CA2106392A1 - Double wire former with flexible dewatering slats - Google Patents
Double wire former with flexible dewatering slatsInfo
- Publication number
- CA2106392A1 CA2106392A1 CA 2106392 CA2106392A CA2106392A1 CA 2106392 A1 CA2106392 A1 CA 2106392A1 CA 2106392 CA2106392 CA 2106392 CA 2106392 A CA2106392 A CA 2106392A CA 2106392 A1 CA2106392 A1 CA 2106392A1
- Authority
- CA
- Canada
- Prior art keywords
- dewatering
- slat
- double wire
- slats
- wire former
- 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.)
- Abandoned
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/48—Suction apparatus
-
- 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
Abstract
ABSTRACT OF THE DISCLOSURE
A double wire former for producing a fiber web, specifically a paper web, from a fiber suspension. The double wire former includes two wires which together form a double wire zone, at least one dewatering zone, and at least one fixed dewatering slat in the dewatering zone.
A flexible, or flexibly arranged, dewatering slat is coordinated with the fixed dewatering slat. The flexible slat is arranged such that a variable contact pressure exists between the slat and one of the wires. The dewatering slats are spaced apart a distance such that a variation of the contact pressure of the flexible slat results in a change of the deflection of the wires at the fixed slat, whereby a change of the dewatering pressure created by the fixed slat is effected.
A double wire former for producing a fiber web, specifically a paper web, from a fiber suspension. The double wire former includes two wires which together form a double wire zone, at least one dewatering zone, and at least one fixed dewatering slat in the dewatering zone.
A flexible, or flexibly arranged, dewatering slat is coordinated with the fixed dewatering slat. The flexible slat is arranged such that a variable contact pressure exists between the slat and one of the wires. The dewatering slats are spaced apart a distance such that a variation of the contact pressure of the flexible slat results in a change of the deflection of the wires at the fixed slat, whereby a change of the dewatering pressure created by the fixed slat is effected.
Description
2~63~2 DOUBLE WIRE FORMER WITH FLEXIBLE DEWATERING SLATS
BACKGROUND OF ~E INVENTION . .:
The invention concerns a double wire former for producing a fiber web, specifically a paper web, from a `;
fiber suspension.
The invention is based on the double wire former -.
known from the British patent document 1,125,906. The characteristics known from this publication are the providing of two wires which together ~orm a double wire zone, the providlng oP at least one dewatering zone, and ~ -the providing of at least one fixed dewatering slat in the dewatering zone. In other words, the characteristics express that the formation of the ~iber web from the stock suspension supplied from the headbox takes place exclusively ~etween two wires. Thus, a so-called single-wire primary dewatering section is missi~gO In a first section of the double wire zone, the two wires form a :
wedge shaped entrance gap, into which empties a stock ~ .
suspension jet discharglng ~rom t~e headbox. This jet ::
imping~s on the two wires at a point where they run ..
across a curved dewatering element. In the case of the British patent document, this element is a stationary, curved forming shoe which is arranged in one of the two wire loops. Its curved wire support surface is formed of numerous slats with interposed dewatering slots. This forming shoe is followed (in a second section of the double wire zone) by a dewatexing slat arranged in the .-one wire loop and, behind it, a dewatering ~lat arranged in t~e former wire loop (and ~ormed by a first suction ~ :
box). Lastly, following in a third section of the double wire zone are everal stationary dewatering elements fashioned as suction ~lat boxes. ~.
:~ Using double wire formers of the prior type, . :.
attempts have been made for dec~des at producing fiber ;."
21~6392 webs (specifically paper webs) of maximally high quality and at relatively high operating speeds. The web formation between two wires has achieved, in particular, a finished fiber web which possesses on both sides extensively the same properties (slight "twosidedness").
However, difficulties are encountered in achieving a maximally uniform fiber distribution in the finished fiber web. In other words, it is dificult to achieve a good "formation." During the web formation there constantly exists the risk that fibers will coagulate to flocks. There~ore, attempts are made to form at the headbox a ma~imally ~lock-free jet of stock suspension, for instance with the aid of a turbulence generator.
