EP0072188A2 - Maschine zur Herstellung von Bahnen - Google Patents

Maschine zur Herstellung von Bahnen Download PDF

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Publication number
EP0072188A2
EP0072188A2 EP82304098A EP82304098A EP0072188A2 EP 0072188 A2 EP0072188 A2 EP 0072188A2 EP 82304098 A EP82304098 A EP 82304098A EP 82304098 A EP82304098 A EP 82304098A EP 0072188 A2 EP0072188 A2 EP 0072188A2
Authority
EP
European Patent Office
Prior art keywords
web
forming
forming roll
band
roll
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82304098A
Other languages
English (en)
French (fr)
Other versions
EP0072188A3 (de
Inventor
Alexander Malashenko
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dominion Engineering Works Ltd
Original Assignee
Dominion Engineering Works Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dominion Engineering Works Ltd filed Critical Dominion Engineering Works Ltd
Publication of EP0072188A2 publication Critical patent/EP0072188A2/de
Publication of EP0072188A3 publication Critical patent/EP0072188A3/de
Withdrawn legal-status Critical Current

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Classifications

    • 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

  • This invention is directed to a web forming machine, and in particular to a machine utilizing two endless web-forming bands or wires and being known as a "twin-wire web former".
  • wires and bands as used herein are intended to cover inter alia fourdrinier wires, "wires” of synthetic fabrics, and felts of various types on which a web can be formed.
  • twin-wire formers particularly in the manufacture of paper webs such as newsprint, has received an enormous amount of development in recent years, and considerable progress has been made towards improvement of web formation, with consequent enhancement of the product.
  • the present invention is directed to an improved web-forming machine wherein unexpected advantages were found in improved web formation.
  • a web-forming machine having first and second endless web-forming bands to receive stock in dewatering web-forming relationship therebetween, a source for depositing stock on at least one said band, a first web-forming roll located within the loop of the first band, the first and second bands passing over an arcuate portion of substantially 30 to 60 0 of the first web-forming roll in convergent wrapping relationship therewith, there being a second web-forming roll which is adjacent the first web-forming roll and is located within the loop of the second band so that the first and second bands pass over the second web-forming roll in reverse wrapping relationship thereabout, and means for dewatering the stock characterized in that the first web-forming roll is an open, non-suction roll and said bands wrap the first web-forming roll so that the web is only partially formed in a first web-forming zone adjacent the first web-forming roll, there being bi-directional dewatering of the stock at the first web-forming roll to form the outer faces of the web while leaving at least an interior portion of the web unformed
  • the machine may thus be used to form a web by arranging that the outer faces of the web are formed at the first web-forming roll during initial dewatering of the web while ensuring that web formation is incomplete interiorly of the web, and by subsequently continuing dewatering of the web about the second web-forming roll, wherein the direction of dewatering flow through the web is substantially reversed for at least a significant portion of the thickness of the web, so that web formation is substantially completed, whereby the interior of the web s effectively formed.
  • a web produced by a machine operating in accordance with the teachings of the present invention may have excellent first pass fines retention, surpassing that of an equivalent fourdrinier machine. Furthermore, the machine of the present invention is particularly stable in sheet formation with respect to stock consistency variations, and the consistency for the entry to the first forming web-forming roll is not critical, but obviously cannot be so thick as to complete formation on the first forming roll.
  • the web-forming rolls are arranged in predetermined spaced apart relation to provide a stretch therebetween along which the bands or webs travel in generally tangential relation to the rolls, having the partially formed web in sandwiched relation therebetween.
  • relative longitudinal band displacement occurs which correspondingly affects the substantially unformed interior of the web to assist in reforming the web, this portion thus tending to modify floc formation within the web. It has been found that while at present the individual quantitative effects of reversed dewatering and differential longitudinal web displacement may not readily be determined, the two effects appear to be complementary and lead to significantly reformed floccing, with enhanced web formation.
  • the initial web-forming zone includes a first stretch of one of the bands, on which stock is deposited from a headbox, the band passing over suitable guide means to facilitate the initial formation of the lower face of the web upon the band, prior to sandwiching by the second band for passage about a portion of the periphery of the first web-forming roll.
  • formation is generally accepted as meaning the distribution of fibres and fibreflocks in a finished sheet viewed when illuminated by light passing through the sheet i.e. backlighted.
  • the fibres become fixed in their relative positions thereby determining their location in the finished sheet and such fixed fibres are deemed as “formed” in the instant disclosure with those fibres or fibreflocks still suspended in sufficient water to permit mobility and change in their relationship or orientation being termed as "unformed”.
  • the second forming roll causes flow in the reverse direction through a portion of the web i.e. the balance of the water flow towards the two wires at the second roll is different from that of the first forming roll so that at least some of the fibres in the interior of the web are subject to flow in the opposite direction which tends to influence their final disposition in the formed sheet.
  • the two wires or web forming bands are substantially parallel and thus there is a section between the two rolls where little drainage occurs and the drainage is in effect interrupted. In this section as above indicated there is also relative machine direction movement between the wires to apply shear to the forming web.
  • a web-forming machine constructed as shown in the accompanying drawings and using web-forming rolls including a non-suction open surfaced roll normally makes possible the provision of a substantially suctionless machine wherein the absence of drag, previously occasioned by the widespread use of suction boxes, permits the driving of one band loop by the other band loop without any significant increase in power requirement, and even with a diminution in drive power requirements considered in relation to an equivalent fourdrinier machine.
  • the improved machine also results in improved band life.
  • the parasitic drag can take up to 60% of the drive power.
  • the drag of such dewatering devices is both speed and moisture content sensitive.
  • the sealing of a band to a suction box surface is largely influenced by the wetness of the band and web. Owing to the enhanced dryness of webs upon completion of dewatering over the second web-forming roll of the machine of the present invention, the drag over any suction boxes being used is correspondingly diminished. Additionally, where suction boxes might be used, they can be operated at correspondingly less vacuum.
  • a machine according to the present invention offers a potential saving of about 25% power consumption.
  • the invention also comprises a method of forming a web between first and second endless web-forming bands comprising depositing stock on at least one of said bands, passing the stock-carrying bands in convergent wrapping relationship over a substantially 30 0 to 60 0 arcuate portion of a first web-forming roll which is located within the loop of the first band, passing the web about a second web-forming roll which is adjacent the first web forming roll and is located within the loop of the second band so that the first and second bands pass over the second web-forming roll in reverse wrapping relationship thereabout, and dewatering the stock characterized in that the web is only partially formed about the first web-forming roll, there being bi-directional dewatering of the stock at the first web-forming roll to form the outer faces of the web while leaving an interior portion of the web unformed, and passing the web about the second web-forming roll so as to effect reversal of internal dewatering through a portion of the thickness of the web at the second web-forming roll, whereby to complete the formation of an internal unformed portion of the web
  • FIGs 1 and 2 there are respectively shown web-forming machines 10, 30, each of which comprises first and second endless foraminous web-forming bands constituted by an upper band loop 14 and a lower band loop 12 each of which is supported on a plurality of guide rolls.
  • the bands 12, 14 which are usually so-called fourdrinier wires, and are generally known as forming fabrics, are arranged to receive stock in dewatering web-forming relation therebetween.
  • a slice portion 18 of a headbox (not shown) is arranged to deposit a layer of stock on a first stretch 20 of the first band 12.
  • the stretch 20 is supported in tensioned relation upon a plurality of drainage elements such as foil sections 13 to provide initial landing of the stock upon the band 12, and to promote satisfactory initial stock-dewatering downwardly.
  • the bands 12 and 14 are in convergent wrapping relationship, and thus in stock pressing relationship, about an open surfaced, non-suction web-forming roll 22, whereby the bands 12, 14 form a first web-forming zone 31 adjacent the roll 22.
  • the roll 22 comprises a grooved roll having a foraminous wire sleeve shrunk thereover.
  • Such a roll 22 desirably has an open area of the order of 80% of its surface area and thus supports the band 12 in water-receiving relation therewith thereby to provide sufficient void space to receive the water draining toward the roll.
  • both the hands 12, 14 sandwich the stock which passes about a portion of the periphery of the roll 22 so that this zone portion 31 provides bi-directional dewatering of the stock at the roll 22 and through the bands 12, 14 to the extent that the web is only partially formed, such dewatering being effected mainly under the effects of band tension and centrifugal force.
  • This partial formation of the web is thus such that the outer faces of the web are formed while leaving at least an interior portion of the web unformed.
  • the angle of wrap of the bands 12, 14 about the roll 22 must be limited in order to preclude total web-formation on the roll 22.
  • the illustrated approximately 45° wrap angle or arc has been found to be effective, but satisfactory results are achieved by operation in the range of 60° to 30° so as to maintain incomplete web-formation with compensation by stock dilution adjustment.
  • the sandwiched stock of the partially formed web passes tangentially from the roll 22 to a further web-forming zone 32 located about a second web-forming roll 24 which is disposed adjacent to the roll 22.
  • the bands 12, 14, pass in tensioned, mutually opposing relation from the roll 22 to the roll 24. After passage about the roll 24, the web is sufficiently dewatered so that the fibres are in substantially fixed relative position and the web is fully formed.
  • the bands 12, 14 pass over the roll 24 in reverse wrapping relationship thereabout. That is to say, the band 14, which was the inner band on the roll 22, becomes the outer band on the roll 24.
  • the roll 24 thus provides a reversal of internal water flow so as to effect, as above described, reverse water flow through a portion of the thickness of the forming web at the roll 24 to complete the formation of the internal unformed portion of the web.
  • the rolls 22, 24 are located in loops in the bands 14, 12 respectively, while in the Figure 2 construction, they are located in loops in the bands 12, 14 respectively.
  • the longitudinal relative movement appears to play some part in reforming the interior of the web by, as is well known in the art, applying oriented shear to the web before formation is completed and the fibre fixed in position by modifying the floc formation prior to its being dewatered on the roll 24 to the extent that formation is then completed.
  • the roll 24 in the embodiments illustrated in Figures 1 and 2 is a plain roll, whereby dewatering will occur substantially solely in an outward direction relative to the roll surface.
  • the bands 12, 14 Upon passage from the roll 24 in the Figure 1 embodiment, the bands 12, 14 pass by way of a guide roll 26 to a table or guide roll 28, whereat the band 14 is entrained around a guide roll 29 so that in a band separation zone it diverges gradually by an angle of not more than 10 and-preferably in the range of 2° to 6° from the web and the band 12.
  • the table roll 28 assists in maintaining the web upon the band 12 for passage about a suction couch roll 30, in known fashion, the passage of the band 12 over the suction couch roll 30 ensuring attachment of the web to the band 12.
  • only the table roll 28 is necessary, in view of the fact that the bands 12, 14 leave the underside of the roll 24.
  • the second forming roll 24 has been found to operate - effectively as a solid roll having a substantially impervious surface to inhibit inward dewatering of the web towards the roll 24 as the web passes around the roll 24, it is contemplated that in certain instances for heavier grades, or using stocks more difficult to dewater, a suction forming or vacuum roll may be used, or an open roll of a construction similar to that of the roll 22. In the latter case, the roll 24 will have an open surface to receive water from the web in an inward dewatering direction relative to the surface of the roll 24.
  • this embodiment is suited for a pulp forming section or for such ⁇ heavyweight low speed kraft grades wherein greater quantities of water are removed.
  • the pre-drainage band stretch 20 is dispensed with and the slice portion 18 is located adjacent the roll 22 to deposit the stock in a zone of convergence of the bands 12, 14.
  • the shortened version shown in Figure 3 can be based upon either the Figure 1 or the Figure 2 embodiment.
  • the web formation produced by the improved former shown in the Figure 1 embodiment has demonstrated superior qualities of symmetry, homogeneous structure and Z-axis direction bond strength, which particularly suits the requirements of many speciality papers.
  • the present invention makes possible the formation of webs using substantially suctionless equipment marked by the absence of vacuum forming rolls and the substantial absence of suction boxes and the like, or the number of such boxes may be reduced and operated at less vauum with reduced drag.
  • the band 14 which constitutes the second wire of the combination does not require to be independently driven, and can be effectively driven by the band 12 which constitutes the first wire, while the wire drive power consumption is effectively diminished, relative to an equivalent fourdrinier machine due to the reduced wire drag, made possible by the reduced use of suction boxes or by operation under less vacuum.
  • the presently disclosed arrangement also leads to extended life of the woven wires or fabrics used in the bands 12, 14, due to the substantially diminished sliding wear across the covers of the suction boxes which were formerly used in most fourdrinier type machines. This benefit applies equally over those twin wire machines relying upon forming shoes to dewater the web.
  • Figure 4A is a photomicrograph of a cross-section of newsprint made by a machine in accordance with the present invention
  • Figure 4B is a like photograph for the same grade of paper made from the same stock on a corresponding fourdrinier machine.
  • Figure 4A shows significantly more long fibres crossing the central plane of the sheet, than for the fourdrinier sheet, Figure 4B, indicating the superior interply bonding indicative of enhanced Z-axis strength achieved by the present invention.
  • Web porosity is substantially diminished i.e. the T/W web is 40% less porous, the tensile strength of the twin wire sheet is about 34% greater in the machine direction; and about 23% greater in the cross machine direction; the web internal bond strength is about 20% greater for the twin wire machine web.

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  • Paper (AREA)
EP82304098A 1981-08-07 1982-08-03 Maschine zur Herstellung von Bahnen Withdrawn EP0072188A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA000383379A CA1157302A (en) 1981-08-07 1981-08-07 Twin-wire web forming section
CA383379 1981-08-07

Publications (2)

Publication Number Publication Date
EP0072188A2 true EP0072188A2 (de) 1983-02-16
EP0072188A3 EP0072188A3 (de) 1984-03-07

Family

ID=4120630

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82304098A Withdrawn EP0072188A3 (de) 1981-08-07 1982-08-03 Maschine zur Herstellung von Bahnen

Country Status (5)

Country Link
EP (1) EP0072188A3 (de)
JP (1) JPS5841993A (de)
BR (1) BR8204635A (de)
CA (1) CA1157302A (de)
FI (1) FI822705L (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0304098A1 (de) * 1987-07-17 1989-02-22 Valmet Paper Machinery Inc. Former für die Bildung einer Papierbahn
WO2003048451A1 (en) * 2001-11-30 2003-06-12 Kimberly-Clark Worldwide, Inc. Paper webs having a watermark pattern

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB949769A (en) * 1962-01-04 1964-02-19 Huyck Corp Method of and apparatus for dewatering wet webs of papermaking fibres
GB993837A (en) * 1963-04-29 1965-06-02 Pulp Paper Res Inst Apparatus for making formed fibrous webs
DE2627102A1 (de) * 1975-06-23 1977-01-20 Karlstad Mekaniska Ab Verfahren und vorrichtung zur bildung einer faserbahn
FR2348316A1 (fr) * 1976-04-14 1977-11-10 Valmet Oy Section de formage a double toile metallique sans fin d'une machine a papier
US4209360A (en) * 1978-02-15 1980-06-24 Ab Karlstads Mekaniska Werkstad Two-sided drainage in a roll-type twin-wire former

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB949769A (en) * 1962-01-04 1964-02-19 Huyck Corp Method of and apparatus for dewatering wet webs of papermaking fibres
GB993837A (en) * 1963-04-29 1965-06-02 Pulp Paper Res Inst Apparatus for making formed fibrous webs
DE2627102A1 (de) * 1975-06-23 1977-01-20 Karlstad Mekaniska Ab Verfahren und vorrichtung zur bildung einer faserbahn
FR2348316A1 (fr) * 1976-04-14 1977-11-10 Valmet Oy Section de formage a double toile metallique sans fin d'une machine a papier
US4209360A (en) * 1978-02-15 1980-06-24 Ab Karlstads Mekaniska Werkstad Two-sided drainage in a roll-type twin-wire former

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0304098A1 (de) * 1987-07-17 1989-02-22 Valmet Paper Machinery Inc. Former für die Bildung einer Papierbahn
WO2003048451A1 (en) * 2001-11-30 2003-06-12 Kimberly-Clark Worldwide, Inc. Paper webs having a watermark pattern
US7070678B2 (en) 2001-11-30 2006-07-04 Kimberly-Clark Worldwide, Inc. Paper webs having a watermark pattern

Also Published As

Publication number Publication date
BR8204635A (pt) 1983-07-26
EP0072188A3 (de) 1984-03-07
FI822705L (fi) 1983-02-08
FI822705A0 (fi) 1982-08-03
JPS5841993A (ja) 1983-03-11
CA1157302A (en) 1983-11-22

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Inventor name: MALASHENKO, ALEXANDER