EP4165956A1

EP4165956A1 - Method for managing a radiofrequency system for thermal treatment of dielectric and/or electrically conductive materials

Info

Publication number: EP4165956A1
Application number: EP21743243.4A
Authority: EP
Inventors: Antonio Polato; Fernando Bressan; Klaus Peter Werner
Original assignee: Officine Di Cartigliano SpA
Current assignee: Officine Di Cartigliano SpA
Priority date: 2020-06-15
Filing date: 2021-06-15
Publication date: 2023-04-19
Also published as: IT202000014209A1; WO2021255628A1

Abstract

A method for managing a radiofrequency system (1; 201; 301; 401; 501; 601; 701 ) for thermal treatment of a dielectric and/or electrically conductive material (M), said system (1; 201; 301; 401; 501; 601; 701 ) comprising at least one electric generator (10; 110; 710) adapted to generate a radiofrequency output signal at an output power and applicator means (80; 180; 680) connected to the electric generator (10; 110; 710), adapted to develop an electromagnetic field at a receiving zone (Z) of the dielectric and/or electrically conductive material (M), wherein the electric generator (10; 110; 710) in turn comprises at least one generating unit (12) of radiofrequency drive signals at a first power level, amplification means (30; 130) adapted to amplify the radiofrequency drive signals of the generating unit (12) from the first power level to the output power, the amplification means (30; 130) comprising one or more amplification stages (30a, 30b, 30c; 130a), each of which comprises at least one solid-state active electronic component (50), and control means (90) adapted to receive at least a first electrical and/or physical parameter indicative of the output power of the electric generator (10; 110; 710) during operation. In particular, the method comprises the steps of operating the radiofrequency signal generating unit (12) to generate a drive signal at a first power level according to a predetermined trend to obtain a predetermined desired trend of said output power to control the amount of power delivered in the process, acquiring and processing the at least a first parameter to identify a deviation in the output power with respect to the predetermined desired trend, and acting on at least one operating parameter of the system (1; 201; 301; 401; 501; 601; 701) through the control means (90) to obtain the predetermined desired trend of the output power.

Description

METHOD FOR MANAGING A RADIOFREQUENCY SYSTEM FOR THERMAL TREATMENT OF DIELECTRIC AND/OR ELECTRICALLY CONDUCTIVE

MATERIALS

The present invention belongs to the field of systems for the thermal treatment of materials with dielectric and/or electrical conductivity features by applying radiofrequency oscillating electromagnetic fields.

In particular, the invention relates to a method for managing said radiofrequency system for thermal treatment of dielectric and/or electrically conductive materials. The employment of radiofrequency equipment for thermal treatment of dielectric and/or electrically conductive materials is commonly known in various fields where there is a need to heat a dielectric and/or electrically conductive material. Radiofrequency equipment may be employed in heating, drying and/or dehumidifying treatments in hide production cycles, treating food products, for example in freeze-drying or pasteurization treatments, as well as in the industrial context of treating polymer substances, for example in the drying treatments of such substances.

Such substances/materials have their own dielectric and/or electrical conductivity features. For example, a dielectric and electrically conductive material of the known type consists of silver-loaded antibacterial polymers.

The known radiofrequency equipment generally comprises an electric generator capable of generating an oscillating voltage at a predetermined frequency in the field of radiofrequencies, hereinafter referred to as an RF generator for simplicity of disclosure, and a unit connected thereto by means of which the oscillating electromagnetic field is applied to the product to be treated/heated. Such a unit, commonly known as an applicator, has suitable shapes according to the nature of the product (or material) to be treated/heated.

In the basic configuration thereof, it substantially consists of two or more electrodes having suitable shape which, in a process chamber or cavity, define a treatment zone where the material to be heated is located or transits. Various types of applicator may be identified, known for example as the "stray-field" or "fringe-field" or "through-field" type, according to the spatial arrangement of the electrodes and the type of connection to the RF generator. In operation, the applicator and the material to be heated define the load for the RF generator. Radiofrequency systems belonging to the prior art essentially are divided into two categories: free-running oscillators (FROs) and 50-ohm technology.

The FRO systems are made by employing an industrial triode in a circuit operating as oscillator and operating under class C conditions. The circuit may be, for example, a Hartley oscillator circuit, known as "tuned anode" circuit, or a "tuned grid" circuit, or again, variants of such circuits.

The radiofrequency systems which use the 50-ohm technology instead implement a vacuum tube/valve technology originating from the communications industry. It is important to combine the impedance levels of the applicator to the 50 ohm required by the generator for this technology. Generally, a so-called matching box (impedance adapter) is introduced between the RF generator and the applicator to obtain this.

Therefore, the technology of the known type frequently provides the RF generator generating RF power by means of vacuum valves in oscillator mode - generally triodes - which are used in a high voltage resonant circuit.

Therefore, the RF power generated by the RF generator is transmitted to the applicator for treating the dielectric and/or electrically conductive material.

Flowever, the known techniques relative to generating RF power have certain recognized limitations and drawbacks.

A first drawback of the known art is associated with the need to use high voltages for the regular operation thereof, in particular in both the generator and the applicator, in order to generate electromagnetic fields with increased intensity in the material to be treated.

Additionally, the known art is inclined to create harmonic components (radio disturbances) when generating high frequency power which are difficult to be shielded.

The results are a difficulty in punctually determining the physical process parameters in real time during the treatment: increased voltages coupled with increased frequencies generate a high intensity magnetic field and make the process in the applicator area costly to detect and control and complicated. Furthermore, direct process parameters such as temperature and/or humidity need to be assessed in the applicator: at the current state there aren’t ways to obtain these parameters by means of the measurements pertaining to the RF generator.

