CA2040509C - Apparatus for reducing the water content of a formed web - Google Patents
Apparatus for reducing the water content of a formed webInfo
- Publication number
- CA2040509C CA2040509C CA 2040509 CA2040509A CA2040509C CA 2040509 C CA2040509 C CA 2040509C CA 2040509 CA2040509 CA 2040509 CA 2040509 A CA2040509 A CA 2040509A CA 2040509 C CA2040509 C CA 2040509C
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- Canada
- Prior art keywords
- web
- press
- water
- pressing
- pressed
- Prior art date
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Abstract
An apparatus and method is disclosed for reducing the water content of a formed web. The apparatus includes a press for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through the press. A dryer is disposed downstream relative to the press for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer. A further press is disposed downstream relative to the dryer for further pressing the dried web such that a third portion of water is removed from the dried web. The further press includes a heated backing roll and an elongate press member which cooperates with the backing roll for defining therebetween an elongate pressing section for the passage therethrough of the dried web. The dried web is subjected to increased pressure and temperature for an extended period during passage through the pressing section so that water vapor is generated within the pressing section for urging the third portion of water in the liquid phase away from the web, thereby inhibiting delamination of the further pressed web.
Description
- - 20~0509 . PATENT APPLICATION
TITLE: AN APPARATUS FOR REDUCING THE WATER CONTENT OF A
FORMED WEB
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for reducing the water content of a formed web. More particularly, the present invention relates to an apparatus for inhibiting delamination of a pressed web during passage of the web through ~ heated elongate pressing section.
INFORMATION DISCLOSURE STATEMENT
In a typical papermaking process, a slurry of paper stock is ejected onto a moving fourdrinier screen where the slurry is initially dewatered in order to provide a formed web which is subsequently removed from the fourdrinier screen. The formed web is then pressed between counter-rotating rolls for removing a further quantity of water from the formed web. The pressed web is then guided around a plurality of drying cylinders until the desired water content of the dried web is achieved.
Because of the enormous thermal input requirement of a typical drying section, various attempts have been made in order to increase the amount of water removed from the formed web in the press section.
Notably, the extended nip press has greatly increased the amount of water removed from the formed web during the pressing operation. Essentially, the extended nip press includes a backing roll and an elongate pressing shoe which cooperates with the backing roll to define therebetween an elongate pressing section. An endless looped blanket extends through the pressing section such that when the formed web is disposed between the blanket and the backing roll, the residence time of the web within the pressing section is increased and a correspondingly greater quantity of water is remo~ed from the web. Consequently, less water is present in the pressed web entering the dryer section, thereby reducing the thermal input requirements of the dryer section.
More recently, as taught in U.S. Patent No. 4,738,752 to Busker et al, it was discovered that by heating the backing roll to an elevated temperature, even greater quantities of water could be removed from the web during the passage of the web through the elongate pressing section. The theory behind the so-called heated extended nip press process was that water vapor generated within the elongate pressing section by the heated backing roll urged water in the liquid phase disposed within the web away from the web.
However, although the heated extended nip exhibited greatly increased water removing capabilities, a problem was experienced in certain paper grades in that the web exiting the extended pressing section tended to delaminate.
Accordingly, the present invention seeks to overcome the aforementioned problem associated with known high temperature extended pressing techniques and provides an apparatus for reducing the water content of a formed web that makes a considerable contribution to the web pressing art.
More particularly, the backing roll of the heated extended nip press of the aforementioned U.S. Patent No.
4,738,752 is heated to a surface temperature in excess of 250 Fahrenheit. The high surface temperature rapidly heats the web as it passes through the extended nip, and the paper fibers are softened thereby. The aforementioned softening of the paper fibers greatly enhances the water removing capabilities of the press section. Such softening also improves sheet property development.
In prior heated extended nip pressing techniques, the web enters the heated elongate pressing section with an in-going web solids content of between 30 to 45 percent by weight.
However, there are several problems with entering a high temperature press nip at such low solids content. First, the high heat transfer rates and low sheet permeabilities result in delamination of the sheet due to excessive vapor flashing at the end of the extended nip.
Second, the combination of high temperature and moisture results in increased tack and adhesion of the sheet to the hot surface of the backing roll.
According to the present invention, the aforementioned problems are overcome by increasing the dryness of the web at 2040~09 the nip entrance by initially wet pressing or drying, or both pressing and drying, the web prior to guiding the web into the heated extended pressing section.
By entering the heated extended pressing section at a higher dryness level, the amount of free water is reduced and the volume of vapor flashed at the end of the nip is reduced.
Also, with less free water in the pores of the web, there is less resistance to the flow of flashing vapor as such flashing vapor exits the web.
The reduction in volume of the aforementioned flashing vapor and the reduction in flow resistance to the vapor exiting the sheet reduces the potential for delamination.
Additionally, it has been shown that moisture acts as a plasticizer and can increase the tackiness of the paper fibers at high temperatures. Also, the free water in the sheet facilitates bonding of such fibers to the hot surface of the backing roll just as it facilitates bonding between adjacent fibers within the sheet. Accordingly, the problem of fiber picking and web adhesion can be greatly reduced by entering the heated extended pressing section at a higher solids content.
Accordingly, a main object of the present invention is the provision of an apparatus which inhibits delamination of a pressed web when such web exits a heated extended pressing section.
Another object of the present invention is the provision of an apparatus which reduces fiber picking and web adhesion to a backing roll when such web exits from a heated extended pressing sectlon.
Another object of the present invention is the provision of an apparatus which provides the maximum effectiveness of the heated extended pressing process while reducing runnability problems to a minimum.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description and drawings contained hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus and method for reducing the water content of a formed web. The apparatus includes a press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through the press means. A dryer means is disposed downstream relative to the press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer means. A further press means is disposed downstream relative to the dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through the further press means. The further press means includes a backing roll and heating means for heating the backing roll.
Additionally, the press means includes an elongate press member which cooperates with the backing roll for defini~g therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through the pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within the pressing section for urging the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
In a more specific embodiment of the present invention, the press means includes a press roll and a further press roll which cooperates with the press roll for defining therebetween a press nip for removing the first portion of water from the formed web.
In an alternative embodiment of the present invention, the press means includes a pressing roll and an elongate pressing shoe which cooperates with the pressing roll for defining therebetween an elongate press section for removing the first portion of water from the formed web.
In either embodiment of the present invention, the dryer means includes a plurality of rotatable dryer drums with the pressed web extending around at least a portion of the heated 20~0S09 periph~eral surface of the dryer drums for removing the second portion of water from the pressed web.
The press means and the dryer means permit the dried web between the dryer means and the further press means to attain a solids content of more than 45 percent by weight such that the web entering the further press means has a solids content of more than 45 percent by weight.
The present invention also includes a method for removing water from a formed web. The method includes the steps of:
pressing the formed web such that a first portion of water is removed from the web during passage of the formed web through a press;
drying the pressed web downstream relative to the press such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer;
further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through a further press; and the further pressing step including subjecting the dried web to increased pressure and temperature for an extended period so that water vapor is generated within a pressing section defined between a heated backing roll and an elongate press member such that the water vapor urges the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.
However, such variations and modifications fall within the spirit and scope of the present invention as defined by the appended claims. Included in such modifications would be the provision of a hydrostatic instead of a hydrodynamic shoe in the further press.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of an apparatus according to a first embodiment of the present invention;
Figure 2 is a side-elevational view of an alternative embodiment of the present invention showing the press means as an extended nip press;
Figure 3 is a graph showing the drying rate to percentage of solids entering the heated extended pressing section for newsprint;
20405~9 ~ igure 4 is a graph for newsprint showing sheet and felt weight changes to solids entering the heated extended pressing section; and Figure 5 is a graph showing for newsprint the percentage of solids in the web exiting the heated extended pressing section to the percentage of solids entering the same.
Similar reference characters refer to similar parts throughout the various embodiments of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of an apparatus generally designated 10 for reducing the water content of a formed web W. The apparatus 10 includes press means generally designated 12 for pressing the formed web W such that a first portion of water is removed from the formed web W during passage of the formed web W through the press means 12.
