Method for online measurement of a plasticizer in an endless filter rod and a device for producing an endless filter rod of the tobacco processing industry

Abstract

A method for online measurement of a plasticizer in an endless filter rod, includes: measuring a resonance shift (A) and line broadening (B) with a microwave resonator at a passing endless filter rod, determining a mass per length of plasticizer from the measurement variables (A, B), measuring a reference mass of plasticizer applied per time with the application of the plasticizer onto the filter tow band, determining an averaged reference mass per length of plasticizer from the measured mass applied over a time period, averaging the values for mass per length of plasticizer, determined using the measurement variables over the same time in which the reference mass of plasticizer is determined, determining a deviation between the averaged reference value for the mass per length and averaged mass per length and correcting the mass per length, determined from the measurement variables of the microwave resonator, according to the determined deviation.

Claims

1. A method for online measurement of a plasticizer in a filter rod at a filter rod maker, the method comprising: measuring a resonance shift (A) and a line broadening (B) of a resonance curve with a microwave resonator at a passing filter rod, determining a mass per length of plasticizer from the measurement variables (A, B) of the microwave resonator, measuring a reference mass of plasticizer applied per time with the application of the plasticizer onto the filter tow band, determining an averaged reference mass per length of plasticizer from the measured mass applied over a time period, averaging the values for mass per length of plasticizer, determined using the measurement variables of the microwave resonator, over the same time period in which the reference mass of plasticizer is determined, determining a deviation between the averaged reference value for the mass per length and the averaged mass per length, and correcting the mass per length of plasticizer determined from the measurement variables of the microwave resonator according to the determined deviation.

2. The method according to claim 1, wherein the time period for determining the reference mass extends at least over the duration of a back and forth run of a lift-off point of the filter tow from a filter tow bale.

3. The method according to claim 2, wherein the averaging of the values determined from the microwave resonator is realized over the time period in which the reference mass is determined.

4. The method according to claim 2, further comprising the following method steps: measuring the intensity S of radiation scattered at the filter tow band in the visible or infrared range, and determining an additive corrective term, depending on the intensity S, for the mass per length of plasticizer determined from the microwave variables.

5. The method according to claim 4, wherein the mass per length m.sub.W of plasticizer is determined from the following expression:
m.sub.W=k0+k1*A+k2*B+P()+k3*log(S*G/F) wherein k0, k1, k2 and k3 are coefficients, A is the resonance shift, B is the line broadening, is the quotient of A and B, P is a polynomial of or a function of , G is the mass of the filter tow band, and F is the mass of an individual fiber of the filter tow band of a defined length.

6. The method according to claim 1, further comprising the mass per length m.sub.W of plasticizer is determined according to:
m.sub.W=k0+k1*A+k2*B+P(), wherein A is the resonance shift, B is the line broadening, k0, k1, k2 are coefficients, is the quotient of A and B, and P is a polynomial depending on or a function of .

7. The method according to claim 6, wherein the value of the constant k0 is corrected by the value of the determined deviation between the averaged triacetin content from the microwave measurements and the reference triacetin content of the reference measurement.

8. The method according to claim 1, further comprising the plasticizer is applied from a storage container onto the filter tow band, and the weight reduction of the storage container is measured for determining the reference mass per length of plasticizer.

9. The method according to claim 1, further comprising the plasticizer is applied from a storage container onto the filter tow band and the change of the fill level of the storage container is measured for determining the reference mass per length of plasticizer.

10. The method according to claim 1, further comprising the plasticizer is applied from a storage container onto the filter tow band and the volume fed into the feed line is measured for determining the reference mass per length of plasticizer.

11. The method according to claim 1, further comprising the average mass per length of plasticizer is determined continuously.

12. The method according to claim 1, further comprising the deviation is determined continuously.

13. The method according to claim 1, further comprising one of claims 1 to 12, characterized in that the mass determined from the measurement variables of the microwave resonator is corrected continuously.

14. The method according to claim 1, further comprising a moisture value for the filter rod is determined depending on the measurement variables of the microwave resonator and the corrected value for the mass per length of plasticizer.

15. The method according to claim 14, wherein a moisture value is determined according to:
=f0+f1*+f2*m.sub.W wherein f0, f1, f2 are coefficients, is the quotient from the resonance shift A and the line broadening B, or a function of the quotient, and m.sub.W is the corrected value for the mass per length of plasticizer.

16. A device for an online measurement of the content of plasticizer in a filter rod of the tobacco processing industry, comprising: a microwave resonator that measures a resonance shift (A) and a line broadening (B) of a resonance curve of the passing filter rod, a reference measurement device that measures a reference mass per time of a plasticizer applied onto the filter tow band, and an evaluation unit supplied with the measured values (A) and (B) of the microwave resonator and the reference measurement device, and which determines a mass per length of plasticizer from the measured values of the microwave resonator, determines an averaged reference mass per length from the measured values (A) and (B) of the reference measurement device, and corrects the mass per length of plasticizer based on a deviation from the averaged reference mass per length of plasticizer.

17. The device according to claim 16, wherein a scale is provided as a reference measurement device that detects a reference mass change per time in a storage container for the plasticizer.

18. The device according to claim 16, wherein the reference measurement device detects the change of the fill level of the storage container.

19. The device according to claim 16, further comprising the reference measurement device has a volume flow meter that detects the volume per time during application of the plasticizer.

20. The device according to claim 16, wherein a laser and an intensity sensor are provided for laser light scattered at the filter tow band, wherein the evaluation unit corrects the mass per length of plasticizer depending on the intensity of the scattered laser light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained in the following in more detail using an exemplary embodiment. In the figures:

(2) FIG. 1 shows a schematic view of a filter rod maker with a microwave sensor at the endless filter rod and a triacetin reference measurement using a scale for the triacetin container,

(3) FIG. 2 shows a schematic view of a filter rod maker with a microwave sensor at the endless filter rod and a triacetin reference measurement using a continuous fill level measuring device for the triacetin container,

(4) FIG. 3 shows a schematic view of a filter rod maker with a microwave sensor at the endless filter rod and a triacetin reference measurement using a flow measurement in the line between the triacetin container and triacetin application unit,

(5) FIG. 4 shows a schematic view of a filter rod maker with a microwave sensor at the endless filter rod, an infrared laser sensor for the improved triacetin correction device for the titer change, and a triacetin reference measurement by means of a scale for the triacetin container,

(6) FIG. 5 shows the dependency of the quotient =B/A of the measurement values A and B for different tow masses and tow titers of triacetin content per filter rod length, and

(7) FIG. 6 shows the dependency of the microwave triacetin value per length for different tow masses and tow titers depending on reference triacetin content per length, and the disruptive influence of moisture fluctuations in the filter tow.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows a schematic view of a filter rod cigarette maker with a microwave resonator 10 and a triacetin scale 13 for the triacetin reference measurement. The endless cigarette filter rod 7 is produced in a known manner. A filter tow band 2 is supplied from a filter tow bale 1 to a filter tow stretching and relaxation unit 3. After the filter tow band has left the stretching and relaxation unit, the triacetin is applied onto it in a following step. The triacetin 17 is applied onto the filter tow band using the triacetin application 4. The filter tow band is supplied to an inlet funnel 5 for forming the rods. Paper for wrapping the rod is supplied from a paper bobbin 6 to the band running in the inlet funnel 5. Glue 8 is supplied to the partially wrapped filter rod and is hardened in a heating zone 9.

(9) A microwave resonator 10 for measuring is provided after the heating zone 9. The produced endless filter rod 7 is subsequently cut by the cutting device 11 into filter rods.

(10) The triacetin 17 is supplied from a triacetin container 12 that is connected by a supply line 15 to the triacetin application 4. The change of mass in the triacetin container 12 is continuously measured using a scale 13 for determining the reference triacetin mass.

(11) The microwave measurement device 16 evaluates the measurement signals of the microwave resonator 10 and the measured values from the scale 13.

(12) The microwave resonator 10 can be a profile resonator for example, in a particular construction with a very small space requirement, so that it can also be installed subsequently in a filter rod maker. The microwave resonator measures the resonance frequency shift A and the line broadening B of the resonance curve caused by the endless cigarette rod, compared to the empty resonator. Due to the dielectric properties of the endless filter rod, the resonance developed in the microwave resonator is shifted in its resonance frequency and the resonance is broadened.

(13) FIG. 2 shows a schematic representation of a filter rod maker with a microwave sensor 10 at the endless filter rod 7, as shown in FIG. 1. However, the triacetin reference measurement is realized here by means of a continuous fill level measurement device 13a for the triacetin container. This continuous fill level measurement can be built as a capacitive sensor, an ultrasonic elapsed time sensor, a microwave elapsed time sensor, or as a mechanical float sensor.

(14) FIG. 3 shows a schematic representation of a filter rod maker with a microwave sensor 10 at the endless filter rod 7, as shown in FIGS. 1 and 2. However, the triacetin reference measurement is realized here by means of a flow measurement of the volume of the triacetin fluid 14 in the supply line 15.

(15) FIG. 4 shows a schematic representation of a filter rod maker with a microwave sensor 10 at the filter rod 7, as in FIGS. 1, 2 and 3, wherein the triacetin reference measurement is made for instance by measuring the weight loss of the triacetin container 12 using a scale 13. Additionally, an infrared laser measurement device 10a is installed at the filter rod 7 in series with the microwave resonator 10 for the purpose of correcting the microwave triacetin signal in the case of a titer change, so that an improved independence of the calibration from the titer is given.

(16) FIG. 5 shows the dependency of the arctan quotient of B and A of triacetin content for four different titer values: there is a clear dependency on the triacetin content with a small increase. The diagram also shows that the quotient of B and A is independent of the filter tow mass and the filter tow titer. At the same time, however, there is a clear dependency on the moisture which is responsible for scattering the measured values about the plotted best fit line. This low dependency on the moisture, which is inherent in the measured values in FIG. 5, can be compensated using the method according to the invention by the periodic comparison to a long-term reference value for the triacetin content, so that through the measurement using a single microwave resonator, the mass of triacetin per length for an endless filter rod can reliably be determined online.

(17) FIG. 6 shows the relationship of the triacetin value per length, which results solely from the data A, B and B/A of a microwave resonator at the filter rod, in comparison to the reference triacetin values. The graph shows that different tow masses and different tow titers barely have any influence on the microwave triacetin value. However, the determined triacetin value per length clearly depends on moisture fluctuations in the filter tow. The plotted best fit lines clearly show that by using the reference measurement of the triacetin mass, the influence due to the moisture fluctuations in the filter tow can be reliably eliminated from the measured values.

(18) The method according to the invention makes use of the fact that the variables A and B are linearly dependent on all individual parameters in the endless filter rod. Although the quotient of A and B is independent of the tow mass and the titer, it is however dependent on the triacetin content and the moisture. Thus, the triacetin content can be given as mass per length through a linear combination of the A, B and B/A if the coefficients of these linear combinations are known. These coefficients are determined by a one-time calibration procedure. In this manner, the mass per length of the applied triacetin results from the following expression:
m.sub.W=k0+k1*A+k1*B+k3*().

(19) Occasionally, the arctan of B/A is referred to also instead of the coefficient =B/A.

(20) Tests have shown that the accuracy the determination of the triacetin content can be increased particularly well by additional higher powers of the quotient =B/A. Thus, for instance, the expression m.sub.W=k0+k1*A+k2*B+k3*+k4*().sup.2 is already more accurate, however, it requires determining a further coefficient k4 in the calibration process.

(21) The quotient =B/A, or respectively the arctan , or another function of the value depends only on the content of triacetin and the moisture of the filter rod, so that the moisture value with a known triacetin value m.sub.W can be expressed as:
=f0+f1*+f2*m.sub.W.

(22) With a known triacetin mass m.sub.W per filter length and moisture value , the amount of the surface density of the tow content can be determined either from the measured value of A and/or the measured value of B. The variable for the tow content is expressed as mass per length according to the expression:
m.sub.T=t0+t1*A+t2*B+t3*m.sub.W+t4*,
wherein t1 to t4 are constants that are determined by calibration.

(23) The values for triacetin mass, moisture and tow surface mass, determined in the equations above, are instantaneous values of the part of the endless filter rod that is located immediately in the measurement range of the microwave resonator. This measurement range can have a length of 1 mm or more. Consequently, in this manner, a profile of the measurement variables can be measured in the endless filter rod, and a local distribution, of the triacetin for example, can be determined.

(24) A triacetin concentration due to dripping triacetin in the application unit for example, can be detected depending on the sensor based high spatial resolution of the measurement. Such filter rods can, after the cutting procedure, be removed from further processing. Chemical burning of holes in the filter rod (hot melt phenomenon) during the production process due to a high triacetin concentration, can be detected in a timely manner, and can be diverted.

(25) Also, an insufficiently adjusted triacetin application due, for example, to incorrect rotational speed of the brushes, can be detected in a timely manner, displayed and corrected.

(26) In addition, moisture fluctuations between different bales can be utilized by a regulation of the tow content so that the finished filter rod, in moisture equilibrium with the environment, has its target weight and its target pressure drop values.

(27) Quality fluctuations in the filter tow, due to filament breakage for example, can be compensated by detecting the filter tow mass per rod so the finished filter rod has its target weight and its target pressure drop value.

(28) The particularly high accuracy also in the values for the profile is attained according to the invention in that there is a long term reference measurement of the triacetin content, in that the triacetin dosing from the triacetin tank is detected by measuring the weight reduction or the reduction of the fill level of the triacetin container over a longer time period. Likewise, the triacetin flow between the storage container and the triacetin application chamber can be determined over a longer time period, wherein this time period must be sufficiently long to average fluctuations in the triacetin flow. At the same time, including the speed of the endless filter rod or the measurement of the rotations of the blade results in that the number of filter rods produced in the same time period is determined, thus, the triacetin content per filter rod can be determined by counting the shaft encoder impulses. On the other hand, the averaged reference triacetin value determined from the supply can be linearly compared with the microwave triacetin value determined during the same time period, and by changing the absolute term k0 with the determination of the triacetin mass, a compensation can be performed so that the triacetin signal acquired from the measurement variables of the microwave resonator concurs with the averaged reference triacetin value from the measurement of the triacetin supply.

(29) Along with the measurement of the long term reference mass per time, which is supplied to the filter tow band, a further signal from an infrared laser measurement device can be referenced that is barely influenced by the triacetin content and the moisture, but in contrast, is significantly influenced by the tow mass. The signal of an infrared laser is formed by deflecting its beam through the scattering on the surface of the individual fiber, and the signal strength after passing through the filter rod is more strongly attenuated when there are more fibers in the beam path. This is a scattering of the beam at the surface of fibers; the moisture or triacetin content of the fiber material have little influence on this scattering. This signal reacts only to variations in the content of the fibers, such as occurs with a change in the type of tow for example. The titer F-Y-G of a filter tow bale is defined by the specification of the mass of a fiber F, and the total mass of the band G in grams at a defined length. If the measured intensity S of the scattered laser light is multiplied by the number of fibers, which is expressed by the coefficient G/F, a filter tow signal results that is independent of the titer. Since on the other hand, the laser signal decreases exponentially with increasing tow mass, a linear relationship exists between log(S*G/F) and the tow mass, which is independent of triacetin and moisture. Therefore, a further improved mass value m.sub.W per length of the plasticizer can be expressed as:
m.sub.W=k0+k1*A+k2*B+k3*B/A+k4*log(S*G/F).

(30) With these variables also, the absolute term k0 is corrected using the averaged reference mass per length determined from the triacetin supply.