US2789800A

US2789800A - Mixing and dispersing devices

Info

Publication number: US2789800A
Application number: US340373A
Authority: US
Inventors: Willems Peter
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-03-12
Filing date: 1953-03-04
Publication date: 1957-04-23
Anticipated expiration: 1974-04-23

Description

April 23, 1957 P. WILLEMS 2,789,800

MIXING AND DISPERSING DEVICES I F'iled March 4, 1953 3 Sheets-Sheet 1 INVENTOR. PETER Mus/-15 April 23, 1957 P. WILLEMS MIXING AND DISPERSING DEVICES 3 Sheets-Sheet 2 Filed March 4, 1953 INVENTOR. Esme l/uuws BY United States Patent MIXING AND DISPERSING DEVICES Peter Willems, Solothurn, Switzerland Application March 4, 1953, Serial No. 340,373

Claims priority, application Switzerland March 12, 1952 29 Claims. (Cl. 259-135) The present invention relates generally to mixing and dispersing devices, and is particularly directed to mixing and dispersing devices which are capable of operating efficiently in mixtures containing relatively large solid particles in a liquid.

In United States Letters Patent, No. 2,619,330, for a Mixing and Dispersing Device, issued to me on November 25, 1952, each of the disclosed devices includes two concentric and axially spaced apart discs defining a chamber therebetween and having circularly arranged, concentric series of teeth extending axially across the space or chamer between the discs. The several series of teeth are arranged in circles of different diameters so that, as the two discs are rotated in opposite directions or one disc is held stationary and the other disc is rotated, the series of teeth pass each other in close proximity to masticate the particles of said material passing radially outward from the chamber or space between the discs. The spaces or interstices between the teeth of the outermost series form the outlets for the dispersed mixture, and the discs are formed with inlet openings therein for entry of the raw mixture into the chamber between the discs. However, the size of the inlet openings limits the maximum dimensions of the solid particles that can be embodied in a mixture acted upon by devices constructed in accordance with my above identified patent. If solid particles larger than the inlet openings are included in the mixture, such large particles become lodged in the inlet openings and obstruct the How of the mixture into the chamber between the discs thereby rendering the device inoperative to mix and disperse the constituents of the mixture.

It is apparent that mixing and dispersing devices capable of homogenizing mixtures which include large solid particles in a liquid will have wide-spread utility in the research and production activities of the chemical, pharmaceutical and other allied fields, as well as in the household in the blending of large solid particles of foods. Accordingly, an object of the present invention is to provide mixing and dispersing devices which are capable of acting upon mixtures containing large solid particles in a most efficient manner to obtain thoroughly homogenized mixtures.

Another object is to provide mixing and dispersing devices of the described character which are relatively compact and simple in construction so that the same may be produced inexpensively and operated for long periods without requiring extensive and costly mainte nance or servicing.

In accordance with the present invention, the above and other objects, features and advantages are obtained by providing a mixing and dispersing device which includes a hollow outer shaft and a central shaft extending axially through the outer shaft. The central and outer shafts are either rotated in opposite directions, or one of the shafts is rotated and the other of the shafts is held stationary. A relatively large diameter disc is carried by the outer shaft and a relatively small diameter disc is carried by the central shaft with only sufficient clearance being provided between the discs to permit free relative rotation of the latter. The large and small discs are provided with concentric, circularly arranged series of axial teeth adjacent the periphery thereof to form two nested baskets opening in the same axial direction and wherein the series of teeth form the side walls of the related baskets. Thus, the open end of the inner basket constitutes an entrance for the mixture which is then pumped radially outward between the relatively rotated teeth, and particles may enter which are as large as the diameter of the mounting circle of the innermost series of teeth. Further, the teeth of the innermost rotated series are preferably formed with knifelike extensions projecting axially or radially beyond the ends of the other teeth to cut up extremely large solid particles as such particles are drawn toward the entrance so that even the diameter of the mounting circle of the innermost series of teeth does not constitute a limitation upon the size of the solid particles that may be dispersed and homogenized in a liquid medium.

