Keyboard musical instrument equipped with hammer shank stopper where hammer assembly rebounds without deflection of shank

Abstract: An acoustic upright piano (10), an electronic sound system (20) and a hammer stopper (31) form in combination a keyboard musical instrument for generating acoustic sounds in an acoustic sound mode and electronic sounds in an electronic sound mode, and the hammer stopper (31) has a rotatable shaft (31a) extending in a lower space under damper blocks of damper assemblies, cushion members (31c) projecting into an upper space over the damper blocks and connecting brackets (31b) provided between the rotatable shaft (31a) and the cushion members (31c), thereby perfectly interrupting hammer (17) motions before an impact on strings (13) in the electronic sound mode.

Description: FIELD OF THE INVENTION This invention relates to a keyboard musical instrument performable selectively through acoustic sounds and electronic sounds, more particularly, to a keyboard musical instrument equipped with a hammer shank stopper where a hammer assembly rebounds without deformation of the hammer shank for preventing strings from an impact. DESCRIPTION OF THE RELATED ART A typical example of the acoustic piano has a soft pedal linked with a hammer rail or a key frame, and the player makes the home positions of the hammer assemblies closer to the strings or offset from the strings by stepping on the soft pedal. When the hammer assemblies become closer to or offset from the strings, the hammer head softly strikes the associated set of strings or strikes the associated strings fewer than the normal number of the strings so as to lessen the loudness. Such a soft pedal is usually used for an artistic representation. Piano tones are too loud for neighbors living an apartment house to be comfortable, and various silencers have been proposed. As used in the present application, the terms "silencer", "silencer system", and "silent system" are used synonymously to designate a mechanism which enables fingering on the keyboard while preventing the generation of acoustic tones or sounds by the strings. One of the silencers is disclosed in U. S. Patent No. 2,250,065, and the silencer picks up the hammer assemblies so as to space them from the key action mechanisms. Even if a player fingers on the keyboard, the depressed keys merely moves the key action mechanisms only, and the hammer assemblies are not driven for rotation by the key action mechanisms. An electronic sound generator is incorporated in the piano disclosed in the U.S. Patent, and generates electronic sounds instead of the acoustic sounds. However, the key touch is quite different from that of the acoustic piano due to the separation of the hammer assemblies from the key action mechanisms, and the piano equipped with the silencer does not satisfy a senior pianist. Another silent system is disclosed in Japanese Patent Publication of Unexamined Application No. 6-59667, and the prior art silent system is illustrated in figure 1 of the drawings. The Japanese Patent Publication of Unexamined Application publishes the invention disclosed in Japanese Patent Application No. 5-157934 which was filed under the domestic priority right of Japanese Patent Application No. 4-174813. Japanese Patent Application No. 4-174813 further provided the Convention Priority Right to U.S. Serial No. 08/073,092, and the U.S. Patent Application resulted in U.S. Patent No. 5,374,775 issued on December 20, 1994. The silent system includes a hammer stopper 1 provided in a narrow space between hammer assemblies 2 and damper assemblies 3. Though not shown in figure 1, a key of the keyboard is functionally connected to a key action mechanism, and the key action mechanism rotates the hammer assembly 2. The damper assembly 3 is respectively provided for a set of string 4, and leaves the associated strings during a hammer impact on the strings 4. When the hammer assembly 2 strikes the strings 4, the strings 4 vibrate for generating an acoustic tone. The function of tone generation is similar to that of an acoustic piano. A rotatable shaft 1a, bracket members 1b and cushion members 1c form parts of the hammer stopper 1. The brackets 1b are attached to the rotatable shaft 1b at intervals in the longitudinal direction of the shaft 1a, and the cushion members 1c are respectively fixed to the cushion members 1b. The rotatable shaft 1a is rotatably supported by side board members, and a driving means such as a motor unit or a manipulative link mechanism bi-directionally rotates the shaft so as to change the cushion members 1c between a free position FP and a blocking position BP. While the cushion members 1c are in the free position FP, the hammer assembly 2 can strike the strings without an interruption of the hammer stopper 1, and the strings 4 generate the acoustic tone. On the other hand, if the cushion member 1c is changed into the blocking position, the hammer assembly 2 rebounds on the cushion member 1c before an impact on the strings 4, and a tone generator (not shown) generates an electronic sound through a headphone. In the prior art keyboard musical instrument disclosed in the Japanese Patent Publication of Unexamined Application, a depressed key actuates the associated key action mechanism, and the jack of the key action mechanism escapes from the associated hammer assembly 2 in both performances through the acoustic tones and the electronic tones. When the jack escapes from the hammer assembly 2, the player feels the unique key touch, and the hammer assembly starts the free rotation toward the strings 4. Thus, the prior art keyboard musical instrument gives the unique key touch to the player, and selectively generates the acoustic tones and the electronic tones. However, the prior art keyboard musical instrument shown in figure 1 encounters a problem in installation of the hammer stopper 1. In detail, a regulating button (not shown) is incorporated in the prior art keyboard musical instrument, and the jack escapes from the hammer assembly upon contact