CA2036446A1 - Forming a fiber web using a widened jet of suspension - Google Patents
Forming a fiber web using a widened jet of suspensionInfo
- Publication number
- CA2036446A1 CA2036446A1 CA 2036446 CA2036446A CA2036446A1 CA 2036446 A1 CA2036446 A1 CA 2036446A1 CA 2036446 CA2036446 CA 2036446 CA 2036446 A CA2036446 A CA 2036446A CA 2036446 A1 CA2036446 A1 CA 2036446A1
- Authority
- CA
- Canada
- Prior art keywords
- nozzle
- jet
- outlet
- suspension
- slot
- 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
- D21F1/02—Head boxes of Fourdrinier machines
-
- 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
- D21F1/02—Head boxes of Fourdrinier machines
- D21F1/028—Details of the nozzle section
-
- 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
Landscapes
- Paper (AREA)
Abstract
FORMING A FIBER WEB USING A WIDENED JET OF SUSPENSION
ABSTRACT OF THE DI DISCLOSURE
A method and apparatus for minimizing damage from impingement of a jet of fiber suspension on a wire, roller surface or the like defining an inlet slot to a forming section which is opposite the headbox outlet nozzle by increasing the angle of spread and therefore the height of the jet where it impinges upon the surfaces. The opening angle of the jet is at least 3°, preferably between 15° and 60°. The jet widens, that is becomes taller, upon leaving the outlet nozzle from the headbox so as to impinge upon one or both of the moving surfaces defining the inlet slot, which surfaces may be defined by one wire or two wires or a wire and a roll. The outlet nozzle from the headbox may have a flow body in it which divides the flow before its exit from the outlet nozzle. A flow constriction at the outlet region of the nozzle, past the flow body if present, widens the jet as it leaves the nozzle. There may be inwardly directed ledges on the lips defining the nozzle near the nozzle outlet.
There may be air inlets in one lip and a hump inside the nozzle on the other lip opposite the air inlets.
ABSTRACT OF THE DI DISCLOSURE
A method and apparatus for minimizing damage from impingement of a jet of fiber suspension on a wire, roller surface or the like defining an inlet slot to a forming section which is opposite the headbox outlet nozzle by increasing the angle of spread and therefore the height of the jet where it impinges upon the surfaces. The opening angle of the jet is at least 3°, preferably between 15° and 60°. The jet widens, that is becomes taller, upon leaving the outlet nozzle from the headbox so as to impinge upon one or both of the moving surfaces defining the inlet slot, which surfaces may be defined by one wire or two wires or a wire and a roll. The outlet nozzle from the headbox may have a flow body in it which divides the flow before its exit from the outlet nozzle. A flow constriction at the outlet region of the nozzle, past the flow body if present, widens the jet as it leaves the nozzle. There may be inwardly directed ledges on the lips defining the nozzle near the nozzle outlet.
There may be air inlets in one lip and a hump inside the nozzle on the other lip opposite the air inlets.
Description
FORMING A FIBER WEB USING A WIDENED JET OF SUSPENSION
The present invention relates to a method and apparatus for forming a fiber web, in particular a paper web, in which a jet of fiber suspension from the outlet nozzle of a headbox impinges against the surfaces which define the inlet slot to the forming section of the paper making machine. According to the ; invention, the jet has an enlarged opening angle so as to not damage the surfaces impinged upon. The shape and orientation of the inlet slot of the forming section and the shape of the outlet nozzle and its spacing from the inlet slot are at the heart of the `~ invention.
Prior methods and apparatus for forming a fiber we~ include Federal Republic of 6~rmany specificat~on 2 10~ 613. It de~cribes a ~ire 8ection ~ or forming section of a paper making machine having a nozzle-like headbox, a forming cylinder which serves to ,~ 20 form the web and has a perforated shell, ~nd two ~ endless wire screens, called wires, which wrap around ; the forming cylinder. In the lower part of the forming cylinder, the wires are supported to define an inlet '~ slot which is open towards the headbox. $n the upperpart of the forming cylinder, the wires run off the ''' ;, ., .
"
,,, j.
203~4~6 shell of the forming cylinder. The wires are separated from each other after the run-off point. One wire carries the formed web with it. The outer wire of the wrapping is the web conductlng wire. The point at which the two wires run off the shell of the forming cylinder is located in the upper ascending quadrant of the forming cylinder.
Other examples of such methods and apparatus are disclosed in T~PI PROCEEDINGS, pages 553 et seq., where a report is given on the engineers' convention of the TAPPI ASSOCIATION in 1987.
U.S. Patent 3,009,517 and U.S. Patent 3,092,538 describe headboxes for paper making machines in further detail. U.S. ~atent 2,832,268 further details a nozzle for a headbox.
In particular, qood formation of the fiber sheet or paper sheet is reguired from such methods and apparatus. The sheet formed, i.e. the web of fiber, should be as uniform as possible in every respect. The basis weight should remain as constant as possible both over the width of the machine and ~n the direction of travel of the web. The so called two dimensional stability should be as great as possible. Bundles of fiber or clouds, which can be seen in transmitted light, should, as far ~s possible, be absent.
The jet emerging from the nozzle of the headbox has, at the place of its emergence, a certain thic~ness perpendicular to the direction of jet travel as well as perpendicular to the length of the outlet slot of the nozzle. It has always been attempted to retain this thickness of the jet constant. Widening of the jet, that is making it taller or larger across the 20364~6 height of the outlet nozzle, on the path of the jet from the outlet of the nozzle up to impingement on the correspondin~ impingement surface, and, therefore, in general, onto th~ wire of the paper making machine, was undesired. Specific disadvantages were sQan, especially with regard to the constancy of the basis weight. See, for example, U.S. Patent 2,832,268, columns 4, 5 and 6. As remedies, there are described particular shapes of the outlet nozzle or certain inserts in this nozzle in order to avoid widening of the jet after its emergence from the nozzle and to nevertheless retain a desired microturbulence in the pulp suspension.