In order that the present invention may be fully understood, illustrative embodiments are hereinafter described in detail, merely by way of example, and shown in the accompanying drawings forming a part hereof and wherein:

Fig. 1 is a side elevational view, partly broken away and in section, of a mixing and dispersing device embodying the present invention;

Fig. 2 is a horizontal sectional view taken along the line 22 of Fig. 1;

Fig. 3 is a partial side elevational view, partly broken away and in section, showing another mixing and dispersing device embodying the present invention;

Fig. 4 is a vertical sectional view showing a modification of the mixing and dispersing elements included in the embodiment of Fig. 3;

Fig. ,5 is a view similar to Fig. 4, but showing another modification of the mixing and dispersing elements;

Fig. 6 is a side elevational view, partly broken away and in section, showing still another mixing and dispersing device embodying the present invention;

Fig. 7 is a side elevational view, partly broken away and in section, of still another mixing and dispersing device embodying the present invention; and

Fig. 8 is a horizontal sectional view taken along the line 88 of Fig. 7.

Referring to the drawings in detail, and initially to Figs. 1 and 2 thereof, a mixing and dispersing device is there illustrated and generally identified by the reference numeral 10. The device 10 includes an electric motor 11 which drives a central shaft 12 and a hollow shaft 13 secured to the casing of the motor 11 and extending around the central shaft 12, with the latter being freely rotatable within the stationary outer or hollow shaft. A suitable packing 14 acts as a bearing for the end of the shaft 12 remote from the motor and also prevents the entry of liquid into the interior of the hollow shaft 13. A disc 15 is suitably secured to the free end of the hollow shaft 13 and has a series of radially directed arms 16 extending from the periphery thereof, with the arms 16 terminating in axially directed teeth 17 extending in the direction away from the hollow shaft 13.

Similarly, a disc 18 is secured to the free end of the central shaft 12, for example, by a nut 19, and is spaced axially from the disc 15 only by a distance sufficient to provide an adequate working clearance for rotation of the disc 18 relative to the disc 15. Radial arms 20 extend from the periphery of the disc 18 and terminate in axially directed teeth 21 which extend in the same direction as the teeth 17, with the radial distance from .3 the axis of rotation of the shaft 12 to the outer surface of each of the teeth 21 being slightly less than the radial distance to the inner surface of each of the teeth 17 so that the disc 18 and its circularly arranged series of teeth 21 are free to rotate with the space defined by the disc 15 and its circularly arranged series of teeth 17. Thus, the disc 15 and teeth 17 and the disc 18 and teeth 21 may be considered to define relatively rotatable nested baskets which open in the same axial direction away from the

shafts

12 and 13. The open end of the inner basket constitutes the inlet or entrance 22 for the mixture to be homogenized, and the interstices 23 between the successive teeth 17 of the outer basket constitute the outlets for the homogenized mixture.

It is apparent that the size of the solid particles in a mixture which may be homogenized by a device of the kind shown in Figs. 1 and 2 is limited only by the diametrical distance across the innermost circularly arranged series of teeth 21 defining the entrance 22. When the inner and outer baskets are rotated relative to each other and immersed in a mixture which may contain large solid particles and a liquid, the raw mixture is drawn axially into the inner basket through the entrance 22 and then propelled radially outward past the relatively moving

teeth

17 and 21 which cut and mash the solid particles to provide a uniform and fine dispersion of the solid material in the liquid. Further, when 'a high speed motor is used, as preferred, for causing relative rotation of the baskets the pressure impulses, occurring when each tooth 21 of the inner basket passes each tooth 17 of the outer basket, attain an ultra-sonic frequency and set up corresponding ultra-sonic pressure waves within the body of the mixture. As is well known, such ultrasonic pressure waves cause disintegration of the solid particles in the mixture so that the homogenization of the mixture results from the disintegrating action of the ultra-sonic pressure impulses as well as from the cutting and mashing cooperative action of the inner and outer teeth. The frequency of the pressure impulses generated within the body of the mixture in which the device is immersed depends upon several factors including the relative rotational speed of the inner and outer baskets and the number of teeth in each of the circularly arranged series of teeth provided on the inner and outer baskets. In order to permit varying of the relative rotational speeds of the inner and outer baskets, the motor 11 driving the embodiment of Figs. 1 and 2 is preferably of the variable speed type and its energizing circuit preferably includes a variable resistance, such as, a rheostat (not shown), for controlling the speed of the motor and actuated by a conviently located control knob 24 located on a handle 15 extending from the motor casing. Of course, the relative rotational speed of the inner and outer baskets may be'varied by other means (not shown), such as, for example, a variable speed gear transmission or a stepless transmission interposed between the motor and the shafts driving the baskets.

