EP0475976A1 - Pressurized forming board. - Google Patents
Pressurized forming board.Info
- Publication number
- EP0475976A1 EP0475976A1 EP19900908446 EP90908446A EP0475976A1 EP 0475976 A1 EP0475976 A1 EP 0475976A1 EP 19900908446 EP19900908446 EP 19900908446 EP 90908446 A EP90908446 A EP 90908446A EP 0475976 A1 EP0475976 A1 EP 0475976A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- forming
- drainage
- forming fabric
- stock
- pressure
- 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.)
- Granted
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
- D21F1/483—Drainage foils and bars
-
- 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
- D21F1/009—Fibre-rearranging devices
-
- 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
- D21F9/02—Complete machines for making continuous webs of paper of the Fourdrinier type
Definitions
- This invention is concerned with the initial formation of paper on machines of the type wherein an aqueous slurry known as the stock is deposited onto a continuous moving forming fabric.
- the stock which contains both fibers and other substances in an amount of from about 0.1% to about 1.5% by weight is fed from a head box slice onto a moving forming fabric. Water is progressively drained from the stock through the forming fabric as it passes over various drainage elements until at the end of the forming section the stock contains some 2% to 4% by weight of solid material. At that point, the distribution and orientation of the fibers and other solids in the still very wet stock is largely determined, and will not change very much in the later paper making steps. Thus at the end of the forming section the formation of the paper is largely completed.
- a conventional paper making machine forming section includes a forming fabric which is supported at the head box slice end by a breast roll, which is followed in sequence by a forming board, and thereafter by a sequence of drainage devices which complete the forming section.
- the nature and placement of these drainage devices varies considerably, and is determined at least in part by whether either a conventional open fabric forming •section or a twin wire or gap former is being used.
- the concepts of this invention are equally applicable to both a twin wire machine, and to a conventional open-surface forming section, that is to improve stock formation in the region of the forming section immediately adjacent the head box slice.
- Curtailing the drainage rate through a conventional design forming board would appear to be simple: all that is needed is to decrease the available drainage area, by widening the support surfaces, and/or moving them closer together. Experiment shows that this is not so and the drainage rate is not significantly reduced. Further, the paper web is marked severely with streaks, of uneven fibre weight across the width of the paper. In other words, such changes can cause significant deterioration in paper quality.
- this invention provides in a paper making machine having a forming section including at least a continuous travelling forming fabric which passes over a breast roll adjacent a head box slice through which aqueous stock is deposited onto the forming fabric, an apparatus for improving stock formation comprising:
- air supply means including a source of positive air pressure; and air pressure control means, such that a positive air pressure sufficient to hinder water drainage from the stock through the foraminous forming board surface but insufficient to interfere with paper formation on the forming fabric on the forming board surface, is maintained in the drainage box;
- the forming board surface provides a pressure tight seal between th. forming fabric and the drainage box;
- the foraminous forming board surface provides a path through which the forming fabric moves which induces a controlled level of uniformly spaced periodic harmonic agitation in the stock;
- the drainage box includes at least one compartment extending across the width of the forming fabric, which has separate air pressure control means and drainage means.
- the positive pressure will generally decrease from a high value adjacent the head box slice to a value approaching ambient atmospheric at the end of the forming board.
- the air supply means provides a positive pressure above ambient atmospheric of from about 1 cm water gauge to about 25 cms water gauge.
- the forming board surface preferably comprises a plurality of thin elongate blades extending across the full width of the forming fabric, so placed as to contribute toward controlled agitation of the stock on the forming fabric. More preferably, at least some of the thin elongate blades are provided with a top surface contour which will induce controlled agitation in the stock on the forming fabric.
- this invention provides a method for improving stock formation in a paper making machine having a forming section including at least a continuous travelling forming fabric which passes over a breast roll adjacent a head box slice through which aqueous stock is deposited onto the forming fabric, comprising: (i) discharging onto the moving forming fabric an aqueous stock; ( i) causing the forming fabric to move over a dewatering device comprising a pressurized drainage box including at least one chamber to which a controlled level of pressure is applied which is sufficient to hinder drainage but insufficient to interfere with paper formation on the forming fabric, which includes a foraminous top support surface for the forming fabric, and which provides a pressure tight seal between the forming fabric and the drainage box; and (iii) inducing a desired level of uniformly spaced periodic harmonic agitation in the stock on the forming fabric on the forming board.
- the air pressure is controlled to be from about 1 cm water gauge (above ambient atmospheric) to about 25 cms water gauge.
- the desired level of agitation is caused and controlled within the stock by controlling the spacing of the support-surfaces comprising the forming board. More preferably, the desired level of agitation is caused within the stock by a support surface with a top surface contour which induces controlled agitation within the stock on the forming fabric.
- the drainage box is either a single box divided into separate compartments by pressure tight transverse walls, or a plurality of contiguous separate boxes, to each of which a different level of pressure can be applied.
- Figure 1 shows diagrammatically the initial part of a paper making machine
- Figure 2 shows schematically one forming board of this invention
- Figure 3 shows several possible support surfaces of the forming board of Figure 2.
- Figure 4 shows schematically an alternative forming board of this invention.
- Figure 1 the initial part of a paper making machine is shown, incorporating a forming fabric 1, which moves in the direction of the arrows shown at 1A and IB.
- the forming fabric moves over a breast roll 2, and various tensioning and idling rollers 3.
- the stock is deposited onto the forming fabric 1 from the head box shown diagrammatically at 4, through a slice opening 5, which extends transversely across the forming fabric 1.
- Adjacent the breast roll 2 and the head box slice 5 is a forming board followed by the first of the many drainage units which comprise the forming section, which in this case is shown as a foil unit 7, based on that originally described by Wrist in US 2,928,465.
- the forming board unit 6 is provided with a plurality of support surfaces shown generally at 12, 13 and 14, of which that nearest the headbox slice, 12, is generally wider, than the others. Each of these surfaces is mounted on a T-bar, as at 10. As shown, the drainage box 6 is merely left open at its bottom to provide gravity drainage.
- FIG 2 is shown one embodiment of the forming board of this invention.
- the unit is now a closed box 20 with a pressurized air supply pipe 28, and the drain pipe 32 has an integral pressure leg, to contain the applied pressure.
- the forming board support surfaces again comprise a T-bar 10 onto which is mounted the elongate blade 17, which extends across the width of the forming fabric.
- sealing pieces are inserted between the blade units to seal the forming fabric effectively to the top surface of the drainage box.
- the shape of the top surface, and also their lateral spacing, will be discussed in more detail below.
- the first blade 18 has to counter the impact of the jet of stock as it exits the slice 5 onto the forming fabric 1.
- this first blade is usually much wider than the others, often being twice the width of the later ones. It has now been found that this need not be so, and a blade substantially the same width as the others can often be used.
- This first blade will also generally have a flat top surface. As is the case with all of the blades, it is mounted onto a conventional T-bar arrangement.
- the placement and shape of the remaining blades 19 is important. It is now known that almost any surface used to support a forming fabric has an effect on the behaviour of the stock on the fabric. The characteristics of the surface can be chosen to produce agitation in the stock which can range from sufficient effectively to lift the stock bodily off the fabric ranging downwardly through visible macroscopic agitation to microscopic agitation which can only be observed by using careful photography and strobe light illumination (i.e., with a simple flat surfaced blade such as the first blade 18). Further, it is also now known that the placement of these blades along the forming fabric is important, particularly for static drainage devices. Although the hydraulic phenomena causing the agitation are not fully understood, it is nevertheless known that they exhibit harmonic characteristics.
- the blades 19 can be placed so that the microscopic agitation which they induce is harmonically spaced apart along the length of the forming board. It then follows that by controlling the amount of agitation imparted by any one blade, the overall level of stock agitation can be controlled.
- the amount of agitation imparted by the blades is largely determined by the shape of the support surface.
- a simple flat blade generates some agitation in the microagitation range, which can be enough for some purposes.
- the blade used to provide microagitation in the stock will cause low or zero drainage.
- Suitable blade types are described by Johnson in US 3,874,998 and by Saad in US 4,420,370. These blades can be constructed using the now standard T-bar support concepts. This invention does not preclude the use of devices which cause some drainage as well as providing the desired amount of agitation.
- Figures 3A and 3B show blades which agitate without draining, as described by Johnson, in U.S. 3,874,998. In each case, the blade 37 or 38 mounts on a T-bar 10.
- the blade 37 has a central depression 39, in its top surface, so that a cross-machine gap of a flat triangular shape, having a depth x, is created below the plane of the forming fabric.
- this depression rather than being triangular, can be a shallow concave shape.
- water enters this depression from the stock on the forming fabric 1, and re-enters the stock, as indicated by the arrows 40 in Figure 3A. Careful choice of the distances x, y, , y ? and z then controls the amount of agitation imparted to the stock.
- the amount of agitation that is needed at this early stage of paper formation is small, in the microagitation range mentioned earlier, and therefore it is possible that not all of the blades will have a depression at all, since, as is noted above, a flat-blade surface also causes some agitation.
- Typical dimensions for a blade such as those shown in Figure 3A or Figure 3B when used to cause microagitation are:
- the preferred value for the depression width z is that it is about half the total width of the blade. This then leaves adequate leading and trailing flat portions (y, and ybal) to get a water seal with the fabric onto the blade in these areas. As the depth also affects the amount of agitation, a wider blade will not necessarily require a deeper depression. In many cases it is found that if the blade is widened then the depth, x, should not be changed, although the width z will increase, to maintain it at about half the total blade width. In selecting a blade for a given circumstance, some care is needed. The narrowest blade that gives adequate support should be used, which will mean that a forming board according to this invention usually will use more support blades than a conventional board.
- all of the blades used can be of the same width.
- the shallowest depression should be used that is needed to cause the desired amount of agitation. If the blade is- made too wide, and the depression is made too deep, then the level of agitation can go far beyond the microagitation needed in this area of the forming fabric to a level where the forming fabric with the stock on it lifts clear of the blades. This is not conducive to the making of good paper. Although it is simpler to use a blade with a single depression, it is realized that in certain circumstances a wider blade with more than one depression might be desirable. If such a blade is used, then the central flat portion between the depressions should be about as wide as the leading and trailing flat surfaces.
- FIG 4 a preferred embodiment is shown.
- the drainage box shown generally at 6 is divided into a series of pressure tight smaller compartments 20, 21, 22, and 23, by transverse walls 24, 25 and 26. Four are shown, but this number is not crucial. Similarly, a series of separate boxes could also be used, with their side walls contiguous.
- Each of the compartments 20 through 23 extends across the full width of the forming fabric. In each case, a blade, as at 27, is placed over each of the transverse walls.
- Each of the compartments is provided with a pressurized air supply pipe 28, 29, 30 and 31, which incorporates a pressure control means (not shown), and also with a drainage leg 32, 33, 34 and 35, which includes suitable means to contain pressure in the compartment while also allowing free drainage. This arrangement permits a different marginal pressure above ambient to be applied to each of boxes 20, 21, 22 and 23.
- the applied pressure will decrease in a stepwise fashion from box 20, adjacent the headbox slice, to box 23 to which a low pressure, or even none at all, is applied. It is also contemplated that situations might arise wherein such a progression is not desirable, and for example the highest pressure might be found desirable in box 21.
Landscapes
- Paper (AREA)
- Press Drives And Press Lines (AREA)
Abstract
La présente invention décrit un banc d'égouttage pour machine à fabriquer du papier, dans lequel on raccourcit et on règle le débit de drainage de la pâte à papier à travers la toile d'égouttage, en appliquant du côté machine de la toile d'égouttage une pression d'air positive basse supérieure à la pression atmosphérique ambiante. On produit en outre un niveau régulé d'agitation dans la pâte à papier sur le banc d'égouttage, afin d'assurer une meilleure formation initiale du papier.The present invention describes a drip bench for a paper-making machine, in which the drainage rate of the paper pulp is shortened and regulated through the drip cloth, by applying on the machine side of the dough cloth. drip low positive air pressure above ambient atmospheric pressure. In addition, a controlled level of agitation is produced in the paper pulp on the drip tray, in order to ensure better initial formation of the paper.
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT90908446T ATE103022T1 (en) | 1989-06-08 | 1990-06-07 | PRESSURE FORM BAR. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US36292589A | 1989-06-08 | 1989-06-08 | |
US362925 | 1989-06-08 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0475976A1 true EP0475976A1 (en) | 1992-03-25 |
EP0475976B1 EP0475976B1 (en) | 1994-03-16 |
Family
ID=23428078
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900908446 Expired - Lifetime EP0475976B1 (en) | 1989-06-08 | 1990-06-07 | Pressurized forming board |
Country Status (7)
Country | Link |
---|---|
EP (1) | EP0475976B1 (en) |
JP (1) | JPH07113194B2 (en) |
AU (1) | AU633100B2 (en) |
CA (1) | CA2057880C (en) |
DE (1) | DE69007479T2 (en) |
FI (1) | FI101819B1 (en) |
WO (1) | WO1990015186A1 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FI121820B (en) | 2006-05-15 | 2011-04-29 | Ramtec Oy | Screening bucket and screening transmission module |
CN106320049A (en) * | 2015-06-29 | 2017-01-11 | 浙江永泰纸业集团股份有限公司 | Control method for headbox of paper or paperboard |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2928466A (en) * | 1955-12-27 | 1960-03-15 | Ontario Paper Co Ltd | Means for improving drainage on paper machines |
US3052296A (en) * | 1958-11-04 | 1962-09-04 | Beloit Iron Works | Uniflow fourdrinier |
US3066068A (en) * | 1960-09-08 | 1962-11-27 | West Virginia Pulp & Paper Co | Means for and method of improving drainage on fourdrinier machines |
US3149026A (en) * | 1961-09-26 | 1964-09-15 | Beloit Iron Works | Air assisted formation method and apparatus |
GB1447486A (en) * | 1972-07-26 | 1976-08-25 | Jwi Ltd | Blades for papermaking machines |
FI49854C (en) * | 1973-12-05 | 1975-10-10 | Valmet Oy | Procedure for streamlining the function of the wire section in a paper machine |
US4306934A (en) * | 1978-11-27 | 1981-12-22 | Seppanen Erkki O | Method and apparatus for forming paper |
-
1990
- 1990-06-07 AU AU56748/90A patent/AU633100B2/en not_active Ceased
- 1990-06-07 EP EP19900908446 patent/EP0475976B1/en not_active Expired - Lifetime
- 1990-06-07 DE DE69007479T patent/DE69007479T2/en not_active Expired - Fee Related
- 1990-06-07 WO PCT/CA1990/000184 patent/WO1990015186A1/en active IP Right Grant
- 1990-06-07 CA CA 2057880 patent/CA2057880C/en not_active Expired - Fee Related
- 1990-06-07 JP JP2507884A patent/JPH07113194B2/en not_active Expired - Fee Related
-
1991
- 1991-12-05 FI FI915762A patent/FI101819B1/en active
Non-Patent Citations (1)
Title |
---|
See references of WO9015186A1 * |
Also Published As
Publication number | Publication date |
---|---|
FI101819B (en) | 1998-08-31 |
FI915762A0 (en) | 1991-12-05 |
DE69007479D1 (en) | 1994-04-21 |
DE69007479T2 (en) | 1994-06-23 |
FI101819B1 (en) | 1998-08-31 |
AU633100B2 (en) | 1993-01-21 |
JPH07113194B2 (en) | 1995-12-06 |
JPH04504148A (en) | 1992-07-23 |
CA2057880C (en) | 1996-05-07 |
EP0475976B1 (en) | 1994-03-16 |
CA2057880A1 (en) | 1990-12-09 |
AU5674890A (en) | 1991-01-07 |
WO1990015186A1 (en) | 1990-12-13 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US5830322A (en) | Velocity induced drainage method and unit | |
US5011577A (en) | Pressure control forming section | |
US3922190A (en) | Vacuum drainage device having a plurality of stepped blades | |
US3823062A (en) | Twin-wire papermaking employing stabilized stock flow and water filled seal(drainage)boxes | |
US5089090A (en) | Continuous controlled drainage | |
US5080760A (en) | Pressurized forming board | |
GB1559277A (en) | Stock formation in a paper making process | |
US3357880A (en) | Apparatus for making fibrous webs | |
US4565603A (en) | Method and device for reducing disturbances during paper web formation | |
CA2057880C (en) | Pressurized forming board | |
US3764465A (en) | Suction box and baffle for fourdrinier type of papermaking machine | |
US3052296A (en) | Uniflow fourdrinier | |
US3149026A (en) | Air assisted formation method and apparatus | |
US3832283A (en) | Method for producing nonwoven fabrics | |
KR100324697B1 (en) | Under felt inclined flat former to produce multilayer or monolayer sheet of paper | |
EP0079316B1 (en) | Web forming method and device | |
US3472733A (en) | Paper-forming suction cylinder roll with arcuate stock delivery nozzle and porous belt in wrapped engagement therewith | |
US3132990A (en) | Paper making apparatus | |
JP2581615B2 (en) | Paper forming method and apparatus | |
US3122470A (en) | Method of supplying stock and stock inlet for a papermaking machine | |
EP0241439A2 (en) | Dewatering apparatus | |
WO1998038380A1 (en) | Rib for a water draining device in a paper machine | |
US4784725A (en) | Vat paper machine |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19911129 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE DK ES FR GB IT LI LU NL SE |
|
17Q | First examination report despatched |
Effective date: 19920813 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AT BE CH DE DK ES FR GB IT LI LU NL SE |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Effective date: 19940316 Ref country code: LI Effective date: 19940316 Ref country code: ES Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY Effective date: 19940316 Ref country code: DK Effective date: 19940316 Ref country code: CH Effective date: 19940316 Ref country code: BE Effective date: 19940316 |
|
REF | Corresponds to: |
Ref document number: 103022 Country of ref document: AT Date of ref document: 19940415 Kind code of ref document: T |
|
REF | Corresponds to: |
Ref document number: 69007479 Country of ref document: DE Date of ref document: 19940421 |
|
ITF | It: translation for a ep patent filed |
Owner name: NOTARBARTOLO & GERVASI S.R.L. |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LU Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19940630 |
|
REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
ET | Fr: translation filed | ||
NLV1 | Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
EAL | Se: european patent in force in sweden |
Ref document number: 90908446.9 |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: SE Payment date: 20020513 Year of fee payment: 13 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20020606 Year of fee payment: 13 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20020620 Year of fee payment: 13 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: AT Payment date: 20020624 Year of fee payment: 13 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20020626 Year of fee payment: 13 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030607 Ref country code: AT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030607 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20030608 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040101 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20030607 |
|
EUG | Se: european patent has lapsed | ||
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040227 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: IT Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20050607 |