EP2865282B1 - Assembly and method for checking rod-shaped articles from the tobacco processing industry - Google Patents

Description

The invention relates to an arrangement for checking transversely supported rod-shaped articles of the tobacco processing industry, in particular for checking liquid-filled capsules in filters of filter cigarettes, with at least one trough conveyor with troughs for receiving and Queraxialen promotion of rod-shaped articles and at least one capacitive RF measuring device at least one measuring capacitor. The invention further relates to a machine of the tobacco-processing industry and a method for checking cross-axially conveyed rod-shaped articles of the tobacco-processing industry, in particular for checking liquid-filled capsules in filters of filter cigarettes.

So far filter rods are manufactured in some filter rod machines, such as in the so-called KDF of the applicant, in the objects, such as flavor liquid filled capsules are inserted. Directly during production, these capsules are tested before further processing, in particular, microwave sensors such as the Applicant's MIDAS-EF are used. It checks whether the filling content 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 thus produced for a certain time, for example, 24 hours, stored and then along a pneumatic conveyor line again on their fill content and whether they are broken, checked. This happens, for example, in the applicant's "FDU" system, in order to prevent capsules from being damaged on the filter strand production machine, which leak out only after some time and are only detected as defective by the microwave sensor in the dry state.

Out DE 23 43 668 A1 For example, a device for checking cigarette ends is disclosed, which comprises a test conveyor in which the cigarettes are conveyed transaxially. Furthermore, the device comprises a capacitive measuring device for the tobacco density. The capacitive measuring arrangement has at least two electrodes arranged stationarily with respect to the test conveyor and connected to a high-frequency voltage source. Their position to the ends of the cigarette is chosen so that at the time of measurement emanating from them high-frequency field through each of the cigarette ends.

Out DE 10 2011 083 052 A1 is a capacitive RF strand measuring device for the capacitive determination of at least one property of an endless material strand of the tobacco processing industry known. The measuring device comprises a housing with at least one measuring capacitor, which can be enforced by the material strand and acted upon by an RF voltage signal. The capacitive RF strand measuring device includes one or more accuracy-determining electronic components in its housing.

The not previously published EP 2 848 133 A1 An arrangement for checking cross-axially conveyed rod-shaped articles of the tobacco-processing industry is known. The arrangement is for checking liquid-filled capsules in filters of filter cigarettes. The arrangement comprises a trough conveyor with troughs for receiving and for transversely axial conveying the rod-shaped article. The inspection of the rod-shaped articles is carried out by means of a microwave measuring device.

In contrast, the present invention has the object to ensure that the quality of the rod-shaped articles of the tobacco processing industry is ensured after the complete processing.

This object of the invention is based on an arrangement for checking transversely promoted rod-shaped articles of the tobacco industry, in particular for checking liquid-filled capsules in filters of filter cigarettes, with at least one trough conveyor with troughs for receiving and queraxialen promotion of rod-shaped articles and at least one capacitive RF measuring device with at least one measuring capacitor, dissolved, wherein the at least one capacitive RF measuring device along a conveying path of the rod-shaped Article has at least one longitudinal, one-sided or two-sided open lateral passageway for a projecting over the respective troughs portion of the article, wherein the at least one passageway laterally penetrates the at least one measuring capacitor, so that projecting portions of the rod-shaped article on its conveying path through the passageway a HF -Messfeld traversed in at least one measuring capacitor, wherein the arrangement is formed by the fact that the at least one measuring capacitor on a first side of the passage channel one of a main body of the RF measuring device insulated conductive electrode surface and on an opposite side of the passage channel at least one with respect to the main body isolated, held on virtual mass capacitor electrode whose surface is smaller than a surface of the conductive electrode surface on the first side of the passageway, wherein the at least one capacitor electrode is arranged centrally along a trajectory of a capsule.

The invention is based on the basic idea that the articles, in particular filter cigarettes, dip laterally laterally into the measurement capacitor and pass through the RF measurement field excited therein. Thus, the protruding portions of the rod-shaped articles completely enter the RF measurement field. With the longitudinally extended, on one side open passageway, the capacitive RF measuring device is also specially designed for this cross-axially promoted lateral passage to allow the corresponding passage through the measuring capacitor. This passageway cuts through or passes through the measuring capacitor. Preferably, the projecting portions of the articles, in particular the capsules, pass through the RF measuring field in a region which is substantially homogeneous in the longitudinal axis of the articles of the RF measuring field.

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 accurately and largely independently of position. This increases the reliability of measurement for the quality of the filters or the capsules contained therein.

With the solution according to the invention it is possible to check the quality of the rod-shaped articles and especially the filters and the capsules inserted therein after the complete production of the articles. At this point in time, the articles have already undergone several processing steps, which in each case could lead to the articles or the filters not meeting the specified requirements.

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

In order to further homogenize the field geometry of the RF measuring field, the measuring capacitor is equipped with two large capacitor surfaces which are larger than the objects to be measured, for example the filter sections of cigarettes. On the one hand, the conductive surface isolated from the main body serves as a capacitor surface Electrode surface, which is acted upon by an RF measurement signal, and on the other hand, the entire opposing surface including the ground potential to ground potential and held on virtual ground capacitor electrode surface. The capacitor electrodes themselves are significantly smaller, for example, in the order of the cigarette filter or even smaller. In the case of an arrangement of a plurality of such capacitor electrodes held on virtual ground on the second side of the passage channel, it is also possible to realize a position determination 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 is acted upon or acted upon by an RF measurement signal and the at least one capacitor electrode on a virtual ground durable or held, in particular by means of a zero detector control loop, 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 at the capacitor electrode. For this purpose, a second oscillator source in frequency, phase and amplitude is controlled so that the voltage at 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 the applicant, the disclosure content of which should be incorporated in full in the present patent application.

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

A further improvement in the measurement results when advantageously the at least one measuring capacitor is connected in parallel with a circuit comprising a compensation capacitance and an amplifier, in particular inverting, whose amplification factor and capacitance value are set or selected such that an empty signal of the measuring capacitor is partially or completely compensated , As a result, the resolution of the measurement is improved because in the measuring range of the measuring capacitance or the measuring capacitor, at the input of the zero detector circuit, already approximately ground potential sets when the signal of the oscillator circuit is zero. This avoids that a large empty signal of the measuring capacitor with the signal of the oscillator circuit, ie the part of the circuit that holds the capacitor electrode to virtual ground, must be compensated. Instead, only the change of the measuring capacitor has to be compensated. This also makes up for a significant part of the noise of the circuit, which is compensated 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 Kompensationskompensators or the compensation capacitor, a circuit comprising a DDS module and two differential amplifiers is advantageously as an oscillator, mutually inverted outputs of the DDS module are connected in opposite directions with the inputs of the differential amplifier wherein the output of a differential amplifier having a first gain factor is connected to an electrode of the at least one measurement capacitor and the output of the other differential amplifier having a second amplification factor smaller than the first amplification factor is connected to an electrode of the compensation capacitance. This makes use of the property of DDS devices (DDS stands for "direct digital synthesis") to generate complementary output signals. By the opposing action on the complementary output signals to the inputs of the differential amplifier two in-phase, but opposing output signals are generated, the amplitudes of which depend on the amplification factors of the two differential amplifiers. Since the compensation capacity is significantly greater than the very small measurement capacitance, the amplification factor of the differential amplifier driving the compensation capacitor has to be correspondingly small.

Also, the controlled oscillator, which is provided for setting a virtual mass output of the measuring capacitor can be advantageously designed as a combination of DDS module and differential amplifier.

In a preferred embodiment of the arrangement according to the invention it is provided that two capacitor electrodes are arranged on both sides of a trajectory of capsules at a desired capsule position, wherein the electronic circuit is designed to perform summation measurements and / or differential measurements of the signals of the two capacitor electrodes. The sum measurements provide information about, for example, the filling state of inserted capsules, while differential measurements give the location of inserted capsules and in particular their deviation from a desired position. Also on the arrangements of several capacitor electrodes are possible.

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

The object underlying the invention is also achieved by a machine of the tobacco-processing industry, in particular filter attachment machine, with an inventive arrangement described above. This machine of the tobacco processing industry has the same characteristics, advantages and properties as the arrangement according to the invention.

Furthermore, the object underlying the invention is also achieved by a method for checking transversely promoted rod-shaped articles of the tobacco processing industry, in particular for checking liquid-filled capsules in filters of filter cigarettes, in particular in a previously described inventive arrangement, wherein rod-shaped articles, in particular Filter cigarettes, are conveyed in troughs at least one trough conveyor transaxially on at least one capacitive RF measuring device with at least one measuring capacitor, the rod-shaped article having a projecting over the respective troughs portion, wherein the projecting portions of the article on its conveying path at least one longitudinally extended, one-sided open lateral passageway of at least one capacitive RF measuring device and traversed on its conveying path through the passageway the at least one Meßkond traverse the insulator, so that the projecting portions of the rod-shaped article on their conveyance through the passageway through an RF measuring field in the at least one measuring capacitor, the method is further developed, that a measuring signal of the at least one measuring capacitor for the presence and / or a filling a capsule is evaluated in a filter and measuring signals from two measuring capacitors are evaluated to a position of a capsule.

The inventive method is based on the same basic idea as the arrangement according to the invention, that the rod-shaped articles are supported transversely axial and a section on the respective wells, in which they are supported protrudes. This projecting portion is conveyed through an elongated, single-sided or double-sided open lateral passageway of at least one RF measuring device and traverses on its conveying path through the passageway the at least one measuring capacitor.

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 insulated from a base body of the HF measuring device, which is acted on by an HF measuring signal, and at least one arranged on an opposite side of the passage channel and to the main body isolated capacitor electrode which is held on virtual ground, in particular by means of a zero detector control loop.

An improvement in the measurement is advantageously obtained if at least one measuring capacitor, in particular the at least one measuring capacitor, a circuit of a compensation capacitor and a, in particular inverting, amplifier is connected in parallel, the gain and capacitance value are set or selected such that an empty signal of at least a measuring capacitor is compensated. Preferably, to avoid phase differences between Measurement and compensation by means of a circuit with a DDS module whose complementary output signals are directed in opposite directions to inputs of two differential amplifiers, generates in-phase inverted signals with different gain factors, with which on the one hand the at least one measuring capacitor and on the other hand the compensation capacity are operated.

Articles whose capsules have improper filling or positioning are preferably removed. This means that they are excluded from further processing or do not get to a packing machine.

The method according to the invention also has the same features, advantages and properties as the arrangement according to the invention.

Further features of the invention will become apparent from the description of embodiments according to the invention together with the claims and the accompanying drawings. Embodiments of the invention may satisfy 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 erfindungsgemäßen Messkondensator,

Fig. 5

eine schematische Darstellung einer erfindungsgemäßen Schaltanordnung und

Fig. 6

eine schematische Darstellung einer weiteren erfindungsgemäßen Schaltanordnung.

The invention will be described below without limiting the general inventive idea by means of embodiments with reference to the drawings, reference being expressly made to the drawings with respect to all in the text unspecified details of the invention. Show it:

Fig. 1

a schematic, known from the prior art course of filter production and verification,

Fig. 2

schematically a part of a well drum,

Fig. 3

schematically a trough drum,

Fig. 4a) - c)

Detailed views and schematic sectional views through a measuring capacitor according to the invention,

Fig. 5

a schematic representation of a switching arrangement according to the invention and

Fig. 6

a schematic representation of another switching arrangement according to the invention.

In the drawings, the same or similar elements and / or parts are provided with the same reference numerals, so that apart from a new idea each.

In Fig. 1 is shown schematically how filter rods with flavor capsules so far produced and reviewed. In process step 1, filter sticks with flavor capsules are produced on a filter rod device, for example with a filter strand made of acetate, for example on a filter rod machine according to the applicant's KDF .. Directly during production, these are processed before further processing by means of microwave sensors, for example the MIDAS-EF Applicant, then examined whether capsules are missing, a double number is introduced in one place, whether a capsule is in the wrong position, whether a capsule is broken or has an irregular filling content.

