WO2004015684A1

WO2004015684A1 - Roll-up electronic piano

Info

Publication number: WO2004015684A1
Application number: PCT/KR2003/001589
Authority: WO
Inventors: Young-So Chang
Original assignee: Young-So Chang
Priority date: 2002-08-07
Filing date: 2003-08-07
Publication date: 2004-02-19
Also published as: AU2003248152A1; EP1436804A1; US20050034591A1; CN1602514A; KR200294131Y1; JP2005521922A

Abstract

The present invention relates to an electronic piano capable of rolling up a keyboard. A roll-up electronic piano according to the present invention comprises a keyboard including piezoelectric material and a control part with a sound chip, which controls and amplifies electrical piezoelectric signals. The roll-up electronic piano has a foldable and unfoldable keyboard and is easy to carry due to ultra-light weight and small size. Particularly, the roll-up electronic piano produces a similar tone to that of a real piano. Therefore, the rollup electronic piano can be conveniently used in music classes and enhance the efficiency of learning. In addition, the roll-up electronic piano can be played anywhere without being restricted by space and can be controlled by a wireless method after the keyboard is separated from the control part.

Description

ROLL-UP ELECTRONIC PIANO

Technical Field

The present invention relates to an electronic piano capable of rolling up a keyboard and, more particularly, to a roll-up electronic piano whose tone is similar to that of a real piano, which is much smaller and lighter than existing electronic pianos, and which is easy to use. The electronic piano according to the present invention comprises a border member which includes a piezoelectric material and performs on/off functions; a keyboard whose cover is made of silicon material and which is capable of being folded/unfolded; and a control part which controls and amplifies piezoelectric signals, can be separated from the keyboard, and can perform wire/wireless send/receive functions.

Background Art The present, invention relates to an electronic piano and, more particularly, to a roll-up electronic piano which controls and amplifies electric signals, whose tone is similar to a real piano, which is effective in music education for children, and which is easy to carry due to small size and low weight.

Generally, children individually have practical training using keyboard instruments similar to a piano for a music class. Among typical personal keyboard instruments for use of children, a hard keyboard is known with about two octaves, which is played through insufflating air by means of a mouth. As an example, Korean utility model patent publication No. 88-13187 discloses an electronic piano using an electronic circuit design with IC (integrated circuit). However, it is impossible for the electronic piano to control the volume of sound according to the strength of force pressing the keyboard. Moreover, the electronic piano has only on/off functions. As a more advanced one, there is a keyboard instrument that can be connected to a computer, but this also has simple on/off functions.

In addition, the above-mentioned keyboard instruments are cumbersome to carry with because of large size thereof and provide little help to a music education due to poor effects of usage and functions. In other words, it is difficult for the existing keyboard instruments to sound similar tone to that of a real piano and to represent the strength of sound.

For another example, the United States patent No. 6,259,006 discloses an electronic piano providing some means capable of coping with the problems. The electronic piano is portable and foldable, has small size and light weight, and can be connected to a computer. Moreover, the tone of the electronic piano is similar to that of a real piano. However, the electronic piano has a problem that when the keyboard is folded with the power on, the keys pressed may generate a loud noise. Moreover, if the user does not turn off the power and rolls up the keyboard carelessly, the keyboard may continue to generate the loud noise for a long time without being perceived by the user because the electronic piano has headphones instead of speakers. Thus, this may have an electrically ill effect on the inside electric devices ofthe electronic piano. The above-mentioned U.S. patent has another problem in a method of generating sounds. A real piano does not have a vibrato effect. However, in the electronic piano without a period for a piezoelectric material to perceive input, if a user first presses a key of the keyboard and, then, changes the pressure of his/her finger, the vibrato effect may occur. In addition, if the user presses slowly and deeply the keyboard, the pressure on the piezoelectric material gradually increases and, therefore, the volume of sound also gradually increases because an electric current increases gradually. On the contrary, if the user slowly relaxes the pressure of his/her finger, the pressure on the piezoelectric material gradually decreases and, therefore, the volume of sound also gradually decreases because an electric current gradually decreases. It may become a considerable problem in reproducing a tone of a real piano. As shown in Fig. 1, a real piano generates sound in a way that a hammer (200) hits a string (300) when a user presses a key (100). Thus, when the user presses a key once, the hammer hits the string once and the vibrato effect cannot occur. The vibrato effect is a technique of vibrating the sound of a voice or a musical instrument, and is different from tremolo as a rapid repetition of a note. For example, the vibrato of string instruments occurs by means of fast movement of a finger on a string and the vibrato of wind instruments, by means of a control of breathing.

The electronic piano according to the above-mentioned American patent, which has an imperfect operating construction of piezoelectric material, can embody a similar tone to that of a real piano in some degree, but cannot embody sound effect that is produced in a way that a hammer hits a string. Moreover, although the above-mentioned American patent can embody a tone of a real piano through using a simple contact method instead of using a piezoelectric material, the simple contact method cannot control the strength ofthe tone. In other words, it cannot embody sound effects according to the strength of pressing a key. The American patent can damp or sustain a sound by using pedals, but cannot embody an effect strengthening the sound.

Another disadvantage of the conventional foldable electronic piano is that a user may not play the electric piano in a place with a narrower width than the length of the keyboard. Generally, a desk in a classroom has a length of about 60 cm and, therefore, the keyboard with more than four-octave whose key has same size as that of a key of a real piano, endows some trouble in rolling it out on the desk. In other words, some section of the keyboard drops downward from the top of the desk, and, therefore, it is practically impossible to play the electric piano because the keys in the folded section are already being pressed.

Disclosure of Invention

Accordingly, the present invention is directed to a new roll-up electronic piano that substantially obviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a roll-up electronic piano, which has small size due to foldable keyboard, can produce sounds according to the strength and the duration of pressure in pressing a key, can embody a similar tone to that of a real piano by preventing a vibrato effect, can be controlled through wire/wireless communications and played even in a narrow space because it has a removable structure capable of separating a keyboard and a control part, and can be used conveniently in a music class for children and students due to small size and light weight. To achieve the object and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention provides a roll-up electronic piano comprising a keyboard made of piezoelectric material and a control part which can control and amplify electrical piezoelectric signals. The keyboard of the electronic piano according to the present invention produces a signal by electromotive force through a piezoelectric polymer film such as poly vinylidene fluoride (hereinafter referred to as "PVDF") or a piezoelectric fiber when a user presses a key of the keyboard. The piezoelectric polymer film generates a voltage according to the strength and the duration of impact. The generated signals is controlled and amplified in the control part with a sound chip and sent to a speaker.

The keyboard of the roll-up electronic piano of the present invention has 4~8 octaves, and can be rolled up to form a cylinder. The keyboard comprises a coupling member for connection with the control part. The coupling member is made of flexible material that can mechanically withstand strains produced by folding/unfolding operations. In addition, white keys and black keys of the keyboard are designed in accordance with the standard configuration of a real piano. Inside the keyboard is a piezoelectric polymer film such as PVDF or a piezoelectric fiber that generates piezoelectric electromotive force corresponding to each key of the keyboard. The covering of the keyboard except the coupling member is made of flexible rubber. Therefore, the electronic piano of the present invention can be easily rolled up to form into a small size and is always portable. The control part comprises an electronic circuit design including a microprocessor and a sound chip. In the electronic piano of the present invention, a loud noise may not be generated although the keyboard is rolled up with the power on and the keys are depressed because the border member of the keyboard part comprises a second piezoelectric material other than the piezoelectric material contained inside the keyboard. The second piezoelectric material generates voltage when it is bent. If the piezoelectric material is bent excessively and the resulting voltage is higher than an adequate voltage, the control part produces a signal based on the voltage which controls the electrical power. Therefore, the roll-up electronic piano can obviate a loud noise that may be produced by the keyboard folded without power- off. The roll-up electronic piano can produce a similar tone to that of a real piano because the present invention can eliminate a vibrato effect. One of general characteristics of the piezoelectric material is a change of voltage due to a change of resistance by pressure. According to the change of voltage, volume of sound generated from a sound chip changes. An electronic piano according to a prior art can sound a real piano tone that a hammer hits a string only when a key is pressed with uniform force. Although a user does not become aware of the difference during playing simple musical notes, he/she can feel inconvenience due to the general characteristics of the piezoelectric material in case of playing complex musical notes. For example, if a first finger presses a first key while a second finger continuously presses a second key, it is difficult for the first finger to continuously press the first key with uniform force. To obviate this problem, the keyboard ofthe electric piano according to the present invention has a function to detect the start of applying pressure and a function to detect change of voltage in the piezoelectric material for a fixed time, thereby preventing the vibrato effect. That is, the start of transformation of the piezoelectric material at more than a fixed pressure is perceived as the contact of a finger on a key, and a voltage immediately after the key is pressed at a desired force is obtained while change of a voltage generated thereafter is not obtained. Then, if the pressure on the key is diminished to less than a fixed pressure and the piezoelectric material is restored to the original state, the keyboard finishes generating a sound. Therefore, in playing the electronic piano, an unnecessary vibrato effect can be prevented.

The roll-up electronic piano according to the present invention can be played effectively in a narrow space because it has a function controlling the number of octaves of the keyboard thereby eliminating the inconvenience in a detaching the keyboard.

In addition, the roll-up electronic piano is divided into the control part and the keyboard and can be controlled by a wire or a wireless method. When the electronic piano is divided into the control part and the keyboard, signals according to change of voltage generated from the keyboard is transformed to digital signals and the digital signals and a unique ID value (a unique number of a apparatus) is transmitted to the control part. The control part identifies the ID value received and generates sounds according to the digital signals received.

The covering of the keyboard is made of flexible material such as rubber, more preferably silicon rubber. The silicon rubber has good thermal endurance, cold resistance, and moisture resistance. The silicon rubber has poor adhesive property, but this disadvantage can be eliminated through reforming the surface thereof.

Of course, the roll-up electronic piano with a simple structure can be produced. If a PCB is used instead of the piezoelectric material and the wireless function is omitted, the roll-up electric piano with sufficient functions can be produced at a low cost.

The roll-up electronic piano according to the present invention, connected to peripheral devices such as a personal computer, can store and reproduce a record of playing as a music file by transforming analog signals into digital signals. Brief Description of the Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a diagram illustrating a principle of sound generation in a real piano;

Fig. 2 is a block diagram describing an electronic piano according to the present invention; Fig. 3a is a cross-sectional view of a keyboard according to an embodiment ofthe present invention;

Fig. 3b is a cross-sectional view of a keyboard according to another embodiment ofthe present invention;

Fig. 3c is a cross-sectional view of a keyboard according to another embodiment of the present invention;

Fig. 4 illustrates a removable structure of a roll-up electronic piano according to the present invention;

Fig. 5 illustrates a roll-up electronic piano with pedals according to the present invention; Fig. 6 illustrates an exterior of a roll-up electronic piano according to the present invention;

Fig. 7 illustrates, in a cross-sectional view, a folded state of the roll-up electronic piano according to the present invention;

Fig. 8 illustrates, in a perspective view, a folded state of the roll-up electronic piano according to the present invention; and

Fig. 9 is a perspective view of a roll-up electronic piano according to the present invention.

Best mode for Carrying Out the Invention

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Referring to Fig. 2, a keyboard (10) outputs a signal of electromotive force using PVDF or a piezoelectric fiber with piezoelectric characteristics, based on the strength and duration of pressure according to play by a user. That is, while an electric current is applied into the PVDF, the PVDF generates a voltage according to the strength and the duration of pressure. The outputted signal is amplified in the control part (20) having a sound chip and then, sound comes out through a speaker (22). The sound chip can provide dozens or hundreds of tones.

In addition, the sound chip (24) according to the present invention can provide the same sound effect as a real piano. The various magnitudes of sound generated when a key of real piano is pressed at various pressures are made into data and the data is compared to a voltage from the piezoelectric material (15), which is generated when a key of keyboard (10) ofthe electronic piano is pressed. Then, the data corresponding to the voltage is stored in the sound chip (24) to generate the same magnitude of sound with that ofthe real piano. In detail, inside the keyboard (10) is the piezoelectric material perceiving pressure, which is enclosed by a conducting pattern film, and an insulator is formed so as to enclose the conducting pattern film. Referring to Fig. 3 a, upper and bottom conducting pattern films (16) are positioned on and underneath the piezoelectric material (15), and upper and lower insulators (17) are positioned so as to enclose the conducting pattern films (16). Then, a shock-absorbing member (18) is positioned on top ofthe upper insulator (17). The covering ofthe keyboard (10) is made of silicon rubber (19). The insulators (17) suppress a static electricity that may be generated on the surface ofthe keyboard (10). In the above-mentioned keyboard structure, the voltage generated when a key of the keyboard (10) is pressed is controlled by a microprocessor (23) of a control part (20). The signal controlled by the microprocessor (23) changes into sound through the sound chip (24), an amplifier, and the speaker. When a user presses a key of the keyboard (10), pressure is applied on the silicon rubber (19) and the pressure is transmitted to the shock-absorbing member (18). The shock- absorbing member (18) does not transmit the pressure to the insulator (17) if the pressure is less than a predetermined value. That is, in case of merely placing a finger on the keyboard, the shock-absorbing member (18) made of a soft material absorbs the pressure to suppress the generation of sound. In addition, the shock- absorbing member (18) may be formed in various density and thickness so as to provide touch of a real piano. If the shock-absorbing member (18) is excessively thin or soft, the keyboard may reduce the feeling of pressing a key of a real piano. If the shock-absorbing member (18) is excessively thick, the keyboard may not be easily rolled up. If the shock-absorbing member (18) is excessively hard, more pressure is required to press the key than for a real piano. Thus, the shock- absorbing member (18) has to be made of a material with an adequate density and thickness according to users' taste.

If adequate pressure is applied on the shock-absorbing member (18), the insulator (17) disposed underneath the shock-absorbing member (18) is pressed and then, the conducting pattern film (16) underneath the insulator (17) is pressed to transmit the pressure to the piezoelectric material (15). The conducting pattern film (16) is a means to transmit the change of voltage on the piezoelectric material (15) to the control part. The pressure transmitted transforms the piezoelectric material (15), thereby changing resistance in the piezoelectric material to change voltage ultimately.

Then, immediately, the microprocessor (23) in the control part generates a first signal. Even after the microprocessor generates the first signal, the pressure continues to increase until it reaches to a desired strength. If the desired strength is transmitted completely, transformation rate of the piezoelectric material (15) is diminished, the microprocessor perceives decrease in the change of voltage and resistance and generates a second signal immediately after detecting the desired strength.

The time interval between the first and second signals corresponds to a period from when a user starts to press a key of a real piano to when he/she finishes to press it with desired strength. That is, the time interval corresponds to a period from when a user presses a key of a real piano to when a hammer in the real piano hits a string. The microprocessor (23) controls the sound chip so as not to generate sound for the time interval between the first and the second signal. The microprocessor (23) generates sound after the second signal is created. In addition, to prevent the vibrato effect brought about by a minute change of the pressure after completely pressing to the desired strength, the magnitude in the change of voltage corresponding to the second signal is compared to the data stored in the sound chip (24) beforehand to generate only a single adequate sound. Therefore, a single sound is generated for each press of a key. The sound generated by the second signal is set up so as to decrease according to the strength of press like a real piano whose sound slowly decreases while the user continues to press the key. In addition, the sound is set up so as to stop sounding immediately after the user removes his finger from the key, same as the real piano. Accordingly, the present invention can prevent changeful electronic sound which may be generated from existing electronic keyboards, and generate clear sound of a real piano. Examples of the changeful electronic sound include a crescendo effect that the volume of sound gradually increases during a time interval between the first and second signal, a vibrato effect which is generated because of fingers' movements in case of pressing a key while continuously pressing another key, and a decrescendo effect that the volume of sound gradually decreases during an instant time interval in which the finger is removed from the key.

The covering of the keyboard is made of a flexible rubber, preferably, silicon rubber so that the keyboard can be rolled up. The silicon rubber has good heat resistance, cold-resistance, and moisture resistance. In addition, a pattern imprinted on the surface of the silicon rubber stands well. On the other hand, the silicon rubber has a defect that adhesion between the silicon rubbers is poor. However, the present invention can overcome the defect by reforming the surface of the silicon rubber. The reformed surfaces of the silicon rubber can firmly adhere each other. A method of reforming the silicon rubber comprises the steps of injecting an inert gas into a vacuum chamber; making the inert gas into a plasma state by applying plasma potential so that the inter gas can move very rapidly; and forming fine grooves on the surface of the silicon rubber using the inert gas in plasma state. An adhesive infiltrates into the fine grooves so that the upper plate of the keyboard covering made of silicon rubber can adhere to the lower plate of the keyboard covering. With reform of the surface of the silicon rubber, an inexpensive general adhesive can be used to connect the upper and lower plates of the keyboard covering instead of an expensive exclusive adhesive for silicon rubber. The reformed silicon rubber can maintain adhesive force with repeated folding and unfolding operations.

Shape of a keyboard is printed on the upper plate ofthe keyboard covering. Here, another advantage of the reformed silicon rubber with fine grooves is that when white keys and black keys are printed on the upper plate of the keyboard covering, the number of times of printing can be markedly reduced because ink can easily infiltrate into the silicon rubber through the fine grooves. For example, in case of using a usual silicon rubber, the white ink is applied three times and the black ink is applied twice in printing. On the other hand, in case of using the reformed silicon rubber, the white ink is applied twice and the black ink is applied once. In addition, a good printing quality can be achieved even with general inks instead of expensive inks.

In the keyboard (10) of the roll-up electronic piano according to the present invention, inside the border member is a second piezoelectric material. The second piezoelectric material is means to overcome the defect that the keyboard generates a loud noise when it is rolled up with the power on. If the second piezoelectric material is bent excessively to more than a particular angle due to a folded keyboard or a careless usage, it is transformed to change resistance thereby changing voltage and, ultimately, the power is turned off. As another embodiment, the voltage generated from the piezoelectric material may turn off the power and the power may be turned on when the piezoelectric material is unfolded to less than a particular angle. Such a power on/off method includes on/off only by a power switch; on/off by a power switch and off by the second piezoelectric material in the border member; on/off by a power switch and on/off by the second piezoelectric material in the border member; and on/off only by the second piezoelectric material in the border member.

The roll-up electronic piano according the present invention can be played easily in a narrow space because the control part (20) has a button that can control an active range of the keyboard (10). The keyboard (10) may have an arbitrary octave range, preferably 3~8 octaves. The control part (20) can choose the active range ofthe keyboard (10) according to the availability of space. For example, the active range of keyboard may be selected from one octave to eight octaves, based on an octave unit or a key unit, starting from the control part (20). Or, the active range of the keyboard can be arbitrarily selected regardless of the vicinity of the control part based on the octave unit or the key unit. Therefore, the roll-up electronic piano can be played conveniently in a narrow space with a simple operation of a button compared to inconvenience of a conventional electronic piano whose keyboard part is detached or attached on occasion.

Referring to Fig. 4, the roll-up electronic piano of the present invention has a removable structure where the control part and the keyboard are separated and can be controlled through a wire or wireless method. In case of controlling through a wireless method, there are required several additional elements such as a separate power supply unit for the keyboard, A/D converter which converts change of voltage generated from the keyboard (10) into a digital signal, a signal processing part which adds a unique ID value (i.e., a unique number of an apparatus) to the digital signal, and a transmitting part which transmits the signal with the unique ID value. The power supply unit, A/D converter, signal processing part, and transmitting part are installed in a coupling member (14). The control part (20) has additionally a receiver that receives the signal from the keyboard (10). The signal received in the control part is perceived only after the microprocessor (23) identifies the unique ID that is included in the signal. To prevent errors that may happen when a plurality of people play the electronic pianos simultaneously.

The roll-up electronic piano of the present invention comprises different components according to the wire or wire/wireless simultaneous method. In case ofthe wire method in which the keyboard (10) is coupled to the control part (20), the sound is generated by an electric analog signal. In case of the wire/wireless simultaneous method, the sound is generated by a process of converting the analog signal into the digital signal. Therefore, the necessary components are adequately selected according as which signal is selected from the digital and analog signals.

In case of the method using the digital signal, the electronic piano can be connected to peripheral devices such as a personal computer and USB drive in order to record the playing into a music file. In addition, in case of wireless method using the digital signal, a software may be used as the control part instead of hardware. For example, a program to be used as the control part can be downloaded from an internet web site. In this method, a receiver, which receives signals from the keyboard, has to be added. In case of using a personal computer instead ofthe control part, a program to be used as the control part is downloaded from an Internet web site and, then, a receiver coupled to a USB receiving board in the computer receives the signal transmitted from the keyboard to generate sound.

When personal telecommunications devices such as a cellular phone and a personal digital assistance (PDA) is used as the control part, a program to be used as the control part is downloaded from an internet web site and, then, a receiver coupled to an interface in the personal telecommunications device receives the signal transmitted from the keyboard to generate sound. In addition, by installing a program to be used as the control part in an external telecommunication equipment, the roll-up electronic piano can be utilized more effectively.

The roll-up electronic piano may have a simpler structure using a PCB (printed circuit board). The PCB is inexpensive and can provide a simple constitution although it has a disadvantage that it cannot embody the strength of sound compared to the method using piezoelectric material and a microprocessor. For example, the roll-up electronic piano comprises a keyboard including two plates of PCB film and silicon rubber and covering of a control part including a simple sound chip without a microprocessor.

Referring to Fig. 3b, a plurality of protrusions (3) made of insulating material are formed at lower surface of a upper PCB (1) to maintain a distance length between the upper (1) and a lower (2) PCB when a key of the keyboard is pressed. When a key is pressed, pressure is first applied to the keyboard covering made of silicon rubber (19) and transferred to a shock-absorbing member (18). If the pressure is less than an adequate value, the shock-absorbing member may not transfer the pressure received to the insulator (17). That is, if a user lightly touches the keyboard with his/her finger, the shock-absorbing member made of a soft material absorbs the pressure to suppress the generation of sound. If the pressure transmitted to the shock-absorbing member is more than an adequate value, the pressure is transferred to the insulator (17) and the PCB in sequence. The upper and lower PCB are connected to the sound chip through metal interconnection for each key. The PCBs (1 and 2) can maintain flexibility and elasticity in repeated folding and unfolding operations and generate sound by an electric current which flows when the upper PCB becomes in contact with the lower PCB.

As another embodiment, the electronic piano may comprise the piezoelectric material and the PCB together. Referring to Fig. 3c, a keyboard (10) comprises a shock-absorbing member (18), insulator (17), piezoelectric material (15), an upper PCB (1), and a lower PCB (2). Such a keyboard structure may simplify functions of the microprocessor (23) and the sound chip (24) compared to the method using only electrical signals, and overcome a disadvantage that in case of using only the PCB that the strength of pressure cannot be perceived. In respect to a correlation between the piezoelectric material (15) and the microprocessor (23), if only the piezoelectric material (15) is used, generation of sound is controlled by pulse signals according to time using a first and second signals. However, if the piezoelectric material and the PCB are used together, the first signal is not required. That is, only one signal is generated because an instant when the voltage generated from the piezoelectric material (15) is reduced after an electric current flows between the upper and the lower PCBs replaces both first and second signals. As soon as the upper PCB becomes in contact with the lower PCB, the magnitude of voltage from the piezoelectric material is perceived and a signal to determine the volume of sound is generated.

A real piano has two or three pedals. The pedals control the strength and the length of sound being related to movement of fingers. There are several types of pedals such as a damper pedal, a soft pedal, a sostenuto pedal, and a muffler pedal. The damper pedal raises all the dampers (the felt pads which rest on the strings to stop the sound) and lets all the strings vibrate without having to hold keys down. If a user presses down the damper pedal, the dampers pressing strings are apart from the strings simultaneously and sustain the vibration of string long after the user removes his/her finger from a key, thereby providing a larger volume of sound, a abundant timbre, and rich tone. If the user presses down the soft pedal, hammers get nearer to strings to shorten the distance that the hammers move to hit the strings, thereby producing soft sound. The sostenuto pedal is a type of selective sustain pedal found in acoustic grand pianos. It sustains only the sounds of keys that were pressed at the time the pedal was engaged. All other notes remain unchanged. If the user presses down the muffler pedal, the felt pads are positioned between the hammers and the strings so that the hammers hit the stings behind the felt pads thereby reducing substantially the volume of sound. Referring to Fig. 5, the various functions of pedals in a real piano can be embodied in the roll-up electronic piano of the present invention through connecting the pedals to the sound chip. The pedals can be selectively set up in accordance with types of pianos, for example, a grand piano or an upright piano and be connected to the control part. Fig. 6 illustrates, in a plane view (30), a left side view (40), and a front view (50), an exterior of the roll-up electronic piano according to the present invention. In the plane view (30), the keyboard (10) comprises four octaves with length of 690.5 mm and width of 170.0mm and, therefore, it has an adequate size for use in a music class. In the front view (50), the keyboard (10) comprises white keys (11) with height of 0.5mm, black keys (12) with height of 0.5mm from the white keys, and a keyboard pad (13) with height of 2.5mm. Therefore, the keyboard has thin thickness of 3.5mm so as to be easily foldable and portable. The height and length of other parts as well as the height of black keys (12) can be arbitrarily adjusted. The coupling member (14) that connects the keyboard (10) with the control part (20) can firmly maintain the coupling with repeated folding and unfolding operations. The control part (20) has preferably length of 120.0 mm, width of 170.0 mm, and height of 38.0 mm. The white keys and black keys are designed in accordance with the standard configuration of a real piano. Inside the keyboard (10) is a piezoelectric polymer film to form a piezoelectric electromotive force corresponding to each key of keyboard. The control part (20) comprises a circuit including an electronic circuit design and a button controlling volume of sound.

Particularly, a standard volume corresponding to the volume of a real piano is marked around the volume button, thereby maximizing the effect of music education. In addition, a music stand may be additionally positioned on the border member of the keyboard at a location where the music stand does not obstruct the function ofthe second piezoelectric material.

The sound chip of the roll-up electronic piano can produce dozens or hundreds of tones. The sound chip has a database for tones and sound effects of dozens or hundreds of instruments such as pianos, guitars, flutes, saxophones, violins, mandolins, harps, and so on as well as data related to tones and the strength of sound according to pressure in a real piano. Particularly, it is important to set up additional functions according to tones selected. For example, in case of selecting a violin tone, an additional function is set up in the microprocessor so as not to generate a signal due to the change of voltage in the piezoelectric material as in the electronic piano because a real violin generates sound not by hitting strings with hammers but by rubbing strings with a fiddle bow.

Fig. 7 illustrates, in a cross-sectional view, a folded state of the roll-up electronic piano according to the present invention. Inside the keyboard (10) part except the coupling member (14) is a soft piezoelectric polymer film or a piezoelectric fiber and the keyboard pad (13) is made of silicon rubber so that the keyboard can be easily rolled up. Therefore, the roll-up electronic piano is easy to carry due to the small size, once folded.

Fig. 8 illustrates, in a perspective view, a folded state of the roll-up electronic piano according to the present invention. Fig. 9 is a perspective view of the roll-up electronic piano according to the present invention.

The roll-up electronic piano according to the present invention can simultaneously generate six notes or more and can be arbitrarily designed from compact 3-4 octaves for use in a music class to 8 octaves for general use.

Industrial applicability

A roll-up electronic piano according to the present invention has a foldable and unfoldable keyboard and is easy to carry due to an ultra-light weight and a small size. Particularly, the roll-up electronic piano produces a similar tone to that of a real piano. Therefore, the roll-up electronic piano can be conveniently used in music classes and enhance the efficiency of learning.

The roll-up electronic piano can be played anywhere without being restricted by space because it can be controlled wirelessly. In addition, the electronic piano can easily produce a music file through connecting the control part to peripheral devices, thereby making it possible to listen to a record of playing repeatedly. The keyboard of the roll-up electronic piano can firmly maintain the adhered state with repeated folding and unfolding operations.

Claims

What Is Claimed Is:

1. A method of generating sound in a roll-up electronic piano comprising the steps of: pressing down a key of a keyboard and transferring pressure to a shock- absorbing member; generating a first signal at the instant that a voltage starts to change due to a transformation of piezoelectric material, the piezoelectric material being transformed by the pressure transmitted from the shock-absorbing member, the shock-absorbing member transmitting the pressure to the piezoelectric material if the pressure is more than a particular magnitude, the shock-absorbing member absorbing the pressure if the pressure is less than the particular magnitude; generating a second signal at the instant that the change of voltage in the piezoelectric material becomes slow or reduced after completely transferring the pressure pressing down the key; and generating sound with predetermined volume which corresponds to a strength ofthe pressure determined by the magnitude of the voltage at the instant of generating the second signal.

2. A method of generating sound in a roll-up electronic piano comprising the steps of: pressing down a key of a keyboard and transferring pressure to a shock- absorbing member: applying an electric current between PCB plates positioned underneath piezoelectric material when the pressure transmitted to the shock- absorbing member is transmitted to the piezoelectric material, the PCB plates having metal interconnection corresponding to each key of the keyboard, the shock-absorbing member transmitting the pressure to the piezoelectric material if the pressure is more than a particular magnitude, the shock-absorbing member absorbing the pressure if the pressure is less than the particular magnitude; and generating sound with predetermined volume which corresponds to a strength ofthe pressure determined by the magnitude of the voltage at the instant that the change of voltage in the piezoelectric material becomes slow or reduced after applying an electric current between the PCB plates. 3. A method of generating sound in a roll-up electronic piano comprising the steps of: pressing down a key of a keyboard and transferring pressure to a shock- absorbing member; applying an electric current between PCB plates with metal interconnection corresponding to each key of the keyboard if the pressure is more than a particular magnitude that the shock-absorbing member can absorb, the shock-absorbing member absorbing the pressure if the pressure is less than the particular magnitude; and generating sound corresponding to the key at the instant of applying an electric current between the PCB plates.

4. A roll-up electronic piano comprising: a foldable/unfoldable keyboard comprising piezoelectric material whose resistance changes corresponding to the strength of pressure applied thereon thereby causing the change of voltage, upper and lower conducting pattern films transmitting the voltage from the piezoelectric material to a control part, a shock-absorbing member transmitting the pressure to the piezoelectric material if the pressure is more than a particular magnitude, the shock-absorbing member absorbing the pressure if the pressure is less than the particular magnitude, a covering forming an exterior ofthe keyboard; and a control part generating a first signal at the instant that the voltage starts to change due to transformation of the piezoelectric material, generating a second signal at the instant that the change of voltage in the piezoelectric material becomes slow or reduced after the pressure pressing a key is completely transmitted, determining a strength of the pressure based on a magnitude of the voltage generated from the piezoelectric material when the second signal is generated, and generating sound with a predetermined volume corresponding to the strength of pressure. . A roll-up electronic piano comprising: a foldable/unfoldable keyboard comprising piezoelectric material whose resistance changes due to the strength of pressure thereby causing the change of voltage, upper and lower conducting pattern films transmitting the voltage from the piezoelectric material to a control part, PCB plates positioned underneath the piezoelectric material, the PCB plates having metal interconnection corresponding to each key of the keyboard, a shock-absorbing member transmitting the pressure to the piezoelectric material if the pressure is more than a particular magnitude, the shock- absorbing member absorbing the pressure if the pressure is less than the particular magnitude, a covering forming an exterior ofthe keyboard; and a control part applying an electric current between the PCB plates when the pressure is transmitted to the piezoelectric material, determining a strength of the pressure based on a magnitude of the voltage at the instant that the change of voltage in the piezoelectric material becomes slow or reduced after applying an electric current between the PCB plates, and generating sound with a predetermined volume corresponding to the strength of pressure. . A roll-up electronic piano comprising: a foldable/unfoldable keyboard comprising PCB plates having metal interconnection corresponding to each key of the keyboard, a shock- absorbing member transmitting the pressure to the piezoelectric material if the pressure is more than a particular magnitude, the shock-absorbing member absorbing the pressure if the pressure is less than the particular magnitude, a covering forming an exterior ofthe keyboard; and a control part generating sound corresponding to a signal from the PCB plates.

7. The roll-up electronic piano as defined by claim 4 or claim 5, wherein the control part comprises a microprocessor which determines the strength of pressure based on the magnitude of voltage at the instant that the change of voltage from the piezoelectric material becomes slow or reduced, and a sound chip which generates sound with a predetermined volume corresponding to the strength of pressure determined.

8. The roll-up electronic piano as defined by claim 6, wherein the control part comprises a sound chip generating sound based on a signal from the PCB plates. 9. The roll-up electronic piano as defined by claim 7, wherein the sound chip comprises database for volume of sound corresponding to the various strength of pressure.

10. The roll-up electronic piano as defined by claim 4, claim 5 or claim 6, wherein the control part has a database for tones of dozens or hundreds of instruments such as pianos, guitars, flutes, saxophones, violins, mandolins, harps, and so on.

11. The roll-up electronic piano as defined by claim 4, wherein the upper and lower conducting pattern films are respectively positioned on and underneath the piezoelectric material. 12. The roll-up electronic piano as defined by claim 11, wherein an upper insulator is positioned on the upper conducting pattern film and a lower insulator is positioned underneath the lower conducting pattern film.

13. The roll-up electronic piano as defined by claim 5, wherein the upper and lower conducting pattern films are respectively positioned on and underneath the piezoelectric material.

14. The roll-up electronic piano as defined by claim 13, wherein an upper insulator is positioned on the upper conducting pattem film, a lower insulator is positioned underneath the lower conducting pattern film, and a third insulator is positioned underneath the PCB pates. 15. The roll-up electronic piano as defined by claim 6, wherein upper and lower insulators are respectively positioned on and underneath the PCB plates. 16. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein the covering ofthe keyboard is made of silicon rubber. 17. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein fine grooves are formed on the surface of the covering, the fine grooves being formed by injecting an inert gas into a vacuum chamber, applying plasma potential and sputtering the inert gas in plasma state.

18. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein inside a border member of the keyboard is a second piezoelectric material which is used as a means to turn off power based on a voltage generated from the second piezoelectric material when the keyboard is bent to more than a particular angle.

19. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein the control part further comprises a selecting member to choose an active range ofthe keyboard.

20. The roll-up electronic piano as defined by claim 5 or claim 6, wherein the PCB plates comprise an upper plate and a lower plate.

21. The roll-up electronic piano as defined by claim 20, wherein a plurality of protrusions are formed underneath the upper PCB plate, a plurality of the protrusions preventing an electric current between the upper and lower PCB plates when a key ofthe keyboard is not pressed down.

22. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein the control part further comprises at least a pedal to control the strength of sound, the length of sound, or the timbre.

23. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein the control part further comprises a volume button to control volume of sound and a standard volume corresponding to the volume of a real piano is marked around the volume button. 24. The roll-up electronic piano as defined by claim 4, claim 5, or claim 6, wherein the control part further comprises an A/D converter to convert a change of voltage generated from the keyboard into a digital signal.

25. The roll-up electronic piano as defined by claim 4 or claim 5, wherein the keyboard and the control part can be separated and are operated by a wire or a wireless method.

26. The roll-up electronic piano as defined by claim 25, wherein the keyboard further comprises a signal processing part which adds a unique ID to a signal received and a transmitting part which transmits an electrical signal from the keyboard to the control part. 27. The roll-up electronic piano as defined by claim 26, wherein the control part comprises a receiver which receives the signal from the transmitting part after identifying the ID of the signal from the transmitting part, an A/D converter which converts the signal received into a digital signal, a microprocessor which determines the strength ofthe pressure based on the magnitude of voltage at the instant that the change of voltage generated from the piezoelectric material becomes slow or reduced, and a sound chip generating sound with a predetermined volume corresponding to the strength of pressure determined.

28. The roll-up electronic piano as defined by claim 26, wherein the control part is a software including functions such as receiving the signal from the transmitting part after identifying the ID of the signal from the transmitting part, converting the signal received into a digital signal, determining the strength ofthe pressure based on the magnitude of voltage at the instant that the change of voltage from the piezoelectric material becomes slow or reduced, and generating sound with a predetermined volume corresponding to the strength ofthe pressure determined. 29. The roll-up electronic piano as defined by claim 6, wherein the keyboard and the control part can be separated and are operated by a wire or a wireless method. 30. The roll-up electronic piano as defined by claim 29, wherein the keyboard further comprises a signal processing part which adds a unique

ID to a signal received and a transmitting part which transmits an electrical signal from the keyboard to the control part.

31. The roll-up electronic piano as defined by claim 30, wherein the control part comprises a receiver which receives the signal from the transmitting part after identifying the ID of the signal from the transmitting part, an A/D converter which converts the signal received into a digital signal, and a sound chip generating sound with a predetermined volume corresponding to the signal from the PCB plates. 32. The roll-up electronic piano as defined by claim 30, wherein the control part is a software including functions such as receiving the signal from the transmitting part after identifying the ID of the signal from the transmitting part, converting the signal received into a digital signal, and generating sound with a predetermined volume corresponding to the signal from the PCB plates.