US3432384A - Fine-spreading and retarding device for the pulp suspension stream in a papermaking machine - Google Patents

Fine-spreading and retarding device for the pulp suspension stream in a papermaking machine Download PDF

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Publication number
US3432384A
US3432384A US461788A US3432384DA US3432384A US 3432384 A US3432384 A US 3432384A US 461788 A US461788 A US 461788A US 3432384D A US3432384D A US 3432384DA US 3432384 A US3432384 A US 3432384A
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Prior art keywords
chamber
spreading
pulp
flow
pulp suspension
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Expired - Lifetime
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US461788A
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English (en)
Inventor
Hans Dahl
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Sulzer Escher Wyss GmbH
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Escher Wyss GmbH
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    • 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
    • D21F1/02—Head boxes of Fourdrinier machines

Definitions

  • FIG.2 FINB-SPREADING AND RETARDING DEVICE FOR THE PULP SUSPENSION STREAM IN A PAPERMAKING MACHINE Filed June 7, 1965 Sheet of 5 FIG! PRIOR ART FIG.2
  • a cylindrical spreading chamber for a papermaking machine including a guide wall-arranged to direct a sus pension of pulp in such a manner that the co-operative relationship between the cylindrical wall and the guide wall will enclose a whirling body of pulp.
  • This invention relates to a fine-spreading and retarding device for the pulp suspension stream in a papermaking machine.
  • Such devices are usually inserted between the pulp pre-spreader and the breast box outlet gap of the machine, and their purpose is to stabilize the paper pulp suspension coming from the spreader, and to main tain constant velocity of flow over the entire width of the machine and in the direction of flow.
  • a known spreading device consists of a tubular spreading chamber having a circular cross section, into which two feed pipes for the pulp suspension open radially. The suspension flows away from this spreading chamber through a narrow slit, which extends over the entire width of the chamber.
  • a second tubular chamber of circular cross section follows, into which the above-mentioned outlet slit opens through a narrow channel.
  • the pulp stream enters the second chamber in such a manner that it forms a secant through the cross section of the second chamber.
  • a fine-spreading and retarding device consists of 'a chamber of substantially pearshaped cross section extending over the entire width of the machine. Streams of high velocity, coming from a coarse spreader, enter this chamber, pass through it radially and finally impinge on a guide wall situated opposite the pulp inlet. The direction of flow is deflected at the said wall, and the pulp suspension is fed to the breast box through one or more perforated rollers.
  • the new fine-spreading and retarding device comprises a spreading chamber of approximately pearshaped cross section extending over the entire machine width, and it has a guide wall for the pulp suspension, as Well as a wall situated opposite said guide wall. Seen in the direction of flow, the pulp inlet is situated in front of the guide wall, and the pulp outlet behind said wall.
  • the device according to the invention is characterised in that the supply connections for the pulp suspension are so arranged that the suspension enters the spreading chamber substantially in the tangential direction of theguide wall.
  • the angle 5, at which the supplied suspension meets the suspension already in the spreading chamber is less than 30", preferably less than 20.
  • a pre-chamber the width of which is substantially equal to the width of the spreading chamber, and the internal width of which, at the inlet point, is substantially equal to the internal width of the pulp suspension flow conduits opening into 'it.
  • the length of the pre-chamber viewed in the direction of flow, may be comparatively short.
  • it is of such dimensions that complete unification of the partial streams and a certain equalization of the flow profile already occur in the pre-chamber.
  • the two large boundary walls of the pre-chamber may be parallel to each other, or may converge in the direction of flow of the pulp suspension.
  • a further safeguard against the formation of flowseparation regions and dead-water zones may be provided if the axis of the flow conduits for the pulp suspension fiow makes an angle 0: of 5 to 20, preferably about 10, with the pre-chamber wall adjacent the spreading chamber.
  • a preferably rotating perforated roller may be arranged in known manner in the pulp discharge gap.
  • the function of the fine-spreading and retarding chamber according to the invention is to render uniform the flow profile of the pulp suspension over the machine width and with regard to time, and to reduce the velocity of flow.
  • the necessary retardation of the flow velocity which is essential to obtain in the breast box following the finespreading and retarding device, a flow controlled over the entire height and particulaly on the free surface, the following numerical values are given:
  • the outlet velocity of the pulp suspension should amount to only 0.3-0.9 m./sec.
  • the inlet velocity may be l-8 m./sec. and the outlet velocity 0.2l.6 m./sec.
  • the ratio between the flow velocities at inlet and outlet from the spreading chamber is about 5:1, with a maximum of about 10:1.
  • FIG. 1 shows a conventional spreading chamber in cross section
  • FIG. 2 shows a simple embodiment of the chamber according to the invention in cross section
  • FIG. 3 shows another embodiment of the chamber according to the invention in cross section
  • FIG. 4 shows another embodiment of the chamber according to the invention in cross section
  • FIG. 5 shows another embodiment of the chamber according to the invention in cross section.
  • FIG. 6 shows another embodiment of the chamber according to the invention in cross section
  • FIG. 7 shows a perspective view of the chamber according to the invention.
  • FIG. 1 shows the form of a known spreading chamber in cross section. It consists of a chamber 1, to which one or more pulp feeding pipes 2 are attached so that the jet of pulp, i.e. the pulp suspension stream 3 passes radially through the chamber. It strikes against the guide wall 4, extending approximately in the direction of the pulp outlet. The stream 3 is deflected into the pulp outlet direction 20 and into the opposite direction 21, forming two whirling bodies 22 and 23, on the one hand, and a uniflow pulp stream 24 on the other.
  • the jet of pulp i.e. the pulp suspension stream 3 passes radially through the chamber. It strikes against the guide wall 4, extending approximately in the direction of the pulp outlet.
  • the stream 3 is deflected into the pulp outlet direction 20 and into the opposite direction 21, forming two whirling bodies 22 and 23, on the one hand, and a uniflow pulp stream 24 on the other.
  • FIG. 2 shows an embodiment of the fine-spreading chamber according to the invention in cross section in which, for producing only one whirling body, the pulp suspension is introduced tangentially.
  • the spreading chamber 1 has a pear-shaped cross section, and after entering the chamber, the suspension stream flows along the guide wall 4. Opposite the guide wall is a bulged wall 25, in which only one whirling body 26 is formed.
  • the device is so constructed that the angle which the pulp suspension stream 3 makes with the suspension already whirling in the spreading chamber is as small as possible. In practice, it has been found that with angles larger than 30 at the point at which the two streams meet, unstable eddies are formed. With angles of less than 30, or still better, less than 20, such eddies are, however, suppressed with certainty.
  • a pre-chamber 6 adjoining the gap-like pulp inlet 5 is a pre-chamber 6, which the pulp suspension first enters.
  • the pre-chamber 6 extends over the entire machine width, but has only an internal width, see FIG. 7, which at the inlet position 9, is substantially equal to the internal width 10 of the flow conduits, i.e. the pipes 2 opening into it. Unification of the individual partial streams and extensive equalizations of the flow profile occur already in the pre-chamber 6.
  • the pulp suspension, thus prestabilized now enters the spreading chamber 1, in which its velocity of flow is reduced and its profile still further equalized.
  • the two boundary walls 11 and 12 of the pre-chamber are arranged parallel to each other. In the embodiments of FIGS. 3 to 5, they converge in the direction of flow. To reduce still further, and even at high velocities to suppress altogether, the tendency of the flowing pulp suspension to form eddies the moment it meets the suspension already present in the chamber, it is proposed to arrange the flow conduits, i.e. the pipes 2 so that their axis 13 (see FIG. 5) makes an angle a of from 5 to with the pre-chamber wall 11.
  • FIG. 3 shows an embodiment of the device according to the invention, in which the cross section of the spreading chamber 1 steadily tapers in the direction of flow of the pulp. There is thus formed a pulp outlet gap 16 of reduced cross section. This step also ensures equalization of the flow profile, and prevents the formation of flakes.
  • a preferably rotating perforated roller 17, as shown in FIGS. 2, 4, 5, 6, 7, or other known throttling elements, for example a perforated plate, a bar roller or the like, may also be arranged in the pulp outlet gap 16.
  • the flow conduits of the pulp suspension flow may be introduced into the spreading chamber in any direction and at any point, one or more guide plates 15 being provided to ensure that the entering pulp suspension stream is deflected into the desired direction (see FIG. 6).
  • the pre-chamber 6 is connected by numerous feed pipes 2 to a coarse spreading device, consisting of a conically tapering pipe 27, from which the pipes 2 branch out at right-anges to the pipe axis.
  • a coarse spreading device consisting of a conically tapering pipe 27, from which the pipes 2 branch out at right-anges to the pipe axis.
  • This spreader belongs to the prior art; it is mentioned here merely as example.
  • the figure shows how the finespreading and retarding device is inserted between the coarse spreader and the breast box.
  • a fine-spreading and retarding device for the pulp suspension stream in a papermaking machine comprising means defining a cylindrical spreading chamber of pearshaped cross section, having cylindrical walls extending across the entire machine width and having a supply connection for the pulp suspension disposed in the region of the bulged end of said pear-shaped cross section and a discharge gap at the tapering end of said pear-shaped cross section; one of said cylindrical walls extending, along the circumference of said pear-shaped cross section, from said supply connection to said discharge gap and serving as a guide wall for the throughflowing pulp suspension, said guide wall having a trailing end arranged to direct the throughflowing suspension into said discharge gap; said supply connection being arranged to introduce the pulp suspension into said spreading chamber substantially in the tangential direction of said guide wall; and the cylindrical wall opposite said guide wall being bowed outward away from said trailing end so as to enclose, with the pulp suspension flowing along said guide wall, a substantially stationary whirling body of pulp suspension.
  • said supply connection for the pulp suspension comprises a prechamber preceding said spreading chamber in the direc tion of flow; flow conduits for feeding the pulp suspension into said pre-chamber, said pro-chamber having two walls which converge in the direction of flow and extend across the entire machine width, said walls forming a gap opening into said spreading chamber and in which at least one of said two pre-chamber walls makes with the flow axis of said flow conduits an angle of from 5 to 20, the internal width of said pre-chamber, in the region where said flow conduits enter it, being substantially equal to the internal width of said flow conduits.