with the regulating button. The distance between the hammer head 2a and the strings 4 at the escaping point is usually regulated to several millimeters, and the hammer stopper 1 in the blocking position BP is expected to interrupt the free rotation of the hammer assembly between the escaping point and the impact on the strings 4. The hammer stopper 1 is located below the damper head 3a, and allows the damper head 3a to retract into a space over the hammer stopper 1. This means that the boss portion of the hammer shank 2b rebounds on the cushion member 1c, and the deformation of the hammer shank 2b at the rebound is not ignoreable. If the hammer stopper 1 is too close to the strings 4, the deformed hammer shank 2b allows the hammer head 2a to touch the strings, and noisy sound is mixed with the electronic tone. On the other hand, if the hammer stopper is too far from the strings 4, the hammer assembly 2 may never strike the strings 4. However, there is a risk of capture of hammer shank 2b between the jack and the hammer stopper 1. Of course, the undesirable capture is avoidable by regulating the escape to an early point. However, such an unusual regulation destroys the unique key touch. The deformation of the hammer shank 2b exerts undesirable load on the hammer butt and the butt flange. The problem may be eliminated from the hammer assemblies 2 by installing the hammer stopper 1 in a space over the damper head 3a, because the leading end portion of the hammer shank 2b rebounds on the cushion member 1c. When the leading end portion of the hammer shank 2b rebounds on the cushion member 1c, the hammer shank 2b is less deformed rather than the rebound of the boss portion because of the short distance between the rebounding point and the hammer head 2a. However, the installation over the damper head 3a is not feasible. In detail, the hammer heads 2 are different in not only the size. The hammer heads 2a for the low pitch tones are largest, and the hammer heads 2a become small from the low pitch tones through middle pitch tones to the high pitch tones. The position of the hammer head 2a and the positions of the damper heads 3a are not constant. For example, the hammer heads 2a for several middle pitch tones are higher than the others, and the associated damper heads 3a are also held in contact with the strings 4 at higher positions than the others. This is because of the fact that the strings 13 cross other strings 13 around these several middle pitch tones. Moreover, the damper block screw 3b rearwardly projects from the damper head 3a, and makes the available space intermittently narrow. As a result, the hammer heads 2a and the damper heads 3a complicate the space available for the hammer stopper 1, and the straight rotatable shaft 1a hardly extends across the complicated space. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a keyboard musical instrument a hammer stopper of which is free from the problems inherent in the prior art keyboard musical instrument. To accomplish the object, the present invention proposes to position a rotatable shaft and a cushion member in a lower sub-space and an upper sub-space, respectively. In accordance with the present invention, there is provided a keyboard musical instrument allowing a player to perform a music selectively through acoustic sounds and electronic sounds, as set forth in claim 1. Preferred embodiments of the invention may be gathered from the dependent claims. 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 side view showing the hammer stopper incorporated in the prior art keyboard musical instrument; Fig. 2 is a front view showing the structure of a keyboard musical instrument according to the present invention; Fig. 3 is a side view showing relation among key action mechanisms, damper assemblies, hammer assemblies, strings and a hammer stopper; Fig. 4 is a front view showing a hammer stopper incorporated in the keyboard musical instrument; Fig. 5 is a bottom view showing the hammer stopper; Fig. 6 is a side view showing the hammer stopper; Fig. 7 is a side view showing the hammer stopper in the blocking position; Fig. 8 is a plan view showing another connecting frame; Fig. 9 is a side view showing a hammer stopper and a damper assembly incorporated in another keyboard musical instrument according to the present invention; Figs. 10A and 10B are modifications of the hammer stopper; and Fig. 11 is a partially cut-away side view showing a damper assembly incorporated in yet another keyboard musical instrument according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring first to figure 2 of the drawings, a keyboard musical instrument embodying the present invention largely comprises an upright piano 10, an electronic sound generating system 20 and a silent system 30, and selectively enters into an acoustic sound mode and an electronic sound mode. While the keyboard musical instrument is staying in the acoustic sound mode, a player can perform a music through acoustic sounds. On the other hand, the player can perform the music through electronic sounds in the electronic sound mode. In the following description, word "front" means a position closer to a player than a position labeled with "rear", and directions "clockwise" and "counter clockwise" are determined on a sheet where a rotating part is illustrated. The upright piano 10 includes a keyboard 11 provided over a key bed 12. Eighty-eight black and white keys 11a form in combination the keyboard 101, and are turnable around balance pins (not shown). The black and white keys 11a extend in a fore-and-aft direction of the upright piano, and front end portions of the black and white keys 11a are exposed to a player. While a force is not being exerted by the player, the black and white keys 11a are staying in respective rest positions. When the player depresses the black and white keys 11a, the black and white keys 11a are downwardly moved, and arrive at respective end positions. Notes of a scale are respectively assigned to the black and white keys 11a, respectively. The