Another drawback of the prior art consists of the poor possibility of controlling the power provided by the RF generator when the impedance of the material to be treated changes locally and/or over time: this factor negatively affects the efficiency and repeatability of the thermal treatment process.

On the basis of the current architecture of the generator, a malfunction of the single triode in the RF generator would cause a situation of system inactivity with a loss of all the material treated in the applicator.

Lastly, according to the process conditions, the working point of the free stroke oscillators may change by skipping from the desired working frequency to out-of- band frequencies. Therefore, the process must be stopped and/or restarted, with the related inefficiencies and/or losses of material.

Thus, starting from the awareness of the aforesaid drawbacks affecting the current state of the art herein considered, the present invention aims to remedy them in a complete and effective manner.

In particular, it is main purpose of the present invention to provide a system for thermal treatment of dielectric and/or electrically conductive materials which is more effective than the systems of the known type.

It is another purpose of the present invention to improve the overall performance of the treatment system with respect to the systems of the known type.

Said purposes are achieved by a method for managing a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material, according to appended claim 1 , as hereinafter referred for the sake of brevity of disclosure.

Particularly, a first aspect of the present invention refers to a method for managing a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material, said system including at least one electric generator suitable to generate a radiofrequency output signal at an output power and applicator means connected to said electric generator, suitable to develop an electromagnetic field at a receiving zone of said dielectric and/or electrically conductive material, said electric generator comprising: at least one generating unit of radiofrequency drive signals at a first power level; amplification means adapted to amplify said radiofrequency drive signals of said generating unit from said first power level to said output power, said amplification means comprising one or more amplification stages, said one or more amplification stages comprising at least one solid-state active electronic component; control means adapted to receive at least a first electrical and/or physical parameter indicative of said output power of said electric generator during operation; wherein the method comprises the steps of: operating said radiofrequency signal generating unit to generate a drive signal at a first power level and having a predetermined trend, to obtain a predetermined desired trend of said output power, and controlling the amount of delivered power in the process; acquiring and processing said at least a first parameter to identify a deviation in said output power with respect to said predetermined desired trend of said output power; acting on at least one operating parameter of said system through said control means to obtain said predetermined desired trend of said output power.

It should be noted that reference is made to an active electronic component when the current-voltage relations are not linear and it is capable of providing a signal amplification or power gain.

Passive components such as capacitors, resistors, inductors, etc. which do not amplify a signal or power level contrast this category.

One of the main aspects of the invention is thus associated with the concept of delivered power, i.e. the power actually provided to the load located in the applicator means: since the delivered power is the only power causing the increase in the load temperature, it is just such a delivered power parameter which is to be controlled in order to ensure a correct thermal treatment process. Further detailed technical operational features of the method for managing a radiofrequency system for thermal treatment of dielectric materials of the present invention are indicated in the related dependent claims.

The aforesaid claims, hereinafter specifically and concretely defined, form an integral part of the present description.

Said purposes and advantages will become more apparent from the following description, related to certain preferred embodiments of the method for managing a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material of the invention, given by way of indicative and non-limiting example, with reference to the accompanying drawings, in which: figure 1 is a schematic view of a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material where the management method according to a preferred embodiment of the invention is implemented; figure 2 is a detailed schematic view of a part of the system in figure 1 ; figures 2A and 2B show parts of a circuit which can be used in a radiofrequency system for thermal treatment of a dielectric and/or electrically conductive material according to the present invention; figure 3 is a constructional variant of figure 2; figure 4 is a constructional variant of the system in figure 1 ; figure 5 is another constructional variant of the system in figure 1 ; figure 6 is a constructional variant of the system in figure 5; figures 6A and 6B show embodiments of a detail in figure 6; figure 7 is a constructional variant of the system in figure 6; figures 8 and 9 show further constructional variants of the system in figure 1. Figure 1 shows a diagrammatic view of a thermal treatment system 1 of a dielectric and/or electrically conductive material M according to the invention, used or useful to implement the method according to a preferred embodiment of the invention. For the sake of simplicity, the term "conductive material" is used below to indicate an electrically conductive material.

System 1 preferably comprises an electric generator 10 adapted to generate a radiofrequency output signal at a desired output power and applicator means 80 connected to the electric generator 10. The applicator means 80 are suitably shaped to develop a desired pattern of electromagnetic field at a receiving zone Z of the dielectric and/or conductive material M.

The applicator means 80, which are outside the specific object of the current invention, generally consist of a plurality of electrodes, usually pairs of electrodes, suitably located spatially to hit the intermediate receiving zone Z of the dielectric and/or conductive material M to be treated with an electromagnetic field oscillating at the working frequency in the radiofrequency field.

For such a reason and only for the sake of simplicity, the applicator means 80 are shown in the drawings as a pair of facing electrodes 82, 84 which define an intermediate zone Z where the dielectric and/or electrically conductive material M to be treated is located.

Similarly, the dielectric and/or conductive material M to be treated is shown as a piece arranged in the intermediate zone Z. It is apparent that the actual shape of the applicator means 80 mainly depends on the nature of the dielectric and/or conductive material M to be treated. For example, if the dielectric and/or conductive material M is liquid, the applicator will consist of one or more tubes inside of which the liquid flows, and a series of electrodes will suitably surround the tubes inside of which the liquid flows.

The geometry of the applicator means 80 in conjunction with the nature of the material to be treated form the load for the electric generator 10, and therefore the impedance of generator 10 or of the optional impedance adapter (matching box), which is better described below.

As said above, the electric generator 10 generates a radiofrequency output signal in the conventional field of radiofrequencies, preferably in the range of frequencies in the range from 300Khz to 300 MFIz, more preferably at a frequency equal to 13.56 MFIz or equal to 27.12 MFIz or equal to 40.68 MFIz (corresponding to the frequencies admitted by the CISPR11 standards, i.e. the ISM - Industrial, Scientific and Medical - bands defined by the International Telecommunication Union).

The electric generator 10 preferably comprises a radiofrequency signal generating unit 12 at a first power level, or small signal generator (SSG), as shown in figure 2. The SSG generating unit 12 preferably has a level of power up to 25 dBm. The generating unit 12 may preferably generate RF signals in the form of PWM (Pulse Width Modulation) pulses or in the form of signals based on an amplitude modulation technique of a sinusoidal waveform CW (acronym for “continuous wave”).

In a further embodiment, the SSG generating unit 12 may also module the signals in phase.

The level of power delivered by the electric generator 10 may preferably be regulated by regulating the duty cycle if the PWM pulse modulation technique is used, or it may be regulated by varying the module of the sinusoidal wave in the amplitude modulation technique.

Moreover, the SSG generating unit 12 consists of a synthesizer, preferably with a filter.

The radiofrequency signal generating unit 12 preferably comprises a management unit 14 adapted to control the generation of the signals. The management unit 14 preferably is implemented by a microcontroller which in addition to managing the signal generating unit 12, manages the signals from and to other units in system 1. In a preferred embodiment, the management unit 14 may be implemented as an independent unit which suitably communicates with other units in the system.

The electric generator 10 comprises a power supply 20 adapted first of all to supply the radiofrequency signal generating unit 12.

The power supply 20 comprises, for example an AC/DC converter having a 6V DC output for supplying the generating unit 12.

The electric generator 10 comprises amplification means (or PA, acronym for “power amplifier”), indicated as a whole by 30, adapted to amplify the radiofrequency signals originating from the generating unit 12 and to raise the power level at the output of the electric generator 10 or at the input of the power combiner 66, as described below.

In the embodiment of figure 2, the amplification means 30 preferably comprise three amplification stages 30a, 30b, 30c.

The amplification stages 30a, 30b, 30c preferably are arranged according to a parallel configuration. In other embodiments (not shown), two or more of such stages could be arranged in series to increase the multiplier amplification factor. In further embodiments (not shown in the accompanying drawings), such amplification stages could be arranged with suitable combinations of parallel and series configuration.

According to an advantageous aspect of the current invention, the amplification stages 30a, 30b 30c comprise at least one solid-state active electronic component 50.

In preferred embodiments, the solid-state active electronic component is a silicon semiconductor device, for example a MOSFET device or an LDMOS device or again an IGBT device. In further alternative embodiment variants, the solid-state active electronic component may preferably be a gallium nitride, or GaN, component.

By way of example, Figure 2A emphasizes the use of two solid-state active electronic components 50 according to the invention, preferably two MOSFETs, in a first possible circuit configuration of an amplification stage 30a, 30b, 30c of the electric generator 10. In such a circuit configuration, the two MOSFETs 50 preferably take a half-bridge configuration (or push-pull configuration).

Similarly, Figure 2B emphasizes the use of four solid-state active electronic components 50 according to the invention, preferably four MOSFETs, in a second possible circuit configuration of an amplification stage 30a, 30b, 30c of the electric generator 10. In such a circuit configuration, the four MOSFETs 50 preferably take an H-bridge configuration.

It’s evident that in other embodiments (not shown in the attached drawings), the amplification stage according to the invention could include a number and/or a combination of solid-state active electronic components different than what’s disclosed herein by way of example, as well as different known type amplification configurations, such as H-bridge, full-bridge, half-bridge, and so on.

The amplification stages 30a, 30b, 30c preferably are supplied by the power supply 20, for example with a VA=65V DC voltage. The power supply 20 preferably comprises a stage 20A of generating such a voltage VA and thus provides the power required by the electric generator 10 from the load during operation. For example, the power supply 20 is sized for a rated power of 10KW. The embodiment in figure 2 also identifies further preferred optional elements with which the electric generator 10 is equipped, as described later.

A power dividing device 60 (also known as power splitter) adapted to divide the signal output from the generating unit 12 prior to the application thereof to the amplification means 30 is preferably provided between the generating unit 12 and the amplification stages 30a, 30b, 30c.

In a preferred embodiment, the outputs of the power splitter 60 are the actuation signals for the amplification stages 30a, 30b, 30c and they’ve the same amplitude and phase so that the amplification stages 30a, 30b, 30c operate synchronously.

A drive device 62 (driver) adapted to pre-amplify the signal originating from the SSG generating unit 12 according to a predetermined amplification factor preferably is interposed between the generating unit 12 and the power splitter 60. The drive device 62 is fed preferably by the power supply 20, more preferably at the voltage VA=65V DC.

A power combining device 66 (also known as PC, acronym for “power combiner”) adapted to combine the power signals output from the amplification stages 30a, 30b, 30c to generate the radiofrequency signal at the desired output power for the applicator means 80 preferably is provided at the output from the amplification stages 30a, 30b, 30c.

According to an aspect of the present invention, the electric generator 10 comprises control means - indicated as a whole by 90 in the drawings below - adapted to receive at least a first electrical and/or physical parameter indicative of the output power of the electric generator 10.

According to the preferred embodiment herein described of the invention shown in figures 1 and 2, the feedback signals 16a, 16b originating from suitable sensors 68a, 68b associated with the output of the electric generator 10 preferably refer to the control means 90.

In a preferred but not binding embodiment, the sensors 68a, 68b comprise transmitted and reflected power sensors 68a, 68b at the output of the electric generator 10.

Preferably but not necessarily, the sensors provide the scalar value of the transmitted power and the scalar value of the reflected power. Just as preferably, but not by way of limitation, the sensors provide the amplitude and phase value of the transmitted power and the amplitude and phase value of the reflected power, or the scalar value of the phase between the transmitted power and the reflected power.

According to an aspect of the present invention, the control means 90 are configured to act on one or more operating parameters of system 1 to control the output power of the electric generator 10.

In the drawings, the control means 90 comprise a plurality of outputs 92a, 92b, 92c, 92d, 92e which act on corresponding operating parameters of system 1 , as better described below.

During operation, the control means 90 may act only on one of the outputs 92a, 92b, 92c, 92d, 92e alone or on any one combination of these outputs.

Moreover, in an embodiment variant, the control means may comprise a single output for acting on one corresponding operating parameter of the system alone. The control means 90 preferably are implemented by a microcontroller and/or a PLC which manages the signals from and to other units in system 1. In a preferred embodiment variant, the control means 90 may be implemented as an independent unit which suitably communicates with other units in the system. According to the preferred embodiment shown in Figures 1 and 2, the first output 92a of the control means 90 interacts with the generating unit 12.

Preferably, the first output 92a of the control means 90 interacts with the generating unit 12 to regulate the duty cycle of the output drive signal of the generating unit 12 when the PWM pulse modulation technique is employed. In an embodiment variant, the first output 92a of the control means 90 interacts with the generating unit 12 to regulate the amplitude of the sinusoidal wave module of the output drive signal of the generating unit 12 when the amplitude modulation technique is employed.

In particular, the second output 92b of the control means 90 interacts with stage 20A of the power supply 20.

Preferably, the second output 92b of the control means 90 interacts with the power supply 20 to regulate the value of the voltage VA with which the amplification stages 30a, 30b, 30c are supplied. For its part, the third output 92c of the control means 90 interacts with the drive device 62.

Preferably, the third output 92c of the control means 90 interacts with the drive device 62 to regulate the amplification factor of device 62 itself. Thereby, the amplitude of the signal originating from the generating unit 12 towards the power splitter 60 may be regulated.

The fourth output 92d of the control means 90, instead, interacts with the power splitter 60.

Preferably, the fourth output 92d of the control means 90 interacts with the power splitter 60 to regulate the amplitude and/or phase value of each drive signal output from the power splitter 60 for the successive amplification stages 30a, 30b, 30c. For an optimal combination efficiency, said scheme with the third output 92d provides an advantage for individually managing the drive signal for the end amplifiers 30a, 30b, 30c both in amplitude and in phase.

The fifth output 92e of the control means 90, instead, interacts with the amplification means 30, more preferably with the three amplification stages 30a, 30b, 30c.

Preferably, the fifth output 92e of the control means 90 interacts with the amplification means 30, more preferably with the three amplification stages 30a, 30b, 30c, to regulate the amplification factor of the amplification means 30, more preferably to regulate the amplification factor of one or more of the three amplification stages 30a, 30b, 30c.

With reference to the configuration of the system 1 described above, possible preferred operating modes of the system 1 according to invention are shown below.

First, the dielectric and/or conductive material M to be treated in the intermediate receiving zone Z of the applicator means 80 is identified. On the basis of the type of material M to be treated and according to the features of the applicator means 80, for example the shape of the intermediate receiving zone Z, a desired trend, or profile, of the delivered power of the electric generator 10 for load M located in the applicator means 80 for completing the desired thermal treatment on material M itself, is preset. For example, the output power of the electric generator 10 may be selected as a constant value over time for the entire duration of the treatment, or take a value over time which changes according to a suitable varying profile.

By doing this, according to that described in the two paragraphs above, the increase in operation temperature or the trend thereof over time may advantageously be kept constant during a given heating process after preliminarily identifying the weight of the material M to be treated and determining the parameter definable as "specific electrical power" (intended as ratio between the electrical power applicable to the material M to be treated and the weight of such a material M), thus avoiding overheating or thermal mishandling of the material M to be treated.

As a result, by means of this operating contrivance implemented in the method of the invention, the efficiency of the thermal treatment by means of radiofrequency carried out on the material M (or load) to be treated advantageously is greater than that which can be obtained in the prior art, shown for example in prior art document EP3280224 A1 , which moreover indicates nothing on the point: indeed, such a known document generally and simply explains that the method described provides for the control system to receive an indication of the load type on which the treatment is to be carried out without any mention of the fact that the predetermined desired trend of said output power is established according to the load M to be treated.

In addition, there is the non-negligible further and prompted advantage of succeeding in optimizing the energy consumption according to the type of material M to be treated (milk for food products, animal hide, plastic material, or other) by the method for managing a radiofrequency system of the invention.

Therefore, the generating unit 12 is programmed to generate a drive signal according to a predetermined trend which allows to obtain such a predetermined trend of the output power at the output of the electric generator 10.

During operation, the control means 90 advantageously acquire the transmitted power and reflected power values through the power sensors 68a, 68b.

The acquired values allow to assess the entity of the deviation in the output power actually delivered to the applicator means 80 with respect to the predetermined desired trend. In particular, the difference between the transmitted power and the reflected power allows to assess the power actually delivered to the applicator means 80.

On the basis of the- increasing or decreasing - deviation entity from the value of desired power, according to the invention, the control means 90 suitably act on one or more of the outputs 92a, 92b, 92c, 92d, 92e to bring back the operation of the system 1 of the invention to provide the value of desired delivered power. Therefore, indeed, the action of the control means 90 aims to increase or decrease the value of the output power of the electric generator 10.

In a preferred embodiment, this is obtained by increasing or decreasing the duty cycle of the output drive signal of the generating unit 12 by acting on the generating unit 12 through the signals transmitted by the first output 92a of the control unit 90. This is an advantageous operating mode since the amplifying means (PA) are working at maximum efficiency.

The method of increasing or decreasing such signals may be selected from one of the known control modes known in the field, for example a proportional (P) or derivative (D) or integrative (I) control or a sigma-delta modulation.

In an alternative and preferred embodiment, regulation is obtained by increasing or decreasing the amplitude of the sinusoidal wave module of the output drive signal of the generating unit 12 by acting on the generating unit 12 through the signals transmitted by the first output 92a of the control means 90.

The control method may preferably be proportional (P) or derivative (D) or integrative (I) or a sigma-delta modulation.

In another preferred embodiment of the invention, the increase or decrease in the output power value of the electric generator 10 is obtained by increasing or decreasing the value of voltage VA with which the amplification stages 30a, 30b, 30c are supplied by acting on the power supply through the signals transmitted by the second output 92b of the control means 90.

In a further preferred embodiment of the invention, the increase or decrease in the output power value of the electric generator 10 is got by increasing or decreasing the amplification value of the drive device 62 by acting on the drive device 62 through the signals transmitted by the third output 92c of the control means 90.

In another preferred embodiment of the invention, the increase or decrease in the output power value of the electric generator 10 is obtained by varying amplitude and/or phase of each output drive signal of the power splitter 60 for the successive amplification stages 30a, 30b, 30c by acting on the power splitter 60 through the signals transmitted by the fourth output 92d of the control means 90.

In a further preferred embodiment of the invention, the increase or decrease in the output power value of the electric generator 10 is obtained by increasing or decreasing the amplification value of the amplification means 30, more preferably of one or more of the three amplification stages 30a, 30b, 30c, by acting on the amplification means 30, and more preferably on one or more of the three amplification stages 30a, 30b, 30c, through the signals transmitted by the fifth output 92e of the control means 90.

In alternative preferred embodiments of the invention, regulating the output power value of the electric generator 10 may envisage a single regulating action of those described above, as well as the combination of two or more of such regulating actions.

Therefore, the system of the invention carries out a monitoring function for assessing a metered value of the reflection coefficient, which is the ratio between the reflected power and the transmitted power.

This reflection coefficient shows the coupling status of the electric generator, which conventionally is 50 ohm, with the load combinations of the applicator means.

The system of the method of the invention also allows the adaptation of power of the electric generator to be retuned according to the working conditions of the applicator means: in the event of failed correspondence due to variation of the properties of the load material, the circumstance may be corrected by automatically tuning the impedance adapter 70 (or matching box) and/or changing the operating frequency within the allowed ISM band width.

Advantageously, in system 1 of the invention, the power for thermal treatment of the dielectric and/or electrically conductive material M is delivered more efficiently with respect to the systems of the known type, since the suitable regulating actions which compensate for the undesired variations of the power involving the dielectric and/or conductive material M are carried out.

In particular, the undesired losses of power caused by the variations of the dielectric and/or conductive material during the treatment and the subsequent variation in impedance are compensated for.

The overall performance of the treatment system is thus improved as compared to the systems of the known type.

With reference to figure 3, a simplified embodiment variant of an electric generator 110 according to invention is described.

Such an embodiment differs from the first embodiment described above with reference to figure 2 first of all because the amplification means 130 comprise a single amplification stage 130a comprising a solid-state active electronic component (e.g. a MOSFET device).

Features and/or component parts of the electric generator 110 in figure 3 corresponding or equivalent to the elements in Figure 2 are identified by the same reference numerals.

The electric generator 110 preferably comprises a radiofrequency signal generating unit 12, a power supply 20 with the supply stage 20A for the amplification stage 130a and transmitted and reflected power sensors 68a, 68b. The transmitted and reflected power sensors 68a, 68b preferably are located downstream of the amplification stage 130a.

The electric generator 110 preferably, but not exclusively, comprises control means 90 comprising two outputs 92a, 92b which are integrated with the generating unit 12 and with the power stage 20A of the power supply 20, respectively. Similarly to the foregoing description, the values of transmitted power and reflected power are acquired by part of the control means 90 through the power sensors 68a, 68b during system operation. The control means 90 suitably act on one or both outputs 92a, 92b so as to bring back the operation of the system to the desired output power value.

The electric generator 110 then preferably, but not exclusively, comprises control means 90 comprising one output 92e which interacts with the amplification stage 130a.

Similarly to the foregoing description, the values of transmitted power and reflected power are acquired by part of the control means 90 through the power sensors 68a, 68b during operation. The control means 90 suitably act on the output 92e by increasing or decreasing the amplification value of the amplification stage 130a to bring back the operation of the system to the desired output power value.

With specific reference to figure 4, an embodiment variant of the current invention is described in which the system is now indicated as a whole with 201.

Features and/or component parts of system 201 in figure 4 corresponding or equivalent to the elements described above are identified by the same reference numerals.

Such an embodiment variant differs from the embodiment described above with reference to figure 1 in that the control means 90 receive a first physical rather than electrical parameter as before, indicative of the output power of the electric generator 10.

Preferably, the first physical parameter comprises the temperature detected in the dielectric and/or conductive material M. The temperature may be measured in different manners, according to the product, material M or load to be treated (liquid, solid, laminar, granular, and more).

For this purpose, system 201 preferably comprises a temperature sensor 268 which provides the control means 90 with the signal corresponding to the temperature detected in the material M to be treated.

The operating mode of system 201 according to such an embodiment substantially is the same as described above, with the substantial difference that the entity of the deviation in the output power actually delivered to the applicator means 80 with respect to the predetermined desired trend is assessed by analyzing the temperature values of material M acquired by the control means 90 through the temperature sensor 268.

In particular, the difference between the temperature in material M detected in real time in a predetermined moment in time and the expected temperature of material M subjected to the existing thermal treatment allows to assess if the power actually delivered to the applicator means 80 is correct or requires adjustments.

In other embodiments of the invention, sensor 268 can measure a first physical parameter other than temperature such as, for example humidity, color or any other parameter distinguishing the dielectric and/or conductive material M treated in the process.

According to an operating mode of the system, the dielectric and/or conductive material M to be treated in the intermediate receiving zone Z of the applicator means 80 is firstly identified. According to the type of material M to be treated and according to the features of the applicator means 80, for example the shape of the intermediate receiving zone Z, a desired trend, or profile, of the output power of the electric generator 10 for the applicator means 80 is preset, to which a predetermined trend, here the temperature T of the material M to be treated, corresponds.

For example, the output power of the electric generator 10 may be selected as a constant value over time for the entire duration of the treatment to preferably maintain a constant temperature value for material M, or to increase the temperature of the material in a linear manner. In an embodiment variant, the output power of the electric generator 10 may be selected according to a suitable profile varying over time with corresponding temperature trend of material M over time.

Naturally, one or more of any other first physical parameter measured by sensor 268 likewise may be used in place of temperature.

Therefore, the generating unit 12 is programmed to generate a drive signal according to a predetermined trend which allows to get the aforesaid predetermined trend of the output power and of the first physical parameter measured by sensor 268, here as mentioned, consisting of the temperature, at the output of the electric generator 10.

During operation, the values are acquired of temperature (or other physical parameters) taken on by the dielectric and/or conductive material M by the control means 90 through the temperature sensor 268 (or sensor of other physical parameters).

As mentioned above, the acquired temperature values (or values of other physical parameters such as those indicated above) allow to assess if the power actually delivered to the applicator means 80 is correct or requires adjustments.

On the basis of the - decreasing or increasing - deviation entity from the value of desired power, according to the invention, the control means 90 suitably bring back the operation of system 1 to the desired output power value with the methods described above.

As yet emphasized, in preferred variants of such an embodiment, the physical parameter detected in the intermediate receiving zone Z of the dielectric and/or conductive material, or directly in the dielectric and/or conductive material, indicative of the output power of the electric generator may comprise one or more of the parameters, such as the residual humidity of the dielectric and/or conductive material, the weight of the dielectric and/or conductive material, the dimensions variations of the dielectric and/or conductive material in terms of surface or volume.

The processing of one or more of such physical parameters allows to assess if the power actually delivered to the applicator means 80 is correct or requires adjustments with respect to that one provided for the undergoing thermal treatment.

For example: excessive values of residual humidity of the dielectric and/or conductive material indicate that the power delivered to the applicator means is lower than that one expected, so the system 1 will act to adjust/increase the power; an excessive decrease in the weight of the dielectric and/or conductive material indicates that the power delivered to the applicator means is greater than that one envisaged, so the system 1 will act to adjust/decrease the power; an excessive decrease in the surface or volume of the dielectric and/or conductive material indicates that the power delivered to the applicator means is greater than that expected one, so the system 1 will act to adjust/decrease the power.

Figure 5 shows an embodiment variant of the invention in which the system is numbered 301 in the assembly.

Features and/or component parts of the system in figure 5 corresponding or equivalent to the elements described above are identified by the same reference numerals.

Such an embodiment of system 301 according to the invention substantially consists of the combination of the two solutions shown in figures 1 and 4 and contemplates for the possibility of the control means 90 intervening to bring back the operation of system 301 to the desired output power value both on the basis of the acquisition of electrical parameters, for example transmitted power and reflected power, and on the basis of a first physical parameter, e.g. temperature, moisture, weight, color and so on.

Figure 6 shows an embodiment variant of system 401 of the invention, which provides using an impedance adapter 70, or matching box, interposed between the output of the electric generator 10 and the applicator means 80 to maximize the transfer of power from generator 10 to the load, consisting of the applicator means 80.

In particular, system 401 according to such an embodiment of the invention corresponds to system 301 shown in figure 5, with the addition of such an impedance adapter 70.

It is evident that the impedance adapter 70 may be used in any other configuration of the system according to the invention, for example that shown in figure 1 or 4. According to such an embodiment, the control means 90 are configured to also act on the impedance adapter 70 to control and/or modulate the output power of the electric generator 10.

For this purpose, the control means 90 comprise an output 92f which interacts with the impedance adapter 70.

Preferably, output 92f of the control means 90 interacts with the impedance adapter 70 to vary the impedance value of the adapter in a continuous or discreet manner. A preferred embodiment of the impedance adapter 70 according to the invention is diagrammatically shown in figure 6A and preferably comprises an inductor L and a variable capacitor Cv. Output 92f of the control means 90 is configured to vary the value of the capacitance of capacitor Cv, preferably continuously, thus varying the impedance value of adapter 70.

Another preferred embodiment of the impedance adapter 70 according to the invention is diagrammatically shown in figure 6B and preferably comprises an inductor L, a plurality of capacitors C1 , C2 and C3, and the respective relays r1 , r2, r3 thereof. Output 92f of the control means 90 is configured to activate the relays r1 , r2, r3 and obtain different configurations with corresponding different discrete impedance values Za of adapter 70.

Therefore, according to the embodiment of the system in figure 6, the power delivered to the applicator means 80 is regulated by acting on the variation of impedance Za of the impedance adapter 70 through the control means 90. Therefore, the new system suggested according to such an embodiment preferably comprises an impedance adapter 70 (matching box) which tunes the impedances between the applicator means 80 and the electric generator 10. The matching box circuit involves tunable reactive components, such as capacitors and inductors, in various possible circuit topologies.

Figure 7 shows a construction variant of system 501 of the invention, which provides using applicator means 180 with variable impedance. In particular, system 501 according to this embodiment corresponds to system 401 (shown in figure 6) using said applicator means 180 with variable impedance.

It is apparent that such applicator means 180 with variable impedance can be used in any other configuration of the system according to the invention, for example that shown in figures 1 , 4 and 5.

Preferably, the applicator means 180 with variable impedance comprise a system for varying the distance between the facing electrodes 82, 84 which define the intermediate zone Z for treating the dielectric and/or conductive material M. According to such an embodiment, the control means 90 are configured to also act on the applicator means 180 with variable impedance to control the output power of the electric generator 10. For this purpose, the control means 90 comprise an output 92g which interacts with the applicator means 180.

Preferably, output 92g of the control means 90 interacts with the applicator means 180 to vary the impedance thereof.

Therefore, according to the embodiment of the system in figure 7, the impedance combined with the applicator means 180 is corrected by acting on the variation of impedance of the applicator means themselves through the control means 90.

With reference to figure 8, an embodiment variant of a system 601 which uses the electric generator 10 described with reference to Figure 1 , is described.

Such a constructional variant shows a possible configuration of system 601 in which the output of the electric generator 10, i.e. the output of the power combining device 66, is connected to several separate power points of the applicator means 680 according to a parallel configuration.

The embodiment of the applicator means 680 is not described in detail in Figure 8, where the applicator means 680 are diagrammatically shown as comprising three modules to which the inputs according to the aforesaid parallel configuration refer. With reference to figure 9, another solution of a system 701 which uses an electric generator 710 according to an embodiment of the invention, is described.

The electric generator 710 according to such an embodiment differs from the first embodiment described above with reference to figure 2 in that the output of the electric generator 710 is defined by the outputs of the amplification stages 30a, 30b, 30c (generator 710 in fact does not have the power combiner and has three outputs).

The outputs of the amplification stages 30a, 30b, 30c are connected to several corresponding separate power points of the applicator means 680 according to a parallel configuration.

In such an embodiment, the transmitted and reflected power sensors 68a’, 68b’, 68a”, 68b”, 68a’”, 68b’” preferably are coupled to the respective outputs of the electric generator 710 to provide the control means 90 with corresponding feedback signals 16a’, 16b’, 16a”, 16b”, 16a’”, 16b’”.

Moreover, several temperature sensors 268a, 268b, 268c are associated with the respective applicator means 680 and provide the control means 90 with the respective signals: such a configuration advantageously allows the treatment of the material to be more promptly and accurately controlled.

It should be noted that the use in the systems described of a solid-state active electronic component 50 rather than vacuum valves (triodes) allows to achieve several advantages.

First of all, the overall dimensions/sizes of the electric generator and of the system as a whole are considerably smaller, with subsequent protection or optimization of the spaces in the factory.

The supply voltages ensuring the operation of the generator according to the present invention, e.g. 65 V DC, are considerably low with respect to the high voltages required for the regular operation of the vacuum valves (triode).

The use of a solid-state active electronic component makes controlling the stability of the working frequency effective with respect to the systems of the known type and/or allows to reduce the presence of harmonic components (radio disturbances) which are difficult to shield in the generation of the power.

This results in an improved behavior with respect to the regulatory and safety standards, including those related to electromagnetic interferences (EMI), and/or a simplification of the system under design in relation to EMI filtering.

The systems used for implementing the method according to the invention allow the physical process parameters to be punctually determined in real time (for example, temperatures and humidity of the receiving zone Z of the material M to be treated) since the processing environment (zone Z) is subject to electrical voltages thar are low in comparison to the systems of known type and which thus reduce the inevitable interferences with measurement sensors and instruments. Similarly, the risks of interference are considerably reduced also due to the feedback signals, or in any case, the limiting parameters for ensuring the correct acquisition of said signals under design are widely reduced.

Therefore, in light of the foregoing description, it can be understood that the method for managing a radiofrequency system according to the present invention achieves the purposes and reaches advantages mentioned above.

Modifications to the radiofrequency system employed in the method of the invention may be made in the implementation step consisting, for example of an electric generator comprising a different number of amplification stages arranged in parallel and/or in series with respect to those described above.

Moreover, in alternative solutions of the radiofrequency system (not shown), two or more electric generators may be provided, arranged in parallel to each other, each generator suitably configured with one or more amplification stages as described above.

In this case, the outputs of the generators may preferably be applied to different applicator means or to separate power points of common applicator means.

Finally, it is apparent that several other variants may be made to the method at hand, without departing from the principles of novelty which are inherent in the inventive idea, as it is apparent that in the practical implementation of the invention, the materials, shapes, and sizes of the details of the system disclosed may be any according to the requirements and may be replaced by other technically equivalent elements. Where the constructional features and techniques mentioned in the following claims are followed by reference signs or numerals, such reference signs were introduced for the sole purpose of increasing the intelligibility of the claims themselves, and therefore such reference signs have no limiting effect on the interpretation of each element identified merely by way of example by such reference signs.

Claims

1. A method for managing a radiofrequency system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701) for thermal treatment of a dielectric and/or electrically conductive material (M), said system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701 ) comprising at least one electric generator (10; 110; 710) adapted to generate a radiofrequency output signal at an output power and applicator means (80; 180; 680) connected to said electric generator (10; 110; 710), adapted to develop an electromagnetic field at a receiving zone (Z) of said dielectric and/or electrically conductive material (M), said electric generator (10; 110; 710) comprising: at least one generating unit (12) of radiofrequency drive signals at a first power level; amplification means (30; 130) adapted to amplify said radiofrequency drive signals of said generating unit (12) from said first power level to said output power, said amplification means (30; 130) comprising one or more amplification stages (30a, 30b, 30c; 130a), each of which comprises at least one solid-state active electronic component (50); control means (90) adapted to receive at least a first electrical and/or physical parameter indicative of said output power of said electric generator (10; 110; 710) during operation, characterized in that it comprises the steps of: operating said radiofrequency signal generating unit (12) to generate a drive signal at a first power level and having a predetermined trend, to obtain a predetermined desired trend of said output power; acquiring and processing said at least a first parameter to identify a deviation in said output power with respect to said predetermined desired trend; acting on at least one operating parameter of said system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701) through said control means (90) to obtain said predetermined desired trend of said output power.

2. A method according to claim 1), characterized in that said at least a first electrical parameter comprises one or more of the parameters of the group comprising: the scalar value of the transmitted power and the scalar value of the reflected power measured at the output of said electric generator (10; 110; 710); the amplitude and/or phase value of the transmitted power and the amplitude and/or phase value of the reflected power measured at the output of said electric generator (10; 110; 710); the amplitude and/or phase value of the voltage and/or current at the output of said electric generator (10; 110; 710).

3. A method according to claim 1) or 2), characterized in that said at least a first electrical parameter is detected through one or more sensors (68a, 68b; 68a’, 68b’, 68a”, 68b”, 68a’”, 68b’”) selected from the sensors of the group consisting of a transmitted and/or reflected power sensor or a voltage and/or current sensor.

4. Method according to any of the preceding claims, characterized in that said at least a first physical parameter comprises a temperature and/or humidity value detected in said receiving zone (Z) and/or directly in said dielectric and/or conductive material (M) and/or the weight and/or dimensions of said dielectric and/or conductive material (M) and/or the colorimetry of said dielectric and/or conductive material (M) and/or the electrical conductivity of said dielectric and/or conductive material (M) and/or the electrical impedance of said dielectric and/or conductive material (M).

5. Method according to any of the preceding claims, characterized in that said at least one operating parameter comprises one or more of the parameters of the group comprising: the duty cycle in the PWM pulse modulation technique of said generating unit (12); the amplitude of the sinusoidal waveform of said drive signal; the supply voltage of said one or more amplification stages (30a, 30b, 30c; 130a); the drive voltage of said amplification means (30; 130).

6. Method according to any of the preceding claims, characterized in that said radiofrequency signal has a frequency in the range from 300Khz to 300MHz, preferably a frequency equal to 13.56 MHz or equal to 27.12 MHz or equal to 40.68 MHz.

7. Method according to any of the preceding claims, characterized in that said at least one operating parameter comprises the amplification factor of said one or more amplification stages (30a, 30b, 30c; 130a).

8. Method according to any of the preceding claims, characterized in that a power dividing device (60), the outputs of which are connected to said one more amplification stages (30a, 30b, 30c; 130a), is placed in said system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701) between said generating unit (12) and said one more amplification stages (30a, 30b, 30c; 130a).

9. Method according to claim 8), characterized in that said at least one operating parameter comprises the voltages and/or phases of said outputs of said power dividing device (60).

10. Method according to any of the preceding claims, characterized in that said system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701 ) comprises a driving and pre-amplification device (62) between said signal generating unit (12) and said amplification means (30; 130).

11. Method according to claim 10), characterized in that said at least one operating parameter comprises the amplification factor of said driving and pre amplification device (62).

12. Method according to any of the preceding claims, characterized in that said system (401 ; 501) comprises an impedance adapter (70) interposed between said electric generator (10; 110; 710) and said applicator means (80; 180; 680).

13. Method according to claim 12), characterized in that said at least one operating parameter comprises the impedance of said impedance adapter (70).

14. Method according to claim 13), characterized in that said step of acting on said at least one operating parameter comprises the operation of continuously or discreetly varying said impedance of said impedance adapter (70).

15. Method according to any of the preceding claims, characterized in that said system (501) comprises applicator means (180) with variable impedance.

16. Method according to claim 15), characterized in that said at least one operating parameter comprises the impedance of said applicator means (80; 180; 680).

17. Method according to any of the preceding claims, characterized in that said step of acting on at least one operating parameter of said system (1 ; 201 ; 301 ; 401 ; 501 ; 601 ; 701) through said control means (90) comprises a proportional or derivative or integral type control or a sigma-delta modulation.

18. Method according to any of the preceding claims, characterized in that said predetermined desired trend of said output power is defined in relation to the dielectric and/or electrically conductive material (M) to be treated.

19. Method according to any of the preceding claims, characterized in that said step of acting on said at least one operating parameter comprises continuously or discreetly varying said at least one operating parameter.

20. Method according to any of the preceding claims when dependent on claim 12), characterized in that said impedance adapter (70) comprises a variable capacitor (Cv) and/or a variable inductance and/or one or more circuits having different impedance, said circuits being mutually selectable.

21. Method according to any of the preceding claims, characterized in that said active electronic component (50) comprises any one of the components of the group consisting of silicon semiconductor elements and/or gallium nitride elements.

22. Method according to claim 21), characterized in that said at least one active electronic component (50) in said amplification means (30; 130) takes a configuration of the H-bridge, full-bridge, or half-bridge type.

23. Method according to any of the preceding claims, characterized in that it comprises a power supply (20) adapted to supply said generating unit (12) with radiofrequency signals at a first power level and/or adapted to supply said one more amplification stages (30a, 30b, 30c; 130a).

24. Method according to any of the preceding claims, characterized in that said one or more amplification stages (30a, 30b, 30c; 130a) are electrically connected according to a parallel configuration, a series configuration, or a combination thereof.

25. Method according to any of the preceding claims, characterized in that a power combining device (66) is located between said one more amplification stages (30a, 30b, 30c) and said applicator means (80; 180; 680).

26. Method according to claim 25), characterized in that the output of said power combining device (66) is connected to several separate power points of said applicator means (680) according to a parallel configuration.

27. Method according to any of the preceding claims, characterized in that the outputs of said one and more amplification stages (30a, 30b, 30c; 130a) are connected to several separate power points of said applicator means (680) according to a parallel configuration.

28. Method according to any of the preceding claims, characterized in that it comprises a plurality of electric generators arranged parallel to one another, the outputs of said electric generators being applied to different applicator means or to separate power points of common applicator means.