US3912231A - Apparatus for treating and mixing particles - Google Patents

Abstract

An apparatus for treating particles with a liquid and for subsequent thorough mixing of the treated particles. The mixer comprises upright, concentric, spaced inner and outer walls, a helical ribbon disposed between the walls and mounted for rotation about an upright axis, means for feeding treated particles to the bottom of the helical ribbon, and means for withdrawing the mixed, treated particles from the top of the ribbon. The inner wall at least partially defines a chamber wherein the particles are treated with a liquid. Augering of the treated particles upwardly along the rotating, helical ribbon provides thorough mixing.

Description

United States Patent 1191 Weber Oct. 14, 1975 [54] APPARATUS FOR TREATING AND MIXING 3,779,033 l2/l973 Swanson 222/241 PARTICLES Primary ExaminerPeter Feldman l t A. W M [75] nven or a sg eber mneapohs Assistant ExammerJames A. N1egowsk1 Attorney, Agent, or Firm-H. Dale Palmatier; James [73] Assignee: Gustafson, Inc., Hopkins, Minn. R H n [22] Filed: Jan. 17, 1974 21 Appl. No.: 434,033 [57] ABSIRACT An apparatus for treating particles with a liquid and for subsequent thorough mixing of the treated parti- [52] 3 42825 45 cles. The mixer comprises upright, concentric, spaced I I2 11/04 inner and outer walls, a helical ribbon disposed beg 259 2 ?g tween the walls and mounted for rotation about an up- 1 3 right axis, means for feeding treated particles to the l 8 g l 2 24 3 bottom of the helical ribbon, and means for withdraw- 9 21 1 ing the mixed, treated particles from the top of the ribbon. The inner wall at least partially defines a [56] References Cited chamber wherein the particles are treated with a liq- UNITED STATES PATENTS uid. Augering of the treated particles upwardly along 2,517,456 8/1950 Wherrett 259/7 the rotating, helical ribbon provides. thorough mixing.

2,953,359 9/1960 Mau 2591s i 3,155,542 11/1964 Cordell et al. 118/303 14 Chums 3 Drawmg Figures 11' {2 ll 1 II 12.5

a4 lllll 12.2 222 q q" l l 225m. 121 22 14 A 51- I "lllll 165 d? .225 2a; .22 22.!

m1 1- I a2! APPARATUS FOR TREATING AND MIXING PARTICLES u BACKGROUND or THE INVENTION Particles, particularly seeds, often are provided with a coating of a liquid such as a pesticide, the relative volumes of particles and liquids being carefully controlled. A convenient manner of coating seeds is to spray falling seeds with small droplets of liquid and thereafter thoroughly mixing the seeds so that the droplets of liquid originally adhering to the seeds are spread over the entire seed surface. In the past, this has required extremely thorough mixing, and large and bulky mixing apparatuses were designed to accomplish this purpose. The seeds must be mixed thoroughly in order to completely cover the seed surface with liquid, and yet the seeds must be handled gently to avoid seed damage. A unitary, portable, compact apparatus capable of treating particles such as seeds with a liquid and thoroughly mixing the treated particles is much to be desired.

BRIEF SUMMARY OF THE INVENTION The present invention relates to a treating and mixing apparatus for applying a liquid to falling particles and for thoroughly mixing or agitating the particles so as to spread the liquid thoroughly over the surface of the particles. The mixer includes upright, concentric, spaced inner and outer walls, the inner wall at least partially defining a chamber within which particles are contacted with a liquid. A helical ribbon is disposed between the walls and is mounted for rotation about an upright axis of rotation. The mixer includes means for feeding treated particles to the bottom of the helical ribbon when the ribbon is rotating about its axis, and means for removing the mixed particles from the top of the ribbon. Upon entering the bottom of the helical ribbon, the treated particles are augered upwardly along the rotating helical ribbon to provide thorough mixing and distribution of liquid upon the particle surfaces.

DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an apparatus of the invention;

FIG. 2 is a cross-sectional view of the apparatus of FIG. 1, taken alongline 22; and

FIG. 3 is a broken away, cross-sectional view taken along line 33 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The treating and mixing apparatus of the invention, designated generally as in FIG. 1, includes aconical hopper 12 into which seeds or other particles to be treated are placed, and acompact housing 14 which houses the treating and mixing apparatus 'of the invention. Thehopper 12 is supported above thehousing 14 by upright struts 14.1. Exteriorly of thehousing 14 is mounted a power source such aselectric motor 16 which is mechanically coupled to a drive shaft 16.1 through a belt and sheave system 16.2 and which in turn serves to drive certain rotating elements within the housing, as will be subsequently explained, through belt and sheave arrangement 16.3 and 16.4

Avertical sleeve 18 is mounted by straps 18.1 to the inner surface of thehopper 12, thesleeve 18 having a stationary distributing cone 18.2 at its lower end, the

upper surface of the cone converging upwardly such that seeds or other particles which are dropped through the hopper contact the upper surface of the cone and are distributed outwardly to fall as a curtain over the outer cone rim 18.3. A movable ring 12.1 slidably encompasses the narrowed throat 12.2 of the hopper, the lower end of the ring confronting the upper surface of the cone. The height of thering 12.] above the cone is regulated by turning of a handle 12.3 located exteriorly of thehousing 14, the handle operating to rotate a threaded shaft 12.4 to raise and lower support arms 12.5 connected by a harness 12.6 to the ring 12.1. The ring serves to regulate the rate at which particles are delivered to the cone; as the ring is lowered toward the cone, the flow rate of particles is reduced.

Adisc 20 is affixed to the end of a shaft 20.1 which in turn passes upwardly through thesleeve 18. A sheave 20.2, connected to the top of the shaft 20.1, is driven by the drive shaft 16.1 through the belt and sheave 16.3. A housing 20.3 for the belt and sheave 20.2 extends internally of thehopper 12 and is held in place by straps 20.4. Thedisc 20 is positioned directly beneath the cone 18.2 and is coaxial with the cone. The disc may have radial serations 20.5, the purpose of which will be subsequently explained.

Afluid delivery tube 21 extends downwardly through the hopper l2 and passes through the cone 18.2 into close proximity with the upper surface of thedisc 20. Thetube 21 is held in place by its passage through thedisc 20 and by a bracket 18.4 within the throat of the hopper. Fluid, such as a pesticide, is delivered totube 21 in measured amounts from an external source (not shown). The liquid may be metered to thetube 21 from a reservoir of liquid by means of a volumetric pump such as a gear pump or by other known measuring devices. Themotor 16 causes the disc to rapidly rotate about its axis, and liquid which is depositedon the upper surface of the disc near its connection with the shaft 20.1 is hurled outwardly by centrifugal force in the form of small droplets which contact the curtain of particles falling from the rim 18.3 of the distributing cone. In the case of seeds, such as soy bean seeds, the liquid may be seen under magnification to be present on the surface of the seeds as small spatters or droplets, and it is the subsequent mixing action which rubs one seed against another and thus spreads the liquid thoroughly and completely over the outer surface of the seeds. The power source may be provided with a variable speed control so that the speed of the rotating disc may be varied as desired.

