EP0241439A2 - Entwässerungsanlage - Google Patents

Entwässerungsanlage Download PDF

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Publication number
EP0241439A2
EP0241439A2 EP87850008A EP87850008A EP0241439A2 EP 0241439 A2 EP0241439 A2 EP 0241439A2 EP 87850008 A EP87850008 A EP 87850008A EP 87850008 A EP87850008 A EP 87850008A EP 0241439 A2 EP0241439 A2 EP 0241439A2
Authority
EP
European Patent Office
Prior art keywords
hydrofoil
forming
plane
forming medium
blades
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.)
Ceased
Application number
EP87850008A
Other languages
English (en)
French (fr)
Other versions
EP0241439A3 (de
Inventor
Otto J. Kallmes
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.)
MK Systems Inc
Original Assignee
MK Systems Inc
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 MK Systems Inc filed Critical MK Systems Inc
Publication of EP0241439A2 publication Critical patent/EP0241439A2/de
Publication of EP0241439A3 publication Critical patent/EP0241439A3/de
Ceased 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
    • D21F1/00—Wet end of machines for making continuous webs of paper
    • D21F1/48—Suction apparatus
    • D21F1/483—Drainage foils and bars

Definitions

  • This invention relates to a hydrofoil support or box for use in a paper making machine of the type wherein hydrofoil blades are positioned beneath a forming medium and extended in the cross machine direction relative to the forming medium for draining water through the formirrg medium from a paper web being formed on the forming medium and for forming the paper web.
  • This invention also relates to a hydrofoil blade and to a method using hydrofoil blades for dewatering and forming a paper web.
  • an aqueous suspension of fibers called the "stock” is flowed from a headbox onto a traveling Fourdrinier wire or medium, generally a woven belt of wire and/ or synthetic material, to form a continuous sheet of paper or paper-like material.
  • a traveling Fourdrinier wire or medium generally a woven belt of wire and/ or synthetic material
  • paper or paper-like material is used in a broad or generic sense and is intended to include such items as paper, kraft, board, pulp sheets and non-woven sheet-like structures.
  • As the stock travels along on the Fourdrinier wire formation of a paper web occurs, as much of the water content of the stock is removed by draining. Water removal is enhanced by the use of such well-known devices as hydrofoil blades, table rolls and/or suction devices. This invention relates to hydrofoil blades.
  • the hydrofoil blades used in papermaking perform two functions.
  • the first function is to create a vacuum pulse over the downward inclined face of the hydrofoil blade. This pulse removes a portion of the white water from the lower side of the stock or three-dimensional fiber suspension which lays upon the forming medium and causes some of the fibers to be laid down and formed into a web.
  • the amount of such water removal and web formation over a given hydrofoil blade is small, and therefore a considerable number of blades is required to form all of the fibers in a stock suspension into a two dimensional web. For example, the use of ten to fifty hydrofoil blades is not uncommon.
  • the sheet forming process is a step-by-step filtration process as the forming me- divan travels over the hydrofoil blades, with some of the fibers in the lower portion of the suspension over the partially-formed web being added to the web at each successive foil blade.
  • the average net change in fiber concentration or consistency of this process ranges from the headbox consistency, which is usually about 0.4% to about 1%, up to about 2.5%
  • the second function of a hydrofoil blade is to maintain the fibers which are still in suspension throughout the forming process in an as-well-as dispersed condition as possible; i.e., in a deflocculated condition.
  • This function is extremely important as fibers in the 0.5-2.5% consistency range have a strong tendency to flocculate into clumps on their own in a matter of milliseconds once the fiber dispersive forces have decayed. This flocculation causes the final paper to behighly nonuniform or flocculated in appearance.
  • the fiber dispersive function of hydrofoil blades is caused primarily by the decay of the dewatering vacuum pulse which imparts a momentary upward force or pulse into the stock.
  • This pulse creates random small scale flows, i.e., turbulence, in the stock above the partially-formed web.
  • the speed of travel of the suspension over the blade is also a factor in determining the intensity of this pulse.
  • the size of the hydrofoil blade angle which can be used is limited lest the vacuum be so large that the pulse created will throw sane of the stock upward into the air. This phenomenon known as "stock jump" can readily damage the uniformity of the sheet.
  • hydrofoil blade dewatering overlooked in the past is that when the vacuum pulse created by the inclined angle of the hydrofoil blade decays back to atmospheric pressure, the decay is somewhat of an unstable phenomenon. This is because the hydrofoil blade generally discharges the water removed from the suspension directly into the atmosphere. In other words, the decay of the vacuum pulse occurs virtually instantaneously at the point where the gap between forming medium and hydrofoil blade becomes too large to support a continuous column of water. The location of this point is extremely sensitive to all of the forces and resistances affecting the dewatering process as evidenced by the highly variable amount of water removed from the suspension across the width of foil blades. This variability can be readily observed on any paper making machine.
  • the water removed from the suspension by any one hydrofoil blade is largely carried along the underside of the forming medium to the next blade whose leading edge skives the water off the underside of the forming medium.
  • the amount of skived water varies very considerably from point to point across the width of a machine at most hydrofoil blade positions.
  • the cross machine direction variability of dawataring of hydrofoil blades is one, if not the primary source of the non-uniformity of the "dry line", i.e., the line across the Fourdrinier where air is first introduced into the wet web over the vacuum foils or suction boxes.
  • This variability ultimately leads to the cross-direction variation in the moisture content of the finished paper, one of the most critical problems facing the paper industry.
  • the hydrofoil blade support for use in a paper making machine of the type wherein hydrofoil blades are positioned beneath a forming medium and extended in the cross machine direction relative to the forming medium for draining water through the forming medium from a paper web being formed on the forming medium and for forming the paper web.
  • the hydrofoil blade support includes at least a first hydrofoil blade comprising a first forming medium bearing surface lying in a first plane and having a first leading edge and a first trailing surface diverging downward relative to the first forming medium bearing surface from a first crease line to a first trailing edge. The first trailing edge lies in a second plane parallel to the first plane.
  • a water directing surface extends downward from the first trailing edge.
  • At least a second adjacent hydrofoil blade is provided comprising a second forming medium bearing surface having a second leading edge, a front surface extending downward from the second leading edge at an acute angle relative to the second forming medium bearing surface, and a second trailing surface diverging downward relative to the second forming medium bearing surface from a second crease line to a second trailing edge.
  • the water directing surface overlaps and is spaced from the front surface, and the first plane is spaced from the second plane in the range of about .05 millimeters to about 4 millimeters, to form means forming a gap between the forming medium and the adjacent hydrofoil blade, when the hydrofoil support is mounted on the paper making machine, so that during the paper making operation the water removed from the paper web by suction created by the hydrofoil blades completely fills the gap in the absence of air thereby preventing expansion and corresponding cavitation of the water in the gap.
  • Figure 1 diagramatically depicts a portion of the forming section of a paper making machine of the type wherein a forming medium 2 receives stock from a headbox at a first end (not shown) and transfers a substantially self-supporting paper web from the forming medium 2 at a second end (not shown), the forming medium travelling in the machine direction generally designated by arrow 4.
  • Hydrofoil blades are provided beneath the forming medium 2. The hydrofoil blades extend in the cross machine direction relative to the forming medium, the cross machine direction generally designated by arrow 6.
  • a hydrofoil support or box 10 which includes at least a first hydrofoil blade 12 comprising a first forming medium bearing surface 14 lying in a first plane and having a first leading edge 16, and a first trailing surface 18 diverging downward relative to the first forming medium bearing surface 14 from a first crease line 20 to a first trailing edge 22.
  • the first trailing edge lies in a second plane parallel to the first plane.
  • the first and second planes are schematically represented at 24 and 26, respectively.
  • a water directing surface 28 extends downward from the first trailing edge 22.
  • a second adjacent hydrofoil blade 30 is also provided.
  • Blade 30 comprises a second forming medium bearing surface 32 having a second leading edge 36, a front surface 34 extending downward from the leading edge at an acute angle relative to the second forming medium bearing surface, and a second trailing surface 38 diverging downward relative to the second forming medium bearing surface 32 from a second crease line 40 to a second trailing edge 42.
  • the water directing surface 28 overlaps and is spaced from the front surface 34.
  • the distance 44 between the first plane 24 and the second plane 26 is in the range of about.05 mullimeters to about 4 millimeters.
  • the distance between surfaces 28 and 34 is also in the range of about 05 millimeters to about 4 millimeters, the spacing between planes 24 and 26 and surfaces 28 and 34 preferably being similar.
  • the interrelationship of the overlapping and spaced surfaces 28, 34 which form a channel 46 between adjacent hydrofoil blades, and the dimensioned distance 44 between planes 24, 26, form means forming a gap between the forming medium 2 and the adjacent hydrofoil blades 12, 30, when the hydrofoil blade support 10 is mounted on the paper making machine, so that during the paper making operation the water removed from the paper web by suction created by the hydrofoil blade completely fills the gap in the absence of air thereby preventing expansion and corresponding cavitation of the water in the gap.
  • hydrofoil blade support 10 includes a plurality of adjacent and alternating pairs of first hydrofoil blades 12 and second hydrofoil blades 30.
  • Each hydrofoil blade is depicted as including a front surface extending downward from each respective leading edge at, an acute angle relative to each respective farming medium bearing surface.
  • Each hydrofoil blade is also depicted as including a water directing surface extending downward from each respective trailing edge.
  • Each forming medium bearing surface lies in the first plane depicted at 24, and each trailing edge lies in the second plane depicted at 26.
  • each of the water directing surfaces overlaps and is spaced from an adjacent front surface, and respective first and second planes are spaced in the range of about .05 millimeters to about 4 millimeters, to form said gap forming means between adjacent hydrofoil blades.
  • hydrofoil blade support 10 includes a blade or blades having a trailing surface which diverges downwardly to a third crease line 48, and includes a boundary forming surface 50 lying in the second plane, identified at 26, and extending from the third crease line to the trailing edge of each blade which includes such structure.
  • each respective boundary forming surface 50 is parallel to each forming medium bearing surface.
  • the distance 44 is measured between the forming medium bearing surface and the boundary forming surface 50 of each hydrofoil blade.
  • boundary forming surface 50 is terminated just ahead of the leading edge of the next hydrofoil blade and is followed by the downward inclined water directing surface which extends at an angle of 30° to 45° relative to the boundary forming surface 50.
  • adjacent front surfaces and water directing surfaces can be parallel as depicted in Figure 1. It is also within the teachings herein that one or more of such surfaces be slightly convergent towards the forming medium bearing surface as depicted in Figure 2 or slightly convergent away from the forming medium bearing surface as depicted in Figure 3.
  • the trailing face of the blade After providing a short parallel or almost parallel channel between the two hydrofoil blades, the trailing face of the blade abruptly changes its angle to 90° relative to the boundary forming surface 50, and the white water is flung into the atmosphere. At this point, the change in pressure is much smaller than that at the point where conventional hydrofoil blades discharge their white water into the atmosphere. Thus, the white water is removed from the underside of the forming medium as a continuous and uniformly thick column of water without an abrupt change in pressure at the face of the forming medium.
  • the height of the gap between the forming medium and the boundary forming surface 50 of the hydrofoil blade controls the amount of its dewatering. Therefore, making the size of this gap controllable is desirable so that the amount of dewatering at every point on the forming medium can be controlled and regulated.
  • the present invention includes features directed to such a variable drainage rate hydrofoil blade.
  • Figure 4 which depicts a hydrofoil blade having a configuration similar to that of Figure 1, reference characters corresponding to those of Figure 1 are used for similar structure.
  • the trailing surface 18 is pivotally connected to the forming medium bearing surface 14, and to the boundary forming surface 50 at the third crease line 48.
  • Figure 4 depicts trailing surface 18 as a flexible member extending from surface 14 to surface 50. It will be apparent to those skilled in the art that other types of pivotal connections can be provided. Means are provided coupled to the boundary forming surface 50 for varying the distance between surface 50 and the first plane, in which lies the fanning medium bearing surface 14, so that such distance can be controlled as desired.
  • Figure 4 schematically depicts a piston 52 and cylinder 54 for hydraulically or pneumatically raising and lowering boundary forming surface 50. In operation, the raising of piston 52 decreases the degree by which surface 50 diverges from surface 14 and decreases the vertical distance between the first plane identified at 24 and the second plane identified at 26 to decrease the size of the gap. Lowering of piston 52 increases the degree by which surface 50 diverges from surface 14 and increases the vertical distance between the planes identified at 24 and 26 to increase the size of the gap.
  • the forming medium bearing surface 14 is about one centimeter in length
  • the trailing surface 18 is about 3 to 15 centimeters in length
  • the boundary forming surface 50 is about 1 to 15 centimeters in length.
  • the diverging angle of the trailing surface 18 is 0° to 5° as described in Wrist, United States Patent No. 2,948,465.
  • a method is provided using hydrofoil blades for dewatering and forming a paper web on a paper machine forming medium by removing water from the paper web, and the fiber suspension carried thereby, by suction created by the hydrofoil blades and including the critical steps of (1) forming a single phase fluid in a gap between adjacent hydrofoil blades and the forming medium, and (2) extending the gap a sufficient distance in the machine direction to prevent expansion and corresponding cavitation of the single phase fluid in the gap.
  • An important aspect of the present invention is to identify the magnitude of distance 44 to assure that the gap between the underside of the forming medium and adjacent hydrofoil blades is filled with water in the absence of air; that is, to cause a single phase fluid to be carried along the underside of the forming medium in the gap.
  • the typical hydrofoil blade is designed to have a trailing surface diverging at an angle of 0° to 5° as described in United States Patent No. 2,948,465, the critical dimension in defining the distance 44 is the length of the trailing surface 18.
  • the height 44 for the blades being used can be ascertained by calculating the difference between the stock thickness at the slice opening and at the end of the forming zone, using the equation: wherein T is the stock thickness, W is the basis weight of the finished sheet, C is the stock consistency expressed as a fraction, R is the overall machine reterition downstream from the point under consideration, and J is the jet-to-forming medium speed ratio.
  • the stock thickness T 2 at the end of the web forming zone can be calculated in a like manner. Assuming that the basis weight W 2 is still 50 g.s.m., the consistency C 2 has increased to 2.5%, the overall machine retention R 2 of the balance of the paper making machine is 90%, and the jet-to-forming medium speed ratio J 2 has increased to 1.0, then the thickness of the stock at the end of the web forming zone is:
  • the thickness of water Q removed from the forming section is equal to the difference between the stock thickness at the slice opening and the stock thickness at the end of the web forming zone, or
  • Dewatering using hydrofoil blades of the present invention differs from that of conventional blades in that the dewatezing is car ried out entirely in a confined and controllable gap, and hence dewatering will be highly uniform along the cross machine direction of each blade. Furthermore, the pressure pulse causing a loss of fines and filler particles will be substantially eliminated, and the so-called "two-sidedness" of paper as well as the intensity of the well-known "wire mark" will be substantially decreased. Finally, the repetitive ridges formed by formation showers will not be subject to destructive pulses, and will carry them much further down the forming medium than is presently the case.
  • FIG. 5 depicts a hydrofoil blade support 60 comprising a plurality of spaced hydrofoil blades 62 which comrprise a forming medium bearing surface 64 lying in a first plane identified schematically at 66 and having a leading edge 68, and a trailing edge 70 lying in a second plane, identified schematically at 72, parallel to the first plane.
  • a first trailing surface 74 diverges downward relative to the forming medium bearing surface 64 from a first crease line 76 to a second crease line 78.
  • a first (boundary forming surface 80 extends from the second crease line 78 to a third crease line 82, and at least one other pair of trailing and boundary forming surfaces extend in tandem between the third crease line 82 and the trailing edge 70.
  • blade 62 includes a plurality of pairs 84, 86, 88 of trailing surfaces 74 and boundary forming surfaces 80 which extend in tandem, one pair following the next in the machine direction.
  • each of the boundary forming surfaces lie in planes, schematically depicted at 80' in Figure 6, parallel to the forming medium bearing surface 64, consecutive of planes 66, 80', 72 being spaced from each other in the range of about .05 millimeters to about 4 millimeters.
  • a water directing surface 90 is provided as in the other embodiments herein extending downward from the trailing edge 70.
  • the height of the gap 92 being consecutive of planes 66, 80', 72 corresponds to dimension 44 of Figure 1, and is measured in the same manner.
  • the equations set forth herein are equally applicable to the embodiment of Figures 5 and 6.
  • the equations demonstrate how to identify the magnitude of gap 44, they are equally applicable in identifying the magnitude of each gap 92, the critical dimension in defining the height of each gap 92 being the length L of each respective trailing surface 74.
  • L can be equated to the length of trailing surface 18 in using the equations to identify the magnitude of gap 44 in Figure 1 or to the length of each trailing surface 74 in Figures 5 and 6 in using the equations to separately identify the magnitude of each gap 92.
  • the water removed at each trailing surface 74 in the embodiment of Figures 5 and 6 travels along each respective gap 92. At the end of each respective gap 92 such moving water continues to travel but under the water being removed by the next trailing surface 74. In other words, the water removed at each trailing surface 74 travels through the gap 92 associated with such trailing surface and is then carried under the water removed by each succeeding trailing surface 74, all of such water being removed at the end of the hydrofoil blade.

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EP87850008A 1986-01-08 1987-01-07 Entwässerungsanlage Ceased EP0241439A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US81703486A 1986-01-08 1986-01-08
US817034 1991-12-30

Publications (2)

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EP0241439A2 true EP0241439A2 (de) 1987-10-14
EP0241439A3 EP0241439A3 (de) 1988-01-07

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Application Number Title Priority Date Filing Date
EP87850008A Ceased EP0241439A3 (de) 1986-01-08 1987-01-07 Entwässerungsanlage

Country Status (7)

Country Link
EP (1) EP0241439A3 (de)
JP (1) JPS62215088A (de)
AU (1) AU591955B2 (de)
BR (1) BR8700034A (de)
CA (1) CA1277531C (de)
FI (1) FI870048A (de)
NO (1) NO865051L (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0545886A1 (de) * 1991-12-02 1993-06-09 HAPA-Verwaltungs-Aktiengesellschaft Verfahren und Vorrichtung zur Entwässerung von über Entwässerungselemente geführten siebbandgestützten Faser-Wasser-Suspensionen
US5562807A (en) * 1995-03-03 1996-10-08 Baluha; Mark R. Cross direction fiber movement and dewatering device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2640292C (en) * 2006-02-03 2014-07-08 Luis Fernando Cabrera Y Lopez Caram Fiber mat forming apparatus and method of preserving the hydrodynamic processes needed to form a paper sheet

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB796374A (en) * 1955-12-27 1958-06-11 Ontario Paper Co Ltd Means for improving drainage on paper machines
US2928465A (en) * 1959-04-27 1960-03-15 Ontario Paper Co Ltd Drainage element for paper machines
US3497420A (en) * 1967-01-30 1970-02-24 Huyck Corp Continuously variable hydrofoils for papermaking wires
FR2078978A5 (en) * 1970-02-23 1971-11-05 Jwi Ltd Dewatering foil
DE2321690A1 (de) * 1973-03-29 1974-10-10 Escher Wyss Gmbh Nassauger einer papiermaschine
GB1382791A (en) * 1971-05-03 1975-02-05 Pulmac Research Ltd Vacuum drainage device
US4123322A (en) * 1977-06-24 1978-10-31 Thermo Electron Corporation Drainage foil element having two wire bearing portions

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB796374A (en) * 1955-12-27 1958-06-11 Ontario Paper Co Ltd Means for improving drainage on paper machines
US2928465A (en) * 1959-04-27 1960-03-15 Ontario Paper Co Ltd Drainage element for paper machines
US3497420A (en) * 1967-01-30 1970-02-24 Huyck Corp Continuously variable hydrofoils for papermaking wires
FR2078978A5 (en) * 1970-02-23 1971-11-05 Jwi Ltd Dewatering foil
GB1382791A (en) * 1971-05-03 1975-02-05 Pulmac Research Ltd Vacuum drainage device
DE2321690A1 (de) * 1973-03-29 1974-10-10 Escher Wyss Gmbh Nassauger einer papiermaschine
US4123322A (en) * 1977-06-24 1978-10-31 Thermo Electron Corporation Drainage foil element having two wire bearing portions

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0545886A1 (de) * 1991-12-02 1993-06-09 HAPA-Verwaltungs-Aktiengesellschaft Verfahren und Vorrichtung zur Entwässerung von über Entwässerungselemente geführten siebbandgestützten Faser-Wasser-Suspensionen
US5562807A (en) * 1995-03-03 1996-10-08 Baluha; Mark R. Cross direction fiber movement and dewatering device

Also Published As

Publication number Publication date
FI870048A0 (fi) 1987-01-07
JPS62215088A (ja) 1987-09-21
NO865051L (no) 1987-07-09
AU6718987A (en) 1987-07-09
BR8700034A (pt) 1987-12-01
AU591955B2 (en) 1989-12-21
EP0241439A3 (de) 1988-01-07
NO865051D0 (no) 1986-12-15
CA1277531C (en) 1990-12-11
FI870048A (fi) 1987-07-09

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