DE3013964A1 - Circuits for stabilising ultrasonic generator and preventing drying - in prodn. of aerosols for breathing machines - Google Patents

Abstract

An ultrasonic generator producing an aerosol in a gas by atomising liq. with a mechanical vibrator supplied with a variable power high frequency signal produced by an oscillator circuit has a protector to prevent damage to the vibrator on dry running and which stabilises the signal during wet running. The vibrator protector has a circuit which detects changes in at least one parameter in the vibrator circuit caused on transition from wet to dry running. The wet running detector circuit includes transistors, esp. in the amplifier section which may be self-excited or externally excited. The air supplied by medical breathing appts. must be kept moist by an aerosol to prevent the patient's air passages drying out, and this appts. must respond to changes, e.g. in the patient's condition or in the viscosity of the commonly used water/oil mixture. The present appts. reduces the need for constant medical observation.

Description

The invention relates to an ultrasonic generator for

zcuguncj a liquid suspension in a gas with a Schwinysystem, that consists of a mechanical oscillator that atomizes the liquid and one the Exciting transducers with an electrical high-frequency signal with variable power There is an oscillator circuit, and with one the oscillator when running dry a self-harming protective device.

Such ultrasonic generators are used, among other things, in medical technology for use where they are used, for example, as aerosol generators, the air supplied to an artificially ventilated patient in a defined manner moisten to prevent damaging dehydration of the patient's airways. The amount of liquid transferred into the suspended state per unit of time, i.e. the moisture content of the breathing air supplied to the patient depends on the ultrasonic power emitted by the mechanical transducer and thus from which is fed to this oscillator in the form of an electrical high-frequency signal electrical power, with the viscosity of each as a further parameter liquid to be atomized is included. As for each patient the moisture content the breathing air is adjusted individually and the viscosity of the essentially Liquid to be atomized consisting of water, for example by adding different amounts of essential oils can have different values, it is necessary, in the case of geids of this kind used in practice an adjustment option for the electrical supplied to the mechanical transducer Provide high frequency energy.

According to the prior art, this is done, for example, in that the operating point of the active component of the one that controls the mechanical oscillator Amplifier part of the oscillator circuit forming transistor by change of Base direct current is changed. For example, this base direct current is from Emitter current supplied by another transistor whose collector is constant Potential is, and its base potential in the normal operating state with the help a tension adjuster that can be changed by a manually adjustable potentiometer can be set to different values.

However, this known device has the disadvantage that the Working point of the amplifier transistor and thus that of the mechanical oscillator supplied high-frequency power or the ultrasonic power emitted by the transducer not only from the position of the potentiometer but also from a number of disturbance variables, such as the operating temperature of the device depends, so that a unique and stable adjustment of the suspension per unit of time Amount of liquid is not possible.

Furthermore, the operation of such aerosol generators results a problem in that it generally consists of a barium titanate crystal mechanical oscillator, which with one of its faces part of the wall of the The liquid contained in the liquid to be atomized forms through this liquid is cooled and very strongly steamed. This has the consequence that in so-called wet operation a significantly higher high-frequency power to generate a certain oscillation amplitude must be supplied than this without this liquid damping, i.e. in dry operation would be required. The mechanical transducer now runs after a certain period of operation dry because the amount of liquid covering it is completely atomized has been, the damping previously exerted by this liquid is no longer applicable, which without further measures would result in a destruction of the then with a much larger one amplitude working oscillator.

So that the operating personnel do not have to constantly use such an aerosol generator Must monitor the transducer from self-harm or self-destruction To preserve, it is already known to provide a protective device that has a to prevent such damage or destruction of the transducer when running dry. According to the prior art, such a protection device comprises one in which the Container containing liquid to be atomized during the atomization process arranged float, which then, when the container runs empty, on its bottom sinks and thereby closes an electrical switch through which the base of the above-mentioned second transistor to a potential that blocks this transistor is placed. This gives the transistor the one that controls the mechanical oscillator Amplifier part of the oscillator circuit - no more base current and the supply of High frequency energy to the mechanical transducer is interrupted.

In practice it has been shown that this is very simple in principle Arrangement has only a low reliability, so that the z-order closing of the Shut-off switch serving floats very often not used and instead an operator is entrusted with the constant monitoring of the aerosol generator will.

In contrast, the invention is based on the object of an ultrasonic generator of the type described above with the least possible technical effort so that a reliable automatic protection of the transducer against Self-destruction in case of dry running is guaranteed.

To solve this problem, the invention provides that the Tlochfrequenzsitjnal in wet operation on each set power stabilizing Circuit arrangement is provided and that the protective device for the oscillator one of the changes caused by the transition between wet and dry operation Detector circuit recognizing at least one electrical parameter in the oscillating system includes.

This inventive arrangement is based on the consideration that through the stabilization of the mechanical transducer applied in wet operation High-frequency power also other electrical quantities occurring in the oscillating system, such as high-frequency currents and high-frequency voltages, the direct current consumption of the Oscillator circuit, etc. are stabilized and that it is due to the resultant Elimination of the devices corresponding to the state of the art during the Drift and disruptive effects that occur during wet operation are possible with dry running of the oscillator associated changes in one or more of these electrical quantities can be recognized with great reliability and signals from this in an unambiguous manner to win, with the help of which more in good time to protect the transducer from the In dry operation there is a risk of self-destructive measures automatically initiated or

can be carried out.

At the same time there is the further advantage that the stabilizing the high-frequency signal in wet operation to the power set in each case Circuit arrangement a very good constancy even over longer periods of operation the emitted ultrasonic power and thus the nebulized or atomized amount of liquid, i.e. the moisture content of the patient supplied breathing air is guaranteed.

It should be remembered that there are basically two types of oscillator circuits are applicable to the ultrasonic generators in question, namely both self-excited as well as externally controlled oscillators.