U.S. Patent 3,092,538 also concerns producing a certain microturbulence in the headbox and retaininq this microturbulence after emergence of the jet from the nozzle. Here also, the fiber material jet retains its thickness after its emergence from the nozzle.
U.S. Patent 3,009,517 describes a headbox with an outlet nozzle which has a venturi constriction.
This constriction is again intended to serve for forming microturbulence.
These demands on the quality of the formation of the sheet have been the sub~ect of discuss~on up to the present time. The efforts have not always led to complete satisfaction of the papermaker. In particular, the uniformity of the formation of the sheet has not always been satisfactory up to now.
2036~
It is an object of the present invention to provide a novel method and apparatus for forming a fiber web. It is another object of the present invention to provide a method and apparatus for forming a fiber web which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.
Accordingly, in one of its aspects, the present invention provides a method of forming a fiber web wherein a fiber sùspension is fed through an outlet nozzle of a headbox in the form of a jet of the fiber suspension and wherein the jet has the width of the fiber web manufacturing machine., the method comprising direct~ng the fiber ~uspension from the outlet nozzle to ~mpn~e upon ~t least one ~oving surface, which surface ~s moving toward the narrow end of a wedge shaped ~lot that is formed in part by the at least one moving surface, ~n order to deposit the fiber suspension for forming a f~ber web there as the jet emerges from the nozzle, w~dening the ~et directly upon its emergence from the nozzle, as ~een ~n s~ae V~QW and in the direc~ion of flow, for forming an opening angle of the ~et of at lea~t 3-.
In another of its aspects, the present invention provides an apparatus for applying a jet of fiber suspension to the slot of a fiber web producing machine, the apparatus comprising:
a headbo~, including an outlet nozzle ~ through which the ~et of fiber suspension is sprayed;
30 a pair of cooperating moving ~urfaces defining a wedqe ~hape~ ~nlet ~lot which i~ wider toward the nozzle and which narrows away from the nozzle, and the nozzle being directea to spray toward the slot and onto ~t le-st one of the moving surfaces, i .
,., 203~
- 4a `-the two surfaces defining the slot being ~o~ble toward the narrow end of the 810t and means for ~o~ing the two surfaces toward the narrow end of the ~lot, the surfaces on which the jet of suspension impinges having a machine width the outlet nozzle from the hsadbox having generally the machine width, the nozzle being defined by an upper lip abo~e ~ nozzle opening and a lower lip beneath the nozzle openin~, the nozzle and its lips being so shaped and ~rranged and the noz~le being 50 spaced from the surf~ces of the ~edge sh~ped slot that the jet of fiber suspension, immediately upon itB
emergence from the nozzle, is ~idened ~nd forms an opening anqle of at lcast 3.
In ~et another of its aspects, the present invention provides a headbox comprising:
nn outlet nozzle through Yhich a jet of fiber suspension i8 sprayed; the nozzle being d~fined by an upper lip ~bovc a nozzle opening and a lower lip 2C bencath the nozzle opening, the nozzle and it~ lips being 80 shaped and ~rr~nged that She jet of fiber suspension, immediately upon its ~mergence from the noz~le, is widened and forms an opening angle`of at least 3.
A feature of the present invention relates to wi~ng the heiqht of the jet, that '~s the th~ekness of the ~et with respect to the thickness of the nozzle outlet 80 that there is less concentr~ted impingement of the fiber suspension on at least one of or both of the surfaces forming the wedge shaped inlet slot of the forming section of the paper making machine. Those surfaces may comprise at least one ~ire ~creen or ~ire, or two of the ~ire ~creens or wires ~hich converge to 2036~S
- 4b -define the inlet slot or one wire ~creen or ~ire and one forming roller which cooperate to define the slot.
The slot is so shaped and placed and the outlet nozzles from the headbox are ~o ~haped and placed that the jet widens sufficiently for accompl~shin~ the objecti~e of the invention and ~o that the jet ~prays upon at least one of the two surfaces comprising a wire ~creen or a roller or on both to the same or unequal extcnts. In particular, the jet forms an opening angle as it leaves lo the outlet nozzle of at least ~-, preferably in the range of 15 to 60, but more prefera~ly 30- to 60.
~ he inventors hsve recognized that, contrary to general opinion and usual practice, a widening of the jet of suspension directly upon its emergence from the headbox nozzle is of great ad~antage. ~hus, in accordance with the in~ention, the jet should impinge upon a much larger surface than has previously been the 203~S
case. The uniformity of the fiber web formed is considerably increased, Investigations which have been subsequently carried out have led to the following discovery. Upon the conventional formation of the jet, in which the jet retains its thickness after emergence from the headbox nozzle, the pressure per unit of area which the jet exerts on the impingement surface is relatively larqe. These forces have led to deformations of the impingement surface and, therefore, in ~eneral of the paper making machine ~ire or, in the case of twin-wire paper making machines, of both the wires. These deformations are particularly disadvantageous if the pressure of the jet is not constant over the entire width of the machine but is instead irregular. ~owever, this cannot be avoided in actual practice. Measurements have shown that it is subject to certain varia~ons both width-wise and over time.
