US3673303A

US3673303A - Voltage generating device for controlling musical tone output from electronic musical instruments

Info

Publication number: US3673303A
Application number: US68748A
Authority: US
Inventors: Hiroshi Amano
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1969-09-03
Filing date: 1970-09-01
Publication date: 1972-06-27
Anticipated expiration: 1989-06-27

Abstract

There is disclosed a voltage generating device of compact structure for controlling musical tone output signals from an electronic keyboard musical instrument to a level corresponding to the magnitude of a key depressing force or the velocity with which the key is depressed. Below the keyboard is positioned a non-magnetic case which supports two parallel magnetic cores and a magnet disposed therebetween which are common to a plurality of keys, and on at least one of the two magnetic cores there are fitted a plurality of coils in a manner that the coils correspond to the respective keys. There is mounted on the underside of each key a magnetic material constituting a magnetic circuit along with the two magnetic cores and the magnet received in the case. On depressing a key, the magnetic material mounted on the key is drawn near the two magnetic cores to generate in the coil a voltage having a level corresponding to the velocity with which the key is depressed, the voltage being used in controlling the corresponding musical tone output signal.

Description

United States Patent [151 3,673,303

Amano June 27, 1972 [54] VOLTAGE GENERATING DEVICE FOR 2,905,039 9 1959 Alvarez ..84/1.15 x

CONTROLLING MUSICAL TONE 3,066,567 12/1962 Kelley.....................................84/l.16

OUTPUT FROM ELECTRONIC MUSICAL INSTRUMENTS [72] Inventor: Hiroshi Amano, Hamamatsu, Japan [73] Assignee: Nippon Galtlti Seizo Kabushilli Keisha,

Hamamatsu-shi, Japan [22] Filed: Sept. 1, 1970 [21} Appl. No.: 68,748

[30] Foreign Application Priority Data Sept. 3, 1969 Japan ..44/835l4 [52] U.S.Cl. ..84/1.01,84/D1G. 7 [5 1] Int. Cl. [58] Field otSearch ..84/1.01,1.15,1.24,1.26D

[56] References Cited UNITED STATES PATENTS 2,510,094 6/1950 Fleury.....................................84/I.15 3,544,695 12/1970 Dijksterhuis ..84/1.26 X 3,553,337 1/1971 Dijksterhuis ..84/1.26 X

1227,015 12/1970 Dijksterhuis et a1. .....84/1.15 X 2,486,545 11/1949 Alvarez ..84/1.15

Primary Examiner-Lewis H. Myers Assistant Examiner-U. Weldon A rtorney-Kcmon, Palmer & Estabrook 57 ABSTRACT There is disclosed a voltage generating device of compact structure for controlling musical tone output signals from an electronic keyboard musical instrument to a level corresponding to the magnitude of a key depressing force or the velocity with which the key is depressed. Below the keyboard is positioned a non-magnetic case which supports two parallel magnetic cores and a magnet disposed therebetween which are common to a plurality of keys, and on at least one of the two magnetic cores there are fitted a plurality of coils in a manner that the coils correspond to the respective keys. There is mounted on the underside of each key a magnetic material constituting a magnetic circuit along with the two magnetic cores and the magnet received in the case. On depressing a key, the magnetic material mounted on the key is drawn near the two magnetic cores to generate in the coil a voltage having a level corresponding to the velocity with which the key is depressed, the voltage being used in controlling the corresponding musical tone output signal.

12 Claims, 15 Drawing Figures Patented June 27, 1972 3,673,303

6 Sheets-Sheet l FIG. 2

Patented June 27, 1972 6 Sheets-Sheet 2 FIG.4A FIG-.48

36 Eff- E i IN'VEXTOR. H/fiosHl AMA/v0 BY J p v52- Z Patented June 27, 1972 3,673,303

6 Sheets-Sheet 5 l 1 50 TONE VARIABLE OUTPUT GENERATOR ATTENUATOR J 5k 2 i 55 OUTPUT AMPLITUDE TIME INVEN'IOR. Hmasm AMA/v0 Patented Jme 27, 1972 6 Sheets-Sheet 4 202.68 owmwmmmmo S52E22 wv KEY DEPRESSED POSITION FIG.

