US1851071A - Dispersion mill - Google Patents

Description

Maw. 29, 1932. R TR VIS 1,851,071

DISPERSION MILL Filed Ju1'1e so. 1928 s Sheet s-Sheet 1 wvENToR Pl EHCE MASON TRAVIS March 29, 1932. p M R v s 1,851,071

DISPERSION MILL 7 Filed June 30. 1928 3 Sheets-Sheet 2 lNVENTOR PiERCE MASON TRAVIS March 29, 1932. p, TRAVIS DISPERSION MILL s Sheets-Sfieet s FiledJune 30; 1928 INVENTOR Pl ERCE MASON TRAVIS ATTORNEY Patented Mar. 29, 1932 PATENT OFFICE EIERCE MASON TRAVIS, OF RIDGEWOOD, NEW JERSEY DISPERSION MILL Application filed Iune 30,

This invention relates to high-speed mechanical dispersion mills of the so-called colloid type, wherein the material to be treated is subjected, while in a liquid vehicle,

to an intensive dispersing action for the purpose of securing fine comminution, defiocculation, colloidal dispersion, emulsification, homogenization, the acceleration of chemical reaction or the like.

The operation of dispersion, or so-called colloid mills is based upon the intense disruptive and dispersive forces set up in a liquid, when confined between closely adjacent, non-contacting surfaces relatively moving at very high speeds. The most effective type of mill embodies concentric surfaces of revolution, and in its best known form comprises a frusto-conical rotor surface surrounded by a frusto-conical stator surface. This concentric cone arrangement serves to retain the materials in an intervening gapor zone of action better than other types, and facilitates fine adj ustment of the minute clearance between the surfaces.

In the operation of the mill, the liquid material may be fed either at the small or ta ered end of the cones or at the large end. f the material is fed at the small end, it will be drawn through the gap by the inherent action of the mill itself, due to the acceleration imparted to the material by the centrifugal force, which progressively increases from the small to the large end of the rotating cone. If the material is fed at the large end of the cones, pressure feeding must be utilized in order to force the material through the gap against the action of the centrifugal force which tends to expel it at the large end of the cone.

Due to the power-saving and larger operating capacity provided thereby, it is much more preferable to utilize feeding at the small end. However, where such manner of feed,- ing is used with present constructions, there is a tendency under various circumstances, for example where the conical slope is pronounced, for the material to be drawn through the Working gap too quickly. As a consequence, the continuity of the stream of 50 material may be broken and the material 19213. Serial No. 289,448.

passed through the greaterpart of the gap in the form of detached particles and too rapidly for proper treatment.

It is an object of my invention to overcome the deficiencies of the prior practice and to provide an improved dispersion mill wherein feeding at the small end is utilized with its inherent advantages, but with the provision of means for avoiding the undesirable effects of unduly accelerated passage of the mate- G0 rial through the mill.

The manner in which I accomplish the same is described in the following specification, taken in conjunction with the accompanying drawings, in which, %ig. 1 is a perspective view of the complete m1 Fig. 2 is a longitudinal vertical mid-section of the same;

Fig. 3 is an enlarged longitudinal view of one type of rotor that may be used therein;

Fig. 4 is a similar view of another type of rotor;

, Fig. 5 is an end view of the larger end of the rotor shown in Fig. 4;

I Fig. 6 is a cross-sectional view'of an impeller groove;

Fig. 7 is a similar view of a slightlymodified form of the same;

Fig. 8 is a cross-section of a further modi s0 fication.

Fig. 9 is an enlarged cross-section of a modified form of stator, and

Fig. 10 is a longitudinal mid-section on a reduced scale of a form of rotor constructed for temperature control.

Referring to the drawings, and in particular to Figs. 1 and 2, reference numeral 11 designates a stator member comprising a shell 12 and a liner 13, which defines an elongated so chamber 14 of frusto-conical form. At its smaller terminal, chamber 14 communicates With a feed chamber 15 and inlet 16, and at its larger terminal, with a discharge chamber 17 and outlet 18 formed in a detachable shell 95 head 19. A detachable shell head 21 covers the opposite end of the shell, and both the stator 11 and shell head 19 are provided with jackets 22 and 23, respectively, for the circulation of a temperature regulating medium. 106

A rotor 24 of a frusto-com'cal form similar to that of the chamber 14 is mounted for rotation therein in closely adjacent, non-contacting, eo-axial relation, the surfaces 25 of the rotor and 26 of the stator defining a narrow working gap or clearance 27, shown in enlarged proportion for clarity, through which the materials to be dispersed are passed.

Conical projections 28 and 29 of greater slope than the rotor proper, extend from the larger and smaller terminals thereof, respectively, for the purposes to be described hereinafter, and these projections may be formed integrally with the rotor proper or detachably secured thereto.

Rotation of the rotor and its accompanying projections is accomplished through the medium of a driving shaft 31, carried in bearings 32 and 33, which is connected directly with an electric motor 34 by means of a flexible coupling 35 of any suitable type. Packing glands 36 and 37 are provided about the shaft 31, adjacentjhe bores in the respective shell heads 19 and 21, to secure proper sealing of the interior of the mill.

As will be noted from an inspection of Fig. 2, the bearing 32 is constructed to permlt longitudinal adjustment of the rotor 24, to vary the clearance between the working surfaces 25 and 26 of the rotor and stator. TlllS bearing comprises a split, babbitt-lined bearing block 38 provided with complementary semi-circular recesses in its removable cap 39 and base 41 respectively, which receive circumferential projections on the rotor shaft 31.

The block 38 is mounted to slide longitudinally in a channel 42, and carries an integral nut 43 which projects through a longitudinal slot 44 in the base of the channel. This nut engages an adjusting screw 45 mounted in bearing lugs 46 and 47, and by means of fixed collars 48 and 49 which-abut the bearing lugs, longitudinal movement of the screw is prevented and rotation thereof is translated into longitudinal movement'of the bearing block and rotor. The screw 45 is actuated by a hand-wheel 51 which carries an indicator 52,

and by proper calibration of a stationary scale 53, determinate adjustment of the clearance in the mill may be readily obtained.

The rotor and stator may be either of the smooth-surfaced type 54, shown in Fig. 3, or of the roughened-surfaced type 24, shown in Figs. 2, 4 and 5. This roughened surface is constituted of generally longitudinal channels 56 preferably having rounded base corners, alternating with generally longitudinal flat faced teeth 57 and a similar surface construction is provided on the surroundin stator. Where a generally applicable and particularly effective construction is de ired. the roughened surface construction is best used. As will be noted from the drawings. the rotor has the form of an elongated frustum of a cone of moderate slope. I have found quite suitable, for example, a frustoconical rotor having the slope of a cone whose apical angle is approximately 1618.

Heretofore, rotors have taken the form of disc-like frustums, either of pronounced slope or of very slight slope. In the first case, while rapid passage of the material over the short dispersion surface results, the effectiveness of treatment suffers accordingly. In the second case, the speed of passage is greatly decelerated, but the advantages of high capacity operation and power efiiciency are lost thereby,and with the short dispersion surface, the resulting treatment still lacks the desired increase in effectiveness. By using an elongated rotor of moderate slope, as in my construction, these deficiencies are supplied, and a reasonably rapid acceleration is obtained over a dispersion surface sufficiently prolonged to assure very effective treatment.

The stator which surrounds the rotor in coaxial relationship therewith is preferably of like conical form.

In Figs. 3, 4 and 5 I have shown a construction for the discharge terminal of the rotor, which substantially remedies the practical deficiencies heretofore accompanying smallend feeding.

This construction comprises impeller grooves 55 formed in the surface of the projection 28, which extend radially thereof to spaced points in the surface of the rotor. In the smooth-surfaced rotor 54, Fig. 3, the grooves terminate flush with the rotor surface, while in the rough-surfaced rotor 24, Fig. 4 and 5, I have found the action to be most effective when the grooves terminate in the channels 56, between the longitudinal teeth 57 on the rotor. These grooves are preferably of rectangular cross-section, as shown in Fig. 6, but may if desired be of the cross-sections shown in Figs. 7 and 8. The essential element of the configuration is that an obstructing face of the groove should be allgned in the direction of movement of the surface 28, either at right angles itheretoas at 58 in Fig. 6, or 59 in Fig. 7, or at an acute angle thereto as at 61 in Fig. 8, in order that the liquid will not flow out of the groove until it reaches the terminus :thereof.

By increasing ordecreasing the number of grooves the retarding effect upon the discharge of the material from the working gap may be respectively intensified or diminlshed, and if a particularly Wide range of retardation is desired, it may be provided for by initially forming the maximum number of grooves, and then inserting fillers, which may be screwed or otherwise detachably affixed in the grooves, as the occasion demands. Such contingency may also be anticipated by providing a series of detachable pro ections 28, each having a different number of grooves. The more pronounced the rotor slope the greater the number ofgrooves necessary to maintain'a uniform retardation.

A conical projection 29 of less pronounced slope than projection 28, is disposed at the smaller terminal of the rotor, to facilitate introduction of the materials into the working gap 27, and this projection may be provided likewise with impeller grooves 62 of the same nature as those on the projections 28, to promote feeding.

In Fig. 9 I have shown a modified form of the unitary stator 11. This split stator 63 is constructed to permit ready access to the interior of the mill for cleaning or other purposes. It comprises complementary sections 64 and 65 hinged together as at 66, either at the base, side or top, which are provided diametrically opposite the hinge, with abutting flanges 67, 68 adapted to be bolted, screwed, or otherwise detachably secured together. To provide for this separable relationship the circumferential stator jacket'is divided into two semi-circumferential sections 69, 70 having individual inlets and outlets.

Fig. 10 shows a rotor construction adapted for internal circulation of a temperature,

regulating medium. This rotor comprises a hollow shell 71 shrunk on the ends of stub shafts 72 and 73. Shaft 72 is provided with a central bore 7 4 which accommodates an inlet pipe 75, and shaft 73 carries at its end a hollow cylindrical bracket '76 which sulpports the projecting terminal of pipe 75. T e wal 77 of the bracket 73 is provided with a number of elongated slots 83 for the passage of the fluid from pipe 75.

Shaft 72 is mounted at its recessed portion 78 in a suitably altered bearing of the general type shown at 32 Fig. 2, and has its terminal portion 79 rotatably mounted in a coupling 80. The coupling 80 comprises an inlet chamber 81 communicating with pipe 75, and an outlet chamber 82 communicating with the discharge passage 7 4, through which con duits cold water, steam, or other suitable temperature regulating medium is circulated through the rotor.

This rotor construction is particularly advantageous where cooling of the working gap is contemplated. Upon rotation the hollow rotor will act in the same fashion as a centrifugal separator, and the coolest and most dense liquid inside the shell will tend tobe maintained in contact with the inner peripheral surface thereof.

The operation of the mi as follows:

The roughened working surfaces 25 and 26 of the rotor and stator, are first spaced to the desired degree by adjustment of the bear ing 32. The effective clearance is relatively slight and is best maintained between very 11 is substantiallynarrow. limits, depending upon the degree of dispersion desired and the peripheral speed of the rotor.

For the fine dispersion of most materials at the high peripheral speeds ordinarily used, a clearance ranging between .002-.O10 inches is very effective, although for some materials this upper limit may be exceeded with good results. At particularly high peripheral speeds, the clearance for fine dispersion may appreciably exceed .010 inches, the specific variance being dependent upon the speed attained and the nature of the material involved. Where a course dispersion provides the material in a satisfactory form, the clearance may be altered as the circumstances dictate.

The rotor is then brought up to a peripheral speed suitable for dispersion, which rarely is less than 3000 ft. min. and ordinarily ranges in the vicinity of 5000 ft. min. and higher. Due to the particular constructional arrangement of my device, I can utilize a rotor of such large diameter that the requisite fore, permits the use of heavy motors of commonly available design, operating at the usual commercial speeds or R. P. M. and facilitates increasing the mill output appreciably.

The material to be introduced into the mill should be provided in liquid form, for in the operation of a true dispersion mill, as distinguished from the old grindingmill, it is essential that an appreciable amount of liquid be present, in order that dispersion, may be accomplished between the non-contacting working surfaces. Where solids are being dispersed, a slurry of the same in a suitable liquid medium is first formed. In emulsification and similar liquid contact, the liquids themselvesgenerally furnish a satisfactory medium. Where plastics are concerned the addition of or conversion to a more liquid medium depends upon the degree of plasticity which the mill will conveniently handle as well as the nature of the dispersion desired.

When a properly liquid material has been prepared, it is continuously introduced through inlet 16 into feed chamber 14 (Fig. 2%, whence it is drawn into the working gap 2 and in the event projection 29 is utilized, with the added accelerative action of that grooved projection.

In its passage through the gap, the material is subjected to a terrific disruptive action, of much greater intensity and of different type in the rough surface mill than in the smooth, which results in thorough dispersion or deflocculation of the aggregated particles.

When materials which are sensitive to heat are being dispersed, it is desirable to pass a suitable cooling medium through the stator and shell head jackets 22 and 23, and if a considerable cooling efiect is necessary, a water cooled rotor of the type shown in Fig. 10 may be used in addition. If heat is desired in the dispersing action, a circulation of steam or other suitable heating medium may be provided.

The conformation of the working gap 27 is such that properly prolonged treatment is afiorded with suitable axial acceleration of passage. It is, however, by the action of the impeller groove construction at the discharge terminal of my rotor that the deficiencies of the prior practice are most markedly remedied. The exact nature of its action is diflicult to predict accurately, but it suflices that I it results in a considerable increase in the effectiveness of the dispersing action, without unduly prolonged or impractically applied retardation. As noted hereinbefore, the number of grooves may be increased or decreased to vary the degree of retardation of discharge of the material.

The dispersed material in the discharge chamber 17 is pumped through the outlet 18 by the pressure in the mill, but this action may be supplemented by a suitable pump connected to the discharge outlet.

I claim as my invention:

1. An apparatus for treating liquid material which comprises a conical rotor adapted for rotation at high velocity, a conical stator surrounding said rotor in closely adjacent, non-contacting relation, means for supplying liquid material to the smaller terminal of the gap between said rotor and stator, and rotatable impeller faces connected with said rotor and disposed radially of said rotor at the larger end thereof for retarding the discharge of material from said gap.

2. An apparatus for treating liquid material which comprises a conical rotor adapted for rotation at high velocity, a conical stator surrounding said rotor in closely adj acent, non-contact ng co-axial relation, means for supplying liquid material to the smaller terminal of the gap between said rotor and stator. and impeller grooves disposed for rotation at the larger end of said rotor whereby the discharge of material from said gap is retarded.

3. In an apparatus for treating liquid material, the combination which compr ses a conical rotor adapted for rotation at high velocity, a conical stator surrounding said rotor in closely adjacent, non-contacting coaxial relation, means for feeding the liquid material at the smaller terminal of said rotor and a rotatable con cal impeller surface mounted in co-axial relation with'said rotor at the larger terminal thereof for rotation therewith and having its base facing said terminal of the rotor, whereby, upon rotation. said surface will set up motion in the liquid in opposition to the flow of liquid induced by the rotor.

4. In an apparatus for treating liquid material, the combination which comprises a conical rotor, a conical stator surrounding said rotor in closely adjacent, non-contacting co-axial relation, means for feeding the liquid material at the smaller terminal of said rotor and a rotatable conical impeller surface of greater slope than said rotor disposed in coaxial but oppositely sloping relation to said rotor and having its base facing the larger terminal face of said rotor, said surface being rotatable with said rotor whereby, upon rotation, said surface will set up motion in the liquid in opposition to the flow of liquid induced by the rotor.

5. In an apparatus for treating liquid material, the comb nation which comprises, a conical rotor, adapted to be rotated at high peripheral speed, a conical stator surrounding, said rotor in closely adjacent, non-contacting concentric relation, and co-axial conical impeller surface projecting from the larger terminal of said rotor, said surface being provided with radially disposed impeller faces.

6. In an apparatus for treating liquid material, the combination which comprises a conical rotor, a conical stator surrounding said rotor in closely adjacent, non-contacting co-axial relation, and a co-axial conical impeller surface integral with the larger terminal of said rotor and having radially disposed impeller faces terminating at the surface of said rotor.

7. An apparatus for dispersing material, which comprises a conical rotor adapted for rotating at high velocity, a conical stator enclosing said rotor in closely adjacent, noncontacting relation, said rotor and said stator having their. opposing surfaces provided with longitudinally extending alternate channels and teeth, and a conical impeller surface rotatably disposed at the larger terminal of said rotor and having radially extend ng grooves terminating directly in the channels of said rotor surface.

8. An apparatus for dispersing material, which comprises a frusto-conical rotor adapted for rotation at high velocity, a frusto-conical stator surrounding said rotor in closely adjacent, non-contacting relation, said rotor and said stator having their opposing surfaces provided with alternate longitudinal channels and teeth, and a conical surface rotatable with said rotor extending from the larger terminal thereof, said surface having radially extending impeller grooves terminating in the channels of said rotor surface, whereby discharge of material from the gap between said rotor and stator is retarded.

9. In an apparatus for treating liquid ma- .terials the combination which comprises, a.

conical rotor adapted for rotation at high velocity, a. conical stator surrounding said rotor in closely adjacent, noncontacting, coaxial relation defining with said rotor a narrow intervening working gap thru which the liquid material is passed, means for supplying the liquid material to the smaller terminal of said gap whence it will tend to be drawn therethru by the centrifugal pumping action set up upon rotation of the rotor, and rotatable means for exerting a fluid pressure varying with the speed of rotation in opposition to the flow produced by said pumping action to retard the discharge of said liquid material from the gap, the speed of rotation of said last named means being automatically increased or decreased respectively as the rotor speed increases or decreases.

10. In an apparatus for treating liquid material the combination which comprises, a

conical rotor adapted for rctation at high velocity, a casing member completely enclosingsaid rotor member and comprising a conical stator member disposed in concentric relationship to said rotor member defining therewith a narrow intervening gap, said casing having a feed chamber at the smaller end of said rotor and a discharge chamber at the larger end of said rotor, and a member rotatable with said rotor and disposed in said discharge chamber for creating a centrifugal fluid back pressure to retard the discharge of liquid material from the gap between said rotor and stator.

In testimony whereof I aflix my signature.

' PIERCE MASON TRAVIS.

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