FI66929B - OVER ANCHORING FOR THE FRAME STOPPING PAPER UNDER THE DOUBLE AVERAGE - Google Patents

Description

R5FH M «DKUm-UTUS PUBLICATION ,, Q0 JÄTä l J '' UTLÄCCNINGSSKIUPT 6 6 929 S c» 101 = 1934 ^ ^ ¢ 1) ItvJlu / hta3 D 21 F 1/00 SUOMI-FINLAND <*) ννμιμ ^ -ρκ'μμμμ ** 3206/73 (22) H »k> iwhpiM - AmelMliiffdH 16.10.73 (23) AHmpaivt — GIMaMadag 16.10.73 (41) Tuflut (afklMfcsi - WlvR offwtJIg 17.04.75 patents · j · advertiser controlled (44) Nihtivtiaip «« is μ kMtjwttaiMMi pm.

Patent · och ragicterttyrtlaan '' AiwNcm utl * d odi ntL * rlft «i ptbUcarad 31 .08.84 (32) (33) (31) ^ rr *« er «« κ> Μμ · «—e * t * rt prior * · * (71) International Paper Company, 220 East 42nd Street, New York, NY 10017, USA (72) George T. Ward, Greenwich, Connecticut, Charles A. Lee, Knoxville,

Tennessee, Warren R. Furbeck, Knoxville, Tennessee, John A. Means,

The present invention relates generally to methods and apparatus for making paper and the like. The present invention relates generally to methods and apparatus for making paper and the like using a double wire fabric and a method and apparatus for making paper using a double wire. . More specifically, the invention relates to methods of forming a web from suitable fibers and to devices for performing these methods. In particular, the invention relates to a method of making fibrous webs in which a fibrous suspension is passed through an inlet device to a web zone formed by a pair of endless apertured web elements which in the web zone run along converging paths and enters a series of dewatering boxes located on the side opposite the suspension of the wire in question.

The invention relates to an apparatus for carrying out a method for forming a fibrous web between converging webs in a webbing zone into which a fiber suspension is introduced from an inlet device and having a series of dewatering boxes on the back of each wire for receiving water from the suspension. inlet openings, each dewatering box being connected to a dewatering device by means of which each wire becomes essentially only the water which is compressed between the wires under the effect of pressure and to a dewatering control device.

In papermaking, an aqueous suspension of papermaking fibers, called pulp slurry, is delivered to the inlet portion of a paper machine that includes a chamber called a headbox. From the headbox, the pulp slurry flows through an opening, commonly referred to as a nozzle, to the web section, discharging into a running, endless, permeable web carrier, commonly referred to as a wire. Water flows out of the pulp slurry through the web carrier so that a web of papermaking fibers is formed on the carrier, which is then dried into paper.

Some irregularity in the finished paper, especially when running at high speeds, may be caused by irregularities in the free surface of the pulp slurry as the pulp slurry travels with the support to the web section where the paper web is formed. These irregularities travel through the entire machine and appear on the finished paper. Therefore, it has proved desirable to be able to control the free surface of the pulp slurry with a support. It is known to use a so-called double wire machine, in which the pulp slurry is directed from the headbox as a free jet into the space between the two endless web supports. However, the turbulence between the headbox and the web supports on the free surfaces of the jet allows a certain inconsistency in the surface of the pulp slurry as it settles between the web carriers, which in turn causes irregularity in the paper.

It is also known to use a pressure webbing machine in which the webbing support passes over a large opening in the headbox outlet and the pulp slurry is forced against the support under pressure. Water is drained from the pulp slurry in this pressure drilling range to form a web on the support. These systems have also included the use of a felt carrier which extends inside the headbox and settles on the web formed as it exits the headbox. Although such a device does not have any uncontrolled free surface of the pulp slurry on the forming support, the pulp slurry in the headbox is turbulent. This condition causes high shear forces that can interfere with the regular formation of the 3 66929 web, leading to non-uniformity.

The method according to the invention and the device for carrying it out are known mainly from the features set forth in claims 1 and 4.

