WO2003046279A1 - A pressing felt - Google Patents

A pressing felt Download PDF

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Publication number
WO2003046279A1
WO2003046279A1 PCT/EP2002/013380 EP0213380W WO03046279A1 WO 2003046279 A1 WO2003046279 A1 WO 2003046279A1 EP 0213380 W EP0213380 W EP 0213380W WO 03046279 A1 WO03046279 A1 WO 03046279A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressing
felt
pressing felt
fiber web
layer
Prior art date
Application number
PCT/EP2002/013380
Other languages
French (fr)
Inventor
Wolfgang Bamberger
Ulrich Begemann
Joachim Grabscheid
Georg Kleiser
Wolfgang Mayer
Ralf Rziha
Thomas Ruehl
Oswald Satzer
Original Assignee
Voith Paper Patent Gmbh
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 Voith Paper Patent Gmbh filed Critical Voith Paper Patent Gmbh
Publication of WO2003046279A1 publication Critical patent/WO2003046279A1/en

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F3/00—Press section of machines for making continuous webs of paper
    • D21F3/02—Wet presses
    • D21F3/029—Wet presses using special water-receiving belts
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00—Other details of machines for making continuous webs of paper
    • D21F7/08—Felts
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F7/00—Other details of machines for making continuous webs of paper
    • D21F7/08—Felts
    • D21F7/083—Multi-layer felts

Definitions

  • the invention relates to a pressing felt for pressing sections for the dewa- tering of paper webs, board webs, tissue webs or other fiber webs, with the fiber web being guided together with at least one flexible, endless and water absorbing pressing felt through a press nip and with the pressing felt having a smooth and/ or soft contact surface with respect to the fiber web.
  • Pressing felts absorb the water pressed out of the fiber web in the press nip. Since the pressing felts are compressed by the pressing pressure, the water absorption capability of the pressing felts in the press nip is generally not sufficient. The superfluous water therefore moves through the pressing felt to the press roll which usually has a profiled surface in the form of grooves and blind bores. If these grooves and blind bores are not sufficiently emptied prior to the entry into the press nip, then a hydraulic counter-pressure builds up in the press nip which hinders the dewatering. If this, moreover, also occurs with a differently strongly pronounced effect transversely to the web running direction, then this has a negative influence on the transverse moisture profile.
  • the pressing felt is designed in a relatively form stable manner in the pressing direction, with the thickness of the pressing felt reducing by a maximum of 40%, preferably by a maximum of 25%, with pressing pressures in the range between 4 and 11 MPa, and with the pressing felt preferably being made up of two layers which are capable of being separated for the purpose of separate treatment.
  • the pressing felt Due to the relatively non-compressible design of the pressing felt, its water absorbing capability in the press nip increases substantially such that the water pressed out of the fiber web can be transported out of the press nip without problem.
  • the open volume of the pressing roll surface is not subjected to water temporarily escaping from the pressing felt into the open volume in the press nip.
  • the pressing felt After the press nip, the pressing felt must again be treated, in particular dried, in a known manner. Since no substantial hydraulic counter-pressure builds up in the press nip, no negative influencing of the transverse moisture profile arises in the press nip.
  • the pressing felt should consist of at least two flexible, water absorbing layers, with the contact layer coming into contact with the fiber web being water permeable and a having a relatively smooth and/ or soft contact surface, and the other form layer being made in a relatively form stable manner in the pressing direction.
  • the contact layer can be made as a nap layer and the form layer can be formed by a preferably water permeable layer structure, fabric or wire.
  • the nap layer is relatively compressible and soft so that no impairment of the surface of the fiber web arises even with a high pressing pressure in the press nip.
  • the form layer is very largely non-compressible and the water storage capacity remaining on pressing pressure should be matched to the demands on the part of the water arising in the press nip in dependence on the type and kind of the fiber web.
  • the compressibility of the pressing felt is, in this connection, substantially determined by the thickness ratio of the two layers and the contact layer should be dimensioned such that there is no impermissible impairment of the surface of the fiber web in the press nip.
  • the pressing felt consists of two flexible, water absorbing belts, with the contact belt coming into contact with the fiber web being water permeable and having a relatively smooth and/ or soft contact surface and the other form belt being made in a relatively form stable manner in the pressing direction. It is advantageous in this connection for the contact belt to be formed by a relatively thin pressing felt and the form belt to be formed by a preferably water permeable pressing wire.
  • This form of realization can have advantages in the manufacture of the belt. In particular, however, the treatment, especially the drying, of the form belt, can be made easier.
  • Figure 1 a schematic cross-section through a pressing felt 2 in accordance with the invention
  • Figure 2 a schematic cross-section through a press arrangement.
  • the pressing felt 2 consists of a form layer 4, which is relatively stable in form in the pressing direction, but is flexible and water permeable, and of a compressible contact layer 3.
  • the contact layer 3 comes into contact with the fiber web to be dewatered and therefore has a soft surface to treat the fiber web 1 gently.
  • the contact layer 3 is formed by a thin fabric having a nap layer at the surface. This nap layer provides the softness and thus presents impregnation of the pressing felt 2 even at the high pressing pressures in the press nip.
  • the form layer 4 is designed in wire form so that the water can be stored in the openings and superfluous water can be led to the pressing roll 7.
  • the form layer 4 is so stable in the pressing direction that the thickness of the pressing felt 2 is reduced by a maximum of approximately 25% at pressing pressures of more than 4 MPa.
  • Figure 2 shows a pressing arrangement comprising a press nip formed by two rotating pressing rolls 7.
  • the press nip is made in an extended manner in the interest of a high dewatering performance, which is why the lower pressing roll 7 has a flexible roll jacket which is guided in the press nip region via a pressing element with a concave pressing surface.
  • One pressing felt 2 each runs through the pressing gap on both sides next to the fiber web 1.
  • the lower pressing felt 2 hands over the fiber web 1 to a belt 10 of a unit succeeding in the web running direction 8.
  • the pressing felt 2 in Figure 2 consists of a flexible and water permeable contact belt 5 with a soft surface and a flexible, but form stable form belt 6 in the pressing direction, which is likewise water permeable.
  • the contact belt 5 here consists of a thin pressing felt and the form belt 6 of a pressing wire, with the form belt 6 encompassing approximately 80% of the thickness of the pressing felt 2 in the unloaded state. At pressing pressures of more than 4 MPa, the thickness of the pressing felt reduces by a maximum of approximately 25%.
  • Sine the pressing felt 2 consists of two belts, these can also be treated separately. This takes place after the handing over of the fiber web 1 to the succeeding unit, with the contact belt 5 and the form belt 6 being led past a respective treatment device 9 separately from one another. This does not only simplify the cleaning of the belts, but also, and to a substantial degree, the drying of, in particular, the form belt 6.
  • the remaining thickness must ensure a sufficient water absorbing capability in the press nip in particular of the form layer 4 or of the form belt 6 respectively.

Abstract

The invention relates to a pressing felt (2) for pressing sections for the dewatering of paper webs, board weds, tissue webs or other fiber webs (1), with the fiber web (1) being guided together with at least one flexible, endless and water absorbing pressing felt (2) through a press nip and with the pressing felt (2) having a smooth and/or soft contact surface with respect to the fiber web (1). In this connection, the water absorbing capability of the pressing felt (2) should be improved in that the pressing felt (2) is designed in a relatively form stable manner in the pressing direction, with the thickness of the pressing felt reducing by a maximum of 40 %, preferably by a maximum of 25 %, with pressing pressures in the range between 4 and 11 MPa, and with the pressing felt preferably being made up of two layers (3, 4, 5, 6) which are capable of being separated for the purpose of separate treatment.

Description

A pressing felt
The invention relates to a pressing felt for pressing sections for the dewa- tering of paper webs, board webs, tissue webs or other fiber webs, with the fiber web being guided together with at least one flexible, endless and water absorbing pressing felt through a press nip and with the pressing felt having a smooth and/ or soft contact surface with respect to the fiber web.
Pressing felts absorb the water pressed out of the fiber web in the press nip. Since the pressing felts are compressed by the pressing pressure, the water absorption capability of the pressing felts in the press nip is generally not sufficient. The superfluous water therefore moves through the pressing felt to the press roll which usually has a profiled surface in the form of grooves and blind bores. If these grooves and blind bores are not sufficiently emptied prior to the entry into the press nip, then a hydraulic counter-pressure builds up in the press nip which hinders the dewatering. If this, moreover, also occurs with a differently strongly pronounced effect transversely to the web running direction, then this has a negative influence on the transverse moisture profile. As a rule, it is even the case in modern fast running paper making machines that even the water transported into the nip by the pressing felt temporarily has to escape into the open volume of the roll surface as a result of the pressing felt compression in the press nip. Frequently a higher water content is measured in practice in the pressing felt before the press nip than after the press nip. It is therefore the object of the invention to ensure a sufficient water absorbing capability in the press nip.
The object has been solved in accordance with the invention in that the pressing felt is designed in a relatively form stable manner in the pressing direction, with the thickness of the pressing felt reducing by a maximum of 40%, preferably by a maximum of 25%, with pressing pressures in the range between 4 and 11 MPa, and with the pressing felt preferably being made up of two layers which are capable of being separated for the purpose of separate treatment.
Due to the relatively non-compressible design of the pressing felt, its water absorbing capability in the press nip increases substantially such that the water pressed out of the fiber web can be transported out of the press nip without problem. In particular, the open volume of the pressing roll surface is not subjected to water temporarily escaping from the pressing felt into the open volume in the press nip. After the press nip, the pressing felt must again be treated, in particular dried, in a known manner. Since no substantial hydraulic counter-pressure builds up in the press nip, no negative influencing of the transverse moisture profile arises in the press nip.
In a preferred compact design, the pressing felt should consist of at least two flexible, water absorbing layers, with the contact layer coming into contact with the fiber web being water permeable and a having a relatively smooth and/ or soft contact surface, and the other form layer being made in a relatively form stable manner in the pressing direction. In this connection, the contact layer can be made as a nap layer and the form layer can be formed by a preferably water permeable layer structure, fabric or wire. The nap layer is relatively compressible and soft so that no impairment of the surface of the fiber web arises even with a high pressing pressure in the press nip. The form layer is very largely non-compressible and the water storage capacity remaining on pressing pressure should be matched to the demands on the part of the water arising in the press nip in dependence on the type and kind of the fiber web. The compressibility of the pressing felt is, in this connection, substantially determined by the thickness ratio of the two layers and the contact layer should be dimensioned such that there is no impermissible impairment of the surface of the fiber web in the press nip.
Another aspect results when the pressing felt consists of two flexible, water absorbing belts, with the contact belt coming into contact with the fiber web being water permeable and having a relatively smooth and/ or soft contact surface and the other form belt being made in a relatively form stable manner in the pressing direction. It is advantageous in this connection for the contact belt to be formed by a relatively thin pressing felt and the form belt to be formed by a preferably water permeable pressing wire. This form of realization can have advantages in the manufacture of the belt. In particular, however, the treatment, especially the drying, of the form belt, can be made easier.
The use of such pressing felts in extended press nips bring about special advantages since these have a high dewatering capacity, with the press nip generally being formed by two rotating pressing rolls. The invention will be described in more detail in the following with reference to an embodiment. The enclosed drawing shows:
Figure 1 : a schematic cross-section through a pressing felt 2 in accordance with the invention; and Figure 2: a schematic cross-section through a press arrangement.
In accordance with Figure 1, the pressing felt 2 consists of a form layer 4, which is relatively stable in form in the pressing direction, but is flexible and water permeable, and of a compressible contact layer 3. The contact layer 3 comes into contact with the fiber web to be dewatered and therefore has a soft surface to treat the fiber web 1 gently. The contact layer 3 is formed by a thin fabric having a nap layer at the surface. This nap layer provides the softness and thus presents impregnation of the pressing felt 2 even at the high pressing pressures in the press nip.
The form layer 4 is designed in wire form so that the water can be stored in the openings and superfluous water can be led to the pressing roll 7.
In this connection, the form layer 4 is so stable in the pressing direction that the thickness of the pressing felt 2 is reduced by a maximum of approximately 25% at pressing pressures of more than 4 MPa.
Figure 2 shows a pressing arrangement comprising a press nip formed by two rotating pressing rolls 7. The press nip is made in an extended manner in the interest of a high dewatering performance, which is why the lower pressing roll 7 has a flexible roll jacket which is guided in the press nip region via a pressing element with a concave pressing surface. One pressing felt 2 each runs through the pressing gap on both sides next to the fiber web 1.
While the upper pressing felt 2 carries the fiber web 1 to the press nip, the lower pressing felt 2 hands over the fiber web 1 to a belt 10 of a unit succeeding in the web running direction 8.
To realize the form stability and a surface which treats the fiber web 1 gently, the pressing felt 2 in Figure 2 consists of a flexible and water permeable contact belt 5 with a soft surface and a flexible, but form stable form belt 6 in the pressing direction, which is likewise water permeable. The contact belt 5 here consists of a thin pressing felt and the form belt 6 of a pressing wire, with the form belt 6 encompassing approximately 80% of the thickness of the pressing felt 2 in the unloaded state. At pressing pressures of more than 4 MPa, the thickness of the pressing felt reduces by a maximum of approximately 25%.
Sine the pressing felt 2 consists of two belts, these can also be treated separately. This takes place after the handing over of the fiber web 1 to the succeeding unit, with the contact belt 5 and the form belt 6 being led past a respective treatment device 9 separately from one another. This does not only simplify the cleaning of the belts, but also, and to a substantial degree, the drying of, in particular, the form belt 6.
In both cases, the remaining thickness must ensure a sufficient water absorbing capability in the press nip in particular of the form layer 4 or of the form belt 6 respectively.

Claims

Claims
1. A pressing felt (2) for pressing sections for the dewatering of paper webs, board webs, tissue webs or other fiber webs (1), with the fiber web (1) being guided together with at least one flexible, endless and water absorbing pressing felt (2) through a press nip and with the pressing felt (2) having a smooth and/ or soft contact surface with respect to the fiber web (1), characterized in that the pressing felt (2) is designed in a relatively form stable manner in the pressing direction, with the thickness of the pressing felt (2) reducing by a maximum of 40%, preferably by a maximum of 25%, with pressing pressures in the range between 4 and 11 MPa, and with the pressing felt (2) preferably being made up of two layers (3, 4; 5, 6) which are capable of being separated for the purpose of separate treatment.
2. A pressing felt (2) in accordance with claim 1, characterized in that the pressing felt consists of at least two flexible, water absorbing layers, with the contact layer (3) coming into contact with the fiber web (1) being water permeable and a having a relatively smooth and/ or soft contact surface, and the other form layer (4) being made in a relatively form stable manner in the pressing direction.
3. A pressing felt (2) in accordance with claim 2, characterized in that the contact layer (3) is made as a nap layer and the form layer is formed by a preferably water permeable layer structure, fabric or wire.
4. A pressing felt (2) in accordance with claim 1, characterized in that the pressing felt (2) consists of two flexible, water absorbing belts, with the contact belt (5) coming into contact with the fiber web (1) being water permeable and having a relatively smooth and/ or soft contact surface and the other form belt (6) being made in a relatively form stable manner in the pressing direction.
5. A pressing felt (2) in accordance with claim 4, characterized in that the contact belt (5) is formed by a relatively thin pressing felt and the form belt (6) by a preferably water permeable pressing wire.
6. Use of the pressing felt (2) in accordance with any one of the preceding claims, characterized in that the press nip is made in an extended manner and is formed by two rotating press rolls (7).
PCT/EP2002/013380 2001-11-28 2002-11-27 A pressing felt WO2003046279A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2001158456 DE10158456A1 (en) 2001-11-28 2001-11-28 press felt
DE10158456.3 2001-11-28

Publications (1)

Publication Number Publication Date
WO2003046279A1 true WO2003046279A1 (en) 2003-06-05

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PCT/EP2002/013380 WO2003046279A1 (en) 2001-11-28 2002-11-27 A pressing felt

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WO (1) WO2003046279A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111764191A (en) * 2020-07-27 2020-10-13 吴文华 Three-layer forming net for papermaking

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3214331A (en) * 1963-03-14 1965-10-26 Huyck Corp Double fabric paper press
US3257268A (en) * 1962-02-13 1966-06-21 Mead Corp Paper pressing process and apparatus utilizing water receiving belt
US4529643A (en) * 1982-10-08 1985-07-16 Tamfelt Oy Ab Press felt for paper making and a method of manufacturing such a felt
EP0665328A1 (en) * 1990-10-11 1995-08-02 Beloit Technologies, Inc. Papermaking apparatus for pressing and drying a web
US5871887A (en) * 1994-06-29 1999-02-16 The Procter & Gamble Company Web patterning apparatus comprising a felt layer and a photosensitive resin layer

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3214330A (en) * 1963-01-24 1965-10-26 Huyck Corp Duplex fabric paper press
US3214327A (en) * 1963-04-16 1965-10-26 Huyck Corp Papermakers' felts and method for dewatering paper and similar webs
DE4138789A1 (en) * 1991-11-26 1993-05-27 Escher Wyss Gmbh Paper making press section to remove water from web of fibre pulp - has a permeable belt against web pulp passing through pressure gap between two surfaces

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3257268A (en) * 1962-02-13 1966-06-21 Mead Corp Paper pressing process and apparatus utilizing water receiving belt
US3214331A (en) * 1963-03-14 1965-10-26 Huyck Corp Double fabric paper press
US4529643A (en) * 1982-10-08 1985-07-16 Tamfelt Oy Ab Press felt for paper making and a method of manufacturing such a felt
EP0665328A1 (en) * 1990-10-11 1995-08-02 Beloit Technologies, Inc. Papermaking apparatus for pressing and drying a web
US5871887A (en) * 1994-06-29 1999-02-16 The Procter & Gamble Company Web patterning apparatus comprising a felt layer and a photosensitive resin layer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111764191A (en) * 2020-07-27 2020-10-13 吴文华 Three-layer forming net for papermaking
CN111764191B (en) * 2020-07-27 2023-11-14 四川成发造纸机械有限公司 Three-layer forming net for papermaking

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