US3185617A

US3185617A - Divided press

Info

Publication number: US3185617A
Application number: US250351A
Authority: US
Inventors: Edgar J Justus
Original assignee: Beloit Corp
Current assignee: Beloit Corp
Priority date: 1963-01-09
Filing date: 1963-01-09
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25

Description

E. J. JUSTUS DIVIDED PRESS May 25, 1965 Filed Jan. 9, 1963 i INVENTOR. [dyar' d c/us ras TTORNE YS United States Patent 3,185,617 DIVHDED PRESS Edgar J. Justus, Beloit, Wis, assignor to Beloit Corporation, Beloit, Win, a corporation of Wiscensin Filed Jan. 9, 1963, Ser. No. 250,351 3 Claims. (Cl. 162-274) This invention relates to a paper machine press structure, and more particularly, a divided press structure for a paper making machine.

In the art of paper making it is conventional to form a wet fibrous Web on a suitable forming surface, such as a forming wire or a cylinder mold, and the wet web is then passed from the forming surface through one or more presses by conveying felts for carrying out preliminary dewatering of the web before it is transferred to the heated dryer drum or drums which are ordinarily used to obtain substantially the degree of dryness desired in the final paper product. A number of structures have been proposed for the presses or the so-called press section, and these include suction presses wherein the web is passed through a press nip defined by at least one perforate suction roll which is ordinarily wrapped by a felt. Such presses often mark the web passing through the nip. In a divided press, the press nip receiving the web on a felt is not defined by one or more suction rolls (so as to avoid any marking of the web) and the felt is separated from the web (after it carries" the Web through the press nip) and passed through a felt only press which receives the felt without any web thereon and dewaters the same.

The instant invention relates to an improvement in the press section arrangement, and more particularly to an improvement in divided press structures. In the instant invention a divided press is provided which is composed of only three rolls, as contrasted to a divided press having one press couple defining a press for receiving the felt with the web thereon and a second press couple defining the felt only press (which two press couples involve -a total of four rolls). In the instant invention, the divided press unit comprises a first or middle press roll which defines with a second press roll a nip for receiving the felt with the web thereon. This first press roll also defines a felt only press nip with a third press roll which is a perforate suction press roll. The perforate suction press roll defines the felt only nip with a surface portion of the first press roll that is substantially undeflected or subjected to a minimum central deflection in the direction of such felt only nip. As will be appreciated, the rather substantial length-to-diameter ratio of press rolls in modern-day paper machines results in a tendency for such rolls to have a central downward deflection (of the centroidal axis thereof) by virtue of the weight of the roll itself, which may be referred to as its inherent deflection, and this tendency toward downward deflection is increased if a second press roll is positioned above the first roll and in press nip defining relation therewith. vIn such instance there is a tendency for deflection to occur in a generally downward direction, but not horizontally toward either side of the roll. The instant invention contemplates the positioning of the comparatively more delicate perforate suction roll shell so as to define a felt only press nip along one side of the first roll, so that the suction press roll will not be subjected to the forces resulting in a tendency toward additional downward central deflection because of the first roll.

It is therefore an important object of the instant invention to provide an improved divided press, and an improved press section containing one or more divided presses.

Tis a further object to provide a divided press comprising a first roll, a second roll defining a first press nip with the first roll, a third roll defining a second press nip with one side of the first roll, and a looped traveling felt wrapping the first roll and carrying a web through the first nip, separating from the web at the off-running side of the first nip, and then passing through the second nip without the web to dewater the felt thereat.

Still another object of the instant invention is to provide an improved press section comprising a first three press rolls defining therebetween a felt and web press nip and a felt only press nip, a second three press rolls defining therebetween a felt and web press nip and a felt only pressnip, a pickup felt conveying a wet web received from a forming surface through the first felt and web press nip and then separating from the web and passing through the first felt only press nip to be dewatered, and a press felt conveying the web separated from the pickup felt through the second felt and web press nip and then separating from the web and passing through the second felt only press nip to be dewatered; each of the felt only presses being defined by a press roll within the loop of one of said felts and a perforate suction press roll outside the loop of each of said felts and positioned at least substantially as high as the press roll with which it defines the felt only press nip.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed dislcosure thereof and the drawings attached hereto and made a part hereof.

As shown in the drawing, a fibrous wet web W is formed in conventional manner on a wire 10 passing over a couch roll 11 having a suction area 1111 shown diagrammatically therein. The wire 10 passes over the suction area 11a of the couch roll 11 and then down around a turning roll 12. This provides a downwardly inclined reach 10a of wire from the couch roll 11 to the turning roll 12.

In its more specific aspects, the instant invention relates to a press section indicated generally by the reference numeral 20, which comprises a looped pickup felt 21, a

first suction pickup roll 22, with a suction area indicated diagrammatically at 22a, within the loop of the pickup felt 21 and urging the felt 21 against the wet web W on the downwardly inclined reach 16a of the forming surface or wire 10 to transfer the web W from the reach forming surface 10a to the underside of the reach of pickup felt indicated at 21a. The first divided press indicated generally by the reference numeral 30 is composed of a middle roll 31 that is a press roll within the loop of the pickup felt 21, and a second roll 32 directly beneath the middle roll 31 and outside of the pickup felt loop, which defines with the middle roll 31 a generally horizontal first press nip N1 receiving the reach of pickup felt 21a with the web thereon (on the underside). The first divided press also includes a third roll 33 which is a perforate suction roll mounted directly above the middle roll 31 and defining therewith a generally horizontal first felt only press nip N-Z which receives the pickup felt 21 without the web and dewaters the felt passing through the felt only nip N-Z. The pressure at the felt only nip N-2 is maintained at least as high as the pressure at the felt and web nip N-l so as to satisfactorily effect the required dewatering 0f the felt 21 passing through the felt only nip N-Z.

As is apparent from the drawing, the initial felt reach 21a carrying the web W enters the nip N-1 from the oncoming side thereof and the felt reach 2111 at the off-running side of the nip N-l is separated from the web W and guided by means of a plurality of

guide rolls

22, 23, 24, 25 and 26. The last guide roll 26 guides the reach of felt 21c approaching the felt only nip N-2 at the oncoming side of the nip whereat the felt reach 21c Wraps a suction area shown diagrammatically at 33a in the perforate suction roll 33. The next reach of felt 21d extends from the off-running side of the felt only nip N-2 on toward the suction pickup roll 22. At the off-running side of the felt only nip N-Z there is provided a save-all 34 which is of areaerv 3 conventional structure and indicated diagrammatically to show that it will receive droplets of water retained in the perforations in the perforate shell at the suction area 33a and then thrown out of these perforations by centrifugal force at the off-running region 33b of the perforate shell relative to the nip N-2.

As indicated in the drawing, the centers of each of the

rolls

31, 32 and 33 lie in substantially the same vertical plane P-1 and the nips N-1 and N-2 are substantially normal to the plane P-1 or substantially horizontal. It will be appreciated, however, that although this is a preferred arrangement for the

rolls

31, 32 and 33, particularly suitable results may be obtained if the center lines of the rolls 31 and 32 and the center lines of the

rolls

31 and 33 in each case lie in the same or different planes which are generally upwardly extending at least at an angle of about 45 from the horizontal, so that the

rolls

31, 32 and 33 may be described as generally superimposed, if not vertically aligned. The perforate suction roll 33 is not subjected to any exterior forces applying a downward loading force across the length thereof, which would tend to cause downward loading force across the length thereof, which would tend to cause downward deflection of the perforate shell. The perforate shell for the roll 33 will, of course, tend to deflect downwardly to a slight extent because of its own weight, but this can be readily counteracted or compensated for by either permitting a corresponding deflection along the top of the intermediate roll 31 in the region of the felt only nip N-2, or by the use of known anti-deflection means in the mounting of the roll 31 to substantially eliminate any (downward) deflection across the width of the felt only nip N-Z.

The instant press section also comprises a second divided press indicated generally by the reference numeral which contains a looped press felt 51 having a conventional bottom run with associated guide rolls (not shown). The press 40 is also a three roll press comprising a central press roll 41 within the loop of the press felt 51, and an upper press roll 42 directly above the roll 41 and defining therewith a press nip N3. The press 4t also comprises a suction press roll 43 generally horizontally aligned with the central press roll 41 so as to define an upwardly extending felt only press nip N4.

As shown, the felt 51 is guided by

guide rolls

52, 53, 54 and 55. The guide roll 53 aligns the reach 51a of the felt 51 at the oncoming side of the nip N-3 and the reach 51a receives the web W at the off-running side of the previously mentioned press nip N-1 as the web separates from the oif-running reach 21b of the pickup felt 21 and the off-running side of the bare press roll 32. The web W is conveyed on the top of the oncoming reach felt 51a into the web and felt press nip N-3. At the off-running side of the press nip N-3 the web W is carried away from the off-running felt reach 51b, in this case by virtue of a tendency of the web W to temporarily adhere to the bare surface of the upper press roll 42; and the web then passes on to a conventional dryer arrangement, such as is indicated in part by the first two dryer rolls 61 and 62. The off-running felt reach 51b is guided away from the central roll 41 by the guide roll 54 and is then fed back into the felt only nip N4. At the oncoming side of the felt only nip N-4 the perforate suction roll 43 has a conventional suction gland indicated diagrammatically at 43a, and water droplets drawn into the perforations in the shell of the roll 43 at the suction area 43:: are thrown back out of the shell into a conventional save-all indicated diagrammatically at 44 along the down-running side of the perforate suction roll 43. As shown in the second divided press 40, an alternative felt run 51b around alternative felt rolls 54'a and 54b is useful not only for separating the felt 51'b from the Web W at the off-running side of the nip N3 but also for use as a conveyor of broke when the web breaks at this location. The middle press roll 41 with which the suction roll 43 defines the felt only press nip N-4 is positioned beneath the bare press roll 42, so that as granite rolls or plain rubber covered rolls.

the application of press forces along the nip N-3 will have a tendency to cause a downward deflection in the central or lower press roll 41. As has already been indicated, various known anti-deflection means may be employed for mounting the roll 41, and these might include a centrally positioned backup roll urging against the central part of the roll 41 generally beneath the center line thereof in the region indicated at A, or such anti-deflection mounting means might include known force couple applying means connected to the bearings mounting the stub shafts of the roll for applying a bending force to the roll. Whether or not such means are employed, the tendency toward deflection is generally vertically downward in the central roll 41, and there is not a tendency to deflect the central portion of the roll 41 toward the felt only nip N-4 or against the central portion of the rotary perforate shell of the suction roll 43. In contrast, the suction roll 43 may define a uniform felt only nip N-4 with the central roll 41, such nip N-4 having a substantially uniform pressure across the width thereof and, therefore, having a substantially uniform dewatering effect. Again, the pressure at the nip N-4 is at least as great as the pressure at the nip N3, so that dewatering may take effect.

The

press rolls

41 and 42 may be suitably mounted on pressure loading arms, which are indicated essentially diagrammatically in dotted lines at '70 and for the

rolls

41 and 42, respectively. The journals 41a of the roll 40 may be carried on arms 70 pivotally mounted at 71 and actuated, for example, by air diaphragms 72 for loading the roll 41 against the suction roll 43 to obtain the desired pressure at the felt only nip N-4. Also, the journals 42a of the upper, bare press roll 42 may be carried in arms 80 mounted on fixed pivots 81 and actuated by air diaphragms 32 and $3 for selectively increasing or decreasing the pressure at the nip N-3. Similar conventional nip pressure control mounting means are employed for the press rolls 31 and 32, so that the felt only nip N-2 will be operated at at least as great a nip pressure as the pressure at the nip N-l. The absence of external loads (other than that of the roll 41) applied to the comparatively more delicate and flexible suction roll 43 thus simplifies the operation at the nip N4.

it will be appreciated that the instant invention provides a unique three-roll divided press arrangement for obtaining maximum efliciency and maximum life for the perforate suction roll shells that are employed to engage and dewater the operating surface of the felts at the felt only press. The perforate suction roll shells engage the same side of the felt 21 or 51 with their

suction areas

33a and 43a, respectively, and this is the side of the felt 21 and 51 which is ultimately exposed to the fibrous web at the Web press nips N-1 and N-3, respectively, so that it is this side of the felts 21 and 5-1 which will ordinarily receive fines (e.g. clay, etc.) and fibers which may separate from the web during the treatment thereof. By applying the suction area to this side of the felt 21 or 51, it will be appreciated that such foreign matter accumulating on the felt surface will be most readily removed at the felt only nips N-2 and N4 during the dewatering of the felt thereat. Showers S within the felt loops also assist in this function. The felt 21 and 51 is in each case dewatered to the extent found to be most suitable for transfer of water from the web to the felt at the web press nips -N-1 and N3.

The plain press rolls 32 and 42 to which the web W is actually exposed are preferably bare press rolls such The

middle press rolls

31 and 41 within the loop of the felts 21 and 51, respectively, may be plain rubber covered rolls, or rubber covered rolls with relatively fine porous all It will also be appreciated that in arrangements wherein the rolls 3'1 and 32 or 41 and 42 defining the web nips N-1 or N3 are generally superimposed, the third perforate suction rolls 3 3 or 43 are preferably positioned with their centers at least about as high as the center of the

rolls

41 or 31 with which they define the felt only nips N-2 and N-4, respectively. This results in a minimum effect of a deflection load against the perforate shells for the

suction rolls

33 and 43.

Also referring specifically to the second press 40, it will be noted that the web W is guided from the off-running side of the press roll 32 and onto the oncoming felt reach 51a by the positioning the guide roll 53 at the oncoming side of the nip N-3. At the off-running side of the nip N-3, the dryer 61 also functions as a guide means for the web W and assists (depending to some etxent upon the inherent adherence between the web W and the top bare press roll 42) in directing the web W away from the off-running felt reach 51b. The guide roll 54, likewise, directs the off-running felt reach 51b away from the web (even in situations where the web W has substantially no adherence to the surface of the bare roll press 42).

It will also be appreciated that the first press 30 provides a transfer press nip N-1 which is also a press nip for receiving the pickup felt 2 1 and the web W and transferring the web from the pickup felt to the press felt 51 (through an open draw and by means of the positioning of the guide roll 53) at the oncoming felt reach 51a.

In addition, the centers of the two rolls 4-1 and 42 defining the felt press nip N-3 lie in a given upwardly extending plane P-Z (preferably vertical), so that deflection forces will act primarily in this plane P-2. In the vertical alignment of the plane P-2 the deflection forces caused by the weight of each of the rolls per se will also act in the plane P2, but if the plane P2 is not truly vertical there may be vertically aligned downward forces representing the weights of each of the rolls, coupled with a deflection force generated at the nip N-3 (by the means 70 and 80) which will be aligned substantially in the plane P-2 of the center lines of the rolls. Accordingly, with the principal deflecting forces in alignment with the plane P 2 of the center lines of the

rolls

41 and 42, it is particularly desirable to align the center lines of the

rolls

41 and 43 in a plane P-3 that is substantially normal to the plane P-Z. In this way the principal deflecting force does not act in or against the roll 41 in the direction of the felt only nip N-4. As a matter of practice, the plane P-3 is aligned preferably at approximately 90 to the plane P-2, but advantages of the instant invention may be obtained by aligning the plane P-3 at an angle of 90 plus or minus 30 to the plane P-2, i.e., at substantially 60 to 120 with the plane P-r2.

It will also be appreciated that, if the roll 41 is provided with a porous surface such as a rubber covered surface with a myriad of minute blind holes as shown in U.S.- Patent No. 3,023,805, or a relatively incompressible wire or fabric covering, then there may be some tendency for water to remain temporarily in the porous surface of the roll at the immediate off-running side of both the web nip N-3and the felt only nip N-4. In such instance save-alls 41b and 41c of conventional structure and provided with a close running trailing edge to function generally as a doctor may be used with advantage at the off-running sides of the nips N-3 and N-4, respectively, and such save-alls 41b and 41c are shown generally diagrammatically in the drawing.

The porous surface (if any) on the middle press rolls 31 and 41 is preferably of such fine porosity that there is a minimum shadow marking effect on the web W at the nips N-1 and N-3, respectively (and certainly substantially less than the pattern ordinarily imparted to a web by a felt covered perforate suction roll). Also, this porosity on the middle press rolls 31 and 41 does not extend through the shell or surface covering into the interior of the roll, in that the pores therein are of limited depth 6 (or expressed in other terms, the rolls have a cover closing out fluid penetration to the central portion of the roll, such that the roll may be a plain-surfaced bare roll or one with the limited fine porosity just described).

The cleaning, conditioning and dewatering that is accomplished at the felt only nips N2 and N4 herein involves dewateri-ng to obtain preferably 60 to 70% moisture content on a dry felt weight basis with the best results being obtained at 65%. The use of the (divided) felt only press nip N-Z with the first press nip N-l has distinct advantages. It has now been found that the suction pickup from the wire may be accomplished using much drier felts than heretofore. The felt moisture content may thus be adjusted to optimum conditions (erg. 65% for conventional woven wool felts) for use at the web nip N-1 by adjustment at the felt only nip N-Q. (prior to suction pickup); and the web nip N-1 thus functions not only as a transfer press nip (which ordinarily removes little or no water) but also as a working press nip operating under adjusted predetermined conditions for best Water removal. This is a particular advantage of a divided press arrangement for the first web nip (i.e. N-il).

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. In a paper machine, a first roll, a second roll defining a first press nip with the first roll, a third roll defining a second press nip with one side of the first roll, a looped traveling felt wrapping the first roll and carrying .a web through the fir-st nip, separating from the web and the first roll surface at the off-running side of the first nip, and then passing through the second nip without the web to dewatcr the felt thereat; said third roll being a perforate suction roll having an inherent downward deflection; said first and second rolls being imperforate rolls; and means in control of loading pressures at the first and second nips with said means applying control-led loading to said first nip to impart to said first imperforate roll a deflection in substantial alignment with the aforesaid inherent downward deflection of said suction roll for application of substantially uniform pressures on the felt across said second nip.

2. In a paper machine, a looped traveling press felt, a first roll within the loop of said felt, means depositing a wet web onto the felt and removing the web from the felt, a second press roll defining with the first roll a substantially horizontal first press nip receiving said felt carrying the web thereon, a third perforate suction press roll having an inherent downward deflection and defining with one side of the first roll a felt only upwardly extending press nip receiving said felt without the Web to dewater the felt thereat, means for selectively loading the second press r-oll against the first press roll to align the downward deflection thereof with that of said suction roll to provide a uniform load across the aforesaid felt only nip, and felt guide means separating the felt from the first roll at the off-running side of the first nip and feeding the felt back into the second nip.

3. In a paper machine, a first roll, a second roll defining a first press nip with the first roll, a third roll defining a second press nip with one side of the first roll, the center lines of the first and second rolls lying in an upwardly extending first plane and the center lines of the first and third roll lying in a plane aligned at substantially 60 to with the first plane, and a looped traveling felt wrapping the firs-t roll and carrying a web through the first nip, separating from the web at the off-running side of the first nip, and then passing through the second nip without the web to dewater the felt thereat, said third roll being a perforate suction roll having an inherent deflection, and means in control of the first nip load imparting to said first roll a deflection substantially aligned with said inherent deflection of the aforesaid perforate 7 third roll for efiecting a substantially uniform crossmachine load at said second pres-s nip, thereby aifording substantially uniform dewaterin g and conditioning across the width of the felt passing through said second nip.

References Cited by the Examiner UNITED STATES PATENTS 8 FOREIGN PATENTS 2,768 1897 Great Britain.

15,127 1903 Great Britain. 189,593 10/07 Germany. 680,349 2/40 Germany.

DONALL H. SYLVESTER, Primary Examiner.

MORRIS O. WOLK, Examiner.

Claims

1. IN A PAPER MACHINE, A FIRST ROLL, A SECOND ROLL DEFIN-