Keyboard instrument equipped with durable hammer stopper for selectively producing acoustic sounds and synthesized sounds

Abstract: In order to allow a player to perform a music without an acoustic sound, a stopper blocks hammer shanks (4k) before impacts of hammer heads (4m) on strings (4d), and recesses (5p) substantially conformal to the hammer shanks (4k) are formed in a cushion member (5o) of the stopper for improving durability of the cushion members.

Description: This invention relates to a keyboard instrument and, more particularly, to a piano-like keyboard instrument for selectively producing acoustic sounds and synthesized sounds. DESCRIPTION OF THE RELATED ART Typical examples of the keyboard instrument are disclosed in Japanese Patent Applications No. 4-174813 filed on June 9, 1992, No. 4-207352 filed on July 10, 1992, No. 4-299234 filed on October 12, 1992 and No. 5-31420 filed on January 27, 1993, and U.S. Serial No. 08/073,092 and European Patent Application EP-A-0 573 963 were filed on the basis of these Japanese Patent Applications. An acoustic piano and an electronic sound producing system form in combination each of the prior art keyboard instruments. While a player is performing music on the keyboard in an acoustic sound mode, the keyboard instrument produces acoustic sounds through vibrations of the strings. However, if the player instructs the keyboard instrument to enter the silent mode, a shank stopper is moved to a blocking position where the hammer shanks are brought into contact with the shank stopper before rebound on the strings. As a result, the strings do not vibrate, and synthesized sounds are produced by the electronic sound producing system instead of the acoustic sounds. Various shank stoppers are proposed in the Japanese Patent Applications. Even though the contact surfaces of the shank stoppers are either flat or curved, the cross section of the cushion members incorporated in the respective shank stoppers are unchanged along the lateral direction of the keyboard, and the contact surface straightly extends along the array of the hammer shanks. For this reason, the hammer shank is initially brought into contact with a relatively narrow area of the contact surface, and is decelerated by deforming the cushion member. If a shank stopper 1 opposes a curved contact surface 1a to a hammer shank 2 as shown in figure 1, the hammer shank 2 is initially brought into contact with a narrow area 1b of the curved contact surface 1a. On the other hand, if another shank stopper 3 opposes a flat contact surface 3a to the hammer shank 2, the hammer shank 2 is initially brought into contact with an elongated narrow area 3b as shown in figure 2. In either shank stopper 1 or 3, the hammer shank 2 impacts at the narrow area 1b or 3b, and the kinetic energy of the hammer assembly is converted into an impact on the narrow area 1b or 3b. Thus, the impact concentrated on the narrow area 1b or 3b repeatedly damages the cushion member 1 or 3, and the cushion member 1 or 3 is finally torn by the hammer shank. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a keyboard instrument which has a shank stopper less damaged by hammer shanks. To accomplish the object, the present invention proposes to form recesses in a stopper for receiving hammer shanks. The invention is achieved as set out in the appended independent claim 1. In accordance with the present invention, there is provided a keyboard instrument selectively entering into an acoustic sound mode for producing acoustic sounds and a silent mode for producing synthesized sounds, comprising: a) an acoustic piano having a-1) & keyboard having a plurality of swingable keys selectively depressed by a player in both acoustic sound and silent modes, a-2) a plurality of key action mechanisms respectively linked with the plurality of swingable keys, and actuated by the depressed keys in both acoustic sound and silent modes, a-3) a plurality of hammer assemblies having respective contact portions, and selectively driven by the key action mechanisms linked with the depressed keys for rotations in both acoustic sound and silent modes, a-4) a plurality sets of strings respectively associated'with the plurality of hammer assemblies, and selectively struck by the hammer assemblies associated with the key action mechanism linked with the depressed keys in the acoustic sound mode for producing the acoustic sounds; b) a controlling system having a stopper, and responsive to an instruction of the player for changing the stopper between a free position in the acoustic sound mode and a blocking position in the silent mode, the hammer assemblies rebounding on the associated sets of strings when the stopper is in the free position, the hammer assemblies rebounding on the stopper before the impacts of the hammer assemblies on the associated sets of strings when the stopper is changed to the blocking position, the stopper having a plurality of recesses for receiving the contact portions of the associated hammer assemblies, an inner surface of each of the recesses conforming to a part of the outer surface of the contact portion of the associated hammer assembly; and c) an electronic sound generating system enabled in the silent mode, and producing the synthesized sounds with notes assigned to the depressed keys. The recesses may be formed by pressing the contact portions against the hammer assemblies. BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the keyboard 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 perspective view showing the prior art shank stopper and the associated hammer shank; Fig. 2 is a perspective view showing another prior art shank stopper and the associated hammer shank; Fig. 3 is a cross sectional view showing the structure of a keyboard instrument according to the present invention; Fig. 4 is a perspective view showing a rotary stopper incorporated in the keyboard instrument shown in figure 3, Fig. 5 is a perspective view showing a modification of the rotary stopper; Fig. 6 is a block diagram showing the arrangement of a sound processing unit incorporated in the keyboard instrument shown in figure 3; Fig. 7 is a perspective view showing another modification of the rotary stopper; Fig. 8 is a perspective view showing yet another modification of the rotary stopper; Fig. 9 is a side view showing essential parts of another keyboard instrument according to the present invention; Fig. 10 is a perspective view showing a stopper incorporated in the keyboard instrument shown in figure 9; Fig. 11 is a side view showing essential parts of yet another keyboard instrument according to the present invention; Fig. 12 is a side view showing essential parts of a keyboard instrument according to the present invention; and Fig. 13 is a side view showing essential parts of a keyboard instrument according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring to figure 3 of the drawings, a keyboard instrument embodying the present invention largely comprises an acoustic piano 4, a controlling system 5 and an electronic sound generating system 6, and selectively enters an acoustic sound mode and a silent mode. While the keyboard instrument is staying in the acoustic sound mode, the keyboard instrument serves as an acoustic upright piano, and not only the sounds but also the key-touch are identical with those of the acoustic upright piano. On the other hand, when the keyboard instrument is changed to the silent mode, the keyboard instrument electronically synthesizes sounds in response to the fingering, or keeps silent. In this instance, the acoustic piano 4 is of the upright type. However, the acoustic piano 4 may be of a grand type. The acoustic piano 4 comprises a keyboard 4a, a plurality of key action mechanisms 4b, a plurality of hammer mechanisms 4c, a plurality sets of strings 4d and a pedal mechanism 4e. The keyboard 4a is mounted on a key bed 4f, and is fabricated from black and white keys 4g. The black and white keys 4g are turnable with respect to balance pins embedded in a balance rail 4h. The key action mechanisms 4b are respectively linked with the rear ends of the black and white keys 40 g, and drive the hammer mechanisms 4c. Each key action mechanism 4b is similar to a key action mechanism for an upright piano, and no further description is incorporated hereinbelow for the sake of simplicity. Each of the hammer mechanisms 4c comprises a butt 4i kicked by the jack 4j of the associated key action mechanism 4b, a hammer shank 4k implanted into the butt 4j and a hammer head 4m coupled with the leading end of the hammer shank 4k. When the jack 4j kicks the butt 4i, the butt 4i and, accordingly, the hammer shank 4i are driven for rotation toward the associated strings 4d, and the hammer head 4m strikes the strings 4d so that the strings 4d vibrate for producing an acoustic sound. When the keys 4g are in the rest position where a player does not depress the keys, the hammer assemblies 4c are staying at home positions thereof. The pedal mechanism 4e usually have three pedals and three pedal link sub-mechanisms respectively associated with the three pedals. One of the three pedals is called as a damper pedal, and allows the strings to prolong the sound. The second pedal is called as a soft pedal, and causes the hammer heads to softly strike the associated strings for lessening the volume. The last pedal is called as a sostenuto pedal, and enables selected notes to be sustained independently from the others. The controlling system 5 comprises a sound processing unit 6a partially shared with the sound generating system 6, a mode shift switch 5a, a motor driver unit 5b and a rotary stopper 5c. The mode shift switch 5a is manipulated by a player, and produces an instruction signal MODE indicative of either acoustic sound or silent mode. The sound processing unit 6a periodically checks an input port assigned to the instruction signal MODE to see whether or not the player changes the operation mode. While the keyboard instrument is staying in the acoustic sound mode, the sound processing unit 6a instructs the motor driver unit 5b to keep the rotary stopper 5c in a free position FP where the hammer heads 4m rebound on the associated strings 1d without interruption of the rotary stopper 5c. On the other hand, if the instruction signal MODE is indicative of the silent mode, the sound processing unit 6a instructs the motor driver 5b to change the rotary stopper 5c from the free position FP to a blocking position BP, and the rotary stopper 5c blocks the hammer assemblies 4c before the impacts of the hammer heads 4m on the strings 4d. For this reason, the strings 4d do not vibrate in the silent mode, and the acoustic sounds are never produced. The rotary stopper 5c is located in the vicinity of the strings 4d, and is closer to the butts 4i rather than the hammer heads 4m. The location of the rotary stopper 5c is desirable, because the hammer shanks 4k are resiliently deformed as if the hammer heads 4m rebound on the associated strings 4d. When the stopper 5c is moved to the blocking position BP, the rotational axis CL of the rotary stopper 4k is substantially perpendicular to a line of action of each hammer shank 4k at the impact, and a moment is not exerted on the rotary stopper 5c. For this reason, a designer makes the rotary stopper 5c compact, and the rotary stopper 5c can be provided in a narrow space between the hammer assemblies 4c and the strings 4d. Turning to figure 4 of the drawings, the rotary stopper 5c is illustrated in an enlarged scale, and comprises a shaft member 5d of either steel, aluminum or plastic, a motor unit 5e, three bracket members 5f, 5g and 5h, three relatively hard cushion members 5i, 5j and 5k and three relatively soft cushion sheets 5m, 5n and 5o. Each of the relatively soft cushion member 5m/5n/5o and each of the relatively hard cushion member 5i/5j/5k form a laminated structure or a cushion member. The shaft member 5d extends in a lateral direction of the keyboard instrument along the array of the hammer assemblies 4c, and has a center axis substantially aligned with a drive shaft (not shown) of the motor unit 5e. The motor unit 5e is bidirectionally rotatable, and the drive shaft is coupled with the shaft member 5d. The motor unit 5e is a stepping motor, and is energized for driving the shaft member 5d in one of the clockwise direction and the counter clockwise direction. In another implementation, the motor unit 5e may be an ultrasonic motor. The ultrasonic motor can maintain the shaft at any position without current, and quietly rotates at a low speed without any backlash. These features are desirable for a musical instrument. Though not shown in the drawings, the shaft member 5d is rotatably supported by action brackets (not shown) and section plates (not shown), and the action brackets and the section plates are connected at upper end portions thereof with a pin block (not shown) by means of action bolts (not shown) and at the lower end portions thereof with the key bed 4f through bracket blocks (not shown). The three bracket members 5f to 5h are attached to the shaft member 5d at intervals, and the three relatively hard cushion members 5i to 5k are attached to the three bracket members 5f to 5h, respectively. The relatively hard cushion members 5i to 5k are formed of felt or urethane. The relatively soft cushion sheets 5m to 5o are similarly formed of felt or urethane, and are bonded to the relatively hard cushion members 5i to 5h. The relatively soft cushion members 5i to 5h effectively takes up the impact of the hammer shank 4j without noise, and the relatively hard cushion members 5m to 5o effectively prevent the strings 4d from the impact of the hammer shank 4k in the silent mode. Thus, the laminated structure of hard and soft cushion members 5f/5g/5h and 5i/5j/5k is desirable for the stopper 5c. Though not shown in figure 4, cushion sheets are further bonded to the shaft member 5d. When a damper head (not shown) is left from the strings, damper wires (not shown) are brought into contact with one of the cushion sheets, and a noise is not produced at the impact. A plurality of recesses 5p are formed in the relatively soft cushion members 5m to 5o, and are conformal to the contact areas of the respective hammer shanks 4k. For this reason, each hammer shank 4k rebounds on the inner surface of the associated recess, and the impact of the hammer assembly 4c is taken up on a relatively wide area rather than the prior art shank stoppers. For this reason, the cushion member is durable against the impacts of the hammer shanks 4k, and the keyboard instrument according to the present invention serves prolonged time period without a maintenance. The formation of recesses 5p is usually carried out before assembly in a piano factory, and the hammer shanks 4k per se or suitable dies are pressed against the relatively soft cushion members 5m to 5p for plastic deformation. The surfaces of the relatively soft cushion members 5m to 5o may be partially cut for forming the recesses 5p as shown in figure 5. Assuming now that a player starts a performance in the silent mode where the rotary stopper 5c is staying in the blocking position BP, the three relatively soft cushion members 5m to 5o are directed to the hammer shanks 4k as indicated by the real line in figure 3. The key action mechanisms 4b sequentially drive the associated hammer assemblies for rotation, and the key action mechanisms 4b and the hammer assemblies give the piano key touch to the player through the escape of the jacks 4j from the associated butts 4i. The hammer assemblies 4c travel over the distance from the home positions thereof to the rotary stopper 5c, and the hammer shanks 4k softly impact on the inner surfaces of the recesses 5p of the associated relatively soft cushion members 5m to 5o or on leather sheets (not shown) bonded to the cushion members 5m to 5o. The hammer assemblies 4c rebounds on the inner surfaces of the recesses 5p before striking the associated strings 4d, and the strings 4d are prevented from vibrations for producing the acoustic sounds. On the other hand, while the player is performing a music in the acoustic sound mode, the rotary stopper is kept in the free position FP as indicated by broken lines in figure 3, and the gap between the hammer shanks 4k and the relatively soft cushion members 5m to 5o is wide enough to allow the hammer shanks 4j to strike the associated strings 4d. The key action mechanisms 4b and the hammer assemblies 4c behave as similar to those of an ordinary upright piano, and the strings 4d vibrate for producing the acoustic sounds. The electronic sound generating system 6 comprises the sound processing unit 6a partially shared with the controlling system 5, a plurality of key sensors 6b, a pedal sensor 6c associated with the damper pedal, an amplifier unit 6d, a speaker system 6e housed in a speaker box 6f, a socket unit 6g and a headphone 6h detachable from the socket unit 6g, and is activated in the silent mode. In this instance, the keyboard instrument is equipped with both of the speaker system 6e and the headphone 6g. However, only the headphone may be incorporated in the electronic sound generating system 6. The key sensors 6b are respectively associated with the plurality of keys 4g, and each of the key sensors 6b comprises a shutter plate 6i fixed to the bottom surface of the associated key and a photo-interrupter 6j for monitoring the shutter plate 6i. Four different slit patterns are formed in the shutter plate 6i, and the four slit patterns sequentially pass through an optical path produced by the photo interrupter 6j when the associated key is depressed. The photo interrupter 6j produces a digital signal variable when the four slit patterns pass the optical path, and supplies the digital signal to the sound processing unit 6a. The sound processing unit 6a determines the key velocity and estimates the time when the associated hammer head 4m strikes the strings 4d. The pedal sensor 6c monitor the damper pedal to see whether or not the player steps on it. If the player steps on the damper pedal, the pedal sensor 6c detects the current position of the damper pedal, and report the current position to the sound processing unit 6a. The sound processing unit 6a is arranged as shown in figure 6 of the drawings, and comprises a supervisor 6k, a data memory 6m for original vibrations, a data processor 6n for original vibrations, a data memory 6o for resonant vibrations, a data processor 6p for resonant vibrations, a data processor 6q for sound spectrum, a working memory 6r, a floppy disk controller 6s, a floppy disk driver 6t, an audio signal generator 6u, an equalizer 6v and a bus system 6w. In this instance, the data memories 6m and 6o are implemented by non-volatile memory devices such as, for example, read only memory devices, and random access memory devices serve as the working memory 6r. The supervisor 6k sequentially scans signal input ports assigned to the instruction signal MODE, the digital signals from the key sensors 6b and the detecting signal from the pedal sensor 6c, and supervises the other components 6m to 6u for producing an audio signal. An internal table is incorporated in the supervisor 6k, and the internal table defines relation between the key numbers, key velocity and timings for producing the audio signal. The audio signal is supplied from the equalizer 6v to the amplifier unit 6d, and the audio signal is distributed to the speaker system 6e and the socket unit 6g for producing synthesized sounds. Various internal registers are incorporated in the supervisor 6k, and one of the internal registers is assigned to a mode flag indicative of the mode operation selected by the player. The data memory 6m for original vibrations stores a plurality sets of pcm (Pulse Code Modulation ) data codes indicative of frequency specular of original vibrations on the strings 4d, and each set of pcm data codes is corresponding to one of the keys 4g. A plurality groups of pcm data codes form a set of pcm data codes, and are corresponding to frequency specular at different intensities or hammer speeds. In general, if a hammer 4m strongly strikes the associated string 4d, higher harmonics are emphasized. The plurality sets of pcm data codes are produced with a sampler (not shown) through sampling actual vibrations on the respective strings 4d at an appropriate frequency. However, the set of pcm data codes may be produced by means of the data processor 6q through a real-time manner. Using a group of pcm data codes, original vibrations produced upon depressing a key 4g are restored, and the supervisor 6k controls the sequential access to a group of pcm data codes stored in the data memory 6m. The data processor 6n for original vibrations is provided in association with the data memory 6m, and modifies a group of pcm data codes for an intermediate hammer speed. The modification with the data processor 6n is also controlled by the supervisor 6k. The data memory 6o for resonant vibrations stores a plurality sets of pcm data codes indicative of resonant vibrations, and the resonant vibrations take place under stepping on the damper pedal. While a player steps on the damper pedal of an upright piano, dampers are held off, and some of the strings 4d are resonant with the string struck by a hammer. The resonant tones range -10 dB and -20 dB with respect to the tone originally produced through striking with the hammer, and time delay of several millisecond to hundreds millisecond is introduced between the originally produced sound and the resonant tones. If the player continuously steps on the damper pedal, the resonant tones continues several seconds. However, the player can rapidly terminate the original and resonant tones by releasing the damper pedal. The electronic sound generating system 6 can impart the same effect to the synthesized sounds, and the pcm data codes stored in the memory 6o are used for synthesizing the resonant tones. Namely, the audio signal generator 6u is responsive to the detecting signal of the pedal sensor 6c, and the supervisor 6k allows the pcm data codes to be sequentially fetched. The pcm data codes stored in the data memory 3o are indicative of frequency specular of the resonant vibrations, and are also produced by means of the sampler or the data processor 6p for resonant vibrations. Each set of pcm data codes is corresponding to one of the depressed keys 4g, and is constituted by six groups of pcm data codes at the maximum. Each group of pcm data codes is corresponding to one of the resonant strings 4d, and the second harmonic to the sixth harmonic are taken into account for strings one octave higher than low-pitched sounds. However, if the depressed key is lower than the thirteenth key from the lowest key in the eighty-eight keys, the string one octave lower than the depressed key should be taken into account. In general, seventy-one dampers are incorporated in a piano. However, another piano may have sixty-six dampers or sixty-nine dampers. As described hereinbefore, the intensity of frequency spectrum is corresponding to the hammer speed, and the intensities are variable with the type and model of the piano. A set of pcm data codes are sequentially read out from the data memory 6o depending upon the depressed key 4g under the control of the supervisor 6k, and the data processor 6p for resonant vibrations modifies the pcm data codes for an intermediate intensity. The memory capacity of the data memory 6o may be large enough to store the pcm data codes at all of the detectable hammer speeds, and the data processor 6p may calculate each set of pcm data codes on the basis of parameters stored in the data memory 6o. The data processor 6q for sound spectrum can produce the group of pcm data codes indicative of frequency spectrum for original vibrations and the set of pcm data codes indicative of frequency specular for resonant vibrations as described hereinbefore. The data processor 6q is further operative to cause the frequency specular to decay. In detail, when a player releases a key of a piano, original vibrations on a string rapidly decays, because an associated damper returns to contact with the vibrating string. The data processor 6q simulates the decay, and sequentially decreases the values of the pcm data codes. The resonant tones continue for several seconds in so far as the player keeps the damper pedal in the depressed state. However, if the player releases the damper pedal, the resonant tones are rapidly decayed. The data processor 6q further simulates these decay, and sequentially decreases the values of the pcm data codes for the resonant vibrations. The decay is not constant. If the player releases the damper pedal through a half pedal, the tones decay at lower speed rather than the ordinary release. Moreover, some players use the half pedal in such a manner as to retard low-pitched tones rather than high-pitched tones, and such a pedal manipulation is called as an oblique contact. On the contrary, if the damper pedal causes all the dampers to be simultaneously brought into contact with the strings, the damper manipulation is referred to as simultaneous contact. The data processor 6q can simulate the gentle decay upon the release through the half pedal as well as the oblique contact, and the values of the pcm data codes are decreased at either high, standard or low speed in the simultaneous contact and at different speed in the oblique contact. The data processor 6q may change the ratio between the fundamental tone and the harmonics thereof for the half pedal and decay high-order harmonics faster than the fundamental tone. The frame of a piano usually vibrates, and the frame noises participate the piano sound. The data processor 6q may take these secondary noises into account and modify the frequency ratio. The audio signal generator 6u comprises a digital filter, a digital-to-analog converter and a low-pass filter, and produces an analog audio signal from the pcm data codes supplied from the data memories 6m and 6o and/or the data processors 6n, 6p and 6q. The pcm data codes are subjected to a digital filtering, and are, then, converted into the analog audio signal. In the digital filtering, the vibration characteristics of the speaker system 6e and vibration characteristics of the speaker box 6f are taken into account, and the pcm data codes are modified in such a manner that the frequency spectrum of produced sounds becomes flat. The digital filter is of the FIR type in this instance. However, an IIR type digital filter is available. An oversampling type digital filter may follow the digital filtering for eliminating quantized noises. After the digital filtering, the digital-to-analog converter produces the analog audio signal, and the analog audio signal is filtered by the low-pass filter, and the low-pass filter is of a Butterworth type for improving group delay. The analog audio signal thus filtered is supplied through the equalizer 6v to the amplifier unit 6d, and the amplifier unit 6d amplifies the analog audio signal for driving the speaker system 6e or the headphone 6h. The floppy disk driver 6t reads out data codes formatted in accordance with the MIDI standards from a floppy disk under the control of the floppy disk controller 6s, and the supervisor 6k allows the audio signal generator 6u to reproduce sounds from the data codes read out from the floppy disk. Therefore, a music can be reproduced in the timbre of another musical instrument such as, for example, a pipeorgan, a harpsichord or a wind musical instrument. The supervisor 6k may format the detecting signals of the key sensors 6b and the detecting signal of the pedal sensor 6c in accordance with the MIDI standards, and the MIDI codes are stored in a floppy disk under the control of the floppy disk controller 6s. If the keyboard instrument can record a performance, the keyboard instrument has three modes of operation, i.e., the acoustic sound and silent modes and the recording mode. As described hereinbefore, the supervisor 6k forms a part of the controlling system 5, and the mode flag indicative of the operation mode is incorporated in the supervisor 6k. The supervisor 6k instructs the motor driver 5b to rotate the motor in either direction depending upon the operation mode, and the rotary stopper 5c enters one of the free position FP and the blocking position BP. As will be appreciated from the foregoing description, the rotary stopper 5c with the recesses 5p softly receives the hammer shanks 4k, and is prolonged the service time of the keyboard instrument without replacement of the cushion members. In the above described embodiment, the recesses 5p are formed in the relatively soft cushion members 5m to 5o before the assembly into the acoustic piano 4. In order to form the recesses 5p, the soft cushion members 5m to 5o of felt may be treated with chemical solutions for a permanent wave commercially used for a woman's hair. The felt is usually formed from wool, and the first chemical solution cuts the cross linking so that the wool is liable to be shaped. A waved die is pressed against the felt for forming recesses, and the second chemical solution recovers the cross linking. Then, the recesses are permanently formed in the felt. One of the commercially available chemical solutions for a permanent is known as "Venezel Home Perma". A soft cushion member of felt or rubber may be shaped under application of heat. Moreover, a milling is available for forming the recesses, and repeated impact accelerates the milling. The recesses may be formed in the relatively soft cushion members 5m to 5o after the assembly of the keyboard instrument by using the hammer shanks 4k. Even after assembled, the repeated impacts of the hammer shanks 4k with or without water form the recesses 5p. The inner surfaces of the recesses 5p may not be equal in radius of curvature to the outer surfaces of the hammer shanks 4j, but are larger than the outer surfaces of the hammer shanks 4j, because the hammer shank 4j needs to rebound on a wider area of the cushion member than the prior art. If the hammer shanks are, by way of example, trapezoid in cross section, the recesses are also trapezoid so as to be conformal with the outer surfaces of the hammer shanks. The cross section of the hammer shank and the recess may be a circle, an octagone or an ellipse. Moreover, a lamination of a relatively hard cushion member 10 and a relatively soft cushion member 11 may be directly bonded to the shaft member 5d as shown in figure 7, and the relatively soft cushion member 11 per se waves for forming the recesses 11p. If the impact of the hammer shank 4j is not so large, a single-level cushion member 12 may be directly attached to the shaft member 5d, and recesses are formed in the top surface of the single-level cushion member 12 as shown in figure 8. Second Embodiment Turning to figure 9 of the drawings, a stopper 21 is incorporated in another keyboard instrument embodying the present invention. The keyboard instrument implementing the second embodiment is similar in structure than the keyboard instrument shown in figure 3 except for the stopper 21 and an associated shifting mechanism 22 shown in figure 10, and the other components are labeled with references designating corresponding parts and units of the first embodiment without detailed description. The stopper 21 comprises a elongated plate member 21a and cushion members 21b attached to the front surface of the plate member 21a at intervals. A plurality of recesses 21c are formed in the cushion members 21b, and are arranged in such a manner that the hammer shanks 4k rebound on the inner surfaces of the associated recesses 21c. The inner surfaces of the recesses 21c are substantially conformal to the contact portions of the hammer shanks 4k. The plate member 21a is suspended through the coil springs 22a and 22b by pin members 22c and 22d fixed to side boards (not shown) of the acoustic piano 4, and is pulled down by means of the shifting mechanism 22. The shifting mechanism 22 comprises a wire 22e coupled with the plate member 21a, a pipe member 22f connected with the wire 22e, a pedal 22g coupled with the pipe member 22f, a step portion 22h formed in a bottom sill of the acoustic piano 4 and a limiter 22i. If a player steps on the pedal 22g and leftwardly pushes the pedal 22g, the pedal 22g is engaged with the step portion 22h, and the shifting mechanism 22 keeps the plate member 21a in the blocking position BP. The plate member 21a thus kept in the blocking position BP inserts the right portion thereof into the limiter 22i, and the step portion 22h and the limiter 22i exactly define the blocking position BP. As will be better seen from figure 9, while the stopper 21 is staying in the blocking position BP, the hammer shanks 4k rebound on the cushion members 21b before impacts on the strings 4d, and the strings 4d never vibrate for producing acoustic sounds. Therefore, the electronic sound producing system 6 synthesizes sounds with notes assigned to depressed keys 4g. However, if the pedal 22g is released from the step portion 22h, the coil strings 22a and 22b pull up the plate member 21a, and the stopper 21 enters the free position FP. In the free position FP, the hammer heads 4m strike the strings 4d before the hammer shanks 4k reach the cushion members 22b. For this reason, the strings 4d vibrate at respective pitches, and produce the acoustic sounds. In this instance, the pedal 22g is changed between two positions. However, one more step may be formed therebetween, and the intermedaite step keeps the stopper 21 at an intermediate for decreasing loudness of the acoustic sounds. The recesses 21c are usually formed in the cushion members 21b before delivery from a piano factory. However, the recesses 21c may be formed in the cushion members 21b after the delivery by pressing the hammer shanks 4k against the cushion members 21b. The keybaord instrument implementing the second embodiemnt achieves all of the advantages of the present invention. Third Embodiment Turning to figure 11 of the drawings, yet another keyboard instrument embodying the present invention is equipped with a swingable stopper 31. The other components of the keyboard instrument implementing the third embodiemnt are similar to those of the first embodiemnt, and are labeled with the references designating the corresponding parts and units without detailed description. The swingable stopper 31 comprises a frame structure 31a swingable around a center axis (not shown) and a cushion member 31b attached to an upper portion of the front surface of the frame structure 31a. A plurality of recesses 31c are formed in the front portion of the cushion member 31b as similar to the cushion members 21b, and the recesses 31c are substantially conformal to the opposite surfaces of the hammer shanks 4k. The cushion member 31b may be split into a plurality of cushion sub-members. A suitable shifting mechanism is provided for the frame strcuture 31a, and the swingable stopper 31 is changed between the free position FP and the blocking position BP. In the free position FP, the hammer shanks 4k do not reach the cushion member 31b, and the hammer heads 4m strike the associated strings 4d without interruption of the swingable stopper 31. The strings 4d vibrates, and produces acoustic sounds. On the other hand, if the swingalbe stopper 31 is changed to the blocking position BP through a swinging motion of the frame structure 31a, the hammer shanks 4k rebound on the inner surfaces of the recesses 31c before the impact, and the electronic sound producing system 6 causes one of the speaker system 6e or the headphone 6h tp produce synthesized sounds with the notes assigned to the depressed keys 4g. The recesses 31c are usually formed before the assembly of the keyboard instrument in a piano factory. However, the recesses may be formed after the delivery from the piano factory by pressing the hammer shanks againt the cushion member 31b. The keyboard instrument implementing the third embodiment achieves all of the advantages of the present invention. Fourth Embodiment Turning to figure 12 of the drawings, still another keyboard instrument embldying the present invention largely comprises a grand piano 41, the electronic sound producing system 6 and a controlling system 42. The grand piano 41 has parts and members corresponding to the upright piano 4, and the parts and the members of the grand piano 41 are labeled with the references corrsponding parts and corresponding members of the acoustic piano 4 without detailed description for the sake of simplicity. The controlling system 42 comprises a swingable stopper 42a provided over the hammer shanks 4k, and the sound processing unit 6a is shared between the electronic sound producing system 6 and the controlling system 42 as similar to the first embodiemnt. The swingable stopper 42a comprises a shaft member 42b, a frame structure 42c swingable around the shaft member 42b and a cushion member 42d, and a plurality of recesses 42e formed in the cushion member 42d. The inner surfaces of the recesses 42e are conformal to the contact portion of the hammer shanks 4k, and the cushion member 42d may be split into a plurality of cushion sub-members. When the swingable stopper 42a is changed to the free position FP, the hammer shanks 4k do not reach the cushion member 42d, and the hammer heads 4m strike the associated strings 4d without interruption of the swingable stopper 42a. The strings 4d vibrates, and produces acoustic sounds. On the other hand, if the swingalbe stopper 42b is changed to the blocking position BP through a swinging motion of the frame structure 42c, the hammer shanks 4k rebound on the inner surfaces of the recesses 42e before the impact, and the electronic sound producing system 6 causes one of the speaker system 6e or the headphone 6h to produce synthesized sounds with the notes assigned to the depressed keys 4g. The recesses 42e are usually formed before the assembly of the keyboard instrument in a piano factory. However, the recesses 42e may be formed after the delivery from the piano factory by pressing the hammer shanks against the cushion member 42d. The keyboard instrument implementing the fourth embodiment achieves all of the advantages of the present invention. Fifth Embodiment Turning to figure 13 of the drawings, a keyboard instrument embodying the present invention also comprises an upright piano 51, an electronic sound producing system (not shown) and a controlling system 52. The upright piano 51 and the electronic sound producing system are similar to those of the keyboard instrument shown in figure 3, and parts and members of the upright piano 51 are labeled with the references designating the corresponding parts and members without detailed description. The controlling system 52 has a swingable stopper 52a and an assocaited shifting mechanism for shifting the swingable stopper 52a between the free position FP and the blocking position BP. The swingable stopper 52a comprises a rotatable shaft member 52b coupled with the shifting mechanism, a frame structure 52c swingably supported by the rotatable shaft member 52b, screw members screwed through the leading end portion of the frame structure 52c, a bracket member 52d attached to the screw members 52d, a cushion member 52f attached to the bracket member 52d and extensions 52g respectively projecting from the hammer heads 4m. The screw members 52d are turnable with a jig member 53, and the position of the cushion member 52f is regulable. A plurality of recesses 52h are formed in the cushion member 52f, and the cushion member 52h may be split into a plurality of cushion sub-members. The receses are usually formed beffore the assembly in a piano factory. However, the recesses 52h may be formed by pressing the extensions 52g against the cushion member 52f after delivery from the piano factory. If the shifting mechanism keeps the swingable stopper 52a in the free position FP, the cushion member 52f is out of the orbits OBT1 of the extensions 52g, and the hammer heads 4m can strike the strings 4d without an interruption of the swingable stopper 52a. As a result, the strings 4d vibrate, and produce an acoustic sound. On the other hand, if the shifting mechanism changes the swingable stopper 52a to the blocking position BP, the cushion member 52f are located inside of the orbits OBT1 and out of the orbits OBT2 of the hammer heads 4m. When a player depresses a key, the assoicated key action mechanism 4b drives the hammer asembly 4c for rotation, and the extension 52g rebounds on the inner surface of the recess 52h before the imact. The strings 4d do not vibrate, and the electronic sound producing system synthesizes a sound with the note assigned to the depresed key. The keyboard instrument implementing the fifth embodiemnt achieves all of the advantages of the present invention. 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 following claims.

Claims: A keyboard instrument having at least an acoustic sound mode for producing acoustic sounds and a silent mode for producing synthesized sounds, comprising: a) an acoustic piano (4; 41; 51) having a-1) a keyboard (4a) having a plurality of keys (4g) selectively depressed by a player in both acoustic sound and silent modes, a-2) a plurality of key action mechanisms (4b) functionally connected to said plurality of keys (4g), respectively, and actuated by the depressed keys in both acoustic sound and silent modes, a-3) a plurality of hammer assemblies (4c) having respective contact portions (4k), and selectively driven by the key action mechanisms functionally connected to said depressed keys for rotations in both acoustic sound and silent modes, and a-4) a plurality of sets of strings (4d) respectively associated with said plurality of hammer assemblies, and selectively struck by the hammer assemblies associated with said key action mechanisms functionally connected to said depressed keys in said acoustic sound mode for producing said acoustic sounds; b) a controlling system (5; 42; 52) having a stopper (5c; 21; 31; 42a; 52a), and responsive to an instruction of said player for changing said stopper between a free position (FP) in said acoustic sound mode and a blocking position (BP) in said silent mode, said hammer assemblies rebounding on the associated sets of strings when said stopper is in said free position, said hammer assemblies rebounding on said stopper before the impacts of said hammer assemblies on said associated sets of strings when said stopper is changed to said blocking position; and c) an electronic sound generating system (6) available for said silent mode, and producing the synthesized sounds with notes assigned to said depressed keys, characterized in that said stopper has a plurality of recesses (5p; 21c; 31c; 42e; 52h) for receiving the contact portions (4k; 52g) of said hammer assemblies, the inner surface of each of said recesses conforming to a part of the outer surface of said contact portion of the associated hammer assembly. The keyboard instrument as set forth in claim 1, in which said recesses (5p; 21c; 31c; 42e; 52h) are formed in said stopper by pressing said contact portions against said stopper. The keyboard instrument as set forth in claim 1, in which said stopper (5c) comprises a rotatable shaft member (5d) rotatably provided in a space between said plurality of hammer assemblies at home positions thereof and said plurality of sets of strings, a relatively hard cushion member means (5i/5j/5k) supported by said rotatable shaft member, and a relatively soft cushion member means (5m/5n/5o) laminated on said relatively hard cushion member means and having said recesses (5p). The keyboard instrument as set forth in claim 1, in which said stopper (21) comprises a plate member (21a) provided in a space between said plurality of hammer assemblies at home positions thereof and said plurality of strings, and having a surface opposing said plurality of hammer assemblies at home positions thereof, a cushion member means (21b) attached to said surface and having said recesses (21c) allowing said contact portions of said hammer assemblies to rebound on the inner surfaces of said recesses, and a shifting mechanism (22) manipulated by said player for shifting between said free position and said blocking position. The keyboard instrument as set forth in claim 1, in which said stopper (31) comprises a frame structure (31a) swingable and provided in a space between said plurality of hammer assemblies at home positions thereof and said plurality of sets of strings, a cushion member means (31b) attached to a surface of said frame structure in opposing relation to said plurality of hammer assemblies, and having said recesses (31c) allowing said contact portions of said hammer assemblies to rebound on the inner surfaces of said recesses, and a shifting means for shifting said cushion member means between said free position and said blocking position through a swing motion of said frame structure. The keyboard instrument as set forth in claim 5, in which said recesses (31c) are formed by depressing said contact portions against said cushion member means. The keyboard instrument as set forth in claim 1, in which said plurality of hammer assemblies (4k) have respective extensions (52g) attached to leading ends thereof, said extensions respectively serving as said contact portions, respectively, and in which said stopper comprises a frame structure (52c) swingable into and out of a space between said extensions of said plurality of hammer assemblies at home positions thereof and said plurality of sets of strings, a cushion member means (52f) supported by said frame structure, and movable into said blocking position when said frame structure is swung into said space, and having said recesses allowing the extensions of said hammer assemblies to rebound on the inner surfaces of said recesses, said cushion member means being shifted to said free position when said frame structure is swung out of said space, and a shifting means for shifting said cushion member means between said free position and said blocking position through a swing motion of said frame structure. The keyboard instrument as set forth in claim 1, in which said acoustic piano is an upright piano. The keyboard instrument as set forth in claim 1, in which said acoustic piano is a grand piano.

Inventors: KAWAMURA KIYOSHI, KONDO MOTOYA, KAWAMURA, KIYOSHI, KONDO, MOTOYA
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1995
Main classification: G10C3
IPC codes: G10C3, G10C5