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
• • 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
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines

Definitions

• the invention concerns a gap former in a paper machine, comprising a twin-wire zone, which is composed of a first forming- wire loop and of a second forming- wire loop and which starts from the forming gap, into which the slice part of the headbox feeds a pulp suspension jet, and which forming gap is defined, from one side, by the first forming wire, which runs over the forming roll, and, from the opposite side, by the substantially straight run of the second forming wire starting from the breast roll to the forming roll, draining equipment being fitted inside the first forming- wire loop after the forming gap and the forming roll, which draining equipment is provided with a deflector duct and with a deflector rib placed against the first forming wire in the lower part of said deflector duct, and, inside the second wire loop, a forming shoe is arranged, which is provided with a ribbed deck consisting of forming ribs and which is loaded against the second forming wire.
• the pulp suspension is passed from the headbox into a gap formed by a forming roll and by two wires, after which gap the two wires and the pulp layer placed between them follow the curve form of the forming roll, most of the water being drained through the wires.
• the necessary dewatering pressure is produced by means of the tension of the outer wire, which tension produces a pressure in the pulp layer, which pressure is proportional to the wire tension and inversely proportional to the curve radius of the forming roll.
• part of the kinetic energy of the pulp jet is converted to pressure energy, and the jet speed is lowered accordingly.
• the dewatering through the outer wire away from the forming roll is intensified by the centrifugal force. Dewatering towards the forming roll can be intensified by means of negative pressure in a zone of the forming roll.
• the present invention is mainly characterized in that the first forming rib of the forming shoe or a unified forming-rib construction composed of two or more forming ribs is mounted so that it can be loaded adjustably, so that the free run of the forming wires from the forming roll to the first forming rib is substantially little.
• the first or the first two forming ribs are mounted on the former resiliently, provides the significant advantage that said rib can be brought very close to the former roll, even so that the rib can be placed facing the former roll, in which case there is no free distance between the former roll and the rib. This improves the stability of the wires and the runnability of the former in different running situations to a substantial extent.
• said rib is mounted resiliently, it can also be mounted adjustably, in which case such an adjustable rib permits running with a number of grammages, thicknesses, etc.
• the solution in accordance with the present invention is particularly usable for different grades of fine paper. Further, it can be stated as a remarkable addi- tional advantage that, in the invention, the deflector rib of the MB-unit can be placed facing the resilient ribbed shoe to improve the draining. In such a case, the deflector rib does not have to be loaded or adjustable, but it may be stationary.
• Figure 1 is a schematic side view of a gap former in accordance with the invention.
• Figure 2 shows an enlarged detail of the gap former as shown in Fig. 1 from the area of the former roll, the resilient forming rib, and the deflector rib.
• Figure 3 is a schematic sectional view of the installation of the resilient former rib in relation to the former roll.
• the former shown in Fig. 1 is a so-called gap former, in which the slice part 31 of the headbox 30 feeds a pulp suspension jet into the forming gap G between the forming wires 10,20.
• the geometry of said forming gap G is determined from above by the forming roll 11 and from below by the breast roll 21 , which guides the second forming wire 20, i.e. , in the illustration in Fig. 1 , the lower wire.
• the forming roll 11 is followed by the MB-unit 40.
• the breast roll 21 has been arranged so that its position can be regulated in the direction of the arrow E, i.e. , in the exemplifying embodiment shown in Fig. 1 , substantially in the vertical direction.
• the geometry of the forming gap G is prefer ⁇ ably such that, on the forming roll 11 , the forming wires 10,20 have a common curve sector a.
• the first forming wire 10 has been formed into a wire loop by means of the forming roll 11 and the guide rolls 14, and, as was already stated above, inside said first forming- wire loop 10, the MB-unit 40 is fitted.
• the MB-unit 40 comprises two draining chambers 41,42, in which a vacuum has been arranged to be effective.
• Each draining chamber 41,42 is provided with a drain duct 43,44, through which the water that has been passed into the draining chamber 41,42 with the aid of said vacuum is drained away from the draining chamber.
• the water enters along the deflector duct 12, 13.
• the deflector rib 12a As is shown in connection with the first deflector duct 12, at the lower end of said deflector duct 12, there is a deflector rib 12a placed against the first forming wire 10.
• the deflector rib 12a defines said deflector duct 12, and the water, which is guided by the deflector rib 12a, is drained through the first forming wire 10 along the first deflector duct 12 into the first draining chamber 41.
