CA2087013C - Multi-ply web former and method - Google Patents
Multi-ply web former and methodInfo
- Publication number
- CA2087013C CA2087013C CA002087013A CA2087013A CA2087013C CA 2087013 C CA2087013 C CA 2087013C CA 002087013 A CA002087013 A CA 002087013A CA 2087013 A CA2087013 A CA 2087013A CA 2087013 C CA2087013 C CA 2087013C
- Authority
- CA
- Canada
- Prior art keywords
- forming
- ply
- web
- forming wire
- wire
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F9/00—Complete machines for making continuous webs of paper
- D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
- D21F11/02—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type
- D21F11/04—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type paper or board consisting on two or more layers
Landscapes
- Paper (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Containers And Plastic Fillers For Packaging (AREA)
Abstract
A multi-ply paper web is formed by bringing a top ply liner into ply-bonding engagement with a base ply web (WB) traveling on a base ply forming wire (36). The top ply liner (WT) is formed between two co-running forming wires (10, 20) in a convex upwardly/concave downwardly curved, substantially horizontal forming zone.
Dewatering in the forming zone is effected by applying sub-atmospheric air pressure solely beneath the lower surface of the top ply liner (WT) being formed. Water is removed from the upper surface of the top ply liner (WT) solely by wire tension, gravity and centrifugal force created by passing the co-running forming wires (10, 20) over the convex upwardly curved path of travel.
This permits a greater concentration of pulp stock fines to remain in the upper surface of the top ply liner (WT) to effect greater ply-bonding affinity with the base ply (WB) when the two plies (WT, WB) are brought together and bonded.
Dewatering in the forming zone is effected by applying sub-atmospheric air pressure solely beneath the lower surface of the top ply liner (WT) being formed. Water is removed from the upper surface of the top ply liner (WT) solely by wire tension, gravity and centrifugal force created by passing the co-running forming wires (10, 20) over the convex upwardly curved path of travel.
This permits a greater concentration of pulp stock fines to remain in the upper surface of the top ply liner (WT) to effect greater ply-bonding affinity with the base ply (WB) when the two plies (WT, WB) are brought together and bonded.
Description
2~37013 Multy-ply web former and method This invention relates to multi-ply paper formation. More specifically, this invention relates to two-wire, multi-ply paper formation. Still more particularly, this invention relates to two-wire, multi-ply web formation wherein the outer ply to be ply-bonded to the base ply of the multi-ply web, has its surface dewatered essentially by wire tension and centrifugal force.
In prior forming arrangements for forming a multi-ply paper web product, a relatively coarse base ply is first produced and a second, outer ply is produced to be brought into ply-bonding contact with the previously formed base ply. The outer ply, which is intended to form the outer surface of the printed container, such as a box, is formed of a finer grade of pulp stock so as to provide a smoother, higher quality surface. In order to form the outer ply at commercially desirable speeds, dewatering was efected through both of its surfaces before the outer ply was brought into ply-bonding contact with the base ply of the paper web sheet. This produces an acceptable paper product, mainly due to the quality of the pulp stock used to produce the outer ply, but the requirements of producing a better product with cheaper pulp, and the need to produce a better product at higher speeds regardless of pulp quality, or a combination of both, have necessitated the conception of an improved multi-ply web former having an outer surface which exhibits the desired printability, and feel and visual smoothness while having an inner ~0 surface which has better ply-bonding characteristics.
In prior apparatus, both sides of the outer ply were dewatered positlvely, that is, they were dewatered by the application of sub-atmospheric air pressure directly to both surfaces to enhance the removal of water through both of the web surfaces. When SUBSTITUTE SHE~
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, WO92/01111 2 0 ~ 6 013 PCT/EP91/01255 both surfaces are positively dewatered, fines and fillers in the pulp stock are urged outwardly in both directions to the respective surfaces of the web and removed during the dewatering process. Thus, while the web is rapidly dewatered, which was the desired effect, the fines and fillers which contribute so much to the ply bonding characteristics of the outer side of the web produced, were removed in large quantities which deleteriously effected web quality as well.
The aforementioned shortcomings, deficien-cies and characteristics of the outer ply in a ply-bonded multi-ply paper web, and the resultant multi-ply paper product, have been obviated by this invention.
In this invention, the outer ply of a multi-ply web, which is sometimes referred to as a "white top liner", is produced by dewatering through one side of the web using only centrifugal force and the force of the tension of the forming wire over the we~. The outer ply is formed in the general direction opposite to the direction of the traveling base ply to which it is ply bonded. The generally upwardly facing surface of the top ply is dewatered by the tension of the upper, outer forming wire being concave downwardly held over the web which has been formed by the aqueous pulp stock slurry projected between the outer and inner forming wires. In addition, one, or more, water collection devices, such as water skimming slots, which may or may not be assisted by a vacuum, assist in removing water expressed inwardly of the outer forming wire. The fines and fillers in the pulp stock slurry are thus exposed to sub-atmospheric (vacuum) pressure only within the lower forming wire in a generally concave downward direction for a relatively long distance. This affects the rate of water removal as well as permits the retention of a greater proportion of fines and fillers in the web, - ~
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WO92/01111 20~ 3 PCT/EPgl/0125 particularly the top surface of the web, due to the fact that migration of the fines and fillers through the lower surface of the web is hindered by the web fibers.
