US2773650A - Method and apparatus for processing and collecting finely divided material - Google Patents

Description

Dec. 11, 1956 w. T. DOYLE METHOD ANO APPARATUS POR PROCESSING ANO COLLECTING PINELY DIVIOEO MATERIAL Filed June 3. 1953 5 Sheets-Sheet '1 /NVENTOR WTZZ@ ATTORNEY Dec. 11, 1956 fw. T. DOYLE METHOD AND APPARATUS PDR PROCESSING AND Y COLLECTING FINELY DIvIDED MATERIAL Filed June 3. 1953 15 Sheets-Sheet 2 .EN N @Px A TTORNEV W. T. DOYLE METHOD AND APPARATUS FOR PROCESSING AND f COLLECTING FINELY DIVIDED MATERIAL Dec. 1l, 1956 3 Sheets-Sheet 3 Filed June 3. 1953 A 'r TOR/vir Marr-ron AND APPARATUS non PnooEssrNGY,v

AND Couperus@ rnsnrr nrvInED MATE- RIAL William T. Doyle, Boston, Mass., assigner.. to Sturtevant Mill Company, Dorchester, Mass., a corporation of Massachusetts Application June 3, 1953, Serial No. 359,363

Claims; (Cl. 241-39)' This' invention relates to apparatus for grinding, classifying and collecting linely divided materials and, particularly, the inventionl is concerned with an improved 4'nited States Patent' classifying and collecting mechanism for a iluid energy 1 type grinding chamber.

It is a general object of the invention to improve methods of grinding, classifying, and collecting finely` divided materials, 'and especially to improve grinding f machines of the fluid energy type indicated with a View to more efficiently producing and collecting in yappreciable quantities, particles of material .occurring in relatively small micron sizes, and also to producing 'rely atively narrow ranges of particlesy in dilerent micron sizes. Another object of the invention is to devise an improved classifier mechanism for use in a grinding chamber of the fluidenergy type, whereby a greater degree of selectivity maybe realized, particularly with respect to particles of very small micron size.` Still 'another object of the. invention is to devise a methodand apparatus for more satisfactorily collecting particles of` ground or pulverized material .with a view .especially to avoiding loss of such particles .in any significant amount, in the discharge end of a fluid. stream which is employedv to induce centrifugalgrinding. Still another. object is to devise a novel .feeding mechanism forruse with grinding and classifying devices of the characterindicated..

These and other objects vand novel features will-be more fully understood and appreciated from the following description of a preferred .embodiment of the".

invention selected for purposes .of illustration and shown in the accompanying drawings, Vin which- Fig. 1 is a plan view of the grinding machine of the invention;

Fig. 2 is a cross-section view taken on the line 2 2 of Fig. l and showing a.portion of the collector mechanism of the invention;

Fig. 3 is another. cross-sectional view taken on the line 3 3 of Fig. 2;

Fig. 4 is a cross-section taken on the line 4 4 of y abandoned, assigned to the assignee of the presentapplication, there has-been disclosed andclaimedacircular grinding chamber ofthe fluid energy type and the'subject matter of the present invention is, in gene-ral, concerned` with'thesame. type of circular grinding chambericonv`l struction, and :deals with certainimprovementsfwhich 2,773,650 Patented Dec. ll., i956 "ic y are vparticularly.adapted foruse in such a fluid energy type grinding chamber.

Included in a lluidf energy type grinding device of the class indicated is a circulargrinding chamber having an outlet axially disposed therethrough; means for furnishing a supply of air or `other fluid to the grinding chamber; a feed `mechanism for delivering particles of material into the grinding chamber; a particle classifier.

device in the grinding chamber; andparticle collector means 'arranged to receive-V and contain material dis-` charged from the grinding chamber through the :outlet Such an apparatusl hasl been found to constitute a desirable means for carrying out pressurized; grindingV of material in a conlined inwardly spiralling stream of fluid to produce very iinely divided particles. processed in such` an apparatusris known to be selectively reduced in size by means of attrition; impact; and; explosive rupture due to normal stresses to `which the particles'may be subjected when `they are within the grinding chamber.

It should be further understood that particles ground in thisv manner' to a suiiciently small size can be selec tively removed from the chamber by reasonI of the fact that relatively small particles in the force field of the inwardly .spiralling fluidstream are acted uponby radially inwardly directed force components which are greater than the centrifugaltforces which these relatiY ely small .particles exert while. in motion.

In accordance 'with the present invention I have conceived of. a novel way of utilizing the energy of inwardly spiralling particles, and l lhave devised a special ferm of f grinding chamber,.classier mechanism, and collector apparatusdesigned to more eliiciently guide. inwardlyY spiralling particles 1and .to utilize their energy for classilication and collecting purposes especially.

An important feature4 of the grinding chamber construction of the `invention, in one 4preferred form, is a combination of conduit forming elements constructed.v and .arranged to define. an elongated annular duct which v communicates Ldirectly .with andA constitutes a continua- .y tion of the inwardly spiralling paths along which rel-4 atively `smaller particles travel.-

l have found thatby providing an elongated annular.'

duct which extends vertically away from the central axis of the grinding chamber, I lam enabled to avoid any abrupt .or sharp change in direction of movement of relatively `small particles moving along inwardly spiralling paths,.and there mayv be realized an improved grind-y ing operation in outer portions of the chamber. Furthermore, one of the components of the elongated annular duct may constitute anintegral portion of a particle classifying structure, and particularlyl a particle clasifying structure of thetype disclosed in the copending application' above referred to.

By means' of the elongated annular duct arrangement l am enabled to lead particles moving radially inwardly of the chamber along spiral paths of gradually decreasing magnitude4 and, a't the same time, the particles may be iled vertically ldownwardly to carry outl an improved classifying operation.v lt is also'found'r that by leading particles which are passed through a narrow aperture type .ofl classifying device and then downwardly along a relativelynarrow annular duct,a part of the energy.: of the particles may be conserved and thereafter utilized to aidfin subsequent particle collecting procedures. lt will be apparent that once particlesv are led into a` relatively narrow elongated annular' duct they automatically becomel concentrated in a relatively smaller space and since'they still retain appreciable spiralling energy these particles will-fchangeI their transverse ldirection of move-Y ment and=willtend to move in radially outwardly spirallingdirections.' "I'hisflatter characteristic is found to be The material important in that if the particles thus confined are abruptly led into a relatively large container, they tend to collect in a substantial layer at the outer walls of the container body while permitting exhaust air coming from the grinding chamber operation to pass upwardly and outwardly without taking material with it.

I have further discovered that in connection with this matter of guiding exhaust air from the grinding process to a suitable discharge point, there may be employed for a discharge conduit one of the tubular components which is utilized to constitute the elongated annular duct. Moreover, I have learned that through the successive operation of grinding and classifying relatively small particles; then confining these classified particles with a stream of grinding tluid in a predetermined region of restriction comprised by an elongated annular duct; and then guiding the Spiralling particles and grinding uid in to a collector of gradually increasing diameter and of correctly chosen axial length, there may be reached a point at which the particles almost entirely separate themselves from the moving gaseous tiuid, and the particle-free uid reverses its direction and passes upwardly out of the collector chamber` I have further found that by thus leading classifying particles and grinding fluid through an elongated annular duct, I may improve and facilitate the feeding of material into the grinding chamber, and I particularly nd that I may not only improve feeding into the chamber from points occurring around the periphery thereof, but I may also very desirably introduce material into the chamber in an axial direction and at points occurring between the central axis of the grinding chamber and its outer peripheral edges.

Considering the annular duct structure of the invention more in detail, attention is directed to the structure shown in the drawings and particularly the structure shown in Figs. l to 4, inclusive. As shown therein, numeral 2 denotes a cylindrical or ring-shaped retaining body having a centrally located rib section 4 of relatively short axial length extending around the periphery thereof. Snugly fitted within the ring-shaped body 2 and maintained in spaced-apart relationship by means of the rib 4 are two converging sections including an upper section 6 and a lower section 8. These sections are recessed to provide a hollow chamber space, the axial dimension of which preferably increases in magnitude in directions radially of the chamber. These recessed surfaces may be of varying contours.

Arranged in concentric relationship with respect to the ring 2 is an outer ring 3 which is normally held in xed spaced relationship to the ring 2 by means of an upper locking plate and a lower locking plate 7 (Fig. 2). These members are secured, for example, by cap screws, as 9 and 11. It will be observed that the members Z and 3 form an annular space, and into this space a compressed gas, such as air, is forced through a pipe 1 connected into the wall 3. Air thus delivered into the space described moves in a generally spiralling stream and passes through jets, as 5', fitted into the ring member 2, as best shown in Fig. l, and thus reaches the chamber S to form a spiralling fluid stream. Into this fluid stream material to be ground and collected is forced through a feed pipe P having a tapered extremity E. The material may be furnished from a hopper H from which material drops down into the path of a stream of com- 1plressed air passing through a jet member J, as shown in ig. l.

The section 6 is formed with an inner annular bearing portion 1t) and slidably received therethrough is a sleeve member 14. A set screw 13 serves to secure the sleeve 14 in any desired position of vertical adjustment in the bearing portion 10, as shown in Fig. 2. Similarly, the section 8 ,is formed with a bearing portion 12 in which is adjustably supported a cylindrical conduit 16. A set screw 18 transversely disposed through the bearing portion 12 may be loosened to allow the conduit 16 to be moved toward or away from the sleeve member 14 and thereafter secured in any desired position of vertical adjustment.

It is pointed out that the extremities of the two members 14 and 16 lie inside of the chamber S and thus cooperate with one another to comprise a particle classifying aperture which communicates radially with the grinding chamber at all points therearound. It will also be seen that the members 14 and 16 are arranged in axially opposed relationship and when moved toward and away from one another the particle classifying aperture defined by the flanges may be varied in magnitude in any desired manner.

The particle classifying aperture thus comprised may also be provided with special particle classifying elements consisting of circular flanges 24 and 25 located at the opposed ends of members 14 and 16, respectively, as noted in Fig. 2. These liange members, which may be constructed integrally with the respective supporting elements, for example, extend outwardly in spaced parallel relationship to one another and are of an appreciable radial width so that they project out into the control region of the spiralling chamber space S for some distance.

When arranged in a position such as that suggested in Fig. 2, the two spaced flanges 24 and 25 cooperate with their respective supporting elements, and with one another, to dene a narrow highly selective particle classifying passageway which is of annular conformation and which is so located with relation to the grinding chamber, and to inwardly spiralling particles moving therein, that a selective removal of particles from a restricted region in the chamber can be carried out.

In accordance with the invention I further provide another important element consisting of an elongated tubular outlet body 22 which .is slidably received in the sleeve 14 and may be held in any desired position of adjustment by means of set screws, as 23, shown in Fig. 2.

An essential feature of this tubular outlet member is that it is constructed of a diameter somewhat smaller than the inner diameter of the conduit 16 and, consequently, there is formed an annular duct which is denoted by the arrow D and best shown .in Fig. 2. This annular duct is designed to communicate with, and form a continuation of, the particle classifying aperture occurring between the opposed ends of the members 14 and 16 and their respective anges.

It will readily be observed that by thus providing an annular duct which extends downwardly away from the classifying particle aperture, there is produced a natural cylindrical passageway along which inwardly spiralling particles will continue their downwardly spiralling movement without interruption and without having to be, in any way, deflected with a consequent loss of energy.

The invention comprehends the utilization, to the fullest possible extent, of energy retained in those inwardly spiralling particles which succeed in passing through the particle classifying aperture described and into the annular duct D. In this connection I have devised and provided a special particle collecting chamber C designed to cooperate with the annular duct D and to direct the energy of inwardly spiralling particles in a manner such that a novel particle collecting operation may be carried out.

I have found that particles entering the annular duct D and guided along this duct for a short distance tend to change with respect to the direction of their transverse force components, and if the particles are conducted from the annular duct into an annular chamber, such as chamber C, of gradually increasing magnitude, these particles seek to ymove radially outwardly and to collect against the walls of -the chamber.

This action proceeds to a gradually increasing extent until a point is reached at which the spiralling stream of airis observed to reverse its axial direction and to aars-,venom startfto spiralupwardly.' VWhen this 4pointfof reversal` is reached-it is found `that the holding effect-of the .airf

for the particles is largely dissipated and the air whichspirals upwardly is almost entirely free from particles. As a result the particlesfwhich ref-leftxin .chamber C are in a form such that-theyr-may-be 'conveniently collected, and the occurrence of loss of particles from exhausting air is almost entirely eliminated.V

The chamber C which I have found will operate in the manner described comprises a casing body which includes a conical section 30; a central-cylindrical section 28; and a lower elongated conical section 34, as is shown in Fig. 5. The cone section 30 is provided with a ring member 26 which is tightly fitted around the member 16 and secured by a set screw, as 32. Secured at the bottom of the conical section 34 is a cylindrical neck portion 36, to which may be attached a bag, or other particle collecting container. Preferably the neck portion has supported thereon partitions 38 and 40 arranged cross- Wise of one another to retard any further spiralling action which may occur here.

One important feature of this casing construction is the provision generally of an elongated annular body portion of suicient axial length to permit an inwardly spiralling mixture of particles and carrier air to separate into the respective components. Another important feature is the provision of an outlet through which the air may escape when it starts to move upwardly. This outlet is comprised by the member 22 above described, and it is pointed out that the lower extremity of the tubular member 22 projects well downwardly through the collector casing to a point at which upward travel of air begins to take place. Thus, it will be seen that the tubular member 22 comprises means for performing two different functions. It is a discharge outlet, in one case, and in the other case it constitutes the inner element of the annular duct forming structure.

As noted above, the presence of the tubular member 22 in the collector also serves to provide a means of guiding particles radially outwardly, as diagrammatically shown in Fig. 5. Gradually the particles collect around the peripheral surfaces of the collector in the form of an annular layer of material, and this material may be periodically dislodged and received in a suitable container.

It should be understood that the annular duct either separately, or in conjunction with the collector device described, may be employed in various other ways than the particular arrangement shown in Figs. 1 4. For example, in Fig. 8 I have disclosed another form of grinding chamber comprising a structure generally similar to that already described but not including the flanges 24 and 25. In this case a particle classifying structure is comprised by a sleeve 50 and conduit 52 in a chamber S and the outlet tube 54 lies in spaced relation to these members, as shown. Various other arrangements may be used.

In Figs. and 6 I have shown a modified form of feeding device which may be employed with the grinding and classifying mechanism of the invention. In this form of feed means the material is introduced along a path parallel to the axis of the grinding chamber, and in a manner such that particles will be directed into the chamber at a point immediately adjacent to the iiange 24, for example. This mechanism comprises a hopper 70 to which material is led through a supply source 72 and from which the material is forced downwardly by a source 74 of compressed gas, such as air. A conduit 76 conducts the air-driven material through a suitable opening formed in the member 10, as suggested in Fig. 5, and the material then moves downwardly toward the adjacent fiange 24 where it is forced outwardly into the grinding chamber.

It is pointed out that the particle classifying structure comprised by the members 14, 22 and 16 are especiallyisuitedfor use'"-with-"a feed a'rrangement,'such as that shownin Fig. 5, and the particle classifying andcollecting mechanism,fby reason of its greater selectivity,

From the foregoing description it will be evident that I have disclosed an improved method and apparatus for f simultaneously grinding, classifying, and collecting finely divided materials,land-in particular Ihave disclosed a unique annular particle collecting duct with-Which has been combined a collector casing so that these members can cooperate with one another in a novel fashion to produce an excellent collecting operation in a highly efficient manner. It is also pointed out that the structure of the invention includes a special arrangement of tubular outlet means whereby at predetermined points exhaust air may be re-routed to pass out of the grinding apparatus and collector casing substantially free from entrained particles of material.

Both the annular duct and collector casing structure, as well as the outlet tube, are combined in such a manner that each of these elements compliments the particle classifying aperture and particle classifying flange elements adjacent the aperture so that the fiow of classified material is interrupted at no point and a smooth continuous iiow of classified material can be carried out.

While I have shown preferred embodiments of the invention, it should be understood that various other changes and modifications may be resorted to in keeping with the invention as defined by the scope of the appended claims.

Having thus described my invention, what I desire to claim as new is:

l. A grinding machine including enclosure means for receiving a confined stream of fluid material, means for feeding particles into the enclosure means, a device for selectively separating and discharging particles from the chamber, said device including a tubular member axially disposed in the enclosure means, and a conduit element arranged concentrically with`respect to the tubular member to define an annular duct, said device further including two radially disposed iianges supported around the said tubular member and adjustable toward and away from one another to control the size of particles passing through said annular duct.

2. A structure as defined in claim l, in which one of the said flanges is mounted upon the said conduit element.

3. An lapparatus for grinding material, comprising a casing having an annular chamber formed therein, means for introducing a fiuid into said chamber to produce a generally spiralling fluid stream, a feeding mechanism for delivering material into said chamber in the path of this stream, a particle classifier device located centrally of the chamber, a particle collector communicating with the classifier device, said classifier device including two cooperating tubular bodies axially disposed through the chamber in adjustably opposed spaced-apart relationship, and a third tubular element concentrically arranged within the said first two tubular bodies and extending into said particle collector to define an elongated annular duct occurring externally of the said chamber.

4. An apparatus for grinding material, comprising a casing having an annular chamber formed therein, means for introducing a iiuid into said chamber to produce a generally spiralling fluid stream, a feeding mechanism for delivering material into said chamber in the path of this stream, a particle classifier device located centrally of the chamber, ya particle collector communicating with the classifier device, said classifier device including two cylindrical classifier elements disposed axially through respective upper and lower sections of the chamber and arranged in opposed spaced-apart relationship to one another, and a third cylindrical classifier element mounted in concentrically spaced relation within the said first two cylindrical classifier elements, said third classifier element extending into said particle collector and said collector being formed with outwardly and downwardly tapering sides which define an annular duct of gradually increasing radial width.

5. A grinding chamber having a discharge outlet formed axially through one side thereof, a materials collecting casing secured to the grinding chamber and communicating with the discharge outlet, a hollow materials guiding member axially disposed through said chamber and projecting into said collector to provide a remotely located fluid outlet, said materials collecting casing including a conical section connected to the chamber and cooperating with the chamber and materials guiding men1 ber to dene annannular discharge duct which is of gradually increasing magnitude. f

References Cited in the le of this patent UNITED STATES PATENTS

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