CA2133604A1 - Method in the drying of a paper web and a dryer section of a paper machine - Google Patents
Method in the drying of a paper web and a dryer section of a paper machineInfo
- Publication number
- CA2133604A1 CA2133604A1 CA002133604A CA2133604A CA2133604A1 CA 2133604 A1 CA2133604 A1 CA 2133604A1 CA 002133604 A CA002133604 A CA 002133604A CA 2133604 A CA2133604 A CA 2133604A CA 2133604 A1 CA2133604 A1 CA 2133604A1
- Authority
- CA
- Canada
- Prior art keywords
- drying
- cylinders
- wire
- paper web
- group
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000001035 drying Methods 0.000 title claims abstract description 135
- 238000000034 method Methods 0.000 title claims abstract description 25
- 239000007787 solid Substances 0.000 claims abstract description 12
- 238000003825 pressing Methods 0.000 claims abstract description 3
- 230000000694 effects Effects 0.000 claims description 6
- 238000007664 blowing Methods 0.000 claims description 5
- 230000005484 gravity Effects 0.000 claims description 3
- 238000009423 ventilation Methods 0.000 claims description 3
- 230000035699 permeability Effects 0.000 claims description 2
- 241001442654 Percnon planissimum Species 0.000 claims 1
- 230000000875 corresponding effect Effects 0.000 description 8
- 238000010276 construction Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 230000018109 developmental process Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000001627 detrimental effect Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000000543 intermediate Substances 0.000 description 2
- 241000183024 Populus tremula Species 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- KNHUKKLJHYUCFP-UHFFFAOYSA-N clofibrate Chemical group CCOC(=O)C(C)(C)OC1=CC=C(Cl)C=C1 KNHUKKLJHYUCFP-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- YSGSDAIMSCVPHG-UHFFFAOYSA-N valyl-methionine Chemical compound CSCCC(C(O)=O)NC(=O)C(N)C(C)C YSGSDAIMSCVPHG-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/02—Drying on cylinders
- D21F5/04—Drying on cylinders on two or more drying cylinders
Landscapes
- Paper (AREA)
Abstract
(57) Abstract Method and dryer section in contact drying of a paper web (W). The paper web (W) is dried by means of heated smooth-faced drying cylinders (10, 20A,20B) by using a number of successive so called normal groups (R1...RN) with single-wire draw, in which the drying cylinders (10) are placed in the upper row and the reversing suction cylinders (11) in the lower row. After the press section of the paper machine, the paper web (W) is dried initially in a number of successive groups (R1...RN) with single-wire draw by pressing the paper web (W) by means of the drying wire (15) of the cylinder group against the heated faces of the drying cylinders (10) and by, in each group (R1...RN) with single-wire draw, passing the paper web (W) on support of the same drying wire (15) from one drying cylinder (10) onto the other drying cylinder over reversing suction cylinders (11) or rolls. By means of the groups (R1...RN) with single-wire draw, the paper web (W) is dried to a dry solids content of k1 =
70...92 %. After the drying steps which were carried out exclusively by means of normal groups (R1...RN) with single-wire draw, the paper web (W) is dried immediately further by means of one single group (RTW) with twin-wire draw to its ultimate dry solids content.
70...92 %. After the drying steps which were carried out exclusively by means of normal groups (R1...RN) with single-wire draw, the paper web (W) is dried immediately further by means of one single group (RTW) with twin-wire draw to its ultimate dry solids content.
Description
~ 2 1 3 3 6 0 ~ ~
Method in the drying of a paper web and a dryer isection of a paper machine ~ -. ~'''""'"~
~e i vention concerns a me ho i con act-dr g of a paper web, wh re t e paper web is dried by means of heated smooth-faced drying cylinders by using a nunmber of successive so called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding reversing suction rolls in the lower row, in which method, after the press section of the paper machine, the paper web is dried initially in a number of successive groups with single-wire draw by pressing the paper web by means of the drying wire of the cylinder group against the heated faces of the drying cylinders and by, in each group with single-wire draw, passing the paper web on sup ort of ^ i -;;
the sarne drying wire from one drying cylinder onto the next drying cyL;inder over ' ' reversing suction cy]inders, and in which method, after the above drying steps, which were carried out exclusively by means of normal groups with single-wire draw, the paper web is dried immediately further by means of one single group with twin-wire draw to its ultimate dry solids content.
~urther, the invention concerns a dryer section of a paper machine, whose initial part is composed of a number of successive so-called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding suction rolls are placed in the lower row, and between which said normal groups the paper web to be dried has closed draws over ;; ;
the group gaps, and which said reversing suction cylinders havje been arranged to be ;
subjected to negative pressure, at least at ~eir drying-wire turning sectors, and in ; ;
which dryer section, after the last group with singl~wire draw, one single groupwith twin-wire draw is provided, in which there are two rows of drying cylinders, one row placed above the other.
-In the way known from prior art, in multi-cylinder dryers of paper machines, twin-wire draw andtor single-wire draw istare employed. In twin-wire draw, the groups - 213~60~1 of drying cylinders include two wires, which press the web, one from above and the other one from below, against the heated cylinder faces. Between the rows of drying cylinders, which are usually horizontal rows, the web has free and unsupported draws, which are susceptible of fluttering, which may again cause web breaks, inparticular since the web is still relatively moist and, therefore, of low strength. Ihis is why, in recent years, increasing use has been made of said single-wire draw, in which each group of drying cylinders has one drying wire only, on whose support the web runs through the whole group so that the drying wire presses the web on the drying cylinders against the heated cylinder faces, whereas, on the reversing cylinders or rolls between the drying cylinders, the web remains at the side of the outside curve. Thus, in single-wire draw, the drying cylinders are placed outside the wire loop and the reversing cylinders or rolls inside said loop.
In prior-art normal groups with single-wire draw, the heated drying cylinders are placed in the upper row and the reversing cylinders in the lower row, which rowsare, as a rule, horizontal and parallel to one another. In the applicant's ~I Patent No. S4,C27 (equivalent to US Pat. 4,202,113) it is suggested that the above normal groups with single~wire draw and so called inverted groups with single-wire draw be placed one after the other, in which said inverted groups the heated drying cylinders are placed in the lower row and the reversing suction cylinders or rolls in the upper row, the principal objective being to dry the web symmetrically from both of itssides. Also, Messrs. Beloit Corp. have made some suggestions for a dryer sectionthat comprises normal and inverted cylinder groups, in which respect reference is made to the published international patent applications WO 88/OC204 and WO
88/OC205. In the following, when ~e terms "normal (drying) group~ and "inverted~(drying) group" are used, what is meant is expressly the cylinder groups with single-wire draw of the sort mentioned above.
In dryer sections that comprise inverted and normal drying groups, various problems have occurred, for which problems the present invention is supposed to suggest novel efficient solutions. These problems include the large length of the dryer section, which increases the costs of the dryer section and of the machine hall.
: :
213 3 ~ o Ll Problems have also been encountered in the runnability of the dryer section and in ~:~
the threading of the web, problems arising from differences in the speeds of different wires, problems in the removal of broke especially in inverted groups, as well as problems related to the control of transverse shrinlcage of the web. As a rule, these S problems tend to become worse as the running speed of the paper machine becomes higher.
- .- . ,~, .- . .
With respeet to the prior art involved in and most closely related to the present invention, reference is made to the following patent publications and articles pub-10 lished in journals~
- W. Haessner, "Trocknungstechnik und deren Entwicklung; ~ ~ ~
DasPapier44, lOA, 1990 ~ ;
. . . . .
nThe Valmet Sym-Run Concept~, PaperAsia, May/Jun 1992 ;
15 - J. Yli-Kauppila, "Dryer Section for High Speed Paper Machinesn, Proceedfngs of the Nelsinki Symposium of Alternate Methods of Pulp and Paper :. . : . .
Drying, Helsinki June 4-7, 1991 ~ ;
- S. Palazzolo, "No~raw drying", Tappi Journal, September 1990 - W. Leitenberger, "Die Contirun-Trockenpartie fur schnellen, sicheren Bahnlaufn, Das Papier, Heft 6, 1992 - US Patents Nos. 3,753,298; 3,868,780; 4,602,439; 4,972,608; 4,982,513;
5,022,163; 5,065,529; 5,146,06, and US-5,177,880 ~ -- V. Korhonen and A. Kuhasalo, "Ropeless tail threading from press to reeln, World Pulp & Paper Technology 1993 25 - H. Lepisto und Pn Eskelinen, "Verbesserung der Lauff~ihighkeit scbneller Papiermaschinen mit Hilfe neuer Ventilationseinrichtungenn, Das Papier 1985, Heft lOA
- Lindberg, Juppi, Eskelinen, "High Speed Dryer Section Developments for Sheet Stabilityn, 78th ~nnual Meenng, Technical Secnon CPPA, 1992.
; ~ ~ `
With respect to the pdor art most closely related to the present invendon and not public on the date of prdordty of the present applicadon, reference is made to the -.. . :
:' ,: '". "; ,.~
- 2133~0'1 International Patent Application No. W093/022494 of Messrs. Beloit Corporation, which is equivalent to the EP Pat. Appl. 93910650.C and which bewne public on November 11, 1993, i.e. after the date of priority of the present application. ;~
S In the following, the problems and requirements of further development that have occurred in the prior-art dryer sections, for example, according to the patents and papers mentioned above, will be dealt with in more detail. As a background, it should be stated that the highest web speeds of paper machines are currently already of an order of 25 m/s (metres per second), but before long even the speed range of 10 25...40 m/s will be taken to use. In such a case, a bottle-neck for the runnability of a paper machine will, to an increasing extent, consist of the dryer section, which will, moreover, with the use of the prior-art dryer concepts, become quite long.
