US3679323A - Mixing and dispersing device - Google Patents

Abstract

A mixing and dispersing device in which an elongated shaft has connected thereto a rigid blade which undulates about a plane that is perpendicular to the shaft, to form a plurality of subblades a number of which are at a positive angle of attack and an equal number of which are at a negative angle of attack.

Description

United States Patent Buck 1 51 July 25, 1972 541 MIXING AND DISPERSING DEVICE 3,504,990 4/1970 Sugden ..416/l76 [72] Inventor: Barry L. Buck, 414 N Lawndale 3,606,577 9/1971 Conn ..4l6/227 X Chicago, 60624 FOREIGN PATENTS OR APPLICATIONS 1 1 Filed= 25, 1971 1,144,900 4/1957 France ..4l6/203 21 A L N J 113 742 1,297,805 5/1962 France ..4l6/l83 1 PP 1,482,898 4/1967 France ..4l6/l83 250,542 1927 Great Britain ..416/183 [52] US. Cl ..416/l83, 416/184, 416/223 [51] Int. Cl. ..B0lf 7/24 Primary Examiner-Everette A. Powell, Jr. [58] Field of Search ..4l6/l 83, 184, 185, I82, 181, Anomey-Lettvin and Gerstman [57] ABSTRACT 6 f [5 1 Re erences Cited A mixing and dispersing device in which an elongated shaft UNITED STATES PATENTS has connected thereto a rigid blade which undulates about a plane that is perpendicular to the shaft, to form a plurality of 1,745,441 2/1930 sub-blades a number of which are at a positive angle of attack 3,044,750 7/ 1952 and an equal number of which are at a negative angle of at- 3,139,034 6/1964 tack. 3,244,410 4/1966 3,336,010 8/1967 4 Claims, 6 Drawing Figures PATENTED 3.679.323

INVENTOR BARRY L. B UCK BY m 4m, (1m

ATTORNEYS MIXING AND DISPERSING DEVICE FIELD OF THE INVENTION This invention relates to an improved device for mixing and dispersing solids and liquids, and more particularly, to a device in which a mixing blade has a novel configuration.

BACKGROUND OF THE INVENTION Prior art mixing devices have various disadvantages. For example, mixing devices using simple propeller-type blades are useful only for limited purposes. The propeller blade rotation causes a build-up of a relatively large vortex thereby causing air to enter the resulting mixture. Although such mixing action is useful in the formation of milk shakes, whipped cream and other food preparations where the entry of air is desirable, such mixing action is deleterious to mixing where air is not wanted.

Another type of prior art device which is widely used is the high-speed disc impeller. This type of device generally gives relatively good dispersement with little vortex formation. However, disc impellers do not afford good mixing except at high peripheral speeds and such high speeds provide cavitation losses. Further, with disc impellers rotating at high speeds, a relatively large amount of heat is generated. This requires a time limit to the amount of mixing provided with a high-speed disc impeller to prevent'the mix from overheating.

I have discovered a form of mixing and dispersing blade which provides stronger mixing action than is obtained with a propeller and can be used at higher peripheral speeds without creating the large vortex that is created by propeller-type blades. At higher speeds, my novel blade provides much of the dispersive action that is generally obtained with the highspeed disc impeller.

Other prior art devices have been tried to achieve various effects by shaping the mixing blade in a predetermined configuration and/or by moving the blade in an unusual manner. For example, in U.S. Pat. No. 189,469, issued to F. M. Johnson on Apr. 10, 1877, a mixing device is disclosed in which the mixing blade comprises four paddles each of which is separated from the other and is serpentine in configuration. The purpose of Johnsons blade is to convey air into the mixture by the up and down motion, and the device is used in a butter churn.

The patent to R. N. Ackles, U.S. Pat. No. 2,918,264, issued Dec. 22, 1959, is an example of the type of device wherein the vortex is limited by controlling the currents in the vicinity of vertical tips which are provided on the mixing blade. This system eliminates radial material transfer to a large extent. On the other hand, my device permits the acceleration of material through substantially radially disposed channels with the mix being forced strongly against the leading edge of the pitched section. There is strong but local turbulence, limited material transfer past the blades in order to limit the vortex, and a high exit velocity into the body of the mix or against the sides of the container.

Accordingly, it is an object of my invention to provide a mixing and dispersing device for use where the entry of a large amount of air is impermissible.

It is a further object of my invention to provide a mixing and dispersing device which provides strong mixing action at relatively low speeds with a reduced vortex and provides considerable dispersive action at relatively high speeds without serious cavitation losses.

A further object of my invention is to provide a mixing and dispersing device having a novel configuration in which a rigid blade undulates about a plane that is perpendicular to the shaft carrying the blade thereon.