It follows from this, in its turn, that bulges or ~impact holes~ are produced in the impingement surface and particularly in the wire. They lead to irregularities ~n the fiber web thereby formed.
With the use of a spray jet in accordance with the invention, the jet pressure per unit of area is naturally correspondingly less. The impact holes either occur only to a reduced extent or no longer occur at all.
The outlet nozzle from the headbox is usually defined between two lips that extend toward the slot. The lips are close together and extend substantially the width of the machine, which is substantially the width of the two surfaces that form 2036~
the inlet slot, that is the two wires or the wire and the cooperating inlet slot ~urf~ce. The outlet nozzle is configured to ~iden the jet of suspension in a selected one of n number of ~ays. One ~y is providing a led~e extending from the outlet cnd region of one lip toward the outlet end re~ion of th~ other lip, and/or including a flow body within the outlet nozzle ~nd which terminates near the outlet region for initially dividing the flow through ~he nozzle ~nd then permitting it to recombine ~ust before exiting the outlet nozzle. Another way ~s to provide ledges on the internal facing ~urfaces of the lips toward tbeir outlet region, possibly cooperating with the flow body within ~he nozzl~, and the ledges ~re locnt~d just after the terminal en~ of the flow body. In ~n alternate design, there are air ~nlets through ~t least one o~ the lip~, ex~ending across th~ machine width and located toward the outlet r~gion of the lip.
Preferably, there ~8 a cooperating hump on ~he interior o~ the other l~p with the tall part of the hump being generally opposite the ~ir ~nlet~ on the other lip.
Embodiments of the lnvention will be described with reference to the attached ~rawings whereln like numerals designate like parts, in which:
Fig. 1 schematically shows a headbos of ~
paper making machine with a corresponding wire sect~on.
Figs. 2 to 5 show var~ous configurations of portions of wire sections.
Figs. 6 to 9 show outlet nozzles of headboxes in cross-sections perpendicular to the plane of the jet and in the direct~on of flow.
2Q36~
The apparatus shown in Figure 1 includes a headbox 1 for a paper making machine with an outlet nozzle 2 for spraying a jet of fibrous suspension. Two endless forming section wire screens, ~ires 3, 4, together form a wedge shaped, diminishing height, inlet or feed slot 5 into which the je~ of fiber or pulp suspension ~s shot out of the nozzle 2. The wires travel around their illustrated guide and support rollers at the same speed and in a direction bac~ from the feed slot 5 away from the nozzle 2. The jet forms a fiber web 6 between the two wires 3 and ~ directly downstream of the wedye ~haped slot 5 along the paths of the wires. The web travels between the two wires 3 and 4 around a forming cylinder 7 and then remains adhering to the wire 3, being finally removed from the wire 3 further along its path. This i~ ~ well ~nown operation.
With the configurations of web or sh~et forming devices in Fi~s. 2 to 5, wedge shaped ~lot ~s in each case formed by the t~o wires 3 and ~. In the three different devices in Figs. 2 to 4, a forminq cylinder ~ is provided which is initially wrapped around ~y one of the two wires, n~mcly the wire ~
directly after the uedge shapea ~lot 5. Then at a certain aistance ~way fro~ initial contact by the first wirc ~, the cylinaer 7 is also ~rapped by the other wire 3.
In the device in Fig. 5, instead of a rotating forming cylinder, there is a ~tationary water-removal surface which is formed of a stationary wire table 17. The two wires 3 and ~ first wrap around ., .
r .~.
,, 2036~S
rolls 8, 9 respectively, which define the entrance region of the wedge shaped slot 5, and the curve of the table 17 establishes where the wires come together closing the end of the wedge shaped slot.
In the four devices of Figs. 2-5, the jet is shown diagrammatically as it emerges from the nozzle 2.
In this connection, the outer limiting spray lines of the jet are indic~ted as dashed l~nes, while the axis of the jet is indicated ~s a dash-dot line. The opening angle of the jet is a minimum of 3, may be in the range of 15 to 60, and preferably is in the range of 30 ~o 60~.
In the device of Fig. 2, the nozzle 2 is oriented so that the axis of the jet extends rather precisely through the end point of the wedge shaped slot 5 at the roll 7.
In the device of Figure 3, the nozzle 2 is inclined so that the axis of the jet strikes predominantly ~gainst the wire 3 and thus is merely tangent to the wire ~.
In the device of Fig. ~, the jet strikes exclusively against the wire 3 while it is at a certain distance from the end point of the wedge shaped slot 5.
In the device of Figure 5, the nozzle 2 is directed so that the jet strikes symmetrically a~ainst the two wires 3 and ~.
As can b~ noted, in all four cases of Figs. 2-5, the area of the wires struc~ by the jet upon its impingement is substantially greater than the area of the jet at the point of its emergence from the nozzle 2. This is due to the opening angle of the jet and the angle of the surfaces being impinged upon with respect to the axis of the jet.
20364~6 g The outlet nozzle is so shaped and configured, for example by one of the technigues described below, and it is so shaped and so spaced by a distance from the two surfaces 3, 4 defining the slot 5 that the combined area of the ~urfaces that is struck by the jet upon the impingement of the jet of flow suspension on those surfaces is equal to the product n x d x a, in which d is the thickness of the jet, a is the width of the jet, that is the machine width, and n is greater than d. Specifically, n may be equal to at least twice d. This widening of the jet sufficiently minimizes the damage to the surfaces on which the jet is being impinged.
The wedge shaped slot 5 may assume angles of different size. In Fig. 2, this angle is equal to about 60 if the wire 4 were extended beyond the place of contact with the forming cylinder 7 so that it would intersect the plane of the wire 3. In the device of Fig. 5, the wedge angle is only about 15. In the devices of Fiqs. 3 and 4, the wedge angle is between 15 and 60. All of these angles may be advantageous depending on the specific use and the nature of the paper to be produced.
The nozzles shown in Figs. 6 to 9 in each case include an upper lip lO and a lower lip ll of thQ
nozzle which extend across the machine along the machine width.
The nozzle of Figure 6 is provided in it~
vertical central region with a flow bvdy 12, which extends laterally over the entire width of the machine and which extends forward and terminates shortly inward of tbe outlet side end of the nozzle 2, so that the two 2036~6 individual streams of suspension which flow around the flow body 12 can combine aqain just before the nozzle outlet. The outlet end of the nozzle 2 is formed of two ledges 13, 14 attached on the lips 10 and 11, respectively, which together form ~ slot. The opposed surfaces of the ledges widen continuously in the direction of suspension discharge.
The nozzle shown in Fig. 7 also includes a flow body 12 between its lips 10 and 11. The flow body 12 is also passed around by two individual streams of suspension. At the point following the flow body where the two individual streams combine to form a single stream, there are two transverse, inwardly projecting ledges 1~, 16 on the lips 10, 11 respectively, which constrict the jet of pulp. The ledges 15, 16 are a short distance bac~ from the nozzle outlet.
The nozzle of Fig. 8 has an upper lip 10 which has one or more air inlets 20 preferably arranged in a row over the machine width. The upper surface of the lower lip 11 of the nozzle has a hump whose high point is located approximately opposite the point of the air inlets 20 so that suspension flow is constricted where the extra air enters.
The nozzle of Figure 9 has a lower lip 11 which is pushed forward in the direction of su~pension flow, as compared with the upper lip 10. The upper lip has a depending impact ledge 21, which effects a sudden constriction of the flow path. The lower lip 11 also has an impact ledge 22 which is forward in the suspension path of the ledge 21, and which extends upward.
~036~
Although the present invention has been described in connection with a plur~lity of preferred embodiments thereof, many other vari~tions and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by th~ specific disclosure herein, but only by the appended claims.
The present invention relates to a method and apparatus for forming a fiber web, in particular a paper web, in which a jet of fiber suspension from the outlet nozzle of a headbox impinges against the surfaces which define the inlet slot to the forming section of the paper making machine. According to the ; invention, the jet has an enlarged opening angle so as to not damage the surfaces impinged upon. The shape and orientation of the inlet slot of the forming section and the shape of the outlet nozzle and its spacing from the inlet slot are at the heart of the `~ invention.
Prior methods and apparatus for forming a fiber we~ include Federal Republic of 6~rmany specificat~on 2 10~ 613. It de~cribes a ~ire 8ection ~ or forming section of a paper making machine having a nozzle-like headbox, a forming cylinder which serves to ,~ 20 form the web and has a perforated shell, ~nd two ~ endless wire screens, called wires, which wrap around ; the forming cylinder. In the lower part of the forming cylinder, the wires are supported to define an inlet '~ slot which is open towards the headbox. $n the upperpart of the forming cylinder, the wires run off the ''' ;, ., .
"
,,, j.
203~4~6 shell of the forming cylinder. The wires are separated from each other after the run-off point. One wire carries the formed web with it. The outer wire of the wrapping is the web conductlng wire. The point at which the two wires run off the shell of the forming cylinder is located in the upper ascending quadrant of the forming cylinder.
Other examples of such methods and apparatus are disclosed in T~PI PROCEEDINGS, pages 553 et seq., where a report is given on the engineers' convention of the TAPPI ASSOCIATION in 1987.
U.S. Patent 3,009,517 and U.S. Patent 3,092,538 describe headboxes for paper making machines in further detail. U.S. ~atent 2,832,268 further details a nozzle for a headbox.
In particular, qood formation of the fiber sheet or paper sheet is reguired from such methods and apparatus. The sheet formed, i.e. the web of fiber, should be as uniform as possible in every respect. The basis weight should remain as constant as possible both over the width of the machine and ~n the direction of travel of the web. The so called two dimensional stability should be as great as possible. Bundles of fiber or clouds, which can be seen in transmitted light, should, as far ~s possible, be absent.
The jet emerging from the nozzle of the headbox has, at the place of its emergence, a certain thic~ness perpendicular to the direction of jet travel as well as perpendicular to the length of the outlet slot of the nozzle. It has always been attempted to retain this thickness of the jet constant. Widening of the jet, that is making it taller or larger across the 20364~6 height of the outlet nozzle, on the path of the jet from the outlet of the nozzle up to impingement on the correspondin~ impingement surface, and, therefore, in general, onto th~ wire of the paper making machine, was undesired. Specific disadvantages were sQan, especially with regard to the constancy of the basis weight. See, for example, U.S. Patent 2,832,268, columns 4, 5 and 6. As remedies, there are described particular shapes of the outlet nozzle or certain inserts in this nozzle in order to avoid widening of the jet after its emergence from the nozzle and to nevertheless retain a desired microturbulence in the pulp suspension.
U.S. Patent 3,092,538 also concerns producing a certain microturbulence in the headbox and retaininq this microturbulence after emergence of the jet from the nozzle. Here also, the fiber material jet retains its thickness after its emergence from the nozzle.
U.S. Patent 3,009,517 describes a headbox with an outlet nozzle which has a venturi constriction.
This constriction is again intended to serve for forming microturbulence.
These demands on the quality of the formation of the sheet have been the sub~ect of discuss~on up to the present time. The efforts have not always led to complete satisfaction of the papermaker. In particular, the uniformity of the formation of the sheet has not always been satisfactory up to now.
2036~
It is an object of the present invention to provide a novel method and apparatus for forming a fiber web. It is another object of the present invention to provide a method and apparatus for forming a fiber web which obviates or mitigates at least one of the above-mentioned disadvantages of the prior art.
Accordingly, in one of its aspects, the present invention provides a method of forming a fiber web wherein a fiber sùspension is fed through an outlet nozzle of a headbox in the form of a jet of the fiber suspension and wherein the jet has the width of the fiber web manufacturing machine., the method comprising direct~ng the fiber ~uspension from the outlet nozzle to ~mpn~e upon ~t least one ~oving surface, which surface ~s moving toward the narrow end of a wedge shaped ~lot that is formed in part by the at least one moving surface, ~n order to deposit the fiber suspension for forming a f~ber web there as the jet emerges from the nozzle, w~dening the ~et directly upon its emergence from the nozzle, as ~een ~n s~ae V~QW and in the direc~ion of flow, for forming an opening angle of the ~et of at lea~t 3-.
In another of its aspects, the present invention provides an apparatus for applying a jet of fiber suspension to the slot of a fiber web producing machine, the apparatus comprising:
a headbo~, including an outlet nozzle ~ through which the ~et of fiber suspension is sprayed;
30 a pair of cooperating moving ~urfaces defining a wedqe ~hape~ ~nlet ~lot which i~ wider toward the nozzle and which narrows away from the nozzle, and the nozzle being directea to spray toward the slot and onto ~t le-st one of the moving surfaces, i .
,., 203~
- 4a `-the two surfaces defining the slot being ~o~ble toward the narrow end of the 810t and means for ~o~ing the two surfaces toward the narrow end of the ~lot, the surfaces on which the jet of suspension impinges having a machine width the outlet nozzle from the hsadbox having generally the machine width, the nozzle being defined by an upper lip abo~e ~ nozzle opening and a lower lip beneath the nozzle openin~, the nozzle and its lips being so shaped and ~rranged and the noz~le being 50 spaced from the surf~ces of the ~edge sh~ped slot that the jet of fiber suspension, immediately upon itB
emergence from the nozzle, is ~idened ~nd forms an opening anqle of at lcast 3.
In ~et another of its aspects, the present invention provides a headbox comprising:
nn outlet nozzle through Yhich a jet of fiber suspension i8 sprayed; the nozzle being d~fined by an upper lip ~bovc a nozzle opening and a lower lip 2C bencath the nozzle opening, the nozzle and it~ lips being 80 shaped and ~rr~nged that She jet of fiber suspension, immediately upon its ~mergence from the noz~le, is widened and forms an opening angle`of at least 3.
A feature of the present invention relates to wi~ng the heiqht of the jet, that '~s the th~ekness of the ~et with respect to the thickness of the nozzle outlet 80 that there is less concentr~ted impingement of the fiber suspension on at least one of or both of the surfaces forming the wedge shaped inlet slot of the forming section of the paper making machine. Those surfaces may comprise at least one ~ire ~creen or ~ire, or two of the ~ire ~creens or wires ~hich converge to 2036~S
- 4b -define the inlet slot or one wire ~creen or ~ire and one forming roller which cooperate to define the slot.
The slot is so shaped and placed and the outlet nozzles from the headbox are ~o ~haped and placed that the jet widens sufficiently for accompl~shin~ the objecti~e of the invention and ~o that the jet ~prays upon at least one of the two surfaces comprising a wire ~creen or a roller or on both to the same or unequal extcnts. In particular, the jet forms an opening angle as it leaves lo the outlet nozzle of at least ~-, preferably in the range of 15 to 60, but more prefera~ly 30- to 60.
~ he inventors hsve recognized that, contrary to general opinion and usual practice, a widening of the jet of suspension directly upon its emergence from the headbox nozzle is of great ad~antage. ~hus, in accordance with the in~ention, the jet should impinge upon a much larger surface than has previously been the 203~S
case. The uniformity of the fiber web formed is considerably increased, Investigations which have been subsequently carried out have led to the following discovery. Upon the conventional formation of the jet, in which the jet retains its thickness after emergence from the headbox nozzle, the pressure per unit of area which the jet exerts on the impingement surface is relatively larqe. These forces have led to deformations of the impingement surface and, therefore, in ~eneral of the paper making machine ~ire or, in the case of twin-wire paper making machines, of both the wires. These deformations are particularly disadvantageous if the pressure of the jet is not constant over the entire width of the machine but is instead irregular. ~owever, this cannot be avoided in actual practice. Measurements have shown that it is subject to certain varia~ons both width-wise and over time.
It follows from this, in its turn, that bulges or ~impact holes~ are produced in the impingement surface and particularly in the wire. They lead to irregularities ~n the fiber web thereby formed.
With the use of a spray jet in accordance with the invention, the jet pressure per unit of area is naturally correspondingly less. The impact holes either occur only to a reduced extent or no longer occur at all.
The outlet nozzle from the headbox is usually defined between two lips that extend toward the slot. The lips are close together and extend substantially the width of the machine, which is substantially the width of the two surfaces that form 2036~
the inlet slot, that is the two wires or the wire and the cooperating inlet slot ~urf~ce. The outlet nozzle is configured to ~iden the jet of suspension in a selected one of n number of ~ays. One ~y is providing a led~e extending from the outlet cnd region of one lip toward the outlet end re~ion of th~ other lip, and/or including a flow body within the outlet nozzle ~nd which terminates near the outlet region for initially dividing the flow through ~he nozzle ~nd then permitting it to recombine ~ust before exiting the outlet nozzle. Another way ~s to provide ledges on the internal facing ~urfaces of the lips toward tbeir outlet region, possibly cooperating with the flow body within ~he nozzl~, and the ledges ~re locnt~d just after the terminal en~ of the flow body. In ~n alternate design, there are air ~nlets through ~t least one o~ the lip~, ex~ending across th~ machine width and located toward the outlet r~gion of the lip.
Preferably, there ~8 a cooperating hump on ~he interior o~ the other l~p with the tall part of the hump being generally opposite the ~ir ~nlet~ on the other lip.
Embodiments of the lnvention will be described with reference to the attached ~rawings whereln like numerals designate like parts, in which:
Fig. 1 schematically shows a headbos of ~
paper making machine with a corresponding wire sect~on.
Figs. 2 to 5 show var~ous configurations of portions of wire sections.
Figs. 6 to 9 show outlet nozzles of headboxes in cross-sections perpendicular to the plane of the jet and in the direct~on of flow.
2Q36~
The apparatus shown in Figure 1 includes a headbox 1 for a paper making machine with an outlet nozzle 2 for spraying a jet of fibrous suspension. Two endless forming section wire screens, ~ires 3, 4, together form a wedge shaped, diminishing height, inlet or feed slot 5 into which the je~ of fiber or pulp suspension ~s shot out of the nozzle 2. The wires travel around their illustrated guide and support rollers at the same speed and in a direction bac~ from the feed slot 5 away from the nozzle 2. The jet forms a fiber web 6 between the two wires 3 and ~ directly downstream of the wedye ~haped slot 5 along the paths of the wires. The web travels between the two wires 3 and 4 around a forming cylinder 7 and then remains adhering to the wire 3, being finally removed from the wire 3 further along its path. This i~ ~ well ~nown operation.
With the configurations of web or sh~et forming devices in Fi~s. 2 to 5, wedge shaped ~lot ~s in each case formed by the t~o wires 3 and ~. In the three different devices in Figs. 2 to 4, a forminq cylinder ~ is provided which is initially wrapped around ~y one of the two wires, n~mcly the wire ~
directly after the uedge shapea ~lot 5. Then at a certain aistance ~way fro~ initial contact by the first wirc ~, the cylinaer 7 is also ~rapped by the other wire 3.
In the device in Fig. 5, instead of a rotating forming cylinder, there is a ~tationary water-removal surface which is formed of a stationary wire table 17. The two wires 3 and ~ first wrap around ., .
r .~.
,, 2036~S
rolls 8, 9 respectively, which define the entrance region of the wedge shaped slot 5, and the curve of the table 17 establishes where the wires come together closing the end of the wedge shaped slot.
In the four devices of Figs. 2-5, the jet is shown diagrammatically as it emerges from the nozzle 2.
In this connection, the outer limiting spray lines of the jet are indic~ted as dashed l~nes, while the axis of the jet is indicated ~s a dash-dot line. The opening angle of the jet is a minimum of 3, may be in the range of 15 to 60, and preferably is in the range of 30 ~o 60~.
In the device of Fig. 2, the nozzle 2 is oriented so that the axis of the jet extends rather precisely through the end point of the wedge shaped slot 5 at the roll 7.
In the device of Figure 3, the nozzle 2 is inclined so that the axis of the jet strikes predominantly ~gainst the wire 3 and thus is merely tangent to the wire ~.
In the device of Fig. ~, the jet strikes exclusively against the wire 3 while it is at a certain distance from the end point of the wedge shaped slot 5.
In the device of Figure 5, the nozzle 2 is directed so that the jet strikes symmetrically a~ainst the two wires 3 and ~.
As can b~ noted, in all four cases of Figs. 2-5, the area of the wires struc~ by the jet upon its impingement is substantially greater than the area of the jet at the point of its emergence from the nozzle 2. This is due to the opening angle of the jet and the angle of the surfaces being impinged upon with respect to the axis of the jet.
20364~6 g The outlet nozzle is so shaped and configured, for example by one of the technigues described below, and it is so shaped and so spaced by a distance from the two surfaces 3, 4 defining the slot 5 that the combined area of the ~urfaces that is struck by the jet upon the impingement of the jet of flow suspension on those surfaces is equal to the product n x d x a, in which d is the thickness of the jet, a is the width of the jet, that is the machine width, and n is greater than d. Specifically, n may be equal to at least twice d. This widening of the jet sufficiently minimizes the damage to the surfaces on which the jet is being impinged.
The wedge shaped slot 5 may assume angles of different size. In Fig. 2, this angle is equal to about 60 if the wire 4 were extended beyond the place of contact with the forming cylinder 7 so that it would intersect the plane of the wire 3. In the device of Fig. 5, the wedge angle is only about 15. In the devices of Fiqs. 3 and 4, the wedge angle is between 15 and 60. All of these angles may be advantageous depending on the specific use and the nature of the paper to be produced.
The nozzles shown in Figs. 6 to 9 in each case include an upper lip lO and a lower lip ll of thQ
nozzle which extend across the machine along the machine width.
The nozzle of Figure 6 is provided in it~
vertical central region with a flow bvdy 12, which extends laterally over the entire width of the machine and which extends forward and terminates shortly inward of tbe outlet side end of the nozzle 2, so that the two 2036~6 individual streams of suspension which flow around the flow body 12 can combine aqain just before the nozzle outlet. The outlet end of the nozzle 2 is formed of two ledges 13, 14 attached on the lips 10 and 11, respectively, which together form ~ slot. The opposed surfaces of the ledges widen continuously in the direction of suspension discharge.
The nozzle shown in Fig. 7 also includes a flow body 12 between its lips 10 and 11. The flow body 12 is also passed around by two individual streams of suspension. At the point following the flow body where the two individual streams combine to form a single stream, there are two transverse, inwardly projecting ledges 1~, 16 on the lips 10, 11 respectively, which constrict the jet of pulp. The ledges 15, 16 are a short distance bac~ from the nozzle outlet.
The nozzle of Fig. 8 has an upper lip 10 which has one or more air inlets 20 preferably arranged in a row over the machine width. The upper surface of the lower lip 11 of the nozzle has a hump whose high point is located approximately opposite the point of the air inlets 20 so that suspension flow is constricted where the extra air enters.
The nozzle of Figure 9 has a lower lip 11 which is pushed forward in the direction of su~pension flow, as compared with the upper lip 10. The upper lip has a depending impact ledge 21, which effects a sudden constriction of the flow path. The lower lip 11 also has an impact ledge 22 which is forward in the suspension path of the ledge 21, and which extends upward.
~036~
Although the present invention has been described in connection with a plur~lity of preferred embodiments thereof, many other vari~tions and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by th~ specific disclosure herein, but only by the appended claims.
Claims (28)
1. A method of forming a fiber web wherein a fiber suspension is fed through an outlet nozzle of a headbox in the form of a jet of the fiber suspension and wherein the jet has the width of the fiber web manufacturing machine, the method comprising directing the fiber suspension from the outlet nozzle to impinge upon at least one moving surface, which surface is moving toward the narrow end of a wedge shaped slot that is formed in part by the at least one moving surface, in order to deposit the fiber suspension for forming a fiber web there; as the jet emerges from the nozzle, widening the jet directly upon its emergence from the nozzle, as seen in side view and in the direction of flow, for forming an opening angle of the jet of at least 3°.
2. The method of claim 1, wherein the at least one moving surface on which the jet is impinged comprises a wire screen for a fiber web manufacturing machine.
3. The method of claim 2, wherein the slot is wedge shaped and is defined by two moving wire screens which move toward the narrow end of the slot and the fiber suspension impinges upon at least one of the wire surfaces.
4. The method of claim 2, wherein the slot is defined by one endless wire screen that moves into the slot and by one shell surface of a roll and the jet is aimed for directing the fiber suspension on at least one of the wire screen and the surface of the roll.
5. The method of claim 1, wherein the opening angle of the jet is between 15° and 60°.
6. The method of claim 1, wherein the opening angle of the jet is between 30° and 60°.
7. The method of claim 1, wherein the wedge shaped slot is defined by two of the moving surfaces which converge to define the slot.
8. The method of claim 7, wherein the opening angle of the jet is between 15° and 60°.
9, The method of claim 7, wherein the nozzle is aimed so that the jet of fiber suspension impinges upon both of the moving surfaces.
10. The method of claim 9, wherein the jet is so shaped and the spacing of the outlet nozzle from the surface upon which the jet impinges is selected so that the Area struck by the jet upon its impingement is equal to the product of the thickness of the jet and the width of the jet further multiplied by a number greater than the thickness of the jet.
11. The method of claim 10, wherein the multiplying number is equal to at least twice the thickness of the jet.
12. Apparatus for applying a jet of fiber suspension to the slot of a fiber web producing machine, the apparatus comprising:
a headbox, including an outlet nozzle through which the jet of fiber suspension is sprayed;
a pair of cooperating moving surfaces defining a wedge shaped inlet slot which is wider toward the nozzle and which narrows away from the nozzle, and the nozzle being directed to spray toward the slot and onto at least one of the moving surfaces, the two surfaces defining the slot being movable toward the narrow end of the slot and means for moving the two surfaces toward the narrow end of the slot, the surfaces on which the jet of suspension impinges having a machine width;
the outlet nozzle from the headbox having generally the machine width, the nozzle being defined by an upper lip above a nozzle opening and a lower lip beneath the nozzle opening, the nozzle and its lips being so shaped and arranged and the nozzle being so spaced from the surfaces of the wedge shaped slot that the jet of fiber suspension, immediately upon its emergence from the nozzle, is widened and forms an opening angle of at least 3°.
a headbox, including an outlet nozzle through which the jet of fiber suspension is sprayed;
a pair of cooperating moving surfaces defining a wedge shaped inlet slot which is wider toward the nozzle and which narrows away from the nozzle, and the nozzle being directed to spray toward the slot and onto at least one of the moving surfaces, the two surfaces defining the slot being movable toward the narrow end of the slot and means for moving the two surfaces toward the narrow end of the slot, the surfaces on which the jet of suspension impinges having a machine width;
the outlet nozzle from the headbox having generally the machine width, the nozzle being defined by an upper lip above a nozzle opening and a lower lip beneath the nozzle opening, the nozzle and its lips being so shaped and arranged and the nozzle being so spaced from the surfaces of the wedge shaped slot that the jet of fiber suspension, immediately upon its emergence from the nozzle, is widened and forms an opening angle of at least 3°.
13. The apparatus of claim 12, further comprising the nozzle having an outlet region at and just before where the fiber suspension leaves the nozzle as a jet, the nozzle having a sudden, sharp constriction at the outlet region for forming the widened opening angle.
14. The apparatus of claim 13, further comprising a flow body in the nozzle extending generally parallel to the nozzle opening, and the nozzle having an outlet region where the suspension leaves the outlet nozzle as a jet, the flow body terminating at the nozzle outlet region, so that the individual streams of suspension that are formed on the opposite sides of the flow body are enabled to combine before leaving the outlet of the nozzle.
15. The apparatus of claim 12, further comprising a flow body in the nozzle extending generally parallel to the nozzle opening, and the nozzle having an outlet region where the suspension leaves the outlet nozzle as a jet, the flow body terminating at the nozzle outlet region, so that the individual streams of suspension that are formed on the opposite sides of the flow body are enabled to combine before leaving the outlet of the nozzle.
16. The apparatus of claim 12, further comprising air inlets in one of the nozzle lips, upstream of the suspension outlet from the nozzle.
17. The apparatus of claim 16, wherein the other lip has an internal hump within the nozzle opening, the hump having the machine width and the hump having a high point which is located approximately opposite the air inlets within the nozzle.
18. The apparatus of claim 13, wherein the opening angle of the jet is between 15° and 60°.
19. The apparatus of claim 13, wherein the nozzle is aimed so that the jet of fiber suspension impinges upon both of the moving surfaces.
20. The apparatus of claim 13, wherein the jet is so shaped and the spacing of the outlet nozzle from the surface upon which the jet impinges is selected so that the area struck by the jet upon its impingement is equal to the product of the thickness of the jet and the width of the jet further multiplied by a number greater than the thickness of the jet.
21. The apparatus of claim 13, wherein the sharp constriction comprises a respective inwardly directed ledge on each lip at the outlet region of the nozzle.
22. The apparatus of claim 21, wherein each ledge has a surface over which the suspension passes and which widens outward of the nozzle.
23. The apparatus of claim 14, wherein the sharp constriction comprises a respective inwardly directed ledge on each lip at the outlet region of the nozzle.
24. The apparatus of claim 23, wherein the ledges are inward of the outlet from the nozzle and just beyond the flow body.
25. A headbox comprising:
an outlet nozzle through which a jet of fiber suspension is sprayed; the nozzle being defined by an upper lip above a nozzle opening and a lower lip beneath the nozzle opening, the nozzle and its lips being so shaped and arranged that the jet of fiber \
suspension, immediately upon its emergence from the nozzle, is widened and forms an opening angle of at least 3°.
an outlet nozzle through which a jet of fiber suspension is sprayed; the nozzle being defined by an upper lip above a nozzle opening and a lower lip beneath the nozzle opening, the nozzle and its lips being so shaped and arranged that the jet of fiber \
suspension, immediately upon its emergence from the nozzle, is widened and forms an opening angle of at least 3°.
26. The headbox of claim 25, further comprising the nozzle having an outlet region at and just before where the fiber suspension leaves the nozzle as a jet, the nozzle having a sudden, sharp constriction at the outlet region for forming the widening opening angle.
27. The headbox of claim 26, further comprising a flow body in the nozzle extending generally parallel to the nozzle opening, and the nozzle having an outlet region where the suspension leaves the outlet nozzle as a jet, the flow body terminating at the nozzle outlet region, so that the individual streams of suspension that are formed on the opposite sides of the flow body are enabled to combine before leaving the outlet of the nozzle.
28. The headbox of claim 27, wherein the sharp constriction comprises a respective inwardly directed ledge on each lip at the outlet region of the nozzle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19904005147 DE4005147A1 (en) | 1990-02-17 | 1990-02-17 | Paper making stock inlet jet - delivers fibre suspension in a stream which opens out without micro-turbulence |
| DEP4005147.1 | 1990-02-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2036446A1 true CA2036446A1 (en) | 1991-08-18 |
Family
ID=6400474
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2036446 Abandoned CA2036446A1 (en) | 1990-02-17 | 1991-02-15 | Forming a fiber web using a widened jet of suspension |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA2036446A1 (en) |
| DE (1) | DE4005147A1 (en) |
| FI (1) | FI910675A (en) |
| SE (1) | SE9100412L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6372092B1 (en) | 1999-01-23 | 2002-04-16 | Voith Sulzer Papiertechnik Patent Gmbh | Headbox and process for supplying a material suspension |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102004009317A1 (en) * | 2004-02-26 | 2005-09-08 | Voith Paper Patent Gmbh | Sheet forming system |
| DE102006049020A1 (en) * | 2006-10-13 | 2008-04-17 | Voith Patent Gmbh | headbox |
| WO2008077585A1 (en) * | 2006-12-22 | 2008-07-03 | Voith Patent Gmbh | Headbox of a machine for the production of a fibrous material web |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1431603A (en) * | 1973-11-26 | 1976-04-14 | Wiggins Teape Ltd | Forming non-woven fibrous material |
| CH613241A5 (en) * | 1976-12-09 | 1979-09-14 | Escher Wyss Gmbh | Headbox device for a papermachine |
-
1990
- 1990-02-17 DE DE19904005147 patent/DE4005147A1/en not_active Ceased
-
1991
- 1991-02-12 SE SE9100412A patent/SE9100412L/en not_active Application Discontinuation
- 1991-02-12 FI FI910675A patent/FI910675A/en not_active Application Discontinuation
- 1991-02-15 CA CA 2036446 patent/CA2036446A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6372092B1 (en) | 1999-01-23 | 2002-04-16 | Voith Sulzer Papiertechnik Patent Gmbh | Headbox and process for supplying a material suspension |
Also Published As
| Publication number | Publication date |
|---|---|
| SE9100412L (en) | 1991-08-18 |
| FI910675A (en) | 1991-08-18 |
| DE4005147A1 (en) | 1991-08-29 |
| SE9100412D0 (en) | 1991-02-12 |
| FI910675A0 (en) | 1991-02-12 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19930815 |