US3111454A

US3111454A - Process and apparatus for forming sheet material from a suspension of solid particles in liquid media

Info

Publication number: US3111454A
Application number: US55097A
Authority: US
Inventors: Warren R Tucker; Robert H Hart
Original assignee: Gulf States Paper Corp
Current assignee: Gulf States Paper Corp
Priority date: 1960-09-09
Filing date: 1960-09-09
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

3,1 1 1,454 FROM 1963 w. R. TUCKER ETAL PROCESS AND APPARATUS FOR FORMING SHEET MATERIAL A SUSPENSION 0F SOLID PARTICLES IN LIQUID MEDIA Filed Sept. 9. 1960 3 Sheets-Sheet 1 INVENTOR. Warren E Tucker BY Fa ber'f' H. Her-l- W M+JAQW 4/70 r/z e ,vs

Nov. 19, 1963 w. R. TUCKER ETAL 3,111,454

PROCESS AND APPARATUS FOR FORMING SHEET MATERIAL FROM A SUSPENSION OF SOLID PARTICLES IN LIQUID MEDIA Filed Sept. 9, 1960 s Sheets-Sheet 2 INVENTOR. Warren 7?. Tucker BY Rober'f H. Hari- H Quiz +40% flfforneys 3 A m m w W 1963 w. R. TUCKER ETAL PROCESS AND APPARATUS FOR FORMING SHEET MATERIAL FROM A SUSPENSIQN OF SOLID PARTICLES IN LI Filed Sept. 9. 1960 3 Sheets-Sheet 3 INVENTOR.

BY 'Roberf H. Harf W, @ZZIV'M flffo r12 eys hire 3,1 l L 54 Patented Nov. 19, 1953 ice 3,111,454 PROES AND APPARATUS FDR FORMING HEET MATEREAL FRGM A SUSPENSEGN GE S PARTICLES IN LIQUID MEDIA Warren H. Tucker and fisher-t H. Hart, Tuseaioosa, Ala assiguors to Gulf States Paper .orporation, Tuscaloosa, Ala, a corporation of Delaware Filed Sept. 9, 1969, Ser. No. 55,ti97 7 (Claims. (Cl. 162-297) This invention relates to a process and apparatus for forming sheet material from a suspension of solid particles in liquid media and more particularly, the invention contemplates forming the sheet material at any selected weight of a wide weight range and at a high speed.

It is an object of our invention to provide a process and apparatus of the character designated in which the fibers of a pulp suspension may be aligned in the direction of rotation of a rotary screen, transversely of the direction of rotation and intermediate positions.

A more specific object of our invention is to provide a process and apparatus of the character designated in which the solid particles are deposited onto the rotary screen and the liquid is removed from the sheet thus formed by positive air or other gas pressure above atmospheric pressure.

Another object of our invention is to provide a process and apparatus of the character designated in which the sheet material is continuously produced by controlling the operating pressures rather than controlling velocities.

Another object of our invention is to provide a process and apparatus for producing a sheet of material from a suspension of solid particles in liquid media in which the sheet may be built up to any desired weight by a single unit rather than having to build up a laminated sheet.

Another object of our invention is to provide a process and apparatus of the character designated in which the liquid of the suspension which passes through the perforated screen passes from a liquid phase exteriorly of the screen to a liquid phase within the rotary screen, there being a negative pressure difierential along the inner surface of the rotary screen relative to the portion of the screen which is in contact with the suspension.

A further object of our invention is to provide a process and apparatus for making a sheet of material from a suspension of solid particles in liquid media in which the newly formed sheet passes from a suspension container to a transition chamber whereby the sheet is not distorted as it leaves the suspension container and excess liquid is removed from the sheet while in the transition chamber.

A further object of our invention is to provide a process and apparatus for making a sheet of material from a suspension of solid particles in liquid media of the character designated in which the newly formed sheet comes into contact with at least one pressure roll while in the transition chamber, whereby excess liquid is removed from the sheet and the sheet is compressed.

A further object of our invention is to provide a process and apparatus for manufacturing a sheet of material from a suspension of solid particles in liquid media in which the solid particles are deposited onto a rotary screen in a uniform manner throughout the entire length of the screen.

A still further object of our invention is to provide a process and apparatus of the character designated which shall be simple of construction, economical of manufacture and one which requires a minimum of maintenance due to the fact that the life of the rotary screen is materially increased since there is no friction or rubbing action between the screen and the materials deposited thereon.

Briefly, our improved process comprises bringing the suspension of solid particles in liquid media continuously into contact with an exterior portion of a rotary, perforatcd screen. Quantities of liquid are constantly held along the inner surface of the rotary screen opposite the portion of the screen which is in contact with the suspension. Liquid is continuously removed from the quantities of liquid at a controlled rate to create a negative pressure differential along the inner surface of the screen relative to the portion of the screen which is in contact with the suspension whereby the liquid passes from a liquid phase exteriorly of the screen to a liquid phase within the screen, thus depositing the solid particles onto the screen in the form of a continuous sheet. The sheet thus formed is then removed from the screen.

Apparatus embodying features of our invention is illustrated in the accompanying drawings, forming a part of this application, in which:

FIG. 1 is a vertical sectional view of the apparatus, partly in elevation;

FIG. 2 is a sectional view taken generally along the lines 22 of FIG. 1;

PEG. 3 is a side elevational view, with parts broken away and in section;

IG. 4 is an enlarged, fragmental plan view, showing the screen covering for the perforated drum; and,

PEG. 5 is a vertical sectional view, partly in elevation, showing a modified form of our invention.

Referring now to the drawings for a better understanding of our invention and more particularly to FIGS. l-4, we show a cylindrical drum 10 which is supported by flange wheels ill, as shown in FIG. 3. The wheels 11 are mounted on shafts 12 which are supported by suitable bearing members 13. Annular rails 1'4 and 16 are provided at the opposite ends of the drum 10 in position to engage the flange wheels 11. Mounted adjacent one end of the drum it) is an annular sprocket 17 which is operatively connected to a drive sprocket 18 by a sprocket chain 39. The drive sprocket 18 is mounted on a shaft 21 of a motor 22.

The central portion of the cylindrical drum 10 is perforated as at 23 whereas the end portions thereof adjacent the annular tracks 14 and 16 are not perforated. Surrounding the outer surface of the perforated portion of the cylindrical drum it is a wire screen 24 which is preferably of the open mesh type, as shown in FIG. 4. The space between the individual strands of wire 24 form openings which register with the openings 23 in the drum it}. Surrounding the wire screen 24 is a wire mesh member 26 which may be of a construction similar to the fourdrinier wire employed on conventional type apparatus for making paper. The wire 24 serves the purpose of holding the wire mesh member 26 in spaced relation to the exterior surface of the rotary drum 10 and the openings 23 therein, whereby free flow of the drain-age liquor is permitted at all times.

Positioned within opposite ends of the rotary drum 10 e supporting plates 27 and 28 which are secured to and supported by suitable support brackets 29 and 31, respectively. The brackets 29 and 31 may be braced by

diagonal braces

32 and 33 respectively, as shown in FIGS. 2 and 3. The support bracket 29 is mounted on a suitable supporting frame 34 while the support bracket 31 is mounted on a supporting frame 36.

Mounted within the cylindrical drum '10 and secured to the stationary supporting plates 27 and 28 is a longitudinally extending platelike member 37 having inturned end portions 38 and 39 which are adapted to engage the inner surface of the perforated portion of the drum 10, as shown in FIG. 1. Suitable seals 41 are provided adjacent the edges of the plate-like member 37 in position to engage the inner surface of the drum 10. Mounted on the plate-like member 37 and extending radially toward the inner surface of the drum are transverse partition members 42 which define a plurality of separate compartments 43. The compartments 43 are thus positioned within the drum it) transversely along the perforated surface thereof and each compartment is closed on all sides except the side toward the perforated surface of the drum, as shown. Communicating with each of the separate compartments 43 is an individual discharge conduit 44 having a control valve 46 therein. That is, there is a separate conduit 44 and control valve 46 for each compartment 43 whereby the amount of liquid removed from each compartment 43 may be controlled.

Mounted adjacent the upgoing side of the rotary drum 10 is a suspension container 47. As shown in FIG. 1, the tip-going side of the cylindrical drum til forms one wall for the suspension container 47 whereby the suspension is in direct contact with the outer sufrace of the perforated drum 10 and the wire carried thereon. The suspension 48, such as a wood pulp stock solution, is introduced into the container 47 through a conduit 49 having a control valve 51 therein. The stock solution or suspension 48 is continuously circulated through the suspension chamber 47 and excess solution is removed and recirculated through a discharge conduit 52 having a control valve 53 therein. A suitable agitator roll 54 is mounted for rotation within the suspension chamber 47 whereby the suspension is thoroughly agitated prior to contacting the perforated drum l0. Communicating with the suspension chamber 47 is a conduit 56 for supplying a suitable gas, such as air, whereby the suspension chamber is maintained under superatmospheric pressure.

Surrounding a portion of the perforated drum 143 immediately adjacent the discharge side of the suspension chamber 47 is a transition chamber 57 which is defined by an :arcuate wall 58 connected by suitable end walls 59. The ends of the end walls 59 and the arcuate wall 53 adjacent the suspension container 47 are secured to the suspension ohamber to form an air-tight joint therebetween. As shown in FIG. 1, the suspension chamber 47 and the transition chamber 57 are separated from each other by a partition wall 61 and a baffle member 62 which is adjustably connected to the partition wall 61 by suitable means, as shown. That is, the baffle member 62 is adjustable whereby it may be moved toward and from the outer surface of the perforated drum 19 to permit the passage of the sheet 63- which is continuously formed on the drum 10.

Mounted for rotation adjacent the discharge end of the transition chamber 57 is a pressure roll 64 which is coated with a suitable resilient material 66, such as rubber or the like. Secured to the discharge end of the arcuate member 53 is a flexible sealing member 67 which is disposed to engage the periphery of the pressure roll 64 whereby a seal is provided between the pressure roll and the arouthe member 58.

Communicating with the transition chamber 57 is a conduit 68 for supplying a suitable gas, such as air, whereby the pressure within the transition chamber 57 substantially equals or balances the pressure in the suspension chamber 47, thus preventing liquid from passing from the suspension chamber 47 into the transition chamber 57. That is, by balancing the pressure between the suspension container and the transition chamber, there is no jetting of the liquid against the newly formed sheet 53, thus preventing any distortion or tearing of the sheet. Also, by maintaining the transition chamber 57 under super-atomspheric pressure, the liquid contained in the sheet 63, is forced through the perforated drum it as it passes between the baffle member 62 and the pressure roll Secured to the supporting plate members 27 and 28 are longitudinally extending scraper plates 69 which are in position to engage and scrape the inner surface of the perforated drum 10, thereby keeping the same in a clean condition as the drum rotates. Also secured to the supporting plate members 27 and Z8 and extending longitudinally of the rotary drum is a plate member 71 which is connected at one end to the plate-like member 37 and at the other end to a suction box 72 which in turn engages the inner surface of the perforated drum it Accordingly, the plate member 71 prevents the liquid discharged into the drum 19, between bafile member 52. and pressure roll 54, from being discharged beneath the apparatus. The suction box 72 removes the liquid thus collected within the cylindrical drum between the bathe member 62 and the pressure roll 64.

After the sheet 63, such as paper, passes the pressure roll 64, the sheet is dry enough to be transferred to a felt belt 73 which passes continuously between a suction roll 74 and the outer surface of the perforated drum 10, as shown in FIG. 1. A suction box 76 is mounted within the suction roll 74 and an air pressure box 77 is mounted within the perforated drum to opposite the suction box 76 whereby the sheet of material 63 is removed by the action of the positive air pressure from the pressure box '77 and the partial vacuum created within the suction box 76. The velocity of the sheet of material 63 removed on the belt 73- is substantially the same as the peripheral velocity of the rotary drum 19, thus preventing distortion of the sheet of material as it is separated from the perforated drum in. A jet 78 is positioned between the suc tion roll 74 and the suspension container 47 for spraying water onto the exterior surface of the drum 1%, whereby it is cleaned prior to re-entering the suspension container.

From the foregoing description, the operation of our improved apparatus shown in FIGS. 1-4 and the manner in which our improved process is carried out will be readily understood. The suspension 48, such as a wood pulp stock solution, is continuously introduced into the suspension container 47 through the conduit 49. The suspension is continuously agitated by the agitator 54 whereby the solid particles are distributed uniformly throughout the suspension at the time the suspension contacts exterior surface of the perforated drum 1% The excess solution is removed through conduit 52 and is recirculated to the head box for the suspension. A suitable gas, such as air, is continuously introduced into the suspension container 47 through conduit 56 whereby the suspension container is maintained under super-atmospheric pressure to force the liquid of the suspension through the wire mesh 26, Wires 24 and the perforations 23 into the individual compartments 43 positioned adjacent the inner surface of the drum it Liquid is continuously removed from the individual compartments 43 through the conduits 44 at a controlled rate to create a negative pressure differential along the inner surface of the drum l0 relative to the portion of the drum which is in contact with the suspension 48, whereby the liquid passes from a liquid phase exteriorly of the drum 1% to a liquid phase within the individual compartments 43). As the liquid passes through the perforated drum, the solid particles are continuously deposited onto the drum in the form of a continuous sheet 63. The control valves 46 in the individual conduits 44 are so regulated that :a uniform removal 0? liquid is provided along the entire area of the drum 10 which is in contact with the suspension 43. That is to say, without the individual compartments 43 for removing selected quantities of liquid, the liquid would not be removed uniformly throughout the length of the drum 10, but a substantial quantity of the liquid would be removed adjacent the discharge means for the liquid. By providing the individual compartments 43, the amount of liquid removed at any selected position along the drum 1%} can be accurately controlled to provide the necessary negative pressure differential between the compartments 43 and the suspension container 47. in actual practice, we have found that a negative pressure differential of from approximately 25 to 30' inches on the water gauge within the com-- partments 43 and approximately from 4,000 to 5,000' inches on the water gauge in the suspension container 47 is satisfactory in every respect. However, the pressure differential will vary for the various types of suspensions employed.

The bafiie 62 is adjusted to a position to permit the sheet 63 to pass from the suspension container 47 into the transition chamber 57. A suitable gas, such as air, is introduced continuously through the conduit 68 into the transition chamber whereby the pressure within the transition chamber balances the pressure within the suspension container. By providing such a balance of pressure, there is no jettin of the suspension between the baiiie member 62 and the newly formed sheet 63, thereby preventing distortion of the slice Also, in view of the fact that the transition chamber 57 is maintained under super-atmospheric pressure, the liquid carried by the sheet 63 is continuously forced through the perforated drum into the space defined between the plate-like member 37 and the longitudinally extending plate 71 where it is removed by the suction box 72. In view of the fact that the suction box 72 is also in contact with the inner surface of the perforated drum 19, it further aids in the removal of liquid from the sheet 63. As the sheet 63 passes from the transition chamber 57, it is engaged by the pressure roll 64, thereby aiding in the removal of liquid and com pressing the sheet.

The felt belt '73 is driven at a speed substantially equal the peripheral velocity of the perforated drum 14 whereby the sheet is not distorted as it leaves the drum. A suitable gas, such as air, is continuously introduced into the pressure box 77 whereby the sheet 63 is forced away from the perforated drum at this point. Also, the suction box 76, which is positioned at the opposite side of the sheet 63 from the pressure box 77, aids in the removal of the sheet from the drum it To clean the exterior surface of the drum ill prior to passin through the suspension chamber 47, water is continuously sprayed onto the exterior surface of the drum by introducing water through jet 73. The water jet is positioned between the point of removal of the sheet 63 from the drum 19 and the point that the drum enters the suspension container 4-7.

Referring now to FIG. 5 of the drawings, we show a modified form of our invention in which a perforated drum 19 is mounted for rotation in the same manner as the perforated drum 1% described hereinabove. Also, the perforated drum 19 is provided with perforations 23 wire screen 24 and wire mesh 26 which are identical in construction and operation to the perforations 23, wire screen 24 and wire mesh 26. Mounted on a suitable stationary support and extending within the perforated drum lid is a plate-like member 37 which has a plurality of partition walls iZ secured thereto to define individual compartments .3 for removing the liquid from the inner surface of the perforated drum Th Communicating with the individual compartments defined by the partition walls 42 are individual discharge conduits 44* which are identical in construction and operation to the discharge conduits 44 described hereinabove.

A suspension container 47 is provided adjacent the upgoing side of the perforated drum 1t and is separated from a transition chamber 57 by a partition wall 61 having an adjustable bathe 62 carried thereby. A suitable as, such as air, is continuously introduced into the suspension container 47 and gas is continuously introduced into the transition chamber 57:: through a conduit 68a whereby the super-atmospheric pressure within the suspension container 47a is balanced by the pressure in the transition chamber.

The continuous sheet of material 63 formed on the perforated drum 1& in the suspension container 47 passes beneath the adjustable baffie member 62 into the transition chamber 57*. Mounted for rotation within the transition chamber 57 is a plurality of pressure rolls 64 which are coated with a resilient material 66 such as rubber or the like. By providing a plurality of pressure rolls 64 within the transition chamber, the sheets 63 is compressed as the liquid is forced through the perforations 23 by the super-atmospheric pressure within the transition chamber. That is, by providing both pressure rolls and super-atmospheric pressure within the transition chamber 57 the liquid is removed more effectively from the sheet 63 The pressure roll 64 adjacent the discharge end of the transition chamber 57 contacts a suitable sealing member 67 whereby the discharge end of the transition chamber is sealed.

Secured to a stationary support member and extending longitudinally within the drum 16 are a plurality of platelilre scraper members 69* which scrape the inner surface of the perforated drum Ill to maintain the same in a clean condition as it rotates. Also mounted on a suitable stationary support and extending longitudinally within the drum Id is a plate member "71 which defines with the plate-like member 37 and the inner surface of the perforated drum 16 a receptable for receiving the liquid which enters the perforations 23 between the bafile member 62* and the discharge end of the transition chamher. A suction box 72 is mounted within the perforated drum 16 adjacent the discharge end of the transition chamber 57 for removing the liquid collected within the perforated drum.

The sheet of material 63 formed on the perforated drum 16 is transferred to a felt belt 73 which revolves at a speed substantially equal the peripheral velocity of the perforated drum 16 The felt belt 7'3 passes over a suitable roller 74 having a suction box 76*- therein which causes the sheet of material 63 to be urged toward the belt 73 at the point of separation from the perforated drum 10 Also, mounted within the perforated drurn Ili opposite the suction box 7& is a pressure box 77 Air or other suitable gas is continuously introduced into the pressure box 77 whereby the sheet 63 is forced away from the perforated drum 19 at the point of separation. The exterior surface of the perforated drum, including the wire mesh 26 and the wire screen 24 is continuously cleaned prior to entering the suspension container 47 by applying water through jet 78 The construction and operation of the apparatus shown in FIG. 5 is substantially the same as the apparatus shown and described in FIGS. 14. The only difference being that a plurality of pressure rolls 64 are mounted within the transition chamber whereby the pressure rolls aid the super-atmospheric pressure in forcing the liquid from the sheet 63 into the perforated drum lit Also, the pressure rolls 64 compress the sheet as it passes through the transition chamber.

From the foregoing, it will be seen that we have devised an improved process and apparatus for forming sheet material from a suspension of solid particles in liquid media. By bringing the suspension continuously into contact with an exterior portion of the perforated drum and constantly holding quantities of liquid along the inner surface of the drum opposite the portion of the drum which is in contact with the suspension, together with the removal of liquid continuously from the quantities of liquid at a controlled rate to create a negative pressure differential along the inner surface of the drum relative to the portion of the drum which is in contact with the suspension, the liquid passes from a liquid phase exteriorly of the drum to a liquid phase within the drum. Accordingly, a uniform deposit of solid particles is obtained throughout the entire area of the perforated drum which is in contact with the suspension container. By thus controlling the deposit of the particles onto the perforated drum, a sheet of paper or the like, may be formed at any selected weight of a wide weight range and at a high speed. Also, by controlling the deposit of the solid particles, such as fibers, onto the perforated drum, the fibers may be aligned in the direction of rotation of the drum, transversely of the direction of rotation and at any selected intermediate positions. Furthermore, by providing a negative pressure differential between the interior of the perforated drum and the suspension container,

7 whereby the liquid passes from a liquid phase exteriorly of the drum to a liquid phase within the drum, our improved process is carried out by controlling the pressure employed rather than controlling velocities.

While we have shown our invention in but two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What we claim is:

1. In apparatus for separating solids from a liquid suspension and forming a sheet thereof,

(a) a perforated drum,

(b) means to rotate said drum,

(c) means to introduce said suspension continuously into contact with a portion of the exterior surface of said rotatable drum,

((1) means deihiing a plurality of separate compartments within said drum for holding liquid, said compartments being positioned transversely along the perforated surface of said drum opposite said portion thereof which is in contact with the suspension,

(e) means to remove liquid continuously from said compartments at a controlled rate to create a uniform negative pressure difierential along the inner surface of the drum relative to said portion of the drum which is in contact with the suspension whereby the liquid is drawn inwardly from a liquid phase exteriorly of said drum to a liquid phase within said drum and solid particles are deposited continuously on said drum in the form of a continuous sheet, and

(7) means to remove the sheet thus formed from said drum.

2. In apparatus for separating solids from a liquid suspension and forming a sheet thereof,

(a) a perforated drum,

(b) means to rotate said drum,

() a suspension container disposed adjacent the upgoing side of said drum whereby the exterior surface of said up-going side of the perforated drum forms a wall for said container.

(d) means circulating said suspension through said container under super-atmospheric pressure,

(2) means defining a plurality of separate compartments within said drum for holding liquid, said compartments being positioned transversely along the perforated surface of said drum opposite said portion thereof which is in contact with the suspension,

(1) means to remove liquid continuously from said compartments at a controlled rate to create a uniform negative pressure difierential along the inner surface of the drum relative to said portion of the drum which is in contact with the suspension whereby the liquid is drawn inwardly from a liquid phase exteriorly of said drum to a liquid phase within said drum and solid particles are deposited continuously on said drum in the form of a continuous sheet, and

g) means to remove the sheet thus formed from said drum.

3. In apparatus for separating solids from a liquid suspension and forming a sheet thereof as defined in claim 2 in which a gas supply conduit communicates with the suspension chamber for maintaining said chamber under super-atmospheric pressure.

4. In apparatus for separating solids from a liquid suspension and forming a sheet thereof,

(a) a perforated drum,

(1:) means to rotate said drum,

(d) means defining a plurality of separate compart ments for holding separate quantities of liquid within g the drum, said compartments being positioned transversely along the perforated surface of said drum opposite said portion thereof which is in contact with the suspension and being closed on all sides except the side toward the perforated surface of the drum,

(e) liquid extraction means in communication with said separate compartments for removing liquid continuously therefrom at a controlled rate to create a uniform negative pressure differential along the inner surface of the drum relative to said portion of the drum which is in contact with the suspension whereby the liquid is drawn inwardly from a liquid phase exteriorly of said drum to a liquid phase within said drum and solid particles are deposit-ed continuously on said drum in the form of a continuous sheet, and

(7') means to remove the sheet thus formed from said drum.

5. In apparatus for separating solids from a liquid suspension and forming a sheet thereof as defined in clairn 4 in which the separate compartments are defined by a generally plate-like member extending longitudinally within and spaced from the inner surface of the drum and a plurality of transverse partition Walls secured at one edge thereof to said plate-like member with another edge thereof in sliding contact with the inner surface of said drum.

6. in apparatus for separating solids from a liquid suspension and forming a sheet thereof,

(a) a perforated drum,

(b) means to rotate said drum,

(c) a suspension container disposed adjacent the upgoing side of said drum whereby the exterior surface of said up-going side of the perforated drum forms a wall for said container,

(d) a gas supply conduit communicating with said suspension container for maintaining the suspension container under super-atmospheric pressure,

(e) means defining separate compartments for holding separate quantities of liquid within the drum, said compartments being positioned transversely along the perforated surface of the drum opposite said exterior surface of the drum which forms a wall for the suspension container and being closed on all sides except the side toward the perforated surface of the drum,

(1) means to remove liquid continuously from said separate compartments at a controlled rate to create a uniform negative ressure differential along the inner surface of the drum relative to said exterior surface thereof which forms a wall for the suspension container whereby liquid is drawn inwardly from a liquid phase exteriorly of said drum to a liquid phase within said drum and solid particles are deposited continuously on said drum in the form of a continuous sheet,

(g) a transition chamber adjacent the suspension container in position to encase the exterior surface of said drum as it passes from the suspension container,

(h) a gas supply conduit communicating with said transition chamber for maintaining a balance of pressure between the suspension container and the transition chamber whereby excess liquid does not pass from the suspension container into the transition chamber to distort the sheet formed on the drum and excess liquid is removed from the sheet after it passes into the transition chamber, and

(i) means to remove the sheet thus formed from said drum.

7. In apparatus for separating solids from a liquid suspension and forming a sheet thereof as defined in claim 6 in which the suspension container is separated from the transition chamber by an adjustable baflie member which is spaced from the exterior surface of the drum a distance to permit passage of the sheet therebetween.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS 1,995,011 Quiller Mar. 19, 1935 2,753,766 Simpson July 10, 1956 2,884,059 Stewart et a] Apr. 28, 1959 18 Miiller June 9, 1959 Fasoli July 5, 1960 FOREIGN PATENTS Germany Mar. 13, 1930 Great Britain Nov. 20, 1957 France Feb. 6, 1956

Claims

6. IN APPARATUS FOR SEPARATING SOLIDS FROM A LIQUID SUSPENSION AND FORMING A SHEET THEREOF, (A) A PERFORATED DRUM, (B) MEANS TO ROTATE SAID DRUM, (C) A SUSPENSION CONTAINER DISPOSED ADJACENT THE UPGOING SIDE OF SAID DRUM WHEREBY THE EXTERIOR SURFACE OF SAID UP-GOING SIDE OF THE PERFORATED DRUM FORMS A WALL FOR SAID CONTAINER, (D) A GAS SUPPLY CONDUIT COMMUNICATING WITH SAID SUSPENSION CONTAINER FOR MAINTAINING THE SUSPENSION CONTAINER UNDER SUPER-ATMOSPHERIC PRESSURE, (E) MEANS DEFINING SEPARATE COMPARTEMTNS FOR HOLDING SEPARATE QUANTITIES OF LIQUID WITHIN THE DRUM, SAID COMPARTMENTS BEING POSITIONED TRANSVERSELY ALONG THE PERFORATED SURFACE OF THE DRUM OPPOSITE SAID EXTERIOR SURFACE OF THE DRUM WHICH FORMS A WALL FOR THE SUSPENSION CONTAINER AND BEING CLOSED ON ALL SIDES EXCEPT THE SIDE TOWARD THE PERFORATED SURFACE OF THE DRUM, (F) MEANS TO REMOVE LIQUID CONTINUOUSLY FROM SAID SEPARATE COMPARTMENTS AT A CONTROLLED RATE TO CREATE A UNIFORM NEGATIVE PRESSURE DIFFERENTIAL ALONG THE INNER SURFACE OF THE DRUM RELATIVE TO SAID EXTERIOR SURFACE THEREOF WHICH FORMS A WALL FOR THE SUSPENSION CONTAINER WHEREBY LIQUID IS DRAWN INWARDLY FROM A LIQUID PHASE EXTERIORLY OF SAID DRUM TO A LIQUID PHASE WITHIN SAID DRUM AND SOLID PARTICLES ARE A CONTINUOUS SHEET, (G) A TRANSITION CHAMBER ADJACENT THE SUSPENSION CONTAINER IN POSITIN TO ENCASE THE EXTERIOR SURFACE OF SAID DRUM AS IT PASSES FROM THE SUSPENSION CONTAINER, (H) A GAS SUPPLY CONDUIT COMMUNICATING WITH SAID TRANSITION CHAMBER FOR MAINTAINING A BALANCE OF PRESSURE BETWEEN THE SUSPENSION CONTAINER AND THE TRANSITION CHAMBER WHEREB Y EXCESS LIQUID LOES NOT PASS FROM THE SUSPENSION CONTAINER INTO THE TRANSITION CHAMBER TO DISTORT THE SHEET FORMED ON THE DRUM AND EXCESS LLIQUID IS REMOVED FROM THE SHEET AFTER IT PASSES INTO THE TRANSITION CHAMBER, AND (I) MEANS TO REMOVE THE SHEET THUS FORMED FROM SID DRUM.