US3450356A - Agitator - Google Patents

Description

Juhe 17, 1969 A. SZEGVARI AGITATOR SZEGVARI Sheet INVENTOR. ANDREW Original Filed March 5, 1964 ATTORNEY June 17,1969 A. SZEGVARI 3,450,355

AGITATOR Original Filed March 5, 1964 Sheet 2 of 4 INVENTOR. ANDREW SZEGVARI ATTORNEY June 17, 1969 A. SZEGVARI 3,450,356

AGITATOR Original Filed March 5, 1964 FIG. 5

FIG. 6

E ZONE 3 /ZONE 2 ZONEYI I j n L I zone: [ZONE 2 zone 3 INVENTOR. v ANDREW SZEGVARI nymc d ATTORNEY Original Filed March a, 1964 Y June 17, 1969 1 AGITATOR Sheet 4 014 FIGIO INVENTOR. ANDREW SZEGVARI ATTORNEY A. SZEGVARI I 3,450,356

United States Patent US. Cl. 241-172 13 Claims ABSTRACT OF THE DISCLOSURE Grinding apparatus which comprises a vessel partially filled with spherical grinding elements, and a central vertical agitator with supports extending different distances therefrom and each provided with a terminal activator.

This is a continuation of my application Ser. No. 349,550, filed Mar. 5, 1964, and now abandoned.

This invention relates to an agitator for spherical attrition elements in a vessel in which a material suspended in liquid is ground fine by the action of the activated attrition elements; and it includes the method of agitation.

The spherical attrition elements are mechanically acted upon by revolving agitating means, and this patent appli cation discloses how to make this agitator means more effective and how to affect the agitator construction to bring about uniform kinetic activation of the grinding media in the matrix thereof throughout the grinding vessel.

Kinetic activation of an attrition aggregate is described in US. Patent No. 2,764,359, according towhich an agitating device imparts continuously sufficient mechanical energy to a large enough number of attrition elements, so that a random distribution of the momenta coupled with an incipient free path develops and these activated elements are kept out of static contact with one another.

The general difiiculty in obtaining kinetic activation encountered (when using a revolving agitator is a tendency to cause circular group movement of the attrition ele ment aggregates whereby the whole system is moved like a coherent solid mass; while kinetic activation occurs only when the adjoining attrition elements meet, having a differing vector of motion. In addition, this has to be brought about with minimum axial circulation of the attrition elements as described in my United States patent application Ser. No. 65,796 filed Oct. 28, 1960 (now US. 3,149,789).

Another difiiculty when generating kinetic activation with agitators commonly used in industry and described in literature is that the action is not uniform, and extends primarily around a peripheral zone of the outermost extension of the agitators. Most of the kinetic activation takes place around the end of an agitator bar, and decreases to zero as one approaches the central shaft along the agitator bar.

It is easily seen that the activating means of the agitator moving through an aggregate system causes most kinetic activation if the velocity gradient in the contacting aggregate system is largest, in other words, the average velocity within this aggregate system is changing fastest from point to point. The largest velocity gradient is obtained at a terminal portion of an agitating means that extends at a right angle to its support and at a right angle to the plane of rotation into the aggregate system. Such a means is herein called an activator.

In order to provide activation throughout the entire cross section of the system of attrition aggregates, activators are placed on support means so as to locate them Patented June 17, 1969 at a certain distance from the axis of the agitator; and in large vessels activators are located on them in several radii. The activators located nearer the axis of the agitator are larger than those located farther away in order to produce the same kinetic activation of the attrition elements when the activators are moved through them.

It is important that these activators should move through a path of the aggregate system which is otherwise not acted upon in order to decrease the group movement of the entire aggregate system. Therefore, the activators in their circular path should be as far apart from each other as practical, and preferably there should be only one activator in each circular path, except in a very large vessel. Further, the paths of an activator or other agitator means should be as far as possible away from all other agitator means, like other activators or activator supports.

If the volume of the vessel is divided into several concentric agitator zones the liquid preferably rises up through the vessel with no intermixing of the material from these various zones.

To provide uniform kinetic activation throughout the entire contents of the vessel, it is necessary to provide equal or nearly equal activation in each zone, and to distribute the activators so as to obtain substantially equal kinetic activation at each level in each zone.

