EP0049254A1

EP0049254A1 - Headbox for a paper machine

Info

Publication number: EP0049254A1
Application number: EP81900825A
Authority: EP
Inventors: Alvi Kirjavainen
Original assignee: Valmet Oy
Current assignee: Valmet Oy
Priority date: 1980-04-11
Filing date: 1981-04-03
Publication date: 1982-04-14
Also published as: ES8300910A1; BR8108308A; IT8121066A0; ES501265A0; FI69664C; CA1157303A; JPS57500515A; FI801167A; IT1194781B; WO1981002903A1; FI69664B; SU1218929A3; IT8121066A1

Abstract

Dans une machine a papier, un bac de tete possedant au moins deux passages d'ecoulement de masse de papier, comprenant des generateurs de turbulence. Le chapeau de distribution du bac de tete possede une forme segmentee, consistant en deux ou plusieurs segments d'alimentation de suspension de pate (21, 22; 121, 122, 123; 131, 132). Chaque segment d'alimentation communique avec un generateur de turbulence relatif (40a; 40b; 41, 42, 43; 141, 142, 143, 144). Les generateurs de turbulence se composent d'une pluralite de passages d'ecoulement paralleles (S1; S2; S3) definis par des elements partiels (71; 72; 73, 74) entre et/ou a l'interieur de ceux-ci. Les elements partiels sont disposes entre les parois (20', 23, 24; 20', 51, 52; 53, 54, 55) du bac de tete et de ses segments partiels. Le bac de tete a une forme de cassette (Fig. 1), le nombre, la construction et/ou les generateurs de turbulence des segments partiels etant interchangeables en fonction des differentes qualites du produit.In a paper machine, a head tray having at least two paper mass flow passages, including swirl generators. The head pan dispensing cap has a segmented shape, consisting of two or more pulp slurry supply segments (21, 22; 121, 122, 123; 131, 132). Each feed segment communicates with a relative turbulence generator (40a; 40b; 41, 42, 43; 141, 142, 143, 144). The turbulence generators consist of a plurality of parallel flow passages (S1; S2; S3) defined by partial elements (71; 72; 73, 74) between and/or within them. The partial elements are arranged between the walls (20', 23, 24; 20', 51, 52; 53, 54, 55) of the head box and its partial segments. The headbox has a cassette shape (Fig. 1), the number, construction and/or swirl generators of the partial segments being interchangeable according to the different qualities of the product.

Description

Headbox for a paper machine

The present invention concerns in a paper machine or equivalent, a headbox having two or more pulp stock flow passages comprising turbulence generators, and through which paper suspension of one or several kinds is supplied by a lip slice (or slices) onto web forming means.

Ganged headboxes are used e.g. in the manufacturing of cardboards and of tissue paper. In that case the web is composed of two or several pulp grades, which are supplied by means of a ganged headbox, or by separate headboxes, to the forming section of the paper machine.

Although the headbox constituting the subject of the present invention is mainly intended for the making of webs built up of a plurality of different pulp grades, of which the stock jet forming the web is assembled, it should be emphasized that such headboxes also are within the scope of the invention in which one single pulp grade is used, but which is distributed (at the initial end of the flow path at least) to travel by two different paths, with aims which will become apparent later on.

Regarding the state of art associated with the invention, the Finnish Patent No. 27191 shall be cited as an example. Therein is disclosed a headbox construction presenting within the lip cone a separator tongue dividing the lip cone into two parts. The said two parts communicate with supply passages carrying different pulp grades.

As regards the state of art closely associated with the present invention, reference is made to the same applicant's Finnish patent application No. 800018 (Jan. 2, 1980). In said application is dis- closed a turbulence generator for a headbox in a paper machine or equivalent, having a plurality of flow passes in parallel, causing turbulence in the pulp stock flowing through these passes. What is essentially novel in the turbulence generator of the present invention is that the turbulence generator consists of a plurality of parallel, and preferably mutually identical, partial elements which. have been disposed between the walls of the headbox, said partial elements being shaped so that in their interstices and/or partially at least within them are formed parallel flow passes for the pulp stock. In the ganged headbox of the present invention, the turbulence generator of said Finnish patent application is utilized in a way enabling new, practically important advantages to be gained.

The drawback of ganged headboxes known in the art has however been that when the grade being produced on the paper machine is changed, one has always been compelled to purchase a new headbox beacuse headboxes of prior art have been of a fixed construction and have had no capacity for modification. Since the price of a headbox is quite more than a million dollars, any change of output grade (or its substantial modification) implies remarkable expenditure and pro¬ longed shut-downs. It has not been possible either, in headboxes of prior art, to adjust to an optimum the construction of the headbox and the properties resultant therefrom in response to the variation of various production parameters, because such adjustments require exceedingly expensive, and permanent, structural changes in any fixed headbox construction of prior art.

The object of the present invention is to provide a ganged headbox which is easily and rapidly modifiable to fit the desired production grade and/or adjustable to be optimized in various characteristics. It is a further object of the invention, to provide a'ganged headbox allowing the number of pulp courses to be varied, that is to increase or reduce their number as required in each instance. It is an additional object of the invention, to provide a headbox modifiable in its essential parts, also regarding its turbulence generators, so that the construction of the headbox is rapidly, and with compara¬ tively minor cost, adjustable accurately enough to fit each pro-

_* duction grade and the special requirements imposed by the conditions of production.

In order to attain this aim, and others that will become apparent^' later on, the invention is mainly characterized in that the distri-

c:.: ^"' bution header of the headbox is of segmentary design, consisting of two or more pulp stock suspension supply segments; that said supply segments communicate each with its own turbulence generator, these generators consisting of a plurality of partial elements defining between and/or within themselves flow passes running in parallel and disposed between the walls of the headbox and/or its partial segments; and that the number, construction and/or the turbulence generators of the partial segments are exchangable as required by different output grades.

In a favourable embodiment of the invention is carried out a ganged headbox provided with turbulence generator and with separate segment distribution header and wherein symmetrical oppositeness of the segmented distribution header with respect to flow has been imple- mented up to the lip cone, whereby the disturbances of flow affecting the transversal profile in the header are compensated in part. By the present invention the headbox design can be made in¬ expensive because, in principle, for instance merely a partition sheet with one thinned-down end divides the single (not ganged) headbox into two parts.

The cassette-resembling, readily modifiable construction of the invention is adaptable to fit any desired flow velocity, con¬ sistency, pulp grade and desired level of turbulence. It is possible to provide more numerous or fewer turbulence generator cassettes or to exchange them in_.case of a substantial change in output grade. By the expedients mentioned, new one, two, three-gang etc. headboxes can be modified, consistent with the intended use in each case. In an advantageous embodiment of the invention, the upper and lower frame halves of the turbulence generator cassette have been di¬ mensioned to be fully symmetrical, whereby they can be used to compose any desired number of generator cassettes with completely equal securing and mating faces, independent of the height of flow cross section of each cassette.

In the present invention have been utilized the favourable properties of the above-mentioned Finnish patent application No. 800018 in such manner that new advantages have been gained. The invention of said Finnish patent application affords the association with the seg- mentary and cassette-type design as taught by the present invention, also of the fast and easy assembly and disassembly feature, and adjustability feature, of the turbulence generators employed in the partial segments, to fit each particular production grade and the design of the headbox in its other parts .

In the following, the invention is described in detail with reference being made to certain embodiment examples of the invention, presented in the figures of the attached drawing, to the details of which the invention is in no way narrowly confined.

Fig. 1 presents, in elevational view, a twin-gang headbox according to the invention, intended in the first place to serve as headbox in a tissue paper machine.

Fig. 2 presents, in like manner as Fig. 1, a triple gang headbox, but in which number of gang members may be varied with comparative freedom.

Fig. 3 presents a twin-gang headbox design according to the invention in a manner equivalent to Figs 1 and 2.

Fig. 4 shows the section along the line IV-IV in Fig. 1.

Fig. 5 shows a structural design for the turbulence generator, and at the same time Fig. 5 is the section along line V-V in Fig. 2.

Fig. 6 presents a structural design of the turbulence generator, and at the same time Fig. 6 is the section along line VI-VI in Fig. 3.

Fig. 7 is the section along line VII-VII in Fig. 3.

The lip slice L of the headbox has been disposed adjacent to the supply throat G defined in contiguity with the breast rolls 10 and 13. This throat G is defined between the wires 11 and 14, or

O ^"v.^' equivalent fabrics, directed to run over the rolls 10 and 13. The headbox of the invention is used to supply the pulp stock, or various different stocks, in between the wires 11 and 14, where the forming of the web W takes place in a manner known in itself in the art through twin-wire formers. Although in the following the invention is described with reference to such embodiment examples in which a twin-wire former is employed, it should be understood that the head¬ box of the invention may in certain instances also be applied in single-wire formers or in those formers which have a single-wire initial portion (most usually fairly short) with a twin-wire forming region following thereafter.

The lower lip beam 20 of the headbox structure is carried by the pivot axle 17 and 18 on the supporting beams 15. The lower lip structure 20 has an upper wall 20' participating in defining the stock suspension flow passage. The lower lip structure 20 is ad¬ justable of its position. To this purpose there has been provided in conjunction with the pivot axle 17, a slide 16 moving on guides 17' and which is displaced by means of a screw and a gear box 16' . Similarly, the lower lip structure is supported at its lower end by a supporting lug 18', which has been attached over a guide 19 to the end face of the lower lip structure 20. Between the supporting lug 18' and the lower lip structure 20 has been inserted a screw driven by the gear box 19'. The supporting lug 18' has been attached by the pivot axle 18.to structures which are supported by the guide 17' from the headbox carrying beam 15. The means just described may be used to displace the lower lip structure ^'20 in the direction of arrows A and B, and thereby an expedient and proper positioning of the lower lip structure 20 and of its upper wall 20' is obtained in each instance.

The headbox comprises an upper wall structure 32,33, consisting of a beam 33 to which the upper lip beam 32 attaches by the pivot 31. The socket of the pivot 31 is defined between the bodies 29 and 30. The body 29 has been affixed to the end flange 28 of the beam 23 constituting the upper wall of the headbox. The lip plate 36 is adjustable by means of a plurality of parallel screws 35, which are rotated by the hand wheels 37, by mediation of arms 34'.. It is in this manner that the fine adjustment of the lip slice L is accomplished in a manner known in itself in prior art. The upper lip structure 32,33 is swivelled about its pivot 31 by the aid of screws operated by the gear boxes 38. Said screws and gear boxes 38 have been connected by cardan shafts 39 and 39' between the beam 33 and the top cover structures of the headbox.

As taught by the invention, the distribution header of the headbox consists of a plurality of segments one upon the other. As depicted in Figs 1 and 4, there are two such segments on top of each other, that is, the segments 21 and 22, and which are separated by the partition 24. Within the segments 21 and 22 are confined the flow passages K_. and K„ of the distribution headers, their directions of flow F_. and F„ opposing each other. In Fig. 4, the entry of pulp stock into the flow passage K_, has been indicated by the arrow F_.. ^{r &} 1 ^J lm and its exit, by the arrowF. . Similarly, the flows in the passage

K„ have been indicated with F„. and F„ 2 2m 2out

An essential feature in the twin-gang headbox of Figs 1 and 4 is the above-described segmented distribution header 21,22, consisting of symmetrically opposed segments having separate input and bypass flows. One achieves hereby a symmetrical and uniform flow distri¬ bution in the transverse profile because the flow disturbances of the opposite segment are partly compensated in the final lip slice flow. One important structural component in Figs 1 and 4 is also the set of turbulence generators 40a and 40b, twisting flow passes S.. having been established in these units, providing in periodically expanding configuration counter-surfaces changing the direction of flow and causing turbulence. At the ultimate end of the passages S₁ , where the lip cone region S, starts, there are tail vanes 71a directed symmetrically in opposition to the vanes 71b of the other segment. The cross-flow produced by the vortices from the bumping surfaces in the periodically expanding passes S, , and by the said tail vanes 71a,71b, efficiently levels out pressure pulsations and disintegrates fibre floes and clouds, thereby also promoting a good paper base formation.

- OB O As shown in Figs 1 and 4, the turbulence generators 40a and 40b consist e.g. of partial elements 71 die-cast of plastic, of which only one type is required. The said cross-flows are achieved by placing the partial elements in the mutually superimposed turbulence generators 40a,40b with different sides up. The partial elements 71 have been provided with wide holes, through which the partial elements have been braced by bolts 70 between the walls 20' and 23 of the headbox. The segments 21 and 22 are supported by the structures 25 and 26, between which at the point 27 the partition 24 between segments has been affixed. The partition 24 has a tapering tip portion 24', whereafter follows the tapering lip cone part S,, which terminates in the lip aperture L.

As shown in Fig. 2, the headbox comprises, disposed between the walls 20' and 55, three separate supply segments 121,122 and 123, ^■ communicating each with its own turbulence generator 41,42,43. After these turbulence generators 41,42,43 follow, separated by the vanes 56,57, flow passages S-., which terminate at the sharp edges 56' ,57' of the vanes 56 tapering down in the direction of flow, and where- after immediately then does follow the lip cone part.

In the triple-gang headbox of Fig. 2, the turbulence generators 41,42,43 consist of mutually separate entities, so-called cassettes, of which one may assemble turbulence operating in single, twin, triple etc. gang arrangement with the greatest conceivable variety of entity and gang grouping dependent on velocity, pulp stock grade, basis weight and other factors influencing the output grade and quality. It is specifically essential in this construction that it is possible with certain definite basic unit components to obtain by their assembly a variety of operational units for production purposes within an immenseliy wide range; this implies that in the case of a radical change of output grade or brand there is no need to procure a whole new headbox. This is nowadays a major problem in such cases where an exceptional grade is being produced during a limited period of time only.

The turbulence generators 41,42,43, the cassettes, of which the design

OMPI PO is readable from Fig. 2, consist^'of upper and lower parts 20',51;52, 53 and 54,55, between which is mounted a turbulence component like that shown in Fig. 5, for instance.

The lowermost turbulence generator cassette 41 in Fig. 2 has its lower part formed by the lower lip wall 20' , with which the upper part connects by securing shoulders 61 and 64 in front and in the rear. The front shoulders 64 provide, on the side of force binding, a fixing shoulder for the socket of the joint 58 of the lip plate 56, its dimensioning being such that the shoulder projections of any one of the alternatives are precisely secured in each and any joint socket. The mode of fixing of the centremost generator cassette 42 is similar to the foregoing. It is specifically significant in the design, as regards the control of forces, that the number of generator cassettes 41,42,43 may be increased or reduced, while the joint socket 58 and the rear shoulders 61,62,63 operate as an accurate and precise locking in each and every alternative.

Upon the wall 55 of the upper generator cassette 43 there is the upper lip supporting beam 23 with socket for the joint 31 of 'the upper lip 32 and with displacing gear box base. It is a characteristi feature of this design that the securing shoulder 66, in front, of the supporting beam 23 is exactly equivalent to the dimension of one half of the joint socket, whereby the supporting beam 23 with its upper lip 32 can be conveniently secured to the shoulder locking means of any alternative, no matter whether this is a single, twin, triple or multiple gang alternative. In the rear, the equivalent shoulder locking 63 is with reference to the supporting beam 23 by the locking rail 63' .

The intermediate lip plates 56,57 located in the lip cone are pivotally carried by journal pins 58 projecting through the side

« walls into the above-mentioned joint sockets and which are used to adjust the position and the "floating" operating attitude of the lip plate 56,57. The aim has been kept in mind to make the hollow structure of the plate 56,57, preferably made of Teflon-coated aluminium, of reinforced plastic or equivalent, such that it has

OM substantially the same specific gravity as the pulp stock.

Fig. 3 shows a multiple gang headbox, its construction having as an essential feature, as in Fig. 2, turbulence generators 141,143 and 142,144 operating in gang 1,2,3 etc. cassettes having for flow guidance and turbulence elements"; for instance, turbulence vanes 73, 74 like those in Figs 6 and 7. A deviation from the preceding is in the embodiment of Fig. 3 the circumstance that the flow formation periods are the same as in the SYM-NOZZLE (Trademark) headboxes presently used by the same applicant, and also the circumstance that, if desired, one may in this design apply flow forming elements with a similar principle of operation (such as e.g. a bunch of pipes, an equalizing chamber, a lamellar portion or equivalent). Thus, after the distribution header segment 131 in the lower cassette part is found a part 141 equivalent to a pipe set part, whereafter follows an equalizing chamber part S_fi and, after this, a turbulence part 143 corresponding to' a lamellar part. Similarly, after- the distribution header segment 132 follows the part 142 equivalent to a pipe set part, the equalizing chamber S-, and the turbulence part 144. The said b chambers and turbulence generators and equalizing parts are confined between the walls 20',51,52 and 53.

The set of turbulence vanes 72 shown in Fig. 5 is mainly used in the turbulence generator 41,42,43 of Fig. 2. The set of flow passes S„ of Fig. 5 is formed in a flow directing part starting on the distribution header side and serving the task of directing the transversal distribution header flow to parallel the machine direction. Hereafter follows a twisting, and periodically expanding, equalizing part, its bumping surfaces and change of flow direction with its turbulence efficiently levelling out pressure pulsations, and disintegrating fibre floes and clouds. In the wider flow passage in the machine direction, the final direction of flow is stabilized, and the actual turbulence level required for paper formation and its configuration become determined at the vertical and horizontal level tail vanes at the ultimate end.

The set of flow guiding vanes 73 of Fig. 6 is more straight-lined and simple of its construction because its main task is to direct the distribution header flow of Fig. 3 to parallel the machine direction, by the aid of its set of passes S ".

The set of turbulence vanes 74 depicted in Fig. 7 consists of vertica and horizontal projections narrowing after the bumping surface adjacent to the equalizing chamber, stepwise, and terminating in the so-called tail vane part. It is essential in view of structures dis¬ closed in prior art, that the flow pattern on the equalizing chamber side contains horizontal projections disposed crosswise with regard to the vertical and by the breadth dimensioning of which it is easy to obtain an open flow cross section conforming to the dimensioned optimum velocity, and the best possible spacing of turbulence vanes. The flow resistance of the bumping surface efficiently damps the flow disturbances in the equalizing chamber. In the stepwise expandin set of flow passes S ' successive vortex zones are formed, which in the ultimate tail vane part attain a finely distributed and short- period microturbulence level, which renders possible a uniform paper base formation.

In Figs 4,5,6 and 7 have only been shown some structural examples of the partial elements of the rubulence generator. It should be understood that within the scope of protection of the invention the design of these partial elements may greatly differ from that which has been shown in the said figures. One may for instance employ all those partial elements which have been disclosed in the same appli¬ cant's Finnish patent application No. 800018, or any other partial elements which may be appropriate to the purpose of application in hand.

In the advantageous embodiment of the invention in Fig. 2, the superimposed headbox segments in cassette construction 121,41;122, 42;123,43 constitute parallel flow passages for the pulp stock, the principal directions of flow in these being radial with reference to each other in such a way that the planes of the principal flow directions intersect substantially at the lip slice L. Although in the foregoing paper machines in general have been con¬ sidered, it is natural that the headbox of the invention may also be applied in other equivalent machines, in cardboard machines for instance.

In the following are stated the claims, various details of the invention being allowed to vary within the scope of the inventive idea thereby expressed.

Claims

1. In a paper machine or equivalent, a headbox with two or more paper stock flow passages, comprising turbulence generators and through which paper pulp suspension of one or several grades is supplied by mediation of a lip slice (L) or of lip slices onto web forming means, characterized in that the distribution header of the headbox is of segmental design, consisting of two or more pulp suspension supplying segments (21,22;121,122,123;131,132) ; that said supplying segments communicate each with its own turbulence generator (40a;40b; 1,42,43;141,142,143-,144) , these latter consisting of a plurality of partial elements (71;72;73,74) confining between and/or within temselves parallel flow passes (S-.;S„;S,) and which have been disposed between the walls (20' ,23,24;20' ,51,52:53,54,55) of the headbox and of its partial segments; and that the headbox is in such manner cassette-designed (Fig. 1) that the numbers, construction of the partial segments and/or the turbulence generators of the partial segments are exchangeable to fit the grades .that are being produced.

2. Headbox in a paper machine or equivalent, characterized in that the flow passage of the lowermost partial segment of the headbox is confined by the upper wall (20') of the lower lip structure (20), preferably position-adjustable, of the headbox; and that the upper wall of the topmost partial segment of the headbox consists of the upper lip structure (23,32) of the headbox.

3. Headbox according to claim 1 or 2, characterized in that the headbox comprises two partial segments one upon the other and which are separated by a partition (24) extending in between the distri¬ bution header segments (21,22) and the turbulence generator segments (40a,40b) into the region of the converging lip cone part of the headbox.

_*

4. Headbox according to claim 1,2 or 3, characterized in that in distribution header segments immediately one upon the other the pulp suspension flow directions (F.. _>F ) are mutually opposed.

5. Headbox according to claim 1,2,3 or 4 in a paper machine or equivalent, characterized in that each distribution header segment and/or turbulence generator segment has its own bottom wall and cover wall and that said walls or part of them at least has been assembled by means of groove-and-projection arrangements (61,62,63,64,65,66) or equivalent, operating as quick-locks, to form one single headbox entity.

6. Headbox according to claim 1,2,3,4 or 5 in a paper machine or equivalent, characterized in that after the turbulence generators the pulp suspension flow passages running side by side are separated by one or several lip plates (56,57) attached at their front end pivotally to the headbox structures and preferably tapering down towards the lip aperture (L) and having a specific gravity substantially the same as that of the pulp suspension.

7. Headbox according to claim 1,2,3,4,5 or 6, char^'acte.rized in that the principal directions of the superimposed segments of cassette- design of the headbox have been so radially arranged that the radial planes placed to contain said principal directions intersect in the region of the lip slice (L) of the headbox.