In addition, efforts are being made toward influencing the dewatering of the fiber suspension during the web ~ormation to the effect that a "reflocculation" is maximally avoided or that after any ~lock formation a l'deflocculation" (i.e., dissolution of the flocks) take~ -place again.
It is known that a curved dewatering element arranged in the first section of the double wire zone, -~
specifically a stationary, curved forming shoe fashioned according to the British patent document 1,125,906, counteracts the risk of reflocculation. Thi~ is true also for the dewatering slats which according to the British patent document are arranged in the second saction of the double wire zone. Nevertheless, khe risk of reflocculation is not completely eliminated with the arrangement according to this British patent document.
Namely, with the number of dewatering slats being very small there, the web formation largely takes place in the area of the following ~lat suction boxes. While these have a high dewatering capacity, so that the web formation can be terminated in the area of the last :';,', 210~392 suction flat box (i.e., the so-called major dewatering zone, in which part of the fiber material is still on hand in the ~orm of a suspension, ends in the area o~ the suction flat hoxes), the suction flat boxes are unable to avoid a reflocculation or to redissolve flocks which have been created.
To master the latter difficulties, a web ~orming system known as "Duoformer D" has been developsd (TAPPI
Proceedings 198~ Annual Meeting, pp. 75 80). This prior web Porming system is part of a double wire former ~ -featuring a single wire primary dewatering zone.
Provid~d in the double wire zone, in the one wire loop, is a number of fixed, but adju~tably supported slats on the underside o~ a suction flat box dewatering upwardly.
In addition, a number of flexibly supported slats are provided in the other wire loop. Due to the ~lexibility o~ the latter slats, the ~ollowing can be achievedO For instance, at an increase oP the suspension quantity fed between the two wires, the flexibly supported slats can somewhat yield. This eliminates the risk ~which exists when fixedly supported slats are solely used) that a backup will form in the fiber suspension in front of the slats. Such backup could again destroy the fiber layers formed up to here on the two wires. In other words, a dewatering pressure once adjusted remains constant ~ith ~ -this web forming system, owing to the flexibly supported slats, also at a change of the supplied suspansion quantity or of th~ dewatering performance of the ~iber suspension. ~hus, an automatic adaptation of the web forming system to the said changed conditions is taking place. -Fiber webs having relatively good formation can be formed with this prior web forming sy~tem. In this respect, though, requirements have recently risen .: '~ ':
210~3~2 considerably, making further improvements desirable.
In particular, it has been demonstrated that the pressure surges created at the edges of a fixed dewatering slat, or for instance thP surges created at the edge of a suction box, partly have a positive and desirable e~fect on the sheet formation, specifically in regards to maintaining a maximally flockfree condition of the suspension and toward accelerating the dewatering~
However, an excessive pressure surge is unfavorable and may entail negative effects on a uniform sheet formation.
The problem underlying the invention is to fashion a double wire former of the initially described type in such a way that an influencing of the pressure surges in the dewatering zone is given. Thus, the ~lality of the fiber web produced increases further and the double wire former is easily adaptable to varying operating conditions, for instance regarding the amount and dewatering per~ormance of the fiber suspension.
SUMMARY OF THE INV~NTION
This problem is solved by the inventive fea~ures of the present invention. Two endless wires together form a -~
double wire zone. At leask one flexible, or adjustably arranged, dewatering slat is coordinated with at least one fixed, or rigidly Aupported, dewatering slat in the double wire zone, which slats contact one of th~ two endless wires such that the double wire zone includes a polygonal train wherein the wires are deflected at aach of said slats. A variable contact pressure exists bekween the adjustable slat and one of the wires. The described dewatering slats are spaced apart a distanre uch that a variation o~ the contact pressure of the ~;
adjustably supported slat results in a cha~ge of the deflection of the wires at the fixed, rigidly supported ~5~ ~0$~
slat, whereby a change of the dewatering pressure created by the rigidly supported slat occurs.
BRIE~ DESCRIPTION OF THE DRAWINGS
The invention will be more fully explained with the aid of the drawings, which illustrate the following:
Figs. 1 though 4 each show a forming shoe with a first and a last fixed dewatering slat and several interposed flexible dewatering slats.
