Vibration-assisted apparatus for mixing immiscible liquids and for mixing powders with liquids or with other powders

Abstract

A batch or continuous mixer for mixing powders, immiscible liquids, or a powder with a liquid includes one or more vibrational energy applicators which propagate vibrational energy into the mixture, causing powders to flow like liquids and breaking up liquid droplets and powder clumps. In embodiments, the vibration frequency and amplitude are selected according to properties of the mixture components. Vibrations can be propagated through container walls, impellers, or other structures within the mixing container. Vibrated structures can be flexibly supported for enhanced propagation of the vibrations. Vibrational energy can be uniform throughout the container, or focused in a desired region. Ultrasonic energy can be simultaneously applied with acoustic energy.

Claims

1. A mixing apparatus for mixing a first substance with a second substance, the mixing apparatus comprising: a mixing container having an interior which is able to contain a mixable combination of the first substance and the second substance, the interior being surrounded by one or more walls of said container; a convection mechanism for applying convective mixing forces to the mixable combination; a vibration application system comprising an exterior vibrational energy applicator that is able to propagate acoustic vibrations through a wall section of a corresponding one of the container walls without directly exposing the exterior vibrational energy applicator to the container interior, the vibration application system being configured to apply vibrational energy to the mixable combination while the convective mixing forces are applied to the mixable combination; and an ultrasonic generator which is able to apply ultrasonic energy to the mixable combination while the convective mixing force and acoustic vibrations are simultaneously applied to the mixable combination.

2. The mixing apparatus of claim 1, wherein the mixing apparatus is a batch mixer.

3. The mixing apparatus of claim 2, wherein the mixing apparatus is a vertical shaft batch mixer.

4. The mixing apparatus of claim 2, wherein the mixing apparatus is a horizontal batch mixer.

5. The mixing apparatus of claim 1, wherein the mixing apparatus is a continuous mixer.

6. The mixing apparatus of claim 5, wherein the continuous mixer includes a mixing tube having a wall with a non-uniform thickness profile.

7. The mixing apparatus of claim 5, further comprising a rotatable mixing shaft contained within a mixing tube of the continuous mixer.

8. The mixing apparatus of claim 7, further comprising a plurality of mixing shafts contained within the mixing tube of the continuous mixer.

9. The mixing apparatus of claim 1, wherein the wall section of the mixing container through which the exterior vibrational energy applicator is able to propagate acoustic vibrations is thinner than surrounding portions of the container walls.

10. The mixing apparatus of claim 1, wherein the wall section of the mixing container through which the exterior vibrational energy applicator is able to propagate acoustic vibrations is coupled to a remainder of the container walls by an elastomeric material.

11. The mixing apparatus of claim 1, wherein the vibration application system further includes an interior vibration applicator that is able to apply vibrational energy to a mixing feature which extends into the interior of the mixing container.

12. The mixing apparatus of claim 11, wherein the mixing feature is a mixing impeller.

13. The mixing apparatus of claim 11, wherein the mixing feature is a fin or baffle attached to one of the walls of the mixing container.

14. The mixing apparatus of claim 13, wherein the fin or baffle is attached to the wall by a flexible attachment which allows movement of the fin or baffle relative to the wall.

15. The mixing apparatus of claim 1, wherein the vibration application system includes a plurality of exterior vibrational energy applicators configured to propagate vibrations through corresponding sections of the one or more walls of the container without directly exposing any of the plurality of exterior vibrational energy applicators to the container interior, the vibration application system being configured to apply the vibrational energy at a substantially uniform intensity throughout the mixable combination.

16. The mixing apparatus of claim 1, wherein the vibration application system includes a plurality of exterior vibrational energy applicators configured to propagate vibrations through corresponding sections of the one or more walls of the container without directly exposing any of the plurality of exterior vibrational energy applicators to the container interior, the vibration application system being configured to concentrate the vibrational energy in a desired sub-region of the interior of the mixing container.

17. The mixing apparatus of claim 1, further comprising a heating apparatus which is able to heat the mixable combination while the convective mixing forces and vibrational energy are applied to the mixable combination.

18. The mixing apparatus of claim 1, wherein the mixing container is configured so that it can be pressurized while the convective mixing force and the vibrational energy are applied to the mixable combination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a perspective view of a large vertical shaft batch mixer of the prior art;

(2) FIG. 1B is a perspective view of a motor, shaft, and impeller of a vertical shaft batch mixer of the prior art;

(3) FIG. 1C illustrates the flow path of a mixture in a typical vertical shaft batch mixer of the prior art;

(4) FIG. 2 is a perspective view of a multi-shaft vertical shaft batch mixer of the prior art;

(5) FIG. 3 is a perspective view of a vertical shaft batch mixer of the prior art having a planetary impeller;

(6) FIG. 4 illustrates the structure of a typical planetary impeller in a vertical shaft batch mixer of the prior art;

(7) FIG. 5 is a perspective view of a V-shaped horizontal batch mixer of the prior art;

(8) FIG. 6 is a perspective view of an enclosed horizontal batch mixer of the prior art;

(9) FIG. 7 is a perspective view of an open horizontal batch mixer of the prior art;

(10) FIG. 8 is a perspective view similar to FIG. 1C showing an embodiment of the present invention applied to walls and to the base of the mixing container; also showing an acoustic horn positioned directly in the mixed material

(11) FIG. 9 is a cross sectional view of a region of a container wall showing an embodiment of the present invention applied to a thin plate sealed to a hole in the container wall by an elastomeric gasket which reduces loss of vibrational energy to the container;

(12) FIG. 10 is a perspective view similar to FIG. 5 showing an embodiment of the present invention applied to walls of the mixing container;

(13) FIG. 11 is a perspective view similar to FIG. 4 showing an embodiment of the present invention applied to the wall, base, and planetary impeller of the mixing container;

(14) FIG. 12A is a cross-sectional side view of a continuous mixer mixing tube which has a wall thickness profile and which includes an embodiment of the present invention which propagates vibrational energy through the mixing tube wall; and

(15) FIG. 12B is a cross-sectional side view of a continuous mixer mixing tube which includes a rotatable mixing shaft, and which includes an embodiment of the present invention which propagates vibrational energy through the mixing tube wall.

DETAILED DESCRIPTION

(16) The present invention is a mixer for mixing immiscible liquids, or for mixing a powder with a liquid or with another powder. The mixer includes one or more vibrational energy applicators that propagate vibrational energy into the mixing container or tube, thereby vibrating droplets and causing them to break into smaller droplets, and/or thereby vibrating powder granules and causing them to flow like a liquid, vibrate against each other and break up clumps, and vibrate away from container walls and baffle and agitator surfaces.

(17) FIG. 9 illustrates an embodiment in which a plurality of vibrational energy applicators 900, 902, 904 are cooperative with the container walls 906 of a vertical shaft batch mixer similar to the mixers of FIGS. 1A through 4. Some of the vibrational energy applicators 900, 904 are located along the sides of the container 100, while others 902 are located along the bottom of the container 100. Some of the vibrational energy applicators 900, 902 are arranged on the sides and bottom of the container 100 and synchronized so as to generate an approximately uniform field of vibrational energy throughout the mixing container 100. In similar embodiments, four mechanical vibrating motors are attached around the circumference of the bottom of a large, round, flat-bottom mixing container 100 such as the mixing chamber 100 of FIG. 9, so as to produce a single harmonized wave of motion and vibration for the entire contents of the mixing container 100.

(18) Other vibrational energy applicators 904 in FIG. 9 are located and synchronized so as to focus vibrational energy in one or more desired regions of the mixing container 100, such as the region immediately surrounding the impeller 106. In similar embodiments, vibrational energy applicators 904 are arranged and synchronized to create within the mixing container 100 a volume containing a particular vibrational energy and/or wave type that enhances the mixing action for the particular materials being processed.

