Press section with frame construction for a paper machine

Abstract: Press section of a paper machine, provided with a frame construction which comprises, in the direction of running of the paper web (W), first a front frame (50) and after that a rear frame (60). In connection with the front frame and the rear frame (50,60) press rolls (13,13′,16,21,31) are mounted. Between the front frame and the rear frame (50,60), above the press roll combination, there is an at least partly open space (T), through which at least most of the press rolls can be replaced. The space (T) also facilitates replacement of the upper press fabrics (10,30). The press roll (13,13′), which forms the second nip (N₂) in the press section, is attached to a first intermediate-frame part (14) separate from the rear and intermediate frames (60,70,90) and arranged pivotable by means of power units (18) around horizontal articulation shafts (14a) into connection with the front frame (50). The press roll (13;13′) is connected to the first intermediate-frame part (14) by the intermediate of a second intermediate-frame part (15) by means of horizontal joints (15a). The second intermediate-frame part (15) can be pivoted around said horizontal articulated joint (15a) by means of power units (15b). Between the first intermediate-frame part (14) and the front frame (50), there are openable and lockable intermediate parts (51), by means of which the first intermediate-frame part (14) can be fixed to the front frame (50) rigidly. The intermediate parts can be opened so that the first intermediate-frame part (14) can be pivoted towards the front frame (50) at least when the suction roll (13) in the press section is being replaced.

Description: The invention concerns a press section of a paper machine, provided with a frame construction as claimed in claim 1. In connection with the present application, a compact press roll combination means a roll combination whose rolls constitute press nips with each other, but between the rolls there may be one or several straight runs of the web, on which the web is supported by a press fabric. Thus, in connection with the present application, the scope of the notion 'compact roll combination' includes the press sections marketed by the applicant both under the trade mark 'Sym-Press II' and under the trade mark 'Sym-Press 0'. In prior-art compact press sections of a paper machine, such as the applicant's so-called Sym-Press (TM) press section, above the press rolls, both at the service side and at the operating side of the paper machine, there have been horizontal beams which connect the front frame and the rear frame of the press section permanently together. In this connection, and so also in the following description, the front frame means the frame part that is placed, in the direction of running of the web, at the front side of the press roll combination. In a corresponding way, the rear frame means the frame part placed at the rear side of the press roll combination. In connection with the prior-art frame parts of said press sections, difficulties have occurred in relation to the replacement both of the press fabrics and of the press rolls. These problems have increased with the increase in the widths of the paper machines, in particular owing to the fact that the press rolls have become ever longer and heavier. Said problems have, for its part, also been increased by the fact that press fabrics which are made of plastic materials and which are rigid in the transverse direction have started being used ever increasingly, which said press fabrics cannot be jammed into a bundle, because they would be thereby wrinkled and become unusable. Beloit Corporation has attempted to solve the problems described above by means of a so-called "Flip-Top" (trade mark of Beloit Corporation) frame construction. In this prior-art frame solution for a press section, such a top frame is used as is provided with a pivot shaft parallel to the transverse direction of the paper machine and placed above the press rolls, whereby either the top part of the front frame or the top part of the rear frame can be opened around said pivot shaft. Both of said two top parts of the frame cannot be opened at the same time. By opening said top part of the front frame, it is possible to facilitate the replacement of the pick-up fabric of the press section and the replacement of the fabric that usually acts as the press fabric in the first nip and in the second nip. The top part of the rear frame is locked as a frame part on whose support the opening-dumping of the top part of the front frame takes place. Correspondingly, when the top part of the front frame is in the closed-locked position, the top part of the rear frame can be dumped so that the press fabric of the third press nip can be replaced. The lower fabric of the first nip, which runs mainly in the basement space, is replaced by means of arrangements in themselves known. The above "Flip-Top" solution can be characterized as a sort of a "drawbridge", which is opened around an articulated joint placed at the middle of the bridge, and only one half of the bridge can be opened at a time. EP-A-0 287 544, which is an intermediate document published after the priority date of this application, discloses within the terms of Article 54(3) a press section of a paper machine, provided with a frame construction which comprises in the direction of running of the paper web first a front frame and after that a rear frame, and in connection with said front frame and rear frame as well as a possible