Method for detecting and tracking a feature of a web of packaging material

Abstract

A method (600) for detecting and tracking a feature of a web of packaging material (102), using a first capacitor (106) placed at a distance (d) from the web of packaging material (102) is provided. The method (600) comprises; feeding (602) a section of the web of packaging material (102) to a first position (p), so that the section influences a dielectric property of the first capacitor (106), measuring (604), at a point of time (t), a capacitance of the first capacitor (106), and determining (612) the feature of the section passing the first capacitor (106) at the point of time (t), based on the capacitance.

Claims

1. A method for detecting and tracking a feature of a section of a web of packaging material, using a first capacitor placed at a distance from the web of packaging material, the method comprising: feeding the section of the web of packaging material to a first position, so that the section influences a dielectric property of the first capacitor; measuring, at a point of time, a capacitance of the first capacitor; determining the feature of the section passing the first capacitor at the point of time based on the capacitance; tracking the feature through a roll fed packaging machine using the point of time of the measurement; and adapting settings of a device of the roll fed packaging machine based on the feature.

2. The method according to claim 1, wherein the method further comprises: measuring, at the point of time, a capacitance of a second capacitor at a second position, wherein the second position is located downstream the first position; and determining a differential capacitance as a difference between the capacitance of the first capacitor and the capacitance of the second capacitor, wherein the step of determining the feature of the section passing the first capacitor at the point of time is based on the differential capacitance.

3. The method according to claim 2, wherein a first capacitor plate of the first capacitor is connected to a second capacitor plate of the second capacitor.

4. The method according to claim 1, wherein a roller of the roll fed packaging machine is placed opposite to the first capacitor and the step of measuring the capacitance is performed with the web being in contact with the roller.

5. The method according to claim 1, wherein the method further comprises: determining oscillations in the web affecting the distance between the first capacitor and the web; and compensating for the oscillations in the step of determining the feature.

6. The method according to claim 1, wherein the distance between the first capacitor and the web of packaging material is 2-5 mm.

7. The method according to claim 1, wherein the first capacitor is a planar capacitor.

8. The method according to claim 1, wherein the feature is related to a thickness of the web of packaging material.

9. The method according to claim 1, wherein the feature is a splice between two ends of the web of packaging material.

10. The method according to claim 1, wherein the feature is an area where material has been added to or removed from the web of packaging material.

11. An arrangement for detecting and tracking a feature of a section of a web of packaging material in a roll fed packaging machine, the arrangement comprising: a first capacitor; a capacitor measurement unit; and a control unit comprising a processor and a memory, the control unit being communicatively connected to the first capacitor, wherein the control unit is configured to: send a request to the capacitor measurement unit to inject a known number of charges to the first capacitor placed at a distance from the web of packaging material, receive indication that the section of the web of packaging material has been fed to a first position, so that the section influences a dielectric property of the first capacitor, measure, by the capacitor measurement unit, at a point of time, a capacitance of the first capacitor, and determine the feature of the section passing the first capacitor at the point of time, based on the capacitance.

12. The arrangement of claim 11, further comprising a second capacitor, wherein the control unit is further configured to: measure, by the capacitor measurement unit, at the point of time, a capacitance of the second capacitor at a second position, wherein the second position is located upstream from the first position, and determine a differential capacitance as a difference between the capacitance of the first capacitor and the capacitance of the second capacitor, wherein the step of determining the feature of the section passing the first capacitor at the point of time is based on the differential capacitance.

13. A roll fed packaging machine, comprising: a reel receiver for receiving a roll of a web of packaging material; a longitudinal sealing device for forming a tube of the web of packaging material; a product filling pipe for filling product into the tube; a transversal sealing device for forming packages, filled with the product, from the tube; and an arrangement for detecting and tracking a feature of the web of packaging material in the roll fed packaging machine configured to perform the method of claim 1.

14. The roll fed packaging machine according to claim 13, wherein a control unit of the arrangement is communicatively connected to a control system of the roll fed packaging machine such that the feature is tracked throughout the roll fed packaging machine; and wherein the control system of the roll fed packaging machine is configured to adapt settings of one or more devices of the roll fed packaging machine based on the feature being tracked.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which

(2) FIG. 1 is a cross sectional view of a placement of a capacitor.

(3) FIGS. 2a and 2b illustrates two different scenarios for a capacitor placed close to a web of packaging material.

(4) FIGS. 3a and 3b illustrates two different scenarios for two capacitors placed close to a web of packaging material.

(5) FIG. 4 illustrates a scenarios for two capacitors placed close to a web of packaging material.

(6) FIG. 5 illustrates an example of a pair of capacitors.

(7) FIG. 6 is a flow-chart of a method for detecting and tracking a feature of a web of packaging material.

(8) FIG. 7 is a schematic view of an arrangement for detecting and tracking a feature of a web of packaging material in a roll fed packaging machine.

(9) FIG. 8 is a schematic view of a roll fed packaging machine.

(10) The figures should not be considered limiting; instead they are used for explaining and understanding.

DETAILED DESCRIPTION

(11) The present invention will now be described more fully hereinafter with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled person.

(12) FIG. 1 illustrates a placement of a capacitor 106 in relation to a web of packaging material 102. When measuring a capacitance of the capacitor 106 to detect a feature of the web of packaging material 102, a suitable placement of the capacitor 106 may be in connection to a roller 104. In this region, vibrations or oscillations of the web 102 are smaller than for instance in between two rollers. The capacitor may be curved with the same diameter as the roller 104, so that it can be placed along the bend where the web of packaging material 102 is in contact with the roller 104. The arrows indicate the moving direction of the web of packaging material.

(13) FIG. 2a illustrates, in a cross-sectional view, the capacitor 106 placed at a distance d from the web of packaging material 102. In the scenario shown in FIG. 2a no distinctive feature is present under the capacitor, at position p. The distance d may be 2-5 mm. How close the capacitor 106 can be placed to the web of packaging material 102 may depend on how much the web vibrates. The distance d should be sufficiently large so that the web of packaging material 102 cannot touch the capacitor 106, since this may cause damage either to the capacitor 106 or to the web of packaging material 102. Further, the distance d should be sufficiently small so that the web of packaging material 102 is fed through a region where it affects the dielectric properties of the capacitor 106. The closer it is, the more clear the effect is.

(14) The dielectric properties can be affected by the distance between the web of packaging material 102 and the capacitor 106. It may also be affected by the thickness of the web of material, since a volume of air is replaced by the same volume of packaging material and the packaging material has different dielectric properties than air.

(15) The distance d may also be dependent on the thickness of the packaging material as illustrated in FIG. 2b. FIG. 2b illustrates, in a cross-sectional view, the capacitor 106 placed at the same distance d as in FIG. 2a from the web of packaging material 102. In the scenario illustrated in FIG. 2b a feature, in the form of a splice, is present under the capacitor 106, at the position p. Due to how the splice is formed, a part of the web reaches closer to the capacitor 106 than the distance d.

(16) Herein, the web of packaging material 102 is slightly tilted, compared to in FIG. 2a. The reason is due to how the splice is formed. When looking at a small region around the splice, this may be a more accurate illustration. Looking at the web of packaging material 102 at a distance, the web 102 is significantly parallel to the capacitor 106 as in FIG. 2a. How the splice is formed and how sections of the web placed next to the splice are affected depend on the packaging material.

(17) The splice can be the junction between two independent reels of packaging material. Normal operation of packaging machines requires the creation of splices when one of the two reels in the Automatic Splicing Unit, ASU, is about to finish. Alternative, the splice can be a doctoring splice. Such a splice can be formed when a part of the web of packaging material has to be removed. The doctoring splice may then be formed to join the two ends created from removing a part of the web. Thus, the splice appears as a thicker part of the web of packaging material because of the junction between two ends. Measuring the capacitance of the scenario in FIG. 2b may yield a higher value than in the scenario in FIG. 2a, because of the thicker part of the web.

(18) The increased thickness of the web of packaging material 102 at the splice, due to the overlapping packaging material, may result in the web of packaging material 102 passing the capacitor 106 at a smaller distance than the distance d. The thicker the packaging material is, the closer the web of packaging material 102 may come to the capacitor 106.

(19) The dielectric properties may be affected by that the distance d is decreased due to the increased thickness caused by the splice, but also in that more packaging material is provided close to the first capacitor 106, i.e. two layers of packaging material are provided.

(20) FIGS. 3a and 3b illustrates the two scenarios of FIGS. 2a and 2b respectively, but with a second capacitor 302 at position p in addition to the first capacitor 106 at position p. The first and second capacitor 106, 302 are herein placed at the same distance d from the web of packaging material 102. Further, the first and second capacitor 106, 302 is placed at a separational distance d from each other. The separational distance d may be large enough so that a feature can affect the capacitance of either the first or second capacitor 106, 302 differently. As an effect, the differential capacitance may indicate the presence of a feature in a clear way. For instance, the separational distance d may be 10 mm.

(21) The feature may be detected either at position p, as illustrated herein, or at position p when the feature has moved upstream.

(22) FIG. 4 illustrates a different type of feature being detected by the first and second capacitor 106, 302. The feature can be an area 402 where material has been added to or removed from the web of packaging material 102. Herein the feature is illustrates as an area 402 where material has been removed. Such an area 402 may be a pre-laminated hole, PLH, i.e. an area in which a carton layer has been removed. The PLH may later be covered by a cap or other opening device Another alternative may be folding lines for folding the web 102 into a package. The folding lines, also sometimes referred to as weakening lines, may be areas in which the packaging material has been compressed. By having these areas, formed as lines, folding of the web can be facilitated and a risk of having unintentional folding can be reduced.

(23) FIG. 5 illustrates, by way of example, an arrangement 500 comprising the first and the second capacitor 106, 302. The first and second capacitors 106, 302 are herein illustrated as interdigital planar capacitors. The plates of the interconnected capacitors may have a plurality of sub-plates. Even though illustrated with ten sub-plates each, the number of sub-plates may vary.

(24) The physical form and construction of a general capacitor may vary widely. However, a typical capacitor has two plates forming two electrical conductors. The two plates are typically separated by a dielectric medium. In the proposed embodiment of FIG. 5, the first and second capacitor 106, 302 comprises a first and second plate respectively, that is connected to each other, thus forming a common plate 504. The first and second capacitor 106, 302 further comprises a third and fourth plate 502, 506 respectively, so that each capacitor comprises two plates separated by a dielectric medium.

(25) The dielectric medium of the first and second capacitor 106, 302 can be formed by the volume of the surrounding air and material, such as the web of packaging material 102.

(26) Alternatively, the common plate 504 may be separated into two plates, one for each capacitor 106, 302.

(27) For low manufacturing costs and low complexity, the plates can be manufactured as a standard flexible printed circuit board, PCB.

(28) The first and second capacitor 106, 302 may have a width w corresponding to a width of the feature to be detected, in order to maximize the variation in capacitance caused by the feature. As a non-limiting example, the width w may be 10-20 mm, or more preferably, 16 mm.

(29) Each plate 502, 504, 506 may be provided with a excitation connector 508a-c, for connecting the capacitors to a source of electrical charges.

(30) As previously mentioned, having two capacitors makes it possible to determine a differential capacitance. The change in capacitance when a feature is present can be in the range of femtofarads. Thus, removing noise by using the differential capacitance is advantageous, and it makes the method robust to common mode noise, varying distance between the capacitors and the web, movement of the web, different types of packaging material, support structure and roller.

(31) FIG. 6 is a flow-chart illustrating the steps of a method 600 for detecting and tracking a feature of a web of packaging material 102, using a first capacitor 106 placed at a distance d from the web of packaging material 102.

(32) In a first step S602, a section of the web of packaging material 102 is fed to the first position p, so that the section influences the dielectric property of the first capacitor 106.

(33) In a second step S604, a capacitance of the first capacitor 106 is measured at a point of time t.

(34) In a third step S612, the feature of the section passing the first capacitor 106 at the point of time t is determined, based on the measured capacitance.

(35) Optionally, in a fourth step S606, the capacitance of the second capacitor 302 may be measured at the point of time t at a second position p. The second position p may be located downstream the first position p. Put differently, the capacitance of the first and second capacitor 106, 302 are measured at the same point of time but on different sections of the web. Hence the two capacitors may experience different dielectric mediums.

(36) Optionally, in a fifth step S608, a differential capacitance may be determined as a difference between the capacitance of the first capacitor 106, and the capacitance of the second capacitor 302.

(37) The step of determining S612 the feature of the section passing the first capacitor 106 at the point of time t may be based on the differential capacitance.

(38) The step of measuring S604 the capacitance may be performed with the first position p at a roller of a roll fed packaging machine.

(39) Optionally, in a sixth step S614, the feature may be tracked, using the point of time t of the measurement.

(40) Optionally, in a seventh step S616, settings of a device of a roll fed packaging machine may be adapted based on the presence of the feature.

(41) Optionally, in an eighth step S610, oscillations in the web 102 affecting the distance d between the capacitor 106, 302 and the web 102 may be determined. The step of determining S608 the feature may be compensated for the determined oscillations.

(42) Even though described in a certain order, the different steps may also be performed in other orders, as well as multiple times. For instance, the web of packaging material may be continuously fed past the capacitor, so that features can be detected in any section of the web. The method may be repeated at a subsequent point of time t so that a feature can be detected at a subsequent section of the web. The subsequent section of the web may partly overlap with the previous section, depending on the speed of the web, and the length of the time interval between the previous and subsequent point of time.

(43) FIG. 7 is a schematic view of an arrangement 700 for detecting and tracking a feature of a web of packaging material 102 in a roll fed packaging machine. The arrangement comprises a first capacitor 702, a capacitor measurement unit 704, a control unit 706 comprising a processor 708 and a memory 710, communicatively connected to the capacitor 702. The memory may hold instruction for the processor to execute. The control unit is configured to send a request to the capacitance measurement unit 704 to inject a known amount of charges to the first capacitor 702 placed at a distance d from the web of packaging material 102, receive indication that a section of the web of packaging material 102 has been fed to a first position p, so that the section influences a dielectric property of the first capacitor 702, measure, by the capacitor measurement unit 704, at a point of time t, a capacitance of the first capacitor 702, and determine the feature of the section passing the first capacitor 702 at the point of time t, based on the capacitance.

(44) The arrangement 700 may further comprise a second capacitor 712. The control unit 706 may be further configured to measure, by the capacitor measurement unit 704, at the point of time t, a capacitance of the second capacitor 712 at a second position p, wherein the second position p is located upstream from the first position p, determine a differential capacitance as a difference between the capacitance of the first capacitor 702, and the capacitance of the second capacitor 712, wherein the step of determining the feature of the section passing the first capacitor 702 at the point of time t, is based on the differential capacitance.

(45) The arrangement may be provided as an update kit to a pre-existing roll fed packaging machine.

(46) FIG. 8 is a schematic view of a roll-fed packaging machine 800. The roll fed packaging machine 800 is enabled for detecting and tracking the feature of a roll of packaging material 102. The roll fed packaging machine 800 can comprise a reel receiver 802 for receiving a reel of packaging material 102, a longitudinal sealing device 804 for forming a tube 806 of the web of packaging material 102, a product filling pipe 808 for filling product 810 into the tube 806, a transversal sealing device 812 for forming packages 814, filled with the product 810, from the tube 806, and an arrangement 700 for detecting and tracking a feature of a web of packaging material in a roll fed packaging machine, as described in connection to FIG. 7. The roll fed packaging machine 800 may be any common roll fed packaging machine provided with the arrangement 700. The arrangement may preferably be provided in connection with a roller of the packaging machine, as illustrated in FIG. 1.

(47) The arrangement 700 may be installed as an integral part of the machine 800, but it may also be installed as an upgrade kit at a later point of time. Further, even though not illustrated, the arrangement 700 may be connected to a remote server such that program code of the arrangement can be updated if required, and also to provide for that reference data linked to features can be retrieved by the arrangement, thereby making it possible to update the arrangement 700 if e.g. a new type of packaging material is to be used. Further, having the arrangement 700 connected to the remote server, data can be collected and combined with similar data retrieved from other similar arrangements. By doing so, the reference data can be continuously improved by using e.g. ML or AI algorithms.

(48) The roll fed packaging machine 800 may further comprise a discarding unit 816 for discarding certain packages. For instance, in case the ASU splice or the doctoring splice is detected in the web, this may be traced through the machine. The package formed from the web and that comprise the ASU splice or the doctoring splice may be discarded. To be on the safe side, a number of packages before and after this package may also be discarded. With an increased traceability made possible by the arrangement 700, a number of discarded packages may be reduced.

(49) The control unit 706 may be communicatively connected to a control system of the roll fed packaging machine 800 such that the feature can be tracked throughout the roll-fed packaging machine 800. Further, the control system of the roll fed packaging machine 800 may be configured to adapt settings of one or more devices of the roll fed packaging machine 800 based on the feature being tracked. As an example, if a splice is present in a package, more power may be provided for the longitudinal sealing. Having two layers of packaging material instead of only one layer may namely require more power, i.e. additional heating, to provide for that a reliable sealing is made. Put differently, if the machine knows when the splice is present, it may alter settings of the longitudinal sealing device 804 to compensate for this. Further, packages 814 comprising the splice may have to be discarded due to food safety reasons. A common practice is to also discard one package before and one package after the package comprising the splice. Again, by tracking the splice, the discarding unit 816 can know what packages 814 to discard.

(50) From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.