Method and device for determining properties of containers made of paper or paperboard

Abstract

A method and apparatus for determining properties of containers made of paper or paperboard. Wherein the container (10) to be inspected is transported along a predetermined transport path and the container (10) has a base region (10a), a base body (10b) for receiving a filling material, and a mouth region, and wherein the container (10) consists at least in sections of a material comprising paper or cardboard, characterized in that the base body (10b) and the mouth region (10b) are connected to the base region (10a) and the base body (10b). According to the invention, at least one wall (12) of the container (10) is arranged between two electrodes (4, 6) and a voltage or an alternating electric field is applied to the electrodes (4, 6) and at least one electrical variable is determined, which characterizes the electric field established between the electrodes, and at least one variable characterizing the container (10) is determined on the basis of the electrical variable.

Description

Technical Field

[0001] The invention relates to a method and a device for determining properties of a container. Background Art

[0002] Such methods and devices are already known from the prior art. For example, it is known to determine properties of plastic containers during their production, such as the wall thickness of the container, etc. These properties are important for drawing inferences about the quality of the manufactured container, for example whether the determined wall thickness is within a set range.

[0003] In these methods, optical measuring devices are usually used; for example, the container is illuminated with light and the transmittance is determined, from which the container wall thickness can again be inferred.

[0004] Recently, there has been a growing desire to manufacture environmentally friendly alternatives to containers. One approach is to manufacture containers from pulp, particularly paper or paperboard pulp. The first attempts were promising. However, a disadvantage of such containers is that they cannot usually be inspected with visible light, since they do not transmit visible light.

[0005] In the prior art, beverage containers in the form of paperboard pulp containers, paper pulp containers, fiber casting containers and the like are known, which are usually produced from an aqueous pulp in several process steps. After sufficient drying, containers of this type can be filled and closed. However, it is also known that the pulp shrinks during the drying process. In this way, for example, a check of dimensional accuracy can only be carried out after sufficient drying.

[0006] Another problem with such containers is that they often still have residual moisture. In the prior art, residual moisture determination can be carried out during carton quality control, for example by means of a hygrometer. This measurement is carried out with a blade sensor. The blade sensor must be in contact with the material until a sufficiently stable measurement value is obtained.

[0007] However, these methods are not suitable for inspecting the containers involved here. In particular, contact measurements can have a significant impact on the performance of the corresponding machines.

[0008] As already mentioned, after the production of such pulp containers, and therefore usually before further processing (filling, closing, etc.), residual moisture is still contained in the container walls. This value should not exceed a specified value so that the container can be handled properly during equipment, storage, etc. (especially with regard to stability, wear resistance, mildew resistance, etc.). As already mentioned, there are various established methods or concepts for the determination of residual moisture, such as weighing, radiation absorption measurement, etc. However, these methods are either slow, complex or expensive or cannot accurately distinguish between differences in wall thickness and different residual moisture contents. Summary of the invention

[0009] The object of the invention is therefore to provide a determination method and a determination device which are particularly suitable for containers made of pulp as described here. According to the invention, these objects are achieved by the subject matter of the independent patent claims. Advantageous embodiments and improvements are the subject matter of the dependent claims.

[0010] In a first method according to the invention for determining container properties, a container to be checked is transported along a predetermined transport path and has a bottom region, a base body for receiving a filling material and a mouth region. Furthermore, the container is made at least in sections and preferably substantially and particularly preferably completely from a material comprising paper or cardboard and / or consists of such a material.

[0011] According to the invention, at least one wall of the container is arranged between two electrodes, a voltage or an alternating electric field is applied to the electrodes, and at least one electrical variable is measured, which characterizes the electric field established between the electrodes, and at least one variable characterizing the container is determined based on the electrical variable.

[0012] In the method according to the invention described here, the container itself or the wall or a part of the wall is examined in order to derive therefrom a value characterizing it, such as residual moisture or wall thickness. The material of the container preferably has a predetermined proportion of liquid, in particular water.

[0013] Due to said water content and / or residual humidity, the container differs in particular from containers known in the prior art, in particular made of glass or plastic. The applicant has therefore developed a solution which is particularly suitable for water-containing materials and / or for paper and / or cardboard materials.

[0014] In a preferred embodiment, the container consists of paper and / or paperboard, and preferably consists of a pulp comprising paper or paperboard.

[0015] Preferably, the mouth of the container has a cross-section that is smaller than the cross-section of the body of the container.

[0016] Furthermore, another method of inspection was identified, namely the above-mentioned possibility of measuring the electric field and thus the capacitance.

[0017] In a preferred method, during the coulometric determination, one of the two electrodes is located outside the container, the other electrode is either located outside the container so that the container (in particular at least in sections), in particular its matrix (in particular at least in sections) is arranged between the two electrodes, or the other electrode is located inside the container in such a way that at least one wall portion of the container is located between the electrodes.

[0018] In one of the two methods described here, at least one electrode, ie the electrode located inside the container, is therefore preferably moved in the transport direction of the container.

[0019] In another preferred method, an alternating electric field, in particular a high-frequency alternating electric field, is established between the electrodes. Preferably, at least one wall forms a dielectric between the electrodes. Preferably, during the measurement, only air is located between the electrodes and at least one wall of the container.

[0020] For example, capacitive sensors are relatively cheap as shortwave radio electronics, even if it requires handling of immersed electrodes into the container. However, it is also possible to measure at much higher frequencies, up to the microwave range.

[0021] Preferably, the measurement frequency range is from 2 MHz to 200 GHz, thus covering the entire radio spectrum from shortwave to UKW, VHF, UHF, microwave, radar to the millimeter wave range.

[0022] In this case, higher frequencies offer the advantage of more directional measurements, allowing measurements to be taken on a small, localized, limited area of ​​the vessel wall, whereas lower frequencies cover a larger area.

[0023] In a further preferred method, one or more measurements are performed at or with the aid of at least two different (measuring) frequencies.

[0024] The first measuring frequency preferably shows a stronger absorption of the hydrocarbon-containing wood fibers of the pulp, the second frequency preferably shows a stronger absorption of water by the residual humidity in the wall.

[0025] Therefore, the two characteristic variables residual moisture and wall thickness can be determined simultaneously.

[0026] A simpler measurement is also possible using only the outer electrodes. In this way, the residual humidity can be evaluated not only at one point on the measuring surface, but also over the entire circumference of the container. By measuring using electrodes arranged above one another as described precisely below, the container can preferably be divided into several vertical areas which can be measured individually.

[0027] In another preferred method, the measurement of the characterizing variable is performed during the movement of the container.It should be noted that this preferred variant is possible for all methods presented here, in particular for capacitive measurements.

[0028] In a further preferred method, the variable characterizing the container is a moisture value, in particular a residual moisture of the container and / or a wall thickness of at least one wall section of the container.

[0029] In another preferred method, the container is rotated during the measurement, in particular relative to its longitudinal direction. In this way, the entire circumferential surface of the container can be measured. It should be noted that this preferred embodiment is applicable to the capacitance measurement described here.

[0030] In a further preferred method, the above-mentioned electrical variable is the amplitude and / or phase of the electric field (in particular established between the electrodes).

[0031] From this quantity, in particular from the two variables, namely the amplitude and the phase of the electric field, the residual humidity and, if necessary, also the wall thickness of the container can be determined.

[0032] Particularly preferably, the wall thickness of the container is determined from a known or constant residual humidity. In this case, it must be taken into account that the wall thickness is also included in the calculation of the residual humidity. If the residual humidity is known or constant, the wall thickness can also be determined from the measurement.

[0033] In a preferred method, the electrode is introduced or immersed into the container. This is preferably achieved through the mouth opening of the container.

[0034] Preferably, one or more electrodes are arranged outside the container. As mentioned above, the measurement of amplitude and phase is preferably carried out, particularly preferably at different high frequencies. It is also particularly preferred to use different geometries, in particular the geometry of the electrodes, to simultaneously measure moisture and wall thickness.

[0035] If the container is preferably rotated, for example by rolling, the entire jacket surface can be measured.

[0036] In the case of constant or at least known residual humidity, compensation and thus direct calculation of the wall thickness is possible. In addition, it is also possible to measure with external electrodes, which makes it possible to measure on freely passing conveyors.

[0037] In another preferred method, the determination and / or measurement of the property is carried out in a contactless manner. An advantage of the above method is that it does not lead to limitations in production performance.

[0038] The method allows quality control of the produced containers. These measured values ​​can also be used for the subsequent drying of the containers. In this way, closed-loop regulation of, for example, material usage, material mix ratio, water content, drying energy, drying time, etc. can also be performed.

[0039] Preferably, the measurements described here are performed on unfilled containers. Preferably, the measurements described here are performed on unclosed containers.

[0040] Preferably, the measurements described here are carried out on containers that are to be filled for the first time.

[0041] The invention also relates to a device for determining properties of containers, comprising a transport device for transporting a container to be inspected (and preferably a plurality of containers to be inspected) along a predetermined transport path, wherein the container has a bottom region, a base body for receiving a filling material and a mouth region, and wherein the container consists at least in sections and preferably completely of a material comprising paper or cardboard.

[0042] The device has at least two electrodes, which are arranged such that at least one wall of the container is temporarily arranged between the two electrodes, and wherein a voltage can be applied to the electrodes, and a measuring device is provided, which determines at least one electrical variable, which is characteristic of the electric field established between the electrodes. Furthermore, an evaluation device is provided, which determines at least one variable characteristic of the container as a function of the electrical variable.

[0043] Therefore, it is also advisable to measure the containers in a contactless manner on the device side.The measurement is also preferably carried out in-line, ie during the manufacturing operation.

[0044] As mentioned above, capacitance measurements are used to measure the corresponding variables.

[0045] Preferably, the variable characterizing the container is the humidity and / or the moisture content and / or the wall thickness, in particular the wall thickness in the region of the bottom or base of the container.

[0046] Particularly preferably, the transport device is a (particularly monorail) conveyor belt or a conveyor chain. Particularly preferably, the container is transported along a straight direction, in particular in a standing position.

[0047] However, the transport device can also have a rotatable carrier on which a plurality of holding elements for holding the containers are arranged, or the containers are transported in a neck handling, in particular into or out of a cavity.

[0048] The electrodes preferably extend in the longitudinal direction of the container, wherein the longitudinal direction of the container preferably extends from the mouth of the container to the bottom.

[0049] In a preferred embodiment, at least one electrode, in particular an outer electrode, has a plurality of electrode parts which can be individually controlled or act at different frequencies, whereby an electric field can preferably be established between this electrode and each individual electrode part of the further electrode. In this way, for example, a residual moisture measurement depending on the height position of the container is possible.

[0050] In a further preferred embodiment, the device has a rotation device which is suitable and designed to rotate the container, in particular relative to its longitudinal direction. It should be noted that this design can be used both for measurements by electromagnetic radiation and for capacitive measurements.

[0051] In a variant, this rotation can be carried out while the measurement is being carried out, but it is also possible to rotate several times in sections along the transport path and also carry out the measurement.

[0052] Preferably, the rotating device can have, for example, transverse guide strips which can be placed on the base body of the container so that a rotation thereof is also achieved.

[0053] The invention also relates to an assembly for treating containers with a device of the type described above and to a drying device for drying containers, wherein the drying device can preferably be controlled as a function of variables characterizing the containers, in particular the residual humidity. Drying is preferably carried out with blown air, which flows through a drying chamber in which the containers are located. The parameters to be controlled can be, for example, the temperature, the flow rate or the vacuum level of the drying air.

[0054] The drying device is preferably arranged downstream of the above-mentioned device. Particularly preferably, the control device allows regulation, in particular regulation in the form of a closed loop or closed-loop regulation.

[0055] Furthermore, the arrangement can include several of the above-described devices. Thus, for example, different measurements can be performed one after another along the transport path, for example, measurements with the aid of near-infrared light and capacitive measurements. For example, the measurement results can be used redundantly, although it is also possible to determine the residual moisture by a first measurement and the wall thickness by another measurement. The person skilled in the art recognizes that the devices proposed here can be combined with one another, for example, measurements with X-ray radiation with measurements with infrared light, or also capacitive measurements with heat measurements or other designs. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Further advantages and embodiments can be seen from the accompanying drawings:

[0057] in:

[0058] Figure 1 A schematic diagram of the device is shown;

[0059] Figure 2 A first graph showing a capacitance measurement; and

[0060] Figure 3 Another illustration of capacitance measurement is shown. DETAILED DESCRIPTION

[0061] Figure 1 A rough schematic diagram of an apparatus 1 is shown. In this case, a transport device 2, for example a conveyor belt, is provided for transporting containers 10 along a transport path P. Although the figure shows an apparatus designed for electromagnetic radiation measurement, the use of the conveyor belt shown can also be used for capacitance measurement. The apparatus, in particular, can also be used accordingly for the capacitance measurement described here.

[0062] Reference numeral 42 denotes a radiation device for irradiating radiation onto the container 10 and reference numeral 44 denotes a sensor device for receiving radiation transmitted or reflected by the container. In the case of the present invention, electrodes may be provided on both sides of the conveyor belt to perform the capacitive measurements described within the scope of this application.

[0063] It is also possible for a first electrode to be arranged next to the transport path and for the other electrode to be introduced into the container and / or to be moved together with the container.

[0064] Reference numeral 14 denotes a drying device for drying the container 10. Preferably, a control device is provided for controlling the drying device, which controls the drying process in particular as a function of measured values ​​determined by the sensor device, such as in particular a determined residual moisture content of the container.

[0065] As mentioned above, the container is a container made of paper or paperboard, in particular a pulp formed of paper or paperboard.

[0066] Figure 2 and Figure 3 The components used for capacitance measurement are shown in Figure 2 In the variant shown, the electrode 4 is introduced into the container and the electric field is measured as a second electrode 6, which in this case has three individual electrodes 6a, 6b and 6c. From the characteristics of this electric field, in particular the amplitude and phase, conclusions can be drawn about the residual humidity in the wall 10b of the container.

[0067] Figure 3 Another variant is shown, in which the two electrodes 4 (4a, 4b, 4c) and 6 (6a, 6b, 6c) are arranged on the outside respectively. This measurement has the advantage that the electrodes do not need to be moved together with the container, which also moves perpendicularly to the plane of the figure.

[0068] The applicant reserves the right to claim that all features disclosed in the application documents are essential to the invention, as long as they are new individually or in combination with respect to the prior art. Further, it is to be noted that features which can be advantageous per se are also described in individual figures. A person skilled in the art will immediately recognize that a certain feature described in a figure can be advantageous even without the use of other features in the figure. In addition, a person skilled in the art will recognize that advantages can also be derived by combining several features shown in a single figure or in different figures.

Claims

1. A method for determining the properties of a container, wherein: A container (10) to be inspected is transported along a predetermined transport path, the container (10) having a bottom region (10a), a base body (10b) for receiving a filling material and a mouth region, wherein the container (10) consists at least in sections of a material comprising paper or cardboard, It is characterized in that At least one wall (12) of the container (10) is arranged between two electrodes (4, 6), a voltage is applied to the electrodes (4, 6), at least one electrical variable is measured, the electrical variable characterizing the electric field established between the electrodes, and at least one variable characterizing the container (10) is determined based on the electrical variable.

2. The method according to claim 1, It is characterized in that During the coulometric measurement, one of the two electrodes (6) is located outside the container (10), and the other electrode (4) is either located outside the container (10), so that the container (10) is arranged between the two electrodes (4, 6), or the other electrode (4) is located at least sectionally inside the container (10), so that at least one wall portion of the container (10) is located between the electrodes (4, 6).

3. The method according to claim 1, It is characterized in that The container (10) is composed of pulp including paper or paperboard.

4. The method according to claim 1, It is characterized in that An alternating electric field is established between the electrodes (4, 6).

5. The method according to claim 1, It is characterized in that The measurements are performed at at least two different frequencies.

6. The method according to claim 1, It is characterized in that The measurement of the characterizing variable is performed during the movement of the container (10).

7. The method according to claim 1, It is characterized in that The variable characterizing the container (10) is a moisture value and / or a wall thickness of at least one wall portion of the container (10).

8. The method according to claim 1, It is characterized in that The electric variable is the amplitude and / or phase of the electric field.

9. The method according to claim 1, It is characterized in that Determination of wall thickness at known and / or constant residual humidity.

10. The method according to claim 1, It is characterized in that The at least one variable characterizing the container (10) is determined segmentally in the longitudinal direction (L) of the container and / or the at least one variable characterizing the container (10) is measured according to the longitudinal direction (L) of the container (10).

11. The method according to claim 1, It is characterized in that The container is rotated during the measurement.

12. A device for determining properties of a container, comprising a transport device (2) for transporting a container (10) to be inspected along a predetermined transport path, wherein: The container (10) has a bottom region (10a), a base body (10b) for receiving a filling material and a mouth region (10c), wherein the container at least partially consists of a material comprising paper or cardboard, It is characterized in that The device has at least two electrodes (4, 6) which are arranged such that at least one wall (12) of the container (10) is temporarily arranged between the two electrodes (4, 6), wherein a voltage can be applied to the electrodes, and a measuring device is provided which determines at least one electrical variable which characterizes the electric field established between the electrodes, and an evaluation device is also provided which determines at least one variable which characterizes the container (10) based on the electrical variable.

13. The device according to claim 12, It is characterized in that At least one electrode (6) has a plurality of individually controllable electrode parts (6a, 6b, 6c).

14. The device (1) according to claim 12, It is characterized in that The device (1) comprises a rotating device adapted and designed to rotate the container relative to its longitudinal direction.

15. An assembly for treating containers, comprising a device (1) according to at least one of the preceding claims and a drying device (12) for drying the containers, wherein: The drying device may be controlled as a function of a variable characterizing the container.

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