~- ~-- .' .,:.
In the inverted drying groups mentioned above, in the case of breaks, a problem consists of the removal of broke, for inverted groups are not self-cleaning by the -- ~-force of gravity. Thus, it is an object of the present invention to provide a dryer section in which no inverted groups are needed at all, but which, yet, meets theother requirements that are imposed. -In prior-art dryer sections in which exclusively groups with single-wire draw are used, in the last wire groups, considerable wear of the drying fabAcs has occurred, in particular in the manufacture of fine papers with a high content of fillers. An object of the present invention is also to reduce this problem, which occurs in the drying groups driven by the drying wire because of the considerable thickness of the drying wire. The differences in speed Imentioned~ above, together with a restricted ~ ~;
drying shAnkage, have caused web breaks in the last groups when exclusively single- i wire draw has been used, which problem is emphasized further if, in the groups with single-wire draw, small~iameter suction rolls proper are used that are provided with an inside suction box. In order to eliminate this problem, in some machines, it has ;
been even necessary to open some group gaps and to lower the level of negative pressure in the suction rolls. ~ ~
':' ' .: ,:.'', '...;
~ . ~ .: ,. . .:,, . . ~ ' ~'"'':'"
2133~0~
s . ~ .~ - .
It is an object of the present invention to provide a novel drying method and dryer ~ ~;
section in which an extreme end of the dryer section is used that is arranged in such a way that the paper web is given a possibility and time to be rela~ed in the free gaps so that any breaks arising from internal strains in the web are eliminated.
It is a further object of the present invention to provide a dryer section whose ;
.~. .
runnability can be brought to a particularly high level. ; ~
.,., , .~ . ~
Further, it is an object of the invention to provide a dryer sec~ion in which so called ~ ~, ropeless tail threading can be applied favourably over the entire length of the dryer ~ ~;
section in the machine direction, which contributes to making the constructions ; :i simpler and any standstill times shorter. ~ ~ ~
. ~
In view of achieving the objectives stated above and those that will come out later, lS the method of the invention is mainly characterized in that by means of said groups with single-wire draw the paper web is dried to a dry solids content of kl = 70...92 %, that, as said reversing suction cylinders, suction cylinders are used which have no inside suction box, the paper web being held on the drying wires by the inter-mediate of the perforated mantle and the grooves in the outside face of said cylinders 20 by means of a difference in pressure against the effect of centrifugal forces when the paper web is on the d~ying wire at the side of the outside curve, and/or that, on the runs between the drying cylinders and reversing cylinders or rolls in said groups with single-wire draw, differences in pressure that disturb the support contact of the paper web are prevented by means of blow boxes or equivalent.
On the other hand, the dryer section in accordance with the invention is mainly characterized in that differences in pressure that disturb the support contact between the drying wire and the paper web on the* joint runs from the drying cylinders onto the reversing suction cylinders in the groups with single-wire draw have been 30 reduced or prevented by means of air-blow devices or equivalent, and/or that said reversing suction cylinders are reversing suction cylinders that are provided with a peAorated mantle and with outside grooves subjected to a vacuum and which said . .-. . ~ . . -2 1 3 3 ~ O ~
: - -cylinders have no inside sucdon box. -~
According to the invention, in the single group with twin-wire draw placed at the end of the dryer section, it is favourably possible to employ free draws of the paper 5 web between the rows of cylinders, on which free draws the paper web is allowed to be relaxed. Alternatively or additionally, in the single group with twin-wire draw, it is also possible to use fully closed draws between the rows of cylinders, forexample closed draws æ described in Figs. 3 and 4 in the applicant's ~I Pstent No.
68,279 (equivalent to US Patent 4,602,439), or other, corresponding prior-art draw lO arrangements.
:"~ i In the dryer section in accordance with the invention, the transverse shrinkage of the ~ ~ ~
web may be increased very 1ittle in comparison to a situation in which the web i5 ~ S~.:
dried by means of a dryer section exclusively consisting of groups with single-wire draw, but espe~ally when a size press or a coating device is used after the dryer section, in the final product, in this respect, no disadvantageous difference is noticed that is unfavourable to the invention.
.
In the present invention, by means of a combination of a number of process stepsand constructional solutions in themselves known, it has been successfully possible to provide a dryer section that is more advantageous in respect of both its construc-tion and its runnabiliq, the paper produced by means of said dryer section having quality properties that meet even very high requirements, also as regards symmetry and dimensional stability.
1 1 , In the following, the invention will be described in detail with reference to some exemplifying embodiments of the invention illustrated schematically in the figures in ;~
the accompanying ~awing, the invention being by no means strictly conflned to the details of said embodiments. ~ -; ., . ~,.,: ~, Figure l is a schematic side view of a dryer section in accordance with the invention that makes use of the method of the invention.
.. i, i, , ....; .~
, ~ ~ ." -, : ,:
~` 2133~
Figure 2 shows a closed draw between a group with single-wire draw and a group with twin-wire draw and an alternative embodiment of a single group with twin-wire draw.
S Figure 3 shows such a final end of a dryer secdon in accordance with the inYention in which two cylinder groups are employed that are fitted in inclined planes, inparticular in view of reducing the length of the dryer secdon.
According to Fig. 1, the paper web W"l is brought into the dryer section from the 10 press section (not shown) onto the drying wire 15 of the first group Rl with single-wire draw, to which wire it is fixed by the effect of the negative pressure in the suction boxes 13. The dryer section includes N pieces of groups Rl,R2...RN with single-wire draw, between which the web W has a closed draw. In the dryer section in accordance with the invention, the number of the normal g,roups Rl N is N =
Method in the drying of a paper web and a dryer isection of a paper machine ~ -. ~'''""'"~
~e i vention concerns a me ho i con act-dr g of a paper web, wh re t e paper web is dried by means of heated smooth-faced drying cylinders by using a nunmber of successive so called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding reversing suction rolls in the lower row, in which method, after the press section of the paper machine, the paper web is dried initially in a number of successive groups with single-wire draw by pressing the paper web by means of the drying wire of the cylinder group against the heated faces of the drying cylinders and by, in each group with single-wire draw, passing the paper web on sup ort of ^ i -;;
the sarne drying wire from one drying cylinder onto the next drying cyL;inder over ' ' reversing suction cy]inders, and in which method, after the above drying steps, which were carried out exclusively by means of normal groups with single-wire draw, the paper web is dried immediately further by means of one single group with twin-wire draw to its ultimate dry solids content.
~urther, the invention concerns a dryer section of a paper machine, whose initial part is composed of a number of successive so-called normal groups with single-wire draw, in which the drying cylinders are placed in the upper row and the reversing suction cylinders or corresponding suction rolls are placed in the lower row, and between which said normal groups the paper web to be dried has closed draws over ;; ;
the group gaps, and which said reversing suction cylinders havje been arranged to be ;
subjected to negative pressure, at least at ~eir drying-wire turning sectors, and in ; ;
which dryer section, after the last group with singl~wire draw, one single groupwith twin-wire draw is provided, in which there are two rows of drying cylinders, one row placed above the other.
-In the way known from prior art, in multi-cylinder dryers of paper machines, twin-wire draw andtor single-wire draw istare employed. In twin-wire draw, the groups - 213~60~1 of drying cylinders include two wires, which press the web, one from above and the other one from below, against the heated cylinder faces. Between the rows of drying cylinders, which are usually horizontal rows, the web has free and unsupported draws, which are susceptible of fluttering, which may again cause web breaks, inparticular since the web is still relatively moist and, therefore, of low strength. Ihis is why, in recent years, increasing use has been made of said single-wire draw, in which each group of drying cylinders has one drying wire only, on whose support the web runs through the whole group so that the drying wire presses the web on the drying cylinders against the heated cylinder faces, whereas, on the reversing cylinders or rolls between the drying cylinders, the web remains at the side of the outside curve. Thus, in single-wire draw, the drying cylinders are placed outside the wire loop and the reversing cylinders or rolls inside said loop.
In prior-art normal groups with single-wire draw, the heated drying cylinders are placed in the upper row and the reversing cylinders in the lower row, which rowsare, as a rule, horizontal and parallel to one another. In the applicant's ~I Patent No. S4,C27 (equivalent to US Pat. 4,202,113) it is suggested that the above normal groups with single~wire draw and so called inverted groups with single-wire draw be placed one after the other, in which said inverted groups the heated drying cylinders are placed in the lower row and the reversing suction cylinders or rolls in the upper row, the principal objective being to dry the web symmetrically from both of itssides. Also, Messrs. Beloit Corp. have made some suggestions for a dryer sectionthat comprises normal and inverted cylinder groups, in which respect reference is made to the published international patent applications WO 88/OC204 and WO
88/OC205. In the following, when ~e terms "normal (drying) group~ and "inverted~(drying) group" are used, what is meant is expressly the cylinder groups with single-wire draw of the sort mentioned above.
In dryer sections that comprise inverted and normal drying groups, various problems have occurred, for which problems the present invention is supposed to suggest novel efficient solutions. These problems include the large length of the dryer section, which increases the costs of the dryer section and of the machine hall.
: :
213 3 ~ o Ll Problems have also been encountered in the runnability of the dryer section and in ~:~
the threading of the web, problems arising from differences in the speeds of different wires, problems in the removal of broke especially in inverted groups, as well as problems related to the control of transverse shrinlcage of the web. As a rule, these S problems tend to become worse as the running speed of the paper machine becomes higher.
- .- . ,~, .- . .
With respeet to the prior art involved in and most closely related to the present invention, reference is made to the following patent publications and articles pub-10 lished in journals~
- W. Haessner, "Trocknungstechnik und deren Entwicklung; ~ ~ ~
DasPapier44, lOA, 1990 ~ ;
. . . . .
nThe Valmet Sym-Run Concept~, PaperAsia, May/Jun 1992 ;
15 - J. Yli-Kauppila, "Dryer Section for High Speed Paper Machinesn, Proceedfngs of the Nelsinki Symposium of Alternate Methods of Pulp and Paper :. . : . .
