HEADBOX AND ARRANGEMENT AND METHOD FOR MOUNTING A VANE THEREOF

Abstract: A headbox in a former for wet-forming of a fibre web has vanes (14) which separate channels (15) in the slice chamber (8) of the headbox, which channels communicate with turbulence channels (6), each vane being mounted to an anchoring element (10) with an arrangement, which comprises a pivot member (16) on the vane and an engagement groove (11) in the anchoring element. In accordance with the invention, the mounting arrangement further has an assembly bar (23) with a protrusion (24) for being received in said engagement groove to form a rigid joint and a journalling groove (25), arranged at a distance from the anchoring element and with a side opening (26) opens towards the vane (14) and having opposite pivot surfaces (27). The pivot member (16) of the vane is arranged to be received in the journalling groove (25) to co-operate with its pivot surfaces (27) to form an axis of pivot (28). The invention also relates to such a mounting arrangement and a method for mounting a vane by means of such a mounting arrangement.

Description: Headbox and arrangement and method for mounting a vane thereof The present invention relates to a headbox for delivering a jet of stock to a forming zone in a former for wet-forming a fibre web, comprising - a slice, having a slice chamber and a slice opening, - a turbulence generator, comprising - a plurality of turbulence channels, arranged in at least two rows across the machine direction and opening out into the slice chamber, and - an elongate anchoring element, arranged between two adjacent rows of turbulence channels and having a continuous engagement groove, which is open in towards the slice chamber, - at least one vane, arranged in the slice chamber to separate two channels from each other, each channel communicating with one of said rows of turbulence channels, which vane comprises a pivot member, extending across the machine direction, and - an arrangement for mounting the vane to said anchoring element, which mounting arrangement comprises said pivot member of the vane and said engagement groove of the anchoring element . The invention also relates to an arrangement for mounting a vane in a headbox for delivering a jet of stock to a forming zone in a former for wet-forming a fibre web, which headbox comprises a slice, having a slice chamber and a slice opening, a turbulence generator, comprising a plurality of turbulence channels, arranged in at least two rows across the machine direction and opening out into the slice chamber, and an elongate anchoring element, arranged between two adjacent rows of turbulence channels and having a continuous engagement groove, which is open in towards the slice chamber, which vane is arranged in the slice chamber to separate two channels from each other, each channel communicating with one of said rows of turbulence channels, and which vane comprises a pivot member, extending across the machine direction, which mounting device comprises said pivot member of the vane and said engagement groove of the anchoring element . The invention also relates to a method for mounting a vane to an anchoring element in a headbox, which anchoring element extends between two rows of turbulence channels that open out into channels on both sides of the vane, and the side of said anchoring element facing the vane has an engagement groove with a pre-determined cross section, and which vane has a pivot member for pivotable journalling of the vane in relation to the anchoring element . SE-511 684 C2 describes a multi-layer headbox with vanes that each have a connection bar with a flexible engagement part for pivotable journalling of the vane to an anchoring element that is fixedly arranged between two rows of turbulence channels. The headbox is of the rectilinear type, i.e. at least the intermediary channels extend in line with the turbulence channels. However, the described fastening of the vane directly to the anchoring element is not applicable in the case of a headbox of the angled type, in which all the vanes and channels in the slice chamber extend at an angle to the turbulence channels, as the axis of pivot is located inside the anchoring element such that the pivoting capacity of the vane would be insufficient as well as the vane and connection bar being too close to the opening of the turbulence channel. Furthermore, the described fastening is not applicable in the case of an anchoring element having a dovetail-shaped groove for the connection bar. Pluralities of different solutions have been suggested for mounting a vane aligned at an angle to an anchoring element in the turbulence generator. US-4,133,715 describes turbulence vanes that each have a connection bar consisting of a flexible material and having an extended intermediate part and a wedge-shaped engagement part that is received in a dovetail groove. A change in the position of the vane, due to differences in pressure between the two channels separated by the vane, result in corresponding bending of the long intermediate part. Repeated bending results in