DE1461155A1 - Method and device for dewatering an aqueous paper stock suspension in paper machines - Google Patents

Description

St. Anne's Board Mill Company Limited, St. Anne's Road,

Bristol 4, England

Method and device for dewatering an aqueous paper stock suspension in paper machines.

The invention relates to a method and an apparatus For dewatering an aqueous paper pulp or a paper stock suspension in paper machines or the like, in particular an apparatus for making the initial fibrous web from a thin-bodied fiber suspension or a thin-bodied one Pulp in paper machines or the like.

Although the present invention is particularly suitable for use in forming equipment for paper machines and is primarily described in connection therewith, it is equally applicable to related devices such as for example the production of cardboard and similar fiber materials

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Certificates applicable.

In the known Fourdrinier machines, dewatering takes place very slowly and in machines with an upper wire it is not constant Pressure exerted through the upper sieve so that the machines have to be made very long and take up excessive space claim.

The purpose of the invention is to provide a faster and even dewatering of the fiber and thus a son ^ - To achieve lere production of a paper web with a shorter design of the machine.

According to the present invention, in the method for dewatering an aqueous pulp or a pulp suspension for the production of paper, cardboard or a similar fiber product in a machine that has a rotating carrier tape or long sieve for the fiber st of f suspension and an upper one, with the carrier tape or fourdrinier wire over part of it Contains web moving upper belt, applied to one of the belts a pressure to press the belts against each other and one generally converging passageway to form, and the pulp sent through the passage for dewatering, the arrangement being such that a substantially constant Maintain pressure on the pulp flowing through the passage will.

The device for dewatering the aqueous paper pulp or paper stock for the production of paper, cardboard or the like Faser product with a circumferential carrier belt or fourdrinier wire, which carries the aqueous fiber material and a circumferential upper belt, which is connected to the carrier belt or fourdrinier wire

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moved over part of its B & hn, contains according to the invention a stationary pressure element which acts on one of the belts, pressing them against one another, and a generally converging one Forms passage through which the aqueous pulp is sent for dewatering, this pressure element so is designed »that an essentially constant pressure that flowing through the converging passage Pulp is maintained.

By fif # maintaining a constant pressure within dtβ 5ft8frttoffes a more effective drainage is achieved. Even there will be a backflow of water and the appearance of a pool in front of the half or the entry gap of the converging passage redusteit. All of these factors contribute to a better one BahnÄUsbil-dipig at.

Preferably, that part of the element in contact with the one band © is curved in the direction of movement of these bands. So this part can be at least partially parabolic be.

A further pressure element can be provided which acts on the other band in the area of the first pressure element, see above that the two elements between them the converging passage for the bands limit and ^ © vote. In a preferred embodiment of the invention, however, the other is tape not supported in the area of the pressure element, which makes it turns during operation.

In the drawing, the invention is, for example, craggy /

OBiS

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Figures IA, IB and IC form one in the order A-B-C

Section through a paper machine embodying the present invention, wherein these three views can be viewed as a single embodiment of a machine have to.

Figure 2 is a partial plan view on an enlarged scale part of the.in Figures IA, IB, IC shown Device along the line II-II of Fig. IB, wherein Parts broken away or not for reasons of simplicity are shown.

FIG. 3 shows the part according to FIG. 2 in a general side view along the line III-III in FIG. 2.

In the figures there is a high-speed pulp device 10 shown, which consists essentially of means for the production and supply of essentially homogeneous, suspended, together Tangled, converging pulp fibers from a thin, generally horizontal, high-performance pulp nozzle on a lower wire section of a Fourdrinier wire or circumferential carrier belt 20, which is around a front and rotating drive roller 21, a breast roller 22 and a couch roller 23 is guided. Each of these rollers 21, 22 and 23 are arranged in suitable bearings, which in turn on a conventional frame, indicated generally at 24, are provided. Special items of the bearing arrangements for this various rollers are not described and shown, since the arrangement of the Fourdrinier wire 20 and its support rollers in is known in all details. In addition, it should be emphasized that the Fourdrinier or carrier belt from the breast roll 22 to the

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Couch roller 23 liters a plurality of "known suction boxes" SB-I "to SB-5 is running, which is a sub-atmospheric pressure on the underside of the Fourdrinier wire or carrier belt 20 while the fiber material and / or the paper web moved on the Fourdrinier wire 20 for the purpose of their dewatering. The support frame for the suction boxes SB-I to SB-5 is partial at 24a and 24b in Figures IB and 10 shown.