The means for providing activation in each zone may take any one of several forms. It is proposed in this application to use radial supports arranged at angles to one another around a central agitator shaft, or to attach additional terminal structures to axial supports spaced at different distances from the agitator shaft to serve as activators of the grinding media.

The invention is further described in connection with the accompanying drawings.

Several specific embodiments of the invention are shown in the drawings, in which:

FIGURE 1 is an elevation in section showing an agitator with agitator bars or rods extending generally axially of the shaft and activators attached thereto, in a tapering vessel;

FIGURE 2 is a detail of the bottom of the same, at right angles to the view shown in FIGURE 1, showing scoops at the bottom of the agitator;

FIGURE 3 is a horizontal section on the line 33 of FIGURE 1;

FIGURE 4 is an elevation in section of an agitator with horizontal arms and activators attached thereto, in a small cylindrical vessel;

FIGURE 5 is a section on the line 5-5 of FIGURE 4;

FIGURE 6 is a plan view of an agitator arm with two activators attached thereto designed for use in a vessel of larger diameter;

FIGURE 7 is an elevation of the same;

IGURE 8 is the same as FIGURE 7, except that the shaft is shown partly in. section, and zones of activation are indicated;

FIGURE 9 is an end view of the agitator arm of FIG- URE 7 on the line 99 thereof;

FIGURE 10 is an elevation in section showing part of the top of a modified type of agitator; and

FIGURE 11 is a plan view on the line 1111 of FIG- URE 10.

FIGURE 1 indicates that when in operation the attrition elements 1 cover the top of the effective portion of the agitator 2, and may be retained in the vessel 3 by a screen 4.

The agitator 2. shown in FIGURES 1 to 3 includes two scoops 5 at its bottom spaced from the bottom of the vessel a distance of about three times the diameter of one of the attrition elements. These lift the attrition elements 1 off the bottom of the vessel 3 when the agitator 2 is put in motion. Scoops may be omitted.

The agitator comprises a central shaft 6 having activator supports 7 extending in the general axial direction of the shaft and attached thereto by means of radial arms 8 as shown in FIGURES 1 to 3. Activators 10 are attached to the activator supports 7.

As the liquid flows upthrough the vessel, the least agitated flow is close to the vertical shaft 6, the kinetic activation being much less there than near the wall of the vessel 3. If the axial activator supports 7 are located at different distances from the shaft 6 of the agitator as illustrated in FIGURES 1 to 4, the activators 10 may be located on only the inner supports instead of on all the supports as there shown.

The agitator of FIGURES 4 and is shown in a cylindrical vessel 20. The activator supports 21 are all of the same length but are so positioned in the holes 22 that one end of each to which an activator 23 is attached projects from the shaft only about half as far as the other end. The support ends are located farther from the shaft than the activators 23 so as to produce substantially uniform agitation over the whole area of the vessel, and the activators 23 are distributed over the area to accomplish this end.

FIGURES 6 to 9 illustrate a structure for use in vessels of larger diameter in which there are a plurality of activators on each support 29. There are many supports in each agitator extending from the shaft 30 in different directions, although only one such support is shown in each of these figures. The support extends through the shaft and is held in place by the pin 32. The configuration would be similar to that shown in FIGURE 4 for a vessel of smaller diameter. The dotted lines indicate three cylindrical zones of activation, numbered 1, 2 and 3, of progressively greater diameters. There may be a larger or smaller number of zones in each of which activator means is located. When the agitator is rotated the activator 31 provides activation in zone No. 1 nearest the shaft. Activator 33 in zone No. 2 is somewhat smaller. The end of the support 34 acts as an activator in zone No. 3. The activator 33 in the intermediate zone is intermediate in its capacity of activation between the activator 31 and the support end 34.

In FIGURE 8 the areas adjacent the different activating means are shaded to indicate the areas of intense agitation immediately adjacent each. An area of somewhat less agitation is indicated as surrounding each of the shaded areas. The different shaded areas overlap as the agitator is rotated.

The leading edge of each support of the agitators shown in the foregoing figures tapers to a knife edge so that there is minimum group rotation of the attrition elements as a mass. (See particularly the end and sectional views of supports 7 in FIGURE 3 and the end view in FIGURE 4.) Kinetic activation is increased as rotational movement of the aggregate system as a whole is minimized.

