US3278368A

US3278368A - Felt and fabric reconditioning method and means for papermaker's fabric press

Info

Publication number: US3278368A
Application number: US299522A
Authority: US
Inventors: Dan B Wicker
Original assignee: Huyck Corp
Current assignee: Huyck Corp
Priority date: 1963-08-02
Filing date: 1963-08-02
Publication date: 1966-10-11
Anticipated expiration: 1983-10-11
Also published as: NL6408711A; GB1037466A; DE1461108A1

Description

Oct. 11, 1966 D. a. WICKER 3,278,368

FELT RIG RECONDITIONING METHOD AND ME PAPERMAKERS FABRIC PRESS Filed Aug. 2, 1965 4 Sheets-Sheet 1 Oct. 11, 1966 D. B. WICKER 3,

FELT AND FABRIC REGONDITIONING METHOD AND MEANS FOR PAPERMAKER'S FABRIC PRESS Filed Aug. 2, 1963 4 Sheets-S w 2 Oct. 11, 1966 D. B. WICKER FELT AND FABRIC RECONDITIONING METHOD AND MEANS FOR PAPERMAKERS FABRIC PRESS 4 Sheets-Sheet 3 Filed Aug. 2, 1965 401* M, W6 D. B. WICKER FELT AND FABRIC RECONDITIONING METHOD AND MEANS FOR PAPERMAKER'S FABRIC PRESS 4 Sheets-Sheet 4 Filed Aug. 2, 1965 3,278,368 FELT AND FABREC RECONDITHONING METHOD AND MEANS FOR PAPERMAKERS FABRIC PRESS Dan l3. Wicker, Loudonville, N.Y., assignor to Huyck Corporation, Stamford, Conn, a corporation of New York Filed Aug. 2, 1963, Ser. No. 299,522 Claims. ((Jl. l62199) This invention relates to an improved method and apparatus for dewatering felts and supporting fabrics used in a papermaking machine, and more particularly relates to the reduction of the water content of the inner fabric of a double fabric press.

This invention is particularly concerned with a double fabric press in which an outer felt is used in conjunction with an inner fabric in transporting a wet web of paper between press rolls.

In forming a continuous web of paper from a pulp slurry, it is usually considered necessary to apply a relatively thick layer of the pulp slurry to a felt while the slurry still has a quite high water content. It may, for example, have a water content of 80-90%, based on the wet weight of the total mixture, at the time it is applied to the first felt in a series of felts normally used in a complete papermaking machine, in the region that is in advance of the point at which the pulp attains the status of a self-sustaining sheet or web. As will be appreciated, the water content of the Wet web of pulp or paper must be transferred to the felt and its supporting fabric, in the early press sections of the machine, in order to bring the consistency of the pulp mixture to the desired point, from the standpoint of its water content, at Which it may be advanced through the final drying stages to make the finished web of paper. As a result of the transfer of the water to the felt and its supporting fabric, particularly in the first press section of the machine, the felt and its supporting fabric reach a relatively high water content in the course of their travel With the paper web, and it is then necessary to remove a substantial part of the water from the felt and its supporting fabric before the latter are again brought into position to receive another portion of the water content of the pulp slurry which is delivered to them.

Various schemes have been suggested heretofore for the purpose of removing water from the felt and its supporting fabric in the course of their advance through a region extending from the point Where they leave the paper web to the point at which they are again brought into the position where they receive another portion of the Wet slurry. Such means have included press rollers between which the felt together with its supporting fabric in the region mentioned have been subjected to a squeezing action to force out a certain part of their water content. In some instances the press used for the purpose has been provided with suction means intended to speed up the removal of water from the felt and its supporting fabric, and also prevent the objectionable accumulation of Water in advance of the nip of the press rollers which has been found to slow down the permissible speed of operation of the machine and to produce objectionable effects upon the Web of paper being formed. However, the various expedients of this character which have heretofore been employed have all been subject to certain objections. They have not made possible any substantial increase in the overall speed of operation of the machine because they have failed to provide the necessary void volume in the felt and its supporting fabric, as they are brought back into 3,278,368 Patented Got. 11, 1966 ice contact with another portion of the web, to enable the felt and its supporting fabric to accept the necessary amount of water from the web for the long sought high speed movement of the latter.

The various methods and means suggested heretofore have all led to certain difficulties which have imposed a definite limitation upon the speed of operation of the machine. One such difficulty has been the accumu lation of excess water at the ingoing side of the nip and this has resulted in diluting of the sheet and crushing. This occurs at relatively slow speeds of operation of the machine, whether the press is a plain press or is provided with a suction roll. The felt, supporting fabric and Web at the mid-point of a suction press are so compressed that the voids in the felt are substantially completely filled, and even excess water may be carried into the nip to force the press rolls somewhat farther apart. The degree of compression in most of the nip region is such as to greatly reduce the porosity of the felt and inhibit the passage of air therethrough under the influence of the suction applied. Attempts have been made to overcome these difficulties, for instance, by the employment of a blind drilled bottom roll in the press. However, none of these schemes have made possible any substantial increase in the speed of operation of the machine Without damage to the paper web. Thus prior efforts to remove water rapidly from the paper, the felt and its supporting fabric have all resulted in objectionable marking of the paper web due to high press roll loadings and the impossibility of preventing more than complete saturation of the felt and its supporting fabric as they are passed, together with the paper Web, through the regular press rollers of the paper machine, With resulting disturbance of the matted relation of the pulp fibers forming the paper due to dislocations arising from the rapidity with which water is caused to exit from the web, both vertically and laterally, on the upstream side of the lower press roller of the machine. Plain presses which have been used up to the present time for squeezing water from the wet paper Web or sheet into the felt and supporting fabric have been found limited to a surface speed of movement of 800-1000 feet per minute in order to avoid difficulties of the character mentioned. A higher speed of movement of the paper web has been attained through the provision of a suction action at the press, but this has also been unduly limited, and it has still left the objectionable effect upon the formation of the desired paper sheet or web when the speed of operation of the machine has been increased to a desired point. One difficulty that has been noted in connection with the provision of the suction means is that a very substantial percentage of the water drawn into the perforations of the roller to which suction is applied will remain in those openings as they pass beyond the suction box, and this water will then be thrown by centrifugal force outwardly from the roller back to the felt or its supporting fabric.

It is an object of this invention to provide a method and apparatus for purging Water from an inner fabric of a double fabric press by use of air at superatmospheric pressures.

A further object of this invention is the provision of a method and apparatus by use of which a travelling inner fabric of a double fabric press may be subjected to a stream or streams of air or gas for a period or periods of time suflicient to achieve useful amounts of dewatering, in accordance with the principles discussed above, and under conditions such that the web will not be disrupted and will not be objectionably marked or crushed.

It is another object of this invention to provide apparatus and methods for purging both the outer felt and inner fabric of a double fabric press by jets of air at superatmospheric pressures.

Other special features of the invention will become apparent as certain specific embodiments of the same are discussed in further detail.

With the foregoing and other purposes of the invention in view, various means and methods of putting into effect the advantageous features above mentioned will now be described in further detail in reference to the accompanying drawings in which:

FIGURE 1 is a schematic view showing one arrangement for purging water from an inner fabric by air under superatmospheric pressure, the means provided for this purpose are shown in relation to the conventional press rolls of a papermaking machine;

FIGURE 2 is a view of the arrangement of the pattern or placement of air jets taken generally along line 22 of FIGURE 1;

FIGURE 3 is a schematic view of another arrangement for purging water from an inner fabric of a double fabric press by air under superatmospheric pressure; the means provided for this purpose are shown in relation to a conventional suction press roll of a papermaking machine;

FIGURE 4 is a schematic view showing another arrangement for purging water from an inner fabric by air under superatmospheric pressure; the means provided for this purpose are shown in relation to a conventional press section of a papermaking machine and further illustrate the use of a concurrent dewatering of the outer felt of a double fabric press; and

FIGURE 5 is a schematic view showing still another arrangement for purging water from an outer felt and inner fabric under superatmospheric pressure; the means provided for this purpose are shown in relation to a suction roll press and with concurrent removal of water by a second purge step.

A primary purpose of the present invention has been to provide an arrangement by which the outer felt and its supporting inner fabric, as they are brought into the regionwhere the receive the paper web from a Fourdrinier wire or the like, have a much lower water content than heretofore. This makes possible the transfer of a higher percentage of water from the paper web into the felt and its supporting fabric before the latter become saturated to the point where water will fiow backwardly around the lower press roll on the upstream side. The present invention has been found to make it possible to operate a papermaking machine at a much higher overall speed without running into the difficulties heretofore encountered through the development of an excess quantity of water in the region of the nip of the press rolls.

The outer felts useful in the practice of this invention include both simplex and duplex felts. A simplex felt is composed of a single layer of felt, or a single layer of fabric which has been fulled. The preferred materials for the outer felt are predominantly natural animal fibers, such as wool. The inner fabric may contain a significant amount of synthetic polymer fibers, such as polyamides, polyesters, and the like. Desirably the synthetic fibers, when used, constitute from about to 100% of the inner fabric, although lesser ratios may 'be used. Synthetic fibers may be blended with wool in the outer felt for durability or stability.

Both the fabrics and felts useful in this invention are capable of retaining water within their structure against the centrifugal forces normally encountered in the press section of papermaking machines. That is, the fabric and felt will receive as much water as in expressed from the paper web in a fabric press, up to about 30 to 70% by weight of the fabric or felt, and will retain a sufficient portion of this water at usual press speeds and felt carrying roll radii. Additional dewatering is required for effective press operations. The felt moisture content at which throwout of water begins, excluding the effect of wet edges, is termed the threshold moisture. Depending on the tightness of weave, material of construction, etc., the felts operable in the practice of this invention have threshold moistures up to about 70% at centrifugal forces about times the force of gravity.

The capability of the fabric or felt to retain water may be due to the tightness of weave and style of weave of the fabric or felt. For instance, a fabric may be formed in a tight weave, such that the interstices between the yarns comprising the fabric are of such small size that the capillary attraction of the woven fabric is sufficient to equal or exceed the centrifugal forces applied. The ability to retain water against centrifugal forces may also be due to the absorptivity of the yarns of which the felt is made. For instance, wool which has a high absorption for water will more easily retain water against the centrifugal forces normally encountered in the press section of papermaking machines.

It has been found highly desirable to effect the purging of the water from the inner fabric by the passage of air or other suitable gas, such as nitrogen, under superatmospheric pressure therethrough, while the inner fabric is separated and moved apart from the outer felt. For example, the outer felt may be made to follow a course passing over a first set of rollers while the inner fabric passes over a second set of rollers running inside the outer felt. In a preferred embodiment the inner fabric passes between a superatmospheric pressure air box and a water receiving box. Air under a desired superatmospheric pressure is constantly fed into the air box through air nozzles. The air from the air box blows through the inner fabric forcing water out of the fabric and into the water receiving box. The water thus purged from the inner fabric is discharged from the water receiving box by any suitable means such as by gravity, a pump, etc.

To bring about the removal of a substantial percentage of the water picked up by the inner fabric as it is squeezed, along with the paper web and outer felt, in passing through a regular press of a papermaking machine, the fabric and felt after being separated from the paper web on the downstream side of the press are separated from each other. Each is separately passed through one or more regions in which its water content is expeditiously and greatly lowered without harmful effects upon its structure. For example, the fabric and the felt are passed through one or more regions in which a blast of air under superatmospheric pressure is forced through successive sections of the fabric or felt as they are being continuously advanced. The arrangement is such that the air under pressure forcibly acts upon the water Within the cavities of their structure, and upon the water coating the fibers and yarns, and urges this water outwardly into a suitable receptacle from which the water may be continuously withdrawn by gravity, positive displacement pump or by an air-water evacuator (suction pump). In one form of the invention the fabric or felt is advanced continuously through one or more regions in which one side is exposed to an air purging device having jets, a slot, or series of slots through which air under superatmospheric pressure may be blown through the fabric or felt. The opposite side of the fabric or felt communicates with a receptacle which is preferably at atmospheric pressure but may be lower, to receive the purged water, the water and air mixture being continuously discharged from the receptacle in order to avoid return of water droplets to the underside of the fabric or felt by reason of turbulence in the receptacle. To produce maximum purging action by the air so blown through the fabric or felt, it has been found highly desirable to have the air at substantially room temperature and not at an elevated temperature. The higher density of the air at lower temperature provides a more effective water purging action. If desired the fabric and felt may be initially air purged prior to separation into individual paths.

To avoid wastage of air and obtain the maximum benefits of the invention most efficiently, it is desirable to confine the air jets to a close packed pattern, such as shown in FIGURE 2, that covers substantially the complete inner fabric across its full width at one time, thus reducing the tendency for water to migrate from an unpurged to a purged section. The linear extent of the air jet region along the inner fabric desirably varies with the thickness of fabric or felt being used, the speed at which the fabric or felt is moving, etc. In any standard equipment of fixed construction, the length of inner fabric travel through which air is delivered is preferably limited to that in which a fabric of maximum thickness will be most economically purged.

Also, to purge water, with a minimum consumption of air, from fabrics of different thicknesses that may be applied to a particular paper machine, it is desirable to construct the air delivering and water receiving boxes to enable their adjustment to extend over different lengths of travel. However, this is not essential and the air delivery box, and the air and water receiving box, may be of fixed dimension and extend over equal areas at opposite sides of the fabric.

The preferred air pressure is between about 4 to p.s.i.g. (pounds per square inch above atmospheric pressure), but higher pressures, up to 100 p.s.i.g. may be used, provided the felt and inner fabric are so supported at the time the air is blown through either of them, that no harm will be done to the felt or inner fabric by the high pressure air.

By an arrangement of the character described, an inner fabric having a water content of say 60 to 75%, wet basis, after separation from the outer felt may be substantially reduced in water content. By percent water content or moisture wet basis is meant the weight of the water in a specimen divided by the total weight of the wet specimen times 100, as determined by the procedure described in ASTM Standards for Textile Materials, Tentative Methods for Quantitative Analysis of Textiles, ASTM designation D629-59T, pages 317-18, 31st Ed., published November, 1960.

It will be understood that the rate of advance of the inner fabric, the pressure of the air which produces the purging action, etc., may be so selected as to achieve maximum economy in the removal of water from the inner fabric. This will make the purging action of air efficient throughout the region specified. If delivery of air is limited to the upstream side there will be no tendency for air to blow freely through channels or passages in the inner fabric that are not filled with water. The high velocity movement of air through the inner fabric after the initial pistorrlike action of the air on the substantially saturated portions of the inner fabric will further decrease the Water content as the air under pressure is delivered to the inner fabric.

To bring about the removal of a substantial amount of water from the inner fabric, the outer felt, or both, by the air purging action, it has been found desirable to subject the inner fabric and outer felt to the action of the air for a substantial fraction of a second. This is in order to achieve an important purpose of the invention, namely the reduction of the water content of the inner fabric and felt to between 10 and 40%, wet basis, before successive proportions are again brought into engagement with the wet paper web. However, one-tenth of a second, or even somewhat less time, is adequate for the purging of a quite substantial amount of water from a wet inner fabric or outer felt.

High speed and eflicient purging will take place if, at the time air under pressure is blown through the inner fabric, the Water in the inner fabric forms a continuous, imperforate film or layer, so that there is no free air passage through the inner fabric. For this purpose the extent of saturation of the inner fabric may be less than complete as it is subjected to the water purging action of air under pressure. To achieve the extent of reduction of water content of the outer felt and inner fabric desired for the primary purpose of the present invention, it is desirable to subject the outer felt and inner fabric to the air purging action while the felt or fabric, or both, are under compression. Some improvement in the extent of water removal by air under pressure is produced by increasing the extent of compression of the felt and inner fabric, but the increase in the rate of water removal after the fabric or felt has been compressed to the extent of about 50% of its normal thickness does not appear to warrant further compression. Thus, compression to the extent of between 30 and 50% is preferred for the purposes of this invention.

It is advantageous to make a preliminary purging of water from the inner fabric and outer felt while they are still juxtaposed. It is also desirable to use a suction roll on the press to remove water at the point prior to further water removal from the fabric or felt or both. In the preferred embodiment where plain press rolls are used the transmission of water through the inner fabric to the press roll is kept to a minimum.

Referring now to FIGURE 1, there is shown a web of paper 10 being delivered from any suitable part of a conventional papermaking machine, such as the Fourdrinier wire or the couch rolls of such a machine, to an outer felt 12 supported by inner fabric 13. The latter may be of any conventional form and will be of the character found preferable for the removal of water from the paper Web, depending on the type of paper being produced. Web 141, outer felt 12, and inner fabric 13 are advanced at a quite rapid rate in the direction indicated by the arrows and passed through the nip of press rolls 14, 16. The press rolls may be of the imperforate type, as shown, adapted to impart simply a squeezing action to the paper web, felt and fabric as they pass through the nip.

After passing through press rolls 14, 16 paper web 10 may be picked up in a conventional manner and delivered to a subsequent portion of the papermaking machine, such as another stage of drying. Outer felt 12 is separated from web 10 and fabric 13, passed around suitable rollers 18 and returned by a predetermined path to transport additional increments of paper webs through the press rolls. Inner fabric 13 is passed through a separate path around suitable rollers 22 and then delivered to the water purging means contemplated by the present invention. The water purging means contemplated by the present invention, as shown, includes a plurality of nozzles 24- which are placed in spaced relation to a water receiving box 26. Inner fabric 13 passes between nozzles 24 and water receiving box 26 in its return path to the nip region of the .press rolls. Water is expelled from the inner fabric by the air streams from nozzles 24l- (as indicated by the arrows) and is blown into Water receiving box 26 from which it drains, or is removed by suction.

As shown in FIGURE 2, air nozzles 24 are mounted on header conduits 27 which may be joined together by connectors 28 to hold the header conduits 27 in spaced relation to each other. The air nozzles 24 are maintained in spaced relation to each other, as shown, providing a maximum coverage of air to the inner fabric.

Throughout the drawings the same numbers are used for similar components.

Turning now to FIGURE 3, the wet web of paper 10 is carried by outer felt 12 and inner fabric 13 between press rolls 14 and 30. After the paper web, outer felt and inner fabric have passed through the nip of the press rolls, the paper web may be picked up in a conventional manner and delivered to a subsequent stage of the papermaking machine.

Inner press roll 30 is a suction press roll and may be perforated, as shown, to aid in the removal of water from the wet paper web, outer felt and inner fabric. Holes 32 extend completely through the press roll throughout its periphery. Suction is applied by drawing a vacuum in the chamber 34 formed with a portion of the inner surface 40 of the press roll by pan 36 and seals 38 between the pan and inner surface 40. Air and water are removed from pan 36 through conduit 42.

Outer felt 12 returns over rolls 18 in its course to the inlet side of the press rolls. Inner fabric 13 is separated from the outer felt and passes around rollers 22. In its return course the inner fabric passes between air box 44 and water receiving box 26. Air box 44 has one continuous outlet 45 along its entire length which is preferably substantially coextensive with the width of the inner fabric being purged. High pressure air is introduced into air box 44 through conduit 46.

Turning now to FIGURE 4, wet paper web is conducted by outer felt 12 supported by inner fabric 13 between press rolls 14, 16. Web 10 is then separated from outer felt 12 and passes on to further stages in the papermaking process.

Outer felt 12 and inner fabric 13 are separated from each other in returning to the press rolls. Inner fabric 13 in its return course passes over rollers 22 and between air box 46 and water receiving box 26. Air box 46 has orifices 48 arranged in the same pattern as air nozzles 24, as shown in FIGURE 2. Superatmospheric pressure air from an external source, not shown, is introduced into air box 46 through conduit 50. The high pressure air purges water from inner fabric 13 and blows the purged water into water receiving box 26, from which it drains, or is removed by suction.

Outer felt 12 in its return course to the inlet side of the press rolls passes over rollers 18 and also passes through apparatus for removing water from the felt. The apparatus is of the type described in copending application, Serial No. 265,827, filed March 18, 1963. If desired, two or more units of the apparatus may be used in series. The air purging means, as shown, includes a drum or cylinder 52 which is held stationary. Drum 52 is connected at one end to conduit 54 through which superatmospheric pressure air is introduced from a source not shown. The periphery of drum 52 is provided with slot 56 which extends substantially across the width of felt 12. The latter is held upwardly against drum 52 in the region of slot 56 by means of cylinders or

rods

58, 60. These cylinders or rods are adapted to retain the felt firmly against the outer periphery of the drum 52 at each side of slot 56 and thus provide an effective seal in the region of slot 56 through which air under pressure is being blown. Suitable sealing means may also be provided adjacent the side edges of the felt to eliminate any tendency of the air under pressure to escape in the lateral direction. Such edge sealing means may be of the same general character as the cylinders or

rods

58, 60. All of these sealing means may be formed of a material which is wear resistant, and which at the same time will not wear out the surface of the felt as the latter is being passed at high speed through the purging region. Suitable materials for this purpose are synthetic plastics, such as Teflon, which is a polymer of tetrafiuoroethylene, or Rulan, which is a polyethylene resin.

It will be noted that the surface of felt 12 which is in contact with the paper web at the nip of the press rolls 14, 16 will be at the underside of the passage between drum 52 and

cylinders

58, 60. This is desirable, because any impurities or particles picked up from the paper web at the press rolls will then be expelled downwardly into a suitable receptacle 62 as the air under pressure within the drum 52 forces the water from the felt with a piston-like action.

In some instances where the speed at which the felt must be advanced is quite high, in order to keep up with the high speed operation of the paper machine, it may be found desirable to support the felt by a strong porous fabric or wire belt in the regions of the purging drum 52. This will permit the provision of circumferentially wide slots 56 which may suitably be subdivided into a number of sections, arranged as shown in FIGURE 2, and will also permit the use of air under relatively higher pressures. Such a belt 66 will assist in holding felt 12 firmly against drum 52 in the region of slot 56 and thus prevent bulging which might occur if the slot is of substantial width and the air pressure is high. Also, belt 66 will assist in maintaining the desired effective seal around air delivering slot 56. As shown in FIGURE 4, belt 66 is supported by idler rollers 68, and by drive roller 69 which may be driven to cause the upper course of the belt to travel in the same direction and at the same speed as the cooperating portion of the felt. By applying an appropriate tension to belt 66, and with the aid of cylinders or

rods

58, 60, a compressing or squeezing action may be imparted to felt 12 in the region of slot 56.

Turning now to FIGURE 5, there is shown an embodiment of this invention in which the transporting fabric and felt are above the web in their passage between the press rolls. Paper web 10 engages felt 12 which is supported by inner fabric 13 and passes between press rolls 14 and 38. After passage between the press rolls, the paper web is separated and passes on to other operations in the papermaking process. As shown, press roll 30 is a suction press roll of the type described above under FIGURE 3. Outer felt 12 and inner fabric 13 are not separated from each other immediately but pass together around roll 70 and through air purging apparatus. The air purging apparatus is the same as described above with regard to FIGURE 4, except that the transporting belt 66 is not used. Rather inner fabric 13 acts much as the belt 66 in the embodiment described above with regard to FIGURE 4.

After passing through the first stage of air purging, the outer felt is separated from the inner fabric and passes around rollers 18 in returning to the inlet side of the press rolls. The inner fabric 13 passes around rollers 22 in returning to the inlet side of the press rolls. The inner fabric 13 also passes between air box 46 and water receiving box 26 which act in the manner described above to purge water from inner fabric 13.

It will be clear from the foregoing that the employment of the present invention makes possible the great reduction in the water content of the outer felt and inner fabric between the time they have separated from the paper web until they are brought back into contact with the latter. This in turn makes possible the removal of a greater amount of water from the paper web than is possible by arrangements previously used or suggested. As a result of this the drying portion of a paper machine may be reduced in size as compared with that found necessary at the present time. Also the present invention makes possible higher speed operations of a papermaking machine.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. A method for removing increased amounts of water from a wet paper web in a double fabric press of a papermaking machine in which the wet web is transported between the press rolls by an outer felt and an inner fabric comprising separating the outer felt and inner fabric, passing said outer felt and inner fabric through separate paths back to the nip region of the press rolls, blowing jets of air at superatmospheric pressure through said inner fabric whereby water is purged from said fabric; compressing said outer felt, and substantially simultaneously blowing streams of air at Superatmospheric pressure through said outer felt at the point where the felt is compressed whereby water is removed from said felt.

2. Apparatus for drying successive portions of an inner fabric of a double fabric press in a papermaking machine in which a wet paper web is transported between press rolls on an outer felt supported by an inner fabric comprising means to direct the outer felt and inner fabric along separate paths in returning them to the inlet side of the press rolls, means having a plurality of discharge outlets for directing streams of gas under substantial superatmospheric pressure through successive portions of said inner fabric, means having a plurality of discharge outlets for directing streams of gas under substantial superatmospheric pressure through successive portions of said outer felt, and means for compressing said outer felt simultaneously with the direction of streams of gas at superatmospheric pressure through said outer felt, whereby water is removed from said inner fabric and from said outer felt.

3. In a papermaking machine the combination of an endless outer felt of porous material and an endless inner fabric of porous material having airand water-permeable openings therethrough, means for driving said outer felt and said inner fabric through an endless path at the linear speed at which a web of paper is being manufactured in said machine, said endless path of said inner fabric including a portion in which said inner fabric runs apart from said outer felt, means positioned in said portion of said endless path of said inner fabric defining an orifice, means for supplying gas at substantial superatmospheric pressure through said orifice for passage through the thickness of said inner fabric to dislodge water from said inner fabric and discharge said dislodged water from said opposite surface of said inner fabric; means having a discharge outlet for directing gas under substantial superatmospheric pressure through successive portions of said outer felt, and means for firmly retaining the successive portions of said outer felt against all portions of the periphery of said discharge outlet to provide an effective seal against the discharge of air along the surface of said outer felt.

4. In a papermaking machine, apparatus for dewatering an outer felt and in inner fabric of porous material having airand water-permeable openings therethrough, comprising means for driving said outer felt and said inner fabric through endless paths at the linear speed at which a web of paper is being manufactured in the papermaking machine, said endless path of said outer felt and inner fabric including a first portion in which said outer felt and said inner fabric run adjacent to each other with one surface of each in contact with one surface of the other, a second portion in which said outer felt runs apart from said inner fabric, and a third portion in which said inner fabric runs apart from said outer felt, a suction roll adjacent said inner fabric in said first portion, means for drying successive portions of said outer felt and said inner fabric in said first portion, a discharge outlet for directing gas under substantial superatmospheric pressure through suc cessive segments of said outer felt and inner fabric, said inner fabric firmly retaining the successive portions of said outer felt against all segments of the periphery of said discharge outlet to provide an effective seal against the discharge of gas along the surface of said outer felt; means positioned in said third portion of said endless path defining an orifice, and means for supplying gas at substantial superatmospheric pressure through said orifice for passage through the thickness of said inner fabric to dislodge water from said inner fabric and to discharge said dislodged water.

5. Apparatus according to claim 4 wherein each of said outer felt and inner fabric has a threshold moisture up to about 70% by weight thereof at centrifugal forces about 85 times the force of gravity.

References Cited by the Examiner UNITED STATES PATENTS 2,903,021 9/1959 Holden et al.

3,013,938 12/1961 Justus et al 162279 3,093,535 6/1963 Brauns et al 162358 FOREIGN PATENTS 1,198,432 6/1959 France.

DONALL H. SYLVESTER, Primary Examiner.

JOHN H. NEWSOME, Assistant Examiner.

Claims

1. A METHOD FOR REMOVING INCREASED AMOUNTS OF WATER FROM A WET PAPER WEB IN A DOUBLE FABRIC PRESS OF A PAPERMAKING MACHINE IN WHICH THE WET WEB IS TRANSPORTED BETWEEN THE PRESS ROLLS BY AN OUTER FELT AND AN INNER FABRIC COMPRISING SEPARATING THE OUTER FELT AND INNER FABRIC, PASSING SAID OUTER FELT AND INNER FABRIC THROUGH SEPARATE PATHS BACK TO THE NIP REGION OF THE PRESS ROLLS, BLOWING JETS OF AIR AT SUPREATMOSPHERIC PRESSURE THROUGH SAID INNER FABRIC WHEREBY WATER IS PURGED FROM SAID FABRIC; COMPRESSING SAID OUTER FELT, AND SUBSTANTIALLY SIMULTANEOUSLY BBLOWING STREAMS OF AIR AT SUPERATMOSPHERIC PRESSURE THROUGH SAID OUTER FELT AT THE POINT WHERE THE FELT IS COMPRESSED WHEREBY WATER IS REMOVED FROM SAID FELT.

2. APPARATUS FOR DRYING SUCCESSIVE PORTIONS OF AN INNER FABBRIC OF A DOUBLE FABRIC PRESS IN A PAPERMAKING MACHINE IN WHICH A WET PAPER WEB IS TRANSPORTED BETWEEN PRESS ROLLS ON AN OUTER FELT SUPPORTED BY AN INNER FABRIC COM-