Drying, Helsinki June 4-7, 1991 ~ ;
- S. Palazzolo, "No~raw drying", Tappi Journal, September 1990 - W. Leitenberger, "Die Contirun-Trockenpartie fur schnellen, sicheren Bahnlaufn, Das Papier, Heft 6, 1992 - US Patents Nos. 3,753,298; 3,868,780; 4,602,439; 4,972,608; 4,982,513;
5,022,163; 5,065,529; 5,146,06, and US-5,177,880 ~ -- V. Korhonen and A. Kuhasalo, "Ropeless tail threading from press to reeln, World Pulp & Paper Technology 1993 25 - H. Lepisto und Pn Eskelinen, "Verbesserung der Lauff~ihighkeit scbneller Papiermaschinen mit Hilfe neuer Ventilationseinrichtungenn, Das Papier 1985, Heft lOA
- Lindberg, Juppi, Eskelinen, "High Speed Dryer Section Developments for Sheet Stabilityn, 78th ~nnual Meenng, Technical Secnon CPPA, 1992.
; ~ ~ `
With respect to the pdor art most closely related to the present invendon and not public on the date of prdordty of the present applicadon, reference is made to the -.. . :
:' ,: '". "; ,.~
- 2133~0'1 International Patent Application No. W093/022494 of Messrs. Beloit Corporation, which is equivalent to the EP Pat. Appl. 93910650.C and which bewne public on November 11, 1993, i.e. after the date of priority of the present application. ;~
S In the following, the problems and requirements of further development that have occurred in the prior-art dryer sections, for example, according to the patents and papers mentioned above, will be dealt with in more detail. As a background, it should be stated that the highest web speeds of paper machines are currently already of an order of 25 m/s (metres per second), but before long even the speed range of 10 25...40 m/s will be taken to use. In such a case, a bottle-neck for the runnability of a paper machine will, to an increasing extent, consist of the dryer section, which will, moreover, with the use of the prior-art dryer concepts, become quite long.
~- ~-- .' .,:.
In the inverted drying groups mentioned above, in the case of breaks, a problem consists of the removal of broke, for inverted groups are not self-cleaning by the -- ~-force of gravity. Thus, it is an object of the present invention to provide a dryer section in which no inverted groups are needed at all, but which, yet, meets theother requirements that are imposed. -In prior-art dryer sections in which exclusively groups with single-wire draw are used, in the last wire groups, considerable wear of the drying fabAcs has occurred, in particular in the manufacture of fine papers with a high content of fillers. An object of the present invention is also to reduce this problem, which occurs in the drying groups driven by the drying wire because of the considerable thickness of the drying wire. The differences in speed Imentioned~ above, together with a restricted ~ ~;
drying shAnkage, have caused web breaks in the last groups when exclusively single- i wire draw has been used, which problem is emphasized further if, in the groups with single-wire draw, small~iameter suction rolls proper are used that are provided with an inside suction box. In order to eliminate this problem, in some machines, it has ;
been even necessary to open some group gaps and to lower the level of negative pressure in the suction rolls. ~ ~
':' ' .: ,:.'', '...;
~ . ~ .: ,. . .:,, . . ~ ' ~'"'':'"
2133~0~
s . ~ .~ - .
It is an object of the present invention to provide a novel drying method and dryer ~ ~;
section in which an extreme end of the dryer section is used that is arranged in such a way that the paper web is given a possibility and time to be rela~ed in the free gaps so that any breaks arising from internal strains in the web are eliminated.
It is a further object of the present invention to provide a dryer section whose ;
.~. .
runnability can be brought to a particularly high level. ; ~
.,., , .~ . ~
Further, it is an object of the invention to provide a dryer sec~ion in which so called ~ ~, ropeless tail threading can be applied favourably over the entire length of the dryer ~ ~;
section in the machine direction, which contributes to making the constructions ; :i simpler and any standstill times shorter. ~ ~ ~
. ~
In view of achieving the objectives stated above and those that will come out later, lS the method of the invention is mainly characterized in that by means of said groups with single-wire draw the paper web is dried to a dry solids content of kl = 70...92 %, that, as said reversing suction cylinders, suction cylinders are used which have no inside suction box, the paper web being held on the drying wires by the inter-mediate of the perforated mantle and the grooves in the outside face of said cylinders 20 by means of a difference in pressure against the effect of centrifugal forces when the paper web is on the d~ying wire at the side of the outside curve, and/or that, on the runs between the drying cylinders and reversing cylinders or rolls in said groups with single-wire draw, differences in pressure that disturb the support contact of the paper web are prevented by means of blow boxes or equivalent.
On the other hand, the dryer section in accordance with the invention is mainly characterized in that differences in pressure that disturb the support contact between the drying wire and the paper web on the* joint runs from the drying cylinders onto the reversing suction cylinders in the groups with single-wire draw have been 30 reduced or prevented by means of air-blow devices or equivalent, and/or that said reversing suction cylinders are reversing suction cylinders that are provided with a peAorated mantle and with outside grooves subjected to a vacuum and which said . .-. . ~ . . -2 1 3 3 ~ O ~
: - -cylinders have no inside sucdon box. -~
According to the invention, in the single group with twin-wire draw placed at the end of the dryer section, it is favourably possible to employ free draws of the paper 5 web between the rows of cylinders, on which free draws the paper web is allowed to be relaxed. Alternatively or additionally, in the single group with twin-wire draw, it is also possible to use fully closed draws between the rows of cylinders, forexample closed draws æ described in Figs. 3 and 4 in the applicant's ~I Pstent No.
68,279 (equivalent to US Patent 4,602,439), or other, corresponding prior-art draw lO arrangements.
:"~ i In the dryer section in accordance with the invention, the transverse shrinkage of the ~ ~ ~
web may be increased very 1ittle in comparison to a situation in which the web i5 ~ S~.:
dried by means of a dryer section exclusively consisting of groups with single-wire draw, but espe~ally when a size press or a coating device is used after the dryer section, in the final product, in this respect, no disadvantageous difference is noticed that is unfavourable to the invention.
.
In the present invention, by means of a combination of a number of process stepsand constructional solutions in themselves known, it has been successfully possible to provide a dryer section that is more advantageous in respect of both its construc-tion and its runnabiliq, the paper produced by means of said dryer section having quality properties that meet even very high requirements, also as regards symmetry and dimensional stability.
1 1 , In the following, the invention will be described in detail with reference to some exemplifying embodiments of the invention illustrated schematically in the figures in ;~
the accompanying ~awing, the invention being by no means strictly conflned to the details of said embodiments. ~ -; ., . ~,.,: ~, Figure l is a schematic side view of a dryer section in accordance with the invention that makes use of the method of the invention.
.. i, i, , ....; .~
, ~ ~ ." -, : ,:
~` 2133~
Figure 2 shows a closed draw between a group with single-wire draw and a group with twin-wire draw and an alternative embodiment of a single group with twin-wire draw.
S Figure 3 shows such a final end of a dryer secdon in accordance with the inYention in which two cylinder groups are employed that are fitted in inclined planes, inparticular in view of reducing the length of the dryer secdon.
According to Fig. 1, the paper web W"l is brought into the dryer section from the 10 press section (not shown) onto the drying wire 15 of the first group Rl with single-wire draw, to which wire it is fixed by the effect of the negative pressure in the suction boxes 13. The dryer section includes N pieces of groups Rl,R2...RN with single-wire draw, between which the web W has a closed draw. In the dryer section in accordance with the invention, the number of the normal g,roups Rl N is N =
3.. 9, preferably N = 5.. 7, and typically N = 6. All the groups Rl.. RN wi~
single-wire draw are s~called normal groups, in which the, e.g., steam-heated smooth-faced drying cylinders 10 are placed in the upper horizontal row and the reversing suction cylinders 11 or equivalent suction rolls are placed in the lower horizontal row. In the last normal group RN, the last two upper cylinders 10' and 20 the single reversing suction cylinder 11' placed between them are placed at a level by the dimension H3 higher than in the preceding groups Rl...RN l. The dimensionH3 is typically H3 ~ 400 mm. The frame part 100 of the dryer section is illustrated quite schematically.
""'",',".. ".,, .,,, ' 25 i Each nor nal group Rll.,..RN has~ a drying wire 15 of its own, which is guided by guide rolls 18. The drying wires 15 press the web W to be dried on the drying ~ ;
cylinders 10 against their smooth heated face, and on the reversing cylinders ll the web W remains at the side of the outside curve on ~he outside face of the wire 15. ~ ;
On the reversing cylinders 11 the web W is ~ept reliably on support of the wire 15 against the effect of centrifugal forces by the effect of the negative pressure present ~ ~, in the grooved faces 12 of the reversing cylindas 11 , whereby transverse shrinkage of the web W is also prevented. The reversiDg suction cylinders 11 that are used are `
2 1 3 3 ~
preferably suction cylinders 11 marketed by the applicant under the trade mark "VAC-ROLLnTM, which cylinders have no inside suction boxes, which cylinders are provided with a perforated mantle and with outside grooves that are subjected to a vacuum, and in respect with whose constructional details reference is made to the applicant's ~I Patent No. 83,680 (equivalent to US Pat. No. S,022,163). The diameters D2 f these suction cylinders 11 are substantially larger than the diameters of normal suction rolls that are provided with an inside suction box and that are used in corresponding positions. Hereby, the remarkable advantage is obtained that, on the turning sectors on the reversing cylinders 11, the web W is subjected to lower centrifugal forces, whereby a more reliable transfer is achieved and/or it is possible to use a lower vacuum level in the grooved faces 12 of the reversing cylinders, compared with normal suction rolls.