Subsequently, the capsules become optional and customer-dependent 24 Hours or more stored and in a process step 2 in a pneumatic conveying device, for example according to the "FDU" (Filter Detection Unit) of the Applicant, for example, in the German patent application DE 10 2009 017 962 A1 the applicant is described, checked again. In this case again the filling content and the broken status are checked, since capsules can easily be damaged on the filter rod machine, which only leak out after some time and thus can only later be detected as defective by the microwave sensor in the dried out state. This microwave device, for example, corresponds to the MIDAS-EF, so a cylindrical microwave resonator with central passage for longitudinally promoted filter rods, as he, for example DE 198 54 550 B4 is known.

Optionally, in a method step 3, a multifilament production is carried out, in which capsule-filled filter plugs are combined with other filter plugs to form a multifilter rod. Again, the capsules can be damaged and possibly dry out for a long time.

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

After process step 2 and optionally process step 3, the respective filter is assembled and connected to a tobacco rod in a process step 4 on a filter attachment machine, for example the machine sold under the name "MAX" by the applicant. At this point and later, there is currently no check of the capsule-filled filters. However, there is a certain likelihood that capsules will also be damaged during cigarette production and subsequent processing steps, causing them to leak out and to the end customer develop no taste effect and thus it comes to complaints. This risk increases as processing steps increase, such as in the manufacture and processing of multifilters.

There is currently no check on a cigarette machine at the last possible check time prior to 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 fragmentary form, on whose cylindrical surface 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 by an arrow. The cigarettes 14 consist of a tobacco rod 17, which is mostly held in each case in a trough 12, to which a filter 16 is attached with a capsule 18 inserted therein. Approximately in the area of the transition from the tobacco rod 17 to the filter 16, the trough 12 and the trough drum 10 end, so that a portion 15 of the cigarette 14 projects beyond the trough 12 and is conveyed freely. These sections 15 of the cigarettes 14 subsequently pass through a measuring device according to the invention.

In Fig. 3 An alternative embodiment of a tray conveyor device is shown in the form of a tray cone drum 20 having a substantially frustoconical circumference. The trough drum 20 rotates in a conveying direction 21 and has on its outer circumferential surface turn troughs 22 in which cigarettes 14 by means of suction air (not shown) are held. Also in this case, the protruding portions 15 of the cigarettes dive 14 in an unillustrated measuring device according to the invention a.

In Fig. 4 In the parts a) to c) various details and views of a capacitive RF measuring device 30 according to the invention are shown. Fig. 4a ) shows a cross section which runs vertically through the conveying trajectory 19 of a cross-axially promoted cigarette 14 with filter 16 and capsule 18 in the center of the filter 16. At this point, the cigarette 14 is conveyed with its projecting portion 15 through a passageway 40 of the capacitive RF measuring device 30. In the Fig. 4a ) wall surface shown above consists of an electrically conductive electrode surface 38 which is isolated by means of an insulation 37 from the likewise metallic base body 36 of the RF measuring device 30. Through the insulation 37, a feed line 39, via which the electrode surface 38 is acted upon by a harmonic RF signal.

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

In Fig. 4b the same capacitive RF measuring device 30 is shown in section in a section which includes the delivery trajectory 19 of the cigarette 14 and 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-segment-shaped configuration or describes a curve whose radius of curvature corresponds to the radius of the trough drum.

Fig. 4c ) shows a plan view of the lower surface of the passageway 40, that is, the grounded side of the capacitive RF measuring device 30. A majority of the surface of this electrode consists of the surface of the held at ground potential body 36. Centrally along the trajectory 19 of a capsule 18th are two capacitor electrodes 42, 42 'are arranged, which are held on virtual ground. The capacitor electrodes 42, 42 'are isolated from the main body 36 by a circumferential insulation 43. However, the actual potential difference 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 a mispositioning of a capsule by an asymmetry in the measurement signals of the capacitor electrodes 42, 42' can be seen.

In Fig. 5 a first circuit of a capacitive RF measuring device 30 according to the invention is shown schematically. In this case, the measuring capacitor 34 is fed by a harmonic signal source, ie an oscillator 50. The oscillator 50 may be constructed, for example, with a DDS circuit with a downstream low-pass filter or with a quartz oscillator. The second terminal of the measuring capacitor 34 is connected to the input of a zero detector circuit 62 whose input through the effect context is held virtually at ground potential 60. Since the input of the zero detector circuit 62 is virtually kept at ground potential 60, the existing stray capacitances 54, 56 of the connection lines of the measuring capacitance 34 are metrologically ineffective.

To the input of the zero detector circuit 62, a further impedance 52 is connected, which may for example be designed as a capacitance or as a resistor, via which a second harmonic signal of a second oscillator 51 is fed. The oscillator 51 is thereby controlled in amplitude and phase by a control device 64 in such a way that the input signal of the zero detector circuit 62 is virtually kept at ground potential 60. For this purpose, the signal applied to the input of the zero detector circuit 62 is measured in 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 magnitude and the loss factor of the measuring capacitance 34. These two variables are forwarded to a higher-level automation unit for further processing (reference numeral 65a) or to the oscillator 51 as manipulated variables (reference numeral 65).

In an advantageous development of this circuit, a compensation capacitor or a compensation capacitor 68 is used to improve the resolution of the measurement, which is fed by an inverting amplifier 66 from the same oscillator 50 as the measuring capacitor 34. In this case, the amplification factor -a of the inverting amplifier 66 and the capacitance value of the compensation capacitor 68 are selected such that approximately ground potential already sets in the measuring range of the measuring capacitor 34 at the input of the zero detector circuit 62 when the signal of the oscillator circuit 51 is zero. This will avoided that a large empty signal of the measuring capacitor 34 must be compensated with the signal of the oscillator 51. Only the change of the measuring capacitor 34 has to be compensated. As a result, the resolution of the measurement can be significantly improved. A further advantage of this compensation circuit is that a substantial part of the noise of the oscillator 50 is compensated since the measurement capacitor 34 and the compensation capacitor 68 are fed from the same signal source.

For the purposes of the invention is as a zero detector control circuit in the circuit according to Fig. 5 the arrangement of zero detector circuit 62, controller 64 and oscillator 51 with impedance 52 are considered, which ensure that the virtual mass 60 is established.

Fig. 6 shows a further embodiment of a circuit arrangement 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 area 38 which is acted upon by an HF measuring signal. Stray capacitance and compensation capacities are in for clarity Fig. 6 not shown, however, are as well as in Fig. 5 , available. Each measuring capacitor 34, 34 'is connected in each case to its own zero detector circuit 62, 62'. Each Nulldetektorschaltungseingang is virtually controlled by a corresponding control device 64, 64 'and oscillators 51, 51' via impedances 52, 52 'to ground potential 60, 60'. 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. Farther a difference signal is formed, which is equal to zero if the capsule in the filter is correctly positioned. If the capsule is not in the middle position, depending on the deviation either a positive or a negative difference signal results.

In an in Fig. 7a ) shown an improved embodiment of an oscillator 50a, which takes the place of the oscillator 50 in Fig. 5 and 6 can be set, the property of DDS devices 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. As a result, two mutually inverted signals U, -αU are generated with different amplification factor , namely, for example, a gain factor 1 in the differential amplifier 81 and a gain factor - α in the differential amplifier 82. The gain α is usually significantly less than 1. The output signal U of the differential amplifier 81 Then, the measuring capacitor 34 (or 34 ') is operated, with the output signal -αU of the differential amplifier 82 of the compensation capacitor 68. Thus, one through the amplifier 66 in Fig. 5 caused disturbing additional phase delay between the measuring capacitor 34 and the Kompensationskompensator 68 are avoided.

Similarly, a DDS device 90 can also be used in an oscillator 51a according to FIG Fig. 7b ), which take the place of the oscillator 51 according to Fig. 5 . 6 can occur. In this case, the DDS module 90 receives the control variables 65 as an input signal. The output signals U ', -U' are converted via a differential amplifier 91 into an output signal U, which via an impedance 52, 52 'according to Fig. 5 . 6 for setting the virtual mass 60, 60 'is used.

LIST OF REFERENCES

1

Capsule insert and first capsule test

2

Capsule test after storage

3

optional multifilter production

4

cigarette manufacturing

10

trough drum

11

conveying direction

12

trough

14

Cigarette

15

protruding section of the cigarette

16

filter

17

tobacco rod

18

capsule

19

Trajectory of a capsule

20

Hollow cone drum

21

conveying direction

22

trough

30

Capacitive RF measuring device

34

measuring capacitor

36

body

37

insulation

38

electrode area

39

supply

40

Passageway

42, 42 '

capacitor electrode

43, 43 '

insulation

44, 44 '

supply

50, 50a

oscillator

51, 51a

oscillator

52, 52 '

impedance

54, 56

stray capacitance

60, 60 '

virtual mass

62, 62 '

Zero detector circuit

63, 63 '

output

64, 64 '

control device

65, 65 '

manipulated variables

65a, 65a '

Manipulated variables for the evaluation unit

66

inverting amplifier

68

compensation capacitor

70

evaluation circuit

80

DDS chip

81, 82

differential amplifier

90

DDS chip

91

differential amplifier

Claims (11)

1. Arrangement 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), with at least one trough conveying device (10, 20) having troughs (12, 22) for receiving and cross-axial conveying of rod-shaped articles (14) and at least one capacitive HF measuring device (30) having at least one measuring capacitor (34, 34'), wherein the at least one capacitive HF measuring device (30), along a conveying path of the rod-shaped articles (14), has at least one longitudinally extended lateral passage channel (40) open on one side or both sides for a section (15) of the articles (14) projecting over the respective troughs (12, 22), wherein the at least one passage channel (40) laterally penetrates the at least one measuring capacitor (34, 34'), so that 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 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) on a first side of the passage channel (40), and on an opposite side of the passage channel (40) at least one capacitor electrode (42, 42') held on a virtual grounding connection (60) insulated with respect to the basic body (36), the surface of which capacitor electrode is smaller than the surface of the conducting electrode surface (38) on the first side of the passage channel (40), wherein the at least one capacitor electrode (42, 42') is centrally located along a course (19) of a capsule (18).
2. Arrangement according to claim 1, characterised in that it includes an electronic circuit, by means of which the electrode surface (38) on the first side of the passage channel (38) can be loaded or is loaded with a HF measuring signal, and the at least one capacitor electrode (42, 42') can be held or is held on a virtual grounding connection (60), in particular by means of a null detector control circuit, wherein in particular each measuring capacitor (34, 34') is associated with its own null detector control circuit.
3. Arrangement according to claim 2, characterised in that a circuit having 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 measuring capacitor (34, 34') is partially or completely compensated, is connected in parallel to the at least one measuring capacitor (34, 34').
4. Arrangement according to claim 3, characterised in that it includes a circuit having a DDS component (80) and two differential amplifiers (81, 82) as oscillator (50a), wherein outputs of the DDS component (80) inverted to one another are inversely connected with the inputs of the differential amplifiers (81, 82), wherein the output of one differential amplifier (81) having a first amplification factor is connected with an electrode of the at least one measuring capacitor (34) and the output of the other differential amplifier (82) having a second amplification factor, which is smaller than the first amplification factor, is connected with an electrode of the compensation capacitor.
5. Arrangement according to any of claims 1 to 4, characterised in that two capacitor electrodes (42, 42') are located on both sides of a course (19) of capsules (18) at a capsule nominal position, wherein the electronic circuit is designed to perform summation measurements and/or differential measurements of the signals of the two capacitor electrodes (42, 42').
6. Arrangement according to any of claims 1 to 5, characterised in that the trough conveying device (10, 20) is designed as a trough drum (10), as a trough cone drum (20), or as a trough conveyor belt.
7. Machine of the tobacco processing industry, in particular a filter attaching machine, having an arrangement according to one of claims 1 to 6.
8. 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), in particular in an arrangement according to any of claims 1 to 7, 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).
9. Method according to claim 8, 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.
10. Method according to claim 9, 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').
11. Method according to one of claims 8 to 10, characterised in that articles (14), the capsules (18) of which have an incorrect filling or positioning, are removed.

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