Patent Description:
Advantageously, the present invention also relates to a packaging machine for the packaging of pourable products, in particular pourable food products, into packages, in particular composite packages, and having at least one sealing device for the sealing of packages.

Furthermore, the present invention also relates to a method of operating a sealing device within a packaging machine for the packaging of pourable products, in particular pourable food products, into packages, in particular composite packages.

As is known, many liquid or pourable food products, such as fruit juice, UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in packages, in particular sealed packages, made of sterilized packaging material.

In the case of aseptic packages for longstorage products, the packaging material also comprises a layer of oxygen-barrier material, e.g. an aluminum foil, which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.

Packages of this sort are normally produced on fully automatic packaging machines, which, in use, advance a web of packaging material through a sterilization unit of the packaging machine for sterilizing the web of packaging material. Then, the sterilized web of packaging material is maintained and advanced within an isolation chamber, and is folded and sealed longitudinally to form a tube, which is further advanced. Furthermore, the tube is filled with a pourable product, and is transversally sealed and cut along equally spaced transversal cross sections within a package forming apparatus of the packaging machine during the tube's advancement.

In more detail, the package forming apparatus comprises a plurality of forming and sealing assemblies, each one, in use, shaping and transversally sealing and cutting the tube so as to obtain the single packages.

Each forming and sealing assembly comprises a respective sealing device for transversally sealing the tube for obtaining a respective transversal seal portion by locally compressing the tube and heating the respective portions of the layers of heat-seal plastic material. The heating may e.g. occur by sealing devices generating ultrasonic vibrations. The sealing devices, which heat by means of ultrasound vibrations comprise a sonotrode configured to generate the ultrasonic vibrations and an anvil, which is designed to cooperate with the sonotrode so as to locally compress the tube. Documents <CIT> and <CIT> may be of interest for the present disclosure. <CIT> discloses a packaging machine for producing sealed packages of pourable food products with sealing means comprising a sonotrode. In <CIT> plots are made of the module and the phase of the impedance as a function of frequency for the sonotrode.

A typical sonotrode comprises a sonotrode head having a sealing surface extending along a longitudinal axis and a vibration control unit connected to the sonotrode head and configured to actuate ultrasonic vibrations of the sonotrode head. In more detail, the vibration control unit comprises a housing shell and one or more piezoelectric transducers arranged within the housing shell and configured to generate ultrasonic vibrations to be coupled into the sonotrode head.

Even though the known sealing devices operate with a high quality and reliability a desire is felt in the sector to further improve the known sealing devices.

In particular, a desire is felt to control the sealing process as well as possible.

In particular, a desire is felt to operate with the respective sonotrodes as long as possible and to avoid any unwanted failures.

It is therefore an object of the present invention to provide in a straightforward and low-cost manner an improved sealing device.

It is a further object of the present invention to provide in a straightforward and low-cost manner a packaging machine having an improved sealing device.

Additionally, it is an object of the present invention to provide in a straightforward and low-cost manner an improved method of operating a sealing device.

According to the present invention, there is provided a sealing apparatus according to the independent claim <NUM>.

Preferred embodiments of the sealing apparatus are claimed in the claims being directly or indirectly dependent on claim <NUM>.

According to the present invention, there is also provided a packaging machine according to claim <NUM>.

Additionally, according to the present invention, there is also provided a method according to claim <NUM>.

A preferred embodiment of the method is claimed in claim <NUM>.

Number <NUM> indicates as a whole a packaging machine for producing packages <NUM>, in particular sealed package <NUM>, of a pourable product, in particular a pourable food product, such as (pasteurized) milk, fruit juice, wine, tomato sauce, salt, sugar etc..

In more detail, packaging machine <NUM> may be configured to produce packages <NUM> from a multilayer packaging material.

In further detail, the multilayer packaging material may comprise at least one layer of fibrous material, such as e.g. a paper or cardboard, and at least two layers of heat-seal plastic material, e.g. polyethylene, interposing the layer of fibrous material in between one another. One of these two layers of heat-seal plastic material defining the inner face of package <NUM> contacting the pourable product.

Moreover, the packaging material may also comprise a layer of gas- and light-barrier material, e.g. aluminum foil or ethylene vinyl alcohol (EVOH) film, in particular being arranged between one of the layers of the heat-seal plastic material and the layer of fibrous material. Preferentially, the packaging material may also comprise a further layer of heat-seal plastic material being interposed between the layer of gas- and light-barrier material and the layer of fibrous material.

In further detail, the multilayer packaging material may be provided in the form of a web <NUM>. In particular, web <NUM> may comprise a plurality of repeated patterns, each pattern defining a respective blank for the formation of one respective package <NUM>.

Furthermore, packaging machine <NUM> may be configured to produce packages <NUM> by forming a tube <NUM> from web <NUM>, longitudinally sealing tube <NUM>, filling tube <NUM> with the pourable product and to transversally seal and cut tube <NUM>.

A typical package <NUM> obtained by packaging machine <NUM> comprises a longitudinal seam portion <NUM> and a pair of a respective first transversal sealing band and a respective second transversal sealing band, in particular arranged at opposite sides of package <NUM>. In particular, the first transversal sealing band may define a transversal top sealing band and the second transversal sealing band may define a transversal bottom sealing band.

With particular reference to <FIG>, packaging machine <NUM> may comprise:.

Moreover, packaging machine <NUM> may also comprise a sterilizing unit configured to sterilize the, in use, advancing web <NUM> at a sterilization station, in particular the sterilization station being arranged upstream of forming station <NUM> along web advancement path P.

In more detail, conveying device <NUM> may be configured to advance tube <NUM> and any intermediates of tube <NUM> along a tube advancement path Q, in particular from forming station <NUM> to package forming unit <NUM>. In particular, under intermediates of tube <NUM> any configuration of web <NUM> is meant prior to obtaining the tube structure and after folding of web <NUM> by tube forming and sealing device <NUM> has started. In other words, the intermediates of tube <NUM> are a result of the gradual folding of web <NUM> so as to obtain tube <NUM>, in particular by overlapping the edges of web <NUM> with one another.

Preferably, tube forming and sealing device <NUM> may be arranged such that tube <NUM> may present a vertical orientation.

In more detail, tube forming and sealing device <NUM> may comprise at least two forming ring assemblies <NUM>, in particular arranged within isolation chamber <NUM>, being configured to gradually fold in cooperation with one another web <NUM> into tube <NUM>, in particular by overlapping the edges of web <NUM> with one another. Thereby, in use, seam portion <NUM> of tube <NUM> is formed.

Additionally, tube forming and sealing device <NUM> may comprise a sealing head <NUM>, in particular arranged within isolation chamber <NUM> and, configured to longitudinally seal tube <NUM>, in particular along seam portion <NUM>.

Moreover, tube forming and sealing device <NUM> may also comprise a pressuring assembly configured to exert a mechanical force on seam portion <NUM> so as to ensure sealing of tube <NUM> along seam portion <NUM>.

Additionally, filling device <NUM> may comprise a filling pipe <NUM> being configured to direct, in use, the pourable product into tube <NUM>. In particular, filling pipe <NUM> may, in use, be at least partially placed within tube <NUM> for feeding, in use, the pourable product into tube <NUM>.

With particular reference to <FIG> and <FIG>, package forming apparatus <NUM> may comprise:.

In particular, package forming apparatus <NUM> may be configured to control forming and sealing assemblies <NUM> and the conveying unit such to transversally seal and cut tube <NUM> along equally spaced transversal cross sections. Even more particularly, package forming apparatus <NUM> may be configured to control forming and sealing assemblies <NUM> and the conveying unit such to transversally seal and cut tube <NUM> also in dependence of the repeated patterns.

In more detail, each forming and sealing assembly <NUM> may comprise:.

Moreover, each forming and sealing assembly <NUM> may comprise a cutting device (not shown) for transversally cutting tube <NUM>.

Preferentially, each sealing apparatus <NUM> may be configured to form a main sealing band, and in particular the respective cutting device may be configured to transversally cut through the main sealing band. Even more preferentially, each main sealing band combines the respective first transversal sealing band of a leading package <NUM> and the respective second transversal sealing band of the successive package <NUM>.

In further detail, each forming shell may comprise at least a first half-shell (not shown and known as such) and a second half-shell (not shown and known as such) configured to at least partially define in cooperation the shape of packages <NUM>. In particular, the first half-shell and the second half-shell may be configured to contact tube <NUM> from opposite sides thereof.

In more detail, each sealing apparatus <NUM> may be of the ultrasonic type; i.e. sealing apparatus <NUM> may be configured to generate ultrasonic vibrations suited to heat portions of the layers of heat-seal plastic material.

Moreover, each sealing apparatus <NUM> comprises at least:.

In further detail, each cutting device may comprise at least one moveable blade so as to transversally cut tube <NUM>.

Furthermore, each sonotrode <NUM> may be associated to one respective first half-shell, in particular defining a first operative portion of the respective forming and sealing assembly <NUM>, and each anvil <NUM> may be associated to one respective second half-shell, in particular defining a second operative portion of the respective forming and sealing assembly <NUM>.

Additionally, the respective blade of the respective cutting device may be associated to the respective sonotrode <NUM> or to the respective anvil <NUM>, in the specific case the respective anvil <NUM>. In other words, each cutting device may either be associated to the respective first operative portion or the respective second operative portion, in the specific case shown to the respective second operative portion.

Furthermore, the conveying unit may be configured to advance the respective first operative portions along a first path and the respective second operative portions along a second path.

Moreover, each first operative portion and the respective second operative portion may be configured to cooperate with one another for forming a package <NUM> when advancing along a respective operative section of the first path and the second path, respectively.

With particular reference to <FIG> and <FIG>, each sonotrode <NUM> comprises at least:.

In more detail, each sealing surface <NUM> may be designed to contact tube <NUM> and to establish an operative connection with the portions of the layers of heat-seal plastic material.

Furthermore, each sealing surface <NUM> may comprise a first portion and a second portion displaced from and being parallel to one another.

Moreover, each sonotrode head <NUM> may comprise a groove <NUM>, in particular interposed between the respective first portion and the respective second portion. In particular, each groove <NUM> may be designed to receive a portion of the respective blade during the transversal cutting of tube <NUM>.

Reverting to <FIG>, each vibration control unit <NUM> may comprise one or more piezoelectric transducer devices <NUM> configured to generate the ultrasonic vibrations to be coupled into the respective sonotrode head <NUM>. In the specific case shown, vibration control unit <NUM> may comprise three piezoelectric transducer devices <NUM>, however, the number may vary in dependence of the format of packages <NUM> and/or in dependence of dimensions of the sealing surface; i.e. in dependence of the format of packages <NUM>, the extension of sealing surface <NUM> may be larger or shorter; in particular a shorter sealing surface <NUM> may require less piezoelectric transducer devices <NUM> than a larger one.

With particular reference to <FIG>, each piezoelectric transducer device <NUM> may comprise a plurality of piezoelectric (ceramic) elements <NUM> stacked one on top of one another. In more detail, each piezoelectric transducer device <NUM> may also comprise a plurality of conductive metal sheets, in particular forming together with piezoelectric elements <NUM> a stack of alternate piezoelectric elements <NUM> and conductive metal sheets.

Additionally, each sealing apparatus <NUM>, in particular the respective vibration control unit <NUM>, may comprise one or more generators <NUM> operatively connected to piezoelectric transducer(s) <NUM>, in particular piezoelectric elements <NUM>, so as to actuate and control the ultrasonic vibrations of piezoelectric transducer(s) <NUM>.

In particular, each generator <NUM> may be configured to introduce a driving signal into the respective piezoelectric transducers <NUM>, in particular into the respective stack of piezoelectric elements <NUM>.

In more detail and with particular reference to <FIG>, such a driving signal may be an AC voltage signal <NUM> (see e.g. <FIG>). In particular, according to such an example piezoelectric transducers <NUM> may be arranged electrically in parallel.

Alternatively, piezoelectric transducers <NUM> may be arranged electrically in series and the driving signal may be an AC current signal.

Advantageously, each sealing apparatus <NUM> comprises a sensor device <NUM> configured to measure, in use, one or more time-dependent electrical parameters or electrical quantities of at least one, e.g. of each one, of the one or more piezoelectric transducer devices <NUM>, in particular of the respective stack of piezoelectric elements <NUM>. For example, the electrical parameters or electrical quantities may be measured at the respective piezoelectric transducers <NUM>, after the driving signal subdivides for each different piezoelectric transducer <NUM>. The measurement may occur for one or more or all the piezoelectric transducers <NUM>.

In particular, each sensor device <NUM> is configured to obtain real-time measurements of the one or more time-dependent electrical parameters.

Example time-dependent electrical parameters or quantities may comprise the electrical current, the electrical voltage and/or the electrical power.

In more detail, each sensor device <NUM> may be configured to determine the time-dependent electrical parameters of each one of the one or more piezoelectric transducer device <NUM>, in particular of the respective stack of piezoelectric elements <NUM>, independently and selectively from the other piezoelectric transducer devices <NUM>, in particular of the other respective stacks of piezoelectric elements <NUM>.

Preferentially, each sensor device <NUM> may be configured to determine respective time-dependent curves of the one or more electrical parameters of each one of the one or more piezoelectric transducer devices <NUM>, in particular of the respective stacks of piezoelectric elements <NUM>.

In the specific case shown and with particular reference to <FIG>, each sensor device <NUM> is configured to determine a first time-dependent curve <NUM> associated to a first one of the three piezoelectric transducer devices <NUM>, a second time-dependent curve <NUM> associated to a second one of the three piezoelectric transducer devices <NUM> and a third time-dependent curve <NUM> associated to a third one of the three piezoelectric transducer devices <NUM>.

Moreover first time-dependent curve <NUM>, second time-dependent curve <NUM> and third time-dependent curve <NUM> may be indicative of the electrical parameters or quantities, e.g. , according to the specific example shown, the first, second and third time-dependent curves <NUM>, <NUM>, <NUM> depict the respective time-dependent electrical currents flowing through the respective piezoelectric transducer devices <NUM>, in particular of the respective stacks of piezoelectric elements <NUM>.

Alternatively, in a similar manner, also other electrical parameters may be determined and their time-dependent curves may be measured.

According to some non-limiting embodiments, each sensor device <NUM> may be configured to measure the respective time-dependent curves for more than one electrical parameter of each piezoelectric transducer device <NUM>, in particular of the respective stacks of piezoelectric elements <NUM>.

Preferentially, each sealing apparatus <NUM>, in particular the respective sensor device <NUM>, may comprise a memory configured to store, in particular at least temporarily store, the electrical parameters and/or the respective time-dependent curves.

In further detail, each sealing apparatus <NUM> may comprise an analyzing unit <NUM> operatively connected, e.g. directly or indirectly, e.g. wirelessly, to the respective sensor device <NUM> and configured to receive and analyze the time-dependent electrical parameters, in particular the respective time-dependent curves.

More specifically, each analyzing unit <NUM> may be configured to:.

The characteristic parameters or features may comprise root-mean-square values, frequencies, powers, instantaneous powers, phase shifts between current and voltage and/or dissipated powers of the one or more time-dependent curves.

In one or more embodiments, the sonotrode may be represented by an (equivalent) electrical circuit comprising a capacitance of the stacks of piezoelectric elements <NUM>, an equivalent resistance, an equivalent inductance and an equivalent capacitance. In other words, a sonotrode circuit may be approximated using the above-mentioned equivalent electrical circuit. The analyzing unit <NUM> may be configured to calculate, as a function of the characteristic parameters or features of the time-dependent curves, the capacitance of the stacks of piezoelectric elements <NUM>, the equivalent resistance, the equivalent inductance and the equivalent capacitance.

Alternatively or additionally, each analyzing unit <NUM> may be configured to determine information, e.g. quality information, about the transversal sealing process of the respective sealing apparatus <NUM> from the determined electrical parameters, in particular the respective time-dependent curves. each analyzing unit <NUM> may use such information for evaluating the quality of the respective transversal sealing process and/or to determine pressures acting on varying portions of the respective main sealing band.

According to some non-limiting embodiments, each analyzing unit <NUM> may be configured to selectively determine respective operating states of the one or more piezoelectric transducer devices <NUM>, in particular of the respective stacks of piezoelectric elements <NUM>, in dependence of the respective electrical parameters, in particular of the respective time-dependent curves, determined by the respective sensor device <NUM>.

Preferentially, each sealing apparatus <NUM> may also comprise a temperature sensing device configured to determine a temperature, in particular a time-dependent temperature-profile, of the respective one or more piezoelectric transducer devices <NUM>, in particular of the respective stacks of piezoelectric elements <NUM>.

Advantageously, each analyzing unit <NUM> may be configured to selectively determine the operating state of the respective one or more piezoelectric transducer devices <NUM> in dependence of the respective electrical parameters, in particular the respective time-dependent curves, determined by the respective sensor device <NUM> and the respective temperature, in particular the respective time-dependent temperature profile, as determined by the respective temperature sensing device.

Preferentially, the operating state of each piezoelectric transducer device <NUM>, in particular the respective stack of piezoelectric elements <NUM>, may contain information about the aging and/or health and/or the remaining life-time of the respective piezoelectric transducer device <NUM>, in particular the respective stack of piezoelectric elements <NUM>.

According to some non-limiting embodiments, each analysis unit <NUM> and/or a processing unit of sealing apparatus <NUM> and/or packaging machine <NUM> may be configured to plan maintenance activities based on the respective operating states of piezoelectric transducer devices <NUM>. In particular, analysis unit <NUM> and/or the processing unit may be configured to plan the maintenance activities as a function of the remaining life-time and/or the aging and/or the health of piezoelectric transducer devices <NUM>. In this way, it is possible to optimize the use of piezoelectric transducer devices <NUM>.

Preferentially, each analysis unit <NUM> and/or the processing unit may be configured to (directly or indirectly) signal the remaining lifetime of a piezoelectric transducer device <NUM> and signal that the maintenance should be executed within a certain time regime.

Alternatively or in addition, each analysis unit <NUM> and/or the processing unit may be configured to assess the possible occurrence of an anomalous working condition of the one or more piezoelectric transducer devices <NUM> in dependence of the respective electrical parameters, in particular the respective time-dependent curves. Moreover, each analysis unit <NUM> and/or the processing unit may be configured to alert about the risk of an anomalous working condition, e.g. by means of a prompt on a human-machine interface (of packaging machine <NUM>) and/or an acoustic message and/or an electronic message or similar.

With particular reference to <FIG>, each sensor device <NUM> may comprise one or more sensor elements <NUM>, each one associated to one respective piezoelectric transducer device <NUM>, in particular the respective stack of piezoelectric elements, for measuring the one or more time-dependent electrical parameters of the respective piezoelectric transducer device <NUM>. For example, each sensor device <NUM> may comprise a plurality of sensor elements <NUM>, that may be associated with a respective plurality of stacks of piezoelectric elements.

Preferentially, each sensor element <NUM> may comprise at least one Hall effect sensor and/or at least one Shunt sensor.

According to some non-limiting embodiments, sensor device <NUM> may comprise a one or more measurement circuits, in particular comprising portions for signal amplification and/or signal filtration.

The one or more measurement circuits may comprise or may be connected to sensor elements <NUM>.

According to some preferred non-limiting embodiments, each sensor device <NUM> may comprise a board carrying the respective sensor elements <NUM>, and in particular also the respective measurement circuits.

According to some non-limiting embodiments, each analysis unit <NUM> may be arranged on the respective board of the respective sensor device <NUM>.

Alternatively or in addition, each sensor device <NUM> may comprise a communication group operatively coupled to the respective analysis unit <NUM> for transferring the respective electrical parameters, in particular the time-dependent curves.

Moreover, each communication group may be configured to communicate with the respective analysis unit <NUM> by means of wiring and/or wirelessly.

According to some possible embodiments, each analysis unit <NUM> may be spaced apart from the respective sensor device <NUM> and/or may be part of and/or may be incorporated into a central analysis unit of package forming apparatus <NUM> and/or of packaging machine <NUM>.

With particular reference to <FIG> and <FIG>, vibration control unit <NUM> may further comprise at least a housing shell <NUM> having an inner space <NUM>.

Additionally, each vibration control unit <NUM> may further comprise at least a housing shell <NUM> (shown in <FIG>; the transparent representation is for illustrative reasons) having an inner space <NUM>. In particular, housing shell <NUM> is in contact with the respective sonotrode head <NUM> so as to seal inner space <NUM> from an outer space.

Preferentially, each piezoelectric transducer device <NUM> and each sensor device <NUM> may be arranged within the respective inner space <NUM>; i.e. being enclosed by the respective housing <NUM>. In particular, the respective boards of each sensor device <NUM> may be arranged within the respective inner space <NUM>. Such solutions allow a compact construction.

In particular, also the respective generator(s) <NUM> may be arranged within the respective inner space <NUM>.

In more detail, each housing <NUM> may comprise a main wall <NUM>, a lateral wall <NUM> extending from main wall <NUM> and an opening opposite to main wall <NUM>.

Moreover, each vibration control unit <NUM> may comprise a coupling portion <NUM> contacting the respective sonotrode head <NUM> along a respective contact surface. Additionally, each piezoelectric transducer device <NUM> may be placed within a respective seat <NUM> (see in particular <FIG>) of the respective coupling portion <NUM> and in contact with coupling portion <NUM> so as to allow for the transmission of the generated ultrasonic vibrations into the respective sonotrode head <NUM>.

In particular, the respective opening of each housing <NUM> may be designed to allow for introducing the respective coupling portion <NUM> into inner space <NUM>.

Moreover, each sensor device <NUM> may be arranged within a portion of the respective inner space <NUM> being interposed between the respective coupling portion <NUM> and a main wall <NUM>. each board may be mounted to the respective main wall <NUM>.

In use, packaging machine <NUM> produces packages <NUM> filled with the pourable product.

In more detail, conveying device <NUM> advances web <NUM> along web advancement path P to forming station <NUM>. Tube forming and sealing device <NUM> forms tube <NUM> from the advancing web <NUM> and longitudinal seals tube <NUM>. Additionally, filling device <NUM> fills tube <NUM> with the pourable product and package forming unit <NUM> forms, transversally seals and transversally cuts tube <NUM> so as to obtain packages <NUM>.

In further detail, during operation of package forming unit <NUM>, forming and sealing assemblies <NUM> form, transversally seal, and in particular also transversally cut tube <NUM> for obtaining respective filled packages <NUM>.

Thereby, the forming occurs by means of the respective forming shell, in particular the cooperation of the respective first half-shell and the second half-shell with one another.

Additionally, the transversal sealing occurs by means of the respective sealing apparatus <NUM>.

Moreover, the transversal cutting occurs by means of the respective cutting device.

In more detail, operation of each sealing apparatus <NUM> comprises at least the following main steps:.

In even more detail, operation of each sealing apparatus <NUM> further comprises the steps of:.

In more detail, during each step b), the respective sealing device <NUM> may measure the respective time-dependent electrical parameters, in particular the respective time-dependent curves.

Preferentially, operation of each sealing apparatus <NUM> may also comprise a step c) measuring, in particular by means of the respective temperature sensing, the temperature of the one or more respective piezoelectric transducers <NUM>.

According to preferred non-limiting embodiments, operation of each sealing apparatus <NUM> may also comprise a step d) of analyzing, in particular by means of the respective analyzing unit <NUM>, the electrical parameters, in particular the time-dependent curves.

In particular, during step d) each analyzing unit <NUM> may:.

In addition or alternatively, during the step d) the remaining life time and/or the aging and/or the health and/or an anomalous working condition of the one or more piezoelectric transducer devices <NUM> may determined.

According to some possible non-limiting embodiments, during step d) also the temperature of the one or more piezoelectric transducer devices <NUM> may be considered.

Furthermore, operation of each sealing apparatus <NUM> may further comprise a step of transferring, during which the measurement results from step b), in particular also from step c) may be transferred to analysis unit <NUM> and/or the processing unit.

Additionally, operation of each sealing apparatus <NUM> may further comprise a step of planning, during which a maintenance is planned based on the operating state of the one or more piezoelectric transducer(s) <NUM>. In particular, in this way, the maintenance can be planned based on the effective remaining life-time and/or aging and/or health of the respective one or more piezoelectric transducer(s) <NUM>.

Moreover, operation of each sealing apparatus <NUM> may also comprise a step of alerting, during which the risk of an anomalous working condition may be signaled, e.g. by means of a prompt on a human-machine interface and/or an acoustic message and/or an electronic message of similar.

The advantages of sealing apparatus <NUM> and/or of packaging machine <NUM> and/or the method according to the present invention will be clear from the foregoing description.

In particular, by each sealing apparatus <NUM> having sensor device <NUM> it is possible to monitor in real-time the respective sonotrode <NUM> by monitoring electrical parameters of piezoelectric transducer devices <NUM>.

A further advantage resides in that it is possible to obtain a direct feedback from piezoelectric transducer devices <NUM> so as to monitor the sealing process.

Another advantage is seen in that sensor device <NUM> can be economically realized.

An even other advantage resides in that sensor device <NUM> enables conditioning monitoring and predictive maintenance.

Moreover, an advantage is also that the data from sensor device <NUM> allows process control.

Claim 1:
Sealing apparatus (<NUM>) for sealing packages (<NUM>) filled with a pourable product within a packaging machine (<NUM>) ;
the sealing apparatus (<NUM>) having at least one sonotrode (<NUM>) comprising at least:
- a sonotrode head (<NUM>); and
- a vibration control unit (<NUM>) connected to the sonotrode head (<NUM>) and configured to actuate ultrasonic vibrations of the sonotrode head (<NUM>);
wherein the vibration control unit (<NUM>) comprises:
- one or more piezoelectric transducer devices (<NUM>) configured to generate ultrasonic vibrations to be coupled into the sonotrode head (<NUM>); and
- a sensor device (<NUM>) configured to measure, in use, one or more time-dependent electrical parameters of at least one of the one or more piezoelectric transducer devices (<NUM>),wherein the sensor device (<NUM>) is configured to determine respective time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>) of the one or more electrical parameters of the one or more piezoelectric transducer devices (<NUM>),
wherein the sealing apparatus further comprises an analyzing unit (<NUM>) operatively connected to the sensor device (<NUM>) and configured to receive and analyze the time-dependent curves, wherein the analyzing unit (<NUM>) is configured to:
- determine one or more characteristic parameters from the one or more time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>) ; and/or
- determine one or more characteristic parameters from the one or more time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>) and compare the determined characteristic parameters with reference parameters; and/or
- calculate, as a function of one or more characteristic parameters of the time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>), a capacitance of the stacks of piezoelectric elements (<NUM>), an equivalent resistance, an equivalent inductance and an equivalent capacitance of an electrical circuit representing the sonotrode; and/or
- compare one or more of the time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>) with reference curves; and/or
- analyze respective shapes of the time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>); and/or
- determine information about the sealing process from the time-dependent curves (<NUM>, <NUM>, <NUM>, <NUM>).