US3410535A - Mixing device - Google Patents

Description

L. L. BALASSA MIXING DEVICE Nov. 12 1968 3 Sheets-Sheet Filed Jan. 23, 1967 FIG. 2

FIG. 3

INVENTOR LESLIE L. BALASSA BY 4% ATTORNEYS L. L. BALASSA MIXING DEVICE Nov. 12, 1968 3 Sheets-Sheet 2 Filed Jan. 25, 1967 B; fin Mm 9 A a 0 R mm N B VL 7 .I 9 3 L 8 G a L I o F.

ATTORNEYS Nov. 12, 1968 BALASSA 3,410,535

MIXING DEVICE Filed Jan. 23,- 1967 3 Sheets-Sheet 5 FIG. 8

FIG. 9

INVENTOR LESLIE L, BALASSA ATTORNEYS United States Patent O 3,410,535 MIXING DEVICE Leslie L. Balassa, Creighton Lane, Scarborough, N.Y. 10582 Filed Jan. 23, 1967, Ser. No. 611,034 18 Claims. (Cl. 259-95) ABSTRACT OF THE DISCLOSURE This disclosure describes a reversible mixing device of the turbine type in which the mixing action is produced by the coaction of a revolving rotor element and a fixed stator element mounted below and in hydraulic shear relation with the rotor element, and in which the flow of the material to be mixed is normally in downward direction. This mixing device is suitable for many purposes such as mixing, blending, homogenizing, dispersing and pumping.

Background the invention In general, turbine type mixing devices are well known in the prior art, but have been predominantly of the upward-flow variety. Examples of such mixing devices are shown, for example, in U.S. Patents Nos. 2,801,083, 3,154,296 and 3,163, 405, issued to the present inventor. Such mixing devices are suitable for use either in the laboratory or in production for the preparation of emulsions vegetable gum and starch dispersions, and for the dispersion of finely divided solids in liquids, such as pigment dispersions.

In the normal operation of the prior art turbine type mixers, the rotor element, which generally comprises a plurality of angled blades, impels or forces the material to be mixed upward through the stator element, which generally comprises a plurality of vanes oriented so as to constrain the material to flow in a substantially axial direction. Because of the close spacing between the blades of the rotor and the vanes of the stator, the coaction of these elements causes hydraulic shearing and consequent homogenization of the material to be mixed. By decreasing the spacing between the rotor and stator, their homogenizing and dispersing action can be increased. Conversely, by increasing the spacing between these elements, their pumping, blending, and mixing action can be increased with a resulting increase in the processing capacity of the mixing device. The use of a sleeve surrounding the rotor and stator so as to form a closed turbine promotes the axial flow of the material and enhances the homogenizing and dispersing action of the device. Removal of the sleeve and operation of the mixing device as an open turbine enhances the mixing action by causing the rotation of the entire mass of the material in the mixing vessel, thus creating a vortex.

Although the prior art upward-flow turbine type mixing devices possess many advantages, they are, nevertheless, subject to certain problems. For example, in the upward-flow device of the prior art, dead spaces are likely to occur immediately below the mixing head and around the edges of the bottom of the mixing vessel. The material in such dead spaces would tend to remain stationary rather than flow through the mixing head to be uniformly homogenized with rest of the material. In order to insure the circulation of the material in such dead spots it was necessary to periodically suspend the homogenizing action and reverse the direction of flow of the material by reversing the direction of rotation of the rotor.

Another problem of the prior art upward-flow turbine type mixing devices is the ditficulty of removing or replacing the sleeve so as to convert the device from a ice closed turbine configuration to an open turbine configuration or vice versa. In the prior art upward-flow devices it was generally necessary to remove the sleeve in a downward direction. This could not be accomplished without removing the mixing head from the mixing vessel. Alternatively, in order to provide for conversion between the open and closed turbine configurations without removing the mixing head from the material to be mixed, it was necessary to resort to a rather complicated arrangement of the type shown in the above-mentioned US. Patent No. 3,163,405.

