CA2212695A1 - Multi-ply web former - Google Patents
Multi-ply web formerInfo
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- CA2212695A1 CA2212695A1 CA 2212695 CA2212695A CA2212695A1 CA 2212695 A1 CA2212695 A1 CA 2212695A1 CA 2212695 CA2212695 CA 2212695 CA 2212695 A CA2212695 A CA 2212695A CA 2212695 A1 CA2212695 A1 CA 2212695A1
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- wire
- forming
- web
- ply
- roll
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Abstract
A twin wire former has a lower wire extending between an open mesh forming roll and a turning roll. An upper wire joins the lower wire over the forming roll and the upper and lower wires follow a curved generally downwardly extending path or forming zone. The top ply is formed between the upper and the lower wires. A headbox supplies a stream of stock onto the lower wire as the lower wire wraps around the open mesh forming roll. As the lower wire approaches the apex of the forming roll it is joined by the top wire. The upper side of the web is dewatered solely by wire tension and centrifugal forces whichprevent fines and filler materials from being removed in the dewatering process.The turning roll brings the upper side of the web into engagement with a base ply on a base wire.
Description
- CA 0221269~ 1997-08-11 E~ 455~5US
PATENT APPLICATION
MULTI-PLY WEB FORMER
FIELD OF THE INVENTION
This invention relates to papermaking machines. More particularly, this invention relates to papermaking machines for the manufacture of multi-ply linerboard.
BACKGROUND OF THE INVENTION
Achieving an effective bond between the plies on multi-ply board formers has commonly presented a problem. One known method employs multi-web forming stock jets directed through a slice from a single headbox into a formingzone between two converging forming surfaces in a papermaking machine. In this process, a multi-ply board is co-formed and limited intermixing between thelayers forms a good bond between the layers. However, as the board thickness increases, dewatering and excessive mixing between the layers can be a problem.
In other linerboard machines heretofore available, mini-fourdriniers and other twin-wire top formers form the top ply first and then bond it to the base sheet with a starch shower which bonds or glues the plies together. The use of costly starch showers and their inherent adverse effects on cleanliness, runnability and operating costs presents a less than ideal solution.
Another approach to forming a multi-ply web on a Fourdrinier machine is the use of secondary or tertiary headboxes which deposit successive layers onto the forming wire as shown in U.S. Patent No. 5,064,502.
Multicylinder board machines use wire-covered cylinders in cylinder forming vats. A single bottom felt picks up multiple layers of paper from the wire cylinders making up the multicylinder board machine.
CA 0221269~ 1997-08-11 A Kobayashi Ultra Former utilizes headboxes which form fiber mats on wire cylinders which are then deposited as paper layers on top of a single felt.
One type of multi-ply former utilizes a blade former which injects paper forming stock between two wires. A web is formed between an upper wire and a lower wire and is dewatered in the forming zone by applying vacuum solely beneath the lower wire. Water is removed from the upper wire solely by wire tension, gravity and centrifugal force by passing the co-running forming wires over a convex upwardly curved path of travel. This permits a greater concentrate of pulp stock fines to remain in the upper surface of the web formedbetween the co-running wires. The greater concentration of pulp stock fines facilitates the bonding of the web to a base ply when the web and the base ply are brought together. This type of former is shown in U.S. patent No. 5,468,348 to Blackledge et al. which is incorporated herein by reference.
Blackledge et al. disclose an exemplary former capable of forming and bonding a layer of high grade fibers to a base layer of lower grade fibers.
However, additional ways of accomplishing the same function would advantageously provide needed flexibility in the design of a former for a particular application.
SUMMARY OF THE INVENTION
The method and apparatus of this invention forms a multi-ply linerboard from a top ply or outer ply (sometimes referred to as "white top liner" generally formed of a higher grade of fiber) and a base ply web. The base ply is generallyformed from one or more plies of lower grade fibers, typically recycled fiber. Atwin wire former has a lower wire extending between an open mesh forming roll and a turning roll which engages a base forming wire. An upper wire joins the lower wire over the forming roll and the upper and lower wires follow a curved generally downwardly extending path. The top ply is formed between the upper and the lower wires. A headbox supplies a stream of stock onto the lower wire as the lower wire wraps around the open mesh forming roll. As the lower wire CA 0221269~ 1997-08-11 approaches the apex of the forming roll it is joined by the top wire which is supported by a lead in roll. The upper and lower wires pass over the forming roll apex and pass beneath a first auto-slice which removes water from the top of the upper wire. Water is caused to flow upwardly through the upper wire by centrifugal force and wire tension. The upper wire has a surface interior to theloop formed by the upper wire which extends along a forming zone between the upper and lower wires as they follow a joint path.
The upper wire interior surface is convex upwardly so that the upper wire generates centrifugal forces as it moves along the joint path of the upper and lower wires. Two additional auto-slices are positioned along the interior surface of the upper wire to receive and remove water expressed from the web by wire tension and centrifugal forces. The web is dewatered through the lower wire by blades forming a curved blade shoe. The blade through hydrodynamic forces creates regions of low pressure which draw water from the forming web. The curved shoe may be augmented with vacuum. Following the shoe two vacuum boxes are positioned below the lower wire which define the path of lower wire.
The second vacuum box extends beneath the line where the upper wire is led away from the lower wire. Thus the second vacuum box keeps the web on the lower wire.
The upper side of the web is dewatered solely by wire tension and centrifugal forces which prevents fines and filler materials from being removed in the dewatering process. Thus the web formed by the twin wire top former has an upper surface comparatively rich in fines and fillers which improves the bonding characteristics of the web formed. Water drawn through the bottom of the web by the shoe and vacuum boxes must pass through the bulk of the web which acts to filter out the fines and fillers leaving them in the upper portion of the web. The turning roll brings the web with the upper side facing the base plyinto engagement with the base ply on the base wire.
CA 0221269~ 1997-08-11 It is a feature of the present invention to provide an apparatus for forming a multi-layer web and cojoining it to another web without a binder.
It is another feature of the present invention to provide a method and apparatus for producing the outer ply of a multi-ply paper sheet wherein the surface to be ply-bonded is dewatered solely by centrifugal force, wire tension and gravity.
It is a further feature of the present invention to provide an apparatus and method for forming linerboard with a white top liner with improved ply-bonding characteristics and a commercially desirable outer surface.
It is yet another feature of the present invention to provide a method and apparatus for forming multi-ply linerboard at higher web speeds.
Further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
The figure is a schematic elevational view of the twin wire former of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to the figure wherein similar parts have like numbers a twin wire former 20 is shown. The twin wire former 20 is mounted above a traveling foraminous base forming wire 22 which moves in an endless loop. The base wire has a base web 24 formed by a forming apparatus (not shown). The base web 24 may be composed of several ply and will normally be formed of lower grade paper fibers, for example recycled fiber or ground wood fibers. In order to have an improved printing surface with a white background a "white top liner" web 26 is formed on the twin wire former 20 and bonded to the CA 0221269~ 1997-08-11 base web 24. Because the furnishes used to make the base web 24 and the top web 26 are different, bonding between the webs 24, 26 can be problematic.
The former 20 provides dewatering of the top web so as to increase the amount of fines and fillers present on the upper side 28 of the top web 26.
Paper forming stock is normally made of paper fibers having a range of sizes and containing various additives such as starch and clay. The formation of a web of paper on a forming wire depends on the longer fibers forming a mat on the forming wire. This mat of fibers then retains the smaller fiber fragments and fillers. The retained fibers, fines, and fillers, if retained or concentrated near one surface of the top ply, increase the ability of that surface to make intimate contact with the base web. It is intimate contract which allows hydrogen bonds to form between the upper web and the base web which in turn hold the webs together.
The former 20 achieves a desired concentration of fiber fines and fillers in the upper surface 28 of the top web 26 by applying vacuum dewatering only to the lower surface 30 of the web 26. The upper surface is dewatered solely through wire tension and centrifugal forces.
Formation of the web 26 starts with a headbox 32 with a slice opening 34 positioned over a first or lower forming wire 36 where the lower forming wire 36wraps around an open mesh forming roll 38. The slice opening 34 is positioned approximately sixty degrees ahead of the forming roll 38 apex 40. An aqueous top ply stock stream is projected from the slice opening 34 onto the lower looped forming wire 36 as the wire passes over the open mesh forming roll 38 to form a top ply web.
A lead in roll 42 brings a second or upper forming wire 44 into co-running engagement with the lower wire 36 approximately thirty degrees ahead of the forming roll apex 40. The top web 26 is formed on the lower wire 36 as it is CA 0221269~ 1997-08-11 supported on the forming roll 38. Thus the web 26 is initially dewatered by drainage downwardly through the forming roll into a saveall 41.
