阅读说明：本技术 烟草加工业的抽吸带式输送机和制条机以及测量装置在制条机的抽吸带式输送机中的使用 (Suction belt conveyor and rod making machine of tobacco processing industry and use of measuring device in suction belt conveyor of rod making machine ) 是由 J·米勒 J·格茨 于 2019-03-06 设计创作，主要内容包括：说明烟草加工业的制条机的、一种用于输送材料、尤其是烟草的抽吸带式输送机,该抽吸带式输送机具有：抽吸带(4),所述抽吸带沿着抽吸带路径得到导引,所述抽吸带路径具有第一区段(I)、第二区段(II)、第三区段(III)以及第四区段(IV)；用于在所述抽吸带路径的第一区段(I)和第二区段(II)的内部向所述抽吸带(4)加载负压的抽吸装置(7)；以及测量装置,其中所述抽吸带路径的第一区段(I)如此布置,从而材料通过所述抽吸装置(7)的抽吸作用积聚在所述抽吸带(4)的沿着抽吸带路径的第一区段(I)得到导引的下分支(4a)上并且在其上面形成材料条,所述抽吸带路径的第二区段(II)在下游邻接所述抽吸带路径的第一区段(I)并且被构造用于导引所述抽吸带(4)连同布置在其上面的并且在所述抽吸带路径的第一区段(I)中形成的材料条,并且所述抽吸带路径的第三区段(III)在下游邻接所述抽吸带路径的第二区段(II)并且被构造用于将所述抽吸带(4)与所述材料条分开。本发明的特点在于,所述测量装置具有至少一个第一传感器(10),所述第一传感器被构造用于在所述抽吸带路径的第四区段(IV)中的位置处测量所述抽吸带(4)的特性并且输出表明所述抽吸带(4)的所测量的特性的第一种测量信号。(A suction belt conveyor for conveying material, in particular tobacco, of a rod maker of the tobacco processing industry, comprising: a suction belt (4) guided along a suction belt path having a first section (I), a second section (II), a third section (III) and a fourth section (IV); a suction device (7) for applying a negative pressure to the suction belt (4) within the first section (I) and the second section (II) of the suction belt path; and a measuring device, wherein the first section (I) of the suction belt path is arranged in such a way that material is accumulated by the suction action of the suction device (7) on a lower limb (4 a) of the suction belt (4) guided along the first section (I) of the suction belt path and forms a material strip thereon, the second section (II) of the suction belt path adjoins the first section (I) of the suction belt path downstream and is designed to guide the suction belt (4) together with the material strip arranged thereon and formed in the first section (I) of the suction belt path, and the third section (III) of the suction belt path adjoins the second section (II) of the suction belt path downstream and is designed to separate the suction belt (4) from the material strip. The invention is characterized in that the measuring device has at least one first sensor (10) which is designed to measure a property of the suction belt (4) at a position in a fourth section (IV) of the suction belt path and to output a first measuring signal which indicates the measured property of the suction belt (4).)

1. A suction belt conveyor for conveying material, in particular tobacco, of a rod maker of the tobacco processing industry, comprising: a suction belt (4) guided along a suction belt path having a first section (I), a second section (II), a third section (III) and a fourth section (IV); a suction device (7) for applying a negative pressure to the suction belt (4) within the first section (I) and the second section (II) of the suction belt path; and a measuring device, wherein the first section (I) of the suction belt path is arranged in such a way that material is accumulated by the suction action of the suction device (7) on a lower limb (4 a) of the suction belt (4) guided along the first section (I) of the suction belt path and forms a material strip thereon, the second section (II) of the suction belt path adjoins the first section (I) of the suction belt path downstream and is designed to guide the suction belt (4) together with the material strip arranged thereon and formed in the first section (I) of the suction belt path, and the third section (III) of the suction belt path adjoins the second section (II) of the suction belt path downstream and is designed to separate the suction belt (4) from the material strip,

characterized in that the measuring device has at least one first sensor (10) which is designed to measure a property of the suction belt (4) at a position in a fourth section (IV) of the suction belt path and to output a first measuring signal which is indicative of the measured property of the suction belt (4).

2. The suction belt conveyor according to claim 1, characterized in that the first sensor (10) of the measuring device is configured for measuring the thickness and/or density of the suction belt (4) and thereby the wear as a characteristic of the suction belt.

3. Suction belt conveyor according to claim 1 or 2, characterized in that the suction belt (4) is configured as a continuously rotating suction belt which is guided along a correspondingly continuously rotating suction belt path.

4. Suction belt conveyor according to claim 1 or 2, characterized in that the first sensor (10) of the measuring device is furthermore configured for detecting the presence of a connection point (4 b) in the suction belt (4) and outputting a second measuring signal showing the presence of such a connection point (4 b).

5. A suction belt conveyor according to claim 4, characterized in that the measuring device has an evaluation unit (16) which is designed to ascertain the speed of movement of the suction belt (4) from at least two second measurement signals following one another.

6. The suction belt conveyor according to claim 1 or 2, characterized in that the measuring device has a second sensor (12) which is configured for measuring a characteristic of the common arrangement of suction belt (4) and material strip at a position in the second section (II) of the suction belt path and outputs a third measuring signal which is indicative of the measured characteristic of the common arrangement of material strip and suction belt (4).

7. The suction belt conveyor of claim 6, wherein the second sensor (12) of the measuring device is configured for: the moisture and/or the density of the common arrangement of the material strip and the suction strip (4) is measured as a characteristic of the common arrangement of the suction strip (4) and the material strip.

8. The suction belt conveyor of claim 7, wherein the measuring device has an evaluation mechanism (16) configured for: the thickness and/or density and/or moisture of the material strip alone is ascertained from the third measurement signal of the second sensor (12) taking into account the first measurement signal of the first sensor (10).

9. Suction belt conveyor according to claim 1 or 2, characterized in that at least one sensor (10, 12) of the measuring device is preferably an optical or capacitive sensor or a microwave sensor.

10. Suction belt conveyor according to claim 1 or 2, characterized in that the second sensor (12) can be a microwave sensor.

11. A suction belt conveyor according to claim 10, characterized in that the second sensor (12) is configured to work as a resonator and to measure the change of the resonance frequency and/or the property and/or the slope on the side edge of the resonance curve by means of transmission and/or by means of reflection and/or to form an average from the measurements obtained by transmission and reflection.

12. The suction belt conveyor of claim 10, wherein the second sensor (12) is configured to operate outside a resonant frequency and measure a change in a scattering parameter.

13. A suction belt conveyor according to claim 12, characterized in that the second sensor (12) is configured for measuring by transmission and/or reflection.

14. Rod maker, in particular tobacco rod maker, of the tobacco processing industry, having a suction belt conveyor (2) according to at least one of the preceding claims.

15. Use of a measuring device according to one of claims 10 to 13 in a suction belt conveyor (2) of a rod maker of the tobacco processing industry for measuring a property of a strip of material, which strip of material is associated with an electrically conductive wrap in a further processing step that follows the measurement.

Technical Field

The invention relates to a suction belt conveyor for conveying material, in particular tobacco, of a rod maker of the tobacco processing industry, comprising: a suction belt guided along a suction belt path having a first section, a second section, a third section, and a fourth section; suction means for applying a negative pressure to the suction belt inside the first and second sections of the suction belt path; and a measuring device, wherein the first section of the suction belt path is arranged in such a way that material is accumulated by the suction action of the suction device on a lower branch of the suction belt guided along the first section of the suction belt path and forms a material strip thereon, the second section of the suction belt path adjoins the first section of the suction belt path downstream and is designed to guide the suction belt together with the material strip arranged thereon and formed in the first section (I) of the suction belt path, and the third section of the suction belt path adjoins the second section of the suction belt path downstream and is designed to separate the suction belt from the material strip. The invention further relates to a rod maker of the tobacco processing industry having such a suction belt conveyor and to the use of a measuring device in such a suction belt conveyor.

Background

In the case of suction belt conveyors such as known, for example, from DE 102011082625 a1, loose material of the tobacco processing industry and in particular tobacco fibers are thrown from below into the strand guide channel of the strand guide and there onto the lower or outer side of the lower limb of the air-permeable suction belt forming the bottom of the strand guide channel, the suction belt being subjected to a negative pressure by the suction device from its rear or upper side. In this way, a tobacco cake in the form of a rod is shaken off from below on the suction belt by the tobacco fibers, which is thereby held on the lower run of the suction belt by the air sucked in by the suction device. By means of the movement of the suction belt along the rod guide channel, the tobacco cake shaken out and accumulated therein is formed into a tobacco rod and is adhesively conveyed there. The lower branch of the suction belt extends through the rod-guiding channel from its beginning, at which the rod-forming zone is located, up to a trimming or trimming device for removing excess tobacco fibres; in this region, a first section of the suction belt path along which the suction belt is guided extends in a horizontal orientation. Thereby, the first section of the suction belt path forms an area in which the tobacco fibres are shaken from below onto the suction belt and form a tobacco rod therefrom. After leaving the first section of the suction belt path, the suction belt follows a second section of the suction belt path, through which the suction belt with the tobacco rod adhered thereon is conveyed further in a horizontal orientation. The suction band is then separated from the tobacco rod in a third section of the suction band path adjacent to the second section. Subsequently, the now empty suction belt follows the fourth section of the suction belt path outside the strip guide.

In order to ensure a high processing quality which is as uniform as possible, measuring devices are provided for which, as required, different measuring methods are used, such as, for example, optical measuring methods, capacitive measuring methods or microwave measuring methods.

The suction belt is a wear member. In order to be able to replace the suction belt without problems, the strip guide channel of the strip guide is open at the bottom. Previously, a fixed time interval was predefined, after which the suction belt was replaced accordingly. For the sake of reliability and to avoid quality losses due to unexpected wear that is too severe or even unpredictable interruptions of operation due to sudden snapping off of the suction belt due to wear that is too severe, the intervals are designed to be relatively short, which causes frequent replacement of the suction belt.

Disclosure of Invention

The object of the invention is to provide measures which make it possible to specifically carry out the required replacement of the suction belt at a point in time at which the suction belt has actually reached such a degree of wear that the subsequent replacement of the suction belt is only required.

In order to solve this object, a suction belt conveyor for conveying material, in particular tobacco, of a rod maker of the tobacco processing industry is proposed, comprising: a suction belt guided along a suction belt path having a first section, a second section, a third section, and a fourth section; suction means for applying a negative pressure to the suction belt inside the first and second sections of the suction belt path; and a measuring device, wherein the first section of the suction belt path is arranged in such a way that material is accumulated by the suction action of the suction device on a lower branch of the suction belt guided along the first section of the suction belt path and forms a material strip thereon, the second section of the suction belt path adjoins the first section of the suction belt path downstream and is designed to guide the suction belt together with the material strip arranged thereon and formed in the first section of the suction belt path, and the third section of the suction belt path adjoins the second section of the suction belt path downstream and is designed to separate the suction belt from the material strip.

The basic idea of the invention is thus to measure the suction strip with a sensor for detecting the instantaneous state of the suction strip. The measurement is carried out in a region in which the suction belt is in an unloaded state and is free of any material, and the measurement is thus carried out at a point before the suction belt enters the strip formation zone in the region of the first section of the suction belt path for loading with material or after the suction belt has been separated from the previously formed material strip in the third section of the suction belt path. Thus, according to the invention, only the suction strip itself is measured. The invention herein makes use of the recognition that: the characteristics of the suction strip vary due to losses, which have an effect on the effective permittivity of the suction strip and thus on the measurement signal. Possible signal fluctuations, for example due to a given state of the suction belt or due to vibrations, can be eliminated by long-term detection. If it is possible from a first measurement signal output by the first sensor and indicating the measured characteristic of the suction belt to recognize that the suction belt has reached such a degree of wear that replacement of the suction belt is required, a warning or maintenance message can be issued on the basis of such a measurement signal, which warning or maintenance message has a prompt for a later, pending, targeted replacement of the suction belt. The advantage of the solution according to the invention is therefore that the suction belt should be replaced only when a certain degree of wear has actually been reached, which then requires replacement of the suction belt. This has the consequence that, as has been found, the use intervals of the suction belt can be extended partially and significantly, without fear of a loss of quality during the processing or even of a sudden stop of the processing due to an unforeseen destruction of the suction belt.

Preferred embodiments and developments of the invention are specified in the dependent claims.

The first sensor of the measuring device is therefore expediently designed to measure the thickness and/or the moisture content and/or the density of the suction strip and thus the wear as a property of the suction strip. Since the thickness of the suction belt is reduced in particular by wear.

The detection of the state of the suction belt and thus the wear can be carried out by a longer observation of the measurement signal.

It is also expedient for the suction belt to be designed as a continuously rotating suction belt which is guided along a correspondingly continuously rotating suction belt path.

Preferably, the first sensor of the measuring device can furthermore be designed to detect the presence of a connection point in the suction belt and to output a second measuring signal which indicates the presence of this connection point. In particular, the connection point causes a significant local signal swing, so that the second measurement signal, in particular of the type with a pulse or a short rectangular signal having a significantly higher peak value, occurs in relation to the first measurement signal. At least one such connection point is included in the suction belt for connecting two sections of the suction belt to each other; if the suction belt is configured as a continuously rotating suction belt, its two ends are connected to one another by such a connection point.

In many cases, the suction belt is operated at an overspeed which at least slightly exceeds the transport speed of the material web, wherein the exact speed of the suction belt is unknown.

In a particularly advantageous development of this embodiment, the measuring device has an evaluation unit which is designed to ascertain the speed of movement of the suction belt from at least two second measurement signals which follow one another. This is done by the time interval between two second measurement signals following one another while taking into account the known length of the suction strip. The presence of the connection point in the suction belt can thereby be used in a simple and at the same time efficient manner to be able to determine the speed of movement of the suction belt accurately for the first time. However, an exact determination of the speed of the suction belt is important in view of the desired transport speed of the material web and thus also in view of the desired processing speed. In this way, it is also possible to detect a lack of prestress of the suction belt and the slippage caused thereby.

A further embodiment of the invention is characterized in that the measuring device has a second sensor which is designed to measure a characteristic of the common arrangement of suction belt and material strip at a position in the second section of the suction belt path and to output a third measuring signal which indicates the measured characteristic of the common arrangement of material strip and suction belt. Such measuring devices are known from DE 102015105353 a1 or from corresponding WO2016/162292 a 1. In such an embodiment, the measurement of the material has been performed in an earlier stage in which the strip of material has not yet been wrapped by the wrapping material. Such an early measurement offers the advantage that deviations from the predefined value can be detected very quickly and thus an immediate adjustment, in particular a transport, of the material can be carried out, whereby material waste can advantageously be reduced.

The second sensor of the measuring device is expediently designed to: the thickness and/or the moisture and/or the density of the common arrangement of the suction belt and the material strip are measured as a characteristic of the common arrangement.

Since the common arrangement of material strip and suction belt is measured by the second sensor, only the part of the third measurement signal output by the second sensor, which represents a characteristic of the suction belt, forms a disturbance variable for the following situations: from the third measurement signal output by the second sensor, only the measured property of the material strip should be ascertained.

In order to compensate for such interference, according to a particularly preferred development of the aforementioned embodiment of the measuring device, the measuring device has an evaluation unit which is designed to: the properties of the material strip alone, and in particular the thickness and/or density and/or moisture, are ascertained from the third measurement signal of the second sensor taking into account the first measurement signal of the first sensor. In this preferred embodiment, it can be said that the actual measurement is carried out by the second sensor, while the first sensor forms the reference sensor. By forming the difference between the third measurement signal and the first measurement signal, the amount of disturbance caused by the suction strip can be faded out. In this way, both the fundamentally existing inhomogeneities of the suction belt and the wear of the suction belt are accordingly taken into account.

At least one of the sensors of the measuring device can preferably be an optical or capacitive sensor or a microwave sensor. If a plurality of sensors are used, these are preferably of the same type, by: for example, all sensors used can be microwave sensors.

In a further preferred embodiment, the second sensor can be a microwave sensor which operates, for example, as a resonator and measures the change in the resonance frequency and/or the behavior and/or the slope on the side edge of the resonance curve by means of transmission and/or by means of reflection and/or forms an average from the measurements obtained by transmission and reflection. However, it is also conceivable to operate outside the resonance frequency and to measure the change in the scattering parameters (amplitude and/or phase) and to measure them here preferably by transmission and/or reflection.

The object of the invention is also achieved by a rod maker, in particular a tobacco rod maker, of the tobacco processing industry having a suction belt conveyor according to the invention described above.

Finally, the object of the invention is achieved by the use of a measuring device for measuring a property of a material strip in a suction belt conveyor of a rod maker of the tobacco processing industry, wherein the second sensor is a microwave sensor for the measuring device, and wherein an electrically conductive wrap is assigned to the material strip in a further processing step that is carried out after the measurement.

It is known to provide the measuring device where the material strip has been wrapped with a wrapping material in order to determine the material properties in respect of the material strip. The reason for this is, on the one hand, that the material strip can be accessed fairly well there with a measuring device. On the other hand, the strip of material then already has its final shape. However, such an arrangement of the measuring device has the disadvantage that the influence of the wrapping material must always be taken into account.

Since the properties of the material, in particular of the tobacco material, are already measured at a very early stage, i.e. in the suction belt conveyor, in which the material strip formed from the material is not yet wrapped with a wrapping material, by means of the solution according to the invention, the solution according to the invention is also suitable in this way for measuring the properties of the material strip by means of microwaves, even if the material strip is then provided with an electrically conductive wrapping in a later processing step, as is the case, for example, for "hot non-burning" products. This is not possible with the measuring devices used hitherto, for which the measurement is only carried out on tobacco rods which have already been wrapped, since the electrically conductive wrapping is already shielded from the microwaves.

Drawings

A preferred embodiment is explained in detail below with the aid of the drawing. Wherein:

fig. 1 shows schematically in a perspective view a suction belt conveyor with a measuring device according to a preferred embodiment of the invention; and is

Fig. 2 schematically shows the suction belt conveyor of fig. 1 in a side view.

Detailed Description

In the drawing a suction belt conveyor 2 according to one embodiment is shown. Such a suction belt conveyor 2 is preferably part of a cigarette rod making machine. Such a cigarette rod making machine, which is not shown in the figures, has a tobacco supply device, to which tobacco fibers are supplied in portions and from which a substantially uniform stream of tobacco fibers is removed. The tobacco fibres are conveyed by the supply device to a suction belt conveyor 2.

The suction belt conveyor 2 shown in the figures is constructed as a double-rod structure and is thus part of a double-rod cigarette maker. In this respect, it is to be noted that, for the sake of simplicity, only those components which are located in fig. 1 toward the observer of fig. 1 are designated by reference numerals in each case among the components which are present in duplicate. However, for the sake of better completeness, it is to be noted in this respect that the arrangement described next can also be implemented without problems on a single machine.

As can be seen from fig. 1 and 2, the suction belt conveyor 2 has two continuously rotating air-permeable suction belts 4 arranged parallel to one another, which are guided around different rollers or rollers, not shown in any more detail in the figures, along corresponding likewise continuously rotating suction belt paths, which are not shown in the figures. At least one of these rollers or rollers, not shown in detail, is set in rotation by a drive, also not shown in the figures, whereby the suction belt 4 is moved along the aforementioned suction belt path in the direction of arrow a.

The suction belt conveyor 2 has a strand guide device which comprises two strand guide channels which are arranged parallel to one another and extend in the direction of movement of the arrow a and open downward. In this strip guide, only the strip guide element 6 located downstream with respect to the direction of movement of the suction belt 4 according to arrow a is illustrated in the drawing together with the strip guide channel 8 formed on its underside. As can be seen from the drawing, the suction belt path, which is not illustrated in the drawing, is designed such that the suction belt 4 is guided with its lower run 4a substantially along a horizontal or slightly preferably downward-inclined direction and almost along the entire lower section of the suction belt conveyor 2. The two strip guide channels 8 are also aligned with respect to the horizontal course of the lower branches 4a of the two suction strips 4, so that each suction strip 4 passes through the strip guide channel 8 with its lower branch 4 a.

The suction belt conveyor 2 is substantially enclosed by a housing, in which for reasons of clarity only the rear wall 2a and the upper section 2b are depicted in the drawing. The arrangement of the housing of the suction belt conveyor 2 is designed such that a negative pressure is applied from the interior space of the housing to the lower branch 4a of the suction belt 4. For this purpose, in the embodiment shown, an opening 7 is formed in the rear wall 2a, to which opening a suction channel, not shown in the figures, is connected, which leads to a suction air source, also not shown in the figures. The opening 7, a suction channel, which is not shown, and a suction air source, which is also not shown, thus form part of a suction device, which is likewise not shown in other respects.

Tobacco fibres, not shown in the figures, are fed to the suction belt conveyor 2 by a tobacco supply device, also not shown in the figures, by: the tobacco fibers are conveyed from below into the downwardly open strand guide channel of the aforementioned strand guide and preferably by means of a pin roller (Stiftwalze), which is not shown in the drawing either, throwing the tobacco fibers from below into the strand guide channel, or by means of a pneumatically operating conveying channel, the outlet of which is aligned with one or both strand guide channels, or by means of a combination of the aforementioned components. Since the lower limb 4a of the air-permeable suction belt 4 forms the bottom of the strand guide channel and is acted upon with a negative pressure from its rear side or upper side by the suction device mentioned, the tobacco fibers adhere to the lower side of the lower limb 4a of the suction belt 4 and are scattered into a tobacco fiber cake in the form of a rod, which is then held in the form of a tobacco strand on the lower limb 4a of the suction belt 4 by means of the negative pressure generated by the suction device. By the movement of the lower branch 4a of the suction belt 4 in the direction of the arrow a, the tobacco cake shaken or accumulated on the lower branch is adhesively conveyed as a tobacco rod.

Excess tobacco fibres are subsequently removed from the tobacco rod so formed by means of an ecreteur or trimmer. These trimming or trimming devices are arranged on the underside of the depicted rod guide element 6 and are more precisely preferably arranged in a height-adjustable manner for the optional adjustment of the thickness and weight of the tobacco rod. More precisely, the trimming or trimming device is not depicted in the attached drawings: however, it can be seen from the drawing that two recesses 6a1 and 6a2 are formed on the underside of the strip guide element 6, which are arranged one behind the other and are each provided for receiving a trimming member or trimmer.

The suction belt 4 moves in the direction of arrow a along a suction belt path, not shown in the figures, in which a first section (I) extends over the entire strip forming zone, which, as can be seen schematically in the figures, ends downstream of the second recess 6a2 in the interior of the strip guide element 6.

The tobacco rod thus formed and adhering to one of the suction strips 4 now passes from the first section I of the suction strip path into the second section II of the suction strip path adjoining the first section as a result of the continued movement of the suction strip 4 in the direction of the arrow a and exits from the downstream end 6b of the rod guide element 6 in the second section II of the suction strip path, while the lower limb 4a of the suction strip 4 now continues, together with the tobacco rod, substantially in a horizontal or slightly preferably downward-inclined direction along the second section II of the suction strip path. As can be seen from the drawing, the second section II of the suction belt path adjoins the first section I of the suction belt path downstream with respect to the direction of movement of the suction belt 4 according to arrow a and then, in the exemplary embodiment shown, runs essentially outside the strand guide element 6.

As can be seen from the figures, a third section III is defined for the suction belt path, which adjoins the second section II downstream with respect to the direction of movement of the suction belt 4. In this third section III of the suction belt path, the suction belt 4 is separated from the tobacco rod, not shown in the drawings, by: the suction band 4 is deflected upwards and thus away from the orientation of the tobacco rod which continues to move approximately in the horizontal direction by means of a roller or roller 9 shown in fig. 2. In the region of the rollers or rollers 9, no or at least a small negative pressure is applied to the suction belt 4, as a result of which the release of the tobacco rod from the suction belt 4 is facilitated.

The remaining section of the suction belt path, along which the suction belt 4 runs in an unloaded and thus empty state, forms a return run and thus adjoins the third section III of the suction belt path downstream with respect to the direction of movement of the suction belt 4 according to arrow a and extends up to the upstream beginning of the first section I of the suction belt path. This remaining section of the suction belt path is defined as the fourth section IV of the suction belt path and represents this entire remaining section which is indicated in the drawing by an arrow with the reference "IV" only in one position in the right half of the drawing.

In the region of the downstream end of the third section III or the upstream beginning of the fourth section IV of the suction belt path, a scraper, not shown in the drawings, is arranged, which engages with the side of the suction belt 4 forming the lower limb 4a, in order to remove the suction belt 4 from residual tobacco that may still be present and/or to facilitate the release of the tobacco rod from the suction belt 4 after separation from the tobacco rod, and which scraper preferably interacts with a roller or roller 9 shown in fig. 2 in that: the suction belt 4 is guided between this doctor blade and the roller or roller 9.

As can be seen from the figure, a first sensor 10 is provided. This first sensor 10 is designed to measure the thickness of the suction belt 4 at a point in the fourth section IV of the suction belt path, where the suction belt 4 moves with its free limb and thus in the unloaded state without any tobacco material. From the instantaneous thickness of the suction belt 4 measured by the first sensor 10, the extent of wear and therefore the wear thereof can be inferred. In principle, it is also conceivable to configure the first sensor 10 such that, alternatively or additionally, other properties of the suction strip 4 can also be detected, which are different from the thickness.

The continuously rotating suction belts 4 are connected to each other at both ends thereof by connection points 4 b. In the region of the connection point, the suction belt 4 has a thickness which is at least double the thickness in the remaining part of the suction belt 4, at least exceeds the thickness and/or density of the suction belt 4 at other locations and is therefore significantly higher. The connection point 4b causes a significant local signal swing at the first sensor 10, which signal swing, depending on the type of pulse or short rectangular signal, occurs with a significantly higher peak value and thus as a second measurement signal, which is therefore significantly different from the first measurement signal mentioned above with regard to its signal profile.

As can be seen from the figures, a second sensor 12 is provided downstream of the rod guide element 6 and adjacent to its downstream end 6b, which is designed to measure the thickness of the common arrangement of suction band 4 and tobacco rod present there in the region of the second section II of the suction band path and to output a corresponding third measurement signal. In principle, it is conceivable to configure the second sensor such that, in addition or alternatively, other properties of the common arrangement of suction strip 4 and tobacco rod, which are different from the thickness, can also be measured.

The first sensor 10 is connected via a cable 13 and the second sensor 12 is connected via a cable 14 to an evaluation unit 16, in which the measurement signals output by the sensors 10, 12 are processed and process signals formed therefrom are generated and output. The two sensors 10, 12, their connecting cables 13, 14 and the evaluation device 16 are thus part of a common measuring device.

Due to the double-strip construction of the illustrated suction belt conveyor 2, either the two sensors 10, 12 are designed in such a way that they can detect each of the two suction belts 4 separately, or one sensor is provided for each suction belt 4 individually and thus a total of two first sensors 10 and two second sensors 12 are provided. For the sake of simplicity, only one sensor and one suction line measured by the sensor will be referred to in the following.

The task of the first sensor 10 is to detect the momentary state of the suction belt 4. Since the first sensor 10 is arranged adjacent to the fourth section IV of the suction band path, the measurement of the suction band path takes place in the region in which the suction band 4 is in the unloaded state and is free of any material, and therefore before the suction band 4 has entered the first section I of the suction band path for loading the tobacco fibers or at a position after the suction band 4 has been separated in the third section III of the suction band path from the tobacco rod previously formed inside the first section I of the suction band path and conveyed along the second section II of the suction band path. Whereby only the suction belt 4 itself is measured. Since the thickness of the suction belt 4 decreases due to losses, which has an effect on the effective permittivity of the suction belt 4 and thus on the first measurement signal output by the sensor, the current wear state of the suction belt 4 can be inferred from the instantaneous value of this measurement signal. Possible signal fluctuations, for example due to a given state of the suction belt 4 or due to vibrations, can be eliminated by long-term detection in the evaluation unit 16. If it is possible to recognize from the first measurement signal, which indicates the instantaneous thickness of the suction belt 4 that is output by the first sensor 10 and measured, that the suction belt 4 has reached such a degree of wear that a replacement of this suction belt 4 is required, the evaluation means 16 outputs a warning or maintenance message with a prompt for a later pending replacement of the suction belt 4 on the basis of such a measurement signal.

Furthermore, the first sensor 10 can be used to measure the speed of movement of the suction belt 4. For this purpose, the second measuring signal output by the first sensor 10 is activated. Since the instantaneous speed of movement of the suction belt 4 can be ascertained in a simple and simultaneously effective manner from two second measurement signals which follow one another. This is done by the time interval between two second measurement signals following one another taking into account the known length of the suction strip 4. This evaluation process is likewise carried out in the evaluation unit 16.

In order to measure the thickness and, if appropriate, further material properties, in particular in order to ascertain the degree of wear of the suction belt 4 and, furthermore, to ascertain the speed of movement of the suction belt 4, only the first sensor 10 is required, but with the aid of the described measuring device it is also possible additionally to ascertain the density and/or the moisture and/or, if appropriate, further material properties of the tobacco rod formed in the first section I of the suction belt path. For this purpose, the second sensor 12 is used and its third measurement signal is used for evaluation. Since the common arrangement of suction band 4 and tobacco rod is measured by second sensor 12, only the part of the third measurement signal output by second sensor 12 that represents the thickness of suction band 4 and, if appropriate, other characteristics, forms a disturbance variable. In order to compensate for or eliminate this disturbance variable, only the thickness of the tobacco rod and, if appropriate, additional properties are ascertained in the evaluation unit 16 from the third measurement signal of the second sensor 12 taking into account the first measurement signal of the first sensor 10, which indicates the thickness and, if appropriate, additional properties of the suction band 4.

If, for example, at time t1, a particular section Δ x of the suction band 4 is located in the measuring region of the second sensor 12, a third measuring signal is generated by this second sensor, which third measuring signal indicates, in particular, the thickness of the common arrangement of suction band 4 and tobacco rod. Due to the continuous movement of the continuously rotating suction belt 4, the same section Δ x of the suction belt 4 reaches the first sensor 10 at a later time t2, the output first measurement signal of which indicates only the thickness and, if necessary, further properties of the suction belt 4, and thus represents the aforementioned disturbance variable. The time t2 can also be derived from the speed of movement of the suction belt 4 and/or from the rotary encoder pulses of a rotary encoder pulse unit, not shown in the figures, of a suction belt drive, also not shown in the figures. The difference between the third measurement signal and the first measurement signal is now formed in the evaluation unit 16 for calculating the disturbance variable and for eliminating it therefrom, so that only an effective quantity remains, which represents only the thickness of the tobacco rod and, if appropriate, further material properties and is included in the third measurement signal as a supplement to the mentioned disturbance variable.

In this way, both the fundamentally existing inhomogeneities of the suction belt 4 and the wear of the suction belt 4 are taken into account accordingly.

In this case, the second sensor 12 thus forms the actual measuring sensor, while the first sensor 10 serves as a reference sensor. For example, the second sensor 12 can have a structure as described in DE 102015105353 a1 or in the corresponding WO2016/162292 a1, the disclosures of which are to be fully incorporated by reference into the present application.

At least one of the sensors 10, 12 can preferably be an optical sensor or a capacitive sensor or a microwave sensor, wherein preferably both sensors 10, 12 are of the same type and in particular are microwave sensors.

It is particularly preferred that the second sensor 12 can be a microwave sensor which operates, for example, as a resonator and measures the change in the resonance frequency and/or the property and/or the slope on the side edge of the resonance curve by means of transmission and/or by means of reflection and/or forms an average from the measurements obtained by transmission and reflection. However, it is also conceivable in this case for the second sensor 12 to operate outside the resonant frequency and to measure the change in the scattering parameter (amplitude and/or phase) and to measure it here preferably by transmission and/or reflection.

After leaving the suction belt conveyor 2, the tobacco rod formed there is wrapped with a wrapping material in a wrapping device arranged downstream and forming another part of the cigarette rod making machine, but not shown in the drawing as such. For this purpose, the tobacco rod has reached, in a third section III of the suction belt path, below the roller or rollers 9 illustrated in fig. 2, a wrapping material, which is likewise not illustrated in the drawings, and is then conveyed together with the tobacco rod lying above it into a wrapping device, which adjoins the suction belt conveyor 2 on the left in the view of the drawings. The wrapping material is wrapped transversely to the transport direction of the tobacco rod and the two longitudinal edges of the wrapping material, which are now opposite one another and extend in the transport direction of the tobacco rod, are glued to one another. Since the described measurement is already carried out in the illustrated suction belt conveyor 2 and therefore before the wrapping device, it is possible without problems to use microwaves for the measurement on the one hand and electrically conductive wrapping material, such as is provided, for example, in "hot unfired" products, on the other hand, without the measurement by means of microwaves being influenced by the otherwise shielded function of the electrically conductive wrapping material.