Still another problem of the prior art turbine type mixing devices involves the difficulty of dispersing ingredients added to the material to be mixed. If such ingredients were simply scattered on the surface of the material to be mixed, the upward flow of material created by the mixing head would cause the added ingredients to be carried outward to the sidewalls of the mixing vessel, downward along the sides of the vessel, and then inward along the bottom of the vessel to the mixing head. This flow pattern permitted the added ingredients to stick to the side walls or bottom of the mixing vessel or become trapped in one of the above-mentioned dead spaces. In order to avoid this problem of the prior art devices, and provide for the immediate dispersion of added ingredients, it was necessary to provide some means such as shown in the above-mentioned US. Patent No. 2,801,083 for introducing the ingredients below the rotor element so that they would be immediately carried upward and dispersed by the coaction of the rotor blades and the stator vanes.

Summary of the invention It is therefore an object of this invention -to provide an improved mixing device which obviates or overcomes the problems of the prior art upward-flow turbine type mixing devices.

More particularly, it is an object of this invention to provide an improved turbine type mixing device which does not permit dead spaces to occur in the mixing vessel.

It is also an object of this invention to provide an improved mixing device which may be easily converted from the open turbine to the closed turbine configuration and vice versa.

It is still another object of this invention to provide an improved turbine type mixing device by means of which added ingredients are immediately dispersed in the material to be mixed.

In accordance with the above and other objects, this invention provides a mixing device of the turbine type wherein the stator is located below the rotor and wherein the normal flow of the material to be mixed is in a downward direction through the combination of rotor and sator. The rotor is mounted at the end of a shaft which projects downward into the mixing vessel from a drive motor which is mounted above the vessel. The stator may be either mounted on the bottom of the mixing vessel or suspended from the drive motor. In either case, means are provided for adjusting the spacing between the rotor and stator. In order to provide closed turbine operation, there is provided a removable sleeve which surrounds the rotor and stator, and which may be supported at its lower end by suitable projections from the lower end of the stator. In order to provide an open turbine operation, the sleeve may be simply drawn upward by means of a control rod or handle attached thereto without removing the mixing head from the material to be mixed. Optionally, there may be provided a second stator located above the rotor and enclosed within the sleeve during closed turbine operation. The coaction of the second stator with the rotor would provide an additional measure of homogenization, particularly when the flow of material is reversed. The angles of the vanes of either or both stators may be adjusted in order to provide a slight, controlled vortex motion to the entire mass of the material to be mixed, thus enhancing the overall effectiveness of the mixin device.

The downward-flow mixing device of the present invention possesses an advantage over the prior art devices with regard to the processing of extremely viscous materials in that the feeding of the material through the mixing head is aided by gravitational force in the downward-flow device.

Another advantage of the improved mixing device of the present invention is that in the configuration including a second stator, the vanes of the second stator serve to block lumps of material thus protecting the rotor from damage.

Other objects and advantages of the present invention will be apparent from the following detailed description and accompanying drawings which set forth the principles of the invention and, by way of example, the best modes contemplated for applying those principles.

Brief description of the drawings FIG. 1 shows a mixing device embodying the present invention.

FIG. 2 is a detailed cross-sectional view of the mixing head of the mixing device shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along the line 3-3 of the rotor of the mixing head shown in FIG. 2.

FIG. 4 is a cross-sectional view taken along the line 44 of the lower stator of the mixing head shown in FIG. 2.

FIG. 5 is a cross-sectional view taken along the line 55 of the upper stator of the mixing head shown in FIG. 2.

FIG. 6 is a view of the mixing head shown in Fig. 2 with the sleve and upper stator removed for open turbine operation.

FIG. 7 is a cross-sectional view of a modified mixing head embodying the principles of the invention.

FIG. 8 is a cross-sectional view of another modified mixing head embodying the principles of the present invention.

FIG. 9 is a cross-sectional view of the longitudinally adjustable coupling connecting the motor shaft and the mixer saft of the mixing device shown in FIG. 1.

Description of the preferred embodiment Referring to the drawings for a more detailed description of the structure and operation of the mixing device of the present invention, FIG. 1 shows a mixing machine comprising a motor 10 mounted in an upright position with its lower end attached to a motor support 11 having a tubular rod 12 extending horizontally therefrom. Rod 12 is secured in a bracket 13 which is adapted to be clamped to a fixed vertical post 14 extending upwardly from a bifurcated pedestal 15. Tubular rod 12 may also serve as a conduit through which cooling air may reach the motor 10 for ventilation purposes. Tubular guide rods 16 are secured to and project downward from motor support 11. The lower ends of guide rods 1'6 are secured to and serve to support mixing head 20 relatively remote from motor 10 and in vertical alignment therewith. Mixer shaft 26 is connected to the drive shaft of motor 10 by means of adjustable coupling device 70 which enables the position of mixer shaft 26 to be vertically adjusted. At the lower end of mixer shaft 20, there is mounted a rotor which, in FIG. 1, is concealed by sleeve 60 of mix ing head 20.

By sliding bracket 13 up or down post 14, motor support 11 together with motor 10 and mixing head 20 may be raised or lowered with respect to mixing vessel 21 shown in dotted lines in FIG. 1. In its operative position,

mixing head 20 extends into mixin vessel 21 beneath the level indicated by dotted line 22 of the material to be mixed.

Referring now to FIG. 2 for a more detailed description of the preferred embodiment of the mixing head of the present invention, there is shown a cross-sectional view of mixing head 20 shown in FIG. 1. Basically, mixing head 20 comprises a rotor 40 mounted on mixer shaft 26, a lower stator 30 journaled on mixer shaft 26, an upper stator 50 also journaled on mixer shaft 26, and a cylindrical sleeve 60 which normally encloses rotor 40 and stators 30 and 50.

Rotor 40 is the heart of mixing head 20. It is preferably made of stainless steel and precision engineered, tempered and balanced for high speed operation. Rotor 40 is mounted on mixer shaft 26 by means of nut 41 which acts against shoulder 42 of shaft 26.

As is more clearly shown in FIG. 3 which is a cross-section taken along the line 3-3 of FIG. 2, rotor 40 consists of a plurality of fiat electric-fan-type blades 43 which radiate outwardly from a central disc 44. Although the preferred form of rotor 40 has five blades 43, there may be more or fewer blades within the scope and spirit of the invention. Blades 43 have a pitch between 10 and degrees, their trailing edges 46 being more remote from motor 10, shown in FIG. 1, than are leading edges 47. In rotation, leading edges 47 and trailing edges 46 of blades 43 produce conical surfaces of revolution arranged in back-to-back relation co-axially with mixer shaft 26.

Lower stator 30 is secured to guide rods 16 by means of nuts 31 which threadedly engage the tips of guide rods 16 which extend through suitable holes 32 in projections 33 which extend horizontally from stator 30 for that purpose. The lower end of mixer shaft 26 is slidably journaled in hub 34 of stator 30. If desired, hub 34 of stator 30 may be provided with an anti-friction sleeve 37 for the purpose of facilitating the rotation of mixer shaft 26 and to reduce problems due to the heat resulting from the friction of rotation. In addition, hub 34 of the stator 30 is provided with an enlarged recess in order to accommodate retaining nut 41 of rotor 40. The journaling of the lower end of mixer shaft 26 in hub 34 of stator 30 serves to stabilize rotor during high-speed operation.

As shown in FIG. 4, stator 30 comprises a plurality of vanes 35 and 36 radiating from a central hub 34. Although there are six vanes 35 and 36 in the preferred form of stator 30, it will be understood that a greater or lesser number of vanes may be employed within the scope and spirit of the invention. The lower ends of the three vanes 35 are extended horizontally to form projections 33 having holes therein for receiving the threaded tips of guide rods 16 as explained above.