After the lower wire 36 joins the upper wire 44 and the two wires pass over the apex 40 of the forming roll 38, an auto-slice 46 with a leading lip 47 removes water from above the upper wire 44. The auto-slice 46 may use vacuum to remove free water on the wire 44 upper surface and deposit the free water in a saveall 49. The vacuum is not applied to the web 26 itself and does not draw water from the web 26. The water removed by the auto-slice 46 is expressed from the web 26 by centrifugal force and wire tension. Wire tension causes compression between the upper wire and the lower wire thus forcing water from the web 26.
After leaving the forming roll 38 the wires 36, 44 with the web 26 therebetween pass over a forming shoe 48. The shoe is made up of blades 50 which are arranged to form the curved shoe 48. The blades 50 create a hydrodynamic action beneath the lower wire 44 which draws water out of the web 26 by the vacuum produced by the hydrodynamic forces. Water removed from the lower side 30 of the web 26 by the shoe 48 flows down into a drain 52.
A second auto-slice 53 with saveall 54 is positioned immediately downstream of the forming shoe 48 to remove additional water from the upper side 28 of the web 26. The twin wires 36, 44 continue to move in a generally downward direction with the web 26 clamped therebetween. The twin wires pass over a first vacuum box 56 and a second vacuum box 58 which control the path of the twin wires. A third auto-slice 60 is positioned between the first vacuum box 56 and the second vacuum box 58 for drawing water expressed from the web 26 upwardly through the upper wire 44 by centrifugal and wire tension forces. The auto-slice 60 also transfers water to a third saveall 61.
An upper wire lead out roll 62 leads the upper wire 44 away from the web 26 at the trailing end 64 of the second vacuum box 58. Because vacuum is still CA 0221269~ 1997-08-11 being applied to the web 26 when the upper wire is pulled away from the web 26 the vacuum holds the web 26 on the lower wire 36.
Following the separation of the upper wire 44 from the lower wire 36 the lower wire and web 26 traverse a turning roll 66 which inverts the web 26 so theupper side 28 is brought into opposition to the upper side 68 of the base web 24and as the web 26 continues around the turning roll 66 the top liner web 26 is brought into engagement with and bonds with the base web 24.
Both the upper wire 44 and the lower wire 36 form complete loops. The upper wire 44 after leaving the forming path travels around the lead out roll 62and then travels around a tension adjusting guide roll 70. A second guide roll 72 directs the upper wire back to the lead in roll 42. The lead in roll 42 and the first auto-slice 46 and saveall 49 are mounted to a pivoting arm 74 controlled by a hydraulic actuator 76 or the like. The former 20 may be opened up for replacing wires etc. by pivoting the arm 74 upwardly and pivoting the vacuum boxes 56, 58 down to move the upper wire 44 and lower wire 36 apart.
The lower wire 36 is removed from engagement with the base wire 22 by a guide roll 78. From the guide roll 78 the lower wire 36 passes over a tension adjusting roll 80 and further guide rolls 81, 82 which direct the wire onto the forming roll 38. Tension in the upper and lower wires can thus be adjusted by controlling the tension guide rolls 70, 80. The turning roll 66 is mounted on a pivotable arm 84 which controls the amount of pressure and wrap of the base wire 22 with the turning roll 66.
Forming the web 26 over the forming roll 38 means an initial mat of fibers is formed on the lower wire 36. This mat then traps the fibers, fines and fiber fillers above the mat. Because the fiber mat is already in place and tends to prevent the fines and fillers from passing through the bottom of the web 26, additional vacuum dewatering from below the web 26 does not remove fines and fillers from the upper portion of the web 26. On the other hand the initial CA 0221269~ 1997-08-11 formation of the mat does deplete fines and fillers from the lower side 30 of the web 26. By utilizing only web tension and centrifugal force to remove water upwardly from the upper side 28, the fines and fillers which have been retained in the upper portion of the web 26 may in large part be kept in the web 26. The presence of the fibers, fines, and web fillers improves the quality and strength of the web 26 and most importantly improves the bonding characteristics of the upper surface 28 of the web 26.
The upper wire interior surface is convex upwardly so that the upper wire generates centrifugal forces as it moves along the joint path. The upper wire 44has a surface 90 interior to the loop formed by the upper wire 44. The surface 90 extends along a forming zone 94 between the upper and lower wires as they follow a joint path. Similarly the loop formed by the lower wire 36 has a surface 92 interior to the loop formed by the lower wire 36. This inner surface 92 is concave downwardly which matches the curvature of the upper wire 44 along the forming zone 94.
It should be understood that although the web is described and claimed as being dewatered solely by centrifugal force and wire tension, included withincentrifugal force and wire tension will be some component of gravity acting together with the aforementioned forces, inasmuch as the downwardly extending path of the wire reduces the apparent force of gravity.
It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.
PATENT APPLICATION
MULTI-PLY WEB FORMER
FIELD OF THE INVENTION
This invention relates to papermaking machines. More particularly, this invention relates to papermaking machines for the manufacture of multi-ply linerboard.
BACKGROUND OF THE INVENTION
Achieving an effective bond between the plies on multi-ply board formers has commonly presented a problem. One known method employs multi-web forming stock jets directed through a slice from a single headbox into a formingzone between two converging forming surfaces in a papermaking machine. In this process, a multi-ply board is co-formed and limited intermixing between thelayers forms a good bond between the layers. However, as the board thickness increases, dewatering and excessive mixing between the layers can be a problem.
In other linerboard machines heretofore available, mini-fourdriniers and other twin-wire top formers form the top ply first and then bond it to the base sheet with a starch shower which bonds or glues the plies together. The use of costly starch showers and their inherent adverse effects on cleanliness, runnability and operating costs presents a less than ideal solution.
Another approach to forming a multi-ply web on a Fourdrinier machine is the use of secondary or tertiary headboxes which deposit successive layers onto the forming wire as shown in U.S. Patent No. 5,064,502.
Multicylinder board machines use wire-covered cylinders in cylinder forming vats. A single bottom felt picks up multiple layers of paper from the wire cylinders making up the multicylinder board machine.
CA 0221269~ 1997-08-11 A Kobayashi Ultra Former utilizes headboxes which form fiber mats on wire cylinders which are then deposited as paper layers on top of a single felt.
One type of multi-ply former utilizes a blade former which injects paper forming stock between two wires. A web is formed between an upper wire and a lower wire and is dewatered in the forming zone by applying vacuum solely beneath the lower wire. Water is removed from the upper wire solely by wire tension, gravity and centrifugal force by passing the co-running forming wires over a convex upwardly curved path of travel. This permits a greater concentrate of pulp stock fines to remain in the upper surface of the web formedbetween the co-running wires. The greater concentration of pulp stock fines facilitates the bonding of the web to a base ply when the web and the base ply are brought together. This type of former is shown in U.S. patent No. 5,468,348 to Blackledge et al. which is incorporated herein by reference.
Blackledge et al. disclose an exemplary former capable of forming and bonding a layer of high grade fibers to a base layer of lower grade fibers.
However, additional ways of accomplishing the same function would advantageously provide needed flexibility in the design of a former for a particular application.
SUMMARY OF THE INVENTION
The method and apparatus of this invention forms a multi-ply linerboard from a top ply or outer ply (sometimes referred to as "white top liner" generally formed of a higher grade of fiber) and a base ply web. The base ply is generallyformed from one or more plies of lower grade fibers, typically recycled fiber. Atwin wire former has a lower wire extending between an open mesh forming roll and a turning roll which engages a base forming wire. An upper wire joins the lower wire over the forming roll and the upper and lower wires follow a curved generally downwardly extending path. The top ply is formed between the upper and the lower wires. A headbox supplies a stream of stock onto the lower wire as the lower wire wraps around the open mesh forming roll. As the lower wire CA 0221269~ 1997-08-11 approaches the apex of the forming roll it is joined by the top wire which is supported by a lead in roll. The upper and lower wires pass over the forming roll apex and pass beneath a first auto-slice which removes water from the top of the upper wire. Water is caused to flow upwardly through the upper wire by centrifugal force and wire tension. The upper wire has a surface interior to theloop formed by the upper wire which extends along a forming zone between the upper and lower wires as they follow a joint path.
The upper wire interior surface is convex upwardly so that the upper wire generates centrifugal forces as it moves along the joint path of the upper and lower wires. Two additional auto-slices are positioned along the interior surface of the upper wire to receive and remove water expressed from the web by wire tension and centrifugal forces. The web is dewatered through the lower wire by blades forming a curved blade shoe. The blade through hydrodynamic forces creates regions of low pressure which draw water from the forming web. The curved shoe may be augmented with vacuum. Following the shoe two vacuum boxes are positioned below the lower wire which define the path of lower wire.