Dryer means generally designated 14 are disposed downstream relative to the press means 12 for drying the pressed web PW such that a second portion of water is removed from the pressed web PW during passage of the pressed web PW
through the dryer means 14.
A further press means generally designated 16 is disposed downstream relative to the dryer means 14 for further pressing the dried web DW such that a third portion of water is removed from the dried web DW during passage of the dried web DW
through the further press means 16.
The further press means 16 includes a backing roll 18 and heating means 20 for heating the backing roll 18. An elongate press member 22 cooperates with the backing roll 18 for defining therebetween an elongate pressing section generally designated 24 for the passage therethrough of the dried web DW
such that during passage of the dried web DW through the pressing section 24, the dried web DW is subjected to increased pressure and temperature for an extended period so that water vapor is generated within the pressing section 24 for urging the third portion of water in the liquid phase away from the web during passage of the web through the pressing section 24 for inhibiting delamination of the further pressed web FPW.
In the embodiment shown in Figure 1, the press means 12 includes a press roll 26 and a further press roll 28 which cooperates with the press roll 26 for defining therebetween a press nip 30 for removing the first portion of water from the formed web W.
Figure 2 shows an alternative embodiment of the present invention in which a press means generally designated 12A
includes a pressing roll 26A and an elongate pressing shoe 32.
The pressing roll 26A cooperates with the pressing shoe 32 for defining therebetween an elongate press section 34 for removing the first portion of water from the formed web W.
In both embodiments of the invention, the dryer means 14,14A includes a plurality of rotatable dryer drums 36,36A
and 38,38A respectively. The pressed web PW extends around at least a portion of the heated peripheral surface 40,42 of the dryer drums 36 and 38 for removing the second portion of water from the pressed web PW.
In both embodiments of the present invention, as shown in Figures 1 and 2, the dried web DW and DWA enter the pressing section 24 and 24A respectively with a solids content of more than 45 percent by weight.
TITLE: AN APPARATUS FOR REDUCING THE WATER CONTENT OF A
FORMED WEB
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for reducing the water content of a formed web. More particularly, the present invention relates to an apparatus for inhibiting delamination of a pressed web during passage of the web through ~ heated elongate pressing section.
INFORMATION DISCLOSURE STATEMENT
In a typical papermaking process, a slurry of paper stock is ejected onto a moving fourdrinier screen where the slurry is initially dewatered in order to provide a formed web which is subsequently removed from the fourdrinier screen. The formed web is then pressed between counter-rotating rolls for removing a further quantity of water from the formed web. The pressed web is then guided around a plurality of drying cylinders until the desired water content of the dried web is achieved.
Because of the enormous thermal input requirement of a typical drying section, various attempts have been made in order to increase the amount of water removed from the formed web in the press section.
Notably, the extended nip press has greatly increased the amount of water removed from the formed web during the pressing operation. Essentially, the extended nip press includes a backing roll and an elongate pressing shoe which cooperates with the backing roll to define therebetween an elongate pressing section. An endless looped blanket extends through the pressing section such that when the formed web is disposed between the blanket and the backing roll, the residence time of the web within the pressing section is increased and a correspondingly greater quantity of water is remo~ed from the web. Consequently, less water is present in the pressed web entering the dryer section, thereby reducing the thermal input requirements of the dryer section.
More recently, as taught in U.S. Patent No. 4,738,752 to Busker et al, it was discovered that by heating the backing roll to an elevated temperature, even greater quantities of water could be removed from the web during the passage of the web through the elongate pressing section. The theory behind the so-called heated extended nip press process was that water vapor generated within the elongate pressing section by the heated backing roll urged water in the liquid phase disposed within the web away from the web.
However, although the heated extended nip exhibited greatly increased water removing capabilities, a problem was experienced in certain paper grades in that the web exiting the extended pressing section tended to delaminate.
Accordingly, the present invention seeks to overcome the aforementioned problem associated with known high temperature extended pressing techniques and provides an apparatus for reducing the water content of a formed web that makes a considerable contribution to the web pressing art.
More particularly, the backing roll of the heated extended nip press of the aforementioned U.S. Patent No.
4,738,752 is heated to a surface temperature in excess of 250 Fahrenheit. The high surface temperature rapidly heats the web as it passes through the extended nip, and the paper fibers are softened thereby. The aforementioned softening of the paper fibers greatly enhances the water removing capabilities of the press section. Such softening also improves sheet property development.
In prior heated extended nip pressing techniques, the web enters the heated elongate pressing section with an in-going web solids content of between 30 to 45 percent by weight.
However, there are several problems with entering a high temperature press nip at such low solids content. First, the high heat transfer rates and low sheet permeabilities result in delamination of the sheet due to excessive vapor flashing at the end of the extended nip.
Second, the combination of high temperature and moisture results in increased tack and adhesion of the sheet to the hot surface of the backing roll.
According to the present invention, the aforementioned problems are overcome by increasing the dryness of the web at 2040~09 the nip entrance by initially wet pressing or drying, or both pressing and drying, the web prior to guiding the web into the heated extended pressing section.
By entering the heated extended pressing section at a higher dryness level, the amount of free water is reduced and the volume of vapor flashed at the end of the nip is reduced.
Also, with less free water in the pores of the web, there is less resistance to the flow of flashing vapor as such flashing vapor exits the web.
The reduction in volume of the aforementioned flashing vapor and the reduction in flow resistance to the vapor exiting the sheet reduces the potential for delamination.
Additionally, it has been shown that moisture acts as a plasticizer and can increase the tackiness of the paper fibers at high temperatures. Also, the free water in the sheet facilitates bonding of such fibers to the hot surface of the backing roll just as it facilitates bonding between adjacent fibers within the sheet. Accordingly, the problem of fiber picking and web adhesion can be greatly reduced by entering the heated extended pressing section at a higher solids content.
Accordingly, a main object of the present invention is the provision of an apparatus which inhibits delamination of a pressed web when such web exits a heated extended pressing section.
Another object of the present invention is the provision of an apparatus which reduces fiber picking and web adhesion to a backing roll when such web exits from a heated extended pressing sectlon.
Another object of the present invention is the provision of an apparatus which provides the maximum effectiveness of the heated extended pressing process while reducing runnability problems to a minimum.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description and drawings contained hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to an apparatus and method for reducing the water content of a formed web. The apparatus includes a press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through the press means. A dryer means is disposed downstream relative to the press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer means. A further press means is disposed downstream relative to the dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through the further press means. The further press means includes a backing roll and heating means for heating the backing roll.
Additionally, the press means includes an elongate press member which cooperates with the backing roll for defini~g therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through the pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within the pressing section for urging the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
In a more specific embodiment of the present invention, the press means includes a press roll and a further press roll which cooperates with the press roll for defining therebetween a press nip for removing the first portion of water from the formed web.
In an alternative embodiment of the present invention, the press means includes a pressing roll and an elongate pressing shoe which cooperates with the pressing roll for defining therebetween an elongate press section for removing the first portion of water from the formed web.
In either embodiment of the present invention, the dryer means includes a plurality of rotatable dryer drums with the pressed web extending around at least a portion of the heated 20~0S09 periph~eral surface of the dryer drums for removing the second portion of water from the pressed web.
The press means and the dryer means permit the dried web between the dryer means and the further press means to attain a solids content of more than 45 percent by weight such that the web entering the further press means has a solids content of more than 45 percent by weight.
The present invention also includes a method for removing water from a formed web. The method includes the steps of:
pressing the formed web such that a first portion of water is removed from the web during passage of the formed web through a press;
drying the pressed web downstream relative to the press such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer;
further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through a further press; and the further pressing step including subjecting the dried web to increased pressure and temperature for an extended period so that water vapor is generated within a pressing section defined between a heated backing roll and an elongate press member such that the water vapor urges the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.
However, such variations and modifications fall within the spirit and scope of the present invention as defined by the appended claims. Included in such modifications would be the provision of a hydrostatic instead of a hydrodynamic shoe in the further press.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of an apparatus according to a first embodiment of the present invention;
Figure 2 is a side-elevational view of an alternative embodiment of the present invention showing the press means as an extended nip press;
Figure 3 is a graph showing the drying rate to percentage of solids entering the heated extended pressing section for newsprint;
20405~9 ~ igure 4 is a graph for newsprint showing sheet and felt weight changes to solids entering the heated extended pressing section; and Figure 5 is a graph showing for newsprint the percentage of solids in the web exiting the heated extended pressing section to the percentage of solids entering the same.
Similar reference characters refer to similar parts throughout the various embodiments of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 is a side-elevational view of an apparatus generally designated 10 for reducing the water content of a formed web W. The apparatus 10 includes press means generally designated 12 for pressing the formed web W such that a first portion of water is removed from the formed web W during passage of the formed web W through the press means 12.
Dryer means generally designated 14 are disposed downstream relative to the press means 12 for drying the pressed web PW such that a second portion of water is removed from the pressed web PW during passage of the pressed web PW
through the dryer means 14.
A further press means generally designated 16 is disposed downstream relative to the dryer means 14 for further pressing the dried web DW such that a third portion of water is removed from the dried web DW during passage of the dried web DW
through the further press means 16.
The further press means 16 includes a backing roll 18 and heating means 20 for heating the backing roll 18. An elongate press member 22 cooperates with the backing roll 18 for defining therebetween an elongate pressing section generally designated 24 for the passage therethrough of the dried web DW
such that during passage of the dried web DW through the pressing section 24, the dried web DW is subjected to increased pressure and temperature for an extended period so that water vapor is generated within the pressing section 24 for urging the third portion of water in the liquid phase away from the web during passage of the web through the pressing section 24 for inhibiting delamination of the further pressed web FPW.
In the embodiment shown in Figure 1, the press means 12 includes a press roll 26 and a further press roll 28 which cooperates with the press roll 26 for defining therebetween a press nip 30 for removing the first portion of water from the formed web W.
Figure 2 shows an alternative embodiment of the present invention in which a press means generally designated 12A
includes a pressing roll 26A and an elongate pressing shoe 32.
The pressing roll 26A cooperates with the pressing shoe 32 for defining therebetween an elongate press section 34 for removing the first portion of water from the formed web W.
In both embodiments of the invention, the dryer means 14,14A includes a plurality of rotatable dryer drums 36,36A
and 38,38A respectively. The pressed web PW extends around at least a portion of the heated peripheral surface 40,42 of the dryer drums 36 and 38 for removing the second portion of water from the pressed web PW.
In both embodiments of the present invention, as shown in Figures 1 and 2, the dried web DW and DWA enter the pressing section 24 and 24A respectively with a solids content of more than 45 percent by weight.
Claims (6)
1. An apparatus for reducing the water content of a formed web, said apparatus comprising:
press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through said press means;
dryer means disposed downstream relative to said press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through said dryer means;
further press means disposed downstream relative to said dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through said further press means;
said further press means including:
a backing roll;
heating means for heating said backing roll; and an elongate press shoe cooperating with said backing roll for defining therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through said pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within said pressing section for urging said third portion of water in the liquid phase away from the web during passage of the web through said pressing section for inhibiting delamination of the further pressed web.
press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through said press means;
dryer means disposed downstream relative to said press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through said dryer means;
further press means disposed downstream relative to said dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through said further press means;
said further press means including:
a backing roll;
heating means for heating said backing roll; and an elongate press shoe cooperating with said backing roll for defining therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through said pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within said pressing section for urging said third portion of water in the liquid phase away from the web during passage of the web through said pressing section for inhibiting delamination of the further pressed web.
2. An apparatus as set forth in claim 1 wherein said press means includes:
a press roll;
a further press roll cooperating with said press roll for defining therebetween a press nip for removing said first portion of water from the formed web.
a press roll;
a further press roll cooperating with said press roll for defining therebetween a press nip for removing said first portion of water from the formed web.
3. An apparatus as set forth in claim 1 wherein said press means includes:
a pressing roll;
an elongate pressing shoe cooperating with said pressing roll for defining therebetween an elongate press section for removing said first portion of water from said formed web.
a pressing roll;
an elongate pressing shoe cooperating with said pressing roll for defining therebetween an elongate press section for removing said first portion of water from said formed web.
4. An apparatus as set forth in claim 1 wherein said dryer means includes:
a plurality of rotatable dryer drums, the pressed web extending around at least a portion of the heated peripheral surface of said plurality of dryer drums for removing said second portion of water from the pressed web.
a plurality of rotatable dryer drums, the pressed web extending around at least a portion of the heated peripheral surface of said plurality of dryer drums for removing said second portion of water from the pressed web.
5. An apparatus for reducing the water content of a formed web, said apparatus comprising:
press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through said press means;
dryer means disposed downstream relative to said press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through said dryer means;
further press means disposed downstream relative to said dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through said further press means;
said further press means including:
a backing roll;
an induction heater for heating said backing roll;
and an elongate press shoe cooperating with said backing roll for defining therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through said pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within said pressing section for urging said third portion of water in the liquid phase away from the web during passage of the web through said pressing section for both inhibiting delamination of the further pressed web and for reducing fiber picking and web adhesion to said backing roll when the web exits from said pressing section.
press means for pressing the formed web such that a first portion of water is removed from the formed web during passage of the formed web through said press means;
dryer means disposed downstream relative to said press means for drying the pressed web such that a second portion of water is removed from the pressed web during passage of the pressed web through said dryer means;
further press means disposed downstream relative to said dryer means for further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through said further press means;
said further press means including:
a backing roll;
an induction heater for heating said backing roll;
and an elongate press shoe cooperating with said backing roll for defining therebetween an elongate pressing section for the passage therethrough of the dried web such that during passage of the dried web through said pressing section, the dried web is subjected to increased pressure and temperature for an extended period so that water vapor is generated within said pressing section for urging said third portion of water in the liquid phase away from the web during passage of the web through said pressing section for both inhibiting delamination of the further pressed web and for reducing fiber picking and web adhesion to said backing roll when the web exits from said pressing section.
6- A method for reducing the water content of a formed web, the method comprising the steps of:
pressing the formed web such that a first portion of water is removed from the web during passage of the formed web through a press;
drying the pressed web downstream relative to the press such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer;
further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through a further press;
and the further pressing step including-subjecting the dried web to increased pressure and temperature for an extended period so that water vapor is generated within a pressing section defined between a heated backing roll and an elongate press shoe such that the water vapor urges the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
pressing the formed web such that a first portion of water is removed from the web during passage of the formed web through a press;
drying the pressed web downstream relative to the press such that a second portion of water is removed from the pressed web during passage of the pressed web through the dryer;
further pressing the dried web such that a third portion of water is removed from the dried web during passage of the dried web through a further press;
and the further pressing step including-subjecting the dried web to increased pressure and temperature for an extended period so that water vapor is generated within a pressing section defined between a heated backing roll and an elongate press shoe such that the water vapor urges the third portion of water in the liquid phase away from the web during passage of the web through the pressing section for inhibiting delamination of the further pressed web.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US51033590A | 1990-04-17 | 1990-04-17 | |
| US07/510,335 | 1990-04-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2040509A1 CA2040509A1 (en) | 1991-10-18 |
| CA2040509C true CA2040509C (en) | 1997-06-17 |
Family
ID=24030328
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2040509 Expired - Fee Related CA2040509C (en) | 1990-04-17 | 1991-04-15 | Apparatus for reducing the water content of a formed web |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH07100914B2 (en) |
| CA (1) | CA2040509C (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0289477A3 (en) * | 1987-04-28 | 1989-03-08 | Valmet Paper Machinery Inc. | Method for hot-pressing of a paper web and a drying device for the implementation of the method |
-
1991
- 1991-04-15 CA CA 2040509 patent/CA2040509C/en not_active Expired - Fee Related
- 1991-04-16 JP JP3083806A patent/JPH07100914B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07100914B2 (en) | 1995-11-01 |
| JPH04222292A (en) | 1992-08-12 |
| CA2040509A1 (en) | 1991-10-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |