US2561013A - Apparatus for thickening pulp - Google Patents

Description

y 1951 J. T. COGHILL EI'AL 2,561,013 APPARATUS FOR THICKENING PULP Filed Sept. 6. 1947 4 Sheets-Sheet 1 H6 1 INVENTOR. JAMES [GOG/JILL syfiompoliuuepou 4 TTOQNE Y y 1951 J. T. cosmu. EI'AL 2,561,013

APPARATUS FOR THICKENING PULP Filed Sept. 6, 1947 4 sheets-Sheet 2 IN VEN TOR.

JAMEJ 7760611111 av Ham/e016. 114N600- A TTORNEY i July 17, 1951 J. 'r. COGHILL Eryn. 2,561,013

APPARATUS FOR THICKENING PULP Filed Sept. 6, 1947 4 Sheets-Sheet 5 W 1| llas H6. 6 Q

July 17, 1951 J. T. COGHILL ETAL APPARATUS FOR THICKENING PULP Filed Sept. 6. 1947 4 Sheets-Sheet 4 fie. c3.

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Patented July 17, 1951 APPARATUS FOR THICKENING PULP James T. Coghill, Fairport, and Howard H. Langdon, Rochester, N. Y., assignors to Consolidated Machine Tool Corporation, Rochester, N. Y., a

corporation of Delaware Application September 6, 1947, Serial No. 772,488 20 Claims. (01. 92-26) The present invention relates to a machine for dewatering or thickening paper-making or other fibrous pulp.

There have been several different types of machines employed or built heretofore for de-watering or thickening pulp. In one type of such machine, a cylinder covered with a wire netting is revolved in a vat of stock; the top of the cylinder extends above the contents of the vat; as the cylinder revolves water passes through to the inside; a layer of pulp is formed on the outside; and a couch roll and so-called doctor, placed above the cylinder, remove this layer of dewatered pulp. In another very similar type machine the pulp is drawn against the cylinder screen by vacuum as the cylinder revolves in the vat; and a valve arrangement shuts off the vacuum and applies air pressure to blow the deposit of pulp off the cylinder as the cylinder surface emerges from the vat. This latter form of machine has increased production and greater efliciency in water extraction, but the cost of operation is increased. In another type machine, the aqueous slurry of pulp is pumped over a screen so that the water runs through the screen and a mat of pulp is deposited on the screen which is scraped off by a traveling sweep arm or blade. In still another type machine, the pulp is pressed against a perforated surface by a worm or screw, which moves the pulp across the surface into a constantly restricting space, thereby forcing the water out through the perforations.

Various other types of de-watering or pulp thickening machines have been built, also. In most prior machines, however, a mat of pulp is allowed to form before the thickened stock is removed from the screen. This mat tends to I clog the screen, therefore,'during most of the time of the de-watering operation, hindering drainage and lowering the water-removal rate. Moreover, because of their principle of operation, all prior machines are massive and require a very considerable floor area to provide any practical rate and volume of water extraction.

The primary purposeof the present invention is to provide a pulp de-watering machine which will be faster and more efficient in operation than any such machine previously built.

Another object of the invention is to provide a machine which will be able to thicken pulp rapidly and efliciently from consistencies in the order of 2% to 4% to consistencies in the order of to 35%.

Another object of the invention is to provide a 2 dewatering machine in which the pulp is so handled as to be self-clearing and self-cleaning as regards the drainage surface.

Another object of the invention is to provide a dewatering machine which will, simultaneously with the thickening of the pulp, separate and classify the expressed water, which contains small quantities of fibre, according to its contents so that the portion of the expressed water, containing the best fibre, is separated from the portionof the expressed water that contains more dirt and fibre debris, whereby the desirable fibre contents of the expressed water can subsequently be reclaimed.

A further object of the invention is to provide a pulp de-watering machine which will be much more compact and require much less space than any pulp thickening machine heretofore built, which at the same time will handle a much greater volume of slurry than previous de-watering machines, and which nevertheless will be simple in construction and in operation.

Still another object of the invention is to provide a machine which will satisfy a need in the industry for a thickener which will deliver uniform heavy consistency pulp when the supply consistency varies, uncontrolled, in the range of 2% to 4%, and without requiring dilution of the supply to a mat-forming consistency,'which is in the order of 1%.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

Fig. 1 is a part elevation, part vertical sectional view of a machine built according to one embodiment of this invention;

Figs. 2 and 3 are a plan view and an elevational view, respectively, on an enlarged scale of one form of sweep head that may be employed in this machine;

Figs. 4 and 5 are a fragmentary plan view and a fragmentary vertical sectional view, respectively, of the sweep head, de-watering plate, and drainage chambers of this machine;

Fig. 6 is a fragmentary sectional view of the line 6-6 of Fig. 4;

Fig. 7 is a perspective view on a greatly enlarged scale showing fragmentarily the structure of the knurled working surface provided on the gyratory upper plate of the machine;

Figs. 8 and 9 are a fragmentary plan view and a fragmentary vertical sectional view, respectively, corresponding to Figs. 4 and 5, and showing the sweep head and tie-watering plate 01' a through a hollow shaft to which a rotary sweep head is secured. The sweep head has a plurality of outwardly xtending arms. The slurry of stock fans out between these arms over a generally conical de-watering surface which lies just beneath the arms and surrounds the shaft. The de-watering surface is perforated so that water can quickly drain through it from the stock into a chambered member that lies just below the dewatering surface. Above the sweep head is a plate which is formed with a knurled or roughened working surface on its under side and which is given continuously a gyratory or orbital motion. The sweep arms extend across the width of the de-watering surface and as the sweep head rotates, the thickening stock deposited on the dewatering surface is continuously displaced by the arms and squeezed between them and the gyrating plate. The gyratory motion of the plate and the rotary motion of the arms tends to roll the stock transversingly under compression between and in tractive contact with the opposed surfaces of the sweep arms and upper plate. This not only squeezes more water out of the ulp but also causes the thickening stock to be formed into nodules so that as the pulp drops over the back of a sweep arm, after having been rolled between that arm and the gyrating upper surface, it is in nodulated condition. In this condition it does not mat, and will leave the water free to run out through the holes of the de-watering surface. Thus faster drainage and consequently faster dewatering per unit of drainage area can be obtained.

As the stock thickens and its consistency in creases it is moved continuously outward toward a discharge area surrounding the working zone of the machine. Where the sweep arms are generally radial of the sweep head, radial traverse of the stock may be improved by making the dewatering surface in the form of a multiplicity of separate plates which are stepped with-reference to one another and arranged so that their leading edges are skew or oblique, that is, tangent to a circle circumscribed about the axis of the sweep head. The steps prevent the stock from sliding around between the de-watering surface and gyrating plate with the sweep arms embedded therein; and they force the stock to progress outwardly with some radial compression as the sweep arms pass over them. If a sweep head is used having spirally shaped arms, a stepped de-watering surface may not be required. The spiral of the sweep arms will effect the desired radialtraverse and compression of the thickened stock.

The upper surfaces of th sweep arms are preferably slightly roughened to grip the stock better as it is rolled between them and the .gyrating upper plate. A degree of back pressure or restraint on the stock flow at the discharge zon is advantageous for efficient tie-watering, and this may be achieved in .various ways.

. With the machine of the present invention it has been demonstrated in commercial scale op eration that water may be removed from 3% sul-,

phite pulp at the rate of 33 gallons per square foot of perforated plate while increasing-the con; sistency to 25%. This represents a capacity. of 7.5 tons per day per square foot of 'de-waterin area which is several times the performance i'of de-watering machines heretofore used. ,7

Referring now to the drawings bynuinerals of reference and particularly to Figs-l to f6' "inclusive, l0 denotes the base or frame of thegmachine. Journaled in this base or-frameli any suitable manner, is a hollow shaft J4. i Theys haft is internally threaded adjacent its upperend to receive and engage the externally threaded portion [5 (Fig. 3) of a rotary sweep headl6; which is adapted to rotate with the shaft.

The sweep head is bored at H (Figs. 2 'and 3) to have an opening aligning with the bore'of the shaft M. It has a plurality of arms 18 which extend approximately radially of the axis of the head, and which, in the embodiment shown, are integral with the head. These arms are all alike. They have generally convex leading surfaces 20 which are smooth and which join inclined roughened surfaces 2|, that, in turn, join flat roughened upper surfaces 22. In the embodiment shown the upper surface 22 of each arm extends from the outer end of the arm radially inwardly only about half the length of the arm. The under surface 24 of each arm is inclined downwardly from the tip to the hub of the arm and is a generally conical surface. The rear surfaces 23 of the sweep arms may be of any desirable shape. As shown they are concave and relieved.

The shaft H is adapted to be driven from a motor 25, which is mounted in the base of the machine, through a shaft 26 which has a, worm 21 integral with it that meshes with and drives a worm wheel 28. The worm wheel 28 is keyed to a sleeve 29 that is fastened in any suitable manner to the shaft I4. Thus, the sweep head [6 may be rotated.

As the sweep arms rotate, they travel over a generally conical de-watering surface 30 (Figs. 4, 5 and 6) made up of a plurality of overlapping perforated plates 33. These plates are riveted or otherwise fastened to a casting 3| in such wise that their leading edges 34 are oblique or skew to the axis a: of shaft l4, that is, are tangent to a circle circumscribed about axis x. The front edge 34 of each plate overlies the rear edge of the next preceding plate around the de-watering surface as clearly shown in Figs. 4 and 6, and the plates slant downwardly from front to rear as shown in Fig. 6 so that their leading edges 34 are tangent to an imaginary cone coaxial with axis 2:. Each plate has a plurality of perforations or holes 4| through which the expressed water may drain. For clearness in illustration. only a part of one surfac is shown perforated in Fig. 4.

The undersurface 24 of each sweep arm I8 is shaped to closely conform to the shape of the generally conical de-watering surface so that as the arms rotate they may readily disclose the thickening stock off of the de-watering surface.

series of angularly spaced holes, the holes of the three series being designated 35, 36 and 31, respectively. These three series of holes communicate, respectively, with the three concentric annular chambers or channels 38, 38 and 48 formed in a member 32 to which casting 3| is secured in any suitable manner. Member 32 is fastened in the base III of the machine. The chambers 38, 38 and 40 are drained by pipes 42, 43 and 44, respectively (Fig. 1), which are connected to holes in the bottoms of the chambers and which may lead to suitable water containers (not shown).

The aqueous slurry of pulp, which is to be dewatered or thickened, is supplied to the machine through a pipe 45, (Fig. 1) which is secured to the frame of the machine by bolts 46 and which communicates and registers with the bore 41 of shaft l4. The shaft has a nose or sleeve 48 secured to its lower end'that is surrounded by a packing member 48. The pipe 45 is secured to this packing member which, in turn, is secured in any suitable manner to the frame Ill.

Mounted upon the base l8 and secured thereto in any suitable manner is an upright or column 58. Journaled in this upright or column is a shaft 5! to which is keyed a pulley 5'2, which may be driven in any suitable manner either from the motor 25 or from a separate motor (not shown) Secured to the inner end of the shaft 5| is a bevel pinion 53 which meshes with and drives a bevel gear 54. This bevel gear 54 is fastened in any suitable manner to a cylindrical barrel 55 which is journaled on suitable bearings 55 and 51 in the upright 58, The barrel is provided with an eccentric bore which is fitted with bearings 58 and 58 to receive the reciprocating rod or plunger 68. The bushings 58 and 58 permit rotation of the barrel 55 on the plunger 60 and reciprocation of the plunger 60 in the barrel 55 during rotation of the barrel.

Secured to the lower end of the plunger 68 is a head or plate 62, which is preferably circular, and whose undersurface 63 is knurled. The upper end of the plunger is connected by means of a pair of universal joints 64 and 85, and a connecting link 66 to the flanged head 61 of a piston rod 38 which projects from one side of a piston III.

This piston is reciprocable in a cylinder H which is rigidly secured to the upright 50. The piston has a piston rod 72 projecting from its upper side. The opposite ends of the cylinder H are closed by the packing glands 14 and I5, which provide suitable guide bearings for the piston rods 68 and 12. The rim of the flanged head 61 is keyed to the cylinder H so that the piston 10 is prevented from rotating as it moves vertical-lyin the cylinder. The piston is adapted to be reciprocated by fluid pressure which may be applied selectively to opposite sides of the piston through the pipes 16 and 11.

When the barrel 55 is rotated, the plunger 60 and plate 62 are caused to travel, relative to the bearings 56 and 51, in a circular path having a radius equal to the eccentricity of the bearings 58 and 59. This provides the desired gyratory or orbital motion of plate 62 and its working surface During the rotation of the barrel 55, the

ready stated, is held against rotation by its keyed connection with the cylinder II. To prevent vibration of the machine, due to the weight of the gyrating parts, a counterweight 89 is secured to barrel 55. This counterbalances the gyrating movement.

Through axial movement of the piston 70, the working surface 63 of the plate 82 can be adjusted to the desired distance above the plane surfaces 22 of the sweep arms l8 to provide a thin working space between the knurled surface 63 of plate 62 and the upper surfaces 2i and 22 of the sweep arms. Through movement of piston III, also, the distance between upper surface 63 and the sweep arms can be varied cyclically, if desired. to aid the de-watering action.

Surrounding the sweep arms I8 is a trough member 8 I This member has a smooth flat surface 88 adjacent the outer ends of the sweep arms and of the de-watering surface 38 which acts as a. discharge area on which the nodulated de-watered stock is discharged by the rotating sweep arms l8 and gyrating upper plate 62. A circular wall 82 integral with member 8| surrounds its discharge area 80. The wall 82 acts as a dam restraining flow of the thickened pulp at the outlet zone, and putting a back pressure on the pulp to insure that water is extracted from the pulp to the desired degree.

Integral with the member 8l' is an outer wall 83 which is spaced from and concentric with inner wall 82. The two walls 82 and 83 define a. trough whose bottom 84 is arranged on a slant so that the stock which discharges over dam 82 may be carried downwardly by suitable means to one point where an opening 85 is provided in bottom wall 84 through which the thickened stock may pass to a receptacle or onto a conveyer for further processing.

This machine is particularly adapted for delivering thickened stock at consistencies ranging from 10% to 40% and therefore one of its advantageous uses is in washing operation; where the thickened pulp will be immediately reslushed to around 3% to 4% consistency. The collection trough illustrated in Fig. 1 is suitable for use in such cases for the dilution water may be added to the stock in the trough. .It will be understood, however, that in cases where the pulp is desired for further treatment at the high consistencies at which it may be delivered by the present machine, a simple trough would not be used but some more positive means of collecting and delivering the pulp to a central discharge point may be employed.

The stock is prevented from riding up over the plate 62 by a ring 18 which is fastened to the plate 62 and which overlaps at all points the flange 19 of an annular guard 86 that is adapted to slide axially on the outside surface 81 of upright 50.

The surfaces 2| and 22 of the sweep arms are preferably somewhat roughened to grip the pulp tractively and resist slippage on the pulp as they rotate relative to the pulp pressed between them and the knurled working surface 63 of the gy-- rating upper plate 62. It is this tractive contact plus the relative motion of the opposed surfaces of sweep arms and plate, plus the compression exerted on the pulp by the surfaces which causes the pulp to be formed into nodules, permitting eflicient extraction of water from the pulp and preventing it from matting.

The surfaces 2| and 22 of the sweep arms need onb' be slightly roughened as by a file, but the surface 63 of the gyrating plate is preferably regularly knurled. We have found that the surface most suitable and most productive for plate 62 consists of a basically fiat or smooth surface upon which are superimposed a multiplicity of tiny protrusions.

One form of suitable knurled surface is shown in Fig. 7. This working surface is comprised of a symmetrical pattern of pointed protrusions 80 in the form of closely spaced regular quadrilateral pyramids which project from the basic'surface 62. The knurled surface of plate 62, however. may take any desired form and may, for instance, have any of the forms of knurled surfaces described specifically in the copending application of James T. Coghill and Harold S. Hill Serial No. 705,540, filed October 25, 1946.

The surfaces 2| of the sweep arms are preferably basically plane surfaces inclined to the axis of the sweep head and to surfaces 22, whereas surfaces 22 are preferably basically plane surfaces perpendicular to the axis of the sweep head and parallel to the basically plane surface 63 of plate 62. Because of the inclination of the surfaces 2|, the stock is subject to progressively increasing compression as it is rolled traversingly between surfaces 2| and 63; and it remains un-. der maximum compression when it is between surfaces 22 and 63. The compression exerted by transition of the stock from inclined surface 2| to parallel surface 22 is caused not only by the rotary movement of the arms |8 but also by the gyratory movement of plate 62, for surfaces 22 do not extend for the full length of the arms ill but are arranged only at the outer ends of the arms tapering off midway the lengths of the arms radially outwardly, also, from surface 2| to surface 22 where it i compressed between surfaces 22 and 63. In Figs. 2 and 3 the roughened surfaces are indicated only on two of the sweep arms and only on parts of the surfaces 2| and 22 of those arms. It is to be understood, however, that preferably the whole of the surfaces 2| and 22 of all the arms are roughened.

In operation, the stock enters the working area of the machine through the pipe 45, the bore 41 of shaft I4, the core I! of sweep head I6, and the spaces between the sweep arms |8. It fans out over the de-watering surface 30 and up against the working surface 63 of gyratory plate 62. As it spreads out over the de-watering surface 38, water drains from the pulp through the holes in the plates 33 and holes 35, 36 and 31 in casting 3| into the several channels 38, 39 and 48. The sweep head rotates clockwise as viewed in Fig. 4; and the sweep arms |8 continuously clear the thickening stock from the de-watering surface 30 while at the same time squeezing portions of the stock between the inclined surfaces 2| and plane surfaces 22 of the sweep arms and the opposed surface 63 of the upper plate 62.

The upper plate 62 is, of course, traveling in an orbital path through rotation of the barrel 55 in a clockwise direction with reference to Fig. 4. Hence, as the sweep arms displace the stock from the de-watering plate it is carried between the roughened surfaces 2| and 22 of the sweep arms and the knurled surface 63 of the plate 62 and has tractive contact with these opposed surfaces so that it is rolled traversingly in different tangential directions with reference to the opposed surfaces by reason of the orbital motion of plate 62. Thus, it is formed into small discrete nodules of pulp in which the fibres are curled and twisted upon one another. These nodules of fibres roll over the'backs 23 of the sweep arms and either join fresh fibre gathered by the next sweep arm or are carried by the gyratory motion of the plate 62 radially outwardly beyond the sweep arms onto the smooth upper discharge surface 88 of well member 8|, depending upon the relative position of each sweep arm and the gyratory plate at any instant. The pulp on the de-watering surface is continuously urged outwardly as well as upwardly by the rotating sweep arms, for it is traversed radially along the leading edges 34 of the plates 33 by the rotation of the sweep arms. The steps in the de-watering surface, which are formed by the leading edges 34 of the plates 33. moreover, prevent the pulp from sliding around between the surfaces 30 and 63 without being worked. 1

The pulp then follows an interrupted path radially or spirally outward with periods of tight compression between tractive surfaces having relative motion which causes it to form into nodules, alternating with periods of relief from such rolling compression, when the thickened nodules thus formed may mix with fresh incoming pulp and are permitted to drain under the influence of more moderate pressure. Under these circumstances the pulp remains relatively loose and does not mat up or jam between the relatively converging surfaces 30 and 63 (Fig. 1). This relative looseness of the pulp between the sweep arms is desirable for proper functioning of the apparatus and is encouraged by the fact that whereas the rotation of the sweep arms is relatively slow, in the order of 100 ft. per minute at their tips, the surface speed of the gyrating upper plate is much faster, in the order of 240 ft. per minute. The pulp is therefore compressed between the tops of the sweep arms and the gyrating plate under constantly changing pressures and directions.

As the thickened pulp piles up it falls over wall 82 into the trough between walls 82 and 83 and is carried down spiral bottom 84 and out of opening 85. In continuous operation, an increasing compression of pulp, over and above that ob tained between surfaces 2| and 22 and surface 63 is obtained by means of the dam 82 and the pulp feed pressure, using the pulp feed pressure rotary motion of the sweep arms is sufficient to nodulate the pulp, but, under certain conditions it may be desirable to vary cyclically the distance between the sweep arms and pulp to alternately increase and decrease the amount of pressure on the pulp. This cyclical variation in the depth of the working space may be effected by reciprocation of piston 18 under control of a suitable valve mechanism such as illustrated, for instance, in the copending application of James T. Coghill and Harold S. Hill, above mentioned.

Instead of using the annular wall 82 as the sole means of damming the stock, auxiliary means may be employed. Thus, as shown in Fig. 12 an auxiliary weighted ring may be used. This ring is mounted to slide on the outer. surface of the guard 88. It is made light enough to be lifted by the pressure of the de-watered pulp, but has its lower surface 91 shaped to provide a more restricted opening than is provided with the wall 82 alone, thereby to put a greater head of pressure against the pulp to insure more complete extraction of the water, from the pulp.

Another means for securing a head of back pressure against the pulp is shown in Fig. 13. Here the discharge surface is made in two parts 8| and 8|" and between the two parts there is interposed a damming ring I00. This ring is made adjustable by a turn buckle IOI which is connected at one end to the under side of the ring and at its opposite end is mounted upon a rigid part of the frame III. By adjustment of this ring, the amount of the discharge opening around the sweep arms can be restricted at will.

Instead of using a sweep member having approximately radial arms and a de-watering surface made of overlapped plates as shown in Figs. 4 and 5, the machine may be equipped with a smooth de-watering surface and with a sweep member having arms spirally curved longitudinally, as illustrated in Figs. 8 and 9. The sweep member in the latter case has a hub portion 6, which threads into shaft I4, and a plurality of arms H8, which are spirally curved longitudinal ly. The front surfaces I 2| of these arms are convex to lift the pulp off the de-watering surface, and to squeeze the pulp between the arms and the upper working surface 63 of the machine. These surfaces IZI are preferably roughened to have tractive contact with the pulp. The under surfaces I24 of the arms are inclined downwardly from the tips of the arms to the head H6 and lie in an approximately conical surface coaxial with axis :0, so that as the arms rotate their undersurfaces closely hug the de-watering surface I30. This surface is here a truly conical surface. It may be formed of separate plates, but the upper surfaces of these plates all lie in the same cone coaxial of axis at.

The surface I is perforated as before and fastened to casting 3|. In fact, surface I30 and sweep head H6 can be directly substituted for surface 30 and sweep head I6 of the embodiment first described. The machine then operates generally in the same way as first described. When the sweep head I I6 rotates, its spiral sweep arms displace the thickening stock, press it upwardly and outwardly against the upper gyrating surface 63.

One of the features of the machine is the fractionation of the water expressed from the pulp. It has been found in practice that the water which first flows out of the aqueous slurry is richest in fibre while that which is expressed last is richest in dirt. Through provision of channels 38, 39 and 40 at different radial positions beneath tie-watering plate 30, the different grades of white water can readily be separated. The white water flowing into channel 38 which is nearest the entry zone of the slurry is richest in good fibre and can be reclaimed, while that collected in channel 40 is full of dirt and fibre debris with a much smaller proportion of good fibre and may be discarded. The water collected in channel 39 is intermediate in quality and under some conditions can be reclaimed like that collected in channel 38.

While the apparatus of the present invention has been described as a machine complete in itself and may be so constructed and sold, it may also form part of a machine for treating thickened pulp such as the machine described in the pending application of James T. Coghill, Serial No. 773,012, filed September 9, 1947. In this latter case, the apparatus of the present invention serves to thicken the pulp prior to further treatment of the pulp in another part of the machine of application Serial No. 773,012.

While the invention has been described in connection with different specific embodiments thereof, it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention perwins and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention. or the limits of the appended claims.

Having thus described our invention, what we claim is:

1. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an inlet through which a slurry of the material may be fed over said drainage plate, a. sweep arm having an under face arranged in operative relation with the drainage plate and movable to gather the thickening material up off of the plate, a second plate having a workin surface opposed to the upper surface of the sweep arm and so disposed relative to said upper surface that the material displaced by the sweep arm is compressed between the upper face of the sweep arm and said second plate on movement of the sweep arm, and means for actuating the sweep arm.

2. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an inlet through which a slurry of the material may be fed over said drainage plate, a sweep arm arranged to scrape from the drainage plate the thickening material deposited on the drainage plate on relative movement between the sweep arm and plate, said sweep arm having its upper face inclined upwardly and rearwardly with reference to the path of relative movement of the arm and drainage plate, an upper working plate having a working surface spaced a slight distance above the upper face of the sweep arm and so disposed to the said upper face that the two surfaces converge rearwardly of the sweep arm, and means for effecting relative movement between the sweep arm and the two plates to cause thickened material to be displaced from the drainage plate and to be compressed between the sweep arm and the upper plate.

3. In a machine for extracting liquid from a papermaking pulp, a perforated drainage plate, an inlet through which a slurry of the pulp may be fed over said drainage plate, a sweep arm arranged in operative relation with the drainage plate and adapted on relative movement forwardly of the drainage plate to pick up thickening pulp deposited on the drainage plate, a second plate mounted above the sweep arm and adapted to be positioned close enoughthereto to engage thickened pulp picked up by the sweep arm and to compress said pulp between itself and the sweep arm, means for imparting forward movement of the sweep arm relative to the drainage plate, and means for imparting relative movement in a different direction between the sweep arm and the second plate.

4. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an

inlet through which a slurry of the material may be fed over said drainage plate, a sweep arm arranged in operative relation with the drainage plate and adapted on relative movement forwardly of the drainage plate to pick up thickening material deposited on the drainage plate, a second plate mounted above the sweep arm and adapted to be positioned close enough thereto to engage thickened material picked up by the sweep arm and to compress said material between itself and the sweep arm, both the second plate and the sweep arm having opposed roughened working surfaces to engage the thickened material tractively, means for imparting forward movement of the sweep arm relative to the drainage plate, and means for imparting movement to the second plate in different directions tangentially of the sweep arm.

5. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an inlet through which a slurry of the material may be fed over said drainage plate, a sweep armarranged in operative relation with the drainage plate and adapted on reltive movement between the drainage plate and the sweep arm to pick up thickened material deposited on the drainage plate, a second plate mounted above the sweep arm and having a roughened working surface opposed to the upper surface of the sweep arm and adapted to be positioned close enough thereto to engage thickened material picked up by the sweep arm and compress said material between itself and the sweep arm, means for effecting relative movement between the drainage plate and the sweep arm, and means for impartin a gyratory orbital motion to the second plate tangentially with reference to the opposed working surfaces of the sweep arm and second plate.

6. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an inlet through which a slurry of the material may be fed over the drainage plate, a rotary sweep arm arranged in operative relation to the drainage plate and having an upper face inclined upwardly and rearwardly with reference to the direction of movement of the arm over the drainage plate, a second plate mounted above the sweep arm and having a working surface inclined to the axis of the sweep arm and having converging relation to the inclined upper face of the sweep arm, means for rotating the sweep arm, and

means for imparting a gyratory oribtal motion to the second plate about an axis extending in the direction of the axis of the sweep arm.

'7. In a machine for extracting liquid from a fibrous material, a perforated drainage plate, an inlet through which a slurry of the material may be fed over the drainage plate, a rotary sweep arm arranged in operative relation to the drainage plate and having a forward face inclined upwardly and rearwardly and terminating in a plane upper surface, -a second plate mounted above the sweep arm and having a substantially plane working surface generally parallel to the plane of the upper surface of the sweep arm, both the inclined and plane surfaces of the sweep arm being roughened and the plane working surface.

of the second plate being roughened, means for rotating the sweep arm, and means for imparting orbital motion to the second plate about an axis extending in the direction of the axis of the sweep arm.

-8. In a machine for extracting liquid from a papermaking pulp, a conical perforated drainage plate, an inlet disposed centrally of the d ainage "all the axis of the plate for collecting separately the liquid which passes through the perforations in the plate at different radial distances from the axis of the plate.

9. In a machine for extracting liquid from a papermaking pulp, a centrally disposed inlet through which a slurry of pulp may be fed, a drainage surface surrounding said inlet and comprising a plurality of circularly arranged overlapping plates, each of which has its leading edge projecting above the rear of the preceding plate and arranged tangentially of a circle about the axis of said inlet and lying in a surface of revolutioncoaxial of said inlet, a rotary head mounted coaxial with said inlet and having a sweep arm which projects generally radially therefrom, and which overlies said drainage surface, and means for continuously rotating said head.

10. In a machine for extracting liquid from a papermaking pulp, an inlet through which a slurry of pulp may be fed, a drainage surface surrounding said inlet and. comprising a plurality of circularly arranged overlapping plates, each of which has its leading edge projecting above the rear of the preceding plate and arranged tangentially of a circle circumscribed about the axis of said inlet, the leading edges of said plates lying in a common surface, a rotary head coaxial with said inlet and having a sweep arm which projects generally radially therefrom and which overlies said drainage surface, the lower surface of said sweep arm closely fitting the surface in which the leading edges of said plates lie,,and a working plate mounted above said sweep arm and adapted to cooperate therewith, means for continuously rotating the sweep head and means for continuously moving the working plate in different directions substantially perpendicular to the axis of the sweep head.

11. In a machine for extracting liquid from a papermaking pulp, a centrally disposed inlet through which a slurry of pulp may be fed, an internal conical drainage plate surrounding said inlet, a rotary sweep arm mounted coaxial with said inlet, said sweep arm having an external conical undersurface overlying said drainage plate and' being spirally curved longitudinally, and means for continuously rotating said sweep arm.

12. In a machine for extracting liquid from a papermaking pulp, a centrally disposed inlet through which a slurry of pulp may be fed, a drainage plate surrounding said inlet, a rotary sweep arm mounted coaxial with said inlet and overlying said plate, said sweep arm having an upper surface inclined upwardly and rearwardly of its direction of rotation, means for continuously rotating the sweep arm to gather thickening stock up off the drainage plate, and a plate mounted above said sweep arm to cooperate with the sweep arm to compress between itself and the sweep arm pulp gathered up by the sweep arm.

13. In a machine for extracting liquid from a papermaking pulp. a centrally disposed inlet through which a slurry of pulp may be fed, a drainage plate surrounding said inlet, a rotary sweep arm mounted coaxial with said inlet and overlying said plate, said sweep arm having an upper surface inclined upwardly and rearwardly with reference to its direction of rotation, means for continuously rotating the sweep arm to gather thickening pulp up off the drainage plate, a second plate mounted above the sweep arm and in operative relation therewith, and means for imparting an orbital motion continuously to said second plate about an axis extending in the direction of the axis of the sweep arm.

14. In a machine for extracting liquid from a papermaking pulp, a centrally disposed inlet through which a slurry of pulp may be fed, a generally conical drainage plate surrounding said inlet and coaxial therewith and inclined upwardly from said inlet outwardly, a rotary sweep head mounted coaxial with said inlet and having a plurality of sweep arms which project outwardly therefrom and which overlie said drainage plate, said sweep arms being curved spirally from end to end and having undersurfaces which closely fit said drainage plate and upper surfaces which are inclined upwardly and rearwardly of the direction of rotation of the arms, means for rotating the sweep head continuously, a second plate mounted above the sweep arms in operative relation therewith, and means for imparting a continuous orbital motion to said second plate about an axis extending in the direction of the axis of the head.

15. In a machine for extracting liquid from a papermaking pulp, a generally conical perforated drainage plate, an inlet disposed centrally of the drainage plate through which a slurry of the pulp may be fed over said drainage plate, a discharge zone around the periphery of the drainage plate, a rotary head journaled centrally of the drainage plate and having a plurality of angularly spaced outwardly projecting arms overlying the drainage plate. each of said arms having a roughened working surface inclined upwardly and rearwardly from the front face of the arm, a second plate mounted above the arms and having a roughened working surface opposed to the working surfaces of the arms and extending in a plane perpendicular to the axis of the head, and

' means for rotating the head to cause the arms to gather thickening pulpoif of the drainage plate and pass it between the arms and said second plate.

16. In a machine for extracting liquid from a papermaking pulp, a generally conical perforated drainage plate, an inlet disposed centrally of the drainage plate through which a slurry of the pulp may be fed over said drainage plate, a rotary head journaled centrally of the plate and having a plurality of angularly spaced outwardly projecting arms over-lying said drainage plate, each of said arms having a roughened surface inclined upwardly and rearwardly from the front of the arm, a second plate mounted above the arms and having a roughened working surface opposed to the roughened surfaces of the arms and extending in a plane perpendicular to the axis of the head, means for rotating the head to cause the arms to sweep thickening pulp up off of the drainage plate and pass it between the arms and said second plate, and means for cyclically varying the distance between the opposed surfaces of the arms and the second plate.

17. In a machine for extracting liquid from a papermaking pulp, a generally conical perforated drainage plate, an inlet disposed centrally of the drainage plate through which a slurry of the pulp may be fed over said drainage plate, a discharge zone around the periphery of the plate, a rotary head journaled centrally of the plate and having a plurality of angularly spaced outwardly projecting arms overlying said drainage plate, each of said arms having a roughened upper surface, a second plate mounted above said arms and having a, roughened working surface opposed to the roughened surfaces of the arms and extending in a direction substantially perpendicular to the axis of the head, means for rotating the head to cause the arms to sweep thickening pulp up off the drainage plate, and means for imparting orbital movement to the second plate about an axis eccentric of the axis of the head.

18. In a machine for extracting liquid from a papermaking pulp, a generally conical perforated drainage plate, an inlet disposed centrally of the drainage plate through which a slurry of the pulp may be fed over said drainage plate, a discharge zone around the periphery of the plate, a rotary head journalei centrally of the plate and having a plurality of angularly spaced outwardly projecting arms overlying said drainage plate, each of said arms having a roughened surface inclined upwardly and rearwardly from the front of the arm, a second plate mounted above the arms and having a roughened working surface opposed to the roughened surfaces of the arms and extending in a plane substantially perpendicular to the axis of the head, means for rotating the head to cause the arms to sweep thickening pulp up off the drainage plate, means for imparting orbital movement to the second plate about an axis eccentric of the axis of the head, and means for restricting flow of thickened pulp into the discharge zone.

19. In a machine for extracting liquid from papermaking pulp, a generally conical perforated drainage plate, a hollow shaft journaled centrally of said plate, a sweep head mounted on said shaft to rotate therewith but to be adjustable axially relative thereto and having a bore aligned with the bore of said shaft, said sweep head having a plurality of sweep arms which are spirally curved longitudinally and which overlie said drainage plate and which have front faces that are inclined rearwardly with reference to the direction of rotation of the sweep arms, a second plate mounted about the arms and having a working surface opposed to the front faces of the arms, means for feeding a slurry of pulp through the bores of the shaft and sweep head over the drainage plate, means for rotating the shaft, and means for simultaneously moving the second plate in changing directions perpendicular to the axis of the shaft.

20. In a machine for extracting liquid from papermaking pulp, a perforated drainage plate, an inlet through which a slurry of pulp may be fed over said drainage plate, a sweep member operable on relative movement between the sweep member and the drainage plate, to sweep up thickened pulp deposited on the drainage plate, a second member mounted in opposed relation to the sweep member and positioned close enough to the sweep member to engage thickened pulp picked up by the sweep member and to compress said thickened pulp between itself and the sweep member, and means for effecting relative movement between the sweep member and both the drainage plate and the second member.

JAMES T. COGHIILV HOWARD H. LANGDON.

(References on following page) 15 REFERENCES CITED Number The following references are of record in the 2-1211275 file of this patent: UNITED STATES PATENTS 2,323,490

Number Name Date 607,312 Westwood July 12, 1898 748,867 Hodge Jan. 5, 1904 Number 1,795,603 HIISSBY Mar. 10, 1931 104,504 1,926,319 Tlmmerman Sept. 12, 1933 10 109,762 2,035,994 Sutherland Mar. 31, 1936 103,083

Name Date Zober June 21, 1938 Sutherland May 2, 1939 Cowles Nov. 14, 1939 Scherff July 6, 1943 FOREIGN PATENTS Country Date Australia 1937 Australia -1 1939 France Apr. 20, 1874

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