Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/04—Arrangements thereof
  • D21F3/045—Arrangements thereof including at least one extended press nip
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/04—Arrangements thereof

Definitions

• the invention relates to a machine for producing fibrous webs, preferably paper webs, with a wire section and with a press section, in particular with the features specified in the preamble of claim 1.
• the press section of this known machine has two so-called long-gap presses.
• the advantages of such long-nip presses are known: the press nip is flat, not essentially linear, as in the case of conventional roller presses. This has the consequence that the pressure (to be exerted on the fibrous web to be dewatered) in the press nip does not start suddenly in the running direction, but can be brought continuously from a low value to a high value. This counteracts the risk that the fibrous web to be dewatered will be pressed in the press nip.
• the flexible press element can be designed as a press hose which is closed at the end, so that no lubricant can penetrate to the outside.
• the press plane there is also arranged horizontally or inclined at approximately 45 degrees.
• disruptive transverse forces occur. Since there is only a single flat press block, the drainage capacity should also not be sufficient for many applications.
• the invention is based on the object of designing a generic machine for producing fibrous webs in such a way that the above-mentioned disruptive transverse forces are avoided and that the dewatering capacity of the press section is increased considerably.
• This object is achieved by the characterizing features of the main claim.
• two independent press nips are formed in the press section. This means that each of the two long-nip presses has its own flexible press element, which, as is known per se, is designed as a press hose which is closed at the end, so that no lubricant can penetrate to the outside.
• the press hose (with the press shoe located therein) and the press roll — as just if known per se — are arranged essentially vertically one above the other. It is decisive in this context, however, that according to the invention the press roll is arranged below the press hose in the first long-nip press and the press roll above the press hose in the second long-nip press.
• the press roll which is provided with recesses for temporarily storing water, is capable of transporting the water penetrated through the lower felt into the recesses in the downward direction without further involvement of the felt. It is important in this context that the water transported downwards by the press roll does not drip into the returning felt, but is caught under the press roll, so that it can run off to the side.
• the lower felt also transports a certain amount of water, which is removed from it there.
• the proportion of water that can be discharged to the outside via the recesses in the press roll jacket is considerably larger when the press roll is at the bottom - thanks to the initial transport direction downwards - than when the press roll is at the top.
• the total amount of water which is withdrawn from the fibrous web in the first extended-nip press is above average.
• the jackets of the press rolls must have recesses (eg blind holes) for the temporary storage of water.
• suction rolls can be provided; rather, suction rolls are excluded because the press rolls - in the usual working widths of the paper machines - must be designed as deflection-setting rolls, the roll shells of which are always liquid-tight.
• the arrangement according to the invention has yet another advantage, since the run-up point of the fibrous web, as already mentioned above, is in the upper ascending quadrant of the circumference of the press roll (according to claim 2, preferably immediately before entering the press nip), so the path of the fibrous web must be slightly inclined upwards from the wire section to the first press nip.
• the first press nip comes to lie at a relatively great height, so that the foundation supporting the long nip press can be arranged at the same height level as the foundation for the wire section and for the subsequent second long nip.
• the press roll of the first extended nip press (above the flexible press element) is arranged in reverse, the path of the fibrous web should be inclined downward.
• the first press nip would have to be arranged at a very low height level. This would undesirably mean that special, deep-lying foundations would have to be provided for the first press.
• US Pat. No. 3,293,121 describes a long-nip press immediately following the wire section, with a press roll underneath and a flexible press element lying on top, which, however, is only pressed onto the press roll by means of air pressure. This means that a press shoe is missing, so that adequate drainage performance cannot be expected.
• the U.S. Re. 30,268 discloses a long-nip press, in turn, with a press roll at the bottom and a flexible press element at the top. This is pressed onto the press roll by means of several press shoes.
• the flexible press element is a press belt rotating over guide rolls. The interior enclosed by this is on the two faces inevitably open.
• the press shoes which have to be supplied with a lubricant, are surrounded by a housing which slidably abuts the press belt. Nevertheless, there is a risk that some of the lubricant will leak out. It is then particularly difficult, if not impossible, with this arrangement to fully absorb this lubricant component which is forced outwards. The risk of contamination of the paper web and the machine parts can practically not be eliminated with this arrangement. This danger is avoided in the arrangement according to DE-OS 34 26 235, thanks to the press hose which is closed at the end.
• a disadvantage of this known arrangement is, however, that the paper web, in this case together with two felts, runs in an approximately horizontal direction to the flat press nip.
• the maximum line force is preferably limited to an average value (e.g. 800 kN / m).
• Another advantage arises from the fact that the fibrous web has to run from top to bottom with an incline from the first to the second press nip. As a result, the second press nip comes to be at the normal level, which is lower than the level of the first press nip.
• the main drainage is directed downwards in the first press and downwards in the second press above. This not only achieves a particularly high total drainage, but also more uniform paper surfaces on the top and bottom of the paper web, i.e. the so-called two-sidedness of the finished paper web is reduced.
• the paper web is preferably transferred from the first to the second press in such a way that the paper web is continuously guided through at least one felt belt.
• the arrangement specified in claim 7 is particularly advantageous. Alternatively, however, the arrangement described in claim 8 can also be provided.
• the drawing shows an exemplary embodiment of the invention in a schematic side view. From a four-wire section on which the paper web is formed in the usual way, a screen suction roll 10 and a screen reversing roll 11 as well as the endless screen belt 12 can be seen. A take-off felt 13 coming from above runs over a take-off roll 14, whereby it web decreases from the sieve belt 12. A felt belt 15 comes from below, which passes over a guide roller 16 and from here together with the paper web and the take-off felt 13 in the direction of the first press
• This long-gap press unit 23, 24 is also only shown schematically.
• a flexible press hose (or “press jacket”) 23 can be seen, which is on a predominantly circular path around a stationary one and not shown in the frame
• a vertically displaceable press shoe 24 is arranged therein, which has a sliding surface for the press hose 23 that is adapted to the shape of the press roll 22 and can press this onto the press roll 22.
• the two felt belts 13 and 15 run through the flat press nip thus formed together with the paper web located between them.
• the path of the two felt belts 13 and 15 in the direction of the first press nip is inclined slightly upward, so that it hits the circumference of the press roll 22 at point A, ie shortly before the entry into the press nip.
• the lower felt 15 runs behind the press nip, initially together with the paper web in an approximately horizontal direction to a guide roller 25 and from this diagonally downwards to a transfer order U, where an upper felt 26 of the second press 30 takes over the paper web by means of a take-off suction roller 27.
• the lower felt 15 then runs down over guide rolls 28 and 29 and then back to the guide roll 16.
• the jacket of the press roll 22, preferably in the form of blind bores, has a storage volume for water which is pressed out of the fibrous web.
• the blind holes are symbolically represented by an interrupted circle. Instead of blind bores, grooves or a fabric jacket or similar can also be 1
• the water transported down through the blind holes is partly removed from the holes by centrifugal force and partly by gravity.
• a scraper 18 is provided for wiping off water.
• the removed water collects in a tub 19 and is discharged to the outside via a line 19 '.
• the second press 30 has a frame-like press frame 31, a press roller 32 and an extended-nip press unit 33, 34.
• the press roller 32 is now above the extended-nip press unit 33, 34 arranged so that the press shoe 34 presses the press jacket 33 in the upward direction against the press roll 32.
• the upper felt 26 runs together with the paper web from the take-off suction roll 27 to a guide roll 35, where it meets with a lower felt 36. From here both felts 26 and 36 run together with the paper web in between on a slightly downward sloping path to the press nip of the second press 30.
• the paper web is completely drained so much that it is free behind the second press nip, i.e.
• the essentially horizontal path of the paper web is designated by 9.
• the upper felt 26 runs upwards via a guide roller 37 and from there back to the take-off suction roll 27.
• the bottom felt 36 runs downwards via a guide roller 38 and from there back to the guide roller 35.
• the two press rolls 22 and 32 are designed in a known manner as deflection setting rolls. This is indicated schematically using the example of the press roll 32: a stationary bending support 32 'extends through the hollow, rotatable roll casing. In the interior of the roll, a hydraulic support device is provided between the bending beam and the roll shell, which transmits the pressing force exerted by the press shoe 34 on the roll shell 32 to the bending beam 32 ', which in turn is supported in the frame 31. 40
• Both press frames 21 and 31 stand on an equally high foundation 8 on which the wire section, for example the rollers 10 and 11, is also supported at the same height.
• the press nip of the first press is at a higher level than the press nip of the second press.

Landscapes

• Paper (AREA)
• Preliminary Treatment Of Fibers (AREA)
• Nonwoven Fabrics (AREA)
• Noodles (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6325640

Family Applications (1)

Country Status (8)

Cited By (10)

Families Citing this family (6)

Citations (6)

• 1988
  • 1988-04-12 AT AT88903245T patent/ATE68540T1/de not_active IP Right Cessation
  • 1988-04-12 EP EP88903245A patent/EP0309530B1/de not_active Expired - Lifetime
  • 1988-04-12 JP JP63503046A patent/JPH01501074A/ja active Granted
  • 1988-04-12 BR BR888806893A patent/BR8806893A/pt not_active IP Right Cessation
  • 1988-04-12 WO PCT/EP1988/000306 patent/WO1988008051A1/de active IP Right Grant
  • 1988-04-12 DE DE8888903245T patent/DE3865618D1/de not_active Expired - Lifetime
  • 1988-12-13 RU SU884613199A patent/RU1830094C/ru active
  • 1988-12-13 FI FI885768A patent/FI93563B/fi not_active Application Discontinuation

Patent Citations (6)

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