upright piano 10 further includes a plurality of sets of strings 13 as shown in figure 3. The plurality of sets of strings 13 extend in front of a frame (not shown), and are stretched between tuning pins (not shown) and hitch pins (not shown). A center rail 14a laterally extends over the rear end portions of the black and white keys 11a, and is bolted to action brackets 14b at both ends and an intermediate point thereof. The upright piano 10 further includes a plurality of key action mechanisms 15 functionally connected to the black and white keys 11a, a plurality of damper mechanisms 16 actuated by the key action mechanisms 15 for momentarily leaving the associated sets of strings 13 and a plurality of hammer assemblies 17 driven for rotation by the key action mechanisms 15. When the player depresses one of the black and white keys 11a, the depressed key 11a causes the damper mechanism 16 to leave the set of strings 13, and actuates the key action mechanism 15 so as to drive the hammer assembly 108 for a free rotation. The hammer assembly 17 strikes the set of strings 13 in the acoustic sound mode, and the vibrating strings 13 generate an acoustic sound. When the player releases the key 11a, the key action mechanism 15 and the hammer assembly 17 return to the initial status or home positions thereof, and the damper mechanism 16 is brought into contact with the strings 13 again, thereby absorbing the vibrations of the strings 13. The key action mechanisms 15 are similar in arrangement to one another, and each key action mechanism 15 includes a whippen flange 15a bolted to a lower end portion of the center rail 14a and a whippen assembly 15b turnably connected to the whippen flange 15a. The whippen assembly 15b has a heel 15c held in contact with a capstan screw 11c implanted into the rear end portion of the black or white key 11a. The key action mechanism 15 further includes a jack flange 15d upright from a middle portion of the whippen assembly 15b, a jack 15e turnably supported by the jack flange 15d, a jack spring 15f inserted between the whippen assembly 15b and a toe 15g of the jack 15e and a regulating button mechanism 15h opposed to the toe 15g. The jack 15e has an L-shape, and a swell 15i is formed in the upper portion of the toe 15g. The jack spring 15f urges the jack 15e in the counter clockwise direction at all times. While the black or white key 11a is staying in the rest position, the whippen assembly 15b is horizontally maintained as shown in figure 3, and the swell 15i of the toe 15g is spaced from the regulating button mechanism 15h. The regulating button mechanism 15h has a regulating button 15j, and the gap between the swell portion 15i and the regulating button 15j is changed by turning a regulating screw 15k. If the gap between the swell portion 15i and the regulating button 15j is increased, the jack 15e escapes from the hammer assembly 17 later. On the other hand, if the gap is decreased, the jack 15e escapes earlier. When the swell portion 15i of the toe 15g is brought into contact with the regulating button 15j, the reaction impedes the turning motion of the whippen assembly 15b and, accordingly, the downward motion of the depressed key 11a, and the player feels the key 11a heavier than before. Thus, the jack 15e and the regulating button mechanism 15h deeply concern a key-touch, and the position of the regulating button 15j defines the starting point of the escape of the jack 15e. The damper mechanisms 16 are similar in arrangement to one another, and each damper mechanism 16 includes a damper lever flange 16a fixed to an upper surface of the center rail 14a, a damper lever 16b rotatably supported by the damper lever flange 16a, a damper spoon 16c implanted into the rear end portion of the whippen assembly 15b, a damper wire 16d projecting from the damper lever 16b, a damper head 16e fixed to the damper wire 16d and a damper spring 16f urging the damper lever 16b in the counter clockwise direction. A damper block 16g, a damper wood 16h, damper felts 16i and a damper block screw 16j as a whole constitute the damper head 16e, and the damper spring 16f presses the damper felts 16i against the set of strings 13. The damper wire 16d is inserted into a mid point of the damper block 16g in the fore-and-aft direction, and the damper block screw 16j fixes the damper wire 16d to the damper wood 16h. The damper screw 16j projects from the front surface of the damper block 16g. For this reason, a space below the lower surface of the damper block 16g is wider than a space over the lower surface of the damper block 16g. While the black or white key 11a is staying in the rest position, the damper spoon 16c does not push the damper lever 16b, and the damper head 16e with the damper felts 16i is held in contact with the set of strings 13. If the player depresses the black or white key 11a from the rest position to the end position, the capstan screw 11c pushes up the whippen assembly 15b, and the whippen assembly 15b turns in the counter clockwise direction, thereby causing the damper spoon 16c to rearwardly push the lower portion of the damper lever 16b. As a result, the damper lever 16b is rotated in the clockwise direction, and the damper felts 16i leave the set of strings 13. On the other hand, when the black or white key 11a is released, the whippen assembly 16b turns in the clockwise direction, and the damper spoon 16c removes the pressure from the damper lever 16b. As a result, the damper spring 16f urges the damper lever 16b in the counter clockwise direction, and the damper felts 16i are brought into contact with the set of strings 13 again. The hammer assemblies 17 are also similar in arrangement to one another. Each of the hammer assemblies 17 includes a hammer butt 17a turnably supported by a butt flange 17b fixed to the center rail 14a, a hammer shank 17c upwardly projecting from the hammer butt 17a, a hammer head 17d fixed to the leading end of the hammer shank 17c, a catcher 17e projecting from the hammer butt 17a, a back check 17f implanted