US1573017A - Process of obtaining powders of great fineness - Google Patents

Description

Feb. 16 1926. 1,573,017

E. PODSZUS PROCESS OF OBTAINING POWDERS OF GREAT FINENESS Filed July 1, 1922 4 I 15 5%1/42]? III Patented Feb. 16, 1926.

UNITED STATES EMIL PODSZUS, Q! BEBLm-FRIEDBIGHSHAGEN, GERMANY.

PROCESS OF OBTAINING POWDERS OF GREAT FRIENESS.

application filed July 1, 1922. Serial No. 572,840.

- To all whom it may concern: I

Be it known that I, EMIL Ponszos, a citizen of Germany, residing at Berlin- Friedrichshagen, German have invented 6 certain new and useful lmprovements in Processes of Obtaining Powders-of Great Fineness, of which the following is a specification.

This invention has reference 10 and means for effecting the comminution and disintegration of material and substances of any kind, particularly of metals, with a view to obtaining powders of extreme fineness which may be increased to colloidal l dispersion. Attempts have already been made heretofore of producing powders of the kind referred to without it having been possible however, to obtain such products- 1n an easy and economical manner. Thus for example, it has been suggested to produce metal powder by spraying and atomizing methods, but these suggestions presente great difficulties on account of the high melting points of several metals, and it was scarcely possible to obtain the desired degrce of purity and fineness, and besides all these methods caused very considerable expense. Similar conditions prevail inregard to the electrolytic-methods.

Among the purely mechanical methods for the disintegration of metals and the-production of powdered metals it is only the disintegrating process usually employed in the manufacture of bronze or brass which has become of some. importance for practical purposes. However, with that process the disintegration and comminution can .only be carried out within comparatively narrow limits. Moreover, the process is rather comrior grades of material of very good tenacity. In the case of comparatively tough, and brittle material of great strength there great difiiculties are encountered in the execution 'of the process in which the metals are first rolled out into thin sheets which are then submitted to a kind of forging and stretching stage by means of which their thickness is further reduced whereupon they are ounded in mortars, Suggestions to "grin metals by means of the usual'mills a large variety of which is in use for the comminution of other metals fail to produce satisfactory results. Even if it should be to a method plicated and calls for comparatively supepossible toobtain a certain degree of disintegration with devices of the kind referred to, it requires a very long time to grind even small quantities, and the operat1on is accompanied with such a very considerable wear of theparts of the mill, as to interfere with the economical working of the rocess; In the case of the majority of meta s, howeven, the said method is not applicable at all. The difliculties, presented in the. methods of disintegrating the metals to powder are due to the peculiar properties of the metals which, moreover, are the cause of their importance in the arts, particularly their tenacity, strength, and the propertyof small metal particles to become easily welded to each other at higher pressures or highertemperatures, and while the strength and the tenacity of the metals require a greater amount of energy, the property last mentioned interferes with the ap lication of considerable forces upon a plura ity of metal particles.

In the case of millsthe action of which is based upon the forcible tearin of the material to be ground between soli bodies or in which the said material is-projected against stationar bodies, an eflicient disintegration, if at a 1 possible is coupled with great impurities particular y in the case of the comminution of metals. Furthermore, the maximum capacity is soon reached beyond which no further disintegration can be effected. At any event, however, the disintegration and comminution requires so much time that economical working becomesimpossible.

Colloid powders could be produced heretofore only by the usual colloidal methods allowin of the obtaining of small quantities only.- Though recently colloidal masses have 95 become the subject of manufacturing methods the extremely lar e wear of the manufacturing instrumenta ities allows only impure products to be obtained, and in the case of hard and tough masses these methods fail to produce good results,-'and the entire procedure is not economical and cannot be used at all in the case of metals.

The knowledge of the'causes involving the 'difiiculties in the manufacture of very fine powders has led to the, present invention by means of which it is possible to obtain powders of any degree of fineness and purity from any kind of metal, without danger of agglomeration or welding together. The

process and the device according to my 'mvention, besides comprising a great number 'of other advantages, are distinguished by the fact that the raw material does not need to consist of a high grade metal of superior quality, but the invention admits the use of waste material, scrap and .the

In accordance with my invention, the lumps or pieces of material to be comminuted are caused to act mechanically upon each other by being submitted to a very rapid continuous circular movement in-thecourse of which they are caused to strike against each other with great force. This impact is continuously repeated, and it'is possible in this manner, by im arting the necessary velocity to the rapid y gyrating whirling material to produce an extraordinarily fine distribution of the masses. in View the several particles are distributed in a current of gas, air or other fluids or liquids, and two or more such currents charged with particles of the masses to .be

treated, are then caused to impinge upon each other. As has already been mentioned, it is of importance that the several particles arecause to perform a circulating movement, that is to say, that after the impact they are immediately carried along by the current, and are again made to impinge against each other. With a view to intensifying the results it is preferable to not only cause the several articles to impinge in a substantially rectilinear path, but to also impart to them a lateral movement, so that the intense whirling motion is also accom anied with as turbulent an interior motion as possible, so as to produce also a friction of the articles during the impact. By proceeding 1n this manner it is ossible to comminute even the toughest kinds of metals with superior degrees of purity .down to a fineness of the powder which it has been impossible to obtain heretofore.

For the fpractice of my invention the production o the whirls is of importance, and consequently the particles are conducted in such a manner that they are prevented from directly impinging upon t e relatively stationary parts of the mill employed, but are caused to move or slide along the same. The Whirling velocity, that is'to sa the velocity of I the currents in the direction of movement recommendable to increase the speed considerably beyond this ratio. In order to produce as extensive an action of the whirling' masses as possible upon each other With this end the necessary-high velocity of they are conducted in such a manner that they are prevented from moving ast each other, so that they are compelle to substalilitially fill up the entire casing of the m1 If the process as heretofore outlined is carried out for many. hours with the same amount of material a very fine powder is obtained thereby in which a colloid is already present. The separation of the colloid from the coarser particles is, however, difiicult, and the roportion of colloid obtained is comparatively small.

However, in the further evolution of the process it is carried out with such perfection that pure colloids may be obtained in large quantities and in a comparatively short time. This is due to the fact that with the process outlined a certain state of equilibrium is obtained after some time in which even after prolonged grinding any appreciable comminution cannot be obtained. This state of equilibrium terminates in the case of coarser articles in the ratio of lightness of weight 0 the material in view of the fact that the mass of individual particles impinging upon each other, is gradually reduced to such an extent that any appreciable progress in the disintegrating operation becomes impossible:

In accordance with another improvement to which my invention refers, fine particles are, therefore, submitted to the comminuting operation accompanied by considerably coarser particles. The coaiser particles possess the necessary mass in order to pro-' duce in this case the necessary forcible impact. With a proper selection of the proportions of the ingredients of fine and coarse particles there are-so many fine particles contained between two impinging coarse particles that the fine particles are pounded, rubbed up or ground between them, while the coarser particles are submitted to only a rather slight or no a preciable wear at all. It ispossible by acting in this manner, to convert the fine material in a very short time into large quantities of colloid.

The process becomes particularly efiicicnt by simultaneously treating only fine and coarse particles, the medium sized granules being eliminated as much as possible, inasmuch as these particles possess only in a very imperfect degreethe qualities referred to of the coarse particles, and because, on the other hand,these medium sized granules interfere with the systematic comminution of the-small particles, and produce a rapid wear of the coarse particles. In the practical execution of the process the fine particles of the material 'to be comminuted particles and of the steel balls the latter do not impinge directlyupon each other, there being always a sufiieiency of fine particles between them when the impact is to take place, and therefore no appreciable or noticeable wear of the steel balls takes place, but only the line particles are rubbed up. Buy this operation quantities of metals may be converted into colloids u to or 80 per cent in from 'four to ve hours. The process may, for instance, be apphed to particles of mass of a size of one hundredth of a millimeter .or less, while the coarser particles, in the present instance the steel balls, possess a diameter of, say one millimeter.

\Vhere the greatest degree of purity of the mass is of importance it- .is advisable to use coarser granules of the mass to be disintegrated itself as a treating medium for the finest powder, instead of using steel balls or other foreign. bodies. According to the experiments made, 'it has been found to be of advantage to employ a large amount of coarse particles or of steel balls or the like. However, the proportion of these coarser ingredients, provided they should not be reatly attacked, should not exceed one hal the amount of the fine powder.

The process may also be carried out in such a manner that instead of adding coarser particles the fine powder is mixed with binding agents in suitable proportions, the said bindin agents causing the formation of lum s oi: some size, and the said lumps being t en caused to act upon each other as coarse ingredients, and effecting the destruction and crushing of the fine particles of powder. In order to reduce masses of very extreme degrees 0 fineness, for example of colloidal fineness without the ad" mixture of coarser particles, the invention provides for the insertion during the process of an additional current, thus for example an air current which is preferably transversely directed with relation to the impinging currents, and which, without interfering therewith, is sufiicient to carry ofi' the finest particles away from the circulation. Into this separate current an additional quantity of air is suddenly introduced which strongl dilutes the additional current referre to and thereby distributes the quantities of powder contained in that additional current to a considerably larger volume of air. It then becomes possible to eliminate the several particles separately from each other from this strongly diluted .air current by means of any suitable well known or other methods, so as to finally arrive at the production of large quantities of absolutely fine particles *without the admixture of coarser particles.

In spite of the great difli'culty presented .by ascertaining the conditions which hereprinciples of my invention is shown by Way of example upon the accompanying drawing in a conventional manner, Fig. I being vertical sectional view, and Fig. 2 being a view of the apparatus of a detail turned through ninety degrees.

In a casing 1 two shafts 2 and 3 are mounted which are provided with air'propellers or the like 4 and 5. In front of these air propellers the transverse members 6 and 7 are arranged, as more clearly shownin Fig. 2. The material to be comminuted, scrap, powder, granules or the like, is charged into the casing 1 through an opening 8 provided with a closure; Then the propellers 4 and 5 are given a rapid rotation in opposite direction by means of the pulleys 9 and 10. The propellers 4. and I) produce air currents which, as indicated by the arrows ll and 12 impinge upon each other in the center part of thecasing. The transverse members 6 and 7, moreover, produce lateral displacements of the air currents, so that the quantities of material carried by the air currents are not only caused to impinge upon each other, but will also be frictionally engaged. The air propellers 4 and 5 draw the air from the lateral portions of the casing, forcing' it against the center of the casing, and producing there a continuous violent impact of the air currents, the currents becoming distributed thereby and being again projected towards the center, so as to set up a continuge; circulation in which the several particles of material are. compelled to participate. In orderto cause the circulation to proceed in a satis-- factory and suflicient manner it is advisable to provide in the casing 1 lateral cavities of suflicient extent at the rear of the air propellers, and of such size and shape as to assistthe formation of the air currents. The propeller blades 4 and -5 are of such pitch that the thrust of the air currents near the center is substantially equal to the thrust occurring at the outer extremities of the blades. 1

The continuous thrust and impact of the individual metal particles upon each other produce, of course, considerable. heating of the entire space of the mill and of the particles themselves. This heating of the particles is of advantage, inasmuch as the strength of most metals is considerably decreased with the rise of temperature, expediting the comminuting operation. The heating of the mill itself requires a special formation of the journal bearing which will stand only a limited temperature, and this formation of bearing also becomes imperative from other reasons.

In constructing the ap aratus referred to so as to conform with t e requirements of practical operation it is of importance, in order to avoid abnormal dimensions of the shafts, to arrange the bearings as closely as possible to the air-propellers 4 and 5 in view of the very considerable forces generated in the casing and at the propellers. On the other hand,.the provision of suflicient spaces for the required circulation at the sides of the propellers being of advantage,

would call for the construction of elongated bearings. Even, when securing the .same against the penetration of particles of powderlby suitable packing means, the bearings are heated to such adegree that it becomes necessary to provide means to prevent excessive heating, water cooling being preferably employed. For this purpose the cavities 15 and 16 are provided through which a circulation of cooling water may take place.

The currents generated in the apparatus are of such force that very considerable amounts of material, thus for instance pieces of wire of from 2 to 3 millimeters in diameter and of about 6 to 7 millimeters in length are whirled around, without the air propellers 4 and 5 or the transverse members 6 and 7 becoming mechanically engaged with the great mass of grinding material deposited upon the bottomv of the apparatus. The small pieces of wire, upon the beginning of the grinding operation, are first compressed at the ends by the force of the im act so as to be given the configuration 0 small dumb-bells. Then, these compressed pieces are gradually pounded more and more, until after some time, almost the entire material in the mill has assumed an almost globular shape. Even by the most careful tests no Wearing out of the air propellers or of the transverse beaters could be ascertained after several hours operation. It is of some importance in connection with the grinding procedure to maintain a certain proportion of the masses charged into the apparatus to the amount of air or of *liquid contained in the apparatus. It is, of

course, of advantage to c arge as large as possible an amount of material into the apparatus, while on the other hand, the formation of the air currents. and. the circulation of the material should not be interfered should be filled with air or li uid, while the remaining one third should e filled with the material to be comminuted.

Through the admission conduits 17 and 18 air or other fluid or liquid may be introduced from the main conduit 19 into the mill so as to create a certain over-pressure therein, and thereby causing the finer particles to be discharged into the'container 21 upon the opening of the slide 20 provided at the upper end of themill. The space of the container. 21 is provided with an air conduit 22 terminating in a tangentially shaped nozzle, the said air conduit 22 at the moment when the particles pass the nozzle,- causing a considerable rarification of the quantity'of air carrying the fine particles, and causing at the same time the burstin apart of any conglomerated or aggregated particles. These particles then. ascend with the increased air current within the container 21 which has a restricted portion at stitutes a funnel 24. In consequence of the -"slowing up of the current in the interior of the upwardly enlarged funnel 24 the coarser particles are thrown down, and are caused to drop into the funnel 25 which is mounted below the restricted portion 23 within the container 21. The coarser particles may then be returned from the funnel 25 into the casing 1. \Vhile this is done the air admission conduits 17 and 18 into the casing 1 are preferably closed. The various stages of procedure, however, vary in accordance with the fineness of the powder it is desired to obtain. One may also operate continuously, or the slide 20 may be opened periodically. From the container 24 the air current is conducted to se arating de-- vices 26 in which it is submitte to filtration and the like by means of sifters, sieves 27 or similar'means. The air current issuing from the short pipe 28 which is freed from admixtures of the powder may be used over again and returned to the apparatus through the conduit 22 or the tubes 17 and 18.

It is of importance in connection with the impinging of the several particles against each other, and for the production of the circulating movements, that the propellers 4 and 5 are not arranged in close proximity to each other, but,as experience has shown, preferably at a distance of from 10 to 20 centimeters from each other; but this feature as well as other considerations depend, of course, upon the particular kind of construction and the size of the mill, and the dimensions of its several parts are preferably detcrmined in each case by experiments according to the. kind of the material to be disintegrated. Obviously the invention also applies'tothe disintegration of materials other than meta-ls. But at any rate, a

certain distance between the propellers must sible degree of efliciency.

My invention is not restricted to the particular mode of operation and the particular arrangement of parts as above described by way of example and for illustrating .purposes only, but modifications and be observed for obtaining the highest pos-.

1 changes may be made to suit different con ditions', and without deviating from the principle of my invention.

I claim as my invention:

1; The process of converting hard materials to a finel powdered state, which consists in producing mutually impinging highvelocity whirling currents of gas or air in a closed space arranged to prevent said currents from passing each other, and causing said currents to circulate within said closed space in all directions at the rate of several thousand times, or more, per minute, thereby causing the particles of the material to continually impinge upon each other with great force.

2. The process as specified in claim 1, in

which the velocity and pressure of the whirling currents are so increased that also heavy and tough metals, e. g. copper, tombac, lead, etc. are converted into a" finely powdered state.

3. Theprocess as specified in claim 1, in which to the whirling currents, and the particles of the material carried thereby,

such a movement is given as tocause them to impinge upon each other both in a rectilinear direction'and a lateral direction.

4. In a device forpulverizing hard materials, the combination with an entirely enclosed casing filled with gas and air of' means for producing therein mutually impinging whirling currents, and circulating them within said casing with great velocity, at a rate of several thousand times per minute, or more, and means for intermittently charging and discharging said casing.

5. In a device for pulverzing hard materials, the combination with an entirely enclosed casing filled with gas or air, of propeller-shaped elements spaced from each other and from the walls of said casing, so as to provide open spaces around saidmembers for "producing a circulation of whirling currents all around said propeller-shaped members, means for revolving said members in opposite .direction to each other with great velocity, at the rate of several thousand times, or more, per minute, and means for intermittently charging and discharging said casing.

6. In a device for pulverizing hard materials, the combination with an entirely closed casing filled with gas, or air, of propellershaped members spaced apart, so as to pro+ vide open spaces around said members in said casing for producing a circulation of whirling currents all around said members, transverse members disposed in front of said propeller-shaped members, means for revolving the I opposed propeller-shaped members and transverse members in opposite directions relative to each other with great velocity at the rate of several thousand times, or more, per minute, and means for intermittently charging and discharging said casing. i p 7 In a device for pulverzing hard materials, the combination with an entirely enclosed casing, of means for admitting there toa fluid, rotatable members for producing a circulation of whirling currents in said casing, means for revolving said members 4 at a high rate of speed, means for intermittently charging and discharging said casing, a compressed fluid conduit connected to the discharging means, the latter having a funnel-shaped enlarged outer portion above said conduit, an open-ended funnel within said discharging means, and separating and fluid discharging means connected to said enlarged outer portion.

In testimony whereof I aflix my signal0 ture.

- EMIL P ODS ZUS

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