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US461788A 1964-06-13 1965-06-07 Fine-spreading and retarding device for the pulp suspension stream in a papermaking machine Expired - Lifetime US3432384A (en)

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DEE0027215 1964-06-13

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US3432384A true US3432384A (en) 1969-03-11

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US (1) US3432384A (de)
AT (1) AT267307B (de)
CH (1) CH430422A (de)
GB (1) GB1115030A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021296A (en) * 1973-11-23 1977-05-03 A. Ahlstrom Osakeyhtio Method and device for manufacturing a continuous material web of elongated fibrous particles
US4964950A (en) * 1985-01-24 1990-10-23 A. Ahlstrom Corporation Method and apparatus for dividing and uniting the flows of high-consistency fibre suspensions
US6461479B1 (en) * 1996-06-27 2002-10-08 áDRITZ-PATENTVERWALTUNGS-GESELLSCHAFT M.B.H. Process and device for distributing a pulp suspension, particularly at medium consistency
US11007461B2 (en) * 2016-07-12 2021-05-18 Valmet S.P.A. Dust-handling device for collecting and handling dust in a paper-making environment

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3255074A (en) * 1964-04-03 1966-06-07 Beloit Corp Headbox for paper-making machine

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3255074A (en) * 1964-04-03 1966-06-07 Beloit Corp Headbox for paper-making machine

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4021296A (en) * 1973-11-23 1977-05-03 A. Ahlstrom Osakeyhtio Method and device for manufacturing a continuous material web of elongated fibrous particles
US4964950A (en) * 1985-01-24 1990-10-23 A. Ahlstrom Corporation Method and apparatus for dividing and uniting the flows of high-consistency fibre suspensions
US6461479B1 (en) * 1996-06-27 2002-10-08 áDRITZ-PATENTVERWALTUNGS-GESELLSCHAFT M.B.H. Process and device for distributing a pulp suspension, particularly at medium consistency
US11007461B2 (en) * 2016-07-12 2021-05-18 Valmet S.P.A. Dust-handling device for collecting and handling dust in a paper-making environment

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Publication number Publication date
GB1115030A (en) 1968-05-22
CH430422A (de) 1967-02-15
AT267307B (de) 1968-12-27

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