A WEARING ELEMENT, SUCH AS A FOIL OR A COVER OF A SUCTIONBOX IN A PAPER MACHINE WIRE SECTION

Description

[0001] The present invention relates to a foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine, and to a method for the manufacturing thereof, as defined in the preambles of appended independent claims.

[0002] The drainage on the wire of a paper machine is brought about by hydrodynamic pressure which is accomplished by drainage elements disposed below the wire, such as foils or vacuum boxes. The wire running on the foils and vacuum box covers abrades the upper surfaces of the foils and the vacuum boxes heavily.

[0003] The endurance of foils made of metal has been improved by providing the upper surfaces of the foils with special ceramic inserts or upper parts, as shown for instance in Finnish Patent Application No. 935600 (corresponding to WO-A-93/00473). Foils are also made of ceramic materials. These foil constructions are, however, very expensive.

[0004] It is known through Svensk Papperstidning, vol. 70, no. 7, 1967; THUNE foils, made of aluminium or stainless steel and having an upper cover made of plastic elements. The plastic elements may be replaced by new ones when worn.

[0005] It is also known from JP-A-61-117266 (upon which the preamble of claims 1 and 5 is based) to manufacture sliding material, for use in paper machines, which is resistant to heat shock cracking and breakage. The base material is made of stainless steel or carbon steel, which has a large thermal expansion coefficient. The surface of the sliding material is covered with ceramic material by plasma thermal spraying. The ceramic material has a lower thermal expansion coefficient than the base material. Thus a base material which is superior in heat shock resistance is said to be achieved.

[0006] It is an object of the present invention to provide an element susceptible to wear in a paper machine and a method of manufacturing it, in which the above problems are minimized.

[0007] The object is in particular to provide an abrasion-resistant foil or the like the purchase price of which is advantageous.

[0008] The above objects are achieved by the invention, which is characterized by the features according to the appended claims.

[0009] Thus a foil, vacuum box cover or drainage element is according to the present invention made of a pressed, extruded or rolled aluminium profile. The surface of the profile is coated, by means of electrolytic plasma coating, thermic spray coating or detonation spray coating, with a layer of oxide to make the profile durable. Aluminium can easily be extruded into a desired profile and in lengths corresponding to the width of the wire.

[0010] Correspondingly a method of manufacturing a foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine is characterized in that

• the foil, the vacuum box cover or the drainage element is made of a pressed or extruded aluminium profile and
• the surface of the profile is coated, by means of electrolytic plasma oxidation, thermic spray coating or detonation coating, with a layer of oxide to make the profile durable.

[0011] According to an advantageous embodiment of the invention, the aluminium profiles are surface treated by means of electrolytic plasma oxidation so that a layer of aluminium oxide, 50 - 400 µm thick, is deposited on the surface of the profile. The aluminium surface is thus electrolytically coated with a relatively thick layer of aluminium oxide, Al₂O₃. The oxide layer produced is hard, abrasion-resistant and forms protection against corrosion by passivating the surface of the profile.

[0012] Normal anodizing, anodical oxidation, of aluminium only produces an oxide layer having a thickness of 5 - 15 µm, which gives protection against corrosion and abrasion but does not substantially improve the hardness of the aluminium profile. An oxide layer thickness of 50 - 400 µm improves, however, the hardness of the aluminium profile considerably.

[0013] Electrolytic plasma oxidation is an environment friendly and energy-saving process. The aluminium profile, which, if necessary, is pretreated, pickled and degreased, is immersed in a weak alkalic electrolytic solution, preferably of 0,001 - 0.05 %, and connected to the anode. A voltage of 120 - 380 V is connected to the system. The aluminium oxide surface which is produced tehereby has a low porosity, about 3 %.

[0014] According to another advantageous embodiment of the present invention, the aluminium profile can be surface treated by means of thermic spray coating, such as plasma spray coating or detonation spray coating. By thermic spray coating, powder of metal and/or non-metallic material is converted into molten or plastic condition and sprayed as molten particles onto the surface to be treated. By means of thermic spray treatment, an aluminium profile can be coated with aluminium oxide, chromium oxide, zirconium oxide, aluminium silicate or carbides.

[0015] The plasma spray coating process utilizes electric energy, whereas the detonation coating process gets the energy needed through combustion. In both coating processes the substrate is held at a low temperature, which in plasma spray coating usually is < 300°C and in detonation coating is between 50 to 100°C.

[0016] All substrates normally require some kind of pretreatment for good adherence of the coating. A strong adherence between the substrate and a ceramic material is, however, achieved even without a binding intermediate layer. The adherence corresponds to a value of 100 MPa at least.

[0017] By thermic spray treatment, a coating having a very low porosity is brought about. The plasma spray coating produces a coating having a porosity of about 3 %, whereas the detonation spray coating produces a coating having a porosity of about 1 %.

[0018] The total cost of foils and vacuum box covers produced according to the invention of surface treated aluminium profiles is considerably lower than the total costs of corresponding foils or vacuum box covers made of steel, plastic and ceramic inserts, as shown for instance in the Finnish Patent Application No. 935600. The aluminium profile is as such cheap and the surface treatment makes it durable. The difference in cost is still greater, if a foil according to the invention is compared with a ceramic foil.

[0019] Repair of worn profile elements can easily be brought about by spray treatment. A completely worn out aluminium profile is, however, usable and relatively valuable as scrap.

[0020] The invention will be described in more detail in the following with reference to the accompanying drawings, in which

FIG. 1

is a schematic view of a foil box with three parallel foils disposed transverse to the direction of the wire, and

FIG. 2

is a schematic, vertical cross-sectional view of a foil taken in the direction of the wire.

[0021] FIG. 1 shows a foil box 10 with three foils 12, 14, and 16 made of extruded aluminium profiles. The foils are disposed transverse to the direction of the wire and attached by means of dovetail profiles to supporting members 18, 20, 22 of steel.

[0022] FIG. 2 shows a vertical cross section of a foil 14 made of an extruded aluminium profile 24. The lower portion of the profile is connected to the supporting member 20 by means of a dovetail joint. The wire 26 bears against the upper surface 28 of the foil. The upper surface of the foil has a 50 - 400 µm thick outer layer 30 of oxide, which makes the foil abrasion-resistant and hard.

[0023] The invention is not limited to the embodiments described and illustrated above, but can be varied in many ways within the scope and spirit of the invention, which is defined in the appended claims.

Claims

1. A foil, a vacuum box cover or corresponding drainage element in the wire section of a paper machine, which foil, vacuum box cover or drainage element is at least partly coated with an oxide layer, which has been achieved by electrolytic plasma coating, thermic spray coating or detonation spray coating, characterized in that the foil, vacuum box cover or drainage element is made of a pressed, extruded or rolled aluminium profile (24).

2. A foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine according to claim 1, characterized in that the aluminium profile (24) is at least partly coated with a 50 - 400 µm thick layer of aluminium oxide (30), which has been achieved by electrolytic plasma oxidation.

3. A foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine according to claim 1, characterized in that the aluminium profile (24) is at least partly coated with an oxide layer (30), which has been achieved by plasma or detonation spray coating.

4. A foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine according to claim 1, characterized in that the aluminium profile is at least partly coated with a surface layer (30) containing chromium oxide, aluminium oxide, zirconium oxide and/or aluminium silicate.

5. A method of manufacturing a foil, a vacuum box cover or a corresponding drainage element in the wire section of a paper machine, characterized by

- coating the surface of a foil, a vacuum box cover or a drainage element made of a pressed or extruded aluminium profile, by means of electrolytic plasma oxidation, thermic spray coating or detonation coating, with a layer of oxide.

6. A method according to claim 5, characterized in that the aluminium profile is coated with a 50 - 400 µm thick layer of aluminium oxide by means of electrolytic plasma oxidation.

7. A method according to claim 5, characterized in that the aluminium profile is coated by means of plasma or detonation spray coating with a surface layer containing aluminium oxide, chromium oxide, zirconium oxide and/or aluminium silicate.

8. A method according to claim 5, characterized in that the aluminium profile is coated by means of plasma or detonation spray coating with a surface layer containing carbides.

Ansprüche

1. Foil, Saugkastendeckel oder entsprechendes Entwässerungselement in der Siebpartie einer Papiermaschine, welches Foil, welcher Saugkastendeckel oder welches Entwässerungselement zumindest teilweise mit einer Oxidschicht überzogen ist, die durch elektrolytische Plasmabeschichtung, thermische Spritzbeschichtung oder Detonations-Spritzbeschichtung erreicht worden ist, dadurch gekennzeichnet, dass das Foil, der Saugkastendeckel oder das Entwässerungselement aus einem gepressten, stranggepressten oder gewalzten Aluminiumprofil (24) gefertigt ist.

2. Foil, Saugkastendeckel oder entsprechendes Entwässerungselement in der Siebpartie einer Papiermaschine nach Anspruch 1, dadurch gekennzeichnet, dass das Aluminiumprofil (24) zumindest teilweise mit einer 50-400 µm dicken Schicht von Aluminiumoxid (30) überzogen ist, die durch elektrolytische Plasmaoxidation erreicht worden ist.