(19) In the embodiment of FIG. 8, the vibrational energy is mainly acoustic energy, which passes through specific locations on the mixing container walls 906 and is propagated into the mixing container 100 as vibrational waves. The vibrational energy applicators 900, 902, 904 in FIG. 8 do not attempt to vibrate or shake the entire mixing container 100 as a whole. Also, FIG. 8 shows an acoustic horn 800 which is positioned in the mixed material for better proximity to the mixing blades and for maximum acoustic energy transfer to the mixed material.

(20) Note that FIG. 8 is intended mainly to illustrate functionality. For example, a preferred shape in practice for the mixing container 100 of FIG. 8 would include sides that meet the bottom over a radius, rather than at a sharp 90 degree angle.

(21) With reference to FIG. 9, in various embodiments the vibrational energy applicators 900 are cooperative with regions of the container walls 906 which include thin metal plates 908 and/or elastomeric materials 910 that enable vibrational energy from the vibrational energy applicators 900 to penetrate more easily into the interior of the mixing container 100. In the embodiment of FIG. 9, a thin plate 908 is sealed over an opening in the container wall 906 using an elastomeric gasket 910 which prevents the mixture from leaking out of the container 100, while reducing the amount of vibrational energy which is transferred from the plate 908 to the wall 906.

(22) FIG. 10 illustrates an embodiment similar to FIG. 8, but applied to a V style horizontal axis mixer, with or without baffles or other mixing structures or devices as is illustrated in FIG. 5. In some embodiments which include either fixed position paddles and/or rotating blades on the inside of the container 100 to increase the mixing action of the rotating container 100, the mounting or attachment of the paddles or blades is flexible, allowing a small amount of movement of the paddles or blades such that vibration energy can be applied directly to the paddles or blades and transmitted by the paddles or blades into the mixture. This has the result of vastly increasing the mixing action on droplets and powder particles at and near the paddles or blades as the mixture tumbles past them during container rotations. The vibration of the paddles or blades causes rapid breakup of droplets and/or de-agglomeration of powder particle clumps, and promotes rapid mixing of immiscible liquids and various sized powder particles.

(23) FIG. 11 illustrates application of an embodiment to a vertical shaft batch mixer which includes a planetary impeller 106. Some vibrational energy applicators 900 are cooperative with the walls of the mixing container 100 and other vibrational energy applicators 902 are cooperative with the bottom of the mixing container 100. In addition, some vibrational energy applicators 1200 are cooperative with the mounting structure 1202 which supports the planetary impeller 106. The result is that the vibrational energy is transferred to the mixing blades of the planetary impeller 106, and imparted by the blades to the material being mixed at the interaction region (e.g. sheer area) between the mixed material and the impeller blades. This approach to applying vibrational energy throughout the interior of the mixing container 100 can be very effective for shortening the mixing time and total mixing energy requirement, especially when blending fine grains or powders together with a liquid.

(24) In FIG. 12A, vibrational energy is applied to a mixture through the outer wall of a mixing tube 1700 which has a profiled wall thickness 1702 forming a passage 1704 with a profiled shape. In the embodiment of FIG. 12B, a rotating mixer shaft 1706 is installed in the mixing tube 1700 of a continuous mixer. The mixer shaft 1706 has a non-round profile which moves the mixture within the passage 1704 and forms momentary areas of rapid and slow flow, and rapid and slow mixing. In various embodiments, the mixing chamber 1704 is smooth and straight-walled, as shown in FIG. 12B. In other embodiments a rotating mixer shaft 1706 is combined with a profiled mixing tube 1702, so as to increase the intensity of the mixing.

(25) Without the vibrational energy of the present invention, the mixer designs illustrated in FIGS. 12A and 12B would be mainly unsuccessful in breaking up droplets in immiscible liquids and in mixing a powder with a liquid. The present invention, by applying vibrations (acoustic, ultra-sonic, or both together) to the mixing tube 1700, causes the liquid droplets and/or the liquid/particle blend to vibrate, and vastly improves the overall mixing action of the device, especially with respect to using a lower quantity of the liquid phase and with respect to breaking up droplets and mixing and dispersing fine grains and powders. By tuning the vibration energy to the droplet or particle sizes of the mixture, the overall mixing forces can be optimized. Also, as previously described, heat (and pressure if needed to prevent boiling of the liquid) can be applied to the transiting mixture so as to reduce the viscosity and improve the dispersion of the powder granules and the breaking up of clumps and/or droplets by the applied vibrational energy.

(26) Tuning the Vibrational Energy

(27) As mentioned above, in various embodiments the frequencies and amplitudes of the applied acoustic and/or ultrasonic vibrational energy are adjusted or tuned according to properties of the substances being mixed, so as to optimize the mixing effectiveness of the vibrations. Following are three examples of materials to be processed and some factors and guidelines to consider when optimizing the speed, time, energy consumption, and quality (completeness for the intended purpose) of the mixing process.

Example 1

(28) In this example a liquid, such as an adhesive or resin, or a liquid used in a paint or a food product, is combined with powder particles of a mineral or another material that must be evenly distributed into the liquid. The relative amount of the liquid can range from a large excess down to the minimum quantity needed to bind the particles together. It is generally more difficult to achieve complete mixing and dispersing of the particles for this situation of minimum liquid or binder. For the purposes of this example, the particle size distribution of the added solid material is assumed to be in the approximate range of 50-1000 microns, but can also be larger than 1000 microns or smaller than 50 microns.

(29) In this example, the application of acoustic vibrational energy will cause the individual particles to move back and forth over a range from about 5% up to more than 100% of their diameters. By adjusting both the amplitude and the frequency of the vibrational energy, combinations of amplitude and frequency can be found for which the total mixture of liquid and solid particles will take on a more fluid-like behavior, and complete mixing will be achieved in less time and will be more complete.

(30) A two-dimensional table or graph can be constructed showing the range of successful frequency and amplitude combinations as a subset of the entire range of possible frequency and amplitude combinations for that particular mixture. Note that for liquids of higher viscosity, a higher vibrational energy will generally be required, which can be achieved by applying a higher frequency, a higher amplitude, or both.

(31) One simple method for obtaining an initial estimate of the range of successful frequency and amplitude combinations is to place only the solid particles into a container and then apply vibrational energy and observe a minimum frequency and amplitude combination at which the particles become more or less fluidized in the container, so that a much lower amount of energy is required to stir or mix the particles. This minimum frequency and amplitude will depend on the particle size distribution and particle density. This dry test data can be very useful as a starting point for the actual mixing process wherein the liquid is also included.

Example 2

(32) In this example, a mixture of a liquid adhesive or resin, or another liquid material is combined with a range of particles of a mineral or other material that must be evenly distributed and dispersed into the liquid. The relative amount of the liquid can range from a large excess down to the minimum quantity needed to bind the particles together. It is generally more difficult to achieve complete mixing and dispersing of the particles for this situation of minimum liquid or binder. For the purposes of this example, the particle size distribution of the added solid material is assumed to be in the approximate range of 0 to 100 microns, which are essentially powdered materials. For this range of particle sizes it will be very useful to apply ultrasonic vibration, ranging from low frequencies up to 15,000 Hz for large powder particles to much higher frequencies of 10,000 Hz to several MHz for very small particles, to cause the individual particles to move back and forth over a range from approximately 5% up to 100% and more of their diameter. This will vastly increase the rate of mixing or dispersion into the liquid phase and will improve the de-agglomeration of particle groups and clumps.

(33) As with Example 1 above, a two-dimensional table or graph can be constructed showing the range of successful frequency and amplitude combinations as a subset of the entire range of possible frequency and amplitude combinations for this particular mixture, and can be further adjusted depending upon the liquid viscosity and the degree of filler loading of powder into the liquid. The dry test method described above can be used to yield useful data for the starting point for when the process is applied to the complete mixture of liquid and solid.

Example 3

(34) In this example, there is included a first quantity of a solid having the rather large particle size distribution of Example 1 and also a second quantity of a solid having the particle size distribution of Example 2. Therefore it will be seen that the application of both acoustic and ultrasonic vibration energies at the same time will facilitate the mixing of the entire range of included particle sizes.

(35) The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.