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WO1999060205A1 - Formeur a double toile avec espace entre les rouleaux dans une machine a papier - Google Patents

Formeur a double toile avec espace entre les rouleaux dans une machine a papier Download PDF

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Publication number
WO1999060205A1
WO1999060205A1 PCT/FI1999/000415 FI9900415W WO9960205A1 WO 1999060205 A1 WO1999060205 A1 WO 1999060205A1 FI 9900415 W FI9900415 W FI 9900415W WO 9960205 A1 WO9960205 A1 WO 9960205A1
Authority
WO
WIPO (PCT)
Prior art keywords
wire
zone
suction
former
forming
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.)
Ceased
Application number
PCT/FI1999/000415
Other languages
English (en)
Inventor
Ari Puurtinen
Samppa J. Salminen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valmet Technologies Oy
Original Assignee
Valmet Oy
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Valmet Oy filed Critical Valmet Oy
Priority to AU41470/99A priority Critical patent/AU4147099A/en
Publication of WO1999060205A1 publication Critical patent/WO1999060205A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F9/00—Complete machines for making continuous webs of paper
    • D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type

Definitions

  • the invention concerns a twin- wire roll-gap former in a paper machine, which former comprises a covering wire guided by guide rolls and a carrying wire guided by guide rolls, from which carrying wire the web that has been formed is removed onto a pick-up fabric or equivalent, and which former comprises a forming gap, into which the stock suspension jet can be fed out of the headbox and which forming gap is defined while guided by the rolls placed inside the loops of said wires, and which wires define a twin- wire zone, in which there are at least two successive water draining and web forming units, of which units one unit is a rib loading unit which comprises a set of guide and support ribs as well as a set of loading ribs operating opposite to said set of guide and support ribs, by means of which said sets or ribs it is possible to produce a controlled loading pressure which presses said wires against each other, and which water draining and web forming units comprise a vacuum box or boxes.
  • Said unequalsidedness also has unfavourable effects on other properties of the web, such as smoothness of the paper faces and oil absorbancy of the paper.
  • the drawbacks referred to above partly arise from the fact that, in prior-art gap formers, said units have usually been placed in an area in which the consistency of the stock layer that is being formed has been decisively higher than the headbox consistency, i.e. clearly higher than about 1.5 %, so that, in the area of the rib loading unit, it has no longer been possible to apply a major effect on the distribution of fines and fillers.
  • the principal object of the present invention is development of the prior art coming out from the papers cited above and development of corresponding prior art so that the drawbacks discussed above can be substantially eliminated.
  • a former in which the length of the twin-wire zone can be made considerably shorter or at least be kept substantially unchanged ion spite of a considerable increase in the web speed.
  • the former in accordance with the invention is mainly characterized in that, after the forming gap confined to the area of the first forming roll, the twin- wire zone comprises the following web forming and water draining elements;
  • (b2) a rib loading unit, which guides the twin-wire zone substantially along a straight run and in which there are
  • the web formation and water drain elements (a),(b),(b 1 ),(b 2 ) and (c) defined above and placed after the forming gap in the twin- wire zone are placed in the sequence given above.
  • the draining of water is highly intensive and symmetric so that the web obtains a structure symmetric in the z-direction and an adequate content of fines and fillers in both of the opposite faces, which is important in particular in the case of writing and printing papers, for whose manufacture the former in accordance with the present invention is supposed to be particularly well suited.
  • an important parameter in the web formation is the vacuums in the different forming elements, which vacuums act in the twin-wire zone preferably alternatingly from opposite sides of the web, so that symmetric draining of water and the other effects aimed at can be achieved.
  • the rib loading unit which was earlier also called MB unit, has been placed in the twin-wire zone in an area in which the dry solids content of the web that is being formed is still sufficiently low so that, by means of varying pressure impulses produced by means of said rib loading unit, it is possible to affect the draining of water and the formation of the web so that the objectives stated above are carried into effect in this respect.
  • the invention is also related to a novel geometry of the carrying wire and the pickup area after the twin- wire zone, which geometry, for its part, reduces the total length of the former and of the press section and by means of which geometry both a compact construction and a draw of the web as linear as possible from the former to the press section without a risk of web breaks even at high web speeds are achieved, which factors constitute objects of the present invention.
  • Figure 1 is a schematic side view of a preferred embodiment of a former in accord- ance with the invention.
  • Figure 2 is an illustration more detailed and on a larger scale than Fig. 1 of a preferred embodiment of a twin- wire former.
  • Figure 3 illustrates an embodiment of the first forming roll and of a water drain box provided with a static ribbed shoe and placed above said forming roll.
  • Figure 4 is a schematic side view of an application of the invention in a former whose former part is substantially horizontal.
  • Figs. 1 and 2 illustrate a roll-gap former in accordance with the invention, in which the twin- wire zone is substantially vertical running upwards. Being guided by the rolls 11, 21, the covering wire 10 and the carrying wire 20 form a forming gap G between them. Into this forming gap G, a stock suspension jet J is fed out of the slice channel of the headbox 15. After the bottom of the forming gap G, the twin- wire zone is curved on the sector 11a of the first forming roll 11 , the magnitude a of said sector being, as a rule, in a range a ⁇ 0...60 0 , preferably a ⁇ 10...45°.
  • the length of the sector 11a has been chosen, as a rule, in a range 100...700 mm, preferably in a range 200...400 mm.
  • the runs of the wires 10,20 are separated from the forming roll 21 and continue their run as a short straight run while guided by an adjustable pre-loading element 28 placed inside the covering wire 20.
  • the length L s of said straight twin-wire run is preferably in a range L s « 200...500 mm.
  • the pre-loading element 28 acts in the area of the middle portion of said straight run.
  • the first pre- loading element 28 is followed, in the twin- wire zone, inside the loop of the covering wire, by a water drain box 17, in which there is a ribbed shoe 18L, ...18L N .
  • the number N of the ribs 18L is, as a rule, in a range N « 4...10, preferably N ⁇ 5...7.
  • the ribs 18L j N are static, and they guide the twin-wire zone as a straight run.