According to the present invention, the pulp slurry is stabilized and the web is kept under control at all times. The pulp slurry has no free surface on the forming supports, and substantially all parts of the pulp slurry move uniformly at the same speed in the same direction. A stabilized pulp slurry moving uniformly at the same speed in the same direction is placed between two forming supports that trap it. The pulp slurry then passes out of the inlet section between the forming conveyors before substantial web formation occurs. For this purpose, the pulp slurry is accelerated in the inlet section by applying forces to it which tend to straighten the fibers, and then the pulp slurry is led along a straight channel for a relatively long distance. Through this, all large turbulences and velocity differences in the mass are attenuated and dissipated until the pulp slurry stabilizes and as a whole moves in substantially the same direction at substantially the same velocity, without turbulence, except for that naturally occurring in the current boundary layer adjacent to the surrounding conduit walls. The stabilized current is then passed between two forming supports which generally run in the same direction as the pulp slurry. The forming supports preferably pass through the end of the inlet portion, and the pulp slurry runs uniformly in the same direction as the forming supports, with the supports leaving the closed inlet portion and passing, between the pulp slurry, into the web section before substantial web formation occurs. The web is then formed in the web section as water exits through both formation supports.

In the web section, each web support passes over its own series of successive sealing boxes. The sealing boxes support the web carriers, causing them to travel along converging paths, and water is forced out of the pulp slurry through the web carriers into the seal boxes as the web carriers converge, forming a web for each web carrier. These webs merge into a single web as the web supports converge. The webs are preferably formed without sudden pressure shocks. For this purpose, according to one aspect of the invention, the inlet ends of successive sealing boxes are kept full of water, and the flow through the different sealing boxes is controlled separately. This controlled flow through the water-filled sealing boxes allows for relatively gentle web formation. In addition, the flow of water through the various sealing boxes can be adjusted so that the direction and velocity of the remaining pulp slurry remain substantially constant, which provides an additional opportunity to control web formation.

Accordingly, it is an object of the present invention to provide an improved apparatus for forming a paper web in which the pulp slurry is stabilized at the inlet portion of the machine and controlled at all times after it leaves the inlet portion until it forms a web. Other objects and advantages of the invention will become apparent from the following detailed description and the accompanying drawing, in which: Fig. 1 is a partially schematic partial sectional view showing a paper machine according to the present invention; Fig. 2 is an enlarged sectional view of the machine inlet of Fig. 1; of the seal shown in Figures 1 and 2, Fig. 1 is a partially schematic plan view showing the machine of Fig. 1 and the pulp slurry and recirculated water flow paths; Fig. 5 is an enlarged sectional view of the machine of Fig. 4 taken along line 5 ~ 5; enlarged sectional view of the machine of Fig. 5 taken along line 6-6, Fig. 7 is an enlarged sectional view of a modified form of the end of the inlet portion of Fig. 2, Fig. 8 is an enlarged sectional view of a modified form of inlet and web portions of the invention for layer Fig. 9 is an enlarged sectional view of another modified form of the inlet and web portions of the invention for making multilayer paper, and Fig. 10 is an enlarged sectional view of a third modification of the inlet and web portions of the invention .

Figure 1 shows a paper machine including an inlet section 10 according to the present invention. The inlet section 10 has an inlet passage 12 for the entry of papermaking fiber slurry and an outlet 14 for the exit of pulp slurry. The pulp slurry flows into the inlet passage 12 from a distribution system 15, which may be a conventional distribution system that delivers an aqueous suspension of papermaking fibers substantially evenly distributed across the width of the paper machine.

As shown in Figures 1 and 2, the pulp slurry may flow in the horizontal inlet portion somewhat above the area where the paper web is formed. The inlet portion 10 expands in the transition region 16, where the curved wall portions 18 and 20 reverse the flow, downstream of the narrow, elongate channel 22. The vanes in the transition section 16 divide the pulp slurry stream into smaller streams and direct these split streams through the bend directly into the narrow channel 22. By dividing the stream into smaller sections and controlling these sections, large-scale turbulence in the flow is avoided. The relatively long channel 22 consists of relatively straight wall portions 26 and 28 which form a channel 22 of substantially constant cross-section and direct the pulp slurry to travel in a certain direction, vertically downwards in the drawing, a relatively long distance sufficient for any vortices to be substantially attenuated.

Thus, when the machine is operating, the papermaking fiber slurry stream enters the inlet passage 12 substantially uniformly distributed over the width of the paper machine, and is directed to a tapered passage 22 in the inlet portion 16. The passage 22 has a significantly smaller cross section 22 than the transition portion 16. The acceleration brought about by this change in cross-section produces * forces which tend to straighten the fibers in the slurry. Acceleration, which changes the speed in the order of 2: 1, has been found to be satisfactory. The accelerated pulp slurry then flows down the relatively long channel 22. Since the cross-section of the channel 22 is substantially constant, the flow therein takes place at a constant velocity. The pulp slurry stabilizes as the current flows in the same direction at a constant rate for a relatively long time, so that as it approaches the outlet 14 the pulp slurry travels substantially uniform in both direction and velocity. So. all the fibers and suspension water travel downward at substantially the same rate. There is, of course, a boundary layer in the vicinity of the wall portions 26 and 28, which will be discussed below.

Two web carriers 30 and 32 are guided into the inlet section 10 from the upstream side of the outlet 14. The wires 30 and 32 enter the part 10 of the seals 34 and 36, which may be plastic sealing members 38 and 40. The wires 30 and 32 enter the inlet portion 10 of the end wall portions 42 and 44 over. As best seen in Figure 3, these end wall portions 42 and 44 are preferably both coated with a plastic coating 43 to alleviate the wear of the wires 30 and 32. The seal 34 passes between the sealing member 38 of the wire 30 and the plastic coating 43 on the end wall portion 42. The seal 36 passes the wire 32 between the plastic cover 43 on the end wall portion 44 and the sealing member 40. The wires 30 and 32 bend over the wall portions 42 and 44 as they enter the inlet portion 10, as this ensures a smooth transition as the wires enter the channel 22. Inside the inlet portion 10, the end wall portions 42 and 44 form the end portions of the walls of the channel 22. These end wall portions 42 and 44 are substantially impermeable to water, as are the straight wall portions 26 and 28, so that the entire stabilized pulp slurry stream can flow uniformly at the same speed as the wires 30 and 32 between them, and in the direction of wire movement as shown in the drawing.

The pulp slurry is trapped between the wires 30 and 32 and travels with them out of the inlet portion 10 into the web portion 46 before substantially forming the web. The web section has a plurality of sealing boxes 48 and 50 located on those sides of the wires 30 and 32 that are on opposite sides to the pulp slurry. The inlet of each sealing box 48, 50 has a permeable wire support 52, 54 which supports the wire 30 and 32, respectively, without substantially interfering with the flow into the sealing boxes 48 and 50. The wire supports 52 and 54 force the wires to converge as they pass down through the web portion 46. As the pulp slurry travels down to the web portion 46 between the wires 30 and 32, the suspension liquid is forced through the wires 30 and 32 and then to the sealing boxes 48, 50 of the wire supports 52, and so on.

54, and then through the sealing boxes themselves.

The wire supports 52 and 54 can take many forms. They may, as in the drawing, be simple, narrow rods extending across the wires 30 and 32, but they may also be complex in shape to provide strength and to minimize water interference through the wires 30 and 32. The machine direction members of the wire supports 52 and 54 are separated from the respective wire 30, 32 so as not to leave marks on the resulting paper. The supports 52 and 54 support the respective wire 30, 32 so that they have to travel along converging paths.

Both sets of sealing boxes 48, 50 are arranged in succession along the respective wire 30, 32 from the outlet 14 of the inlet portion 10 to the convergence point of the wire supports 52, 54, which forms the outlet 56 of the web portion 46.

When the suspension liquid is removed from the suspension, the suspended fibers deposit on both wires 30, 32 to form a web on each wire. The two webs merge into a single, combined web as the wires 30, 32 converge. Convergence of the wires between the wire supports 52 and 54 prevents the pulp slurry from exiting the outlet 56 of the web section 46, passing only the wires 30 and 32 and the integrated web between them out of the web section 46.

Both sets of sealing boxes 48 and 50 are preferably each attached to their own common support member, which is fixedly movable, so that the outlet 56 of the web portion 46 can be adjusted to different wires 30 and 32 and different web thicknesses.

After the web has left the web portion 46, additional water can be removed therefrom by conventional means, such as suction boxes 58, and then dried with a conventional or other dryer not shown.

The wire 30 is supported in its passage by rollers 60, 62, 64, 66, 68, 70 and 72 and by an end wall portion 42 and a wire support 52. The wire 32 is supported in its passage by rollers 72, 74, 76, 78 and 80 and an end wire portion 44 and a wire support 54. At least one roll in each group is a motor-driven drive roller on which both wires 30 and 32 are driven at the same line speed. Some of the rollers may be adjustable or run-loaded to maintain proper tension in both wires 30 and 32.

8 66929

The formed web is confined between the wires 30 and 32 to a web transfer roll 82, where the wire 32 moves away from the dough, leaving the web supported by the wire 30. With the web transfer suction roll 84, the web can be transferred to the drying felt 86.

The complete flow paths for the pulp slurry and recycled water are shown in Figures 4, 5 and 6. The pulp slurry is replenished in the conventional manner in the pulp sludge replenishment tank 100. For this purpose, water is supplied down line 102 from the wire tank 104, which is a reservoir of water. Fibers and other additives are supplied to the replenishment type from storage type 106 up to line 108. The pulp slurry is pumped from the pulp sludge replenishment type 100 down the line 110 by the mixing pump 112 down the lines 114 and 116 to the distribution system 15. The flow and pressure can be controlled by a valve 118 between the lines 114 and 116 and by adjusting the pump speed. Additional control is provided by a bypass line 120 with a bypass control valve 122. The bypass line returns a controlled portion of the pressure flow of the mixing pump 112 from line 114 to wire rod 104.

As described above, the distribution system 15 evenly distributes the pulp slurry over the width of the inlet line 12 of the inlet section 10. From the inlet section 10, the pulp slurry flows under pressure generated by the mixing pump 112 to the web section 46, where water is forced from the pulp slurry through the wires 30 and 32 to the sealing boxes 48, 50. As best seen in Figures 4, 5 and 6, the sealing boxes 48, 50 are closed to the atmosphere. Each sealing box 48, 50 has its own closed outlet line 124 leading from the respective sealing box to the wire cone 104, where it discharges below the normal water surface of the cone. Each outlet line 124 has its own flow meter 126 and control valve 128. Indicating pressure gauges may be located at various points in the flow path. Water discharged from the recycling system is replaced by adding fresh water to wire rod 104 down line 129 from a source not shown.

An important aspect of the invention is that the machine can be driven flooded. This knows that boxes 48 and 50 are kept full of water. This ensures that the inlets of each sealing box 48 and 50 are filled with water. Since the flow of pulp slurry from the mixing pump 112 to the web section 46 is blocked, no air enters the system until the web has formed and exited the web section 46 through this outlet 56. As can be seen from the drawing, the sealing boxes 48 and 50 are inclined upwards from their inlets so that air which may have entered the system, for example at start-up, or air dissolved in the pulp slurry into the mixing pump 112 or ground during grinding rises above the inlets of the sealing boxes 48 and 50. The drain lines 124 may exit the respective sealing boxes 48 and 50 at their highest point to ensure that the sealing boxes remain filled with water.

The sealing boxes 48 and 50 are closed chambers except for their open inlets, which are covered by wire supports 52 and 54, and for their outlet lines 124. They consist of impermeable top walls 134, bottom walls 136, back walls 38, end walls 140 (Figure 5) and common walls 142 separating adjacent sealing boxes. At the open inlet, the common walls 142 are attached to the wire supports 52 and 54 in such a way that the wire support members keep the adjacent sealing boxes substantially separate up to the respective wire 30 or 32, thus providing them with separate flow control.

The dewatering control is performed by control valves 128. These are particularly effective when the drain line 124 is full of water at least up to the control valves 128. Flow meters 126 can be used to monitor flow so that control valves 128 can be set to provide desired flow rates. In general, the pulp slurry should preferably flow through the web section 46 at a constant rate. Otherwise, turbulence will occur, which may break the web formation. For this purpose, the flow through successive sealing boxes 48, 50 is adjusted by the respective valves 128 so that it corresponds exactly to the reduction in cross-section caused by the convergence of the webs 30 and 32, ensuring the flow of the remaining pulp slurry directly through.

Although the convergence paths of the wires 30 and 32 in the web section 46 can be made multifaceted, in the preferred form of the invention they are symmetrical so that water drains equally from both sides of the pulp slurry. As can be seen from the drawing, according to the most preferred embodiment of the invention, the passageways are straight over the entire web portion 46, so that the web can be formed uniformly along the passageway. However, it is also within the scope of the invention that the passageways are designed so that water is removed at different speeds, for example so that the web in its delicate initial part is formed more slowly and gently than in the rest of the part.

The dewatering according to the invention, in particular the controlled dewatering of the pulp slurry from liquid to liquid, is less violent than the dewatering in conventional flat wire machines using register rollers, discharge strips and suction boxes in the web area. When water is removed from the pulp slurry without sudden pressure shocks caused by shaking and pulse in conventional machines, web formation is better controlled and zero pulp is better retained in the web without rinsing through the wire jacket. According to one aspect of the invention, the resulting web is spared such pressure shocks until its consistency is at least about 12%. This results in a cheaper product without compromising on quality. This also reduces the zero-mass rotation to zero-water and reduces the wastewater discharge problem.

As mentioned above, the convergence of the wires 30 and 32 closes the pulp slurry out of the outlet 56 of the web section 46. This ensures that water is removed from the pulp slurry before the formed web leaves the web section. After convergence, the wires 30 and 32, the web formed between them, exit the web section 46. Immediately after the points where the wires 30 and 32 leave the wire support 52 and the like. 54, the inlets of the sealing boxes 48 and 50 are closed by sealing members 130 and 132 to prevent water from flowing back out of the sealing boxes behind the wires 30 and 32.

An important advantage of the liquid-to-liquid dewatering system according to the invention is that the amount of entrained air and the resulting foam, which is difficult to handle, is reduced.

This also prevents the oxidation of some additives that may be present in the pulp slurry. This is further facilitated by the discharge of the sealing boxes 48 and 50 below the water surface into the wire rod 104.

Various modifications can be made to the structure without departing from the scope of the invention. For example, the wall portions 26 and 28 have been described above as substantially impermeable, except, of course, in that they pass through the wires 30 and 32, but these also enter through the seals 34 and 36, respectively. On the other hand, it is also within the scope of the present invention to remove some flowing pulp slurry before it completely exits the inlet section 10. More specifically, it is sometimes advantageous to remove at least part of the pulp slurry boundary layer adjacent to the wall portions 26 and 28, especially in so-called plug flow conditions. may be formed for reasons well known in the art.

As is known, under plug flow conditions, the pulp slurry moves as a substantially uniform plug, except at flow interfaces, adjacent to the boundary walls. These boundary layers are 11,669,929 fiber-free, and it is sometimes advantageous to remove this fiber-free water to maintain control of the flowing suspension. This phenomenon is explained in an article entitled "Rheological Models and Laminar Shear Flow of Fiber Suspensions," Bugliarello and Daily, The TAPPI Journal of the Technical Association of The Pulp and Paper Industry, December 1961, vol. 44, No. 12, p. 881-895. The article discusses the presence of fiber-free water and the effect of turbulence in fiber-free water on the rupture of the plug flow space.

In order to alleviate the problems caused by the boundary layer flow, this layer can be either partially or completely removed with the modified structure according to Fig. 7. As can be seen from this figure, the walls 26 and 28 are made slightly permeable to water just upstream of the wires 30 and 32, and the boundary layers flow in the wall portions 26 and resp. 28 holes 180 and resp. 190 through collection to boxes 192 and 194, from which water can be drained in the same manner as water accumulated in sealing boxes 48 and 50.

The stabilized center portion of the pulp slurry then settles between the wires 30 and 32 and extends therefrom from the inlet portion 10 without substantially any web formation on the wires 30 and 32.

The amount of pulp slurry removed as a boundary layer is negligible compared to the amount of medium flow.

One of the advantages achieved by the adjustment according to the present invention is the possibility of producing paper which is almost equally strong in both directions. In a conventional paper machine, the fibers are oriented primarily in the machine direction, giving the resulting paper significantly better strength in the machine direction. According to the present invention, it is possible to make the machine direction and transverse strength almost equal by giving the wires 30 and 32 substantially the same speed as the pulp slurry. On the other hand, according to the invention, the ratio of the strength in the machine rising direction and the transverse direction can be adjusted by adjusting the speed of the wires compared to the speed of the pulp slurry.

The present invention is particularly suitable for the production of multilayer paper. Modifications of the invention for making multilayer paper are shown in Figures 8, 9 and 10.

Figure 8 shows a modification for the production of two-ply paper. A second pulp slurry stream is supplied to the inlet section 10 along the second feed passage 196, and the two streams are held apart by a septum 198 which may extend substantially to the web section 46 to ensure that the webs form substantially separately from the respective pulp slurry wires 30 and 32. parallel and ♦ * '12 66929 thus together with the wall parts 26 and 28 form two parts of the channel 22, each of which stabilizes its own pulp slurry flow. After the end edge of the septum 196, the webs are joined and processed as above. The two wires may consist of different fibers or fibers of different colors to produce paper of different quality. It is also within the scope of the invention to use different types of fibers, such as wood fibers and man-made fibers.

Figure 9 shows a modification for the production of three-ply paper with the outer layers of the same pulp slurry. In this case, a second pulp slurry stream is fed to the inlet section 10 up to the second inlet line 200. A second pulp slurry stream is passed between the two portions of the first stream and separated from them by partitions 202 and 204 which are parallel to the wall portions 26 and 28 and stabilize the respective pulp deposits. In this form of the invention, the second pulp slurry, as in the preferred embodiment of Fig. 9, can be effectively introduced into the web section 46 only after considerably water has been removed from the first pulp slurry by the wires 30 and the like. 32 so that considerable webs of fibers from the first pulp slurry have formed on the wires before any water is removed from the second pulp slurry.

Figure 10 shows a further modified form of the invention, which is particularly suitable for the production of filler-containing paper. In many papers, it is advantageous to use additives such as clay, which gives the paper greater opacity. The filler is often in the form of relatively fine particles, many of which are washed out of the web in conventional flat wire paper machines. In the embodiment of the invention of Figure 10, the filler particle slurry is introduced into the web portion 46 only after the paper fiber webs are at least partially formed on the wires 30 and 32, with the webs retaining more filler particles in the paper than when the filler is mixed into the paper fiber slurry. As in the embodiment of Figure 9, the second slurry is fed into the feed tube 206 and therefrom between the walls 208 and 210 to the web portion 46 between the wires 30 and 32, at a point somewhat downstream of the web formation start point.

The present invention can be applied to the formation of webs from various materials. It should therefore be noted that the term "paper" as used herein is not limited to webs made from any particular fibers. In addition to the relatively short wood fibers commonly used in the manufacture of paper, according to the invention, relatively long synthetic fibers can be used to form the web or its various layers. When long fibers are used, they can be fed under pressure after the mixing pump 112 to avoid the difficulty of punching long fibers.

Claims (4)

A method of producing fiber webs, wherein a fiber suspension is inserted through an inlet device (10, 12, 14) to one. web forming zone (46) formed by a pair of endless orifice web forming elements (30, 32) which in the forming zone run in converging webs, the fiber web being formed in the forming zone by dewatering, which water is extruded out of the suspension under pressure without suction and received in a series of dewatering slides (48, 50) located adjacent to the respective wires, in relation to the opposite side of the suspension, characterized in that the water level in each dewatering slab is poured at a level which is above the level of introduction of water into respective slides. wrap so that both sides of the wires (30, 32) are covered with liquid in the forming zone. Process according to claim 1, characterized in that during the forming the fiber web is protected against sudden pressure shocks until the consistency is at least about 12%. Method according to Claim 1, characterized in that the convergence of the wires (30, 32) substantially prevents the suspension from flowing out of the forming zone (46) and that each wire is water-covered on both sides until the consistency of its web is at least about 12% but not thereafter. . Apparatus for carrying out the method according to claim 1 for forming a fibrous web between converging webs (30, 32) in a web forming zone (46) into which the fiber suspension is introduced through an inlet device (10, 12, 14), in which the device is provided. a series of dewatering slides (48, 50) at the rear of each wire for receiving water from the suspension, which dewatering slides (48, 50) include supports (52, 54) for controlling the wires in converging paths in the forming zone and facing the wires, each dewatering drawer is connected to a drainage device (124) for receiving from each wire substantially only the water which is compressed between the wires by pressure, and to a control device (128) for the removal of water, characterized in that each dewatering drawer (48, 50) is arranged to containing water up to a level which is above the level of introduction of water into respective leaks from respective wires (30, 32), by means of the dewatering device (124 ) the hearing device (128).