US3846230A - Fibrous sheet former wherein concentrated stock is passed through separate channels into a deflection chamber and out through an outlet channel - Google Patents

Fibrous sheet former wherein concentrated stock is passed through separate channels into a deflection chamber and out through an outlet channel Download PDF

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US3846230A
US3846230A US00352565A US35256573A US3846230A US 3846230 A US3846230 A US 3846230A US 00352565 A US00352565 A US 00352565A US 35256573 A US35256573 A US 35256573A US 3846230 A US3846230 A US 3846230A
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suspension
sheet
outlet channel
chamber
fibrous particles
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US00352565A
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D Wahren
B Norman
K Grundstrom
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Ahlstrom Corp
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Ahlstrom Corp
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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
    • 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
    • D21F1/028—Details of the nozzle section

Definitions

  • FIBROUS SHEET FORMER WHEREIN CONCENTRATED STOCK IS PASSED THROUGH SEPARATE CHANNELS INTO A DEFLECTION CHAMBER AND OUT THROUGH AN OUTLET CHANNEL Filed April 19, 1973 2 Sheets-Sheet 2 N G Y W United States Patent 3,846,230 FIBROUS SHEET FORMER WHEREIN CONCEN- TRATED STOCK IS PASSED THROUGH SEPA- RATE CHANNELS INTO A DEFLECTION CHAM- BER AND OUT THROUGH AN OUTLET CHANNEL Douglas Wahren, Taby, Bo Norman, Sweden, and Karl-Johan Grundstrom, Solna, Sweden, assignors to A.
  • the invention relates to the field of web forming from a suspension of fibrous particles having a relatively high concentration.
  • Fibre suspension i.e. (more or less freely flowing) pulp fibres in water, distributed roughly over the width of the machine by a distribution system, for instance, a transverse distributor.
  • a distribution system for instance, a transverse distributor.
  • the aim is that the fibres shall divide themselves evenly even in micro scale with the aid of irregular movements (turbulence) in the transporting medium.
  • turbulence irregular movements
  • the distributing system e.g. comprising an oblique speed profile in the head box, which in addition to giving directly an uneven surface weight profile across the paper Web even indirectly is the cause of unstable flow with roughscale turbulence which becomes evident in the wire section 3,846,230 Patented Nov. 5, 1974 and disturbs the sheet forming
  • most often a number (2 -to 5) perforated rolls are placed in the path of the flow.
  • the fibres in suspension have a tendency to become conglomerated owing to mechanogeometric reasons.
  • the task of the perforated rolls includes also generating of tur-blent shear fields which break up the appearing fibre flocks. Because of the tendency of the fibres to form flocks, which is accentuated at increased concentration, a higher fibre concentration than aprox. 0.5 percent cannot be kept if acceptable paper is to be made. (0.5% includes 5 g. fibre per litre, kg., water).
  • the suspension is portioned from the head box, in the best case with fibres evenly distributed, through a small slot, in a horizontal jet which lands on the wire (a more or less *gauzy screen of metal or plastic), which moves at the same speed as the jet.
  • the thickness of the jet may vary from 10 mm. up to and over 50 mm.
  • On the Wire most of the Water has to be removed.
  • concentration has to be increased from 0.5 to approx. 10%. With a jet height of 40 mm. and with an initial fibre concentration of 0.5% this means thus that about 40 litres of water is removed per square metre of wire and with the present machine speeds on a high-speed machine, this takes place within a space of time of about one second. Water removal takes place with the aid of different types of dewatering devices which, depending on the circumstances can both improve or worsen the sheet formation. Anyhow, this process is very hard to control.
  • the bed has the same speed as the jet itself.
  • the actual sheet formation may therefore be compared to a sedimentation process, although it may be a forced one because of the dewatering elements.
  • the sheet will be built up from below in such a manner that the remaining water has to be drained, practically through the entire sheet.
  • the arriving fibres have a certain dispersion according to size and there occurs always a bigger or smaller part of fine fraction where the fibres or rather the fibre fragments are so small that they go with the water in the draining.
  • the retention i.e. the part of the fibre material which remains on the Wire, is often only 50% or even less. Because of this mechanism a certain two-sidedness is also obtained in the sheet, i.e.
  • the pulp fibres are deposited on a wire cloth in one way or another and when the dewatering has been going on for so long that the strength of the sheet formed permits it to be lifted from the wire, it is transported further to the press part where further water is removed.
  • the final dry content of the paper is obtained when the paper has been dried against a number of heated cylinders.
  • the suspension is first divided into several series and parallel coupled units, comprising a tubular chamber with a constriction and an impact face after the constriction as Well as several radial outlets with smaller diameters around the impact face.
  • each outlet of the last units is coupled each to its respective inlet of a transverse row of inlets in the sheet forming equipment.