  • a suction box 27 in whose interior there are loading elements 29, which have been illustrated schematically by means of arrows only.
  • the loading elements 28 and 29 are provided with a rib part, whose wear- resistant front face rubs against the inner face of the carrying wire 20. The friction between the front face of said rib and the inner face of the wire 20 and the wear of the parts placed against each other are reduced partly by the water drained from the web.
  • These loading elements 29 act, in a way in itself known, preferably in the middle areas of the gaps between the ribs 18L with an adjustable force F.
  • the number of the loading elements 29 is N-l, i.e. , as a rule, in a range 3...9, preferably 4...6.
  • the loading elements 29 are most appropriately loaded with a pneumatic pressure medium, if necessary, so that the force of each of the different loading elements 29 can be adjusted independently.
  • the construction of the loading elements 29 is preferably such that their loading force remains substantially unchanged irrespective of the position of the element. With respect to the details of the construction of such a loading element, reference is made to the applicant's FI Patent 95,935.
  • the first static rib 181 ⁇ of the box 17 is placed at the distance of a short gap ⁇ L s /2 from the adjustable pre-loading element 28, and it is placed at the front edge of the curved wall 17a of the suction box 17.
  • the water drain boxes 17,27 with their sets of ribs 18L and 29 form a rib loading unit 40, which has also been called MB unit in the applicant's earlier patent applications.
  • This rib loading unit 40 guides the twin-wire zone precisely and in a stable way so that, in respect of this unit 40, the cross-direction profiles of the web W can be made sufficiently uniform.
  • the linear set of ribs 18L, 29 is followed by a forming suction box 19 fitted inside the loop of the covering wire 10, in which box 19 there is a static set of guide ribs 19L.
  • This set of ribs 19L guides the twin-wire zone 10,20 to be curved with a curve radius Ri towards the loop of the covering wire 10.
  • the curve radius R is, as a rule, chosen in a range Ri ⁇ 2000...10, 000 mm, preferably in a range ⁇ ⁇ 5000...8000 mm.
  • the web W is separated from the covering wire 10 and follows the carrying wire 20.
  • Said angle c of change in direction is, as a rule, in a range c « 5...30°, preferably c ⁇ 10...20°. This for its part secures a reliable transfer free of disturbance of the web W from the forming wire 20 onto the pick-up felt 30 even at high web speeds and even at speeds of an order of 2000 m/min or higher.
  • the lower wire 20 After the guide roll 22a, the lower wire 20 has a drive roll 22b, after which the carrying wire 20 continues its run, being guided by the guide roll 22, onto the breast roll 21.
  • the covering wire 10 is guided outside the twin- wire zone by the first forming roll 11, by the drive roll 13, and by the guide rolls 12.
  • the suction zones on the second forming roll 23 are covered by a water drain channel 13a, which communicates with a water drain trough 13b.
  • the curved wall 17a of the water drain box 17 placed inside the loop of the covering wire 10 defines an intermediate space RR between said wall and the perforated mantle 11 ' of the forming roll 11.
  • This draining of water is illustrated by the arrow DW 4 , which is caught along with the water flow DW 2 departing at a high velocity by means of an ejector effect, and the water flow DW 2 + DW 4 formed in this way is removed through the water drain duct 14a into a water drain channel 16a passing to the other side of the machine.
  • the kinetic energy of the water is utilized by passing the water further into the duct 14a and into the water drain channel 16a.
  • the draining of water taking place through the carrying wire 20 in the areas of the forming gap G and of the curve zone a is illustrated by the arrow DW, .
  • the waters DWi are passed, in the way shown in Fig. 1, through a downwards inclined duct 24a into a cross-direction channel 26a without undue splashing or water mist.
  • the suction box 27 of the rib loading unit 40 has been connected by means of a duct 27a to a suction source 45, which is illustrated schematically.
  • the draining of water taking place from the suction box 27 is illustrated by the arrow DW 3 .
  • the waters DW 3 pass, in the way shown in Fig. 1, through a downwards inclined duct 24b into a channel 26b.
  • the zones subjected to a vacuum Po > P ⁇ ,P2'P3'P4 are placed alternatingly at both sides of the web, which for its part produces a symmetric draining of water and a sufficiently high content of fines and fillers at both of the opposite faces of the web W that is being formed.
  • the water drain box 17 can also be connected to a suction source, such as to the last suction box 19, which has been connected through the duct 19a above the wall 17b between the boxes 17 and 19. Said draining of water is illustrated by the arrow DW 5 in Fig. 2, and these waters DW 5 are passed through the downwards inclined duct 14b into the channel 16b, which is illustrated in Fig. 1.
  • the development of the dry solids content k of the web is typically as follows.
  • the consistency k ⁇ of the stock discharge jet J is typically I Q « 0.7...1.5 % .
  • the consistency of the stock layer after the curve zone a on the roll 11 is k, « 1.5...2.5 % .
  • the web W can be given good formation and a symmetric structure partly because the set of ribs 18L/29 causes pressure pulsation in the web, and the effect of said pulsation is increased further at high speeds. Further, by means of the loading element 28 and the set of ribs 18L/29, a stable run is obtained for the twin-wire zone, even though said run is substantially linear in the area of said elements.
  • the construction of the twin-wire zone is particularly compact, and the efficiency of dewatering in said zone is high, which factors contribute to a sufficiently short twin-wire zone even at high web speeds and to a reasonable height H of the former.
  • the maximal height H of the former shown in it is relatively little.
  • said height H is H ⁇ 7...8 m.
  • the length L w of the twin-wire zone from the forming gap to the point at which the web W is separated from the covering wire 10 is, as a rule, L ⁇ 9...13 m.
  • Fig. 2 illustrates the pressurized forming zones in accordance with the invention when the invention is applied to a vertical former.
  • Fig. 2 it is one possible modification that the forming suction box 29 is arranged as filled with water, and the draining of water from said box is controlled by means of a throttle valve which is fitted in connection with the water drain duct departing from the box 29. It is a second modification that the water drain boxes in the rib loading unit 40 are also connected to a suction source 45, in which way draining of water through the covering wire 10 is pro- moted.
  • the lower- wire loop 20 is guided by the breast roll 21, guide rolls 22, by a wire suction roll 22a provided with a suction zone 22aa, and by a drive roll 25.
  • the loop of the upper wire 10 is guided by guide rolls 12 and by the first forming suction roll 11.
  • the initial parts of the water drain elements in the twin- wire zone are substantially similar to that described above and comprise a first adjustable loading element 28, a rib loading unit 40 A, in which there are loading elements 29 which load the twin- wire zone against a stationary set of ribs 18L.

