Method of determining the volume flow and the filling degree at a packaging machine

Abstract

A method of operating a sealing station of a packaging machine for producing, in the case of possibly varying filling degrees, packages with at least substantially similar package appearances, the method comprising the execution of a comparison between a detected pressure curve and a reference pressure curve, and the calculation of a filling degree of the package positioned within the sealing station on the basis of the comparison between the detected pressure curve and the reference pressure curve, and/or the calculation of a volume flow with respect to the pressure curve or the reference pressure curve, and the setting of at least one process parameter at the packaging machine with due regard to the calculated filling degree and/or the volume flow.

Claims

1. A method of operating a sealing station of a packaging machine for producing, in case of varying filling degrees, packages with at least substantially similar package appearances, the method comprising: filling a free package volume with a gas from an initial pressure prevailing in the package volume up to a predetermined gas flushing pressure for creating a desired atmosphere, the free packaging volume enclosed between a lower and an upper packaging material and defined by at least one package positioned within the sealing station; detecting a pressure curve using at least one pressure-detecting sensor system connected to the package volume at least temporarily during the filling of the package volume, the pressure curve being detected based on a time-dependent pressure curve between the initial pressure and the predetermined gas flushing pressure; comparing the detected pressure curve with a reference pressure curve, the reference pressure curve being detected based on a time-dependent pressure curve for filling a known free reference package volume of at least one reference package positioned within the sealing station with the gas between the initial pressure and the predetermined gas flushing pressure; calculating at least one of a filling degree of the at least one package positioned within the sealing station and a volume flow for the package volume based on the comparison between the detected pressure curve and the reference pressure curve; and setting at least one process parameter of the packaging machine with regard to the calculated filling degree and/or the volume flow.

2. The method according to claim 1, wherein a quotient resulting from a ratio of a time detected for the pressure curve and a time detected for the reference pressure curve is subtracted from a whole for calculating the filling degree.

3. The method according to claim 1, wherein the calculating is carried out in real time per machine cycle, and the method further comprises executing an automated adaptation of the at least one process parameter based on the real-time calculation of the filling degree and/or the volume flow.

4. The method according to claim 1, wherein the at least one process parameter is an offset pressure used during one of the filling process or at least one subsequent filling process, to fill the package volume with gas until a reduced pressure is reached, wherein the reduced pressure results from a gas flushing target pressure for finished packages minus a calculated offset pressure.

5. The method according to claim 4, further comprising determining a calculated offset pressure using the Boyle-Mariotte law, taking into account a partial volume of the package volume displaced by a sealing stroke and the free package volume, which can be determined in view of the calculated filling degree, including the gas flushing target pressure of finished packages to be generated in the free package volume.

6. The method according to claim 1, wherein the at least one process parameter comprises a gas velocity reached at respective gas pins configured for filling the package volume.

7. The method according to claim 1, wherein the at least one process parameter comprises a valve setting value which influences an evacuating process and/or the gas flushing process.

8. The method according to claim 1, wherein the at least one process parameter triggers a malfunction indicator at the packaging machine.

9. The method according to claim 1, wherein the free package volume is operably connected to a collecting volume of known size and the free package volume is calculated using a detected pressure compensation.

10. The method according claim 1, wherein the at least one process parameter is continuously adjusted based upon averaged values of at least one of the filling degree and the volume flow.

11. The method according to claim 1, wherein the filling of the free package volume is performed such that a pressure compensation between a plurality of packages positioned within the sealing station occurs during a sealing stroke.

12. The method according to claim 1, wherein calculating the filling degree includes subtracting a supply line volume connected to the package volume.

13. A packaging machine for producing, in case of varying filling degrees, packages with at least substantially similar package appearances, the packaging machine comprising: a sealing station and a control unit, the control unit being functionally connected to a sensor system provided at the sealing station and operable to detect a pressure of a package volume provided within the sealing station; wherein the control unit is operable to calculate at least one of a filling degree associated with the package volume and a volume flow associated with the package volume based on a comparison between a time-dependent pressure curve and a time-dependent reference pressure curve, wherein the time-dependent pressure curve is detectable between predetermined pressure levels at least temporarily during a filling process of the package volume enclosed within the sealing station and the time-dependent reference pressure curve is representative of a filling process of a known reference volume and stored in the control unit between the predetermined pressure levels; and wherein the control unit is operable to set at least one process parameter of the packaging machine based upon at least one of the calculated filling degree and the volume flow.

14. A method of operating a sealing station of a packaging machine for producing, in case of varying filling degrees, packages with at least substantially similar package appearances, the method comprising: filling a free package volume enclosed between a lower and an upper packaging material and defined by at least one package positioned within the sealing station with a gas, the gas intended to be used for creating a desired atmosphere, and the free package volume is filled from an initial pressure prevailing in the package volume up to a predetermined gas flushing pressure; detecting, at least temporarily during filling of the package volume, a pressure curve using at least one pressure-detecting sensor system connected to the package volume, the pressure curve being detected based on a time-dependent pressure curve between the initial pressure and the predetermined gas flushing pressure; comparing the detected pressure curve with a reference pressure curve detected based on a pressure curve, which is time-dependent, for filling a known free reference package volume of at least one reference package positioned within the sealing station with the gas between the initial pressure and the predetermined gas flushing pressure; and setting at least one process parameter of the packaging machine based upon the comparison of the detected pressure curve with the reference pressure curve.

15. The method according to claim 14, wherein the at least one process parameter comprises an offset pressure used during the filling process and/or during at least one subsequent filling process, so as to fill the package volume with gas until a reduced pressure is reached, wherein the reduced pressure results from a gas flushing target pressure for finished packages minus a calculated offset pressure.

16. The method according to claim 14, wherein the at least one process parameter comprises a gas velocity reached at respective gas pins configured for filling the package volume.

17. The method according to claim 14, wherein the at least one process parameter comprises a valve setting value which influences an evacuating process and/or the gas flushing process.

18. The method according to claim 14, wherein the at least one process parameter triggers a malfunction indicator at the packaging machine.

19. A packaging machine for producing, in the case of varying filling degrees, packages with at least substantially similar package appearances, the packaging machine comprising: a sealing station and a control unit, the control unit being functionally connected to a sensor system that is provided at the sealing station and operable to detect a pressure of a package volume provided within the sealing station, wherein the control unit is operable to run a comparison between a time-dependent pressure curve and a time-dependent reference pressure curve; wherein the time-dependent pressure curve is detectable between predetermined pressure levels at least temporarily during a filling process of the package volume enclosed within the sealing station, and the time-dependent reference pressure curve is representative of a filling process of a known reference volume and stored in the control unit between the predetermined pressure levels; and the control unit is operable to set at least one process parameter of the packaging machine based upon the comparison between the time-dependent pressure curve and the time-dependent reference pressure curve.

Description

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) In the following, an advantageous embodiment of the present invention will be explained in more detail making reference to a drawing, in which the individual figures show:

(2) FIG. 1 is a schematic section view of a sealing station known in the art;

(3) FIG. 2 is a schematic side view of one embodiment of a packaging machine in accordance with the teachings of the present disclosure and configured in the form of a thermoform packaging machine;

(4) FIG. 3 is a schematic section view of one embodiment of a sealing station in accordance with the teachings of the present disclosure; and

(5) FIG. 4 is a schematic flow chart of one embodiment of a method in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

(6) The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures.

(7) The following detailed description of the invention references specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The present invention is defined by the appended claims and the description is, therefore, not to be taken in a limiting sense and shall not limit the scope of equivalents to which such claims are entitled.

(8) FIG. 1 shows in a schematic representation a sealing station S′ according to the prior art. The sealing station S′ comprises a sealing tool upper part SO′ as well as a sealing tool lower part SU′, which is adapted to be closed by the sealing tool upper part SO′ and configured for accommodating preshaped packaging troughs VM′. The packaging troughs VM′ shown in FIG. 1 accommodate therein package contents I′, in other words, products, with different filling degrees FG′.

(9) In FIG. 1, the sealing station S′ defines a sealing chamber SK′, in which the packaging troughs VM′ enclose, together with a top film O′ positioned thereabove, an airtight package volume P′ consisting of a partial volume V1′ and a partial volume V2′. The partial volume V1′ is composed of the sum of the respective packaging trough volumes created by the packaging troughs VM′ and not occupied by the products. The partial volume V2′ is an imaginary partial volume enclosed between the top film O′ and an imaginary plane E′ shown by a broken line. Based on the partial volume V2′, a connection gap SP′ is formed above the packaging troughs VM′, which, in particular during the filling process, allows the gas G′ to spread within the whole package volume P′.

(10) According to FIG. 1, a sealing tool SW′, for example, a vertically adjustable sealing frame, used for a sealing process is positioned within the sealing tool upper part SO′, the sealing tool SW′ being configured for moving, by means of a stroke movement H′, the top film O′ for the sealing process in the direction of the packaging troughs VM′ provided therebelow.

(11) In the embodiment shown in FIG. 1, the package volume P′, which consists of the sum of the respective partial volumes V1′, V2′, is first filled with a gas G′ up to a preset gas flushing pressure so as to create a desired atmosphere. The gas flushing pressure is traditionally generated from a difference between a gas flushing target pressure of finished packages and a preset gas offset pressure. By means of the subsequent stroke movement H′, the sealing tool SW′ forces the gas quantity contained in the partial volume V2′ into the partial volume V1′ not occupied by the product contents I′ within the packaging troughs VM′, so that, based on the assumption of a homogeneous filling level distribution, in other words, in the case of non-varying filling levels, the gas flushing target pressure can be established in the finished packages.

(12) As has already been explained hereinbefore in the introduction to the specification, the respective filling degrees of the packages provided may vary so that the above offset approach, which, contrary to actual circumstances, is based on the assumption of a homogeneous filling level distribution, results in the production of packages having different appearance characteristics.

(13) FIG. 2 shows, in a schematic view, a packaging machine 1 configured in the form of a thermoform packaging machine T. The packaging machine 1 comprises a forming station 2, a sealing station 3, a transverse cutting unit 4 as well as a longitudinal cutting unit 5. These components are arranged in this order in a working direction R on a machine frame 6.

(14) The machine frame 6 of the packaging machine 1 has arranged thereon a supply roll 7 from which a bottom film U is unwound as a lower packaging material 8. The bottom film U is conveyed into the forming station 2 by a feed unit, which is not shown. Using a thermoforming process carried out there, packaging troughs 14 are formed into the bottom film U using the forming station 2. Subsequently, the packaging troughs 14 are advanced to an infeed line 15, where they can be filled with a product 16 manually or in an automated manner. Subsequent to the infeed line 15, the packaging troughs 14 filled with the products 16 are advanced to the sealing station 3. Using the sealing station 3, the packaging troughs 14 can be sealed with a top film O, which defines an upper packaging material 10, so that closed packages V will be produced by sealing the top film O onto the packaging troughs 14. The closed packages V can be separated from one another using the transverse cutting unit 4 and the longitudinal cutting unit 5 and taken away using a discharge unit 13. It may be that the articles conveyed comprise empty packages LV, for example, due to an interruption in the package providing process.

(15) In addition, the packaging machine 1 shown in FIG. 2 is provided with an operating terminal 9, where process parameters can be set for the respective working stations provided at the packaging machine 1. The operating terminal 9 comprises a control unit 11, which is shown only schematically. The control unit 11 is configured to carry out arithmetic operations, in particular in real time during the production process, so as to control on this basis the packaging machine in a process-based manner, in other words, to cause the respective process parameters of the packaging machine to be adapted in a process-controlled manner, if necessary.

(16) The control unit 11 is connected to a sensor system 12 for detecting a pressure P.sub.IST (cf. FIG. 3) of a package volume P formed within the sealing station 3 according to FIG. 3. Making use of the sensor system 12, current pressure values, in other words, respective pressure curves, can be transmitted continuously to the control unit 11 during the production process, in other words, during the gas flushing and/or evacuating process.

(17) FIG. 2 additionally shows that the control unit 11 is connected to a schematically shown memory 17, so that, for generating process parameters, in particular for adapting the latter, the control unit 11 can resort to reference values stored in this memory 17. For example, it can compare the pressure curve detected as an input variable at the sealing station 3 using the sensor system 12 with a respective reference pressure curve of the memory 17. In so doing, it determines a filling degree and/or a volume flow using an algorithm in a first step and generates, based thereon, at least one process parameter as an output variable in a further step. On the basis of this process parameter, the production process can be adapted, so that the packaging machine 1 will be able to optimally adapt the production process taking place thereon to the respective filling states.

(18) FIG. 3 shows, in an isolated view, the sealing station 3 of the packaging machine 1 shown in FIG. 2.

(19) The sealing station 3 comprises a sealing tool upper part 20 as well as a sealing tool lower part 21, which enclose a sealing chamber 23. FIG. 3 additionally shows that two packaging troughs 14 with respective products 16 are accommodated in the sealing tool lower part 21, the respective filling degrees 22 of these packaging troughs 14 differing from one another.

(20) The packaging troughs 14 accommodated within the sealing station 3 enclose, together with the top film O arranged thereabove, a package volume P. An imaginary plane E, which is shown by a broken line, extends through the package volume P, thus dividing the latter into a partial volume V1 and a partial volume V2. The packaging trough 14 having a lower filling degree 22 and located on the right, when seen in the image plane, constitutes a part of the package volume P that is larger than that of the other packaging trough 14 with a higher filling degree 22 shown on the left next to the first-mentioned packaging trough 14.

(21) According to FIG. 3, the partial volume V2 enclosed by the top film O and the imaginary plane E as well as the partial volume V1 (free package volume P) provided within the packaging troughs 14 are adapted to be filled with a gas G via a line 26 and gas pins 29 provided thereon. For supplying gas, a gas source Q is provided. An evacuating process can be controlled using a (vacuum) pump VP. For the filling process and the evacuating process, valves 27a, 27b are formed in the line 26, these valves being controllable in particular in a process-controlled manner, for example, on the basis of detected pressure values.

(22) The line 26 has connected thereto a pressure sensor 18 as a sensor system 12 for detecting the pressure P.sub.IST prevailing within the package volume P. The pressure sensor 18 is functionally connected to the control unit 11, which is configured to use the pressure P.sub.IST, which is transmitted thereto as an input variable, for further calculations. In particular, the control unit 11 is able to determine the pressure curve resulting from the detected pressure values P.sub.IST during the filling of the package volume P and to compare it, optionally a section thereof, with a preset reference pressure curve so as to calculate on this basis using an algorithm a filling degree and/or a volume flow with respect to the packages V positioned within the sealing station 3, the control unit 11 generating on this basis at least one process parameter PP as an output variable.

(23) According to FIG. 3, the line 26 has connected thereto a collecting volume AV, which can be used for calculating the package volume P. In addition, FIG. 3 shows a supply line section 30 whose volume can be subtracted when the filling degree 22 is calculated.

(24) FIG. 4 shows in a schematic representation a method making use of the present invention.

(25) To begin with, the free package volume P is filled with a gas G via the line 26 in a first method step A, so as to create a desired atmosphere.

(26) During the filling process according to step A, the pressure is detected within the package volume P using the sensor system 12 according to method step B. This allows detection of a time-dependent pressure curve 27 for the pressure P.sub.IST prevailing within the package volume P between an initial pressure P1 and a predetermined gas flushing pressure P2. The control unit 11 may here be configured such that only a section of the pressure curve 27 will be taken into account for the continued process.

(27) According to FIG. 4, the pressure curve 27 detected in method step B is a linear pressure curve K.sub.IST.

(28) According to the further method step C, a comparison VG between the detected pressure curve 27 and a reference pressure curve 28 is made. The control unit 11 retrieves the reference pressure curve 28 from the memory 17 for making the comparison VG. The control unit 11 may be configured for retrieving, with respect to at least one process parameter predetermined for the production process at the packaging machine 1, in particular at the sealing station 3, a suitable reference pressure curve 28 from a plurality of reference pressure curves 28 provided on the memory 17. According to the reference pressure curve 28, a time-dependent reference pressure curve K.sub.REF is presented, which would occur in particular if empty packages LV used for the production process were gas flushed. For carrying out a meaningful comparison as well as for expediently deriving the filling degree 22, it will be advantageous to assume equal volume flows for the respective pressure curves 27, 28.

(29) After the execution of method step C, in other words, after having compared the respective gradients of the pressure curve 27 and of the reference pressure curve 28, the filling degree 22 and/or the volume flow {dot over (V)} is/are calculated according to the subsequent method step D. This is based in particular on the respective time intervals t and t* that elapsed for the pressure curve 27 as well as for the reference pressure curve 28, taking as a basis the package volume P and the respective pressure levels P1, P2.

(30) The calculated filling degree 22 and/or volume flow {dot over (V)} can be used by the control unit 11 in a further method step E for calculating at least one process parameter PP. The control unit 11 calculates, for example, an offset pressure P.sub.OFF, a gas velocity V.sub.GAS, a valve setting value x and/or it triggers, on this basis, a malfunction indicator y.

(31) Making use of the offset pressure P.sub.OFF, the control unit 11 will be able to calculate, in the light of a desired gas flushing target pressure P.sub.SOLL of finished packages V, a pressure P.sub.RED, the filling process A being controlled until this pressure P.sub.RED is reached. This is schematically shown in FIG. 4 by the broken line EZ.

(32) The principle according to the present invention is excellently suitable for use with a process-controlled packaging machine, in which respective working processes take place on a measurement-signal basis, so that, all things considered, both optimum process times as well as products of improved quality can be provided.

(33) From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.

(34) The constructions and methods described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention.

(35) As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.