The downwardly directed, relatively gentle dewatering through the lower surface of the outer web ply is effected by subjecting the ply to a sub-atmospheric pressure over a relatively long dewatering zone, which can take the form of a vacuum or suction box, or a plurality of spaced foil blades, or a combination of both.
Accordingly, it is an object of this invention to provide a method and apparatus for _ producing a multi-ply paper sheet hàving improved ply-bond characteristics.
Another object of this invention is 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.
A feature and advantage of this invention is the provision of a white top liner in a multi-ply paper sheet, which sheet can be produced at improved speeds while exhibiting improved ply-bonding characteristics and a commercially desirable outer surface.
These and other objects, features and advantages of the invention will become readily apparent to those skilled in the art upon reading the following description of the preferred embodiments in conjunction with the attached drawings.
Figure 1 is a side-elevational view of the former showing a foil box within the first wire for substantially the length of the forming zone between the throat and the turn1ng roll.
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, W O 92/01111 2 0 8 7 ~ 13 PC~r/EP91/01255 -Figure 2 is a side-elevational view of the former showing a foil box followed by two suction boxes within the first, or lower, top ply forming wire.
Figure 3 is a side-elevation view, similar to that shown in Figure l, but including a forming shoe within the lower top ply forming wire upstream of where the second, or upper, top ply forming wire comes into-co-running engagement with the web over the first forming wire.
10 As shown in Figure 1, a first, lower looped top ply forming wire 10 is shown looped about guide rolls 12, 12', 12'' and turning roll 14. Disposed within the first forming wire is a foil box 16 which has an outer contour defined by a plurality of foils 18 arranged to distend the first forming wire in a concave downwardly, or convex upwardly, shaped curve which defines a forming zone extending substantially between guide roll 12 and turning roll 14.
Disposed above the first, lower forming wire 10 is a looped second, upper forming wire 20 which is directed to travel in its looped path by guide rolls 22, 22', 22'' and 22'''.
Guide rolls 12, 22 direct their respective forming wires 10, 20 into a throat 24 which converges near the leading edge of foil ~ox 16. In the embodiment shown in Figure 1, the throat 24 extends to just after the beginning of foil box 16.
The second forming wire 20 is guided to . remain over the first forming wire for a short circumferential distance over the surface of turning roll 14. Turning roll 14 is a suction roll having a vacuum chamber 26 extending between circumferentially spaced seals 28, 30. The first and second forming wires are shown engaged for a short distance past the upstream va~uum chamber seal 28.
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WO92/01111 2 ~ g ~ PCT/EP91/01255 Positioned within the looped second forming wire 20 is a save-all 32, which can take the form of a so-called autoslice. In either configuration, the save-all or auto-slice represents a blade, lip or slot 33 which is positioned in closely spaced adjacency, or even non-pressure contact, with the inner side of looped forming wire 20. More than one such lip or slot 33 may be used.
A headbox 34 is positioned to direct an aqueous slurry of stock fibers into the throat 24.
Depending on operating parameters, such as machine speed, stock consistency and, posslbly, the type of forming wires- used~ the headbox sllce nozzle may -be dlrected sllghtly toward one or the other of the formlng wires.
Beneath the top ply former, which is the designation for the apparatus ~ust descrlbed, is a base ply forming wire 36 on which a base ply web WB has been formed upstream of the top ply former by other means. A
pivoted guide roll 38 wraps the base ply forming wire 36 around a portion of the periphery of the turning roll 14 beginning at a point over the trailing seal 30. The top ply web WT is thus brought into co-running engagement with the base ply web WB, and ply-bonding occurs between the webs during thls period of contact. Transfer of the composite, multi-ply paper sheet so formed to the base ply wire 36 is assured by the application of vacuum pressure in transfer box 40.
A source of sub-atmospheric a r pressure 42 is optionally linked to the foll box 16 to provlde vacuum pressure to the lower slde of the web being formed between the co-running forming wires lO, 20 over the foil blades 18 in the foil box. Water is removed from the lnner side of the looped second forming wire by , , ~ - . . . . .
, . , . . : . .
.. . ..
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.' WO92/01ll1 ~ Q 13 PCT/EP91/01255 a drain 44, and water is removed from within the looped first forming wire by drain 46.
In the various configurations shown in Figures 1-3, corresponding elements in each figure will be correspondingly numbered with a letter postscript to distinguish between corresponding elements in the various figures. Similarly, like elements within a particular figure will be distinguished by a different number of prime superscripts after each element number.
As shown in Figure 2, the dewatering elements within the first forming wire lOa comprise a foil box 16a, and two vacuum boxes 17a, 17a'. The last ---forming box 17a', in the downstream -direction, effects the transfer of the newly formed top ply web WT onto the first forming wire.
Within the looped second forming wire 20a, is a first auto-slice 48a following the foil box, and a second auto-slice 48a' intermediate the two vacuum boxes 17a, 17a'. ~oth auto-slices have a leading lip 33a, 33a' -which is mounted in closely spaced ad~acency, or non-pressure contact, with the inner side of looped forming wire 20a. A headbox 34a discharges an aqueous stock fiber stream into the throat 24a formed between the forming wires lOa, 20a converging over guide rolls 12a, 22a.
