Keyboard instrument having catcher stopper for silent performance on keyboard

Abstract: An acoustic piano (1), an electronic sound producing system (3) and a controlling system (2) form a keyboard instrument for selectively producing acoustic sounds and electronically synthesized sounds, and the controlling system has a catcher stopper (2c) for restricting rotations of catchers before hammer heads strike sets of strings in the electronic sound producing mode, thereby giving the unique piano key-touch to a player without mixing noise with the synthesized sounds.

Description: FIELD OF THE INVENTION This invention relates to a keyboard instrument and, more particularly, to a keyboard instrument selectively entering into an acoustic sound mode and a silence mode. DESCRIPTION OF THE RELATED ART A piano given a unique touch to a player, and an electronic keyboard synthesizer does not exactly imitates the unique key-touch, and an attempt was made on a compromise between a piano and an electronic synthesizer. The compromise or the piano-like musical instrument has key action mechanisms coupled between the keyboard and the hammer assemblies and a tone generator system, and sounds are synthesized by the tone generator system. However, the key action mechanisms drives the hammer assemblies for striking the strings, and gives the unique key-touch to the player. However, when a hammer strikes the strings, the strings vibrate, and produce an acoustic sound. The acoustic sound is mixed with the synthesized sound, and an audience feels the mixed sounds strange. One of the piano-like keyboard instruments is disclosed in Japanese Publication of Examined Patent Application (Kokoku) No. 1-30155, and teaches how to decrease the loudness of the acoustic sounds. According to the Japanese Publication of Examined Application, a damper mechanism originally incorporated in the piano is brought into contact with the strings, and the damper mechanism restricts the vibrations on the struck strings. Another muting mechanism incorporated in a grand piano is disclosed in Japanese Publication of Unexamined Utility Model Application (Kokai) No. 51-67732, and the muting mechanism restricts a hammer motion by means of a resilient member. According to the Japanese Publication of Unexamined Utility Model Application, the hammer concurrently strikes the resilient member and the associated strings, and the impact is split between the resilient member and the strings. As a result, the strings weakly vibrate, and the sound is lessened. The prior art piano-like keyboard instruments can decrease the loudness of acoustic sounds. However, the prior art piano-like keyboard instruments can not perfectly eliminate the acoustic sounds from electrically synthesized sounds. If the resilient member is moved to a closer position to the home position of the hammer, the hammer strikes the resilient member only, and the acoustic sound is not produced. However, the resilient member closer to the home position does not allow the jack to escape from the butt, and the key action mechanism can not give the unique key touch to the player. If the hammer is removed, the strings never vibrate, and acoustic sounds are not mixed with the synthesized sounds. However, the keys are too light to give an appropriate resistance against the fingers of the player, and the key action mechanisms without hammers can not imitate the unique key-touch. Thus, there is a trade-off between the acoustic sounds and the key-touch, and all of the prior art keyboard instruments do not satisfy players. WO-A-9107740 relates to a striking mechanism for a piano, grand piano or similar string instrument, wherein the power from the key is transferred to the hammer via a rod system so adapted that the connection of the key and the hammer is never interrupted. The rod system is supported during the striking movement against deflection by a first guide boss or roller supported by a first curve guide, and during the return movement by a second guide boss or roller supported by a second curve guide. The first curve guide can swing between a first, advanced position in which it is releasably locked by a locking pawl and the rod system is capable of causing the hammer to touch the string when the key is pressed down, and a released second retracted position in which this is no longer possible. This ensures that the hammer is withdrawn so rapidly after having struck the string that the string can vibrate freely and deliver its note. Further, attention is drawn to DE-A-3707591 disclosing a piano including a device for suppressing the acoustic piano sound by intercepting the movement of the hammers before the hammers strike the strings. SUMMARY OF THE INVENTION It is therefore an important object of the present invention to provide a keyboard instrument which gives the unique key-touch to a player without acoustic sounds. To accomplish the object, the present invention proposes to interrupt the rotational of a catcher before an associated hammer strikes strings. In accordance with the present invention, there is provided a keyboard instrument selectively entering a mechanical sound producing mode and an electronic sound producing mode, comprising: a) an acoustic piano including a-1) a keyboard having a plurality of keys turnable with respect to a stationary board member, the plurality of keys being selectively depressed in both mechanical and electronic sound producing modes by a player, a-2) a plurality of key action mechanisms respectively coupled with the plurality of keys, and selectively actuated by the plurality of keys when the player depresses, the plurality of key action mechanisms having respective whippens functionally connected with the plurality of keys, respectively, respective catchers respectively projecting from butts and respective back checks respectively projecting from the whippens so as to be brought into contact with the catchers when the player releases the associated keys, a-3) a plurality of hammer mechanisms respectively associated with the plurality of key action mechanisms, and having respective hammer heads and the butts supporting the hammer heads, respectively, the plurality of key action mechanisms being driven for rotation by the plurality of key action mechanisms when the player selectively depresses the plurality of keys, and a-4) a plurality of strings associated with the plurality of hammer mechanisms, and struck by the hammers in the mechanical sound producing mode when the player selectively depresses the plurality of keys; b) an electronic sound producing means monitoring the plurality of keys to see what keys are depressed by the player in the electronic sound producing mode, and operative to electronically produce sounds corresponding to the keys depressed by the player; and c) a controlling means having a plurality of movable stoppers associated with the catchers, and a driver unit responsive to an instruction of the player for driving the plurality of movable stoppers between a free position in the mecanically sound producing mode and a blocking position in the electronically sound producing mode, the catchers being freely moved together with the associated butts without interruptions of the plurality of movable stoppers while the movable stoppers are staying in the free position, the catchers being brought into contact with the movable stoppers in the blocking position before the associated hammer heads strike the plurality of strings. 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 cross sectional view showing the structure of a keyboard instrument according to the present invention; Fig. 2 is a side view showing, in an enlarged scale, a key action mechanism associated with a catcher stopper incorporated in the keyboard instrument; Fig. 4 is a block diagram showing the arrangement of a data processing unit incorporated in the keyboard instrument; Figs. 5A and 5B are flow charts showing a program sequence executed by a data processing unit incorporated in the keyboard instrument shown in Fig. 4; Fig. 3 is a block diagram showing the arrangement of the sound producing unit; Figs. 4A and 4B are flowcharts showing a program sequence executed by the sound producing unit; Fig. 5 is a side view showing the structure of a catcher stopper incorporated in another keyboard instrument according to the present invention; Fig. 6 is a side view showing the structure of a key action mechanism accompanied with a catcher stopper incorporated in yet another keyboard instrument according to the present invention; Fig. 7 is a plan view showing stoppers retained by a movable bracket member incorporated in the keyboard instrument shown in Fig. 6; Fig. 8 is a side view showing a catcher stopper associated with a key action mechanism incorporated in still another keyboard instrument according to the present invention; Fig. 9 is a front view showing a part of a driving mechanism of the catcher stopper; and Fig. 10 is a perspective view showing the structure of the driving mechanism. DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment Referring first to Fig. 1 of the drawings, a keyboard instrument embodying the present invention largely comprises an acoustic piano 1, a controlling system 2 and an electronic sound generating system 3, and selectively enters a mechanical sound producing mode and an electronic sound producing mode. In the following description, words "clockwise" and "counter-clockwise" are determined on a referenced figure. While staying in the mechanical sound producing 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 an acoustic upright piano. On the other hand, the keyboard instrument electronically synthesizes sounds in response to keying-in in the electronic sound producing mode, and the acoustic sounds are not produced. The acoustic piano 1 comprises a keyboard 1a, a plurality of key action mechanisms 1b, a plurality of hammer mechanisms 1c, a plurality sets of strings 1d and a pedal mechanism 1e. The keyboard 1a is mounted on a key bed 1f, and is fabricated from black and white keys 1g. In this instance, the key bed 1f serves as a stationary board member. Each of the black and white keys 1g is associated with one of the key action mechanisms 1b, one of the hammer mechanisms 1c and a set of strings 1d, and a note is assigned to each of the keys 1g. Since all of the action lines from the keys 1g to the hammer mechanisms 1c are similar to one another, description is made on one of the action lines, and the key, the key action mechanism, the hammer mechanism and the set of strings of the action line are also labeled with 1g, 1b, 1c and 1d, respectively. The key 1g is turnable with respect to a balance pin embedded in a balance rail 1h, and the associated key action mechanism 1b is respectively linked with the rear end of the key 1g. The key action mechanism 1b drives the associated hammer mechanism 1c for rotation when the associated key 1g is depressed. As will be better seen from Fig. 2, the key action mechanism 1b comprises a capstan button 1i projecting from the rear end of the associated key 1g, an whippen 1j held in contact with the capstan button 1i and a jack 1k provided on the whippen 1j, and the jack 1k causes a the associated hammer mechanism 1c to strike the associated set of strings 1d. The hammer mechanisms 1c comprises a butt 1m kicked by the jack 1k, a hammer shank 1n implanted in the butt 1m and a hammer head 1o coupled with the leading end of the hammer shank 1n. While a player is depressing the key 1g from the rest position to a first intermediate position, the jack 1k slowly drives the butt 1m for rotation in the clockwise direction, and the hammer head 1o is also slowly moved toward the set of strings 1d. When the key 1g reaches the intermediate position, the jack 1k is brought into contact with a regulating button 1p, and the rotation of the whippen 1j is converted to the elastic force of a spring 1q. When the key proceeds to a second intermediate position, the jack 1k kicks the butt 1m, the butt 1m and, accordingly, the hammer head 1o are driven for rotation at high speed toward the set of strings 1d, and the hammer head 1o strikes the set of strings 1d so that the strings 1d vibrate for producing an acoustic sound. Upon the strike at the set of strings 1d, the hammer head 1o rebound on the set of strings 1d, and the butt 1m and the hammer heads 1o rotate in the counter clockwise direction so as to return to the home position. The key action mechanism 1b further comprises a catcher 1r backwardly projecting from the butt 1m, a catcher skin 1s attached to the catcher 1r, a hack check block 1t upwardly projecting from the whippen 1j and a back check felt 1u attached to the back check block 1r. While the butt 1m is rotating in the clockwise direction, the catcher 1r also rotates in the clockwise direction. After the rebound on the set of strings 1d, the catcher 1r returns to the home position together with the butt 1m. The key 1g released from the end position causes the whippen 1j and, accordingly, the back check block 1t to rotate in the clockwise direction, and the back check felt 1u softly decelerates the catcher 1r. Thus, the key action mechanisms 1b, the hammer mechanisms 1c, the pedal mechanism 1e and the damper mechanisms 1v are similar to those of an upright piano, and the upright piano is available for the acoustic piano 1. Turning back to Fig. 1, the pedal mechanism 1e usually have three pedals and three pedal link sub-mechanisms respectively connected with the pedals. One of the pedal is called as a damper pedal, and allows the strings 1d to prolong the sound. The second pedal is called as a soft pedal, and causes the hammer heads 1o to strike fewer than the normal number of 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 keyboard instrument further comprises a damper mechanisms 1v. However, the damper mechanisms and the pedal mechanism 1e are well known to a person skilled in the art, and no further description is incorporated hereinbelow. The controlling system 2 comprises a sound processing unit 3a, a mode shift switch 2a, a driver unit 2b and a catcher stopper mechanism 2c. The mode shift switch 2a is manipulated by a player, and produces an instruction signal MODE indicative of one of the mechanical sound producing mode and the electronic sound producing mode. As shown in Fig. 2 in detail, the catcher stopper mechanism 2c comprises a movable bracket member 2d of wood shared between all of the key action mechanisms 1b, a solenoid-operated actuator unit 2e responsive to a driving signal indicative of the electronic sound producing mode for projecting and retracting the movable bracket member 2d in directions indicated by arrow X and a plurality of stoppers 2f respectively associated with the catchers 1r of the plurality of key action mechanisms 1b. When the solenoid-operated actuator unit 2e leftwardly moves the movable bracket member 2d, the stoppers 2f enter into a free position, and the catchers 1r can rotate together with the butts 1m without interruption of the stoppers 2f. On the other hand, when the solenoid-operated actuator unit 2e rightwardly moves the movable bracket member 2d, the stoppers 2f enter into a blocking position, and the catchers 1r are brought into contact with the stoppers 2f before the hammer heads 1o strike the associated sets of strings 1d. Each of the stoppers 2f is analogous to a capstan screw of a grand piano, and has a bolt member 2g screwed in the movable bracket member 2d at respective positions over the associated catchers 1r and a leather pad 2h attached to the lower surface of the bolt member 2g. The leather pads 2h are confronted to the upper surfaces of the catchers 1r, and the upper surfaces of the catchers 1r are brought into contact with the leather pads 2h of the stoppers 2f in the blocking position. The leather pads 2h are replaceable with felt pads or cloths. Through-holes 2i are respectively formed in the bolt members 2g, and a regulating tool 2j is insertable into the through-holes 2i. Namely, while the keyboard instrument is standing idle, a tuner regulates the projection of each stopper 2f by turning the stoppers 2f with the tool 2j. In this instance, distances between the stoppers 2h and the catchers 1r are regulated in such a manner that the catchers 1r are brought into contact with the stoppers 2f at appropriate timings between escapes of the associated jacks 1k and strikes at the strings 1d. The distances between the toes of the backs 1k and the regulating buttons 1p are regulated to about 3 millimeters for low-pitched tones, 2.5 millimeters for middle-pitched tones and 2 millimeters for high-pitched tones, and the distances between the catchers 1r and the leather pads 2h are not less than these regulated values. This regulation of the stoppers 2f allows the butts 1m to escape from the associated jacks 1k, but does not allow the hammer heads 1o to strike the associated sets of strings 1d. In other words, the key action mechanisms 1b give the unique key touch to the player without acoustic sounds. Turning back to Fig. 1, the electronic sound producing system 3 comprises a sound processing unit 3a, an array of key sensors 3b for monitoring key actions, an array of pedal sensors 3c for monitoring pedal actions, an amplifier system 3d, a speaker system 3e housed in a speaker box 3f, a socket unit 3g and a head phone 3h detachable from the socket unit 3g. The sound processing unit 3a periodically checks an input port assigned to the instruction signal MODE to see whether or not the player changes the operation mode. While staying in the mechanical sound producing mode, the sound processing unit 3a instructs the driver unit 2b to keep the stoppers 2f in the free position. On the other hand, if the instruction signal MODE is indicative of the electronic sound producing mode, the sound processing unit 3a instructs the driver unit 2b to change the stopper 2c from the free position to the blocking position BP. The plurality of key sensors 3b are respectively associated with the plurality of keys 1g, and each of the key seniors 3b comprises a shutter plate 3i fixed to the bottom surface of the associated key and a photo-interrupter 3j monitoring the shutter plate 3i. Four different patterns are formed in the shutter plate 3i, and the four patterns sequentially passes through an optical path produced by the photo interrupter 3j when the associated key is depressed. Time intervals between the four patterns are reported from the photo interrupter 3j to the sound processing unit 3a, and the sound processing unit 3a determines the key velocity and estimates the time when the associated hammer head 1o strikes the strings 1d. The pedal sensors 3c monitor the three pedals to see whether or not the player steps on any one of the three pedals. If the player steps on one of the pedals, the pedal sensors 3c detect the motion of the pedal, and report the pedal manipulated by the player to the sound processing unit 3a. Turning to Fig. 3 of the drawings, the sound processing unit 3a comprises a supervisor 3k, a data memory 3m for original vibrations, a data processor 3n for original vibrations, a data memory 3o for resonant vibrations, a data processor 3p for resonant vibrations, a data processor 3q for sound spectrum, a working memory 3r, a floppy disk controller 3s, a floppy disk driver 3t, an audio signal generator 3u, an equalizer 3v and a bus system 3w. The supervisor 3k sequentially scans signal input ports assigned to the instruction signal MODE, the detecting signals from the key sensors 2b and the detecting signals from the pedal sensors 2c, and supervises the other components 3m to 3u for producing an audio signal. An internal table is incorporated in the supervisor 3k, 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 3v to the amplifier unit 3d, and the audio signal is distributed to the speaker system 3e and the socket unit 3g for producing synthesized sounds. Various internal registers are incorporated in the supervisor 3k, and one of the internal registers is assigned to a mode flag indicative of the operation mode selected by the player. The data memory 3m for original vibrations stores a plurality sets of pcm (Pulse Code Modulation ) data codes indicative of frequency specular of original vibrations on the strings 1d, and each set of pcm data codes is corresponding to one of the keys 1g. 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 1o strongly strikes the associated string 1d, 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 1d at an appropriate frequency. However, the set of pcm data codes may be produced by means of the data processor 3q through a real-time manner. Using a group of pcm data codes, original vibrations produced upon depressing a key 1g are restored, and the supervisor 3k controls the sequential access to a group of pcm data codes stored in the data memory 3m. The data processor 3n for original vibrations is provided in association with the data memory 3m, and modifies a group of pcm data codes for an intermediate hammer speed. The modification with the data processor 3n is also controlled by the supervisor 3k. The data memory 3o for resonant vibrations stores a plurality sets of pcm data codes indicative of resonant vibrations, and the resonant vibrations take place under a step on the damper pedal. While a player steps on a damper pedal of a piano, dampers are held off, and some of the strings 1d are resonant with the string struck by an associated hammer. The resonant tones range -10 dB and -20 dB with respect to the tone originally produced through striking with a hammer 1o, 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, and the audio signal generator 3u is responsive to the detecting signal of the pedal sensors 2c for the rapid termination. 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 for resonant vibrations 3p. Each of the plurality nets of pcm data codes is corresponding to one of the depressed keys 1g, 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 1d, 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. 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. However, 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 3o depending upon the depressed key 1g under the control of the supervisor 3k, and the data processor for resonant vibrations 3p modifies the pcm data codes for an intermediate intensity. The memory capacity of the data memory 3o may be large enough to store the pcm data codes at all of the detectable hammer speeds, and the data processor 3p may calculate each set of pcm data codes on the basis of parameters stored in the data memory 3o. The data processor 3q for sound spectrum can produce a group of pcm data codes indicative of frequency spectrum for original vibrations and a set of pcm data codes indicative of frequency specular for resonant vibrations as described hereinbefore. The data processor 3q 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 1v is brought into contact with the strings 1d. The data processor 3q 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 3q further simulates the decay, and sequentially decreases the values of the pcm date 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 rapidly 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 called as a simultaneous contact. The data processor 3q 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 3q 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 tone. The data processor 3q may take these secondary noises into account and modify the frequency ratio. The audio signal generator 3u 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 3m and 3o and/or the data processors 3n, 3p and 3q. 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 3e and vibratory characteristics of the speaker box 3f 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. 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 3v to the amplifier unit 3d, and the amplifier unit 3d amplifies the analog audio signal for driving the speaker system 3e. The floppy disk driver 3t reads out data codes formatted in accordance with the MIDI standards from a floppy disk under the control of the floppy disk controller 3s, and the supervisor 3k allows the audio signal generator 3u 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 3k may format the detecting signals of the key sensors 2b and the detecting signals of the pedal sensors 2c in accordance with the MIDI standards, and the MIDI codes are stored in a floppy disk under the control of the floppy disk controller 3s. If the keyboard instrument can record a performance, the keyboard instrument has three modern of operation, i.e., the mechanically and electronically sound producing modes and the recording mode. The keyboard instrument thus arranged executes a program sequence illustrated in Fig. 4A. Namely, the supervisor 3k reads out the mode flag from the internal register as by step S1, and checks the mode flag to see whether the player instructs the mechanically sound producing mode, the electronic sound producing mode as by step S2. If the player has instructed the mechanically sound producing mode through the mode shift switch 2a, the supervisor 3k proceeds to step 3, and instructs the motor driver 2b to change the stoppers 2f to the free position. Then, the stoppers 2f allow the catchers 1r to freely move together with the butts 2m, and the hammer heads 1o can strike the associated sets of strings 1d without any interrupt of the stoppers 2f. After the stopper 2c thus moved to the free position , the player selectively depresses the black and white keys 1g, and the key action mechanisms 1b associated with the depressed keys drive the hammer mechanisms 1c for striking the strings. The behaviors of the keys 1g, the key action mechanisms 1b and the hammer mechanisms 1c are similar to those of the upright piano, and no further description is incorporated hereinbelow for the sake of simplicity. While the player is performing a music in the mechanically sound producing mode, the supervisor 3k periodically checks the input port assigned to the instruction signal MODE to see whether or not the player changes the mode from the mechanically sound producing mode to the electrically sound producing mode as by step S4. If the answer to the step S4 is given negative, the supervisor 3k repeats the step S4, and the player continues to perform the music. However, if the player manipulates the mode shift switch 2a, the answer to the step S4 is given positive, and the supervisor 3k returns to the step S2. If the answer to the step S2 is indicative of the electronically sound producing mode, the supervisor 3k rewrites the mode flag, and the supervisor 3k instructs the driver unit 2b to change the stoppers 2f to the blocking position as by step S5. Then, the leather pads 2h are confronted to the catchers 1r. While the player is selectively depressing the block and white keys 1g in the electronic sound producing mode, the sound processing unit 3a electronically synthesizes sounds through on electronically sound producing sub-routine S6 in cooperation with the key sensors 3b, the pedal sensors 3c, the amplifier 3d and the speaker system 3d. If the player hears the sounds through the headphone 3h, the speaker system 3d keeps silence, and the synthesized sounds do not disturb people sleeping in bed. In the electronically sound producing mode, when the player depresses one of the keys 1g, the associated key action mechanism 1b, the associated hammer mechanism 1c and the catcher stopper 2c behave as follows. On the way from the rest position to the first intermediate position, the capstan button 1i pushes the whippen 1j, and the whippen 1j rotates in the clockwise direction. The jack pushes the butt 1m, and the butt 1m slowly rotates in the clockwise direction. Upon reaching the first intermediate position, the toe of the jack 1k is brought into contact with the regulating button 1p, and the catcher 1r is close to the leather pad 2h. While the player is depressing from the first intermediate position to the second intermediate position, the whippen 1j compresses the spring 1q, and the regulating button 1p and the leather pad 2h keep the relative position between the jack 1k and the butt 1m. When the key 1g reaches the second intermediate position, the elastic force accumulated by the spring 1q causes the jack 1k to escape from the butt 1m, and the unique key touch is given to the player. However, the catcher 1r rebounds on the leather pad 2h before the hammer head 1o strikes the set of the strings 1d. When the player releases the key 1g, the key returns from the end position toward the rest position, and the whippen 1j moves the back check felt 1u toward the catcher 1r. The back check felt 1u is brought into contact with the catcher skin 1s, and stops the catcher 1r and the butt 1m at the home position. Fig. 4B illustrates the electronic sound producing sub-routine. Upon entry of the electronic sound producing sub-routine S6, the supervisor 3k monitors the input port assigned to the detecting signals from the key sensors 3b, and receives the detecting signal from the key sensors 3b as by step S61, if any. After the receipt of the detecting signal, the supervisor 3k identities the depressed key, and determines the key velocity on the basis of the detecting signal. The supervisor 3b further checks the input port assigned to the detecting signals from the pedal sensors 3c to see whether or not one of the pedals is moved as by step S62. If the answer to the step S62 is given negative, the supervisor 3k accesses one of the groups of pcm data codes associated with the depressed key in the data memory 3m or instructs the data processor 3q to tailor a group of pcm data codes for the depressed key. The supervisor 3k accesses the internal table thereof, and determines appropriate timing for producing the audio signal as by step S64. The supervisor 3k waits for the appropriate timing, and supplies the group of pcm data codes to the audio signal generator 3u for producing the audio signal as by step S65. Then, the audio signal is amplified by the amplifier 3d, and the speaker system 3e produces a synthesized sound corresponding to the depressed key. After the step S65, the supervisor 3k returns to the program sequence shown in Fig. 5A, and proceeds to step S7 in Fig. 4A. However, if one of the pedal such as the damper pedal is moved, the answer to the step S62 is given positive, and the supervisor 3k checks the detecting signal from the pedal sensors 3c to see whether or not the pedal is pushed down as by step S66. If the player steps on the pedal, the answer to the step S66 is given positive, and the supervisor 3k accesses the pcm data codes in the data memory 3m or instruct the data processor 3q to tailor the pcm data codes as by step S67. The supervisor further accesses the pcm data codes in the data memory 3o or instructs the data processor 3p to tailor the pcm data codes as by step S68 so as to simulate the resonant vibrations on the related strings. The supervisor 3k controls the timing of the pcm data codes for the original vibrations and the timing of the pcm data codes for the resonant vibrations as by step S69, and time delay is introduced between the timing for the original vibrations and the timing for the resonant vibrations. Upon completion of the step S69, the supervisor 3k proceeds to the step S65. On the other hand, if the pedal is upwardly moved to the rest position, the answer to the step S66 is given negative, and the supervisor 3k instructs the data processor 3q to sequentially decrease the values of the pcm data codes at a selected speed so as to decay the synthesized tone and the resonant tones as by step S70. Then, the supervisor 3k proceeds to the step S65. Turning back to Fig. 4A, while the player is performing the music in the electronic sound producing mode, the supervisor 3k periodically checks the input port assigned to the instruction signal MODE to see whether or not the mode is changed to the mechanically sound producing mode as by step S7. If the answer to the step S7 is given negative, the supervisor 3k returns to the step S6, and reiterates the loop consisting of the steps S6 and S7. However, if the answer to the step S7 is given positive, the supervisor 3k returns to the step S2 again. Thus, the supervisor 3k sequentially executes the loop consisting of the steps S2 to S7, and the player performs the music in either sound producing mode. As will be appreciated from the foregoing description, the keyboard instrument according to the present invention is equipped with the catcher stopper 2c switched between the free position and the blocking position, and the player can enjoy a music without disturbing his family and neighborhood. Moreover, the catcher stopper 2c is added to an upright piano for providing the acoustic piano 1 without change of a component member of the upright piano, and upright piano already used can be easily remodeled. The catcher 1r is shorter than the hammer shank 1n, and the moment exerted on the leather pad 2h is small. For this reason, the leather pads 2h can serve for long time without change. Second Embodiment Turning to Fig. 5 of the drawings, another catcher stopper 20 is illustrated, and is incorporated in another keyboard instrument embodying the present invention. The keyboard instrument implementing the second embodiment also largely comprises an acoustic piano, a controlling system and an electronic sound generating system, and selectively enters a mechanical sound producing mode and an electronic sound producing mode as similar to the first embodiment. The acoustic piano and the electronic sound generating system of the second embodiment are similar to those of the first embodiment, and the controlling system is only different in the structure of a catcher stopper 20 from the controlling system 2 of the first embodiment. For this reason, description is focused on the catcher stopper 20. The catcher stopper 20 comprises a movable bracket member 20a having a plurality of threaded holes, a plurality of screws 20b respectively associated with catchers 21 and screwed into the threaded holes, a solenoid-operated actuator 20c for shifting the movable bracket between the free position and the blocking position and a plurality of cushion sheets attached to the upper surfaces of the catchers 21. The solenoid-operated actuator 20c is responsive to a driving signal supplied from a driver unit (not shown), and projects and retracts the movable bracket member 20a into and from the blocking position. While the movable bracket member 20a is in the free position, the catcher 21 and the associated butt freely rotate without interruption of the screws 20b. On the other hand, the screws 20b in the blocking position restrict the rotations of the catchers 21, and the key action mechanisms give the unique piano key-touch to a player without acoustic sound. The screws 20b is turnable without any special tool, and allow a tuner to easily regulate the distance from the associated catchers 21. Third Embodiment Turning to Fig. 6 of the drawings, a catcher stopper 30 embodying the present invention is associated with one of the key action mechanisms 31 incorporated in yet another keyboard instrument according to the present invention. The keyboard instrument implementing the third embodiment also largely comprises an acoustic piano, a controlling system and an electronic wound generating system, and selectively enters a mechanical sound producing mode and an electronic sound producing mode as similar to the first embodiment. The acoustic piano and the electronic sound generating system of the third embodiment are similar to those of the first embodiment, and the controlling system is only different in the structure of a catcher stopper 30 from the controlling system 2 of the first embodiment. For this reason, components corresponding to those of the first embodiment are labeled with the references used in Fig. 2 without detailed description, and description is focused on the catcher stopper 30. The catcher stopper 30 comprises a movable bracket member 30a shared between all of the key action mechanisms 1b, a plurality of projecting members 30b fixed to the movable bracket member 30a through screws and respectively associated with the key action mechanisms 1b, a plurality of cushion members 30d respectively attached to the lower surfaces of the projecting members 30b and an actuator 30e responsive to a driving signal from a driver unit (not shown) for shifting the projecting members 30b between the free position and the blocking position. As will be better seen from Fig. 7, slits 30f are respectively formed in boss portions of the projecting members 30b, and the screws 30c press the boss portions to the upper surface of the movable bracket member 30a. The leading end portions of the projecting members 30b are longer than the thickness of the catchers (see Fig. 6), and are oblique with respect to the upper surfaces of the catchers 1r. When a tuner regulates the distance between the upper surfaces of the catchers 1r and the cushion sheets 30d, the screws 30c are loosened, and projects or retracts the projecting members 30b with respect to the front edge of the movable bracket member 30a. If a projecting member 30b is projected from the front end, the cushion sheet 30d becomes closer to the upper surface of the associated catcher 1r. On the other hand, if a projecting member 30b is retracted, the cushion sheet 30d is further spaced from the upper surface of the catcher 1r. Thus, the tuner can access the screws 30c from the front side of the keyboard instrument, and the regulation is easily carried out. Fourth Embodiment Turning to Fig. 8 of the drawings, essential parts of still another keyboard instrument embodying the present invention is illustrated. The keyboard instrument implementing the fourth embodiment also largely comprises an acoustic piano, a controlling system and an electronic sound generating system, and selectively enters a mechanical sound producing mode and on electronic sound producing mode as similar to the first embodiment. The acoustic piano of the third embodiment is analogous to the acoustic piano 1, and the electronic sound generating system is similar to that of the first embodiment except for an array of hammer sensors 40. For this reason, component parts corresponding to those of the first embodiment are labeled with the references used in Fig. 2 without detailed description, and description is focused on the catcher stopper 30. In the fourth embodiment, the hammer sensors 40 are respectively associated with the hammer mechanisms 1c, and detect the respective hammer motions instead of the key sensors 3b. Each of the hammer sensors 40 is implemented by the combination of a photo-interrupter 40a and a shutter plate 40b. Between action brackets 40c is provided a rail member 40d to which the photo-interrupters 40a are fixed in association with the hammer shanks 1n of the hammer mechanisms 1c. The photo-interrupter 40a is the combination of a photo-emitting element and a photo-detecting element, and the shutter plate 40b passes across an optical path between the photo-emitting element and the photo-detecting element. The controlling system is only different in the structure of a catcher stopper 30 from the controlling system 2 of the first embodiment. A slit 40d is formed in the shutter plate 40b, and the photo-interrupter 40a produces an electric signal with two peak voltages while the shutter plate 40b is passing across the optical path. The lapse of time between the peaks is proportional to the hammer velocity, and a supervisor incorporated in a sound processing unit estimates the impact of the hammer head 1o at the associated strings 1d. The controlling system of the fourth embodiment comprises a plurality of catcher stoppers 41 spaced at intervals and a driving mechanism 42 for the catcher stopper 41. Each of the catcher stoppers 41 is shared between selected catchers 1r. The catcher stoppers 41 are shifted between a free position and a blocking position by a player. While the catcher stoppers 41 are in the free position, the catchers 1r are movable without any interruption of the catcher stoppers 41. However, if the catcher stoppers 41 enter into the blocking position, the catchers are brought into contact with the associated catcher stoppers 41 before the hammer heads 1o strike the associated strings 1d. As will be better seen from Figs. 9 and 10, the driving mechanism 42 comprises a pedal 42a projecting from the lower front board 43, a link mechanism 42b connected at one end thereof with the peal 42a, an arm member 42c connected with the other end off the link mechanism 42b, a rod member 42d rotatably supported by journal units 42e and connected with the arm member 42c and a return spring 42f connected with the arm member 42c. The rod member 42d is formed of wood, metal or synthetic resin, and well withstands impacts of the catchers 1r. The journal units 42e are supported by the action brackets 40c, and the return spring is anchored at a stationary board member of the acoustic piano. The arm member 42c is partially cut away, and a felt member 42g is bonded to the periphery. The link mechanism 42b passes on the felt member 42g, and in terminated at the arm member 42c. The felt member 42g allows the link mechanism 42b to move without noise. When the player steps on the pedal 42a, the link mechanism 42b pulls down the arm member 42c, and the rod member 42 is driven for rotation so that the catcher stopper 41 enters into the blocking position. If the player laterally pushes the pedal 42a, the lower front board 43 keeps the catcher stopper 41 in the blocking position. On the other hand, if the player pushes the pedal 42a in the opposite direction and releases his foot from the peal 42a, the return spring 42f pulls down the opposite end of the arm member 42c, and the rod member 42d is driven for rotation in the opposite direction so as to recover the catcher stopper 41 from the blocking position to the free position. Each of the catcher stoppers 41 comprises a bracket member 41a attached to the rod member 42d, a cushion member 41b attached to the bracket member 41a and a protection sheet 41c attached to the cushion member 41b. The cushion member 41b absorbs the impact of the catcher 1r, and is formed of urethane in this instance. The protection sheet 41c is formed of excenu, and prolongs the service life of the cushion member 41b. 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 claims. For example, a keyboard instrument according to the present invention may further have a silence mode where neither acoustic sound nor synthesized sound is produced.

Claims: A keyboard instrument selectively entering a mechanical sound producing mode and an electronic sound producing mode, comprising: a) an acoustic piano (1) including a-1) a keyboard (1a) having a plurality of keys (1g) turnable with respect to a stationary board member (1f), said plurality of keys being selectively depressed by a player, a-2) a plurality of key action mechanisms (1b) respectively coupled with said plurality of keys, and selectively actuated by said plurality of keys when said player depresses, said plurality of key action mechanisms having respective whippens (1j) functionally connected with said plurality of keys, respectively, respective catchers (1r/1s; 21) respectively projecting from butts (1m) and respective back checks (1t/1u) respectively projecting from said whippens so as to be brought into contact with said catchers when said player releases the associated keys, a-3) a plurality of hammer mechanisms (1c) respectively associated with said plurality of key action mechanisms, and having respective hammer heads (1o) and said butts (1m) supporting said hammer heads, respectively, said plurality of key action mechanisms being driven for rotation by said plurality of key action mechanisms when said player selectively depresses said plurality of keys, and a-4) a plurality of strings (1d) associated with said plurality of hammer mechanisms, and struck by said hammer heads in when the player selectively depresses said plurality of keys; b) an electronic sound producing means (3a/3b/3c/3d/3e/3g/3h) monitoring said plurality of keys to see what keys are depressed by said player in said electronic sound producing mode, and operative to electronically produce sounds corresponding to the keys depressed by said player; and c) a controlling means having a movable stopper means (2f; 20b; 30b/30c/30d; 41a/41b/41c) associated with said catchers, and a driver unit (2b/2d/2e; 20a/20c; 20a/30e; 42) responsive to an instruction of said player for driving said movable stopper means between a free position in said mechanically sound producing mode and a blocking position in said electronically sound producing mode, said catchers being freely moved together with the associated butts without interruptions of said movable stopper means while said movable stopper means is staying in said free position, said catchers being brought into contact with said movable stopper means in said blocking position before the associated hammer heads strike said plurality of strings. The keyboard instrument as set forth in claim 1, in which said movable stopper means is implemented by a plurality of movable stoppers (2f; 20b; 30b) respectively associated with said catchers (1r/1s; 21), and said driver unit comprises a bracket member (2d; 20a; 30a) shared between said plurality of movable stoppers, an actuator (2e;20c;30e) connected with said bracket member for projecting and retracting said bracket member and a driver circuit (2b) for energizing said actuator, said plurality of movable stoppers entering into said blocking position when said actuator projects said bracket member, said plurality of movable stoppers entering into said free position when said actuator retracts said bracket member. The keyboard instrument as set forth in claim 2, in which each of said plurality of movable stoppers (2f) comprises a bolt member having a threaded portion (2g) screwed into said bracket member and a head portion, and a cushion means (2h) attached to a lower surface of said head portion and faced to the associated catcher in said blocking position. The keyboard instrument as set forth in claim 3, in which a hole (2i) is formed in said head portion so that a tuner regulates a distance between a lower surface of said cushion means (2h) and said associated catcher (1r/1s) by rotating said head portion with a tool (2j) inserted into said hole. The keyboard instrument as set forth in claim 2, in which each of maid plurality of movable stoppers comprises a bolt member (20b) having a threaded portion screwed into said bracket member (20a) and a head portion engageable with a tool, and a cushion means (20d) attached to an upper surface of the associated catcher (21) and faced to a leading end of said threaded portion in said blocking position. The keyboard instrument as set forth in claim 2, in which each of said plurality of movable stoppers comprises a projecting member (30b) having a boss portion with an elongated slit (30f) and a leading end portion, a bolt (30c) screwed through said elongated slot into said bracket member (30a) for pressing said boss portion onto said bracket member and a cushion means (30d) attached to a lower surface of said leading end portion and faced to the associated catcher in said blocking position. The keyboard instrument as set forth in claim 1, in which said driver unit (42) comprises a pedal member (42a) engageable with a board member (43) of said acoustic piano for maintaining depressed state, a link mechanism (42b) connected with said pedal member, a rod member (42d) journaled at stationary portions of said acoustic piano, a converting means (42c) operative to convert a motion of said link mechanism into a rotation of said rod member and a return spring (42f) for allowing said pedal member to return to a rest position when said pedal member is released from said board member, and said plurality of movable stoppers (41) are attached to an outer surface of said rod member at spacings, said plurality of movable stoppers entering said blocking position when said pedal member is depressed, said plurality of movable stoppers entering said free position when said pedal member is released. The keyboard instrument as set forth in claim 7, in which each of said plurality of movable stoppers (41) is shared between selected catchers. The keyboard instrument as set forth in claim 7, in which each of said plurality of movable stoppers (41) comprises a bracket member (41a) attached to said outer surface of said rod member, a cushion member (41b) attached to said bracket member for absorbing an impact of the catcher and a protecting sheet (41c) attached to said cushion member for prolonging a service time of said cushion member.

Inventors: KAWAMURA KIYOSHI, KAWAMURA, KIYOSHI, KAWAMURA, KIYOSHI, C/O YAMAHA CORPORATION
Applicants: YAMAHA CORP, YAMAHA CORPORATION
Application year: 1993
Main classification: G10C3
IPC codes: G10C3, G10C5