US3245535A - Vertical pressure type pulp screen - Google Patents

Vertical pressure type pulp screen Download PDF

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Publication number
US3245535A
US3245535A US282666A US28266663A US3245535A US 3245535 A US3245535 A US 3245535A US 282666 A US282666 A US 282666A US 28266663 A US28266663 A US 28266663A US 3245535 A US3245535 A US 3245535A
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United States
Prior art keywords
screen
pulp
screen plate
core member
impeller
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Expired - Lifetime
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US282666A
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English (en)
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Cowan Ben
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Individual
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Individual
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Priority to US282666A priority Critical patent/US3245535A/en
Priority to NO00152409A priority patent/NO128122B/no
Priority to FI640560A priority patent/FI43811C/fi
Priority to SE03912/64A priority patent/SE328463B/xx
Application granted granted Critical
Publication of US3245535A publication Critical patent/US3245535A/en
Anticipated expiration legal-status Critical
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21D—TREATMENT OF THE MATERIALS BEFORE PASSING TO THE PAPER-MAKING MACHINE
    • D21D5/00—Purification of the pulp suspension by mechanical means; Apparatus therefor
    • D21D5/02—Straining or screening the pulp
    • D21D5/06—Rotary screen-drums

Definitions

  • VERTICAL PRESSURE TYPE PULP SCREEN Filed May 23, 1963 5 Sheets-Sheet 3 INVENTOR FYI-7.- El BEN Cow/m A TTORNE YS United States 3,245,535 VERTECAL PRESSURE TYPE PULP SiIREEN Ben Cowan, 5460 Patricia Ave., Montreal, Quebec, Canada Filed May 23, 1963, Ser. N 0. 2$2,666 4 Claims. (ill.
  • This invention relates to rotary pulp screens of the vertical pressure type and particularly to a screen in which the rejects and that portion of acceptable fibres carried with the rejects are passed to a lower restricted annular area where the acceptable fibres and the rejects are separated from each other with the fibres being passed through the screen and the rejects are discharged through a reject discharge chamber and through a reject discharge opening.
  • the conventional pressure or drowned type screen has been used recently in applications where it is necessary to prevent the entry of air into the'pulp.
  • the screening operation is conducted under a slight pressure, in a completely closed system from feed'to discharge.
  • the reject material remains in the inside of the screen plate and a current must be induced along the face of the plate to move the rejects positively to the discharge point.
  • a large amount of good fibre must be rejected together with the true rejects, in order to discharge the rejects from the screen.
  • the usual practice is to rescreen the rejects and their attached fibres over a coarse screen which accepts of the fibre back into the system. The net result is a screening whose cf".- ciency is determined by rejects screening and not the primary screening.
  • the medium carrying the rejects i.e., the mixture of pulp and liquor
  • a clear liquor which is maintained at a pressure in excess of that of the screen feed pressure. This clear liquor under pressure separates the pulp from the rejects and washes it through the screen and the rejects continue down, carried by the clear liquor, into a reject chamber and to the reject discharge outlet.
  • the invention consists essentially in the provision of a vertically disposed rotary impeller which is provided with a core in the form of a hollow frustrurn of a cone whose apex is pointed in the direction of the stock inlet of the screen.
  • the impeller is provided with a series of vertically disposed blade-s radiating outwards at right angles to the axis of the impeller and extending along the surface of the impeller core and projecting upwards to the top level of the screen.
  • a stationary core formed from a frustrum of a cone, axially mounted about the drive shaft supporting the impeller, projects upwardly into the lower portion of the impeller core and is spaced radially inwards of the inner surface of the impeller core.
  • a white water or clear liquor supply is connected to an opening in the side of stationary core to direct an annular jet downwards towards the annular reject chamber formed at the periphery of the large diameter end of the stationary core and also directs jets through the apertures in the adjacent wall of the impeller core and into the annular space between the lower end of the impeller core and the adjacent surface of the screen. It is in this annular space Where the rejects are washed to separate the Patent 'ice fibres which are passed radially outwards through the screen while the rejects are carried axially downwards by the liquor flow into the annular reject chamber.
  • the conical section of the impeller core with the large end of the cone located adjacent the reject discharge provides a continually decreasing area of flow axially towards the reject end of the screen and maintains the axial velocity of flow of the rejects along the inside of the screen towards the reject discharge.
  • the axial section of the stationary corerelative to the impeller core provides a continually decreasing area of flow axially of the white water and ensures passage of the white water, or liquor under centrifugal force, through the apertures in the impeller core to mix with and dilute the rejects in the constricted area between the impeller core and the inner surface of the screen and thus to separate the fibres still clinging to the rejects.
  • the dilution liquor is used to wash away, through the screen, the acceptable fibres and the rejects are then discharged through the annular reject chamber.
  • the object of the invention is to provide a vertical type pulp screen operating under pressure in which approximately all of the pulp fibres are screened from the reject material.
  • a further object of the invention is to provide a vertical type pulp screen operating under pressure in which, in the final stage, the mixture of pulp fibres and reject material remaining Within the screen is washed and separated by liquor other than that carrying the pulp into the screen.
  • a further object of the invention is to provide a vertical type pulp screen operating under pressure in which the impeller includes a conical member eflecting a continually decreasing area of flow of pulp stock axially downwards towards the reject end of the machine.
  • a further object of the invention is to provide a vertical type pulp screen in which a conical member will maintain the axial velocity of flow of the rejects along the inside of the screen plate towards the reject end of the machine.
  • a further object of the invention is to provide a vertical type pulp screen in which the impeller includes a pair of conical members having concentric annular openings at their lower end aligned with an annular reject receiving chamber.
  • a further object of the invention is to provide a vertical type pulp screen in which an outer conical member is provided with jet apertures by means of which jets of white Water are directed on to the reject material to wash any fibres clinging to the rejects out through the screen.
  • FIG. 1 is a vertical side elevation of the pulp screen looking on the inlet and discharge openings.
  • FIG. 2 is a horizontal section of the screen taken on the line 2-2 of FIG. 1.
  • FIG. 3 is an enlarged vertical section of the screen taken on the line 33 of FIG. 1.
  • FIG. 4 is a vertical elevation of the screen rotor partly in section.
  • FIG. 5 is a bottom plan view of the rotor shown in FIG. 4.
  • FIG. 6 is a vertical section of the fixed conical section of the machine showing the reject discharge from the screen.
  • the pulp screen 5 is of the vertical type adapted to operate under pressure and consists of an outer circular casing 6 whose wall is slightly tapered to provide a larger diameter at its lower discharge end than at its upper inlet end.
  • the casing 6 is closed at its top end by the plate 7 and at its lower end by the annular plate 8 which supports on its under side the annular reject discharge chamber 9 to which the reject discharge outlet 10 is connected.
  • the annular screen plate 13 has its lower end 14 secured to the plate 8 at the outer periphery of the annular reject chamber 9.
  • a stationary core member 15 in the form of a frustrum of a cone has its base secured to the plate 8 at the inner peripheral edge of the annular reject discharge chamber 9.
  • the upper end of the core member 15 is closed 05 by a plate 16 having a centrally aligned seal ring 17, the purpose of which will be explained later.
  • the upper end of the annular screen plate 13 is secured to the annular plate 13 which is secured to. the inner surface of the casing 6 at a predetermined distance down from the top of the casing to define an inlet chamber 1?.
  • the plate 18 is supported in place by a series of brackets 20.
  • the annular space 21 between the screen plate 13 and the casing 6 defines a screened fibre chamber having a pulp fibre discharge opening 22.
  • a pulp fibre inlet 23 leads to the inlet chamber 19 of the machine.
  • the impeller 24 of the machine has a core 25 in the form of a frustrum of a cone whose larger diameter is located in the horizontal plane of the bottom end 26 of the impeller.
  • the peripheral edge 27 of the large end. of the cone 25 is such that when the impeller is axially aligned with the core member 15 the peripheral edge 27 of the core member 25 is located approximately midway of the radial width of the annular reject chamber 9 (FIG. 3) and approximately a similar distance from the adjacent edge of the stationary core, member 15.
  • the core member 25 is closed off at the top by the plate 28.
  • a plate 29 parallel with the plate 28 is located intermediate the height of the core 25.
  • the plates 28 and 29 are provided with axial apertures 30 and 31 and an axial sleeve 32 is located between these two plates.
  • a series of vertically disposed blades 33 are secured along their inner vertical edges 34 to the outer surface of the core 25.
  • the blades 33 radiate outwards from the axis of the impeller 24. and each project above the top of the core 25 and are secured at their topmost edges 35 to the annular ring 36.
  • the top of the impeller, defined by the annular ring 36 is approximately level with the plate 18 securing the top end of the screen plate 12 in the casing 6.
  • a series of nozzle apertures 37 are located in the tapered wall of the impeller core 25 near its lower end and etween each of the impeller blades 33.
  • the impeller 2 is driven by means of the drive shaft 38 extending upwards into the sleeve 32 and secured thereto by the key 39.
  • the shaft 33 is an extension of the drive sleeve 49 to which is secured the drive pulley 41 which, in turn, is driven by the motor 42 through the belt drive 43.
  • a drive shaft bearing assembly .4 is mounted between the upper and lower horizontal plates 8 and 45 of the screen supporting base 11 to support the drive shaft 38-40, in its vertically aligned position. Suitable belt tensioning means 46 are provided for tensioning the belt 43.
  • the impeller 24 is secured against axial movement by the nut 47 threaded on the threaded extension 48 of the shaft 38.
  • the seal member 17 provides a fluid seal between the stationary and moving members of the screen.
  • a separate source of white liquor is fed through the pipe 59 and through the wall of the stationary core member 15 into the space 51. between the core member 15 and the adjacent walls of the rotating core member 25 of the impeller 24.
  • An eyebolt S2 is provided for removal of the top cover plate 7, eyebolts 53 provide for removal of the impeller 24- while eyebolts 54 provide for removal of the stationary core 15.
  • the screen is designed to operate under pressure i.e. with the interior of the screen being completely filled with pulp stock.
  • the pulp stock is delivered to the inlet chamber 19 at the top of the screen through the pulp inlet 23. From the chamber 19 the pulp stock is directed downwards between the blades 33 and over the surface of the conical core 25 in the direction of the arrows A, shown in FIG. 3, towards the interior surface of the screen plate 13.
  • the pulp stock In the area between the impeller top ring 36 and the bottom of the screen plate 13, a large portion of the pulp fibres are washed through the screen plate 13 and are discharged from the screen through the discharge outlet 22.
  • the conical core member 25 of the impeller there is provided a continually decreasing area of flow axially of the pulp fibres towards the annular opening 55 from the interior of the screen into the annular reject chamber 9, and therefore there is maintained an axial velocity of how of the reject material along the inside of the screen plate 13.
  • the reject material is subjected to a separate washing by liquor fed through the pipe into the space 51.
  • the liquor is projected through the nozzle apertures 37 against the reject material to thoroughly wash and sep arate only pulp fibres still clinging to the reject material, forcing the pulp fibres through the screen plate 13 and into the stream of pulp fibres being discharged through the pulp outlet 22.
  • the heavier reject material falls down through the annular opening into the reject chamber 9 and is dis-' charged through the discharge outlet 10.
  • Suitable valves at the inlet and outlets of the screen ensure that the screen is kept filled at all times.
  • the axial flow of the heavier reject material is maintained downwards along the interior of the screen and through the rericted annular opening 55 into the annular chamber 9, and by the use of a separate source of washing liquor and not pulp stock, the reject material is thoroughly washed to the extent that in actual operation less than 1% of the good fibre in the feed of the screen may be discharged with the rejects, whereas this may be as high as 20% with conventional pressure type screens hitherto in use.
  • the basic principle behind the design of this screen is the use, in a screen under pressure, of an external liquid to displace the pulp medium used to carry the tailings through the screen, and thereby to carry the tailings from the screen in a medium free from acceptable material. This gives a complete separation of acceptable and unacceptable material in a single screen which is kept under pressure.
  • the open type of screen cannot be used in certain applications where exposure to air will cause entrainment of air bubbles in the liquid medium with consequent production of foam and ill eifects on the pulp or paper making process.
  • This screen combines all the advantages of conventional open screen with perfect separation and a closed screen with no air entrainment.
  • valve 56 in the feed water pipe 50 is closed oif and the unit operated as an ordinary pressure screen.
  • a pulp screening machine of the vertical pressure operated type including a base, a bearing vertically aligned in the said base, a drive shaft in said bearing and means to drive the said shaft, a casing axially mounted on said base with respect to the said drive shaft, a top closure plate for said casing, a pulp feed inlet to the said casing adjacent the top end thereof and a pulp discharge outlet adjacent the lower end of said casing, an annular perforated screen plate within said casing and supported on said base, means to support the top end of said screen plate to said casing at a point adjacent the lowermost edge of the said pulp feed inlet and defining with said casing a pulp feed chamber above said screen plate, a rotary impeller axially mounted on said drive shaft, the said impeller comprising a core member in the form of a frustrum of a cone whose larger diameter is located immediately above the said base and spaced inwardly of the said screen plate to define a restricted annular reject discharge opening whose smaller diameter is locate-d a distance downwards
  • a pulp screening machine of the vertical pressure operated type including a vertically disposed casing having top and bottom closure plates, a pulp feed inlet to the casing adjacent its top end and a pulp discharge outlet to the casing adjacent its lower end, an annular perforated screen plate within said casing supported on the said bottom closure plate, means to support the top end of the said screen plate at a point adjacent the lowermost edge of the said pulp feed inlet and defining a pulp feed chamber above said screen plate, a rotary impeller axially mounted within said screen plate, the said impeller comprising a core member whose lower end is located in the horizontal plane of the lower end of said screen plate, the said core member effecting a progressive reduction in area of the screening chamber in a downward direction and a series of vertically disposed blades secured to the surface of said core member and radiating outwards therefrom towards said screen plate, the lower ends of said core member and said screen plate defining a first annular reject discharge outlet, a stationary core member projecting upwardly from the said bottom closure plate within
  • a pulp screening machine of the vertical pressure operated type including a vertically disposed casing having top and bottom closure plates, a pulp feed inlet to the casing adjacent its top end and a pulp discharge outlet to the casing adjacent its lower end, an annular perforated screen plate within said casing supported on the said bottom closure plate, means to support the top end of the said screen plate at a point adjacent the lowermost edge of the said pulp feed inlet and defining a pulp feed chamber above said screen plate, a rotary impeller axially mounted within said screen plate, the said impeller comprising a core member whose lower end is located in the horizontal plane of the lower end of said screen plate, the said core member effecting a progressive reduction in area of the screening chamber in a downward direction and a series of vertically disposed blades secured to the surface of said core member and radiating outwards therefrom towards said screen plate, the lower ends of said core member and said screen plate defining a first annular reject discharge outlet, a stationary core member in the form of a frustum of
  • a pulp screening machine of the vertical pressure operated type including a vertically disposed casing having top and bottom closure plates, a pulp feed inlet to the casing adjacent its top end and a pulp discharge outlet to the casing adjacent its lower end, an annular perforated screen plate within said casing supported on the said bottom closure plate, means to support the top end of the said screen plate at a point adjacent the lowermost edge of the said pulp feed inlet and defining a pulp feed chamber above said screen plate, a rotary impeller axially mounted within said screen plate, the said impeller comprising a core member whose lower end is located in the horizontal plane of the lower end of said screen plate, the said core member effecting aprogressive reduction in area of the screening chamber in a downward direction and a series of vertically disposed blades secured to the surface of said core member and radiating outwards therefrom towards said screen plate, the lower ends of said core member and said screen plate defining a first annular reject discharge outlet, a stationary core member projecting upwardly from the said bottom closure

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  • Mechanical Engineering (AREA)
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US282666A 1963-05-23 1963-05-23 Vertical pressure type pulp screen Expired - Lifetime US3245535A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US282666A US3245535A (en) 1963-05-23 1963-05-23 Vertical pressure type pulp screen
NO00152409A NO128122B (enrdf_load_stackoverflow) 1963-05-23 1964-03-12
FI640560A FI43811C (fi) 1963-05-23 1964-03-16 Pystysuora painetyyppinen massaseula
SE03912/64A SE328463B (enrdf_load_stackoverflow) 1963-05-23 1964-03-31

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Application Number Priority Date Filing Date Title
US282666A US3245535A (en) 1963-05-23 1963-05-23 Vertical pressure type pulp screen

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US3245535A true US3245535A (en) 1966-04-12

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US282666A Expired - Lifetime US3245535A (en) 1963-05-23 1963-05-23 Vertical pressure type pulp screen

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US (1) US3245535A (enrdf_load_stackoverflow)
FI (1) FI43811C (enrdf_load_stackoverflow)
NO (1) NO128122B (enrdf_load_stackoverflow)
SE (1) SE328463B (enrdf_load_stackoverflow)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3363759A (en) * 1964-04-29 1968-01-16 Bird Machine Co Screening apparatus with rotary pulsing member
US3420373A (en) * 1966-04-01 1969-01-07 Allen Bruce Hunter Pulp screens
US3508651A (en) * 1968-04-19 1970-04-28 Hooper & Co Ltd S W Method and apparatus for screening pulp
FR2092333A5 (enrdf_load_stackoverflow) * 1970-05-11 1971-01-21 Hooper & Co Ltd
US3898157A (en) * 1973-03-23 1975-08-05 Hooper & Co Ltd S W Two stage pressure pulp screen device with stationary cylindrical screen
US3914172A (en) * 1972-08-31 1975-10-21 Highratio Screens Ltd Pulp stock pressure screen
US4000063A (en) * 1973-03-12 1976-12-28 Kamyr, Inc. Apparatus for separating knots from pulp
DE3015833A1 (de) * 1979-05-03 1980-11-13 Uniweld Inc Siebvorrichtung fuer pulpe
US4234417A (en) * 1979-03-29 1980-11-18 Gauld Equipment Manufacturing Co. Fibrous stock screen
EP0025310A1 (en) * 1979-08-27 1981-03-18 The Black Clawson Company Pressurized rotary screening apparatus
US4287055A (en) * 1978-07-11 1981-09-01 Firma Hermann Finckh Maschinenfabrik Gmbh & Co. Method of sorting fibre suspensions as well as a pressure sorter for performing the method
DE3240487A1 (de) * 1982-11-02 1984-05-03 Naučno-issledovatel'skij i proektno-konstruktorskij institut celljuloznogo mašinostroenija "NIICMAŠ", Petrozavodsk Drucksichter fuer fasersuspensionen
US4749474A (en) * 1986-08-27 1988-06-07 Ingersoll-Rand Company Screening apparatus
EP0404624A3 (en) * 1989-06-05 1991-07-31 Valmet Paper Machinery Inc. Method for controlling pressurized screening device and pressurized screening device
WO2011078764A1 (en) * 2009-12-21 2011-06-30 Metso Paper, Inc. Unit, arrangement and method for screening of cellulose pulp

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1696354A (en) * 1927-05-17 1928-12-25 Haug Anton Joseph Pulp-screening machine
US1722874A (en) * 1928-01-13 1929-07-30 Harold D Wells Pulp screen
US1856176A (en) * 1928-09-06 1932-05-03 Edward J Trimbey Method of and apparatus for screening paper pulp
US1990992A (en) * 1933-08-08 1935-02-12 American Voith Contact Co Inc Method and means of mechanically separating slimy substance from fiber stock

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1696354A (en) * 1927-05-17 1928-12-25 Haug Anton Joseph Pulp-screening machine
US1722874A (en) * 1928-01-13 1929-07-30 Harold D Wells Pulp screen
US1856176A (en) * 1928-09-06 1932-05-03 Edward J Trimbey Method of and apparatus for screening paper pulp
US1990992A (en) * 1933-08-08 1935-02-12 American Voith Contact Co Inc Method and means of mechanically separating slimy substance from fiber stock

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3363759A (en) * 1964-04-29 1968-01-16 Bird Machine Co Screening apparatus with rotary pulsing member
US3420373A (en) * 1966-04-01 1969-01-07 Allen Bruce Hunter Pulp screens
US3508651A (en) * 1968-04-19 1970-04-28 Hooper & Co Ltd S W Method and apparatus for screening pulp
FR2092333A5 (enrdf_load_stackoverflow) * 1970-05-11 1971-01-21 Hooper & Co Ltd
US3914172A (en) * 1972-08-31 1975-10-21 Highratio Screens Ltd Pulp stock pressure screen
US4000063A (en) * 1973-03-12 1976-12-28 Kamyr, Inc. Apparatus for separating knots from pulp
US3898157A (en) * 1973-03-23 1975-08-05 Hooper & Co Ltd S W Two stage pressure pulp screen device with stationary cylindrical screen
US4287055A (en) * 1978-07-11 1981-09-01 Firma Hermann Finckh Maschinenfabrik Gmbh & Co. Method of sorting fibre suspensions as well as a pressure sorter for performing the method
US4234417A (en) * 1979-03-29 1980-11-18 Gauld Equipment Manufacturing Co. Fibrous stock screen
FR2455651A1 (fr) * 1979-05-03 1980-11-28 Uniweld Inc Dispositif rotatif d'epuration de la pulpe
DE3015833A1 (de) * 1979-05-03 1980-11-13 Uniweld Inc Siebvorrichtung fuer pulpe
EP0025310A1 (en) * 1979-08-27 1981-03-18 The Black Clawson Company Pressurized rotary screening apparatus
US4267035A (en) * 1979-08-27 1981-05-12 The Black Clawson Company Pressurized rotary screening apparatus
DE3240487A1 (de) * 1982-11-02 1984-05-03 Naučno-issledovatel'skij i proektno-konstruktorskij institut celljuloznogo mašinostroenija "NIICMAŠ", Petrozavodsk Drucksichter fuer fasersuspensionen
US4749474A (en) * 1986-08-27 1988-06-07 Ingersoll-Rand Company Screening apparatus
EP0404624A3 (en) * 1989-06-05 1991-07-31 Valmet Paper Machinery Inc. Method for controlling pressurized screening device and pressurized screening device
WO2011078764A1 (en) * 2009-12-21 2011-06-30 Metso Paper, Inc. Unit, arrangement and method for screening of cellulose pulp
CN102666978A (zh) * 2009-12-21 2012-09-12 美佐纸业股份有限公司 用于筛选纤维素纸浆的单元、结构和方法
CN102666978B (zh) * 2009-12-21 2016-08-03 维美德技术有限公司 用于筛选纤维素纸浆的单元、结构和方法

Also Published As

Publication number Publication date
SE328463B (enrdf_load_stackoverflow) 1970-09-14
FI43811C (fi) 1971-06-10
FI43811B (enrdf_load_stackoverflow) 1971-03-01
NO128122B (enrdf_load_stackoverflow) 1973-10-01

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