Thus, the frequency of the pressure impulses generated within the body of the mixture may be accommodated to the requirements of the constituents of the mixture. Further, the amplitude of the pressure impulses may be altered to provide conditions most suitable for homogenization of the materials contained in the mixture, for example, by changing the shapes of the

teeth

17 and 21 or the clearance therebetween in the radial direction. In this connection it is to be understood that the teeth 21 of the inner basket may have any shape which favors the cutting, mashing and impulse generating effectiveness thereof, and they may be rectangular, as shown, or round, fiat, prismatic or arched.

While the mixing and dispersing device illustrated in Figs. 1 and 2 is intended to be portable and to be supported manually at the handle 25 with the inner and outer baskets disposed in a vessel containing the mixture to be homogenized, it is to be understood that the 4- device may be permanently supported in a fixed position or carried by a suitable overhead crane or conveyor for transportation between the various containers in which it is to be employed.

It is also intended that the present invention be applied to mixing and dispersing devices wherein the mixing and dispersing elements, constituting the nested and relatively rotatable baskets, are permanently arranged within the container and the driving motor is installed in a base for the container fro-m which the latter is separable, with a suitable separable coupling being provided between the motor and the shaft carrying the inner basket within the container. Further, while the inner and outer baskets open downwardly in the embodiment of Figs. 1 and 2, in an embodiment of the invention of the kind herein referred to, such baskets may open upwardly, as shown in Fig. 3. In the device illustrated in Fig. 3, a container 26 is provided with a hollow bushing 27 extending fixedly through its bottom wall. A base 28, having a driving motor (not shown) therein, is adapted to support the container 26 and may be formed with pads 29 extending from the top wall of the base and on which the container rests when in its operative position. A shaft 30 is rotatable in the bushing 27, and at its lower end the shaft 30 is formed with a non-circular socket 31 to receive a complementary projection 32 on the upper end of the motor shaft 33 extending cen trally from the base 23. Thus, the socket 31 and projection 32 form an axially separable coupling for transmitting the rotation of the motor shaft on the base 28 to the shaft 30 carried by the container.

The outer or fixed basket of the mixing and dispersing assembly in Fig. 3 includes a disc 15a secured to the bushing 27 and having radiating arms 16a which terminate in upwardly directed axially extending teeth 17a. The inner basket includes a disc 18a secured on the upper end of the shaft 30 above the disc 15a and spaced only slightly from the latter. Arms 20a radiate from the disc 18a and terminate in upwardly directed, axial teeth 21a forming a rotatable, circularly arranged series of teeth within the circularly arranged series of fixed teeth 17a. Thus, the inner and outer baskets open upwardly to define a large entrance 22a for the mixture being homogenized.

In order to adapt the mixing and dispersing devices embodying the present invention for operation on mixtures containing solid particles which dimensionally exceed the distance across the inner circularly arranged series of teeth, these inner teeth may be formed with extensions, in the form of knives, directed axially, or radially and axially, beyond the ends of the outer, circularly arranged series of teeth, so that, as the inner series of teeth is rotated, the knife-like extensions thereof cut-up the large solid particles of the mixture in the area adjacent to the entrance to the inner basket and reduce these large solid particles to fragments which may easily enter into the inner basket. For example, in the embodiment of Fig. 3, the teeth 21a are formed with knife-like extensions 34 which are directed axially beyond the tips of the outer teeth 170. Thus, as the inner basket is rotated with the shaft 30, the knife like extensions 34 of the inner teeth cut a circular swath in the mixture immediately above the entrance 22a. As the large solid particles are drawn down into the entrance 22a, the knife-like extentions 34 cut these large particles into smaller fragments for easy entrance into the inner basket, and these fragments are further cut and mashed between the teeth 17a and 21a during the radial movement of the mixture from the inner basket to provide 'a uniform and fine dispersion of the solid material in the liquid.

The embodiment of Fig. 3 is also adapted for operation under conditions producing pressure impulses ofultrasonic frequency within the body of the mixture so that these pressure impulses contribute to the homogenizing action, in the manner previouslydescribed in connection with, the embodiment of Figs. 1 and 2.

:While the embodiment of Figs. 1 and 2 includes four teeth 21, in the inner ring or circularly arranged series, and eight teeth 17 in the outer ring or series, the numbers of teeth in the several rings or series may be varied to obtainthe effect that is most desirable for the particular mixture being worked. Thus, where the solid particles are most easily dispersed-in a solvent by. breaking up the large solid particles and causing intense friction between the solid particles and the solvent, for example, in dispersing latex or a resin in a suitable organic solvent, it may be,;desir'abl-e to employas few as two teeth in each of the inner and outerseries of teeth, with the speed of relative rotation of the teeth being selected to provide the rapid circulation of the liquid solvent necessary for achieving the desired intense friction between the solvent and the particles broken 'up by the coacting teeth. By way of illustrating some of the possible variations in the numbers and configurations of the teeth making-up the inner and outer rings or series, reference is made to the embodiments of Figs. 3, 4 and 5. In Fig. 3, the inner and outer rings include four teeth, while in' each of the embodiments shown in Figs. 4 and 5, the inner and outer series of teeth are each made up of only two teeth. Of course, it is to be understood that the numbers of teeth included in the embodiments of Figs. 3, 4 and 5 may be increased or otherwise varied as the operating conditions, including the constituents of the mixture, may dictate.

In Fig. 4, which shows a modification of the configuration of the teeth of inner and outer baskets for use in an embodiment of the kind illustrated in Fig. 3, the inner teeth 21b and the outer teeth 1717 are inclined away from the axis of rotation in the direction toward the entrance 22b so that the diameter of the entrance is increased without any increase inv the size of a downwardly tapering container, for example, a container of the kind shown in Fig. 3. Further, the knife-like extensions 34b on the teeth 215, or at least certain of these extensions, may be directed radially outward, as shown in Fig. 4, so that such radial knife-like extensions act to cut-up the large particlesboth above and to the side of the entrance 22b.

In the-modification illustrated in Fig. 5, the inner and outer teeth 21c and 17c, respectively, are once again parallel to the axis of rotation of the inner basket, while the knife-like extensions 340 on the inner teeth are inclined relative to the axis of. rotation with certain of theextensions 34c being directed upwardly and others being directed downwardly. Thus, the knife-like extensions 34c operate to cut up the large particles of the mixture, as such particles move towards the entrance 22c from above, and also in the portions of the container extending around the outer series of. teeth.

In dissolving solid particles in a suitable liquid solvent, it is sometimes desirable to initially keep the large solid particles out of actual contact with the teeth of the mixing and dispersing elements .until preliminary dissolution of such particles has been accomplished merely by causing rapid'flow of the solvent around the particles. The embodiment of the invention illustrated in Fig. 6 is particularly adapted for the above purpose and includes a container 26d having a hollow bushing 27d fixed in the bottom thereof and seated on a base 28d which contains the driving motor '(not shown). The motor shaft 33d extends rotatably through-the bushing 27d, and the disc 1821 of the inner, rotatable basket is fixed to the upper end of the motor shaft within the container 26:! and supports the inner circularly arranged series of teeth 21d. The disc 15d of the outer basket is fixed on the bushing 27d between the disc 13d and the bottom of the container and supports the outer circularly arranged series of teeth 17d.

In order to support the solid particles to be dissolved, a perforated platform or sieve 35 is mounted in the container 26d'above the nested, relatively rotatable baskets; and the platform 35 is dimensioned so that the peripherythereof is spaced from the side wall of the container to leave an annular space 36 through which the liquid solvent can flow. The perforated platform or sieve 35 is preferably formed with a cylindrical depending collar 37 which, at its lower edge, is formed with separated resilient fingers 38 to grip the upper ends of the stationary fingers In addition to the collar 37 described above, the perforated platform 35 is preferably held in place by brackets 3% secured to the side wall of the container 26d. Finally, the container 26d is preferably formed with a pouring spout 40 extending from the bottom thereof and closed by a removable cap 41.

In employing the device of Fig. 6 for dissolving solid particles in a solvent, the solid particles 42 are placed on the perforated platform 35 and the container 26d is supplied with the liquid solvent. When the inner teeth 21d are rotated relative to the outer teeth 17d, the liquid solvent is drawn downwardly through the solid particles 42 and the perforated platform 35 into the interior of the collar 37 and the inner basket. The centrifugal action then causes the liquid solvent to flow radially outward between the relatively rotated inner and outer series of teeth and then upwardly through the annular space 36. Thus, a continuous circulation of the liquid solvent is produced to cause the solvent to flow repeatedly through the solid particles on the platform 35. When the particles have been dissolved sufficieutly, so that the dimensions thereof are reduced to less than the size of the openings in the perforated platform 35, the small particles will flow with the solvent into the collar 37 and the inner baskets to be exposed to the cutting and mashing action of the relatively rotated teeth 17d and 21d. As the solvent is recirculated, the concentration of the dissolved solid material therein will be progressively increased and the cap 41 may be removed, during the operation of the device, to draw-off the mixture of the desired richness. By replenishing the supply of solid particles and solvent during the operation of the device, at a rate which corresponds to the withdrawal of the dispsersed mixture through the spout 40, the device of Fig. 6 may be used in a continuous operation. Since the circulation of the liquid within the container, as indicated by the arrows A, tends to displace the solid particles toward the center of the perforated platform, there is no danger that the solid particles, added during continuous operation, will fall through the annular space 36.

Since the dissolution of the solid particles on the platform 35 is enhanced by an increased rate of flow of the solvent through the platform, it is preferable to extend the teeth 21d radially inward in the form of paddles 43 to improve the performance of the inner basket as a centrifugal pump.

While the previously described embodiments of the invention have each included one inner circularly arranged series of teeth and one outer circularly arranged series of teeth, it is to be understood that the present invention may be applied to mixing and dispersing devices which include more than two concentric circularly arranged series of teeth. Thus, referring to Figs. 7 and 8, an embodiment of the invention is there shown which includes a hollow shaft 44 supporting a hub 45 at its lower en Arms 46 radiate outwardly and downwardly from the hub 45 and support a continuous circular ring 47. An inner, circularly arranged series of teeth 48 and an outer, concentric, circularly arranged series of teeth 49 depend from the ring 47, with the series of teeth 48 suitable anti-friction bearing 51. A packing or gland 52 seals the space between the hub 45 and the central shaft 50 to prevent the entrance of liquid into the space V between the shafts 44 and 50. A disc 53 is secured on the lower end of the central shaft 50 and has arms 54 radiating therefrom and supporting a ring 55 at their outer ends within the ring 47. A circularly arranged series of axial teeth 56 depend from the ring 55 and carry a ring 57 at their lower ends. The ring 57 extends radially outward below the teeth 48 and carries a circularly arranged series of upwardly directed axial teeth 58 which project into the annular space between the

teeth

48 and 49.

When the shafts 44 and 50 are rotated relative to each other, for example, by holding the hollow shaft 44 stationary while rotating the central shaft 50, the circularly arranged series of

teeth

56 and 58 rotate relative to the series of

teeth

48 and 49, and the mixture to be homogenized is drawn axially upward through the entrance 59, defined by the inner edge of the ring 59, and then propelled centrifugally in the radially outward direction, as indicated by the arrows B on Fig. 7. As the mixture passes radially outward, the solid particles of the mixture are cut and mashed between the

teeth

56 and 48, then between the

teeth

48 and 58 and finally between the

teeth

58 and 49 before passing through the outlet openings 60 (Fig. 8) defined between the teeth 49. Thus, the cutting and mashing action is repeated during a single passage of the mixture through the device.

While the main flow of the mixture is along the paths indicated by the arrows B (Fig. 7), the arms 54 supporting the ring 55 define openings or ports 61 there between through which a supplemental flow, indicated by the arrows C, can take place. In order to avoid clogging of the ports 61 by large solid particles, it is advantageous to successively speed-up and slow-down the motor (not shown) which drives the central shaft 50, and this may be accomplished either by suitable manual control of the motor or by automatic devices which are not shown and form no part of the present invention.

Even though the ports 61 for the supplemental flow may become clogged, the large entrance 59 will ensure the reliable operation of the mixing and dispersing device with mixtures having large solid particles. However, if the mixture to be worked has particles which are larger than the entrance 59, knife elements 62 are preferably secured to or formed integral with certain of the teeth 56 forming the innermost series and extend axially beyond the ring 57 to cut up these large particles into fragments which can pass easily through the entrance 59. I

It is apparent that all of the above described embodiments of the invention include two nested and relatively rotatable basket-like elements which open axially in the same direction and have circularly arranged series of teeth forming the side walls of the basket-like elements to cause a flow of the mixture axially into the inner basket-like element through the open end of the latter and then radially outward between the series of teeth so that the latter cut and mash the solid particles for thorough dispersion in the mixture. Since the open end of the inner basket is unobstructed, the devices may be used in homogenizing mixtures having large solid particles.

While several specific embodiments of the invention have been shown in the drawings and described in detail, it is to be understood that the invention is not limited to these precise embodiments and that many changes and modifications, which are obvious to one skilled in the art, ma be made therein without departing from the a scope of the invention as defined in the appended claims.

If required, instead of having teeth the outermost basket may have radial passages of any shape and size. So the basket could, as an example, form a sieve-like cylinder.

What I claim is:

1. A mixing and dispersing device comprising a hollow member, 'a shaft extending axially through said member, nest ed inner and outer basket-like elements, said inner aiid outer element being secured to an end of the central shaft and hollow member, respectively, each or said ele ments including circularly and sp'acedly arranged teeth, the teeth of both elements extending beyond said ends of the hollow member and shaft, the teeth of the inner element being surrounded by the teeth of the outer element in close radial proximity, means for rotating the central shaft and the inner element at a relatively high speed, the inner element when driven being adapted, with both elements immersed in a mixture to be treated, to exert a suction action upon the mixture, thereby exposing the mixture as it is drawn in to a cutting attack of the cooperating teeth of both elements, the relative rotation of the elements also propelling drawn in mixture portions outwardly through the teeth of the inner and outer elements.

2. in the device according to claim 1, each of the two elements being provided with at least a single series of circularly and spacedly arranged teeth, the teeth of both elements being concentrically arranged.

3, In the device according to claim 2, each of the elements including a series of teeth at the periphery thereof.

4. In the device according to claim 1, the elements having their teeth at portions remote from the center to offer the largest possible freely accessible suction opening.

5. In the device according to claim 1, at least some of the teeth of the inner element extending beyond the teeth of the outer element.

6. In the device according to claim 5, said extensions being directed outwardly away from the axis of rotation of said shaft.

7. The device according to claim 1, wherein said outer basket-like element includes a disc member secured to said hollow member and having arms radiating from the eriphery thereof with said teeth of the outer basket-like element extending from the terminating ends of said arms, and wherein said inner basket-like element includes a disc member secured to said shaft adjacent the first mentioned disc member and having arms radiating from its periphery with the last mentioned arms terminating radially inward of said arms of the outer basket-like element, said teeth of the inner basket-like element extending from the terminating ends of said arms of the inner basket-like element.

8. In the device according to claim 1, a housing, said means including a motor mounted in the housing and having a drive shaft connected to the first named shaft to rotate the latter, said hollow member being fixed to the motor housing so that the outer basket-like element is held stationary while the inner basket-like element is rotated.

9. In the device according to claim 1, the teeth of both elements extending parallel to the axis of rotation of the inner element, all the teeth terminating in the same radial plane.

10. The device according to claim 1, wherein said inner basket-like element includes a plurality of concentric and radially spaced, circularly arranged series of sub stantially axially directed teeth, and said outer basketlike element includes a plurality of concentric and radially spaced, circularly arranged series of substantially axially directed teeth, said series of teeth of said outer basket-like element being alternated radially with said series of teeth of said inner basket-like element.

1.1. The device according to claim 10, wherein one of said series of teeth of said inner basket-like element is disposed radially innermost.

12. The device according to claim 1, wherein said outer basket-like element includes a hub fixed on said hollow member and having arms radiating therefrom, a ring carried by the outer ends of said arms and having two concentric and radially spaced apart circularly arranged series of teeth extending from said ring in the direction away from said hollow member, and wherein said inner basket-like element includes a disc secured to said shaft and having arms radiating from the periphery thereof, a first ring carried by the ends of said arms radiating from the disc and fitting rotatably within said ring of the outer basket-like element, a first circularly arranged series of teeth extending axially from said first ring radially inward of the innermost series of teeth of said outer basket-like element, a second ring carried by said first series of teeth in axially spaced relationship to said first ring and extending radially under said ring of the outer basket-like element, and a second circularly arranged series of teeth extending axially from said second ring between said two concentric and radially spaced apart circularly arranged series of teeth of the outer basket-like element.

'13. The device according to claim 1, comprising a container, a hollow bushing extending fixedly through the bottom of the container and constituting said hollow member, a first and a second mixing and dispersing element constituting said outer and inner basket-like element, respectively, the teeth of said first and second elements extending substantially axially and concentric with said shaft, both the first and the second element including means supporting the respective teeth at their lower ends so that the upper ends of the teeth of each element define an upwardly open circular space and the teeth of the second element also define an unobstructed axial entrance for the mixture to be treated.

14. The device according to claim 13, wherein said means supporting the teeth of the first element includes a disc fixed on the upper end of said bushing, and said means supporting the teeth of the second element includes a disc fixed on the upper end of said shaft immedi ately above the first mentioned disc.

15. The device according to claim 13, further com prising a perforated platform in said container above said nested mixing and dispersing elements, said perforated platform being dimensioned to provide a substantial clearance between its periphery and the inner surface of the container side wall so that, when solid particles are placed on said platform, with a liquid solvent in the container, rotation of said second element will cause circulation of the solvent downwardly through the central portion of said platform and upwardly around the periphery of the platform.

16. The device according to claim 15, further including a cylindrical imperforate collar depending from said platform and engaging said teeth of the first element to define a channel for directing the flow of the circulated solvent downwardly into said upwardly opening entrance.

17. The device according to claim 13, wherein said container, at least in the lower portion thereof, tapers downwardly, and wherein said circularly arranged series of teeth diverge upwardly away from the axis of rotation of said shaft for providing a larger entrance opening.

18. The device according to claim 13, wherein said teeth of the second mixing and dispersing element are formed with longitudinal knife-like extensions projecting beyond the ends of said teeth of the first mixing and dispersing element for breaking-up large solid particles of a mixture before such particles arrive at said entrance.

19. The device according to claim 18, wherein certain of said knife-like extensions extend axially beyond said teeth of said first element and other of said knife-like extensions extend radially outward beyond said teeth of the first element.

20. The device according to claim 13, wherein at least certain of said teeth of said second mixing and dispersing element are formed with flattened radial projections extending inwardly therefrom to act as impeller blades when said second element is rotated for intensifying the centrifugal pumping action on a mixture in the container.

References Cited in the file of this patent UNITED STATES PATENTS