The second vacuum box extends beneath the line where the upper wire is led away from the lower wire. Thus the second vacuum box keeps the web on the lower wire.
The upper side of the web is dewatered solely by wire tension and centrifugal forces which prevents fines and filler materials from being removed in the dewatering process. Thus the web formed by the twin wire top former has an upper surface comparatively rich in fines and fillers which improves the bonding characteristics of the web formed. Water drawn through the bottom of the web by the shoe and vacuum boxes must pass through the bulk of the web which acts to filter out the fines and fillers leaving them in the upper portion of the web. The turning roll brings the web with the upper side facing the base plyinto engagement with the base ply on the base wire.
CA 0221269~ 1997-08-11 It is a feature of the present invention to provide an apparatus for forming a multi-layer web and cojoining it to another web without a binder.
It is another feature of the present invention to provide a method and apparatus for producing the outer ply of a multi-ply paper sheet wherein the surface to be ply-bonded is dewatered solely by centrifugal force, wire tension and gravity.
It is a further feature of the present invention to provide an apparatus and method for forming linerboard with a white top liner with improved ply-bonding characteristics and a commercially desirable outer surface.
It is yet another feature of the present invention to provide a method and apparatus for forming multi-ply linerboard at higher web speeds.
Further objects, features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
The figure is a schematic elevational view of the twin wire former of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring more particularly to the figure wherein similar parts have like numbers a twin wire former 20 is shown. The twin wire former 20 is mounted above a traveling foraminous base forming wire 22 which moves in an endless loop. The base wire has a base web 24 formed by a forming apparatus (not shown). The base web 24 may be composed of several ply and will normally be formed of lower grade paper fibers, for example recycled fiber or ground wood fibers. In order to have an improved printing surface with a white background a "white top liner" web 26 is formed on the twin wire former 20 and bonded to the CA 0221269~ 1997-08-11 base web 24. Because the furnishes used to make the base web 24 and the top web 26 are different, bonding between the webs 24, 26 can be problematic.
The former 20 provides dewatering of the top web so as to increase the amount of fines and fillers present on the upper side 28 of the top web 26.
Paper forming stock is normally made of paper fibers having a range of sizes and containing various additives such as starch and clay. The formation of a web of paper on a forming wire depends on the longer fibers forming a mat on the forming wire. This mat of fibers then retains the smaller fiber fragments and fillers. The retained fibers, fines, and fillers, if retained or concentrated near one surface of the top ply, increase the ability of that surface to make intimate contact with the base web. It is intimate contract which allows hydrogen bonds to form between the upper web and the base web which in turn hold the webs together.
The former 20 achieves a desired concentration of fiber fines and fillers in the upper surface 28 of the top web 26 by applying vacuum dewatering only to the lower surface 30 of the web 26. The upper surface is dewatered solely through wire tension and centrifugal forces.
Formation of the web 26 starts with a headbox 32 with a slice opening 34 positioned over a first or lower forming wire 36 where the lower forming wire 36wraps around an open mesh forming roll 38. The slice opening 34 is positioned approximately sixty degrees ahead of the forming roll 38 apex 40. An aqueous top ply stock stream is projected from the slice opening 34 onto the lower looped forming wire 36 as the wire passes over the open mesh forming roll 38 to form a top ply web.
A lead in roll 42 brings a second or upper forming wire 44 into co-running engagement with the lower wire 36 approximately thirty degrees ahead of the forming roll apex 40. The top web 26 is formed on the lower wire 36 as it is CA 0221269~ 1997-08-11 supported on the forming roll 38. Thus the web 26 is initially dewatered by drainage downwardly through the forming roll into a saveall 41.
After the lower wire 36 joins the upper wire 44 and the two wires pass over the apex 40 of the forming roll 38, an auto-slice 46 with a leading lip 47 removes water from above the upper wire 44. The auto-slice 46 may use vacuum to remove free water on the wire 44 upper surface and deposit the free water in a saveall 49. The vacuum is not applied to the web 26 itself and does not draw water from the web 26. The water removed by the auto-slice 46 is expressed from the web 26 by centrifugal force and wire tension. Wire tension causes compression between the upper wire and the lower wire thus forcing water from the web 26.
After leaving the forming roll 38 the wires 36, 44 with the web 26 therebetween pass over a forming shoe 48. The shoe is made up of blades 50 which are arranged to form the curved shoe 48. The blades 50 create a hydrodynamic action beneath the lower wire 44 which draws water out of the web 26 by the vacuum produced by the hydrodynamic forces. Water removed from the lower side 30 of the web 26 by the shoe 48 flows down into a drain 52.
