US1421664A - Method of and apparatus for washing pulp - Google Patents

Description

'0. B. BROWN, H. K. MOQRE HPPARKER, AND H. M. MARTINSON.'V

METHOD OF AND APPARATUS FORWASHING PULP.

. Patented July 4, 1922.

6. drawn Map APPHCATION FILED'OCL 22, I919- 0. 8. BROWN, H. K. MOORLH. 'PARKER A'ND H. M. MARTINSON. METHOD OF AND APPARATUS FOR WASHlNG PULP.

APPHCAUQN FILED OCT. 22, 1919. I

A Patented July 4, 1922.

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METHOD OF AND APPARATUS FOR WASHING PULP.- APPHCAUON FILED o er-22,1919.

Patented July 4, 1922.

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METHOD OF AND APPARATUS FOR WASHING PULP.

APP.ICAT!0N FILED- OCT. 22, 1919.

Patented July 4,1922.

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ofs. BROWN, H. K. MOORE, H. PARKER, AND H. M. MARTINSON.

METHODOF AND APPARATUS FOR WASHING PULP. I

APPHGAHON FlL ED0C TP 22, L919.

' Patented July 4, 1922.

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UNITED STATES PATENT orr ca.

ORTON B. BROWN,'HUGH K. MOORE, AND HOWARD PARKER, OI BERLIN,'NEW HAMP- SHIRE, AND HmAN M. MARTINSON, 01 LA TUQUE, QUEBEC, CANADA, AB- BIGNORS TO BROWN CONPANY, OP PORTLAND, MAINE, A CORPORATION OF MAINE.

METHOD OF AND APPARATUS FOR WASHING PULP.

Specification of Letters Patent.

Application filed October 22, 1918. Serial Io. 832,402.

resident of La Tuque, Province of Quebec,

Dominion of Canada, have invented new and useful Improvements in Methods of and Apparatus for Washing Pulp, of which the following is a specification.

The object of this invention is to provide a method and apparatus for effectively washing pulp, and while we shall describe them in connection with the washing of sulphate pulp so-called, it will be apparent to those skilled in the art, after reading this specification, that they may be used with advantage in the washing of soda or sulphite pulp or any other fibrous material,

from which it is desired to remove impuri-' ties of one kind or another.

The washing of pul produced by the sulphate process, is ren ered especially difii;

cult because of the viscous nature and high surface tension of the black liquor resulting from the digestion of the wood whichis mixed intimately therewith. The agitation,

whichis necemary thoroughly to' mix the in the liquor in which it is washed,

pulp and liquor are at a airly high temperature in order to avoid the expense necessary to chill these products or to store them in large storage tanks until the products have cooled under ordinary atmospheric conditions. Furthermore, as it is customary to subject the black liquorto evaporation and smelting processes in the recovery of the soda products, it is desirable to prevent excessive loss of heat between the cooking operation and the evaporating operation; Again it may be pointed out that this black liquor, to which We have referred. is more easily filtered when it is heated than when it is at atmospheric temperature. As the liability of the black liquor to foam, however, is greater when it is heated than when it is cold, it is apparent that the washing is usually carried on under the worst conditions as to foaming.

In general, in accordance with the process which we shall hereinafter describe in detail,

there is a countenfiow of the pulp and the washing liquor; that is to say, the pulp to bewashed is fed into one end of the apparatus and passes through successive baths in 'which'it is washed; whereas the washing water, which forms the baths, is fed into the other end of the apparatus and passes from bath to bath, and the two pass during the operation, the stron est liquor being discharged from that en of the a paratus into i which the pulp is initially ed, and the washed pul emer 'ng from the bath into which the c ear wasiiing liquor is fed.

' The apparatus, which we shall describe for carrying on the continuous process of washing, by which the pulp which is strongl impregnated with the blackliquor is final y discharged in a substantially pure condition free from all but small traces of impurities, comprises" a series of sections each consistin of a storage tank for containing a poo of the wash liquor, an a itator tank containing the bath in whicli't e pulp is agitated and washed, and a cylinder through which the liquor passes and by which the pulp is strained therefrom and delivered to the next adjacent agitator tank or bath. The various storage tanks are so arranged to form successive pools of washing'liquor, and so to provide for a substantially continuous flow of the washing liquor from pool topool from the end to which it is fed to the other end of the apparatus. In these several baths and pools, the liquor gradually increases in strength and density, the pool and-bath into which the pure water is initially fed having the least strength and density and those from which it is finally delivered from the apparatus being of the greatest density and containing the Patented July 4, 1922.

age tank? The pulp, however, as has been stated, which is mixed with and washed in the bath of washing liquor in the agitator tank of one section and flows into the cylinder tank, is picked up by the cylinder,

and, after being removed therefrom by the couch roll, is deposited or scraped into the purer bath contained in the agitator tank of the next adjacent section, this all occurring 7 at a level above the level of the storage tanks, so that the pulp travels in one direction at one level and the washing liquor travels in the opposite direction at the lower level, from one end of the machineto the other. In order to ensure this flow of the washing liquor, the partitions between the storage tanks decrease in height from the end of the machine to which the washing water is fed to the end of the apparatus from which it is delivered, such partitions, however, being of sufficient height to ensure the formation of apool consisting of a considerable quantity of the washing liquor and to prevent the formation of counter-cun rents.

In orderd to overcome the difficulty experienced from the liability of the washing liquor to foam, due to the incorporation of air or gas therein by the agitation of the commingled pulp and liquor, the rotation of the cylinder therein and the flow of the screened liquor from the cylinder to the storage tank, we have provided an instrumentality into which the strained liquor flows as it is discharged from the cylinder,

this comprising an upright conduit or well whose lower end communicates with a perforated pipe submerged in the storage tank with automatically controlled valves to maintain a column of liquor in and to regulate the height thereof in the well. upper end of each of the wells is exposed to the atmosphere so that whatever foaming occurs is within the well, and the air or other gas of the bursting bubbles may pass into the atmosphere without passing into the storage or other tanks. There is a pump for the storage tank of each section, the function of which is to supply each relatively shallow agitator tank with therequisite amount of washing liquor from the large pool in the associated storage tank. In order to prevent any foaming, due to the passage of the liquor from the storage tank to the agitator tank, the conduits are so arranged that the liquor is delivered to the The of the conduit being thus submerged in the agitator tank and there being a solid column of liquor in the conduit. Preferably the delivery end of the conduit is provided with a .check valve which is lifted by the incoming liquor but which prevents the back-flow of liquor and pulp in the event that the pump is not in operation.

We provide what we believe to be a novel construction of the cylinder in order to se cure the squeezing and compression of the pulp so as to express therefrom so far as possible any of the liquor that may be mixed therewith as the pulp is carried on the surface of the cylinder. That is to say, we pro- 'vide a cylinder which is of rigid construe tion, consisting preferably of a c lindrical metallic shell capable of withstan ing relatively high pressure and having perforations formed in the metal for the passage of the liquor. The couch roll is so adjusted and located in reference to the shell that-the pulp is compressed at the nip and theliquor squeezed therefrom. The cylinder is so reinforced internally as to prevent any undue yielding of the metallic shell. By the employment of a substantially rigid cylinder, in which the relatively thick shell is provided'with relatively large perforations, say approximately to t of an inch in diameter, more or less, we have secured surprising re sults in the output of the apparatus. The

- use of a perforated suhstantially-rigid metallic shell is of material assistance in decreasing the foaming of the liquor, and yet at the same time the matting of the fibrous pulp upon the cylinder takes place in such way as to prevent any material portion of the pulp flowing through the perforations i into the cylinder even though the perforations be of relatively large size as t of an inch or greater, of course within reasonable lim its. Even should a small quantity of pulp pass through'the perforations in the metallic l shell with the liquor, it is again pumped with the liquor back from the pool into the agitator tank and subsequently recovered. On the accompanying drawings, we have shown a washing apparatus which may be utilized in racticing our process and which itself emb ies various features of the present' invention.

Referring to the drawings,--- Figure 1 illustrates diagrammatically the operation of the apparatus, showing the flow of the pulp and of the Washing liquor through the apparatus and indicating graphically the gradual removal of the black liquor and lignin material from the pulp. and the increasing density of the washing li nor as it is passed through the apparatus.

igure 2 represents partially in side elevation and partially in section an apparatus embodying the invention. In this figure,

" indicate the direction of flow/thereof from transverse section the line 66 of Figure igure 7 illustrates in section a portion of one of the c linders.

Fi re 8 i lustrates a small portion of the meta lic casing forming a component of the cylinder.

Figures, ofone of the clutches.

Figures 13 and 14 show the details for adpistab'ly mounting the couch roll.

igures 15 and 16 illustrate the doctor or scraper for removing the pulp from the couch roll,

Before proceeding to describe the process and the apparatus which is illustrated u on the drawings, we desire to have it un erstood that the drawings are more or less conventional because of their small scale, that various changes ma be made in the apparatus without departing from the spirit and scope of the invention as .expressed in the claims, and that, while the apparatus and the process are described more especially in connection with the washing of sulphate pulp, they are equally available for washing other fibrous material.

Before proceeding to describe the apparatus in detail. we may explain, with the aid of Figure 1, the principles involved in the process and in the operation of the apparatus. In this figure, the storage tanks, in the order oi: the direction in which the washing liquid passes from poolto pool therein, are indicated at 1, 2, 3, 4, 5, 6, 7, 8 and 9. Associated with each tank and located conveniently above it, there is an agitator tank and a cylinder tank, with the necessary agitatorycylinder and couch roll, all of which are generallydndicateddn the order of the.

direction of the flow of stock at 1, 2'53, 4', 5313, 7", 8 and 9. The washin water is indicated by parallel lines and .t e arrows tank l'to tank 9; and, as indicating the increasing density of the water due to theaddition thereto of the black liquor and lignin material and other impurities contained in the pulp, we have superimposed upon the parallel lines indicating the water, small circles which gradually increase in number.

The stock is indicated by the small crosses and its direction of flow from the agitator at travels from last couch roll, and we sated the passage of ure 3, through two of lignin,

.over the couch rolls in grad 9 to 12 illustrate variousdetails 1' to 9 is indicated by the arrows. The stock,of course, is constant but more or less water passes with it from bath to bath as it the first agitator tank to the have therefore india small quantity of water with the pulp over the couch roll. The third constituent of the mixture, to wit, the lignin is indicated by circles. It will be observed from the diagram that the quantit that passes with the pulp throgg the series'of baths in the agitator tanks and cylinder tanks, gradually ecreases so that, as the pulp is finally delivered from the couch roll atv 9, it is substantially free from li nin, soda content or other impurities.

T e water, lignin and other impurities,

which pass with the pulp in each instance ually diminishing proportion, are delivered to the pool in the stora e tank from which they are fed to the cylinder, and so pass with the main flow of water or washing liquor from the tank 1 to the tank 9. As a practical matter, to ensure the best commerical desirable results, we prefer to employ nine sections or efiects, in washing sulphate pulp,- as we find that, by so doing, the pulp, when delivered from the apparatus, is substantially free of foreign material; but," of. course, it will be understood that the number of sections or effects ma ,be increased or decreased as may be deslred, or as may be required by the articular material which is being was ed. While it is not necessary, we find it commercially desirable to feed the pulp into the initial agitator tank with a certain quantity of black liquor as delivered from the digester to rinse it to flow, readil through the con dui s, but, if desired, tl i ties as may pass with the pulpfrom the digester, after the chips have been subjected to the sulphate cooking process; and consequently in using the term lignin we mean roughly to include not only the cementitious content of the wood but also the chemicals, free or combined, and other impurities which are in admixture therewith.

Referring now to the apparatus as illusthe other figures of the drawtrated upon ings,-20 indicates an elongated trough or body sufficient in length for the number of sections which are to be employed. The ends of the trough are closed and it is divided into storage tanks by a series of vertical transverse pla'rtitions 21 which are graduated in heig t to provide for a series of pools e pulp, after theblack liquor has settled and roughly strained mon end walls 30 to be explained,

of wash liquor from which the liquor overflows from pool to pool; The se leral storage tanks are indicated at 1 to 9 inclusive. Around the outside of the trough and at the upper edge thereof, there is a channel iron 22 to stiffen it, for upon the trough are supported the various other tanks and instrumentalitles to which reference will be made. In each of the storage tanks there is a depending baflle 23.

Associated with each storage tank there is an agitator tank 24 and a cylinder tank for a bath of wash liquor. These two tanks are made of metal and are supported upon the top of the main trough. As shown, the first agitator tank 24 may be located at the end of the main trough where it may conveniently receive the pulp and black liquor which isfed thereto. the mixture of ensures a regular flow thereof to the initial receiving and a itator tank 24. agitator tank t ere'is located an suitable form of agitator, such for examp e as that shown, which comprises a shaft 46 having disks 28 thereon with longitudinal blades or cylinders and the agitators may for convenience, be provided with comwhich are spaced apart a distance somewhat less than the width'of the main trough, and between these end walls t ere are located the suitable partitions 31, he partitions or walls 31 between the associated cylinder each section are only of suflicient desirable body of the all,

tank and so as to permit the flow of a steady stream of the mixture therefrom to the associated cylinder tank 25. We should not regard it as a departure from the spirit and scope of the invention if the partitions 31 were omitted, so that the agitator and the storage screen or cylinder would be located ment, althou h we should re omission as ighly undesirab washer for reasons which will be apparent to those skilled in the art. Each of the walls 'or partitions 31 is provided with a movable and adjustable dam 33, which may, under the circumstances subsequently be adjusted to a height which will prevent the passage of the material from the agitator tank to the associated e in a pulp may be with cylinder tank of the same section. Any suitable means for effecting the vertical adjustment and final securement after adjustment of the dam may be utilized. I

In each of the agitator tanks succeedlng the initial agitator tank, there is an agitator, of any suitable or desirable construction, for washing the batch of pulp therein. For example, we have illustrated a shaft 34 provided with a series of ing a plurality of radial arms 35 having angular-1y arranged blades 36. The shafts 34 extend at one end through stuffing boxes in, the front wall 30 and are provided With spur gears 37 which intermesh with and are riven by.complemental spur gears 38 journaled upon a stud shaft 39, see Figure 6.

Journaled on each shaft 39 there is a bevel lngs afforded by brackets attached to the front wall of the main trough. The shaft 42 has power imparted thereto by any suitable means from a convenient source of power. As shown in Figure 2, the shaft 42 convenience mad short lengths, each section of by a slidin and moved into and out of engagement with the bevel gear by a clutch lever 45, as shown ,in Figures 9 to 12 inclusive. By this construction, it is apparent that the agitators may be all driven simultaneousl but, if desired, any one of them ma be disconnected or unclutched from the riving shaft 42. While a batch is being agitated in a constant flow of pulp and liquor from the a itator tank 24 over the dam 33 into the cy inder tank 25. Located within the cylinder tank, there is the cylinder the function of which is twofold, namely to strain the pulp from the liquor and remove the pulp from the bath so that it into the bath in the proportion of the liquid which is mixed therewith. Each c linder is mounted upon a shaft 50, the 881d shafts being journaled in suitable bearings supported by the end' e in relatively cylinder tank 25 that it is partially subwith an annular flan e 52 thereon. Suitable packing 53, held in p ace by a metallic sleeve 54, encircles the tubular portions of the cylinder heads and the annular flanges 52 to revent the .escape of 1i uor at the joint. fhe sleeve 54 is preferab y provided with means whereby it may be contractedas the packing wears. Each cylinder head is provided with a plurality of radiating spokes 55 with angular braces 56 so as to furnish an effective support for the shell of the cylinder, as will be explained. Between the cylinder heads there are numerous spiders indicated as a whole at 57 which are rovided with spokes and braces similar to t ose at 55 and 56. The several spiders are spaced apart by any suitable means. Connecting the ends of all of the spokes and braces as at 55, 56, on

- the cylinder head and spiders, there are lon 'tudinal rods 58 secured at their ends to t e cylinder head by nuts 59, and on these rods there are tubular spacers or sleeves 60. Between the cylinder heads the cylinder is provided with a'cylindrical shellfil which is preferably of such thickness that it Wlll not yield materially under pressure. 1 As giving some indication of the character of this shell, we have found that a curved steel plate,

approximately 4, of an inch in thickness, may

be employed and the desirable results secured. This shell is provided with numerous s'aced perforations, 62, which, as previous y stated, may vary from to 0 an inch in diameter. Of coursethese several dimensions may be varied in accordance with circumstances or requirements of the particular material being washed. The shell is rigidly reinforced, the spacers preferably being at a distance of approximately 2.5 inches. Supported at the extremities of the spokes and braces 55, 56, ofthe spiders, there are rods 63, the ends of which are inserted in sockets in the confronting faces of the cylinder heads. These rods are spaced but a short distance apart, and between their ends are rigidly braced by the spiders. By this construction, it will be seen that the perforate'd shell is so supported and braced that it is substantially incapable of yielding under pressure. The ends of the shell are, as shown in Figure 7, clam ed between the confronting faces of the cylinder heads, the rods 58 and nuts 59 being utilized to secure this clamping action;

Each of the cylinders is so located in the merged in the mixture contained therein, and

so that the liquid may be strained from the pulp and flow through the perforations 62 in the shell into the interior of the cylinder and pass outwardly through the cylinder heads, the matted fibers being carried onthe upwardly moving side of the cylinder to a point above the level of the mixture in the tank. Associated with each cylinder, there is acouch roll secured upon a shaft 71 mounted in suitable bearings at its ends. Each couch roll is preferably made of iron or steel and is of such length that it will engage onl the perforated shell of the associated cy inder. The bearings forthe shaft 71 are indicated at 72, and are supported by the ends of a cover to be described. The are preferably adjustable so that the yiel mg pressure of the couch roll upon the cylin er may be increased or decreased as desired to secure the required expressing action upon the pulp carried upwardly by the cylinder. In Figures 13 and 14,.we have illustrated the bearing 72 (located at each end of the shaft) as belng movable in guides 150 and as being under the ressure of a spring 151. The pressure may varied by adjusting the screw 152 which is in threaded engagement with the removable angle bar 153. Abutment screws 154 are employed to limit the movement of the couch roll toward the cylinder.. The bearings are hung on rods 155 which pass loosely through the angle bar 153 and have adjustable nuts 156 and washers 157 between which and the angle bar are lo cated springs 158. By removing the bolts 159, the angle bars, the bearings and the roll may be removed. The cover has a detachable plate 160 covering a large slot therein and which may be removed when the couch roll is to be adjusted or to be taken from the machine.

To prevent the mechanical crushing of the pulp, the couch roll and the cylinder must be driven at the same peripheral s eed, and for this purpose they are geare together. It will be observed that the shaft 50 of each cylinder is provided with a ear 73 intermeshing with a gear 74 on the s aft 71. The ratio of these gears is the same as the diametrical ratio of the cylinder shell and the couch roll, but the lntermeshing teeth of the gears'73, 74, are of suflicient length to permit the requisite adjustment of the couch roll. The shafts 50 at their front ends are projected forwardly through stuffing.boxes and are journaled in suitable bearings. Said shafts are sectional, the front sections being journaled 'in bearings indicated at 75, and being provided on their extremities with bevel gears 76 intermeshin with and driven by complements-l beve gears 77 on a shaft 78 which extends lengthwise of the trough and is mounted in suitable bearings indicated at 79. The shaft 78, like that at 42, is preferably made in short lengths, one for each section of the apparatus, and these short lengths of the shaft may be driven separately or may be connected together by couplings indicated at 80. Preferably each gear 73 is fast on the front section of the associated shaft 50, and between the sections of the shaft 50 is a movable clutch 81 fast on the front section of the shaft 50 and operated by any convenient means to connect or disconnect the sections. Ordinarily the clutches 81 are in clutched. relation and are only moved into inactive position when it is desired to throw the cylinder out of operation.

The strained liquor, which passes through the shells of the cylinders and out from the ends thereof, is delivered into compartments or outlet boxes indicated at 82, 82, which are located in front and in rear of the walls 30 at the ends of the respective cylinders. Each of these outlet boxes is formed by an outer wall 83, the end walls 84, 85, and the wall 30. Each of these boxes may be of the same depth as the associated c linder tank, and provision is made, as will explained, for permitting the strained liquor received by these boxes to pass therefrom to the pool in the storage tank from which it was drawn into the associated agitator tank. For this purpose, as shown in Figures 2, 3, 5 and 6, there is located adjacent each box a well 86 which consists of a vertical casin one side'of which is formed by the en wall 84. In .said end wall there is. a vertically elongated port 87, so that the liquor may flow from the chamber or compartment 82 into the well. Associated with this port, there is a sliding gate or dam 88, having connected thereto a rack 89 by which it may be raised and lowered. The rack intermeshes with a pinion 90 on a shaft 91. This shaft extends across the top of the cylinder chamber so that the gates 88 for each section may be adjusted simultaneously.

'Upon the rear end of the shaft 91 there is a hand wheel 92 by which it may be rotated. Extending downwardly from each of the wells 86 into the storage tank immediately below it, there is a vertical stand-pipe 93 (of which the well is practically an extension) which terminates in a horizontally arranged conduit 94 submerged in the pool of liquor contained in the said tank. This conduit 94 is provided with numerous perforations for the emission of the liquor, itsends being closed by caps 95 as shown in Figure 6. The perforations in the conduit are indicated at 97. It will now be seen that the liquor which paxes out of the cylinder of any one section into the cham hers or compartments 82, flows into the wells 86 and down through the vertical stand-pipes 93 thereof into the conduit 94, whence it emerges in the storage tank of the same section of the apparatus below the level of the pool therein. The wells 86 are open to the atmosphere at their upper ends, so that the entrained gas, escaping from the foam or bubbles in the well, may escape into the atmosphere.

By the perforated pipe 94, which is kept full of liquor flowing therethrough, and the perforations in the pipe, we prevent the formation of foam or bubbles in the storage tanks, and ensure the delivery of the strained liquor in small streams into the main body of liquor in the tanks,rso as to effect a much more thorough mixture than if the vertical stand-pipes merely delivered a large unbroken stream into the tanks.

cans are provided for maintaining a constant column of liquid in the stand-pipes 93 and well 86, as will now be explained. On reference to Figures 2 and 6, it will be observed that the lower end of each standpipe 93 extends a short distance into the interior of the horizontal conduit 94 so as to constitute, as it were, a valve seat. For cooperation with each seat, there is a conical valve 98, which at its apex is suspended.

upon a chain or other flexible member 99. This chain passes over the pulley 100, located at some distance above the apparatus, and on its other end has attached thereto a counterbalancing weight 101. These weights are of such size as to hold the valve in closed position until a column of the desired height is formed in the wells and stand-pipes. As the liquor increases in density or specific gravity, the counterbalancing weights 101 are correspondingly heavier. Preferably the parts are so adjusted and related that the column of the liquor in each well is normally at a level slightly below the upper end of the gate or dam 88.

We have found by practical experience, by the provision of the instrumentalities which we have described, that foaming of the liquor in the storage tanks and in other parts of the apparatus is substantially prevented, even though the liquor be at a temperature of 160 F., more or less.

From the pool in each storage tank the liquor is supplied to the bath in the agitator tank associated in the same section therewith. For this purpose, there may be immersed in each storage tank a horizontallyarrangcd pump 104 which is driven by a vertical shaft 105 extending above the apparatus and equipped with a pulley 106 by which it may be rotated. The inlet of the pump is indicated in Figure 6 at 107, and communicating with the outlet thereof there is a conduit 108, having an upright limb 109 terminating inthe bottom of the agitator tank which is immediately thereabove. At the upper end of this conduit,there is a circular check valve 110 movable on vertical It will be seen that in each section of the and of the cy couch roll being apparatus the liquor is pumped from a storage tank up into the bottom of the agitator tank, thence passes with the pulp into the associated cylinder tank, out through. the

ends of the cylinder into the compartments 82, thence through the .welland stand-pipe, back into the storage tank from whence it started, so that there is a constant circulation of the wash liquor in each section.

Of course it will be understood that the apparatus is provided with all of the necessar cross braces to ive it sufiicient rigidity, an with other deta1 s of construction which are not necessary to describe.

Across portions of each agitator. tank, there is preferably a cover indicated at 119, which may be removably bolted in place, adjacent which there is a hinged section of the cover indicated at 121 which covers the remainder of the a itator tank and the adjacent cylinder tan This hinged section of the cover ma be made of .a casting and the pivots therefor are indicated at 122. On swin ing this section 121 of the cover upwardly andto the left (see Figure 4), t e interior of the portion of the agitator tank hnder tank are exposed, the

carried upwardly with the cover so that t e surface of the cylinder is ex ed.

t will doubtless be understood from the explanation thus far given that, as the cylinder of one section rotates in the mixture of Washing liquor, lignin and pulp, on the up-moving portion of its periphery it carries a relatively thick mat of pulp which is passed between the nip of the cylinder and the couch roll and is subjected to compression for expressing a greater portion of the liquid from the pulp.- The couch roll removes the pulp from the cylinder and carries it in the direction of the arrow in Figure 4. From the couch roll the pulp is stripped by a blade or doctor 123 and is discharged into the bath contained in the adjacent agitator tank of the next adjacent section. Each doctor or scraper 123 is located at the upper end of the wall 32 of the agitator tank and is preferably adjustable in reference to the couch roll, as indicated in Figures 15 and 16, so as to bear thereagainst with the necessary pressure.

The pulp, which is continuously fed into the first agitator shown at the left end of Figure 1, passes with the black liquor, which is fed into the tank therewith, into the associated cylinder tank, and emerging from the ends of the cylinder passes through the instrumentalities described into the storage tank 9. The pulp, which is removed from the cylinder tank by the cylinder and the couch roll, is dropped into the next bath contained in the adjacent agitator tank where it is mixed with liquor which is of less density and is less impregnated or mixed with lignin, and is-again agitated and washed. Thus the pulp is carried through with the bottom of the tank 130 by the con duit 132. Tracing now the path of the washing water or liquor, it will be observed that above the last couch roll there is located a water pipe 133 which directs a stream of water upon the doctor or scraper so that this fresh water delivered from the pipe 133 is received in the tank 130 and does not pass through the apparatus. Water at seasonable temperatures may be employed for this purpose, although we preferably use the white water from a paper machine. In lieu of this method of procedure, however, we ma dispense with the pump 131, the conduit 1'32 and the water pipe 133, since the pulp is dry enough, after being passed between the last cylinder and the couch roll, so that it may be conveyed from the tank 130 by any suitable conveyor. In fact, in lieu of the tank 130, the pulp from the last couch roll may be delivered into a screw conveyor for delivery at a point desired.

Above the next to the last couch roll, there is located a pipe 135 for delivering upon the doctor or scraper a stream of warm or hot water which is utilized for washing the pill and which passes therefrom into the at tank therebeneath, and finally through various baths, and the ools in the storage tanks numbered consecutively 1 to 9. The volume of fresh water, which is utilized for this purpose. is relatively small and is delivered in quantities much less than has heretofore been possible for a given amount of stock. The water, of course, is fed continuously so that the water in storage tank 1, which is utilized for the bath in which the before its final delivery from the last or associated cylinder is washed, ,is practically clear water and free from all but traces of lignin, chemicals or other impurities.

As it sometimes happens in the commercial operation of the'apparatus that it is necessary to effect minor repairs upon the instrumentalities included in one or the other section of the apparatus, it is desirable that such repairs may be effected without throwing the entire apparatus out of action. We

have provided, therefore, means by which and thence into the pool in the storage valves which are normally closed. In the event that it be desired to cut out any one section, the valve of the by-pass pipe 140 around such section is opened and the dam or gate 33 leading from the agitator tank of such section to the cylinder tank is raised to a height sufiicient to cut off the flow from the one to the other. By means of the clutches which have been previously described, the shaft 34 for the agitator and the shafts 50 for the cylinder of that section are unclutched from their respective driving shafts. of the section, which is being thrown out of action, of course is stopped by removing the driving belt or otherwlse. If desired, bypasses may be arranged for the storage tanks, but we have not deemed it necessary to show these as their construction and use will be apparent.

Reference has been made to the fact that a relatively small amount of water can be used for washing a relatively large amount of pulp. This is rendered possible by the use of cylinders having the construction which we have herein described. Heretofore it has been universally the practice, so far as we are'aware, in single or doubleefi'ect machines for washing pulp, to employ cylinders which are covered with wire gauze such as Fourdrinier wire. One might logicall conclude that, by having a foraminous sur. ace with a. multiplicity of relatively small apertures or interstices for the passage of the water, the water might flow more readily into the cylinder and the pulp caught on the surface thereof. Our experience has shown, however, that the opposite is true. Where the main body of the cylinder consists of wire gauze, the pulp mats thereon and is more or less carried into the interstices so as to prevent the free fiowof the water through the wire gauze into the interior of the cylinder. The ends of the fibers tend to pass lengthwise into these small interstices so as to choke them and finally practically the entire surface of the gauze is coated with a layer of pulp interlocked with the wires in such way that it is almost impossible to remove it. B employing a rigid shell formed of a re atively thick plate provided with relatively large perforations or openings, all of the troubles that are encountered in the use of a wire gauze cylinder are obviated. We have found, toour surprise, that the production of the machine is increased many times by the employment of a cylinder such as herein described, and that, in addition, by employin a cylinder of proper rigidity, the pulp, w ich is passedbetween the nip of the cylinder and the couch roll, has ex ressed' therefrom the greater portion 0 the liquid that was commingled therewith as the pulp was carried upwardly by the cylinder. Consequently, as the pulp The pump for the storage tank- ,ing and using the travels from the receiving end to the delivery end of the machine, in passing from one bath to the next succeeding bath, it carries with it a minimum proportion of lignin and chemicals. Inasmuch as the surface of the cylinder is fairly smooth and the holes relatively large, the layer of pulp thereon is removed in practically continuous slab by the couch roll, so that air is not carried down into the cylinder tank by the entrainment with projecting fibers as in the case where a wire cylinder is employed. The apertures in the, cylinder are sufliciently large to permit the escape of air from the apertures and from the interior of the cylinder without being carried down into the li uor.

t has alread been pointed out that, by the process and apparatus which we have herein described, we are able to wash a maximum quantity of pulp with a minimum quantity of water, notwithstanding thatthe materials being washed from the pulp are of a nature which render the washing exceedingly difiicult. Black liquor, resulting from the digestion of wood by the sulphate process, is, as has been stated, of a highly viscous nature and has a high surface tension. These conditions are not met with in those machines or processes in which a small quantity of fiber is washed with an excess or maximum amount of water. In such latter case, the considerations of viscosity and siirface tension are not compelling; whereas, in the washing of sulphate with a relatively smalllquantit of water, the washed liquor as it passes t rough the apparatus becomes increasingly dense and viscous and its surface tensiongradually increases. So far as We are aware, we are the first to have provided a multiple-effect apparatus for continuously washing sulphate pulp and delivering it in a from foreign substances. In accordance with the present process, there is in the storage tank, from which the washing liquor .ls delivered from the machine, a liquor of maximun concentration which, under some circumstances, may be concentrated and evaporated for the recovery of the soda in its various forms or else may be employed for partially filling the digesters preparatog to cooking a fresh batch of wood.

aving thus ex lained the nature of our said invention an described a way of maksame, although without attempting to set forth all of the forms in which it may be made or all of the modes of its use, what we claim is 1. A continuous process of washing fibrous material, which consists in continuously feeding said material to and agitating and washing it in succesive baths of wash liquor, straining the liquor therefrom as it paxes from bath to bath, and causing the liquor to constant stream practically free 30 frelativeljg-pure, liquor togthe first pool,

How in the opposite direction to form such successive baths for the on-coming fibrous. material. V I v 2. A continuous process of w'as hingfibrous material, which consists in circulating the wash liquor in a seriesof baths, causing such liquor to fiow successively from one bath to the next adjacent bath. agitating and wash ing the fibrous materialsinsaid baths, succe$ively feedin saidinateriallfrom bath to bath in a direction opposite to the main flow of liquor, and in its passage from bath to bath squeezingsuch fibrousmaterialfor the expression of, liquor therefrom..

3. A process of. washing fibrous material, which consists in, simi iltaneously agitating and wash'inga plurality of. batches of said fibrous material'in' baths of washing-1i uor, successively,; teedingthe said material; rom bath,;to' bath;.and strainingthe washin liquor therefrom, collectin suchg straine liquor in separate pools ant;

conveying por- ..tionsthereoffback,to thebath s whence they some, ndx s ha-l q eete.l ewatmme.

poollto in aldirectionoppositeithedirec-i tio'n Lof travelof the gfibrous grna'teriah 4i 1A t a es t Washin which consists in ,f orminga succession of.

pools of wash liquorfcausing the liquor to fiowsuccessivelynfrom pool to pooLsupply- "aha withdrawing the liquor fromthe-dash,

pool, circulatingwashdiquor fromeach pool 1 through a bath, continuquslyjeedingfibrous A. material, through thesuccessive: baths. but in .7 l a direction opposite-the main'fiow of said i liquor. through said pools -simultaneously agitatingand, the batches of fibrous material in th baths. and, expressing from .said fibrous material as it isbeing fed irombath ito" bath, a portion of the liquor imingled therewith, ,;to restore such, liquor to ,the bath whence it'ca ne..-

which consists in forming ,a pool and a 5. A process ,ofwashing fibrous material,

bath of wash liquor, the bath being at the higher elevation, continuously supplying such liquor from said pool to said bath. continuously supplying said fibrous material to saidbath, continuously delivering the washed material from said bath and straining the liquor therefrom. causing such strained liquor to flow back. to said pool. and maintaining a column of such strained liquor with its surface exposed to the atmosphere for the escape of gas mixed or entrained therewith prior to its delivery to the pool.

6. A process of washing fibrous material. which consists in forming a pool and a bath of wash liquor, the bath being a; a higher elevation, continuously supplying such liquor from said" pool to said bath. continuousli supplying said fibrous material to said hath continuously delivering the washed material ,fibrous material; j 8. An apparatus washing i from causing such strained liquor to flow hack to said pool, maintaining a, column of such strained liquorwith its surface exposed to the atmosphere for the escape of gas mixed or entralnedtherewith, and delivering such strained liquor from such column into the pool at a point below the level thereof.

- 7. A process of washing fibrous material, which consists in forming a pooland a bath of wash liquor, the bath being at'the higher .elevation,- continuously supplying fresh liquor to. and delivering the-more impure liquor from said pool, continuously feeding the fibrousmaterial .to and washing it in said bath, continously delivering the washed material. from said bath and straining the liquor therefrom, ,causing such?- strained liquor to flow back tothe pool 'while maintaming a column thereofwith its surface exposed, tothelatmosphe're, and continuously supplying-the wash' liquor from said pool toflthe -bottom-,of :;said bath, whereby the liquor is circulated'continuously through the pool and thebath, and excessive foaming is material, which comprisesa series of associated washing and@screenin'g..--tanks :provided with agitators and rotary screens, means for causingtheLwash liquor to be passed continuously ,-:and successively therethrough in one direction, and "means;-for'ecausing the fibrous material to be'passedtherethrough in the oppositeedirection'. whereby the said fibrous material and the:.wash liquor are deliveredat opposite ends of the apparatus.

9. An apparatus l atom washing .fibrous materiaL. which comprises a plurality of sections arranged in series, each section ineluding a washing tank having an agitator and atank havinga rotary screen, means for causing the washed pulp to-bedelivered successively from the screen of one section to. the agitator tank of the next section, and

means for causing the passagepf the wash liquor in the opposite direction through the agitator and cylinder tanks of the successive sections.

10. An apparatus for washing fibrous materials. comprising aplurality of sections arranged in series, each consisting of a storage tank. a washingand agitator tank and a cylinder tank, said storage tanks being arranged for the flow of wash liquor successively therethrough, means for ensuring the passage of the fibrous material in the opposite direction through said agitator and cylinder tanks successivelypand means at each section for causing a circulation of the liquor through the stora cylinder tanks.

11. An apparatus for washing fibrous material, comprising a series of sections each ge, agitator, and

from saidbath and strainingthe liquortherehaving a storage tank, an agitator tank, a.

' communicating cylinder tank, means ifor means for ensuring-the fl()W '0f WlSll liquor in the opposite direction through'the storage tanks of said sections. 12.-An--'apparatus for washing fibrous material, comprising a plurality of sections arranged 'in series, each having an agitator tank with an agitator therein, a cylinder tank with ascreen cylinder therein, a storage 1 tank "below said first-mentioned tanks,

"and meansfor circulating the wash liquor rt-hroughsa-id tanks; means for deliwze'ringthe stock from each cylinder to the agitato'r tankofthe next'succeeding section; and

' meanswhe'reby the wash liquor 'is caused to I flowthrough 'the storage tanks successively.

An apparatus for-washing fibrous materizli comprising a plurality of sections arrang in ser1es, each -having an agitator utanlf with'ian agitatorthereing' acylinder tankswith a screen-cylinder therein, a storage tank below said '-'first-1me ntioned tanks. out- 3: storage tank, f and means for pumpir'ig liquor ,flOm'ithB storage tank to the agitator;--and means 'forrfeeding the washed stockfromeach-:cylinder to the'agitator'tank of the let 4 boxes \or' receiving the screened liquor from-the ,cylinder, communi'( :ating .with the tors "-thereinf'hn l cylinder tanks with screen "cylinders-therein, all arranged in alternanext succeeding section.-

I 14. An apparatus for washingfibrous material, comprising a plurality of sections arranged in series, eachhaving an agitator tankwith an agitatorthereim' a cylinder tank with asereen cylinder therein, a storage tankbelow said first-mentioned tanks, outlet boxes for receiving the screened liquor from the cylinder, communicating with the storage tan and means for pumping liquor from the-stora tank tothe agitator tank; means for f ing the washed stock from each, cylinder to the agitator tank of the next succeeding section; and means where by the liquor is caused-to flow; in the opposite direction through thestoragetanks. 15.. An apparatus for washing fibrous material, comprising a pluralitv-lot sect-ions'-ar-.

ranged in series, 'each'havin an agitator tank with an agitator'therein, a cylinder tank with a screen cyinder therein, a storage tank below said-first-mention- Ttanks.

means for pumping the wash liquor from the storage tank to the -bottom of the agitator tank, and means for delivering the screened liquor from the cylinder to the stor- -age tank; meansfor transferring the stock from each cylinder to the agitator-tank of the next succeeding section: and means for z-ausing the-liquor to flow through the stor agetanks in succession.

terial, comprising a plurality of sections arranged in series, each having an agitator tank with an agitator therein, a cylinder tank witlr a screen cylinder therein,'a storage tank below said first-mentioned tanks. outlct boxes at the ends of the cylinder to receive the screened liquor, open conduits for conducting such liquor to the storage tanks, means for maintainingra column of liquor in said conduits above the level of the liquor in the storage tanks, and means for pumping liquor from the storage tank to the agitatortank';'and means fortransferring the fibrous material from each cyl-- "inder to the agitator tank of the next suceceding section. L 17. An apparatus for washing pulp, comprising a series of agitator tanks with agitators therein, and cylinder tanks with screen cylinders therein, "all arranged in alternat1on",-il it h" means for permitting the flow of washed material from each agitator tank to the "next cylinder tank; means for transferring the washed pulp from each cylinder to' the ncxt'succeeding agitator tank, and

means-for supplying wash liquor to the successive agitator tanks.

"E18; Anapparatus for washing pulp, comprising a series of agitator tanks with agitatlon, withmeans'for' permitting theilow of washed material from eachagitator tank to the next cylinder tank; means for transferring the washed ulp from-each cylinder to the next succeeding'agitator tank, a plu-' rality of storage tanks; means ,for 'circulating the wash liquor'from each storage tank 'th1migli' ah agitator tank and a cylinder tank; means for supplying to the storage tank, at the end of the apparatus at which the washed pulp is delivered, a stream of reltivcly pure wash liquor; and means for conducting from the storage tank at the other the impurities washed from the fibrous material.

19. An apparatus for washing fibrous materialycom'prising a series of washing and screening instrumentalit-ies arranged in altemation, means for transferring a constant stream of washed fibrous material from each body of fibrous material travels.

. 2 0. An apparatus for washing fibrous ma terial. comprising a series of washing and "end of the apparatus the liquor containing screening instrumentalities arranged in alternation, means for transferring a constant stream. of washed fibrous material from' -each screening instrumentali ty't'o the next flSilC- ceeding washing 'instrument'ality; means for forming successive pools of wash liquor and causing the wash liquorto flow through pools, 'in a direction opposite"the direction of travel of the body of' fibrous material; and means for circulating wash liquor from the series of pools through the respective washing and screening instrumentahties.

21'. An apparatus forwashingfibrous matcrials, comprising a-storage t'ank for containing a pool of wash liquor, an agitator tank thereabove, a'screen tank communicating with the agitator jtanklto receive the washed pulp and the liquor, means tor feeding' fibrous material continuously -to' said agitator tank,"m eans for transferring the washed pulp from said screen tank,a pump for continuously feeding liquor .from said storage tank to said agitator tank, an outlet box to receive the screened. liquor, "and' an open conduit for "conveying the screened liquor from the outlet bogp and havingits delivery end" submerged in the liquor in the storage tank. g g F; I l 22. An apparatus for wii shing fibrous materialsfcomprisin 'a'fstorage tank for containinga poo l o cas liquor, an agitator tank thereabove, a screen tank communicating with the agitatortankto receive-the washed pulp and the liquor. m'eansj'o'r feeding' fibrous material continuously" to said agitatbftank, means for transferring the washed pulp from said screen tank, a pump for continuously feeding liquor fromsaid' storage tank to said agitator tank, an outlet box to receive the-screened liquor, an open conduit for conveyingthe screened liquor from the outlet box, andaf'substantially horizontal perforated conduit connected to the delivery end of'said first mentioned conduit and submerged inthef'p'ool inthestoragetank. Y 23. An apparatus for washing fibrous ma- 'terials, comprisin a storage tank for contaming apool o wash liquor, an agitator tank thereabove, a screen tank communicating with the* agitator tank to receive the washed-pulp and "the liquor, means forfeeding'fibrous material continuouslyto 's'aid agitator tank, means for transferring "the washed pulp'from said screentank, a pump for continuously feeding liquor from said storage tank to said-agitator tank, an outlet box to receive the screened liquor, an open conduit for conveying the screened liquor from the outlet box and having its delivery end submergedin the liquor in the storage tank, and means for automatically 'maintaining in said conduit a column of liquor above the level of the pool in the storage tank. A

'24. An apparatus for washing fibrous materials, comprising a storage tank for containing a pool of wash liquor, an agitator tank thereabove, a screen tank communicating with the a itator tank to receive the washed pulp an the liquor, means for feedin fibrous material continuously to said agitator tank, means for'transferring the washed pulp from said-screen tank, a pump for continuouslyfeeding liquor from said storage tank to said agitator tank, an outlet box to receive the' screened liquor, an

tank t ereabove, a'screen tank'communicating with the a itatoritank to receive the washedfpulp an 'th'elliquor, means for feeding" fibrous material' continu'ouslyto said agitator tank, means for screening and transferring the" washed pulp' from said screen tankfan ,outlet box to receive the screened liqii og'aniopen conduit for conveying the screened. liquor from the outlet box and having its .delivery' end submerged in thefliquor in the'jjstorag e tank, and means for pumping the liquor from said pool into the a'gitat-or tank and having delivery end submerged in the mixture of fibrous material and liquor therein.

26'. A machine for washing rpaper pulp, comprising a tank, 'acouch rollfiand a rotary screen cylinderjsaidcylinder having a rigid perforated metallic shell with an exposed smooth cylindrical surface.

127. A machine for washing paper pulp, comprising a tank, a couch roll, and a rotary screen cylinder, said cylinder having open heads, and anintervenlng rigid perforated rpllzfiively' thick exposed smooth metalli c s e q I I 28. A.machine"for washing paper pulp, comprising a-ta'nk, a'couch roll, and a rotary screen cylinder, said cylinder having open heads, an intervening rigid perforated relatively thick metallic shell with an exposedsmooth surface, and spaced means for racing said shell internally against yielding under pressure of the couch roll.

29. A machine for washing paper pulp, comprising a tank, a couch roll, and a retary screen cylinder said cylinder having open heads, and an intervening exposed or 60 including a washing instriimentality, a screening instruincntality anda storage tank for containing a pool of wash liquor, means,

' agitator tank with rotary'agita'tor, a cyl cylinder, outflow boxesat "thee l tality of one section-Ito.the-washinginstruopen heads, an intervening exposed or uncovered relatively thick-cylindrical .metal combination a cylindrical roll anda couch roll for carrying the pulp froina hath subjecting it to relat vely severe compression at the nip to express the wash liquor therefrom, said cylinder hai i iiga substantially unyielding relatively'"oute'r exposed vthick metal shell with perforations there through for the passage of the wash liquor, in combin'atioi' lwith means for. removin' the pressed pulp j'fiom. said couchjrollgfl ii 32. An apparatus foriivashiiig'paper piilp, comprising a series of sections, each having a storage tank fora pool of wash j'liquor, an

inder tank with a rotary Lopen en cylinder, verticalstaridiiipes ends are submerged in 'th' M age tank andwho'se recei n endsai'eope i to the atmospher'e andfomm rii cateiwith said out-flow* lpoxes, and ap'u'i'np for co in'g liquor" from said po'ol to tank; "means for vdeliveri ii the storagetank'of aneiji'f section a discharging the liq lq fwith its ooi 'itained impurities from the'storage' tkinkatth" h end section;' niean s for causing the to flow through the tanks; inf'si' ocession; means for transferring the washed the opposite direction from the cylindep-o one section to' the'ag itator tank of theji iext section; and means, graduated according the density or specific gravity .jofi theliquor in the several pOol for naintaitiing in said standpipe columns of liquor above the levels" (if-the respective pools. .,I it 33, An apparatus for' washing sulphate pulp, comprising a series of sections, each including a washing instrumentality a screening instrumcntality and a storage tank for containing a pool of washrliquorg means for transferring the pulp progressively in one direction from the screening instrumenmentality of the, next adj acentsectiongmeans for circulating the washliquor from tln: e ;p o.ol of each section through the washing and screening instruinentalities thereof; and

means for prevcnting the passage of foam into the pools. 34. An apparatus for, washing sulphate pulp,.comprising a series of sect ons, each for transferring the pulp progressively in tality of one section to the washing instrumentality of the next adjacent section means for c rculatingthe wash liquor from the pool of each sect on through the washing and screening instrunientalities thereof; means for preventing thepas'sage of foam into the pools; and. .meansfor causing the flow of 'wash 'li'quorpro'gressively from pool to pool inia direction opposite the direction of travel 'of the ulpl through the said sections.

35. n apparatus for washing paper pulp, which comprises a-series of communicating tanks for containing pools of wash liquor;

means fondelivering pure liquor to the pool at one'end of the series and withdrawing the liquor from the pool at the other end of the series, a-"scries of associated I tanks for containingbaths of liquor; means for circulating liquor, from said pools through said bachggme ns for transferringthe pulp proessiyeiy through said baths in' a direction opposite the'rlirection of travel of'the'wash liquor through said'pools; and instrumentalities in said bath for washing the pulp t rei -Q a which comprises a series of communicating .anks for containing pools of Wash liquor; means foi delivering pure liquor tolthe pool at oile end bjf theseri es and withdrawing the lligii ii'lifromfthefLphbljat the other'end of these ies, a seri's of as sociated tanks for contairiinghaths of liquor; means for circulating liqiioi' fromsaid pools through said hathspmeans for transferring the pulp pro: gi'esi\ 'ely.throi1gh said baths in a direction opposite .the' direction of travel of the wash .ligll gl; throughfsaid'pools; instrumentalities,

in saidbathsf'for washingthe pul therein, and means, for by-passing the mixture of pulpand liquor around any one of said baths to. the ne t 4 succeeding f bathQ I 37. 'Anapparatus for washing pulp, comprisingan elongated trough having partitions of' decreasing height dividing it into communicating storage tanks for pools of wash liquor; a series of associated washing and screening tanks supported on said trough having instrumentalit es for washing the pi lpvand rotary screens for screening the pul from the wash liquor; nieans,.for circulatingiwash liquor from each storage tank through its associated tanks; and means for transierring the pulp fromthe rotary screensof each washing tank to the next succeeding washing tank.

@361 An appafratusfor 38. an apparatus for, washing pulp,

of the cylinder to receive the screened wash liquor, vertical conduits arranged to receive cal conduits; flexible members sustaining said valves and assing through said vertical conduits; u eye over which said members pass an weights on the free ends of said members to maintain said valves closed -phere and t the wash liqpor 1n the storage tank; valves e submerged ends of said ver-' tical conduits; flexible members sustaining said valves and passing through said vertiuntil columns of li nor of the desired height are formed in said vertical'conduitsQ 89. An apparatus for washing pulp, which comprises a stora tank for apool ofwash l1 uor" an agitator tank and a cylinder ta thereabove having an agitator and axle en-end rotary screen or cylinder respectiv y; means for removing the stock ,from said cylinder a pump andconduit for supplying liquor from the storage tank to the agitator tank; out-fiow'boxes at the ends of, the cylinder to receive the screened wash the liquor from the out-flow boxes and having'their up r ends exposed to the atmoseir lower ends submerged in located at t pectively conduits arranged to receive cal conduits; pulleys over which said members ass; weights on the free ends of-said memlgersto maintain said valves closed until columns of liquorof the desired hei Mare formed in said vertical conduits; am a perforated pipe or manifold submerged in the liquor in said storage tank for receivin the liquor delivered fromsaid vertical con ui ts. 40. An apparatus for washingpulp,

which comprises a storage. tank for a pool of wash liquor; an agitator tank and, a cylinder tank thereabove having an agitator and an open-end rotary screen or cylinder resmeans forremovin the stock rom said cylinder, a pump an conduit for supplying liquor from the storage tank to the agitator tank; out-flow boxes at the ends of the cylinder to receive the screened wash liquor, vertical conduits arranged to receive the liquor from the out-flow boxes and having their upper ends exposed to the atmosphere and t eir lower ends submerged in the wash liquor in the storage tank; and ad- Lustable gates or dams between said out-flow oxes and said vertical conduits.

In testimony whereof we have hereunto afiixed our signatures.

ORTON B. BROWN. HUGH K. MOORE. HOWARD PARKER. HERMAN M. MARTINSON.

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