T he agitator of FIGURES and 11 utilizes flat plates 40 for activator supports which cut through the bed of attrition elements with minimum movement of them as a whole and minimum displacement, one from another. The plates are spaced radially of the shaft 41 to locate the activators 42, 43 on all sides of the shaft, and they are spaced axially of the shaft so that no two activators move in the same annular zone about the shaft. Alternate activators 42 and 43 are spaced different distances from the shaft so as to kinetically activate the attrition elements in zones spaced different distances from the shaft. Thus, the activators are so located as to most efficiently effect kinetic activation of the attrition elements throughout the whole of the vessel in which the agitator is located.

The invention is covered in the claims which follow.

I claim:

1. Apparatus for fine grinding which includes a vessel with an agitator and spherical grinding elements therein in such quantity as to partially fill the vessel about the bottom of the agitator, the agitator comprising a central 4 vertical shaft with supports radiating therefrom and individual terminal activators attached to the separate supports and so exposed thereon that each activator generates a path different from that generated by the support to which it is attached when the agitator is rotated about its vertical axis.

2. The apparatus of claim 1 in which the activators are attached to the supports at different distances from the shaft and so exposed thereon that when the agitator is rotated grinding elements located at all distances from the central shaft are agitated.

3. The apparatus of claim 1 in which the frontal elevation of each support is less than the frontal elevation of the one or more activators fastened thereto so that the supports cause substantially no driving action in the medium in which the agitator is located when the agitator is rotated about the vertical shaft.

4. The apparatus of claim 1 in which the supports are relatively thin compared to their width and and are flat in horizontal planes and substantially perpendicular to the central shaft and extend outwardly from only a small portion of the shaft circumference and each have at least one activator extending perpendicularly therefrom.

5. Apparatus for fine grinding which includes a vessel with an agitator and spherical grinding elements therein in such quantity as to partially fill the vessel about the bottom of the agitator, the agitator comprising a central vertical shaft with linear supports spaced from the shaft and extending lengthwise of the shaft, with activators protruding from the supports at spaced intervals.

6. The apparatus of claim 1 in which the activators are distinct from one another and supported by the shaft at different radial distances from the shaft.

7. A bed of grinding media in a grinding vessel, and extending down into said bed an agitator with an axis of rotation and equipped with activators on supports at different distances from said axis, the activators with the smaller radial distances from the axis being larger than the activators at the larger radial distances, the relative size of each activator being varied inversely with the radial distance.

8. The combination of claim 7 which includes a central vertical shaft, supports extending substantially perpendicularly therefrom, and activators of different activating capacities on the supports and extending generally axially of the shaft.

9. An activatable bed of grinding media in a grinding vessel, and extending down into said bed an agitator which includes openings through the shaft in various directions and a support in each opening which extends from each side of the shaft, with at least one activator extending away from each support on each side of the shaft in a direction generally perpendicular thereto.

10. Apparatus for fine grinding which includes a vessel with an agitator and spherical grinding elements therein in such quantity as to partially fill the vessel around the bottom of the agitator, the agitator comprising a central vertical shaft with supports attached thereto and activators of different sizes attached to the supports at different distances from the central shaft, with the vertical cross-sectional area of each activator perpendicular to a line radiating from the central shaft, varying inversely with the radial distance between it and the central shaft.

11. Apparatus for fine grinding which includes a vessel with an agitator and spherical grinding elements therein in such quantity as to partially fill the vessel around the bottom of the agitator, the agitator comprising a central vertical shaft with supports attached thereto and activators attached to the supports, with the supports each extending through an opening in the central shaft and at least one activator extending away from each support on each side of the shaft in a direction generally perpendicular to the support.

12. Apparatus for fine grinding which includes a ves sel with an agitator and substantially spherical grinding 5 elements therein in such quantity as to partially fill the vessel about the bottom of the agitator, which agitator comprises a central shaft with elements of the agitator extending perpendicularly outward from the shaft and extending different distances away from the shaft on opposite sides of the shaft.

13. Apparatus for fine grinding which includes a vessel with an agitator and substantially spherical grinding elements therein in such quantity as to partially fill the vessel about the bottom of the agitator, which agitator cornprises a central shaft with elements extending perpendicularly outward from the shaft which are positioned asymmetrically with respect to the center of the shaft.

6 References Cited UNITED STATES PATENTS GERALD A. DOST, Primary Examiner.

US. Cl. X.R.

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