Fig. 5 shows a forming shoe with alternating fixed and flexible slats.
Fig. 6 shows a forming shoe with a collecting chute.
Fig. 7 shows an alternate embodiment of the arrangement of Figs. 1 through 6, wherein the adjustable springs are replaced with pneumatic bearings.
DESCRIPT_N OF THE PREFERRED EMEIODIMENTS
The inventors have recognized that a combination of fixed, or rigidly supported, dewatering slats and flexible, or adjustable, dewatering slats may be combined in such a way thak the pressure surge created by the fixed dewatering slats may be changed. This is due to a variation of the adjustable dewatering slats that results in an extremely high quality increase of the finished ~iber web, such that the web meets even the highest -requirements.
Preferably, the adjustable dewatering slats are resiliently supported. In this event, the double wire ~- -former is insensitive to changes in the quantity of suspension supplied or in the concentratio~ of the fiber suspension, and can be easily ad~u~ted to different ~ -ituations without having to accept any qua}ity impairment It is important that the spacing of the adjustable slat from the fixed slat be such that a variation of the contact pressure of the adjustably supported slat with the wire results in a change of the ' ' .' '.", '' "' "
21~392 deflection of tha wires at the fixed slat, thereby changing the dewatering pressure created by the fixed slat. In practice, the distance between the two adjacent slats may be between about 40 and 400 mm.
By changing the contact pressure of the adjustable slat or slats it is possible to adjust the polygon train of the wire running across the slats such that different pressure levels in the suspension, and differently large deflection angles of the wires, result at the contact points of the wire with the slats, including the fixed slat or slats. These different pressures are suited to effect an adaptation of the dewatering, ~or instance to different fiber materials. Furthermore, the dif~`erent deflection angles enable a control by amount and direction of the water thrown off outwardly. The -arrangement of a collection device above the outer wire is also possible, for instance in the form of a chute or a suctioning device which extends across the machine width, so that the wire water thrown off the outer wire by wire deflection at a dewatering slat can be collected by this device.
Fig. 1 through 4 show in exemplary fashion a forming shoe with a ~irst fixed, or rigidly supported, dewatering slat 1 and a last fixed dewatering slat 7. Arranged between the dewatering slats 1 and 7, in exemplary fashion, are five other flexibly designed, or adjustable, dewatering slats 2 through 6. Extending across the polygon train created by the dewatering slats 1 through 7 is the wire 10. Fig. 1 also includes the complete forming shoe comprising a box 14 which directly supports fixed slats 1 and 7, and which comprises a perforated wall 15 to support the adjustable slats 2 to 6. In this embodiment, each slat 2 to 6 is supported by a spring 8 which i~ adjustable (symbolically illustrated by an ' ~ ' ,., ' .
' ' " ' ~
arrow). Box 14 has a discharge opening 16 for water. In the normal manner, each wire 10, 11 forms an endless wire loop (not completely shown). The wires, and the fiber suspension 9 therebetween, are guided by wire rolls 12, 13 onto the forming shoe.
Fig. 1 through 4 differ in the adjustment of the dewatering slats, creating a different pressure distribution of the dewatering slats on the wire. Thus, Fig. 1 shows a uniform polygon, which also results in a uniform pressure distxibution. In Fig. 2, a steadily increasing dewatering pressure is created from left to right. Fig. 3 shows the opposite effect. There exists at first a very strong dewatering pressure, which steadily diminishes toward the end o~ the ~orming shoe.
An extreme case is depicted in Fig. 4, where the highest dewatering pressure is generated on the center dewatering slat 4.
Ths embodiment of the forming shoe shown in Fig. 5 includes a slat structure alternating between fixed and ~ -adjustable slats. -~
Fig. 6 once again shows a forming shoe such as illustrated in Figs. 1 through 4. However, in this embodiment there is arranged beneath the wire a collection device or chute 20, which in this embodiment also is adjustable in height. Arrows 30 and 31 indicate the direction of the wire water thrown off at the dewatering slat 5. Reference 30 shows a water direction created by a high wire speed, whereas the flatter curve 31 illustrates the course of the wire water at a low wire speed.