• the second forming wire 20 has been formed into a wire loop by means of the breast roll 21 and the guide rolls 21a.
• a first forming rib 22 of a forming shoe is arranged, which is placed against the second forming wire 20 and which is followed by a number of forming ribs 23, which are placed at a distance from one another and which have been arranged as a set or ribs or as a ribbed deck.
• the set of ribs or the equivalent ribbed deck has been integrated as a common box 24, which can be subjected to a vacuum if necessary, by means of which vacuum the draining through the second forming wire 20 is intensified.
• the first set of ribs or the equivalent ribbed deck is substantially straight or slightly curved.
• a second set or ribs 25 or an equivalent ribbed deck which is fitted inside the second forming- wire loop 20 and which has been integrated similarly as a box 26.
• the open ribbed deck of the second set of ribs 25 has been formed as curved so that, owing to this curve form, a compression is applied to the stock web running between the wires 10,20. whereby this compres ⁇ sion, together with the centrifugal force produced by the curve form of the ribbed deck 25 , produces draining of water out of the stock web through the first forming wire 10.
• This water that has been drained out of the stock is passed along the second deflector duct 13 into the second draining chamber 42, being aided by a vacuum that is preferably effective in said chamber 42.
• the draining is intensified and promoted further by the deflector rib (not shown) placed in the lower part of the second deflector duct 13.
• suction boxes 27 are provided with a ribbed deck and by whose means draining of water out of the stock web through the second forming wire 20 is produced, and by means of which suction boxes 27 it is achieved at the same time that the stock web follows along with the second forming wire 20 as the runs of the wires 10,20 are separated from one another.
• the second forming roll 28 which is provided with a suction zone 29 for further removal of water out of the stock web and so as to guarantee that the stock web remains on the second forming wire 20.
• Fig. 2 shows an enlarged detail of the former as shown in Fig. 1 from the area of the forming gap G and of the first forming rib or the equivalent rib construction.
• the first forming-rib construction 22 comprises two successive forming ribs 22a, 22b, which are interconnected by means of a fastening member 22c or equivalent.
• This forming-rib construction 22 is supported on the frame 22d of the former or the box 24 by means of adjustable loading members, preferably loading hoses 22e, so that, by feeding a pressure medium into these loading hoses 22e in the desired way, the rib construction 22 can be made to be positioned in the desired position in relation to the wires 10,20 and to the forming roll 11.
• the installation of the forming-rib construction 22 is resilient, in which case the ribs 22a, 22b are placed automatically in the correct position if, for example, the thickness of the pulp suspension layer fed into the forming gap G is changed.
• the pressure of the pressure medium in the loading hoses 22e can be regulated even during running. Besides the possibility of regulating the pressure of the ribs against the second forming wire 20 by means of the loading hoses 22e, by means of said loading hoses 22e it is also possible to regulate the angle of the ribs 22a,22b in relation to the forming wire 20.
• the forming rib 22a in accordance with the invention can be placed fully facing the forming roll 11, in which case there is no such free distance a at all.
• the elimination of this free distance improves the stability of the wires 10,20 and the runnability of the former in different running situations essentially.
• the free run from the forming roll 11 to the first forming rib 22a is preferably in the range of 0...70 mm.
• Such an adjustable, either resilient or non- resilient installation is particularly favourable when grades of fine paper are run, in which case the common curve sector of the wires 10,20 on the forming roll 11 is very little and the streaks occurring in the fibre stock are more common than in cases in which a larger curve sector a is used.
• a rib 22a, 22b or equivalent rib construction 22 whose position can be adjusted can be pulled apart from the forming wire 20 when the machine is being started or run down. Also otherwise, if necessary, the rib can be pulled apart from the wire 20.

Landscapes

• Paper (AREA)
• Making Paper Articles (AREA)
• Folding Of Thin Sheet-Like Materials, Special Discharging Devices, And Others (AREA)
• Diaphragms For Electromechanical Transducers (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8540921

Family Applications (1)

Country Status (8)

Cited By (3)

Families Citing this family (1)

Citations (2)

• 1994
  • 1994-06-15 FI FI942832A patent/FI112509B/fi active
• 1995
  • 1995-05-22 CA CA002168119A patent/CA2168119C/en not_active Expired - Fee Related
  • 1995-05-22 EP EP95920084A patent/EP0712454B1/en not_active Expired - Lifetime
  • 1995-05-22 DE DE69523257T patent/DE69523257T2/de not_active Expired - Lifetime
  • 1995-05-22 JP JP50168396A patent/JP3828148B2/ja not_active Expired - Fee Related
  • 1995-05-22 WO PCT/FI1995/000276 patent/WO1995034713A1/en active IP Right Grant
  • 1995-05-22 AT AT95920084T patent/ATE207154T1/de active
  • 1995-05-22 KR KR1019960700771A patent/KR100356281B1/ko not_active IP Right Cessation

Patent Citations (2)

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