EP2252737A1

EP2252737A1 - Dewatering apparatus of a fiber web machine and a method for manufacturing a dewatering apparatus of a fiber web machine

Info

Publication number: EP2252737A1
Application number: EP09711379A
Authority: EP
Inventors: Lauri Aaltio; Markku Koivumäki; Markku Pohjola
Original assignee: Metso Paper Oy
Current assignee: Valmet Technologies Oy
Priority date: 2008-02-13
Filing date: 2009-01-26
Publication date: 2010-11-24
Also published as: WO2009101243A1; FI20085127A0; FI20085127L; CN101946038B; FI120365B; EP2252737A4; CN101946038A

Abstract

The invention relates to a dewatering apparatus of a fiber web machine including a frame construction (13) greater in its length than width. The frame construction (13) has intermediate supports (14) fastened thereto at an interval of each other which are set in the cross direction relative to the longitudinal direction of the frame construction (13). The dewatering apparatus also includes at least one foil blade support (15), longitudinal relative to the frame construction (13), which is supported to openings (16) arranged in the intermediate supports (14). The opening (16) includes a bottom (30). In addition, the foil blade support (15) is set at a desired distance from the bottom (30) of the opening (16) in each intermediate support (14), and there is a weld connection (18) between the foil blade support (15) and the intermediate support (14). The invention also relates to a method for manufacturing a dewatering apparatus of a fiber web machine.

Description

DEWATERING APPARATUS OF A FIBER WEB MACHINE AND A METHOD FOR MANUFACTURING A DEWATERING APPARATUS OF A FIBER WEB MACHINE

The invention relates to a dewatering apparatus of a fiber web machine including a frame construction greater in its length than width, intermediate supports fastened to the frame construction at an interval of each other and set in the cross direction relative to the longitudinal direction of the frame construction, and at least one foil blade support longitudinal relative to the frame construction, supported to openings arranged in the intermediate supports .

The invention also relates to a method for manufacturing a dewatering apparatus of a fiber web machine.

Dewatering apparatuses are used particularly in a so called web forming section of a fiber web machine where water is removed from the fiber suspension spread on the fabric for forming a web. The web forming section is also called a wire section. The web forming section is provided with several dewatering apparatuses in succession, generally located above the fabric. Dewatering apparatuses of the web forming section are based on dewatering blades, which are also called foils. In addition, the dewatering foils are supported to a box-like frame construction, in which case such dewatering apparatuses are called foil boxes. Each foil box has usually several dewatering foils, although it is also possible to adapt individual dewatering foils in the forming section. Dewatering foils are in contact with the fabric and a gap is created between successive dewatering foils. Thus the web is subjected to successive pulses which improve the removal of water. It is also possible to create a vacuum in a foil box for improving dewatering.

A foil box is attached to a fiber web machine by both of its ends . Known foil boxes are manufactured from several sheet metal components by welding. To achieve sufficient rigidity, various supports and stiffeners are used additionally. Consequently, the foil box becomes heavy and its manufacturing is slow. Furthermore, local stress peaks are created in the foil box during use and setting the dewatering foils in a correct position is difficult at a sufficient accuracy.

Foils wear in use and can also break, in which case foils must be replaced at times. European patent No. 1482088 discloses a dewatering apparatus in which the frame construction is formed of massive supporting beams with transverse intermediate supports fastened thereto. Each intermediate support has two parts and is provided with profiled gap-like openings for fastening the dewatering foils. In addition, each dewatering foil in- eludes a profiled support blade that creates a form-lock against the gap in the intermediate support.

The above described dewatering apparatus is firstly extremely heavy and massive because the frame construction is made of beam-like constructions and thick components. In addition, the manufacture of the components requires a lot of machining and the various components must be fastened using unreliable screw connections. Frame constructions for different applications must also be designed and manufactured separately. Often it is required that dewatering foils create a surface that is as planar as possible. With the above described solution, planar- ity is rarely achieved since the dewatering foils deflect along with the deflection of the frame construction. On the other hand, achieving forms that deviate from a planar surface is impossible or at least it requires using custom-built intermediate supports. In addition, the profiles in the supporting beams and the holes required by the screws collect loose matter.