In the first case, the transducer which emits the ultrasonic power forms at the same time the frequency-determining element, i.e. it is with one the attenuation losses compensating amplifier, which at the same time practically the entire oscillator circuit forms, interconnected to form a feedback, self-oscillating circle. in the In the second case, there is no feedback between the mechanical oscillator and the the amplifier driving it, which instead has its own radio frequency-wise frequency-determining component, for example an oscillating circuit comprising an oscillating crystal is controlled.

What both types of oscillator circuits have in common, however, is that they an amplifier part which controls the transducer emitting the ultrasonic power have the high-frequency power delivered to the transducer due to its operating state Are defined. The thought of stabilizing and recognizing precisely this performance suitable for the transition between wet and dry operation, changing accordingly electrical quantities within the oscillator circuit and in particular within Monitoring and evaluating your amplifier section is therefore essential in both cases equally applicable. In this sense it is to be understood if only in the following generally from the oscillator circuit or the mechanical oscillator directly driving amplifier part of the oscillator circuit is spoken without referring to a special circuit structure to go into detail.

The high frequency power supplied to the mechanical transducer can varies in different ways and therefore also very different due to the influence electrical parameters be stabilized. This is how it is, for example possible to send a pulse-shaped modulated high-frequency signal to the mechanical transducer to apply, i.e. a sinusoidal signal, for example, the amplitude of which has a predetermined Repetition frequency alternates between a fixed maximum value and the value zero, where the repetition frequency is higher than the high frequency of the sinusoidal signal. In this This can change the high-frequency power applied to the transducer be that one varies the duty cycle of the modulation pulses. According to the invention is preferably provided for such a case that the stabilization of the Set power serving circuit arrangement via an actuator the Pulse-pause ratio of the oscillator circuit in the wet mode influencing controller includes.

Another way to vary the amount on the mechanical transducer emitted high-frequency power consists in the fact that although it is uninterrupted High-frequency signal is present, the amplitude of which, however, can be changed.

Looks for this case particularly preferred because of its simplicity the invention proposes that the stabilization of the set power is used Circuit arrangement a via an actuator the amplitude of the mechanical Vibrator applied electrical high-frequency signal in wet operation influencing Includes regulator.

The two alternatives just mentioned have in common the idea to stabilize the high-frequency power delivered to the mechanical transducer and thus the ultrasonic power available for aerosol generation Use a control loop that is independent of the nature of the disturbance variables that occur ensures the required constancy of the controlled variable, in this case the output power.

In both cases it is advisable to give the controller the am High-frequency voltage applied to the oscillator via a first rectifier circuit and to supply a manually adjustable stabilized DC voltage as a setpoint. In this way, the controller can easily make the required setpoint / actual value comparison Way by putting two DC voltages in relation to each other sets, one of which is used to set the desired setting in the respective application Power level can be changed by hand and the other of which can be changed by one with Rectifier arrangement that can be realized with little circuitry effort an electrical one that is clearly related to the controlled variable Parameter, namely the amplitude of the high-frequency voltage drop across the transducer is derived. This direct linkage of the controlled variable and \ ii actual value extraction signal used a particularly good control accuracy achieve.

The change in amplitude required to change the high frequency power the high-frequency oscillation applied to the oscillator by the oscillator circuit can be made particularly easy by changing the DC supply voltage of the Achieve oscillator circuit or the amplifier part. Therefore, preferably as Actuator is the supply voltage of the amplifier part which controls the oscillator the oscillator circuit changing circuit arrangement is provided.

For all those cases where at least the amplifier part of the oscillator circuit is supplied with a higher DC voltage than the rest of the electronics, is advantageous provided that the the supply voltage of the amplifier part of the oscillator circuit changing circuit arrangement between the amplifier part and the negative Supply voltage connection is switched. As a result, this circuit arrangement can namely operated at the same supply voltage level as the previous circuit parts, and it avoids the circuit complexity that would be required to work with the one output by the wet operation controller that is connected to the low supply voltage Signal on directly to the high maximum supply voltage of the amplifier section to operate the actuator connected to the oscillator circuit.

It follows in connection with this that the amplifier part of the Oscillator circuit comprises a transistor as an active component, on its collector-emitter path the supply voltage is applied and its base connected to the positive pole of the supply voltage is connected, the further advantage that a automatic adaptation of the base current required for this transistor is achieved will. This base current must be large if there is a large supply voltage on the amplifier section is applied and the transistor is working at full power, and can become smaller, if to reduce the output high frequency power on the amplifier part effective supply voltage is reduced by the fact that the actuator The emitter potential of the transistor is increased, which is because of the constant Collector potential does not just reduce the collector-emitter voltage but also a reduction in the size of the base current defining (base-emitter voltage has the consequence.

Preferably there is the supply voltage of the oscillator circuit changing circuit arrangement of two in the manner of a Darlington pair with each other connected transistors, one of which with its emitter-collector path in the one leading from the oscillator circuit to the negative pole of the supply voltage management lies. Thus it can be that mall this transistor drives more into the conductive or more into the blocked state, the one falling off of it Part of the supply voltage and thus also that for the oscillator circuit or the remainder of their amplifier part can vary within a wide range.

As already mentioned, an essential idea of the invention consists in the mechanical oscillator does not run dry as in the prior art a monitoring of the liquid level in the container in question but through it to recognize that changes occur with the transition between wet and dry operation suitable electrical quantities in the oscillation system, i.e. either on the transducer itself or in the oscillator circuit driving it by a detector device recorded and evaluated in the right way.

Regarding the selection and the way of monitoring these There are various possibilities for electrical quantities. In the simplest case it can E.g. only a single electrical parameter can be examined, whereby it is either be a direct current or direct voltage value or a high frequency signal can. In the latter case there is the alternative, either the amplitude or else the phase position of the signal in relation to the oscillator running dry to investigate any changes that occur.

Despite the slightly larger circuitry effort, it according to the invention to obtain absolutely unified and reliable criteria vorzuyt that the detector circuit to detect the relative changes of two different ones, tapped on the oscillating system High frequency signals is trained. For example, the Hoctl frequency voltage applied to the transducer is used for this purpose and the high frequency current flowing into the transducer or alternatively one in the Oscillator circuit falling high frequency voltage and a in the oscillator circuit flowing high frequency current suitable. However, a mixed form in the is preferred Way used that the detector circuit a dropping at the oscillator high-frequency voltage and a high frequency current flowing in the amplifier part of the oscillator circuit reproducing signal are supplied, which in practice is particularly has proven beneficial if one of the signals fed to the detector circuit the hole frequency emitter current flowing into the transistor of the amplifier part of the oscillator circuit reproduces.

Since in all these cases it is a matter of comparing two high-frequency signals acts, there is also the alternative here, either shifting the relative Phase position or relative changes in amplitude of these two signals as a characteristic for the mechanical oscillator to run dry. The amplitude comparison becomes particularly simple if the detector circuit consists of a DC voltage comparator consists, to which the two selected high-frequency signals each via a rectifier circuit are supplied.

As already explained in detail, the wet operation controller receives its actual value information in that it receives the high-frequency voltage applied to the transducer is fed through a rectifier. A particularly simple formwork structure thus results from the fact that this rectifier scarf. tuny with that of the equal-voltage comparator the rectifier circuit upstream of the detector circuit is identical.

Thus, in this embodiment, the inventive Device supplied to the detector circuit two DC voltage signals, of which one is the amplitude of the high-frequency voltage dropping across the mechanical oscillator and the other the amplitude of the transistor driving the oscillator into the emitter represents the current flowing in the amplifier part of the oscillator circuit. The relationship of these two DC voltages is an excellent criterion for whether the transducer is dampened by a sufficient amount of liquid or when it is dry State swings. It is of particular importance that this criterion is a provides a clear statement regardless of the high-frequency power with which the Oscillator is controlled. It is therefore possible by specifying a corresponding setpoint value for the wet operation controller the high frequency power applied to the mechanical transducer and thus also the ultrasonic power it emits within wide limits to vary without thereby affecting the informative value of the output of the DC voltage comparator the signal appearing on the detector circuit would be adversely affected. By simple circuit-related measures, the DC voltage comparator can now be designed in such a way that that the signal appearing at its output is independent of that to the transducer output och frequency power in digital manner from a first to a second Value changes when the input of the DC voltage comparator Signals through their relative change the transition from wet operation to dry operation show and vice versa. This switching of the output signal of the thus simultaneously Further measures can then also be initiated as a comparator designed as a control stage which serve to prevent the transducer from self-destruct in dry operation to preserve. As an alternative to this, the comparator and control stage can also be mutually exclusive be set up separately.

It has already been stated that because of the to be nebulized Liquid damping of the oscillator this during wet operation In general, a high-frequency power must be supplied to it when it is no longer available excessive damping, damage or destruction of the transducer would excite leading vibration amplitudes. Because the amount of this high frequency power is specified by the setpoint specification for the wet operation controller and this controller tries to keep their value constant, the invention provides that between the wet mode controller and the actuator a controlled by the control stage, closed when the first value occurs and more closed when the second value occurs open switch is switched, after opening this switch for this it is ensured that the actuator is controlled in such a way that it affects the transducer applied high-frequency power in a manner that eliminates the risk of destruction changes.

This control of the actuator can take place in various ways. It is thus possible to completely interrupt the supply of high-frequency power to the transducer, by, for example, the supply voltage of the oscillator circuit so far reduces that it stops vibrating. However, this also has the consequence that the criterion with the help of which the oscillator is running dry is no longer applicable became. In order not to become an unstable here; Switching back and forth between one vibrational state emitted high high frequency power and a non-vibratory state to come, it must be ensured that the actuator after the connection switch has been opened to the wet operation regulator, with certainty in which the hole frequency power supply is held to the vibrator-inhibiting state.

However, this would mean, firstly, that the aerosol generator is not easy can thereby be returned to the normal operating state that one adds new liquid to the transducer by replenishing it, and secondly, the danger there is that the device is due to some short-term interference voltage switches off automatically and remains in this switched-off state, although the Transducer did not run dry.

In order to avoid such reliability risks, a particularly preferred embodiment of the ultrasonic generator according to the invention a second regulator is provided, the output of which is also via a control stage controlled, opened when the first value occurs and when the second value closed switch is connected to the actuator and the Actuator controls so that the amplitude of the applied to the mechanical oscillator High frequency signal at a low level, excluding damage to the transducer Value is held.

The basic idea of this variant is the mechanical transducer not simply shut down in the event of dry running detected by the detector circuit, but to let it continue to oscillate at a performance level that of the reduced Damping is adapted so that there is no damage or destruction of the oscillator can come. This has the advantage that even after switching to dry mode the detector circuit still has the correct information available about it indicates whether the transducer is damped or not. Because of this still existing Information is not required to switch in the above-mentioned manner make self-blocking, so that it is enough to simply put in the aerosol generator again to refill liquid to get from the reduced again return to full vibration power. In addition, the circuit can then, if it "accidentally" switched from wet to dry mode due to an interfering signal has, automatically and without any risks, to full output again return as soon as the interfering signal disappears.

For the second controller, the actual value is preferably that of the one with the actuator connected supply voltage input of the amplifier part of the oscillator circuit existing DC voltage and an adjustable partial amount of the an DC voltage present on the other supply voltage input of the amplifier section fed. This circuit-wise very simple measures is practically the DC supply voltage of the amplifier part of the oscillator circuit as a controlled variable is used and kept at a predetermined low value by the controller. Because the amount of high-frequency power delivered by the amplifier section to the transducer is clearly related to this supply voltage, this leads to the desired result, especially since a much lower control accuracy in dry operation than is necessary in wet operation.

In order to avoid it in the short period during which the Detector switching from wet to dry operation or from dry to wet operation switches to undefined ones, conjuring up a tendency to oscillate in the entire circuit Conditions comes, is preferably one of the actuator during the switching process provided with a defined input signal supplying circuit arrangement.