In Fig. 7 the springs are replaced with pneumatic bearings 8', in the form of tubular pressure cushions.
Each pressure cushion 8' is connected to a pressure line 17 via valve 18 to vary the contact pressure.
~; , .
.
' ~'' ': : ~`~' .' , ' . ' :
21~63~2 While this invention has been described as having a preferred design, the invention can be further modified within the spirit and SGOpe of this disclosure. This application is therefore intended to cover any variations, uses or adaptations of the invention using its general principles. Further, this application is intend~d to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall : -within the limits of the appended claims.
; , `'','' . " . : ' . ' , - : ', '~. . .,.,.` ' ~ ' ' , ' . , ' . , . ' ' ' ., ' : ' .
BACKGROUND OF ~E INVENTION . .:
The invention concerns a double wire former for producing a fiber web, specifically a paper web, from a `;
fiber suspension.
The invention is based on the double wire former -.
known from the British patent document 1,125,906. The characteristics known from this publication are the providing of two wires which together ~orm a double wire zone, the providlng oP at least one dewatering zone, and ~ -the providing of at least one fixed dewatering slat in the dewatering zone. In other words, the characteristics express that the formation of the ~iber web from the stock suspension supplied from the headbox takes place exclusively ~etween two wires. Thus, a so-called single-wire primary dewatering section is missi~gO In a first section of the double wire zone, the two wires form a :
wedge shaped entrance gap, into which empties a stock ~ .
suspension jet discharglng ~rom t~e headbox. This jet ::
imping~s on the two wires at a point where they run ..
across a curved dewatering element. In the case of the British patent document, this element is a stationary, curved forming shoe which is arranged in one of the two wire loops. Its curved wire support surface is formed of numerous slats with interposed dewatering slots. This forming shoe is followed (in a second section of the double wire zone) by a dewatexing slat arranged in the .-one wire loop and, behind it, a dewatering ~lat arranged in t~e former wire loop (and ~ormed by a first suction ~ :
box). Lastly, following in a third section of the double wire zone are everal stationary dewatering elements fashioned as suction ~lat boxes. ~.
:~ Using double wire formers of the prior type, . :.
attempts have been made for dec~des at producing fiber ;."
21~6392 webs (specifically paper webs) of maximally high quality and at relatively high operating speeds. The web formation between two wires has achieved, in particular, a finished fiber web which possesses on both sides extensively the same properties (slight "twosidedness").
However, difficulties are encountered in achieving a maximally uniform fiber distribution in the finished fiber web. In other words, it is dificult to achieve a good "formation." During the web formation there constantly exists the risk that fibers will coagulate to flocks. There~ore, attempts are made to form at the headbox a ma~imally ~lock-free jet of stock suspension, for instance with the aid of a turbulence generator.
In addition, efforts are being made toward influencing the dewatering of the fiber suspension during the web ~ormation to the effect that a "reflocculation" is maximally avoided or that after any ~lock formation a l'deflocculation" (i.e., dissolution of the flocks) take~ -place again.
It is known that a curved dewatering element arranged in the first section of the double wire zone, -~
specifically a stationary, curved forming shoe fashioned according to the British patent document 1,125,906, counteracts the risk of reflocculation. Thi~ is true also for the dewatering slats which according to the British patent document are arranged in the second saction of the double wire zone. Nevertheless, khe risk of reflocculation is not completely eliminated with the arrangement according to this British patent document.
Namely, with the number of dewatering slats being very small there, the web formation largely takes place in the area of the following ~lat suction boxes. While these have a high dewatering capacity, so that the web formation can be terminated in the area of the last :';,', 210~392 suction flat box (i.e., the so-called major dewatering zone, in which part of the fiber material is still on hand in the ~orm of a suspension, ends in the area o~ the suction flat hoxes), the suction flat boxes are unable to avoid a reflocculation or to redissolve flocks which have been created.
To master the latter difficulties, a web ~orming system known as "Duoformer D" has been developsd (TAPPI
Proceedings 198~ Annual Meeting, pp. 75 80). This prior web Porming system is part of a double wire former ~ -featuring a single wire primary dewatering zone.
