CA1172484A - Method of forming a multi-ply paper web in a twin- wire former and twin-wire former for carrying out the method - Google Patents

Abstract

Attorneys Docket No. 6960 INVENTOR: ALFRED BUBIK

INVENTION: METHOD OF FORMING A MULTI-PLY PAPER WEB IN A
TWIN-WIRE FORMER AND TWIN-WIRE FORMER FOR
CARRYING OUT THE METHOD

ABSTRACT OF THE DISCLOSURE

A twin-wire former for multi-ply paper or cardboard webs contains a plurality of headbox outlet openings or slices. As to the stock suspension jets or streams which are maintained separated from one another even after departure from the headbox outlet openings by partition or separation elements, at least the first stock jet or stream is pre-dewatered at a pre-dewatering path of the first wire, before all of the stock jets or streams enter a gap zone or region of the twin-wire, between which at least the last of the stock jets or streams experiences its initial dewatering. Consequently, there is possible a separate influencing of the pre-dewatering of the individual stock jets or streams used in the sheet or web formation.

Description

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' CROSS REFERENCE TO RELATED APPLICATION
'~ ' This application is related to my commonly assigned, copending Canadian application Serial No. 397,230, filed February 26, 1982, entitled "Headbox for a Papermakiny Machine"O

' BACICGROUND OF THE INVENTION
- - --~,~ The present invention relates to a new and improved ,., i';?~ method of forming a multi-ply paper web in a twin-wire former, ~`~ and further pertains to a twin-wire former for carrying out the inventive method.
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','.'`' ., ', Generally speaking, the method for forming a ;~
multi-ply paper web in a twin-wire former utilises a first endless revolving wire and a second endless revolving wire, which conjointly travel through a curved path generating dewatering pressure, while such wires partially contact one ~-~ another and are under tension. By means of at least two stock '" jets or streams effluxing separately from the headbox outlet openings or slices and guided essentially in neighbouring plies : or layers, the twin~wires are still maintained spaced from one another over a certain path by the stock jets at a downstream location of the outlet openings by partition or separation - elements extending in the flow direction.

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The twin-wire former oE the present development is of the type comprising headbox devices containing at least two mutually separated stock infeeds and a corresponding number of outlet openings or slices which are bounded by boundary walls extending over the width of the headbox devices and essentially parallel to the stock flow. Partition elements are arranged between the stock jets or streams and maintain separate from one another the stock jets over a predetermined path downstream of the outlet openings or slices. There is provided a first revolving endless wire and a second revolving endless wire, which conjointly partially train about a dewatering ; roll or cylinder and at the region of their inbound location at the dewatering cylinder form a converging gap or space for receiving the paper web which is in the process of being formed.
, > Wire sections for the production of multi-ply: paper webs are finding ever increasing acceptance in the ~:~ papermaking industry, in order to be able to use stock or fibre suspensions of different quality which are distributed over the cross-section of the paper web.
While previously there generally were used for this ' purpose secondary headboxes over the longitudinal wire sections, by means of which a further web layer or ply could be deposited upon an already finished formed preceding ply, at the present time attempts are being made ' 1~724~

because of the improved mutual ply adherence or connection, to deposit the stock jet or s~ream for a subsequent ply as much as possible upon a not yet finished-formed preceding ply. Usually for reasons of reduction of the installation costs attempts are made to remove different stock jets or streams from the same headbox. For this purpose the headbox is appropriately , .. ~
subdivided or, depending upon requirements, can be subdivided. In particular, in the case of twin-wire lG formers which are gaining increasing importance in the ; papermaking industry, and which are suitable or maximum operating speeds, there is generally required the use oE
multi-ply headboxes, since frequently there is not available the space for using a possible secondary headbox.

An apparatus of the previously mentioned type has ~ been disclosed, for instance, in United S~ates Patent No.
; ~ 4,141,788. With the there described equipment the total stock jet or stream which is subdivided by intermediate , ::
walls within a headbox channel, into three separate individual stock jets or streams, is directly introduced ,.::,.~:, or infed, and specifically, in a practically symmetrical arrangement, into the converging infeed gap or space between a twin-wire. Both of the flexible self-aligning partition elements extend between the three stock jets or streams past the outlet opening or slice of the headbox into the converging infeed gap between the wires.

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Consequently, the intermediate jet or stock stream first arrives at a later location for dewatering, both of the outer stock streams~ however, immediately come into contact with the related wires and are dewatered under the action of the converging wire gap. According to a further embodiment described in such United States Patent No~ 4,141,788, which illustrates the use of the corresponding headbox at a twin-wire former with solid or closed forming roll, the partition elements have different lengths since the dewatering of the stock webs only is accomplished to one side, but the total stock flow also in this case enters directly into the converging region between both of the wires, so that the dewatering pressure is determined .in its entirety by the geometry of the gap region.

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Similar arrangements are disclosed, for instance, in German Patent Publication No. 2,916,351, corresponding to : United States Patent No. 4,349,414, United States Patent No.

3,923,593 and United States Patent No. 4,181,568~ wherein , .
however the partition elements between the stock jets or streams do not protrude past the outlet slice or opening of the headbox.

. SUMMARY OF THE INVENTION

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.; Therefore, with the foregoing in mind it is a primary object of the present invention to provide a new and improved method of forming a multi-ply paper web in a ' ~

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2 4 8 4 twin-wire former and a twin-wire Eormer for carrying out the inventive method, in a manner not aEflicted with the ~` aforementioned drawbacks and limitations of the prior art constructions.
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~ ~nother and more specific object of the present - invention aims at providing a new and improved method of . . ~. .
~ the previously mentioned type for the formation of a ., ,~
` multi-ply web by means oE a twin-wire formeL, wherein it is possible to accomplish an individual dewatering of the individual stock jets or streams or plies, respectively, ` under different conditions over a sufEiciently long path, and wherein, however, the individual stock streams can be ~,~ maintained extensively separated from one another.

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In order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the inventive method is manifested by the features that initially at least the first stock jet or stream neighbouring a first of both wires is pre-dewatered at this first wire without the action of the second wire and the dewatering pressure of the curved path, into a formed paper web, and at least the last stock jet or stream guided bv the last partition element and not bounded towards the outside by a partition element is introduced ~or dewatering directly into the converging gap region or space formed by the wires.
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1 1~2~84 Consequently, the stock jets or streams arriving at khe first wire forwardly of the converging gap region or space, if necessary, can be dewatered in a very protective manner by the first wire undee the static pressure of its inherent liquid column. In the pre-dewatering path there can be used below the first wire certain elements which, however, also influence the dewateriny action, such as wire table elements, suction ledges or fcils or suction boxès. Advantageously, such elements are arranged such that at the region of the ~ .
- arrival of each further stock jet or stream at the first : ~
wire there prevails a somewhat higher negative pressure ~ for dewatering, since each successive stock jet or stream .~:, must be dewatered through the already deposited Eibre web .~
of the preceding stock jeks or strearns.