A second auto-slice 53 with saveall 54 is positioned immediately downstream of the forming shoe 48 to remove additional water from the upper side 28 of the web 26. The twin wires 36, 44 continue to move in a generally downward direction with the web 26 clamped therebetween. The twin wires pass over a first vacuum box 56 and a second vacuum box 58 which control the path of the twin wires. A third auto-slice 60 is positioned between the first vacuum box 56 and the second vacuum box 58 for drawing water expressed from the web 26 upwardly through the upper wire 44 by centrifugal and wire tension forces. The auto-slice 60 also transfers water to a third saveall 61.
An upper wire lead out roll 62 leads the upper wire 44 away from the web 26 at the trailing end 64 of the second vacuum box 58. Because vacuum is still CA 0221269~ 1997-08-11 being applied to the web 26 when the upper wire is pulled away from the web 26 the vacuum holds the web 26 on the lower wire 36.
Following the separation of the upper wire 44 from the lower wire 36 the lower wire and web 26 traverse a turning roll 66 which inverts the web 26 so theupper side 28 is brought into opposition to the upper side 68 of the base web 24and as the web 26 continues around the turning roll 66 the top liner web 26 is brought into engagement with and bonds with the base web 24.
Both the upper wire 44 and the lower wire 36 form complete loops. The upper wire 44 after leaving the forming path travels around the lead out roll 62and then travels around a tension adjusting guide roll 70. A second guide roll 72 directs the upper wire back to the lead in roll 42. The lead in roll 42 and the first auto-slice 46 and saveall 49 are mounted to a pivoting arm 74 controlled by a hydraulic actuator 76 or the like. The former 20 may be opened up for replacing wires etc. by pivoting the arm 74 upwardly and pivoting the vacuum boxes 56, 58 down to move the upper wire 44 and lower wire 36 apart.
The lower wire 36 is removed from engagement with the base wire 22 by a guide roll 78. From the guide roll 78 the lower wire 36 passes over a tension adjusting roll 80 and further guide rolls 81, 82 which direct the wire onto the forming roll 38. Tension in the upper and lower wires can thus be adjusted by controlling the tension guide rolls 70, 80. The turning roll 66 is mounted on a pivotable arm 84 which controls the amount of pressure and wrap of the base wire 22 with the turning roll 66.
Forming the web 26 over the forming roll 38 means an initial mat of fibers is formed on the lower wire 36. This mat then traps the fibers, fines and fiber fillers above the mat. Because the fiber mat is already in place and tends to prevent the fines and fillers from passing through the bottom of the web 26, additional vacuum dewatering from below the web 26 does not remove fines and fillers from the upper portion of the web 26. On the other hand the initial CA 0221269~ 1997-08-11 formation of the mat does deplete fines and fillers from the lower side 30 of the web 26. By utilizing only web tension and centrifugal force to remove water upwardly from the upper side 28, the fines and fillers which have been retained in the upper portion of the web 26 may in large part be kept in the web 26. The presence of the fibers, fines, and web fillers improves the quality and strength of the web 26 and most importantly improves the bonding characteristics of the upper surface 28 of the web 26.
The upper wire interior surface is convex upwardly so that the upper wire generates centrifugal forces as it moves along the joint path. The upper wire 44has a surface 90 interior to the loop formed by the upper wire 44. The surface 90 extends along a forming zone 94 between the upper and lower wires as they follow a joint path. Similarly the loop formed by the lower wire 36 has a surface 92 interior to the loop formed by the lower wire 36. This inner surface 92 is concave downwardly which matches the curvature of the upper wire 44 along the forming zone 94.
It should be understood that although the web is described and claimed as being dewatered solely by centrifugal force and wire tension, included withincentrifugal force and wire tension will be some component of gravity acting together with the aforementioned forces, inasmuch as the downwardly extending path of the wire reduces the apparent force of gravity.
It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.
