Paper machine for manufacturing structured soft paper

Information

  • Patent Grant
  • 6287426
  • Patent Number
    6,287,426
  • Date Filed
    Thursday, September 9, 1999
    25 years ago
  • Date Issued
    Tuesday, September 11, 2001
    23 years ago
Abstract
A paper machine for manufacturing a structured soft paper web are described, which machine has a wet section, a press section, a drying section and a web-carrying clothing running around a suction device close to a smooth impermeable belt in the press section for the creation of a transfer point. In accordance with the invention, structuring means for structuring the web are arranged between the press section and the drying section. The structuring means comprise either said clothing in the shape of a permeable wire, the structure of which is made up of depressions and arched surface parts, including knuckles in a quantity of 25-150 knuckles per cm2, and a suction device that, at a vacuum of 40-80 kPa, draws the web to the structured side of the wire so that the web acquires the structure of the wire, wherein the wire operates at a speed less than or equal to the speed of the belt, or a creping doctor that is located in a space between the belt and the clothing and in scraping contact with the belt so as to loose the web during simultaneous crinkling, the suction device having a suction gap for initial suction of the web firmly to the clothing for transfer to a drying cylinder. The web-carrying clothing operates then at a speed that is less than the speed of the belt.
Description




FIELD OF THE INVENTION




The present invention relates to a paper machine and method for manufacturing a structured fibrous web of soft paper. The invention relates more particularly to such a paper machine and method in which through-air drying of the web is avoided.




BACKGROUND OF THE INVENTION




Paper machines for manufacturing soft paper with high bulk are known through a number of patent specifications. Usually a texturing wire or a texturing felt is used, which, together with the formed paper web, runs through a press nip in which the paper web is pressed into the texturing wire and thus acquires a textured pattern on one of its sides. Paper machines with such texturing wires and press nips are described in U.S. Pat. No. 3,301,746, U.S. Pat. No. 3,537,954, U.S. Pat. No. 4,309,246, U.S. Pat. No. 4,533,437, U.S. Pat. No. 5,569,358, U.S. Pat. No. 5,591,305 and WO 91/16493 (corresponding to SE-466 063). The disadvantage with paper machines in accordance with these patents is that the dewatering in the press nip is relatively low, so that the dry solids content of the paper web is low when the paper web is transferred to the drying cylinder, which results in the output of the paper machine being relatively low.




U.S. Pat. No. 4,849,054 describes a machine for manufacturing a textured fibrous web with high bulk, where the fibrous web is pressed in a single-clothed roller press having a transfer roll, which, together with a texturing wire, defines a nip at a transfer point for the web. The press dewaters the web to a dry solids content of 30 to 50 percent. At the transfer point, the texturing wire runs around a stationary suction pipe, which has a slot opening facing the nip, the slot opening being sufficiently wide that the fibrous web is not compressed when it runs through the nip. By means of the suction from the suction pipe via the slot opening, the fibrous web is transferred to the texturing wire and formed in accordance with the surface of the texturing wire facing the fibrous web, which surface has a three-dimensional pattern. Before the transfer point, the fibrous web has a speed which is greater than the speed of the texturing wire. The roller that carries the fibrous web up to the non-compressing nip has a smooth surface and it is well known that, in practice, there are problems associated with transferring a fibrous web that has been pre-pressed to a dry solids content of 30-50 percent from a smooth surface to a wire and retaining it on the wire. If the suction, for any reason, were to stop or be reduced, the fibrous web would continue with the smooth roller, which might result in shut-down and damage to the machine. The paper machine in accordance with U.S. Pat. No. 4,849,054 cannot be operated at the high speeds that are demanded today, because of the configuration of the press and the transfer point with a stationary suction pipe, around which the texturing wire runs with high friction between them.




A similar arrangement is shown in U.S. Pat. No. 4,834,838, particularly

FIG. 9

, where the fibrous web passes a suction opening so that it is drawn to the wire, whereby the surface facing the wire should acquire a wave-shaped pattern corresponding to the wire, while the other surface of the fibrous web should be smooth. The patent is concerned with the manufacture of fibrous tape base material of the type used in making masking tape, rather than soft structured paper. A foremost concern of the patent is imparting stretchability to the tape base material in the machine direction while making the tape surface smooth and attaining a thin caliper. Differences in speed between the wire and the opposite web-carrying element are used to make the web stretchable. The fibrous web has been dewatered before it reaches said suction opening, but no description is given of how this dewatering is effected in this specific embodiment. In any event, it is not apparent from this patent specification that a bulk should be recreated after pressing in a roller nip. The wave shape, limited to one surface, will be partially or completely destroyed during the subsequent contacts with different elements, such as drying cylinders and felts, although the stretchability achieved in the fibrous web is purportedly retained.




U.S. Pat. No. 5,411,636 describes the manufacture of soft paper, where the paper web is formed on a forming wire, pre-pressed in a double-felted press nip and transferred to a coarse-meshed wire. The paper web, while being carried by the coarse-meshed wire, is subjected to an abrupt vacuum pulse in a suction zone so that the paper web is drawn into the openings and depressions of the wire so that the paper web acquires an increased thickness and, thus, increased bulk. The coarse-meshed wire then carries the paper web to the drying cylinder. The double-felted press nip results in the dry solids content of the paper web after the press nip being relatively low, namely 25-30 percent. As no dewatering can be carried out in the nip at the drying cylinder, the dry solids content of the paper web when it is transferred to the drying cylinder is correspondingly low.




To increase the dry solids content of the paper web up to the drying cylinder without subjecting the paper web to extreme compressing forces in one or several press nips, the technique of through-blow drying is often used, as shown, for instance, in U.S. Pat. No. 3,301,746, U.S. Pat. No. 5,411,636, U.S. Pat. No. 5,667,636 (corresponding to WO 95/00706), U.S. Pat. No. 4,440,597, U.S. Pat. No. 5,364,504, U.S. Pat. No. 5,529,664, U.S. Pat. No. 3,994,771 (corresponding to SE-7605986-4), and U.S. Pat. No. 4,529,480. This technique produces a paper web with high bulk. A paper machine with through-blow drying does, however, entail high investment costs as well as high running costs, mainly with respect to energy consumption.




SUMMARY OF THE INVENTION




The present invention seeks to provide an improved paper machine with which it is possible, without through-blow drying, to re-create at least an essential part of the bulk reduction experienced by the paper web when it is initially dewatered in a roll-press or shoe-press nip, and to manufacture a fibrous web with high bulk and a high dry solids content before the drying cylinder so as to achieve high production at a reasonable cost.




The invention also seeks to provide an improved paper machine that produces a paper web that qualitatively equals the results achieved by through-blow drying, but at a lower cost in respect of installation as well as operation and without hot air being required.




The invention further seeks to provide a paper machine that has a press section in which a high level of dewatering of the paper web is carried out and which has webstructuring components arranged before the drying cylinder that re-create an essential part of the bulk lost during pressing.




In accordance with a preferred embodiment of the invention, a paper machine comprises a wet section operable to form a wet fibrous web, a press section arranged to receive the web from the wet section and to dewater the web, an endless clothing that receives the web downstream of the press section, and a drying section having a drying cylinder that forms a transfer nip with a transfer roll about which the clothing with the web carried thereon passes. The press section includes at least one press having two cooperating press members forming a press nip therebetween, the press further including a smooth impermeable belt and a press felt arranged to pass through the press nip with the web enclosed therebetween. The endless clothing runs in a loop and is arranged to receive the web from the impermeable belt downstream of the press section. The clothing is arranged to pass over a transfer device disposed proximate to the impermeable belt and the transfer device is operable to suction the web onto the clothing at a transfer point, the clothing with the web carried thereon then passing around the transfer roll. The web passes through the transfer nip and is transferred onto the drying cylinder in the transfer nip. The paper machine further includes at least one web-structuring component for structuring the web disposed downstream of the press section and upstream of the drying section. The web-structuring component comprises one of (1) the clothing formed as a permeable wire with a web-contacting structured side having depressions defined therein, and a suction device disposed in the loop of the clothing and in slidable contact with a side of the clothing opposite from the structured side thereof, the suction device being operable to draw the fibrous web into intimate contact with the structured side of the clothing so that the fibrous web is deflected into said depressions and assumes the structure of the structured side, and wherein the clothing travels at a speed equal to or less than that of the smooth impermeable belt; and (2) a creping doctor in scraping contact with the smooth impermeable belt at a location proximate to and upstream of the transfer point where the web is transferred onto the clothing, the creping doctor being operable to scrape the web from the impermeable belt and to crepe the web, and wherein the clothing carrying the web to the drying cylinder travels at a speed that is less than that of the smooth impermeable belt.




Preferably, the clothing, onto which the web is transferred from the impermeable belt, travels at a speed less than that of the impermeable belt. Accordingly, a “rush-transfer” onto the clothing is achieved, which imparts micro-crinkling of the web so as to foreshorten the web in the machine direction and further structure the web to increase bulk.




When the web-structuring component comprises the clothing formed as a permeable wire and the suction device, the structured side of the clothing preferably includes arched surface parts situated between the depressions, the arched surface parts defining knuckles distributed over the structured side such that there are about 25 to 150 knuckles per cm


2


, and more preferably about 50 to 100 knuckles per cm


2


. The suction device preferably is operable to exert a vacuum of about 40 to 80 kPa.




When the web-structuring component comprises the creping doctor, the impermeable belt is arranged to carry the web past the transfer device such that the web at one point passes closely adjacent to the transfer device, and the creping doctor is disposed downstream of the point where the web passes closely adjacent the transfer device.




In a preferred embodiment of the invention, the impermeable belt is arranged to form a non-compressing nip with the transfer device, or alternatively, the impermeable belt is arranged such that the web and the transfer device form a gap therebetween where the belt passes closest to the transfer device. The gap preferably has a width greater than the thickness of the web.




Preferably, the creping doctor has a doctor blade that forms an acute angle with the smooth impermeable belt of about 5° to 25°. The press section preferably is operable to dewater the fibrous web to achieve a dry solids content of about 35 to 48 percent.




The invention is described further in the following with reference to the drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

shows a paper machine in accordance with a first embodiment of the invention.





FIG. 2

shows a paper machine in accordance with a second embodiment of the invention.





FIG. 3

shows a paper machine in accordance with a third embodiment of the invention.





FIG. 4

shows a paper machine in accordance with a fourth embodiment of the invention.





FIG. 5

shows a paper machine in accordance with a fifth embodiment of the invention.





FIG. 6

shows, in perspective, a surface part of a wire included in the paper machines in accordance with

FIGS. 1-5

.





FIG. 7

shows a paper machine in accordance with a sixth embodiment of the invention.





FIG. 8

shows an enlarged view of a creping doctor and a suction shoe, which are included in the paper machine in accordance with FIG.


7


.





FIG. 9

shows a paper machine in accordance with a seventh embodiment of the invention.











DETAILED DESCRIPTION OF THE INVENTION




The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.




In

FIGS. 1-5

,


7


and


9


, parts of paper machines for manufacturing a structured fibrous web


1


of soft paper, such as tissue and other paper products with low density, are shown schematically. Each of the paper machines comprises a wet section


2


, a press section


3


and a drying section


4


. The wet section


2


comprises a headbox


7


, a forming roll


8


, an endless carrying inner clothing


9


and an endless covering outer clothing


10


consisting of a forming wire. The inner and outer clothings


9


and


10


run in separate loops around several guide rolls


11


and


12


respectively. The drying section


4


comprises a drying cylinder


5


, which is covered by a hood


30


. Preferably, the drying cylinder and hood collectively comprise a Yankee dryer. At the outlet side of the drying section a creping doctor


21


is arranged to crepe the fibrous web


1


off the drying cylinder


5


. An application device


31


is provided for applying a suitable glue on the envelope surface of the drying cylinder


5


just before a transfer nip. The press section


3


comprises a press, which has two cooperating first and second press members


14


and


19


, which press members


14


and


19


together define a press nip. Further, the press section comprises an endless press felt


15


, which runs in a loop around the first press member


14


and guide rolls


6


, and an endless impermeable belt


16


, which has a smooth surface facing the fibrous web. The smooth impermeable belt


16


runs in a loop around the second press member


19


and a plurality of guide rolls


18


.




In the embodiments shown in

FIGS. 1-3

, the press is a shoe press, the first and second press members of which consist of a shoe press roll


14


and a counter roll


19


. The shoe press roll


14


and the counter roll


19


define between them an extended press nip.




In the embodiments shown in

FIGS. 4

,


5


,


7


and


9


, the press is a roll press, the first and second press members of which consist of a suction roll


14


and a smooth roll


19


. In the embodiment shown in

FIG. 9

, the press section has two presses, namely the aforementioned roll press, followed by a shoe press, comprising a shoe press roll


32


and a counter roll


33


, which together define an extended press nip. The clothings of the shoe press may preferably be the same as the clothings


15


and


16


of the roll press, that is to say that the press felt


15


and the impermeable belt


16


run through the extended press nip in the shoe press. The shoe press roll


32


is arranged in the loop of the press felt


15


, which loop comprises a side loop part


34


, which runs to an extended suction zone around the suction roll


14


and around guide rolls


37


and then to the extended press nip. Thus rewetting of the fibrous web is prevented and water is removed from the press felt


15


. The counter roll


33


is arranged in the loop of the impermeable belt


16


. In the embodiment shown in

FIG. 9

the same counter roll is used for the two press nips.




In the embodiments shown in

FIGS. 2 and 4

, the inner clothing


9


of the wet section


2


is a felt, which is conveyed to the press section


3


to be utilized as a press felt


15


as well and which thus runs in a loop back to the forming roll


8


.




In the embodiment shown in

FIG. 3

, the inner clothing


9


of the wet section


2


is a smooth impermeable belt, which is conveyed to the press section


3


to be utilized as its belt


16


as well and which thus runs in a loop back to the forming roll


8


.




In the embodiments shown in

FIGS. 1

,


5


, and


7


, the inner clothing


9


of the wet section


2


is a wire, the press felt


15


running around a pick-up roll


20


arranged close to the loop of the wire


9


so that the press felt


15


and the wire


9


run in contact with each other for transfer of the fibrous web from the wire


9


to the press felt


15


. The pick-up roll


20


may be provided with a suction shoe (not shown). Alternatively, the pick-up roll and suction shoe may be replaced by a pick-up suction box. The embodiment shown in

FIG. 9

may have a wet section similar to the one shown in FIG.


7


.




An endless clothing


22


is arranged to run in a loop around a suction device


23


, located adjacent to the smooth belt


16


to define a transfer point


40


for transfer of the fibrous web from the smooth belt


16


to the clothing


22


. The suction device


23


forms a suction zone


41


, designed to enable the suction attachment of the fibrous web and its continued adherence to the clothing


22


as desired. Further, the clothing


22


runs around a transfer roll


24


, which defines a non-compressing nip with the drying cylinder


5


for transfer of the paper web from the clothing


22


to the drying cylinder


5


. In the embodiments shown in

FIGS. 1-5

, said suction device


23


is a suction roll, with which the smooth belt


16


defines a non-compressing nip, wherein the suction zone


41


encompasses a sector angle sufficient to secure the transfer of the fibrous web from the smooth belt


16


to the clothing


22


. In the embodiment shown in

FIGS. 7-9

, the suction device is a suction shoe. In

FIGS. 7 and 8

, the suction shoe


23


and the smooth belt


16


are arranged so close to each other that a non-compressing nip is defined between the clothing


22


and the belt


16


. In

FIG. 9

, the suction shoe


23


and the smooth belt


16


are arranged at a distance from each other so that during operation a gap


42


exists between the clothing


22


and the belt


16


, which is greater than the thickness of the web. In the embodiments shown in

FIGS. 7-9

, the suction zone


41


of the suction shoe


23


is located downstream of said non-compressing nip or, as the case may be, gap


42


.




The shown paper machines also comprise special structuring means for structuring the paper web, before it reaches the drying roll


6


, in order to achieve increased bulk.




In the embodiments shown in

FIGS. 1-5

, said structuring means comprise said clothing


22


, that is in the shape of a wire, and a powerful suction device


25


.

FIG. 6

shows an enlargement of a cut-out surface section of the wire


22


, where the machine direction is indicated by an arrow. The wire


22


has a web-contacting side with a structure that is made up of depressions


35


and arched or convex surface parts


36


situated therebetween. The depressions


35


are through-going such that air can be sucked through the wire


22


to the desired extent. The depressions


35


and the arched surface parts


36


are in turn made up of the strands of the wire


22


running longitudinally and transversely as seen in the machine direction, the longitudinal strands exhibiting oblong arc-shaped ridges


36




a


and the transverse strands exhibiting knuckles


36




b


, which knuckles produce bowl-shaped pits in the fibrous web during the structuring process. In the embodiment shown in

FIG. 6

, the wire has 100 knuckles


36




b


per cm


2


. Generally, it may exhibit 25-150 knuckles per cm


2


, preferably 50-100 knuckles per cm


2


. The powerful suction device mentioned is placed in the loop of the wire


22


upstream of the transfer roll


24


in sliding contact with the wire. The powerful suction device, which may consist of one or several suction boxes, operates at a high vacuum, which acts on the inside of the permeable wire. A suitable vacuum is within the range 40-80 kPa. When the fibrous web passes the powerful suction device together with the wire, the fibrous web is deflecting into the depressions of the wire


22


, whereby the fibrous web will assume the structure of the wire as an impression. As the fibrous web is subjected to a high vacuum and the fibrous web is still damp during this suction phase, the structure of the fibrous web will remain after the suction device. To achieve the desired structuring it is also important that the speed of the wire


22


is equal to and preferably less than the speed of the smooth impermeable belt


16


. Most preferred, this difference in speed is 10-25 percent.




In the embodiments shown in

FIGS. 7-9

, said structuring means comprise a creping doctor


26


, the doctor blade


43


of which is aimed against the movement direction of the smooth impermeable belt


16


and forms an acute angle a with the belt


16


. This angle α can be in the range 5°-25°, preferably 10°-15°. The creping doctor


26


operates continuously with its doctor blade


43


against the smooth surface of the belt


16


so that the fibrous web is loosed from the belt


16


through scraping and crinkled in the same way as during creping of the fibrous web from the drying cylinder


5


. The fibrous web, crinkled through scraping, is conveyed away from the belt up towards a downstream section of the suction shoe


23


having a suction slit


27


, which the fibrous web passes during suction attachment to the clothing


22


, which may be a wire or a felt. The creping doctor


26


is arranged at a short distance from and downstream of the non-compressing nip (

FIGS. 7

,


8


) or, as the case may be, gap


42


(

FIG. 9

) that is defined by the suction shoe


23


and the smooth belt, so that a small space is created between the suction shoe


23


and the creping doctor


26


, as measured at the edge of the doctor blade


43


. To achieve the desired structuring, that is creping, the speed of the wire or felt


22


is less than the speed of the smooth impermeable belt


16


. Most preferred, the difference in speed is 10-25 percent. By the use of the creping doctor


26


, the fibrous web obtains a crinkled structure that results in increased stretchability and bulk. The nip between the transfer roll


24


and the drying cylinder


5


is non-compressing and the improved properties are not negatively affected by the transfer of the fibrous web to the drying cylinder


5


.




As mentioned above, the transfer point at the suction device


23


as shown in

FIGS. 1-8

has a non-compressing nip between the clothing


22


and the smooth belt


16


. A non-compressing nip is desired particularly for bulk-sensitive grades, for instance tissue. The expression “non-compressing nip” means that the nip should compress the web to such a small extent that after the nip the web substantially regains the bulk it had before the nip. To ensure that as high bulk as possible is maintained, the distance between the suction device


23


and the belt


16


may be pre-set, while the paper machine is not running, so that a small gap is created between the clothing


22


and the belt


16


. When a suction roll


23


as shown in

FIGS. 1-5

is used, or a suction shoe with a suction zone in the same position, the suction from the suction roll


23


or, alternatively, the suction shoe will during operation lift the belt


16


with the web lying thereon into contact with the wire to define said non-compressing nip. This facilitates a so-called “rush transfer” or “microcontraction”, that is to say that the wire


22


runs at a lower speed than the belt


16


so that the web is contracted lengthways causing fine crinkling, so-called micro-creping, as the web runs through the non-compressing nip. The contraction results in increased web thickness. The web will be subjected to a micro-creping when it passes the noncompressing nip at the transfer point as shown in

FIGS. 1-5

even if said pre-setting is not carried out, provided that the wire runs at a lower speed than the belt


16


. It will be apparent that a greater difference in speed between the wire and the belt will result in augmented fine crinkling. Micro-creping is also obtained in the embodiment shown in

FIGS. 7 and 8

when the web passes the non-compressing nip, which lacks a suction zone, since the clothing


22


operates at a lower speed than the belt


16


to achieve creping when the web is loosed from the belt by the creping doctor.




In the embodiments shown in

FIGS. 1-3

, the counter roll


19


is a smooth roll and is arranged in the loop of the smooth impermeable belt


16


. In alternative embodiments (not shown) of the press section shown in

FIGS. 1-3

, the positions of the rolls


14


,


19


are reversed, that is to say that the shoe press roll


14


is arranged in the loop of the smooth impermeable belt


16


and the counter roll


19


in the loop of the press felt


15


. In such a configuration, the counter roll


19


may be a suction roll, a grooved roll or a blind-drilled roll.




The paper web is carried to the single-felted press section either by the press felt


15


(

FIGS. 1

,


2


,


4


,


5


,


7


,


9


) directly from the forming roll (

FIGS. 2 and 4

) or from the inner forming wire


9


(

FIGS. 1

,


5


,


7


and


9


) or by the smooth belt


16


(

FIG. 3

) to be conveyed through the press nip whilst enclosed between the press felt


15


and the smooth belt


16


. By use of the shown presses, the paper web obtains a dry solids content of at least 35 percent and preferably in the range 38-45 percent. After the single press nip or the second press nip (FIG.


9


), the press felt


15


is conveyed away from the smooth belt


16


, which in all the embodiments carries the paper web up to the clothing


22


.




Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.



Claims
  • 1. A paper machine for manufacturing a structured fibrous web of soft paper, comprising:a wet section operable to form a wet fibrous web; a press section arranged to receive the web from the wet section and including at least one press having two cooperating press members forming a press nip therebetween, the press further including a smooth impermeable belt and a press felt arranged to pass through the press nip with the web enclosed therebetween; a clothing running in a loop and arranged to receive the web from the impermeable belt downstream of the press section, the clothing being arranged to pass over a transfer device disposed proximate to the impermeable belt and the transfer device being operable to suction the web onto the clothing at a transfer point, the clothing with the web carried thereon passing around a transfer roll; a drying section including a drying cylinder forming a transfer nip with the transfer roll such that the web passes through the transfer nip and is transferred onto the drying cylinder thereat; and at least one web-structuring component for structuring the web disposed downstream of the press section and upstream of the drying section, the web-structuring component comprising one of: (1) the clothing formed as a permeable wire with a web-contacting structured side having depressions defined therein, and a suction device disposed in the loop of the clothing and in slidable contact with a side of the clothing opposite from the structured side thereof, the suction device being operable to draw the fibrous web into intimate contact with the structured side of the clothing so that the fibrous web is deflected into said depressions and assumes the structure of the structured side, and wherein the clothing travels at a speed equal to or less than that of the smooth impermeable belt; and (2) a creping doctor in scraping contact with the smooth impermeable belt at a location proximate to and upstream of the transfer point where the web is transferred onto the clothing, the creping doctor being operable to scrape the web from the impermeable belt and to crepe the web, and wherein the clothing carrying the web to the drying cylinder travels at a speed that is less than that of the smooth impermeable belt.
  • 2. The paper machine of claim 1, wherein the web-structuring component comprises the clothing formed as a permeable wire and the suction device, and wherein the clothing travels at a speed less than that of the impermeable belt.
  • 3. The paper machine of claim 1, wherein the web-structuring component comprises the clothing formed as a permeable wire and the suction device, and wherein the structured side of the clothing includes arched surface parts situated between the depressions, the arched surface parts defining knuckles distributed over the structured side such that there are about 25 to 150 knuckles per cm2.
  • 4. The paper machine of claim 3, wherein the structured side of the clothing has about 50 to 100 knuckles per cm2.
  • 5. The paper machine of claim 3, wherein the suction device is operable to exert a vacuum of about 40 to 80 kPa.
  • 6. The paper machine of claim 1, wherein the web-structuring component comprises the creping doctor, the impermeable belt being arranged to carry the web past the transfer device such that the web at one point passes closely adjacent to the transfer device, and the creping doctor being disposed downstream of said one point where the web is closely adjacent the transfer device.
  • 7. The paper machine of claim 6, wherein the impermeable belt is arranged to form a non-compressing nip with the transfer device at said one point.
  • 8. The paper machine of claim 6, wherein the impermeable belt is arranged such that the web and the transfer device form a gap therebetween at said one point.
  • 9. The paper machine of claim 8, wherein the gap has a width greater than the thickness of the web.
  • 10. The paper machine of claim 6, wherein the creping doctor has a doctor blade that forms an acute angle with the smooth impermeable belt of about 5° to 25°.
  • 11. The paper machine of claim 1, wherein the press section is operable to dewater the fibrous web to achieve a dry solids content of about 35 to 48 percent.
  • 12. The paper machine of claim 1, wherein the press section comprises two presses.
  • 13. The paper machine of claim 12, wherein the two presses share a common press member that forms two nips with a pair of cooperative press members, the press felt and the impermeable belt being arranged to pass through the two nips with the web enclosed therebetween.
Priority Claims (1)
Number Date Country Kind
9803041 Sep 1998 SE
CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/113,175 filed Dec. 21, 1998.

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Provisional Applications (1)
Number Date Country
60/113175 Dec 1998 US