does not affect the motion of the jack 106e. After the jack 106e escapes from the hammer butt 108a, the hammer head 108d rushes toward the set of strings 104. However, the hammer stopper sub-system 320 in the free position FP does not interrupts the hammer action. In other words, the hammer head 108d strikes the strings 104. In this instance, when the hammer reaches a point 2 to 3 millimeters spaced from the strings 104 by softly depressing the key not to strike the strings 104, the escape is completed. The hammer head 108d rebounds on the set of strings 104 (as shown in figure 8B), and returns to the home position on the hammer rail cloth 108k. The set of strings 104 vibrates, and generates the acoustic sound. On the other hand, when the player wants to perform a music without an acoustic sound, the player pulls the nob 321d, and the flexible wire 321c rotates the lever 321a in the counter clockwise direction, and the hammer stopper sub-system 320 enters into the blocking position BP. The link sub-system 340 transfers the rotation of the lever 321a to the reaction generator 3310, and the escape accelerating sub-system 330 enters into the active position. Thus, the keyboard musical instrument enters into the silent mode. Figures 9A and 9B illustrate the key action mechanism 106 and the hammer assembly 108 in the silent mode. Assuming now that the player depresses the white key 101b in the silent mode, the capstan button 101c pushes up the whippen assembly 106b, and the whippen assembly 106b and the jack 106e is rotated around the whippen flange 106a in the counter clockwise direction. The rear surface 106n of the jack 106e is brought into contact with the cushion sheet 333 of the reaction generator 331 before the contact between the swell portion 106i and the regulating button 106j as shown in figure 9A. However, the jack 106e does not start the rotation around the jack flange 106d. After the contact with the reaction generator 331, the capstan button 101c is upwardly pushing the whippen assembly 106b and the jack 106e, and the contact point with the reaction generator 331 is moved along the slope 310a (see figure 3) of the cam member 310. While the reaction generator 331 is sliding on the slope 310a, a part of the force for the rotation of the whippen assembly 106b is converted to a force exerted on the jack 106e for rotating in the clockwise direction. As a result, the jack 106e rapidly escapes from the hammer butt 108a, and the escape of the jack 106e is completed at an earlier position where the hammer head 108d reaches 6 to 8 millimeters from the strings 104. The sliding motion along the slope 310a exerts a load against the white key 101b. However, the load is approximately equal to that in the acoustic performance. Even though the jack 106e completes the escape earlier than the escape in the acoustic sound mode, the load is exerted to a finger of the player at the contact with the reaction generator 331 substantially concurrent to the contact between the swell portion 106i and the regulating button sub-system 106j, and the player feels the key touch unchanged. After the escape, the hammer heads 108 rushes toward the set of strings 104 as shown in figure 9B, and the hammer shank 108c rebounds on the cushion member 320d before a strike at the strings 104. Thus, the hammer stopper sub-system 320 prevents the set of strings 104 from the strike of the hammer head 108d, and the set of strings 104 do not vibrate. The escape of the jack 106e in the silent mode is completed earlier than the escape in the acoustic sound mode, and, for this reason, the hammer shank 108 does not get between the jack 106e and the cushion member 320d. After the rebound on the cushion member 320d, the hammer assembly 108 returns to the home position. As will be appreciated from the foregoing description, although the escape accelerating sub-system 330 according to the present invention causes the jack 106e to complete the escape from the hammer butt 108a earlier than the regulating button 106j, the change of the load exerted to the key 101a/101b moving from the rest position to the end position is substantially same as the regulating button 106j. For this reason, the player feels the key touch unchanged between the acoustic sound mode and the silent mode without a capture of the hammer shank 108c between the jack 106e and the hammer stopper sub-system 320. Moreover, the regulating button mechanism 106h is adjustable independently from the adjustment work on the reaction generator 331, and the assembling work and the adjusting work/ the tuning work are easier than the keyboard musical instrument disclosed in Japanese Utility Model Application No. 5-38463. The escape accelerating sub-system 330 according to the present invention is simpler than the spacers insertable beneath the regulating buttons in the silent mode and disclosed in Japanese Utility Model Application No. 5-56462, and the reaction generator 331 is less affectable by an aged deterioration rather than the spacers. Second Embodiment Figure 10 illustrates essential parts of another keyboard musical instrument embodying the present invention. The keyboard musical instrument implementing the second embodiment also largely comprises an acoustic piano 500, an electronic system (not shown) and a silent system 600. The acoustic piano 500 is similar to the acoustic piano 100, and component parts of the acoustic piano 500 are labeled with the same references as those of the acoustic piano 100 without detailed description. The silent system 600 includes a hammer stopper sub-system 610, an escape accelerating sub-system 620 and a link mechanism 630, and the hammer stopper sub-system 610 and the link mechanism 630 are similar to those of the first embodiment. For this reason, description is focused on the escape accelerating sub-system 620 only for the sake of simplicity. The escape accelerating sub-system 620 is implemented by a reaction generator 621 only. As to the reaction generator 621, the contact point with the jack in the active position is limited, and a cum is not provided on the jack 106e. In other words, the reaction generator 621 is similar to the reaction generator 310 except for the cum 310 and the contact point with the jack 106e. In detail, the jack 106e is turnable around the jack flange 106d, and a pin 501 provides a center of the turning motion. The reaction generator 621 is arranged in such a manner that the distance between the pin 501 and a contact point with the rear surface 106n is shorter than the distance between the pin 501 and the swell portion 106i. In this instance, the reaction generator 621 serves as a reaction generating means. In the silent mode, the jack 106e is brought into contact with the reaction generator 621 at the point 502, and the point 502 provides a reaction point to the turning motion of the jack 106e. Since the distance between the pin 501 and the point 502 is shorter than the distance between the pin 501 and the swell portion 106i, the angular velocity at the leading end 503 of the jack 106e is larger than the angular velocity in the acoustic sound mode, and the jack 106e completes the escape in the silent mode earlier than the escape in the acoustic sound mode. The rear surface 106n of the jack 106e is brought into contact with the reaction generator 621 substantially in concurrence with the contact between the swell portion 106i and the regulating button 106j, and, for this reason, the player feels the key touch unchanged. However, the jack 106e completes the escape in the silent mode earlier than the escape in the acoustic sound mode, and the hammer shank 108c never get between the jack 106e and the hammer stopper 610. The escape accelerating sub-system 620 is simpler than the escape accelerating sub-system 330, and achieves all the advantages over the prior arts. Although particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention as defined in the appended claims. For example, the upright piano may be replaced with another keyboard musical instrument such as, for example, a grand piano, a harpsichord or a celesta. If a grand piano is used, the term "hammer butt" is read as "hammer roller", then the description is applicable to the keyboard musical instrument having the grand piano. The keyboard musical instrument according to the present invention may be equipped with an automatic playing system for reproducing a performance by selectively actuating the keys. In this instance, the keyboard musical instrument according to the present invention further has a playback mode and/or a recording mode. The hammer stopper 320 and the reaction generator 330 may be changed by means of an electric motor unit or a solenoid-operated actuator, and may be respectively associated with change-over means for independently changing the positions. Finally, the hammer stopper sub-system may have a plurality of cushion peaces moved in a lateral direction by a half of the pitch between the adjacent hammer shanks. In this instance, if the cushion peaces are opposed to the hammer shanks in the silent mode, the hammer shanks rebound on the cushion peaces. However, if the cushion peaces are moved by the half pitch, the hammer shanks pass the gaps between the cushion peaces.

Claims: A keyboard musical instrument having at least an acoustic sound mode for a performance through acoustic sounds and a silent mode for a performance without an acoustic sound, comprising: an acoustic keyboard instrument (100; 500) including a keyboard (101) having a plurality of keys (101a/101b) respectively assigned to notes of a scale and selectively depressed by a player in both of said acoustic sound mode and said silent mode, a plurality of key action mechanisms (106) functionally connected to said plurality of keys (101a/101b), respectively, and having respective jacks (106e), each jack having a first portion (106n) and a second portion (106g) angularly spaced from said first portion (106n), and a regulating sub-mechanism (106h) associated with said jacks (106e), said second portions (106 g) of said jacks being brought into contact with said regulating sub-mechanism (106h) so as to start escapes when said plurality of keys (101a/101b) are depressed by said player in both of said acoustic sound mode and said silent mode, a plurality of hammer assemblies (108) respectively associated with said plurality of key action mechanisms (106) and respectively driven for rotation through said escapes of the first portions (106n) of said jacks (106e) by said plurality of key action mechanisms (106) when said player selectively depresses said plurality of keys (101a/101b), and a plurality of string means (104) respectively assigned to said notes and respectively struck by said plurality of hammer assemblies (108) for producing acoustic sounds in said acoustic sound mode; and a silent system (300; 600) including a hammer stopper (320; 610) changed between a free position (FP) in said acoustic sound mode and a blocking position (BP) in said silent mode, said plurality of hammer assemblies (108) being allowed to strike said plurality of string means (104) without an interruption of said hammer stopper in said free position (FP), said plurality of hammer assemblies (108) rebounding on said hammer stopper (320; 610) in said blocking position (BP) before a strike at said string means (104), and an escape accelerator (330; 620) associated in said plurality of key action mechanisms (106) and causing said jacks (106e) to complete said escapes in said silent mode earlier than in said acoustic sound mode, wherein said escape accelerator (330; 600) exerts force on said first portions (106n) of said jacks (106e) in said silent mode for accelerating said escape. The keyboard musical instrument as set forth in claim 1, in which said escape accelerator (330) includes a reaction generator (331) changed between an inactive position in said acoustic sound mode and an active position in said silent mode, and cam members (310) respectively attached to surfaces (106n) of said jacks (106e) and engaged with said reaction generator (331) maintained in said active position when said plurality of keys (101a/101b) depressed by said player move said plurality of key action mechanisms (106), each of said cam members (310) engaged with said reaction generator (331) forcing the associated jack (106e) to complete the escape in said silent mode earlier than the escape in said acoustic sound mode. The keyboard musical instrument as set forth in claim 2, in which each of said cam members (310) has a first surface (310b) spaced from the surface (106n) of the associated jack (106e) and a second surface (310a) connecting said surface (106n) of said associated jack (106e) to said first surface (310b), an engaging point with said reaction generator (331) being moved from said surface (106n) of said associated jack (106e), said second surface (310a) and said first surface (310b) so as to force said associated jack (106e) to escape from the associated hammer assembly (108). The keyboard musical instrument as set forth in claim 3, in which the surface (106n) of said associated jack (106e) is engaged with said reaction generator (331) substantially in concurrence with said contact between said jack (106e) and said regulating sub-mechanism (106h). The keyboard musical instrument as set forth in claim 1, in which said escape accelerator (620) includes a reaction generating means (621) changed between an inactive position in said acoustic sound mode and an active position in said silent mode, each of said jacks (106e) being engaged with said reaction generating means (621) maintained in said active position so as to be forced to escape from the hammer assembly (108), a distance between a turnably supporting point (501) of said each of said jacks (106e) and an engaging point (502) with said reaction generating means (621) being shorter than a distance between said turnably supporting point (501) and the contact point (106i) with said regulating sub-mechanism (106h). The keyboard musical instrument as set forth in any of claims 2-5, in which said silent system (300;600) further includes a link mechanism (340; 630) connecting said hammer stopper (320; 610) to said reaction generating means (331; 621) so as to synchronize a change between said free position (FP) and said blocking position (BP) with a change between said inactive position and said active position. The keyboard musical instrument as set forth in claim 6, in which said link mechanism (340; 630) has an adjusting sub-mechanism (340e/340f/340g) for regulating said active position of said reaction generating means (331;621) with respect to said jacks (106e). The keyboard musical instrument as set forth in any of the preceding claims , further comprising an electronic system responsive to key motions of the keys depressed by said player in said silent mode for generating electronic sounds having the notes of said scale corresponding to said keys depressed by said player.

Inventors: AOYAGI TAKASHI, HAYASHIDA HAJIME, INOUE SATOSHI, AOYAGI, TAKASHI, HAYASHIDA, HAJIME, INOUE, SATOSHI
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1995
Main classification: G10C3
IPC codes: G10C1, G10C3, G10C5