US3434593A - Methods and apparatus for air classifying and screening of finely divided material - Google Patents

Methods and apparatus for air classifying and screening of finely divided material Download PDF

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Publication number
US3434593A
US3434593A US565648A US3434593DA US3434593A US 3434593 A US3434593 A US 3434593A US 565648 A US565648 A US 565648A US 3434593D A US3434593D A US 3434593DA US 3434593 A US3434593 A US 3434593A
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Prior art keywords
screen
particles
casing
air
finely divided
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US565648A
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English (en)
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Daniel J Sullivan
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Sturtevant Mill Co
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Sturtevant Mill Co
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B4/00—Separating solids from solids by subjecting their mixture to gas currents
    • B07B4/02—Separating solids from solids by subjecting their mixture to gas currents while the mixtures fall
    • B07B4/025—Separating solids from solids by subjecting their mixture to gas currents while the mixtures fall the material being slingered or fled out horizontally before falling, e.g. by dispersing elements

Definitions

  • An air classifier for classifying finely divided materials comprises inner and outer casing members and a fan member for inducing a flow of air upwardly through cascading particles introduced at the top of the casing members.
  • Adjustable screen means of the invention are located adjacent to the fan member and function to selectively provide for a separation of coarse particles not removed by conventional air classifying apparatus.
  • This invention relates to improved methods and ap paratus for processing finely divided materials and, more particularly, the invention is concerned with machines for air classifying and screening finely divided substances such as minerals, vegetable substances, chemicals and other similar products.
  • Patent No. 2,774,476, owned by the assignee of the present invention a typical form of air classifying ap paratus of the general type referred to is disclosed wherein a cascading mass of finely divided material is subjected to a centrifuging action and the centrifuged material is displaced radially outwardly into a fan-induced current of air flowing upwardly through the centrifuged mass to obtain a separation of fine particles from relatively coarser particles.
  • Machines of the class referred to are very effective in removing controlled percentages of relatively fine particles and separating them from relatively coarse particles. This is accomplished by the fine particles being lifted upwardly by a fan-induced flow of air and these fine particles are led into an outer casing which is separated from an inner tailings casing for coarse particles.
  • Another object of the invention is to provide a method of combining the steps of air classifying with novel mechanical screening in such a manner that there may be realized a controlled extension of the range of coarse particle sizes recovered while also obtaining a desired recovery of relatively fine particles in a suitable product mixture.
  • Another object of the invention is to provide an improved apparatus for processing finely divided material such as limestone and the like whereby standard forms of air classifying machines of the type disclosed in the above-noted patent may, by relatively simple modification, be adapted to a novel type of screening operation.
  • Still another object is a method of combined classifying and screening of finely divided materials to produce a product mix occurring in a range of predetermined relatively coarse sizes from which a specified range of fines may be substantially removed.
  • FIGURE 1 is a plan view of an air classifying apparatus of the invention in one preferred form
  • FIGURE 2 is a side elevational view with portions broken away at one side thereof;
  • FIGURE 3 is a vertical cross section of the machine shown in FIGURES 1 and 2;
  • FIGURE 4 is another fragmentary cross sectional view of the machine with portions thereof broken away to indicate diagrammatically the path of flow of fine particles and coarse particles induced by rotative movement of a fan member;
  • FIGURE 5 is a detail fragmentary exploded view of a portion of the inner casing of the machine and screening means of the invention.
  • I may accomplish this screening operation by displacing particles of a specific desired size radially outwardly through protectively arranged screen means having openings or perforations arranged to avoid interference with normal air classifying and whose size, arrangement, and accessibility in the machine may be adjusted in accordance with a particular coarse particle size requirement.
  • I provide a plurality of screen elements detachably secured in the walls of an inner casing of the air classifier and provided with adjustable screen covers by means of which the screen apertures may be opened or closed as desired to regulate passage of particles outwardly therethrough.
  • the screen elements are disposed immediately below radially projecting casing top edges and protective flange portions so that the screen elements occur in a relatively sheltered relationship and fine particles passing downwardly over the outer edges of the inner casing top are thus prevented from entering between the screens and the screen covers.
  • I further locate the screen elements in the inner casing of the machine in positions so chosen with respect to the air classifier fan as to subject particles to a maximum exposure of the radially displaced stream of air occurring in the immediate vicinity of the fan tips.
  • numeral 2 denotes a closed cylindrical casing which is formed with a conically shaped lower section 4 and a top section 2a.
  • the section 2a has vertically supported therethrough a bearing B in Which is received a shaft S driven by a belt L and a motor M.
  • the bearing B and the motor M are preferably supported on transverse beam members 3 in turn secured at the upper side of the top section 2a.
  • a pulley P is driven by the belt L as suggested in FIGURE 3.
  • Located in spaced relation to the outer casing 2 is an inner cylindrical casing 30 carried on supporting brackets 32 projecting inwardly from the inner periphery of casing 2.
  • the casing 30 is provided with a top rim portion 31 which projects radially outwardly as shown in FIGURES 3 and 4 for an appreciable distance and also provided immediately under the rim 31 are reinforced channel shaped members 33 providing overhanging lower edges 35.
  • a rotary a'pparatus including the distributor plate 10 which is supported on suitable bearing means 10a.
  • a plate member 11 Located in spaced relation above the distributor plate 10 and rotatable with it is a plate member 11 to which is secured vanes as .13.
  • the spacing of the vanes 13 may be varied to provide a means of rejecting certain ranges of coarse particles as is disclosed in Patent No. 2,774,476.
  • Finely divided material is delivered into the machine through an inlet chute 6 formed at the upper side of the machine as shown in FIGURE 3. Also supported for rotation with the distributor plate 10 and the member 11 is a fan member F which is adapted to rotate and induce an upwardly directed pulling force on material centrifugally displaced from the distributor plate 10.
  • the inner casing 30 extends upwardly to a point just below the fan member F as shown in FIGURE 3 and also includes a lower conically shaped section 12 around which is supported a plurality of adjustable vanes. Supported immediately below the vanes is a second conically shaped section 15, at the lower extremity of which is attached a tubular tailings conduits 18. The latter member projects downwardly through one side of the conical section 4 as best shown in FIGURE 3. As will be observed in FIGURE 3 the tailings conduit 18 occurs in spaced relation to inner peripheral portions of the conical section 4 so as to define a fines outlet 24.
  • finely divided material is directed into the feed inlet 6 and passes downwardly around the bearing and rotating shaft S to fall onto the rotating plate 10.
  • the material drops down onto the distributor plate it is centrifugally displaced towards the inner casing 30, and some of the relatively coarse particles begin to fall downwardly around the inner peripheral surfaces of the conical section12.
  • relatively fine particles are classified as described above and, in addition, I provide for discharging a selected range of relatively coarse particles radially outwardly through the inner casing section 30 and into the path of downward fiow of the fines particles passing down through passageway 17.
  • the inner casing member 30 with a plurality of spaced apart openings 40, one of which is shown in FIGURES 2 and 5.
  • the openings 40 may, if desired, be fitted with enclosing frames of some suitable nature detachably secured therein.
  • I further provide a plurality of screen elements as 42 (FIGURE 2).
  • the screen elements may, for example, consist of rectangularly shaped plates of perforated metal or other suitable screen material and each of the screen elements are further curved into an arcuate shape to coincide with the curvature of the cylindrical casing 30.
  • An important feature of the invention is the location of the screen elements and screen covers in the recessed position described relative to the casing rim 31 to provide a sheltering action. It will be appreciated that when the fan F is revolving at relatively high operating speeds, it exerts a considerable upward suction force in the direction indicated by the arrows A and there conceivably could arise a tendency for this suction force to draw fine particles from the passageway 17 inwardly through the screen elements unless this is prevented. This would result in an undesirable recycling of fine particles.
  • the screen elements 32 are disposed so as to form a multiplicity of openings all the way around the inner peripheral surface of the casing 30. Moreover, the tops of these screen elements are located immediately below the tips of the fan F. I find that in this region of close proximity to the tips of fan F, centrifuged material is continuously swept around and against the screen openings by the air stream of the fan and a maximum screening action is produced as regulated by the size of the openings employed in the screen and the speed of the fan induced.
  • Example I A conventional agricultural limestone product was produced from 1000 pounds of limestone aggregates having the following analysis:
  • This example after being subjected to an air classifying operation of conventional nature, provided 20 pounds of particles which were held on a 100 mesh screen, and 1160 pounds of particles which passed through a 100 mesh screen.
  • Example II There was provided a similar 1000 pound sample of limestone aggregates with the same relative percentages of coarses and fines specified in the sample of Example I, i.e.
  • this product had the required quantity of coarse particles 20% (200 pounds) as specified above and held a total product mix of 540 pounds of acceptable agricultural limestone.
  • openings of screens 42 may be varied as desired to meet any given specification. It may also be desired to increase the number of screen elements used by forming openings at other points in the cylindrical casing members and locating screen elements therein at different levels.
  • I may as shown in FIGURES 2 and 3, form openings in the conical lower section 12, and I may mount therein screened elements as 60 which are secured to rods as 62 slidably supported in bearings 64 in the outer casing 2.
  • the invention may also be practiced utilizing other forms of screen members such as screen cloth, spaced bar sections, and the like.
  • the invention may be utilized with a wide range of finely divided materials other than agricultural limestone and various other advantages may be realized.
  • finely divided materials other than agricultural limestone and various other advantages may be realized.
  • it may be required to have a specified range of coarse particles and only a limited percentage of fines of some smaller range of sizes, and by utilizing the combined air and screen operation there can be realized a sharper control the quantity of fines present in the coarse particles which are passed through the tailings outlet of the machine and thus a better concrete sand product is realized for some requirements.
  • a method of air classifying and screening a finely divided material the steps which include delivering a free falling mass of finely divided solid material downwardly upon a rotating distributor plate for centrifugal dispersion within a closed chamber having a top portion with an outlet port formed therein and screen means in the sidewalls thereof, supplying air through a conduit means opening into said closed chamber below said dispersing mass, evacuating the air supplied to said chamber upwardly through said finely divided dispersed material by a vacuum fan rotating at a predetermined speed and located at the outer side of the closed chamber with its inlet connected with said outlet port for entraining relatively fine particles of the dispersed material, travelling the air and entrained fine particles through a rotating sizing device located between the distributor plate and the outlet port of said chamber, discharging the flow of air and entrained fine particles from said vacuum fan into a second closed chamber for deposit of portions of the dispersed material at the bottom portion thereof, and simultaneously displacing air and relatively coarser particles radially outwardly through the screen means
  • a method according to claim 1 including the further steps of radially displacing coarse particles through screen apertures occurring at progressively lower levels in the closed chamber.
  • an outer closed casing having a cone with a discharge opening at the bottom thereof and a drum above said cone, said drum including a top wall portion, an inner closed casing composed of a cone with a lower discharge conduit portion extending through the cone of the outer conical casing, said inner closed casing having a drum above the cone and said drum including a top wall portion with a projecting rim, said inner closed casing being spaced from the outer casing and defining a chamber therebetween, driven shaft means projecting through the top Wall of the outer casing and within the inner casing, a centrifugal distributor plate mounted on the lower end portion of said shaft and spaced from the top wall portion of the drum of said inner casing, a rotary sizing device positioned within the inner casing above the distributor plate, means for connecting the shaft, said rotary sizing device and said distributor plate to provide a uniform continuous rotation of the parts, means for introducing finely divided solid material into said inner casing and upon said distributor
  • the screen means includes a plurality of adjustable closure plates for opening and closing the openings in the screen means.
  • an outer casing having a bottom outlet for discharging relatively fine particles and an inner casing located in spaced relation to the outer casing to define an annular chamber which communicates with the said bottom outlet, said inner casing being formed with bottom conduit means located through the outer casing for discharging relatively coarse particles, driven shaft means vertically disposed through the outer casing and extending downwardly into the inner casing, a distributor plate fixed to the shaft, means for introducing finely divided material into the inner casing onto the rotating distributor plate to provide a centrifuged dispersion of particles in the inner casing, suction fan means mounted in the top of the inner casing for lifting centrifuged particles upwardly and travelling the particles into the said annular chamber, screen means located adjacent said suction fan means in the wall of said inner casing, and having openings for selectively passing therethrough relatively coarse centrifuged particles into said annular chamber.
  • the screen means includes perforated screen plates detachably secured in the inner casing and cover elements slidably disposed in the outer casing for opening and closing the openings in the said screen plates.
  • a structure according to claim 10 in which the screen plates are arranged in recessed relation to a top rim of the inner casing and the said cover means when moved into a position immediately below the said top rim cooperates with the screen elements to provide regions of partial vacuum for rejecting fine particles in the said annular chamber.
  • a structure according to claim 11 in which the screen elements are disposed in the inner casing in immediate proximity to the region of the tips of the said fan whereby a maximum eifect of the air stream induced by the fan is exerted on centrifuged particles to sweep them around the inner periphery of the inner casing and discharge them through the apertures in the screen elements into the annular chamber.

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  • Combined Means For Separation Of Solids (AREA)
US565648A 1966-07-06 1966-07-06 Methods and apparatus for air classifying and screening of finely divided material Expired - Lifetime US3434593A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS50141758A (it) * 1974-05-02 1975-11-14
US4759943A (en) * 1985-08-23 1988-07-26 Holly Farms Poultry Industries, Inc. Classification of food meals made from animal by-products
US5149727A (en) * 1990-02-26 1992-09-22 Medical Sterilization, Inc. Irradiation device for fluoropolymers
US5296113A (en) * 1990-02-26 1994-03-22 Luniewski Robert S Irradiation device for fluoropolymers
US6193075B1 (en) 1996-09-30 2001-02-27 Colgate-Palmolive Company Air classification of animal by-products
CN109158316A (zh) * 2018-09-07 2019-01-08 天津水泥工业设计研究院有限公司 一种用于料床粉磨系统的紧凑型组合式选粉机

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1108542A (en) * 1914-02-16 1914-08-25 Elbert Finley Anderson Centrifugal sand screening and separating machine.
US1165869A (en) * 1915-03-30 1915-12-28 George Holt Fraser Separator.
US1735479A (en) * 1928-02-04 1929-11-12 Sturtevant Mill Co Air separator
US1958726A (en) * 1931-03-07 1934-05-15 Sturtevant Mill Co Air separator
DE694739C (de) * 1939-06-18 1940-08-07 Polysius Akt Ges G Windsichter
US2774476A (en) * 1954-10-25 1956-12-18 Sturtevant Mill Co Machine for classifying and separating materials

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1108542A (en) * 1914-02-16 1914-08-25 Elbert Finley Anderson Centrifugal sand screening and separating machine.
US1165869A (en) * 1915-03-30 1915-12-28 George Holt Fraser Separator.
US1735479A (en) * 1928-02-04 1929-11-12 Sturtevant Mill Co Air separator
US1958726A (en) * 1931-03-07 1934-05-15 Sturtevant Mill Co Air separator
DE694739C (de) * 1939-06-18 1940-08-07 Polysius Akt Ges G Windsichter
US2774476A (en) * 1954-10-25 1956-12-18 Sturtevant Mill Co Machine for classifying and separating materials

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS50141758A (it) * 1974-05-02 1975-11-14
US4759943A (en) * 1985-08-23 1988-07-26 Holly Farms Poultry Industries, Inc. Classification of food meals made from animal by-products
US5149727A (en) * 1990-02-26 1992-09-22 Medical Sterilization, Inc. Irradiation device for fluoropolymers
US5296113A (en) * 1990-02-26 1994-03-22 Luniewski Robert S Irradiation device for fluoropolymers
US6193075B1 (en) 1996-09-30 2001-02-27 Colgate-Palmolive Company Air classification of animal by-products
CN109158316A (zh) * 2018-09-07 2019-01-08 天津水泥工业设计研究院有限公司 一种用于料床粉磨系统的紧凑型组合式选粉机
CN109158316B (zh) * 2018-09-07 2024-04-23 天津水泥工业设计研究院有限公司 一种用于料床粉磨系统的紧凑型组合式选粉机

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