A system for controlling the movement of sliders in musical instruments with pipes and the like

The present invention relates to a system for controlling the movement of sliders in musical instruments with pipes and the like.

Musical instruments called pipe organs 1 (fig. 1) are devices in which the sound sensation is obtained through the passage of a flow of air generated by a fan 2 within one or more hollow cylindrical elements, called pipes. Their material, diameter and length differ according to the desired tone, and are positioned on a body called wind-chest 4, which serves as a pressure tank containing the ventilated air. The pipes 3 and the wind-chest 4 connected with each other through a slit 5, under which is positioned a movable sluice gate, called slider 6, which, opening in more or less ample fashion, allows the passage of a more or less large quantity of air, thereby generating, as a consequence, a more or less intense sound sensation.

In so-called traditional or mechanical pipe organs, the movement of each slider 6 is operated by the organ player by pressing on each individual key 7 of the keyboard, wherefrom branch a series of lever mechanisms 8. The musical characteristic of this kind of instrument, highly appreciated by organ player, resides in the ability gradually to calibrate the opening of the slider 6, acting in equally gradual fashion on the corresponding key 7, thereby assuring a coloratura of the sound, which fully expresses all sound intensity hues, of each part of the piece to be performed. It should be noted that multiple sliders 6, belonging to different wind-chests, can be connected to a same key 7.

In particular, said gradualness distinguishes and enhances the musical qualities of the instrument, since it enables an experienced and sensitive organist to obtain a particular sound modulation phase, called "attack transient". This phase generally develops in the first 2 mm of travel of the key 7 (fig. 1, 2 e 3), and it is characterised by the emission of a particular, not yet full, distorted sound, which expresses the musician's personality and expertise. It is originated by the fact that the air coming from the wind-chest 4 (fig. 1) takes a short fraction of time to bring the sound of the pipes 3 to steady state. Once this phase is over, the remaining millimetres of travel of the key 7 instead produce a proportional increase in sound power. This effect, which, as we shall see, thanks to the present invention, is now finally reproducible on any pipe organ, is so important as to be a debated subject among specialists, starting as early as mid nineteenth century. For additional information, the reader is referred to the prestigious journal "ARTE ORGANARIA E ORGANISTICA"' ("ORGAN MAKING AND ORGAN PLAYING"), published by CARRARA, and to the articles by Dr. G. Pedrini, which report on studies on this subject conducted by world renowned experts such as Vierling and Sennheiser, Howard F. Pollard, Bazzanella and Debiasi, and others.

Over time, the evolution of the requirements of playing for concerts or ceremonies, together with technological development, has led to the introduction in such instruments of some devices, moved by pneumatic or electrical energy, to simplify the mechanical part composed by the lever mechanisms 9. In practice, the most important innovation has enabled the physical detachment between pipes/wind-chests and keyboard, which, as can be observed, for examples, in installations situated in places of worship, is now often positioned in areas distanced even tens of meters from the area where sound is emitted.

In this case, the complex cinematic chain constituted, in traditional organs, by the lever mechanisms 8, has been replaced by an actuator device 9 (fig. 2), which, when it receives the signal from the key 7, opens the corresponding slider 6 (fig. 1). For technical reasons inherent in available technology, however, known actuator devices have a functional characteristic that reduces the quality of the sound thus emitted lower relative to the one obtained by an identical pipe organ, which is provided with mechanical control.

Known non-mechanical actuators 9 can assume only two defined physical states, which we shall define, for the sake of simplicity, ON / OFF. Because of this characteristic, whatever the pressure or the travel imposed by the organist on the key 7, the result is always the same fixed opening travel 10 (fig. 1) of the respective slider 6, whose dynamics, always identical in itself, does not reflect the emphasis imparted by the organist. This fact thus generates a sound response that is not modulated, as the musical score would instead require, and lacking the "attack transients" which, as explained above, are typical of organs provided with a rigid mechanical control. Over time, this innovation has been met favourably, mostly thanks to the operating advantages it entailed. On the other, it created a type of instrument that is often poorly suited to the hands of experienced organists. Such hands have usually developed and acquired the sensitivity and familiarity of touch that is typical of mechanically actuated organs. This is why in some cases accomplished organists, because of the high sensitivity they have developed on traditional organs, do not like to perform concerts on instruments with more modern actuation systems, since such instruments are not able to return to the audience all the refined touch sensations (s)he imparts to the keyboard.

Obviously, the technical response time of known non mechanical actuators 9 causes, for instance, in fast passages between different notes, an ear that is not particularly experienced not to be able fully to detect the substantially difference, for the same musical piece, of its performance on organs with mechanical actuation system 8 (fig. 1) (and hence with proportional opening of the slider 6), instead of with ON / OFF opening. In fact, this aspect has always interested aficionados of this musical genre, because it is one of the ways in which the organist performs the expressive and emphasis characteristics of each piece, in compliance with the composer's indications.

Over the past few decades, the development of electronic technology has had its influence on such instruments, providing them with additional operating functionalities, capable of improving and expanding its capacities; however, all this (excluding some incomplete attempts), without succeeding in providing an organ with non mechanical control with the same expressive capacity of the mechanical control organ illustrated above.

WO 94/11856 discloses a system for calibrating the movements of the mechanical parts of a pipe organ comprising for each wind-chest:

• an organ case, air-fed and comprising openings that communicate with a chamber,
• sliders that control the flow of air of each opening, each slider being actuated with the aid of a key,
• and pipes, whose foot is engaged in an orifice provided in the chamber, the opening of the orifices being regulated by means of registers. In this system:

• a first series of position sensors is arranged to sense the displacement of each slider,
• a second series of position sensors is arranged to sense the displacement of each register,
• and electronic means assure for each position sensor of the first and of the second series the acquisition and the calibration of the evolution over time of the position of the sliders and of the register.

Moreover, a third series of position sensors is arranged to detect the displacement of each key, whilst a conversion circuit establishes a correspondence between the displacements of the position sensors of the first series and the respective ones of the third series.

In this arrangement, to control slider displacement, electromagnetic actuation means are provided, in which an electromagnet comprises coils that act on a magnetic head borne by an arm articulated about an axis. Each arm is provided at its free end, opposite to the articulated one, with a fork, within which is engaged a rod for directly actuating a slider. The action of closing the slider, instead, is controlled by elastic return means.

This is a common characteristic of prior art actuators, or of the ON / OFF type 9 (fig. 2), in which an oscillating arm is provided with a wing, which is attracted by the respective magnet, thereby controlling only the opening motion of the slider; leaving instead to a simple mechanical spring 30 (fig. 2), whose force is obviously not adjustable, the task of returning the slider to the closed position.

This structure of prior art, or ON / OFF, actuators, thus does not allow to obtain a movement of the slider that is completely proportional to the travel of the respective key, with the consequence that the musician cannot modulate sound as desired.

The present invention, starting from the notion of said drawback, aims to remedy it.

Therefore, the main object of the present invention is to provide a system for controlling the movement of sliders in pipe musical instruments and the like, which allows, though using non mechanical actuators, to achieve a movement of the sliders that is fully proportional to the travel of the respective keys, thereby obtaining a new type of organ or similar instrument, which retrieves all expressive musical characteristics that are typical of traditional organs, enabling to concentrate in a single instrument all the advantages of the different types of organs developed over time.

In view of said object, the present invention provides a system for controlling the movement of sliders in musical instruments with pipes and the like, whose essential characteristic is set out in claim 1.

Further advantageous characteristics are set out in the dependent claims.

The aforesaid claims are understood to be integrally reported herein.

The present invention shall become more readily apparent from the detailed description that follows, with reference to the accompanying drawings, provided purely by way of non limiting example, in which:

fig. 1

is a diagram with sectioned parts of a traditional pipe organ with mechanically operated keyboard (with lever mechanisms);

fig. 2

schematically illustrates an electro-mechanically operated keyboard, of the so-called ON / OFF type;

fig. 3

schematically shows an electronically operated keyboard, with proportional technology, according to the present invention,

fig. 4

schematically shows the travel of a key and of the respective slider;

fig. 5

is an elevation view of an actuator device with proportional technology, according to a first embodiment of the present patent application;

fig. 6

is a schematic section illustration of a comparison, by way of example, between a double action pneumatic cylinder and a single-action pneumatic cylinder with spring-operated return;

Figures 7, 8 and 9

are sectioned schematic views, respectively showing different states of equilibrium of the forces at play on a slider, depending on the number of registers made operational;

fig. 10

is a graphic indicating the laws of proportionality, linking the travel of a key and of the respective slider;

fig. 11

is a global functional diagram of the system according to the invention, with actuator device with proportional technology according to fig. 5;

fig. 12

is a block diagram of the means for automatically selecting the Proportional or ON / OFF operation.

fig. 13

shows a template of data of the predefined threshold values, for attributing each value of voltage of the input signal, to each related function (for example: Learning, Proportional - ON / OFF, Anti-interference);

fig. 14

is a block diagram of the means for protection from interference, due to the thermal drift of the components;

fig. 15

is a block diagram of the means for activating the self - learning procedure;

fig. 16

is a schematic elevation view of a compact embodiment, in which the actuating device with proportional technology, according to fig. 5, is connected in close proximity to a slider, for direct application inside the wind-chest;

fig. 17

is a similar scheme to that of Fig. 11, but illustrates another embodiment of the system according to the invention.

The system for controlling the movement of sliders in musical instruments with pipes and the like, according to a first example of embodiment of the invention, comprises an electromagnetic actuation device 11 (fig. 3), that is light and compact, provided with a functionally autonomous and dedicated microprocessor, able to command the movement, in completely proportional fashion, of one or of a plurality of sliders 6 (fig. 1).

Said actuator, whose position is controlled in closed loop by means of a position transducer 12 (fig. 3) (for example, a Hall effect probe), is connected, upstream, to a microprocessor 13. Said microprocessor 13 in turn receives and processes, with a very high, predetermined frequency, the signal coming from a position transducer 14 (also constituted, for example, by a Hall effect probe), associated to a respective key 7, and sends its corresponding voltage signal to coils 15 and 16 of the actuator 11, in order to cause the corresponding slider 6, practically in real time, to the position corresponding to the one indicated by the key. Said actuator 11 is connected to the corresponding slider 6 by means of a rod or rigid tie rod 19.

The system according to the invention allows to establish, in simple and automatic fashion, a direct correspondence between the total amplitude 17 (fig. 3) of the travel executable by the key 7 and the total amplitude 10 (fig. 1) of the travel executable by the slider 6 (fig. 1). In practice, once the respective values of total travel are determined, N intermediate positions 18 are calculated, stored and mutually combined (fig. 4), thereby enabling the sliders to behave exactly as if they were moved by a keyboard connected to them by means of traditional mechanical lever mechanisms, with all deriving advantages.

Obviously, the subdivision of the travels into N intermediate positions, is defined in such a way as to be so thick as to give the listener the feeling that the variation in intensity of the sound emitted by the pipes is continuous, and not "stepped" as it in fact is.

In order fully to understand the importance of the concept described above, it should be remembered that, in the case of the wind organs, unlike string keyboards like the piano, the increase in sound intensity is not a function of the speed and of the acceleration with which the organist presses on the key, but rather on the travel of the key which, as explained causes a more or less ample opening of the slider, creating a larger or smaller passage of volume of ventilated air, inside the corresponding pipes, consequently creating a sound emission with more or less pronounced intensity.

In the control system of the present invention, the fundamental difference described above was duly taken into consideration, and the system is particularly simple, rapid and effective. The microprocessor 13 is not engaged in calculation sub-programs on the dynamics of the motion of the key (as we have seen such data are useless for operating purposes), but is limited to transforming the position signal coming from the key, into a simple voltage signal to be sent to the actuator 11, and corresponding to the correct position of the respective slider, acquired and stored as explained previously.

This simplification of the calculation function thus allows to apply high data recalculation and transmission frequencies, in order to reduce to a far lower value than the threshold of perception of the delay between the time the key is pressed and the time the slider oscillates to the corresponding position, thus enabling to achieve the predetermined object, i.e. to provide a "remote" keyboard with the same musical functionalities that are typical of a mechanical or traditional keyboard.

Since mention has been made of the functional difference between the keyboard of the piano and of the organ, it should in any case be recalled that, if required by particular needs, the system of the present invention is in turn able to operate as if it were moved from a piano keyboard, in which the power of the sound emission is directly proportional to the power with which the key is stricken. Obviously, this is an operating mode that, though it is provided and is part of the state of the art, at this time is not necessary for the purposes set out herein. However, it could be, if a keyboard for pipe organ had to be produced, which could also serve, with an appropriate selection, as a keyboard for an instrument, such as a piano, which instead needs a dynamic keyboard. In this case, from the design point of view, it will be necessary to provide the necessary variants to hardware and software choices, without thereby departing from the scope of the present invention.

It should also be recalled that it is possible, for equal travel 17 (fig. 3) of the key 7, to have the slider 6 perform a corresponding travel 10 (fig. 1), of reduced total amplitude, for example in such a way as to emphasise, in proportion, the sound characteristics of the initial phases, such as the "attack transient", variation which can be gradual and adjustable, for example, by means of an appropriate selector, positioned in proximity to the musician.

The actuator 11 (fig. 3 and 5), described herein in a preferred, but not limiting, embodiment of the present invention, contains in itself all necessary elements both for its autonomous operation and for the continuous control of its position. It is substantially composed by a mechanical part, able to actuate the opening and closing motion of the slider 6 (fig. 1) by means of the tie rod 19 (fig. 1), and an electrical /electronic part for controlling and commanding the motion itself, in a manner that is fully proportional to the travel of the respective key.

The mechanical part of the actuator 11 essentially comprises a fixed base 20 (fig. 5), whereon is hinged the free end of the rod of an anchor 21 (fig. 5), in freely oscillating fashion about an axis 22. Said rod of the anchor 21, at its other end, is fastened relative to an end of a rigid rod 19, in turn connected to a slider 6, and it bears two specularly opposite fixed wings 23. At the opposite parts of the rod of said anchor 21 are positioned the electromagnets 15 and 16, integral with the base 20 and each underlying a respective wing 23 of the anchor 21. Each of said electromagnets 15, 16, when electrically excited, attracts the respective wing 23 of the anchor 21, proportionately to the intensity of the induced currents, thereby causing the corresponding downwards or upwards motion of the tie rod 19, and, consequently, the opening or closing of the respective slider 6.

The base 20 also supports a sustaining column, extending parallel to the axes of the electromagnets 15, 16 and proximate to one (15) of the electromagnets themselves, which supports said position transducer 12. At the end of one of said wings 23 of the anchor 21 is fastened a fixed reference body 24 (fig. 5), which indicates to the position transducer 12 the instantaneous position of the anchor 21, and hence of the related slider 6, in space.

Said sustaining column also supports the electrical / electronic circuits 25 (fig. 5) of the actuator 11 provided on an appropriate board 26 and including the circuit components required to control the motion of the anchor 21, such as a microprocessor 27 and said position transducer 12. Said microprocessor 27 continuously reads, in closed loop fashion, the position of the anchor 21 as indicated by the position transducer 12, compares it with the position indicated by the position transducer 14 associated to the corresponding key 7 and sends to the actuator 11 the current signal necessary to bring the actuator to the position required by the key. To avoid interference coming from the electromagnetic fields generated by the coils 15 and 16 (fig. 5), the board 26 is protected from interference by a shielding wall 28 (fig. 5).

As is apparent from the above, the anchor 21 is provided with the two opposite wings 23, each of which faces the polar expansion 29 (fig. 5) of a respective independent electromagnet 15, 16 (or of a plurality of respective independent magnets). Said electromagnets determine, when excited, an oscillation of the anchor respectively in one or in the other sense of oscillation about the axis 22, then keeping it in oscillated position with the force necessary to hold (through the tie rod) the respective slider 6 instantaneously and stably in the required position of oscillation, thereby controlling, in gradual and adjustable fashion, both the opening and the closing motion of the slider itself. It should be noted that the polar expansions 29 simultaneously act with antagonist forces on both the portions 23 of the anchor 21.

In prior art devices, or of the ON / OFF type 9 (fig. 2), instead, the oscillating arm, provided with only one wing, is attracted by the respective magnet in only one sense of oscillation about the respective axis, thereby controlling only the opening motion of the slider, whilst a simple mechanical spring 30 (fig. 2), whose force is obviously not adjustable, is tasked with returning the slider to the closed position.

Using as a means of comparison the devices in use in the pneumatic sector, one can say that the control system according to the invention allows to achieve the technical effects of a double action cylinder 31 (fig. 6), whilst the prior art control system allows to achieve only the technical effects of a single action cylinder, with spring-actuated return 32.

The possibility to control a slider 6 in fully proportional fashion in both directions of travel (opening, closing) is determining for the purposes of obtaining the stability of the desired sound, since, on each slider 6 (fig. 1), in the transient corresponding to its opening, pressure variations are created (whose origin shall be explained below), such as to cause appreciable variations in the force needed for its opening and closing.

Some technical explanations are provided, which allow to understand the variability of the force that act on each slider:

• CASE A (fig. 7): the slider 6 is closed. On the side 33 of the slider acts the over-pressure 34 created by the fan inside the wind-chest 4. On the side 35 presses atmospheric pressure 36. To be opened, the slider must be subjected to a force 37, exceeding the difference between the overpressure 34 and atmospheric pressure 36.
• CASE B (fig. 8): the slider 6 is opened, and only one register 61 is open. On the side 33 of the slider acts the usual over-pressure 34 (fig. 7 and 8); on the side 35 (fig. 7 and 8), in the transitory opening phase, instantaneously bears a pressure 38, different from atmospheric pressure 36 as mentioned above. To be opened farther, the slider must be subjected to a force 39, exceeding the difference between the overpressure 34, and the pressure 38 is in any case already different from the force 37 as per case A above.
• CASE C (fig. 9): the slider 6 is opened, and several registers 61 are open. On the side 33 of the slider acts the usual over-pressure 34 (fig. 7, 8 and 9). On the side 35, in the transitory opening phase, instantaneously bears a pressure 40, different from atmospheric pressure 36 (fig. 7) as per case A. To be opened farther, the slider must be subjected to a force 41 (fig. 9), which exceeds the difference between the overpressure 34 (fig. 7, 8 and 9), and the pressure 40 (fig. 9), but in any case is itself still different from the forces 37 (fig. 7) and 39 (fig. 8), as per cases A and B.

Moreover, the equilibrium point between the two pressure on the opposite faces of the slider, varies in continuous and non linear fashion, as the slider itself progressively moves away from the slit 5 (fig. 1, 7, 8 and 9). It is less and less influenced by its suction effect (Venturi effect), being progressively more and more immersed inside the wind-chest, and hence in a volume of air having a progressively more and more stable pressure. To this is added the existence of a high number of variables, which influence the stability of instantaneous pressure inside the wind-chest (number of registers and/or sliders open simultaneously, existence of instantaneous turbulent states, etc. ).

Said variability of forces acting on the slider makes it practically impossible for a prior art actuator, with single action and with spring-actuated return 32 (fig. 6), to assure a satisfactory control of its motion. An overly rigid spring will subtract power from the actuator when pulling, forcing its over-dimensioning, and will cause the slider to close before the key is completely released. On the other hand, an overly weak spring will cause it to close after the key is completely released. In both cases, with negative consequences entailing a flattened musical performance.

If necessary, the flexibility of the system allows to link the travel 17 (fig. 3 and 10) of each key 7 and the travel 10 of the corresponding slider 6 (fig. 1 and 10) by means of a specific motion law, e.g. linear 42 (fig. 10), parabolic 43 (fig. 10), mixed 44 (fig. 10), etc.. This could be useful when the manner of playing of a traditional mechanical organ is to be reproduced with precision. A non linearity of the curve could allow to limit the influence which the inevitable mechanical play of the lever mechanisms 8 (fig. 1) have on sound dynamics; or to store the characteristic curves of motion of each slider, typical of each model and brand of organ, to be able to recall them and use them at will.

Summarising the inventive concept in a simple block diagram (fig. 11), the control system with proportional actuator of the present invention essentially comprises:

• electrical - electronic circuit means 25 (fig. 5 and 11), including a board 26, provided with a microprocessor 27 installed aboard, having a single multi-function analogue input 45 (fig. 11), which receives the voltage signal 46 (ranging between 0 and 5 V) corresponding to the position of the key 7 (fig. 3 and 11) and coming from a remote central unit 13. Said microprocessor 27 transforms said data into current values 47 and 48 (fig. 11) sent to the respective coils 16 and 15 of the actuator 11, which exert on the wings 23 (fig. 5 and 11) of the anchor 21 the force necessary to move and securely to hold the slider(s) 6 (fig. 1 and 11) in the desired position;
• actuation means 11 (fig. 5 and 11) [whose position is controlled in closed loop by said micro-processor 27, by means of the internal position transducer 12 (Fig. 3, 5 and 11)]. Said actuation means 11 are connected, by means of one or a plurality of rigid rods or tie rods 19 (fig. 1, 5 and 11), to one or to a plurality of sliders 6 (fig. 1, 4 and 11), whereof they control the motion proportionately to the travel executed by the corresponding key 7 (fig. 3 and 11).

OPERATIVE FUNCTIONS - In its simplicity and compactness, the control system of the invention contains and allows the indispensable functions for the correct operation of the installation, such as:

- FUNCTIONS FOR HANDLING FAULTS

For this purpose, the system comprises:

• non volatile memory means 49 (Fig. 11), for example of the Flash type, for storing the calibration data (fig. 10) of each individual movement, positioned near the microprocessor 27 (fig. 11);
• visual indicator means (LED) 50, 51 and 52 (fig. 11) to signal operating faults, located, in redundant fashion, both near the keyboard 7 (fig. 11), and near each actuator;
• an intelligent automatic switching device 53 (fig. 12) of each individual actuator 11 (fig. 11), from the proportional operating mode 54 (fig. 12) to the two state, ON/OFF mode 55 (fig. 12), in case of faults in the data; this function, generally called "fault tolerant", allows to play in any case, though with non proportional performance, even in case of sudden faults.

- FUNCTIONS ACTIVATED BY MEANS OF THRESHOLD COMMANDS

The single analogue input 45 (Fig. 11), which, as described above, provides the system with the characteristic of construction, installation and operating simplicity, enables in equally simple fashion to activate different functions. The microprocessor 27 and the calculation and memory means use the voltage signal 46 (fig. 11, 12, 14 and 15) reached by the input signal 45, and maintained for a certain interval of time, to include and activate various functions such as those described below. Said voltage signal 46 is continuously compared with a template 56 (Fig. 13) containing the predetermined threshold levels P, Q, R, S, T, U (fig. 15), to understand which activity is to be performed.

ENABLING PROTECTION AGAINST SOUND EMISSIONS, CONSEQUENT TO THERMAL

DRIFT IN AUTOMATED COMPONENTS - Although current electronic components are considered highly reliable, it may still occur that, even in the absence of pressure on the keys 7 (fig. 14), the actuator receives, for thermal drift reasons, small electrical signals, and that consequently undesired sound are involuntarily emitted. To prevent this action, the input voltage signal 46 (fig. 14), is analysed by appropriately programmed electronic means 57 (fig. 14), according to the system illustrated in the previous paragraph, and recognised as a signal coming from the key 7 (Fig. 14), only if its value exceeds a certain safety threshold defined by experience; in this way, said small, stable and continuous signal 46 (fig. 14) is recognised to belong to the threshold ranging between P and Q (fig. 13) and eliminated, thereby preventing this annoying anomaly from occurring.

ENABLING THE LEARNING FUNCTION - The learning phase is carried out at the time the organ is installed, or when it is reactivated after periods of inactivity or maintenance. It consists of having a plurality of actuators 11 individually perform, in automatic, (fig. 1 and 11) the matching of each intermediate position 18 (fig. 4) of each key 7 with each intermediate position 18 of each respective slider 6, as described above. For safety reasons, the system is provided with an appropriate command 58 (fig. 11), whose insertion sends with a predetermined logic an input voltage signal 46 (fig. 15) to each actuator 11 (fig. 11), which is analysed by appropriately programmed electronic means 59 (fig. 15), in the manner illustrated above. In this way, said strong, stable and continuous signal 46 is recognised to belong to the threshold ranging between R and S, activating the related learning function.

ENABLING THE SYSTEM FUNCTION AND OTHER SPECIAL FUNCTIONS - According to the same principle, the system test function is recognised and executed at the time the system is turned on, or in other situations when it is deemed necessary; and, following the same principle, additional functions can also be implemented.

COMPACT VERSION - fig. 16 shows a compact version of the assembly formed by an actuator 11, according to the present invention, and by a corresponding slider 6, connected at close distance by means of a tie rod articulated, at one side, to an end of a wing of the anchor of the actuator and, at the other side, to the free end of the slider.

It is also possible to provide an integrated version of the assembly formed by an actuator 11, according to the present invention, and by a corresponding slider 6, in which the anchor of the actuator is integral with the slider and oscillates relative to an axis shared with the slider itself.

VERSION WITH LINEAR ACTUATOR - Figure 17 schematically shows another embodiment of the system for controlling the movement of sliders in musical instruments with pipes and the like, according to the present invention.

With reference to said figure, the movement of the slider 6 is controlled by means of an actuation device with linear movement 68, instead of the actuator 11 (fig. 5), and still oscillating. In said figure, the parts similar to those described above are designated by the same reference numbers and are not further explained.

The mechanical part of said actuation device 68 comprises a base 63, whereon is positioned an electromagnetic actuator with linear motion 66. Said linear actuator 66 comprises a fixed part provided with electromagnetic control means 64 which, when electrically excited through the electrical connection 48 (fig. 17) and as a result of the movements of the respective key 7, generate a corresponding magnetic field, determining corresponding reciprocating linear displacements of a movable member 65 able to move along an axis 67, proportionately to the intensity of the induced currents, in one and in the other sense of oscillation of at least one respective slider 6, which is thus actuated to open or close with respect to the corresponding orifice 5, and maintaining said movable member 65 with the force required to secure said slider 6 instantly and stably in its oscillated position. In particular, the displacement of the movable member 65 determines the corresponding movement of the tie rod 19 and, consequently, the opening or the closing of each slider 6 associated to the respective key 7.

To one end of the movable rod 65 is fastened a reference body 69, which indicates to the position transducer 12 (fixed with respect to the base 63), its instantaneous position, and hence the position of the related slider, in space.

The electrical / electronic part 25 comprises a board 26, with the components necessary to control the movement of the rod 65 of the linear actuator 66, such as the microprocessor 27, the position transducer 12 and the other components, which perform the same functions already illustrated and described with reference to fig. 11. In particular, the microprocessor 27 continuously reads, in closed loop fashion, the position of the rod 65 of the actuator 66, as indicated by the position transducer 12, compares it with the position indicated by the position transducer 14 associated to the corresponding key 7 (fig. 3), and sends to the actuator 66 the current signal necessary to bring the rod 65 of the actuator to the position required by the key. To avoid interference coming from the electromagnetic fields generated by the actuator 66, the board 26 is protected therefrom by a shielding wall 70.

This embodiment of the system according to the invention also allows to achieve the technical advantages explained with reference to the first embodiment.

As is readily apparent from the above, the control system according to the invention comprises actuator means (11; 68), in which a movable member (21, 23; 65) is driven to perform reciprocating movements proportionately to the movements of the respective key (7) and controls, directly and in correspondingly proportional fashion, the movement of at least a respective slider (6) both in its opening travel and in the closing travel with respect to the corresponding orifice (5).