Provid~d in the double wire zone, in the one wire loop, is a number of fixed, but adju~tably supported slats on the underside o~ a suction flat box dewatering upwardly.
In addition, a number of flexibly supported slats are provided in the other wire loop. Due to the ~lexibility o~ the latter slats, the ~ollowing can be achievedO For instance, at an increase oP the suspension quantity fed between the two wires, the flexibly supported slats can somewhat yield. This eliminates the risk ~which exists when fixedly supported slats are solely used) that a backup will form in the fiber suspension in front of the slats. Such backup could again destroy the fiber layers formed up to here on the two wires. In other words, a dewatering pressure once adjusted remains constant ~ith ~ -this web forming system, owing to the flexibly supported slats, also at a change of the supplied suspansion quantity or of th~ dewatering performance of the ~iber suspension. ~hus, an automatic adaptation of the web forming system to the said changed conditions is taking place. -Fiber webs having relatively good formation can be formed with this prior web forming sy~tem. In this respect, though, requirements have recently risen .: '~ ':
210~3~2 considerably, making further improvements desirable.
In particular, it has been demonstrated that the pressure surges created at the edges of a fixed dewatering slat, or for instance thP surges created at the edge of a suction box, partly have a positive and desirable e~fect on the sheet formation, specifically in regards to maintaining a maximally flockfree condition of the suspension and toward accelerating the dewatering~
However, an excessive pressure surge is unfavorable and may entail negative effects on a uniform sheet formation.
The problem underlying the invention is to fashion a double wire former of the initially described type in such a way that an influencing of the pressure surges in the dewatering zone is given. Thus, the ~lality of the fiber web produced increases further and the double wire former is easily adaptable to varying operating conditions, for instance regarding the amount and dewatering per~ormance of the fiber suspension.
SUMMARY OF THE INV~NTION
This problem is solved by the inventive fea~ures of the present invention. Two endless wires together form a -~
double wire zone. At leask one flexible, or adjustably arranged, dewatering slat is coordinated with at least one fixed, or rigidly Aupported, dewatering slat in the double wire zone, which slats contact one of th~ two endless wires such that the double wire zone includes a polygonal train wherein the wires are deflected at aach of said slats. A variable contact pressure exists bekween the adjustable slat and one of the wires. The described dewatering slats are spaced apart a distanre uch that a variation o~ the contact pressure of the ~;
adjustably supported slat results in a cha~ge of the deflection of the wires at the fixed, rigidly supported ~5~ ~0$~
slat, whereby a change of the dewatering pressure created by the rigidly supported slat occurs.
BRIE~ DESCRIPTION OF THE DRAWINGS
The invention will be more fully explained with the aid of the drawings, which illustrate the following:
Figs. 1 though 4 each show a forming shoe with a first and a last fixed dewatering slat and several interposed flexible dewatering slats.
Fig. 5 shows a forming shoe with alternating fixed and flexible slats.
Fig. 6 shows a forming shoe with a collecting chute.
Fig. 7 shows an alternate embodiment of the arrangement of Figs. 1 through 6, wherein the adjustable springs are replaced with pneumatic bearings.
DESCRIPT_N OF THE PREFERRED EMEIODIMENTS
The inventors have recognized that a combination of fixed, or rigidly supported, dewatering slats and flexible, or adjustable, dewatering slats may be combined in such a way thak the pressure surge created by the fixed dewatering slats may be changed. This is due to a variation of the adjustable dewatering slats that results in an extremely high quality increase of the finished ~iber web, such that the web meets even the highest -requirements.
Preferably, the adjustable dewatering slats are resiliently supported. In this event, the double wire ~- -former is insensitive to changes in the quantity of suspension supplied or in the concentratio~ of the fiber suspension, and can be easily ad~u~ted to different ~ -ituations without having to accept any qua}ity impairment It is important that the spacing of the adjustable slat from the fixed slat be such that a variation of the contact pressure of the adjustably supported slat with the wire results in a change of the ' ' .' '.", '' "' "
21~392 deflection of tha wires at the fixed slat, thereby changing the dewatering pressure created by the fixed slat. In practice, the distance between the two adjacent slats may be between about 40 and 400 mm.
