Apparatus for the continuous mixing of granular materials

Abstract

A mixing apparatus adapted for use with granular or semi-solid material and embodying a mixer trough within which are disposed two parallel companion shafts each of which has mounted thereon a linearly straight row of flat slanting parallel mixing blades of interrupted-elliptical shape, the two rows of blades functioning when the shafts are rotated in opposite directions to propel the material forwardly while at the same time exerting thereon a slicing action whereby progressively diminishing masses of the material are tossed from side to side and are repeatedly sliced into smaller increments as they progress along the trough.

Description

PERTINENT PRIOR ART

Atkins, U.S. Pat. No. 3,248,092, Apr. 26, 1966, transverse turntable bearings, disk having an interrupted-elliptical contour as clearly shown in FIG. 9, the blade being affixed to the hub 74 so that the plane thereof intersects the axis of the shaft at a relatively sharp angle which may be on the order of 45°. eachsemi-elliptical interrupted-elliptical mixer blades which, instead of being truly semi-elliptical, possess areas of sand regression by reason of the fact that not all of the areas which ordinarily would produce backward sand movement are relieved. Such a mixer blade is illustrated in the diagrammatic disclosure of FIG. 12 wherein the blade relief area on the blades 270 276 and the relief area on the opposed blades 376 are on the order of 90°. These interrupted-elliptical three-quarters elliptical blades may conveniently be formed in the same manner as the blades 76 and 176 are welded to central hubs (not shown) in order to produce mixer blade units similar to the units 72 and 172 of FIG. 1 which are then mounted on the shafts 70 and 170 in place of the units 72 and 172.

Reference to FIG. 12 will reveal the fact that varying amounts of blade overlap take place during the entire 360° cycle of blade operation except for the exact instant of time when the blades are in their 0° and their 180° positions. Maximum blade overlap occurs in the 90° and 270° positions where there is an approximate 25% blade overlap. The same slope and pitch conditions obtain in connection with the blades 276 and 376 as obtain in connection with the blades 76 and 176, as does the same condition of reverse rotation of the shafts 70 and 170.

It will be appreciated that in the overlap regions which, in the various positions illustrated in FIG. 12, are shown as being shaded, a portion of the mixer blade 276 which overlaps a portion of the mixer blade 376 represents a portion which exerts a backward thrust upon the sand. This portion opposes a portion of the blade 376 which exerts a forward thrust upon the same. Therein lies the squeezing or scrubbing action which invariably is sought for in a commercial said sand mulling apparatus. Furthermore, since the predominant thrust which is exerted upon the sand by all of the blades, considered collectively, forward sand movement along the trough 52 is continuously maintained.

In either of the above-described forms of the invention, certain principles of mixing hold true. Generally speaking, the degree of the mix is a function of the length of the trough 52 and the configuration of the blades, while the rate of flow of the material undergoing mixing from the discharge outlet 68 is a function of the r.p.m. of the shaft assemblies 72 and 172 and the pitch angle of the blades.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. For example, although the trough channels 52a and 52b are illustrated and described herein as being curved on a cylindrical bias, while the contour of the various mixer blades is stated to be semi-elliptical, it is within the purview of the invention to construct the blades so that they present a semi-circular contour, in which case the curvature of the trough channels will be shaped so as to be commensurate with the surfaces of revolution which are generated by the particular shape of the blades when the shafts on which they are mounted are rotated. Thus, throughout this specification and in the appended claims, the term "elliptical" is to be construed as being inclusive of a circle which, in a sense, is a special form of an ellipse or, in other words, it is an ellipse in which the major and minor axes are equal in length. Furthermore, although the various blades 76 and 176 in the first described form of the invention, and the blades 276 and 376 in the second form of the invention, have been shown and described as existing in longitudinal alignment along the respective shafts on which they are mounted, it is contemplated that under certain circumstances it may be found advantageous to arrange these blades in a helical row of long pitch so that each blade assumes a slightly angularly displaced position with respect to the adjacent blades on the shaft. By such an arrangement, the cooperation between companion blades on the two shafts will remain the same as has been described herein. Therefore, only insofar as the invention is particularly pointed out in the accompanying claims is the same to be limited.

Claims

1. In a mixing apparatus for granular material, in combination, an elongated mixing trough providing a longitudinal flow path and having a receiving and a discharge end, a pair of parallel companion shafts rotatable in said trough, a plurality of axially spaced sloping parallel interrupted-elliptical disk-like mixing blades on each shaft, the blades on the two shafts having equal but reverse pitch angles and being disposed in transverse pairs, said blades, in one position of the shafts, projecting predominately laterally in the same direction, the maximum radial projection of the blades from the shaft being slightly less than the distance between said shafts, and means for rotating said shafts in unison and in opposite directions whereby the blades of each pair traverse a common portion of said flow path alternately.

2. In a mixing apparatus, the combination set forth in claim 1 and wherein the blades on each shaft are effectively disposed entirely on one side of a longitudinal axial plane whereby overlapping of the paired blades is avoided.

3. In a mixing apparatus, the combination set forth in claim 1 and wherein said mixing trough is provided with a divided trough bottom establishing a pair of trough channels along said flow path and the surfaces of the channels are extended surfaces of revolution which are generated by revolution of said blades about the axes of the companion shafts.

4. In a mixing apparatus, the combination set forth in claim 3 and wherein each semi-elliptical interrupted-elliptical blade has a major and a minor axis both of which intersect the longitudinal axis of the associated companion shaft, the minor axis extending at a right angle to said longitudinal axis and the major axis being inclined relatively thereto.

5. In a mixing apparatus, the combination set forth in claim 4 and wherein said trough channels are separated by a linear saddle peak.

6. In a mixing apparatus, the combination set forth in claim 4 and wherein the pitch angle of each blade is on the order of 45°.

7. In a mixing apparatus, the combination set forth in claim 4 and wherein each blade is in the form of an ellipse which is divided linearly along its major axis so as to define a half-ellipse.

8. In a mixing apparatus, the combination set forth in claim 1 and wherein each blade has a portion thereof which projects laterally from its associated shaft in a direction opposite to said predominant direction whereby, upon rotation of said shafts in opposite directions, progressive overlapping of said latter portions of the paired blades periodically takes place.

9. In a mixing apparatus, the combination set forth in claim 1 and wherein each blade is fixedly mounted on a central tubular sleeve-like hub, the various hubs are telescopically and removably mounted on the respective companion shafts in end-to-end contiguity, and means are provided for preventing both angular turning and longitudinal shifting of the hubs on their respective shafts. 10. In a mixing apparatus, the combination set forth in claim 1 and wherein the blades on each shaft are the same in size and shape, are arranged in registering relation, and are all inclined in one direction. 11. In a mixing apparatus, the combination set forth in claim 10 and wherein each blade is substantially semi-elliptical and has its dividing line along its major aixs. 12. In a mixing apparatus, the combination set forth in claim 10 and wherein each blade is substantially three-quarters elliptical. 13. In a mixing apparatus, the combination set forth in claim 10 and wherein each blade is flat and imperforate.