US2928465A - Drainage element for paper machines - Google Patents

Description

March 15, 1960 P. E. WRIST 2,928,465

DRAINAGE ELEMENT FOR PAPER MACHINES Filed April 27, 1959 3 Sheets-Sheet 1 FIG. 1

Inventor Atlorne March 15, 1960 A P. E. WRIST 2,928,465

DRAINAGE ELEMENT FOR PAPER MACHINES Filed April 27, 1959 s Sheets-Sheet z FIG. 3

In ventor Attorney March 15, 1960 P. E. WRIST DRAINAGE ELEMENT FOR PAPER MACHINES 3 Sheets-Sheet 3 Filed April 27, 1959 FIG. 5

Inventor ETER E. R/ST W Attorney 2,928,465 DRAINAGE ELEMENT FOR PAPER MACHINES Peter E. Wrist. Chillicothe, Ohio, assignor to The Ontario Paper Company Limited, Thor-old, Ontario, Canada 7 Application April 27, 1959, Serial No. 809,180

13 Claims. ((315162-352) A further embodiment of my invention relates to an 7 improved form of suction box for use in improving and regulating the drainage of water from Fourdrinier machines.

In a Fourdrinier machine a suspension of fibres or stock is discharged through an orifice or slice on to a moving endless wire screen or wire. The greater part of the water associated with the stock as discharged from the slice is drained away through the wire, leaving most of the fibres on the wire in the form of a continuous felted fibre mat. Such drainage occurs principally in the vicinity of certain wire-supporting means as hereinafter described. v

In the making of paper on a Fourdrinier paper machine several problems are current. One of these is' the problem of obtaining the necessary drainage of the water from the stock without excessive removal of the fine fibres or fines as they are known in the art. .A second problem is that of kick-up, namely, the formation, in the course of travel of the stock on the wire over the Fourdrinier table of upward splashings or columns,of stock projecting above the mass of the stock on the wire. Kick-up becomes manifest and increasingly severe [as the speed of the paper machine increases and is materially affected by the suction exerted as a result of drainage at or near certain wire-supporting means as presently employed. Such kick-up occurs in the region immediately following the contact of a tableroll with the wire and more particularly at those table rolls immediately following the breast roll. To those skilled in the art, it

United States is well understood that kick-up is deleterious to the formation of the web because it disrupts the uniformity of distribution of the stock over the wire, thereby producing a sheet of poor quality. In addition, the agitation of the forming fibre mat reduces the retention offines On a Fourdrinier machine of the old and slower type,

the stock is delivered from the slice onto the wire at the location of the breast roll, whence the wirebearing the stock passes over the table rolls, suction boxes and couch roll, at which point the stock, now in the form of a web or sheet, is transferred into the press section. The drainage capacity of a given'table roll increaseswith the speed of the wire travel and is also directly proportional to the roll diameter. On high speed machines, therefore, the drainage of water occurs so suddenly that disturbance or kick-up is caused to a degree which is harmful to the formation of the web, Since the breast roll is of relatively' large diameter, the rate of drainage at the breast roll becomes very high as the machine speed increases. This results in objectionable kick-up at the breast roll at lower speeds than those at which kick-up becomesobjectionable "at the table rolls: For this reason at high 2,928,465 Patented Mar. 15, 196i) assisted by the suction action exerted by the tableirolls and by the suction boxes.

" Kick-up at high speeds is particularly prevalent in the region of the table rolls. Two factors especially contribute to the formation of kick-up in this region: first, the suction effect exerted by the table rolls and, secondly,

the action of water carried into the in-going nip of a table roll, either from having been .carried on the underside of the wire, or having been thrown onto the table roll by a preceding roll. Various attempts have been made to solve this problem. .Bafiie plates of varying designs and sizes have been employed between thetable rolls to deflect the draining water from entering the nip of the succeeding roll. These bafiies have sometimes taken'the form of scrapers coming into contact with the underside of the Fourdrinier wire. Scrapers serve the triple function of removing water from the underside of the wire, of providing the necessary deflection of this water and of supporting the wire between the table rolls. These various methods have been moderately satisfactory, but by no means solve the problem, nor do they permit ready control of the water drainage.

The object of my invention is to provide a stationary drainage element in substitution for the revolving table rolls whereby kick-up may be diminished or substantially eliminated without objectionable impairment of the drainage capacity. 1

A further object of my invention is to provide such an element which is adjustable in order to allow the drainage capacity to be varied to suit the varying stock and machine conditions.

A further object of my invention is the provision of an improved form of suction box incorporating my drainage element. I

My invention consists broadly in the provision of -a stationary drainage element adapted to support the wire and extending across the machine transversely of the direction of machine travel; said element having an acute angled leading or scraping edge, a flat portion in contact w th the wire, and a trailing portion diverging from the, wire and so dimensioned and proportioned as to effect) My invention may be understood by reference to the a accompanying drawings in which Fig. 1 is a schematic cross-section of a drainage element. constructed so as to emb ody features of this invention and Fig. 2 isa crosssection of a drainage element constructed according to a second embodiment of my invention. Fig. 3'is a vertical cross-section taken through a suction box constructed so as to embody features of the further embodiment 0f "my invention; Fig. 4 is a plan view partly broken away of a suction box cover embodying features of the-invention in which the drainage elements run transversely and at right angles to the direction of wire .travel; and Fig 5 is a further plan view similar to Fig. 4 in which the drainage elements run transversely to the direction oflwire travel at an angle other than a right angle;

Referring to Fig. 1, 1 is a Fourdrinier wire of a paper machine which is travelling from left to rightas viewed inthe drawing. A drainage element which is indicated generally at 2 extends transversely across the width of the wire and may be supported in any suitable manner.

down over the scraping edge will be adequate so that The leadingedge 3 acts.

as a scaper to remove water clinging to the underside of the wire. For this reason" V the leading edge' should be formed at an acute angle. it has been found in general practice that'an angle Off approximately 30f will effect the scraping in a satisfactory manner. Where'ascra'ping device is used aheadof the drainagelelementithe acute angle of the leading edge may be. dispensed with. The drainage element i s adapted to support thewire and to efiect drainage therefrom.

' a To these ends the upper surface of the drainage element trailing portion 5,-the angled divergence between the trailingportion and the wire and the machine speed,

Kick-up is also influenced by the condition of the stock 7 above the wire when .this passes 'over the leading edge of the drainage element. Kick-up tends to lee-cumulative "and any pre-existing disturbance will becomefurther accentuated under. conditions .conducive to kick-up. It is v cognized tha ext nsive hickp se u e cu c 9- erating practice over andffollow'ing certaindramage elecomprises a flat portion 4 in co nta ct with the wireand a trailing portion 5 which diverges from the .wire. The 'lcngth of the flat portion 4 is not critical. It should, however, be ofsutficient length to'provide the necessary support for the .v'vire and to elfect the scaling function "which will be describedindetail hereinafter.

' The length of the: trailing portion 5 and the magnitude ofjthe .angle of divergence'hetween the wire and the t s aid trailing portion are both critical.

. For a given length of trailing portion, a given machine speed, and .a

m ntsin common use ,qn-ah 'gh sp 'd rdri er p p machine on any-gi en m hin t hete c cr'sqmenegree of kick-up can be tolerated and, in practice ,'is t0leratedn Diminutjon of kick-up is, however, desirable and. the precise detailsofiiny invention will-.be' determined by the factors hereinbefore discussed having regard to the,extent of kick-up which is operationally acceptable.

given stock" condition, the volume of drainage is sn b- V 'stantially proportional to the magnitude of-the angle up to a maximum. critical angle of approximately 5 beyond which drainage ceases. the lowerlimit to the angle of the trailing portion is zero, wear of the surface contour makes it' difficult to maintain angles less than approximately 1. 7 In addition, since angles lessthan 1 produce very small drainage capaci- Although theoretically ties for the element, itis advisable to maintain the angle in the range of approximately li to approximately 5. For a given stock, increasing the length of the trailirig portion increases the drainage up to a point Where the drainage resistance of the stock becomes controlling and thereafter very little further drainage occurs with further. increase'of length of the trailing portion; The

By way of exampleand to indicate dimensions and vother conditions which I have found to give a' 'satisfaca tory result for a'newsprint machinerunningwith a head box stock consistency "of 0.6% a stationaryeletnent hay ing a trailing portion four inches long may be used with an angle of divergence between the wire and the surface of the trailing portion up to 2% (measured when thewire is stationary), at speeds of approximately 1,500 feet per minute with negligible 'kick-np With the same stock and machine speeds of the orderof 2,500 feet per minute,

the maximum angle which may be used without signifi- Q cantkick-upoccurring is approximately 1% similarly measured. A stationary'elernent having a'trailing portion 1 2. inches --longandan angle of divergenceofS" 1 may be used at machine speeds up to 2,000 'feet per minute with similar steel; without producing. s gnificant maximum length oftrailing portion forfa given angle decreases according to the position 'of the element along the direction of machine travel; This length decreases as the distance from the slice increases. Inptactice it has'becn found that the length of training portions should be maintained less than approximately 6 inches] rnr'a given stock and a'given length of trailing portion, drainage also increases as machine speed increases; The prac it will be vention deserib'ed thus-far-must be specifically designed to; suit the operating conditions 'on a given paper machine. The angle ofdivergence ofthe trailing portions from the appreciated that the embodiment of my in-.

e must be -predetermined, as already pointed out, to

su f given' 'stock consistency and given machine operating tical limitations'of the. speed-drainage irelatiQnare'determined by'the point at which'thedsuction developed in the drainage zone is sut licient to" cause cavitation and by the extent of kick-up as hereafter-discussed. It' will,

of -course,' be recognized that the drainage. capacity of 'my invention is influenced by the characteristics of the "gstock being drained. The operation is one of filtration and the properties of any particular stock'which influence myinvention. V o The trailing portion acts to create afzone ofsuction means is not provided at the leading edge of element 2 ts .filterability will similarly influence the application of this suction will also draw air into the'nip overthe .leads ing edge, thereby causing a loss of drainage capacity. In my invention sealing is provided by two means: first,.tl,1 e' scrapingor leading edge'3 causes water'carried on theunderside of the wire to flow down over thelscraping cdgegthns preventing air being drawn into the nip},-

secondly g tlie provision of the flafportion 4 in contact" with the wire assists in providing a seal against the entry of air.- fA /z inchflat portion will generally be found tojbe satisfactory except that, where the rate of drainage;

high, the sealing action provided bylthe fiow of water flat portion maybe reduced or dispensed with. f

9; kid 12 in r s s s a fun on qt t inmates eharacteristics obtained by the use of my invention.

jrr vids mutua .5 is as speed. Once a drainage element as illustrated in'Fig. i has been-designed andfinstalled under particular 'oper' atingconditions,"the'rateiof drainage effected by such nnitf is as; subject toadjustment. The embodiment of.

a machine speeds-encountered 'in' any given installation and that the rate of; drainage or the elements may be varted through a corresponding adjustment of this angle. ,Re

; terring'now to FigQ Z, I is the Fourdrinier wire whicl1 as i s'hownfis travelling fronrgleft to right. The drainage element which terms this" inventionis indicated generally at} in which the flat portion 4 provides the necessary support for the wircflandassists in the sealing efiect here- 'inb'efore described. The fiat portion 4 is provided with anaeuteiangled leading edge 3, which acts as a scraper removingl water' adhering to the underside of the wire. Thet railingportion 5 i s attached to the supporting; beam -'6 "by means f'of a'hinged connection 7 and a hinge pin 8,

1 which isfixedly securedto'the support 6. The flatportion 4 is also ifixedly secured to'the supportingbeam :61

by means ofscrews 9. The'fiatportion 4 maybe atftached to thejbeam 6 in the manner described, or may be integrally formed therewith. The trailing portion 5. at

' its forward edge 10 is curved'in the form of an arc, of

which thefcentre is thecentre of the"hinge pin 8 and is a d tp lani u siwi h'h s i wnt '0 di rea rwardcnd of the' flatpmtion 4. It is desirable to make maturit e o'an n) gress 9f a between the.lsurfacesldandlj. if air were ern1ittedtotcutcr the s ace between-these t o c f w.

Mathews; the an ient sf dra nage.

w th, isq't a th y ma ward end '12 of the trailing portion is preferably rounded. This assists in drawing the water drained by the trailing portion 5 downward away from the wire, thus assisting in its subsequent removal by a following scraper.

Referring to the further embodiment of my invention, it has been recognized in the past that it is desirable to keep to a minimum the bearing area of a suction box upon the underside of the Fourdrinier wire. A limiting factor in this regard has been the necessity of providing adequate structural strength in the suction boxtop. In addition, the rate of drainage from a suction box is a function of the vacuum applied. In order to obtain an increased drainage rate, it has in the past been necessary to apply a'higher vacuum and this higher vacuum increases the rate at which the underside of the wire is worn away by the stationary top of the suction box.

The further embodiment of my invention consists broadly in the provision of a suction box having a plurality of drainage elements extending transversely across the Fourdrinier wire; at least one, and preferably more or all of the said drainage elements being dimensioned and arranged so that the passage of the wire over the draina'ge element surfaces produces a suction effect which supplements the drainage caused by the vacuum applied to the suction box. The invention may be better understood from a consideration of the following detailed .description taken in conjunction with Figs. 3 to 5 of the attached drawings. In Figs. 3 to 5 of the drawings, 21 represents a Fourdrinier wire which is travelling from left to right. The suction box is indicated generally as at 22 and is connected by way of an outlet 23 to a source of vacuum. The forward portion of the top of the box comprises a fiat portion 24 adapted to support the wire 21, together with a trailing portion 25 which acts in manner as hereinbefore described. The rearward portion of the top of the box comprises a fiat portion 26. Between these two extremities of the suction box are interspaced a plurality of drainage elements 28a, 28b, etc. These drainage elements extend transversely to the direction of wire travel and across the machine. Each drainage element consists of a leading edge 29 which acts as a scraper to remove water adhering to the underside of the wire, a flat portion 30 which serves to support the wire and to effect a seal in a manner as hereinbefore described, and a trailing portion 31 diverging from the wire. The leading edge 29 may be inclined to the vertical making an acute angle with the direction of wire travel. Thelength of the flat portion 30 is not critical. It should, however, be of sufficient length to provide the necessary support for the wire and to provide the sealing effect. In order to provide lateral rigidity to the suction box top bridges 27 may be located at appropriate intervals betweenadjacentdrainage elements. These should preferably be recessed below the level of the wire. 31 and the angle of divergence between the trailing portion and the wire are critical and must be carefully chosen. For angles of up to 5 (measured when the wire is stationary), the supplementary drainage provided by this diverging portion is substantially proportional to the magnitude of the angle and to the length of this trailing portion 31. Depending upon the amount of supplementary drainage required, the angle will vary from O to about 5. Above 5 the supplementary effect of the trailing portion of the drainage element on the drainage is lost. The useful length of trailing portion is dependent upon the consistency of the stock on the wire above the suction box. As the consistency increases, the useful length of the trailing portion decreases. For the first box in a conventional Fourdrinier machine, where the consistency is of the general order of 2%, a length of to /2 of an inch is the maximum useful length.

It will be appreciated that the entry of air into the zone between the trailing portion 31 and the underside of the wire 21 will reduce the supplementary drainage effect.

The length of the trailing portion 6 The entry of such air is, in accordance with my invention, precluded by two means. First, water adhering to the underside of the wire is scraped off by the leading edge 29 of each drainage element and then flows down the leading edge, providing a seal. Secondly, the flat portion 30 of each drainage element 28a, 28b, etc. is of sufficient length to provide a restriction to air flow.

The spacing of the drainage elements is determined by the extent to which drainage resulting from the suction action of the applied vacuum is desired. The separation between the drainage elements determines the area over which the applied vacuum is operative. The relative proportions of drainage caused by the two mechanisms, i.e., the applied vacuum and the supplementary suction can, therefore, be varied by adjusting the spacing of the drainage elements and the length of the trailing portion.

In a conventional slotted suction box the dimensions of the grid bars and their separation is determined by the need to provide sufiicient rigidity in the drainage elements and to prevent excessive deflection of the wire over the slots. In such a suction box the whole width of the top of each drainage element bears against the underside of the wire and its dimension is determined by structural requirements. In my invention only a small part of the total Width of the drainage elements which serve as grid bars bears against the underside of the wire. Because of the supplementary drainage effect of the trailing portions, less applied vacuum is required to achieve the same overall drainage as would be needed without use of the trailing portion and, therefore, the tendency of the wire to be drawn downwards between the supporting flat surfaces for the same over-all drainage is reduced.

When in the specification and claims I use the expression transversely of the direction of wire travel, I mean to include not merely installations in which the drainage elements are strictly at right angles to the direction of wire travel, for example as shown in Fig. 4, but also installations in which the drainage elements are at angles other than right angles, as for example as illustrated in Fig. 5.

While I have described my invention in the embodiments mentioned above, it is to be understood, however, that these are given by way of illustration only and are not to be construed as limitations of my invention. Such embodiments of my invention, therefore, as come within the scope and purview of the appended claims are to be considered as part of my invention.

This application is a continuation-in-part of my applications Serial Nos. 555,643 and 555,719, both filed December 27, 1955, both now abandoned.

What I claim, as my invention is:

1. A stationary drainage element for a paper machine disposed in supporting relationship to the Fourdrinier wire and extending across the machine transversely of the direction of wire travel and having a trailing portion diverging from the said wire at an angle therefrom greater than 0, but not greater than 5, said angle being measured when the wire is not in motion.

2. A stationary drainage element for a paper machine disposed in supporting relationship to the Fourdrinier wire and extending across the machine transversely of the direction of wire travel and having an acute angled leading edge and a trailing portion diverging from the said wire at an angle therefrom greater than 0, but not greater than 5, said angle being measured when the wire is not in motion.

3. A stationary drainage element for a paper machine disposed in supporting relationship to the Fourdrinier wire and extending across the machine transversely of the direction of machine travel and having a flat portion in engagement with the Fourdrinier wire and a trailing portion diverging from the said wire at an angle therefrom greater than 0, but not greater than 5, said angle being measured when the wire is not in motion.

trailing edge ofthe drainage element.

4. A sratifonary'erainage element'torsniper-machine eisposeninstippotting relationship to the Fourdrinier wire and eatenaing across theinaehine transversely of the di reetien or wire travel andhaving' an acute angled leading" edge, a flat ortion in engagement with the Fourdrinier wire and extending across wire and a trailingportion diverging from the .said wire 7 at an aiigl angle being measured when the wire is n'ot in motion.

'5; A stationary drainage element for a paper machine.

disposed in sup orting relationshi to the Fourdrinier wire and extendin neross the machine transversely of the direction at, wire travel and having an acute angled eater than ,but notgreater than Sffsaid thediretion ofwiref travel and having an acute angled leading edge, a flat portionin engagement with the Foarg dri'nier wire and a trailing portion diverging from the said Wire atan angle-therefrom in the range 5 to 1 1 mease ured when the wire is not in motion, the magnitude of the angle' diininisliingas the speed of the machine increases in which the length of the trailing portion is not more than six inches 'inwhich th'e'length of the flatportion is som cient'to provide a substantial seal against the entry of air into the zone. lying between the Fourdrinier wire and the trailing edge of the drainage element;

leading edge, a net portion in engagement withfthe Poorer-inter wire and a trailing portion" diverging from the said wire at an angle therefrom, measured when the wire is not in inotionseleeted front within the range of 5's to t 7 wire atan angl ther enoin in the range 5"z'to :1", men's;-

iire'dwhen the wire is not in motion, the magnitude of the angle diminishing as' the speed of thermachine' ing creases in which the length or the trailing portion is not 7 more than silt i ches 7'. A stationary drainage element for a paper machine disposed in supporting relationshi to the Fourdrinier Wire 7 and extending across the machine transversely of the diand amending across the machine transversely of the i ree'tien or wire travel and having an acute angled leading edge,- a hat portion in engagement with the Fourdrinier wire and a trailing portion diverging from the said wire atan angle therefrom greater than 0, but not greater than 5; and said angle being measured when the wire is not in motion in Qwhich the length of the flat portion "sufficient to provide "a stibsta'ritial seal against the: entry of air into the Zone lying between the Fourdrinier wire and the trailing portion of the draina e elem nt.

8; A stationary draina e element for a paper machine disposed .in supporting relationship to the Fourdrinier wire and extending across the machine transversely of the.

direction of wire travel and havingan acute angled leading edge, a flat portion in engagement with the Fourdrinier wire and a trailing portion diverging from the said 'wir eat an angle therefrom in the range 5 to lf rneasuredj when the wire is not in motiohiythernagiiitude erthe angle diminishing as the speed of the machine increases in which the length of the flat portion is 's'ufiicient to provide a substantial seal against the fentryof air into the zone lying between the Fourdrinier wire and the 9. A stationary drainage element for a paper machine disposed in supporting relationship to the Fourdrinier '10;- Astationarydrainage element for a paper machine disposedinsupporting relationship to the Fourdrinierwire and extending across tho-machine transversely offthe direction ofwire' travel and having an acute angled leading edge, a flat portion in engagement with the Fourdriniet wire and a trailing portion diverging from the said'wire at an angle therefrom greater than'O", but not greater than 5", said angle being measured whenlthe wire is not in motion, the said trailing portion being adapted to artic ulate to provide anfangle of divergence of variable magnitude;

1 1 A suction box for a Fourdrinier paper machine; comprising in combination means for withdrawing air fronrsaid box to create a sub=atmospheric pressure .therin and supplementarydrainage-promoting means compris= ing' aplurality of stationary drainageelements secured therein in supporting relationship to the Fourdrinier wire and extending across the-machine transversely of' the directionoi wire travel, said drainage elements having a fiat portion in engagement with the Fourdrinier' wire and atrailing portion diverging from the said wirelat an angle therefrom greater than 0", but not greater than 5, said tangle being measured when the wire is not in motion 12. A suction box for a Fourdrinier paper machine, a

plurality of stationary drainage elements secured therein in supporting relationship to the Fourdrinierwire and ex tending across the machine transversely of the direction of wire travel, said drainage elements having an acute angled leading edge, a flat portion in engagement with the Fourdrinier wire and a trailing portion diverging from the said wire at an angle therefrom greater than 0', but not greater than 5 said angle being measured when the wire is not in motion; T j a t Y t 13: In a suction box for a Fourdrinier aper machine;

-a'plurality of stationary drainage'elements secured therea in in "supporting relationship tothe' Fourdrinier wire and extendingacross the machine transversely of the direc tron of wiretravehsaid drainage elements having an acute angled leading edge,- a'flat portion in engagement with' the -Fourdrinierwire and a trailing portion diverging from thesaid wire at an-ang'le'therefrorn (measured when the wire is not in motion) greater thanO", but not greater it than 5, and of a length not greater than one half inch;

No references cited.

the machine transversely

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