Method and apparatus for identifying capsule defects in filters for the tobacco processing industry

Abstract

The invention relates to a method for identifying capsule defects in filters in the tobacco processing industry, wherein a microwave measuring device measures values indicating the density and / or the moisture of the filter along the longitudinal direction of the filter, the method having the following steps: a. comparing the measured values with a threshold value, below which a capsule defect is present in the filter; and b. determining a value for the degree of fluctuation of the measured values in the region before and / or after a measurement point in which at least one measured value is below the threshold value; c. comparing the degree of fluctuation with a predetermined capsule threshold value, wherein: i. a ruptured capsule is present in the case of exceeding the capsule threshold value; and ii. a missing capsule is present in the case of falling below the capsule threshold value.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for identifying capsule defects in filter tips of the tobacco processing industry. BACKGROUND

[0002] Filter tips of the tobacco processing industry can exist as filter rods, cut filter rods or as filter segments connected to a cigarette. For taste reasons, capsules with aromas are embedded in the filter tips, which are crushed directly before the cigarette is smoked in the filter tip and thus release their aroma in the filter tip. Widely popular aromas are, for example, menthol. The advantage in using such filter tips with one or more embedded capsules is that the aroma is already located in the filter tip and is not burned with the tobacco, but is added to the tobacco smoke unburned. Thereby, the formation of health-damaging substances due to the burning of the aroma can be avoided. Also, a change in the aroma due to the burning with the tobacco can be ruled out.

[0003] Different parameters of the capsules can be measured with suitable sensor systems at the time of manufacture and / or at the time of checking the manufactured product and their quality can be monitored. Parameters of the capsules that are of interest here are, for example, their position in the filter tip and their spacing as well as their state, i.e. whether the capsules are intact or damaged.

[0004] From EP 2 249 670 a different sensor system for checking capsules is known, which can detect the state and the presence of the capsules in the filter rod.

[0005] From EP 2 207 027 a method for measuring mass or density and / or for measuring humidity in a plurality of division cells in a non-metallic carrier material is known. The microwave measuring device consists of at least one microwave resonator for generating at least one resonance mode, which measures in a measurement region which is limited in terms of location. The microwave measuring device measures at least one characteristic quantity of the resonance mode when only the carrier material without the division cells is located in the measurement region and when the division cells are at least partially located in the measurement region, respectively. An evaluation processing unit extracts the quantity measured for the carrier material from the measured values for the division cells and determines the value for the humidity and / or for the mass or density of the division cells from at least one difference on a composite characteristic curve.

[0006] In practice, intact capsules show a distinct local maximum in the density signal of the filter tip. If the capsule is broken, the liquid aroma first disperses in the filter tip and then evaporates. At the location of the capsule, its broken capsule shell remains. Depending on the size and properties of the capsule and its shell and on the extent of its damage, the remaining capsule shell causes one or more density signals. By the amplitude of the density signal, a defective capsule in the filter tip can be reliably identified. The filter tip can then be sorted out of production if the capsule has a defect. However, it cannot be reliably distinguished whether the capsule is missing or whether the capsule has been damaged. That is, capsule defects of missing capsules and of broken capsules cannot be distinguished from one another. There is therefore a technical need to reliably obtain additional information about capsules and capsule defects in filter tips at low cost. SUMMARY

[0007] The object on which the invention is based is to provide a method and a device which reliably allow an accurate analysis of the measurement signals for capsule defects of filter tips in the tobacco processing industry.

[0008] According to the invention, the object is achieved by a method for identifying capsule defects in filter tips in the tobacco processing industry according to the invention and by a device for measuring capsule defects in filter tips in the tobacco processing industry according to the invention.

[0009] The method for identifying capsule defects in filter rods in the tobacco processing industry according to the invention uses a microwave measurement device which measures the density and / or the moisture of the filter tip along the longitudinal direction of the filter tip.

[0010] In a first method step, the maximum of the measurement values is compared with a threshold value in a defined region of the measurement curve. The measurement values here indicate the density and / or the moisture, which means that a value for the density and / or the moisture can be determined from the measurement values or, in the case of a further parameter, from the measurement values. A capsule defect is identified in the filter tip if the threshold value is undershot. In order to accurately analyze the capsule defect, the degree of fluctuation for the density and / or the moisture is detected in the region before and / or after the measurement point. As measurement point, the region around the nominal position of the capsule is used here. In a second method step, the value for the degree of fluctuation determined for this region is compared with a capsule threshold value for the measurement values. A broken capsule is identified if the capsule threshold value is exceeded. A missing capsule is identified in the filter tip if the capsule threshold value is equal to or undershot. The value for the degree of fluctuation is compared with the capsule threshold value, respectively. The selection of the measurement point is particularly relevant for the identification of a missing capsule. Only if a capsule should be there, a missing capsule can be identified as a defect. The nominal position or the predicted position is therefore selected as measurement point.

[0011] The application is based on the observation that a broken capsule increases the fluctuations in the measurement signal and thus causes greater values in terms of the degree of fluctuation compared to a pure filter tip in which the capsule is missing, and which shows a uniform density and thus a small degree of fluctuation of the measurement signal without residues of broken capsules and / or of the outflowing aroma. Since the second comparison is not made on the measurement signal of the density and / or humidity itself, but on the degree of fluctuation thereof in the region of the capsule defect, information on the capsule condition is reliably obtained with little technical outlay.

[0012] In a preferred further development, a fitting straight line is determined for the individual measurement values in a matching region around the measurement point, and the degree of fluctuation relative to the fitting straight line is determined. The matching region can for example have a predetermined spacing before and after the measurement point. Preferably, the fitting straight line is formed by a linear regression of the measurement values in the matching region. The application of the fitting straight line is based on the insight that humidity fluctuations and density fluctuations which are not due to the capsule or the contents of the capsule change more slowly in terms of location and thus can be well reflected by a linear regression.

[0013] In a preferred further development, the microwave measurement device is designed as a microwave resonator which measures at least one change in the resonance width and / or a shift in the resonance frequency. By means of a filter tip with an introduced capsule or a filter tip without an introduced capsule, the dielectric properties in the microwave resonator change. This causes the resonance curve to broaden and the resonance frequency of the resonance curve to shift. In the analysis of the measurement signal of the microwave measurement device, the change in the width of the resonance curve and the shift in the resonance frequency can be analyzed as a humidity value and a density value. In the analysis of the signal, the change in the resonance curve relative to an empty resonator is generally detected. It is also possible to operate a suitable microwave measurement device in two or more resonance modes and to analyze the signal change between the different resonance modes. In general, it is sufficient for the method according to the application to measure values for the density signal and / or the humidity signal and to determine the change in the density signal and the humidity signal from the degree of fluctuation in the spatial region.

[0014] In a preferred further development of the method according to the application, values for the degree of fluctuation are determined for predetermined sections along the longitudinal direction of the filter tip. The sections of this further development must coincide with the expected position of the capsule. The predetermined sections can for example be located before and / or after the expected position of the capsule for which the measured maximum values for the density and / or humidity lie below the threshold value. The predetermined sections can for example also coincide with the matching region for the fitting straight line.

[0015] In a preferred design of the method, a position is predetermined in which a capsule is predicted along the longitudinal direction. This can be produced, for example, by the manufacturing process of the capsule filter rod itself, for example in that the capsules are introduced into the filter with a predetermined spacing starting from an initial position. The predetermined position can also be determined, for example, by means of a predefined spacing between the capsules, for example in that the presence of a capsule is measured, for example, as exceeding a threshold value, and from there the predicted position of a further capsule is determined by means of the given spacing value. In the manufacture of a capsule filter rod in a production machine, it is important that the position of the capsules in the continuous capsule filter rod relative to the knife that divides the rod into individual filter rods is correct.

[0016] In a further improvement of the method that is suitable for the purpose, a value for the degree of fluctuation can be determined in the region before and / or after the predicted capsule position, respectively. In this version, the value for the degree of fluctuation is calculated continuously, independently of whether the measured value for the density and / or the humidity has fallen below the threshold value. The analysis of the standard deviation is then also carried out for past sections in the case of a fall below the threshold value.

[0017] In a preferred design, the filter rod is a filter rod that is transported along its longitudinal direction. The filter rod is manufactured from a filter rod and is transported in one piece before it is cut. The detection of the filter rod can take place on the continuous rod or / and after the filter rod has been cut into individual filter rods. The method according to the application can be used not only in the manufacture, but also in the detection of manufactured cigarettes. The filter rod to be measured here is a filter segment of a cigarette that is transported along its longitudinal direction.

[0018] The measurement and detection of the manufactured filter segment on the cigarette preferably take place in a test station, but in principle can also take place in the context of the manufacturing process for the cigarette.

[0019] In the method according to the application, experiments have shown that the material of the capsule and of the filter rod likewise has no noteworthy influence on the capsule threshold value as does the moisture content of the filter rod, so that the capsule threshold value can also be determined independently of the material and does not have to be adjusted in the event of a change in the capsule material or the filter rod material.

[0020] Preferably, the value for the degree of fluctuation is determined as the standard deviation.

[0021] The object according to the invention is also achieved by a device for measuring capsule defects in filter rods of the tobacco processing industry according to the invention. The device is for measuring capsule defects in filter rods of the tobacco processing industry. The device has a microwave measuring device and a controller, wherein the controller can also be part of the microwave measuring device. The microwave measuring device measures a value which is indicative of the density and / or the moisture in the filter rod, wherein the controller is configured to compare the measured value with a threshold value and to identify a capsule defect in the case of a value below the threshold value. As already in the method according to the invention, the controller is furthermore configured to reliably distinguish between a broken capsule and a missing capsule by comparison of the value for the degree of fluctuation with a capsule threshold value. Preferably, the device is part of a filter rod testing station. The device can also be part of a device for manufacturing filter rods, for example a filter rod machine or a machine which combines different filter segments into a combined filter rod (filter rod combiner). The device can furthermore be part of a device for manufacturing cigarettes, for example a cigarette machine.

[0022] Preferably, the controller is configured to determine the standard deviation as the value for the degree of fluctuation. BRIEF DESCRIPTION OF DRAWINGS

[0023] The invention is further illustrated according to the following figures. In the figures:

[0024] Figure 1 The density signal is shown for intact capsules and broken capsules with regard to the position in the filter bundle;

[0025] Figure 2 The density signal is additionally shown for missing capsules;

[0026] Figure 3 The density signal is shown in a filter rod with four capsules;

[0027] Figure 4 The value of the standard deviation is shown in the case of a broken capsule and in the case of a missing capsule; and

[0028] Figure 5 The measured density values for intact capsules and broken capsules and the fitted straight line in the case of a missing capsule are shown. DETAILED DESCRIPTION

[0029] Figure 1The measured density values (plotted dimensionlessly) are shown in relation to the position in millimeters for a filter rod. Two measurement curves are depicted here, the measurement curve 10 in solid line shows the measured sealing values for a filter strand with an intact capsule, and the measurement curve 12 shows the measured values of the density in the case of a broken capsule. It is apparent that in the region from 56 millimeters to approximately 61-62 millimeters and from 76 millimeters on, the two measurement curves show identical density values. In the region in between, the intact capsule leads to significantly greater measured values, which rise up to 170. The measured values of the broken capsule rise to values slightly above 140.

[0030] An intact capsule can be reliably identified in the filter strand by means of the upper threshold value 14, which has a value of approximately 158. The measured values of the curve 10 significantly exceed the upper threshold value 14, so that an intact capsule is reliably identified. Figure 1 A lower threshold value 16 is also shown, which has a value slightly below 140. In the example shown, the signal for a broken capsule can be distinguished by means of the lower threshold value 16.

[0031] The method shown in Figure 1 is in principle also suitable for identifying the case of a missing capsule. Figure 2 The change curve 18 in the case of a missing capsule in the filter strand is shown. The measurement curve 10 in Figure 1 The threshold values 14 and 16 shown in

[0032] The above-described depicted method has a series of significant disadvantages for practice, however. In particular in the case of the use of small capsules, the distinction between a missing capsule and a signal of a broken capsule is not very great. That is, a reliable distinction between these capsule defects cannot be made. It also occurs in practical applications that a broken capsule is in different pieces, so that instead of a maximum value, a different, less pronounced local maximum value occurs in the signal. Here, a distinction between a missing capsule and a broken capsule cannot be made. A particularly important disadvantage in terms of measurement technology is that in the two threshold comparisons, the absolute values for the measurement signal are made. These absolute values vary very strongly with the environmental conditions, in particular the humidity value. If the moisture content in the filter strand changes, the absolute values change strongly and cannot be processed with the same threshold values as in the case of a dry filter strand. This impedes the practical application of the measurement method with two threshold values and does not allow a reliable distinction between a missing capsule and a broken capsule.

[0033] Figure 3The measured density signals for four capsules located in a filter rod are shown, with intact capsules and with broken capsules, respectively. Here, a filter rod that has been cut is involved, which has four individual filter tips.

[0034] In the method according to the application, the surrounding area is identified as an area with capsule defects below a threshold value for the measured signal. The standard deviation of the measured signal is calculated in the surrounding area, for example in an area of + / - 10 mm, preferably + / - 5 mm. Figure 4 The measured standard deviations for the measured signals are shown. Here, the standard deviation is measured for each signal, independently of whether the measured signal is below the threshold value or not. The standard deviation is determined by Figure 4 It is known that the standard deviation determined for the signal with the broken capsule is significantly greater than the standard deviation of the signal in the case of a missing capsule. By using a capsule threshold value 20 for the standard deviation, it is thus possible to reliably distinguish the two capsule defects from one another. A particular advantage here is also that the value for the standard deviation does not change as a result of environmental conditions and / or material components and properties, for example the moisture of the filter tow. This means that the capsule threshold value 20 can be used uniformly in different applications. Small capsules do not impede reliable differentiation of the two capsule defects.

[0035] Overall, the use of the standard deviation has a number of advantages: In particular for smaller capsules, it is possible to determine a relatively large relative difference between the signals of a broken capsule and a missing capsule. The differentiation of the damage pattern can thus be achieved with a high degree of accuracy. Furthermore, the differentiation between a broken capsule and a missing capsule is independent of the absolute value and can thus be used independently of the filter tow density and moisture content.

[0036] Figure 5 The measured density of the filter tow is shown. Two maxima of the density value are shown in signal values 22 and 28. The maxima 22 and 28 point to the presence of intact capsules. The signal value 24 points to a broken capsule with its lower value.

[0037] A missing capsule can be well identified by calculating the standard deviation relative to the average value of the density of the filter tow, in particular in the case of a uniform density of the filter tow of the filter tip. However, in the case of a non-uniform density of the filter tow, the standard deviation relative to the average value increases and is only limitedly suitable for detecting a missing capsule. In an advantageous further development, a fitting straight line is determined for the individual measurement points in the area around the nominal position by linear regression. The fitting straight line 26 shows a trend in the density of the filter tow, for example. The degree of fluctuation of the measurement values relative to the fitting straight line is here a suitable criterion for differentiating between a broken capsule and a missing capsule.

[0038] Figure 5A 100 mm long filter rod is shown, which should contain 4 capsules. The two capsules in positions 22 and 28 are intact, the capsule in position 24 is broken and the capsule in position 26 is missing. In the region between approximately 50 mm and 80 mm the density of the filter tow is not uniform and monotonically increasing in this region. Although there is no broken capsule, the density standard deviation from the density average is increased in this region. Also visible in the graph is the fitted straight line 26 (+ / - 5 mm) around the nominal capsule positions. The degree of fluctuation of the measured values relative to this fitted line is low. The background for this is that in the case of a broken capsule a non-monotonic signal deviation would occur, which would also increase the degree of fluctuation of the measured values relative to the fitted line.

Claims

1. A method for identifying capsule defects in filters in the tobacco processing industry, wherein, A microwave measuring device measures values indicative of the density and / or the moisture of the filter along the longitudinal direction of the filter, the method having the steps of: a. comparing the measured values to a threshold value, in case of which below the capsule defect is present in the filter; and b. determining a value for the degree of fluctuation of the measured values in the area before and / or after a measurement point in which at least one measured value is below the threshold value; c. comparing the value for the degree of fluctuation to a predetermined capsule threshold value, wherein: i. in case of which the capsule threshold value is exceeded a ruptured capsule is present; and ii. in case of which the capsule threshold value is undershot a missing capsule is present.

2. The method of claim 1, wherein, A fitting straight line is determined for the measured values in a matching area around the measurement point and the degree of fluctuation relative to the fitting straight line is determined.

3. The method according to claim 1 or 2, characterized in that, A maximum search is performed around the measurement point.

4. The method according to claim 1 or 2, characterized in that, The microwave measuring device is configured as a microwave resonator for which at least one change in the width of the resonance curve of the microwave resonator and / or a shift of the resonance frequency of the microwave resonator is measured.

5. The method according to claim 1 or 2, characterized in that, The microwave measuring device is configured as a microwave resonator for which a density signal and / or a moisture signal is measured.

6. The method of claim 1 or 2, wherein, The value for the degree of fluctuation is determined for a predetermined length of the area along the longitudinal direction.

7. The method according to claim 1 or 2, characterized in that, A capsule is predicted in a determined position along the longitudinal direction.

8. The method of claim 7, wherein, The value for the degree of fluctuation is determined in an interval around the predicted capsule position, respectively.

9. The method of claim 1 or 2, wherein, The filter is configured as a filter rod or as a filter strand which is transported along the longitudinal direction.

10. The method of claim 1 or 2, wherein, The filter is configured as a filter segment of a cigarette which is transported along the longitudinal direction.

11. The method of claim 1 or 2, wherein, The capsule threshold value is independent of the material of the capsule and / or the filling of the capsule.

12. The method of claim 1 or 2, wherein, The capsule threshold value is independent of the surrounding filter strand.

13. Device for measuring capsule defects in filters in the tobacco processing industry, the device comprising a microwave measuring arrangement and a controller processing the measured values: a. the microwave measuring device measures a value indicative of density and / or moisture in the filter tip, wherein, The controller is configured for comparing the measured values to a threshold value and identifying a capsule defect in case of which the threshold value is undershot; b. The controller is configured for determining a value for the degree of fluctuation of the measured values in the area before and / or after a measurement point in which at least one measured value is below the threshold value and comparing the value for the degree of fluctuation to a capsule threshold value, wherein i. a ruptured capsule is identified in case of which the capsule threshold value is exceeded; and ii. a missing capsule is identified in case of which the capsule threshold value is undershot.

14. The apparatus of claim 13, wherein, The device is configured as part of a filter rod testing station.

15. The apparatus of claim 13 or 14, characterized in that, The device is configured as part of a production machine for cigarettes or filters.

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