into the front end portion of the whippen assembly 15b, a bridle tape 17g extending between the catcher 17e and a bridle wire 17h implanted into the front end portion of the whippen assembly 15b and a butt spring 17i urging the hammer butt 17a in the clockwise direction. While the black or white key 11a is staying in the rest position, the top surface of the jack 15e is held in contact with a butt skin 17j attached to a lower surface of the hammer butt 17a, and the hammer shank 17c is resting on a hammer rail cloth 14c attached to a hammer rail 14d. The hammer rail cloth 14c defines initial status or a home position of the hammer assembly 17. A space is formed between the strings 13 and the hammer assemblies 17 at the home positions, and the damper assemblies 16 are installed and moved in the space. For this reason, the space is partially occupied by the damper assemblies 16, and a secondary space is left in the space. The secondary space is imaginary divided into a lower sub-space below the lower surfaces of the damper assemblies 16 and an upper sub-space over the lower surfaces, and the lower sub-space and the upper sub-space are available for the silent system 30. The hammer rail 14d is supported through hammer rail hinges 14e by the action brackets 14b, and the hammer rail hinges 14e are turnable around the action brackets 14b. A soft pedal 18a (see figure 2) is connected to the hammer rail hinges 14e, and the angular position of the hammer rail 14d is changed by manipulating the soft pedal 18a. On the other hand, while the depressed key 11a is rotating the whippen assembly 15b and the jack 15e around the whippen flange 15a in the counter clockwise direction, the jack 15e pushes up and rotates the hammer assembly 17 in the counter clockwise direction. When the swell portion 15i is brought into contact with the regulating button 15j, the jack 15e is rotated in the clockwise direction around the jack flange 15d, and escapes from the hammer butt 17a. The jack 15e kicks the hammer butt 17a at the escape, and the hammer assembly 17 starts a free rotation toward the set of strings 13. In this instance, the hammer assembly 17 starts the free rotation at 3 to 5 millimeters between the strings 13 and the hammer head 17d. If the keyboard musical instrument is operating in the acoustic sound mode, the hammer head 17d strikes the strings 13, and the vibrating strings 13 generate the acoustic sound having the note assigned to the depressed key 11a. As described hereinbefore, when the swell portion 15i is brought into contact with the regulating button 15j, the jack 15e starts the escape. The escape is completed upon the release from the hammer butt 17a. When the jack 15e starts the escape, friction between the top surface of the jack 15e and the butt skin 17j and the elastic force of the jack spring 15f cause the player to feel the depressed key 11a heavy. When the jack 15e completes the escape or the hammer butt 17a starts the free rotation, the friction is removed, and the jack spring 15f is stretched again so as to recover the jack 15e into the initial status with respect to the whippen assembly 15b. As a result, the player feels the key 11a 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. After the strike of the strings, the hammer assembly 17 turns in the clockwise direction. When the key 11a reaches the end position, the catcher 17e is brought into contact with the back check 17f. 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 17e rebounds on the back check 17f, the bridle tape 17g links the whippen assembly 15b with the hammer assembly 17, and prevents the set of strings 13 from a double strike. Moreover, if the player repeats the key 11a, the bridle tape 17g accelerates the returning motion of the hammer assembly 17, and the jack spring 15f urges the jack 15e so as to come into contact with the butt skin 17j again. The key action mechanisms 15, the damper mechanisms 16 and the hammer assemblies 17 are similar to those of a standard upright piano. Turning back to figure 2 of the drawings, the electronic system 20 comprises a plurality of key sensors 21 respectively provided under the black and white keys 11a for producing key position signals KP indicative of actual key positions, a controlling unit 22 responsive to the key position signals KP for generating an audio signal AD and a headphone 23 for generating electronic sounds. The key sensors 21 and the controlling unit 22 are similar to those disclosed in U.S.P. 5,374,775, and no further description is incorporated hereinbelow for the sake of simplicity. Referring to figure 3 of the drawings again, the silent system 30 includes a hammer stopper 31, and a rotatable shaft 31a, a connecting frame 31b, cushion members 31c for the hammer shanks 17c, a link mechanism 31d, a pedal 31e and cushion members 31f and 31g form in combination the hammer stopper 31. The rotatable shaft 31a is supported by suitable bearing units (not shown) mounted on metal brackets 32 of, for example, steel, and the metal brackets are fixed to the upper surface of the center rail 14a. The metallic brackets 32 are aligned with the action brackets 14b, and do not interfere in the motions of the key action mechanisms 15. The rotatable shaft 31a laterally extends in parallel to the center rail 14a in the lower sub-space of the afore-mentioned secondary space. The connecting frame 31b is connected at the boss portion thereof to the rotatable shaft 31a, and projects into the upper sub-space of the secondary space. As shown in figures 4 and 5, the connecting frame 31b is split into sections 31ba, 31bb and 31bc, and the action brackets 14b do not interfere in the angular motion of the hammer stopper 31. The hammer heads 17d for the several middle pitch tones are higher than the other hammer heads 17d, and the damper heads 16e are also higher than the others. For this reason, the middle section 31bb is upwardly curved, and allows the cushion member 31c to be opposed to the leading end portions of the hammer shanks 17c. The cushion members 31c are attached to the front surface of the connecting frame 31b, and are opposed to leading end portions of the hammer shanks 17c. The cushion members 31f are directly attached to the rotatable shaft 31a, and are opposed to the damper wires 16d. The cushion members 31g are attached to the rear surface of the connecting frame 31b, and the damper block screws 16j are brought into contact with the cushion members 31g. The height of the rotatable shaft 31a is equal to that of the prior art hammer stopper 1. However, the rotatable shaft 31a is adjusted in the fore-and-aft direction to a position where the damper wires 16d are brought into contact with the cushion members 31f upon arrival at maximum. Thus, the rotatable shaft 31a serves as a damper rail, and no damper rail is incorporated in the keyboard musical instrument. The lower sub-space is wide enough to accommodate the rotatable shaft 31a, the cushion members 31f and the boss portion of the connecting frame 31b. Although the upper sub-space is narrower than the lower sub-space, it allows the leading end portion of the connecting frame 31b and the cushion members 31c to be changed between a free position and a blocking position. In order to decrease a moment exerted on the connection between the rotatable shaft 31a and the connecting frame 31b, it is desirable to make the rotatable shaft 31a as close to the lower surface of the damper blocks 16j as possible. As shown in figure 6 of the drawings, an arm member 31da is fixed to the rotatable shaft 31a, and a flexible wire 31db connects the arm member 31da to the pedal 31e. A return spring 31dc is further connected between the arm member 31da and a suitable stationary member, and urges the hammer stopper 31 in the counter clockwise direction. The arm member 31da, the flexible wire 31db and the return spring 31dc form parts of the link mechanism 31d. Stopper rings 31h are bolted to both end portions of the rotatable shaft 31a, and the stopper rings 31h maintain the alignment between the hammer stopper 31 and the hammer assemblies 17 in cooperation with counter members (not shown) fixed to the action brackets 14b. If the player steps on the pedal 31e, the shaft 31a and, accordingly, the cushion members 31c turn in the clockwise direction, and the hammer stopper 31 is changed from a free position to a blocking position. The connecting frame 31b is rigid, and the deflection due to the rebound of the hammer shanks 17c is ignoreable. The connecting frame 31b is rearwardly bent, and the cushion members 31c in the free position are maintained out of the trajectories of the hammer shanks 17c in the acoustic sound mode. While the hammer stopper 31 is staying in the free position, the hammer assemblies 17 strike the strings 13 without an interruption of the hammer stopper, and the strings 13 generate the acoustic sounds. On the other hand, the cushion members 31c in the blocking position are in the trajectories of the hammer shanks 17c, and the hammer shanks 17c rebound on the cushion members 31c before the hammer heads 17d reach the strings 13. When the hammer shank 17c rebounds on the cushion member 31c, the front surface of the cushion member 31c is in parallel to the hammer shank 17c as shown in figure 7. This feature, i.e., the parallel contact between the hammer shank 17c and the cushion member 31c is desirable, because the hammer shank 17c exerts a force in the tangential direction only. The hammer stopper 31 does not undesirably shake, and is prevented from breakage. Thus, the cushion members 31c receive the hammer shanks 17c in parallel, and are equal in thickness over the width. The hammer assembly 17 and the damper assembly 16 shown in figure 7 are provided for the strings 13 for a high pitch tone. If the player releases the pedal 31e, the return spring 31dc changes the hammer stopper 31 from the free the cushion members 31c enters into the blocking position. In this instance, the hammer assembly 17 starts the free rotation at respective positions where the hammer heads 17d reach 3 to 5 millimeters from the strings 13, and the hammer stopper 31 can perfectly prevent the strings 13 from undesirable vibrations in the electronic sound mode. The prior art hammer stopper 1 shown in figure 1 requires 10 to 15 millimeters so as to perfectly prevent the strings 4 from undesirable vibrations due to the deflection. In this instance, only the section 31bb is partially bent. However, another connecting frame 41 may have sections 41a, 41b and 41c which have respective front edges differently spaced from a rotatable shaft 42. As described hereinbefore, the hammer heads 17d are different in size, and a space between the hammer heads 17d and the damper heads 16e is increased from the low pitch tones through the middle pitch tones to the high pitch tones. In this situation, the sections 41a, 41b and 41c allow the manufacturer to change the positions of the cushion members, and all the hammer shanks 17c rebound on the cushion members at leading end portions as close to the hammer heads 17d as possible. Description is hereinbelow made on the behaviors of the keyboard musical instrument in a performance on the keyboard. First, a player is assumed to perform a music through the acoustic sounds. The player keeps the pedal 31e released, and the return spring 31dc urges the arm member 31da in the counter clockwise direction. As a result, the hammer stopper 31 remains in the free position, and the keyboard musical instrument is in the acoustic sound mode. When the player depresses the key 11a in the performance, the capstan button 11c pushes up the whippen assembly 15b, and the whippen assembly 15b and the jack 15e are rotated around the whippen flange 15a in the counter clockwise direction. The jack 15e is not rotated around the jack flange 15d until the swell portion 15i is brought into contact with the regulating button 15j. The jack 15e pushes the hammer butt 17a, and forcibly rotates the hammer assembly 17 in the counter clockwise direction. The depressed key 11a declines the damper soon 16c, and the damper