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  • Paper (AREA)

Abstract

L'invention concerne un formeur à double toile avec espace entre les rouleaux dans une machine à papier, lequel formeur comprend une toile de revêtement (10) et une toile de transport (20). Après l'espace de formation (G) confiné à la zone du premier rouleau de formation (11), la zone à double toile comprend les éléments de formation de bande et de purge d'eau, qui sont énumérés comme suit: une zone courbe (a) se trouvant sur le premier rouleau de formation (11); un trajet rectiligne partant de la zone courbe (a) dans lequel sont placés, à l'intérieur de la boucle de la toile de transport (20); un élément de préchargement (28) et une unité de chargement à nervures guidant la zone à double toile le long d'un trajet rectiligne sur lequel sont ménagées un ensemble de nervures (18L1 à 18LN) dans la boucle de la toile de revêtement (10); une caisse d'aspiration (27) placée dans la boucle de la toile de transport (20) et des éléments de chargement (29) placés dans la caisse d'aspiration à l'aide de laquelle les éléments de chargement viennent se plaquer contre l'ensemble de nervures (18L1à18Ln). Les éléments comprennent aussi un second rouleau d'aspiration-formation (23) qui garantit, à l'aide de la zone d'aspiration (23b), la séparation de la bande (W) de la toile de revêtement (10) et qui suit la toile de transport (20).
PCT/FI1999/000415 1998-05-18 1999-05-14 Formeur a double toile avec espace entre les rouleaux dans une machine a papier Ceased WO1999060205A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU41470/99A AU4147099A (en) 1998-05-18 1999-05-14 Twin-wire roll-gap former in a paper machine

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI981098 1998-05-18
FI981098A FI981098A7 (fi) 1998-05-18 1998-05-18 Paperikoneen kaksiviirainen tela-kiraformeri

Publications (1)

Publication Number Publication Date
WO1999060205A1 true WO1999060205A1 (fr) 1999-11-25

Family

ID=8551746

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1999/000415 Ceased WO1999060205A1 (fr) 1998-05-18 1999-05-14 Formeur a double toile avec espace entre les rouleaux dans une machine a papier

Country Status (3)

Country Link
AU (1) AU4147099A (fr)
FI (1) FI981098A7 (fr)
WO (1) WO1999060205A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001044568A1 (fr) * 1999-12-16 2001-06-21 Valmet-Karlstad Ab Machine a fabriquer le papier a air traversant simplifiee possedant une section de formation entre deux toiles
DE10157467A1 (de) * 2001-11-23 2003-05-28 Voith Paper Patent Gmbh Former
AT412098B (de) * 2002-11-11 2004-09-27 Andritz Ag Maschf Vorrichtung zur trennung einer papierbahn von einem sieb
EP1489229A1 (fr) * 2003-06-18 2004-12-22 Voith Paper Patent GmbH Section de formage à deux toiles d'une machine de fabrication d'une bande de matériau fibreux

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0627523A1 (fr) * 1993-05-18 1994-12-07 Valmet Paper Machinery Inc. Section de formage à double toile dans une machine à papier
US5395484A (en) * 1992-01-17 1995-03-07 Valmet Paper Machinery Inc. Twin wire web former for a paper machine
WO1997047803A1 (fr) * 1996-06-11 1997-12-18 Valmet Corporation Formeur d'espace a double toile avec rouleau et lame pour machine a papier
DE19652485A1 (de) * 1996-12-17 1998-06-18 Voith Sulzer Papiermasch Gmbh Siebpartie und Verfahren zum Entwässern einer Faserstoffbahn in einer Siebpartie

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5395484A (en) * 1992-01-17 1995-03-07 Valmet Paper Machinery Inc. Twin wire web former for a paper machine
EP0627523A1 (fr) * 1993-05-18 1994-12-07 Valmet Paper Machinery Inc. Section de formage à double toile dans une machine à papier
WO1997047803A1 (fr) * 1996-06-11 1997-12-18 Valmet Corporation Formeur d'espace a double toile avec rouleau et lame pour machine a papier
DE19652485A1 (de) * 1996-12-17 1998-06-18 Voith Sulzer Papiermasch Gmbh Siebpartie und Verfahren zum Entwässern einer Faserstoffbahn in einer Siebpartie

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001044568A1 (fr) * 1999-12-16 2001-06-21 Valmet-Karlstad Ab Machine a fabriquer le papier a air traversant simplifiee possedant une section de formation entre deux toiles
US6398916B1 (en) 1999-12-16 2002-06-04 Valmet Karlstad Ab Simplified through-air drying paper making machine having a twin wire forming section
DE10157467A1 (de) * 2001-11-23 2003-05-28 Voith Paper Patent Gmbh Former
AT412098B (de) * 2002-11-11 2004-09-27 Andritz Ag Maschf Vorrichtung zur trennung einer papierbahn von einem sieb
EP1489229A1 (fr) * 2003-06-18 2004-12-22 Voith Paper Patent GmbH Section de formage à deux toiles d'une machine de fabrication d'une bande de matériau fibreux
DE10327425A1 (de) * 2003-06-18 2005-01-05 Voith Paper Patent Gmbh Doppelsiebformer einer Maschine zur Herstellung einer Faserstoffbahn

Also Published As

Publication number Publication date
FI981098A0 (fi) 1998-05-18
FI981098A7 (fi) 1999-11-19
AU4147099A (en) 1999-12-06

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