ZOEmOQ .rmwm Ex XD E 9.52052 FIG INVENTOR. H, oam Hrmwo BY Aim,

Patented June 27, 1972 6 Sheets-Sheet 5 FIG.8B

FIG.8C

INVEXTOR.

Hines/n HMANO BY m M7541 Patented June 27, 1972 6 Sheets-Sheet 6 FIG.

FIG. 10

0 w fl 7 A: w x 2/ H Mr VOLTAGE GENERATING DEVICE FOR CONTROLLING MUSIC AL TONE OUTPUT FROM ELECTRONIC MUSICAL INSTRUMENTS BACKGROUND OF THE INVENTION The present invention relates to an electronic musical instrument and more particularly to an electronic musical instrument provided with a voltage generating device for controlling musical tone output signals therefrom in accordance with the magnitude of a key depressing force.

With a keyboard musical instrument other than an electronic musical instrument, for example, a piano, there arises a prominent difference in the volume of musical tones obtained between the case where the key is strongly, or quickly depressed and the case where they key is lightly or slowly depressed.

However, with the conventional electronic musical instrument, for example, an electronic organ, when a key is depressed, it only causes a key switch associated therewith to be closed and signals from a tone generator corresponding to the key to be conducted to another prescribed circuit. Accordingly, key depression, whether effected quickly or slowly, does not give rise to any change in tones, namely, a mere key operation fails to produce a diversified performance.

It is therefore preferred that an electronic musical instru ment such as an electronic organ, be provided with means for detecting the magnitude of a key depressing force or more precisely the velocity with which the key is depressed, thereby to control musical tone output signals and particularly desired that such means be installed in position below the keys arranged at a small space.

SUMMARY OF THE INVENTION It is, accordingly, an object of this invention to provide a voltage generating device for controlling musical tone output signals which is of sufiiciently compact construction to be installed in position below a plurality of keys.

It is another object of this invention to provide the aforesaid device being capable of quickly controlling the volume of musical tones to a value corresponding to the magnitude of a key depressing force, when a key is depressed.

The control voltage generating device of the present invention comprises movable magnetic materials or magnets fitted to the undersides of the respective keys; two magnetic cores disposed below the keyboard so as to extend in the direction of key arrangement, at least one of which is provided on one side with a plurality of projections arranged at a prescribed interval, the projections corresponding to the respective keys; a magnet or magnetic material positioned between the magnetic cores; a case of non-magnetic material for receiving the mag netic cores and the stationary magnet or magnetic material interposed therebetween; and coils wound around the respective projections. When a key is depressed, the movable magnetic material or magnet mounted on its underside is drawn near the two magnetic cores to induce into the coil associated with the depressed key a voltage based on the changed magnetic flux corresponding to the magnitude of a key depressing force or the velocity with which the key is depressed, and the voltage is supplied to control a variable attenuator cascade connected to the tone generator.

Another feature of the present invention is that the movable magnetic material or magnet mounted on the underside of the key assumes such a shape that when a key is depressed half way, it is drawn nearest to the two magnetic cores, enabling musical tone output to be produced immediately upon key depression with a level corresponding to the magnitude of a key depressing force.

BRIEF EXPLANATION OF THE DRAWINGS FIG. I is a schematic side view, partly in section, of the keyboard mechanism of an electronic organ provided with a control voltage generating device according to an embodiment of the present invention;

FIG. 2 is a similar side view to that of FIG. I at the time of key depression;

FIG. 3 is an exploded perspective view of the major parts of the control voltage generating device of the present invention;

FIGS. 4A and 4B are schematic side views illustrating the operation of the control voltage generating device of the present invention;

FIGS. 5A and 5B jointly present a circuit for controlling musical tones by output signals from the control voltage generating device of the present invention;

FIGS. 6A and 63 indicate wave forms used for illustrating the operation of the circuits of FIGS. 5A and 5 B;

FIG. 7 is a curve diagram showing the relationship of the depressed position of the key and the magnitude of magnetic flux passing through the magnetic cores at the key depression;

FIGS. 8A, 8B and BC are schematic side views, partly in section, illustrating the operation of a control voltage generating device according to another embodiment of the invention;

FIG. 9 is a schematic side view, partly in section, of a control voltage generating device according to still another embodiment of the invention; and