  • a twosided feeding of suspension flows should, however, be used, ie with two rows of holes arranged on diametrically opposed sides of the sheet forming equipment, so that the flows meet and mix together right before the inlet channel.
  • Such a bilaterally fed apparatus should not be placed right above a wire or felt as the inlet pipes to the lower row of holes takes the space required by the wire which will be placed parallel with and right below the outlet channel.
  • the distribution arrangement and the sheetforming arrangement are built together to one compact unit, in which the distribution apparatus comprises a transverse distributor having a row of openings alongside its one long wall, wherein each opening of the row opens into a disc-formed hollow space with a number of peripherically arranged openings with a smaller diametre at regular distances from each other.
  • These perpherically arranged openings form two parallel rows of holes arranged one on top of the other, which rows lead to a chamber divided into two zones one on top of the other by means of a partition which extends a bit into the outlet channel in which the flows from both rows of holes become reunited.
  • This arrangement operates also with a two-sided feeding of the suspension even if the form is more compact than in the preceding case. Further, this arrangement is relatively sensitive for blocking due to the fact that the pulp is forced through smaller and smaller holes, the number of which, however, increases to a corresponding degree. The blocking results in a striped and thus inacceptable paper quality.
  • the object of the present invention is to create a method to form a continuous material web of fibrous particles, by which the blocking tendency of the highly-concentrated pulp is eliminated and at which the suspension can be fed one-sidedly to the chamber as well as an apparatus with which the web may be deposited on wire or felt and which arrangement is considerably more safe in operation and simpler as to its construction than hitherto.
  • the highly concentrated suspension is divided over and sprayed through several parallel-coupled apertures, after which the suspension jets are accelerated and sprayed at high velocity into at least one chamber in which the jets are reunited and deflected, then the suspension flow is accelerated and deflected anew, and finally the turbulence is allowed to decay in order to form a consolidated threedimensional net structure of fibrous particles before they are deposited.
  • the highly concentrated suspension is distributed over and sprayed through many parallel-coupled outlets or channels in which the velocity of the suspension jets increases;
  • suspension jets are sprayed at high speed into at least one chamber in which the jets are united and deflected;
  • the turbulence is allowed to decay in order to form a consolidated three-dimensional web structure of fibrous particles before they are deposited.
  • the highly concentrated pulp is fed by a transverse distributor of conventional type through a row of parallel-coupled channels whose outlets narrow down to a row of slots through which the pulp is fed at high speed into a chamber common for the channels, into which the accelerated flow is lead again by a throttling for acceleration of the flow before it is again deflected and fed in an outlet channel for decaying of the flow before the three-dimensional web structure, consolidated in it, is deposited.
  • the method according to the invention comprises thus in turn two increases in velocity as well as two changes of direction of the suspension before it is allowed to decay, where-at the second throttlng may be adjusted according to the concentration of the pulp, velocity and type of fibre.
  • the transverse distributor is conveniently diagonal in relation to the channels, so that the channels are connected to the transverse distributor in a diagonal angle, whereat the area of the inlet openings grow in a corresponding degree.
  • FIG. 1 shows a cross-section of a high-concentrate sheet former in accordance with the invention.
  • FIG. 2 is a partial section alongside the line IIII on FIG. 1 and
  • FIG. 3 shows a cross-section of an alternate mode of arrangement of the invention.
  • FIG. 1 the wire or the felt is marked with the reference number 1 and the high-concentration sheet former arranged on the wire or felt with reference number 2.
  • the inlet side of the sheet former 2 has been beveled so that the transverse distributor 3 fastened on its forms an oblique angle with the longitudinal axis of channels 5. Because the inlet side of sheet former 2 has been beveled even the inlets of channels 5 become titled and have a bigger inlet area which decreases the danger of flock formation at the inlets.
  • the channels 5 are cylindrical but change in section 6 into a more and more flattened form and at outlet 7 they are in the horizontal plane very elongated with a small bulge in the lower centre part (FIG.
  • channel 5, 6 The purpose for the flattening of channel 5, 6 is to divide it evenly laterally in chamber 11. In practice, the form shown on FIG. 2 has proved to be the most advantageous. All channels 5, 6 alongside of each other and arranged in the same plane end in the same transverse chamber 11 which has a particular form.
  • the accelerated jets from channel sections 6 hit a wall surface 9, which deflects the suspension flow approx. 90 downwards into chamber 11. Then the deflected suspension flow is forced through a constriction 8 into chamber 11, whereat the velocity of the flow is quickly accelerated and after this the flow is deflected anew 90, so that it meets the bottom surface 10 of chamber 11. After this the turbulent flow is led into an outlet channel 12, in which the turbulence is allowed to decay so that a consolidated three-dimensional web structure is formed by the fibrous particles. The pulp web 13 is finally deposited on the wire or felt 1.
  • the suspension flow 4 is first distributed over a number of channel 5, in which the velocity of the suspension jets is increased in sections 6, after which the jets are sprayed at high velocity into a common chamber 11, in which the jets reunite and deflect, the velocity of the suspension flow is increased and deflected anew in order to increase the intensity of the turbulence and decrease its graduation so that the fibres may arrange themselves freely into a three-dimensional web structure in outlet channel 12 at the decay of the turbulence.
  • the length of the outlet channel is selected or adjusted in a convenient manner so that the web structure has time to consolidate before web 13 is deposited on the Wire or felt 1.
  • Fibres suspended in water have the tendency to cluster together and to form flocks, local web structures. This tendency is due to several factors. Above all the high ratio length-radius of the fibre as well as the fact that the fibre has a certain rigidity which makes it possible for the fibres to tighten themselves against each other and remain in clamped positions. This circumstance, which causes much trouble in conventional paper making, is made use of for sheet forming in the present invention. Instead of trying to hinder flock forming, it is facilitated to the utmost extent and in such a manner that a continuous web structure comes about. In order to create such a thing on the whole, it is required that the amount of fibres per volume unit is sufliciently big, i.e. the concentration must be high.
  • the initial thickness of the web structure will be determined by the surface weight of the paper desired as well as of the fibre concentration used. With, for instance, a surface weight of 50 g./m. (newsprint) and with a fibre concentration of 5%, the thickness will be 1 mm.
  • a very concentrated suspension whereat the fibre concentration is at least equal to twice the sedimentation concentration defined by the formula:
  • C represents the sedimentation concentration
  • r is the fibre radius
  • h is the fibre length.
  • C is 0.20.4% for pine sulphate and 0.60.9% for mechanical pulp. 16% is a suitable concentration interval which is up to ten times more than what is usually used in the prior art. This means that considerably less water has to be removed from the pulp web which again results in smaller losses in material.
  • the most advantageous fibre length is 1-5 mm. and the thickness most suitably is -50 m.
  • the fibre type used may vary within wide limits from natural fibres to artificial fibres, etc.
  • the threedimensional sheet, made according to this invention shows improved strength qualities in a direction perpendicular 6 to the plane of the sheet. Further, it should be noted that the apparatus according to the invention is remarkably smaller than the earlier known apparatuses and considerably cheaper, too.
  • the pulp web 13' already at the start has a high dry content and a relatively good strength, it can be deposited directly on the press felt, between two felts or on a corresponding device for handling of the pulp web, for further transportation to a press or other water removal body.
  • transverse distributor 3 of conventional type may be used, which, however, was not possible with the arrangement in accordance with the US. Patent application Ser. No. 157,120, now abandoned, according to which specially formed and expensive distributing units were required.
  • FIGS. 1 and 3 are on the whole designed to natural scale. If the sizes of the head boxes according to FIGS. 1 and 3 are compared with those of conventional head boxes, it can clearly be observed that a revolutionary decrease of all dimensions has been achieved. Of course, this decrease extends also to all auxiliary units which the head box requires for its operation according to the invention. The reason for this depends on the fact that far more concentrated pulp is being treated than up to now, i.e. far smaller volume flows of water. Thus even the pumping energy for the suspension is reduced, as well as the work required by water removal from the formed pulp web.
  • the suspension In order to obtain an even product of good quality, the suspension should obtain at the sheet forming a sulficient amount of energy per suspension volume unit. Thus there may arise difficulties at a sheet form with fixed dimensions and constructed for high surface weights and speeds when driven at low surface weights and/or low speeds. A low surface weight may be compensated with high speed but only to a certain limit. However, speeds of 6-14 m./s. can be well-controlled with an ap paratus according to the invention.
  • the apparatus in accordance with FIG. 3 differs from the head box according to FIG. 1 in that in the former the constriction 8 in chamber 11 is adjustable for the regulation of energy density per suspension volume unit.
  • the head box has been divided into a lower part 14, comprising the channels 5, 6 and into an upper part 15, horizontally movable on the lower part.
  • This upper part and the mating lower part 14 define between themselves the chamber 11 and also the outlet channel 12.
  • the outlet channel 12 is enclosed' by the upper part 15 and the lower lip 19 made of thin plate connected to the underside of the lower part 14.
  • the upper part 15 rests on the horizontal upper side of the lower part 15 and extends downwards opposite the lower lip 19 and thereafter parallel to it.
  • the moving is achieved by turning the screw 16 which is arranged horizontally between the upper part 15 and a counterpiece on the lower part 14.
  • one wall in the chamber is formed by a springy plate 17 which has a thickness of approx. 0.5-1 mm. and which is mounted between the plates 21 and 22 on the underside of the upper part 15.
  • Plate 17 is tightened against the lower part 14 with the aid of a transverse hose 18 fitted in between plate 7 17 and the upper part and filled with compressed air or the like.
  • the pressure is released in air hose 18, the upper part 15 is moved and pressure is again fed.
  • the height of the outlet channel 12 may be varied. This is achieved with suitable inserts 21 of different thicknesses. In a large head box, this adjustment can, of course, be arranged for continuous operation.
  • the pulp web 13 is deposited at a certain angle on the wire or felt 1. In certain cases this disturbs the sheet structure in an unfavourable manner.
  • the length of outlet channel 12 may be unnecessarily long for certain fibre types at which the web structure force will form especially quickly.
  • outlet channel 12 By putting a high fall of pressure over the last slot 8 the surface weight profile as a matter of fact, will be determined there to a great extent.
  • the function of outlet channel 12 is mainly limited to keeping the suspension together until a web structure is formed. Therefore the upper part of outlet channel 12 may be made rather soft in the outermost part. By making the outlet channel 12 soft in the outer section, it can follow the form of the sheet even during putting down on the wire or felt and during the first water removal.
  • the length of the upper part of the outlet channel 12 should be made as short as possible; however the turbulence must have had time to decay and a web structure time to form before putting down.
  • transverse distributor 3 is sufliciently narrow, one is able to alter the area of the transverse distributor 3 with clamps 20 or similar devices and with it the velocity of flow and the pressure of the grist and as a result of this the flow in the equipment and then also to a certain extent the profile of surface Weight and velocity in the actual sheet former 2. This is possible only at highconcentration sheet forming, in accordance with the invention, wherein relatively small volume amounts of water are treated.
  • the head box according to the invention can also be simply modified for the production of a pulp web having several layers, conveniently so that two or several head boxes with appurtenant rows of channels and chambers are arranged on top of each other, so that the different suspension flows are united only when their turbulence has decayed sufficiently so that a mixture of the layers takes place only at their border layer in order to bind the layers to each other.
  • the method has particularly proved to be suitable for the production of multi-layer cardboard in conventional manner, i.e., so that the lowest layer is deposited and dewatered first, after which the following layers are deposited and dewatered in turn on the underlaying layers.
  • the head boxes work with a considerably higher consistency than before, the d'ewatering zones laying in between can be made shorter in a corresponding degree and the dewatering devices smaller and cheaper, as considerably smaller amounts of water are removed from the pulp web.
  • Method for forming a continuous material web of fibrous particles starting from a suspension of fibrous particles with a fibre concentration of about 1% to about 6% by weight, comprising in combination the following steps: the highly concentrated suspension is divided over and sprayed through several parallel-coupled apertures; after which the suspension jets are accelerated and sprayed at high velocity into at least one chamber in which the jets are reunited and deflected; then the suspension flow is accelerated and deflected anew; and finally the turbulence is allowed to decay in order to form a consolidated three-dimensional net structure of fibrous particles before they are deposited.
  • Apparatus for forming a continuous material web of fibrous particles starting from a suspension of fibrous particles having a concentration of at least twice the sedimentation concentration of fibrous particles comprising at least one means forming a transverse distributor, means forming several parallel-coupled channels, means form ing a chamber, one end of each channel opening onto one sidewall of said transverse distributor and an opposite end of each channel opening through a wall of said chamber, the opposite wall of which chamber forms an impact face for the jets from channels for deflection and mixing of the jets in the chamber, the outlet opening of the channels being flattened in a direction which is at right angles to the extension of the outlet opening row in order to achieve an even distribution, the chamber further comprising a constriction as well as an impact face downstream of the constriction for renewed deflection of the turbulent suspension, and finally means forming an outlet channel with suflicient length to give the fibrous particles time to form a consolidated three dimensional net structure before the pulp web is deposited.
  • Apparatus as claimed in claim 4 in which the im- References Cited pact faces stand essentially at right angles to the flow.
  • UNITED STATES PATENTS 10.

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US00352565A 1972-04-21 1973-04-19 Fibrous sheet former wherein concentrated stock is passed through separate channels into a deflection chamber and out through an outlet channel Expired - Lifetime US3846230A (en)

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SE05255/72A SE362458B (de) 1972-04-21 1972-04-21

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US (1) US3846230A (de)
JP (1) JPS4920408A (de)
AT (1) AT324112B (de)
AU (1) AU468046B2 (de)
CA (1) CA989656A (de)
DE (1) DE2319906A1 (de)
ES (1) ES413905A1 (de)
FR (1) FR2180917B1 (de)
GB (1) GB1427584A (de)
IT (1) IT986070B (de)
NL (1) NL170971C (de)
NO (1) NO142452C (de)
SE (1) SE362458B (de)
SU (1) SU856393A3 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3937273A (en) * 1973-11-26 1976-02-10 Wiggins Teape Limited Forming non-woven fibrous material
US3954558A (en) * 1973-07-13 1976-05-04 J. M. Voith Gmbh Feeding device for paper machines
US3963562A (en) * 1974-01-14 1976-06-15 Lodding Engineering Corporation Slurry distributor
DE2620033A1 (de) * 1975-05-06 1976-11-25 St Annes Board Mill Co Ltd Stoffauflauf
US4021296A (en) * 1973-11-23 1977-05-03 A. Ahlstrom Osakeyhtio Method and device for manufacturing a continuous material web of elongated fibrous particles
US4345970A (en) * 1979-02-28 1982-08-24 The Wiggins Teape Group Limited Process and apparatus for controlling the deposition of a liquid on to a moving surface
DE3422846A1 (de) * 1983-06-20 1984-12-20 Mitsubishi Jukogyo K.K., Tokio/Tokyo Papiermaschinen-stoffauflauf

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5195228A (de) * 1975-01-27 1976-08-20
CH608049A5 (de) * 1976-01-23 1978-12-15 Escher Wyss Gmbh
FI62872C (fi) * 1978-06-06 1983-03-10 Ahlstroem Oy Anordning foer silning av fibersuspensioner
SE412078B (sv) * 1978-06-21 1980-02-18 Svenska Traeforskningsinst Forfarande for bildande av en kontinuerlig materialbana av fibrosa partiklar samt anordning for genomforande av forfarandet
DE10257799A1 (de) * 2002-12-11 2004-07-15 Voith Paper Patent Gmbh Verfahren zur Erzeugung von Scherströmungen und von Turbulenzintensitäten in einer durch einen Stoffauflauf einer Papier- oder Kartonmaschine geleiteten Faserstoffsuspension und Stoffauflauf

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2281293A (en) * 1936-12-19 1942-04-28 American Voith Contact Co Inc Apparatus for delivering paper stock to paper making machines
GB854529A (en) * 1956-12-27 1960-11-23 Beloit Iron Works Improvements in or relating to stock distributors for paper making machines
FR1203678A (fr) * 1957-03-26 1960-01-20 Rice Barton Corp Distributeur pour une pâte fluide
JPS44721Y1 (de) * 1964-05-21 1969-01-13
US3661702A (en) * 1969-12-15 1972-05-09 Time Inc Stock flow system for paper-making machine

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3954558A (en) * 1973-07-13 1976-05-04 J. M. Voith Gmbh Feeding device for paper machines
US4021296A (en) * 1973-11-23 1977-05-03 A. Ahlstrom Osakeyhtio Method and device for manufacturing a continuous material web of elongated fibrous particles
US3937273A (en) * 1973-11-26 1976-02-10 Wiggins Teape Limited Forming non-woven fibrous material
US3963562A (en) * 1974-01-14 1976-06-15 Lodding Engineering Corporation Slurry distributor
DE2620033A1 (de) * 1975-05-06 1976-11-25 St Annes Board Mill Co Ltd Stoffauflauf
US4345970A (en) * 1979-02-28 1982-08-24 The Wiggins Teape Group Limited Process and apparatus for controlling the deposition of a liquid on to a moving surface
DE3422846A1 (de) * 1983-06-20 1984-12-20 Mitsubishi Jukogyo K.K., Tokio/Tokyo Papiermaschinen-stoffauflauf

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NL170971C (nl) 1983-01-17
NO142452C (no) 1980-08-20
CA989656A (en) 1976-05-25
AU5395073A (en) 1974-10-17
DE2319906A1 (de) 1973-10-25
JPS4920408A (de) 1974-02-22
AU468046B2 (en) 1975-12-18
NO142452B (no) 1980-05-12
FR2180917B1 (de) 1977-08-19
NL7305564A (de) 1973-10-23
IT986070B (it) 1975-01-10
SU856393A3 (ru) 1981-08-15
SE362458B (de) 1973-12-10
AT324112B (de) 1975-08-11
ES413905A1 (es) 1976-01-16
GB1427584A (en) 1976-03-10
NL170971B (nl) 1982-08-16
FR2180917A1 (de) 1973-11-30

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