US1623040A - Method and apparatus for grading solid materials - Google Patents

Description

April 5b, 1927'. A 11,623,040

3. R. BAKER ET AL METHOD ND APPARATUS FOR GRADING SOLID MATERIALS Filed Jan. 51. 1924 4 Sheets-Sheet 1 Aprily 5,1927. G. R BAKER ET AL A www@ METHOD AND APPARATUS FOR GRADING SOLID MATERIALS' Filed Jan. 31. 1924 4 Sheets-Sheet 2 emga @dph lanka, William Edward @660K TTOR/VEY.'

l/VVEWTORS Chaffee WlSn-d Gilerdale.

April s, 1927. 1,623,040

G. R. BAKER ET AL METHOD AND AFPARATUS FOR GRADING soLIn MATERIALS Filed Jan. 31. 1924 4 Sheets-Sheet 3 INVENTORS Gerg A|?a1|ph laker, Wflh'am Edward @escom/ Charles Wfed Gilda-dale.

Afro/Mfr.' WMM@ 1,623,040 April 5 1927' G. R. BAKER ET AL I METHOD AND APPARATUS FOR GRADING SOLID MATERIALS Filed Jan. 51.l 1924 4 sheets-sheet 4' /N VE N TURS" Georg {Qa lph emh'efv William Edward @6560K v charles wilg@ Gnafdaf.

Arm/mfr.' m

Patented Apr. 5, i927.

UNTED STATELS PATENT @lilld'i GEORGE RALPH BAKER AND W'ILLIAM EDWARD PRESCGTT, OF LONDON, AND CHARLES VJILFRED GILDERDALE, 0F NEW EARSVVICK, ENGLAND, ASSIGNORS TO ROWN TREE AND COMDANY LIMITED, 0F YORK, ENGLAND.

METHOD AND APPARATUS FOR GRADTNG SOLTD MATERIALS.

Application filed. Eanuary 31, 1924, Serial No. 689,737, and in Great Britain February 26, 1923.

This' invention relates to methods and apparatus for grading solid materials.

in th-e art to which the present invention relates it is a fact that as the size of partici-es of a powdered substance is decreased said particles become more and more easily influenced by air currents, and when an extremely fine powder is produced it may readily be carried in a gentle current of air, even when the material has a high specific gravity.

ln other words the smaller' the particles of a powdered substance, the more important becomes the inuence of the surface friction of' a current of air thereon in relation to the force of gravity. This fact is made use of in the separators generally used for grading iin-e powders, in which powderdaden vair is blown into a settling chamber, the coarsest grade being deposited most quickly and falling near the air inl-et, the finest powder on the other hand being deposited at the point farthest from the air inl-et. Diiculties .arise however where this method is employed for very ne powders in that the air current employed has to be very gentle and eddies due to temperature variation or other causes quickly interfere with the correct working of the settling chamber, furthermore such a device has to be very large to obtain any reasonable output of material.

The object of the present invention is to provide a novel and more accurate and positive method than at present in 'use for grading particles of `solid material by means of a current of air.

According to the present embodiment of our invention shown in the drawings, currents of air in which the material to be graded is distributed are caused to pass inwards through a revolving separator where by the material and air are caused to rotate with the rotor of the separator and to be subjected to the action of centrifugal force, the regulation being such' that the air cur.- rent overbalances the centrifugal force as regards the smaller or light particles and the centrifugal force overbalances the air current as regards the larger' or heavy particles so that the latter are projected outwards against the air current whereas the smaller' or light particles are carried by the air current.

In the operation of such a method the particles of solid material in the air will be acted upon by three forces, viz

Firstly, the skin friction of the .air current which has carried them into the zone of action of the rotating member and exerts a force on the particles tending to carry them with the air current towards the centre of said member.

Secondly, the force of gravity, and

Thirdly, the centrifugal force acting on the particles as they are carried round by the rotating member.

If the speed of the rotating member or rotor is at all high, the force of gravity becomes extremely small in relation to th-e centrifugal force so that there are substantially but two opposing forces acting on the particles, viz, that of'centrifugal force tending to carry the particles outward from the centre and the skin friction of the air current moving towards the centre of the rotor. rThe smaller the particles the stronger will be the influence of the air current when the rotor is running at a constant speed and it will be apparent that with a given rotor speed and speed of air current all particles larger than a certain size will be rejected or driven off centrifugally, whilst `all smaller particles will be carried by the air current towards the centre of the rotor. lf the rotor speed 1s increased, still finer particles will be rejected and only those particles of such size that the skin friction of the air current overcomes the centrifugal force due to the speed of the rotor will be carried in the air current towards the centre.

As the centrifugal force due to the speed of the rotor and the strength of the air current passing through the lines of centrifugal force may be varied within extremely wide limits, it will be seen that a very exact and readily controlled means of grading granulated or powdered substances is provided by which it has been found possible to grade very line powders far more accurately and efciently than. by any means hitherto known.

Furthermore a great saving in the size of apparatus is effected, dueto the fact that relatively large forces are .employed compared with gravity. ln any ordinary expansion separator an air current is used against gravity and for very line powders only very gentle air currents can ber employed, and this necessitates aV very bulky apparatus.

In this invention high air velocities can be used. to balance high centrifugal force, so that the saine' amount of fine material can be' carried over' in a very much smaller appa',- ratus.

A further advantage is that by balancing the two large forces as stated eddy currents have little or no etl'ect on the efficiency of separation, whereas in an ordinary expansien chamber they= seriously interfere with the accuracy of grading ot very fine pow# ders.

'Ifheinvention may also be employed for separating two powdered materials ot ditt-erent `specific giafvitiesf andV in this case'tlie partieles'tobe separated need not necessarily bel ot ditferent sizes;

An embodiment ot apparatus tor car fying out the present invention: is` illustrated in the` accompanying drawings in which Fig. l is a vvertical central section. Fig; 2 is asectional elevation at right -anglesfto/Fig. 1. Fig. Eris-a7 sectional@ plan on the4 lineiA-B ot' Fig: 1, and Fig: t isa partiiall planshowin-gthetailings" chute hereinafter referred to andr with parts removed for clearness ot illustration;

The" apparat-ns shown in` the idrawings compnises an'o-uterstationary casing@ provided at thet-opwith means, showiras comprisingA a hopper ai' and worin conveyor a2', for feeding inz tiheinatlerial;y Thiscasing is carried by a snitabl'ehollow pillar as andf is open below and shaped: toprovide av chute Z) for discharge of: tailings or heavier particles into whieln chnteleadsv an inlet b1 tor air trom anyy suitable source, .suoli as a cyclone seperator, it the material treated is passed thereto after treatmentin the presentv appa rat-ns, as may possibly be done.,V Located in the=oasing* a-is'the rotor which comprises a central`v conical: drum c' carrying a` number of radialvanes c1 bet-ween' which areV arranged a' Series ot spaced plates or battles'c2 'shown-as inclined butv whiclr may alsobe flat, and the drum being provided abovey with aconioal and axial outlet 03 lextending into-the' cover at ot the casing and connected to a trunk` or pipedy which leads to afan, blowerA on other air exhausting devicei d* of-r any' appropriate kind and which, iff desired-,.mayfhavef-a delivery Z2 tothecyclone separat-er before-mentioned.' The vanes c preferably extend for the wholeA length of the rotorbetween end members formed by thepantsi 63,04 andfairontlets may be provided on both said end members so that the .cunrenti ot ain mayK be sucked oft at'l both ends; if-rdtisired.` The tan isfshow'nasV drivenr by. pulley. di" and belt df" from` any suitable sourceof. power. 'llhebaseotY` tlie'= drum c substantially closing the end of the rotor and the rotor as aJ whole is carried by a vertical sha-tt c, carried by ant-iliriotion bearings el and suitably enclosed in a tubular housing e? extci'iding through the pillar a3 and tailingsV chute I; the 'shaft being provided at? its' lower end within the bot-tom ot' the pillar with a pulley c3 driven by belt et from a pulley f on a. main drive shaft f1, from which also the teed worm a? is driven through belt and pulley gear j,

The cuter casing a is also Vprovided on its inner surface with' radialv van'es -glbetween which are mounted a number of inclined plates orbatllcs g1 (which may also be flirt similarly to th-oplat'es c2 or et other required shape) the inner edges of which pass between the outer edges ofthe drum plates and extend beyond said outer edges for a short distance intoy the spaces between" them; Thesepla-tes' and the cuter casing carrying theniare made in halves so that they lit together between the plates c2 of the rotating member. The outer edges ot' said plates g1 are atv varying distances from the wall of they casing a to ferm gradually decreasing passages g2 from' below upwards.

Frointhe above description itz willj bev apparent that the interior of the rotor is sub jectedV to the suctionall effect ot the tan', tending. todraw the air and particles carried thereby towards the Centrethereo-, andi in" the operation o tthe device the material fedi intothe top of the casing by theworm a2 isfdirectedl byl aI depending deflector h, falls alternately ontotlieinclined:plates 02 of the rotor and g1 of` the casing inl su'c'cession'- in a zig-zagv course, whilst the rotorisrotatedl The air entering at the inletV b1 passes through the 'channels between the casing platesr g1 and in approaching the rotor carries with it the deseending material', it then crosses the region between' tlieirotor plates c2` where itfis=suhjected tothe action ot centrifugal force which removes the heavier` particles; then carrying with it the'lighter para ticlesthe air current passes up the face of' t-he conical drum 0 and out atA the top tliiouglr the` trunli cl, for subsequent delivery to the (Liyclone separator or tobc` collected in some other way.V

The above descriptionE discloses .in` zu gcneralfwa-y the function ot theapparatusbut there are other considerations for theA eiii'- cient vorlring ot the apparatus which; will now be referred to.

Inorder to obtain accurate grading"l it isV llt) important that the velocity ofv the air curthrough the rotor should be approximately equal at allu active points'ot its surface.4 One way ot' obtaining; this re-` sult iss-:by the construction above' described` iii-which the rotor is dividedinto at number otsections byF the plates= el intersecting.: the`A radial vanes c1 and with the axial passages# rent pasf a 01 between the latter ensuring that the air passing through the rotor from the outside inwards crosses the regions between all the plates at substantially th-e same velocity and travels inwards in directions passing through the axis of the rotor whilst crossing said regions. This result is assisted by the provision of the axial out-let c2 for the rotor at one end and the conical drum c forming the hub of said roter, the base of the drum being situated at the closed end of the rotor and the apex of the drum adjacent the air outlet, thus ensuring that the air entering the rotor travels inwards at an approximately uniform velocity in all parts of the rotor. This result is also assisted by the .fact that the hub of the rotor is conical, that the spaces between the rotor plates c2 and the hub increase in an upward direction, and that the spaces bet-ween the casing plates and the casing decrease in an upward direction.

It is also important to ensure that all particles passing` into the region of the rotor are acted on by centrifugal force of the same intensity, or in other words, that once the particles enter the separation Zone of the rotor they kare positively carried round therewith, this result being obtained by the provision of the radial vanes e1 and plates c2 as above described.

. All portions of the material are brought equally under the influence of the air passing into the rotor and the heavier material rejected by the rotor is successively returned to it to ensure that all fine particles are separated therefrom.

Such result is obtained by the relativelarrangement of the rotor and casing plates c2 and g1 as above described since in operation and more particularly at higher rotor and fan speeds the heavier particles rejected by the rotor take a zig-zag path upwards again between the adjacent edges of said plates and fall back again thereon for further treatment. Also the action of the centrifugal force may force the material over the outer edges of the casing plates 71 but the current of air outside same will bring it back to bc further treated, these operations being repeated until the remaining heavier particles become so densely distributed in the air entering the rotor that they finally pass to the tailings chute 7).

An important feature of the action of the present apparatus is that the centrifugal force does not merely drive or flick the material olf the rotor plates o2 as in centrifugal separators of known construction but acts positively thereon at all times against the counter current of air drawn inwards towards the centre of the rotor, and after leaving said plates the centrifugal force practically ceases to act on the material, a

uniform and definitely controlled separation being thus obtained.

The invention also contemplates the employment of a series of apparatus such as described above so that particles of any desired size may be isolated from those of larger or smaller size than those required. lt will be apparent that this can be readily accomplished by presenting the fine product passing over with the air through the rotor of one apparatus, to the rotor of a second apparatus running at a higher speed, which will reject the largest of the particles passing the first rotor.

It will be observed that in the apparatus shown in the drawings (which is merely illustrative of one of the various forms in which our invention may be embodied) a continuously-flowing current of air which carries in suspension the material to be separated is maintained, and this current as a whole, with all of its particles held in suspension therein, is positively given a whirling movement. This obviously gives to each suspended particle a certain centrifugal force, the strength of which depends upon the speed at which the current is whirled.

It maintains the particle-bearing current continuously flowing radially of, that is inward toward, the axis of rotation. In fact, the apparatus specifically illustrated maintains a plurality of such currents. Each pair of adjacent vertical vanes 01 with the bottom cone c4 and top cone c3, between which the vanes extend, forms in substance a duct or passageway which serves to lead the air radially inward toward the axis of the rotor. This duct or passage encloses that portion of the current, and as the rotor revolves it causes this duct or passageway and consequently the entire body of current enclosed by it to be rotated as a whole, and it and all air-borne particles therein are positively rotated at the same angular speed. As a consequence, substantially all parts of the current in such duct have substantially equal velocities and substantially all the airborne particles therein are subjected to substantially the same intensity of centrifugal force. Undesired eddy currents with the resultant diminished effectiveness of the ajiiparatus are therefore avoided.

The vertical vanes 0l obviously act in the illustrated embodiment both as the side of such duct or passageway and as a means for causing the current to be given a positive whirling movement.

We are aware that our invention'claimed may be embodied or carried out by forms other than that illustratedand described.

lVhat we claim as our invention and desire to secure by Letters Patent of the United States is Vl. The method of grading particles of llt) iis

eiienf' continuously flowing radially' in? taeosly positivelyv whirling said" euri-ent and varying at least one of said steps to' vary tli'eA Isi'zeof tlie product".

3. Tlie nietliod1 of grading particles of solid material" by tlie use of a current' ofaii Wliieli'ris Wliiiled on an anis, eonipiising maintaining said* euri-ent continuously tion'n ing inwai'dt'ovird said ax'is", and simultaneously positively whirling saidieu'i'rent'bo'd ily on said' axis in suoli manner that substanti ally all parts thereof move at: tlie saine angular 1 speed.

Ll". Apparatus for grading 'particles of solid mateiial by means offalr currents in Wliieli tlie niateiial is" distributed, comprisiug'a rotor inclu-ding a Central hub, a" pl:ifv rality of radial varies mounted on said hub' and eild members on saidliub liaving an aX- ia'l' air outlet and' between' Wliieli' tlle radial va'iiese'xtend for tli'e'Wlil length.

5; Apparatus for grading `particles of' solid inat'erial by means of air' currents iii Wliieli the material is' distributed, comprising a i'ot'oi" includingl a centralx hub, a' pliifi'ality of radial vanes mounted on said liub and extending completely betweenI end meinbersi oti'1 tli'e'liub lia-'ving an axial' aii"`oul'let', said rotor'being divided into a nuii'iber of sections by plates intersecting said radial vanes and provided with passages in tlie intei'ibrof the rotbr'eonn'eeting all said seetioiis'witli theV air outlet aforesaid.'v

GQ Apparatus for grading particles ol solid material4- by means of air' currents in wliioli the' niateiif'ill is distributed; ve'o'inprising a rotor having an aYial airoiitleft at one end and closed at tlieopposi'te eiidVy and including a conieal liu'b'l tlieA base oi" WliieliE is loeated at said elosede'ndadtlie' apex` adja'eentf said'air' outlet', aiid a phirallty of radial valles-mounted on' said hub and eX'- tendingil eoiilpletely betni'ejen eild ineiiib'ersy carried by the blib,

7. Apparat-iis for grading pal-tides o ij"` solid'niateiia-l by means of air currents in" which" the iiiatijra1` is distr'ib'ted", comprising a rotor having an axial air outlet at one end and Closed at tlle opposite end and in? @aiding Conan hun the' basa of which: is" located atsaid' elo'eedeid andthe` apex' adi' jaa-ent: saai air outlay and ai pimaiiiy' of la: dial vaes mounted; on sai-d hub extend'- ing completely betiveen e1`id` members ear! Y i'ied by tlieli'ub, said rotoi" being divided iii' toa" nuiiibeiot seetions by plates 'i'nte'iseet'ing-- said radial varies ai'idlpiovided with passages; interioily' of the r'otoi" connecting aill saidE seetions ivilih tlie aforesaid airo'utlet;

s. Appiaais: fer grading particles 0f solidv m'ate'rialfby ii'iean's of aix* e'uiients in which tlie material distributed, Compris"` iiig a rotfoi" including ai Central liub,` a pl`u' rality of iadial vaiies mounted onsaid liub and extending completely bet-Ween end ,ineiiil bers 'on said' liub and havingr an azial air outlet and ai cylindrical air elifa'mbei' enclosing the iot'oi' andpivided Witl interior# ly directed'platesY Witliiii ivliieli tlie` rotor"` reL volvesyr said plates being so disposed that air' entering the man# apprea'ciiesaie naar inl directions' passing through its axis.

QQ fpparatfus for giadiri'g piitieles' of Sand material by nie-uis of air cui-rents ia which the iii ateiial isdfstribiited; comprising a iot'i' ilieliitllng a Central lill'b, al plurality of1 `radial vanesuotili'te'd oil said hub and extending completely between' @iid members on the liub having an aXial al'r ot'lei','saidv rotor beinlgdlvi'deftl into a' nuibe'r 'of s'eetions by* pla-tes'inteistiiigfsaid adialva'ies` and pinvid'eu with" passages' in-` the' interior of' t'lieifto" eoineetii'g all said sections ivitlif tlle'aiifotlof afj'sild, and a: Cylln'tlllal ai"H cha ber enclosing the fotonV -and provided Wit' linteiiiorly direetedl platesivitllin Wliieh the rotor i"evolvesgj said'last ment'ioiledf plite's beiiigl's'o dispsed tll'a't ali' entering' the rotor approaches" the71V latter inV diieet'ins passing iii-insign iis axis;

1'05 Appaitus `ller y grading particles of solid ii'i'ateiii'l' by iiea'ii's of'aiiciiii'ents' in' Wliieh the iiia'teilal is' distribiited,l compi-is-` ing'a rotoi""l1aviiig ali aiial'air o'utlet at one end and ineludih'gl a" ceiitralli'ub, a plli'l'ality of radial" valles' iiiou'nted oh said Huband extending ciiiipletelyn be't'ivee'rl eiid members tliereoiii, a plurality"fplateseariied;by said radial' vane's and iit'ersee'tiiigE saine tov di# vide` tile rotoi" ihtbl a? ni'iinber`- of' s'etioiisg` said platesi being provided vvitlY passages" Connecting` all Se'et'ioii'sivitli the aiifoiit iet; and a @aanraden-air engineer' enc-losing tlief rotor and provided: with" ii'itrorly di reet'ed"v plates ivitliiil ivliieli die rbtbr r'e'- volves,` saidE last mentionedr plates being so disposed`l tlill'tair" entering the rotor ap' praelies tlie latte-r in dii''etlb'iis passing tliliig'liits'af si' v end and including a central hub, a plurality of radial vanes mounted on said hub and extending completely between end members thereon, a plurality ot plates carried by said radial vanes and intersecting same to di-y vide the rotor into a number of sections, said plates being provided with passages connecting all said sections with the air outlet, and a cylindrical air chamber enclosing the rotor and provided with interiorly directed plates within which the rotor revolves, said last mentioned plates being so disposed as to leave a progressively smaller air space between their exterior edges and the wall-ot the air chamber as they approach the air outlet.

12. Apparatus for grading particles of solid material by means ot' air currents in which the material is distributed, comprising a rotor revolvable about a vertical axis and having an axial air inlet at one end and an axial air outlet at the other, said rotor including a central hub, a plurality ot radial vanes mounted on said hub and extending between end members thereon, a plurality of outwardly directedl inclined cones on the rotor intersecting the radial vanes, a cylindrical casing surrounding the rotor and a series ot' stationary tunnel shaped cones in the casing located to alternate with the inclined cones on the rotor, the inner diameter of the stationary cones being smaller than the outside diameter o the rotor cones whereby on material being fed by gravity from the top ot the apparatus and air entering from below, the material passes through the apparatus in a zig-zag course, falling iirst on a rotating cone then on a stationary one Yfrom which it slides down again onto a rotating cone and so on, being thoroughly separated by the current ot air being drawn into the rotor.

13. An apparatus for grading solid inaterial carried by a continuously-iiowing current of air comprising a plurality ot' rotatable vanes arranged to whirl said current positively, and means arranged to cause substantially the entire body of said current to pass radially inward from without the path of travel of said vanes.

14. An apparatus for grading particles ot' material from a current of aiil carrying said particles in suspension, comprising a duct enclosing said current and leading the same inwardly toward an axis of rotation, means ior bodily rotating said duct and current on said axis, and means for maintaining the tlow oi' said current continuously.

15. An apparatus for grading particles of material from a current ot' air carrying said particles in suspension, comprising a duct enclosing said current and leading the saine inwardly toward an axis of rotation, means ior bodily rotating said duct and current on said axis, means :tor maintaining the iiow of said current continuously, and means tor varying at least one of said elements to vary the size of the resulting product.

16. An apparatus for grading particles ot solid material carried by a whirling air current, comprising conducting means arranged to lead said air radially inward in such inanner that substantially all parts or" said current shall have substantially equal velocity, and centrifugally-acting means for positively whirling said current in such direction that substantially all air-borne particles` therein shall be subjected to substantially the same intensity of centrifugal force.

In witness whereof we have signed this speciiication.

GEORGE RALPH BAKER. WlLLIAIVl EDWARD PRESCOTT. CHARLES WILFRED GL'DERDALF..

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