FIG. I0 is a schematic side view, partly in section, of a control voltage generating device according to a further embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. I and 2, the reference numeral 1 represents the body of one of a plurality of keys constituting the keyboard of an electronic musical instrument, which are arranged side by side at a small space in a direction perpendicular to the plane of the paper. The key body I is made of, for example, plastics material, and to the rear part of the key body (opposite to that part of the key body at which it is depresed) is fixedly secured a key arm 2 formed of magnetic material, for example, cold rolled steel plate or ferrite, the arm extending in the longitudinal direction of the key body I. While, in this embodiment, the key body I and key arm 2 constitute a key, the key body I is referred to as a key by way of simplification. Of course, the key body I and key arm 2 may be integrally prepared from plastics material, and there may be attached a magnetic material to the underside of that part of the key corresponding to the key arm. The rear end of the key arm 2 is rotatably supported, as is well known, by a supporting plate 3 fixed to the rear end of a keyboard supporting frame 4. Between the rear end of the key arm 2 and one end of the supporting plate 3 is disposed a spring 5 for keeping the forward end of the key I upwardly urged. On the underside of forward end of the key I is formed a downwardly projecting stopper section 8.

The stopper section 8 has a member I0 integrally fitted thereto, the upper surface of which faces the end plane 9 of the stopper section 8. Between the member 10 and the end plane 9 of the stopper section 8 is positioned a stopper member 12, both sides of which are fitted with a buffer member I3 permissibly made of felt. This stopper member 12 is intended to define the range within which the key I is allowed to rock vertically. To the underside of the key arm 2 is fitted an actuating rod 14 in such a manner as to penetrate the keyboard supporting frame 4 and the bottom of a switch box 15 mounted under the keyboard supporting frame 4. In the switch box I5 are provided a group of movable contact strips 16 penetrating the actuating rod I4 and a plurality of fixed contact strips 17 disposed near the ends of the movable contact strips I6. When a key is depressed, there is produced a musical tone signal having a desired tone color by the tone generator associated with the depressed key. Below the switch box I5 is placed a switch 18 which, upon key depression, is operated by the actuating rod 14 to operate the later described control circuit. Between the keyboard supporting frame 4 and stopper member I2 is disposed a case 20 housing the major part of a device for generating a control voltage. The case 20 is disposed between one end of the keyboard supporting frame 4 through an adjustable spring l9 and one end of the stopper member 12. The voltage generating device is shown in detail in FIG. 3.

The case is formed ofa non-magnetic material, for example, rubber or plastics material. The case 20 has upwardly projecting partition walls 23 jointly defining a rectangular space set up at the central part between the opposite

longitudinal sections

21 and 22 of the bottom plate and two projecting rods 24 and 25 arranged at a prescribed space along the central line of the area defined by the partition walls 23. in the case 20 are placed two magnetic cores extending along the inner surfaces of the longitudinal partition walls 23, that is, a first magnetic core 26 assuming a combed shape which is provided on the upper edge with a plurality of projections 27 arranged at a prescribed space so as to correspond to the respective keys and a second magnetic core 28 formed into a flat plate which is perforated with two rectangular apertures 29 disposed at a prescribed space along the longitudinal central line. These two

cores

26 and 28 consist ofa magnetic material such as iron or barium ferrite and have substantially the same length as the inner surface of the longitudinal partition walls 23 and a mutually equal height. Further along the longitudinal central line of the bottom plate of the case 20 and between the magnetic cores is placed a permanent magnet 30 perforated with two apertures 31 spaced from each other at the same interval as the aforesaid projecting rods 24 and 25 of the case 20, the projecting rods 24 and 25 being fitted into the apertures 31. The permanent magnet 30 assumes a rectangular cross section and has substantially the same length as the two

magnetic cores

26 and 28 disposed along the inner surfaces of the longitudinal partition walls 23 and a sufficient width closely to contact them. The magnetic poles of the permanent magnet 30 are so oriented as to face the

magnetic cores

26 and 28 respectively. The permanent magnet 30 is pressed downward by a retaining late 32. The retaining plate 32 of substantially the same length and width as the permanent magnet 30 has a pair of first engaging strips 33 to be inserted into the two rectangular apertures 29 of the second fiat plate magnetic core 28, and a pair of second engaging strips 34 to be fitted into the interspace between the adjacent projections of the first combshaped magnetic core 26, and further two apertures 35 formed at the same space as the two projecting rods 24 and 25 of the supporting case 20.

Engagement of the first engaging strips 33, second engaging strips 34 and two apertures 35 of the retaining plate 32 with the corresponding parts permits the permanent magnet 30 to be securely set in the supporting case 20. The heads of the projecting rods 24 and 25 of the supporting case 20 which rise above the plate 32 are pressed flat by, for example, being properly heated, thereby causing all the parts to be tightly held in the supporting case 20. Referring to the first and second engaging

strips

33 and 34 of the retaining plate 32, it will be sufficient if there is formed at least one of these first and second strips.

There is fitted a bobbin 36 having a coil 37 wound thereabout on to the projections 27 of the comb-shaped magnetic core 26. Both

terminals

38 and 39 of the coil 37 are connected to the terminals 40 provided outside of the partition walls 23 on the longitudinal section 21 of the bottom plate of the case 20. The latter terminals 40 are connected to the later described control circuit.

As mentioned above, the supporting case 20 is fixed to the stopper member 12 and the keyboard frame 4 at its opposite

longitudinal sections

21 and 22 using proper means. If, in this case, one of said fixing means consists of, for example, the adjustable spring [9 so as to cause the supporting case 20 to have a changeable vertical position with respect to the key arm 2, then it is possible minutely to control an electromotive force generated in the coil upon key depression, thus offering great advantage.

To assure the tight contact of the first and second

magnetic cores

26 and 28 through the permanent magent 30 interposed therebetween, it is preferred that there be interposed a corrugated plate spring 4 between one of the

magnetic cores

26 and 28 and the inner surface of one of the longitudinal partition walls 23. It is also possible to use, if necessary, other fixing means than described above in order firmly to hold the parts received in the supporting case 20. In the foregoing embodiment, only the first magnetic core 26 is formed into a combed shape, but the second magnetic core 28 may also assume a similar combed shape. In this case, it is possible to fit coil bobbins having coils on to the mutually facing projections of both

magnetic cores

26 and 28, connect the coils of the bobbins in series, thereby using the total sum of voltages drawn out of the coils as a control voltage.

There will now be described the operation of a keyboard mechanism involving the voltage generating device of the present invention constructed as described above. FIG. 1 represents the normal position of the key I when it is not depressed. Under this condition, there is not produced any musical tone signal. Since, in this state, no magnetic circuit is formed between the permanent magnet 30, the first and second

magnetic cores

26 and 28, and the key arm 2 of a magnetic material, with air gaps prevailing between the key arm 2 and the

magnetic cores

26 and 28, there is not generated any voltage in the coil 37. Since most of the magnetic flux from the permanent magnet 30 leak as illustrated in FIG. 4A, there is also produced no attractive force between the key arm 2 and the permanent magnet 30.

Depression of the key 1 brings about the condition of FIG. 2. Now the actuating rod 14 is brought down, causing the movable contact strip 16 to contact the fixed contact strip [7 to draw out of the tone generator a signal having a pitch corresponding to the depressed key 1. Further, the switch 18 is closed to actuate the control circuit. On the other hand, the key depression breaks up the normal state of the aforesaid magnetic circuit, closing the magnetic circuit and varying the magnetic flux flowing through the

magnetic cores

26 and 28, so as to generate in the coil 37 associated with the depressed key an electromotive force corresponding to the magnitude of a key depressing force or more precisely the velocity with which the key is depressed. The electromotive force e may be expressed by the following equation:

e n (ddJ/ where: n number of coil windings d; magnetic flux passing through a coil The magnetic flux reaches a maximum when the depressed key is brought to its final position as shown in FIG. 48 where the magnetic resistance due to air gaps is minimum. However. the maximum attractive force exerted by the permanent magnet 30 at this time is so designed as to be smaller than the tensile force of the spring 5. Accordingly, when the key is released from its depressed position indicated in FIGS. 2 and 48, then the key will be brought back to its original position illustrated in FIGS. 1 and 4A.

