A DEWATERING ELEMENT FOR A WEB FORMING MACHINE, A METHOD FOR FORMING A DEWATERING ELEMENT USED IN A WEB FORMING MACHINE, AND A SURFACE PART FOR A DEWATERING ELEMENT IN A WEB FORMING MACHINE

The object of the invention is a dewatering element for a web forming machine where the dewatering element includes a support part and a surface part and the support part includes fastening profiles for the support part and the surface part includes fastening profiles for the surface part. The invention also relates to a corresponding method and a surface part .

Dewatering elements manufactured from ceramics are widely known in prior art. Ceramic dewatering elements are typically manufactured from block ceramics. Block ceramics has certain drawbacks . One drawback to be mentioned when manufacturing a dewatering element from block ceramics is that aligning the blocks relative to each other is very challenging. Publication EP1408154 proposes one solution for this. In this publication block ceramic plates are assembled by pushing them together in the longitudinal direction of a support blade. Then the grooves and connecting elements in the block ceramic plates form a connection which binds the block ceramic plates to each other in an aligned manner. Although this embodiment can reduce alignment problems of block ceramic plates, many other problems are involved in the use of block ceramic plates. For example, inserting block ceramic plates one by one is slow. The positioning, alignment and gluing of block ceramic plates also take a remarkable amount of time. Particularly the profile grinding required after this is technically challenging, takes time and is expensive. Therefore, using plates manufactured from block ceramics in dewatering elements is expensive.

The object of the invention is to provide a novel dewatering element with a more uniform design than before. The

characteristic features of the dewatering element according to this invention are that the fastening profiles of the support part and the fastening profiles of the surface part are adapted to allow connecting the surface part to the support part by pushing the surface part to the direction of the support part. Another object of the invention is to provide a novel method for forming a dewatering element used in a web forming machine. The method enables forming the dewatering element in a simpler way than before. The characteristic features of the method according to this invention are that the surface part is fastened to the support part by pushing the surface part toward the support part. Still another object of the invention is to provide a novel surface part for a dewatering element in a web forming machine. The characteristic features of the surface part according to this invention are that the fastening profiles are adapted to allow connecting the surface part to the support part by pushing the surface part toward the support part .

A dewatering element used in a web forming machine influences the water removal from the web . The web refers to board and paper webs. The term 'web forming machine', in turn, is used to refer to machines designed for manufacturing paper, board, tissue or pulp. The dewatering element includes a support part and a surface part. The surface part is connected to the support part by pushing the surface part toward the support part. The support part includes fastening profiles for the support part and the surface part includes fastening profiles for the surface part. In addition, a connection with a form closure is created between the fastening profiles of the support part and the fastening profiles of the surface part when the surface part is pushed toward the support part. No separate fastening elements are thus needed but the fastening profiles themselves create the connection with a form closure. When the surface part is connected to the support part by pushing the surface part to the support part, connecting is

very easy and fast to perform.

In one embodiment the fastening profiles of the surface part include fastening profiles of the front portion of the surface part and fastening profiles of the rear portion of the surface part, and the fastening profiles of the support part include fastening profiles of the front portion of the support part and fastening profiles of the rear portion of the support part. In addition, for creating a connection with a form closure, the fastening profiles of the front edge of the support part are set to align with the fastening profiles of the front edge of the surface part and the surface part is then pushed toward the support part from the rear edge. Thus the fastening profiles at the rear edge of the surface part create a connection with a form closure with the fastening profiles at the rear edge of the support part. As the fastening profiles of the rear edge create a connection with a form closure last, the connection with a form closure of the rear portion must be opened first when removing the surface part from the support part . When the fabric and the web pass the dewatering element meeting first the front portion of the surface part, forces that would open the connection with a form closure of the rear portion are not subjected to the surface part.

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 cross-sectional view of a dewatering element according to the invention,

Figure 2 is a perspective view of a dewatering element according to the invention, Figure 3 shows dewatering elements according to the invention in a dewatering assembly, Figure 4 shows a forming section of a web forming machine equipped with dewatering elements according to the

invention, and Figure 5 is a partial enlargement of Figure 4.

Figure 1 provides a cross-sectional view of a dewatering element 10 according to the invention. The dewatering element is designed to be used in a web forming machine. The dewatering element 10 includes a support part 12 and a surface part 14. Furthermore, the support part 12 includes fastening profiles 16 for the support part 12 and the surface part 14 includes fastening profiles 18 for the surface part 14. In addition, the fastening profiles 16 for the support part 12 and the fastening profiles 18 for the surface part 14 are adapted to allow connecting the surface part 14 to the support part 12 by- pushing the surface part 14 to the direction of the support part 12.

The fastening profiles 18 of the surface part 14 are adapted to allow connecting the surface part 14 to the support part 12 by- pushing the surface part 14 toward the support part 12, as shown in Figure 1. More precisely, the surface part 14 includes a top component 20, a lateral front component 22 and a lateral rear component 24 for forming fastening profiles 18 and for fastening the surface part 14 to the support part 12. In addition, a bending neck 19 is formed in the lateral rear component 24 for fastening the surface part 14 to the support part. The bending neck 19 in the surface part 14 yields when the surface part 14 is fastened to the support part 12. However, the bending neck is so formed that it keeps the surface part 14 fastened to the support part 12 during use.

In the dewatering element 10 according to the invention shown in Figure 1, the fastening profiles 16 of the support part 12 and the fastening profiles 18 of the surface part 14 are adapted to allow detaching the surface part 14 from the support part 12 by pulling the surface part 14 away from the support part 12. The detachment can be performed, for example, by

inserting a detachment tool, such as a screwdriver, between the end of the surface part and the support part from the proximity thereof. Separate detachment points can be formed between the surface part and the support part which allow inserting thereto the tip of a screwdriver, for example.

In the dewatering element 10 according to the invention shown in Figure 1, the surface part 14 and the support part 12 are adapted to be fastened to each other directly. When fastening is performed without separate intermediate components, fastening the surface part and the support part to each other is extremely easy. In addition, manufacturing is easy when a separate intermediate component does not need to be manufactured. Separate intermediate components can, for example, fall from their positions during installation and therefore removing them from the process causes unnecessary efforts .

In the dewatering element according to the invention shown in Figure 1, the thickness a of the surface part 14 is 1 - 5 mm, advantageously 2 - 4 mm. Thus the surface layer of the dewatering element requires only a reduced amount of material and it is inexpensive to manufacture. In addition, bending of the surface layer during connecting enables simple fastening profiles. By the dimensioning, it can be influenced in which position and how much the surface part bends.

The surface part 14 of the dewatering element 10 according to the invention shown in Figure 1 includes a top component 20, a lateral front component 22 and a lateral rear component 24. When the surface part is composed of clearly separate components, the material of the surface part is thin compared to the total thickness of the surface part. Thus the surface part can be manufactured from small amounts of material. Advantageously, the height b of the lateral rear part 24 is 10 - 30 mm, more advantageously 15 - 25 mm. The arrow 26 indicates

the movement direction of the fabric and the web in connection with the dewatering element. The fabric and the web arrive to the proximity of the dewatering element from the lateral front side of the dewatering element and leave the proximity of the dewatering element from the lateral rear side of the dewatering element .

The surface part 14 of the dewatering element 10 according to the invention shown in Figure 1 has a cover 28. The cover 28 enables manufacturing the frame 30 of the surface part 14 from very many different materials because the frame of the surface part does not contact the fabric which is in connection with the dewatering element during the use of the dewatering element. Advantageously the cover is a thermally sprayed ceramic or carbide coating or a hard coating manufactured in some other method. A thermally sprayed ceramic or carbide cover provides good properties for the dewatering element. Particularly the surface roughness is advantageously low and the wear resistance is excellent.

The surface part 14 of the dewatering element 10 according to the invention shown in Figure 1 has a frame 30. This frame is advantageously of metal since metal can be covered. In addition, metal provides the frame with desired properties for locking the surface part to the support part. The support part, in turn, is advantageously of plastic or glass fiber. Support parts of a desired form can be manufactured in a simple way from plastic and glass fiber. The construction concerned can be manufactured, for example, by casting, machining, pultrusion or extrusion. When the support part is manufactured as a continuous profile by pultrusion or extrusion, for example, manufacturing is very cost-efficient. In addition, plastic and glass fiber enable manufacturing a support part with a light weight .

Figure 2 provides a perspective view of a dewatering element 10 according to the invention. The fastening profiles 18 of the surface part 14 and the fastening profiles 16 of the support part 12 form connections 32 with a positive form closure.

In the dewatering element according to the invention shown in Figure 2, the surface part 14 is composed of one surface block 34, which is advantageous. In this case the measure of the surface block is the machine width of the web forming machine, i.e. the length of the dewatering element. The surface 36 is thus continuous over the entire width of the web forming machine, in which case pressure variation is not generated in the web due to purposeless openings in the dewatering element. In other words, purposeless pressure variation, which causes marking in the web, can then be avoided. More generally, the surface part can be composed of several surface blocks measuring at least 1 m, typically at least 2 m.

Figure 3 shows a dewatering element 10 according to the invention as used in a forming section 38. The forming section 38 is from a web forming machine including a fabric 40 for supporting a web 42 to be manufactured. The web 42 is formed by supplying pulp suspension 46 from a headbox 44 to between wires 46, i.e. fabrics 40. The fabric 40 is a part of the forming section 38, since water is removed between the fabric. The dewatering element 10 includes a support part 12 and a surface part 14. The support part 12 includes fastening profiles 16 of the support part 12 and the surface part 14 includes fastening profiles 18 of the surface part 14. The surface part 14 is adapted to contact the fabric 40 during use. In addition, the fastening profiles 16 of the support part 12 and the fastening profiles 18 of the surface part 14 are adapted to allow connecting the surface part 14 to the support part 12 by pushing the surface part 14 to the direction of the support part 12.

In the embodiment shown in Figure 3, the dewatering element 10 according to the invention is a suction box 39. The cover 41 of the suction box 39 has openings 43 for removing water from the web 42 through the fabric 40. In this embodiment the dewatering element according to the invention has a length of 100 - 800 mm, advantageously 200 - 500 mm.

Figure 4 illustrates a forming section 38 of a web forming machine provided with dewatering elements 10 according to the invention. The forming section 38 also includes fabrics 40 between which water is removed from the web 42.

Figure 5 is a partial enlargement of Figure 4. The circles 50, 52 and the arrow 54 indicate how the partial enlargement has been taken. The partial enlargement shows that the dewatering elements 10 include a support part 12 and a surface part 14. The support part 12 includes fastening profiles 16 of the support part 12 and the surface part 14 includes fastening profiles 18 of the surface part 14. In addition, the fastening profiles 16 of the support part 12 and the fastening profiles 18 of the surface part 14 are adapted to allow connecting the surface part 14 to the support part 12 by pushing the surface part 14 to the direction of the support part 12. The travel direction of the web 42 is from left to right as indicated by the arrow 58.

In the embodiment shown in Figure 5, the dewatering element 10 according to the invention is a loading blade 56. The loading blade is set above the web in connection with a suction box. In turn, loading of the loading blades below the web is adjustable. In this embodiment the dewatering element according to the invention has a length of 5 - 100 mm.

Recoating the surface part of a dewatering element according to the invention can be performed more easily and more economically than before. Recoating becomes easier when the

item to be covered is only the surface part, in which case the support part of the dewatering element need not be moved to the coating location. As regards economic efficiency, it is essential that only the surface part needs to be delivered for coating. Thus transferring the component to be covered for coating does not cost so much as a freight delivery. In addition, the environment is less loaded when the replaceable part is only the surface part. In other words, the support part can be reused with several surface parts.