To prevent the dewatering pressure, resulting from the wire tension and the radius of curvature of the curved path, with a curvature determined by a roll jacket or shell, from directly acting with its full force at the last stock jet or stream, the curvature path preferably is structured so as to have an increasing curvature. This can be accomplished; as a practical matter, in that the dewatering roll or cylinder has mounted forwardLy thereof a displaceable shoe having a convex curved surface, the curvature of which is less than that of the curvature of the jacket or shell of the dewatering roll or cylinder.
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In order to be able to alter the dewatering paths '~`1 for the individual stock jets or streams within certain ....
~ limits, the guides or guide means for the individual stock ,. .
~" jets or streams and which are formed by the partition or separation elements, are variably arranged, preferably as `~ to their position, externally of the outlet opening or slice of the headbox. For the performance of the method it is of course significant that the partition elements, the construction of which will be described more fully -.. .
hereinafter, possess a sufficient length. Of course, the ; length of the partition elements must be accommodated in accordance with the desired impact point or location for the individual stock jets.

The described sheet forming method offers an ou~standing possiblity of individually treating the ; individual closely juxtapositioned, guided stock jets or streams for a multi-ply paper web during the first - dewatering operation and for the immediate sheet formation, in a manner such that the desired sheet properties can be obtained and regulated. In particular, with progressive web thickness there can be attained a stepwise increasing pressure difference for the dewatering, and there are practically combined with one another the advantages of a longitudinal wire section and a twin-wire former.

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An exemplary embodiment of apparatus suitable for the performance of the inventive method is manifested by the features that the first wire, prior to inbounding at . ~.
~ the dewatering roll or cylinder, is guided over a ;
pre-dewatering path. At the start of such pre-dewatering ~`` path there is located at least one outlet opening or slice "` of the headbox means or devices. The partition elements are constructed and guided in such a manner that at the start of the pre-dewatering path only the first stock jet or stream neighbouring the first wire impinges upon the first wire, and at least the last partition element `~; possesses such a length that the last stock jet or stream which is carried by such partition element can be directly directed between the wires into the converglng gap or space.

The pre-dewatering path can have a curved or ; straight course of travel. In the case of a straight course of travel there is provided at the start of the pre-dewatering path, for reasons of the arrangement of the . .
headbox, advantageously, and as otherwise conventional, a breast roll about which there is trained the first wire in the pre-dewatering path. The dewatering roll or cylinder about which there is trained both of the wires can be constituted by a roll having a closed or solid surface, as such is used for instance in the case of tissue formers where the dewatering is essentially accomplished by the wire facing away from the roll. ~lowever, the dewatering .~ .

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~ 1 ~2~4 ~ roll also can be designed as a roll upon which there is .. ..
placed a grid-like grate structure from which there is outwardly propelled the water at the side facing away from the wire. Such dewatering roll or cylinder also can be structured so as to have open bores or perforations, in which case there can be provided a suction box internally of the dewatering roll. Such constructions are preferably employed for twin-wire Eormers for printing paper. A
grid-like grate structure at the dewatering roll fulfils, in contrast to blindhole bores, the requirement that air can escape in the transverse direction out of the water-receiving depressions or recesses.
In order to be able to alter the converging gap or space between both of the running together wires, it is advantageous to design the guide roll which deflects the second wire at the gap region so as to be adjustable, as the same has been described in United States Patent No.
4,176,005.

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The partition or separation elements between the individual stock jets or streams require a special ` construction, since they must be relatively long for thedescribed arrangement. It is completely possible to design the pre-dewatering path so as to have a length of up to 150 centimetres. Here, the last partition element generally must extend over the entire length of such pre-dewatering :

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path. Continuous flexible partition elements, as the same have been described in United States Patent No. 4,141,788, afford the advantage that they automatically can accommodate themselves to the stock flow. However, if they are too long they tend to vibrate or begin to flutter.
Therefore, within the teachings of the present invention it is preferred to construct the partition elements both within the headbox channel in the form of rigid partition walls as well as also externally of the headbox outlet openings or slices as extensively rigid partition surfaces. If the partition walls are rigid within the headbox channel, then it is immaterial whether the headbox forms a single unit for the different stock streams or jets Quite to the contrary, it can he assembled toqether in a modular system from individual units for the di.fferent stock jets or streams. Also a stock stream or jet, preferably the last stock stream, can be infed by means o a separately arranged unit.

In both instances a stepped diffusor-headbox is quite suitable for a twin-wire former of the type herein disclosed. Since such headbox usually anyway comprises a plurality of stepped diffusor rows for larger throughput quantities of stock, there is possible, in a most simple manner, a subdivision of the therewith merging headbox channel by fixed partition walls in accordance with the diffusor rows into a number of separate chambers. Owing to , .. ....
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: ~72~4 tlleir compact construction it is possible, however, to also unite mutually independent, single-row stepped diffusor - units within a relatively small amount of space into a - corresponding headbox system for a plurality of web plies.
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Generally, there only comes under consideration ,, the construction of double or triple-ply webs. During the production of double-ply webs it can be advantageous to construct the individual partition walls with the thereat meeging partition surfaces externally of the outlet opening - 10 or slice as a rigid unit. However, preferabl~ both of the outer wall boundaries oE the headbox channel should be adjustable, in order to be able to appropriately control the individual stock jets. Also, with an arrangement for a triple-ply web it can be adequate if, when using two rigid ; partition surfaces, the outer wall boundaries of the headbox channel are adjustable. In this case the intermediate stock jet or stream can be regulated by means of the quantity of water, something which should be readily possible for many fields of application. However, it is advantageous with an arrangement for a triple-ply web to ,~ design the upper, second partition or separation surface so ~; as to be movable, and it can be positionally adjusted by the action of external actuation means. This second partition surface extends over a greater length.
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72~84 Movable partition surfaces are advantageously hingedly connected at the region of the outlet openings of the headbox at the partition walls between the individual channels or passages. The partition surfaces themselves can be rigidly structured. The hinge or pivot connection of the partition surfaces can be accomplished just shortly externally of the outlet openings or slices of the headbox. In this case, the connection can be accomplished such that the partition surfaces can be easily exchanged from externally of the headbox.

In principle, it is possible to allow pivotably mounted partition surfaces to freely adjust themselves in their position between the stock streams or jets. However, when working with a greater length of the partition surfaces it is advantageous to equip such with external adjustment elements. These can be in the form of adjustment elements which Airectly engage in a positive or Eorm-locking manner, for instance at the lateral ends of the partition surfaces, such as adjustment spindles and the , .
like. However, it would also be possible to use purely force-locking or frictionally engaging elements, such as for instance electromagnetic spacer holders or spacers.
Such can consist of an electrically powered magnetic ledge below the wire, preferably integrated in a dewatering element The force of the electrically powered magnetic ; ledye can act in a repelling fashion, and therefore, in a ., ' . . , .

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spacer-like functioning way upon permanent magnets located at the partition or separation surface.

Since, in particular, the last stock stream or jet must move through a relatively long path upon the partition surface, it can be advantageous and necessary to provide the surfaces of the partition surfaces at least partially with structure which produces micro-turbulence.

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To the extent that the stock streams or jets and the wires move through a curvilinear or acuate path, then the partition surfaces, especially when usiny a rigid design, must be appropriately accomrnodated as to their ` cross-sectional proEile or shape.

.:`, ;~ BRIEF DESCRIPTION OF THE DRAWINGS
,:, The invention will be better understood and ~` objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereo~. Such description makes reference to the annexed drawings wherein:

Figure 1 is a schematic illustration of a headbox and shee~ forming region of a twin-wire former for preferably fabricating printing paper;

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2~4 Figure 2 is a schematic illustration of a twin-wire forrner for multi-ply tissue webs;

Figure 3a is an enlarged schematic illustration of the sheet forming region of an arrangement similar to that shown in Figure l;

Figures 3b and 3c respectivel~ show sectional views, taken along the section lines ~ and ~, respectively, ,;
~- of Figure 3a, and` illustrating the cross-sectional appearance of the partition elements;
~' ~ 10 Figure 4 illustrates a further embodiment of a ,` twin-wire ~ormer for multi-ply webs;
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Figure 5 illustrates a further embodiment of a twin-wire former for a double-ply web;
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Figure 6 schematically illustrates a twin-wire former for multi-ply cardboard webs with a separately .- arranged headbox-exit opening or slice for the third web ply in the form of a secondary headbox, and a partition element is shown extendiny from the first headbox to the . second headbox;
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Figure 7 is an illustration corresponding to the showing of Figure 6, wherein the second partition or .: .

' 72~84 separation element first starts downstream of the ~irst headbox; and Figure 8 schematically illustrates an exemplary embodiment corresponding to the showing of Figure 6, wherein the second partition element is first connected at the secondary headbox.

DETAILED DESCRIPTION OF THE P~EFERRED EMBODIMENTS

`i- Describing now the drawings, it is to be understood that only enough of the construction of the twin-wire former or web forming apparatus has been !:
illustrated as will enable those skilled in this' art to readily understand the underlying principl~s and concepts of the present development, while simplifying the showing of the drawings. Turning attention now to Figure 1 the therein partially illustrated twin-wire former contains an ; inner or lower wire 1 which is guided about a breast roll 2 or equivalent structure. This inner or lower wire 1 extends from the breast roll 2 through an essentially linear pre-dewateri~g path 3 and is guided so that it partially wraps about a dewatering roll or cylinder 4.

Leading from above to the lower wire 1 is an outer or upper wire 6 which is trained about a deflection roll 5. The upper wire 6 is then likewise guided so as to wrap or train about the dewatering roll or cylinder 4, so that also at ' ' ~ ~ ~24~L

the inbound or run-on region there is ~ormed at the dewatering roll or cylinder 4 a converging gap region or space 7 between the upper wire 6 and the lower wire 1. The deflection roll 5 of the upper wire 6 is attached to a p~Q~rde or pivotable arm 8. By appropriately pivoting this pivotal arm 8 it is possible to alter ~he geometry of the gap region or space 7, and speciically, the upper wire 6 can be selectively raised to a desired degree from the lower wire 1 for this purpose.

To the extent that within this disclosure there is ` referred to a first wire and a second wiee, t:hen this distinction is dependent only upon at which of both wires of the twin-wire former the first stock ply is dewater~d.
In this context the first wire equally can constitute an upper wire, a lower wiret an inner wire or an outer wire, provided that the structural arrangement enables the pre-dewatering of the first stock stream or jet coming into contact with a wire at such wire.
,.~, . Below the linear pre-dewatering path 3 of the lower wire 1 there are arranged different dewatering elements 9. At the first region or section behind the breast roll 2 such dewatering elements are constituted by wire table elements or suction ledges or foils 10 and at the following section or region such are constituted by suction boxes 11. Directly before the location of run-on '''~

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~ ~72~4 or contact of the lower wire 1 with the dewatering roll or cylinder 4 there is provided a wire shoe 12 having a curved surface 12a. The radius of curvature of the curved guide surface 12a of the wire shoe 12 is greater than that of the dewatering roll or cylinder 4. Since the dewatering pressure exerted upon the web at the curved web guide region about the dewatering roll 4 increases for a given wire tension with increasing curvature of the web guide, such a wire shoe having a lesser curvature is advantageously arranged forwardly of the dewatering roll 4, in order to preclude the dewatering pressure from suddenly increasing upon run-on or contact of the wire at the dewatering roll or cylinder 4.

In the illustrated exemplary embodiment the wire shoe 12 and the dewatering roll or cylinder 4 possess a curvature extending in the same sense or direction.
However, it is also wholly possible to allow the wire behind the curved wire shoe to pass through a turning or deflection point, in order to then impart thereto an opposite sense or direction of curvature about the dewatering roll 4.

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Above and forwardly or upstream of the breast roll 2 there is arranged a headbox device or headbox means in the form of a multi-ply headbox 13. This headbox 13 can be constructed, for instance, as a stepped-diffusor headbox. `

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The headbox 13 has three outlet openings or slices 14, 15 and 16 which are conjointly bounded towards the outside by two boundary walls 17 and 18 or e~uivalent structllre. The - three outlet openings or slices 14, 15 and 16 are delimited ~rom one another by the partition or separation walls 19 and 20. The headbox channels or passages 13a which are separated and limited from one another in the aforementioned manner and leading to the- three outlet openings or slices 14, 15 and 16 are connected with mutually independent stock infeed or supply devices 21, 22 and 23. Between the stock infeed devices 21, 22 and 23 and the headbox channels 13a there can be arranged, for -instance, stepped diEfusor rows which only have been illustrated in the drawinq in a simplified manner as simple throughflow channels 24.
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There directly merge with the rigidly constructed partition walls 19 and 20 located at the headbox channels 13a, behind the outlet openings or slices 14, 15 and 16, the partition or separation elements 25 and 26 which extend over an appreciable length downstream of these outlet openings or slices 14~ 15 and 16. The partition or separation elements 25 and 26 are preEerably also of rigid construction and can be fixed and retained in their deslred ~ position by external holding and adjustment elements, which : !
~ in the schematic showing of the drawings have not been ; particularly depicted in greater detail since such may be . . , . .~ .
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~ conventional and d~e~ not Eorm particular subject matter of i the instant development. It is however to be further mentioned that the upper partition wall 20 is pivotably mounted at the related headbox channel or channels, in order to be able to vary the cross-sectional relationship of the outlet openings or slices 15 and 16 with respect to one another. Usually also the ends of the boundary walls 17 and 18 which limit the outlet openings or slices are positionally adjustable for enabling further control of the issuing stock jets or streams. With these adjustment possibilities it is possible to intentionally affect the cross-section of all three o~ the outlet openings or slices 14, 15 and 16.

From the schematic illustration of Figure 1 it will be clearly recognised that the first stock stream or jet A effluxing from the outlet opening or slice 14 already ~ impinges at point I upon the first wire, here the lower ; wire 1, and is extensively dewatered at the region of thewire table elements or suction ledges or foils 10 or equivalent structure. Since the lower partition element 25 extends for a conslderable extent into such region, the second stock stream or jet B which effluxes out of the outlet opening or slice 15 is dewatered for the most part already at the region of the suction boxes 11. This second stock jet B is maintained separate from the stock jet or stream A and the paper web ply already formed therefrom by .
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the ac~ion oE the partition element 2~ and until a location shortly forwardly or upstream of the suction boxes 11. The third and uppermost stock jet or stream C which effluxes from the outlet opening or slice 16 impinges against the upper wire 6 at the point II. However, it is maintained still separate from both of the remaining stock jets or therefrom formed paper web plies, respectively, past such point II by the action of the upper partition element 26 which protrudes into the gap region or space 7. First following the end of the partition element 26 does there occur a common further dewaterinq of the formed plies B and C at the curved path of the wire shoe 12 and the dewatering roll or cylinder 4, and it can be assumed that at this point in time there has already been completely accomplished the formation of a web ply from the stock stream or jet A.

' ~ By virtue of the described arrangement it is ; readily possible to individually control or influence the ~` dewatering of the individual stock streams or jets of the multi-ply web. This is particulaely a significant ~t~, advantage when forming web plies of difEerent quality and ,. .
different dewatering behaviour.
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An arrangement similar to Figure 1 has been illustrated in Figure 3a. Instead of the suction ledges . il.
~ and suction boxes illustrated in detail in the arrangement ~ : ' .""'' '""

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Of FiguLe 1 r here however there has only been schematically depicted several dewatering elements 9. It is to be observed that with this embodiment the partition or separation elements 25' and 26' extend approximately to the same extent into the gap region or space 7 between the wires 1 and 6, so that after there has been extensively completed the pre-dewatering of the stock stream or jet A
: in the pre-dewatering path 3 the stock streams or ietS B
and C are first conjointly dewatered at the gap region or space 7. The dewatering can be preferably accomplished towards one side or face of the web, but also could be accomplished to both sides or faces thereof. This is totally dependent upon the construction of the dewatering roll or cylinder 4. If it is designed as a closed or solid forlning roll or cylinder it can acaomplish a dewatering action in its direction only to the extent that the wire mesh o~ the lower wire 1 can take-up water. The dewatering roll or cylinder 4 can be, however, also constructed as a perforated or interrupted roll or as a roll containing suction boxes or equivalent structure.
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~- The partition elements 25' and 26' additionally deviate in their structure from the embodiment of Figure 1 in that they possess two cross-sectional or thickness reduction portions 27 and 28. To a point beyond the region of the outlet openings or slices 14, 15 and 16 the partition elements 25' and 26' still possess essentially .~, ., ... .....

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the cross-section of the partition walls 19 and 20 in the related headbox channels, and thus, constitute their direct extension, as best seen by referring to Figure 3b. The cross-sectional transitions at the points or locations 27 ~, .
and 28 of the partition elements 25' and 26' thus exert a diffusor action, as the same is similarly known from ~- stepped-diffusor headbox constructions. From the showing of Figures 3b and 3c it will be apparent that the partition elements 25' and 26' are mutually interconnected in a :lO hose-like manner at their outer boundary edges. The stock ; ~et B guided between the partition elements 25' and 26' is .~ therefore also guided in an isolated fashion towards the ~` web edges with respect to the other stock jets or streams A
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~ and C.
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~' Figure 2 illustrates in schematic view the complete wire section of a twin-wire former for multi-ply -: tissue webs. It is to be appreciated that the same ; ~ reference characters are here also generally employed to .~ denote the same or ~ ~7~ r~ elements as have been 2G described above with regard to the arrangement of Figure ;;.j.;. 1. The first wire, in this case, constitutes the inner wire or auxiliary wire 6.

. With this arrangement both of the wires l and 6 also form endless loops or bands and conjointly train about the dewatering roll or cylinder 4 over a portion of its ' ,, .
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circumEerence. Additional guide rolls 29 serve as the wire guide of the inner wire 6, whereas the primary or main wire 1 is yuided over additional guide rolls 30.

, Following or downstream of the dewatering roll or cylinder 4 both of the wires 1 and 6 form an essentially linear common section or region which leads to a separation device 31. This separation device 31 contains two rolls 32 and 33. The roll 33 simultaneously can form a guide roll for the inner wire 6. Both of the rolls 32 and 33 can be solid rolls. However, it is also possible to design the roll 32, as illustrated, in the form of a suction roll.
Following the separation device 31 both of the wires 1 and ; 6 or equivalent structure travel separate. The wire 6 has a portion which extends upwardly at an inclination, beneath which there is arranged a catch vat or receptacle 34 serving for receiving not particularly illustrated wire cleaning devices arranged at this region of the installation or machine above the wire 6. The primary wire 1 extends from the separation device 31 to a take-off or pick-off device 35 which is composed of one of the guide rolls 30 as well as a take off or pick-off roll 36. A felt ., .,~ .
A~ 37 is guided over the take-off roll 36, which can be constructed as a suction roll. This felt 37 serves for ; removing or taking-off the not particularly illustrated paper web from the wire 1 and for further transporting the same into a here not particularly shown drying section of the papermaking machine.

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Located below the dewatering roll or cylinder 4 is .~ a catch container or receptacle 38 for the water which has . ~
been separated-out at the curved or curvilinear path of the dewatering roll 4. Following the catch container 38 is a suction box 39. Arranged below this suction box 39 is a further catch container or receptacle 40 which can serve for receiving spray water as well as further water, which can result from the action of additional, not particularly shown, dewatering elements arranged at the regi.on o the suction box 39. Finally, a catch container 41 is located above the wire 6 behind the dewatering roll or cylinder 4.
1., ~ This catch container or receptacle 41 serves to receive the ii~ water which has been propelled away Erorn the dewatering ~ roll 4. The arrangement oE this catch container 41 is :. ~
~. possible since both wires 1 and 6 assurne an inclined ~s .~ downwardly extending course of travel following the ,;~
?`r~ dewatering roll or cylinder 4.
'?~' :'1 ' `?~ Arranged above the wire 6 and ~orwardly or . upstream of the dewatering roll or cylinder 4 is a .'. 20 multi-ply headbox 13 which can be constructed in the same manner as the multi-ply headbox 13 depicted in the embodiment of Figure 1. Also the headbox 13 of Figure 2 has three outlet openings or slices which are separated ; from one another by two partition walls at which directly merge the partition elements 25 and 26. While the lower partition element 25 already terminates forwardly or '';

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upstream o~ the run-on or contact region of the wire 6 at the dewatering roll or cylinder 4, the upper partition element 26 extends for a greater extent into the gap region or space between both oE the wires 1 and 6, in fact up to the proximity of the wrap region of the wire about the dewatering roll or cylinder 4. A:Lso in this case the first stock ~et or stream impacts at polnt I upon the first wire, here the inner wire 6, and is pre-dewatered with the aid of an only schematically indicated dewatering element 9. Both of the residual stock jets or streams which are further retained separated from one another by the partition element 26 are first dewatered at the gap region or space between the wires 1 and 6 and at the curved region of the dewatering roll 4. Reference numeral II here likewise designates the point at which the uppermost stock jet or stream impinges against the wire 1. The dewatering at the gap or curved region preferably is accomplished towards the i~.
i ~ outside in the direction of the catch container 38. The ! ' :`. waker which has been sucked-off from the dewatering roll or cylinder 4, constructed as a solid forming roll, and out of .- the wire mesh of the wire 6 and which is then outwardly ~ propelled, is caught by the catch container or receptacle :~ 41.

Figure 4 illustrates an embodiment of a twin-wire former for a double-ply web, wherein the second or inner : wire or the like forms the jaclcet or outer surface of a ~, .~' .

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-- _ . _ .. . .

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~ ~72~B4 suction roll 44 which simultaneously constitutes the dewatering roll or cylinder. The lower wire 1, after being deflected about a breast roll 2 or the like, moves through a relatively short linear pre-dewatering path 3 aEter it has been guided while partially trained about the upper located suction roll or cylinder 44 and is then again guided back away from such suction roll 44 about a guide roll 30. The suction roll 44 is provided internally thereof with suction boxes 42 extending over More than one-half of its circumference, so that after outfeed of the . ~, ; wire 1 from the suction roll 44 the not particularly ; illustrated paper web remains adhering to the suction roll ~ 44 due to the vacuum prevailing in the suction boxes 42 and `~ is further dewatered. Thereafter it is then take-over or picked-up at a location following the suction boxes 42 at ~; the upper region of the suction roll 44 by a felt 43 or ~; equivalent structure with the aid of a couch roll 45 or the like in order to be further processed.

.
The headbox 46 is constructed as a double-ply headbox, and therefore, possesses apart from the outer boundary walls 19 and 20 only an inner partition or separation wall 47 which continues in the form of a partition or separation element 48 externally of the outlet openings or slices, which partition element then extends up ' to the gap region or space formed by the wire 1 with the jacket of the suction roll or cylinder 44. The lower first :~ `

~7~4~

stock jet or stream A impinges at point or location I at the first wire, here the wire 1, and is downwardly dewatered through the wire 1 at the essentially linear pre-dewatering path 3. The second upper stock jet or stream B impinges at point II at the jacket or outer surface of the suction roll 44 and is maintained separate from the lower stock jet or stream A and the web already preformed from such lower stock jet or stream A, as the case may be, by the action of the partition or separation element 48 to a point shortly past such point or location II. The dewatering of the stock jet or stream B then is accomplished exclusively upwardly through the suction roll or cylinder 44.

., .
~, A similar arrangement containing a headbox 46 for ~ a double-ply web is illustrated in the embodiment of Figure .~ 5. Once again there are utilised two wires 1 and 6 which ~; conjointly train or wrap about a dewatering roll or . cylinder 50 which, in this case, is constructed as an open ~ dewatering roll. Below the pre-dewatering path 3 of the ;~ 20 wire 1 there are arranged, in this case, dewatering . . ~
elements 49 by means of which there is accomplished at this ~ region or zone an extensive pre-dewatering of the lower .: stock jet or stream A. Since the dewatering roll 50 is not constructed as a suction roll, rather as an open dewatering .~ roll, the dewatering oE the upper stock jet or stream B
occurs behind the end of the partition or separation : ~;

.X17~84 element 48 both towards the outside through the already formed web fabricated from the stock stream or jet A and through the wire 1 and also inwardly through the wire 6 and :~.` the jacket or outer surface of the dewatering roll 50.
- This double-directed dewatering action upon the stock jet .~, . .
or stream B has been lndlcated by the arrows designated by ~;~ reference characters Bl and B2.

.;~ Continuing, in Figures 6 to 8 there has been . schematically illustrated a twin-wire former which . . .
. 10 essentially serves for the production of multi-ply .~ cardboard. The lower wire 1 possesses essentially the ,~.,, course of a standard longitudinal wire section in that it trains or wraps about a breast roll 2, and from that ' location is guided over dewatering elements in the form of ~.
., wire table element.s or suction ledges or foils 10 and -~, suction boxes 11 and 51, then is guided or trained about a ;: suction roll 52 and back over wire guide rolls 30 to the,~ ~
breast roll 2. sehind or downstream of the suction roll 52 ~; the paper web is deposited by means of a suction take-off ,.:
~......... 2~ roll 36, ~rom the wire 1 onto a felt 37 or equivalent web ' :' .~ pick-off structure. The twin-wire arrangement is located at the region between the suction box units 11 and 51 in that there is run together from above a second or upper wire 6 with the lower wire 1. The upper wire 6 is guided back over wire guide rolls 29.

:~ .
,~

~ ~ ~24~
Located behind the breast Loll 2 and above the lower wire 1 is a double-ply headbox 46 containing upper and lower boundary walls 18 and 17 for the headbox channel means as well as an intermediately situated partition or separation wall 47 which collectively delimit two outlet openings or slices 53 and 54. The partition wall 47 of the headbox 46 continues in the downstream direction of the outlet openings or slices 53 and 54 in the form of a partition or separation element 48 which extends into the region of the suction boxes 11. The lowermost or first stock iet or stream A effluxing out of the outlet opening or slice 53 is pre-dewatered and formed at the Eirst or lower wire 1 by means of the wire table elements or suction ledges or foils 10 or equivalent strllcture and a portion of the suction boxes 11 before, at a location behind the end ~ oE the partition element 48, there has already been .~ pre-dewatered the second stock jet or stream B at the remaining region of the suction boxes 11, this second stock jet B effluxing out of the outlet opening or slice 54.

Behind or downstream of the end of the suction box group or assembly 11 there is arranged forwardly of the run-in or inbound region of the twin-wire arrangement a secondary headbox 55 containing a single outlet opening or slice 56, from which effluxes the uppermost and last stock jet or stream C. At a location behind or downstream of the secondary headbox 55 the joined together wires 1 and 6 wrap a~72 :, with a slight curvature about a dewatering device 57 located within the upper wire 6. The dewatering device 57 likewise can consist of suction boxes. Behind the suction : ,:
~` dewatering device 57 the wires 1 and 6 are then curved in ; an opposite di.rection with a predetermined wrap angle about a dewatering or forming roll 4 located within the lower ` wire 1. The wrapping action about the dewatering roll or cylinder 4 is achieved by a subsequently arranged guide roll 58 located in the upper wire 6. After the guide roll 58 the wires 1 and 6 conjointly wrap again in an opposite direction of curvature about a guide roll 59 which is , ~
located within the lower wire 1, whereafter the upper wire 6 then returns over one of its guide rolls 29 and the lower :.
wire 1 tagether with the not particularly illustrated paper weh located thereon is further fed or guided over the suction boxes 51.

With this arrangement the curved path generating a dewateeing pressure, and through which there are conjointly guided both wires 1 and 6 against one another, consists of a number of sections which in each case have an alternate direction of curvature. Also in this case, howeverf the curvature increases in a stepwise fashion for the purpose of increasing the dewatering pressure. The surface 57a of the dewatering device 57 only possesses a slight curvature, whereas the roll jacket or outer surface of the dewatering roll or cylinder 4 already possesses a more intensified or :

:

.
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.. ..

. . .

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pronounced curvature. Also the wire deflection rolls 5~
and 59 which have a still smaller diameter, and therefore - .:
possess a still more intensified curvature, likewise -; contribute to the further dewatering action.
: .~
What is particularly noteworthy of mention for this arrangement is the fact that a further partition or separation element 60 is provided which, at the point or location 61, is hingedly connected with the upper boundary wall 18 of the first headbox 46 and limits towards the top the second stock jet or stream B. This partition element 60 is guided over the entire pre-dewatering path 3 up to the secondary headbox 55 and further into the gap region or ~- space between the wires l and 2, in order to also malntain separate at the region of the dewatering devices 57 the third stock jet or stream C from both o~ the already pre-formed webs of the stock streams or jets A and B. This arrangement, with appropriate dimensioning oE the partition or separation element 60 and the dewatering ratio, possesses the advantage that the stock jet C, which impinges at point II at the upper wire 6, need not be brought into direct contact with the already pre-formed web plies A and B, rather itself can be first pre-dewatered to a certain extent, so that during uniting of the ply C with the plies A and B there prevail approximately the same dewatering conditions. Consequently, there is avoided, on the one hand, that the already formed web plies A and B
:, .
~.
., ~ - 32 -~2~8~

will again be destroyed by the stock jet or stream C, and, on the other hand, it is however possible to regulate or control the dewatering action such that the web plies when joined together are still in a condition which requires a further dewatering at the twin-wire region, so that by ~irtue of the liquid transverse flows or currents there is obtained a better felting action and binding between the individual web plies, without the fibres of the plies appreciably admixing with one another. Consequently, this arrangement possesses an advantage for the fabrication of cardboard, particularly in relation to such wire sections or portions wherein finished formed and extensively pre-dewatered web plies are merely couched upon one another.

The embodiment of Figure 7 corresponds to that of Figure 6 with one single difference in that, here, instead of the continuous partition or separation element 60 there is provided a partition or separation element 60' which is :
attached at a stationary holder or support 62 which is ; independent of the headbox 46. This holder 62 is provided downstream oE the outlet opening or slice 54 of the headbox ,:, 46. The stock iet or stream B, after departing from the outlet slice or opening 54, initially is not limited towards the top, in order to then thereafter enter into the boundary region or space between the partition elements 48 and 60'.
';
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r ,~ ~
~inally, in Figure 8 there is disclosed an .~ embodiment wherein there is provided a.partition or separation ~ element 60" which first emanates from the lower boundary or .~ limiting wall 63 of the secondary headbox 55. The stock jet or stream B thus, in this case, moves from the first headbox 46 up ~ ~ .
~- to the secondary headbox 55 with an upwardly free surface and ~: then first moves below the partition element 60" at the region .
; of the secondary headbox 55. By means of the partition element .~ 60" this stocX jet or stream B is maintained separated over a 10 certain path or distance from the stock jet or stream C.
., ,:
,.`,'' '~
Since, in particular, the partition or separation elements 60 and 60' of the embodiments of Figures 6 and 7 limit towards the top of the second stock jet or stream over a longer path, they are advantageously provided with surfaces which produce microturbulence within the stock jet, in order to .~ prevent any de~locculation of the stock in the flow path where ' ';!'' ~
~- there has not yet been accomplished any dewatering of the ~, ~ relevant stock jet or stream.
'' ' The partition elements or equivalent structure are ` 20 advantageously retained by any suitable means over the region of their extent and, to the extent that they are not completely i~ rigidly attached, they can be adjusted in their position by ; appropriate adjustment devices, such as the adjustment device ,:
100 shown in the a~rarlcfement of Figure 1.

.. i !~

~ :
;~ ~
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'''' : .

Claims (39)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of forming a multi-ply paper web in a twin-wire former, comprising the steps of:
providing a first endless revolving wire and a second endless revolving wire;
conjointly passing both wires, while partially contacting one another and while under tension, through a curved path of travel generating dewatering pressure;
said two wires passing in relation to one another such as to form a converging space at a run-on zone at the curved path of travel and serving to receive therebetween a paper web which is in the process of being formed;
maintaining in separate relationship from one another over a predetermined path, by means of at least two partition elements, stock jets separately effluxing from outlet openings of a headbox and guided essentially in neighbouring plies;
at least two essentially rigid partition walls extending at least up to the region of said outlet openings of the headbox;
a respective one of each of said two essentially rigid partition walls being operatively associated with a respective one of said two partition elements;

at least one of said two essentially rigid partition walls being adjustable in position;
fixing said at least one essentially rigid adjustable partition wall in a desired position essentially corresponding to a desired velocity of a related stock jet which is bounded by said at least one adjustable essentially rigid partition wall, so as to ensure for a predetermined outlet velocity of said related stock jet from its outlet opening of the headbox;
said stock jets being maintained separate from one another over said predetermined path downstream of the outlet openings by the partition elements substantially extending in the direction of flow of the stock jets;
pre-dewatering at least a first one of the stock jets which neighbours a first one of both wires at said first wire without the action of the other wire defining a second wire and the dewatering pressure of the curved path in order to form a paper web ply; and directly introducing into the converging space formed by the wires at least the last stock jet for dewatering which is guided by a last one of the partition elements and which is not bounded towards the outside by a partition element.

2. The method as defined in claim 1, further including the steps of:

pre-dewatering the first stock jet and the further stock jets, with the exception of the last stock jet, at the first wire.

3. The method as defined in claim 1 or 2, further including the steps of:
performing the pre-dewatering at the first wire essentially by means of the inherent static and dynamic pressure of the liquid columns of the stock jets.

4. The method as defined in claim 1 or 2, further including the steps of:
controlling the pre-dewatering at the first wire by dewatering elements arranged at a rear side of the wire.

5. The method as defined in claim 1, further including the steps of:
subjecting at least the last stock jet and the web already formed at least from the first stock jet to an increasing dewatering pressure at a curved path possessing increasing curvature.

6. The method as defined in claim 1, further including the steps of:

maintaining the stock jets separated from one another by essentially completely rigid partition elements until deposition thereof at the first and second endless revolving wires.

7. The method as defined in claim 1, further including the steps of:
controlling guiding the individual stock jets by partition elements located externally of the outlet openings.

8. A method of forming a multiply paper web in a twin-wire former, comprising the steps of:
providing two web forming elements;
conjointly passing both web forming elements through a predetermined path of travel generating dewatering pressure;
said two web forming elements extending in relation to one another such as to form a converging space at a run-on zone at the path of travel and serving to receive therebetween a paper web which is in the process of being formed;
maintaining in separate relationship from one another over a predetermined path, by means of at least two partition elements, stock jets separately effluxing from outlet openings of a headbox and guided essentially in neighbouring plies;
at least two essentially rigid partition walls extending at least up to the region of said outlet openings of the headbox;

a respective one of each of said two essentially rigid partition walls being operatively associated with a respective one of said two partition elements;
at least one of said two essentially rigid partition walls being adjustable in position;
fixing said at least one essentially rigid adjustable partition wall in a desired position essentially corresponding to a desired velocity of a related stock jet which is bounded by said at least one adjustable essentially rigid partition wall, so as to ensure for a predetermined outlet velocity of said related stock jet from its outlet opening of the headbox;
said stock jets being maintained separate from one another over said predetermined path downstream of the outlet openings by the partition elements substantially extending in the direction of flow of the stock jets;
pre-dewatering at least a first one of the stock jets which neighbours a first one of both web forming elements at said first web forming element without the action of the other web forming element defining a second web forming element and the dewatering pressure of the path of travel in order to form a paper web ply; and directly introducing into the converging space formed by the web forming elements at least the last stock jet for dewatering which is guided by a last one of the partition elements.

9. The method as defined in claim 1, wherein:
said rigid partition walls serve to establish and maintain different velocity and pressure conditions in respective passageways within said headbox which are at least partially formed by said rigid partition walls, in order to thereby enable selective deposition of the separate stock jets at predetermined locations externally of the outlet openings of the headbox, so as to control the dewatering of the stock jets.

10. The method as defined in claim 1, further including the steps of:
influencing the outlet velocity of said related stock jet such that the same is higher than the outlet velocity of a precedingly deposited stock jet.

11. The method as defined in claim 1, further including the steps of:
influencing the outlet velocity of the related stock jet such that the same is higher than the velocity of travel of said first wire.

12. A twin-wire former for a papermaking machine for forming a multi-ply paper web, comprising:
headbox means;

at least two mutually separated stock infeed means for a stock suspension and a corresponding number of outlet openings provided for said headbox means;
boundary walls for bounding said outlet openings;
said boundary walls extending over the width of the headbox means and substantially parallel to the direction of flow of the stock suspension;
at least two partition elements arranged between stock jets of the stock suspension for maintaining separate from one another the stock jets over a predetermined path downstream of the outlet openings;
at least two essentially rigid partition walls extending at least up to the region of said outlet openings of the headbox means;
a respective one of each of said two essentially rigid partition walls being operatively associated with a respective one of said two partition elements;
means pivotably mounting at least one of said two essentially rigid partition walls to be adjustable in position;
means for fixing said at least one adjustable essentially rigid partition wall in a desired adjusted position essentially corresponding to a desired velocity of a related stock jet which is bounded by said one adjustable essentially rigid partition wall to ensure for a predetermined outlet velocity of such related stock jet from the related outlet opening of the headbox means;

a first endless revolving wire;
a second endless revolving wire;
a dewatering roll;
said first and second endless revolving wires conjointly at least partially wrapping about said dewatering roll;
said first and second endless revolving wires forming at their run on location at the dewatering roll a converging space for receiving a paper web which is in the process of being formed;
means defining a pre-dewatering path;
said first wire prior to contact with the dewatering roll being guided over said pre-dewatering path;
said pre-dewatering path including a starting portion;
said headbox means having at least one of its outlet openings located at said starting portion;
said partition elements cooperating with said starting portion of the pre-dewatering path in a manner such that only the first stock jet neighbouring the first wire impinges at the first wire; and at least the last partition element possessing a length such that the last stock jet supported by said last partition element is directly directed into the converging space between the wires.

13. The twin-wire former as defined in claim 12, further including:
a breast roll for guiding the first wire in an essentially linear path of travel through the pre-dewatering path.

14. The twin-wire former as defined in claim 13, wherein:
said means defining said pre-dewatering path including means located at the pre-dewatering path below the first wire for influencing the dewatering action.

15. The twin-wire former as defined in claim 14, wherein:
said influencing means comprise wire table means.

16. The twin-wire former as defined in claim 14, wherein:
said influencing means comprise suction ledge means.

17. The twin-wire former as defined in claim 14, wherein:
said influencing means comprise suction box means.

18. The twin-wire former as defined in claim 14, wherein:
said influencing means produce increasing negative pressure.

19. The twin-wire former as defined in claim 13 or 14, further including:
a wire shoe having a convex curved surface;
said wire shoe being arranged forwardly of said dewatering roll below the first wire;
said convex curved surface having a curvature which is less than the curvature of an outer surface of the dewatering roll; and said convex curved surface being at least partially wrapped by said second wire.

20. The twin-wire former as defined in claim 12, wherein:
said dewatering roll comprises a forming roll about which there is guided the first wire at the pre-dewatering path.

21. The twin-wire former as defined in claim 12, wherein:
said dewatering roll comprises a solid roll.

22. The twin-wire former as defined in claim 12, wherein:
said dewatering roll comprises a roll containing grid means arranged at the roll surface.

23. The twin-wire former as defined in claim 22, further including:
a suction box provided for said dewatering roll

24. The twin-wire former as defined in claim 12, further including:
a positionally adjustable deflection roll for influencing the converging space; and said second wire being guided by said deflection roll before joining-up with the first wire.

25. The twin-wire former as defined in claim 12, wherein:
said partition elements are structured as rigid partition surfaces between the individual stock jets.

26. The twin-wire former as defined in claim 25, wherein:
said fixing means comprises externally located adjustment means for adjusting the partition surfaces so as to assume a predetermined position.

27. The twin-wire former as defined in claim 25, wherein:
said partition surfaces are structured with respect to their pivotably mounting means such that they can be exchanged from externally of the headbox means.

28. The twin-wire former as defined in claim 25, wherein:
said partition surfaces possess a curved configuration in accordance with wire guides.

29. The twin-wire former as defined in claim 25, wherein:
said partition surfaces are structured to possess at least in part a surface structure which produces a microturbulence.

30. The twin-wire former as defined in claim 25, wherein:
at least two of the outlet openings of the headbox means comprise neighbouring outlet openings of a multi-ply headbox;
the neighbouring boundary walls of said two outlet openings being formed by a common partition wall; and a partition element directly merging at said common partition wall.

31. The twin-wire former as defined in claim 30, especially for a double-ply web, wherein:
a single partition surface is provided which is rigidly connected with the common partition wall; and means for adjusting both outer boundary walls of the outlet openings for influencing the stock jet.

32. The twin-wire former as defined in claim 30, especially for a triple ply web, wherein:
the partition wall neighbouring the first wire and the partition surface are substantially rigid structures;
means for pivotably mounting the second partition surface and the related partition wall; and means for adjusting outer boundary walls of the headbox means.

33. The twin-wire former as defined in claim 32, wherein:
said means for pivotably mounting said second partition surface and the related partition wall enables adjustment of said second partition surface and said related partition wall.

34. The twin-wire former as defined in claim 30, especially for a triple-ply web, wherein:

both of the partition walls and/or the partition surfaces are structured as a channel-shaped unit connected at its outer edges.

35. The twin-wire former as defined in claim 25, especially for a triple-ply web, wherein:
the outlet opening of the last stock jet located downstream of the outlet openings for two other of said stock jets defining first and second stock jets is arranged at a location at which there has not yet been terminated the forming of the web from the second stock jet.

36. The twin-wire former as defined in claim 35, wherein:
the partition element for separating the second stock jet and the last stock jet begins at a location downstream of the outlet openings for the first stock jet and the second stock jet.

37. The twin-wire former as defined in claim 12, wherein:
said rigid partition walls serve to establish and maintain different velocity and pressure conditions in respective passageways within said headbox which are at least partially formed by said rigid partition walls, in order to thereby enable selective deposition of the separate stock jets at predetermined locations externally of the outlet openings of the headbox, so as to control the dewatering of the stock jets.

38. The twin-wire former as defined in claim 12, wherein:
said partition elements possess a length sufficient to preclude commingling of any of the stock jets within the headbox means.

39. A twin-wire former for a papermaking machine for forming a multi-ply paper web, comprising:
headbox means;
at least two mutually separated stock infeed means for a stock suspension and a corresponding number of outlet openings provided for said headbox means;
boundary walls for bounding said outlet openings;
said boundary walls extending over the width of the headbox means and substantially parallel to the direction of flow of the stock suspension;
at least one partition element arranged between stock jets of the stock suspension for maintaining separate from one another the stock jets over a predetermined path downstream of the outlet openings;
at least one essentially rigid partition wall extending at least up to the region of the outlet openings of said headbox means;

said at least one essentially rigid partition wall being operatively associated with said at least one partition element;
means pivotably mounting said essentially rigid partition wall to be adjustable in position;
means for fixing said at least one adjustable essentially rigid partition wall in a desired adjusted position essentially corresponding to a desired velocity of a related stock jet which is bounded by said one adjustable essentially rigid partition wall to ensure for a predetermined outlet velocity of such related stock jet from the related outlet opening of the headbox means;
a first endless revolving wire;
a second endless revolving wire;
a dewatering roll;
said first and second endless revolving wires conjointly at least partially wrapping about said dewatering roll;
said first and second endless revolving wires forming at their run-on location at the dewatering roll a converging space for receiving a paper web which is in the process of being formed;
means defining a pre-dewatering path;
said first wire prior to contact with the dewatering roll being guided over said pre-dewatering path;

said pre-dewatering path including a starting portion;
said headbox means having at least one of its outlet openings located at said starting portion;
said partition element being structured and guided such that at the starting portion of the pre-dewatering path only the first stock jet neighbouring the first wire impinges at the first wire; and said partition element possessing a length such that a last stock jet supported by said partition element is directly directed into the converging space between the wires.