In a preferred embodiment of the invention, the support contact between the web W
and the drying wire 15 is.also kept good on the straight runs between the dryingcylinders 10 and the reversing cylinders 11, at least on the runs talcing place from the drying cylinders 10 to the reversing cylinders 12, by using blow-suction boxes 17, by whose means formation of negative pressures induced by the wire lS is prevented in the closing wedge-shaped nip spaces between the wire lS and the cylinder 12 mantle. In respect of the details of the constructions of these blow-suction boxes 17, which are marketed by the applicant under the trade mark "UNO
RUN BLOW BO~nTM, reference is made to the applicant's ~I Patents Nos.
S9,C37, 65,460, and 80,491 (equivalent to US Pats. Nos. 4,441,263, 4,515,330, and 4,905,380. After the introduction of the "UNO RUN BLOW BOX"TM, the applicant's competitors~ have also suggested some blow-box solutions, in whose respect reference is made to the US Patents 4,502,231 U.M. Voith GmbH) and 4,661,198 (Beloit Corp.), whose applications in the positions of the blow boxes 17 are also included in the scope of the overall concept of the present invention.
30 In the groups RlRN with single-wire draw, blow boxes 16 are also used in the gaps between the reversing cylinders 12, by means of which boxes said intermediate spaces are air~onditioned and evaporation from the web W is promoted. The faces 2133~0~
9 ::'.' -.,.,' of the drying cylinders 10 are kept clean by the doctors 14.
In the invention, it is a further essential feature and advantage that broke removal by the force of gravity can be applied in the groups Rl...RN with single-wire draw,5 which extend over the m~jor part of the overall length L of the dryer section, for the groups Rl. ..RN with single-wire draw are open towards the bottom so that the paper web WS that becomes broke can be removed without any particular arrangements onto the broke conveyor (not shown) placed in the basement space of the paper machine. ~ ~-.: .
It is an essential feature of the method of the invention that, in the normal groups ~ -R1 N~ the web W has time to reach a certain, quite high dry solids content of kl~ 70 %92 ~O, preferably kl ~ 80 % 85 %, depending on thepaper grade. At this dry solids content kl, the web W is so strong that, for its further drying, it is 15 possible to apply a group with twin-wire draw without a risk of detrimental breaks.
Thus, it is an essential feature of the invention that, in the final end of the dryer - ~ ~;
section, there is expressly just one single group RrW with twin-wire draw. In this ;
single twin-wire group RTW, there are two horizontal rows of contact-drying . ~
cylinders 20A and 20B, one row placed above the other, of which cylinders, in ;
20 connection with the upper cylinders 20A, there is an upper wire 25A, which isguided by wire guide rolls 21A fitted in the gaps between the cylinders 20A and by other guide rolls 28. The web W is pressed into a drying contact against the heated faces of the lower cylinders 20B by means of the lowa wire 25B, which is guided by the wire guide rolls 21B fitted in the gaps between the cylinders 20B and by other 25 ~ guide rolls 28.
According to Fig. 1, in the twin-wire group RIW~ a draw arrangement marketed by ~ ''h2'~
the applicant under the trade mark ~ RUNnTM is used, in which ~e guide rolls 21A and 21B are placed so that the drying wires 25A and 25B accompany the web from the drying cylinders 20A and 20B onto the next one so that the free draws ~ ~ `
W0 of the web W can be made shorter, as compared with free draws of full length.In this draw arrangement, at the proximity of the wire guide rolls 21A and 21B and - 2133~0~ ~
at the inlet side of the web W and the drying wire 25A and 25B, air-blow bo~ces 22A,22B are used. Out of the blow bo~es æA,22B, which are used in the "IW~I-RUN"lM concept and which are fitted in the gaps between the drying cylinders 20A,20B, air jets of suitable direction and blow velociq are applied to the viciniq 5 of the runs of the drying wires 25A,25B placed at their proximiq and to the viciniq of the free sectors of the wire guide rolls 21A,21B, by means of which jets the support contact between the drying wires 25A,25B and the web W is promoted, formation of detrimental differences in pressure and fluttering of the web W on the free draws W0 are prevented. Said blowings can also be applied through the drying 10 wires 25A,25B, whereby it is possible to promote the ventilation of the pocket spaces P formed in the gaps between the drying cylinders 20A,20B. With respect to the further details of the "TWIN-RUN"TM concept and of the blow bw~es æA,22B, re~erence is made to the applicant's ~I Pat. 80,103 (equiv. to DE Pat. 3,818,600).
In connection with the drying cylinders 20A,20B, there are doctors 24. Accordingto Pig. 1, the last two cylinders 10' in the last normal group RN are placed in the - ;;~
same horizontal plane as the upper cylinders 20A in the single twin-wire group Rn whereby it is possible to guarantee a transfer of the web W free of problems.
According to Pig. 1, the web W is passed from the last cylinder in thc last normal 20 group RN onto the first lower cylinder 20B in the single twin-wire group RTW as an open draw Wl, whose arrangement is similar to the free draws W0 of the web W in the twin-wire group RTW-.Y . ;: ~:
In Pig. 1, the overall horizontal length of the dryer section in the machine direction 25 ' is L # 70 m when siX normal groups Rl N (N = 6) are used, and the correspon ;~
ding horizontal length of the singb twin-wire group RTW is LrW # 10 m, when fouruppcr cylinders 20A and four lower cylinders 20B are used in the twin-wire groupRlW. In the example of dimensioning given above, the length L~w f the twin-wiregroup RTW is about 14 % of the overall length. As a rule, the length of the single ~ ~
tvin-wire group L,rW is about 10.. 20 %, preferably 12.. 16 ~O, of the overall ~ ;
horizontal length L of the dryer section. In a dryer section concept in accordance ~ ;~
with this example of dimensioning, in practice, a reduction of about 5 metres is' ~.' '~ ', ~,, ;.
' ' ~ ~'. ` " '"':
21335~'~
achieved in the overall length L of the dryer section, as compared with a situation in which exclusively groups with single-wire draw are employed, and in this way the costs of the construction investment in the paper machine hall and the other costs indirectly related to se are also reduced considerably.
The number Nl of the drying cylinders 10 used in each of the normal groups R
is in a range of Nl = 4...8, preferably Nl = 5...7, and the to~l number of the drying cylinders 20A and 20B used in the single twin-wire group RTW is N2 a 4...14, preferably N2 = 8...10.
In view of prevention of transverse shrinkage of the web W, it is particularly important that, in particular in the dry solids content of k > 65 % of the web W, the web is kept constantly in reliable contact with the drying wires 15. This holding effect is produced on the reversing cylinders 11 by means of the negative pressure 15 present in the grooved mantle 12 of their outer face and on the straight draws between the cylinders 10 and the reversing cylinders 11 by means of the pressurelevels arranged by means of blow-suction boxes 17.
Fig. 2 shows an embodiment of the invention in which a closed draw Wc of thc web20 W is employed between the last normal group RN and the twin-wire group R~v which closed draw has been achieved by passing the drying wire 15 and the web W
supported on it into contact with the first upper cylinder 20A in the single twin-wire group RT~ to whose smooth face the web W adheres and is transferred, being pressed by the upper wire 25A guided by the guide roll 2&, over the first upper 25 cylinder 20A in the group RTW. In Fig. 2, the guide rolls 21A, and 21B placed, in the gaps between the drying cylinders 20A and 20B are placed symmetrically in the ccntre plane passing through the centre a~is of the adjacent drying cylinder, in which case the free draws W0 of the web W passing between the rows of cylinders 20A
and 20B are of full length and unshortened, differing from the ~TwIN RuN~
30 arrangement shown in Fig. 1. This solution is also included in the scope of the present invention even though it is not in all cases equally advantageous as theshortened free gaps W0 shown in Fig. 1. A drawback of the free draws W0 of full ' '' '" """"~' ~ ~.
213~6~`~
length is slightly higher tendency of fluttering of the web W, but, on the other hand, longer free gaps W0 allow more time for evaporation of water and for relaxing ofthe web tensions in the gaps W0 between the rows of cylinders 20A and 20B. In Fig 2, the drying cylinders 10 in the last normat group RN are placed in a plane slightly 5 lower (dimension H4) than the upper cylinders 20A in the twin-wire group RTW.
The scope of the invention also includes embodiments in which the fr~e gaps W0, described above, between the rows of cylinders 20A,20B in the single group RTW
with tvin-wire draw have been rcplaced fully or partially by fully closed draw 10 arrangements which are in themselves known in prior art. With respect to these draw arrangements, reference is made to Figs. 3 and 4 in the applicant's ~I Patent NoC8,279 (equivalent to US Patent 4,C02,439), to US Patent 3,7S3,298, and to the paper mentioned above by Lindberg, Juppi, Eskelinen, "High Speed D~er Section Developments for Sheet Stabilityn, 78~Mcc~g, Tc~uricol Sc~on 15 C~PP~
In the present invention, it is favourably possible to apply so called ropeless thread~
ing. Ropeless threading can be applied in the normal groups Rl...RN by means of the drying wires 15 and by means of the reversing suction cylinders 11 as well as on 20 the straight runs of the wires placed in connection with them by means of blow boxcs 17 and by means of negative pressure applied to the reversing suction cylin~
ders 11. Substantially similar arrangements can also be used in the single groupRTW with twin-wire draw. If necessary, at the doctors 14 and 24, it is also possible to use blow arrangements by whose means the threading is promoted. With respect 25 to these arrangements, I reference, isl made to the applicant's ~I Pate:lt Application No. 904841 (equivalent to US Pat. Appl. No. 07/766,039).