The cone and rotatingdisc are housed within a pair of concentric, spaced, upright,cylindrical walls 22 and 24, as shown in FIG. 2. Theouter wall 22 arises from the periphery of acircular floor 26 to form a drumshaped container, and the inner surfaces of theouter wall 22 andfloor 26 are provided with a low friction plastic surface 22.1, 22.6, such as Teflon. Ashaft 28 passes upwardly through a central aperture in the floor, and is provided with an exterior sheave 28.1 which is rotatably driven by the belt and sheave system 16.4. Theshaft 28 rises only a short distance above the surface of the floor and is provided with a slot in which is carried anelongated paddle 30 of generally rectangular cross section. The ends 30.1 of the paddle are bent as shown in FIG. 3 to define a generally planar superior surface oriented at an obtuse angle with respect to thefloor 26. The paddle is attached, as by welding, to the lower edge 24.1 of theinner wall 24 and serves to support the inner wall spaced above the top surface of the floor. Cross struts 30.2 are attached to thepaddle 30 and extend outwardly from the paddle for attachment to points 24.2 about the lower periphery of theinner wall 24. Thepaddle 30, and cross struts 30.2, support the inner wall in spaced relationship above the floor and rotate the inner wall about the axis of the cone and disc when theshaft 28 is rotated by themotor 16. The bottom edge of thepaddle 30 is in contact with and scrapes or sweeps the upper surface of the floor as the paddle is rotated, thereby urging fallen seeds or other particles outwardly beneath the upwardly spaced lower edge 24.1 of theinner wall 24.

One or morehelical ribbons 32 are rigidly attached, as be welding, to the outer surface of theinner wall 24, as depicted in FIG. 2, and extend laterally outwardly into sliding contact with the low friction surface 22.1 of theouter wall 22. Although one or more helical ribbons may be thus employed, good results have been obtained with two helical ribbons, helically interlaced about the inner wall. Each helical ribbon at its bottom end contacts a bent end of thepaddle 30, the superior surface of the helical ribbon at its lower end merging into the superior surface of the bent paddle end such that seeds or other particles which are swept outwardly across the floor towards the periphery of the outer wall are cammed upwardly by the bent paddle ends to enter the helical passages defined by the helical ribbons. The helical ribbons rotate with theinner wall 24 and thepaddle 30, and seeds or other particles are augered upwardly through the helical passages, movement of the particles in this fashion giving rise to thorough rubbing and mixing between particles so as to uniformly coat each particle with the liquid. An opening 22.2 is provided at the upper end of theouter wall 22 so that particles which have reached the top-most surface of the helical ribbons may pour outwardly in the direction shown by arrow 22.3 into the space between thehousing 14 and theouter wall 22, for subsequent collection in a suitable container. Each helical ribbon is provided at its upper end with an upright deflection plate 32.1 oriented at an acute angle to a plane passing through the plate and through the axis of rotation of theshaft 28 so as to urge particles advancing upwardly along the superior surface of the upper end of the helical ribbon in an outwardly direction so that the particles exit through the opening 22.2 in theouter wall 22.

Anannular cover 34 having an inverted U configuration fits over the upper edges of the inner andouter walls 24 and 22 to cover the annular space between these walls and to prevent dust or the like from escap- As noted above, the disc may have a radially serated edge as shown in FIG. 2. The purpose of the serated edge is to increase the surface area of the disc across which liquid is transported by centrifugal force and also to expand the vertical distance within the chamber in which liquid droplets are hurled outwardly from the periphery of the disc. Liquid which departs from the disc at a seration peak will travel in a generally horizontal plane outwardly. Liquid departing from the disc at a valley portion of the serated edge will be hurled outwardly in a generally horizontal plane slightly lower than the first plane. Thus, the vertical distance in which outwardly hurled liquid droplets may contact the falling curtain of particles increases with increasing seration depth, and a greater proportion of the falling particles may thus be contacted by the outwardly hurled liquid droplets. The disc may be rotated at any convenient speed which is sufficiently high to give the desired results. For a disc approximately 6 inches in diameter, a suitable speed for liquid having a viscosity on the order of that of water is 2,800 revolutions per minute. The speed may be adjusted upwardly, or downwardly, as desired, and it has been found that for optimum results, different speed settings within a range of from about 1,500-2,8OO revolutions per minute are desired for liquidsof different viscosities. It has generally also been found that the ability of the liquid to contact a large proportion of the falling particles is increased as the liquid flow rate to the spinning disc is decreased within limits. High liquid flow rates to the spinning disc result in large droplets of liquid being hurled from the disc. As the flow rate is reduced. the droplet size is likewise reduced. For optimum results, it is desired that the spinning disc form an outwardly directed, mist-like spray of droplets. Again, the droplet size is also dependent upon the speed of the spinning disc, and more precisely upon the linear velocity of the periphery of the disc.