By changing the contact pressure of the adjustable slat or slats it is possible to adjust the polygon train of the wire running across the slats such that different pressure levels in the suspension, and differently large deflection angles of the wires, result at the contact points of the wire with the slats, including the fixed slat or slats. These different pressures are suited to effect an adaptation of the dewatering, ~or instance to different fiber materials. Furthermore, the dif~`erent deflection angles enable a control by amount and direction of the water thrown off outwardly. The -arrangement of a collection device above the outer wire is also possible, for instance in the form of a chute or a suctioning device which extends across the machine width, so that the wire water thrown off the outer wire by wire deflection at a dewatering slat can be collected by this device.
Fig. 1 through 4 show in exemplary fashion a forming shoe with a ~irst fixed, or rigidly supported, dewatering slat 1 and a last fixed dewatering slat 7. Arranged between the dewatering slats 1 and 7, in exemplary fashion, are five other flexibly designed, or adjustable, dewatering slats 2 through 6. Extending across the polygon train created by the dewatering slats 1 through 7 is the wire 10. Fig. 1 also includes the complete forming shoe comprising a box 14 which directly supports fixed slats 1 and 7, and which comprises a perforated wall 15 to support the adjustable slats 2 to 6. In this embodiment, each slat 2 to 6 is supported by a spring 8 which i~ adjustable (symbolically illustrated by an ' ~ ' ,., ' .
' ' " ' ~
arrow). Box 14 has a discharge opening 16 for water. In the normal manner, each wire 10, 11 forms an endless wire loop (not completely shown). The wires, and the fiber suspension 9 therebetween, are guided by wire rolls 12, 13 onto the forming shoe.
Fig. 1 through 4 differ in the adjustment of the dewatering slats, creating a different pressure distribution of the dewatering slats on the wire. Thus, Fig. 1 shows a uniform polygon, which also results in a uniform pressure distxibution. In Fig. 2, a steadily increasing dewatering pressure is created from left to right. Fig. 3 shows the opposite effect. There exists at first a very strong dewatering pressure, which steadily diminishes toward the end o~ the ~orming shoe.
An extreme case is depicted in Fig. 4, where the highest dewatering pressure is generated on the center dewatering slat 4.
Ths embodiment of the forming shoe shown in Fig. 5 includes a slat structure alternating between fixed and ~ -adjustable slats. -~
Fig. 6 once again shows a forming shoe such as illustrated in Figs. 1 through 4. However, in this embodiment there is arranged beneath the wire a collection device or chute 20, which in this embodiment also is adjustable in height. Arrows 30 and 31 indicate the direction of the wire water thrown off at the dewatering slat 5. Reference 30 shows a water direction created by a high wire speed, whereas the flatter curve 31 illustrates the course of the wire water at a low wire speed.
In Fig. 7 the springs are replaced with pneumatic bearings 8', in the form of tubular pressure cushions.
Each pressure cushion 8' is connected to a pressure line 17 via valve 18 to vary the contact pressure.
~; , .
.
' ~'' ': : ~`~' .' , ' . ' :
21~63~2 While this invention has been described as having a preferred design, the invention can be further modified within the spirit and SGOpe of this disclosure. This application is therefore intended to cover any variations, uses or adaptations of the invention using its general principles. Further, this application is intend~d to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall : -within the limits of the appended claims.
; , `'','' . " . : ' . ' , - : ', '~. . .,.,.` ' ~ ' ' , ' . , ' . , . ' ' ' ., ' : ' .
