Press unit and press section of fiber web machine

Abstract

The invention relates to a press unit of a fiber web machine, comprising: a roller pair adapted to form a press nip; a nip frame of the press unit on which the roller pair is supported, the nip frame comprising a first vertical frame before the press nip and a second vertical frame after the press nip, the first vertical frame and the second vertical frame being adapted on opposite sides of the press unit; upper and lower fabric rings having fabric adapted to run through the press nip; and a suction roller adapted on the lower fabric ring behind the press nip for loosening the web from the fabric of the upper fabric ring. In the press unit, at least a second vertical frame of the nip frame is provided with an opening. The suction roller is adapted substantially according to the same vertical line as the second vertical frame, and the opening adapted to the second vertical frame is adapted to serve as a passage opening for replacing the suction roller on the press unit. The invention also relates to a press section of a fiber web machine.

Description

Field of the Invention

[0001] The present invention relates to a press unit of a fibrous web machine, the press unit comprising:

[0002] - a roll pair adapted to form a press nip;

[0003] - a nip frame of the press unit, on which the roll pair is supported, and the nip frame includes a first vertical frame before the press nip and a second vertical frame after the press nip, the first vertical frame and the second vertical frame being adapted to opposite sides of the press unit;

[0004] - an upper fabric loop and a lower fabric loop, having a fabric adapted to run through the press nip,

[0005] - a suction roll adapted to the lower fabric loop after the press nip for releasing the web from the fabric of the upper fabric loop.

[0006] Furthermore, the present invention also relates to a press section of a fibrous web machine. Background Art

[0007] Wet pressing (Nasspressen) is a function in the production of paper and cardboard, which removes moisture from the web by mechanically pressing the web. The part in the fibrous web machine that performs this function is called the press section. In the press section, mechanical pressing is performed by pressing the fibrous web between two rolls or between a roll and a shoe to remove moisture from the web. In the press section of a fibrous web machine, a fabric is used to transport the web. In the press section of a fibrous web machine that is fast-running in terms of performance, two successive press nips are used, which have fabric loops. Here, the web must be laid from one fabric to another in the press section.

[0008] The press section immediately following the forming section of a fibrous web machine is currently most commonly formed by two successive single press units, where the fibrous web is guided from one press nip to another at least supported by a felt, generally by a fabric, and the web runs a path between two fabrics or supported by two fabrics.

[0009] In Figure 1 an example of a press section of a fibrous web machine according to the prior art is shown. It represents the press section of a paper machine, where the press nip N formed by two rolls or a roll pair has two parts. The wet web W is conveyed through the press nip N between two press fabrics.

[0010] When the web W is guided from the first press 20, or the so-called primary press, to the second press 40, or the so-called secondary press, the web W must first be released from the first fabric 22 of the first press 20, for example the top press fabric 22, and held on the second fabric (for example the bottom press fabric 24). Then, the web W is guided under the load of the second fabric 24 to the second press 40, where the web W is conveyed onto the fabrics 42, 46 of the second press 40. It occurs in such a way that the web W is first brought into contact with the first fabric of the second press 40, in this case the top press fabric 42, released from the second fabric or the bottom press fabric 24 of the first press 20 and held on the first fabric 42 of the second press 40, and brought into contact with the second fabric or the bottom press fabric 46 of the second press.

[0011] In the two press units 10, the web W runs into the influence range of the suction roll 32' after the press nip N. The suction roll 32' is sometimes also referred to as a felt suction roll. When entering the influence range of the suction roll 32', the top press fabrics 22, 42 are separated from the web W, while the bottom press fabrics 24, 46 hold the web W on themselves through the suction roll 32'.

[0012] When the web W runs through the press nip N, a large amount of moisture is removed from the web. Part of the moisture is removed through the press fabric into the suction box or the corresponding dewatering device, and part of the moisture remains in the press fabric. Now, in the solutions according to the prior art, if the web W remains in contact with the two press fabrics for a relatively long time after the press nip N until the suction roll 32', where the web W is sucked onto the fabrics 24, 46 and released from the first fabrics 22, 42, part of the liquid present in the press fabric will be sucked back into the web W and cause the web to be re-wetted again. The re-wetting itself is problematic, mainly because when the water is sucked back into the web W again, the high dry matter content already obtained by the web in the press nip N will be significantly reduced.

[0013] In today's press section, the re-wetting after the press nip N has a more important impact. The web W can suck back a large amount of water from the two fabrics during the long guiding period from the press nip N to the suction roll 32'. The distance between the press nip N and the subsequent transfer suction roll 32' is partly determined by the press nip N itself, one or more drainage grooves (not shown) after the press nip N, the diameter of the transfer suction roll 32' (the width of the machine also has an impact on this), and the support position of the transfer suction roll 32'. With the current technology, the relevant distance can only be shortened to a limited extent.

[0014] There are also some known technical solutions that attempt to solve problems especially related to rewetting. In these technical solutions, a suction box is arranged after the press nip N and relatively close to the press nip. However, these related technical solutions have speed limitations. The solutions using suction boxes are only applicable to slower machines, while in modern fast machines, suction rolls are used to convey the web onto the next press fabric.

[0015] In addition to the problem of rewetting, the modernization of the known press sections in the prior art is also particularly challenging due to space limitations. When the press section is arranged between the forming section and the drying section, the available space for it is relatively limited in the machine direction. Summary of the Invention

[0016] The object of the present invention is to provide a more compact press unit for a fibrous web machine. Another object of the present invention is to provide a press unit for a fibrous web machine that is shorter in length in the machine direction.

[0017] According to the present invention, an opening is adapted on the second vertical frame on at least one side of the press unit, or more precisely, on the vertical frame arranged after the press zone. In addition, a transfer suction roll for adapting the web to leave the action range of the upper fabric loop after the press nip of the press unit is adapted substantially along the same vertical line as the vertical frame after the press nip, and the opening adapted on the vertical frame serves as a passage opening when replacing the suction roll in the press unit.

[0018] According to the present invention, a transfer suction roll for adapting the web to leave the action range of the upper fabric loop after the press nip of the press unit is adapted between the press nip frames of the press unit, more specifically, between the second vertical frame or the vertical frame arranged after the press nip. Here, compared with, for example, arranging a suction roll for detaching the web from the fabric of the upper fabric loop of the press unit in the space between the supports (Stuhlungen) of the press unit, the suction roll following the press unit can be very close to the press unit and the frame, or alternatively, the transfer suction roll of the drying section can be very close to the preceding press unit.

[0019] At least one vertical frame after the press nip of the press unit, preferably two vertical frames or the vertical frames on the guide roll side arranged after the press zone, are equipped with support parts for the suction roll, or more precisely, bearing seats are assembled in an opening adapted to the vertical frame. In addition, the support part can also have a transfer mechanism for roll replacement on at least one side above the opening, where the roll is axially displaced at least a part of the distance during the replacement process.

[0020] According to the present invention, the vertical frames of the nip frame are very different in terms of material throughout their vertical length. According to one application form, the total width of the frame beams of the vertical frame at the opening height in the machine direction can be less than 50% of the width of the frame beams of another vertical frame. Thus, according to the present invention, the overall economy of the frame of the press unit can be improved, especially due to a compact and shorter press section.

[0021] With the present invention, the frame structure of the press unit becomes more uniform and structural differences are reduced. This accelerates and simplifies the construction of the press frame.

[0022] With the present invention, the distance for rewetting, or the distance where the web contacts the two fabrics, is shortened. Therefore, the present invention enables the fabrics to be separated from each other earlier after the press nip. In other words, the upper press fabric can be released from the web and the lower press fabric earlier, and the web is continuously guided under the load of the lower press fabric after passing through the transfer suction roll. The technical solution according to the present invention allows the use of a suction roll closer to the press nip, thereby reducing the time for water to be suctioned back from the fabric to be released into the web.

[0023] The advantages achieved according to the technical solution of the present invention particularly also lie in: a lower rewetting rate (higher dry matter content) after the press nip and a smaller requirement for the total space. This is particularly significant for so-called retrofit situations where an existing press section is modified. Other advantages achieved by the present invention will be described in the description part and the specific feature part of the claims. Description of the Drawings

[0024] The present invention will be described in more detail below with reference to the drawings, but is not limited to the application forms shown below, where:

[0025] Figure 1 An example of the press section of a fiber web machine according to the prior art is shown in a side view.

[0026] Figure 2 An example of the press unit of a fiber web machine according to the present invention is shown in a side view,

[0027] Figure 3 Shown in an enlarged view is the second vertical frame belonging to Figure 2 the shown nip frame, and

[0028] Figure 4 An example of the press section of a fiber web machine according to the present invention is shown in a side view. Detailed Description of the Invention

[0029] In Figure 2An application form of the pressing unit 10 according to the present invention is shown. The pressing section 102 of a fibrous web machine may have at least one such pressing unit 10, Figure 4 An example of the pressing section is shown and is the subject of the present invention. Now, two presses 20, 40 of the pressing section 102 correspond to the pressing unit 10 shown in Figure 2 this figure.

[0030] As Figure 4 shown, the web W runs here from the forming section 101 (not shown) on the left to the pressing section 102 and then continues to run to the drying section 103 (not shown) following the pressing section 102. Now, the pressing section 102 includes two pressing nip zones N, at least one of which is part of the pressing unit 10 according to the present invention. Generally, the pressing section 102 includes at least one pressing nip zone N, which is in particular a shoe press nip zone in the shown application form. The pressing nip zone N is formed by a roll pair 13. In the shown application form, the roll pair 13 is formed by an upper shoe roll 29 and a lower counter roll 30.

[0031] In the example according to Figure 2 this figure, the pressing unit 10 of the fibrous web machine first guides the fibrous web W from the forming section 101 to the pressing unit 10 and then from one pressing unit 10 to another. In Figure 2 this figure, mainly the first press 20 of the pressing section 102 is shown, which is also often referred to as the primary press in the pressing section 102. Only the first roll of the sequentially arranged second press 40 or the secondary press of the pressing section 102 is shown, in particular the transfer suction roll 44 before the pressing nip zone N, which has a support beam.

[0032] Figure 2 The first press 20 in this figure is represented by an upper press fabric 22, a lower press fabric 24, a suction roll 26, a shoe press section 28 forming the pressing nip zone N, a felt suction roll 32, a fabric guide roll 34, and a plurality of other guide rolls 21, 31, which form fabric loops 14, 15 around which the fabrics 22 and 24 running through the pressing nip zone N are guided.

[0033] The web W is carried from the wire of the forming section 101 to the upper press fabric 22 of the first press 20 by the suction roll 26 and is guided, while being carried by the upper press fabric 22, into the press nip N formed by the shoe roll 29 and the counter roll and is guided through there. Before the press nip N, the web W also contacts the lower press fabric 24. In the illustrated form of application, the lower press fabric 24 already contacts the web W before the press nip N or is guided at least almost parallel to the web W into the press nip N. In an alternative embodiment of the press nip, it is possible to arrange for the lower press fabric 24 to contact the web W only just before the press nip N or only in the press nip N. In any case, the fabrics 22, 24 are adapted to guide the web W through the press nip N while being supported on both sides.

[0034] After passing through the press nip N formed by the shoe roll 29 and the counter roll 30, the web W continues to be guided between the fabrics 22 and 24. The lower press fabric 24 and the web W located thereon are released from the fabric 22 of the upper fabric loop 14 by the negative pressure formed by the transfer suction roll 32 arranged in the region of the guide roll 34 between the press nip N and the lower fabric loop. The transfer suction roll 32 is also commonly referred to as a felt suction roll or simply as a suction roll. The transfer suction roll 32 arranged below the lower press fabric 24 sucks the web W through the lower press fabric 24 while removing moisture from the lower press fabric 24. If at the same time the running direction of the lower press fabric 24 may be changed slightly to be slightly different from the running direction of the upper press fabric 22, the web W tends to be released from the upper press fabric 22 and remain in the inertia of the lower press fabric 24 in order to be further guided in the press section 102. Here, the upper press fabric 22 continues to run above the web W and separates from the web in a different direction compared to the lower press fabric 24.

[0035] In the above-mentioned pressing unit 10, the web W drawn out from the forming section 101 runs through the pressing nip N between two pressing fabrics 22, 24. In other words, the pressing fabrics 22 and 24 run together with the web W without separation in the lower fabric loop 15 until they reach the transfer suction roll 32 which is adapted as a common configuration (gemeinsame Aufführung) after the pressing nip N. From this configuration, the term felt sandwich is different from a technical solution where, for example, the pressing fabrics 22, 24 run along different routes immediately after coming out of the pressing nip N. In other words, the pressing fabrics 22, 24 run with the web W located therebetween up to the height of the subsequent transfer suction roll 32, and the web W and the second pressing fabric or the current lower pressing fabric 24 of this configuration start to follow on the side of the transfer suction roll 32 from here. Therefore, the web W starts to follow the lower pressing fabric 24 listed thereon after the transfer suction roll 32 and runs onto the pressing fabric 42 of the upper fabric loop 14' adapted to the second press 40 through the transfer suction roll 44 in the next stage.

[0036] The upper pressing fabric 22 of the first press 20 is turned upwards again to the return route under the support of the guide roll 21 of the upper fabric loop 14. The relevant guide roll 21 is the first guide roll of the upper fabric loop after the pressing nip N here. This guide roll 21 is adapted to the transfer suction roll 32.

[0037] In addition, the pressing unit 10 further includes a support structure, for example, the rollers 29, 30, 26, 21, 31, 32, 34 are rotatably supported on this support structure. This support structure is connected in the transverse CD direction to the pressing frame 11 on the guide roll side and the drive roll side of the pressing section 102 of the fiber web machine. Figure 2 Only the pressing frame 11 is shown from one side view. The roll pair 13 forming the pressing nip N is supported on the nip frame 11. The nip frame 11 is connected along the transverse direction CD of the pressing section 102 to a horizontal beam (not drawn) adapted therebetween.

[0038] The nip frame 11 further includes a first vertical frame 12.1 and a second vertical frame 12.2 adapted to the opposite sides or the guide roll side and the drive side of the pressing unit 10 along the transverse direction CD of the pressing section. The first vertical frame is adapted in front of the pressing nip N along the machine direction MD, and the second vertical frame is adapted after the pressing nip N along the machine direction MD. And the vertical frames 12.1, 12.2 are connected to each other again, now by horizontal beams 35.1, 35.2 along the machine direction MD. In addition, the vertical frames 12.1, 12.2 are supported from below on the base plate (Fundamentplatte) 19 of the fiber web machine.

[0039] According to Figure 2 and Figure 3, an opening 16 is adapted on at least the second vertical frame on one side of the nip frame 11, that is to say, on the vertical frame 12.2 arranged after the press nip N. Figure 3 The second vertical frame 12.2 of the nip frame 11 belonging to the press unit 10 is shown, which is simply enlarged without other equipment belonging to the press unit 10. The transfer suction roll 32 adapted in the running direction of the web W after the press nip N is substantially adapted on the same vertical line V as the second vertical frame 12.2 of the nip frame 11, and this transfer suction roll releases the web W from the fabric of the upper fabric loop 14.

[0040] The opening 16 adapted on the second vertical frame 12.2 is adapted to be used as a passage opening for the suction roll 32 at least on one side of the press unit, and the roll in the press unit 10 is replaced through this opening. Therefore, the size of the opening 16 at least on one side of the press unit corresponds at least to the diameter of the suction roll 32, so that the suction roll 32 can be removed via the opening 16 between the nip frames 11, and in particular between the second vertical frames 12.2, and can also be brought between the nip frames 11, in particular between the second vertical frames 12.2, from the relevant side of the press unit. This enables the successively arranged presses 20, 40 to be arranged closer to each other from the supports. In addition, this also enables the latter press 40 and the drying section 103 to be arranged closer to each other from the supports. Here, for example, the suction roll 45 for releasing the web W in the drying section 103 can be arranged closer to the latter press unit or the second press 40 together with the support. As a result, the technical solution according to the present invention is very suitable for the modernization of, for example, the press section 102 according to Figure 1 . In addition, by arranging the suction roll 32 between the nip frames 11, the rewetting rate of the web W after the press nip N is also reduced. In other words, this makes the distance from the press nip N to the release point of the fabrics 22 and 24 significantly smaller than the distance at which rewetting occurs according to the prior art. Here, the distance L (see Figure 3 ) between the suction roll 32 and the press nip N is shortened to the same as the diameter of the suction roll 32 in the best case. According to one application form, the diameter of the suction roll 32 can be, for example, 700 - 1000 mm, and preferably 700 - 950 mm.

[0041] The vertical frame 12.2 having the opening 16 can also be referred to as the opening frame of the suction roll 32. Here, the opening 16 is according to Figure 3It is formed between the frame beams 17.1 and 17.2 of the vertical frame 12.2. There can be at least one vertical frame 12.2 with an opening 16 arranged behind the compression zone, or both can be equipped with the opening 16. Here, the vertical frame 12.2 on the guide roll side and / or the drive side, that is, after the nip zones N, N2 of the press, is equipped with the opening 16. Here, the shaft head (Wellenkopf) of the transfer suction roll 32 can extend outside the vertical frame via the opening 16 on the guide roll side or extend to the side of the press section. Here, the normal suction joint and other joints of the transfer suction roll 32 can also be easily realized through the shaft head. At the same time, the shaft head extending outside the opening 16 or to the side of the press section can also be used as a point that can carry the transfer suction roll 32 during replacement or at least at the beginning of replacement on the guide roll side.

[0042] If the opening 16 has been formed on both vertical frames 12.2, the openings do not have to be the same size on both vertical frames 12.2. If the suction roll 32 is suitable for being replaced on the guide roll side, when the diameter of the roll is equal to or less than the diameter of the bearing housing 37, the size of the opening 16 on the guide roll side is at least the size of the bearing housing 37. If the diameter of the suction roll 32 is greater than the bearing housing 37, the opening 16 on the guide roll side has at least the diameter size of the suction roll 32, so that the suction roll 32 can be replaced through the opening 16. On the drive side, the size of the opening 16 can be designed only according to the bearing housing 37.

[0043] The structural profile of the vertical frame 12.2 is wider in the machine direction MD at the height of the opening 16 than the frame beam 18 above the opening 16. However, the vertical frame 12.2 is lighter in structure at the height of the opening 16 than the frame beam 18 above the opening. According to an application form, in Figure 3 the total width w (= w1 + w2) of the frame beams 17.1 and 17.2 forming the opening 16 in the machine direction MD at the height of the opening is less than 50% of the width w3 of the frame beam 18 of the second vertical frame 12.2 above the opening 16 ( Figure 3 ). This makes the frame structure of the press unit 10 simpler and saves structural materials. The opening 16 can be arched at the upper part and box-shaped starting from the frame beams 17.1 and 17.2. The widths of the frame beams 17.1 and 17.2 forming the opening 16 can correspond to the width of the frame beam 18 above the opening 16 in the cross direction CD of the press section 102 in the cross direction CD.

[0044] The support part 36 of the suction roll 32 is adapted to the opening. The support part 36 now includes the bearing housing 37 of the suction roll 32, which is adapted to the lower surface, i.e., the bottom, or the side surface of the base plate 19 of the opening 16, and the box-shaped structure forming the opening 16 is fastened to the bearing housing. A slider 25 ([ Figure 3 ) equipped with wheels can also be arranged between the bearing housing 37 and the bottom of the opening 16 for the suction roll 32 to move away from between the nip frames 11 and back between the nip frames in the axial or transverse direction via the opening 16.

[0045] In addition, according to Figure 3 , a support structure 38' of the fibrous web machine, such as a crossbeam 38, can also be arranged in the height of the opening 16 and between the vertical frames 12.2 in the transverse direction CD for the replacement of the transfer of the suction roll 32. The support structure 38' is adapted to the opening 16 on the drive side for the slider 25 below the bearing housing 37 or to the corresponding transfer mechanism 25'. Through the transfer mechanism 25', the transfer suction roll 32 moves away from the position covering the opening 16 and is correspondingly guided into the opening 16. When replacing the transfer suction roll 32, the transfer suction roll can be supported, for example, on the shaft head / neck from the outside of the opening 16, from the side of the fibrous web machine, from above, for example, by a sling on the guide roll side, and at the same time, in the axial direction, through the opening 16 of the vertical frame 12.2, and from below, the opposite end or the drive side end of the transfer suction roll is supported on, for example, the slider 25 or the corresponding transfer mechanism 25'. Through the slider 25, the transfer suction roll 32 can be moved outwards only a little through the opening 16, and then it can also be supported by the drive side end or the sheath area of the suction roll 32 by a corresponding sling as on the guide roll side.

[0046] According to an application form, the suction roll 32 can also be constructed as non-driven. Here, the drive of the lower fabric loop 15 after the press nip N is adapted to be carried out on the guide roll 34 of the lower fabric loop 15, which is adapted after the suction roll and is now adapted to provide the drive. The guide roll 34 of the lower fabric loop 15 can also be supported on the second vertical frame 12.2 after the press nip N and also after the suction roll 32. The suction roll 32 can have chambers in terms of suction performance.

[0047] According to an application form, the size of the opening 16 is adapted such that the doctor blade 33 ([ Figure 2 ) of the suction roll 32 is also adapted to be replaced through the opening 16, where the suction roll 32 remains stationary. In addition to the suction roll 32, the drainage grooves 27 arranged thereon are also adapted between the second vertical frames 12.2 of the nip frame 11. According to an application form, the doctor blade 33 can be fastened to the grooves 27.

[0048] In the illustrated application form, the pressing unit 10 is equipped, for example, with a fabric changing device 23 adapted to the nip frame 11 or a normal filling body (normalen ). Here, the fabric changing device 23 adapted to the second vertical frame 12.2 of the nip frame 11 is located between the frame beams 17.1, 17.2 adapted to form the opening 16 and the upper frame beam 18.

[0049] The guide roller 21 of the upper fabric loop 14 is also supported on the second vertical frame 12.2 after the pressing nip N (from where the upper pressing fabric 22 starts its return journey), and openings adapted to the suction roller 32 are also arranged on this second vertical frame. Here, the guide roller 21 of the upper pressing fabric 22 is also arranged on the suction roller 32 at the height adapted to the opening 16, wherein the suction roller 32 is adapted between the second vertical frames 12.2 of the nip frame 11. When the guide roller 21 is arranged on the second vertical frame 12.2, the distance over which the web W is rewetted is also shortened. In the illustrated application form, the second guide roller 31 of the upper fabric loop 14, after the pressing nip N (where the upper pressing fabric 22 continues to run from here) and after the first guide roller 21 enters its return journey, is now also supported in a known manner on the same second vertical frame 12.2, on which openings 16 adapted to the suction roller 32 are also arranged.

[0050] In addition to the pressing unit 10, the subject matter of the present invention also includes a pressing section 102, Figure 4 An example is shown. The pressing section 102 includes at least one pressing unit 10. At least one pressing unit 10 of the pressing section 102 is a pressing unit according to the present invention as described above. In the illustrated application form, both pressings 20, 40 are pressing units 10 according to the present invention.

[0051] Regarding the first pressing unit 20, reference is made to the above description regarding Figure 2 As Figure 4 shown, before the relevant fabric 24 changes its route downward around the guide roller 34, the web W is removed from the lower pressing fabric 24 of the primary pressing 20 by means of a transfer suction roller 44 before the pressing nip N2 of the second pressing 40. The transfer suction roller 44 of the pressing 40 releases the web W from the lower pressing fabric 24 in the same way as the transfer suction roller 32 arranged after the pressing nip N of the first pressing 20 described above. By means of the transfer suction roller 44, the upper pressing fabric 42 belonging to the second pressing 40 continues to guide the web W until the lower pressing fabric 46 of the second pressing 40 is guided to turn around the guide roller 48 from below, where the web W is again guided between the two fabrics 42, 46 into the pressing nip N2 of the second pressing 40.

[0052] According to an application form, the transfer suction roll 44 of the second press unit 40 following immediately after the first press unit 20 of the press section 102 is arranged in front of the press nip N2 of the second press unit 40, and at least partially overlaps vertically with the guide roll 34 belonging to the lower fabric loop 15 of the first press unit 20, which is adapted after the suction roll 32 of the first press unit 20. This also slightly shortens the distance between the successively arranged presses 20, 40, and thus saves space in the press section 102.

[0053] The invention is suitable for use, for example, in combination with the press sections of paper machines, board machines, tissue machines, and cellulose machines. Thus, the above-mentioned web W can be understood as paper, board, tissue, or a cellulose web. The speed of the fiber web machine can be, for example, 1000 - 2000 m / min.

[0054] It should be understood that the above description and the associated drawings are only intended to describe the invention. Therefore, the invention is not limited to the above-described embodiments, and for those skilled in the art, there are obviously many different variations and transformations of the invention, and these variations and transformations all fall within the framework of the inventive concept of the invention defined by the claims.

Claims

1. A pressing unit comprising - a pair of rolls (13) adapted to form a pressing nip (N), - a nip frame (11) of the press unit (10), the roll pair (13) being supported on the nip frame, and the nip frame (11) comprising a first vertical frame (12.1) before the press nip (N) and a second vertical frame (12.2) after the press nip (N), the first vertical frame and the second vertical frame being adapted on opposite sides of the press unit (10), - an upper fabric ring (14) and a lower fabric ring (15) having fabrics (22, 24) adapted to run through the press nip (N), - a suction roll (32) adapted on the lower fabric ring (15) after the pressing nip (N) for releasing the web (W) from the fabric (22) of the upper fabric ring (14), It is characterized in that - at least one vertical frame (12.2) of the nip frame (11) is adapted with an opening (16), - the suction roller (32) is adapted substantially along the same vertical line (V) as the second vertical frame (12.2), and the opening (16) adapted to the second vertical frame is adapted to serve as a passage opening for the suction roller (32) when the suction roller (32) is replaced on the pressing unit (10).

2. The pressing unit according to claim 1, characterized in that A vertical frame (12.2) is adapted to be formed by frame beams (17.1, 17.2) at the height of the opening (16), the total width (w) of the frame beams at the height of the opening (16) in the machine direction (MD) being less than 50% of the width (w3) of the frame beams (18) of the second vertical frame (12.2) above the opening (16).

3. The pressing unit according to claim 1 or 2, characterized in that The suction roller (32) has a cavity.

4. The pressing unit according to any one of claims 1 to 3, characterized in that The diameter of the suction roller (32) is 600-1000 mm, preferably 700-950 mm.

5. The pressing unit according to any one of claims 1 to 4, characterized in that - the suction roller (32) is preferably not driven, - The guide roller (34) of the lower fabric ring (15) is adapted to provide a drive, the guide roller being adapted after the suction roller (32).

6. The pressing unit according to any one of claims 1 to 5, characterized in that The support portion (36) of the suction roller (32) is adapted to fit on the opening (16).

7. The pressing unit according to any one of claims 1 to 6, characterized in that The second vertical frame (12.2) comprises a fabric changing device (23) which is adapted between frame beams (17.1, 17.2) of the second vertical frame (12.2) forming the opening and a frame beam (18) located above the opening (16).

8. The pressing unit according to any one of claims 1 to 7, characterized in that The pressing unit (10) has a guide roller (21) of the upper fabric ring (14) after the pressing nip (N), adapted on the suction roller (32), the guide roller (21) being supported on the second vertical frame (12.2).

9. The pressing unit according to any one of claims 1 to 8, characterized in that The lower fabric ring (15) of the pressing unit (10) comprises a guide roller (34) adapted after the pressing nip (N), which guide roller is supported on the second vertical frame (12.2).

10. The pressing unit according to any one of claims 1 to 9, characterized in that The speed of the fiber web machine is 1000-2000 m / min.

11. The pressing unit according to any one of claims 1 to 10, characterized in that A transfer mechanism (25'), such as a slide (25) for replacing the suction roller (32), is adapted on the opening (16).

12. The pressing unit according to any one of claims 1 to 11, characterized in that The opening (16) is adapted to form an arched structure on the second vertical frame (12.2).

13. A pressing unit according to any one of claims 1 to 12, characterized in that The vertical frame (12.2) on at least one side of the pressing unit (10) is an open frame, and therefore the second vertical frame (12.2) is arranged at least on the guide roller side.

14. A press section of a fiber web machine, comprising at least one press unit (10, 20, 40), the press unit comprising: - a pair of rolls (13) adapted to form a pressing nip (N), - a nip frame (11) of the press unit (10, 20, 40), the roll pair (13) being supported on the nip frame, and the nip frame (11) comprising a first vertical frame (12.1) before the press nip (N) and a second vertical frame (12.2) after the press nip (N), the first vertical frame and the second vertical frame being adapted on opposite sides of the press unit (10, 20, 40), - an upper fabric ring (14) and a lower fabric ring (15) having fabrics (22, 24) adapted to run through the press nip (N), - a suction roll (32) adapted on the lower fabric ring (15) after the pressing nip (N) for releasing the web (W) from the fabric (22) of the upper fabric ring (14), Characterized in that at least one pressing unit (10, 20, 40) of the pressing section (102) is a pressing unit according to any one of claims 1 to 13.

15. The press section according to claim 14, characterized in that The transfer suction roll (20) of the second pressing unit (40) following the first pressing unit (20) is adapted to at least partially overlap with the guide roll (34) of the lower fabric ring (15) belonging to the first pressing unit (20), and the guide roll is adapted behind the suction roll (32) of the first pressing unit (20).

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