US3590134A

US3590134A - Electronic musical system with magnetic field responsive switch and volume control

Info

Publication number: US3590134A
Application number: US809800A
Authority: US
Inventors: Mikio Ogi
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1968-03-29
Filing date: 1969-03-24
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29

Abstract

An electronic musical system has a DC power supply and a tone generator with a first resistance connected in series between them. A second resistance has one end connected to the series circuit between the power supply and the tone generator and the other end connected to ground. One of the resistances is a magnetoresistor the electric resistance of which varies in accordance with the intensity of the magnetic field applied thereto. A key is movably mounted above the magnetoresistor with a magnet element mounted thereon close to the magnetoresistor, so that movement of the key controls the electrical resistance of the magnetoresistor depending on the amount the key is moved, and thus controls the volume of the tone generator.

Description

United States Patent [72] Inventor Mikio Ogi Hamamatsu-shi, Japan [21] Appl. No. 809,800 [22] Filed Mar. 24, 1969 [45] Patented June 29, 1971 73] Assignee Nippon Gakld Seizo Kabushiki Kaisha Hamamatsu-shi; Shizuoka-ken, Japan [32] Priority Mar. 29, 1968, Mar. 29, 1968 [33] Japan [31] 43/25029 and 43125030 [54] ELECTRONIC MUSICAL SYSTEM WITH MAGNETIC FIELD RESPONSIVE SWITCH AND VOLUME CONTROL 7 Claims, 8 Drawing Figs. [52] US. Cl 84/126, 84/1 .08, 84/1 1 7, 307/88, 335/2, 338/32 [51] Int.Cl 61% 1/02 [50] 84/ 1 .0 1, 1.09, 1.1, 1.13-1.15, 1.26, 1.27, 423,427, 4 33, 439, 440, 1.28; 307/259, 309; 323/94 H [56] References Cited UNITED STATES PATENTS 2,878,708 3/1959 Hanert 84/108 Primary ExaminerD. F. Duggan Assistant Examiner- U. Weldon A!r0rneyWenderoth, Lind & Ponack ABSTRACT: An electronic musical system has a DC power supply and a tone generator with a first resistance connected in series between them. A second resistance has one end connected to the series circuit between the power supply and the tone generator and the other end connected to ground. One of the resistances is a magnetoresistor the electric resistance of which varies in accordance with the intensity of the magnetic field applied thereto. A key is movably mounted above the magnetoresistor with a magnet element mounted thereon close to the magnetoresistor, so that movement of the key controls the electrical resistance of the magnetoresistor depending on the amount the key is moved, and thus controls the volume of the tone generator.

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- BYMuJaII/LIXLL U ELECTRONIC MUSICAL SYSTEM WITH MAGNETIC FIELD RESPONSIVE SWITCH AND VOLUME CONTROL BACKGROUND OF THE INVENTION Generally, electronic musical instruments are provided with tone generators and switches which control the outputs of said tone generators. Accordingly, many electric contacts are necessary for electronic musical instruments, and as the electric contacts, metal-to-metal contacts or metal-to-conductive rubber contacts are used. However, these are liable to cause miscontacts owing to the formation of sulfides or oxides of metals or deposits of dust on the surfaces of the contacts, and therefore they are unreliable. Moreover, said contacts can only switch electric signals on and off and it is impossible to vary the volume of sound in proportion to the strength with which the key is depressed.

SUMMARY OF THE INVENTION A principal object of the present invention is to provide a keying device for electronic musical instruments with which it is possible to effect a so-called touch-sensitive control without using an electric contact in switching the output of a tone generator. That is, the keying device of the present invention is able to control the volume of the sound in response to the strength with which the key is depressed.

Another object of the present invention is by utilizing the characteristics of a magnetoresistor which causes the electric current flowing through the element to vary in response to the intensity of the applied magnetic field, to provide a keying device for electronic musical instruments which comprises a magnetoresistor connected between a DC electric power source and a tone generator and forming part of a potential divider, and either the magnetoresistor or the magnet is mounted on a key and the other one of them is mounted on a stationary part so that they cooperate with each other, whereby the magnetic field applied to said magnetoresistor is varied by the manipulation of the key so as to control the sound volume in response to the depression ofeach key.

Still another object of the present invention is to provide a keying device for electronic musical instruments comprising two magnetoresistors connected between an electric power source and a tone generator as a potential divider, and further one of said two magnetosensitive elements or a magnet is mounted on a key and the other one of them is mounted on a stationary part so that they cooperate with each other, whereby the magnetic field applied to said two magnetoresistors is varied in response to the manipulation of the key so as to control the sound volume.

The magnetoresistor used in the embodiments of the present invention is one the electric resistance of which increases as the intensity of the applied magnetic field increases.

Other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein several embodiments of the invention are illustrated. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram illustrating the principle of a keying device according to the invention;

FIG. 2 is a vertical cross-sectional view of a keyboard having thereon an embodiment of a keying device according to the invention;

FIG. 3 is an enlarged perspective view of the main part of the embodiment of FIG. 2;

FIG. 4 is another circuit diagram illustrating another embodiment ofa keying device according to the invention;

FIG. 5 is an enlarged perspective view of the main part of the keying device of the embodiment shown in FIG. 4;

FIG. 6 is a vertical cross-sectional view of a keyboard fitted with a multiple keying device according to the invention;

FIG. 7 is a circuit diagram illustrating a further embodiment of a keying device according to the invention; and

FIG. 8 is a vertical cross-sectional view of a keyboard having thereon the embodiment shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the FIGS., reference number I designates a DC electric power source the details of which are omitted, and the

numbers

2,2, 2a and 2b designate magnetoresistors, respectively. Reference number 4 designates a tone generator the details of which are omitted. The output and hence the volume of sound produced is proportional to the power supplied to it.

Reference numbers

5 and 5 designate magnets.

In FIG. 1, a magnetoresistor 2 is connected in series between the electric power source 1 and a power input terminal 21 of the tone generator 4, and a fixed resistor 3 is connected between the output side of the magnetoresistor 2 and ground, and a potential divider is formed by said magnetoresistor 2 and the fixed resistor 3. Said tone generator 4 has an output terminal 22. Said magnetoresistor 2 has an electric resistance which increases as the intensity of applied magnetic field increases. The intensity of the magnetic field of said magnet 5 applied to the magnetoresistor 2 becomes the maximum when the key is in the off state and the intensity of the magnetic field of said magnet 5 becomes less or zero when the key is in the on state, thus no sound is produced when the key is in the off state, because the electric resistance of the magnetoresistor 2 is a maximum, and the power is not supplied to the tone generator 4. On the contrary, a sound is produced when the key is in the on state, as the electric resistance of the magnetoresistor 2 becomes less and the power is supplied to the tone generator 4. When the key is pushed down a small amount, the amount of power supplied to the tone generator 4 is small, and when the key is pushed down to a large extent, the amount of power supplied to said generator 4 becomes larger, whereby so-called touch-sensitive control can be attained.

FIGS. 2 and 3 illustrate the positions of said magnet 5 and the magnetoresistor 2, wherein the magnet 5 is horseshoe shaped and is mounted by a screw 8 on a key 6 with nonmagnetic spacer 7 between it and the key, and the magnetoresistor 2 is fixed to a holding block 10 which is mounted on the keyboard frame 9. Consequently, the magnetoresistor 2 is fixed and the magnet 5 moves with the movement of the key 6. The magnet 5 and the magnetoresistor 2 are positioned as near to each other as possible, with the best arrangement being as shown in FIG. 3, that is the magnetoresistor 2 is between the north pole and the south pole of the magnet 5, and the intensity of the magnetic field of the magnet 5 becomes a maximum when the key 6 is in the off state and becomes less or zero when the key 6 is in the on state.

FIG. 4 shows a circuit diagram of another embodiment according to the invention, wherein the magnetoresistor 2 and the fixed resistor 3 in FIG. I have been substituted for each other. When the magnetoresistor 2 is similar to that of FIG. 1, wherein the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2 becomes a minimum when the key is in the off state, and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2 becomes larger when the key is in the on state, then the same result as in the case of FIG. 1 is attained.

Furthermore, if the magnetoresistor is replaced by a magnetosensitive diode, the electric current through the diode is varied according to the direction of the applied magnetic field, and almost the same results are obtained as when a magnetoresistor is employed. FIG. 5 illustrates an example of a specific keying device by which a large control ratio can be obtained by utilizing the characteristics of a magnetosensitive diode. That is, a magnetosensitive diode 2' is used, said diode 2 being movable between poles of a multipolar magnet 5 having the polarities as shown in FIG/5, wherein when the key is in the on state the magnet is positioned to apply the magnetic field in the direction to permit electric current to flow through the magnetosensitive diode 2' and when the key is in the off state the magnet is positioned to apply the magnetic field in the direction not to permit current to flow through the magnetosensitive diode 2'. According to this device, there is no fear of producing a signal leakage when the key is in the off state.

FIG. 6 illustrates an example of a keyboard comprising multiple keying device having a plurality of magnetoresistors and a multipolar magnet. Said

magnetoresistors

2, 2, are mounted on a holding block 10 at suitable distances from each other and said holding block 10 is mounted on the keyboard frame 9. The multipolar magnet 5' is fixed to a spring holder I V 12 through spring plates 11 so as to be driven directly or indirectly by a driving piece by the action of the key 6, and said spring holder 12 is fixed to the keyboard frame 9. The magnet 5' and each magnetoresistor 2 are positioned as near to each other as possible and the intensity of the magnetic field to the multipolar magnet 5 applied to each magnetoresistor 2 becomes the maximum when a key is in the off state and becomes less or zero when the key is in the on state. F urthermore, when each element is a magnetosensitive diode, and when it is used such that the direction of magnetic field applied to each diode is reversed on the movement of the key to the on or off state the control ratio of the power supply becomes larger and it is more effective.

FIG. 7 illustrates still another circuit diagram of an embodiment according to the invention, wherein a magnetoresistor 2a is connected in series between a power source 1 and a tone generator 4 and another magnetoresistor 2b is connected between the output side of the magnetoresistor 2a and ground, a potential divider being formed by said two

magnetoresistors

2a and 2b. The magnetoresistors are magnetosensitive resistors the electric resistances of which increase as the magnetic field increases. That is, the intensity of the magnetic field of the mag net 5 applied to the magnetoresistor 2a becomes a maximum and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2b becomes a minimum when the key is in the off state, and conversely, the intensity of the magnetic field of magnet 5 applied to the magnetoresistor 2a becomes a minimum and the intensity of the magnetic field of magnet 5 applied to the magnetoresistor 2b becomes a maximum when the key is in the on state.

Accordingly, when the key is in the on state, a large amount of power is supplied to the tone generator 4, because the electric resistance of the magnetoresistor 2a is a minimum-and the electric resistance of the magnetoresistor 2b is a maximum.

Next, when the key is in the off state, hardly any voltage from the power source 1 is supplied to the tone generator 4, and no sound is produced, because the electric resistance of the magnetoresistor 2a is a maximum and the electric resistance of the magnetoresistor 2b is a minimum.

Generally, a magnetoresistor has some value of resistance even when no magnetic field is applied to it, and furthermore, it is impossible to diminish the intensity of magnetic field applied to the magnetoresistor 2b or zero owing to the structural limitation of the distance between the

magnetoresistors

2a and 2b. According to the present embodiment, however, even in such case, the electric voltage across the terminals of the magnetoresistor 2b becomes smalland the power source voltage supplied to thetone generator 4 diminishes almost to zero, because the electric resistances of the

magnetoresistors

2a and 2b vary oppositely and the electric resistance of the element 2a becomes large and the control ratio of the tone generator becomes extremely large.

In the above description, although there is described the case where the key is in the full on or off position, it will be understood that the amount of power supplied from the power source 1 to the tone generator 4 varies in response to the extent the key is depressed, because the values of the resistances of the

magnetoresistors

2a and 2b vary depending on the strength of the magnetic field which in turn varies with the extent the key is depressed. Since the keys are spring loaded, such as by a spring 11 in FIG. 2, the output of the tone generator 4 varies in accordance with the strength with which the key is depressed, and thus so-called touch-sensitive control can be effected.

FIG. 8 illustrates an arrangement of said magnet and said magnetoresistors, wherein the magnet 5 is fixed to the key 6 by a nonmagnetic spacer 7, and the

magnetoresistors

2a and 2b are fixed to a holder plate 10' which is mounted on the keyboard frame 9. Consequently, the

magnetoresistors

2a and 2b are stationary and the magnet 5 moves with the movement of the key 6. In this case, the magnet 5 and the

magnetoresistors

2a and 2b are positioned as near to each other as possible, and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2a becomes a maximum and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2b becomes a minimum when the key is in the off state, and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2a becomes a minimum and the intensity of the magnetic field of the magnet 5 applied to the magnetoresistor 2b becomes a maximum when the key is in the on state.

Furthermore, it is clear that the same functional effect is obtained when the positions of the power source 1 and the tone generator 4 in the circuit as shown in FIG. 7 are exchanged.

In the above embodiments, it will be understood that a plurality of magnets may be used instead of the multipolar magnet, and an electromagnet may be used in place of a permanent magnet.

Although, in the above embodiments, the magnets are fixed to the keys and the magnetoresistors are fixed to the stationary parts, the same functional effects may be obtained even if the magnetoresistors are fixed to the keys and the magnets are fixed to the stationary parts.

As above described, the keying device of this invention is very effective practically, overcoming several prior art defects by switching the output of the tone generator without using any contacts, increasing the reliability and reducing the complexity of the device itself. Moreover it provides a touch-sensitive control effect when the occasion demands, and is able to provide a large control ratio.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood, however, that such embodiments are only illustrative and that numerous variations are possible without departing from the purview of the invention as defined in the following claims.

What I claim is:

1. An electronic musical system comprising a DC electric power source, a tone generator, a first resistance means connected in a series circuit between said power source and said tone generator, a second resistance means having one end connected to the series circuit between said first resistance and said tone generator and the other end connected to ground, at least one of said resistance means being a magnetoresistor the electrical resistance of which varies in accordance with the intensity of the magnetic field applied thereto, a key means movably supported in said system so as to be depressed when it is moved, and a magnet element mounted on said key means close to said magnetoresistor and movable therewith for controlling the electrical resistance of said magnetoresistor in accordance with the amount said key means is depressed.

2. An electronic musical system as claimed in claim 1 wherein said first resistance means is said magnetoresistor and said second resistance means is a fixed resistor.

3. An electronic musical system as claimed in claim 1 wherein said first resistance means is a fixed resistor and said second resistance means is said magnetoresistor.

4. An electronic musical system as claimed in claim 1 wherein both said first and second resistance means are magfaces the other of said poles when said key means is depressed. 6. An electronic musical instrument as claimed in claim 5 wherein said two poles are positioned parallel in a horizontal direction.

7. An electronic musical instrument as claimed in claim 5 wherein said two poles are arranged on a collinear vertical line.

Claims

4. An electronic musical system as claimed in claim 1 wherein both said first and second resistance means are magnetoresistors the electrical resistance of which varies in accordance with the intensity of magnetic field applied thereto, and said magnet element is positioned close to and controls both of said magnetoresistors so that the electrical resistance of said magnetoresistors varies oppositely from each other.

5. An electronic musical instrument as claimed in claim 1 wherein said magnet element is a magnet having two opposite poles spaced from each other, and said magnetoresistor faces one of said poles when said key means is not depressed and faces the other of said poles when said key means is depressed.

6. An electronic musical instrument as claimed in claim 5 wherein said two poles are positioned parallel in a horizontal direction.