US3091563A

US3091563A - Method of and apparatus for quickly and safely withdrawing water from fiber suspensions

Info

Publication number: US3091563A
Application number: US832657A
Authority: US
Inventors: Meyer Heribert
Original assignee: JM Voith GmbH
Current assignee: JM Voith GmbH
Priority date: 1958-08-14
Filing date: 1959-08-10
Publication date: 1963-05-28
Anticipated expiration: 1980-05-28

Description

May 28, 1963 H. MEYER METHOD OF AND APPARATUS FOR QUTOKLY AND SAFELY wTTHDRAwING WATER FROM FIBER sUsPENsIONs FlledAug 1o, 1959 2 Sheets-Sheet 1 W monononvm INVENTOR. r/,erf e/Veh BY May 28, 1963 H. MEYER :091,563

METHOD OF AND APPARATUS FOR QUICKLY AND SAFELYl WITHDRAWING WATER FROM FIBER sUsPENsIoNs Flled Aug l0, 1959 2 Sheets-Sheet 2 United States Patent On ice 3&91563' Patented May 28, 1963 3,091,563 METHGD OF AND APPARATUS FR QUICKLY AND SAFELY WITHDRAWHNG WATER FROM FIBER SUSPENSIONS Heribert Meyer, Chillicothe, Ohio, assignor to I. M. Voth G.m.b.H., Heidenheim (Brenz), Germany Filed Aug. 10, 1959, Ser. No. 832,657 Claims priority, application Germany Aug. 14, 1958 16 Claims. (Cl. 162-217) The present invention relates to a method and apparatus for withdrawing water in a quick and iiber-saving manner from iber suspensions, from which paper sheets, carton sheets or the like are made, by means of a breast roll designed as suction roll.

It is well-known that generally in a paper making machine, the water is withdrawn from the paper sheets in the wire portion which latter consists primarily of a breast roll, table rolls, suction boxes and a wire suction roll. In view of the relatively great number of these elements required for a satisfactory Withdrawal of the water, such wire portions are rather long, particularly if they are designed for high machine speeds.

Therefore, in order to speed up Ithe water withdrawal operation, in other words, in order to increase the speciic water withdrawal and thereby to reduce the wire portion, it has been suggested to design the breast roll as suction roll and to Ithis end to provide a suction box in the roll. Such suction box was designed either with stationary walls or with walls adjustable along the circumference of the suction roll. For purposes of obtaining a quick withdrawal of the water, a low or sub-atmospheric pressure is always maintained during the operation in the suction box which low pressure is produced by a suction pump connected to one or both sides of the suction roll. This pump simultaneously withdraws the waste water passing from the suspension through the wire into the box. The withdrawal of water by means of such breast rolls is, however, rather limited, While these relatively narrow limits are caused by the structurally possible design of the lateral discharge conduit, especially the cross section thereof. Therefore, the heretofore known breast-suction rolls are hardly able to conduct away the great quantities of water which have to be discharged at the start of the water withdrawal operation. Furthermore, the lateral discharge of the waste waters or the lateral arrangement of the low pressure producers may bring about pressure differences over the width of the sheet as a result of which a regular sheet formation will ensue.

A particular disadvantage of breast-suction rolls of the type involved consists in that the suction box is-charac terized by a substantially constant pressure course in the direction of movement of the sheet being formed. As a result thereof, the suspension, when reaching the suction zone, is instantly subjected to a great pressure diiference so that the suspension is practically slammed against the wire with the result that a great portion of the finest iibers contained in the suspension drops through the meshes of the wire. Therefore, in order to avoid such sudden instantaneous pressure difference, it has been suggested to arrange a plurality of suction boxes, partially with different pressures, one behind the other in the direction of rotation of the suction roll in order in this way to obtain a stepwise pressure course. Such an arrangement, however, requires specially designed pumps which complicate the entire apparatus.