3. Foil, Saugkastendeckel oder entsprechendes Entwässerungselement in der Siebpartie einer Papiermaschine nach Anspruch 1, dadurch gekennzeichnet, dass das Aluminiumprofil (24) zumindest teilweise mit einer Oxidschicht (30) überzogen ist, die durch Plasma- oder Detonations-Spritzbeschichtung erreicht worden ist.

4. Foil, Saugkastendeckel oder entsprechendes Entwässerungselement in der Siebpartie einer Papiermaschine nach Anspruch 1, dadurch gekennzeichnet, dass das Aluminiumprofil zumindest teilweise mit einer Oberflächenschicht (30) überzogen ist, die aus Chromoxid, Aluminiumoxid, Zirconiumoxid und/oder Aluminiumsilikat besteht.

5. Verfahren zur Herstellung eines Foils, eines Saugkastendeckels oder eines entsprechenden Entwässerungselements in der Siebpartie einer Papiermaschine, dadurch gekennzeichnet, dass

- die Oberfläche eines Foils, eines Saugkastendeckels oder eines Entwässerungselements, die aus einem gepressten oder stranggepressten Aluminiumprofil gefertigt sind, durch elektrolytische Plasmaoxidation, thermische Spritzbeschichtung oder Detonations-Beschichtung mit einer Oxidschicht überzogen ist.

6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass das Aluminiumprofil mit einer 50-400 µm dicken Aluminiumoxidschicht durch elektrolytische Plasmaoxidation beschichtet wird.

7. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass das Aluminiumprofil durch Plasma- oder Detonations-Spritzbeschichtung mit einer Oberflächenschicht überzogen wird, die Aluminiumoxid, Chromoxid, Zirconiumoxid und/oder Aluminiumsilikat enthält.

8. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass das Aluminiumprofil durch Plasma- oder Detonations-Spritzbeschichtung mit einer Oberflächenschicht überzogen wird, die Karbide enthält.

Revendications

1. Foil, couverture de boîte à vide ou élément de drainage correspondant dans la section toile d'une machine à papier, lequel foil, couverture de boîte à vide ou élément de drainage étant au moins partiellement recouverts d'une couche d'oxyde, obtenue par revêtement électrolytique à plasma, revêtement par pulvérisation thermique ou revêtement par pulvérisation par détonation, caractérisés en ce que le foil , la couverture de boîte à vide ou l'élément de drainage est fait à partir d'un profilé d'aluminium (24) pressé, extrudé ou roulé.

2. Foil, couverture de boîte à vide ou élément de drainage correspondant dans la section toile d'une machine à papier selon la revendication 1, caractérisés en ce que le profilé en aluminium (24) est au moins partiellement recouvert d'une couche d'oxyde d'aluminium (30), de 50 à 400 µ m d'épaisseur, qui a été obtenue par une oxydation électrolytique par plasma.

3. Foil, couverture de boîte à vide ou élément de drainage correspondant dans la section toile d'une machine à papier selon la revendication 1, caractérisés en ce que le profilé en aluminium (24) est au moins partiellement recouvert d'une couche d'oxyde (30), qui a été obtenue par revêtement par pulvérisation à plasma ou à détonation.

4. Foil, couverture de boîte à vide ou élément de drainage correspondant dans la section toile d'une machine à papier selon la revendication 1, caractérisés en ce que le profilé d'aluminium est au moins partiellement recouvert d'une couche de surface (30) contenant de l'oxyde de chrome, de l'oxyde d'aluminium, de l'oxyde de zirconium et / ou du silicate d'aluminium.

5. Procédé de fabrication d'un foil, d'une couverture de boîte à vide ou d'un élément de drainage correspondant dans la section toile d'une machine à papier, caractérisé en ce qu'il comprend l'étape consistant à :

- revêtir d'une couche d'oxyde la surface d'un foil , d'une couverture de boîte à vide ou d'un élément de drainage, fait à partir d'un profilé d'aluminium pressé ou extrudé, au moyen d'une oxydation électrolytique à plasma, d'un revêtement par pulvérisation thermique ou un revêtement par détonation.

6. Procédé selon la revendication 5, caractérisé en ce que le profilé d'aluminium est revêtu d'une couche d'oxyde d'aluminium de 50 à 400 µm d'épaisseur au moyen d'une oxydation électrolytique à plasma.

7. Procédé selon la revendication 5, caractérisé en ce que le profilé d'aluminium est revêtu, au moyen d'un revêtement par pulvérisation à plasma ou à détonation, d'une couche de surface contenant de l'oxyde d'aluminium, de l'oxyde de chrome, de l'oxyde de zirconium et / ou du silicate d'aluminium.

8. Procédé selon la revendication 5, caractérisé en ce que le profilé d'aluminium est revêtu, au moyen d'un revêtement par pulvérisation à plasma ou à détonation, d'une couche de surface contenant des carbures.

Drawing