US3281313A - Stock removing slice for paper making machine and method of making paper - Google Patents

Description

Oct. 25, 1966 B. w. ATTWOOD 3,281,313

STOCK REMOVING SLICE FOR PAPER MAKING MACHINE AND METHOD OF MAKING PAPER Flled Aug 6 1963 2 Sheets-Sheet l Biz a0 Oct. 25, 1966 w, -rwoo 3,281,313

, B. STOCK REMOVING SLICE FOR PAPER MAKING MACHINE AND METHOD OF MAKING PAPER Filed Aug. 6, 1963 2 Sheets-Sheet 2 INVENTOR. Bria/7 M'Z/("am flzz wooo.

3,281,313 STUCK REMQVING SHOE FOR PAPER MAKING MAQHINE AND METHOD OF MAKING PAPER Brian William Attwood, Hanharn, near Bristol, England, assignor to St. Annes Board Mill Company Limited, Bristol,England, a corporation of England Filed Aug. 6, 1963, Ser. No. 300,215 Claims priority, application Great Britain, Jan. 30, 1963, 3,744/ 63 7 Qlaims. (Cl. 162-203) This invention relates to an endless web forming machine such as a paper or paperboard making machine and to a method of making an endless web of felted fibers. More particularly, the invention relates to a machine and method for making an integral felted-fiber web of the desired thickness and of improved formation characteristics such that the web has a more uniform, high-strength upper and lower surface yet is free from any tendency to delaminate.

In recent years, machines have been developed for the manufacture of paper or board products in which the stock, as it flows along with the traveling forming wire, is led into a gap where it is de-watered by being squeezed between the main forming wire and a lower converging run of an upper forming wire. At one or more points further downstream of the first such squeezing operation, one or more stock feed boxes are located to provide additional stock for felting and bonding with the initially at least partly formed stock layer by similar de-watering steps also accomplished by squeezing the layer of stock between the main forming wire and a lower converging run of an upper forming wire. Machines and methods of this general type for making endless webs of felted fibers are more particularly disclosed and claimed in patents owned by the assignee of the present application.

When running machines of the above general kind, it is normal practice to deliver more stock than that required to form a web of predetermined basis weight, and some difficulties have arisen, particularly when the machines are run at low speeds, because the'surplus stock supplied builds up in advance of the stock-filled gap, more especially after the second stock feed box and subsequent sets of cooperating active runs of the main forming wire and of the upper forming wire between which the de-watering of the stock is effected by the squeezing operation referred to above. There is a tendency of the ponds, if allowed to build up beyond a predetermined optimum height, to cause poor sheet formation, possibly due to a slowing up of some of the stock in the pond in its flow toward the stock-filled gap marking the start of the stock squeezing operation between the cooperating wire runs. In some cases, there is even a backing up of the stock pond toward the stock inlet and this may result in agglomeration of the stock due to stagnant portions in the pond, with the result that a wild formation of paper, or paperboard, is obtained. Such stagnant areas in the pond have actually been observed during periods of operation of the machine when poor sheet formation was also being obtained.

Attempts to increase basis weight or thickness of the final paperboard by forcing more stock on to the machine usually result in objectionable pond formation with attendant poorer sheet formation.

My present invention greatly reduces and even eliminates in many instances the troublesome result just noted. This is accomplished by removing excess stock from the pond, or ponds, so as to limit the height of the pond to the optimum height of stock on the main forming wire that can be accommodated by the gap that marks the entrance of the stock to the zone where it is squeezed between cooperating active runs of the forming wires and the del nited States Patent 3,28 l ,3 l 3 Patented Get. 25, 1966 "ice watering occurs. The excess of stock in the pond, over and above the optimum height, may be removed or such excess may be prevented in various ways, as by means of devices having stock-diverting openings, mouths, or barriers positioned in the ponds at the proper level, so that stock above such proper level is diverted and removed and the level is maintained at the optimum point for efficient operation of the machine. Not only is the formation of the finished paper or paperboard greatly improved by these means, but a given board making machine employing such means can be operated to give paperboard of higher basis weight and/ or of greater thickness than had heretofore been possible. These improved results can be attained with the use of various stock furnishes and various consistencies of stock not satisfactorily usable on board making machines of the general type herein referred to when not equipped with the stock-removal means of my present invention.

It is therefore an important object of this invention to provide an improved endless felted web making machine that is capable of producing paper and paperboard products having improved properties and characteristics not heretofore attainable when similar machines, but not embodying the principles of my present invention, are operated under comparable conditions of speed, composition of stock furnish and consistency of stock.

It is a further important object of this invention to provide means whereby endless web making machines of the type herein described are rendered more efficient in their operation at slower speeds than they were initially designed for, and whereby the increased flexibility as to machine operating conditions is accompanied by superior results with respect to the formation of the sheet, the surface characteristics of the sheet, its strength and other properties.

It is a further important object of this invention to provide a method for making paper and paperboard products whereby forming stocks of varying furnishes and consistencies may be efiiciently utilized in the making of paper and paperboard having improved formation characteristics within a wider range of basis weights than heretofore was possible.

Other and further important objects of this invention will become apparent from the following specification and the appended drawings, wherein a preferred embodiment of my invention is illustrated, and wherein:

FIGURE 1 is a fragmentary, diagrammatic view, illustrating the wet end, or web-forming section, of a machine embodying the principles of my invention and useful for manufacturing a two-ply board;

FIGURE 2 is an enlarged, fragmentary view, partly in side elevation and partly in section, of the preferred embodiment of my invention illustrated diagrammatically in FIGURE 1;

FIGURE 3 is a fragmentary, side elevational view of a second embodiment of my invention;

FIGURE 4 is a fragmentary, side elevational view of a third embodiment of my invention;

FIGURE 5 is a broken, front elevational view taken substantially along the lines VV of FIGURE 2;

FIGURE 6 is a fragmentary, side elevational view of a fourth embodiment of my invention; and

FIGURE 7 is a broken, top plan view of the stockdiver-ting device of FIGURE 6.

As shown on the drawings:

The reference numeral 10 indicates generally a stock flow box, or head box, from which stock is fed onto a main forming wire 11 in a flowing, open top stream, or layer, indicated by the reference character 12. Said main forming wire 11 extends as an endless loop between a breast roll 13 at the feed end and a couch roll 14 at the delivery end of the web-forming section of the machine.

Said wire 11, as is usual in Fourdrinier type machines, is in the form of an endless band or loop, with its upper run 11a supported by a plurality of rollers between the breast roll 13 and the couch roll 14. Thus, at the position where the stock is still fluid, there are a number of relatively small diameter table rolls 15, while at other positions the wire 11 is supported 'by larger rollers 80. These rollers 80 permit pressure to be applied to the partly formed web as it is carried along above them, for instance, by upper rollers 17. Guide and tension rollers 16 cooperate with the lower run 116 of said wire in a conventional manner.

A second head box a is positioned downstream from the head box 10 for supplying additonal stock, indicated by the reference numeral 12a, onto the active upper run 11a of the forming wire.

An upper forming wire, indicated generally by the reference numeral 21, is positioned downstream from the head box 10 in cooperative relationship with the first set of rollers 15, 80. Said upper, or top forming wire, 21, is also in the form of an endless loop, with its lower active run 21a extending from a roll 22, which may be either a permeable or impermeable roll, positioned in fairly closely spaced relationship to the feed box 10, and a second roll 23 located downstream from said roll 22. The upper return run 2112 of the top wire 21 is trained over and under a plurality of supporting and guiding rolls 24.

A second top wire, indicated generally by the reference numeral 25, in all respects similar to the top wire 21, serves a similar function with respect to a second section of the main forming Wire 11 and rolls a, 17a and 80a. The lower run 25a of said second top wire 25 extends between a roll 26, spaced in fairly close relationship to the second head box 1011, and a second roll 27 mounted downstream above and in substantial alignment with the couch roll 14.

With reference to the first section of the main forming wire which include the first head box 10, it should be noted that the roll 22 is mounted in slightly spaced relation to and above the active upper run 11a of the main forming wire 11, and above an unsupported portion of said run 11a lying between a pair of spaced table rolls 15. Thus, the lower or active run 2111 of the top forming wire 21 provides a gap, indicated at G, between said active runs 11a and 21a of the respective main and top forming wires. The gap G is preferably of very low height (e.g. 1"), but it varies from gap to gap, that is to say, according as to whether it controls the first layer of stock or a subsequent layer and according to the consistency of the stock being fed. The height of the gap G has been exaggerated in the drawings for purposes of clarity. The pond of stock 12, previously referred to, forms ahead of the mouth of said gap G and flows into the gap to fill the same and to fill the space of gradually decreasing height between the converging portions of the active runs 21a and 11a of the top and main forming wires. Said converging portions are brought itno a state of convergency, except for the layer of stock therebetween, by a de-watering device, indicated generally by the reference numeral 30, which will be more fully described in connection with FIGURE 2. By means of the dewatering device 30, the water and such fine fibers as can pass through the meshes of the active run 21a of the top forming wire 21 are removed upwardly from above the upper surface of said active portion 21a. The pressure of the de-watering device 30, which presses on an unsupported section of the wires 21 and 11, is such that a major portion of water is removed from the stock. In fact, immediately the web passes downstream from beneath the edge 52 the web is formed to the extent that the fibers assume a structural relationship to one another that thereafter remains substantially unaltered. The resulting Web thereafter is squeezed between the upper and lower sets of rolls 17 and 80. Preferably, said rolls 17 are permeable, as is also the roll 22.

With particular reference to the second functional grouping that includes the second flow box 10a, it will be noted that this arrangement is closely similar to that already described. There is a second de-watering device, indicated generally by the reference numeral 30a, for effecting a dewatering of the stock flowing from the pond 12a into the converging gap between the main forming wire active run 11a and the active run 25a of the top forming wire 25. As the active run 1111 of the main forming wire moves beyond the roll 23, it carries on its upper surface a web W. Such web, as a result of the first de-watering operation at the device 30 and the pressure of the rolls 17, 80, has a fiber content of the order of 15% by weight on a bone dry basis and is composed of fibers that have become interfelted or interlocked in substantially the same way and to substantially the same extent that the fibers are interfelted and interlocked in the final sheet when dried. Consequently, as the fresh supply of stock, indicated at 12a, flows from the second head box 10a, such fresh supply of stock flows on top of the already partially formed web W, with the result that drainage of the water downwardly through the active run 11a of the main forming wire 11 is greatly slowed down. It is largely because of this that the fresh flow of stock 12:: tends to build up into a pond in advance of the next de-watering stage that begins at the gap G-1 and extends to the second de-watering device 30a. It is at this point that the stock removal means of my present invention finds particular application for solving the problems that otherwise arise for the reasons previously indicated.

As best shown in FIGURE 2, the preferred embodiment of the stock removal device of my present invention, represented generally by the reference numeral 40, includes a suction conduit 41 that extends transversely and above the active run 11a of the main forming wire 11. Said conduit 41 may be suitably supported at its ends, as by means of brackets 42 attached to a wall of the head box 1011 from hangers 43 dependently carried by said brackets 42 and vertically adjustable with respect thereto. For this purpose, each of the hangers 43 may have a threaded shank 44 in threaded engagement with an internally threaded bore 45 in each bracket 42. Horizontal adjustment of the conduit 41 may also be provided by forming each of said brackets 4-2 of a plurality of relatively extensible slotted portions that can be clamped by means of a wing nut and bolt 45a in the desired extended position. A source of suction (not shown) is connected at one or both ends of the conduit 41 by means of a pipe, or pipes 46. As illustrated, the conduit 41 has a transversely extending and slightly downwardly inclined extension 47 terminating in a lower opening, or mouth, as at 48, defined by edges which lie substantially in a horizontal plane when the conduit is in its adjusted position. The extension 47 may suitably comprise a pair of relatively closely spaced plane walls with the lower of the Walls coming off tangentially from the generally cylindrical conduit 41 and defining a stock-removal passageway into the interior of said conduit 41.

The open layer of stock indicated at 12a, as previously stated, tends to build up in advance of the gap G-l, to a level such as that indicated by the dotted line 49, or even higher, that would normally continue to closely adjacent the lower surface of the roll 26. The level 49 will depend in part upon the speed of travel of the main forming wire 11, the composition of the stock furnish and other factors that have an effect upon the permeability of the Web W at this point to the water tending to drain by gravity through the web W and the active forming wire run 11a. Whatever the cause, the tendency is for the level 49 to rise above the top of the gap G-1 and to form a pond P upstream therefrom. The pond P sometimes runs back almost as far as the feed box 10a. Due to stagnant areas U in the pond -P, .and possibly other causes, including the backward flow of stock from the forming wire 25 just ahead of the gap G-ll, there is a tendency to build up agglomeration of fibers in the pond and these are liable to cause a clotted fiber formation in the finished paper or paperboard.

All of these difliculties and troubles can be largely or wholly eliminated by properly adjusting the stock removal device 40, which is preferably adjusted while the machine is operating. The lower mouth 48 of the extension 47 limits the height of the pond P. It is usually found preferable to permit a small pond to remain at the entrance to the gap G1 because this insures that suflicient stock passes into said gap to provide a webof the consistency and thickness desired. Thus, the device 40 is set so that its mouth 48 is at the highest depth desired for the pond. A typical upper level for the stream of stock is indicated by the dotted line 50 in FIGURE 2.

The excess of stock over that required to provide the web is drawn off by the device 40 and is returned to the stock box for reuse, or to some prior part of the machine for redelivery to the stock box.

Downstream of the mouth, or entrance to the gap G-l, the lower active run 25a of the top forming wire 25 is inclined gradually downwardly toward the active run 11a of the main forming wire 11, until said active run 25a reaches a scraper board, or doctor 51, forming a part of the de-watering device 30a. Said doctor 51 is preferably a thin board that inclines upwardly and downstream from its lower wire-engaging straight edge 52. Water, usually termed white water, from the stock between the convergent runs 25:: and 11a, as a result of the hydraulic head and forward momentum of the stock, passes through the otherwise confining portion of the active run of wire 25a and is swept towards and picked up from the upper side of said wire by the inclined doctor 51. The majority of the water, however, passes through the run 25a at the position where said run passes beneath the edge 52 of the doctor 51, so that an instantaneous formation takes place at said edge. The water so picked up is discharged into a collecting trough 53. The trough is connected by one or more pipes 54, usually through a pump (not shown) back to the head box a, or to a stock chest in advance of the machine for the return of the white water for reuse in the web making process. Simultaneously with the de-watering of the stock that has just been described, there is a certain amount of drainage by gravity of the water from the stock through the active run 11a of the main forming wire as the wire passes over the table rolls 15a. When the stock passes downstream of the position represented by the straight edge 52, the upper layer is substantially dewatered to form a well defined web in which the fibers are felted and interlocked much to the same extent as in the final board, but without any distinct planes of separation between the strata such that delamination can be easily effected. In other words, the web is relatively uniform and of an integral character. It will be seen that the straight edge 52 lies over an unsupported port-ion of the cooperating active runs 11a and 25a of the wire. After passing from under the straight edge 52, the cooperating runs of wire pass over a roll 80a, which is similar to the corresponding one of the lower rolls 80, and thence into the second group of rolls 17a, 80a. As the active wire run-s 11a and 25a pass respectively beyond the couch roll 14 and the end roll 27 on their return runs, the now-unsupported web W is ready for delivery to the first press section of the board making machine or to another main forming wire constituting a portion of a further web-building section similar to the section 1%, 2 5, 40 already described.

In FIGURE 3, wherein similar elements of the machine are designated by the same reference numerals as in FIG- URES 1 and 2, a suction conduit 60, instead of being supported froma wall of a head box as was the suction conduit 41, is supported from a non-rotating stub shaft 61 coaxial with the axis of the roll 26. Bracket arms 62, having at their inner ends split clamping portions 63 and bolt tightening means 64 and having at their free ends conduit engaging portions 65, serve to support said conduit 60 for adjustment about the stubshaft as a pivot point. Since said conduit is formed with a downwardly extending arcuate portion 66 closely spaced from and conforming generally in curvature to the surface of the roll 26, any adjustment of said conduit results in the raising or lowering of its open end 67 without appreciably changing the spatial relationship between said open end and the surface of the roll 26. As before, the conduit 60 is connected to a source of suction (not shown) to draw off stock from the pond P immediately ahead of the mouth of the gap G-2 to maintain the predetermined optimum level 50.

In FIGURE 4, a pair of stationary deckle boards '70 having apertures 71 in horizontal alignment at the optimum pond level serve to maintain the desired level 50 at the gap G-3. Preferably the apertures 71 are in open flow communication with a suction manifold 72 for aiding in withdrawing stock laterally from the pond P and maintaining the height thereof at the optimum level 50.

FIGURES 6 and 7 illustrate another embodiment of my invention in which a slice or scraper is directed towards the head box 10a so that it acts to skim off stock in a pond above a predetermined height. In this case the slice comprises a plate-like member 81 extending across the wire 11a having an upstanding wall 82 that is curved transversely so as to deflect surplus stock to each side of the wire 11a, where it is collected for reuse.

By the use of any of the foregoing embodiments, the improved results previously referred to can be realized. By way of example, when the paper making machine is operated at between 150 and 400 per min., it is possible when a mechanical, or ground wood pulp is used, by forcing more stock on to the wire, to obtain up to a maximum of 50% increase in basis weight over that obtainable without the use of my stock-removal attachment.

By the use of my invention, the operating range of a normal machine of this type may be extended by allowing boards of higher basis weights to be produced, by improving formation, by permitting the machine to operate at lower speeds and permitting lower consistencies of stock to be used. These improvements may be obtained either individually or in combination.

For example, boards whose basis weight is 50% more than those previously manufactured, have been produced; speeds as low as per min. have been successfully used, and the lowest limit is not yet known; stock consistencies of 0.2% have been used; and in all these examples a wide range of furnishes have been employed.

In the particular form of machine illustrated, no mechanism similar to the mechanism 40 is shown between the head box 10 and the gap G., i.e. at the first forming section, but it is to be understood that under some circumstances of speed and stock consistencies a pond may build up too high at the gap G and in this case a mechanism 40 will be arranged to operate at said gap.

Reference is made to the Thomas et al. Patent No. 2,821,120 for a showing of the general arrangement and operation of machines to which this improvement relates. Conventional driving mechanisms (not here shown) are used in the operation of such machines, acting through the driven elements thereof, such as the couch rolls and other rolls, to drive the active runs of the upper and lower forming wires in the same direction and at the same rate of speed.

From the foregoing, it will be understood that modifications and variations may be effected without departing from the novel concepts of this invention.

I claim as my invention:

1. In an endless web making machine including a main forming wire having an active upper run, a plurality of stock inlets at longitudinally spaced intervals along said upper run to supply stock thereto, a top wire for each of said inlets having an active bottom run starting adjacent the corresponding inlet and converging toward said main forming wire downstream from said inlet, means at said downstream position for pressing said converging active runs of said Wires towards each other thereby forming a gap of progressively decreasing height and squeezing stock therein, and means for driving said wires so that their respective converging active runs travel in the same direction, the improvement which comprises means positioned upstream of said gap and extending thereinto for limiting the height of stock immediately ahead of the starting point of at least one of said active bottom runs by the removal of stock in advance of the corresponding gap.

2. In an endless web making machine including a main forming wire having an active upper run for receiving stock thereon for drainage therethrough, a plurality of stock inlets at longitudinally spaced intervals along said upper run, a roll downstream from one stock inlet other than the first mounted for rotation in vertically spaced relation to said active upper run, a top wire trained around each said roll to provide an active lower run of wire converging toward said main forming wire active run downstream of said rolls, means at said downstream position for pressing the respective portions of said active runs towards each other thereby forming a convergent gap between said portions for receiving stock and squeezing the stock therebetween to de-water same, and means for driving said active wire runs in the same direction and at the same speed, the improvement which comprises a pair of deckle boards having longitudinally spaced apertures at about the level of said maximum height for removing stock from above said main forming wire ahead of at least one of said convergent gaps but downstream of its stock inlet to maintain the level of the remaining stock at a predetermined maximum height at the entrance to said gap.

3. In an endless web making machine including a main forming wire having an active upper run, a stock inlet to supply stock to said upper run, a top wire having an active bottom run converging toward said main forming wire downstream from said inlet to form a stock-filled gap of progressively decreasing height downstream, means for driving said Wires so that their respective converging active runs travel in the same direction and means pressing the respective converging active runs of said wires toward each other to squeeze the stock therebetween, the improvement which comprises means upstream of said gap and extending into said gap for limiting the height of stock immediately ahead of the starting point of said active bottom run by the removal of stock in advance of the stock-filled gap.

4. An endless web making machine as defined by claim 3 wherein said height-limiting means is a suction device having a stock-removing opening positioned immediately ahead of said gap and at approximately the predetermined maximum height level of the stock that is to be maintained above said main forming wire.

5. An endless web making machine as defined by claim 3, wherein said height-limiting means comprises a suction conduit extending the full width of the main forming wire and spaced thereabove and in advance of said corresponding gap and having a stock-removing portion extending toward said corresponding gap and having an opening at a point approximately that of the predetermined height level of stock that is to be maintained in advance of said gap.

6. An endless web making machine as defined by claim 3, wherein said stock removal means comprises stationary apertured deckle boards providing a plurality of said fluid receiving openings.

7. In a method of making a fibrous web which includes advancing an open top layer of stock into the mouth of a converging gap between a top forming wire and a bottom forming wire, advancing the forming wires with the stock therebetween and squeezing said wires toward each other to de-water said stock and form said stock into a web, the improvement which comprises the steps of delivering stock in excess of that required to make the web and controlling the height of said open top layer of stock immediately in advance of said converging gap by the removal of stock from within the gap itself.

References Cited by the Examiner UNITED STATES PATENTS 1,662,226 3/1928 Witham 162-344 1,818,777 8/1931 Aldrich et al. 162345 1,889,819 12/1932 Berry 162345 2,193,032 3/1940 Mackenzie 162-337 2,821,120 1/1958 Thomas et a1. 162300 2,881,676 4/1959 Thomas 162-203 DONALL H. SYLVESTER, Primary Examiner.

J. H. NEWSOME, Assistant Examiner.

Claims (2)

1. IN AN ENDLESS WEB MAKING MACHINE INCLUDING A MAIN FORMING WIRE HAVING AN ACTIVE UPPER RUN, A PLURALITY OF STOCK INLETS AT LONGITUDINALLY SPACED INTERVALS ALONG SaID UPPER RUN TO SUPPLY STOCK THERETO, A TOP WIRE FOR EACH OF SAID INLETS HAVING AN ACTIVE BOTTOM RUN STARTING ADJACENT THE CORRESPONDING INLET AND CONVERGING TOWARD SAID MAIN FORMING WIRE DOWNSTREAM FROM SAID INLET, MEANS AT SAID DOWNSTREAM POSITION FOR PRESSING SAID CONVERGING ACTIVE RUNS OF SAID WIRES TOWARDS EACH OTHER THEREBY FORMING A GAP OF PROGRESSIVELY DRIVING SAID WIRES SQUEEZING STOCK THEREIN, AND SAID MEANS FOR DRIVING SAID WIRES SO THAT THEIR RESPECTIVE CONVERGING ACTIVE RUNS TRAVEL IN THE SAME DIRECTION, THE IMPROVEMENT WHICH COMPRISES MEANS POSITIONED UPSTREAM OF SAID GAP AND EXTENDING THEREINTO FOR LIMITING THE HEIGHT OF STOCK IMMEDIATELY AHEAD OF THE STARTING POINT OF AT LEAST ONE OF SAID ACTIVE BOTTOM RUNS BY THE REMOVAL OF STOCK IN ADVANCE OF THE CORRERSPONDING GAP.

7. IN A METHOD OF MAKING A FIBROUS WEB WHICH INCLUDES ADVANCING AN OPEN TOP LAYER OF STOCK INTO THE MOUTH OF A CONVERGING GAP BETWEEN A TOP FORMING WIRE WITH BOTTOM FORMING WIRE, ADVANCING THE FORMING WIRES WITH THE STOCK THEREBETWEEN AND SQUEEZING SAID WIRES TOWARD EACH OTHER TO DE-WATER SAID STOCK AND FORM SAID STOCK INTO A WEB, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF DELIVERING STOCK IN EXCESS OF THAT REQUIRED TO MAKE THE WEB AND CONTROLLING THE HEIGHTOF SAID OPEN TOP LAYER OF STOCK IMMEDIATELY IN ADVANCE OF SAID CONVERGING GAP BY THE REMOVAL OF STOCK FROM WITHIN THE GAP INSELF.

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