Turning roll 14a, which in this configuration is a plane surfaced roll with no vacuum chamber, brings the first forming wire around its surface and into co-running engagement with the base ply web W~ being carried on base ply forming wire 36a.
In the embodiment shown in Figure 3, a blade forming shoe 50 has been mounted within the first forming wire lOb upstream of the foil box 16b. The second forming wire 20b is brought into engagement with the we~ oveF the first forming wire lOb just prior to .
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W092/01111 2d~ ~ ~13 PCT/EP91/01255 the beginning of their co-running travel over the foil box 16b. The first forming wire is guided onto the leading edge of foil box 16b by a guide roll 12b. The headbox 34b discharges an aqueous slurry of stock onto the first forming wire over the surface of guide roll 12b. As in the embodiment shown in Figure 2, the second vacuum box 17b effects the transfer of the newly formed top ply web WT onto the first forming wire which is directed lnto ply-bonding contact with the base ply web WB to form the multi-ply web W in a manner similar to that described in con~unction with Figure 2.
While the cross-sectional profile of the - first forming wire contour-over blade forming shoe 50, or forming board, may be substantially planar, or concave downward, the overall contour of the forming zone extending from before the leading edge of the forming shoe 50 to the trailing edge of vacuum box 17b' is concave downwardly/convex upwardly as shown which is similar to the configurations shown in Figures 1 and 2.
The vacuum pressure beneath forming wire lOb is zero or low, regardless of how it is induced, so as to promote better formation, and improved web propertles, such as directional strength.
In the embodiments shown in Figure 2 and 3, foil boxes 16a, 16b and vacuum boxes 17a, 17a' and 17b' are connected to a source of sub-atmospheric air pressure whlch are designated generally as 52a, 52a', 52b and 52b'. The profile contours of the wire-contactlng surfaces of the foil boxes and vacuum boxes is concave downwardly/convex upwardly. While the surface of the foil boxes is defined by a series of spaced foils whlch are parallel and spaced in the machine direction and which extend in the cross-machine direction, the contours of the vacuum boxes are usually comprised of an arcuate surface which is perforated, such as with holes .~. .. - - - . ' ` ' . . - -.
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WO 92/Ot111 ~ ~ 8 7 ~ 1 3 PCT/EP9l/01255 --drilled through their covers, which permit the application of vacuum pressure to the underside of the first looped forming wire.
In operation, with particular reference to Figures 1 and 2, the headbox discharges an aqueous stock slurry into the throat between the co-running forming wires. Since the only application of sub-atmospheric air pressure to the fibrous stock slurry between the forming wires is provided by the foil box or vacuum boxes beneath the first forming wire 10, lOa, lOb, water is urged from the stock slurry outwardly and downwardly through the lower top ply web WT to within the looped first forming wire. Due to the tension--of the second-forming wire 10, lOa, lOb over the stock slurry over the first forming wire water is expressed outwardly through the top ply web W~ being formed between the first and second forming wires and into the save-all 32, or auto-slices 4~a, 48a', 48b, 48b'. The water is also urged outwardly through the upper surface of the top ply web by centrifugal force and the force of yravity in the slightly down-turning portions of co-running forming wlre travel in the generally horizontally disposed, concave downwardly forming zone. The blades in the foil box 16, 16a, 16b, operating with or without sub-atmospheric vacuum pressure, urge the water gently towithin the foil boxes. Downstream, at a point where the web is more dewatered, higher'sub-atmospheric vacuum pressure is applied to vacuum boxes 17a', 17b' to further dewater the top ply web through the lower surface thereof.
In the embodiment shown in Figure 3, the ; headbox discharges the stock slurry onto the first forming wire and additional dewatering through the lower surface of the top ply web is effected by the blades 51 contacting the inner surface of the first forming wire ' : :' ,.. : . : , ~. . - : . , . .: . : -: , , , . . , , . : , ` wo92/01111 2~ t ,~ PCT/EP91/01255 over the forming shoe 50. This is substantially similar to the water removal operation at the beginning of a conventional fourdrinier.
In all of the embodiments, the application 5 of sub-atmospheric air pressure solely to the lower side of the top ply web through the first forming wire urges the fines and any fillers in the stock slurry to migrate downwardly toward the lower surface of the top ply web.
Thus, while some of the fines near the lower surface of lO the top ply web over the first forming wire are removed from the web, a relatively large proportion of the fines lnitially near the upper surface of the top ply web - ad~acent the second forming --wire---remain in the web during the dewatering effected by the sub-atmospheric l5 air pressure. Not only do these fines remain in the web, but a relatively larger total proportion of the fines initially in the stock remain in the web due to the absence of any application of sub-atmospheric air pressure to the stock slurry between the forming wires 20 through the second forming wire. In other words, the only forces urging water out of the upper surface of the s top ply web are centrifugal f,orce, forming wire tension and, in the slightly downwardly extending portion of forming wire travel in the substantially horizontally 25 disposed forming section, gravity. Water expressed through the top (second) forming wire, therefore, need only be collected by the save-all or auto-slices: it is not urged through the top wire by these elements.
Thus, a relatively higher proportion of 30 fines remain in the upper surface of the top ply web being formed, and it is this surface which is brought into ply-bonding contact with the upper surface of the base ply web WB over the turning roll. Since ply-bonding is enhanced by a higher proportion of fines in the 35 surface of one, or both, of the webs at their interface, ~ .
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, WO92/01111 ~ PCT/EP91/01255 _ ply-bonding between the top ply web WT and the base ply web WB is promoted by this invention. This allows ply-bonding to be achieved at lower web moisture levels and faster machine speeds, or some combination of both.
S In this invention, both upward (through the second forming wire) and downward (through the first forming wire) dewatering is effected, but the dewatering is controlled as described. More fines remain at or near the top surface of the top ply web for better ply bonding, and more fines and fibers remains in the whole top ply web due to the application of sub-atmospheric pressure on only the lower side through the first forming wire.----In-other words, the bottom of the top ply web is also of a hi~her quality. This promotes good top ply smoothness and printing properties in the composite multi-ply web W.
~; Naturally, variations in the method and apparatus described can be made without departing from the spirit of the invention snd scope of the claims. For example, the throat can extend from upstream of the ;, place where the top ply forming wires are gulded to travel in substantially the same direction to where the wires converge. Also, while the foil boxes, and forming shoe, have been described as operated in con~unction wlth sub-atmospheric air pressure, it is contemplated that, under certain circumstances, they need not be so operated. Finally, it is to be understood that the terms web, sh-et and paper include the term board.
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In prior forming arrangements for forming a multi-ply paper web product, a relatively coarse base ply is first produced and a second, outer ply is produced to be brought into ply-bonding contact with the previously formed base ply. The outer ply, which is intended to form the outer surface of the printed container, such as a box, is formed of a finer grade of pulp stock so as to provide a smoother, higher quality surface. In order to form the outer ply at commercially desirable speeds, dewatering was efected through both of its surfaces before the outer ply was brought into ply-bonding contact with the base ply of the paper web sheet. This produces an acceptable paper product, mainly due to the quality of the pulp stock used to produce the outer ply, but the requirements of producing a better product with cheaper pulp, and the need to produce a better product at higher speeds regardless of pulp quality, or a combination of both, have necessitated the conception of an improved multi-ply web former having an outer surface which exhibits the desired printability, and feel and visual smoothness while having an inner ~0 surface which has better ply-bonding characteristics.
In prior apparatus, both sides of the outer ply were dewatered positlvely, that is, they were dewatered by the application of sub-atmospheric air pressure directly to both surfaces to enhance the removal of water through both of the web surfaces. When SUBSTITUTE SHE~
~ .
. .......... .
, ,., "........... :
, WO92/01111 2 0 ~ 6 013 PCT/EP91/01255 both surfaces are positively dewatered, fines and fillers in the pulp stock are urged outwardly in both directions to the respective surfaces of the web and removed during the dewatering process. Thus, while the web is rapidly dewatered, which was the desired effect, the fines and fillers which contribute so much to the ply bonding characteristics of the outer side of the web produced, were removed in large quantities which deleteriously effected web quality as well.
The aforementioned shortcomings, deficien-cies and characteristics of the outer ply in a ply-bonded multi-ply paper web, and the resultant multi-ply paper product, have been obviated by this invention.
In this invention, the outer ply of a multi-ply web, which is sometimes referred to as a "white top liner", is produced by dewatering through one side of the web using only centrifugal force and the force of the tension of the forming wire over the we~. The outer ply is formed in the general direction opposite to the direction of the traveling base ply to which it is ply bonded. The generally upwardly facing surface of the top ply is dewatered by the tension of the upper, outer forming wire being concave downwardly held over the web which has been formed by the aqueous pulp stock slurry projected between the outer and inner forming wires. In addition, one, or more, water collection devices, such as water skimming slots, which may or may not be assisted by a vacuum, assist in removing water expressed inwardly of the outer forming wire. The fines and fillers in the pulp stock slurry are thus exposed to sub-atmospheric (vacuum) pressure only within the lower forming wire in a generally concave downward direction for a relatively long distance. This affects the rate of water removal as well as permits the retention of a greater proportion of fines and fillers in the web, - ~
, .
:
- ' . - : .
- ' ' , ~ .
WO92/01111 20~ 3 PCT/EPgl/0125 particularly the top surface of the web, due to the fact that migration of the fines and fillers through the lower surface of the web is hindered by the web fibers.
The downwardly directed, relatively gentle dewatering through the lower surface of the outer web ply is effected by subjecting the ply to a sub-atmospheric pressure over a relatively long dewatering zone, which can take the form of a vacuum or suction box, or a plurality of spaced foil blades, or a combination of both.
Accordingly, it is an object of this invention to provide a method and apparatus for _ producing a multi-ply paper sheet hàving improved ply-bond characteristics.
Another object of this invention is 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.
A feature and advantage of this invention is the provision of a white top liner in a multi-ply paper sheet, which sheet can be produced at improved speeds while exhibiting improved ply-bonding characteristics and a commercially desirable outer surface.
These and other objects, features and advantages of the invention will become readily apparent to those skilled in the art upon reading the following description of the preferred embodiments in conjunction with the attached drawings.
Figure 1 is a side-elevational view of the former showing a foil box within the first wire for substantially the length of the forming zone between the throat and the turn1ng roll.
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., .
... . , - .: ..
. .
, W O 92/01111 2 0 8 7 ~ 13 PC~r/EP91/01255 -Figure 2 is a side-elevational view of the former showing a foil box followed by two suction boxes within the first, or lower, top ply forming wire.
Figure 3 is a side-elevation view, similar to that shown in Figure l, but including a forming shoe within the lower top ply forming wire upstream of where the second, or upper, top ply forming wire comes into-co-running engagement with the web over the first forming wire.
10 As shown in Figure 1, a first, lower looped top ply forming wire 10 is shown looped about guide rolls 12, 12', 12'' and turning roll 14. Disposed within the first forming wire is a foil box 16 which has an outer contour defined by a plurality of foils 18 arranged to distend the first forming wire in a concave downwardly, or convex upwardly, shaped curve which defines a forming zone extending substantially between guide roll 12 and turning roll 14.
Disposed above the first, lower forming wire 10 is a looped second, upper forming wire 20 which is directed to travel in its looped path by guide rolls 22, 22', 22'' and 22'''.
Guide rolls 12, 22 direct their respective forming wires 10, 20 into a throat 24 which converges near the leading edge of foil ~ox 16. In the embodiment shown in Figure 1, the throat 24 extends to just after the beginning of foil box 16.
The second forming wire 20 is guided to . remain over the first forming wire for a short circumferential distance over the surface of turning roll 14. Turning roll 14 is a suction roll having a vacuum chamber 26 extending between circumferentially spaced seals 28, 30. The first and second forming wires are shown engaged for a short distance past the upstream va~uum chamber seal 28.
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WO92/01111 2 ~ g ~ PCT/EP91/01255 Positioned within the looped second forming wire 20 is a save-all 32, which can take the form of a so-called autoslice. In either configuration, the save-all or auto-slice represents a blade, lip or slot 33 which is positioned in closely spaced adjacency, or even non-pressure contact, with the inner side of looped forming wire 20. More than one such lip or slot 33 may be used.
A headbox 34 is positioned to direct an aqueous slurry of stock fibers into the throat 24.
Depending on operating parameters, such as machine speed, stock consistency and, posslbly, the type of forming wires- used~ the headbox sllce nozzle may -be dlrected sllghtly toward one or the other of the formlng wires.
Beneath the top ply former, which is the designation for the apparatus ~ust descrlbed, is a base ply forming wire 36 on which a base ply web WB has been formed upstream of the top ply former by other means. A
pivoted guide roll 38 wraps the base ply forming wire 36 around a portion of the periphery of the turning roll 14 beginning at a point over the trailing seal 30. The top ply web WT is thus brought into co-running engagement with the base ply web WB, and ply-bonding occurs between the webs during thls period of contact. Transfer of the composite, multi-ply paper sheet so formed to the base ply wire 36 is assured by the application of vacuum pressure in transfer box 40.
A source of sub-atmospheric a r pressure 42 is optionally linked to the foll box 16 to provlde vacuum pressure to the lower slde of the web being formed between the co-running forming wires lO, 20 over the foil blades 18 in the foil box. Water is removed from the lnner side of the looped second forming wire by , , ~ - . . . . .
, . , . . : . .
.. . ..
:~ . . .: . .
.' WO92/01ll1 ~ Q 13 PCT/EP91/01255 a drain 44, and water is removed from within the looped first forming wire by drain 46.
In the various configurations shown in Figures 1-3, corresponding elements in each figure will be correspondingly numbered with a letter postscript to distinguish between corresponding elements in the various figures. Similarly, like elements within a particular figure will be distinguished by a different number of prime superscripts after each element number.
As shown in Figure 2, the dewatering elements within the first forming wire lOa comprise a foil box 16a, and two vacuum boxes 17a, 17a'. The last ---forming box 17a', in the downstream -direction, effects the transfer of the newly formed top ply web WT onto the first forming wire.
Within the looped second forming wire 20a, is a first auto-slice 48a following the foil box, and a second auto-slice 48a' intermediate the two vacuum boxes 17a, 17a'. ~oth auto-slices have a leading lip 33a, 33a' -which is mounted in closely spaced ad~acency, or non-pressure contact, with the inner side of looped forming wire 20a. A headbox 34a discharges an aqueous stock fiber stream into the throat 24a formed between the forming wires lOa, 20a converging over guide rolls 12a, 22a.
Turning roll 14a, which in this configuration is a plane surfaced roll with no vacuum chamber, brings the first forming wire around its surface and into co-running engagement with the base ply web W~ being carried on base ply forming wire 36a.
In the embodiment shown in Figure 3, a blade forming shoe 50 has been mounted within the first forming wire lOb upstream of the foil box 16b. The second forming wire 20b is brought into engagement with the we~ oveF the first forming wire lOb just prior to .
- . . . . .. ... .. . .
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W092/01111 2d~ ~ ~13 PCT/EP91/01255 the beginning of their co-running travel over the foil box 16b. The first forming wire is guided onto the leading edge of foil box 16b by a guide roll 12b. The headbox 34b discharges an aqueous slurry of stock onto the first forming wire over the surface of guide roll 12b. As in the embodiment shown in Figure 2, the second vacuum box 17b effects the transfer of the newly formed top ply web WT onto the first forming wire which is directed lnto ply-bonding contact with the base ply web WB to form the multi-ply web W in a manner similar to that described in con~unction with Figure 2.
While the cross-sectional profile of the - first forming wire contour-over blade forming shoe 50, or forming board, may be substantially planar, or concave downward, the overall contour of the forming zone extending from before the leading edge of the forming shoe 50 to the trailing edge of vacuum box 17b' is concave downwardly/convex upwardly as shown which is similar to the configurations shown in Figures 1 and 2.
The vacuum pressure beneath forming wire lOb is zero or low, regardless of how it is induced, so as to promote better formation, and improved web propertles, such as directional strength.
In the embodiments shown in Figure 2 and 3, foil boxes 16a, 16b and vacuum boxes 17a, 17a' and 17b' are connected to a source of sub-atmospheric air pressure whlch are designated generally as 52a, 52a', 52b and 52b'. The profile contours of the wire-contactlng surfaces of the foil boxes and vacuum boxes is concave downwardly/convex upwardly. While the surface of the foil boxes is defined by a series of spaced foils whlch are parallel and spaced in the machine direction and which extend in the cross-machine direction, the contours of the vacuum boxes are usually comprised of an arcuate surface which is perforated, such as with holes .~. .. - - - . ' ` ' . . - -.
. ~ ..
~ .:
: . -:- ,. - . - , ~ :
.
:
WO 92/Ot111 ~ ~ 8 7 ~ 1 3 PCT/EP9l/01255 --drilled through their covers, which permit the application of vacuum pressure to the underside of the first looped forming wire.
In operation, with particular reference to Figures 1 and 2, the headbox discharges an aqueous stock slurry into the throat between the co-running forming wires. Since the only application of sub-atmospheric air pressure to the fibrous stock slurry between the forming wires is provided by the foil box or vacuum boxes beneath the first forming wire 10, lOa, lOb, water is urged from the stock slurry outwardly and downwardly through the lower top ply web WT to within the looped first forming wire. Due to the tension--of the second-forming wire 10, lOa, lOb over the stock slurry over the first forming wire water is expressed outwardly through the top ply web W~ being formed between the first and second forming wires and into the save-all 32, or auto-slices 4~a, 48a', 48b, 48b'. The water is also urged outwardly through the upper surface of the top ply web by centrifugal force and the force of yravity in the slightly down-turning portions of co-running forming wlre travel in the generally horizontally disposed, concave downwardly forming zone. The blades in the foil box 16, 16a, 16b, operating with or without sub-atmospheric vacuum pressure, urge the water gently towithin the foil boxes. Downstream, at a point where the web is more dewatered, higher'sub-atmospheric vacuum pressure is applied to vacuum boxes 17a', 17b' to further dewater the top ply web through the lower surface thereof.
In the embodiment shown in Figure 3, the ; headbox discharges the stock slurry onto the first forming wire and additional dewatering through the lower surface of the top ply web is effected by the blades 51 contacting the inner surface of the first forming wire ' : :' ,.. : . : , ~. . - : . , . .: . : -: , , , . . , , . : , ` wo92/01111 2~ t ,~ PCT/EP91/01255 over the forming shoe 50. This is substantially similar to the water removal operation at the beginning of a conventional fourdrinier.
In all of the embodiments, the application 5 of sub-atmospheric air pressure solely to the lower side of the top ply web through the first forming wire urges the fines and any fillers in the stock slurry to migrate downwardly toward the lower surface of the top ply web.
Thus, while some of the fines near the lower surface of lO the top ply web over the first forming wire are removed from the web, a relatively large proportion of the fines lnitially near the upper surface of the top ply web - ad~acent the second forming --wire---remain in the web during the dewatering effected by the sub-atmospheric l5 air pressure. Not only do these fines remain in the web, but a relatively larger total proportion of the fines initially in the stock remain in the web due to the absence of any application of sub-atmospheric air pressure to the stock slurry between the forming wires 20 through the second forming wire. In other words, the only forces urging water out of the upper surface of the s top ply web are centrifugal f,orce, forming wire tension and, in the slightly downwardly extending portion of forming wire travel in the substantially horizontally 25 disposed forming section, gravity. Water expressed through the top (second) forming wire, therefore, need only be collected by the save-all or auto-slices: it is not urged through the top wire by these elements.
Thus, a relatively higher proportion of 30 fines remain in the upper surface of the top ply web being formed, and it is this surface which is brought into ply-bonding contact with the upper surface of the base ply web WB over the turning roll. Since ply-bonding is enhanced by a higher proportion of fines in the 35 surface of one, or both, of the webs at their interface, ~ .
.''~
,.
- . : - . :.
.. . . . .: . :
-- ~ , .. . . . ~ , :
. : . . .
, WO92/01111 ~ PCT/EP91/01255 _ ply-bonding between the top ply web WT and the base ply web WB is promoted by this invention. This allows ply-bonding to be achieved at lower web moisture levels and faster machine speeds, or some combination of both.
S In this invention, both upward (through the second forming wire) and downward (through the first forming wire) dewatering is effected, but the dewatering is controlled as described. More fines remain at or near the top surface of the top ply web for better ply bonding, and more fines and fibers remains in the whole top ply web due to the application of sub-atmospheric pressure on only the lower side through the first forming wire.----In-other words, the bottom of the top ply web is also of a hi~her quality. This promotes good top ply smoothness and printing properties in the composite multi-ply web W.
~; Naturally, variations in the method and apparatus described can be made without departing from the spirit of the invention snd scope of the claims. For example, the throat can extend from upstream of the ;, place where the top ply forming wires are gulded to travel in substantially the same direction to where the wires converge. Also, while the foil boxes, and forming shoe, have been described as operated in con~unction wlth sub-atmospheric air pressure, it is contemplated that, under certain circumstances, they need not be so operated. Finally, it is to be understood that the terms web, sh-et and paper include the term board.
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, . , , . - . . . , . . . . - - . . . .
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Claims (10)
[received by the International Bureau on 30 October 1991 (30.10.91);
original claims 1,6 and 7 amended;
other claims unchanged (3 pages)]
1. A method for forming a multi-ply paper web, comprising the steps:
forming a base ply web on a traveling foraminous base forming wire;
bringing first and second looped forming wires into co-running engagement over a concave downwardly/convex upwardly curved, substantially horizontal, path of travel;
projecting an aqueous top ply stock stream onto one or the other, or both, of the first and second looped forming wires closely upstream of a throat formed by the converging first and second forming wires;
dewatering the top ply stock stream through the first forming wire by applying sub-atmospheric air pressure to the stock stream solely beneath its substantially horizontal path of travel to thereby form a lower web surface of a top ply web;
expressing water upwardly through the second forming wire over its substantially horizontal path of travel solely by wire tension and centrifugal force to thereby form an upper web surface of the top ply web;
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 multiply web.
forming a base ply web on a traveling foraminous base forming wire;
bringing first and second looped forming wires into co-running engagement over a concave downwardly/convex upwardly curved, substantially horizontal, path of travel;
projecting an aqueous top ply stock stream onto one or the other, or both, of the first and second looped forming wires closely upstream of a throat formed by the converging first and second forming wires;
dewatering the top ply stock stream through the first forming wire by applying sub-atmospheric air pressure to the stock stream solely beneath its substantially horizontal path of travel to thereby form a lower web surface of a top ply web;
expressing water upwardly through the second forming wire over its substantially horizontal path of travel solely by wire tension and centrifugal force to thereby form an upper web surface of the top ply web;
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 multiply web.
2. The method as set forth in claim 1, further including the steps of:
. guiding the second forming wire away from the first forming wire downstream of the dewatering through the first forming wire;
subjecting the top ply web to additional sub-atmospheric dewatering through the first forming wire downstream of where the second forming wire is guided away.
. guiding the second forming wire away from the first forming wire downstream of the dewatering through the first forming wire;
subjecting the top ply web to additional sub-atmospheric dewatering through the first forming wire downstream of where the second forming wire is guided away.
3. The method as set forth in claim 1, wherein:
the top ply stock stream is projected onto the first forming wire upstream of the throat; and further including the step dewatering the top ply stock stream downwardly within the first forming wire before the first and second forming wires converge into co-running engagement.
the top ply stock stream is projected onto the first forming wire upstream of the throat; and further including the step dewatering the top ply stock stream downwardly within the first forming wire before the first and second forming wires converge into co-running engagement.
4. The method as set forth in claim 3, further including the steps of:
guiding the second forming wire away from the first forming wire downstream of the dewatering through the first forming wire;
subjecting the top ply web to additional sub-atmospheric dewatering through the first forming wire downstream of where the second forming wire is guided away.
guiding the second forming wire away from the first forming wire downstream of the dewatering through the first forming wire;
subjecting the top ply web to additional sub-atmospheric dewatering through the first forming wire downstream of where the second forming wire is guided away.
5. The method as set forth in claim 3, wherein:
the dewatering of the top ply stock stream before the first and second forming wires converge is effected by the application of sub-atmospheric air pressure.
the dewatering of the top ply stock stream before the first and second forming wires converge is effected by the application of sub-atmospheric air pressure.
6. Apparatus for forming a multi-ply paper web, comprising, in combination:
a looped base ply forming wire for carrying and dewatering a base ply web;
first and second looped top ply forming wires arranged to converge in a throat and travel in co-running engagement in a concave downwardly/convex upwardly, substantially horizontal, path of travel together;
headbox means for depositing an aqueous top ply stock slurry on the first forming wire closely upstream of the throat, or in the throat to initiate formation of a top ply web having lower and upper surfaces;
sub-atmospheric air pressure dewatering apparatus within the first 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 first forming wire;
means for receiving water expressed upwardly and inwardly through the second looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the second wire;
guide means for guiding the second forming wire away from the first forming wire;
turning means for directing the first 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 and the base ply web.
a looped base ply forming wire for carrying and dewatering a base ply web;
first and second looped top ply forming wires arranged to converge in a throat and travel in co-running engagement in a concave downwardly/convex upwardly, substantially horizontal, path of travel together;
headbox means for depositing an aqueous top ply stock slurry on the first forming wire closely upstream of the throat, or in the throat to initiate formation of a top ply web having lower and upper surfaces;
sub-atmospheric air pressure dewatering apparatus within the first 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 first forming wire;
means for receiving water expressed upwardly and inwardly through the second looped forming wire solely by centrifugal force and forming wire tension, the upper surface of the top ply web facing the second wire;
guide means for guiding the second forming wire away from the first forming wire;
turning means for directing the first 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 and the base ply web.
