Abstract:
Packaging Machine operable to produce sealed packages made of heat-seal sheet packaging material and containing a food product, and comprising an ultrasonic sealing device including an electrical power signal source operable to generate an electrical power signal; an ultrasonic transducer electrically coupled to the electrical power signal source to receive the electrical power signal and responsively heat seal the sheet packaging material; and an electronic counter operable to count the ultrasonic sealing cycles of the ultrasonic sealing device.

Description:
This patent application is a U.S. National Phase of International Patent Application No. PCT/EP2010/057280, filed 26 May 2010, which claims priority to European Patent Office 09161595.5, filed 29 May 2009, the disclosures of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates in general to pourable food product packaging by transversely sealing a sheet packaging material tube filled continuously with the pourable food product. More specifically, the present invention relates to an electronic counter operable to count the ultrasonic sealing cycles of an ultrasonic sealing device in a Packaging Machine operable to produce sealed packages containing a food product. 
     BACKGROUND ART 
     As is known, many pourable food products, such as fruit or vegetable juice, pasteurized or UHT (ultra-high-temperature treated) milk, wine, etc., are sold in packages made of sterilized packaging material. 
     A typical example of this type of package is the parallelepiped-shaped package for pourable food products known as Tetra Brik Aseptic®, which is made by folding and sealing laminated strip packaging material. 
     The packaging material has a multilayer sheet structure substantially comprising one or more stiffening and strengthening base layers typically made of a fibrous material, e.g. paper, or mineral-filled polypropylene material, covered on both sides with a number of heat-seal plastic material layers, e.g. polyethylene film. In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a gas- and light-barrier material layer, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a heat-seal plastic material layer, and is in turn covered with another heat-seal plastic material layer forming the inner face of the package eventually contacting the food product. 
     Packages of this sort are produced on fully automatic Packaging Machines  1 , also known as Filling Machines, of the type shown in  FIG. 1 , wherein a continuous vertical tube  2  is formed from the web-fed packaging material  3 , which is sterilized by applying a chemical sterilizing agent such as a hydrogen peroxide solution, which, once sterilization is completed, is removed, e.g. evaporated by heating, from the surfaces of the packaging material. The web-fed packaging material  3  is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form the vertical tube  2 . 
     The vertical tube  2  is then filled downwards with the sterilized or sterile-processed pourable food product by means of a filling pipe  4  extending inside the tube  2  and equipped with a flow-regulating solenoid valve  5 , and is fed by known devices along a vertical path to a forming station  6 , where it is gripped along equally spaced cross sections by a jaw system including two or more pairs of jaws, which act cyclically and successively on the tube  2 , and seal the packaging material of the tube  2  to form a continuous strip of pillow packs  7  connected to one another by transverse sealing strips. Pillow packs  7  are then separated from one another by cutting the relative sealing strips, and are conveyed to a final folding station (not shown) where they are folded mechanically into the finished, e.g. substantially parallelepiped-shaped, packages  8 . 
     In the case of aseptic packages with an aluminium layer as the barrier material, the tube  2  is normally sealed longitudinally and transversely by an induction sealing device, which induces parasitic electric current in the aluminium layer to locally melt the heat-seal plastic material. More specifically, for transverse sealing, one of the jaws in each pair comprises a main body made of non-conducting material, and an inductor housed in a front seat in the main body; and the other jaw is fitted with pressure pads made of elastically yielding material, such as rubber. 
     When the relative pair of jaws grips the tube  2 , the inductor is powered to seal a cross section of the tube  2  by heat sealing the plastic cover material. When powered, the inductor generates a pulsating magnetic field, which in turn produces parasitic electric current in the aluminium sheet in the packaging material from which the vertical tube is made, thus locally melting the heat-seal plastic cover material. 
     In the case of packages without an aluminium layer or other electrically conductive materials, the tube  2  is normally transversely sealed by a hot plate which locally heats the packaging material from the outside to the inside. More specifically, one of the jaws in each pair is equipped with the hot plate, and the other jaw is fitted with one or more pressure pads made of elastically yielding material. In this type of sealing, known as hot plate sealing, a relatively long time is needed for the hot plate to locally melt the heat-seal plastic cover material, which results in a low package production rate. 
     In order to improve the performance of the Filling Machines, ultrasonic sealing devices of the type disclosed for example in EP-B-615907 in the name of the present Applicant have been introduced, which essentially comprise an anvil and an ultrasonic transducer, also known as sonotrode, operable to convert electrical energy into ultrasonic mechanical vibratory energy, which are mounted on respective jaws in each pair and cooperate in heating the packaging material by means of ultrasonic vibrations. 
     DISCLOSURE OF THE INVENTION 
     Components of ultrasonic sealing devices are typically quite expensive and hence warranty claims may occur if the lifetime thereof is shorter than warranted. Generally, a product warranty is contingent upon proper and regular use of the warranted product, and hence in order to meet both the manufacturers&#39; and the purchasers&#39; need for fair warranty terms and conditions and for fair settlements of warranty disputes, the need is felt by both parties for a solution that allows the operation of the ultrasonic sealing devices to be directly and continuously monitored over time and certified. 
     However, the operation of ultrasonic sealing devices has proven to be not easily directly monitorable because some components of ultrasonic sealing devices may be used in different Filling Machines at different times. Similarly, indirect monitoring of ultrasonic sealing devices based on production-related data has proven to be unreliable or even unfeasible when this data is not available. 
     The objective of the present invention is to provide a solution that allows the operation of ultrasonic sealing devices to be continuously, easily, reliably and efficiently monitored over time. 
     This objective is achieved by the present invention in that it relates to a Packaging Machine and an ultrasonic sealing device, as defined in the appended claims. 
     The operation of the ultrasonic sealing device is monitored over time by an electronic counter associated with the ultrasonic transducer of the ultrasonic sealing device to count the ultrasonic sealing cycles of the ultrasonic sealing device in the Packaging Machine. The electronic counter may be arranged either in the ultrasonic transducer housing or in a separate housing and electrically connected to the ultrasonic transducer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, a preferred embodiment, which is intended purely by way of example and is not to be construed as limiting, will now be described with reference to the attached drawings, wherein: 
         FIG. 1  shows a perspective view, with omitted parts removed, of a Packaging Machine operable to produce sealed packages containing food products from a tube of packaging material; 
         FIG. 2  shows an electric diagram of an electronic counter operable to count the number of sealing cycles of an ultrasonic sealing device in a Packaging Machine; and 
         FIG. 3  shows time charts of electric signals in the electronic counter of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is presented to enable a person skilled in the art to make and use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, without departing from the scope of the claimed invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein and defined in the appended claims. 
       FIG. 2  shows an electric diagram of an electronic counter provided in an ultrasonic sealing device in the Filling Machine shown in  FIG. 1  to count the sealing cycles or operations performed by the ultrasonic sealing device. 
     The electronic counter, referenced by  10 , includes:
         a couple of input terminals  11 . 1 ,  11 . 2  intended to be electrically connected to an ultrasonic sealing device  12 , the sealing operations of which, hereinafter referred to as ultrasonic sealing cycles, are to be counted;   a balanced capacitive voltage divider  13  connected to the input terminals  11 . 1 ,  11 . 2 ;   a voltage bridge rectifier  14  connected to the balanced capacitive voltage divider  13 ;   a stabilized electrical power supply  15 , a voltage meter  16  and a counting pulse generator  17  connected to the voltage bridge rectifier  14 ; and   a microprocessor-based counter  18  connected to the stabilized electrical power supply  15 , the voltage meter  16  and the counting pulse generator  17  and configured to count both the ultrasonic sealing cycles of the ultrasonic sealing device  12  and the production cycles of the Filling Machine  1 .       

     More in detail, the ultrasonic sealing device  12  is shown schematically in  FIG. 2  limited to only those parts thereof that are necessary to understand the operation of the electronic counter  10  according to the present invention. The ultrasonic sealing device  12  includes an electrical power source  19  operable to supply a pulsed AC power signal V US , and an ultrasonic transducer or sonotrode  20  electrically coupled to the electrical power source  19  to receive and responsively convert the pulsed AC power signal V US  into ultrasonic mechanical vibrations to heat seal the sheet packaging material  3 . 
     The electronic counter  10  may be arranged either in the ultrasonic transducer housing or in a separate housing and electrically connected to the ultrasonic transducer  20 . Serial numbers of both the electronic counter  10  and the ultrasonic transducer  20  are indissolubly associated with each other during assembly and recorded in an appropriate paper or electronic register kept by the ultrasonic transducer manufacturer. 
     As shown in  FIG. 3 , the pulsed AC power signal V US  is a train of AC voltage signals spaced apart by one and the same electrical dwell time DT, the value of which depends on the capacity (packages/hour) of the Filling Machine  1  and may be e.g. 0.7 sec. Each AC voltage signal is a sine wave voltage signal with a frequency of few tens of kHz, an RMS (Root Mean Square) amplitude of about a thousand of volts, and a time duration which varies depending on the operation to be performed. In the specific example described, each sine wave voltage signal has a time duration TD which may be either not lower than 70-80 msec, typically 100 ms, during ultrasonic sealing, or of about 50 msec during calibration of the ultrasonic sealing device  12 . In fact, typically every 10 ultrasonic sealing cycles, a calibration cycle is performed to determine the loadless power absorption of the ultrasonic transducer  20  so as to compensate for wear-related drifts thereof. 
     The balanced capacitive voltage divider  13  is connected to the input terminals  11 . 1 ,  11 . 2  to receive the pulsed AC power signal V US  and is designed to output a divided pulsed AC power signal V DIV  having the same time and frequency characteristics as the pulsed AC power signal V US , but a reduced amplitude of the AC voltage signals. In the specific example shown in  FIG. 2 , the balanced capacitive voltage divider  13  includes an even number of capacitors, in the number of six in the example shown in  FIG. 2 , which are series-connected between the input terminals  11 . 1 ,  11 . 2 , and wherein the intermediate node of series-connected capacitors defines the output of the balanced capacitive voltage divider  13 . 
     The voltage bridge rectifier  14  is connected to the output of the balanced capacitive voltage divider  13  to receive the divided pulsed AC power signal V DIV  and is operable to full-wave rectify the divided pulsed AC power signal V DIV  and output a pulsed full-wave rectified power signal V RT . As shown in  FIG. 3 , the pulsed full-wave rectified power signal V RT  is a train of full-wave rectified voltage signals spaced apart by the aforementioned electrical dwell time DT. Each full-wave rectified voltage signal is a positive or negative half-sine wave voltage signal with a time duration TD equal to that of an AC voltage signal in the pulsed AC power signal V US , a frequency twice that of an AC voltage signal and a positive or negative amplitude half the peak-to-peak amplitude of an AC voltage signal. Moreover, from an operational point of view, each full-wave rectified voltage signal represents an ultrasonic sealing pulse supplied to the ultrasonic transducer  20  of the ultrasonic sealing device  12 , and results in an ultrasonic sealing cycle of the ultrasonic sealing device  12 . 
     The stabilized electrical power supply  15  is connected to the output of the voltage bridge rectifier to receive the pulsed full-wave rectified power signal V RT  and is designed to output a stabilized supply voltage V ST , for example of 3.3 or 5 volts, for the microprocessor-based counting circuit  18 . In particular, the stabilized electrical power supply  15  comprises an input stage  21  and a cascade-connected electrical power supply stage  22 , wherein the input stage  21  includes an capacitor and a parallel-connected Zener diode which are provided to receive the pulsed full-wave rectified power signal V RT  and to output an electrical voltage for the cascade-connected electrical power supply stage  20 . More in detail, the capacitor has such a high capacitance, in the example shown in  FIG. 2  of about 100 μF, to maintain the electrical voltage across thereto almost stable between successive ultrasonic sealing cycles, which electrical voltage in turn represents the electrical voltage supplied to the cascade-connected electrical power supply stage  20  and would tend to drop between successive ultrasonic sealing cycles due to the power consumption of the microcontroller-based counting stage  18 . The Zener diode is instead provided to limit the maximum electrical voltage supplied to the cascade-connected electrical power supply stage  20  and protect it against higher voltage. 
     The voltage meter  16  essentially includes an RC filter which is connected to the input stage  21  of the stabilized electrical power supply  15  to receive the same electrical voltage as that supplied to the cascade-connected electrical power supply stage  20  of the stabilized electrical power supply  15 , and is designed to output a voltage level signal V LEV  indicative of the amplitude of the electrical voltage across the capacitor of the input stage  21  of the stabilized power supply  15 . 
     The counting pulse generator  17  essentially includes an RC filter connected to the output of the voltage bridge rectifier  14  to receive the pulsed full-wave rectified power signal V RT  and designed to generate counting pulses V P  for the microprocessor-based counting circuit  18 . In particular, the RC filter is designed to generate a generally rectangular counting pulse for each full-wave rectified voltage signal in the pulsed full-wave rectified power signal V RT . In view of the characteristics of each of full-wave rectified voltage signal, as shown in  FIG. 3 , a counting pulse represents an ultrasonic sealing cycle of the ultrasonic sealing device  12  and hence will have a time duration TD equal to that of a full-wave rectified voltage signal supplied to the ultrasonic transducer  20 , namely equal to or higher than 70-80 msec during ultrasonic sealing, or of about 50 msec during calibration of the ultrasonic sealing device  12 . 
     The microprocessor-based counter  18  includes a microcontroller  23  connected to the stabilized electrical power supply  15  to receive the stabilized supply voltage V ST , to the voltage meter  16  to receive the voltage level signal V LEV , and to the counting pulse generator  17  to receive the counting pulses V P ; a time clock  24  in the form of a piezoelectric crystal (quartz) oscillator connected to the microcontroller  23  to provide the latter with a stable clock signal; a programming connector or port  25  connected to the microcontroller  23  to allow the latter to be programmed by an appropriately programmed external electronic programming device when the ultrasonic sealing device  12  is inoperative; and a reading/writing connector or port  26 , such as an RS-232 serial port, connected to the microcontroller  23  to allow the latter to be read/written by an appropriately programmed external electronic reading/writing device when the ultrasonic sealing device  12  is inoperative. 
     The microcontroller  23  is supplied with electrical power from either the electrical power source  19  of the ultrasonic sealing device  12 , when the ultrasonic sealing device  12  is operative, or an external electronic device connected to either the programming port  25  or the reading/writing port  26 , when the ultrasonic sealing device  12  is inoperative. In particular, when the ultrasonic sealing device  12  is operative, the pulsed AC voltage signal V US  supplied by the electrical power source  12  thereof is first converted by the stabilized power supply  16  into a stabilized supply voltage V ST , which is then supplied to an appropriate supply pad of the microcontroller  23 . 
     Moreover, depending on the source of electrical power, the microprocessor  23  is appropriately programmed to operate in three mutually exclusive operating modes:
         in a Counting Mode, when the ultrasonic sealing device  12  is operative and the microcontroller  23  is supplied with electrical power from the electrical power source  19  of the ultrasonic sealing device  12 ;   in a Terminal Mode, when the sealing device  12  is inoperative and the microcontroller  23  is supplied with electrical power from the external electronic reading/writing device connected to the reading/writing port  26 ; and   in a Programming Mode, when the sealing device  12  is inoperative and the microcontroller  23  is supplied with electrical power from the external electronic programming device connected to the programming port  25 .       

     In the Counting Mode, the microcontroller  23  implements a volatile counter, in the form of a temporary internal register of the microcontroller  23 , to count the ultrasonic sealing cycles of the ultrasonic sealing device  12 , and, optionally, an additional volatile counter, in the form of a temporary internal register of the microcontroller  23 , to count the continuous production cycles of the Filling Machine  1  on which the ultrasonic sealing device  12  is installed. 
     In particular, as far as the ultrasonic sealing cycle counter is concerned, the microcontroller  23  is programmed to discriminate between ultrasonic sealing cycles and calibration cycles of the ultrasonic sealing device  12 , so as to increase the ultrasonic sealing cycle counter when an ultrasonic sealing cycle occurs. To do so, the microcontroller  23  is programmed to:
         distinguish the counting pulses V P  having a time duration TD equal to or higher than 70-80 msec from those having a time duration TD lower than about 50 msec by appropriately determining the time duration TD of each counting pulse supplied thereto. To do so, the time duration TD of each counting pulse V P  is determined and then compared with a time threshold having an intermediate value between the aforementioned time durations TD; and   increase by one the value in the ultrasonic sealing cycle counter when an ultrasonic sealing cycle is distinguished.       

     As far as the production cycle counter is concerned, the microcontroller  23  is programmed to determine when a production cycle of the Filling Machine  1  occurs, defined as the time span between the Filling Machine  1  being switched on and off, so as to increase the production cycle counter when a production cycle ends. To do so, the microcontroller  23  is programmed to:
         sense the voltage level signal V LEV  supplied by the voltage meter  16  to detect the amplitude of the electrical voltage across the capacitor of the input stage  21  of the stabilized power supply  15  falling below a switching-off supply voltage of the microcontroller  23 , this event being indicative of the ultrasonic sealing device  12  being switched off and the production cycle of the Filling Machine  1  being terminated; and   increase by one the value in the production cycle counter when the voltage level signal V LEV  is indicative of the production cycle of the Filling Machine  1  being terminated.       

     In the end, in order to prevent the values in both the ultrasonic sealing cycle counter and the production cycle counter from being lost when the microcontroller switches off, the microcontroller  23  is further programmed to:
         permanently, unresettably and unerasably store in an internal non-volatile memory, such as an EEPROM, of the microcontroller  23  the values in both the ultrasonic sealing cycle counter and the production cycle counter when the voltage level signal V LEV  is indicative of the amplitude of the electrical voltage across the capacitor of the input stage  21  of the stabilized power supply  15  falling below the switching-off supply voltage of the microcontroller  23 .       

     When the ultrasonic sealing device  12  is again operated, the ultrasonic sealing cycle counter and the production cycle counter are again implemented and initialized to the values stored in the internal non-volatile memory of the microcontroller  23 . 
     In the Terminal Mode, data such as the serial number of the electronic counter  10 , the amount of the ultrasonic sealing cycles of the ultrasonic sealing device  12  and the amount of the production cycles of the Filling Machine  1 , may be read from the internal non-volatile memory of the microcontroller  23  via appropriate reading commands sent by an external electronic reading/writing device. Data, such as the serial number of the electronic counter  10  and, optionally, the serial number of the associated ultrasonic transducer  20 , may also be written in the internal non-volatile memory of the microcontroller  23  via appropriate writing commands sent by the external electronic reading/writing device. Other reading/writing commands may also be sent to the microcontroller  23  by the external electronic reading/writing device to read/write other internal registers of the microcontroller  23  for testing/debugging purposes. 
     In the end, in the Programming Mode the microcontroller  23  is appropriately programmed to operate as previously described. 
     The advantages that the electronic counter  10  according to the present allows to achieve may be readily appreciated by the skilled person. In particular, the electronic counter  10  allows the operation of an ultrasonic sealing device  12  to be directly and continuously monitored over time, and in particular the amount of ultrasonic sealing cycles performed by the ultrasonic sealing device  12  to be easily, reliably and efficiently determined, so allowing warranty-related issues to be fairly tackled.