WO2024227902A1 - Brush unit for a corrugated-board installation and method for controlling a brush unit - Google Patents

Abstract

The invention specifies a brush unit (2) for a corrugated-board installation (4), having a movable actuator (8) and at least one brush (10), which is fitted on the actuator (8), wherein the brush (10) has a holder (18) and a cluster (20, 20a, 20b) of bristles, which is fastened on the holder (18) and has a plurality of bristles (22), wherein the cluster (20, 20a, 20b) of bristles has a front portion (28) and a rear portion (30), which is located between the front portion (28) and the holder (18), wherein the cluster (20, 20a, 20b) of bristles is more flexurally rigid on the rear portion (30) than on the front portion (28). Also specified is a method for controlling such a brush unit (2).

Description

Description Brush unit for a corrugated board machine and method for controlling a brush unit

The invention relates to a brush unit for a corrugated cardboard plant and a method for controlling such a brush unit.

A corrugated cardboard machine is used to produce corrugated cardboard. To do this, several layers of paper are glued together, with one or more of the layers also being corrugated. In this way, a corrugated cardboard web is produced from several paper webs. The corrugated cardboard web is then cut into individual sheets using the corrugated cardboard machine, for example using a combination of a longitudinal cutter, e.g. a cutting and creasing machine, and a cross cutter, e.g. a short cross cutter. The individual sheets are distributed to different conveyor paths as required, e.g. sheets are divided into several different conveyor paths depending on the order or depending on their respective dimensions or position transverse to the conveyor direction.

For example, DE 10 2008 033 775 B4 describes a switch unit which has a support element segmented transversely to the conveying direction. This is designed like a comb and has several elongated, finger-shaped prongs which can be pivoted independently of one another around a switch axis. The prongs each have a flexible or elastic extension at the free ends. The extensions ensure a particularly smooth transition. Furthermore, reference is made to DE 19824 694 A1 and DE 10 2013 215 068 A1, which each describe the use of brushes for braking and/or depositing sheets.

The problem with using a brush unit is that its bristles sometimes continue to vibrate strongly during operation, i.e. they vibrate with a large amplitude. This is particularly caused by a jerky movement when the brushes are pivoted, e.g. using hydraulics. When the brushes are pivoted, they and their bristles are accelerated abruptly from a rest position and then braked again just as abruptly at a target position. For example, pivoting from a first to a second position takes just 100 ms to 200 ms. The resulting vibration of the bristles in the target position can then lead to incorrect interaction with a subsequent sheet, so that it is diverted onto the wrong conveyor path, for example, or becomes jammed or damaged in the corrugated cardboard system.

Against this background, it is an object of the invention to improve the interaction of a brush unit with a bow. In particular, the vibration behavior of the bristles, i.e. the brush dynamics, is to be improved. For this purpose, a correspondingly improved brush unit and a method for controlling such a brush unit are to be specified. In addition, the combination of tines and flexible extensions described in the aforementioned DE 10 2008 033 775 B4 is also to be improved.

The object is achieved according to the invention by a brush unit with the features according to claim 1 and by a method with the features according to claim 15. Advantageous embodiments, further developments and variants are the subject of the subclaims. The object is also achieved in particular by a brush for a brush unit as described below and by a corrugated cardboard system with a brush unit as described below. The statements in connection with the brush unit also apply mutatis mutandis to the brush, the corrugated cardboard system and the method and vice versa. If steps of the method are implicitly or explicitly described below are specified, advantageous embodiments for the brush unit result in that it is designed to carry out one or more of these steps, in particular by means of a correspondingly designed control unit.

A key idea of the invention is in particular to locally stiffen a bristle bundle of a brush unit in order to optimize the vibration behavior of the bristle bundle during operation. The corresponding stiffening takes place on a rear section of the bristle bundle so that this rear section is stiffer than a front section, which regularly acts on the arch.

The brush unit is used in a corrugated cardboard plant. The corrugated cardboard plant in turn is used to produce corrugated cardboard from several layers of paper. The brush unit has a movable actuating element and at least one brush which is attached to the actuating element. In a suitable embodiment, several brushes, which are then expediently of the same design, are attached to the actuating element. In a likewise suitable embodiment, the brush unit has several actuating elements, each with one or more brushes. The actuating element is preferably a rigid component, e.g. a profile part and in particular made of metal, and is movable overall, e.g. pivotable about an axis of rotation. The specific design of the actuating element depends on the specific function of the brush unit within the corrugated cardboard plant. The brush unit is generally preferably arranged in the so-called dry end of the corrugated cardboard plant.

In a suitable embodiment, the actuating element is a swivel arm, at one end of which the brush is attached. The combination of swivel arm and brush is also referred to as a "paddle". The brush unit is then preferably part of a paddle station (also referred to as a switch unit, as in DE 10 2008 033 775 B4) of the corrugated cardboard plant, whereby the paddle station is designed to guide a sheet to one of several different conveying levels (ie conveying paths) by swiveling the actuating element. The paddle serves as an adjustable ramp, which, depending on the position, leads to one of several conveying levels, in particular those lying one above the other. Depending on how far the When the paddle is pivoted, one of the conveying levels is controlled. The brush unit expediently even has several paddles which are arranged next to one another transversely to the conveying direction and which can be pivoted in particular about the same axis of rotation.

In the following, without restricting generality, a brush unit is assumed to be part of a paddle station of the corrugated cardboard plant as described above. However, the statements also apply analogously to other sub-units of the corrugated cardboard plant that use a brush unit, e.g. for the brush unit of a braking and/or depositing device of the corrugated cardboard plant.

The actuating element in combination with the brush serves in particular to interact with the sheets which are produced by the corrugated cardboard system and which are guided by it along a conveying direction (machine direction). Accordingly, the brush unit is expediently arranged downstream of a cross cutter of the corrugated cardboard system. The cross cutter cuts the previously endless corrugated cardboard web into individual sheets in the cross machine direction, i.e. perpendicular to the conveying direction. Cutting in the longitudinal direction, i.e. in the conveying direction, e.g. by means of a cutting and creasing machine, can take place before or after the cross cutter and before or after the brush unit, so that several sheets can also be conveyed next to one another in the cross direction if necessary. “Interaction” is understood in particular to mean guiding, steering, redirecting, deflecting, holding down, braking or the like. For this purpose, the brush touches a corresponding sheet at least temporarily or at least acts as a guide or guiding element for the sheet. The same applies in particular to the actuating element, at least in the case of a paddle station. Due to the movement of the actuating element, the bristle bundle regularly vibrates, which can adversely result in deflection, damage or other impairment of a sheet that is being guided over the brush at that time. It should also be noted that the actuating element regularly moves while a sheet is in contact with it, so that the guidance of the sheet is impaired accordingly. For example, in a paddle station the sheets follow one another in the conveying direction at a distance which usually only corresponds to the cutting width of the preceding cross cutter, i.e. typically at a distance of just 1 mm and thus essentially directly one after the other. If the adjusting element is now to be moved in order to redirect a subsequent sheet to a different conveying level, the movement takes place while the preceding sheet is still on the adjusting element and above the brush. The sheet is raised or lowered accordingly and may therefore be bent at the ends as it enters the previously selected conveying level. This also may subject the bristles to bending stress. In any case, however, the movement (or more precisely acceleration) of the adjusting element with the brush already leads to bending stress on the bundle of bristles, which then vibrates accordingly and may then incorrectly redirect or damage the subsequent sheet or something similar.

The brush has a holder and a bundle of bristles which is attached to the holder and which has several bristles. The holder serves in particular on the one hand to bundle the bristles and on the other hand to attach the brush as a whole to the actuating element. In a suitable design, the holder has a hole, e.g. a circular blind hole, into which the bristles are inserted. The bristles are expediently cast in the hole, e.g. with an adhesive. The holder itself is, for example, a simple wooden block which is screwed to the actuating element. Other shapes, materials and/or attachments are also generally suitable.

The bristles each extend in a longitudinal direction from a rear end to a front end and have a total length measured between these ends. The rear end is also referred to as the base, the front end as the tip. Analogously, each individual bristle also has a base and a tip. The base is attached to the holder, e.g. inserted into it as described above, the tip, on the other hand, is in particular freely swinging, for interaction with an arch. The bristles are combined to form the bristle bundle, whereby the bristles run in particular parallel to one another, at least at the base. The bristles are also designed to be the same length and arranged flush, ie the tips of the bristles are aligned in the transverse direction (perpendicular to the longitudinal direction).

The bundle of bristles has a front section and a rear section, which lies between the front section and the holder. The front section preferably begins at the tips of the bristles and ends at the beginning of the rear section. The rear section then ends at the holder. The part of the bristles that may lie within the holder is not included in the rear section. Depending on the design, the total length of the bristles is then correspondingly greater than the sum of the lengths of the two sections.

According to the invention, the bristle bundle now has a greater flexural rigidity on the rear section than on the front section. This makes the bristle bundle stiffer at the back than at the front. Overall, this results in a flexural rigidity of the bristle bundle that varies in the longitudinal direction, with the flexural rigidity decreasing towards the tip. In the simplest case, a first flexural rigidity is realized along the rear section and a second flexural rigidity along the front section, which is lower than the first flexural rigidity, so that a discrete transition is realized. A continuous change in the flexural rigidity along the longitudinal direction is also suitable.

The different bending stiffness along the bristle bundle optimizes the overall vibration behavior of the bristle bundle. An excessively large amplitude of the bristle bundle and a correspondingly faulty interaction with the bow are advantageously avoided. Any after-vibration of the bristle bundle is reduced, while at the same time a sufficient elasticity of the bristle bundle is maintained. In particular, vibration amplitudes of vibrations with a low vibration frequency (< 10 Hz) are particularly strongly dampened. Stiffness is generally understood to mean the resistance of a component, in this case the bundle of bristles, to elastic deformation, which is imposed by an external load. Stiffness therefore conveys the connection between a load on the component and its deformation. In this case, this specifically refers to flexural stiffness, which indicates the resistance of the component when subjected to bending around a bending axis. Elastic deformation is defined by the elasticity of the component, which is understood to be the property of the component to change its shape from an original shape under the action of force (in this case a bend) and to return to its original shape when the force is removed. Bending stiffness and stiffness in general are determined in particular by the material of the component and its geometry. In this case, the bristles' generally elongated and thin design means that they have a flexural stiffness such that a completely elastic deflection is possible within certain limits.

To increase the bending stiffness of the rear section relative to the front section, several different solutions are described below, which can also be combined with each other.

In a suitable embodiment, the rear section has a greater flexural rigidity in that the bristle bundle has a jacket along the rear section, which envelops the bristles and presses them together. The jacket is also referred to as a tube. The jacket is formed along the entire rear section, i.e. the jacket and the rear section are the same length. Alternatively, the jacket is longer than the rear section and then also reaches into the holder, but in no case reaches into the front section. The jacket completely surrounds the bristles and is, for example, cylindrical. The jacket consists in particular of an elastic material. The jacket expediently has a thickness of 0.5 mm to 2 mm. The front section, on the other hand, is in particular jacket-free. On the one hand, the jacket envelops the bristles and thereby holds them together, on the other hand, the jacket also presses the bristles together, i.e. generates a force in the radial direction. Direction (perpendicular to the longitudinal direction). This causes the bristles to rub against each other when subjected to bending loads, so that vibration energy is dissipated through friction. This improves the vibration behavior of the bristle bundle, ie the brush dynamics, overall. In particular, low vibration frequencies that regularly occur during operation when the actuator is moved and/or when interacting with an arch are primarily dampened. This also prevents an excessively large vibration amplitude of the bristle bundle and a correspondingly faulty interaction with an arch.

The jacket is advantageously a shrink tube that is shrunk onto the bristles. This design is particularly simple and cost-effective. In addition, compared to a solution using a cable tie to hold the bristles together, a shrink tube has the advantage that a bow that is guided over or past the jacket does not get caught, but can slide on unhindered. A shrink tube is a jacket made of a thermoplastic (e.g. a polyolefin or PVC) that has an oversize during production and is then shrunk by the application of heat. This achieves optimal adaptation to the bristles and at the same time a force in the radial direction in order to achieve optimal friction between the bristles in the event of bending loads.

Suitably, the sheath is made of silicone or PTFE and preferably consists entirely and only of one of these materials.

Alternatively or additionally, the rear section in a suitable embodiment has greater rigidity in that the bristles along the rear section are connected to one another by means of an elastic material. The elastic material is arranged in particular along the entire rear section and optionally also extends into the holder. A suitable elastic material is silicone. In contrast to the above-mentioned casing, the bristles are not just grouped together around the circumference, but the elastic material fills the various gaps (gussets) between the bristles, adheres to them and in this way connects the bristles to one another. It is important that the elastic material is elastic in itself. This means that the bristles are not particularly firmly connected to one another, as is the case with an adhesive, but are still somewhat flexible relative to one another, although less flexible than without the elastic material, so that the rear section has a higher bending stiffness overall than the front section. The front section is notably free of such an elastic material. A possible disadvantage of the elastic material is that, depending on the specific design, it can wear out over time and with repeated bending stress and then tear, so that the increased bending stiffness is reduced again accordingly.

Alternatively or additionally, the rear section has greater rigidity because the bristles along the rear section each have a larger diameter than along the front section. The larger diameter is formed along the entire rear section. In the longitudinal direction, at least two different diameters are formed, so that the bristles are thinner towards the tip than towards the base. The transition is either discrete, e.g. stepped, or continuous. So-called conical bristles are particularly suitable as bristles, in which the diameter decreases continuously and in particular linearly from the base to the tip, e.g. by 50% to 90%. Such bristles are more expensive than bristles with a constant diameter, but they intrinsically have a higher flexural rigidity towards the base, which then also leads to a higher flexural rigidity in the bristle bundle overall in the direction of the holder. In addition, conical bristles are also packed more densely in the direction of increasing diameter, so that the friction between them also increases with increasing diameter.

All of the above solutions have in common that special measures along the rear section provide increased flexural rigidity. Of the solutions mentioned, the solution with a jacket, especially with a shrink tube, is particularly preferred, as it is the simplest, most cost-effective and most robust compared to the other solutions. Above all, This solution is particularly easy to retrofit even to existing brush units.

A particularly useful embodiment is one in which the brush unit has several adjusting elements and brushes as described above, but at least two types (a first type and a second type) of bristle bundles are designed such that their rear section is of different lengths or of different rigidity or both. This generally also means that two types of brushes and optionally also two types of adjusting elements are designed. The statements already made and the following apply to both types of bristle bundles. The adjusting elements are in particular movable independently of one another, at least the adjusting elements with bristle bundles of one type are movable independently of the adjusting elements with bristle bundles of another type. The different types advantageously serve different requirements. For example, different conveying paths are to be served, which require a different movement (e.g. deflection) of the adjusting elements and thus lead to different levels of bending stress on the brushes. One type of bristle bundle is now used for each of the conveying paths, which is then optimized with regard to the respective bending stress.

Different types of bristle bundles can be realized by designing the rear section with increased flexural rigidity of different lengths. Alternatively or additionally, the rear sections of different types, which may even be of equal length, have different flexural rigidities; these can be realized with the solutions already mentioned above, if necessary in combination. In a particularly simple design, the bristle bundle has an additional jacket on the rear section, which is shorter than the rear section. This means that the rear section is again divided into two, with two subsections with different flexural rigidities. Here too, the flexural rigidity preferably increases towards the front of the bristle bundle. The same statements apply to the additional jacket as already mentioned above for the jacket, so the additional jacket is preferably also a shrink tube. The additional jacket is inside the jacket or arranged around it. The additional jacket preferably begins at the holder. The additional jacket can also be advantageously combined with the other solutions. The additional jacket is particularly useful for those bristle bundles that experience a higher bending stress compared to other bristle bundles, e.g. have to be moved over a longer distance within the same time.

Advantageously, the bristles are each made of glass fiber, i.e. made of glass. The bristle bundle is then a glass fiber bundle. In particular, the bristles are made exclusively of glass. Glass fibers are characterized by high abrasion resistance and at the same time sufficient elasticity.

The bristle bundle is preferably a round bundle, i.e. the individual bristles are arranged as far as possible within a circle when viewed in cross-section perpendicular to the longitudinal direction. This is in contrast to a flat bundle, for example, in which the bristles are arranged next to each other in a row. A round bundle offers an optimal level of friction between the bristles in the event of bending stress.

In a suitable embodiment, the bristle bundle has at least 5 and at most 20 bristles. A bristle bundle having 10 bristles is particularly preferred.

Each bristle is preferably circular in cross-section. Alternatively or additionally, each bristle has a diameter in the range of 1 mm to 3 mm, a diameter of 1.5 mm is particularly suitable. The diameter is measured perpendicular to the longitudinal direction.

Suitably, a respective bristle has a length measured from the holder to the tip in the range of 120 mm to 140 mm, in particular 130 mm. The total length (from the base to the tip) of a respective bristle is the sum of the aforementioned length, ie the length outside the holder, and optionally an additional length inside the holder, provided that the bristles are in These are used. The total length is then, for example, in the range of

140 mm to 190 mm.

The rear section preferably has a length which corresponds to 1/4 to 3/4, particularly preferably 1/2 to 3/4 of the length of a bristle outside the holder. The front section accordingly has a length which corresponds to the difference between the length of a bristle outside the holder and the length of the rear section. If an additional casing is present, its length is expediently in the range of 1/2 to 3/4 of the length of the rear section.

Advantageously, grinding of the sheets on the bristle bundle, especially on the rear section, is avoided as far as possible in order to keep wear on the bristle bundle as low as possible, especially wear on a casing and/or additional casing as described. In a suitable embodiment, the adjusting element projects transversely to the bristle bundle (i.e. perpendicular to the longitudinal direction and perpendicular to both the conveying direction and the transverse direction) in such a way that, at least in a resting position of the bristle bundle, a sheet which is guided over the adjusting element and the bristle bundle does not grind over the rear section. For this purpose, the bristle bundle is suitably set back from the adjusting element transversely to the longitudinal direction by a certain distance, e.g. by 5 mm to 20 mm. The adjusting element and the bristle bundle extend together in the longitudinal direction, with the bristle bundle forming an extension of the adjusting element in the longitudinal direction. A sheet which is now conveyed through the corrugated cardboard system in the conveying direction is first conveyed over the adjusting element and then over the associated brush. When the adjusting element is moved (or adjusted), the bristle bundle is set into vibration and swings out of a resting position transversely to the longitudinal direction. The bow then typically comes into contact with the bristle bundle. After a while, however, the vibration has subsided and the bristle bundle is back in the resting position. In this situation, a bow guided over the adjusting element and brush no longer touches the bristle bundle, at least not more the rear section, so that wear on it is largely avoided.

In the method, the actuating element is moved, preferably pivoted, from a first position to a second position as described above and stopped at the second position, so that the bundle of bristles begins to oscillate, which is dampened by the greater bending stiffness on the rear section. In other words: the oscillation has an oscillation amplitude which is advantageously limited by the greater bending stiffness on the rear section. The actuating element is moved, for example, using a hydraulic cylinder, which leads to a correspondingly jerky movement. The movement from the first to the second position takes place in particular within just 100 ms to 200 ms.

In the following, embodiments of the invention are explained in more detail with reference to a drawing. In each case, the following schematically shows:

Fig. 1 a brush unit in a side view,

Fig. 2 a corrugated board plant,

Fig. 3 a brush unit in a plan view,

Fig. 4 a paddle station of the corrugator from Fig. 2,

Fig. 5 a brush,

Fig. 6 a variant of the brush from Fig. 5,

Fig. 7 a bristle bundle in a front view,

Fig. 8 a variant of the bristle bundle from Fig. 7, Fig. 9 a bristle in a side view.

Fig. 1 shows an embodiment of a brush unit 2 in a side view. The brush unit 2 is used in a corrugated cardboard system 4, e.g. as shown in Fig. 2. The corrugated cardboard system 4 in turn is used to produce corrugated cardboard 6 from several layers of paper. The brush unit 2 has a movable actuating element 8 and at least one brush 10, which is attached to the actuating element 8. Typically, several similarly designed brushes 10 are attached to the actuating element 8, e.g. as can be seen in the top view in Fig. 3. Fig. 3 also shows a design in which the brush unit 2 has several actuating elements 8, each with several brushes 10. In the embodiment shown, the actuating element 8 is a rigid component, e.g. a profile part made of metal, and is movable overall, in this case pivotable about an axis of rotation D.

In the embodiment shown here, the adjusting element 8 is a pivoting arm, at one end of which the brush 10 is attached. The combination of pivoting arm 8 and brush 10 is also referred to as a “paddle”. The brush unit 2 is then part of a paddle station 12 of the corrugated cardboard system 4. As shown schematically in Fig. 2 and in detail in Fig. 4, the paddle station 12 is designed to guide a sheet 14 to one of several different conveying levels E1, E2, E3 (i.e. conveying paths) by pivoting the adjusting element 8. The paddle serves as an adjustable ramp which, depending on the position, leads to one of several superimposed conveying levels E1, E2, E3. Depending on how far the paddle is pivoted, one of the conveying levels E1, E2, E3 is controlled. In the present case, the brush unit 2 even has several paddles which - as can be seen in Fig. 3 - are arranged next to one another transversely to the conveying direction F and which can be pivoted about the same axis of rotation D.

The statements made here also apply analogously to other sub-units of the corrugated cardboard system 4 which use a brush unit 2, e.g. for a braking and/or depositing device of the corrugated cardboard system 2. The adjusting element 8 in combination with the brush 10 serves to interact with the sheets 14 which are produced with the corrugated cardboard system 4 and are guided by it along a conveying direction F. Accordingly, the brush unit 2 is arranged, for example, downstream of a cross cutter 16 of the corrugated cardboard system. The cross cutter 16 cuts the previously endless corrugated cardboard web 6 in the transverse direction Q, ie perpendicular to the conveying direction F, into individual sheets 14.

Cutting in the longitudinal direction, i.e. in the conveying direction F, e.g. by means of a cutting and creasing machine, can take place before or after the cross cutter 16 and before or after the brush unit 2, so that if necessary several sheets 14 can be conveyed next to one another in the transverse direction Q.

5 and 6 show two different embodiments of the brush 10, each in a side view. The brush 10 has a holder 18 and a bristle bundle 20, which is attached to the holder 18 and which has a plurality of bristles 22. The holder 18 serves on the one hand to bundle the bristles 22 and on the other hand to attach the brush 10 as a whole to the actuating element 8. In the embodiments shown here, the holder 18 has a hole, e.g. a circular blind hole, into which the bristles 22 are inserted. The holder 18 itself is then screwed to the actuating element 8. The bristles 22 each extend in a longitudinal direction L from a rear end to a front end and have a total length G measured between these ends. The rear end is also referred to as the base 24, the front end as the tip 26. The base 24 is attached to the holder 18, the tip 26, however, is freely swinging, for interaction with an arch 14. The bristles 22 are combined to form the bristle bundle 20, wherein the bristles 22 run parallel to one another, at least at the base 24. The bristles 22 are also of the same length and arranged flush, i.e. the tips 26 are aligned in the transverse direction Q (perpendicular to the longitudinal direction L).

Due to the movement of the adjusting element 8, the bristle bundle 20 regularly vibrates, e.g. as shown in Fig. 1. At the paddle station 12, the sheets 14 follow in the conveying direction F at a distance from one another which only corresponds to the cutting width of the preceding cross cutter 16. , ie typically at a distance of only 1 mm and thus essentially directly on top of one another. If the adjusting element 8 is now to be moved in order to redirect a subsequent sheet 14 to a different conveying plane E1, E2, E3, the movement takes place while the preceding sheet 14 is still on the adjusting element 8 and above the brush 10. The sheet 14 is raised or lowered accordingly and may therefore be bent at the end as it enters the previously selected conveying plane E1, E2, E3. The movement of the adjusting element 8 with the brush 10 leads to a bending stress on the bundle of bristles 20, which then vibrates accordingly and may incorrectly redirect or damage the subsequent sheet 14 or the like.

The bristle bundle 20 has a front section 28 and a rear section 30, which lies between the front section 28 and the holder 18. The front section 28 begins at the tips of the bristles 22 and ends at the beginning of the rear section 30. The rear section 30 then ends at the holder 18. The part of the bristles 22 which may lie within the holder 18 is not added to the rear section 30. In Figs. 5 and 6, the total length G of the bristles 22 is then correspondingly greater than the sum of the lengths of the two sections 28, 30.

The bristle bundle 20 now has a greater flexural rigidity on the rear section 30 than on the front section 28. As a result, the bristle bundle 20 is stiffer at the back than at the front. Overall, this results in a flexural rigidity of the bristle bundle 20 that varies in the longitudinal direction L, with the flexural rigidity decreasing towards the tip 26. In the simplest case, a first flexural rigidity is realized along the rear section 30 and a second flexural rigidity, which is lower than the first flexural rigidity, is realized along the front section 28, so that a discrete transition is realized. A continuous change in the flexural rigidity along the longitudinal direction L is also possible. The different flexural rigidity along the bristle bundle 20 optimizes the vibration behavior of the bristle bundle 20 overall. An excessively large amplitude of the bristle bundle 20 and a correspondingly faulty Interaction with the arch 14 is avoided. Any oscillation of the bristle bundle 10 is reduced, while at the same time a sufficient elasticity of the bristle bundle 10 is maintained.

To increase the flexural rigidity of the rear section 30 relative to the front section 28, several different solutions are described below, which can also be combined with one another.

In one possible embodiment, the rear section 30 has greater flexural rigidity in that the bristle bundle 20 has a jacket 32 along the rear section 30, by which the bristles 22 are enveloped and compressed. Two exemplary embodiments of this are shown in Figs. 5 and 6. Fig. 7 shows the bristle bundle 20 from Fig. 5 in a front view. The jacket 32 is also referred to as a tube and is formed along the entire rear section 30, i.e. both are the same length. Alternatively, the jacket 32 is longer than the rear section 30 and then also extends into the holder 18. The front section 28, on the other hand, has no jacket. The jacket 32 completely surrounds the bristles 22 and is cylindrical in this case. The jacket 32 consists of an elastic material and is a shrink tube which is shrunk onto the bristles 22.

Alternatively or additionally, the rear section 30 has greater rigidity in that the bristles 22 are connected to one another along the rear section 30 by means of an elastic material 34, e.g. silicone. An exemplary embodiment of this is shown in Fig. 8, which, like in Fig. 7, shows a bundle of bristles 20 in a front view. The elastic material 34 is arranged along the entire rear section 30 and fills the various gaps (gussets) between the bristles 22, adheres to them and in this way connects the bristles 22 to one another. The elastic material 34 is elastic in itself. The front section 30 is free of such an elastic material 34. Alternatively or additionally, the rear section 30 has greater rigidity in that the bristles 22 along the rear section 30 each have a larger diameter X than along the front section 30. An exemplary embodiment of this is shown in Fig. 8, which shows a single bristle 22 in a side view. The larger diameter X is formed along the entire rear section 30. In the longitudinal direction L, at least two different diameters X are thus formed, so that the bristles 22 are thinner towards the tip 26 than towards the base 24. The transition is either discrete, e.g. step-shaped, or continuous, as shown in Fig. 8, which specifically shows a so-called conical bristle in which the diameter X decreases continuously and linearly from the base 24 to the tip 26.

As already described, Fig. 3 shows a design in which the brush unit 2 has several adjusting elements 8 and brushes 10. In addition, in the embodiment of Fig. 3, two types (a first type and a second type) of bristle bundles 20a, 20b are designed such that their rear section 30 is of different lengths or different degrees of rigidity or both. The adjusting elements 8 can move independently of one another; at least the adjusting elements 8 with bristle bundles 20a of one type can move independently of the adjusting elements 8 with bristle bundles 20b of another type. The different types serve different requirements. In the present case, different conveying paths are to be served, which require a different movement of the adjusting elements 8 and thus lead to different degrees of bending stress on the brushes 10. In the present case, these different conveying paths are the two conveying levels E2, E3 as shown in Fig. 4, for each of which a type of bristle bundle 20a, 20b is used, specifically bristle bundle 20 as shown in Fig. 5 for the lower conveying level E2 and bristle bundle 20 as shown in Fig. 6 for the higher conveying level E3.

Different types of bristle bundles 20 can be realized by designing the rear section 30 with increased bending stiffness to have different lengths. Alternatively or additionally, the rear sections 30 of different types, which may even be of equal length, have different Bending stiffnesses, these can be implemented with the solutions already mentioned above, if necessary in combination. In the exemplary embodiment according to Fig. 6, the bristle bundle 20 has an additional jacket 36 on the rear section 30, which is shorter than the rear section 30. As a result, the rear section 30 is again divided into two, with two corresponding subsections 30a, 30b with different flexural stiffnesses. Here, too, the flexural stiffness increases towards the front (tip 26) of the bristle bundle 20. The same statements apply to the additional jacket 36 as already mentioned above for the jacket 32, so the additional jacket 36 is also a shrink tube in this case. The additional jacket 36 is arranged inside the jacket 32 (not shown) or around it (as in Fig. 6). The additional jacket 36 begins at the holder 18. The additional jacket 25 can also be combined with the other solutions.

In the embodiments shown here, the bristles 22 are each a glass fiber and consist exclusively of glass. The bristle bundle 20 is then a glass fiber bundle. The bristle bundles 20 shown here are also round bundles overall, i.e. the individual bristles 22 are arranged as far as possible within a circle when viewed in cross-section perpendicular to the longitudinal direction L, as in Figs. 7 and 8. The bristle bundles 20 shown here as examples each have 10 bristles 22. Each bristle 22 is circular in cross-section and has a diameter X in the range of 1 mm to 3 mm. Measured from the holder 18 to the tip 26, each bristle 22 has a length Y in the range of 120 mm to 140 mm. The total length G (from the base 24 to the tip 26) of each bristle 22 is the sum of the aforementioned length Y and, if applicable, also the length within the holder 18.

The rear section 30 has a length which corresponds to 1/2 to 3/4 of the length Y. The front section 30 has a length which corresponds to the difference between the length Y and the length of the rear section 30. If an additional jacket 36 is present, its length is in the range of 1/2 to 3/4 of the length of the rear section 30. Grinding of the arches 14 on the bristle bundle 20, especially on the rear section 30, is avoided as far as possible in order to keep wear on the bristle bundle 20 as low as possible. For this purpose, the adjusting element 8 projects transversely to the bristle bundle 20 (ie perpendicular to the longitudinal direction L and perpendicular to both the conveying direction F and the transverse direction Q) in such a way that, at least in a rest position (as shown in Fig. 4) of the bristle bundle 20, an arch 14 which is guided over the adjusting element 8 and the bristle bundle 20 does not grind over the rear section 30. For this purpose, the bristle bundle 20 is set back from the adjusting element 8 transversely to the longitudinal direction L by a distance Z, e.g. by 5 mm to 20 mm. The adjusting element 8 and the bristle bundle 20 extend together in the longitudinal direction L, with the bristle bundle 20 forming an extension of the adjusting element 8 in the longitudinal direction L. A sheet 14, which is now being conveyed through the corrugated cardboard system 4 in the conveying direction F, is first conveyed via the adjusting element 8 and then via the associated brush 10. When the adjusting element 8 is moved, the bristle bundle 20 is set into vibration and swings out of the rest position transversely to the longitudinal direction L (as shown in Fig. 1). The sheet 14 now typically comes into contact with the bristle bundle 20. After some time, however, the vibration has subsided and the bristle bundle 20 is back in the rest position. In this situation, a sheet 14 guided over the adjusting element 8 and brush 10 no longer touches the bristle bundle 20, at least no longer touches the rear section 30.

In the method, the actuating element 8 is moved as described above from a first position (drawn with a solid line in Fig. 4, to the conveying plane E1) to a second position (drawn with a dashed line in Fig. 4, to one of the conveying planes E2, E3), in this case pivoted, and stopped at the second position, so that the bristle bundle 20 begins to oscillate, which is dampened by the greater bending stiffness on the rear section 30. list of reference symbols

2 brush units

4 corrugated board lines

6 corrugated cardboard

8 actuator

10 brushes

12 paddling stations

14 sheets

16 cross cutters

18 holders

20, 20a, 20b bristle bundles

22 bristles

24 base

26 points

28 front section

30 rear section

30a, 30b subsection

32 jacket (hose)

34 elastic material

36 additional jacket

D axis of rotation

E1, E2, E3 conveyor level

F conveying direction

G total length

Q transverse direction

X diameter

Y length

Z distance

Claims

claims 1. Brush unit (2) for a corrugated cardboard machine (4), a. which has a movable adjusting element (8) and at least one brush (10) which is attached to the adjusting element (8), b. wherein the brush (10) has a holder (18) and a bundle of bristles (20, 20a, 20b) which is attached to the holder (18) and which has a plurality of bristles (22), c. wherein the bundle of bristles (20, 20a, 20b) has a front section (28) and a rear section (30) which lies between the front section (28) and the holder (18), d. wherein the bundle of bristles (20, 20a, 20b) has a greater flexural rigidity on the rear section (30) than on the front section (28). 2. Brush unit (2) according to claim 1, wherein the rear portion (28) has a greater flexural rigidity in that the bristle bundle (20, 20a, 20b) has a jacket (32) along the rear portion (30), by which the bristles (22) are enveloped and compressed. 3. Brush unit (2) according to claim 2, wherein the jacket (32) is a shrink tube which is shrunk onto the bristles (22). 4. Brush unit (2) according to claim 2 or 3, wherein the casing (32) is made of silicone or PTFE. 5. Brush unit (2) according to one of claims 1 to 4, wherein the rear portion (30) has a greater rigidity in that the bristles (22) along the rear portion (30) are interconnected by means of an elastic material (34). 6. Brush unit (2) according to one of claims 1 to 5, wherein the rear portion (30) has a greater rigidity in that the bristles (22) along the rear portion (30) each have a larger diameter (X) than along the front portion (28). 7. Brush unit (2) according to one of claims 1 to 6, wherein it has a plurality of adjusting elements (8) and brushes (10), wherein at least two types of bristle bundles (20, 20a, 20b) are designed such that their rear section (30) is of different lengths or of different flexural rigidity or both. 8. Brush unit (2) according to one of claims 1 to 7, wherein the bristle bundle (20, 20a, 20b) has an additional jacket (36) at the rear portion (30) which is shorter than the rear portion (28). 9. Brush unit (2) according to one of claims 1 to 8, wherein the bristles (22) are each a glass fiber. 10. Brush unit (2) according to one of claims 1 to 9, wherein the bristle bundle (20, 20a, 20b) has at least 5 and at most 20 bristles (22). 11. Brush unit (2) according to one of claims 1 to 10, wherein a respective bristle (22) is circular in cross-section and has a diameter (X) in the range of 1 mm to 3 mm. 12. Brush unit (2) according to one of claims 1 to 11, wherein a respective bristle (22) has a length (Y) in the range of 120 mm to 140 mm, measured from the holder (18) to a tip of the bristle (22). 13. Brush unit (2) according to one of claims 1 to 12, wherein the adjusting element (8) projects transversely to the bristle bundle (20, 20a, 20b) in such a way that at least in a rest position of the bristle bundle (20, 20a, 20b) an arc (14) which is guided over the adjusting element (8) and the bristle bundle (20, 20a, 20b) does not drag over the rear section (30). 14. Brush unit (2) according to one of claims 1 to 13, wherein the brush unit (10) is part of a paddle station (12) of the corrugated cardboard system (4), wherein the adjusting element (8) is a pivoting arm, at one end of which the brush (10) is attached, wherein the paddle station (12) is designed to guide a sheet (14), which is produced with the corrugated cardboard system (4), to one of several different conveying levels (E1, E2, E3) by pivoting the adjusting element (8). 15. Method for controlling a brush unit (2) according to one of claims 1 to 14, wherein the actuating element (8) is pivoted from a first position to a second position and is stopped at the second position, so that the bristle bundle (20, 20a, 20b) begins to oscillate, which is dampened by the greater flexural rigidity on the rear section (30).