US3150037A

US3150037A - Papermaking machine utilizing centrifugal dewatering

Info

Publication number: US3150037A
Application number: US164229A
Authority: US
Inventors: Lee Charles Allen
Original assignee: Huyck Corp
Current assignee: ER-WE-PA und EISENGIESSEREI HERBERT KARL SCHMIDT A GERMAN Co
Priority date: 1962-01-04
Filing date: 1962-01-04
Publication date: 1964-09-22
Anticipated expiration: 1981-09-22
Also published as: SE308244B; GB949769A; DE1411902B1

Description

Sept. 22, 1964 c, E 3,150,037

PAPERMAKING MACHINE UTILIZING CENTRIFUGAL DEWATERING Filed Jan. 4, 1962 2 Sheets-Sheet l fizz 17222" oer 42255 4. 455

MM, alau qflw, 62:6

Jigs/5 C. A. LEE

Sept. 22, 1964 PAPERMAKING MACHINE UTILIZING CENTRIF'UGAL DEWATERING Filed Jan. 4, 1962 2 Sheets-Sheet 2 United States Patent Yorlr Filed Sen. 4, 1962, Ser. No. 164,229 4 Claims. ill. 162-408) The invention relates generally to methods and apparatus for making paper. More specifically, the invention relates to a method of forming a web for papermaking fibers and to apparatus for carrying out the method. The invention is particularly directed to means for dewatering a wet web of papermaking fibers after it has been formed on the forming medium or carrier.

In known equipment, initial dewatering of the web, either in the web-forming region or in the region adjacent to the web-forming region, generally has been accomplished in a number of ways. These have included the directing of the incoming stream of stock, which contains the papermaking fibers, against the forming carrier at such an angle and with such velocity as to carry a substantial portion of the white water through the carrier; the use of gravity to eifect drainage of the white Water through the carrier; and the application of suction to the web through the forming carrier, either by means of a suction box underlying the path of the web or by a suction roll around which the forming carrier is wrapped.

After such initial dewatering has been accomplished by one or more of the foregoing steps, the web is transferred from the forming carrier to one or more felts for transportation through a press section for further dewatering. Eventually, the web is passed to a drier in which heat is applied to evaporate the remaining part of the moisture which is to be ultimately removed from the resulting paper.

The final drying of the web with heat in a drier is relatively expensive and, consequently, it is desirable that the web enter the drier with a minimum of water content. In high speed papermaking equipment the production of a web having a desirably low water content for the drier has always presented a problem. The problem has previously been met by the provision of large and extremely expensive equipment which often runs into a capital investment of hundreds of thousands of dollars. Attempts have been made to decrease the cost of equipment and to increase its dewatering ability, but none of these attempts have been entirely successful.

Accordingly, the principal objects of the invention are the provision of an improved method of dewatering a web, and the provision of papermaking equipment for carrying out such a method. A more specific object of the invention is the provision of a papermaking method and apparatus which is operable to etficiently dewater a wet web at high speeds and with greatly reduced capital expenditure for equipment.

Further objects of the invention are the provision of a method and an apparatus for extracting water from a web by subjecting the web to directional changes while protecting the web against disruption due to such changes in direction. Other objects of the invention are the provision of a method and an apparatus for dewatering a wet web by subjecting the web to air streams of relatively high velocity.

Other objects and advantages of the invention will become known by reference to the following description and the accompanying drawings of several illustrative examples of equipment which embody various of the features of the invention.

3,15,637. Patented Sept. 22, 1964 In the drawings:

FIGURE 1 is a fragmentary diagrammatic view of one type of papermaking apparatus which includes various of the features of the invention;

FIGURE 2 is an enlarged fragmentary elevational View showing a portion of the construction of one of the members of the apparatus shown in FIG. 1;

FIGURE 3 is a fragmentary diagrammatic view of another type of papermaking apparatus embodying various of the features of the invention; and

FIGURE 4 is a fragmentary diagrammatic view of still another type of paperrnaking apparatus embodying vari ous of the features of the invention.

In its most general aspects, the method of the invention involves the effecting of rapid changes in direction of the wet web while it is traveling at relatively high speeds on the foraminous forming carrier. The rapid changes in direction cause a substantial amount of the free moisture or water contained in the Wet web to be ejected from the web by centrifugal action, the foraminous carrier supporting the web so that the web is not physically damaged incident to the forces applied to the web during the changes in direction.

As another feature of the method, streams of air or other gas in relatively high velocity may be directed through the web preferably in the regions of directional change to further facilitate dewatering.

In the preferred embodiment of the invention, the Web in the region of directional change is supported between a pair of foraminous carriers which engage opposite sides of the web. The confining foraminous carriers serve to minimize any disruption of the web in the region of the directional change. Also, if the streams of pressurized air are employed in aiding the extraction of water, the pair of foraminous carriers aid materially in maintaining the integrity of the web and distributing the air streams uniformly through the web.

Further, if the opposed foraminous carriers are fabricated from synthetic fibers which are stretchable, the relative movement of the web and the foraminous carriers in the regions of directional change momentarily induces lengthwise stresses in the web which tend to compress and work the web in such a manner that additional water is freed from the web.

In the apparatus shown in FIGURES 1 through 4, the directional changes are effected by passing the Web while confined between opposed foraminous members around the convex surfaces of one or more supporting members which are shown in the drawings as rotatable cylinders or rolls. However, a curvilinear shoe, which guides the travel of the web, may be readily substituted for one or more of the rolls.

Changing the direction of travel of the web by wrapping it around a roll or other curvilinear surface involves acceleration of the web in a direction perpendicular to its previous plane of travel, which acceleration can be readily computed. It has been determined that even with nominal values of web velocity and roll accompanying size that the force acceleration away from the previous plane of travel will be many times the force of gravity.

By employing the method of this invention, it is possi* ble to obtain almost instantaneously a consistency in the web of 20 to 30 percent (percent of fibers by weight in the web). In normal equipment this degree of dewatering requires considerable travel on a wire or other form ing carrier. The consistencies referred to above may be materially increased by the provision of the air streams which will be hereinafter described in greater detail.

When the path of travel of the web is fixed as by the use of rolls or a curvilinear shoe, and the web is held between a pair of opposed foraminous carriers, the opposed foraminous carriers are held in closely overlying relationship with the opposite surfaces of the web. This contact between the surfaces of the Web and the foraminous carriers minimizes imperfections in, and physical damage to, the surfaces of the web incident to the change in direction. Further, maintaining both surfaces of the web in contact with the opposed foraminous carriers facilitates working of the opposite surface of the web by the foraminous carriers so as to obtain further removal of moisture from the web, while conditioning the surfaces of the web by the foraminous carriers.

The method of the invention also contemplates the carrying of the web around a multiplicity of rolls so as to provide a change of direction in the travel of the web, first in one direction and then in another. For example, the web and its associated foraminous carriers may be passed through a generally S-shaped path. By this pro cedure, the web is first subjected to forces which tend to eject water in one direction and then it is next subject to forces which tend to eject water in the opposite direction. When this method is employed, the pair of foraminous carriers engaged against opposite surfaces of the web travel through a reversely curved path. When the web is carried in the reversely curved path the velocities of the foraminous carriers vary, depending upon the relative positions of the carriers with reference to the convex roll surfaces in proportion to their radial distances from the center of curvature. Thus, there are provided zones wherein the foraminous members shift relative to each other, as well as to the web. This relative movement induces the aforementioned working of the Web which aids in the expressing of moisture from the web and the conditioning of the Web surface.

In connection with all of the various methods of changing direction of the web which have been described in the preceding paragraphs, the centrifugal action caused by changing the direction of travel of the web may be enhanced by establishing a positive flow of gas through the web while it is supported between the foraminous members. The gas may be hot air, cold air, various heated gases such as a product of combustion, superheated steam or the like. In fact, any gas may be employed which will carry water out of the sheet, the gas being chosen, however, on the basis of cost and whether a hot or cold gas will provide the best operation. The flow of gas through the web provides a spraging action which aids in breaking surface tension and in expressing water from the web by a spraying action. As will be pointed out in the illustrative examples which follow, the streams of gas pass through the web in the same direction as the dewatering forces applied to the web incident to changing its direction of travel. Thus, the streams of gas enhance the action of the centrifugal force and effect movement of the moisture away from the roll or other supporting surface.

It has been determined that the employment of a fluid flow through the web, in addition to the centrifugal force resulting from the changes in direction of the web, will result in almost instantaneous increases in the consistency of the web to as much as thirty percent or even more.

As will be subsequently pointed out in connection with the description of examples of suitable apparatus, the increases in consistencies which are accomplished may be obtained with minimal capital investment and require a minimum of space for installation.

. The methods disclosed herein are applicable for use in various types of papermaking apparatus. One type of papermaking apparatus is shown in FIGURE 1 which includes suitable means in the form of a pending chamber 21 for flowing a stock of papermaking fibers onto a foraminous carrier 23 which, at least initially, serves as a forming medium and is trained around a breast roll 25. The foraminous carrier 23 extends along a generally un supported horizontal run 27 from the breast roll 25 to provide an opportunity for gravitational drainage of the white water in the stock so as to form a wet web 29 on the foraminous carrier 23. If desired, one or more table rolls, such as indicated at 31, can be employed to support the foraminous carrier 23 along the run 27.

As the web travels along the horizontal run 27, a second foraminous carrier 33 is overlaid onto the web 29 by suitable means. In the disclosed construction, such means includes a rotatable roll 35 which may be either of solid construction or include a porous outer shell as will be hereinafter described. The second foraminous carrier 33 extends downwardly, as illustrated, and is en g-aged against a point on the periphery of the roll 35 prior to the time when that point of the periphery of the roll approaches the web 29.

After the foraminous carrier 33 is disposed on the roll 35, the web 29 on the foraminous carrier 23 is trained onto the surface of the member 33 and the resulting three-ply assembly or sandwich 36, consisting of the

foraminous members

23 and 33, with the web confined therebetween, is wrapped partially around the roll as illustrated to cause the assembly to move through an upwardly extending, arcuate path 37 around the periphery of the roll 35. The assembly 36 is then passed over a roll 3 which is located so that its peripheral surface contacts the foraminous carrier 23.

The axes of rotation of the

rolls

35 and 39 are parallel to one another and are offset relative to one another as illustrated, to provide a wrap around each of the rolls of approximately 60 degrees. As a result, the web 29 confined between the

foraminous carriers

23 and 33, rapidly changes direction twice and is accelerated in opposite directions, the assembly 36 traveling first along the generally horizontal run 27, then along the first curved path 37 around a portion of the periphery of the first roll 35, along an upwardly extending, run 41 extending from the first roll 35 to the second roll 39, then along a curved path 43 around a portion of the periphery of the second roll 39, and finally, along a second generally horizontal run 45 extending from the second roll 39.

After passage from the second roll 39, the three-ply assembly 36 can be passed to a suitable press section (not shown) for further dewatering of the web, after which the web can be transferred to a drier, schematically illus trated as a Yankee drier 47. In the illustrated construction, the foraminous carrier 33 is carried away from the web around a suitable roll 49 prior to transfer of the web 29 to the drier 47. From the roll 49, the foraminous carrier 33 is trained around suitable guide rolls (one guide roll being shown at 51) and through suitable tensioning means (not shown) and cleaning showers (not shown) for return travel around the roll 35.

Transfer of the web to the drier 47 occurs incident to passage of the web 29 and the foraminous carrier 23 through a nip formed between the periphery of the drier 47 and an adjacent roll 53. From the roll, the foraminous member 23 travels past suitable guide rolls, showers, suctionpboxes, and tensioning rolls (not shown) back to the breast roll 25.

After leaving the carrier 23, the web 29 passes around the drier 47 and after it is dried to the proper moisture content it is doctored from the surface of the drier by a doctor 48 in the usual manner. Any suitable type of ponding chamber construction can be employed to discharge the stock suspension of papermaking fibers onto the foraminous carrier 23. In the illustrated construction, the pending chamber 21 is a pressurized head box and includes an air pad 55 and one or more rotating distributing rolls 57.

The breast roll 25 can be of any known construction either solid, open, or vacuum, the latter two types being primarily used when the stock suspension is discharged onto a portion of the foraminous carrier 23 which is disposed in overlying relation to the breast roll 25. ireferably, the foraminous carriers 23 and 33' are elastic in nature, at least to the extent of expanding and contracting without permanent set or damage during their passage through nips and around rolls as described. A suitable carrier for the practice of the invention has been constructed from nylon. Nylon is a well known polyamide synthetic fiber which has excellent strength and yet is elastic, and it can be woven or otherwise processed into a fabric which is suitable for use as a forming carrier. It will be apparent that other materials, particularly in the synthetic fiber field such as polyester fibers sold under such trademarks as Dacron, acrylic fibers sold under such trademarks as Orion and Dynel, and vinyl derivative fibers sold under such trademarks as Saran may be used in the construction of other suitable forming fabrics or carriers. The mesh or fineness of weave of the forming carrier will depend, as in present papermaking practice, on the particular type and weight of paper to be manufactured.

The foraminous carriers which are employed must be capable of draining water from the web carried thereby at a substantial rate. This distinguishes them from the felts and canvasses which are often used in connection with dewatering a paper web.

For comparative purposes, the top felt of a conventional papermaking machine will drain about 0.01 cubic feet of water per second per square foot under inches Water head. A typical forming carrier or fabric will drain over fifty times as much water, a representative value being .5 cubic foot of water per second per square foot under 10 inches water head.

Suitable carriers may be fabricated in accordance with the disclosure of Holden Patent 2,903,021, granted on September 8, 1959, and assigned to the assignee of the present invention.

The use of a synthetic fiber carrier fabricated from a fiber such as nylon provides substantial advantages over the use of a metallic wire. It avoids the breaking away of the web from the forming carrier as it passes around the

rolls

35 and 39, and also it makes possible passing the web and the

carriers

23 and 33 through pressure nips in a press section prior to the transfer of the web to the drier.

The use of the synthetic fiber carrier also is preferred over the use of felts or canvasses since it minimizes crushing of the web and avoids the problems of filling up the felt during the ejection of moisture with fines and other material. Also, the synthetic fiber carrier provides more efficient water removal than either the felt or metallic Wire.

Travel of the web 29 around the rolls serves to eject moisture from the web as an incident to acceleration of the web in the direction away from the direction of travel of the previous run. During travel along the runs, and especially along the curved paths connecting the runs, the confinement of the web 29 between the

foraminous carriers

23 and 33 serves to prevent disruption of the web. In the apparatus illustrated, moisture is ejected first from one side of the Web and then from the other. In addition, travel of the assembly 36 along the resultant reversely curved paths serves to aid in the expressing of moisture from the web 29 by virtue of the movement of the

forarninous carriers

23 and 33 relative to the ad jacent surfaces of the web thereby creating oppositely directed forces acting along the surfaces of the web.

Moisture which has been expressed from the Web by the acceleration effect, or as a result of the movement of the

foraminous carriers

23 and 33 relative to the surfaces of the web, can be removed from the foraminous carriers overlying the outer or convex face of the assembly 36 during travel along the

curved paths

37 and 43 by the provision of one or more suitably located doctor blades. In this regard two doctor blades 5% are located to bear on the carrier 23 in the area adjacent the first roll 35 so as to remove liquid clinging to the carrier 23 prior to contacting the roll 35 and to remove any such liquid remaining on the surface of the carrier 23 at the end of the curved path 37. In like manner, a doctor blade 6% can be located at the end of the curved path 43 so as to remove liquid from the surface of the carrier 33 as it leaves the roll 39.

Further, substantially increased dewatering can be achieved by subjecting the web 29 during travel along the curved paths 37 and 4-3 to transverse gas flow through the assembly 36, which flow is in the direction of the dewatering or ejecting force created by centrifugal action. In the apparatus of FIGURE 1, two arrangements are shown for achieving a transverse gas flow across the assembly 36, as above described. In one arrangement, the concave face of the assembly 36 is subjected to a positive pressure, i.e., a pressure above atmospheric, as a result of a radially outwardly directed gaseous stream. In the second arrangement, a negative pressure, i.e., a pressure below atmospheric, is established on a convex side of the assembly 36 so as to draw gas radially outwardly through the assembly 36.

Although either arrangement can be associated with either of the first and

second rolls

35 and 39, the employment of a positive pressure in the form of a How of a gaseous medium against the concave side of the assembly 36 is most effectively utilized in connection with the curved path 37 around the first roll 35 because the moisture expressed from the upwardly moving assembly 36 is directed outwardly and downwardly so as to be thereafter carried by gravity away from the assembly 36.

More specifically, the roll 35 is also shown in FIG- URE 2 and is constructed with an outer shell 61 having a smooth, perforated surface which permits the flow of a gaseous medium. In this connection, the outer shell 61 comprises a cylindrical member 62 of suitable material, such as steel, which member includes a generally all-over staggered pattern of closely spaced ports or openings 63.

Pressurized gas is supplied to the ports 63 by suitable means 68 including a pressure box which is suitably connected to a source of pressurized gas and which is fixedly located within the outer shell 61 to direct the fiow of pressure gas toward the concave side of the assembly 36 within the area of the roll 35 engaged by the upwardly curving assembly. The pressure box includes an elongated, generally U-shaped channel 69 which longitudinally extends for the full length of the cylindrical shell 61 along a portion of its inner surface. Suitable sealing means 70 supported on the arm of the U-shaped channel 69 between the channel and the inner surface of the shell 61 prevents escape of the pressurized gas and confines the gas flow to the predetermined area.

In operation, the pressurized gas is discharged through the ports 63 causing gas flow through the assembly 36 and the wet web 29 in the same direction as the dewatering force caused by the rotation of the roll 35 thereby aiding in the reduction of surface tension and the ejection of water. While the construction has been de scribed in connection with a roll, it is equally applicable if a stationary curvilinear member is employed in place of a roll.

In connection with the second roll 39, the establishment of a negative pressure along the convex side of the assembly 36 may be preferred in order to remove the water from the surface of the assembly 36, thereby avoiding return of expressed water into the web 29. In this connection, there is located above the web 33 along the stretch of web which passes over the periphery of the second roll 39 and along the horizontal run 45 leading from the second roll, a series of suction boxes '71 which co-operate with the forces of acceleration to dewater the web and, in addition, to remove the expressed liquid through suitable conduits (not shown) so as to prevent return of the expressed liquid into the assembly 36.

Another embodiment of the apparatus is shown in FIGURE 3. In the apparatus shown in FIGURE 3, a stock suspension of papermaking fibers is discharged from a pressure forming inlet 81 into a web-forming region defined, in part, by a nip of synthetic fiber as previously described.

Trained around the slice roll 85 in position to be overlaid on the exposed surface of the Web 87 formed on the first foraminous carrier 89 is a second forarninous carrier 91 of synthetic fiber. As a result, when the Web 87 leaves the web-forming region, i.e., travels between the nip formed by the breast roll 83 and the slice roll 85, it is confined between the

foraminous carriers

89 and 91. r The pressure forming inlet 81 may be constructed and operated in various ways so long as it serves to deliver a stream of stock suspension of papermaking fibers onto the foraminous carrier 89. In pressure forming arrangements such as shown, where the inlet 81 serves to discharge the stock suspension onto a region of the foraminous carrier 89 trained around the breast roll 83, the breast roll is generally of open vaned construction in order to permit immediate settling of the Web 87 on the foraminous carrier 89. However, if desired, the slice roll 85 can be positioned in spaced relation to the breast roll 83, so as to permit discharge of the stock suspension through a portion of the foraminous carrier 89 extending unsupported between the breast roll and the slice roll. In such cases, a solid breast roll can be employed and the web-forming region can be considered to terminate downstream in the area where the foraminous carrier begins its travel around the slice roll.

Immediately after leaving the web-forming region, the assembly consisting of the two

foraminous carriers

89 and 91 with the web 87 confined therebetween, is trained upwardly and partially around the slice roll 85, consequently undergoing a sharp change in direction along a first, fixed, curved path 93. During travel of the web upwardly along the first, fixed, curved path, the web is protected from disruption by the confining

carriers

89 and 91.

The assembly is trained for travel around a substantial portion of the periphery of the slice roll 85 by means including an elevated, transversely extending roll 95 about which the assembly is also at least partially trained so as to cause travel of the assembly through a second, fixed path 97 which is reversely curved as compared to the first curved path 93 around the slice roll 85. As a result after the web 87 leaves the web-forming region, it is immediately subject to movement along the first, fixed, curved path 93 defined by the slice roll 85 and to an oppositely directed movement along the second, reyersely curved, fixed path 97 defined by the second roll 95. In addition to the dewatering caused by the acceleration from the planes of previous travel, the web is subject to dewatering by reason of the movement of the

foraminous carriers

89 and 91 relative to each other and to the surfaces of the web 87 as the assembly travels along the S-shaped path.

Preferably, the apparatus shown in FIGURE 3 also includes a doctor blade 99 positioned in closely adjacent relation to the travel of the foraminous member 89 in the area of the slice roll 85 so as to aid in the removal of moisture from the assembly. In addition, if desired, one or more doctor blades 100 can also be employed in the region of the reversely curved path 97 around the second roll 95. If desired, one or more suction boxes 101 can also be located in the area around the periphery of the second roll 95 to carry off liquid expressed from the web.

Further, substantially increased dewatering can be obtained during travel of the assembly around the slice roll 85 by employing a pressurized construction such as discussed above in connection with the apparatus shown in FIGURE 1. r

The apparatus shown in FIGURE 3 functions to dewater the web 87 immediately after its passage from the web-forming region by subjecting the liquid in the web to acceleration incident to travel of the web around the slice roll while at the same time protecting the web from injury by confinement between the

foraminous carriers

89 and 91.

Subsequent to passage of the web 87 around the slice roll 85, the web travels through the reversely curved path 97 while continually confined between the

foraminous carriers

89 and 91 so as to be subject to oppositely directed centrifugal action. As pointed out, liquid removal from the assembly can be aided by the use of doctor blades 99 and 100, and suction boxes 101, as well as by the use of a rotating slice roll having a perforated outer shell and means for directing a radially outwardly flow of gas through the porous shell and through the assembly to eject the liquid from the web.

The apparatus shown in FIGURE 4 is illustrative of another type of apparatus adapted for making paper in accordance with the invention. More specifically, the apparatus shown in FIGURE 4 includes a breast roll 111, around which there is trained a first forarninous carrier 113 of synthetic fiber for receiving a stream of a stock suspension of paperrnaking fibers from an upwardly open, generally vertical conduit 115 positioned adjacent the outer side of the breast roll 111 so as to form a wet web 117.

Located adjacent to the breast roll 111 to define, together with the first forarninous carrier 113, the downstream end of the web-forming region is a rotatable slice roll 119. Trained around the slice roll is a second foraminous carrier 121 of synthetic fiber, which is directed onto the exposed surface of the web 117 formed on the first carrier 113.

In a manner substantially the same as that disclosed with respect to the apparatus shown in FIGURE 3, the foraminous carriers 113 and 121, with the web confined therebetween, are trained partially around a substantial portion of the slice roll 119 as the assembly leaves the web-forming region to thereby define a fixed curved path 123. From the slice roll, the web 117 passes, while still confined between the overlying foraminous carriers 113 and 121, around a fixed, reversely curved path defined by a second roll 127 located in generally elevated relation to the slice roll 119.

As in the other embodiments, one or more suitable doctor blades 129 may be positioned in the region of the fixed

curved paths

123 and 125 extending respectively around the slice roll 119 and the second roll 127 to aid in the removal of liquid from the assembly. In addition, a series of suction boxes 131 can be located, if desired, along the convex sides of the path of the assembly to draw liquid radially outwardly from the assembly as the web is subject to dewatering forces during travel of the Web along the curved paths.

As also in the other embodiments, either or both of the slice roll 119 and the second roll 127 may be formed with a perforated out-er surface and means for directing a stream of gas radially outwardly through the web as it travels along the curved paths around the slice roll and the second roll.

The invention disclosed herein provides efiective initial dewatering of the web immediately after the web-forming region by utilizing sharp or rapid directional changes in the travel of the web to create effective dewatering forces and by working the web by virtue of opposed forces operating generally along the opposite surfaces of the web. In addition, the invention provides for the application of a pressure differential from one side of the web to the other side in such manner as to cooperate with the action of the other liquid extracting forces to thereby provide still further increased liquid removal. Moreover, the invention also makes unnecessary transfer of the web from the forming carrier to a felt for passage of the web through the press section and for delivery of the web to the drier.

Various features of the invention are set forth in the following claims.

What is claimed is:

1. In a method of making paper, the steps of forming a wet single ply web of papermaking fibers on a moving, flexible, foraminous, synthetic fiber carrier member, immediately thereafter and closely adjacent the web-forming region, overlying a second flexible, foraminous, synthetic fiber carrier member on said first foraminous carrier memher and above said wet web for movement therewith, the foraminous carrier members and the wet web lying therebetween forming a moving three-ply assembly, rapidly changing the direction of movement of said assembly at a position near the web-forming region by causing said assembly to move along a sharply curved path to thus work said wet web incident to the relative movement between the foraminous carrier members and the wet web as said assembly changes direction, and to simultaneously eject water from the wet web by centrifugal force, thereafter again changing the direction of said assembly by moving said assembly along a reversely curved path to thus further work said Web and eject further water therefrom by centrifugal force, and applying a pressure differential across said assembly as said assembly moves along at least one of said curved paths to aid in the ejection of water from said wet web.

2. Papermaking apparatus comprising a first moving, flexible, foraminous, synthetic fiber carrier member, means for forming a wet single ply web of papermaking fibers on said carrier member, a second flexible, foraminous, synthetic fiber carrier member, means adjacent the web-forming region for overlying said second foraminous carrier member on the exposed face of said web for move ment with said wet web and with said first foraminous carrier member, the first and second foraminous carrier members with the wet web therebetween forming a three-ply moving assembly, a first curved guide means adjacent said web-forming region extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving threeply assembly through a sharply curved path to thereby work said web incident to the relative movement between the flexible, foraminous carrier members and the wet web when said assembly changes direction, and to simultaneously eject water by centrifugal force, a second curved guide means spaced from said first curved guide means and extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving three-ply assembly through a sharply reversely curved path to thus further work said wet web and eject water therefrom by centrifugal force, and means for emitting air in the direction of the centrifugal force through said first and second guide means under said three-ply assembly in the direction of the centrifugal force to aid in the ejection of water from said wet web.

3. Papermaking apparatus comprising a first moving, flexible, foraminous, synthetic fiber carrier member, means for forming a wet single ply web of papermaking fibers on said carrier member, a second flexible, foraminous, synthetic fiber carrier member, means adjacent the webforming region for overlying said second foraminous carrier member on the exposed face of said web for movement with said Wet web and with said first foraminous carrier member, the first and second foraminous carrier members with the wet web therebetween forming a threeply moving assembly, a first guide roll adjacent said webforming region extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving three-ply assembly through a sharply curved path to thereby work said web incident to the relative movement between the flexible, foraminous carrier members and the wet web when said assembly changes direction, and to simultaneously eject water by centrifugal force, a second guide roll extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving three-ply assembly through a sharply reversely curved path to thus further work said wet web and eject water therefrom by centrifugal force, and means for applying a pressure differential in the direction of the centrifugal force across the surface of said first and second guide rolls to further aid in the ejection of water from said wet web.

4. Paperrnaking apparatus comprising a first moving, flexible, foraminous, synthetic fiber carrier member, means for forming a wet single ply web of papermaking fibers on said carrier member, a second flexible, foraminous, synthetic fiber carrier member, means adjacent the webforming region for overlying said second foraminous carrier member on the exposed face of said web for movement with said wet web and with said first foraminous carrier member, the first and second foraminous carrier members with the wet web therebetween forming a three-ply moving assembly, a first perforated guide roll adjacent said web-forming region extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving threeply assembly through a sharply curved path to thereby work said web incident to the relative movement between the flexible, foraminous carrier members and the wet web when said assembly changes direction, and to simultaneously eject water by centrifugal force, a second perforated guide roll extending transversely of the direction of movement of said three-ply assembly and engaging the same for directing said moving three-ply assembly through a sharply reversely curved path to thus further work said wet web and eject water therefrom by centrifugal force, and means for emitting air through the perforated surfaces of said guide rolls in the direction of the centrifugal force to aid further in the ejection of water from said wet web as said assembly passes around said rolls.

References Cited in the file of this patent UNITED STATES PATENTS 1,722,503 Millspaugh July 30, 1929 1,875,075 Mason Aug. 30, 1932 2,903,021 Holden et a1. Sept. 8, 1959 2,969,114 Baxter Jan. 24, 1961 3,056,719 Webster Oct. 2, 1962 FOREIGN PATENTS 4,182 Great Britain 1881 246,048 Great Britain Jan. 21, 1926 813,509 Great Britain May 21, 1959

Claims

1. IN A METHOD OF MAKING PAPER, THE STEPS OF FORMING A WET SINGLE PLY WEB OF PAPERMAKING FIBERS ON A MOVINGFLEXIBLE, FORAMINOUS, SYNETHETIC FIBER CARRIER MEMBER, IMMEDIATELY THEREAFTER AND CLOSELY ADJACENT THE WEB-FORMING REGION, OVERLYING A SECOND FLEXIBLE, FORAMINOUS, SYNTHETIC FIBER CARRIER MEMBER ON SAID FIRST FORAMINOUS CARRIER MEMBER AND ABOVE SAID WET WEB FOR MOVEMENT THERWITH, THE FORAMINOUS CARRIER MEMBERS AND THE WET WEB LYING THEREBETWEEN FORMING A MOVING THREE-PLY ASSEMBLY, RAPIDLY CHANGING THE DIRECTION OF MOVEMENT OF SAID ASSEMBLY AT A POSITION NEAR THE WEB-FORMING REGION BY CAUSING SAID ASSEMBLY TO MOVE ALONG A SHARPLY CURED PATH TO THE WORK SAID WET WEB INCIDENT TO THE RELATIVE MOVEMENT BETWEEN THE FORAMINOUS CARRIER MEMBERS AND THE WET WEB AS SAID ASSEMBLY CHANGES DIRECTION, AND TO SIMULTANEOUSLY EJECT WATER FROM THE WET WEB BY CENTRIFUGAL FORCE, THEREAFTER AGAIN CHANGING THE DIRECTION OF SAID ASSEMBLY BY MOVING SAID ASEMBLY ALONG A REVERSELY CURVED PATH TO THUS FURTHER WORK SAID WEB AND EJECT FURTHER WATER THEREFROM BY CENTRIFUGAL FORCE, AND APPLYING A PRESSURE DIFFERENTIAL ACROSS SAID ASSEMBLY AS SAID ASSEMBLY MOVES ALONG AT LEAST ONE OF SAID CURVED PATHS TO AID IN THE EJECTION OF WATER FROM SAID WET WEB.