The rotational speed of theinner wall 24 and the attached helical'ribbons is of importance to proper operation of the apparatus of the invention. At least some difference is required between the rotational speed of the helical ribbons and the rotational speed, if any, imparted'to the seeds or other particles in order for the ribbons to auger the particles upwardly. If the rotational speed of the helical ribbons is too low, the seeds or other particles will become seated on the superior surfaces of the ribbons and will rotate with the ribbons, the helical passages eventually becoming obstructed withparticles. In general, higher rotational speeds are required for smaller particles. Because of the intimate contact which occurs between the walls of the helical passages and the particles passing through these passages, the particles will normally acquire some angular momentum by the time they reach the top-most. ends of the helical ribbons. It is required that the rotational speed of the helical ribbons be such as to provide at least some, though varying, differential between the angular velocity of the seeds and the ribbons as the seeds are augered upwardly through the helical passages. For an apparatus of the invention having two interlaced helical ribbons each making approximately six revolutions about the periphery of the inner wall, the outer and inner diameters of the inner and outer walls respectively being 12 and 18 inches, an angular speed of 250 revolutions per minute has yielded good results with soy bean seeds.

If desired, an upright, stationary scraper bar may be oriented against the inner surface of theinner wall 24 so that as the wall rotates during operation of the apparatus, seeds or other particles which may adhere to the inner wall are scraped from the wall and fall to thefloor 26. It will further be understood that the rotational speed of theshaft 28 driving the helical ribbons may be widely varied with respect to the rotational speed of the shaft 20.1 driving thespinning disc 20, since the speed of thedisc 20 is largely dependent upon the viscosity and quantity of liquid which is dispensed through thetube 22, as noted above, whereas the rotational speed required for the helical ribbons is largely dependant upon the size and density of the treated particles. It will be understood that other devices, such as liquid spray nozzles or the like may be employed for treating particles with liquid prior to mixing the particles.

While I have described a preferred embodiment of the present invention, it should be understood that various changes, adaptations, and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In combination with a treating apparatus for applying a liquid to falling particles',a mixer for mixingthe treated particles, the mixer including upright, concentric, spaced inner and outer walls defining an annular space therebetween, the inner wall defining walls of a central particle-treating chamber wherein particles are treated with a liquid, a rotatable, helical ribbon disposed in the annular space and having an upright axis of rotation, means for feeding treated particles from the particle-treating chamber to the'bottom of the helical ribbon, means for rotating the ribbon about its axis to auger upwardly the treated particles, with concurrent mixing, within the annular space, and means for removing the mixed, treated particles from the top of the ribbon.

2. The apparatus of claim 1 wherein the inner wall is mounted for rotation about the axis of rotation of the helical ribbon and wherein the helical ribbon is attached to the inner wall for rotation therewith.

3. The apparatus of claim 2 including a floor positioned to receive fallen particles after treatment of the same with a liquid, and means for transporting the fallen particles outwardly for reception by the bottom of the helical ribbon.

4. The apparatus according to claim 3 wherein the floor and outer wall are stationary with respect to the inner wall and attached helical ribbon.

5. The apparatus of claim 4 including a power source, a rotatable shaft driven by the power source and extending upwardly through the floor coaxial with the axis of rotation of the helical ribbon, and a paddle mounted to the shaft and adapted to sweep fallen treated particles on the floor outwardly for reception by the bottom of the helical ribbon, the paddle having outwardly extending ends attached to the inner wall, rotation of the shaft causing the paddle, the inner wall, and the helical ribbon to rotate about the axis of rotation of the latter, the paddle sweeping fallen particles outwardly of the stationary floor for reception by the bottom of the rotating helical ribbon.

6. The apparatus of claim 5 wherein the annular space between the inner and outer walls houses a plurality of helical ribbons attached to the outer surface of the inner wall, the helical ribbons being helically interlaced to define separate helical passages.

7. The apparatus according to claim 6 wherein the inner wall has a lower edge spaced above the floor to permit outwardly swept treated particles to pass beneath the lower edge of the inner wall for reception by the bottom of the rotating helical ribbon, the outer wall being rigidly connected at its lower edge to the floor, and the paddle ends extending outwardly beneath the inner wall and having superior surfaces oriented at an obtuse angle with respect to the floor and which merge into respective superior surfaces of the lower ends of the helical ribbons.

8. The apparatus according to claim 7 wherein the outer wall has an opening adjacent the upper end of the helical ribbon through which treated and mixed particles may pass outwardly of the annular space between the inner and outer walls, each helical ribbon terminating upwardly in an upright 'deflec'tion plate so oriented as to urge particles outwardly so that the 'same may pass through the opening in the-outer wall for subsequent collection. 7

9. A treating andmixing apparatus for applying a liquid to particles, and mixing the latter, comprising:

a. means for treating particles with a liquid including .a distributing cone having a vertical axis and an upwardly convergent "u-ppe'r'surfacefa chute for dispensing particles onto the 'upper surface of the cone, the particles falling in a curtain from the periphery of the cone, and a motor-driven disc rotatably mounted coaxially below the cone, the disc being adapted to rotate rapidly about its axis and to hurl liquid in small droplets outwardly into contact with the falling curtain of particles;

b. a stationary floor, and an outer, upright, cylindrical wall arising from the floor and having an outward opening adjacent its upper end;

c. a motor-driven, upright shaft extending upwardly through the floor and coaxial with the axis of the cone;

(1. a paddle mounted to the shaft and adapted to rotate therewith to sweep fallen treated particles outwardly toward the outer wall;

e. an inner wall spaced concentrically within the outer wall and mounted to the paddles for rotation about the axis of the cone, the inner wall having a bottom edge spaced from the floor, and the floor and inner wall at least partially defining a treatment chamber within which is housed the cone and disc;

9f. a helical ribbon positioned between the inner and outer walls and mounted to the inner wall for rota tion therewith about the axis of the cone, the ribbon having a bottom end for receiving outwardly swept particles from the floor and conveying the particles upwardly with concurrent mixing, the ribbon terminating at its upper end in a plate so oriented as to deflect the particles laterally outwardly through the opening in the outer wall.

10. The apparatus according to claim 9 wherein the paddle ends extend outwardly beneath the inner wall, each end having a superior surface obtusely angled with respect to the floor and merging with the superior surface of the lower end of a helical ribbon so as to deflect particles from the floor upwardly onto the lower end of the helical ribbon.

11. The apparatus of claim 9 wherein the floor and the outer wall are provided with internal low-friction surfaces.

12. In a treating apparatus for applying a liquid to falling particles, the improvement which comprises a mixer for mixing the treated particles, the mixer comprising a pair of concentric, substantially vertical cylindrical walls spaced from one another to define an annular space therebetween, a stationary floor for receiving fallen particles and attached at its periphery to the outer wall, a helical ribbon mounted within the annular space and attached to the inner wall for rotation therewith, a paddle attached to the inner wall and urging fallen particles outwardly along the floor'into the annular space for reception by the helical ribbon at its lower end, and means for rotating the inner wall and helical ribbon to auger particles upwardly within the annular space with concurrent mixing.