In the case of the ultrasonic generators under discussion here, there is Possibility of suspension of the oscillator oscillations due to some defect comes. Would such an error occurs during wet operation, the controller in question would initially simply determine that the actual value of the The amplitude of the high-frequency voltage applied to the mechanical oscillator is not the same corresponds to the specified setpoint value and would try to use the DC supply voltage of the amplifier part of the oscillator circuit to increase here again to one Compensation to arrive. But since the oscillator circuit no longer oscillates, would these control attempts remain unsuccessful and damage or loss could result. Destruction of the transistors of the actuator and / or the one supplying the amplifier part Power supply come.

To avoid this, in a preferred embodiment the two rectifier circuits connected upstream of the DC voltage comparator operated with such different biases that if the High-frequency signals the DC voltage comparator receives input signals that are a Dry operation. So, for some reason, the Oscillator from, then both the high-frequency voltage applied to it and the high-frequency current flowing into the emitter of the amplifier transistor.

This gives the two associated rectifier circuits due the specially selected bias voltages from signals that run dry in the detector circuit simulate the transducer. This switches the detector circuit of the wet mode controller to the dry mode controller, and since the latter does not change its actual value from one High-frequency signal, but rather from the one prevailing between the actuator and the amplifier part Discharge direct voltage potential is the above-mentioned risk of damage or destruction banned.

The circuit according to the invention can be particularly advantageously shown in Use in connection with crystal oscillators, as with these the (efa1ir a self-destructive caused by running dry <j} rfXs) nders {3ruß is.

The invention is illustrated below using an exemplary embodiment described with reference to the drawing; in this shows: Fig. 1 a schematic Block diagram of an ultrasonic generator according to the invention, FIG. 2 a detailed illustration Circuit diagram of an embodiment constructed according to the diagram in FIG. 1, FIG. 3 one of the input characteristics of the DC voltage comparator of the detector circuit reproducing graphical representation and FIG. 4 with dimensioning information Circuit diagram of a particularly preferred high-frequency part provided for the components used of the ultrasonic generator according to the invention.

According to FIG. 1, an ultrasonic generator according to the invention comprises a Oscillating system 10, which in the present case consists of a crystal oscillator shown mechanical oscillator 11 and an oscillator circuit 12 is made with the mechanical oscillator interconnected to form a self-oscillating series resonance circuit is. The oscillator circuit 12 is supplied with direct current via the lines 14 and 15, the line 14 being connected directly to a, for example, positive supply voltage V1 connected. is, while the line 15 via an actuator 17 to the system ground connected is. The throttle 16 is shown here only symbolically, to indicate that action is being taken to keep line 15 in the area the oscillator circuit 12 does not flow high-frequency currents to the actuator 17 and the line 18 branched off between the throttle 16 and the actuator 17 arrive.

The from the oscillator circuit 12 to the mechanical oscillator 11 applied high frequency voltage is through a rectifier 20th rectified and fed to a detector circuit 23, which is also from the rectifier 21 a, the amplitude of the high frequency flowing into the oscillator circuit 12 Receives the signal representing the amplifier. The detector circuit 23 includes one Comparator, not shown in FIG. 1, which the rectifiers 20 and 21 compares the output signals with each other and if their relative Size changes, via a control stage also not shown in FIG. 1 emits suddenly changing signal, with the help of which the two switches 30 and 31 can be operated. Furthermore, the output signal of the rectifier 20 is fed to the actual value input of a controller 25, which has a stabilized by a circuit arrangement shown symbolically as a potentiometer 28 and receives manually adjustable DC voltage as a target value.

As shown in Fig. 1 by the double arrow A, the Switches 30 and 31, which of course also take the form of electronic switches can be, bring from the position shown in a position in which the switch 31 is open and the switch 30 is closed.

The output of the controller 25 is then in this state with the input of the actuator 17 connected, which is controlled by him so that it is through a corresponding change of the falling at the amplifier part of the oscillator circuit 12 Supply voltage possibly occurring changes of this amplifier unit The floch frequency power output to the mechanical oscillator 11 just counteracts it. The oscillation system 10, the controller 25 and the actuator 17 thus form one through the switch 30 closes or separable first control loop, with the help of which in so-called wet operation, i.e. when the mechanical oscillator 11 is from a covered with a sufficient amount of liquid and thus strongly damped is the high frequency delivered to the oscillator 11 power and thus also the one available for the generation of a liquid mist Ultrasonic power on the by the manually adjustable circuit arrangement 28 predetermined value is maintained.

In addition, a second control circuit is provided that controls the oscillating arrangement 10, the controller 26 and the actuator 17 and closed by the switch 31 or can be opened. This second control circuit is used in so-called dry operation, that is, when the mechanical oscillator 11 is no longer being sputtered by a Liquid is damped in its oscillation amplitude, which is supplied to the oscillator High frequency performance on a non-dangerous, self-harm with certainty to keep the exclusive lower value. For this purpose, the controller 26 ats Actual value between the actuator 17 and the associated supply voltage input the oscillator circuit 12 present DC voltage potentiometer as a target value adjustable by a circuit arrangement 29 shown symbolically as a potentiometer Fraction of the supply voltage V1 supplied. This fraction is chosen so that the corresponding DC voltage drop across the oscillator circuit 12 and the high-frequency power thus coupled to the oscillator 11 is sufficient are small, so that the transducer does not have to be operated on for a longer period of time in dry conditions Exposure to risk of damage.

If the entire arrangement works in wet mode, it is the oscillator 11 damped in its oscillation amplitude by a sufficient amount of liquid, so this detects the detector circuit 23 based on you via the rectifier 20 and 21 supplied signals, on the basis of which it keeps the switch 30 closed, so that the controller 25 is connected to the actuator 17. The mechanical one is now running Schwinger 11 dry, then the one adjacent to it changes first High-frequency voltage and thus also the signal emitted by the rectifier 20 not, since the controller 25 ensures that these values are constant. Due to the However, the attenuation in line 15 of the oscillator circuit, which eliminates the need for dry running, decreases 12 flowing high-frequency current from strong, so that the output from the rectifier 21 Gieichspannungssignai its value compared to that output by the rectifier 20 Signal changes very much. This change is recognized by the detector circuit 23, which then changes the value or the amplitude of its output signal abruptly, whereby the switch 30 is opened and the switch 31 is closed. Simultaneously wirl a display device connected to the output of the detector circuit 23 35 activated, for example by an optical or acoustic signal Operator provides an indication that the aerosol generator is not liquid contains more.

By closing the switch 31, the second described above occurs Control loop in action and protects the mechanical Schwinyer 11 from damage. The circuit arrangement 33 is also connected to the input of the actuator 17, which is used during the switching of the switches 30 and 31 at the input of the actuator a defined voltage and thus overall a defined state of the overall system maintain.

The embodiment of an ultrasonic generator according to the invention, the detailed circuit diagram of which is shown in FIG. 2 has the same principle Structure as described in connection with FIG. 1. The corresponding Circuit units are each summarized by dashed lines and with The same reference numerals are provided as were also used in FIG. 1.

Here, too, the oscillating arrangement 10 consists of a crystal oscillator 11, and an oscillator circuit driving it 1 2.

The oscillator circuit comprises an active amplifier component Transistor 40, which with its collector-emitter path on the DC supply voltage lies and with its collector via the capacitor 41 and with its base directly to the mechanical oscillator 11 and a parallel connected thereto Resistor 42 is connected. This arrangement forms a self-oscillating oscillator circuit in series resonance, the DC voltage termination of the emitter of the transistor 40 on the one hand via a capacitor 47 to the base of the transistor and on the other hand is connected via a capacitor 48 to the collector of this transistor. In the collector line of the transistor 40, a choke 45 is arranged, which for this purpose serves to prevent a short circuit of the high frequency voltage across the power supply. To keep the positive supply voltage connection V1 free of high frequency, a capacitor 46 is connected between it and the system ground.

The decoupling of the transistor 40 to the mechanical oscillator 11 applied high-frequency voltage takes place via a capacitor 49, which this Signal to the input voltage divider consisting of two resistors 57 and 58 the rectifier circuit 20 passes on a diode serving as a rectifier 56 and a charging capacitor 71 comprises.

The primary winding 38 is in the emitter line of the transistor 40 a transformer used to decouple the high-frequency current flowing here 37 qelegt, the secondary winding 39 of which with the two ends of the Einyangswiderstandes 61 dr second rectifier circuit 21 verist, tied one as a rectifier serving diode 60 and a charging capacitor 112, wherein the The anode of the diode 60 with one connection of the resistor 61 and its cathode connected to the other terminal of the resistor 61 via a resistor 62 is.

The circuit arrangement that has been added compared to the block diagram from FIG. 1 22 comprises a consisting of the resistors 67, 68 and 69 voltage divider, the one end to the system ground and the other end to a DC voltage which is branched off from the supply voltage V1 (e.g. 45 V) and replaced by a Zener diode 65 and its current limiting resistor 66 is stabilized. The one at the connection point higher DC voltage that can be tapped off between resistors 67 and 68 of the voltage divider (e.g. 0.55 V) is the cathode of the rectifier diode 56 via a resistor 59 fed to the rectifier circuit 20, while the one between the resistors 68 and 69 tappable lower DC voltage (e.g. 0.48 V) at the connection point of the resistors 61 and 62 of the rectifier circuit 21 is applied. This will be the rectifier circuits 20 and 21 operated with different bias voltages, which then if for some reason the them from the oscillator circuit 12 supplied high frequency signals fail, at their outputs DC voltage level apply that simulate dry operation of the aerosol generator according to the invention.

The output from the diode 56 of the rectifier circuit 20, for High-frequency voltage on the mechanical oscillator 11 proportional DC voltage signal arrives via a differential amplifier 70 connected as an impedance converter, its Signal input is connected to the system ground via the charging capacitor 71, on the one hand to the detector circuit 23 and on the other hand to the anode of a decoupling diode 75 of the wet operation controller 25, the cathode of which has a series resistor 76 is connected to the inverting input of a differential amplifier 77. Of the non-inverting input of this differential amplifier 77 is variable with a Resistor 85 connected to a fixed resistor 86 to build a voltage divider is connected in series, one end of which with the system ground and the other End is connected to a DC voltage from a second supply voltage V2 (e.g. 24 V) and derived through eilJu Zener diode 83 and its current limiting resistor 84 is stabilized. With the help of this voltage divider circuit 28, the target value changed for the controller 25 and thus the output from the mechanical oscillator 11 Ultrasonic power in wet operation can be set to a desired value.

The output of differential amplifier 77 is in the usual manner via a capacitor 81 and a resistor 80 connected in series therewith the inverting input, which is also connected via a resistor 78 is connected to the system ground.

The second, attached to the mechanical transducer 11 in dry mode Output high-frequency power stabilizing regulator 26 consists essentially from a differential amplifier 96, whose non-inverting input has a consisting of the resistors 90, 91 and 92 voltage divider on the negative Supply voltage input of the oscillator circuit 12 present DC voltage is supplied as an actual value, with the between the connection point of the resistors 90 and 91 and the system ground switched capacitor 93 for filtering out any still existing high frequency components is used.

The inverting input of the differential amplifier 96 is on the one hand with its output via the usual negative feedback, opposed 94 and one with it connected in series capacitor 95 and on the other hand to the center point a voltage divider composed of resistors 105 and 106 is placed, the one end to the system ground and the other end to the cable contact . a variable resistor 104 is connected, which in turn with the Resistor 103 forms a voltage divider, one end of which is connected to the supply voltage V1 and at its other end to one through a Zener diode 101 and its with current limiting resistor 102 connected to its other end to system ground defined DC voltage.

The voltage divider arrangement formed from the components 101 to 106 is used to specify a setpoint value for the controller 26, which is an adjustable fraction that is present at the positive supply voltage input of the oscillator circuit 12 Represents DC voltage V1.

As already mentioned, the output from the rectifier 20 and signal not only amplified in its power by the differential amplifier 70 to the wet operation controller 25, but also to one input of the detector circuit 23. Here it is first the upper end of one of the series resistors 113 and 114 existing voltage divider supplied to the lower end with connected to the system ground. The resistor 113 is designed as a potentiometer, whose tap is connected to the anode of a diode 115, the cathode of which is connected to the Connection point of two resistors 118 and 119 connected in series is. The other end of the resistor 118 is connected to the center of one of the Series resistors 116 and 117 formed voltage divider connected between the lower supply voltage V2 and the system ground. The second ending of resistor 119, however, is connected to the non-inverting input one Comparator 110 connected. The inverting input of this comparator 110 is Via a resistor 111, the high-frequency current flowing in the emitter of transistor 40 is connected to the high-frequency current proportional output signal of the rectifier circuit 21 supplied by the charging capacitor 112 is freed from high-frequency components that are still present.

The one previously described, the non-inverting input of the comparator 110 upstream diode-resistor network serves to ensure the almost linear course the characteristic of the voltage rectifier by suppressing the small voltages to arerzerren in the starting area of the rectifier characteristic so that it follows the course corresponds to the significantly more non-linear characteristic of the current rectifier. This is used in particular for the input lines of the comparator 110 approximately the course reproduced in FIG. 3 and explained in more detail below achieve.

The output of the comparator 110 is direct current via the resistor 120 fed back to the non-inverting input so that there is a hysteresis its switching function results.

This means that if the rectified current is proportional Voltage Vi is greater than the rectified high frequency voltage Vu, the output voltage of the comparator 110 is approximately 0 volts, and when the rectified Current proportional voltage Vi smaller than the rectified high frequency voltage Vu becomes abrupt, which corresponds to the mechanical oscillator running dry increases to about +24 volts and vice versa.

These two levels of the output signal emitted by the comparator 110 are chosen so that in the one case (0 volts = wet operation) the diode 79 of the controller 25 is blocked so that this controller works and with its output signal over the decoupling diode 128 and the still to be described circuit 33 to the input of the actuator 17 acts so that this acts on the mechanical oscillator 11 delivered high-frequency power on one of the voltage divider circuit 28 holds the corresponding value specified. On the other hand, the In this operating state, regulator 26 is rendered inoperative by diode 97. in the other case (output voltage of the comparator 110 approximately +24 volts = dry operation) the controller 25 is blocked via the diode 79 and put out of operation while the controller 26 is switched on via the diode 97 and now in turn via the Decoupling diode 127 and the circuit 33 acts on the actuator 17 so that this the dropping at the oscillator circuit 12 supply voltage and thus also the output from the oscillator circuit to the mechanical oscillator 11 Radio frequency power limited to a low, safe level.

The two diodes 79 and 97 take over here in connection with the polarities of the inputs of the differential amplifiers 77 controlled by them and 96 and the associated resistors 78 and 92, the function of that shown in FIG. 1 separately shown switches 30 and 31. The embodiment of FIG. 2 thus provides an example of how these switches can be designed as electronic switches can. However, since they are included here to a very large extent in controllers 25 and 26 are, it did not make sense to represent them irl of FIG. 2 as a separate assembly.

The voltage prevailing at the output of the comparator 110 also serves in addition, the base of a driver transistor via the voltage divider 123, 124 122, which is directly connected to the system ground with its emitter and a lamp 125 is connected in the collector line. This display device 35 is used to indicate to the operator when the detector circuit 23 is on Dry running of the mechanical oscillator detected and by the wet operation controller 25 has switched to the dry mode controller 26.

During this switching, it could happen that the oscillator 12 for stops oscillating for a few milliseconds, which then also causes the detector circuit 23 examined criterion would be omitted; thus the entire circuit could be in get into an undefined state. To avoid this, is between the connection point the decoupling diodes 127 and 128 and the input of the actuator 17 a circuit arrangement 33, which essentially consists of two series-connected resistors 130 and 131, one leading from the connection point of these resistors to the system ground Resistor 132 and a series circuit arranged in parallel with this resistor 132 consists of a resistor 133 and a capacitor 134. This capacitor 134 serves as a charging capacitor, which ensures that the transition of the control of the Actuator 17 from the wet operation controller 25 to the dry operation controller 26 is not abrupt but takes place smoothly. As a result, it can no longer be an even if only briefly The oscillator vibrations are suspended.

Finally, the actuator 17 comprises one of the transistors 152 and 153 formed Darlington configuration, with transistor 152 in the DC power supply line of Oszialltors 12 is arranged. It gets its base current from one of the resistors 154 and 155 formed voltage divider, which the emitter resistance of a transistor 153 forms, which is connected to the lower supply voltage V2 with its collector and receives the signals coming from the circuit arrangement 33 at its base.

As already explained in detail, these signals come from one the two controllers 25 and 26 and cause that depending on whether to enlarge or reduction of the high-frequency power delivered to the mechanical oscillator 11 the operating voltage dropping across transistor 40 of oscillator circuit 12 is increased or is to be reduced in size, the transistor 152 further into the conductive or further is controlled in the locked state, which has the consequence that a smaller or a larger part of the total supply voltage available V1 drops.

In this context it should be pointed out again that the mentioned enlargement, 1Vzw. Reduction of the output to the mechanical oscillator Radio frequency power may be required for three fundamentally different reasons can, namely either because a switchover from the dry mode controller 26 to the Wet operation controller 25 or vice versa has taken place, or because the setpoint specification for the ultrasonic power to be emitted by the mechanical transducer by adjusting of the manually operable potentiometer 85 has occurred, or because an incipient, tendency to decrease or increase the high frequency due to interference performance should be counteracted.

In Fig. 3 are in the form of a diagram at the two inputs of the DC voltage comparator 110 of the detector circuit 23 applied voltages Vi and Vu plotted against each other. As already mentioned, this is what it is to DC voltages, which are clearly related to that in the Emitterlaietsuiansistors 40 flowing high-frequency current or with that on the mechanical oscillator 11 can be tapped High frequency voltage.

As to adapt the ultrasonic power emitted by the mechanical oscillator 11 to the various applications, the high-frequency voltage dropping across the transducer 11 can be set to various values using potentiometer 85 can, in the diagram of FIG. 3 is the one proportional to this high-frequency voltage DC voltage V plotted on the abscissa. It can be seen that for every value of Vu belongs to two different values of Vi, the two clearly different from each other High-frequency emitter currents of the transistor 40 correspond. The bigger of the two Values are obtained when the mechanical oscillator 11 has sufficient Amount of liquid to be nebulized is steamed, while the smaller of the two Vi values corresponds to an undamped mechanical oscillator. So you get the two characteristic curves shown in Fig. 3, of which the upper is the wet operation and the lower corresponds to the dry operation of the aerosol generator according to the invention. It is assumed that the two inputs of the DC voltage comparator 110 are the same Have sensitivity, then the switching threshold runs when you look for the the same scale is used for both coordinate axes, in the manner shown at an angle of 450.

The shape of the wet and dry characteristics shown in the diagram is based in particular on the effect of the non-inverting input of the differential amplifier 110 upstream diode-resistor network 113 to 119 and the different Bias voltages of rectifiers 20 and 21. This network is designed so that one of the two characteristic curves completely above and the other completely below the switching threshold lies, as this is the only way to have a unique value for each set value of Vu Operating state for the entire circuit can be achieved. Would be one of the characteristics cross the switching threshold shown in dashed lines or both characteristics on the same side of the switching threshold, the device could be completely random Way and regardless of whether the mechanical vibrator of liquid is covered or not, jump back and forth between the two characteristic curves, whereby not only is a reasonable operation no longer guaranteed, but also a risk of destruction for the Schwinger would be given.

It is possible, by appropriately dimensioning the diode resistor network 113 to 119 show the idealized linear characteristic curve shown in FIG. 3 to achieve, but this is not absolutely necessary.

The works even with kinked or wavy characteristics The arrangement is flawless as long as there is no overlapping of the characteristic curves or comes with the switching threshold.

In practice an attempt will be made to keep the characteristic curves in their lower Range as close as possible to the zero point in order to also use these low power ranges to be able to exploit. However, there are certain limits here, in particular then, if you only use the rectifiers 20 and 21 shown in Fig. 2, wants to drive low circuit complexity, the DC voltages V. and V has a noise component superimposed on it, which is 1 u if the characteristics are too close to the switching threshold would lead to the circuit in an undefined manner changes from one characteristic to the other.

This noise is much stronger in wet operation than in dry operation, because here individual droplets from the mist generated by the oscillator 11 are back in the liquid fall back and thus a kind of "microphone effect" creates an interfering signal that cannot occur in dry operation.

The circuit diagram shown in FIG. 4 is a particularly preferred one Embodiment of the high frequency part of an ultrasonic generator according to the invention it can be seen that the oscillator circuit 12, the rectifier circuits 20 and 21 and the bias generating circuit 22 in a common high frequency density Housing are housed, with all lines via feed-through capacitors 51,52,53,54 and 55 are led out. The charging capacitors shown in FIG 71 and 112, the feed-through capacitors 55 and 54 are connected in parallel, so that their capacity increases accordingly.

The choke 36 shown in FIG. 4, like the capacitor 50 can be omitted if necessary.

The transformer 37 consists of a core M 33, 14 0 x 8, a coil body, a connection carrier and a bracket.

The winding 1 consists of 40 turns CuL 0.18 in two layers, while the winding 2 comprises one turn CuL 0.4, so that there is a transmission ratio 40: 1 results. The encoders 41, 47 and 48 are multilayer plastic encoders.

L e r s e i t e

Claims (30)

Ultrasonic generator claims 1. Ultrasonic generator for Generation of a liquid suspension in a gas with an oscillating system that from a mechanical oscillator atomizing the liquid and one the oscillator with a high-frequency electrical signal with variable power There is an oscillator circuit, and with one the oscillator when running dry a protective device that protects against self-damage, thus not applicable i c h n e t that the high-frequency signal in wet operation to the respectively set Power stabilizing circuit arrangement (20,25,17) is provided and that the Protective device for the transducer (11) a and dry operation related changes of at least one electrical parameter in the oscillation system (10) detecting detector circuit (23) comprises. 2. Ultrasonic generator according to claim 1, characterized in that g e k e n n -z e i c h n e t that the circuit arrangement used to stabilize the set power one via an actuator the pulse-pause ratio one in pulse mode a High-frequency signal of constant amplitude emitting oscillator circuit in wet operation influencing controller includes. 3. Ultrasonic generator according to claim 1, characterized in that g e -k e n n z e i c h n e t that the circuit arrangement used to stabilize the set power Via an actuator (17) the amplitude of the to the mechanical oscillator (11) applied electrical high-frequency signal in wet operation influencing controller (25) includes. 4. Ultrasonic generator according to claim 2 or 3, characterized g e k e n N z e i c h n e t that the wet operation controller (25) as the actual value that on the transducer (11) applied high-frequency voltage via a first rectifier circuit (20) is fed. 5. Ultrasonic generator according to claim 4, characterized g e -k e n n z e i c h n e t that the wet operation controller (25) for power setting as a target value a stabilized DC voltage adjustable by fIand is supplied. 6. Ultrasonic generator according to one of claims 3 to 5, characterized g e k e n n n z e i c h ne t that as the actuator (17) one is the supply voltage of the amplifier part of the oscillator circuit (12) which controls the oscillator (11) changing circuit arrangement is provided. 7. tjltraschaliqenerator according to claim 6, characterized g e -k e n nz e i c h n e t that the the supply voltage of the amplifier part of the oscillator circuit (12) changing circuitry between the Amplifier part and the negative supply is connected. 8. Ultrasonic generator according to claim 7, characterized in that g e -k ta n n z e i c h n e t that the amplifier part of the oscillator circuit (12) is active Component comprises a transistor (40), on whose collector-emitter path the Supply voltage is applied and its base via a resistor (43,44) with the positive pole of the supply voltage is connected. 9. Ultrasonic generator according to one of claims 6 to 8, characterized gek e n n n n z e i c h n e t that the supply voltage of the oscillator circuit (12) changing circuit arrangement (17) consisting of two in the manner of a Darlington circuit interconnected transistors (152,153), one of which (152) with its emitter-collector path in the from the oscillator circuit (12) to negative pole of the line carrying the supply voltage. 10. Ultrasonic generator according to one or more of the preceding Claims, characterized in that the detector circuit (23) to detect the change in the DC current consumption of the amplifier part of the Oscillator circuit (12) is formed. 11. Ultrasonic generator according to one or more of claims 1 to 10, thereby g e k e n n n z e i c h -n e t that the detector circuit (23) for Detection of the change in the amplitude and / or phase position of an on the Schwingsysl.em (10) tapping frequency voltage formed i.st. 12. Ultrasonic generator according to one or more of claims 1 to 11, characterized in that the detector circuit (23) for detection the end of the amplitude and / or phase position of a flowing in the oscillating system (10) High frequency current is formed. 13. Ultrasonic generator according to one or more of claims 1 to 9, characterized in that the detector circuit (23) for detection the relative change of two different ones tapped on the oscillating system (10) High frequency signals is formed. 14. Ultrasonic generator according to claim 13, characterized in that g e -k e n n z e i c h n e t that the detector circuit (23) is connected to the transducer (11) High-frequency voltage and the high-frequency current flowing into the oscillator (11) reproducing signals are supplied. 15. Ultrasonic generator according to claim 13, characterized in that g e -k e n n z e i c h n e t that the detector circuit (23) is a one in the oscillator circuit (12) falling high frequency voltage and one in the oscillator circuit (12) flowing high-frequency current are fed again rotating signal. 16. Ultrasonic generator according to claim 13, characterized in that g e -k e n n z e i c h n e t that the detector circuit (23) has a falling at the oscillator (11) High frequency voltage and one in the amplifier part of the oscillator circuit (12) flowing high-frequency current reproducing signal are supplied. 17. Ultrasonic generator according to claim 16, characterized in that cj e -k e n n z e i c h n e t that one of the signals fed to the detector circuit (23) those flowing into the transistor (40) of the amplifier part of the oscillator circuit (12) Reproduces high frequency emitter current. 18. Ultrasonic generator according to one of claims 13 to 17, characterized it is noted that the detector circuit (23) one the relative Phase comparator evaluating the phase position of the high-frequency signals supplied to it includes. 19. Ultrasonic generator according to one of claims 13 to 17, characterized it is noted that the detector circuit (23) detects the amplitudes the comparator (110) comparing the high-frequency signals fed to it includes. 20. Ultrasonic generator according to claim 19, characterized in that g e -k e n n z E i c h n e t that the comparator (110) is designed as a DC voltage comparator is to which the high-frequency signals are each via a rectifier circuit (20,21) are supplied. 21. Ultrasonic generator according to claims 4 and 20, thereby g e it is not indicated that the upstream of the wet operation controller (25), the High-frequency voltage applied to the oscillator (11), rectifying rectifier circuit (20) with one of the rectifier circuits connected upstream of the DC voltage comparator (110) is identical. 22. Itrasonic generator according to one of claims 18 to 21, characterized it is noted that the protective device for the transducer (11) is a Control stage (110,120) comprises, the output signal depending on whether the Detector circuit (23) a wet operation or a dry operation of the oscillator (11) recognizes, jumps digitally from a first to a second value. 23. Ultrasonic generator according to claim 22, characterized in that g e -k e n n z e i c h n e t that between the wet operation controller (25) and the actuator (17) controlled by the control stage (110, 120), closed when the first value occurs and when the second value occurs, the open switch (30) is switched. 24. Ultrasonic generator according to claim 23, characterized in that g e -k e n n z e i c h n e t that a second controller (26) is provided, the output of which is via one also controlled by the control stage (110,120) when the first occurs Value opened and closed when the second value occurs (31) is connected to the actuator (17) and which controls the actuator so that the Amplitude of the high-frequency signal applied to the mechanical oscillator (11) kept at a low value that prevents damage to the transducer will. 25. Ultrasonic generator according to one of claims 22 to 24, characterized it is not indicated that the SMuerstuEe (110,120) is a switch from Wet to the dry mode indicating display device (35) is connected downstream. 26. Ultrasonic generator according to claim 24 or 25, characterized g e k e n n z e i c h n e t that the second controller (26) as the actual value is the one with the Actuator (17) connected to the supply voltage input of the amplifier part of the Oscillator circuit (12) existing c: current voltage and an adjustable value as a target value Partial amount of the existing at the other supply voltage input of the amplifier part DC voltage is supplied. 27. Ultrasonic generator according to one of claims 23!> Is 26, characterized it is noted that the two switches (30,31) are combined and are designed as an electronic switch. 28. Ultrasonic generator according to one of claims 24 to 27, characterized g e k e n n n n z e i c h n e t that the actuator (17) during the switching process from the wet operation controller (25) to the dry operation controller (26) with a defined Circuit arrangement (33) supplying the input signal is provided. 29. Ultrasonic generator according to one of claims 20 to 28, characterized it is noted that the two of them are connected to the DC voltage comparator (110) upstream rectifier circuits (20, 21) with such different bias voltages be operated that in the absence of high-frequency signals of the DC voltage comparator Receives input signals that correspond to dry operation. 30. Ultrasonic generator according to one of the preceding claims, in that the mechanical oscillator (11) is a crystal oscillator is.