US2828675A - Method and apparatus for continuously forming a fibrous web from a liquid suspension and progressively removing liquid therefrom - Google Patents

Description

Apnl 1, 1958 s. E. SEAMAN 2,828,675

METHOD AND APPARATUS FOR CONTINUOUSLY FORMING A FIBRCUS was FROM A LIQUID SUSPENSION AND PROGRESSIVELY REMOVING LIQUID THEREFROM Filed Feb. 21, 1956 s Sheets-Sheet l INVENTOR 57WAET F. SEAMAN.

ATTORNEY Aprll 1958 s. E. SEAMAN 2,828,675

METHOD AND APPARATUS FOR CONTINUOUSLY FORMING A FIBRJUSWEB FROM A LIQUID SUSPENSION AND PROGRESSIVELY REMOVING LIQUID THEREFROM Filed Feb. 21, 1956 3 Sheets-Sheet 2 INVENTOR yin A7 6 56/: M14

ATTORNEY Apnl 1, 1958 s. E. SEAMAN 2,828,675 A METHOD AND APPARATUS FOR CONTINUOUSLY FORMING A FIBROUs WEB FROM A LIQUID SUSPENSION AND PROGRESSIVELY REMOVING LIQUID THEREFROM Filed Feb. 21, 1956 5 Sheets-Sheet 3 ATTORNEY Unite States Patent "Office 2,828,675 Patented Apr. 1, 1 95 8 METHOD AND MPARATUS FOR CONTINUOUS- LY FONG A FIBRGUS WEB FROM A LIQUID SUSPENSEQN AND PROGRESSIVELY REMOV- lNG LIQUID THEREFRQM Stewart E. Seaman, White Plains, N. Y.

Application February 21, 1956, Serial No. 566,844

13 Ciaims. (Cl. 92-38) This invention relates to the art of forming a substantially uniform web or mat of fibrous material from a liquid suspension of fibers, and is useful, for example, in the manufacture of board and the like from fibers such as ground wood, pulp, cotton linters, bagasse, straw, etc. It is also useful in the manufacture of chemical pulp and in the production of alkali cellulose to control the ratio of alkali to cellulose in the alkali cellulose.

One of the principal objects of the invention is to provide a way to form a web continuously from a suspension of fibers and mechanically to compact and firm the web and remove the maximum amount of liquid therefrom in a less expensive operation and with less expensive apparatus than has heretofore been required.

The conventional way to form such a webhas been to cause a deposit of fibers from suspension upon a moving perforate or foraminous backing such as a cylindrical mold or a Fourdrinier wire, suflicient liquid being removed therefrom while on such backing to produce a web of low consistency, after which the web in this weak condition is delivered upon a traveling felt and passed between press rolls, the liquid content being progressively reduced until the desired consistency is reached. Suction boxes underneath the Fourdrinier wire augment gravity in the removal of liquid and a couch roll at the end of the wire just before delivery to the felt exerts opposing pressures upon the web and expresses liquid to perhaps a consistency of 25%, the consistency being raised to around 40% in the press rolls, after which in the making of board the drying of the web is completed in a steam heated dryer.

A specific objective of the present invention is to dispense with the costly wet end, Fourdrinier wire and felt in the production of fiber webs from suspension. Another object is to reduce the size and floor space requirements of apparatusfor the purpose. Still other objects will appear as the description proceeds. j

In accordancewith this invention, the web is preliminarily formed on a stationary member which is in the form of a smooth perforate plate disposed at an inclination so that the stock material will flow down over the plate by gravity, being meanwhile sulficiently dehydrated by the escape of liquid through-the perforations to cause the fibers to be deposited upon the plate and mat into a more or less uniform web.

' Preferably the web moves from this plate on to a comparatively short foraminous conveyor and while it is car} ried on this conveyor it is compressed and somewhat firmed and further dehydrated by passing through successive rollers of progressively increasing pressure.

The conveyor delivers the web directly without the use offelt into the nip or bite of press rolls which complete the mechanical dehydration. The lower roll is so constructed that the liquid expressed from the web escapes through the periphery of the roll, thereby avoiding the formation of a pool of liquid at the bite and the creation of an hydraulic pressure in the web counter to its movement and the consequent rupturing of the web, as would the plate 10 is set according to the type and consistency.

otherwise be likely to occur in the absence of a felt toabsorb the liquid.

In its commercial form the contact surface of the roll is made up of a series of closely spaced rings which are internally mounted upon and supported by axially extending bars on spokes which radiate from hubs fixed at spaced intervals upon an axial drive shaft. The expressed liquid escapes through the spaces between the rings.

Preferably there are two such lower rolls which have pressure engagement with a single top roll, and the top roll may be solid roll or it too may be made up of spaced rings. The press rolls may comprise two or more pairs instead of a three-roll construction, and in either form the pressure of the lower rolls is adjustable and in operation the pressure upon the web progressively increases as it passes through the press rolls.

The surface of the rolls may be smooth or it may be serrated. In the latter case the surface of the rings will be peaked or saw toothed in cross section and the surface of the top roll will be serrated and complementary to that of the lower rolls.

Preferably the rings are tapered on their sides so as to provide annular intervening spaces of increasing width that will afford relief for the fibers that drain off with the liquid and avoid clogging. In such case intervening spacing plates will be similarly tapered.

The invention comprehends other features of construction and has other objects and advantages as will appear from the following description of the embodiment of the invention illustrated in the accompanying drawings to which reference is now made.

Fig. 1 is a diagrammatic side view of an apparatus embodying the invention;

Fig. 1A is a fragmentary face view of a portion of the inclined perforate plate;

Fig. 2 is a diagrammatic side view of the press roll portion of the apparatus showing the rollers in end'view and the pressure adjusting means for the lower rolls;

Fig. 3 is an enlarged side elevation of one of the lower rolls with some of the rings removed and one ring shown in section and in position to be added;

Fig. 4 is a perspective of a spacing plate and of the attaching pins shown spaced from the plate;

Fig. 5 is a fragmentary section of a portion of a bottom roll having a smooth surface and taken on line 5-5 of bottom roll andof the mating top roll showing serrated mating faces and taken on a 10-40 of Fig. 7. V

The apparatus, as shown in Fig. 1, includes a'smooth inclined plate 10 which is perforated, as shown in Fig.

line corresponding to line lA,'with holes of a predetermined size andspacing, and

which is disposed with its upper end in position to reccive stock from a head box and stock regulator 11. The stock is a liquid suspensionof fiber such as ground wood, pulp, cotton linters, alkali cellulose, etc., the consistency of which is controlled and the inclination of of the stock. With wood pulp, for example, the con sistency' would be approximately 1 /2% and at the bottom of the incline the consistency would be 5 or 6fpercent. a e 7 At its lower end the plate 10 delivers on to a horizon tal foraminous endless conveyor 12 which runs, over pulleys 13 one of which is driven. Below and in contact with the top run of the conveyor are a series of three rollers 14 which are respectively opposed by three rollers 15 on the top of the conveyor. Theserollers are driven and the pressure exerted by the pairs of rollers progressively increases so that at the end of the conveyor the web is substantially firm and the consistency is 12 to 15 percent.

From the conveyor 12 the web passes into the bite of press rolls in direct contact with the rolls without the interposition of felt, the bottom roll being so constructed as to receive and dispose of the expressed liquid in a direction normal to the web as will be explained hereinafter.

The web will be subjected to two successive pressings by the press rolls, the pressure on the second pressing being greater than that on the first pressing. This may be done by two pairs of press rolls or, as shown in Fig. 1, two bottom rolls 16 and 17 may coact with one top roll 18. In the latter case the top roll is preferably larger than the bottom rolls, being, for example, from twentyfour to thirty inches in diameter and the bottom rolls being of the same or approximately the same size from eighteen to twenty-four inches in diameter.

The conveyor 12 is preferably disposed with its top run above the level of the bite of rolls 16 and 18 and so as to deliver the web as close as possible to the bite. The web is firm enough to enter into the bite without rupture and it is further firmed and dehydrated as it passes between rolls 16 and 18. it is then strong enough to pass into the bite between rolls 17 and 18 the pressure of which is greater than that of rolls 16 and 18. The liquid expressed by the press rolls passes by gravity down through the lower rolls and the web is led from the press rolls on to an endless conveyor 19 which may be foraminous and runs over pulleys 20 one of which is driven. From the conveyor 19 the web goes to a dryer or to a picker if it is to be used at once.

The press rolls are power driven and the pressures will be regulated so as to complete the dehydration to a consistency of from fifty to sixty percent. Fig. 2 illustrates a mounting for the lower rolls 16 and 17 which enables the obtaining of the desired differential pressures. Roll 16 bears in a pair of arms 21 (one being shown) and roll 17 bears in a pair of arms 22 (one being shown). These arms have a common pivot 23 at their inner ends and their outer ends are pivotally con nected to the ends of the piston rods 24 and 25, respectively, of pneumatic loading cylinders 26 and 27, respec tively, these cylinders having pivotal attachment to feet on axes parallel to those of the connections of the arms to the piston rods. The cylinders are independently controlled and constitute independent power means for adjusting the bearings of the shafts of rollers 16 and 17, thereby independently adjusting the pressures of the bottom rolls with respect to the top roll. The pressure exerted on the outer ends of the arms is regulatable and is set so that the pressure of roll 17 exceeds that of roll 16. I

The liquid which is drained or expressed from the web during its dehydration is caught in a tank or pan 28 and provision is made to return this to the machine chest from which the stock is fed to the head box 11 or to pass it to dialyzers for purifying before returning to the machine chest.

As shown the tank is partitioned'into sections. The first section catches the dripping from plate 10 and conveyor 12 and runs into a bottom header 29 from where it is pumped by pump 30 through pipe 31 tothe machine chest. A second section of tank 28 catches the liquid from the first press roll 16 and a third section catches the liquid from the second press roll 17. These sections discharge into drain pipes which have valves 32 and 33,

respectively, which in one position pass the liquid down into header 29 and in another position direct the liquid to pipes 34 and 35, respectively, which lead to dialyzers.

The construction of the two bottom rolls 16 and 17 is shown in Figs. 3 to 11, inclusive. They are composed of a series of rings which are spaced slightly so as to allow the expressed liquid to pass between them into the hollow interior of the rolls and to drain therefrom into the tank 28. These rings may have a smooth cylindrical surface or they may be peaked or in the form of a salient angle in cross section to increase the surface area. Their sides are preferably undercut or bevelled inwardly to avoid clogging.

The rings are strongly internally braced in view of the considerable pressure ,to which they are subjected. Wheel-like structures are fixed at intervals along an axial drive shaft and bars on the fellies at the outer ends of the spokes extend axially and the rings are fitted over these bars and are supported by them. Alternate bars carry spacing plates which fit between the rings and are pinned to their sides.

The rings 40 shown in Fig. 3 have a smooth cylindrical peripheral surface and a series of such rings are disposed in spaced relation on the inner structure of the roll. This inner structure has an axial drive shaft 41 and at spaced intervals wheel-like structures 42 are keyed thereon. These have a hub portion 43, a series of radial spokes 44 and a felly 45. On the fellics are a series of axial bars which tie the wheel fellies together. As shown, there are eight spokes and eight bars set into grooves in the fellies; one opposing each spoke. Four of these bars 46 are attached to the fellies by screws and have arcuate outer faces on which the rings fit. These bars 46 are equally spaced and oppose four alternate spokes. Between the bars 46 and opposing the intermediate spokes are plate supporting bars 47 which also have arcuate outer faces fitting within the rings. These bars 47 are secured to the fellies, as by screws, and they are provided with transverse slots 48 into which fit the inner ends of spacing plates 49 that are disposed between the rings.

As shown particularly in Fig. 5, the rings have their sides tapered or bevelled, the inner axial dimension being less than the outer thus reducing the tendency of fibers carried by the expressed liquid from clogging in the spaces between the rings. The rings have two through holes radially opposite each plate 47 and pins 50 are carried by .the plates 49 and project equally on opposite sides of the plate and enter half way into the through holes in each adjacent ring. The plates are shaped to fit into the tapered space between the rings.

The rings are clamped against longitudinal shifting on the bars by end clamping rings 55, one of which is shown in Fig. 6, which are secured in clamping position by lock collars 56. The spacing between the rings will usually be one-sixteenth of an inch or less.

Instead of smooth face rings, they may be peaked as shown in Fig. 10 and form a corrugated surface for the roll cooperative with a complementary corrugated surface of the top roll with the resultant greater surface area and increased yield.

The top roll 18 may be a solid face roll or it too may have spaced circumferential slots to receive the expressed liquid.

For vsome materials the pressure of the two bottom rolls may be the same.

What is claimed is:

1. The method of forming a web of fibrous material from a stock consisting of a liquid suspension of fibers, said method comprising continuously flowing the stock in a uniform sheet upon a stationary inclined perforated plate having a smooth surface and causing the sheet to slide downwardly upon said surface by gravity at a speed to drain sufiicient liquid therefrom through the perforations during the downward movement to form a web of the fibers, causing the web so formed to progress continuously and subjecting the web as it progresses to preliminary opposing pressures sulficient to compact the web and express liquid therefrom and partially dehydrate the web, and continuing the movement of the partially dehydrated Web and subjecting it to final opposing pressures substantially greater than the preliminary pressures and completing the desired dehydration and conducting the liquid expressed from the web during such greater pressure from the web in a downward direction normal thereto.

2. The method defined in claim 1 in which there are a plurality of gradually increasing preliminary opposing pressures.

3. The method defined in claim 1 in which there are a plurality of progressively increasing final pressures.

4. The method of forming a web of fibrous material from a stock consisting of a liquid suspension of fibers, said method comprising continuously flowing the stock in a uniform sheet upon a stationary inclined perforated plate having a smooth surface and causing the sheet to slide downwardly upon said surface by gravity at a speed to drain sufiicient liquid therefrom through the perforations during the downward movement to form a web of the fibers, continuously progressing the web so formed and subjecting it to opposing pressures sufficient to express liquid therefrom to a desired consistency and conducting the liquid expressed therefrom by such opposing pressures from the web in a downward direction normal thereto.

5. An apparatus for forming a web of fibrous material, comprising an inclined perforate stationary plate having a smooth surface and adapted to have fiber suspension stock which is delivered to its top end flow down its said surface by gravity and partially drain the liquid therefrom and allow fibers in suspension to mat thereon, and press rolls positioned to receive the web so formed into their bite, the bottom roll being hollow and formed of a plurality of spaced rings.

6. An apparatus for forming a web of fibrous material as defined in claim 5 in which the bottom roll comprises an axial drive shaft, a plurality of spoke bearing hubs fixed on the shaft in spaced relation, bars on the ends of the spokes extending parallel with the shaft, and a plurality of spaced rings fitting over and secured to the bars.

7. An apparatus as defined in claim 6 together with spacing plates between successive rings supported by certain of said bars and secured to the lateral face of an adjacent ring.

8. An apparatus as defined in claim 5 in which the press rolls comprise a top roll and two bottom rolls successively contacting the top roll, each bottom roll being hollow and formed of a plurality of spaced rings and having an axial drive shaft mounted in adjustable bearings, together with an independent power means for adjusting the bearings of each bottom roll shaft and thereby independently adjust the pressures of the two bottom rolls with respect to the top roll.

9. An apparatus as defined in claim 5 in which the external circumferential face of the rings is peaked in cross section, whereby the rings collectively make a serrated cylindrical surface, and in which the top roll has .a complementary serrated cylindrical surface.

10. An apparatus as defined in claim 7 in which the sides of the rings converge inwardly and the spacing plates are tapered to fit between adjacent rings.

11. An apparatus for forming a web of fibrous material, comprising an inclined perforate stationary plate having a smooth surface and adapted to have fiber suspension stock which is delivered to its top end flow down its said surface by gravity and partially drain the liquid therefrom and allow fibers in suspension to mat thereon, a traveling foraminous conveyor disposed at the bottom of the plate in position to receive the web therefrom, and press rolls positioned to receive the web from the conveyor into their bite, the bottom roll being hollow and formed of a plurality of spaced rings.

12. An apparatus as defined in claim 11 together with at least one pair of rollers disposed in opposition on opposite sides of the conveyor and adapted to compact and express liquid from the web on the conveyor passing between the rollers.

13. An apparatus as defined in claim 12 in which there are a plurality of pairs of rollers disposed in succession along the conveyor and in which the rollers of the successive pairs are progressively disposed in greater pressure relation.

References Cited in the file of this patent UNITED STATES PATENTS 923,870 Meader June 8, 1909 990,950 Barber May 2, 1911 1,493,536 Haug May 13, 1924 1,503,605 Shaw Aug. 5, 1924 1,553,463 Nishina Sept. 15, 1925 2,209,756 Berry July 30, 1940 2,488,700 Bidwell Nov. 22, 1949

Claims (1)

11. AN APPARATUS FOR FORMING A WEB OF FIBROUS MATERIAL, COMPRISING AN INCLINED PERFORATE STATIONARY PLATE HAVING A SMOOTH SURFACE AND ADAPTED TO HAVE FIBER SUSPENSION STOCK WHICH IS DELIVERED TO ITS TOP ENF FLOW DOWN ITS SAID SURFACE BY GRAVITY AND PLURALITY DRAIN THE LIQUID THEREFROM ANS ALLOW FIBERS IN SUSPENSION TO MAT THE BOTTOM A TRAVELLING FOAMINOUS CONVEYOR SIDSPOSED AT THE BOTTOM OF THE PLATE IN POSITION TO RECEIVE THE WEB THEREFORM, AND PRESS ROLLS POSITIONED TO RECEIVE THE WEB FROM THE CONVEYOR INTO THEIR BITE, THE BOTTOM ROLL BEING HOLLOW AND FORMED OF A PLURALITY OD SPACED RINGS.

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