The object of the invention is to provide a novel dewatering apparatus for a fiber web machine, in which dewatering foils form a desired shape more accurately than before and which is lighter in weight than before, yet sufficiently rigid. Another object of the invention is to provide a novel method for manμ- facturing a dewatering apparatus for a fiber web forming ma- chine, which method is simpler and faster than before, yet more precise, and which provides the dewatering apparatus with new and surprising characteristics. The characteristic features of the dewatering apparatus according to this invention are that an opening includes a bottom and a foil blade support is set at a desired distance from the bottom of the opening in each intermediate support, and there is a weld connection between the foil blade support and the intermediate support. In addition, the characteristic features of the method according to the invention are that the foil blade support is adapted to the opening and set at a desired distance from the bottom of the opening in the intermediate support, after which the foil blade support is fastened to the intermediate support by welding. According to the invention, the distance between the foil blade support and the cross support can vary in the different posi- tions of the dewatering apparatus. Thus the shape of the dewatering apparatus touching the fabric is always precisely as desired. Using the method according to the invention, this shape can be easily changed. Of course, dewatering apparatuses of very different types and forms can be provided even from similar components . In spite of the variability, the number of components required in the manufacture of the dewatering apparatus is reduced and the manufacture is fast. A complete dewatering apparatus is light in weight, yet rigid. In addition, the dewatering apparatus is easy to keep clean and addi- tional functions can also be included in it.

The invention is described below in detail by making reference to the enclosed drawings, which illustrate some of the embodiments of the invention, in which Figure 1 is a lateral view of a web forming section of a fiber web machine according to prior art,

Figure 2a is a partially cross-sectional view of a dewatering apparatus according to the invention, Figure 2b is a basic diagram showing the manufacture of a second application of the dewatering apparatus according to the invention,

Figure 3 is a basic diagram of a small part of the dewatering apparatus , Figure 4 is a cross-sectional view of a frame construction of a third application of the dewatering apparatus according to the invention.

Figure 1 shows a web forming section of a fiber web machine, conventional per se, in which fiber suspension is spread to a so called bottom fabric 11 from a headbox 10. The term 'fiber web machine' is used to refer to paper, board, tissue and pulp drying machines. Several dewaterαng apparatuses are arranged in succession below the bottom fabric. In practice, immediately upon arriving at the bottom fabric, the fiber suspension is subjected to pulses which assist in the removal of water from the fiber suspension and thereby the web formation. The web forming section shown also includes a so called top fabric 12, in which case water is removed upwards as well . After the web forming section, the web is led to a press section (not shown) .

In addition to the fourdrinier forming section shown in the figure, gap forming sections, for example, are used.

Figure 2a shows a cross-section of a dewatering apparatus according to the invention. The dewatering apparatus includes a frame construction 13 greater in its length than width, the dimensioning and shape of which can vary in different applications. The longitudinal direction of the frame construction 13 is indicated with arrow Y and the lateral direction with arrow x. In practice, the frame construction is thus transverse relative to the web machine. The frame construction 13 has intermediate supports 14 fastened thereto at an interval of each other, located in the cross direction relative to the longitudinal direction of the frame construction 13. In addition, the dewatering apparatus includes at least one foil blade support 15 that is longitudinal relative to the frame construction 13 and is supported to openings 16 arranged in the intermediate supports 14. The openings in the intermediate support 14 comprise a bottom 30 and lateral walls 31. Advantageously, the openings 16 are rectangular. An actual dewatering foil 17, contacting the fabric, is fastened to the foil blade support. Figure 2a shows only three of the total four foil blade supports 15 so that the openings 16 in the intermediate supports 14 are clearly visible. According to the invention, the depth of the opening 16 is so adapted that the foil blade support 15 is set at a desired distance from the bottom 30 of the opening 16 in each intermediate support 14. Thus the dewatering foils can be set accurately at a desired place and to a desired position whereby dewatering is as uniform as possible. The foil blade support 15 is fastened to the intermediate support 14, to the lateral walls 31 of the openings 16 in the intermediate support 14, by means of a weld connection 18. Advantageously, the weld connection between the foil blade support 15 and the intermediate support 14 is only between the lateral walls 31 of the opening 16 and the foil blade support 15. In this case the foil blade support and the intermediate support form a part of a load-bearing frame construction whereby the rigidity of the dewatering apparatus is excellent. The frame construction of the dewatering apparatus resists well to a varying load and the dewatering foils keep in designed places .

The rigidity and accuracy of shape of the frame construction are further improved by the intermediate supports made of sheet metal material. In other words, the intermediate supports are sheet metal components . Sheet metal can be laser-cut whereby the intermediate supports and the openings made in them are precisely as desired. Thus the foil blade supports and hence also the dewatering foils keep in a correct position both during and after the installation. Generally the sheet metal thickness varies from 0.5 to 5 mm, more advantageously from 1 to 4 mm. In Figure 2a, the frame construction 13 is extended with a fastening shelf 19 through which the dewatering apparatus is fastened to the frame constructions of the fiber web machine. A traditional fastening shelf is made of a thick sheet material, whereas the corresponding functional element in the application of Figure 4 is made of thin sheet metal as a part of the frame construction (not shown) .