Claims (6)
1. A method for forming a multi-ply web, comprising the steps of:
forming a base ply web on a traveling foraminous base forming wire;
bringing upper and lower looped forming wires into co-running engagement in a forming zone formed by a path followed by the upper and lower forming wires, the lower wire extending between an open mesh forming roll and a turning roll disposed within the lower looped forming wire, wherein the overall, substantially continuous contour of the forming zone has the lower forming wire having a surface interior to the loop of the lower wire curved concave downwardly, and the upper forming wire having a surface interior to the loop of the upper wire curved convexly upwardly along the path;
projecting an aqueous top ply stock stream onto the lower looped forming wire as the wire passes over the open mesh forming roll to form a top ply web;
dewatering the top ply stock stream through the lower forming wire by applying vacuum to the stock stream solely beneath the lower concave downward path to thereby form a lower web surface of the top ply web;
expressing water upwardly through the upper forming wire over its path of travel solely by wire tension and centrifugal force to thereby form an upper web surface of the top ply web;
collecting the water expressed through the upper forming wire within the upper forming wire at least one location above the convex upwardly curved inner surface of the upper forming wire; and bringing the upper web surface of the top ply web into co-running engagement with the base ply web to effect ply-bonding therewith to form a multi-ply web.
forming a base ply web on a traveling foraminous base forming wire;
bringing upper and lower looped forming wires into co-running engagement in a forming zone formed by a path followed by the upper and lower forming wires, the lower wire extending between an open mesh forming roll and a turning roll disposed within the lower looped forming wire, wherein the overall, substantially continuous contour of the forming zone has the lower forming wire having a surface interior to the loop of the lower wire curved concave downwardly, and the upper forming wire having a surface interior to the loop of the upper wire curved convexly upwardly along the path;
projecting an aqueous top ply stock stream onto the lower looped forming wire as the wire passes over the open mesh forming roll to form a top ply web;
dewatering the top ply stock stream through the lower forming wire by applying vacuum to the stock stream solely beneath the lower concave downward path to thereby form a lower web surface of the top ply web;
expressing water upwardly through the upper forming wire over its path of travel solely by wire tension and centrifugal force to thereby form an upper web surface of the top ply web;
collecting the water expressed through the upper forming wire within the upper forming wire at least one location above the convex upwardly curved inner surface of the upper forming wire; and bringing the upper web surface of the top ply web into co-running engagement with the base ply web to effect ply-bonding therewith to form a multi-ply web.
2. An apparatus for forming a multi-ply paper web, comprising:
a frame;
an open mesh forming roll rotatably mounted on the frame;
a turning roll rotatably mounted on the frame downstream of the forming roll;
a looped base-ply-forming wire for carrying and dewatering a base ply web;
an upper looped top ply forming wire;
a lower looped top ply forming wire which extends between the open mesh forming roll and the turning roll, wherein the upper forming wire and the lower forming wire are arranged to converge over the forming roll and travel in co-running engagement along a path, and wherein the overall, substantially continuous contour of the forming zone extending between the forming roll and the turning roll has the lower forming wire having an inner surface curved concave downwardly, and the upper forming wire having an inner surface curved convex upwardly along the path of the co-running engagement;
headbox means for depositing an aqueous top ply stock slurry onto the lower wire as it passes over the forming roll to initiate formation of a top ply web having lower and upper surfaces;
vacuum dewatering apparatus located solely within the lower top-ply-forming wire for dewatering the top ply stock stream downwardly therethrough and forming a top ply web having its lower surface on the lower forming wire;
first means for receiving water expressed upwardly and inwardly through the upper looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the upper wire, the means for receiving water being located above the open mesh forming roll;
second means for receiving water expressed upwardly and inwardly through the upper looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the upper wire, the second means for receiving the water located above the convex upwardly curved inner surface of the upper forming wire;
guide means for guiding the upper forming wire away from the lower forming wire, the apparatus arranged so that the upper surface of the top ply is dewatered upwardly solely by centrifugal force and forming wire tension; and said turning roll arranged for directing the lower forming wire and web into co-running engagement with the base ply web to effect ply bonding between the upper surface of the top ply web and the base ply web.
a frame;
an open mesh forming roll rotatably mounted on the frame;
a turning roll rotatably mounted on the frame downstream of the forming roll;
a looped base-ply-forming wire for carrying and dewatering a base ply web;
an upper looped top ply forming wire;
a lower looped top ply forming wire which extends between the open mesh forming roll and the turning roll, wherein the upper forming wire and the lower forming wire are arranged to converge over the forming roll and travel in co-running engagement along a path, and wherein the overall, substantially continuous contour of the forming zone extending between the forming roll and the turning roll has the lower forming wire having an inner surface curved concave downwardly, and the upper forming wire having an inner surface curved convex upwardly along the path of the co-running engagement;
headbox means for depositing an aqueous top ply stock slurry onto the lower wire as it passes over the forming roll to initiate formation of a top ply web having lower and upper surfaces;
vacuum dewatering apparatus located solely within the lower top-ply-forming wire for dewatering the top ply stock stream downwardly therethrough and forming a top ply web having its lower surface on the lower forming wire;
first means for receiving water expressed upwardly and inwardly through the upper looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the upper wire, the means for receiving water being located above the open mesh forming roll;
second means for receiving water expressed upwardly and inwardly through the upper looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the upper wire, the second means for receiving the water located above the convex upwardly curved inner surface of the upper forming wire;
guide means for guiding the upper forming wire away from the lower forming wire, the apparatus arranged so that the upper surface of the top ply is dewatered upwardly solely by centrifugal force and forming wire tension; and said turning roll arranged for directing the lower forming wire and web into co-running engagement with the base ply web to effect ply bonding between the upper surface of the top ply web and the base ply web.
3. In an apparatus for forming a multi-ply paper web of the type having a looped base-ply-forming wire for carrying and dewatering a base ply web; upper and lower looped top-ply-forming wires arranged to travel in co-running engagement wherein the overall, substantially continuous contour of co-running engagement is curved downwardly; a headbox for depositing an aqueous top-ply stock slurry to travel the co-running engagement between the upper and lower wires; vacuum dewatering apparatus located solely within the lower top-ply-forming wire for dewatering the top ply stock stream downwardly therethrough and forming a top ply web having its lower surface on the lower forming wire; at least one auto-slice which receives water expressed upwardly and inwardly through the upper looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the upper wire, the auto-slice located above the convex upwardly curved inner surface of the upper forming wire; and a turning roll arranged for directing the lower forming wire and web into co-running engagement with the base ply web to effect ply bonding between the upper surface of the top ply web and the base ply web;
wherein the improvement comprises:
an open mesh forming roll having an open structure through which water contained in the stock passes, the forming roll positioned within the lower wire loop so the lower wire wraps around the forming roll, the forming roll having an uppermost point defining an apex and wherein the headbox has a slice opening positioned to deposit the aqueous top-ply stock slurry onto the lower wire as it moves towards the apex;
a saveall positioned beneath the forming roll to receive water passing through the forming roll, wherein the upper wire comes into co-running engagement with the lower wire over the forming roll; and an auto-slice positioned above the upper wire and over the forming roll for removing water passing through the upper wire.
wherein the improvement comprises:
an open mesh forming roll having an open structure through which water contained in the stock passes, the forming roll positioned within the lower wire loop so the lower wire wraps around the forming roll, the forming roll having an uppermost point defining an apex and wherein the headbox has a slice opening positioned to deposit the aqueous top-ply stock slurry onto the lower wire as it moves towards the apex;
a saveall positioned beneath the forming roll to receive water passing through the forming roll, wherein the upper wire comes into co-running engagement with the lower wire over the forming roll; and an auto-slice positioned above the upper wire and over the forming roll for removing water passing through the upper wire.
4. The apparatus of claim 3 wherein the slice opening is positioned approximately 60 degrees in front of the apex of the forming roll so the stock travels approximately 60 degrees from the slice opening to the apex of the forming roll.
5. The apparatus of claim 4 wherein the upper wire joins the lower wire at a position approximately thirty degrees upstream of the apex of the forming roll.
6. The apparatus of claim 5 wherein the auto-slice positioned over the forming roll is closely spaced downstream of the apex of the forming roll.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US73019096A | 1996-10-15 | 1996-10-15 | |
| US08/730,190 | 1996-10-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2212695A1 true CA2212695A1 (en) | 1998-04-15 |
Family
ID=24934325
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2212695 Abandoned CA2212695A1 (en) | 1996-10-15 | 1997-08-11 | Multi-ply web former |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH10131079A (en) |
| CA (1) | CA2212695A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110373934A (en) * | 2019-08-23 | 2019-10-25 | 广东理文造纸有限公司 | A kind of resistance to process units for breaking not stratified paper and its production method |
-
1997
- 1997-08-11 CA CA 2212695 patent/CA2212695A1/en not_active Abandoned
- 1997-10-15 JP JP28152097A patent/JPH10131079A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110373934A (en) * | 2019-08-23 | 2019-10-25 | 广东理文造纸有限公司 | A kind of resistance to process units for breaking not stratified paper and its production method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH10131079A (en) | 1998-05-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |