US2412680A - Metering mill - Google Patents

Description

Search R00! Dec. 17, 1946. c. FISHER ETI'AL METERING MILL Filed Aug. 3, 1943 S m g. T H A N N J H R E J 0 v M T m c m IONGITUD/NALLY FUIL FLOA 77,116

1.1-1. ouuu lvll-i l [Zl'iIp I, w n |UN QUCllbll l\UUl R DISINTEGHAI lON O Patented Dec. 17, 1946 UNITED STATES PATENT OFFICE METERING MILL Leslie 0. Fisher, Farmingdale, and Henry Imshaug, Flushing, N. Y., assignors to Edwin G. Eppenbach, Manhasset, N. Y.

Application August 3, 1943, Serial No. 497,268

3 Claims.

invention, therefore, is the provision of means for producing relatively free-flowing colloidal compounds which contain solids of uniform, microscopic size, and wherein the solids are perprovision of means for producing a colloidal com- 5 manently and uniformly suspended within their pound which is composed of minute solids borne fluid carrier. by a liquid carrier, and wherein the ultimately The foregoing and numerous important other desired size of the solids is accurately metered objects and advantages of the present invention in the process of production to such a proportion will become more readily apparent from the folthat when the compound is finished, the solids lowing explanation and description of the accomwill permanently remain in colloidal suspension panying drawing, which latter illustrates one of within the fluid carrier. the many possible forms of our proposed mill While we are well aware of the existence of and wherein: numerous devices relating to the present art, we Fig. 1 is a side elevation of a presently prebelieve that the principle of our device repreferred form of our device, partially in section, sents an important step forward in the field of representingadouble mill unit in accordance with producing ready-flowing homogeneous colloidal our invention; compounds wherein the solids are maintained in Fig. 2 is an enlarged detail plan view of the permanent, uniform suspension in their liquid milling discs employed in our mill; and carrier. Fig. 3 is a section taken on line 33 through In order to establish the vital differences, beg- 2. tween heretofore employed devices and our pres- Referring now specifically to the drawing, Fig. ent invention, we shall broadly set forth the un- 1 represents 011'! device in its Presently Preferred derlying principles involved. arrangement, and is designed to accommodate When it is contemplated to produce a, r latwo sets of mill units. Numerals l0 and II detively fluid colloidal compound of a homogeneous note, respective y, t left a right hand end structure, one of the essential prerequisites of housing each of Which accommodates One Of such structure is a uniform distribution of solids e mi l u e middle housing section within the fluid carrier in such a way that the place etw n the n housings. i p ovide solids will always remain in floating suspension with a fixed mill sup I3 for the left-hand within the carrier, irrespective of the volume of mill unit and a movable support N fo e rightthe colloidal compound considered. Thus, a large hand mill unit. Both mill units comprise gebody of such compound, as well as one droplet spectively, Stator discs igndfllfihaiiimtor-discs thereof, must evidence the same uniformity of l1 and I8, which latter are mounteiimon a homogeneousness in its physical structure. In es-fl t ng driveshaftis; The shaft extends the heretofore known art colloidal mills have been from both end housing and is journaled in produced, wherein the milling surfaces were made bearings exteriorly to the housing, not shown. adjustable for reducing the size of solids to ap- T e mou t o t Shaft is such as o Permit proximately the magnitude desired. Other dethe latter to shift in longitudinal direction while velopments in colloidal mills constitute devices being driven by ot D not o wherein the solids are subjected to an inter- Movable disc mounting I4 is provided with a abrasive action between particles of the solid threaded extension 20, the threads of which are material itself. However, in neither type of such engaged by an internally threaded annular memdevices stress is laid on exact control, whereby ber 2|, with which latter is fi e y associated a both the size of the solids in suspension, as well 5 Worm gear s Worm gear is adapted o be as an absolute uniformity of the ultimately deactuated by worm 23, which is journaled within sired product may be assured. Such control is a compartment provided in middle housing secof especial importance when the contemplated tion l2. size of the solids has to be so minute that it will Mill adjustment correspond to a 1200 mesh or smaller.

The present invention contemplates the proy Operating Worm gear 23 in either c duction of colloidal compounds wherein the solid wise or anti-clockwise di ecti s. t e te al y particles suspended in the fluid are of an inthreaded annular member 2| is turned and will flnitesimal size, discernible only by microscopic cause movable disc mounting It to travel in either right-hand or left-hand directions. When observation. One of the objects of the present the mounting I4 is caused to travel in righthand direction, its stationary disc l6 will move against rotary disc 18 and, after engaging the latter, will also cause shaft 19 to shift in righthand direction, whereby rotary disc I! of the left mill unit will be brought closer to stationary disc l5.

When the rotation of worm gear 23 is reversed, movable mill support M will travel in left-hand direction, and as the two movable discs rotate, the separation of the discs in both mill units takes place. In this manner both mill units become uniformly and simultaneously adjusted.

Taking into consideration the structural details of the adjusting arrangement, it is readily evident that a very minute and virtually a fine metering adjustment of the mill discs is contemplated in our device. The importance of such fine metering adjustment will be better appreciated when the principle of our method becomes.

fully understood.

Mill disc construction In Figs. 2 and 3, some of the important details of the mill discs employed in our device are disclosed. These mill discs, of which disc 18 is the movable disc, are made of relatively hard and tough material, and are mounted upon more readily maohineable disc supports 24 and 25, respectively, as clearly seen from Fig. 3. Each of the discs actually constitutes a ring with relatively spacious central apertures 26 and 21, for accommodating shaft l9, and for receiving the supply of the mixture of solids and fluids.

The smooth, absolutely parallel milling surfaces of both discs are providedwith a, plurality of saber- shaped grooves 28 and 29, which grooves diminish in 'cross section in radially goutward direction; their'reduced ends terminating a substantial distance from the outer periphery of the discs, so as to provide a relatively broad annular margin 30, the surface of which is unbroken and smooth.

Arranged in the fields between each two adjacent saber grooves is a plurality of substantially cylindrical recesses, which latter progressively diminish in size from within to without so that the larger recesses 3| are closest to the central opening of the discs, the next smaller series of recesses 32 are placed substantially centrally between the large and small groove ends, and the smallest series of recesses 33 are arranged between the reducin tip ends of the grooves.

It will be observed from Fig. 2 that the outer margins of smallest recesses 33 are placed along and within a circle that coincides with that at which the reduced ends or tips of the grooves terminate, whereby the smooth, annular peripheral field 30 of the discs is maintained. The importance of the marginal smooth fields of the discs will'be discussed presently.

All recesses are preferably of a cylindrical shape and rave fiat bottoms. The depths of the recesses may either be uniform or may vary. We prefer the recesses to be gradually diminishing in depth from within to without, in the same manner as the saber-shaped grooves diminish in depth in outward direction. It may however be advantageous to maintain the depth of the recesses uniform, or reverse the progress of their depth so that the larger recesses near the center opening of the discs will be less deep than the smaller recesses near the periphery.

Discs I6 and I! have internal chamfers 34, forming a feeding groove for the re p n Of material to be milled, and external chamfers 34' in which latter chamfered surfaces are provided equally spaced, inclined grooves 35, which are designed to facilitate the discharge of the milled compound.

Operation such that the groove tips pointtowardseach l other when one disc moves in one dlrection,-while the other either is at rest or moves in the opposite direction. In this manner a veritableshee'i in operation between the grooves will take place. Such sheering operation becomes progressive Qsiifie grooves move against each other from their reduced termini towards their enlarged interior ends. A similar sheering operation takes place between the recesses arranged in the fields between each two adjacent grooves.

As the compound of liquid and solid materials enters the large ends of the grooves, and is forced by centrifugal action from within to without, and thus is being pressed into progressively smaller cross sections of the grooves, the solid particles of the compound are pushed beyond the surfaces of the discs and are thus being subjected to an inter-abrasive action. The "overflow of the particles from the grooves to the solid and smooth disc faces are trapped within the recesses between the grooves, and as they gradually accumulate within, and finally fill the recesses, they are caused eventually to "overflow from the recesses to the surfaces of the discs, thus augmenting the abrasive action between the solids, whereby the sizes of the latter are progressively diminished.

Following the transfer of the solids from the grooves to the recesses, there ensues a re-transfer from the recesses back to the grooves, at points progressively nearer to the disc periph eries. Such process of transfer and re-transfer continues until the compound reaches the annular, smooth fields 30 of the discs.

Accompanying this transfer and re-transfer of solids is a progressive abrasing action, which causes the solid particles to gradually, but progressively diminish in their size in the direction from the inner peripheries of the discs towards their outer peripheries.

When the solid particles reach the circle at which the grooves and recesses terminate, their size will have diminished to the required minimum. They now form with the fiuid carrier a relatively thin flowing compound, which enters the metered space between the two adjacent smooth, annular zones or fields 30. In consequence of the exact adjustment of the discs, only those solid particles which have acquired the devised minute size can pass through the metered zone space, while larger particles will be left behind to be caught by the grooves and recesses for an additional milling operation, until their size is small enough to pass the metered zone space Thus a product containing solids of only the required smallness will be propagated to the outer periphery of the mill units.

The centrifugal force to which the compound is subjected will cause the compound to leave the space between the adjacent disc surfaces at a LH. OULIU lVlH I illiffiL LQIIVHVHNU l iUN dumb" R DISINTEGRATION considerable force. In the event however the viscosity of the compound should be so great, due to the possible separation of the liquid carrier from the solids, to cause a temporary accumulation of solid or semi-solid matter along the bev- 5 diminishing of the solid particles reaches a stage eled edges 34 of the discs, inclined grooves 35 prowhen the particles are substantially uniform in vided' in these beveled edges are designed to break size. For the purpose of exactly metering the up such accumulation of matter and to cause the solids of the ultimate product, the mixture is latter to separate from the disc peripheries. forced through an exactly metered passage formed between two adjacent surfaces, at least Metering adjustment one of which surfaces is in motion. Having thus The provision of the smooth annular peripheral forcibly gauged the solid particles of the comfields or margins 30 arranged at both discs is pound before releasing it, the desired uniformity primarily intended for the purpose of exactly in size of the solids within the compound is effecgauging the size of the solid particles permitted tively assured. to pass through the space between these fields. Modifications Depending upon the adjustment of the discs relative to each other, the space between the discs While in the submitted drawings the adjacent may be either enlarged or reduced, thereby govsurfaces of the annular peripheral fields 30 oi. erning the size of the solid particles in the finthe discs are shown to form continuations of the ished product issuing from the peripheries of the disc surfaces disposed in the same planes, it is mill. quite obvious that these peripheral fields may Inasmuch as the present invention contemplates slightly :taper against each other, or that they a method for producing a compound wherein all may be both conically off-set in one direction in the solid particles are intended to remain permarespect to the interior disc planes. Furthermore, nently in suspension within their carrier, the it is also obvious that while these peripheral fields magnitude of the particles borders on infinitesiare shown tobe of the same material from which mality. In order to produce such very small the disc bodies are made, it may be advantageous particles, as is required in accordance with our to employ different material for the peripheral invention, the adjustment of the two discs, or disc sections. more specifically, the adjustment of the periph- Conclusion eral fields 30, is of utmost importance. For this reason we have devised the afore-described ad- While the aforedescribed device for producing lusting arrangement which affords imparting to colloidal compounds has been dealt with in a the discs very minute movements, which movemore or less specific manner, it is self-evident ments may be readily indicated on the shaft of that changes in the pp u may ve to e worm 23. The provision of a gauging device bemade in order to meet different problems arising ing obvious, no specific illustrations thereof are from the type o products to be manufactured. submitted. Sufflce it to say, however, that the Thus, fOr instance, when it is desired to produce adjustment must be very accurate and simulin a fuel compound, such as an oil and coal mixtaneously uniform for both mill units. ture, the size of solid coal p ticles must be such Referring again to Figure 1 it will be observed that the latter will remain permanently in unithat middle housing section I2 is provided with form suspension within the oil. It has been an inlet 36, through which the combined mixture found that in order .to meet such requirement, the of a fluid carrier and of relatively large solid parsolids of the compound m st pp te a S ze ticles enters the device. When a sufllcient quancorresponding to 1,200 mesh, and that in order tity of the mixture accumulates within the middle to render the compound sufilciently fluid to persection, it passes through central openings 26 of mit its being sprayed effectively through nozzles, the stationary mill discs l5 and I6, from where the proportion of coal particles to the fuel oil it is propagated in the manner stated, i. e. from must approximate 40 percent of the former to 60 the interior to the exterior peripheries of the percent of the latter. di s. When compounds are to be produced wherein The finished product then issues from the outer the difierence between the specific gravity of the peripheries of the discs into the respective end fluid carrier and that of the solids is either housings of the two mill units and is eventually greater or smaller than the diilerence in specific discharged through outlet ports 31. gravity existing between fuel oil and coal dust, From the above description the different steps both the proportion between liquid and solids, of our procedure employed to produce a unias well as the size of the solids will have to be formly homogeneous compound, which will assure altered. Nevertheless, neither the basic principle permanency in suspension of solid particles with- 0f the present invention, nor the working prinin their carrier, are clearly indicated. To repeat, ciple o the app at o Practicing it Will be it is contemplated to first introduce a mixture of eff cted by the physical chan e in r the P a liquid carrier and relatively large-sized solid portion of the compon t of t t particles into the middle housing section, which cept that the mechanism of the mill arrangement latter may be considered a mixing chamber. y have to be co r p n in ly adiusted. From this chamber mixture is drawn in While, therefore, the above description deals tween the discs of the mill units and there it is with specific forms of our invention, be it undersubjected to a progressive action of first breakstood that the same shall not be construed in a ing up the larger particles into smaller particles limiting sense, and that changes and improveand then s j t e solids o a reciprocal 7o ments may be incorporated therein -without abrasive action, by successively transferring the departing from t broad scope of t underlyin solids fr m h di ans or su h s lids hav n principle of our invention, as defined in the angreater capacities to holding means having prox d l im gressively smaller capacities, rthereby gradually W claim: retarding he pr f e solids in outw 1. In a metering mill, a pair of cooperating milling discs, at least one being rotatable relative to the other, both having grinding surfaces provided with spaced, curved. grooves diminishing in cross section from within to without and terminating with their reduced ends along a circular curve which is concentric with and is substantially spaced from the outer circumference of the discs, a plurality of flat-bottom, cylindrical recesses provided in the fields between each two adjacent grooves and diminishing in sizes from within to without, the extreme edges of the smallest recesses being also located along the circle at which the groove ends terminate, the portions of the discs between the circle and the outer periphery of the discs providing substantially broad rims having unbroken surfaces, the discs being so arranged in respect to one another that their curved grooves and cylindrical recesses are disposed in opposite positions, and means for providing a metering adjustment of the space between the disc faces.

2. In a metering mill, two cooperative grinding discs having grooved and recessed interior and smooth peripheral outer surface areas at their adjacent planes, the grooves being sabrecurved and equally spaced, their depth and cross sections diminishing in radially outward direction, the recesses being grouped in the spaces between the grooves and having cylindrical shapes with fiat bottoms and diminishing in size from within to without, the ends of the grooves and the peripheries of the outermost, smallest recesses of both discs extending to circles parallel with and substantially spaced from the outer peripheries of the discs, whereby relatively broad, annular outer fields are provided having unbroken, smooth surfaces, and annular bevels arranged adjacent to said outer, smooth-surfaced l fields, and a plurality of radially disposed, conicaliy inclined peripheral recesses provided in the bevels and extending into the outer, smoothsurfaced fields, thg dg'ectionnfsthe mfg l' w and the grouping of the recesses in the two dis'fi being arranged in just opposite relations, so that [progressively increasing. shearing ..action between the cooperating discs is prgducedflwhen -at reast one-or them mpvesir'frespgm to theeother, said peiipfiral rcessessewing for facilitating the discharge of matter processed between the discs, and means for facilitating a fine, metering adjustment of the space between the smoothsurfaced peripheral fields of the discs.

. 3. In a metering mill, at least two annular grinding discs having closely adjacent cooperating parallel grinding faces, in both of which are provided exactly like patterns of a combination of grooves and recesses of the same relative shapes and depths, arranged at one disc in exact opposite relations to that of the other disc, the grooves and recesses of both discs diminishing in their retention capacities from within to without and terminating a substantial and uniform distance from the outer peripheries of the discs so as to provide ring-shaped, relatively broad margin areas having unbroken surfaces, the combination of grooves and recesses consisting of a plurality of substantially sabre-curved grooves extending from the interior rims of the discs towards their ring-shaped, unbroken marginal surface areas, and diminishing in cross section in outward direction, and a plurality of straight-bottom. substantially cylindrical recesses arranged between each two adjacent grooves, said recesses diminishing in size in outward direction.

LESLIE C. FISHER. HENRY IMSHAUG.

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