WO2001006487A1

WO2001006487A1 - Electromagnetic device for the detection of the descending travel of keys in electronic keyboards.

Info

Publication number: WO2001006487A1
Application number: PCT/IT1999/000229
Authority: WO
Inventors: Mario Agostinelli
Original assignee: Mabel Di Agostinelli, Mario
Priority date: 1999-07-20
Filing date: 1999-07-20
Publication date: 2001-01-25
Also published as: AU5192499A

Abstract

The present invention relates to an electromagnetic device for the detection of the descending travel of keys in electronic keyboards, which includes one or more coils (4) for each key (1) immersed in an electromagnetic field generated by one or more coils (5) traversed by electric current, which are elastically displaced during the descending travel of the key (1).

Description

Electromagnetic device for the detection of the descending travel of keys in electronic keyboards.

The present patent application relates to an electromagnetic device for the detection of the descending travel of keys in electronic keyboards or electronic accordions. As it is known, in acoustic keyboards, such as piano keyboards, different sound tones and volumes are obtained based on the pressure made on the keys and therefore on the descending speed.

For long time in the past electronic keyboards were not able to produce this effect, since the pressing of a key (regardless of the pressure made and of the descending speed) always determined an electric contact to close in the same way, causing a variation in the status of a control electronic circuit that enabled the generation of sound.

Most of the times this type of keyboards made use of three different systems, capable of detecting only the ON-OFF status change, that is systems using simple contact springs (or mechanical contacts) to open and close the electric contact or systems provided with sensors capable of detecting the approximation of a magnet (based on the so-called HALL effect). In any case, in electronic keyboards using traditional systems it was not possible to obtain sounds with different volume and tone based on the pressure made on the keys. This fact, of course, considerably limited the expressive possibilities of musicians.

For this reason electronic keyboards capable of modulating the sound based on the pressure made on the key - more exactly on the higher or lower descending speed of the key - have been developed recently. As a matter of fact, the new keyboards are provided with devices capable of evaluating the descending speed of the key and consequently regulating the emission of sounds. It must be noted that a higher descending speed of the key results in the /06487

generation of sounds with high volume (that is particularly loud sounds), while a lower descending speed of the key results in the generation of sounds with low volume (that is quite weak sounds). So far the devices capable of detecting the descending speed of the keys in electronic keyboards have made use of optical systems to detect the key travel, in co-operation with a suitable electronic circuit with microprocessor capable of measuring the descending speed of the key by processing the data on the descending time and travel. The signal emitted by the electronic circuit is sent to the expander of the musical instrument, which generates a sound whose volume is proportional to the descending speed of the key (the higher the volume the faster the descending speed of the key). After a careful study of the state of the art, to remedy the main disadvantages of the present technology the applicant has designed an innovative device for the detection of the descending travel of keys, interfaced with the expander and perfectly suitable to provide electronic keyboards with the capability of modulating the volume and tone of the sound at the musician's discretion. The new device designed by the applicant for the detection of the descending travel of the keys in electronic keyboards is made up of one or more coils, referred to as "transmitting" coils, located in the proximity of one or more coils, referred to as "receiving" coils, capable of emitting an electric signal that is proportional to the descending travel of the key.

More exactly, "transmitting" coils indicate coils traversed by electrical current, capable of generating an electromagnetic field, in which the "receiving" coils are immersed. At every variation of the electromagnetic field, an induced current is generated on the "receiving" coils, which is directly proportional to the descending travel of the key, since - as illustrated in details below - the variation of the electromagnetic field in which the "receiving" coil is immersed is determined by the descending travel of the key, which causes a variation in distance between the "transmitting" and "receiving" coils. In particular, in order to be elastically flexible, the "transmitting" coils are welded on a printed circuit, whose support board is located above the parallel series of levers actuated by the keys, while the "receiving" coils are printed on the printed circuit.

In the preferred embodiment of the present invention, the "transmitting" coils are welded on the printed circuit in projected position, so that they interfere with the levers actuated by the keys each time the keys are pressed. In particular, the levers push the "transmitting" coils from the bottom upwards, thus moving them away from the "receiving" coils.

Each rising of a "transmitting" coil corresponds to a variation of the electromagnetic field in which the corresponding "receiving" coil is immersed, on which an induced current is generated, which is proportional to the descending travel of the key, since the variation of the electromagnetic field is due to the fact that the "transmitting" coils move away from the "receiving" coils.

In view of the above, the device in question is assisted by a microprocessor capable of detecting the variation of the magnetic field produced between each "transmitting" coil and the corresponding "receiving" coil and calculating the variation time and therefore the descending speed of the key. The electric signal emitted by the device according to the present invention is sent to a suitable electronic circuit provided with microprocessor, capable of measuring the descending speed of the key starting from the detected descending travel and the time of the travel.

The information on the higher or lower descending speed of the key is instantaneously sent to a traditional expander that regulates the tone and the volume of the generated sound consequently. From the functional viewpoint and in terms of performance, the device according to the present invention is certainly to be preferred to all the traditional systems that are unable to regulate the generation of sound based on the pressure made on the keys, including the systems using the HALL effect and the REED bulbs, also in consideration of the lower production cost. Moreover, the device according to the present invention is to be preferred to the more recent systems that are capable of evaluating the descending speed of the keys based on the travel detection by means of an optical device. As a matter of fact, the device according to the present invention is characterised by the same performance as the optical detection systems, with the advantage of featuring more functional stability in time, total insensitivity to dust, reduced cost and limited energy consumption. It is understood that each key requires the presence of a pair of "transmitting" and "receiving" coils.

For major clarity the description of the device according to the present invention continues with reference to the enclosed drawing, which is intended for purposes of illustration and not in a limiting sense, whereby: - Figure 1 is the electric diagram of the device according to the present invention;

- Figure 2 is a schematic axonometric view of a preferred realisation and assembling of the device in question in the mechanism of a keyboard. With particular reference to figure 2, the mechanism of the keyboard usually comprises a series of keys (1) actuating corresponding levers (2). The support board (3) of a printed circuit is mounted just above the parallel series of levers (2), on which a series of "transmitting" coils (4) is welded, with one coil for each key. In particular, a "transmitting" coil (4) is located above each lever (2). A "receiving" coil (5) is printed on the pπnted circuit below each "transmitting" coil (4) and immersed in the electromagnetic field generated by the corresponding "transmitting" coil (4), shaped like a "U", it being provided that its free ends (4a) are welded on the support board (3) of the printed circuit in proximity of the rear longitudinal edge, while the opposite end (4b) of the coil (4) projects with respect to the board (3).

Thanks to their projection, the front ends (4b) of the "transmitting" coils (4) interfere with the levers (2) of the keys (1), when they tend to rise as a consequence of the pressure made on the keys (1) by the musician. More exactly, the rising of each lever (2) of the keys (1) pushes the above "transmitting" coil (4) upwards. In this way the coil (4) moves away from the "receiving" coil (5), thus determining a variation of the electromagnetic field in which the coil (5) is immersed, on which an induced current is generated, /06487 - 5 -

which is proportional to the displacement of the coil (4) and the descending travel of the key (1).

It must be said that the intrinsic flexibility of each "transmitting" coil (4) allows it to bend upwards - under the thrust of the corresponding lever (2) - and to automatically return to the rest position, just above the "receiving" coil (5) as soon as the interference of the lever (2) ends when the pressure on the key (1) is interrupted.

With reference to the electrical diagram of figure 1 , number (6) indicates the generator that electrically supplies the coils (4), while number (7) indicates the amplification circuit of the induced current generated on the coil (5) at each variation of the electromagnetic field in which it is immersed. The signal "S" coming out of the electromagnetic device according to the present invention is sent to the expander "E" provided in the musical instrument, through the interposition of an electronic device "G" capable of processing the signal "S" and generate MIDI data.

Claims

- 5 -

Claims

) Electromagnetic device for the detection of the descending travel of keys in electronic keyboards or electronic accordions, in co-operation with the expander provided with the musical instruments, which, according to the signal received from the device, generates a sound whose volume is proportional to the descending speed of the key - the higher the volume the faster the descending speed of the key; device characterised by the fact that it comprises a printed circuit whose support board (3) is mounted in proximity of the series of parallel levers (2) actuated by the keys (1) of the keyboard and by the fact that one or more coils (4) for each key (1) of the keyboard are printed on the printed circuit and immersed in the electromagnetic field generated by one or more coils (5) welded on the printed circuit and traversed by electric current, which are elastically bent due to the interference with the corresponding lever (2) during the descending travel of the key (1), thus generating an electric signal on the coils (4) which derives from the variation of the electromagnetic field in which the coils (4) are immersed and is proportional to the descending travel of the key (1).

2) Electromagnetic device for the detection of the descending travel of keys in electronic keyboards or electronic accordions according to claim 1 , characterised by the fact that it comprises an amplification circuit (7) of the electric signal coming out of the coils (5).