The electromotive force e generated in the coil 37 is used as a voltage for controlling musical tone output signals. While there may be contemplated various types of musical tone controlling circuit, there will now be described two examples of such circuit presented in FIGS. 5A and 5B. Throughout these figures, the voltage generating device is indicated as a moving magnet type. While the embodiment of FIG. 1 involved a variable reluctance type of voltage generator in which the magnet was fixed in a supporting case 20 made of non-magnetic material and the magnetic material of the key arm 2 was made movable, the type may be easily converted to a moving magnet type by replacing the permanent magnet 30 received in the supporting case 20 with a magnetic material and mounting on the underside of the key arm 2 a permanent magnet whose poles are oriented in the longitudinal direction of the key. The variable reluctance type and moving magnet type of voltage generating device have the undermentioned advantages over the moving coil type.

Referring to FIG. 5A, the reference numeral 50 denotes a moving magnet fitted to a key so as to move in the direction of the arrow. 51 is a magnetic core having a coil 52 wound thereabout. One end of the coil 52 is grounded and the other is connected to the anode of a diode 53. Across a serial circuit including the coil 52 and the diode 53 is connected a capacitor 54. To the capacitor 54 is connected in parallel a serial circuit consisting of a resistor 55 and normally closed contact 56. Where the diode 53 is connected as shown in FIG. 5A, the juncture of the diode 53 and the capacitor 54 is supplied with a positive voltage alone. The voltage is used in controlling a variable attenuator $7 cascade connected to a tone generator 58. Output from the variable attenuator $7 is conducted to a prescribed circuit.

There will now be described the operation of the aforesaid control circuit. When the key is depressed the magnet 50 moves to the coil 52 to induce thereinto an electromotive force 0 corresponding to the magnitude of a key depressing force indicated by the aforementioned formula. The electromotive force e is rectified by the diode 53 to charge the capacitor 54. The normally closed contact 56 is included in the switch 18 disposed below the switch box shown in FIG. 1 and, upon key depression, is opened by the actuating rod I4 to keep the capacitor 54 continuously charged with a voltage corresponding to the electromotive force e until the key is released from depression. When the key depression comes to an end, the normally closed contact 56 which has been opened up to this point is closed to cause the voltage charged into the capacitor 54 to be discharged through the resistor 55. The charged voltage of the capacitor 54 is supplied to the variable attenuator 57 to control signals from the tone generator 58 to a level corresponding to the magnitude of a key depressing force or the velocity with which the key is depressed. The variable attenuator 57 may consist of a filed effect transistor shown in FIG. 5B.

The numerals 71 and 72 of FIG. 6A represent the wave forms of control D.C. signals from the control circuit having voltage levels corresponding to different magnitudes of a key depressing force. The

numerals

73 and 74 of FIG. 68 indicate the patterns of musical tone outputs from the variable attenuator 57 having levels corresponding to the control voltages 71 and 72. Normally, when a key is not depressed, the variable attenuator 57 is, of course, prevented by, for example, a key switch means (not shown) from being supplied with musical tones from the tone generator 58.

FIG. 5B is a modification of the circuit arrangement shown in FIG. 5A. The voltage generated in the coil 52 is conducted through a capacitor 59 to a transistor amplifier 60 and the amplified output is rectified by the diode 53. The rectified voltage or control voltage charged into the capacitor 54 is supplied to the gate electrode of the variable attenuator 57 consisting of a field effect transistor 61 to vary its internal resistance. As the gate electrode of the field effect transistor 61 is supplied with increasing control voltage, its internal resistance decreases to permit a larger output of musical tones. The source electrode of the field effect transistor 61 is connected through a capacitor 62 to a tone generator 58 and grounded through a resistor 63. The drain electrode of the transistor M is connected through a capacitor 64 to a prescribed circuit, and grounded through a resistor 65. The control circuit of FIG. 5B performs the same operation as that of FIG. 5A, excepting that the voltage generated in the coil 52 is amplified by the amplifier 60. The same parts of FIG. 58 as those of FIG. 5A are denoted by the same numerals and description thereof is omitted.

The object and operation of the control voltage generating device according to the present invention will be apparent from the foregoing description.

Now let us consider in detail by reference to FIGS. 4A and 4B the characteristics of the voltage generating device used in the embodiment of FIG. 1. After key depression, the magnetic flux flowing through the

magnetic cores

26 and 28 gradually increases and reaches a maximum when the key is brought to the most depressed position where the key arm 2 is drawn closest to the

magnetic cores

26 and 28 as shown in FIG. 4B. This relationship is represented by the curve a of FIG. 7.

As apparent from this figure, the magnetic flux little varies at the initial stage of key depression, but gradually increases as the depression approaches its end. Accordingly, the electromotive force generated in the coil 52 is small at the initial stage of key depression, but gradually grows large toward the end of the depression. At the initial stage of key depression, therefore, there is only obtained a small control voltage, permitting a little or no output of musical tones, whereas when the key is fully depressed, the control voltage increases to permit a large output of musical tones. This will, however, result in an appreciable delay in the rise of musical tone signals derived from key depression during the performance of an electronic musical instrument. Particularly where performance is to be made at quick tempo, the player will feel considerable difficulties in playing the instrument.

In view of such fact, the present invention has further developed other embodiments illustrated in FIGS. 8, 9 and I0 which are so designed as to obtain immediately after key depression musical tone output signals having a voltage level corresponding to the magnitude of a key depressing force. The same parts of these figures as those of FIG. I are denoted by the same numerals and description thereof is omitted.

Referring to FIGS. 8A, 8B and 8C, the key arm 2 fitted to the underside of the rear end portion of the key I may consist of a proper kind of metal or plastics material capable of being integrally formed with the body of the key I. 0f the two

magnetic cores

26 and 28 received in the supporting case 20, the first magnetic core 26 disposed near the front side of the key and fitted with the coil 37 has a greater height than the second magnetic core 28. To the underside of the key arm 2 is fixed by suitable means, for example, screws 83 an induced iron piece having two leg members 8! and 82 formed by bending both ends thereof substantially at right angles to the main body in such a manner as to cause the two leg members 8I and 82 to face the

magnetic cores

26 and 28 respectively in slightly offsetting relationship with respect thereto. Of the two leg members 8I and 82 of the induced iron piece 80, the leg member 82 facing the second magnetic core 28 having a smaller height than the first magnetic core 26 is formed longer than the other leg member 8| facing the first magnetic core 26 having a greater height than the second magnetic core 28, so that at the time of key depression, these two leg members 8! and 82 approach simultaneously the first and second

magnetic cores

26 and 28 with an equal space therebetween. The aforementioned arrangement permits the two

leg members

81 and 82 of the induced iron piece 80 to approach closest to the

magnetic cores

26 and 28 when the key is depressed substantially half way as shown in FIG. 88. At this time the magnetic flux passing through the

magnetic cores

26 and 28 attains a maximum value shown by the curve b of FIG. 7, so that an electromotive force generated in the coil 37 also grows largest. Where the key is most depressed as shown in FIG. BC, the

leg members

81 and 82 of the induced iron piece 80 are removed from the first and second

magnetic cores

26 and 28, so that the magnetic flux travelling therethrough is reduced with the resultant decrease of the electromotive force induced into the coil 37. As apparent, however, from the aforementioned two control circuits, the control voltage supplied to the variable attenuator 57 upon key depression is derived from the voltage charged into the capacitor 54 which has a level corresponding to the electromotive force induced into the coil 37 upon key depression. Under the arrangement of FIG. 8, therefore, the control voltage resulting from the maximum electromotive force obtained when the key is depressed sub stantially half way is conducted to the variable attenuator 57 even after key depression is finished. According to the embodiment of FIG. 8, therefore, there occurs a far less delay in the rise of musical tone output signals than in the embodiment of FIG. 2, thus permitting a quick tempo performance to be carried out easily. With the embodiment of FIG. 8, the induced iron piece 80 may of course be replaced by a magnet having the same form. In this case, the permanent magnet 30 received in the supporting case 20 may also be substituted by a magnetic material.

FIG. 9 is a modification of the embodiment of FIG. 8. According to the embodiment of FIG. 9, the key arm 2 of FIG. I made of magnetic material has two projecting cutout strips 91 and 92 which functionally correspond to the aforesaid two

leg members

81 and 82 of the induced iron piece 80 of FIG. 8. Under such arrangement, the projecting output strips 91 and 92 of the key arm 2 are drawn nearest to the

magnetic cores

26 and 28 respectively when the key is depressed substantially half way between the position (indicated by a broken line) where the key stands at rest and the position (indicated by a solid line) where the key finishes its depression, thus serving the same purpose as the embodiment of FIG. 8. In this case, the ends of the

magnetic cores

26 and 28 may, upon key depression, be inserted into the

apertures

93 and 94 resulting from the formation of the projecting output strips 91 and 92. With this embodiment, the key arm may, of course, be replaced by a magnet and the permanent magnet in the supporting case 20 may also be substituted by a magnetic material.

In the embodiment of FIG. 10, the key arm 2 made of magnetic material is simply perforated with two apertures 95 and 96 instead of being provided with projecting cutout strips as in FlG. 9. At the initial stage of key depression, the ends of the

magnetic cores

26 and 28 approach the peripheral surfaces of the apertures 95 and 96 and thereafter are inserted thereinto, permitting the further depression of the key. Like the embodiments of FIGS. 8 and 9, the embodiment of FIG. quickens the rise of musical tone output signals derived from key depression. With this embodiment, the key arm may, of course, be replaced by a magnet and the permanent magnet in the supporting case may also be substituted by a magnetic material.

As mentioned above, according to this invention, a nonmagnetic case supporting two magnetic cores and magnet or magnetic material disposed therebetween which are common to a plurality of keys is disposed below the keys, and separate coils corresponding to the respective keys are fitted on to at least one of the magnetic cores. Accordingly, the present controlling voltage generating device is of compact construction and saves space effectively with respect to the keyboard in which there are arranged a plurality of keys at a small interval.

Further, since the elements constituting the magnetic circuit are separated into movable and fixed parts, the voltage generating device can be easily assembled. According to the present invention, if the coil used as a detection element is fixed, it is less subject to damage due to abnormal vibrations or shocks than in the moving coil type, so that it withstands a semipermanent use.

With the prior art electronic musical instrument, the keys undergo and appreciably great pressure exerted by the return spring attached thereto and various contacts within the switch box, rendering the key touch unduly heavy. In contrast, the electronic musical instrument of the present invention has the advantage that the key touch feels light due to an attractive force arising between the key and the magnet upon key depression.

What is claimed is:

1. For use in a keyboard type electronic musical instrument, a voltage generating arrangement for producing electrical signals in response to depression of the keys comprising in combination:

a plurality of keys arranged side by side, each supported so as to allow one end thereof to rock vertically in a conventional musical keyboard arrangement;

an elongated non-magnetic housing positioned beneath said keys in a plane substantially parallel thereto and extending substantially transversely of the longitudinal axes of the individual keys;

a pair of elongated magnetic core members supported in spaced parallel relation to each other within said housing, at least one of said core members having a plurality of spaced parallel pole piece projections equal in number to the number of keys;

a plurality of coils, one wound around each of said pole piece projections;

an elongated first member of magnetic material received within said housing, positioned between and in contact with the lower portion of said core members and defining therewith a substantially channel shaped magnetic circuit, the open side of said channel facing vertically upwardly toward the underside of said keys;

a second member of magnetic material attached to the underside of each of the keys, one of said first and second magnetic members being a permanent magnet;

whereby when anyone of said keys is depressed, a voltage is generated in the corresponding coil and the magnitude of said voltage is a function of the speed with which the key is depressed.

2. The voltage generating device according to claim 1 5 wherein said housing is supported at one end by a keyboard supporting frame and at the other end by a stopper member for regulating the range of key depression.

3. The voltage generating device according to claim 2 wherein said housing is supported by the keyboard supporting frame by means capable of varying the position of the case with respect to the keyboard.

4. The voltage generating device according to claim I wherein said housing has partition walls jointly defining a rectangular space set up on the bottom plate thereof; said first and second magnetic cores are received in said case in such a manner as to extend along the inner surfaces of the opposite longitudinal partition walls; said first member is interposed between said two magnetic cores in close contact therewith; and a corrugated plate spring inserted into the space defined between at least one of said magnetic cores and the inner surface of one of the opposite longitudinal partition walls.

