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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F9/00—Complete machines for making continuous webs of paper
  • D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type

Definitions

• the invention relates to a method for dewatering a water-containing nonwoven fabric on Fourdrinier paper machines according to the preamble of claim 1 and to a dewatering unit according to the preamble of claim 6.
• the method or the dewatering unit for each of the types described above is known, for example, from DE-OS 27 20 046.
• the base plate of the dewatering box is designed as a rigid shoe that bulges downward.
• the distance between the Fourdrinier wire and the upper circulating wire in the area of the middle Fourdrinier wire section is therefore not variable or, in other words, constant in the running direction of the Fourdrinier wire. Since the water-containing nonwoven fabric on the fourdrinier wire is continuously dewatered upwards during the passage in the area of the middle fourdrinier wire section, the layer thickness of the nonwoven fabric decreases continuously.
• a drainage unit is known from DE-PS 31 53 305, in which support elements running transversely to the direction of travel of the Fourdrinier wire are provided on the underside of the middle Fourdrinier section, which can even be adjusted in the vertical direction.
• the middle long wire section and the upper circulating wire as well as an additionally provided lower circulating wire are arched upwards, so that the two circulating screens in the middle long wire section experience a deflection which is opposite to their deflection on the associated deflecting rollers is directed and thus affects both screens in their lifespan.
• the elements acting from below on the middle Fourdrinier section are pure support or abutment elements without any own drainage function.
• a dewatering method is known in which the nonwoven fabric is guided past a dewatering box by means of a twin-wire section, on the other side of which the sieve has a guideway which consists of strips lying close together. These strips sit with their side facing away from the screen on an elastic base layer and can follow deflections of the screen individually and / or in groups and thereby form an abutment.
• the strips are equipped with a cavity which has a suction slot open towards the sieve side.
• Drainage by means of the strips is only possible at the same time as drainage of the drainage box located on the other side of the screen. Because, in particular due to the elastic base layer underneath the strips, the abutment formed by the strips is then not suitable for Drainage of the nonwoven if no drainage box is provided on the opposite side of the twin-wire section.
• the invention is based on the object of designing the dewatering method of the type mentioned at the beginning and the dewatering unit likewise of the type initially mentioned such that, in addition to intensifying the dewatering of the nonwoven fabric, a fundamentally improved quality and, in particular, improved homogeneity and strength of the dewatered nonwoven or the later completely dried paper web.
• the quality of the paper to be produced is improved because the "two-sidedness" of the paper is reduced by the two-sided drainage, ie the structure of the top and bottom of the finished paper is more identical to each other than with one-sided drainage. This also applies to the fine and filler content of the paper seen from the top and bottom. It cannot be overlooked, moreover, that a better connection (gassing) can be achieved with multi-layer papers, so that they have a considerably improved gap strength.
• this route should be carried out in such a way that the fiber web is successively passed alternately with its upper and lower sides past a drainage area. This further improves the quality of the advantages achieved above.
• the above-mentioned sieves only have to be guided in such a way that, viewed in the running direction of the wire, taking into account the "thinning" of the fiber fleece achieved by a preliminary dewatering phase, they can approach each other accordingly, which is easily achievable in terms of device technology in that the Dewatering surfaces are arranged with respect to the pass-through path of the central fourdrinier section and the section of the upper circulating sieve located there in such a way that the above-mentioned mutual approximation of the sieves occurs, which can easily be achieved in that the successive dewatering surfaces of the successive dewatering boxes can each be arranged closer to the center line of the addressed continuous path.
• the single figure shows a schematic side view of the dewatering section of a Fourdrinier paper machine.
• the nonwoven fabric to be dewatered is guided through the dewatering section by means of a central wire screen section 1 and at the same time is covered on the upper side by an upper circulating screen 2.
• the direction of transport of the nonwoven fabric is indicated by an arrow 3.
• a total of six drainage boxes namely three upper drainage boxes 4a, 4b, 4c and three lower drainage boxes 5a, 5b, 5c, are provided within the drainage section.
• the upper drainage boxes 4a - 4c are arranged to be adjustable in the vertical direction. With this adjustable arrangement, an approximation of the upper circulating sieve 2 and the middle Fourdrinier section 1 can be achieved on the device side, viewed in the running direction 3 of the nonwoven fabric.

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• Paper (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6383250

Family Applications (1)

Country Status (3)

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Family Cites Families (4)

• 1990
  • 1990-06-21 WO PCT/DE1990/000474 patent/WO1990015899A1/de not_active Ceased
  • 1990-06-21 CS CS310590A patent/CS274937B2/cs unknown
  • 1990-06-21 EP EP19900909624 patent/EP0429621A1/de not_active Withdrawn

Non-Patent Citations (1)

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