~ :'" '' ' '',,`'~ ,;, As to the dimensioning of the various cylinders and rolls in the dryer section, it should be stated that the diameters Dl of the drying cylinders 10 in the normal 30 groups RN are advantageously substantially equal to the diameters Do of the cylin-ders 20A and 20B in the single twin-wire group RTW, i.e. Dl # Do. As a rule, said diameters Dl and Do are chosen as Do # Dl s 2.5 m, preferably Dl # D
' " "' ' ;'';~'~' 21336~'~
1.8...2.2 m. The diameter D2 f the reversing suction cylinders 11 or of correspon-ding normal suction rolls is, as a rule, chosen in a range of D2 # 0.6...1.8 m. As was stated above, in the invention, preferably reversing suction cylinders 11 are used which have no inside suction box, which are provided with perforated mantles and5 with outside grooves 12 that are subjected to a vacuum, and the diameter D2 of said cylinders is chosen in the range of D2 # 1.0 ... 1.8 m, preferably D2 # 1.2 ... 1.5 m. Fig. 2 also shows the horizontal distance A between the cylinders in a normalgroup RN and the corresponding horizontal distance B in the single twin-wlre group RT~ which distances are in Fig. 1: A = 2130 mm and B = 2430 mm, when Do =
10 Dl, in which case, in a normal group 15, the vertical distance between the cylinders lO,l l is Hl = 1600 mm, and in the twin-wire group RTw the corresponding vertical distance bet veen the cylinders 20A and 20B is H2 = 2Q00 mm. The diameter D3 of the guide rolls 18,28,21a,21b is typically in a range of D3 # 400...700 mm, depending on the width of the machine.
A regulation pawneter that can be utilized in the invention and by whose means the symmetry of the drying of the opposite sides of the web W can be controlled is the tensions TN and TTW of the drying wires 15 and 25A,25B. In a preferred embodi~
ment of the invention, TN is chosen in a range of TN # 2...4 kN/m, and TTW is 20 chosen in a range of TTW # 4...8 kN/m. It is also possible to use an arrangement of tcnsion of the drying wires 15 in which, also in the normal group Rl N~ the wiretension TN is increased constantly as the drying makes progress, in accordance with the principles ~hat are described in the applicant's FI Patent No. 83,441.
... .~
25 Moreover, the wire tensions TTWA and TTWB of the lower and upper wire 25A and25B in the single twin-wire group RTW can also be chosen as different from each ~ " .
other if the symmetry of the drying of the web W should require that. Such an S~;
embodiment is particularly advantageous in which the tension TTWB of the wire 25B
of the lower cylinders 20B is higher than the tension TTWA of the upper wire 25A.
30 Hereby, the symmetry of drying is promoted by in the single twin-wire group RrW
drying the upper side of the web W to a greater extent. The symmetry of drying can also be promoted by in the twin-wire group RTW using different steam pressures and ; - ' -~ 2~335~-~
cylinder-face temperatures in the upper cylinders 20A as compared with the lowercylinders 20B. Preferably, in the lower cylinders 20B, a higher steam pressure and cylinder-face temperature are employed than in the upper cylinders 20A, whereby,wgether with the difference in tension TTWB > TTWA between the wires 25A and 5 25B, the symmetry of the drying of the web W is promoted further by, in the single twin-wire group RTW drying the upper face of the wire W to a greater extent thanthe lower face, whose drying proportion was in the normal groups Rl N. owing to the cylinders 10, higher than the drying of the upper face. The above symmetry of drying can be promoted further by choosing the permeabilities of the upper wire 25A
10 and the lower wire 25B different.
~, ~ "
When the web W departs from the dryer section at WOUt, its dry solids content koUt :
is, as a rule, in a range of kout ~ 92...98 %, whereas the dry solids content of the web W on its arrival in the dryer section is k,l, ~ 40 % ... 50 %.
Fig. 3 shows such a modification of a dryer section as shown in Fig. 1 in which the last two groups RSN 1 and RSN in the single-wire groups Rl N are particular - - ~
groups of inclined alignments, in which the first three co~ltact~rying cylinders lOS ;
are placed in a plane Tl that is inclined downwards in the direction of running of the web W, and the next three corresponding cylinders lOS are placed in an upwards inclined plane T2. In Fig. 3, the reversing cylinders in the groups RSN I and RSN ;~
are denoted with the reference 1 lS and the leading rolls with the reference 18S and the wires with the reference 15S. Said inclined groups are preceded by normal single-wire groups R~--RN-3 similar to those shown in Fig. 1, the web W having closed draws between said normal single-wire groups and the inclined groups RSN I
and RSN. In stead of the inclined groups RS, it is also possible to use vertical or almost vertical cylinder groups. With respect to said vertical groups, reference is made to the applicant's ~I Patents Nos. 53,333 and 82,097 (equivalent to US Pats.
Nos. 3,868,780 and 4,972,C08) as well as to the US Patent No. ~,177,880 of Messrs J.M. Voith GmbH. At least the lower parts of the inclined groups RS may ~ ;
extend to below the floor level of the paper machine hall into its basement space. ~ ;
.: '~ ' ' ' :: '~ ' .~. ,-: :,.':, ::, ', ' ~ : .
, ., , ' ,:.,: "~;"
213350~
~ :
The scope of the invention also includes embodiments in which the ove~all length of ;
the dryer section has been made shorter in respect of the groups Rl...RN with single-wire draw by, in one or several groups Rl...RN, fitting the drying cylinders 10 in two or more horizontal, vertical or inclined planes.
S
In the following, the patent claims will be given, and the various details of the - . ;~
invention may show variation within the scope of the inventive idea defined in said ;~
, . . ,. -:
claims and differ from what has been stated above for the szlce of example only.
; -: . . - ;- i ,.. .
' ' ;. .;; ;i,;
: ,; ~ ,, .. ,,i ".~"-, " ~ , ., ~ ,, . ~ , ~,-~....
.- ~ -i ....
~, ,. . -.
': ~','-',"',;
.
:, . ., - .
~ ~ ,:, ;' ;,.
:,, , .".,~,~.. . .
,.~. ',''','.. ",'.. ',~.'.',, :' ,.-. ,.~".,".~.
. . ....
: ., ~.;:
. ..,:
:; ~
.: ..: ~ , . . . .:
: : :,.
single-wire draw are s~called normal groups, in which the, e.g., steam-heated smooth-faced drying cylinders 10 are placed in the upper horizontal row and the reversing suction cylinders 11 or equivalent suction rolls are placed in the lower horizontal row. In the last normal group RN, the last two upper cylinders 10' and 20 the single reversing suction cylinder 11' placed between them are placed at a level by the dimension H3 higher than in the preceding groups Rl...RN l. The dimensionH3 is typically H3 ~ 400 mm. The frame part 100 of the dryer section is illustrated quite schematically.
""'",',".. ".,, .,,, ' 25 i Each nor nal group Rll.,..RN has~ a drying wire 15 of its own, which is guided by guide rolls 18. The drying wires 15 press the web W to be dried on the drying ~ ;
cylinders 10 against their smooth heated face, and on the reversing cylinders ll the web W remains at the side of the outside curve on ~he outside face of the wire 15. ~ ;
On the reversing cylinders 11 the web W is ~ept reliably on support of the wire 15 against the effect of centrifugal forces by the effect of the negative pressure present ~ ~, in the grooved faces 12 of the reversing cylindas 11 , whereby transverse shrinkage of the web W is also prevented. The reversiDg suction cylinders 11 that are used are `
2 1 3 3 ~
preferably suction cylinders 11 marketed by the applicant under the trade mark "VAC-ROLLnTM, which cylinders have no inside suction boxes, which cylinders are provided with a perforated mantle and with outside grooves that are subjected to a vacuum, and in respect with whose constructional details reference is made to the applicant's ~I Patent No. 83,680 (equivalent to US Pat. No. S,022,163). The diameters D2 f these suction cylinders 11 are substantially larger than the diameters of normal suction rolls that are provided with an inside suction box and that are used in corresponding positions. Hereby, the remarkable advantage is obtained that, on the turning sectors on the reversing cylinders 11, the web W is subjected to lower centrifugal forces, whereby a more reliable transfer is achieved and/or it is possible to use a lower vacuum level in the grooved faces 12 of the reversing cylinders, compared with normal suction rolls.
In a preferred embodiment of the invention, the support contact between the web W
and the drying wire 15 is.also kept good on the straight runs between the dryingcylinders 10 and the reversing cylinders 11, at least on the runs talcing place from the drying cylinders 10 to the reversing cylinders 12, by using blow-suction boxes 17, by whose means formation of negative pressures induced by the wire lS is prevented in the closing wedge-shaped nip spaces between the wire lS and the cylinder 12 mantle. In respect of the details of the constructions of these blow-suction boxes 17, which are marketed by the applicant under the trade mark "UNO
RUN BLOW BO~nTM, reference is made to the applicant's ~I Patents Nos.
S9,C37, 65,460, and 80,491 (equivalent to US Pats. Nos. 4,441,263, 4,515,330, and 4,905,380. After the introduction of the "UNO RUN BLOW BOX"TM, the applicant's competitors~ have also suggested some blow-box solutions, in whose respect reference is made to the US Patents 4,502,231 U.M. Voith GmbH) and 4,661,198 (Beloit Corp.), whose applications in the positions of the blow boxes 17 are also included in the scope of the overall concept of the present invention.
30 In the groups RlRN with single-wire draw, blow boxes 16 are also used in the gaps between the reversing cylinders 12, by means of which boxes said intermediate spaces are air~onditioned and evaporation from the web W is promoted. The faces 2133~0~
9 ::'.' -.,.,' of the drying cylinders 10 are kept clean by the doctors 14.
