Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/48—Suction apparatus
  • D21F1/483—Drainage foils and bars

Definitions

• a wearing element such as a foil or a cover of a suctionbox in a paper machine wire section
• the present invention relates to an element susceptible to wear, such as a foil or a vacuum box cover for a paper machine.
• 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.
• 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.
• Foils are also made of ceramic materials. These foil constructions are, however, very expensive.
• foils, vacuum box covers and corresponding drainage elements in the wire section are made of pressed or extruded aluminium profiles. Aluminium can easily be extruded into a desired profile and in lengths corresponding to the width of the wire.
• the aluminium profiles are surface treated by means of electrolytic plasma oxidation so that a layer of aluminium oxide, 50 - 400 ⁇ m thick, is deposited on the surface of the profile.
• the aluminium surface is thus electrolytically coated with a relatively thick layer of aluminium oxide, A1 2 0 3 .
• the oxide layer produced is hard, abrasion-resistant and forms protection against corrosion by passivating the surface of the profile.
• 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 %.
• the aluminium profile can be surface treated by means of thermic spray coating, such as plasma spray coating or detonation spray coating.
• 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.
• an aluminium profile can be coated with aluminium oxide, chromium oxide, zirconium oxide, aluminium silicate or carbides.
• the plasma spray coating process utilizes electric energy, whereas the detonation coating process gets the energy needed through combustion.
• 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.
• 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.
• 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 %.
• 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.
• 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.
• 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.
• 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 ⁇ m thick outer layer 30 of oxide, which makes the foil abrasion-resistant and hard.

Landscapes

• Paper (AREA)
• Coating By Spraying Or Casting (AREA)
• Filters For Electric Vacuum Cleaners (AREA)
• Packaging Of Annular Or Rod-Shaped Articles, Wearing Apparel, Cassettes, Or The Like (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=8542814

Family Applications (1)

Country Status (6)

Families Citing this family (3)

• 1995
  • 1995-02-09 FI FI950559A patent/FI96437C/fi not_active IP Right Cessation
• 1996
  • 1996-02-08 AT AT96901815T patent/ATE205901T1/de not_active IP Right Cessation
  • 1996-02-08 EP EP96901815A patent/EP0817885B1/de not_active Expired - Lifetime
  • 1996-02-08 JP JP8524022A patent/JPH10513507A/ja active Pending
  • 1996-02-08 WO PCT/FI1996/000072 patent/WO1996024717A1/en active IP Right Grant
  • 1996-02-08 DE DE69615351T patent/DE69615351T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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