US3364103A - Apparatus for dewatering paper - Google Patents

Description

Jan. 16, 1968 E. KUSTERS I APPARATUS FOR DEWATERING PAPER 3 heets-Sheet 1 Filed Jan. 11, 1965 5 m 0 7 T 5 N Wm m A77 avg Jan. 16, 1968 E. KUSTERS 3,364,103

APPARATUS FOR DEWATERING PAPER 3 Sheets-Sheet 2 Filed Jan. 11, 1965 INVENTOR. fam/w Kusraw mgr M7 Y Arrow/5 Jan. 16, 1968 E. KUSTERS 9 3 APPARATUS FOR DEWATERING PAPER Filed Jan. 11 1965 3 Sheets-Sheet 3 INVENTQR. 00 420 /1 057515 ATTOP/VEFS United States Patent 3,364,193 APPARATUS FOR DEWATERING PAPER Eduard Kusters, Gladhacherstrasse 457, Krefeld, Germany Filed Jan. 11, 1965, Ser. No. 424,756 Claims priority, application Germany, Jan. 21, 1964, K 51,895 6 Claims. (Cl. 162-358) ABSTRACT OF THE DISCLOSURE A dewatering apparatus has a set of rotative press rolls with one or both of these rolls having circumferentially separated liquid passageways into which the water from the paper is pressed. These passageways are filled with water as they arrive at the nip formed by the set of rolls and are sealed when leaving the nip against loss of the additional Water pressed into these passageways. The latter are of course unsealed while at the nip so that the water from the paper can be pressed into them.

This invention relates to a process and apparatus for dewatering paper. The principles involved may be applied whenever it is desired to remove liquid mechanically from any material having the physical characteristics of paper and in which the liquid is absorbed initially.

Dewatering is done in the Wet end of a paper machine by press roll sets each including at least two rolls forming a nip through which the continuously traveling wet web passes. These rolls press towards each other and apply compressive pressure to the paper web, which as first formed necessarily has a high water content, the resulting compression of the paper mechanically squeezing the water from the paper web as it goes through the nip of the rolls.

The paper web is in the form of intertangled cellulosic fibers and acts like a sponge absorbing the water. When compressed the water is squeezed to the surfaces of the paper. When the compressive pressure is released, the paper re-expands and reabsorbs water on its surfaces.

The foregoing applies to the normal action which occurs during the dewatering of paper by the press rolls in the wet end of a paper machine. It has caused a longstanding problem in connection with obtaining dewatering to the degree theoretically possible, because water pressed to the surfaces of the paper web in the nip of the rolls is reabsorbed by the web when it expands after leaving the nip.

Current paper web traveling speeds prevent the use of press rolls having impervious surfaces which would press the water in a direction counter to the webs traveing direction and thus avoid the problem of reabsorption. The flow velocity of the water through the web would tear the web apart. Therefore, the rolls must have pervious surfaces as provided by the use of perforations or radial holes, or circumferentially grooved surfaces, so that the water is pressed from the web at right angles to the webs surfaces. From these surfaces the water is reabsorbed when the compression of the paper is released upon leaving the roll nip.

The prior art patent literature contains various proposals for improving the efiiciency of the dewatering effected mechanically by press rolls. Each of these proposals has encountered problems when placed in actual operation and the need for further improvement is apparent to everyone connected with the manufacture of paper.

With the foregoing in mind, the primary object of the present invention is to improve on the efficiency of de- 3,364,l3 Patented Jan. 16, 1968 watering paper by using press rolls, and to do this in a manner that is practical in the commercial sense.

The present invention makes use of the principles involved when using a pipette. Thus, if a pipette is complete ly filled with liquid so it is free from air or other gas and its upper end is sealed air-tightly, the liquid is held in the pipette in a hydraulically locked condition providing there is no air between the liquid and the sealed upper end. The lower open end of this filled and sealed pipette may be placed against a compressed absorbent material and when the compressing pressure is released the material can not suck the liquid from the lower end of the pipette. The

ipette may be swung so as to apply centrifugal force to the liquid without the liquid being thrown from the pipettes lower end, and the liquid can not fall gravitationally from this open endv Now, if a pipette completely filled with liquid but with its upper end open has its lower end pressed against a web absorbent material so as to compress the latter, the liquid squeezed from the material will be forced into the pipette While forcing from the pipettes upper end an equal amount of the liquid used to prefill the pipette. By then air-tightly and liquid-tightly sealing the upper end of the pipette, the pressure on the absorbent material may be released without reabsorption of the liquid from the pipettes lower end by the expanding absorbent material. Now the pipette may be removed from the material with the liquid pressed from the material by the compression hydraulically locked in the pipette.

To put the above principles to practical work in connection with dewatering paper, for example, perforated press rolls may be used which compress the paper web as the latter passes through the roll nip. If a felt or felts are used the action is on them as well. Although perforated rolls having radial holes are described in this explanation, because the radial holes correspond to a series of pipettes, the same principles may be applied when the effect of the holes is provided by porous arrangements or other provisions are made for the passage of the liquid into the rolls surfaces. The perforations or holes should be prefilled with liquid so that they are free from air as they approach the roll nip where the rolls apply compression to the web. In the nip the water pressed from the web displaces an equal amount of the liquid with which the perforations were prefilled.

Next, just as the perforations leave the nip and the web starts to re-expand so as to try to reabsorb water, the inner or exit ends of the perforations are sealed airtightly so as to put into effect the hydraulic lock principle explained above. Therefore, as the perforations leave the nip they hold the hydraulically locked liquid firmly against reabsorption by the expanding web and against being thrown out mechanically by the centrifugal force created by the rotation of the rolls. Once the perforations reach locations where the water they trapped can not reach the dewatered web, the sealing effect may be discontinued with the result that the water would then be centrifugally thrown or might gravitationally fall from the perforations.

The same efiect is obtained when felts are passed through the roll nip with the paper and, of course, also if only one felt is used, as previously indicated.

The above principle may be applied in the case of any surface that is pervious to the water pressed from the material being dewatered.

With the above introduction, reference is now made to the specific examples illustrated by the accompanying drawings, in which.

FIG. 1 is a front view of a set of press rolls incorporating the described principles and showing a paper Web being dewatered when using felts;

FIG. 2 is a vertical cross section taken on the line 22 in FIG. 1;

FIG. 3 is an enlarged view showing the two press rolls of the preceding two figures partly in cross section and partly in elevation;

FIG. 4 is a longitudinal section taken on the line 4-4 in FIG. 3;

FIG. 5 shows a press roll set incorporating a modification;

FIG. 6 is a longitudinal vertical section taken on the line 66 in FIG. 5;

FIG. 7 partly in cross section and partly in elevation shows a set of press rolls incorporating a second modification;

FIG. 8 is a view partly in elevation and partly in longitudinal section taken on the line S-8 in FIG. 7', and

FIG. 9 shows a set of press rolls as an end view with one roll in cross section, and illustrates a third modification.

Referring first to the example shown by FIGS. 1-4, in FIG. 1 is shown a press roll frame 1 journaling identical rolls 2 between which run felts 3 guided by rollers 4.

The paper web W comes in from the upper portion over one of the felts 3 and then goes downwardly through the nip formed between the two rolls 2 to be thereafter guided horizontally by a roller 5. The web W comes to the rolls 2 as a paper web impregnated or saturated with water which is to be removed to the greatest extent possible before the web W leaves the roll nip and goes around the roller 5. It is to be understood that the rolls 2 are pressed together by any conventional means (not shown) so that as the web W and the felts go through the nip of a the two rolls 2 they are compressed to a degree pressing or squeezing out a large amount of the water they contain.

To effect the working of the principles previously outlined, as shown by FIGS. 3 and 4, each of the rolls 2 is formed with a circumferential series of circumferentially interspaced and axially extending recesses 6 each containing a porous metal insert 7 extending for the working length of each roll. These inserts 7 may be made of any of the sintered metal porous materials such as are used for filtration and the like, but are preferably made from small steel or bronze balls which have been sintered together to provide a porous structure. By porous is meant that each of the inserts 7 may pass water or liquids relatively freely while at the same time providing a maze of very small passageways of a tortuous nature.

Each of the rolls 2 is in the form of a cylindrical shell providing axially extending passageways 3 along the bottom or inner ends of each of the recesses 6. The ends of these passageways are open so water may flow from them at the roll ends beyond the paper web and the felts. As to any one of the recesses 6 and axially extending passageways 8, there is no circumferential communication with respect to the adjacent elements of corresponding nature.

Because the web compression pressures or the necessary roll pressures may be relatively great, each of the inserts 7 is internally supported by a longitudinally perforated plate 9 which may be metal and strong and extends along the bottom of each insert 7, in each instance, between the insert and the passageway 8.

Futhermore, the reason the rolls 2 are in the form of cylindrical shells or sleeves or hollow rolls is because each roll 2 is made as disclosed by the Appenzeller Patent 2,908,964, dated Oct. 20, 1959. Thus, each cylindrical shell-like or sleeve roll 2 encircles an internal core or beam 10 having longitudinally extending seals 11 defining chambers or spaces on both sides of each beam or core 10 between it and the inside of the sleeves or shells in each instance. Passages 12 provide for the introduction of hydraulic pressure to the chambers which face each other, as do the two rolls, so that the roll nip is formed by surfaces under uniform hydraulic pressure which therefore apply, because the sleeve members are defiectableto some extent, uniform pressure to the web W throughout the width of the latter. The end seals required to close the hydraulic fluid chambers that face each other, are not shown because this is not considered necessary in view of the well-known commercially available roll constructions made under the previously mentioned Appenzeller patent. Any leakage beyond the seals 11 is removed through passages 13, the passages 12 and 13, of course, connecting with axially extending passages through which, as required, hydraulic fluid under pressure is introduced and leakage is removed.

One or both of the rolls 2 is powered to rotate so that the web W may pass through the nip formed by these rolls without being stressed so as to cause rupture. The roll pressure is great enough to compress the web W and drive the pressed or squeezed-out water through the porous inserts 7 into the axially extending passageways 8 which then empty at the ends of the rolls. When the' felts 3 are used they too are subject to the roll pressure and the water in them is correspondingly squeezed out so as to pass through the inserts 7.

Now to apply the principles of the present invention, the ends of each of the inserts 7 are sealed off air-tightly and liquid-tightly by sealing means 14 at each end. Further, all of the voids within each insert 7 and the passageways 8 are prefilled with water while approaching the nip of the two rolls, by means of water-flooding nozzles 15. This flooding or prefilling with water should leave no air of any substantial amount within the porous inserts 7 or the passageways 8 or the holes of the perforated backup plate Q. Therefore, as the assemblies approach the roll nip there is the analogy to the prefilled or fully flooded pipette.

In the event there is a tendency for the water, or other liquid used, to run axially through the passageways 8 so rapidly as to risk the formation of air voids, each of the rolls may be provided with stationary seals 16 which slidingly seal 05 the ends of the passageways 8 until just as each of the inserts begins to apply compressive pressure to the web W in the nip formed by the two rolls.

In the nip between the two rolls the web W is compressed and the water is driven laterally from it at right angles to the travel of the web so as to displace water through the open ends of the passageways 8 which extend axially with respect to the rolls in each instance.

Now, as each of the porous inserts 7 leave the nip the web W, of course, expands and momentarily remains in contact with the insert and tries to reabsorb the water squeezed from it and which is now within the interstices and little passageways formed by the sintered metal particles from which each insert 7 is formed.

Therefore, to obtain the hydraulic lock effect previously described, seals 17 are located stationarily so as to close the ends of the passageways 8 as the latters inserts 7 leave the roll nip so that the web W is trying to suck the water back from them. These end seals 17, like the seals 16, are stationan'ly mounted so that the ends of the passageways 8 slide past them to permit free rotation of the rolls but so as to obtain the effect of sealing fluid-tightly the ends of the passageways 8 while passing these seals.

It can be seen that by the use of these seals 17 the water is hydraulically locked in the completely waterfilled passageways 8, the holes of the plates 9 and within the little voids and passageways formed by the character of the sintered metal porous inserts 7. The water can not be sucked back into the web because of the hydraulic lock and because of the same reason it can not be thrown out by the action of centrifugal force so as to get back on the web W.

Reference has been made extensively to the web W because it is the material that must be dewatered. The felts 3 which ride between the web W and the rolls are necessary to provide paper having a good finish and the action of water removal with respect to the felts is the same as if the web W went through the roll nip without using the felts. In either instance, the web or webs passing through the nip of the rolls is an absorbent material that is compressible so that water can be squeezed from it and which then tends to re-expand and reabsorb the water when the compression is removed. If the paper is to have only a smooth surface on one side, only one felt may be used, all of this depending upon the paper-making technique involved. As the inserts 7 leave the zone where water thrown from them can contaminate the web W, which when felts are used extends to the zone where the felts separate from the paper web W, the passageways 8 may be unsealed as by leaving the circumferential ends of the seals 17. When this occurs, the hydraulic lock is broken and the water may be thrown out centrifugally or gravitationally.

One problem encountered when using perforated rolls for paper dewatering, as exemplified by the perforated rolls used under internal suction is the case of prior art attempts to achieve the results of the present invention, is that the perforated or porous surfaces of the rolls tend to become clogged with particles of the paper, which is, of course, a matting or felting of cellulosic fibers, so as to be rendered unserviceable.

In the case of the present invention, which avoids the use of suction with all of its attendant disadvantages, at a location remote from the roll nip, each roll is provided with a nozzle 18 which seals against the ends of passageways 8 and which is supplied through inlets 19 with water under relatively high pressure and at an adequate flow rate so as to reversely flush out each of the inserts 7 as its passes the zone where the nozzles 18 are located. The flushed water and any contamination contained by it may be caught by catch basins 20 from which the flushed-out material may be carried to a suitable waste location or for recovery of the cellulosic fibers representing the majority of the contamination.

It is to be understood that the seals 16, 17 and the water nozzles 18 are located at each of the ends of each of the rolls. This is necessary to achieve the functions required by this new process and apparatus of assuring that as the roll surfaces approach the roll nip their perforations or pervious surfaces or whatever arrangement is used for the radial passage of water therethrough, are completely filled with water. The sealing arrangement must terminate as required to provide for the escape longitudinally with respect to the rolls of the water squeezed from the web or the felts or both in the roll nip. Immediately thereafter, all of the water-conveying passageways of all kinds must be sealed fluid-tightly to provide for the hydraulic lock which traps the water solidly and firmly against escape either due to reabsorption by the reexpanding web or felts or because of centrifugal force or gravitationally. Once safely away from the web or felts, unsealing is permissible with the result that the water may then be thrown out centrifugally or gravitationally. Thereafter the flushing is desirable to clean out the water flow passageways and to free the roll surfaces from contamination which might clog the roll surfaces and prevent free water flow radially inwardly.

It is to be understood that the water prefilling should start to occur shortly before the seals 16 take effect so that there will be a water flow flushing out air that might be entrapped. It is desirable to remove all of the air so that the roll surface water passageways, of any kind used, approach the roll nip completely flooded with liquid.

The trouble with entrapped air is that air is elastic and, therefore, prevents the proper functioning of the desired hydraulic lock. For example, a pipette with air entrapped above the liquid column will permit escape of the liquid when centrifugal force is applied because the air is elastic and can not lock the entrapped column of water solidly as is effected when air is absent and there is nothing but the relatively imcompressible water locked solidly in the pipette. This principle should be followed in the case of the present invention.

In 'FIG. 5 there is a single dewatering roll shown at 21,

this being in the form of a seal having simple radial holes 2-2, counterpressure being provided by an imperforate roll 23 and the roll 22 being backed up or supported by a roll 24. Here, there is a direct analogy to the pipette in that the holes 22 generally correspond to the interior of a pipette. While approaching the roll nip, the holes 22 are prefilled solidly with water by a nozzle 25. When each hole is at the roll nip, its inside end is open so that water can escape due to the squeezing of water from the web W which displaces the prefilled water. If the roll 21 is filled with water to assure that the holes retain their prefilled condition, there should be provision for the escape of water as required to make room for water pressed from the web being dewatered. Immediately beyond the roll nip the inside ends of the holes 23 are sealed off by a sealing roll 26 which is journaled by a mounting 27 with the proper eccentricity relative to the roll 21 to accom' plish the just-stated purpose. This roll '21 is separately journaled by means (not shown). With the inside end of each hole 22 sealed fluid-tightly as it leaves the roll nip, the water within this hole is hydraulically locked. When the hole is safely away from the web W the eccentricity of the sealing roll 26 relative to the roll 21 unseals the inner end of the holes 22.

In the modification shown by FIGS. 5 and 6, no felts are used, but they could be used.

In the second modification shown by .FIGS. 7 and 8 each roll 28 has a circumferential series of axially extending bores 29 which open to one or both ends of the roll in each instance. These bores 29 connect with the surface of the roll 28 in each instance by way of two or more radially flaring holes or passageways 30. Prefilling nozzles '31 flood the holes 30 and the bores 29 with water during the approach to the roll nip. At each open end of the bores 29 check valves 32 are provided which permit outward flow but not inward fluid flow. These valves are of the spring-closed type and require some pressure to open, so they hold in the prefiiled water.

When this modification of FIGS. 7 and 8 is in operation the fully flooded holes 36 and passages 29 receive the water squeezed from the web in the nip of the rolls. While the water is being squeezed out it escapes through the check valves 32 but the moment there is any chance for a vacuum to be formed, as by reason of the expanding web trying to suck back the pressed water, the check valves 32 automatically close and produce the desired hydraulic lock. If the valves 32 are adequately effective during the rest of the rotation required to again reach the nozzles 31, the latter might not be needed because all of the passageways would remain permanently flooded with water, the amount squeezed out in the nip of the rolls from the web flowing out through the check valves in each instance.

Finally, in the third modification shown by FIG. 9, the roll 2 of the first example is again shown. The difference here is that the sealing roll 26 of the second example is used instead of the side seals 17. This example requires little discussion other than to point out one other way for obtaining the effect of the fundamental principles of operation of the present invention.

Furthermore, in all cases the pervious rolls can receive what is in effect circumferentially separted water or liquid columns. The pervious inserts of the first example form water columns extending for most of the lengths of the rolls, even though the columns are formed by the water or liquid throughout the interstices between the sintered metal particles. In the cases of the holes or perforations there is a multitude of separate water columns. Thus, always there is a passageway having an entrance facing the material from which the water or liquid is pressed, and an exit which can be sealed to trap and hydraulically lock the water or liquid in the column formed by the passageway.

It is to be understood that the principles of this invention may be applied to any material having the physical charcteristics of paper, such as the felts used during dewatering or other materials of a spongy nature, that is to say materials which are absorbent and can be compressed to squeeze out liquid in or absorbed by the material and which are elastic enough to spring back more or less after the compressing pressure is removed so as to tend to absorb or reabsorb liquid squeezed from the materials.

What is claimed is:

1. Apparatus for removing liquid from a traveling web of any material having the physical characteristics of paper and in which the liquid is absorbed, said apparatus including a set of rotative press rolls of which at least one has a pervious surface with circumferentially separated liquid passageways having entrances at said surface and exits spaced therefrom, said rolls forming a nip through which said web passes and having means for applying roll pressure at said nip to press the liquid from said web and through said entrances at said nip, means for sealing said passageways exits as they leave said nip and for unsealing them when they arrive at said nip, and means for maintaining said passageways filled with liquid as they arrive at said nip.

2. The apparatus of claim 1 in which said entrances are formed by sintered porous metal means.

3. The apparatus of claim 1 in which said passageways include parts extending axially with respect to said roll having the pervious surface and said exits are located at least at one end of this roll, said sealing means comprising stationary seals slidingly closing said exits and located to seal said exits as the connecting ones of said entrances leave said nip.

4. The appartus of claim 1 in which said roll having said pervious surface is in the form of a sleeve and said passageways extend therethrough and said exits are on the inside of this roll, said sealing means comprising a roller mounted eccentrically inside of this roll and hearing against its inner surface to seal said exits at locations when their connecting entrances are leaving said nip.

5. The apparatus of claim 1 in which said passageways include parts extending axially with respect to said roll having the pervious surface and said exits are located at least at one end of this roll, said sealing means comprising check valves at each of said exits and which open to outward pressure and close to inward pressure.

6. The apparatus of claim 1 and including at least one felt, said felt being mounted to go through said nip between said web and said roll having the pervious surface.

References Cited UNITED STATES PATENTS 3,098,788 7/1963 Hornbostel 162358 X DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

Images