spoon 16c pushes the lower portion of the damper lever 16b in the clockwise direction. The damper felts 16i leaves the strings 13, and allow the strings 13 to vibrate. When the damper wire 16d is brought into contact with the cushion member 31f, the damper assembly 16 stops the rotation in the clockwise direction, and is maintained on the cushion member 31f. If the damper block screw 16j widely projects from the damper block 16g, the damper block screw 16j may be brought into contact with the cushion member 31g. In this situation, the damper assembly 16 is maintained on the cushion member 31g. When the swell portion 15i is brought into contact with the regulating button 15j, the rotation of the whippen assembly 15b causes the jack 15e to rotate in the clockwise direction around the jack flange 15d against the jack spring, and the jack 15e escapes from the hammer butt 17a. Thus, the jack 15e starts the escape at the contact with the regulating button 15j, and completes the escape from the hammer butt 17a. The player feels the key touch as similar to a standard acoustic upright piano. After the jack 15e escapes from the hammer butt 17a, the hammer assembly 17 starts the free rotation toward the set of strings 13. The hammer stopper 31 in the free position does not interrupt the hammer action, and the hammer head 17d strikes the strings 13. The hammer head 17d rebounds on the set of strings 13, and returns to the home position on the hammer. The set of strings 13 vibrates, and generates the acoustic sound. On the other hand, if the player wants to perform music without an acoustic sound, the player steps on the pedal 31e, and engages the pedal 31e with a step 31i (see figure 2). The pedal 31e pulls down the flexible wire 31db, and the flexible wire 31db rotates the arm member 31da in the clockwise direction. The hammer stopper 31 enters into the blocking position, and the cushion members 31c are positioned in the trajectories of the hammer shanks 17c. Thus, the keyboard musical instrument enters into the electronic sound mode. Assuming now that the player depresses the key 11a during the performance in the electronic sound mode, the capstan button 11c pushes up the whippen assembly 15b, and the whippen assembly 15b and the jack 15e are rotated around the whippen flange 15a in the counter clockwise direction. The damper assembly 16 behaves similar to that in the acoustic sound mode, and the behavior is not described for avoiding repetition. The swell portion 15i is brought into contact with the regulating button 15j, and the rotating whippen assembly 15b causes the jack 15e to escape from the hammer butt 17a as similar to that in the acoustic sound mode. The cushion members 31c in the upper sub-space prevent the hammer shanks 17c from undesirable wide deflection, and the escaping point is regulated to that of the standard acoustic upright piano. For this reason, the hammer shank 17c is never caught between the jack 15e and the hammer stopper 31. While the jack 15e is escaping form the hammer butt 17a, the key action mechanism 15 varies the load exerted on the finger, and the player feels the key touch as usual. After the escape, the hammer heads 17d starts the free rotation toward the set of strings 13, and the hammer shank 17c rebounds on the cushion member 31c before striking the strings 13. The leading end portion of the shank 17c is brought into contact with the cushion member 31c, and the hammer shank 17c is merely deflected slightly. For this reason, although the escaping point is not changed, the hammer head 17d does not touch the strings 13, and the acoustic sound is never generated. After the rebound on the cushion member 320d, the hammer assembly 108 returns to the home position. As will be understood from the foregoing description, the cushion members 31c in the upper sub-space cause the hammer shanks 17c to rebound without wide deflection, and the jacks 15e escape from the associated hammer butts 17a at the same points as those of the standard acoustic upright piano. For this reason, the keyboard musical instrument according to the present invention gives the same key touch to the player in both acoustic and electronic sound modes as the standard acoustic upright piano. The difference between the hammer heads 2a and 17d due to the deflection of the hammer shanks 2b and 17c is analyzed as follows. The hammer assembly is a cantilever, and the deflection is in proportional to the cube (third power) of the length. The distance between the rebounding point and the center of hammer head is further assumed to be 49 millimeters for the prior art hammer assembly 2, and 27 millimeters for the hammer assembly 17. Then, the ratio of the deflection is calculated as follows. (27/49) 3 = 0.167 Thus, the rebounding point as close to the center of the hammer head as possible is effective against the undesirable noise due to the touch with the strings. Moreover, the hammer shanks/heads 17c and 17d do not exert large moment on the hammer butts 17a, and the hammer assemblies 17 are less liable to be broken. The present inventors compare the load exerted on the hammer assembly of the prior art hammer assembly 2 with the load exerted on the hammer assembly 17. The hammer assemblies 2 and 17 have the moment of inertia IH and the length L from the rotational center of the hammer butts and the rebounding points. The length L is assumed to be 52 millimeters (L1) for the prior art hammer assembly, and 74 millimeters (L2) for the hammer asembly 17 according to the present inention. The equivalent mass Mel at the rebounding point is calculated for the prior art hammer assembly 2 as follows. Mel = IH/L1 2 The equivalent mass MeL at the rebounding point is calculated for the hammer assembly 17 according to the present invention as follows. MeL = IH/L2 2 The ratio between the equivalent masses is given by Equation 3. Mel/MeL = L1 2 / L2 2 = (L1/L2) 2 = (52/74) 2 = 0.5 Thus, the load exerted on the hammer assembly 17 is decreased to half of that of the prior art, and the hammer shank 17c is less liable to be broken than the hammer shank 2b. Another advantage is derived from the angle of the cushion members 31c. Namely, the angle of the cushion members 31c is regulated in such a manner that the hammer shanks 17c become parallel to the cushion members 31c at the rebound, and an undesirable component in the normal direction is not exerted on the hammer stopper 31. As a result, the hammer stopper 31 is durable. The separation between the cushion members 31c and the rotatable shaft 31a eliminates noise from the performance through the electronic sounds, because the connecting frame 31b absorbs the vibrations due to the imapct against the cushion members 31c. The cushion members 31f attached to the rotatable shaft 31a receive the damper wires 16d, and a damper rail is not required in the keybaord musical instrument according to the present invention. Finally, in case where the edge of the connecting frame 31b is varied depending upon the hammer heads 17d, the manufacturer can optimize the rebounding points. Second Embodiment Turning to figure 9 of the drawings, a hammer stopper 51 is incorporated in another keyboard musical instrument embodying the present invention. The keyboard musical instrument also comprises an acoustic upright piano, an electronic sound system and a silent system, and the hammer stopper 51 forms a part of the keyboard musical instrument. The acoustic upright piano and the electronic sound system are similar to those of the first embodiemnt, and the description is focused on the hammer stopper 51 only for the sake of simplicity. The hammer stopper 51 is provided between hammer assemblies 17 and the damper assemblies 16, and includes a rotatable shaft member 51a, cushion members 51b, a connecting frame 51c and a change-over mechanism (not shown) for changing the cushion members 31c between a free position and a blocking position. The rotatable shaft 51a and the cushion members 51c are similar to those of the hammer stopper 31. However, the connecting frame 51c is partially embossed. As a result, the middle portion of the connecting frame 51c projects from the lower portion and hte upper portion of the connecting frame 51c. While the hammer stopper 51 is staying in the free position, the middle portion 51d allows the damper block screw 16j to project without an interruption of the hammer stopper 51. For this reason, the hammer stopper 51 does not have the cushion embers 31g. Even though the cushion members 31g are not attached to the rear surface of the connecting frame 51c, the damper block screw 16j never generates noise, and the performance through the electronic sounds is more comfortable. A connecting frame 52 may be formed by bonding or welding upper/middle/lower plate members 51e/51f/51g as shown in figure 10A. Figure 10B shows yet another connectig frame 53 constituted by a partially bent plate member 53a and a lower straight plate member 53b bolted to the partially bent plate member 53b. The connecting frames 52 and 53 are desirable, because the manufacturer easily optimizes the difference between the middle portion and the upper/lower portions. In the modification shown in figure 10B, the partially bent plate member 53a may have an elongated bolt hole so as to adjust the cushion members 51b to appropriate positions of the hammer shanks 17c. Third Embodiment Turning to figure 11 of the drawings, a damper head 61 is incorproated in yet another keybaord musical instrument embodying the present invention. The keyboard musical instrument implementing the third embodiment also comprises an acoustic upright piano, an electronic sound system and a silent system. However, the electronic sound system and the silent system are similar to those of the first embodiemnt, and the acoustic upright piano is similar to the upright piano 10 except for the damper assemblies 61. For this reaosn, description is made on the damper asembly 61 only. The damper assembly 61 includes a damper wood 61a, damper felts 61b attached to the damper wood 61a, a damper lever (not shown), a damper wire 61c projecting from the damper lever, and a damper block 61d of metal or plastic resin fixed to the damper wood 61a by means of a damper block screw 61e. A damper block is usually formed of wood, and distance D1 is long so as to prevent the damper block from cracking. However, the damper block 61d of metal or plastic resin is free from cracking, and the distance D1 is shorter than that of the damper block of wood. For this reason, the distance D2 of the damper block 61d is shorter than that of the damper block of wood, and the cushion members 31g are eliminated from the hammer stopper incorporated in the keyboard musical instrument implementing the third embodiment. The damper block of metal or plastic resin is so large in mechanical strength that the manufacturer can make the damper block 61d small. However, wide contact area with the damper wood 61a is required, and, for this reason, a flange 61f is formed along the peripehry of the damper block 61d. 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 keybaord musical instrument according to the present invnetion may be equipped with solenoid-operated actuators provided below the keyboard for an automatic playing, and the controller may record and playback a performance. The key sensors may be replaced with hammer sensors. The hammer sensors monitor hammer motions for determining hammer motions, and a controller decides depressed keys and impacts on the strings on the basis of the hammer motions. The silent system may further include a controlling mechanism for changing gaps between the toes and the regulating buttons. Another controlling mechanism for the regulating buttons may accelerate the jacks so as to quickly escape from the hammer butts in the electronic sound modes. A plurality of shaft members connected through suitable coupling members may form the rotatable shaft 31a. A hand grip manipulative by a player may be connected to the flexible wire, and an electric motor may be directly connected to the rotatable shaft.

Claims: A keyboard musical instrument allowing a player to perform a music selectively through acoustic sounds and electronic sounds, comprising: an acoustic piano (10) including a plurality of keys (11a) selectively fingered by a player during a performance, a plurality of string means (13) vibrative for generating said acoustic sounds, a plurality of hammer assemblies (17) respectively turning from home positions toward said plurality of string means (13) for producing vibrations in said plurality of strings (13), a first space being formed between said plurality of string means (13) and said plurality of hammer assemblies (17) at said home positions, a plurality of key action mechanisms (15) respectively transferring forces exerted on said plurality of keys (11a) to said plurality of hammer assemblies (17) so as to cause said plurality of hammer assemblies (17) to turn, and a plurality of damper assemblies (16; 61) provided in a part of said first space and temporarily spacing from said plurality of string means (13) so as to allow said plurality of string means (13) to vibrate when said plurality of keys (11a) are depressed, a second space being left in said first space; an electronic sound generating system (20) determining depressed keys of said plurality of keys (11a) for generating said electronic sounds corresponding to said acoustic sounds; and a silencer system (30) including a hammer stopper (31; 41; 51; 52; 53) changed between a free position and a blocking position, said hammer stopper (31) in said free position allowing said plurality of hammer assemblies (17) to strike said plurality of string means (13), said hammer stopper (31) in said blocking position causing said plurality of hammer assemblies (17) to rebound thereon without a strike at said plurality of string means (13), characterized in that said hammer stopper (31) has a rotatable shaft (31a; 42; 51a) extending in a lower sub-space of said second space under a virtual plane which is perpendicular to the direction the sting means are stretched in and over which damper blocks (16g; 61d) of said plurality of damper assemblies (16; 61) project, and a cushion means (31c; 51b) supported by said rotatable shaft (31a; 42; 51a), said cushion means being located in an upper sub-space of said second space over said virtual plane and being movable between said free position and said blocking position. The keyboard musical instrument as set forth in claim 1, in which damper blocks (16g; 61d) connect damper wires (16d; 61c) turnable with respect to said plurality of string means (13) to damper woods (16h; 61a) holding damper felts (16i; 61b), and a lower surface of at least one of said damper blocks (16g; 61d) is coplanar with said virtual plane. The keyboard musical instrument as set forth in claim 2, in which said plurality of damper mechanisms (16; 52; 61) are rotatably supported by a center rail (14a), and said lower sub-space is higher than said center rail (14a). The keyboard musical instrument as set forth in claim 1, in which said cushion means (31c; 51b) is provided on a connecting frame (31b; 41a/41b/41c; 51c; 51e/51f/51g; 53a/53b) fixed to said rotatable shaft (31a; 42; 51a). The keyboard musical instrument as set forth in claim 4, in which said connecting frame is formed by a plurality of plate members (31ba/31bb/31bc; 41a/41b/41c) spaced apart from one another along the rotatable shaft (31a; 42), and cushion members (31c) respectively attached to said plate members form in combination said cushion means. The keyboard musical instrument as set forth in claim 5, in which one of said plate members (31bb) has a curved edge varied in distance from said rotatable shaft (31a). The keyboard musical instrument as set forth in claim 5, in which said plate members (41a/41b/41c) have respective leading edges different in distance from said rotatable shaft (42). The keyboard musical instrument as set forth in claim 4, in which said connecting frame has a middle portion (51d; 51f) retracted toward said plurality of hammer assemblies (17) rather than a lower portion (51g) connected to said rotatable shaft (51a) and an upper portion (51e) maintaining said cushion means (51b). The keyboard musical instrument as set forth in claim 8, in which said middle portion (51f), said lower portion (51g) and said upper portion (51e) are welded or bonded to one another. The keyboard musical instrument as set forth in claim 8, in which said middle portion is merged with said upper portion (53a), and is bolted to said lower portion (53b). The keyboard musical instrument as set forth in claim 10, in which a connecting point between said middle portion and said lower portion is adjustable (53b). The keyboard musical instrument as set forth in claim 2, in which said damper blocks (61d) are formed of a substance selected from metal and plastic resin. The keyboard musical instrument as set forth in claim 12, in which said damper blocks (61d) have respective flanges (61f) attached to damper woods (61a) holding damper felts (61b).

Inventors: AOYAGI TAKASHI, HAYASHIDA HAJIME, INOUE SATOSHI, KAWAMURA KIYOSHI, NOZUE RINGI, SATO SHIGEAKI, AOYAGI, TAKASHI, HAYASHIDA, HAJIME, INOUE, SATOSHI, KAWAMURA, KIYOSHI, NOZUE, RINGI, SATO, SHIGEAKI
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1995
Main classification: G10C3
IPC codes: G10C3, G10C5