US3691010A

US3691010A - Method and apparatus for dewatering paper webs

Info

Publication number: US3691010A
Application number: US58487A
Authority: US
Inventors: Kenneth V Krake
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Corp
Priority date: 1970-07-27
Filing date: 1970-07-27
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: GB1362566A; ATA645171A; AT331113B; CA935001A; FR2103353A5; DE2139591A1; AU3165771A; ZA715001B

Abstract

PAPER WEBS, PARTICULARLY TISSUE PAPERS, FORMED BY THE WET PROCESS FROM AN AQUEOUS FIBER SLURRY, ARE DEWATERED BY A NOVEL PRESS ARRANGEMENT. THE METHOD IS ACCOMPLISHED BY EXPELLING WATER FROM A CARRYING FELT-NEWLY FORMED WEB COMBINATION AND SO ELIMINATING THE WATER THAT THE FELT IS NOT REWETTED BY IT AND CRUSHING OF THE SHEET IS AVOIDED. VERY HIGH MANUFACTURING SPEEDS ARE ATTAINABLE.

Description

m 2. 1912 K. v. KRAKE 3,691,010

METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Filed July 27, 1970 s Sheets-Sheet 1 K. V. KRAKE METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Filed July 27, 1.9670

6 Sheets-Sheet 2 A li/ 1w K. V. KRAKE METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Filed July 27. 1970 6 Sheets-Sheet 5 P 1972 K. v. KRAKE 3,691,010

METHOD AND APPARATUS FOR DE WATERING PAP-ER WEBS Filed July 27, 1970 6 Sheets-Sheet 4 K. V. KRAKE METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Filed July 27, 1970 6 Sheets-Sheet 5 q 1972' K. v. KRAKE 3,691,010

METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Filed July 27, 1970 e Sheets-Sheet .e

FIG. 7

UnitedStates Patent once Patented Sept. 12, 1972 3,691,010 METHOD AND APPARATUS FOR DEWATERING PAPER WEBS Kenneth V. Krake, Neenah, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis. Filed July 27, 1970, Ser. No. 58,487 Int. Cl. D21f 11/00; D21j U.S. Cl. 162206 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the dewatering of (tissue) paper webs as they are formed and dried. More specifically, the invention is concerned with large volume water removal from a web carrying felt as it passes through a pressure nip between a Yankee dryer and a pressure roll. Still more specifically, the invention is directed to equipment arrangements and to methods for water removal from paper webs in the course of high speed production of the webs.

Paper webs, particularly tissue paper, are commonly wet formed. Basically, a thin stream of a pulp stock in very dilute form is fed to a moving forarninous wire of a paper-making machine. The stock drains on the wire and fibers of the pulp form into a wet web trapping much Water. The traveling wet sheet is then, in conventional practice, removed from the wire by a traveling felt and, while carried on the felt, is subjected to sequential pressing operations to provide an integral web structure. Pressing usually is followed by heating on a Yankee dryer to eliminate substantially all water.

Manufacture of paper webs includes tissue paper which is to be creped, i.e., carried out usually in the generally described manner and at relatively low speeds of web, wire and felts. The operation is quite successful. It has been recognized, of course, that higher operating speeds would improve the economics if all other factors remained substantially the same. Higher operating speeds, however, it has been found, result in many difiiculties.

A basic problem resulting from simply speed increase is that much of the water removal from the traveling web must be effected in a much shorter time period. Such leads, of course, to the necessity for improved press and felt operation; it has been found, however, that crushing of the traveling sheet occurs with increase in the pressures applied to the web-felt combination. Also, the filling of the felt itself, a frequent difficulty even at low speeds, becomes much more acute as speed increases; further, where several presses in sequence are employed, sheet stealing, that is, the tendency of the sheet to transfer itself improperly to secondary felts or the like becomes an important consideration.

In the art of crepe tissue manufacture, speeds of 3800 f.p.m. of web formation have previously been achieved. In this art the usual web is of relatively light basis weight and water removal is, to some extent, facilitated by this factor. Speeds above about 3800 f.p.m. have been difficult to obtain, however, due to problems such as those indicated above.

I have found that a major step in the attainment of increased speeds of tissue paper manufacture involves adequate water removal from traveling web and felt at a nip between the Yankee dryer and an associated press roll. I have repeatedly and easily operated equipment at speeds of up to 5000 f.p.m. by carefully providing for web and felt dewatering in the vicinity of the Yankee dryer. Other considerations, of course, contribute to the overall effect but, as will become apparent, the novel equipment arrangement and method of operation described herein are key contributions.

More in detail, in usual operations, the Yankee dryer is a large diameter drum on which drying of the web is substantially completed and from which the Web is usually creped. While complete drying or creping are not necessary to the practice of my invention, my method and equipment arrangement are capable of providing for these frequently desired results. Also, the web and felt approaching the incoming nip of the Yankee dryer with an adjacent pressure roll may vary somewhat but typically is in the range of 1.0-1.3 pounds of water per pound of felt in the felt, and 9-13 pounds of water per pound of fiber in the wet web. My equipment arrangement at a Web speed of about 5000 f.p.m. is quite adequate to remove substantially all of this water prior to removal of the web from the Yankee while employing conventional dryer temperatures.

In a preferred embodiment of the invention, I provide a first press roll nip operating at a relatively low pressure in pounds per lineal inch to largely dewater the Web and the felt carrying the web; the web, separated from the felt at the outgoing side of the first nip, passes to a somewhat higher pressure roll nip with the Yankee to effect further Water removal. The dewatered felt is directed free of the dryer from the first nip to this second nip to aid further dewatering of the web in this preferred embodiment. The endless dewatering fabric or felt is itself suitably well cleaned and dried before receiving the pulp stock in the forming zone of the paper machine.

The invention will be more fully understood by reference to the following detailed description and accompanying drawings wherein:

FIG. 1 is a schematic view in side elevation illustrating one equipment arrangement for the practice of the invention, the forming wire of the equipment being only partially shown;

FIG. 2 is an enlarged and more detailed view particularly illustrating the relationship of the Yankee dryer with first and second press roll arrangements of the equipment;

FIG. 3 is a perspective view of the equipment arrangement set out in FIG. 2;

FIG. 4 is a detail view of an adjustable device useful in connection with the mechanism of FIG. 2;

FIG. 5 is a view particularly illustrating useful angular relationships of the web and felt at the outgoing side of the first press nip;

FIG. 6 illustrates a detail view of an air knife arrangement useful in connection with the equipment of FIGS. 1 to 4; and

FIG. 7 is a view like that of FIG. 1 but illustrating a further embodiment of the invention, the travel of the carrying felt being only partially indicated.

' Referring to the drawings and first, particularly, to FIGS. 1 to 3 inclusive, the numeral 1 generally designates a papermaking machine which embodies the principles of the invention. The machine has an inlet 2 of the pressure forming type as described in U.S. Pats. 3,224,928; 3,326,- 745; 3,400,045; and 3,378,435, all assigned to the same assignee as the present invention. The inlet 2 is adapted to discharge a fibrous papermaking stock of suitable consistency between a forming wire 3 and a dewatering fabric or papermarkers felt 4. The forming wire is an endless conventional paper web forming wire used in Fourdrinier machines and is made up of interwoven warp and shute strands providing usual drainage openings. Only the pertinent portion of the wire is shown in FIG. 1 as arrangements for support of the wire are well known and are included in the abovementioned patents.

As shown, the wire 3 passes in the direction of the arrows about roll 5 and through the nip formed between rolls 5 and 6. Roll 6 is conveniently termed a forming roll. Pressure between the wire 3 and felt 4 provides for web formation, and this pressure is increased as the felt and wire travel around forming roll 6; this pressure causes some dewatering of the felt and stock. The magnitude of the pressure varies with the tension on the wire and the radius of curvature of roll 6, the pressure increasing with increased wire tension and decreased roll radius. Centrifugal force also aids dewatering. To further consolidate the web quickly, a dewatering roll 7 may be employed, and such, I have found, is quite effective in lowering felt water content at web forming speeds of up to about 4000 f.p.m. The extent to which roll 7 is significantly useful apparently is somewhat dependent upon web speed, web weight, and the nature of the stock. In many instances at high speeds (5000 f.p.m.) and low web weights, I prefer not to employ this dewatering roll 7 as dynamic balance then becomes much more critical.

Roll 8 is simply a turning roll and separation of the web and felt from the Wire 3 occurs as the wire passes about roll 8. The wire, as already mentioned, is endless and is handled as indicated in US. Pat. 3,326,745, noted above, for example.

The web and felt passing toward the hydrofoil vacuum boxes with the web 9 laying on the underside of the felt (FIG. 1) together contain a very substantial volume of water. I have found the upside down vacuum boxes 10 are very effective in removing water from this felt-web combination. Such boxes, however, tend to cause a considerable drag on the equipment, resulting in higher horsepower demands. At the higher speeds of machine operation, in accordance with the invention, I do not find that the boxes 10 are absolutel necessary, though they have utility. The extra drag they produce limits the upper limit of speed for fixed power to the machine.

The web 9 and felt 4 are directed as indicated by the arrow (FIG. 1) over turning rolls 11, 12 and by the beta gauge 13 to a nip 14 formed between a suction press roll 15 and a Yankee dryer 16. The dryer 16 is generally of the conventional type employed in crepe tissue paper formation and is commonly quite large, 12 to 15 feet in diameter.

Depending upon a number of considerations, including the specific nature and construction of felt 4, the fiber stock forming the web 9, the use or non-use of dewatering rolls 7 and vacuum boxes 10 and machine speed, for example, the web consistency and the quantity of water per pound of felt may vary somewhat as the combination of felt and web enter nip 14. The water content, however, with the single felt system described here, will be relatively large and a considerable demand is imposed upon the water removal equipment. Additionally, I have found after extensive experimentation that the dewatering operation is a relatively critical one at high web forming speeds. This is for the reasons that the water must be eliminated from the fabric (felt)-web combination in such manner that the felt is not rewetted b expelled water and also that crushing of the web is avoided.

I prefer to employ as the first suction pressure roll 15 a shrink sleeve jacketed roll. Such sleeves, as that indicated at 17 in FIG. 2, are known and have been found useful in presses for water removal in paper manufacture. I have also found that a 24% to about 30% open area of the suction roll is most useful in operations similar to that of FIG. 1. With such an arrangement, the water content of the sheet after nip 14 tends to be substantially a constant over a relatively wide range of machine speeds for a given felt-web water content condition entering the suction press roll.

The felt 4 carries the wet web to nip 14 on its outer side and presses the web to the surface of dryer 16. The nip is adapted to pass therethrough the felt-web combination while providing a sufficient pressing action to dewater the web and adhere the web to the dryer surface; the traveling felt is withdrawn from the web in the exit side of nip 14 on roll 15. In this dewatering action the nip pressure may be relatively loW. With the aid of a jacketed suction roll as the felt-web combination enters the nip and pressure is applied water urged from the felt enters interstices of the covering of the jacketed roll and the water is drawn vertically out of the felt preventing water flow laterally in the felt length. The resistance to flow under these conditions is low and large quantities of water are successfully withdrawn to the vacuum roll.

The partially dewatered felt 4 (FIG. 1) still containing a very considerable quantity of water is drawn from the suction press roll 15 to the upper surface of a deflector 20 for the felt 4; deflector 20 is positioned in the outgoing side of nip 14 and is essentially a guardboard which prevents water thrown from the roll 15 from rewetting the felt. The deflector 20 is so arranged as to prevent any significant wrapping of the roll 15 by the felt after nip 14. Very suitably (FIG. 5) the felt extends from the nip 14 tangentially to roll '15 toward deflector 20. I have found that generally angles of about 5 upwardly to about 10 below the tangent line indicated by dash lines at A and B respectively in FIG. 5 are quite effective although such may vary somewhat with conditions such as roll diameter, felt flexibility and the like. This general relationship provides that water thrown from the roll 15 will move towards the deflector underside and to collector pan 22. The detailed arrangements of the felt deflector and collector pan will be discussed more fully hereinafter in connection with FIGS. 2 and 4.

In the course of my experimentation, I have further found that, as the machine speeds increase, there is an increasing possibility of crushing and working of the formed web in nip 14. I found that, for most purposes, the vacuum zone designated 18 in FIG. 2 should have a limited arc, suitably between about and 170 with about preferred, be stationary, and terminate closely adjacent the center of nip 14. Such roll constructions are known, and the limits of the zone are defined by fixedly positioned

seals

18a, 18b. This is particularly useful because it allows the trailing edge 18a of the vacuum zone to be at the centerline of the pressure roll/dryer nip, thus allowing complete transfer of sheet to dryer. If this vacuum box is rotated through the nip to, in effect, hold the water in suction holes so that the felt is not re-wetted, then the wet sheet will split over the suction hole areas and part of the sheet will follow the felt. This will produce film bundles or popcorn" at the nipout roll and this, in turn, will dirty the felt. It is vitally important to have a dry" felt for efficient Wet pressing at the second pressure roll nip, and the guardboard deflector (tongue depressor) affords an extremely useful way of preventing rewetting of the felt after first pressure roll nip without causing splitting of the sheet.

A nip-out roll 23 (FIG. 1) receives the traveling felt from the felt deflector and redirects it to a second nip 24 formed between a second and grooved suction roll 25 and the dryer 16. The felt passing to nip 24 still has a significant quantity of water and, desirably, water removal in nip 24 should be highly efficient. The grooved roll, while not necessary to operation, will, I have found, in this position generally give 2 to 3 percent higher sheet consistency than a plain roll and it is less sensitive to speed change in its operation; particularly, it is eflicient at desired speeds above 4500 r.p.m. Suitably, such second press roll 25 has a drilled hole pattern giving a 24 percent open area with about eight grooves per inch, and the roll has a vacuum zone provided by

seals

25a, 25b of about 55 arc The water removal capability of the jacketed first pressure roll and the grooved second press roll operating against the dryer as described is effective to provide a sufiiciently dewatered sheet to the rotary dryer that, in conjunction with dryer hood apparatus at H, operated in conventional manner, the web creped off by blade 26 (FIG. 1) even at speeds exceeding 5000 f.p.m. is substantially dry and of excellent quality. The drying load imposed in the two press nips with the dryer may be reduced somewhat as already noted by the inclusion of auxiliary equipment preceding the presses. Additionally, I have found that the load may be lessened if desired by so treating the felt as to maintain it thoroughly clean and to present it to the forming roll 6. One quite adequate system to provide for felt cleaning and prevent felt filling is illustrated in FIG. 1; other usual systems would serve quite well, however, to provide high manufacturing speeds with the press construction and arrangement described.

The felt 4 is directed from second press roll 25 successively through a detergent shower 27, an X-ray inspection gauge 28, a high volume cold Water shower 29 applied to its underside, and a low volume cold water shower applied to the upper side to maintain the felt surface fluid and suitably wetted. A hitch roll 30 of small radius bearing on the underside of the felt aids the movements of Water through the felt so that fiber fines, fibers, etc. are forced through and collected by a pan 31. The hitch roll 32 reverses felt direction and pan 33 collects excess water draining from the felt. The felt is then directed to suction boxes 34 and over turning rolls 35, 36 to a high volume shower of water at 37.

The high volume shower 37 is oriented toward a guard 39 and collector pan 40 for directing fibers, etc. washed off the felt by the shower. Additionally, pan 41 receives material thrown off the opposite felt side as the felt moves over roll 42. A further shower 43 and guard 44 with pan -'45 further aid removal and collection from the felt of fibers, fiber fines, and other debris commonly associated with felt operation.

Vacuum boxes

46, 47 on either side of roll 48 assist dewatering of the felt as it moves to turning roll 49 past the beta gauges 50. Thus, the felt is cleaned and dewatered before again receiving the paper stock; the more effective the cleaning action, the longer the felt life, and the more dewatered the felt is at the inlet to the forming roll, the more efficiently the felt will aid in dewatering the web.

Referring now more in detail to FIGS. 2, 3 and 4, the mounting of the fabric or felt deflector 20 and the collector pan are set out in detail. Only one side of the machine is shown since opposed sides have essentially the same profile structurally unless otherwise noted. As illustrated in FIG. 3, a housing 51 at the end of suction press roll 15 and itself carried by base 52 mounts a horizontally extending support bar 53. Bar 53 extends transversely of the machine adjacent the roll 15. The bar is secured by a brace 54 to a bracket 55. A stud shaft 56 is carried by bearing 57 which is mounted on the bracket 55. The stud shaft is also fixedly secured to frame 58 by plate 59 and, accordingly, the frame is rotatably mounted with respect to the bracket. The bracket 55 also includes an angle iron 60 pivotally carrying bolt 61 and which itself threadedly receives nuts 62, 63. A ball socket element 64 rotatably mounted on the threaded bolt 61 is contoured to conform to the adjacent curvilinear surfaces of

nuts

62, 63. The ball element 64 is connected by a stud 65 and nut 66 to the frame 58. Vertical adjustment of the nuts 62, 63 on the bolt 61 controls movement of the ball element 64 and pivoting of the frame 58 relative to the bracket and the roll 15. The contouring of the nuts provides for relative sliding move ment of the nuts and ball element so that bending of bolt 61 is avoided.

Deflector 20 is carried in a dove-tail 67 of support 68 which extends transversely the full width of the machine with frame 58. The deflector 20 is adapted to be slidably positioned and retained in position solely by pressure of the traveling felt. The deflector may, of course, be fixed in position, but the described arrangement permits adjustment or replacement while the machine is in operation. For example, a new deflector may be inserted in one end of the dove-tail and used to push out the old deflector as the new one is positioned.

I have found that a high density polyethylene board material serves very well with papermaking felts to provide both long board life and aid felt life. However, the function of the board is generally independent of the specific material and others will serve.

The board assembly, including the felt deflector, deflector support and frame 58 serve to direct water thrown from the press roll \15 to the pan 22. The fabric receiving face fronts toward the dryer, and the rearward intercepts the water. The flow of water is quite large in the operation described and the collector pan is so proportioned and arranged as to take the flow of water and direct it to the side of the equipment without run-over back onto the felt.

The suction roll 15, when operated with the shrink sleeve jacketed roll 17, is capable of extracting large quantities of water quite readily from the small pockets naturally occurring in such sleeves. To aid water removal at high speeds and to further insure the presentation to the incoming felt-web combination of a dewatered sleeve, I found that an air-knife 70 (FIG. 6) is useful. The air knife includes a longitudinal nozzle 71 and a supply conduit 72. Additionally, I have employed the air-knife structure as a sealing strip at 73 between the roll and pan (FIG. 6) and find this arrangement to be particularly suitable.

In a specific application, when producing a web of 7.5 1bs./2880 sq. ft. at about 5000 f.p.m., the total bone dry fiber weight in web form produced in one minute at conventional dryer and hood temperatures is about 13.0 pounds per foot of width. The quantity of water associated with this fiber weight as the felt-web combination enters the suction roll 15 area, is about 103.6 pounds. The felt weight entering the first nip then at a weight of 1291 pounds would carry 1677 pounds of water. The sheet through the first nip then passes to the felt about 72.2 pounds of water and the felt leaving the first nip has 838.5 pounds of water per 1291 pounds of felt. The web on the dryer passing to the second nip then carries about 31.5 pounds of water per 14.1 pounds of fiber. The water expelled in such first nip is about 83 8.5 pounds per minute. This water is thrown off at a considerable velocity and most of it emanates from the compression zone in the nip, the length of such zone being about /2 inch. The direction of water movement is such that the felt is substantially not rewetted. Essentially, the first nip operated at a pressure of about 200 pounds per lineal inch raises the web consistency from about 9-12% to about 3133% when the jacketed roll is employed.

The first pressure roll is commonly operated, in my arrangement, at -200 p.l.i. and the second pressure roll at 200-350 p.l.i.

In the absence of the jacket in the first suction pressure roll, the consistency after the first nip would be about 29% at 3800 f.p.m. However, it would be substantially impossible to run at 5000 f.p.m. because of severe crushing and shadow marking due to the ineflficiency of the standard suction roll press.

A particular advantage of the FIG. 1 arrangement is that relatively low pressures of 100-200 pounds per lineal inch may be employed in the first nip, thus avoiding sheet crushing.

I have found it quite possible to attain with conventional steam dryer pressures of about 31 psi. gauge and hood H temperature of 70 to 750-a dry web at 500 f.p.m.

The foregoing description has been directed largely to a machine operation involving a single felt in which the web is formed on the felt and carried thereby to the Yankee dryer for dewatering, some variations providing for the use of auxiliary equipment for dewatering prior to presentation to the suction roll-dryer nip. In FIG. 7 an arrangement similar to that of FIG. 1, but involving a second felt 74, is illustrated. The second felt is mounted on turning rolls 75 and is directed over the lower roll 76 of a conventional two roll main press having upper roll 77. The other equipment of FIG. 7 is similar to that of FIG. 1 and the same numerals are applicable, and, accordingly, no further specific description of such mechanism is necessary. However, it is to be noted that at high speeds of 4500 f.p.m. and above web stealing by the lower felt, that is, the tendency of the lower felt to draw the web from the upper felt, tends to be a problem. I have found, however, that woven bottom felts serve the purpose of dewatering well.

In a further embodiment not considered necessary to specifically describe since such general arrangements are known, the top felt may receive the web from a conventional Fourdrinier forming wire rather than having the web formed with the pressure type inlets of FIGS. 1 and 7. More specifically, the wet web may be formed in a number of ways, including forming the web and transferring it to a dewatering fabric or forming it with the aid of the dewatering fabric itself. In either case, the wet web is formed and carried on the dewatering fabric to a surface of a rotary dryer which may be preceded by other dewatering means than the fabric itself.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. In web manufacturing apparatus in which a fibrous web of wet stock is formed and is carried on a moving dewatering fabric to a surface of a rotary dryer, a suction press roll forming a nip with the dryer and having a stationary suction box on the ingoing side of the nip only and which nip is adapted to pass the fabric and fibrous web therethrough to dewater the web and press the web to the dryer, and a guardboard deflector assembly including a fabric deflector in the outgoing side of the said nip positioned to direct the dewatering fabric away from the press roll to prevent any significant wrapping of the press roll by a dewatering fabric following the nip and to thereby inhibit rewetting of the fabric by liquid thrown tangentially from the press roll.

2. Apparatus according to claim 1 in which the press roll has a shrink sleeve cover.

3. Apparatus according to claim 1 in which the said fabric deflector has a first dewatering fabric receiving face fronting toward the dryer surface and a rearward face directed toward the press roll to intercept water thrown off by the press roll and to thereby inhibit rewetting of the dewatering fabric.

4. Apparatus according to claim 1 in which the suction press roll has a wide angle suction box of between at least about 120 and 170 and the said box lies on the ingoing side of the nip terminating at about the nip so that vacuum pressure does not extend substantially beyond the nip on the outgoing nip side.

5. Apparatus according to claim 1 in which the fabric deflector is located so that it fronts toward the said surface of the dryer and the angle formed between a line of tangency to the press roll at the nip and a line between the fabric deflector and press roll at the nip is less than 10 and the line between the deflector and press roll is on1 lthe side of the tangent line which is toward the press r0 6. The method of drying a continuously traveling wet web of paper comprising carrying the wet web on a dewatering fabric to a nip formed between a peripheral surface of a rotating rotary dryer and a suction press roll, applying suction pressure to the press roll on the ingoing side of the nip only, pressing the combination of wet web and fabric in the nip to adhere the web to the rotating dryer surface and withdraw water from the combination under suction, snubbing the fabric over a fabric deflector in the outgoing side of the nip to withdraw the fabric from the wet web on the dryer surface and to prevent any substantial contact of the dewatering fabric with the periphery of the suction press roll on the outgoing side of the nip to inhibit rewetting of the fabric by the expression from the press roll of water withdrawn in the pressing operation, and completing the drying of the web.

7. The method as claimed in claim 6 and which includes applying suction pressure to the combination of fabric and wet web on the press roll on the ingoing side of the first nip and terminating the application of suction pressure to the fabric-web combination at a zone prior to the nip center, and doctoring with an air knife between the outgoing side of the nip and the ingoing side of the nip water from the press roll not expressed under the influence of centrifugal force.

8. In a machine for tissue papermaking a rotary Yankee dryer, a suction press roll forming a nip with the dryer and having a stationary suction box on the ingoing side of the nip only, a dewatering fabric partially wrapping said suction press roll on the ingoing nip side adapted for carrying a wet fibrous web to said nip between the Yankee dryer and press roll to press a wet paper web to the surface of the Yankee dryer, the improvement which comprises a combination of a guardboard and dewatering fabric deflector positioned in the outgoing side of said nip to receive said dewatering fabric on a first face of the guardboard deflector fronting toward the Yankee dryer to maintain said dewatering fabric free of the press roll on the outgoing side of the nip and also positioned to intercept on its rearward face water removed from a fibrous web at the nip and expelled by the suction press roll in its rotation as it carries the dewatering fabric through the nip.

9. In a machine for tissue papermaking according to claim 8 and in which the suction press roll has a shrink sleeve cover.

10. In a machine for tissue paper manufacture according to claim 8 and in which the guardboard deflector assembly includes a frame, a deflector support on the frame, and a fabric deflector which is mounted for slidable movement in the axial direction of the rotary dryer.

References Cited UNITED STATES PATENTS HOWARD R. CAINE, Primary Examiner US. Cl. X.R. 162-359