It has furthermore been suggested to combine a breast roll-not designed as suction roll-of a paper making machine with a further imperforate roll which rests upon the paper sheet and is offset in the direction of movement of said sheet with regard to the breast roll in such a way that a converging passage will be formed between the two rolls and a continuous pressure increase will form in said passage. The suspension above the wire will thus pass into a chamber with decreasing volume while the water contained in the suspension will flow oli through the meshes of the wire, and a sheet will be formed on the wire. One of the drawbacks of this type of apparatus consists in that the wire is freely suspended over a larger distance over which it sags so that the wire is rather stressed over said distance. Another disadvantage of this apparatus consists in that, regardless of the direction of rotation of the upper roll, a sub-atmospheric pressure will form behind the point of contact of the upper roll with the sheet surface, which sub-atmospheric pressure is able to lift off and throw off at least a portion of the formed sheet.

It is, therefore, an object of the present invention to provide a method of and device for withdrawing water from fiber suspensions such as paper pulp or paper stock in a quick and fiber-saving manner, which will overcome the above mentioned drawbacks.

lIt is another object of this invention to provide a method of and apparatus for a quick and safe withdrawal of water from iiber suspensions, which will assure a uniform and careful sheet formation and a good felting of the ibers.

It is still another object of this invention to provide a method and apparatus of the type set forth in the preceding paragraphs, which will bring about an increased withdrawal of water from the suspension so that a number of the heretofore required table rolls and in some instances also suction boxes will be saved.

A further object of this invention consists in the provision of a method and apparatus as outlined above, which will greatly save the very iine stock material contained in the suspension.

Still another object of this invention consists in the provision of a method of and device for withdrawing water from iiber suspensions for making paper sheets, carton sheets and the like, which will result in the formation of a low or sub-atmospheric pressure which will steadily change in the direction of movement of the sheet being formed while the pressure will be constant over the width of said sheet.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. l is a section of a diagrammatic side view of an apparatus according to the present invention.

FIG. 2 represents a portion of a longitudinal section through the breast-suction roll of FIG. 1 but on a smaller scale than that of the latter.

FIG. 3 shows a special `design for the drive of the eccentric roll.

FIG. 4 illustrates `similar to FIG. 2 illustrates simil-ar to FIG. 2 `a portion of a longitudinal section of a modified breast-suction roll which is equipped with :an adjusting device for the eccentric roll.

FIG. 5 is a View of the arrangement shown in FIG. l as seen in the `direction of the arrow A, with the head box or flow box and certain containers below said suction roll omitted.

FIG. 6 illustrates a wire arrangement over the said suction roll according to the present invention, said suction roll being designed as wire suction roll.

General Arrangement In order to overcome the above mentioned drawbacks and to obtain a quick and safe withdrawal of 'water from a iiber suspension with a suction roll preferably employed as breast roll or wire suction roll, according to Ithe present invention the low pressure or sub-atmospheric pressure is produced in such a way that it will have a continuous course along an axis parallel surface line or generatrix of the roll and that the said low pressure or sub-atmospheric pressure will change in the direction of rotation of the roll along a continuous curve the initial portion of which preferably has the shape of a sine curve. This combination according to the present invention of a low pressure which is constant over the width of the sheet or web with the feature that the `low pressure varies in the direction of movement of the sheet according to a steady curve, brings about above all a uniform and careful -sheet formation as well las a good -felting of the fibers. The uniform lsheet 4formation is obtained by the uniform local pressure distribution over the width of the sheet which pressure distribution maintains everywhere the same hydrodynamic conditions and thus `assures a locally uniformly high withdrawal of water. Due to the fact that the low pressure varies in the direction of movement of the sheet along a steady curve land not by steps, also .the withdrawal of water from the fiber suspension and the formed sheet will be steady so that the fibers will have the possibility to deposit relatively -slowly on the wire or upon the -already formed sheet and `well to felt with each other after they have been deposited. By distributing the deposit over .a longer distance, it is Ialso possible to withdraw a greater yquantity of water from the suspension so that quite a number of the table rolls normally following the breast roll, `and possi-bly also suction boxes will be saved. The very fine stock in the suspension will, with the water withdrawal laccording to the invention due to the relatively slowly effected deposit of the fibers, be maintained to a great extent even with an ample quantity of water being withdrawn.

in conformity with a speci-al design of the apparatus according to the invention, the low pressure or sub-atmospheric pressure is produced in the suction roll itself. In this way, it -is not necessary to produce a low pressure or sub-atmospheric pressure by means of a suction pump placed outside the suction roll. Consequently, also lateral pipe connections lfrom the pump to the suction rolls as they have heretofore been required will not be necessary.

According to a further development of the invention, a suction roll in form of a hollow cylinder provided with small bores distributed over the entire circumference of said -cylinder is employed in which, for purposes of producing sub-atmospheric or low pressure, there is rotatably journalled an eccentrically arranged roll likewise designed as hollow but substantially imperforate cylinder. This llast mentioned hollow cylinder -is so arranged that its surface contacts the inner surface of the suction lroll mantle and, more specifically, that side thereof which faces the draining zone.

In conformity with a further development yof the invention, for purposes of adjusting the maximum low pressure or sub-'atmospheric pressure with a similar occurs of the pressure in the direction of movement of the sheet, the eccentric roll may be driven at an angular velocity which deviates from that of the suction roll and is adjustable. Advantageously, to this end, the eccentric roll is driven by a speed variable motor.

According to the present invention, the outer periphery of the suction roll and the end faces thereof are to a great extent covered by la cover arranged .at a slight distance from the surface of the suction roll with the exception of the web or sheet forming zone, the two openings at the end faces for passing the bearing studs of the eccentric roll therethrough, and of the opening for the discharge of the waste water -and possibly also with the exception of the opening for the passage of the wire into the space between the suction roll vand said cover. The purpose of said cover consists in preventing the air from entering the suction roll, especially behind the sheet forming zone. The `said cover furthermore has the -task to assure that the Waste water will Ibe able to escape only through slots provided in the high pressure range of the suction roll along two axis parallel cylinder lines. A further purpose of said cover consists in assuring that the bores of the suction roll will prior to the entry into the sheet forming zone be filled with liquid as far as possible.

The discharge of the waste water is effected by slots in the cover while, in conformity with the location of the wire and in conformity with the Wire drive, `at least one slot is provided within the loop of the wire when the looping angle is small and the wire is driven through the intervention of a wire deviating roll. When a relatively great looping angle is involved and the wire is driven through the intervention of the suction roll, at least one discharge slot is provided in the cover portion within the loop of the wire and at least another discharge slot is arranged in said cover outside the loop of the wire. In the last mentioned instance, the slots are so designed tha-t the major portion of the waste water is passed through the slot arranged in the cover portion inside the loop of the wire, whereas the remaining portion of the waste water is discharged through the slot outside the loop of the wire. The width of the sl'ots is adjustable for controlling the high pressure in the lower part of the crescent-shaped chamber.

Structural Arrangement Referring now to the drawings in detail and FIGS. 1 and 2 thereof in particular, the apparatus shown therein com-prises la head box or flow box 1 containing the ber suspension or stock from which the respective paper sheet, carton sheet or thelike is to be formed. As will be evident from FIG. '1, the stock or ber suspension passes yfrom head box 1 through a discharge nozzle 3 upon a wire 4. The end wall 2 of the head box 1 and the discharge nozzle 3 may in a manner known per se (not shown in the drawings) be displaced and adjusted. As will be evident from FIG. 1, wire 4 is passed over a great looping angle partially over the suction roll 5 which latter is provided over its entire circumference with small bores 11, said suction roll 5 being designed as a hollow cylinder. This .hollow cylinder 'has its ends or sides closed by means of end walls 12 as will be evident from FIG. 2. Suction-roll S is, over the major portion of its circumference namely seen from point 7 in the direction of rotation 13 up to point 10 with short interruptions at 8 and 9, sealed against the entrance of air. This sealing is effected by means of -a multi-part mantle or housing 20.

Within suction roll 5 and eccentrically with regard thereto there is provided an eccentric roll 6 which is rotatably journalled in suction roll 5. The eccentric roll 6 is provided with a smooth and closed surface and is mounted within the suction roll 5 in such .a way that eccentric roll 6 contacts suction roll 5 with liquid friction at that side which faces the head box 1. In this way, there will be formed a crescent-shaped chamber `15 within the suction roll 5.

When suction roll 5 rotates, also eccentric roll 6 will rotate in the same direction 14 as suction roll 5 either with the same angular velocity as suction roll S or with a different angular velocity. When rotating the eccentric roll 6, corresponding to the same hydraulic laws governing the table roll ow, a low pressure or sub-atmospheric pressure will subsist in the crescent-shaped chamber v15 which pressure will change continually in the direction of movement 21 of the sheet being formed. The said low pressure or sub-atmospheric pressure will at point 10 correspond substantially to the pressure of the flowin the nozzle 3 and will reach atmospheric pressure, following a maximum low or sub-atmospheric pressure at about point 7. Between point 7 and point 8, a gradual increase in pressure in the direction of rotation 113 of suction roll 5 will occur as -a result of which the major portion of the water will be discharged at 8 and the minor portion of the water twill be discharged at 9. The water will flow into the containers 16, `17 from where it is discharged throughconduits 18 and 19. The discharge opening l9 serves as water seal against the entrance of air into the suction roll 5 between point-

s

9 and 10.

As will ybe evident from FIG. 5, the

discharge openings

8 and 9 are designed as slots extending over the entire length of the cover 20. The discharge width of said slots may be adjusted by means of adjustable slides 22 and 23 (see FIG. 1).

As will be clear from FIG. 2, suction roll 5 is, by means of anti-friction bearings 29, rotatably journalled in hollow studs 28 protruding yfrom the end face 12 `of the suction roll. Rotatably supported by anti-friction bearings 29 are hollow studs y3K1 journalled in frame 30. The drive of suction roll 5 is effected by a motor 24 through the intervention of a

gear transmission

25, 26. Gear is connected to a shaft 27 of a motor 24, whereas gear 26 is connected to one 4of the hollow studs 28.

The eccentric roll 6 `arranged in hollow suction roll 5 is rotatably supported by frame 30 through the intervention of hollow studs 31 -and extensions 32 thereof which latter have journalled therein studs 33` connected to the end walls 38 of eccentric roll 6. Eccentric roll 6 is driven by means of a variable speed motor 34 through la belt drive 3S, shaft 36,

gear

3,7 and ya gear ring 39 which is provided with inner teeth and is connected to the 'adjacent end wal-l 38 of the eccentric roll 6.

F IG. 3 illustrates a drive of the eccentric roll 6 by means of a change gear transmission 40 and a constant speed moto-r 41.

In order to adjust the suction zone in the direction of movement of the sheet being formed, in conformity with a further development of the present invention, the imperforate surfaced eccentric roll 6 placed within the suction roll 5 is movable bodily -about the central axis of the suction roll 5 (FIG. 4). To this end, the bearing stud 3.1 is rotatably journalled in frame 30 and can be rotated through the -intervention `of a worm wheel drive 43V in conformity with the desired adjustment of the suction zone. Such an arrangement makes it possible to adapt the suction zone to the head box the flow conditions of which at the entry into the sheet forming zone can never be fully judged in advance.

With the heretofore described embodiments of an apparatus according to the present invention, the wire 4 passes over suction roll 5 over la large looping angle, and the drive of wire 4 is effected by means of the suction roll y5 itself. As will be evident from FIG. l, the discharge slot 8 of cover 20 for the discharge of the major portion of the waste water is arranged within the l-oop of wire 4, whereas slot 9 for the remainder to be discharged is arranged outside the loop of wire `4.

In contrast thereto, with the arrangement of lFIG. 6, wire l4 passes over a short peripheral portion of a suction roll 50, i.e. has ia smal-l looping angle, and the drive of the wire is effected by means of a wire return roll 44. The discharge of the waste water in this embodiment is effected through one slot 45 only which is arranged in the cover 46 within `the loop of wire 4.

While .the eccentrically supported inner roll 6 has been illustrated and described as imperforate, it will be understood that it is not absolutely essential for this roll to be compeltely without perforations. A completely imperfor-ate roll in this location produces the best results, but it will be apparent that a ro-ll with a few perforations therein, or a yroll with many extremely small perforations, would effect substantially the same results .although with somewhat reduced efliciency. The reduced eiciency would come about because the perforated roll with the inner chamber thereof would fill with liquid and at least a portion would pass therefrom and interfere with the reduction of pressure in the crescent -shaped chamber zone between the inner and outer rolls.

It will yaccordingly be understood that where the term substantially imperforate is employed in the claims, this i-s intended to mean a -roll having -no perforati-ons or perforations in a small enough number or of such small size that the intended effect of the present invention is realized, namely, the controlled pressure variation about the crescent `shaped region between the rolls.

It is, tof course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawings but also comprises any modifications within the scope of the appended claims. Thus, the employment of breast rolls as suction rolls i-n conformity with the preceding description of the present invention with self-producing low pressure or sub-atmospheric pressure is correspondingly also possible for suction couch rolls or other suction rolls. The invention is also I'applicable to cylinder paper machines.

What I claim is:

l. In the method tof withdrawing large quantities of liquid from a dilute suspension, especially fiber suspension, for producing a fiber web in a web-forming zone of a foraminous or perforated hollow cylinder, the steps of: delivering the suspension to said web-forming zone on the outside of the cylinder, -creating a reduced pressure on the inside of said cylinder in said web-forming zone, varying said reduced pressure from .a minimum to a maximum continuously and steadily and in the direction of movement of the web being formed while maintaining said reduced pressure constant at any line extending across the width of said web being formed, exerting said reduced pressure on said `suspension over said web-forming zone to withdraw liquid from the `suspension into said cylinder, and discharging the drained-off liquid from the inside of said cylinder through the perforations thereof :and across the entire width thereof.

2. I-n the method of withdrawing large quantities of liquid from ya dilute suspension, especially fiber suspension, for producing a fiber web in `a web-forming zone by means of a perforated suction roll and a wire passing over said `suction roll in close contact therewith along at least said web-forming zone, the steps of: delivering the suspenion to the unit in the weh-forming zone, creating `a reduced pressure on the inside of said suction roll in the web-forming zone, varying said reduced pressure from zero to a maximum continuously and `steadily and in the tdirection of movement of the web being formed while maintaining said reduced pressure constant at any line extending across the width of said web being formed, exerting said reduced pressure radially through said roll and wire on said suspension lover said web-forming zone to withdraw liquid .from the suspension into said suction roll, and discharging the drained-off liquid from the inside of ysaid suction roll through the perforatio-ns thereof and `across the entire width thereof.

3. In `a web forming machine, especially paper web forming machine: a rotatable perforated Jhollow suction r-oll, a draining zone having a relatively short portion thereof arranged adjacent said suction roll, `and a substantially imperforate eccentric roll rotatably located within said suction roll and eccentrically arranged with regard thereto and extending axially over -the entire length of the perforated portion of said suction roll, said eccentric roll having a rotating peripheral surface portion in line contact with the inner surface of said suction roll at a portion thereof which is adjacent the beginning point of said relatively short portion of said draining zone while the respective remaining peripheral router surface of said eccentric roll and the respective inner suction roll surface facing said respective remaining peripheral 4outer surface of said eccentric roll confine with each other a crescent-shaped gap.

4. A web forming machine according to claim 3, in which said eccentric roll forms a hollow cylinder.

5. A web forming machine `accor-ding to claim 3, which includes means for varying the angular velocity of said eccentric roll.

6. In a web forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, `a draining zone having a lrelatively short portion thereof arranged adjacent said suction roll, a substantially imperforate eccentric roll rotatably located within said suction roll and eccentrically larranged with regard `thereto and extending axially over the entire length of `the perforated portion of said suction roll, sai-d eccentric Aroll having a rotating peripheral surface portion in line `contact with the inner surface of said suction roll at a ingly connected to said eccentric roll for driving the same at variable speed.

7. In a web-forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, a draining Zone having a relatively short portion thereof arranged adjacent said suction roll, a substantially imperforate eccentric roll rotatably located Within said suction roll and eccent-r-ically arranged with regard thereto and extending axially over the entire length of the perforated portion of said suction roll, Said eccentric roll having a rotating peripheral surface portion in line contact with the inner surface of said suction roll at -a portion thereof which is adjacent the starting point of Isaid relatively short portion of said draining zone while the respective remaining peripheral outer surface of said eccentric roll and the respective inner suction roll surface facing said respective remaining peripheral outer surface of said eccentric roll confine with each other a crescentshaped gap, and means operatively connected to said eccentric roll for adjusting the `same in a complete circle around the central axis of said suction roll while maintaining said line contact with the inner surface of -said suction roll.v

8. -A web yforming machine according to claim 7 in which the said means for -adjusting the eccentric rollcomprises a worm wheel connected with said eccentric roll, and a Worm gear meshing with said worm wheel rotatable for rotating said worm wheel for eifecting'the said bodily adjustment of said eccentric roll.

9. In a web forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, wire means passing over a portion of said suction roll, a draining zone having a relatively short portion thereof arranged adjacent said suction roll for forming a web upon atportion of said Wire means, a substantially imperforate eccentric roll rotatably located within said suction roll and eccentrically arranged with regard thereto and extending axially over the entire length of the perforated portion rof said suction roll, said eccentric roll having a'rotating peripheral surface portion in line contact with the inner surface of said suction roll at .a portion of the latter which is adjacent the beginning point of said relatively short portion of said draining zone while the respective remaining peripheral outer surface of said eccentric roll and the respective inner suction roll surface facing said respective remaining peripheral outer surface of said eccentric roll conine with each other a crescent-shaped gap, and cover means slightly spaced from the outer surface-of said suction roll and surrounding said suction roll while permitting the discharge of water Withdrawn through said suction troll and also permitting the passage Yof the respective wire portions between said suction roll and said draining zone.

10. A web forming machine according to claim 9, in which said cover means includes discharge slots extending at least over the width of the web being formed.

1l. In -a web forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, wire means passing over a relatively short portion of said suction roll, means drivingly connected to said wire means for driving the same, a draining zone having `a relatively short portion thereof arranged adjacent said suction roll for forming a web upon a portion of said vwire means, a substantially imperfo-rate eccentric roll ro- Statably located `within Vsaid suction roll andeccentrically arranged with regard thereto and extending axially over the `entire length -of the perforated portion of said suction roll, said eccentric roll having a rotating peripheral surface portion in line contact with the inner surface 'of said suction roll -at a portion of the latter which is adjacent the beginning point of said relatively short portion of said `draining zone while the respective remaining peripheral outer surface of said eccentric roll and the respective inner suction roll surface facing said respective remaining peripheral outer surface of said eccentric roll confine with each other a crescent-.shaped gap, and cover means slightly spaced from and extending along a major portion of the outer surface of said suction roll while comprising at least one discharge slot for discharging waste water from the inside of said cover means, said discharge slot being arranged in the cover means at a point inside said wire means.

12. In a web forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, wire means passing over a relatively large portion of said suction roll and rotatable by the latter, means drivingly connected to said suction roll for rotating the same, a draining zone having a relatively short portion thereof arranged adjacent said suction roll for forming a web upon a portion of said wire means, a substantially irnperforate eccentric roll rotatably located within said suction roll and eccentrically arranged with regard thereto and extending axially `over the entire length of the perforated portion of said suction roll, said eccentric roll having a rotating peripheral surface portion in l-ine contact with the inner surface of said suction roll at a portion of the latter which is adjacent the beginning point 0f said relatively short portion of said draining zone While the respective remaining peripheral outer surface of said eccentric roll and the respective inner suction roll surface facing said respective remaining peripheral outer surface of said eccentric roll confine with each other a crescentshaped gap, and cover means slightly spaced from and extending along an outer sur-face portion of said suction roll while leaving a passage between the latter and said relatively short portion of said draining zone for passing said wire means therethrough, said cover means including at least one main discharging slot for discharging the major portion of the water withdrawn through said suction roll and also including at least one auxiliary slot for discharging the remainder of the water withdrawn through said suction roll, saidmain slot being arranged in that portion of said cover means which is arranged inside said wire means, and said auxiliary slot being arranged in Vthat portion of said cover means which is arranged outsideI said wire means.

13. yIn a web forming machine, especially paper web forming machine: a rotatable perforated hollow suction roll, wire means passing over a portion of said suction roll, a draining zone having a relatively short .portion thereof arranged adjacent said suction roll for forming a web upon a portion of said wire means, a substantially imperforate eccentric roll rotatably located within said suction roll and eccentrically arranged withregard thereto and extending axially over the entire length of the perforated portion of -said suction roll, said Veccentric roll having a rotating peripheral surface portion in line contact with the inner surface of said suction roll at a portion of the latter which is `adjacent the beginning point of said relatively short portion of said drainingzone while the respective remaining pelipheral outer surface of said eccentric roll and the respective inner suction `roll surface of said eccentric roll confine with each yother a crescent-shaped gap, and cover means slightly spaced from the outer surface of said suction roll and surrounding said suction roll while permitting the passage of the respective wire portions between said suction roll and said relatively short portion of said draining Zone, said cover means including adjustable slot means for discharging water from the interior of `said suction roll.

14. In a paper machine, in combination, a rotatably mounted foraminous cylinder, `an inlet adjacent said cylinder arranged for feeding stock to the 11p-running side of the cylinder for depositing a fibrous web thereon, iirst sealing means for the cylinder in the region of lthe bottom of the inlet, second sealing means for the cylinder beginning at the top of the cylinder and extending in the direction of rotation of the cylinder, and means arranged Within the cylinder and operable `for ere-ating suction Within the cylinder between said first and second sealing means, said suction creating means consisting of a substantially imperforate lroll eccentrically rotatably arranged Within and in close running relation to the inner periphery of said cylinder.

15. In a paper machine, in combination, a looped forming Wire, a rotatably mounted foraminous cylinder Within the loop of the wire, an inlet adjacent the cylinder arranged for feeding stock to the Wire on the up-running side of the cylinder for depositing a iibrous web thereon, means arranged Within the cylinder and creating suction Within the cylinder, Isaid suction creating means consisting of a substantially imperforate roll eccentrically rotatably arranged in close running relation to the inner periphery of said cylinder and controlling the rlloW of water from the stock through said foraminous cylinder, said roll l@ defining a tapered gap with Ithe inner periphery of said cylinder.

16. |In a paper machine, in combination, a looped forming Wire, a rotatably mounted foraminons cylinder Within the loop of the Wire, an inlet adjacent the cylinder arranged for feeding stock to the Wire on the A11p-running side of the cylinder for depositing a fibrous web thereon, means arranged within the cylinder and creating suction Within the cylinder, said suction crea-ting means consisting of a substantially impe-rforate roll eccentrically arranged -so as to form` a tapered gap With `the inner periphery of said cylinder, and mounting means adjustably connected to said roll for selectively bodily -rotating the same about the central axis of said cylinder.

References Cited in the iile of this patent UNITED STATES PATENTS 550,353 Parker Nov. 26, 1895 1,864,580 Brawn lune 28, 1932 2,348,340 Goodwillie et al. May 9, 1944 2,353,991 Vickery July 4, 1944 2,694,345 Hornbostel Nov. 16, 1954 2,943,678 Fasoli July 5, 1960 3,018,825 Han etal Jan. 30, 1962

Claims

1. IN THE METHOD OF WITHDRAWING LARGE QUANTITIES OF LIQUID FROM A DILUTE SUSPENSION, ESPECIALLY FIBER SUSPENSION, FOR PRODUCING A FIBER WEB IN A WEB-FORMING ZONE OF A FORAMINOUS OR PERFORATED HOLLOW CYLINDER, THE STEPS OF: DELIVERING THE SUSPENSION TO SAID WEB-FORMING ZONE ON THE OUTSIDE OF THE CYLINDER, CREATING A REDUCED PRESSURE ON THE INSIDE OF SAID CYLINDER IN SAID WEB-FORMING ZONE, VARYING SAID REDUCED PRESSURE FROM A MINIMUM TO A MAXIMUM CONTINUOUSLY AND STEADILY AND IN THE DIRECTION OF MOVEMENT OF THE WEB BEING FORMED WHILE MAINTAINING SAID REDUCED PRESSURE CONSTANT AT ANY LINE EXTENDING ACROSS THE WIDTH OF SAID WEB BEING FORMED, EXERTING SAID REDUCED PRESSURE ON SAID SUSPENSION OVER SAID WEB-FORMING ZONE TO WITHDRAW LIQUID FROM THE SUSPENSION INTO SAID CYLINDER, AND DISCHARGING THE DRAINED-OFF LIQUID FROM THE INSIDE OF SAID CYLINDER THROUGH THE PERFORATIONS THEREOF AND ACROSS THE ENTIRE WIDTH THEREOF.