US3540981A

US3540981A - Web formation between a pair of foraminous belts

Info

Publication number: US3540981A
Application number: US805957*A
Authority: US
Inventors: John S Finnila; Edgar J Justus
Original assignee: JOHN S FINNILA
Current assignee: JOHN S FINNILA
Priority date: 1969-02-20
Filing date: 1969-02-20
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17

Description

Nov. 17, 1970 J. 5. FINNILA ErAL 3,540,981

WEB FORMATION BETWEEN A PAIR OF FORAMINOUS BELTS Original Filed Oct. 20, 1965 3 Sheets-Sheet 1 TTORNEYS Nov. 17, 1970 J- 5. FINNILA ETAL 3,54,981

WEB FORMATION BETWEEN A PAIR OF FORAMINOUS BELTS 3 Sheets-Sheet 2 Original Filed Oct. 20, 1965 IIYVENT OILS 5; fin/.71 la s w W U r w S V. E N R 0 A Nov. 17, 1970 J 5. FlNNlLA E1 AL {gggzgq WEB FORMATION BETWEEN A PAIR OF FORAMINOUS BELTS Original Filed Oct. 20. 1965 3 Sheets-Sheet 3 0 \Z /6/ A? I I ///4 I N VEN TOR5 dob 5T Filip/7a Edgar d (IE/5M6 /44%-. ATTORNEYS United States Patent 3,540,981 WEB FORMATION BETWEEN A PAIR OF FORAMIYOUS BELTS John S. Finnila, 421 Oakland, South Beloit, Ill., and Edgar J. Justus, 2471 E. Ridge Road, Beloit, Wis. Continuation of application Ser. No. 498,422, Oct. 20, 1965. This application Feb. 20, 1969, Ser. No. 805,957 Int. Cl. D21f l/OO U.S. Cl. 162301 4 Claims ABSTRACT OF THE DISCLOSURE A paper forming machine and proces having upper and lower converging wires supported by cantilever means defining a forming zone in a uniplanar relationship in a downwardly inclined direction for maintaining uniform pressure throughout the forming zone.

This application is a continuation of SN. 498,422, filed Oct. 20, 1965 and now abandoned.

The instant invention relates to the art of paper making, and more particularly, to a specific paper making machine having unusual capabilities with respect to highspeed, high-quality web formation as well as its performance in the light of the necessity for making wire changes which occurs regularly in ordinary production in the making of paper in conventional paper making machinery.

As is known, in paper making machinery, the stock or dilute aqueous suspension of fibers is fed onto and/or between what are known as forming wires, which are actually traveling looped foraminous belts usually of very fine weave metal or plastic material which will relatively readily pass the water of the aqueous suspension but which retain the fibers and thereby form the paper web. These foraminous belts or forming wires as they are more connnonly known must travel at substantially the same speed as the jet of stock fed thereonto and this speed is now relatively high in commercial paper making machinery, i.e., being in the order of 2000 to 3000 feet per minute in order to produce paper at competitive cost. The instant invention is specific to the concept of web formation between a pair of such fast moving foraminous belts, and the instant invention affords a solution to some of the more difficult problems that arise from high speed production using this particular web forming arrangement. For instance, the stock fed between such traveling foraminous belts commences to deposit fibers on each in the form of partial webs which increase in thickness and resistance to water flow therethrough during the dewatering process. The high speed jet of stock initially fed into the forming area maintains a pressur at the oncoming side of the forming area or zone which pressure is preferably maintained substantially uniform throughout substantially the entire forming zone in order to avoid such defects as rolling and streaking which are understood to be caused by non-uniform pressures in the forming zone. The instant invention affords a unique structural arrangement for facilitating maintenance and/or control of uniform pressure in the forming zone and, further, for easy adaptation of the structural arrangement of the forming zone to accommodate the desired, controlled pressure conditions therein for a variety of different types of stock.

Another problem solved by the instant invention is that of providing a structural arrangement which facilitates and expedites wire changes during ordinary production. The forming wires have a tendency to wear out, fold, crease, or otherwise become unusable after a given period of time and it then becomes necessary to shut down the paper making machine and replace the used and/or ice broken wire with a new forming wire. During this shutdown, of course, there is a substantial production loss and forming wires themselves are not inexpensive. It is for this reason that the method and means for changing forming wires should be simplified as much as possible so that they may be expedited and potential damage to the new wire is minimized.

The instant invention relates to an improvement essentially in this general aspect of the art of papermaking It is, therefore, an important object of the instant invention to provide an improved papermaking arrangement.

Another object of the invention is to provide a papermaking machine having an improved and versatile web forming arrangement.

It is a further object of the instant invention to provide an improvement in papermaking machinery which affords ready replacement of forming wires, whenver this may be necessary.

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 hereto and made a part hereof.

On the drawings:

FIGS. 1A and 1B should be considered together and these two figures represent, in combination, a side elevational view of a paper machine embodying the instant invention, with parts shown in detail, in section, and in some instances merely schemtically; and

FIGS. 2 and 3 show other embodiments of the invention in schematic elevation.

As shown on the drawings:

The instant invention relates to a paper forming machine embodying an upper forming wire 11 and a lower forming wire 12 which converge together initially in the general region indicated at 13 to receive stock from a slice 14 feeding into this area of convergence 13. The stock feeding device 14 is of generally conventional structure and need not be described in extensive detail herein. It is sufficient to note, for example, that copending application Ser. No. 338,424, filed Jan. 17, 1964, now Pat. No. 3,309,264 as well as U.S. Pat. No. 3,098,787 are disclosures of stock jet generating devices which are used for the device 14. The device indicated as being preferred in the aforesaid application is employed as the stock jet generating device 14 here shown, except that the stock is fed into the device at 14a through a cross-machine header 14b and then upwardly through a channel and into the main stock jet generating elongated channel 14d (which elongated channel is that described in the aforesaid application). The means and method of generating a stock jet for use in the practice of the instant invention do not per se form a part of the instant invention, except for the fact that the instant stock jet is generated in a downward incline as contrasted to a generally horizontal stock jet emitting from the channel 14d. In general, the stock jet is generated by substantially complete distribution of discrete individual fibers in the dilute stock which moves at very high speed through the channel 14d and which is sufficiently uniformly distributed by the time it reaches the convergence point 13 that is characterized by the skilled workers in the art as a jet or thin stream or ribbon of substantially homogeneous suspended entangled co-moving stock fibers in dilute aqueous system. The stream or ribbon thickness is approximately of an inch and the speed employed is substantially the speed of peripheral travel of the co-moving top and bottom wires 11 and 12, which are spaced apart in the initial region of convergence, 13 receiving such stock jet, 'a distance of only slighlty more than the height of the stock jet itself plus the thickness of the top and bottom walls for the channel 14d, all of which totals somewhat more than approximately one inch in height.

The overall inlet structure 14 is generally relatively immobile in the paper machine, although a certain amount of limited movement is permitted. The instant invention does not, however, require any significant movement of the overall channel structure 14 in the practice of the instant invention.

Referring briefly first to the upper wire 11, it will be seen that this wire passes into the initial area of convergence 13 over what is indicated generally as a foil box 15, which causes the upper wire 11 to be forced down against the rapidly forming moist fibrous mat or web. between the wires 12 and 11. The foil box 15 is provided with a plurality of slanted cross-machine foils indicated generally at 15a which engage the inner periphery of the wire and guide the wire 11 through a generally curved (parabolic) line of movement. The foil box 15 is not readily adapted to substantial movement. It will be seen that it is mounted generally on pivot means 16 which are in turn connected to an adjustable sleeve indicated diagrammatically at 17 for limited movement axially of such sleeve ;17. In addition, the foil box 15 is mounted at its forward end with a jack-screw JS-l and at its rear end with a jack-screw JS-2 for limited tilting movement thereof. The foils in the forward end of the box 15 are indicated diagrammatically at 15a as being slanted so as to readily receive water forced through the upper wire 11 and into the box 15 and the lower end 15b of the box 15 may or may not be equipped with a device (not shown) for creating subatmospheric pressure therein to assist in water removal via the foils 15a. For the purposes of the instant invention it will be appreciated that the foil box 15 assists in dewatering but it is comparatively immobile in other respects, particularly with respect to the changing of the wire 11.

The wire .11 passes downwardly from the foil box 15 along a generally downwardly slanted path and around a suction roll 18 having an enlarged suction area indicated at 18a, so that the moist web W that is formed at this stage in the travel of the forming wire 11 will be retained on the outer periphery thereof and fed upwardly and onto a pickup felt 11 which has traveled around a turning roll 20 and travels around a suction roll 21 for pickup from the forming wire at its suction area 21a. The forming wire 11 then continues around a series of

guide rolls

22, 23, 24, 25 and optionally 26. The optional roll 26 may be urged against the outer periphery of the wire 11 to tension the same, whereas the other guide rolls are within the periphery of the wire 11 and these

rolls

18, 22, 23, 24 and 25, overall, tend to apply the desired tension to the wire 11 by being urged against the inner periphery thereof. Actually, the roll 24 is essentially a guide roll which keeps the wire 11 tracking in the proper longitudinal direction; and the

rolls

22 and 25 are primarily idler rolls that maintain the wire in its generally desired overall configuration. The roll 23, however, is a tensioning roll and it will be seen that this roll is provided with a mounting arm 30 carrying its bearing 23a (all of the bearings for the rolls being indicated by the roll reference numeral by a), but the arm 30 is shown pivotally mounted at 31 and equipped with so-called air springs or air diaphragm 32 and 33 which, respectively,

.serve to position the roll 23 in approximately the desired position by substantial movement thereof and then apply selectively and carefully controlled pressure thereto in order to effect exactly the desired application of tension in the wire 11, hence the two air springs 32 and 33 for carrying out the two functions. A second pivoted arm 30a actuated for substantial swinging movement by a jackscrew J S-3 carries the mounting arm 30 via the air springs 32 and 33 and affords substantial lowering of the roll 23 to position 23'.

It will also be seen that a cross beam 34 is provided to mount the pivot 31 as well as the bearings 25a and 24a. The cross beam 34 has depending

elements

35 and 36 which in turn connect to a lower cross beam 37 that carries the bearing 181111 for the large suction roll 18. Also, the

framing

34, 36, 37 carries a saveall indicated diagrammatically at 38 for the suction roll 18. The cross beam 34 plus its depending element 36 also serves to carry the mounting elements JS-1, JS-2 and 17 for the foil box 15, as is apparent from an observation of the drawings. It will thus be seen that the cross beam framework 3437 carries essentially the entire roll and guide means for the upper wire 11. It will further be noted that the cross beam 34 is carried by a pair of cross-machine cantilever beams indicated at 39 and 40. The cantilever beams 39 and 40 extend the full cross-machine dimension of the instant machine, and of course the upper wire 11, and these cantilever beams 39, 40 are mounted at the rear side of the machine on rear framing elements indicated diagrammatically at F and P In this respect it should be noted that in papermaking machinery the front or operating side is usually the side that is shown in drawings and it is the side from which the operators work most of the time. On the other hand, on the rear side of the paper machine the drive devices and other complicated machinery will be mounted and these will obscure generally the overall view of the machine, hence the front side of the machine is usually shown in views of paper machines. On the other hand, the rear sides of the paper machine generally carries the heavy framing not only for the drive means but for whatever other auxiliary equipment might have to be carried. In this particular instance the rear framing F and F is indicated only diagrammatically because those skilled in the art recognize fully the nature and character of this framing and it need not be described in further detail. The significant feature hereof resides in the fact that the cantilever beams 39 and 40 are actually supported at the rear side by the rear framing F F and extend as load bearing beams the full cross-machine dimension of the instant device, carrying the entire weight load when this becomes necessary. In fact, the cantilever beams 39, 40 are mounted on the rear framing F F so that they are sprung upwardly slightly and there is a tendency for them to lift slightly when weight is relieved therefrom. Again, this type of mounting is well understood by those skilled in the art and need not be described in further detail herein.

It will be seen, however, that on the front side of the instant machine a pedestal indicated generally at 50 is provided and the pedestal 50 is segmented so as to have a bottom replaceable segment 50a, an intermediate relatively fixed segment 50b, an upper segment 500 which is substantially opposite the two wires 11 and 12 in this location and finally a top segment previously indicated by the reference numeral 35, all of which

segments

50a, 50b, 50c and 35 are connected in rigid assembly by bolts (not shown) to afford ready disconnection when desired. This pedestal 50 will, of course, carry a load if the same is applied thereto and it is used during operation as a load bearing pedestal.

In addition, a second load bearing pedestal is indicated as being supported like the first pedestal 50 on the floor F-l and this second pedestal 51 is shown beneath the main suction roll 18 extending upwardly to a removable (bolted) segment element 51a that is bolted to and engages in rigid assembly the lower cross beam 37 carrying the bearing 18am for the suction roll 18. It will be appreciated that the segment 51a is opposite the wire 11 and is on the front side of the machine, so that this segment 51a and the previously mentioned segment 500 may be removed readily when the machine is shut down and it is necessary to change the top wire 11. In order to take the tension off the top wire 11, it will be appreciated that the tensioning roll 23 is dropped to the position 23' and this can be done by the jack-screw JS-3. It will be appreciated that a slight dropping of the tensioning roll 23 could be accomplished through the air diaphragms 32 and 33, but generally somewhat greater lowering of this roll 23 is required for a wire change and the jack-screw JS3 is preferably used for this purpose so that the wire 11 will then be slack on the various guide means therefor which include the guide rolls 22, 24, 25, the foil box 15 and the suction roll 18, It should also be noted that the lower forming wire 12 is mounted on a movable breast roll 61 which can be dropped away readily so that the wire 12 will not interfere with the changing of the wire 11 opposite the foil box 15.

In changing the wire 11, the procedure employed is conventional with respect to the use of wire changing poles which are moved axially of the periphery of the wire 11 into approximately the positions of the top guide rolls 23, 24 and 25 so as to carry the new wire axially (on such poles) into the operating position of the wire 11. The poles themselves are of conventional structure and are not shown herein, being fully understood as to structure and use by those skilled in the art.

It will be seen that the two pedestal elements 50c and 51a are readily removed (thereby permitting the front end of the cantilever beams 39, 40 to spring upwardly slightly) for purposes of removing the old wire and replacing the upper wire 11 while the cantilever beams 39, 40 carry the entire weight load of the various guide and mounting means for the upper wire 11. Of course, the optional roll 26 that is shown outside the loop of the upper wire 11 is readily moved away from any interferring position during the wire change and may be moved back by conventional means (not shown).

Referring to the lower wire 12, it will be seen that this wire is mounted on a breast roll 61, a driven couch roll 62 and guide rolls 63 and 64, all of which engage the inner periphery of the wire loop 12 and may be urged against the inner periphery of the wire loop 12 to effect controlled tensioning thereof. Still another gide roll 65 is mounted on the floor F-l outside the loop of the wire 12. The rolls 61 through 65 are carried by conventional bearings 61a through 65a.

An elongated lever arm 66 centrally pivoted at 66a on the pedestal segment 50b carries the couch roll 62 via its bearings 62a at one end and is connected to a jackscrew 18-4 at its opposite end to afford limited swinging movement thereof for adjusting the position of the couch roll 62. The jack-screw JS-4 is in turn carried on a third cross-machine cantilever beam 67 which, in turn, is carried at the back side of the machine by cantilever mounting means shown diagrammatically at F The crossmachine cantilever beam 67 is connected by conventional bolt flanges 67a to the pedestal segment 50b and by bolted flanges 67b and c to an angle beam 68 which is also connected by bolted fianges (not shown) to the pedestal segment 50b at one end and is further mounted on another (removable) pedestal segment 52a via bolted flanges 68a. The connected beam 68 and pedestal segment 50b define generally the configuration of an inverted U with the bottoms thereof supported by the removable pedestal segments 52a and 50a which are in turn mounted on the floor F1. These last-mentioned removable pedestal segments 50a and 52a are shown opposite runs of the wire 12 and are, of course, removed during wire change for the lower wire 12.

As indicated also, the outside roll 65 and the inside roll 63 are both mounted on relatively immobile bearings 65a and 63a mounted, respectively, on the floor F-l and the beam 68. The guide roll 64 is also a tensioning roll and is carried via its bearings 64a on a first pivot arm 69a connected to a relatively immobile pivot 70 which is in turn connected to the beam 68. A second pivot arm 6% is also connected to the same pivot 70 and an air spring 71 is interposed between the swinging ends of the

arms

69a, and 69b to afford delicate, controlled application of tension to the wire 12 via the guide roll 64. The

pivot arm 69b carrying the air spring 71 is connected for controlled swinging movement to a jack-screw JS-S which in turn is pivotally mounted to the angle beam 68. The jack-screw JS-S affords substantial movement of the guide and tensioning roll 64 inwardly of the wire loop 12 to not only relax the tension thereof but to afford ease of axial movement of a wire during wire change. In addition, the breast roll 61 is carried via its bearings 61a on still another pivot arm 61b connected by a conventional pivot mounting 61c to the angle beam 68 at one end of the arm 61b and carried at the other end of the arm 61b via a conventional rod 61d and chain 612 takeup assembly mounted on drive and guide

rotary elements

61 and 61g, all of which arrangement is essentially old and well known for swinging movement of a pivot arm such as the pivot arm 61b, but in this particular case such overall assembly 61c through 61g permits ease of dropping of the breast roll 61 (plus disconnection between the rod 61d and chain 61c) so as to assist in partial separation of the top wire 11 and the bottom wire 12 as well as reduce tension in the bottom wire 12 to facilitate the wire changing operation. It will be appreciated that in order to change the lower wire 12 in the instant arrangement, the removable pedestal segments 50a, 52a and 500 are taken out and the swingably mounted breast roll 61 and guide and tensioning roll 64 are swung back inwardly of the loop 12 to relieve tension thereon and facilitate the wire change. The pedestal segment 50c is unique in its ability to carry out a multiplicity of functions including that of support of the structure during operation and permitting both the upper wire 11 and the lower wire 12 to pass through the pedestal structure '50 at its location merely by the removal of such pedestal segment 500, as a single removable element.

It will also be appreciated that, with the

removable pedestal segments

50a, 50c and 52a having been disconnected and removed, the cross-machine cantilever beam 67 will then carry the entire weight load of all of the rotary elements 61 through 64 that engage the inner periphery of the wire loop 12. The cantilever beam 67 will also carry the entire weight of the relatively immobile dewatering elements acting against the inner periphery of the upper run 12a of the looped wire 12, such dewatering elements being indicated by the reference numeral in FIGS. 1A and 1B (and also by the reference numeral in FIG. 2 and 280 in FIG. 3). As indicated in FIGS. 1A and 1B, the dewatering elements 80 comprise a flat deflector 80a at the uprnnning side of the dewatering assembly 80 and engaging the inner periphery of the wire loop 12 opposite but downstream of the foils 15a in the foil box 15 engaging the inner periphery of the upper wire 11. Downstream of the flat deflector 18a are mounted a plurality of suction boxes or flat boxes 80b through 80e. The flat deflector 80a as well as the suction boxes 80b through 80e extend in the full crossrnachine direction and operate in contact with the inner periphery of the wire loop 12, functioning in what is essentially the conventional manner of functioning for deflectors and suction boxes, the functions of which are well known and understood by the skilled workers in the art. The suction boxes have perforate tops (not shown) through which the inner periphery of the wire loop 12 is exposed to subatmospheric pressure that is maintained within the interior of the suction boxes 8% through 80e by conventional connections to a vacuum pump (not shown). Such a vacuum pump may also be a vacuum pump indicated diagrammatically at V which would also be used to evacuate the foil box chamber 15b under certain operating conditions for the instant machine. It will thus be seen that, if subatmospheric pressure is used in the foil box 15 and in the suction boxes 80b through 80e, the dewatering operation involved in the machine of FIGS. 1A and IE will effect (first a pressure differential across the lower run 11a of the upper wire 11 throughout most of the converging zone 13, whereby water removal from the stock in the converging zone 13 takes place via water movement upwardly of the converging zone 13 and past the foils into the foil box 15, and water removal takes place simultaneously downwardly from the converging zone 13 through the unsupported lower wire reach 12a between the breast roll 61 and the fiat deflector 80a. As the moist web passes beyond the fiat deflector 80a, then the pressure differential is reversed to the extent that subatmospheric pressure in the suction boxes 8% through 80c acts against the underside of the lower wire run 12 while the inner periphery of the upper wire run 11 is exposed essentially to atmospheric pressure (and the direction of pressure differential is once more reversed at the suction area |18a of the large suction roll 18 which involves a dewatering function upwardly through the upper wire 11 as well as a retention of the Web on the outer periphery of the upper wire 11 until it can be transferred to the felt 19 in the manner already mentioned). For various purposes such manipulation of the direction and extent of pressure differentials applied during dewatering of the web W sandwiched between the wires 11 and 12 may afford a number of advantages in web formation. In addition, it will be appreciated that the generally downward slope of the contiguous wire runs 11a and 12a between which the web W is sandwiched during such dewatering operation will necessarily result in a controlled hydraulic pressure within the stock in the converging zone 13 and the water in the moist web during formation between the wires 11 and 12. The hydraulic head is controlled with unusual facility and in order to obtain uniquely uniform pressures by virtue of the angle of downward slope of the sandwiched forming and dewatering assembly 111a, W, 12a. It will be understood that the rate of downward slope of such sandwich assembly (and/or its angle of slope from the horizontal) will determine the internal hydraulic pressure within the stock and/or moist web which the gradually increasing pressure of the hydraulic head tends to impart with each incremental downward movement of the aforesaid sandwiched assembly. Of course, the various dewatering devices employed at the inner periphery of the upper wire and/ or the lower wire will effect the rates of dewatering and consequently will tend also to effect the internal pressure within the stock and/or moist web at a given location during operation under controlled conditions. This is even more apparent, in situations involving the use of subatmospheric pressure as in the foil box 15 and/or the suction boxes 8%, etc. Essentially the superior result obtained in the practice of the instant invention involves the maintenance of the hydraulic head pressure or a tendency to impart internal pressure within the stock and moist web, which tendency to impart pressure via the increasing hydraulic head is controlled by virtue of the rate of descent of the sandwiched assembly, which in turn is controlled by the angle of slope of the path PP which the sandwiched assembly ta kes. As indicated generally in FIGS. 1A and 1B, the path PP which the assembly takes is downwardly sloped from a theoretically horizontal line I-Iby a predetermined angle X, which angle may range from a nominal departure from the horizontal of about 10 to a substantial departure from the horizontal of as much as 80 or 90 (which latter direction would be vertical). Preferably, however, the angle of slope X is within the range of about 30 to 60 and, as here shown, the example of the angle X is substantially 30. The path for the aforesaid assembly 11a, W, 12a is indicated here diagrammatically at PP as being substantially that of the lower wire run 12a which is also shown diagrammatically at P P to indicate in an exaggerated manner that the travel path PP of the web W is centered along a plane substantially parallel to but slightly above the theoretical plane P P through which the lower wire run 12a moves. As previously indicated, the center line of the stock jet entering into the open end of the zone of convergence 13 is only a fraction of an inch above the bottom wire run 12a As a matter of fact, however, it will be appreciated that the plane P P is theoretically the common touching plane for the breast roll 61 and the couch roll 62. If the breast roll 61 and the couch roll 62 have the same radii, then the plane P P would be the common tangent plane, but if their radii are different it is more properly defined as the common touching plane (which is tangent to both of these rolls only if their radii are the same, or is substantially tangent thereto only if the rolls are spaced apart a very substantial difference and their radii are not critically different). Actually, the center line of the stock jet exiting from the inlet 14 will run a very small fraction of an inch above but parallel to the final center line of the dewatered web in the region of the couch roll 62, but this distinction is not extremely significant in a consideration of the general direction PP for the moment. The general direction of the plane PP will, of course, determine, in conjunction with the wire speed, the rate at which the theoretical internal stock and/ or moist web pressure increases by virtue of the in creased hydraulic head during operation. As a matter of fact, the rate of increase of the hydraulic head is controlled in the operation of the instant machine the effects on such internal pressure caused by the rates and nature of the dewatering functions being carried out simultaneously will be compensated for relative to the internal stock and/or wet web pressure and a substantially uniform internal pressure will be maintained during the web formation. Such substantially uniform internal pressure during the critical stages of web formation precludes localized cross-machine and/or non-uniform downstream liquid movement, thereby resulting in defects generally characterized as rolling and streaking.

The inlet 14 herein shown has the structure of the preferred embodiment shown in copending application Ser. No. 467,664, filed June 28, 1965, and owned by the assignee of the instant application now Pat. No. 338,143 (such preferred embodiment being shown specifically in FIG. 7, for example). Since the structure of the inlet 14 per se is not as such a separate part of the instant invention, but rather one of the elements of the overall combination, specific details thereof are not disclosed herein except by reference incorporating all of the disclosure of the application just mentioned. Essentially, however, it is sufficient to note that the inlet 14 delivers a stock stream ribbon or jet in the manner previously described in the instant application and this stream is a very thin stream having a center plane indicated herein at PP (and indicated in said application Ser. No. 467,664 at PPPP'. Likewise, the structural definition of the con- Vergence zone 13 shown in FIG. 1A via convergence of the upper Wire run 11a traveling over the parabolic contour defined by the bottoms of the foils 15a to converge with the bottom wire run 12a lying generally in the plane P -P involves convergence in the manner shown more specifically in FIG. 3 of said application Ser. No. 467,664, but for the purposes of the instant invention, it is sufficient to note that this convergence involves travel through a parabolic contour for the upper wire run 11a in the converging zone 13 such that the upper wire run 11a will preferably intersect the mid plane PP of the stock jet during the course of convergence and as it approaches its closest running movement relative to the lower wire run 12a. The inlet 14 is, however, mounted on tilting and/or vertical adjusting devices A-1 and A-2, plus a machine direction moving device A-3, all of which are shown diagrammatically in FIG. 1A hereof and which involve well known mounting means which need not be described in further detail for purposes of paper making industry. These adjusting devices A-1 through A-3 will afford relative positioning and/ or tilting of the center plane PP of the stock jet so that it may be aligned at slight angles from the theoretical line of the plane P P of the lower wire run 12a. This feature of adjustment is consistent with the concept of controlled pressure in the forming and/or converging zone 13, for the reason that stock velocity will be translated to pressure upon direct and/or partial impingement against one of the forming wires, and an important feature of the instant invention involves the ability to control the internal pressure within the convergence zone 13 so that there will be pressure uniformity and substantial rates of uniform dewatering so as to obtain the best forming conditions. Adjustment of the various adjustable elements in the instant paper machine for this purpose is, however, greatly facilitated by the overall downward slope of the travel of the sandwiched assembly 11a, W, 12a.

In FIG. 2 the elements shown in the drawing corresponding to those already described in connection with FIGS. 1A and 1B are designated by the same reference numeral in the 100 series; and FIG. 3 the elements cor responding to those already described in more detail in connection with FIGS. 1A and 1B and/or FIG. 2 are designed by the same reference numeral in the .200 series.

It will be seen that the essentially diagrammatic view of FIG. 2 shows a foil box 115 with foils 115a (here indicated diagrammatically) engaging the inner periphery of the upper wire run 111a, with the foils 115a slanted slightly downwardly from the horizontal, by at least approximately 2 to 20, but here by only substantially 5". This arrangement permits the foils to effect water removal essentially by virtue of the internal hydraulic head within the convergence zone 113 as well as the effect of gravity itself; and no subatmospheric pressure need be maintained in the water takeoff and of the foil box 115b. Likewise, no subatmospheric pressure need be generated on the underside of the sandwich 111a, W-100, 112a, so that no suction box assembly need be used to operate against the underside of the lower wire run 112a. Thus a flat deflector 180a immediately downstream of the foil box 115 is employed (just after the contact between the moving wire run 111a and the foils 115a is completed), and the remaining cross-machine deflectors 18% through 1802 are essentially foils of presently known structure in that they have a slightly curved upstream end just touching the underside of the wire run 112a and, as shown in the drawing of FIG. 2, the down-running side of these foils 18012 through 180:: separates gradually along an angle of about 3 from the inner periphery of the wire run 112a so as to generate a slight pumping action (and a slight generation of subatmospheric pressure) which facilitates water removal but does not cause any disruption of the formation characteristics for the web sandwiched between the wires 111a and 112a. The essential feature of the embodiment of FIG. 2 is that the expense of a substantial vacuum pump operation for either the foil box 115 or the water removal assembly 180 is not required.

FIG 3 differs essentially from FIG. .2 in that the upstream deflector foil 18% of FIG. 2 has been replaced by a suction box 280b in FIG. 3. The nature of the suction box operation has already been explained and the essence of the showing in FIG. 3 is that of an embodiment involving a plurality of different types of water removing devices engaging the nderside of the lower wire run 212a to effect controlled water removal in the most advantageous manner for a particular type of stock and/or web formation. Also, the embodiments shown in FIGS. 2 and 3 demonstrate the versatility which the instant overall structure affords which is, in turn, feasible to a great extent by virtue of the downwardly sloped travel of the stock and web through the zones of

convergence

13, 113, 213 and into the generally sandwiched structure hereinbefore mentioned. This downward movement affords the desired pressure control in order to achieve the substantial uniformity in the pressure internally and/or between 10 the converging and traveling wire runs Illa-112a or 211a212a.

It will further be appreciated that the overall arrangement herein shown not only makes possible an extremely compact high speed web forming arrangement, with unique versatility with respect to relative movement between the elements thereof to afford easy and rapid wire changes, but also the relative movement between the elements hereof makes possible a limited but significant amount of adjustment of the overall downwardly inclined substantially uniplanar web forming travel path (i.e. of the sandwiched structure 11a, W, 12a of FIG. 1). It will thus be seen that the couch roll 62 is movable through limited pivotal swinging movement away from the large suction roll 18 to facilitate wire change and this couch roll 62 also is moved to a limited extent in conjunction with, for example, upward movement of the swingably mounted breast roll 61 and slight swinging of the dewatering assembly (on its frame 80g) about the pivot 66a mounted on the pedestal segment 50b. Such limited movement of these

elements

61, 80,62 affords a limited but significant adjustment in the downward incline of the bottom wire reach 12a, as slight upward and downward movement of the foil box 15 affords a similar limited but significant adjustment of the downward incline of the top Wire run 11a. As previously mentioned, the stock stream inlet 14 is also mounted for limited vertical, horizontal and/or tilting movement, so that the stock jet being fed into the converging zone 13 may be aligned (along the previously mentioned plane PP) so that it will effect not only the desired maintenance of a substantially uniform pressure and/ or hydraulic head throughout the downward inclined substantially uniplanar movement of the substantially contiguous opposed wire runs 11a and 12a but also the adjustment of the inlet 14 makes possible a slight but critical deliberate misalignment of the plane PP with respect to the bottom wire plane P -P so as to effect substantially uniform rates of dewatering toward both of the opposed wire runs 11a and 12a. Such misalignment may involve directing the stock jet to intersect the generally parabolic travel path at slightly different locations (in the wire run 12a over the foil box 15) so as to make the limited compensations necessary to effect substantially uniform partial (initial) web formation on both the wires 11a and 12a in the converging zone 13. But this compensation also involves such factors as stock dilution, characteristics and speed; wire speeds; dewatering rates; etc. and, of course, pressures in the foil box 15 (which has the preferred structure shown in said application Ser. No. 338,424).

Expressed in other terms, the invention embodying the instant invention is essentially a device for forming a fibrous web from a dilute aqueous fiber suspension or stock, and comprises first and second web-forming belt loops 11 and 12 having respectively first and second opposed belt runs 11a and 12a presenting substantially contiguous outer peripheral surface portions (11a, 12a) defining therebetween an initial converging zone 13 for web deposition on both surface portions followed immediately by an elongated constricted web dewatering zone in substantially uniplanar (PP) relationship to the initial zone 13 and in a downwardly inclined direction, drive means (indicated diagrammatically at D, D) for driving each said loops at substantially the same peripheral speed, stock feed means 14 for generating and feeding a thin high speed stock jet of substantially homogeneous suspended entangled co-moving stock fibers into the large end of such converging zone 13 and draining stock through and depositing fibrous Webs on to both loop surface portions 11a, 12a in such converging zone 13 just after the stock jet enters thereinto, said stock means 14 directing the stock jet in substantially the aforesaid downwardly inclined substantially uniplanar direction P--P, and first and second dewatering means 15, 80 positioned within the first and second loops 11 and 12, respectively, and cooperating with the drive means D, D' and the stock feed means 14 to maintain substantially continuously during web formation a hydraulic head in the stock traveling from the stock jet downwardly into the aforesaid uniplanarly aligned zones 13, 13a.

Processwise, the invention comprises the steps of driving first and second foraminous web forming belt loops peripherally at substantially the same speed and through first and second opposed belt runs presenting substantially contiguous outer peripheral surface portions defining therebetween an initial converging zone for web deposition on both surface portions of such loops in the zone, followed immediately by an elongated constricted web dewatering zone 13a extending from the converged end of the initial zone 13 in substantially uniplanar relationship to the initial zone and in a downwardly inclined direction, generating and feeding a thin high speed stock jet of substantially homogeneous suspended entangled co-moving stock fibers into the large end of such converging zone 13 and draining stock through and depositing fibrous webs onto both loop surfaces 11a and 12a in such converging zone 13 just after the stock jet enters thereinto, aligning such stock jet in substantially the aforesaid downwardly inclined substantially uniplanar direction, and withdrawing water from the stock in such zones through the wire runs 11a and 12a in controlled manner to maintain substantially continuously a hydraulic head on the stock between the wire runs, while withdrawing water from the stock through the opposed wire runs at a controlled rate to deposit substantially uniforrnly fibrous webs on the aforesaid comoving foraminous loops, thereby to effect substantially uniform web surface characteristics on both sides of the web being formed and dewatered.

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.

We claim as our invention:

1. In a machine for forming a fibrous web from a dilute aqueous fiber suspension, in combination, first and second belt mounting means, first and second foraminous webforming belt loops mounted respectively on said first and second belt mounting means and having respectively first and second opposed belt runs presenting substantially contiguous outer peripheral surface portions defining therebetween an initial converging zone for web deposition on both surface portions followed immediately by an elongated constricted web dewatering zone extendingfrom the converged end of the initial zone in substantially uniplanar relationship to the initial zone and in a downwardly inclined direction, said belt mounting means including adjustable means for varying the angle of inclination of the direction of said elongated constricted web dewatering zone with respect to the horizontal, drive means for driving each said loops at substantially the same peripheral speed, stock feed means for generating and feeding a thin high-speed stock jet of substantially homogeneous suspended entangled co-moving stock fibers into the large end of such converging zone and draining stock through and depositing fibrous webs onto both loop surface portions in such converging zone just after the stock jet enters thereinto, said stock feed means directing the stock jet in substantially the aforesaid downwardly inclined substantially uniplanar direction, and first and second dewatering means positioned within the first and second loops, respectively, and cooperating with the drive means and the stock feed means to maintain substantially continuously during web formation a hydraulic head in the stock travelling from the stock jet downwardly in the aforesaid substantially uniplanarly aligned zones.

2. The invention as defined in claim 1, wherein said stock feed means comprises means for varying the angle of inclination of the direction of the stock jet as it is fed to said converging zone.

3. The invention as defined in claim 1, wherein said first dewatering means positioned within said first loop comprises a plurality of spaced foils inclined downwardly from the horizontal and providing forward guiding edges for defining generally parabolic contour to the upstream end of said first run at the initial converging zone for controlled dewatering through said first run.

4. The invention as defined in claim 3, wherein said second dewatering means comprises a water deflector engaging the inner periphery of said second run downstream from the initial converging zone so as to provide a substantially unsupported second wire run opposite said foils and at one side of said initial converging zone to effect a controlled rate of dewatering through said second run.

References Cited UNITED STATES PATENTS 2,928,464 3/1960 Western et al. 162-347 2,934,140 4/ 1960 Goodwillie 162-347 X 3,010,510 11/1961 Cirrito 162347 X 3,025,909 3/ 1962 Hart 162---273 3,186,902 6/1965 Grater 162273 3,215,594 11/1965 Baxter et al. 162-20=3 X 3,311,533 3/1967 de Montigny et al. 162303 X HOWARD R. CAINE, Primary Examiner US. Cl. X.R.