Using foil blade supports that are fastened by welding surprisingly enables using fewer intermediate supports than before. According to the invention, the interval between the intermedi- ate supports is 500 - 1000 mm, more advantageously 600 - 800 mm. However, the frame construction becomes rigid because the foil blade support is an open or closed rectangular profile. Thus the opening is formed of two narrow grooves 20 or one gap 21 equal in size with the foil blade support 15. In Figure 3, the foil blade support 15 on the right-hand side is a U profile for which the intermediate support 14 is provided with two narrow grooves 20. Correspondingly, the foil blade support 15 on the left-hand side is a profile pipe, in which case the intermediate support 14 has a gap 21 of a corresponding size. With laser cutting, the grooves and gaps can be made precisely conforming to the foil blade support, which facilitates installation. In addition, the grooves and gaps can be accurately oriented enabling the foil blade support to be set precisely in a correct position.

During the manufacture of the dewatering apparatus, first a frame construction greater in its length than width is manufactured, to which intermediate supports, transverse relative to the frame construction, are fastened at an interval of each other. Openings are also made in the intermediate supports and the intermediate supports are advantageously laser-cut from a sheet metal material. Finally, at least one foil blade support, longitudinal relative to the frame construction, is supported to the openings arranged in the intermediate supports . According to the invention, the foil blade support is adapted in the opening and set at a desired distance from the bottom of the opening in the intermediate support, after which the foil blade support is fastened to the intermediate support by welding. The foil blade support is advantageously welded to the vertical walls of the openings in the intermediate support. In this way, machining of the frame construction is completely avoided. In addition, the desired shape is achieved in the dewatering apparatus easily and precisely. In other words, the dewatering foils can be put in the designed position and location. In most applications, the target is to achieve dewatering foils that are located as planarly as possible. With the method according to the invention, it is, however, possible to manufacture a dewatering apparatus including several foil blade supports in which the foil blade supports are arranged in a curve in the longitudinal and/or cross direction relative to the frame construction. With a longitudinal curvature it is possible, for example, to compensate deformations caused by the deflection of the frame construction. Thus the complete dewatering apparatus is curved but will straighten to a straight form when put in place in use, whereby dewatering will be as uniform as possible over the entire fabric width. 'Transverse curvature' refers to the application shown in Figure 2b in which the foil blade supports 15 are at different heights and positions relative to each other and the intermediate support 14.

Each foil blade support is set in its opening in a designed manner. According to the invention, the opening is equal in width with the foil blade support within tolerances, but the depth of the opening is excessive. Thus it is possible to vary the distance between the foil blade support and the intermedi- ate support during manufacture. Advantageously, it is made use of an auxiliary device 22 which is put in a desired position and location relative to the frame construction 13 and the distance between the foil blade support 15 and the intermediate support 14 is determined by means of the auxiliary device 22. Such an auxiliary device can be a ruler, for example, adjusted at the intermediate support. After this, the foil blade support is lifted up in contact with the ruler and the foil blade support is fastened to the intermediate support by welding. Instead of an individual ruler, it is possible to use a set of rulers or an adjustable lifting device which simultaneously supports the foil blade supports during welding.

Figure 3 shows two different applications of the foil blade support 15. In both, a fastening rod 23, to which a dewatering foil is threaded, is arranged in the foil blade support 15. In this way, the dewatering foil can be replaced easily and quickly. In the application on the left-hand side, the fastening rod 23 is fastened to the foil blade support 15 with a weld connection 24. Thus the fastening rod itself partly stiffens the frame construction and a continuous weld connection pre- vents loose matter from penetrating between the foil blade support and the fastening rod. In the application on the right- hand side, a nut or a rivet nut 25 is used, in which case the fastening rod is fastened with a hexagonal socket-head screw 26, for example. In this case it is possible to use a fastening rod made of fiber reinforced plastic or glass fiber, for example. By using a foil blade support according to the invention, deflection of the fastening rod is avoided. In the application of Figure 3 it has been desired to make the surface constituted by the dewatering foils as uniform as possible. In such a case, a straight ruler is used as an auxiliary device, the location of which is indicated with broken line in Figure 3. The lower broken line illustrates a situation in which the foil blade supports 15 are first fastened to the intermediate support 14 while the fastening rods 23 will be fastened to the foil blade supports 15 only at the final stage. The upper broken line illustrates a situation in which the fastening rods 23 have first been installed to the foil blade supports 15 and the foil blade supports 15 have been welded to the intermediate supports 14 only after that.

A construction according to the invention can be applied in connection with different frame constructions. For example, intermediate supports and foil blade supports can be welded to a traditional box-like frame construction (Figure 2b) . Figure 4 shows a totally novel frame construction. According to the invention, the frame construction 13 is manufactured from a sheet metal material as a closed casing construction. This makes the frame construction as a whole light in weight, yet extremely rigid. In addition, the frame construction is closed, which prevents soiling and, on the other hand, facilitates cleaning. The frame construction is assembled from sheet metal components and the casing construction has also stiffening flanges 27 made of sheet metal at suitable intervals within it. In shorter frame constructions, however, stiffening flanges can be completely left out. Such a frame construction includes only a few tens of components. Moreover, the frame construction is particularly rigid and above all notably lighter in weight than known constructions. The proposed application has additionally two longitudinal stiffening blades 28, at which a longitudinal weld seam connecting the sheet metal components is located. In a simulation, the mass of the frame construction has been defined to be about 20% of the mass of a corresponding known dewatering apparatus. The mass of a seven meters long dewatering apparatus would thus become about 280 kilograms, while it is as much as 1600 kilograms with a manufacture ac- cording to a known technique. Correspondingly, the width would be 700 mm and the height would be 600 mm and the thickness of stainless sheet metal would be 2 mm. With the mass remaining reasonable, the frame construction can be manufactured wider than before enabling thereby to fit a greater number of dewatering foils than before in one dewatering apparatus . The dewatering apparatus can also be connected to a vacuum source in which case the water removal from the web is improved with a vacuum.

With laser cutting, components with high dimensional and shape accuracy are achieved. Correspondingly, with laser welding, a narrow and deep weld is achieved, whereby it is also possible to connect components with different thicknesses. Due to low thermal conduction, harmful deformations can be avoided. A laser-welded seam is ready without after-machining and the welds are reliable in spite of a high welding speed.

Claims

1. A dewatering apparatus of a fiber web machine including a frame construction (13) greater in its length than width, intermediate supports (14) fastened to the frame .construction (13) at an interval of each other and set in the cross direction relative to the longitudinal direction of the frame construction (13), and - at least one foil blade support (15) that is longitudinal relative to the frame construction (13), supported to openings (16) arranged in the intermediate supports (14) , characterized in that, the opening (16) has a bottom (30), and the foil blade support (15) is set at a desired distance from the bottom (30) of the opening (16) in each intermediate support (14), and between the foil blade support (15) and the intermediate support (14) there is a weld connection (18) .

2. A dewatering apparatus according to claim 1, characterized in that the weld connection between the foil blade support (15) and the intermediate support (14) is only between the lateral walls (31) defined by the opening (16) in the intermediate support (14) and the foil blade support (15) .

3. A dewatering apparatus according to claim 1 or 2 , characterized in that intermediate supports (14) are sheet metal components .

4. A dewatering apparatus according to any of claims 1 - 3 , characterized in that the foil blade support (15) is an open or closed rectangular profile, whereby the opening (16) is formed of two narrow grooves (20) or one slot (21) equal in size with the foil blade support (15) .

5. A dewatering apparatus according to any of claims 1 - 4, characterized in that the foil blade support (15) has a fasten- ing rail (23) arranged therein, which is fastened to the foil blade support (15) with a weld connection.

6. A dewatering apparatus according to any of claims 1 - 5, characterized in that the dewatering apparatus includes several foil blade supports (15) that are arranged in a curve in the longitudinal and/or cross direction of the frame construction

(13) .

7. A method for manufacturing a dewatering apparatus of a fiber web machine, in which method a frame construction (13) greater in its length than width has intermediate supports (14) that are transverse relative to the longitudinal direction of the frame construction (13) fastened thereto at an interval of each other, the intermediate supports having openings (16) arranged therein to which at least one foil blade support (15) longitudinal relative to the frame construction (13) is supported, characterized in that the foil blade support (15) is adapted to the opening (16) and set at a desired distance from the bottom (30) of the opening (16) in the intermediate support

(14) , after which the foil blade support (15) is fastened to the intermediate support (14) by welding.

8. A method according to claim 7 , characterized in that the foil blade support (15) is fastened by welding to lateral walls (31) defined by the opening (16) in the intermediate support (14) .

9. A method according to claim 7 or 8 , characterized in that the method uses an auxiliary device (22) which is set in a desired position and location relative to the frame construction (13), and the distance of the foil blade support (15) from the intermediate support (14) is determined using the auxiliary device (22) .

10. A method according to any of claims 7 - 9, characterized in that the frame construction (13) is manufactured from a sheet metal material as a closed box construction.