7. Apparatus for forming a multi-ply paper web as set forth in claim 6, wherein:
the headbox deposits the top ply stock onto the first top ply forming wire closely upstream of where the first and second forming wires converge;
dewatering means are disposed beneath the first forming wire upstream where the first and second forming wires converge.
the headbox deposits the top ply stock onto the first top ply forming wire closely upstream of where the first and second forming wires converge;
dewatering means are disposed beneath the first forming wire upstream where the first and second forming wires converge.
8. Apparatus for forming a multi-ply paper web as set forth in claim 6, wherein:
the turning means comprises a suction roll.
the turning means comprises a suction roll.
9. Apparatus for forming a multi-ply paper web as set forth in claim 6, wherein:
the means for receiving water comprises an auto-slice.
the means for receiving water comprises an auto-slice.
10. Apparatus for forming a multi-ply paper web as set forth in claim 6, wherein:
the sub-atmospheric dewatering apparatus comprises a first vacuum forming shoe and at least one vacuum box downstream of the forming shoe.
the sub-atmospheric dewatering apparatus comprises a first vacuum forming shoe and at least one vacuum box downstream of the forming shoe.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP90113178.9 | 1990-07-10 | ||
| EP90113178A EP0465698A1 (en) | 1990-07-10 | 1990-07-10 | Multi-ply web former and method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2087013C true CA2087013C (en) | 1995-01-17 |
Family
ID=8204198
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002087013A Expired - Fee Related CA2087013C (en) | 1990-07-10 | 1991-07-04 | Multi-ply web former and method |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0465698A1 (en) |
| JP (1) | JPH0823117B2 (en) |
| KR (1) | KR100191140B1 (en) |
| AU (1) | AU657691B2 (en) |
| BR (1) | BR9106629A (en) |
| CA (1) | CA2087013C (en) |
| FI (1) | FI930080A0 (en) |
| PL (1) | PL167967B1 (en) |
| WO (1) | WO1992001111A1 (en) |
| ZA (1) | ZA915311B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2309537A1 (en) | 1997-12-19 | 1999-07-01 | E.I. Du Pont De Nemours And Company | Interlayer structure for laminated glass |
| DE19903943A1 (en) * | 1999-01-28 | 2000-08-03 | Voith Sulzer Papiertech Patent | Method and device for forming a fibrous web |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7017764A (en) * | 1969-12-06 | 1971-06-08 | ||
| US4153504A (en) * | 1977-01-31 | 1979-05-08 | Beloit Corporation | Twin-wire fibrous web former and method |
| FI70739C (en) * | 1977-04-28 | 1986-10-06 | Valmet Oy | BANBILDNINGSENHET VID FRAMSTAELLNING AV FLERSKIKTSKARTONG |
| DE2807894A1 (en) * | 1978-02-24 | 1979-08-30 | Voith Gmbh J M | PAPER MACHINE |
| AU5903086A (en) * | 1986-04-30 | 1987-11-24 | Beloit Corporation | A web forming apparatus |
| GB8710428D0 (en) * | 1987-05-01 | 1987-06-03 | Beloit Corp | Multi-ply web forming apparatus |
-
1990
- 1990-07-10 EP EP90113178A patent/EP0465698A1/en not_active Withdrawn
-
1991
- 1991-07-04 JP JP3511632A patent/JPH0823117B2/en not_active Expired - Fee Related
- 1991-07-04 KR KR1019930700044A patent/KR100191140B1/en not_active IP Right Cessation
- 1991-07-04 AU AU82139/91A patent/AU657691B2/en not_active Ceased
- 1991-07-04 CA CA002087013A patent/CA2087013C/en not_active Expired - Fee Related
- 1991-07-04 WO PCT/EP1991/001255 patent/WO1992001111A1/en active Application Filing
- 1991-07-04 BR BR919106629A patent/BR9106629A/en not_active IP Right Cessation
- 1991-07-04 PL PL91297609A patent/PL167967B1/en not_active IP Right Cessation
- 1991-07-09 ZA ZA915311A patent/ZA915311B/en unknown
-
1993
- 1993-01-08 FI FI930080A patent/FI930080A0/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05507970A (en) | 1993-11-11 |
| AU657691B2 (en) | 1995-03-23 |
| PL167967B1 (en) | 1995-12-30 |
| BR9106629A (en) | 1993-06-01 |
| FI930080A (en) | 1993-01-08 |
| AU8213991A (en) | 1992-02-04 |
| JPH0823117B2 (en) | 1996-03-06 |
| PL297609A1 (en) | 1992-07-13 |
| FI930080A0 (en) | 1993-01-08 |
| KR100191140B1 (en) | 1999-06-15 |
| EP0465698A1 (en) | 1992-01-15 |
| WO1992001111A1 (en) | 1992-01-23 |
| ZA915311B (en) | 1992-04-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |