Device for dewatering or cleaning fabric in paper machine and paper machine comprising such device

Abstract

The invention relates to a device for dewatering or cleaning a fabric in a paper machine, the device (1) comprising:-a contact portion (2) arranged on a first side (A) of the device (1) for contacting the fabric in the paper machine,-an air device (4) for conveying air to or from the fabric, -an air device (2) operably connected to at least one opening (3) in the first side for supplying or removing air through the at least one opening, and-a vibration generator (5) operably connected to the contact portion and configured to vibrate the contact portion during operation of the device. The invention also relates to a paper machine (100, 100 ') comprising at least one such device.

Description

Technical Field

[0001] The present invention relates to an apparatus for dewatering or cleaning fabric in a papermaking machine, and to a papermaking machine comprising such an apparatus. In particular, the papermaking machine may be a machine for making tissue paper. Background Art

[0002] A papermaking machine typically operates by injecting stock into a forming gap in a forming section to produce a paper web that moves through various sections to be formed, dewatered, dried, and optionally structured to form the finished paper. The paper web is conveyed over a series of wires or fabrics (e.g., felts) that are arranged in an endless loop for forming and protecting the paper web and optionally also for creating structure in the paper web.

[0003] Since the moisture content of the raw material is usually around 97%, removing water is a major goal when making paper, and this is achieved by a combination of pressing, suction and heating. In certain parts of the paper machine, water or air is conveyed through a wire or felt in order to absorb water from the paper web or to allow airflow or hot air to reach the paper web. After the paper web has been transferred to other parts in the paper machine, some pulp fibers from the paper web will be trapped in the felt or wire, or remain on the surface, and for this purpose, washing equipment is provided for washing and drying the felt or wire during its return to the point where it picks up the paper web again.

[0004] Existing cleaning equipment for wires or felts has some problems, such as high energy consumption for removing water to make the wires or felts dry enough to receive the paper web. In addition, it is difficult to thoroughly clean the wires or felts to remove all residual pulp fibers in a short time before the paper web is received again.

[0005] Dewatering and drying of paper webs is also cumbersome, and due to the high cost and energy consumption of heating steam and air, it is very desirable to remove as much water as possible prior to the drying stage involving hot air or heated rolls.

[0006] Therefore, improvements are needed in both cleaning wires or felts and dewatering paper webs. Summary of the invention

[0007] The object of the present invention is to eliminate or at least minimize the above mentioned problems. This is achieved by an apparatus for dewatering or cleaning fabrics in a paper making machine and by a paper making machine comprising such an apparatus according to the attached independent claims.

[0008] The apparatus of the present invention comprises: a contact portion, which is arranged on a first side of the apparatus and is used to contact a fabric in a papermaking machine; an air device, which is used to convey air to or from the fabric, and the air device is operably connected to at least one opening in the first side and is used to supply or remove air through the at least one opening; and a vibration generator, which is operably connected to the contact portion and is configured to cause vibration of the contact portion during operation of the apparatus.

[0009] By causing vibrations in the contacting parts, washing or dewatering becomes more efficient because water and any remaining pulp fibers are loosened from the fabric and can be more easily removed by air equipment providing compressed air (pressurized air) or vacuum. The efficiency of washing the fabric is significantly improved because a more thorough cleaning and removal of residual pulp fibers can be achieved. At the same time, when the device is used to dewater a fabric carrying a paper web, dewatering is significantly improved, which can significantly save costs and energy consumption. This is both because less dewatering equipment can be used to achieve a higher dryness of the paper web, and because the residual moisture content that must be removed by hot air or steam is reduced.

[0010] Suitably, at least one opening is arranged in the downstream end of the first side and the contact portion is arranged in the upstream end of the first side.Thus, after vibrating the fabric, suction or blowing of air is immediately performed to immediately remove water and optionally paper fibers loosened by the vibration.

[0011] Alternatively, at least one opening is arranged in the upstream end and the contact portion is arranged in the downstream end of the first side. Thus, the suction or blowing affects the fabric immediately before it starts to vibrate, which is very efficient in removing water and optionally pulp fibers, because the vibration of the fabric will propagate from the contact point with the contact portion, causing the water and optionally pulp fibers to be loosened.

[0012] In another alternative, at least one opening is arranged in the contact portion so that air is supplied to or removed from the fabric through the contact portion. Thus, suction or blowing takes place where the vibrations are transmitted to the fabric and this is very efficient in removing water and optionally residues adhering or trapped in the fabric.

[0013] In some embodiments, only one opening is provided in the device, but in other embodiments, multiple openings are provided, and multiple openings can be placed upstream and / or downstream of the contact portion and in the contact portion itself. It is very advantageous to provide one or more openings near the contact portion so that the removal of water and optional residues occurs where the vibration amplitude is large.

[0014] In some embodiments for dewatering or washing, the air device is a suction device for drawing air from the fabric into the opening. This is also advantageous when the fabric carries a paper web, as it provides efficient suction combined with vibration without damaging the paper web. This helps to increase the amount of water removed compared to conventional suction devices, such as an Uhle box.

[0015] In other embodiments for cleaning fabrics, the air device is an air knife for blowing air from an opening onto the fabric. This is advantageous for thoroughly cleaning the fabrics, as any remaining residue is blown away along with the water, and the combination of the air knife and vibration provides a significant improvement over known air knives.

[0016] Suitably, the vibration generator is configured to operate at a frequency of at least 10 kHz, preferably at least 15 kHz, more preferably at least 20 kHz.Thereby, the contact portion vibrates at a suitable frequency that is easily transferred to the fabric.

[0017] The vibration generator may be configured to cause an amplitude of at least 10 μm, preferably at least 15 μm, more preferably at least 20 μm of the contact portion during operation of the device. In some embodiments, the amplitude may be up to 50 μm. Thus, the fabric vibrates, thereby efficiently removing water. A larger amplitude is advantageous because it improves the removal of water from the fabric.

[0018] The device may also include at least two contact portions, and the vibration generator may be operably connected to each of the contact portions and configured to vibrate the contact portions independently of each other. This is advantageous in providing a more durable device with a longer life because vibration of one contact portion can occur even if vibration of another contact portion fails or is damaged. In addition, the frequency and / or amplitude of the contact portions can be varied to increase the efficiency of removing water from the fabric. An additional benefit is that multiple contact portions and multiple openings are more efficient in removing water than a single contact portion with a single opening.

[0019] In some embodiments, the contact portion is a cylinder, preferably a TAD cylinder for a paper machine, and a plurality of openings are distributed in the contact portion for enabling air to be transported through the contact portion. Thus, the benefits of the present invention are achieved by vibrating the surface of the TAD cylinder.

[0020] The invention also relates to a papermaking machine comprising an apparatus as described above. This enables more efficient removal of water from the fabric in an energy-efficient and cost-effective manner than known prior art solutions. The papermaking machine of the invention comprises at least one apparatus according to the invention, but may optionally comprise a plurality of apparatuses for dewatering or washing or both dewatering and washing.

[0021] Suitably, at least one device is arranged in a forming section of the paper machine and is configured to dewater a first fabric carrying the paper web. Thus, dewatering in the forming section is improved, resulting in a reduced moisture content, when the paper web is transferred to a subsequent section.

[0022] At least one device can be arranged in the press section of the paper machine and is configured to dewater the second fabric carrying the paper web. Thus, dewatering in the press section is improved, so that subsequent washing and optional drying are improved.

[0023] Suitably, at least one device is arranged in the structured section of the paper machine and is configured to dewater the third fabric carrying the paper web.Thereby, dewatering in the structured section is improved, thereby reducing the water content before the final drying stage.

[0024] In some embodiments, the structuring section is a through air drying section TAD. Thus, the combined structuring and drying can be improved to reduce the need for hot air.

[0025] Suitably, at least one device is arranged in a drying section of the paper machine and is configured to dewater the fabric carrying the paper web.Thereby, the removal of residual moisture in the paper web is more efficient, thereby reducing the consumption of steam or hot air.

[0026] At least one device is suitably arranged in a washing section for washing fabrics.Thereby, the washing of fabrics is improved compared to washing sections of the prior art.

[0027] Numerous other benefits and advantages of the present invention will be readily apparent to those skilled in the art in view of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 Schematically disclosed is a device according to the invention; Figure 2a A top perspective view of an apparatus according to a first embodiment is disclosed; and Figure 2b Public Figure 2a A bottom perspective view of the device; Figure 3a discloses a side perspective view of an apparatus according to a second embodiment; Figure 3b The side view is revealed Figure 3a The floor plan of the equipment; Figure 3c Public Figure 3b An enlarged cross-sectional view of an upper portion of a device; Figure 4 Schematically discloses a papermaking machine according to a first embodiment of the present invention; and Figure 5 A papermaking machine according to a second embodiment of the present invention is schematically disclosed.

[0029] All the figures are schematic, not necessarily drawn to scale, and generally show only parts necessary for the elucidation of the various embodiments, while other parts may be omitted or merely suggested. Unless otherwise indicated, any reference numeral appearing in several figures refers to the same object or feature in all figures. DETAILED DESCRIPTION

[0030] In the context of the present invention, the term "fabric" is used to refer to any wire, band, structured fabric or belt used in a paper machine to form or carry a paper web. Such bands or belts include wires, such as forming wires and structured wires, and also include felts and other textiles used in paper machines.

[0031] As used herein, a paper machine refers to any machine suitable for producing paper from pulp. Such machines include, but are not limited to, machines for producing tissue, paper and paperboard.

[0032] When two components are operably connected to each other, it is understood that the components are connected to each other in a manner that a signal, motion or force can be transmitted from one component to another. Thus, a vibration generator operably connected to a contact portion is understood to mean that the vibration generator is capable of causing the contact portion to vibrate.

[0033] As used herein, the terms "upstream" and "downstream" are related to the direction of movement of a fabric or paper web in a paper machine. Thus, a position upstream of another position is a position that any given point on the fabric or paper web passes before reaching the other position. The terms "before" and "after" are used to indicate that any given point on the fabric or paper web passes a position "before" another at an earlier point in time than it passes a position "after".

[0034] A paper web is defined as pulp fibers traveling together on a fabric to form a continuous paper web from the forming nip, where the paper web is formed from a pulp suspension, to the curling section, where the paper web arrives as finished paper. "Entrapped residue" or simply "residue" is used to refer to the material or particles that remain in or on the fabric after the paper web has been transferred to the subsequent section of the paper machine. Such materials or particles include adhesives, coatings, dust, pulp fibers, etc.

[0035] The present invention will now be described. Figure 1 An embodiment of the device schematically shown in FIG. 1 is then Figure 2a-2bThe preferred embodiment shown in FIG. Then, the papermaking machine according to the present invention will be described with reference to two embodiments, which show different ways of producing paper (especially household paper). It should be noted that the present invention can be used for any kind of papermaking machine.

[0036] Figure 1 An apparatus 1 for dewatering or cleaning a fabric according to the invention is disclosed. The apparatus 1 comprises a contact portion 2 arranged on a first side A of the apparatus 1, and the first side A is the side in a paper machine intended to face a fabric F. The fabric F is schematically disclosed in Figure 2, the travel direction D of the fabric F being indicated by an arrow pointing to the left hand side of the figure.

[0037] The contact portion 2 is operably connected to a vibration generator 5, which is configured to cause vibration of the contact portion 2 when the device 1 is in use. The vibration generator 5 is shown as being connected to the contact portion 2 via a connector 5', but in some embodiments, the vibration generator 5 can be integrated with the contact portion 2, or arranged to contact the contact portion 2 without the connector 5'. The vibration generator 5 is suitably connected to a power source (not shown). The device 1 also suitably includes a housing 6, in which at least some components of the device 1 are arranged.

[0038] The contact portion 2 may extend along the entire length l of the device 1 on the first side A of the device 1, but in other embodiments may include only a portion of the length l. Furthermore, in some embodiments, the contact portion 2 extends across the entire width w of the device 1, but in other embodiments may include only a portion of the width w. The length l is defined as the extension of the device 1 on the first side A in the direction of travel of the fabric F, while the width w is the extension of the device 1 on the first side A in a direction perpendicular to the length l. Figure 1 The length l of the device 1 is disclosed, and Figure 2a Both the length l and the width w are shown.

[0039] In some embodiments, the contact portion 2 is a single part of the device 1 , but in other embodiments, the device 1 may include a plurality of contact portions 2 that are individually or collectively connected to the vibration generator 5 .

[0040] The device 1 further comprises an air device 4 for conveying air to or from the fabric F, and further comprises at least one opening 3 in the first side A for supplying or removing air. The at least one opening 3 can be an opening in the contact portion 2, an opening upstream of the contact portion 2, an opening downstream of the contact portion 2, or a combination of these options. In some embodiments, there can also be at least one opening 3 parallel to the contact portion 2, i.e. beside the contact portion 2 in a direction transverse to the travel direction D of the fabric F. In most embodiments, a plurality of openings 3 are arranged in the first side A, but it should be noted that a single opening 3 can also be within the scope of the invention.

[0041] When the at least one opening 3 is arranged upstream US of the contact portion 2 , then the contact portion 2 is downstream DS of the at least one opening 3 , and vice versa.

[0042] The first side A of the device 1 may include both the housing 6 and the contact portion 2, and at least one opening 3 is an opening extending into the first side A of the device 1 through the housing 6 or through the contact portion 2. In the case where a plurality of openings 3 are provided, these openings may be openings 3 in the housing 6, openings 3 in the contact portion 2, or openings 3 in both.

[0043] In some embodiments (see Figure 2a-2b ), the first side A of the device may include only the contact portion 2, and at least one opening 3 is an opening extending into the first side A in the device 1 through the contact portion 2.

[0044] The air device 4 is connected to at least one opening 3 via an air connection 4', which is suitably a pipe or duct, so that air can pass between the air device 4 and the opening 3. The device 1 also comprises a delivery connection 4", which may suitably be a pipe or duct for delivering air between the air device 4 and a separate unit (not shown).

[0045] In some embodiments, the air device 4 is a suction device, such as a suction box or the like, which operates by generating a negative pressure (commonly referred to as a vacuum) to draw air into the opening 3 of the air device 4. In such an embodiment, the delivery connection 4" may lead to a receiving container for receiving air as well as water, residues and optionally other matter (such as dust or particles from the fabric F). The air device 4 suitably generates a negative pressure of at least 10 kPa, more suitably at least 30 kPa, or even more suitably at least 65 kPa.

[0046] In other embodiments, the air device 4 is instead an air knife, which operates by blowing compressed air through at least one opening 3. In such embodiments, the delivery connection 4" may lead to a compressed air source. The compressed air is suitably supplied at a pressure of at least 0.5 bar, more suitably at least 5 bar, even more suitably at least 10 bar. Higher pressures are advantageous for improving the removal of water and optional residues from the fabric.

[0047] The vibration generator 5 is configured to vibrate the contact portion 2, thereby generating vibrations in the fabric F when the fabric F passes through the device 1 during operation. In some embodiments of the paper machine, the device 1 is configured to contact the fabric F, but in other embodiments, the device 1 can be arranged close to the fabric F instead, so that the vibration of the contact portion 2 makes it contact with the fabric F, or alternatively, the vibration of the contact portion 2 close to the fabric F also causes the fabric F to vibrate. Suitably, the vibration generator 5 is configured to operate the contact portion 2 at a frequency of at least 10kHz, preferably at least 15kHz, and more preferably at least 20kHz. Higher frequencies cause the fabric F to vibrate more strongly, thereby helping to release trapped water and residues. In some embodiments, the vibration generator 5 is configured to cause an amplitude of at least 10μm, preferably at least 15μm, and more preferably at least 20μm. In some embodiments, the amplitude can be 50μm or more. In embodiments with both low and high frequencies, a larger amplitude is advantageous because it further increases the release of water and residues from the fabric F.

[0048] Figure 2a-2b A first embodiment of a device 1 having a plurality of openings 3 distributed along a contact portion 2 is disclosed. The device 1 is held by a holder 7 which also involves connections such as a delivery connection 4" and a power supply. The provision of a plurality of openings 3 facilitates the generation of a uniform air suction or blowing, thereby washing or dehydrating the entire width of the fabric F. Furthermore, the provision of the contact portion 2 over the entire width of the fabric F facilitates the generation of vibrations of the entire fabric F to release trapped water and residues. Figure 2a-2b The preferred embodiment of the invention is applicable both when the air device is a suction device and when the air device is configured to supply compressed air to the opening 3. The device 1 further comprises a housing 6.

[0049] Figure 3a-3cA second embodiment of the device 1 is disclosed, which has two contact parts 2a, 2b and a plurality of transducers 5 used as vibration generators 5. In the second embodiment, a first row of transducers 5a is arranged in a cross-machine direction (i.e., a direction perpendicular to the travel direction D of the fabric F) and is connected to the first contact part 2a; a second row of transducers 5b is arranged in a cross-machine direction and is connected to the second contact part 2b. In this way, each row of transducers 5a, 5b is configured to vibrate one of the contact parts 2a, 2b. The device 1 is connected to an air device 4 (not shown), which provides suction or compressed air to the opening 3. In Figure 3a-3c In the embodiment, air is delivered to or from the opening 3 inside the housing 6, so that the interior of the housing 6 is at a negative pressure so that the device 1 can be sucked in through the opening 3, or at a high pressure so that the air can be blown out of the device 1 through the opening 3.

[0050] The contact portions 2 a , 2 b suitably comprise metal sheets susceptible to being vibrated by the transducer 5 .

[0051] By operatively connecting a vibration generator 5 to each contact portion 2a, 2b, the contact portions 2a, 2b can vibrate independently of each other. Figure 3a-3c The vibrations of the two contact parts 2a, 2b are caused by individual transducers of each contact part 2a, 2b as shown, or alternatively can be caused by a single vibration generator 5, which is operatively connected to the two contact parts 2a, 2b in a manner that enables individual vibrations of the two contact parts 2a, 2b. The vibration generator 5 can be in the form of a sonotrode or a flat ultrasonic transducer (e.g. an ultrasonic plate).

[0052] In some embodiments, the contact portions 2a, 2b are configured in this way to vibrate at different frequencies and / or different amplitudes, but in other embodiments, the contact portions 2a, 2b may alternatively be configured to vibrate at the same frequency and / or amplitude.

[0053] In some embodiments, the contact portions 2a, 2b are instead connected to the vibration generator 5 in such a way that they vibrate together.

[0054] In a third embodiment, the contact portion 2 is in the form of a cylinder or a part of a cylinder, the first side A being the outside of the cylinder. In this embodiment, the at least one opening 3 is a plurality of openings 3 distributed in the contact portion, enabling air to be conveyed through the contact portion 2, i.e. from the inside of the cylinder to the outside (blowing) or from the outside of the cylinder to the inside (suction). Suitably, the apparatus 1 in this embodiment forms a TAD (Through Air Drying) cylinder configured to improve the drying of the paper web by a combination of vibrations of the contact portion 2 and airflow through the plurality of openings 3.

[0055] For all embodiments disclosed herein, the air device 4 is disclosed as a suction device, and the device 1 can be modified to have the air device 4 as an air knife instead. Similarly, where an embodiment is described with an air knife, this can be changed to a suction device without substantial modification of the device 1. In some embodiments, the air device 4 can also have dual functionality and be configured to switch between a suction function and a blowing function.

[0056] Now refer to Figure 4 and Figure 5 A papermaking machine 100, 100' according to the present invention is described. It should be noted in particular that the present invention includes any kind of papermaking machine, as long as at least one device 1 according to the present invention is installed therein. However, the present invention is particularly advantageous in papermaking machines for making tissue paper, because the cleaning and dewatering of structured fabrics used in tissue papermaking machines are particularly difficult.

[0057] Figure 4 A paper machine 100 having a through air drying (TAD) design according to a first embodiment of the present invention is disclosed. The paper machine 100 comprises at least one but preferably a plurality of devices 1 according to the present invention in any or all of the press section 20, the structuring section 30 and the cleaning section 60. In other embodiments, at least one device 1 may also be included in any other section of the paper machine 100 where appropriate.

[0058] The paper machine 100 comprises a forming section 10 where a stock comprising a diluted stock is injected into a forming nip between a first fabric 71, which may be referred to as a forming fabric, and a second fabric 72, which may be referred to as an inner wire. This results in the production of a paper web P which is conveyed on the second fabric 72 through a press section 20 for pressing and dewatering. The paper web P is then transferred to a third fabric 73, which may be referred to as a structured fabric, and is conveyed through a structured section 30 for structuring and drying on at least one, but suitably two, dryer rolls 31, 32. Thereafter, the paper web P is transferred to a drying section 40, which suitably comprises a Yankee dryer, for removing residual moisture, and from which the finished paper is transferred to a curling section 50 for curling. Such operation of a through air dryer TAD is well known in the art.

[0059] The first, second and third fabrics 71, 72, 73 all form an endless loop and are configured to travel in the machine direction M when carrying the paper web P and return in the opposite direction when the paper web P has been transferred to the subsequent section. During the return, each of the fabrics 71, 72, 73 is cleaned. For the third fabric 73, a cleaning section 60 is provided to allow thorough cleaning and drying.

[0060] In the press section 20, at least one device 1 may be arranged to dewater the second fabric 72 and thereby the paper web P by combining the vibration of the contact portion 2 with the negative pressure from the air device 4 as a suction device. This has the advantage of making the paper web P adhere more firmly to the second fabric 72 and dewatering the second fabric 72 and thereby the paper web P efficiently.

[0061] In the structuring section 30, at least one device 1 may be arranged to dewater the third fabric 73 before, between or after the dryer rollers 31, 32. Similar to the use of the device 1 in the press section 20, the air device 4 is configured to act as a suction device by providing negative pressure to dewater the third fabric 73. This has the same advantages as when used in the press section 20, by combining efficient dewatering and improved adhesion to the third fabric 73.

[0062] In the washing section 60, at least one device 1 may be arranged in a washing station (not shown) in which the third fabric 73 is washed by supplying a washing fluid such as water and is dried by dehydration.

[0063] In the prior art, cleaning is usually performed by spraying cleaning liquid onto the fabric under high pressure and sucking the liquid from the fabric or blowing the liquid off the fabric by using at least one suction box or air knife.

[0064] In the papermaking machine 100 of the invention, at least one such suction box or air knife can be replaced by the apparatus 1 according to the invention. It is advantageous to provide the apparatus 1 with an air device 5 used as a suction device when cleaning the third fabric 73, because this improves the efficiency of removing fluid compared to a conventional suction box. However, it is also advantageous to provide the apparatus 1 with an air device 5 configured to blow compressed air toward the third fabric 73, because this removes fluid efficiently and the third fabric 73 does not carry the paper web P when in the cleaning section 60.

[0065] It is particularly advantageous to combine at least one device 1 used as a suction device in the washing section 60 with at least one device 1 used as an air knife to supply compressed air to the third fabric 73, because this provides both thorough washing and drying of the third fabric 73. The device 1 of the present invention can be provided before the third fabric 73 enters the washing station 61, inside the washing station 61, or after entering the washing station 61, or any combination thereof.

[0066] In the forming section 10, at least one device 1 according to the invention may be arranged to dewater or clean the first fabric 71 during its return to the forming nip FN. The device 1 may be configured as a suction device or a blowing device, and in case a plurality of devices 1 are provided, the plurality of devices 1 may be configured in the same way or in different ways.

[0067] The drying section 40 may also optionally comprise an apparatus 1 according to the invention, which is arranged before the drying on the Yankee dryer 41 .

[0068] Among the many possible arrangements of the apparatus 1 according to the invention, it may be particularly advantageous to provide the apparatus 1 in conjunction with the first roll downstream of the forming nip FN. It is also particularly advantageous to provide the apparatus 1 in connection with the rolls transferring the paper web to the third fabric 73, or downstream of these rolls but upstream of the TAD cylinder.

[0069] Figure 5 A papermaking machine 100' according to a second embodiment of the present invention is disclosed. The papermaking machine 100' is a DCT (dry crepe tissue) papermaking machine, comprising a crescent former suitable for producing household paper, and Figure 5 The paper machine 100' of the second embodiment differs from the paper machine 100 of the first embodiment mainly in that it does not include the structured section 30. Sections and components of the paper machine 100' of the second embodiment that are similar or identical to those of the paper machine 100 of the first embodiment are denoted by the same reference numerals with a '.

[0070] Thus, the paper machine 100' of the second embodiment comprises a forming section 10' where the stock is injected into the forming nip FN' and formed between a first fabric 71' (which may be referred to as a forming fabric) and a second fabric 72' (which may be referred to as a felt) to form a paper web P'. In the press section 20', the paper web P' is carried on the second fabric 72' and is pressed and dewatered before reaching the drying section 40'; at the drying section 40', the paper web P' is transferred to a Yankee dryer 41' to remove residual moisture before being transferred to a curling section 50' for curling. As in the first embodiment, the first fabric 71' and the second fabric 72' are washed during their return, and for the second fabric 72', a washing section 60' is provided with a washing station 61'.

[0071] The apparatus 1 of the present invention can be arranged in any of the forming section 10', the pressing section 20' and the cleaning section 60'. For an arrangement in which the drying section 40' includes components before the Yankee dryer 41', at least one apparatus 1 can also be arranged in the drying section 40'.

[0072] For the first embodiment, the device 1 is suitably used for dewatering a paper web P', wherein the paper web P' is carried by the second fabric 72' and the air device 5 is configured as a suction device in order to protect the paper web P' and improve adhesion to the second fabric 72'.

[0073] In the case where the device 1 is arranged in connection with the first fabric 71' or in connection with the second fabric 72' at the washing station 60', or in the case where the second fabric 72' does not carry the paper web P', the air device 5 is appropriately configured as a suction device similar to a suction box, or as a blowing device similar to an air knife. The combination of vibration and suction is very advantageous in the washing and dehydration of the first fabric 71' or the second fabric 72', and the combination of vibration and blowing compressed air is very advantageous in the washing and drying of the first fabric 71' or the second fabric 72'.

[0074] The apparatus 1 of the present invention can be installed in a paper machine 100, 100' during its manufacture, but can also be used to modify an existing paper machine to form a paper machine 100, 100' of the present invention by adding at least one apparatus 1 according to any embodiment of the present invention disclosed herein.

[0075] It is to be noted that features from the various embodiments described herein may be combined freely, unless it is explicitly stated that such a combination is inappropriate.

Claims

1. An apparatus for dewatering or cleaning fabric in a papermaking machine, the apparatus (1) comprising: a contact portion (2) arranged on a first side (A) of the device (1) for contacting a fabric in a paper machine, - an air device (4) for conveying air to or from the fabric, the air device (4) being operatively connectable to at least one opening (3) in the first side (A) for supplying or removing air through the at least one opening (3), and - a vibration generator (5) operatively connected to the contact portion (2) and configured to cause the contact portion (2) to vibrate during operation of the device (1).

2. Device according to claim 1, wherein the at least one opening (3) is arranged in the downstream end (DS) of the first side (A), and the contact portion (2) is arranged in the upstream end (US) of the first side (A).

3. Device according to claim 1, wherein the at least one opening (3) is arranged in an upstream end (US) and the contact portion (2) is arranged in a downstream end (DS) of the first side (A).

4. Apparatus according to claim 1, wherein the at least one opening (3) is arranged in the contact portion (2) such that air is supplied to or removed from the fabric through the contact portion (2).

5. Device according to any of the preceding claims, wherein the air device (4) is a suction device for sucking air from the fabric into the opening.

6. The device according to any one of claims 1 to 4, wherein the air device is an air knife for blowing air from the opening toward the fabric.

7. The device according to any of the preceding claims, wherein the vibration generator (5) is configured to operate at a frequency of at least 10 kHz, preferably at least 15 kHz, and more preferably at least 20 kHz.

8. The device according to any of the preceding claims, wherein the vibration generator (5) is configured to cause the contact portion to vibrate with an amplitude of at least 10 μm, preferably at least 15 μm and more preferably at least 20 μm during operation of the device.

9. The device according to any one of the preceding claims, further comprising at least two contact portions (2a, 2b), and wherein the vibration generator (5) is operably connected to each of the contact portions (2a, 2b) and is configured to vibrate the at least two contact portions (2a, 2b) independently of each other.

10. An apparatus according to claim 4 or according to any one of claims 5-8 when dependent on claim 4, wherein the contact part (2) is a cylinder, preferably a TAD cylinder for a papermaking machine, and wherein a plurality of openings (3) are distributed in the contact part (2) for enabling air to be transported through the contact part (2).

11. A papermaking machine comprising at least one device (1) according to any one of claims 1-10.

12. The papermaking machine according to claim 11, wherein the at least one device (1) is arranged in a forming section (10, 10') of the papermaking machine (100, 100') and is configured to dewater a first fabric (71, 71') carrying a paper web.

13. The papermaking machine according to claim 9 or 10, wherein the at least one device (1) is arranged in a press section (20, 20') of the papermaking machine (100, 100') and is configured to dewater a second fabric (72, 72') carrying a paper web.

14. The papermaking machine according to any one of claims 11 to 13, wherein the at least one device (1) is arranged in a structured section (30) of the papermaking machine (100, 100') and is configured to dewater a third fabric (73) carrying a paper web, and wherein the structured section (30) is preferably an air-through drying section TAD.

15. The papermaking machine according to any of claims 11-14, wherein the at least one device (1) is arranged in a drying section (40, 40') of the papermaking machine (100, 100') and is configured to dewater a fabric carrying a paper web.

16. Papermaking machine according to any of claims 11-15, wherein the at least one device (1) is arranged in a washing section (60, 60') for washing a fabric.

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