5. The voltage generating device according to claim 4 wherein at least two projecting rods are erected at that part of the bottom plate of said case which is defined by its partition walls so as to be arranged in a straight line with a predetermined spacing in the direction of key arrangement; and said first member is perforated with at least two apertures similarly arranged in a straight line in the direction of key arrangement with the same spacing at which said projecting rods are disposed, said apertures allowing said projecting rods to pass therethrough thereby securely to fix said first member.

6. The voltage generating device according to claim 1 wherein the magnetic core other than the magnetic core fitted with said coils is perforated with at least one aperture, and a retaining plate having at least one first engaging strip integrally formed therewith and fitted into said aperture and at least one second engaging strip integrally formed therewith and inserted into the interspace between the adjacent projections formed on said magnetic core, whereby the fitting of said first engaging strip into said aperture and the insertion of said second engaging strip into the interspace between the adjacent projections formed on said latter magnetic core enable said first member to be securely held in place.

7. The voltage generating device according to claim 1 wherein each of said second members are bent at both ends to form two leg members extending in slightly offsetting relationship with respect to said two magnetic cores respectively, whereby, when each ofsaid keys is depressed halfway said two leg members are drawn closest to said two magnetic cores.

8. The voltage generating device according to claim 7 wherein one of said two leg members which is positioned closer to the point at which each of said keys is supported has a greater length than the other, and one of said magnetic cores which corresponds to the longer leg member has a smaller height than the other which corresponds to the shorter leg member, so that, upon key depression, the two leg members can approach simultaneously said two magnetic cores with a substantially equal space therebetween.

9. The voltage generating device according to claim 1 wherein each of said second members has two projecting cutout strips corresponding to said first and second magnetic cores respectively, so that when each of said keys is depressed halfway, the projecting cutout strips approach closest to said first and second magnetic cores.

second magnetic cores enter said two apertures respectively.

11. The combination defined by claim I in which said first members are permanent magnets.

12. The combination defined by claim I in which said second members are permanent magnets.

i i U i Q

Claims

1. For use in a keyboard type electronic musical instrument, a voltage generating arrangement for producing electrical signals in response to depression of the keys comprising in combination: a plurality of keys arranged side by side, each supported so as to allow one end thereof to rock vertically in a conventional musical keyboard arrangement; an elongated non-magnetic housing positioned beneath said keys in a plane substantially parallel thereto and extending substantially transversely of the longitudinal axes of the individual keys; a pair of elongated magnetic core members supported in spaced parallel relation to each other within said housing, at least one of said core members having a plurality of spaced parallel pole piece projections equal in number to the number of keys; a plurality of coils, one wound around each of said pole piece projections; an elongated first member of magnetic material received within said housing, positioned between and in contact with the lower portion of said core members and defining therewith a substantially channel shaped magnetic circuit, the open side of said channel facing vertically upwardly toward the underside of said keys; a second member of magnetic material attached to the underside of each of the keys, one of said first and second magnetic members being a permanent magnet; whereby when anyone of said keys is depressed, a voltage is generated in the corresponding coil and the magnitude of said voltage is a function of the speed with which the key is depressed.

2. The voltage generating device according to claim 1 wherein said housing is supported at one end by a keyboard supporting frame and at the other end by a stopper member for regulating the range of key depression.

4. The voltage generating device according to claim 1 wherein said housing has partition walls jointly defining a rectangular space set up on the bottom plate thereof; said first and second magnetic cores are received in said case in such a manner as to extend along the inner surfaces of the opposite longitudinal partition walls; said first member is interposed between said two magnetic cores in close contact therewith; and a corrugated plate spring inserted into the space defined between at least one of said magnetic cores and the inner surface of one of the opposite longitudinal partition walls.

7. The voltage generating device according to claim 1 wherein each of said second members are bent at both ends to form two leg members extending in slightly offsetting relationship with respect to said two magnetic cores respectively, whereby, when each of said keys is depressed halfway said two leg members are drawn closest to said two magnetic cores.

10. The voltage generating device according to claim 1 wherein each of said second members is perforated with two apertures facing said first and second magnetic cores, so that when each of said keys is depressed halfway, each of said second members is drawn nearest to said first and second magnetic cores, and upon further key depression, said first and second magnetic cores enter said two apertures respectively.

11. The combination defined by claim 1 in which said first members are permanent magnets.

12. The combination defined by claim 1 in which said second members are permanent magnets.