In the invention, it is a further essential feature and advantage that broke removal by the force of gravity can be applied in the groups Rl...RN with single-wire draw,5 which extend over the m~jor part of the overall length L of the dryer section, for the groups Rl. ..RN with single-wire draw are open towards the bottom so that the paper web WS that becomes broke can be removed without any particular arrangements onto the broke conveyor (not shown) placed in the basement space of the paper machine. ~ ~-.: .
It is an essential feature of the method of the invention that, in the normal groups ~ -R1 N~ the web W has time to reach a certain, quite high dry solids content of kl~ 70 %92 ~O, preferably kl ~ 80 % 85 %, depending on thepaper grade. At this dry solids content kl, the web W is so strong that, for its further drying, it is 15 possible to apply a group with twin-wire draw without a risk of detrimental breaks.
Thus, it is an essential feature of the invention that, in the final end of the dryer - ~ ~;
section, there is expressly just one single group RrW with twin-wire draw. In this ;
single twin-wire group RTW, there are two horizontal rows of contact-drying . ~
cylinders 20A and 20B, one row placed above the other, of which cylinders, in ;
20 connection with the upper cylinders 20A, there is an upper wire 25A, which isguided by wire guide rolls 21A fitted in the gaps between the cylinders 20A and by other guide rolls 28. The web W is pressed into a drying contact against the heated faces of the lower cylinders 20B by means of the lowa wire 25B, which is guided by the wire guide rolls 21B fitted in the gaps between the cylinders 20B and by other 25 ~ guide rolls 28.
According to Fig. 1, in the twin-wire group RIW~ a draw arrangement marketed by ~ ''h2'~
the applicant under the trade mark ~ RUNnTM is used, in which ~e guide rolls 21A and 21B are placed so that the drying wires 25A and 25B accompany the web from the drying cylinders 20A and 20B onto the next one so that the free draws ~ ~ `
W0 of the web W can be made shorter, as compared with free draws of full length.In this draw arrangement, at the proximity of the wire guide rolls 21A and 21B and - 2133~0~ ~
at the inlet side of the web W and the drying wire 25A and 25B, air-blow bo~ces 22A,22B are used. Out of the blow bo~es æA,22B, which are used in the "IW~I-RUN"lM concept and which are fitted in the gaps between the drying cylinders 20A,20B, air jets of suitable direction and blow velociq are applied to the viciniq 5 of the runs of the drying wires 25A,25B placed at their proximiq and to the viciniq of the free sectors of the wire guide rolls 21A,21B, by means of which jets the support contact between the drying wires 25A,25B and the web W is promoted, formation of detrimental differences in pressure and fluttering of the web W on the free draws W0 are prevented. Said blowings can also be applied through the drying 10 wires 25A,25B, whereby it is possible to promote the ventilation of the pocket spaces P formed in the gaps between the drying cylinders 20A,20B. With respect to the further details of the "TWIN-RUN"TM concept and of the blow bw~es æA,22B, re~erence is made to the applicant's ~I Pat. 80,103 (equiv. to DE Pat. 3,818,600).
In connection with the drying cylinders 20A,20B, there are doctors 24. Accordingto Pig. 1, the last two cylinders 10' in the last normal group RN are placed in the - ;;~
same horizontal plane as the upper cylinders 20A in the single twin-wire group Rn whereby it is possible to guarantee a transfer of the web W free of problems.
According to Pig. 1, the web W is passed from the last cylinder in thc last normal 20 group RN onto the first lower cylinder 20B in the single twin-wire group RTW as an open draw Wl, whose arrangement is similar to the free draws W0 of the web W in the twin-wire group RTW-.Y . ;: ~:
In Pig. 1, the overall horizontal length of the dryer section in the machine direction 25 ' is L # 70 m when siX normal groups Rl N (N = 6) are used, and the correspon ;~
ding horizontal length of the singb twin-wire group RTW is LrW # 10 m, when fouruppcr cylinders 20A and four lower cylinders 20B are used in the twin-wire groupRlW. In the example of dimensioning given above, the length L~w f the twin-wiregroup RTW is about 14 % of the overall length. As a rule, the length of the single ~ ~
tvin-wire group L,rW is about 10.. 20 %, preferably 12.. 16 ~O, of the overall ~ ;
horizontal length L of the dryer section. In a dryer section concept in accordance ~ ;~
with this example of dimensioning, in practice, a reduction of about 5 metres is' ~.' '~ ', ~,, ;.
' ' ~ ~'. ` " '"':
21335~'~
achieved in the overall length L of the dryer section, as compared with a situation in which exclusively groups with single-wire draw are employed, and in this way the costs of the construction investment in the paper machine hall and the other costs indirectly related to se are also reduced considerably.
The number Nl of the drying cylinders 10 used in each of the normal groups R
is in a range of Nl = 4...8, preferably Nl = 5...7, and the to~l number of the drying cylinders 20A and 20B used in the single twin-wire group RTW is N2 a 4...14, preferably N2 = 8...10.
In view of prevention of transverse shrinkage of the web W, it is particularly important that, in particular in the dry solids content of k > 65 % of the web W, the web is kept constantly in reliable contact with the drying wires 15. This holding effect is produced on the reversing cylinders 11 by means of the negative pressure 15 present in the grooved mantle 12 of their outer face and on the straight draws between the cylinders 10 and the reversing cylinders 11 by means of the pressurelevels arranged by means of blow-suction boxes 17.
Fig. 2 shows an embodiment of the invention in which a closed draw Wc of thc web20 W is employed between the last normal group RN and the twin-wire group R~v which closed draw has been achieved by passing the drying wire 15 and the web W
supported on it into contact with the first upper cylinder 20A in the single twin-wire group RT~ to whose smooth face the web W adheres and is transferred, being pressed by the upper wire 25A guided by the guide roll 2&, over the first upper 25 cylinder 20A in the group RTW. In Fig. 2, the guide rolls 21A, and 21B placed, in the gaps between the drying cylinders 20A and 20B are placed symmetrically in the ccntre plane passing through the centre a~is of the adjacent drying cylinder, in which case the free draws W0 of the web W passing between the rows of cylinders 20A
and 20B are of full length and unshortened, differing from the ~TwIN RuN~
30 arrangement shown in Fig. 1. This solution is also included in the scope of the present invention even though it is not in all cases equally advantageous as theshortened free gaps W0 shown in Fig. 1. A drawback of the free draws W0 of full ' '' '" """"~' ~ ~.
213~6~`~
length is slightly higher tendency of fluttering of the web W, but, on the other hand, longer free gaps W0 allow more time for evaporation of water and for relaxing ofthe web tensions in the gaps W0 between the rows of cylinders 20A and 20B. In Fig 2, the drying cylinders 10 in the last normat group RN are placed in a plane slightly 5 lower (dimension H4) than the upper cylinders 20A in the twin-wire group RTW.
The scope of the invention also includes embodiments in which the fr~e gaps W0, described above, between the rows of cylinders 20A,20B in the single group RTW
with tvin-wire draw have been rcplaced fully or partially by fully closed draw 10 arrangements which are in themselves known in prior art. With respect to these draw arrangements, reference is made to Figs. 3 and 4 in the applicant's ~I Patent NoC8,279 (equivalent to US Patent 4,C02,439), to US Patent 3,7S3,298, and to the paper mentioned above by Lindberg, Juppi, Eskelinen, "High Speed D~er Section Developments for Sheet Stabilityn, 78~Mcc~g, Tc~uricol Sc~on 15 C~PP~
In the present invention, it is favourably possible to apply so called ropeless thread~
ing. Ropeless threading can be applied in the normal groups Rl...RN by means of the drying wires 15 and by means of the reversing suction cylinders 11 as well as on 20 the straight runs of the wires placed in connection with them by means of blow boxcs 17 and by means of negative pressure applied to the reversing suction cylin~
ders 11. Substantially similar arrangements can also be used in the single groupRTW with twin-wire draw. If necessary, at the doctors 14 and 24, it is also possible to use blow arrangements by whose means the threading is promoted. With respect 25 to these arrangements, I reference, isl made to the applicant's ~I Pate:lt Application No. 904841 (equivalent to US Pat. Appl. No. 07/766,039).
~ :'" '' ' '',,`'~ ,;, As to the dimensioning of the various cylinders and rolls in the dryer section, it should be stated that the diameters Dl of the drying cylinders 10 in the normal 30 groups RN are advantageously substantially equal to the diameters Do of the cylin-ders 20A and 20B in the single twin-wire group RTW, i.e. Dl # Do. As a rule, said diameters Dl and Do are chosen as Do # Dl s 2.5 m, preferably Dl # D
' " "' ' ;'';~'~' 21336~'~
1.8...2.2 m. The diameter D2 f the reversing suction cylinders 11 or of correspon-ding normal suction rolls is, as a rule, chosen in a range of D2 # 0.6...1.8 m. As was stated above, in the invention, preferably reversing suction cylinders 11 are used which have no inside suction box, which are provided with perforated mantles and5 with outside grooves 12 that are subjected to a vacuum, and the diameter D2 of said cylinders is chosen in the range of D2 # 1.0 ... 1.8 m, preferably D2 # 1.2 ... 1.5 m. Fig. 2 also shows the horizontal distance A between the cylinders in a normalgroup RN and the corresponding horizontal distance B in the single twin-wlre group RT~ which distances are in Fig. 1: A = 2130 mm and B = 2430 mm, when Do =
10 Dl, in which case, in a normal group 15, the vertical distance between the cylinders lO,l l is Hl = 1600 mm, and in the twin-wire group RTw the corresponding vertical distance bet veen the cylinders 20A and 20B is H2 = 2Q00 mm. The diameter D3 of the guide rolls 18,28,21a,21b is typically in a range of D3 # 400...700 mm, depending on the width of the machine.
