US3285806A - Web transfer assembly for a papermaking machine - Google Patents

Description

Nov. 15, 1966 E. J. JUSTUS ETAL 3,285,806

WEB TRANSFER ASSEMBLY FOR A PAPERMAKING MACHINE Filed 001 17, 1963 4 Sheets-Sheet 1 1 N 41 R 3 x \R INVENTOR.

a, $9., k wmmrmsys Nov. 15, 1966 J, us L s L, 3,285,806

WEB TRANSFER ASSEMBLY FOR A PAPERMAKING MACHINE Filed Oct. 17, 1965 4 Sheets-Sheet 2 Era //4 fig Z PRIOR A27 g a b b gag (K475 2 26 in 3917/746 6. 5%0/75/7 TTOR NE YS Nov. 15, 1966 J. JUSTUS ETAL WEB TRANSFER ASSEMBLY FOR A PAPERMAKING MACHINE 4 Sheets$heet Filed Oct. 1'7, 1963 aqwh INVENTOR. i afg'ar (f zfazzzs' flex/114;? C. (2 0/14 wwwbzwwmws vN 15, 1966 E. J. JUSTUSETAL v 3,285,806

WEB TRANSFER ASSEMBLY FOR A PAPERMAKING MACHINE Filed Oct. 17, 1965 4 Sheets-Sheet 4 INVENTOR.

fima'sv C (Ia/7422 ATTORNEYS United States Patent 3,285,806 WEB TRANSFER ASSEMBLY FOR A PAPERMAKING MACHINE Edgar J. Justus and Dennis C. Cronin, Beloit, Wis., as-

signors to Beloit Corporation, Beloit, Wis., a corporation of Wisconsin Filed Oct. 17, 1963, Ser. No. 317,024 7 Claims. (Cl. 162-306) The present invention relates to an improvement in devices for removing liquid from a liquid-containing web material, and more particularly to an improved couch assembly for use in paper making machinery.

Although the instant invention may have a number of uses in different fields, it is used to particular advantage in the art of paper making and will be described primarily in connection therewith. In the Fourdrinier-type paper making machine the stock or dilute suspension of fibers is fed onto a traveling forming wire at one end of a generally planar reach and as the wire moves forward (i.e. longitudinally) water passes through the wire and the fibers retained on the upper surface of the wire form what is generally referred to in the art as a moist paper web. As this moist paper web moves forward further on the forming wire, further dewatering thereof is usually carried out next with the so-called suction boxes, which are devices for creating subatmospheric pressure beneath the forming wire and thereby causing a pressure differential across the moist web on the forming wire to effect dewatering of the moist web. Next, the web traveling on the forming Wire reaches what is known as the couch roll, which i the roll supporting the wire at the longitudinal end of the upper reach on which the web has been formed and partially dewatered. Often a turning roll is employed in conjunction with the couch roll and the forming wire itself will be reversed in direction either at the couch roll or the turning roll. In some machines the web is removed from the forming wire at the reach between the couch roll and the turning roll, but any device such as a felt covered suction pickup roll or the like urged against the web on the wire run between these rolls can employ only a nominal amount of pressure and if the water film on the underside of the wire is retained or is even increased by a moderate pressing action, it will be found that the web is not easily removed from this reach of forming wire and operating diffioulties are encountered.

In the practice of the instant invention, however, the pickup of the moist web from the forming wire is accomplished at a nip between a felt covered device such as a pickup roll and the couch roll itself. Ordinarily, the couch roll is a perforate suction roll of large 'but otherwise conventional suction roll structure with the expensive auxiliary equipment characteristic of suction rolls, and any nip load at the couch has a number of operating hazards, which include the possibility of damage to the very expensive suction couch roll. Also, any nip load coupled with the pressuredifferential created by the suction area in the suction couch rol-l will tend to drive the web into the interstices of the screen-like forming wire and removal of the web from the forming wire is thus made more difficult, even if some dewatering is effected.

One important advantage of the instant invention resides in the fact that a perforate suction couch roll is not employed and, instead, a sturdy, durable couch roll is employed with an unusual surface structure of alternating generally circumferential grooves and lands which carries out a number of unique functions with respect to the operation of the instant device. In fact, the instant device will ordinarily involve a transfer type of mechanism which will be a felt covered plain or suction roll or a felt covered series of inverted suction boxes, or some 3,285,806 Patented Nov. 15, 1966 similar device which will actually exert nominal pressure against the web carried on the forming wire by the grooved couch roll of the invention, but will not tend to drive the web fibers into the forming wire (nor will there be a suction within the grooved couch roll to effectively draw loose Web fibers into the interstices of the wire), and this transfer mechanism will then carry the moist delicate web on the underside of 'a pickup felt to a second, i.e. transfer nip where the web is transferred from the pickup felt to a second carrier medium, usually another felt, and at such transfer nip another grooved roll is preferably employed for again accomplishing additional dewatering of the web while simultaneously effecting such transfer.

The instant grooved rolls have a number of operating advantages including their very simple sturdy structure, the economical operation thereof and the inexpensive original cost thereof. Maintenance costs are extremely nominal in connection with such grooved rolls also.

It is, therefore, an important object of the instant invention to provide an improved couch assembly.

It is a further object of the instant invention to provide an improved couch assembly wherein a moist web is transferred from a Fourdrinier-type wire to the press section by means which include a device for partial dewatering of the web in cooperation with a grooved couch roll and preferably additional partial dewatering of the web in cooperation with a grooved roll at a transfer 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 disclosure thereof and the drawings attached thereto and made a part hereof.

On the drawings:

FIGURE 1 is a couch and press assembly embodying the instant invention shown in generally diagrammatic side elevation view;

FIGURE 1A is a fragmentary sectional detail view taken substantially along the line AA of FIGURE 1;

FIGURE 2 is a fragmentary detail sectional view of a prior art suction roll nip;

FIGURE 3 is a view comparable to that of FIGURE 2, but showing still another prior art nip structure in fragmentary detail view, in this case employing blind drilled holes in one roll, as used in the prior art;

FIGURE 4 is a view comparable to FIGURES 2 and 3, but showing a portion of a grooved press nip taken substantially along the line IV-IV of FIGURE 1;

FIGURE 4A is a fragmentary detail sectional elevational view taken substantially along the line A-A of FIGURE 4;

FIGURE 5 is a view comparable to FIGURE 4A, but taken substantially along the line VV of FIGURE 1 showing another grooved press nip employed in the practice of the invention;

FIGURE 5A is a fragmentary enlargement taken from the encircled portion marked VA of FIGURE 5;

FIGURE 6 is a view comparable to FIGURES 4A and 5, but taken substantially along the line VIVI of FIGURE 1;

FIGURE 7 is a view comparable to FIGURES 4A, 5, and 6, but taken substantially along the line VII--VII of FIGURE 1;

FIGURE 7A is a view comparable to FIGURES 4A, 5, 6 and 7, but taken substantially along the line AA of FIGURE 9; and

FIGURES 8 through 11 hereof are essentially diagrammatic side elevational views of different embodiments of the instant invention.

As shown on the drawings:

In FIGURE 1, it will be seen that there is shown a couch assembly, which includes a partial showing of a forming wire F-l looped around a grooved couch roll 13 and reversed in its travel about a turning roll 8. It will be seen that there is a forward reach FR-1 of the forming wire extending from the couch station, at a nip designated N11 to the turning roll 8, but in the embodiment of FIGURE 1 the web W-1 carried on the forming wire F-1 is not removed from the forming wire F-1 at the aforesaid forming wire reach FR1 and is instead removed from the forming wire F1 at the couch station, which is here designated generally by the nip N-11 formed between the wire wrapped grooved roll 13 and a felt wrapped plain roll 12. For better control of water movement which is quite substantial in the area of the nip N-11, it will be seen that a guard sheet g is positioned in close-running relation to the off-running side of the nip N-11 between the forming wire reach FR-l and the felt 11 wrapping the pickup roll 12, so that water thrown from either of the rolls 12 or 13 will have its movement controlled by the guard sheet g, which is merely a sheet metal element typical in general structure of the usual saveall structure, but which will be used primarily to prevent undesirable throwing of water from the forming wire F-1 to the moist web W-1 at the underside of the felt covered roll 12 and vice versa.

It will be appreciated that the forming wire F-l as Well as its forward reach FR1 is all part of a continuous woven looped metal screen-like material of conventional structure for the Fourdrinier forming wire and this material does have a substantial amount of open area (being indicated in the sectional view of FIGURE 7 merely as -a screen F-l); whereas the pickup felt 11 is a relatively close-weave felt wrapping a plain roll 12 so that ambient atmosphere may not easily reach the back side of the felt 11 and this will then create a slight vacuum or subat'mospheric pressure in the felt 11 as it expands leaving the nip N-11 and such reduced pressure will tend to cause the web W-1 to adhere to the underside of the felt 11 wrapping the pickup roll 12.

Next, the web W-1 is carried on the underside of the felt 11 a very short distance to the transfer nip N-12 which is defined by the pickup roll 12 wrapped by the felt 11 and a second grooved roll 14 wrapped by a press felt 23. In general, transfer of a web from one felt 11 to another felt 23 is ordinarily accomplished by the use of less openness or a closer weave in the felt to which it is desired to have the web W-l adhere and a relatively open weave in the felt 11 which is intended to release the web W1 by virtue of ambient atmosphere entering the back side of the felt 11 at A-11 in FIG- URE 1 so as to break the internal vacuum or subatmospheric pressure in the felt 11 at the off-running side of the nip N-12.

It has already been explained, however, that the felt 11 is preferably a fairly closely-woven felt itself so that it will satisfactorily effect the transfer of the web W1 from the wire F-l at the couch station N-11. In addition, the roll 14 is a grooved roll being provided with a structure comparable to the grooved couch roll 13 in that it has a surface of generally alternating, substantially circumferentially aligned grooves and ridges, with the grooves, indicated at 140 in FIGURE 6 being effectively vented to ambient atmosphere at both the oncoming and off-running sides of the nip N-12. In the particular arrangement, however, the off-running felt run 11R of the pickup felt is exposed to ambient atmosphere at its back side A-11 shortly after it leaves the transfer nip N-12 and using felts 11 and 23 of substantially comparable weave and openness, the alignment of the felt run 11R will be suflicient to cause the web W-l to transfer to the lower felt 23 which is actually still wrapping the grooved roll 14 at the off-running side of the nip N-12 opposite the air exposed area A-11 for the off-running felt run 11R.

The web W-1 then continues on the press felt 23 into a first press nip N-13 defined between an upper plain roll 21 and a lower grooved roll 22, where substantial dewatering of the web W1 is effected and the web then continues at the off-running side of the nip N-13 on top of the felt 23. It will be noted that in the case of an upper granite roll 21 or Microrok roll 21, there may be a tendency for the web W1 to adhere momentarily to the uprunning side of the roll 21 and it might then travel in the direction indicated in the dashed lines marked W1 or might merely lift slightly with the uprunning side of the roll 21 and drop back down onto the felt 23. In any event, substantial dewatering is accomplished at the first press nip N-13 and the felt 23 then continues around guide rolls 23a, 23b and 230 through a felt only nip N-14l defined between an upper plain roll within the loop of the felt 23 and a lower grooved roll 15 outside the loop of the felt 23 for acting upon the operating or outer peripheral surface of the felt 23 to dewater, clean and recondition the same in preparation for the transfer function at the nip N-12. It will be seen from FIGURE 1A that the grooved roll 15 is provided with a simple groove structure with alternating generally circumferential grooves 150 and lands 15b of substantially equal axial dimensions indicated at x-l and y-l in FIGURE 4A, which is actually a fragmentary section of the nip area N-14 between the grooved roll 15 and the plain roll 16.

The pickup felt 11, separates from the web W1 at the off-running run 11R and then passes around conventional guide and tensioning felt rolls 11b, 11c, 11d and 11a, in that order and back to the couch station or nip N-11. At the oncoming side of the couch station or nip N-11,

however, there is a separate felt only nip N15 defined by a plain roll 16a within the loop of the felt 11 and a grooved roll 16b outside the loop of the felt 11 for purposes of acting upon the outer peripheral or operating face of the felt 11 to dewater, recondition and clean the same. The structure of the grooved roll 15a and the plain roll 16a is substantially the same as the structures of the grooved roll 15 and the plain roll 16 hereinbefore described except that the nip N-15 is reversed with respect to the positions of the two rolls 15a, 16a.

The function of grooved rolls of the general structure of the roll 15 in a felt only press is described in considerable detail in the previously filed application of Edgar I. Justus, Serial No. 258,391, filed February 14, 1963, which is a continuation in part of E. J. Justus application Serial No. 214,589, filed August 3, 1962, both of which are now abandoned and both of which disclosures are incorporated herein by reference for purposes of simplifying the present disclosure.

In said application Serial No. 258,391, it is pointed out that preferably the lands and grooves are not substantially equal in axial dimension, but instead as indicated in FIG- URES 5 and 5A hereof (which show fragmentary details of the nip N-13 of FIGURE 1 hereof), the grooves 220 have a relatively small axial dimension x2 whereas the lands 22b in grooved rolls of the invention such as the roll 22 have an axial dimension 3 -2 that is preferably at least about three times the width of the groove mouth x-2 and may be as much as twenty times. In any event, the land width, indicated generally as y, is preferably significantly greater than the groove mouth width, indicated generally as x herein, or reasons which are discussed in considerable detail in said application Serial No. 258,391 and will be only in part repeated herein for purposes of simplifying the instant disclosure.

Considering again the felt only presses N-14 and N15 shown herein, it will be appreciated that no web passes through these two press nips N14, N-15 and only the felts 23 and 11, respectively, pass through these nips and the felts are dewatered at the nips and reconditioned by the application of nip pressures, per lineal inch, that are at least as great as and generally some 50 to pounds greater than the corresponding web-receiving nip pressures per lineal inch (i.e. the nip pressure for the nip N-lS-is greater than the nip pressures at N-11 and N-12, both of which receive the web W1); and the nip pressure at N14 is about 50 pounds greater than the nip pressure of approximately 200 pounds at the first web press N-13 in the cycles of the press felt 23, as well as being substantially greater than the relatively lower nip pressure at the transfer nip N-12, which pressure may be about 100 pounds per lineal inch.

It will further be noted that double-headed arrows are shown centered on certain of the rolls indicated diagrammatically in FIGURE 1 and in other views hereof, and these double-headed arrows are symbols indicating to the skilled worker in the art that the rolls involved are mounted on known anti-deflection means, such as are shown in a number of recently issued patents to Edgar I. Justus, and such double-headed arrows also indicate fluid actuated moving and loading means for mounting the aforesaid rolls to move the same into position and to load the nips to the desired, controlled extend found to be most satisfactory. Although the grooved rolls of the invention are defined by a grooved cover (usually a solid elastomer cover) on an imperforate ductile iron shell (indicated fragmentarily at 15x, 22x, 14x and 13x in FIGURES 4A, 5, 6 and 7, respectively), the grooved rolls have groove openings therein on the surface thereof, but they are in fact mounted on imperforate shells and may thus be readily mounted on the known anti-deflection mounting means and to the extent that these rolls lend themselves readily to use in anti-deflection mounting means, such anti-deflection mounting means are a part of the invention, although the mounting means per se form the subject matter of a separate, distinct and earlier invention made by Edgar J Justus.

Referring again to the felt only press nips N-14 and N15, it will be appreciated that the grooved rolls 15 and 15a, in each case, are mounted within saveall structures m which are per se sheet metal structures that are designed to conform to the shapes and sizes desired, but which are used to particular advantage herein because they provide protection to minimize water movement between the off-running felt 11 or 23 from the nips N-15 and N-14 and they also mount conventional doctors d at the oncoming side of the nips N-14, N-15 to dry the lands and further they are provided with pumping type wipers w which tend to suck or pump water out of the grooves of the rolls at locations remote from the nip areas N-14 and N-15 to assist in cleaning and dewatering the grooves of the rolls 15, 15a. In this manner, water is removed from the felts 11 and 23 and such felts are reconditioned for their other uses within the travel of the felt loops, which will be described hereinafter.

Briefly, for consideration of the theoretical aspects and principles here involved, reference should be made to certain prior art press nip theories, Which are represented in FIGURES 2 and 3 hereof. It will be appreciated that grooved rolls in the art of pressing paper were considered and discarded several generations agov For example, as early as 1915, US. Patent No. 1,123,388 issued to Schaaning and was directed to a grooved press roll allegedly intended to replace felt covered rolls and having grooves of such configuration that Schanning alleged that they would retain water by capillary action. Various other grooved roll structures have been disclosed from time to time, but in the early 1920s it was found that the suction press roll was distinctly superior to any such grooved rolls known in general performance and since that time and up to the present day, suction rolls have been used commercially. Referring to FIGURE 2, in the suction press nip N-4, the roll shell 31 is a perforate shell, being provided with a multiplicity of holes 32, 32 of substantial size (i.e. at least about A inch in diameter and usually having flared peripheral mouths 32a of greater size) which are drilled entirely through the roll shell 31 (having at least about 1 inch thickness) to communicate with the suction gland G extending the full width of the roll shell 31 iuteriorly opposite the nip N-4. At the suction press nip N-4, a press felt 33 is interposed between the web W2 and the perforate suction roll shell 31 (primarily as a water-permeable protective layer for the web W-Z), and water expressed from the web W-2 passes completely through the felt 33 and into these holes 32, 32 in the perforate shell 31. Some water continues into the glands G and some is usually retained in these holes 32, 32 at the off-running side of the nip N4, where the subatmospheric pressure in the gland 6 tends to counteract centrifugal forces, and the subatmospheric pressures created within the expanding felt, both of which tend to urge water back out of the holes 32, 32 and into the felt 33 under conditions of ambient atmospheric pressure.

Because of the suction gland G the felt 33 may thus remain in contact with the Web W-2 at such off-running side of the nip N4 without substantial rewetting of the web W-2 (via water drawn back into the felt 33 from the suction roll holes 32, 32). Also, savealls (not shown) are conventionally positioned between the felt 33 and the perforate roll shell 31 at the immediate off-running side of the gland G to catch droplets released from the suction roll holes 32, 32 particularly after these holes pass beyond the limit (i.e. the off-running seal not shown) of the interior suction gland G so there is no longer a pressure differential holding the droplets in the holes 32, 32. The off-running felt 31 must be guided to avoid such saveall and this often results in guiding the felt with or against the web at the off-running side of the nip N-4 and the perforate suction roll with its suction gland 6,, with or without the saveall, thus functions to carry away substantially all of the water expressed from the web at the nip.

In spite of the excellence of the performance of perforate suction rolls for a number of uses in paper making, it must be conceded that these rolls and their auxiliary equipment are expensive to manufacture, maintain and use. The suction gland therein, also, substantially precludes the use of conventional anti-deflection roll structures for greater versatility and uniformity in nip pressure control. In addition the substantial size of the perforation mouths 32, coupled with the pressure differential created by the suction gland G against the unsupported portions of the felt 33 opposite such perforations 32, has a tendency to cause shadow marking of the web in certain instances.

Only in recent times, after many years of commercial use of perforate suction rolls, there has been developed what is known as the divided press type of structure which does not require the use of the perforate suction roll at the web press. In the divided press, the felt alone is cleaned, dewatered and conditioned at a separate press nip, and then fed with the moist web into what is called the web press nip which is defined between rolls having imperforate shells (as contrasted to the perforate suction roll shells). As indicated in FIGURE 3, ordinarily the amount of water load at such web nip N-S is such that at least one of the press rolls 35, 35a is provided with recesses 36 on the surface thereof to temporarily take the load of water entering the nip N-S to prevent crushing of the web W-3 carried by the felt 37. As indicated in FIGURE 3, a preferred form of such recesses 36 is provided by a rubber cover on a press roll 35 that contains a myriad of comparatively fine blind drilled holes (i.e. approximately to 4 inch or even less diameter, as in the case of Walker US. Patent No. 3,023,805); and such fine holes 36, 36 will in the case of most conventional webs W3 and felts 37 substantially avoid or eliminate not only shadow marking characteristic of the performance of certain perforate suction rolls, but also crushing which would occur if there were no place for the excess water load to goat the nip N-5. In

essence, the term crushing is used in the art to explain what is evidenced by minor fractures in the web resulting from excessive water flow in any local area in the plane of the web W-3, for example, by virtue of too much water coming into the nip and this in turn is evidenced by a buildup of a puddle of water at the on-coming side of the nip which shows that so much water is trying to enter the nip N-3 that this water is actually being pressed out of the nip but in flow directed backwardly or back into the web W-3 and/ or felt 37 to such an extent that an undesirable damage to the web structure results and this is called crushing, which is a problem that will be explained in greater detail hereinafter.

In the embodiment of FIGURE 3, it is desired to avoid crushing by driving this excess water into the blind holes in a direction generally normal to rather than within the plane of the web W-3 at the nip N5. Excess water at the nip N which is driven into the blind holes perforations 36, 36 to relieve the load at the nip N-5, however, ordinarily entraps a certain amount of air in the bottom of these blind perforations 35, 36 and this coupled with the ability of the felt to absorb water when it expands at the off-running side of the nip N-5, results in a substantial removal of water from the system via the felt 37 which, as previously mentioned, is then passed through a felt only press where it is dewatered to the extent de sired at a separate pressnip. The principle of water removal at the web press nip N5 of the divided press has the advantage that it involves a comparatively good force balance at the nip itself because the water in the blind holes is usually loaded against entrapped compressed air therein, but the fundamental principle of the divided press is entirely different from that of the suction press in that in the suction press nip of FIGURE 2, it will be appreciated that water is actually removed from both the web and felt by being retained in the perforations whereas in the divided press nip shown in FIGURE 3, at the web press nip N5, water is temporarily removed from both the felt and Web at the nip, in the blind holes 36, 36, but this water is not actually removed from the web and felt combination permanently at such a nip N-5 and is actually returned to the felt 37 almost entirely at the offrunning side of the nip N5 and the felt must thus be separated from the web W3 quite rapidly at the offrunning side to avoid rewetting of the web W-3. The actual removal of water from the system thus must be carried out at the separate so-called felt only press nip of the divided press (which felt only press nip is not shown herein, but which may be a suction press nip or it may even be a press nip such as the previously described felt only press nip N-14 of FIGURE 1). In addition, imperforate shells 35, 35a of the divided press do effectively define the web press nip N-5 using anti-deflection roll structures and various other devices which may be used with imperforate shells but cannot easily be used with the perforate suction roll shell, and the divided press thus affords substantial advantages in versatility of nip pressure control and maintenance of generally uniform axial nip loads. It will be seen that in the practice of the instant invention these advantages are also available.

In the instant invention, as exemplified in the embodiments of FIGURES 4 and 4A, previously described in general, as well as in the improvements shown in FIG- URES 5 through 7 hereof, it will be seen that an entirely different and distinct principle is involved. For one thing, the instant invention provides a unique improvement in the divided press assembly (FIGURE 1) whereby a grooved roll is used at the web press nip (e.g. the roll 22 at the nip N13, as shown better in FIGURES 5 and 5A) and this grooved roll has the unique advantage of actually effecting removal of water from both the felt 23 and the web W-1 at the web nip N-13, without the disadvantages of shadow marking and/ or crushing. Essentially, this is because the grooves 220 in the peripheral surface of the roll 22 are vented to ambient atmosphere and, therefore, offer substantially no resistance to the movement of water gen-' erally normal to the plane of the web W-1 at the nip N-13. Such movement occurs through the felt 23, and into the grooves 220, which carry away a substantial amount of water from the felt 23 and web W-1 at the web press nip N-13. It is true that additional reconditioning, dewatering and cleaning are conveniently carried out at a separate divided press nip N-14, as indi-. cated in FIGURE 1, but it is also important to note that in the practice of the invention such divided press nip N-14 is used as an added control for the water movement and not the sole means of removing water from the felt 23. Thus the divided felt only nip N-14 provides added advantages in the practice of the invention, and improved moisture movement control, rather than providing the sole means for control of moisture movement out of the traveling loop of the felt 23.

The versatility and unique utility of grooved .pres's rolls in the various positions and having the various structures shown in FIGURE 1 can be appreciated only by a consideration of the function of the separate nips N-ll through N-15 thereof. For example, one of the essential concepts of the instant invention involves the use of a grooved roll 15 with land areas 15b and a grooved roll 22 with land areas 22b at the different nip locations N-14 and N13 (as shown in greater detail in FIGURES 4, 4A, 5 and 5A). In each case, the lands 15b and 22b are substantially circumferentially continuous so that the land areas present generally continuous cylindrical, smooth exterior or peripheral outer operating surfaces for engaging the web material or felt 23 and supporting the same and causing the same to bridge the grooves. Circumferentially discontinuous land areas are substantially impossible to clean during rotation of the roll. Also essential in the consideration of this concept is the use of such land areas having very narrow axial dimensions 1-1 and y-Z between the alternating grooves 13c, 220 which are also of small axial dimension x-1, y1, but which are vented (peripherally) to ambient atmosphere so that the water pressed at the press nips N-13 and N-14 will have no resistance in this respect to flow through the web matcrial or felt axially as well as radially or normal to the plane of the web into the vented groove mouths (which are themselves wide enough to readily receive the water under pressure). The grooves are provided in a size of sufiicient magnitude to receive the water load at the press nip, while being vented to ambient atmosphere and thus in a manner so as not to resist flow into the grooves, by virtue primarily of the groove depth or volume (as compared to increased groove axial dimensions x to accommodate increases in water load). The groove depth r in most paper machine uses must be substantially greater than the groove mouth width x at the roll periphery, so that the very essential venting func tion is accommodated. In practice, the ratio of groove depth r to groove axial dimension x at the groove periphery or mouth is preferably at least about 2:1 and may be as much as 10:1 or more depending upon practical additional considerations such as roll strength, ease of cutting the grooves, etc. In addition, it has been found important to make sure that the groove is able to receive readily the water load in that it is provided with preferably generally radial side walls -1, 15c-2 or 22c-2, 22c-2 which are at least as far apart as the groove mouth x for at least an initial groove depth substantially equal to the groove mouth dimension x with larger grooves or a minimum of about 0.05 inch, and preferably r is about inch and the grooves are cut generally radially for their entire depth r. In FIGURE 5, the groove width x-2 is preferably 0.020 inch, but may be as great as 0.025 inch, so with a minimum limitation of about 0.050 inch groove depth r, it will be appreciated that the cross-sectional area of any such groove in the 9 views of FIGURES 4A and 5A (which cross-sectional area would be a measure of the volume) should be at least twice x squared and is preferably in the neighborhood of about four or five times x squared or more. This concept would preclude interior groove axial dimensions greater than the axial mouth dimension x, if the forming of the same is practical and does not subtract from the strength and other commercial considerations such as cleaning of the roll, but this concept would preclude very shallow tapered grooves which would be intended to resist the entrance of water therein (and/or be intended to resist the venting thereof) but a taper between the walls of relatively deep grooves, such that the walls would be functionally parallel (for the operating purposes described) in the region of the groove mouths would not be precluded. Nor would the use of somewhat more shallow tapered or otherwise formed grooves which have radially inward extensions thereto of significant volume to make sure that the venting function is carried out.

It is important that the grooves c and 220 readily accommodate the receipt of water by being continuously vented to ambient atmosphere at both the oncoming and off-running sides of the press nips involved. In this respect, th axial dimensions 31-1 and y-2 of the lands 15b and 22b must also be relatively small so that the venting effect of the grooves 150 and 220 is readily available to water in the compressed felt. As indicated in FIGURE 5A, the maximum axial distance which water must travel through the compressed felt 23 is from approximately the midpoint M (in the machine direction) of the land area 22]) to the edge of the groove 22c adjacent thereto. Such midpoint M lies in a generally radial plane bisecting the individual ridge 22b and land area thereon and the distance is thus approximately one-half of y in any given roll.

Liquid per se in any medium, such as water in the web type of medium provided by the felt 23, resists flow under any circumstances, and in the compressed felt 23, wh ch has a dimension within the range of about to inch, the resistance to water fiow is suificiently great to cause considerable care to be taken in defining the dimension /2 y so as to maintain maximum dewatering efliciency at the nip. In this respect, the axial land dimension y should be about 25% to 200% of the radial felt thickness t in compression for the best performance in waterfiow axially laterally through the compressed felt and into the grooves 22c on either side of each land area 2212 (that is contacted, touched, or in the language of the art, covered or wrapped by the felt 23). It will also be seen that to a great extent this rule of the invention applies even at the nip N11 when the relatively incompressible forming Wire F-l (FIGURE 7) is used at the nip N-ll in place of a felt as a protective barrier between the Web W-l and the grooves 130 between the lands 13b in the rubber cover 13a on the ductile iron shell 13x of the grooved couch roll 13. The preferred range of axial land dimension y to felt thickness t in compression is within 1:2 to 1:1 when a felt is used. Since flow in the plane of the relatively incompressible forming wire Fl is not resisted as much as it is in a compressed felt, it will be appreciated that the ratio of land width y3 (FIGURE 7) to radial thickness of the forming wire F1 may be as much as 5: 1, but is preferably in the neighborhood of about 2:1 to 3:1.

Still another important consideration in the practice of the instant invention with respect to the axial groove dimension x at the mouth thereof, when a felt 23 is used, is that of shadow marking in the case of webs W-l passing through the nip N13. Again, it will be appreciated that the relatively incompressible forming wire Fl will minimize shadow marking caused by the grooves 130 at the grooved couch 13, but the pressure at the nip N4 is relatively nominal to minimize driving the web too deeply into the interstices of the forming wire F-l so as to damage the web and/ or subject the same to excessive 10 wire marking, even though the present arrangement provides for substantially effective and complete removal of any wire marks at the first transfer nip N-12 where the web is pressed against the felt 23, and/or at the first press nip N-13 where substantially the same thing occurs. It will further be appreciated that shadow marking is not of any consequence in connection with a felt only press such as the nips N-14 and N-15 and in this respect larger widths x1 of inch or even up to substantially greater widths in the neighborhood of 4; inch might be used to accomplish merely the dewatering and reconditioning of the felt. The limitation in the width x-1 is not based upon such considerations as shadow marking but rather on the desirability of avoiding too much penetration of the body of the felt 23 into the mouths of the grooves 150, such that this manipulation of the felt 23 will cause excessive wear thereof.

In the case of nips involving felts 23 covering grooved rolls 14 or 22, however, a careful study of this matter has revealed that the axial groove dimensions x should not be significantly greater than about 0.035 inch (and preferably slightly less at inch) because larger grooves with conventional felts tend to cause undesirable marking in certain webs and/ or undesirable temporary entrance of the felts of most weights into the grooves under the nip load, so as to increase the wear of the felts; and a maximum groove dimension of 0.035 inch has been found to be very significant as a cutoff point for most web pressing operations. The minimum practical axial groove dimension x which accommodates receipt of water and the essential venting function, is in the neighborhood of about 0.005 inch. As previously indicated, excellent results are obtained using a groove axial dimension of substantially 0.025 inch, although more recent work indicates a distinct preference for 0.020 inch, in the case of felt covered grooved rolls. The considerations for the grooved couch involve somewhat different principles for the reason that the relatively incompressible and relatively non deformable forming wire F1 covers the grooves 130 and rests on the lands 13b. The parameters with respect thereto will be considered hereinafter.

It will be appreciated that doctors d are shown at the oncoming side of all of the grooved roll nips of the invention and these doctors perform a distinct function in this position. Essentially, of course, they do not reach into the grooves and they function only to wipe the: land areas dry, but in wiping the peripheral land areas dry of all droplets of water, these doctors d serve to avoid the necessity for Water being driven back into the Wire or felt and then forced at the nip axially through the wire or felt back into the grooves. These doctors thus function at the oncoming side of the nip to avoid water actually being carried on the roll as well as to remove water deposited on the surface of the roll as mist or otherwise. In general, the doctor should be within about of the nip itself, but in certain special situations when this is not possible because of the structures involved, the doctor should be as close to the oncoming side of the nip as possible and preferably within about of the nip (as in the case of the roll 14 hereof). It will be appreciated that mechanical doctors function very readily forv this purpose, but air doctors or other doctoring devices may be used. Essentially they are substantially axially continuous devices functioning in close-running relation or actually pressed against the land areas of the rolls. It will be appreciated that if some of the moisture is wiped from the land areas back into the grooves by the doctor this is not as detrimental as might appear, because the grooves are designed to be deep enough to accommodate a certain amount of excess water and still carry out their essential venting function. The important essential function of the doctor is to remove the moisture from the surface of the land areas so that it will not have to travel through the felt and/or wire in the cross-machine direction to reach a groove in the manner hereinbefore described at the nip.

Still another very important point to consider, which involves not only the grooved couch roll 13 but the various grooved press rolls here shown and which is thus, like the positioning of the doctors d, of interest in the operation of all of the grooved rolls, is that the grooved rolls, such as the press roll 22 (or the press rolls 15, 14, 13, etc), which are preferred in their particular positions and/or uses in the instant invention are in each case provided with generally circumferential, alternating grooves eg 220 and ridges e.-g. 22b which are in the form of continuous but very slow spirals, as contrasted to exactly ciroumtferentially aligned and exactly spaced grooves and ridges throughout the entire roll periphery. This latter structure can be used in the practice of the instant invention with a number of desirable results. The spiral grooving is distinctly superior from the point of view of manufacturinguse. Machine tools are available for cutting spiral grooves with considerably greater case than the cutting of exactly circumferentially uniformly spaced grooves can be accomplished. It is appreciated that the spiral angle or the angle of the grooves 220 with the cenitroidal axis of the roll shell 22, for example, should be comparatively small. This is true of all of the grooved rolls. Such small angle, alpha, might be expressed for a 20-inch diameter press roll (i.e. -inch radius) as tan- Igent alpha equals approximately 0.125. divided by 10, or 0.0125. The range for tangent alpha should be within about 0.003 to about 0.03, preferably in the case of all grooved rolls of the invention including the grooved couch 13.

It will be appreciated that the grooving at this relatively slow spiral has substantially no axial movement relative to the felt and/or wire which is moving with the roll surface at the nip, so that the felt wear is minimized, and the wire wear on the grooved couch roll 13 is minirnized. On the other hand, stationary objects such as the doctor at hereinbefore described will be continuously wiped or cleaned by the spiral effect of the grooves. In this respect also, it will be appreciated that the cleaning of the grooves themselves would be complicated except for a device which is employed in the practice of the instant invention and this device constitutes a pumping type wiper as shown diagrammatically at w herein. The pumping type wiper is unique for wiping a grooved roll in that it does not penetrate the grooves. The wiper is a unique simple structure of sheet metal or the like that carries out the :function at the oncoming side of the doctor d so as to draw water out of the grooves and, if any is left on the land areas, the doctor may remove the same. In essence, the wiper w is an axially continuous surface sheet or portion which extends from close proximity (there being presumed to be a slight water film) to the surface portion or land areas of the rolls and the wiper w then presents a surface portion extending gradually away from such close proximity or line of contact to the roll at such land areas so as to define at the off-running side of the wiper a gradually diverging pair of surfaces which automatically create a pumping effect for driving the liquid out of the grooves. It will be appreciated that a wiper w of this type has distinctly superior function in connection with spiral grooves, not only in that it is not required to penetrate the grooves but also in that the nature of the spiral grooves will serve to continuously clean the surface of the wiper.

' It will be appreciated that in the case of the roll 15 shown in FIGURE 4A, the land and groove widths x and y are actually substantially equal, so that the open area is about 50%. Open areas within the range of about 25 to 50% may be used in felt only presses, as here indicated, even using relatively large groove widths in the neighborhood of about inch, but land areas of 25% or below are distinctly preferred in both felt only and web nips, and even in the couch nip. Preferably the ratio of x to y is thus at least as low as about 1:3. It will thus be appreciated that the general groove and land struc- 12 ture of the roll 22 is preferred for use to replace the grooved rolls 15, 15A of the felt only nips N14, N-15 hereof. I

Extensive research has revealed that distinctly superior performance is obtained using a substantially smaller open area of not more than about 25 (e.g. for a maximum groove size of about 1, inch, thus with & inch lands). This is a significant difference between the rolls 15 and 22 and for that matter between the rolls 15 and 13. This is true notwithstanding the fact that an essential aspect of the invention involves the ease of reception of water into the grooves. The reason for the preferred open area upper limit of about 25 and preferably 20% (with 0.020 to 0.025 inch grooves and approximately 0.08 to 0.1 inch lands) is that it .has been found that this comparatively low open area does not significantly impede water removal from the web (via the felt) at the nip pressures used and at the small axial dimensions /2 used, while this reduced open area does carry out perhaps the second most important function of the invention and that is that it provides for considerable versatility in the use of the grooved roll of the invention. This function is that of minimizing rewetting of the felt at the off-running side of the nip. Although this function greatly assists the dewater-ing operation in the web press nip (if a divided press is used) and reduces or minimizes the water load carried away by the felt from the web at the web press in the divided press, it must be appreciated that this function is also capable of effecting substantially all water removal (via a grooved roll at a web press nip) so as to replace a conventional suction roll web press at such nips as N-1 2 and N-13 in FIGURE 1 hereof, without the absolute necessity of using the felt only press nip N-14 (notwithstanding the fact that the use of the felt only nip N-14 does have a number of advantages in affording additional more sophisticated control of moisture movement in the system).

It will be appreciated that as the felt expands at the off-running side of the nip (eg. in the location indicated at P of the nip N-14 in FIGURE 4), the expansion of the felt is so rapid that there is created partial vacuum in the interior of the felt and this partial vacuum or subatmospheric pressure P creates a driving force for forcing water at substantially ambient atmospheric pressure P out of the grooves and back into the felt. Using the relatively deep grooves herein described and the relatively limited open area at the groove mouths herein described, it will be appreciated that the travel path of the water is quite long at the off-running side and the driving force is only in the neighborhood of about 10 or 12 pounds per square inch (i.e. the difference between about 2 to 5 pounds per square inch, absolute pressure P within the felt, and the ambient atmospheric pressure P in the grooves), and the time interval of such expansion at least in the immediate vicinity of the nip at operating speeds is in the neighborhood of about 10- of a second. In this same very short time interval at the oncoming side of the nip the pressure is changed from ambient atmospheric pressure P to the maximum nip load pressure P but this may involve a change to several hundred pounds per lineal inch and perhaps twice this much in pounds per square inch, so the driving force tending to drive water out of the felt (and web if present) is very substantial and the grooves are very readily and quickly filled, being vented to ambient atmosphere to begin with. The driving forces in the short time interval that tend to drive water into the grooves are thus of substantial magnitude and certainly much greater than those tending to return the water from the grooves at the off-running side of the nip, so the function of the more limited open area in the neighborhood of 20 to 25 or less is significant.

In this respect, reference should also be had to the nip N-11 at the couch station herein, wherein the grooved couch 13 is covered by the relatively incompressible forming Wire F11 which in turn is covered by a very moist web W-1 that in compression will function as a barrier that is substantially impermeable to ambient atmosphere at the loads and times here involved. Thus, the felt 11 wrapping the roll 12 (as indicated in FIGURE 7) will undergo some compression at the relatively lightly loaded nip N-11 and it will undergo a certain amount of expansion at the off-running side of the nip N-ll, so as to create therein the partial vacuum or subatmospheric pressure, previously described in connection with the nip N14 by the symbol P This subatmospheric pressure at the off-running side of the couch nip N-ll, however, will serve primarily only to retain the web W-l on the felt 11 and remove such web W-1 from the surface of the forming wire F-l.

The forming wire F-l, in contrast, is a Woven material and will be ordinarily permeable to ambient atmosphere so that it would readily break the partial pressure or vacuum tending to be created between the web W-1 and the forming wire F-l, except for the fact that the couch nip N-11 has an excessive amount of water present. Of course, to some extent the open wire may function in this respect. On the other hand, the wire is usually substantially loaded with water in that the interstices thereof are filled with water and it will thus function to a substantial extent as a barrier against the movement of ambient atmosphere. As indicated in FIGURE 1, it will be appreciated that air may readily enter between thetraveling wire reach FR-l and the web W-l on the felt 11, generally in the region of the leading edge of the guard g, so that the separation between the web W-l and the forming wire F-l is readily accomplished without damage to the web W-l. On the other hand, the forming wire run FR-l may be so full of water that as it separates from the surface of the grooved couch 13 it will tend to create somewhat of a pumping effect at the off-running side of the couch nip N-11 between the grooved couch 13 and the downwardly inclined wire run FR-l. Such pumping effect is not fatally defective to the operation of the device, although it should ordinarily be minimized for better control of moisture movement in this system. By the use of a relatively smaller open area of no more than about 33%, and preferably no more than about 25% on the surface of the grooved couch 13, it will be appreciated that the amount of water pumped back out of the grooves 13c at the oif-running side of the nip N-11 by the waterladen forming wire reach FR-l is minimized, at least to the extent that there is no throwing of water from the couch 13 and/or forming wire reach FR-l against the underside of the separating web W-l carried away by the felt 11. The guard g assists in precluding this phenomenon. The saveall m associated with the grooved couch 13 will also assist in controlling moisture movement to the extent that is desired. Actually, water simply carried away in the interstices of the forming wire run FR1 will not in and of itself cause any trouble and there is a substantial amount of water carried away in this manner. The primary concern here is that of avoiding any type of pumping or similar action which might throw water from the forming Wire reach FR-l back onto the underside of the web W-l; and this is accomplished to a considerable extent by the use of deep grooves 130 in the couch 13, by the use of a relatively small open area and/ or relatively low ratio of groove mouth dimension x-3 to land dimension y-3 of 1:2 or 3 as a maximum and by the use of the simple expedient of the guard g indicated herein.

Referring briefly to FIGURE 6, it will be seen that in the embodiment thereof, the groove width is about 0.020 and the land width is about 0.1 for an open area of approximately 16%, but the groove depth r-14 is preferably significantly greater than that described in connection with the roll 22. The reduced open area as compared to the previously described couch roll 13 is thus comparable to the preferred open area for the web press roll 22, but in the case of the roll 14 the press felt must remain in contact with the surface thereof for a substantial period of time at the off-running side of the transfer nip N-12, and there will thus be established a substantial equilibrium between the moisture in the press felt 23 and the bottom of the grooves 140 in the roll 14-. In other words, the relatively substantial time period of contact between the press felt 23 and the surface of the grooved roll 14 at the off-running side of the nip N-12 affords an opportunity for the expanding felt 23 (with a relatively impervious ambient atmosphere barrier in the form of the web W1 in the top side thereof) to return to substantially ambient atmospheric pressure and this is done primarily via the grooves 140. The excessive depth r-14 of the grooves 146, however, makes possible for some ambient" atmosphere to return through these vented grooves 140 and thus make up some of the pressure loss within the felt 23 at the off-running side of the nip N12 and the moisture driven into the grooves 14c will thus not necessarily be completely returned to the felt 23 in spite of this relatively long period of contact. The groove depth r-14 in the roll 14 is thus preferably at least as great as the maximum depth hereinbefore described of about inch and may be as much as A1 inch, whereas the groove width will preferably be reduced to about the minimum practical width of perhaps 0.010 to 0.020 inch for purposes of cutting the grooves 140 with conventional machinery. It will thus be seen that the cross-sectional area of the grooves 140 shown in FIGURE 6 is preferably in the neighborhood of 5 to 10 or even 20 times the square of the mouth width x and with significant volumes of this type in the grooves 140, it will be appreciated that the grooves will not be filled wholly with water at the comparatively lower load of perhaps to 200 pounds per lineal inch at the nip N-IZ, and the grooves 140 will be filled with a mixture of air and water, so that air may serve primarily to satisfy the partial vacuum created in the off-running felt 23 at the nip N-12. It will further be appreciated that if the felt 23 is a felt of particularly open weave and the felt 11 is a relatively hard or closelywoven felt, which is preferred in the practice of the instant invention, then the partial vacuum within the felt 11 at the off-running side of the nip N-12 may be substantially greater and substantially more slowly satisfied by the ambient air at A-11, so that the web W1 will tend to follow the upwardly inclined felt run 11R momen' tarily and separate from the felt 23 momentarily at the off-running side of the nip N-12 before it falls back down onto the felt 23 and in such instance, it will be appreciated that the temporarily created partial vacuum in the felt 23 at the off-running side of the nip N12 may be satisfied to a substantial extent by ambient atmosphere from beneath the web W-1 as well as from the air being received through the peripheral vents defined by the deep grooves 14c in the roll 14.

Otherwise, the roll 14 has water drawn from the grooves thereof by the pumping type wiper and removed from the lands thereof by the doctor mounted in the save all and designated by the previously indicated symbols w, d and m, respectively.

In general, one of the more difficult problems in the entire operation of press sections involves avoidance of crushing of the web which is perhaps a poorly chosen but very meaningful word of the artactually meaning incipient fracture of the Web-caused by excessive, poorly directed water flow in the web at the nip. Such water flow is generally in the plane of the web at the nip. It will thus be appreciated that if the grooves are too small to take the water load in the couch 13 and/ or the pressure applied at the nip N11 is too great to permit the full receipt of the water entering the nip N-11 in the very moist web W1, there would be created a puddle of water and/or stock at the oncoming side of the nip N-l and this would cause potential problems in proper web formation. Quite probably such a puddle would cause wholly undesirable disruption of the web W-l.

Accordingly, the grooves 13c are of substantial volume and the nip load N-11 is relatively nominal, being in the neighborhood of about 50 to 100 pounds per lineal inch. Such nip load must be nominal to avoid any wire damage to the forming wire F-I, although greater nip loads can be used if a plastic forming wire is employed instead of the conventional metallic forming wire. The rubber cover 13a on the grooved couch 13 will also resiliently receive a metal forming wire or a plastic forming wire F-l to the extent that damage will be minimized even at relatively high nip loads, but it must be appreciated that this is a consideration in determining the nip load involved.

Besides the wear on the wire F-1, however, the important consideration in determining the structure of the nip N-11 and its function is a combination of nip load and couch roll groove 13c size and function. In other words, the effects of crushing must be avoided. It will be appreciated that the web W1 is in a somewhat more fluid state on the forming wire F-l and the problems of crushing are not substantially identical to those encountered in, for example, the first Web press nip N-13. There is a relationship, however. A study of the crushing problem in connection with the web press nip N-13 has already been discussed herein in that web crushing may be effected not only by a backward flow of water from the maximum pressure load line (P in the crossmachine direction toward the ambient atmospheric pressure at the back side of the nip N-13, but crushing may also be accomplished by excessive water flow from the maximum pressure area P (FIGURE 5A) along the center lines of the ridges, at M, in the cross-machine direction to the vented or ambient atmospheric pressure P at the groove mouths 220. To a substantial extent the same principles will apply at the nip N11. The undesirability of creating a backflow of water at the nip N-11 has already been discussed and this can be avoided by the use of grooves 13c of substantial volume of, per haps, at least two times the square of the mouth width x3 and preferably volumes measured in terms of crosssectional areas in the neighborhod of five to ten times the square of the groove mouth dimension x-3. In addition, the land width y-3 is relatively narrow, as previously indicated. This land width y-3 is not limited to the definition of the extremely low open areas suggested for press rolls such as the roll 22, because the problem of drawing water back out of the grooves at the couch nip N-ll is not the same as it is in the case of felt press nips involving the rolls 14 and 22, for example. Nevertheless, the lands y3 are preferably about to inch and the grooves are preferably inch in width, so that adequate groove volume is afforded for the free flow of water through the forming wire F-1, with the forming wire F-l thus protecting the web W-1 against any marking which might be caused by the grooves 13c. In addition, the relatively narrow land width y-3 will minimize any local areas of undesirable cross-machine Water flow (which should take place primarily in the body of the forming wire F-1 itself which is relatively incompressible). In addition, the grooves 130 carry out the very valuable supplemental function of tending to remove a water sheet or film that might otherwise tend to be formed along the backside of the downrunning wire reach FR1. This water sheet or film has the tendency to function as an ambient air impervious barrier so that air cannot penetrate the wire from the back side and the web W-1 has a tendency to adhere to the wire run FR-1 and/ or staple thereto, if this moisture film or sheet is not adequately broken up and/or removed. The structure of the grooved couch 13 functions to minimize this undesirable effect, so that the felt 11 may lift the web W-l substantially in tact from the wire run FR-l. Again, this is accomplished by the use of grooves 130 of sufficient volume and depth to afford venting of ambient atmosphere at least to a limited extent to the under surface of the forming Wire run FR-l in spite of the rather substantial amount of water being handled at the couch nip N-11.

It will thus be seen that in the concept of the instant invention, the minimum volume of the grooves for the grooved rolls herein used is still approximately twice the square of the groove mouth (expressed in terms of the cross-sectional area), as in the case of the felt press roll 22, but the preferred groove volumes for the greater water loads envisioned at the couch nip N-11 and the transfer nip N-12 call for a distinct preference in the use of substantilly greater volumes of perhaps 5 to 10 or even 20 times the square of the groove mouth width x (again using the cross-sectional area of the groove to express the volume). It will be appreciated that Within these parameters the groove volumes may readily be selected by the skilled worker in the art and they will depend to a substantial extent upon the contemplated paper machine speed, which in turn will determine the amount of water that must be handled at any given nip and/or the speed at which water must move in any specific nip location.

In the embodiment of FIGURE 1, it will be appreciated that the simplest form of pickup assembly is employed, using a plain rubber covered roll 12 wrapped by the pickup felt 11, with the thought that the even relatively limited couch nip pressure will be sufficient to create the desired partial pressure in the felt 11 to effect the transfer of the web W1 from the forming wire F-l to the press felt 23 in the manner herein described.

It will be seen that in the embodiment of FIGURE 8 hereof, substantially the same concept is used, except that the pickup roll 112 is shown in substantially greater size relative to the rolls for better arrangement of the various felt and Wire runs; whereas in FIGURES 9 through 11, section pickup devices are used. In FIGURE 9, for example, the roll 212 is a suction pickup roll with suction areas a, b and 0 indicated diagrammatically within the suction roll 212, and it will be appreciated that the couch nip N-19, shown fragmentarily in FIGURE 7A has essentially the structure indicated in FIGURE 7, but the principal difference is that the roll shell for the roll 212 is provided with conventional suction roll perforations which are wrapped by the pickup felt 211 to protect the web W-9. Otherwise, in FIGURE 9, it will be seen that the turning roll 208 is changed in its position so as to afford somewhat greater Wire wrap around the grooved couch 213, because the effect of the suction pickup roll 212 will be such that the web W11 will be transferred readily to the pickup felt 211. The remaining elements shown in the partial view of FIGURE 9 which correspond to elements shown in FIGURE 1 are designated by the same reference numeral in the 200 series and need not be discussed in greater detail herein.

In FIGURE 8, however, it will be seen that certain essential differences in the arrangement shown therein are significant, although elements corresponding to elements described in connection with FIGURE 1 are shown designated by the same reference numeral in the series. Thus the grooved couch 113 has substantially the structure of the previouusly described grooved couch 13 and it forms a nip N81 with a rather large pickup roll 112. In the bottom part M-113 of the saverall m for the groove couch 113, it will be seen that a modification is proposed and this involves generally a barrier 113x within the saveall m for defining a reduced pressure zone M-113 at the bottom thereof communicating with the grooves 113c at the off-running side of the grooved couch 113 via a suitable vacuum header V, indicated diagrammatically. This will serve to assist in water removal from the grooves in the grooved couch 113 and this device M-113 actually consists of nothing more than a hood that is in substantial sealing engagement with the off-running area of the grooved couch 113 for purposes of creating a partial vacuum for drawing water out of these grooves and such device is used in instances where excessive Water loads are involved. The forming wire F-8 returns about turning rolls 108 and 108a and is also equipped with the previously mentioned guard g. It will be appreciated that if the water load is not great, the device M-113 will have to be controlled in its operation so that it does not create a subatmospheric pressure at the underside of the wire F-S so as to make the wire resist removal of the web W8 to the underside of the pickup felt 111, but if the water load is great enough, the functioning of the device M13 is relatively simple and it merely serves to avoid flooding or crushing at the oncoming of the nip N-Sl (since it may communicate complete- 1y through the underside of the forming wire F-S to the grooves 113s at the oncoming side of the nip N81). The larger pickup roll 112 is proposed in the instant use primarily for purposes of obtaining better alignment of the press felt 123 with respect to the transfer grooved roll 114 (which press felt 123 is also provided with an appropriate guard g which is important here to avoid substantial rewetting of the press felt 113 at the oncoming side of the nip N-82). It will be seen that the grooved transfer roll 114 has substantially the same structure as the grooved roll 14 hereinbefore described, and the essential difference in the operation thereof involves the run of the press felt 123, which passes around an oncoming guide roll 123a to substantially align this felt with the common tangent between the rolls 112 and 114, and at the off-running side of the nip N-82 the press felt 123 tends to separate rather quickly from the web W-8, and much in the manner previously described with respect to the roll 14, this press felt does travel on the surface of the roll 114 for a substantial distance, down to the guide rolls 123k and 1230. The felt 111, however, is moving on the larger diameter pickup roll 112 and will thus have much less opportunity for any ambient atmosphere to reach the back side thereof, so the web W-8 does follow the felt 111 briefly and separates quite promptly from the press felt 123, only to fall back later onto a paper guide roll 170 generally positioned to guide the rather rapidly traveling web W-S into the nip of the first web press N-83. In this respect, the transfer press N82 is a Web press but it is not generally referred to in the art as the first web press, because the transfer press loads are lower and the transfer of the web from one felt to another is the essential function of the transfer press nip N82, whereas the essential function of the web press nip N-83 is to effect maximum practical dewatering. This is done on a divided press assembly which comprises a stack of three rolls, a top plain roll 121 contacting the web W8, an intermediate grooved roll 122 having the structure of the previously described grooved roll 22 and wrapped by the press felt 123 (and within the loop of the felt 213), plus a bottom grooved roll 124 which is outside the loop of the press felt 123 and which defines with the middle grooved roll 122 a felt only press nip N-84 designed to dewater, clean and condition the press felt 123 at the immediate oncoming side of the web press nip N-83. In this respect, the felt run has certain advantages over that of FIGURE 1, at least with respect to the best control of moisture movement and dewatering effect at the web press nip N-83. The pumping type wipers, doctors and savealls indicated at w, d and m, respectively, in connection with the three-roll divided press 121, 122, 124are shown symbolically so that their use and position may be readily understood and need not otherwise be described in greater detail. The felt is passed over guide rolls 123d and 1232 so that it will pass through the felt only press nip N-89 in substantially tangential alignment with respect to both grooved rolls 122 and 124, and the guide rolls 123 and 123g then guide the felt 123 through the web press nip N-83, again, in substantially tangential alignment with the two rolls 121 and 122 which define the web press N-83. This alfords an excellent arrangment for control of moisture 18 movement throughout the entire three-roll divided press system 121, 122, 124.

In addition, the divided press arrangement for the felt 111 also involves one less press roll, in that a top grooved roll 117 cooperates with the top side of the plain pickup roll 112 to effect cleaning, conditioning and dewatering of the felt 111, acting upon the outer peripheral or working surface thereof, with the use of a grooved roll 117 having substantially the structure shown for the grooved roll 22 hereinbefore described (i.e., having a grooved width of 0.020 inch and a land width of 0.100 for an open area of about 16%). Again, the doctor at, pumping wiper w and saveall m for the roll 117 are shown diagrammatically so as to be self-explanatory to the skilled worker. The felt only press nip N- is thus shown in simplified structure, with felt guide rolls He and 11d guiding the felt 111 generally tangentially through the nip N-85 and the other felt guide rolls 11a, 11b and being generally conventional in function and position.

Referring now to FIGURES 10 and 11, it will be seen that with respect to the forming wires F-10 and F-11 and their mountings, elements having the same functions as those already described herein, particularly in FIG- URE 8 hereof, are given the same reference numeral in the 300 and 400 series, respectively. Likewise, in FIG- URES 10 and 11 the elements relating to the press felts 323 and 423 and associated grooved press rolls are designated by the same reference numerals as those used in FIGURE 8, except that in FIGURE 10 they are in the 300 series and in FIGURE 11 they are in the 400 series. The nips of FIGURE 10 are designated, in succession N-101 (at the couch), 102 at the transfer nip and 103 at the first press nip, Whereas in FIGURE 11 the nips are successively N-111 at the couch station, 112 at the transfer nip and 113 at the first press nip. The press roll arrangements shown in FIGURES l0 and 11 are actually essentially those of the rolls 14,, 21 and 22 of FIGURE 1 and the press felts 323 and 423 actually run directly from the transfer grooved T011 314 or 414 directly to the web press nips between the rolls 321322 of FIGURE 10 and 421-422 of FIGURE 11, also in a manner comparable to the arrangement shown in FIG- URE l. The essential difference being that in FIGURE 11 the oncoming press felt 423 at the transfer nip N112 is in the improved alignment indicated in FIGURE 8, rather than that of FIGURE 1; and in FIGURE 10 this is also true for the oncoming press felt alignment 323 for the transfer nip N102 and in addition at the offrunning side of the transfer nip 102, it will be seen that an additional felt guide roll 323/1 is employed for purposes of maintaining the press felt substantially tangential to the grooved transfer roll 314 at the area of the nip N-102, again for purposes of better control of moisture movement between the grooved roll 314 and the felt 323 at the off-running side of the nip area N-102. It will be appreciated, for example, that a guide roll 32311 could be positioned in a corresponding location in the embodiment of FIGURE 8 and this would serve to furnish additional web support at the off-running side of the nip N-82, even if the felt 123 were then to turn about this roll and go down to the presently shown guide roll 1231) so that the web W-8 would still have to move through a brief open draw and perhaps over the web guide roll into the nip N-83.

Essentially, FIGURES 10 and 11 show a different web pickup mechanism from the various rolls 12, 112 and the suction roll 212 hereinbefore described. The arrangement of FIGURE 11 involves a plurality of suction boxes 482 generally aligned with their open or porous faces 482a at the bottom side thereof and covered by a traveling porous rubber 483, which moves with the pickup felt 411, so that the pickup felt will not drag over the stationary suction box tops 482. The rubber felt 483 may be relatively short and is mounted on conventional guide rolls therefor 483a through d and is made of rubber preferably for the reason that the rather substantial amount of water present in this operation will thus function as a very satisfactory lubricant for the rubber belt so that it may travel over the operating lower faces of the suction boxes 482 and accomplish this with a minimum amount of drag and therefore a minimum amount of wear on the rubber belt. The rubber belt is porous and the reduced pressure is transmitted therethrough to the pickup felt 411 so that the pickup felt 411 may function in many respects as a suction pickup felt in transferring the web W11 from the forming wire F-11 to the press felt 423 at the transfer nip N-112. An advantage of the use of this suction box arrangement 482-483 is that a relatively substantial amount of travel is afforded between the grooved couch 413 and the grooved transfer roll 414 and this permits improvements in the alignment and travel of both the forming wire F-11 at the offrunning side of the couch nip N11 and the press felt 423 at the oncoming side of the transfer nip N-112.

In FIGURE 10, it will be seen that suction boxes 38] are also used with a traveling press rubber belt 383 mounted substantially as described in connection with FIGURE 11. The essential difference is that the suction boxes 381d and 381s in the region of the grooved transfer roll 314 are provided with curved operating faces so as to present a moving curved surface 383 on which the pickup felt 311 travels carrying the web W- on the underside thereof and transferring the same to the grooved transfer roll 314 wrapped by the press felt 323. This configuration of the suction boxes 3810. and 381a thus permits an improvement in the press felt alignment between the guide rolls 3230 and 323/1 to afford generally tangential alignment which is preferred from the point of view of minimizing the problems of the expanding felt 323 at the off-running side of the transfer nip N-102 tending to reabsorb water from the grooves in the grooved rol'l 314. The arrangement of FIGURE 10 thus affords better control of moisture movement at the transfer nip N-102.

It will be appreciated that modifications may be made without departing from the spirit and scope of the invention described and claimed herein.

Weclaim:

1. In a paper machine couch assembly, in combination, a couch roll within a forming wire loop, a looped pickup felt outside the forming wire loop, a plurality of aligned suction boxes with their suction areas covered by a porous solid elastomer traveling loop within the pickup felt loop and urging the pickup felt against the couch roll to pickup a moist web traveling on the Wire over the couch roll at a couch nip, said couch roll being a grooved roll having an imperforate shell presenting to the wire a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such wire smooth generally cylindrical closely axially spaced land areas for supporting the wire to bridge the grooves, and said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the couch nip.

2. The machine of claim 1 including a looped press felt outside the wire and pick-up felt loops and a transfer press roll within the press felt loop and receiving the web from the pick-up felt at a transfer nip defined by such transfer roll wrapped by the press felt and urging the same against such pick-up felt opposite one of such suction boxes spaced from others of such suction boxes urging the pick-up felt against the couch roll to pickup the moist web, said transfer press roll being a grooved roll formed of an imperforate press roll shell presenting to the felt touching the same a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such felt smooth generally cylindrical closely axially spaced land areas for supporting the felt and permitting the felt to bridge the'grooves and thereby protect against substastial marking in the case of any web carried on the felt into the nip defined by such grooved roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the nip defined by such grooved roll to facilitate reception of water from the felt at the nip.

3. The machine claimed in claim 2 including a web press defined by a first press roll outside of the press felt loop and a second press roll within the press felt loop, said second press roll within the press felt loop being a grooved roll formed of an imperforate press roll shell presenting to the press felt touching the same a peripheral surface portion having a plurality of alternating gen erally circumferentially aligned grooves and ridges, said ridges presenting to said felt smooth generally cylindrical closely axially spaced land areas for supporting the felt and permitting the felt to bridge the grooves and thereby protect against substantial marking in the case of the web carried on the press felt into the nip defined by such press roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the press nip defined by such grooved press roll to facilitate reception of water from the felt at the nip.

4. In a paper machine couch assembly, in combination, a couch roll within a forming wire loop, a looped pickup felt outside the forming wire loop, a pickup roll within the pickup felt loop and urging the pickup felt against the couch roll to pick up a moist web traveling on the wire over the couch roll at a couch nip, said couch roll being a grooved roll having an impreforate shell presenting to the wire a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such wire smooth generally cylindrical closely axially spaced land areas for supporting the wire to bridge the grooves, and said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the couch nip, a looped press felt outside the wire and pickup felt loops, and a transfer press roll within the press felt loop and receiving the web from the pickup felt at a transfer nip defined with said pickup roll being a grooved roll formed of an imperforate press roll shell presenting to the felt touching the same a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such felt smooth generally cylindrical closely axially spaced land areas for supporting the felt and permitting the felt to bridge the grooves and thereby protect against substantial marking in the case of any web carried on the felt into the nip defined by such grooved roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the nip defined by such grooved roll to facilitate reception of water from the felt at the nip.

5. In a paper machine couch assembly, in combination, a couch roll within a forming wire loop, a looped pickup felt outside the forming wire loop, a suction pickup roll within the pickup felt loop and urging the pickup felt against the couch roll to pick up a moist web traveling on the wire over the couch roll at a couch nip, said couch roll being a grooved roll having an imperforate shell presenting to the wire a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such wire smooth generally cylindrical closely axially spaced land areas for supporting the Wire to bridge the grooves, and said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the touch nip, a looped press felt outside the wire and pickup felt loops, and a transfer press roll within the press felt loop and receiving the web from the pickup felt at a transfer nip defined with said pickup roll, said transfer press roll being a grooved roll formed of an imperforate press roll shell presenting to the felt touching the same a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such felt smooth generally cylindrical closely axially spaced land areas for supporting the felt and permitting the felt to bridge the grooves and thereby protect against substantial marking in the case of any web carried on the felt into the nip defined by such grooved roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the nip defined by such grooved roll to facilitate reception of water from the felt at the nip, and a plurality of successive suction glands Within said suction pick-up roll including a first gland opposite the couch nip, a second gland opposite the transfer nip and a third gland intermediate the first and second.

6. In a paper machine couch assembly, in combina tion, a couch roll within a forming wire loop, a looped pickup felt outside the forming wire loop, a pickup roll Within the pickup felt loop and urging the pickup felt against the couch roll to pickup a moist web traveling on the Wire over the couch roll at a couch nip, said couch roll being a grooved roll having an imperforate shell presenting to the Wire a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such wire smooth generally cylindrical closely axially spaced land areas for supporting the wire to bridge the grooves, and said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the couch nip, 2. looped press felt outside the Wire and pickup felt loops, and a transfer press roll within the press felt loop and receiving the web from the pickup felt at a transfer nip defined with said pickup roll, and a web press defined by a press roll outside the press felt loop and a press roll within the press felt loop, said transfer press roll and said press roll within the press felt loop each being a grooved roll formed of an imperforate press roll shell presenting to the felt touching the same a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such felt smooth generally cylindrical closely axially spaced land areas for supporting the felt and permitting the felt to bridge the grooves and thereby protect against substatial marking in the case of any web carried on the felt into the nip defined by such grooved roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the nip defined by such grooved roll to facilitate reception of water from the felt at the nip.

7. In a paper machine couch assembly, in combination, a couch roll within a forming wire loop, a looped pickup felt outside the forming wire loop, a suction pickup roll within the pickup felt loop and urging the pickup felt against the couch roll to pickup a moist web traveling on the wire over the couch roll at a couch nip, said couch roll being a grooved roll having an imperforate shell presenting to the wire a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such wire smooth generally cylindrical closely axially spaced land areas for supporting the wire to bridge the grooves, and said grooves being vented to ambient atmosphere at the oncoming and olf-running sides of the couch nip, a looped press felt outside the wire and pickup felt loops, and a transfer press roll Within the press felt loop and receiving the web from the pickup felt at a transfer nip defined wtih said pickup roll, and a web press defined by a press roll outside the press felt loop and a press roll within the press felt loop, said transfer press roll and said press roll Within the press felt loop each being a grooved roll formed of an imperforate press roll shell presenting to the felt touching the same a peripheral surface portion having a plurality of alternating generally circumferentially aligned grooves and ridges, said ridges presenting to such felt smooth generally cylindrical cloosely axially spaced land areas for supporting in felt and permitting the felt to bridge the grooves and thereby protect against substantial marking in the case of any web carried on the felt into the nip defined by such grooved roll, said grooves being vented to ambient atmosphere at the oncoming and off-running sides of the nip defined by such grooved roll to facilitate reception of water from the felt at the nip, and a plurality of successive suction glands within such suction pick-up roll including a first gland opposite the couch nip, a second gland opposite the transfer nip and a third gland intermediate the first and second.

References Cited by the Examiner UNITED STATES PATENTS 1,483,562 2/1924 Wagner 162-3 58 2,850,951 9/1958 Holden 162--358 FOREIGN PATENTS 201,776 11/1889 France. 166,308 7/ 1921 Great Britain. 694,033 7/ 1953 Great Britain.

OTHER REFERENCES The Paper Industry and Paper World, August 1943 pg. 530.

DONALL H. SYLVESTER, Primary Examiner.

J. H. NEWSOME, Assistant Examiner.

Claims (1)

1. IN A PAPER MACHINE COUCH ASSEMBLY, IN COMBINATION, A COUCH ROLL WITHIN A FORMING WIRE LOOP, A LOOPED PICKUP FELT OUTSIDE THE FORMING WIRE LOOP, A PLURALITY OF ALIGNED SUCTION BOXES WITH THEIR SUCTION AREAS COVERED BY A PORPUS SOLID ELASTOMER TRAVELING LOOP WITHIN THE PICKUP FELT LOOP AND URGING THE PICKUP FELT AGAINST THE COUCH ROLL TO PICKUP A MOIST WEB TRAVELING ON THE WIRE OVER THE COUCH ROLL AT A SOUCH NIP, SAID COUCH BEING A GROOVED ROLL HAVING AN IMPERFORATE SHELL PERSENTING TO THE WIRE A PERIPHERAL SURFACE PORTION HAVING A PLURALITY OF ALTERMINATING GENERALLY CIRCUMFERENTIALLY ALIGNED GROOVES AND RIDGES, SAID RIDGES PRESENTING TO SUCH WIRE SMOOTH GENERALLY CYLINDRICAL CLOSELY AXIALLY SPACED LAND AREAS FOR SUPPORTING THE WIRE TO BRIDGE THE GROOVES, AND SAID GROOVES BEING VENTED TO AMBIENT ATMOSPHERE AT THE ONCOMING AND OFF-RUNNING SIDES OF THE COUCH NIP.

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