DE102023103265A1 - Method for operating a stranding machine in the tobacco processing industry or a stranding machine for producing drinking straws and stranding machine - Google Patents

Abstract

The invention relates to a method for operating a strand machine (2) in the tobacco processing industry or a strand machine (2) for producing drinking straws, wherein first a strand (11) in the tobacco processing industry or drinking straw industry is produced and then the strand (11) is cut into a plurality of rod-shaped articles (10) in the tobacco processing industry or drinking straw industry by means of a cutting device (13), wherein the strand (2) is conveyed longitudinally axially at a strand speed, characterized in that between the production of the strand (11) and the cutting to length, the strand speed is measured directly and, on the basis of at least one measured value of the strand speed, an operating parameter of the strand machine (2) which influences the length of the cut-to-length rod-shaped articles (10) is controlled or regulated.

Description

The invention relates to a method for operating a strand machine in the tobacco processing industry or a strand machine for producing drinking straws. The invention also relates to a strand machine for producing rod-shaped articles in the tobacco processing industry or the drinking straw industry. The invention also relates to the use of a measured strand speed of a strand of a strand machine in the tobacco processing industry or a strand machine for producing drinking straws.

When manufacturing rod-shaped articles in the tobacco processing industry or the drinking straw industry, for example filter cigarettes, filter rods, heat-not-burn products or drinking straws, it is desired that the articles produced have a predeterminable, uniform, and as identical as possible, length. It is known that fluctuations in the length of rod-shaped articles can occur during operation. Rod-shaped articles that have a significantly different length must sometimes be sorted out as rejects, which means additional process steps and inefficient use of resources.

Out of EP 3 682 749 A1 A method for operating a machine in the tobacco processing industry or a machine for producing drinking straws is known, wherein a strand is cut into a plurality of rod-shaped products in a strand machine, wherein the length of the rod-shaped products is then measured during operation of the machine and then an operating parameter of the strand machine which influences the length of the rod-shaped products is controlled or regulated.

Out of WO 03/055338 A2 A device for measuring the properties of multi-segment filters is known, whereby a transmitted light method can be used to check whether the intended filter components are present and whether the density of the filter components corresponds to a predefined density. Rod-shaped products that do not fall within the tolerance range are excluded from further processing.

It is an object of the present invention to produce rod-shaped articles of the tobacco processing industry or drinking straws of high quality and constant and predetermined length, in particular in a resource-saving manner.

The object is achieved by a method for operating a strand machine in the tobacco processing industry or a strand machine for producing drinking straws, wherein first a strand of the tobacco processing industry or drinking straw industry is produced and then the strand is cut to length into a plurality of rod-shaped articles of the tobacco processing industry or drinking straw industry by means of a cutting device, wherein the strand is conveyed longitudinally axially at a strand speed, which is further developed in that between the production of the strand and the cutting to length, in particular during ongoing operation of the strand machine, the strand speed is measured directly and on the basis of at least one measured value of the strand speed an operating parameter of the strand machine which influences the length of the cut-to-length rod-shaped articles is controlled or regulated.

The basic idea of the invention is to directly measure the strand speed, i.e. the speed at which the strand actually moves. This speed is a decisive parameter for the length of the rod-shaped articles, in addition to the cutting frequency of the cutting device that cuts a rod-shaped article from the strand. Depending on the directly measured strand speed, one or more operating parameters of the strand machine are adjusted so that rod-shaped articles of constant, predetermined length are continuously produced.

The direct measurement of the strand speed has the advantage of not distorting an indirect measurement, which can contain additional measurement errors. For example, the conveying speed of a conveyor device, such as a format belt of a format device, is usually measured and the conveying speed of the strand conveyed by the conveyor device is determined on the basis of the measured values. However, due to slippage between the strand and the conveyor device, this does not correspond to the actual strand speed. Another advantage, e.g. compared to measuring the length of articles that have already been cut, is that the speed is measured before cutting and can therefore be adjusted/corrected at an early stage, so that fewer rejects of unacceptable lengths are produced in a way that conserves resources. Furthermore, a direct speed measurement enables frequent, even continuous, monitoring of the strand speed, so that errors in the article length that increase over time can be corrected early on even for small deviations. A reliably ensured constant article length also enables continuous operation with fewer interruptions to operation due to technical errors in processing and thus high cost efficiency with little need for repair and maintenance.

An immediate measurement of the strand speed is also understood to mean a direct measurement of the strand speed. An immediate measurement of the strand speed is carried out directly on the moving strand.

A rod making machine is a machine known in the context of the tobacco processing industry that is used to produce a rod in the tobacco processing industry and to produce rod-shaped articles cut to length from a rod. A rod in the tobacco processing industry is, for example, a tobacco rod, a cigarette rod or a filter rod. Rod making machines are also intended for use in the drinking straw industry, where a rod in the drinking straw industry is, for example, a hollow tube, in particular made of paper or other materials. During cutting, a virtually infinitely long rod is cut into segments or articles of a specific length, for example a filter rod into filter pieces or filter rods of twice the length, which are cut again during the further course of cigarette production, or drinking straws of a single length, where each rod-shaped article has a predetermined length.

In embodiments, a single-strand machine or a double-strand machine is provided as the strand machine, wherein a double-strand machine is designed to produce two strands for the tobacco processing industry or drinking straw industry simultaneously and on a parallel conveyor path.

According to the invention, the strand is conveyed longitudinally axially at a strand speed. In particular, the strand is conveyed by means of a format belt of a format device designed to form a strand conveyed longitudinally axially. In other embodiments, the strand is conveyed by means of a further or different conveying device, such as a pulling format device.

In the context of this invention, the strand speed, which is measured directly, refers to the actual speed of the strand. The strand speed can be dependent on a conveyor belt speed, i.e. the speed of a conveyor belt by means of which the strand is conveyed longitudinally axially, for example a format belt speed, but can deviate from this. A difference between the strand speed and the conveyor belt speed arises, for example, due to slippage between the strand and the conveyor belt.

In the context of this invention, "during operation" means that the strand machine produces a strand that moves in a longitudinal axial direction or that is conveyed in a longitudinal axial direction. A longitudinal axial direction is in the longitudinal axis of the strand. The strand speed is measured immediately or directly on the strand moving in the longitudinal axial direction.

According to the invention, the strand speed is measured directly. This means that the strand speed is measured directly. In particular, it is not a direct measurement of the strand speed if a strand speed is determined from several position measurements and their time intervals. In particular, no direct measurement takes place if markings applied to the wrapping material are detected on the wrapping material and a speed is determined on the basis of these.

According to the invention, an operating parameter of the strand machine, which influences the length of the rod-shaped articles cut to length, is controlled or regulated on the basis of at least one measured value of the strand speed. Preferably, an average of the measured values of the strand speed is used for controlling or regulating. In this way, fluctuations in the measured value are compensated. A moving average of the measured values with a predetermined or predeterminable averaging period is preferred, the averaging period being in particular between 1 second and 60 seconds, in particular between 3 seconds and 30 seconds, in particular between 5 seconds and 20 seconds, in particular between 8 seconds and 14 seconds. In one embodiment, an operating parameter of the strand machine is regulated by means of a PID controller.

The method is preferably characterized in that the strand speed is measured without contact, in particular by means of a laser Doppler speed measuring device. The advantage of a non-contact measurement is a precise and reliable measurement, which is less maintenance-intensive in the long term due to the lack of wearing parts.

A non-contact measurement is in particular a measurement of the strand speed at which the strand is not touched by the measuring device.

One possibility for non-contact measurement of the strand speed is a laser doppler ler speed measuring device. A laser Doppler speed measuring device is in particular a laser Doppler velocimeter, which is also referred to as a laser Doppler anenometer or laser surface velocimeter. A laser Doppler velocimeter is a non-contact, optical measuring device for determining the speed of moving particles or surfaces. For this purpose, a measuring area, in this case an area of the conveyed strand, is irradiated with two laser beams from different directions and the reflected light is evaluated to determine the speed. The beat detected in the intensity of the reflected light, resulting from the interference of the two laser beams, is a measure of the speed of the particle or surface. The functional principle is described in more detail in 3 shown. In particular, a laser beam is first split into two laser beams, which are then used to irradiate an area of the conveyed strand from different directions and the reflected light is evaluated to determine the speed.

In one embodiment, the strand speed is measured using a two-beam laser Doppler velocimeter. In particular, a laser Doppler velocimeter is operated in a heterodyne mode. In the heterodyne mode, a frequency of a laser is shifted by an offset, for example an offset of 40 MHz, and this offset frequency is included in the evaluation of the detector for determining the strand speed. In another embodiment, a laser Doppler velocimeter is operated in a homodyne mode, i.e. without a shift of a laser frequency by a predetermined offset.

The laser Doppler speed measuring device preferably has a laser of laser class 3B. This means that a high light intensity is available for the measurement. The laser Doppler speed measuring device preferably has a laser with a wavelength of 780 nm. The laser Doppler speed measuring device is preferably a device of the type µSPEED-Smart/STD/S5/120/dt from ELOVIS GmbH.

Alternatively, the contactless measurement can be carried out using a radar Doppler speed measuring device. The radar Doppler effect is used for this, whereby a radar Doppler velocimeter sends out a radar signal which is reflected by the strand as the object to be measured and is then detected and analyzed by the velocimeter. Due to the movement of the strand, the reflected radar signal has a frequency shifted by one Doppler frequency.

Alternatively, the contactless measurement can be carried out using a spatial filter principle speed measuring device, which is based on the spatial filter principle. For this purpose, a measuring object is illuminated with a light source, for example an LED white light source, whereby the light reflected from the measuring object is imaged through a lens onto a CCD cell. The CCD cell does not work for image recording as is often the case, but can be used as an optical grating. A moving measuring object causes a grating modulation in the CCD cell with a signal frequency, from which the speed of the measuring object can be determined together with system parameters such as image scale and grating period.

Preferably, the non-contact measurement is carried out without any markings on the strand, such as prints.

Preferably, the strand speed is measured by means of contact measurement, in particular by means of a measuring wheel. A contact measurement enables the strand speed to be measured in a simple manner without an indirect measurement via positions or other sensors. Due to slippage and/or wear, a measurement by means of contact measurement, in particular by means of a measuring wheel, is usually less accurate than a non-contact measurement, but is technologically simpler and more cost-effective.

The method is preferably characterized in that the operating parameter is a conveying speed of a format belt of a format device of the strand machine designed to form a longitudinally axially conveyed strand and/or a cutting frequency of the cutting device. By choosing this operating parameter, the length of the rod-shaped articles is easily influenced and thus precisely adjusted or regulated.

Although the conveying speed of a format belt is not identical to the strand speed, the conveying speed of a format belt is particularly preferred as an operating parameter. The format belt is advantageously the last conveying device of the strand machine, which conveys the strand longitudinally axially before it is cut to length using the cutting device. The conveying speed of the format belt therefore has a significant influence on the strand speed at the cutting device and thus on the length of the rod-shaped articles.

The conveying speed of the format belt is controlled in particular by means of a format belt drive means. In particular, in one embodiment, the operating parameter is a rotational speed of a format belt drive means, in particular a format belt drive roller, or a peripheral speed of a format belt drive means. Within the scope of this protective right, the term conveying speed of a format belt also includes a rotational speed of a format belt drive means or a peripheral speed of a format belt drive means.

Typically, the strand speed is slightly lower than the conveying speed of the format belt due to slippage, and the format belt is therefore overspeeding the strand. Preferably, the overspeed of the format belt is used as an operating parameter, in particular as a further operating parameter. In particular, it is preferred that the overspeed of the format belt is monitored. This enables the strand machine to be constantly checked and provides information about possible changes and signs of wear.

Another preferred operating parameter is a cutting frequency of the cutting device. A cutting frequency is, for example, a cycle or a speed of the cutting device. In embodiments, a cutting device is a cutting knife drum, i.e. a drum provided with several knives, whereby in a single-strand machine each knife cuts a rod-shaped product from the strand during one revolution of the cutting knife drum, i.e. cuts it. The operating parameter cutting frequency includes, for example, a speed of a drive device of the cutting device or a cutting frequency, in particular with a unit of cuts per minute.

It is preferred if, on the basis of at least one measured value of the strand speed, one operating parameter of the strand machine or several operating parameters of the strand machine which influence the length of the cut rod-shaped articles are controlled or regulated.

The method is advantageously characterized in that after cutting to length, the rod-shaped articles are passed on to a transverse axial conveyor, in particular by means of a transfer device or a push-in drum. Efficient further processing is possible by means of a transverse axial conveyor of the rod-shaped articles.

A transfer device is, for example, a device such as the one from the EP 1 164 878 B1 known device with a plurality of trough-shaped receptacles for one article each, which can also be referred to as a “spider”.

Preferably, the strand speed is measured immediately downstream of a formatting device of the strand machine designed to form a strand conveyed longitudinally axially and/or immediately upstream of a cutting device. When measuring immediately upstream of a cutting device, the strand speed that is also the strand speed on the cutting device is advantageously measured precisely, so that the predetermined length of the rod-shaped articles can be achieved particularly precisely. When measuring the strand speed immediately downstream of a formatting device, the greatest dependence is on the conveying speed of a formatting belt of the conveying device, so that control or regulation is particularly simple and direct. In embodiments, the strand speed is measured where the strand is structurally easily accessible in the strand machine for the speed measuring device or the strand speed measurement.

The term immediately downstream or immediately upstream is in particular a distance of 50 cm or less, in particular 30 cm or less, in particular 20 cm or less, in particular 15 cm or less, in particular 10 cm or less, from the other device. In addition, “immediately upstream” or “immediately downstream” means that preferably no other functional component of the strand machine is arranged between the format device or the cutting device and the location of the measurement of the strand speed. Such a functional component is, for example, a density sensor or a moisture sensor.

The strand is advantageously a sheath-free strand, in particular a sheath-free filter tow strand. The lack of sheathing makes the speed measurement all the more precise, especially with non-contact measurement. In addition, the requirements for equal lengths are particularly high for rod-shaped articles that are sheath-free because they were made from a sheath-free strand, as these often undergo numerous further processing steps. In addition, the lengths of sheath-free filter tow strands in particular can vary more significantly due to the lack of a sheath to stabilize the length of the rod-shaped articles, which is why, in the case of sheath-free filter tow strands in particular, precise control or regulation of the speed of the filter strand leads to small differences in the length of the rod-shaped articles cut from the strand.

Furthermore, the method is advantageously characterized in that two strands conveyed in parallel are produced and the two strands conveyed in parallel are cut to length into a plurality of rod-shaped articles for the tobacco processing industry or drinking straw industry, wherein the strands are conveyed longitudinally axially at one strand speed each, wherein both strand speeds are measured and the operating parameters of the strand machine are controlled or regulated on the basis of at least one measured value of the strand speeds. The processing of two strands conveyed in parallel makes it possible to increase the production quantity very efficiently.

In another embodiment of a method for a double-strand machine with two strands conveyed in parallel, the strand speed of exactly one strand is measured and an operating parameter that influences the length of the cut rod-shaped articles of both strands is controlled or regulated. The cutting frequency of the two strands is particularly suitable as an operating parameter for this purpose.

For example, an operating parameter for both strands of the stranding machine is controlled or regulated based on measured values of the strand speed of one strand.

In another embodiment, at least one measured value of the strand speeds of each strand is compared or offset against each other so that differences between the strand speeds can be identified. Advantageously, measured values of the strand speeds are offset against each other as an average value, whereby this is particularly advantageous in a double-strand machine if the cutting frequency of a cutting device that cuts both strands serves as the operating parameter.

A method is also advantageous which is characterized in that the two strands conveyed in parallel are a first strand and a second strand, the first strand being conveyed at a first strand speed and the second strand being conveyed at a second strand speed, a first operating parameter of the stranding machine which influences the length of the rod-shaped articles cut from the first strand being controlled or regulated on the basis of at least one measured value of the first strand speed, and a second operating parameter of the stranding machine which influences the length of the rod-shaped articles cut from the second strand being controlled or regulated on the basis of at least one measured value of the second strand speed. This is advantageous because the strand speed can be measured separately for each strand and an optimal length of the rod-shaped articles can be achieved separately for each strand by controlling or regulating.

Preferably, the method is characterized in that the strand speed or strand speeds are measured, in particular only, in a predetermined starting period, wherein the starting period begins when the strand machine is started up. This method is particularly energy and cost efficient, because in particular in a starting period, i.e. in a period after the strand machine has been started up, the strand machine has not yet warmed up and is not yet in a state of equilibrium, so that regulating and/or controlling an operating parameter brings about a particularly large increase in quality.

A start period is, for example, 45 minutes or less, 20 minutes or less, 10 minutes or less, or 5 minutes or less, whereby the start period begins when the strand machine starts up. The start-up of the strand machine refers, for example, to the point in time at which articles of sufficient quality for use can be produced for the first time using the strand machine after a standstill.

In another embodiment, the method is characterized in that the measuring and/or the controlling or regulating is carried out at a higher frequency during the start period and at a lower frequency after the start period. In another embodiment, the control parameters of the control of the operating parameter or of a control device for the operating parameter are time-dependent, i.e. the control parameters are adjusted time-dependently in a predetermined or predeterminable manner, in particular from the time the strand machine is started up. For example, with a PID controller as the control device, the integral component can be smaller or set to zero when the strand machine is started up and increased after a predetermined or predeterminable time. The proportional component can be larger at the beginning and reduced after a predetermined or predeterminable time.

The object is also achieved by a strand machine for producing rod-shaped articles of the tobacco processing industry or the drinking straw industry, whereby a strand of the tobacco processing industry or the drinking straw industry can be produced by means of the strand machine, whereby the strand machine comprises a format device for forming a strand conveyed longitudinally axially at a strand speed and a cutting device by means of which the rod-shaped articles can be cut to length from the strand, whereby the strand machine is further developed in that the strand machine comprises a measuring device for directly measuring the strand speed.

A measuring device for the direct measurement of the rod speed is advantageous because it enables rod-shaped articles for the tobacco processing industry or drinking straws of high quality and constant, predetermined length to be produced in a resource-saving manner.

For the properties and further embodiments of the strand machine and its components, express reference is made to the details of the process described above.

Preferably, the strand machine is further developed in that the measuring device is set up for a contactless measurement of the strand speed, wherein in particular the measuring device comprises a laser Doppler speed measuring device, and/or the measuring device is set up for a contact measurement of the strand speed, wherein in particular the measuring device comprises a measuring wheel. By means of a contactless measurement, a measurement is possible without damaging or influencing the strand and a contact measurement of the strand speed is advantageous due to low costs.

The measuring device for a contactless measurement is in particular a laser Doppler speed measuring device, in particular a laser Doppler anenometer, laser Doppler velocimeter or laser surface velocimeter. In other embodiments, the measuring device has a radar Doppler speed measuring device or has a spatial filter principle speed measuring device. For a contact measurement, the measuring device preferably comprises a measuring wheel. In embodiments, the measuring device comprises a measuring device for a contactless measurement and a measuring device for a contact measurement. In one embodiment, an evaluation device evaluating the measured values is set up in such a way that the measured values of a contactless measurement and the measured values of a contact measurement are compared with one another.

The measuring device is advantageously arranged directly downstream of the formatting device and/or directly upstream of the cutting device. Appropriate positioning ensures optimal measurement of the strand speed and thus the highest possible quality of the rod-shaped articles.

The strand machine preferably comprises an evaluation device for processing the measured values of the strand speed, wherein the evaluation device is set up to receive at least one measured value of the strand speed from the measuring device and, on the basis of the at least one measured value of the strand speed, to control or regulate an operating parameter of the strand machine that influences the length of the rod-shaped articles that can be cut or are cut by the cutting device. An evaluation device set up for controlling or regulating enables the strand speed to be adjusted and thus the length of the rod-shaped articles to be corrected during operation.

In one embodiment, the evaluation device has a PID controller. In another embodiment, the evaluation device is designed to calculate a moving average from measured values of the strand speed as the input variable of a controller. Preferably, the input variable of a controller is a moving average of the measured values with a predetermined or predeterminable averaging period, the averaging period being in particular between 1 second and 60 seconds, in particular between 3 seconds and 30 seconds, in particular between 5 seconds and 20 seconds, in particular between 8 seconds and 14 seconds.

The evaluation device is advantageously set up to output a control signal for controlling an operating parameter of the strand machine to a machine control of the strand machine. The control signal is either the result of the evaluation device for controlling or the result of the evaluation device for regulating the strand machine. For example, a control signal is output to a drive device of a format belt or to a drive device of a cutting device.

Furthermore, the object is achieved by a strand machine for producing rod-shaped articles of the tobacco processing industry or the drinking straw industry, wherein a strand of the tobacco processing industry or the drinking straw industry can be produced by means of the strand machine, wherein the strand machine comprises a cutting device by means of which the rod-shaped articles can be cut to length from the strand, wherein the strand machine is set up for operation by means of a method described above.

Furthermore, the object is achieved by using a measured strand speed of a strand of a strand machine of the tobacco processing industry or a strand machine for the production of drinking straws, wherein the strand speed is measured directly and is used to control or regulate a cutting device by means of which rod-shaped articles of the tobacco processing industry or drinking straw industry can be or are cut to length from the strand, and/or to control or regulate a conveying device by means of which the strand can be or is conveyed longitudinally axially to a cutting device set up for cutting rod-shaped articles of the tobacco processing industry or drinking straw industry to length. Such use enables highly precise measurement and thus efficient and resource-saving production of rod-shaped articles, without having to take possible errors of an indirect measurement into account.

The method described and the stranding machines described and their components include different aspects of the invention. The stranding machine is intended in embodiments to implement the method in all described embodiments and the method can be applied using a stranding machine described above.

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.

• 1 eine schematische Seitenansicht eines Teils einer ersten erfindungsgemäßen Strangmaschine,
• 2 eine schematische Seitenansicht eines Teils einer zweiten erfindungsgemäßen Strangmaschine,
• 3 eine schematische Skizze des Funktionsprinzips einer Laser-Doppler-Geschwindigkeitsmessvorrichtung.

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:

• 1 a schematic side view of a part of a first strand machine according to the invention,
• 2 a schematic side view of a part of a second strand machine according to the invention,
• 3 a schematic sketch of the operating principle of a laser Doppler velocity measuring device.

Within the scope of the invention, features marked with “in particular” or “preferably” are to be understood as optional features.

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.

1 shows a schematic side view of a part of a first strand machine 2 according to the invention. A strand 11, for example a filter strand, is conveyed on a format belt 12 in the longitudinal axial conveying direction 16. The format belt 12 is driven by a drive roller 43 and runs deflected by two deflection rollers 44. The construction of the strand 11 has already taken place upstream in the production process and therefore not in 1 In the formatting device 100, which is only shown schematically, the strand 11 is formed as usual.

The strand 11 is cut into individual rod-shaped articles 10 by the cutting device 13, which is, for example, a rotating drum provided with knives. In this embodiment, these are filter rods of double the usable length. The rod-shaped articles 10 are conveyed further by means of a conveyor track 41 to a push-in drum 50, which transfers the rod-shaped articles 10 from a longitudinal axial conveying direction 16 to a transverse axial conveying direction 15. A transfer and acceleration device, which transfers the rod-shaped articles from the conveyor track 41 to the push-in drum 50, is not shown.

Between the format belt 12 and the cutting device 13, a sensor device 42 for examining the strand 11 is provided, which can correspond to a conventional sensor device and is set up, for example, to measure the density of the strand 11.

A laser Doppler speed measuring device 60 is arranged downstream of the sensor device 42. The laser Doppler speed measuring device 60 is a laser Doppler velocimeter in this strand machine 2. It is arranged in the strand machine 2 without contact with the strand 11, i.e. at a distance from the strand. The laser Doppler speed measuring device 60 sends two laser beams 61 from different directions onto the strand 11. The strand 11 reflects the laser light back to the laser Doppler speed measuring device 60, which detects the backscattered light and converts it into a strand speed.

An evaluation device 40 retrieves the measured values of the strand speed of the strand 11 from the laser Doppler speed measuring device 60. The evaluation device 40 is set up to analyze the measured values of the strand speed, to transfer them to a control loop and then to determine at least one operating parameter of the strand machine. In this embodiment, the evaluation device 40 is set up to average the measured values of the strand speed over the last 10 seconds and send them as an input variable to the control circuit. By means of a proportional control, this determines a new value for the rotational speed of the drive roller 43 of the format belt 12. The evaluation device 40 sends a corresponding control signal to the drive roller 43 or the associated machine control. If, for example, the strand speed of the strand 11 is slower than a preset target value, the rotational speed of the drive roller 43 is increased.

In another embodiment, the evaluation device 40 is designed to send a control signal to the drive device of the cutting device 13. If, for example, the measured strand speed is greater than a predetermined target strand speed, in this embodiment the rotational speed of the cutting device 13 is also increased so that the resulting lengths of the rod-shaped articles 10 reach their target value.

In the 1 In the embodiment shown, the laser Doppler speed measuring device 60 is arranged immediately upstream of the cutting device 13. This enables the most precise possible speed measurement directly at the cutting location.

2 shows a schematic side view of a part of a second strand machine 2 according to the invention, the structure of which is very similar to that shown in 1 described strand machine 2. The two strand machines 2 differ in the positioning of the sensor device 42 and the laser Doppler speed measuring device 60. In this embodiment, the laser Doppler speed measuring device 60 is positioned immediately downstream of the format belt 12 and thus immediately downstream of the format device 100. This enables the sensor device 42, which measures the density of the strand 11, for example, to be arranged immediately before the cutting device 13. This is advantageous depending on the process design.

3 shows a schematic sketch of the operating principle of a laser Doppler velocity measuring device 60. A particle P, which can also be a point P of the strand 11 or the strand surface, moves along the arrow at a certain speed.

The laser Doppler speed measuring device 60 has a laser light source, in particular a laser diode, which emits laser light with a wavelength of 780 nm, for example. The laser beam of the laser diode is split into two laser beams, for example by means of a beam splitter. These laser beams are guided within the laser Doppler speed measuring device so that a first laser beam 305 is directed at the particle P from a first laser window 301 and a second laser beam 306 is directed at the particle P from a second laser window 302. The two laser beams 305, 306 preferably have the same angle to the perpendicular to the direction of movement of the particle P.

The laser light is reflected from the particle P and detected by the laser Doppler velocity measuring device in the detector 303. For example, the detector 303 is a photodetector that converts the detected light into an electrical signal, translates it via an analog/digital converter and evaluates it in an integrated circuit.

Due to the different propagation directions of the first laser beam 305 and the second laser beam 306, the two laser beams 305, 306 are Doppler-shifted differently when reflecting particles P, i.e. they change their frequency by a different amount that depends on the speed of the particle P. The different frequency of the reflected laser beams causes the signal in the detector 303 to beat. This beat has a significantly lower frequency than the laser light and is detected in the intensity of the scattered light. The Doppler shift and thus the speed of the particle P can be determined from the beat frequency.

All of the features mentioned, including those that can be taken from the drawings alone and also individual features that are disclosed in combination with other features, are considered essential to the invention alone and in combination. Embodiments according to the invention can be fulfilled by individual features or a combination of several features.

List of reference symbols

2

Strand machine

10

rod-shaped article

11

strand

12

Format tape

13

Cutting device

15

transverse axial conveying direction

16

longitudinal axial conveying direction

40

Evaluation device

41

Conveyor track

42

Sensor device

43

Drive roller

44

Pulley

50

Push-in drum

60

Laser Doppler Velocimeter

61

Laser beams

100

Formatting device

301

first laser window

302

second laser window

303

detector

305

first laser beam

306

second laser beam

P

Particles

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 3682749 A1 [0003]
• WO 03055338 A2 [0004]
• EP 1164878 B1 [0033]

Claims (16)

Method for operating a strand machine (2) in the tobacco processing industry or a strand machine for producing drinking straws, wherein first a strand (11) in the tobacco processing industry or drinking straw industry is produced and then the strand (11) is cut to length into a plurality of rod-shaped articles (10) in the tobacco processing industry or drinking straw industry by means of a cutting device (13), wherein the strand (11) is conveyed longitudinally axially at a strand speed, characterized in that between the production of the strand (11) and the cutting to length, the strand speed is measured directly and, on the basis of at least one measured value of the strand speed, an operating parameter of the strand machine (2) which influences the length of the cut-to-length rod-shaped articles (10) is controlled or regulated. Procedure according to Claim 1 , characterized in that the strand speed is measured without contact, in particular by means of a laser Doppler speed measuring device (60). Procedure according to Claim 1 or 2 , characterized in that the strand speed is measured by means of contact measurement, in particular by means of a measuring wheel. Procedure according to one of the Claims 1 until 3 , characterized in that the operating parameter is a conveying speed of a format belt (12) of a format device (100) of the strand machine (2) designed to form a longitudinally axially conveyed strand (2) and/or a cutting frequency of the cutting device (13). Procedure according to one of the Claims 1 until 4 , characterized in that after cutting to length, the rod-shaped articles (10) are passed on to a transverse axial conveyor, in particular by means of a transfer device or a push-in drum (50). Procedure according to one of the Claims 1 until 5 , characterized in that the strand speed is measured immediately downstream of a format device (100) of the strand machine (2) designed to form a longitudinally axially conveyed strand (11) and/or is measured immediately upstream of a cutting device (13). Procedure according to one of the Claims 1 until 6 , characterized in that the strand (11) is a sheath-free strand (11), in particular a sheath-free filter tow strand. Procedure according to one of the Claims 1 until 7 , characterized in that two parallel conveyed strands (11) are produced and the two parallel conveyed strands (11) are cut to length into a plurality of rod-shaped articles (10) of the tobacco processing industry or drinking straw industry, wherein the strands (11) are conveyed longitudinally axially at a strand speed each, wherein both strand speeds are measured and the operating parameters of the stranding machine (2) are controlled or regulated on the basis of at least one measured value of the strand speeds. Procedure according to Claim 8 , characterized in that the two strands (11) conveyed in parallel are a first strand (11) and a second strand (11), the first strand (11) being conveyed at a first strand speed and the second strand (11) being conveyed at a second strand speed, a first operating parameter of the stranding machine (2) which influences the length of the rod-shaped articles (10) cut from the first strand (11) being controlled or regulated on the basis of at least one measured value of the first strand speed, and a second operating parameter of the stranding machine (2) which influences the length of the rod-shaped articles (10) cut from the second strand (11) being controlled or regulated on the basis of at least one measured value of the second strand speed. Procedure according to one of the Claims 1 until 9 , characterized in that the measurement of the strand speed or strand speeds is carried out, in particular only, in a predetermined starting period, wherein the starting period begins when the strand machine (2) is started up. Strand machine (2) for producing rod-shaped articles (10) for the tobacco processing industry or the drinking straw industry, wherein a strand (11) for the tobacco processing industry or the drinking straw industry can be produced by means of the strand machine (2), wherein the strand machine (2) comprises a format device (100) for forming a strand (11) conveyed longitudinally axially at a strand speed and a cutting device (13) by means of which the rod-shaped articles (10) can be cut to length from the strand (11), characterized in that the strand machine (2) comprises a measuring device for directly measuring the strand speed. Strand machine (2) to Claim 11 , characterized in that the measuring device device is set up for a contactless measurement of the strand speed, wherein in particular the measuring device comprises a laser Doppler speed measuring device (60), and/or the measuring device is set up for a contact measurement of the strand speed, wherein in particular the measuring device comprises a measuring wheel. Strand machine (2) to Claim 11 or 12 , characterized in that the measuring device is arranged immediately downstream of the format device (100) and/or immediately upstream of the cutting device (13). Strand machine (2) according to one of the Claims 11 until 13 , characterized in that the strand machine (2) comprises an evaluation device (40) for processing the measured values of the strand speed, wherein the evaluation device (40) is set up to receive at least one measured value of the strand speed from the measuring device and, on the basis of the at least one measured value of the strand speed, to control or regulate an operating parameter of the strand machine (2) which influences the length of the rod-shaped articles (10) which can be cut to length or have been cut to length by the cutting device (13). A strand machine (2) for producing rod-shaped articles (10) of the tobacco processing industry or the drinking straw industry, wherein a strand (11) of the tobacco processing industry or the drinking straw industry can be produced by means of the strand machine (2), wherein the strand machine (2) comprises a cutting device (13) by means of which the rod-shaped articles (10) can be cut to length from the strand (11), characterized in that the strand machine (2) is designed to operate by means of a method according to Claim 1 until 10 is set up. Use of a measured strand speed of a strand (11) of a strand machine (2) of the tobacco processing industry or of a strand machine (2) for producing drinking straws, wherein the strand speed is measured directly and is used to control or regulate a cutting device (13) by means of which rod-shaped articles (10) of the tobacco processing industry or drinking straw industry can be or are cut to length from the strand (11), and/or to control or regulate a conveying device by means of which the strand (2) can be or is conveyed longitudinally axially to a cutting device (11) set up for cutting rod-shaped articles (10) of the tobacco processing industry or drinking straw industry from the strand (11).

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