Claims (12)
1. A double wire former for producing a fiber web from a fiber suspension, comprising:
a first and second endless wire which together form a double wire zone;
at least two dewatering slats in the double wire zone, which slats contact one of the two endless wires such that the double wire zone includes a polygonal train wherein the wires are deflected at each of said slats;
one of the two dewatering slats being rigidly supported, and the other of the two dewatering slats being adjustably supported and arranged such that a contact pressure of said adjustably supported slat with said one wire is variable;
the two dewatering slats being spaced apart a distance such that a variation of the contact pressure of the adjustably supported slat results in a change of the deflection of the wires at the rigidly supported slat, whereby a change of the dewatering pressure created by the rigidly supported slat is effected.
a first and second endless wire which together form a double wire zone;
at least two dewatering slats in the double wire zone, which slats contact one of the two endless wires such that the double wire zone includes a polygonal train wherein the wires are deflected at each of said slats;
one of the two dewatering slats being rigidly supported, and the other of the two dewatering slats being adjustably supported and arranged such that a contact pressure of said adjustably supported slat with said one wire is variable;
the two dewatering slats being spaced apart a distance such that a variation of the contact pressure of the adjustably supported slat results in a change of the deflection of the wires at the rigidly supported slat, whereby a change of the dewatering pressure created by the rigidly supported slat is effected.
2. The double wire former of claim 1 including means for varying the contact pressure between the at least one adjustably supported dewatering slat and the first wire.
3. The double wire former of claim 1 comprising means for keeping the contact pressure of the at least one adjustably supported dewatering slat constant irrespective of a height position of the at least one adjustably supported dewatering slat.
4. The double wire former of claim 2 comprising means for keeping the contact pressure of the at least one adjustably supported dewatering slat constant irrespective of a height position of the at least one adjustably supported dewatering slat.
5. The double wire former of claim 1 further comprising a plurality of springs for forcing the at least one adjustably supported dewatering slat on the first wire.
6. The double wire former of claim 5 wherein the springs are adjustable.
7. The double wire former of claim 1 wherein the at least one adjustably supported dewatering slat comprises a pneumatic bearing.
8. The double wire former of claim 7 wherein the contact pressure is pneumatically generated and variable.
9. The double wire former of claim 6 further comprising means, dependent on the consistency of the fiber web, for adjusting the contact pressure via a control or regulating circuit.
10. The double wire former of claim 8 further comprising means, dependent on the consistency of the fiber web, for adjusting the contact pressure via a control or regulating circuit.
11. The double wire former of claim 1 further comprising a plurality of adjustment devices distributed across the width of the fiber web, whereby a location-specific regulation of the contact pressure is provided.
12. The double wire former of claim 1 wherein the adjustably supported slat is resiliently supported.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEG4230921.2 | 1992-09-16 | ||
| DE19924230921 DE4230921A1 (en) | 1992-09-16 | 1992-09-16 | Double fourdrinier papermaking machine - has fixed and pliable bar at water extraction zone to give adjustable pressure impact for improved paper quality |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2106392A1 true CA2106392A1 (en) | 1994-03-17 |
Family
ID=6468053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2106392 Abandoned CA2106392A1 (en) | 1992-09-16 | 1993-09-16 | Double wire former with flexible dewatering slats |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH06212591A (en) |
| CA (1) | CA2106392A1 (en) |
| DE (1) | DE4230921A1 (en) |
| FI (1) | FI934032A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102015224390A1 (en) * | 2015-12-07 | 2016-12-29 | Voith Patent Gmbh | Suction box inside a paper machine |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4026953C2 (en) * | 1990-01-26 | 1995-11-30 | Escher Wyss Gmbh | Dewatering device and method for dewatering on a twin wire former |
| DE9017714U1 (en) * | 1990-02-21 | 1991-10-17 | J.M. Voith Gmbh, 7920 Heidenheim, De | |
| DE4019884A1 (en) * | 1990-06-22 | 1992-01-09 | Voith Gmbh J M | PERFORMANCE SUPPLY SUPPORT FOR A SCREENING BELT |
-
1992
- 1992-09-16 DE DE19924230921 patent/DE4230921A1/en not_active Withdrawn
-
1993
- 1993-09-14 FI FI934032A patent/FI934032A/en not_active Application Discontinuation
- 1993-09-16 CA CA 2106392 patent/CA2106392A1/en not_active Abandoned
- 1993-09-16 JP JP23052193A patent/JPH06212591A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| FI934032A (en) | 1994-03-17 |
| JPH06212591A (en) | 1994-08-02 |
| DE4230921A1 (en) | 1994-03-17 |
| FI934032A0 (en) | 1993-09-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |