WEB FINISHING SECTION IN A PAPER MACHINE

Abstract: The invention concerns a web finishing section in a paper machine, which finishing section comprises at least a dryer section composed of one or several dryer groups (RN), a calender (20), and a reel-up (30). The calender (20) is placed at least partly underneath the reel spool storage space (33) of the reel-up (30) so that the reel-up (30) is placed substantially directly after the calender (20), in which case the web is passed directly from the calendering nip onto the reel cylinder or to a substantially short distance from the calender (20), the web being passed over one guide member that supports and/or spreads the web onto the reel cylinder.

Description: Web finishing section in a paper machine The invention concerns a web finishing section in a paper machine, which finishing section comprises at least a dryer section composed of one or several dryer groups, a calender, and a reel-up. In the prior-art embodiments of finishing sections in paper machines, both before the calender and in particular from the calender to the reel-up, the web has long, substantially free or unsupported draws, which increases the length of the finishing section in the paper machine to a substantial extent and requires threading ropes for the threading of the leader of the web. Further, at these draws, various quality measurement devices are fitted for measurement and monitoring of the quality of the paper web. Costs have, of course, also arisen from the paper guide rolls required by the draws. Thus, the long draws of the paper web have also required threading ropes and related arrangements of equipment and equivalent, by whose means the leader of the paper web is carried during threading from one stage into the other, which has increased the costs of equipment further. The object of the invention is to provide a finishing section for a paper machine in which the problems described above have been eliminated or at least minimized. It is a further object of the invention to provide a finishing section for a paper machine in which the length of the finishing section can be made shorter compared with the solutions currently in use. In view of achieving the objectives stated above and those that will come out later, the finishing section in a paper machine in accordance with the present invention is mainly characterized in that the calender is placed at least partly underneath the reel spool storage space of the reel-up so that the reel-up is placed substantially directly after the calender, in which case the web is passed directly from the calendering nip onto the reel cylinder or to a substantially short distance from the calender, the web being passed over one guide member that supports and/or spreads the web onto the reel cylinder. The arrangement in accordance with the present invention permits a ropeless threading, because there are no long unsupported draws, in which case, for threading, it is possible to use, for example, guide plates and/ or equivalent suitable for full- width transfer of the web. For example, in an application in which the calender is a belt calender and the reel-up is a belt reel-up, ropeless threading can be arranged particularly simply so that the web is passed from the last drying cylinder in the dryer section by means of guide plates or equivalent directly onto the belt in the belt calender, on whose belt the web is passed through the calendering nips and further onto the belt in the belt reel-up. One belt calender is described in the applicant's FI Patent Application No. 931021, and one application of a belt reel-up is described in the applicant's FI Patent Application No. 935669. The arrangement in accordance with the present invention is partly made possible by the fact that, at present, various quality meters are in themselves known whose size is considerably smaller than the size of meters that were in use earlier, in which case such meters can be fitted in a simple way in connection with a calender, in particular with a soft calender, and/or with a reel-up without a separate support construction provided for such meters. By means of an arrangement in accordance with the invention, considerable economies of length are obtained in the finishing section, which economies of length correspond, for example, to a distance in which a group consisting of six drying cylinders can be accommodated, in which case the capacity of the dryer section can be increased without changing the overall length of the machine. On the other hand, with the same overall length, the production rate can be increased, for example, from 615 tons to 735 tons per day, or the speed from 1500 metres per minute to 1800 metres per minute, which corresponds to an increase in production of about 16 per cent. Of course, owing to the present invention, it is also possible to construct a machine of shorter length, compared with the prior art, with unchanged capacity, in which case economies can be obtained, for example, in the costs of construction of the paper machine hall, which costs in themselves constitute a major cost item, since the cost per metre of a paper machine hall is about one million FIM. By means of an arrangement in accordance with the invention, modernizations of existing paper machines in view of increasing their capacity are also made possible, which modernizations could not be carried out earlier because of lack of space. In the arrangement in accordance with the invention, the short web draws after the calender permit a full-width threading of the web based on a what is called coanda effect, because the exclusively airborne support and guiding of the web, which is difficult to control over unduly long distances, can be reduced to the minimum. In the arrangement in accordance with the invention, economies are also obtained in the paper guide rolls (2 rolls), and just one pulper is needed, because a common pulper can be used for the dryer section and for the reel-up as the distance between them becomes shorter. If cooling of the web is needed between the calender and the reel-up, it is possible to use various cooling devices in themselves known, such as a blow box. The advantages of the present invention are manifested particularly well in a combination of a soft calender and a reel-up marketed by the applicant with the trade mark Optireel™, which reel-up is described in more detail, e.g. , in the applicant's FI Patent Application No. 905284 (equivalent to US Patent No. 5,251,835). In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing, the invention being, however, not supposed to be in any way strictly confined to the details of said illustrations. Figure 1A is a schematic illustration of a prior-art arrangement, in which the last group in the dryer section is a dryer group with twin-wire draw. In Fig. IB the finishing section shown in Fig. 1A is illustrated schematically as an arrangement in accordance with the present invention. Figure 2A is a schematic illustration of a prior-art arrangement of a finishing section in a paper machine, wherein the last group in the dryer section has been arranged as a group with single- wire draw, and Figure 2B is a schematic illustration of the finishing section of Fig. 2 A in a paper machine, wherein an arrangement in accordance with the present invention is used. In the following figures, corresponding reference numerals refer to corresponding parts, and the letter symbol A refers to arrangements known from the prior art. In the prior-art arrangement shown in Fig. 1A, the last dryer group RA N in the dryer section in the finishing section makes use of twin-wire draw, after which group the web is passed as a draw 26 A to the soft calender 20 A, which is followed by a second draw 25A, supported by paper guide rolls 27A, to the reel-up 30A. The pulpers 41 A and 42 A of the dryer section and of the reel-up are placed below the machine level in the so-called basement space. In the twin-wire draw in the dryer group RA N the wires 10A,11A run, being guided by the guide rolls 16A,17A, over the drying cylinders 12A,13A and the reversing rolls 14A,15A in the mode of twin-wire draw. Between the rows of drying cylinders 12 A, 13 A the web has free draws. From the dryer group RA N the paper web is passed over the guide roll 28 A as the draw 26 A into the first calendering nip NNi in the calender 20A, from which the web is passed further into the second calender- ing nip NA 2 , and from there as the draw 25 A over the guide rolls 27 A to the reel-up 30 A, whose storage space for reel spools is denoted with the reference numeral 33 A, the reel spool change devices with 34A, the reel cylinder with 31 A, and the paper reel that is being formed with the reference 32A, and the complete machine reel with the reference 35A. As is shown in Fig. IB, the length of the finishing section in the paper machine has been made shorter so that the draws 26A,25A between the last dryer group R N and the soft calender 20 and between the soft calender 20 and the reel-up 30 have become substantially shorter. The reel spool storage space 33 of the reel-up 30 is placed above the soft calender 20, and the pulpers of the dryer section and of the reel-up have been combined as a single pulper 41. In the dryer group R N the drying wires are denoted with the reference numerals 10,11, and they run, guided by the guide rolls 16,17, over the drying cylinders 12,13 and the reversing rolls 14,15. Between the rows of drying cylinders 12,13 the web has free draws. From the last drying cylinder the web is passed as a short draw over the roll 28 into the first calender nip N j in the calender 20, from which it is passed into the second calender nip N 2 . Over the roll 37, past the quality meter 29, the web is passed over the reel cylinder 31 to be reeled as the paper reel 32. The reel spool storage space in the reel-up 30 is denoted with the reference numeral 33, the reel spool change device with the reference 34, and the complete machine reel with the reference 35. As is shown in Figs. 1A and IB, economies of length are achieved in the arrangement in accordance with the invention. By way of example, it can be stated that in an embodiment the economies of length L j in a transition from an arrangement as shown in Fig. 1A into an arrangement as shown in Fig. IB are 7650 mm. Fig. 2 A is a schematic illustration of a prior-art arrangement for a finishing section in a paper machine, in which the last dryer group RA N in the dryer section is a dryer group with single-wire draw. The pulper 41 A of the last dryer group RA N is placed in the basement space. From the last dryer group RA N the paper web is passed as the draw 26 A to the soft calender 20A, where it is calendered from both sides in calendering nips NA l 5 NA 2 , after which the web is passed to the reel-up 30A, where a machine reel 32A,35A is formed out of the web. In the dryer group RA N in the dryer section the drying wire is denoted with the reference numeral 50A, the wire guide rolls are denoted with the reference 51 A, the drying cylinders with the reference 52A, and the vac rolls in the lower row with the reference 53A. The paper web to be dried runs, in the single-wire draw, from the drying cylinders 52 A onto the reversing rolls 53 A while constantly supported by the drying wire 50 A. After this, the run of the web further is similar to the arrangement shown in Fig. 1A. In the embodiment shown in Fig. 2A, a quality measurement device 29 A is fitted between the calender 20A and the reel-up 30A. In the schematic illustration of the embodiment shown in Fig. 2B, the finishing section in the paper machine has been made shorter in accordance with the invention, in which connection the draw 26 from the dryer section to the soft calender 20 has been made slightly shorter and the draw from the soft calender 20 to the reel-up 30 has been eliminated completely as the reel spool storage space 33 in the reel-up 30 has been placed above the soft calender 20, whereby considerable economies of space have been achieved. The dryer group R N is a dryer group with single- wire draw, in which the paper web runs on the support of the drying wire 50 from the drying cylinders 52 in the upper row onto the vac rolls 53, which are placed in the lower row. The wire 50 guide rolls are denoted with the reference numeral 51. The draw in the final part of the finishing section is substantially similar to that described above in relation to Fig. IB. In a transition from the arrangement of Fig. 2 A to the arrangement of Fig. 2B, the economies of length L2 that are achieved are, for example, 6300 mm. In accordance with the invention, when the finishing section is made shorter, the upper roll of the second nip N 2 in the soft calender 20 can be raised from the machine directly upwards through the reel spool storage space 33, which results in an easy and quick replacement of the roll, i.e. the production efficiency of the machine is increased as the time taken by the change of roll becomes shorter. In the reel spool storage space 33 above said roll, parts, for example latches or equivalent, are opened and permit lifting of the roll through the frame system of the reel spool storage space 33. The frame system of the reel spool storage space 33 is supported on the floor level by means of columns of its own from outside the frame system of the soft calender 20 in order to avoid detrimental effects of oscillations in the soft calender 20. The frame system is supported from both of its ends in the machine direction. By means of the operations described above, easy and quick change of roll is achieved in the soft calender 20, and oscillation-free storage 33 is obtained for the reel spools. Spreading of the effects of formation of dust that may occur in the reel- up 30 to the calender 20 is prevented by, if necessary, constructing an air jet and/or a detachable shield wall (not shown) between the calender 20 and the reel-up 30. A quality measurement beam is constructed between the columns placed between the calender 20 and the reel-up 30 in an integrated way in consideration of attenuation of vibrations. For the reel-up 30 and for the calender 20, just one pulper 41 is needed, which is installed so that the web can be passed from the dryer section R N , from the calender 20 and from the reel-up 30 into the pulper. The chutes 45 of the pulper 41 are designed sufficiently long and, if necessary, the pulper 41 is mounted sufficiently far down below in order to provide an inclination downwards. The frame of the reeling equipment 30 is separate from the frames of the reel spool storage space 33 and of the calender 20, in which case vibrations and resonance of different components are avoided. In Figs. IB and 2B, some preferred exemplifying embodiments are illustrated of the web finishing section in accordance with the invention in a paper machine. This is, of course, not supposed to confine the invention to such finishing sections alone, but variations of many other, different types are also possible. For example, in stead of the cylinder dryer groups illustrated in the figures, the dryer groups can be con- structed, for example, by employing a dryer concept based on the heat pipe effect (CONDEBELT), by means of airborne web dryers, dryers based on infrared radiation, etc. Of course, the reel-up and the calender shown in the figures can also differ from the embodiments illustrated in the figures. For example, in stead of a soft calender it is possible to use calenders of different types, a machine stack, a supercalender, etc. Above, the invention has been described with reference to some preferred exemplifying embodiments of same only, and the invention is by no means supposed to be strictly confined to the details of said embodiments. Many variations and modifications are possible within the scope of the inventive idea defined in the following patent claims.

Claims: Claims 1. A web finishing section in a paper machine, which finishing section comprises at least a dryer section composed of one or several dryer groups (R^), a calender (20), and a reel-up (30), characterized in that the calender (20) is placed at least partly underneath the reel spool storage space (33) of the reel-up (30) so that the reel-up (30) is placed substantially directly after the calender (20), in which case the web is passed directly from the calendering nip onto the reel cylinder or to a substantially short distance from the calender (20), the web being passed over one guide member that supports and/or spreads the web onto the reel cylinder. 2. A finishing section as claimed in claim 1, characterized in that the calender (20) is placed substantially directly after the last dryer group (R N ) in the dryer section, in which case the web is passed directly from the calendering nip onto the reel cylinder or to a substantially short distance from the last dryer group (R N ), the web being passed over one guide member that supports and/or spreads the web onto the reel cylinder. 3. A finishing section as claimed in claim 1 or 2, characterized in that the last dryer group (R N ) in the dryer section is a dryer group that makes use of twin-wire draw (FIG. IB). 4. A finishing section as claimed in claim 1 or 2, characterized in that the last dryer group (R N ) in the dryer section is a dryer group that makes use of single-wire draw (FIG. 2B). 5. A finishing section as claimed in claim 1 or 2, characterized in that the last dryer group in the dryer section is a dryer group based on the heat pipe effect. 6. A finishing section as claimed in claim 1 or 2, characterized in that the last dryer group in the dryer section is a dryer group based on airborne web dryers. 7. A finishing section as claimed in claim 1 or 2, characterized in that the last dryer group in the dryer section is a dryer group based on infrared radiation drying. 8. A finishing section as claimed in any of the claims 1 to 7, characterized in that the calender is a soft calender (20). 9. A finishing section as claimed in any of the claims 1 to 7, characterized in that the calender is a machine stack. 10. A finishing section as claimed in any of the claims 1 to 7, characterized in that the calender is a supercalender. 11. A finishing section as claimed in any of the claims 1 to 10, characterized in that the latter calendering nip (N 2 ) in the calender (20) is placed completely under- neath the reel spool storage space (33) of the reel-up (30). 12. A finishing section as claimed in any of the claims 1 to 11, characterized in that the dryer section, the calender (20) and the reel-up (30) in the finishing section have a common pulper (41).

Inventors: KILPIAE JUKKA, LEHTONEN SIRKKA, RANTANEN JYRKI, KILPIAE, JUKKA, LEHTONEN, SIRKKA, RANTANEN, JYRKI
Applicants: KILPIAE JUKKA, LEHTONEN SIRKKA, RANTANEN JYRKI, VALMET CORP, KILPIAE, JUKKA, LEHTONEN, SIRKKA, RANTANEN, JYRKI, VALMET CORPORATION
Application year: 1998
Main classification: D21G1
IPC codes: B65H19, D21F5, D21G1