Method for sucking fibres from pulp using a suction device and a suction device

Abstract

A method for sucking fibers from a pulp (210) using a suction device (320) with a suction tool (340) and a suction device (320) for sucking fibers from a pulp (210) with a suction tool (340) are described, which has a plurality of cavities (350) for sucking fibers, wherein the cavities (350) have a surface with a plurality of openings which are connected to a common suction line via channels, and wherein the suction power is changed during a suction process.

Description

Technical area

[0001] A method for sucking fibers from a pulp using a suction device with a suction tool and a suction device for sucking fibers from a pulp with a suction tool are described, which has a plurality of cavities for sucking fibers.

[0002] Fibrous materials are increasingly being used to produce packaging for food (e.g., trays, capsules, boxes, etc.) and consumer goods (e.g., electronic devices, etc.), as well as beverage containers. Everyday items such as disposable cutlery and tableware are also made from fibrous materials. Fibrous materials include natural fibers or synthetic fibers. Recently, there has been an increasing use of fibrous materials that contain natural fibers or are made from fibers that can be obtained, for example, from renewable raw materials or waste paper. The natural fibers are mixed with water and, if necessary, other additives such as starch in a so-called pulp. Additives can also affect the color, barrier properties, and mechanical properties. This pulp can contain, for example, 0.1 to 10% by weight of natural fibers.The proportion of natural fibers varies depending on the process used to produce packaging, etc., and the product properties of the product to be manufactured. background

[0003] The production of fiber-containing products from pulp generally takes place in several work steps. For this purpose, a fiber processing facility has several stations or forming stations. In a forming station, for example, fibers can be sucked into a cavity of a suction tool, whereby a preform is shaped or formed. For this purpose, the pulp is provided in a pulp supply and the suction tool with at least one suction cavity, the geometry of which essentially corresponds to the product to be manufactured, is at least partially immersed in the pulp. During immersion, suction takes place via openings in the suction cavity, which are connected to a corresponding suction device, with fibers from the pulp collecting on the surface of the suction cavity. The sucked-in fibers (filter cake) can then be brought via the suction tool into a pre-pressing tool, whereby a preform is pre-pressed. For this purpose, for example,Elastic molded bodies are used which are inflated for pressing and in the process exert pressure on the preforms. During this pre-pressing process, the fibers in the preform are pressed and the water content of the preform is reduced. The preforms are then pressed into finished molded parts in a hot press. Here, preforms are placed in a hot-pressing tool which, for example, has a lower tool half and an upper tool half that are heated. In the hot-pressing tool, the preforms are pressed in a cavity with heat input, with the pressure and heat removing residual moisture so that the moisture content of the preforms is reduced from approximately 60% by weight before hot pressing to, for example, 5-10% by weight after hot pressing.

[0004] A suction tool and a manufacturing method using the methods described above are known, for example, from DE 10 2019 127 562 A1.

[0005] For the so-called wet fiber process, a so-called filter cake is pre-formed from the pulp (cellulose / water mixture) for further processing. This pre-forming usually takes place by suction from aqueous pulp (primary forming) using negative pressure. During suction, the aqueous mixture adheres to a filter mesh, with the cellulose fibers in the mold insert (suction cavity) forming the filter cake and the excess water in the mixture being transported through a mesh / membrane that forms the surface of the suction cavity and thus separated from the pulp. The remaining water bound in the filter cake is separated mechanically in subsequent steps by pressing or evaporation. In order to ensure consistent quality throughout the subsequent processing cycle and when multiple mold inserts are used, an even material distribution in the cavities of a suction tool, even during suction, is of great importance.

[0006] In molds with more than one mold insert and mold cavities on the same level parallel to the pulp surface of a pulp container, the effective volume flow fluctuates significantly at a constant suction vacuum due to the statistically greater or lesser access / distance to the pulp. Cavities located at the edges of the mold due to the shape of the suction box of a suction tool initially clog their mold cavity at a constant vacuum via a suction unit. Subsequently, the entire volume flow is available to the inner mold cavities with "closed" outer cavities. They then suddenly become clogged with more material (fibers) and a higher relative volume flow. This difference can only be compensated for with a long waiting time below pulp level, which dramatically increases the cycle time for the process step, which negatively impacts the production time for molded parts made of fibrous material.The weight distribution of the individual filter cakes in the suction tools therefore varies greatly at the end of a suction process. Task

[0007] In contrast, the task is to provide a solution that provides fiber suction from a pulp, whereby a uniform filter cake formation is achieved for the suction of fibers across multiple cavities, regardless of the position of the cavities, and a uniform weight / material distribution of sucked-in fibers is achieved for all cavities during a suction process. Furthermore, the cycle time for sucking fibers should not be extended compared to conventional suction processes. Solution

[0008] The above-mentioned object is achieved by a method for sucking fibers from a pulp using a suction device with a suction tool having a plurality of cavities, wherein the cavities have a surface with a plurality of openings which are connected via channels to a common suction line, wherein the suction power is changed during a suction process.

[0009] By specifically altering the suction power, changing pressure levels and flow rates, and / or positioning the cavities at different levels relative to the pulp surface, the suction flow rate can be influenced in such a way that material distribution is even with a comparatively shorter cycle time. In this case, outer cavities can still clog first during the suction process. As soon as the effective flow rate and the accumulation of material shift to the inner cavities, the flow rate and suction (negative) pressure can be switched, which, for example, causes middle cavities to clog less or more evenly than the outer cavities.

[0010] This can involve switching between at least two states, or relocating the suction tool relative to the pulp surface. Advantageously, this allows for uniform material distribution regardless of the position of the cavities on a suction tool without compromising cycle time.

[0011] The term "channels" also includes spaces through which suction can take place, so that this does not imply any restriction to specific geometries or extensions.

[0012] In further embodiments, a negative pressure can be generated in the cavities for suction, with the negative pressure for suction having at least two different states. This means that after reaching a definable state with regard to the clogging of the cavity surface or after a certain period of time, a switch can occur so that the different pressure states reduce the suction effect on the already clogged cavities, thus allowing only little / no further material to accumulate there, whereas the relatively free cavities have a sufficient suction effect.

[0013] In other designs, the intake capacity can be adjusted continuously or in stages. This allows for a very precise distribution, as the clogging is adjusted either continuously or in stages.

[0014] In other versions, the intake power can be adjusted automatically or manually. An automatic adjustment can be specified, for example, based on pre-determined intake times and pressures or based on measured information. A manual adjustment can be adjusted and / or modified, for example, by entering process or product information.

[0015] In further embodiments, the change in suction power can be controlled or regulated according to the geometry of the cavities, the position of the cavities on the suction tool, the suction duration, the pulp composition, properties and / or temperature, the weight of fibers already sucked in, the clogging of the cavities, etc. The arrangement of the cavities can be taken into account. For example, cavities can be arranged in a circle around a central cavity, resulting in a gradual change in suction power from the outside to the inside. The same applies, for example, to a suction tool with multiple cavities, where these form rectangular groups that, for example, surround an inner cavity core like a frame. The suction power can be changed for each group / frame depending on the distance from the center or the edge.

[0016] In further embodiments, at least one of the aforementioned conditions or properties can be monitored, and once certain limit values ​​are reached, a change in the intake capacity can be initiated via the control system. For this purpose, sensor units can be provided, which, for example, detect a change in the volume flow during a suction process when clogging occurs and initiate a change depending on the value.

[0017] The above-mentioned object is also achieved by a suction device for sucking fibers from a pulp with a suction tool which has a plurality of cavities for sucking fibers, wherein the cavities have a surface with a plurality of openings which are connected via channels to a common suction line, comprising a control device via which the suction power can be changed during a suction process.

[0018] The suction device allows for a uniform weight / material distribution across the individual cavities in a wet fiber process. This ensures consistent product quality for molded parts made of fiber-containing materials during a subsequent hot-pressing process. The drying time is determined based on the cavity with the highest material weight (filter cake; preform), ensuring that there are no differences in the results of hot-pressed / dried molded parts with the same material weight.

[0019] This results in a reduction in scrap and a reduction in cycle time because there are no (significant) material fluctuations in the filter cakes / preforms. When operating a fiber processing system with a suction device, the drying time is determined according to the cavity with the highest material weight. Smaller variations result in more consistent operation and significantly improved quality of the molded parts.

[0020] In further embodiments, the control device can have at least one valve designed to change the cross-section of the common intake line to alter the intake capacity. For example, in further embodiments, switching between pressure levels can be achieved both by throttling (pressure elimination) in a bypass, as well as with multiple base pressures or leakage air via a bypass.

[0021] For example, a bypass valve can be arranged in the common intake line, which can throttle the effective volume flow during intake via the adjustable cross-section.

[0022] In further embodiments, the suction device can have at least one sensor unit for monitoring at least the suction pressure in the channels and / or the suction line, the suction duration, the pulp composition, properties and / or temperature, the weight of fibers already sucked in, and the clogging of the cavities. The at least one sensor unit is connected to the control device, which is configured to change the suction power according to the feedback provided by the at least one sensor unit. Thus, the switching or change in the suction power can occur depending on the actual suction state, further improving the product quality of the molded parts to be produced.

[0023] Further features, embodiments and advantages emerge from the following presentation of embodiments with reference to the figures. Short description of the characters

[0024] In the drawings shows: Fig. 1 is a schematic representation of a fiber processing device; Fig. 2 is a schematic representation of a suction process with a suction device; and Fig. 3 is a schematic representation of the arrangement of cavities. Detailed description of implementation examples

[0025] The following figures illustrate exemplary embodiments of the technical teaching described herein with reference to the figures. The same reference numerals are used for identical components, parts, and processes in the description of the figures. Components, parts, and processes that are not essential to the technical teaching disclosed herein or that would be obvious to a person skilled in the art are not explicitly shown. Features stated in the singular are also included in the plural, unless explicitly stated otherwise. This applies in particular to statements such as "a" or "an."

[0026] Fig. 1shows a schematic representation of a fiber processing device 1000 for producing three-dimensional molded parts from a fiber-containing material. In the illustrated embodiment, the fiber-containing material for producing molded parts is processed in a pulp tank 200 of the fiber processing device 1000. For this purpose, water and fiber materials, as well as any additives, can be introduced into a pulp tank 200 via a liquid supply, and the pulp can be processed in the pulp tank 200 by mixing the individual components with heat input and aids such as a stirrer.

[0027] Pulp is an aqueous solution containing fibers. The fiber content of the aqueous solution can range from 0.1 to 10% by weight. It may also contain additives such as starch, chemical additives, wax, etc. The fibers can be natural fibers, such as cellulose fibers, or fibers from a fibrous source material (e.g., waste paper). A fiber processing plant offers the possibility of processing pulp in large quantities and making it available to several fiber processing facilities.

[0028] The fiber processing device 1000 can be used to produce, for example, biodegradable cups 3000, capsules, bowls, plates, and other shaped and / or packaging parts (e.g., as holder / support structures for electronic devices). Since the raw material for these products is a fibrous pulp with natural fibers, the products produced in this way can themselves be used as raw materials for the production of similar products after use or can be composted, as they are generally completely decomposable and do not contain any harmful, environmentally hazardous substances.

[0029] The Fig. 1The fiber processing device 1000 shown has a frame 100, which can be enclosed by a casing. The supply units 300 of the fiber processing device 1000 include, for example, interfaces for the supply of media (e.g., water, pulp, compressed air, gas, etc.) and energy (power supply), a central control unit 310, at least one suction device 320, line systems for the various media, pumps, valves, lines, sensors, measuring devices, a BUS system, etc., as well as interfaces for bidirectional communication via a wired and / or wireless data connection. Instead of a wired data connection, a data connection via a fiber optic cable can also exist. The data connection can exist, for example, between the control unit 310 and a central controller for several fiber processing devices 1000, to a fiber processing plant, to a service center, and / or other facilities.The fiber processing device 1000 can also be controlled via a bidirectional data connection using a mobile device, such as a smartphone, tablet computer or the like.

[0030] The control unit 310 is in bidirectional communication with an HMI panel 700 via a bus system or a data connection. The HMI (Human-Machine Interface) panel 700 has a display that shows operating data and states of the fiber processing device 1000 for selectable components or the entire fiber processing device 1000. The display can be designed as a touch display, so that settings can be made manually by an operator of the fiber processing device 1000. Additionally or alternatively, further input means, such as a keyboard, a joystick, a keypad, etc., can be provided on the HMI panel 700 for operator inputs. These can be used to change settings and influence the operation of the fiber processing device 1000.

[0031] The fiber processing device 1000 comprises a robot 500. The robot 500 is designed as a so-called 6-axis robot and is thus capable of picking up parts, rotating them, and moving them in all spatial directions within its operating radius. Instead of the robot 500 shown in the figures, other handling devices can also be provided that are designed to pick up and twist products or to rotate them and move them in various spatial directions. Furthermore, such a handling device can also be designed differently, whereby the arrangement of the corresponding stations of the fiber processing device 1000 can deviate from the illustrated embodiment.

[0032] A suction tool 520 is arranged on the robot 500. In the exemplary embodiment shown, the suction tool 520 has cavities designed as negatives of the three-dimensional molded parts to be formed, such as cups 3000, as suction cavities. The cavities can, for example, have a net-like surface to which fibers from the pulp adhere during suction. Behind the net-like surfaces, the cavities are connected to a suction device via channels in the suction tool 520. The suction device can, for example, be realized by a suction device 320. Pulp can be sucked in via the suction device if the suction tool 520 is located within the pulp basin 200 such that the cavities 522 are at least partially located in the aqueous fiber solution, the pulp. A vacuum orA negative pressure for sucking in fibers when the suction tool 520 is located in the pulp tank 200 and the pulp can be provided via the suction device 320. For this purpose, the fiber processing device 1000 has corresponding means in the supply units 300. The suction tool 520 has lines for providing the vacuum / negative pressure from the suction device 320 in the supply units 300 to the suction tool 520 and the openings in the cavities 522. Valves are arranged in the lines, which can be controlled via the control unit 310 and thus regulate the suction of the fibers. Instead of suction, the suction device 320 can also "blow out" the fibers, for which purpose the suction device 320 is switched to a different operating mode depending on its design.

[0033] During the production of molded parts from a fiber material, the suction tool 520 is immersed in the pulp and a negative pressure / vacuum is applied to the openings of the cavities 522 so that fibers are sucked out of the pulp and, for example, adhere to the network of cavities 522 of the suction tool 520.

[0034] The robot 500 then lifts the suction tool 520 from the pulp tank 200 and moves it, along with the fibers adhering to the cavities 522, which still have a relatively high moisture content of, for example, over 80% by weight of water, to the pre-press station 400 of the fiber processing device 1000, wherein the negative pressure in the cavities 522 is maintained for transfer. The pre-press station 400 has a pre-press tool with pre-press molds. The pre-press molds can, for example, be designed as positives of the molded parts to be produced and can have a size appropriate to the shape of the molded parts to accommodate the fibers adhering in the cavities 522.

[0035] During the production of molded parts, the suction tool 520, with the fibers adhering to the cavities, is moved to the pre-pressing station 400 so that the fibers are pressed into the cavities 522. The fibers are pressed together in the cavities, creating a stronger bond between the fibers. Furthermore, the moisture content of the preforms formed from the suction-adhered fibers is reduced, so that the preforms formed after pre-pressing only have a moisture content of, for example, 60% by weight. Flexible pre-pressing molds can be used to press out water. These molds are inflated, for example, using compressed air (process air), thereby pressing the fibers against the wall of a cavity of another suction tool part. This "inflating" both presses out water and reduces the thickness of the suction-adhered fiber layer.

[0036] During pre-pressing, liquid or pulp can be sucked out and returned via the suction tool 520 and / or through additional openings in pre-pressing molds or tool parts (cavities). The liquid or pulp emerging during suction via the suction tool 520 and / or during pre-pressing in the pre-pressing station 400 can be returned to the pulp basin 200.

[0037] After pre-pressing in the pre-press station 400, the preforms thus produced are moved on the suction tool 520 via the robot 500 to a hot-press station 600. For this purpose, the negative pressure is maintained on the suction tool 520 so that the preforms remain in the cavities 522. The preforms are transferred via the suction tool 520 to a lower tool body, which can be moved along the production line from the hot-pressing device 610. When the lower tool body is in its extended position, the suction tool 520 is moved to the lower tool body so that the preforms can be placed on the molding devices of the lower tool body. Subsequently, overpressure is generated via the openings in the suction tool 520 so that the preforms are actively deposited from the cavities 522, or the suction is stopped so that the preforms remain on the molding devices of the lower tool body due to gravity.By providing overpressure at the openings of the cavities 522, pre-pressed preforms that are in contact / adherent in the cavities 522 can be released and dispensed.

[0038] Thereafter, the suction tool 520 is moved away over the robot 500 and the suction tool 520 is immersed into the pulp tank 200 to suck in further fibers for producing molded parts from fibrous material.

[0039] After the preforms have been transferred, the lower tool body moves to the hot-pressing station 600. In the hot-pressing station 600, the preforms are pressed into finished molded parts under heat input and high pressure. For this purpose, an upper tool body is brought onto the lower tool body via a press. The upper tool body has cavities corresponding to the molding devices. After the hot-pressing process, the lower tool body and the upper tool body are moved away from one another relative to one another, and the upper tool body is moved along the fiber processing device 1000 in the production direction. After hot-pressing, the finished molded parts are sucked in via the upper tool body and thus remain within the cavities. The finished molded parts are thus removed from the hot-pressing station 600 and, after the process, deposited via the upper tool body onto a conveyor belt of a conveyor device 800.After the parts are deposited, the suction action via the upper mold body is terminated, and the molded parts remain on the conveyor belt. The upper mold body returns to the hot-pressing station 600, and another hot-pressing process can be performed.

[0040] The fiber processing device 1000 further comprises a conveyor device 800 with a conveyor belt. The finished molded parts made of fiber-containing material can be placed on the conveyor belt after final molding and hot pressing in the hot-pressing station 600 and removed from the fiber processing device 1000. In further embodiments, after the molded parts have been placed on the conveyor belt of the conveyor device 800, further processing can take place, such as filling and / or stacking the products. Stacking can be performed, for example, by an additional robot or another device.

[0041] The fiber processing device 1000 from Fig. 1shows a possible embodiment. A fiber processing device according to the technical teaching described herein can also have only one forming station with an exchangeable tool, for example a suction tool 520 or a hot-pressing tool, in which fiber-containing material can be processed, wherein various tools for producing different three-dimensional molded parts can be accommodated in the at least one forming station. The further for the fiber processing device 1000 of Fig. 1 The stations and devices shown are not absolutely necessary for the implementation of the technical teaching.

[0042] Fig. 2 shows a schematic representation of a suction process with a suction device 320. The suction device 320 has a suction tool 340 with a plurality of cavities 350. The arrangement of the cavities 350 on the underside of the suction tool 340 can, as in Fig. 3shown schematically for various tool designs. In further embodiments, cavities 350 can be round, oval, or polygonal instead of having a rectangular cross-section, as viewed toward the underside of the suction tool 340. In still further embodiments, cavities of suction tools 340 can be arranged in a circular or polygonal manner.

[0043] In the illustrated embodiments, the cavities 350 have a mesh-like structure on the inner suction surface. Channels extend from the mesh-like structure within the suction tool 340, which converge into a common suction line for all channels of the cavities 350. A negative pressure for sucking in fibers is applied via the common suction line when the suction tool 340 is located in the pulp 210 in such a way that the fibers can be sucked in via the inner surface of the cavities 350.

[0044] The suction line is connected to a control device 360, which in the embodiment shown has a throttle valve. The cross-section of the suction line can be changed via the throttle valve, so that in the schematically shown example two different pressure states P1 and P2 can be established for sucking in fibers from the pulp 210. For suction, a negative pressure is provided via the shared suction line and the control device, which, for example, in an initial state, i.e. at the start of the suction process, can be P1 = 0.3 to 0.6 bar absolute pressure. After a definable time interval, when the outer cavities 350 are relatively heavily clogged, i.e. when a relatively large amount of fibers has already settled on the cavity surface, the throttle valve is actuated via the control device 360, so that the cross-section of the suction line is changed.This changes the intake pressure, which in the exemplary embodiment is P2. The intake vacuum P2 can, for example, be between 0.7 and 0.9 bar absolute pressure. In still other embodiments, the pressure can be changed gradually or continuously, for example by changing the free cross-section in the intake line. In addition to a time specification for switching between the pressure states P1 and P2, the intake vacuum can be determined according to the information from at least one sensor unit, which, for example, detects the volume or mass flow in the intake line and passes it on to the control device 360. As soon as the volume or mass flow exceeds at least one limit value, a switch to at least one different pressure level of the intake pressure can take place or the intake vacuum can be continuously changed.

[0045] In yet further embodiments, a change in the suction pressure can additionally or alternatively be achieved by displacing the suction tool 320 relative to the pulp surface in the pulp tank 200. It is essential that the cavities 350 lie in one plane and that the suction tool 320 with the cavities 350 is displaced parallel to the surface so that the resulting changed pressure situation has the same effect for all cavities 350. This also applies to suction in the pulp tank 200 in general, whereby a suction pressure can only have a uniform effect if the pressure situation in the cavities 350 is the same (i.e., for example, no inclined immersion of the suction tool 320, etc.).

[0046] The pressure change by a displacement of the suction tool 320 during the suction process can, for example, take place continuously or in stages, wherein at least two stages can be provided.

[0047] The pulp 210 can, in the embodiment shown, be present, for example, as an aqueous fiber mixture in concentrations of 0.2%-1.5% by weight of fibers in a pulp tank 200, from which the suction tool 320 sucks in the required amount of pulp 210 or fibers, as in Fig. 2 shown schematically by the arrows. The resulting intake volume flow depends essentially on the shape and arrangement of the cavities 350 of the intake tool 320.

[0048] After the suction process begins, the outer cavities 350 become clogged first. This is due, on the one hand, to the fact that more fiber material can be supplied across the entire lower surface of the suction tool 320 in the outer area. The amount of sucked-in fiber material is lower in the inner cavities 350 because additional cavities 350, which also suck in fiber material, are arranged in the immediate vicinity. As soon as the outer cavities 350 have sucked in a sufficient amount of fiber, if the initial suction negative pressure is maintained, the inner cavities 350 would suddenly suck in more fiber material, so that they would ultimately contain the most material. Therefore, after a pre-determined period of time or, as stated above, by measuring parameters, at least a switch is carried out so that the suction negative pressure is reduced. This ensures that the inner cavities 350 do not become excessively clogged.As a result, a uniform clogging of all cavities 350 is achieved.

[0049] In Fig. 3 The undersides of suction tools 320 with multiple cavities 350 are shown. In the upper example, the suction tool 320 has two inner cavities 350 and ten outer cavities 350. The dashed line surrounds the inner cavities 350 and highlights the two different cavity groups. With regard to the process and switching described above, two different suction pressures (see P1 and P2) are sufficient.

[0050] In the example below from Fig. 3The underside of a suction tool 320 is shown, which has three groups I, II, III of cavities 350. For this suction tool 320, for example, a step-by-step switching can take place for each of the groups I, II, III. The switching can, as explained above, be time-dependent or after exceeding or falling below limit values, which are compared with parameters that are recorded by at least one sensor unit and transmitted to the control device 360. The control direction 360 can, as a result of the transmitted information or by a specification, change, for example, the opening cross-section of a common suction line via a valve or another device. In the example of Fig. 3For example, the cavities 350 of the first group are first clogged. For this purpose, the initial suction negative pressure is changed after a first time interval. Subsequently, the clogging of the second group of cavities 350 increases, so that after a second time interval, the changed suction negative pressure is changed again, whereby finally the cavities 350 of the third group in the center of the suction tool 320 become clogged and the sucked-in fiber material in the cavities 350 has the final weight or quantity of fibers.

[0051] By adjusting the suction power (e.g., suction vacuum) of a suction tool 320 described herein, as well as by designing a suction tool 320, a significant improvement in suction can be achieved in a fiber molding process (wet fiber process). All cavities 320 of a multi-cavity suction tool 320, which has at least one inner and one outer suction cavity 350, exhibit a uniform fiber distribution, so that the suctioned filter cakes and ultimately preforms and final molded parts do not exhibit any significant weight or material differences. This particularly benefits downstream manufacturing processes, such as hot pressing in a hot pressing station 600, because the introduced thermal energy leads to uniform heating of all preforms, since they do not have different weights and therefore also do not have different water quantities. List of reference symbols

[0052] 100Frame 200Pulp basin 210Pulp 300Supply units 310Control unit 320Suction device 340Suction tool 350Cavity 360Control device 400Pre-press station 500Robot 520Suction tool 600Hot-press station 610Hot-press device 700HMI panel 800Conveyor device 810Camera 1000Fiber processing device 3000Cup

Claims

1. A method for sucking fibers from a pulp using a suction device with a suction tool having a plurality of cavities, the cavities having a surface with a plurality of openings connected via channels to a common suction line, the suction power being varied during a suction process.

2. The method according to claim 1, wherein a negative pressure is generated in the cavities for suction and the negative pressure for suction has at least two different states.

3. Method according to claim 1 or 2, wherein the suction power is changed continuously or stepwise.

4. Method according to one of claims 1 to 3, wherein the change in the intake power is changed automatically or manually.

5. Method according to one of claims 1 to 4, wherein the change in the suction power is controlled or regulated in accordance with the geometry of the cavities, the position of the cavities on the suction tool, the suction duration, the pulp composition, properties and / or temperature, the weight of fibers already sucked in, the clogging of the cavities, etc.

6. Method according to claim 5, wherein at least one of the conditions or properties mentioned in claim 5 is monitored and, after limit values ​​are reached, a change in the intake power is initiated via the control device.

7. Suction device for sucking fibers from a pulp with a suction tool which has a plurality of cavities for sucking fibers, wherein the cavities have a surface with a plurality of openings which are connected via channels to a common suction line, comprising a control device via which the suction power can be changed during a suction process.

8. Intake device according to claim 7, wherein the control device has at least one valve which is designed to change the cross section of the common intake line in order to change the intake power.

9. Suction device according to claim 7 or 8, comprising at least one sensor unit for monitoring at least the suction pressure in the channels and / or the suction line, the suction duration, the pulp composition, properties and / or temperature, the weight of fibers already sucked in, the clogging of the cavities, wherein the at least one sensor unit is connected to the control device which is designed to carry out a change in the suction power in accordance with the feedback provided by the at least one sensor unit.

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