intermediate frame, if any, press rolls are mounted, which form a relatively compact press roll combination, in which there are press nips formed between press rolls, the press fabrics being passed through said nips, and which said frame construction comprises: an at least partly open space placed between said front and rear frame, not directly connected to each other, and above said press roll combination, through which said space at least most of the press rolls in said press roll combination can be replaced, and which said space also facilitates the replacement of the upper press fabrics placed in its connection; a press roll of the press roll combination mounted in connection with the rear side of the front frame; a smooth-faced centre roll of the press, which is mounted in connection with the rear frame, preferably in connection with its projection part, and which forms the second nip in the press together with the press roll mentioned above. Furthermore, EP-A-0 287 544 discloses that the press roll, which forms the second nip in the press section and which is a hollow-faced press roll, is attached to a first intermediate-frame part, which is separate from the rear and intermediate frames and which is arranged pivotably by means of power units around horizontal articulation shafts into connection with the front frame, that said press roll is connected to the first intermediate-frame part by the intermediate of a second intermediate-frame part by means of horizontal articulated joints, that the second intermediate-frame part can be pivoted around said horizontal articulated joint by means of power units so as to load the second nip, openable and lockable intermediate parts are fitted between the intermediate frame part and the rear frame, and that said intermediate parts can be opened so that the first intermediate-frame part can be pivoted towards the front frame at least when the hollow faced roll in the press section is being replaced. From this state of the art the invention differs in that between the first intermediate-frame part and the front frame, openable and lockable intermediate parts are fitted, by means of which the first intermediate-frame part can be fixed rigidly to the front frame. Through this construction an easier and more effective maintenance of the press section is achieved. Furthermore, the alternative features that a separate intermediate frame is foreseen to bear the smooth faced centre roll and that the press roll which forms a second nip can also be a suction roll are not known from EP-A-0 287 544. An object of the present invention is to provide a frame construction by means of which replacements of felts can be made faster in particular in the case of the first felt and the pick-up felt. A further object is to provide a press frame construction wherein it is necessary to pivot the frame of the second press roll to the upper position exclusively in connection with a replacement of the press-suction roll. When compact press roll arrangements are used, problems of space are also encountered, because several different press rolls with their auxiliary devices must be accommodated in a relatively limited space. This is why it has been necessary to place the frame parts that connect the front frame and the rear frame to each other or to the intermediate frame, with their opening and closing means, in highly congested spaces, which results in problems both for the construction and for the operation. A particular object of the present invention is to provide a novel press section with frame construction by application of which the weight of the constructions can be reduced further. A further object of the invention is to provide a press section with frame construction by means of which the replacement of press fabrics and press rolls can be automated highly extensively and the various replacement operations be carried out on the basis of control impulses given from the central control room. The objective with this is expressly that it should be possible to make the standstills resulting from replacements of press fabrics and rolls ever shorter and thereby to increase the efficiency of operation of the paper machine. According to the invention as claimed in claim 1, a separate front frame and a rear frame not connected to one another are employed so that above the compact press roll arrangement a constantly at least partly open space remains, which is at least not closed completely, and the front frame and the rear frame are not bound together, at least not by means of robust and space-consuming frame parts proper. If necessary, said open space can be made wider by arranging the foremost guide roll of the second upper fabric as journalled on the bearing supports of the centre roll and as detachable as well as displaceable to an inner position in connection with replacement of the press rolls or of the second upper fabric. The press section with frame construction in accordance with the invention can be applied, e.g., in connection with the applicant's so-called 'Sym-Press I', 'Sym-Press II', and 'Sym-Press 0' press sections as well as in other, corresponding compact press sections. When a frame construction of a press in accordance with the invention is applied, the front frame and the rear frame are dimensioned separately sufficiently rigid in view of various phenomena of oscillation. Recently, it has been noticed surprisingly that connecting of the front frame and the rear frame by means of an intermediate frame does not reduce the tendencies of oscillation of the frame parts, at least not to a decisive extent. In connection with a frame construction in accordance with the invention, it is possible to use either press fabrics in the form of a closed loop, most appropriately plastic fabrics, or so-called seamable press fabrics, in which latter case, in connection with the side frames of the frame parts, openable and closable intermediate pieces are not necessarily needed, which, for its part, simplifies the frame construction and makes is less expensive. Further embodiments of the invention are claimed in claims 2 to 10. In the following, the invention will be described in detail with reference to an exemplifying embodiment of the invention illustrated in the figures in the accompanying drawing, the invention being by no means strictly confined to the details of said embodiment. Figure 1 is a schematical side view of a first press section provided with a frame construction in accordance with the invention. Figure 2 shows a second embodiment of the invention, which is applied in a so-called Sym-Press 0 press section. Figure 3 shows replacement of press fabrics in a press section in accordance with Fig. 2. Figure 4 shows replacement of press rolls in a press section in accordance with Fig. 2. The press section shown in Fig. 1 (Sym-Press II) comprises a closed press-roll combination 13,16,21,31, whose press rolls form three press nips N₁,N₂ and N₃, which remove water from the web W, between them. Moreover, the press section includes a fourth, separate nip N₄, which is formed between the press rolls 33 and 43. The press section comprises a first upper fabric 10 and a first lower fabric 20 (as a rule, felts), both of which said fabrics run through the first nip N₁ and of which said fabrics the first fabric 10 acts as the pick-up fabric and, moreover, as the press fabric in the second nip N₂. The second upper fabric 30 runs through the third nip N₃, and the fourth press fabric 40, which is a lower fabric, acts as the lower press fabric in the fourth nip N₄. In Fig. 1, inside the loop of the first fabric 10, there is a pickup roll 11 provided with a suction zone 11a, which transfers the web from the forming wire 27 to the run between the rolls 13a and 13b. The figure also shows a part of the upper wire 28 and its guide rolls 29a and 29b. The fabric 10 is guided by the guide rolls 12,12a, 12b. The lower fabric 20 runs as guided by the guide rolls 22. In a corresponding way, the second upper fabric 30 is guided by the guide rolls 32,32a,32b. The fourth fabric 40, which transfers the web W from the location of the transfer roll 78 into the last nip N₄, runs as guided by the suction-transfer roll 41 and by the guide rolls 42. The lower roll 21 of the first nip N₁ is journalled on the intermediate part 23. The intermediate part 23 is attached to the front frame 50 by means of articulation shafts 25. The intermediate part 23 can be pivoted by means of hydraulic cylinders 24, by means of which it is also possible to provide loading of the nip N₁. The suction roll 13 is journalled in connection with the front frame 50 by the intermediate of intermediate frames 14 and 15. Seen from the side, the first intermediate frame 14 has a triangular shape, and from its bottom part it is connected to the front frame 50 by means of horizontal articulated joints 14a, which are placed in connection with flange parts 14b. The second intermediate frame 15 is attached to the first intermediate frame 14 by means of horizontal articulated joints 15a, the bearing supports of the suction roll 13 being attached to said second intermediate frame 15. The first and the second frame 14 and 15 can be pivoted in relation to one another around a horizontal joint 15a by means of a hydraulic cylinder 15b. The first intermediate frame 14 can be pivoted by means of a wormgear 18 or hydraulic cylinder relative the articulated joints 14a. The nip N₂ can be loaded by means of hydraulic cylinders 15b. When the suction roll 13 is in its operation position, the first intermediate frame 14 has been pivoted so that there are intermediate pieces 51 between its side placed at the side of the front frame 50 and the front frame 50, by means of which said intermediate pieces the intermediate frame 14 is attached to its location of operation reliably and so that it does not oscillate. The intermediate pieces 51 are attached by means of eyebolts (not shown) or by means of equivalent instant connectors to the front frame 50 and to the intermediate frame 14. As a rule, detaching of the intermediate pieces 51 is necessary only in connection with replacement of the suction roll 13. The fabric 10 can be replaced by just pivoting the frame parts 14 and 15 relative one another by means of the hydraulic cylinders 15b. In connection with the upper part of the first intermediate frame 14, the guide roll 12 of the fabric 10 is journalled, which moves along with the intermediate frame 14 when the latter is pivoted around the articulated joint 14a. The front frame 50 is provided with intermediate pieces 55. When the intermediate pieces 55 are opened and the front frame 50 is cantilevered, the upper fabric 10 can be replaced. In connection with the replacement, the nips N₁ and N₂ are open. For replacement of the upper fabric 30, the rear frame 60 is provided with intermediate pieces 75. In a corresponding way, the rear frame 60 is provided with an intermediate piece 76 for replacement of the fourth fabric 40. In Fig. 1, the upper roll 33 of the fourth nip N₄ is journalled from above on the rear frame 60 by the intermediate of the frame parts 68. The lower roll 43 of the fourth nip N₄ is mounted on the intermediate part 70, which is attached to the rear frame 60 by means of articulation shafts 71. The intermediate part 70 can be pivoted by means of hydraulic cylinders 72 so as to open and to load the nip N₄. The press roll 31 of the third nip N₃ is journalled on an intermediate part 61, which is attached to the front part of the rear frame 60 by means of articulation shafts 62. The intermediate part 61 can be pivoted by means of hydraulic cylinders 63 to an upper position so as to open the nip N₃ and to replace the third fabric 30. In connection with replacement of the fabric 30, the intermediate part 61 can be locked in connection with the projection part 66 of the front frame 60 by means of locking devices 65a and 65b. The foremost guide roll 32a of the third fabric 30 is journalled on the frame part 92, which is again attached in connection with the intermediate frame 90 above said frame 90, most appropriately in connection with the bearing supports of the centre roll 16. In Fig. 1, the passage of the web W beginning from the pick-up point P is the following. The suction sector 11a of the pick-up roll 11 detaches the web W from the wire 27 and makes it adhere to the bottom face of the fabric 10, on which the web W passes through the twin-wire nip N₁. The lower roll 21 of the nip N₁ is provided with a hollow face 21′. After the nip N₁, the web W follows the first upper fabric 10 by the effect of the suction sector 13a of the suction roll 13. The web W is transferred in the second nip N₂ onto the face of the smooth-faced 16′ centre roll 16, e.g. a rock roll, and further into the third nip N₃, after which the web W follows along with the centre roll 16 and, being guided by the transfer roll, is transferred onto the fabric 40 on the suction sector 41a of the suction roll 41 and, being supported by the fabric 40, further into the nip N₄. After the nip N₄, the web W follows along with the smooth-faced press roll 33, from which it is transferred onto the alignment roll 46 and onto the single-wire-draw fabric 44 in the drying section, which said fabric 44 is guided by the lead rolls 49. The web W passes as a single-fabric draw to the drying section, of which three upper cylinders 47 and two lower cylinders 48 are shown in the figure. The frame construction in accordance with Fig. 1 comprises a front frame 50 and a completely separate rear frame 60, which is not connected to the front frame. The front frame 50 and the rear frame 60 are in such a way separate that they are separated by a space T open at the top, which said space T can be utilized in accordance with the invention in replacement of the press rolls 13,16 and 31. Said open space T also facilitates replacement of the upper fabrics 10 and 30. The invention is also suitable for use in presses in which there are two nips with fabrics of their own placed in connection with the centre roll 16. The separate frame parts 50 and 60 are designed so that, even when separate, they are sufficiently rigid, e.g., in view of various phenomena of oscillation. The press-frame construction shown in Fig. 1 further includes an intermediate frame 90, on which the centre roll 16 of the compact press is supported and journalled. In the figure, the intermediate frame 90 is separate in relation to the front frame 50 and to the rear frame 60 in such a way that the lower fabric 20 and the fourth fabric 40 can be replaced. When a separate nip N₄ is employed in addition to a compact press-roll combination, it is advantageous to use an intermediate frame described above, separate from the front frame 50 and from the rear frame 60, to permit replacement of the lower fabric 40. In such a case, the invention can also be carried into effect so that the centre roll 16 is supported on the front side of the rear frame 60 directly or by the intermediate of a projection part or equivalent. In such a case, the roll geometry must be altered to some extent from that shown in the figures, in particular in respect of the rolls 18,31,32 and 41. If no nip N₄ is employed, such a variation is also possible in which the intermediate frame 90 is connected to the rear frame 60 by means of horizontal beams or equivalent. According to Fig. 1, the foremost guide roll 32a of the second upper fabric 30 is journalled on supports 92, which are again attached to the bearing supports of the centre roll 16, which are again attached to the intermediate frame 90. When the guide roll 92a is arranged detachable from its supports 92, a path can be opened for replacement of the press rolls. Another, alternative mode, which is, however, obviously not equally advantageous, of supporting the guide roll 32a is to arrange it in connection with the intermediate part 61 of the press roll 31. In such a case, when the intermediate part 61 is pivoted to the upper position, the guide roll 32a is displaced out of the way for replacement of the press rolls or, if necessary, in this case as well, the press roll 32a can be arranged so that it can be detached and shifted to an inner position 32a′. In the following, the replacement of the various fabrics and press rolls in the press section of Fig. 1 will be described. when the first fabric 10 is being replaced, the intermediate pieces 55 and the pick-up point P as well as the press nips N₁,N₂ are opened, the latter one by pivoting the intermediate frame 14 by means of the wormgear 18 to the upper position around the articulated joint 14a, whereby, at the same time, the roll 12 moves towards the front frame 50. Hereupon, the guide roll 12a of the fabric 10 is shifted along the route a₀ to the position 12a′ to the parking site 51. In a corresponding way, the second upper guide roll 12b is shifted along the route b₀ to the position 12b′ to the parking site 51. Hereupon the new fabric 10 can be passed through the spaces made free by the opened intermediate pieces 55 to its location. In Fig. 1, the upper fabric 30 is replaced as follows. The foremost guide roll 32a of the fabric 30 is detached from its supports 92 and shifted along the route a₁ to the inner upper position 32a′ to the parking site 67. In a corresponding way, the rearmost guide roll 32b of the upper fabric is shifted along the route b₁ to the inner position 32b to the parking site 68. The intermediate pieces 75 and the nip N₃ are opened by lifting the intermediate part 61 by means of the actuating members 63 to the upper position. Hereupon the new fabric 30 is passed around the guide rolls to be placed inside the fabric through the spaces in the side frame which were allowed to remain free by the intermediate pieces 75. Hereupon the new fabric 30 is spread out to its full length by shifting the guide rolls 32a′ and 32b′ to their normal operating locations, the nip N₃ is closed, and the fabric 30 is tensioned. In the press section shown in Fig. 1, the lower fabric 40 of the fourth nip is replaced so that the intermediate pieces 45 and 76 are opened and the lower guide rolls of the fabric are shifted in the direction of the arrows a₂ and b₂ to the upper position 80a and 80b, whereupon the new fabric 40 is passed through the spaces made free by the opened intermediate pieces 45 to its operating location while the nip N₄ is open. Hereupon the rolls 80a and 80b are shifted into the basement space to their lower positions (not shown). In a corresponding way, the second fabric 20 is replaced by opening the intermediate pieces 55′ and 56 and by shifting the lower guide roll 80c to the upper position in the direction of the arrow c₂. When the nip N₁ is open, the new fabric 20 is placed as suitably spread-out around its guide rolls, and the guide roll 80c is shifted into the basement space to its lower position (not shown). In Fig. 1, the press rolls 13,16 and 31 are replaced as follows by making use of the open space T that remains between the separate frame parts 50 and 60. In order to replace the suction roll 13, if necessary, it is possible to open the intermediate pieces 51 between the intermediate frame 14 and the front frame 50 and to pivot the front frame 14 around its articulation shaft 14a by means of a wormgear 18 or a hydraulic cylinder towards the front frame 50, whereby the guide roll 12 is shifted along, and in this way more open space is produced above the roll 13 to facilitate its replacement. In connection with the replacement of the rolls 13 and 31, the upper fabrics 10 and 30 have been removed. The guide roll 32a of the second upper fabric 30 is detached from its supports and shifted to the upper position 32a′ to the parking site 67. The intermediate frame 61 is pivoted to the upper position and fixed in that position by means of locking devices 65a and 65b. Hereupon the press roll 31 can be lifted freely by means of a crane through the open space T. The suction roll 13 can also be lifted through the open space T between the front frame 50 and the rear frame 60. In the figure the width of the open space T is denoted with L. This width is calculated as the horizontal distance between the outermost point at the front frame 50 and the outermost point at the rear frame 60 in the machine direction. According to the invention, the front frame and the rear frame are fitted in relation to each other and dimensioned so that the width L of said free space T is clearly larger than the largest diameter of the press rolls, which said diameter is, in the figure, the diameter D of the centre roll 16. When a sufficiently wide free space T is employed in accordance with the invention, at least the centre roll 16, whose weight may be up to about 70,000 kgs, can be lifted without lateral shiftings, which might cause dangerous swinging and a risk of damage to the centre roll. A sufficiently wide (L) free space also facilitates the replacement of the relatively massive suction roll 13 and also of other components. For the lifting of the press rolls 13,16 and 31, it is possible to use either lifting by the axle journals or so-called centre lifting, which means that the roll is suspended on one crane hook only by means of lifting lines, which support the roll in downwardly open V-form symmetrically at both sides of their vertical centre plane. It is an advantage of centre lifting that the roll can be turned in the horizontal plane around its vertical centre axis, which usually facilitates the shifting of the rolls even in most congested premises. When a roll is lifted by means of its axle journals, the roll can usually be shifted only so that it retains its longitudinal direction, because the use of two cranes in joint operation is difficult and risky in view of safety at work. For the lifting of rolls, as a rule, a normal traverse crane operating above the paper machine hall is used. The shifting of fresh rolls to their positions takes place by means of the open space T by carrying out the operations described above in the reversed sequence. If seamable felts are used, it is not necessary to provide the different frame parts with openable and closable intermediate pieces 55,56,45, 75,76, because the fabrics can also be replaced without such pieces. In the following, with reference to Figures 2,3 and 4, a second embodiment of the invention will be described. In the following, the constructions of the press section will be described mainly with reference to Fig. 2 and in the respects only in which they differ from what is shown in Fig. 1. According to Fig. 2, the press section is a so-called Sym-Press 0 press section, wherein, differing from Fig. 1, the suction roll 13 does not form a nip with the centre roll 16, but after the suction roll 13 the web and the upper felt 10 have a substantially vertical straight common run. The second nip N₂ is formed between the hollow-faced 13″ press roll 13′ and the centre roll 16. In the embodiment shown in Fig. 2, the press roll 13′ corresponds to the suction roll 13 of Fig. 1 in respect of its support mode and position. Thus, in accordance with Fig. 2, the press roll 13′ is attached in connection with the front frame 50 by the intermediate of intermediate frames 14 and 15, which are similar to the corresponding parts described in relation to Fig. 1. According to Fig. 2, the intermediate frame 14 is not connected to the bearing support 92 of the centre roll 16, but, in addition to its fastening taking place by means of the horizontal articulated joints 14a, the intermediate frame 14 is attached in connection with the front frame 40 by means of openable intermediate pieces 51 in a way corresponding to Fig. 1. Opening of the intermediate pieces 51 and pivoting of the frame 14 around its horizontal articulated joints 14a are, as a rule, necessary only when the suction roll 13 and the press roll 13′ of the second nip N₂, placed above the suction roll 13, are replaced. The arrangement of the third nip N₃ and the arrangement of the third fabric 30 are similar to what is described in Fig. 1. The press section in accordance with Fig. 2 does not have a fourth nip, but the web is passed from the centre roll 16 onto the drying fabric 49, which carries the web further into the drying section, which consists of the lines of drying cylinders 47 and 48. In the press section shown in Figs. 2,3 and 4, an essential feature is the difference in height H between the central axes of the suction roll 13 and of the centre roll (Fig. 3), which is, as a rule, of an order of H = 1...2.5 m. In this way, sufficiently large space is created in the press-roll combination so that a number of different parts can be fitted and supported on the different frame parts 50,60,70 without interfering with one another, whereby the replacement of press fabrics and rolls is also facilitated. The frame construction of a press section in accordance with the invention comprises a front frame 50 and a separate rear frame 60. The front frame 50 and the rear frame 60 are in such a way separate that they are separated by a space T open at the top, which said space can be utilized in accordance with the invention in replacement of press rolls. Said open space T also facilitates the replacement of the upper fabrics 10 and 30. The invention is also suitable for use in presses in which there are three nips in connection with the centre roll 16. The rear frame 60 in accordance with Figs. 2,3 and 4 includes a projection part 70, on which the centre roll 16 of the press is supported and journalled from below. Said projection part 70 may also be separate in relation to the front frame 50 and to the rear frame 60, being, however, arranged so that the lower fabric 20 can be replaced. In the following, with reference to Fig. 3, the replacement of the different fabrics 10,20,30 will be described in connection with a frame construction in accordance with Fig. 2. When the upper fabric 10 is being replaced, the old fabric is removed and the intermediate pieces 55 in the side part at the service side are opened so that free intermediate spaces 55A are opened at the side of the service side of the front frame 50. The suction roll 11 is shifted to the open position 11A. The press roll 13′ placed inside the fabric loop 10 is shifted to the position 13A that opens the nip N₂ by pivoting the intermediate frame 14 to the position 14A by means of the gear 18A. The nip N₁ is opened by means of the power units 24. In order that all the rolls to be placed inside the loop of the fabric 10 could be located close enough to one another, the upper guide roll 12a, placed on the tensioning devices 25, is shifted along the route A to its parking site to the position 12A. Likewise, the second guide roll 12b above the front frame 50 is shifted to its parking site, placed on the projection part 52 of the front frame, to the lower position 12B. When the pick-up point P and the nips N₁ and N₂ are open and the rolls 12a and 12b in the lower positions 12A and 12B as well as when the intermediate pieces 55 have been opened, the fresh fabric loop is passed through the intermediate spaces 55A at the service-side side frame to form a loop 10A in accordance with Fig. 3 opened from the fabric roll 200, which said roll 200 is suspended on a replacement pole 205. The replacement pole 205 is supported from both of its ends by means of lifting wires 210, which are attached to the traversing crane (not shown) in the paper machine hall. Hereinafter the loop 10A is widened to full width and length by unwinding the fabric 10 from the two-fold roll 200 while, at the same time, shifting the guide rolls 12A and 12B to their normal operation positions along the routes A and B. After the fabric 10 has been spread out and tensioned, the pick-up point P and the nips N₁ and N₂ are closed and the intermediate pieces 55 and the fabric 10 are tightened. When the lower fabric 20 is being replaced, the guide roll 22a placed in the basement on the tensioning means 86 is shifted along the route E to the upper position 22A, the lowest intermediate piece 55 as well as the intermediate pieces 56 are opened so that open spaces 56A are formed, and the fabric loop 20A is passed from the roll 400 to around the beams 112,113, the press roll 21, and the guide rolls 22, whereupon the intermediate pieces 55 and 56 are closed, the roll 22A is shifted into the basement space, and the fabric 20 is tensioned by means of the devices 86. According to Fig. 3, the second upper fabric 30 is replaced so that the old fabric is removed, the intermediate pieces 65 are opened, and the foremost guide roll 32a is shifted along the route C to its parking site in the inner position 32A. Correspondingly, the rearmost guide roll 32b is shifted along the route D to its parking site alongside the roll 32A to the position 32B. The nip N₃ is opened by shifting its roll 31 to the upper position 31A by pivoting the intermediate part 61 to the position 61A by means of the power units 63B. Hereupon the fabric roll 300 supported by the replacement pole 305 and the lifting wires 310, having been spread out into a loop 30A, is passed to around the press roll 31A and the guide rolls 32,32A and 32B through the intermediate spaces 65A, whereupon the rolls 32A and 32B are shifted along the routes C and D to their operating positions while at the same time unwinding and spreading the fabric 30A from the roll 300, whereinafter the nip N₃ is closed, the fabric 30 is tensioned by means of the tensioning devices 68 of its guide roll 32b. Within the scope of the invention, it is also possible to use seamable press and transfer fabrics. In such a case, no openable intermediate pieces 55,56 and 65 are needed in the frame parts. In the following, with reference to Fig. 4, the replacement of the pick-up roll 11 and of the different press rolls will be described. When the pick-up roll 11 is being replaced, it is in the position 11B and the fabric 20 has been removed. The loops 221 of the pairs of lifting wires 220 are attached to the axle journals of the pick-up roll 11B. The lifting wires 220 are attached to the traversing crane in the paper machine hall. The hollow-faced press roll 13′ of the second nip N₂ is replaced so that the intermediate frame 14 is pivoted by means of the power units 18B to the open position 14B, whereby the guide roll 12 of the fabric 10 is also shifted to the inner position 12′. In this way a relatively large space is opened between the centre roll 16 and the press roll 13B′. The axle journals of the press roll 13B′ are attached to the lifting loops 121 of the lifting wire 120, and the lifting is carried out by means of the lifting hooks 125 of the traversing crane. The upper roll 13 of the first nip N₁ is replaced after removal of the roll 13B′ by making use of the open space T between the frame parts 50 and 60. The roll 13B (suction roll) may also be replaced by means of lengthwise pulling without removing the roll 13B′. After the fabric 10 has been removed, the roll 13B is suspended on the hook 340 by means of the loops 341, detached from its bearing supports, and lifted by means of the traversing crane, by making use of the space T, to above the press section. The lower roll 21 of the first nips N₁ is replaced after removal of the rolls 13 and 13′ by making use of the space T so that the roll 21 is detached from its bearing supports and supported on the wire loops 251 from its axle journals. Hereinafter the roll 21 is lifted up by means of the lifting wires, or removed by means of lengthwise pulling by making use of the roll-out beam placed underneath the roll and of the roll-out carriage at the operation side as an aid. The centre roll 16 is replaced by lifting it on the lifting loops 441 on the lifting hook 440 by making use of the space T. The upper roll 31B of the third nip N₃ is replaced by lifting by means of the wire loops 541 on the lifting hook 540 by making use of the space T. According to Figs. 1 and 2, the guide rolls 12 and 32a of the fabrics 10 and 30 are placed substantially at the same level. Between these rolls there is a constantly open space T o , which is placed above the second nip N₂, because the first intermediate-frame part 14 is not connected to the bearing supports 93 of the centre roll 16, but it is connected to the rear side of the front frame 50 by means of the intermediate parts 51. In stead of the supporting by the axle journals, which was described above, the press rolls, at least the heaviest ones, can also be lifted as so-called centre lifting, wherein the lifting takes place by means of one lifting wire, which is placed at the vertical plane of the centre of gravity of the roll to be lifted, lifting loops arranged in the form of a downwardly open V being provided around the roll at both sides of said plane. Centre lifting provides the advantage that, by its means, the roll can be turned more freely above the frame construction of the press section to the machine direction, whereby displacement of the roll becomes easier. The new rolls can be brought to their place in a corresponding way. The new rolls are brought to their place by performing the operations described above in the reversed sequence. In the following, the patent claims will be given, whereat the various details of the invention may show variation within the scope of the inventive idea defined in said claims and differ from the details given above by way of example only.

Claims: Press section of a paper machine, provided with a frame construction which comprises, in the direction of running of the paper web (W), first a front frame (50) and after that a rear frame (60), whereby in connection with said front frame and rear frame (50,60) and a possible intermediate frame (70,90), press rolls (13,13',16, 21,31) are mounted, which form a relatively compact press roll combination, in which there are press nips (N₁,N₂,N₃) formed between press rolls, press fabrics (10,30,40) being passed through said nips, and wherein said frame construction further comprises: an at least partly open space (T) between said front and rear frame (50,60), which are not directly connected to each other, and above said press roll combination, through which said space at least most of the press rolls in said press roll combination can be replaced and which said space also facilitates the replacement of the upper press fabrics (10,30); a press roll (13) or press rolls (13,13') of the press roll combination mounted in connection with the rear side of the front frame (50); a smooth-faced (16') centre roll (16) of the press, which is mounted in connection with the rear frame (60), preferably in connection with its projection part (70) or with a separate intermediate frame (90), and which forms the second nip (N₂) in the press together with the press roll (13,13') mentioned above, the press roll (13;13') which forms the second nip (N₂) in the press section and which is either a suction roll (13, Fig.1) or a hollow-faced (13'') press roll (13', Fig. 2), being attached to a first intermediate-frame part (14), which is separate from the rear and intermediate frames (60,70,90) and which is arranged pivotable by means of power units (18) around horizontal articulation shafts (14a) into connection with the front frame (50), said press roll (13;13') being connected to the first intermediate-frame part (14) by means of a second intermediate-frame part (15) by means of horizontally articulated joints (15a), enabling the second intermediate-frame part (15) to pivot around said horizontally articulated joint (15a) by means of power units (15b) so as to load the second nip (N₂), between the first intermediate-frame part (14) and the front frame (50), openable and lockable intermediate parts (51) being fitted, by means of which the first intermediate-frame part (14) can be fixed to the front frame (50) rigidly, and said intermediate parts (51) can be opened so that the first intermediate-frame part (14) can be pivoted towards the front frame (50) at least when the suction roll (13) in the press section is being replaced. Press section as claimed in claim 1, wherein above said intermediate-frame part (14) the guide roll (12) of the first upper felt (10) of the press is journalled. Press section as claimed in claim 1 or 2, wherein in connection with the first intermediate-frame part (14), by the intermediate of the second intermediate-frame part (15), the suction roll (13) of the press is journalled, in connection with which suction roll (13) the first, most appropriately two-felt (10,20), press nip (N₁) as well as the second press nip (N₂) are formed against the smooth-faced (16') centre roll (16) of the press, and in connection with which said centre roll (16), the third press nip (N₃) in the press is formed, which is mounted in connection with the front side of the rear frame (60) by the intermediate of a pivotable frame part (61) (Fig. 1). Press section as claimed in claim 1 or 2, wherein in connection with the rear side of the front frame (50), the suction roll (13) of the press is journalled stationarily, which said suction roll (13) forms the first nip (N₁) in the press together with the hollow-faced roll (21) placed underneath, and above said suction roll (13), at the distance of the gap (H), there is a hollow-faced press roll (13'), which is attached in connection with the second intermediate-frame part (15), which is again connected to the first intermediate-frame part (14) by means of horizontal articulated joints (15a), said hollow-faced (13'') press roll (13') forming the second nip (N₂) in the press above the first nip (N₁) in connection with the smooth-faced (16') centre roll (16), a third press nip (N₃) being formed further in connection with said centre roll (16) in connection with the hollow-faced roll (31), which said hollow-faced roll (31) is attached in connection with the front side of the rear frame (60) by means of a pivotable intermediate-frame part (61) (Fig. 2). Press section as claimed in any of the claims 1 to 4, wherein the first intermediate frame (14) consists of side frames, which are shaped substantially as angle arms, whose arm parts are, at the lower ends, attached in connection with the rear side of the front frame (50) by means of horizontal articulated joints (14a), said intermediate parts (51) being fitted between the vertical side of the first intermediate-frame part (14) and the opposite vertical rear side of the front frame (50), which said intermediate parts (51) can be opened and locked by means of eyebolts or other, corresponding locking members. Press section as claimed in claim 5, wherein, at its upper part, the second intermediate-frame part (15) is attached in connection with the outer part of the first intermediate-frame part (14) placed next to the rear frame (60) to be pivotable by means of hydraulic cylinders (15b) or equivalent fitted between the first and the second intermediate-frame parts (14,15). Press section as claimed in any of the claims 1 to 6, wherein the upper guide rolls (12a,12b) of the first upper fabric (10) can be shifted to inner positions (12a',12b'; 12A,12B) in connection with replacement of said upper fabric (10). Press section as claimed in any of the claims 1 to 7, wherein in connection with the bearing supports (93) of the centre roll (16) of the press, the foremost guide roll (32a) of the second upper fabric (30) is fitted, which is displaceable to an inner position (32a';32A) placed in connection with the rear frame (60) in relation to replacement of the second upper fabric (30). Press section as claimed in any of the claims 1 to 8, wherein the first intermediate-frame part (14) and the rearmost guide roll (12) of the first felt (10) placed in connection with same are placed substantially at the same level as the foremost guide roll (32a) of the second upper felt (30) and that between said guide rolls there is a constantly open intermediate space (T o ) above the second nip (N₂). Press section as claimed in any of the claims 1 to 9, wherein the rearmost guide roll (32b) of the second upper fabric (30) is displaceable to an inner position (32b; 32B) in connection with replacement of the second upper fabric (30).

Inventors: PAJULA JUHANI, PAJULA, JUHANI
Applicants: VALMET PAPER MACHINERY INC, VALMET PAPER MACHINERY INC.
Application year: 1989
Main classification: D21F3
IPC codes: D21F3, D21F7