Other objects and advantages will be more apparent from the following description and claims, and the illustrations in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a top plan view of a mixing and dispersing device in accordance with the principles of the present invention;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a side elevational view of a first modified form of the invention;

FIG. 4 is a side elevational view of a second modified form of the invention;

FIG. 5 is a side elevational view of a third modified form of the invention; and

FIG. 6 is a side elevational view of a fourth modified form of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS Referring to FIGS. 1 and 2, it is seen that the device comprises a shaft 10 having connected thereto a blade 12 formed of eight sub-blades 14. No limitation is intended with respect to the number of sub-blades 14, as there could be more or less than eight sub-blades, if desired.

Blade 12 is formed of a rigid material, such as steel, and is configurated so as to undulate about a plane a-a that is perpendicular to the axis of shaft 10. It can be seen from FIG. 2 that the portion of blade 12 above perpendicular plane aa is symmetrical to the portion of the blade below the perpendicular plane.

In the embodiment of FIGS. 1 and 2, the blade is formed of a continuous fabrication and the undulations are substantially triangular in cross-sectional configuration with the peaks and nadirs of each undulation including an angle of The subblades 14 form a series of radial channels which guide the material to be mixed radially outward with a tangential component resulting from rotation of the sub-blades, causing acceleration of the material against the positive faces of the subblades.

Other configurations than triangular may be used successfully. Referring to FIG. 3, it is seen that the configuration is rectilinear in cross-section with alternating sectors of the blade being successively horizontal and vertical and joined at an angle of 90.

In FIG. 4, the blade has a sinusoidal cross-sectional configuration. The embodiment of FIG. 5 is similar to the embodiment of FIG. 2, except that each of the sub-blades 14 is separated from its adjacent sub-blades, with the separations 16 occurring at the peaks and nadirs of the undulations. It can be seen that sub-blades 14 are each formed of a separate metal stamping and are fastened to the shaft 10 at the hub thereof.

The embodiment of FIG. 6 has a substantially sawtooth cross-sectional configuration, but differs from the FIG. 3 embodiment because alternate portions 20 of sub-blades 14 extend in a vertical plane when shaft 10 is vertical, while intermediate portions 22 are disposed between alternate portions 20 and each include 45 angles at the peaks and nadirs of the undulations.

It can be seen that my mixing device includes a number of sub-blades at a negative angle of attack and an equal number of sub-blades at n positive angle of attack, with one set of subblades providing working of the material and the other set of sub-blades providing guidance of the material. Material feed is limited to eliminate the vortex radial to the shaft and resulting mixture of air.

The blades are arranged in such a way that the material being mixed undergoes successive impact impingement, shear and reentry into a condition to repeat these processes on a successive blade, this reentry being by flow into the space voided by the first blade. The device utilizes the inertia of a fluid which may be too thin to allow dispersion by shear and approximates a shear effect by briefly and violently accelerating the material over and over against the blade surface and at the same time severely restricting the amount of material transferred past the device. Because of the unique construction of my blade, good mixing and dispersion can be obtained at relatively low rim speeds, such as 1,000 feet per minute, in contrast to a speed of more than 3,000 feet per minute needed with prior art blades.

Although illustrative embodiments of the invention have been shown and described, it is to be understood that various modifications and substitutions may be made by those skilled in the art without departing from the novel spirit and scope of the present invention.

WHAT IS CLAIMED IS:

1. A mixing and dispersing device which comprises: an elongated shaft for connection to a drive means, said shaft having connected thereto a rigid blade comprising a plurality of subblades, said rigid blade being symmetrical about a plane that is perpendicular to said shaft and intersects said blade, each of said sub-blades having a planar surface and forming a triangular configuration with its adjacent blade, said sub-blades extending outwardly from the shaft with the vertices of the triangles being free from contact with any supporting means.

2. A mixing and dispersing device as described in claim 1, wherein the included angle of each triangle is about 3. A mixing and dispersing device as described in claim 1, wherein the included angle of each triangle is about 45 and each alternate sub-blade extends parallel to the axis of the shaft.

4. A mixing and dispersing device as described in claim 1, wherein each sub-blade is separated from its adjacent subblades, with the separations occurring at the corners of the triangles.

Claims (4)

1. A mixing and dispersing device which comprises: an elongated shaft for connection to a drive means, said shaft having connected thereto a rigid blade comprising a plurality of subblades, said rigid blade being symmetrical about a plane that is perpendicular to said shaft and intersects said blade, each of said sub-blades having a planar surface and forming a triangular configuration with its adjacent blade, said sub-blades extending outwardly from the shaft with the vertices of the triangles being free from contact with any supporting means.

2. A mixing and dispersing device as described in claim 1, wherein the included angle of each triangle is about 90* .

3. A mixing and dispersing device as described in claim 1, wherein the included angle of each triangle is about 45* and each alternate sub-blade extends parallel to the axis of the shaft.

4. A mixing and dispersing device as described in claim 1, wherein each sub-blade is separated from its adjacent sub-blades, with the separations occurring at the corners of the triangles.

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