A regulation pawneter that can be utilized in the invention and by whose means the symmetry of the drying of the opposite sides of the web W can be controlled is the tensions TN and TTW of the drying wires 15 and 25A,25B. In a preferred embodi~
ment of the invention, TN is chosen in a range of TN # 2...4 kN/m, and TTW is 20 chosen in a range of TTW # 4...8 kN/m. It is also possible to use an arrangement of tcnsion of the drying wires 15 in which, also in the normal group Rl N~ the wiretension TN is increased constantly as the drying makes progress, in accordance with the principles ~hat are described in the applicant's FI Patent No. 83,441.
... .~
25 Moreover, the wire tensions TTWA and TTWB of the lower and upper wire 25A and25B in the single twin-wire group RTW can also be chosen as different from each ~ " .
other if the symmetry of the drying of the web W should require that. Such an S~;
embodiment is particularly advantageous in which the tension TTWB of the wire 25B
of the lower cylinders 20B is higher than the tension TTWA of the upper wire 25A.
30 Hereby, the symmetry of drying is promoted by in the single twin-wire group RrW
drying the upper side of the web W to a greater extent. The symmetry of drying can also be promoted by in the twin-wire group RTW using different steam pressures and ; - ' -~ 2~335~-~
cylinder-face temperatures in the upper cylinders 20A as compared with the lowercylinders 20B. Preferably, in the lower cylinders 20B, a higher steam pressure and cylinder-face temperature are employed than in the upper cylinders 20A, whereby,wgether with the difference in tension TTWB > TTWA between the wires 25A and 5 25B, the symmetry of the drying of the web W is promoted further by, in the single twin-wire group RTW drying the upper face of the wire W to a greater extent thanthe lower face, whose drying proportion was in the normal groups Rl N. owing to the cylinders 10, higher than the drying of the upper face. The above symmetry of drying can be promoted further by choosing the permeabilities of the upper wire 25A
10 and the lower wire 25B different.
~, ~ "
When the web W departs from the dryer section at WOUt, its dry solids content koUt :
is, as a rule, in a range of kout ~ 92...98 %, whereas the dry solids content of the web W on its arrival in the dryer section is k,l, ~ 40 % ... 50 %.
Fig. 3 shows such a modification of a dryer section as shown in Fig. 1 in which the last two groups RSN 1 and RSN in the single-wire groups Rl N are particular - - ~
groups of inclined alignments, in which the first three co~ltact~rying cylinders lOS ;
are placed in a plane Tl that is inclined downwards in the direction of running of the web W, and the next three corresponding cylinders lOS are placed in an upwards inclined plane T2. In Fig. 3, the reversing cylinders in the groups RSN I and RSN ;~
are denoted with the reference 1 lS and the leading rolls with the reference 18S and the wires with the reference 15S. Said inclined groups are preceded by normal single-wire groups R~--RN-3 similar to those shown in Fig. 1, the web W having closed draws between said normal single-wire groups and the inclined groups RSN I
and RSN. In stead of the inclined groups RS, it is also possible to use vertical or almost vertical cylinder groups. With respect to said vertical groups, reference is made to the applicant's ~I Patents Nos. 53,333 and 82,097 (equivalent to US Pats.
Nos. 3,868,780 and 4,972,C08) as well as to the US Patent No. ~,177,880 of Messrs J.M. Voith GmbH. At least the lower parts of the inclined groups RS may ~ ;
extend to below the floor level of the paper machine hall into its basement space. ~ ;
.: '~ ' ' ' :: '~ ' .~. ,-: :,.':, ::, ', ' ~ : .
, ., , ' ,:.,: "~;"
213350~
~ :
The scope of the invention also includes embodiments in which the ove~all length of ;
the dryer section has been made shorter in respect of the groups Rl...RN with single-wire draw by, in one or several groups Rl...RN, fitting the drying cylinders 10 in two or more horizontal, vertical or inclined planes.
S
In the following, the patent claims will be given, and the various details of the - . ;~
invention may show variation within the scope of the inventive idea defined in said ;~
, . . ,. -:
claims and differ from what has been stated above for the szlce of example only.
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.
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,.~. ',''','.. ",'.. ',~.'.',, :' ,.-. ,.~".,".~.
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: : :,.
Claims (23)
1. Method in contact drying of a paper web (W), wherein the paper web (W) is dried by means of heated smooth-faced drying cylinders (10,20A,20B) by using a number of successive so called normal groups (R1...RN) with single-wire draw, inwhich the drying cylinders (10) are placed in the upper row and the reversing suction cylinders (11) or corresponding reversing suction rolls in the lower row, in which method, after the press section of the paper machine, the paper web (W) isdried initially in a number of successive groups (R1...RN) with single-wire draw by pressing the paper web (W) by means of the drying wire (15) of the cylinder group against the heated faces of the drying cylinders (10) and by, in each group (R1...RN) with single-wire draw, passing the paper web (W) on support of the same drying wire (15) from one drying cylinder (10) onto the next drying cylinder over reversing suction cylinders (11), and in which method, after the above drying steps, whichwere carried out exclusively by means of normal groups (R1...RN) with single-wire draw, the paper web (W) is dried immediately further by means of one single group (RTW) with twin-wire draw to its ultimate dry solids content, c h a r a c t e r -i z e d in that, by means of said groups (R1...RN) with single-wire draw, the papa web (W) is dried to a dry solids content of k1 = 70...92 %, that, as said reversing suction cylinders (11), suction cylinders are used which have no inside suction box, the paper web (W) being held on the drying wires (15) by the intermediate of theperforated mantle and the grooves (12) in the outside face of said cylinders by means of a difference in pressure against the effect of centrifugal forces when the paper Web is on the drying wire (15) at the side of the outside curve, and/or that, on! the.
runs between the drying cylinders (10) and reversing cylinders (11) or rolls in said groups (R1...RN) with single-wire draw, differences in pressure that disturb thesupport contact of the paper web (W) are prevented by means of blow boxes (17) or equivalent.
runs between the drying cylinders (10) and reversing cylinders (11) or rolls in said groups (R1...RN) with single-wire draw, differences in pressure that disturb thesupport contact of the paper web (W) are prevented by means of blow boxes (17) or equivalent.
2. Method as claimed in claim 1, c h a r a c t e r i z e d in that the diameters D1 of the drying cylinders (10) in the normal groups (RN) and the diameters D0 of the cylinders (20A,20B) in the twin-wire group (RTW) are chosen as D0 ? D1 ? 2.5 m, preferably D0 ? D1 ? 1.8...2.2 m.
3. Method as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the diameter D2 of said reversing suction cylinders (11) which have no inside suction box andwhose outside faces are provided with grooves (12) that are subjected to a vacuum is chosen in the range of D2 ? 1Ø..1.8 m, and the ratio of diameters D1/D2 is chosen in the range of D1/D2 ? 1.2...4, preferably in the range D1/D2 ? 1.2...2.
4. Method as claimed in any of the claims 1 to 3, c h a r a c t e r i z e d in that, in the single group (RTW) with twin-wire draw, blow boxes (22A,22B) are employed, which are fitted in the spaces between both the upper and the lower drying cylinders (20A,20B) at the proximity of the wire guide rolls (21A,21B) fitted in said spaces and by means of which boxes the support contact between the drying wires (25A,25B) is promoted, the fluttering of the paper web (W) on the free draws (W0) is reduced, and/or the ventilation of the closed pocket spaces (P) that remain in the gaps between the drying cylinders (20A,20B) is promoted.
5. Method as claimed in any of the claims 1 to 4, c h a r a c t e r i z e d in that the symmetry of the drying of the opposite sides of the paper web (W) is promoted by in the last single twin-wire group (RTW) in the dryer section using a wire tension (TTW) that is higher than in the preceding normal groups (TN).
6. Method as claimed in any of the claims 1 to 5, c h a r a c t e r i z e d in that the symmetry of the drying of the paper web (W) is promoted by in. the last, single twin-wire group (RTW) in the dryer section using different wire tensions (TTWA and TTWB) in the upper wire as compared with the lower wire (25A,25B) and/or by using different steam pressures in the upper row of drying cylinders as comparedwith the lower row (20A,20B) and/or by using different permeabilities in the upper wire as compared with the lower wire (25A,25B), preferably so that, in the group(RTW) with twin-wire draw, the proportion of drying of the upper face of the paper web (W), which takes place on the lower cylinders (20B), is arranged larger than the corresponding proportion of drying taking place on the upper cylinders (20A).
7. Method as claimed in any of the claims 1 to 6, c h a r a c t e r i z e d in that, by means of said groups (R1...RN) with single-wire draw, the paper web (W) is dried to a dry solids content of k1 ? 80 %...85 %.
8. Method as claimed in any of the claims 1 to 7, c h a r a c t e r i z e d in that, in the event of breaks, the removal of the paper web (WS) that becomes broke is carried out downwards from the open groups (R1...RN) with single-wire draw substantially by the force of gravity onto a broke conveyor or equivalent placedunderneath.
9. Method as claimed in any of the claims 1 to 8, c h a r a c t e r i z e d in that, between the last group (RN) with single-wire draw and the following single group(RTW) with twin-wire draw, either an open draw (W1) of the web (Fig. 1) or a closed draw (Wc) of the web is used, which latter draw is preferably arranged sothat the drying wire (15) of the last group (RN) with single-wire draw has a contact sector or a turning sector with the first drying cylinder (20A) in the group (RTW) with twin-wire draw, in which case the paper web (W) is separated from the last-mentioned drying wire (15) and is transferred onto the smooth face of the last-mentioned drying cylinder (20A) (Fig. 2).