flexure fatigue in the material and a risk of the intermediate part fracturing. The bending of the intermediate part also causes the vane to be displaced in its plane so that the downstream end of the vane changes its position relative to the slice opening in proportion to the magnitude of the bending of the intermediate part. Such a change in position of the downstream edge is not acceptable in respect of a stock-separating vane in a multi-layer headbox, as it would affect the layers of the jet of stock detrimentally in the proximity of the slice opening. WO 98/50625 describes vanes that each have a connection bar made of stainless steel. The connection bar has an extended intermediate part that is curved to retain the vane at an angle to the turbulence channel . The engagement part of the connection bar is dovetail -shaped to co-operate securely with the dovetail groove in the engagement part to provide a rigid joint. It will be appreciated that the vane and the connection bar are subjected to significant and repeated strains when differences in pressure arise between the two channels that are separated by the vane, so that there is a significant risk of a fracture occurring in the vane adjacent to the connection bar and/or in the connection bar, especially at the root of the dovetail-shaped engagement part. The last-mentioned document acknowledges the problem with such a rigid anchoring of the vane and therefore suggests a modified connection bar, the engagement part of which is fashioned with a circular cross section to form a joint so that the vane can pivot. A potential pivoting of the vane results in a change in position of the downstream edge of the vane, which is not acceptable for a stock-separating vane in a raulti-layer headbox. However, it will be appreciated, of course, that the pivoting function is lost after a relatively short period of operation, as the circular joint will get wedged and assume a stationary position impervious to pivoting, which wedge locking occurs because of the tensile forces created by the stocks in the vane. Accordingly, the modified connection bar will function in the same unsatisfactory way as the first described connection bar with the rigid dovetail joint. When a vane and/or its connection bar with the fastening systems described above has (have) been damaged, there has hitherto been no alternative and better arrangement for the mounting of the vane to reduce the operational disruptions and replacements. This applies particularly to headboxes where the anchoring elements of the turbulence generator are provided with dovetail grooves and the vanes are positioned at an angle relative to the turbulence channels. Further suggestions for fastening a vane to a turbulence generator are described in SE-440 924, US-4, 617, 091, US-4, 941, 950 and US-5 , 013 , 406. The object of the present invention is to eliminate the problems mentioned above and to provide a mounting arrangement for the vanes of the headbox that is simple in its construction and easy to install and which reduces the risk of damage to the vanes and their potential connection bars. The invention offers a simple and s; 0 τi IP tr rt φ •o iΩ CQ - 1 Ω H TJ rt < 0 0 <τS Hi Φ 1 SD h-x rt H SD Hi 3 Hi H- X Hi H- Hi ii X h-x 4 H{ SD 0 t 3 H- 0 SD T3 • τS Hi μ- 0 h- SD tr ø -x 0 0 Φ 1 * 1- φ <! 0 0 φ φ 0 0 μ- 3 SD i 0 • φ φ SD sQ LQ SD 0 rt Φ Hi Hi 0 -> X TJ 0 0 Hi 3 rt 0 &• U3 Hi SD O Ω Φ 0 ø μ- SD 0 rt SD Φ 0 H- H- H- rt <! tP Φ φ H < μ- SD Ω rt o CQ P. Ω P. 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SD Q £D h-x -• 3 0 rt ø <! rt l-h 3 T-i i- * X 3 SD 3 SD 0 μ- & φ IP 0 μ- Φ t SD φ Φ 0 . h- χ Φ μ- Ω μ- Φ * 0 φ SD ø Φ Hi ø X SD CQ 0 ø 3 0J 0 μ- ra X Cb 3 rt SD U.! 4 0 rt P. 3 rt rt Hi rt ra h-x 0 CQ ø < 0 rt Φ X i rt Φ £ μ- 0 μ- IP SD Hi Hi P, μ- 0 SD SD SD ø- 0 rt Φ SD 0 £, -S SD rt 0 0 μ- CQ ii Hi X 0 rt Φ Pi tr h-> 0 0 μ- H- X Φ Φ H 3 rt 0 SD Pi μ- Φ h-> - rt 0 μ- 3 ID 0 0 0 rt CQ SD ø X CP ω μ- φ Hi < ø- μ- cp SD CQ Φ Φ CQ SD Figure 1 shows schematically parts of a multi-layer headbox with mounting arrangements for its vanes. Figure 2 shows, in an enlarged view, two vanes with mounting arrangements in accordance with Figure 1. Figure 1 shows schematically a headbox, designed to deliver a three-layer jet of stock into a gap 1, leading to a forming zone in a twin-wire former of roll type. The twin-wire former has an inner forming wire 2, a rotatable forming roll 3, an outer forming wire 4 and a rotatable breast roll 5. The headbox has a turbulence generator, comprising a group of turbulence channels 6 and a slice 7, arranged downstream of the turbulence channels 6 and containing a chamber 8 which, from its upstream end, converges in the direction of the flow of stock and, at its downstream end, terminates in a slice opening 9. The turbulence channels 6 are arranged in three sections for feeding, for instance, three different stocks into the slice chamber 8, the lower section and the upper section each having two rows of turbulence channels 6 arranged closely adjacent to each other and the middle section having four such rows of turbulence channels 6. The rows of turbulence channels 6 extend across the machine direction and adjacent rows of turbulence channels 6 are separated by elongate, steady anchoring elements 10 that extend across the machine direction. The anchoring element 10 has an elongate, continuous engagement groove 11 (see Figure 2) , which is open at its ends turned away from each other and has a side opening 12, facing the slice chamber 8. The cross section of the engagement groove 11 is dovetail-shaped. The turbulence channels 6 debouch with their discharge openings 13 directly into the slice chamber 8, and said anchoring elements 10 are located adjacent to these discharge openings 13, in level with each other, for instance, as illustrated. The group of turbulence channels 6 is, at its upstream end, connected to a feeding system (not shown) , comprising three stock supplies and suitable flow distributors for even distribution of each stock to the rows of turbulence channels 6 in the appurtenant section and for even distribution of the stock within each row of turbulence channels 6. In the embodiment shown, the headbox has eight vanes 14, dividing the slice chamber 8 into nine converging channels 15 that communicate with the rows of turbulence channels 6. Two of the vanes 14 constitute stock-separating vanes 14a, arranged to separate the three stocks from each other and extending at a pre-determined distance out from the slice opening 9 for forming a jet thus consisting of three layers. The stock-separating vanes 14a also have a turbulence-generating function. The other vanes are solely turbulence vanes 14b, which have their free ends located inside the slice chamber at a pre-determined distance from the slice opening. The vanes 14 are relatively stiff and can be made of a metal material, usually titanium, or of a plastic material, usually glass- or carbon-fibre-reinforced epoxy plastic. The vanes 14 are sufficiently stiff to sustain different pressures and speeds in the flows of stock. Each vane 14 has a pivot member 16, extending across the machine direction and forming part of an arrangement for detachable mounting of the vane 14 to said anchoring element 10. In the embodiment shown, the vane 14 comprises an elongate connection bar 17 (see Figure 2) that is provided with said pivot member 16, which is in the shape of a rod-like pivot element with a circular cross section. The connection bar 17, which is made of metal, for instance bronze, is as long as the vane 14 is wide and comprises, in turn, a downstream engagement part 18, an intermediate part 19 and an upstream pivot-forming engagement part, which thus forms said pivot element 16. The engagement part 18 is provided with an elongate, through-running groove 20 for receiving the upstream end part of the vane 14 and engagement dowels 21 arranged in the vane 14 for securing the vane 14 and the connection bar 17 to each other seen in the machine direction. The groove 20 is provided with inner support walls 22 for the engagement dowels 21. Said dovetail engagement groove 11 of the anchoring element 10 and circular pivot element 16 of the connection bar 17 form parts of said mounting arrangement. In accordance with the present invention, the mounting arrangement further comprises a special assembly bar 23, extending along the anchoring element 10. At its upstream end, the assembly bar 23 is designed with a continuous protrusion 24, having the same dovetail shape as the engagement groove 11 of the anchoring element 10 to be received in the same with good lateral fit, i.e. without play, and to be brought into locking wedge co-operation with the engagement groove 11 with good fit, i.e. without play, between the assembly bar and the anchoring element so that the assembly bar 23 is secured to the anchoring element 10 by forming a tight joint resistant to torsion. Further, the assembly bar 23 has a continuous journalling groove 25 that extends through the downstream end part of the assembly bar 23 and is open at the ends turned away from each other of the assembly bar 23. The journalling groove 25 has a continuous side opening 26, facing the slice chamber 8 and, more particularly, the vane 14. The journalling groove 25 is dimensioned to receive without friction the circular pivot element 16 of the connection bar 17 from the side, across the machine direction, the width of the side opening 26 being smaller than that of the circular edge or a pivot element arranged within its upstream end portion. The invention has been described in connection with a multi-layer headbox. Obviously, it can be applied to a single-layer headbox provided with one or several turbulence vanes. The invention is particularly applicable in respect of a headbox in which all the vanes form an obtuse angle with the turbulence channels so that the flows of stock change direction when they enter the slice chamber, as illustrated in Figure 1. However, it is applicable in respect of a rectilinear headbox, in which the turbulence channels and the slice chamber are designed so that no such change of direction occurs or occurs only in respect of the outer vanes .

Claims: C L I M S 1. A headbox for delivering a jet of stock to a forming zone in a former for wet-forming a fibre web, comprising - a slice (7) , having a slice chamber (8) and a slice opening (9) , - a turbulence generator, comprising - a plurality of turbulence channels (6) , arranged in at least two rows across the machine direction and opening out into the slice chamber (8) , and - an elongate anchoring element (10) , arranged between two adjacent rows of turbulence channels (6) and having a continuous engagement groove (11) , which is open in towards the slice chamber (8) , - at least one vane (14) , arranged in the slice chamber (8) to separate two channels (15) from each other, each channel (15) communicating with one of said rows of turbulence channels (6) , which vane (14) comprises a pivot member (16) , extending across the machine direction, and - an arrangement for mounting the vane (14) to said anchoring element (10) , which mounting arrangement comprises said pivot member (16) of the vane (14) and said engagement groove (11) of the anchoring element (10) , characterized in that the mounting arrangement additionally comprises an assembly bar (23) , extending along the anchoring element (10) and having - a protrusion (24) that is arranged to be received in the engagement groove (11) of the anchoring element (10) to form a rigid joint and - a continuous journalling groove (25) that is arranged at a pre-determined distance from the anchoring element (10) and is open towards the vane (14) by way of a side opening (26) , and has opposite pivot surfaces (27) , and that the pivot member (16) of the vane (14) is arranged to be received in the journalling groove (25) to co-operate with its pivot surfaces (27) to form an axis of pivot (28) . 2. A headbox as claimed in claim 1, characterized in that the journalling groove (25) of the assembly bar (23) has its side opening (26) faced in a direction that diverges from the direction of the adjacent turbulence channel (6) . 3. A headbox as claimed in claim 1, which comprises two or several vanes (14) , characterized in that all the vanes (14) form obtuse angles with their appurtenant turbulence channels (6) and that each vane (14) is mounted to its anchoring element (10) by means of said assembly bar (23) . 4. A headbox as claimed in any one of claims 1-3, characterized in that said pivot member (16) is formed in the upstream edge of the vane . 5. A headbox as claimed in any one of claims 1-3, characterized in that the vane (14) comprises a connection bar (17) , which encloses the upstream edge portion of the vane (14) with an engagement part (18) , provided with a groove, and that said pivot member (16) is formed in the upstream edge of the connection bar (17) . 6. A headbox as claimed in any one of claims 1-5, characterized in that said pivot member (16) is in the form of a rod-like pivot element with a circular cross section. 7. A headbox as claimed in any one of claims 1-6, characterized in that said pivot member (16) is located in the plane of the vane (14) . 8. A headbox as claimed in any one of claims 1-7, characterized in that the assembly bar (23) is made of metal, preferably bronze. 9. An arrangement for mounting a vane (14) in a headbox for delivering a jet of stock to a forming zone in a former for wet-forming a fibre web, which headbox comprises a slice (7) , having a slice chamber (8) and a slice opening (9) , a turbulence generator, comprising a plurality of turbulence channels (6) , arranged in at least two rows across the machine direction and opening out into the slice chamber (8) , and an elongate anchoring element (10) , arranged between two adjacent rows of turbulence channels (6) and having a continuous engagement groove (11) , which is open in towards the slice chamber (8) , which vane (14) is arranged in the slice chamber (8) to separate two channels (15) from each other, each channel (15) communicating with one of said rows of turbulence channels (6) , and which vane (14) comprises a pivot member (16) , extending across the machine direction, which mounting arrangement comprises said pivot member (16) of the vane (14) and said engagement groove (11) of the anchoring element (10) , characterized in that the mounting arrangement additionally comprises an assembly bar (23) , extending along the anchoring element (10) and having - a protrusion (24) that is arranged to be received in the engagement groove (11) of the anchoring element (10) to form a rigid joint and - a continuous journalling groove (25) that is arranged at a pre-determined distance from the anchoring element (10) and is open towards the vane (14) by way of a side opening (26) , and has opposite pivot surfaces (27) , and that the pivot member (16) of the vane (14) is arranged to be received in the journalling groove (25) to co-operate with its pivot surfaces (27) to form an axis of pivot (28) . 10. An arrangement as claimed in claim 9, characterized in that the journalling groove (25) of the assembly bar (23) has its side opening (26) faced in a direction that diverges from the direction of the adjacent turbulence channel (6) . 11. An arrangement as claimed in claim 9, which comprises two or several vanes (14) , characterized in that all the vanes (14) form obtuse angles with their appurtenant turbulence channels (6) and that each vane (14) is mounted to its anchoring element (10) by means of said assembly bar (23) . 12. An arrangement as claimed in any one of claims 9-11, characterized in that said pivot member (16) is formed in the upstream edge of the vane. 13. An arrangement as claimed in any one of claims 9-11, characterized in that the vane (14) comprises a connection bar (17) , which encloses the upstream edge portion of the vane (14) with an engagement part (18) , provided with a groove, and that said pivot member (16) is formed in the upstream edge of the connection bar (17) . 14. An arrangement as claimed in any one of claims 9-13, characterized in that said pivot member (16) is in the form of a rod-like pivot element with a circular cross section. 15. An arrangement as claimed in any one of claims 9-14, characterized in that said pivot member (16) is located in the plane of the vane (14) . rt X Φ < SD 0 Φ —- H . — tJ μ- < 0 rt μ- ø ιp SD tr 0 rt ø rt X Φ m SD 3 φ •

Inventors: HARALDSSON ULF, HARALDSSON, ULF
Applicants: HARALDSSON ULF, VALMET KARLSTAD AB, HARALDSSON, ULF, VALMET-KARLSTAD AB
Application year: 2001
Main classification: D21F1
IPC codes: D21F1