The crash frame shown in Figure IB for the initial Suction box Sb-I carries a transverse masonry frame 24c, which a disk 25 is supported which engages the underside of the wire 20, the disk 25 being stationary is held and the slow motion moves relative to it. The disc 25 supports the underside of the Fourdrinier wire 20 and supports at the same time the removal of water droplets, welehe tend to be on the underside of the Fourdrinier 2.0. in the area of the immediately running side of a instead of «

see form or pressure element in the form of a box 30 collect, which is shown in detail in Figures 2 and 3. The disc 25 has a rounded front edge 25a provided for initial engagement with the underside of the screen 20, followed by a generally flat or planar surface, which gradually differs from the Underside of the wire 20 lifts off at a relatively small angle of about 5 ° in order to support a pumping effect to generate the water removal. The disk 25 is placed on washers or other suitable devices, in order to enable a vertical adjustment, which is shown diagrammatically by the double arrow at A in a bearing block 24o of the MgullB.

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A tension roller works with the lower run of the Fourdrinier wire 20 26 together with adjustment means, which is also indicated by a double arrow A for the purpose of adjusting the total voltage the Fourdrinier wire or carrier tape 20 is indicated. It can thus be seen that the relative position of the sieve portion 20a between the top of the breast roll 22 and the top of the disc 25 not only due to the adjustable mounting of the disc 25, but also by the adjustable tensioning of the Fourdrinier wire 20 by the tensioning roller 26. Even the breast roll 22 itself can be adjusted for additional ease in adjusting the overall bearing of the screen section 20a, which moves generally in the longitudinal direction or in the direction of the fiber to ff movement.

From Figure IA it can be seen that the high-performance fiber düa s device 10 has an inner channel 10a, which the the same width as the Fourdrinier wire or belt 20. The pulp device or casserole 10 is on a stand 11 and upright Hahmn ^ 12 and 13, which are upright, a nozzle generating and forming means 14a, 14b carry, which are connected to a pulp source 15 in connection. The pulp is fed to the head or source 15 at a controlled rate by a pulp feed device such as for example one shown schematically with F in FIG Vane pump supplied at a speed sufficient to achieve a desired speed and other properties.

the nozzle at 10b in FIG. 1B in the pulp stream emerging from the opening / out reach. The pulp nozzle opening 10b sees a 4.m essential horizontal pulp nozzle stream generally at the Top of the breast roll 22 before. The stream is preferred

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ο ο the top of the breast roll or within 10 or 15 up fed to each side of the upper part thereof, which depends on the transverse dimension and the longitudinal speed of the wire section 20a is tuned in the immediate vicinity of the disc 10b and brought into a correct relationship. One some limited adjustment of the position of the breast roll 22 can be done via the bearings B, as can be done by the two Double arrows AA is indicated. A limited setting of the pulp nozzle production device 10 itself can also be achieved by spaced, vertical, adjustable devices, as indicated by the double arrows A-I and A-2, as can also be achieved by a horizontal adjustment device in the sense of the double arrow A-3.

Suitable devices for generating a pulp nozzle stream, which when using the present invention in the arrangement and as a complete replacement for the one indicated here at 10 The device shown can be used, for example shown in American patent 3,098,787. These pulp devices include several vortex-generating arrangements, which in the present schematic Represented in or upstream of section 14a and essentially for initial implementation a complete distribution of separated individual fibers in the thin-bodied fiber material can be used, which is generated for a high-performance feed through the continuous channel 10a, which in Fig. 1A through the sections 14a and 14b. The essence of the pulp nozzle arrangement 10 also includes the creation of an initial vortex

in front of the area of the channel 10a for uniform fiber cleaning · .-, ■ -. ■ ■ ■ · ■ ■ .. ·., · ■■■ .. ·. ■ distribution ^ which is followed by a widespread vortex,

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which is supposed to keep the fibers in their own separate and dispersed state, while at the same time keeping the thin ones Paser distribution or suspension is finally applied to the Fourdrinier wire 20 at an extremely high speed will. The thin stream of pulp has about only one Height of 2.5 cm (in reality essentially 1.9 cm) in the area of the nozzle opening or disc 10b when it is removed from the channel 10a at an extremely high speed (around to 900 or more meters per minute) at the required high pressures and in a generally horizontal, with a Line 200 is fed in the direction aligned in FIG. The line 200 is an imaginary straight line, which in a tangential en plane is drawn generally from the top of the breast roll 22 at the nozzle opening 10b and extends up to the top of the disc 25 extends. Ie is the line which theoretically coincides with the Fourdrinier wire 20. However, since that Fourdrinier wire 20 is not without some elasticity and flexibility, regardless of how high a tension is placed on the wire the roller 26 or in another way is exercised, the screen 20 can be slightly down under the imaginary line 200 through the force exerted by the pulp on the upper part. However, in practicing the present invention the forming wire 20 must be at a relatively high tension by using the tension roller 26 or other conventional Means are retained so that the lower portion 20a of the forming screen between the breast roll 22nd

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and the disk 25 is maintained substantially planar, i.e. the portion 20a of the screen 20 is substantially a straight line as shown in FIG. 1B and the screen 20 is is essentially with the imaginary straight line 200 of the Figure 3 aligned by maintaining the high tension. If so the general direction of the wire section 20a is changed perpendicular to a horizontal direction (i.e., by relative adjustment of the breast roll 22 and the disc 25) then becomes a setting of the various Devices A-1 through A-3 for the pulp stream generating device 10 are designed to provide the desired general orientation of the pulp stream nozzle at 10b in substantially the direction of the wire section 20a. the end For practical reasons, the nozzle flow and the forming

ο
Fourdrinier no more than about 30% from a generally horizontal direction to be in accordance with preferred operation of the present invention.

As shown in Figures 1B and 1G, is in the training According to the present invention, an upper revolving belt in the form of a forming screen 40 is foreseen. The top Screen 40 runs under a static pressure element along and is supported by it on the upper side, which of a box 30 approximately in the area of the nozzle outlet 10b (Fig. 1B) is formed .. Das.Sieb 40 runs mUöh um.fitende

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Guide and tension rollers 41 _f 42, 43 »44, 45 and 46 around. Although it is essentially schematic !! is shown, it can be seen that the horizontal frame 24 is provided with upright frame parts 24d, 24e and 24f, the frame part 24f carrying the guide roller 46 for rotation and separation of the upper wire 40 from the formed paper web W which is on the lower Fourdrinier 20 is led away, as shown in Fig. 1C. Me upright support 25f is also the main support for a couch pressure, which is determined by the smooth lower couch pressure roller 23 and an upper couch pressure roller 47 within the loop of the upper wire 40, which is carried at the two opposite ends on fixed and movable pivot pins 47a and 47b . The movable pivot pin 47b is attached to a power cylinder 47c, which in turn is connected to a lower extension of the frame at 24 ff for regulating the load on the couch roll feed gap Ή, which is limited between the sieves 20 and 40 and the smooth pressure rollers 23 and 47. By these means, excess water at the location of the nip N can be removed by mechanical means prior to a subsequent treatment of the web W as it is fed into the rest of the machine on the Fourdrinier wire 20. The advantages of a couch press 23 to 47 are known. Successful use, however, has hitherto been limited, if at all possible, for the reason that it is necessary to form a reasonably firm path before the

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Apply some pressure to their drainage have, and webs of this firmness have hitherto usually not been possible in such an early state or in such a way early stage in the educational process or at such close distance from the pulp nozzle disc 10b as indicated here. The in particular the molding or press box 30 having the initial Formeinricbtung is constructed so that it is a allows maximum dewatering speed and a maximum speed for forming a solid web, which allows the use of the couch press 23 to shown here 47 makes possible.

From Figure 1B it can be seen that the upright frames 24d and 24e are provided with * Querrahmen24h and 24g, which are on both Pages “ά. sieves 20 and 40 are arranged so that they

At opposite ends of the operating device / holding, a bearing block 24ee is arranged on the upright support 24e for holding the wire guide roller 45. A support 24dd forms an extension of the upright support 24d for supporting the guide roller 42. A support 24xx is on. _: the side of the bracket 24d for holding the guide roller 41. Conventional jack screws or screwdriver spindles JS-1 and J ° -2 are arranged on the upper outer frame 24g for an adjustment of the guide s * - and tensioning rollers 43 and 44. In each case, double arrows at A indicate approximately the direction in which an adjustment for the rollers 43 and 44 is possible, so that these

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Rollers actually for guidance and tension for the upper one Formsiob 40 can be used.

The lower part of the molding and pressing box 30 is arranged in a suction box housing 31, which can be pivoted at its front end on the bearing block 24 xx and in a general vertical direction by using a screw spindle JS-4 is adjustable. The rear end of the housing 31 is open. a hanging frame arranged 24hh, which has a screw. JS-spindle 4 carries, which 'allows a limited vertical Einstellunng or movement according to the double arrow A. · The Schraübspindein JS JS-3 and-4 thus constitute setting means for "Transmitted, ^r cause a relative tilting of the housing 31 and the lower - · Operating part of the box 30 which actually comes into contact with the; .- · inside of the loop of the Pörmsieben- ^ s 40 in contact. ·· ,.

A side suction vent 33 is provided at the rear end of the housing 31 with an overflow dam 35 within the housing 3t · ■ so that water “can be drained off through the box 30” falls over the roof 35 and from the side 'of the machine _..; as · in 'Verbindung'mit the suction boxes SB-1 to SB-5 used-be) ahgeweraäfet: is * ■ / ■ the dam 35 regulates to a certain extent the water level j alert check continuously in the lower Part. .

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of the housing 31 accumulates while the top of the housing 31 is closed and is held at sub-atmospheric pressure by suction discharge 33. ·

The upper forming screen 40 runs down around the guide roller 41 and then around a curved solid surface or shoe 50, which with these for guidance along the lower edges 51a-60a of a plurality of spaced apart in the longitudinal direction, transverse blades 51 to 60, which are arranged within the box 30. The single ones in the longitudinal direction at a distance, transversely extending blades 51 to 60 are in side view in Figure 3 by a

30th
Side wall 30a of the box / covered and partially in plan view

shown in FIG.

For a general explanation of the structure and the arrangement of a single blade, the blade 52 is described, which is shown, for example, in both Figures 2 and 3 as a second blade in the longitudinal direction _; i8t. The top edge of the scoop 52 is shown in solid lines at 52x and extends from the top edge of the side wall 30a of the box 30. A ramp or caulking piece 30b is attached to the side wall 30a and extends along the lower part of the side wall 30a. It is a hard, generally curvilinear lower surface,

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which can be seen more clearly at the front or left end 3Obb. In the plan view, only the part 30b ^{1 is} visible at the front end, and the upper planar part 30b ¹¹ can be seen at the rear or right-hand end of the sealing piece 30b in FIG. The remainder of this is at least partially obscured by the various inclined blades 51-60. The blades 51-60 extend downwardly from the upper exposed edges 51x to 60x down to the bottom portions 51b to 60b. The bottom or lower portions 51b to 60b are engaged with and secured to the top of the side seal piece 30b.

The middle parts of the individual blades 51 to 60 extend downwards under the sealing pieces 30b, from which one on each side of the box 30, and stand with the upper side of the rotating screen 40 along its machined smooth Leading edges 51a to 60a in engagement. From Figure 2 it can be seen that the blade 52 extends from the upper edge 52z from downwards and to the left to a part 52b along its edge which is in engagement with the sealing strip 30b. and then extends to an edge 52a which is drawn further to the left in Figure 2 and with the inside of the loop of the upper screen 40 engages and controls its position. The outermost lower edges 51a to 60a of the blades 51-60 provide supports for the sieve 40 with a relatively narrow spacing in the longitudinal direction and determine in the

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generally a parabolic curve, with reference to the theoretical or imaginary straight line 200 «-" - _Λ ,

A sealing piece, 31a. is .an-.dem rear end of the _box; 30 attached j which with a flange 31, b for attaching the
Box 30 on the Saugkasteng, ehäuse _: 31 is provided. The rear planescii ~ 31b and the side piece _: 30a for the box 30 are provided with openings for receiving visual bolts. ..
• at the cost of 3Q *. the bottom of the overall suction box housing 31
Conventionally: to attach .. .E ^ n front sealing., ■ piece 31c is at the front or left end of the box 30 _; · ..; ■ _. to complete the seal and the connection with the Saugkastengehäus.e 31 attached.-The yor4er§ sealing piece _; ,.,;. 31.0: has> ej-ne, unterje smooth. Storage area, which is a continuation. the . Storage area of the shoe. 5.0 forms «and as the initial ...., .., guide surface for the sieve 40d i ent., This initial - total guide surface. l $ i, generally ■ cylindrical, in circumference for _v a smooth ^^ movement .. of the _r sieve above and for a. Feed
d es si ebes, 40th in, each _: smooth en ;. uninterrupted way, directly _; - ■ on the spaced, smooth, lower guide edges. , 51 a-60a_ of the blades 51-60. . . ,,, ..., ■, .... r, ■ -,., ..

The significant, characteristic of the overall arrangement of the box 3P i ^ t ,, the. curvilinear. Type / deriF ^ ormr or.preiäfläche, which byQh.,,. ■ the longitudinally spaced lower J & _r -

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of blades 51a-60a is formed. The preferred embodiment is a parabolic curve which is generally based on a theoretical abscissa lying along the imaginary line 200 (enlargements or increases are indicated by the letter P, which is shown in FIG. 3 as a pop-up arrow) and along one lies generally by the center line OL in Figure 3 shown ordinate (increases are shown by the Bush letter H with a poplar arrow in Fig. 3). The theoretical zero point for the parabola i is at the intersection of the abscissa 200 with the ordinate CL

H = CP ^k

where H is the distance in cm vertically upwards from the line. 200, P is the distance in inches to the right or in the positive Direction from line CL of Figure 3 and C and k are constants ». It follows from FIGS. 1B and 3 that the upper sieve 40 completely from above through the smooth surfaces of the ... shoe 50 and piece 31c is worn, which has a point P: (Figure 3) feed on the ordinate OL. Another. Point P .. (and of course at the slightly higher point P) the height is H. of the sieve .40. over the line .200 (and therefore, over demßieb 20 on the breast roll 22) essentially the height of the pulp nozzle flow, which comes out at 10b (the same as above suggested is essentially 1.9 cm and about 900 Meter per. In the case of the present exemplary embodiment,

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The leading edge 51a for the first paddle 51 is drawn in the figure at point P ₁ so that P _Q - P _{1 is} approximately equal to the pulp nozzle flow height or substantially equal to 1.9 cm. Before the point P, the surfaces of the shoe 50 and the piece 31c render the screen 40 impermeable. The zone between points P and P. is initially an open area for the wire 40, where an initial dewatering of the pulp is carried out, the water running through the wire 40 into the box 30. In front of this zone, the solid supports 50 and 31c lie very close to the top of the part 14b for the pulp nozzle inlet 10b (and the wire 40 runs between them in a very close running relationship), such that essentially the full pulp nozzle pressure is applied to both the upper and the the lower wire 40 and 20 is exerted substantially immediately behind or at the region P to P- with negligible backflow and / or pressure loss by a backward or upward flow of the pulp between the inlet part 14b and the firmly supported wire 40. For reference purposes, point P _Q is considered to be on the ordinate 01, and the distance from P _Q to P ^ is assumed to be approximately 2.5 cm (actually 1.9 cm). The curve P _Q to P ₁ is considered to be generally cylindrical (or circular cross-section), and (the pulp jet stream at 10b is considered as if it would have in the «« ssentliehen the same structure ¹ in width, height, spd> ndigfce4fe umt. : iras blond in height like the one who duroh die-10 ^] βΛίΙλι ^ 1 #. jffi &'Oiäafty even if it is not the

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The outlet of the supporting part 14b may be at precisely this point. When considering the more essential features of the For purposes of reference, it is assumed for the moment that line 200 is horizontal.

The critical point in the operation of the forming area is the zone forming the converging sheet immediately after the pulp leaves the damming device 10b and runs onto the fourdrinier wire 20. This zone is the converging inlet gap, where you see the upper wire 40 approaches the Fourdrinier wire 20 and where the water is drawn off from the pulp both upwards and downwards by leaving the fiber deposited between the two wires 20 and 40, around the Sheet or finally the web W to form. The function of the upper sieve 40 in connection with the lower sieve 20 consists in addition to the formation of a partition or passage wall through which the sheet or sheet can be discharged upwards as well as downwards off the air and thus provide stability and control of the broth when it is dewatered to the forming * in order for this stability "is present at high speeds, it is essential that the serving for the formation of intake gap converges in such a way that the slurry "is subjected to a substantially constant pressure as the web is forming, until the chew resistance of the slurry is so sufficient as to cause an" increase in the pressure

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falls between sieves 20 and 40 no damaging effect on the in the formation process W

Tests on Yersuchs mold units have shown that the convergence of the mold entry gap is critical. The intake gap is formed in that the tension in the lower, slow sieve 20 or lower sieve part.2Qa is maintained and the upper sieve is also drawn under tension against the shaped bottom cover of the upper molding box 30, as is the case with the ₍ in the longitudinal direction in the Spaced edges 51a, 52a, 535a, etc. As shown above, the critical portion of the box 30 from P = 1.9 to 15 or 20 cm is machined into a parabolic curve H = OI), where 0 and k are constants, which are determined by the web weight, degree of refining or crispness and fluidity, while the surface of the cover from P = O to D = 1.9 em, which is less crystalline, will work in such a way that it is soft Transition from the beginning of the collar to the curve H = QjP forms, "From P == 15 or 20 cm to the epde of the box 30, the slope of the curve can be made greater than H ^ 033 in order to avoid higher forces between the sieves for to make use of increased drainage »beep can be made, since at P m 15 to 20 cm the strength of the formed web W is high enough to cause tingm g © rrfi§n and damage due to considerably higher watering driloke resist,

Pie machined surface of the; recently used on the box 30

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Mold coverage can be as shown in the curve shown in Figure 3 above be considered registered. This is the recommended curve for "slow" or a low freeness pulp such as that used for newsprint or coated stock is used. Typical C and k values for the curve H = CD for Zeitun, £ spapier ^ creation with the embodiment described can be C = 0.516 and k = 0.284. For a fiber that dewaters more freely, the (lower) k-value would be in the negative direction increase, and when running at a smaller consistency the C value would be high to run a larger one Volume to allow pie areas for practical purposes for the upper and lower values of G and k, C = 0.5 - 1.6 and k = 0.2-0.8.

Thus, it can be seen that due to the shape of the box 30, the pulp nozzle does not change in composition, hone, width, etc. from its exit from the supporting structure 14b to substantially point P. From point P to T ₁ over the entire transverse dimension of the machine there is an initial rapid upward flow and, depending on the exact position of the breast roll 22, probably also downward at the same time. However, this is extremely difficult to regulate and control. Raw. speaking, the lower or Fourdrinier wire 20 remains tangentiafeijBU of the breast roll and should in theory be essentially horizontal in most cases whereas the upper wire 40- see through a cylindrical or curved surface

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of a relatively large radius for a very short distance of less than 2.5 cm and preferably over 1.9 cm ■ moved, the sieves 20 and work with these dimensions. 40 as rigid, inflexible supports, even if a certain and even a substantial amount of drainage may occur, which from a practical standpoint is not a perceivable one Web formation and / or increase in the remaining fiber consistency on the wires 20 and 40 results. After D = 1.9cm then the drainage and web formation becomes critical and that upper sieve 40 must form the parabolic curve:

H = CD ^k

Excessive pressures cause some deflection in the lower one . Sieve 20 down in this area, maybe like one Chain line, but probably in a parabolic shape although funds (26, etc.) have been earmarked for the high To maintain tension on it and the deflection between ■ the breast roll 22 and. the slide 25 to reduce. Might be presented Drive controls for the two screens 20 and 40 also perform this function.

The purpose of pulping in this critical area is essentially the same internal pressure within the pulp on both the top and the top

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maintain lower strainer. Therefore the bend, which the part 20a of the lower screen 20 in this area below the theoretical line 200 should be taken into account in designing the shape of the box 30. The relative The location of the upper screen 40 is fairly well defined by the bands of the closely spaced blades 51, 52, etc. what determines the parable explained above. The longitudinal speeds of the two screens 20 and 40 are essentially aligned with each other by known sieve drive control means.

Bs has been found that there is the effect of the Paserstoffhochleistunf'.sdüse Metz, which actually not acting on the downward moving screen 40 to substantially to the point P, and therefore not generated within itself ^the: maximum dewatering pressure to about to this area, whereupon the parabolic curve H = CU becomes important so that the inner fibrous body is subjected to the same pressure for the next 15 to 20 cm, during which the critical and sensitive web formation takes place, and essentially at the end of this web spacing the fiber body has assumed a substantially uniform composition or consistency over its entire height. This is not incompatible with a complete and final merging of the continuously forming or just formed webs on the two screens and grants a more or less final opportunity for one

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absolute integration of the fibers accumulated on each sieve into a single web that does not have any mean separation line that has already been recognized. DieVes "allows the screens 20 'and 40, continue with" continuous Teiher drainage of dazwischenliegendön train ^to: move to and including the au Gautschdruck 23-47 ·

Thus, in front of the area of the parabolic curve, the wires are brought together generally in accordance with the shape of the curve, above the parabolic curve, dewatering is effected at a constant fiber pressure, and after the parabolic curve the wires are moved together in order to to gradually effect water removal at elevated pressure. ^; There is no need for extreme caution when carrying out the drainage with increased pressure, because the strength of the web behind the area of the bar is strong enough ^; 'is to avoid damage at -significant, higher pressures EU ^; resist, and there is no real Yernetzung front of the area of the parabola wegea of substantially V "erdün ^now S ^ ^is to beschädigeia pulp or destroy. In the critical Be * ei oh <the augenblickliohen parable but the JPaservernetzung begins on ä © n Upper and lower sieves 40 and 20 on ^ ubaue.n,. and at the same time | .g speaks the vethä ^ * ^{n is} moderately low oil resistance (that is, the relatively larger water ratio) between these susceptible fiber networks on the upper and lower sieves 40 JU ₁ Dd SO on the change in pressure

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the seven and it is important for a short time to have an essentially constant pressure on such a network or overall system to maintain on each sieve until there is a substantial equalization among the consistencies.

The fiber consistency for newsprint (ie, as large as $ 0.5 up to even 1, OfS) is much greater than that of so-called tissue paper (ie, which is in the lower order of about 0.1 ^ to about 0.5 weight percent stands). Because of the extraordinarily high speed at which the water ¹ passes through the forming screen, it must be recognized that the comparable speed at which a web is built up on the forming screen is so slow in a tissue paper machine that the device in question here with a large gate part in the tissue paper machine, but can be used over a correspondingly larger distance D. In other words, on the tissue paper machine the consistency is so low that the rate of building a web or septum on the wire is slower than that which occurs on a machine which has both upper and lower active functions shark; ie. Sieves which are an inevitable dewatering ejureh "föküuin ^ etc., upterwofen. Hence the parabolic festalt'iXi? ®s. Lower sieve in a tissue paper machine can provide many, if not all, of the advantages of the parabolic upper design eir.es. upper sieve in a high consistency - (ie, Zeitun ^ s ^ · paper) machine .hanen, which because of its high 'consistency

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not only adapts the desired parabola along the upper sieve, but also the lower sieve in a corresponding matching one Curve drifts, though not to an identical curve to that of the true parabola. It should be mentioned that the initial area 20a of the lower wire 20 from the breast roll 22 to the disk 25 is otherwise unsupported, and the configuration the parabola above is such that there is neither a true chain line nor a true support bend in the lower sieve is obtained. Instead, the initial forces exerted on it are considerably higher than those applied later (as the sieve area 20a approaches the paddle 25), and this gives a parabolic curve which is final is not circular in shape. ■

Bs-it goes without saying that amendments will be made can without the meaning, scope and scope of the new thoughts of the to leave the present invention. So the box 30 can with the lower sieve instead of the upper sieve of the machine work together. The box does not need to have a working surface which is really parabolic, but it can do something of. this iOrm go off. Appropriate drainage can be effected by using a linear pressure element. The other tape or sieve opposite the formadben or pressing element 30 kanr ^ with * e-ißf m corresponding element instead of supported to seia; -ve3rsßhönnwe ^ cleB, provided a constant bridge will be as | s # en laser material during the initial Drainage exercised.

80 9 8 1

Claims (1)

St / p 4536 B / We 11/19/65 Claims Process for dewatering aqueous fibrous material or an aqueous laser material suspension for the production of paper, Cardboard or a similar fiber product on a machine, which has a circumferential carrier tape or contains a long and circumferential upper band, which, with moves the fourdrinier over part of its path and thus generally forms a converging passage through which the fibrous material passes through for dewatering, characterized in that a / i stationary pressure on one of the belts is exerted to urge the bands (20, 40) against one another and form a generally converging passage, whereby a substantially constant pressure is maintained on the pulp flow through the passage. Device for dewatering aqueous pulp or a Fiber suspension for the production of paper, cardboard or a similar fiber product for carrying out the method according to claim 1, characterized in that a. static Pressure element (30) acts on one of the bands (40), the bands (20, 40) pushes against each other and a generally converging one Forms passage, Device according to claim 2, characterized in that the 809813/0658 St / ρ 4536-Έ / fe 19.11 * 65. Part (51a, 52a, etc.) of the element (3Q) in contact with the a belt (40) in the direction of movement of the belts (20, 40) is curved,. . ,., ..... ....,., ...... · Device according to claim 3, characterized in that the Part (51a, 52a, etc.) is at least partially parabolic. Device according to one of Claims 2 - 4, characterized in that that for the other band (2-Q.) in the., area of the pressure element (30) no support is provided so that it can bend during operation. ... Device according to claim 5, characterized by means (22, 25,.: 26) to, divide one and. Changing the tension in the other Band (20), thereby changing the deflection. Device according to fine.m dj? A.ns | irüo _: hf? 3 ■ * ■ 6, in that the printer again (3Θ) on ή§ ^ cfbere Sgnd (40) etnii Fixture «ng | ia. @ H ^ A> §p? U @ h .. 4-, 5 _? f _? | ^ duiPh gekeniizeiehlipt, da.fi d ^ s other pfgy fyHg§Bfe ^ rid / bsi, JjaRgiigb (2Q) im weseKtli0, hen linear. In m9 $% ^ flftle | eRe.m Ζμ§1ί§η ^ Yfyl ^ ft and with dej? a ^ arabel §usaramj $$ s ^ lt Qde? p ^ rgllgl to her v Device nj ^ ch Aii§pruQh 8, thatJUTßfe.marked that the Carrier tape o ^ er! Fourdrinier wire (20) and fine breast roller (22) running around St / p 4536 B / We 11/19/65 where the radius passes through the point at which the roller and the wire part is perpendicular to the wire and coincides with or parallel to the ordinate with the parabolic part to him is ■ Device according to claim 9 »characterized, that the Point on the breast roll (22) at the beginning of the parabolic Part coincides. . . Device according to one of the preceding claims, characterized characterized in that the stationary element (30) is formed by or provided with a plurality of blades (51 to 60) is, whose spaced-apart edges (51a to 60a) are supported against the one band (40). . .. Device according to claim 11, characterized in that the blades (5-1. To -60) extend transversely over the belts (2p, 40) and diagonally with reference to never direction of movement of the Ribbons are arranged. Vo ^ ri ^ pAiliite, according to claim 12, characterized in that the Distance ^ ^. Shuffle the .Schauieln (b1 to 60) a little to the Hold the three removed from the pulp over the paddles Water or are in contact with it. 809813/0 658 St / p 4536 B / We 11/19/65 Device according to one of the preceding claims, characterized by means for maintaining a sub-atmospheric pressure behind the element (30) in order to ensure the dewatering of the To support the fiber material upwards. Device according to one of the preceding claims, - characterized characterized in that a film or disc (25) against the element other band (20) behind the stationary print / (30) printed thereby removing water through both belts (20, 40). Device according to one of claims 2 to 15, characterized in that that through the spout (10) the fiber nozzle is held so that it is on the carrier tape or wire (20) on or in the Is directed near the highest point of the breast roll (22), over which the fourdrinier runs, and on the converging one Passage is aligned. Apparatus according to claim 16, characterized in that the position of the pulp box (15) is adjustable. Device according to one of Claims 4 to 20, characterized in that the stationary element (30) is also adjustable in order to change the size and position of the converging passage ^ u. ■ ■■ '''■ ·· - ^: .- ■ · ■■ ■ ■ ■ · ■: ■■, ■■■■: - ■, ■