13. In combination with a treating apparatus plying a liquid to falling particles, a mixer for mixing the treatedparticl'es, the mixer including upright, concentric, spaced inner and outer walls defining an annular space-therebetween, a rotatable, helical ribbon disposed in the annular space and having gin-upright axis of rotation, the inner wall being mounted to the helical ribbon for rotation therewith and defining walls of a central, particle-treating chamber wherein particles are treated with a liquid, means for feeding treated particles from the particle-treating chamber to the bottom of the helical ribbon, meansfor rotating the ribbon about its axis to auger upwardly the treated particles within the annular space with concurrent mixing of the particles, and means for removing the mixed, treated particles from the top of the ribbon.

forap i 14. A mixerfor mixing particles treated with a liquid, the mixer including an upright, stationary, cylindrical outer wall, a rotatable inner wall which is concentric with but spaced inwardly of the outer Wall to provide an annular space between the walls, the inner wall defining walls of a central chamber, a rotatable, helical ribbon disposed in the annular space and having an upright axis of rotation, the helical ribbon being attached to the inner wall for rotation therewith, a stationary floor at the bottom of said chamber and spaced below the inner wall for reception of liquid-treated particles, means for feeding the fallen treated particles to the bottom of the helical ribbon, and means for rotating the ribbon and inner wall to auger upwardly the treated particles within the annular space for concurrent particle mixing.

Claims (14)

1. In combination with a treating apparatus for applying a liquid to falling particles, a mixer for mixing the treated particles, the mixer including upright, concentric, spaced inner and outer walls defining an annular space therebetween, the inner wall defining walls of a central particle-treating chamber wherein particles are treated with a liquid, A rotatable, helical ribbon disposed in the annular space and having an upright axis of rotation, means for feeding treated particles from the particle-treating chamber to the bottom of the helical ribbon, means for rotating the ribbon about its axis to auger upwardly the treated particles, with concurrent mixing, within the annular space, and means for removing the mixed, treated particles from the top of the ribbon.

2. The apparatus of claim 1 wherein the inner wall is mounted for rotation about the axis of rotation of the helical ribbon and wherein the helical ribbon is attached to the inner wall for rotation therewith.

3. The apparatus of claim 2 including a floor positioned to receive fallen particles after treatment of the same with a liquid, and means for transporting the fallen particles outwardly for reception by the bottom of the helical ribbon.

4. The apparatus according to claim 3 wherein the floor and outer wall are stationary with respect to the inner wall and attached helical ribbon.

5. The apparatus of claim 4 including a power source, a rotatable shaft driven by the power source and extending upwardly through the floor coaxial with the axis of rotation of the helical ribbon, and a paddle mounted to the shaft and adapted to sweep fallen treated particles on the floor outwardly for reception by the bottom of the helical ribbon, the paddle having outwardly extending ends attached to the inner wall, rotation of the shaft causing the paddle, the inner wall, and the helical ribbon to rotate about the axis of rotation of the latter, the paddle sweeping fallen particles outwardly of the stationary floor for reception by the bottom of the rotating helical ribbon.

6. The apparatus of claim 5 wherein the annular space between the inner and outer walls houses a plurality of helical ribbons attached to the outer surface of the inner wall, the helical ribbons being helically interlaced to define separate helical passages.

7. The apparatus according to claim 6 wherein the inner wall has a lower edge spaced above the floor to permit outwardly swept treated particles to pass beneath the lower edge of the inner wall for reception by the bottom of the rotating helical ribbon, the outer wall being rigidly connected at its lower edge to the floor, and the paddle ends extending outwardly beneath the inner wall and having superior surfaces oriented at an obtuse angle with respect to the floor and which merge into respective superior surfaces of the lower ends of the helical ribbons.

8. The apparatus according to claim 7 wherein the outer wall has an opening adjacent the upper end of the helical ribbon through which treated and mixed particles may pass outwardly of the annular space between the inner and outer walls, each helical ribbon terminating upwardly in an upright deflection plate so oriented as to urge particles outwardly so that the same may pass through the opening in the outer wall for subsequent collection.

9. A treating and mixing apparatus for applying a liquid to particles and mixing the latter, comprising: a. means for treating particles with a liquid including a distributing cone having a vertical axis and an upwardly convergent upper surface, a chute for dispensing particles onto the upper surface of the cone, the particles falling in a curtain from the periphery of the cone, and a motor-driven disc rotatably mounted coaxially below the cone, the disc being adapted to rotate rapidly about its axis and to hurl liquid in small droplets outwardly into contact with the falling curtain of particles; b. a stationary floor, and an outer, upright, cylindrical wall arising from the floor and having an outward opening adjacent its upper end; c. a motor-driven, upright shaft extending upwardly through the floor and coaxial with the axis of the cone; d. a paddle mounted to the shaft and adapted to rotate therewith to sweep fallen treated particles outwardly toward the outer wall; e. an inner wall spaced concentricAlly within the outer wall and mounted to the paddles for rotation about the axis of the cone, the inner wall having a bottom edge spaced from the floor, and the floor and inner wall at least partially defining a treatment chamber within which is housed the cone and disc; 9f. a helical ribbon positioned between the inner and outer walls and mounted to the inner wall for rotation therewith about the axis of the cone, the ribbon having a bottom end for receiving outwardly swept particles from the floor and conveying the particles upwardly with concurrent mixing, the ribbon terminating at its upper end in a plate so oriented as to deflect the particles laterally outwardly through the opening in the outer wall.

10. The apparatus according to claim 9 wherein the paddle ends extend outwardly beneath the inner wall, each end having a superior surface obtusely angled with respect to the floor and merging with the superior surface of the lower end of a helical ribbon so as to deflect particles from the floor upwardly onto the lower end of the helical ribbon.

11. The apparatus of claim 9 wherein the floor and the outer wall are provided with internal low-friction surfaces.

12. In a treating apparatus for applying a liquid to falling particles, the improvement which comprises a mixer for mixing the treated particles, the mixer comprising a pair of concentric, substantially vertical cylindrical walls spaced from one another to define an annular space therebetween, a stationary floor for receiving fallen particles and attached at its periphery to the outer wall, a helical ribbon mounted within the annular space and attached to the inner wall for rotation therewith, a paddle attached to the inner wall and urging fallen particles outwardly along the floor into the annular space for reception by the helical ribbon at its lower end, and means for rotating the inner wall and helical ribbon to auger particles upwardly within the annular space with concurrent mixing.

13. In combination with a treating apparatus for applying a liquid to falling particles, a mixer for mixing the treated particles, the mixer including upright, concentric, spaced inner and outer walls defining an annular space therebetween, a rotatable, helical ribbon disposed in the annular space and having an upright axis of rotation, the inner wall being mounted to the helical ribbon for rotation therewith and defining walls of a central, particle-treating chamber wherein particles are treated with a liquid, means for feeding treated particles from the particle-treating chamber to the bottom of the helical ribbon, means for rotating the ribbon about its axis to auger upwardly the treated particles within the annular space with concurrent mixing of the particles, and means for removing the mixed, treated particles from the top of the ribbon.

14. A mixer for mixing particles treated with a liquid, the mixer including an upright, stationary, cylindrical outer wall, a rotatable inner wall which is concentric with but spaced inwardly of the outer wall to provide an annular space between the walls, the inner wall defining walls of a central chamber, a rotatable, helical ribbon disposed in the annular space and having an upright axis of rotation, the helical ribbon being attached to the inner wall for rotation therewith, a stationary floor at the bottom of said chamber and spaced below the inner wall for reception of liquid-treated particles, means for feeding the fallen treated particles to the bottom of the helical ribbon, and means for rotating the ribbon and inner wall to auger upwardly the treated particles within the annular space for concurrent particle mixing.

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