US2269412A - Air separator - Google Patents

Description

- Jan. 6, 1942. 'r. J sTUR'rEVANT I 9 2 AIR SEPARA-TOR Filed July 18, 1940 3 Sheets-Sheet; 1

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AIR SEPARATOR I Filed July 18, 1940 3 Shegts-Sheei 2 Patented Jan. 6, 1942' .UNITED STATES PATENT OFFICE AIR .snrnas'ron Thomas J. Sturtevant, Wellesley, Mass, assignor to Stnrtevant Mill Company, Boston, Mass., a corporation of Massachusetts Application July 18, 1940, Serial No. 346,184 6 Claims. .(01. 209-144) diificult, especially by reason of the high speed of the fan, to seal or close ofi such clearance, there is opportunity for oversized or undesirably coarse particles to leak through such clearance into the outlet opening and thus to appear in the finished or separated product emerging from said opening. The entry of oversized or relatively coarse particles into the outlet opening is fostered in actual practice by the greater degree of suction in the outlet opening than in the separating chamber and, accordingly, bya positive flow of air from the chamber through the cleara ance into the outlet opening.

In accordance with the present invention, greater selectivity or sharpness of separation is accomplished in an air separator of the forego- 'ing type by causing flow of air through the clearance between the upper end of the fan .and the top cover of the separating chamber in a direction into the separating chamber while the stream or air carrying particles'ls passing into the space swept by therejector fan. There are Y 35 a main rotary fan l9, which generates an upvarious expedients by which such desired flow of air through the clearance may-be induced. For instance, it is possible to do so. by opening the clearance to the outside atmosphere, in which case air from the atmosphere may be sucked into both the separating chamber and/or the outlet opening while the separator is .in operation. Again, it is possible to provide the rejector fan at a region neighboring the clearance with auxiliary vanes that create a suctional current'lo- 'calized essentially at the clearance and serving to draw airfrom the outlet opening through the clearance into the separating chamber. With the foregoing and other features and ob- Jects in view, the present inventionwill now be described in further detail with particular reference tov the a'ccompamring drawings, wherein Fig. 1 is a} largely vertical sectional view through 'anair separator embodying the present invention as assembled with auxiliary apparatus shown-in elevation.

annularspace in the separating chamber below Fig. 2 is an enlarged similar view through the rejector fan portion.

3 represents a vertical section through the rejector fan portion of a modified form of the 5 invention.

Fig. 4 is a similar view of still another form of the present invention.

Fig. 5 is a composite half section through the rejector fan on the line 5-5 of Fig. 3 and a half top plan view of said fan.

As shown in Fig. l, the separating chamber. 4

,of the air separator hereof may be defined by a casing HI whose upper portion may be essentially cylindrical and whose lower portion may be funnel-shaped. The pulverulent or particulate material to be air-separated 0r classified may be fed into the lower end portion of the chamber by a worm-feed conveyor ll driven as bya pulley l2. The feed hopper Ha. of the conveyor may be located outside of the separating chamber andits discharge end llb may'be arranged centrally somewhat above the air-inlet I4 near the lower end of the chamber so that the rising air cur-- rents may suspend therein and carry upwardly therewith the particulate material to be subjected to the separating or classifying action of the rejector fan. A discharge door l5 at the lower'end of the chamber 9 makes possible periodic discharge, as desired, of the rejected relatively coarse particles or tailings.

- The top of the separating chamber is closed off .by a cover I6 through which there is a cen-' traloutlet opening ll. Immediately above the top cover is a cylindrical chamber l8 for housing ward draft or surge of air through the separating chamber 4 whoseoutlet ll opens directly into the chamber l8 through its bottom plate 9. vanes or blades I So of the main fan l9 are sup- 40 ported by arms 20 projecting radially from a hub 2|, which is keyed to a vertical shaft 22 extending axially through the fan chamber l8 and thence downwardly through the opening I! into the separating chamber.

portion of the shaft 22, to which is keyed a hub 23 having an outwardly projecting annular flange 23a constituting a suitable shelf or support for a rejector fan structure consisting essentially of a rotary cage of vanes adapted to sweep an The bottom plate 9 of the main fan chamber I8 is shown as comprisor intake openings.

its outlet opening and thereby to cast from the particle-laden air stream as it passes to said opening the oversized particles present therein. The rejector fan structure comprises a lower annular plate 24 Whoseinner marginal portion is fixed, as by bolts 25, to the flange 23a. It comprises further an annular series of spaced blades or vanes and an upper annular plate 21 arranged immediately about the lower end of the flange 9a and slightly below the inner marginal edge l6a of the top cover IS. The blades 26 extend edgewise from the lower plate 24 to the upper plate 21 and are secured to these plates, as by being welded thereto. It, is preferable that these blades 26, whose outer and inner ends terminate on substantially concentric cylindrical surfaces, extend non-radially between such surfaces, as appears best in Fig. 5, so as to defin'e therebetween a succession of non-radial ducts through which the particle-laden stream of air passes. While thus passing through these ducts, the stream of 7 air undergoes such batting and centrifugal action by the rapidly rotating blades 26 as tend to cast out of the stream the oversized or relatively coarse particles. The blades 26 may be of any suitable width. However, when they are stationed at such pronounced angularity relative to air enters the annular zone described by the rotating rejector fan blades 26 immediately below and around the lower end of the flange 9a, the particlesare subjected to the vigorous batting or colliding action of the rapidlymoving surfaces of such blades, in consequence of which the undesirably large or oversized particles are thrownin the conduit 36 is preferably controlled by a gate or valve 1, which thus enables regulation of the volume of the air stream passing through the rejector fan and, accordingly, the fineness of particle size in the selected or classified product. The selected product in the collector 31 may be discharged, as desired, through a discharge door 39 at its lower end.

v The .modified form of rejector fan shown in Fig. 3 is characterized by an upper annular baffle plate 40 of much larger diameter than that of the lower annular bailie plate 24. Indeed, the outer marginal edge of the plate 40 may occur slightly beyond the outer edges of the main fan blades I9a so that relatively narrow fan blades or ribs 4| may be mounted on the plate 4|] to clear just under the cover and extend radially outwardly even beyond the outermost edges of the main fan blades I90. and thus create locally a I clearance region 42 under greater suction than that prevailing at the center region 3 of the rejector fan subject to the influence of the main fan. The clearance region 42 may, as illustrated, communicate with the center region 3 of the rejector fan by way of a clearance 43 between the inner marginal edge of the baffle plate 40 and the lower margin of the flange 9a, wherefore, there will be during the operation of the rejector fan a constant flow or suctional drag of a thin layer of air next to the flange 9a past the clearances 9a and 42 and into the separating chamber. In short, the effect is to recirculate or bleed back in an air current to the separating chamber a small portion of the already selected particulate material by way of fine channels provided between the upper end portion of the rejector fan and the separating chamber outlet I 1.

The rejector fan structure shown in Fig. 4 is similar to that of Fig. 2, excepting that there is no collar upstanding from the upper annular baflie plate 21 of the rejector fan and further that the top cover l6 of the separating chamber out of suspension from the stream and are caused to settle as tailings at the lower end of the separating chamber.

Escape or leakage of particles through the clearance between the inner marginal edge lBa of the cover l6 and the flange 9a is obviated, in accordance with the present invention, by placing such clearance under a suctional current induced by the main fan. Thus, as illustrated in Fig. 2, such clearance is'partitioned by a collar 29 which may be fixed in upstanding position at the inner marginal portion of. the upper annular baffle 21, into two channels, one of which 30 communicates directly with the central suctional zone 3 below the main fan and the other 3| of which communicates-with the suctional space immediately above and outside of the rejector-fan ducts There is thus no tendency whatever for unselected or coarse particles to escape from the separating chamber into the outlet ,opening l1;" and all material leaving the outlet opening I] has necessarily undergone the selective action of the rejector fan.

The air stream carrying the selected or deis turned downwardly at its inner margin to present a flange I60. encompassing .the'flange 9a and defining therewith an annular air duct clearing the upper face of the upper baffle plate 21 and leading on one side by way of a clearance 45 to the separating chamber outlet l1 and on the other side by way of another clearance 46 to the separating chamber itself. It is thus seen that air from the outside atmosphere is constantly bled through the annular duct 44 past a clearance between the upper end portion of the rejector fan and the top of the separating chamber and thence into the separating chamber and also into its outlet opening leading to the main fan chamber, thereby maintaining the desired directionality of flow of all particulate material from the separating chamber to the zone of action of the rejector fan.

The shaft 22 may, as shown in Fig. 1, continue upwardly from the main fan chamber l8 through a stufling box 32 formedin the base 33 of a yoke- 34 in whose upper end-portion 34a the shaft may be journalled for rotation and between whose upper end portion 340. and the base 33 the shaft may carry a driving pulley .35 suitably fixed thereto. The bottom portion 3 of the main fan chamber It may be arranged at slightly spaced relationship above the top 'cover l6 of the separating chamber 4; and such bottom portion 3 and top cover l6 may be interconnected by bolts 41 or in any other suitable manner. The I feeding of particulate raw material into the separating chamber, the discharge of tailings or rejected particles therefrom, and the discharge of collected particulate material from the collector 31 may be effected in such manner as to avoid the introduction or discharge or any substantial volume of air from the system. Again, excess air, such as is bled into the system, may be relieved from a suitable point in the system,

say, from a point 381; in the air-returnduct 3 8,

into a suitable filter cllector.- It is possible also to-use the air separator hereof in a so-called opencircuit system, in which case all the air from the collector 31 may be filtered prior to discharge. into the "atmosphere and atmospheric air may be drawn into the intake or lower end of the air separator.

It should be understood that various further I modifications are possible in the air separatorhereof and/or in the auxiliary equipment of the system in which such separator is used-while falling within the spirit and scope of the present invention'as defined by the appended claims.

Iclaim: I 1. An air-separating system comprising a sep- 1a: flange and below said cover plate, the cen-' tral opening in said baiileplate being in communication with said air outlet, said reiector Ian comprising also an annular 'series of fan blades .deflning ducts for leading the-particle-laden stream of air inwardly from said separating chamber to said'central plate opening and said air outlet and thence into said main-fan chamber, and meansfor rotating said shaft and there- -by causing said stream of particle-laden air to' be drawn upwardly from said separating chamber through said rejector ran and into said mainfan chamber and thereby also causing-said re jector fan blades to cast out oversized particles from said stream of air, said cover plate con-" taining an opening substantially surrounding said annular flange and said air outlet, said clearance communicating with the atmosphere through said last-named opening to permit atmospheric air to be drawn therethrough into the separating chamber and also into said air outlet.

arating chamber having an upper end'cover plate, means for delivering particulate material into said chamber,'said. chamber'having' an air inlet for delivering a stream 'of air' thereinto at a 3. An air separator comprising a separating chamber, a cover plate ionsald chamber, said cover plate having an outlet through which is drawn from said chambera stream of air carryingv particles or desired fineness, a main-Ian chamber arranged above said separating chamregion to cause suspension in said stream of said v particulate material and having also anair outlet in said upper. end cover plate, an air-suction chamber arranged above said separating chamher and containing a main fan for drawing said stream of air out through said outlet into said main-fan chamber, and a rejector fan within said separating chamber and adjacent to said ber and comprising a bottom opening encompassed by an annular flange projecting downwardly into said air outlet, a rotary rejector ian stationed inside of said separating chamber ad- 'jacent to said air outlet, said fan comprising an annular upper end baflle plate arranged at a .clearance aboutsaid annular flange'and below said cover plate, the 'central opening in said baiile plate being in communication with said air outlet, said fan comprising also an annular series of fan blades defining ducts for leading the particle-laden stream of air inwardly from said chamber to said central plate opening and said air outlet, and means for rotating said rejector Ian and thereby causing said blades to cast out oversized particles from said stream of air, said I cover plate containing an opening substantially surrounding said annular flange and said air'outlet, said clearance communicating with the atmosphere through said last-named opening to permitatmospheric air to be drawn therethrough in a. direction into the separating chamber and also in a direction into said air outlet.

2. An air-separating system comprising a, separating chamber having an upper end cover plate,- means for delivering particulate material into said chamber, said chamber having an air inlet for delivering a stream of air thereinto at a region to cause suspension in said stream of said particulate material and having also an air outlet in said upper end. cover plate, a main fan chamber arranged above said separating chamber and comprising a' bottom opening encompassed by an annular flange projecting downwardly into said air outlet, a rotary main fan in said mainfan chamber, a rotary rejector fan stationed inside of said separating chamber adjacent to said air outlet, 9, single shaft on whichboth said rotary main fan, and said rejector fan are carried, said shaft extending through said main-fan chamber and projecting downwardly through said air outlet into said separating chamber, said rejector fan comprising an annular upper end baffle arranged at a clearance about said annuoutlet, said fan consisting essentially of a rotary cage of vanes adapted to sweep an annular space in said chamber below said outlet and thereby to cast, from said stream oversized particles, said cage comprising a baflle plate arranged at a clearance adjacent to 'said cover plate and containing an opening substantially surrounding said outlet and in communication with .said outlet, said clearance communicating with the atmosphere through said opening and said main fan serving additionally as means for inducing fiow of at- 'mospheric' air through said opening and thence through said clearance in ,a direction into the separating chamber while said entire stream of air carrying particles is passing into the space swept by said vanes and thence through said outlet into said main-fan chamber.

' outlet, said fan consisting essentially of 'a rotary cage of vanes adapted to sweep an annular space in said chamber below said outlet and thereby to cast from said stream oversized particles, said cage comprising a battle plate arranged at a clearance adjacent to said cover plate and containing an opening substantially surrounding said outletand in communication with said outlet,

said clearance communicating with theatmosphere through said opening and said suction means serving additionally as means for inducing I of air carrying particles is passing into the space flow of atmospheric air through said opening and thence through said clearance in a direction into the separating chamber while said entire stream swept by said vanes and thence through said outlet into said suction chamber.

- 5. An air separator comprising a separating chamber, a cover plate for said chamber, said cover plate having an outlet through which is drawn from said chamber a stream of air carrying particles of desired fineness, a rejector fan within said separating chamber and adjacent to said outlet, said fan consisting essentially of a rotary cage of vanes adapted to sweep an annular space in said chamber below said outlet and thereby to cast from said stream oversized particles, said cage comprising a bafile plate arranged at a clearance adjacent to said cover plate and containing an opening substantially surrounding said outlet and in communication with said outlet, said clearance communicating with the atmosphere through said opening, and means for inducing flow of atmospheric air through said opening and thence through said clearance in a direction into the separating chamber while saidentire stream of air carrying particles is passing and thence delivering a stream of air thereinto at a region to cause suspension in said stream of said particulate material and having also an air outlet in said upper end cover plate, a rotary rejector fan tral plate opening and thence through said air outlet, said cover plate containing an opening substantially surrounding said air outlet, said clearance communicating with the atmosphere through said last-named opening,- means for rotating said rejector fan and thereby causing said blades to cast out oversized particles from said stream of air, and means for inducing air to stream in a direction into the separating cham-r ber through said last-named opening and thence through said clearance between said annular upper-end baffle plate and said cover plate.

THOMAS J. STURTEVANT.

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