The fiat upper surfaces 35' and 36 of vanes 35 and 36 are inclined downwardly and outwardly at an angle between 10 and 35 degrees to the horizontal. As shown in FIG. 2, this angle conforms to the angle of the trailing edges 46 of blades 43 of rotor 40. As a result of the close relation between trailing edges 46 and upper surfaces 35' and 36, the co-action of rotor 40 with stator 30 produces a hydraulic shearing of the material to be mixed. More particularly, the configuration of blades 43 is such that a wedge-like area is formed between trailing edges 46 and upper surfaces 35' and 36'. This area diminishes progressively and rapidly as the whirling of rotor 40 causes trailing edges 46 to sweep across surfaces 35 and 36 thereby producing a smooth and effective shearing action.

As shown in FIG. 5, upper stator 50 comprises a plurality of vanes 51 radiating from hub 52, Hub 52 is journaled on mixer shaft 26 as shown in FIG. 2. Although there are four vanes in the preferred form of stator 50, it will be understood that a greater or lesser number of vanes may be employed within the spirit and scope of the invention. The lower surfaces 51 of vanes 51 are inclined upwardly and outwardly at an angle at approximately degrees to the horizontal. This angl conforms to the angle of the leading edges 47 of blades 43 of rotor 40. If desired, the lower surfaces 51' of vanes 51 may be flat so as to provide a hydraulic shearing action with edges 47 of blades 43 especially when the direction of rotation of rotor 40 is reversed. Alternatively, the upper or leading edges 54 of vanes 51 may be rounded and the lower or trailing edges 51 may be tapered so as to streamline vanes 51 in order to reduce the resistance of vanes 51 to the flow of the material through mixing head 20. In order to further reduce the resistance of vanes 51 to the flow of material through mixing head vanes 51 may be slightly canted so as to conform to the direction of rotation of the material to be mixed as imparted by the action of rotor 40. In addition, to reducing the resistance to the flow of material, the canting of vanes 51 promotes a slight rotary motion of the entire mass of the material within mixing vessel 21 shown in FIG. 1, thus enhancing the overall mixing action of the apparatus. On the other hand, in some applications, a vertical orientation of vanes 51 or perhaps even a slight canting in the opposite direction may be preferred in order to prevent the rotation of the mass of material to be mixed and thus prevent the possible formation of a vortex with the consequent and, in some applications, disadvantageous, entrainment of air into the mixture.

In the preferred form of the mixing machine of the present invention, the outer extremities of vanes 51 of stator 50 are rigidly connected, as by welding, to the inner surface of cylindrical sleeve 60 the lower end of which is supported by the horizontal projections 33 of vanes 35. Sleeve 60 closely encloses rotor 40 and stators and 50 thus causing mixing head 20 to operate as a closed turbine. In this manner, sleeve 60 promotes the smooth axial flow of the material to be mixed and prevents the action of rotor from imparting vortex motion to the mass of material in the mixing vessel. :It is noted that during the normal operation of the machine, the downward flow of the material to be mixed forces sleeve 60 firmly into contact with projections 33 thereby obviating the need for any locking devices in order to maintain sleeve 60 in its correct operational position.

In order to convert the mixing machine of FIG. 1 to open turbine operation, all that is necessary is to draw sleeve 60 upward by means of handle or control rod 91 which is attached thereto and which extends upward adjacent to motor 10 for easy access by the operator. The vertical motion of sleeve 60 is guided by means of guide rings 61 which project from the outer surface of sleeve 60 and engage guide rods 16. FIG. 6 shows the mixing head 20 of FIG. 2 open during turbine operation.

It is noted that because of the construction of the mixing machine of the present invention, sleeve 60 may be drawn upward without otherwise moving mixing head 20 from its position in mixing vessel 21. Further, it is noted that sleeve 60 may be lowered again into position by control rod 91 and firmly seated against projections 33 by means of the downward flow action described above similarly without moving mixing head 20 from its position. Hence, it is seen that the mixing machine of the present invention may be converted from closed turbine to open turbine operation and vice-versa without removing the mixing head from the mixing vessel. This feature provides a substantial advantage over the prior art upward flow mixing machines which had to be withdrawn from the mixing vessel in order to permit the removal of the sleeve which was commonly fastened in position by means of bayonet locks or the like and was removable only in a downward direction.

FIG. 7 shows a modified form of the mixing machine of the present invention. More particularly, FIG. 7 shows a modified form of the mixing head 20 shown in FIG. 2 in which guide rods 16 have been eliminated and stator is supported instead of means of legs 39 which rest on are rigidly connected to the bottom of mixing vessel 21. This arrangement simplifies somewhat the disassembly and cleaning of the mixing head.

FIG. 8 shows another modification of the mixing machine of the present invention. More particularly, FIG. 8 shows a modification of the mixing head 20 of FIG. 2 wherein stator 30 is located above and stator 50 below rotor 40. As in FIG. 2, stators 30 and 50 are journa'led on mixer shaft 26. Stator 30 is supported by guide rods 16 to which it is connected by any suitable means such as, for example, by means of recesses tapped into vanes 35 of stator 30 which threadedly engage the tips of guide rods 16. But, in the modification of FIG. 8, sleeve 60 and stator 50 are locked into position for closed turbine operation by means of bayonet locks comprising slots 63 in sleeve 60 and lugs 38 projecting from vanes 35 of stator 30. Hence, it is noted that in the modification of FIG. 8, sleeve 60 must be removed in a downward direction in order to convert the mixing machine from closed turbine to open turbine operation.

FIG. 9 is an enlarged fragmentary view, partly in section, of the adjustable coupling device 70 shown in FIG. 1. Adjustable coupling device 70 permits mixer shaft 26 to be adjusted in an axial direction thereby providing adjustment of the clearance between the trailing edges 46 of rotor blades 43 and the cooperating surfaces 35' and 36 of stator vanes 35 and 36. Decreasing the clearance between these operating elements serves to increase the homogenizing and dispersing action of the mixer. Increasing the clearance between the operating elements serves to increase the pumping, blending, and mixing action as well as the capacity of the machine. Referring to FIG. 9, drive shaft 25 of motor 10 is shown in vertical alignment with mixer shaft 26. The driving force of motor 10 is transmitted from drive shaft 25 to mixer shaft 26 by means of crenelated coupling consisting of sleeve 27, the opposite ends of which enclose the opposed ends of shafts 25 and 26. In the embodiment shown in FIG. 7, the crenelation consists of diametrically opposed pairs of slots 28 and 29 formed in the ends of sleeve 27. Pairs of slots 28 and 29 cooperate with pins 28 and 29' which project diametrically outward from the sides of the ends of shafts 25 and 26. Slots 28 and 29 extend sufficiently far in the axial direction to allow the axial adjustment of mixer shaft 26 as described below.

The mechanism for raising or lowering mixer shaft 26 and, consequently changing the relative spacing of the rotor end of the stator, includes cylindrical adjusting unit 70. The upper end of adjusting unit 70 is externally threaded to engage internal threads formed within the lower end of motor support 11. The upper end of unit 70 is internally formed to provide the outer race 73 of a ball bearing the other race 74 of which is tightly fitted to the upper end of mixer shaft 26 which, for this purpose, is reduced in diameter to form a shoulder 75 against which the inner race 74 is seated. A series of balls 75' between the races provide an anti-friction bearing for this end of shaft 26. The outer race of this hearing need not necessarily be an integral part of unit 70 since the bearing may instead be a conventional one mounted in the unit as an insert.

The coupling sleeve 27 in FIG. 7 is positioned above race member 74, and its upper end is closed by a cover through which shaft 25 passes. A spring 82 surrounds shaft 25 between the cover and a shoulder 8-3 so as to not only keep the cover seated as a grease shield, but to urge the sleeve downwardly against race member 74. The unit 70 may be conveniently turned by engaging a hole 76 in its lower end, while at the same time holding shaft 26 against rotation by inserting a tool in a hole 77 through shaft 26. For example, if unit 70 is turned to ride the threads upwardly it will rise and carry the ball races with it lifting sleeve 27 and, since shaft 25 is in a fixed position its pin 28 will also remain stationary, so that sleeve 27 in rising will compress spring 82 because of the aforesaid clearances between pin 28 and associated slots 28. Shaft 26 will thus be moved upwardly, due to its connection to race 74, resulting in decreasing the distance separating the opposed ends of the shafts and lifting the rotor 40 with respect to the stator 30. In this manner, or by reversing the procedure, a close or coarser relationship of the stator and rotor parts of the operating head may be accomplished to selectively obtain a fine or coarser granulation of the particles in suspension in the emulsion in container 21.

Although the preferred form of the present downward flow mixer has been described with reference to both closed turbine and open turbine operation, it will be recognized that other changes may be made in the operational structure of mixing head 20 without departing from the principles of the invention. For example, the present invention contemplates a mixing machine having a mixing head similar to the mixing head 20 shown in FIG. 2 except that upper stator 50 is omitted.

Further, it is noted that because the mixing machine of the present invention combines an upper and a lower stator with an axially adjustable rotor, it is particularly Well suited to reversible operation. When the present mixing machine is operated in the downward flow direction, there is a hydraulic shearing action between the rotor and the lower stator. When the machine is operated in the upward flow direction, there is a hydraulic shearing action between the rotor and the upper stator. In both cases the shearing action, and consequent homogenization of the material to be mixed, is determined by the axial position of the rotor under control of the adjustable coupling device which connects the motor shaft to the mixer shaft.

As mentioned above, the downward flow mixing machine of the present invention possesses an advantage over the prior art upward flow machines in that ingredients added to the mixture are carried toward the center of the mixing vessel and then downward through the mixing head for rapid dispersion into the mixture. If desired, there might be provided a small disc mounted on the mixer shaft immediately above the mixing head in order to break up lumps of material before they reach the mixing head thus avoiding possible damage to the rotor. Such a disc may have a diameter two or three times the diameter of the mixer shaft but much smaller than the diameter of the rotor. The effectiveness of such a disc may be enhanced by providing it with small vanes or wavy edges.

Additionally, in order to achieve a more immedite dispersion of added ingredients there might be provided a simple pipe or conduit for introducing ingredients directly above the mixing head or the rotor itself. Such a conduit might extend downward parallel to the mixer shaft from a suitable position adjacent the motor 10 shown in FIG. 1 to a position immediately above the mixing head.

Alternatively, ingredients may be introduced into the mixture by means of a hollow mixer shaft having a plurality of exit ports spaced about the periphery of the shaft immediately above the mixing head for the rotor itself. Such an arrangementis described in conjunction with an upward flow mixer in US. Patent No. 2,891,083, issued July 30, 1957 to the present inventor.

Although the preferred embodiment and several modifications of he mixing machine of the present invention have been described as having unitary cylindrical sleeves 60 which must be removed in an axial direction, it will be understood that the principles of the present invention embrace other types of sleeves. For example, a sleeve comprising several segments adapted to swing outward in order to convert the mixing machine from closed turbine to opened turbine operation might be employed. Such an arrangement is described in US. Patent No, 3,163,405 issued Dec. 29, 1964 to the present inventor.

While the preferred embodiment has been descirbed as oriented in a vertical direction, it will be appreciated that the mixing device of the present invention can be operated in any orientation with good results. For example, the mixing device of the present invention may be operated as a side entering unit or may be mounted on the bottom of the mixing vessel and driven by a shaft entering the vessel from below.

It will further be apparent to those skilled in the art that other modifications and adaptions of the apparatus may be made without departing from the spirit and scope of the invention as set forth with particularity in the appended claims.

What is claimed is:

1. A mixing device for mixing material within a vessel comprising:

a mixing head for operation within said vessel, said mixing head comprising a stator and a rotor, said stator comprising a central hub with a plurality of vanes radiating therefrom, each of said vanes having a flat upper surface which is inclined downwardly and outwardly and defines a substantial angle to the horizontal, said rotor having a plurality of fan-like blades having a pitch of from 10 to 35, the leading and the trailing edges of said blades producing conical surfaces of revolution arranged in back-to-back relation, with the leading edges of said blades being more remote from the upper surfaces of said vanes than said trailing edges, said trailing edges being in hydraulic shearing relation to said upper surfaces,

remote drive means for said rotor, and

a shaft connecting said drive means to said rotor.

2. A mixing device for mixing material within a vessel comprising:

a mixing head for operation within said vessel, said mixing head comprising a stator and a rotor, said stator comprising a central hub with a plurality of vanes radiating therefrom, each of said vanes having a smooth upper surface which is inclined downwardly and outwardly and defines a substantial angle to the horizontal, said rotor having a plurality of fan-like blades, the leading and the trailing edges of said blades producing conical surfaces of revolution arranged in back-to-back relation, with the leading edges of said blades being more remote from the upper surfaces of said vanes than said trailing edges, said trailing edges being in hydraulic shearing relation to said upper surfaces, remote drive means for said rotor, a shaft connecting said drive means to said rotor, and

an open-ended cylindrical sleeve coaxial with said shaft and surrounding said rotor and said stator for converting said mixing device to a closed turbine configuration.

3. A mixing device of the type described in claim 2,

further comprising:

means for removing said sleeve upward coaxially with said shaft so as to convert said mixing device to an open turbine configuration.

4. A mixing device of the type described in claim 3, wherein the means for removing said sleeve comprises a control rod connected to said sleeve and extending upward substantilally parallel to said shaft to a position adjacent said drive means.

5. A mixing device of the type described in claim 3, further comprising:

means coupled to said shaft for moving said shaft longitudinally with respect to said stator so as to vary the spacing between the blades of said rotor and the upper surfaces of the vanes of said stator.

6. A mixing device for mixing material within a vessel comprising:

a drive motor,

motor support means for supporting said drive motor above said vessel,

a mixer shaft connected to said drive motor and projecting downward into said vessel,

a rotor mounted at the lower end of said mixer shaft,

a first stator journaled on said mixer shaft above and in close proximity to said rotor, said first stator having a central hub and a plurality of vanes radiating therefrom,

a second stator mounted below and in close proximity to said rotor, said second stator having a central hub with a plurality of vanes radiating therefrom, said rotor having a plurality of fan-like blades, the upper edges of the blades being in hydraulic shearing relation with the undersurfaces of the vanes of said first stator, and the lower edges of said blades being in hydraulic shearing relation to the upper surfaces of the vanes of said second stator.

7. A mixing device for mixing material within a vessel comprising:

a drive motor,

motor support means for supporting said drive motor above said vessel,

a mixer shaft connected to said drive motor and projecting downward into said vessel,

a rotor mounted at the lower end of said mixer shaft,

a stator mounted below and in close proximity to said rotor, said stator having a central hub with a plurality of vanes radiating therefrom, each of said vanes having a smooth upper surface which is inclined downwardly and outwardly and defines a relatively sharp angle to the horizontal, said rotor having a plurality of fan-like blades, the leading and trailing edges of said blades producing conical surfaces of revolution arranged in back-to-back relation coaxially with said drive shaft with the leading edges of the blades being more remote from the upper surfaces of the vanes of said stator, the trailing edges of said blades being in hydraulic shearing relation to the upper surfaces of the vanes of said stator, and

adjustment means for raising and lowering said mixer shaft so as to vary the spacing between the blades of said rotor and the upper surface of the vanes of said stator.

8. A mixing device of the type described in claim 7,

wherein said adjustment means comprises:

coupling means coupling the drive shaft of said drive motor to said mixer shaft, and

a housing journaled on said mixer shaft adjacent its coupled end and threadedly engaging said motor supporting means so that rotating said housing with respect to said motor supporting means varies the distance separating said rotor and said stator so as to selectively provide fine and coarse granulation of the mateirals to be mixed.

9. A mixing device of the type described in claim 7,

further comprising:

an open-ended cylindrical sleeve coaxial with said shaft and surrounding said rotor and said stator for converting said mixing device to a closed turbine configuration.

10. A mixing device of the type described in claim 9,

further comprising:

means for removing said sleeve upward coaxially with said shaft so as to convert said mixing device to an open turbine configuration.

11. A mixing device for mixing material within a vessel comprising:

a drive motor having a drive shaft,

motor support means for supporting said drive motor above said vessel.

a mixer shaft projecting downward from said drive motor into said vessel,

coupling means coupling said mixer shaft to the drive shaft of said drive motor,

a first stator journaled on said mixer shaft,

a rotor mounted on said mixer shaft below said first stator and in close proximity thereto, and

a second stator located below said rotor and in close proximity thereto, said first stator having a central hub with a plurality of vanes radiating therefrom each of said vanes having a smooth undersurface which is inclined upwardly and outwardly and defines a relatively sharp angle to the horizontal, said second stator having a central hub with a plurality of vanes radiating therefrom, each of said vanes having a smooth upper surface which is inclined downwardly and outwardly and defines a relatively sharp angle to the horizontal, said rotor having a plurality of fan-like blades so pitched that in rotation the upper and lower edges of said blades produce conical surfaces of revolution arranged in back-to-back relation, with the upper edges of said blade being in hydraulic shearing relation to the undersurfaces of the vanes of said first stator and the lower edges of said blades being in hydraulic shearing relation to the upper surfaces of the vanes of said second stator.

12. A mixing device of the type described in claim 11, further comprising:

an open-ended cylindrical sleeve coaxial with said mixer shaft and surrounding said rotor and said first and second stators so as to provide a closed turbine configuration.

13. A mixing device of the type described in claim 12, wherein said sleeve is rigidly connected to said first stator and the combination of said sleeve and said first stator is removable upward coaxially with said mixer shaft so as to provide an open turbine configuration comprising said rotor and said second stator.

14. A mixing device of the type described in claim 12, wherein said sleeve is rigidly connected to said second stator and the combination of said sleeve and said second stator is removable in a downward direction so as to provide an open turbine configuration comprising said rotor and said first stator.

15. A mixing device of the type described in claim 11, further comprising:

adjustment means for raising and lowering said mixer shaft so as to vary the spacing between the blades of said rotor and the upper surface of the vanes of said stator.

16. A mixing device of the type described in claim 15, wherein said adjustment means comprises:

coupling means coupling the drive shaft of said drive motor to said mixed shaft, and

a housing journaled on said mixer shaft adjacent its coupled end and threatedly engaging said motor supporting means so that rotating said housing with respect to said motor supporting means varies the distance separating said rotor and said stator so as to selectively provide fine and coarse granulation of the materials to be mixed.

17. A mixing device of the type described in claim 11, wherein said stator is mounted Within said vessel in spaced relation with the bottom and sides thereof.

18. A mixing device of the type described in claim 11, wherein said stator is carried by a plurality of support rods extending downward from said motor support means in substantially parallel relation to said mixer shaft.

References Cited UNITED STATES PATENTS 2,450,802 10/ 1948 Johnson 259-96 2,801,083 7/1957 Balassa 259-24 X 3,154,296 10/1964 Balassa 259 3,163,405 12/1964 Balassa 10389 X 3,197,181 7/1965 Hill. 3,197,182 7/1965 Hill. 3,229,965 1/1966 Hill.

ROBERT W. JENKINS, Primary Examiner.

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