EP1788154A1

EP1788154A1 - Arrangement in headbox

Info

Publication number: EP1788154A1
Application number: EP06077089A
Authority: EP
Inventors: Harri Kronholm
Original assignee: Vaahto Oy
Current assignee: Vaahto Paper Technology Oy
Priority date: 2005-11-17
Filing date: 2006-11-13
Publication date: 2007-05-23
Also published as: CN1974924A; FI20051174A0; FI20051174A

Abstract

An arrangement in a headbox (1) of a paper, tissue or board machine, which arrangement comprises several laminar guide plates which are in the flow direction fastened from their leading edge into connection with a turbulence generator or an equivalent support structure of the headbox, and which guide plates are free from their trailing edge and extend in the cross-direction substantially for the width of the headbox. At least one fastening slot (9) has been formed between flow openings (8, 8') of the turbulence generator or an equivalent, in which slot a counter element (12, 12') of the guide plate (6) fits.

Description

Background of the invention

The invention relates to an arrangement in a headbox of a paper or board machine according to the preamble of claim 1.
The invention relates to a headbox of a paper, board or tissue machine. The invention especially relates to the fastening of a flow guide plate, such as a lamella or a baffle plate, of the headbox.
As is known, in the fastening of a flow guide plate, especially a baffle plate or a lamella, of paper, board or tissue machines have been used hinge arrangements by means of which free movement of the flow guide plate has been allowed in a lip channel in relation to the cross-directional axle of the headbox. A hinged lamella of the headbox of a paper machine has been described in FI patent 115648 which is corresponded by published application US2005196283 A1 . A disadvantage of the fastening of such a hinged guide plate is, inter alia, a large space requirement in the fastening point. The fastening point is typically in connection with a flow dividing plate of the headbox which plate has several flow openings side by side and on top of each other. Then, the distance between flow-opening rows on top of each other can become quite great i.e. typically around 10-15 mm. This causes a large step in the flow direction. For its part, one has tried to diminish this using different fastening pieces the thickness of which has however quite accurately corresponded the thickness of the space required by the hinge. One has further tried to diminish this thickness, for its part, stepwise in the flow direction when approaching a lip opening of the headbox in order to the flow remain on the surface of the lamella as well as possible. The described structure has not operated satisfactorily which has been visible in the deterioration of formation in the end product. The structure further impedes the operation of the headbox and is also expensive in respect of its manufacturing technique.
The object of this invention is to achieve a totally novel solution using which the disadvantages of known prior art are avoided and to provide a novel solution for controlling fibre orientation and formation. Another object is to provide a more advantageous solution than earlier for the above-mentioned purpose in respect of its manufacturing technique.

Brief description of the invention

It is mainly characteristic for the arrangement according to the invention that at least one fastening slot, in which a counter element of the guide plate fits, has been formed between the flow openings of a turbulence generator or an equivalent.
The arrangement according to the invention is further characterised by what is stated in claims 2-16.
The solution according to the invention has numerous significant advantages. By means of the solution according to the invention, the guide plate can be directed to the flow direction, whereby disadvantageous oscillation of the lamella can be decreased and the pulp flow is obtained smoother than using solutions according to prior-art, especially using guide plates provided with a hinge fastening. Using the solution according to the invention, openings or opening rows, pipe rows or equivalents directing the flow to a lip chamber are obtained adequately close to each other so that the flow remains close enough to the lamella or an equivalent. The solution according to the invention enables an easy installation. The structure is also advantageous in respect of its manufacturing technique. In headboxes using the arrangement according to the application, the distance of turbulence pipes remains quite small, whereby the headbox can be used also without guide plates without increasing the residual variation of the end product too much.

Brief description of the figures

Next, the invention will be described in detail by means of an example with reference to the accompanying drawing in which

Fig. 1 shows an arrangement in connection with a headbox according to the invention, and
Fig. 2 shows a detail from Fig. 1.

Detailed description of the invention

Fig. 1 shows a partially sectioned side view of a part of a headbox using an arrangement according to the invention. Fig. 2 shows the final part of the headbox in the pulp flow direction. The headbox comprises known as such a feed system of pulp suspension, which divides the suspension for the width of the headbox, at least one first flow resistor, such as a hole plate provided with flow holes and/or a piping. From the headbox, pulp suspension is directed via a lip gap 3 of at least one chamber, such as a distributing chamber and/or a lip chamber 2, to a forming wire or an equivalent. The figure shows at least one guide plate 6 i.e. a baffle plate of pulp flow arranged to the lip chamber. In the embodiment of the figure, there are two guide plates 6. The guide plates are arranged on top of each other in the lip chamber. The lip chamber 2 is limited by a lower lip wall 4 and an upper lip wall 5. The guide plates are typically manufactured of metal, plastic or other suitable materials.
Fig. 2 shows a fastening point of the guide plate used in an arrangement according to Fig. 1 in more detail. For the guide plate is arranged at least one fastening slot 9, in which the guide plate 6 can be set, between outlet openings 8, 8', 8" of a turbulence piping or an equivalent flow resistor 7. In the guide plate 6, there is on the input side of flow a counter element 12, 12' which fits to the fastening slot 9. According to an embodiment of the invention, the guide plate can be set in place typically either from the side or front. The counter element 12, 12' can be of many different types. The figures show an advantageous embodiment in which tongues 12, 12' directed to opposite directions together forming a counter element have been formed to the flow input side. The tongues 12, 12' can be formed e.g. by cutting strips to the edge of the input side of the plate 6 which strips are deflected to at least one direction, most suitably adjacent strips 12, 12' to opposite directions so that a counter element is formed. The fastening slot 9 is a transverse slot in the cross-direction of the machine. In the pulp flow direction, the fastening slot is followed by a support slot 14 of the guide plate the thickness of which is smaller than the fastening slot 9 but somewhat larger than the thickness of the guide plate 6. The support slot 14 is most suitably larger than the thickness of the guide plate 6 so that the guide plate can be easily moved to its place when installing the guide plate 6. The clearance between the support slot 14 and the guide plate 6 is around 0.5-5 mm, advantageously 1-2 mm, most suitably around 1.5 mm. In an embodiment, the clearance between the support slot 14 and the guide plate 9 is around 1.5 mm. For decreasing dirtying, one tries to form the clearance as small as possible. The guide plates 6 are around 1-20 mm, advantageously around 3-8 mm, most suitably around 4-6 mm thick plates. The guide plates 6 are in an embodiment typically plates of around 5-mm thickness. The headbox being in an inactive state, the guide plates, depending on their own rigidity, deflect in the chamber room so that a trailing edge 16 of the guide plate 6 is closer to the lower-lip wall 4 of the chamber than the fastening point of the guide plate. The guide plates are however formed and arranged in the lip chamber so that they are not damaged even though they are able to deflect in the inactive state. The fastening of the guide plates to the headbox can typically be considered a so-called rigid fastening. The counter element 12, 12' is an element arranged or formed to the guide plate which element prevents the transfer of the guide plate in the direction of the main flow direction of pulp flow. It can be thought that as a counter element can be used, inter alia, round bars, dowels, edgings etc. the purpose of which is to prevent the guide plate from sliding from the slot to the lip chamber and further to the wire. In the embodiment according to Fig. 2, there is a wall 13 on the input side in the flow direction of the fastening slot 9, advantageously in the cross-direction of the machine.
In headboxes using an arrangement according to the application, the distance of turbulence pipes 8, 8' on top of each other remains quite small (in an embodiment around 6 mm), whereby the headbox 1 can be used also without guide plates 6 without increasing the residual variation of the end product too much.
Typically, the guide plate 6 extends substantially to the whole width of the headbox. Also guide plates 6 extending only for a part of the width of the headbox can be used. Then, different guide plates having different characteristics can be easily formed for the width of the headbox.
The guide plate 6 is arranged in the flow direction of the chamber following the flow resistor to a first wall and to extend at a distance from the first wall. In the embodiment of Fig. 1, second guide plates are arranged to a front wall or an equivalent of the lip chamber in which wall the input flow openings or pipes of the turbulence generator of the figure arrive.
It is obvious to those skilled in the art that the invention is not limited to the embodiments described above, but it may be varied within the scope of the enclosed claims. When necessary, the features possibly described in this specification together with other features may also be used separate from each other.

Claims

An arrangement in a headbox (1) of a paper, tissue or board machine, which arrangement comprises several laminar guide plates which are in the flow direction fastened from their leading edge into connection with a turbulence generator or an equivalent support structure of the headbox, and which guide plates are free from their trailing edge and extend in the cross-direction substantially for the width of the headbox, characterised in that at least one fastening slot (9), in which a counter element (12, 12') of the guide plate (6) fits, has been formed between flow openings (8, 8') of the turbulence generator or an equivalent.
An arrangement according to claim 1, characterised in that the fastening slot (9) is a slot in the cross-direction of the machine.
An arrangement according to claim 1 or 2, characterised in that between the fastening slot (9) and a chamber room (2) there is a support slot (14).
An arrangement according to any one of claims 1-3, characterised in that the guide plate (6) can be set in its place from the side or from the direction of the chamber (2).
An arrangement according to any one of claims 1-4, characterised in that the flow openings (8, 8') are flow openings on top of each other.
An arrangement according to any one of claims 1-5, characterised in that walls (10, 10') of the support slot (14) are between the flow openings (8, 8').
An arrangement according to any one of claims 1-6, characterised in that the counter element (12, 12') of the guide plate (6) is formed to the leading edge of the guide plate (6).
An arrangement according to any one of claims 1-5, characterised in that the counter element (12, 12') of the guide plate (6) is formed by deflecting the guide plate.
An arrangement according to any one of claims 1-5, characterised in that the counter element (12, 12') of the guide plate is at least when set to the fastening slot thicker than the support slot (14).
An arrangement according to any one of claims 1-9, characterised in that strips (12, 12') most suitably directed to opposite directions together forming a counter element have been formed to the guide plate (6) to the input side of flow.
An arrangement according to any one of claims 1-10, characterised in that the strips (12, 12') have been formed by cutting cuts to the edge of the input side of the plate (6) the strips between which are deflected to at least one direction, most suitably adjacent strips (12, 12') to opposite directions so that a counter element is formed.
An arrangement according to any one of claims 1-11, characterised in that, in the pulp flow direction, the fastening slot (9) is followed by the support slot (14) of the guide plate the thickness of which is smaller than the fastening slot (9), but somewhat larger than the thickness of the guide plate (6).
An arrangement according to any one of claims 1-12, characterised in that the support slot (14) is most suitably larger than the thickness of the guide plate (6) so that the guide plate can be easily moved to its place when installing the guide plate (6).
An arrangement according to any one of claims 1-13, characterised in that the clearance between the support slot (14) and the guide plate (6) is around 0.5-5 mm, advantageously 1-2 mm, most suitably around 1.5 mm.
An arrangement according to any one of claims 1-14, characterised in that the guide plates (6) are around 1-20 mm, advantageously around 3-8 mm, most suitably around 4-6 mm thick plates.
An arrangement according to any one of claims 1-15, characterised in that the counter element (12, 12') is an element arranged or formed to the guide plate which element prevents the transfer of the guide plate in the direction of the main flow direction of pulp flow.