10. Method as claimed in any of the claims 1 to 9, c h a r a c t e r i z e d in that, in the last single group (RTW) with twin-wire draw in the dryer section, free gaps are used which are shorter than a free draw of full length of the paper web (W) and which are produced by means of asymmetric locations of the wire guide rolls (21Aand 21B) placed in the gaps between the drying cylinders (20A,20B) (Fig. 1).
11. Method as claimed in any of the claims 1 to 10, c h a r a c t e r i z e d inthat, in the dryer section, so-called ropeless tail threading is applied by, in the threading, guiding the web by means of differences in pressure and by means of blowings.
12. Method as claimed in any of the claims 1 to 11, c h a r a c t e r i z e d inthat, between the rows of drying cylinders (20A,20B) in the single group (RTW) with twin-wire draw, free draws (W0) of the paper web are used, on which draws the paper web (W) is allowed to relax.
13. Method as claimed in any of the claims 1 to 12, c h a r a c t e r i z e d inthat, between the rows of drying cylinders (20A,20B) in the single group (RTW) with twin-wire draw, closed draws of the paper web (W) are used.
14. Dryer section of a paper machine, whose initial part is composed of a numberof successive so-called normal groups (R1...RN) with single-wire draw, in which the drying cylinders (10) are placed in the upper row and the reversing suction cylinders (11) are placed in the lower row, and between which said normal groups (R1...RN)the paper web (W) to be dried has closed draws over the group gaps, and which said reversing suction cylinders (11) have been arranged to be subjected to negative pressure, at least at their drying-wire (15) turning sectors (12), and in which dryer section, after the last group (RN) with single-wire draw, one single group (RTW)with twin-wire draw is provided, in which there are two rows of drying cylinders(20A,20B), one row placed above the other, c h a r a c t e r i z e d in that, differ-ences in pressure that disturb the support contact between the drying wire (15) and the paper web (W) on their joint runs from the drying cylinders (10) onto the reversing suction cylinders (11) in the groups (R1...RN) with single-wire draw have been reduced or prevented by means of air-blow devices (17) or equivalent, and/or that said reversing suction cylinders (11) are reversing suction cylinders (11) that are provided with a perforated mantle and with outside grooves (12) subjected to a vacuum and which said cylinders have no inside suction box.
15. Dryer section as claimed in claim 14, c h a r a c t e r i z e d in that the diameter D2 of said reversing suction cylinders (11) which have no inside suction box and whose outside faces are provided with grooves (12) that are subjected to a vacuum has been chosen in the range of D2 ? 1Ø..1.8 m, preferably D2 ? 1.2...1.5 m, and that the ratio of the diameter D1 of the drying cylinders (10) in the normal groups (RN) and the diameter D2 of the reversing suction cylinders (10) has beenchosen in the range of D1/D2 ? 1.2...4, preferably in the range D1/D2 ? 1.2...2.
16. Dryer section as claimed in claim 14 or 15, c h a r a c t e r i z e d in that, in the spaces between the drying cylinders (20A,20B) in the single group (RTW) withtwin-wire draw, preferably both in the upper row and in the lower row of drying cylinders, air-blow boxes (22A,22B) are provided, by means of which blowings of such directions and velocities can be applied to the drying wires (25A, 25B) running at their proximity and to the free sectors of the opposite wire guide rolls (21A,21B) that the blowings promote the support contact between the drying wires (25A,25B)and the paper web (W), reduce the fluttering of the free draws (W0) of the paperweb (W) and/or promote the ventilation of the closed pocket spaces (P) defined in the gaps between the drying cylinders (20A,20B).
17. Dryer section as claimed in any of the claims 14 to 16, c h a r a c t e r i z e d in that the paper web (W) has free unsupported draws (W0) on the runs between the drying cylinders (20A,20B) in said single group (RTW) with twin-wire draw.
18. Dryer section as claimed in any of the claims 14 to 17, c h a r a c t e r i z e d in that the paper web (W) has closed draws between the rows of drying cylinders (20A,20B) placed one above the other in the single group (RTW) with twin-wire draw.
19. Dryer section as claimed in any of the claims 14 to 18, c h a r a c t e r i z e d in that the horizontal length (LTW) in the machine direction of the last single group (RTW) with twin-wire draw is about 10 %...20 %, preferably about 12 %...16 %, of the overall horizontal length (L) of the dryer section in the machine direction.
20. Dryer section as claimed in any of the claims 14 to 19, c h a r a c t e r i z e d in that the number of the groups (R1...RN) with single-wire draw is N = 3...9, preferably N = 5...7, that the number of the drying cylinders (10) used in the groups (R1...RN) with single-wire draw has been chosen in a range of N1 = 4...8,
21 preferably in a range of N1 = 5...7, and that the total number of the drying cylinders (20A,20B) used in the single twin-wire group (RTW) has been chosen in a range of N2 = 4...14, preferably in a range of N2 = 8...10.
21. Dryer section as claimed in any of the claims 14 to 20, c h a r a c t e r i z e d in that, in one or several groups (R1...RN) with single-wire draw, the drying cylinders (10) have been arranged in two or more horizontal, inclined, or vertical planes so that the overall length of the dryer section can be made shorter.
21. Dryer section as claimed in any of the claims 14 to 20, c h a r a c t e r i z e d in that, in one or several groups (R1...RN) with single-wire draw, the drying cylinders (10) have been arranged in two or more horizontal, inclined, or vertical planes so that the overall length of the dryer section can be made shorter.
22. Dryer section as claimed in any of the claims 14 to 21, c h a r a c t e r i z e d in that one or several of the groups (R1...RN) with single-wire draw, preferably of the last groups (RSN-1, RSN), is/are a group of inclined alignment, in which the first drying cylinders (10S) are placed in a plane (T1) that is inclined downwards in the direction of running of the paper web (W), and the next drying cylinders (10S) are placed in a corresponding upwards inclined plane (T2) (Fig. 3).
23. Dryer section as claimed in any of the claims 14 to 22, c h a r a c t e r i z e d in that the dryer section includes means for producing the differences in pressure and/or the guiding air blowings necessary in so-called ropeless tail threading.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI934367A FI934367A7 (en) | 1993-10-05 | 1993-10-05 | Method for drying paper web and drying section of paper machine |
| FI934367 | 1993-10-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2133604A1 true CA2133604A1 (en) | 1995-04-06 |
Family
ID=8538713
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002133604A Abandoned CA2133604A1 (en) | 1993-10-05 | 1994-10-04 | Method in the drying of a paper web and a dryer section of a paper machine |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0653515A3 (en) |
| CA (1) | CA2133604A1 (en) |
| FI (1) | FI934367A7 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5661911A (en) * | 1994-02-17 | 1997-09-02 | Valmet Corporation | Dryer section of a paper machine |
| FI93875C (en) * | 1994-02-17 | 1995-06-12 | Valmet Paper Machinery Inc | Procedure for drying a paper web and drying part in a paper machine |
| FI93036C (en) * | 1994-03-29 | 1995-02-10 | Valmet Paper Machinery Inc | Procedure for contact drying of a paper web and drying portion of a paper machine |
| FI95059C (en) * | 1994-06-14 | 1995-12-11 | Valmet Paper Machinery Inc | Drying lot for a paper machine |
| US5505006A (en) * | 1994-09-08 | 1996-04-09 | J.M. Voith Gmbh | Device for drying a running web |
| US6126787A (en) * | 1995-02-01 | 2000-10-03 | Valmet Corporation | Dry end of a paper machine |
| FI98387C (en) * | 1995-02-01 | 1997-06-10 | Valmet Corp | Process for making surface-treated paper, especially fine paper, and dry end for a paper machine |
| DE10217571A1 (en) * | 2002-04-19 | 2003-11-06 | Voith Paper Patent Gmbh | drying section |
| CN102888777A (en) * | 2012-10-23 | 2013-01-23 | 河南江河纸业股份有限公司 | High-speed paper machine drying part |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI80491C (en) * | 1987-09-02 | 1990-06-11 | Valmet Paper Machinery Inc | FOERFARANDE OCH TORKNINGSGRUPP I MAONGCYLINDERTORKEN AV EN PAPPERSMASKIN. |
| US4821429A (en) * | 1987-11-30 | 1989-04-18 | J. M. Voith, Gmbh | Air guide box for stabilizing the run of a web, for instance a paper web |
| FI83680C (en) * | 1988-03-09 | 1991-08-12 | Valmet Paper Machinery Inc | FOERFARANDE OCH ANORDNING VID DRAGNINGEN AV BANAN I EN PAPPERSMASKIN SAMT CYLINDER FOER ANVAENDNING VID DRAGNINGEN AV BANAN. |
| US4967489A (en) * | 1988-12-14 | 1990-11-06 | Valmet Paper Machinery Inc. | Multi-cylinder dryer with twin-wire draw and web transfer between the cylinder groups |
| DE9110134U1 (en) * | 1991-08-16 | 1991-09-26 | J.M. Voith Gmbh, 7920 Heidenheim | Arrangement for transferring a running web |
| US5269074A (en) * | 1992-04-24 | 1993-12-14 | Beloit Technologies, Inc. | Single tier dryer section for curl control |
| DE9414963U1 (en) * | 1994-09-16 | 1994-11-03 | J.M. Voith Gmbh, 89522 Heidenheim | Dryer section |
-
1993
- 1993-10-05 FI FI934367A patent/FI934367A7/en unknown
-
1994
- 1994-10-04 EP EP94850170A patent/EP0653515A3/en not_active Withdrawn
- 1994-10-04 CA CA002133604A patent/CA2133604A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| FI934367A0 (en) | 1993-10-05 |
| EP0653515A2 (en) | 1995-05-17 |
| FI934367A7 (en) | 1995-04-06 |
| EP0653515A3 (en) | 1996-02-21 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |