EP2865282B2 - Assembly and method for checking rod-shaped articles from the tobacco processing industry - Google Patents

Description

The invention relates to a method for checking cross-axially conveyed rod-shaped articles in the tobacco processing industry, in particular for checking liquid-filled capsules in filters of filter cigarettes.

To date, some filter rod machines, such as the applicant's so-called KDF, have been used to produce filter rods into which objects, such as capsules filled with flavoring liquid, are inserted. These capsules are checked directly during production before further processing, with microwave sensors such as the applicant's MIDAS-EF being used in particular. This checks whether the fill level of the capsules is correct or whether they are broken, whether capsules are missing, whether double capsules are inserted and whether the position in the strand direction is correct.

In some cases, the filter rods produced in this way are stored for a certain period of time, for example 24 hours, and then checked again along a pneumatic conveyor line for their fill level or whether they are broken. This is done, for example, in the applicant's facility known as "FDU" in order to rule out the possibility that capsules have been damaged on the filter rod production machine, which only leak after some time and are only detected as faulty by the microwave sensor when they are dry.

Out of DE 23 43 668 A1 A device for testing the ends of cigarettes is disclosed, which comprises a test conveyor in which the cigarettes are conveyed transversely axially. The device also comprises a capacitive measuring arrangement for the tobacco density. The capacitive measuring arrangement has at least two electrodes arranged stationary with respect to the test conveyor and connected to a high-frequency voltage source. Their position in relation to the cigarette ends is selected such that at the time of measurement a high-frequency field emanating from them penetrates the cigarette ends.

Out of EN 10 2011 083 052 A1 A capacitive HF strand measuring device for capacitively determining at least one property of an endless strand of material in the tobacco processing industry is known. The measuring device comprises a housing with at least one measuring capacitor through which the strand of material can pass and to which an HF voltage signal can be applied. The capacitive HF strand measuring device comprises one or more accuracy-determining electronic components in its housing.

The unpublished EP 2 848 133 A1 A system for checking rod-shaped articles conveyed cross-axially in the tobacco processing industry is known. The system is used to check liquid-filled capsules in filters of filter cigarettes. The system comprises a trough conveyor device with troughs for receiving and cross-axially conveying the rod-shaped articles. The rod-shaped articles are checked using a microwave measuring device.

In contrast, the present invention is based on the object of ensuring that the quality of the rod-shaped articles of the tobacco processing industry is ensured after complete processing.

This object underlying the invention is solved by a method according to claim 1.

The invention is based on the basic idea that the articles, in particular filter cigarettes, are inserted laterally into the measuring capacitor in a transverse axial direction and pass through the HF measuring field excited therein. The protruding sections of the rod-shaped articles thus enter the HF measuring field completely. With the longitudinally extended, one-sided open lateral passage channel, the capacitive HF measuring device is also specially designed for this transverse axially promoted lateral passage. to enable the corresponding passage through the measuring capacitor. This passage channel also cuts through or passes through the measuring capacitor. Preferably, the protruding sections of the articles, in particular the capsules, pass through the RF measuring field in an area of the RF measuring field that is essentially homogeneous along the longitudinal axis of the articles.

The measure according to the invention has the advantage that changes in the density, for example of a cigarette filter, or in the liquid filling of a liquid-filled capsule in the cigarette filter can be detected very precisely and largely independent of position. This increases the measurement reliability for the quality of the filters or the capsules contained therein.

The solution according to the invention makes it possible to check the quality of the rod-shaped articles and in particular the filters and the capsules inserted therein after the articles have been completely manufactured. At this point, the articles have already undergone several processing steps, each of which could have resulted in the articles or the filters not meeting the requirements.

The at least one measuring capacitor has a conductive electrode surface on a first side of the passage channel that is insulated from a base body of the HF measuring device. On an opposite side of the passage channel, it has at least one capacitor electrode that is insulated from the base body and held on virtual ground, the surface of which is smaller than a surface of the conductive electrode surface on the first side of the passage channel. The capacitor surfaces are thus designed as two surfaces or sides of the passage channel, one side being supplied with an HF signal of typically approximately 1 MHz to 100 MHz and the other being held on ground. The base body is usually made of metal and is held on ground. The capacitor electrode that is not supplied with an HF signal is held virtually on ground. The difference between the virtual ground of the capacitor electrode and the ground potential of the base body is typically less than 1 mV to approximately 1 mV. This ensures a very homogeneous field geometry.

In order to further homogenize the field geometry of the HF measuring field, the measuring capacitor is equipped with two large capacitor surfaces that are larger than the objects to be measured, for example the filter sections of cigarettes. The capacitor surface is the conductive electrode surface isolated from the base body, which is acted upon by an HF measuring signal, and the entire opposite surface, including the base body surface at ground potential and the capacitor electrode surface held on virtual ground, serves as the capacitor surface. The capacitor electrodes themselves are significantly smaller, for example on the order of the size of cigarette filters or even smaller. If several such capacitor electrodes held on virtual ground are arranged on the second side of the passage channel, it is also possible to determine the position of capsules in filter rods, for example.

Preferably, an electronic circuit is included, by means of which the electrode surface on the first side of the passage channel can be or is subjected to an RF measurement signal and the at least one capacitor electrode is held or maintained on a virtual ground, in particular by means of a zero detector control loop, wherein in particular each measuring capacitor is assigned its own zero detector control loop. Such a circuit comprises, for example, a harmonic oscillator source for generating the RF measurement signal and a circuit part which generates a virtual ground on the capacitor electrode. For this purpose, a second oscillator source is controlled in frequency, phase and amplitude so that the voltage on the electrode is kept at zero. This is preferably done by means of a zero detector control loop. Such circuits are known, for example, from German patent application No. 10 2011 083 052.9 known to the applicant, the disclosure content of which is intended to be included in full in the present patent application.

Since the input of the zero detector circuit is virtually kept at ground potential, existing stray capacitances on the connection side and the ground capacitance are metrologically ineffective, so that the measurement result is improved.

A further improvement in the measurement is achieved if, advantageously, a circuit comprising a compensation capacitor and an amplifier, in particular an inverting one, is connected in parallel to the at least one measuring capacitor, the gain factor and capacitance value of which are set or selected such that an empty signal from the measuring capacitor is partially or completely compensated. This improves the resolution of the measurement because an approximately ground potential is already established in the measuring range of the measuring capacitor or the measuring capacitor, at the input of the zero detector circuit, when the signal from the oscillator circuit is zero. This avoids having to compensate for a large empty signal from the measuring capacitor with the signal from the oscillator circuit, i.e. the part of the circuit that keeps the capacitor electrode at virtual ground. Instead, only the change in the measuring capacitor needs to be compensated. This also compensates for a significant portion of the noise in the circuit resulting from the harmonic oscillator that generates the RF measurement signal, since both the measurement capacitor and the compensation capacitor are fed from the same signal source.

In order to avoid amplifier-induced phase shifts between the input signals of the measuring capacitor and the compensation compensator or the compensation capacitance, it is advantageous a circuit with a DDS module and two differential amplifiers as oscillators, wherein mutually inverted outputs of the DDS module are connected in opposite directions to the inputs of the differential amplifiers, wherein the output of a differential amplifier with a first gain factor is connected to an electrode of the at least one measuring capacitor and the output of the other differential amplifier with a second gain factor, which is smaller than the first gain factor, is connected to an electrode of the compensation capacitor. This makes use of the property of DDS modules (DDS stands for "direct digital synthesis") to generate complementary output signals. By applying the complementary output signals to the inputs of the differential amplifiers in opposite directions, two in-phase but opposite output signals are generated, the amplitudes of which depend on the gain factors of the two differential amplifiers. Since the compensation capacitance is significantly larger than the very small measuring capacitance, the gain factor of the differential amplifier driving the compensation capacitance must be chosen to be correspondingly small.

The controlled oscillator, which is intended to set a virtual ground at the output of the measuring capacitor, can also advantageously be designed as a combination of DDS module and differential amplifier.

In a preferred embodiment of the arrangement according to the invention, two capacitor electrodes are arranged on both sides of a trajectory of capsules at a desired capsule position, with the electronic circuit being designed to carry out total measurements and/or difference measurements of the signals of the two capacitor electrodes. The total measurements provide information about, for example, the filling state of inserted capsules, while difference measurements provide the location of inserted capsules and in particular their deviation from a desired position. Arrangements of several capacitor electrodes are also possible.

The trough conveyor device is preferably designed as a trough drum, as a trough cone drum or as a trough conveyor belt.

In a preferred embodiment of the method according to the invention, the at least one measuring capacitor has on a first side of the passage channel a conductive electrode surface which is insulated from a base body of the HF measuring device and which is supplied with an HF measuring signal, and at least one capacitor electrode arranged on an opposite side of the passage channel and insulated from the base body, which is held at virtual ground, in particular by means of a zero detector control loop.

An improvement in the measurement is advantageously achieved if a circuit comprising a compensation capacitor and an amplifier, in particular an inverting one, is connected in parallel to at least one measuring capacitor, in particular the at least one measuring capacitor, the gain factor and capacitance value of which are set or selected such that an empty signal of the at least one measuring capacitor is compensated. Preferably, in order to avoid phase differences between measurement and compensation, in-phase inverted signals with different amplification factors are generated with which on the one hand the at least one measuring capacitor and on the other hand the compensation capacitance are operated.

Articles whose capsules are not properly filled or positioned are preferably rejected. This means that they are excluded from further processing or do not reach a packaging machine.

Further features of the invention will become apparent from the description of embodiments of the invention together with the claims and the accompanying drawings. Embodiments of the invention may fulfill individual features or a combination of several features.

Fig. 1

einen schematischen, aus dem Stand der Technik bekannten Verlauf einer Filterherstellung und Überprüfung,

Fig. 2

schematisch einen Teil einer Muldentrommel,

Fig. 3

schematisch eine Muldenkegeltrommel,

Fig. 4a) - c)

Detailansichten und schematische Schnittdarstellungen durch einen Messkondensator,

Fig. 5

eine schematische Darstellung einer Schaltanordnung und

Fig. 6

eine schematische Darstellung einer weiteren Schaltanordnung.

The invention is described below without limiting the general inventive concept using exemplary embodiments with reference to the drawings, whereby express reference is made to the drawings for all details of the invention not explained in more detail in the text. They show:

Fig.1

a schematic, state-of-the-art process of filter production and testing,

Fig.2

schematically a part of a trough drum,

Fig.3

schematic of a trough cone drum,

Fig. 4a) - c)

Detailed views and schematic sectional views through a measuring capacitor,

Fig.5

a schematic representation of a circuit arrangement and

Fig.6

a schematic representation of another switching arrangement.

In the drawings, identical or similar elements and/or parts are provided with the same reference numbers, so that a repeated presentation is dispensed with in each case.

In Fig.1 is a schematic representation of how filter rods with flavor capsules have been manufactured and checked to date. In process step 1, filter rods with flavor capsules are manufactured on a filter rod device, for example with a filter rod made of acetate, for example on a filter rod machine according to the KDF sold by the applicant. Directly during production, before further processing, these are checked using microwave sensors, for example the applicant's MIDAS-EF, to determine whether capsules are missing, whether a double number has been inserted in one place, whether a capsule is in the wrong position, whether a capsule is broken or has an irregular fill level.

The capsules are then optionally stored for 24 hours or more, depending on the customer, and in a process step 2 are fed into a pneumatic conveying device, for example according to the applicant's "FDU" (Filter Detection Unit), which is described, for example, in the German patent application EN 10 2009 017 962 A1 The filling level and the broken status are checked again, as capsules can easily be damaged on the filter rod machine, which only leak after some time and can therefore only be detected as faulty by the microwave sensor later when they are dry. This microwave device also corresponds, for example, to the MIDAS-EF, i.e. a cylindrical microwave resonator with a central passage for longitudinally axially conveyed filter rods, as is the case, for example, with DE 198 54 550 B4 is known.

Optionally, in process step 3, multi-filter production takes place, in which capsule-filled filter plugs are combined with other filter plugs to form a multi-filter rod. Here, too, the capsules can be damaged and possibly dry out over a longer period of time.

In some cases, testing in process step 2 is not possible due to a lack of appropriate facilities at the manufacturer.

After process step 2 and optionally process step 3, in process step 4 the respective filter is assembled and connected to a tobacco rod on a filter attachment machine, for example the machine sold by the applicant under the name "MAX". At this point and later, no testing of the capsule-filled filters is carried out. However, there is a certain probability that capsules will be damaged during cigarette production and in subsequent processing steps, so that they leak and have no taste effect for the end customer, thus leading to complaints. This risk increases with the number of processing steps, for example in the production and further processing of multi-filters.

There is currently no test on a cigarette machine at the last possible test point before packaging. The MIDAS measuring devices with centrally interspersed cylindrical resonators according to, for example, DE 198 54 550 B4 are not set up for this purpose.

In Fig.2 a trough conveyor device in the form of a trough drum 10 is shown in detail, on the cylindrical surface of which a sequence of troughs 12 is arranged, which hold cigarettes 14 with suction air (not shown). The trough drum 10 moves the cigarettes 14 in a conveying direction 11, which is shown with an arrow. The cigarettes 14 consist of a tobacco rod 17, which is mostly held in a trough 12, to which a filter 16 with a capsule 18 inserted therein is attached. The trough 12 and the trough drum 10 end approximately in the area of the transition from the tobacco rod 17 to the filter 16, so that a section 15 of the cigarette 14 protrudes over the trough 12 and is conveyed freely. These sections 15 of the cigarettes 14 then pass through a measuring device.

In Fig.3 an alternative embodiment of a trough conveying device is shown in the form of a trough cone drum 20 with a substantially frustroconical circumference. The trough cone drum 20 rotates in a conveying direction 21 and has troughs 22 on its outer circumferential surface in which cigarettes 14 are held by means of suction air (not shown). In this case too, the protruding sections 15 of the cigarettes 14 dip into a measuring device (not shown).

In Fig.4 In parts a) to c) various details and views of a capacitive RF measuring device 30 that can be used according to the invention are shown. Fig. 4a ) shows a cross-section that runs vertically through the conveying trajectory 19 of a cross-axially conveyed cigarette 14 with filter 16 and capsule 18 in the middle of the filter 16. At this point, the cigarette 14 is conveyed with its protruding section 15 through a passage channel 40 of the capacitive HF measuring device 30. The Fig. 4a ) The wall surface shown above consists of an electrically conductive electrode surface 38, which is insulated from the likewise metallic base body 36 of the HF measuring device 30 by means of an insulation 37. A supply line 39 runs through the insulation 37, via which the electrode surface 38 is exposed to a harmonic HF signal.

The Fig. 4a The part of the capacitive HF measuring device 34 shown below the cigarette 14 comprises, as the underside of the passage channel 40 or the opposite side, the electrically conductive base body 36, which is held at a ground potential, and two capacitor electrodes 42, 42', which are electrically insulated from the base body 36 by means of insulation 43, 43' and are connected to an electrical circuit via leads 44, 44'. These capacitor electrodes 42, 42' are held on a virtual ground. Since the potential between the virtual ground and the ground on which the base body 36 lies only differs by up to approx. 1 mV, a very homogeneous HF measuring field is formed in the entire passage channel 40 between the electrode 38 to which an HF measuring signal is applied and the opposite surface, which lies on ground or virtual ground.

In Fig. 4b the same capacitive HF measuring device 30 is shown in a section, which includes the conveying trajectory 19 of the cigarette 14 or the filter 16 with the capsule 18. Since this is conveyed in a trough on a trough drum in the exemplary embodiment, the passage channel 40 in this area has a ring-section-shaped design or describes a curve whose radius of curvature corresponds to the radius of the trough drum.

Fig. 4c ) shows a top view of the lower surface of the passage channel 40, i.e. the side of the capacitive HF measuring device 30 that is held at ground potential. A large part of the surface of this electrode consists of the surface of the base body 36 that is held at ground potential. Two capacitor electrodes 42, 42' that are held at virtual ground are arranged centrally along the trajectory 19 of a capsule 18. The capacitor electrodes 42, 42' are insulated from the base body 36 by a circumferential insulation 43. The actual potential difference, however, is only up to one or a few mV. The capacitor electrodes 42, 42' are arranged to the left and right of the trajectory 19, so that incorrect positioning of a capsule can be recognized by an asymmetry in the measurement signals of the capacitor electrodes 42, 42'.

In Fig.5 a first circuit of a capacitive HF measuring device 30 that can be used according to the invention is shown schematically. The measuring capacitor 34 is fed by a harmonic signal source, i.e. an oscillator 50. The oscillator 50 can be constructed, for example, with a DDS circuit with a downstream low-pass filter or with a quartz oscillator. The second connection of the measuring capacitor 34 is connected to the input of a zero detector circuit 62, the input of which is virtually held at ground potential 60 by the causal relationship. Since the input of the zero detector circuit 62 is virtually held at ground potential 60, the existing stray capacitances 54, 56 of the connection lines of the measuring capacitor 34 are ineffective in terms of measurement technology.

A further impedance 52 is connected to the input of the zero detector circuit 62, which can be designed as a capacitor or a resistor, for example, through which a second harmonic signal from a second oscillator 51 is fed. The oscillator 51 is controlled in amplitude and phase by a control device 64 so that the input signal of the zero detector circuit 62 is virtually held at ground potential 60. For this purpose, the signal present at the input of the zero detector circuit 62 is measured for amplitude and phase and transmitted as an output signal 63 to the control device 64. The required manipulated variables 65 in amplitude and phase are a measure of the amount and the loss factor of the measuring capacitor 34. These two variables are forwarded to a higher-level automation unit for further processing (reference numeral 65a) or given to the oscillator 51 as manipulated variables (reference numeral 65).

In an advantageous development of this circuit, a compensation capacitance or a compensation capacitor 68 is used to improve the resolution of the measurement, which is replaced by an inverting Amplifier 66 is fed from the same oscillator 50 as the measuring capacitor 34. The gain factor -a of the inverting amplifier 66 and the capacitance value of the compensation capacitor 68 are selected so that in the measuring range of the measuring capacitor 34 at the input of the zero detector circuit 62, an approximate ground potential is already established when the signal of the oscillator circuit 51 is zero. This avoids having to compensate for a large empty signal of the measuring capacitor 34 with the signal of the oscillator 51. Only the change in the measuring capacitor 34 needs to be compensated. This can significantly improve the resolution of the measurement. A further advantage of this compensation circuit is that a significant part of the noise of the oscillator 50 is compensated because the measuring capacitor 34 and the compensation capacitor 68 are fed from the same signal source.

In accordance with the invention, the zero detector control circuit in the circuit according to Fig.5 the arrangement of zero detector circuit 62, control device 64 and oscillator 51 with impedance 52, which ensure that the virtual ground 60 is established.

Fig.6 shows a further embodiment of a circuit arrangement that can be used according to the invention. In this arrangement, two measuring capacitors 34, 34' are connected to a harmonic oscillator 50 as a signal source. Both measuring capacitors 34, 34' are the same as in Fig.4 This also means that the two measuring capacitors 39, 39' share the electrode surface 38 which is exposed to an RF measuring signal. Stray capacitances and compensation capacitances are shown in Fig.6 not shown, but are as in Fig.5 , present. Each measuring capacitor 34, 34' is connected to its own zero detector circuit 62, 62'. Each zero detector circuit input is virtually regulated to ground potential 60, 60' by a corresponding control device 64, 64' and oscillators 51, 51' via impedances 52, 52'. The corresponding output signals 65a, 65a' of the two control devices 64, 64' are further processed in an evaluation circuit 70. In this evaluation circuit 70, on the one hand, sum signals are formed which make it possible to detect the presence and the correct content of the capsules. In addition, a difference signal is formed which is zero when the capsule is correctly positioned in the filter. If the capsule is not in the center position, either a positive or a negative difference signal results depending on the deviation.

In a Fig. 7a ) shown improved embodiment of an oscillator 50a, which replaces the oscillator 50 in Fig.5 and 6 can be set, the property of DDS components 80 is used to generate complementary output signals U' , -U' . These are connected in opposite directions to the inputs of two differential amplifiers 81, 82. This generates two mutually inverted signals U, -αU with different amplification factors, namely, for example, an amplification factor of 1 in the differential amplifier 81 and an amplification factor of -α in the differential amplifier 82. The amplification factor α is usually significantly smaller than 1. The measuring capacitor 34 (or 34') is then operated with the output signal U of the differential amplifier 81, and the compensation capacitor 68 is operated with the output signal -αU of the differential amplifier 82. In this way, a signal generated by the amplifier 66 in Fig.5 caused disturbing additional phase delay between the measuring capacitor 34 and the compensation compensator 68 can be avoided.

A DDS module 90 can also be used in a similar way in an oscillator 51a according to Fig. 7b ) which replaces the oscillator 51 according to Fig.5 , 6 In this case, the DDS module 90 receives the manipulated variables 65 as an input signal. The output signals U', -U' are converted via a differential amplifier 91 into an output signal U, which is fed via an impedance 52, 52' according to Fig.5 , 6 used to set the virtual mass 60, 60'.

List of reference symbols

1

Capsule use and first capsule testing

2

Capsule testing after storage

3

optional multi-filter production

4

Cigarette production

10

Trough drum

11

Conveying direction

12

trough

14

Cigarette

15

protruding section of the cigarette

16

filter

17

Tobacco stick

18

capsule

19

Trajectory of a capsule

20

Trough cone drum

21

Conveying direction

22

trough

30

capacitive RF measuring device

34

Measuring capacitor

36

Base body

37

insulation

38

Electrode area

39

Supply line

40

Passage channel

42, 42'

Capacitor electrode

43, 43'

insulation

44, 44'

Supply line

50, 50a

oscillator

51, 51a

oscillator

52, 52'

Impedance

54, 56

Stray capacity

60, 60'

virtual mass

62, 62'

Zero detector circuit

63, 63'

Output signal

64, 64'

Control device

65, 65'

Control variables

65a, 65a'

Control variables for the evaluation unit

66

inverting amplifier

68

Compensation capacitor

70

Evaluation circuit

80

DDS module

81, 82

Differential amplifier

90

DDS module

91

Differential amplifier

Claims (4)

1. Method for checking cross-axially conveyed rod-shaped articles (14) of the tobacco processing industry, in particular for checking liquid-filled capsules (18) in filters (16) of filter cigarettes (14), wherein rod-shaped articles (14), in particular filter cigarettes (14), are conveyed cross-axially past at least one capacitive HF measuring device (30) having at least one measuring capacitor (34, 34') in troughs (12, 22) of at least one trough conveying device (10, 20), wherein the rod-shaped articles (14) have a section (15) projecting over the respective troughs (12, 22), wherein the projecting sections (15) of the articles (14) cross through at least one longitudinally extended passage channel (40), open on one side, of the at least one capacitive HF measuring device (30) on their conveying path and cross through the at least one measuring capacitor (34, 34') on their conveying path through the passage channel (40), so that the projecting sections (15) of the rod-shaped articles (14) cross through a HF measuring field in the at least one measuring capacitor (34, 34') on their conveying path through the passage channel (40), characterised in that a measuring signal of the at least one measuring capacitor (34, 34') is evaluated for the presence and/or filling of a capsule (18) in a filter (16), and measuring signals of two measuring capacitors (34, 34') are evaluated for positioning of a capsule (18).
2. Method according to claim 1, characterised in that the at least one measuring capacitor (34, 34') has a conducting electrode surface (38), insulated from a basic body (36) of the HF measuring device (30), which is loaded with an HF measuring signal, on a first side of the passage channel (40), and at least one capacitor electrode (42, 42'), located on an opposite side of the passage channel (40) and insulated with respect to the basic body (36), which capacitor electrode is held on a virtual grounding connection (60, 60'), in particular by means of a null detector control circuit.
3. Method according to claim 2, characterised in that a circuit of a compensation capacitor (68), and an, in particular inverting, amplifier (66, 82), the amplification factor and capacitance value of which are adjusted or chosen so that an empty signal of the at least one measuring capacitor (34, 34') is compensated, is connected in parallel with at least one measuring capacitor (34, 34'), particularly the measuring capacity (34, 34').
4. Method according to one of claims 1 to 3, characterised in that articles (14), the capsules (18) of which have an incorrect filling or positioning, are removed.

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